JPS59140649A - Optical disk recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a fixed track space by dividing the laser light into three beams by means of a grating and setting the 0 order beam right above a reproduction track and the + or -1 order beams set by half on the reproduction track in a reproduction mode respectively through distribution of the grating. CONSTITUTION:The laser beam delivered from a semiconductor laser source 201 is divided into three beams, that is, 0 and + or -1 order diffracted beams through a grating 203. These beams are turned toward the track on a disk, and three beam spots are obtained in response to said three diffracted beams. A photodetector 280-2 detects the reflected light sent from the beam spot of the primary diffracted light. A switch 416 is closed at the time of recording, and the output of a constant current source 415 which is equal to the voltage value which increases when the beam comes half over a track is added to the output of a power supply voltage converting circuit 401. Then a tracking mirror 205 is moved in accordance with the difference between the above-mentioned added voltage and the voltage value (output of 402) related to the spot of the other primary diffracted light.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an optical disc recording and reproducing apparatus that continuously records discs at constant track intervals.

BACKGROUND OF THE INVENTION Conventionally, this type of apparatus has been known to have a configuration as shown in FIG. In FIG. 1, a laser beam emitted from a laser light source 101 is transmitted to a polarizing beam splitter 102.
The light is reflected by the beam, passes through a 174-wavelength plate 103, and is focused onto a disk 105 by an objective lens 104, where recording is performed. The light reflected from the disk 105 passes through the objective lens +0
The light passes through the 4 and 174 wavelength plates 103-t-, the polarizing beam splitter 102, the astigmatism optical system 112, and is irradiated onto the quadrant photodetector 107. In this way, the autofocus signal is collected and the lens drive device 105
The optical system described above, which performs autofocus by driving the recording head 108, is arranged on one substrate, and is collectively called a recording head 108.

A head drive mechanism 109 and a head drive motor 110 move the recording head 108 in the radial direction of the disk, and a motor control circuit 111 controls the motor 110 so that the recording head 108 moves at a constant speed. There is. Further, the disk 105 is rotated by a spindle motor 1OB, and this spindle motor 10B
is controlled by a spindle motor control circuit 107 to rotate at a constant angular velocity.

In this way, by feeding the recording head +08 at a constant speed and rotating the disk 105 at a constant speed, recording is performed with a constant track interval.

However, when recording at close track intervals, there is a limit to mechanical accuracy, so it is necessary to perform recording under control.

Purpose In view of the above-mentioned points, an object of the present invention is to provide an optical disc recording/reproducing device equipped with a control means configured to keep the track spacing constant when recording with dense track spacing on a disc without pregrooves. The aim is to provide the following.

In order to achieve such an object, the present invention uses a grating to split a laser beam into three beams and performs tracking in an optical disk recording and reproducing apparatus that uses a recording and reproducing optical head. Play the zero-order light divided by
The apparatus also includes means for rotating the grating so that half of the ±1st-order light is applied to each reproduced track, and half of the ±1st-order light is applied to the track that was recorded before grating.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 shows an optical system according to an embodiment of the present invention. In other words, this figure shows an optical system when the present invention is applied to a recording/reproducing head of a magneto-optical disk. The laser beam emitted from the semiconductor laser source 2ol has its plane of polarization adjusted by a polarizer 202, and further passes through a grating 203 to be split into three beams as θ-order and ±1st-order diffracted light. Thereafter, the light passes through the polarizing beam splitter 204, is directed toward the track on the disk by the tracking mirror 205, and is focused onto the disk 2+1 via the objective lens 208.

In this way, three beam spots of θ-order and ±1st-order diffracted light are obtained.

The laser beam reflected from the disk 2'll passes through the objective lens 206 and the tracking mirror 205, and
It is reflected by the polarizing beam splitter 204, passes through the astigmatism optical system 206, the polarized light of the signal component is separated by the analyzer 207, and reaches the photodetector 208.

From the photodetector 20, autofocus, autotracking, and Rf information signals are obtained.

In the optical system shown in Figure EPJ2, when reproducing data, three beam spots on the disk (the laser beam has a constant output that does not allow recording),
As shown in FIG. 3(A), it is arranged with respect to the track 301. Here, the optical spot 303 is a spot for reproducing recorded information. Also, light spot 30
4 and a light spot 305 are each placed only half on the track 301 in order to obtain a signal for tracking on the track 301.

In the optical system shown in FIG. 2, when recording data, the laser beam emitted from the laser source 201 has recordable energy and is modulated by information No. 46. The grating 203 is rotated by a small angle, as shown in FIG.
As shown in B), three beam spots are arranged.

Here, track 301 is a track recorded one round before the f disk, track 302 is a track currently being recorded, that is, spot 308 is a recording spot (spora), and 307 is a tracking spot. F signal! Track 30 recorded one lap ago to
1 by V1. The laser powers of these three spots are distributed such that the central spot 30B has an output that is sufficient to perform recording, and the other two spots 307 and 308 have an output that does not allow recording. For example, if the power is 4 mW or more, an information track will be formed on the medium surface, and if it is not 4 mW or more, the center spot 306 will be 6
-, spots 307 and 308 are distributed with power by grating 203 so that each has 2 mW. When forming a recording pattern on a disk, the laser is emitted at the above-mentioned output, and when no recording pattern is to be formed, the laser is emitted at half this output.

The grating 203 has a structure that allows it to rotate around the optical axis (not shown).
Stretch the member 20B from the spring 20B during playback.
On the other hand, during recording, the grating 203 is pulled by the electromagnet 210 and the grating 203 is slightly rotated. For example, track radius is 1 μs + t track pitch is 24 m.
, when the distance between the three beams is 504 m each, the angle between the line connecting the centers of the three beams and the track is α = 0.57° (see @3 (A)) during reproduction, and β = during recording. Thus, if the length of the member 208 is now 3011II11, it is sufficient to lower the end of the member by 0.8111 m.

FIG. 4 shows a block diagram of the tracking circuit according to this embodiment. The laser beam reflected from the beam spot 304 or 308 shown in FIG.
Reach 8-1. Also, the radome from the beam box 305 or 30B reaches the photodetector 208-2. The light %i current from photodetectors 208-1 and 208-2 is transferred to current-voltage conversion circuit 4 (ll).

402, it is converted into voltage. Then, during reproduction, this difference is calculated using a differential amplifier circuit 403, and the track deviation is obtained as a voltage value 404 (racking signal).

FIG. 5(A) shows a tracking signal 404 corresponding to FIG. 3(A), where the vertical axis represents the voltage and the horizontal axis represents the position of the central beam. Circuit 405. Switch 4o6° drive circuit 40
The tracking mirror 205 is driven through the mirror 7 to perform tracking.

The switch 406 is set to the A side during playback and to the B side during recording.
30 tracking spots? .

Of 308, only 307 is on the track, so this spot 30? Only the output signal 81B of the photodetector 208-1 that receives reflected light from the photodetector 208-1 is used. The output voltage of the current-voltage conversion circuit 402 is then compared with a constant voltage signal 408 by a differential amplifier 410.

Figure 5 (B) shows the differential amplifier 4 corresponding to Figure 3 CB).
10 output signals 411, here 5 constant voltage characteristics 40
When the reflected light when the spot 307 is only half on the track 301 reaches the photodetector 208-1 and is supplied to the differential amplifier 410 via the current-voltage conversion circuit 402 The output signal 411 of the differential amplifier 410 drives the tracking mirror 205 via the 1-phase compensation circuit 412, switch 40e, and drive circuit 407 to perform tracking.

Note that the means for rotating the grating 203 is not limited to a spring or an electromagnet, but may also be rotated by a motor, a piezoelectric element, or the like.

FIG. 6 shows another embodiment of the tracking circuit. first,
The reflected light from the beam spot 308 is detected by the photodetector 208-
Detected by 2. Then, when recording, turn the switch to 41.
6 is closed, and the output of the constant voltage fi 415, which is equal to the voltage value that increases when half of the beam is applied on the track, is added to the output of the voltage conversion circuit 401, and this is combined with the voltage value regarding the spot 307 ( According to this alternative embodiment, in which the tracking mirror 205 is moved in accordance with the difference between the output of the optical disc 402 and the output of the optical disc 402, it is possible to ignore large dirt on the disc, differences in reflectivity due to devices on the disc, and the like.

Effects As explained above, according to the present invention, when recording information on a disc without a pregroove, the track spacing can be maintained even if there is shaft wobbling due to motor precession or eccentricity due to disc removal. Since it is possible to record uniformly, signals that are sent intermittently can be recorded on the disk.
Accordingly, it is possible to obtain an optical disc recording and reproducing device that enables smooth recording as a single track.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of a conventionally known optical disc recording/reproducing device, Fig. 2 is a perspective view showing an optical system according to an embodiment of the present invention, and Figs. 3 (A) and CB). 4 is a block diagram showing the tracking circuit according to this embodiment, and FIGS.
A diagram explaining the operation of the tracking circuit shown in the figure, and FIG. 8 is a block diagram showing another embodiment of the tracking circuit. 101... Motor, 102... Polarizing beam splitter, 103... 174 wavelength plate, 104... Objective lens, 105... Disc, 108... Spindle motor, +07... Motor control circuit, 10B... Recording head, 10fl... Head drive mechanism, 110... Motor, Ill... Motor control circuit, 112... Astigmatism optical system, 201... Semiconductor laser light source, 202... - Polarizer, 203... Grating, 204... Polarizing beam splitter, 205... Tracking mirror, 206... Astigmatism optical system, 207... Analyzer, 208.208-1,208- 2...Photodetector, 2H
...Spring, 210...Electromagnet, 211...Disk, 301.302...Track. 303.304,305,308,307,308...
・Beam spot, 401.402... Current voltage conversion circuit, 403...
Differential amplifier circuit, 404... Tracking signal, 405... Phase compensation circuit, 40B... Switch, 407... Drive circuit, 408... Constant voltage signal, 410... Differential amplifier, 411 ...output signal, 412...phase compensation circuit, 415...constant voltage source, 416...switch. # Applicant Canon Co., Ltd. 1 10. +07

Claims (1)

[Claims] (1) In an optical disc recording and reproducing apparatus using an optical head for recording and reproducing, which divides a laser beam into three beams using a grating and performs tracking, the zero beam divided by the grating is used during reproduction. an optical means for arranging the grating so that the next light is applied to the true depth of the reproduction track, and half of the ±1st order light is applied to the reproduction track;
- means for rotating the grating so that one of the ±1st-order lights covers only half of the track recorded one round before. 2) ) iiJffi Detects the reflected light from the disk surface of a laser beam arranged so that it covers only half of the track movement of one lap before, and obtains a track deviation signal during recording by increasing or decreasing the detection output, thereby performing tracking. An optical disc recording and reproducing apparatus according to claim 1, characterized in that the optical disc recording and reproducing apparatus is configured as follows.