When the numerical display devices with 7 segments were minutely observed on segments constituting figures, the luminous unevenness within a segment and the luminous difference among each segments had been found.
If the luminous unevenness exists, visual impression is not only bad, but it is feared to cause misreading by decreasing the visibility of figures.
Then various tests were carried to investigate throughly the relations between the luminous unevenness and visibility.
The following results were given from the various tests.
(1) The permissible luminous difference was 1.4% to 4.2% among segments with rated luminance.
(2) The luminous ununiformity caused from figures have given the different visibility and also shown the more difference of the threshold to recognize figures.

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Lamp characteristics are related to the temperature of the arc plasma in high-pressure discharge lamps in which local temperature equilibrium in established. In this paper the relationship between radial temperature profile of the arc plasma measured by optical methods and a mathematical model for lamps is discussed. These discussions can lead to an improvement of the mathematical model after taking into account the temperature frofile. The coefficients of the mathematical model equation are determined statistically by using the simplex method. The usefulness of this improved model is discussed, comparing the simulated results With experimental results for discharge lamps operated by resistance ballast.

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High frequency characteristics of operating HID lamps were presented over a frequency range of 60 Hz to 20, 000 Hz. But in order to develope a new solid state ballast, it is necessary to investigate the characteristics over 20, 000 Hz.
While operating HID lamps on high frequency power, the arc instability is observed. Arc flutters, snakes and sometimes extinguishes. This is called an acoustic resonance. This phenomenon occurs when the sound wave inside the arc tube specified by the tube shape and gases is resonant with the imposed high frequency power.
Metal-halide lamp is difficult to operate stably on high frequency power because the wide unstable frequency range exists between 20 kHz and 50 kHz.
The resonant frequency ranges of high pressure sodium lamp are narrow and exhibited at intervals. Therefore, HPS lamp is easy for the stable high frequency operation at the suitable selected frequency.
The stable frequency range of mercury lamp is relatively narrow and it can be easily shif ted with the lamp tolerance and the lamp watt variation for the same rated lamp. And so the high frequency operation is difficult for mercury lamp.
To eliminate the acoustic resonance, four ways of stable operation are presented. The first is to operate HID lamp at a frequency above all the acoustic resonancl frequencies. Secondly, square wave operation is good way for the stable operation The third is to operate with suitable frequency modulated waves. The last is to operate sinuous high frequency wave superposed with the 3rd harmonic frequency.
The third and the last are better for designing ballast. That is because these ways of operation would be realized by the practical circuit (approxmately 20-50 kHz) as the fluorescent lamp is operated.
The HID lamp solid state ballast should be developed by the way described in this paper.

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The initiation of arc on a newly developed cathode has been investigated experimentally as a function of the pulse voltage and the repetition time of the pulse. It is found that glow current is expressed as i=I₀e^αt before arc is initiated, where I₀ depends on the voltage and the repetition time, and α depends on the voltage but is nearly constant in the range of repetition time from 10 ms to 70 ms. The time lag at which arc occurs becomes shorter as the pulse voltage increases or as the repetition time decreases.
Two methods for prompting the occurrence of arc discharges are also reported. One is to apply a prepulse of a weak discharge before each main pulse. The other is to apply the same voltage with the main pulse to a metal ring outside the glass envelope of discharge lamp.
The former is more effective than the latter. Sometimes, no time lag of glow-to-arc transition was observed by the prepulse method, whereas the effect of the extenal ring is only to reduce the time lag to a half.

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The cathode spot is easily formed where the mercury is adjacent to the surface of glass plate contaminated with sputtered materials. Utilizing this fact, we developed such a new cold mercury cathode for pulsed arc discharge lamps that enables glow-to-arc transition to occur so quickly that current of several ten amperes can flow within several μs after each pulse voltage below 1kV is applied. The cathodes of different structures are tested in order to examine the stability and longevity of arc spots and the delay time with which glow-to-arc transition takes place. It is found that the cathode structure involving a piece of glass on the metal plate is of best performance.

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A generalized method of predicting photometric error sources due to the light emitting properties of the light source to be measured, is proposed. This method is based on a comparison of the radiant energy distributions of both test and standard sources on each axis in the space that characterizes the light emitting properties. As a result of applying this method to luminance measurement of color TV picture tubes, the following are determined to be error sources: (1) unusual spectral power distribution, (2) non-uniform luminance distribution over a phosphor screen, (3) deviation from the perfect diffusion, and (4) pulsed light due to electron beam scanning. Quantitative error analysis for a typical measurement shows that photometric errors due to the above sources are 2.6%, 0.1%, 1% and 2%, respectively.

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Two methods were proposed to determine accurately the relative spectral integrating sphere efficiency which plays an important role in the colorimetry for fluorescent materials by means of conventional color-measuring spectrophotometers.
The first method measures directly the relative spectral sphere efficiency by use of the irradiating light so urce and the reference white diffuser with the arrangement where either the fluorescent material or the standard white diffuser is placed alternately at the sample port of the integrating sphere. In this method the relative spectral sphere efficiency can be determined without using the spectral characteristics of the light source and the reference white diffuser.
The second method is an indirect estimation method which gives the efficiency by the calculation on the basis of the two quantites; the estimated value of the sphere wall reflectance based on the measurements where a light trap or a white diffuser is placed at a sphere port, and the ratio of the spectral sphere wall radiances when the standard white diffuser or the fluorescent material is placed alternately at the sample port. The accuracy of the second method was confirmed by comparing the values obtained from the method with the values directly measured by the first method. As a result, the color difference was less than 1.6 CIE LUV unit for several fluorescent materials.
Further, a simplified calculation method of the integrating sphere efficiency tried first by Billmeyer, Jr. et al. was also compared. As a result, this simplification method can include the error caused by neglecting the effect of the re-absorption and the re-emission of the fluorescence in addition to the error caused by the assumption of ideal integrating sphere. The errors of the colorimetric quantities are estimated to be more than 2.0 CIE LUV units for several fluorescent materials.

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High pressure sodium lamps have been known as convection phenomena of the arc are so small. Recently, the arc tubes with larger diameter and high pressure xenon filling have been used for the HPS lamps with high color rendition or high luminous efficacy. It was found the convection phenomena were not negligible in such HPS arc tubes. This phenomenon was confirmed by measuring the 475.1nm sodium line intensity and knowing the displacement of the arc axis. The results are:
(1) the convection becomes larger with increasing arc tube diameter and filling xenon pressure,
(2) the convection becomes smaller with increassing the power input. And the temperature difference of the upper and lower side of the arc tube wall inthe horizontal operation was estimated 40-50°C and this local heating of the arc tube will be a problem in the life of HPS lamps.

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This CAD system consists of two stages. In the first stage, a shape for the reflector is designed automatically which provides a candlepower distribution by the reflector as close to a required distribution as possible within a range of dimensional limits. Many shapes for the reflector are usually designed depending on designing parameters which are already decided by the designer. In the second stage, a precise prediction of the candlepower distribution of the designed reflector is made, considering the luminance distribution on a lamp surface. The prediction is made for the shapes of the reflector which have adequate values of candlepower distribution and luminaire efficiency in the former stage.
The CAD system changes the design of luminaire reflectors by designers into the automatical design by computer, and provides us highly efficient reflectors and rapid design of the reflectors.

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The optical target-coordinator is the important element in automatic infrared tracking systems for moving target. In this paper, we propose a method for optical-coordinator which is possible to determine the coordinates of the target with its surrounding background noise. This system has two kinds of optical modulating discs aligned with cascade on co-optical-axis and rotated in one direction with different velocity.
One of them is an involute reticle reported previouslly by the authors, which has excellent characteristics for suppression of background noise. And the other is used for determination of the target location, named “coordinate reticle” here.
Usually, the problem in such a double reticle system is a false signal causd by projection from the front reticle to the rear ond. This is, however, avoidable by means of separating each main path-band of spatial transfer function of two reticles. Validity of this approch is proved theoretically and experimentally. And effectiveness for the coordinator is confirmed through some experimental results.

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