JP3391041B2 - Magneto-optical disk device and magneto-optical recording / reproducing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk device, and more particularly to a means for reading a signal from a magneto-optical disk having both a read-only area for information and a recordable / reproducible area.

In recent years, beam-irradiated information read-only area (ROM) in which read-only information such as a program that does not need to be rewritten is previously recorded with uneven pit signals or the like, and information that requires rewriting of data or the like. A so-called partial ROM having a recordable / reproducible area (hereinafter abbreviated as RAM) recorded by a magneto-optical signal (hereinafter abbreviated as MO signal) formed by heating to a Curie point or higher by applying a vertical magnetic field. Magneto-optical disks called (with P-ROM) have also been shipped to the market.

In order to improve performance and increase capacity, magneto-optical disks such as P-ROMs are required to be capable of high-density recording, accurate, and high in access speed.

[0004]

2. Description of the Related Art As an optical system of a conventional magneto-optical disk device, as a reference, Nikkei McGraw-Hill, Sep. 1987, 10
Issued daily, "Optical Magnetic Disk Technology Handbook" P76-77
The knife edge method of the optical head for the magneto-optical disk shown in FIGS. 3 and 26 of FIG. 3 and the astigmatism method shown in FIG. .

4A and 4B are explanatory views of the principle of the conventional astigmatism method. FIG. 4A is a perspective view of a main part optical system and FIG. 4B is an explanatory view of a detected focus signal. In addition, in order to make the description of the configuration and operation easy to understand, the same reference numerals are given to the same portions throughout the drawings, and the duplicated description thereof will be omitted.

In FIG. 1A, an arrow P indicates an optical path direction of a light beam detected from a servo system detection optical path (not shown), 1 is a condenser lens for condensing the detected light beam, and 2 is a condenser lens. The cylindrical lens 3 is composed of a four-division photodetector (hereinafter abbreviated as 4D-PD).

FIG. 3B shows a beam shape appearing on the 4D-PD surface corresponding to the relative positions of the optical head and the disk (not shown) and the outputs a to 4 of the 4-division photodetector.
The value of d satisfies the relational expression of the values obtained by adding the diagonals as shown in the column of the light amount.

Further, it is known that the focus error signal can be obtained by taking the difference between the diagonals. FIG. 5 shows a servo circuit diagram based on the conventional astigmatism method, in which a focus error signal is obtained from the output of (corresponding to the difference between the sums of the diagonals) and from the output of (corresponding to the difference between the sums of adjacent pixels). A track error signal is obtained. , AGC (no error will occur even if there is power fluctuation during writing) is applied,
The normal drive means is to amplify the current with and apply current to the focus actuator and track actuator to apply servo.

If a circuit capable of reversing shown in a frame surrounded by a broken line is further inserted, a track servo can be applied to a land portion or a groove portion which will be described below by the output thereof.

FIG. 6 is a diagram showing a relationship between a conventional disc and a recording signal in a magneto-optical disc with a partial ROM. FIG. 6A shows the case of ROM signal reproduction, and FIG. 6B shows the case of MO signal recording / reproduction. Indicate the case.

In FIG. 1A, reference numeral 4 denotes a disk, 5 denotes a recording groove 5 formed in a concentric or spiral shape on the surface of the disk 4, and one recording groove 5 has an uneven shape and a ROM signal 8 is formed. And a groove portion 7 adjacent to which a MO signal 9 is formed by the magneto-optical recording method. The groove portion 7 is concentrically or spirally adjacently developed to form the land portion 6. 6a, 6b ..., The groove portions 7 are arranged every other groove portion 7a, 7b.

The arrangement means for arranging the recording signals in the ROM and the RAM has been previously proposed by the present applicant as Japanese Patent Application No. 04-228526, dated August 27, 1992. That is, a system in which a RAM signal is written in a portion corresponding to a groove and a ROM signal is written in a portion corresponding to a land portion is called a double-density partial ROM magneto-optical disk.

In FIG. 5A, when reproducing the uneven ROM signal 8, for example, the inversion circuit in FIG.
The central part of the ROM signal 8 of 6a is irradiated. The diagram shown in the lower part of the figure (a) shows the light amount distribution characteristic of the beam spot to be irradiated in the width direction of the recording groove, and the maximum part of the irradiation light amount irradiates the central part of the ROM signal 8. The ROM signal 8 can now be reproduced. However, the adjacent MO signal 9 also enters from the bottom of the light quantity of the beam spot, and there is crosstalk.

On the contrary, when recording and reproducing the MO signal 9,
(B) As shown in the figure, a beam spot is applied to the central portion of the MO signal written in the groove portion 7a. In this case, for example, the MO signal 9 can be recorded or reproduced by switching the inverting circuit in FIG. However, the ROM where the bottom of the light quantity of the beam spot is adjacent
It also goes into signal 8 and has crosstalk.

[0015]

As a conventional magneto-optical disk with double density partial ROM, an MO signal (RAM signal) is written in a portion corresponding to a groove portion and a ROM signal is recorded in a portion corresponding to a land portion. It was However, this method requires ROM to RAM or RA
When switching from M to ROM, it takes time to change the setting of the tracking between the adjacent land and groove portions. Also, since the skirt of the light quantity distribution of the focused spot is large, the ROM signal is mixed with the MO signal. There was a problem of so-called crosstalk.

The present invention has been made in view of the above-mentioned conventional drawbacks, and at the time of seeking of an optical head with respect to a ROM and a RAM which are adjacent to each other, simultaneous reproduction can be performed without losing tracking to shorten the access time, Also R
An object of the present invention is to provide a magneto-optical disk device and a magneto-optical recording / reproducing system that eliminate crosstalk of ROM signals mixed in AM signals and further improve the recording density in the radial direction of the disk.

[0017]

In order to achieve the above object, as shown in FIG. 1, a plurality of rows of land portions 6 in which a read-only signal is recorded in a concavo-convex shape on the surface of a disk 4 and the respective lands. A recording groove having a concentric circle shape or a spiral groove, which is formed between the rows of the sections and forms a recordable / reproducible signal by the magneto-optical recording method, and the recording groove is provided along the groove section 7 through the objective lens 25. In a magneto-optical disk device having an optical head 20 for converging and irradiating a beam, a light beam generation source 21 for generating at least the light beam on the optical head 20 and a light beam emitted from the light beam generation source 21 are mutually A light beam splitting means 23 for splitting into two parallel light beams, and a main beam formed at a predetermined position on the groove part 7 when the split two light beams are condensed by the objective lens 25. The pot 12 and the left sub-light having a light intensity smaller than that of the main beam spot 12 formed on the land portion 6 adjacent on both sides of the main beam spot 12 in the radial direction of the disc 4 and the main beam spot 12. A beam spot 13a and a spot positioning means 10 for the right sub-beam spot 13b are provided, the main beam spot 12 is used during recording, and the main beam spot 12 and the sub-beam spots 13a and 13b are simultaneously reflected from the reflected light at the time of reproduction, respectively. It is configured to read the signal.

Further, the reading of the main beam spot 12 is stopped by using the above device, and the sub beam spots 13a, 13a,
Signals can be read simultaneously using only one of the main beam spot 12 and one of the main beam spot 12 and one of the sub beam spots 13a and 13b.

Further, by using the above device, the main beam spot
Reading of 12 is stopped, and both of the sub beam spots 13a and 13
It is possible to read the signal at the same time using only both of b. In addition, memories 48 and 49 each having a recording capacity of two rounds of the land portion 6 are provided in the signal processing path for reading out the corresponding reproduction-only signals at the same time by using only both of the sub beam spots 13a and 13b. While the reproduction-only signal accommodated in one round is transferred to the next stage, the reproduction-only signal for the next one rotation is read.

[0020]

Operation: Two light beams parallel to each other are made incident on the objective lens 25, and these light beams are condensed to form a main beam spot 12 on the surface of the disk 4 and two sub-beams having a light intensity smaller than this. Beam spots 13a and 13b are formed, and the formed beam spots are aligned in the radial direction of the disk 4. The main beam spot 12 is in the groove portion 7, and both sub-beam spots 13a and 13b are in the groove portion 7, respectively. By forming the land portions 6 adjacent to each other, it is possible to record and reproduce the MO signal with respect to the groove portion 7, and also possible to simultaneously reproduce the ROM signal with respect to the land portions 6 respectively adjacent to the groove portion 7. Moreover, in the case of this reproduction, the tracking control does not require setting change. Therefore, the access time can be shortened and the recording density in the radial direction of the magneto-optical disk can be improved. In addition, there is an effect that crosstalk between the sub beam spots 13a and 13b adjacent to the main beam spot 12 can be reduced.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram for explaining the principle of the present invention, in which (a) is a block diagram, (b) is an enlarged view of a focused spot,
(C) is a principle diagram of the light beam splitting means, and (d) is a light amount distribution diagram of a focused spot on the disk.
The diagram (a) will be described with reference to each of the diagrams (d).

In FIG. 1A, 4 is a magneto-optical disk having a magneto-optical recording medium formed by forming a perpendicularly magnetized film on a transparent substrate, 20 is an optical head, and reference numerals 10 and 21 to 49 will be described later. It is composed of various parts. Reference numeral 21 is a laser beam generation source, 22 is a beam shaper, and 23 is a light beam splitting means. For example, a prism having a V-shaped cross section as shown in FIG. Divide without reducing efficiency.

If the power of the laser beam generating source 21 is sufficient, there is a method of dividing the beam into two parts in the diameter direction by using a light shielding band instead of a prism, but there is a drawback that the light utilization efficiency is lowered.

Reference numeral 24 is a polarization beam splitter, and 25 is an objective lens, which collects a light beam split into two parallel optical paths and irradiates it onto the surface of the disk 4, as shown in an enlarged view (b). Main beam spot 12 and left sub-beam spot 13
The a and the right sub-beam spot 13b are formed on the surface of the disk 4.

The phenomenon in which two sub-beam spots having a light intensity smaller than that of the main beam spot are formed by changing the intensity and phase distribution of the light beam entering the condenser lens. It is a phenomenon derived from a means for realizing a spot diameter smaller than a focused spot diameter formed when a uniform light beam is incident, and is known as a so-called super-resolution technique in the literature [Publisher: New Technology Communication, Issue Date: 1992. September, 2015 (O Plus E) No 154; 81
Pp. 83, Yutaka Yamanaka et al.].

At this time, the main beam spot 12 is formed at a required position on the groove portion 7 by the spot positioning means 10, and the left sub beam spot 13a and the right sub beam spot 13a are respectively formed on the land portions 6 adjacent on both sides of the main beam spot 12. The sub beam spot 13b is formed. The light intensity of the sub beam spots 13a and 13b formed at this time is generally smaller than that of the main beam spot 12.

The spot positioning means 10 comprises an optical head 20.
It can be realized by mechanically rotating and fixing the relative position of the whole and the disk 4, or by bypassing the optical system. The distance between the main beam spot 12 and the sub-beam spots 13a and 13b and the crosstalk can be adjusted by the distance between the two beams formed by the light beam splitting means 23 and the optical characteristics of the objective lens 25.

FIG. 6D shows a light quantity distribution chart of the focused spot on the disk. In the left figure, the horizontal axis shows the distance in the width direction of the recording groove, and the vertical axis shows the light quantity. In the right figure, the horizontal axis shows the distance in the tangential direction of the recording groove, and the vertical axis shows the amount of light. The light amount distribution diagram shown by the broken line is a light amount distribution diagram of a focused spot formed when a conventional single uniform light beam is focused by the objective lens 25.

On the other hand, the distribution chart shown by the solid line is the light quantity distribution chart of the three light beam spots formed on the disk 4 by the above-mentioned super-resolution technique, and the diameter of the main beam spot 12 is a broken line. The diameter of the recording spot is smaller than that of the main beam spot 12, and the left and right sub-beam spots 13a and 13b are smaller than the light amount of the main beam spot 12. It can be formed side by side. The present invention utilizes this feature.

The beam emitted from the laser beam generation source 21 (for example, TEM ₀₀ mode) is corrected by the beam shaper 22 to have a beam cross section of a perfect circular shape, and then is converted into a beam in the TEM ₁₀ mode by the light beam splitting means 23. The light beams are shaped into parallel light beams, are transmitted through the polarization beam splitter 24, and are condensed and irradiated onto the surface of the disk 4 by the objective lens 25.

At this time, the main beam spot 12 is moved by the spot positioning means 10 as shown in the enlarged view of FIG.
And the left sub-beam spot 13a and the right sub-beam spot 13b are aligned in a direction orthogonal to the recording groove 5 (radial direction of the magneto-optical disk), the main beam spot 12 is on the groove portion 7 and the left sub-beam spot is 13a and the right sub beam spot 13b are formed on the land portion 6 adjacent to the groove portion 7, respectively.

The main beam spot 12 thus formed on the recording groove 5 is, as described above, both sub-beam spots.
Since the amount of light is larger than that of 13a and 13b, only the groove portion 7 is heated above the Curie point to record the MO signal.
The land portions 6 adjacent to both sides of the groove portion 7 have an effect of suppressing the Curie point or less.

Further, the respective reflected lights of the main beam spot 12 and both sub-beam spots 13a and 13b formed on the recording groove 5 travel backward in the incident light path of the two beams with respect to the objective lens 25 and are reflected by the polarization beam splitter 24. The light beam reflected by the next polarization beam splitter 26 is guided to the MO signal detection system, and the transmitted light beam is guided to the ROM signal detection system and the servo signal detection system.

27 is a half-wave plate, 28 is a condenser lens, and two light beams incident on this are converted into P polarization and S polarization by a polarization beam splitter 29 via the condenser lens 28. While being separated, they are formed into a main beam spot and two sub-beam spots, which are incident on the light receiving elements 32 and 33 similarly to the phenomenon that occurs when the light is focused by the objective lens 25.

Reference numerals 30 and 31 denote apertures for masking two sub-beam spots unnecessary for detecting the MO signal, and 34.
Is a differential circuit, and the MO signal is obtained by the differential circuit 34 which takes the difference between the outputs of the light receiving elements 32 and 33.

Part of the two light beams transmitted through the polarization beam splitter 26 and guided to the half mirror 35 is transmitted and guided to the servo signal detector 46, and the other part is reflected and collected. Although separated in the orthogonal direction via the light lens 36 and the half mirror 37, the two light beams condensed by the condensing lens 36 are separated into the main beam spot and the two light beams as in the case of the condensing lens 28. It is formed in the sub beam spot and is incident on the light receiving elements 40 and 41.

38 and 39 are apertures for masking unnecessary portions for detecting only the right or left sub-beam spots, 42 and 43 are amplifiers for amplifying the outputs of the light receiving elements 40 and 41, respectively. , 45 are memories for temporarily storing the outputs of the amplifiers 42, 43, and the necessary ROM signals can be obtained simultaneously with the MO signals from the outputs of the memories 44, 45. That is, the reproduction speed can be increased up to 3 times as compared with the conventional one.

However, one rotation after the MO signal and the ROM signal adjacent thereto are simultaneously read and rotated once, it becomes possible to read the adjacent MO signal and the ROM signal adjacent thereto which has not been read previously by the tracking setting, The reading of these ROM signals can be solved by designating the storage address.

By using this device, the pitch of the recording groove 5 composed of the land portion 6 and the groove portion 7 can be made equal to the center position interval of the ROM signals sandwiching the MO signal, so that the recording in the radial direction of the disk 4 is performed. It is possible to improve the density.

Further, the reading of the main beam spot 12 is stopped and the ROM signal on the necessary side is read by using only one of the sub beam spots 13a and 13b, or the main beam spot 12 and the both sub beam spots 13a and 13b are read. It is possible to read the MO signal and the ROM signal on the necessary side at the same time by using one of 13b.

Further, using the above apparatus, the main beam spot
The reading of 12 is stopped, and the ROM signals on both sides can be read simultaneously by using both the sub-beam spots 13a and 13b. FIG. 2 is an explanatory view of the first embodiment of the present invention,
FIG. 3A is a block diagram, and FIG. 2B is an enlarged view of a split type light receiving element. In both figures, comparing this first embodiment with the configuration shown in FIG. 1, a laser beam generator 21 shown in FIG. 1 and FIG. The operations up to 36 and the servo signal detection unit 46 are the same.

Reference numeral 47 denotes a split type light receiving element, which is composed of a two split type light receiving element having a dead region having a required width in the central portion as shown in FIG. As in the case of the condenser lens 28, the two light beams incident on the condenser lens 36 have a left sub-beam spot Lb and a right sub-beam spot Lc sandwiching the main beam spot La on the surface of the split type light receiving element 47. Formed on.

At this time, the widths of the dead area and the light receiving area are formed in advance so that the main beam spot La can be formed in the dead area and the left and right sub beam spots Lb, Lc can be formed on the light receiving surfaces divided into two parts. To do.

Therefore, the ROM signals on both sides can be simultaneously read from the output of the split type light receiving element 47. 42 and 43 are the same as the amplifier shown in FIG. Reference numerals 48 and 49 are memories provided in a signal processing path for simultaneously reading out corresponding ROM signals by using both sub-beam spots Lb and Lc, and 50 is a signal transfer unit.

The memories 48 and 49 each have a recording capacity equal to or more than two rounds of the land portion 6 shown in FIG.
While the ROM signal stored in one cycle is being transferred to the next stage by the signal transfer unit 50, the ROM signal for the next one cycle is read. With this transfer method, ROM signals corresponding to both sub-beam spots Lb and Lc can be read at high speed.

3A and 3B are explanatory views of the second embodiment of the present invention. FIG. 3A is a block diagram and FIG. 3B is an enlarged view of a three-divided light receiving element. In both figures, this second embodiment is shown in FIG.
Compared with the configuration shown in FIG. 3, the operations from the laser beam generator 21 to the half-wave plate 27, the condenser lens 28, and the polarization beam splitter 29 via the polarization beam splitter 26 are the same. Reference numerals 51 and 52 are three-division type photo detectors as shown in FIG. 2 (b), which have output terminals A, B, C and D, respectively.
It is composed of three rows of light receiving elements having E and F.

The two light beams that have entered the condenser lens 28 are converged by the condenser lens 28 and are polarized by the polarization beam splitter 29.
It is divided into two, and each light beam is a three-division type photo detector
The left and right sub-beam spots Lb and Lc sandwich the main beam spot La on the surfaces 51 and 52.

At this time, taking the three-division type light receiving element 51 as an example,
(B) Output the main beam spot La to the output terminal B as shown in the figure.
And the widths of the light receiving regions of the respective light receiving elements are formed so that the left and right sub-beam spots Lb and Lc can be formed on the left and right light receiving elements having the output terminals A and C, respectively. Form in advance.

The MO signal can be reproduced by obtaining the output difference between the B terminal of the three-division type light receiving element 51 and the E terminal of the three-division type light receiving element 52 by the differential circuit 34. Similarly, the left ROM signal can be reproduced by obtaining the output sum of the A terminal and the D terminal by the synthesis amplifier 53, and the right ROM signal can be reproduced by obtaining the output sum of the C terminal and the F terminal by the synthesis amplifier 54. Become. Memories 48, 49 and signal transfer unit 50
The operation of is similar to that of FIG. The transmitted light of the polarization beam splitter 26 is guided to the servo signal detector 46.

In the case of the second embodiment configured as described above, the half mirror 35 to the signal transfer unit in the first embodiment is used.
Since there is no need for ROM signal reproduction paths up to 50, there is an effect that weight and simplification can be achieved.

Further, ROM signals can be detected from the land portions 6 adjacent to both sides of the groove portion 7 as a whole, and when the MO signal and the ROM signal are combined, the maximum read speed is three times as high as the conventional read speed. There is.

When the laser power is increased during recording, only the main beam spot 12 reaches the Curie point and only the MO signal can be recorded. At this time, since the temperature of the ROM does not rise to the Curie point and the recorded magnetization direction is not reversed because of the sub-beam spot, it does not affect the recording of the ROM signal.

[0053]

As is apparent from the above description, according to the present invention, the recording density in the radial direction is improved with respect to the ROM and the RAM in the magneto-optical disk with the double density partial ROM, and the switching speed of the tracking is significantly increased. The effect is that it can be raised to zero and crosstalk is almost eliminated.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is an explanatory diagram of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of the principle of a conventional astigmatism method.

FIG. 5: Servo circuit based on conventional astigmatism method

FIG. 6 is a diagram showing a relationship between a conventional disc and a recording signal.

[Explanation of symbols]

4 magneto-optical disk 5 recording groove 6 land section 7 Groove part 10 Spot positioning means 12 Main beam spot 13a Left vice beam spot 13b Right vice beam spot 20 optical head 21 Laser beam source 23 Light beam splitting means 25 Objective lens 48,49 memory

Continuation of front page (56) Reference JP-A-5-62275 (JP, A) JP-A-4-69818 (JP, A) JP-A-3-156729 (JP, A) JP-A-4-123319 (JP , A) JP 61-239447 (JP, A) JP 6-76362 (JP, A) JP 4-337530 (JP, A) JP 5-325309 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 11/10-11/105 G11B ^7/ 12-7/22

Claims (4)

(57) [Claims] 1. A plurality of rows of land portions (6) in which a read-only signal is recorded in a concavo-convex shape on the surface of a disk (4), and a recordable and reproducible signal interposed between the rows of the land portions is magneto-optically recorded. An optical head for concentrating and irradiating a light beam through the objective lens (25) along with the groove part (7) is provided with a concentric circular or spiral recording groove composed of the groove part (7) formed by the method. In the magneto-optical disk device having 20), a light beam generation source (21) for generating at least the light beam in the optical head (20) and a light beam emitted from the light beam generation source (21) are parallel to each other. A light beam splitting means (2
3), a main beam spot (12) formed at a required position on the groove part (7) when the two divided light beams are condensed by the objective lens (25), and the main beam spot. spot
The main beam spot (12) and the main beam spot (12) formed side by side in the radial direction of the disc (4) on the land (6) adjacent to each other on both sides of (12) Left side beam spot (13a) and right side beam spot (13a)
b) The spot positioning means (10) is provided, the main beam spot (12) is used during recording, and the main beam spot (12) and the both sub-beam spots are used during reproduction.
(13a, 13b) A magneto-optical disk device characterized in that the signals are simultaneously read from the reflected light from (13a, 13b). 2. The reading of the main beam spot (12) according to claim 1 is stopped, and the both sub-beam spots (13a, 13b)
Only one of the main beam spots (1
A magneto-optical recording / reproducing system characterized in that signals are simultaneously read out by using 2) and one of the sub beam spots (13a, 13b). 3. The reading of the main beam spot (12) according to claim 1 is stopped, and the both sub-beam spots (13a, 13b)
A magneto-optical recording / reproducing system characterized in that signals are read out simultaneously by using both of the above. 4. The both sub-beam spots (13) according to claim 3.
a, 13b) are used to simultaneously read the corresponding read-only signals on the signal processing paths, and each of the two land portions (6)
A memory (48, 49) with a recording capacity of more than one cycle is provided, and while the read-only signal accommodated in the first one cycle is transferred to the next stage, the read-only signal for the next one cycle is read. A magneto-optical recording / reproducing system characterized in that