Abstract:
A color printer ( 10 ) for imaging onto a photosensitive medium ( 140 ) that contains four or more layers for providing images having an expanded color gamut. Color printer ( 10 ) directs polarized light from each of four or more light sources ( 12 ) to a spatial light modulator ( 20 ) for forming an image to be printed. Modulated light is conditioned as necessary, then focused through a print lens ( 110 ) onto photosensitive medium ( 140 ). Light sources  12  can be lasers, LEDs, or other suitable components. Embodiments may use a single spatial light modulator ( 20 ) shared with each color path or a spatial light modulator ( 20 ) in each of the four color paths.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Reference is made to commonly-assigned copending U.S. patent application Ser. No. 10/082,936, filed Feb. 26, 2002, entitled FOUR COLOR IMAGE SENSING APPARATUS, by Roddy et al.; and U.S. patent application Ser. No. 10/067,929, filed Feb. 6, 2002, entitled PRINTING APPARATUS FOR PHOTOSENSITIVE MEDIA USING DICHROIC PRISM IN ILLUMINATION PATH, by Roddy et al., the disclosures of which are incorporated herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of color printers or writers and is specifically concerned with writing digital color images onto motion picture film for theater projection. 
     BACKGROUND OF THE INVENTION 
     For quite some time writers have existed that can take electronic/digital image data and use it to expose color motion picture film. The most mature of the technologies, still in use today, uses the color cathode ray tube (CRT). Celco is one of several manufacturers in this field. Another is Management Graphics which makes the Solitaire CRT film writer. The electron beam generated by the CRT strikes the red, green, and blue (RGB) phosphors on the surface of the tube. The phosphors then emit light which is imaged onto the film. The image is written in a raster scan. 
     Laser writers for film, capable of higher resolution and generally higher speeds than their CRT counterparts, have been in use for a decade. The Kodak Cineon System uses a laser writer with red, green, and blue gas laser sources. The lasers are raster scanned by a rotating polygon mirror onto a moving drum. A more recent introduction, the Arrilaser by Arri, uses a flat platen instead of a drum and a single faceted scanner mirror (monogon). The red, green, and blue lasers use solid state or diode laser technology, but the basic approach is the same. Three primary color sources, red, green, and blue, are used to expose the three emulsion layers (red sensitive, green sensitive, and blue sensitive) to produce three color dye layers in the developed film. Typically, in a color negative media, the dyes are the subtractive color primaries: cyan, magenta, and yellow. 
     For example, U.S. Pat. No. 6,018,408 discloses a RGB raster scan laser projector using polygon/galvo scanner. A white light laser is separated into RGB components for modulation and projection. Similar devices are designed to demagnify the image for film exposure. 
     As another example, U.S. Pat. No. 5,537,258 discloses a laser projection system with red, green, and blue dye lasers providing the primary colors for forming an image using a single shared spatial light modulator. In this case, instead of a raster scan, the entire image area is exposed simultaneously, by using an area modulation device. 
     FIG. 1 shows a familiar color gamut representation using CIE 1976 L*u*v* conventions, with the perceived eye-brain color gamut in u′-v′ coordinate space represented as a visible gamut  100 . Pure, saturated spectral colors are mapped to the “horseshoe” shaped periphery of the visible gamut  100  curve. The interior of the “horseshoe” contains all mappings of mixtures of colors, such as spectral red with added blue, which becomes magenta, for example. The interior of the horseshoe can also contain mixtures of pure colors with white, such as spectral red with added white, which becomes pink, for example. The overall color area defined by the “horseshoe” curve of visible gamut  100  is the full range of color that the human visual system can perceive. It is desirable to represent as much as possible of this area in a color display, to come as close as possible to representing the original scene as we would perceive it if we were actually viewing it. 
     The gamut available using conventional color motion picture film is shown by a conventional motion picture film gamut triangle  102  in FIG.  1 . The approximate wavelengths of vertices of the triangle are shown as red (620 nm), green (540 nm), and blue (455 nm). Any color within the bounds of this triangle can be displayed. Colors lying outside the triangle but within the “horseshoe” curve can be perceived by the human eye but cannot be represented with conventional color film. Such colors are out-of-gamut colors, such as turquoise (blue-green), for example. 
     FIG. 2 shows the same curve  100  with the human eye response, but this time a polygon  106 , representing the gamut achievable using a four color laser display is shown. The vertices of gamut polygon  106  are the laser wavelengths: red  116  at 649 nm, green  114  at 514 nm, blue-green  112  at 488 nm, and blue  108  at 442 nm. Lasers, by their very nature, are monochromatic, providing fully saturated colors, unlike most light sources. Saturated colors lie on the periphery of the “horseshoe” curve. The resulting four laser gamut covers virtually the whole range of visual color space. Clearly, the introduction of a fourth color into this display provides a considerable gamut increase over that of conventional motion picture film as shown in FIG.  1 . 
     With respect to digital projection apparatus, there have been some attempts to expand from the conventional three-color model in order to represent color in a more accurate, more pleasing manner. Notably, few of these attempts are directed to expanding the color gamut. For example, U.S. Pat. No. 6,256,073 (Pettit) discloses a projection apparatus using a filter wheel arrangement that provides four colors in order to maintain brightness and white point purity. However, the fourth color added in this configuration is not spectrally pure, but is white in order to add brightness to the display and to minimize any objectionable color tint. It must be noted that white is an “intra-gamut” color addition; in terms of color theory, adding white actually reduces the color gamut by desaturating the color. Similarly, U.S. Pat. No. 6,220,710 (Raj et al.) discloses the addition of a white light channel to standard R, G, B light channels in a projection apparatus. As was just noted, the addition of white light may provide added luminosity, but constricts the color gamut. 
     U.S. Pat. No. 6,191,826 (Murakami et al.) discloses a projector apparatus that uses four colors derived from a single white light source, where the addition of a fourth color, orange, compensates for unwanted effects of spectral distribution that affect the primary green color path. Again, the approach disclosed in the Murakami patent does not expand color gamut and may actually reduce the gamut. 
     Patent Application WO 01/95544 A2 (Ben-David et al.) discloses a display device and method for color gamut expansion using four or more primary colors. However, the approach disclosed in WO 01/95544 is directed to apparatus for projection of digital images, but does not provide a suitable solution for imaging onto a photosensitive medium. It must be emphasized that there are significant differences between display and printing of digital color images. For example, image brightness, which must be optimized in a display system, is not a concern in printing apparatus design. Resolution, on the other hand, while not as important for images displayed on-screen, is very important for images printed on film or paper. Timing requirements are not as demanding for color printing, since successive exposures can be used for successive layers of a photosensitive medium. Notably, the apparatus disclosed in WO 01/95544 forms an image by projecting four colors, but uses three-color RGB data as input for computing a four-color value. It can be appreciated that there would be advantages in obtaining and processing four-color data throughout the imaging process, rather than using interpolation algorithms to compute a fourth color coordinate from three-color data. 
     It would be advantageous to have a color film equivalent to the extended gamut of a four laser display as represented in FIG.  2 . Digital cinema, now in its infancy, can take immediate advantage of this increased gamut to enhance the theatrical experience of the movie audience. Although digital projection may gradually replace many of the 35 mm film projectors in existence today, it would be economically advantageous for filmmakers to have the capability to have their movies shown on film projectors as well as on digital cinema projectors, and NTSC and HDTV television. However, merely exposing a conventional color film to these four laser sources would not change the gamut available beyond that of FIG.  1 . 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a color printer for photosensitive media that provides four different color light sources to print on photosensitive media that has four separate spectral sensitivities depositing four dyes upon processing to expand the color gamut of the resultant image. 
     Briefly, according to one aspect of the present invention a color printer for printing to a photosensitive medium comprises a first light source for generating a first color beam and a first modulator for modulating the first color beam. A second light source for generating a second color beam and a second modulator for modulating the second color beam. A third light source for generating a third color beam and a third modulator for modulating the third color beam. A fourth light source for generating a fourth color beam and a fourth modulator for modulating the fourth color beam. An optical system combines and images the modulated beams onto the photosensitive medium. 
     It is an advantage of one embodiment of the invention to provide a compact unit for high speed writing, having four light sources and four modulators in a single plane. 
     It is an advantage of another embodiment to provide to provide a simple printer that combines four light sources and a single modulator in a single optical path to provide sequential exposure. 
     It is an advantage of another embodiment to provide a compact sequential writer that uses an x-cube to combine four light sources. 
     It is an advantage of yet another embodiment to provide a writer with high optical efficiency by utilizing four polarized lasers as light sources. 
     The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the human visual color perception space in u′, v′ coordinates based on the CIE convention. Also shown for comparison is the triangular color gamut that can be achieved by conventional motion picture film. 
     FIG. 2 shows the human visual color gamut along with the extended gamut achieved by a four color laser display. 
     FIG. 3 shows the human visual gamut along with the extended gamut that can be achieved by a color film with four sensitive layers. 
     FIG. 4 is a schematic view of a four color simultaneous writer optical system with four light sources (red, green, blue-green, and blue) and four spatial light modulators. 
     FIG. 5 is a schematic view of a four color sequential writer optical system which uses a multicolor LED array source and a single spatial light modulator. 
     FIG. 6 is a schematic view of a four color sequential writer optical system which uses four single-color sources, combined through a dichroic prism, and a single spatial light modulator. 
     FIG. 7 is a schematic view of a four color simultaneous writer optical system with four independently modulated laser sources (red, green, blue-green, and blue) and a raster scan polygon-galvo mirror deflection system. 
     FIG. 8 is a schematic view of a four color sequential writer optical system with four laser sources (red, green, blue-green, and blue) and a single spatial light modulator. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be directed in particular to elements forming part of, or in cooperation more directly with the apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. 
     It has been shown that the color gamut of conventional film is limited to a triangular region by the three dyes that are formed in the three color sensitive layers during the process of color development of the photographic film. Simply exposing conventional color film to four light sources (red, green, blue and a fourth color, such as blue-green or yellow, for example) will not extend the color gamut. What is required is a fourth color sensitive layer that forms a fourth dye upon processing. 
     Comparing FIGS. 1 and 2, one obvious choice for the color of the fourth dye is in the blue-green region of the spectrum around 490 nm in order to achieve the largest possible polygon area and color gamut. Such a film gamut  120  is shown in FIG.  3 . The red  121 , green  122  and blue  124  vertices are the same as FIG. 1, assuming that the original dyes are unchanged. The blue and the red dyes could be modified also to achieve an even greater gamut. The new blue-green vertex  123  is located near 490 nm. It should be understood that the dyes formed are not quite as saturated as laser sources, such that the vertices are near, but not on, the periphery of the “horseshoe” curve of visible gamut  100  that defines human vision. Nonetheless, a substantial improvement in gamut is achieved. 
     It is not necessary to design both a negative and a print film with four color capability. A single reversal film, basically a slide film, can suffice. The productivity burden is then placed on the four source writer that exposes this film. The color gamut of the resultant image is determined by the dyes in the processed film, not by the exposure sources. Therefore, LEDs or filtered tungsten lamps could be used in place of lasers as exposure sources, taking care to avoid printup/punchthrough of an adjacent color. In addition, the light color used for film exposure need not be the color in the original scene or the color of the dye deposited in processing. For example, blue-green dye could be deposited by infrared exposure, where the fourth layer is infra-red sensitive. 
     The Fuji Photo Film Co. Ltd., of Tokyo, Japan offers several color negative films with four color sensitive layers. The outermost is a blue sensitive layer, then a green sensitive layer, then a cyan (blue-green) sensitive layer, then a red sensitive layer. When processed, these layers form the complementary or subtractive primary dyes. Uppermost is the yellow negative image, then a magenta negative image, then a light-magenta negative image, and finally a cyan negative image. Interimage effects on the red sensitive layer from the light-magenta image formed by the cyan sensitive layer are used to approximate the red negative lobe of the eye color matching function. This results in a film system that more closely matches the human eye&#39;s response to color, but does nothing to increase the gamut of colors reproducible by the system. 
     U.S. Pat. Nos. 6,159,674 and 6,197,489 describe in detail the construction of a film with four sensitive layers. U.S. Pat. No. 6,159,674 discloses a film with an red dye forming layer in addition to the standard cyan, magenta, and yellow dye forming layers, while U.S. Pat. No. 6,197,489 discloses a film with a blue dye forming layer in addition to the standard cyan, magenta and yellow dye forming layers. U.S. Pat. No. 6,197,489 does mention that it could be used with a digital printer that has four light sources to improve color gamut. The gamut extension noted is in the blue or red region, however, not in the blue-green region. Extension to both the red and blue regions may best be accomplished with a three dye system where the center wavelengths of the red and blue dyes are positioned farther out on the visual curve toward the red and blue extremities. In any case, films with an additional color sensitive layer forming an additional dye image are indeed possible. 
     U.S. Pat. No. 6,215,547 discloses an RGB printer based on red, green, and blue LED sources that prints on photographic paper and film. U.S. Pat. No. 5,982,407 discloses a photographic printer that uses red, green, and blue LED sources and also allows for a white LED to expose monochromatic images onto color film. 
     The flying spot laser raster scan approach to digital printing is disclosed in U.S. Pat. No. 4,728,965. The laser is usually sequentially modulated on a pixel by pixel basis by an acousto-optic modulator. The high-speed horizontal scan is accomplished by a polygon or hologon scanner. The slower speed vertical scan is generally accomplished by a precision film transport or by a galvanometer driven mirror. 
     FIG. 4 shows a color printer  10  designed to write on an extended gamut photosensitive media with four color sensitive layers. The printer has four sources, shown here as red  12 R, green  12 G, blue-green  12 BG, and blue  12 B. These would typically be lasers or LEDs but could be filtered white light sources also or any combination of sources. Following the blue channel, the beam from the source  12 B passes through a uniformizer  14 B, which can be an integrator bar or a lenslet array. A condenser lens  16 B images the uniformized light beam through a polarization beamsplitter  18 B onto the spatial light modulator  20 B, shown here as a reflective LCD device. The light must be polarized for the LCD to work properly. The plane of polarization is out of the plane of the paper as indicated by the dot before the polarization beamsplitter prism  18 B. 
     The LCD modulator has a large number of pixel sites which are electrically addressed by the blue image data (not shown). Depending upon the amount of voltage applied to a given pixel, the plane of polarization of the light from that pixel is rotated such that part or all of it is horizontal and lies in the plane of the paper as indicated by the arrow after the prism. 
     The image modulated beam then passes through a half wave plate  22 B which rotates the plane of polarization back to vertical (out of the plane of the paper) so that it will be reflected by an x-cube  86  and be imaged by a print lens  110  onto a photosensitive medium  140 . The red channel is handled in an identical manner. The green  12 G and blue-green  12 BG channels are shown to have opposite polarizations and are combined by a dichroic mirror  19  before entering a polarization beamsplitter  18 G. This design takes advantage of the fact that x-cube  86  will pass light of either polarization only in this particular direction. The uniformized beam of the appropriate color strikes the appropriate modulator  20 G or  20 BG and the image modulated beam is sent to x-cube  86 . The coatings of a standard x-cube may have to be adjusted slightly so that x-cube  86  passes both blue-green and green in this direction. Both the blue-green and green light pass through x-cube  86  and are imaged by print lens  110  onto photosensitive medium  140 . 
     This design allows a compact arrangement of all the optical components in a single plane and allows all four colors to be exposed simultaneously. It is possible to have both G and BG sources with S-polarization, allowing an analyzer to improve contrast, but this approach is likely to require a custom x-cube coating. Light sources  12 R,  12 B,  12 G, and  12 BG can be LED arrays, lasers, filtered white light sources, or any combination. It should be noted that the color of the exposing light source  12  need not be the same as the color of the dye deposited in film processing. For example, the blue-green dye could be deposited as a result of exposure of that photosensitive layer to a source of infra-red or ultra-violet light. The chemical couplers determine which dye gets deposited. The sensitivity of the film layer has to be responsive to the wavelength of the intended source. Likewise, blue dye could be deposited as a result of exposure to ultra-violet light. The term “light”, as used here, can refer to any portion of the electromagnetic spectrum, and not just the visible region. X-ray sources could also be included. (In fact, the exposure of photographic film led to the discovery of x-rays.) Moreover, although blue-green is used in the preferred embodiment, some other primary color in the visible spectrum could alternately be used. 
     FIG. 5 is another embodiment of color printer  10  where a single spatial light modulator  20  is used. The use of a single spatial light modulator  20  reduces the cost, complexity, and alignment requirements of the writer. Image data is input to modulator  20  sequentially, color by color. The appropriate color light source  12  is turned on while image data of that color is present on modulator  20 . In a preferred embodiment, a single multicolor LED array is used as light source  12  where the number of LEDs used for a given color in inversely proportional to film sensitivity. The light is collected by a field lens  15  and uniformized by uniformizing optics  14  such as a lenslet array or integrator bar. Condenser lens  16  images the uniformized light onto spatial light modulator  20 . The light first passes through a polarizer  17  and polarization beamsplitter prism  18 . The uniform light is modulated by spatial light modulator  20  and the modulated image light, now horizontally polarized as shown by the arrow, is imaged onto photosensitive medium  140  by print lens  110 . A second polarizer  17  can be used to improve contrast. Light source  12  could also be a multicolored laser and polarizing beamsplitter  18  could be a wire grid device rather than a prism. Polarizers  17  could be sheet plastic or could also be wire grid devices. The advantages of a single spatial light modulator (SLM)  20  are lower cost, reduced complexity, and ease of alignment. The four colors do not have to be registered to each other. This function is accomplished automatically because the same modulator  20  device is used for all colors. The colors are exposed sequentially and the setup parameters for modulator  20  may need to be changed for each color. Since the exposures are sequential and all four color sources must fit in a single array, more time is required to write each image than with the simultaneous writer of FIG.  4 . 
     FIG. 6 is very similar to the writer of FIG. 5, using four separate light sources combined through x-cube  86  to allow faster writing speeds. The four light sources  12 R,  12 G,  12 BG, and  12 B must be polarized. Polarizers  17  are shown, assuming the sources are unpolarized LEDs. Green and blue green sources  12 G and  12 BG are combined through a dichroic mirror  19  and then enter x-cube  86 . Lens  15  collects the light and the beams pass through a collimator lens  36  and a uniformizing optics  14 , a lenslet array in the preferred embodiment. The uniformized light is imaged onto spatial light modulator  20  by condenser lens  16 , through polarization beamsplitter prism  18 . The image modulated light passes through prism  18  and is imaged onto photosensitive medium  140  by print lens  110 . A second polarizer  17  can be located before print lens  110  to improve contrast. Note that the fourth light source  12  is shown as a blue-green LED array to deposit blue-green dye in the output film. It could just as well be an infra-red source if the fourth film layer is designed for infra-red sensitivity and deposits blue-green dye, as noted previously. 
     FIG. 7 is yet another embodiment of color printer  10  using four colors, but this time using a raster scan method rather than an area array modulator. The four light sources  12  are typically lasers: a red laser  12 R, a green laser  12 G, a blue-green laser  12 BG, a the blue laser  12 B. All color channels are handled similarly. Following the red channel, the beam is focused into a light modulator  32 R, typically an acousto-optic modulator, by a lens  27 R. The pixel information for the red image is sent on a pixel by pixel basis to modulator  32 R, which can also function as a shutter. Lens  27  and the following lens  36 , form a beam expander. The red beam passes through a dichroic beam combiner  35 , which allows all four color beams to be collinear. The beam passes through the beam shaping optics  38  and strikes a rotating polygon mirror  41  driven by a motor  42 . Rotating polygon mirror  41  provides the high speed horizontal scan. The slower speed vertical scan is provided by a galvanometer driven mirror  43  controlled by a galvanometer actuator  44 . The scanning beam is then focused to a scanning spot onto photosensitive medium  140  by print lens  110 . The other color channels are handled in a similar manner. Instead of being transmitted by all the dichroic mirrors in combiner  35 , they are reflected off the appropriate mirror and are transmitted by the remainder. All four colors are imaged simultaneously. The timing, drive, and datapath electronics are not shown but are well known in the art of three color RGB writers. 
     FIG. 8 shows color printer  10  as a four laser writer that uses a single spatial light modulator  20  for sequential exposure of color images. The four light sources  12  are typically polarized lasers: the red laser  12 R, the green laser  12 G, the blue-green laser  12 BG, and the blue laser  12 B. All color channels are handled similarly. Following the red channel, the beam is focused into a shutter  26 R, which could be an acousto-optic modulator, by a lens  27 R. This lens and the following lens  36 , form a beam expander. The red beam passes through the dichroic beam combiner  35 , which allows all four color beams to be collinear. Uniformizer  14  can be a lenslet array or integrator bar. Condenser lens  69  images the uniform light onto spatial light modulator  20  via polarization beamsplitter prism  18 . The input laser light should be plane polarized, perpendicular to the plane of the paper as shown by the dot. Because the lasers are already plane polarized, the light loss (typically 60%) of placing an input polarizer in the beam is avoided. The pixel information for the red image is sent to modulator  20 . Modulator  20  rotates the plane of polarization of the light on a pixel by pixel basis. The rotated, or image-containing component of the light is polarized parallel to the plane of the paper, as shown by the arrow. This light is imaged onto photosensitive medium  140  by print lens  110 . Polarizer  17  is used to improve the contrast ratio of the image. 
     It should be noted that many variations of the above designs are possible by one skilled in the art. For instance, one of light sources  12  could be a filtered tungsten lamp or a filtered xenon lamp. The wavelengths used for light sources  12  could be selected appropriately to optimize response of photosensitive medium  140 . LEDs and lasers can be interchanged with appropriate optical modifications. Wire grid devices can used for polarizers  17  and in place of polarization beamsplitting prism  18 . Digital micromirror devices (DMDs), transmissive LCDs, gated light valves, acousto-optical devices, or electro-optic modulators combined with polygon scanners, could alternately be used for spatial light modulators  20 , with corresponding changes to support illumination and beam conditioning optics, as is well known in the optical arts. Acousto-optic modulators can be replaced with electro-optic modulators. Uniformizers  14  can be optical mirror tunnels as well as integrator bars and lenslet arrays. 
     In a preferred embodiment, photosensitive medium  140  is a motion picture film. However, photosensitive medium  140  could alternately be some other type of medium having four sensitive color layers, such as a motion picture negative film, a motion picture print film, a motion picture reversal film, a photographic film, a photographic negative film, a photographic print film, a photographic reversal film, or a photographic paper, for example. The design of photosensitive medium  140  need not be limited to four sensitive layers. Sensitivities to additional colors can be added to expand the gamut. The sensitivity of any of the film layers need not be to the same color of light as the color of the dye that gets deposited in processing, because this is not a camera negative. The “blue-green” layer could be sensitive to infra-red light, as previously noted. For that matter, the “red” layer could be sensitive to infra-red light and the “blue-green” layer might be made sensitive to red light or even UV light. The sensitivities can be chosen to optimize film performance or can be based on availability of light sources. The color printer  10  is then designed based on the film sensitivity, not on the color of the dye in the processed output film. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
     PARTS LIST 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 PARTS LIST 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10. 
                 Color printer 
               
               
                   
                 12. 
                 Light source 
               
               
                   
                 12R. 
                 Red light source 
               
               
                   
                 12G. 
                 Green light source 
               
               
                   
                 12B. 
                 Blue light source 
               
               
                   
                 12BG. 
                 Blue-green light source 
               
               
                   
                 14. 
                 Uniformizing optics 
               
               
                   
                 14R. 
                 Uniformizing optics, red light path 
               
               
                   
                 14G. 
                 Uniformizing optics, green light path 
               
               
                   
                 14B. 
                 Uniformizing optics, blue light path 
               
               
                   
                 14BG. 
                 Uniformizing optics, blue-green light path 
               
               
                   
                 15. 
                 Field lens 
               
               
                   
                 16. 
                 Condenser lens 
               
               
                   
                 16R. 
                 Condenser lens, red light path 
               
               
                   
                 16G. 
                 Condenser lens, green light path 
               
               
                   
                 16B. 
                 Condenser lens, blue light path 
               
               
                   
                 16BG. 
                 Condenser lens, blue-green light path 
               
               
                   
                 17. 
                 Polarizer 
               
               
                   
                 18. 
                 Polarizing beamsplitter 
               
               
                   
                 18R. 
                 Polarizing beamsplitter, red light path 
               
               
                   
                 18G. 
                 Polarizing beamsplitter, green and blue-green light path 
               
               
                   
                 18B. 
                 Polarizing beamsplitter, blue light path; 
               
               
                   
                 19. 
                 Dichroic mirror 
               
               
                   
                 20. 
                 Spatial light modulator 
               
               
                   
                 20R. 
                 Spatial light modulator, red light path 
               
               
                   
                 20G. 
                 Spatial light modulator, green light path 
               
               
                   
                 20B. 
                 Spatial light modulator, blue light path 
               
               
                   
                 20BG. 
                 Spatial light modulator, blue-green light path 
               
               
                   
                 22. 
                 Half waveplate 
               
               
                   
                 22R. 
                 Half waveplate, red light path 
               
               
                   
                 22B. 
                 Half waveplate, blue light path 
               
               
                   
                 26. 
                 Shutter 
               
               
                   
                 26R. 
                 Shutter, red light path 
               
               
                   
                 26G. 
                 Shutter, green light path 
               
               
                   
                 26B. 
                 Shutter, blue light path 
               
               
                   
                 26BG. 
                 Shutter, blue-green light path 
               
               
                   
                 27. 
                 Lens 
               
               
                   
                 27R. 
                 Lens, red light path 
               
               
                   
                 27G. 
                 Lens, green light path 
               
               
                   
                 27B. 
                 Lens, blue light path 
               
               
                   
                 27BG. 
                 Lens, blue-green light path 
               
               
                   
                 32. 
                 Pixel sequential light modulator (AOM) 
               
               
                   
                 32R. 
                 Modulator, red light path 
               
               
                   
                 32G. 
                 Modulator, green light path 
               
               
                   
                 32B. 
                 Modulator, blue light path 
               
               
                   
                 32BG. 
                 Modulator, blue-green light path; 
               
               
                   
                 35. 
                 Dichroic combiner 
               
               
                   
                 36. 
                 Collimator lens 
               
               
                   
                 38. 
                 Beam-shaping optics 
               
               
                   
                 41. 
                 Polygon mirror 
               
               
                   
                 42. 
                 Motor 
               
               
                   
                 43. 
                 Galvanometer-driven mirror 
               
               
                   
                 44. 
                 Galvanometer actuator 
               
               
                   
                 69. 
                 Condenser lens 
               
               
                   
                 86. 
                 X-cube 
               
               
                   
                 100. 
                 Visible gamut 
               
               
                   
                 102. 
                 Conventional motion picture film gamut 
               
               
                   
                 106. 
                 Four-source gamut 
               
               
                   
                 108. 
                 Polygon vertices for laser sources 
               
               
                   
                 112. 
                 Polygon vertices for laser sources 
               
               
                   
                 114. 
                 Polygon vertices for laser sources 
               
               
                   
                 116. 
                 Polygon vertices for laser sources 
               
               
                   
                 110. 
                 Print lens 
               
               
                   
                 120. 
                 Extended gamut polygon of four color film 
               
               
                   
                 121. 
                 Red vertex near 620 nm 
               
               
                   
                 122. 
                 Green vertex near 540 nm 
               
               
                   
                 123. 
                 Blue-green vertex near 490 nm 
               
               
                   
                 124. 
                 Blue vertex near 455 nm 
               
               
                   
                 140. 
                 Photosensitive medium