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背投三维.pdf

背投三维.pdf

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简介:本文档为《背投三维pdf》,可适用于硬件技术领域,主题内容包含JOURNALOFDISPLAYTECHNOLOGY,VOL,NO,AUGUSTLowCrosstalkMultiViewTrackingDDisp符等。

JOURNAL OF DISPLAY TECHNOLOGY, VOL. 7, NO. 8, AUGUST 2011 411 Low Crosstalk Multi-View Tracking 3-D Display of Synchro-Signal LED Scanning Backlight System Jian-Chiun Liou, Kuan Lee, and Juy-Fong Huang Abstract—Many people believe that in the future, autostereo- scopic 3D displays will become a mainstream display type. Achievement of higher quality 3D images requires both higher panel resolution and more viewing zones. Consequently, the trans- mission bandwidth of the 3D display systems involves enormous amounts of data transfer. This study integrated a viewer-tracking system and a synchro-signal LED scanning backlight module with an autostereoscopic 3D display to reduce the crosstalk of right/left eye images and data transfer bandwidth, while maintaining 3D image resolution. Light-emitting diodes (LED) are a dot light source of the dynamic backlight module. When modulating the dynamic backlight module to control the display mode of the stereoscopic display, the updating speed of the dynamic light-emit- ting regions and the updating speed of pixels were synchronal. For each frame period, the viewer can accurately view three-dimen- sional images, and the three-dimensional images displayed by the stereoscopic display have full resolution. The stereoscopic display tracks the viewer’s position or can be watched by multiple viewers. This study demonstrated that the three-dimensional image dis- played by the stereoscopic display is of high quality, and analyzed this phenomenon. The multi-viewer tracking stereoscopic display with intelligent multiplexing control of LED backlight scanning had low crosstalk, below 1%, when phase shift was 1/160 s. Index Terms—Crosstalk, scanning backlight, synchro-signal, three-dimensional (3D), view tracking. I. INTRODUCTION I N THE PAST decade, flat panel displays have become amajor global product. In view of this phenomenon, LCD- type 3D displays could potentially dominate the 3D display market in the future. Based on flat panel display infrastructure, two main types of 3D display exist: time-multiplexed and spa- tial-multiplexed 3D displays [1]–[5]. The former utilizes a high frequency response LCD panel to increase display frequency. With appropriate accessories like shutter glasses or an optical switch device, a time-multiplexed display separately displays two different views for each eye, giving the viewer a parallax and ultimately 3D effect. The latter distributes different images to different viewing-zones, showing 3D content by adding op- tical devices, like a lenticular lens or parallax barrier, to control the direction of the backlight and allocate the images to different viewing-zones. Manuscript received July 27, 2010; revised October 25, 2010, December 30, 2010, and February 17, 2011; accepted March 08, 2011. Date of current version June 15, 2011. The authors are with the Electronics and Optoelectronics Research Labo- ratories of the Industrial Technology Research Institute (EOL/ITRI), Hsinchu, Taiwan 31040 (e-mail: jcliou@itri.org.tw). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/JDT.2011.2134830 Our innovative 3D technology for multi-viewer tracking stereoscopic display included a display panel, a dynamic-back- light module featuring many light-emitting regions, and a tracking panel placed between the display panel and the dy- namic-backlight module. During a frame period, the display has an updated region and a non-updated region. The display panel displays according to a synchro-signal, and the updated and non-updated regions separately display left and right eye images. The light-emitting regions are activated by a syn- chro-signal. During the frame period, parts of the light-emitting regions corresponding to the updated region are synchronally turned on while other parts of the light-emitting regions cor- responding to the non-updated region are synchronally turned off. The tracking panel features many slit sets. At least one of the slit sets is turned on according to the position information of the viewer and the synchro-signal. Light is provided by the parts of the turned-on light-emitting regions that pass through one of the slit sets and the display panel in such a way that the non-updated region only displays one of the single-eye images. To display 3D content, we must transmit at least stereo image pair of image content to the 3D display, indicating that more views require more bandwidth for transmittance. However, due to limited bandwidth, with ghosting (a faint secondary image produced by an optical system), fixed viewing point or tracker, or split image—half resolution often causes the resolution of the 3D images for each viewing-zone to be reduced [6]–[12]. Use of a viewer-tracking technique could resolve this problem entirely. This study integrated a viewer-tracking technique with a 3D display to verify the feasibility of such a technique and its performance. II. VIEWER-TRACKING 3D DISPLAY This study integrated an autostereoscopic display with a viewer-tracking system. Fig. 1 illustrates the basic structure of the display and Table I shows the specifications of the image liquid crystal panel. In the proposed structure, a retarder in- serted between the image panels rotated the light beam at 90 ; simultaneously, a lenticular plate adjusted the light direction to show the light slit from the tracking display. Retarder film is a clear birefringent material that alters the phase of a polarized beam of light. A quarter wave plate can convert linearly polar- ized light (oriented at 45 from the direction of the fast/slow axis) into circularly polarized light. Conversely, the wave plate can convert a circularly polarized beam into linearly polarized light. In this study, when the polarization direction of the incident light formed an included 45 angle with the optical axis of the retarder, the polarization of the light passing through the retardation regions rotated by 90 and became orthogonal to the polarization of the light passing though the 0 retardation 1551-319X/$26.00 2011 IEEE 412 JOURNAL OF DISPLAY TECHNOLOGY, VOL. 7, NO. 8, AUGUST 2011 Fig. 1. The structure of the proposed viewer-tracking display panel. TABLE I IMAGE LIQUID CRYSTAL PANEL SPECIFICATION regions. The molding method fabricated the lenticular plate with polymeric film as the substrate material. One of the light slit pattern pairs adjusted the direction of light from the tracking panel to the viewer’s eyes through the lenticular plate. In this display, the PDLC panel played an important role in the function of the 2D/3D switch. When the PDLC panel was turned to clear state, the microretarder interacted with the po- larizers to form a parallax barrier pattern, making the display autostereoscopic. In a case where the PDLC panel is in a dif- fusive state, the light passing through the PDLC destroys the polarization. The microretarder then loses its function as a par- allax barrier, and the display becomes a general 2D display. In this display, the light slit tracking display panel played an important role in the function of light slit selection of the eight viewing zones. The tracking panel controlled whether the light of the backlight module passed through or not. The tracking panel features many tracking slit patterns and switches these patterns according to the synchronization signal of the display TABLE II MICROSOFT WEBCAM SPECIFICATION Fig. 2. Pattern of a microretarder. panel. Based on a viewer’s position, the viewer-tracking-based autostereoscopic display sends different pairs of stereo images; each viewed image has full-panel resolution and can be im- plemented in an eight-view autostereoscopic display. In the experiments, a webcam captured the image of the viewer for tracking (Table II shows the specification of the Logitech webcam). Image processing determined the viewer’s position. Therefore, using the recognized position of the viewer moving in the viewing range of the display, the light slit tracking display panel sent corresponding stereo images, thus providing motion parallax that follows the viewer’s movement. A microretarder is a plate consisting of two optical retar- dation states that are micro-patterned within different regions. Fig. 2 shows a microretarder with and 0 retardation in a column-interleaved pattern. When the polarization direction of the incident light formed an included angle of 45 with the optical axis of the microretarder, the polarization of the light passing through the retardation regions rotated 90 and be- came orthogonal to the polarization of the light passing though the 0 retardation regions. This explains why the microretarder forms a parallax barrier in autostereoscopic displays. The retar- dation of the area scanned by laser beams is erased and becomes a 0 retardation region, while the area without scanning remains at retardation. A. Viewer-Tracking 3D Display System This study developed autostereoscopic display apparatus and a display method. The autostereoscopic display apparatus in- cluded a display panel, a backlight module, a tracking slit panel and an optical lens array. In a frame time, the display panel and tracking panel share the same synchronization signal for the dis- play panel. The tracking panel controls the light of the back- light module. The tracking panel features tracking slit patterns and switches the slit patterns according to the synchronization signal. Until all screen data is updated, the backlight module is inactive during the frame time. A light provided by the part of the backlight regions passes through the tracking slit set, optical lens array, and the display panel in such a way that each eye sep- arately perceives images. As shown in Fig. 3, when the viewer LIOU et al.: LOW CROSSTALK MULTI-VIEW TRACKING 3-D DISPLAY OF SYNCHRO-SIGNAL LED SCANNING BACKLIGHT SYSTEM 413 Fig. 3. Relations between viewer and tracking panel. moves to the left, the tracking slit set changes its pattern to dis- play the correct image. The autostereoscopic display integrated a webcam as the real- time detection device for tracking of the viewer’s head/eye po- sitions, so that the display showed left and right eye images correctly. The computer vision-based tracking method detects viewer’s eyes over a specific range and under conditions of low and fluctuating illumination. By capturing the image of the viewer in front of the display, the viewer’s position is calcu- lated and the related position data is transferred to the field pro- grammable gate array (FPGA) controller through RS232. When the viewer recognizes that he/she is standing at the borders of the viewing zones, analyzing the captured viewer images deter- mines the border positions of the viewing zones. The resulting eye reference pattern allows the tracker to locate the viewer’s eyes in live video images. If an observer moves away from his original position, the tracking slit will vary its pattern according to the viewer’s new position. The viewer still perceives two eye images separately before exceeding the webcam detection range. Fig. 4 shows the viewer-tracking system. This paper addresses the specific technological challenges of autostereoscopic 3D displays and presents a novel system that integrates a real-time viewer-tracking system with an au- tostereoscopic display. Our successfully designed prototype uti- lized a FPGA system to synchronize between a display panel and tracking slit panel. With 120 Hz display and tracking panels, only a pair of page-flipped left and right eye images was neces- sary to produce a multi-view effect. Furthermore, full resolution was maintained for the images of each eye. The loading of the Fig. 4. Viewer-tracking 3D display system. transmission bandwidth was controllable, and the binocular par- allax and motion parallax is as good as the usually lower reso- lution multi-view autostereo display. B. LED Backlight Architecture Many types of LED backlights are applied to 2D or 3D dis- plays [13]–[18]. To date, research on 3D display systems has generally focused on providing uniform, collimated illumina- tion of the LCD, rather than addressing low crosstalk issues. This study investigated the method of using an autostereoscopic multi-viewer tracking 3D display with a synchro-signal LED scanning backlight module to reduce the crosstalk of right eye and left eye images, enhancing data transfer bandwidth while maintaining image resolution. Fig. 5(a) is a schematic view of a stereoscopic display. Fig. 5(b) is a block diagram illustrating the stereoscopic display; the stereoscopic display can track the viewer’s position and be watched by multiple viewers. The backlight module of the stereoscopic display is a dy- namic backlight module featuring many light-emitting regions R(1) R(4). Fig. 5(a) excludes the control unit and optical lens array. In the stereoscopic display, the graphic card outputs and transmits the vertical synchro-signal to the control unit. After receiving the synchro-signal, the control unit outputs the syn- chro-signal to control (turn on or off) the light-emitting regions R(1) R(4). To meet the requirements of different one-eye images, we propose that the dynamic LED backlight tracking panel has have many backlight slit sets. According to the position infor- mation of viewer O and the vertical synchro-signal, one of the slit sets of the tracking panels is selected and turned-on. Each slit set includes either left or right eye slits. Light emitted from the dynamic backlight module passes through the either left or right eye slit and the display panel, and projects onto one eye of viewer O. Similarly, light emitted from the dynamic backlight 414 JOURNAL OF DISPLAY TECHNOLOGY, VOL. 7, NO. 8, AUGUST 2011 Fig. 5. (a) Schematic view and (b) block diagram. of stereoscopic display. module passes through the either left or right eye slit and the dis- play panel, and projects onto the other eye of viewer O. In this way, the pair images are projected to the two eyes of viewer O, who can see accurate three-dimensional images. For example, light emitted from the dynamic backlight module passes through the left eye slit of the slit set and the display panel, and projects onto the left eye of viewer O. Similarly, light emitted from the dynamic backlight module passes through the right eye slit of the slit set and the display panel, and projects onto the right eye of viewer O. The one-eye slits are stripe-shaped and the lengths of the one-eye slits are approximately equal to the lon- gitudinal length of the display panel. When the display panel displays an image based on the ver- tical synchro-signal, the slit set of the tracking panel is enabled. Meanwhile, pixels in the updated region of the display panel dis- play a left-eye image, but pixels in the non-updated region of the display panel still display the previous right-eye image. Light passing through the slit set of the tracking panel and the non-up- dated region of the display panel can be projected onto left eye of viewer O (i.e. a crosstalk phenomenon) if no alternative methodology is applied. This paper proposes using a dynamic backlight module to suppress the crosstalk. The light-emitting regions R1 R4 of the dynamic backlight module are sepa- rately controlled according to the vertical synchro-signal. During a frame period, the light-emitting regions R(1) and R(2) corresponding to the updated region are turned on and the light-emitting regions R(3) and (4) corresponding to the non-up- dated region are turned off. In this way, only the light-emit- ting regions R(1) and R(2) provide light, so that no light passes through the slit set of the tracking panel and the non-updated region of the display panel. This reduces the crosstalk phenom- enon of the stereoscopic display system. As shown in Fig. 5(a) and Fig. 5(b), the display method of the stereoscopic display comprises the following steps: First, slit data banks (Ds) corresponding to the many viewing angles of the stereoscopic display apparatus is established. Next, the control unit receives information (Dv) on the position of the viewer. The control unit compares the position information and the slit data banks stored in advance. Meanwhile, the control unit outputs the vertical synchro-signal from the graphic card to con- trol the output mode of the dynamic backlight module and op- eration mode of the tracking panel. The display panel is driven to display images (i.e. image updating) according to the ver- tical synchro-signal output from the graphics card. Many of the light-emitting regions (R(1) R(4)) of the dynamic backlight module are stripe-shaped and the light-emitting regions R(1) R(4) extend across the slits of the tracking panel. The extending direction of the light-emitting regions R(1) R(4) is perpendic- ular to the extending direction of the slits of the tracking panel. Many of the light-emitting regions [i.e., R(1) R(4)] of the dy- namic backlight module are array in an arrayed manner. Fig. 6 shows a novel controlled circuit architecture of scan- ning regions for high-resolution stereoscopic display with 120 Hz frequency using scanning backlight method. All parameters of the scanning backlight method operate by determining the sum of turning times between LED backlight regions 4 and 2. If the counted times equal 100 then the next backlight region be- gins operating. For a 4-region scanning backlight method, when the panel is filled in regions (1), (2), (3), and (4) by the new image, the backlight lights up for regions (3), (4), (1), and (2). In anticipation of region (1) of the panel displaying left-eye and right-eye images, we turned on region (3) of the backlight unit and analogized the image shown in region (2), turning on re- gion 4 of the backlight unit. According to the 2-region scanning the backlight method, when the new image fills regions (1) and (2) of the panel, the backlight lights up in the corresponding re- gions (2) and (1). To avoid seeing both the L-image and R-image at the same time, the backlight region R(1) must be turned off until the image fills R(1). The sample operative principles apply to the backlight regions of R(2). Incomplete isolation of the left and right image channels so that one leaks (leakage) or bleeds into the other. Looks like a double exposure. Crosstalk is a physical entity and can be ob- jectively measured, whereas ghosting is a subjective term. III. CROSSTALK ANALYSIS To avoid ghost images, the backlight modular provides backlight control signals which are dependent on the position of an associated part of the panel. The system is provided for LIOU et al.: LOW CROSSTALK MULTI-VIEW TRACKING 3-D DISPLAY OF SYNCHRO-SIGNAL LED SCANNING BACKLIGHT SYSTEM 415 Fig. 6. Synchronization signal LED backlight architecture. Fig. 7. Schematic diagram of scanning backlight method. controlling synchronization timing between backlighting and pixel refresh, in dependence of a location of a section within the display panel. The backlight unit is separated into several regions. Let’s take 4 regions as the example as in Fig. 7. the pixel response time is less than three fourths of the frame time when the illumination period is one quarter of the frame time. Optical sensor and CS-100 Spot Chroma Meter of luminance crosstalk measurement of the 4-regions, 2-regions scanning and strobe backlight method without lenticular. Frame sequen- tial(page flip, temporal multiplexed) process, the process is referred to as alternate frame sequencing. Crosstalk is a critical factor determining the image quality of stereoscopic displays. Also known as ghosting or leakage, high levels of crosstalk can make stereoscopic images hard to fuse and lack fidelity. Crosstalk is measured by displaying full-black and full-white in light-emitting regions R(1) R(4) of the dis-

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