JPH0196826A - Optical disc recording/playback device and optical disc - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 track pitch can be halved by using the ↑4 surfaces of the grooves, whose radial cross section is approximately V-shaped or inverted trapezoidal, as the information signal surface. to improve recording density,
In addition, a method has been proposed to keep crosstalk from adjacent trucks small. (Unexamined Japanese Patent Publication No. 57-10582
(Publication No. 8) 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 Figure 6, when 8 pages have been recorded, 0
If you try to track to the surface, the reflected light intensity distribution will change when surface 8 is unrecorded, and it will not be possible to track to the center of surface 0. Tracking of recording and reproduction on the 0th side depends largely on the recording state of the 8th side and the 0th side, making tracking control unstable. As a method for solving this problem, Japanese Patent Laid-Open No. 155528/1983 has been proposed. this is,
Forming pits with different optical properties at two different frequencies in the peaks and valleys of the figure 7 or reverse trapezoid groove,
In this method, the amount of reflected light from the disk changes at two different frequencies, and the frequency components of each frequency component during the change in light amount are made equal, thereby tracking the slope of a figure-7 or inverted 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 f2 is formed in the peaks as pits. The pit in FIG. 7 is an example of a hole pit. a, b, and C are intensity distributions focused on L of the optical disk. 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 f1. Moreover, if the light beam shifts toward the valley (at the time of distribution C), conversely, the change in light amount at frequency fl becomes larger than the change in light amount at frequency f2. That is, when a light beam is irradiated to the center of the slope, which is exactly in the middle of the peak and valley (distribution a), the frequencies f1 and f
The amplitudes of the changes in light amount at 2 are equal. Therefore, fl, f
Tracking to the center of the slope is performed by equalizing the amplitude of the change in light amount that changes at the two frequencies (2).

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 separate the tracking signal band of two types of frequency components and the data signal band for recording and reproduction, which has the problem of complicating the circuit system and limiting the data signal band. The present invention has been made in view of the above, and an object of the present invention is to provide an optical disc recording/reproducing apparatus and an optical disc that perform tracking control to the center of a slope without any restriction on the data signal band.

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 an inverted trapezoid shape on the optical disk, and the ridges or valleys of the groove are formed in the track direction. Tracking pits that are symmetrical and have different positions at a first position offset from the center of the inclined surface and a second position offset in the opposite direction from the center of the shifted first position are formed at regular intervals on the optical disk. When recording or reproducing information by irradiating a focused light beam spot along each of the slopes forming the V-shape or inverted trapezoid, the slope of the groove is determined based on the tracking pit signal of the optical disc. This is an optical disc recording and reproducing device that tracks a light spot at the center of the disc.

Effect of the Invention With the above-described configuration, the present invention irradiates a narrowed light beam spot along each of the V-shaped or inverted trapezoidal inclined surfaces of an optical disc to record or reproduce information. signals of a constant period of different tracking pits that are symmetrical in the track direction of the valley and have a first position shifted from the center of the slope and a second position shifted in the opposite direction from the center of the shifted first position; Therefore, it is possible to control the tracking of the light spot accurately at the center of the inclined surface of the groove.

Embodiment On an optical disk, a groove whose radial cross section is V-shaped or inverted trapezoidal is symmetrical in the track direction of the peaks or valleys, and the first position is offset from the center of the inclined surface and the first position is offset from the center of the inclined surface. Tracking pits having different optical properties at a second position shifted in the opposite direction from the center are formed at regular intervals. 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 at the tracking pit, and by making the amplitude of the change in light amount equal to that of the pit at the first position and the pit at the second position of the inclined surface, or by changing the light intensity of each pit. By detecting and making the phase difference equal, tracking is performed on the inclined surface of the V-shaped or inverted 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, a first position that is symmetrical in the track direction of the crests or troughs of the groove of the optical disc and is offset from the center of the inclined surface, and a second position that is offset from the center of the shifted first position in the opposite direction. Tracking pits with different optical properties are formed at different positions. This pit is an example of a hole pit. d, e, and f represent temporal changes in the light intensity distribution of the reproduced signal 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 TI (waveform d) when it passes through the tracking pit P2 at the first position on the slope (waveform d), and becomes large at time T2 when it passes through the tracking pit P2 at the second position. Here, when the light beam scans with a slight shift toward the valley S from the center of the slope (waveform e), the signal amplitude of the tracking pit PI at the first position increases at time TI, and at the second
The signal amplitude of the tracking pin P2 at the position decreases at time T2. Furthermore, when the light beam scans with a slight shift toward the peak T from the center of the slope (waveform f), the signal amplitude of the tracking pit Pl at the first position decreases at time T1, and the signal amplitude at the second position decreases. The signal amplitude of the tracking beep P2 increases at time T2. 1! I, when scanning the center of the slope that is exactly in the middle of the valley S and the peak T (waveform d
), the signal amplitudes at times T1 and T2 are equal. Therefore, by making the signal amplitudes at times T1 and T2 equal, tracking to the center of the slope A can be achieved.

Alternatively, when the light beam scans the slope A of the V-groove in the track direction (waveform g), the time T3 reaches the maximum after passing through the tracking pit Pl at the first position;
The phase difference at time T4 which reaches the maximum after passing through P2 (Pit for tracking at the second position) and pit P1 for tracking
A tracking control signal is obtained from the signal amplitude of pit P2, and tracking to the center of the slope can be performed.

Next, a specific example will be described 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 irradiating a focused light beam; 2
1 is a signal processing circuit that calculates a tracking error signal for tracking control from the digital signal obtained by the A/D conversion circuit 1, 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 tracking pitch (P) of the first position of the slope based on the amount of reflected light of the optical disk obtained by the A/D conversion circuit 1.
a signal processing unit 5 that detects the signal amplitude of I at time T1;
Similarly, 6 is the signal processing unit 2 which detects the signal amplitude of the tracking pin P2 at the second position on the slope from the amount of reflected light obtained from 4 at time T2, and 6 is the signal amplitude detected by the signal processing unit l. This is an amplitude calculation unit that calculates the difference between the signal amplitude detected by the signal processing unit 2 and the signal amplitude detected by the signal processing unit 2. In the above block, A
The signal processing unit 4 detects the signal amplitude of the pit Pl at time TI from the signal amplitude of the optical disc obtained by the /D converter l, and the signal processing unit 2 detects the signal amplitude of the pit P2 at time T2. PI) detected by the amplitude calculation unit 6
Beep) A tracking error signal is obtained by determining the difference in signal amplitude of P2, and by outputting it to the D/A conversion circuit 3, an error signal for tracking control can be obtained and controlled.

FIG. 4 is a processing block diagram showing another embodiment of the present invention. 7 is a signal processing unit 3 that detects the peak time T3 of the signal amplitude of the tracking pit (PI) at the first position on the slope from the amount of light reflected from the optical disc, and 8 is the signal of the tracking pit P2 at the second position. The signal processing section 4 detects the time T4 of the amplitude peak, and 9 is a phase difference calculation section that calculates the phase difference from the time T3 and the time T4 detected by the signal processing section 3. In the above block, the A/D converter l
The signal processing unit 3 of 7 detects the peak time T3 of the signal amplitude of the tracking pit Pl from the tracking pit signal component obtained from the tracking pit signal component, and the signal processing unit 4 of 8 detects the signal 1 of the tracking pit P2. Width peak time T4
is detected, and the phase difference calculation unit 9 calculates the peak time T3 of the signal amplitude.
By obtaining a tracking error signal from the phase difference and signal amplitude from T4 and outputting it to the D/A conversion circuit 3, it is possible to obtain an error signal for tracking control and perform control.

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, ■ tracking pits must be formed symmetrically to the slope B of the groove. Therefore, tracking control is possible by changing the polarity in the signal processing section 2 or by providing an inversion circuit to invert the polarity of the obtained tracking error signal. That is, by switching the tracking error signal, it becomes possible to track the slope of the groove. Further, since tracking pits with a constant period are used and the space between them is used as a data area, recording and reproduction without any restriction on the signal frequency band of data is possible.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the optical disc L is provided with a groove whose radial cross section is V-shaped or inverted trapezoidal,
When recording or reproducing information by irradiating a focused light beam spot along each of the inner slopes forming the V-shape or inverted trapezoid, the slopes are symmetrical in the track direction of the peaks and valleys of the groove. Different tracking pits are formed at regular intervals at a first position offset from the center of the surface and a second position offset in the opposite direction from the center of the first shifted position, and the tracking pits of the optical disc are formed at regular intervals. From the signal
The optical spot can be tracked and controlled at the center of the inclined surface of the groove, and can be provided in an optical disc recording/reproducing device and an optical disc that have no restrictions on the data signal band, and its practical effects are great.

[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 the groove, and FIG. 7 is an explanatory diagram of a conventional means for tracking on the slope of the V-groove. l... 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 ・--1--------------I2L-111 1111~-J Figure 5 Figure 6 Figure 7 Figure 8 ν-Sapa-

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 performing recording or reproducing, a first position symmetrical in the track direction of the crests or valleys of the groove and offset from the center of the slope, and a first position offset from the center of the shifted first position in the opposite direction. 2 tracking pits at different positions are formed at regular intervals, and a light spot is tracked to the center of the slope of the groove based on the tracking pit signal of the optical disc to record or reproduce high-density information. Characteristic optical disc recording/playback device. (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) A groove having a V-shaped or inverted trapezoidal cross section in the radial direction is provided on the optical disk, and a first position of the crest or valley of the groove is symmetrical in the track direction and is offset from the center of the inclined surface. An optical disc in which different tracking pits are formed at regular intervals at a second position offset in the opposite direction from the center of the shifted first position.