Evaluation of HDR tone‐mapping algorithms using a high‐dynamic‐range display to emulate real scenes

Abstract— Current HDR display technology approaches the dynamic‐range capabilities of the fully adapted human visual system. As such, this technology has potential for performing as a surrogate for real‐world scenes in the perceptual evaluation of high‐dynamic‐range (HDR) image‐reproduction algorithms that aim to map HDR scenes to the limited dynamic ranges available in typical display and print technology. Compared with direct image assessment in comparison with real‐world scenes, it is clear that use of HDR display technology has the benefit of simplicity in experimental design while maintaining the HDR of the original scene. To evaluate this potential application of HDR display technology, seven published versions of well‐known HDR tone‐mapping algorithms were benchmarked for perceptual rendering accuracy against each of four real‐world scenes constructed in the laboratory and against corresponding images on an HDR display. The results illustrate that visual assessments obtained from the HDR display and those obtained from real‐world scenes are in good agreement, validating the potential for HDR display technology as an evaluation tool in this context.     

A YC‐separation‐type projector: High dynamic range with double modulation

Abstract— An experimental projector that features double modulation to obtain high‐resolution (4096 × 2160 pixels) and high‐dynamic‐range images has been developed. Although a conventional projector contains three modulators for red, green, and blue and outputs light after combining the modulated light from these three sources, our projector has an additional modulator for luminance that modulates the combined RGB modulated light. It can display high‐resolution color images by combining three low‐resolution panels for chrominance modulation and one high‐resolution panel for luminance modulation. In addition, the dynamic range is dramatically improved because the double‐modulation scheme minimizes black levels in projected images. The projector demonstrates an extremely high dynamic range of 1.1 million to 1 and 10‐bit tone reproduction.     

Tone mapping to minimize visual sensation distortion considering brightness and local band‐limited contrast

We propose a tone‐mapping algorithm that minimizes the function that represents the visual sensation distortion that occurs after tone mapping. For the function, we consider both brightness and local band‐limited contrast to reduce darkening of images that have high dynamic range when they are displayed with conventional contrast‐based tone mapping using histogram on devices that have low dynamic range. By exploiting human visual characteristics, we simplify the problem and find a closed‐form solution that minimizes the function that represents distortion of visual sensation. In both subjective and objective evaluations, the proposed algorithm achieves a processed image that is most similar to the original image and has the best subjective image quality.     

A perceptually optimized mapping technique for display images

Liquid crystal displays (LCDs) are often viewed in the energy‐saving mode or under high ambient illumination. However, both these conditions compress the tonal dynamic range of the display device, resulting in undesirable visual perception effects. In this paper, we propose a local algorithm for improving the display image quality under either of these conditions. The proposed algorithm is based on a tone mapping technique, and it reproduces the image appearance to almost its original quality with a lower dynamic range. We also develop a more accurate definition of the image distortion, which takes into account the difference in pixel values to reduce the distortion significantly. By minimizing the differences in contrast and pixel intensity between the input and output images, the algorithm preserves the contrast while simultaneously providing brightness compensation. Simulation results show that the proposed algorithm can effectively maintain image quality while enabling power savings of 30%–50%.     

Ambient‐light‐adaptive image quality enhancement for full‐color e‐paper displays using a saturation‐based tone‐mapping method

Full‐color e‐paper displays that have a small color gamut encounter image tone distortions and contour artifacts in high‐saturation regions. To solve these issues, in this paper, we comprehensively measure the colorimetric responses of input image signals and demonstrate that the perceptual colorfulness in terms of chroma abnormally declines when the input saturation is beyond a certain value. Accordingly, saturation‐based tone‐mapping curves are developed to map the abnormal high saturation to the range that the display is able to normally render. By testing several test charts and natural images, the recoveries of the original image tones and the removals of the contour artifacts are experimentally verified. More important, by discussing how to conduct a database of tone‐mapping curves for different ambient lights and utilize the database for an unknown ambient light, the proposed method is proven to be completely ambient light adaptive.     

Evaluation of jerkiness of moving three‐dimensional images produced by high‐density directional display

Abstract— The jerkiness of moving three‐dimensional (3‐D) images produced by a high‐density directional display was studied. Under static viewing conditions in which subjects' heads did not move, jerkiness was more noticeable when moving 3‐D images were displayed in front of the display screen and was less noticeable when moving 3‐D images were displayed behind the screen. We found that the perception of jerkiness depended on the visual angular velocities of moving 3‐D images. Under dynamic viewing conditions in which subjects' heads were forced to move, when moving 3‐D images were displayed in front of the screen, jerkiness was less noticeable when the subjects' heads and 3‐D images moved in opposite directions and was more noticeable when they moved in the same direction. When moving 3‐D images were displayed behind the screen, jerkiness was less noticeable when subjects' heads and 3‐D images moved in the same direction and was more noticeable when they moved in opposite directions.     

A time‐sequential multi‐projector autostereoscopic display

Abstract— We describe a new 28‐view 25‐in. autostereoscopic display that combines both time‐sequential and multi‐projector technology. It is constructed from four time‐sequential subsystems, which abut behind a single ferroelectric liquid‐crystal shutter. The display has a resolution of 512 × 384 pixels in 24‐bit color. It allows multiple viewers to simultaneously view stereoscopic images without the need for special glasses or headgear.     

A touch‐sensitive display with embedded hydrogenated amorphous‐silicon photodetector arrays

Abstract— A new touch‐sensitive hydrogenated amorphous‐silicon (a‐Si:H) display with embedded optical sensor arrays is presented. The touch‐panel operation was successfully demonstrated by fabricating a prototype of a 16‐in. active‐matrix liquid‐crystal display (AMLCD). The proposed system, obviating the need for the extraction of information from the captured images in real time, provides the location of the finger touch. Due to the simple architecture of the system, the touch‐panel operation can be readily integrated within large‐area displays.     

Dual layered display that presents auto‐stereoscopic 3D images to multiple viewers in arbitrary positions

Dual layered display or also called tensor display that consists of two panels in a stack can present full‐parallax 3D images with high resolution and continuous motion parallax by reconstructing corresponding light ray field within a viewing angle. The depth range where the 3D images can be displayed with reasonable resolution, however, is limited around the panel stack. In this paper, we propose a dual layered display that can present stereoscopic images to multiple viewers located at arbitrary positions in observer space with high resolution and large depth range. Combined with the viewer tracking system, the proposed method provides a practical way to realize high‐resolution large‐depth auto‐stereoscopic 3D display for multiple observers without restriction on the observer position and the head orientation.     

High‐resolution autostereoscopic 3‐D projection display with a space‐dividing iris‐plane shutter

Abstract— A high‐resolution autostereoscopic 3‐D projection display with a polarization‐control space dividing the iris‐plane liquid‐crystal shutter is proposed. The polarization‐control iris‐plane shutter can control the direction of stereo images without reducing the image quality of the microdis‐play. This autostereoscopic 3‐D projection display is 2‐D/3‐D switchable and has a high resolution and high luminance. In addition, it has no cross‐talk between the left and right viewing zones, a simple structure, and the capability to show multi‐view images.     

A continuous‐viewing‐angle‐controllable liquid‐crystal display using a blue‐phase liquid crystal

Abstract— A continuous‐viewing‐angle‐controllable liquid‐crystal display (LCD) using a blue‐phase liquid crystal is proposed. To realize both wide‐viewing‐angle (WVA) mode and narrow‐viewing‐angle (NVA) mode with a single liquid‐crystal panel, each pixel is divided into a main pixel and a subpixel. The main pixel is for displaying images in both modes. The subpixel is for displaying images in WVA mode and controlling the viewing angle in NVA mode. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

一种亮度可控与细节保持的高动态范围图像色调映射方法

高动态范围(High dynamic range, HDR)图像通常需压缩其动态范围,以便于进行存储、传输、重现. 本文提出一种具有亮度可控与细节保持特性的HDR图像的全局色调映射方法.该方法对HDR图像 照度直方图进行裁剪与补偿,令色调映射后的低动态范围(Low dynamic range, LDR)图像仍能够保持原有的细节特性, 同时利用概率模型估算出输出LDR图像的亮度与标准差,进而调整直方图亮度区域的分配, 使得输出LDR图像的亮度接近用户设置的亮度,最后以分段直方图均衡的方法进行HDR色调映射处理. 仿真结果表明,该方法能对HDR图像动态范围进行合理的压缩映射,输出的LDR图像的亮度可由用户控制或自适应选择, 同时能保持图像的细节信息,令图像的主观视觉感受对比和谐.     

Projection‐type integral 3‐D display with distortion compensation

Abstract— Our research is aimed at developing a spatial‐imaging‐type integral three‐dimensional (3‐D) display based on an integral photography method using an extremely high‐resolution projector. One problem with the projection‐type integral 3‐D display is that geometrical distortion in projected elemental images causes spatial deformation of the displayed 3‐D image. In this study, a general relationship between the geometric distortion of elemental images and the spatial deformation of reconstructed 3‐D images were analyzed. A projection‐type integral 3‐D display with a distortion compensator which corrects the geometrical distortions of projected images in real‐time have been developed. The deformation of the displayed 3‐D images was significantly reduced by the distortion compensation, and the displayed 3‐D images had a resolution of 182 (H) × 140 (V) pixels and a viewing angle of 24.5°.     

PIN‐OLEDs for active‐matrix‐display use

Abstract— Novaled's PIN‐OLED® technology allows for highly efficient, temperature stable, and long‐lived OLEDs suited for a variety of display applications. This paper delivers an overview about Novaled's state of the art, including top‐ and bottom‐emitting structures. It is discussed how PIN‐OLEDs give rise to an increased manufacturing yield. The main focus of this paper is the development of white OLEDs for display use. When the RGBW color‐filter approach is used in combination with white OLEDs, the resulting full‐color OLED display is able to deliver high color quality and remain highly power efficient. For such a case, the manufacturing infrastructure of OLEDs for lighting can be used. We use tandem architectures, bottom‐ and top‐emission architectures, and developed specific high‐temperature stable OLED stacks. The importance of matching color coordinates of the white OLED and the targeted display white color point is of outstanding importance. Results have mainly been achieved under the German‐funded project CARO and the European‐funded project AMAZOLED.     

Stereoscopic 3‐D display with optical correction for the reduction of the discrepancy between accommodation and convergence

Abstract— This paper describes a method for reducing the discrepancy between accommodation and convergence when viewing stereoscopic 3‐D images. The method uses a newly developed stereoscopic 3‐D display system with a telecentric optical system and a mobile LCD. The examination of a mono‐focal lens showed that a correction lens having the appropriate refractive power and conditions for presenting stereoscopic 3‐D images clearly reduces the discrepancy between accommodation and convergence. The authors also developed a stereoscopic 3‐D display that uses dynamic optical correction to reduce the discrepancy between accommodation and convergence. The display equalizes the theoretical points of accommodation and convergence. The purpose of the development was to expand the regeneration range of a stereoscopic 3‐D image having the appropriate accommodation. An evaluation of the developed display showed that it resolves the discrepancy between convergence and accommodation.     

Resolution enhancement of integral‐imaging three‐dimensional display using directional elemental image projection

Abstract— A new approach to resolution enhancement of an integral‐imaging (II) three‐dimensional display using multi‐directional elemental images is proposed. The proposed method uses a special lens made up of nine pieces of a single Fresnel lens which are collected from different parts of the same lens. This composite lens is placed in front of the lens array such that it generates nine sets of directional elemental images to the lens array. These elemental images are overlapped on the lens array and produce nine point light sources per each elemental lens at different positions in the focal plane of the lens array. Nine sets of elemental images are projected by a high‐speed digital micromirror device and are tilted by a two‐dimensional scanning mirror system, maintaining the time‐multiplexing sequence for nine pieces of the composite lens. In this method, the concentration of the point light sources in the focal plane of the lens array is nine‐times higher, i.e., the distance between two adjacent point light sources is three times smaller than that for a conventional II display; hence, the resolution of three‐dimensional image is enhanced.     

Two‐parallax‐barriers‐based autostereoscopic liquid‐crystal display without cross‐talk

Abstract— An autostereoscopic liquid‐crystal display (LCD) consists of two parallax barriers and an LCD including a liquid‐crystal panel, and a backlight panel is proposed. Parallax barrier 1 is located between the backlight panel and the liquid‐crystal panel, and Parallax barrier 2 is located between the liquid‐crystal panel and viewers. The operation principle of the autostereoscopic display and the calculation equations for the parallax barriers are described in detail. The autostereoscopic LCD was developed and produces high‐quality stereoscopic images without cross‐talk at the optimal viewing distance and less cross‐talk than a conventional one based on one parallax barrier at other viewing distances.     

Practical implementation of a depth‐feeling‐enhanced two‐plane electro‐floating display system using three‐dimensional integral images

Abstract— Although there are numerous types of floating‐image display systems which can project three‐dimensional (3‐D) images into real space through a convex lens or a concave mirror, most of them provide only one image plane in space to the observer; therefore, they lack an in‐depth feeling. In order to enhance a real 3‐D feeling of floating images, a multi‐plane floating display is required. In this paper, a novel two‐plane electro‐floating display system using 3‐D integral images is proposed. One plane for the object image is provided by an electro‐floating display system, and the other plane for the background image is provided with the 3‐D integral imaging system. Consequently, the proposed two‐plane electro‐floating display system, having a 3‐D background, can provide floated images in front of background integral images resulting in a different perspective to the observer. To show the usefulness of the proposed system, experiments were carried out and their results are presented. In addition, the prototype was practically implemented and successfully tested.     

Spatial gamut mapping algorithms for cross‐display color reproduction

Abstract— Owing to the fast developments of computer networks and color imaging technologies, there is a tendency towards remote proofing in the printing or textile industries. More cases such as cross‐display color matching will occur in the future information society. The problems of color mismatching we usually find in cross‐display devices have been widely discussed today. In this paper, to achieve equivalent color matching between a sRGB monitor and an Adobe RGB monitor, the spatial gamut mapping algorithm (SGMA), which introduces sigmoidal tone mapping, multi‐mapping paths, and unsharp mask (USM) operation into a sRGB color‐management system, is proposed. According to the designs of USM locations, this proposed SGMA can be further developed into pre‐USM, post‐USM, and double‐USM types. Besides, two critical image characteristics, edge map and color histogram, are investigated to establish the relationship between image content and SGMA. The psychophysical experimental results show that double‐USM SGMA obtains better color matching than the other spatial types.     

Development of a 42‐in. 2‐D/3‐D switchable display using multi‐view technology for public‐information‐display applications

Abstract— A 42‐in. 2‐D/3‐D switchable display operating in a parallax‐barrier‐type system consisting of liquid‐crystal displays (LCDs) has been developed. The system displays 2‐D images in full resolution, without any degradation to the original 2‐D images, and 3‐D autostereoscopic images with resolutions higher than SVGA with wide viewing zones electrically controlled by the parallax‐barrier system. The system is intended for use in public‐information displays (PIDs), a booming field, and as displays for gaming, medical, and simulation applications.