JPS63131377A - Information reproducing device - Google Patents

Abstract

PURPOSE:To attain high accuracy while eliminating the effect onto outputted information even if a distortion takes place in a waveform of the reproduced signal by reproducing the information by an interval between centers of the reproduced pulse detected by a center detection means. CONSTITUTION:A reproducing signal is inputted to a binarizing means and a binary-coded reproducing pulse is outputted. Moreover, a center detection means detects the center of the reproducing pulse and the information is recovered by the interval between the centers of the reproduced pulses. In using the interval between the centers of the reproduced pulses as the information in this way, the effect of the reproduced pulse having a deviation (l) of the reproduced signal waveform onto the interval between the centers of the reproduced pulses is decreased into 1/2l, the probability of the information L'' being an error is low, and the information at the interval between the bits with high accuracy is obtained. Even if a peak of a recovered waveform is horizontal, it is not effective to the detection of the center position of the recovered pulse and the interval between the pits is obtained surely.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical information reproducing apparatus that reproduces information recorded on an optical disk recording medium or the like using a light beam.

<Prior Art> In recent years, optical information recording and reproducing devices have become widely known as an effective means for recording information on a recording medium at high density. This information recording and reproducing device records information by irradiating the recording medium with a light beam and forming pits on the recording medium according to the information to be recorded, and the information is reproduced by irradiating the first beam onto the pits. This is done by converting changes in the rotation angle of the polarization plane of the reflected or transmitted light into changes in the amount of light and detecting the changes. There are the following two methods shown in FIG. 4 as a method for recording information by providing pits in the recording medium. That is, the first method converts the signal "I!" of the binary information to be recorded in FIG.
The data is recorded as pits on the recording medium as is, and when it is reproduced, the reversal position of the reproduced signal is detected as shown in Figure 1 (n), and the interval (pit length) between the reversal positions is determined. This is a method in which the information represents the number of consecutive "bi"("■!') signals of the binary information (C). The second method is to provide a pit of a certain length as shown in FIG. The positions of the pits are detected by the reproduced signal shown in FIG.
This is a method in which the information represents the consecutive number of I■'').

In the first method, if the length of the recording pit changes due to changes in the recording medium or recording device over time or changes in the environment, the reproduced information will contain an error because the pit length itself is used as information. However, the second method is
Even if the length of the pits changes due to changes over time, the relative positions of the pits do not change, so the spacing between the pits does not change.
The reproduced information does not constitute an error.

Conventionally, in an information reproducing apparatus in which pits of a certain length are provided at the inverted position of binary information to be recorded on a recording medium and the interval between the pits is determined, the method shown in FIG. 4(p) shown in FIG. 5(q) is used.
There are two methods for detecting the interval between pits on a recording medium from a reproduced signal corresponding to . First of all
The method shown in Fig. 5 (r
), the interval between pits is obtained from the interval between one edge (for example, the rising edge) of the reproduced pulse, which is binarized and fU#ed. The second method is to differentiate the reproduced signal (q) to obtain the waveform shown in FIG. 5(S), detect its zero-crossing points, and obtain the interval between pits from the interval between the zero-crossing points. Hereinafter, the former will be referred to as level detection, and the latter will be referred to as peak detection.

<Problems to be Solved by the Invention> However, since the level detection described above uses the interval between one edge of the reproduced pulse as information, scratches or scratches may occur on a part of the shoulder of the reproduced signal as shown in FIG. 6(t). When waveform distortion occurs due to stiffness, etc., as shown in Figure 6 (U), if the edge used as the base point for determining the interval between the pits of the reproduced pulse is affected, other edges are not affected. Regardless of whether or not this is the case, there is a problem in that the spacing between the pits is largely deviated, which can cause errors. In addition, since peak detection uses the interval between zero-crossing points of the waveform obtained by differentiating the reproduced signal Q) as information, distortion may occur in the reproduced signal (t) as shown in Figure 6(V). However, the influence on the zero-crossing position of the differential waveform is small (the broken line in FIG. 6 is the reproduced signal in the normal case). However, Fig. 7 (w
), when the peak of the reproduced signal waveform becomes horizontal,
The differential waveform becomes as shown in FIG. 7 (X), and there is a problem that the zero crossing point becomes unclear and becomes a cause of error.

SUMMARY OF THE INVENTION An object of the present invention is to provide an information reproducing device that is less affected by waveform distortion occurring in the reproduced signal waveform and can accurately determine the interval between pits even if the reproduced signal waveform is at its peak or horizontal. There is a particular thing.

<Means for solving the problems> In order to achieve the above object, the information reproducing device of the present invention has the following features:
In an information reproducing apparatus that provides pits representing binary information to be recorded on a recording medium and reproduces the information by determining the interval between the pits, binarization that binarizes the signal reproduced from the recording medium and a center detection means for detecting the center of the reproduction pulse outputted from the binarization means, and information is reproduced based on the interval between the centers of the reproduction pulses detected by the center detection means. It is characterized by

<Operation> A reproduction signal is obtained by irradiating, for example, a forward beam onto a recording medium provided with pits representing binary information to be recorded. ”
The bipedal reproduction signal is input to the binarization means and output as a binarized reproduction pulse.

Furthermore, the centers of the reproduction pulses are detected by a center detection means, and information is reproduced based on the interval between the centers of the reproduction pulses. Therefore, even if the reproduced signal waveform is distorted, it has little effect on the interval between pits, and even if the peak of the reproduced signal waveform is horizontal, the interval between pits can be reliably determined.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 is a circuit diagram of an embodiment of the invention. In FIG. 1, a comparator l, which is a binarization means, binarizes a manually input reproduction signal using a resistor 11v (based on a certain level determined by the user's intention) and outputs it as a reproduction pulse.Integrator 11 .12 has the same configuration, consisting of an operational amplifier 2°3, resistors Ra, la, capacitors C, C, and a switch 4°5.The above switch 4.5
is "closed" to reset the integral "Zll,12".

The switch 7.8 is a switch for opening and closing the connection between the integrator 11.12 and the delay element 9 or the resistor rtb of the voltage dividing circuit, and the flip-flop 6 is a switch for connecting the integrator 11.12 to the delay element 9 or the resistor rtb of the voltage dividing circuit.
It generates and outputs a signal instructing the reset timing of ' and the switching timing of the switches 7 and 8. Comparator lO outputs a signal representing the center position between both edges of the reproduction pulse based on the signals output from delay element 9 and resistor 11b. The integrator It,
12, flip-flop 6, switch 7.8, delay element 9, resistor nb, voltage divider circuit consisting of nb, comparator 1
0 constitutes the center detection means.

FIG. 2 shows signal waveforms at each stage from when a reproduction signal is input to the information reproduction apparatus configured as described above until a signal representing the center position between both edges of the reproduction pulse is output. The operation of the information reproducing apparatus will be described below with reference to FIG. 1.2.

A recording medium provided with bits as shown in the top row of FIG. 2 is irradiated with a light beam, and the reproduced signal shown in FIG. 2(a) is obtained from the reflected light. When this reproduced signal (a) is input from the first diagram, it is binarized by the comparator l and output as a reproduced pulse as shown in FIG. do.

The flip-flop 6 is connected to the integrator 11.1 as described above.
It generates the reset timing of 2 and the opening/closing timing of the switch 7.8, and every time a pulse signal is input from the comparator 1 to the terminal GK, a signal "11" is output from the terminal Q alternately, At the same time, output signals "L" and "H" opposite to the output signal of terminal Q from terminal Q alternately. Further, the terminal Q is connected to the switch 4 and the switch 8, and the terminal Q is connected to the switch 5 and the switch 7. By outputting "H" and closing the switch 4, the integrator 2
is reset to 1, while the switch 8 is "closed" and the signal integrated by the integrator 12 is sent to the delay elements and the resistor nb. At the same time, the terminal silkworm outputs a signal "L" to turn the switch 5 "open" to enable the integrator 12 to operate, while the switch 7 is "open" to cut off the signal from the integrator It. Next, the next pulse signal input from the comparator I enables the integrator 2 to operate with the signal output from the terminal Q, while the switch 8 becomes "open" and cuts off the signal from the integrator 12. At the same time, the signal from the terminal stone resets the integrator 12, while the switch 7
becomes "closed" and allows the signal integrated by the integrator 11 to pass through. Thereafter, the above operation is repeated every time a pulse signal is input to the terminal CK. As a result, the integrator 11 outputs the second
A signal obtained by integrating every other reproduction pulse signal (b) as shown in FIG. A signal obtained by integrating the pulse is output. Then, by switching the switch 7.8, the signal (c), (
Figure 2 (a) is obtained from the signals (c) and (d) by cutting off the distortion caused by the resistance when the switch 4.5 is "closed" that occurs during resetting, as shown by arrow C in d). The signal (c) is inputted to the delay cable 9 and the resistor l''Lb via the signal shown in FIG.

Next, the signal (c) is delayed by the delay element 9 to obtain the signal shown in FIG. signal(
Obtain a signal with a peak value that is 1/2 of the peak value of e).

At this time, the signal (r) has a wave height of 1/
The vicinity of part 2 is delayed by a time such that it overlaps the horizontal part of the waveform of signal (g) before the delay. Therefore, the signal (f) is set at the level of the signal (g) by the above comparator l.
When the signal is binarized by O, a pulse signal as shown in FIG. 2(h) is output from FIG. 1B. Therefore, the center position of the reproduction pulse (b), that is, the signal (F)
The center position of the integral waveform is relatively indicated as the rising position of the pulse of signal (h). That is, the signal (h)
By using the interval between the rising edges of the pulses as information, information on the interval between the centers of the reproduced pulses (b) can be obtained.

As shown in FIG. 3(i), if distortion as shown by the solid line E occurs in a part of the reproduced signal waveform and a shift of Q occurs in the level when binarizing, as shown in FIG. As shown in D, in the case of information reproduction using the level detection, which is a conventional example, there is a high probability that a deviation of the same value Q as the above-mentioned deviation of the reproduced waveform occurs in the information, resulting in an error.However, As shown in FIG. 3(k), if the interval between the centers of the reproduced pulses is used as information, the influence of the deviation Q of the reproduced signal waveform on the interval between the centers of the reproduced pulses is reduced to I/2Q. ,
There is a low probability that information L" will be an error, and information can be reproduced with highly accurate intervals between pits.Also, even if the peak of the reproduced waveform is horizontal, it does not affect the detection of the center position of the reproduced pulse. , the distance between the pits can be reliably determined.

Further, the center detecting means for detecting the center of the reproduction pulse shown in FIG. 2(b) is not limited to the above embodiment. The center of the reproduced pulse may be digitally obtained by zumbling the generated high-frequency clock pulse.

<Effects of the Invention> As is clear from the above, the information reproducing device of the present invention has the following effects:
A binarizing means for binarizing a signal reproduced from a pit representing binary information to be recorded on a recording medium, and a center detecting means for detecting the center of a reproduction pulse output from the binarizing means. Therefore, even if distortion occurs in the waveform of the signal reproduced from the pit, it will have little effect on the information to be output, and the information will be reproduced based on the interval between the centers of the detected reproduction pulses. Information can be reproduced accurately and reliably based on the intervals between pits as long as the peak of the waveform of the signal reproduced from the pits is horizontal.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an information reproducing device that is an embodiment of the present invention, Fig. 2 is a diagram showing waveforms at each stage of input signal processing in the embodiment of Fig. 1, and Fig. 3 is a diagram showing waveforms obtained from pits. A diagram showing the influence of distortion of the reproduced signal waveform on information reproduction,
FIG. 4 is an explanatory diagram of the optical information recording and reproducing method, and FIG. 5 is an explanatory diagram of the conventional method of reproducing information from the interval between pits.
FIG. 6 is a diagram showing the influence of the distortion of the reproduced signal waveform in FIG. 5 on information reproduction, and FIG. 7 is a diagram showing the effect that the shape of the reproduced signal waveform in peak detection does not have on the differential waveform. 1.10... Comparator, 6... Flip-flop, 7.8... Switch, 9... Delay element, II,
+2...Integrator.

Claims (1)

[Claims] (1) In an information reproducing apparatus that provides pits representing binary information to be recorded on a recording medium and reproduces the information by determining the interval between the pits, the signal reproduced from the recording medium is binarized. Binarization means; and center detection means for detecting the center of the reproduction pulse outputted from the binarization means, and information is reproduced based on the interval between the centers of the reproduction pulses detected by the center detection means. An information reproducing device characterized in that: