| 摘要 |
PROBLEM TO BE SOLVED: To reduce a stray light by increasing light using power efficiency. SOLUTION: This device is provided with a light emitting/receiving element for irradiating an optical disk with a laser light and receiving a return light, a diffraction grating for separating a laser light 3 into beams, and a light converging optical system for converging the laser light on the recording surface of the optical disk. The diffraction grating has plural grooves, and the depth of each groove is decided such that 1st order light diffraction efficiency when a first light beam is made incident is larger than that when a second light beam having a wavelength shorter than that of the first is made incident. |
