Patent ID: 9672860
Date: 2017-06-06
CPC Classifications: G11B

Claim:
1. A recording/reproducing apparatus comprising: an objective lens which focuses guide light on a guide layer in an information recording medium and which focuses information recording light on an information recording layer in the information recording medium; an area-dividing diffraction grating which divides return light from the guide layer in accordance with a plurality of areas, including a first area and a second area that does not overlap the first area; an astigmatic optical system which imparts astigmatism to a zero-order beam, a positive first-order beam and a negative first-order beam, into which the return light is divided by the area-dividing diffraction grating; a light-receiving element including (i) a first light-detecting cell group which receives a zero-order beam to which astigmatism is imparted by the astigmatic optical system, (ii) a second light-detecting cell group which receives at least one of a positive first-order beam and a negative first-order beam, which passes the first area and made astigmatic by the astigmatic optical system, and (iii) a third light-detecting cell group which receives at least one of a positive first-order beam and a negative first-order beam, which passes the second area and made astigmatic by the astigmatic optical system; and a generation circuit which generates a focus error signal based on an amount of light falling on the first light-detecting cell group, and generates a wobble reproduction signal based on an amount of light falling on the second light-detecting cell group and the third light-detecting cell group, wherein the generation circuit generates a tracking error signal based on the amount of light falling on the second light-detecting cell group, generates a sub tracking signal based on the amount of light falling on the third light-detecting cell group, and generates the wobble reproduction signal by multiplying the sub tracking signal by a positive constant, adding a resultant mathematical product to the tracking error signal, and extracting a high-frequency component corresponding to a result of addition.