Patent ID: 6438091
Filing Date: 2002-08-20
Classification: G11B

Abstract:
An optical head comprising:a light source; an object lens which condenses a light emitted from said light source; a photo-detecting device operable to divide a light beam reflected from an information recording medium to a plurality of light beam portions spatially and to detect the plurality of light beam portions; a processing device operable to process signals of the plurality of light beam portions detected by said photo-detecting device to supply a tracking error signal; and a tracking controller operable to control said object lens according to the tracking error signal to make a light spot on the information recording medium follow an information track formed on the information recording medium; wherein said photo-detecting device divides a light beam reflected from the information recording medium to a plurality of light beam portions by a first division line extending along a direction of the information track and at least one light-shielding area, wherein said at least one light-shielding area is arranged along a second line extending through a center of the light beam and being perpendicular to the first division line, so that said at least one light-shielding area on one side of the first division line and said at least one light-shielding area on the opposite side of the first division line are symmetrical with respect to the first division line, and wherein the processing signals to supply the tracking error signal in said processing device are not affected by a light going inside of said at least one light-shielding area.