| 摘要 |
PURPOSE:To prevent occurrence of out-of-focus by not applying servo, but driving a convergent lens in the direction in which the focal point of the convergent lens approaches the surface of a disk when the focal point of the convergent lens is separated from the disk surface and a focus error signal is in an area showing an S-curve. CONSTITUTION:A focus error signal FQE is inputted to a processor 20 through an A/D converter 19. The processor 20 sends a signal to a selector 11 based on the signal FQE by means of a built-in program and controls the connection between input terminals 13, 15, and 16 and the output terminal 14 of the selector 11. When the signal FQE is in an area showing nonlinearity by an S-curve, the processor 20 does not drives a convergent lens in the direction in which the focal point of the convergent lens approaches the surface of a disk. Therefore, out-of-focus seldom occurs. |
