JPH01294226A - Servo method for multibeam optical pickup - Google Patents

Abstract

PURPOSE:To improve the reliability of recording and reproducing on an optical disk by applying focusing and tracking to a recording beam at the time of the recording mode and applying focusing and tracking to a reproducing beam at the time of the reproducing mode. CONSTITUTION:A recording beam A and a reproducing beam B reflected on an optical disk 50 are led to individual detecting systems to detect a focus servo signal and a track servo signal with respect to each beam, and focusing and tracking are performed based on the focus servo signal and the track servo signal obtained from the recording beam A at the time of the recording mode, and focusing and tracking are performed based on the focus servo signal and the track servo signal obtained from the reproducing beam B at the time of the reproducing mode. Thus, a fresh servo method is obtained where optical information is recorded and reproduced with a very high reliability with respect to the multibeam optical pickup.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a servo method in a multi-beam optical pickup.

(Prior art) An illumination optical path is configured so that a plurality of beams from a semiconductor laser array can be guided to an optical disk through a common optical path, one of the plurality of beams is for recording and the other is for reproduction. A multi-beam optical pickup has been put into practical use that uses a recording beam to write recorded information in recording mode, performs confirmation playback using a reproducing beam, and reproduces recorded information using a reproducing beam in playback mode. intended.

Recording on an optical disc is done in two modes: recording and confirmation playback, so with the conventional single-beam method, it takes a long time to record, but with a multi-beam optical pickup, writing and confirmation playback are performed almost simultaneously. , this recording time problem can be effectively solved.

Part 3'@ schematically shows only the essential parts of an example of a conventional multi-beam optical pickup.

This example is a two-beam type multi-beam optical pickup.

The semiconductor laser array 10 has two light emitting parts.

Each light emitting part can emit a beam independently. Now, when beams A and B are emitted from each light emitting part,
Each of the beams A and B is collimated by the collimating lens 12, reflected upward in FIG. 3 by the beam splitter 14, and then transmitted through the objective lens 16. The light is focused as spots SA and SB. The collimating lens 12, the beam splitter 14, and the objective lens 16 are a common optical path that guides the optical disks 50 heavy beams A and B from the semiconductor laser 10, which is a light source, and constitute an illumination optical path.

The optical disc 50 moves in the direction of the arrow by rotation.

Therefore, in the movement relative to the optical disk 50, beam A is a leading beam and is used for recording.

That is, beam A is a recording beam. On the other hand, beam B
is a trailing beam and is used for confirmation reproduction in the recording mode, and used for reproducing recorded information in the reproduction mode. That is, beam B is a reproduction beam.

When the recording beam A and the reproducing beam B are reflected by the optical disk 50, they pass through the objective lens 16 and the beam splitter.
14 and separated from the illumination optical path.

The light is condensed by a condenser lens 18, respectively. An aperture 20 is provided near the light condensing section.

This aperture 20 blocks the recording beam A.

The reproducing beam B is passed through. When the reproduction beam B passes through the aperture 20, it is condensed again by another condensing lens 22, and a part of it enters the prism mirror 24,
A part of the light is incident on the two-divided light receiving element 28. prism 24
The light incident on the light receiving element 26 is reflected and enters the two-split light receiving element 26.

The focus servo signal is transmitted to the light receiving element 2 by the knife method in which the edge of the prism mirror 24 is used as a knife edge.
The track servo signal is obtained as the difference between the signals from each light receiving section of the light receiving element 26, and since the reflection intensity of the track servo signal by the push-pull method corresponds to the sum of the outputs of the respective light receiving sections of the light receiving element 26, for example, this can be converted into an RF multiplied signal. I can do it.

In recording mode, the focus servo signal is obtained by continuously lighting the reproduction beam B at a constant intensity.

While focusing jig and tracking are performed based on the track servo signal, the recording beam A is intensity-modulated with the recording information signal to perform writing, and the written recording information is immediately confirmed and reproduced using the reproduction beam B. In addition, in the reproduction mode, only the reproduction beam B is continuously lit at a constant intensity, and the sum of outputs of each light receiving part of the light receiving element 26 is multiplied by RF while performing focusing jig and tracking based on the obtained focus servo signal and track servo signal. The recorded information is played back.

Such multi-beam optical pickups have the following problems.

That is, since each servo signal is obtained from the reproduction beam during the recording mode, there will be no deviation in the reproduction beam, but there is a possibility that deviation will occur in the recording beam, which will reduce the reliability of the written bits. . In recording mode, confirmation playback is performed, so as long as confirmation playback is performed correctly, it can be considered that recording was performed properly.However, if playback is performed using a different optical pickup However, there is a possibility that reproduction of recorded information may be hindered due to deviation of the recording beam.

(Purpose) The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a novel method that allows extremely reliable recording and reproduction of optical information in a multi-beam optical pickup. Provides servo method.

(Structure) In the following description of the present invention, two types of servo methods are proposed. In all of these, the illumination optical path is configured so that multiple beams from the semiconductor laser array can be guided to the optical disk through a common optical path, one of the multiple beams is for recording and the other is for reproduction. In a multi-beam optical pickup, in the recording mode, the recording beam writes recorded information, while the reproducing beam performs confirmation reproduction, and in the reproducing mode, the reproducing beam reproduces the recorded information. This method performs focusing and tracking in recording mode and playback mode.

In the method of claim 1, the recording beam and the reproducing beam reflected by the optical disk are guided to separate detection systems so that a focus servo signal and a track servo signal can be detected for each beam, and in the recording mode, Focusing and tracking are performed based on the focus servo signal and track servo signal obtained from the recording beam, and in playback mode, based on the focus servo signal and track servo signal obtained from the playback beam.
Performs focusing and tracking.

In the method of claim 2, the recording beam and the reproducing beam reflected by the optical disk are guided to separate detection systems, and one beam generates a focus servo signal and a track servo signal, and the other beam generates a track servo signal. In the recording mode, tracking is performed based on the track servo signal obtained from the Koto-Otoshino beam, and focusing is performed based on the focus servo signal, and in the playback mode, while focusing is performed based on the focus servo signal, Tracking is performed based on a track servo signal obtained from the reproduction beam.

(Example) A specific example will be described below with reference to one drawing.

FIG. 1 schematically shows only the essential parts of an embodiment of the invention according to claim 1. In order to avoid complication, the same reference numerals as in FIG. 3 are used for parts that are unlikely to cause confusion.

This embodiment is also a two-beam type multi-beam optical pickup, in which a semiconductor laser array 10 is connected to an optical disk 5.
The illumination optical path leading to zero is the same as the pickup of FIG. Light beam A is a recording beam, and light beam B is a reproduction beam.

Recording beam A reflected by optical disk 50.

The reproduction beam B is transmitted through the objective lens 16 and the beam splitter.
14, is separated from the illumination optical path, and is connected to the condenser lens 1.
The light is focused by 8. The focused recording beam A is further focused by a focusing lens 22, and the - portion is reflected by a prism mirror 24 and enters a light receiving element 26 for generating a track servo signal, and the remaining beam is used for generating a focus servo signal. The light is incident on the light receiving element 28.

On the other hand, the reproducing beam B focused by the condenser lens 18 is reflected by the prism mirror 19 disposed near the condensing part and further condensed by the condenser lens 23, and a part of the beam is reflected by the prism mirror 25. The reflected light enters a light receiving element 27 for generating a track servo signal, and the rest enters a light receiving element 29 for generating a focus servo signal. For both the recording beam A and the reproducing beam B, the focus servo signal is obtained by the Knifezi method, and the track servo signal is obtained by the push-pull method. In this way, in the multi-beam optical pickup shown in FIG. 1, the focus servo signal,
A track servo signal is obtained.

In the recording mode, focusing and tracking are controlled based on the focus servo signal and track servo signal obtained from the recording beam A, while writing is performed by intensity modulating the recording beam with the recording information signal, and the reproduction beam B Continuously light up at a constant intensity and perform confirmation playback.

At this time, since focusing and tracking are performed based on the focus servo signal and track servo signal obtained by the recording beam A, there is no deviation from the recording beam A, so writing is performed accurately and appropriately. It will be done.

On the other hand, regarding the reproduction beam B used for confirmation reproduction, there is a possibility that a slight deviation may occur, but the allowable range of deviation for reproduction is gentler than that for recording. Since the confirmation reproduction is performed accurately, the confirmation reproduction can be performed satisfactorily even if a slight deviation occurs in the reproduction beam B.

In addition, in the reproduction mode, only the reproduction beam B is lit continuously at a constant intensity, and each light receiving part of the light receiving element 27 performs focusing and tracking based on the focus servo signal and track servo signal obtained by the beam B. The sum of the outputs is converted into an RF signal and reproduced.

In this reproduction mode, focusing and tracking are performed using the servo signal obtained by the reproduction beam B, so there is no deviation in the reproduction beam B, and the recorded bits are recorded accurately and reliably by the recording beam A. Since it is highly reliable and can be read out accurately with the reproduction beam B, an extremely good reproduced image can be obtained.

FIG. 2 schematically shows only the essential parts of an embodiment of the invention according to claim 2.

In this figure as well, the same reference numerals as in FIGS. 1 and 3 are used for parts that can be easily confused.

. The recording beam A and the reproducing beam B from the semiconductor laser array 10 are guided to the optical disc 50 by a common illumination optical path, and each of these beams is reflected by the optical disc and separated from the illumination optical path before passing through the condenser lens 18. Also, the recording beam A that is focused is focused by the focusing lens 22, the prism mirror 24, the light receiving element 26 .
28 is the same as the embodiment shown in FIG.

The difference from the embodiment shown in FIG. 1 is that the reproduction beam B focused by the condenser lens 18 directly enters the light receiving element 21 for detecting the track servo signal.

That is, in this embodiment, the track servo signal is detected for both the recording beam A and the reproducing beam B, but the focus servo signal is detected only for the recording beam A. Detection of the focus servo signal is performed by the Knifezi method, and detection of the track servo signal is performed by the push-pull method.

In the recording mode, the recording beam A performs focusing and tracking based on the focus servo signal and track servo signal obtained by the recording beam A.
Modulates and writes.

At this time, the reproduction beam B is lit continuously at a constant intensity,
The sum of the outputs of the respective light receiving sections of the light receiving element 21 is converted into an RF multiplied signal and reproduced for confirmation.

In playback mode, both recording beam A and playback beam B are lit continuously at a constant intensity, focusing is performed using a focus servo signal obtained from recording beam A, and tracking is performed based on a track servo signal obtained from playback beam B. .

Therefore, in this embodiment as well, as in the embodiment shown in FIG. 1, good writing and confirmation reproduction are possible, and the reliability of the recorded pits is high.

In addition, the reproduction beam B does not cause track deviation in the reproduction mode, and since the beams A and B emitted from each light emitting part of the semiconductor laser array have the same wavelength, they are focused by the same objective lens 16. In this case, each beam is focused at the same position in the optical axis direction, so when the recording beam A is focused on the optical disk 50, the reproducing beam B is also focused on the optical disk 50. The light is focused on. Therefore, even if focusing is performed using the focus servo signal obtained from the recording beam A in the reproduction mode, the reproduction beam B can be correctly focused on the optical disk 50, and therefore the tracking and focusing for the reproduction beam B can be performed appropriately. Therefore, recorded information properly recorded with a recording beam can be reproduced satisfactorily.

In the embodiment shown in FIG. 2, the focus servo signal is obtained from the recording beam A, but the focus servo signal is obtained from the reproduction beam B, and in the recording mode, the focusing for the recording beam is controlled by the focus obtained from the reproduction beam. In any case, in the method of claim 2, the recording beam and the reproduction beam are turned on both in the recording mode and in the reproduction mode, and in the reproduction mode, each beam A, Both lights B need to be lit continuously at a constant intensity. However, since the focus servo signal is detected for only one beam, the detection system is simpler than that of the first aspect of the invention.

(Effects) As described above, according to the present invention, a novel servo method in a multi-beam optical pickup can be provided.

In both the inventions of claims 1 and 2, focusing and tracking are performed on the recording beam in the recording mode, and focusing and tracking are performed on the reproduction beam in the reproduction mode.
Since tracking is performed, proper optical information recording and reproduction can be performed.

Therefore, the reliability of recording and reproduction on the optical disc is greatly improved. Note that the detection of servo signals for each beam is not limited to the method disclosed in the embodiment, and any known method can be used as appropriate.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically illustrating only the essential parts of an embodiment of the invention of claim 1, Fig. 2 is a diagram schematically illustrating only the essential parts of an embodiment of the invention of claim 2, and Fig. 3 is a diagram illustrating the prior art and its related art. FIG. 3 is a diagram for explaining a problem. 10., semiconductor laser array, 50. , , optical disc.

Claims (1)

[Claims] 1. The illumination optical path is configured so that a plurality of beams from the semiconductor laser array can be guided to the optical disk through a common optical path, and one of the plurality of beams is for recording and the other is for recording. In a multi-beam optical pickup, one is for reproduction, and in the recording mode, the recording beam is used to write recorded information, while the reproduction beam is used for confirmation reproduction, and in the reproduction mode, the reproduction beam is used to reproduce recorded information. There,
The recording beam and the reproduction beam reflected by the optical disk are guided to separate detection systems so that a focus servo signal and a track servo signal can be detected for each beam. A servo method characterized by performing focusing and tracking based on a focus servo signal and a track servo signal obtained from a reproduction beam, and performing focusing and tracking based on a focus servo signal and a track servo signal obtained from a reproduction beam in a reproduction mode. . 2. The illumination optical path is configured so that a plurality of beams from the semiconductor laser array can be guided to the optical disk through a common optical path, one of the plurality of beams is for recording and the other is for reproduction, In a multi-beam optical pickup, in the recording mode, the recording beam is used to write recorded information, while the reproduction beam is used to perform confirmation reproduction, and in the reproduction mode, the reproduction beam is used to reproduce the recorded information.
The recording beam and the reproduction beam reflected by the optical disk are guided to separate detection systems, and a focus servo signal and a track servo signal are obtained from one beam, and a track servo signal is obtained from the other beam, and the recording mode is set. Sometimes, tracking is performed based on a track servo signal obtained from the recording beam, and focusing is performed based on the focus servo signal.
A servo method characterized in that, in a reproduction mode, focusing is performed based on the focus servo signal and tracking is performed based on a track servo signal obtained from a reproduction beam.