| 摘要 |
PURPOSE:To correct a focus always to a proper position and to improve the error rate by converging a light from a light source onto a disc, changing a focus position, discriminating and storing the error rate at various focus position, discriminating the optimum focus position and setting the focus means to the focus corresponding to the result. CONSTITUTION:In loading the optical disc to the optical disc device, a CPU discriminates it as the error rate check mode, its signal is outputted to a control circuit 82. Then the control circuit 82 uses a conversion table to calculate a start track number and the start section of a focus check area (a). When the count of a sector counter 37 is coincident with the start sector, the reproduction of data to the focus check area (a) is started. The laser light L led to a polarized beam splitter 44 passes through a 1/4 wavelength plate 45 after the splitter 44 and made incident on an objective lens 46. The rays of light are focused to the recording film 19a of the optical disc 19 by the objective lens 46.
|
