Patent ID: 12222528

DETAILED DESCRIPTION

Referring generally to the figures, embodiments of a surface illuminator are provided. The surface illuminator is configured to disinfect a surface, such as a touch panel, using ultraviolet light, especially ultraviolet light in the UV-C band. Embodiments of the surface illuminator include a line emitter, a curved surface reflector, and an exit aperture. Ultraviolet light from the line emitter is collected by the curved surface reflector and is directed out the exit aperture over the illuminated surface. In certain embodiments, the line emitter is a light diffusing rod configured to scatter ultraviolet light from a light source. Advantageously, the design of the surface illuminator has fewer components and provides more efficient disinfecting coverage than certain conventional designs. These and other aspects and advantages will be discussed in relation to the embodiments provided below and in the drawings. These embodiments are presented by way of illustration and not by way of limitation.

FIG.1depicts an embodiment of a surface illuminator100. The surface illuminator100is configured to disinfect any of a variety of surfaces using ultraviolet light (in particular light having a peak wavelength in the range of 100 nm to 400 nm), particularly ultraviolet light in the C band (UV-C), which has a peak wavelength in the range of 100 nm to 280 nm. In the embodiment depicted inFIG.1, the surface illuminator100is positioned to disinfect a touch panel102. In particular, the touch panel102includes a touch-enabled display surface104. The touch panel102includes a plurality of edges, shown as edges106a-106d, that bound the display surface104. The surface illuminator100is positioned adjacent at least one edge106a-106din order to emit ultraviolet light onto the display surface104to disinfect it.

FIG.2depicts a side view of the surface illuminator100and touch panel102. The display surface104of the touch panel102defines a first plane108. The surface illuminator100includes an exit aperture110that defines a second plane112. The second plane112is transverse to the first plane108. In embodiments, the second plane112forms an angle α with the first plane108of 70° to 90°, in particular 80° to 89°.

FIG.3depicts a cross-sectional view of the surface illuminator100as positioned on the edge106aof the touch panel102. In embodiments, the surface illuminator100includes a housing114configured to hold a line emitter116. As used herein, a “line emitter” is an element configured to emit light continuously and uniformly over a length. In an embodiment, the line emitter116is a light diffusing rod. In another embodiment, the line emitter116is an ultraviolet-emitting discharge tube. In still another embodiment, the line emitter116is at least one light emitting diode extending continuously along the emitter length. Power for the surface illuminator100may be supplied by an internal power source (such as a battery) of the surface illuminator, a power source in the touch panel, or from an external source (e.g., a plug connected to an electrical outlet).

The housing114defines an interior118within which the line emitter116is positioned. In various embodiments, the housing114may be an integral part of an exterior shell enclosing all of the components of the surface illuminator100, or the housing114of the surface illuminator100may be enclosed within said outer shell. Housing114includes a curved reflector surface120. In the housing114, the line emitter116is positioned between the curved reflector surface120and the exit aperture110. Light from the line emitter116is collected by the curved reflector surface120and directed through the exit aperture110onto the display surface104of the touch panel102. In embodiments, the light provided through the exit aperture110is at a power density sufficient to disinfect the all or a substantial portion of the display surface104. For example, in embodiments, the light provided through the exit aperture110irradiates at least 90% of the surface area of the display surface104, or at least 95% of the surface area of the display surface104.

In embodiments, the curved reflector surface120comprises a substrate, preferably with an optical quality finish, with a highly reflective coating. For the UV-C band, a versatile coating comprises protected metal, such as aluminum with an overcoat. The substrate can be manufactured from a variety of materials, such as glass, metal, or plastic. In embodiments, the curved reflector surface120defines an extruded acylindrical shape such that the curved reflector surface120has the same cross-sectional profile along its length. An acylindrical surface can be defined as a function of height according to the relationship

z=y2R1+1-(K+1)⁢yR2+∑nCn⁢yn

where R is the radius of curvature, K is the conic constant, Cnis the aspheric coefficient for the n-th term in the series, y is the height above the optical axis and z is the position along the optical axis. The number of terms used in the power series is determined by the designer and may be as few as zero. Other asymmetric surface forms may also be used. Examples of such surfaces include toroids, anamorphic aspheres, and XY polynomials, among others. Further, in embodiments, the radius of curvature and.or aspheric coefficient can be varied (continuously or discontinuously) as a function of the x-coordinate for certain applications.

Ultraviolet light from the line emitter116illuminates the curved reflector surface120, and the curved reflector surface120directs the ultraviolet light through the exit aperture110. As shown inFIG.3, the exit aperture110includes a window122. The window122is made of a material that is transparent to ultraviolet light, such as high purity fused silica, specialized glasses, or certain plastics. In embodiments, the material of the window122transmits at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of light in the range of 100 nm to 400 nm through the thickness of the window122. In one or more embodiments, the material of the window122transmits at least 90% of light at least a portion of the range of 100 nm to 400 nm (e.g., 100 nm to 350 nm, 100 nm to 300 nm, 100 nm to 250 nm, 100 nm to 200 nm, 150 nm to 400 nm, 200 nm to 400 nm, 250 nm to 400 nm, 300 nm to 400 nm, or 200 nm to 300 nm) through the thickness of the window122.

In embodiments, the window122includes a coating124configured to reduce transmission of the ultraviolet light over a portion of the window122. For example, in embodiments, the coating124covers 50% of the window122or less, in particular 40% of the window122or less, more particularly about 33% or less. Further, in embodiments, the coating124covers at least 20% of the window122. The coating124is neutral density filter having an optical density of at least 1.0, or at least 1.5, or at least 2.0. In embodiments, the neutral density filter has an optical density of at most 3.0. Further, in embodiments, the coating124may have a gradient of neutral density filter in which a higher optical density is provided at the bottom of the window122with a decreasing optical density as the neutral density filter extends toward the top of the window122.

An exemplary embodiment of a coating124that operates as a neutral density filter is a coating of aluminum with magnesium fluoride. In general, metal layers work well as neutral density filters because metals are less sensitive to wavelength and incident angle. However, a neutral density filter made of a dielectric coating stack could also be used. At a wavelength of 265 nm, aluminum has an index of refraction with a real part of 0.216 and an imaginary part of 2.163, and magnesium fluoride has an index of refraction with a real part of 1.299 and an imaginary part of 0.000. In order to prepare a coating124that acts as a neutral density filter with an optical density of 1.0, the coating is provided with an optical thickness of 0.530 (0.241 Al and 0.289 MgF2) and a thickness of 0.0748 μm (0.0202 μm Al and 0.0546 μm MgF2). The optical density can be increased from 1.0 by increasing the thickness of the aluminum and magnesium fluoride layers.FIG.12depicts a graph of transmittance for the neutral density filter coating124having an optical density of 1.0. As can be seen inFIG.12, the transmittance is about 10% across the UVC band. Further,FIG.13depicts a graph of reflectance for the neutral density filter coating124having an optical density of 1.0. The reflectance is about 80% across the UVC band, and thus, in view of the 10% transmittance and the 80% reflectance, only about 10% of the UVC light is absorbed. Advantageously, the UVC light reflected from the coating124can be redirected from the curved reflector surface120through the exit aperture110. In this way, the UVC light emitted from the line emitter116is efficiently used for disinfecting of a surface.

FIG.14further demonstrates transmittance of incident light in the UVC band as a function of incident angle from the curved reflector surface120. As can be seen, the transmittance is about 10% over the UV band between 200 nm and 300 nm. The transmittance remains at about 10% until the incident angle reaches approximately 40°. Thereafter, the transmittance drops to 0% as a result of total internal reflection.

Referring again toFIG.3, the line emitter116can be any of a variety of suitable elements that emit UVC light in a substantially uniform manner along an emission length of the line emitter116. In a particular embodiment, the line emitter116is a light diffusing rod126.FIG.4schematically depicts the light diffusing rod126positioned within the housing114. In embodiments, the light diffusing rod126has at least one end coupled to a UVC light source128, such as a UVC light emitting diode (LED). Other UV light sources that can be coupled to the light diffusing rod126include lamps, lasers, diodes, and laser diodes. Further, in other embodiments, an optical element is used to couple the light diffusing rod126to the light source128. In embodiments, the optical element may collect, collimate, focus, and/or otherwise process light supplied from a light source128. For example, the optical element may be a solid glass element, a solid polymer or plastic element, a glass or polymer optical fiber, a lens, or other coupling element. In certain embodiments, each end of the light diffusing rod126is coupled to a UVC light source128, e.g., at opposite ends of the housing114.

The light-diffusing rod126has a maximum cross-sectional dimension and a length dimension. As shown inFIG.4, the length dimension L is the dimension in the direction in which light propagates through the light diffusing rod126, and the cross-sectional dimension may be the direction transverse to the direction of light propagation. The length of the light diffusing rod126may be at least 1 cm, or at least 5 cm, or at least 20 cm, or at least 50 cm, or at least 100 cm, or at least 500 cm. The length of the light diffusing rod126may be between 1 cm and 500 cm, or between 1 cm and 100 cm, or between 1 cm and 50 cm, or between 1 cm and 20 cm, or between 5 cm and 100 cm, or between 5 cm and 50 cm, or between 5 cm and 20 cm. In most applications, the length of the light diffusing rod126is no more than 1 m, although this limit is illustrative only. The specifics of a particular application and diffusive properties of the rod will inform each specific embodiment.

In embodiments in which the light diffusing rod126is cylindrical, the cross-section is circular, and the maximum cross-sectional dimension is a diameter of the circular cross-section. However, in other embodiments, the cross-section of the light diffusing rod defines a shape having one or more round or flat sides. For example, in embodiments, the shape of the cross-section is selected from circle, oval, square, rectangle, triangle, polygon, and shapes including a combination of round and flat sides (such as a semi-circle or semi-ellipse). In embodiments, the narrowest and/or flattest side would be directed towards the curved reflector surface120to approximate an idealized line source. As used herein, the maximum cross-sectional dimension refers to the longest straight-line distance that connects two points of the outline (e.g. circumference, perimeter) of the cross-section.

FIG.5depicts an example cross-section of a cylindrical light diffusing rod126. In embodiments, the light diffusing rod126has a maximum cross-sectional dimension D of at least at least 0.1 mm, or at least 0.5 mm, or at least 1 mm, or at least 2 mm. In embodiments, the light diffusing rod126has a maximum cross-sectional dimension in the range of 0.1 mm to 20 mm, or between 0.1 mm and 15 mm, or between 0.1 mm and 10 mm, or between 0.1 mm and 5 mm, 0.5 mm to 20 mm, or between 0.5 mm and 15 mm, or between 0.5 mm and 10 mm, or between 0.5 mm and 5 mm, 1 mm to 20 mm, or between 1 mm and 15 mm, or between 1 mm and 10 mm, or between 1 mm and 5 mm, or between 2 mm and 20 mm, or between 2 mm and 10 mm, or between 2 mm and 15 mm, or between 2 mm and 5 mm.

The light diffusing rod126is configured to scatter light propagating along the length of the light diffusing rod126through an outer surface130of the light diffusing rod126. In order to propagate and scatter light along its length, the light diffusing rod126is formed from a material with low UV absorption and, in particular, a material substantially free from UV absorbing defects or elements. For example, in embodiments, the material of the light diffusing rod126absorbs no more than 10% of light having a peak wavelength in the range of 100 nm to 400 nm over its length. Further, in embodiments, the material of the light diffusing rod126is free of defects that absorb 10% or more of ultraviolet light having a peak wavelength in the range of 100 nm to 400 nm. In embodiments, the light diffusing rod126is formed from high purity fused silica.

In order to scatter light propagating along the length of the light diffusing rod126, the light-diffusing rod126comprises internal voids. Light passing longitudinally along the length of the light diffusing rod126is scattered by the internal voids in a direction transverse to the longitudinal axis of the light diffusing rod126.

In embodiments, the internal voids have a cross-section with a dimension in the range from a few hundred nanometers to several microns. In exemplary embodiments, the cross-sectional dimension of the internal voids is from 100 nm to 20 μm, or from 500 nm to 10 μm, or from 500 nm to 5 μm. Further, the internal voids have a length in the range from a few microns to a few millimeters. In exemplary embodiments, the length of the internal voids is from 1 μm to 5 mm, or from 3 μm to 2 mm, or from 5 μm to 1 mm. In embodiments, the internal voids within the light diffusing rod126include a distribution of cross-sectional dimensions and lengths. Further, in embodiments, the internal voids may be configured in a random or non-periodic arrangement.

In embodiments, the internal voids occupy a fill fraction of 0.5% to 20% of the light diffusing rod126, or 1% to 15% of the light diffusing rod126, or 2% to 10% of the light diffusing rod126. As used herein, fill fraction refers to the fraction of the cross-sectional area occupied by the internal voids. To a good approximation, the fill fraction corresponds to the volume fraction of internal voids. Thus, in embodiments, the volume fraction of voids within the light diffusing rod126is from 0.5% to 20%, or 1% to 15%, or 2% to 10%.

In certain embodiments, the internal voids are distributed throughout the cross-section of the light diffusing rod126, and in other embodiments, the internal voids are localized within one or more discrete regions of the light diffusing rod126.FIGS.5and6illustrate examples of two spatial distributions of internal voids within the light diffusing rod126.

FIG.5depicts a cross-section of a light-diffusing rod126in which the internal voids132are distributed throughout the cross-section. In the detail view ofFIG.5, it can be seen that the internal voids132are distributed within the low UV absorbing material134of the light diffusing rod126. InFIG.5, the internal voids132are shown as having substantially uniform cross-sectional size and shape, but in practice, a distribution of sizes and shapes for the internal voids132will be present.

FIG.6depicts a cross-section of a light diffusing rod126in which the internal voids are localized in an annular structured region136. In this way, the cross-section of the light diffusing rod126includes an inner region138substantially free of any internal voids separated from an outer region140substantially free of any internal voids by the annular structured region136containing internal voids132. In embodiments, the inner region138and the outer region140comprise solid high purity fused silica or another low UV absorbing material. In embodiments, the annular structured region136comprises a width that is in the range from 5% to 90% of the cross-sectional dimension of the light-diffusing rod126, or from 10% to 90% of the cross-sectional dimension of the light-diffusing rod126, or from 30% to 90% of the cross-sectional dimension of the light-diffusing rod126.

In each of the embodiments of the light diffusing rod126, including the exemplary embodiments depicted inFIGS.5and6, the cross-sectional distribution of internal voids132may vary at different positions along the length of the light-diffusing rod126. As noted, the length and cross-sectional attributes (e.g. shape and size) of the internal voids132may vary. The variations may also occur in the axial or length direction of the element. Since the length of the internal voids may not extend the full length of the element, particular internal voids may be present in some cross-sections and absent in other cross-sections.

In embodiments, the internal voids132are filled with a gas. Suitable gases include SO2, noble gases, CO2, N2, O2, air, or mixtures thereof.

The light-diffusing rod126may be configured to scatter light along all or some of its length by controlling the placement of the internal voids132. Regions of the light diffusing rod126that include a high volume fraction of internal voids132may scatter more light than regions of the light diffusing rod126having a lower volume fraction of internal voids132. In this way, the scattering intensity along the length of the light diffusing rod126can be made uniform by, e.g., increasing the volume fraction of internal voids132along the length of the light diffusing rod126as the distance from the light source128increases. If two light sources128are provided at opposing ends of the light diffusing rod126, then, for example, the highest fill fraction of voids may be provided at or near the midpoint of the light diffusing rod126.

The intensity of ultraviolet emission from the light-diffusing rod126relates to the efficiency at which the surface illuminator100provides the disinfecting action. In this regard, a higher scattering loss generally increases the intensity of emission of the light-diffusing rod126. In embodiments, the scattering loss is at least 0.1 dB/m, or at least 1 dB/m, or at least 5 dB/m, or at least 100 dB/m.

As mentioned, the light diffusing rod126can be configured to provide uniform intensity along the length of the light-diffusing rod126. Uniformity of intensity can be considered in terms of the maximum and minimum intensity of scatter light passing through the outer surface130of the light diffusing rod126. In embodiments, a light diffusing rod126having a substantially uniform intensity has a minimum intensity of scattered light that is within 30%, in particular within 20%, and more particularly within 10% of the maximum intensity of scattered light in the ultraviolet band (i.e., 100 nm to 400 nm).

Information regarding the fabrication and the processing of the light diffusing rods126described herein may be found in U.S. Pat. Nos. 7,450,806 and 8,926,143, the disclosures of which are incorporated herein in their entirety by reference thereto.

In the embodiment shown inFIG.7, the light-diffusing rod126includes a surface coating142. In embodiments, the surface coating142is in direct contact with the outer surface130of the light-diffusing rod126. In certain such embodiments, the light-diffusing rod126may lack a cladding typically associated with light diffusing optical fibers and instead have a cladding provided by ambient air. In embodiments, the surface coating142is a curable composition or a thin shrink tubing. Further, in embodiments, the surface coating142comprises a material having a high transmittance (e.g., 70% or more) of ultraviolet light having a peak wavelength in the range of 100 nm to 400 nm through the thickness of the surface coating142. In particular embodiments, the surface coating142comprises a fluoropolymer or a cyclic olefin copolymer. More particular, the surface coating142comprises a material having a lower refractive index than the light diffusing rod126. In embodiments, the thickness of the surface coating is 100 μm or less, more particularly 25 μm or less.

In embodiments, the surface coating142includes a scattering layer that may control or modify the angular distribution of light scattered by the internal voids132, e.g., to enhance the distribution and/or the nature of the scattered light. For example, in such embodiments, surface coating142may include scattering material144that may make the angular distribution of light scattered by the internal voids more uniform.

In embodiments, the scattering material144comprises nano- or microparticles with an average diameter of from about 200 nm to about 10 μm. In exemplary embodiments, the average diameter of the scattering particles may be about 200 nm, or 300 nm, or 400 nm, or 500 nm, or 600 nm, or 700 nm, or 800 nm, or 900 nm, or 1 μm, or 2 μm, or 3 μm, or 4 μm, or 5 μm, or 6 μm, or 7 μm, or 8 μm, or 9 μm, or 10 μm. The concentration of the scattering material144may vary along the length of the element or may be constant and may be present in a weight percent sufficient to provide uniform scattering of light while limiting overall attenuation. The weight percentage of the scattering particles in the scattering layer may comprise about 1%, or 2%, or 3%, or 4%, or 5%, or 6%, or 7%, or 8%, or 9%, or 10%, or 11%, or 12%, or 13%, or 14%, or 15%, or 16%, or 17%, or 18%, or 19%, or 20%, or 25%, or 30%, or 35%, or 40%, or 45%, or 50%. The surface coating142may comprise small particles or colloids of a scattering material that may include a metal oxide or other high refractive index material, such as TiO2, Al2O3, ZnO, SiO2, or Zr. The scattering material may also comprise micro- or nanosized particles or voids of low refractive index, such as gas bubbles. The width of the scattering layer may be greater than about 1 μm, or 2 μm, or 3 μm, or 4 μm, or 5 μm, or 6 μm, or 7 μm, or 8 μm, or 9 μm, or 10 μm, or 20 μm, or 30 μm, or 40 μm, or 50 μm, or 60 μm, or 70 μm, or 80 μm, or 90 μm, or 100 μm.

In a particular embodiment, the scattering material144comprises TiO2-based particles, such as a white ink, which provides for substantially angle-independent distribution of light scattered from the internal voids of the light-diffusing rod126.

Further, in embodiments, the scattering material144occupies a sublayer within the surface coating142. For example, the scattering material144may be localized to a layer having a thickness of about 1 μm to about 5 μm.

In embodiments, the surface coating142may be a protective polymer jacket or tube. The polymer jacket may include a scattering material or component, either internally as a filler or applied to the external surface of the jacket (e.g. a white diffusing paint), to make the angular distribution of light intensity from the element more uniform.

The polymer jacket may be incorporated as a surrounding layer with a scattering layer. A scattering layer may surround the light-diffusive element and the polymer jacket may surround the scattering layer. The scattering layer may be in direct contact with the polymer jacket and/or in direct contact with the outer surface130of the light-diffusing rod126.

In general and with reference back toFIG.3, a light diffusing rod126is configured to emit light radially or circumferentially through the entire perimeter of the outer surface130. However, the ultraviolet light for the surface illuminator100is designed to shine through the exit aperture110, and thus, it is desirable that ultraviolet light emitted from the light diffusing rod126is efficiently directed at the curved reflector surface120for maximum output through the exit aperture110. For this reason, in embodiments, the light diffusing rod126is configured to emit light through less than the entire perimeter of the light diffusing rod126, in particular through 50% or less of the perimeter. Accordingly, in embodiments, the light diffusing rod126or other non-directional line emitter116is disposed in a reflective jacket146as shown inFIGS.8and9.

Referring first toFIG.8, the reflective jacket146is depicted in the form of a trough148. In embodiments, the trough148comprises a plastic or metal, such as aluminum. Further, in embodiments, the trough148may comprise a highly reflective diffuser material, such as phase separated glass tube. As can be seen, the trough148includes a first sidewall150and a second sidewall152connected by a curved wall154, thereby defining a U-shape. The trough148includes a reflective inner surface designed to direct light emitted by the light diffusing rod126or line emitter116through the open end between sidewalls150,152. In embodiments, the open end between the sidewalls150,152has a width that is approximately equal to the maximum cross-sectional dimension of the line emitter116or light diffusing rod126. In other embodiments in which the line emitter or light diffusing rod126is not cylindrical, the width between the sidewalls150,152may be approximately equal to the smallest side length of the polygonal cross-section or a minor axis of a curved polygonal cross-section.

Referring now toFIG.9, the reflective jacket146is depicted in the form of a coating156having a gap158through which light is emitted. In embodiments, the coating156is in the form of a deposited reflective material (such as aluminum). In such embodiments, a polymer shrink tube142may be applied outside the reflective coating to provide additional mechanical support for the line emitter116or light diffusing rod126. In embodiments, the width of the gap158is determined by power transmission and the focal length of the curved reflector surface120. In particular, the gap148is preferably as small as practicable to approximate an idealized line source. In an example embodiment, the gap148was 1 mm.

With reference to bothFIGS.8and9, the reflective jacket146is configured to direct light at the curved reflector surface120. In this regard, embodiments of the surface illuminator100arrange the open end or gap158of the reflective jacket146at a particular angle β relative to the second plane112of the exit aperture110. In embodiments, the angle β is up to 30°. Still further, the reflective jacket146also allows for support elements160to be positioned along the length of the line emitter116or light diffusing rod126to provide further mechanical support without obscuring the ultraviolet light being emitted. In embodiments, the line emitter116or light diffusing rod126is supported by one or more support elements160along the length thereof.

Having described the structure the surface illuminator100, the illumination properties will be described. The curved reflector surface120of the surface illuminator directs light out of the exit aperture110. While the line emitter116is configured to emit a single continuous and substantially uniform line of ultraviolet light in order to make the most economical use of the ultraviolet light, the ultraviolet light leaving the exit aperture110will disperse over the surface to be illuminated. In general, regions nearer to the surface illuminator100will experience a greater intensity of ultraviolet light than regions farther away from the surface illuminator100. In this regard, it is desirable that the lowest intensity of illumination is still effective for disinfecting the surface and that the highest intensity of illumination will not damage the surface (e.g., the display and/or touch functionality of the surface).

FIG.10depicts a plot of the irradiance (W/mm2) for a surface illuminated by an embodiment of the surface illuminator100. The surface illuminator100modeled to produce the graph considered a line emitter positioned 1 mm from an edge of the surface and 4 mm above the surface. The surface was angled 1° relative to horizontal (i.e., the angle α between the first plane108of the surface104and the second plane112of the exit aperture110as shown inFIG.2was 89°). A third of the window122of the exit aperture110had a neutral density filter coating124with an optical density of 2, and the opening or gap of the reflective jacket146around the line emitter116was angled at 20° (i.e., angle β was 20° relative to the second plane112of the exit aperture110).

As shown inFIG.10, the intensity is greatest between −100 mm and 100 mm on the x-axis between about −50 mm and −70 mm on the y-axis. In the graph beneath the plot ofFIG.10, the irradiance along the y-axis at x=0 mm is shown. Again, the peak irradiance is shown to be between about −50 mm and −70 mm.

FIG.11depicts a plot of irradiance similar to what is shown inFIG.10with the exception that the surface illuminator100was modeled with angle β at 10°, instead of 20°. As can be seen the region of peak intensity is increased in magnitude and in length and width. In particular, the width of the peak region is expanded beyond −100 mm and 100 mm along the x-axis, and the length of the peak region is expanded between about −75 mm and −45 mm.

Thus,FIGS.10and11demonstrate that the angle β at which the line emitter116is arranged with respect to the curved reflector surface120can increase or decrease the irradiance as needed to meet the requirements of disinfecting for the surface as well as to avoid damage to the surface.

FIGS.15and16demonstrate the effect of the optical density of the neutral density filter coating124. The surface illuminator100considered inFIGS.15and16was modeled as described above in relation toFIGS.10and11except that the angle β is set at 25° for bothFIGS.15and16. In the plot ofFIG.15, the model considers a neutral density filter coating124with an optical density of 2.0, and in the plot ofFIG.16, the model considers a neutral density filter coating124with an optical density of 1.0.

InFIG.15, the peak irradiance extends the entire width of the surface, and the peak has a length between about −70 mm and about −10 mm on the y-axis; although, the largest peak is primarily between about −60 mm and about −50 mm. However, the irradiance leading up to the peak (−80 mm to −70 mm) is relatively low compared to the end of the peak (e.g., from 40 mm to 90 mm).

InFIG.16, the irradiance plot and graph demonstrate dual peaks. One peak shown inFIG.16is located in substantially the same position as the peak ofFIG.15(i.e., between −60 mm and −50 mm), and the peak has approximately the same magnitude. The other peak shown inFIG.16is between about −100 mm and −80 mm on the y-axis. Overall, the dual peaks of irradiance expand the coverage of ultraviolet light at the end of the surface where the surface illuminator is positioned. Thus,FIGS.15and16demonstrate that the level of optical density of a neutral density filter can be used to manipulate the irradiance of the surface illuminator.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article “a” is intended to include one or more than one component or element, and is not intended to be construed as meaning only one.

It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosed embodiments. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the embodiments may occur to persons skilled in the art, the disclosed embodiments should be construed to include everything within the scope of the appended claims and their equivalents.