| 摘要 |
PURPOSE:To improve the precision of tracking control by envelope-detecting a signal by means of a reflected light quantity from an optical disk, which is image-formed in a four-dividing photo-detector, and obtaining a tracking error signal. CONSTITUTION:The form of a laser light guiding track is set to be pit string structure by widening the width of a group 10a or a land 10b and narrowing the width of the land 10b or the group 10a, and the depth of the land 10b is set to be (lambda/8n)-(lambda/10n) (lambda: the wave length of a laser light and n: the refractive index of a substrate 10). The recording and reproducing device envelope-detects a modulation signal by a strength distribution detected in a four-dividing photodetector part 12 in circuits 15 and 16, and obtains the tracking error signal from the detected signal. Thus, the amplitude of the modulation signal obtained in the pit string of the group 10a or the land 10b is large, and the amplitude of the obtained tracking error signal is set almost similar to that of a continuous group or a continuous land, whereby the precision of tracking control is improved. |
