The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 25, 1990
Filed:
Dec. 01, 1988
Seikosha Co., Ltd., , JP;
Abstract
A photometric circuit comprises a switching circuit which causes a photo conductive element which responds to the luminance of an object of measurement to be selectively connected with an oscillation circuit so that the photo conductive element functions as a frequency determining element and a frequency ratio calculating circuit which calculates a ratio of the oscillation frequency obtained when the photo conductive element is in connection with the oscillation circuit to the oscillation frequency obtained when the photo conductive element is not connected with the oscillation circuit. Thus, it is possible to reduce the required capacitance of the capacitor operating as a frequency determining element, lower the voltage required to drive the circuit and yet achieve high measuring accuracy.