JP3362652B2 - Magnetic recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention stably detects a high-accuracy tracking error signal and stores it on a magnetic storage medium such as a fixed magnetic disk or a floppy disk. The present invention relates to a magnetic recording device (IPC G11B 11/10) capable of accurately recording, reproducing, or erasing information. 2. Description of the Related Art Conventionally, in a magnetic disk system for recording information on a magnetic storage medium, a track pitch is 2 bits.
Compared to about 00 μm, which is much larger than about 1.6 μm on an optical storage medium, rough track positioning was mechanically performed using a stepping motor or the like. However, in recent years, a track pitch of several μm to several tens of μm has been desired in order to realize a higher capacity, and in this case, more accurate tracking control than in the past is required. FIG. 4 shows an example of a conventional magnetic recording apparatus for detecting a tracking error signal using light. As shown in FIG. 4, the conventional magnetic recording apparatus includes a semiconductor laser light source (hereinafter, referred to as “light source”) 1 for emitting a divergent beam (hereinafter, referred to as “beam”) 70 of linearly polarized light, and a semiconductor laser light source (hereinafter, referred to as “light source”) 1. Element 16 that receives the split beam 70 and splits into a plurality of beams, and a beam 70 that has passed through the diffraction element 16.
Objective lens 17 that receives light and condenses it on magnetic storage medium 4
And a support 21 that can be adjusted in the Z direction to accurately determine the focal position for supporting the objective lens 17 on the magnetic storage medium 4, and that the light is reflected and diffracted by the magnetic storage medium 4 and passes through the objective lens 17 again. The beam 7 split by the diffraction element 16
0, a photodetector 15 that outputs an electric signal corresponding to the amount of received light, a signal processing unit 61 that processes the electric signal output from the photodetector 15 and outputs a tracking error signal,
The objective lens 17 includes a tracking error signal detection optical system and a magnetic head 14 for recording and reproducing information upon receiving a tracking error signal output from the signal processing unit 61.
A drive unit 91 for adjusting the relative position between the base 13 having the opening 2 for narrowing the beam 70 transmitted through the magnetic storage medium 4 to an appropriate spot size and the magnetic storage medium 4
It is composed of In the diffraction element 16, a region 16A is formed on the surface near the light source 1, and a region 16B is formed on the surface on the opposite side. Then, the divergent beam of linearly polarized light emitted from the light source 1 enters the region 16A of the diffraction element 16 and is branched into three beams of 0th-order diffracted light and ± 1st-order diffracted light. The beam is further split into a plurality of beams, such as a 0th-order diffracted light ± 1st-order diffracted light, in the region 16B. Light source 1 to objective lens 1
In the optical path leading to region 7, the region 16B is formed such that only the 0th-order diffracted light of each of the three beams out of the diffracted light generated in the region 16B enters the aperture of the objective lens 17.
Lattice pitch is designed. In addition, the magnetic storage medium 4
The three beams 70 reflected and diffracted at the region 16B of the diffraction element 16 are split into a plurality of diffracted lights, and only the ± first-order diffracted lights 71 and 72 are received by the photodetector 15. FIG. 5 shows the relationship between a magnetic storage medium and a focused beam in a conventional magnetic recording apparatus. As shown in FIG. 5, in the magnetic storage medium 4, a guide groove is formed in the middle of tracks (areas where information is recorded or reproduced by the magnetic head 14) at equal intervals, and the guide groove and other parts are formed. The tracking error signal can be optically detected based on the difference in reflectance between the portions.
In FIG. 5, Tn-1, Tn, Tn + 1... Are tracks,
Gn-1, Gn, Gn + 1... Are guide grooves. The track pitch pt is set to, for example, 20 μm, and the width of the guide groove is set to 2 μm. [0006] Of the beam 70, 70A is the diffraction element 16
The 0th-order diffracted light 70B, 70C generated in the area 16B based on the 0th-order diffracted light generated in the area 16A is generated in the area 16B based on the ± 1st-order diffracted light generated in the area 16A of the diffraction element 16. 0-order diffracted light. The three beams 70A to 70C are arranged so as to have an interval of pt / 4 when the pitch between the guide grooves Gn adjacent to the guide groove Gn on the magnetic storage medium 4 is pt. FIGS. 6A and 6B show grating patterns of a diffraction element in a conventional magnetic recording apparatus, and FIG.
2 shows the relationship between a photodetector and a beam in a conventional magnetic recording apparatus. As shown in FIGS. 6A and 6B, the grating patterns formed in the regions 16A and 16B of the diffraction element 16 are patterns having the same pitch, respectively. Are orthogonal. As shown in FIG. 6C, the ± first-order diffracted lights 71 and 72 received by the photodetector 15 are composed of three beams 71A to 71C and 72A to 72C, respectively. The photodetector 15 has six light receiving sections 15A to 15F, and a beam 71A is a light receiving section 15B and a beam 71A.
B is the light receiving unit 15A, the beam 71C is the light receiving unit 15C,
The beam 72A is received by the light receiving unit 15E, the beam 72B is received by the light receiving unit 15D, and the beam 72C is received by the light receiving unit 15F. As shown in FIG. 6C, the light source 1 is disposed on a photodetector 15 obtained by etching a silicon substrate. Further, a mirror 150 is formed on the silicon substrate, and the beam 70 emitted from the light source 1 is reflected by the mirror 150, and the light receiving units 15A to 15A of the photodetector 15 are formed.
The light is emitted in the Z-axis direction perpendicular to the XY plane on which the F is formed. FIG. 7 shows a circuit configuration of a signal processing unit in a conventional magnetic recording apparatus. As shown in FIG. 7, the light receiving portions 15A, 15B, 15C (or 15D,
15E and 15F) correspond to the IV converters 355 and 3 respectively.
54, 353. Thereby, the light receiving sections 15A, 15B, 15C (or 15D,
15E, 15F) are converted into voltage signals by the IV converters 355, 354, 353, respectively. The voltage signals v5 (or v6, v7) output from the IV converters 355, 354, 353 are approximated when the beam 70 has a displacement x from the center of the guide groove (for example, Gn) of the magnetic storage medium 4, respectively. The following (Equation 1) ~
The waveform is represented by (Equation 3). [0010] ## EQU2 ## ## EQU3 ## In the above (Equation 1) to (Equation 3), A1 to
A3 is an amplitude, and B1 to B3 are DC components. The IV converters 353 and 354 are respectively provided with variable gain amplifiers 476 and 476.
It is connected to the operation calculation unit 374 via 77. As a result, the voltage signals v5 and v6 output from the IV converters 353 and 354 are output from the variable gain amplifiers 476 and 476, respectively.
After being adjusted to a desired amplitude at 77, operation calculation is performed by an operation calculation unit 374 and output as a voltage signal v8. Also,
Voltage signal v output from IV conversion units 354 and 355
5 and v7 are adjusted to desired amplitudes by the variable gain amplifying sections 478 and 479, respectively, are operated and operated by the operation calculating section 375, and are output as the voltage signal v9. The voltage signals v8 and v9 output from the operation calculators 374 and 375 are expressed by the following (Equation 4) and (Equation 5), respectively.
And a sine wave whose phase differs by π / 2. (Equation 4) [Equation 5] In the above (Equation 4) and (Equation 5), A4 is the amplitude. The operation calculators 374 and 375 are connected to the operation calculator 433 via the variable gain amplifiers 474 and 475, respectively.
It is connected to the. Thereby, the operation calculation units 374, 3
The voltage signals v8 and v9 output from 75 are adjusted to desired amplitudes by the variable gain amplifiers 474 and 475, respectively, added by the calculation unit 433, and output as the voltage signal v10. The voltage signal v10 has a waveform represented by the following (Formula 6), and is output from the output terminal 403 as a tracking error signal. [Equation 6] In the above (Equation 6), K3 and K4 are the gains of the variable gain amplifiers 474 and 475, respectively, and Φ1 is -π
/ 4. The tracking error signal v10 has a gain K3,
By properly selecting K4, a signal having an arbitrary phase and amplitude is obtained. Next, the tracking operation in the magnetic recording apparatus configured as described above will be described. As shown in FIG. 4, a linearly polarized divergent beam 70 emitted from the light source 1
And is split into three beams of 0-order diffracted light and ± 1st-order diffracted light. The three beams generated in the area 16A are further split into a plurality of beams in the area 16B.
Only the zero-order diffracted light of the diffracted light generated in the region 16B enters the opening of the objective lens 17. These three diffracted lights 7
The light beams 0A to 70C are focused on the magnetic storage medium 4 by the objective lens 17 (FIG. 5). Reflected by the magnetic storage medium 4,
The diffracted beams 70A to 70C are returned to the objective lens 17 again.
And is incident on the region 16B of the diffraction element 16 to be branched into a plurality of diffracted lights. Then, only the ± first-order diffracted lights 71A to 71C and 72A to 72C of the branched diffracted lights are received by the light receiving units 15A to 15F of the photodetector 15 (FIG. 6C). Light receiving units 15A to 15 of photodetector 15
F outputs an electric signal corresponding to the received light amount of each beam to the signal processing unit 61 (FIG. 7). This electric signal is processed by the signal processing unit 61 and output to the drive unit 91 as a tracking error signal. Upon receiving the tracking error signal, the drive unit 91 operates on the base 1 including the optical system and the magnetic head 14.
3 and the relative position of the magnetic storage medium 4 are adjusted. As a result, tracking is performed on a desired track. The method of detecting this tracking error signal is as follows.
This is known as a beam method. However, in the conventional magnetic recording apparatus configured as described above, the light output from the light receiving section 15A (or 15B, 15C) of the photodetector 15 is a magnetic storage. Since it is a detection signal based on only one beam 70A (or 70B, 70C) condensed on the medium 4, the signal output is small, and the reflectance variation of the magnetic storage medium 4 or the guide grooves Gn-1, Gn, Gn. There is a problem that the signal-to-noise ratio is reduced due to the influence of optical noise caused by the shape defect of +1... And the tracking operation becomes unstable. An object of the present invention is to provide a magnetic recording apparatus capable of detecting a tracking signal having a high signal-to-noise ratio in order to solve the above-mentioned problems in the prior art. In order to achieve the above object, a magnetic recording apparatus according to the present invention comprises a disk-shaped information recording medium having equally-spaced guide grooves, and a beam emitted from a light source. A first diffractive element that generates three beams upon receiving the light, a second diffractive element that generates three more beams from the three beams, and condenses the beams as minute spots on the information recording medium. Condensing optical system and reflected from the information recording medium, diffracted, a photodetector that receives each beam again passing through the condensing optical system and generates an output according to each received light intensity, Signal processing means for generating a tracking error signal from the outputs of the photodetectors, and changing the relative position between the light collecting optical system and the guide groove according to the tracking error signal. A driving device, wherein the distance between the beams generated into three beams by the second diffraction element and focused on the information recording medium is set to be an integral multiple of the distance between the guide grooves. A magnetic recording apparatus, wherein three beams generated by the first diffraction element on the information storage medium further pass through the second diffraction element. By adjusting the magnification of the condensing optical system, a total of nine beams are moved to a position where the three beams generated by the second diffraction element have the same phase as the periodic physical change on the information storage medium. By condensing light, 3
As a result, the tracking error signal with a good signal-to-noise ratio is generated because the amount of light increases due to the detection of two beams, and the influence of optical noise generated due to variations in reflectivity on the information storage medium and shape defects in the guide grooves decreases. It becomes detectable. FIG. 1 is a block diagram showing an embodiment of a magnetic recording apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram showing a relationship between a magnetic storage medium and a focused beam in the magnetic recording apparatus according to the present invention. FIG. 3 is a diagram showing a relationship between a photodetector and a beam in the magnetic recording apparatus according to the present invention. As shown in FIG. 1, FIG. 2 and FIG. 3, the basic configuration is the same as the configuration shown in FIG. 4, FIG. 5 and FIG. The description is omitted. The differences from the above-described conventional embodiment are as follows. That is, in the above conventional example, the grating pitch of the region 16B is designed such that only the 0th-order diffracted light of the diffracted light generated in the region 16B is incident on the objective lens 17. However, in the embodiment of the present invention, The grating pitch of the region 16B is designed such that ± 1st-order diffracted lights 73 and 74 in addition to the 0th-order diffracted light 70 of the diffracted light generated in the region 16B enter the objective lens 17. As a result, as shown in FIG. 2, the beams 70A, 70B, 70C and 73 appear on the magnetic storage medium 4.
A total of nine beams A, 73B, 73C and 74A, 74B, 74C are focused. Of these beams, 70A is the 0th-order diffracted light generated in the area 16B from the 0th-order diffracted light generated in the area 16A of the diffraction element 16,
Reference numerals 70B and 70C denote 0th-order diffracted light generated in the region 16B from the ± 1st-order diffracted light generated in the region 16A, 73
A and 74A represent 0 generated in the region 16A of the diffraction element 16.
The ± 1st-order diffracted lights 73B and 74B further generated in the region 16B from the first-order diffracted light are the ± 1st-order diffracted lights further generated in the region 16B from the + 1st-order diffracted light generated in the region 16A, and 73C and 74C are generated in the region 16B. ± 1st-order diffracted light further generated in the region 16B from the -1st-order diffracted light thus generated. The distance between the beams 70 and 73 and the distance between the beams 70 and 74 are equal, and they are determined by the method described later.
Are arranged at intervals that are integral multiples of. As shown in FIG.
The beam 7 reflected and diffracted by the magnetic storage medium 4 and transmitted again through the same condensing optical system and incident on the region 16B of the diffraction element 16
The light beams 0, 73, and 74 are split into a plurality of diffracted light beams, of which ± first-order diffracted light beams 71 and 72 of the beam 70 are received by the photodetector 15 as in the conventional example. In addition, in the embodiment of the present invention, the zero-order diffracted lights 75, 7 of the beams 73, 74 are provided.
6 also follows the same optical path as the beams 71 and 72, and
5 is received. As shown in FIG.
A, 75B and 75C are beams 71A and 71B, respectively.
71C, the light receiving portions 15B, 15A, and 15C overlap the beams 72A, 76B, and 76C, respectively.
A, 72B, and 72C overlap light receiving units 15E, 15D,
The light is received at 15F. Next, an embodiment for setting the beams 70, 73 and 74 to have the same phase with respect to the guide groove will be described. FIG.
As shown in (b), a base 13 including a magnetic head 14 for recording and reproducing information is provided with a photodetector 15 and a diffraction element 16.
Is attached so as to be adjustable in the Z direction. The support 22 to which the objective lens 17 is mounted is mounted on the support 22 so as to be adjustable in the Z direction. The support 21 and the support 22 first
0 is temporarily attached to the magnetic storage medium 4 so as to be substantially in focus. Next, since the interval between the beam 70 and the beam 73 (or 74) is determined by the magnification of the condensing optical system, the beam interval becomes equal to the guide groove interval pt, that is, the beam 7
The magnification is adjusted by adjusting the position of the support 21 on which the objective lens 17 is attached in the Z direction so that 0, 73, and 74 are in phase with the guide grooves. Finally, if the focus position is shifted from the magnetic storage medium 4 as a result of adjusting the position of the support 21, the support 22 is adjusted in the Z direction so as to be in focus. With the above configuration, the beams 70, 73, and 74 have the same phase with respect to the guide grooves. As a result, the beams 73 and 74 in addition to the beam 70 are reflected and diffracted by the magnetic storage medium 4 and added by the photodetector to output a signal. Therefore, the signal output of the photodetector conventionally obtained only by the beam 70 is output. The signal intensity is higher than that of beam 73
And 74, the signal-to-noise ratio with respect to the electrical noise is improved, and the detection is carried out with a plurality of beams. Since there is an effect of averaging and reducing noise, it is possible to obtain a tracking error signal having an improved signal-to-noise ratio with respect to optical noise as compared with the conventional embodiment. As described above, according to the magnetic recording apparatus of the present invention, three beams generated by the first diffraction element on the information storage medium further pass through the second diffraction element. By adjusting the magnification of the condensing optical system, a total of nine beams generated by performing the above operation are used to adjust the three beams generated by the second diffraction element to the same phase as the periodic physical change on the information storage medium. By focusing on the position
It is possible to detect a tracking error signal having a better signal-to-noise ratio than the conventional detection method using three beams.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is a diagram schematically showing a main part of a magnetic recording apparatus according to an embodiment of the present invention, and FIG. 1 (b) is a side view showing a main part of the magnetic recording apparatus. FIG. 2 is a plan view showing a relationship between a magnetic storage medium and a focused beam in the magnetic recording device. FIG. 3 is a plan view showing a relationship between a photodetector and a beam in the magnetic recording device. a) a diagram schematically showing a main part of the conventional magnetic recording apparatus; and (b) a side view showing a main part of the magnetic recording apparatus. FIG. 5 is a view showing a magnetic storage medium of the magnetic recording apparatus and a focused beam. FIG. 6A is a plan view showing a grating pattern of a diffraction element used in the magnetic recording apparatus. FIG. 6B is a plan view showing another diffraction element grating pattern used in the magnetic recording apparatus. Plan view (c) Plan view showing the relationship between a photodetector and a beam in the magnetic recording apparatus [ 7 is an electric circuit diagram showing a signal processing unit used in the magnetic recording apparatus. [Description of References] 1 Semiconductor laser light source 2 Opening 4 Magnetic storage medium 13 Base 14 Magnetic head 15 Photodetectors 15A to F Light receiving units 16 Diffraction element 16A Area 16B Area 17 Objective lens 21 Support 22 Support 61 Signal processing unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G11B 5/56-5/60 G11B 21/10 G11B 7/09-7/10

Claims (1)

(57) Claims 1. A disc-shaped information recording medium having equally-spaced guide grooves, a first diffraction element that receives a beam emitted from a light source and generates three beams, A second diffractive element that generates three more beams from the three beams, a condensing optical system that condenses the beams as minute spots on the information recording medium, and a light source that reflects and diffracts the light from the information recording medium. A photodetector for receiving each beam again passing through the condensing optical system and generating an output corresponding to the intensity of the received light, and a signal processing for generating a tracking error signal from the output of the photodetector Means, and a driving device for changing a relative position between the condensing optical system and the guide groove in accordance with the tracking error signal, and each of the second diffractive element converts the light into three beams. Is made is, the interval of the beam condensed on the information recording medium,
It is set to be an integral multiple of the interval between the guide grooves.
A magnetic recording device, wherein the first storage medium is provided on the information storage medium.
The three beams generated by the diffraction element of
9 generated by passing through the diffraction elements
To adjust the magnification of the focusing optical system.
Therefore, the three beams generated by the second diffraction element are
Be in phase with periodic physical changes on the information storage medium
A magnetic recording device, which focuses light at a position.