Patent Publication Number: US-3876878-A

Title: Control system for color pattern generator

Description:
United States Patent Frank et al. Apr. 8, 1975 [54] CONTROL SYSTEM FOR COLOR PATTERN 3,120,782 2/l964 Goddard et al. 250/226 X GENERATOR 3.336.482 8/1967 Mierendorf et al 250/229 3,425.146 2/1969 Winstanley [75] Inventors: Bruce Allen Frank, 121 Lmn St., 3 564 332 2/1971 B|ake5lee..  
 Ithaca, NY. 14850; John Arlington 3,609,038 9/1971 Kolshom Miles, Demarest, N..l.; James C. 3,724,954 4/ I973 Dreyfoos. Jr. 356/175 Ahlstrom, Ithaca, N.Y.  
 [73] Assignee: said Frank, by said Miles and Primary E.\&#39;aminer-Walter Stolwein Ahlstrom Attorney, Agent, or Firm-Wolder 8!. Gross [22] Filed: Apr. 12, 1974 [2l] Appl. No.: 460,327 [57] ABSTRACT Related US. Application Data [62] Division of Ser. No. 255 789 May 22 1972 Pat. No. The apparatus Produces Va&#39;ymg Patterns 3 805 049 object and comprises a plurality of color producing units connected together in an assemblage. Each unit 52 1.8. CI. 250/226- 250/205&#39; 355/38 comprises a Curved Surface which SUPPWIS a blue- [51] Int. Cl. G0lj 3/50 and a green light Source An object is Supported a [58] Field of Search 250/226 205 209 preselected distance from the assemblage by an asso- 3l5/l5l 152 153 5 6 ciated support device. A control device connected to 240731 10 DIG. the light sources is adapted to selectively vary the intensity of the light sources of each one of the plurality [56] References Cited of color producing units to obtain color patterns. UNlTED STATES PATENTS 5 Claims, 7 Drawing Figures 3,038.06] 6/1962 O&#39;Reilly 240/3.l  
 CONTROL SYSTEM FOR COLOR PATTERN GENERATOR This is a division, of application Ser. No. 255,789  
 filed May 22, I972, now US. Pat. No. 3,805,049. This invention relates generally to an apparatus for producing varying color patterns on an object and, more particularly, pertains to an apparatus for varying the color patterns on a translucent object or the like to enhance the value of the same as an art form.  
  In the past, many attempts have been made to enhance an art form or object in such a manner that the result will be aesthetically pleasing as well as interesting to the viewer. Some of the earlier attempts have resulted in devices wherein different colored lights were moved relative to the object to produce varying color patterns. Other devices have included the use of flexible reflecting material from which colored lights were reflected while the material was manually or automatically flexed by an appropriate mechansim. However, all of these prior attempts to obtain what may be referred to as a color pattern generator had many drawbacks associated with their use.  
  For example, in those devices where the lights executed a repetitious motion the color patterns were simply repeated on a cyclical basis. As a result, the viewer lost interest shortly in the device and the aesthetic value of the device was minimal. On the other hand, the devices of the type which used continuously flexible material produced randomly varying patterns. However, this produced a problem in and of itself because the viewer had no control whatsoever over the patterns produced.  
  Accordingly, an object of the present invention is to provide an improved color pattern generator.  
  A more specific object of this aspect of the invention is to provide a color pattern generator which produces both aesthetically pleasing and continuously interesting color patterns on an object of an art form.  
  Another&#39;object of the invention is the provision of a color pattern generator wherein the colors may be modulated in a desired manner.  
  A further object of the invention resides in the novel details of construction which provide a color pattern generator of the type described wherein the patterns produced thereby may be controlled in a desired manner.  
  Accordingly, a color pattern generator produced in accordance with the present invention comprises at least a curved support having a preselected radius of curvature. Light source means comprising at least first and second different colored light sources are mounted on the support with their central axes lying along radii of curvature. Object support means is placed in spaced relationship from the curved support and is adapted to support the object to be illuminated. Control means is provided which is connected to the first and second light sources for selectively varying the first and second light sources to produce the varying color patterns.  
  A feature of the present invention is to provide a color pattern generator wherein colors in an object are modulated without changing the composition or form of the object.  
  Other features and advantages of the present invention will become more apparent from a consideration of the following detailed description when taken in 2 conjunction with the accompanying drawings, in which:  
  FIG. 1 is a front elevational view of a color pattern generator constructed in accordance with the present invention;  
  FIG. 2 is a partial sectional view taken along line 22 of FIG. 1;  
  FIG. 3 is a schematic view. to an enlarged scale, of the light sources in a color unit of the generator shown in FIG. 1, illustrating the light pattern produced by the mm;  
  FIG. 4 is a front elevational view, to an enlarged scale, of a color unit shown in FIG. 1, illustrating the light pattern appearing on the object;  
  FIG. 5 is a schematic circuit wiring diagram for controlling two of the light sources;  
  FIG. 6 is a schematic wiring diagram illustrating a portion of the control circuit for the third light source in a color unit; and  
  FIG. 7 is a vertical sectional view of a key-operated device which may be used to control the circuits shown in FIGS. 5 and 6.  
  A color pattern generator constructed according to the present invention is designated generally by the reference numeral 10 in FIGS. 1 and 2 and includes an enclosure 12 having a rear wall 14, a top wall 16, a bottom wall 18, and opposed side walls 20. The walls 16, 18 and 20 define a front opening 22 in which is received a transparent sheet of material 24 (FIG. 2). Similar sheet 26 is spaced beyond the sheet 24. The sheets 24 and 26 extend beyond the side walls 20 and define a slot 28 therebetween which is adapted to receive an art form or an object upon which the varying color patterns produced by the generator of the present invention will be projected. The sheets 24 and 26 may be composed of any type of material which will pass light.  
  The rear wall 14 comprises a plurality of color producing units, each one of which is designated generally by the reference numeral 30. As shown in FIG. 1, nine such color units 30 are provided in a 3 X 3 matrix. However, this is for illustrative purposes only and is not to be interpreted as being a limitation on the present invention. That is, the present invention contemplates that each color producing unit 30 may be fabricated independently of any other color producing unit and may be connected thereto by appropriate brackets (not shown in the drawings). Since all of the units 30 are identical in construction, only one unit will be described in detail.  
  A color producing unit 30 as shown in FIG. 1, is generally in the shape of a&#39;square. However, the interior supporting surface 32 (FIG. 3) of the unit 30 is curved and has a radius of curvature such that the curved support surface 32 forms a portion of a sphere with the center of curvature of the spherical surface being located at point 34. Mounted on the support surface 30 by any conventional means are three light sources respectively designated 36, 38 and 40. The light sources are mounted with respect to the curved support surface 32 such that their central axes are perpendicular to a tangent to the spherical surface at the point of connection. In other words, as shown schematically in FIG. 3, the central axes 42, 44 and 46 of the respective light sources 3640 lie along radii of the curved surface or support 32 and intersect at the center of curvature 34.  
  As schematically shown in FIG. 3, the slot 28 which receives the object upon which the varying color patterns are projected lies in the plane of the center of curvature of the surface 32. Accordingly, each one of the light sources 36-40 will produce a light pattern at the slot 38 which overlaps the light pattern of the other light sources associated with the particular unit so that the light pattern produced by any one color producing unit 30 will be circular as shown by the dash lines 48 in FIG. 4. It is to be emphasized that FIG. 3 is only a schematic representation of the arrangement of the light sources and the curved surface to illustrate how the light pattern is formed. In practice, the light sources will be grouped as triads as shown in FIGS. 1 and 4.  
  Ideally, the light sources 36-40 are different colored lamps which, in combination, may be operated upon to produce varying colored circles 48 of light on the object received within the slot 28. More specifically, the light sources 36-40 are monochromatic sources of light. The light source 36 is a red light source; the light source 38 is a green light source; and, the light source 40 is a blue light source. A control unit designated generally by the reference numeral 50 in FIG. 2 is connected to the light sources in each of the color producing units 30 by a table 52. As noted in greater detail below. the control unit 50 is adapted to vary the intensity of the individual light sources in each unit thereby to produce the varying color patterns on the object.  
  In other words, the color of the circle of light 48 projected on the object will be dependent upon the contribution made by each one of the light sources. For example, if only the red light source 36 in a unit is energized, the color produced by that particular unit will be red. On the other hand, if the green and blue lamps are energized equally, a different color will result. Therefore, the ultimate color projected on the object may be controlled by controlling the intensity of the light sources 36-40 in the same manner that the color is reproduced on a color television set by controlling the intensity of the color triads red, green and blue on the face of a television tube.  
  While the intensity of the light sources 36-40 may be controlled in any manner, the control unit 50 is adapted to control the intensities of the respective light sources from a multi-frequency source wherein the low frequency signals control the intensity of the red light source 36, the intermediate frequency signals control the intensity of the green light source 38 and the high frequency signals control the intensity of the blue light source 40. Alternatively. the intensity of the light sources may be controlled by a pulse generator so that both. the intensity and repetition rate of the light sources may be selectively controlled. As another alternative. the intensity of the light sources may be controlled by an external key-operated device similar to piano keys wherein the length of travel of a depressed key produces a corresponding change in intensity in the light source.  
  FIG. 5 illustrates the portion of the control unit 50 which controls the illumination intensity of the red light source 36. The control circuitry for the green light source 38 is identical to that shown in FIG. 5 with the exception noted below. In a like manner, the control circuit for the blue light sources 40 is substantially similar; however, the differences are shown in FIG. 6.  
  Accordingly, a pair of input terminals 54 are provided which are adapted to be connected to&#39; a conventional AC source of potential. Connected across the input terminals 54 through a series circuit comprising a single-pole single-throw on-off switch 56 and a fuse 58 is a full wave bridge rectifier 60. Connected in parallel with the rectifier 60 is a pilot lamp 62 which is adapted to be illuminated when the switch 56 is closed to indicate that the control unit is operating. The positive terminal of the rectifier 60 is connected to one side of all of the lamps 36 in the pattern generator 10 via a lead 64. The lamps 36 are divided into two groups. As shown in FIG. 1, nine color producing units 30 are provided. Accordingly, four of the lamps 36 are connected to a lead 66 through a silicon controlled rectifier or SCR 68. The other five light sources 36 are connected to the lead 66 through an SCR 70. The lead 66 is connected tothe negative output terminal of the bridge rectifier 60. Thus, the group of light sources 36 connected to the SCR 68 will be illuminated when the SCR 68 is tired whereas the group of lamps 36 connected to the SCR 70 will be illuminated when the SCR 70 is tired. Essentially, the conduction cycle of the SCR 68 and SCR 70 are controlled in a preselected manner thereby to control the intensity of the lamps 36. The lead 64 is connected to the lead 66 through a series circuit comprising a resistor 72, the resistance of a potentiometer 74, a resistor 76, and a capacitor 78. The sliding arm of the potentiometer 74 is connected to the second base ofa unijunction transistor through a resistor 82. Base 1 of the transistor 80 is connected to the lead 66 through a resistor 84 and to the gate electrode of the SCR 68 by a lead 86.  
  The emitter electrode of the transistor 80 is connected to the collector electrode of a transistor 88. The emitter electrode of the transistor 88 is connected to a lead 90 through a resistor 92. The base electrode of the transistor 88 is connected to one terminal of the secondary winding of an audio transformer 94 through a diode 96 by a lead 98. The diode 96 is polarized so that the anode electrode thereof is connected to the base of the transistor 88. The other terminal of the secondary winding of the transformer 94 is connected to the lead 90. Connected in parallel with the secondary winding of the transformer 94 is a capacitor 100. One end of the primary winding of the transformer 94 is connected to one end of a potentiometer 102. The other end of the primary winding of the transformer is connected to the sliding arm of the potentiometer 102. The potentiometer 102 is connected to a pair of input terminals 104 which are adapted to be connected to a multifrequency source of a signal such as a phonograph or the like.  
  The capacitor together with the secondary winding of the transformer 94 form a filter which, in the case of the light sources 36 form a resonant filter so that only the frequencies at the low end of the spectrum from the multi-frequency source are passed to the succeeding circuitry. The circuitry for controlling the intensity of the green light sources 38 is identical to that shown in FIG. 5 with the exception that the value of the capacitor 100 is changed so that the capacitor 100 and the secondary winding of the transformer form a filter which only passes intermediate frequencies. Therefore, the intermediate frequencies of the multi-frequency signal will control the intensity of the green light source 38. The base of the transistor 88 is also connected to the lead 90 via a capacitor 106 and a resistor 108. Additionally, a series circuit comprising a diode 110 and a capacitor 112 is connected between the leads 98 and 90. The diode 110 is polarized so that the anode electrode thereof is connected to the base of the transistor .88. The junction of the capacitor 112 and the diode is connected by a lead 114 to the lead 66 through a series circuit comprising a resistor 300 and a photoresistor 116. The lead 114 is connected to the lead 90 through a resistor 118.  
  A diode connects the junction of the resistor 72 and the resistance of the potentiometer 74 to the lead 90. The diode is polarized so that the cathode electrode thereof is connected to the lead 90. Additionally, a capacitor 122 is connected between the leads 66 and 90. Additionally, a zener diode 132 connects the junction of the resistor 72 and the potentiometer 74 to the lead 66. The diode 132 is polarized so that the anode electrode thereof is connected to lead 66. The diode 120 provides a constant bias on the lead 90 while the capacitor 122 functions as a filter capacitor.  
  The circuit thus far described controls the firing of the SCR 68 and thereby controls the intensity of the group of light sources 36 connected thereto. Similar circuitry is provided to control the group of light sources 36 connected to the SCR 70. More specifically, the gate electrode of the SCR 70 is connected by a lead 124 to base 1 of a unijunction transistor 126. Base 1 of the transistor 126 is also connected to the lead 66 through a resistor 128. Base 2 of the transistor 126 is similarly connected to the cathode of diode 132 through a resistor 130. Additionally, the end of the resistor 130 connected to the diode 132 is also connected to the sliding arm of a potentiometer 134 and to one end thereof. The other end of the potentiometer 134 is connected via a resistor 136 to the emitter electrode of the transistor 126. A capacitor 140 connects the emitter of the transistor 126 to a lead 142. The lead 142 is also connected to the lead 66.  
  The emitter electrode of the unijunction transistor 126 is connected to the collector electrode of a transistor 144 via a lead 146. The emitter electrode of the transistor 144 is connected to the lead 90 through a resistor 148. The parallel circuit of a capacitor and a resistor 152 connect the base electrode of the transistor 144 to the lead 90. Additionally, the base electrode of the transistor 144 is connected to one terminal of the secondary winding of an audio transformer through a diode 162. The anode electrode of the diode 162 is connected to the base electrode of the transistor 144. The other terminal of the secondary winding of the transformer 160 is connected to the lead 90 by a lead 164. Similarly to the capacitor 100, a capacitor 166 is connected in parallel with the secondary winding of the transformer 160 and for the same reasons as the capacitor 100. The primary winding of the transformer 160 is connected between the sliding arm and one end of a potentiometer 168. A similar multi-frequency source as the one adapted to be connected to the terminals 104 is adapted to be connected to terminals 170 which, in turn, are connected to the respective ends of the potentiometer 168.  
  Also connected between the base electrode of the transistor 144 and the lead 90 is a series circuit comprising the diode 172 and a capacitor 174. The diode 172 is polarized so that the anode electrode thereof is connected to the base electrode of the transistor 144. A lead 176 is connected to the junction of the diode 172 and the capacitor 174. A resistor 175 connects the lead 176 to the lead 90. Additionally, a series circuit comprising a resistor 301 and a photoresistor 178 is connected between the lead 176 and the lead 142. The lead 176 is connected to the sliding arm of a potentiometer 180 through a diode 182, the anode electrode of which is connected to the junction of the capacitor 174 and the diode 172.  
  The resistance portion of the potentiometer 180 is connected at one end to the lead 90 at the other end to a resistor 182. The other end of the resistor 182 is connected to the collector electrode of a transistor 184, the emitter electrode of which is connected to the lead 142. The collector electrode of the transistor 184 is connected to the base electrode of a transistor 186 through the series circuit comprising a capacitor 188 and a diode 190. The diode 190 is polarized so that the cathode electrode thereof is connected to the base of the transistor 186. Additionally, the junction of the diode 190 and the capacitor 188 is connected to the lead 90 through a resistor 192 and a potentiometer 194, the sliding arm of which is adapted to short out portions of the resistance section. The collector electrode of the transistor 186 is connected to the lead 90 through a resistor 196. Additionally, the collector electrode of the transistor 186 is connected to the base electrode of the transistor 184 through a resistor 198. The transistors 184 and 186 and the interconnecting circuitry form an astable multivibrator.  
  The triggering of the multivibrator is controlled from a unijunction transistor oscillator which includes the unijunction transistor 200. Thus, base 1 of the transistor 200 is connected to the base electrode of the transistor 184 through a resistor 202. Additionally, base 1 of the transistor 200 is connected to the lead 142 through a resistor 204. Base 2 of the transistor 200 is connected to the lead 90 through a resistor 206. A capacitor 208 is connected between the lead 142 and the emitter electrode of the transistor 200. Additionally, the emitter electrode of the transistor 200 is connected to the lead 90 through a resistor 210 and the resistance of a potentiometer 212, the sliding arm of which is adapted to short out various portions of the resistance.  
  Connected in parallel with the potentiometer 180 is a poteniometer 214. The sliding arm of which is connected via a diode 216 to the lead 114. The diode 216 is polarized so that the anode electrode thereof is connected to the lead 114.-  
  In operation, the art form to be illuminated by the collor pattern generator 10 is inserted into the slot 28. Thereafter, the on-off switch 56 is closed to energize the cortrol unit 50. The light sources 36-38 of each control unit may then be illuminated in any one or more of the manner outlined below to control the intensity of the respective light sources 36-40 in groups of twos, as noted above.  
  That is, the respective potentiometers 74 and 134 are adjusted so that the respective unijunction transistors 80 and 126 begin conducting at a preselected point in their cycle of operation, thereby causing the associated SCR 68 and SCR 70 to fire. The firing of the SCR 68 and SCR 70 causes the light sources associated therewith to illuminate. Thus, the intensity of the light sources connected to the respective SCRs 68 and 70 will be determined by the point at which the respective transistors 80 and 126 begin conducting.  
 The point at which the transistors 80 and 126 begin conducting is determined by the charge on the respective capacitors 78 and 140. The charge on the capacitors 78 and 140 is determined by the current controlled by the transistors 88 and 144. Thus, the control signal applied to the base of the transistors 88 and 144 will determine the rate of accumulation of charge on the capacitors 78 and 140, respectively, and thereby determine the intensity of the lamps controlled by the SCRs.  
  The potential applied to the base electrodes of the transistors 88 and 144 may be derived from three different sources which may be individually applied to the base electrodes of the transistors 88 and 144 or may be applied thereto in combination. It is to be noted that the diodes 110, 96 and 216 isolate the respective sources from each other as do the diodes 182, 162 and 172.  
  More specifically, the multi-frequency source of signals connected to the respective terminals 104 and 170 will be applied to the base electrodes of the transistors 88 and 144 respectively through the respective filters formed by the secondary winding of the transformer 94 and the capacitor 100 and the secondary winding of the transformer 160 and the capacitor 166. These multifrequency signals are rectified by the respective rectifiers 96 and 162 and are applied to the respective base electrodes of the transistors 88 and 144 thereby to operate the light sources in the manner noted above. While the circuit shown in FIG. is designed for the passage of low frequencies to the base electrode, it is noted that where the green light source is concerned, the filter will pass intermediate frequencies.  
  Alternatively, the photoresistors 116 and 178 are normally of substantially high resistance so that no potential will be applied to the base electrodes of the transistors 88 and 114 through the respective photoresistors. However, as additional light is permitted to impinge on the photoresistors 116 and 178, the respective resistances decrease so that a greater portion of the potential is applied to the base electrodes of the transistors 88 and 144. Accordingly, the light falling on the photoresistors 116 and 178 will therefore control the current flow through the respective transistors 88 and 144 thereby to control the intensity of illumination of the two groups of light sources 36. It is to be noted that if more light is permitted to fall on the photoresistor 116 than the photoresistor 178, the intensity of the lamps connected to the SCR 68 will be greater than the intensity of the lamps connected to the SCR 70 since the capacitor 78 will accumulate charge at a greater rate than the capacitor 140.  
  A third source of control signals comprises the unijunction transistor 200 which is connected as an oscillator, as noted above. The setting of the potentiometer 212 determines the frequency of the oscillator, in the conventional manner. Accordingly, trigger pulses will cyclically be applied to the astable multivibrator comprising the transistors 184 and 186 thereby to cause the transistors to produce output pulses the height of which is controlled by the potentiometers 214 and 180. These pulses are applied to the base electrode ofthe transistor 88 through the diodes 216 and 110 and to the base electrode of the transistor 144 through the diodes 182 and 172 thereby again to control the rate of charge of the capacitors 78 and 140. Thus, the intensity of the group of lamps 36 connected to the SCR 68 will be controlled by the setting of the potentiometer 214 while the intensity of the group of light sources 36 connected to the SCR 70 will be controlled by the setting of the potentiometer 180. It is to be noted that if two or more of the sources of signal for the base electrodes of the transistors 88 and 144 are utilized, the signal having the greatest amplitude will control the intensity of the lamps.  
  As noted hereinabove, the circuitry for controlling the blue light sources 40 is slightly different than the circuit utilized to control the red and green light sources. In particular, the circuits are identical except for the filter arrangement connected to the multifrequency source of signals. Accordingly, the variation of the circuit for controlling the blue light source is shown in FIG. 6 wherein similar numerals indicate identical elements as in FIG. 5 with only the differences being shown in FIG. 6.  
  Thus, the lead 90 is connected to the cathode electrode of the diode 96 by a resistor 218. Additionally, the cathode electrode of the diode 96 is connected to one terminal of the secondary winding of the transformer 94 through a capacitor 220. The other terminal of the secondary winding of the transformer 94 is connected to the lead 90. The capacitor 120, resistor 218 and the secondary winding of the transformer 94 form a high pass filter so that only the high frequencies in the multi-frequency source are rectified by the diode 96 and applied as a control signal to the base electrode of the transistor 88.  
  The light impinging on the photoresistors 116 and 178 may be controlled by a key-operated device of the type shown in FIG. 7. Thus, an enclosure 222 is provided having a front wall and right side wall which are not shown in the figure. The enclosure 222 includes a bottom wall 224, &#39;a left side wall 226 and a rear wall 228. Pivotally mounted on the rear wall 228 are keys 230, 232, 234 and 236. Depending from each key is a partition 238 having an aperture 240 therethrough.  
  Mounted on the bottom wall 24 are spaced upstanding partitions 242 alternate ones of which support the respective photoresistors 116 and 178, as shown in the figure. Each one of the photoresistors is in juxtaposition to one side of the partitions 238. In juxtaposition to the other side of the respective partitions 238 are upstanding walls 244 having through bores 246 which are in alignment with theopposed photoresistors. A lamp 248 is received between each pair of walls 244 in alignment with the bores 246.  
  The keys 230-236 are normally biased upwardly so that the partition 238 is received between a photoresistor and the opposed bore 246. Hence, the light from the lamps 248 is prevented from reaching the associated photoresistor. However, as a key is depressed the aperture 240 moves into registration with the juxtaposed bore 246 and associated photoresistor thereby permitting light to reach the photoresistor and decrease the resistance thereof. It is obvious that the further a key is depressed, the more light will reach a photoresistor and, accordingly, a stronger control signal will be applied to the base electrode of the controlling transistor to cause the intensity of the associated lamps to increase. Thus, for example, complete depression of the key 234 permits all of the light to pass through the bore 246, the aperture 240 and reach the photoresistor 116 thereby reducing the resistance of the photoresistor 116 to a minimum value. Hence, the control signal applied to the base electrode of the transistor 88 will be a maximum and the intensity of the group of light sources connected to the SCR 68 will thereby increase.  
  Accordingly, a color pattern generator has been dis: closed which can produce varying color patterns on a translucent art form or the like which are both aesthetically pleasing and continuously interesting and may be selectively controlled by the viewer.  
  While a preferred embodiment of the invention has been shown and described herein, it will become obvious that numerous omissions, changes and additions may be made in such embodiment without departing from the spirit and scope of the present invention.  
 What is claimed is:  
  1. Control apparatus for controlling the illumination of at least a first, second and third light source comprising first radiation responsive intensity means for controlling the intensity of said first light source, second radiation responsive intensity means for controlling the intensity of said second light source, and third radiation responsive intensity means for controlling the intensity of said third light source, input terminals adapted to be connected to a multi-frequency signal source, first filter means connected between said input terminals and said first intensity means for passing a first band of frequencies to said first intensity means to control the operation thereof; second filter means connected between said input terminals and said second intensity means for passing a second band of frequencies to said second intensity means to control the operation thereof, and third filter means connected between said input terminals and said third intensity means for passing a third band of frequencies to said third intensity means to control the operation thereof.  
 2. Control apparatus as in claim 1, in which said first light source is a high frequency light source, and said first band of frequencies is a high frequency band; said second light source is an intermediate frequency light source, and said second band of frequencies is an intermediate band; and said third light source is a low frequency light source, and said third band of frequencies is a low band.  
  3. Control apparatus as in claim 2, and respective pulse producing means connected to said first, second and third intensity means for controlling the operation thereof.  
  4. Control apparatus as in claim 1, in which said first, second and third intensity means are responsive to light signals for controlling the intensity of the associated light source in proportion to the value of the light signal; and respective light signal means for applying selectively variable light signals to said first, second and third intensity means.  
  5. Control apparatus as in claim 4, in which each of said intensity means includes a photoresistor, and each of said light signal means comprises a source of illumination, an aperture in alignment with said source of illumination and said photoresistor, and a shutter having a through bore movable into and out of registration with said aperture to control the amount of light transmitted to said photoresistor, and moving means for selectively moving said shutter to vary the degree of registration between said bore and said aperture.