JPS59132430A - Information reproducing device - Google Patents

Abstract

PURPOSE:To detect a peak value of information by constituting a photodetector receiving reflected or transmitted light from a recording medium by >=2 photodetecting sections at least and forming a difference of signals from each photodetecting section. CONSTITUTION:Outputs of the photodetectors 16a, 16d are added and a signal 30 proportional to the intensity of one side of a distributed pattern is obtained. Another signal 31 is obtained similarly by the photodetectos 16d, 16c. Further, a signal 33 representing the change in the entire reflected light amount is obtained by the photodetectors. A waveform risen at the zero point is formed by passing the signal 32 through a comparator 40 for detecting the zero point, inputted to a monostable multivibrator 41 from which a pulse is outputted in response to the leading. The signal 33 outputs a pulse keeping ''1'' while the spot passes through a pit through a comparator 42. A gate 43 passes through the output of the 41 by taking an output of the 42 as a gate signal. Then, a pulse is outputted when the spot is made incident to the center of the pit. This pulse represents accurately the center of the pit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an information reproducing device, and particularly to a device for detecting the peak value of a digital information signal waveform recorded on a disk.

[Background of the invention]

Optical disks, which have a storage capacity that is orders of magnitude higher than conventional magnetic disks and magnetic tapes, are currently expected to be used as large-capacity digital information memories.

At this time, the recording pattern for recording digital information on the optical disc is pit LL Q II, II I II
It is recorded with or without elliptical holes (hereinafter referred to as pits) corresponding to .

Normally, when reading digital information recorded in a magnetic tape etc., II OgH, II I
From a waveform with a continuous pattern of H, +
Detect the peak value of the waveform corresponding to 10 Hg, ri 1 gg, and from the timing relationship with the reproduced clock.
o”.

The pattern of "l" is being determined. At this time, the method to detect the peak value is to use a differentiation circuit.
Various methods can be considered, such as using a combination of a delay line and a differential amplifier, or modifying the frequency characteristics of the filter.

[Purpose of the invention]

As a peak detection method, the present invention proposes a peak detection method that utilizes the principle operation of an optical disk, which is different from the method used for conventional magnetic disks.

[Summary of the invention]

FIGS. 1A to 1C are explanatory diagrams of the principle of the present invention.

In the figure, reference numeral 6 is a cross-sectional view of a phase-type pit (information is recorded as a change in unevenness) created by a known method. FIGS. 2A to 2C show how the intensity distribution pattern of the reflected light changes on the surface of the photodetector depending on the positional relationship between the pit 6 and the laser spot 7.

In FIG. 1(A), spot 7 is at the left end of pit 6.

At this time, the distribution 17(a) on the photodetector 16'2 becomes unbalanced on the left and right (as shown in FIG. 2(A)). Furthermore, when the spot 7 comes to the center of the pit as shown in FIG. 1(B), the distribution pattern 17(b) at that time becomes symmetrical (
It is shown in FIG. 2(B). ), On the other hand, if spot 7 comes to the right side of the pit as shown in Fig. 1(C), the distribution pattern 17(C) at that time becomes unbalanced in the opposite direction to 17(a) (Fig. 2( (C). The principle of the present invention is to realize peak detection using the above operating principle.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using Examples. Third
The figure is a diagram illustrating a signal extraction portion of a photodetector.

The installation position of the photodetector in FIG. 3 is the same as the relationship between the photodetector and the reflection pattern in FIG. 1. Photodetector 16(a) and 1
The outputs of 6(d) are added by an adder 20 to obtain a signal 30 proportional to the intensity on one side of the distribution pattern. Photodetector 16 (
The outputs of b) and 16(c) are added by an adder 21 to obtain a signal 30 proportional to the intensity of the other distribution pattern. The outputs of the photodetectors 16(d) and 16(c) are added to the adder 21.
A signal 31 proportional to the intensity of the other distribution pattern is obtained. Further, by adding the signals by the four photodetectors 22, a signal 33 indicating a change in the total amount of reflected light is obtained.

FIG. 4 shows how the aforementioned signal changes when spot 40 passes over pins 1-6 (as shown in FIG. 4(a)). FIGS. 4(b) and 4(c) show the output signals of the adders 20 and 21, that is, the behavior of 30.31 representing the intensity of the diffracted light, respectively. FIG. 4(d) shows the behavior of the signal 32 obtained by taking the difference between the signals 30 and 31, which indicates an unbalance of the diffracted light.

In this waveform, from the correspondence with FIG. 1, it becomes zero when the light spot is located at the center of the pit. FIG. 4(e) shows the overall change in the amount of reflected light, and the level decreases while the light spot is irradiating the pit.

FIG. 5 is an explanatory diagram of peak position detection according to the present invention. The signal 32 is passed through a comparator 40 for zero point detection (circuits and elements may be of known type) and the signal 32 is passed from II OII to s at the zero point.
A waveform that rises at r 1 u is created, and this is input to a monostable multivibrator 4, which outputs a pulse with a short pulse width in response to the rise of the waveform. The signal 33 outputs a pulse that remains "1" only while the spot passes through the pit through the comparator 42. A pulse indicating a zero cross (output of 41) is input to the gate circuit 43, and the output of 42 is used as a gate signal to pass the output of 41 only during "1". Then, when the spot is in the middle of the pit, it emits a pulse. The point at which this pulse reduces the reflected light to its maximum, and also the point at which the amount of reflected light reaches its peak, i.e.
Accurately represents the center of the pit.

〔Effect of the invention〕

As described above, according to the present invention, the center of a pit can be accurately detected by simply adding a simple circuit.

The present invention is particularly effective when the frequency of recorded information is high.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams for explaining the present invention in detail, and FIG. 3 is a diagram showing the configuration of main parts of an embodiment of the present invention.
FIG. 4 is an explanatory diagram of its operation, and FIG. 5 is a diagram showing another configuration of essential parts of an embodiment of the present invention. Figure 4 Figure 5

Claims (1)

[Claims] 't. In an information reproducing device that optically reproduces information recorded on a recording medium, a photodetector that receives reflected or transmitted light from the recording medium is composed of at least two or more light receiving sections. , an information reproducing apparatus characterized in that the peak value of the information is detected by taking the difference between the signals from each light receiving section.