OPTICAL SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide an optical system which can inspect and adjust an optical head without the influence of disk characteristics. SOLUTION: The optical system 10 is provided with a diffraction grating 13 which transmits and reflects a part of the light projected from the optical head 11, diffracts the light concerned and radiates a sharing interference light; a converging lens 14 which converges the light radiated from the diffraction grating; a moving mechanism 25 which moves the diffraction grating in the direction of its normal; an image-receiving body 16 which receives the light converged by the converging lens as an image; a processing device 17 which detects defocus components from the interference image of the sharing interference light received by the image-receiving body as an image; and a measuring mechanism 33 which measures the output signal of the optical head.