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:
Dec. 13, 2011
Filed:
Feb. 06, 2009
Masahisa Shinoda, Tokyo, JP;
Masahisa Shinoda, Tokyo, JP;
Mitsubishi Electric Corporation, Tokyo, JP;
Abstract
An optical pickup has a semiconductor laser device that can emit laser beams with different wavelengths. A beam splitter and objective lens direct the emitted beam onto a rotating optical disc. Reflected light returns through the objective lens and beam splitter to a photodetector. A pair of liquid crystal elements on the optical path from the optical disc to the photodetector have controllable lens functions acting in different directions to produce an adjustable astigmatic effect that enables the photodetector to generate a focus error signal with a linear range appropriate for the type of optical disc, the number of signal layers in the optical disc, and the spacing between the layers.