The discharge voltage waveform deteriorates as the discharge tube diameter is reduced. The relationship between discharge voltage waveform and discharge characteristics are calculated using Fourier series expansion, and examined by experiment. The deterioration causes a high sustaining line voltage and a low lamp power factor. High sustaining line voltage in a narrow-tube lamp requires a lower discharge voltage than that for a conventional fluorescent lamp. This produces one of the limitations for reducing discharge tube diameter. The circuit methods that alleviate the above limitation are investigated. In the result, superimposition of pulsed voltage on the discharge voltage during the relight phase proves to be a very efficient way of reducing wareform deterioration. A small capacitance of 0.068 μF connected across the lamp improves the lamp power factor by 1.2%. The other method, the ballast-plus-switching-circuit, can increase lampefficacy by 5.2%.

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This paper is concerned with the: investigation of the open circuit characteristics of the lead-peak type ballast. First, the exciting characteristics based on the equivalent circuits of the secondary core portion involving the bridged core is derived, and its theoretical characteristics are compared with the experimental results. Secondly, the wave shape of the secondary induced voltage is discussed to compare with its exciting characteristics theoretically and experimentally. It is apparent from these results that the maximum value of the induced voltage depends both on the maximum value of the applied voltage and the turns ratio of the lead-peak type transformer, and its RMS value depends on the reluctance ratio of the shunt path to the secondary core path. The calculating formula of the crest factor of the induced voltage is also derived.

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This paper represents a new continuous dimming circuit for fluorescent and High-Intensity Discharge(HID) lamps controlled by inverse parallel connected thyristors with a newly introduced auxiliary step-up transformer. The dimming circuit can not only regulate the light output over range from 100% to 1% continuously, but also can sustain lamp burning steady even if in a lower ambient temperature. These features of the dimming circuit are due to giving a sufficient high reignition voltage to discharge lamps and continuing the lamp current, even though the thyristors are in off period, by the auxiliary step-up transformer.

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The purpose of this study is to investigate the just readable threshold of Chinese characters of different styles as a function of the adaptation luminance. The test objects are 44 Chinese characters comprising from 2 to 19 elements from among those most frequently appearing in news papers and the styles of which are Gothic, Ming, semi-cursive and pen-written square, in daily use. The observers are of all normal vision, and the just readable threshold coressponding to 50% threshold is used. Results obtained are as follows.
(1) The relation between the just readable threshold by style and adaptation luminance are approximated by following formulas:
Gothic style: θ=(3.514(0.3394+L^1/4)⁴/L (minutes)
Ming style: θ=(3.590(0.3485+L^1/4)⁴/L (minutes)
Semi-cursive style: θ=(3.721(0.3528+L^1/4)⁴/L (minutes)
Pen-written style: θ=(3.815(0.3978+L^1/4)⁴/L (minutes)
where θ is the visual angle (minutes) of the character’s height at the just readable threshold, and L is the adaptation luminance (cd/m²).
(2) Comparison between above formulas and approximate curve of minimum angle of resolution of the break width of the Landolt ring shows that the line width of the Gothic styles at the threshold are considerable lower than those estimated from the visual acuity. The heights of the characters measured in terms of visual angle at the threshold are 9.2 times as large for Gothic, 9.5 times for Ming, 10 times for semi-cursive and 11 times for pen-written square as that of break width of Landolt rings.
(3) To recognize a Chinese character, first of all it must be of a certain size, and the line composing the character must be a certain width in order to distinguish the details, from the correspondence with the approximate curve of visual acuity.

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In recent years, microcomputers have been widely used in connection with sensors or transducers for special use in applied measurements and controls. Visual photometric methods have been largely replaced commercially by physical photometric methods and their application techniques. In this study the authors made a trial model of an interface between a TV camera and a microcomputer. The interface consists of three main parts: a sample & hold circuit, an A-D converter circuit, and a timing control circuit. Work was carried out for simple measurement of the luminance distribution pattern of a luminaire with FL20 W×2 on a color CRT device which displays eight gray levels.

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