In industrial working condition, signals by an instrumentation with an optical sensor are inaccurate because of noise. If the signal and the noise are separated in the frequency domain, the noise can be reduced by filtering or using a cepstrum. In this paper, we produced two signals. In order to do this we connected two serial sensors thereby producing one signal. The other signal was produced by connecting the inverse of these two sensors. This method enables us to obtain a reliable signal without any noise on the signal line even if signal and noise could not be separated in the frequency domain. In this case “any noise” means under a quarter frequency of the analog switch. We propose to call this method alternating Noise Cancelling (ANC). The accuracy of the ANC method has been verified by examples using sinusoidal and other noises.
Various lighting environments of residential streets were simulated by computer graphics. By means of these visualized images, subjective impressions of outdoor pedestrian lighting were investigated. As a result, the following three points were clarified:(1) Subjective impressions of night-time residential streets, could be classified into three groups. namely ‹brightness› impression, ‹uniformity› impression and ‹comfort› impression, including impression of security;(2) The combination of Eh (ave) and Ev (min) is important for realizing a comfortable and functional lighting environment in residential area, because these two photometric values had relatively good correlations with the two factors of subjective impressions; and (3) Observing computer graphic images, the subjects could easily assess the impressions. Furthermore, various parameters can be easily and systematically changed or kept constant by CG. Computer graphics can be, therefore, one of the effective methods for appraisal of subjective impressions received from the lighting environment.
The perceptual uniformity of chroma-spacing in the Munsell renotation system was examined by comparing Munsell chroma-differences with perceived colour-differences on the basis of the data obtained by visual experiments in which ratio method had been used to estimate perceptual colour-differences for color chips with constant value (V=6) and hues (5R, 5YR, 5Y, 7.5GY, 3.5G, 10BG, 2.5PB, and 5RP) and varying only chroma. It was cleared that the Munsell chroma did not completely retain perceptual uniformity. Results obtained are summarized as follows: (1) For any hue except 5R, 5Y, and 2.5PB in the hues treated, the perceived colour-differences tend to become relatively small with increasing saturation. This tendency is remarkable in the hues of 5YR, 7.5GY, and 10BG. (2) The above means that the chroma spacings in the Munsell renotation system become narrow with increasing saturation as compared with perceptual chroma spacings. In the instance of 7.5GY, the perceived colour-difference per unit Munsell-chroma at 9-10C is 0.45 times as large as that at 0-1C. (3) The Munsel chroma for 5R may roughly retain the perceptual uniformity in the range of lower chroma than 10C, and the same thing may be stated in respect of the hue 5Y within lower chroma than 7C and the hue 2.5PB within lower chroma than 9C. But, at the remainders of chroma for 5R and 5Y, the perceptual chroma-spacings become relatively small with increasing chroma. (4) The experimental values of perceived colour-difference per unit colorimetric one can be approximated by the function that consists of a term of one-third power, a linear term, and a constant term within the mean square errors less than 5.31×10-2 for all the hues.
The pulsed operation of high pressure sodium lamps has been analyzed. In pulsed operation, spectral intensities for the radiations with higher excited energy levels increase and spectral intensities for the radiations with lower excited energy levels decrease. By this spectral change correlated color temperatures of the lamps become higher. On the contrary luminous efficacies decrease by the increase of heat conduction losses, comparing with sine wave operation. The method for measuring time dependent arc temperature profiles has been established and applied to the cause of spectral changes, to suitable pulse conditions for spectral change and to time dependent lamp voltages. The increase of radiations with higher excited energy levels is due to the increase of arc temperature during pulse. The suitable conditions on pulsed operation for spectral change are lower pulse duty, lower frequency and smaller keep-alive current. These conditions correspond to the larger change of arc temperature in one cycle. Concerning with lamp voltage, the contribution from keep-alive current region is proved to be large when arc temperature becomes lower in that region.
The lightness for 39 test color chips was investigated under various illuminance levels covering 0.01 to 3000 lx. The experimental method was to match the lightness of test stimuli of color chips with a gray scale and to express the lightness by the equivalent value of the gray scale. The test stimuli was presented in a foveal 10° field. Gray background of value N6 was used. The results show that the equivalent lightness for the red, green, blue and purple test color chips increased with the increasing of the chroma in the photopic range. The equivalent lightness for the yellow test color chips did not change in the photopic range, but it decreased with the decreasing of illuminance in the mesopic range. The equivalent lightness for the blue test color chips increased with the decreasing of illuminance in the mesopic range. To explain this phenomenon, a formula is proposed by three functions, the rod achromatic channels, the cone achromatic channels and the cone chromatic channels for the equivalent lightness under various illuminance levels.
“Visual clarity” of lighting environment is affected significantly by changing the color-rendering property of its illumination. As the results of our previous studies for this phenomenon, it has already been confirmed that “visual clarity” of illumination is closely related to the affection of contrast on object colors under the illumination. Now, in order to establish a method for assessing “visual clarity” based on the affection of contrast, a comparison was made between the subjective estimations on affection of contrast and its predictions on various light sources. The results are as follows. 1) The change in affection of contrast by changing the color-rendering property of light sources can be estimated effectively by using a four-color combination composed of red, yellow, green, blue with high saturation. 2) The illuminance of equal affection of contrast is predicted by using the gamut area made by the component colors of the four-color combination in the color-appearance space on brightness and colorfulness. 3) The “equal gamut-area illuminance” of each light source well correlates to the “equal visual-clarity illuminance”. Concequently, the change in “visual clarity” of lighting environment by changing the color-rendering property of its illumination can be estimated appropriately based on the affection of contrast using the gamut area of the four-color combination in the color appearance space on brightness and colorfulness.