JPH0279226A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To control the subject device corresponding to an unfavorable effect which is varied in accordance with the defective kinds by detecting a defect of a recording medium in discriminating which should have the defect, on a recording surface or a protective substrate surface. CONSTITUTION:The device is provided with a means 7 for detecting the defect by discriminating a defect on the recording surface and a defect on a transparent protective layer surface respectively from a change in reflected light by the recording medium C with a light beam irradiating the recording medium C provided with the transparent protective layer on its recording surface. That is, the defect of the recording medium C is discriminated to be detected as to which is involved, the defect on the recording surface or the defect on the transparent protective layer surface from a change in the light quantity distribution of the reflected light and a change of the total light quantity, and a tracking control is corrected according to these individual cases. By this method, a significant trouble can thus be evaded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical information recording/reproducing device such as an optical disk or an optical card.

[Conventional technology]

Conventionally, an optical head of an optical information recording/reproducing device includes a light source such as a laser, a collimator lens that converts the light beam from the light source into a parallel light beam, and an objective that narrows down this light beam and irradiates it onto the recording surface of a record carrier as a minute light spot. It consists of an optical system such as a lens, and a photodetector that receives the light beam reflected by the recording surface.

During recording, a beam of light modulated by predetermined information and focused by an objective lens is irradiated onto the recording surface of the record carrier, and information is recorded by causing a temperature rise or chemical reaction on the recording surface. Also, during playback, it is reflected from the recording surface,
A light beam optically modulated by recorded information is received by a photodetector, and the optical signal detected here is converted into an electrical signal to obtain desired reproduction information.

Record carriers used for recording/reproducing such optical information include optical video discs, optical digital audio discs, optical cards, and the like. The information to be recorded is, for example, recorded on concentric or spiral tracks in the case of a disc-shaped carrier (hereinafter referred to as an optical disc), and in a plurality of tracks arranged in parallel in the case of a card-shaped carrier. Ru. This information track is caused by unevenness, the presence or absence of bits, changes in reflectance, changes in magnetization direction, etc.

In order to record information accurately without causing problems such as crossover between information tracks, it is necessary to control the irradiation position of the light spot in a direction perpendicular to the scanning direction of the information pattern (auto tracking, (hereinafter referred to as rATJ). In addition, in order to irradiate the light beam as a stable minute spot despite the bending and mechanical errors of the record carrier, it is necessary to control it in the direction perpendicular to the recording surface (
Autofocusing, hereinafter referred to as AFJ. Furthermore, AT and AF are necessary during playback as well.

[Problem that the invention is trying to solve] However,
In the above conventional example, when recording or reproducing using a light spot on an information recording medium, medium defects on the recording surface of the information recording medium,
If there are defects such as scratches, dust, dirt, fingerprints, etc. on the surface of the transparent protective layer, the tracking servo may be disturbed and the AT may become misaligned, making recording or playback impossible during this period, which is an inconvenient problem. was there.

[Means for solving problems]

According to the present invention, a defect in a recording medium is detected by distinguishing whether it is a defect on the recording surface or a defect on the surface of a transparent protective layer based on a change in the light amount distribution of reflected light and a change in the total light amount. By correcting the tracking control in response to this, serious troubles such as AT misalignment can be avoided.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a drawing that best represents the features of the present invention,
In the figure, 1 is a system controller, 4 is an AT control circuit, 6 is an optical head, and 7 is a defect detector. Further, FIG. 2 is a circuit diagram showing the configuration of the defect detector 7. As shown in FIG.

FIGS. 3(a) and 3(b) are diagrams for explaining the structure of the optical recording medium C and the focusing state of the light beam from the objective lens 6d, which is the focusing means of the optical head 6, respectively. Diagram (a)
, C1 is a transparent protective layer, C2 is a recording medium, and C3 is a back substrate. In addition, the objective lens 6d of the optical head 6
The light beam emitted from the AF control circuit 5 forms a light spot C on the recording medium C2. Same figure (b)
1 is a diagram illustrating the state of the optical spot C on the surface of the recording medium. The position of the optical spot P is controlled by the AT control circuit 4 on a pre-group 4 for tracking formed on the surface of the recording medium. C5 indicates a bit that has already been recorded.

First, the operation of the defect detector 7 will be explained. In FIG. 2, the reflected light detection sensor 6h of the optical head 6 is divided into three parts in the track direction and two parts in the direction orthogonal to the track, and is a six-part sensor having light receiving surfaces 6h, 6h. The output signals of these sensors are also input to the defect detector 7 via the AT control circuit 4.

6 h, ~ to monitor the change in the total amount of reflected light.
A summation signal St of all sensors 6h6 is generated by an adder 7a, and passed through a low-pass filter 7C to distinguish it from a signal due to recording bits to generate a signal Sv. This signal Sv passes through a comparator 7d and becomes a binary signal sh. Also, it was divided into three in the track direction (6hI + 6h
4)! (6h 2+ 6h a) (63+6h6)
The sum of the two sensors in the center is 6h2+6h, and the sum of the four sensors on both sides is 6h, +6h3+6h 4+6
Similarly, the signal Lt obtained by taking the difference from h6 is passed through a low-pass filter 7e to generate a signal Lv in order to distinguish it from a signal due to recording bits.

This signal Lv is binarized by comparators 7f and 7g, and the logical sum of the respective output signals Lf"" and Lf- is
The R circuit 7h takes the signal and generates a surface defect determination signal Lh.

Here, as will be described later, when there is a surface defect, the signal Lv generates a signal with both positive and negative polarities, so after it is binarized, it is logically summed and used as a surface defect determination signal. . Moreover, the cutoff frequency of the low-pass filter 7e is
It is set lower than the cutoff frequency of the low-pass filter 7c, and has the function of distinguishing from the recording bit signal and at the same time distinguishing between defects on the recording medium surface C2 and surface defects.

In other words, defects on the surface of the recording medium are scanned by the focal point of the light beam, for example, a light spot of about 3 μm in diameter, while defects on the surface are scanned by a light spot on the non-focal plane of the light beam, for example, 100 μm in diameter.
Since the surface defect is scanned with a light spot of about 100 psi, the frequency component in the time axis direction of the light reflected by the defect is relatively lower for the surface defect.

Next, the generation of defect discrimination signals sh and Lh for defects on the recording medium surface and the protective layer surface will be explained using FIGS. 4 and 5.

In Fig. 4, lO is a defect with low reflectance on the surface of the recording medium, and when the position of the spot P scans in the direction of the arrow in the figure, the signal Sv that detects the total amount of reflected light is at the defective part. The amount of reflected light decreases, and the signal level accordingly decreases to below the reference voltage (2) of the comparator 7d, and the defect discrimination signal sh becomes high level. On the other hand, the reflected light pattern detection signal Lv becomes a signal as shown in FIG. 4 because the pattern of reflected light at the defective portion is not disturbed much, and the surface defect discrimination signal Lh remains at a low level.

Furthermore, in FIG. 5, numeral 10 indicates a defect on the surface of the protective layer, and as the light beam scans, the defective portion becomes S'v
Signal is low. Here, the Sv multiplied signal becomes W-shaped because when the defect is located off the optical axis of the light beam, both the incident light and the reflected light are blocked by the defect.
This is because the amount of reflected light is lower than when the defect is on the optical axis of the light beam. Next, it passes through the Sv times signal comparator 7d and becomes the sh times signal.

On the other hand, when the reflected light pattern approaches a defect, as shown in FIG. 6(a), the image moves from both sides in the scanning direction toward the center, and as shown in FIG. 6(c), the image moves from the defect to the center. When nuki is released, the image moves from the center to both sides. The reflected light pattern detection signal Lv is obtained by dividing the photodetector into three parts in the scanning direction and calculating the difference between the sum of the photodetectors at both ends and the photodetector in the center. The result is a signal that changes between positive and negative. Therefore, using comparators 7f and 7g, binary level signals Lf'' and Lf- are obtained, and OR,
The surface defect detection signal Lh becomes high level by the circuit 7h.

As described above, the defect detector 7 receives the defect discrimination signal sh
and a surface defect determination signal Lh.

Next, the operation of the system controller 1 after receiving the Sh and Lh multiplied signals from the defect detector 7 will be explained. When Sh and Lh are at low levels, the system controller 1 controls so that normal operation is performed since no defect has been detected. Next, when only sh is at a high level, it means that a defect on the recording medium surface has been detected. Since defects on the surface of the recording medium pass in a relatively short time, the system controller (1) controls the AT control circuit 4 so as not to follow the defects by reducing the gain of the AT control system, etc. On the other hand, when sh and Lh are at high levels, it is a defect on the surface of the protective layer.
Since this affects the AT control system for a relatively long time, the system controller 1 must forcibly fix the spot position by holding the tracking error signal at a constant value for a certain period of time to prevent tracking due to defects. is A
Controls the T control circuit 4.

Furthermore, in a system that performs so-called sequential recording or sequential reproduction, in which recording or reproduction is performed continuously on adjacent tracks, predictive AT control can be performed using the Lh times signal. That is, since a pattern change is used to detect surface defects, the Lh times signal is detected differently for the same surface defect depending on its position in the cross-track direction. For example, the influence on the reflected light pattern changes depending on whether the position of the surface defect is directly above the track that is currently being followed or is shifted from the track currently being followed, and the magnitude of the detection signal Lv varies. This causes a difference in the length of time that the signal Lh is at a high level. Therefore, the system controller 1 detects the state in which the surface defect is slightly affected within this short period of time. Before a problem occurs, try truck jumping, etc.
Processing such as changing the recording track to continue recording or controlling AT control to fix the spot position during reproduction is performed as described above.

The present invention can be applied in various ways in addition to the embodiments described above. For example, in the above embodiment, the light detection sensor for detecting the reflected light pattern is divided into three parts in the scanning direction. In addition, in the example,
When a defect on the recording surface is detected, the gain of the control system is changed. However, if it is possible to substantially reduce the tracking performance, such as changing the phase characteristics, what other means can be used? may also be used. In addition, we have described a method of holding the value of the tracking error signal at a constant value for a certain period of time when a defect on the surface of the protective layer is detected.
Any method that temporarily turns the control loop into an oven may be used.

〔Effect of the invention〕

As explained above, according to the present invention, by distinguishing and detecting whether a defect in a recording medium is on the recording surface or on the surface of a protective substrate, the device can be controlled.

In addition, when a defect on the surface of the protective layer is detected, by performing predictive control, the AT of the track adjacent to the defect is
Stable recording or reproducing operations can be performed while avoiding any influence on control.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the optical information recording/reproducing apparatus of the present invention, FIG. 2 is a circuit diagram showing a specific example of the defect detector shown in FIG. 1, and FIGS. b) is a diagram showing how information is recorded on a recording medium each having a transparent protective layer;
Figures 4 (a) to (e) are diagrams each explaining how defects are detected on the recording surface, and Figures 5 (a) to (e) are diagrams each explaining how defects are detected on the surface of the protective layer. Figure 6 (a)
) to (f) are diagrams each illustrating a change in a reflected light pattern when a light beam passes through a defect on the surface of a protective layer.

Claims (3)

[Claims] (1) In an optical information recording and reproducing device that records and/or reproduces information by irradiating a light beam onto an optical information recording medium having a transparent protective layer on the recording surface, the change in reflected light by the medium . An optical information recording and reproducing apparatus, comprising means for separately detecting defects on the recording surface and defects on the surface of the transparent protective layer. (2) A means for irradiating a light beam onto an optical information recording medium having a transparent protective layer provided on the recording surface, and tracking control for correcting misalignment between the irradiation position of the light beam and the track formed on the medium. an optical information recording and reproducing apparatus for recording and/or reproducing information on the medium, the apparatus comprising: a means for distinguishing defects on the recording surface and defects on the surface of the transparent protective layer from changes in light reflected by the medium; Separately detecting means is provided, and when a defect on the recording surface is detected, the responsiveness of the tracking control means is lowered, and when a defect on the transparent protective layer is detected, the tracking control means is made inoperable for a predetermined period of time. An optical information recording and reproducing device characterized by: (3) A means for irradiating a light beam onto an optical information recording medium having a transparent protective layer provided on the recording surface, and tracking control for correcting misalignment between the irradiation position of the light beam and the track formed on the medium. an optical information recording and reproducing apparatus for recording and/or reproducing information on the medium, comprising means for detecting a defect on the surface of the transparent protective layer from a change in light reflected by the medium; 1. An optical information recording and reproducing apparatus characterized in that, when a defect is detected, a track adjacent to the detected track is controlled in advance so that an abnormality in tracking control due to the defect does not occur.