With spread of office automation system, Visual Display Terminal (VDT) became offen and usually used in office works. CRT (Cathode Ray Tube) displays are most usual unit of VDT. For most common positive contrast type display, wherethe character luminance is higher than the background luminance, lighting conditions on the display screen bring essential influence on visibility of the characters on the screen. Especially in these conditions, reflection of external light sources on the display screen has very important influence on the visibility of the characters. Experimental study using subjective appraisal was carried out to find out permissible range of reflected luminance related to the charactor luminance and the backgroud luminance. The results are as follows: (1) Preferable luminance of the charactor Lc' related to the background luminance Lb', which is proportional to the normal or vertical illuminance on the screen, is expressed with the empirical formula Lc'=16×Lb'0.71 (2) Under above condition, permissible value of the refrlected luminance Lr' is expressed with the empirical formula Lr'≅1.9Lb'0.19 or with the contrast form (luminance ratio) C=Lr'/Lb'≅1.9×Lb'-0.09 (3) Furthermore, for the practical range of the Lb', this contrast (Lr'/Lb') nearly constant and about 1. 2, for the display used in the experiment. To avoid reflected luminance, Lr' should be kept under 1. 2×Lb'. Where every Lc', Lb' and Lr' is total luminance overlapped with reflected component of the diffuse reflection on the screen.
The electron swarm parameters in Hg/Ar mixtures, which are important in connection with making Hg discharge lamps, are analysed using a Boltzmann equation in which Penning and cumulative ionizations are properly taken into consideration. This method is shown to be appropriate, since the present Townsend ionization coefficients are in good agreement with the experimental values of Burgmans et al over almost the whole range of E/P0 and ratio of the Hg to the total atom concentrations K where the experiments were carried out. The range of E/P0 where Penning, cumulative or direct impact ionization is dominant is quantitatively shown. The excitation coefficient for the 63p1 level of Hg from which 253.7 nm light radiates is obtained as a function of E/P0 and K, and is discussed in connection with the output of luminous flux of fluorescent discharge lamps.
The warm up characteristics of fluorescent lamp dosed with amalgam have been analyzed. The main amalgam is con tained in the exhaust tube and a pieces of amalgam is located near each electrode. The results are as follows; (1) The warm up characteristics of the lamp depend strongly on the off-time. (2) The mercury weight in auxiliary amalgam increases in proportion to the off-time. The mercury amount in auxiliary amalgam influences the warm up characteristics of the lamp. (3) The warm-up time of the lamp depends on the time required for the mercury in auxiliary amalgam to diffuse in to the discharge space and then to be absorbed on the main amalgam.
A simulation model which describes the time-dependent behavior of the positive column of a low-pressure mercury-rare gas discharge was developed. Excitation processes of Hg 61P1 level was analysed by comparing afterglow characteristics of the observed discharge with those of an elementary model. A stepwise excitations from Hg 63P levels were shown to be dominant processes, and were introduced into the model. From the experimental analyses, the electron energy distribution function was proved to be non-Maxwellian in the discharge under consideration. In the model calculation, the distribution function was approximated with a two-temperature representation. Relative intensities of the Hg 254 nm and 185 nm radiations from a 24 mm diameter tube were measured for coldest spot temperatures between 20 and 60°C. There was a good agreement between the measurement and the calculation for the 254 nm radiation. The calculated 185 nm radiation power was found to be larger than the observed results at the low mercury pressure end.