| 摘要 |
PURPOSE:To adjust automatically the interval between a condenser lens and record carrier by gradually approximating the interval between the both to the lead-in range where focus control operation is performed, by detecting the interval between the both being beyond the lead-in range. CONSTITUTION:Condenser lens 4 is so located that when focus control is not exercised, the interval between the surface of disk 5 and condenser lens 4 is much greater than a proper distance. In the start of the device, signals from lead-in range detecting circuit 14 to switches 10 and 11 are therefore at L to turn on switch 10 while turning off switch 11. Simultaneously with the start of the device, a start pulse is supplied to lamp waveform generator 12 to develop an output voltage of 0V and this generator 12 is further supplied with pulses from pulse generator 13, so that the output voltage will rise by steps according to the number of those pulses. The output of lamp waveform generator 12 is applied to condenser lens driver 3 via condenser lens driving circuit 2 to move condenser lens 4 gradually, which approaches disk 5. |
