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. 28, 2006
Filed:
Oct. 16, 2003
Seiji Nishiwaki, Kobe, JP;
Kazuo Momoo, Hirakata, JP;
Youichi Saitoh, Hirakata, JP;
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
An optical disk device is provided that can realize favorable recording/reproduction of signals on/from an optical disk having a plurality of signal planes arranged in proximity to each other. In this optical disk device, a hologram () is divided into n(n≧2) regions Ak(k=1, 2, . . . , n) by a straight line that intersects with an optical axis, and a photodetector () is divided into at least two regions A and A'. Light emitted from a light source () is focused on a signal plane () or () included in a plurality of signal planes of the optical disk by an objective lens (). Light reflected from a first signal plane () and light reflected from a second signal plane () pass through the objective lens () to turn into light beams a and a′, respectively, that enter the hologram (). 1st-order diffracted light beams ak and ak′ having a common diffraction optical axis are derived from the light beams a and a′ that have entered the regions Ak of the hologram (), respectively, and are projected on the photodetector (). Distributions of the 1st-order diffracted light beams ak and ak′ on the photodetector () are approximately inverted with respect to an intersection point of the diffraction optical axis and a detection plane. The 1st-order diffracted light beam ak is approximately within the region A and the 1st-order diffracted light beam ak′ is approximately within the region A′.