Patent ID: 6339562
Filing Date: 2002-01-15
Classification: G11B

Abstract:
An optical pickup device, in which a light beam emitted from a light source is converged onto an optical recording medium through an optical system, and a shift which a focal point of the light beam has made from the optical recording medium is detected based on return light returning from the optical recording medium through said optical system, said optical pickup device comprising:main light receiving means having at least two main light receiving sections, each main light receiving section producing a main signal in accordance with a quantity of the return light incident thereon; sub light receiving means having sub light receiving sections, when the shift of the focal point is beyond a dynamic range and the return light becomes incident also on outside said main light receiving sections and partly on said sub light receiving sections, each sub light receiving means producing a sub signal in accordance with a quantity of the part of the return light that is incident thereon; and error signal producing means for producing a focus error signal by compensating the main signal by using the sub signal, wherein said sub light receiving means adjusts an offset of the focus error signal due to an arrangement error of an optical element constituting said optical system, by using the sub signal.