JPS6299923A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain accurate tracking control by using a correction signal to correct the tilt component of a disc and a pickup in a tracking error signal. CONSTITUTION:A photodetection means 3 split horizontally to a track of a disc, low pass filters 11, 12 extracting a low frequency component of an output signal of the photodetection means 3, the 1st differential means 13 generating atracking error signal from the output signal of the low pass filters, high pass filters 15, 19 extracting a high frequency component of the output signal of the means 3, detection means 16, 20 detecting the output signal of the high pass filters, the 2nd differential means 18 generating a correction signal from the output signal of the detection means and the 3rd diffferential means 23 subracting the correction signal from the tracking error signal are provided and the correction signal is used to correct the tilt component of the disc and pickup from the tracking error signal. Thus, one beam is used to apply the accurate recording/reproduction of the information and the tracking control 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording and reproducing apparatus for optically recording and reproducing information on a disc such as a video disc and a digital audio disc.

[Summary of the invention]

The present invention provides an optical information recording and reproducing device, which includes a light receiving means divided in the left and right direction of a track of a disk, which receives reflected light of light irradiated onto a disk for recording and reproducing information, and an output signal of the light receiving means. a low-pass filter for extracting a low-frequency component of the output signal of the light-receiving means; a first differential means for generating a tracking error signal from the output signal of the low-pass filter; a high-pass filter for extracting a high-frequency component of the output signal of the light-receiving means; A detection means for detecting the output signal, a second differential means for generating a correction signal from the output signal of the detection means, and a third differential means for subtracting the correction signal from the tracking error signal are provided.

The correction signal corrects the tilt component of the disk and pickup in the tracking error signal, thereby making it possible to accurately record and reproduce information and control tracking using one beam.

[Conventional technology] In order to accurately record and reproduce information in an optical information recording and reproducing apparatus, it is necessary to track the light emitted from the light source with respect to the track on the disk. Although there are various methods for tracking control, the configuration of the pickup can be simplified if information recording/reproduction and tracking control can be performed using a single beam.

In such a one-beam tracking method, a light receiving means for receiving reflected light of light irradiated onto a disk for recording and reproducing information is divided into two parts in the left and right direction of the track of the disk. The respective output signals from the left and right divided light receiving elements are as shown in FIGS. 6(a) and 6(b), for example. That is, for example, if the level of the signal corresponding to the average amount of light received between the tracks of the right light receiving element is D, then the level on the track! is αD (α is a coefficient).

On the other hand, the signal level between the tracks of the left photodetector is (D+ΔD), and the signal level on the track is β(D+
ΔD) (β is a coefficient), ignoring disturbances in the RF envelope due to optical MTF (mechanical transfer function) and other influences, and fluctuations on the upper side of the RF envelope, the right side light received through the low-pass filter The output R of the means is as follows.

R=D-(1/4) αI] + (1/4)aho""" ...(1) Also, the output of the left photodetector is L=D+ΔD-(1/4)β(D+ΔD) + (1/4
) β (D+Δo)ei (wt-J)...
(2) becomes. Therefore, the tracking error signal E obtained from the difference between each low-pass filter is:

E=R-L =D-(1/4) αD + (1/4) αDa'hi'] -(D+ΔD-(1/4)β(D+ΔD)+(1/4
) β (D+ΔH-,) ei(t-5)==
[D-(D+ΔD)-(1/4)(αD-β(D+ΔD
))] + (1/4) CaD eicwt"D
(D+AD) eicw′e-” )・・・・
(3) It becomes. Here, ω is the angular frequency when the pickup crosses the track in the radial direction of the disk, and δ is the phase difference between the diffracted light generated in the left and right light receiving elements. The second right-hand side of equation (3)
The first term includes a phase difference component, and the first term includes a DC offset component thereof.

By the way, as shown in FIG. 7, in a pickup in which the light reflected from the disk 1 is received by the light receiving element 3 via the objective lens 2, if only the objective lens 2 is moved parallel to the disk 1 for tracking control, the optical axis The position of the principal ray 5 relative to 4 is displaced, and the position of the spot 6 on the light receiving element 3 is moved relative to the two divided light receiving elements 31 and 32),
The DC component of equation (3) changes.

Further, as shown in FIG. 8, when the relative angle between the pickup (optical axis 4) and the disk 1 is tilted, the relative light amounts of the left and right light receiving elements 31 and 32 change, and the DC component similarly changes.

[Problem that the invention seeks to solve]

Therefore, in the conventional device in which the output signals of the light receiving elements 31 and 32 are extracted through low-pass filters and a tracking error signal is generated from the difference signal, a DC offset occurs in the tracking error signal, making it difficult to achieve accurate tracking servo. I couldn't do that. The offset in the case shown in FIG. 7 can be prevented by driving not only the objective lens 2 but also the entire pickup in the tracking direction, but this requires making the entire pickup smaller and lighter. However, there are limits to miniaturization and weight reduction, and even if the entire device is driven, offset as shown in FIG. 8 cannot be prevented.

[Means for solving problems]

FIG. 1 is a block diagram of an optical information recording/reproducing apparatus according to the present invention. In the figure, reference numerals 11 and 2 are low-pass filters, which extract low-frequency components from the outputs of light-receiving elements 31 and 32, which are divided left and right with respect to the tangential direction of the track. The outputs of the low-pass filters 11 and 12 are supplied to a differential means 13 such as a differential amplifier, and the difference signal is sent to the differential means 2.
3 to the tracking control circuit 14. 15 is a high-pass filter that extracts high-frequency components from the output of the light-receiving element 31; 16 is a detection circuit that detects the output of the high-pass filter 15;

17 is a low-pass filter that smoothes the output of the detection circuit 16 and extracts its low-frequency components;
The output of is supplied to the differential means 18. - The output of the force photodetector 32 is also supplied to the differential means 1.8 via the high-pass filter 19, the detection circuit 20, and the low-pass filter 21, and the output of the differential means 18 is further supplied to the differential means 1.8 as a correction signal for correcting the tracking error signal. It is supplied to the moving means 23.

[Effect]

The operation will now be explained. A light beam emitted from a light source (not shown) is incident on an objective lens 2 and converged onto a disk 1. The light beam reflected by the disk 1 passes through the objective lens 2.
The light is irradiated onto the light receiving element 3 through the light receiving element 3. Since the amount of reflected light changes as it is modulated by pits etc. on the disk 1, the information signal can be reproduced by demodulating the summed output of the light receiving elements 3 and 32.

On the other hand, as mentioned above, the signals obtained from the outputs of the light receiving elements 31 and 32 through the low-pass filters 1 and 12 are shown in Figs. 2(a) and 2(b), respectively, ignoring disturbances on the upper side. It comes to show. Further, if the DC component of the tracking error signal output by the differential means 13 is El, then from equation (3).

E, =D-(D+ΔD)-(1/4)(αD-β(D+ΔD))... (4). The coefficients α and β do not change when only the objective lens 2 is moved, but when the disk 1 is tilted with respect to the pickup, they change to α' and β', respectively, as shown in FIG. Therefore, the output signals of the low-pass filters 11 and 12, respectively, are as shown in FIG. 2(a).

It changes as shown in (b) to (c) and (d).

At this time, the high-frequency component (RF multiplied signal) is extracted from the output of the light-receiving element 31.32 by a high-pass filter 15.19, and detected by a detection circuit 16.20, as shown in Fig. 2 (8).
, (f) can be obtained. Therefore, when the low-frequency components (RF signal envelope) of the outputs of the detection circuits 16 and 20 are detected by the low-pass filters 17 and 21, and the difference is obtained by the differential means 18, the modulation degree (α', β ') is the signal E proportional only to
, l, E'= (1/4)(α'(D-D')-β' (
D+ΔD+D'')'t... (5) is obtained.

On the other hand, when the disk and the pickup are tilted, the DC component E2 of the signal output from the differential means 13 is E2=((D-D')-(D+ΔD+D"))-(
1/4) (α'(D-D') - β'CD+ΔD+D")) ... (6), which is the difference between the component of the difference in the reflection level of the disk mirror surface (between tracks) and the amount proportional to the modulation degree. Therefore, the differential means 23 sets E and -E.

If we obtain E, −E□= (D−D' )−(D+ΔD+D”)=
CD-(D+ΔD)) -(D'+D") ... (7), and the DC offset component caused by the change in modulation degree is canceled out,
When the entire pickup is driven in the tracking direction by the tracking control circuit 14, the output of the differential means 23 shown in equation (7) is proportional to the relative angle between the pickup and the disk. The output is (D' + D"), which is ΔD (
=D-(D+ΔD)) is the residual offset. In other words, by correcting the difference signal between the outputs of the light-receiving elements 31 and 32 by ΔD, which corresponds to the residual offset, E, -E, = D'+D" (8), and the difference between the disc and the pickup. Only when a change occurs in the relative angle will a signal proportional to that angle be output.

Note that when the output of the light receiving element 31 (or 32) as shown in FIG. 4(a) is extracted through the high-pass filter 15 (or 19), the level between the upper and lower peaks is as shown in FIG. 4(b). corresponds to the modulation degree (α), so the level between these peaks may be detected.

FIG. 5 represents another embodiment of the invention. In this embodiment, the output of the differential means 13 is directly supplied to the tracking control circuit 14 to perform tracking control, and the output of the differential means 18 is output to the tilt control circuit 22 to adjust the tilt of the pickup with respect to the disk. is now being adjusted.

〔effect〕

As described above, the present invention provides an optical information recording/reproducing device that includes:
a light-receiving means divided in the left-right direction of the tracks of the disk, which receives reflected light of the light irradiated onto the disk for recording and reproducing information; and a low-pass filter that extracts a low-frequency component of the output signal of the light-receiving means. a first differential means for generating a tracking error signal from the output signal of the low-pass filter; a high-pass filter for extracting a high-frequency component of the output signal of the light-receiving means; a detection means for detecting the output signal of the high-pass filter; second differential means for generating a correction signal from the output signal of the disc and third differential means for subtracting the correction signal from the 1-racking error signal; Since the tilt component is corrected, it is possible to accurately record/reproduce information and control tracking using one beam.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the optical information recording and reproducing apparatus of the present invention, FIGS. 2 and 4 are waveform diagrams thereof, FIG. 3 is a characteristic diagram thereof, and 5- is a block diagram of another embodiment. FIG. 6 is a waveform diagram of a conventional optical information recording/reproducing device, and FIGS. 7 and 8 are a schematic side view and a plan view of its pickup. 1...Disc 2...Objective lens 3.31.3
2... Light receiving element 4... Optical axis 5... Principal light vA
6...Spot 11.12.17.21...Low pass filter 13.18.23...Differential means 14...Tracking control circuit 15.19...High pass filter 16.20...Detection Circuit 22...Tilt control circuit or higher

Claims (1)

[Claims] A light-receiving means divided in the horizontal direction of the tracks of the disk, which receives the reflected light of the light irradiated onto the disk for recording and reproducing information, and a low-pass filter that extracts the low-frequency component of the output signal of the light-receiving means. a first differential unit that generates a tracking error signal from the output signal of the low-pass filter; a high-pass filter that extracts a high-frequency component of the output signal of the light-receiving unit; and a detector that detects the output signal of the high-pass filter. an optical type, comprising: a second differential means for generating a correction signal from the output signal of the detection means; and a third differential means for subtracting the correction signal from the tracking error signal. Information recording and reproducing device.