Patent ID: 9728219
Date: 2017-08-08
CPC Classifications: G11B

Claim:
1. An optical information reproduction device which reproduces information from an optical information storage medium by using holography, comprising: a laser light source for generating a reference beam; an image-capturing unit for detecting a diffracted beam to be reproduced from the optical information storage medium; an optical detection unit having at least two light-receiving surfaces and used for detecting a diffracted beam reproduced by irradiating the optical information storage medium with the reference beam; a light-shielding unit for shielding a part of the diffracted beam detected by the optical detection unit; and an error signal calculation unit for generating an angle error signal from a detection signal outputted by the optical detection unit, wherein the light-shielding part is disposed at a position other than a focal point of the diffracted beam, and shields at least one end in a multiplexing direction of the diffracted beam detected by the optical detection unit or in a direction perpendicular to the multiplexing direction, wherein the optical detection unit outputs different detection signals with respect to reference beams having different angles, and wherein the angle error signal calculation unit generates the angle error signal of the reference beam based on the a differential operation signal of at least two detection signals output from the optical detection unit.