JPH0536077A - Optical disk reproducer - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to the reproduction of information recorded by the pit position system, suppresses the influence of the peak shift due to the deviation of the pit interval, reduces the error and increases the margin of the entire system. The most important feature is to plan. A peak detection circuit 14 detects a peak of a differential signal with respect to an analog signal 11 from a differentiating circuit 13.
The phase delay circuit 15 receives the detection output from the peak detection circuit 14 and outputs a signal whose phase is delayed from the peak position by about half of the interval between adjacent recording pits. The bottom detection circuit 16 detects the bottom of the differential signal. The phase comparison circuit 17 is configured to give priority to the output from the bottom detection circuit 16 in the area of the recording pits adjacent to each other at the shortest interval, and to generate the output from the phase delay circuit 15 in the other areas. There is.

Description

Detailed Description of the Invention

 [Object of the Invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus for reproducing information recorded by, for example, a pit position system.

[0002]

2. Description of the Related Art The pit position method is a method in which data is determined by the position of pits (holes, shape changes, phase changes, magneto-optical disk domains, etc.) formed by the heat of a laser beam of about 1 μm focused on the optical disk. It is used to reproduce (information) and is relatively widely used in the field of optical disks because it can relatively reduce jitter.

Conventionally, as a data reproduction circuit used in the pit position system, an amplitude detection circuit (reference level slice circuit) for slicing a raw reproduction signal (analog signal) with a certain reference voltage or a differential detection circuit (peak detection) Circuit) is commonly used.

Amplitude detection circuits are widely used because of their relatively simple circuit construction. However, the reproduction output may be affected by fluctuations in the reproduction light intensity, variations in the medium composition and film thickness on the optical disk, and fluctuations in the pit size due to various factors such as the servo characteristics of the reproducing apparatus.

In theory, the differential detection circuit always detects the center position of the pit, and has the advantage that it is less affected by fluctuations in the pit size. However, medium noise, laser return light noise, and the like are sometimes mixed in the reproduced signal. As a countermeasure against this noise mixing, a means such as giving a hysteresis characteristic to the comparator part or using amplitude detection together may be taken. Further, in recent years, noise has been decreasing due to progress in manufacturing technology of optical discs and lasers, and it is becoming more convenient to use a differential detection circuit.

The raw reproduction signals of the optical disk can be roughly classified into two categories in time series. One is when the pit spacing is sufficiently far from the spot diameter of the laser light (isolated pit), and the other is when the pit spacing is about the same as the spot diameter (continuous pit). The waveform of the raw reproduction signal is substantially mountain-shaped in the isolated pit portion and is close to a sine wave in the continuous pit portion.

By the way, in the case of the existing optical disk for recording by the heat of the laser beam, the phenomenon that the position of the pit is displaced sometimes occurs. Most frequently, the first first pit adjacent to the pit at the shortest interval is formed later than the predetermined position. This is the same result that the power of the laser light for the pit to be formed later in the continuous pits was increased by the residual heat effect of the laser light irradiated to the previous pit, and the power for the latter pit was increased. This is because it is formed earlier in time.

The waveform of this reproduced signal has a low initial peak,
The second and subsequent mountains will be higher. Further, the position of the first peak is shifted after the normal position (peak shift). In particular, this phenomenon is exacerbated when the distance between the adjacent pit with the shortest distance and the preceding pit is long.

With respect to such a signal, a data reproduction signal different from the original pit interval is output from the amplitude detection circuit or the differential detection circuit. Therefore, the phase margin of the reproducing system is reduced, and in an extreme case, an error may occur.

[0010]

As described above, in the conventional case, there is a drawback that the phase margin is reduced and an error occurs when affected by the peak shift.

Therefore, an object of the present invention is to provide an optical disk reproducing apparatus capable of reducing the influence of peak shift, reducing errors, and increasing the margin of the entire signal processing system.

[Constitution of the Invention]

[0013]

In order to achieve the above object, in the optical disc reproducing apparatus of the present invention, the information recorded in the pit position system is reproduced on the optical disc. Of peak detection means for detecting the peak of the analog signal corresponding to each pit, delay means for delaying the peak detection output of the peak detection means by a predetermined time, and bottom detection means for detecting the bottom of the analog signal. A comparison means for comparing the delayed output for each peak of the delay means with the bottom detection output immediately after each peak detected by the bottom detection means and for generating a signal in accordance with the output that appears first. ing.

[0014]

According to the present invention, since the deviation can be detected and corrected in real time by the means described above, it is possible to reproduce the signal which is always faithful to the recorded information.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic structure of a data reproducing circuit according to the present invention.

That is, the data reproducing circuit includes an amplifier 12 for amplifying an analog signal (raw reproducing signal) 11 corresponding to each recording pit of data (information) recorded on the optical disk by the pit position system, and a differentiating circuit. 13, a peak detection circuit 14 for detecting a peak of the analog signal, a phase delay circuit 15, a bottom detection circuit 16 for detecting a valley of the analog signal, and a phase comparison circuit 17.

The differentiating circuit 13 includes an amplifier 13a, a resistor R,
The analog signal 11 amplified by the amplifier 12 is differentiated by a well-known capacitor including a capacitor C and a capacitor C.

The peak detection circuit 14 is the differentiation circuit 13 described above.
Among the zero-cross points of the differential signal from, the falling side is used to detect the edge corresponding to each peak of the analog signal 11.

The phase delay circuit 15 generates an edge at a time point delayed from the detected edge corresponding to each peak detected by the peak detection circuit 14 by approximately half of the adjacent recording pits at the shortest interval. .. That is, when the recording pits formed on the optical disk are, for example, 2-7-modulated data, the peak-to-peak interval 3T between adjacent recording pits at the shortest distance 3T is detected corresponding to each peak. The output is delayed by 3 / 2T.

The bottom detection circuit 16 is composed of, for example, a comparator 16a and an inverter 16b, and of the zero-cross points of the differential signal from the differentiating circuit 13, the rising side is used to correspond to each bottom edge of the analog signal 11. Is to detect.

The phase comparison circuit 17 is the phase delay circuit 1 described above.
5 and the output of the bottom detection circuit 16 are compared,
It is for generating a data reproduction signal to be output to a demodulation circuit (not shown) in the subsequent stage. That is, the phase comparison circuit 17 outputs the delayed output edge for each peak or the bottom detection edge immediately after each peak, whichever appears first, as the data reproduction signal.

Next, the operation of the above configuration will be described.

FIG. 2 shows recording pits and signal waveforms of respective outputs corresponding to the recording pits.

For example, it is now assumed that recording pits as shown in FIG. 3A are formed on the optical disk. In this case, the portions shown by 21 in the drawing are recording pits adjacent to each other at the shortest distance.

Then, as the analog signal 11, a waveform as shown in FIG. The analog signal 11 has a waveform in which the trailing peaks are large in the recording pit portions 21 adjacent to each other at the shortest interval. This is because the first recording pit is behind the original position and 2
This is because it is formed smaller than the first recording pit.

From the peak detection circuit 14, an output as shown in FIG. In this case, the first peak detection edge 22 in the adjacent recording pit portion 21 at the shortest interval is delayed from the ideal position 23 by the time t.

As shown in FIG. 3D, the phase delay circuit 15 outputs a signal whose phase is delayed from the peak position by about half the interval between adjacent recording pits. in this case,
The delay time t is stored in the portion of the edge 25 with respect to the first peak in the recording pit portion 21 adjacent to each other at the shortest interval.

On the other hand, from the bottom detection circuit 16,
As shown in (e) of the figure, the bottom detection edge 24 immediately after the peak of the first peak of the recording pit portions 21 adjacent to each other at the shortest interval is shorter than the peak detection edge (delayed output edge 25) thereof. However, a fast output can be obtained. The time difference here almost coincides with the delay time t.

As a result, the phase comparison circuit 17 obtains the pulse train output as shown in FIG. In this case, the output (bottom detection edge 24) from the bottom detection circuit 16 is prioritized in the recording pit portions 21 adjacent to each other at the shortest interval. Therefore, the output of the peak detection circuit 14 for the first peak (peak detection edge 22)
Even if there is a delay, it is not reflected in the final data reproduction signal (output of the phase comparison circuit 17). Therefore, it is possible to always obtain a correct data reproduction signal having a correct front-rear positional relationship (pit interval).

The present invention focuses on the fact that the bottom (valley) following the first peak of the recording pit portions 21 adjacent to each other at the shortest distance has a smaller shift amount than the peak, and detects the detected edge. I am trying to use it. The bottom can be easily detected by using the rising side of the zero-cross point of the differential signal, which is opposite to the falling side used for peak detection.

By using this bottom detection edge, regardless of the delay of the first peak in the adjacent recording pit portions 21 at the shortest interval, the original (no delay) is generated.
The detection signal is obtained at a position close to the midpoint of the two recording pit positions. That is, it is possible to output a signal close to ideal.

On the other hand, in the other portions, the delay from the peak position of the bottom detection edge increases, and the relationship between the output signal and the pit position becomes incorrect. Therefore, with respect to portions other than the recording pit portion 21 adjacent to each other at the shortest interval, a normal peak position is detected, and a signal delayed from the detected edge by half the interval of the adjacent recording pits is used. ing.

That is, the final data reproduction signal is obtained by taking out the edge that appears first among the phase detection output edges for the bottom detection edge and the peak detection output.

By the way, the amount of edge shift of the data reproduction signal when a random signal having a shortest pit pitch of 1.5 μm was recorded / reproduced on the innermost circumference of the 90 mm diameter using a prototype of a magneto-optical disk was used. When measured, it was about 7 nsec.

When the same data was reproduced using a conventional peak detection circuit, the shift amount was about 11 nsec, which was equal to the peak shift amount. Most of this peak shift occurred in the recording pits adjacent to each other at the shortest interval, and it was revealed by measurement with a time interval analyzer.

As described above, the deviation can be detected and corrected in real time.

That is, regarding the recording pit portions which are adjacent to each other at the shortest interval, the bottom following the first peak is detected, and by utilizing this, the midpoint between two recording pit positions which is originally not delayed. I try to get the signal at a position close to. As a result, it is possible to obtain a signal close to an ideal signal regardless of the delay of the first peak with respect to the recording pit portions adjacent to each other at the shortest interval. Therefore, it is possible to always reproduce the signal faithfully to the recorded data, and to suppress the influence of the peak shift as much as possible.

The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the invention.

[0040]

As described above in detail, according to the present invention, the influence of the peak shift can be reduced and the error can be reduced.
At the same time, it is possible to provide an optical disk reproducing device capable of increasing the margin of the entire signal processing system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a data reproducing circuit according to an embodiment of the present invention.

FIG. 2 is likewise a waveform chart of each signal shown for explaining the operation.

[Explanation of symbols]

11 ... Analog signal (raw reproduction signal), 12 ... Amplifier,
13 ... Differentiation circuit, 14 ... Peak detection circuit, 15 ... Phase delay circuit, 16 ... Bottom detection circuit, 17 ... Phase comparison circuit.

Claims (1)

Claim: What is claimed is: 1. An optical disc reproducing apparatus for reproducing information recorded on an optical disc by a pit position method, a peak detecting means for detecting a peak of an analog signal corresponding to each pit of the information. A delay means for delaying the peak detection output of the peak detection means by a predetermined time, a bottom detection means for detecting the bottom of the analog signal, a delay output for each peak of the delay means and the bottom detection means. An optical disc reproducing apparatus comprising: a comparison unit that compares the detected bottom detection output immediately after each peak and generates a signal according to the output that appears first.