Optical information reproducing device

Abstract

An optical information reproducing device capable of reproducing an information medium of a high-density mark edge recording method and stably accommodating variations in a recording power, recording sensitivity and reflectance, wherein a mark center positional signal is obtained by detecting mark edge recording method information of an optical disk with a center detection circuit including a split-half optical detector and then the signal is converted into a mark edge positional signal by an edge signal generation circuit.

Description

technical field [0001] The present invention relates to an optical information reproducing device for reproducing an optical information medium of a mark edge recording method in which digital information and the like are recorded corresponding to edge positions of marks. Background technique [0002] In the mark edge recording method, "1" and "0 (zero)" of the digital information are associated with "presence" and "absence" of the mark edge, and marks of different lengths are recorded. An example of a method for reproducing recorded information will be described below. When a laser beam is scanned along a recording mark and the reflected beam is converted into a reproduction signal by a photodetector, the reproduction signal is modulated by the recording mark. For example, in CD-ROM discs, phase change discs, etc., when the light spot is on a recording mark, the reproduction signal is at a low level, and when it is at a space between recording marks, it is at a high level....

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Problems solved by technology

[0004] Additionally, if Figure 5 As shown in (b), when the information is recorded, due to excessive recording power or high recording sensitivity of the information medium, the mark that should be the size of the curve 52 may be recorded as a mark larger than the curve 54

At this time if Figure 5 As shown in (c), the center of the read signal 55 deviates downward from the slice level 56 as shown in the curve 57, and a detection error of the mark edge position occurs.

And when the recording power is too low, or the recording sensitivity of the information medium is too low, the center of the read signal 55 deviates upward from the limit level 56, resulting in a detection error of the mark edge position.

In addition, when the reflectivity of the information medium changes, such as Figure 5 As shown in (c), the center of the read signal 55 also deviates downward or upward from the limit level 56 as shown in the curve 57, and a detection error of the mark edge position occurs.

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