Color management of reflective‐type LCDs in terms of adaptation of the human visual system to light‐source variation

We have investigated the color management, in terms of the color adoption property of the human visual system, of a reflective‐type TFT‐LCD (R‐LCD). Since the R‐LCD depends on ambient light as the light source, it is expected that the colorimetric color on the R‐LCD must be changed if the source of the ambient light is changed. However, due to the adaptation property of the human visual system, the eye does not perceive colorimetrically corrected colors as the same color even for an R‐LCD. In this research, first, we conducted a subjective experiment to obtain the RGB code value that is required in order to display a corresponding color on the R‐LCD under varying ambient‐light conditions. The result of the experiment shows that the corresponding color of the experimental results was reasonably approximated by the color obtained by using the von Kries model. Secondly, we proposed a color‐compensating mechanism that is described as a cascaded simple 3 × 3 linear matrix. Actual colors displayed are adjusted according to the ambient light. The evaluation of the picture quality of the R‐LCD showed that the proposed model is effective.     

Effects of contrast and ambient illumination on visual discomfort of autostereoscopic display

The conflict between vergence and accommodation is the main perceptual factors contributing to visual discomfort when viewing autostereoscopic display. The key factors relevant to the accommodation and vergence are the ambient illumination and the contrast. The current study was a 2 × 3 × 3 mixed design comparing VFSI and VIMS symptoms between 2D and 3D video clips with three contrast levels under three ambient illumination levels on the autostereoscopic display. Twenty participants were required to evaluate the degree of discomfort by filing out questionnaires after watching those video clips. According to the result analysis, the 3D viewing participants reported more severe symptoms compared to 2D. The moderate contrast conditions were found to be the optimum for viewing comfort. The difference between VFSI and VIMS symptoms become larger with increasing contrast. The results also suggested the optimum 3D illumination condition should not be too high to effectively relieve visual discomfort. VIMS symptoms were more sensitive to the changes in ambient illumination than VFSI. Moreover, significant interaction between contrast and ambient illumination was found. Participants felt the most comfortable in the combination effect of moderate level of contrast and the high level of ambient illumination.     

Effects of illumination conditions on preferred viewing distance of portable liquid‐crystal television

This study explored the effect of TV size, light source, and ambient illumination on the preferred viewing distance of portable liquid‐crystal‐display televisions. Results showed that the mean preferred viewing distance was 1389 mm. TV size had significant effects on preferred viewing distance. The larger the screen size, the greater the preferred viewing distance, at around 6.7–14.7 times the width of the screen (W). Light sources revealed no significant effect on preferred viewing distance. The effect of ambient illumination on preferred viewing distance was significant. The higher the ambient illumination was, the longer the preferred viewing distance.     

Predicting the viewing direction performance of e‐paper displays with front light under ambient lighting conditions

The inherent advantages of reflective e‐paper displays (EPD) – wide viewing direction range and excellent readability even under bright sunlight – can be extended into low‐light conditions by the addition of an integrated lighting unit (ILU) such as a front light. A methodology for predicting the viewing direction dependence of ambient contrast and color from display measurements and illumination models is here applied to reflective EPD where the ILU is switched on. The predictions can be used to optimize task lighting. The ILU improves the indoor performance of EPD without compromising their superior daylight performance.     

Effect of DLP projector white channel on perceptual gamut

Abstract— The effect of white‐channel enhancement as implemented in the Texas Instrument DLP? digital projector technology is evaluated theoretically using both the CIELAB and the CIECAM02 color appearance models and experimentally through psychophysical testing using real images. Both theory and test results confirm a compression of perceptual gamut in both chroma and colorfulness as a result of the added white channel. Hence, while this technology is ideal for viewing graphics and text under ambient conference‐room conditions where lightness contrast is important, it is necessarily less than ideal for viewing images or in home‐theater environments where color is important.     

Antireflection displays with ambient contrast enhancement for extended device battery lifetime and reduced energy consumption

Antireflection (AR) coatings can improve the viewing experience of a display, including mobile electronic devices such as smartphones, tablets, and laptops that are typically operated on battery power and protected with chemically strengthened glass. In this work, we discuss the trade‐offs between optimal user viewing experience in brightly lit environments and battery lifetime for an AR versus a non‐AR mobile display. We show that under 400–1,000 lux ambient illumination, an AR‐based display can be operated at >30% lower luminance than a non‐AR display with similar human perception of contrast based on a perceptual contrast length model, resulting in a potential improvement of >15% in device battery lifetime and a similar proportion of energy savings.     

Effect of disparity and viewing ambient illumination on stereoscopic viewing: An eye movement approach

Researchers have found that factors related to viewing content and viewing environment could influence viewers' stereoscopic viewing experiences. In this paper, the effect of both disparity and viewing ambient illumination condition on stereoscopic viewing was investigated by using an eye movement approach. The eye movement responses to random dot stereograms (RDS) stimuli in stereoscopic viewing were studied by performing a fusion range measurement experiment involving a judgment task. The fusion ranges under two ambient illumination conditions, eye movement responses to RDS stimuli and effects of disparity on eye movement parameters, were analyzed, respectively. The experimental results showed that fusion range under two ambient illumination conditions were different, and changes of eye movement parameters were different among various disparities when ambient illumination conditions varied. As a result, in order to improve viewers' viewing experiences when viewing different 3D contents, the arrangement of viewing ambient illumination conditions and the selection of disparity should be appropriately considered. The findings in this paper provide guidelines to reasonably arrange the viewing ambient illumination condition and efficiently produce healthy disparity in stereoscopic viewing.     

Dynamic adaptation model and equal‐whiteness CCT curves for the choice of display reference white

Abstract— A dynamic adaptation model (DAM), based on the variations in the luminance levels under the same chromaticity viewing conditions and equal‐whiteness correlated‐color‐temperature (CCT) curves (EWCCs) derived by using the proposed DAM, is proposed. The proposed model was obtained by the transformation of the test colors for high luminance into the corresponding colors for low luminance. In the proposed model, the optimal coefficients are obtained from the corresponding color data from Breneman's experiments. From the experimental results, it was confirmed that the chromaticity errors between the predicted colors by the proposed model and the corresponding colors of Breneman's experiments are 0.004 in u′v′ chromaticity coordinates. The prediction performance of the proposed model is excellent because this error is the threshold value that distinguishes two adjacent color patches. Equal‐whiteness CCT curves (EWCs) are also proposed using the proposed DAM. By using the proposed EWCCs, an analysis of the difference between the selected video‐display‐unit reference‐white CCT values can be made. Additionally, the proposed EWCCs can be used as the theoretical standard which determines the reference white of the color video display units.     

Energy‐efficient liquid‐crystal displays (e2‐LCDs) using a photonic‐crystal backlight system

Abstract— Cholesteric liquid crystals automatically form one‐dimensional photonic crystals. For a photonic crystal in which light‐emitting moieties are embedded, unique properties such as microcavity effects and simultaneous light emission and light reflection can be expected. Three primary‐color photonic‐crystal films were prepared based on cholesteric liquid crystal in which fluorescent dye is incorporated. Microcavity effects, i.e., emission enhancement and spectrum narrowing, were observed. Two types of demonstration liquid‐crystal displays (LCDs) were fabricated using the prepared photonic‐crystal films in a backlight system. One is an area‐color LCD in which a single photonic‐crystal layer is used for each color pixel and the other is a full‐color TFT‐LCD in which three stacked photonic‐crystal layers are used as light‐conversion layers. The area‐color LCD was excited by using 365‐nm UV light, and the full‐color TFT‐LCD was excited by using 470‐nm blue LED light. Because of the photonic crystal's unique features that allow it to work as light‐emitting and light‐reflecting layers simultaneously, both LCDs demonstrate clear readable images even under strong ambient light, such as direct‐sunlight conditions, under which conventional displays including LCDs and OLED displays cannot demonstrate clear images. In particular, an area‐color LCD, which eliminated color filters, gives clear images under bright ambient light conditions even without backlight illumination. This fact suggests that a backlight system using novel photonic‐crystal layers will be suitable for energy‐efficient LCDs (e²‐LCDs), especially for displays designed for outdoor usage.     

Luminance effects influencing perception of 3‐D TV imagery

Abstract— This study investigates whether screen luminance or ambient illumination has a significant effect on the perception of 3‐D TV imagery for static images and dynamic films. Two types of stimuli were shown on a multi‐view stereoscopic display: the static image, which included computer‐generated and photographic images, and dynamic film, which contained real‐life and animation images. In each treatment with a different level of screen luminance, subjects completed psychophysical and physiological measurements and subjective comfort evaluations. The results showed that when subjects viewed 3‐D static images, the ambient illumination affected psychophysical visual fatigue and screen luminance had a significant effect on subjective comfort evaluation and visual discrimination performance. However, when subjects viewed 3‐D dynamic films, screen luminance was the major factor causing psychophysical visual fatigue, and ambient illumination significantly affected subjective comfort evaluation. The outcomes contribute to knowledge concerning the suitable viewing conditions for the 3‐D viewing experience. Future work will explore the intolerance threshold of the lowest display luminance or the effect of decomposition of the screen on other physiological measurements.     

Evaluation of contrast metrics for liquid‐crystal displays under different viewing conditions

Abstract— A psychophysical experiment was carried out to assess the perceptual contrast on a large‐sized liquid‐crystal display (LCD) under nine phases of viewing conditions. Based on the results, six contrast models employing different color attributes or the index of just‐noticeable difference (JND) were developed. Their performances were also tested by the visual data of the nine phases, which indicated that the model C_Q employing CIECAM02 brightness gives the best performance in predicting visual data under different viewing conditions among those models. A preprocessing step was also proposed to utilize the contrast model C_Q conveniently in the practical contrast evaluation of LCDs.     

Effects of display properties on perceived color‐gamut volume and preference

Abstract— The effect of varying the color gamut of an extended‐gamut LCD on color appearance and preference was measured psychometrically in two experiments at each of two separate laboratories over a representative set of 10 images each. The first experiment measured the effect of color gamut on appearance, and the effect on the appearance attribute colorfulness was shown to be relatively strong compared with other attributes as the volume of display color gamut is varied. Overall, colorfulness monotonically increased at constant sensitivity as the gamut area in xy chromaticities increased while tending to become less and less sensitive to increasing the gamut volumes in CIELAB and CIECAM02. In the second experiment, the overall preference indicated an optimal color gamut for the display gamut volume even though the results were shown to be highly scene dependent.     

Switchable transmissive and reflective liquid‐crystal display using a multi‐domain vertical alignment

Abstract— A wide‐view transflective liquid‐crystal display (LCD) capable of switching between transmissive and reflective modes in response to different ambient‐light conditions is proposed. This transflective LCD adopts a single‐cell‐gap multi‐domain vertical‐alignment (MVA) cell that exhibits high contrast ratio, wide‐viewing angle, and good light transmittance (T) and reflectance (R). Under proper cell optimization, a good match between the VT and VR curves can also be obtained for single‐gamma‐curve driving.     

Evaluation of Three Tablet Computers at Two Levels of Ambient Illumination

Background: Tablet computers are increasingly widespread in this digital era. During tablet computer use, two important factors are display quality and ambient illumination. The purpose of this experiment was to understand the effects of the display quality of tablet computers (a Sony, a Samsung, and an iPad) and ambient illumination levels (200 lx, 500 lx) on visual fatigue, comfort perception, and task performance.

Methods: Thirty-five university students (17 males and 18 females) were recruited for this experiment. They performed six 40-min trials of playing computer games in all experimental conditions. Visual fatigue, comfort perception, and task performance were collected at the end of each trial.

Results and Discussion: There were no interactions between display model and ambient illumination. Display model had a significant effect on visual fatigue and visual performance, and the best display quality caused less visual fatigue during long periods of viewing. We found no significant effect between 200 lx and 500 lx of ambient illumination on visual fatigue or visual performance; therefore, further research should be conducted to determine what levels of ambient illumination, both high and low, can affect visual fatigue and task performance.     

Improvement of off‐axis color shift on hybrid viewing‐angle device using dual γ‐voltage method

We have mass production on one kind of liquid crystal display (LCD) device with hybrid viewing‐angle (HVA), which can be switched between the wide viewing‐angle (WVA) and narrow viewing‐angle (NVA) by one button. This device adopts the single cell design that with lower cost, and utilizes the optical properties of electrically tilted LC to achieve the function of NVA display. An issue has received less attention in the past and been indeed found in the production process. It is that the off‐axis color shift will appear in NVA mode. We put forward one method to improve this issue here, which is combined with the concepts of Gray Frame Insertion (GFI) and Impulse‐type driving. By switching the voltage between two different γ values, the color shift will be perfected on the produce.     

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.     

A survey of skin-color modeling and detection methods

Skin detection plays an important role in a wide range of image processing applications ranging from face detection, face tracking, gesture analysis, content-based image retrieval systems and to various human computer interaction domains. Recently, skin detection methodologies based on skin-color information as a cue has gained much attention as skin-color provides computationally effective yet, robust information against rotations, scaling and partial occlusions. Skin detection using color information can be a challenging task as the skin appearance in images is affected by various factors such as illumination, background, camera characteristics, and ethnicity. Numerous techniques are presented in literature for skin detection using color. In this paper, we provide a critical up-to-date review of the various skin modeling and classification strategies based on color information in the visual spectrum. The review is divided into three different categories: first, we present the various color spaces used for skin modeling and detection. Second, we present different skin modeling and classification approaches. However, many of these works are limited in performance due to real-world conditions such as illumination and viewing conditions. To cope up with the rapidly changing illumination conditions, illumination adaptation techniques are applied along with skin-color detection. Third, we present various approaches that use skin-color constancy and dynamic adaptation techniques to improve the skin detection performance in dynamically changing illumination and environmental conditions. Wherever available, we also indicate the various factors under which the skin detection techniques perform well.     

Improving content visibility for high‐ambient‐illumination viewable display and energy‐saving display

Abstract— Nowadays, low‐contrast viewing of LC displays (LCDs) occurs very often, which includes the viewing of mobile LCDs at high ambient illumination and the viewing of LCDs at low‐power mode. These cases result in low‐content visibility and low contrast, leading to an unpleasant viewing experience. In this paper, a technique to improve the perceived contrast and visibility of images at low‐contrast viewing conditions is proposed. The proposed approach enhances image brightness with content and ambient adaptive image brightening and highlights visual parts and boundaries with non‐photorealistic rendering. The proposed technique enables longer battery life for mobile LC devices and makes mobile LC devices viewable at high ambient illumination. It also enables TVs with extreme low‐power consumption and smart‐grid responsive TVs.     

Time optimal control of a dielectrophoretic system

This paper examines a time optimal control problem for a dielectrophoretic system. The system consists of a neutrally buoyant and neutrally charged particle in a chamber filled with a fluid flowing with a low Reynolds number. At the bottom of this chamber is a series of parallel electrodes with a controlled time‐varying voltage. The voltage on the electrodes creates a time‐varying nonuniform electric field inducing a dipole moment in the particle. This induced dipole moment interacts with the electric field to generate a force on the particle. There are two state variables x and y, where x is the position of the particle and y is the induced dipole moment in the particle. The system has two parameters α and c which depend on the electric characteristics of the particle and the ambient fluid. The parameter c is always positive by the laws of physics, but α can have either sign. We solve the time optimal control problem for this system when α≥0 and y(0) is arbitrarily prescribed. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Multi‐view 3‐D display employing a flat‐panel display with slanted pixel arrangement

Abstract— A flat‐panel display with a slanted subpixel arrangement has been developed for a multi‐view three‐dimensional (3‐D) display. A set of 3M × N subpixels (M × N subpixels for each R, G, and B color) corresponds to one of the cylindrical lenses, which constitutes a lenticular lens, to construct each 3‐D pixel of a multi‐view display that offers M × N views. Subpixels of the same color in each 3‐D pixel have different horizontal positions, and the R, G, and B subpixels are repeated in the horizontal direction. In addition, the ray‐emitting areas of the subpixels within a 3‐D pixel are continuous in the horizontal direction for each color. One of the vertical edges of each subpixel has the same horizontal position as the opposite vertical edge of another subpixel of the same color. Cross‐talk among viewing zones is theoretically zero. This structure is suitable for providing a large number of views. A liquid‐crystal panel having this slanted subpixel arrangement was fabricated to construct a mobile 3‐D display with 16 views and a 3‐D resolution of 256 × 192. A 3‐D pixel is comprised of 12 × 4 subpixels (M = 4 and N = 4). The screen size was 2.57 in.