Abstract:
A cathode ray tube (CRT) device is disclosed that increases image resolution. The CRT device includes a plurality of electron guns to produce a plurality of electron beams. A plurality of separate phosphor dots corresponding to separate colors are produced when impacted by the electron beams. The CRT device also includes steering electronics to guide the electron beams to the plurality of separate phosphor dots that form part of separate and shifted color planes.

Description:
BACKGROUND  
         [0001]    In commonly owned United States Patent Applications: (1) Ser. No. 09/916,232 (“the &#39;232 application”), entitled “ARRANGEMENT OF COLOR PIXELS FOR FULL COLOR IMAGING DEVICES WITH SIMPLIFIED ADDRESSING,” filed Jul. 25, 2001; (2) Ser. No. 10/278,353 (“the &#39;353 application”), entitled “IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL RENDERING WITH INCREASED MODULATION TRANSFER FUNCTION RESPONSE,” filed Oct. 22, 2002; (3) Ser. No. 10/278,352 (“the &#39;352 application”) entitled “IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL RENDERING WITH SPLIT BLUE SUBPIXELS,” filed Oct. 22, 2002; (4) Ser. No. 10/243,094 (“the &#39;094 application), entitled “IMPROVED FOUR COLOR ARRANGEMENTS AND EMITTERS FOR SUBPIXEL RENDERING,” filed Sep. 13, 2002; (5) Ser. No. 10/278,328 (“the &#39;328 application”), entitled “IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS WITH REDUCED BLUE LUMINANCE WELL VISIBILITY,” filed Oct. 22, 2002; (6) Ser. No. 10/278,393 (“the &#39;393 application”), entitled “COLOR DISPLAY HAVING HORIZONTAL SUB-PIXEL ARRANGEMENTS AND LAYOUTS,” filed Oct. 22, 2002, novel subpixel arrangements are therein disclosed for improving the cost/performance curves for image display FINNEGAN HENDERSON devices and herein incorporated by reference.  
           [0002]    These improvements are particularly pronounced when coupled with subpixel rendering (SPR) systems and methods further disclosed in those applications and in commonly owned United States Patent Applications: (1) Ser. No. 10/051,612 (“the &#39;612 application”), entitled “CONVERSION OF RGB PIXEL FORMAT DATA TO PENTILE MATRIX SUB-PIXEL DATA FORMAT,” filed Jan. 16, 2002; (2) Ser. No. 10/150,355 (“the &#39;355 application”), entitled “METHODS AND SYSTEMS FOR SUB-PIXEL RENDERING WITH GAMMA ADJUSTMENT,” filed May 17, 2002; (3) Ser. No. 10/215,843 (“the &#39;843 application”), entitled “METHODS AND SYSTEMS FOR SUB-PIXEL RENDERING WITH ADAPTIVE FILTERING,” filed May 17, 2002; (4) Ser. No. ______ (“the ______ application) entitled “IMAGE DATA SET WITH EMBEDDED PRE-SUBPIXEL RENDERED IMAGE”, filed Apr. 7, 2003.  
           [0003]    Additionally, the present application is also related to commonly owned: (1) Ser. No. 10/047,995 (“the &#39;995 application”) entitled “COLOR DISPLAY PIXEL ARRANGEMENTS AND ADDRESSING MEANS” filed Jan. 14, 2002; (2) Ser. No. ______ (“______ application”) entitled “IMPROVED PROJECTOR SYSTEMS” filed May 20, 2003; (3) Ser. No. ______ (“______ application”) entitled “IMPROVED IMAGE CAPTURE DEVICE AND CAMERA” filed May 20, 2003; and (4) Ser. No. ______ (” application”) entitled “IMPROVED PROJECTOR SYSTEMS WITH REDUCED FLICKER” filed May 20, 2003.  
           [0004]    The above-referenced and commonly owned applications are hereby incorporated herein by reference. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    The accompanying drawings, which are incorporated in, and constitute a part of the specification, illustrate exemplary implementations and embodiments of the invention, and, together with the detailed description, serve to explain principles of the invention.  
         [0006]    [0006]FIG. 1 illustrates a side view of a prior art projector projecting images, in a frontal view, to a central point on an imaging screen.  
         [0007]    [0007]FIG. 2 illustrates a side view of a projector, projecting images, in a frontal view, to a central point on an imaging screen in which the three colors are offset from each other.  
         [0008]    [0008]FIG. 3A illustrates a side view of a prior art CRT projecting images to a central point on an imaging screen.  
         [0009]    [0009]FIG. 3B illustrates a portion of the phosphor screen of the prior art CRT illustrated in FIG. 3A, focusing Gaussian spots to a single point on an imaging screen.  
         [0010]    [0010]FIG. 4A illustrates a side view of a CRT projecting images to an imaging screen in which the three colors are offset from each other.  
         [0011]    [0011]FIG. 4B illustrates a portion of the CRT illustrated in FIG. 4A focusing Gaussian spot to a phosphor screen in which the three color spots are offset by one-third pixel in the horizontal direction.  
         [0012]    [0012]FIG. 4C illustrates a portion of the CRT illustrated in FIG. 4A focusing Gaussian spot to a phosphor screen in which the green color spots are offset in the diagonal direction.  
         [0013]    [0013]FIG. 5 illustrates a prior art arrangement of pixels for electronic information display projectors.  
         [0014]    [0014]FIGS. 6, 7, and  8  illustrates an arrangement of pixels for each of the colors green, red, and blue, respectively.  
         [0015]    [0015]FIG. 9 illustrates the arrangements of FIGS. 6, 7, and  8  overlaid on one another to show how a full color image is constructed.  
         [0016]    [0016]FIG. 10 illustrates the overlaid image of FIG. 9 with one full color logical pixel  
         [0017]    [0017]FIGS. 11 and 12 illustrates the green and red image planes, respectively, with a single column of logical pixels turned on.  
         [0018]    [0018]FIG. 13 illustrates the red and green image planes of FIGS. 11 and 12 overlaid;  
         [0019]    [0019]FIGS. 14A-14B and  15 A- 15 B illustrate the green and red image planes, respectively, with two columns of logical pixels turned on.  
         [0020]    [0020]FIGS. 16A and 16B illustrate the green and red image planes of FIGS. 14A-14B and  15 A- 15 B overlaid, respectively.  
         [0021]    [0021]FIG. 17 illustrates two images of the pixel arrangement of FIG. 6 overlaid, offset by one-half pixel, to demonstrate how a single imaging plane can build up a higher resolution image using field sequential color, or to demonstrate how two imaging planes of a multi-panel may be offset to build up a higher resolution image.  
         [0022]    [0022]FIG. 18 illustrates splitting of an image path into two different paths for different colors through an inclined plate made of a chromodispersive material.  
         [0023]    [0023]FIG. 19 illustrates a prior art arrangement of pixels.  
         [0024]    [0024]FIG. 20 illustrates an overlay of the arrangement of prior art FIG. 19 in which the two colors are offset by one-half pixel in the diagonal direction.  
         [0025]    [0025]FIG. 21 illustrates the overlaid arrangement of FIG. 20 with two color logical pixels at different addressable points.  
         [0026]    [0026]FIG. 22 illustrates the overlaid arrangement of FIG. 20 with an alternative color logical pixel and a column line of logical pixels.  
         [0027]    [0027]FIG. 23 illustrates an overlay of FIG. 8 for three colors in which the colors are offset by one-third pixel each, with one full color logical pixel turned on.  
         [0028]    [0028]FIG. 24A is a chart showing the chromaticity coordinates of the emitters of a prior art three color display.  
         [0029]    [0029]FIG. 24B is a chart showing the chromaticity coordinates of the emitters of an improved three color display, compared to the chromaticity coordinates of FIG. 24A.  
         [0030]    [0030]FIG. 25 is a chart showing the chromaticity coordinates of the emitters of a novel four color display.  
         [0031]    [0031]FIG. 26 is a chart showing the chromaticity coordinates of the emitters of a novel five color display.  
         [0032]    [0032]FIG. 27 illustrates the reconstruction points of the prior art display of FIG. 19 overlaid on the appearance of the display.  
         [0033]    [0033]FIG. 28 illustrates the reconstruction points of the novel display shown in FIG. 20.  
         [0034]    [0034]FIG. 29 illustrates the arrangement of emitters and reconstruction points of a novel twinned projector arrangement with coincident color planes.  
         [0035]    [0035]FIG. 30 illustrates the arrangement of emitters and reconstruction points of another novel twinned projector arrangement with displaced color planes.  
         [0036]    [0036]FIGS. 31A and 31B illustrate a prior art arrangement of a multi-sensor chip camera in which all of the color plane sample areas are coincident, sampling an image and the resulting data set respectively.  
         [0037]    [0037]FIGS. 32A and 32B illustrate a novel arrangement of a multi-sensor chip camera in which two of the color plane sample areas are displaced, sampling an image and the resulting data set respectively.  
         [0038]    [0038]FIGS. 33A and 33B illustrate a novel arrangement of a multi-sensor chip camera in which three of the color plane sample areas are displaced, sampling an image and the resulting data set respectively.  
         [0039]    [0039]FIG. 33C is the illustrates displaying the processed image of FIG. 33B onto a higher resolution, conventional prior art display.  
         [0040]    [0040]FIGS. 34A and 34B illustrate a novel arrangement of color filter array for a two chip color camera, one with a red/green checkerboard, the other a lower resolution sensor for imaging blue image component, respectively.  
         [0041]    [0041]FIG. 35A illustrates a novel display arrangement of the color planes on a display.  
         [0042]    [0042]FIGS. 35B, 35C, and  35 D illustrate the color planes overlaid on each other to create a full color image as shown in FIG. 35A.  
         [0043]    [0043]FIGS. 36A and 36B illustrate how this moiré distortion is eliminated by the arrangement of FIG. 35A.  
         [0044]    [0044]FIG. 37 illustrates a prior art color wheel filter of three colors.  
         [0045]    [0045]FIGS. 38A, 38B,  38 C, and  38 D illustrate novel color wheel filters of three colors.  
         [0046]    [0046]FIGS. 39A and 39B illustrates novel color wheel filters of three colors and black.  
         [0047]    [0047]FIG. 40 illustrates a novel color wheel filter of four colors, one of which is white.  
         [0048]    [0048]FIGS. 41, 42A,  42 B,  42 C, and  42 D illustrate a spatial light modulator and a method of reducing data bandwidth, image size, while maintaining image quality using spatio-temporally displaced filtering and reconstruction.  
     
    
     DETAILED DESCRIPTION  
       [0049]    Reference will now be made in detail to exemplary implementations and embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Furthermore, the following description is illustrative only and not in any way intended to be limiting.  
         [0050]    Prior art projectors typically overlaps the three-color images (e.g. RGB) exactly coincidentally, with the same spatial resolution. As taught in the &#39;995 application, the color imaging planes are overlaid upon each other with an offset of about one-half pixel. By offsetting the color imaging planes, an electronic image capture, processing, and display having higher resolution images is created by increasing the resolution of the system.  
       Cathode Ray Tube Displays, Projector Displays, and Subtractive Flat Panel Displays  
       [0051]    [0051]FIG. 1 is schematic of a prior art projector  100  having a light beam  102  that projects red (R), blue (B), and green (G) images  106  on to an imaging (or projection) screen  104 . Prior art practices converge the red, the blue, and the green images to a point  110  on the projection screen  104 . In contrast, FIG. 2 illustrates schematic of a projector  200  having a light beam  202  that projects through an optical element (or lens)  204  red  206 , blue  208 , and green images  210  on to an imaging (or projection) screen  212 . As illustrated in this example, such a projector will separate and differentially shift the red, green, and blue images. Thus, the image is again formed, but the image is shifted optically to separate the red, blue, and green color planes about one-half pixel.  
         [0052]    A similar procedure is used with a Cathode Ray Tube (CRT) video display, as illustrated in prior art FIG. 3A. An electron gun  300  projects an electron beam  302  inside the CRT  304  onto a phosphor surface  306  with an array of color primary emitting phosphor dots. Prior art practices converge the red, the blue, and the green image pixel to a circular Gaussian spot  308  on the phosphor surface  306 . The CRT  304  can direct the electron beam  302  towards the phosphor surface  306  electrostatically or magnetically. FIG. 3B illustrates a portion of the phosphor screen  306  in which the CRT focuses Gaussian spot  308  to a single point on the phosphor screen  306 .  
         [0053]    In contrast, FIG. 4A shows a diagrammatic illustration of a CRT video display having electron guns  400  that project electron beams  402  inside the CRT  404  onto a phosphor surface  406 . As illustrated in this example, CRT  404  will separate and differentially shift the red  416 , green  420 , and blue  418  images  408 . This can be accomplished by misconverging the electron beams with steering electronics, such as yoke coils, electrostatic deflection plates, or by appropriately displacing the electron guns. Thus, the image is again formed, but the image is shifted to separate the red  416 , blue  418 , and green  420  color planes by about one-third pixel or by shifting just the green  420  color plane by one-half pixel. FIG. 4B illustrates the portion of the phosphor screen in which the CRT focuses so that pixel color spot  408  consists of red  416 , green  420 , and blue  418  spots that are offset by one-third pixel in the horizontal direction. This modification allows CRTs so adjusted to use the very same subpixel rendering techniques utilized in the art on conventional RGB stripe architecture liquid crystal display (LCD) panels. FIG. 4C illustrates a portion of the phosphor screen  406  in which the CRT focuses the Gaussian spots so that the green  420  color spot is offset by one-half pixel in the diagonal direction from the converged red  416  and blue  418  spots.  
         [0054]    Subpixel rendering can also be supported on conventional CRTs without major modification to the CRT. Instead, the timing of the data going to the CRT is modified. This could be accomplished by a modification of the video graphics card on a computer.  
         [0055]    In one embodiment, one dimensional subpixel rendering could be supported. For example, the red data would lead, the green delayed by one third (⅓) of a pixel clock, the blue delayed by two thirds (⅔) of a pixel clock. This can be accomplished by using a “subpixel clock” (shown schematically as element  422  in FIG. 4A) at three times the usual pixel clock for the data D/A converters. The result will be that a single “pixel” will paint displaced red  416 , green  420 , and blue  418  spots as shown in FIG. 4B. This modification could be made to the video graphics card and would make a CRT look like an RGB stripe LCD and compatible commercial subpixel rendered text such as that disclosed in Hill, et al., U.S. Pat. No. 6,188,385. It might be advantageous to use a system to turn on and off the new mode, either globally or locally by detecting the presence of the subpixel rendered text using a suitable method, as disclosed in the ______ application noted above.  
         [0056]    It is also possible to simulate a two dimensionally subpixelated flat panel display. For example, the timing of the color data could be switched every row. The odds rows will have the red data lead with the green data delayed by one half (½) of a pixel clock. On the even rows, the green data will lead while the red data is delayed by one half (½) pixel clock. The blue data is always delayed by one third (⅓) of a pixel clock. The pixel clock is half the frequency of a “normal” pixel clock.  
         [0057]    The above system will allow presubpixel rendered images to be displayed on the with minimal processing. Further, the CRT can support higher resolution than ordinarily possible by doubling the number of rows, doubling the horizontal frequency, while using the same bandwidth amplifiers, cables, and memory.  
         [0058]    Contrary to prior art projectors, subtractive flat panels, or t CRT displays which are not subpixelated, the projectors, subtractive flat panel displays, or CRT displays discussed herein are subpixelated and may thus take advantage of subpixel rendering techniques.  
         [0059]    Multi-image plane color projectors often use a single white light source that is broken into narrower spectral regions and separate beam paths through the use of dichroic beam splitting filters. The separated colors illuminate separate spatial light modulators. The modulated light is bought back together and focused onto an imaging screen to be viewed as a full color image.  
         [0060]    [0060]FIG. 5 illustrates a prior art arrangement  510  of square pixels  512 , and in this example, forming an array of 12×8 pixels. For prior art projection or subtraction displays, three planes of 12×8 pixels would be overlaid to create a set of 12×8 logical pixels. This is a total of ninety-six (96) pixels comprising two-hundred-eighty-eight (288) color elements.  
         [0061]    [0061]FIGS. 6, 7, and  8  are illustrate an arrangement of pixel images for each color of green, red, and blue, respectively, for projectors. The same FIGS. 6, 7, and  8  are also illustrations of an arrangement of subpixels for each color of magenta, cyan, and yellow, respectively, for subtractive color flat panel displays. Magenta is equivalent to subtracting green from white. Cyan is equivalent to subtracting red from white. While yellow is equivalent to subtracting blue from white. For example, a multispectral light source is illuminated, illuminating panels of magenta, cyan, and yellow that are offset from one another in x and y by substantially less than 100%. In the following discussions regarding the theory of operation of the arrangement of subpixel elements, the additive color projector is used as an example. However, for subtractive flat panel display, the same theory of operation applies if one applies additive to subtractive color transforms well known in the art.  
         [0062]    [0062]FIG. 9 illustrates the resulting multipixel image  20  of overlaying the images  14 ,  16 , and  18  of FIGS. 6, 7, and  8 , respectively, for a three-color plane projector or subtractive flat panel display. The resulting multipixel image  20  of FIG. 9 has the same number of logical pixels  24  as illustrated in FIG. 10 and the same addressability and MTF as the image formed by the arrangement of prior art FIG. 5. However, the same image quality is achieved with only one-hundred-twenty-three (123) color elements, less than half of the number required by the prior art arrangement illustrated in FIG. 5. As the costs increase with the number of elements, the reduction in the number of elements offers the same image quality at a significantly lower cost, significantly higher image quality at the same cost, or a higher image quality at lower cost, when compared to the prior art arrangement illustrated in FIG. 5.  
         [0063]    In each of the imaging devices discussed above, the beams (or panels) are convergent by substantially less than about 100%, with less than about 75% preferred, and with about 50% more preferred.  
         [0064]    One advantage of the three-color plane array disclosed here is improved resolution of color displays. This occurs since only the red and green pixels (or emitters) contribute significantly to the perception of high resolution in the luminance channel. Offsetting the pixels allows higher perceived resolution in the luminance channel. The blue pixel can be reduced without affecting the perceived resolution. Thus, reducing the number of blue pixels reduces costs by more closely matching human vision.  
         [0065]    The multipixel image  22  of FIG. 10 illustrates a logical pixel  24  showing a 50% of the input value associated with that logical pixel  24 . Surrounding and overlapping this central pixel  26  are four pixels  28  of the opposite color of the red/green opposition channel (in this case it is red) that is set at 12.5% of the input value associated with that logical pixel  24 . Partially overlapping and offset is a blue pixel  30 , which is set at about 25% of the input value associated with that logical pixel  24 .  
         [0066]    The logical pixel  24  of FIG. 10 illustrates that the central area defined by the central pixel  26  is the brightest area, at 31.25%, while the surrounding area, defined by the surrounding pixels  28  of the “opposite” color (not overlapping with the central pixel  24 ) remains at 6.25% brightness. This approximates a Gaussian spot, similar to those formed by the electron gun spot of a CRT.  
         [0067]    Images  52  and  68  are built up by overlapping logical pixels as shown in FIGS. 13 and 16, respectively. For ease of illustration, the blue plane in each figure has not been shown for clarity. The arrangement of the pixels of each color plane  14 ,  16 , and  18  illustrated in FIGS. 6, 7, and  8 , respectively, are essentially identical to some of the effective sample area arrangements found in many of the above-referenced applications that are incorporated by reference. Further, the arrangement of this present embodiment use the same reconstruction points of the pixel arrangements disclosed in the above-referenced applications.  
         [0068]    For projected image or subtractive color flat panel displays, the present application discloses using the same pixel rendering techniques and human vision optimized image reconstruction layout. However, a smoother image construction is created in the present application due to the overlapping nature of the pixels. For an example of a multipixel image  52  having the smoother image construction, FIG. 13 illustrates a vertical line  54  comprising the green component image  40  and the red component image  50  of FIGS. 11 and 12, respectively. As illustrated in the multipixel image  40  in FIG. 11, a vertical line  41  comprises central green pixels  42  and outer green pixels  44 . As illustrated in the multipixel image  50  in FIG. 12, a vertical line  51  comprises central red pixels  46  and outer red pixels  48 . For clarity, the blue color plane is not shown in FIG. 13. This example assumes that the vertical line  54  displayed at about 100% of the input value and is surrounded on both sides by a field at 0% of the input value.  
         [0069]    [0069]FIG. 13 illustrates that the central red pixels  46  of the vertical line are offset from the central green pixels  42  when superimposed onto each other. These central pixels  42  and  46  are each set at 75%. The outer pixels  44  and  48  are each set at 12.5%. The areas of overlap of the central pixels  42  and  46  form a central series of smaller diamonds  56  that are at 75% brightness. The overlap of pixels  44  and pixels  46 , and the overlap of pixels  48  and pixels  42 , respectfully, form two series, just outside of the said central series, of smaller diamonds  58  that are at 43.75% brightness. The overlap of the outer pixels  44  and  48  form two series of smaller diamonds  60  that are at 12.5% brightness. While the areas of the outer pixels  44  and  48  that do not overlap form an outermost series of smaller diamonds  62  that are at 6.25% brightness. This series of brightness levels, 6.25%, 12.5%, 43.75%, 75%, 43.75%, 12.5%, and 6.25% exhibits a Gaussian distribution. Further, if one were to imagine an infinitely narrow vertical line segment, at least several pixels long, moving across the displayed vertical line  54 , integrating the brightness, the resulting function would be a series of smooth segments joining the brightness levels, from zero to 75% to zero. Thus, the resulting cross-sectional brightness function, integrated over several pixels tall, along the displayed line, closely approximates a smooth Gaussian curve. This displayed vertical line can be moved over by about one-half pixel, such that the addressability would be about one-half pixel.  
         [0070]    In moving the vertical line, the amount of improvement is proportional to the amount that the red and green planes are out of phase. Having the image planes out of phase at a value of substantially less than about 100% is preferred, with less than about 75% more preferred, and with the images being exactly out of phase by about one-half pixel, or about 50%, is ideal.  
         [0071]    [0071]FIGS. 16A and 16B illustrate two multipixel images  68  and  68   b  of two vertical lines  69  and  69   b , respectively, displayed to demonstrate that the MTF is about one-half of the addressability, which is the theoretical limit for subpixelated displays. FIG. 16A illustrates the two vertical lines  69  comprising the green component image  64  and the red component image  66  of FIGS. 14A and 15A, respectively. As illustrated in the multipixel image  64  in FIG. 14A, the central green pixels  70  and outer green pixels  72  comprise two vertical lines  65 . As illustrated in the multipixel image  66  in FIG. 15A, the central red pixels  76  and outer red pixels  78  comprise two vertical lines  67 . For clarity, the blue color plane is not shown in FIG. 16A. This example assumes that the vertical line  69  is displayed at about 100% of the input value and is surrounded on both sides by a field at 0% of the input value.  
         [0072]    The central red pixels  76  of the two vertical lines  69  are offset from the central green pixels  70  when superimposed as in FIG. 16A. These central line pixels  70  and  76  are each set at 75%. The outer pixels  72  and  78  are each set at 12.5%. The pixels  74  and  80  between the two central lines of pixels  76  and  70  are set at 25%.  
         [0073]    The outer edges, those not adjoining the other line, have the same sequence of brightness levels as described for the case of FIG. 13. That is, the areas of the outer pixels  72  and  78  that do not overlap form an outermost series of smaller diamonds  88  at 6.25% brightness. The overlap of the outer pixels  72  and  78  form two series of smaller diamonds  84  that are at 12.5% brightness. The overlap of pixels  72  and pixels  76 , and the overlap of pixels  78  and pixels  70 , respectfully, form two series, just outside of the central line series  86 , of smaller diamonds  82  that are at 43.75% brightness. The areas of overlap of the central line pixels  70  and  76  form a central series of smaller diamonds  92  that are at 75% brightness.  
         [0074]    The space between the two central vertical lines  69  has three series of smaller diamonds  90  and  94 . The overlap of red central line pixels  76  and green interstitial pixels  74 , and the overlap of green central line pixels  70  and red interstitial pixels  80 , respectively, form a series of smaller diamonds  90  at 50% brightness. The overlap of interstitial pixels  74  and  80  form a series of smaller diamonds  94  at 25% brightness. Theoretically, this represents samples of a sine wave at the Nyquist limit, exactly in phase with the samples. However, when integrating over an imaginary vertical line segment as it moves across from peak to trough to peak, the function is that of a triangle wave. Yet, with the MTF of the projection lens limiting the bandpass of the projected image, the function is that of a smooth sine wave. The display effectively removes all Fourier wave components above the reconstruction point Nyquist limit. Here, the modulation depth is 50%. As long as this is within the human viewer&#39;s Contrast Sensitivity Function (CSF) for a given display&#39;s contrast and resolution, this modulation depth is visible.  
         [0075]    [0075]FIG. 16B illustrates the two vertical lines  69   b  comprising the green component image  64   b  and the red component image  66   b  of FIGS. 14B and 15B, respectively. These images are designed to be ‘sharper’ than those of FIGS. 16A, 14A, and  15 A. As illustrated in the multipixel image  64   b  in FIG. 14B, the green pixels  70   b  comprise two vertical lines  65   b . As illustrated in the multipixel image  66   b  in FIG. 15B, the red pixels  76   b  comprise two vertical lines  67   b . For clarity, the blue color plane is not shown in FIG. 16B. This example assumes that the vertical lines  69   b  are displayed at about 100% of the input value and is surrounded on both sides by a field at 0% of the input value. Here, the values of both the red pixels  76   b  and the green pixels  70   b  are set at 100% output value, while the pixels,  74   b  and  80   b , between the double lines  67   b  and  65   b  are set at 0% output value. Likewise the pixels,  72   b  and  78   b , outside the double lines  67   b  and  65   b  are set at 0% output value. These values are generated by using sharpening coefficients in the filter matrix used in the subpixel rendering operation.  
         [0076]    [0076]FIG. 17 illustrates an overlay  96  of the image  14  of FIG. 6 offset 50% with itself. This represents an alternative embodiment of a single panel projector, using field or frame sequential color that is well known in the art. In this embodiment, the array is again formed from diamonds, but the image  14  is shifted optically to separate the red and green color planes by about one-half pixel. This color shift may be accomplished as shown in FIG. 18 by an inclined plane lens  98  of a suitable chroniodispersive transparent material. Such an arrangement will separate and differentially shift the red, green, and blue images due to the different index of refraction for each wavelength. This lens element may be a separate flat plane lens, or may be an inclined curved element that is an integral part of the projection lens assembly. Such modifications to the lens assembly may be designed using techniques well known in the art.  
         [0077]    These optical and mechanical means for shifting the color image planes can be used to improve display systems that use prior art arrangements  100  of pixels as illustrated in FIG. 19. The green image  102  may be shifted from the red image  104  by about one-half pixel in the diagonal direction as illustrated in the arrangement  106  in FIG. 20. This allows subpixel rendering to be applied to the resulting system. FIG. 21 illustrates two logical pixels centered on a square grid that lies on corner interstitial  108  and edge interstitial  110  points in the arrangement  106  of FIG. 20. FIG. 22 illustrates arrangement  106  with a logical pixel and a column line  112  of overlapping logical pixels centered on pixel quadrants defined by the pixel overlaps.  
         [0078]    In examining the example of a logical pixel  114 ,  116 , and  118  shown in FIG. 22, the output value of each pixel is determined by a simple displaced box filter in which four input pixels are averaged for each output pixel. Each input pixel uniquely maps to one red output pixel  114  and one green output pixel  118  that overlaps by one quadrant  116 . Thus, the addressability of the display has been increased four fold, twice in each axis. With one input pixel at about 100% value surrounded by a field at 0% value, the red output pixel  114  and the green output pixel  118  are set at 25% output. The area of overlap  116  is at 25% brightness while the areas of the output pixels  114  and  118  not overlapping are at 12.5% brightness. Thus, the peak brightness is in the overlapping quadrant.  
         [0079]    In examining the vertical line  112  displayed in FIG. 22, it is displaying a line at about 100% input value surrounded on both sides by a field at 0% input value. The overlapping logical pixels are additive. Thus, the red output pixels  120  and the green output pixels  124  are set at 50%. The area of overlap  122  is at 50% brightness while the areas of the output pixels  120  and  124  that are not overlapping are at 25% brightness. Thus, the area of peak brightness corresponds with location of the displayed line  112 .  
         [0080]    In examining and evaluating the display system, it can be noted that while the addressability of the display has been doubled in each axis, the MTF has been increased by a lesser degree. The highest spatial frequency that may be displayed on the modified system is about one-half octave higher than the prior art system. Thus, the system may display 2.25 times more information on four times as many addressable points.  
         [0081]    In the above systems the blue information has been ignored for clarity. This is possible due to the poor blue resolving power of human vision. However, in so far as the blue filter or other blue illumination system is less than perfect and allows green light that will be sensed by the green sensing cones of human vision, the blue image will be sensed by the green cones and add to the perception of brightness in the luminance channel. This may be used as an advantage by keeping the blue pixels in registration with the red pixels to add to the red brightness and to offset the slight brightness advantage that green light has in the luminance channel. Thus, the red output pixels may be, in fact, a magenta color to achieve this balance of brightness.  
         [0082]    If a system were designed in which the “blue” image has significant leakage of green, and possibly yellow or even red, the “blue” image may be used to further increase the effective resolution of a display. The “blue” color may be closer to a pale pastel blue, a cyan, a purple, or even a magenta color. An example of such a display  126  is illustrated in FIG. 23. FIG. 23 illustrates three images of the array of pixels shown in FIG. 8 overlaid with a shift of one third of a pixel each. A logical pixel  128  is illustrated on the resulting image  126  in FIG. 23. The red pixel  130 , green pixel  132 , and “blue” pixel  134  overlap to form a smaller triangular area  136  that is at the center of the logical pixel. This overlap area is brightest, followed by the three areas where there are only two pixels overlapping, while the areas with no overlap have the lowest brightness. The manner of calculating the values of the pixels follows in a similar manner as outlined above.  
         [0083]    Another embodiment of the present invention is shown in FIG. 35A in which the red  3504 , blue  3502 , and green  3506  color planes shown in FIGS. 35B, 35C, and  35 D respectively are overlaid one another to form the full color arrangement  3510 . The color planes are overlaid each other such that they are substantially “out of alignment” as shown in FIG. 35A.  
         [0084]    This arrangement is characterized by having a green plane  3506  that is higher resolution than both the red  3504  and blue  3502 . In this present arrangement, the red  3504  and blue  3502  have the same resolution, but this need not be the case. It is contemplated that all three of the color planes might be different resolutions. For example, one might use the high resolution green color plane  3506  of FIG. 35D, with the red color plane  3504  of FIG. 35B, and the blue color plane  18  of FIG. 8, overlaying thus such that they are all substantially “out of alignment”. Alternatively, the red color plane may be the higher of the three planes. However, in practice, given the luminances found in most projector systems, the green color plane will be found to be the best choice for the highest resolution.  
         [0085]    More particularly, if the green luminance is approximately half the total luminance, as is commonly found in projectors, there may be an advantage to the particular arrangement shown in FIG. 35A in which the green color plane  3506  is twice that of the red  3504  and blue  3502  color planes. This is not to say that the resolution ratio is determined by the luminance ratio, rather it is the fact that one can achieve the same resolution from the offset red  3504  and blue  3502  color planes as from the green color plane  3506  alone. These are then set to be substantially offset from one another, the green  3506  from the virtual magenta (combined red  3504  and blue  3502 ). The advantage found in this arrangement is that moiré distortion when reconstruction a high resolution image may be significantly reduced with a minimal number of color reconstruction points.  
         [0086]    Moiré distortion occurs when the desired signal is 90° out of phase with the reconstruction points of the display. For example, if one is attempting to display a single pixel wide line halfway between two pixels, the two pixels would be set to 50%. One could still see that the total signal strength and position is present, but the image is not as sharp. If two single wide lines were to be displayed with only a single pixel between them, but offset by half a pixel, then the two grey lines would be smeared together, and it would no longer be distinguishable from a wide grey line. FIGS. 36A and 36B illustrate how this moiré distortion is eliminated by the arrangement of FIG. 35A. When narrow lines  3515  are in phase with the pixels of the green color plane  3506 , the lines are out of phase by 90° for both the red  3504  and blue  3502  color planes as shown in FIG. 36A. When the narrow lines  3515   b  are out of phase with the pixels of the green color plane  3506 , the lines are in phase with the red  3504  and blue  3502  color planes as shown in FIG. 36B.  
       Twinned Projectors  
       [0087]    In the prior art, when brightness is required that is beyond the capability of a single projector to supply, two projectors may be used. The images are conventionally converged 100%, as if the twinned units were in fact one unit. The combined image might be like that shown in FIG. 27, which shows the fully converged pixels  2705  and the associated reconstruction points  2701 . The image may have twice the brightness of that from a single projector, but has the same resolution.  
         [0088]    One improvement of this system may be to displace the full color pixel images from one of the projectors by one-half pixel in the diagonal direction as shown in FIG. 29. This gives similar, and in some aspects superior, performance improvements as that of the displaced color planes of FIGS. 20, 21,  22 , and  28 . FIG. 28 shows the displaced color arrangement of FIGS. 20, 21, and  22 , and the associated color plane reconstruction points  2801  and  2803 . Comparing FIGS. 28 and 29 illustrate the differences. FIG. 29 has full color reconstruction points  2901  at each position where FIG. 28 has either a first color (e.g. red)  2801  or second color (e.g. green)  2803  reconstruction point. Thus, for monochrome images, the twinned projector arrangement of FIG. 29 is similar to the single projector arrangement of FIG. 28. However, for highly saturated color images, the increased addressability of the twinned projector arrangement of FIG. 29 allows a single color to have twice as many reconstruction points.  
         [0089]    A further improvement for twinned projectors is to displace the color planes of both projectors. One of the projectors has the arrangement shown in FIG. 28, while the other has the mirror arrangement, resulting in the overlapped and fully displaced four image planes of FIG. 30. This arrangement has the same saturated color image quality as that of FIG. 29, but has additional monochrome addressability, resulting in significantly improved overall image quality when suitably subpixel rendered.  
         [0090]    Any system that traditionally uses converged, overlapped color and/or white pixels can take advantage of the concepts taught herein. Examples given above included a color CRT display used for computer monitor, video, or television display may also be improved by shifting the color components and applying appropriate subpixel rendering algorithms and filters. A simple and effective change for computer monitors is to shift the green electron spot as described above for FIG. 4B and FIG. 22. This deliberate misconvergence will seem counter-intuitive to those most knowledgeable in the CRT art, but the resulting improvement will be as described above. The displacement of the multi-color display imaging planes by a percentage of a pixel creates a display of higher resolution images by increasing the addressability of the system. Additionally, the MTF is increased to better match the design to human vision. A projector system using three separate panels can be optimized to better match the human vision system with respect to each of the primary colors. These results can be achieved in a single panel, field sequential color projector using an inclined plane chromodispersive lens element.  
       Film Scanners, Cameras, and Film Printers  
       [0091]    The improvements and arrangements described herein may also help image capture and printer devices.  
         [0092]    One embodiment may be an improved video or still camera. Some prior art cameras use multi-chip sensors, along with color filters or dichroic beam splitters. These may be considered to be the inverse operations of the projectors described herein, and may benefit from the same or similar arrangements of pixels. For example, FIG. 27 may represent the arrangement of fully converged color planes of a prior art multi-chip color camera. FIG. 28 may represent the offset color plane arrangement of a multi-chip color camera. Such an arrangement may be formed by offsetting one or more of the sensor chips such the image formed upon it is displaced by substantially one-half pixel. This would create a camera that directly and automatically captures and delivers a subpixel rendered data set. If the data set were delivered for display to a projector with the same resolution and arrangement, then the image data set would need no further processing, and yet provide a superior image than a conventional, fully converged, camera, image data set, and projector arrangement. Thus, the entire system, from image capture to display, is a matched, improved, system. Such a system performs as though it was a higher resolution system with perceptually encoded “lossless” compression.  
         [0093]    [0093]FIG. 31A shows a prior art arrangement of fully converged sensor elements sampling an exemplary image, in this case a “w” character, giving rise to the resulting image data set shown in FIG. 31B. It is to be understood that any natural image will behave in like manner. When the same exemplary image “w” is potentially sampled by a novel sensor arrangement (such as shown in FIG. 28), the resulting image data set is illustrated in FIG. 32B. FIGS. 31B and 32B may also be seen as representing the resulting images of projecting, displaying the resulting data sets on matching projector systems, a prior art projector in the case of FIG. 31B and the novel projector of one embodiment of the present invention in the case of FIG. 32B. Comparing the resulting image quality, the novel system represented by FIG. 32B would be an improvement over that of the prior art. If the system analysis is extended to three offset image capture planes and projector planes, as shown in FIGS. 33A and 33B respectively, the image quality continues to increase.  
         [0094]    Similarly, the pixel arrangements of FIGS. 6, 7, and  8  may be used to capture images on a sampling plane that appears as that shown in FIG. 9. Again, when the resulting captured image data set is directly displayed on a matching projector or flat panel display, the image quality will be superior to that of the prior art systems.  
         [0095]    With multi-chip image sensors, each having independent electronic shutter control, creating the image data set to be displayed on matching, or at least compatible, display means, another improvement is possible—namely, reduced jutter. Jutter occurs when objects that move across a scene are displayed in a series of still frames at a moderately low rate, such as the twenty-four (24) frames per second for film, or twenty-five (25) to thirty (30) frames per second for most television type video systems, the image appears to be jumping from frame image to frame image and smeared in the direction of motion as the eye smoothly tracts the average position of the moving image, but the image formed on the retina is lagging, then leading the average position for half of the frame period each. With the ability to stagger the shutter timing such that each color plane captures and represents a different point in time during the frame, i.e. represents subframes or fields, the jutter will be reduced as, on average, more of the reconstructed image energy will be closer to the average position of the ideal smoothly moving image. The display means is similarly timed such that each color field is updated with the same relative timing as the original electronic shutters. This aspect of the present invention, of displaced timing for the color planes may be combined with the spatial displacement of the sample and reconstruction points, or it may be used in conventional fully converged systems to equal advantage.  
         [0096]    Note, that though the above examples used identical resolution camera sensor and projectors, such need not be the case and yet still gain improved performance of the total system. Images captured directly in a subpixel rendered format may be scaled up or down, to be shown on either subpixelated or fully converged displays, and potentially retain the performance benefit of the displaced image capture. For example, using the data set of FIG. 33B, the image may be processed, converted, and shown on a higher resolution conventional fully converged projector or other display as shown in FIG. 33C. Note that the image quality is higher than the image that would have been possible using the fully converged camera sensor arrangement of FIG. 31A.  
         [0097]    An alternative multi-chip image sensor may have one of more of the sensors include a color filter array. One such example is shown in FIGS. 34A and 34B. FIG. 34A shows an arrangement of square sensors with red  3404  and green  3406  color filters affixed thereupon. FIG. 34B illustrates the lower resolution blue sensor plane. This blue sensor may or may not have a blue filter depending upon on whether the image beam splitter in the camera assembly was a dichroic filter. If a dichroic filter that splits off the red and green colors from the blue is used, then the blue plane may not need an additional filter.  
         [0098]    Other sensors with color filter arrays may be used to advantage to create subpixel rendered images that are directly displayed on suitable subpixelated display means. For example, the conventional prior art Bayer pattern, and its improved variants, may be used with minimal processing. Said processing comprising the interpolation of surrounding red samples to fill in the missing red samples where the blue samples interrupt the red sample grid.  
         [0099]    Scanners, devices that are used to convert still images, or movie film frames, to a digital or analog video format will also benefit from the teaching herein. Offset scanning, either mechanically or electronically may provide a direct subpixel rendered image data set, similar to those described above, which may be used in like manner to improve total system image quality.  
         [0100]    Another embodiment would be to offset, electronically, physically, magnetically, and/or electrostatically the raster scan of a multi-tube video camera. Likewise, if the resulting direct subpixel rendered data set were delivered to a suitably matched display, such as a CRT or subpixelated flat panel display, the image quality would be increased.  
         [0101]    Conversely, color image printers, either photographic (film printer: CRT or laser scanning, spatial light modulator, etc.), xerographic (laser printer), or mechanical (ink jet, dye sublimation, dye transfer, etc.) may also benefit from the teaching herein, in which subpixel rendering of conventional high resolution image data sets or direct printing of previously subpixel rendered image data sets is used on a printer system with matching displaced color image planes.  
         [0102]    One complete system that uses the teaching contained herein may comprise original image capture using conventional color film photography and color film print presentation, with subpixel rendered film digitization, editing and manipulation, followed by subpixel rendered film printing. Such a system potentially would use modified equipment and processes presently used in film production, have the same size image data files, etc., but due to the benefits of subpixel rendering techniques taught herein, exhibit significantly better image quality in the final product. The process may have the additional benefit that the digitized image is in a subpixel rendered format that may be used in matching electronic cinema projectors with minimal or no further processing, again exhibiting improved image quality.  
       Additional Color Planes  
       [0103]    Most conventional projector displays utilize three emitter colors, providing a color gamut that includes the inside of a triangle when charted on the 1931 CIE Color Chart, an example of which is shown in FIG. 24A. These colors are typically substantially red  2404 , green  2406 , and blue  2402 . The luminances of these color emitters are typically unequal. For several reasons, some projectors displays are constructed with a fourth color emitter. Prior art four color displays usually use white as the fourth color. This is typically done to increase the brightness of the display, as the colors are usually created using dichroic filters. The white is created by removing a color filter; the light of the lamp which, being white  2408  already, is allowed to pass to the spatial light modulator unobstructed or modified. The four colors collectively are grouped into a pixel that may show any color within the triangle defined by the saturated colors, with the added ability to show lower saturation colors at a higher brightness by the addition of the appropriate amount of white.  
         [0104]    For displays that are to be driven using subpixel rendering, the choice of a non-filtered white color plane or field creates a serious problem. Subpixel rendering depends on the ability to shift the apparent center of luminance by varying the brightness of the subpixels. This works best when each of the colors has the same perceptual brightness. Blue subpixels are perceived as substantially darker than the red and green, thus do not significantly contribute to the perception of increased resolution with subpixel rendering, leaving the task to the red and green subpixels. With the addition of an unfiltered white, the white color plane or field, being significantly brighter than both the red and green subpixels, the red and green lose much of their effectiveness in subpixel rendering.  
         [0105]    In an ideal display, the luminance of each of the subpixels would be equal, such that for low saturation image rendering, each subpixel has the same luminance weight. However, the human eye does not see each wavelength of light as equally bright. The ends of the spectrum are seen as darker than the middle. That is to say that a given energy intensity of a green wavelength is perceived to be brighter than that same energy intensity of either red or blue. Further, due to the fact that the short wavelength sensitive cones, the “S-cones”, those giving rise to the sensation of ‘blue’, do not feed the Human Vision System&#39;s luminance channel, blue colors appear even darker.  
         [0106]    In most prior art projector systems, the splitting of the white spectrum is usually done so that the red  2404  and the blue  2402  color points have the greatest color saturation as possible, while the green  2406  point is formed from the middle of the spectrum, having both more energy and brightness than the red  2404  and blue  2402  combined.  
         [0107]    One embodiment for a three color system shown in FIG. 24B entails using wider bands for red  2404  and blue  2402 , pushing them up the chart towards the apex slightly to create new red  2404   b  and blue  2402   b  color points, while the green  2406   b , being narrower, also is pushed toward the apex. This increases the energy of the red  2404   b  and blue  2402   b , while reducing the energy of the green  2406   b . The white point  2408  remains in the same place. This remapping of the spectrum to the color triangle improves the subpixel rendering performance, but shifts the color gamut. For many applications, this improvement may be quite satisfactory and economical.  
         [0108]    One embodiment that reduces the above problem adds a fourth color that substantially takes its energy from the shorter wavelength green part of the spectrum. In a system of dichroic beam splitters or regenerating color wheel assembly, this will reduce the energy being used on the “green” color plane, splitting it between a yellowish green  2506  and a cyan  2508  color as shown in FIG. 25. The total brightness and light efficiency remains the same, but the red  2504 , yellowish-green  2506 , and cyan  2508  beams have the substantially the same brightness. A further advantage is that the color gamut thus formed from the four color system is wider than the prior art three color system. Yet a further advantage of this invention is that the additional color beam may be independently modulated as a displaced subpixelated image, thus increasing the image quality of the resulting subpixel rendered image, with three color planes with near equal perceived brightness.  
         [0109]    With three planes of near equal perceived brightness, the arrangement of subpixelated color planes of FIG. 23 may be used to full benefit. FIG. 23 illustrates three images of the array of pixels shown in FIG. 8 overlaid with a shift of one third of a pixel each. A logical pixel  128  is illustrated on the resulting image  126  in FIG. 23. The red pixel  130 , green pixel  132 , and “blue” (now possibly cyan) pixel  134  overlap to form a smaller triangular area  136  that is at the center of the logical pixel. This overlap area is brightest, followed by the three areas where there are only two pixels overlapping, while the areas with no overlap have the lowest brightness.  
         [0110]    This process of increasing the number of color points and displaced color plane images can be performed again to yield a five color system as shown in FIG. 26. Here, the red  2604  and blue  2602  may be further pushed into their respective ‘corners’ by restricting their bandpasses at the edges of the visible spectrum, increasing the color gamut. The mid-spectrum is divided into three equally, perceptually, bright color points; greenish-yellow  2605 , deep-green  2606 , and deep-cyan  2608 . This, along with the red  2604 , gives four planes of effective subpixel rendered image. For good measure, the blue plane may be made coincident, fully converged, with the red to add to its brightness, giving a magenta color plane. These four colors may be used with arrangement of pixels of FIG. 30 to advantage.  
         [0111]    In yet another embodiment, there is a possibility for integrating a “front-to-back” system (i.e. from image capture and/or generation to image render) using five colors. Each of the colors is subpixel rendered, from the camera to the projector. The color points are chosen carefully to both cover a wide gamut and be approximately the same luminance. Each color comes from narrow spectral band defined by dichroic filter-beam splitters. When the projector recombines the light, save for random loss, all of the light from the lamp is used to recreate the same white light.  
         [0112]    Several color arrangements are possible. For example, here are two that use the colors R=red; Y=yellow; C=cyan; G=green and B=blue—in either a diamond or square matrix layout:  
             C                 Y                 C                 Y                                                                                                                       R                 Y                 R                 Y                            G                 R                 G                                                                                                                         C                 G                 C                 G               Y                 C                 Y                 C                                                                                                                       R                 Y                 R                 Y                            R                 G                 R                                                                                                                         C                 G                 C                 G                               
 
         [0113]    Of course, other matrices are possible—with other colors also selected. It should also be possible to use the blue plane at a lower resolution.  
         [0114]    As well as separating the sample points of each color in space, by subpixel rendering, the color plane samples are displaced in time as well. Not only will this reduce temporal aliasing of moving objects, but it will significantly reduce jutter. The four longer wavelength colors are shuttered on a rotating basis, 90 degrees from the preceding and following color plane. That means there is also a color shuttered at 180 degrees from each color. The blue plane may be shuttered at any point since it will not greatly add to brightness. But if one of the other colors is the dimmest, the blue may be shuttered with it to keep its transition roughly the same amplitude as the others to eliminate flicker. With four major colors to work with, the addressability is increased by a factor of four and the MTF is doubled in each axis.  
         [0115]    This process of breaking up the spectrum and increasing the number of subpixel rendering planes may be performed up to any arbitrary number, N.  
       Flicker Reduction in Field Sequential Color Systems  
       [0116]    The perception of flicker in Field Sequential Color (FSC) systems is primarily caused by the unequal luminances of the color components that are time sequentially flashed onto the screen or to the viewer&#39;s eyes. The largest luminance difference in prior art three color systems is between the green color and the blue color, the blue color having comparatively little or no perceived luminance. Prior art methods of reducing the perception of flicker have included increasing the temporal frequency at which the three or more colors fields are presented. However, for some spatial light modulators, this is impractical either due to the bandwidth limits being less than that required to transfer the image of each field or to the time required for the spatial light modulator to present a high contrast image of the field (e.g. Liquid Crystal response time) being too long for the desired field rate.  
         [0117]    A novel method of reducing the perception of flicker comprises the reduction of the total time that the dark, low luminance, color, such as blue, is presented to the viewer. Another novel method is to increase only the dark, low luminance, color frequency. Additionally, the two methods listed above may be combined to advantage.  
         [0118]    For direct view applications, Light Emitting Diodes (LEDs) may be used as the illuminants. In this case, the practice is to use very brief flashes of monochromatic light for each color field. Thus, the set-up time for the spatial light modulator is often the limiting factor for the field and frame rates. As described above one method to reduce flicker perception is to increase the blue flash rate. In this case, instead of the prior art order of color flashes, which is typically something like: . . . red, green, blue, red, green, blue, red, green, blue . . . , the following order of color flashes may be substituted: . . . red, blue, green, blue, red, blue, green, blue . . . , etc. Note this will slow the frame rate if the field rate is kept constant. This will however, increase the frequency of the blue flashes, countered by the higher luminance flashes, namely red and green in the above example, reducing the perception of flicker. If the time for setting up the blue field image on the spatial light modulator may be reduced by a suitable method, the time between the red or green fields and the blue field flash may be reduced to maintain the same frame rate as the prior art field order. In each of the above, the total illumination intensity of each color component, averaged over the frame, is adjusted to maintain the desired white point; Specifically, the intensity of the doubled blue flashes may be reduced in half, or one may be one fourth (¼) and the other flash may be three fourths (¾) of the single flash intensity.  
         [0119]    For projectors that use color filter wheels, the color wheel may be modified to provide the same or similar novel arrangement of color flashes as above. In FIG. 37, a prior art color wheel arrangement  3700  is illustrated. In this color wheel  3700  there are three color filter regions blue  3702 , red  3704 , and green  3706 . The color wheel spins at the same rate as the frame rate of the display system, illuminating the spatial light modulator: . . . red, green, blue, red, green, blue, red, green, blue . . . , etc. FIGS. 38A, 38B,  38 C, and  38 D illustrate novel color wheels, with various combinations of reduced low luminance color component (e.g. blue) time or doubled low luminance color component frequency, or combinations of the two.  
         [0120]    [0120]FIG. 38A illustrates a novel color filter wheel  3800  that reduces the size of the low luminance color (e.g. blue) filter region  3802 . Reducing the time that the blue illumination is the only light being viewed reduces the strength of the Fourier signal energy from the luminance variation. Reduced Fourier signal energy reduces the visibility of the perceived flicker.  
         [0121]    [0121]FIG. 38D illustrates a novel color filter wheel  3830  that has four color regions, two of which are low luminance (e.g. blue) color  3832 , while the two are higher luminance colors. These may be red  3834  and green  3836 . Thus, this may provide the following color field sequence: . . . red, blue, green, blue, red, blue, green, blue . . . , etc. Note this will slow the frame rate if the field rate is kept constant. This will however, increase the frequency of the blue flashes, countered by the higher luminance flashes, namely red and green in the above example, reducing the perception of flicker.  
         [0122]    If the time for setting up the blue field image on the spatial light modulator may be reduced by a suitable method, the field time may be reduced to maintain the same frame rate as the prior art field order. FIGS. 38B and 38C illustrate examples where both the blue time period is reduced and the frequency increased. The color filter wheel  3810  of FIG. 38B has the property that the combined angular area and/or angular distance of the two blue regions  3812  is the same of that of either of the other two colors, red  3814  or green  3816 . This gives the advantage that the illumination balance is identical to the prior art color filter wheel  3700  of FIG. 37. FIG. 38C illustrates a color filter wheel  3820  that has both doubled and reduced angular area and/or angular distance blue filter regions  3822 . This doubles the blue dark frequency and reduces the total time at that lower luminance, reducing the perception of flicker.  
         [0123]    [0123]FIG. 39A illustrates a novel color filter wheel  3900  that places a very low luminance and low radiance (e.g. black) filter region  3912  opposite the low luminance color (e.g. blue) filter region  3902 . The opposition of black and blue doubles the temporal frequency of low luminance, reducing the perception of flicker. FIG. 39B illustrates the same color filter wheel  3900  with the addition of two additional very low luminance color (e.g. black) filter regions  3912   b  and  3912   b  that break up the red filter region  3904  and green filter region  3906  of FIG. 39A into two red filter regions  3904   b  and  3904   b  and two green filter regions  3906   b  and  3906   b . The spatial light modulator may remain displaying the same red or green color field information during the black time intervals created by the superimposed black filter region  3912   b  or  3912   b . The presence of the two additional black filter regions  3912   b  and  3912   b  further increases the temporal frequency of the low luminance signal, reducing the perception of flicker.  
         [0124]    [0124]FIG. 40 illustrates a novel color filter wheel  4000  of four colors. The fourth color may be comprised of high transmissive, and therefore, high luminance (e.g. white or clear) regions  4008 . These clear regions  4008  may be placed in opposition, such that their higher luminance temporal frequency is doubled, reducing perception of flicker. The low luminance color (e.g. blue) regions  4002  may be placed in opposition, such that their lower luminance temporal frequency is doubled, reducing the perception of flicker. Further, the high luminance and low luminance regions may be placed next to each other such that one leads or follows the other. This juxtaposition creates higher temporal frequency Fourier signal components than if they were not so juxtaposed, reducing the perception of flicker.  
         [0125]    In addition to using the timing of Light Emitting Diodes and the transmission sequence of color filter wheels, other color timing methods may be similarly modified. For example, the use of Liquid Crystal based PI cell color modulators, colored fluorescent backlights, or electrically controlled, color selecting, holograms may be modified such that the timing follows the above examples.  
       Bandwidth Reduction  
       [0126]    Bandwidth reduction, to allow faster transfer of data to the spatial light modulator, or to allow greater image compression for transmission or storage, may be facilitated by another embodiment. This bandwidth reduction may enable the reduced time to form the image on the spatial light modulator, which in turn may enable reduced time and/or divided low luminance color field display as disclosed above. This bandwidth reduction may be implemented with spatio-temporally displaced filtering and reconstruction to maintain addressability and Modulation Transfer Function, maintaining image quality.  
         [0127]    [0127]FIGS. 41, 42A,  42 B,  42 C, and  42 D illustrate a data set that is spatio-temporally displaced filtered and reconstructed. FIG. 41 illustrates the original data set  4100 . It may also represent a matching prior art spatial light modulator  4100  which is to be used to reconstruct the spatio-temporally displaced filtered data set. Examining FIG. 42A, data points  4205  are grouped together into larger data points  4215 , applying a suitable filter to the original data points  4205 , perhaps a simple box filter. This creates a lower resolution image data set, with less data points, thus reducing the bandwidth required to transmit the image. Turning to FIG. 42B, again, data points  4205  are grouped together into larger data points  4225 . Note that these larger data points  4225  comprise a different grouping of original data points  4205 , than does the first larger data points  4215 . The groupings  4215  and  4225  are displaced diagonally by one half. This is functionally similar to the displaced filtered and reconstructed image of FIG. 20. When these two data sets are sequentially displayed, one after another, each time that color field is displayed, the temporal integration of the human eye composites the two lower resolution images as a higher resolution image, in a manner very similar to that described above for images that are simultaneously presented. Examining FIGS. 42C and 42D, note that each groups original data points  4205  into larger data points  4235  and  4245  respectively. Again, note that the larger groupings are displaced from one another, and from both of the previously discussed groups  4215  and  4225 . When all four are presented sequentially, each time for that color field, the temporal integration of the human eye composites the four lower resolution images as a higher resolution image, in a manner very similar to that described above for images that simultaneously presented. This is functionally similar to the displaced filtered and reconstructed image of FIG. 30.  
         [0128]    While the above example used square grid data samples, box filters, of two by two original data points  4205  going to each output data resample  4215 ,  4225 ,  4235 , and  4245 , it will be appreciated that other combinations of input samples (e.g. 3×3, 4×5, etc), filters (e.g. tent, Gaussian, Difference-Of-Gaussians, etc), and output resample grid (e.g. FIGS. 6, 7, and  8 , etc.) will also function in a similar manner. All such variations are contemplated.+ 
         [0129]    While the invention has been described with reference to exemplary implementations and embodiments, it will be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.