Although the surface-integration method is fundamental way to calculate the illuminance by a flat surface source, its application to a complex source has been considered to be difficult,
It, however, turned out that this problem can be solved by the perspective figure of the flat surface source on a horizontal picture plane in the height of v from illuminated plane is obtained by the via-perspective method.
Then, the illuminance obtained from elementary area t·dtde of the perspective figure in polar-system is calculated by the surface-integration method, as shown in the following equations.
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Where E=the illuminance at calculating point, L=the luminance of the source, t=the radius vector to the elementary area, p=the radius vector to the contour, θ= the radious vector angle from the y axis, n=the intercept on the y axis, l= the distance between the elementary area and the calculating point.
The above second intermediate equation obtained from the double-definite-integration when solved for t is transformable to the modiffied-cotour-integration formula, as shown in the third equation.
Since this modiffied-contour-integration formula is applicable to all forms of the flat surface source, the application range of surface-integration method can extend even to all types of complex fiat surface source.

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Reduction of discomfort glare from a lighting installation is one of important factors for comfortable lighting.
In a practical room, there are several light sources located at various positions. If an occupant look around room, he will see the light sources in both central and peripheral vision.
Therefore it is important to establish criteria of discomfort glare effect for two or more sources in both central and peripheral positions.
For the discussion on the criteria, the difference of the glare effects between central and peripheral visions needs to be clarified.
However, the experiments in former studies are not sufficient for this purpose. Authours conducted an experimental study of subjective appraisal regarding the comparison of glare sensation from the light sources in the central vision and peripheral vision.
Authours compared glare of light source in the central vision with each light source in the peripheral vision of upper side, right side and lower side location.
The results are as follows:
(1) Both source positions have similar slope in the equal-glare curve showing the relationship between source and surrounding luminance.
(2) As far as the glare effects from solid angle of a source, peripheral vision of right side and lower side source positions is similar to central vision, but peripheral vision of upper side source position is not similar.
(3) The results regarding the peripheral vision of upper side source position, show some similarities to the study by Hopkinson and Bodmann.

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In order to study the average road surface luminance that should be provided by lighting installations, drivers' behaviour at dusk related to the use of clearance lights and or headlights of cars, were surveyed at a number of average road sites, including a motorway stretch, under average traffic conditions.
Cars were counted at 1 minute intervals to determine what percentage of cars were using headlights, using only clearance lights, or not using lights at all.
Finally, the luminance values, when the percentages of cars using clearance lights or headlights were at certain predetermined levels, were derived and compared with previous studies. It was found that the road surface luminance values have increased by a factor of about 2 during these past thirty years or so.
Based on the survey, the road surface luminances of 1.8, 1.5 and 2.5 candela per square meters, respectively, are recommended for average roads without glare shielding for oncoming traffic, those with glare shielding, and motorways with glare shielding on the central strip.

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Since daylight is natural light which consists of light from the sun and that from the sky, it varies according to the altitude of the sun and the meteorological condition. So, it is very difficult to carry out the daylighting design by using absolute value of daylight illuminance. Therefore, in the field of daylighting design, the configuration factor is widely used as an index of brightness because it is not affected by variation of illuminance.
So far, researchers, in order to obtain the configuration factor, have devised various methods on the optical photographic photometry such as a globoscope and a camera with a fish-eye lens. By the above methods, however, the configuration factor is obtained only through laying an equi-configuration factor diagram on a picture and counting the parts produced by the meshes. Those methods involve troubelsome work.
Therefore, the authors have developed a method to calculate the configuration factor by a personal computer system using pictures taken by an instantaneous camera. By this calculation method, the configuration factor on any point in the room is obtained by using several pictures taken by the instantaneous camera.
As an example, the configuration factor of the hall where the multilateral daylighting is used is calculated. Futhermore, the authors obtain the iso-configuration factor curves by the computer graphics.
Besides, by this method, the configuration factor is obtained more simply in a shorter time. This paper deals with this calculation method.

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Reduction of reflected glare on such visual tasks as works on printed papers in an office is one of the most important factors of office lighting designs.
Conventional evaluating method based on the contrast of printed characters to thebackground paper is complicated for practical lighting design works.
Experimental studies have been carried out to find out a practical design guide of permissible luminance limits of reflected light source related to the illuminance on a paper.
As objects for visual tasks, printed papers in six reflectance combinations of characters and papers by white, gray and black were adopted.
Authors adopted the total feeling levels of the permissible reflection including the legibility of the characters as the criteria.
The results are:
(1) As far as the experimental condition using 40W fluorescent lamp lightng fittings, reflection of light source is permissible for a wood free paper and a mechanical printing paper.
(2) In the most general case of black characters on a white art paper, the practical guide of the permissible luminance for 500 lx illuminance design would be 1800cd/m² for uniform luminance light source, 4500cd/m² for non-uniform luminance light source, in terms of category “Agreeable”.

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The design of a back-lighting system for color LCDs using hot cathode fluorescentlamps requires consideration of the lamps' life, heat evolution and thin making. We developed a long life hot cathode fluorescent lamp whose diamiter is 10 mm. The improved cathode design, installation of getter and pre-heat operation brought about an excelent long life of more than 5000 hrs. under continuous operation and 60000-80000 cycles under flickering test. We described the practical heat design of the back-lighting system. The center-gap cored transformer of the inverter contributed to lowering the heat evolution of the system, when the inverter was packed in a chassis to keep the display system off an electro-magnetic interference. As the exhaust tip of the lamp was settled outside the lamp house, the lamp was easy to re-start at high surface temperature of the lamp above 100°C. The lamp showed good adaptability to edge-lighting of a thin back-lighting system with little increase in temperature of the illumination surface. Moreover we discussed the possibility of the possibility ofthe application of this system for a re-chargable battery driven hand-held conputer.

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This paper reports the results of MTF (Modulation Transfer Function) measurement and simulation of petterns in fog. Fog was produced in a fog chamber. First, temporal density change of fog and particle size distribution of water in fog, were investigated. To evaluate optical properties, MTF properties using grating patterns, was measured. One grating pattern was displayed on a white diffuse flat panel illuminated by installed fluorescent lamps, and another was displayed on a panel illuminated by other lamps from outside. Estimating the MTF properties of assumed fogs from the MTF properties obtained, simulation of patterns passed through the fogs, were carried out by a computer graphic device, and those pattern perceptibility were compared. As a result, the detailed shape of the pattern should depend on imaging aspects of transmitting light with slighttly scattering. Moreover, perceptibility of signal pattern under the fog density indicated by visibility distance: 1500m, was discussed.

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The CIE glare safeguard system is based on a series of experiments by Söllner/Bodmann. In their experiments, a great variety of lighting conditions were presented to many observers, using one-third scale model rooms. The observers were asked to evaluate the degree of discomfort glare under each condition. In these experiments, söllner/Bodmann assumed that the evaluation of the discomfort glare corresponds to the luminance of the central unit of all luminaires seen by the observer. This luminance is taken as the glare luminance.
But it can be logically assumed that discom ort glare is influenced not only by glare luminance but also by other luminaires' luminance. Therefore, to investigate the validity of the glare luminance proposed by Söllner, /Bodmann, a series of experiment were conducted.
In the experiments, six lighting conditions, in which glare luminances were constant, were presented to observers. Each observer was asked to compare the degrees of discomfort glare of those lighting conditions and to say whether the degrees of their discomfort glare were constant or not.
From the result, it was found that the degrees of discomfort glare under those lighting conditions were not constant, even if those glare luminance were constant. Furthermore, it was found that the value of glare luminance does not always correspond to glare sensation of the room.

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