OPTICAL DISK DEVICE

PROBLEM TO BE SOLVED: To prevent the saturation of a photodetector by a difference in the reflectivity on the recording surfaces of optical disks and the light output of the laser beam to be used in recording or reproducing a plural variety of the optical disks. SOLUTION: The laser beam 16 oscillated from a semiconductor laser 14 is made to irradiate the recording surface 32 of the optical disk 30, by which recording or reproducing is executed. A photodiode 24 detects the light output of the laser beam 16. A photodiode 40 detects return light 16c. Transmittance variable type filters 22, 36 are arranged on the incident optical axes 21, 35 of the photodiodes 24, 40. A control circuit 50 decreases the incident light quantity of the photodiodes 24, 40 by decreasing the transmittance of the transmittance variable type filters 22, 36 when the reflectivity of the optical disk 30 is high or when the light output of the laser beam 16 is large.