This study aimed to understand the subjective contrast between a chromatic patch and its achromatic background by using equivalent color difference. It also aimed to examine whether the color difference in color spaces explains the subjective contrast. We defined subjective contrast as the subjective and comprehensive differences between a patch and its background. We carried out an experiment in which subjects selected the combination of an achromatic patch and its achromatic background that had the same visual difference between a chromatic patch and its achromatic background. The color difference of the selected achromatic combination was defined as the equivalent color difference. The relation between the equivalent color difference and the color difference in color spaces was clarified. Subjective contrast was explained better as the color space of lightness and chroma than that of brightness and colorfulness in CIECAM02 or than the CIELAB color space.
The fiber composition label in accordance with the Household Goods Quality Labeling law is determined by identification and quantitative analysis of fiber mixtures in JIS L 1030-1,-2 (Japan Industrial Standards). But, this method involves destructive inspection, and a lot of time is necessary for the analysis. In this study, using textile products of cotton and polyester, we examined the possibility of qualitative and quantitative analysis of fiber composition by infrared spectroscopy and SIMCA (soft independent modeling of class analogy) and PLS (partial least squares regression). By using SIMCA, we tried to classify the infrared absorption spectrum of textile products to composition fiber. And by using PLS regression, the fiber composition could be forecast from the infrared absorption spectrum of textile products. The technique that we propose is nondestructive and quick.
Integrating sphere photometers are simple systems to measure the total luminous flux. However, the issue of self-absorption exists especially for LED measurement. For example, a high-power LED includes parts other than the light emitting point in the integrating sphere, such as a large heat sink and electric circuit module. As a solution, we introduced the integrating hemisphere for the measurement of the total luminous flux of these devices. The integrating hemisphere was composed of a hemisphere whose inside wall was coated with BaSO4 and a high reflectance mirror, which was installed along the equatorial plane. The light source under test was set inside the hemisphere near the central part of the mirror. The spherical integration surface consisted of the real image on the integration hemisphere side and the virtual image on the mirror side because the light source was set up at the center of the mirror that was arranged in the equatorial plane. One of the advantages was that only the light source sat inside the integrating hemisphere while the lamp supporter, driving devices and other parts were outside. Even for the measurement of a high-power LED installed in a temperature control module with a large heat sink, only the illuminant part is in the integration space. Moreover, its emitting part was located at the center of an ideal integration space by the virtual image from the mirror. As a result, the self-absorption of the sample was be significantly reduced.