JPH06243504A - Device for recording and reproducing optical disk - Google Patents

Abstract

PURPOSE:To reduce the erroneous detection of a groove on a disk in an optical disk recording and reproducing device. CONSTITUTION:An optical disk 1 is provided with the groove 2 and a wide land 3 on which a signal is recorded. Two laser beam spots S1 and S2 with a spot pitch smaller than the groove pitch of the optical disk 1 are scanned by an actuator 4 in the radial direction of the disk. The signals reflected from the grooves 2 and 3 by irradiating the spots S1 and S2 are detected by detectors D1 and D2. The output of the detector D1 is amplified by a reproducing amplifier circuit A1 to be inputted to the noninverted terminal of a comparator C1, and the output of the detector D2 is attenuated by an attenuation circuit ATT2 to be inputted to the inversion terminal of the C1. A groove signal detected by the D1 is detected correctly by the comparator C1 based on the signal inputted to the inversion terminal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing apparatus, and more particularly to an optical disk recording / reproducing apparatus in which erroneous detection of grooves on an optical disk is reduced.

[0002]

2. Description of the Related Art In a conventional recording / reproducing apparatus using an optical disc, an RF traverse signal is used to detect a track information, particularly a position of a groove of the optical disc. It was possible to detect whether the spot is on the land or the groove by detecting the output level of the groove with a beam spot (hereinafter referred to as a spot) and one detector and comparing it with the zero level. However, in a wide-land optical disc that records multi-channel HD signals and the like on the land, such detection is impossible because the RF traverse signal waveform is different from that of the conventional one.

Therefore, conventionally, the following method has been proposed as a method for detecting the groove of the optical disk. The proposed method will be described below based on the detection characteristics of a disc in which a signal is recorded on a land, as shown in FIG. First, the first
In the method of (1), a method of comparing a signal level at a land and a signal level at a groove reflected by irradiating a signal of a single spot with a predetermined direct current (DC) level has been considered.

As a second method, a method of irradiating a signal of a single spot and comparing the signal reflected from the land and groove with the signal after passing through the low pass filter of the reflected signal can be considered. Was there.

However, in the first method, there is a possibility that a groove may be erroneously detected due to a difference in reflectance between discs, a change in laser output power, or a change in detector sensitivity. Further, in the second method, since the output of the low-pass filter follows the RF traverse signal, there is no possibility of erroneous detection due to a difference in reflectance between disks, a change in laser output power, and a change in detector sensitivity. For example, it is difficult to distinguish between a groove and a land due to a small reflectance difference on the disc where the reflectance changes between the recorded portion and the unrecorded portion, and the groove may be erroneously detected.

[0006]

In view of the above problems, the present invention eliminates the possibility of erroneous detection and enables groove position detection by a spot without adding special detection means. The point is to provide disk recording / playback.

[0007]

In the optical disk recording / reproducing apparatus of the present invention, an optical disk having grooves and lands is irradiated with the first and second lasers arranged at a spot pitch different from the groove pitch of the optical disk. A beam spot, a first detector that detects a signal from the first laser beam spot, a second detector that detects a signal from the second laser beam spot, and the first and second detectors. First and second regenerative amplifier circuits for amplifying the output signal of 1., an attenuator circuit for attenuating the output of the second regenerative amplifier circuit to a predetermined level, an output of the first regenerative amplifier circuit and an output of the attenuator circuit. Or a comparator to which is input,

Alternatively, the first and second laser beam spots, which are irradiated onto an optical disk having grooves and lands and are arranged at a spot pitch different from the groove pitch of the optical disk, and from the first laser beam spot A first detector for detecting a signal, a second detector for detecting a signal from the second laser beam spot, and first and second reproductions for amplifying output signals of the first and second detectors. An amplifier circuit and the first
The first and second attenuating circuits for attenuating the outputs of the regenerative amplifying circuit and the second regenerative amplifying circuit by a predetermined level, and the outputs of the first regenerative amplifying circuit and the second attenuating circuit are input. A first comparator, and a second comparator to which the output of the second regenerative amplifier circuit and the output of the first attenuating circuit are input.

The first and second laser beam spot pitches are smaller than the groove pitch of the optical disk.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of the entire apparatus for explaining an embodiment for detecting a groove in an optical disk recording / reproducing apparatus of the present invention. In FIG. 1, reference numeral 4 denotes an optical head actuator, which is tracked by the actuator 4 and its interval (spot pitch).
Is different from the groove pitch of the optical disk 1, for example, two spots S1 and S2 having a small pitch, and the reflected signals from the groove 2 and the land 3 of the optical disk 1 by these spots S1 and S2 are detected and converted into electrical signals. The optical head is equipped with two detectors D1 and D2 for conversion. As an example, the spots S1 and S2 are located in the radial direction of the optical disc.

Further, a reproduction amplification circuit A1 and a reproduction amplification circuit A for amplifying the detection signals of the detectors D1 and D2.
2. It is provided with comparators C1 and C2 for comparing the output signals of the reproduction amplifier circuits A1 and A2 as input signals. Each of the comparators C1 and C2 has, on one side of its input terminals, for example, an inverting input terminal side, the regenerative amplifier circuit A1.
Attenuation circuits ATT1 and ATT2 for attenuating the output signals of A2 and A2 to 1 / x (x> 1) are provided.

In this case, the comparator C2 and the attenuating circuit ATT2 can be omitted if the output of the comparator C2 is not required.

The operation of the embodiment will be described below with reference to FIG. 2 in comparison with the detection characteristic of the conventional example shown in FIG. For example, in the case of an optical disc in which the reflectance of the groove 2 is lower than the reflectance of the land 3, the level of the reproduction signal thereof is changed with respect to the position of the actuator 4, that is, the movement of the spots SI and S2 in the radial direction of the optical disc. The output characteristics are as shown in FIG. The output characteristic of the present invention shown in FIG. 2 represents the level input to the comparators C1 and C2, where the output of the regenerative amplifier circuit A1 is CH1 and the output of the regenerative amplifier circuit A2 is CH2.

As described above, this level changes depending on the change in the reflectance of the disc, the change in the laser output power, the change in the detector sensitivity, and the write state of the disc.
Therefore, in the conventional method, as shown in FIG. 3, as compared with the direct current (DC) level or the low-pass filter output signal indicated by the broken line, it is possible to accurately detect whether the spot illuminates the groove or the land. Can not do it.

On the other hand, in the case of the present invention, the spot S1
The output levels of S2 and S2 are the change in reflectance of the optical disc 1, the change in laser output power, the change in detector sensitivity,
Since the output is obtained by utilizing the fact that there is a strong correlation with the change due to the writing state of the disc and that the distance between the spots (spot pitch) and the groove pitch are different, the output of the groove and the land is changed as shown in FIG. The groove signal can be easily detected from the comparator C1 or C2 by identifying the signal. At this time, due to the pitch difference,
The two spots S1 and S2 do not illuminate the groove at the same time.

Then, the attenuators ATT1 and ATT2
The value of x is determined by the degree of groove modulation of the optical disk 1 and the rate of change in reflectance due to writing / not writing so that the output of the groove 2 can be sufficiently detected.

The detection signal of the present invention shown in FIG. 2 will be described in detail below. From the state where the two spots S1 and S2 irradiate adjacent lands at the same time, the two spots S1 and S2 move the actuator 4 to the right side in FIG. 1, that is, the two spots move in the radial direction of the optical disc and the spot S
1 illuminates the groove 2, and the spot S2 illuminates the land 3,
In the output signal obtained by sequentially moving the spot to the right, the signal CH1 obtained by amplifying the output signal of the detector D1 by the regenerative amplifier A1 is input to the non-inverting input terminal of the comparator C1.

Further, the signal CH2 obtained by amplifying the output of the detector D2 by the regenerative amplifier A2 is used as a 1 / x attenuation circuit ATT1.
It is attenuated by and is input to the inverting input terminal of the comparator C1.
FIG. 2A shows changes in the output signal levels from the groove 2 and the land 3 input to the comparator C1.

As is apparent from FIG. 2A, the detection signal of the detector D1 and the detection signal of the detector D2 are input to the comparator C1 and the output of the comparator C1 based on the signal levels from the groove and the land. Is the CH2 output input to the inverting terminal side.
The 1 output signal is compared with the reference level CH2 output × 1 / x, and the signal from the groove illuminated by the spot S1 is output from the comparator C1 as the groove detection pulse of CH1 without error.

FIG. 2B shows the signal output levels of CH1 and CH2 input to the comparator C2.
As is apparent from FIG. 2B, the detection signal of the detector D1 and the detection signal of the detector D2 are input to the comparator C2, and the output of the comparator C2 based on the signal levels from the groove and the land is inverted. CH1 input to the terminal side
When the output level x1 / x is used as the reference level, the CH2 output signal is compared with the reference level CH1 output level x / x, and the signal from the groove illuminated by the spot S2 is detected from the comparator C2 without error. It is output as a pulse. As described above, it is obvious that the detection of the signal from the groove can be facilitated without using special hardware, and the erroneous detection of track information, especially the groove can be reduced.

In the above embodiment, the case where the spot pitch is smaller than the groove pitch has been described. However, if the spot pitch has a pitch which is not an integral multiple of the groove pitch, the pitch mode can be selected as necessary. It is clear that there is.

[0022]

According to the present invention, since the signal level of each spot is compared, a groove is erroneously detected due to a difference in reflectance between discs, a change in laser output power, or a change in detector sensitivity. The likelihood is reduced. Further, it is possible to realize an optical disc recording / reproducing apparatus capable of detecting a groove without error without adding special detection hardware.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is an output level characteristic diagram provided for explaining an embodiment of the present invention.

FIG. 3 is an output level characteristic diagram for explaining a conventional example.

[Explanation of symbols]

 1 Optical Disc 2 Groove 3 Land 4 Actuator S1, S2 Laser Beam Spot D1, D2 Detector A1, A2 Regenerative Amplifier Circuit C1, C2 Comparator ATT1, ATT2 Attenuation Circuit

Claims (3)

[Claims] 1. A first and a second laser beam spot irradiated onto an optical disc having a groove and a land and arranged at a spot pitch different from the groove pitch of the optical disc, and from the first laser beam spot. A first detector for detecting a signal, a second detector for detecting a signal from the second laser beam spot, and first and second reproductions for amplifying output signals of the first and second detectors. An optical disk comprising an amplifier circuit, an attenuator circuit for attenuating the output of the second reproduction amplifier circuit to a predetermined level, and a comparator to which the output of the first reproduction amplifier circuit and the output of the attenuation circuit are input. Recording / playback device. 2. A first and a second laser beam spot irradiated onto an optical disc having a groove and a land and arranged at a spot pitch different from the groove pitch of the optical disc, and from the first laser beam spot. A first detector for detecting a signal, a second detector for detecting a signal from the second laser beam spot, and first and second reproductions for amplifying output signals of the first and second detectors. An amplifying circuit; first and second attenuating circuits for attenuating outputs of the first and second reproducing and amplifying circuits by a predetermined level; and outputs of the first and second reproducing and amplifying circuits. An optical device comprising a first comparator to which the output of the attenuator circuit is input, and a second comparator to which the output of the second regenerative amplifier circuit and the output of the first attenuator circuit are input. Disk recording / playback device. 3. The optical disk recording / reproducing apparatus according to claim 1, wherein the first and second laser beam spot pitches are smaller than the groove pitch of the optical disk.