| 摘要 |
PURPOSE:To perform correctly automatic focus control regardless of temperature variation by correcting an error of a defocusing detection signal even if the defocusing detection signal has the error owing to variations in the ambient temperature inside and outside the device. CONSTITUTION:A thermistor 20 which detects the temperature of an optical head mount is arranged nearby a collimator lens 2. The 1st differential amplifier 25 inputs the voltage between the thermistor 20 and ground and the voltage between the 3rd resistance and ground. A defocusing detecting circuit 10, on the other hand, consists of two buffer amplifiers 26 and 26 and the 2nd differential amplifier 27 which calculates their output difference; outputs of the buffer amplifiers 26 and 26 is inputted to the 1st adding circuit 28 and the output of the 1st differential amplifier 25 and the output of the 1st adding circuit 28 are inputted to a multiplier 29. The outputs of the 2nd differential amplifier 27 and multiplier 29 are inputted to the 2nd adder 30, whose output is inputted to an actuator driving circuit 11. |
