Optical pickup and optical disk unit

An optical disk unit comprising:

• drive means for rotationally driving an optical disk;
• an optical pickup for applying light through optical focusing means to said optical disk which rotates, and for detecting returning light from a signal recorded surface of said optical disk through said optical focusing means;
• a biaxial actuator for supporting said optical focusing means so that said optical focusing means is movable in two axial directions;
• a signal processing circuit for producing a reproduction signal on the basis of a detection signal from said optical pickup;
• and
• a servo circuit for moving said light focusing means in said two axial directions on the basis of said detection signal from said optical pickup,
• said optical pickup including:
• a light source;
• optical focusing means for focusing a light beam emitted from said light source on a signal recorded surface of an optical disk which is rotationally driven;
• optical separating means placed between said light source and said optical focusing means;
• and
• an optical detector including light-receiving sections for receiving a returning light beam from said signal recorded surface of said optical disk, which undergoes separation through said optical separating means,
• wherein said optical separating means is, in its light source side surface, equipped with a first diffraction grating and an optical path branching section composed of a plurality of surfaces having normal vectors different from each other and is, in its optical disk side surface, equipped with a second diffraction grating composed of a continuous area,
• said first diffraction grating dividing light from said light source into main and side beams, while said second diffraction grating allows said light from said light source to pass and diffracts returning light from said optical disk toward said optical path branching section, and
• said optical path branching section divides said returning light from said optical disk to lead the divisions to said light-receiving sections of said optical detector.