JP2000276745A - Optical information recording and reproducing head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make obtainable stable servo signals and to make suppressible a T/F cross talk too, even though a magneto-optical disk having a different track pitch is set. SOLUTION: Reflected laser light beams from a disk, on which optical information is recorded, are bisected by a hologram 18 and defocuses in positive and negative directions concerning an optical axis directions are generated. Photodetecting elements 22a and 22b are arranged on an approximately same plane to receive the bisected light beams. Each of the pair of photodetecting elements has at least three photodetecting elements that are divided by dividing lines parallel to a tracking equivalent direction. Based on the outputs of these elements, focus error signals and the signals indicating wavelength fluctuation of the laser beams are detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing head device for recording, reproducing, and erasing information on a magneto-optical disk.

[0002]

2. Description of the Related Art Hitherto, there has been known an optical information recording / reproducing apparatus having a structure in which reflected light from an optical information recording medium such as a magneto-optical disk is divided and received by a pair of light receiving elements to obtain a servo signal. For example, an optical information recording / reproducing head device disclosed in Japanese Patent Application Laid-Open No. 7-326084 is configured as follows. The reflected laser light (return light) from the magneto-optical disk is separated into three light beams having different polarization directions by a Wollaston prism, one of which is used as a servo signal light beam, and the other two light beam is used as a data signal light beam. . Further, the hologram plate separates the servo signal light beam in a direction orthogonal to the light beam separation direction by the Wollaston prism, and causes these separated light beams to defocus in the positive and negative directions with respect to the optical axis direction. The servo signal light beam emitted from the hologram plate is incident on a pair of servo sensors via a condenser lens, and a servo signal is obtained based on the output of the servo sensor. In the optical information recording / reproducing head device, the data signal light beam split into two light beams is also split by the hologram plate in a direction orthogonal to the light beam separation direction by the Wollaston prism, and is positioned above and below the pair of servo sensors. It is configured to be incident on two pairs of data sensors and obtain a data signal (MO) based on the outputs of the data sensors.

FIG. 11 shows a signal processing section 52 of the above-mentioned conventional optical information recording / reproducing head device, and data sensors 50, 50, and 50.
It is a figure which shows the connection relation between 50 ', 50' and the servo sensors 51, 51 '. The light beam of the reflected laser light from the magneto-optical disk is split in a direction corresponding to the tracking direction (hereinafter, referred to as a tracking-equivalent direction). The servo sensors 51 and 51 'are respectively arranged at the center of the pair of data sensors 50 and at the center of the pair of data sensors 50'. Each of the servo sensors 51 and 51 ′ has a divided light receiving surface 51 a to 51, which is divided into three by a division line in which the direction of the division line is orthogonal to the direction corresponding to the tracking.
c, 51a 'to 51c'.

[0004] The signal processing section 52 is composed of an operation IC and includes adders 53 to 59 and subtractors 60 to 62. Each adder 53-58 and each sensor 50,51,5
0 'and 51' are connected as shown in FIG. 11, and each of the subtractors 60 to 62 and the adder 59 are connected as shown in FIG.
, And the focus error signal FES and the tracking error signal TE.
S, the data signal MO is generated, and the preformat signal RO is generated by the adder 59.

According to the above-described conventional optical information recording / reproducing head device, the focus error signal and the tracking error signal are hardly affected by the polarization state of the return light from the optical information recording medium (disk on which optical information is recorded). . Also, since there are relatively few adjustment parts and adjustment locations, the number of adjustment steps is also small. Further, since it is not necessary to electrically separate the signal into bands, an inexpensive general-purpose IC can be used, and an optical information recording / reproducing head device having a great cost advantage can be provided.

[0006]

By the way, in this type of optical information recording / reproducing head device, since the diffracted light component fluctuates every time the light spot crosses the track of the magneto-optical disk, the optical information is actually read. A focus error signal (focus error signal due to T / F crosstalk) is generated as if defocus had occurred even though the objective lens of the optical pickup was not defocused on the information recording surface of the magnetic disk. There was a problem. For this reason, in the conventional optical information recording / reproducing head device,
Adjustments have been made to minimize this T / F crosstalk when a magneto-optical disk having a predetermined track pitch is set.

However, in recent years, due to a demand for a large capacity of a magneto-optical disk, a disk having a small track pitch has been used. Normally, in an optical information recording / reproducing head device, the wavelength of a semiconductor laser (LD), the numerical aperture (NA) of an objective lens, and the effective diameter of the objective lens are constant.

However, the diffraction angle of the diffracted light reflected by the magneto-optical disk is different due to the shape of the groove of the track and the pitch of the groove. The size and intensity distribution of the diffraction component of the light spot received by the light receiving surface are different.

The diffraction angle θ of the m-th order diffracted light is sin θ = ± m ·, where λ is the wavelength of the laser light and Tp is the track pitch.
It is known that it is represented by λ / Tp.

Therefore, the tracking error signal generated by the servo sensor, the amplitude intensity of the focus error signal, and the sensitivity per unit change are affected by the change in the track pitch Tp, and the T / F crosstalk is also reduced by the track pitch Tp. Affected by change.

In the conventional optical information recording / reproducing head device, the directions of the dividing lines of the servo sensors 51 and 51 'are shown in FIG.
As shown in FIG. 12, since the direction is orthogonal to the direction corresponding to the tracking, when a magneto-optical disk having a different track pitch is set, each of the divided light receiving surfaces 51 a to 51
The positions of the ± 1st-order diffracted light components (portions indicated by oblique lines) 64 corresponding to c, 51a ′ to 51c ′ and overlapping the 0th-order light component 63 change. That is, each of the divided light receiving surfaces 51a to 51c,
The directions of the three dividing lines 51a 'to 51c' are orthogonal to the direction corresponding to the tracking, and only spots formed by the ± 1st-order diffracted light components 64 are each divided into two as shown in FIG. Therefore, for example, when a magneto-optical disk having a narrow track pitch is set and the interval between the ± 1st-order diffracted light components 64 is increased as shown by a broken line, ± 1st-order diffracted light received by each divided light receiving surface is obtained. Ingredient 64
Greatly changes, and the T / F crosstalk tends to occur.

In the conventional optical information recording / reproducing head device, when a magneto-optical disk having a predetermined track pitch is set, the T / F crosstalk is adjusted to be minimized. When a magneto-optical disk having a pitch is set in an optical information recording / reproducing head device, T / F crosstalk is not sufficiently canceled,
It may remain. However, in practice, it is desirable that T / F crosstalk be sufficiently suppressed even when magneto-optical disks having different track pitches are set in the optical information recording / reproducing head device.

Contrary to the above case, an optical information recording / reproducing head device which is adjusted so that T / F crosstalk is minimized for a high density (large capacity) magneto-optical disk having a narrow track pitch. Even when a low-density magneto-optical disk having a large track pitch is set, it is desirable that stable servo operation be performed and high-speed seeking be performed.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to obtain a stable servo signal even when a magneto-optical disk having a different track pitch is set.
An object of the present invention is to provide an optical information recording / reproducing head device capable of suppressing F crosstalk. Also, in the case of a sensor system in which a light beam is divided using a hologram plate to form a light spot on each of the two sensors, the diffraction angle fluctuates due to fluctuation in the wavelength of the light beam, and the distance between the light spots changes. The detection signal may be adversely affected. An object of the present invention is to provide an optical information recording / reproducing head device capable of suppressing the influence of such wavelength fluctuation.

[0015]

According to a first aspect of the present invention, a laser beam reflected from a disk on which optical information is recorded is divided into two parts, and each of the two divided light beams is divided into positive and negative directions with respect to the optical axis direction. A light beam splitting means for generating defocus; and a pair of light receiving elements for receiving the split light beam, wherein at least a focus error signal and a wavelength variation of the laser light are detected based on an output of the light receiving element. It is characterized by doing. According to the invention described in claim 2, it is preferable that each of the pair of light receiving elements has at least three light receiving elements divided by a dividing line parallel to a direction corresponding to a radial direction of the disk. . The light beam splitting means can be constituted by a diffraction element that splits the light beam in a direction corresponding to the tangential direction of the disk.

According to the third aspect of the present invention, the focus error signal can be corrected based on the wavelength fluctuation of the laser light.

According to a fourth aspect of the present invention, there is provided a light beam which divides a reflected laser beam from a disk on which optical information is recorded into two and generates a defocus in each of the two divided light beams in the positive and negative directions with respect to the optical axis direction. Splitting means, and a pair of light receiving elements for receiving the split light beam, wherein each of the pair of light receiving elements is divided into at least three by a dividing line parallel to a direction corresponding to a radial direction of the disk. And at least six light receiving elements divided into two by a dividing line parallel to a direction corresponding to the tangential direction of the disk, and based on outputs of the light receiving elements of the pair of light receiving elements. A focus error signal, a track error signal, and a wavelength variation of the laser beam. The light beam splitting means can be constituted by a diffraction element that splits the light beam in a direction corresponding to the tangential direction of the disk. Further, the pair of light receiving elements can be arranged on substantially the same plane (claim 6).

According to a seventh aspect of the present invention, the reflected laser light from the magneto-optical recording medium is reflected by a servo signal light beam traveling along an optical axis in a direction orthogonal to the tracking direction of the magneto-optical recording medium. In a first direction corresponding to
A light beam separating means for separating three light beams having different polarization directions from a pair of data signal light beams traveling in a symmetrical direction about the optical axis, and a second light beam in a second direction corresponding to the tracking direction of the magneto-optical recording medium; A diffraction element that divides the separated servo signal light beam and the pair of data signal light beams into two, and generates defocus in the positive and negative directions with respect to the optical axis direction for each of the two divided light beams; A pair of servo signal light receiving elements for receiving the split servo signal light beam, and a data signal light receiving element for receiving the two split data signal light beam; Is divided into two by a dividing line parallel to the first direction and divided into three by a dividing line in a direction parallel to the second direction. The equipped, l the output of the first line of one of the 6 divided light receiving surfaces of the pair of servo-receiving element k from left to right, a, g, 2 line output from the left,
b, h, and the output of the first row of the other six divided light receiving surfaces of the pair of servo light receiving elements is e, in order from the left,
When the outputs of the i, c, and second rows are f, j, and d in order from the left, (k + 1 + g + h + i + j)-(a + b + e + f + c +
d), a focus servo signal is generated, and {(k + 1) − (g + h)} + ｛(c + d) + (e +
f) A magneto-optical head device, wherein the focus servo signal is corrected based on｝.

[0019]

FIG. 1 is a perspective view showing the structure of an optical information recording / reproducing head according to the present invention. The optical information recording / reproducing head has a light source unit 1, an objective optical system 2, a signal detection unit 3, and a processing unit 4. The light source unit 1 includes a semiconductor laser 5 that generates divergent laser light, a collimator lens 6 that converts the divergent laser light emitted from the semiconductor laser 5 into a parallel light flux, and a cross section of the laser light that has been converted into a parallel light flux by the collimator lens 6. It has an anamorphic prism 7 for shaping the shape. The parallel light beam shaped by the anamorphic prism 7 is guided to the prism block 8.

The prism block 8 has an anamorphic prism 9, a condenser lens 10, and a right-angle prism 11. The condenser lens 10 is joined to the anamorphic prism 9. The anamorphic prism 9 further shapes the parallel light beam shaped by the anamorphic prism 7,
The light beam has a substantially circular cross section. The joint surface between the anamorphic prism 9 and the right-angle prism 11 is formed as a half mirror surface 12. Half mirror surface 12
Reflects a part of the parallel light flux emitted from the light source unit 11 toward the condenser lens 10. The condenser lens 10 converges a light beam on a light receiving element 13 for auto power control (APC). The output of the semiconductor laser 5 is automatically controlled based on the light receiving output of the light receiving element 13.

The objective optical system 2 is roughly composed of a rising mirror prism 14 and an objective lens 15. A parallel light beam having a circular cross section transmitted through the half mirror surface 12 is reflected upward (toward the magneto-optical disk 16) in the drawing by the rising mirror prism 14, and information is recorded on the magneto-optical disk 16 by the objective lens 15. Converged on the surface.

The magneto-optical disk 16 has concentric recording tracks formed on the back surface as an information recording surface, and is rotated by rotation driving means (not shown). FIG. 1 shows an orthogonal coordinate system including coordinate axes X'Y'Z '. X '
The axis indicates the radial direction of the disk 16 (that is, the tracking direction), the Y 'axis indicates the direction orthogonal to the tracking direction (tangential direction), and the Z' axis indicates the focusing direction (the optical axis direction of the objective lens 15). The objective lens 15 is provided together with the rising mirror prism 14 in an optical head (not shown) driven in the radial direction (tracking direction) X ′ of the magneto-optical disk 16.
The objective lens 15 is moved in the Z ′ direction by driving an actuator in the optical head, and is focused on the information recording surface of the magneto-optical disk 16.

The reflected laser beam reflected by the magneto-optical disk 16 passes through the objective lens 15 and is deflected by 90 degrees toward the prism block 8 by the rising mirror prism 14 and is reflected by the half mirror surface 12. 9
The light is deflected by 0 degrees and guided to the signal detection unit 3. Here, the signal detection unit 3 defines an XYZ orthogonal coordinate system. The X, Y, and Z axes in the signal detection unit 3 correspond to the X ', Y', and Z 'axes on the disk, respectively.

The signal detector 3 has a Wollaston prism 17 as a light beam splitting means, a hologram plate 18 as a light beam splitting means, a condenser lens 19, and a composite sensor 20. The Wollaston prism 17 is a crystalline polarizing element having birefringence. This Wollaston prism 17
As shown in FIG. 2, which is an enlarged view of the signal detection unit 3, an arrow P
The reflected laser beam L linearly polarized in the direction a is separated into three light beams A1, B1, and C1 having different deflection directions in a specific plane. Here, the reflected laser light from the magneto-optical disk is divided into three light beams having different polarization directions, (1) a light beam for a servo signal traveling along the optical axis O, and (2) a light beam for the magneto-optical disk centered on the optical axis O. The light beam is separated into a pair of data signal light beams separated in the tracking equivalent direction X corresponding to the above-described tracking direction X ′.

In order to obtain a predetermined light quantity division ratio, the Wollaston prism 17 sets the crystal axis direction of the first crystal material with respect to the tracking equivalent direction (X direction) when viewed from the light beam incident side. +45 degrees around 0 or-
Similarly, the second crystal material is inclined at −71.5 degrees or +71.5 degrees around the optical axis 0 with respect to the Y direction,
It is constituted by joining these two crystal materials. Note that the combination of crystal directions is not limited to this, and a desired light amount division ratio can be obtained by any other combination of crystal axis directions.

The light beam A1 is a polarization component having a polarization direction substantially parallel to the polarization direction Pa of the light beam L, and the light beam C1 is a polarization component having a polarization direction of a direction Pb substantially orthogonal to the polarization direction Pa of the light beam L. is there. The light beam B1 located between the light beam A1 and the light beam C1 has polarization components in both the Pa and Pb directions.

The hologram plate 18 is made of a phase-type non-polarization hologram element having no polarization characteristics, and is prepared by a method similar to the usual patterning. Originally, such a hologram was obtained by adding a reference wavefront to the wavefront of a light beam reflected by an object or the wavefront of a light beam transmitted through an object to cause interference, and recording the intensity of the interference fringes on a recording medium. A well-known defocus wavefront (spherical wave), tilt wavefront (tilted plane wave), and the like are recorded singly or in combination as an interference pattern.

FIG. 3 is a sectional view of the hologram plate 18.
The hologram plate 18 is formed by cutting out a part of a transparent base material 19 ′ having a large number of concavo-convex portions 18 a and 18 b which are concentric and have a rectangular cross section.

As shown in FIG. 4, concentric concave and convex portions 18 are formed.
The centers of curvature of a and 18b are located on the Y axis. That is, the concavo-convex portions 18a and 18b as arc-shaped patterns are formed of concentric defocus patterns of the transparent base material 19 '.
Any pattern shifted from the center in the Y-axis direction can be considered as a cutout pattern. The duty ratio between the adjacent concave portion 18a and convex portion 18b is approximately 1: 1.

However, the concave and convex portions 18a and 18b have a pitch Tp closer to the outer periphery of the concentric defocus pattern.
And a concentric pattern (defocusing wavefront generating function) in which the density becomes quadratic in density, and uneven portions 18a, 18a in the X-axis direction.
b and a linear pattern (tilt wavefront generation lateral power) having the same pitch.

That is, the hologram plate 18 can divide the incident light beam in the Y-axis direction and give positive and negative defocus to the divided light beam in the optical axis direction.

When the laser beam is properly converged on the information recording surface of the magneto-optical disk 16, the spots of the pair of beams split by the hologram plate 18 are formed to have substantially the same circular shape. Is set to This pair of light beams is generated by the separation and approach of the optical head with respect to the magneto-optical disk 16.
When the information recording surface is not properly focused, the shape of the spot formed on the pair of servo light receiving elements changes, so that the light receiving output changes. The received light output is subjected to a predetermined arithmetic processing described later to obtain a focus servo signal and a tracking servo signal.

Although the hologram plate 18 has a rectangular cross section here, it is not limited to this.
Other shapes such as a sine wave shape, a step wave shape, and a sawtooth shape may be used. By changing the groove depth Td shown in FIG. 3, a desired light amount ratio can be set.

The hologram plate 18 is divided into three light beams A 1, B 1, B 4 in the vertical direction (the direction corresponding to tracking: X direction) in FIG. 2 by the Wollaston prism 17.
C1 is divided into two light flux groups A2, B2, C in a direction orthogonal to this direction (tangential equivalent direction: Y direction).
2 and light flux groups A2 ', B2', C2 '
As shown in FIG. 5, the defocused light in the positive and negative directions with respect to the optical axis O direction (± first-order diffracted light transmitted through the lens 19) converges on the hologram plate side and the opposite side with respect to the sensor position. Defocus).
In FIG. 5, F1 is a focus position by + 1st-order diffracted light, and F2 is a focus position by -1st-order diffracted light. Here, the optical axis O refers to the central axis of the signal detection unit 3.

The light beam L is divided into six by the Wollaston prism 17 and the hologram plate 18. Of the six divided light beams, light beams A2 and A2 'and light beams C2 and C2
2 ′ is received by a data light receiving element described later, and a magneto-optical recording signal MO as a data signal and a preformat R
Used to generate O. The light beams B2 and B2 'are received by a servo light receiving element, which will be described later, and serve as a focus error signal FES and a tracking error signal TE as servo signals.
Used to generate S.

The light beams A2, A2 ', B2, B2', C2,
Since all the spots C2 'are defocused, when out of focus, the upper and lower spots have different diameters, and the left and right spots have substantially the same diameter. That is, when out of focus, the spot diameters of the light fluxes A2, B2, and C2 are substantially the same, and the spot diameters of the light fluxes A2 ', B2', and C2 'are also substantially the same, but the light fluxes A2, B2, and C2, Are different from the spot diameters of the light beams A2 ', B2', and C2 '.

As shown in FIG. 2, FIG. 5, and FIG. 6, the composite sensor 20
9, light receiving elements 21a, 21b, which respectively receive and convert the six-divided light fluxes into electric signals.
23a and 23b and servo light receiving elements 22a and 22b. These light receiving elements 21a, 21b, 23a, 2
The packages 3b, 22a, and 22b are housed in the package 20a and are compacted while being arranged on the same plane orthogonal to the light beam L.

Light receiving elements 21a and 21b, 22a and 22
b, 23a and 23b are each paired. The pair of servo light receiving elements 22a and 22b are divided into two by a dividing line in a direction orthogonal to the tracking equivalent direction (X direction) and divided into three by a dividing line in a direction parallel to the tracking direction. Surface (light receiving element). 1 of the light receiving element for servo 22a
The divided light receiving surfaces of the row are denoted by k, a, and g in order from the left in the figure, and the divided light receiving surfaces of the second row are denoted by l, b, and h in order from the left. E, i, c on the divided light receiving surfaces in order from the left f, i on the second line divided light receiving surfaces in order from the left
The symbols of j and d are assigned. Also, the light receiving element for data 21
m, n, P, q on the light receiving surfaces of a, 21b, 23a, 23b
Is assigned. Further, in the following description, the same reference numerals as those assigned to the respective light receiving surfaces are used for the output of each light receiving surface.

The output of the light receiving surface is input to the processing unit 4,
The processing unit 4 detects a focus error signal and a track error signal. In the optical information recording / reproducing head of this embodiment, the focus error signal is detected by the spot size method, and the track error signal is detected by the radial push-pull method.

As shown in FIG. 7, the processing section 4 has a first adder 24 to an eleventh adder 34 and a first subtractor 35 to a third subtractor 37. The first adder 24 adds the outputs i, h, and l, the second adder 25 adds the outputs j, k, and g,
An adder 26 adds the outputs a, f, and d, and a fourth adder 27
Adds the outputs b, c, and e. The fifth adder 28 outputs the first
The addition output (i + h + l) of the adder 24 and the second adder 25
And outputs the added output (i + h + l + j + k + g) to one input terminal of the first subtractor 35. The sixth adder 29 outputs the third adder 26
Is added to the sum output (a + f + d) of the fourth adder 27 and the sum output (a + f + d +) is obtained.
b + c + e) is output to the other input terminal of the first subtractor 35.

The first subtractor 35 generates a focus error signal FES by taking the difference between the added output (i + h + l + j + k + g) of the fifth adder 28 and the added output (a + f + d + b + c + e) of the sixth adder 29.

The seventh adder 30 adds the output (j + k + g) of the second adder 25 and the output (a +
f + d) and an addition output (j + k + g + a + f)
+ D) is output to one input terminal of the second subtractor 36, and the eighth adder 31 outputs the added output (i + h +) of the first adder 24.
1) and the addition output (b + c + e) of the fourth adder 27, and outputs the addition output (i + h + l + b + c + e) to the other input terminal of the second subtractor 36. Second subtractor 36
Is the addition output (j + k + g + a + f +) of the seventh adder 30
d) and the added output of the eighth adder 31 (i + b + 1 + b + c)
+ E), the tracking error signal TES is generated.

The ninth adder 32 is provided with the data light receiving element 23.
The outputs p and q of the a and b are added, and the tenth adder 33 adds the outputs m and n of the light receiving elements for data 21a and 21b. The eleventh adder 34 adds the addition output (p + q) of the ninth adder 32 and the addition output (m + n) of the tenth adder 33, and outputs a preformat signal RO. The third subtractor 37 adds the output of the ninth adder 32 (p + q).
The data signal MO is generated by taking the difference between the sum and the output (m + n) of the tenth adder 33.

According to the present invention, as shown in FIG. 8, the direction of the division line 65 related to the generation of the focus error signal FES is made parallel to the tracking equivalent direction (X direction), and each divided light receiving surface is Focus error signal FES by spot size method by devising wiring to signal processing unit 4
Therefore, even if the interval between the ± 1st-order diffracted light components 64 changes on the light receiving surface of the servo light receiving element 22a (22b) due to the different track pitch,
The spot formed by the ± 1st-order diffracted light component 64 is divided into three in parallel with the tracking direction, and the ± 1st-order diffracted light component received in the inner area (a, i, b, j) 64 and the outer area (k, l, e, f, g,
The ratio of the ± 1st-order diffracted light components 64 received at h, c, d) is less likely to change than in conventional sensors. Therefore, it is possible to suppress a change in the received light amount of the ± 1st-order diffracted light component 64 on each divided light receiving surface based on a change in the interval between the ± 1st-order diffracted light components 64 due to the difference in the track pitch. Therefore, T due to different track pitches
/ F crosstalk can be reduced as much as possible.

In FIG. 8, the diffracted light component 64 indicated by the solid line is
The position of the ± 1st-order diffracted light component 64 of the return light reflected by the magneto-optical disk having a wide track pitch is shown.
A diffracted light component 64 indicated by a broken line indicates a ± 1st-order diffracted light component 64 of the return light reflected by the magneto-optical disk having a narrow track pitch. The hatched lines indicate the change in the light receiving area of the ± 1st-order diffracted light component 64 on each divided light receiving surface, and ± 1
Even if the interval between the next diffracted light components 64 is widened, the rate of change of the light receiving area on each divided light receiving surface is smaller than in the conventional case.

The tracking error signal TES is divided into two parts by the push-pull method so that the direction of the dividing line 66 of the servo sensors 22a and 22b is in the direction (Y direction) orthogonal to the tracking equivalent direction X (Y direction). Has been generated. For this reason, the light receiving surfaces of the servo sensors 22a and 22b are divided into six as a whole, and the number of the divided light receiving surfaces is increased. A circuit configuration can be employed. Therefore, a general-purpose calculation IC can be used without using a special calculation IC (custom IC) for the sensors 22a and 22b, and the focus error signal and the tracking error signal can be generated without increasing the cost. Can be.

The direction in which the reflected laser light is separated into three light beams by the light beam separating means is defined as a direction orthogonal to the direction corresponding to tracking, and the direction in which the hologram plate 18 splits the light beam into two directions is defined as tracking direction. Since the configuration is adapted, the overall device can be made thinner.

In an optical information recording / reproducing head, the temperature of a laser diode as a light source changes due to a difference in power of a laser beam between data recording and reproducing, and for other reasons. May change. In the optical information recording / reproducing head configured as described above, when the wavelength of the laser beam changes, the angle of diffraction by the hologram plate 18 changes with the wavelength.
There is a problem that the interval between the spots on the pair of light receiving elements changes.

That is, since the distance between the beam spots S in FIG. 7 fluctuates (ie, the position of each beam spot shifts in a direction orthogonal to the direction corresponding to tracking) due to the fluctuation of the wavelength of the laser beam, the focusing signal FES A problem that an error occurs occurs.

FIG. 9 shows the focus error sensitivity (the relationship between the defocus amount and the intensity of the focusing error signal).
Is a graph showing for each variation width of the spot width. In the case of this example, the diameter of the spot S is approximately 200 μm,
The focus error sensitivity obtained when the width of the sensor area at the center of the divided sensor (the width in the short side direction of the areas a, b, i, and j in FIG. 7) is set to approximately １ ／ of the diameter of the spot S. Shown and used as a reference. As shown in the figure,
When the variation of the spot width is about 0 μm to 20 μm,
The intensity of the focusing error signal with respect to the defocus amount is substantially constant, but when the variation of the spot width exceeds 50 μm, the intensity of the focusing error signal with respect to a certain defocus amount becomes smaller than usual. In other words, if the wavelength of the laser beam fluctuates and the beam spot interval on the light receiving element changes, the focusing operation performed based on the focusing error signal becomes insufficient for the actual defocus amount and is completely defocused. The focus cannot be removed.

Further, when the variation width of the spot reaches 100 μm, the focusing signal intensity becomes almost 0 regardless of the defocus amount, and it becomes impossible to detect the defocus based on the focusing signal.

For this reason, in the present embodiment, the focus error signal FES is corrected by detecting a change in the spot width due to the wavelength change.

FIG. 9 shows an example of a circuit for correcting the focus error signal FES. Note that the circuit shown in FIG. 9 is also included in the processing unit 4 like the circuit in FIG. 7, but in order to avoid complicating the drawing, only the correction circuit is shown.

The correction circuit includes adders 38 to 41 and a subtractor 4
2 and 43 and an adder 44. The adder 38 adds the outputs k and l, the adder 39 adds the outputs g and h, the adder 40 adds the outputs c and d, and the adder 41 adds the outputs e and f to output. The subtractor 42 outputs the difference (k + 1) − (g + h) between the outputs of the adders 38 and 39, and the subtracter 43 outputs the difference (c + d) − (e + f) between the outputs of the adders 40 and 41.
Is output. Then, the adder 44 outputs the sum {(k + 1) − (g + h)} +
{(C + d)-(e + f)} is output. This adder 4
The output of No. 4 is a wavelength signal α indicating a change in the spot interval due to the wavelength change. The correction circuit further includes an amplifier 45. The amplifier 45 is an amplifier having an amplification factor represented by the function G (α) of the wavelength signal. When the focus error signal FES is input, the amplifier 45 reduces the focus error sensitivity with respect to the increase in the spot width shown in FIG. The corrected focus error signal CFES amplified so as to cancel out is output.

The variation of the spot interval shown in FIG.
This is an example, and this value differs depending on the configuration of the apparatus, and the focus error signal corrected by the present invention is not limited to the one corresponding to the fluctuation width of the spot interval shown in FIG.

[0056]

As described above, according to the present invention, the servo sensor is divided into three so that the direction of the dividing line of the servo sensor involved in the generation of the focus error signal is parallel to the direction corresponding to the tracking. The servo sensor involved in the generation of the tracking error signal is divided into two parts so that the direction of the dividing line of the servo sensor is orthogonal to the direction corresponding to the tracking, and the focus error sensitivity is deteriorated due to wavelength fluctuation. The configuration is such that the focus error signal is corrected so as to cancel out. Therefore, even when magneto-optical disks having different track pitches are mounted, T / F crosstalk can be suppressed and a stable servo signal can be obtained. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an essential configuration of an optical information recording / reproducing head device according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a signal detector of the optical information recording / reproducing head device shown in FIG.

FIG. 3 is an enlarged sectional view partially showing a section of the hologram plate shown in FIG. 1;

FIG. 4 is a plan view of the hologram plate shown in FIG.

FIG. 5 is a side view of the signal detection unit shown in FIG. 2 as viewed from the side.

FIG. 6 is a plan view of the signal detection unit shown in FIG. 2 as viewed from above.

FIG. 7 is a circuit diagram showing an open connection between a light receiving element and a processing unit.

FIG. 8 is an explanatory diagram showing a beam spot formed by a zero-order light component and ± 1st-order diffracted light components on a light receiving element for servo.

FIG. 9 is a graph showing focus error sensitivity.

FIG. 10 is a circuit diagram showing a connection relationship between a light receiving element and a correction circuit.

FIG. 11 is a circuit diagram showing a connection relationship between a conventional sensor and a double processing unit.

FIG. 12 is a plan view for explaining a direction of a dividing line of a conventional servo sensor.

[Explanation of symbols]

 Reference numeral 16: magneto-optical disk 17: Wollaston prism (light beam separating means) 18: hologram plate (diffraction element) L: reflected laser light

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 11/105 556 G11B 11/105 556B

Claims (7)

[Claims] 1. A light beam splitting means for splitting a reflected laser beam from a disk on which optical information is recorded into two, and generating a defocus in each of the split light beams in the positive and negative directions with respect to the optical axis direction. An optical information recording / reproducing head device, comprising: a pair of light receiving elements for receiving the light beam thus detected; and detecting at least a focus error signal and a wavelength variation of the laser light based on an output of the light receiving element. 2. The device according to claim 1, wherein each of the pair of light receiving elements has at least three light receiving elements divided by a dividing line parallel to a direction corresponding to a radial direction of the disk. The optical information recording / reproducing head device according to the above. 3. The optical information recording / reproducing head device according to claim 1, further comprising a correction unit configured to correct the focus error signal based on a wavelength variation of the laser light. 4. A light beam splitting means for splitting a reflected laser beam from a disk on which optical information is recorded into two and generating a defocus in each of the split light beams in the positive and negative directions with respect to the optical axis direction; And a pair of light receiving elements for receiving the light beam, wherein each of the pair of light receiving elements is divided into at least three parts by a dividing line parallel to a direction corresponding to a radial direction of the disk, and a tangent of the disk is provided. And at least six light receiving elements divided into two by a dividing line parallel to the direction corresponding to the central direction, and a focus error signal and a track error based on outputs of the light receiving elements of the pair of light receiving elements. An optical information recording / reproducing head device for detecting a signal and a wavelength variation of the laser beam. 5. The optical information recording / reproducing apparatus according to claim 2, wherein the light beam splitting means is a diffraction element that splits a light beam in a direction corresponding to a tangential direction of the disk. head. 6. The light receiving element according to claim 2, wherein said pair of light receiving elements are provided on substantially the same plane.
An optical information recording / reproducing device according to any one of the above. 7. A laser beam reflected from a magneto-optical recording medium, the beam of the servo signal traveling along the optical axis, and the optical axis in a first direction corresponding to the tracking direction of the magneto-optical recording medium. A beam separating means for separating a pair of data signal beams traveling in a symmetrical direction from the center into three beams having different polarization directions, and a second direction corresponding to a direction orthogonal to the tracking direction of the magneto-optical recording medium. A diffraction element that divides the separated servo signal light beam and the pair of data signal light beams into two, and generates defocus in the positive and negative directions with respect to the optical axis direction for each of the two divided light beams; A pair of servo signal light-receiving elements for receiving the split servo signal light beam; and a data signal light-receiving element for receiving the two split data signal light beam. The pair of servo light receiving elements is divided into three by a dividing line parallel to the first direction and divided into two by a dividing line in a direction parallel to the second direction. A divided light receiving surface of the pair of servo light receiving elements, the output of the first row of one of the six divided light receiving surfaces of the pair of servo light receiving elements is k, a, and g in order from the left, and the output of the second row is l in order from the left. b, h, the outputs of the first row of the other six divided light receiving surfaces of the pair of servo light receiving elements are e, i, c in order from the left, and the outputs of the second row are f, j in order from the left. , D, (k + l + g + h + i + j)-(a + b + e + f + c +
d), a focus servo signal is generated, and {(k + 1) − (g + h)} + ｛(c + d) + (e +
f) A magneto-optical head device, wherein the focus servo signal is corrected based on｝.