| 摘要 |
PURPOSE:To make the constitution inexpensive and to reduce the drift and the secular change by constituting a standardizing processing means with an A/D converter which takes a difference output as the analog input and takes a sum output as the reference input. CONSTITUTION:After an analog switch 16 is switched to the side of a focus error signal, an A/D converter (standardizing processing means) 17 is sampled, and the output is latched in a latch circuit 18 after the end of A/D conversion. A focusing servo circuit is constituted in this manner. The output subjected to A/D conversion by this series of operations is an error signal obtained by standardizing the focus error signal (difference signal) impressed to the input terminal of the A/D converter 17 by the sum signal impressed to the reference terminal of the A/D converter 17. In the next cycle, the A/D converter 17 is sampled after this analog switch 16 is switched to the side of a tracking error signal, and the output is latched in the latch circuit 18 after the end of A/D conversion. A tracking servo circuit is constituted in this manner.
|
