| 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 to 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 which obtains the information read signal, focusing position detecting signal and tracking position detecting signal and an arithmetic circuit 40 which obtains a detecting signal for the tilt of an 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. Adders 41-44 are provided, and an adder 47 adds the electric signal sent from a subtractor 45 to the electric signal from a subtractor 46. A detecting signal for tilt of the radial direction to the surface of the disk 6 is obtained from an output terminal 47a. While a subtractor 48 performs subtraction of electric signals between subtractors 45 and 46. Then a detecting signal for tilt of the tangential direction to the surface of the disk 6 is obtained from an output terminal 48a. |
