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:
Feb. 09, 1988
Filed:
Jun. 13, 1985
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
An optical head in which the light emitted from a light source is narrowed to a minute spot of light and applied to a recording medium such as a disk thereby to effect recording and reproduction, or reproduction alone. A focusing plate or prism is provided in the optical path for forming the image of the light reflected from the recording medium. The focusing plate or prism has a first surface which reflects and transmits the reflected light and a second surface which is located closer to the image-forming position than the first surface and reflects the reflected light which is transmitted or reflected by the first surface. The optical head is further provided with a photodetector which is divided into at least two portions which individually receive the light rays which are respectively reflected from the first and second surfaces. A focusing servo control signal is obtained from the difference between the respective outputs of the divided photodetector portions. Moreover, a tracking servo control signal is obtained from the difference between the respective outputs of the peripheral portions among the divided photodetector portions.