JPH0816984B2 - Optical recording / reproducing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus such as an optical disk, and more particularly to an optical recording / reproducing apparatus having an optical track tracking means utilizing diffracted light from a track.

[0002]

2. Description of the Related Art As a conventional technique, the depth of a track groove recorded on the surface of a recording medium is (2
n-1) λ / 4 (n = 1, 2, 3, ...) When the light beam deviates from the track, the track tracking is performed by utilizing the asymmetry of the diffracted light caused by the edge of the track groove. There is an apparatus for performing the above (for example, Japanese Patent Laid-Open No. 52-62)
037).

FIG. 1 is a diagram for explaining a track tracking device using diffracted light from a reflective optical disk. The light beam emitted from the light source 1 is condensed by the lens 2, passes through the prism 3, the galvanometer mirror 4, and the converging lens 5 and is focused as a spot of about 1 μm on the reflection type disk 6.

The optical depth of (2n-1) λ / 4 (n = 1, 2,
3 ,. ． ． ) Is provided, and when the light spot is located in the track, a diffracted light pattern including track information is generated in the reflected light.
This reflected light again passes through the converging lens 5 and the galvanometer mirror 4, the optical path is separated by the prism 3, and is guided to the photodetector 7 which is divided into two. The photodetector 7 is located far away from the conjugate point c of the converging lens 5 in order to detect the diffracted light component of the reflected light from the track 61 on the disk 6. The relationship between the photodetector 7 and the diffracted light component (shown by diagonal lines) at this time is shown in FIG. 2 (a) is a light beam tracks 6
1 is shown on the left side with respect to 1, and the diffracted light component becomes strong on the left side 7a of the photodetector 7. FIG. 2B shows the case of being located at the center, which is even on the left and right. FIG. 2C shows the case where the light beam is located on the right side of the track 61, and the diffracted light component becomes strong on the right side 7 b of the photodetector 7. In this way, the diffracted light component on the photodetector 7 changes depending on the positional relationship between the light beam and the track.
When the two outputs are differentiated by the differential amplifier 8 in FIG. 1, a deviation signal can be obtained for the track tracking in FIG. By guiding this signal to the servo circuit 9 and performing feedback control of the galvanometer mirror 4, the light beam is directed to the target track 6.
It can be located at the center of 1.

However, in the optical track tracking device having such a configuration, the photodetector 7 is located apart from the conjugate point c of the converging lens 5. Therefore, when the galvanometer mirror 4 is shaken for track tracking, the light beam on the surface of the photodetector 7 shakes correspondingly, and the track deviation is included in the track deviation signal, so that track tracking is normally performed. The problem of disappearing occurred.

Numerically converting this shake, when the positions of the respective constituent elements are set as shown in FIG. 1, the shake x of the light beam on the photodetector surface is expressed by the following equation.

X = (m × d × l × L) / (Tl + T ² ) where m: magnification of the converging lens 5 d: deflection of the light beam on the surface of the disk 6 l: between the converging lens 5 and the galvano mirror 4 L: Distance from conjugate point c of converging lens 5 to photodetector T: Distance from galvano mirror 4 to conjugate point c For example, m = 20, d = 0.2 mm, l = 30 mm, L =
When the contact amount is calculated based on this equation with 10 mm and T = 150 mm, the beam contact amount on the detector is about 20% of the light beam diameter, which is a non-negligible amount for the track deviation signal.

[0008]

SUMMARY OF THE INVENTION The present invention is an optical recording system capable of correcting a deviation signal caused by a deflection of a light beam on a photodetector surface during track tracking, thereby achieving more accurate track following. It is to provide a reproducing apparatus.

[0009]

Means for Solving the Problems The problems described above include a recording medium having a track, a light irradiating section for irradiating a light beam for recording / reproducing information on / from the recording medium, and an electric device which receives the reflection of the light beam. A photodetector for outputting a signal, a track deviation detecting means for obtaining a track tracking signal indicating a deviation of the light beam with respect to the track by the electric signal, and a first component including a relatively high frequency component from the track tracking signal.
And a second means for producing a second control signal containing a relatively low frequency component from the track tracking signal, and the light beam responsive to the first control signal Third means for suppressing the left and right of the track from swinging to a relatively high frequency, and third means for suppressing the light beam from swinging to the left and right of the track at a relatively low frequency in response to the second control signal. 4 means, and the first and second
And a fifth means for compensating the phase of the control signal of the above, wherein the third and fourth means cooperate to control the irradiation position of the light beam so that the light beam tracks the track. Be done.

[0010]

The normal tracking control circuit system is provided with another servo system capable of mainly correcting low frequency components, and phase compensation means is provided in these servo systems to correct the deviation signal due to the beam shake.

[0011]

FIG. 4 is a diagram showing the positional relationship between a photodetector for detecting a tracking control signal and a light spot. FIG. 5 shows what happens to the offset component of the tracking control signal TR when the light spot moves from the position indicated by the solid line to the position indicated by the dotted line in the direction causing the imbalance of the diffracted light. The relationship between the spot movement amount Δ and the tracking control signal offset differs depending on the spot distribution shape on the photodetector surface, but if the movement amount Δ is sufficiently smaller than the spot size, it is considered to be proportional. good. In addition, there is a proportional relationship between the driving signal of the actuator that moves the galvanometer mirror and the lens in the direction perpendicular to the optical axis and the movement amount of the spot. Therefore, the low-frequency component of the drive signal is separated by a low-pass filter, and another actuator is driven to cancel the offset.

An embodiment of the present invention will be described with reference to FIG. Looking at the frequency spectrum of the polarized mind that must be tracking control, a large component of a frequency equivalent to the rotational frequency of the disk (basic frequency component) is best. Therefore, in advance if it only this frequency component is followed by another actuator, higher order frequency components of the polarized heart can be reduced. Therefore, the above effects can be ignored.

Therefore, as shown in FIG. 6, for the low frequency component, the entire optical head 140 is moved by using an actuator having a poor frequency characteristic such as the linear motor 141. Here, the optical head 140 is connected to the linear motor 141 via the frame body 142, and moves on the rail 144 by the rotary roller 143.

An actuator 145 that moves in response to a higher-order frequency component moves the objective lens 5 in a direction (tracking direction) perpendicular to the optical axis. The light emitted from the light source 1 is collimated by the coupling lens 2 and collimated by the semi-transparent mirror 3 ′ to enter the objective lens 5.
A spot is formed on the disk 6. The reflected light again passes through the objective lens 5, the light detector 7a, 7 through the half mirror 3 '
incident on b.

FIG. 7 is a diagram showing an electric circuit system of the embodiment shown in FIG. The tracking control signal TR is transferred to the buffer amplifier 1
10, the signal is first input to the low-pass filter 118, and then input to the drive circuit 116 that drives the linear motor 141 via the appropriate phase compensation circuit 117, so that the eccentric low-frequency component is input to the optical head. Follow the whole.

Further, the output from the buffer amplifier 110 is extracted through a high-pass filter or a band-pass filter 111 to extract eccentric high-order frequency components, and the objective lens 5 is moved in a direction perpendicular to the optical axis via a phase compensation circuit 112. It is input to the drive circuit 113 that drives the actuator 145 that causes the light spot to follow the track.

FIG. 8 is a modification of the embodiment of FIG. The same elements have the same numbers. The integration circuit 119 detects the average value of the higher-order frequencies, and the integration circuit 1
The output of 19 is added by the adder 120 to the output from the phase compensation circuit 117, and the output is input to the drive circuit 116.
In this way, by superimposing the average value of high-order frequencies on the low-frequency components, it is possible to improve the tracking performance of the low-frequency components.

[0018]

According to the present invention, there is provided an optical recording / reproducing apparatus capable of correcting a deviation signal due to the deflection of a light beam on a photodetector surface during track tracking, thereby achieving more accurate track following. can do.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional device.

FIG. 2 is a conceptual diagram showing the relationship between diffracted light and a detector.

FIG. 3 is a graph of the output of the differential amplifier.

FIG. 4 is a conceptual diagram showing a relationship between a spot movement and a detector.

FIG. 5 is a graph showing the relationship between the amount of movement of the spot and the offset of the tracking signal.

FIG. 6 is a block diagram of an embodiment of the present invention.

FIG. 7 is a block diagram of an embodiment of the present invention.

FIG. 8 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

 110. . Buffer amplifier, 118. . Low pass filter, 117, 112. . Phase compensation circuit, 141. . . Linear motor, 113,116. . . Drive circuit, 111. . . High pass filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Sugiyama 5 Noguchi, Shirotori-cho, Toyokawa-shi, Aichi 9-share company Hitachi Co., Ltd. Yokohama Plant Toyokawa Plant (72) Inventor Motoo Uno 1 Higashi Koikeku, Kokubunji, Tokyo 280-chome, Hitachi, Ltd. Central Research Laboratory (72) Inventor, Seiji Yonezawa 1-280, Higashi Koigokubo, Kokubunji, Tokyo (72) Hitachi, Ltd. Central Research Laboratory (72) Inventor, Tadahiko Kameyama 2880, Kozu, Odawara-shi, Kanagawa Stock Company Company Hitachi Ltd. Odawara Plant (72) Inventor Tokuya Kaneda 2880 Kozu, Odawara City, Kanagawa Stock Company Hitachi Ltd. Odawara Plant (56) Reference JP-A-55-12594 (JP, A) JP-A-51-46018 (JP, A)

Claims (4)

[Claims] 1. A recording medium having a track, an optical head for irradiating a light beam for recording / reproducing information to / from the recording medium, and a first driving means comprising a linear motor for moving the optical head , Inside the optical head, second driving means for moving the optical axis of the light beam relative to the optical means forming the optical head; and the light beam returning from the recording medium for receiving the light beam from the recording medium. First control means for driving the first drive means based on the track tracking signal, and the first control means based on the track tracking signal. Second control means for driving the second drive means, wherein the first control means is a low range
A pass filter and a first phase compensation circuit,
The second control means is a high pass filter or band pass filter.
A filter and a second phase compensation circuit.
The light beam is controlled by the first and second control means.
The first and second drive means so as to follow the rack
An optical recording / reproducing apparatus characterized by controlling the . 2. The second driving means is provided in the optical head.
Claim to move the galvanometer mirror of the part
Item 1. The optical recording / reproducing apparatus according to item 1. 3. The second drive means is provided in the optical head.
The lens of a part is moved, The claim 1 characterized by the above-mentioned.
Optical recording and reproducing device. 4. The input of the output of the second phase compensation circuit
Integrating circuit, an output of the integrating circuit, and the first phase compensation
It has an adder that adds the output of the circuit,
The first driving means is controlled based on the above.
Optical recording according to any one of claims 1 to 3.
Playback device.