Colorimetric Performance Research Articles

Principal Component Analysis of Multi-Pigment Scenario in Full-Color Electrophoretic Display

In this paper, we present a methodology to characterize the colorimetric performance of a full-color electrophoretic display (EPD) with multiple pigment formation. We use the principal component analysis to formulate the composite hybrid color-mixing system by using a single eigen-spectral component for each sub-pixel channel. Proposed model was validated to predict the chromatic features with high accuracy (ΔE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVE_CIEDE2000</sub> <;0.2) for both micro-cup type and micro-encapsulated type EPD samples. This study is effective to uncover the underlying physical features from only colorant-mixture information in a novel color system.

Reconstruction of total radiance spectra of fluorescent samples by means of nonlinear principal component analysis

Nonlinear principal component analysis (NLPCA) was used for compression and reconstruction of the total radiance factors (TRFs) of fluorescent samples. The spectral dataset included a total of 358 fluorescent reflectance spectra in the visible range of the spectrum. Spectral data compression was followed by extracting the parameterized nonlinear manifolds using the NLPCA technique. To compare the performance of NLPCA-based compression with the linear method, the orthonormal feature vectors of the dataset were also extracted by the linear PCA. The spectral performance of NLPCA and PCA-based compression approaches was assessed by the root mean square error and the goodness-fitting coefficient between the real and the reconstructed spectra. The percentages of feasible spectra by each method, i.e., those with nonnegative TRFs, were also reported as other criteria for the evaluation of methods. Furthermore, the colorimetric performance of methods were appraised by the measuring the CIELAB 1976 color difference values between the actual and reconstructed spectra under illuminants D65 and A and the 1964 standard observer. The NLPCA-based compression method performed significantly better than the standard PCA-based technique particularly in the lower dimensional spaces of the spectral radiance factors of fluorescent colors.

P‐79: Principal Component Analysis on Characterizing Full‐Color Electrophoretic Display

AbstractA methodology is introduced to characterize colorimetric performance of full‐color electrophoretic display. The concept of principal component analysis benefited simplifying the complicated hybrid color‐mixing system by means of one eigenspectrum for each RGB channel. Proposed model was validated to predict the chromatic feature with high accuracy (ΔEAVE_CIEDE2000&lt;0.2). Due to its simplicity and invertibility, proposed technique will certainly has a promising impact on the color reproduction in emerging novel displays using hybrid color‐mixing system.

Establishing a Consistent Baseline Reference for High-Definition Cameras

With the rise of high-definition television, consistent picture quality is critical if the end user is to enjoy to the full extent of what the system has to offer. In maximizing the potential of high-definition television, the service provider must give camera line-up the attention it needs. Camera technology lightens the load on the vision engineer to use those craft skills to better advantage. Camera line-up requires more than a simple black-and-white balance at the correct exposure. In order to achieve the most consistent pictures across several days on a multicamera shoot, several factors need attention. Recent advances in line-up charts make this easier than with traditional versions, but limitations still exist. This paper showcases new camera line-up technology in which many former limitations are overcome. New technology allows analysis of a camera's colorimetric performance, identifying areas of deficiency and giving the user the tools necessary to make improvements. Finally, what does the future hold? And what can we learn from today so that future standards change for the better?

Colorimetric comparison of light-filtering intraocular lenses and human crystalline lenses at various ages

To perform colorimetric characterization of 2 blue light-filtering intraocular lens (IOL) models and an IOL that filters ultraviolet-violet (UV-v) light and compare the charactizations with those of a standard UV light-filtering IOL and the human crystalline lens at various ages. Department of Clinical Physiopathology, University of Florence, and National Institute of Applied Optics, CNR, Florence, Italy. Experimental study. Three IOLs of each model with different dioptric powers (16.0, 21.0, and 26.0 diopters) were analyzed. The colorimetric coordinates of the IOLs were calculated by measuring their transmission spectra using a microspectroscopy technique. Subsequently, a parameter (ΔE) that was proportional to the perceived color differences was defined. The results of the IOLs and of the human crystalline lens at different ages (4, 22, 41, 53, and 72 years; values taken from the literature) were compared. The colorimetric analysis was performed using Commission Internationale de l'Éclairage standards. The maximum ΔE value was with the standard UV light-filtering IOL at any crystalline lens age and was greatest with a 72-year-old human lens. The minimum ΔE value was obtained for both blue light-filtering IOLs with middle-aged human lenses. None of the analyzed IOLs had the same colorimetric performance of the human crystalline lens. The 2 blue light-filtering IOLs best reproduced yellowing of the human lens at 40 to 50 years of age. No author has a financial or proprietary interest in any material or method mentioned.

75.5: Evaluating Procedure of Color Rendering Property on Reflective LCD

AbstractAn evaluating procedure was introduced and demonstrated to reveal the impact of color appearance induced by ambient illumination for reflective‐type LCDs. The concepts of Color Rendering Index and Color Quality Scale were cooperated to account for the differences of color rendering between LED lightings with identical correlated color temperature but various spectra. The results showed that the colorimetric performance of reflective LCD was strongly dependent on various LED spectra and light level. And the proposed assessments, CRI and CQS, can effectively describe how well LED lighting renders the reflective‐type LCD.

Energy transfer and colorimetric properties of Eu 3+/Dy 3+ co-doped Gd 2(MoO 4) 3 phosphors

Dy 3+ single-doped and Eu 3+/Dy 3+ co-doped gadolinium molybdate (Gd 2(MoO 4) 3) phosphors were synthesized by a traditional solid-state reaction method. The XRD was used to confirm the crystal structure of the phosphors. The energy transfer between Eu 3+ and Dy 3+ was observed and studied. The Eu 3+ concentration can hardly affect the blue and yellow emission intensities of Dy 3+, and the Eu 3+ emission intensity increases with the increase of Eu 3+ concentration. Co-doping with Eu 3+ compensated the red emission component of the Dy 3+ doped Gd 2(MoO 4) 3 phosphor. Introducing proper amount of Eu 3+ can improve the colorimetric performance of the phosphors.

Colorimetric comparison between different filtered IOLs and human crystalline lenses at various ages

Abstract Purpose To perform the colorimetric characterization of two different blue light filtered IOLs (Intra Ocular Lenses, from Alcon, USA and Hoya Corporation, Japan) and one UV‐violet filtered IOL (Bausch &amp; Lomb, USA) comparing them with standard UV filtered IOL (Alcon) and human crystalline lenses at various ages. Methods Three IOLs of each model with different dioptric power (16, 21 and 26 D) were analyzed. The colorimetric coordinates of the IOLs were calculated by measuring their transmission spectra by a spectrophotometric technique. Consequently, we defined a parameter (ΔE) proportional to the perceived color differences. A comparison was then performed between the various IOLs and human crystalline lenses of different ages (4, 22, 41, 53 and 72 years) considered from the literature. The CIE (Commission Internationale de l'Éclairage) standards were adopted for the colorimetric analysis. Results The color distance ΔE was calculated for the 4 IOL models considered, respect to human lenses at different ages between 4 and 72 years. The maximum ΔE value was found respect to the standard UV filtered IOL for any other crystalline lens age and greatest for a human 72 year old lens. The minimum value for ΔE was obtained for both blue‐filtered IOLs respect to middle‐aged human lenses. Conclusion None of the analyzed IOLs has the same colorimetric performance of the human crystalline lens. The two blue‐filtered IOLs reproduce at best the human lens yellowing of 20 to 50 years, among all the tested IOLs.

Unsupervised illuminant estimation from natural scenes: an RGB digital camera suffices

A linear pseudo-inverse method for unsupervised illuminant recovery from natural scenes is presented. The algorithm, which uses a digital RGB camera, selects the naturally occurring bright areas (not necessarily the white ones) in natural images and converts the RGB digital counts directly into the spectral power distribution of the illuminants using a learning-based spectral procedure. Computations show a good spectral and colorimetric performance when only three sensors (a three-band RGB camera) are used. These results go against previous findings concerning the recovery of spectral reflectances and radiances, which claimed that the greater the number of sensors, the better the spectral performance. Combining the device with the appropriate computations can yield spectral information about objects and illuminants simultaneously, avoiding the need for spectroradiometric measurements. The method works well and needs neither a white reference located in the natural scene nor direct measurements of the spectral power distribution of the light.

2007 Topical Meeting on Optical Interference Coatings: Manufacturing Problem

Measurements are described on the experimental filters submitted to the Third Optical Thin Film Manufacturing Problem in which the object was to produce multilayers with a measured colorimetric performance that is as close as possible to that specified. The perceived colors of the coating, when illuminated with randomly polarized light incident at 7 degrees by a source representing average daylight with a correlated color temperature of approximately 6500 K, were to be yellow and blue, respectively, in light reflected from its two surfaces, and the color was to appear white when viewed in transmission mode. Eleven teams from 7 different countries submitted a total of 18 samples.

Image‐based spectral reflectance reconstruction using the matrix R method

AbstractThe ultimate goal of spectral imaging is to achieve high spectral accuracy, so that the spectral information can be used to calculate colorimetrically accurate images for any combination of illuminant and observer. A new spectral reconstruction method, called the matrix R method, was developed to reconstruct spectral reflectance factor accurately while simultaneously achieving high colorimetric performance for a defined illuminant and observer. The method combines the benefits of both colorimetric and spectral transformations. Tristimulus values were predicted by a colorimetric transformation from multi‐channel camera signals, while spectral reflectance factor was estimated by a spectral transformation from the same signals. The method reconstructed reflectance factor by combining the fundamental stimulus from the predicted tristimulus values with the metameric black from the estimated spectral reflectance, based on the Wyszecki hypothesis. The experimental results verified the new method as a promising technique for building a spectral image database. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 343–351, 2007

Chemical identification of 2,5-dimethoxy-4-bromoamphetamine (DOB)

The consumption of synthetic drugs, generally known as designer drugs, has increased drastically in all parts of the world. Typical constituents of designer synthetic drugs are chemical substances derived from amphetamine but significant differences in effects caused and duration may result. In May, 2005, the civil state police of Sao Paulo seized thirty-one gelatinous capsules containing a very small quantity of a white powder inside (approximately 1.5 mg per capsule). This paper describes the analytical assays that were used to identify the seized material. Preliminary assays using colorimetric tests and high performance thin-layer chromatography indicated that the capsules content could be an amphetamine derivative. In the capillary zone electrophoresis assay, it was possible to observe that the analyzed material had basic characteristics. Mass spectrometry analysis revealed that the compound had the same molecular mass as 2,5-dimethoxy-4-bromoamphetamine (DOB) and its identity was confirmed through collision-induced dissociation (CID) experiments. Finally, the comparison of infrared sample spectrum with a spectra library provided further evidence of the DOB presence in the seized material. Although a reference standard material was not available, the information gathered from the different assays allowed the conclusion that the substance was, in fact, DOB, a substance with a powerful hallucinogenic action of proscribed use in the country and which was seized and identified for the first time in Brazil.

LEDs for General Illumination: The State of the Science

Light emitting diodes (LEDs) are emerging as a viable source for the general illumination of the built environment. Recent product development efforts have focused on four areas: increased light output, increased conversion efficiency, minimization of color shifts, and increased color rendering index (CRI) for white LED sources. Although little can be argued against the first three areas of development, using CRI as a spectral design criterion may be misguided. Other measures of color preference or color discrimination may be better suited to optimize LEDs for general illumination. In the future, due to the nature of the LED spectral distributions, virtually any source spectrum may be possible, which begs the question: should product development efforts aim to match reference sources that are not optimal in terms of color preference or discrimination? This paper summarizes current theories about LEDs and color. Color shift is discussed as it relates to temperature, age, input current, and dimming. The methods of making white light with LEDs are described and contrasted in terms of chromaticity coordinates, correlated color temperature (CCT), and CRI. The colorimetric potential of LEDs is discussed in consideration of numerous measures of colorimetric performance.

Application of a Colorimetric Evaluation Model to Multispectral Color Image Acquisition Systems

With the recent advances in color management systems, the estimation of accurate colorimetric values of objects being imaged by the use of sensor responses becomes an important function of color image acquisition devices such as digital cameras and color scanners. Therefore, colorimetric evaluation of a set of sensors is important to evaluate the colorimetric performance of the sensors. It is well known that the colorimetric quality of the sensors depends not only on the spectral sensitivities but also on the noise present in them. Although several evaluation models have been proposed, application of the models to real color image acquisition devices has not been appeared since it was impossible without prior knowledge about the noise present in the devices. In this article, a new model to estimate the noise variance of an image acquisition system is proposed based on the colorimetric evaluation model and for the first time the evaluation model was applied to real multispectral cameras by using the estimated noise variance. It is confirmed by the experiments that the proposed colorimetric quality is in good agreement with the experimental results and that the noise variance of the image acquisition system can be accurately estimated by the proposal.

Linear color camera model for a skylight colorimeter with emphasis on the imaging pipeline noise performance

We develop a digital camera model with the purpose of simulating the performance of a sky radiance colorimeter, based on a single-sensor camera equipped with a charge-coupled device imager. To provide a color image, the sensor is covered with a Bayer color filter array (CFA). The model input is the radiance, expressed in radiometric units. Demosaicking of the CFA is performed using three common interpolation methods. Color characterization is performed by calculating 3×3 matrices, based on either the maximum-ignorance assumption or computer-generated sky radiance training sets. For the model to be reliable, we incorporate multiple noise sources. We also parameterize many critical characteristics of the simulated imager, for example, temperature-related dark-current generation and pixel size. Error propagation analysis is performed, including an analysis for the demosaicking methods. Colorimetric performance results, expected measurement accuracy, and validation of the derived noise propagation equations are presented.

Application of Spectral Estimation Methods to the Design of a Multispectral 3D Camera

This article reports on the colorimetric improvement of a multispectral 3D digitizer through scanning at a small number of nearoptimal wavelengths. Optimal wavelengths were first investigated theoretically based on the criterion of minimal color differences over some sets of reflectance curves using PCA-based and spline-based spectral estimation methods. Sets of three, four and five optimal sampling wavelengths were derived to within &#xB1;5 nm for each one based on the spread of variation for different combinations of the method and the data set used for the derivation. This provided a basis for the selection of HeCd, ArKr, HeNe and DPSS commercial laser lines for which the colorimetric performance was predicted. This was then tested in the laboratory, where color rendition charts were scanned with the camera at seven wavelengths, after which the charts were computer rendered on a CRT display. Both the theoretical prediction and the experimental observation indicate that four well-chosen wavelengths are adequate for proper rendition of the charts.

P-70: Characterization Methods for LCD Devices with Crosstalk Issues

An approach is introduced for building accurate and compact color look-up tables (CLUTs) to describe the colorimetric performance of liquid crystal display (LCD) devices. In an experiment, a novel analysis technique was found to be useful in guiding the choice of samples used in the building of the CLUT. The experiment demonstrated that an 8×8×8 CLUT produced through the new sampling method delivered comparable results to an 18×18×18 made from a different sampling technique. The technique will allow for future automation of choosing optimal samples for building LCD CLUTs.

Evaluation of TV System Colorimetric Performance

The average performance for groups of color samples is often used in the evaluation of colorimetric color-reproduction quality in TV. An experimental investigation regarding this use of group averages is described here, referring to data for a broadcast-quality TV system with perfect cameras and real monitors. For two groups of eight samples each, it is shown that the average does not give more information about whether the performance is satisfactory than a single sample of skin-tone chromaticity gives. To the extent that this can be considered generally valid, performance analysis should therefore not be based on group averages, but on the results for individual color samples.

On Testing the Colorimetric Performance of TV Cameras

On Testing the Colorimetric Performance of TV Cameras

Visual Evaluation of Daylight Simulators for the Colorimetry of Luminescent Materials

AbstractThe accuracy of several methods for assessing the colorimetric performance of daylight simulators as practical realizations of CIE standard daylight illuminants such as D65 was studied by visual methods. Eight luminescent samples containing various fluorescent whitening agents were used. Visual differences between sample pairs, each consisting of a luminescent sample and its nonluminescent substrate, were judged under a reference source simulating D65 and six test sources with different ultraviolet content from the reference source but nearly the same spectral irradiance in the visible region. Over 3000 observations were made by eight observers. Visual scale values were derived and compared to indices calculated by five published methods. The results show that four methods based on colorimetric weighting gave significantly better correlations than one based on radiometric weighting, with little choice among them; that the CIELAB color‐difference equation was preferred to CIELUV; and that the choice of 2° or 10° standard observer had no effect.