METHODS AND APPARATUS FOR EYEGLASS LENS CURING USING ULTRAVIOLET LIGHT AND IMPROVED COOLING

Abstract: Method and apparatus for making and coating a plastic lens. Oxygen barrier containing photoinitiator is used to cure incompletely cured lens portions. Radiation pulses are used to control lens curing rate. Lens is postcured while in a mold cavity using a conductive heat source. Air may be directed toward the mold cavity to help remove heat from the lens. An in-mold scratch resistant coating may be formed from two separate material which both contain a photoinitiator.

Description: TITLE: METHODS AND APPARATUS FOR EYEGLASS LENS CURING USING ULTRAVIOLET LIGHT AND IMPROVED COOLING BACKGROUND OF THE INVENTION 1 Field ofthe Invention The present invention relates generally to methods and apparatus for making plastic lenses using ultraviolet light 2 Description of Related Art It is conventional in the art to produce optical lenses by thermal curing techniques from the polymer of diethylene glycol bιs(allyl)-carbonate (DEG-BAC) ln addition, optical lenses may also be made using ultraviolet ("UV") light curing techniques See, for example, U S Patent Nos 4,728,469 to Lipscomb et al , 4,879,318 to Lipscomb et al , 5,364 256 to Lipscomb et al , 5,415,816 to Buazza et al , 5,529,728 to Buazza et al , 5,514,214 to Joel et al , and U S patent application serial nos 07/425,371 filed October 26, 1989, 08/454,523 filed May 30, 1995, 08/453,770 filed May 30, 1995, 07/932,812 filed August 18, 1992, 08/636,510 filed April 19, 1996, all of which are hereby specifically incorporated hereby by reference Curing of a lens by ultraviolet light tends to present certain problems that must be overcome to produce a viable lens Such problems include yellowing of the lens, cracking of the lens or mold, optical distortions in the lens, and premature release of the lens from the mold In addition many of the useful UV-curable lens forming compositions exhibit ceπain characteristics which increase the difficulty of a lens curing process For example, due to the relatively rapid nature of ultraviolet light initiated reactions it is a challenge to provide a composition which is UV curable to form an eyeglass lens Excessive exothermic heat tends to cause defects in the cured lens To avoid such defects the level of photoinitiator may be reduced to levels below what is customarily employed in the ultraviolet curing art While reducing the level of photoinitiator addresses some problems, it may also cause others For instance, lowered levels of photoinitiator may cause the material in regions near an edge ofthe lens and proximate a gasket wall in a mold cavity to incompletely cure due to the presence of oxygen in these regions (oxygen is believed to inhibit curing of many lens forming compositions or materials) Uncured lens forming composition tends to result in lenses with "wet" edges covered by sticky uncured lens forming composition Furthermore, uncured lens forming composition may migrate to and contaminate the optical surfaces of the lens upon demolding The contaminated lens is then often unusable Uncured lens forming composition has been addressed by a variety of methods (see. e g , the methods described in U.S. Patent No 5,529,728 to Buazza et al). Such methods may include removing the gasket and applying either an oxygen barrier or a photoinitiator enriched liquid to the exposed edge of the lens, and then re- lrradiating the lens with a dosage of ultraviolet light sufficient to completely dry the edge ofthe lens prior to demolding During such irradiation, however, higher than desirable levels of irradiation, or longer than desirable periods of irradiation, may be required The additional ultraviolet irradiation ma> in some circumstances cause defects such as yellowing in the lens The low photoinitiator levels utilized in many ultraviolet curable lens forming compositions may produce a lens which, while fully-cured as measured by percentage of remaining double bonds, may not possess sufficient crosslink density on the lens surface to provide desirable dye absoφtion characteristics duπng the tinting process Various methods of increasing the surface density of such U V curable lenses are described in U S Patent No 5,529,728 to Buazza et al In one method, the lens is demolded and then the surfaces of the lens are exposed directly to ultraviolet light The relatively short wavelengths (around 254 nm) provided by some UV sources (e.g., a mercury vapor lamp) tend to cause the material to crosslink quite rapidly An undesirable effect ofthis method, however, is that the lens tends to yellow as a result of such exposure Another method involves exposing the lens to relatively short wavelengths while it is still within a moid cavity formed between glass molds The glass molds tend to absorb the more effective short wavelengths, while transmitting wavelengths of about 365 nm This method generally requires long exposure times and often the infrared radiation absorbed by the lens mold assembly will cause premature release ofthe lens from a mold member The lens mold assembly may be heated prior to exposure to high intensity ultraviolet light, thereby reducing the amount of radiation necessary to attain a desired level of crosslink density This method, however, is also associated with a higher rate of premature release It is well known in the art that a lens mold/gasket assembly may be heated to cure the lens forming composition from a liquid monomer to a solid polymer It is also well known that such a lens may be thermally postcured by applying convective heat to the lens after the molds and gaskets have been removed from the lens In this application the terms "lens forming material" and "lens forming compositions" are used interchangeably SUMMARY OF THE INVENTION One aspect ofthe invention relates to applying an oxygen barrier around the exposed edges of a lens to initiate the reaction of incompletely cured lens forming material proximate the lens edges ln an embodiment, a liquid polymerizable lens forming composition is placed in a mold cavity having at least two molds and/or a gasket Ultraviolet rays may be directed toward at least one ofthe mold members to substantially cure the lens forming composition to a lens having material proximate the edges ofthe lens that is not fully cured The gasket may be removed to expose the edges ofthe lens, and an oxygen barrier comprising a photoinitiator may be placed around the exposed edges ofthe lens such that at least a portion ofthe oxygen barrier photoinitiator is proximate lens forming composition that is not fully cured A portion ofthe incompletely cured material may be removed manually prior to the application ofthe oxygen barrier Subsequently another set of ultraviolet rays may be directed towards the lens such that at least a portion of the oxygen barrier photoinitiator initiates reaction of lens forming composition while the oxygen barrier substantially prevents oxygen from outside the oxygen barrier from contacting at least a portion of the lens forming composition The lens may be allowed to cool and the oxygen barrier may be removed The lens may be tinted after the cure is completed The oxygen barrier may include a flexible, stretchable. self-sealing film that is at least partially transparent to ultraviolet rays The oxygen barrier may include polyethylene impregnated with a photoinitiator The film may include a strip of high density polyethylene that is about 0 01- 1 0 mm thick, and more preferably about 0 01-0 10 mm thick Thicker films tend to be less conformable and stretchable The oxygen barrier may include a plastic film that is less than about 0 025 mm thick (e g , about 0 0127 mm thick) and that was made by (a) immersing or running a plastic film in or through a solution comprising a photoinitiator and an etching agent (b) removing the plastic film from the solution, and (c) drying the plastic film A surface on the plastic film may be chemically etched prior to or while immersing the plastic film in the solution Another aspect ofthe invention relates to applying conductive heat to the face of a lens in an embodiment ofthe invention, a liquid polymerizable lens forming composition is placed in a mold cavity having a first mold member and a second mold member First ultraviolet rays may be directed toward at least one ofthe mold members to cure the lens forming composition to a lens A mold member may be applied to a substantially solid conductive heat source Heat may be conductively applied to a face of the lens by (a) conductively transferring heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the face of the lens In an embodiment, a flexible heat distributor may be placed between the heat source and the mold member to partially insulate the mold member and to slowly and uniformly transfer heat to the face ofthe mold member The distributor may be shaped to conform to the face of a mold member The heat source may include a concave element that may conform to the convex face of a mold member The heat source may include a convex element that may conform to the concave face of a mold member The temperature of the heat source may be thermostatically controlled Heat may be conductively applied through a mold member to the back face ot the lens, thereby enhancing the cross-linking and tintabihty of the lens formmg material proximate to the surface ofthe back face ofthe lens (e g , when an untintable scratch resistant coating is on the front face ofthe lens) ln an embodiment ofthe invention an eyeglass lens may be formed by (a) placing a liquid, polymerizable lens-forming composition in a mold cavity defined by at least a first mold member and a second mold member, (b) applying a plurality of preferably high intensity ultraviolet light pulses to the lens forming composition, at least one ofthe pulses having a duration of less than about one second (more preferably less than about 0 1 seconds, and more preferably between 0 1 and 0 001 seconds), and (c) curing the lens forming composition to form a substantially clear eyeglass lens in a time period of less than 30 mmutes (more preferably less than 20 mmutes, and more preferably still less than 15 minutes) The pulses preferably have a sufficiently high intensity such that reaction is initiated in substantially all ofthe lens forming composition that is exposed to pulses in the mold cavity In one embodiment reaction is initiated in substantially all of any cross section ofthe lens forming composition that is exposed to pulses in the mold cavity Preferably the temperature begins to rise after such application of UV light The lens forming composition may be exposed to UV light from one, two, or multiple sources Two sources may be applied on opposite sides of the mold cavity to apply light to the lens formmg composition from two sides. In an alternate embodiment, the lens forming composition is exposed to a relatively low intensity ultraviolet light before or while the pulses are applied Such pulses are preferably relatively high in intensity, and are preferably applied to the other side ofthe mold cavity than the relatively low intensity light The lens forming composition is preferably exposed to a relatively low intensity ultraviolet light while the pulses are applied, the relatively low intensity light having an intensity of less than 0 01 watt/ cπr (and more preferably less than 0 001 watt/ cm 2 , and more preferably still 2-30 milliwatts/ cm-), as measured on an outside surface of a mold member of the mold cavity The relatively low intensity light tends to provide a low amount of light to keep the reaction going in a more steady or even manner between pulses Preferably at least one or even all ofthe pulses has an intensity of at least 01 watt/ cm 2 , as measured on an outside surface of a mold member ofthe mold cavity Alternately at least one or even all ofthe pulses have an intensity of at least 0 1 or 1 watt/ cm 2 Sufficient ultraviolet light can be applied such that the temperature ofthe lens forming composition begins to increase Then in one embodiment at least 5 minutes of waiting or darkness occurs before applying additional light (e g , pulses) The waiting or darkness allows heat to dissipate, thus tending to prevent excessive heat buildup in the mold cavity In one embodiment at least 5, 10, or 20 pulses are applied to the lens formmg composition before waiting for about 5-8 minutes and then additional light is applied The eyeglass lens has an average thickness of at least about 1 5-2 0 mm Thicker lenses tend to be more difficult to cure with continuous non-pulsed light The mold cavity is preferably cooled with air or cooled air One significant advantage of light pulses is that ambient air may be used to cool the mold cavity, instead of cooled air Thus significant lens curmg costs may be avoided since air coolers tend to be costly to purchase and operate The pulses preferably emanate from a flash source of light (I e , "a flash light") such as a xenon light source Preferably pulses are applied such that the lens forming composition is oversaturated with ultraviolet light duπng at least one pulse Flash lights are advantageous in that they have a short "warm-up' time (as opposed to continuous lights that tend to require 5-60 minutes to stabilize) Lenses may be formed with pulsed light that have more difficult to case prescriptions such as lenses with a power greater than positive 2 diopters, or lenses with a power less than minus 4 diopters One advantage of pulsed light application via flash lights is that even though higher intensities of light are applied, because the duration ofthe pulses is so short the total amount of light energy applied to cure the lens forming composition is lessened Thus less radiant heat is applied to the mold cavity, thereby reducing cooling requirements Moreover, energy is saved In one embodiment less than 20, 10, 5, or 1 Joule/ cm 2 of energy is applied to cure the lens forming composition into a lens Preferably the ultraviolet light is applied as a function ofthe temperature ofthe lens forming composition, as measured directly or indirectly by measuring a temperature within the chamber (e g , a temperature of at least a portion ofthe mold cavity) or by measuring a temperature of air in or exiting the chamber In another embodiment ofthe invention, an eyeglass lens may be cured by (a) placing a liquid, polymerizable lens forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition comprising a photoinitiator, (b) applying ultraviolet light at an intensity to the lens forming composition through at least one ofthe mold members for a selected period of time such that a temperature of the composition begins to increase, (c) decreasing the intensity ofthe ultraviolet light to inhibit the temperature of the lens forming composition from increasing to a selected first temperature, (d) allowing an exothermic reaction ofthe lens forming composition to increase the temperature ofthe lens formmg composition to a second temperature, the second temperature being less than the selected first temperature, (e) curmg the lens forming composition to form a substantially clear eyeglass lens by (I) applying ultraviolet light at an intensity to the lens forming composition through at least one ofthe mold members, and (n) decreasing the intensity ofthe ultraviolet light, and (0 wherein the eyeglass lens is formed from the lens forming composition in a time period of less than about 30 minutes ln another embodiment ofthe invention an eyeglass lens may be made by (a) placing a liquid, polymerizable lens-forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition compnsmg a photoinitiator, (b) applying first ultraviolet light to at least one ofthe mold members for a selected first period of time such that a temperature ofthe lens forming composition begins to increase, (c) removing the first ultraviolet light from at least one of the mold members, thereby inhibiting the temperature of the composition from increasing to a selected first temperature, (d) repeatedly and alternately performing the following steps to complete the formation of a lens (1) apply mg second ultraviolet light to at least one of the mold members for a selected second period of time and (n) removing the second ultraviolet light from at least one ofthe mold members for a selected third period of time In an altemate embodiment ofthe invention an eyeglass lens may be made by (a) placing a liquid, polymerizable lens forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition comprising a photoinitiator, (b) directing ultraviolet light at a first intensity toward at least one of the mold members for a selected first period of time such that a temperature ofthe composition begins to increase, (c) decreasing the first intensity of ultraviolet light from at least one ofthe mold members, (d) repeatedly directing a plurality of pulses of ultraviolet to the lens forming composition through at least one of the mold members to complete formation of a substantially clear eyeglass lens, at least one ofthe pulses lasting for a second period of time, and wherein a third period of time exists between application of at least two of the pulses An apparatus ofthe invention may include (a) a first mold member having a casting face and a non- casting face, (b) a second mold member having a casting face and a non-casting face, the second mold member being spaced apart from the first mold member durmg use such that the casting faces ofthe first mold member and the second mold member at least partially define a mold cavity, (c) a first pulse light generator adapted to generate and direct a pulse of ultraviolet light toward at least one ofthe first and second mold members during use, and (d) a controller adapted to control the first pulse light generator such that ultraviolet light is directed in a plurality of pulses toward at least one of the first and second mold members, at least one of the pulses having a duration of less than one second A system ofthe invention may include (a) a lens forming composition comprising a photoinitiator, (b) a first mold member having a casting face and a non-casting face, (c) a second mold member having a castmg face and a non-casting face, the second mold member being spaced apart from the first mold member during use such that the castmg faces ofthe first mold member and the second mold member at least partially define a mold cavity for the lens formmg composition, (d) a first pulse light generator adapted to generate and direct a pulse of ultraviolet light toward at least one of the first and second mold members during use, (e) a controller adapted to control the first pulse light generator such that ultraviolet light is directed in a plurality of pulses toward at least one of the first and second mold members, at least one ofthe pulses having a duration of less than one second, and (f) wherein the system is adapted to cure the lens forming composition to form a substantially clear eyeglass lens m less than 30 minutes The lens forming composition preferably compπses at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl, and/or an aromatic containing bιs(allyl carbonate)-functιonal monomer A system of the invention may include (a) a lens formmg composition comprising a photoinitiator, (b) a mold cavity chamber comprising a first mold member having a casting face and a non-casting face, a second mold member having a castmg face and a non-casting face, the second mold member being spaced apart from the first mold member durmg use such that the casting faces ofthe first mold member and the second mold member at least partially define a mold cavity for the lens forming composition, (c) a first light generator adapted to generate and direct a ultraviolet light in a first intensity toward at least one ofthe first and second mold members during use, (d) a temperature sensor adapted to sense a temperature m the chamber or a temperature of air exiting the chamber, (e) a controller coupled to the temperature sensor and adapted to control the first light generator such that the first intensity of ultraviolet light directed toward at least one ofthe first and second mold members is decreased when a temperature measured by the temperature sensor substantially increases, and (0 wherem the system is adapted to cure the lens forming composition to form a substantially clear eyeglass lens in less than 30 mmutes An apparatus ofthe invention may include (a) a first mold member having a casting face and a non- casting face, (b) a second mold member having a casting face and a non-casting face, the second mold member being spaced apart from the first mold member during use such that the casting faces ofthe first mold member and the second mold member at least partially define a mold cavity for a lens forming composition, (c) an ultraviolet light generator adapted to generate and direct ultraviolet light toward at least one ofthe first and second mold members during use, (e) a controller for controlling the intensity of light directed by the light generator, (f) a light sensor adapted to measure the intensity of light directed by the ultraviolet light generator, the light sensor being adapted to signal the light generator to vary the intensity ofthe ultraviolet light being produced, and (g) a filter adapted to inhibit light other than ultraviolet light from impinging upon the light sensor In an alternate embodiment, a system for making an eyeglass lens may include (a) a first mold member having a casting face and a non-casting face, (b) a second mold member having a casting face and a non-castmg face, the second mold member being spaced apart from the first mold member duπng use such that the castmg faces ofthe first mold member and the second mold member at least partially define a mold cavity for a lens forming composition, (c) an ultraviolet light generator adapted to generate and direct ultraviolet light toward at least one ofthe first and second mold members during use, (d) a distributor adapted to direct air toward the non- casting face of at least one ofthe mold members, (e) a thermoelectric cooling system adapted to cool the air, and (f) a first blower adapted to receive effluent air that has contacted the non-casting face of the mold member and to recvcle the effluent air to the distributor in an embodiment, an eyeglass lens may be made by (a) placing a liquid, polymerizable lens forming composition m a mold cavity defined at least partially by a first mold member and a second mold member, the lens formmg composition comprising a photoinitiator, (b) directing a plurality of pulses of ultraviolet light toward the lens forming composition through at least one ofthe mold members to initiate reaction ofthe lens formmg composition, at least one ofthe pulses having an intensity of at least about 10 mιllι\satts/cm 2 , (c) subsequent to the step of directing the plurality of puises toward the lens forming composition, directing ultraviolet light of a second intensity toward the lens forming composition through at least one ofthe mold members to form a substantially clear eyeglass lens, the second intensity being less than about 350 microwatts/cm 2 , and (d) substantially simultaneously with the step of directing ultraviolet of a second intensity toward the lens formmg composition, directing air onto a non-casting face of at least one ofthe mold members to remove heat from the lens forming composition A lens having a scratch resistant coating may be formed by placing a first coating composition withm a mold member, the mold member comprising a casting face and a non-casting face the coating composition comprising a photoinitiator and being curable upon exposure to ultraviolet light, (a) placing a first coating composition within a mold member, the moid member comprising a casting face and a non-casting face, the coating composition comprising a photoinitiator and being curable upon exposure to ultraviolet light, (b) spinning the mold member to distribute the first coating composition over the castmg face, (c) directing ultraviolet light at the moid member to cure at least a portion ofthe first coating composition, (d) placing a second coating composition within the mold member, the second coating composition comprising a photoinitiator and being curable upon exposure to ultraviolet light, (e) spinning the mold member to distribute the second coating composition over the portion ofthe first coating composition that has been cured, (f) directing ultraviolet light at the mold member, thereby curing at least a portion ofthe second coating composition and forming a substantially clear combination coat comprising at least a portion of each ofthe first and second coating compositions, (g) assembling the mold member with a second mold member to form a mold having a cavity between the mold members, (h) placing a lens-forming composition within the cavity, the lens-forming composition comprising a photoinitiator and being curable upon exposure to ultraviolet light, and (I) directing ultraviolet light at the mold to cure at least a portion ofthe lens-forming material to form a lens, and wherein the combination coat adheres to the cured portion of the lens-forming material BRIEF DESCRIPTION OF THE DRAWINGS The above brief description as well as further objects, features and advantages of the methods and apparatus of the present invention will be more fully appreciated by reference to the followmg detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present mvention when taken in conjunction with the accompanying drawings in which Fig 1 is a perspective view of an apparatus for producing a plastic lens Fig 2 is a cross-sectional view ofthe apparatus taken along line 2-2 of Fig 1 Fig 3 is a cross-sectional view of the apparatus taken along line 3-3 of Fig 2 Fig 4 is a detail view of a component ofthe apparatus Fig 5 is a detail view of a component of the apparatus Fig 6 is a cross-sectional view of a lens cell for use in an apparatus ofthe invention Fig 7 is a view of an embodiment of a shutter system Fig 8 is a top and side view of an embodiment of a heat distributor to be placed between a heat source and a mold surface Fig 9 is a schematic block diagram of an alternate process and system for making and postcurmg a plastic lens Fig 10 is a schematic diagram of an apparatus to apply UV light to a lens or mold assembly Fig 1 1 is a view of an embodiment of a lens Fig 12 is a view of an embodiment of an oxygen barrier with photoinitiator Fig 13 is a schematic diagram of a lens curing apparatus with a light sensor and controller Fig 14 is a schematic view ofthe front of a lens curing apparatus Fig 15 is a schematic view of the side of a lens curing apparatus Fig 16 is a view of an embodiment of a heat source and a heat distributor Fig 17 is a view of various embodiments of a heat source and heat distributors Fig 18 is a view of an embodiment of a heat source and a heat distributor Fig 19 is a view of an embodiment of two mold members and a gasket Fig 20 is a graph illustrating a temperature profile of a continuous radiation cycle Fig 21 is a graph illustrating temperature profiles for a continuous irradiation cycle and a pulse irradiation cycle employed with a mold/gasket set having a 3 OOD base curve, and while applying cooled air at 58 ° F to the mold/gasket set Fig 22 is a chart illustrating qualitative relationships among curing cycle variables Fig 23 is a graph illustrating temperature profiles for one curing cycle for a mold/gasket set having a 6 OOD base curve and used with three different light levels Fig 24 is a graph illustrating contmuous and pulsed temperature profiles for a curing cycle employing a mold/gasket set with a 6 OOD base curve Fig 25 is a graph illustrating continuous and pulsed temperature profiles for a curing cycle employing a mold/gasket set with a 4 50D base curve Fig 26 is a graph illustrating continuous and pulsed temperature profiles for a curmg cycle employing a mold/gasket set with a 3 OOD base curve Fig. 27 is a view of an embodiment of a system simultaneously employing both a flash light source and a contmuous UV (e g , fluorescent) source Fig 28 is an embodiment of a system simultaneously employing two flash light sources Fig 29 is an embodiment of a system employing an ultraviolet light controller Fig 30 depicts a schematic view of a lens curing apparatus Fig 31 depicts a detail view of a thermoelectric cooling system Fig 32 depicts a cross sectional view of a thermoelectric cooling system Fig 33 depicts a thermoelectric module Fig 34 depicts a flash lamp curing cycle Fig 35 depicts a cross sectional view of a flat-top bifocal mold DESCRIPTION OF THE PREFERRED EMBODIMENTS Apparatus, operating procedures, equipment, systems, methods, and compositions for lens curing using ultraviolet light are available from Rapid Cast, Inc., Q2100, Inc., and Fast Cast, Inc. in East Rockaway, New York and Louisville, Kentucky. The Fast Cast. Inc. publication entitled "Operation Manual For The FastCast LenSystem" is hereby incoφorated by reference. Referring now to Fig. 1, a plastic lens curing chamber of the present invention is generally indicated by reference numeral 10. The lens curing chamber 10 preferably communicates through a plurality of pipes 12 with an air source (not shown), the puφose of which will be discussed below As shown in Fig. 2, the plastic lens curing chamber 10 may include an upper lamp chamber 14, an irradiation chamber 16, and a lower lamp chamber 18. The upper lamp chamber 14 may be separated from the irradiation chamber 16 by a plate 20. The lower lamp chamber may be separated from the irradiation chamber 16 by a plate 22. The upper lamp chamber 14, the irradiation chamber 16. and the lower lamp chamber 18 may be isolated from ambient air by upper lamp chamber doors 24. irradiation chamber doors 26, and lower lamp chamber doors 28, respectively. While the upper lamp chamber doors 24, the irradiation chamber doors 26 and the lower lamp chamber doors 28 are shown in Fig. 1 as including two corresponding door members, those of ordinary skill in the art will recognize that the doors 24, 26 and 28 may include single or multiple door members. The upper lamp chamber doors 24, the irradiation chamber doors 26 and the lower lamp chamber doors 28 may be slidingly mounted in guides 30. As shown in Fig. 2, vents 32 may communicate with upper lamp chamber 14 and lower lamp chamber 18 by way of corresponding vent chambers 34 and openings 36 disposed in plate 20 and plate 22. Each vent 32 may be shielded by a vent cover 38. As shown in Fig. 3, vents 33 may be disposed in the irradiation chamber doors 26 and communicate with irradiation chamber 16. Each vent 33 may be shielded by a vent cover 35. As shown in Figs. 2 and 3, a plurality of light generating devices or lamps 40 may be disposed within each of upper lamp chamber 14 and lower lamp chamber 18. Preferably, upper lamp chamber 14 and lower lamp chamber 18 each include three lamps 40 that are arranged in a triangular fashion tn which the lamps 40 in the upper lamp chamber 14 are disposed with the point of the triangle pointing upwards whereas the lamps 40 in the lower lamp chamber 18 are disposed with the point of the triangle pointing downward. The lamps 40, preferably, generate ultraviolet light having a wavelength in the range of at least approximately 300 nm to 400 nm since the effective wavelength spectrum for curing the lens forming material lies in the 300 nm to 400 nm region. The lamps 40 may be supported by and electrically connected to suitable fixtures 42. An exhaust fan 44 may communicate with upper lamp chamber 14 while an exhaust fan 46 may communicate with lower lamp chamber 18. As noted above, the upper lamp chamber 14 may be separated from the irradiation chamber 16 by plate 20 Similarly, lower lamp chamber 18 may be separated from the irradiation chamber 16 by plate 22 The plates 20 and 22 may include apertures 48 and 50, respectively, through which the light generated bv lamps 40 may be directed so as to impmge upon a lens cell 52 (shown in phantom in Fig 2) The diameter of the lens cell 52 is preferably approximately 74 mm The apertures 48 and 50 preferably range from about 70 mm to about 140 mm In one embodiment an upper light filter 54 rests upon plate 20 while a lower light filter 56 rests upon plate 22 or is supported by brackets 57 The upper light filter 54 and lower light filter 56 are shown in Fig 2 as being made of a single filter member, however, those of ordinary skill in the art will recognize that each of the upper light filter 54 and lower light filter 56 may include two or more filter members The components of upper light filter 54 and lower light filter 56 preferably are modified depending upon the characteristics ofthe lens to be molded For instance, in a preferred embodiment for making negative lenses, the upper light filter 54 includes a plate of Pyrex glass that is frosted on both sides resting upon a plate of clear Pyrex glass The lower light filter 56 includes a plate of Pyrex glass frosted on one side resting upon a plate of clear Pvrex glass with a device for reducing the intensity of ultraviolet light incident upon the center portion in relation to the edge portion of the lens being disposed between the plate of frosted Pyrex and the plate of clear P\rex glass Conversely, in a preferred arrangement for producing positive lenses, the upper light filter 54 includes a plate of Pyrex glass frosted on one or both sides and a plate of clear Pyrex glass resting upon the plate of frosted Pyrex glass with a device for reducing the intensity of ultraviolet light incident upon the edge portion in relation to the center portion of the lens being disposed between the plate of clear Pyrex glass and the plate of frosted Pyrex glass The lower light filter 56 includes a plate of clear Pyrex glass frosted on one side resting upon a plate of clear Pyrex glass with a device for reducing the intensity of ultraviolet light incident upon the edge portion in relation to the center portion of the lens being disposed between the plates of clear Pvrex glass In this arrangement, in place of a device for reducing the relative intensity of ultraviolet light incident upon the edge portion of the lens, the diameter of the aperture 50 can be reduced to achieve the same result, i e to reduce the relative intensity of ultraviolet light incident upon the edge portion ofthe lens It will be apparent to those skilled in the art that each filter 54 or 56 could be composed of a plurality of filter members or include any other means or device effective to reduce the light to its desired intensity, to diffuse the light and/or to create a light intensity gradient across the lens cell 52 Alternately, in certain embodiments no filter elements may be used Preferably, the upper light filter 54 or the lower light filter 56 each include at least one plate of Pyrex glass having at least one frosted surface Also, either or both of the upper light filter 54 and the lower light filter 56 may include more than one plate of Pyrex glass each frosted on one or both surfaces, and/or one or more sheets of tracing paper After passing through frosted Pyrex glass, the ultraviolet light is believed to have no shaφ intensity discontinuities which is believed to lead to a reduction in optical distortions in the finished lens in some instances Those of ordinary skill in the art will recognize that other means may be used to diffuse the ultraviolet light so that it has no shaφ intensity discontinuities Preferably disposed within the irradiation chamber 16 are a left stage 58, a center stage 60, and a right stage 62, each of which preferably includes a plurality of steps 64 The left stage 58 and center stage 60 define a left irradiation chamber 66 while the right stage 62 and center stage 60 define a right irradiation chamber 68 A cell holder 70, shown in phantom in Fig 2 and in detail in Fig 4, may be disposed within each of left irradiation chamber 66 and right irradiation chamber 68 The cell holder 70 may include a peripheral step 72 that is designed to allow a cell holder 70 to be supported upon complementary steps 64 of left stage 58 and center stage 60, and center stage 60 and right stage 62, respectively As shown in Fig 4, each cell holder 70 also may include a central bore 74 to allow the passage therethrough of ultraviolet light from the lamps 40 and an annular step 76 which is designed to support a lens cell 52 in a manner described below As shown in Fig 6, each lens cell 52 may include opposed mold members 78, separated by an annular gasket 80 to define a lens molding cavity 82 The opposed mold members 78 and the annular gasket 80 may be shaped and selected in a manner to produce a lens having a desired diopter The mold members 78 are preferably formed of any suitable mateπal that will permit rays of ultraviolet light to pass therethrough The mold members 78 are preferably formed of glass Each mold member 78 has an outer peripheral surface 84 and a pair of opposed surfaces 86 and 88 with the surfaces 86 and 88 being precision ground Preferablv the mold members 78 have desirable ultraviolet light transmission characteristics and both the casting surface 86 and non-casting surface 88 preferably have no surface aberrations, waves, scratches or other defects as these may be reproduced in the finished lens As noted above, the mold members 78 are adapted to be held in spaced apart relation to define a lens molding cavity 82 between the facing surfaces 86 thereof The mold members 78 are preferably held in a spaced apart relation by a T-shaped flexible annular gasket 80 that seals the lens molding cavity 82 from the exterior of the mold members 78 In use, the gasket 80 may be supported on the annular step 76 ofthe cell holder 70 In this manner, the upper or back mold member 90 has a convex inner surface 86 while the lower or front mold member 92 has a concave inner surface 86 so that the resulting lens molding cavity 82 is shaped to form a lens with a desired configuration Thus, by selecting the mold members 78 with a desired surface 86, lenses with different characteristics, such as focal lengths, may be made by the apparatus 10 Rays of ultraviolet light emanating from lamps 40 pass through the mold members 78 and act on a lens forming mateπal disposed in the mold cavity 82 in a manner discussed below so as to form a lens As noted above, the rays of ultraviolet light may pass through a suitable filter 54 or 56 to impmge upon the lens cell 52 Ihe mold members 78, preterably, are formed from a material that will not allow ultraviolet radiation having a wavelength below approximately 300 nm to pass therethrough Suitable materials are Schott Crown, S-l or S-3 glass manufactured and sold by Schott Optical Glass Inc , of Duryea, Pennsylvania or Corning 8092 glass sold by Coming Glass of Coming, New York A source of molds may be Opticas Devlyn S A (Mexico City, Mexico) and/or Titmus Inc (Fredπcksburg, Virginia) The annular gasket 80 may be formed of vinyl material that exhibits good lip finish and maintains sufficient flexibility at conditions throughout the lens curing process In a preferred embodiment, the annular gasket 80 is formed of silicone rubber mateπal such as GE SE6035 which is commercially available from General Electric In another preferred embodiment, the annular gasket 80 is formed of copolymers of ethylene and vinyl acetate which are commercially available from E I DuPont de Nemours & Co under the trade name ELVAX7. Preferred ELVAX7 resms are ELVAX7 350 having a melt index of 17 3-20 9 dg/min and a vinyl acetate content of 24 3-25 7 wt %, ELVAX7 250 having a melt index of 22 0-28 0 dg/min and a vinyl acetate content of 27 2-28 8 wt %, ELVAX7 240 having a melt index of 38 0-48 0 dg/min and a vinyl acetate content of 27 2-28 8 wt %, and ELV AX7 150 having a melt index of 38 0-48 0 dg/mm and a vinyl acetate content of 32 0-34 0 wt % Regardless of the particular material, the gaskets 80 may be prepared by conventional injection molding or compression molding techniques which are well-known by those of ordinary skill in the art As shown in phantom in Fig 2, in section in Fig 3, and tn detail in Fig 5, an upper and lower air distribution device 94 is disposed in each of left irradiation chamber 66 and right irradiation chamber 68 Each air distribution device 94 is connected to a pipe 12 As shown in Fig 5, each air distribution device 94 includes a plenum portion 95 and a substantially cylindrical opening 96 having orifices 98 disposed therein to allow for the expulsion of air from the air distribution device 94 The diameter of the orifices 98 may be constant, or may vary around the circumference of cylindrical opening 96 preferably reaching a maximum when directly opposite the plenum portion 95 of air distribution device 94 and preferably reaching a minimum immediately adjacent the plenum portion 95 In addition, the orifices 98 are designed to blow air toward a lens cell 52 that may be disposed in a lens cell holder 70 and installed in left irradiation chamber 66 or right irradiation chamber 68 In operation, the apparatus of the present invention may be appropriately configured for the production of positive lenses which are relatively thick at the center or negative lenses which are relatively thick at the edge To reduce the likelihood of premature release, the relatively thick portions of a lens preferably are polymerized at a faster rate than the relatively thin portions of a lens The rate of polymerization taking place at various portions of a lens may be controlled by varying the relative mtensity of ultraviolet light incident upon particular portions of a lens The rate of polymerization takmg place at various portions of a lens may also be controlled by directing air across the mold members 78 to cool the lens cell 52 For positive lenses the intensity of incident ultraviolet light is preferably reduced at the edge portion of the lens so that the thicker center portion of the lens polymerizes faster than the thinner edge portion of the lens. Conversely, for a negative lens, the intensity of incident ultraviolet light is preferably reduced at the center portion of the lens so that the thicker edge portion of the lens polymerizes faster than the thinner center portion of the lens. For either a positive lens or a negative lens, air may be directed across the faces of the mold members 78 to cool the lens cell 52. As the overall intensity of incident ultraviolet light is increased, more cooling is needed which can be accomplished by either or both of increasing the velocity of the air and reducing the temperature of the air. It is well known by those of ordinary skill in the art that lens forming materials having utility in the present invention tend to shrink as they cure. If the relatively thin portion of a lens is allowed to polymerize before the relatively thick portion, the relatively thin portion will tend to be rigid at the time the relatively thick portion cures and shrinks and the lens will either release prematurely from or crack the mold members 78. Accordingly, when the relative intensity of ultraviolet light incident upon the edge portion of a positive lens is reduced relative to the center portion, the center portion polymerizes faster and shrinks before the edge portion is rigid so that the shrinkage is more uniform. Conversely, when the relative intensity of ultraviolet light incident upon the center portion of a negative lens is reduced relative to the edge portion, the edge portion polymerizes faster and shrinks before the center becomes rigid so that the shrinkage is more uniform. The variation of the relative intensity of ultraviolet light incident upon a lens may be accomplished in a variety of ways. According to one method, in the case of a positive lens, a ring of opaque material may be placed between the lamps 40 and the lens cell 52 so that the incident ultraviolet light falls mainly on the thicker center portion of the lens. Conversely, for a negative lens, a disk of opaque material may be placed between the lamps 40 and the lens cell 52 so that the incident ultraviolet light falls mainly on the edge portion ofthe lens. According to another method, in the case of a negative lens, a sheet material having a variable degree of opacity ranging from opaque at a central portion to transparent at a radial outer portion is disposed between the lamps 40 and the lens cell 52. Conversely, for a positive lens, a sheet material having a variable degree of opacity ranging from transparent at a central portion to opaque at a radial outer portion is disposed between the lamps 40 and the lens cell 52. Those of ordinary skill in the art will recognize that there are a wide variety of techniques other than those enumerated above for varying the intensity of the ultraviolet light incident upon the opposed mold members 78. In some embodiments, the intensity of the incident light has been measured and deteπnined to be approximately 3.0 to 5.0 milliwatts per square centimeter (mW/cm 2 ) prior to passing through either the upper light filter 54 or the lower light filter 56 and the total intensity at the thickest part of the lens ranges from 0.6 to 2.0 mW/cm 2 while the intensity at the thinnest portion of the lens ranges from 0.1 to 1.5 mW/cm 2 . In some embodiments the overall light intensity incident on the lens cell 52 has less of an impact on the final product than the relative light intensity incident upon the thick or thin portions of the lens so long as the lens cell 52 is sufficiently cooled to reduce the polymerization rate to an acceptable level It has been determined that in some embodiments the finished power of an ultraviolet light polymerized lens may be controlled by manipulating the distribution of the incident ultraviolet light striking the opposed mold members 78 For instance, for an identical combination of mold members 78 and gasket 80, the focusing power of the produced lens may be increased or decreased by changing the pattern of intensity of ultraviolet light across the lens mold cavity 82 or the faces ofthe opposed mold members 78 As the lens forming material begins to cure, it passes through a gel state, the pattern of which within the lens cell 52 leads to the proper distribution of internal stresses generated later in the cure when the lens forming material begins to shrink As the lens forming material shrinks during the cure, the opposed mold members 78 will preferably flex as a result of the different amounts of shrinkage between the relatively thick and the relatively thin portions of the lens When a negative lens, for example, is cured, the upper or back mold member 90 will preferably flatten and the lower or front mold member 92 will preferably steepen with most of the flexing occurring in the lower or front mold member 92 Conversely, with a positive lens, the upper or back mold member 90 will preferably steepen and the lower or front mold member 92 will preferably flatten with most of the flexing occurring in the upper or back mold member 90 By varying the intensity of the ultraviolet light between the relatively thin and the relatively thick portions of the lens in the lens forming cavity 82, it is possible to create more or less total flexing Those light conditions which result in less flexing will tend to minimize the possibility of premature release The initial curvature of the opposed mold members 78 and the center thickness of the lens produced can be used to compute the theoretical or predicted power of the lens The ultraviolet light conditions can be manipulated to alter the power of the lens to be more or less than predicted The greater the diameter of the disk of opaque material, the more negative (-) power the resultant lens will tend to exhibit When the lenses cured by the ultraviolet light are removed from the opposed mold members 78, they are typically under a stressed condition It has been determined that the power of the lens can be brought to a final restmg power, by subjecting the lenses to a post-curing heat treatment to relieve the internal stresses developed durmg the cure and cause the curvature of the front and the back of the lens to shift Typically, the lenses are cured by the ultraviolet light in about 10-30 minutes (preferably about 15 minutes) The post-curing heat treatment is conducted at approximately 85-120 °C for approximately 5-15 mmutes Preferably, the post-curing heat treatment is conducted at 100-110 °C for approximately 10 mmutes Prior to the post-cure, the lenses generally have a lower power than the final restmg power The post-curing heat treatment reduces yellowing of the lens and reduces stress in the lens to alter the power thereof to a tinal power 1 he post-curing heat treatment can be conducted in a conventional convection oven or any other suitable device In addition, as described below, in certain embodiments heat may be conductively applied to the molds and/or lens, thereby enhancing the quality ofthe cured lenses The ultraviolet lamps 40 preferably are maintained at a temperature at which the lamps 40 deliver maximum output The lamps 40, preferably, are cooled because the intensity of the light produced by the lamps 40 fluctuates when the lamps 40 are allowed to overheat In the apparatus depicted in Fig 2 the cooling of the lamps 40 is accomplished by sucking ambient air into the upper lamp chamber 14 and lower lamp chamber 18 through vent 32, vent chambers 34 and openings 36 by means of exhaust fans 44 and 46, respectively Excessive cooling of the lamps 40 should be avoided, however, as the intensity of the light produced by the lamps 40 is reduced when the lamps 40 are cooled to an excessive degree As noted above the lens cell 52 is preferably cooled during curing of the lens forming material as the overall intensity of the incident ultraviolet light is increased Cooling of the lens cell 52 generally reduces the likelihood of premature release by slowing the reaction and improving adhesion There are also improvements in the optical quality, stress characteristics and impact resistance of the lens Cooling of the lens cell 52 is preferably accomplished by blowing air across the lens cell 52 The air preferably has a temperature ranging between 15 and 85°F (about -9 4°C to 29 4°C) to allow for a curing time of between 30 and 10 minutes The air distπbution devices 94 depicted in Fig 5 have been found to be particularly advantageous as they are specifically designed to direct air directly across the surface of the opposed mold members 78 After passing across the surface ofthe opposed mold members 78, the air emanatmg from the air distribution devices 94 is vented through vents 33 Alternately the air emanating from the air distribution devices 94 may be recycled back to an air cooler The lens cell 52 may also be cooled by disposing the lens cell in a liquid cooling bath The opposed mold members 78 are preferably thoroughly cleaned between each curmg run as any dirt or other impurity on the mold members 78 may cause premature release The mold members 78 are cleaned by any conventional means well known to those of ordmary skill m the art such as with a domestic cleanmg product, l e , Mr Clean™ available from Proctor and Gamble Those of ordinary skill m the art will recognize, however, that many other techniques may also be used for cleaning the mold members 78 Yellowing of the finished lens may be related to the monomer composition the identity of the photoinitiator, and the concentration ofthe photoinitiator When casting a lens, particularly a positive lens that is thick m the center, cracking may be a problem Addition polymerization reactions, including photochemical addition polymerization reactions, are exothermic Durmg the process, a large temperature gradient may build up and the resulting stress may cause the lens to crack The formation of optical distortions usually occurs during the early stages of the polymerization reaction durmg the transformation of the lens forming composition from the liquid to the gel state Once patterns leading to optical distortions form they are difficult to eliminate When gelation occurs there typically is a rapid temperature rise The exothermic polymerization step causes a temperature increase, which m turn causes an increase in the rate of polymerization which causes a further increase in temperature If the heat exchange with the surroundings is not sufficient enough there will be a runaway situation that leads to premature release, the appearance of thermally caused striations and even breakage Accordingly, when continuous UV light is applied, it is preferred that the reaction process be smooth and not too fast but not too slow Heat is preferably not generated by the process so fast that it cannot be exchanged with the surroundings The incident ultraviolet light intensity preferably is adjusted to allow the reaction to proceed at a desired rate It is also preferred that the seal between the annular gasket 80 and the opposed mold members 78 be as complete as possible Factors that have been found to lead to the production of lenses that are free from optical distortions are (1) achieving a good seal between the annular gasket 80 and the opposed mold members 78, (2) using mold members 78 having surfaces that are free from defects, (3) using a formulation having an appropriate type and concentration of photoinitiator that will produce a reasonable rate of temperature rise, and (4) using a homogeneous formulation Preferably, these conditions are optimized Premature release ofthe lens from the mold will result in an incompletely cured lens and the production of lens defects Factors that contribute to premature release are (1) a poorly assembled lens cell 52, (2) the presence of air bubbles around the sample edges, (3) imperfection in gasket lip or mold edge, (4) inappropriate formulation, (5) uncontrolled temperature rise and (6) high or nonuniform shrinkage Preferably, these conditions are minimized Premature release may also occur when the opposed mold members 78 are held too rigidly by the annular gasket 80 Preferably, there is sufficient flexibility in the annular gasket 80 to permit the opposed mold members 78 to follow the lens as it shrinks Indeed, the lens must be allowed to shrink in diameter slightly as well as in thickness The use of an annular gasket 80 that has a reduced degree of stickiness with the lens during and after curmg is therefore desirable In a preferred technique for filling the lens molding cavity 82, the annular gasket 80 is placed on a concave or front mold member 92 and a convex or back mold member 90 is moved mto place The annular gasket 80 is then pulled away from the edge of the back mold member 90 at the uppermost point and a lens forming composition is injected into the lens molding cavity 82 until a small amount of the lens formmg composition is forced out around the edge The excess is then removed, preferably, by vacuum Excess liquid that is not removed could spill over the face of the back mold member 90 and cause optical distortion in the finished lens Despite the above problems the advantages offered by the radiation cured lens molding system clearly outweigh the disadvantages The advantages of a radiation cured system include a significant reduction in energy requirements, curing time and other problems normally associated with conventional thermal systems The lens forming material may include any suitable liquid monomer or monomer mixture and any suitable photosensitive initiator The lens forming mateπal, preferably, does not include any component, other than a photoinitiator, that absorbs ultraviolet light having a wavelength in the range of 300 to 400 nm The liquid lens forming material is preferably filtered for quality control and placed in the lens molding cavity 82 by pulling the annular gasket 80 away from one of the opposed mold members 78 and injecting the liquid lens forming material into the lens molding cavity 82 Once the lens molding cavity 82 is filled with such material, the annular gasket 80 is replaced into its sealing relation with the opposed mold members 78 Those skilled in the art will recognize that once the cured lens is removed from the lens molding cavity 82 by disassembling the opposed mold members 78, the lens can be further processed in a conventional manner, such as by grinding its peπpheral edge According to the present invention a polymerizable lens forming composition includes an aromatic-containing bιs(allyl carbonate)-functιonal monomer and at least one polyethylenic-functional monomer containing two ethylenically unsaturated groups selected from acrylyl and methacrylyl In a preferred embodiment, the composition further includes a suitable photoinitiator In other preferred embodiments, the composition may include one or more polyethylenic-functional monomers containing three ethylenically unsaturated groups selected from acrylyl and methacrylyl, and a dve Aromatic-containing bιs(allyl carbonate)-functιonal monomers which can be utilized in the practice of the present mvention are bιs(allyl carbonates) of dihydroxy aromatic-containing mateπal The dihydroxy aromatic-containing material from which the monomer is derived may be one or more dihydroxy aromatic-containing compounds Preferably the hydroxyl groups are attached directly to nuclear aromatic carbon atoms of the dihydroxy aromatic-containing compounds The monomers are themselves known and can be prepared by procedures well known in the art 1 he aromatic-containing bιs(allyl carbonate)-functιonal monomers can be represented by the formula (I) in which A, is the divalent radical derived from the dihydroxy aromatic-containing material and each R o is independently hydrogen, halo, or a C,-C 4 alkyl group The alkyl group is usually methyl or ethyl Examples of Ro include hydrogen, chloro, bromo. fluoro, methyl, ethyl, n-propyl, isopropyl and n-butyl Most commonly Ro is hydrogen or methyl, hydrogen is preferred A subclass ofthe divalent radical A, which is of particular usefulness is represented by the formula in which each R, is independently alkyl containing from 1 to about 4 carbon atoms, phenyl, or halo, the average value of each a is independently in the range of from 0 to 4, each Q is independently oxy, sulfonyl, alkanediyl havmg from 2 to about 4 carbon atoms, or alkylidene having from 1 to about 4 carbon atoms, and the average value of n is in the range of from 0 to about 3 Preferably Q is methylethylidene, viz . isopropyiidene Preferably the value of n is zero, in which case A, is represented by the formula (R,)a (R,)a in which each R,, each a, and Q are as discussed in respect of Formula 11 Preferably the two free bonds are both in the ortho or para positions The para positions are especially preferred The dihydroxy aromatic-containing compounds from which A, is derived may also be polyol-functional cham extended compounds Examples of such compounds include alkaline oxide extended bisphenols Typically the alkaline oxide employed is ethylene oxide, propylene oxide, or mixtures thereof By way of exemplification, when para, para-bisphenols are chain extended with ethylene oxide, the bivalent radical A, may often be represented by the formula (R,)a (R,)a - J Λ( θ >--<OCH 2 CH 2 )r' (IV) where each R,, each a, and Q are as discussed in respect of Formula II, and the average values of j and k are each independently in the range of from about 1 to about 4 The preferred aromatic-containing bιs(allyl carbonate)-functιonal monomer is represented by the formula (V) and is commonly known as bisphenol A bιs(allyl carbonate) A wide variety of compounds may be used as the polyethylenic functional monomer containing two or three ethylenically unsaturated groups The preferred polyethylenic functional compounds containing two or three ethylenically unsaturated groups may be generally described as the acrylic acid esters and the methacrylic acid esters of aliphatic polyhydric alcohols, such as, for example, the di- and tπacrylates and the di- and tπmethacrylates of ethylene glycol, triethylene glycol, tetraethylene glycol, tetramethylene glycol, glycidyl, diethyleneglycol, butyleneglycol, propyleneglycol, pentanediol, hexanediol, trimethylolpropane, and tripropyleneglycol Examples of specific suitable polyethylenic - functional monomers containing two or three ethylenically unsaturated groups include trimethylolpropanetπacrylate (TMPTA), tetraethylene glycol diacrylate (TTEGDA), tπpropylene glycol diacrylate (TRPGDA), 1 ,6 hexanedioldimethacrylate (HDDMA), and hexanedioldiacrylate (HDDA) In general, a photoinitiator for initiating the polymerization of the lens forming composition of the present mvention, preferably, exhibits an ultraviolet absoφtion spectrum over the 300-400 nm range High absoφtivity of a photoinitiator in this range, however, is not desirable, especially when casting a thick lens The following are examples of illustrative photoinitiator compounds withm the scope of the invention methyl benzoylformate, 2-hydroxy-2-methyl-l-phenylpropan-l-one, 1-hydroxycyclohexyl phenyl ketone, 2,2-dι-sec- butoxyacetophenone, 2,2-dιethoxyacetophenone. 2.2-dιethoxy-2-pheny l-acetophenone, 2,2-dιmethoxy-2- phenyl-acetophenone, benzoin methyl ether, benzoin isobutyl ether, benzoin, benzil benzyl disulfide, 2.4-dιhydroxybenzophenone, benzylideneacetophenone. benzophenone and acetophenone Preferred photoinitiator compounds are 1 -hydroxycyclohexyl phenyl ketone (which is commercially available from Ciba-Geigy as Irgacure 184), methyl benzoylformate (which is commercially available from Polysciences. Inc ), or mixtures thereof Methyl benzoylformate is a generally preferred photoinitiator because it tends to provide a slower rate of polymerization The slower rate of polymerization tends to prevent excessive heat buildup (and resultant cracking ofthe lens) during polymerization In addition, it is relatively easy to mix liquid methyl benzoylformate (which is liαuid at ambient temperatures) with many acrylates, diacrylates, and allyl carbonate compounds to form a lens forming composition The lenses produced with the methyl benzoylformate photoinitiator tend to exhibit more favorable stress patterns and uniformity A strongly absorbing photoinitiator will absorb most of the incident light in the first millimeter of lens thickness causing rapid polymerization in that region The remaining light will produce a much lower rate of polymerization below this depth and will result in a lens that has visible distortions An ideal photoinitiator will exhibit high activity, but will have a lower extinction coefficient in the useful range A lower extinction coefficient of photoinitiators at longer wavelengths tends to allow the ultraviolet radiation to penetrate deeper mto the reaction system This deeper penetration of the ultraviolet radiation allows photoinitiator radicals to form uniformly throughout the sample and provide excellent overall cure Since the sample can be irradiated from both top and bottom, a system in which appreciable light reaches the center of the thickest portion of the lens is preferred The photoinitiator solubility and compatibility with the monomer system is also an important requirement An additional consideration is the effect of the photoinitiator fragments in the finished polymer Some photoinitiators generate fragments that impart a yellow color to the finished lens Although such lenses actually absorb very little visible light, they are cosmetically undesirable Photoinitiators are often very system specific so that photoinitiators that are efficient in one system may function poorly in another In addition, the initiator concentration to a large extent is dependent on the incident light mtensity and the monomer composition The identity ofthe initiator and its concentration are important for any particular formulation A concentration of initiator that is too high tends to lead to cracking and yellowing of the lens Concentrations of initiator that are too low tend to lead to incomplete polymerization and a soft material Dyes and/or pigments are optional materials that may be present when high transmission of light is not necessary The listing of optional ingredients discussed above is by no means exhaustive These and other ingredients may be employed in their customary amounts for their customary puφoses so long as they do not seriously interfere with good polymer formulating practice According to a preferred embodiment of the present invention, the preferred aromatic-containing bιs(allyl carbonate) functional monomer, bisphenol A bιs(allyl carbonate) is admixed with one or more faster reacting polyethylenic functional monomers containing two acrylate or methacrylate groups such as 1,6 hexanediol dimethacrylate (HDDMA), 1,6 hexanediol diacrylate (HDDA), tetraethylene glycol diacrylate (TTEGDA), and tπpropylene glycol diacrylate (TRPGDA) and optionally a polyethylenic functional monomer containing three acrylate groups such as trimethylolpropane tπacrvlate (TMPTA) Generally, compounds containing acrylate groups polymerize much faster than those containing allyl groups In one embodiment, the lamps 40 generate an intensity at the lamp surface of approximately 4 0 to 7 0 mW/cm 2 of ultraviolet light having wavelengths between 300 and 400 nm, which light is very uniformly distπbuted without any shaφ discontinuities throughout the reaction process Such bulbs are commercially available from Sylvania under the trade designation Sylvania Fluorescent (F15T8/2052) or Sylvania Fluorescent (F15T8/350BL/18") GTE As noted above, ultraviolet light having wavelengths between 300 and 400 nm is preferred because the photomitiators according to the present invention, preferably, absorb most efficiently at this wavelength and the mold members 78, preferably, allow maximum transmission at this wavelength It is preferred that there be no shaφ intensity gradients of ultraviolet radiation either horizontally or vertically through the lens composition during the curing process Shaφ intensity gradients through the lens may lead to defects in the finished lens According to one embodiment of the present invention, the liquid lens forming composition mcludes bisphenol A bιs(allyl carbonate) in place of DEG-BAC The bisphenol A bιs(allyl-carbonate) monomer has a higher refractive mdex than DEG-BAC which allows the production of thmner lenses which is important with relatively thick positive or negative lenses The bisphenol A bιs(allyl-carbonate) monomer is commercially available from PPG Industries under the trade name HIR1 I or CR-73 Lenses made from this product sometimes have a very slight, barely detectable, degree of yellowing A small amount of a blue dye consisting of 9, 10-anthracenedιone, I-hydroxy-4-[(4-methylphenyl)amιno] available as Thermoplast Blue 684 from BASF Wyandotte Coφ is preferably added to the composition to counteract the yellowing In addition, the yeilowmg tends to disappear if the lens is subjected to the above-described post-cure heat treatment Moreover, if not post-cured the yellowing tends to disappear at ambient temperature after approximately 2 months TTEGDA. available from Sartomer and Radcure, is a diacrylate monomer that, preferably, is mcluded in the composition because it is a fast polymerizing monomer that reduces yellowing and yields a very clear product If too much TTEGDA is included in the most preferred composition, 1 e greater than about 25% by weight, however, the finished lens may be prone to cracking and may be too flexible as this material softens at temperatures above 40NC If TTEGDA is excluded altogether, the finished lens may to be brittle HDDMA, available from Sartomer, is a dimethacrylate monomer that has a very stiff backbone between the two methacrylate groups HDDMA, preferably, is included in the composition because it yields a stiffer polymer and increases the hardness and strength of the finished lens This material is quite compatible with the bisphenol A bιs(allyl carbonate) monomer HDDMA contributes to high temperature stiffness, polymer claπty and speed of polymerization TRPGDA, available from Sartomer and Radcure, is a diacrylate monomer that, preferably, is mcluded m the composition because it provides good strength and hardness without adding bπttleness to the finished lens This mateπal is also stiffer than TTEGDA TMPTA, available from Sartomer and Radcure, is a triacrylate monomer that preferably, is included m the composition because it provides more crosslinking in the finished lens than the difunctional monomers TMPTA has a shorter backbone than TTEGDA and increases the high temperature stiffness and hardness of the finished lens Moreover, this material contributes to the prevention of optical distortions in the finished lens TMPTA also contributes to high shπnkage during polymerization The inclusion of too much of this material in the most preferred composition may make the finished lens too brittle Certain of the monomers that are preferably utilized m the composition of the present invention, such as TTEGDA, TRPGDA and TMPTA, include impurities and have a yellow color in certain of their commercially available forms The yellow color of these monomers is preferably reduced or removed by passing them through a column of alumina (basic) which includes aluminum oxide powder - basic After passage through the alumina column, the monomers absorb almost no ultraviolet light Also after passage through the alumina column differences between monomers obtained from different sources are substantially eliminated It is preferred, however, that the monomers be obtained from a source which provides the monomers with the least amount of impurities contained therein The composition preferably is filtered pπor to polymerization thereof to remove suspended particles The composition of the present invention, preferably, may be prepared according to the following protocol Appropriate amounts of HDDMA, TTEGDA, TMPTA and TRPGDA are mixed and stirred thoroughly, preferably with a glass rod The acrylate/methacrylate mixture may then be passed through a purification column A suitable purification column may be disposed within a glass column having a fitted glass disk above a teflon stopcock and havmg a top reservoir with a capacity of approximately 500 ml and a body with a diameter of 22 mm and a length of about 47 cm The column may be prepared by placing on the fitted glass disk approximately 35 g of activated alumina (basic), available from ALFA Products Johnson Matthey, Danvers. MA in a 60 mesh form or from Aldrich in a 150 mesh form Approximately 10 g of an inhibitor remover (hydroqumone/methylester remover) available as HR-4 from Scientific Polymer Products. Inc . Ontario, NY then may be placed on top ofthe alumina and, finally, approximately 35 g of activated alumina (basic) may be placed on top ofthe inhibitor remover Approximately 600 g of the acrylate/methacrylate mixture may then be added above the column packmg An oveφressure of 2-3 psi may then be applied to the top of the column resulting in a flow rate of approximately 30 to 38 grams per hour Parafilm may be used to cover the junction of the column tip and the receiving bottle to prevent the infiltration of dust and water vapor The acrylate/methacrylate mixture, preferably, may be received in a container that is opaque to ultraviolet radiation An appropriate amount of bisphenol A bιs(allyl carbonate) may then be added to the acrylate/methacrylate mixture to prepare the final monomer mixture An appropriate amount of a photoinitiator may then be added to the final monomer mixture The final monomer mixture, with or without photoinitiator, may then be stored in a container that is opaque to ultraviolet radiation An appropriate amount of a dye may also be added to the final monomer mixture, with or without photoinitiator After edging, the ultraviolet light cured lenses of the present invention demonstrate excellent organic solvent resistance to acetone, methylethyl ketone, and alcohols For best results, both the casting surfaces 86 and non-casting surfaces 88 of the mold members 78 are finished to optical quality For instance, a wave on the non-casting surface 88 may be reproduced in the finished lens as a result ofthe distortion ofthe incident light Mold markings cause differential light intensity conditions under the marking, even when the mark is on the non-casting surface 88 of the mold members 78 The fully exposed region of the lens will tend to be harder, and the lens may have stresses because of this The portion ofthe lens under the mark will also tend to be weaker at the end of the curmg period This effect has been observed and may cause premature release or induce crack mg Mold defects at the edges interfere with the sealing conditions and frequently induce premature release It is believed that as the reaction proceeds, the heat generated tends to reduce the adhesion between the shrinking lens and the mold face This reduction in adhesion tends to cause the lens to pull away from the mold In high curvature (i e. high power) lenses this problem tends to be even more pronounced because of two factors (1) these lenses have more thickness and thus more material that is generating heat (which thus speeds up the reaction and generates more heat), and (2) these lenses have a greater thickness differential between the thick and thin portions ofthe lens, which tends to cause stress on the molds due to differential shrinkage It is also possible that the temperatures generated relatively deep inside a thick lens may cause some vaporization of the monomer The vaporized monomer may then migrate to the lens/mold interface, breaking the vacuum between the two Because of the problem of premature release, preferably high power lenses are cured to maintain aαhesion to the molds Preferably the molds flex and accommodate stress Preferably the cooling fluid used is air at a temperature of less than 50°C The fluid may be below 0°C, however in a preferred embodiment the fluid was at a temperature of between 0°C and less than 20°C, preferably about 0-15°C, more preferably about 0-10°C, more preferably still about 3-8°C In one preferred embodiment the fluid temperature was about 5°C As shown m Figure 9, a lens forming apparatus 300 for making a plastic lens may include a cooler 312 for supplying cool fluid to the apparatus 300 via conduit 314 The fluid may be supplied to the apparatus 300 and then discharged via conduit 320 The fluid discharged via conduit 320 may be vented via conduit 318 or it may alternately be recirculated via conduit 316 to the cooler 312 The cooler 312 preferably includes a Neslab CFT-50 water/antifreeze chiller (Newmgton, N H , U S A ) A Neslab-built blower box designed for a minimum temperature of 3°C and 8 cubic feet (about 0 224 cubic meters) per minute of air per air distributor 94 was used with the chiller The blower box included a heat exchanger coil through which chilled water was circulated, a blower, and a plenum-type arrangement for supplying air to the conduit 314 If lenses are produced with continuous UV light without any mold cooling, the temperature of the mold- lens assembly may rise to above 50°C Low diopter lenses may be prepared in this fashion, but higher plus or mmus diopter lenses may fail Certain lenses may be made by controlling (e g , cooling) the temperature of the lens mateπal during cure with circulating uncooled fluid (i e , fluid at ambient temperatures) The ambient fluid in these systems is directed towards the mold members in the same manner as described above Circulating ambient temperature fluid permits manufacture of a wider range of prescriptions than manufacture of the lenses without any mold cooling at all Most polymerization factors are interrelated The ideal temperature of polymerization is related to the diopter and thickness of the lens being cast Thermal mass is a factor Lower temperatures (below about 10°C) are preferred to cast higher + or - diopter lenses when using continuous UV light These lower temperatures tend to permit an mcrease in photoinitiator concentration, which in turn may speed up the reaction and lower curing tune Preventing premature release when using continuous UV light is also somewhat dependent upon the flowrates of cooling fluid, as well as its temperature For instance, if the temperature of the cooling fluid is decreased it may also be possible to decrease the flowrate of cooling fluid Similarly, the disadvantages of a higher temperature cooling fluid may be somewhat offset by higher flowrates of cooling fluid In one embodiment the air flow rates for a dual distributor system (1 e . an air distributor above and below the lens composition) are about 1-30 standard cubic feet ("scf) (about 0 028 - 0 850 standard cubic meters) per minute per distributor, more preferably about 4-20 cubic feet (about 0 1 13-0 566 standard cubic meters) per minute per distributor and more preferably still about 9-15 (about 0 255-0 423 standard cubic meters) cubic feet per minute per distributor "Standard conditions," as used herein, means 60 °F (about 15 556°C) and one atmosphere pressure (about 101 325 kilopascals) The thickness of the glass molds used to cast polymerized lenses may affect the lenses produced A thmner mold tends to allow more efficient heat transfer between the polymerizing material and the cooling air, thus reducmg the rate of premature release In addition, a thmner mold tends to exhibit a greater propensity to flex A thinner mold tends to flex durmg the relatively rapid differential shrinkage between the thick and thin portions of a polymerized lens, again reducing the incidence of premature release In one embodiment the first or second mold members have a thickness less than about 5 0 mm, preferably about 1 0-5 0 mm, more preferably about 2 0-4 0 mm, and more still about 2 5-3 5 mm "Front" mold or face means the mold or face whose surface ultimately forms the surface of an eyeglass lens that is furthest from the eye of an eyeglass lens wearer "Back" mold or face means the mold or face whose surface ultimately forms the surface of an eyeglass lens that is closest to the eye of a eyeglass lens wearer In one embodiment the lens forming material is preferably cured to form a solid lens at relatively low temperatures, relatively low continuous ultraviolet light intensity, and relatively low photoinitiator concentrations Lenses produced as such generally have a Shore D hardness of about 60-78 (for the preferred compositions) when cured for about 15 minutes as described above The hardness may be improved to about 80-81 Shore D by postcure heating the lens in a conventional oven for about 10 minutes as described above In a preferred embodiment, UV light may be provided with mercury vapor lamps provided in UVEXS, Inc Model CCU or 912 curing chambers (Sunnyvale, CA, U S A ) In an alternate method for makmg a lens, the desired curvature (l e , power) of the lens may be varied usmg the same molds, but with different light distributions In this manner one mold may be used to prepare different lenses with different curvatures The method includes the steps of ( 1) placing a polymerizable lens formmg mateπal in a mold cavity defined in part between a first mold member and a second mold member, and wherein the cavity defines a theoretical curvature that is different from the desired curvature, (2) directing ultraviolet rays towards at least one of the first and second mold members, and wherein the ultraviolet rays are directed towards the first or second mold member such that the material cures to form a lens with the desired curvature, and (3) contacting fluid agamst the first or second mold member to cool the first or second mold member The resulting lens curvature may vary depending on the way the ultraviolet light is directed towards the first or second mold members That is, by varying the relative intensity of the light across the lens material radii, it is possible to vary the curvature ofthe resulting lens EXAMPLE 1 Formulation: 17% Bisphenol A BisAllyl Carbonate 10% 1 ,6 Hexanediol dimethacrylate 20% Trimethylolpropane triacrylate 21% Tetraethyleneglycol diacrlate 32% Tripropyleneglycol diacrlyate 0 012% 1 Hydroxycyclohexyl phenyl ketone 0 048 Methylbenzoylformate <10PPMHydroquιnone & Methylethylhydroquinone Hydroqumone and Methylethylhydroquinone were stabilizers present in some of the diacrylate and/or triacrylate compounds obtained from Sartomer Preferably the amount of stabilizers is mmunized since the stabilizers affect the rate and amount of curmg. If larger amounts of stabilizers are added, then generally larger amounts of photomitiators must also be added Light Condition: mW/cm 2 measured at plane of sample with Spectroline DM 365N Meter from Spectronics Coφ. (Westbury, N Y ) Center Edge Top' 0.233 0.299 Bottom 0.217 0.248 Air Flow 9 6 standard cubic feet ("CFM") per manifold - 19.2 CFM total on sample Air Temperature 4 4 degrees Centigrade Molds 80 mm diameter Coming #8092 glass Radius Thickness Concave 170.59 2.7 Convex 62.17 5 4 Gasket General Electric SE6035 silicone rubber with a 3 mm thick lateral lip dimension and a vertical hp dimension sufficient to provide an initial cavity center thickness of 2 2 mm. Filling The molds were cleaned and assembled into the gasket The mold/gasket assembly was then temporarily positioned on a fixture which held the two molds pressed against the gasket lip with about 1 kg of pressure The upper edge of the gasket was peeled back to allow about 27 4 grams of the monomer blend to be charged into the cavity The upper edge of the gasket was then eased back into place and the excess monomer was vacuumed out with a small aspirating device It is preferable to avoid having monomer drip onto the noncasting surface ofthe mold because a drop tends to cause the ultraviolet light to become locally focused and may cause an optical distortion in the final product Curmg The sample was irradiated for fifteen minutes under the above conditions and removed from the "FC-104" curing chamber (l e , the chamber shown in Figures 14 and 15) The molds were separated from the cured lens by applying a shaφ impact to the junction ofthe lens and the convex mold The sample was then postcured at 1 10 C C in a conventional gravity type thermal oven for an additional ten minutes, removed and allowed to cool to room temperature Results The resulting lens measured 72 mm in diameter, with a central thickness of 2 0 mm, and an edge thickness of 9.2 mm The focusing power measured ~5 05 diopter. The lens was water clear ("water-white"), showed negligible haze, exhibited total visible light transmission of about 94%, and gave good overall optics The Shore D hardness was about 80 The sample withstood the impact of a 1 inch steel ball dropped from fifty mches m accordance with ANSI 280 1-1987, 4 6 4 test procedures ADDITIONAL IMPROVEMENTS POSTCURE WITH AN OXYGEN BARRIER ENRICHED WITH PHOTOINITIATOR In certain applications, all of the lens forming composition mav fail to completely cure by exposure to ultraviolet rays when forming the lens In particular, a portion of the lens forming composition proximate the gasket often remains in a liquid state following formation of the lens It is believed that the gaskets are often somewhat permeable to air, and, as a result, oxygen permeates them and contacts the portions of the lens formmg material that are proximate the gasket Since oxygen tends to inhibit the photocuring process, portions ofthe lens forming composition proximate the gasket tend to remain uncured as the lens is formed Uncured lens forming composition proximate the gasket is a problem for several reasons First, the liquid lens forming composition leaves the edges of the cured lens in a somewhat sticky state, which makes the lenses more difficult to handle Second, the liquid lens forming composition is somewhat difficult to completely remove from the surface of the lens Third, liquid lens forming composition may flow and at least partially coat the surface of lenses when such lenses are removed from the molds This coating is difficult to remove and makes application of scratch resistant coatings or tinting dyes more difficult This coating tends to interfere with the interaction of scratch resistant coatings and tinting dyes with the cured lens surface Fourth, if droplets of liquid lens forming material form, these droplets may later cure and form a ridge or bump on the surface of the lens, especially if the lens undergoes later postcure or scratch resistant coating processes As a result ofthe above problems, often lenses must be tediously cleaned or recast when liquid lens formmg composition remains after the lens is formed in an initial cure process The problems outlined above can be mitigated if less liquid lens formmg composition remains proximate the gasket after the lens is formed One method of lessening this "wet edge problem relates to increasing the amount of photoinitiator present in the lens forming composition (i e , increasmg the amount of photomiator in the lens forming composition above about 0 15 percent) Domg so, however, tends to create other problems Specifically, increased photoinitiator levels tend to cause exothermic heat to be released at a relatively high rate during the reaction ofthe composition Premature release and/or lens cracking tends to result Thus it is believed that lower amounts of photoinitiator are preferred The wet edge problem has been addressed by a variety of methods described in U S patent application seπal number 07/931 ,946 Such methods relate to removing the gasket and applying either an oxygen barπer or a photoinitiator enriched liquid to the exposed edge of the lens The lens is then re-irradiated with sufficient ultraviolet light to completely dry the edge ofthe lens prior to demoldmg An embodiment of the invention relates to improving the methods described in the 07/931 ,946 application This embodiment relates to combining an oxygen barrier with a photoinitiator Specifically, in one embodunent an oxygen barrier 970 (e g , a thin strip of polyethylene film or the like as shown m Fig 12) is embedded or impregnated with a photoinitiator 972. The oxygen barrier is then wrapped around the edge of a cured lens which is still encased between two molds (but with the gasket removed). While still "in the mold," the lens is then exposed to ultraviolet light, thereby drying its edge. An improvement ofthis method over those previously disclosed is that there is a significant reduction in the UV dosage necessary to bring the lens edge to dryness. A plastic oxygen barrier film which includes a photoinitiator may be made by: (a) immersing a plastic film in a solution comprising a photoinitiator, (b) removing the plastic film from the solution, and (c) drying the plastic film. The solution may include an etching agent. Preferably a surface ofthe plastic film is etched prior to or while immersing the plastic film in the solution. In one example, thin strips (e.g., about 10 mm wide) of high density polyethylene film (approximately 0.013 mm thick) may be soaked in a solution of 97% acetone and 3% Irgacure 184 (a photoinitiator commercially available from Ciba Geigy located in Farmingdale, New Jersey) for about five minutes. The polyethylene film may be obtained from Tape Solutions, Inc. (Nashville, Tennessee). In a more preferred embodiment, 0.5% Byk 300 (a flow agent commercially available from Byk Chemie located in Wallingford, Connecticut) may be included in the soaking solution. It is believed that xylene in the Byk 300 tends to etch the surface ofthe film and make the film more receptive to absoφtion ofthe Irgacure 184. In a still more preferred embodiment, the treated polyethylene strips may be dipped in acetone for about ten seconds to remove excess Irgacure 184. Excess photoinitiator may be seen as a white powder which coats the strips after drying. In either case, the strips are then allowed to air dry before applying them to the edge ofthe lens as described above. In one alternate embodiment of the invention, a plastic eyeglass lens may be made by the following steps: (1) placing a liquid polymerizable lens forming composition in a mold cavity defined by a gasket, a first mold member, and a second mold member; (2) directing first ultraviolet rays toward at least one of the mold members to cure the lens forming composition so that it forms a lens with a back face, edges, and a front face, and wherein a portion ofthe lens forming composition proximate the edges ofthe lens is not fully cured; (3) removing the gasket to expose the edges ofthe lens; (4) applying an oxygen barrier which includes a photoinitiator around the exposed edges ofthe lens such that at least a portion ofthe oxygen barrier photoinitiator is proximate lens forming composition that is not fully cured; and (5) directing second ultraviolet rays towards the lens such that at least a portion ofthe oxygen barrier photoinitiator initiates reaction of lens forming composition while the oxygen barrier substantially prevents oxygen from outside the oxygen barrier from contacting at least a portion ofthe lens forming composition. The first and second ultraviolet rays may (a) be at the same or different wavelengths and/or intensities , (b) be continuous or pulsed, and (c) be from the same or different light source. A puφose of the steps 4-5 is to reduce the amount of uncured liquid lens forming composition that is present when the lens is separated from the molds and/or gasket. It has been found that reducing the amount of liquid lens forming composition is especially advantageous if such reduction occurs before the molds are separated from the cured lens. Separating the molds from the cured lens may cause uncured liquids to at least partially coat the lens faces This coating occurs because uncured liquid lens forming composition tends to get swept over the faces when the molds are separated from the lens It is believed that curing of the lens tends to create a vacuum between the lens and the mold Air may sweep over the mold faces to fill this vacuum when the molds are separated from the lens This air tends to take liquid lens forming composition into the vacuum with it In step 4 above, an oxygen barrier which includes a photoinitiator is applied to the edges or sides of the lens after the gasket is removed Preferably this oxygen barrier is applied while the lens are still attached to the molds In an altemate embodiment this oxygen barrier is also applied to the edges or sides of the molds at the same time it is applied to the sides ofthe lens In a preferred embodiment, the sides of the lenses are first cleaned or wiped to remove at least a portion of the uncured liquid lens forming composition before the oxygen barrier is applied After the oxygen barπer is applied, second ultraviolet rays are directed towards the lens After the second ultraviolet rays are directed toward the lens, at least a portion of the liquid lens formmg composition which was not cured in the initial cure steps is cured It is believed that the photoinitiator embedded in the oxygen barrier facilitates faster and more complete curing of the uncured lens forming composition As such, less second ultraviolet rays are employed, thereby lessening the time and energy required in this step Furthermore, lens quality tends to be enhanced since a lower application of the second ultraviolet rays tends to reduce the potential for lens yellowing In a preferred embodiment, substantially all of the remaining liquid lens forming composition is cured after the second ultraviolet ravs are directed toward the lens More preferably, the lens is substantially dry after the second ultraviolet rays are directed towards the lens After the second ultraviolet rays are directed toward the lens, the lens mav then be demolded The lens may then be tinted After the lens is demolded, a scratch resistant coating may be applied to the lens In one embodiment, a scratch resistant coating is applied to the demolded lens by applying a liquid scratch resistant coating composition to a face of the lens and then applying ultraviolet rays to this face to cure the liquid scratch resistant coatmg to a solid In an embodiment, the intensity of the ultraviolet rays applied to the face of the lens to cure the liquid scratch resistant coating composition to a solid is about 150-300 mW/cm 2 at a wave length range of about 360- 370 nm, and about 50-150 mW/cm 2 at a wave length range of about 250-260 nm The lens may be heated after removal from the molds, or after application of a scratch resistant coating to the lens In a preferred embodiment, the total intensity of the first ultraviolet rays directed toward the mold members is less than about 10 mW/cm 2 In an embodiment, the intensity ofthe second ultraviolet rays directed toward the lens is about 150-300 mW/cm 2 at a wave length range of about 360-370 nm, and about 50-150 mW/cm 2 at a wave length range of about 250-260 nm Preferably the second ultraviolet rays are directed towards the lens for less than about 1 minute In a preferred embodiment, the above method may further include the additional step of directing third ultraviolet rays towards the lens before the oxygen barrier is applied These third ultraviolet rays are preferably applied before the gasket is removed Preferably, the second and third ultraviolet rays are directed toward the back face ofthe lens (as stated above, the second and third ultraviolet rays are preferably applied while this lens is in the mold cavity) The third ultraviolet rays are preferably about the same range of intensity as the second ultraviolet rays The same apparatus may be used for both the second and third ultraviolet rays In a preferred embodiment, the method described above also includes the step of removing the oxygen barrier from the edges ofthe lens The second and third ultraviolet rays may be repeatedly directed towards the lens For instance, these ultraviolet rays may be applied via a light assembly whereby the lens passes under a light source on a movable stand The lens may be repeatedly passed under the lights Repeated exposure of the lens to the ultraviolet rays may be more beneficial than one prolonged exposure Preferably the oxygen barrier includes a film, and more preferably a plastic, flexible, and/or elastic film In addition, the oxygen barrier is preferably at least partially transparent to ultraviolet rays so that ultraviolet rays may penetrate the oxygen barrier to cure any remaming liquid lens formmg composition Preferably the oxygen barrier is stretchable and self-sealing These features make the film easier to apply Preferably the oxygen barrier is resistant to penetration by liquids, thus keeping any liquid lens formmg composition in the mold assembly Preferably, the oxygen barrier includes a thermoplastic composition It is anticipated that many different oxygen barriers may be used (e g , saran wrap, polyethylene, etc ) In one preferred embodiment, the film is "Parafilm M Laboratory Film" which is available from American National Can (Greenwich, CT, U S A ) The oxygen barrier may also include aluminum foil Preferably the oxygen barrier is less than about 1 0 mm thick More preferably the oxygen barrier is 0 01 to 0 10 mm thick, and more preferably still the oxygen barπer is less than 0 025 mm thick If the oxygen barrier is too thick, then it may not be readily stretchable and/or conformable, and it may not allow a sufficient amount of light to pass through it If the oxygen barrier is too thin, then it may tend to tear An apparatus for applying a scratch resistant coating composition to a lens and then curing the scratch resistant coating composition is described in U.S patents 4,895,102 to Kachel et al and 3,494,326 to Upton (both of which are incoφorated herein by reference) In addition, the apparatus schematically shown m Figure 10 may also be used to apply the scratch resistant coating Figure 10 depicts an apparatus 600 with a first chamber 602 and a second chamber 604 This apparatus can be used to apply scratch resistant coating to a lens, to postcure a lens, or to apply ultraviolet light to a lens mold assembly The first chamber 602 includes an opening 606 through which an operator can apply lenses and lens mold assemblies to the lens holder 608 Lens holder 608 is partially surrounded by barrier 614 First chamber 602 may include an inspection light 610, and an opening 618 in the floor ofthe chamber Lens holder 608 is attached to device 612 It is envisioned that device 612 may be a spinning device which would permit the apparatus 600 to be used to apply scratch resistant coatmgs to lenses In such case device 612 would connect directly to lens holder 608 through a hole in the bottom of barrier 614 In a preferred embodiment, however, device 612 just connects the lens holder 608 or barrier 614 to moving device 616 It has been found that a separate spinner (not shown) may provide better results for application of scratch resistant coatings to lenses Preferably barπer 614 has an interior surface that is made or lined with an absorbant material such as foam rubber Preferably this absorbant material is disposable and removable The absorbant mateπal absorbs any liquids that fall off the lens holder 608, keeping in the interior surface ofthe barrier 614 clean In an embodiment, shutter 621 is used to inhibit the ultraviolet light from light assembly 622 from contactmg barrier 614 It is preferred that lens holder 608 be exposed to the ultraviolet light from light assembly 622 while shutter 621 blocks at least a portion ofthe light from contacting barrier 614 Shutter 621 may also inhibit any liquid lens forming mateπal that falls from lens holder 606 from curing on barrier 614 Shutter 621 thus tends to inhibit the formation of flakes on the surface of barrier 614 Shutter 621 operates after barrier 614 drops, thus shielding barrier 614 while allowing UV light to contact the sample In an embodiment, apparatus 600 may be used to apply a precoat to lens before the hardcoat is applied The precoat may serve to increase the "wettability" of the surface to which the hardcoat is to be applied A surfactant has been conventionally employed for this puφose, however surfactants tend to affect the volatility and flow characteristics of lens coatings in an unfavorable manner The precoat may include acetone and/or Byk 300 Upon even distribution of the hardcoat onto a lens in lens holder 608, the coating may be wiped near the edges of the lens to prevent the formation of excessive flakes during curmg In another embodiment, the precoat and hardcoat are distributed onto lens holder 608 Ultraviolet light is directed toward the coatmgs at least until a gel is formed A lens forming material may be placed on top of the gel and cured Second chamber 604 includes an openmg 620 in its floor It also includes an ultraviolet light assembly 622, which may include multiple lights and a light reflector The apparatus 600 includes an air filtering and distribution system. Air is pulled into a chamber 628 by fans 626 through a filter 624 (the quantity and locations of the fans and filters may vary). The filtered air is distributed by the fans 626 throughout chambers 602, 604, and 617. Air flows from point 613 to point 615 via ab ¬ ducts (not shown) to reach chamber 617. The temperature of the lights and/or the second chamber may be controlled by turning various fans 629 on and off as needed to suck air out of chamber 604. Air is distributed from chamber 617 through hoies 636 that are proximate the lower part of the opening 606 in the first chamber 602. Air is also sucked by fans 627 from the first chamber 602 to chamber 630 through holes 634 that are proximate the top part of the opening 606 in the first chamber 602. This arrangement tends to prevent contaminants from entering first chamber 606. Air is discharged from chamber 630 to the surroundings via fans 627. During use a lens or lens mold assembly may be placed on the lens holder 608. A button can be pressed, causing the moving device 616 to move device 612, lens holder 604, and the barrier 614 so that they are under the opening 620 in the second chamber 604. Light is thus applied to the lens or lens mold assembly from light assembly 622. After a set period of time, the moving device 616 moves everything back to a location underneath the opening 618 in the first chamber 602. The lens holder 608 may include a suction cup connected to a metal bar. The concave surface of the suction cup may be attachable to a face of a mold or lens, and the convex surface of the suction cup may be attached to a metal bar. The metal bar may be attachable to a lens spinner. The lens holder may also alternately include movable arms and a spring assembly which are together operable to hold a lens against the lens holder with spring tension during use. In an alternate method of the invention, a lens may be cured between two mold members. The gasket may be removed and any remaining liquid lens composition may be removed. At this point a mold member may be applied to a substantially solid conductive heat source. Heat may then be conductively applied to a face of the lens by (a) conductively transferring heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the face of the lens. The oxygen barrier enriched with photoinitiator may then be applied, and second ultraviolet rays may be directed towards the iens to cure the remaining lens forming composition. OXYGEN BARRIER EXAMPLE #1 A liquid lens forming composition was initially cured as in a process and apparatus similar to that specified in Example 1. The composition was substantially the same as specified in Example 1, with the exception that hydroquinone was absent, the concentration of methylethylhydroquinone was about 25-45 ppm, the concentration of 1 hydroxycyclohexyl phenyl ketone was 0.017 percent, and the concentration of methylbenzoylformate was 0.068 percent. The composition underwent the initial 15 minute cure under the "1st UV " The apparatus was substantially the same as described for the above Example 1, with the following exceptions 1 The air flowrate on each side of the lens mold assembly was estimated to be about 18-20 cubic feet per minute 2 The apparatus was modified in that air flowed to and from the openings 96 and orifices 98 (which were themselves substantially unchanged) through a duct behind the lens formmg chamber, instead of through pipes (e g pipe 12 in Figure 5) Essentially plenum portion 95 was expanded so that the walls of the chamber are the walls ofthe plenum portion 95 Figure 14 depicts a front view of this lens curing apparatus 800 Air in apparatus 800 flows from the orifices 98, over the lens mold assembly 802, through ducts 804, through fan 806, through heat exchanger 808, and then through ducts 810 and back to orifices 98 via air return conduits 824 (shown on Figure 15) Figure 14 also shows a water chiller 812 which cools water and then sends it through conduits 814 and through heat exchanger 808 Figure 14 also shows lights 816 and frosted glass 818 The chamber 820 surrounding lights 816 is not connected to the chamber 822 around the mold assembly 802 In this manner chilled air from orifices 98 does not contact and cool the lights 816 (such cooling tends to cause excessive changes in light output) The chamber 820 is cooled by fans (not shown) which turn on and off depending on the temperature of the surface of the lights 816 Figure 15 shows a side view of apparatus 800 3 The air flowrate in and out of the chamber surrounding the lights was varied in accordance with the surface temperature of lights The air flowrate was varied in an effort to keep the temperature on the surface of one ofthe lights between 104 5 ° F and 105 ° F 4 The ultraviolet light output was controlled to a set point by varying the power sent to the lights as the output of the lights varied 5 Frosted glass was placed between the lights and the filters used to vary the intensity of the ultraviolet light across the face of the molds Preferably the glass was frosted on both sides The frosted glass acts as a diffuser between the lights and these filters This frosted glass tended to yield better results if it was placed at least about 2 mm from the filter, more preferably about 10-15 mm, more preferably still about 12 mm, from the filter Frosted glass was found to dampen the effect of the filters For instance, the presence of the frosted glass reduced the systems' ability to produce different lens powers by varying the light (see Example 1 and Figure 1) 6. ln Figure 3 the center lights 40 are shown in a triangular arrangement when viewed from the side. These lights were rearranged to provide an in-line arrangement. After mitial cure, the lens mold assembly was removed from the curing chamber The lens mold assembly included a lens surrounded by a front mold, a back mold, and a gasket between the front and back molds (see, e.g , the assembly in Figure 6) At this point the protocol in Example 1 stated that the lens was demolded (see above) While demolding at this point is possible, as stated above generally some liquid lens forming composition remained, especially in areas of the lens proximate the gasket Therefore the lens was not demolded as stated in Example 1 Instead, the gasket was removed, liquid lens forming composition was wiped off the edges of the lens, and a layer of oxygen barrier (Parafilm M) with photoinitiator was wrapped around the edges of the lens while the lens was still between the molds. The Parafilm M was wrapped tightly around the edges of the lens and then stretched so that it would adhere to the lens and molds (i.e in a manner similar to that of Saran wrap) The lens mold assembly was then placed in apparatus 600 so that the back face of the lens (while between the molds) could then be exposed to second ultraviolet light This second ultraviolet light was at a substantially higher intensity than the initial cure light, which was directed at an intensity of less than 10 mW/cm 2 . The mold assembly was passed in and out of second chamber 604 in Figure 10 (i.e., a UVEXS Model 912) when the light was set at the high setting Passing in and out of the chamber took about 22 seconds. The total light energy applied during these 22 seconds was about 4500 millijoules per square centimeter ("mJ/cm 2 ") Preferably the total light energy applied per pass under the second and third ultraviolet ray lights was in the range of about 500-10,000 mJ/cm 2 , more preferably about 3000-6000 mJ/cm 2 , and more preferably still 4000-5000 mJ/cm 2 Light energy may be varied by varying the time of exposure, or the intensity of the light Light energy was measured with a Model IL390B Light Bug from International Light, Inc (Newburyport, MA, U.S.A.). The total light energy represents the total amount of ultraviolet light over the range of 250 to 400 nm. It has been found that applying ultraviolet light at this point helped to cure some or all of the remaming liquid lens formmg composition The second ultraviolet light step may be repeated In this example the second ultraviolet light step was repeated once. It is also possible to expose the front or both sides of the lens to the second ultraviolet light. After the second ultraviolet light was applied, the mold assembly was allowed to cool The reactions caused by exposure to ultraviolet light are exothermic The ultraviolet lights also tend to emit infra-red light which m turn heats the mold assembly. The lens was then demolded. The demolded lens was substantially drier and harder than lenses that are directly removed from mold assemblies after the initial cure step OXYGEN BARRIER EXAMPLE #2 The protocol of Oxygen Barrier Example H 1 was repeated except that prior to removal of the gasket the lens mold assembly was positioned so that the back face of the lens was exposed to third ultraviolet light In this case the third ultraviolet light was at the same intensity and for the same time period as one pass ofthe second ultraviolet light It has been found that applying third ultraviolet light at this point helped to cure some or all of the remaining liquid lens forming composition so that when the gasket was removed less liquid lens formmg composition was present All of the remaining steps in Oxygen Barrier Example # 1 were applied, and the resultant lens was substantially dry when removed from the molds CONDUCTIVE HEATING An embodiment ofthe invention relates to postcurmg a polymerized lens contained in a mold cavity by applying conductive heat to at least one ofthe molds that form the mold cavity, prior to demolding the lens More particularly, one embodiment of the invention includes the following (1) placing a liquid lens forming composition in a mold cavity defined by at least a first mold member and a second mold member, (2) directing ultraviolet rays toward at least one ofthe mold members to cure the lens formmg composition so that it forms a lens with a back face, edges, and a front face, (3) applying a mold member of the mold cavity to a substantially solid conductive heat source, and (4) conductively applying heat to a face of the lens by (a) conductively transferring heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the face ofthe lens In an embodiment described as follows, a lens cured by exposure to ultraviolet light is further processed by conductive heating Such conductive heating tends to enhance the degree of cross-linking in the lens and to increase the tintabihty of the lens A lens forming material is placed in mold cavity 900 (illustrated in Fig 19), which is defined by at least first mold member 902 and second mold member 904 Ultraviolet rays are directed toward at least one ofthe mold members, thereby curmg the lens forming material to a lens Heat distributor 910 (shown in Fig 16) may be adapted to distribute conductive heat from conductive heat source 912 to at least one mold member Heat distributor 910 is preferably flexible such that at least a portion of it may be shaped to substantially conform to the shape of face 906 or face 907 of first mold member 902 or second mold member 904, respectively Heat distributor 910 is preferably placed in contact with conductive heat source 912, and mold member 902 is placed on heat distributor 910 such that face 906 ofthe mold member rests on top ofthe heat distributor 910 Heat distributor 910 may be coupled to heat source 912 Heat is conductively applied to the heat distributor 910 by the heat source 912 Heat is conducted from the heat distributor 910 through the mold member to a face ofthe lens The heat distributor may be shaped to accommodate face 906 of first mold member 902 or face 907 of second mold member 904 such that the heat is applied to front face 916 or back face 915 ofthe lens (shown in Fig 11) The temperature of heat source 912 may be thermostatically controlled In an embodiment, hot plate 918 (shown in Fig 17) is used as a heat source to provide conductive heat to the lens A number of other heat sources may be used In an embodiment heat distributor 910 may include countershape 920 Countershape 920 may be placed on top ofthe hot plate to distribute conductive heat from the hot plate The countershape is preferably flexible such that at least a portion of it may substantially conform to the shape of an outside face of a mold member The countershape may be hemispherical and either convex or concave depending upon whether the surface ofthe mold assembly to be placed upon it is convex or concave For example, when the concave surface ofthe back mold is utilized to conduct heat into the lens assembly, a convex countershape is provided to rest the assembly on Countershape 920 may include a glass mold, a metal optical lap, a pile of hot salt and/or sand, or any of a number of other devices adapted to conduct heat from heat source 912 It should be understood that Figure 17 includes combinations of a number of embodiments for illustrative puφoses Any number of identical or distmct countershapes may be used in combination on top of a heat source In an embodiment, a countershape includes a container 922 filled with particles 924 The particles preferably include metal or ceramic material Countershape 920 may include heat distributor 910 A layer 914 of material may be placed over the countershape 920 or heat distributor 910 to provide slow, smooth, uniform heat conduction into the lens mold assembly This layer TM preferably has a relatively low heat conductivity and may be made of rubber, cloth, Nomex fabric or any other suitable material that provides slow, smooth, uniform conduction In an embodiment, countershape 920 includes layer 914 (e g , a bag or container) filled with particles 924 such that the countershape may be conveniently shaped to conform to the shape of face 906 or face 907 In an embodiment, the countershape is essentially a "beanbag" that contains particles 924 and is conformable to the shape of a mold face placed on top of it Particles 924 may include ceramic material, metal material, glass beads, sand and/or salt The particles preferably facilitate conductive heat to be applied to face 906 or face 907 substantially evenly ln an embodiment, the countershape 920 is placed on top of heat source 912 for a sufficient time for a portion of the countershape to attain a temperature substantially near or equal to the temperature on the surface of the heat source The countershape may then be "flipped over" such that the heated portion ofthe countershape that has a temperature substantially near or equal to that ofthe surface ofthe heat source is exposed A mold may be placed on top ofthe heated portion ofthe countershape, and the countershape is preferably conformed to the shape ofthe face ofthe mold In this manner, the rate of conductive heat transfer to the lens may begin at a maximum Heat is preferably conductively transferred through the countershape and the mold face to a face of the lens The temperature ofthe heated portion ofthe countershape may tend to decrease after the mold is placed onto the countershape In an embodiment, heat distributor 910 may partially insulate a mold member from conductive heat source 912 The heat distributor preferably allows a gradual, uniform transfer of heat to the mold member The heat distributor is preferably made of rubber and/or another suitable material The heat distributor may mclude countershapes of various shapes (e.g., hemispherical ly concave or convex) and sizes that are adapted to contact and receive mold members. In an embodiment, hot plate cover 930 (shown in Fig. 8) is used to distribute conductive heat to face 906 of mold member 902. Cover 930 is adapted to rest directly upon hot plate 918 (or any other heat source). Cover 930 preferably includes portion 932, which is substantially conformed to the shape of face 906. Portion 932 preferably includes a convex surface or a concave surface (not shown) adapted to receive face 906. Portion 932 is preferably made of rubber and causes slow, uniform transfer of conductive heat to face 906. In an embodiment, a hot plate cover having concave indentations substantially conformed to the shape of face 907 is used to distribute heat through a mold member to a lens. In an embodiment, heat is conductively applied by the heat source to only one outside face of one mold member. This outside face may be face 906 or face 907. Heat may be applied to back face 915 ofthe lens to enhance crosslinking and/or tintability ofthe lens material proximate to the surface ofthe back face ofthe lens. In a preferred embodiment, thermostatically controlled hot plate 918 is used as a heat source. Glass optical moid 928 is preferably placed convex side up on hot plate 918 to serve as a countershape. The glass optical mold preferably has about an 80 mm diameter and a radius of curvature of about 93mm. Rubber disc 929 may be placed over this mold 928 to provide uniform conductive heat to the lens mold assembly. The rubber disc is preferably made of silicone and preferably has a diameter of approximately 74 mm and a thickness of about 3 mm. The lens mold assembly preferably is placed on mold 928 so that outside face 906 of a mold member ofthe assembly rests on top of mold 928. It is preferred that the edge ofthe lens mold assembly not directly contact the hot plate. The lens mold assembly preferably receives heat through the rubber disc and not through its mold edges. To achieve good yield rates and reduce the incidence of premature release while using the conductive heat method, it may be necessary for the edge ofthe lens be completely cured and dry before conductive heat is applied. If the lens edge is incompletely cured (i.e., liquid or gel is still present) while conductive heat is applied, there may be a high incidence of premature release ofthe lens from the heating unit. In an embodiment, the edges of a lens are treated to cure or remove incompletely cured lens forming material (see above description) before conductive heat is applied. The mold cavity may be defined by at least gasket 908, first mold member 902, and second mold member 904. Ultraviolet rays are directed toward at least one ofthe mold members, thereby curing the lens forming material to a lens preferably having front face 916, a back face 915. and edges. Upon the formation of the lens, the gasket may be removed from the mold assembly. An oxygen barrier may be used to cure any remaining liquid or gel on the lens edge according to any ofthe methods ofthe above-detailed embodiments. An oxygen barrier treated with photoinitiator is preferably employed. Alternatively, any remaining liquid or gel may be removed manually. Once the edge ofthe lens is dry, a face ofthe lens may be conductively heated using any ofthe methods described herein. In an embodiment, a lens is tinted after receivmg conductive heat postcure treatment in a mold cavity During tinting ofthe lens, the lens is preferably immersed in a dye solution CONDUCTIVE HEATING EXAMPLE A liquid lens forming composition was initially cured in a process and apparatus similar to that specified in Example 1 except for post-cure treatment which was conducted as follows After the sample was irradiated for 15 mmutes, the lens was removed from the FC-104 chamber and then passed through the above-mentioned UVEXS Model 912 curing chamber (see Figure 10) to receive a dose of about 1500 mJ/cm (+/- 100 mJ) of ultraviolet light per pass The gasket was then removed from the mold assembly and the edges ofthe mold were wiped with an absorbent tissue to remove incompletely cured lens forming material proximate the mold edges A strip of plastic material impregnated with photoinitiator was wrapped around the edges ofthe molds that were exposed when the gasket was removed Next, the mold assembly was passed through the UVEXS curmg chamber once to expose the front surface of the mold to a dose of about 1500 mJ/cm The mold assembly was then passed through the UVEXS four more times, with the back surface of the mold receiving a dose of about 1500mJ/cm per pass A hot plate was operated such that the surface ofthe hot plate reached a temperature of 340 degrees F (+/- 50 degrees F) A conformable "beanbag" container havmg a covermg made of Nomex fabric was placed on the hot plate The container contamed glass beads and was turned over such that the portion ofthe container that had directly contacted the hot plate (i.e , the hottest portion of the container) faced upward and away from the hot plate The mold assembly was then placed onto the heated, exposed portion ofthe container that had been in direct contact with the hot plate The concave, non-casting face ofthe mold was placed onto the exposed surface ofthe container which substantially conformed to the shape of the face Heat was conducted through the container and the mold member to the lens for 13 mmutes A lens having a Shore D hardness of 84 was formed PULSED ULTRAVIOLET LIGHT APPLICATION A polymerizable lens forming composition may be placed in a mold/gasket assembly and contmuously exposed to appropriate levels of ultraviolet light to cure the composition to an optical lens The progress ofthe curing reaction may be determined by monitoring the internal temperature ofthe composition. The lens formmg composition may be considered to pass through three stages as it is cured (1) Induction, (2) Gel Formation & Exotherm, and (3) Extinction These stages are illustrated in Fig 20 for a - 75 -1 00 power lens cured by contmuous application of UV light Figure 20 shows temperature withm the mold cavity as a function of tune throughout a contmuous radiation curmg cycle The induction stage occurs at the beginning ofthe curing cycle and is typically characterized by a substantially steady temperature (or falling temperature when the curing chamber temperature is below that ofthe composition) ofthe lens forming composition as it is irradiated with ultraviolet light During the induction period, the lens forming composition remains in a liquid state as the photoinitiator breaks down and consumes inhibitor and dissolved oxygen present in the composition As the inhibitor content and oxygen content ofthe composition fall, decomposing photoinitiator and the composition begin to form chains to produce a pourable, "syrup-like" material As irradiation continues, the "syrup" proceeds to develop into a soft, non-pourable, viscous, gel A noticeable quantity of heat will begin to be generated durmg this soft gel stage The optical quality of the lens may be affected at this point Should there be any shaφ discontinuities in the intensity of the activatmg ultraviolet light (for example, a drop of composition on the exterior of a mold which focuses light into a portion ofthe lens forming composition proximate the drop), a local distortion will tend to be created in the gel structure, likely causing an aberration in the final product The lens forming composition will pass through this very soft gel state and through a firm gel state to become a crystalline structure When using OMB-91 lens formmg composition, a haze tends to form momentarily during the transition between the gel and crystalline stages As the reaction contmues and more double bonds are consumed, the rate of reaction and the rate of heat generated by the reaction will slow, which may cause the internal temperature ofthe lens forming composition to pass through a maximum at the point where the rate of heat generation exactly matches the heat removal capacity ofthe system By the time the maximum temperature has been reached and the lens formmg composition begms to cool, the lens will typically have achieved a crystalline form and will tend to crack rather than crumble if it is broken The rate of conversion will slow dramatically and the lens may begin to cool even though some reaction still may be occurrmg Irradiation may still be applied through this extinction phase Generally, the curing cycle is assumed to be complete when the temperature of the lens forming composition falls to a temperature near its temperature at the beginning of exotherm (I e , the point where the temperature of the composition increased due to the heat released by the reaction) The contmuous irradiation method tends to work well for relatively low mass lenses (up to about 20-25 grams) under the FC-104 curmg chamber conditions (see, e g , U S Patents 5,364,256 and 5,415,816) As the amount of material bemg cured increases, problems may be encountered The total amount of heat generated duπng the exothermic phase is substantially proportional to the mass of the lens formmg material Dunng curing of relatively high mass lenses, a greater amount of heat is generated per a given time than durmg curmg of lower mass lenses The total mold/gasket surface area available for heat transfer (e g , heat removal from the lens formmg composition), however, remains substantially constant Thus the internal temperature of a relatively high mass of lens formmg material may rise to a higher temperature more rapidly than typically occurs with a lower mass of lens formmg material For example, the internal temperature of a low minus cast-to-finish lens typically will not exceed about 100 F, whereas certain thicker semi-finished lens "blanks" may attain temperatures greater than about 350 F when continually exposed to radiation. The lens forming material tends to shrink as curing proceeds and the release of excessive heat during curing tends to reduce the adhesion between the mold and the lens forming material. These factors may lead to persistent problems of premature release and/or cracking during the curing of lens forming material having a relatively high mass. A significant advantage ofthe present invention is the production of relatively high-mass, semi¬ finished lens blanks and high power cast-to-finish lenses without the above-mentioned problems of premature release and cracking. Methods ofthe present invention as described below allow even more control over the process of curing ophthalmic lenses with ultraviolet light-initiated polymerization than previous methods. By interrupting or decreasing the activating light at the proper time during the cycle, the rate of heat generation and release can be controlled and the incidence of premature release can be reduced. An embodiment ofthe invention relates to a method of controlling the rate of reaction (and therefore the rate of heat generation) of a UV light- curable, lens forming material by applying selected intermittent doses (e.g., pulses) of radiation followed by selected periods of decreased UV light or "darkness". It is to be understood that in the description that follows, "darkness" refers to the absence of activating radiation, and not necessarily the absence of visible light. More particularly, an embodiment ofthe invention relates to: (a) an initial exposure period ofthe lens forming material to radiation (e.g., continuous or pulsed radiation) extending through the induction period, (b) interrupting or decreasing the irradiation before the material reaches a first temperature (e.g., the maximum temperature the composition could reach if irradiation were continued) and allowing the reaction to proceed to a second temperature lower than the first temperature, and (c) applying a sufficient number of alternating periods of exposure and decreased UV light or darkness to the lens forming material to complete the cure while controlling the rate of heat generation and/or dissipation via manipulation of the timing and duration of the radiation, or the cooling in the curing chamber. Figure 21 shows the temperature within the mold cavity as a function of time for both (a) continuous ultraviolet light exposure and (b) pulsed ultraviolet light exposure. In the context of this application, a "gel" occurs when the liquid lens forming composition is cured to the extent that it becomes substantially non-pourable, yet is still substantially deformable and substantially not crystallized. In the following description, it is to be understood that the term "first period" refers to the length of time ofthe initial exposure period where radiation (e.g., in pulses) is applied to the lens forming composition, preferably to form at least a portion ofthe composition into a gel. "First ultraviolet" rays or light refers to the radiation applied to the lens forming composition during the initial exposure period. "Second ultraviolet" rays or light refers to the radiation that is applied to the lens forming composition (e.g., in pulses) after the composition has been allowed to cool to the "third temperature" mentioned above. "Second period" refers to the duration of time that second ultraviolet rays are directed to the lens forming composition. "Third period" refers to the duration of decreased UV light or darkness than ensues after UV light has been delivered in the second period. In an embodiment of the invention, the lens forming material is placed in a mold cavity defined in part between a first mold member and a second mold member. The first mold member and/or second mold member may or may not be continuously cooled as the formation of the lens is completed during the second period and/or third period. One method of removing heat from the lens forming material is to continuously direct air at a non- casting face of at least one ofthe mold members. It is preferred that air be directed at both the first and second mold members. A cooler may be used to cool the temperature ofthe air to a temperature below ambient temperature, more preferably between about 0 C and about 20 C, and more preferably still between about 3 C and about 15 C. Air may also be used to cool at least one ofthe mold members (in any ofthe manners described previously) during the first period. In an embodiment ofthe invention, the first period ends when at least a portion ofthe lens forming composition begins to increase in temperature or form a gel, and the first ultraviolet rays are decreased or removed (e.g., blocked) such that they cease to contact the first or second mold members. It is preferred that the first period be sufficient to allow the lens forming material to gel in the mold cavity such that there is substantially no liquid present (except small amounts proximate the edge of the material). The interruption of irradiation prior to complete gelation may in some circumstances produce optical distortions. It is preferred that the length ofthe first period be selected to inhibit the lens forming composition from reaching a first temperature. The first temperature is preferably the maximum temperature that the lens forming composition could reach if it was irradiated under the system conditions (e.g., flow rate and temperature of any cooling air, wavelength and intensity of radiation) until the "exothermic potential" (i.e., ability to evolve heat through reaction) ofthe composition was exhausted. According to an embodiment ofthe invention, the reactions within the composition are allowed to proceed after the first ultraviolet rays are removed until the composition reaches a second temperature. The second temperature is preferably less than the first temperature. The first temperature is preferably never reached by the composition. Thus, preferably the composition is prevented from achieving the first temperature and then cooling to the second temperature. The composition preferably is allowed to cool from the second temperature to the third temperature. This cooling may occur "inactively" by allowing heat to transfer to the ambient surroundings, or at least one ofthe mold members may be cooled by any ofthe methods described above. In an embodiment of the invention, the curing ofthe lens forming material is completed by directing second ultraviolet rays (e.g., in pulses) toward at least one ofthe mold members. The second UV rays may be directed toward the mold member(s) for a second period that may be determined according to the rate of reaction ofthe lens forming composition. The change in temperature of the composition or a portion ofthe mold cavity, or the air in or exiting the chamber is an indicator ofthe rate of reaction, and the second period may be determined accordingly. The second period may be varied such that subsequent pulses have a longer or shorter duration than previous pulses. The time between pulses (i.e., the third period) may also be varied as a function of the temperature and/or reaction rate ofthe composition. To achieve a light pulse, (a) the power to a light source may be turned on and then off, (b) a device may be used to alternately transmit and then block the passage of light to the lens forming composition, or (c) the light source and/or mold assembly may be moved to inhibit ultraviolet light from contacting the lens forming mateπal The second and/or third periods are preferably controlled to allow rapid formation of a lens while reducing the incidence of (a) premature release of the lens from the first and/or second mold member and/or (b) cracking of the lens In an embodiment, the second period is preferably controlled to inhibit the temperature ofthe composition from exceeding the second temperature The temperature ofthe lens forming composition may continue to increase after radiation is removed from the first and/or second mold members due to the exothermic nature of reactions occurring within the composition The second period may be sufficiently brief such that the pulse of second ultraviolet rays is removed while the temperature ofthe composition is below the second temperature, and the temperature ofthe composition increases during the third period to become substantially equal to the second temperature at the point that the temperature ofthe composition begins to decrease In an embodiment, the third period extends until the temperature ofthe composition becomes substantially equal to the third temperature Once the temperature ofthe composition decreases to the third temperature, a pulse of second ultraviolet rays may be delivered to the composition In an embodiment, the second period remains constant, and the third period is controlled to maintain the temperature ofthe composition below the second temperature The third period may be used to lower the temperature of the composition to a temperature that is expected to cause the composition to reach but not exceed the second temperature after a pulse is delivered to the composition In an embodiment, shutter system 950 (shown in Fig 7) is used to control the application of first and/or second ultraviolet rays to the lens formmg mateπal Shutter system 950 preferably includes air-actuated shutter plates 954 that may be inserted into the curing chamber to prevent ultraviolet light from reaching the lens formmg material Shutter system 950 may include programmable logic controller 952, which may actuate air cylmder 956 to cause shutter plates 954 to be inserted or extracted from the curing chamber Programmable logic controller 952 preferably allows the insertion and extraction of shutter plates 954 at specified time intervals Programmable logic controller 952 may receive signals from thermocouple(s) located inside chamber, proximate at least a portion the mold cavity, or located to sense the temperature of air m or exiting the chamber, allowing the time mtervals tn which the shutters are inserted and/or extracted to be adjusted as a function of a temperature withm the curmg chamber The thermocouple may be located at numerous positions proximate the mold cavity and/or castmg chamber The wavelength and intensity ofthe second ultraviolet rays are preferably substantially equal to those ofthe first ultraviolet rays It may be desirable to vary the intensity and/or wavelength ofthe radiation (e g, first or second ultraviolet rays) The particular wavelength and intensity ofthe radiation employed may vary among embodiments accordmg to such factors as the identity ofthe composition and curmg cycle variables Numerous curing cycles may be designed and employed The design of an optimal cycle should include consideration of a number of interacting variables Significant independent variables mclude 1 ) the mass ofthe sample of lens formmg material. 2) the intensity ofthe light applied to the material, 3) the physical characteristics of the lens forming mateπal. and 4) the cooling efficiency of the system Significant curing cycle (dependent) variables include 1) the optimum initial exposure time for induction and gellmg, 2) the total cycle time, 3) the tune period between pulses 4) the duration ofthe pulses, and 5) the total exposure time Most of the experiments involving methods ofthe present invention were conducted using below descnbed OMB-91 monomer and the above-mentioned FC-104 curing chamber set at an operating temperature of 55 degrees F, although tests have been performed using other lens forming materials and curing chamber temperatures The OMB-91 formulation and properties are listed below OMB-91 FORMULATION INGREDIENT WEIGHT PERCENT Sartomer SR 351 (Trimethylolpropane Triacrylate) 20 0 +/- 1 0 Sartomer SR 268 (Tetraethylene Glycol Diacrylate) 21 0 +/- 1 0 Sartomer SR 306 (Tπpropylene Glycol Diacrylate) 32 0 +/- 1 0 Sartomer SR 239 (1 ,6 Hexanediol Dimethacrylate) 10 0 +/- 1 0 (Bisphenol A Bιs(Allyl Carbonate)) 17 0 +/- 1 0 Irgacure 184 (1-Hydroxycyclohexyl Phenyl Keytone) 0 017 +/- 0 0002 Methyl Benzoyl Formate 0 068 +/- 0 0007 Methyl Ester of Hydroqumone ("MeHQ") 35 ppm +/- 10 ppm Thermoplast Blue P (9,10 - Anthracenedione, 0 35 ppm +/- 0 1 ppm 1 -hydroxy-4-((4-methyl phenyl) Amino) MEASUREMENTS/PROPERTIES PROPERTY PROPOSED SPECIFICATION Appearance Clear Liquid Color (APHA) 50 maximum (Test Tube Test) Match Standard Acidity (ppm as Acrylic Acid) 100 maximum Refractive Index 1 4725 +/- 0002 Density 1 08 +/- 0 005 gm/cc at 23 degrees C Viscosity @ 22 5 Degrees C 27 0 +/- 2 centipoise Solvent Weight (wt %) 0 1 Maximum Water (wt %) 0 1 Maximum MeHQ (from HPLC) 35 ppm -ι7- 10 ppm It is recognized that methods and systems ofthe present invention could be applied to a large variety of radiation-curable, lens forming materials in addition to those mentioned herein It should be understood that adjustments to curing cycle variables (particularly the initial exposure time) may be required even among lens forming compositions ofthe same type due to variations in inhibitor levels among batches ofthe lens formmg compositions In addition, changes m the heat removal capacity ofthe system may require adjustments to the curmg cycie variables (e g duration ofthe cooling periods between radiation pulses) Changes in the cooling capacity of the system and/or changes in compositions of the lens forming material may require adjustments to curing cycle variables as well Significant variables impacting the design of a pulsed curing cycle include (a) the mass ofthe material to be cured and (b) the intensity ofthe light applied to the material A significant aspect of methods ofthe present invention is the initial exposure period If a sample is initially overdosed with radiation, the reaction may progress too far and increase the likelihood of premature release and/or cracking If a sample is underdosed initially in a fixed (I e , preset) curing cycle, subsequent exposures may cause too great a temperature rise later m the cycle, tending to cause premature release and/or cracking Additionally, if the light intensity varies more than about +/- 10% in a cycle that has been designed for a fixed light intensity level and/or fixed mass of lens formmg matenal, premature release and/or cracking may result An embodiment of the present invention involves a curing cycle having two processes A first process relates to forming a dry gel by continuously irradiating a lens forming composition for a relatively long period The material is then cooled down to a lower temperature under darkness A second process relates to controllably discharging the remaining exothermic potential ot the material by alternately exposing the material to relatively short periods of irradiation and longer periods of decreased irradiation (e g , dark cooling) The behavior ofthe lens forming material duπng the second process will depend upon the degree of reaction ofthe lens forming material that has occurred during the first process For a fixed curing cycle, it is preferable that the extent of reaction occurring in the first process consistently fall withm a specified range If the progress of reaction is not controlled well, the incidence of cracking and/or premature release may rise For a curing cycle involving a composition having a constant level of inhibitor and initiator, the intensity ofthe radiation employed is the most likely source of variability in the level of cure attained in the first process Generally, a fluctuation of +/- 5% in the intensity tends to cause observable differences in the cure level achieved in the first process Light intensity variations of +/- 10% may significantly reduce yield rates The effect of various light intensities on the material being cured depends upon whether the intensity is higher or lower than a preferred intensity for which the curing cycle was designed Fig 23 shows temperature profiles for three embodiments in which different light levels were employed If the light intensity to which the material is exposed is higher than the preferred intensity, the overdosage may cause the reaction to proceed too far In such a case, excessive heat may be generated, increasing the possibility of cracking and/or premature release during the first process of the curing cycle If premature release or cracking ofthe overdosed material does not occur in the first process, then subsequent pulses administered during the second process may create very little additional reaction If the light intensity is lower than the preferred intensity and the lens forming material is underdosed, other problems may arise The material may not be driven to a sufficient level of cure in the first process Pulses applied durmg the second process may then cause relatively high amounts of reaction to occur, and the heat generated by reaction may be much greater than the heat removal capacitv of the system Thus the temperature of the lens forming material may tend to excessively increase Premature release may result Otherwise, undercured lenses that continue generating heat after the end ofthe cycle may be produced The optimal initial radiation dose to apply to the lens forming material may depend primarily upon its mass The initial dose is also a function of the light intensity and exposure time A method for designing a curmg cycle for a given mold/gasket/monomer combination may involve selecting a fixed light intensity Methods ofthe present invention may involve a wide range of light intensities Usmg a relatively low mtensity may allow for the length of each cooling step to be decreased such that shorter and more controllable pulses are applied Where a fluorescent lamp is employed, the use of a lower intensity may allow the use of lower power settings, thereby reducing the load on the lamp cooling system and extending the life ofthe lamp A disadvantage of using a relatively low light intensity is that the initial exposure period tends to be somewhat longer Relatively high intensity levels tend to provide shorter initial exposure times while placing more demand upon the lamp drivers and/or lamp cooling system, either of which tends to reduce the life of the lamp In an embodiment. General Electric F15T8BL lamps powered by Mercron HR0696-4 drivers may be used in conjunction with an FC 104 curing chamber having one piece of double-frosted diffusing glass and one 2 piece of clear PO-4 acrylic plate The light intensity settings may be 760 microwatts/cm for the top lamps and 2 950 microwatts/cm for the bottom lamps Once a light intensity is selected, the initial exposure time may be determined A convenient method of monitoring the reaction during the cycle involves fashioning a fine gage thermocouple, positioning it inside the mold cavity, and connecting it to an appropriate data acquisition system The preferred thermocouple is Type J, 0 005 inch diameter, Teflon-insulated wire available from Omega Engineering The insulation is stripped back about 30 to 50 mm and each wire is passed through the gasket wall via a fine bore hypodermic needle The needle is then removed and the two wires are twisted together to form a thermocouple junction inside the inner circumference ofthe gasket The other ends ofthe leads are attached to a miniature connector which can be plugged into a permanent thermocouple extension cord leading to the data acquisition unit after the moid set is filled The data acquisition unit may be a Hydra 2625A Data Logger made by John Fluke Mfg Company It is connected to an IBM compatible personal computer running Hydra Data Logger software The computer is configured to display a trend plot as well as numeric temperature readings on a monitor The scan interval may be set to any convenient time period and a period of five or ten seconds usually provides good resolution The position ofthe thermocouple junction in the mold cavity may affect its reading and behavior through the cycle When the junction is located between the front and back molds, relatively high temperatures may be observed compared to the temperatures at or near the mold face The distance from the edge ofthe cavity to the junction may affect both absolute temperature readings as well as the shape ofthe curing cycles' temperature plot The edges of the lens forming material may begin to increase in temperature slightly later than other portions ofthe material Later in the cycle, the lens forming material at the center may be somewhat ahead ofthe material at the edge and will tend to respond little to the radiation pulses, whereas the material near the edge may tend to exhibit significant activity When performing experiments to develop curing cycles, it is preferred to insert two probes into the mold cavity, one near the center and one near the edge The center probe should be relied upon early in the cycle and the edge probe should guide the later stages of the cycle Differing rates of reaction among various regions ofthe lens forming material may be achieved by applying a differential light distribution across the mold face(s) Tests have been performed where "minus type" light distributions have caused the edge ofthe lens forming material to begin reacting before the center of the material The potential advantages of using light distributing filters to cure high mass semi-finished lenses may be offset by nonuniformity of total light transmission that tends to occur across large numbers of filters The U V light transmission ofthe PO-4 acrylic plates (Cyro Industries, Piano, Texas) used over the apertures in the FC-104 curing chamber tends to be considerably more consistent than that of silk-screened filter plates After the selection and/or configuration of (a) the radiation intensity, (b) the radiation-curable, lens forming material, (c) the mold/gasket set, and (d) the data acquisition system, the optimum initial exposure period may be determined It is useful to expose a sample of lens formmg material to continuous radiation to obtain a temperature profile This will provide an identifiable range of elapsed time withm which the optimal initial exposure time will fall Two points of interest are the time where the temperature rise in the sample is first detected ("T initial" or "Ti"), and the time where the maximum temperature ofthe sample is reached ("Tmax") Also of mterest is the actual maximum temperature, an indication ofthe "heat potential" of the sample under the system conditions (e g., in the presence of cooling) As a general rule, the temperature of high mass lenses (i e , lenses greater than about 70 grams) should remain under about 200 F and preferably between about 150 F and about 180 F Higher temperatures are typically associated with reduced lens yield rates due to cracking and/or premature release Generally, the lower mass lenses (l e . lenses no greater than about 45 grams) should be kept under about 150 F and preferably between about 1 10 F and about 140 F The first period may be selected according to the mass of the lens forming material In an embodiment, the lens formmg material has a mass of between about 45 grams and about 70 grams and the selected second temperature is a temperature between about 150 F and about 200 F According to another embodiment, the lens forming material has a mass no greater than about 45 grams and a second temperature less than about 150 F In yet another embodiment of the invention, the lens forming material has a mass of at least about 70 grams and a second temperature between about 170 r and about 190 F An experiment may be performed in which the radiation is removed from the mold members slightly before one-half of the time between T initial and Tmax The initial exposure time may be interatively reduced or increased accordmg to the results ofthe above experiment in subsequent experiments to provide a Tmax tn the preferred range This procedure may allow the determination of the optimal initial exposure time for any given mold/gasket set and light intensity A qualitative summary of relationships among system variables related to the above-described methods is shown in Fig 22 After the initial exposure period, a series of irradiation pulse/cooling steps may be performed to controllably discharge the remaining exothermic potential ofthe mateπal and thus complete the cure There are at least two approaches to accomplish this second process The first involves applying a large number of very short pulses and short cooling periods The second approach involves applying a fewer number of longer pluses with correspondingly longer cooling periods Either of these two methods may produce a good product and many acceptable cycles may exist between these extremes A significant aspect ofthe invention relates to using pulsed application of light to produce a large range (e g , from -6 to +4 diopter) of lenses without requiring refrigerated cooling fluid (e g , cooled air) With proper light application, air at ambient may be used as a cooling fluid, thus significantly reducing system costs Some established cycles are detailed in the table below for three semifinished mold gasket sets a 6 OOD base curve, a 4 50D base curve, and a 3 OOD base curve These cycles have been performed using an FC- 104 curing chamber in which cooling air at a temperature of about 56 degrees F was directed at the front and back surfaces of a mold assembly Frosted diffusing window glass was positioned between the samples and the lamps, with a layer of PO-4 acrylic material approximately 1 inch below the glass A top light intensity was adjusted to 760 mιcrowatts/cm : and a bottom light intensity was adjusted to 950 microwatts/cm 2 , as measured at about the plane ofthe sample A Spectroline meter DM365N and standard detector stage were used An in-mold coating as described in U S application seπal no 07/931,946 was used to coat both the front and back molds Figures 24, 25, and 26 each show temperature profiles of the above-detailed cycles for a case where the ultraviolet light exposure is continuous and a case where the ultraviolet light delivery is pulsed In Figures 23-26, "Io" denotes the initial intensity ofthe ultraviolet rays used in a curing cycle The phrase "Io=760/950" means 2 that the light intensity was adjusted to initial settings of 760 microwatts/cm for the top lamps and 950 2 microwatts/cm for the bottom lamps The "interior temperature" of Figures 23-26 refers to a temperature ofthe lens formmg material as measured by a thermocouple located within the mold cavity The following general rules for the design of pulse/cooling cycles may be employed to allow rapid curmg of a lens while inhibiting premature release and/or cracking ofthe lens The duration ofthe pulses preferably does not result in a temperature that exceeds the maximum temperature attained m the initial exposure period The length of the cooling period may be determined by the length of time necessary for the internal temperature ofthe lens forming material to return to near the temperature it had immediately before it received a pulse Following these general rules during routine experimentation may permit proper curing cycles to be established for a broad range of lens forming materials, light intensity levels, and cooling conditions Preferably light output is measured and controlled by varying the amount of power applied to the lights in response to changes in light output Specifically, a preferred embodiment of the invention includes a light sensor mounted near the lights This light sensor measures the amount of light, and then a controller increases the power supplied to maintain the first ultraviolet rays as the mtensity of the first ultraviolet rays decreases duπng use, and vice versa Specifically, the power is varied by varying the electric frequency supplied to the lights A filter is preferably applied to the light sensor so that light waves other than ultraviolet light impinge less, or not at all. on the light sensor In one embodiment, a piece of 365N Glass made by Hoya Optics (Fremont, California) was applied to a light sensor to filter out visible rays One "lamp driver" or light controller was a Mercron Model FX0696-4 and Model FX06120-6 (Mercron, Inc , Dallas, Texas, U S A ) These light controllers may be described in U S patents 4,717,863 and 4,937,470 Figure 13 schematically depicts the light control system described above The lights 40 in apparatus 10 apply light towards the lens holder 70 A light sensor 700 is located adjacent the lights 40 Preferably the light sensor 700 is a photoresistor light sensor (photodiodes or other light sensors may also be usable in this application) The light sensor 700 with a filter 750 is connected to lamp driver 702 via wires 704 Lamp driver 702 sends a current through the light sensor 700 and receives a return signal from the light sensor 700 The return signal is compared against an adjustable set point, and then the electrical frequency sent to the ultraviolet lights 40 via wires 706 is varied depending on the differences between the set point and the signal received from the light sensor 700 Preferably the light output is maintained within about +/- 1 0 percent In an embodiment ofthe invention, a medium pressure mercury vapor lamp is used to cure the lens forming mateπal and the lens coating This lamp and many conventional light sources used for ultraviolet light curing may not be repeatedly turned on and off since a several minute warm-up period is generally required prior to operation Mercury vapor light sources may be idled at a lower power setting between exposure periods (l e , second periods), however, the light source will still generate significant heat and consume electricity while at the lower power setting In an embodiment, a flash lamp emits ultraviolet light pulses to cure the lens forming material It is believed that a flash lamp would provide a smaller, cooler, less expensive, and more reliable light source than other sources The power supply for a flash lamp tends to draw relatively minimal current while charging its capacitor bank The flash lamp discharges the stored energy on a microsecond scale to produce very high peak intensities from the flash tube itself Thus flash lamps tend to require less power for operation and generate less heat than other light sources used for ultraviolet light curing A flash lamp may also be used to cure a lens coatmg In an embodiment, the flash lamp used to direct ultraviolet rays toward at least one of the mold members is a xenon light source The lens coating may also be cured using a xenon light source Referring to Fig 29, xenon light source 980 preferably contains photostrobe 992 having a tube 996 and electrodes to allow the transmission of ultraviolet rays The tube may include borosilicate glass or quartz A quartz tube will generally withstand about 3 to 10 times more power than a hard glass tube The tube may be m the shape of a rmg, U, helix, or it may be linear The tube may include capacitive trigger electrode 995 The capacitive trigger electrode may include a wire, silver strip, or conductive coating located on the exterior of tube 996 The xenon light source is preferably adapted to deliver pulses of light for a duration of less than about 1 second, more preferably between about 1/10 of a second and about 1/1000 of a second, and more preferably still between about 1/400 of a second and 1/600 of a second The xenon source may be adapted to deliver light pulses about everv 4 seconds or less The relatively high intensity of the xenon lamp and short pulse duration may allow rapid curing of the lens forming composition without imparting significant radiative heat to the composition In an embodiment, controller 990 (shown in Fig 29) controls the intensity and duration of ultraviolet light pulses delivered from ultraviolet light source 980 and the time interval between pulses Ultraviolet light source 980 may mclude capacitor 994, which stores the energy required to deliver the pulses of ultraviolet light Capacitor 994 may be adapted to allow pulses of ultraviolet light to be delivered as frequently as desired Temperature monitor 997 ma\ be located at a number of positions within mold chamber 984 The temperature monitor may measure the temperature within the chamber and/or the temperature of air exiting the chamber The system may be adapted to send a signal to cooler 988 and/or distributor 986 (shown in Fig 27) to vary the amount and/or temperature ofthe cooling air The temperature monitor may also determine the temperature at any of a number of locations proximate the mold cavity and send a signal to controller 990 to vary the pulse duration pulse intensity, or time between pulses as a function of a temperature within mold chamber 984 In an embodiment, light sensor 999 is used to determine the intensity of ultraviolet light emanatmg from source 980 The light sensor is preferably adapted to send a signal to controller 990, which is preferably adapted to maintain the intensity ofthe ultraviolet light at a selected level Filter 998 may be positioned between ultraviolet light source 980 and light sensor 999 and is preferably adapted to inhibit visible rays from contacting light sensor 999, while allowing ultraviolet rays to contact the sensor The filter may include 365 N glass or any other material adapted to filter visible rays and transmit ultraviolet rays In an embodiment a cooling distributor is used to direct air toward the non-casting face of at least one ofthe mold members to cool the lens forming composition The air may be cooled to a temperature of below ambient temperature prior to being directed toward at least one of the mold members to cool the composition ln an embodiment, air at ambient temperature may be used to cool the lens torming composition Since the xenon flash generally has a duration of much less than about one second, considerabl y less radiative heat tends to be transferred to the lens forming composition compared to curing methods emplo\ mg other ultraviolet sources Thus, the reduced heat imparted to the lens forming composition mav allow for air at ambient temperature to remove sufficient heat of exotherm to substantially inhibit premature release and or cracking ofthe lens In an embodiment, the xenon source is used to direct first ultraviolet rays toward the first and second mold members to the point that a temperature increase is measured and/or the lens forming composition begms to or forms a gel It is preferred that the gel is formed with less than 15 pulses of radiation, and more preferably with less than about 5 pulses It is preferred that the gel is formed before the total time to which the composition has been exposed to the pulses exceeds about 1/10 or 1/100 of a second In an embodiment, a reflecting device is employed in conjunction with the xenon light source The reflecting device is positioned behind the flash source and preferablv ailows an even distribution of ultraviolet rays from the center ofthe composition to the edge ofthe composition In an embodiment, a xenon light flash lamp is used to apply a plurality of ultraviolet light pulses to the lens forming composition to cure it to an eyeglass lens in a time period of less than 30 minutes, or more preferably, less than 20 or 15 minutes The use of a xenon light source also may allow the formation lenses over a wider range of diopters Higher power lenses exhibit greatest thinnest to thickest region ratios, meaning that more shrinkage-induced stress is created, causing greater mold flexure and thus increased tendency for premature release Higher power lenses also possess thicker regions Portions of lens forming material withm these thicker regions may receive less light than regions closer to the mold surfaces Continuous irradiation lens forming techniques typically require the use of relatively low light intensities to control the heat generated during curing The relatively low light intensities used tends to result in a long, slow gelation period Optical distortions tend to be created when one portion ofthe lens is cured at a different rate than another portion Methods characterized by non-uniform curmg are typically poorly suited for the production of relatively high power lenses, since the deeper regions (e g „ regions within a thick portion of a lens) tend to gel at a slower rate than regions closer to the mold surfaces The relatively high intensity attainable with the xenon source may allow deeper penetration mto, and/or saturation of, the lens forming material, thereby allowing uniform curing of thicker lenses than in conventional radiation-initiated curing More uniform gelation tends to occur where the lens formmg material is dosed with a high mtensity pulse of ultraviolet light and then subjected to decreased UV light or darkness as the reaction proceeds without activating radiation Lenses having a diopter of between about +5 0 and about -6 0 and greater may be cured It is believed that light distribution across the sample is less critical when curmg and especially when gelation is induced with relatively high intensity light The lens forming mateπal may be capable or aDSoromg an amount ot energy per time mat is oeiow mat αenvereα αuπng a relatively nign intensity pulse The lens forming material may be "oversaturated" with respect to the light delivered via a high mtensity flash source In an embodiment, the xenon source is used to cure a lens having a diopter between about -4 0 and about -6 0 In an embodiment, the xenon source is used to cure a lens having a diopter between about +2 0 and about +4 0 In an embodiment, more than one xenon light source is used simultaneously to apply ultraviolet pulses to the lens forming composition Such an embodiment is shown in Fig 28 Xenon light sources 980a and 980b may be positioned around mold chamber 985 so that pulses may be directed toward the front face of a lens and the back face of a lens substantially simultaneously Mold chamber 985 is preferably adapted to hold a mold in a vertical position such that pulses from xenon source 980a may be applied to the face of a first mold member, while pulses from source 980b may be applied to the face of a second mold member In an embodiment, xenon source 980b applies ultraviolet light pulses to a back surface of a lens more frequently than xenon source 980a applies ultraviolet light pulses to a front surface of a lens Xenon sources 980a and 980b may be configured such that one source applies light to mold chamber 984 from a position above the chamber while the other xenon source applies light to the mold chamber from a position below the chamber In an embodiment, a xenon light source and a relatively low intensity (e g , fluorescent) light source are used to simultaneously apply ultraviolet light to a mold chamber As illustrated in Fig 27, xenon source 980 may apply ultraviolet light to one side of mold chamber 984 while low intensity fluorescent source 982 applies ultraviolet light to another side ofthe mold chamber Fluorescent source 982 may include a compact fluorescent "light bucket" or a diffused fluorescent lamp The fluorescent light source may deliver continuous or substantially pulsed ultraviolet rays as the xenon source delivers ultraviolet pulses The fluorescent source may deliver continuous ultraviolet rays having a relatively low intensity of less than about 0 1 watts/cm Methods of the present invention allow curing of high-mass semi-finished lens blanks from the same material used to cure cast-to-finish lenses Both are considered to be "eyeglass lenses" for the puφoses ofthis patent These methods may also be used to cure a variety of other lens forming materials Methods of the present invention have been successfully used to make cast-to-finish lenses in addition to semi-finished lenses PULSE METHOD EXAMPLE 1 : USE OF A MEDIUM PRESSURE VAPOR LAMP An eyeglass lens was successfully cured with ultraviolet light utilizing a medium pressure mercury vapor lamp as a source of activating radiation (l e , the UVEXS Model 912 previously described herem) The curmg chamber included a six inch medium pressure vapor lamp operating at a power level of approximately 250 watts per inch and a defocused dichroic reflector that is highly UV reflective A high percentage of mfrared radiation was passed through the body ofthe reflector so that it would not be directed toward the material to be cured The curing chamber further included a conveyer mechanism for transporting the sample underneath the lamp With this curing chamber, the transport mechanism was set up so that a carriage would move the sample from the front ofthe chamber to the rear such that the sample would move completely through an irradiation zone under the lamp The sample would then be transported through the zone again to the front ot the chamber In this manner the sample was provided with two distinct exposures per cycle One pass, as defined hereinafter, consists of two of these distinct exposures One pass provided a dosage of approximately 275 milliJoules measured at the plane ofthe sample using an International Light IL 1400 radiometer equipped with a XRL 340 B detector A lens cavity was created using the same molds lens forming composition, and gasket of Pulsed Method Example 2 below The reaction cell containing the lens forming material was placed on a supporting stage such that the plane ofthe edges ofthe convex mold were at a distance of approximately 75 mm from the plane ofthe lamp The lens cavity was then exposed to a series of UV doses consisting of two passes directed to the back surface ofthe mold followed immediately by one pass directed to the front surface ofthe mold Subsequent to these first exposures, the reaction cell was allowed to cool for 5 minutes in the absence of any activating radiation tn an FC-104 chamber as described in Pulsed Method Example I at an air temperature of 74 6 degrees F and at an air flow rate of approximately 15 to 25 scf per minute to the back surface and 15 to 25 scf to the front surface of the cell The lens cavity was then dosed with one pass to the front mold surface and returned to the cooling chamber for 6 minutes Then the back surface was exposed in one pass and then was cooled for 2 mmutes Next, the front surface was exposed in two passes and then cooled for 3 5 minutes The front surface and the back surface were then each exposed to two passes, and the gasket was removed to expose the edges of the lens A strip of polyethylene film impregnated with photoinitiator was then wrapped around the edge ofthe lens and the front and back surfaces were exposed to another 3 passes each The back surface of the cell was then placed on the conductive thermal in-mold postcure device using "bean-bag" container filled with glass beads on a hot plate at about 340 F described previously (see conductive heating example 1 ) for a time period of 13 minutes, after which the glass molds were removed from the finished lens The finished lens exhibited a distance focusing power of -6 09 diopters, had excellent optics, was aberration-free, was 74 mm in diameter, and had a center thickness of 1 6 mm During the cooling steps , a small surface probe thermistor was positioned against the outside ofthe gasket wall to monitor the reaction The results are summarized below PULSE METHOD EXAMPLE 2: USE OF A SINGLE XENON FLASH LAMP An eyeglass lens was successfully cured with ultraviolet light utilizing a xenon flash lamp as a source of activating radiation The flash lamp used was an Ultra 1800 White Lightning photographic strobe, commercially available from Paul C Buff Incoφorated of Nashville, Tennessee This lamp was modified by replacing the standard borosilicate flash tubes with quartz flash tubes A quartz flash tube is preferred because some of the ultraviolet light generated by the arc inside the tube tends to be absorbed by borosilicate glass The strobe possessed two semicircular flash tubes that trigger simultaneously and are positioned to form a ring approximately 73 millimeters in diameter The hole in the reflector behind the lamps, which normally contams a modeling lamp for photographic puφoses, was covered with a flat piece of highly-polished ultraviolet reflective material, which is commercially available under the trade name of Alzac from Ultra Violet Process Supply of Chicago, Illinois The power selector switch was set to full power The ultraviolet energy generated from one flash was measured using an International Light IL 1700 Research Radiometer available from International Light, Incoφorated of Newburyport, Massachusetts The detector head was an International Light XRL 340 B, which is sensitive to radiation in the 326 nm to 401 nm region The window of the detector head was positioned approximately 35 mm from the plane ofthe flash tubes and was approximately centered within the ring formed by the tubes The results showed the power of one flash to be about 940 microwatts A mold cavity was created by placing two round 80 mm diameter crown glass molds into a silicone rubber ring or gasket which possessed a raised lip around its inner circumference The edges ofthe glass molds rested upon the raised lip to form a sealed cavity in the shape of the lens to be created The inner circumference of the raised lip corresponded to the edge ofthe finished lens The concave surface ofthe first mold corresponded to the front surface ofthe finished lens and the convex surface ofthe second mold corresponded to the back surface ofthe finished lens The height of the raised lip ofthe rubber ring mto which the two glass molds are inserted controls the spacing between the two glass molds, thereby controlling the thickness ofthe finished lens By selecting proper gaskets and first and second molds that possess various radii of curvature, lens cavities can be created to produce lenses of various powers A lens cavity was created by placing a concave glass mold with a radius of curvature of 407 20 mm and a convex glass mold with a radius of curvature of 65 26 mm into a gasket which provided spacing between the molds of 1 8 mm measured at the center of the cavity Approximately 32 grams of a lens forming monomer was charged into the cavity The lens forming material used for this test was OMB-91 lens monomer The reaction cell containing the lens forming material was placed horizontally on a supporting stage such that the plane ofthe edges ofthe convex mold were at a distance of approximately 30 mm from the plane ofthe flash tubes and the cell was approximately centered under the light source The back surface ofthe lens cavity was then exposed to a first series of 5 flashes, with an interval of approximately 4 seconds in between each flash The cell was then turned over and the front surface was exposed to another 4 flashes with intervals of about 4 seconds in between each flash It is preferable to apply the first set of flashes to the back surface to start to cure the material so that any air bubbles in the liquid monomer will not migrate from the edge ofthe cavity to the center ofthe optical zone ofthe lens Subsequent to these first nine flashes, the reaction cell was allowed to cool for five minutes in the absence of any activating radiation in the above-described FC-104 chamber To cool the reaction cell, air at a temperature of 71 4 degrees F and at a flow rate of approximately 15 to 25 scf per minute was applied to the back surface and air at a temperature of 71 4 degrees F and at a flow rate of approximately 15 to 25 scf per minute was applied to the front surface of the cell The back surface of the lens cavity was then dosed with one more flash and returned to the cooling chamber for four minutes Next, the cell was exposed to one flash on the front surface and cooled in the cooling chamber for seven mmutes Then the cell was exposed to one flash on the front surface and one flash on the back surface and cooled for three minutes Next, the cell was exposed to two flashes on the front surface and two flashes on the back surface and cooled for four and a half minutes The cell was then exposed to five flashes each to the back surface and front surface and the gasket was removed to expose the edges ofthe lens A strip of polyethylene film impregnated with photoinitiator (Irgacure 184) was then wrapped around the edge ofthe lens, and the cell was exposed to another tive flashes to the front surface and fifteen flashes to the back surface. 1 he back surface ofthe cell was then placed on the conductive thermal in-mold postcure device (i.e., "bean bags" filled with glass beads sitting on a hot plate at approx. 340 ° F) as described previously (see conductive heating example above) for a time period of 13 minutes, after which the glass molds were removed from the finished lens. The finished lens exhibited a distance focusing power of -6.16 diopters and a +2.55 bifocal add power, had excellent optics, was aberration-free, was 74 mm in diameter, and had a center of thickness of 1.7 mm. During the cooling steps , a small surface probe thermistor was positioned against the outside ofthe gasket wall to monitor the reaction. Tne results are summarized below. FURTHERIMPROVEMENTS IMPROVEDULTRAVIOLETLENSCURINGAPPARATUS FIG 30 depicts a schematic view of an embodiment of an ultraviolet lens curing apparatus 400 The apparatus preferably includes a first light generator 402 and a second light generator 404 for generating and directing ultraviolet light towards lens cell 52 First light generator 402 is preferably configured to direct ultraviolet light toward a first mold member of the lens cell, and second light generator 404 is preferably configured to direct ultraviolet light toward a second mold member ofthe lens cell The light generators 402 and 404 may be medium pressure mercury lamps for continuously directing ultraviolet light towards the lens cell or may be strobe light sources for delivering pulses of ultraviolet light to the lens cell In an embodiment, the strobe light source is a xenon source having a flash tube made of quartz In an alternate embodiment, the strobe light source is a xenon source having a flash tube made from, for example, borosilicate The apparatus may include shutter system 950 (shown in Fig 7) and programmable logic controller 952 The shutter system is preferably operable to block at least a portion of the ultraviolet light directed toward at least one ofthe mold members Programmable logic controller 952 is preferably coupled to the shutter and adapted to activate the shutter system The shutters are preferably adapted to extend to block passage of ultraviolet light toward the lens cell and are preferably adapted to retract to allow passage ofthe ultraviolet light toward the lens cell Apparatus 400 preferably includes an air manifold 406 that may substantially surround irradiation chamber 407 Air distribution device 94 is preferably disposed on the surface ofthe air manifold to direct air toward the non-casting face of at least one ofthe mold members The irradiation chamber preferably communicates with air plenum 412, which directs "effluent air" away from the irradiation chamber As described herein, "effluent air" is taken to mean air that has contacted at least one ofthe mold members to remove heat from the lens forming material contained within the mold cavity The lens cell is preferably secured within a lens holder of lens drawer 410 prior to being inserted into the irradiation chamber The lens drawer may be inserted within and removed from the irradiation chamber and is preferablv adapted to form a substantially airtight seal with the air manifold when inserted into the irradiation chamber Apparatus 400 preferably includes a first cooling assembly 414 and a second cooling assembly 416 for reducing the temperature ofthe air (and preferably cooling the air to a temperature below ambient temperature) before it is passed from air distribution device 94 to the lens cell FIG 32 depicts a cross-sectional view ofthe irradiation chamber and the cooling assemblies Irradiation chamber 408 is preferably enclosed with substantially airtight seals to inhibit or prevent cooling air from escaping from the chamber In an embodiment, members 420 and 422 may be positioned on the air distribution devices to form a substantially airtight seal Member 420 is preferably disposed between light generator 402 and the first mold member, and member 422 is preferably disposed between light generator 404 and the second mold member Members 420 and 422 may be plates and are preferably substantially transparent to the ultraviolet light delivered from light generators 402 and 404, respectively In an embodiment, members 402 and 404 are substantially clear borosilicate glass In an altemate embodiment, members 402 and 404 are light diffusers for diffusing the ultraviolet light directed to the lens cell The light diffusers are preferably made of borosilicate glass that has been sandblasted to "frost" the glass In an altemate embodiment, member 402 and 404 may be made from quartz glass In an embodiment, cooling assemblies 414 and 416 are thermoelectric cooling systems Cooling assembly 414 may be used to cool air directed toward the first mold member, and cooling assembly 416 may be used to cool air directed toward the second mold member The cooling assemblies are preferably sized to cool the air to a temperature between about 0°C and about 20°C Cooling assembly 414 preferably includes a thermoelectric module 422 for creating a temperature differential to allow the air to be cooled to below ambient temperature An exemplary thermoelectric module is shown in FIG 33 The thermoelectric module is preferably connected to a DC power source 440 The thermoelectric module is preferably a semiconductor wafer and preferably mcludes a plurality of semiconductor pn-couples disposed between a pair of ceramic plates 448 and 450 containing metallization 446 The pn-couples are preferably connected thermally in parallel and electrically in series The thermoelectric module may be a single-stage or cascade module When the thermoelectric module is connected to the DC power source, a phenomenon (I e , "the Peltier effect") occurs whereby heat is absorbed on cold side 448 and heat is dissipated from hot side 450 It is to be understood that the flow of current may be reversed to cause side 448 to dissipate heat while side 450 absorbs heat The publication entitled "An Introduction to Thermoelectπcs", available from Tellurex Coφ of Traverse City, Michigan discusses such thermoelectric modules and is incoφorated by reference as if fully set forth herein The pamphlet entitled "A Thermoelectric Bible on How to Keep Cool", available from Supercool Coφ of Minneapolis, Minnesota also describes a thermoelectric module and is incoφorated by reference as if fully set forth herein In FIG 31, the side ofthe thermoelectric module facing upwards is the hot side Cooling assembly 414 preferably includes a heat sink 428 coupled to the hot side to facilitate the dissipation of heat from the thermoelectric module The heat sink may be directly coupled to the hot side or the heat sink may be indirectly coupled to the hot side via a member having a relatively high thermal conductivity In FIG 31 , the heat sink is indirectly coupled to the hot side by conductive block 424 Insulation 426 preferably substantially surrounds the thermoelectric module and the conductive block In an embodiment, a fan 434 is used to direct air across heat sink 428 to mcrease the rate of heat dissipation from the thermoelectric module The heat sink preferably includes a plurality of fins which serve as a heat transfer surface The cold side of the thermoelectric module is preferably coupled to a cold side heat smk 430 serving to absorb heat to cool the air directed toward the lens cell The cold side heat sink may be located withm air conduit 453 and preferably contains a plurality of fins through which the air is passed to cool it Coolmg assembly 416 preferably includes second thermoelectric module 423, second conductive block 425, second hot side heat sink 429, and second fan 435. each of which may operate m the manner as described above for the elements included within cooling assembly 414 In an alternate embodiment, cooling assemblies 414 and 416 may be independently operable to allow air directed toward the first mold member to have a different temperature than air directed toward the second mold member A first blower 432 is preferably configured to direct air through air conduit 453, which communicates with air distribution device 94a Second blower 433 is preferably configured to direct air through air conduit 454, which communicates with air distribution device 94b As described herein, a "blower" is taken to mean any device operable to drive a fluid such as air through a conduit The first blower preferably drives air that is distributed across the non-casting face ofthe first mold member The second blower preferably drives air that is distributed across the non-casting face ofthe second mold member Effluent air that has contacted the non- casting face of at least one ofthe mold members is preferably passed through air plenum 412 and to blowers 432 and 433 for recycling to air distribution devices 94a and 94b Each of the thermoelectric modules is preferably sized to cool about 1-30 cubic feet per minute of heated effluent air to a temperature of about 0-20°C In an alternate embodiment, the cooling assemblies may be used to reduce the temperature ofthe recirculated air to ambient temperature or a temperature above ambient temperature The cooling assemblies may be activated when the cooling air exceeds a predetermined temperature level above ambient temperature The thermoelectric cooling system has been found to operate more quietly, efficiently, and reliably than some conventional cooling systems Recirculating the effluent air through the closed cooling loop tends to reduce the heat duty on the cooling system, since the effluent air in air plenum 412 preferably has a temperature less than ambient temperature In an embodiment, a control panel 418 is operable to manually or automatically control operation of apparatus 400 The control panel may include an electronic controller for automatic control of svstem variables and a digital display 415 indicating the temperature ofthe cooling air at various locations in the air conduits, irradiation chamber, and air plenum The control panel is preferably adapted to receive electronic signals from temperature sensors 460, 462, and 464 Cavities may also be formed in conductive blocks 424 and 425 to hold temperature sensors placed therein The blowers 432 and 433 may be activated or deactivated and the coolmg assemblies may be engaged or disengaged by switches on the control panel or by a programmable logic controller The flow rate of air passed across the mold members may be adjusted via the control panel, or the flow rate may be maintained at a constant rate during operation of blowers 432 and 433 A programmable logic controller 417 may be housed within the control panel Controller 417 is preferably adapted to independently control operation ofthe light generators 402 and 404 such that ultraviolet light is directed in a plurality of pulses toward at least one ofthe mold members The controller 417 is preferably programmable such mat a predetermined time elapses between eacn ot tne pulses to optimize tne curmg cycle The controller 417 may be adapted to cause the strobes to fire at predetermined times through the curmg cycle, thereby controlling the rate of polymerization and exothermic heat generation ofthe lens forming composition One programmable logic controller that has been found to perform adequately is the Little Star Microcontroller combined with a Relay Six relay board, both commercially available from Z- World Engineering of Davis, California The strobe firing sequence may be written in Dynamic C programming language The Ultra 1800 White Lightning photographic strobes, commercially available from Paul C Buff, Incoφorated of Nashville, Tennessee, have been found to perform adequately It is to be understood that embodiments of apparatus 400 may be combined with the methods and apparatus ofthe preferred embodiments described above in previous sections IMPROVED LENS CURING APPARATUS EXAMPLE An 80 mm diameter glass 28 flattop bifocal mold with a distance radius of curvature of -5 98 diopters and a +2 50 diopter bifocal add power was sprayed with a mixture of isopropyl alcohol and distilled water in equal parts and wiped dry with a lint free paper towel The mold was assembled into a silicone rubber gasket in combination with a cleaned convex mold possessing a radius of curvature of +4 1 1 diopters A raised hp present on the inner circumference ofthe rubber gasket provided a spacing of 4 2 mm between the two molds at the center point The mold/gasket assembly was positioned on a filling stage and the edge of the gasket was peeled back to permit the cavity to be filled with 14 4 grams of OMB-91 lens forming composition, commercially available from the FastCast Coφoration of Louisville, Kentucky The edge of the gasket was returned to its sealing relationship with the edges ofthe molds and excess lens forming composition was vacuumed off the non-casting surface ofthe back mold with a suction device The filled mold/gasket assembly was transferred from the filling stage to a stage incoφorated into a lens drawer of a strobe curing chamber The assembly was irradiated on both its sides according to the exposure cycle shown in FIG 34, which was controlled by a programmable logic controller The power settings on the strobes were adjusted to maximum power Duπng the irradiation, the lens cell was continuously exposed to streams of recirculated air directed by the blower and cooled by the thermoelectric cooling module shown in Figs 31 and 32 At the beginning ofthe cycle, the air temperature was 68 degrees F and at the end ofthe cycle is was measured at 73 degrees F The air temperature varied during the rest ofthe cycle up to temperatures as high as 90 degrees F, primarily as a result of the heat added to the system from both the strobe flash lamps and the exothermic heat generated by the lens formmg composition It is anticipated that the operating temperatures of the air could be reduced to well below ambient temperature and the curing cycle could be shortened by use of thermoelectric coolers having a greater capacity than those used in this experiment Ihe casting cell was turned over in the chamber so that its convex surface faced upwards and was dosed with 13 flashes to the convex surface and 10 flashes to the concave surface The casting cell was removed from the strobe chamber, the gasket was stripped from the assembly, and residual uncured mateπal was wiped from the exposed edge of the lens The cell was returned to the chamber with its concave side facing up and was dosed with an additional 13 flashes to the concave surface and 10 flashes to the convex surface The non-casting surfaces of both the front and the back molds were placed in contact with thermal transfer pads, commercially available from the FastCast Coφoration of Louisville. Kentucky, at temperatures of approximately 150 to 200 degrees F for ten minutes The assembly was removed from the thermal transfer pad and the back mold was removed with a slight impact from an appropriately sized wedge The lens with the front mold attached was placed in a container of water at room temperature and the lens separated from the front mold The now finished lens was sprayed with a mixture of isopropyl alcohol and water in equal parts and wiped dry The finished lens was 4 0 mm thick at the center and was 74 mm in diameter The lens exhibited a focusing power of + 1 98 -0 02D with a bifocal addition power of +2 54D, provided good optical quality, and was non- yellow IMPROVED LENS CURING PROCESS When casting an eyeglass lens with ultraviolet light, the gelation pattern ofthe lens forming composition may affect the resultant optical quality ofthe lens If there are localized discontinuities in the light intensities received by the monomer contained in the casting cavity during the early stages of the polymerization process, optical distortions may be seen in the finished product Higher power lenses are, by definition, thicker in certain regions than relatively lower power lenses ofthe same diameter The layers of a lens closest to the mold faces of the casting cavity tend to receive a higher light intensity than the deeper layers because the lens forming composition absorbs some of the incident light This causes the onset of polymerization to be delayed in the deeper layers relative to the outer layers, which may cause optical distortions in the finished product It ts believed that concurrent with this differential curing rate, there is a difference in the rate of exothermic heat generation, specifically, the deeper regions will begin to generate heat after the outer regions in the cavity have already cured and the effectiveness ofthe heat removal may be impaired, contributing to optical waves and distortions in the finished product This phenomena is particularly observable in high powered positive lenses due to the magnification of such defects In an embodiment, the lens forming composition contained within the casting cavity is exposed to relatively high intensity ultraviolet light for a time period sufficient to initialize the reaction Irradiation is terminated before the polymerization ofthe lens formmg composition proceeds far enough to generate a substantial amount of heat This initial relatively high intensity dose preferably substantially uniformly gels the material within the casting cavity such that the difference in the rate of reaction between the inner and outer layers ofthe lens being cured is reduced, thereby eliminating the waves and distortions often encountered when using continuous low intensity irradiation to initialize the reaction, particularly with high dioptric power positive lenses In an embodiment, the relatively high intensity dose of ultraviolet light is applied to the lens formmg composition in the form of pulses The pulses preferably have a duration of less than about 10 seconds, preferably less than about 5 seconds, and more preferably less than about 3 seconds The pulses preferably have an intensity of at least about 10 mιllιwatts/cm 2 , more preferably at least about 100 mιllι\vatts/cm 2 , and more preferably still between about 150 mιllιwatts/cm 2 and about 250 milliwatts/cm 2 It is preferred that substantially all ofthe lens forming composition forms into a gel after the initial application ofthe relatively high mtensity ultraviolet light In an embodiment, no more than an insubstantial amount of heat is generated by exothermic reaction of the lens forming composition durmg the initial application of the relatively high intensity ultraviolet light Subsequent to this initial high intensity dose, a second irradiation step is performed in which the material contained within the casting cell is preferably irradiated for a relatively longer time at a relatively lower intensity while cool fluid is directed at the non-casting surface of at least one ofthe molds forming the cavity The coolmg fluid preferably removes the exothermic heat generated by the polymerization of the lens forming composition If the intensity ofthe ultraviolet light is too great duπng this second irradiation step, the rate of heat generation will tend to be too rapid and the lens may release prematurely from the casting face of the mold and/or crack Similarly, should the rate of heat removal from the lens forming composition be too slow, the lens may release prematurely and/or crack It is preferred that the mold/gasket assembly containing the lens forming composition be placed withm the cooling environment as shortly after the initial dose of ultraviolet light as possible In an embodiment, the ultraviolet light applied to the lens forming composition during the second irradiation step is less about 350 microwatts/cm 2 , more preferably less than about 150 microwatts/cm 2 , and more preferably still between about 90 microwatts/cm 2 and about 100 microwatts/cm 2 During the second irradiation step, the ultraviolet light mav be applied to the lens forming composition continuously preferred or in pulses A translucent high density polyethylene plate may be positioned between the ultraviolet light generator and at least one ofthe mold members to reduce the intensity ofthe ultraviolet light to within the preferred range In an embodiment, relatively high intensity ultraviolet light is applied to the lens curing composition in a third irradiation step to post cure the lens subsequent to the second relatively low intensity irradiation step In the third irradiation step, pulses of ultraviolet light are preferably directed toward the lens formmg composition, although the composition may be continuously irradiated instead The pulses preferably have an intensity of at least about 10 milhwatts/cnr. more preferably at least about 100 mιllιwatts/cm 2 , and more preferably still between about 100 mιllιwatts/cm 2 and about 150 milliwatts/cm 2 Each ofthe above-mentioned irradiation steps is preferably performed by directing the ultraviolet light through each ofthe first and second mold members The eyeglass lens is preferably cured in a total time of less than 30 mmutes and is preferably free of cracks, striations, distortions, haziness, and yellowness It is believed that the above-described methods enable the production of whole lenses in prescription ranges beyond those currently attainable with continuous low intensity irradiation The method can be practiced in the curing of relatively high or low power lenses with a reduced incidence of optical distortions in the finished lens as compared to conventional methods It is to be understood that the above-described methods may be used independently or combined with the methods and apparatus ofthe preferred embodiments described above m the previous sections IMPROVED CURING PROCESS EXAMPLE An 80 mm diameter glass progressive addition mold with a nominal distance radius of curvature of -6 00 diopters and a +2 50 diopter bifocal add power was sprayed with a mixture of isopropyl alcohol and distilled water in equal parts and wiped dry with a lint free paper towel The progressive mold was lenticulaπzed to provide an optical zone 68 mm in diameter along the 180 degree meridian and 65 mm in diameter along the 90 degree meridian The non-casting face ofthe mold was mounted to a suction cup, which was attached to a spindle The spindle was placed on a spinning device provided m the FastCast UX-462 FlashCure Unit, commercially available from the FastCast Coφoration of Louisville, Kentucky A one inch diameter pool of liquid Primer was dispensed into the center ofthe horizontally positioned glass mold from a soft polyethylene squeeze bottle equipped with a nozzle with an orifice diameter of approximately 0 040 inches The composition ofthe Primer is discussed in detail below (see Scratch Resistant Lens Formation Process Example) The spin motor was engaged to rotate the mold at a speed of approximately 850 to 900 revolutions per mmute, which caused the liquid material to spread out over the face ofthe mold Immediately thereafter, a steady stream of an additional 1 5 to 2 0 grams of Primer material was dispensed onto the casting face ofthe spinning mold with the nozzle tip positioned at a 45 degree angle approximately 12 mm from the mold face such that the stream was flowing with the direction of rotation of the mold The stream of Primer material was directed first at the center of the mold face and then dispensed along the radius of the mold face m a direction from the center toward the edge ofthe mold face The solvent present in the Primer was allowed to evaporate off for 8 to 10 seconds while the mold was rotated The rotation was stopped and the Primer coat present on the mold was cured via two exposures to the ultraviolet output from the medium pressure mercury vapor lamp contained in the UX- 462 FlashCure unit, totaling approximately 300 mJ/cm 2 The spin motor was again engaged and approximately 1 5 to 2 0 grams of HC8-H Hard Coat (see description below), commercially available from the FastCast Coφoration of Louisville, Kentucky was dispensed onto the spinning mold in a similar fashion as the Primer coat The solvent present in the HC8-H was allowed to evaporate off for 25 seconds while the mold was rotated The rotation was stopped and the HC8-H coat was cured in the same manner as the Primer coat The mold was removed from the FlashCure unit and assembled into a sihcone rubber gasket m combination with a cleaned convex mold possessing a radius of curvature of +2 00 diopters The raised lip present on the mner circumference ofthe rubber gasket provided a spacing of 6 3 mm between the two molds at tne center point, l ne moid/gasκet assembly was positioned on a tilling stage and tne edge ot tne gasket was peeled back to permit the cavity to be filled with OMB-91 lens forming composition, commercially available from the FastCast Coφoration of Louisville, Kentucky. The edge ofthe gasket was returned to its sealing relationship with the edges ofthe molds and the excess lens forming composition was vacuumed off the non- casting surface ofthe back mold with a suction device. The filled mold/gasket assembly was placed on a stage in the UX-462 FlashCure unit and subjected to four exposures ofthe ultraviolet ouφut from the six inch medium pressure mercury vapor lamp, totaling approximately 600 mJ/cm 2 . Immediately following this initial dose of high intensity ultraviolet light, the assembly was transferred to the FC-132 curing chamber where the casting cell was continuously exposed to streams of air having a temperature of 42 degrees F while being irradiated with very low intensity ultraviolet light for eight minutes. The light intensity measured approximately 90 microwatts/cm 2 from above plus approximately 95 microwatts/cm 2 from below, which is below the plus lens light distribution pattern called for by the manufacturer. The lamp racks are typically configured to deliver ultraviolet light having an intensity of about 300 microwatt/cm 2 for the standard fifteen minute curing cycle. The reduction in ultraviolet light intensity was accomplished by inserting a translucent high density polyethylene plate into the light distribution filter plate slot along with the plus lens light distribution plate. A translucent high density polyethylene plate was positioned between the front mold member and one light distribution plate and between the back mold member and the other light distribution plate. The assembly was subsequently returned to the UX-462 FlashCure unit and the non-casting surface of the back mold was exposed to four doses of high intensity UV light totaling approximately 1150 mJ/cm 2 . The gasket was stripped from the assembly and residual uncured material wiped from the exposed edge ofthe lens. An oxygen barrier strip (polyethylene) was wrapped around the edge of the lens and the mold was exposed to two more doses of high intensity UV light totaling 575 mJ/cm 2 to the non-casting surface ofthe front mold followed by eight more flashes to the non-casting surface ofthe back mold totaling 2300 mJ/cm 2 . The non-casting surface of the back mold was placed in contact with a thermal transfer pad, commerciaUy available from the FastCast Coφoration of Louisville, Kentucky, at a temperature of approximately 150 to 200 degrees F for thirteen minutes. The assembly was removed from the thermal transfer pad and the back mold was removed with a slight impact from an appropriately sized wedge. The front mold with the lens attached thereto was placed in a container of room temperature water and the lens separated from the front mold. The now-finished lens was sprayed with a mixture of isopropyl alcohol and water in equal parts and wiped dry. The lens read +3.98 D with an addition power of +2.50, was clear , non-yellow, and exhibited good optics. IMPROVED SCRATCH RESISTANT LENS FORMATION PROCESS The "in-mold" method involves forming a scratch resistant coating over an eyeglass lens by placing the liquid coating in a mold and subsequently curing it. The in-mold method is advantageous to "out-of-mold" methods since the in-mold method exhibits less occurrences of coating defects manifested as irregularities on the anterior surface ofthe coating Using the in-mold method produces a scratch resistant coating that replicates the topography and smoothness ofthe mold casting face However, a problem encountered when using conventional in-mold scratch resistant coatings is that minute "pmholes" often form m the coating It is believed that the pmholes are caused by either contaminants on the mold, airborne particles falling on the coating before it is cured, or bubbles formed during the application ofthe coating which burst afterwards The formation of such pmholes is especially prevalent when using a flat-top bifocal mold, such as the one depicted in Fig 35 As illustrated, an indentation 452 ofthe bifocal segment 454 below the main surface 456 of the mold reduces the smoothness ofthe casting face When a coating is spin-coated over the mold face, this indentation becomes an obstacle to the even flow ofthe castmg face The pinhole defects are mainly a problem in tinted lenses because the dye used to tint a lens can penetrate through the pmholes, resulting m a tiny speck of dye visible in the lens According to an embodiment ofthe invention, a first coating composition, i e , a polymerizable "primer" material is passed through a filter and then placed within a mold member having a casting face and a non-casting face The first coating composition preferably contains a photoinitiator to make it curable upon exposure to ultraviolet light The mold member may then be spun so that the first composition becomes distributed over the casting face The mold member is preferably rotated about a substantially vertical axis at a speed between about 750 and about 1000 revolutions per minute Further, a dispensing device may be used to direct an additional amount ofthe first composition onto the casting face while the mold member is spinning The dispensing device preferably moves from the center ofthe mold member to an edge of the mold member so that the additional amount is directed along a radius of the mold member Ultraviolet light is preferably directed at the mold member to cure at least a portion ofthe first composition A second coating composition may then be placed upon the first composition in the mold member The second coating is also preferably curable when exposed to ultraviolet light because it contains a photoinitiator The mold member is again spun to distribute the second coating composition over the cured portion of the first coating composition The mold member may also be spun simultaneously while adding the second composition to the mold member Ultraviolet light is then preferably directed at the mold member to simultaneously cure at least a portion ofthe second coating composition and form a transparent combination coat having both coating compositions The combination coat is preferably a substantially scratch-resistant coating The mold member may then be assembled with a second mold member by positioning a gasket between the members to seal them Therefore, a mold having a cavity shared by the original two mold members is formed An edge ofthe gasket may be displaced to insert a lens-forming composition into the cavity The combmation coat and the lens-forming material preferably adhere well to each other This lens-forming composition preferably comprises a photoinitiator and is preferably cured usmg ultraviolet light Air which preferably has a temperature below ambient temperature may be directed toward a non-casting face of the second mold member to cool the lens- forming composition while it is being cured The pnmer coat preferably comprises a mixture of high viscosity monomers, a low viscosity, low flashpoint organic solvent, and a suitable photoinitiator system The solvent may make up about more than 80 % ofthe mixture, preferably about 93% to 96% This mixture preferably has low viscosity and preferably covers any surface irregularity duπng the spin application, for example the segment line of a flat-top bifocal mold The low flashpoint solvent preferablv evaporates off relatively quickly, leaving a thin layer of high viscosity monomer, containing photoinitiator, which coats the casting face ofthe mold The cured primer coat is preferably soft to allow it to adhere well to the glass mold face Since the primer coat is soft, it may not possess scratch resistant characteristics However, applying a high scratch resistance hard coating (l e the second coatmg composition) to the primer coat preferably results m a scratch resistant combination coat The hard coat preferably contains a solvent which evaporates when the mold member is rotated to distribute the hard coatmg over the primer coat In general, the ideal primer material preferably possesses the following characteristics exhibits chemical stability at normal storage conditions, e g at room temperature and in the absence of ultraviolet light, flows well on an irregular surface, especially over a flat-top bifocal segment, when cured with a specified ultra¬ violet dose, leaves a crack-free coating, with a high double bond conversion (approximately greater than 80%), maintains adhesion with the mold face through the lens forming curing cycle, especially the segment part ofthe flat-top bifocal mold, and is chemically compatible with the hard coat which is subsequently applied on top of it, e g forms an optically clear combmation coat Even though pinhole defects may be present in either the primer coat or the hard coat, it is highly unlikely that defects in one coat would coincide with defects of another coat Each coat preferably covers the holes ofthe other coat, resulting in less pmholes in the combination coat Thus, the finished m-mold coated lens may be tinted using dye without problems created by pmholes It is also preferably free of cracks, yellowness, haziness, and distortions In an embodiment, the gasket between the first mold member and the second mold member may be removed after a portion of the lens-forming material has been cured The removal of the gasket preferably exposes an edge of the lens An oxygen barrier having a photoinitiator may be placed around the exposed edge of the lens, wherem the oxygen barrier photoinitiator is preferably near an uncured portion of the lens-forming composition Additional ultraviolet rays may then be directed towards the lens to cause at least a portion of the oxygen barrier photoinitiator to initiate reaction ofthe lens- forming material The oxygen barrier preferably prevents oxygen from contacting at least a portion ofthe lens formmg composition during exposure ofthe lens to the ultraviolet rays According to one embodiment, a substantially solid conductive heat source is applied to one ofthe mold members Heat may be conductively transferred from the heat source to a face of the mold member Further, the heat may be conductively transferred through the mold member to the face of the lens SCRATCH RESISTANT LENS FORMATION PROCESS EXAMPLE A first coating composition, hereinafter referred to as "Primer", was prepared bv mixing the following components by weight 93 87% acetone, 3 43% SR-399 (dipentaerythritol pentaacrylate), available from Sartomer, 2 14% CN-104 (epoxy acrylate), available from Sartomer, 0 28% Irgacure 184 (1-hydroxycyclohexylphenylketone), available from Ciba-Geigy, and 0 28% Darocur 1 173 (2-hydroxy-2-methyl-l-phenyl-propan-l -one) available from Ciba-Geigy A second coating composition, hereinafter referred to as "HC8-H" was prepared by mixing the following components by weight 84 69% 1 -methoxy 2-propanol 9 45% SR-399 (dipentaerythritol pentaacrylate), available from Sartomer, 4 32% SR601 (ethoxylated bisphenol A diacrylate), available from Sartomer, and 1 54% Irgacure 184 (1 -hydroxycyclohexyl- phenyl ketone), available from Ciba-Geigy Each of these coating compositions was prepared by first dissolving the monomers into the solvent, then addmg the photoinitiators, mixing well, and finally passing the composition through a one micron filter prior to use An 80 mm diameter glass 28 mm flattop mold with a distance radius of curvature of -6 00 diopters and a +2 00 diopter bifocal add power were sprayed with a mixture of isopropyl alcohol and distilled water in equal parts The flattop mold was wiped dry with a lint free paper towel The non-casting face of the mold was mounted to a suction cup, which was attached to a spindle The spmdle was placed on the spinning device provided in the FastCast UX-462 FlashCure Unit, commercially available from the FastCast Coφoration of Louisville, Kentucky A one inch diameter pool of liquid Primer was dispensed into the center of the horizontally positioned glass mold The Primer was dispensed from a soft polyethylene squeeze bottle equipped with a nozzle havmg an oπfice diameter of approximately 0 040 inches A spin motor of the spinning device was engaged to rotate the mold at a speed of approximately 850 to 900 revolutions per mmute, causmg the liquid Primer to spread out over the face ofthe mold Immediately thereafter, a steady stream of an additional 1 5 to 2 0 grams of Primer mateπal was dispensed onto the casting face ofthe spinning mold The stream of Primer material was directed onto the castmg face with the nozzle tip positioned at a 45 degree angle approximately 12 mm from the mold face This positioning ofthe nozzle tip made the stream to flow with the direction of rotation of the mold The stream of rTimer material was directed tirst at tne center oi tne moid tace and men dispensed aiong tne raoius ot tne mold face in a direction from the center toward the edge ofthe mold face The solvent present in the Primer was allowed to evaporate off for 8 to 10 seconds durmg rotation ofthe mold The rotation was stopped and the Primer coat which remained on the mold was cured via two exposures to the ultraviolet output from the medium pressure mercury vapor lamp contained in the UX-462 FlashCure unit, totaling approximately 300 mJ/cm 2 . All light intensity/dosage measurements cited herein were taken with an International Light IL-1400 Radiometer equipped with an XLR-340B Detector Head, both commercially available from International Light, Inc. of Newburyport, Massachusetts. Upon exposure to the ultraviolet light, the spin motor was again engaged and approximately 1 5 to 2.0 grams of HC8-H Hard Coat, commercially available from the FastCast Coφoration of Louisville, Kentucky was dispensed onto the spinning mold in a similar fashion as the Primer coat. The solvent present in the HC8-H was allowed to evaporate off for 25 seconds while the mold was spinning The rotation was stopped, and the HC8-H coat was cured in the same manner as the Primer coat The mold was removed from the FlashCure unit and assembled into a silicone rubber gasket in combination with a cleaned convex mold possessing a radius of curvature of +7 50 diopters. The raised lip present on the inner circumference ofthe rubber gasket provided a spacing of 1 8 mm between the two molds at the center point. At this point, the mold/gasket assembly was positioned on a filling stage and the edge ofthe gasket was peeled back to permit the cavity to be filled with OMB-91 lens forming composition, commercially available from the FastCast Coφoration of Louisville, Kentucky. The edge ofthe gasket was returned to its sealing relationship with the edges ofthe molds and the excess lens forming composition was vacuumed off the non-castmg surface of the back mold with a suction device The filled mold/gasket assembly was transferred from the filling stage to an FC-132 curing chamber, commercially available from the FastCast Coφoration of Louisville, Kentucky While in the chamber, the assembly was continuously irradiated from both sides for a period of 15 minutes at approximately 300 microwatts/cm 2 from above and at approximately 350 microwatts/cm 2 from below, according to the minus lens light distribution pattern called for by the manufacturer. During the irradiation, the casting cell was continuously exposed to streams of air having a temperature of 42° F. The mold/gasket assembly was subsequently returned to the UX-462 FlashCure unit. The non-castmg surface ofthe back mold was exposed to four doses of high intensity UV light totaling approximately 1 150 mJ/cm 2 . The gasket was stripped from the assembly and residual uncured material was wiped from the exposed edge of the lens. An oxygen barrier strip (polyethylene) was wrapped around the edge ofthe lens. The mold/gasket assembly was exposed to two more doses of high intensity UV light, wherein 575 mJ/cm 2 total was directed to the non-castmg surface ofthe front mold. Subsequently, eight more flashes ofthe UV light were directed to the non-casting surface of the back mold, totaling 2300 mJ/cm 2 The non-casting surface ofthe back mold was placed in contact with a thermal transfer pad, commercially available from the FastCast Coφoration of Louisville, Kentucky, at a temperature of approximately 150 to 200° F for thirteen minutes The mold/gasket assembly was removed from the thermal transfer pad, and the back mold was removed with a slight impact from an appropriately sized wedge The front mold with the lens attached thereto was placed in a container of room temperature water While within the water, the lens became separated from the front mold The now-finished lens was sprayed with a mixture of isopropyl alcohol and water in equal parts and wiped dry The lens was positioned in a holder and placed into a heated dye pot for 5 mmutes The dye pot contained a solution of BPI Black, commercially available from Brain Power Inc of Miami, Florida, and distilled water at a temperature of approximately 190 degrees F The lens was removed from the dye pot, rmsed with tap water, and wiped dry The lens exhibited a total visible light absorbance of approximately 80% When inspected for cosmetic defects on a light table, no pinhole defects were observed Further, the tint which had been absorbed by the back surface of the lens was found to be smooth and even NON-POLYMERIZABLE SCRATCH RESISTANT COATING PROCESS METHOD A non-polymeπzable coatmg composition, hereinafter referred to as "Precoat' , was prepared by mixing the following materials by weight 99 80% acetone, and 0 20% BYK-300, a slip agent commercially available from BykChemie An 80 mm diameter glass 28 mm flattop mold with a distance radius of curvature of -6 00 diopters and a +2 00 diopter bifocal add power was sprayed with a mixture of isopropyl alcohol and distilled water in equal parts The mold was subsequently wiped drv with a lint free paper towel The non-castmg face of the mold was mounted to a suction cup, which was attached to a spindle The spindle was placed on the spinning device provided in the FastCast UX-462 FlashCure Unit, commercially available from the FastCast Coφoration of Louisville, Kentucky A spin motor ofthe spinning device was engaged to rotate the mold at a speed of approximately 850 to 900 revolutions per mmute A steady stream of approximately 2 0 to 3 0 grams of Precoat material was dispensed onto the casting face ofthe spmnmg mold with the nozzle tip positioned at a 45 degree angle approximately 12 mm from the mold face, thereby causing the stream to flow with the direction of rotation ofthe mold The stream of Precoat mateπal was directed first at the center ofthe mold face The stream was then dispensed along the radius ofthe mold face in a direction from the center toward the edge ofthe mold face The intended puφose of the Precoat was to improve the wetting characteristics of the glass mold so that the HC8-H material would flow over it more evenly The solvent present in the Precoat evaporated off the spinning mold almost instantly, and approximately 1.5 to 2.0 grams of HC8-H Hard Coat was dispensed onto the casting face of the spinning mold. The HC8-H Hard Coat was directed onto the casting face along the radius ofthe mold face in a direction from the center toward the edge. The nozzle tip was positioned at a 45 degree angle approximately 12 mm from the mold face such that the stream was flowing with the direction of rotation of the mold. The solvent present in the HC8-H was allowed to evaporate off for 25 seconds while the mold was spinning. The rotation was stopped, and the HC8-H coat was cured via two exposures to the ultraviolet output from the medium pressure mercury vapor lamp contained in the UX-462 FlashCure unit, totaling approximately 300 mJ/cm 2 . The mold was removed from the FlashCure unit and assembled into a silicone rubber gasket in combination with a cleaned convex mold possessing a radius of curvature of +7.50 diopters. The raised lip present on the inner circumference ofthe rubber gasket provided a spacing of 1.8 mm between the two molds at the center point. The mold/gasket assembly was positioned on a filling stage and the edge ofthe gasket was peeled back to permit the cavity to be filled with OMB-91 lens forming composition, commercially available from the FastCast Coφoration of Louisville, Kentucky. The edge of the gasket was returned to its sealing relationship with the edges ofthe molds. The excess lens forming composition was vacuumed from the non- casting surface of the back mold with a suction device. The filled mold/gasket assembly was transferred from the filling stage to an FC-132 curing chamber, commercially available from the FastCast Coφoration of Louisville, Kentucky. The assembly was continuously irradiated from both sides for a period of 15 minutes at approximately 300 microwatts/cm 2 from above and approximately 350 microwatts/cm 2 from below, according to the minus lens light distribution pattern called for by the manufacturer. During the irradiation, the casting cell was continuously exposed to streams of air having a temperature of 42° F. The assembly was subsequently returned to the UX-462 FlashCure unit. The non-casting surface ofthe back mold was exposed to four doses of high intensity UV light, totaling approximately 1 150 mJ/cm 2 . The gasket was stripped from the assembly, and residual uncured material was wiped from the exposed edge ofthe lens. An oxygen barrier strip (i.e., polyethylene) was wrapped around the edge of the lens and the cell was exposed to two more doses of high intensity UV light, wherein 575 mJ/cm 2 total were directed to the non-casting surface ofthe front mold. Eight more flashes of high intensity UV light followed. The eight flashes exposed the non-casting surface ofthe back mold to a total of 2300 mJ/cm 2 . The non-casting surface ofthe back mold was placed in contact with a thermal transfer pad at a temperature of approximately 150 to 200° F for thirteen minutes. The assembly was removed from the thermal transfer pad, and the back mold was removed with a slight impact from an appropriately sized wedge. The front mold with the lens attached thereto was placed in a container of room temperature water in order to cause the lens to be separated from the front mold. The now-finished lens was sprayed with a mixture of isopropyl alcohol and water in equal parts and wiped dry. The lens was positioned in a holder and placed into a heated dye pot for 5 minutes The dye pot contained a solution of BPI Black, commercially available from Brain Power, Inc of Miami, Florida, and distilled water at a temperature of approximately 190° F The lens was removed from the dye pot, rinsed with tap water and wiped dry The lens exhibited a total visible light absorbance of approximately 80% When inspected for cosmetic defects on a light table, several pinhole tint defects were observed They appeared to be in the range of 0 2 mm to 0 05 mm in diameter However, the tint which had been absorbed by the back surface of the lens was found to be smooth and even Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view ofthis description Accordingly, this description is to be construed as illustrative only and is for the puφose of teaching those skilled in the art the general manner of carrying out the invention It is to be understood that the forms ofthe invention shown and described herein are to be taken as the presently preferred embodiments Elements and materials may be substituted for those illustrated and descnbed herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention Changes may be made in the elements and compositions described herein or in the features or in the sequence of features ofthe methods described herein without departing from the spirit and scope ofthe invention as described in the following claims

Claims: What is claimed is 1 A method for making a plastic eyeglass lens, comprising placmg a liquid polymerizable lens forming composition in a mold cavity defined by at least a gasket, a first mold member, and a second mold member, directing first ultraviolet rays toward at least one ofthe mold members to substantially cure the lens formmg composition so that it forms a lens with a back face, edges, and a front face, and wherem a portion ofthe lens forming composition proximate the edges ofthe lens is not fully cured, removing the gasket to expose the edges ofthe lens, applying an oxygen barrier comprising a photoinitiator around the exposed edges ofthe lens such that at least a portion ofthe oxygen barπer photoinitiator is proximate lens forming composition that is not fully cured, and directing second ultraviolet rays towards the lens such that at least a portion ofthe oxygen barrier photoinitiator initiates reaction of lens forming composition while the oxygen barrier substantially prevents oxygen from outside the oxygen barrier from contacting at least a portion ofthe lens formmg composition 2 The method of claim 1 wherein the lens forming composition is cured to form the lens m less than thirty minutes 3 The method of claim 1 wherein the first and second ultraviolet rays have substantially similar intensities and substantially similar wavelengths 4 The method of claim 1 , further comprising tinting the lens 5 The method of claim 1 wherein a portion of the liquid lens forming composition proximate to the gasket remams a liquid after the first ultraviolet rays are directed towards at least one of the mold members 6 The method of claim 1, wherein a portion ofthe liquid lens forming composition proximate to the gasket remams a liquid after the first ultraviolet rays are directed towards at least one ofthe mold members, and further comprising removing at least part of such remaining liquid lens forming composition from the lens after the gasket is removed but before the second ultraviolet rays are directed towards the lens The method of claim 1 wherein at least a portion ofthe lens forming composition is cured by application ofthe second ultraviolet rays 8 The method of claim 1 wherein the edges ofthe lens are substantially dry after the second ultraviolet rays are directed towards the lens The method of claim 1 , further comprising directing third ultraviolet rays towards the lens before the gasket is removed 10 The method of claim 1 , further comprising removing the oxygen barrier 1 1 The method of claim 1, further comprising cooling the lens or allowing the lens to cool, and then removing the oxygen barrier 12 The method of claim 1 wherein the oxygen barrier comprises a flexible film that is at least partially transparent to ultraviolet rays 13 The method of claim 1 wherem the oxygen barrier comprises a stretchable self-sealing film that is at least partially transparent to ultraviolet rays 14 The method of claim I wherein the oxygen barrier comprises polyethylene impregnated with a photoinitiator 15 The method of claim 1 wherein the lens forming composition compπses less than about 0 15 percent photoinitiator 16 The method of claim 1 wherein the oxygen barrier comprises a film that was made by applying a solution comprising a photoinitiator to a plastic film 17 The method of claim 1 wherein the oxygen barrier compπses a film that was made by applymg a solution comprising an etching agent and a photoinitiator to a plastic film 18 The method of claim 1 wherein the oxygen barrier comprises a film that was made by (a) immersmg a plastic film in a solution comprising a photoinitiator, (b) removing the plastic film from the solution, and (c) drying the plastic film 19 The method of claim 1 wherein the oxygen barrier compπses a film that was made by (a) immersmg a plastic film in a solution comprising a photoinitiator, (b) removing the plastic film from the solution, (c) applying a solvent to the plastic film, and (d) drying the plastic film 20. The method of claim 1 wherein the oxygen barrier comprises a film that was made by (a) immersing a plastic film in a solution comprising a photoinitiator and an etching agent (b) removing the plastic film from the solution, (c) applying a solvent to the plastic film, and (d) drying the plastic film. 21. The method of claim 1 wherein the oxygen barrier comprises a plastic film that is less than about 0.025 mm thick. 22. The method of claim 1 , further comprising applying a mold member of the mold cavity to a substantially solid conductive heat source and conductively applying heat to a face ofthe lens by (a) conductively transferring heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the face ofthe lens. 23. The method of claim 1, further comprising: shaping a flexible heat distributor placed on top of a conductive heat source such that the shape of the heat distributor substantially conforms to a shape of an outside face of a mold member of the mold cavity; applying the mold cavity to the heat distributor such that the outside face of such mold member is on top of the shaped heat distributor; and conductively applying heat to a face ofthe lens by (a) conductively transferring heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the face of the lens. 24. The method of claim 1, further comprising: applying a mold member of the mold cavity to a conductive heat source, the conductive heat source comprising a flexible member; shaping the flexible member such that it substantially conforms to a face of a mold member; and conductively applying heat to a face of the lens by (a) conductively applying heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the lens. 25 A method of making a plastic oxygen barrier film comprising a photoinitiator, compnsmg (a) immersing a plastic film in a solution comprising a photoinitiator, (b) removing the plastic film from the solution, and (c) drying the plastic film 26 The method of claim 25, further comprising applying a solvent to the plastic film before drying the plastic film 27 The method of claun 25 wherein the solution further comprises an etching agent 28 The method of claim 25. further comprising chemically etching a surface on the plastic film prior to or while immersing the plastic film in the solution 29 A lens made by the method of claim 1 30 An oxygen barrier comprising a film that is at least partially transparent to ultraviolet ra\s, the film adapted to cover at least a portion of a lens edge and inhibit oxygen from contacting the lens edge, and wherem the film is flexible and comprises a photoinitiator 31 The barrier of claim 30 wherem the film comprises high-density polyethylene 32 The barrier of claim 30 wherein the film comprises a strip of high density polyethylene, the strip bemg about 001 to 0 1 mm thick 33 The barrier of claim 30 wherein the film is less than about 025 mm thick 34 A method for making a plastic eyeglass lens, comprising placmg a liquid polymerizable lens forming composition in a mold cavity defined by at least a first mold member and a second mold member, directing first ultraviolet rays toward at least one ofthe mold members to cure the lens formmg composition so that it forms a lens with a back face, edges, and a front face, applymg a mold member ofthe mold cavity to a substantially solid conductive heat source, and conductively applying heat to a face of the lens by (a) conductively transferring heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the face of the lens 35 The method of claim 34 wherein the mold cavity further comprises a gasket, and further compnsmg removing the gasket from the mold cavity after the lens is formed but before conductively transferring heat to the face ofthe mold member 36 The method of claim 34, further comprising treating the edges ofthe lens to cure or remove incompletely cured lens forming material before conductively applying heat 37 The method of claim 34 wherein heat is substantially uniformly applied to the face ofthe mold member 38 The method of claim 34 wherein the heat source comprises a substantially concave element configured to substantially conform to a substantially convex face of a mold member 39 The method of claim 34 wherem the heat source compπses a substantially convex element configured to substantially conform to a substantially concave face of a mold member 40 The method of claim 34, further comprising using a heat distributor between the mold member and the heat source 41 The method of claim 34, further compπsing using a heat distributor between the mold member and the heat source to partially insulate the mold member from the heat source, and such that heat is gradually transferred from the heat source to the mold member 42 The method of claim 34, further comprising thermostatically controlling the temperature ofthe heat source 43 The method of claim 34, further comprising using a flexible heat distributor between the mold member and the heat source 44 The method of claim 34, further compnsmg using a flexible heat distributor between the mold member and the heat source, and wherein the heat distributor comprises a container containmg particles 45 The method of claim 34, further comprising using a flexible heat distributor between the mold member and the heat source, and wherem the heat distributor comprises a container contammg particles of a metal or ceramic material 46 The method of claim 34, further comprising using a flexible heat distributor between the mold member and the heat source, and further comprising shaping the flexible heat distributor to substantially conform to a face of a mold member 47. The method of claim 34 wherein heat is only conductively applied to one outside face of one mold member. 48. The method of claim 34 wherein heat is conductively applied through a mold member to the back face of the lens, thereby enhancing cross-linking ofthe lens forming material proximate to the surface of the back face ofthe lens. 49. The method of claim 34 wherein heat is conductively applied through a mold member to the back face of the lens, thereby increasing the tintability ofthe back surface ofthe lens. 50. The method of claim 34, further comprising tinting the lens. 51. The method of claim 34, further comprising tinting the lens by immersing the lens in a dye solution without substantially agitating the dye solution. 52. A method for making a plastic eyeglass lens, comprising: placing a liquid polymerizable lens forming composition in a mold cavity defined by at least a gasket, a first mold member, and a second mold member; directing first ultraviolet rays toward at least one ofthe mold members to cure the lens forming composition so that it forms a lens with a back face, edges, and a front face; shaping a flexible member such that it substantially conforms to a face of a mold member; applying a mold member ofthe mold cavity to the flexible member, the flexible member being on top of a conductive heat source; conductively applying heat to a face ofthe lens by (a) conductively applying heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the lens. 53. The method of claim 52 wherein the flexible member is coupled to the conductive heat source. 54. A lens made by the method of claim 52. 55. A system for making a plastic eyeglass lens, comprising: (i) a lens forming apparatus, comprising: a first mold member having a casting face and a non-casting face: a second mold member having a casting face and a non-casting face, the second mold member being spaced apart from the first mold member during use such that the casting faces of the first mold member and the second mold member at least partially define a mold cavity; and a light generator for generating and directing ultraviolet light against at least one ofthe first and second mold members during use; and (ii) a conductive heating apparatus, the conductive heating apparatus being adapted to conductively apply heat to a face of a mold member during use. 56. The system of claim 55, further comprising a heat distributor on top of heat source, the heat distributor being configurable to substantially conform to a non-casting face of a mold member during use 57. The system of claim 55 wherein the conductive lens heating apparatus is adapted to substantially uniformly apply heat to the face ofthe mold member during use. 58. The system of claim 55, further comprising a heat distributor comprising a substantially concave element configured to substantially conform to a substantially convex face of a mold member during use. 59. The system of claim 55, further comprising a heat distributor comprising a substantially convex element configured to substantially conform to a substantially concave face of a mold member during use. 60. The system of claim 55, further comprising a heat distributor between a non-castmg face of a mold member and the heat source during use. 61. The system of claim 55, further comprising a heat distributor between a non-casting face of a mold member and the heat source during use, and further comprising an insulator between the non-casting face ofthe mold member and the heat source. 62. The system of claim 55, further comprising a heat distibutor adapted to partially insulate the mold member from the heat source during use. 63. The system of claim 55, further comprising a heat distributor adapted to gradually transfer heat from the heat source to the mold member during use. The system of claim 55, further compnsmg a controller connected to thermostatically control the heat source during use The system of claim 55, further comprising a heat distributor flexibly configurable such that the heat distributor can be shaped to substantially conform to a noncasting face of mold member dunng use The system of claim 55, further comprising a heat distributor comprising a container contammg particles The system of claim 55. further comprising a heat distributor compnsmg a container containmg particles, and wherein the particles comprise a metal or ceramic material The system of claim 55 wherein the conductive lens heating apparatus is adapted to conductively apply heat through a mold member to the back face of the lens during use, thereby enhancing cross-linking of the lens forming material proximate to the surface of the back face ofthe lens during use The system of claim 55 wherein the conductive lens heatmg apparatus is adapted to conductively apply heat through a mold member to the back face ofthe lens during use, thereby increasing the tintability of the back surface of the lens during use A method for making an eyeglass lens, comprising placmg a liquid, polymerizable lens-forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition compπsing a photoinitiator, applying a plurality of high mtensity ultraviolet light pulses to the lens formmg composition, at least one of the pulses having a duration of less than about one second, curmg the lens forming composition to form a substantially clear eyeglass lens m a time period of less than 30 minutes The method of claim 70 wherein at least one ofthe pulses has a duration of less than about 0 1 seconds The method of claim 70 wherein at least one ofthe pulses has a duration of less than about 0 01 seconds The method of claim 70 wherein the pulses have a sufficiently high intensity such that reaction is initiated m substantially all ofthe lens formmg composition that is exposed to pulses in the mold cavity 74. The method of claim 70 wherein the pulses have a sufficiently high intensity such that the temperature begins to rise in substantially all ofthe lens forming composition that is exposed to pulses in the mold cavity. 75. The method of claim 70 wherein the lens forming composition is exposed to a relatively low intensity ultraviolet light while the pulses are applied. 76. The method of claim 70 wherein one side ofthe mold cavity is exposed to a relatively low intensity ultraviolet light while the pulses are applied to another side ofthe mold cavity. 77. The method of claim 70 wherein the pulses are applied through both mold members to reach the lens forming composition. 78. The method of claim 70 wherein the lens forming composition is exposed to a relatively low intensity ultraviolet light while the pulses are applied, the relatively low intensity light having an intensity of less than 0.01 watt/cm 2 , as measured on an outside surface of a mold member ofthe mold cavity. 79. The method of claim 70 wherein at least one ofthe pulses has an intensity of at least 0.01 watt/cm 2 , as measured on an outside surface of a mold member ofthe mold cavity. 80. The method of claim 70 wherein at least one ofthe pulses has an intensity of at least 0.01 watts/cm 2 , as measured on an outside surface of a mold member of the mold cavity. 81. The method of claim 70 wherein at least one ofthe pulses has an intensity of at least one watts/cm 2 , as measured on an outside surface of a mold member ofthe mold cavity. 82. The method of claim 70, further comprising applying sufficient ultraviolet light such that the temperature ofthe lens forming composition begins to increase, and then waiting at least 5 minutes before applying pulses. 83. The method of claim 70 wherein at least 5 pulses are applied to the lens forming composition. 84. The method of claim 70 wherein at least 10 pulses are applied to the lens forming composition. 85. The method of claim 70 wherein at least 20 pulses are applied to the lens forming composition. 86. The method of claim 70 wherein the eyeglass lens has an average thickness of at least about 1.5 mm. 87. The method of claim 70 wherein the eyeglass lens has an average thickness of at least about 2.0 mm. 88 The method of claim 70 wherein the pulses are substantially discontinuous 89 The method of claim 70 wherein the pulses are applied such that the lens forming composition cures to form a substantially clear eyeglass lens in a time period of less than 20 minutes 90 The method of claim 70 wherein the pulses are applied such that the lens formmg composition cures to form a substantially clear eyeglass lens in a time period of less than 15 mmutes 91 The method of claim 70, further comprising cooling the mold cavity 92 The method of claim 70, further comprising applying air to the mold cavity to remove heat from the mold cavity 93 The method of claim 70, further comprising cooling air and then applying cooled air to the mold cavity to remove heat from the mold cavity 94 The method of claim 70, further comprising cooling air to between about 0 and 20 ° C, and then applying the cooled air to the mold cavity 95 The method of claim 70, further compnsmg directing air towards the faces ofthe molds 96 The method of claim 70 wherein the pulses emanate from a xenon light source 97 The method of claim 70 wherein the pulses are applied such that the lens forming composition is oversaturated with ultraviolet light during at least one pulse 98 The method of claim 70 wherem the formed lens has a power greater than positive 2 diopters 99 The method of claim 70 wherein the formed lens has a power less than minus 4 diopters 100 The method of claim 70 wherein less than 20 Joule/cm 2 of energy is applied to cure the lens formmg composition from a liquid into a lens 101 The method of claim 70 wherem less than 10 Joule/cm 2 as measured at 365 nm of energy is applied to cure the lens forming composition from a liquid mto a lens 102 The method of claim 70, further comprising charging a capacitor with energy and then using the charged energy to provide the pulses 103 The method of claim 70, further comprising applymg a relatively low level of ultraviolet light to the lens forming composition while the pulses are being applied and while the pulses are not bemg applied 104 The method of claim 70, further comprising applying sufficient ultraviolet light such that the temperature ofthe lens forming composition forms a gel, and allowing heat to dissipate from mold cavity for at least 5 mmutes before applying additional pulses 105 The method of claun 70, further comprising applying ultraviolet light as a function of the temperature of the lens forming composition 106 The method of claim 70, further comprising applying ultraviolet light as a function of the temperature of at least a portion the mold cavity 107 The method of claim 70, further compnsmg applying ultraviolet light as a function ofthe temperature of air in or exiting a chamber enclosing the mold cavity 108 A method for making an eyeglass lens, compnsmg placmg a liquid, polymerizable lens forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition comprising a photoinitiator, and curing the lens forming composition to form a substantially clear eyeglass lens by applying a plurality of high intensity ultraviolet light pulses to the lens forming composition, the pulses having a duration of less than about one second, the pulses being applied such that the lens forming composition cures to form a substantially clear eyeglass lens in a time period of less than 30 minutes 109 A method for making an eyeglass lens, compπsing placing a liquid, polymerizable lens forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition compnsmg a photoinitiator, applying ultraviolet light at an mtensity to the lens formmg composition through at least one of the mold members for a selected period of time such that a temperature of the composition begins to increase, decreasing the intensity of the ultraviolet light to inhibit the temperature of the lens formmg composition from increasing to a selected first temperature, allowing an exothermic reaction ofthe lens forming composition to increase the temperature ofthe lens forming composition to a second temperature, the second temperature being less than the selected first temperature. curing the lens forming composition to form a substantially clear eyeglass lens by (a) applying ultraviolet light at an intensity to the lens forming composition through at least one ofthe mold members, and (b) decreasing the intensity ofthe ultraviolet light, and wherein the eyeglass lens is formed from the lens forming composition in a time period of less than about 30 mmutes The method of claim 109, further comprismg repeatedly and alternately performing the following steps to cure the lens forming composition to form a substantially clear eyeglass lens (a) applying ultraviolet light at an intensity to the lens forming composition through at least one ofthe mold members, and (b) decreasing the intensity ofthe ultraviolet light The method of claim 109, further comprising allowing the lens forming composition to cool to a third temperature, the third temperature being less than the second temperature The method of claim 109 wherein the intensity ofthe ultraviolet light is decreased to substantially zero in at least one step The method of claim 109, further comprising cooling the lens-forming material by directing air toward a noncasting face of at least one of the mold members during the application of ultraviolet light The method of claim 109 wherein the amount of time that the ultraviolet light remains decreased is varied as a function of a rate of reaction ofthe lens forming composition in at least one step The method of claim 109 wherem the amount of time that the ultraviolet light remams decreased is varied as a function of a temperature ofthe lens-forming composition in at least one step The method of claim 109, further comprising continuously cooling the lens forming composition by directing air toward a noncasting face of at least one ofthe mold members, and wherein the air is at a temperature of below about ambient temperature The method of claim 109 wherein the initial ultraviolet rays are applied toward at least one ofthe mold members until substantially all ofthe lens forming composition has reacted beyond its gel point me method ot claim 109, turther comprising selecting the intensity ot the ultraviolet light to maintain a temperature ofthe lens forming composition below the second temperature The method of claim 109 wherem a period of time that the ultraviolet light is decreased is controlled to maintain a temperature of the composition below the second temperature The method of claim 109, further comprising continuously coolmg the lens forming composition by directing air toward a noncasting face of at least one ofthe mold members, and wherem the air is at a temperature between about 0 C and about 20 C The method of claim 109 wherein the lens forming composition has a mass of at least about 70 grams, and the selected first temperature is less than about 200 F The method of claim 109 wherein the lens forming composition has a mass no greater than about 45 grams, and the selected first temperature is less than about 150 F The method of claim 109 wherein the selected first temperature is a maximum temperature that the lens forming composition would reach without decreasing the ultraviolet light A method for making an eyeglass lens, comprising placing a liquid, polymerizable lens-forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition comprising a photoinitiator, applying first ultraviolet light to at least one of the mold members tor a selected first period of time such that a temperature ofthe lens forming composition begins to increase, removing the first ultraviolet light from at least one ofthe mold members, thereby inhibiting the temperature ofthe composition from increasing to a selected first temperature, and repeatedly and alternately performing the following steps to complete the formation of a lens (a) applymg second ultraviolet light to at least one ofthe mold members for a selected second period of tune and (b) removing the second ultraviolet light from at least one ofthe mold members for a selected third period of time The method of claim 124, further compnsmg cooling the lens forming composition by directing air toward the face of at least one of the mold members 126. The method of claim 124 wherein the lens forming composition is cured to form a substantially clear eyeglass lens in a time period of less than 30 minutes. 127. A method for making an eyeglass lens, comprising: placing a liquid, polymerizable lens forming composition in a mold cavity defined by at least a first mold member and a second mold member, the lens forming composition comprising a photoinitiator; directing ultraviolet light at a first intensity toward at least one ofthe mold members for a selected first period of time such that a temperature ofthe composition begins to increase: decreasing the first intensity of ultraviolet light from at least one of the mold members; and repeatedly directing a plurality of pulses of ultraviolet to the lens forming composition through at least one of the mold members to complete formation of a substantially clear eyeglass lens, at least one of the pulses lasting for a second period of time, and wherein a third period of time exists between application of at least two of the pulses. 128. The method of claim 127 wherein the pulses are directed from a pulse light source to the lens forming composition. 129. The method of claim 127 wherein the pulses are directed from a xenon light source to the lens forming composition. 130. The method of claim 127 wherein the second period is less than about one second. 131. The method of claim 127 wherein the first ultraviolet light is in the form of pulses. 132. The method of claim 127 wherein the first ultraviolet light is in the form of pulses from a xenon light source. 133. The method of claim 127 wherein the first ultraviolet light is in the form of pulses from a pulse light source, and wherein a gel is formed by exposure ofthe lens forming composition to less than 1 second of ultraviolet light. 134. The method of claim 127, further comprising directing air toward at least one of the mold members to cool the lens forming composition. 135 ihe method of claim 127. further comprising directing air at substantially ambient temperature toward at least one ofthe mold members to cool the lens forming composition 136 The method of claim 1278 wherein the first ultraviolet light is in the form of pulses from a xenon light source, and wherein a temperature increase in the lens forming composition occurs less than about 30 seconds after a first pulse is directed toward at least one ofthe mold members 137 The method of claim 128. further comprising reflecting light from a reflecting device and into the lens formmg composition 138 The method of claun 128 wherein the second period is varied as a function of a temperature of the lens formmg composition withm the mold cavity 139 The method of claim 128 wherein the third period is varied as a function of a temperature ofthe lens forming composition within the mold cavity 140 The method of claim 128 wherein an amount of ultraviolet light per unit of time that contacts the lens forming composition is greater than a maximum amount of ultraviolet light that can be absorbed by the lens forming composition per such unit of time 141 The method of claim 70 wherem the lens forming composition comprises at least one polyethylenic- functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl 142 The method of claim 70 wherein the composition comprises at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, and at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl 143 The method of claim 70 wherein the composition comprises at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, and at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl, and an aromatic contammg bιs(allyl carbonate)- functional monomer 144 The method of claim 109 wherein the lens formmg composition comprises at least one polyethylenic- functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl 145. The method of claim 109 wherein the composition comprises at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, and at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl. 146. The method of claim 109 wherein the composition comprises at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, and at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl. and an aromatic containing bis(allyl carbonate)-functional monomer. 147. The method of claim 127 wherein the lens forming composition comprises at least one polyethylenic- functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl. 148. The method of claim 127 wherein the composition comprises at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, and at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl. 149. The method of claim 127 wherein the composition comprises at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, and at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl, and an aromatic containing bis(allyl carbonate)-functional monomer. 150. An apparatus for making an eyeglass lens, comprising: a first mold member having a casting face and a non-casting face; a second mold member having a casting face and a non-casting face, the second mold member being spaced apart from the first mold member during use such that the casting faces ofthe first mold member and the second mold member at least partially define a mold cavity; a first pulse light generator adapted to generate and direct a pulse of ultraviolet light toward at least one ofthe first and second mold members during use; and a controller adapted to control the first pulse light generator such that ultraviolet light is directed in a plurality of pulses toward at least one ofthe first and second mold members, at least one ofthe pulses having a duration of less than one second 151 The apparatus of claim 150 wherein the first pulse light generator is adapted to direct light toward the first mold member, and further comprising a second pulse light generator adapted to generate and direct a pulse of ultraviolet light toward the second mold member 152 The apparatus of claim 150 wherein the first pulse light generator is adapted to direct light toward the first mold member, and further comprising a second pulse light generator adapted to generate and direct a pulse of ultraviolet light toward the second mold member, and wherein the controller is adapted to control the first and second pulse light generators such that ultraviolet light is directed in a plurality of pulses toward the first and second mold members, at least one ofthe pulses having a duration of less than one second. 153. The apparatus of claim 150 wherein the first pulse light generator is adapted to direct at least one ofthe pulses for less than about 0.1 seconds. 154 The apparatus of claim 150 wherein the first puise light generator is adapted to direct at least one of the pulses for less than about 0.01 seconds. 155 The apparatus of claim 150 the first pulse light generator is adapted to generate and direct pulses with a sufficiently high intensity such that reaction is initiated in substantially all ofthe lens forming composition that is exposed to pulses in the mold cavity 156 The apparatus of claim 150 wherem the first pulse light generator is adapted to generate and direct pulses with a sufficiently high mtensity such that the temperature begins to rise in substantially all of the lens formmg composition that is exposed to pulses in the mold cavity 157. The apparatus of claim 150, further comprising a relatively low intensity ultraviolet light generator adapted to generate and direct relatively low intensity ultraviolet light towards at least one mold member 158 The apparatus of claim 150, further comprising a relatively low intensity ultraviolet light generator adapted to generate and direct relatively low intensity ultraviolet light towards one mold member, and wherein the first ultraviolet light generator is adapted to generate and direct ultraviolet light pulses towards the other mold member. 159 The apparatus of claim 150, further comprising a relatively low intensity ultraviolet light generator adapted to generate and direct relatively low intensity ultraviolet light towards one mold member, the relatively low intensity light having an intensity of less than 0 1 watt/ cm", as measured on an outside surface of a mold member ofthe mold cavity, and wherein the first ultraviolet light generator is adapted to generate and direct ultraviolet light pulses towards the other mold member 160 The apparatus of claim 150 wherein the first ultraviolet light generator is adapted to generate and direct ultraviolet light such that at least one of the pulses has an intensity of at least 0 01 watt/ cm " , as measured on an outside surface of a mold member ofthe mold cavity 161 The apparatus of claim 150 wherein the first ultraviolet light generator is adapted to generate and direct ultraviolet light such that at least one ofthe pulses has an intensity of at least 0 1 watt/ cm 2 , as measured on an outside surface of a mold member ofthe mold cavity 162 The apparatus of claim 150 wherein the controller is adapted to apply sufficient ultraviolet light such that the temperature ofthe lens forming composition begins to increase, and then to control the first ultraviolet light generator such that at least 5 minutes passes before additional ultraviolet light pulses are directed towards at least one ofthe mold members 163 The apparatus of claim 150 wherein the first ultraviolet light generator is adapted to generate and direct substantially discontinuous pulses 164 The apparatus of claim 150 wherein the controller is adapted to apply the pulses such that the lens formmg composition cures to form a substantially clear eyeglass lens in a time period of less than 20 mmutes 165 The apparatus of claim 150 further comprising a cooler adapted to cool the mold cavity 166 The apparatus of claim 150, further comprising a distributor adapted to apply air to the mold cavity to remove heat from the mold cavity 167 The apparatus of claim 150, further comprising a cooler adapted to cool air to between about 0 and 20 C, and then to apply the cooled air to the mold cavity 168 The apparatus of claim 150 wherein the first ultraviolet light generator comprises a xenon light source 169 The apparatus of claim 150 wherem the controller is adapted to control the ultraviolet light generator such that less than 20 Joule/ cm 2 of energy is applied to cure the lens forming composition into a lens 170. The apparatus of claim 150 wherein the controller is adapted to control the ultraviolet light generator such that less than 10 Joule/cm 2 as measured at 365 nm of energy is applied to cure the lens forming composition into a lens. 171. The apparatus of claim 150, further comprising a capacitor coupled to the controller and the ultraviolet light generator, the capacitor adapted to supply energy to the ultraviolet light generator to provide the pulses. 172. The apparatus of claim 150, further comprising a temperature monitor in a chamber comprismg the mold cavity, the temperature monitor coupled to the controller and being adapted to apply ultraviolet light as a function of a temperature in the chamber. 173. The apparatus of claim 150, further comprising a temperature monitor coupled to at least a portion of the mold cavity, the temperature monitor coupled to the controller and being adapted to apply ultraviolet light as a function of a temperature of at least a portion of the mold cavity. 174. The apparatus of claim 150, further comprising a temperature monitor adapted to monitor the temperature of air in or exiting a chamber comprising the mold cavity, the temperature monitor coupled to the controller and being adapted to apply ultraviolet light as a function of a temperature of air in or exiting a chamber enclosing the mold cavity. 175. The apparatus of claim 150 wherein the first ultraviolet light generator comprises a photostrobe having a quartz tube. 176. A system for making an eyeglass lens, comprising: a lens forming composition comprising a photoinitiator; a first mold member having a casting face and a non-casting face; a second mold member having a casting face and a non-casting face, the second mold member being spaced apart from the first mold member during use such that the casting faces ofthe first mold member and the second mold member at least partially define a mold cavity for the lens forming composition; a first pulse light generator adapted to generate and direct a pulse of ultraviolet light toward at least one ofthe first and second mold members during use; a controller adapted to control the first pulse light generator such that ultraviolet light is directed in a plurality of pulses toward at least one ofthe first and second mold members, at least one of the pulses having a duration of less than one second, and wherein the system is adapted to cure the lens formmg composition to form a substantially clear eyeglass lens in less than 30 minutes The system of claim 176 wherein the lens forming composition further comprises at least one polyethylenic-functional monomer containmg at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl The system of claim 176 wherem the composition further comprises at least one polyethylenic-functional monomer containing at least three ethylenically unsaturated groups selected from acrylyl and methacrylyl The system of claim 176 wherein the composition further comprises an aromatic containing bιs(allyl carbonate)-functιonal monomer A system for making an eyeglass lens, comprising a lens forming composition comprising a photoinitiator, a mold cavity chamber comprising a first mold member having a casting face and a non-casting face, a second mold member havmg a casting face and a non-castmg face, the second mold member being spaced apart from the first mold member during use such that the casting faces ofthe first mold member and the second mold member at least partially define a mold cavity for the lens forming composition, a first light generator adapted to generate and direct a ultraviolet light m a first intensity toward at least one ofthe first and second mold members during use, a temperature sensor adapted to sense a temperature in the chamber or a temperature of air exiting the chamber, a controller coupled to the temperature sensor and adapted to control the first light generator such that the first intensity of ultraviolet light directed toward at least one ofthe first and second mold members is decreased when a temperature measured by the temperature sensor substantially increases, and wherem the system is adapted to cure the lens formmg composition to form a substantially clear eyeglass lens in less than 30 minutes 181. The system of claim 180 wherein the controller is adapted to apply ultraviolet light to the lens forming composition through at least one ofthe mold members for a selected period of time such that a temperature ofthe composition begins to increase. 182. The system of claim 180 wherein the controller is adapted to apply ultraviolet light to the lens forming composition through at least one ofthe mold members for a selected period of time such that the lens forming composition begins to gel. 183. The system of claim 180 wherein the controller is adapted to vary the amount of time that the ultraviolet light remains decreased as a function of temperature sensed by the temperature sensor. 184. The system of claim 180 wherein the lens forming composition has a mass of at least about 40 grams, and the controller is adapted to control the ultraviolet light such that the temperature ofthe lens forming composition does not exceed about 200 C. 185. The system of claim 180 wherein the lens forming composition has a mass less than about 45 grams, and the controller is adapted to control the ultraviolet light such that the temperature ofthe lens forming composition does not exceed about 150 C. 186. The system of claim 180 wherein the temperature sensor is adapted to sense the temperature of at least a portion ofthe mold cavity and to transmit a signal to the controller. 187. The system of claim 180 wherein the temperature sensor is adapted to sense a temperature of air in or exiting the mold cavity and to transmit a signal to the controller. 188. The system of claim 180 wherein the controller is adapted to substantially remove ultraviolet light from at least one of the mold members. 189. The system of claim 180 wherein the controller is adapted to apply and remove ultraviolet light to and from the lens forming composition as a function of a sensed temperature. 190. The system of claim 180 wherein the first ultraviolet light generator comprises a flash light source. 191. The system of claim 180 wherein the first ultraviolet light generator comprises a xenon light source. 192. The system of claim 180 wherein the controller is adapted to apply a plurality of pulses of ultraviolet light to the lens forming composition. 193 T he system ot claim 180 wherein the controller is adapted to apply a plurality ot pulses ot ultraviolet light to the lens forming composition, at least one ofthe pulses having a duration of less than 1 second 194 The system of claim i 80. further comprising a reflector adapted to reflect ultraviolet light into the lens formmg composition 195 The system of claim 180 wherein the first ultraviolet light generator is configured to emanate to the lens forming composition an amount of ultraviolet light per time that is greater than a maximum amount of ultraviolet light that can be absorbed by the lens forming composition per such unit of time 196 An apparatus for making a plastic lens, comprising a first mold member having a casting face and a non-castmg face, a second mold member having a casting face and a non-casting face, the second mold member being spaced apart from the first mold member during use such that the casting faces of the first mold member and the second mold member at least partially define a mold cavity, an ultraviolet light generator adapted to direct ultraviolet light rays toward at least one ofthe first and second mold members during use, an ultraviolet light controller adapted to control an intensity of light directed by the ultraviolet light generator, a light sensor adapted to measure the intensity of light directed by the ultraviolet light generator, and a filter adapted to inhibit light other than ultraviolet light from impinging upon the light sensor 197 The apparatus of claim 196 wherein the light sensor comprises a photoresistor 198 The apparatus of claim 196 wherein the light sensor comprises a photodiode 199 The apparatus of claim 196 wherein the ultraviolet light generator is adapted to receive a signal from the light sensor and vary the intensity ofthe ultraviolet light directed toward at least one of the mold members as a function ofthe signal 200 The apparatus of claim 196 wherein the ultraviolet light generator is adapted to receive a signal from the light sensor and send a selected voltage to the ultraviolet light generator to vary the intensity ofthe ultraviolet light directed toward at least one ofthe mold members, the selected voltage varied as a function of the signal 201 A system for making an eyeglass lens, comprising a first mold member having a casting face and a non-castmg face, a second mold member having a casting face and a non-castmg face, the second mold member bemg spaced apart from the first mold member during use such that the casting faces ofthe first mold member and the second mold member at least partially define a mold cavity, a first light generator for generating and directing ultraviolet light against at least one ofthe first and second mold members durmg use, a first distributor adaptable to direct air toward the non-casting face of at least one ofthe mold members during use, a thermoelectric cooling system for coolmg the air, the thermoelectric cooling system comprising a first thermoelectric module and being adapted to cool the air, and a first blower for directing air to at least one ofthe mold members, the blower being adapted to receive effluent air that has contacted the non-casting face of at least one of the mold members and to recycle the effluent air to the distributor 202 The system of claim 201 , further comprising a plate connected to the first distributor to form a substantially airtight seal, the plate being substantially transparent to the ultraviolet light generated by the first light generator 203 The system of claim 201 , further comprising a plate connected to the first distributor to form a substantially airtight seal, the plate comprising substantially clear borosilicate glass and being substantially transparent to the ultraviolet light generated by the first light generator 204 The system of claim 201 , further compnsmg a light diffuser for diffusing the ultraviolet light, the light diffuser being located between the first light generator and the first distributor and compnsmg sandblasted borosilicate glass 205 The system of claim 201, further comprising a light diffuser adapted to diffuse the ultraviolet light, the light diffuser being connected to the first distributor to form a substantially airtight seal 206 The system of claim 201, further comprising a quartz plate connected to the first distributor to form a substantially airtight seal, the plate being substantially transparent to the ultraviolet light generated by the first light generator 207 The system of claim 201 wherein the first light generator is adapted to direct the ultraviolet light toward the first mold member during use and further comprising a second light generator adapted to direct ultraviolet light toward the second mold member during use 208 The system of claim 201 wherein the first light generator comprises a photostrobe having a quartz tube 209 The system of claim 201 , wherein the first light generator comprises a photostrobe having a borosilicate tube 210 The system of claim 201. wherein the first thermoelectric module compπses a plurality of pn-couples disposed between a pair of metallized ceramic plates 211 The system of claim 201, wherem the thermoelectric cooling system comprises a DC power source 212. The system of claim 201, wherein the first thermoelectric module comprises a hot side and a cold side, and further comprising a hot side heat sink coupled to the hot side for dissipating heat from the first thermoelectric module 213 The system of claim 201 , wherem the first thermoelectric module comprises a hot side and a cold side, and further compnsmg a hot side heat sink coupled to the hot side for dissipating heat from the first thermoelectric module, the hot side heat sink comprising a plurality of fins 214 The system of claim 201, wherein the first thermoelectric module comprises a hot side and a cold side, and further comprising a hot side heat sink coupled to the hot side for dissipating heat from the first thermoelectric module, and further comprising a fan adapted to direct air onto the hot side heat sink to facilitate dissipation of heat 215 The system of claim 201 , wherein the first thermoelectric module compπses a hot side and a cold side, and further comprising a cold side heat smk coupled to the cold side, the cold side heat sink providmg a coolmg surface for the air directed to at least one ofthe mold members 216 The system of claun 201, wherein the first thermoelectric module comprises a hot side and a cold side, and further comprising a cold side heat sink coupled to the cold side, the cold side heat sink providing a coolmg surface for the air directed to at least one ofthe mold members, the cold side heat sink comprising a plurality of fins 217 The system of claim 201. wherein first thermoelectric module comprises a hot side and a cold side, and further comprising a hot side heat sink coupled to the hot side for dissipating heat from the first thermoelectric module, and further comprising a conductive block disposed between the hot side and the hot side heat sink 218 The system of claim 201 , wherein the first thermoelectric module comprises a hot side and a cold side, and further comprising a conductive block mounted to the hot side, and further comprising insulation substantially surrounding the first thermoelectric module and the conductive block 219 The system of claim 201, wherein the first thermoelectric module cools air directed at the first mold member, and wherem the thermoelectric cooling system further comprises a second thermoelectric module adapted to cool air directed toward the second mold member to a temperature between about 0°C and about 20°C 220 The system of claim 201 , wherein the first blower is adapted to recycle the effluent air toward the first mold member and further comprising a second blower adapted to receive the effluent air that has contacted the non-castmg face of at least one of the mold members and to recycle the effluent air toward the non-casting face of the second mold member 221 The system of claim 201, further comprising an irradiation chamber for containing the mold members during use, the irradiation chamber being substantially airtight 222 The system of claim 201 , further comprising an irradiation chamber for containing the mold members during use, and further comprising an air plenum communicating with the irradiation chamber, the air plenum being configured to direct effluent air from the irradiation chamber to the first blower during use 223 The system of claim 201 , further comprising an irradiation chamber for containing the mold members during use, the irradiation chamber being substantially airtight, and further comprising a lens drawer for positioning the mold members withm the irradiation chamber, the lens drawer being adaptable to being inserted within and removed from the irradiation chamber 224 The system of claim 201 , further comprising a shutter system operable to block at least a portion of the ultraviolet light directed toward at least one ofthe mold members during use. and further comprising an automatic controller coupled to the shutter and adapted to activate the shutter during use 225 The system of claim 201, further comprising a conductive heatmg apparatus, the conductive heatmg apparatus being adapted to conductively apply heat to a face of at least one ofthe mold members during use 226 The system of claim 201 wherein the first light generator is adapted to direct ultraviolet light m pulses toward at least one ofthe mold members, the pulses each lasting less than about one second 227 The system of claim 201 , further comprising a controller to control operation ofthe light generator such that ultraviolet light is directed in a plurality of pulses toward at least one of the mold members and wherem the controller is programmable such that a predetermined time elapses between each of the pulses 228 The system of claim 201 , wherein the first thermoelectric module is adapted to cool the air to a temperature between about 0°C and 20°C 229 A method for making an eyeglass lens, comprising placing a liquid, polymerizable lens forming composition in a mold cavity defined at least partially by a first mold member and a second mold member, the first and second mold members each comprising a casting face and a non-casting face the lens forming composition comprising a photoinitiator. directing ultraviolet light toward the lens forming composition through at least one of the mold members to form a substantially clear eyeglass lens, substantially simultaneously with the step of directing ultraviolet light toward the lens formmg composition, directing air toward at least one ofthe non-castmg faces ofthe first and second mold members to remove heat from the lens forming composition, and cooling the air to a temperature below ambient temperature in a thermoelectric cooling system, the thermoelectric cooling system comprising a first thermoelectric module 230 The method of claim 229, further comprising recycling effluent air that has contacted at least one of the mold members, cooling the effluent air in the thermoelectric cooling system, and directing the cooled effluent air toward at least one ofthe non-castmg faces ofthe first and second mold members to remove heat from the lens forming composition 231 The method of claim 229, further comprising directing the ultraviolet light toward the lens formmg composition in a plurality of pulses, at least one of the pulses having a duration of less than about one second 232 The method of claim 229, further comprising directing the ultraviolet light toward the lens formmg composition in a plurality of pulses, at least one ofthe pulses having a duration of less than about one second, and further compnsmg controlling application ofthe ultraviolet light with a programmable controller such that a predetermined time elapses between each ofthe pulses 233 The method of claim 229 wherein the effluent air is cooled to a temperature between about 0 D C and about 20°C 234 The method of claim 229 wherem the ultraviolet light is directed through both ofthe mold members to form the eyeglass lens 235 The method of claim 229 wherein the cooled effluent air is directed toward the non-casting faces of the first and second mold members 236 The method of claim 229 wherein a first portion of the effluent air is cooled to a first temperature below ambient temperature by the first thermoelectric module, and wherein a second portion of the effluent air is cooled to a second temperature below ambient temperature by a second thermoelectric module, the first temperature bemg different than the second temperature 237 The method of claim 229 wherem the first thermoelectric module comprises a plurality of pn-couples disposed between a pair of metallized ceramic plates 238 The method of claim 229 wherein the first thermoelectric module comprises a hot side and a cold side, and further comprising dissipating heat from the hot side from a hot side heat sink coupled to the hot side 239 The method of claim 229 wherein the first thermoelectric module comprises a hot side and a cold side, and further compπsing directing air onto a hot side heat sink to dissipate heat from the hot side, the hot side heat smk being coupled to the hot side 240 The method of claim 229 wherein the first thermoelectric module comprises a hot side and a cold side, and further comprising directing air across a plurality of fins contained in a hot side heat sink thereby dissipating heat from the hot side, the hot side heat smk being coupled to the hot side 241 The method of claim 229 wherein the first thermoelectric module comprises a hot side and a cold side, and wherein the step of recycling the effluent air compπses passing the effluent air across a cold side heat sink coupled to the cold side, thereby cooling the effluent air 242 The method of claim 229 wherein the first thermoelectric module comprises a hot side and a cold side, and wherein the step of recycling the effluent air comprises passing the effluent air across a plurality of fins contained in a cold side heat sink that is coupled to the cold side, thereby cooling the effluent air 243. The method of claim 229 wherein first thermoelectric module comprises a hot side and a cold side, and further comprising conductively passing heat from the hot side through a conductive block mounted to the hot side and to a hot side heat sink coupled to the conductive block, and further comprising dissipating the heat from smk 244 The method of claim 229 wherein first thermoelectric module comprises a hot side and a cold side, and further comprising conductively passing heat from the hot side through a conductive block mounted to the hot side and to a hot side heat sink coupled to the conductive block, and further compnsmg dissipating the heat from the hot side heat sink, and wherein the conductive block and the thermoelectric module are substantially surrounded by insulation 245 The method of claim 229 wherem the step of directing ultraviolet light toward the lens forming composition is performed while the mold cavity is located withm a substantially airtight irradiation chamber 246 The method of claim 229. further comprising passing the effluent air from at least one ofthe mold members to an air plenum, the air plenum communicating with a blower, and further comprising recirculating the effluent air with the blower from the air plenum to the non-casting face of least one ofthe mold members 247 The method of claim 229. further comprising operating a shutter to block at least a portion ofthe ultraviolet light directed toward at least one ofthe mold members, thereby directing ultraviolet light toward at least one ofthe mold members in a pulse having a duration of less than about one second 248 A method for making an eyeglass lens, comprising the steps placing a liquid, polymerizable lens forming composition in a mold cavity defined at least partially by a first mold member and a second mold member, the lens forming composition comprising a photoinitiator, directing a plurality of pulses of ultraviolet light toward the lens forming composition through at least one ofthe mold members to initiate reaction ofthe lens forming composition, at least one ofthe pulses having an intensity of at least about 10 milliwatts/cπr subsequent to the step of directing the plurality of pulses toward the lens forming composition, directmg ultraviolet light of a second intensity toward the lens forming composition through at least one ofthe mold members to form a substantially clear eyeglass lens, the second intensity being less than about 350 microwatts/cm 2 , and substantially simultaneously with the step of directing ultraviolet of a second intensity toward the lens forming composition, directing air onto a non-casting face of at least one of the mold members to remove heat from the lens forming composition 249 The method of claim 248, wherem at least one ofthe pulses has an intensity of at least about 100 mιllιwatts/cm 2 250 The method of claim 248. wherein at least one of the pulses has an intensit y of between about 100 milliwatts/cm 2 and about 150 milliwatts/cm 2 251 The method of claim 248, wherem the second intensity is less than about 150 microwatts/ cm 2 252 The method of claim 248, wherein the second intensity is between about 90 microwatts/ cm 2 and about 100 microwatts/ cm 2 253 The method of claim 248, wherein the ultraviolet light is directed from an ultraviolet light generator toward the lens forming composition, and further comprising positioning a translucent high density polyethylene plate between the ultraviolet light generator and at least one ofthe mold members to reduce an intensity ofthe ultraviolet light to the second intensity 254 The method of claim 248, wherein the step of directing the plurality of pulses toward the lens formmg composition comprises forming at least a portion ofthe lens forming composition into a gel 255 The method of claim 248, wherem the step of directing the plurality of pulses toward the lens forming composition comprises formmg substantially all ofthe lens forming composition into a gel 256 The method of claun 248, wherein a substantial amount of heat is generated by exothermic reaction of the lens forming composition only after the step of directing ultraviolet light ofthe second intensity toward the lens formmg composition 257 The method of claim 248, wherein the ultraviolet light having the second intensity is directed toward the lens forming composition substantially continuously 258 The method of ciaim 248, wherein the ultraviolet light having the second intensity is directed toward the lens formmg composition in pulses, and wherein at least one ofthe pulses has a duration of less than one second 259 The method of claim 248, wherein the eyeglass lens is cured in a total time period of less than about 30 mmutes 260 The method of claim 248, wherein the eyeglass lens is substantially free of cracks, striations, distortions, hazmess, and yellowness 261 The method of claim 248, further comprising, subsequent to the step of directing ultraviolet light ofthe second intensity toward the lens formmg composition, directing a second plurality of pulses of ultraviolet light toward the lens formmg composition to form the eyeglass lens, at least one ofthe second plurality of pulses havmg an mtensity of at least about 10 milliwatts/cm 2 262 The method of claim 248. further comprising coolmg the air to a temperature below ambient temperature prior to directing the air onto the non-casting face of at least one ofthe mold members 263 The method of claim 248,, further comprising coolmg the air to a temperature between about 0° C and about 20° C prior to directing the air onto the non-casting face of at least one of the mold members 264 The method of claim 248, wherein the air is directed onto the non-castmg faces of both the first and second mold members 265 The method of claim 248, wherein the step of directing the plurality of pulses toward the lens forming composition comprises directing pulses of ultraviolet light through each ofthe first and second mold members 266 The method of claim 248, wherein the step of directing ultraviolet light of a second intensity towards the lens forming composition comprises directing the ultraviolet light through each of the first and second mold members 267 The method of claim 248, wherein the pulses are directed from xenon light source, and wherein the ultraviolet light having the second intensity is directed from a mercury vapor lamp 268 The method of claim 248, wherein the lens forming composition comprises (a) at least one polyethylenic-functional monomer containing at least two ethylenically unsaturated groups selected from acrylyl and methacrylyl, and (b) an aromatic containing bιs(allyl carbonatej-functional monomer 269 The method of claim 248 wherein the eyeglass lens has a dioptric power of at least about ± 2 OOD and is substantially free of distortions, striations, cracks, haziness, and yellowness 270 The method of claim 248, wherein the eyeglass lens has a dioptric power of less than about ± 2 OOD and is substantially free of distortions, striations, cracks, haziness, and yellowness 271 A method for making an eyeglass lens, comprising placing a first coating composition within a mold member, the mold member comprismg a castmg face and a non-castmg face, the coating composition comprising a photoinitiator and being curable upon exposure to ultraviolet light, spinning the mold member to distπbute the first coating composition over the casting face, directing ultraviolet light at the mold member to cure at least a portion ofthe first coatmg composition, placmg a second coatmg composition withm the mold member, the second coating composition comprising a photoinitiator and being curable upon exposure to ultraviolet light, spinning the mold member to distribute the second coating composition over the portion ofthe first coating composition that has been cured, directing ultraviolet light at the mold member, thereby curing at least a portion ofthe second coatmg composition and forming a substantially clear combination coat comprising at least a portion of each ofthe first and second coating compositions, assembling the mold member with a second mold member to form a mold having a cavity between the mold members, placing a lens-forming composition withm the cavity, the lens-forming composition comprising a photoinitiator and being curable upon exposure to ultraviolet light, and directing ultraviolet light at the mold to cure at least a portion ofthe lens-forming mateπal to form a lens, and wherein the combination coat adheres to the cured portion ofthe lens-forming material 272 The method of claim 271 , wherein the combination coat is curable to form a substantially scratch- resistant coating 273 The method of claim 271, wherein the cured portion ofthe first coatmg composition comprises a pinhole defect, and wherein the second coating composition substantially covers the pinhole defect 274 The method of claim 271 , further comprising applying dye to the lens to color the lens 275 The method of claim 271 , wherein the first coating composition substantially adheres to the non-castmg face of the mold member 276 The method of claim 271 , wherein the second coating composition is curable to form a substantially scratch-resistant hardcoat 277 The method of claim 271 , wherein the first coatmg composition further comprises an organic solvent and a monomer comprising at least one ethylenically unsaturated group selected from the group consisting of acrylyl and methacrylyl 278. The method of claim 271, wherein the second coating composition further comprises an organic solvent and a monomer comprising at least one ethylenically unsaturated group selected from the group consisting of acrylyl and methacrylyl. 279. The method of claim 271. further comprising preparing the first coating composition by dissolving at least one monomer in an organic solvent, the monomer comprising at least one ethylenically unsaturated group selected from acrylyl and methacrylyl, the solvent making up greater than about 80% ofthe first coating composition, and further comprising passing the first coating composition through a filter prior to placing the first coating composition within the mold member. 280. The method of claim 271 , further comprising preparing the second coating composition by dissolving at least one monomer in an organic solvent, the monomer comprising at least one ethylenically unsaturated group selected from acrylyl and methacrylyl, the solvent making up greater than about 80% of the second coating composition, and further comprising passing the second coating composition through a filter prior to placing the second coating composition within the mold member. 281. The method of claim 271 , wherein spinning the mold member to distribute the first coating composition over the casting face comprises spinning the mold member about a substantially vertical axis at a speed between about 750 and about 1000 revolutions per minute. 282. The method of claim 271 , wherein spinning the mold member to distribute the second coating composition over the casting face comprises spinning the mold member about a substantially vertical axis at a speed between about 750 and about 1000 revolutions per minute. 283. The method of claim 271 , further comprising directing an additional amount of the first coating composition onto the casting face ofthe mold member while the mold member is spinning. 284. The method of claim 271, further comprising directing an additional amount of the first coating composition onto the casting face ofthe mold member from a dispensing device while the mold member is spinning, and wherein the dispensing device moves relative to the mold member in a direction from a center of the mold member to an edge ofthe mold member such that the additional amount is directed along a radius ofthe mold member in a direction from the center ofthe mold member to an edge ofthe mold member. 285. The method of claim 271 , wherein the step of placing the second coating composition within the mold member is performed simultaneously with the step of spinning the mold member to distribute the second coating composition over the portion of the first coating composition that has been cured. 286 The method of claim 271 , wherein the mold is a flat top bifocal mold comprising a segment line, and wherein the first coating composition has a sufficiently low viscosity to be distributed over the segment line by the spinning of the mold member 287 The method of claim 271, wherein the first coatmg composition comprises a solvent, and wherein substantially all ofthe solvent is evaporated during the step of spinning the mold member to distribute the first coating composition over the casting face 288 The method of claim 271, wherein the second coating composition comprises a solvent, and wherein substantially all ofthe solvent is evaporated during the step of spinning the mold member to distribute the second coatmg composition over the portion ofthe first coating composition that has been cured 289 The method of claim 271 , wherein the first coating composition comprises a solvent, and wherem a substantial portion of the solvent is evaporated during the step of spinning the mold member to distribute the first coating composition over the casting face 290 The method of claim 271 , wherein the second coating composition comprises a solvent, and wherem a substantial portion of the solvent is evaporated during the step of spinning the mold member to distribute the second coating composition over the portion of the first coating composition that has been cured 291 The method of claim 271, wherein the combination coat is substantially free of cracks, yellowness, haziness, pinhole defects, and distortions 292 The method of claim 271 , wherein, upon curing, the first coating composition has a double bond conversion greater than about 80% 293 The method of claim 271, wherein the step of assembling the mold member with a second mold member to form a mold comprises positioning a gasket between the mold members 294 The method of claim 271 , wherein the step of assembling the mold member with a second mold member to form a mold comprises positioning a gasket between the mold members, and wherein the step of placing a lens- forming composition withm the cavity comprises displacing an edge ofthe gasket to expose the cavity and inserting the lens-formmg composition therein 295 The method of claim 271 , wherein the second mold member comprises a non-castmg face, and further comprismg directing air towards at least one of the non-castmg faces to cool the mold substantially sunultaneously with the step of directing ultraviolet light at the mold to cure at least a portion of the lens-formmg material 296. I he method ot claim 271 , wherem the second mold member comprises a non-castmg tace, and further comprising directing air towards at least one ofthe non-casting faces to cool the mold substantially simultaneously with the step of directing ultraviolet light at the mold to cure at least a portion ofthe lens-forming material, the air having a temperature below ambient temperature. 297. The method of claim 271, wherein the second mold member comprises a non-casting face, and further comprising directing air towards the non-casting faces ofthe mold members to cool the mold substantially simultaneously with the step of directing ultraviolet light at the mold to cure at least a portion of the lens-forming material. 298. The method of claim 271 , wherein the second mold member comprises a non-casting face, and further comprising directing air towards the non-casting faces ofthe mold members to cool the mold substantially simultaneously with the step of directing ultraviolet light at the mold to cure at least a portion of the lens-forming material, the air having a temperature below ambient temperature. 299. The method of claim 271, wherein the step of assembling the mold member with a second mold member to form a mold comprises positioning a gasket between the mold members, and further comprising: removing the gasket to expose an edge ofthe lens after the step of directing ultraviolet light at the mold to cure at least a portion ofthe lens-forming material to form a lens; applying an oxygen barrier comprising a photoinitiator around the exposed edge ofthe lens such that at least a portion of the oxygen barrier photoinitiator is proximate lens-forming composition that is not fully cured; and directing additional ultraviolet rays towards the lens such that at least a portion of the oxygen barrier photoinitiator initiates reaction of lens forming composition while the oxygen barrier substantially prevents oxygen from outside the oxygen barrier from contacting at least a portion ofthe lens forming composition. 300. The method of claim 271 , further comprising: applying one ofthe mold members to a substantially solid conductive heat source: and conductively applying heat to a face ofthe lens by (a) conductively transferring heat to a face of a mold member from the conductive heat source, and (b) conductively transferring heat through such mold member to the face ofthe lens. 301 A system tor making an eyeglass lens, comprising a first mold member having a casting face and a non-castmg face, a second mold member having a casting face and a non-casting face, the second mold member bemg spaced apart from the first mold member during use such that the casting faces of the first mold member and the second mold member at least partially define a mold cavity, and a first light generator for generating and directing ultraviolet light against at least one ofthe first and second mold members during use 302 A method for making an eyeglass lens, comprising placing a liquid, polymerizable lens formmg composition in a mold cavity defined at least partially by a first mold member and a second mold member, the first and second mold members each comprising a castmg face and a non-casting face, the lens forming composition comprising a photoinitiator, and directing ultraviolet light toward the lens forming composition through at least one of the mold members to form a substantially clear eyeglass lens

Inventors: BUAZZA OMAR M, LUETKE STEPHEN C, POWERS GALEN R, BUAZZA, OMAR, M., LUETKE, STEPHEN, C., POWERS, GALEN, R.
Applicants: Q2100 INC, Q2100, INC.
Application year: 1997
Main classification: B29D11
IPC codes: B29C35, B29C37, B29C39, B29D11, B29K105, C08J7