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. 22, 1994
Filed:
Jun. 08, 1993
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
A multi-beam optical recording-reproducing device is capable of detecting the focusing and tracking errors of respective beams independently of each other by means of a simple optical system. The optical system for independent tracking error detection may include a wedge prism 39 and a four-partitioned photosensor 42, and that for the independent focusing error detection may include a half prism 33 for dividing the beams into reflected and transmitted portions, first and second knife-edges 34 and 19 for the reflected and transmitted beams, respectively, and a first and second two-partitioned photosensors 35 and 20 for receiving the beams via the first and the second knife-edge, respectively (FIG. 7). Alternatively, the optical system for independent focusing error detection may include a single knife-edge plate 61 having two knife-edges, and a four-partitioned photosensor 64 (FIG. 10), or a wedge prism 71 and an eight-partitioned photosensor 74 (FIG. 12). Further, the optical system for independent tracking error detection may include a concave cylindrical lens 83 (FIG. 14) forming a far field pattern perpendicular to the tracks on the information storage optical medium 9.