Patent ID: 8159909
Filing Date: 2012-04-17
Classification: G11B

Abstract:
1. An optical drive apparatus comprising: an optical head that applies laser light onto a recording medium having a plurality of information recording layers for recording and/or reproduction and that detects reflected light from the recording medium; a signal generating circuit that generates a focusing error signal, a tracking error signal, and an information signal on the basis of the reflected light detected by the optical head; a reproduction circuit that obtains reproduction information by processing the information signal generated by the signal generating circuit; and a servo circuit that performs focusing servo operation and tracking servo operation according to the focusing error signal and the tracking error signal generated by the signal generating circuit, wherein the optical head includes a laser light source for emitting the laser light, an optical system that produces 0-order diffracted light, +1-order diffracted light, and −1-order diffracted light from the laser light emitted from the laser light source, that forms an optical path for applying the 0-order diffracted light, the +1-order diffracted light, and the −1-order diffracted light onto the recording medium, and that forms an optical path for guiding the reflected light from the recording medium, and a light-receiving device for receiving and detecting the reflected light guided by the optical system, wherein the light-receiving device includes a first light-receiving section divided at least in a tangential direction of a recording track on the recording medium to detect reflected light of the 0-order diffracted light, two second light-receiving sections divided at least in the tangential direction of the recording track on the recording medium to detect reflected light of the +1-order diffracted light and reflected light of the −1-order diffracted light, and two third light-receiving sections provided near each of the two second light-receiving sections and at positions such as not to receive reflected light of the 0-order diffracted light, reflected light of the +1-order diffracted light, and reflected light of the −1-order diffracted light from a target information recording layer of the information recording layers to be accessed, the third light-receiving sections receiving stray light reflected from one or more information recording layers other than the target information recording layer, wherein the third light-receiving sections each have an area equivalent to the area of photoreceptors of the two second light-receiving sections, and wherein the signal generating circuit generates the tracking error signal in a differential push-pull method on the basis of detection signals from the first, second, and third light-receiving sections, wherein the signal generating circuit generates a first push-pull signal for the 0-order diffracted light on the basis of the detection signal from the first light-receiving section, generates a second push-pull signal for the +1-order diffracted light and a third push-pull signal for the −1-order diffracted light on the basis of the detection signals from the second light-receiving sections, standardizes the first, second, and third push-pull signals, generates the tracking error signal by operation on the standardized first, second, and third push-pull signals, and generates, on the basis of the detection signal from the third light-receiving sections, standardization signals used to standardize the second and third push-pull signals.