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:
Nov. 15, 1994
Filed:
Mar. 29, 1993
Tomoyuki Shirai, Tokyo, JP;
Asahi Kogaku Kogyo Kabushiki Kaisha, Tokyo, JP;
Abstract
A relative velocity sensing device for sensing an optical beam spot, for example, by using a tracking error difference signal that fluctuates as a sine-wave in accordance with a movement of the beam spot. The tracking error difference signal is converted into a first sawtooth wave signal, and a second sawtooth wave signal, having a phase which is offset from the first sawtooth wave signal by one half of the period thereof. A first differential signal is obtained in accordance with the first sawtooth wave signal, and a second differential signal is obtained in accordance with the second sawtooth wave signal. The level of a tracking error sum signal is shifted to obtain a level-shifted signal, so that a polarity signal is obtained. The first differential signal is selected when the polarity signal is positive, and the second differential signal is selected when the polarity signal is negative and, thus, a velocity signal showing the velocity of the beam spot with a high accuracy may be obtained.