There exists a growing body of research findings uncovering the non-visual effects of artificial lighting. In a recently completed field study we compared the effects of two types of fluorescent lighting, the daylight tube versus the common white tube. Persons working in two otherwise identical drawing offices were studied for one year. The results support the conclusion that light from the daylight tube blocks the production of the sleep hormone melatonin to a greater extent than light from the white fluorescent tube. Sitting indoors in window-less localities also changes the production of stress hormones like cortisol. That not only light but the total visual environment is important was demonstrated in a study of high versus low visual complexity. The results showed that colours and patterns stimulate the brain’s electrical activity. In contrast, the pulse rate was lowered in the complex room, which might be interpreted as a compensatory response to visual overstimulation. In conclusion, the results indicate that the total visual environment has a much deeper influence upon people than has been supposed hitherto.

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Calculations of the luminous flux which is an output of discharge lamps are necessary in the overall analysis of the operating circuit for such lamps. In this paper, we calculate the instantaneous luminous flux of a 40 W clear mercury lamp operated by simple two circuits: one is a resistance type operating circuit, and the other a chopper type operating circuit. After the discussion on the relationship between the lamp’s instantaneous conductance and the temperature of the arc plasma in discharge lamps, the instantaneous temperature of the arc plasma is determined by the lamp’s instantaneous conductance which can be calculated by using the lamp model equation. Then, the instantaneous luminous flux, which depends on the sum of the line spectral intensities, is calculated by this instantanous temperature of the arc plasma. Finally, the usefulness of this calculation method is discussed, comparing the calculated results with experimental results.

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This paper describes the harmonic characteristics of 40W-fluorescent lamp operating circuit with a leakage transformer. The research has been carried out in the following sequence. First, as source voltage is varied, Fourier series are derived on voltage and current waveforms at each element of the operating circuit. Then, by using the Fourier expansion, each harmonic component at each element of the operating circuit is obtained, from experimental waveforms. The following are clarified from the research.
(1) A vector diagram is obtained for each harmonic and their characteristics are clarified.
(2) The impedance (its resistance and reactance component) is obtained for each harmonic, and their characteristics are clarified.
(3) The equivalent circuit is obtained for each harmonic, and their characteristics are clarified.
(4) The following is revealed. There exists ‘giving and receiving’ of active and reactive power of each harmonic between the 40W-fluorescent lamp and the secodnary winding of the leakage transformer. And their characteristics are clarified.

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The Monte Carlo method is applied to the predetermination of a luminous intensity distribution in luminaire design. In this technique, the random travels of light quanta such as photons are statistically analyzed to obtain the luminous intensity distribution. That is, the behavior of many photons are determined using random numbers. The photon paths are traced until either they are absorbed by intercepting surfaces or until they are emitted outside the luminaire. Basic procedures of simulating photon emissions and photon reflections are described. These procedures together with photometric properties measured on elements composing a luminaire, are applied to predetermining the luminous intensity distribution of a luminaire composed of a fluorescent high pressure mercury lamp and a reflector with a blasted aluminum surface of revolution. It is revealed that approximately 10⁶ trials are required to predetermine a luminous intensity distribution with a precision of 1%.

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In order to study the perceptual scaling of chroma, perceived chroma-differences of colour chips are subjectively estimated by means of ratio estimation method under standard illuminant A and daylight D₆₅. The subjectively estimated values are compared with their colorimetric colour-differences in the CIE 1976 L^*u^*v^* and L^*a^*b^* uniform colour spaces. The set of colour chips used in the experiment consists of eight hues (5R, 5YR, 5Y, 7.5GY, 3.5G, 10BG, 2.5PB and 5RP) with constant vlue 6, and chromas are form 0.3 to 13.7 at intervals of about 0.5 in the Munsell renotation system. Results obtained are summarized as follows:
(1) Relative values of perceived colour-differences change little even when the illuminant is changed from the daylight D₆₅ to the illuminant A, and the constancy of perceived colour-difference holds as well as in the case of hue-difference.
(2) Colorimetric chroma-differences in the L^*u^*v^* and L^*a^*b^* spaces generally do not change much when the illuminant is changed.
But, because of the insufficient compensation of chromatic adaptation, those of colours of 3.5G in both spaces change slightly.
(3) Except for colours of 5Y and 3.5G, relative values of perceived colour-differences to colorimetric ones tend to become small generally with the increase in saturation.
(4) For colours of 5Y and 7.5GY, the correlation between perceived colour-differences and colorimetric ones is slightly low in both colour spaces irrespective of the illuminant.

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