We made a series of asymmetric color matching experiments between an actual color chip under different illuminant and a CRT simulated color chip, by changing surround, illuminant and matching criteria. The observers were asked to match hue, saturation and luminance of two stimuli at apparent-color match criteria, and were asked to match as if the two stimuli were made of the same surface at surface-color match criteria. At the condition without adaptation, and without any surround, the observer was not able to make surface-color match and the results for apparent-color match were the same with the physical chromaticity of the stimulus. At the same time, the condition with gray surround, we could find a shift in color appearance toward color constancy in both criteria, and at the condition with mondrian surround, the degree of color constancy for apparent-color match were improved by the increase of surround color information. However, at the condition without adaptation, the results for apparent-color match were less complete than the results for surface-color match, in terms of the degree of color constancy. At the condition with 15minutes of adaptation to the illuminant, the results for apparent-color match achieved almost the same degree of color constancy with the results for surface-color match. Our results imply that the perfect color constancy will be achieved not only by surround stimulus, but also by the adaptation to the illuminant.

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This paper introduces a fluorescent lamp inverter with low distotion input-current. The reduction of input current distortion is achieved by the neutral-point inverter circuit and a low pass filter. The capacitor charging current prevents the generation of the current pause periode in the inverter circuit. It is demonstrated that the improved electronic ballast is effective in decreasing the harmonic currents. We also report on the result of comparison between this inverter with othre types.

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Daylight is composed of direct sunlight and skylight. Skylight is direct sunlight and light reflected from the earth's surface that have been scattered by the atmosphere and clouds. The correlated color temperature (CCT) of daylight varies hourly, and the CCT of skylight varies extensively due to changes in the spectral alvedo of the earth's surface, the solar altitude and the angular distance from the sun to a sky component, the atmospheric transmittance of visible radiation and the amount of cloud. This paper discusses causes of variations and local differences of skylight CCT and proposes a formula for skylight CCT as a function of cloud amount.

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A visual experiment was carried out to clarify the optimum intensity for legibility of light signals composed of multiple point light sources. In this experiment, 3 to 7 sources were placed in a row, 3 ×3 to 7 × 7 sources were placed in a matrix, and other multiple-source signals were also employed as test stimuli on a screen panel. The separation of neighbouring points was 2 to 32 minutes of arc. The results show that the optimum average luminance of E-shaped lights and arrow-shaped lights agrees well with that of the row lights and the matrix lights. It was clarified that using the average luminance of the light is an effective method of obtaining the optimum intensity for legibility of light signals composed of multiple point light sources.

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The three-dimensional nature of illumination processes has been paid little attention in comparison with measurements and predictions of illuminance distributions upon specified surfaces or planes. Nevertheless, this is an area worthy of notice, especially in daylighting designs where the distribution of the flow of light plays an important role in human vision.
This paper treats such three-dimensional light values as the spatial illumination vector and the vector flow, which are newly defined at the center of many unit minor spaces. These are formed by uniformly subdividing the lighting space using many imaginary transparent partitions. An application of Monte Carlo simulation (MCS) to the three-dimensional distributions of the spatial illumination vector is examined in a model lighting room with up to 64, 000 subdivisions. These values are also confirmed experimentally by using a trial six-surface-illumination meter.
Two Methods of determining the spatial illumination vector in the lighting space with single light sources on the ceiling and a side wall are compared for numerical experimental values by MCS.
It is found that the spatial illumination vectors obtained by MCS coincide well with experimental ones obtained with the six-surface-illumination meter, and the two sets of numerical experimental values from these two methods agree well with each other to within a few percent. Furthermore, it is clearly found that obstructive screens have a significant effect on the flow of vectors, the distribution of which is greatly disturbed by such screens.

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Various kinds of large-scale membrane structure have recently been constructed and utilized for multiple purposes, such as baseball stadiums. In a baseball stadium it is important to create a suitable visual environment for both players and spectators to see the ball.
An experiment was carried out inside a membrane structure to examine the factors that affect the visibility of flying balls and the threshold luminance contrast for the ball, that is, the visibility of the balls hit by a machine was subjectively evaluated by observers. In the experiment, the luminance of flying balls and the background and other conditions were set at various appropriate levels. Luminance contrast C of the ball was defined as
C=L_T-L_B/L_T(for L_B<L_T)-L_B-L_T/L_B (for L_B>L_T)
L_T: luminance of ball
L_B: luminance of background.
The major results obtained in this experiment are as follows:
(1) There is a linear correlation between evaluations of visibility of flying balls and luminance contrasts of the balls.
(2) Under positive contrast conditions, the threshold luminance contrast of the ball is 0.3. For negative contrast, it is 0.4.
(3) Under relatively light backgrounds, the evaluations are almost the same whether the contrast is positive or negative if the absolute values of both contrasts are the same.
(4) Under negative contrast, the visibility is evaluated as being lower for low background luminance.
(5) As the angular velocity of the balls decreases, the evaluated visibility increases.
(6) The visibility of flying balls is not influenced by ball color.
(7) If the hitting point of the ball is not visible, the evaluated visibility decrease as compared with the visible case when luminance contrast of the ball is low.

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The luminous environment in architectural space in the daytime should fundamentally depend on daylight. However, it is very difficult to investigate daylit environments because the daylight fluctuates, sometimes smoothly but sometimes very violently.
The goal of this research is to get advanced knowledge about the real dynamic state of luminous environments in daylit architectural space. For this purpose, various kinds of data on daylit environments have been gathered from daylit architectural space, for instance, office areas, apartments, and houses by field measurements under various daylight conditions in different seasons. And many useful suggestions have been obtained from the results of analyses of the data gained.
This paper reports the results of a study on a house lit only by Daylight, without any artificial illumination. The following important conclusions were made.
1) The state of fluctuation of horizontal illuminance, illumination vector, scalar illuminance, and cylindrical illuminance at the same point by daylight are similar, and unrelated to room style.
2) The level of horizontal illuminance by daylight on the floor is different at different point, but the state of fluctuation of illuminance is similar throughout a whole day.
3) The state of fluctuation of illumination vector altitude and vector scalar ratio is extremely stable under various sky conditions throughout a whole day.
4) The state of fluctuation of the above illuminances is not greatly affected by using shoji, Japanese paper sliding doors.

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This paper proposes a statistical method for modeling the voltage versus current characteristics of a fluorescent lamp. Parameters of the model are selected from various parameters by applying a maximum R² improvement method to keep generality of the model. The voltage-current characteristic of the fluorescent lamp is expressed by an equivalent resistance as a function of instantaneous lamp power and its differential coefficient. Therefore, the fluorescentlamp is modeled without knowing physical constants such as the electron impact excitation cross sections of mercury atoms.The. simplicity of the equivalent resistance of the fluorescent lamp reduces instability and the computation time required for an analysis of the lamp circuit.
Numerical simulations under various conditions are performed using Electro-Magnetic Transient Program (EMTP). Results calculated for applied sinusoidal voltages of 60 Hz and 1 kHz agree well with experimental results. The proposed model is confirmed to be independent of voltage waveform and also to be applicable to various types of lighting circuits such as an inductive ballast and an electronic ballast.
The stable characteristic of the proposed model opens a way of a computer aided design of a lighting equipment.

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It is well known that perceived color is not determined by the photometric values but instead depends on the surrounding pattern and the adapting condition of the eye. It is important that we know how color in complex patterns appears because the scenes we usually see are complicated. In this study we estimated the surround effect for appearance of achromatic color with two and four surrounds by using a new matching method that gives us the equiluminance of the simple uniform surround. The magnitude of surround effects of plural stimuli can be qualitatively described by the equivalent luminance. The results show that the average luminance of surround stimuli cannot explain the total surround effects of plural stimuli, but the spatial additivity of surround effects depends on the stimulus conditions. In addition, some characteristics of the surround effects differ between conditions with gap and conditions without gap. The spatial additivity of surround effects in the present study can be expressed by the summation of the luminance values of each surround weighted as a function of the luminance of a central patch.

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We examined the effects of light sources used in high-definition television scene lighting on the subjective preference quality of color reproduction of television scenes. Observers evaluated the subjective preference quality of television scenes illuminated by five kinds of lamps: the tungsten halogen lamp for TV studio, the metal halide lamp A (Ra92, 6000K), the metal halide lamp B (Ra70, 3800K), both the metal halide lamp B and a high pressure sodium lamp, and a color improved high pressure sodium lamp.
The results show two conditions for better light sources for television scene lighting: (1) higher general color rendering index (Ra) and (2) better color reproduction balance are needed. We propose a color-reproduction-balance index for assessing the colorimetric properties of light sources for high-definition television scene lighting.

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Solutions for the temperature rise and heat flow within a heated plate are determined by computer analysis of a simulated electrical resistance-capacitance network equivalent to the given thermal system Water evaporation at surfaces of the substance is simulated by a resistor, r.
This analysis assumes that only the surface of the substance is radiation-heated and that the substrate is heated only by thermal conduction. It also assumes that irradiated heat flow input of each surface, q₀is constant (though it actually decreases a little as heated surface temperature rises) and that the heated substance behaves like pure water.
Some important conclusions are that when both sides of the plate are heated the steady state temperature rise at a constant evaporation rate is given by rq₀, that this steady state is reached faster when r is smalle, and that equal heating throughout the substance is obtained as heating proceeds and approaches the steady state.
When only one side of the plate is irradiated and no evaporation takes place at the other side, the same equal heating characteristic is also obtained, when evaporation takes place at both surfaces, however, the heated surface temperature rise becomes greater than that of the other surface. That is, unequal heating within the substance occurs. The difference between surfaces temperatures depends on the ratio of r to water thermal resistance.

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