| 摘要 |
PURPOSE:To control correctly the focus by controlling the focus by the sum signal of the output from a temp. detecting means in a device and the detection signal for out-of-focus so that the discrepancy between the detection signal for the out-of-focus and a focusing state is corrected even if such discrepancy arises with a temp. change. CONSTITUTION:A thermistor 15 detects the temp. in the device and produces the output signal alphaDELTAT proportinal to a temp. change DELTAT. The output 18 from the temp. detecting means is added to the detection signal 14 for the out-of-focus obtd. from an out-of-focus detector 6 and an out-of-focus detecting circuit 10 by an adder 19 and is outputted as the sum signal 20. The signal 20 is always zero as far as an objective lens 4 focuses correctly at a recording medium 5, i.e., DELTAC=0, even if the temp. of the device changes from the initially set temp. The signal 20 is therefore inputted to an actuator driving circuit 11 and the lens 4 is moved in the optical axis direction by an actuator 12 so that the signal 20 is kept always zero. The exact automatic focus control is thus executed. |
