JP2002092905A5 - - Google Patents

Claims (5)

 An irradiation optical system that focuses a light beam on a track on an information recording surface of an optical recording medium to form a spot, and a light detection optical system that guides return light reflected and returned from the spot to a photodetector And an optical pickup device that detects a focus error of the light beam, and extends in a direction perpendicular to the extension direction of the track and a direction perpendicular to the extension direction on a plane perpendicular to the optical path of the return light. The first to fourth quadrants divided from the center of the optical path with two dividing lines as a boundary, and each other around the optical path to the return light passing through the adjacent region on the same side with the dividing line as the boundary A focusing error detecting optical element for providing astigmatism in a direction rotated by 90 degrees and separating the return light into at least four for each region, and receiving the separated return light, each receiving astigmatism. In an optical system with aberration A plurality of spaced apart light receiving areas each having a contour line corresponding to the parting line on the image plane where the light beam is circular and divided by two parting lines extending substantially parallel to one of the contour lines. A light comprising: a photodetector having a light receiving element; and a sub light receiving element disposed adjacent to each light receiving region along the contour line corresponding to the dividing line of the light receiving element. Pickup device.  2. The optical pickup device according to claim 1, wherein the two-part dividing line of the light receiving element extends in a direction perpendicular to an extension direction of the track.  The two dividing lines of the light receiving element are the two light receptions of the light receiving element caused by the spot of the return light received on the light receiving element on the image plane where the light beam is circular in the optical system provided with astigmatism. 3. The optical pickup device according to claim 1, wherein the optical pickup device extends to a position where signals output from the region become substantially equal.  The sum of the differences of the signals output from the sub light receiving elements is added to the sum of the differences of the signals connected to the light receiving elements and the sub light receiving elements and output from the two light receiving regions of the light receiving elements. The optical pickup device according to claim 1, further comprising a focus error signal correction arithmetic circuit that generates a focus error signal.  The focus error detecting optical element includes a cylindrical lens centering on the extending direction of the dividing line, which is arranged at one diagonal position in the first to fourth quadrant regions, and the other diagonal position. A cylindrical lens having a central axis in a direction that forms 90 degrees with respect to the extending direction of the dividing line that is arranged, and the central axis of each of the cylindrical lenses arranged in at least one diagonal region is The optical pickup device according to claim 1, wherein the optical pickup device is eccentric in parallel with the dividing line.