A far infrared spectral irradiance standard radiator has been developed. It consists of a 20-mm diameter, 40mm-long silicon carbide tubular heater and an aperture consisting of a double structure of aluminum plates. The surface temperature of the radiator is about 920K peak radiation wavelength is about 3.1μm and consumption power is 400W. The relative spectral irradiance was calibrated against a silicon carbide cavity (black body) radiator of the same type. The absolute irradiance value was determined by measuring the total irradiance using a broad bandpass filter and a thermal detector (thermopile) at a wavelength of 1. 5-4μm and by measuring the spectral irradiance of an ETL halogen lamp standard at 1. 5 2.5μm. These two methods gave results that agreed within 3%. The irradiance at a distance of 400mm were 0.2mW·cm^-2· nm^-1 at 1.5μm, 1.3mW·cm^-2·nm^-1 at 3μ, and 0.04mW·cm^-2· nm^-1 at 12μm. The change in spectral irradiance was less than 1.5% after 100 hours of operation.

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We describe a method for rendering the surface of water, focusing on the problem of realistic color rendering. This method takes into account scattered and absorbed light, interreflection between objects located above the water surface and between those in the water, the shape of the bottom surface of the water and shadows cast on/under the water surface. It can be applied to point light sources with various characteristics of luminous intensity distributions and spectra. Two examples show the effect of the depth and quality of water on this color, comparing simulations with photograph of a pool. They suggest that this method is useful for designing lighting for scenery surrounding water

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One can immediately grasp the illumination conditions of a room and correctly judge the colors of various objects in it by looking around the interior when one entering the room. This is because one establishes a fully recognized visual space of illumination for the room by using the illuminated objects as the initial visual information about the room. If one is provided only with incomplete initial visual information, however, the recognized visual space of illumination is also incomplete and one cannot see the correct colors of objects. In the present experiment we controlled the amount of initial visual information by the size of the window through which subjects saw a room illuminated by a type A light source from a room illuminated by a type A light source. We investigated the formation of the recognized visual space of illumination by judging the colors of colored stimuli. The colors gradually shifted from those of light reflected from the objects to those of the objects themselves indicating a gradual formation of the recognized visual space of illumination with increasing amount of initial visual information. However, some colors showed no color shift in spite of the increasing window size. An explanation of the color shift mechanism is presented.

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The characteristics of a transistor inverter for a discharge lamp ballast are calculated. The inverter is composed of a power transistor, two inductors (L₁, L₂), three capacitors (C₁, C₂, C₃) and a control circuit that drives the power transistor. Under appropriate values of L₁, L₂, C₁, C₂ and C₃, the power transistor can be switched at zero voltage, which reduces the power dissipation in it. The inverter generates a high voltage ac output. At high resistance loads, the output voltage is several times the input voltage. At low resistance loads, the output currentis held constant. These features are suitable for a discharge lamp ballast. The dependence of the output voltage on trigger frequency and load resistance is calculated, and the design of the ballast is also described.

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This Monte Carlo simulation of the sky luminance and the daylight illuminance showed that
(1) when the sky is overspread with cloud whose properties are equal in the horizontal direction, the sky luminance is close to the CIE standard overcast sky luminance as the optical thickness of cloud increases. Then, if the sky luminance Lm is expressed as a function of the clear sky luminance Lc and the overcast sky luminance L_o, that is, L_m=e^-A×τL_c+ (1-e^-A×τ) Lo (where τ is the optical thickness), the coefficient A will become 0.16-0.28 when the sun altitude is 30-60 degrees. On the other hand, if the daylight illuminance Sr is expressed as S_r =S_o^-B × τthe coefficient B will become 0.012-0.027. And if the sky is darkly overcast, the optical thickness of the cloud becomes 52-32 when the sun altitude is 30-60 degrees.
(2) when the sky condition is the intermediate sky whose clouds are scattered, the sky luminance L_m is calculated as L_m= (1-C/10) L_c+ (C/10) {e^-A×τ L_c+ (1-e^-A×τ) L_o} (where C is the total cloud amount) if the average distribution of the cloud amount in the sky is constant. In the case of the daylight illuminance, the average value decreases with the increase of the total cloud amount but the maximum value and the minimum value do not necessarily decrease.

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We statistically studied several problems related to critical flicker fusion frequency (CFF), which was used to design the interlaced scanning method of television systems. Since CFF values closely depend on the physical and mental state of the observer, statistical treatment of data is essential. We studied the difference between up and down discrimination threshold series and the coincidence between CFF values for equal energy colors, mainly by adapting a variance method analysis.

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