Characteristics of a fluorescent lamp in direct current operation under high ambient-temperature conditions are investigated for application to the back-light system. It is shown that the problems relating to direct current operation of fluorescent lamps, which are light output reduction and short electrode life due to cataphoresis, can be solved by operating the lamp in such a high ambient-temperature obtained in closed fixtures of back-light systems. When the wall temperature was kept to be approximately 80°C, the total light output was approximately 6% higher in direct current operation than in alternate current operation. This may be due to the fact that the mercury atom density in the positive column is closer to the optimum value in direct current operation than in alternate current operation, when the lamp is operated in high ambient-temperature. The electrode life in direct current operation is as long as that in alternate current operation. The high mercury atom density in the cathode region due to cataphoresis may be effective to improve electrode life because of reducing cathode fall voltage.

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The rectangular discharge tube will be used for back light sources of a liquid crystal display because the uniform luminance over a wide range is expected. In this tube, the spectral intensity distributed in a cosine function. If a DC transverse magnetic field was applied to the positive column perpendicularly to the tube axis, the spectral intensity distribution was deflected to a tube wall. Therefore, AC transverse magnetic field would make the time averaged spectral intensity into a flat distribution. In this paper, the major axis distributions of the radiation intensity in the rectangular discharge tube were measured for helium, neon and argon as functions of gas pressure and AC magnetic field. The spectral characteristics were also measured for these gases. The tube used for measurements has a rectangular profile of 2×4 cm. The discharge current was 20 mA. The gas pressure was varied from 0.2 to 5.0 Torr. Then the experimental results were discussed qualitatively.

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Recently, low wattage HID lamps are developed and used steadily for an indoor illumination such as offices or stores. The ballast for the lamps is required to be in smaller size and lighter weight, and moreover it is required to have excellent function with good controllability. If the simulation model of the HID lamps is given for the behavior in transient such as in starting period, it is very useful for analysis and design of the ballast. In the paper, a simulation model for high pressure mercury lamps is proposed by means of state variable method. The equations are taken account of the state of each portion such as pressure, temperature and mercury vapor density, etc. The coefficient values of the equations are investigated physically and determined referred to experiment. The calculated results are in good agreement with the experimental results. Then, it is verified that the simulation model is available for the high pressure mercury lamps.

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Configuration factor can be obtained either from an area of orthographic projection on the unit-sphere method or from a means of illuminance calculation. The illuminance values can be obtained from dimensions of a building or horizontal and vertical angle values from calculating point by the via-perspective method. Therefore the calculation method using illuminance values is better rather than measuring the area of distorted figure which looks like particular barrel for orthographic projection on the unit-sphere method. Especially a method using angle values method is useful for computing required value rapidly from values measured by a transit at actual spot.

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