| 摘要 |
PURPOSE:To prevent the S/N deterioration of a read signal by detecting the tilt of the optical axis of a condenser lens system against the surface of a recording carrier and therefore assembling an optical information reader so that the optical axis is vertical to the surface of the recording carrier. CONSTITUTION:Two prisms 13 and 14 which divide a read beam into two pieces are provided together with two 4-split photodetecting elements 15 and 16. Then an arithmetic circuit for information reading signal, an arithmetic circuit for detecting signal of tracking position, an arithmetic circuit for detecting signal of focusing position and an arithmetic circuit 20 which obtains a detecting signal for tilt of the optical axis B of a condenser lens system 7 to the surface of a disk 6 are connected to the elements 15 and 16 respectively. A subtractor 30 performs subtraction between electric signals given from adders 28 and 29, and a signal is obtained from an output terminal 30a to detect the radial tilt to the surface of the disk 6. At the same time, a subtractor 30 performs subtraction between electric signals of adders 32 and 31. Then a signal is obtained from an output terminal 33a to detect the tangential tilt to the surface of the disk 6. |
