Abstract:
This invention discloses a system and method for displaying 3-D stereoscopic images, in which stereoscopic image data are processed separately by two graphic processing channels. The operation of the two channels is synchronized, so that the processed stereoscopic images are outputted simultaneously to be displayed either by a polarization system or a head-mounted LCD system. Such a display system allows a viewer&#39;s left eye to see only a left image and the right eye to see only the right image, yet seeing the same pair of stereoscopic images at the same time, to create a natural 3-D image illusion.

Description:
CROSS REFERENCE  
       [0001]     This application claims the benefits of U.S. patent application Ser. No. 60/728,026, which was filed on Oct. 17, 2005, and entitled “Use MultiGPU to do stereo rendering”. 
     
    
     BACKGROUND  
       [0002]     The present invention relates generally to a 3-D stereoscopic image display system using polarizing filters and glasses or head-mounted LCD for viewing 2D images on a screen to give the illusion of 3-D images.  
         [0003]     Stereoscopic display creates a 3-D illusion with a pair of 2-D images, one for the left eye, and the other for the right, representing two perspectives of the same object, with a minor deviation similar to the perspectives that both eyes naturally receive in binocular vision. The viewer&#39;s brain merges the pair of images and extracts depth information from the slightly different images. The depth information is the basis for providing the viewer with the sense of a three dimensional (3-D) image. On the other hand, if the pair of images perceived by the two eyes is identical, then the brain will interpret it as a flat 2-D image.  
         [0004]     There are many ways to separately display different images to both eyes in order to create the 3-D image. For example, the head-mounted display is one of the mechanisms that generate the 3-D effect. The user typically wears a helmet or a pair of glasses installed with two small liquid crystal displays (LCD) with magnifying lenses, one for each eye. Another way is to use liquid crystal (LC) shutter glasses that will let light go through in synchronization with the images on the screen using the concept of alternate-frame sequencing.  
         [0005]     For the alternate-frame sequencing, a 3-D movie is first filmed with two cameras with different perspectives. Then the images are placed into a single strip of film in alternate order. In other words, there is a first left-eye image, then a corresponding right-eye image, then a next left-eye image, followed by a corresponding right-eye image and so on.  
         [0006]     The film is then run at a predetermined speed such as 48 frames-per-second instead of the traditional 24 frames-per-second. An audience wears specialized LC shutter glasses having lenses that can open and close in rapid succession according to the required speed. The glasses also contain special radio receivers. The projection system has a transmitter that instructs the glasses to open and shut one of the glasses. That is, the left-eye glass opens with the right-eye glass shut when left-eye image is on the screen; and the right-eye glass open with left-eye glass shut when the right-eye image is on the screen.  
         [0007]     LC shutter glasses system is generally used in home 3-D movie systems. For public venues, polarizing filter systems are a more popular solution. In a linearly polarized glass system, stereoscopic images are projected and superimposed onto a screen through orthogonally polarizing filters. A viewer wears a pair of orthogonally polarizing glasses. If the left-projector filter is a horizontally polarizing one, then the viewer&#39;s left-eye glass is a matching horizontally polarizing one, with a right-projector filter and a right-eye glass being vertically polarizing ones. As each filter only passes light, which is similarly polarized and blocks the orthogonally polarized light, each eye only sees one of the images, the 3-D effect is thus similarly achieved as in the LC shutter glass system. However, linearly polarizing glasses require the viewer to keep his head level, as a tilting of the viewing glasses will cause the images of the left and right channels to interfere with each other.  
         [0008]     Circularly polarizing system can solve this problem, where two images are projected and superimposed onto the same screen through circularly polarizing filters of opposite handedness. The viewer wears eyeglasses which contain a pair of circularly polarizing glasses mounted in reverse handedness. Light that is left-circularly polarized is extinguished by the right-handed glass; while right-circularly polarized light is extinguished by the left-handed glass. The result is similar to that of stereoscopic viewing using linearly polarizing glasses, except the viewer can tilt his or her head and still maintain left and right image separation.  
         [0009]     However, alternate-frame sequencing has drawbacks and limitations. First, only one eye can see an image at a time, and two eyes alternately see images. It is contradictory to the operation of the human visual system, where two eyes always see images at the same time. This may attribute to the adverse physical reactions including eyestrain, headaches and nausea experienced by some viewers when watching this kind of display for an extended period of time. Second, since each eye sees images only half of the time, the stereoscopic display is only half as bright if a normal projector is used. Third, in computer rendered graphics, it places quite a burden on the graphic processing unit (GPU), as GPU has to render twice as many images (both left and right images) for the stereoscopic display. Fourth, when displaying stereoscopic images on a computer monitor, the monitor&#39;s refreshing rate also has to be doubled to achieve the same result.  
         [0010]     As such, what is needed is an improved system and method for processing stereo graphic images in separate channels and separately presented to the viewer&#39;s eyes at the same time to generate a natural 3-D illusion.  
       SUMMARY  
       [0011]     In view of the foregoing, this invention provides a method and system for displaying stereoscopic 3-D images with both left and right images displayed simultaneously.  
         [0012]     A system according to one embodiment of this invention provides two independent graphic processing channels. Stereoscopic images are separately supplied to each channel, instead of alternate-frame sequenced, with the left image processed by a left channel and the right image processed by a right channel. The operation of both channels is synchronized, so that the stereoscopic images are presented to the display system at the same time.  
         [0013]     The construction and method of operation of the invention, however, together with additional objectives and advantages thereof will be best understood from the following descriptions of specific embodiments when read in connection with the accompanying figures. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  presents a diagram showing an overview of a duo-channel stereoscopic 3-D image display system according to one embodiment of the present invention.  
         [0015]      FIG. 2  is a component diagram showing a displaying stereoscopic 3-D image being implemented in the duo-channel projection system.  
         [0016]      FIG. 3  shows sections of a duo-frame movie film for a duo-channel stereoscopic 3-D movie.  
         [0017]      FIG. 4  shows a section of a traditional stereoscopic 3-D movie film employing an alternate-frame sequencing method.  
         [0018]      FIG. 5  presents a simplified flow-chart of rendering command issuing in a computer graphics rendering system for stereoscopic display.  
         [0019]      FIG. 6  presents a diagram showing components of a duo-channel pixel-based display system for stereoscopic 3-D image display according to another embodiment of the present invention.  
         [0020]      FIG. 7  presents a diagram showing components of a duo-channel head-mounted display system for stereoscopic 3-D image display according to another embodiment of the present invention. 
     
    
     DESCRIPTION  
       [0021]      FIG. 1  presents a diagram showing an overview of a stereoscopic 3-D image display system according to one embodiment of the present invention, which includes two graphic processing channels—left  110  and right  115 , a synchronizing unit  130  and a stereo display module  140 . The two channels  110  and  115  separately process stereoscopic image data inputs  100  and  105 , and output the processed image data  120  and  125  to the stereo display module  140 , which let viewer&#39;s left eye see only left image  120 , and the right eye sees only right image  125 . The synchronizing unit  130  ensures that the same pair of stereoscopic images is sent simultaneously to the stereo display module  140 , so that both eyes can see the same pair of stereoscopic images at the same time.  
         [0022]      FIG. 2  is a further illustration of the aforementioned stereo display system having projectors  210  and  215 , polarizing filters  220  and  225  of opposite polarization, screen  260  and viewer&#39;s polarizing glasses  250  with filters  252  and  254  of opposite polarization. Through polarizing filters  220  and  225  respectively, left and right images are projected and superimposed on the screen  260 . A viewer must wear the pair of polarizing glasses  250  to view the stereoscopic 3-D image. The same side of the projector filter and viewing glass must have the same orientation of polarization, and two sides are opposite to each other. For instance, if the left-projector filter  220  and the left-polarizing glass  252  are vertically polarizing ones, then the right-projector filter  225  and the right-polarizing glass  254  are horizontally polarizing ones, and vice versa.  
         [0023]     In case of projecting a movie film, the image data inputs  240  and  245  are films taken by a pair of stereoscopic cameras, they are kept in their original sequence as shown in  FIG. 3 , instead of being placed in an alternate-frame sequence as shown in  FIG. 4 . Then the graphic processing channels  200  and  205  are simply film reel machines. A synchronizing unit  230  could simply be a shaft of a motor where both reels are mounted on so that the two films are winded at the same speed.  
         [0024]     In  FIG. 3 , frames  310  and  320 , etc. on left film  300  are kept in their original sequence; so are frames  315  and  325 , etc. on right film  305 . Both films  300  and  305  are run simultaneously, so that the same pair of stereoscopic images is projected simultaneously on the screen. With the assistance of the polarization system, viewer&#39;s left eye can see only the left image and the right eye can see only the right image, but both eyes can see the same pair of stereoscopic images at the same time.  
         [0025]     In  FIG. 4 , according to another embodiment of the present invention, frames  410  and  420 , etc. are taken by a first camera, and frames  415  and  425 , etc. are taken by another camera, but they are placed alternately on the same film  400  to form an alternate-frame sequence to be projected by a traditional single channel stereoscopic 3-D movie system.  
         [0026]     Referring back to  FIG. 1 , for projecting computer rendered images, each graphic processing channel  110  or  115  includes at least one graphic processing unit (GPU) to render images from graphic input data  100  and  105 . Left channel data  100  and right channel data  105  are processed independently, so that the load on the GPU is less than that in alternate-frame-sequencing systems where only one graphic processing channel has to process alternately both left and right channel data. Since both graphic processing channels  110  and  115  are run on the same system clock, which functions as a synchronizing unit  130 , their outputs, i.e. computer rendered stereoscopic image pair, can be synchronized and sent simultaneously to the stereo display module  140 .  
         [0027]     In the above rendering systems, differences between rendering a pair of left and right frames are only in transformation matrices, which are mathematical calculations in 2D or 3D transformation. So rendering commands for both channels are often identical, except for some predetermined values for certain variables or constants used for calculations. Often an application program can issue the same rendering commands to both channels at the same time. Only commands for sending transformation matrices, which are different for each channel, are issued separately to individual channels, as shown in  FIG. 5 , in which common command blocks  510  and  540  are commands identical for both channels, and they are issued to both channels at the same time. Command blocks  520  and  530  are for sending transformation matrices, so they are issued separately and carry certain data that is different from each other due to the difference between the rendered left and right images, with block  520  going to a left channel, and block  530  to a right channel. In this way, the computer system&#39;s central processing unit, or CPU, has less processing to do for issuing commands for this purpose, and also the related application program logics become simpler.  
         [0028]     In systems where the stereo display system employs a pixel-based display device, such as liquid crystal display (LCD) or plasma display, as shown in  FIG. 6 , the column pixels are divided into two groups, odd columns  640  connects to left channel  610 , and even columns  645  connects to right channel  615 . In order to separate the stereoscopic image pair, and let the left eye view only the left image, and the right eye views only the right image, a polarizing system as aforementioned is also employed. The difference is that here an interlaced polarizing filter is attached to the display screen  660 , with horizontally polarizing columns  650  placed at odd pixel columns  640 , and vertically polarizing columns  655  placed at even pixel columns  645 . With a viewer wearing polarizing glasses  670 —left eye horizontally polarizing and left eye vertically polarizing, the viewer&#39;s left eye can see only left image  600  displayed by the odd column  640 , and right eye can see only right image  605  displayed by the even column  645 .  
         [0029]     Based on the same principle, pixel rows instead of columns can be divided, and the polarizing screen is then interlaced horizontally. However, one drawback of this kind of stereo display system is that its display resolution drops by half, as the stereoscopic image pair is displayed side-by-side and interlaced, instead of superimposed as in a projection system.  
         [0030]     The stereo display system can also be embodied in a head-mounted display system as shown in  FIG. 7 , where a helmet  730  holds a pair of small liquid crystal displays (LCDs)  740  and  745 . Since these small LCDs are held fairly close to the viewer&#39;s eyes, magnifying lenses are used, and one eye can only see one LCD. Here the left LCD  740  receives the left image  700  from the left graphic processing channel  710 , and the right LCD  745  receives the right image  705  from the right graphic processing channel  715 . Since the left and right images are already separately displayed to each eye, the stereoscopic 3-D image is displayed.  
         [0031]     Although illustrative embodiments of this invention have been shown and described, other modifications, changes, and substitutions are intended. Specific examples of components and processes are described to help clarify the disclosure. These are, of course, merely examples and are not intended to limit the disclosure from that described in the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure, as set forth in the following claims.