Accurate Color Reproduction Research Articles

A comparative analysis of machine learning methods for display characterization

This paper explores the application of various machine-learning methods for characterizing displays of technologies LCD, OLED, and QLED to achieve accurate color reproduction. These models are formed from input (device-dependent RGB data) and output (device-independent XYZ coordinates) data obtained from three different displays. Training and test datasets are built using RGB data measured directly from the displays and corresponding XYZ coordinates measured with a high-precision colorimeter. A key aspect of this research is the application fuzzy inference systems for building interpretable models. These models offer the advantage of not only achieving good performance in color reproduction, but also providing physical insights into the relationships between the RGB inputs and the resulting XYZ outputs. This interpretability allows for a deeper understanding of the display’s behavior. Furthermore, we compare the performance of fuzzy models with other popular machine-learning approaches, including those based on neural networks and decision trees. By evaluating the strengths and weaknesses of each method, we aim to identify the most effective approach for display characterization. The effectiveness of each method is assessed by its ability to accurately reproduce and display colors, as measured by the ΔE00 visual error metric. Our findings indicate that the Fuzzy Modeling and Identification (FMID) method is particularly effective, allowing for an optimal balance between high accuracy and interpretability. Its competitive performance across all display types, combined with its valuable interpretability, provides insights for potential future calibration and optimization strategies. The results will shed light on whether machine learning methods offer an advantage over traditional physical models, particularly in scenarios with limited data. Additionally, the study will contribute to the understanding of the interpretability benefits offered by fuzzy inference systems in the context of LCD display characterization.

Inkjet‐printed quantum dot light‐emitting diodes: Development and challenges for display applications

AbstractQuantum dot (QD) technology is rapidly advancing and draws much attention for display applications where accurate and vibrant color reproduction is highly required. Currently, significant research is being conducted in developing quantum dot light‐emitting diode (QD‐LED) as next‐generation displays. QD‐LEDs offer several advantages, including high color purity, wide color gamut, and lower manufacturing costs. Recent advancements in QD synthesis and device engineering have significantly improved the performance of QD‐LEDs, but several challenges must be addressed for the successful commercialization. In this article, we provide an overview of QD‐LED developments and key issues that are required to be solved for realizing practical inkjet‐printed QD‐LED displays.

Introducing a novel approach to dental color reproduction using AI technology.

This article aims to describe a systematic method for tooth color reproduction with ceramics restorations employing artificial intelligence (AI) software named Matisse. It provides a comprehensive analysis of the entire process, beginning with shade-taking and extending to ceramic application in a complex clinical case in the anterior region-specifically, a single central restoration supported by an implant. The clinical case presented highlights the potential of Matisse software for generating ceramic (inSync-Jensen Dental, USA) and staining (Miyo-Jensen Dental, USA) recipes over a zirconia abutment (Katana-Noritake Dental, Japan). This approach achieves an optimal single central restoration utilizing CAD-CAM and layering techniques. The systematic method employing the Matisse software achieved accurate color reproduction for a single central restoration supported by an implant. This result was achieved by the dental ceramist within the first attempt and without seeing the patient in the entire process. The Matisse AI-assisted protocol offers a systematic and scientifically grounded method for color reproduction in dentistry for indirect restorations.

FPGA-based control system for real-time driving of UHD Micro-LED display with color calibration

Micro-LED technology offers numerous advantages, including high brightness, low power consumption, and superior color performance. However, driving micro LED displays requires complex control algorithms and high-speed data processing. To address these challenges, this paper presents the development of a real-time FPGA-based control system for a 68-inch 4K/60Hz micro-LED display. The objective of this project was to create a high-performance control system capable of driving the micro-LED display with precise color accuracy, supporting 10-bit color depth for enhanced color rendition. One crucial aspect of the system is color calibration, which ensures accurate color reproduction across the display, maintaining consistent and vibrant colors. By incorporating advanced color calibration techniques, the system achieves excellent color consistency and fidelity, providing a visually stunning viewing experience. Moreover, the system incorporates hot plug functionality, allowing for seamless reconnection of the display after Ethernet disconnection. This feature ensures uninterrupted operation and enhances user experience. In FPGA design, the proposed system demonstrates the feasibility and effectiveness of real-time control in driving micro-LED displays, offering improved color performance and reliable operation in various applications.

Improving Accuracy of Color Reproduction on Mobile Displays

Improving Accuracy of Color Reproduction on Mobile Displays

Colour reproduction evaluation of whole-slide imaging scanners for digital pathology

ABSTRACT Digital pathology using whole-slide imaging (WSI) scanners aids pathologists challenged by diagnostic volume and novel diagnostic methods. Colour reproducibility of WSI scanners is crucial for accurate digital diagnoses. We propose an objective and quantitative method for evaluating colour reproduction in digital images of pathological specimens from two perspectives: true colour value reproduction and colour discrimination. We define 57 critical features for evaluation, extract tissue structures, and establish diagnostic criteria. Our method is unique and useful for clinical use. We tested a prototype scanner, and it satisfied all criteria for true colour value reproduction (all the colour samples corresponding to the selected tissue evaluation points were experimentally within the acceptable range) and colour discrimination (the colour difference ΔE2000 calculated from the corresponding colour sample combinations exceeded the lower permissible limit for the selected discrimination points). This evaluation method and WSI scanner can contribute to accurate colour reproduction in digital pathology.

Colorimetric characterization of multispectral imaging systems for visualization of historical artifacts

Multispectral imaging has long been used in the study of cultural heritage artifacts, particularly manuscripts with low-contrast text. The goal of multispectral imaging systems has largely been to enhance the text by imaging outside the spectral response of the human visual system and by applying various image processing techniques. However, there is a desire to use multispectral images for high quality, true color rendering of the artifacts as well. We use two multispectral imaging systems in this work. One of them is the Multispectral Imaging System for the study of Historical Artifacts (MISHA) which has been demonstrated to have significant utility at a lower cost and better ease of use compared to commercially available systems. This system was specifically designed and built for the purpose of imaging artifacts, particularly manuscripts and works on paper with illegible text due to deterioration and other environmental causes. Given this goal of “discovering” low-contrast text (and other features) on planar objects, the system has not been optimized for color reproduction purposes. The second system is a commercially available MegaVision EVTM Spectral Imaging System. This system is also used for cultural heritage imaging. In this work, we develop an approach to colorimetrically characterize these cameras and illumination systems, adding an option for accurate color reproduction to their capabilities. To do this, we present two different approaches. The first approach we call the Color Transformation Method. Here we use a Macbeth ColorChecker to first linearize the camera photometric response, and then find a linear matrix transformation from the camera response to CIEXYZ tristimulus values. The second approach we call the Illuminant Method. Here we consider each output by the camera as a reflectance factor value at the known wavelength of a narrowband illuminator. We then convert these values to the color of the object in terms of CIEXYZ tristimulus values. We show that the Color Transformation Method using a Macbeth ColorChecker leads to a more accurate result. Meanwhile, the Illuminant Method is much simpler and produces acceptable results, particularly considering accurate color reproduction was not a goal in designing the MISHA camera system. The same methods are applied to both imaging systems to show the robustness and applicability of the approaches developed herein to other imaging systems. Results are shown for both quantitative calibration targets as well as artifacts of interest to the field of cultural heritage studies. It is worth noting that we are not comparing the two imaging systems overall or the color processing software available from MegaVision. Rather, we simply show that the two approaches developed here are applicable to different multispectral imaging systems, from a very cost-effective system, i.e., MISHA to a more expensive one, i.e., MegaVision.

High-fidelity color characterization in virtual reality across head mounted displays, game engines, and materials.

We present a comprehensive colorimetric analysis of three head mounted displays (HMDs) - HTC Vive Pro Eye, Pimax 8K X DMAS, and Varjo Aero - focusing on their color calibration and uniformity across different game engines (Unity and Unreal) and for different materials/shaders. We developed a robust methodology combining hardware and software tools, including spectroradiometry and imaging colorimetry, to characterize and calibrate these HMDs for accurate color reproduction. The study showcases substantial advancements in colorimetric accuracy, with a reduction in the average deltaE00 of 90% or more across all tested HMDs and conditions. This level of color reproduction quality is below human discrimination thresholds, ensuring that any color inaccuracies remain imperceptible to the human eye. We also identified key areas for improvement, particularly in display uniformity, which could impact peripheral color reproduction. By making our tools and code publicly available, this study aims to facilitate future research and development in virtual reality (VR) technology, emphasizing the importance of color fidelity in virtual environments. The new insight enabled by our work is the extension and application of a traditional calibration method to currently available HMDs.

Estimation of color reproduction accuracy using a tunable source based on an acoustic-optical tunable filter

Estimation of color reproduction accuracy using a tunable source based on an acoustic-optical tunable filter

Color arrestor pixels for high-fidelity, high-sensitivity imaging sensors

Abstract Silicon is the dominant material in complementary metal-oxide-semiconductor (CMOS) imaging devices because of its outstanding electrical and optical properties, well-established fabrication methods, and abundance in nature. However, with the ongoing trend toward electronic miniaturization, which demands smaller pixel sizes in CMOS image sensors, issues, such as crosstalk and reduced optical efficiency, have become critical. These problems stem from the intrinsic properties of Si, particularly its low absorption in the long wavelength range of the visible spectrum, which makes it difficult to devise effective solutions unless the material itself is changed. Recent advances in optical metasurfaces have offered new possibilities for solving these problems. In this study, we propose color arrestor pixels (CAPs) as a new class of color image sensors whose composite spectral responses directly mimic those of the human eye. The key idea is to employ linearly independent combinations of standardized color matching functions. These new basis functions allow our device to reproduce colors more accurately than the currently available image sensors with red-green-blue filters or other metasurface-based sensors, demonstrating an average CIEDE2000 color difference value of only 1.79 when evaluating 24 colors from the Gretag-Macbeth chart under standard illuminant D65. Owing to their high fidelity to the human eye response, CAPs consistently exhibit exceptional color reproduction accuracy under various spectral illumination compositions. With a small footprint of 860 nm height and 221 nm full-color pixel pitch, the CAPs demonstrated high absorption efficiencies of 79 %, 81 %, and 63 % at wavelengths of 452 nm, 544 nm, and 603 nm, respectively, and good angular tolerance. With such a high density of pixels efficiently capturing accurate colors, CAPs present a new direction for optical image sensor research and their applications.

Quality of Colour Rendering in Photographic Scenes Illuminated by Light Sources with Light-Shaping Attachments

In both commercial and scientific photography, achieving accurate colour reproduction is essential. This study investigates the influence of light-shaping attachments on colour rendering indices (CRIs) under various lighting conditions. Through 180 measurements of different lighting combinations, statistical analysis reveals significant interactions between light sources, modifiers, and CRI test colour samples (TCS). Snoots consistently produce superior CRIs, while interactions between light sources and other light modifiers vary, affecting CRIs differently based on spectral distributions and material properties of the modifiers. Combining light sources and modifiers from the same manufacturer is found to enhance colour accuracy. These findings offer valuable insights for photographers, highlighting the importance of understanding light properties and light-shaping attachment effects on colour rendition. By informing best practices, this research contributes to achieving high-quality photographs across commercial and scientific domains, ensuring both accurate data representation and visually appealing results.

Charge Management Enables Efficient Spontaneous Chromatic Adaptation Bipolar Photodetector.

Solution-processed photodetectors have emerged as promising candidates for next-generation of visible-near infrared (vis-NIR) photodetectors. This is attributed to their ease of processing, compatibility with flexible substrates, and the ability to tune their detection properties by integrating complementary photoresponsive semiconductors. However, the limited performance continues to hinder their further development, primarily influenced by the difference of charge transport properties between perovskite and organic semiconductors. In this work, a perovskite-organic bipolar photodetectors (PDs) is introduced with multispectral responsivity, achieved by effectively managing charges in perovskite and a ternary organic heterojunction. The ternary heterojunction, incorporating a designed NIR guest acceptor, exhibits a faster charge transfer rate and longer carrier diffusion length than the binary heterojunction. By achieving a more balanced carrier dynamic between the perovskite and organic components, the PD achieves a low dark current of 3.74nAcm-2 at -0.2V, a fast response speed of <10 µs, and a detectivity of exceeding 1012 Jones. Furthermore, a bioinspired retinotopic system for spontaneous chromatic adaptation is achieved without any optical filter. This charge management strategy opens up possibilities for surpassing the limitations of photodetection and enables the realization of high-purity, compact image sensors with exceptional spatial resolution and accurate color reproduction.

A SEMI-AUTOMATED METHODOLOGY FOR 3D IMAGING OF LARGE VAULTED CEILING PAINTINGS

Abstract. 3D imaging of large painted and vaulted historic ceilings offers many challenges, including those due to complex small and large-scale geometry, environmental conditions and limited access. In this paper we introduce CHAPI (Cultural Heritage Automated Photogrammetric Imaging), a low cost solution to these problems which provides an efficient, semi-automated method of capturing large vaulted ceiling paintings in high detail, with a consistent photogrammetric network and in limited time. We will present and examine two different case studies from the Plafond3D project, the baroque ceiling paintings of the Schloss Rheinsberg Spiegelsaal (mirror room) and the Ansbach Residence Festsaal (great hall/ballroom). The paper will examine the particular challenges of capturing large painted areas with accurate colour and geometric reproduction, and suggest how the photogrammetric recording and reconstruction process of ceilings can be optimised for large rooms. This paper also gives technical specifications and Open Access Code for the CHAPI build.

Color Reproduction by Multi-Wavelength Bragg Diffraction of White Light.

Accurate color reproduction is highly important in multiple industrial, biomedical and scientific applications. Versatile and tunable light sources with high color-rendering quality are very much in demand. In this study, we demonstrate the feasibility of multi-wavelength Bragg diffraction of light for this task. Tuning the frequencies and amplitudes of bulk acoustic waves in the birefringent crystal demonstrates high precision in setting the number, wavelengths and intensities of the monochromatic components necessary to reproduce a specific color assigned according to its coordinates in the CIE XYZ 1931 space. We assembled a setup based on multi-bandpass acousto-optic (AO) filtration of white light and verified the reproduced color balance in multiple experiments. The proposed approach delivers almost full coverage of the CIE XYZ 1931 space and facilitates building compact color reproduction systems (CRSs) for various purposes.

ВІДПОВІДНІСТЬ ВІДТВОРЕННЯ КОЛЬОРУ НА МОНІТОРІ ПРИ ПРОЕКТУВАННІ АРХІТЕКТУРНИХ ТА ДИЗАЙНЕРСЬКИХ ОБ’ЄКТІВ

The paper substantiates the importance of appropriate color reproduction when designing architectural and designer objects in computer systems. Most studies of color in architecture and design are related to its characteristics, lighting conditions, the influence of the source, environment, visual perception, etc., rather than the accuracy of its reproduction. The color selected by the designer and the customer from the standard palettes may be distorted when displayed on a monitor in the software. Color deviations from the palette samples can be significant and visually noticeable on the monitor, which is undesirable. The article compares two monitors in terms of color reproduction quality. For this purpose, was described software and tool methods for configuring monitors. The monitors were calibrated and profiled using an instrumental method using a spectrophotometer. The obtained profiles were analyzed in comparison with sRGB and the color differences of the test scale fields were analyzed by color difference ∆E 2000. The suitability of each monitor for project visualization was determined based on monitor calibration and profiling results. The authors compared the coverage of sRGB, Adobe RGB, and ProPhoto RGB and gave practical recommendations for choosing a working profile when working and controlling color by monitor. The algorithms for calculating and using unreproducible colors were analyzed when switching from a larger color gamut to a smaller one. The article also includes practical recommendations for preparing the monitor for working with color. Therefore, it is possible to improve the color reproduction accuracy and get the color close to standard palettes on the monitor by calibrating and profiling it. The process of setting up a monitor is especially relevant in the case of preparing projects in digital form with their visualization in software.

전면 카메라로 촬영한 얼굴 사진의 선호도 분석 - 삼성전자 Galaxy S22 Ultra와 Apple iPhone 13 ProMax를 중심으로

The use of the front camera, or the ‘selfie camera’ is increasing among the young generation. The act of taking self-photos is not only to capture the moment, but also to enhance ones’ self-esteem and even as a way of self-branding. The current camera manufacturers are aiming for high specification and high performance of the camera. However, accurate color reproduction of the camera may not correlate with high satisfaction of the users. This study focuses on the selfie camera of the two representative smartphone brands, Samsung Galaxy S22 Ultra and Apple iPhone 13 Pro Max. The study asked the participants to take selfies under four different lighting environments with three colored backgrounds using the two smartphones. Participants evaluated preference scores for each portrait on the two smartphones in the range of 7, where 1 is the least preferred and 7 for the most preferred. The results for the preference of the selfie camera showed that the average preference score was higher for Samsung Galaxy S22 Ultra than Apple iPhone 13 Pro Max by 0.44. The preference for the two displays were very similar with difference of only 0.01. For the background color, light pink and light yellow was preferred for Samsung Galaxy S22 Ultra but dark blue was preferred for Apple iPhone 13 Pro Max. Relatively dark environment with low color temperature was referred for both smartphones. The interview revealed that the users preferred Samsung Galaxy S22 Ultra for the skin color and less detailed expression for the skin texture. Users who preferred Apple iPhone 13 Pro Max liked the captured atmosphere of the photo, especially at low luminance low color temperature environment. This study places the significance on understanding how the users evaluate the photos taken by the selfie camera.

Comparative Analysis of Color Simulation between Offset Printing and Inkjet Printing

This paper presents an analysis of the color output capability and accuracy of an inkjet printer, specifically the Epson L1800, used for simulating offset printing. The colorimetric values of the printer's cyan, magenta, yellow, and black primaries were found to be different from those used in offset printing, and attempts to adjust the maximal output ink level and tone curve were not able to fully eliminate the differences. As a result, the Epson printer's color gamut did not completely meet the requirements of offset printing, particularly in terms of high-chroma colors. However, the printer calibration process improved the printer's capacity and overall color output accuracy within the offset color gamut, with significant color differences only occurring for colors outside the printer's gamut. This study provides insights into the challenges and limitations of using an inkjet printer for simulating offset printing and highlights the importance of printer calibration for achieving accurate color reproduction in this context. Further research may focus on developing more advanced calibration methods or exploring alternative printer technologies to improve the accuracy of offset printing simulation using inkjet printers.

Developing a Quality Evaluation System for Color Reproduction of Color 3D Printing Based on MATLAB Multi-Metrics.

Color 3D printing has been widely used in many fields such as cultural, medical, industrial, and food. The color reproduction accuracy of 3D printed products in these fields is becoming increasingly demanding, which requires more reproduction methods and practical tools. At present, most color 3D printing devices use one quantitative index, that is, color difference, to directly predict the color reproduction quality. However, this single quantitative index is not optimal for the curved surface of 3D printed color objects. Based on color evaluation principles, in this study, five new quantitative metrics consisting of color gamut comparison index, color SSIM index, color FSIM index, iCID index, and subjective scaling values are proposed for comparison, and the corresponding GUI design and code implementation of new color quality evaluation system are performed by MATLAB. Moreover, the comprehensive color assessment of color 3D printed products is confirmed by utilizing standard image acquisition and microscopic imaging methods that are not limited to printing materials and sampling locations. The operation of this system is validated to provide interactivity, simplicity and high efficiency. As a result, the system can provide new valuable feedback for color separation and output calibration of color 3D printing devices.

Study of color reproduction in pigment digital printing

In pigment ink digital printing, the color difference between the original and the printed product can be visible due to the varied color gamut of devices and the impact of fabric characteristics on the color-presenting effect. To improve the color reproduction accuracy of digital printing, two methods, the full-process optimized (FPO) method and the neural network aided original adjustment (NNAOA) method, were proposed to reduce printing color difference during the color-transferring process. The FPO method, based on accounting for the fabric type and the characteristics of the printing machine, was proposed by optimizing the printing parameter settings in the color management process. Here, the optimal single-channel ink limit was determined and dot gain was compensated using the inverse function correction method, and then the International Color Consortium profile was generated. After using the FPO method, the color difference between the printed sample and the original was reduced from 20.8 to 5.254 compared with performing the original color management. To reduce the reliance on personal experience in color adjustment, the NNAOA method was proposed and implemented for 20 color patches with the largest color differences in the FPO method, allowing the color of the originals to be adjusted with the establishment of the general regression neural network model. This method predicted the input CMYK values of the original using measured L*a*b* values for the printed sample. The results showed that the color difference of the 20 color patches was reduced from 8.54 to 6.60. Consequently, both methods offered distinguishable improvements in the color reproduction effect.

Affordable Spectral Measurements of Translucent Materials

We present a spectral measurement approach for the bulk optical properties of translucent materials using only low-cost components. We focus on the translucent inks used in full-color 3D printing, and develop a technique with a high spectral resolution, which is important for accurate color reproduction. We enable this by developing a new acquisition technique for the three unknown material parameters, namely, the absorption and scattering coefficients, and its phase function anisotropy factor, that only requires three point measurements with a spectrometer. In essence, our technique is based on us finding a three-dimensional appearance map , computed using Monte Carlo rendering, that allows the conversion between the three observables and the material parameters. Our measurement setup works without laboratory equipment or expensive optical components. We validate our results on a 3D printed color checker with various ink combinations. Our work paves a path for more accurate appearance modeling and fabrication even for low-budget environments or affordable embedding into other devices.