Patent Publication Number: US-2002001045-A1

Title: Parallax viewing system

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to a viewing system, and more particularly, to a method and apparatus for displaying images and multi-dimensional time-varying data with parallax viewing.  
       BACKGROUND OF THE INVENTION  
       [0002] Conventional display systems exhibit parallax free viewing. Parallax free viewing occurs when an object being viewed does not reveal whatever is behind the object when the viewer changes his or her viewpoint from left to right. For example, the object  110  shown in FIG. 1A is directly in front of object  120 , and the viewer is viewing the image from a viewpoint  1 . If the viewer changes his or her viewing position to viewpoint  2  or viewpoint  3 , as shown in FIG. 1B, in an attempt to see object  120 , conventional display systems are still incapable of displaying object  120 . Instead, conventional display systems will present the same view from viewpoints  2  and  3  as viewed from viewpoint  1 . In other words, viewpoint  1  is repeated from all angles of the viewer&#39;s range.  
       [0003] Conventional display systems provide such a single viewpoint from all viewing angles to permit the viewer to view an image from various horizontal positions, at eye-level. In other words, conventional display systems are optimized for variations in horizontal viewing positions, while assuming the vertical viewing position will remain at a nominal eye level. Thus, current fabrication techniques for active matrix liquid crystal displays, for example, provide a single viewpoint with the widest possible horizontal viewing angle. In addition, conventional active matrix liquid crystal displays provide the greatest possible contrast over the wide angle.  
       [0004] Three dimensional display systems have generally required some form of eyewear, such as red and green glasses, liquid crystal shuttered glasses or polarized glasses, to achieve a three dimensional effect on a two dimensional display. However, such eyewear can be bulky and impractical for many applications and can add significant expense when an image must be presented to a group of individuals.  
       [0005] As apparent from the above-described deficiencies with conventional display systems, a need exists for an improved method and apparatus for displaying images with parallax viewing. A further need exists for a method and apparatus for displaying three dimensional images on a two dimensional display without requiring eyewear.  
       SUMMARY OF THE INVENTION  
       [0006] Generally, according to one aspect of the present invention, a three dimensional parallax viewing system is disclosed that permits a viewer to change viewpoints and look around objects by providing the viewer with multiple viewpoints. The parallax viewing system can include a plurality of viewpoints in each viewing direction of a two dimensional display. A viewpoint/parallax generator causes a liquid crystal array to vary its viewing angle over time across a plurality of viewpoints  1  through N, while applying the appropriate image data for the respective viewpoint.  
       [0007] Accordance to a further aspect of the invention, the liquid crystal array (or other suitable display technology) is fabricated with a narrow viewing angle. In addition, the liquid crystal material should be selected to handle a wide bias voltage (contrast) variation. Thus, by varying the applied bias voltage, the viewing angle of the display system may be tuned from left to right, for example, by varying the bias voltage.  
       [0008] In an illustrative three dimensional implementation, the input image signal is encoded with a left eye (LE) and right eye (RE) image for each viewpoint. In addition, the input image signal may optionally contain viewpoint data, including an indication of the viewing angle in each direction corresponding to the respective LE/RE image, for a variable viewpoint implementation. The LE/RE image signals for each viewpoint can be obtained from a conventional three dimensional camera system. For example, one suitable three dimensional camera system is a dual camera system providing LE and RE image signals. Alternatively, an infinite number of viewpoints can be obtained, for example, using a 360° camera, or a 360° by 360° camera. 
     
    
    
     [0009] A more complete understanding of the present invention, as well as further features and advantages of the present invention, will be obtained by reference to the following detailed description and drawings.  
     BRIEF DESCRIPTION OF DRAWINGS  
     [0010]FIGS. 1A and 1B illustrate the concept of parallax free and parallax viewing of two objects, respectively;  
     [0011]FIG. 2 is a schematic block diagram of an exemplary three dimensional parallax viewing system in accordance with the present invention;  
     [0012]FIG. 3 illustrates a representative input image encoded with left eye (LE) and right eye (RE) image data for a plurality of viewpoints;  
     [0013]FIG. 4 is a schematic block diagram of the viewpoint/parallax generator of FIG. 2;  
     [0014]FIG. 5 is a schematic block diagram of an alternative implementation of the three dimensional parallax viewing system of FIG. 2; and  
     [0015]FIG. 6 is a flow chart describing the processes performed by the viewpoint/parallax generator of FIG. 4. 
    
    
     DETAILED DESCRIPTION  
     [0016]FIG. 2 illustrates a parallax viewing system  200  in accordance with the present invention. The illustrative parallax viewing system  200  shown in FIG. 2 is a three dimensional display system that also permits a viewer to change viewpoints and to look around objects by providing the viewer with multiple viewpoints. In the illustrative implementation disclosed herein, the parallax viewing system  200  provides three viewpoints, such as the three viewpoints shown in FIG. 1B. The parallax viewing system  200  could easily be extended, however, to include an infinite number of viewpoints for each direction in a two dimensional display, as would be apparent to a person of ordinary skill in the art based on the disclosure herein.  
     [0017] As shown in FIG. 2, the three dimensional parallax viewing system  200  includes a viewpoint/parallax generator (VPPG)  400 , discussed further below in conjunction with FIG. 4, that provides a signal to a multi-dimensional data viewpoint driver  220 . The driver  220  in turn causes a liquid crystal array  230  (or other suitable display technology) to vary its viewing angle over time across a plurality of viewpoints  1  through N, while applying the appropriate image data for the respective viewpoint. The liquid crystal array  230  may be backlit by a lighting source  240 , in a known manner.  
     LIQUID CRYSTAL ARRAY FABRICATION  
     [0018] In accordance with a feature of the present invention, the liquid crystal array  230  is fabricated with a narrow viewing angle, on the order of θ n  degrees. The magnitude of the viewing angle is application dependent, and varies, in part, in accordance with the number of desired viewpoints and the display technology used. The narrow viewing angle is necessary for achieving three dimensional viewing, as well as the parallax aspects of the display  230 .  
     [0019] In addition, the liquid crystal material should be selected to handle a wide bias voltage (contrast) variation. In this manner, by varying the applied bias voltage the viewing angle of the display system  200  may be tuned from left to right, for example, by varying the bias voltage. As discussed further below, the bias voltage can be synchronized, for example, for left most viewing of the viewer&#39;s left eye or right most viewing of the viewer&#39;s right eye. It has been found that if the various left and right viewpoint images are modulated at a rate of 120 Hertz, for example, flicker is avoided, while producing a three dimensional image without the use of specialized eye wear.  
     INPUT IMAGE SIGNAL  
     [0020] In a three dimensional implementation, the input image signal, is encoded with a left eye (LE) and right eye (RE) image for each viewpoint. For a two dimensional video signal, the input image signal would consist of a single image for each video frame, as would be apparent to a person of ordinary skill in the art. In addition, the input image signal may optionally contain viewpoint data, including an indication of the viewing angle in each direction corresponding to the respective LE/RE image, for a variable viewpoint implementation. As previously indicated, the illustrative parallax viewing system  200  disclosed herein provides the three viewpoints defined in FIG. 1B. Thus, since the viewing angles are known, they need not be transmitted with the LE/RE image data.  
     [0021] A representative input image signal format  300  for the illustrative three dimensional parallax viewing system  200  is shown in FIG. 3. The input image signal  300  includes the three dimensional (LE/RE) viewpoint image data  330  for a given scan line between two synchronization points  310 ,  320 . The illustrative input image signal  300  consists of a series of left eye (LE) and right eye (RE) images for each available n viewpoints. It is noted that the odd and even fields of the video frame (where one odd and one even field comprises a single video frame) can be used to expand the number of viewpoints in a particular application with a specific display technology. In addition, standard video broadcast transmission, together with a decoder, can be used to send three dimensional parallax video.  
     [0022] The LE/RE image signals for each viewpoint can be obtained from a conventional three dimensional camera system (not shown). A left eye (LE) and right eye (RE) image can be obtained for a given viewpoint, for example, using two conventional cameras. For example, one suitable three dimensional camera system is a dual camera system providing LE and RE image signals. Alternatively, an infinite number of viewpoints can be obtained, for example, using a 360° camera, such as the camera disclosed in U.S. Pat. No. 5,745,305, entitled “Panoramic Viewing Apparatus,” assigned to the assignee of the present invention, incorporated by reference herein, as modified for a three dimensional viewpoint data video output format.  
     VIEWPOINT/PARALLAX GENERATOR  
     [0023]FIG. 4 provides a block diagram of the VPPG  400 . The processes performed by the VPPG  400  are discussed below in conjunction with FIG. 6. The VPPG  400  includes a signal format decoder  410  to interpret the input image signal format, such as the input image signal  300  (FIG. 3). In addition, the VPPG includes a left eye/right eye driver  420  to generate a signal that provides for synchronization of the left eye (LE) and right eye (RE) image information present at the signal input to the liquid crystal array  230 . In addition, the viewpoints driver  430  generates a signal that includes a plurality of viewing angles over time, thereby presenting the viewer with a plurality of viewpoints in real-time. In other words, the VPPG  400  synchronizes the viewing angle of the LCA  230  to the appropriate LE/RE image pair. Thus, as the image data LE 1  and RE 1 , shown in FIG. 3, are presented, the VPPG  400  generates a signal that is provided to the multi-dimensional data viewpoint driver  220 , and in turn the LCA  230 , that adjusts the viewing angle of the display  230  to the angle corresponding to the first viewpoint. In this manner, the three dimensional parallax free viewing system  200  provides a three dimensional image with parallax viewing.  
     [0024] An alternate implementation of the three dimensional parallax free viewing system in accordance with the present invention is shown in FIG. 5. The three dimensional parallax free viewing system  500  shown in FIG. 5 utilizes cathode ray tube (CRT) technology. In the implementation of FIG. 5, the back lighting of FIG. 2 is replaced by a CRT display monitor  510  to provide the LE/RE image signals and inherent backlighting of the LCD  230 . Thus, the LCD  230  now functions as a viewpoint filter and provides the parallax viewing capability, resulting in a three dimensional image with parallax viewing.  
     [0025] As previously indicated, the VPPG  400  executes a three dimensional/parallax process  600 , shown in FIG. 6, to provide a three dimensional image with parallax viewing. The three dimensional/parallax process  600  initially receives the input video signal  300  (FIG. 3) during step  610 . Thereafter, the input video signal  300  is decoded during step  620  in accordance with the defined (but arbitrary) signal format.  
     [0026] The left eye/right eye (LE/RE) image data for the current viewpoint is provided during step  630  to the multi-dimensional data viewpoint driver  220  with a viewpoint synchronization signal to adjust the viewing angle of the display  230  to the current viewpoint. A test is performed during step  640  to determine if there are additional viewpoints to be processed for the current scan line. If it is determined during step  640  that there are additional viewpoints to be processed for the current scan line, then program control returns to step  630  to process the remaining viewpoints in the manner described above.  
     [0027] If, however, it is determined during step  640  that there are no additional viewpoints to be processed for the current scan line, then program control terminates.  
     APPLICATIONS  
     [0028] As previously indicated, the parallax viewing system  200  generally permits a viewer to change viewpoints and to look around objects by providing the viewer with multiple viewpoints. In an aircraft guidance system implementation, for example, the parallax viewing system  200  permits unobstructed views of the sky in heavy traffic areas. In addition, the parallax viewing system  200  can be utilized to simultaneously present the same information in a different format. For example, a document to be presented to an audience, for example, on a large screen, may be displayed simultaneously in different languages, with a first language version, such as an english language version, presented to the audience members associated with viewpoint  1  and one or more corresponding translated versions, such as german and french versions, simultaneously presented to the audience members associated with viewpoints  2  and  3 , respectively.  
     [0029] Likewise, the parallax viewing aspects of the viewing system  200  can be utilized in a medical application to allow physicians to look around body objects during a surgical procedure using video assistance. In a further medical application, the parallax viewing system  200  can be utilized to simultaneously present the same information in a different format. For example, an anatomical view of a surgical procedure can to be presented to a surgeon in a first viewpoint, with a functional view of the surgical procedure, such as a positron emission tomograph (PET) or a single photon emission computer tomography (SPECT), presented to the surgeon in a second viewpoint. In addition, the viewing system can act as a multimodal fusion viewer to present a superimposed and calibrated image of both the anatomical and functional view can be simultaneously presented in a third viewpoint. In this manner, the viewing system  200  can be utilized both for the rehearsal and the actual surgical procedure. The present invention allows simultaneous presentation of data and visual objects in applications covering visualization of abstract data, such as an electro encephalogram (EEG) measuring brain signals through sensors distributed over the head.  
     [0030] In addition, the present invention allows a computer-aided drug design system, capable of receiving and transmitting spherical abstract data, and capable of feedback and subsequent control, such as designing a drug antibody for a virus antigen, to utilize a three dimensional spherical model display of the virus, providing real-time modification using spherical feedback.  
     [0031] It is to be understood that the embodiments and variations shown and described herein are merely illustrative of the principles of this invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.