JPH06325381A - Optical disk recorder and optical disk reproducing device - Google Patents

Abstract

PURPOSE:To always and accurately record and reproduce data even on any track of an optical disk recording medium, in a magneto-optical disk recording and reproducing device. CONSTITUTION:A light spot (d) outgoing from a semiconductor laser 10 is scanned in a direction along the track by a polygon mirror 13. At a recording time, the polygon mirror 13 is rotated synchronizing with the recording data (a), and further, the frequency of a recording clock (1) controlling timing for generating the recording data (a) is switched according to linear velocities in respective tracks. Thus, the light spot (d) is allowed to follow up the linear velocities of the optical disk recording medium 23. At a reproducing time, the polygon mirror 13 is rotated synchronizing with a reproducing clock (k), and the frequency of the reproducing clock (k) is switched according to the linear velocities in respective tracks. Thus, the light spot (d) is allowed to follow up a recording mark.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording apparatus and an optical disk reproducing apparatus, and more specifically, it irradiates a rotating optical disk recording medium with a light spot and raises the temperature of the irradiated portion to form a recording mark. The present invention relates to an optical disk recording apparatus for forming and an optical disk reproducing apparatus for irradiating a rotating optical disk recording medium on which recording marks are formed with a light spot and generating reproduction data based on reflected light or transmitted light from the irradiated portion.

[0002]

2. Description of the Related Art Generally, a magneto-optical disk recording apparatus uses an optical disk recording medium magnetized in one direction, and a weak magnetic field in the opposite direction is first applied to a portion to be recorded. Then, the portion is irradiated with laser light to raise the temperature of the portion. As a result, the magnetization direction is reversed only in that portion, and the data is recorded.

On the other hand, in a magneto-optical disc reproducing apparatus, first, a linearly polarized laser beam is applied to an optical disc recording medium. Since the plane of polarization of the reflected light from the irradiated portion is rotated by the Kerr effect, the data is reproduced by detecting the difference in the rotation angle.

[Prior Art 1] A conventional optical recording apparatus is disclosed in, for example, Japanese Patent Laid-Open No. 58-182134.
In this conventional example, data is recorded by irradiating a rotating optical disc recording medium with a light spot a number of times corresponding to the length of recording data and forming a recording mark having a length proportional to the number of times.

However, as shown in FIG. 17, since the optical disc recording medium moves at a certain linear velocity in the x direction with respect to the light spot d, the shape of the recording mark m is not a perfect circle but a teardrop shape. There was a problem of becoming. Recording mark m
Are recorded in the order of the head of the recording mark m shown in FIG. 17A, the center of the recording mark shown in FIG. 17B, and the tail of the recording mark m shown in FIG. 17C. Therefore, the heat accumulation increases as the process proceeds to (a), (b), and (c), and the heat accumulation more or less remains at the tail of the recording mark m. For this reason, the temperature distribution Ta has a shape that spreads before and after the recording mark m as shown in FIG. 17D, and moreover, the head and the tail are likely to be asymmetric. As a result, only the portion where the temperature distribution Ta exceeds the threshold value Tsh becomes the recording mark m, and its shape becomes a teardrop shape. As described above, in the optical disc recording apparatus in which the recording medium moves at the linear velocity proportional to the data transfer rate, the temperature distribution T
It was very difficult to adjust a and it was difficult to form a uniform recording mark.

[Prior Art 2] On the other hand, a conventional optical disk reproducing apparatus is disclosed in, for example, Japanese Patent Publication No. Sho 63-56612. In this conventional example, in order to absorb the uneven rotation of the optical disk recording medium, the galvano mirror is driven to scan the optical spot in the direction along the track,
As a result, the relative speed between the light spot and the recording mark is kept constant.

However, as in the case of the recording apparatus, the optical disk reproducing apparatus also moves the recording medium at a certain linear velocity with respect to the light spot g, as shown in FIG. Becomes dull, S / N (signal to noise ratio)
There was a problem that it decreased. That is, since the light spot d continuously moves in the order of the head of the recording mark m shown in FIG. 19A, the center shown in FIG. 19B, and the tail shown in FIG. Read signal g gradually changes to (a), (b) and (c), and its waveform becomes dull. As described above, in the optical disc reproducing apparatus including the optical disc recording medium that rotates at the linear velocity proportional to the data transfer rate, there is a problem that the reliability of the reproduced data is lowered.

Further, as shown in FIG. 18 (d), even if the temperature distribution is made symmetrical so that a record mark having a uniform shape can be formed, the head mark and the tail end of the record mark m are recorded at the time of recording the record mark. Since the temperature of the portion is lower than that of the central portion and the threshold value required for reversing the magnetization is barely reached, the reversal of the magnetization is not clear and the contour of the recording mark m becomes irregular. Since this portion is a region having a low S / N ratio, there is a problem that the rising portion and the falling portion of the read signal g corresponding to this portion have a low S / N ratio and the reliability of reproduced data is lowered. It was

[Prior Art 3] In order to solve these problems, an optical disc recording / reproducing is performed in which the optical spot is vibrated in the direction along the track to reduce the relative speed between the optical spot and the recording medium to perform recording and reproduction. The device is disclosed in Japanese Patent Application Laid-Open No. 2-26333.

According to this recording / reproducing apparatus, when the optical disk recording medium rotates at a constant linear velocity or in the case of an optical card having parallel tracks, it is possible to form recording marks having a uniform shape and to reproduce accurate reproduced data. Obtainable.

[0011]

However, when the optical disk recording medium rotates at a constant angular velocity, any measure can be taken although the linear velocity of the recording medium greatly varies depending on the position of the track on which recording or reproducing is performed. It was not given.

Further, in this recording / reproducing apparatus, since the light spot is oscillated in the direction along the track, the light spot makes a reciprocating motion, and even if it follows the recording mark in the forward path, it does not follow in the backward path. For this reason, the same time as the forward scan time is required for the backward scan, making high-speed scanning difficult. Furthermore, it is difficult to always perform scanning at a constant speed because it is necessary to reduce the scanning speed once to zero and then accelerate in the opposite direction at the moment of switching from the forward path to the backward path or from the backward path to the forward path.

Although the recording operation has been described here, the reproducing operation also has the same problem, and detailed description thereof will be omitted.

The present invention has been made to solve such a problem, and its main object is to provide an apparatus capable of always performing accurate recording or reproducing regardless of the position of a track.

[0015]

The present invention is an optical disk recording apparatus for forming a recording mark by irradiating a rotating optical disk recording medium with a light spot, the light spot irradiating means, the light spot scanning means, and the scanning means. Speed switching means. The light spot irradiation means irradiates the optical disk recording medium with the light spot. The light spot scanning means is
The light spot emitted by the light spot irradiating means is repeatedly scanned within a certain range in the direction along the track of the optical disc recording medium so that the recording mark has a predetermined shape. The scanning speed switching means switches the speed at which the light spot scanning means scans the light spot according to the linear speed of the portion of the optical disk recording medium where the light spot irradiation means irradiates the light spot.

Further, according to the present invention, a rotating optical disk recording medium having recording marks formed thereon is irradiated with a light spot,
An optical disk reproducing device for generating reproduction data based on reflected light or transmitted light from the irradiated portion,
It includes a light spot irradiation means, a light spot scanning means, and a scanning speed switching means. The light spot irradiation means irradiates the optical disk recording medium with the light spot. The light spot scanning means matches the light spot emitted by the light spot irradiating means with the recording mark, and repeatedly scans in a direction along the track of the optical disc recording medium within a certain range. The scanning speed switching means switches the speed at which the light spot scanning means scans the light spot according to the linear speed of the portion of the optical disk recording medium where the light spot irradiation means irradiates the light spot.

On the other hand, the present invention is an optical disk recording apparatus for forming a recording mark by irradiating a rotating optical disk recording medium with a light spot, which comprises a light spot irradiation means, a light spot scanning means, and a scanning speed control means. including. The light spot irradiation means irradiates the optical disk recording medium with the light spot. The light spot scanning means repeatedly scans the light spot irradiated by the light spot irradiating means within a certain range in the direction along the track of the optical disc recording medium so that the recording mark has a predetermined shape. The scanning speed control means matches the speed at which the light spot is scanned by the light spot scanning means with the average linear speed from the innermost peripheral portion to the outermost peripheral portion of the recording area of the optical disc recording medium.

Further, according to the present invention, a light spot is irradiated onto a rotating optical disk recording medium on which recording marks are formed,
An optical disk reproducing device for generating reproduction data based on reflected light or transmitted light from the irradiated portion,
It includes a light spot irradiation means, a light spot scanning means, and a scanning speed control means. The light spot irradiation means irradiates the optical disk recording medium with the light spot. The light spot scanning means matches the light spot emitted by the light spot irradiating means with the recording mark, and repeatedly scans in a direction along the track of the optical disc recording medium within a certain range. The scanning speed control means matches the speed at which the light spot is scanned by the light spot scanning means with the average linear speed from the innermost peripheral portion to the outermost peripheral portion of the recording area of the optical disc recording medium.

On the other hand, the present invention is an optical disc recording apparatus for forming a recording mark by irradiating a rotating optical disc recording medium with a light spot, and a recording area in the optical disc recording medium is a plurality of concentric circles composed of a plurality of tracks. The optical disc recording apparatus includes a light spot irradiation unit, a light spot scanning unit, and a scanning speed switching unit. The light spot irradiation means irradiates the optical disk recording medium with the light spot. The light spot scanning means repeatedly scans the light spot irradiated by the light spot irradiating means within a certain range in the direction along the track of the optical disc recording medium so that the recording mark has a predetermined shape. The scanning speed switching means, according to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the zone where the light spot is irradiated by the light spot irradiating means,
The speed at which the light spot is scanned by the light spot scanning means is switched.

Further, according to the present invention, a rotating optical disk recording medium having recording marks formed thereon is irradiated with a light spot,
An optical disk reproducing device for generating reproduction data based on reflected light or transmitted light from the irradiated portion,
The recording area in the optical disc recording medium includes a plurality of zones formed of a plurality of tracks, and the optical disc reproducing apparatus includes a light spot irradiating means, a light spot scanning means,
And scanning speed switching means. The light spot irradiation means irradiates the optical disk recording medium with the light spot. The light spot scanning means matches the light spot emitted by the light spot irradiating means with the recording mark, and repeatedly scans in a direction along the track of the optical disc recording medium within a certain range. The scanning speed switching means scans the light spot by the light spot scanning means according to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the zone where the light spot is irradiated by the light spot irradiating means. To change the speed.

[0021]

According to the optical disk recording apparatus according to the present invention, the scanning speed of the optical spot is switched according to the linear speed of the portion where the optical spot is irradiated, so that it can be applied to any track of the optical disk recording medium. The light spot is scanned following the linear velocity. Therefore, the relative speed between the light spot and the recording medium is reduced in any track, and the temperature distribution at the head and tail of the recording mark becomes uniform. Therefore, it is possible to form recording marks having a uniform shape from the innermost peripheral portion to the outermost peripheral portion of the optical disc recording medium,
The reliability of the reproduction data can also be improved.

Further, according to the optical disk reproducing apparatus according to the present invention, since the scanning speed of the light spot is switched according to the linear speed of the portion where the light spot is irradiated, any track of the optical disk recording medium is selected. Also in, the light spot is scanned following the linear velocity.
Therefore, the relative speed between the light spot and the recording medium is reduced on any track of the optical disc recording medium. Therefore, it is possible to read only the center of the optical disc without reading the head or tail of the recording mark from the innermost portion to the outermost portion. Therefore, the read signal of the recording mark becomes large and the waveform becomes steep, so that the S / N ratio can be improved.

On the other hand, according to another optical disk recording apparatus according to the present invention, the scanning speed of the light spot is made to coincide with the average linear speed from the innermost peripheral portion to the outermost peripheral portion of the recording area on the optical disc recording medium. Therefore, the relative speed between the light spot and the recording medium is reduced on average from the outermost peripheral portion to the innermost peripheral portion. Therefore, the temperature distribution at the head and tail of the recording marks can be made uniform on any track of the optical disk recording medium. Therefore, it is possible to form a recording mark having a substantially uniform shape from the outermost peripheral portion to the innermost peripheral portion of the optical disc recording medium, and it is possible to improve the reliability of reproduced data.

Further, according to another optical disk reproducing apparatus according to the present invention, the scanning speed of the light spot is made to match the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the recording area on the optical disc recording medium. Therefore, the relative speed between the light spot and the recording medium is reduced on average from the outermost peripheral portion to the innermost peripheral portion. Therefore, it is possible to read only the center of the recording mark without reading the beginning or the end of the recording mark. Therefore, the read signal of the recording mark becomes large on average from the innermost peripheral portion to the outermost peripheral portion of the optical disc recording medium, and the waveform thereof becomes steep, so that the S / N ratio can be improved.

On the other hand, according to still another optical disk recording apparatus according to the present invention, the scanning speed of the light spot is determined according to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the zone irradiated with the light spot. Is switched, the light spot is scanned following the linear velocity of the recording medium. Therefore, the relative speed between the light spot and the recording medium is reduced on average from the innermost peripheral portion to the outermost peripheral portion of the zone. Therefore, the temperature distribution at the head and tail of the recording mark can be made substantially uniform in each zone. Therefore, it is possible to form a recording mark having a substantially uniform shape from the innermost peripheral portion to the outermost peripheral portion in each zone, and it is possible to improve the reliability of reproduced data.

Further, according to still another optical disk reproducing apparatus according to the present invention, the scanning speed of the light spot is switched according to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the zone. The light spot is scanned following the linear velocity of the recording medium. Therefore, the relative speed between the light spot and the recording medium is reduced on average in each zone. Therefore, it is possible to read only the center of the recording mark without reading the beginning or the end of the recording mark. Therefore, the read signal of the recording mark increases from the innermost peripheral portion to the outermost peripheral portion of the optical disc recording medium, and the waveform thereof becomes steep, so that the S / N ratio can be improved.

[0027]

Embodiments of an optical disk recording apparatus and an optical disk reproducing apparatus according to the present invention will now be described in detail with reference to the drawings.

[Embodiment 1] FIG. 1 is a block diagram showing the structure of a magneto-optical disk recording / reproducing apparatus according to a first embodiment of the present invention.

As shown in FIG. 1, this magneto-optical disk recording / reproducing apparatus includes a semiconductor laser 10, a semiconductor laser drive circuit 11, a beam splitter 12, a polygon mirror 13, a motor 14, and a motor drive circuit 15. including.
The magneto-optical disk recording / reproducing apparatus further includes a photodetector 1
6 and a reproduction circuit 17. The magneto-optical disk recording / reproducing apparatus further includes a recording clock generating circuit 18, a clock frequency switching circuit 19, and a recording data generating circuit 20.
A reproduction clock generation circuit 21 and a changeover switch 22.

The semiconductor laser 10 includes a beam splitter 1
The optical spot d is irradiated onto the optical disk recording medium 23 via the 2 and the polygon mirror 13. The semiconductor laser drive circuit 11 drives the semiconductor laser 10. The beam splitter 12 straightly transmits the laser beam emitted from the semiconductor laser 10 to the polygon mirror 13, and at the same time reflects the laser beam reflected by the optical disc recording medium 23 to the photodetector 16. The polygon mirror 13 is formed by vapor-depositing aluminum or the like on each side surface of a regular polygonal column, and is rotated at a high speed so that the laser beam emitted from the semiconductor laser 10 via the beam splitter 12 is unidirectional within a certain range. Scan repeatedly. The motor 14 rotates the polygon mirror 13 at high speed. The motor drive circuit 15 drives the motor 14,
Control to a predetermined rotation speed.

In this embodiment, the semiconductor laser 10 and the semiconductor laser drive circuit 11 constitute the light spot irradiation means 24. Further, the polygon mirror 13, the motor 14 and the motor drive circuit 15 constitute the light spot scanning means 25.

First, the recording operation of this magneto-optical disk recording / reproducing apparatus will be described. In response to the recording clock 1 from the recording clock generating circuit 18, the recording data generating circuit 20 outputs the recording data a. The recording data a is input to the semiconductor laser drive circuit 11 and the changeover switch 22. At the time of recording,
The changeover switch 22 selects the recording data a and inputs it to the motor drive circuit 15.

Recording data a to the semiconductor laser drive circuit 11
Is input, the semiconductor laser 10 emits a laser beam in response to the control signal b from the semiconductor laser drive circuit 11.

On the other hand, the recording data a from the recording data generating circuit 20 is transferred via the changeover switch 22 to the motor drive circuit 1
Input to 5. The motor drive circuit 15 inputs the control signal c to the motor 14 in response to the recording data a.

Here, the recording area of the optical disc recording medium 23 includes a plurality of zones composed of a plurality of tracks. Therefore, the frequency of the recording clock 1 generated by the recording clock generation circuit 18 is the same as that of the clock frequency switching circuit 1.
It is switched by 9 according to each zone. That is, as shown in FIG. 2, average linear velocities V1, V2, V3, V4 from the innermost peripheral portion Rin to the outermost peripheral portion Rout of each zone.
The frequency is increased in proportion to. In order to simplify the description, FIG. 2 illustrates the case where the zone is divided into four zones.

Therefore, since the linear velocity at the center position in each zone becomes the average linear velocity of that zone, the scanning velocity of the light spot d by the polygon mirror 13 becomes the average linear velocity V1, V2, V3, V4. Matched. That is, the motor drive circuit 1 that drives the polygon mirror 13
5 drives the motor 14 according to these average linear velocities V1, V2, V3 and V4, and this motor 14 rotates the polygon mirror 13. As a result, the scanning speed of the light spot d is switched for each zone.

In FIG. 3, the laser beam is a polygon mirror 1.
3 is a diagram showing a state in which a light spot is reflected by 3 and a light spot is scanned thereby. As shown in FIG. 3, (a),
When the polygon mirror 13 is rotated as in (b) and (c), the laser beam is incident from the same direction, but its reflection direction changes.

FIG. 4 shows (a), (b), and FIG.
(C) At each moment, the light spot d is recorded on the recording medium 23.
FIG. 6 is a diagram showing a state in which the same spot P on the recording medium 23 is always irradiated with a light spot d by following the linear velocity of FIG.

As shown in FIG. 4, the recording medium 23 moves in the x direction shown by the arrow in FIG. 4, but the light spot d is referred to as (a), (b), (c) while being synchronized with the recording data a. Scan sequentially in order. As a result, the light spot d
Is always applied to the same location P on the recording medium 23.

Therefore, as shown by the solid line in FIG. 4 (d), the temperature distribution T of the recording medium 23 has a steep characteristic in which it becomes maximum at the center of the light spot d. By the way, as indicated by a broken line in (d), the temperature distribution Ta generated by the conventional recording method has a blunt characteristic as compared with the temperature distribution T generated by the method of the present invention.

Since the recording mark m is a portion where the temperature distribution T exceeds the threshold temperature Tsh, the recording mark m having a uniform shape can be formed. Further, since there is no forward scanning of the light spot d, it is possible to start the scanning for forming the next recording mark immediately after forming the recording mark m.

As described above, according to the magneto-optical disk recording / reproducing apparatus of the present invention, it is possible to form the recording mark m having a substantially uniform shape on any track.

Next, the reproducing operation of this magneto-optical disk recording / reproducing apparatus will be described. First, in the reproduction operation, the changeover switch 22 is switched to the reproduction clock generation circuit 21 side, and the reproduction clock k is input to the motor drive circuit 15. In this state, the semiconductor laser driving circuit 11 drives the semiconductor laser 10, and the semiconductor laser 10 is driven.
Emits a weak laser beam with a constant intensity. This laser beam enters a rotating polygon mirror 13 via a beam splitter 12, and is reflected by the polygon mirror 13 toward an optical disk recording medium 23. Therefore, this laser beam is applied to the optical disc recording medium 23 as a light spot d, and the light spot d is repeatedly scanned within a certain range in the direction along the track of the optical disc recording medium 23.

In this magneto-optical disk recording / reproducing apparatus, the optical disk recording medium 23 rotates at a constant angular velocity, so that the linear velocity becomes higher toward the outer peripheral track. Therefore, the reproduction clock k has a higher frequency in the outer peripheral zone, like the recording clock 1. Motor drive circuit 15
Drives the motor 14 based on the reproduction clock k, the polygon mirror 13 rotates in synchronization with the reproduction clock k. Therefore, the light spot d is scanned according to the average linear velocities V1, V2, V3, and V4 of each zone.

Further, the reflected light f from the optical disk recording medium 23 is reflected / separated by the beam splitter 12 in the perpendicular direction and then guided to the photodetector 16. The reflected light f is converted into a read signal g by the photodetector 16, and the reproducing circuit 17 generates reproduced data h based on the read signal g.

In FIG. 5, the optical spot d is scanned in the order of (a), (b) and (c) of FIG.
It is a figure which shows a mode that it is irradiated to 3. FIG. 5 (a),
As shown in (b) and (c), the light spot d is scanned according to the linear velocity of the optical disc recording medium 23, and is always irradiated on the same position on the optical disc recording medium 23. That is, the optical disk recording medium 23 is moving in the x direction in the figure, but the optical spot d is continuously scanned in the order of (a), (b), (c) in synchronization with the reproduction clock k, and the optical disk The linear velocity of the recording medium 23 is made to follow. As a result, the light spot d is always applied to the center of the same recording mark m on the optical disc recording medium 23 at the moment of reading. Therefore, the head portion and the tail portion of the recording mark m are not read by the light spot d, and only the central portion is always read. Therefore, as shown in FIG. 5D, the read signal g has the same magnitude in any of (a), (b), and (c). Therefore, the waveform of the read signal g becomes steeper than in the conventional case, and the S / N ratio is improved.

Here, the case where the recording mark m having a uniform shape in which the magnetization reversal is clear is read has been described. However, even when the recording mark m in which the magnetization reversal is unclear is read, the central portion thereof is mainly read. Therefore, the noise from the beginning and the end of the recording mark m is removed.
That is, the light amount of the light spot is larger at the center and smaller at the peripheral portion. Therefore, since the head and tail portions of the recording mark m are read by the peripheral portion of the light spot, the amount of reflected light is small and the noise is also small. Therefore, also in this case, the S / N ratio can be similarly improved, and the reliability of the reproduced data can be further improved.

As described above, according to the magneto-optical disk recording / reproducing apparatus, the optical spot always follows the linear velocity from the outermost peripheral portion to the innermost peripheral portion of the optical disc recording medium 23, so that accurate recording and recording can be performed. Playback can be performed. Moreover, since the light spot d is scanned by the polygon mirror 13 in only one direction, recording and reproduction can be performed at a higher speed than in the third conventional example in which the light spot d is vibrated.

In the above embodiment, the example in which the scanning speed is switched in four steps has been shown, but the invention is not limited to this.
You may switch 3 steps or less or 5 steps or more.

[Embodiment 2] FIG. 6 is a block diagram showing the structure of a magneto-optical disk recording / reproducing apparatus according to a second embodiment of the present invention.

As shown in FIG. 6, this magneto-optical disk recording / reproducing apparatus includes a semiconductor laser 10, a semiconductor laser driving circuit 11, a beam splitter 12, and a polygon mirror 1.
3, a motor 14, and a motor drive circuit 15. This magneto-optical disc recording / reproducing apparatus further includes a photodetector 16
And a reproducing circuit 17. The magneto-optical disk recording / reproducing apparatus further includes a recording clock generating circuit 18, a clock frequency switching circuit 19, a recording data generating circuit 20, a reproducing clock generating circuit 21, and a changeover switch 22.

The magneto-optical disk recording / reproducing apparatus according to the first embodiment forms a recording mark by a so-called mark position recording system, but the magneto-optical disk recording / reproducing apparatus according to the second embodiment has a so-called mark edge. The recording mark is formed by the recording method. The difference between the magneto-optical disk recording / reproducing apparatus according to the second embodiment and the magneto-optical disk recording / reproducing apparatus according to the first embodiment is that the recording clock 1 is input to the motor drive circuit 15 at the time of recording instead of the recording data a. Is. In addition, in the drawings, the portions denoted by the same reference numerals indicate the same or corresponding portions.

First, the case of forming recording marks by this mark edge recording method will be described.

According to this method, as shown in FIG. 7, the light spot d is synchronized with the recording clock l, not the recording data a, and the light spot m is irradiated from the innermost circumference to the outermost circumference of the zone. It is made to follow the average linear velocity to the part.

Therefore, the light spot d is P (n), P
(N + 1), ... P (n + m) in order, with a constant interval S, and jumping one after another. Since the light spot p is synchronized with the recording clock 1, this constant interval S corresponds to the cycle Sa of the recording clock 1.

Here, when the strong light spot d is irradiated when the recording data a is "1", the temperature of the recording medium 23 rises only in the irradiated portion. Temperature distribution T in this case
Shows steep characteristics as shown in FIG. 7, and the temperature distribution T at the head and tail of the recording mark m can be made uniform. By the way, the temperature distribution Ta generated by the conventional mark edge recording method is, as shown in FIG. 7, compared with the temperature distribution T generated by the mark edge method of the present invention.
The characteristics become dull, and the temperature distributions at the head and tail of the recording mark are not uniform.

Next, a method of reproducing the recording mark m by this mark edge recording method will be described with reference to FIG.

As shown in FIG. 8, the optical spot d is synchronized with the reproduction clock k and the optical disk recording medium 23.
Is irradiated. As a result, the light spot d is scanned according to the linear velocity of the irradiated portion, and P
Irradiation is performed at regular intervals S in the order of (n), P (n + 1), ... P (n + m). This constant interval S corresponds to the cycle Sa of the reproduction clock k.

As described above, also in the mark edge recording method, as in the mark position recording method, the light spot d is always irradiated to the center of the same recording mark m on the optical disk recording medium 23 at the moment of reading. , The head and tail portions of the recording mark m are not read, and only the central portion is always read. Therefore, the read signal g becomes large and its waveform becomes steep, so that S
The / N ratio can be improved. Further, since the reproduction data h is generated in synchronization with the reproduction clock k based on the read signal g, its reliability can be further improved.

Further, even when the recording mark m in which the magnetization reversal is unclear is read, it is possible to remove the noise from the head and tail portions thereof. Therefore, also in this case, the S / N ratio can be improved and the reliability of the reproduced data can be improved.

In the first and second embodiments, the recording data a may be synchronized with the recording clock l, and conversely, the recording data a may be synchronized with the recording clock l.

[Third Embodiment] FIG. 9 is a block diagram showing a third embodiment of the magneto-optical disk recording / reproducing apparatus according to the present invention.

Although the driving speed of the motor 14 is switched in accordance with the recording data a or the recording clock 1 in the above-described first or second embodiment, the driving speed switching circuit 26 is provided as shown in FIG. , By directly inputting the switching signal n to the motor drive circuit 15,
The rotation speed of 4 may be switched. The drive speed switching circuit 26 detects the linear speed of the optical disk recording medium 23 at the portion where the light spot d is currently irradiated, and generates the switching signal n in accordance with this. In order to detect the linear velocity of the optical disk recording medium 23, for example, the current position of the pickup device is specified by the address information from the sensor or the read signal, and the rotation speed of the spindle motor for rotating the optical disk recording medium 23 is specified. Further, the linear velocity may be calculated by the CPU based on these.

[Embodiment 4] In the above embodiment, the recording area of the optical disk recording medium is divided into four zones, and the scanning speed of the light spot is switched stepwise according to the average linear velocity in each zone. As shown in FIG. 10, the innermost circumference Rin
The scanning speed of the light spot may be made to coincide with the average linear velocity Vmean of the linear velocity Vmin and the linear velocity Vmax of the outermost peripheral portion Rout. In this case, the average linear velocity Vmean
According to the above, the motor 14 may be driven to rotate the polygon mirror 13.

Compared with the above embodiment, the relative speed between the light spot d and the recording mark m becomes larger at a position closer to the innermost peripheral portion or the outermost peripheral portion, but accurate recording and reproducing are performed by a relatively simple structure. Can be done.

[Embodiment 5] FIG. 11 is a block diagram showing a fifth embodiment of a magneto-optical disk recording / reproducing apparatus according to the present invention. As shown in FIG. 11, the polygon mirror 13
Instead of this, a hologram disc 27 is provided, and the number of revolutions of the hologram disc 27 is switched according to the linear velocity of the portion irradiated with the light spot d, so that the outermost peripheral portion to the innermost peripheral portion of the optical disc recording medium 23 are changed. The light spot d may be made to follow the linear velocity over a part.

The hologram disk 27 is formed by arranging linear gratings at equal intervals in a concentric pattern. For example, "Electronics Society of Japan, Photographic Industry Supplement, Imaging, Part 3, p28-35," Printer Output Device and Recording The topic of materials is disclosed in "December 20, 1988".

[Sixth Embodiment] FIG. 12 is a block diagram showing a sixth embodiment of the magneto-optical disk recording / reproducing apparatus according to the present invention.

As shown in FIG. 12, this magneto-optical disk recording / reproducing apparatus is the same as the semiconductor laser 1 in the first embodiment.
0, the polygon mirror 13, the motor 14, and the motor drive circuit 15 are replaced by three semiconductor lasers 28, 29 and 30, a semiconductor switch circuit 31, and a switch control circuit 32.

The semiconductor switch circuit 31 switches the drive current from the semiconductor laser drive circuit 11 by means of the switch control circuit 32 to sequentially output the semiconductor lasers 28, 29 and 3.
It sends it to 0.

When data is recorded on the optical disk recording medium 23 by this magneto-optical disk recording / reproducing apparatus, the changeover switch 22 is first switched to the recording data generating circuit 20 side. Therefore, the recording data a from the recording data generating circuit 20 is guided to the semiconductor laser driving circuit 11 and the switch control circuit 32. A drive current is sent from the semiconductor laser drive circuit 11 to the three semiconductor lasers 28, 29, 30 via the semiconductor switch circuit 31, but in the semiconductor switch circuit 31, the drive current is switched by the switch control circuit 32. Are sequentially sent to the semiconductor lasers 28, 29, 30.

On the other hand, the frequency of the recording clock 1 from the recording clock generation circuit 18 is the clock frequency switching circuit 19
Thus, the light spots d1, d2, and d3 are switched according to the linear velocity of the irradiated portion at the present time.
In this way, the switch control circuit 32 controls the recording clock l
Since the semiconductor switch circuit 31 is controlled in synchronism with the recording data a generated based on the above, the light spots d1, d2, d3 emitted from the semiconductor lasers 28, 29, 30 to the optical disk recording medium 23 are The linear velocity of the optical disk recording medium 23 in the irradiated portion is made to follow. Therefore, the relative speed between the light spots d1, d2, d3 and the optical disk recording medium 23 becomes zero, and it is possible to form a recording mark having a uniform shape.

FIG. 13 shows the light spot d shown in FIG.
1, d2 and d3 are always the optical disc recording medium 2
It is a figure which shows a mode that the same location P on 3 is irradiated.

As shown in FIG. 13, the optical disk recording medium 23 is moving in the x direction in the figure, and the light spots d1 and d
Along with this, 2 and d3 are made to follow intermittently in the order of (a), (b), and (c). As a result, the light spot d
Since 1, d2 and d3 are always applied to the same portion P on the optical disc recording medium 23, a steep temperature distribution T as shown in FIG. 13D is generated on the optical disc recording medium 23. be able to. The temperature distribution Ta shown by the broken line in the figure is generated by the conventional method.

As described above, in the present embodiment, the three semiconductor lasers 28, 29, 30 are driven sequentially in synchronization with the recording data a, so that the semiconductor lasers 28, 29, 3 are driven.
The light spots d1, d2, and d3 irradiated from 0 are made to follow the linear velocity of the part where they are irradiated, and the temperature distributions at the beginning and the rear of the recording mark can be made uniform, so that they are uniform. It is possible to form the recording mark m having any shape. Next, when reproducing data with this magneto-optical disk recording / reproducing apparatus, the changeover switch 22 is first switched to the reproduction clock generating circuit 21 side. Therefore, the switch control circuit 32 uses the reproduction clock k
The semiconductor switch circuit 31 is controlled in accordance with the above, and the three semiconductor lasers 28, 29, 30 are sequentially switched. Moreover,
The frequency of the reproduction clock k is set by the clock frequency switching circuit 19 at the present time to the light spots d1, d2, d.
Since 3 is switched according to the linear velocity of the irradiated portion, the light spots d1, d2, d3 are made to follow the linear velocity of the optical disk recording medium 23 of the irradiated portion. In this way, the semiconductor lasers 28, 29,
Light spots d1 and d of weak constant intensity emitted from 30
2, d3 are reflected by the optical disk recording medium 23, and the reflected lights f1, f2, f3 are reflected / separated in the orthogonal direction by the beam splitter 12 and then guided to the photodetector 16. The reflected light f1, f2, f3 is converted into a read signal g in the photodetector 16, and the reproduced data h is further generated in the reproducing circuit 17.

FIG. 14 shows the light spot d shown in FIG.
1, d2 and d3 are always the optical disc recording medium 2
FIG. 6 is a diagram showing how the same recording mark m on 3 is irradiated.

As shown in FIG. 14, although the optical disk recording medium 23 is moving in the x direction in the figure, the light spots d1,
d2 and d3 are synchronized with the reproduction clock k (a),
The scanning is performed in the order of (b) and (c), and the linear velocity of the optical disk recording medium 23 is made to follow. As a result, the light spots d1, d2, d3 can be applied to the same recording mark m on the optical disc recording medium 23 at the moment of reading. Therefore, the head portion and the tail portion of the recording mark m are not read by the light spots d1, d2, d3, and only the central portion is always read. Therefore, the read signal g from the recording mark m is read in the order of (a), (b), and (c) as shown in FIG. , Its waveform becomes steep. Therefore, the S / N ratio can be improved.

Further, even when reading is performed from the recording mark m in which the magnetization reversal is unclear, noise from the head and tail portions can be removed, so that the S / N ratio can be further improved and the reproduction can be performed. The reliability of the data h can be further improved.

Here, three semiconductor lasers 28, 29,
Although the example using 30 is shown, the invention is not limited to this, and two or four or more semiconductor lasers may be used. The larger the number of semiconductor lasers, the closer the scanning of the intermittent light spot to the continuous scanning. Further, although the case of the mark position recording method has been described here, the mark edge recording method can be applied similarly to the first embodiment.

In the first to sixth embodiments, the light spot is scanned only on the outward path and is not scanned on the return path. Therefore, the light spot is made to sufficiently follow the linear velocity of the portion irradiated with the light spot. You can Therefore, the power of the light spot can be concentrated at one place and the energy can be used efficiently. Therefore, the power of the light spot required for recording can be reduced and the power consumption can be reduced as compared with the conventional case. Further, generally, the shorter the wavelength of the semiconductor laser is, the more difficult it is to achieve high output, which hinders high density. However, according to the present invention, the energy can be used efficiently even at a low output,
Recording and reproduction of recording marks are facilitated, and high density is possible.

[Seventh Embodiment] FIG. 15 is a diagram showing a seventh embodiment of the magneto-optical disk recording / reproducing apparatus according to the present invention.

As shown in FIG. 15, a galvano mirror 33 may be provided instead of the polygon mirror 13 in the first embodiment. In this embodiment, the galvano mirror 33 is vibrated to move the light spot d to the optical disc recording medium 2.
While scanning in the direction along the track No. 3, the vibration cycle is switched according to the linear velocity of the portion irradiated with the light spot d. Therefore, it is difficult to keep the scanning speed constant from the start to the end of scanning, but the relative speed between the light spot d and the optical disk recording medium 23 is reduced in any track, so that it is lower than in the conventional case. Recording and reproduction can be performed accurately.

[Embodiment 8] FIG. 16 is a block diagram showing an eighth embodiment of a magneto-optical disk recording / reproducing apparatus according to the present invention.

As shown in FIG. 16, this magneto-optical disk recording / reproducing apparatus has a polygon mirror 1 according to the first embodiment.
In place of 3, an objective lens 34 capable of vibrating in parallel to the surface of the optical disc recording medium 23 is provided. The magneto-optical disk recording / reproducing apparatus further includes an objective lens drive circuit 35 for driving the objective lens 34. The objective lens drive circuit 35 receives the record data a during recording and the reproduction clock k during reproduction. To be done. Therefore, the vibration cycle of the objective lens 34 is switched in synchronization with the recording data a or the reproduction clock k, whereby the light spot d is made to follow the linear velocity of the portion irradiated with it.
Therefore, recording and reproduction can be accurately performed from the innermost peripheral portion to the outermost peripheral portion of the optical disc recording medium 23.

[Others] In the above-described embodiment, the recording area of the optical disk recording medium 23 is divided into a plurality of zones composed of a plurality of tracks, and the scanning speed of the light spot d is switched according to the average linear velocity in each zone. However, it goes without saying that the light spot d can more faithfully follow the linear velocity of the portion irradiated with the light spot d by switching the scanning velocity for each track.

Further, an objective lens for appropriately focusing the light spot d may be provided between the polygon mirror 13, the hologram disc 27 or the galvanometer mirror 33 and the optical disc recording medium 23 in the above-mentioned embodiment.

Further, in the above-mentioned embodiment, the reproduction is carried out by using the reflected light from the recording mark, but a light spot is irradiated from the back surface of the optical disk recording medium, and the rotation angle of the polarization plane due to the Faraday effect of the transmitted light. The reproduction may be performed by detecting the. Further, the light that has once passed through the optical disc recording medium may be reflected again for detection.

Further, in the above embodiment, the so-called light modulation method of modulating the light spot according to the recording data has been described, but the present invention is not limited to this, and the so-called magnetic field modulation method of biasing the external magnetic field may be used. Has the same effect.

Further, if the optical disk recording medium 23 having the recording marks formed by the magneto-optical disk recording / reproducing apparatus according to the above-mentioned embodiment is reproduced by the conventional optical disk reproducing apparatus, the reproduction data having higher reliability than the conventional one can be obtained. it can.

The master of the magneto-optical disk recording medium may be photo-resisted by the optical disk recording / reproducing apparatus according to the present invention to prepare the master disk. By duplicating the optical disc recording medium by injection molding or contact exposure using this master disc, it is possible to provide an optical disc recording medium from which highly reliable reproduction data can be obtained.

Further, although the optical disk device is taken as an example in the above-mentioned embodiment, the present invention is not limited to this, and the present invention can be applied to any device whose linear velocity is not constant.

In addition, the same effect can be obtained even if the following velocity is switched or the average linear velocity is followed by using the AO module or EO module device according to the third conventional example as in the above embodiment. can get.

[0093]

According to the optical disk recording apparatus of the first aspect of the present invention, since the scanning speed of the light spot is switched according to the linear speed of the portion irradiated with the light spot, At a moment, the light spot can be made to follow the linear velocity of the portion irradiated with the light spot from the innermost peripheral portion to the outermost peripheral portion of the optical disk recording medium. Therefore, the relative speed between the light spot and the optical disc recording medium can be constantly reduced, and a recording mark having a uniform shape can be formed in all recording areas of the optical disc recording medium. Further, when the reproduction is performed using the optical disc recording medium on which the recording mark is formed by the optical disc recording device, the reproduction data with high reliability can be obtained.

Further, according to the optical disk reproducing apparatus of the second aspect of the present invention, since the operation speed of the light spot is switched according to the linear speed of the portion where the light spot is irradiated, the reproduction is performed. At the moment of, the light spot can be made to follow the linear velocity of the portion irradiated with the light spot from the outermost peripheral portion to the innermost peripheral portion of the optical disc recording medium. Therefore, the relative speed between the light spot and the optical disc recording medium can be constantly reduced, and the reproduction data can be accurately generated from all the recording marks formed on the optical disc recording medium.

According to the optical disk recording apparatus of the third aspect of the present invention, the scanning speed of the light spot is set to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the recording area of the optical disc recording medium. Since they coincide with each other, the light spot can be made to substantially uniformly follow the linear velocity of the portion irradiated with the light spot from the innermost peripheral portion to the outermost peripheral portion of the optical disc recording medium at the moment of recording. For this reason,
The relative speed between the light spot and the optical disc recording medium can be reduced on average, and the recording marks having a uniform shape can be formed almost uniformly over the front surface of the recording area of the optical disc recording medium.

According to the optical disc reproducing apparatus of the fourth aspect of the present invention, the scanning speed of the light spot is set to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the recording area of the optical disc recording medium. Since they are matched with each other, at the moment of reproduction, the optical spot can be made to substantially follow the linear velocity of the portion irradiated with the optical spot from the outermost peripheral portion to the innermost peripheral portion of the optical disk recording medium. For this reason,
The relative speed between the light spot and the optical disk recording medium can be reduced, and almost accurate reproduction data can be obtained on average from all the recording marks formed on the optical disk recording medium.

Further, according to the optical disk recording apparatus of the fifth aspect of the present invention, the light spot is formed according to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the zone irradiated with the light spot. Since the scanning speed is switched, the light spot can be made to substantially follow the linear velocity of the part irradiated with the light spot from the innermost peripheral portion to the outermost peripheral portion of the optical disc recording medium at the moment of recording. Therefore, the relative speed between the light spot and the recording medium can be substantially reduced, and a recording mark having a substantially uniform shape can be formed over the front surface of the recording area of the optical disc recording medium.

Further, according to the optical disk reproducing apparatus of the sixth aspect of the present invention, the light spot is responsive to the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the zone where the light spot is irradiated. Since the scanning speed of is switched,
At the moment of reproduction, the light spot can be made to substantially follow the linear velocity of the portion irradiated with the light spot from the innermost peripheral portion to the outermost peripheral portion of the optical disk recording medium. Therefore, the relative speed between the light spot and the optical disc recording medium can be substantially reduced, and almost accurate reproduction data can be obtained from all the recording marks formed on the optical disc recording medium.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of a magneto-optical disk recording / reproducing apparatus that is a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing how the scanning speed of a light spot is switched in the magneto-optical disk recording / reproducing apparatus shown in FIG.

FIG. 3 is an explanatory diagram showing a manner in which a light spot is scanned by a polygon mirror in the magneto-optical disk recording / reproducing apparatus shown in FIG.

FIG. 4 is an explanatory diagram showing how a light spot follows a recording medium when recording is performed by the magneto-optical disc recording / reproducing apparatus shown in FIG.

FIG. 5 is an explanatory diagram showing how a light spot follows a recording mark when reproducing is performed by the magneto-optical disk recording / reproducing device shown in FIG.

FIG. 6 is a block diagram showing the overall configuration of a magneto-optical disk recording / reproducing apparatus that is a second embodiment of the present invention.

FIG. 7 is a diagram for explaining a recording operation by the magneto-optical disc recording / reproducing apparatus shown in FIG.

FIG. 8 is a diagram for explaining a reproducing operation by the magneto-optical disk recording / reproducing device shown in FIG.

FIG. 9 is a block diagram showing an overall configuration of an optical disk recording / reproducing apparatus which is a third embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a scanning speed of a light spot in a magneto-optical disk recording / reproducing apparatus which is a fourth embodiment of the present invention.

FIG. 11 is a block diagram showing the overall configuration of an optical disc recording / reproducing apparatus which is a fifth embodiment of the present invention.

FIG. 12 is a block diagram showing an overall configuration of an optical disc recording / reproducing apparatus which is a sixth embodiment of the present invention.

13 is an explanatory diagram showing a state in which an optical spot follows a linear velocity of an optical disc recording medium when recording is performed by the magneto-optical disc recording / reproducing device shown in FIG.

FIG. 14 is an explanatory diagram showing how a light spot follows a recording mark when reproducing is performed by the magneto-optical disk recording / reproducing device shown in FIG.

FIG. 15 is a diagram showing a main part of an optical disc recording / reproducing apparatus which is a seventh embodiment of the present invention.

FIG. 16 is a block diagram showing the overall configuration of a magneto-optical disk recording / reproducing apparatus that is an eighth embodiment of the present invention.

FIG. 17 is an explanatory diagram showing a state of recording by a conventional optical disc recording device.

FIG. 18 is an explanatory diagram showing a state of reproduction by a conventional optical disc reproducing device.

[Explanation of symbols]

 10, 28, 29, 30 Semiconductor laser 11 Semiconductor laser drive circuit 12 Beam splitter 13 Polygon mirror 14 Motor 15 Motor drive circuit 16 Photodetector 17 Reproduction circuit 18 Recording clock generation circuit 19 Clock frequency switching circuit 20 Recording data generation circuit 21 Reproduction Clock generation circuit 22 Changeover switch 23 Optical disc recording medium 26 Drive speed changeover circuit 27 Hologram disc 31 Semiconductor switch circuit 32 Switch control circuit 33 Galvano mirror 34 Objective lens 35 Objective lens drive circuit

Claims (6)

[Claims] 1. An optical disc recording apparatus for irradiating a rotating optical disc recording medium with a light spot to form a recording mark, the optical spot irradiating unit irradiating the optical disc recording medium with the light spot, and the optical spot irradiation. A light spot scanning means for repeatedly scanning the light spot irradiated by the means within a certain range in the direction along the track of the optical disk recording medium so that the recording mark has a predetermined shape; Depending on the linear velocity of the portion of the optical disc recording medium on which the spot is illuminated,
An optical disc recording apparatus, comprising: a scanning speed switching unit that switches a speed at which the light spot is scanned by the light spot scanning unit. 2. An optical disk reproducing apparatus for irradiating a rotating optical disk recording medium on which a recording mark is formed with a light spot and generating reproduction data based on reflected light or transmitted light from the irradiated portion, A light spot irradiating means for irradiating the optical spot on the optical disk recording medium, and a light spot irradiating by the light spot irradiating means are aligned with the recording marks within a certain range in a direction along a track of the optical disk recording medium. In accordance with the linear velocity of the portion of the optical disk recording medium on which the light spot is irradiated by the light spot scanning means for repeatedly scanning with the light spot irradiation means,
An optical disk reproducing apparatus, comprising: a scanning speed switching unit that switches a speed at which the light spot is scanned by the light spot scanning unit. 3. An optical disk recording device for forming a recording mark by irradiating a rotating optical disk recording medium with a light spot, and a light spot irradiation unit for irradiating the optical disk recording medium with the light spot, and the light spot irradiation. A light spot scanning means for repeatedly scanning the light spot emitted by the means within a certain range in the direction along the track of the optical disk recording medium so that the recording mark has a predetermined shape; and a recording area in the optical disk recording medium. An optical disk recording apparatus, comprising: scanning speed control means for matching the speed at which the light spot scanning means scans the light spot with the average linear velocity from the innermost peripheral portion to the outermost peripheral portion. 4. An optical disk reproducing apparatus for irradiating a rotating optical disk recording medium on which a recording mark is formed with a light spot and generating reproduction data based on reflected light or transmitted light from the irradiated portion, A light spot irradiating means for irradiating the optical spot on the optical disk recording medium, and a light spot irradiating by the light spot irradiating means are aligned with the recording marks within a certain range in a direction along a track of the optical disk recording medium. And a scanning for making the speed at which the optical spot is scanned by the optical spot scanning means coincide with the average linear velocity from the innermost peripheral portion to the outermost peripheral portion of the recording area of the optical disc recording medium. An optical disk reproducing apparatus including speed control means. 5. An optical disc recording apparatus for forming a recording mark by irradiating a rotating optical disc recording medium with a light spot, wherein a recording area of the optical disc recording medium comprises a plurality of concentric zones composed of a plurality of tracks. The optical disc recording device may include an optical spot irradiating unit that irradiates the optical spot onto the optical disc recording medium, and the optical spot that is irradiated by the optical spot irradiating unit so that the recording mark has a predetermined shape. A light spot scanning unit that repeatedly scans within a certain range in a direction along a track of a recording medium, and an average line from the innermost peripheral portion to the outermost peripheral portion of the zone where the light spot is irradiated by the light spot irradiation unit. Scanning for switching the speed at which the light spot is scanned by the light spot scanning means according to the speed And a degree switching means, the optical disc recording apparatus. 6. An optical disk reproducing apparatus for irradiating a rotating optical disk recording medium on which a recording mark is formed with a light spot and generating reproduction data based on reflected light or transmitted light from the irradiated portion, The recording area of the optical disc recording medium includes a plurality of concentric zones composed of a plurality of tracks, the optical disc reproducing apparatus includes a light spot irradiating unit that irradiates the optical spot onto the optical disc recording medium, and the light spot irradiating unit. A light spot scanning means for causing a light spot irradiated by the means to coincide with the recording mark and repeatedly scanning within a certain range in a direction along the track of the optical disk recording medium; and a light spot irradiated by the light spot irradiation means. Depending on the average linear velocity from the innermost circumference to the outermost circumference of the zone, The Tsu preparative scanning means comprises a scanning speed switching means for switching the speed at which the light spot is scanned, the optical disk reproducing apparatus.