Patent ID: 7502301

Claim:
An optical pickup apparatus comprising: a light source portion in which a first semiconductor laser light source and a second semiconductor laser light source for respectively emitting light of a first wavelength and a second wavelength which are at least two different wavelengths are provided inside the same package; a converging optical system in which a first light beam having the first wavelength emitted from the first semiconductor laser light source and a second light beam having the second wavelength emitted from the second semiconductor laser light source respectively pass through an objective lens placed in a position opposed to an optical record medium and thereby each the light beam is caused to converge on the optical record medium; a photodetector for receiving a light beam for detection reflected by the optical record medium and outputting a current; a light detection optical system for guiding the light beam for detection to the photodetector, a diffraction grating for plural wavelengths including: two or more first grating regions which have periodic protrusions and depressions in sectional shape and extend in a first direction perpendicular to a repeat direction of the protrusions and depressions, and two or more second grating regions which have periodic protrusions and depressions in sectional shape and have the depressions set to depths different from groove depths of the depressions of the first grating regions and extend in the first direction perpendicular to the repeat direction of the protrusions and depressions, wherein the two or more first and the two or more second grating regions are alternately and repeatedly placed in a second direction perpendicular to the first direction and in a direction perpendicular to an incident direction of light so that all the protrusions and depressions are located in the same surface side and thereby both the grating regions are constructed in striped shape; each one of the second grating regions is arranged between adjacent two of the first grating regions in the second direction; groove depths of each the depressions of the first and the second grating regions are set so that the first grating regions transmit incident light of a first wavelength and also diffract incident light of a second wavelength different from the first wavelength and the second grating regions transmit incident light of the second wavelength and also diffract incident light of the first wavelength; and the diffraction grating for plural wavelengths is placed between the objective lens and the light source portion of the converging optical system so that a longitudinal direction of each of the grating regions in the objective lens portion is aligned with a radial direction of the optical record medium.