GB1097558A - Radiation measuring apparatus - Google Patents

Abstract

1, 097, 558. Photo-electric systems. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 16, 1965 [Dec. 28, 1964 (2)], No.53367/65. Heading G1A. Apparatus for measuring the intensity of radiation comprises a plurality of pairs of diodes, the diodes in each pair being connected in opposite conducting relationship and at least one diode of each pair being radiation sensitive, means connected to one end of each pair of diodes applying a varying voltage thereto, and means connected to the other end of each pair to measure the total current through said pairs. When the sawtooth voltage applied to the diode pairs by driver 12, Fig. 1 is negative the diodes 20 are back biased, but as its value goes through zero they conduct the leakage current of the photo-diodes. This leakage current is controlled by the illumination of the photo-diodes, and the total current is dependent upon the number of photo-diodes illuminated. The delay due to the capacitance of the diode pair in switching after the sweep voltage passes through zero depends upon the intensity of illumination and may be used to determine how many photo-diodes are illuminated by various intensities of light. The diode pairs may be arranged in a two dimensional array to measure the area of objects interrupting uniform illumination of the array. The position of an object may be determined by connecting the diode pairs to points on a D. C. voltage divider, Fig. 6. As the sweep voltage is applied by driver 144 the diodes 120 switch on in turn and the total current increases in steps except where the photo-diode is obscured by the object 142. The changes in total current are detected by a differentiating transformer 132A, B. The battery 122 may be replaced by a transistor constant current source, Figs. 8 and 9 (not shown). The diodes and photo-diodes may be formed as a continuous three layer wafer as in Specification 1, 010, 583.