JPH07105058B2 - Optical information recording / reproducing device - Google Patents

Description

The present invention relates to an optical information recording / reproducing apparatus for recording / reproducing data on / from an optical disk, and particularly to optical information suitable for realizing high-speed data reproduction. The present invention relates to a recording / reproducing device.

[Conventional technology]

Hitherto, as one of the functions required of an optical information recording / reproducing apparatus optical disk apparatus used as a digital data recording / reproducing apparatus, high-speed data transfer has been mentioned. One of the methods to achieve this is to install multiple laser light generators and record / record with multiple light beams simultaneously.
There is a multi-beam system for reproduction. However, this system requires a plurality of optical systems, servo systems, and signal processing systems, and is not suitable for OA equipment and household equipment, which are required to be compact and inexpensive. Therefore, conventionally, in order to obtain a multi-beam more easily, a method of obtaining a plurality of light beams from one laser light generator by an optical method has been proposed. As an example of this type of apparatus, there is JP-A-58-125244.

[Problems to be solved by the invention]

By the way, the general method for recording on an optical disc is
This is performed by modulating the laser light generator with data to be recorded, and generating a light beam of strong and weak intensity according to the recorded data from the laser light generator. Therefore, when one light beam emitted from the one laser light generator is used after being split into a plurality of light beams, if the laser light generator is modulated with recording data, a plurality of light beams obtained can be obtained. The same data is simultaneously recorded on a plurality of tracks that are simultaneously modulated and irradiated, which is a practical problem. In addition, sufficient consideration has not been given to the tracking method for simultaneously scanning a plurality of tracks.

It is an object of the present invention to provide an optical information recording / reproducing apparatus which enables single-track recording and multi-track reproduction and can realize high-speed data reproduction.

[Means for solving problems]

The object is to split the light beam output from the first laser light generation device into a plurality of light beams, and convert the light beam output from the second laser light generation device into one of the plurality of light beams. This is achieved by combining and inputting to the tracking control circuit a servo signal corresponding to one light beam selected from reflected light or transmitted light of a plurality of light beams.

[Action]

During the recording operation, the second laser light generator is modulated by the recording data so that the output light beam has a recordable power, and the beam is reproducible by the first laser light generator. The power is combined into one of a plurality of light beams, and only one of the plurality of light beams reaches the recording power. As a result, recording is performed only on the track irradiated with the light beam having reached the recording power.

During the reproducing operation, the second laser light generator is stopped or brought into the low power output state, and all the plurality of light beams are set to the reproducing power. Therefore, by detecting reflected light or transmitted light of a plurality of light beams by a plurality of photodetectors and demodulating the outputs of these photodetectors, it is possible to reproduce the recorded data of a plurality of tracks at the same time.

Further, in tracking control, of the output signals of the plurality of photodetectors, the output signal (servo signal) of the photodetector that detects the tracking servo signal pre-recorded on the disk is input to the tracking control circuit. The signal generated by the tracking control circuit is used.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical information recording / reproducing apparatus (optical disk apparatus) of the present invention.

It should be noted that FIG. 1 shows blocks relating to the optical system and the servo system. Actually, an access system included in the optical disc device for moving the optical pickup to a desired track,
A signal processing system for generating sectors of recorded data and reproduced data, error correction, etc., and an interface system for connecting to a host computer are omitted. This is because it has nothing to do with the present invention.

In FIG. 1, 1 is a phase change type optical disk (hereinafter, simply referred to as an optical disk), 2 is a first laser light generator (hereinafter, referred to as a first laser diode), 3 is a diffraction grating,
Reference numeral 4 is a lens, and 5 is a second laser light generator (hereinafter referred to as the second laser light generator).
Laser diode), 6 is a prism, 7 is a beam splitter, 8 is a quarter-wave plate, 9 is a tracking mirror, 10 is an objective lens, 11 is a lens, and 12 is a photodetector group consisting of three photodetectors. , 13 (a) to 13 (c) are amplifiers, 14
(A) to 14 (c) are switches, 15 (a) to 15 (c) are demodulators, 16 is a modulator, 17 is a tracking control circuit, 18 is a focus control circuit, 19 is a clock reproduction circuit, and 20 is a motor. Is.

In this embodiment, the sampling servo system is adopted.

Here, the sampling servo system will be described with reference to FIG. In FIG. 5, 50 and 51 are tracking servo signals preformatted on the optical disc 1 (hereinafter referred to as servo marks), 52 is a spot of a light beam irradiated on the optical disc 1, 53 is a center line of a virtual track, and 54 is a center line. Playback signals 55 (a) and 55 (b) are tracking control circuits 17
The sample-and-hold signal 56 is supplied to the modulator 16 and is a servo area signal that divides the area in which the servo mark is preformatted and the area in which data is recorded and reproduced, and is supplied to the modulator 16.

The optical disk 1 according to the sampling servo system does not have the track groove pre-formatted, and the servo mark
50 and 51 are recorded so as to sandwich the center line 53 of the virtual track and offset from the center line of the track. Then, when the light beam 52 is tracing on the center line 53 of the virtual track, that is, when the tracking offset is 0, the reproduction signal 54 is the servo mark 50 as shown in FIG. Signals of the same level are obtained for 51 and 51. On the other hand, when the light beam 52 is offset upward with respect to the center line 53 of the virtual track as shown in FIG. 5 (b), the reproduction signal 54 is large with respect to the servo mark 50 and with respect to 51. Becomes smaller. On the contrary, when the light beam 52 is offset downward from the center line 53 of the virtual track as shown in FIG.
Small for 51 and large for 51. Therefore, in the sampling servo system, it is understood that the light beam 52 may be controlled (tracking control) so that the reproduction signals of both servo marks are at the same level.

Such tracking control is specifically performed by the circuit shown in FIG. 6 which constitutes the tracking control circuit 17. That is, a tracking error signal is obtained by detecting the difference between the outputs of the sample hold circuits 57 (a) and 57 (b) by the differential amplifier 58, and the tracking mirror 9 of FIG. 1 is driven by this tracking error signal. By. Sample hold circuits 57 (a) and 57 (b)
Is the sample hold signal 55 (a), 55 (b) of FIG.
And holds the reproduction signal of the servo mark 50 and the reproduction signal of the servo mark 51, respectively.

In FIG. 1, the optical disc 1 is rotated by a motor 20, and the light beam 52 is irradiated onto the optical disc 1 at this time, whereby the servo marks described above and the recording / reproduction of data described later are performed.

The light beam output from the first laser diode 2 is
It is divided into a plurality of light beams by the diffraction grating 3 and the lens 4. In this embodiment, 3 of 0th order diffracted light and ± 1st order diffracted light
The book is divided into light beams. The obtained three light beams are combined with the light beam output from the second laser diode 5 by the prism 6. However, this combination is adjusted so that it is performed only on one of the three light beams. In this embodiment, synthesis is performed only on the 0th-order diffracted light beam. The combined single light beam and the remaining light beams are input to the beam splitter 7. The beam splitter 7 is for separating reflected light described later. The light beam that has passed through the beam splitter 7 is converted into a circularly polarized wave by the quarter-wave plate 8, and then passes through the tracking mirror 9 and the objective lens 10 and is irradiated onto the optical disc 1 as three light beam spots. To be done.

The tracking control for accurately tracing the light beam on the track is performed by changing the angle of the tracking mirror 9 as described above. In the focus servo for focusing the light beam on the optical disc 1, the same reproduction signal as that supplied to the tracking control circuit 17 is supplied to the focus control circuit 18, and accordingly the focus control circuit 18 is supplied. This is performed by moving the objective lens 10 up and down according to a signal output from.

The reflected light of the light beam from the optical disk 1 is supplied to the beam splitter 8 via a path opposite to the above-mentioned incident light, that is, the objective lens 10, the tracking mirror 9, and the 1/4 wavelength plate 8. The reflected light supplied to the beam splitter 7 leaves the path of the incident light, passes through the lens 11, and is incident on the photodetector group 12. The photodetector group 12 is composed of three photodetectors corresponding to the three incident light beams, and each photodetector converts the intensity of the incident light into an electric signal and outputs it. The output of each photodetector is the amplifier 13 (a), 13
(B), 13 (c) amplified, demodulation circuit 15 (a), 15
It is demodulated in (b) and 15 (c), and then sent as reproduction data to a signal processing system (not shown).

The reproduced signals output from the amplifiers 13 (a), 13 (b), 13 (c) are sent to switches 14 (a), 14 (b), 14 (c) provided corresponding to these amplifiers. Is also supplied. In the present embodiment, only one of these switches is turned on and one selected reproduction signal among the three reproduction signals is used as a servo signal for the tracking control circuit 17, the focus control circuit 18, and the clock reproduction. Circuit 19
Supply to.

FIG. 2 is a diagram showing an example of the power (laser power) of the light beam with which the optical disc 1 is irradiated and the resulting change in the reflectance of the optical disc 1. In the figure, the reflectance of the optical disk 1 remains unchanged from the initial value until the light beam power reaches the level of point A. However, when the point A is exceeded, the reflectance rapidly changes, and when the light beam power is further increased, it becomes saturated. Once this reflectance change occurs, it will not return even if the light beam power is lowered. Therefore,
If the light beam power when the digital recording data is "1" is set to W and the light beam power when it is "0" is set to R,
It is possible to form a reflectance change on the optical disc 1 according to the recording data. Further, at the time of data reproduction, it is necessary to prevent the reflectance from changing with the reproduction light beam. For this reason, it is necessary to set the light beam power at the time of reproducing data to the point A or lower. However, if it is too low, the amount of light will be insufficient and reflected light cannot be detected. Therefore, an appropriate power of the reproducing light beam is required. In this embodiment, the same R as the light beam power when recording data “0” is used.
Is set to.

In FIG. 1, the first laser diode 2 is fixedly driven so that the output light beam power is at the R level on the optical disc 1. On the other hand, the second laser diode 5 is driven by a signal obtained by modulating recording data sent from a signal processing system (not shown) by the modulation circuit 16, and when the modulation signal is "1", the second laser diode 5 is driven. Diode 5
The power of the light beam that is combined with the output light of the optical disc 1
It is set to the level of W above. When the modulation signal is “0”, the light emission is stopped so that the power of the combined light beam is at the R level on the optical disc 1, or is almost at the R level on the optical disc 1. Is set to output low power.

As described above, the optical disc 1 has servo marks pre-formatted at regular intervals in the circumferential direction so as to conform to the sampling servo system. In the radial direction of the optical disc 1, servo marks are recorded every 3 tracks. That is, tracks without servo marks are formed on both sides of the track on which servo marks are recorded. The track pitch matches the pitch of the spots of the three light beams emitted onto the optical disc 1. Therefore, when data is recorded / reproduced on a track having no servo mark, tracking control is performed on an adjacent track having a servo mark.

FIG. 3 is a diagram showing a trace state of a light beam during data recording. In the figure, 52 (a), 52 (b), 52 (c)
Is the spot of the light beam, of which 52 (b) is the second
Is a combined light beam from the laser diode 5 of FIG.
(C) is a reproduction-only light beam. Assuming that the track (Tr) on which servo marks are recorded is (n) and the tracks without servo marks are (n-1) and (n + 1), respectively, (i) in FIG. 3 is recorded on track (n). If (ii) is recorded on track (n-1), (ii)
i) shows the case of recording on track (n + 1).

In (i) of FIG. 3, since the track for tracking and the track for recording data coincide with each other, the switch 14 (b) of FIG.
The reflected light detection signal of the servo area portion in (b) is used as a servo signal. Since data cannot be recorded in the servo area, the power of the light beam 52 (b) is set to the reproducing state. In (ii),
The light beam 52 (b) for recording on the (n-1) track
Will trace (n-1) tracks, and track (n) will be traced by the light beam 52 (c). Therefore, the switch 14 (c) is turned on and the light beam 52
The reflected light detection signal of (c) is used as a servo signal. Similarly in (iii), since the light beam 52 (b) traces the track (n + 1) to record data, the light beam 52 (a) traces the track (n). Therefore, the switch 14 (a) is turned on, and the reflected light detection signal of the light beam 52 (a) is used as a servo signal.

At the time of data reproduction, as shown in Fig. 4, the light beam
52 (a) is track (n-1), 52 (b) is (n), 52
(C) traces (n + 1). Therefore, during reproduction, the switch 14 (b) is turned on, and the reflected light detection signal of the light beam 52 (b) is used as a servo signal. During data reproduction, all the three light beams are in the reproduction state, so that the data recorded on the three tracks are reproduced at the same time.

In this embodiment, the reference clock for recording / reproducing uses the clock reproduced by the clock reproducing circuit 19 based on the servo signal detected from the track (n). Therefore, in this embodiment, data is recorded in the same phase on each of the three tracks,
In reproduction, three signals can be processed simultaneously with a single clock timing.

As described above, according to this embodiment, tracking,
By providing only one servo system for focus, clock reproduction, etc., three tracks can be reproduced at the same time, so that high-speed data reproduction can be realized while satisfying the demand for downsizing and cost reduction of the device. In the present embodiment, two laser diodes are required, but one of these laser diodes is sufficient for the low power specification capable of outputting the power required for reproduction, and therefore does not cause a cost increase.

It should be noted that the present invention is not limited to the optical disc recording method, servo method, number of light beams, and data reproducing method described in the above embodiments, and it will be apparent that the present invention can be applied to other methods.

〔The invention's effect〕

According to the present invention, the data recorded on a plurality of tracks can be simultaneously reproduced by using one servo system, so that there is an effect that high-speed data reproduction can be realized. Further, even if the optical system is set to trace a plurality of tracks at the same time, it is possible to record on a single track.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the relationship between light beam power and reflectance.
FIG. 3 is a diagram showing a light beam tracing state during recording, FIG. 4 is a diagram showing a light beam tracing state during reproducing, and FIG.
The figure is a figure for explaining the sampling servo system, the sixth
The figure is a block diagram showing an example of the tracking control circuit of FIG. 1 ... Optical disc, 2 ... First laser diode, 3
...... Diffraction grating, 5 ... Second laser diode, 6 ...
Prism, 7 ... Beam splitter, 8 ... Quarter wave plate, 9 ... Tracking mirror, 10 ... Objective lens, 12
...... Photodetector group, 13 (a) to 13 (c) …… Amplifier, 14
(A) ~ 14 (c) ... switch, 15 (a) ~ 15 (c) ...
Demodulator, 16 Modulator, 17 Tracking control circuit, 18 Focus control circuit, 19 Clock recovery circuit.

Claims (3)

[Claims] 1. An optical information recording / reproducing apparatus for recording / reproducing by using a disk-shaped recording medium having concentric or spiral tracks, and irradiating a light beam along the track of the medium. A first light flux generating means for generating a plurality of light fluxes for recording, a second light flux generating means for generating a single light flux for recording, and a plurality of light fluxes for reproducing the medium, and Light flux control means for superposing a recording light flux on one of the plurality of reproduction light fluxes, modulation means for modulating the recording light flux, and a plurality of reflected light or transmitted light by the plurality of reproduction light fluxes. A plurality of photodetection means for detecting the output, a plurality of demodulation means for demodulating the outputs of the plurality of reproduction light detection means, and an output of one photodetection means from the outputs of the plurality of photodetection means Selecting means for inputting to the light flux controlling means The light flux controlling means simultaneously controls the plurality of reproducing light fluxes and the recording light flux, and the selecting means switches the light flux to be selected each time recording of one track is completed. Information recording / reproducing apparatus. 2. A plurality of reproduction light fluxes are arranged in a radial direction of the medium, and the recording light fluxes are superposed on a central light flux of the reproduction light fluxes. The optical information recording / reproducing apparatus according to claim 1. 3. An optical information recording / reproducing apparatus according to claim 1, wherein the medium has a servo signal recorded on each track in a radial direction of the recording medium at intervals of the number of light beams for reproduction. .