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:
Oct. 20, 1992
Filed:
Jun. 19, 1990
Makoto Hino, Tokyo, JP;
Ricoh Company, Ltd., Tokyo, JP;
Abstract
In a method and an apparatus for measuring a rotary speed of a rotary body, right and left circularly or elliptically polarized lights are incident to a polarizer attached onto a rotary face of the rotary body as a measured object. An optical beat signal is generated when the polarized lights are incident to the polarizer. This optical beat signal is detected a photodetector, etc. The rotary speed of the rotary body is calculated from a beat frequency of the optical beat signal. An optical rotator may be arranged on an optical path on which the right and left circularly polarized lights obtained through a 1/4 wavelength plate are transmitted toward the polarizer. A corner-cube prism may be arranged between the rotary face and the polarizer to reflect the light beam transmitted through the polarizer toward the photodetector. The apparatus may have an optical member for totally reflecting the light beam reflected on the rotary face of the rotary body through the polarizer and guiding the totally reflected light beam to the photodetector.