Yu-Kuo Cheng

Design and Evaluation of Light Spread Function for Area-Adaptive LCD System

A methodology, based on two-dimensional super-Gaussian light spread functions (LSFs), was studied for the light-emitting-diode (LED) backlighting system in the high dynamic range (HDR) liquid crystal displays (LCDs). We proposed a novel LED-based optomechanical configuration to implement the desirable luminous pattern. A dual-liquid-crystal-panel system was constructed as a pseudo-HDR LCD to evaluate the super-Gaussian illumination. The proposed HDR scheme was verified via the current platform: overall luminance uniformity, contrast ratio and processing speed could be improved by factors of 1.55, 1.95-4.15, and 4.82, respectively. The design flexibility made the methodology applicable to any panel dimension and backlight division of the HDR LCDs, and to the conventional full-on backlighting LCDs as well.

Two-Field Scheme: Spatiotemporal Modulation for Field Sequential Color LCDs

A novel displaying method, two-field driving scheme, was proposed for field sequential color LCDs without color filter. A spatially modulated color backlight provided multi-primary low-resolution optical stimuli, which were then compensated by an LC panel to display detailed colorful images. That is, the manipulation on three (or more) spatial and two temporal degrees of freedom was sufficient to convey full color information. The simulation results showed that the proposed method achieved acceptable color reproduction accuracy, average CIEDE2000 color difference (DeltaE00) < 3. The least number of fields particularly alleviated the demand for fast-response LC modes in sequential-type LCDs. Furthermore, color break-up suppression was observed due to less chrominance difference between the two fields.

Colorimetric Characterization of High Dynamic Range Liquid Crystal Displays and Its Application

A modified colorimetric model was proposed to characterize the high dynamic range liquid crystal display (HDR LCD). Backlight intensity was incorporated to account for the display chromatic properties. Images, exemplifying regular and random backlight intensity distributions, were designed to evaluate the model. The results showed that chromaticity of three primaries was instable, and thus the device-dependent color transformation was inadequate in the HDR LCD. Moreover, the proposed model, in comparison with the model dedicated for the conventional LCD, was in average of less CIEDE2000 color difference values. Therefore, the proposed model was applicable for colorimetric color reproduction in the HDR LCD.

Relative Contrast Sensitivity for Color Break-Up Evaluation in Field-Sequential-Color LCDs

A single-valued index, relative contrast sensitivity (RCS), was developed to quantitatively evaluate color break-up (CBU) phenomenon. The sensibility of CBU fringe was hypothesized to strongly correlate with RCS, which was defined as the integrated difference of the opponent-color signals filtered by spatial contrast sensitivity functions. Psychometric experiments, based on methods of category scaling and adjustment respectively, were conducted to examine the proposed numerical metric. The results showed that the maximal correlation coefficient was as high as 98.9% between the subjective judgments and the computed numerical values of current experimental results. A useful application of RCS index was demonstrated by the evaluation of four driving schemes for CBU suppression.

64.3: Super-Gaussian Light Spread Function for High Dynamic Range Displays

Super-Gaussian light spread function was designed for high dynamic range liquid crystal displays. A dual-liquid-crystal-panel system was constructed to simulate an HDR display, and to evaluate the implementation of the proposed super-Gaussian and a general Gaussian distributions. According to the results, luminance uniformity and processing time of super-Gaussian LSF are superior to those of Gaussian LSF by factors of 1.55 and 178, respectively. Contrast ratio is improved by a factor about 2 to 4.15 as well. In addition, the undesired artifact, grid lines, can be suppressed to be invisible.

P‐40: A Visual Model of Color Break‐Up for Design Field‐Sequential LCDs

A model to evaluate the color break-up (CBU) of field-sequential color liquid crystal display (FSC-LCD) had been successfully established. In order to quantify the CBU, “Color Break-Up Angle (CBUA)” was proposed as the evaluation index. From the psychophysical experiments, the CBUA=0.22° was reported as the averaged threshold value for indistinguished color break-up. Consequently, the minimum frame rate could be derived from the model to suppress CBU in the various FSC-LCDs.

P-69: A Localized Partition Approach for High-Dynamic-Range Display

A mosaic-form backlight system for high-dynamic-range display was introduced. The backlight unit consisting of a side-emitting LED, a quadratic light guide, and a concentric prism sheet can form an isolated square super-Gaussian distribution over the local area of liquid crystal panel. By means of our approach, high-dynamic-range display system can reduce the time required for processing compensated image signal.

18.1: Invited Paper: Eco-Display - An LCD-TV Powered by a Battery?

Color break-up (CBU) is a lethal issue of a high light efficiency field-sequential-color (FSC) LCD. Applying local color-backlight-dimming technology to FSC-LCDs, we demonstrated “Stencil-FSC” methods with a field rate as low as 120Hz to render a high luminance “multi-color” image on the first-field and effectively suppress CBU at the same time. In addition, the color filterless LCD with an intelligent LED backlight and even non-polarized LC cell, optical thruput can increase by a factor of 10, yet with lower material cost/count for an Eco-Display.

High Dynamic Range Display Adopting High Dynamic Range Imaging Technique

Technique of high dynamic range imaging (HDRI) was introduced into conventional high dynamic range display (HDRD). Sharpness of image was further enhanced by improving local contrast ratio in the HDRI-based high dynamic range display

43.1: Color Optimization Model for High Dynamic Range LCDs with RGB Color Backlights

The high dynamic range liquid crystal display (HDR-LCD) with the color controlled backlight can achieve low power consumption, high color saturation and high contrast ratio. A modified color model for the RGB LEDs backlight system was proposed to optimize the color appearance in this paper. By applying the model, the color accuracy of the HDR-image could be much improved with the clear image details.