Optimal Linear RGB-to-XYZ Mapping for Color Display Calibration

Color display calibration, in part, involves mapping input RGB values to corresponding output values in a standardized color space such as CIE XYZ. A linear model for RGB-to- XYZ mapping is based on a 3-by-3 linear transformation matrix T mapping data from (linearized) RGB to XYZ. Such a mapping is often determined by least squares regression on the difference between predicted and measured XYZ values. However, since displays are calibrated for viewing by human observers, it likely would be better to optimize relative to a perceptually uniform color space. Two new methods are proposed which optimize the total error relative to CIELAB or CIEDE2000. The first method uses weighted least squares with weights based on the rate of change of CIELAB coordinates as a function of change in XYZ. The second method uses Nedler-Mead nonlinear optimization to minimize directly in CIELAB or CIEDE200. Experiments based on calibrating 2 CRT monitors, 3 LCD monitors and 2 LCD projectors show significantly better results than the standard least squares calibration

Unsynchronized 4D Barcodes

We present a novel technique for optical data transfer between public displays and mobile devices based on unsynchronized 4D barcodes. We assume that no direct (electromagnetic or other) connection between the devices can exist. Time-multiplexed, 2D color barcodes are displayed on screens and recorded with camera equipped mobile phones. This allows to transmit information optically between both devices. Our approach maximizes the data throughput and the robustness of the barcode recognition, while no immediate synchronization exists. Although the transfer rate is much smaller than it can be achieved with electromagnetic techniques (e.g., Bluetooth or WiFi), we envision to apply such a technique wherever no direct connection is available. 4D barcodes can, for instance, be integrated into public web-pages, movie sequences or advertisement presentations, and they encode and transmit more information than possible with single 2D or 3D barcodes

An Investigation of Soft Proof to Print Agreement under Bright Surround

Color quality is a vital concern in the printing industry. The ability of an LCD monitor to accurately and consistently predict the color of a printed work is often in doubt. According to Chung (2005), color reproduction technology is different for soft proofing and hard proofing which could lead a layman to believe that the two technologies may not produce the same result. Nevertheless, it is still possible for both reproduction technologies to achieve a metameric match which gives the same perceived color sensation between display and print. ISO/CD 14681 provides guidelines for creating the conditions required to perform soft proofing. This standard builds on ISO 12646 requirements for monitors and introduces a new softproofing environment (lightbooth with integrated monitor) to better meet the needs of industrial users. The ISO 14681 integrated viewing environment removes one important obstacle to achieving print to softproof match, i.e., the problem of simultaneous color contrast inherent in using a dim monitor surround with a bright paper viewing condition for soft proofing. Thus, the first objective of this research was to assess print to softproof visual match in the ISO 14681 integrated viewing environment. Nevertheless, even in this environment, inconsistency between paper white and monitor white remains as the next major obstacle to achieving consistent print to softproof match. Thus, a second objective of this research is to develop a methodology for matching the monitor\u27s white point to the white point of the paper viewed in an ISO 14681 integrated viewing environment. The methodology for fulfilling these objectives began with the creation of the hardware/software environment required to support experimentation. This environment consisted of a 24-inch EIZO CG242W display conforming to ISO 12646 and an integrated viewing environment conforming to the P2 specification in ISO 3664:2009. Two ISO 12647-2 conformed press sheets were prepared and became the reference for the experiment. The researcher next developed a methodology for matching the monitor white point to the white point of the paper under the P2 viewing condition. Finally, a panel of observers was used to compare print to softproof match for four display conditions in a paired comparison experiment. The results of the experiment were highly encouraging. The mismatch between monitor and paper white points, as measured by the sum of the differences in R, G, and B counts between the monitor and the paper, was reduced by nearly 90%. In addition, the paired comparison experiment demonstrated that the use of a custom monitor white point and optimized monitor gamma outperformed the use of standard D65 and D50 white points with the same optimized gamma at a .05 level of significance

Differentiable Display Photometric Stereo

Photometric stereo leverages variations in illumination conditions to reconstruct per-pixel surface normals. The concept of display photometric stereo, which employs a conventional monitor as an illumination source, has the potential to overcome limitations often encountered in bulky and difficult-to-use conventional setups. In this paper, we introduce Differentiable Display Photometric Stereo (DDPS), a method designed to achieve high-fidelity normal reconstruction using an off-the-shelf monitor and camera. DDPS addresses a critical yet often neglected challenge in photometric stereo: the optimization of display patterns for enhanced normal reconstruction. We present a differentiable framework that couples basis-illumination image formation with a photometric-stereo reconstruction method. This facilitates the learning of display patterns that leads to high-quality normal reconstruction through automatic differentiation. Addressing the synthetic-real domain gap inherent in end-to-end optimization, we propose the use of a real-world photometric-stereo training dataset composed of 3D-printed objects. Moreover, to reduce the ill-posed nature of photometric stereo, we exploit the linearly polarized light emitted from the monitor to optically separate diffuse and specular reflections in the captured images. We demonstrate that DDPS allows for learning display patterns optimized for a target configuration and is robust to initialization. We assess DDPS on 3D-printed objects with ground-truth normals and diverse real-world objects, validating that DDPS enables effective photometric-stereo reconstruction

Visual Performance under Varying Illumination Conditions while using an Indigenously Developed Wrist Wearable Computer

Ambient illumination conditions have significant impact on users’ visual performance while carrying out onscreen reading tasks on visual display units, especially smaller screen sizes. Present study assessed the visual performance responses of different ambient illumination levels during onscreen reading on Wrist Wearable Computer (WWC) developed for the command-control-communication between the control room and the soldiers operating in remote locations. Ten (10) Indian Infantry soldiers performed two different types of loud reading tasks on the display of WWC under three different ambient illumination (mean ±SEM) conditions namely, Indoor controlled (450.00±10.00 lx), Outdoor daylight (11818.7±582.91 lx) and Indoor dark (0.12±0.03 lx) environments. While reading, participants wore an eye tracking glass which recorded the eye movement responses. Visualisation techniques were used to predict the association of illumination levelof surrounding with visual performance of the user. Subjective legibility rating was also applied to understand participants’ preferences towards physical attributes of the onscreen information and illumination level. Results indicated that illumination had a significant effect on eye movement parameters like fixation frequency, fixation duration and scanpath length while completing the tasks. Overall, participants performed better under indoor controlled illumination conditions in terms of fixation profile and scanpath length, apart from improved subjective legibility ratings as compared to other two illumination conditions. Future research attempts need to be directed towards the optimum performance of the display across wide range of ambient illumination conditions and to establish how the display of indigenously developed wearable computer performs in comparison to other such displays available across the globe

A Compressive Multi-Mode Superresolution Display

Compressive displays are an emerging technology exploring the co-design of new optical device configurations and compressive computation. Previously, research has shown how to improve the dynamic range of displays and facilitate high-quality light field or glasses-free 3D image synthesis. In this paper, we introduce a new multi-mode compressive display architecture that supports switching between 3D and high dynamic range (HDR) modes as well as a new super-resolution mode. The proposed hardware consists of readily-available components and is driven by a novel splitting algorithm that computes the pixel states from a target high-resolution image. In effect, the display pixels present a compressed representation of the target image that is perceived as a single, high resolution image.Comment: Technical repor

Construction of a Three-sided Immersive Telecollaboration System

In this article the setup and working principle of a new telecollaboration system “blue-c” is described. This system is an attempt to meet the rising expectations from industry of an IT-supported telecollaboration system. One basic requirement is that a three-dimensional representation of objects be possible together with threedimensional representations of the remote users. Since gesture and mimicry represent an important information channel during a discussion, a realistic 3D video representation is used instead of simple animated avatars. A simultaneous projection and image acquisition of the user in a telecollaboration system is necessary to allow simultaneous work of all team members. Thus, in the introduced system, problems had to be overcome such as providing, simultaneously, illumination for the image acquisition by the cameras and darkness for a bright projection to be seen by the user. A new approach was taken to integrate the cameras into the system by placing them behind active projection walls, which can be switched from transparent to opaque electrically. Unlike other systems, the cameras are therefore not visible to the user, who thus behaves more naturally. In addition, since the cameras are placed outside of the projection room, there is more space to move inside the immersive environment. The article describes the technology and functionality of the system, as well as the gathered experiences.ISSN:1054-7460ISSN:1531-326

The effects of blue light from digital displays on visual fatigue

With the ever-increasing viewing time of digital displays, the potential effects of blue light emitted from these displays on eye health and eye fatigue are a real concern. This study presents a literature review of six laboratory studies conducted between 2014 and 2022 on the effect of using filters to attenuate the harmful effects of blue light. The review delves into smartphone and computer screen effects, recent literature reviews on blue light, and potential hazards associated with short-wavelength light. Although the majority of the studies recommended blue light filters, only three of the six laboratory studies (Shi et al. 2021, Tu et al. 2021, Lin et al. 2017) found significant positive effects. A pilot study was conducted with six participants, focusing on the immediate effects of blue light exposure from an 18-inch screen of a laptop computer, while playing a graphic-based and a text-based game with three filter conditions, no-filter, an eyeglass filter, and a digital filter. Eye fatigue symptoms of tired eyes, sore eyes, dry eyes, and blurred vision showed a reduction of perceived ratings when blue light filters were used. Symptoms of tired eyes, and dry eyes reached a significant level of p-value ,\u3c 0.5 improvement over no filter. The digital filter, which has not been tested before for computer screens, provided a statistically significantly better rating than the eyeglass filter. While the results suggest an improvement for those using blue light filter technologies and may help to advocate for more blue light blocking technology in workplace design, the overall conclusion underscores the ongoing need for comprehensive research, considering limitations such as the small sample size of the pilot study and the absence of long-term effects research

액정기반 발광형 디스플레이를 위한 용액공정 내재형 편광판에 관한 연구

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2020. 8. 이신두.Recently, the advancement of the liquid crystal display (LCD) technology has greatly focused on the clear image quality together with the natural color. According to the demand for the image quality, the in-cell polarizers have been attracted much attention owing to the advantages of improving the contrast ratio and reducing the thickness of LCD. In this work, we proposed the QD-based emissive LCD with the in-cell polarizer composed of dichroic dyes. The in-cell polarizer was fabricated through the solution-processing of a dichroic dye solution. The QD layer was constructed on the inner surface of the top substrate, and the in-cell polarizer was subsequently prepared on the QD layer to prevent the depolarization of the emission light and the degradation of the QDs. The intensity of the incident light for exciting QDs was modulated by the phase retardation through the LC layer, depending on the magnitude of the applied voltage. This leads directly to the modulation of the emission spectra of QDs with the color gamut extended to about 80 % of the BT.2020 standard. The architecture based on the in-cell polarizer will provide a simple and viable method of constructing the QD-based emissive LCD with high color purity in a cost-effective manner.최근 액정 디스플레이(LCD) 기술들은 자연스러운 색상과 더불어 선명한 화질을 중심으로 크게 발전했다. 고화질 영상에 대한 수요와 함께, 내재형 편광판 (in-cell polarizer)는 대조율 향상과 LCD 두께 감소라는 다양한 장점들로 인해 더 많은 관심을 끌었다. 본 연구에서는 이색성 염료로 구성된, 내재형 편광판를 적용한 양자점 기반 광 발광 액정 디스플레이를 제안하였다. 양자점 층은 상단 기판의 내부 표면에 구성되었고, 이후 양자점 층에 내재형 편광판를 도입하여 입사광의 편광상태를 유지하고 양자점의 성능 저하를 방지하였다. 내재형 편광판은 용액 공정을 통해 이색성 염료를 정렬하여 제작되었다. 양자점 광 발광을 위한 입사광의 세기는 적용된 전압의 세기에 따라 액정 셀을 통한 위상 지연에 의해 변조되었다. 이는 색 영역이 BT.2020 표준의 약 80%까지 확장된 높은 색 순도를 보여준다. 내재형 편광판에 기반한 액정 디스플레이 구조는 비용-효율적인 방법으로 높은 색 순도를 가진 양자점 기반 광 발광 액정 디스플레이를 구성하는 간단하고 실행가능한 방법을 제공할 것이다.1. Introduction 1 1.1. Overview of liquid crystal-based displays 1 1.1.1. Main LCD Modes 3 1.1.2. Types of backlight unit for LCDs 9 1.2. Outline of thesis 15 2. LCD with QD color filters 16 2.1. Types of polarizers 16 2.2. Architecture of QD-LCD with in-cell polarizer 19 3. Experiments 24 3.1. Fabrication of photoluminescence QD patterns 24 3.2. Dichroic dye-based in-cell polarizer 26 3.3. Solution-processed in-cell polarizer with QD-based LC cell 29 3.4. Measurements of optical and photoluminescence characteristics 30 4. Results and Discussion 31 4.1. Analysis of polarizing characteristics of in-cell polarizer 31 4.2. Photoluminescence characteristics of QD-based LC cell with in-cell polarizer 34 4.3. Microscopic images of QD-based LC cell with in-cell polarizer 35 5. Conclusion 38 Bibliography 39 국문 초록 43Maste