JPH0196825A - Optical disk recording and reproducing device and optical disk - Google Patents

Abstract

PURPOSE:To decrease a crosstalk by providing a groove, in which the cross section of the radius direction is V-shaped or reverse ladder-shaped, on an optical disk, providing a bit for tracking having a different phase with the same frequency between a crest and a valley respectively, irradiating an optical spot in the center of the inclination surface of a groove and executing the tracking. CONSTITUTION:On an optical disk, a groove is provided in which the cross section of the radius direction is V-shaped or reverse ladder-shaped, and a bit for tracking having a different phase with the same frequency is formed between a crest and a valley. The bit, for example, is formed by a hole bit, and at present, when the optical beam stopped onto the optical disk is moved in a track direction, the hourly change of the light intensity distribution obtained by two-divided optical detector is as shown by (d) and (e). At this time, when a time T1 to pass through a bit for tracking of a valley S and a time T2 to pass through the bit for tracking of a crest T are made equal, the signal amplitude at the times T1 and T2 is made equal. Therefore, a signal processing is executed and at the position where the amplitude is made equal, the optical spot is positioned.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc recording and reproducing apparatus and an optical disc related to optical information processing.

2. Description of the Related Art In recent years, optical disk recording and reproducing devices that utilize laser light have been developed as large-capacity information recording and reproducing devices.

By the way, in order to double the recording density of a recording/reproducing disk, the slope of a groove whose radial cross section of the optical disk is approximately V-shaped or inverted trapezoid shape is used as the information signal surface.
A method has been proposed in which the track pitch is halved to improve recording density and to keep crosstalk from adjacent tracks small. (Unexamined Japanese Patent Publication No. 57-105828
(Patent Publication) This premise requires that a light beam spot be irradiated along one slope of a figure 7 shape or an inverted ladder shape, that is, tracking must be possible.

Here, it is possible to perform recording and reproduction by applying tracking along the troughs S or crests T of the grooves (Fig. 5). For example, this can be done by controlling the reflected light intensity distribution on the lens surface to be symmetrical with respect to the track direction.
This is known as tracking by r -F 1eld). (2) Tracking to one slope of the groove can also be controlled by intentionally shifting the tracking control to the valley S.

However, as shown in FIG. 6, when attempting to track to the sixth surface where the B surface has already been recorded, the reflected light intensity distribution changes when the B surface is unrecorded, making it impossible to track to the center of the sixth surface. Tracking of recording and playback to side 6 is not possible with side B or 9.
Tracking control becomes unstable as it largely depends on the recording state of the surface. As a way to solve this problem,
-155528 has been proposed. This forms pits with different optical properties at two different frequencies in the peaks and valleys of a V-shaped or inverted trapezoidal groove, and the amount of light reflected from the disk changes at two frequencies. By making each frequency component equal while changing the light amount,
This is a method of tracking the slope of a figure-7 or reverse trapezoid groove. Here, the pits may be hole pits that give a phase difference to light inside and outside the pits, or may be formed as dark and light pits with varying reflectance or transmittance.

This method will be explained with reference to FIG. 7 for the case of the groove. A tracking signal of frequency f1 is formed in the troughs, and a tracking signal of frequency r2 is formed in the peaks as pits. 7th
The pit in the figure is an example of a hole pit. a, b, and C
is the focused intensity distribution on the optical disc. When the light beam is irradiated with a slight deviation from the center of the slope toward the mountain, for example, when the light intensity distribution is as shown in b, the stronger light will be irradiated on the signal part of frequency f2, The change in light amount becomes larger than the change in light amount at frequency fl.

Also, if the light beam shifts toward the valley (at distribution C),
Conversely, the change in light amount at frequency f1 is greater than the change in light amount at frequency f2. That is, when the light beam is irradiated to the center of the slope, which is exactly in the middle of the peak and the valley (distribution a), the amplitude of the light amount change at frequencies f1 and f2 becomes equal. Therefore, tracking to the center of the slope is performed by equalizing the amplitude of the change in the amount of light that changes at the two frequencies fl and f2.

Problems to be Solved by the Invention However, with the above configuration, pits with different optical properties are formed at two different frequencies in the peaks and valleys of the figure-7 or inverted trapezoidal groove. It is necessary to detect the tracking signals of two types of frequency components, which makes the circuit system complicated, and if the signal amplitudes of the tracking signals of the two types of frequency components are different, tracking to the center of the slope cannot be performed. Crosstalk increases,
There was a problem that the information could not be read correctly.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical disc recording/reproducing device and an optical disc that accurately perform tracking control to the center of a slope.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a groove whose radial cross section is V-shaped or inverted trapezoid shape on the optical disk, and the grooves have identical grooves at each of the peaks and valleys of the groove. Tracking lenses having different phases at different frequencies are formed on the optical disk, and a focused light beam spot is irradiated along each of the V-shaped or inverted trapezoidal inclined surfaces to record or reproduce information. When performing this, the tracking video of the optical disc is
The present invention is an optical disc recording/reproducing apparatus that tracks an optical groove to the center of the inclined surface of the groove based on a point signal.

Operation The present invention has the above-described configuration, and when recording or reproducing information by irradiating a narrowed light beam spot along each of the V-shaped or inverted trapezoidal slopes of the optical disc, By tracking and tracking signals having the same frequency and different phases for each valley, it is possible to accurately track the optical spot at the center of the slope of the groove.

Embodiment Tracking pits with different optical properties having the same frequency and different phases are formed on each of the peaks and valleys of a groove whose radial cross section is V-shaped or inverted trapezoidal on an optical disk. The pits may be hole pits that give a phase difference to the light inside and outside the pits, or may be dark and light pits with varying reflectance or transmittance. The amount of light reflected from the optical disk changes with the frequency of the tracking pit, and the phase difference can be made equal by equalizing the amplitude of the change in light amount at each peak and valley due to the phase difference, or by detecting the change in light amount at each peak and valley. By doing so, tracking is performed on the inclined surface of the figure-7 or reverse trapezoidal groove. This method will be explained for the case of (1) grooves.

FIG. 1 is a schematic diagram illustrating an optical disc recording/reproducing apparatus and an optical disc tracking control method according to the present invention. In FIG. 1, tracking signals having the same frequency and different phases are formed as pits in the valleys and peaks of the optical disc.

This pit is an example of a hole pit. d and e represent time-dependent changes in the light intensity distribution of the two-divided optical detector when a focused light beam on the optical disc scans in the track direction. When the light beam scans the slope A of the V-groove in the track direction, it becomes large at time T1 when it passes through the tracking pit of valley S (waveform d), and becomes large at time T2 when it passes through the tracking pit of mountain T. (waveform e
). Here, when the light beam scans with a slight deviation from the center of the slope toward the valley, the signal amplitude of the tracking pit in the valley S increases at time TI, and the signal amplitude of the tracking pit in the mountain T increases as follows. It decreases at time T2. Furthermore, when the light beam scans with a slight deviation from the center of the slope toward the peak, the signal amplitude of the tracking pit in the valley S decreases at time TI, and the signal amplitude of the tracking pit in the peak T decreases at time TI. Increases at T2. That is, when scanning the center of the slope, which is exactly in the middle of the valley and the peak, the signal amplitudes at times TI and T2 become equal. Therefore, by making the signal amplitudes at times T1 and T2 equal, tracking to the center of the slope can be achieved.

As another method, when the light beam scans the slope A of the V-groove in the track direction, the light beam passes through the tracking pit of the valley S and reaches its maximum at time T3, and the light beam passes through the tracking pit of the mountain T and reaches its maximum. A tracking control signal is obtained from the phase difference at time T4 and the signal amplitude of the tracking pit, and tracking to the center of the slope can be performed.

Next, a specific configuration example will be explained using FIGS. 2 and 3. FIG. 2 shows a signal processing configuration for implementing the tracking control of the present invention, and FIG. 3 is a block diagram showing the processing contents. In Fig. 2, 1 is an A/D conversion circuit that converts an analog signal of the amount of light reflected from an optical disk into a digital signal by irradiation with a patterned light beam; A signal processing circuit that calculates a tracking error signal for tracking control from a digital signal, and is composed of, for example, a microcomputer. 3 is a D/A conversion circuit that converts the digital tracking error signal obtained by the signal processing circuit 1 into an analog signal. It is possible to perform tracking control by configuring a tracking control loop including conventional phase compensation using the tracking error signal obtained in step 3 and driving a tracking actuator. Next, a processing method of the signal processing circuit 2 that calculates the tracking error signal will be explained.

4 is a filter processing unit for detecting the signal component of the tracking pit from the amount of light reflected from the optical disc obtained by passing through the A/D conversion circuit;
6 is a signal processing unit 2 that detects the signal amplitude of the mountain T at time T2; 7 is a signal processing unit 2 that detects the signal amplitude of the mountain T at time T2; This is an amplitude calculation unit that calculates a difference in signal amplitude. In the above block, the filter processing section 4 extracts the tracking pit signal components of the peaks and valleys of the groove, and the signal processing section 5 detects the signal amplitude of the valley S from the extracted signal components, and the signal amplitude of the valley S is detected from the extracted signal components.
The signal processing unit 2 of 6 detects the signal amplitude of the peak T, and the amplitude calculation unit 7 calculates the difference between the signal amplitudes of the valley S and the peak T to obtain a tracking error signal. By outputting the signal to , it is possible to obtain and control an error signal for tracking control.

FIG. 4 is a processing block diagram showing another embodiment of the present invention. Similarly, 4 is a filter processing unit for detecting the signal component of the tracking pit from the amount of reflected light of the optical disk obtained by the A/D conversion circuit 1, and 8 is a filter processing unit for detecting the time T3 of the peak of the signal amplitude of the valley S. In the signal processing section 3, 9
A signal processing unit 4 detects the time T4 of the peak of the signal amplitude of the peak T, and 10 is a phase difference calculation unit that calculates the difference between the phases detected at time T3 and time T4 detected by the signal processing unit 3. . In the above blocks, the filter processing unit 4 extracts the tracking pit signal components of the peaks and valleys of the groove,
From the extracted signal components, the signal processing unit 8 (8) detects the time T3 of the peak of the signal amplitude of the valley S, and the signal processing unit 4 (9) detects the time T4 of the peak of the signal amplitude of the mountain T,
A tracking error signal is obtained from the phase difference and the signal amplitude in the phase difference calculating section 10, and is output to the D/A conversion circuit 3, whereby an error signal for tracking control can be obtained and controlled.

It goes without saying that the above configuration can be configured either analog or digitally (hardware or software).

In addition, we have described the case where the light beam tracks the slope A of the V-groove, but in order to track the slope B of the groove, the polarity must be changed in the signal processing section 2, or the tracking error obtained Tracking control is possible by providing an inversion circuit that inverts the polarity of the signal. That is, by switching the tracking error signal, V
Track kinging is possible on the inner slope of the groove.

As described in detail, according to the present invention, the optical disc-E is provided with a groove whose radial cross section is V-shaped or inverted trapezoidal, and each of the inclined surfaces forming the V-shape or inverted trapezoid is provided with a groove. When recording or reproducing information by irradiating a focused light beam spot along the groove, tracking pits having the same frequency and different phases are formed in each of the peaks and valleys of the groove, and the tracking pits are used for tracking the optical disc. Based on the pit signal, a light spot can be provided at the center of the inclined surface of the groove by a disc recording/reproducing device and an optical disc capable of tracking control, and the practical effects thereof are significant.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the track king control system according to the present invention, Fig. 2 is a signal processing configuration diagram, Fig. 3 is a block diagram of one embodiment, Fig. 4 is a block diagram of another embodiment, and Fig. 5 FIG. 6 is a perspective view showing recording on a V-groove, and FIG. 7 is an explanatory diagram of a conventional means for tracking on a slope of a groove. 1... A/D conversion circuit, 2... signal processing section, 3...
・Name of D/A conversion circuit agent Patent attorney Toshio Nakao (1 person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6, 8. Rage

Claims (3)

[Claims] (1) A groove whose radial cross section is V-shaped or inverted trapezoid is provided on the optical disk, and a focused light beam spot is irradiated along each of the inclined surfaces forming the V-shape or inverted trapezoid, and the information is When recording or reproducing data, tracking pits with the same frequency and different phases are formed in each of the peaks and valleys of the groove, and a tracking pit signal of the optical disc is used to direct light to the center of the slope of the groove. An optical disc recording/reproducing device characterized by recording or reproducing high-density information by tracking spots. (2) A switching circuit is provided to switch the polarity of the tracking pit signal of the optical disc, and the optical spot is tracked at the center of both slopes of a groove whose radial cross section is V-shaped or inverted trapezoidal on the optical disc. , the optical disc recording and reproducing apparatus according to claim 1, characterized in that said switching circuit is switched. (3) Having a groove whose radial cross section is V-shaped or inverted trapezoidal on the optical disk, and forming tracking pits with the same frequency and different phases in each of the peaks and valleys of the V-shaped or inverted trapezoidal groove. optical disc.