Inverse display characterization: A two‐step parametric model for digital displays

Abstract— A simple additivity model is often used as a basic model for digital‐display characterization. However, such a simple model cannot satisfy the needs of demanding color‐management applications all the time. On the other hand, systematic sampling of the color space and 3‐D interpolation is an expensive method in terms of measurement and computation time when precision is needed. This paper presents an enhanced method to characterize the XYZ‐to‐RGB transform of a digital display. This parametric method exploits the independence between the luminance variation of the electro‐optic response and the colorimetric responses for certain display types. The model is generally applicable to digital displays, including 3‐DMD projectors, single DMDs, CRTs, LCDs, etc., if the independence condition is satisfied. While the problem to solve is a 3‐D‐to‐3‐D transformation (from XYZ to RGB), the proposed parametric model is the composition of a 2‐D transform followed by a 1‐D transform. The 2‐D transform manages the chromatic aspects and, in succession, the 1‐D transform manages the luminance variations. This parametric digital model is applicable in the field of color management, with the objective of characterizing digital displays and applying a reference look such as a film look.     

Processes,characterizations, and system applications of color‐filter liquid‐crystal‐on‐silicon microdisplays

Abstract— A color‐filter liquid‐crystal‐on‐silicon (CF‐LCOS) microdisplay that integrates color filters on silicon for color will be presented. The color‐filter process on silicon was optimized to achieve fine resolution and precise alignment of the color filters on the pixel array, good adhesion to the silicon suface, and a flat surface for the liquid‐crystal cell assembly. Important optical and electrical parameters of the color filters were extracted to establish an electro‐optical model of the CF‐LCOS microdisplays for device simulation. Thermal, chemical, and light‐stability characterizations were performed to ensure the stabilty of the color filters and CF‐LCOS microdisplays. With color CF‐LCOS microdisplays already available, the projection or viewing optics is greatly simplified. This CF‐LCOS microdisplay is ideal for near‐to‐eye displays because of its low‐power consumption and compactness. The CF‐LCOS microdisplay could also withstand medium light illumination for medium‐sized projectors. A single‐panel projector based on one CF‐LCOS microdisplay of 1280 × 768 × RGB resolution was demonstrated.     

Color‐tuning projection system for adaptive combination of high brightness and wide color gamut

Abstract— The demand for projectors with high brightness and wide color gamut has been increasing; however, UHP lamp projectors cannot deliver those two qualities efficiently and simultaneously because of its color‐separation system. The newly developed projection system — “Color‐Tuning Projection System” — realizes the adaptive combination of high brightness and wide color gamut with one projector. This projector features a fourth liquid‐crystal panel — “Color Tuner” — with a 3LCD optical engine, which controls yellow light separately from the RGB light of a UHP lamp. This color‐tuner‐based optical engine — “Color‐Tuning Optical Engine” — and a new color‐conversion signal‐processing algorithm — “Adaptive Color Conversion Algorithm” — controls the yellow‐light volume and corrects color‐shifted pixels according to the brightness and chromaticity analysis of the input image, key technologies of the Color‐Tuning Projection System. This additional panel system enables the projector to ach ieve up to 115% higher brightness and 120% wider color gamut according to the input image. This paper presents an innovative design concept, a novel technology regarding brightness and a color‐gamut conversion projection system, and the characteristics of the prototype.     

Spatially uniform colors for projectors and tiled displays

Abstract— A major issue when setting up multi‐projector tiled displays is the spatial non‐uniformity of the color throughout the display's area. Indeed, the chromatic properties do not only vary between two different projectors, but also between different spatial locations inside the displaying area of one single projector. A new method for calibrating the colors of a tiled display is presented. An iterative algorithm to construct a correction table which makes the luminance uniform over the projected area of one single projector is presented first. This so‐called intra‐projector calibration uses a standard camera as a luminance measuring device and can be processed in parallel for all projectors. Once the color inside each projector is spatially uniform, the set of displayable colors — the color gamut — of each projector is measured. On the basis of these measurements, the goal of the inter‐projector calibration is to find an optimal gamut shared by all the projectors. Finding the optimal color gamut displayable by n projectors in time O(n) is shown, and the color conversion from one specific color gamut to the common global gamut is derived. The method of testing it on a tiled display consisting of 48 projectors with large chrominance shifts was experimentally validated.     

Multi‐primary‐color LCD: Its characteristics and extended applications

Abstract— The development of multi‐primary‐color (MPC) display systems is one of the big paradigm shifts in recent display technologies and induces new potentials of display devices. The development of MPC display systems for different goals is briefly reviewed. Especially, by employing MPC systems, it is possible to reproduce the real material colors faithfully and efficiently. For signal processing, MPC systems have a big advantage in the so‐called color‐reproduction redundancy. A number of applications can be derived from this characteristic, such as improving the viewing‐angle dependency issue and power savings. On the other hand, MPC systems have a typical trade‐off versus RGB‐standardized input signals, especially for reproducing bright green. New algorithms to moderate this trade‐off on MPC systems by employing color‐reproduction redundancy are proposed. The goal of our algorithms is to maintain the compatibility with RGB‐based input signals though the initial display design so that the characteristics of MPC systems are not changed or lost. These algorithms indicate that MPC display systems are applicable not only for a specifically limited objective but also for other applications, e.g., TV broadcasting.     

Metameric failure assessment and reduction between RGB and laser phosphor projectors

Metameric failure is commonly observed when different types of displays reproduce the same color, as it is defined by a colorimetry system, but the outputs do not match visually. Metameric failure is impacted by the used colorimetry system and the relation between the involved displays' spectral power distributions (SPDs). In this work, we assess the metameric failure between the upcoming types of theatrical projectors, RGB laser, and laser phosphor (LaPH) and propose a method to reduce it. Our analysis starts by evaluating the performance of existing colorimetry systems in terms of metameric failure reduction. Among the colorimetry systems tested, the CIE 2006 2° (CIE06 2°) system resulted in the least observed metameric failure for a large portion of the participants but not their absolute majority (>50%). The limited performance of existing colorimetry systems led us to questioning the feasibility of successful perceptual color matching between the two projectors. To explore and potentially rule-out this scenario, we performed a subjective color matching experiment. The analysis of the results revealed the key role that the projectors' SPD differences play on color matching. Based on the observations of the first two studies, we propose a novel colorimetry system that reduces further than existing colorimetry the systems the metameric failure between RGB and LaPH projectors. Our proposed system is a modified version of CIE06–2° that accounts for the spectral differences of the two light sources. Evaluation showed that our solution outperforms existing colorimetry systems.     

Paradigm for achieving color‐reproduction accuracy in LCDs for medical imaging

Abstract— A methodology and associated software modules for calibration, characterization, and profiling of color LCDs for color‐critical applications in medical imaging is described. Supporting analyses reveal very high color‐reproduction accuracy as determined by CIE DE2000 color differences for 21 0 test colors uniformly distributed in CIE Lab color space. The impact of the LCD tone‐reproduction curve on color‐reproduction accuracy is compared for two tone‐reproduction curves of special interest in medical imaging: the DICOM gray‐scale standard display function and the CIE L* standard lightness function. The initial results from a psychophysical investigation of the diagnostic performance of trained pathologists viewing “virtual” breast biopsy slides are reported and the diagnostic performance achieved with calibrated, color‐managed LCDs with uncalibrated LCDs without the benefits of color management is compared.     

多投影仪拼接显示的实现

介绍了一种基于PC和普通投影仪实现多屏幕无缝拼接的方法,该方法利用一台摄像机使系统快速、准确的校正。分析了系统的结构和用到的关键技术,包括几何校正、边缘融合、颜色校正。     

Mechanism of color breakup in field-sequential-color projectors

Abstract— To investigate color breakup in field-sequential-color projectors, we measured the threshold of color fusion frequency relative to retinal velocity of the moving edge on the color flicker field. The characteristic changed as the velocity approached saccade. The result suggests that the mechanism of color breakup differs according to the velocity of the image on the retina.     

How to shop on the Web without seeing red

Abstract— Using the World Wide Web to order goods and services is a rapidly increasing activity. Experience with mail‐order catalogs has shown that failure of goods to match the catalog color is a major category of complaint. Ordering colored goods on the Web poses even greater challenges. Useful devices to standardize cathode‐ray tubes, and other self‐luminous displays, are available, but these only address the problem of display set‐up. Other relevant problems include the effects of changes in the level of luminance, lack of color constancy of goods with changes in illuminant color, departures from a set of color‐matching functions of the spectral sensitivities of acquisition devices, observer metamerism, the effect of the surround on the appearance of the display, and limitations in the gamut and in the resolution of typical displays. The extent to which these factors are likely to be important is discussed, and ways in which some of their effects might be mitigated are considered.     

Color performance of an MVA‐LCD using an LED backlight

Abstract— The color performance, including color gamut, color shift, and gamma curve, of a multi‐domain vertical‐alignment (MVA) liquid‐crystal display (LCD) using an LED backlight are calculated quantitatively. Simulation results indicate that an LED backlight exhibits better angular color uniformity and smaller color shifts than a CCFL backlight. Color gamut can be further widened and color shift reduced when using a color‐sequential RGB‐LED backlight without color filters, while the angular‐dependent gamma curves are less influenced using different backlights. The obtained quantitative results are useful for optimizing the color performance and color management of high‐end LCD monitors and LCD TVs.     

Projection displays: New technologies,challenges, and applications

The achievable color gamut and light output of projection displays based on light‐emitting diodes (LEDs), phosphor conversion, and lasers are discussed. The color appearance phenomena, colorfulness, and the Helmholtz–Kohlrausch effect are discussed in the context of LED and laser illumination of projection displays, as well as some pitfalls concerning the interpretation of the Helmholtz–Kohlrausch effect. Also the laser speckle phenomenon and the characterization of it are addressed. The importance of both the American National Standards Institute (ANSI) contrast and the sequential contrast of projectors, as well as the discrepancy between measured and perceived contrasts, are explained. Visibility criteria for contouring artifacts are explained and compared with new emerging electro‐optical transfer functions that are more adapted to this issue. Stereoscopic solutions and early prototypes of autostereoscopic multi‐view, super multi‐view projection displays, and electro‐holographic displays are discussed as well as the limiting factors of these systems in the context of display resolution, and LED and laser light sources.     

彩色图像工程中常用颜色空间及其转换

颜色空间是彩色图像工程面对的首要问题.为了对颜色进行量化的、确定性的管理以及综合性的应用,时彩色图像工程中经常用到的颜色空间进行了分类和系统地阐述,并从工程应用的角度重点介绍了这些颜色空间的应用背景及其之间转换.为研究设备彩色特性,进行色彩管理和处理彩色图像打下了基础.     

Relationship between mode‐boundary from surface color to fluorescent appearance and preferred gamut on wide‐gamut displays

Abstract— Color‐gamut design is a major concern in wide‐gamut displays. To determine a preferred gamut for displaying object color in natural scenes on a wide‐gamut display, subjective evaluations were conducted to investigate the preferred color and acceptable limit. Then, simple synthesized images were used to determine the mode boundary between surface color and fluorescent color appearance. It was found that (1) observers perceived the colors with high saturation and high lightness as fluorescent colors and (2) the fluorescent appearance decreased preference. The color‐mode index (CMI) was defined as an evaluation index of the color‐appearance mode so that the boundary between surface color and fluorescent color appearance was defined as CMI 100. Additionally, it was found that the CMI 100 loci could be interpreted as an optimal color loci. Then, it was clarified that the mode boundary and the preferred gamut were closely related and that the acceptable limit for L* was 1.1 times L* for CMI 100.     

多投影显示墙画面校正技术综述*

由投影仪阵列组成的多投影显示墙是目前实现高性能、低成本大型绘制平台的首选解决方案。为了保证多投影显示墙画面的完整性,需要通过一定的方法来预补偿由于投影仪特性差异造成的画面几何扭曲与色彩不均衡。结合实际研究工作,从多投影显示墙存在的问题、几何变换矩阵求取、颜色模型估计和全局颜色校正等几个方面对多投影显示墙画面校正的研究情况进行综述, 讨论了存在的问题和进一步的发展方向。     

Color‐breakup evaluation of spatio‐temporal color displays with two‐ and three‐color fields

Abstract— Spatio‐temporal color displays have higher transmission and resolution than conventional LCDs, but suffer from color breakup. In this paper, a 120‐Hz display with two‐color filters and two‐color fields is described and the amount of color breakup is compared with that of a 180‐Hz full‐color‐sequential display with no color filters and three‐color fields. The results indicate that color breakup in a color‐filterless display is annoying, whereas it is just visible in displays with two‐color filters even though the refresh rate is much lower.     

High performance color‐converted micro‐LED displays

A full‐color micro‐LED display can be achieved by red, green, and blue (RGB) chips or by a blue/ultraviolet (UV) micro‐LED array to pump downconverters. The latter helps relieve the burden of epitaxial growth of tri‐color micro‐LED chips. However, such a color‐converted micro‐LED system usually suffers from color crosstalk and low efficiency due to limited optical density of color converters. With funnel‐tube array and reflective coating on its inner surface, the crosstalk is eliminated, and the optical efficiency can be improved by more than two times. In addition, the ambient contrast ratio is also improved because of higher light intensity. The color gamut of this device is approximately 92% of DCI‐P3 standard.     

Laser + LCOS projection‐technology revolution

Abstract— The advent of affordable direct‐diode lasers changes all the rules for optical designs and the associated technologies that generate the images from laser light. These new lasers are forseen as driving fundamental changes in the size, power consumption, cost, resolution, and even the uses for pico‐projectors. This paper discusses these topics from the perspective of laser‐light‐illuminated LCOS microdisplays.     

A dual‐gap RGBW transflective TFT‐LCD with adjustable color gamut

Abstract— An adjustable‐color‐gamut dual‐gap RGBW transflective liquid‐crystal display that uses a four‐color manufacturing process and a color‐processing algorithm to achieve the appropriate color performance in both the transmissive and reflective modes is presented. Based on superior‐color‐transformation units, the total brightness and color gamut can be modified under different ambience. The highest NTSC color gamut in the reflective mode (reflectance, 4.4%) that has been fabricated successfully for a RGBW 1.5‐in. dual‐gap panel is 23% with a 7%, 17%, and 40% NTSC color gamut in the transmissive mode by using different algorithms. Compared to a typical RGB panel, it not only provides flexibility for any environment but also satisfies a variety of personal requirements. Based on personal preference, users have more choices to adjust the LCD settings such as color saturation, brightness, etc. The smart RGBW TRLCD will definitely become the developing trend towards sunlight‐readable LCDs in the near future.     

A new field‐sequential‐color LCD without moving‐object color break‐up

Abstract— A new display method for field‐sequential‐color liquid‐crystal displays (FS‐LCDs) that reduces the negative effects of color break‐up associated with moving objects has been developed. The method is called Adjustment of Color Element on the Eyes (ACE), and it relies on the position on the eyes of RGB color sub‐images. It was confirmed that color break‐up also does not occur for peripheral objects when using ACE.