Automatic Light Distribution Measuring Equipment

A precise and feasible equipment for the measurement of light distribution is described. It consists of a light-source support, a revolving mirror, an optical system, servo systems for photometry and recording-pen speed control, and a polar coordinates recorder. The revolution of the optical system on the light receiver is synchronized with the revolving mirror in order to keep the normal incidence to the detector. The method of automatic balancing flicker photometry with a rotating chopper is newly adopted in the measurement of luminous intensity from a light source in order to eliminate the error caused by the fluctuation of luminous flux and by that of detector sensitivity. The intensity of light as a relative value to a luminous flux emitted in a certain direction is, therefore, measured. An automatic controller which keeps the speed of the recording pen approximately constant in a polarcoordinates recording by varying the rotating speed of the revolving mirror, is also newly introduced to perform the precise and efficient recording. One complete measurement in a vertical plane takes about four minutes. Maximum weight of the luminaire mountable is 100 kg.