Abstract:
A video projection system and method for synchronizing images are provided. An image source provides a video signal with at least two streams of sequential images. A color switching device is operable to present fundamental colors and one or more non-fundamental colors at least once during each of a plurality of phases of the video signal. A light processing element controls projection of light with the two streams of sequential images sequentially through the presentation of the colors of each phase. An eye-switching adjustment element modifies a timing of the colors presented by aligning with the non-fundamental color, an unstable transition phase between different states of an eye-switching device to which the video signal is provided. The eye-switching adjustment element also modifies the video signal to deliver the images synchronously with the eye-switching device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This non-provisional patent application is a continuation of U.S. patent application Ser. No. 14/052,672, filed Oct. 11, 2013, which is a continuation of U.S. Pat. No. 8,556,429, issued Oct. 15, 2013, which is a continuation of U.S. Pat. No. 8,066,377, issued Nov. 29, 2011, the priority dates of which are claimed and the disclosures of which are incorporated by reference. 
     
    
     FIELD 
       [0002]    This invention relates in general to systems and methods for synchronizing a 3D video projector and in particular to a video projection system and method for synchronizing images. 
       BACKGROUND 
       [0003]    Two dimensional video projectors have been widely available for many decades. Recently, three dimensional (3D) stereoscopic video projectors have been developed that produce flickerless 3D stereoscopic images in part by increasing the video projector&#39;s operating frequency from approximately 60 frames per second (FPS) to approximately 85 FPS and beyond. This higher frame rate is important because rates below 85 FPS can give the impression of excessive flickering to the viewer. 
         [0004]    As shown in  FIG. 1 , in order to view the images from a 3D stereoscopic video projector  12  connected to an image source  11 , special optical devices may be used and/or special eyewear may be worn by the viewer, such as a pair of liquid crystal (LC) shutter-based glasses  13 . Such glasses  13  include shutters  14 A,  14 B that cover the user&#39;s eyes and alternately transition between clear and opaque via a shutter control signal, generally referred to as  22 . A video signal  20  is delivered from the image source  11  to the video projector  12  which then controls the production and delivery of the images  18 ,  19  synchronously with the shutters  14 A,  14 B so that only the left eye is presented a left eye image  18  and the right eye is presented a right eye image  19 . 
         [0005]    As shown in  FIG. 2 , other 3D stereoscopic video projector systems are found in the prior art that utilize a polarization flipping device  16  to alternate the polarization of light exiting the video projector  12 . An example of a polarization flipping device is one sold by Real D, Inc. of Beverly Hills, Calif. under the trademark Z SCREEN. The video projector  12  is connected to an image source  11 , and projects an image (designated  18 ,  19 ) through a polarization flipping device  16  and onto a polarization preserving screen (not shown) which is watched by a viewer wearing passive polarized eyewear  17 . The image source  11  sends a flipping device control signal  22 ′ to control the flipping device  16 . 
         [0006]    Recently, semiconductors, called digital light processors or digital micro-mirror devices (DMDs) (Texas Instruments, Inc. sells a digital light processor under the trademark DLP) have been developed to manipulate light digitally. DMDs act as light switches consisting of up to and beyond 1.3 million microscopic mirrors, each of which is able to tilt back and forth up to 5,000 times per second. In 3D stereoscopic video projector systems the movement of the DMD is coordinated with the projector&#39;s light source, and with the video or graphic signals transferred to an eye-switching device to produce seamless images to the viewer. Today, 3D video projectors with three DMDs are relatively common with a single DMD being assigned to one of three critical colors. Unfortunately, such 3D video projectors are relatively expensive. 
         [0007]    Another type of 3D video projector utilizes a single DMD. While 3D video projectors with a single DMD are less expensive than 3D video projectors with three DMDs, they also employ a color wheel divided into several color segments which filter the white light from the projector&#39;s light source into specific colors which are passed in succession onto the single DMD. A color sequencing firmware, (hereinafter referred to as firmware) is also employed to control the operation of the single DMD. 
         [0008]    3D video projector systems used with LC shutter glasses  13  must use an eye-switching signal  22  to synchronize the eyewear&#39;s shutters  14 A,  14 B. This eye-switching signal  13  is typically generated externally from the video projector, for instance at the image source  11  as shown in  FIG. 1 . Thus when used with single DMD projectors, the eye-switching signal  22  is indirectly synchronized with the projector&#39;s color wheel. As the color wheel spins during operation, the eye-shutters on the glasses  13  quickly alternate to create transparent and opaque periods. Unfortunately, the transition between the transparent and opaque periods is not instantaneous which reduces the overall quality of the image seen by the viewer. For example, when the transition period occurs during the Red color segment, some of the time normally required to complete a full Red duty cycle may be lost, causing the Red color in the image to appear weak. It is especially problematic when presenting human faces which appear noticeably pale or lifeless. This transition either between transparent and opaque periods or between opaque and transparent periods shall be referred to as the “unstable transition phase.” While adjustments could be made to the video projector to move the problem from one color segment to another, the problem, heretofore, has not been resolved. 
       SUMMARY 
       [0009]    It is an object of the present invention to provide an improved system and method for producing higher-quality 3D stereoscopic images from a 3D video projector. 
         [0010]    It is another objective of the present invention to provide such a system and method that addresses the image quality problems associated with a 3D video projector utilizing a single DMD. 
         [0011]    These and other objects are addressed by the system and method disclosed herein specifically intended to be used with a video projector that includes a color switching device, such as a color wheel, and a light processing element, such as a single DMD. The light processing element transmits or blocks the light from the color switching device. While the preferred embodiment of the invention uses a color wheel as a color switching element and a single DMD as a light processing element, the invention should not be construed as being limited to these structures. For example, the color switching device can also be LED, Laser diode, and OLED-related components that are designed to produce at least three separate (Red Blue and Green) colors. The light processing elements can include LCD elements and other displays products such as those sold by Three Five Systems, Inc. of Tempe Ariz., under the trademark LCOS and display products sold by Victor Company, Ltd or Yokomoto, Japan under the trademark D-ILA. 
         [0012]    In the preferred embodiment, a color wheel is used which is divided into at least one Red segment, at least one Blue segment, and at least one Green segment, which are referred to as ‘critical color segments’ because together they represent the fundamental colors required to create a white balance. The color wheel may include other color, clear or opaque segments called non-critical segments. Some non-critical segments may be transmissive such that they allow transmission of light through the color wheel. Such transmissive non-critical segments include clear segments, White segments, and all other color segments except black. Black segments and segments covered by a physical barrier are known as non-transmissive and act to block the transmission of light through the color wheel during operation. Different color wheels are shown herein that include various combinations of the three critical color segments listed above along with one or more non-critical segments located or electronically created at different locations on the color wheel. 
         [0013]    The system includes accompanying firmware that controls the projection of light from the projector to an eye-switching device so that the transmission of light from the projector is momentarily discontinued during the eye-switching device&#39;s unstable transition phase. When the color switching device is a color wheel, a transmissive non-critical segment located on the color wheel is presented in front of the projector&#39;s lamp during the eye-switching device&#39;s unstable transition phase. In another embodiment of the color wheel, at least one non-transmissive non-critical element is created that block light from the projector altogether when presented. In still another embodiment of the color wheel, the non-critical segment is eliminated from the color wheel and a modified version of the firmware is used that controls the DMD so that it momentarily discontinues illumination during the device&#39;s unstable transition phase. In every embodiment of the color wheel disclosed herein, the duration of the physical or non-physical, non-critical segment must be sufficient to mask the unstable transition phrase. 
         [0014]    The type of firmware used depends on the type of color wheel and the type of eye-switching device used to view 3D images. When a compatible color wheel, firmware and eye-switching device are used and when a non-critical segment is presented in front of the projector&#39;s lamp, all of the light from the projector is either passed on or blocked out. The firmware controls the emission of light from the projector and the timing of the color sequencing matched with a particular color wheel, so that a non-critical segment is passed over and the light from the projector is momentarily discontinued during the unstable transition phase. In this manner, the color fading or deteriorating defect commonly experienced with 3D single digital light processing video projectors found in the prior art is substantially reduced or eliminated altogether. 
         [0015]    In an alternative embodiment, a projector and color switching device is used but the firmware to modify control of the DMD is replaced or supplemented by an eye-switching adjusting device or program installed or loaded into the image source or intermediate device located between the image source and the projector. The image timing hardware and/or firmware modifies the shutter or flipping device control signal to the eye-switching device so that the unstable transition phase occurs during a non-critical segment of the color switching device and modifies the image source in order to control the production and delivery of the images synchronously with the shutters. 
         [0016]    In addition to controlling the timing of the color sequence, the firmware controls the video projector&#39;s speed so that it operates at approximately 85 FPS or higher which is needed to perceive flickerless images. In the preferred embodiment, the video projector operates at approximately 120 FPS 
         [0017]    A further embodiment provides a video projection system and method for synchronizing images. An image source provides a video signal with at least two streams of sequential images. A color switching device is operable to present fundamental colors and one or more non-fundamental colors at least once during each of a plurality of phases of the video signal. A light processing element controls projection of light with the two streams of sequential images sequentially through the presentation of the colors of each phase. An eye-switching adjustment element modifies a timing of the colors presented by aligning with the non-fundamental color, an unstable transition phase between different states of an eye-switching device to which the video signal is provided. The eye-switching adjustment element also modifies the video signal to deliver the images synchronously with the eye-switching device. 
         [0018]    A still further embodiment provides a video projection display system for synchronizing presentation of a plurality of images projected onto a display. A display includes a screen surface suitable for presentation of images. A video projection unit is configured to control production and delivery of the images on the display. An image source includes at least two streams of the images ordered into a sequence of appearance. A color switching device is operable to continually select a color out of a set consisting essentially of a plurality of fundamental colors. Each fundamental color is selected for presentation on the display for a fixed time segment. A light processing element is interposed between the image source and the color switching device and is operable to block and permit transmission of the light received from the image source in each color selected by the color switching device on to the display during each fixed time segment. The light includes the at least two streams of sequential images. A synch signal generator is in control of the light processing element and is configured to time presentation of the light by the light processing element on to the display and of control signals to a viewing device of the display. The presentation of the light and of the control signals being timed in synchrony with the fixed time segments only during a transition state of the viewing device. A wearable eye-switching device, which functions as the viewing device, is operable to obstruct and permit viewing of the display through the wearable eye-switching device in response to the control signals. The transition state includes an interval occurring between a state permitting viewing of the display through the wearable eye-switching device and a state preventing viewing of the display through the wearable eye-switching device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an illustration of a projected stereoscopic 3D image system used in the prior art that uses a single chip DMD-based video projector combined with LC shutter glasses and shows the left and right oriented images and the shutters being synchronized so that the viewer&#39;s right eye only sees the right-oriented image, and the left eye sees only the left-oriented image. 
           [0020]      FIG. 2  is an illustration showing an alternate stereoscopic 3D projection system used in the prior art that uses the polarization-flipping device to alternate the polarization of light exiting the projector. 
           [0021]      FIG. 3  is an illustration showing a video projector with resident firmware coupled or loaded into the projector&#39;s memory with either a three color, four color, five color, six color, seven color, or eight color wheel located in the projector. 
           [0022]      FIG. 4  is an illustration showing a four segment color wheel and the coordination of the timing of the shutter signal to the eye-switching device and the timing of the color sequence for the projector, whereby the unstable transition phase of the eye-switching device occurs at the start of the Red segment of the color wheel. 
           [0023]      FIG. 5  is an illustration showing the same four color wheel shown in  FIG. 4  with shutter timing signal and the timing of the color sequence being coordinated so that the unstable transition phase occurs when the non-critical White segment is presented. 
           [0024]      FIG. 6  is an illustration of the projector with a four segment color wheel showing the movement of the color wheel, the production of the left and right images and the coordination of the lenses of the eye-switching device being appropriately transparent or opaque during the critical color segments R, G, and B, and undergoing transition during the non-critical (White segment). 
           [0025]      FIG. 7  is an illustration showing a four segment color wheel with a Black, non-transmissive segment and the coordination of the shutter timing signal with the timing of the color sequence so that the Black non-transmissive non-critical segment is presented with the unstable transition phase. 
           [0026]      FIG. 8  is an illustration showing the coordination of the shutter timing signal and the timing of the color sequence on an alternate four color wheel that uses enlarged Red, Green and Blue segments and a narrow non-critical Black non-transmissive segment which is presented with the unstable transition phase. 
           [0027]      FIG. 9  is an illustration showing the coordination of the shutter timing signal and the timing of the color sequence on a four segment color wheel in which a dark sequence is electronically inserted into the image by the firmware at the start of each critical and non-critical segment and with the dark sequence located at the beginning of the Red segment being coordinated with the unstable transition phase. 
           [0028]      FIG. 10  is an illustration showing the coordination of the shutter timing signal and the timing of the color sequence on a five color wheel with a non-critical Black non-transmissive segment located between each critical and non-critical segment and with the non-transmissive segment located at the beginning of the Red segment being coordinated with the unstable transition phase. 
           [0029]      FIG. 11  is an illustration showing the coordination of the shutter timing signal and the timing of the color sequence on a three color wheel that uses three electronic dark sequences located between the three color segments with the unstable transition phase being coordinated with the dark sequence between the Blue and Red color segments. 
           [0030]      FIG. 12  is an illustration showing an image source transmitting a video signal and an eye-switching signal to the video projector. Connected to the projector is a wired or wireless transmitter which transmits an eye-switching signal to a compatible eye-switching device. 
           [0031]      FIG. 13  is an illustration similar to the illustration shown in  FIG. 12  showing the image source transmitting a video signal to the video projector and transmitting an eye-switching signal via a wired or wireless communication device such as an RF or IR transmitter to the eye-switching device. 
           [0032]      FIG. 14  is an illustration showing an image source transmitting a video signal and an eye-switching signal to an eye-switching adjusting device or program. The eye-switching adjusting device or program then forwards a modified eye switching signal to the projector that then transmits via a wired or wireless communication device such as an RF or IR transmitter, to the eye-switching device. Alternatively, the eye-switching adjusting device or program then forwards a modified eye-switching signal via a wired or wireless communication device such as an RF or IR transmitter, directly to the eye-switching device or program. The eye-switching adjusting device or program also modifies the image source video signal and transmits it to the projector in order to control the production and delivery of the images synchronously with the shutters. 
           [0033]      FIG. 15  is an illustration similar to the illustration shown in  FIG. 14  but with the eye switching adjusting device or program built into or loaded into the memory of the image source. A modified eye-switching signal is then transmitted via a wired or wireless communication device, such as an RF or IR transmitter and eventually to the eye-switching device. The image source video signal is also modified by the eye-switching adjusting device or program and transmitted to the projector in order to control the production and delivery of the images synchronously with the shutters. 
           [0034]      FIGS. 16A-E  are illustrations that show an alternative embodiment of the system shown in  FIGS. 14 and 15  that uses a 3D video projector and color switching device but with the firmware that modifies control of the DMD being replaced or supplemented by an image timing hardware and/or firmware loaded into the image source or intermediate device(s) located between the image source and the projector. The image timing hardware and/or firmware both modifies the signal to the eye-switching device so that the unstable transition phase occurs during a non-critical segment and modifies the image source in order to control the production and delivery of the images synchronously with the shutters. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Referring to the accompanying Figs., there is shown a system, generally indicated by reference number  10  for producing higher quality 3D stereographic images from a single chip DMD video projector. Located inside the video projector  12  is a color switching device that controls the light transmitted from the projector&#39;s light source to the DMD. Referring more specifically to  FIG. 3 , the video projector  12  includes working memory  15  and color sequencing firmware  9 . In the preferred embodiment, the color switching device is one of six, multiple color wheels (three, four, five, six, seven and eight color wheels) referenced as  30 ,  40 ,  50 ,  60 ,  70  and  80 , respectively. Each color wheel  30 ,  40 ,  50 ,  60 ,  70 , and  80  includes at least at least one Red segment, at least one Blue segment, and at least one Green segment, which are referred to as ‘critical color segments’. 
         [0036]    Five color wheels  40 ,  50 ,  60 ,  70  and  80  include a physical non-critical segment,  48 ,  58 ,  68 ,  78 ,  88  respectively, that precedes or follows the other critical color sections located thereon. There are two types of physical non-critical segments—a transmissive non-critical segment that allows light to be transmitted through the color wheel, and a non-transmissive non-critical segment that blocks or impedes light from being transmitted through the color wheel. Clear segments and all color segments except Red, Blue, Green and Black may be used as transmissive non-critical segments. Non-transmissive non-critical segments include a Black segment and any physical barrier placed on the color wheel that blocks the transmission of light through the color wheel. In the color wheels shown in the accompanying Figs, all include the three critical color segments and some include at least one non-critical segment. With some color wheels, the firmware is used to control the DMD to block the transmission of light during a non-critical segment. With other color wheels the physical, non-critical segment has been eliminated (see color wheel  30 ) and the firmware electronically creates a non-critical segment at different locations on the color wheel. 
         [0037]    As noted above, the color fading problem associated with single DMD 3D video projectors is caused by the occurrence of the eye-switching device&#39;s unstable transition phase during any critical color segment of the color wheel being used. In the first embodiments shown herein, the firmware  9  is used to control the timing of the color sequence and controls the emission of light from the video projector  12  so that a non-critical segment is passed over or is electronically inserted in the color wheel to discontinue transmission of light during the unstable transition phase. By this means the color fading or deteriorating defect commonly experienced with single DMD 3D video projectors is substantially reduced or eliminated. 
         [0038]    The functional activities of the firmware  9  depend on the type of color wheel used. For example, when the color wheel includes a transmissive non-critical segment that has been aligned with the unstable transition phase, the firmware  9  controls the DMD so that it discontinues transmission of light from the DMD during said non-critical segment. If the color wheel includes a non-transmissive non-critical segment, the firmware  9  may or may not control the DMD to discontinue transmission of light since transmission of light through the color wheel is blocked. 
         [0039]    In another embodiment of the system, color wheels with both critical color segments and non-critical segments are used, but the DMD is not controlled by the firmware to modify the color sequence such that a non-critical color segment is presented during the unstable transition phase. Instead, an eye switching adjusting device or program built into or loaded into the memory of the image source or located in an intermediate device controls the eye switching device generally referenced as 99 in  FIGS. 6, 12-15 , so that the unstable transition phase aligns in time with an eligible non-critical color and modifies the image source video data in order to deliver uniformly left- and right-oriented images synchronously with the eye-switching device. 
         [0040]    Another important feature of the firmware  9  is that it designed to adjust the speed of the video projector  12  so that it operates at least 85 FPS for flickerless images. 
         [0041]    Once the firmware  9  has been loaded into the working memory  15 , a color wheel similar or equivalent to one of the six representative color wheels,  30 ,  40 ,  50 ,  60 ,  70  or  80  noted above is selected and installed in the projector  12 . In  FIGS. 4, 5, 7-11, and 16A  there are shown representative color wheels and graphs that illustrate the coordination of the timings of color sequence and the shutter signals. 
         [0042]    More specifically,  FIG. 4  shows a four segment color wheel  40  (Red (R)  41 , Green (G)  42 , White (W)  43  and Blue (B)  44  color segments). The numbers 1-4 represent the order that the color segments are displayed from 1 to 4 in a clockwise rotation. Also shown is a graph  45  of the timing of the color sequencing from the video projector  12 . The actual sequence of color segments varies from projector manufacturer to projector manufacturer. Located above the timing of color sequence graph  45  is a second graph  46  that shows the timing of the shutter signal and the unstable transition phase  47  of the eye-switching device  99  used with the projector  12 . With color wheel  40 , without modification to the firmware controlling the color sequencing, a critical color segment, in this case the Red (R) segment  41 , is shown aligning undesirably with the unstable transition phase  47  of the eye-switching device  99 . This results in the color fading or deteriorating defect commonly experienced with 3D single DMD video projectors 
         [0043]      FIG. 5  is an illustration of the first embodiment showing the same four segment color wheel  40  shown in  FIG. 4  with the timing of the color sequence shown in graph  45  being modified by an embodiment of the firmware  9  so that the non-critical color segment (denoted W (White) segment  43 ) is aligned with the unstable transition phase  47  of the eye-switching device  99 . During use, the firmware  9  controls the DMD so that no light is transmitted from the projector  12  while the White segment  43  is presented. 
         [0044]      FIG. 6  is another illustration of the first embodiment showing sequential images of the video projector  12  and an eye-switching device  99  showing the left and right signals  18 ,  19 , respectively, being transmitted to the eye-switching device  99  which is appropriately transparent or opaque during the critical color segments R, G, and B, and undergoing transition during the non-critical (White segment). 
         [0045]      FIG. 7  is an illustration of a second embodiment of a four segment color wheel, designated  40 ′ with the White segment shown in  FIGS. 4 and 5  being replaced with a non-transmissive Black non-critical segment  48 . As shown in the accompanying graphs  45 ,  46  with this color wheel  40 ′, the timing of the color sequence is adjusted and the DMD is controlled by the firmware so that the non-transmissive Black non-critical segment  48  is aligned with the unstable transition phase  47  of the eye-switching signal. More specifically, the black non-critical segment  48  blocks transmission of light through the color wheel  40 ′. 
         [0046]      FIG. 8  is an illustration of a third embodiment showing the timing of the shutter signal and timing of the color sequence and a four segment color wheel  90  that includes enlarged Red, Green and Blue segments,  92 ,  94 ,  96 , and a narrow non-transmissive Black segment,  98 , respectively. The firmware  9  adjusts the color sequencing so that the non-transmissive Black segment  98  is aligned with the unstable transition phase  47 . In this embodiment, the color bandwidth can be redistributed to the remaining color segments to increase color precision. 
         [0047]    It should be understood that the non-transmissive non-critical segment is not limited to a Black segment. For example, it could be a physical blocking layer, made of plastic that is laminated to the color wheel  90  capable of blocking the transmission of light. 
         [0048]      FIG. 9  is an illustration showing the timing of the color sequence and timing of the shutter signal used with the four segment color wheel  40  as an example, with another embodiment of the firmware  9  being used to automatically re-define a ‘dark’ segment  49  at the start of each color segment  41 - 44 . The firmware  9  controls the operation of the DMD so that one of the dark segments  49  is being coordinated with the unstable transition phase  47  (in this case the dark segment formed at the start of the Red Segment). It should be noted that with this embodiment, because a dark segment  49  is displayed between every color segment  41 - 44 , the overall brightness of the image is diminished. 
         [0049]      FIG. 10  is an illustration of a fifth embodiment that uses an alternative five color segment color wheel  40 ″ as an example with non-transmissive Black segments  72 ,  74 ,  76 ,  78  located between each color segment  41 - 44 , respectively. As shown in the graph  45 ,  46  the timing of the shutter and timing of the color sequence is the same as used with the four color wheel  40  shown in  FIG. 9 , but with a physical Black or ‘dark’ non-transmissive segment being inserted between each color segment. By using physical non-transmissive segments, the contrast ratio is increased. 
         [0050]      FIG. 11  is an illustration of a sixth embodiment of a three segment color wheel  30  with Red  31 , Green  32 , Blue  33 , wherein the color wheel  30  does not include a physical non-critical segment. With the color wheel  30  the firmware  9  inserts a ‘dark’ sequence  39  into a portion of every critical color segment. The firmware  9  controls the operation of the DMD so that one of the dark segments  39  is being coordinated with the unstable transition phase  47  (in this case the dark segment formed at the start of the Red Segment). The duration of the ‘dark’ sequence is at least equivalent to the duration of the unstable transition phase of the eye-switching device. 
         [0051]      FIG. 12  is an illustration showing an image source  11  transmitting a video signal  100  and an eye-switching signal  110  to the video projector  12 . Connected to the projector  12  is a wired or wireless communication means  115 , which transmits an eye-switching signal  110  to a compatible eye-switching device  99 . 
         [0052]      FIG. 13  is an illustration similar to the illustration shown in  FIG. 12  but with the image source  11  transmitting a video signal  100  to the video projector  12  and transmitting the eye-switching signal  110  directly to the eye-switching device  99 . It should be understood that the eye-switching signal could be transmitted to an intermediate device  115 , such as a wireless RF or IR transmitter which transmits the signal to the eye-switching device  99 . 
         [0053]    In an alternative embodiment, a projector and color switching device is used but the firmware to modify control of the DMD is replaced or supplemented by an image timing hardware and/or firmware loaded into the image source or intermediate device(s) located between the image source and the projector. The image timing hardware and/or firmware both modifies the signal to the eye-switching device so that the unstable transition phase occurs during the color switching device&#39;s non-critical segment and modifies the image source in order to control the production and delivery of the images synchronously with the eye-switching device. For optimum stereo operation, light needs to be discontinued from the projector for at least the duration of the eye-switching device&#39;s unstable transition phase. If the non-critical segment is non-transmissive, the process is complete in and of itself. If the non-critical segment is transmissive, the projector firmware must command the DMD to discontinue the light from the projector for at least the duration of the eye-switching device&#39;s unstable transition phase. 
         [0054]      FIG. 14  is an illustration showing an image source  11  transmitting the video signal  100  and eye-switching signal  110  to an intermediate eye-switching adjusting device or program  125 . The eye-switching adjusting device or program  125  then forwards a modified eye switching signal  130  to the projector  12  that then transmits via a wired or wireless communication device, such as an RF or IR transmitter  115 , to the eye-switching device  99 . Alternatively, the eye-switching adjusting device or program  125  then forwards a modified eye-switching signal  130  via a wired or wireless communication device, such as a RF or IR transmitter  115 , directly to the eye-switching device  99 . The eye-switching adjusting device or program  125  also modifies the image source signal  100  and creates a modified signal  105  that is transmitted to the projector  12  in order to control the production and delivery of the images synchronously with the eye-switching device  99 . 
         [0055]      FIG. 15  is an illustration similar to the illustration shown in  FIG. 14  but with the eye-switching adjusting device or program  125  built into or loaded into the memory of the image source  11 . A modified eye-switching signal  130  is then transmitted via a wired or wireless communication device, such as an RF or IR transmitter  115  and eventually to the eye-switching device  99 . A modified image source video signal  105  is produced by the eye-switching adjusting device or program  125  and transmitted to the projector  12  in order to control the production and delivery of the images synchronously with the eye-switching device  99 . 
         [0056]    As stated above, the system includes a means for selectively discontinuing transmission of light from the projector  12 . In one embodiment, the means for selectively discontinuing transmission of light from the projector is a physical non-transmissive segment of the color wheel presented in front of the projector&#39;s light source when the unstable transition phase of the eye-switching device occurs. In another embodiment, the means for selectively discontinuing transmission of light from the projector is the coordinating software program resident in the projector and hardware referred to as firmware  9 . The firmware  9  may be used to discontinue light from projector via control of the DMD during a transmissive or non-transmissive non-critical segment which has been aligned with the unstable transition phase of the eye-switching device  99 . 
         [0057]      FIG. 16A  is an illustration showing the system utilizing a projector and a four color wheel  40  but without the firmware  9  referenced above to modify control of the DMD. Because control of the DMD is not modified, the unstable transition phase occurs during the Red segment  41  thus diminishing the Red color in the image as noted above. 
         [0058]      FIG. 16B  is an illustration that shows the modified timing signal and modified image color data that occurs using the system depicted in  FIG. 14 or 15 . The eye-switching signal is shifted in time by the eye-switching adjusting device or program loaded into memory of the image source, the intermediary device or the projector. The device or program modifies the eye-switching signal so that the unstable transition phase occurs while the non-critical segment (in this case the White segment) is presented. As a result, some of the color data will now be out of phase with respect to the eye-switching signal. 
         [0059]    There are at least three approaches to fixing this problem through the modification of the image source video signal, all of which intentionally mix the left and right color data before input to the video projector, in order to be properly resolved after color sequencing by the video projector and filtering by the eye-switching device. The first approach, shown in  FIG. 16C  delivers phase corrected images synchronously with the modified eye-switching signal. The “incorrect eye” (out of phase) critical color data (in this case Red and Green) must be promoted to the next stereo input frame. This ultimately delivers uniform left and right color data from the same stereo frame to each eye during the corresponding eye-switching signal. Non-critical color data is typically irrelevant, since it is not typically an input color, but rather created by processing the critical input colors Red, Green and Blue. 
         [0060]      FIG. 16D  illustrates a second approach whereby the “correct” (in phase) color data (in this case the Blue) is demoted or moved backwards by one stereo frame in order to deliver uniform (but polarity reversed) left and right color data from the same stereo frame to each eye during the corresponding eye-switching signal. The polarity of the eye-switching signal is then reversed. 
         [0061]      FIG. 16E  illustrates a third approach, whereby either in phase or out-of-phase color data is rearranged in order to deliver uniform left and right color data from mixed stereo frames to each eye during the corresponding eye-switching signal. When necessary, the polarity of the eye-switching signal is then switched. In this case, the “correct” (in phase) Blue color data is promoted forward by one stereo input frame. Regarding  16 E, other solutions may promote, demote, swap or otherwise move either “correct” or “incorrect” color data in order to deliver uniform left and right color data from mixed stereo frames to each eye during the corresponding eye-switching signal. While not an optimum solution, due to the mixing of stereo frame data—note that in the above example, while all critical color data is uniformly left or right eye data during the corresponding eye-switching signal, the blue color data presented to each eye is one frame out of phase with the other critical colors—it may be an acceptable solution for some non-critical applications. 
         [0062]    Using the above described system, a method for improving the stereoscopic 3D image from the preferred embodiment of a single chip DMD video projector, comprises the following steps:
       a. selecting a DMD video projector that uses a color wheel to produce images for projection onto a viewing surface;   b. selecting a color switching device and color sequencing firmware, said color switch device produces at least three critical color segments and optionally one or more non-critical color segment(s), said firmware capable of controlling the color sequence timing from said video projector such that the said non-critical color segment is utilized during the unstable transition phase of the eye-switching device, while discontinuing illumination of the non-critical color segment;   c. selecting an eye-switching device capable of filtering multiple images transmitted by said video projector synchronous with an eye-switching control signal such that each eye sees a separate image;   d. positioning said eye-switching device between said projector&#39;s light source and the viewer;   e. operating said video projector to transmit an image onto a viewing surface for viewing by the user utilizing said eye-switching device; and,   f. transmitting the eye-switching signal to the eye-switching device.       
 
         [0069]    In compliance with the statute, the invention described herein has been described in language more or less specific as to structural features. It should be understood, however, that the invention is not limited to the specific features shown, since the means and construction shown is comprised only of the preferred embodiments for putting the invention into effect. The invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the amended claims, appropriately interpreted in accordance with the doctrine of equivalents.