Color rendering property (Ra) is one of the important indexes to evaluate the performance of illuminant. Controlling the light intensities for the four kinds of color LEDs (red, green, blue and white) on the portable-sized full-color LED panel, and then adding blue LED with different wavelength, the authors gained the high rendering property of Ra=96. At that time the Ra of the white LED was 87. This result concludes that it is possible to obtain superior color rendering property (Ra) even if the Ra of the white illumination alone is not high.

We have investigated the minimum discharged power to maintain lamp plasma in terms of dependence on buffer gas condition and driving frequency of the electrodeless compact fluorescent lamp (ECFL). It is essential for realization of the low-frequency driven ECFL with inductively coupled plasma technique for household use. Considering the point of cost, the driving frequency of the electrodeless discharge lamp should be lowered because high frequency driving (> 1MHz) requires special components for reduction of EMI noise and circuit power loss with the increase in driving frequency. But it is difficult to maintain plasma at low frequency driving, since induced electric fields, which excited with the induction coil is declined and not receive energy for ionization and discharge sufficiently. Here, we indicated that the condition of minimum power to maintain the H-mode (inductively coupled) discharge described as simple functions of buffer gas pressure and driving frequency for a fixed lamp bulb shape and found that the relation can represent the measured data well. Using that relation, we can easily predict optimum buffer gas pressure from driving frequency and required minimum maintenance power on the commercially available (practical) standpoint.

Super high pressure mercury discharge lamps have been used as UV light sources for photolithography, such as patterning LCDs, PCBs and semiconductors. The bulbs of the lamps are generally made of silica glass. This study evaluates optimal shapes for various lamp bulbs under internal pressure employing the Finite Element Method (FEM). As the result, the optimal shape of the bulb was obtained and the relationship between the rupture stress and the bulb wall thickness t was clarified. The optimal shape of the bulb obtained is 0.7 ≤ D/L ≤ 0.85, where L is the total length of the bulb and D is the diameter. Static water pressure-tests were conducted in order to verify the numerical results. It was found that tendency between the numerical results and experiments were in fairly good agreement.

Several mathematical models for discharge lamps have already been offered. However, all these models are only used for the operating state. There are not any models for the starting process. This paper is concerned with the mathematical model for the starting process of discharge lamps. Newly introducing the concept of heat quantity, the authors were able to produce a mathematical model to represent the starting process of the low pressure sodium lamp. In this paper, the following comparison between the theoretical results using this model and experimental results on the low pressure sodium lamp are discussed.(1) Lamp voltage and current waveforms in the starting process.(2) Evaluation whether or not the lamp can get to operating state.These investigations showed that this model is available for representing the starting process of the low pressure sodium lamp.