JPH0622060B2 - Optical information processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An apparatus for magnetically writing data to or reading data from a magneto-optical disk by utilizing light and magnetism,
A first optical system for writing and reading and a second optical system for error detection for aligning the spot of the first optical system with the guide groove of the magneto-optical disk are provided. In any of these optical systems, an optical waveguide formed on a substrate, a light source for introducing laser light into the optical waveguide, and lens means for emitting light propagating through the optical waveguide obliquely upward and converging it two-dimensionally Is equipped with. The first optical system further includes at least two light receiving elements that receive reflected light from obliquely above, and an analyzer in which the principal axes of the light receiving elements are offset from each other by 90 °. The second optical system is provided with means for receiving light reflected obliquely from above and detecting tracking error and focusing error.

BACKGROUND OF THE INVENTION (1) Technical Field The present invention is capable of recording, reproducing, and erasing extremely high-density data, and writing (recording, erasing) and / or writing data on a magneto-optical disk which is expected to be put to practical use in the future. Further, the present invention relates to an optical information processing device for reading (reproducing).

(2) Prior art Magneto-optical discs have been actively researched because they have the characteristic of being able to freely write / read data, which has been difficult with optical discs. The device is being prototyped.

The recording principle of the magneto-optical disk is as follows. A recording medium such as a magneto-optical disk is irradiated with light to locally raise its temperature, and at the same time, magnetism is applied from the outside to change the direction of magnetization of the local portion. When the laser beam is focused, the area where the temperature is raised can be set to an extremely small range of about 1 μm in diameter, which enables high-density recording. The magnetic field required for magnetic recording generally decreases as the temperature of the recording medium increases, and recording is possible even with an extremely weak magnetic field.

At present, two methods are considered for recording and erasing. One is a magnetic field modulation method, which constantly irradiates a recording medium with laser light and changes the applied magnetic field according to the data to be recorded. The other is a light modulation method in which a direct-current magnetic field is always applied and the laser light to be applied is blinked in accordance with data.

It is said that the optical reproduction method includes a direct light reproduction method and an indirect light reproduction method. The direct light reproduction method utilizes that the recording location is directly irradiated with linearly polarized light and the polarization direction of the reflected light (or transmitted light) is rotated by the magneto-optical effect. The indirect light reproduction method is a method in which a recording pattern is transferred to a magnetic thin film and then this is read out by light.

In any case, the magneto-optical recording / reproducing device which has been trial-produced up to now, especially the reproducing portion thereof, has an isolator optical system for separating the light irradiated onto the optical disc and the reflected light from the optical disc, and the light irradiated onto the optical disc at 1 μm. It is equipped with a beam focusing optical system that focuses on a spot of a diameter, an error detection optical system for detecting focusing errors and tracking errors, etc. These optical systems include semiconductor lasers as light sources and various lenses. , Prisms, diffraction grating, mirror, quarter-wave plate, photo diode,
Since it is configured by appropriately combining elements such as a polarizer and an analyzer, the optical system is complicated and alignment of the optical axis is troublesome, and the optical axis is easily displaced due to vibration, the number of parts is large, and it takes time to assemble. However, since the optical parts are expensive, the cost is high as a whole, the optical parts are large, the optical pickup device is also large, and a mechanism for holding the optical parts is required. There is.

SUMMARY OF THE INVENTION (1) Object of the Invention An object of the present invention is to provide an optical information processing apparatus that is small in size, lightweight, and has a simple structure.

(2) Configuration and Effect of the Invention The optical information processing device according to the present invention is a device for writing data to and / or reading data from the magneto-optical disk. A first optical system for projecting a focused light spot on the magneto-optical disk and receiving the reflected light, and for causing the light spot of the first optical system to follow the guide groove of the magneto-optical disk A second optical system for detecting an error, and the first optical system includes an optical waveguide formed on the substrate, a light source of laser light introduced into the optical waveguide, an optical waveguide formed on the optical waveguide, Lens means for emitting light propagating in the waveguide obliquely upward and condensing it two-dimensionally, light receiving means having at least two light receiving elements for receiving light reflected obliquely above, and the above light receiving element A second optical system is provided with an analyzer whose main axes are offset from each other by 90 °, an optical waveguide formed on the substrate, a light source of laser light introduced into the optical waveguide, and an optical waveguide formed on the optical waveguide. It is characterized in that it is provided with lens means for emitting light propagating through the optical waveguide obliquely upward and condensing it two-dimensionally, and means for receiving light reflected from obliquely upward.

The present invention is applicable to both the magnetic field modulation method and the optical modulation method described above, and can also be applied to the direct optical reproduction method. It goes without saying that a coil for applying a magnetic field is provided for recording.

In the present invention, the lens, the prism, the diffraction grating, the mirror, the quarter-wave plate and the like as the optical parts are not used, so that the size and weight of the device can be reduced.
In particular, both the first optical system for writing and reading and the second optical system for error detection are configured to emit laser light obliquely upward from the optical waveguide and receive reflected light from obliquely upward. Therefore, the isolator optical system can be omitted.

Description of Embodiments (1) Outline of Head Configuration FIG. 1 shows an example of the configuration of a magneto-optical writing / reading head 9. Only the optical system is shown in this figure, and the coils that generate the magnetic field necessary for magneto-optical writing are not shown.

First, an optical system (second optical system) for detecting focusing error and tracking error will be described.

A semiconductor laser 13 as a light source and a substrate 11 are mounted on a base 10.
Are placed and fixed.

The substrate 11, for example Si crystal is used, after the SiO ₂ buffer layer is formed on the substrate 11 upper surface by vapor deposition or sputtering of the substrate 11 of the top Si thermal oxidation or SiO _2, for example, sputtering a glass such as Corning 7059 By doing so, the optical waveguide layer 12 is formed. The semiconductor laser 13 is optically coupled to one end of the optical waveguide layer 12 by a butt edge coupling method. Laser light emitted from the semiconductor laser 13 enters and propagates in this optical waveguide layer 12. Optical waveguide layer
12 on top of collimating lens 14, coupling
The lens 15, the leak light detecting element 16, the leak light blocking groove 17, and the light receiving section 20 are provided in this order arrangement. The collimating lens 14 is for converting a laser beam having a spread emitted from the semiconductor laser 13 into parallel light.
The collimating lens includes a Fresnel lens as shown and a Bragg grating.
There are lenses, Reneburg lenses, geodesic lenses, etc. The coupling lens 15 emits the laser light propagating through the optical waveguide layer 12 obliquely upward, and
The light is focused two-dimensionally (focusing). This coupling lens is called a two-dimensional focusing grating coupler.
Two lenses have a light emitting function and a two-dimensional condensing function. This is composed of an arc-shaped grating whose period (interval) becomes smaller as it goes in the traveling direction of light. A point P indicates that the emitted laser light is condensed to form a spot (about 1 μm diameter). This laser spot is at the same point as a laser spot for reading and writing which will be described later, and the head 9 is arranged so that this point P is located on the information recording surface of the magneto-optical disk, especially in its guide groove. It

The light receiving section 20 is for receiving the reflected light from the surface of the magneto-optical disk, and is arranged at a position where the light reflected obliquely downward from the position of the laser spot P can be received.

The light receiving section 20 is composed of four independent light receiving elements 21 to 24.
The light receiving elements 21 and 22 are arranged adjacent to the center, and other light receiving elements 23 and 24 are provided in front of and behind these light receiving elements 21 and 22, respectively. The portions where the light receiving elements 21 to 24 are to be formed are covered with a mask when the buffer layer and the optical waveguide layer 12 are formed, and the formation of the optical waveguide layer 12 is excluded.
Then, the light receiving elements 21 to 24 are constructed by diffusing impurities in this portion to form a PN junction (photodiode). Output signals of the light receiving elements 21 to 24 are taken out by a wiring pattern (not shown) formed on the substrate 11.

Not all of the light propagating through the optical waveguide layer 12 is emitted (air coupled) by the coupling lens 15, but is not emitted and passes through the position of the lens 15 and leaks toward the light receiving unit 20. There is also light. The leaked light detection element 16 detects the intensity of this leaked light. Since the intensity fluctuation of the light propagating through the optical waveguide layer 12 also appears as the intensity fluctuation of the leaked light, the intensity of the light propagating through the optical waveguide layer 12 is indirectly detected by detecting the intensity of the leaked light. The detected intensity signal is fed back to the drive circuit (not shown) of the semiconductor laser 13 to stabilize the output light of the semiconductor laser 13. Amorphous silicon as the sensing element 16
(a-Si), CdTe, CdS or the like is used, and is directly formed on the optical waveguide layer 12 by a CVD method, a vapor deposition method, a sputtering method or the like. The detection signal of the detection element 16 is taken out to the outside by a wiring pattern (not shown) formed on the optical waveguide layer 12.

Not all the leaked light from the coupling lens 15 is consumed by the detection element 16. Light receiving part 20 is the same substrate 11
Since it is formed in the above, if there is leaked light that passes through the detecting element 16, it may be detected.

The leak light blocking groove 17 is provided between the detecting element 16 and the light receiving section 20, and propagates the light passing through the position of the detecting element 16 toward the light receiving section 20 to the light on the wall surface of the groove 17. It also has the role of preventing it by reflection and attenuation. This groove 17 is formed on the substrate by ion beam processing, electron beam processing or laser processing.
It may be directly formed on the optical waveguide layer 12 of 11. The length of the groove 17 is larger than the width of the propagating light. The depth of the groove 17 may be about the thickness of the optical waveguide layer 12.

An optical system (first optical system) for writing and reading data on the magneto-optical disk is also the same as the above-mentioned optical system.
Semiconductor laser 33, collimating lens 34, coupling lens 35, leak light detection element 36, leak light blocking groove
It has 17 and a light receiving section 40. The emitted light from the semiconductor laser 33 is collimated by the collimating lens 34, then emitted from the coupling lens 35 into the air, and focused on the point P described above. Then, the reflected light from the magnetic recording surface of the magneto-optical disk is received by the light receiving section 40. The roles of the light detecting element 36 and the blocking groove 37 are the same as those of the same 16 and 17.

A polarizer piece 38 is attached on the coupling lens 35. The polarizer piece 38 converts the light emitted from the coupling lens 35 into linearly polarized light.

The light receiving section 40 has a large number of light receiving elements 41a and 42a (see FIG. 2). These light receiving elements 41a and 42a are also the light receiving elements 2
It is made in the same way as 1-24. These light receiving elements 4
Analyzer pieces 41 and 42 are attached on the 1a and 42a, respectively. The analyzer pieces 41 and 42 are arranged such that their principal axes are offset from each other by 90 °. Further, analyzer pieces 41 and 42 arranged so as to be offset from each other by 90 ° are alternately provided.

In the above embodiment, the optical waveguide layer 12 is not formed in the light receiving elements 21 to 24, 41a, 42a, but C is directly formed on the optical waveguide layer 12.
Amorphous silicon (a
-Si) may be formed. Besides, CdTe, CdS, etc. can be used as the material of the light receiving element.

The coupling lens has a Fresnel type grating lens having a function of focusing parallel light on the optical waveguide layer 12, and a function of emitting light propagating through the optical waveguide layer 12 into the air and condensing it in a straight line. It can also be configured by combining with a chirp type grating coupler. The grating coupler is a linear grating whose period (interval) decreases in the traveling direction of light. If the focal point of the grating lens and the focal point of the grating coupler are at the same point P, the light emitted from the optical waveguide layer 12 is focused at one point P.

In FIG. 1, an optical system for emitting light into the air and a light receiving optical system are provided on one substrate, but these optical systems may be provided on separate substrates. Further, the optical waveguide layer may not be formed on the substrate or the substrate portion on which the light receiving optical system is provided.

In addition, nGaAs crystal is used as the substrate, and AlG is
An optical waveguide layer of pGaAs may be formed via the aAs layer, and the semiconductor laser may be formed integrally with the substrate.

Further, as the optical system for error detection, the one-beam system is adopted in FIG. 1, but the two-beam system and the three-beam system may be used. In this case, the light collimated by the collimating lens 14 is split into two or three light beams, which are independently emitted into the air by two or three coupling lenses and placed at separate positions. Just collect it. The spots of the light beam 2 or 3 are formed in the vicinity of the spot P of the optical system for writing and reading. An example of a three-beam optical system is described in, for example, Japanese Patent Application No. 59-184777. With this optical system, of course, focusing error and tracking error can be detected.

(2) Principles of writing and reading Writing of data on the magneto-optical disk depends on a magnetic field modulation method or an optical modulation method. In this case, laser spot P
A coil is arranged in the vicinity of.

The reading of data from the magneto-optical disk depends on the direct optical reproduction method.

Arrows a and b in FIG. 4 indicate the principal axis directions of the analyzer pieces 41 and 42. Thus, the directions of the principal axes of the analyzer pieces 41, 42 differ by 90 °.

FIG. 3 shows an example of the reading circuit. Output signal of the light receiving element 41a below one of the analyzer pieces 41 (terminals A1 to A5)
Are input to the adder circuit 51 and are added to each other. Output signal of the light receiving element 42a under the other analyzer piece 42 (terminals B1 to B5)
Are input to the adder circuit 52 and are added to each other. The outputs of these adder circuits 51 and 52 are sent to the differential amplification circuit 53 and the difference between them is calculated.

The light emitted from the coupling lens 35 and converted into linearly polarized light by the polarizer 38 strikes the magneto-optical disk surface and is reflected, and is detected by the light receiving elements 41a and 42a through the analyzer pieces 41 and 42. Thick solid line arrow c in FIG. 5 (A)
Indicates the polarization direction of the light reflected by the portion of the magneto-optical disk where no data is recorded. It is assumed that the polarization direction of this reflected light is inclined ± 45 ° with respect to the principal axis directions of the analyzer pieces 41, 42. In this case, the magnitudes of the outputs of the adder circuits 51 and 52 are equal, and this is set as Io. When the light hits the magnetic recording portion of the magneto-optical disk, the polarization plane of the reflected light rotates by a certain angle θ due to the magneto-optical effect (Kerr effect). The polarization direction of the reflected light at this time is shown by an arrow c in FIG. 5 (B). The outputs of the adder circuits 51 and 52 at this time are (Io
+ Aθ), (Io−Aθ). Here, A is a constant. Therefore, the output signal of the differential amplification circuit 53 becomes 2Aθ. This is a read signal, and the magnitude of this signal is proportional to the magnitude of the signal recorded on the magneto-optical disk.

(3) Detection of Focusing Error On the information recording surface of the magneto-optical disk, a guide groove is formed along the track as a guide for writing and reading data. FIG. 6 shows the positional relationship between the magneto-optical disk 81 and the writing / reading head 9 by cutting the magneto-optical disk 81 along its circumferential direction. Coupling·
The laser light emitted from the lens 15 is reflected by the information recording surface of the magneto-optical disk 81 (the portion including the guide groove 82 in FIG. 6) and is received by the light receiving section 20. In FIG. 6, the light receiving elements 21 to 24 are illustrated as slightly projecting for easier understanding. FIG. 7 shows the range in which the reflected light from the magneto-optical disk 81 irradiates the light receiving section 20.

In the magneto-optical disk 81 and the guide groove 82 shown by solid lines in FIG. 6, the distance between the disk 81 and the head 9 is optimum, and the outgoing light is correctly focused on the disk 81. It shows the situation. The irradiation area of the reflected light in the light receiving unit 20 at this time is indicated by Q. This irradiation area Q is located on the central light receiving elements 21 and 22, and the other light receiving elements 23 and 24 do not receive the reflected light.

The position of the disk 81 when the distance between the magneto-optical disk 81 and the head 9 is relatively large or small and proper focusing is not performed is shown by a chain line in FIG. When the distance between the disk 81 and the head 9 becomes relatively small (displacement of -Δd), the irradiation area of reflected light (represented by Q1) is closer to the light receiving element 23 side.
Since the light receiving element 23 is connected to the negative side of the differential amplifier 71 and the light receiving element 24 is connected to the positive side thereof, the output of the differential amplifier 71 shows a negative value in this case, and this value is the displacement amount − It represents the size of Δd.

When the distance between the disk 81 and the head 9 is relatively large (displacement of + Δd), the reflected light irradiation area (Q
2) is closer to the light receiving element 24 side. The output of the differential amplifier 71 shows a positive value, and this value is the displacement amount + Δd.
Represents

In this way, whether the focusing of the light beam emitted from the head 9 is proper, and if a focusing error occurs, the direction and magnitude of the error are detected from the output of the differential amplifier 71. The output of the differential amplifier 71 is zero when there is no focusing error.

(4) Detection of tracking error FIG. 8 shows the guide groove 82 formed in the magneto-optical disk 81 and the light receiving elements 21 and 22 of the light receiving section 20 arranged on the same plane. FIG. 3 is a diagram showing the light receiving elements 21 and 22 as seen through the magneto-optical disk 81 in its surface direction. Differential amplifier 72
Are illustrated for the purpose of clarifying the electrical connection relationship with the light receiving elements 21 and 22. Figure 8 (A) shows the laser beam
It shows that the spot P is accurately positioned on the center of the track (guide groove 82) in the width direction. FIGS. 8 (B) and 8 (C) show how the spot P is slightly deviated to the left and right of the track (guide groove 82), and a tracking error occurs. In each case, it is assumed that the object is properly focused.

The laser spot P hits the information recording surface of the magneto-optical disk 81, and the intensity of the reflected light is modulated by the existence of the guide groove 82. That is, the presence of the guide groove 82 reduces the light intensity received by the light receiving unit 20.

The light receiving elements 21 and 22 are divided into left and right with the optical axis as a boundary. When the center of the laser spot P coincides with the center of the guide groove 82 in the width direction, the amounts of light received by the light receiving elements 21 and 22 are equal, and the output of the differential amplifier 72 is zero.

As shown in FIG. 8 (B), the laser spot P has a guide groove 8
When it is shifted to the left side of 2, the amount of light received by the light receiving element 21 is larger, and a positive output is generated from the differential amplifier 72. On the contrary, as shown in FIG. 8 (C), when the laser spot P shifts to the right of the guide groove 82, a negative output is produced in the differential amplifier 72.

In this way, whether the beam spot P is exactly along the track of the disk 81 due to the output of the differential amplifier 72, or whether a tracking error has occurred, that is, on the left,
It is detected which of the errors is offset to the right.

(5) Focusing and tracking drive mechanism FIGS. 9 to 11 show the focusing drive mechanism and the tracking drive mechanism.

A support member 101 is erected on one end of the support plate 100. Both lower ends of the support member 101 are notched (reference numeral 10).
2). The movable member 103 is located above the other end of the support plate 100. Four leaf springs 12 that can be elastically bent in the vertical direction 12
One end of 1,122 has both upper and lower cutouts of the support member 101.
It is fixed to 102, and the other end is fixed to both sides of the upper end and the lower end of the movable member 103. Therefore, the movable member 103 is supported by the support member 101 via the leaf springs 121 and 122 so as to be movable in the vertical direction.

The stage 110 on which the head 9 is placed has a rectangular frame 112,
It is composed of both legs 114 and 115 extending downward from both ends of the rectangular frame 112 and a central leg 113 extending downward from a central portion of the rectangular frame 112. The head 9 is placed and fixed on the rectangular frame 112. One end of each of the four leaf springs 131 that can be elastically bent in the lateral direction is fixed to both upper and lower portions of the movable member 103, and the other end is fixed to both upper and lower portions of the central leg 113 of the stage 110. The stage 110 is movably supported in the lateral direction (corresponding to the left-right direction in FIG. 8) via these leaf springs 131. Therefore, the stage 110 is movable in the vertical direction (focusing) and the horizontal direction (tracking).

Support plate 100, support member 101, movable member 103, and stage 1
Reference numeral 10 is made of a non-magnetic material such as plastic.

The yokes 104 and 10 are provided on the inner surfaces of the support member 101 and the movable member 103.
5 is fixed. The yoke 104 is composed of a vertical portion 104a fixed to the support member 101, another vertical portion 104b spaced apart from the vertical portion 104a, and a horizontal portion connecting both of these portions 104a, 104b at their lower ends. It is configured. The yoke 105 also has exactly the same shape as the yoke 104, and includes two vertical portions 105a and 105b that are separated by a certain distance.

Permanent magnets 106 having an S-pole on the inner surface side are fixed to the inner surfaces of the vertical portions 104a and 105a of the yokes 104 and 105, respectively. Then, between the other vertical portions 104b and 105b of the yokes 104 and 105 and the permanent magnet 106, the stage
The legs 114 and 115 of the 110 are inserted without touching them.

A focusing drive coil 123 is horizontally wound around both legs 114 and 115 of the stage 110. Further, a tracking drive coil 133 having a portion facing the vertical direction in a portion facing the permanent magnet 106 is wound around a part of the legs 114, 115.

The focusing drive mechanism is best shown in FIG. The magnetic flux H generated from the permanent magnet 106 is directed to the vertical portions 104b and 105b of the yokes 104 and 105, respectively, as shown by the chain line. When a drive current is applied to the coil 123 arranged horizontally across the magnetic field in the direction toward the paper surface in FIG. 10, a force Ff directed upward is generated. This force Ff moves the stage 110 upward. The amount of movement of the stage 110 can be adjusted by the magnitude of the current passed through the coil 123. Therefore, focusing control can be performed by switching the direction of the drive current according to the output signal of the differential amplifier 71 described above, and adjusting the magnitude of the current or turning the current on and off.

The tracking drive mechanism is best represented in FIG. When a drive current is applied to a portion of the coil 133 which is disposed across the magnetic field H in the vertical direction, for example, in the direction toward the paper surface in FIG. 11 (downward in FIG. 9), the drive current is moved upward in FIG. A facing force (a lateral force in FIG. 9) Ft is generated, and the stage 110 moves in the same direction. Tracking control can be performed by turning on and off the current flowing through the coil 133 according to the output signal of the differential amplifier 72 described above, and adjusting the direction of the current and, if necessary, its magnitude.

[Brief description of drawings]

FIG. 1 is a perspective view showing a magneto-optical writing / reading head. FIG. 2 is a plan view showing the structure of the reading light receiving section. FIG. 3 shows the reading circuit. FIG. 4 is a diagram showing the direction of the principal axis of the analyzer piece, and FIG. 5 is a diagram showing the reference polarization direction of the reflected light and the polarization direction rotated by the magneto-optical effect. FIG. 6 is a sectional view showing the positional relationship between the magneto-optical disk and the magneto-optical writing / reading head. FIG. 7 is a diagram showing the principle of detecting a focusing error on the light receiving portion. FIG. 8 is a diagram showing the principle of tracking error detection. 9 to 11 show a focusing and tracking driving mechanism. FIG. 9 is a perspective view, FIG. 10 is a sectional view taken along line XX of FIG. 9, and FIG. 11 shows a head removed. FIG. 9 ... Magneto-optical writing / reading head, 11 ... Substrate, 12 ... Optical waveguide, 13,33 ... Semiconductor laser, 14,34 ... Collimating lens, 15,35 ... Coupling lens, 20 , 40 …… light receiving part, 21 to 24,41a, 42a …… light receiving element, 41,42 …… analyzer piece, 104,105 …… yoke, 106 …… permanent magnet, 110 …… stage, 121,122,131 …… leaf spring, 123 …… Focusing drive coil, 133 …… Tracking drive coil.

Claims (1)

[Claims] 1. An optical information processing apparatus for writing data to a magneto-optical disk and / or reading data from a magneto-optical disk, wherein a focus is placed on the magneto-optical disk for writing and / or reading. A first optical system that projects a connecting light spot and receives the reflected light, and a second optical system that detects an error so that the light spot of the first optical system follows the guide groove of the magneto-optical disk. And the first optical system has an optical waveguide formed on the substrate, a light source of laser light introduced into the optical waveguide, and light formed on the optical waveguide and propagating through the optical waveguide obliquely upward. Lens means for converging and two-dimensionally converging, light receiving means having at least two light receiving elements for receiving light reflected obliquely from above, and the main axes are arranged on the light receiving element so that their main axes are offset from each other by 90 °. The second optical system is provided with an optical analyzer formed on the substrate, a second optical system is provided with an optical waveguide formed on the substrate, a light source of laser light introduced into the optical waveguide, and light propagating through the optical waveguide that is obliquely upward. An optical information processing apparatus, comprising: a lens unit that emits light to and that collects light in a two-dimensional manner; and a unit that receives light reflected obliquely from above.