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:
May. 30, 1989
Filed:
Dec. 21, 1987
Peter Coops, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
Apparatus for scanning a radiation-reflective information plane (2). A scanning beam of radiation (b) from a diode laser (4) is focused by an objective lens (6) on the information plane and the beam reflected therefrom is deflected by a composite diffraction grating (9) so as to form two asymmetrical radiation spots (V.sub.1, V.sub.2) respectively focused on respective pairs of photodiodes (18, 19; 20, 21). The relative outputs of the photodiodes in each pair control focusing of the scanning beam on the information plane. The photodiodes in each pair are separated by a strip (22',23') positioned so that it is at an acute angle to the line (22, 23) along which the asymmetrical reflected radiation spot formed on the relevant diode pair becomes displaced as a result of variations in the wavelength of the scanning beam. Such angle is set so the separating strip is on the line along which the center of the intensity distribution of such radiation spot becomes displaced as a result of such variations. Consequently, such variations do not affect the relative outputs of the photodiode pairs and so are prevented from affecting focusing of the scanning beam on the information plane.