In making the design of interior lighting system, there are many cases in which the average illumination on the work plane becomes a subject of discussion, in accordance with lumen method which uses the idea of interreflections; besides, of interior interreflections, many studies have hitherto been made, but they have remained a mathematical analysis of integral equations under various conditions.
The authors attempt in this paper, to make a general remark on such a method of calculating illumination as follows: Availing itself of the fact that the luminous group that makes interreflections can be represented by electric networks, the calculation is made by the luminous analogue computer; the luminosity of each surface element, which constitutes the interreflection group, simulating electric potential ; coefficients, which represent both the reflection rate of each surface element and the luminous fl ux transfer between respective surface elements, simulating electric resistance; and the authors make a detailed study of the method of calculating illumination, in which the luminous analogue computer is made use of. That is, noticing the luminosity ratio of both the cylindrical room and the rectangular one within the range of an idealized room, and researching into this ratio, as compared with the data that have ever been published, the authors have carried out the experiment by the luminous analogue computer with a view to investigating the possibility of the equivalent replacement between the cylindrical room and the rectangular one (through the application of room coefficient kr); and obtained such a result as is mentioned in this paper.
Authors also described the effect of no. of wall section and the calculating method of the utilization factor U'.