Patent ID: 7616548

Claim:
An optical pickup apparatus, comprising: a light emitting section for emitting a first laser beam having wavelength λ 1 and a second laser beam having wavelength λ 2 different from the wavelength λ 1 ; a surface relief type first diffraction grating having a phase height of two steps produced by being equipped with a first phase grating and a second phase grating arranged at opposite sides of the first phase grating and adapted to split the laser beam of the wavelength λ 1 into three beams and transmit substantially all of the laser beam of the wavelength λ 2 ; a surface relief type second diffraction grating having a phase height of two steps produced by being equipped with a first phase grating and a second phase grating arranged at opposite sides of the first phase grating and adapted to split the laser beam of the wavelength λ 2 into three beams and transmit substantially all of the laser beam of the wavelength λ 1 ; an objective lens for converging the laser beams emitted from the light emitting section onto an optical disc; an optical element for branching optical paths of return light reflected by the optical disc; and a light receiving section for receiving the return light branched by the optical element, wherein the light emitting section emits a first laser beam having a wavelength λ 1 of about 660 nm and, the first diffraction grating includes a first phase grating having a width not smaller than 62% and not greater than 75% of the pitch of the diffraction grating and a phase height not smaller than 1.01 times and not greater than 1.24 times of λ 1 /(N 1 −1) and a second phase grating arranged at opposite sides of the first phase grating and having a width not greater than 19% of the pitch of the diffraction grating and a phase height not smaller than 0.34 times of λ 1 /(N 1 −1), where N 1 being the refractive index for the laser beam of the wavelength of λ 1 entering the diffraction grating.