Photoelectric colorimeter

Abstract

Abstract PURPOSE: To widen a measurement range and accurately indicate color coordinates, by logarithmically compressing the output current of a light receiver to pick out the current. CONSTITUTION: Logarithmic compression light measuring circuits are composed of light receivers PD 1 WPD 3 , diodes D 1 WD 3 and operational amplifiers OA 1 WOA 3 . Spectra of light applied to the light measuring circuits through filters F 1 WF 3 are changed into signals corresponding to three logarithmecally compressed stimulus values X, Y, Z. The signals are picked out and supplied to an A/D converter 4 through a multiplexer 2 in a time series manner so that the signals are changed into digital signals. The digital signals are applied to a calculation circuit 6, which performs prescribed calculation and index conversion to indicate chromaticity coordinates by a dispaly circuit 8. Since the outputs of the light receivers are picked out through logarithmic compression, the amplitude of the handled signals is reduced. This results in widening the measurement range and enabling the indication of accurate chromaticity coordinates. COPYRIGHT: (C)1981,JPO&Japio

Inventors

• 👤 Yoshio Yuasa

Bibliographic Details