Abstract:
A 3D display system includes an image source and a display device. The image source is configured to provide a 2D video signal consisting of multiple side-by-side frames for representing an image and generate an upsampled 2D video signal by increasing the frame rate of the source 2D video signal. The display device includes an identical frame detector and a 2D/3D converter. After identify corresponding pairs of side-by-side frames in the upsampled 2D video signal, the identical frame detector instructs the 2D/3D converter to extract a predetermined half of each side-by-side frame in the upsampled 2D video signal, and convert the extracted halves of the side-by-side frames alternatively into a series of right-eye images and a series of left-eye images constituting a 3D video signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is related to a display device for use in a 3D display system and a related 3D display system, and more particularly, to a display device for use in a frame sequential 3D display system and a related frame sequential 3D display system which performs 2D/3D conversion without using a frame buffer. 
         [0003]    2. Description of the Prior Art 
         [0004]    Three-dimensional (3D) display technology provides more vivid visual experiences than traditional two-dimensional (2D) display technology. In general, the stereoscopic image processing involves two camera systems in which two different images or videos are taken from slightly different camera angles and locations. Techniques to artificially create a perception of depth on a 2D surface include the use of presenting different images to the left and right eyes of the viewer. In such frame sequential 3D display system, a sequence of alternating frames wherein each successive frame carries the image meant for one or the other eye is presented to each eye using shutter glasses having a left-eye lens and a right-eye lens, each of which may be made from electronically controllable liquid crystal assemblies. The lenses are configured to be alternatively switched on and off in sync with the alternating frames such that the right eye only views the right-eye images and the left eye only views the left-eye images. The two series of images are combined by the brain in such a way to perceive depth. 
         [0005]    Most recently released 3D high-definition televisions (HDTVs) operate according to the frame sequential 3D display method described above. However, this doesn&#39;t mean that the input signal to the 3D HDTV has to be in a frame-sequential format. Instead, many 3D HDTVs can process signals in a variety of different formats and perform on-the-fly conversion of the incoming video signal into a frame sequential format. While frame-sequential 3D is part of the blu-ray 3D specification, the video data in a side-by-side format is often preferred when it comes to airing 3D content over cable/air. 
         [0006]      FIG. 1  is a diagram illustrating a method of creating a 1280×720 full resolution side-by-side frame SBS from an original left-eye frame L and an original right-eye frame R of the same full resolution. The side-by-side frame SBS consists of two halves on the left and right, with the entire left-eye frame L scaled down horizontally to fit the left-half of the side-by-side frame, and the entire right-eye frame R scaled down horizontally to fit the right-half of the side-by-side frame. Thus, the side-by-side frame SBS consists of the horizontally down-scaled left-eye frame L′ with a resolution of 640×720 and adjacent to it, the corresponding horizontally down-scaled right-eye frame R′ with the same 640×720 resolution. 
         [0007]    Many display devices, such as televisions, have a scan rate of 60 Hz (ex. in the United States) or 50 Hz (in some countries other than the United States). In regular 2D mode, a frame sequential television displays a new image fifty or sixty times per second in order to present a dynamic video presentation to the viewer. In 3D mode, the effective refresh rate of the frame sequential television is halved since each eye needs a separate picture. Therefore, for a 3D display device capable of receiving and converting a source 2D video signal in side-by-side format, the frame rate of the 50/60 Hz source 2D video signal needs to be doubled for generating a corresponding 100/120 Hz upsampled 2D video signal, based on which each half of the side-by-side frames may be sequentially extracted and processed for obtaining corresponding full resolution right-eye and left-eye images constituting a corresponding 100/120 Hz 3D video signal. 
         [0008]      FIG. 2  is a functional diagram illustrating a prior art frame sequential 3D display system  100 . The frame sequential 3D display system  100  includes an image source  110 , a 3D display device  120 , and shutter glasses  140 . The image source  110  may provides a source 2D video signal S 1  consisting of multiple side-by-side frames representing an image. The 3D display device  120  is a frame sequential display which includes a frame rate converter  12 , a frame buffer  14 , a 2D/3D converter  16 , a shutter controller  18 , and a screen  20 . 
         [0009]    The 3D display device  120  may convert the source 2D video signal S 1  consisting of side-by-side frames into a corresponding 3D video signal S 3  consisting of left-eye and right-eye sequential frames. The frame rate converter  12  is configured to increase the total number of side-by-side frames in the source 2D video signal S 1  by inserting new side-by-side frames between two neighboring side-by-side frames of the original source 2D video signal S 1 , thereby generating a corresponding upsampled 2D video signal S 2  with a higher frame rate. The 2D/3D converter  26  may then split each side-by-side frame of the upsampled 2D video signal S 2  for extracting two series of down-scaled frames, based on which the 3D video signal S 3  may be generated. The 3D video signal S 3  consists of two series of alternating sequential frames, one of which corresponds to left-eye images and the other of which corresponds to right-eye images. According to the 3D video signal S 3 , the frame sequential display device  130  may display the right-eye and left eye images in an alternative manner and control the lenses of the shutter glasses  140  accordingly so that each eye only views the images intended for that eye. 
         [0010]      FIG. 3  is a diagram illustrating the operation of the prior art 3D display device  120 . Assume that the source 2D video signal S 1  includes data represented by a sequence of side-by-side frames SBS 1 -SBS N  each consisting of a down-scaled left-eye frame and a corresponding down-scaled right-eye frame. The down-scaled left-eye frames and the down-scaled right-eye frames constituting corresponding side-by-side frames SBS 1 -SBS N  are represented by L 1 ′-L N ′ and R 1 ′-R N ′, respectively. The frame buffer  14  is used to store the side-by-side frames SBS 1 -SBS N  received during corresponding periods. Therefore, the frame rate converter  22  may output each of the side-by-side frames SBS 1 -SBS N  for two consecutive times so as to generate the corresponding upsampled 2D video signal S 2  having twice the number of side-by-side frames (SBS 1 -SBS N  and SBS 1 ′-SBS N ′) compared to those in the original source 2D video signal S 1 . According to each pair of side-by-side frames in the upsampled 2D video signal S 2 , the 2D/3D converter  16  may extract a corresponding one of the down-scaled left-eye frames L 1 ′-L N ′ and a corresponding one of the down-scaled right-eye frame R 1 ′-R N ′, in a sequence of L 1 ′, R 1 ′, L 2 ′, R 2 ′, . . . , L N ′ and R N ′. Using up-scaling algorithms, the down-scaled left-eye frames L 1 ′-L N ′ and the down-scaled right-eye frames R 1 ′-R N  may then be respectively re-scaled to full resolution left-eye frames L 1 -L N  and right-eye frame R 1 -R N  which constitute the 3D video signal S 3 . The 3D display device  100  may then display the left-eye frames L 1 -L N  and right-eye frame R 1 -R N  alternatively in a frame-sequential manner which is in sync with the shutter glasses  140  whose operation may be illustrated by a left-eye ON signal and a right-eye ON signal in  FIG. 3 . 
         [0011]    In the prior art 3D display device  120 , the frame buffer  14  is required to store each side-by-side frame over a period of time for doubling each side-by-side frame. Therefore, there is a need for a 3D display device capable of performing 2D/3D conversion without using a frame buffer. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention provides a frame sequential 3D display system including an image source and a display device. The image source is configured to provide a source 3D video signal having a plurality of side-by-side frames each consisting of a corresponding pair of horizontally down-scaled right-eye and left-eye frames for representing an image and generate an upsampled 2D video signal by outputting each side-by-side frame of the source 2D video signal for two consecutive times. The display device includes a 2D/3D converter configured to receive the upsampled 2D video signal, extract a predetermined half of each side-by-side frame in the upsampled 2D video signal, and convert the extracted halves of the side-by-side frames alternatively into a series of right-eye images and a series of left-eye images constituting a 3D video signal; and a screen for alternatively displaying the series of right-eye images and the series of left-eye images according to the 3D video signal. 
         [0013]    The present invention also provides a display device for use in a frame sequential 3D display system and including a 2D/3D converter and a screen. The 2D/3D converter is configured to receive an upsampled 2D video signal directly from an image source, extract a predetermined half of each side-by-side frame in the upsampled 2D video signal, and convert the extracted halves of the side-by-side frames alternatively into a series of right-eye images and a series of left-eye images constituting a 3D video signal, wherein a frame rate of the upsampled 2D video signal is equal to a frame rate of the 3D video signal. The screen alternatively displays the series of right-eye images and the series of left-eye images according to the 3D video signal. 
         [0014]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a diagram illustrating a method of creating a full resolution side-by-side frame. 
           [0016]      FIG. 2  is a functional diagram illustrating a prior art frame sequential 3D display system. 
           [0017]      FIG. 3  is a diagram illustrating the operation of a prior art frame sequential 3D display device. 
           [0018]      FIG. 4  is a functional diagram illustrating a frame sequential 3D display system according to a first embodiment of the present invention. 
           [0019]      FIG. 5  is a diagram illustrating the operation of a frame sequential 3D display system according to the present invention. 
           [0020]      FIG. 6  is a functional diagram illustrating a frame sequential 3D display system according to a second embodiment of the present invention. 
           [0021]      FIG. 7  is a diagram illustrating the operation of a display device according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 4  is a functional diagram illustrating a frame sequential 3D display system  200  according to a first embodiment of the present invention. The frame sequential 3D display system  200  includes an image source  210 , a 3D display device  220 , and shutter glasses  240 . The image source  210  may include any electronic appliances installed with application software (such as Media Player) which may display images in various modes. Therefore, according to a source 2D video signal S 1  consisting of side-by-side frames representing an image, the image source  210  may generate a corresponding upsampled 2D video signal S 2  by playing back each of the side-by-side frame in the source 2D video signal S 1  for two consecutive times. 
         [0023]    The 3D display device  220  is a frame sequential display which includes a 2D/3D converter  26 , a shutter controller  28  and a screen  20 . The 3D display device  220  is configured to convert the upsampled 2D video signal S 2  consisting of side-by-side frames into a corresponding 3D video signal S 3  consisting of sequential frames which alternatively correspond to left-eye images and right-eye images. The left-eye and right-eye images may then be displayed on the screen  20  alternatively in a frame sequential manner for viewing with the shutter glasses  240  in order to create stereoscopic effects. 
         [0024]      FIG. 5  is a diagram illustrating the operation of the 3D display device  220  according to the present invention. Assume that the source 2D video signal S 1  includes data represented by a sequence of side-by-side frames SBS 1 -SBS N  each consisting of a down-scaled left-eye frame and a corresponding down-scaled right-eye frame. The down-scaled left-eye frames and the down-scaled right-eye frames constituting corresponding side-by-side frames SBS 1 -SBS N  are represented by L 1 ′-L N ′ and R 1 ′-R N ′, respectively. In the frame sequential 3D display system  200  of the present invention, the image source  210  is configured to provide the upsampled 2D video signal S 2  which has twice the number of side-by-side frames compared to those in the original source 2D video signal S 1 . As depicted in  FIG. 5 , the upsampled 2D video signal S 2  inputted to the 3D display device  220  consists of pairs of side-by-side frames SBS 1 -SBS 1 ′, SBS 2 -SBS 2 ′, . . . , and SBS N -SBS N ′. According to each pair of side-by-side frames in the upsampled 2D video signal S 2 , the 2D/3D converter  26  may extract a corresponding one of the down-scaled left-eye frames L 1 ′-L N ′ and a corresponding one of the down-scaled right-eye frame R 1 ′-R N ′, in a sequence of L 1 ′, R 1 ′, L 2 ′, R 2 ′, . . . , L N ′ and R N ′. Using up-scaling algorithms, the down-scaled left-eye frames L 1 ′-L N ′ and the down-scaled right-eye frames R 1 ′-R N ′ may then be respectively re-scaled to full resolution left-eye images L 1 -L N  and right-eye images R 1 -R N  which constitute the 3D video signal S 3 . The 3D display device  220  may then display the left-eye images L 1 -L N  and right-eye images R 1 -R N  alternatively in a frame-sequential manner which is in sync with the shutter glasses  240  whose operation may be illustrated by a left-eye ON signal and a right-eye ON signal in  FIG. 5 . 
         [0025]    In the frame sequential 3D display system  220 , the 3D display device  220  directly receives the upsampled video signal S 2  provided by the image source  210  and may perform direct 2D/3D conversion without using a frame buffer. 
         [0026]    As illustrated, up-sampling is performed by the image source 210 and 2D/3D format conversion is performed by the 3D display device  220  in the present invention. Regarding two consecutive side-by-side frames in the upsampled 2D video signal S 2 , they may be two identical side-by-side frames based on which a corresponding pair of left-eye and right-eye images may be generated (such as the two consecutive side-by-side frames SBS 1  and SBS 1 ′ based on which the corresponding images L 1  and R 1  are generated), or two side-by-side frames based on which a left-eye image in a certain pair of left-eye and right-eye images and a right-eye image in another pair of left-eye and right-eye images may be generated (such as the two consecutive side-by-side frames SBS 1 ′ and SBS 2  based on which the images R 1  and L 2  are generated). Therefore, there is a need to identify the relationship between two consecutive side-by-side frames in the upsampled 2D video signal S 2  in order to guarantee the synchronization between the operation of the shutter glasses  240  and the 3D video signal S 3 . 
         [0027]      FIG. 6  is a functional diagram illustrating a frame sequential 3D display system  300  according to a second embodiment of the present invention. The frame sequential 3D display system  300  includes an image source  210 , a 3D display device  320 , and shutter glasses  240 . Similar to the frame sequential 3D display system  200  according to the first embodiment of the present invention, the 3D display device  320  of the frame sequential 3D display system  300  further includes an identical frame detector  38 . The identical frame detector  38  is configured to analyze the image characteristics of the side-by-side frames SBS 1 -SBS N  and SBS 1 ′-SBS N ′ for a predetermined period of time, thereby identifying the corresponding frame pairs in the upsampled 2D video signal S 2 . Next, the identical frame detector  38  may instruct the 2D/3D converter  26  to begin format conversion and the shutter control  28  may operate the lenses of the shutter glasses  240  in sync with respective left-eye and right-eye images. 
         [0028]      FIG. 7  is a diagram illustrating the operation of the 3D display device  320  according to the present invention. The identical frame detector  38  may perform image analysis on the upsampled 2D video signal S 2  for a predetermined period of time, such as on the first n frame pairs SBS 1 , SBS 1   1 , SBS 2 , SBS 2 ′, . . . , SBS n , SBS n ′ (n is an integer smaller than N) for identifying the corresponding frame pairs based on checksum or histogram of the side-by-side frames, or based on other image characteristics well-known to those skilled in the art. For any three consecutive side-by-side frames such as SBS 1 , SBS 1 ′, and SBS 2  in the upsampled 2D video signal S 2 , the image characteristic of the side-by-side frame SBS 1 ′ is identical to that of the side-by-side frame SBS 1  but differs from that of the side-by-side frame SBS 2  since the side-by-side frames SBS 1  and SBS 1 ′ are replicas. Therefore, if two consecutive side-by-side frames in the upsampled 2D video signal S 2  have identical image characteristics, they may be identified as a corresponding frame pair. Next, the 2D/3D converter  26  may thus perform 2D/3D conversion on the side-by-side frames SBS n+1 -SBS N ′ and the shutter control  28  may switch on/off the lenses of the shutter glasses  240  in an alternative fashion when respective left-eye and right-eye images are outputted, as depicted by a left-eye ON signal and a right-eye ON signal in  FIG. 7 . 
         [0029]    In one embodiment of  FIG. 7 , only three consecutive side-by-side frames such as SBS 1 , SBS 1 ′, and SBS 2  in the upsampled 2D video signal S 2  are required for identifying the corresponding frame pairs. In another embodiment of  FIG. 7 , more consecutive side-by-side frames such as SBS 1 , SBS 1 ′, SBS 2 , SBS 2 ′, . . . , SBS n , SBS n ′ in the upsampled 2D video signal S 2  may be used for identifying the corresponding frame pairs so as to achieve better accuracy. 
         [0030]    The present invention may be applied to a glass-type frame sequential 3D display system which requires shutter glasses for creating stereoscopic effect, as depicted in  FIGS. 4-7 . However, the present invention may also be applied to other types of frame sequential 3D display system, such as a naked-eye directional backlight time sequential 3D display system or a time-multiplexed polarizer 3D projector. 
         [0031]    In the frame sequential 3D display system of the present invention, up-sampling is performed by the image source. The 3D display device may thus perform 2D/3D conversion directly according to the upsampled signal received from the image source without using a frame buffer. 
         [0032]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.