Kuen Lee

Investigation of Designated Eye Position and Viewing Zone for a two-view autostereoscopic display

Designated eye position (DEP) and viewing zone (VZ) are important optical parameters for designing a two-view autostereoscopic display. Although much research has been done to date, little empirical evidence has been found to establish a direct relationship between design and measurement. More rigorous studies and verifications to investigate DEP and to ascertain the VZ criterion will be valuable. We propose evaluation metrics based on equivalent luminance (EL) and binocular luminance (BL) to figure out DEP and VZ for a two-view autostereoscopic display. Simulation and experimental results prove that our proposed evaluation metrics can be used to find the DEP and VZ accurately.

System-crosstalk effect on stereopsis human factor study for 3D displays

The ghost image induced by System-Crosstalk (SCT) of 3D display, due to optical hardware imperfections, is the major factor to jeopardize stereopsis. The system crosstalk can be measured by optical measuring instrument and describes the optical leakage from the neighboring viewing zones. The amount of crosstalk reduces the ability of the viewer to fuse the stereo-images into 3D images. The Viewer-Crosstalk (VCT), combined with hardware and content issues, is an overall evaluation of the ghost image and can be easily interpreted based on the principle of binocular 3D display. The examination of different SCT values was carried out with a seven-grade subjective evaluation test. In our previous study, it was shown that many other factors, such as contrast ratio, disparity and monocular cues of the images, play important roles in the stereopsis. In this paper, we study the factors of stereo-images with different crosstalk levels that may affect stereopsis. For simulate the interference between stereo-images, digital image processing are employed to assign different levels of crosstalk to each other at properly specified disparity between images. Results of this research can provide valuable reference to the content makers and for the optimized design of 3D displays with minimum System Crosstalk.

Challenge of 3D LCD Displays

A multiview autostereoscopic LCD display with a localized 2D/3D switching function is developed based on the actively switchable parallax barrier technology. This switchable barrier comprises of an electro-optically switchable liquid crystal (LC) and a microretarder. Polymer dispersed liquid crystal (PDLC) with switchable clear and diffusing states and twisted nematic liquid crystal (TNLC) with polarization switching function are used as switching devices. The microretarder is prepared by self-developed multibeam laser scanning process, which is clean, friendly to the environment, and easy for scale up and mass production. The influence factors on the image qualities of 3D displays based on LCD panel technology are analyzed and discussed. Some solutions have proposed to solve the commercial application issues.

The fabrication of microretarder for in-cell stereoscopic LCD using reactive liquid crystal

A microretarder for stereoscopic display is a film consisting of horizontal or vertical stripes with alternating null and half-wave phase retardation states. An LCD with a microretarder attached on the front side can display good-quality stereoscopic images when viewed with polarization glasses. It is now the easiest and cheapest way to present stereoscopic images on a flat-panel display. However, the space caused by the glass between the retarder layer and the LC layer of the panel seriously limits the vertical view angle, which, in turn, limits the application of this technology. In this paper, a process for thin-film microretarder is developed using reactive liquid crystal. The material and the process are essentially compatible with current LC panel processes. Since the thin-film microretarder is to be fabricated in the cell of an LC panel, the retarder layer and the LC layer can be fabricated as close to each other as possible. A nearly unlimited 3D view angle can be achieved for the display.

Human factor study on the crosstalk of multiview autostereoscopic displays

Stereoscopic depth perception has been analyzed in many laboratory experiments since Wheatstones (1838) discovery that disparity is a sufficient and compelling stimulus for the perception of depth with mirror-type stereo displays. In this paper, mirror-type stereo displays were used as the instrument to simulate the 3D image in the human factor experiment. It can be used to simulate the 9 view 3D display by image processing method with different multi-view crosstalk levels measured from luminance measurement device. The disparity of multi-view images to form stereopsis with depth perception is decided by the 9-view autostereoscopic 3D display that subject can properly fuse the image to get the proper visual depth. Computer graphic method applied for multi-view content rendering with shooting distance of 70 cm for each virtual camera. The distance between cameras is 5.6 cm with parallel capture to simulate the images accepted by human eyes. The experimental design was used for testing subjective evaluations based on the questionnaire, and ANOVA methods were used for analysis. Experimental variables of this human factor study for multi-view 3D display are five levels of crosstalk distribution from measured data, with or without shadow effects and perspective line shown within tested images. In addition, the result of acceptable system crosstalk level for multi-view stereoscopic display is between Level 4.7 and Level 5.9 in average for the four tested images.

Autostereoscopic display optical properties evaluation

Autostereoscopic displays have wider and wider applications, and optical quality evaluation is the bedrock for market development. Unfortunately, we lack the 3D display measurement standard (3D DMS), human factor and even standardized measurement instruments currently. Some studies reported the autostereoscopic display measurement using current optical measurement instrument such as luminance meter, CCD and conoscope1, 2, 3, 4, but the problem now is how to verify those data? In this paper, we measured the optimal viewing distance (OVD), designated eye positions (DEP) and system-crosstalk of an autostereoscopic display and discussed some specific issues, like the affection of pupil size and measurement distance, method to find out the OVD, etc. which is usually met in 3D display measurement, and calculate the designated eye positions from the raw data using one-point method and two-point methods. The measurement was made by a luminance meter and the results were compared to the designed parameters.

System crosstalk measurement of a time-sequential 3D display using ideal shutter glasses

The market of stereoscopic 3D TV grows up fast recently; however, for 3D TV really taking off, the interoperability of shutter glasses (SG) to view different TV sets must be solved, so we developed a measurement method with ideal shutter glasses (ISG) to separate time-sequential stereoscopic displays and SG. For measuring the crosstalk from time-sequential stereoscopic 3D displays, the influences from SG must be eliminated. The advantages are that the sources to crosstalk are distinguished, and the interoperability of SG is broadened. Hence, this paper proposed ideal shutter glasses, whose non-ideal properties are eliminated, as a platform to evaluate the crosstalk purely from the display. In the ISG method, the illuminance of the display was measured in time domain to analyze the system crosstalk SCT of the display. In this experiment, the ISG method was used to measure SCT with a high-speed-response illuminance meter. From the time-resolved illuminance signals, the slow time response of liquid crystal leading to SCT is visualized and quantified. Furthermore, an intriguing phenomenon that SCT measured through SG increases with shortening view distance was observed, and it may arise from LC leakage of the display and shutter leakage at large view angle. Thus, we measured how LC and shutter leakage depending on view angle and verified our argument. Besides, we used the ISG method to evaluate two displays.

A method of fabricating micro-retarder plates by a laser system

Different fabrication methods, such as chemical process, laser heating method, etc., can be used to make micro-retarder plates. In this paper, a CO2 laser scanning system is applied to produce a serious of line patterns on the commercial compensator (or the retarder film, such as PC film, PVA film, or Arton film, etc.) to make micro-retarder plates, which are important optical components in stereoscopic 3D displays. Our study is focused on the development of high quality fabrication method, for example, the relationship of a well-defined stripe boundary with the CO2 laser process under single beam or multiple beams. The laser scanning system in this paper is installed with an orthogonal pair of precise translation stages, a steadily controlled laser power output, and an adjustable spot-size optical head to make patterns of micro-retarder plates for stereo-LCTVs up to 42 inches.

Stereoscopic display gray to gray crosstalk measurement

There are several studies on estimating crosstalk of 3D displays. Crosstalk is an important factor in determining image quality of stereoscopic display. In previous study, gray to gray crosstalk model has been modified. In this paper, we use six commercial stereoscopic displays including passive polarized glasses and active shutter glasses, both left and right eyes were measured by a luminance meter to verify the gray to gray crosstalk model and analyze the stability of the measurement data using our standard operating procedure (SOP). According to the SOP, we use simple statistical method to verify the repeatability of data. Experimental results indicate that our measurement system can be used to estimate the value of gray to gray crosstalk of stereoscopic display, the uncertainty below 0.8% for FPR display and 3% for shutter glasses display at 95% confidence level. These results, can be used as an important parameters in stereoscopic display visual quality, also can be used as a design feedback for engineer.