JP3739130B2 - Method and apparatus for detecting displacement of moving object - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a displacement detection method and apparatus for converting a mechanical angle, a positional displacement, and the like into an electrical signal.
[0002]
[Prior art]
Conventionally, optical linear encoders are widely used as displacement detection devices for moving objects for positioning in mechanical devices. The optical linear encoder measures the length and the rotation angle by providing slits on the rotating plate and the fixed plate, respectively, and converting the light that has passed through both slits into an electrical signal by a photoelectric converter and outputting it.
[0003]
An example of the conventional optical encoder will be described with reference to FIG. FIG. 9 is a configuration diagram of a conventional optical linear encoder.
In FIG. 9, reference numeral 101 denotes a light source, and light emitted from the light source 101 is converted into parallel light by a collimator lens 102 and irradiates a fixed slit plate 103. A moving slit plate 104 having slits that are equal in pitch and parallel in the groove direction is provided facing the fixed slit plate 103, and light that has passed through the slit of the fixed slit plate 103 passes through the slit of the moving slit plate 104. The light beam passing therethrough is received by a light receiving unit 105 comprising a photoelectric converter and converted into an electric signal.
[0004]
The light source 101, the collimator lens 102, the moving slit plate 104, and the light receiving unit 105 constitute a moving unit 106. Normally, the moving unit 106 is integrally fixed to the moving object so that the arrangement direction of the slits formed on the moving slit plate 104 is the moving direction, and moves at the same speed as the moving object. On the other hand, the fixed slit 103 is fixed to a reference object that is stationary relative to the moving object.
[0005]
The operation of the optical linear encoder configured as described above will be described below.
The light emitted from the light source 101 is collimated by the collimator lens 102 and irradiates the fixed slit plate 103. Since the moving unit 106 moves in a direction parallel to the slit of the fixed slit plate 103, the amount of emitted light passing through the slit of the moving slit plate 104 changes. This change in the amount of light is converted into an electrical signal by the light receiving unit 105 disposed on the moving slit plate 104, and the amount of movement of the moving unit 106 is detected.
[0006]
[Problems to be solved by the invention]
However, in the moving object positioning device using the above-described conventional optical linear encoder as a displacement detection device, the light source 101 or the collimator lens 102 must be mounted on the moving object, which increases the weight of the moving object and increases the speed. It had the problem that it became difficult to move. Further, since the moving object needs to move including the lead wires of the light source 101 and the light receiving unit 105, there is a problem that it is difficult to move at a higher speed.
[0007]
In addition, when a moving object such as a magnetic head is positioned with respect to a rotating plate such as a magnetic disk, there is a problem in that it cannot be accurately positioned on an information track on the disk surface due to eccentricity of the rotating plate. .
[0008]
Therefore, an object of the present invention is to increase the speed of movement and improve the positioning accuracy in a displacement detection method and apparatus for a moving object.
[0009]
[Means for Solving the Problems]
In order to achieve the above-described object, in the displacement detection method for a moving object of the present invention, Forming a concentric first pattern substantially concentrically with the rotation axis of the rotating plate, and providing a second pattern superimposed on the concentric first pattern on a moving object that moves in a space facing the rotating plate; The displacement of the moving object is detected from a change in intensity of light transmitted through or reflected from the first pattern and the second pattern.
[0010]
According to the present invention, it is possible to obtain a displacement detection method for a moving object capable of increasing the speed of movement and improving the positioning accuracy.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Claims of the invention 1 In the moving object displacement detection method described above, a concentric first pattern is formed substantially concentrically with the rotation axis of the rotating plate, and the concentric first pattern is formed on the moving object that moves in a space facing the rotating plate. A second pattern to be superimposed is provided, and the displacement of the moving object is detected from a change in the intensity of light transmitted through or reflected from the first pattern and the second pattern. Since it is not necessary to mount a lens, the load weight is reduced, and thus high-speed movement is possible.
[0012]
Claims of the invention 2 The moving object displacement detection method described in claim 1 A moving object displacement detection method as described above, wherein the rotating plate is a magnetic disk, an optical disk, or a magneto-optical disk, and it is not necessary to provide a guide groove on the optical disk or the like for head access or tracking. Therefore, the configuration of the apparatus can be simplified.
[0013]
Claims of the invention 3 The moving object displacement detection method described in claim 1 or claim 2 The moving object displacement detection method according to claim 1, wherein the moving object is a magnetic head body, an optical head body, a magneto-optical head body, or a support and transfer mechanism thereof, and a tracking control signal is detected by the head. Therefore, the transfer weight is reduced and thus high speed access is possible.
[0014]
Claims of the invention 4 The moving object displacement detector described above includes a first pattern forming unit that forms a first concentric circle pattern substantially concentrically with a rotation axis of the rotating plate, and a moving object that moves in a space facing the rotating plate. A second pattern forming unit that generates a second pattern superimposed on one pattern; and a light receiving unit that receives light transmitted through or reflected from the first pattern and the second pattern. The displacement of the moving object is detected from the change in the intensity of the light transmitted through or reflected from the first pattern and the second pattern. With this configuration, since it is not necessary to mount a light source or a lens on the moving object, the load weight is reduced, and thus high speed movement is possible.
[0015]
Claims of the invention 5 The moving object displacement detection device according to claim 4 The moving object displacement detection device according to claim 1, wherein the light receiving means is provided on the moving object, and the intensity of the light transmitted through or reflected by the first pattern and the second pattern on the moving object. The displacement of the moving object is detected from this change. With this configuration, it is possible to detect the displacement of the moving object by itself and to perform position control by itself.
[0016]
Claims of the invention 6 The moving object displacement detection device according to claim 4 Or claims 5 In the moving object displacement detection apparatus described above, the first pattern forming means is fixed substantially coaxially with the rotation axis of the rotating plate, and is concentric even when eccentricity occurs due to rotation of the rotating plate. Since the first pattern also generates the same eccentricity, the positioning accuracy of the moving object with respect to the rotating plate is not impaired.
[0017]
Claims of the invention 7 The moving object displacement detection device according to claim 4 ~ Claim 6 The displacement detection device for a moving object according to any one of the above, wherein the first pattern forming means is constituted by a phase type or amplitude type concentric diffraction grating, and is a phase type or amplitude type concentric diffraction. A first pattern is formed by the lattice.
[0018]
Claims of the invention 8 The moving object displacement detection device according to claim 4 ~ Claim 6 The displacement detection device for a moving object according to any one of the above, wherein the first pattern forming means is configured by a conical prism, and the first pattern is formed by the conical prism.
[0019]
Claims of the invention 9 The moving object displacement detection device according to claim 7 The phase-type diffraction grating is a rectangular wave-type phase grating, where the refractive index of the base material is n and the wavelength of light is λ. But,
(N-1) d = λ / 4
The 0th order light and the higher order light are suppressed as the orders of the diffracted light, and only ± 1st order light is generated and the contrast of the first pattern is improved. Therefore, the displacement detection accuracy of the moving object is improved, and the positioning accuracy is improved.
[0020]
Claims of the invention 10 The moving object displacement detection device according to claim 4 ~ Claim 9 The moving object displacement detecting device according to any one of the above, wherein the rotating plate is a magnetic disk, an optical disk or a magneto-optical disk, and a guide groove is provided on the optical disk or the like for head access or tracking. Since it is not necessary to provide the apparatus, the configuration of the apparatus can be simplified.
[0021]
Claims of the invention 11 The moving object displacement detection device according to claim 10 The moving object displacement detection device according to claim 1, wherein the moving object is a magnetic head main body, an optical head main body, a magneto-optical head main body, or a support and transfer mechanism thereof, and a tracking control signal needs to be detected by the head. Therefore, the transfer weight can be reduced, so that high speed access is possible.
[0022]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
( Reference example 1)
FIG. 1 illustrates the present invention. Reference example 2 is a conceptual diagram illustrating a moving object displacement detection method in FIG.
[0023]
In FIG. 1, reference numeral 1 denotes a minute moving object generally called a micromachine, for example, which is moved in a moving space xyz by a driving means (not shown) such as a piezoelectric actuator. The moving space xyz of the moving object 1 is a space such as a pipe in a nuclear power plant, for example. A first pattern 2 (described later) is formed in the moving space xyz, and a slit is formed on the moving object 1. Or a second pattern 3 formed of a diffraction grating or the like.
[0024]
An example of a method for forming the first pattern 2 will be described with reference to FIG.
In FIG. 2, 4 is a mutually coherent light source composed of a first coherent light source 4a and a second coherent light source 4b, and the two light sources 4a and 4b are spatially and temporally coherent light sources and move. Arranged in the space xyz. These light sources are not necessarily independent, and may be so-called secondary light sources that are divided from one light source. In FIG. 2, two light sources are used, but three or more light sources may be used.
[0025]
As is well known, light emitted from a plurality of mutually coherent light sources 4a and 4b arranged in this way is intensified with each other when the optical path length difference is an even multiple of a half wavelength. On the contrary, in the case of an odd multiple of a half wavelength, they are weakened to form a dark part. In this way, the first pattern 2 is formed.
[0026]
The displacement of the moving object 1 is detected by detecting a change in the intensity of the light transmitted through or reflected by both the first pattern 2 and the second pattern 3 by an intensity change detecting means (not shown) formed of, for example, a photoelectric converter. Is detected.
[0027]
Like this Reference example According to 1, since it is not necessary to mount a light source or a lens on the moving object 1, the load weight is reduced, and thus high-speed movement can be achieved. When applied to a small moving object 1 generally called a micromachine, a particularly remarkable effect can be obtained.
[0028]
Furthermore, if the intensity change detecting means is arranged not in the moving object 1 but in the moving space xyz, not only the weight can be further reduced, but also the power line and signal line for the intensity change detecting means in the moving object 1. Need not be supplied, and the line load can be reduced. Needless to say, this can further increase the speed.
[0029]
If the intensity change detecting means is arranged on the moving object 1, it is possible to detect the displacement of the moving object 1 by itself and to perform position control by itself.
Another example of the method for creating the first pattern 2 will be described with reference to FIG.
[0030]
In FIG. 3, 5 is a light source, and 6 is a slit. The slit 6 is composed of, for example, an etched metal plate, a liquid crystal panel displaying a pattern, or the like.
By irradiating the slit 6 with the light source 5, the first pattern 2 is formed in the movement space xyz. In particular, when the light source 5 is a coherent light source, a strong pattern generally called a Fourier image is formed in the optical axis direction with a period d represented by the formula (1). In equation (1), λ is the wavelength of light and P is the pitch of the slits.
[0031]
d = λ × λ / P (1)
According to this first pattern creation method, the first pattern 2 can be formed with high density in the moving space zyz.
[0032]
The second pattern 3 can also be formed by generating interference fringes of a plurality of lights that are branched from the light emitted from the light source, like the first pattern 2.
(Embodiment 1 )
FIG. 4A shows an embodiment of the present invention. 1 FIG. 4B is a conceptual diagram illustrating a displacement detection method for a moving object in FIG. 4, and FIG. 4B is a diagram illustrating a first pattern.
[0033]
In FIG. 4, reference numeral 7 denotes a rotating flat plate made of, for example, a magnetic disk, an optical disc or a magneto-optical disc. A concentric pattern (first pattern) 9 is formed on the rotating flat plate 7. A moving object 8 is provided opposite to the rotating plate 7 and moved in a lower position (moving space) by a driving means (not shown) such as a piezoelectric actuator. The moving object 8 is, for example, a magnetic head, an optical head, a magneto-optical head, or a support and transfer mechanism thereof, and a second pattern 10 is formed on the moving object 8 by a slit or a diffraction grating.
[0034]
The rotating plate 7 forms the first pattern in the moving space of the moving object 8, and the intensity of the light transmitted through or reflected from both the first pattern 9 and the second pattern 10 is not shown. For example, the displacement of the moving object 8 is detected by detecting by an intensity change detecting means comprising a photoelectric converter.
[0035]
At this time, if the moving object 8 moves only in one radial direction on the rotating plate 7, for example, the x direction, the first pattern 9 does not need to be concentrically formed, and may be a linear pattern. . However, when the moving object 8 moves two-dimensionally on the rotary plate 7, it must be concentric as in this embodiment.
[0036]
Thus, the present embodiment 1 According to the present invention, it is not necessary to provide a guide groove in advance for access and tracking of the head that is the moving object 8 on the optical disk that is the rotating plate 7, so that the configuration of the apparatus can be simplified. In addition, since both the focusing control signal and the tracking control signal are obtained from the beam focused on the optical disk surface, mutual interference between the two control signals that are inevitably generated can be prevented, enabling high-speed access and high-accuracy tracking. Become. Further, since it is not necessary to detect the tracking control signal with the optical head, the transfer weight can be reduced, and thus high speed access is possible.
[0037]
In FIG. 4A, the configuration for detecting the light transmitted through the first pattern 9 and the second pattern 10 has been described. Of course, the same effect can be obtained by the configuration for detecting any reflected light. .
( Reference example 2 )
Hereinafter, the present invention Reference example 2 A moving object displacement detection apparatus will be described with reference to FIGS.
[0038]
FIG. 5 illustrates the present invention. In Reference Example 2 It is a block diagram of the displacement detection apparatus of a moving object.
In FIG. 5, reference numeral 11 denotes a coherent light source that emits substantially parallel light. In the first pattern forming unit 12, interference fringes of a plurality of lights branched by the light emitted from the light source 11 are generated. For example, the first pattern is formed in the space xyz in which the moving object 13 moved by an electrostatic motor or the like moves. The first pattern forming means 12 is constituted by a diffraction grating in FIG. On the moving object 13, there is provided second pattern forming means 14 for forming a second pattern that overlaps the first pattern. The second pattern forming means 14 is formed of a slit made of, for example, an etched metal plate, a liquid crystal panel displaying a pattern, or the like. The second pattern forming means 14 may be constituted by a diffraction grating.
[0039]
Further, on the lower surface of the moving body 13, there is provided light receiving means 15 made of, for example, a photoelectric converter, which detects the light transmitted through the first pattern and the second pattern and converts it into an electric signal.
[0040]
Book Reference example 2 The operation of the displacement detection apparatus will be described with reference to FIGS.
The light emitted from the light source 11 is incident on the diffraction grating 12 as the first pattern forming means substantially in parallel. In general, the diffraction angle θ of the emitted light when parallel light is incident on the diffraction grating 12 is expressed by Expression (2). In Equation (2), P is the pitch of the diffraction grating, λ is the wavelength of light, and m is the diffraction order.
[0041]
θ = sin−1 (mλ / P) (2)
Therefore, a large number of parallel lights having a diffraction angle θ represented by the formula (2) are emitted, and they interfere with each other, so that a large number of first patterns are formed in the moving space xyz.
[0042]
On the other hand, since the second pattern is formed on the moving object 13 by the slit, the intensity of light transmitted through the first pattern and the second pattern changes as the moving object 13 moves. By detecting this by the light receiving means 15, the displacement of the moving object 13 can be detected.
[0043]
Another example of the first pattern creating means 12 will be described with reference to FIG.
In FIG. 6, reference numeral 16 denotes a prism, which is configured so that parallel light enters in FIG. Such parallel incident light is refracted according to Snell's law on the right and left slopes of the prism 16 and exits in parallel with each other. In the moving space xyz, interference occurs such that the optical path length difference is strengthened when it is an even multiple of a half wavelength and weakened when it is an odd multiple. As a result, a first pattern is formed in the movement space xyz.
[0044]
Further, another example of the first pattern creating means 12 will be described with reference to FIG.
In FIG. 7, 17 a and 17 b are mirrors, and 18 is a beam splitter, which is configured such that parallel light enters the beam splitter 18. The light branched into two by the beam splitter 18 is turned back by the mirror 17a and the mirror 17b, respectively. In the movement space xyz of these two optical paths, interference occurs such that the optical path length difference is strengthened when it is an even multiple of a half wavelength and weakened when it is an odd multiple. As a result, a first pattern is formed in the movement space xyz.
[0045]
in this way Reference Example 2 Therefore, since it is not necessary to mount a light source or a lens on the moving object 13, the load weight can be reduced and high-speed movement can be achieved. When applied to a small moving object generally called a micromachine, a particularly remarkable effect can be achieved.
[0046]
Further, if the light receiving means 15 is arranged not in the moving object 13 but in the moving space xyz, not only can the weight be further reduced, but also the power line and signal line for the light receiving means 15 are supplied to the moving object 13. It is no longer necessary and the line load can be reduced. Needless to say, this further increases the speed of movement.
[0047]
Further, by arranging the light receiving means 15 on the moving object 13, it is possible to detect the displacement of the moving object 13 by itself and to perform the position control independently.
Needless to say, even if the first pattern forming means 12 is constituted by a slit irradiated by the light source 11, the same effect can be obtained. Further, the light receiving means 15 may detect light that reflects either the first pattern or the second pattern instead of the light transmitted through the first pattern and the second pattern.
[0048]
( Reference example 3 )
Hereinafter, the present invention Reference example 3 A moving object displacement detection apparatus will be described with reference to FIG.
[0049]
FIG. 8 illustrates the present invention. In Reference Example 3 It is a block diagram of the displacement detection apparatus of a moving object.
In FIG. 8, reference numeral 19 denotes a rotating plate such as a magnetic disk, an optical disk, or a magneto-optical disk. A rotating shaft 20 of the rotating plate 19 has a first concentric circle that rotates integrally with the rotating plate 19. First pattern forming means 22 for forming a pattern is fixed. The first pattern forming means 22 is constituted by a concentric diffraction grating in FIG.
[0050]
Reference numeral 21 denotes a moving object which is, for example, a magnetic head, an optical head, a magneto-optical head, or a support and transfer mechanism thereof. The moving object 21 is moved in a moving space xyz on the rotary plate 19 by a driving means (not shown) such as a piezoelectric actuator. Move in. A concentric pattern as a first pattern is formed in the moving space xyz.
[0051]
Further, second pattern forming means 23 comprising a slit made of, for example, an etched metal plate or a liquid crystal panel displaying a pattern is provided on the upper surface of the moving object 21, and the first pattern and the first pattern are formed on the lower surface of the moving object 21. Light receiving means comprising, for example, a photoelectric converter, for detecting light transmitted through two patterns and converting it into an electrical signal (Not shown) Is provided.
[0052]
A concentric pattern as the first pattern is formed in the moving space xyz. On the other hand, since the second pattern is formed on the moving object 21, both the first pattern and the second pattern are transmitted. By detecting the light intensity change by the light receiving means 24, the displacement of the moving object 21 is detected.
[0053]
Book like this Reference example 3 According to this, since it is not necessary to previously provide a guide groove in the optical disk or the like that is the rotating plate 19 for access or tracking of the head that is the moving object 21, the configuration of the apparatus can be simplified. In addition, since both the focusing control signal and the tracking control signal are obtained from the beam focused on the optical disk surface, mutual interference between the two control signals that are inevitably generated can be prevented, enabling high-speed access and high-accuracy tracking. Become. Further, since it is not necessary to detect the tracking control signal with the optical head, the transfer weight can be reduced, and thus high speed access is possible.
[0054]
Further, since the first pattern forming means 22 is fixed substantially coaxially with the rotating shaft 20 and is rotated integrally therewith, even when eccentricity occurs due to the rotation of the rotating plate 22, the concentric first pattern is formed. Since the same eccentricity occurs, positioning accuracy of the moving object 21 with respect to the rotary plate 19 is not impaired, and highly accurate position control can be performed.
[0055]
In particular, the book Reference example 3 The first pattern forming means 22 is used when the displacement detecting device of the moving object is used in a device generally called a servo track writer of a hard disk, which writes a servo track to a magnetic disk in advance by a magnetic signal at the time of shipment. Can be coaxially mounted on the rotating shaft 20 of the rotary plate 19 to be written, and the moving object 21 as the writing magnetic head can be positioned with reference to the concentric first pattern formed by the first pattern forming means 22; The first pattern forming means 22 may be removed after the writing is completed.
[0056]
The first pattern forming means 22 is a rectangular wave phase diffraction grating, and the groove depth d satisfies the formula (3) when the refractive index of the grating substrate is n and the wavelength of light is λ. If the diffraction grating is used, as is well known, zero-order light and high-order light are suppressed as the orders of diffracted light, and only ± first-order light is generated, thereby improving the contrast of the first pattern.
[0057]
(N-1) d = λ / 4 (3)
As a result, the displacement detection accuracy of the moving object 21 is improved, and the positioning accuracy can be improved.
Even if a conical prism is used as the first pattern forming means 22, a concentric first pattern can also be formed.
[0058]
Although the configuration for detecting the light transmitted through the first pattern and the second pattern has been described with reference to FIG. 8, the same effect can be obtained when the reflected light is detected by the light receiving means 24.
[0059]
Further, if the moving object 19 moves only in one radial direction on the rotating plate 21, for example, the x direction, the first pattern does not need to be concentrically formed, and may be a linear pattern. However, if the moving object 21 moves two-dimensionally on the rotating plate 19, Reference example It must be concentric like
[0060]
【The invention's effect】
As described above, according to the present invention, since the first pattern is formed in the moving space of the moving object, it is not necessary to mount a light source or a lens on the moving object, so that the load weight can be reduced and high-speed movement can be achieved. Can be made possible. Further, when applied to a minute moving object generally called a micromachine, a particularly remarkable effect can be obtained.
[0061]
Further, if the light receiving means for detecting the change in light intensity is arranged not in the moving object but in the moving space, the weight can be further reduced. Further, the power line and the signal line for the light receiving means are provided on the moving object. There is no need to supply, and the line load can be reduced, which can further increase the speed.
[0062]
And claims 2 Or claims 10 According to the described invention, when the displacement detection device of the present invention is used for a rotating plate such as a magnetic disk or an optical disk instead of a conventional linear encoder, the optical disk or the like is previously guided for head access and tracking. Since it is not necessary to provide a groove, the configuration of the apparatus can be simplified. In addition, since both the focusing control signal and the tracking control signal are obtained from the beam focused on the optical disk surface, mutual interference between the two control signals that are inevitably generated can be prevented, enabling high-speed access and high-accuracy tracking. Become.
[0063]
And claims 3 Or claims 11 According to the described invention, since it is not necessary to detect the tracking control signal with the optical head, the transfer weight can be reduced and high-speed access can be achieved.
[0064]
And claims 5 According to the described invention, by providing the light receiving means on the moving object, it is possible to detect the displacement of the moving object by itself and to perform the position control by itself.
[0065]
And claims 9 According to the described invention, the 0th order light and the higher order light are suppressed as the orders of the diffracted light, and only ± 1st order light is generated, so that the contrast of the first pattern can be improved. As a result, the displacement detection accuracy of the moving object is improved. The positioning accuracy can be improved.
[0066]
And claims 6 According to the described invention, the first pattern forming means is fixed substantially coaxially with respect to the rotation axis of the rotating plate and is rotated integrally with the rotating plate, so that even when eccentricity occurs due to the rotation of the rotating plate. Since one pattern generates the same eccentricity, the positioning accuracy of the moving object with respect to the rotating plate is not impaired, and highly accurate position control can be performed.
[Brief description of the drawings]
FIG. 1 of the present invention Reference example 2 is a conceptual diagram illustrating a moving object displacement detection method in FIG.
[Figure 2] Same Reference example 2 is a diagram illustrating an example of a first pattern creation method in FIG.
[Figure 3] Reference example 6 is a diagram for explaining another example of a first pattern creation method in FIG.
FIG. 4 is an embodiment of the present invention. 1 FIG. 2 is a conceptual diagram for explaining a displacement detection method for a moving object in FIG. 1 and a diagram showing a first pattern.
FIG. 5 shows the present invention. Reference example 2 It is a block diagram of the displacement detection apparatus of the moving object in.
[Fig. 6] Reference example 2 It is a figure explaining another example of the 1st pattern formation means in.
[Figure 7] Reference example 2 It is a figure explaining another example of the 1st pattern formation means in.
[Figure 8] Book Reference example 3 It is a block diagram of the displacement detection apparatus of the moving object in.
FIG. 9 is a configuration diagram of a conventional displacement detection device.
[Explanation of symbols]
1, 8, 13, 21 Moving object
2 First pattern
3 Second pattern
4a, 4b Coherent light sources
5,11 Light source
6 Slit
7,19 rotating plate
9 Concentric pattern (first pattern)
10 Second pattern
12, 22 First pattern forming means
14, 23 Second pattern forming means
15 Light receiving means
16 prism
17a, 17b Mirror
18 Beam splitter
20 axis of rotation

Claims (11)

Forming a concentric first pattern substantially concentrically with the rotation axis of the rotating plate, and providing a second pattern superimposed on the concentric first pattern on a moving object that moves in a space facing the rotating plate ; A displacement detection method for a moving object, characterized in that the displacement of the moving object is detected from a change in intensity of light transmitted through or reflected from the first pattern and the second pattern. 2. The moving object displacement detection method according to claim 1, wherein the rotary plate is a magnetic disk, an optical disk, or a magneto-optical disk . 3. A displacement detection method for a moving object according to claim 1, wherein the moving object is a magnetic head main body, an optical head main body, a magneto-optical head main body, or a support and transfer mechanism thereof . First pattern forming means for forming a concentric first pattern substantially concentrically with the rotation axis of the rotating plate, and a second pattern superimposed on the first pattern on a moving object moving in a space facing the rotating plate. An apparatus for detecting displacement of a moving object, comprising: second pattern forming means for generating; and light receiving means for receiving light transmitted through or reflected by the first pattern and the second pattern. 5. A displacement detection apparatus for a moving object according to claim 4, wherein the light receiving means is provided on the moving object. 6. The displacement detection device for a moving object according to claim 4, wherein the first pattern forming means is fixed substantially coaxially with the rotation axis of the rotating plate. 7. The moving object displacement detection device according to claim 4, wherein the first pattern forming means is constituted by a phase type or amplitude type concentric diffraction grating . The displacement detection apparatus for a moving object according to any one of claims 4 to 6, wherein the first pattern forming means is constituted by a conical prism . The phase type diffraction grating is a rectangular wave type phase type grating. When the refractive index of the base material is n and the wavelength of light is λ, the groove depth d of the grating is:
(N-1) d = λ / 4
The displacement detection apparatus for a moving object according to claim 7, wherein the apparatus is configured to satisfy the following . 10. The displacement detection device for a moving object according to claim 4, wherein the rotating plate is a magnetic disk, an optical disk, or a magneto-optical disk . 11. The displacement detection apparatus for a moving object according to claim 10 , wherein the moving object is a magnetic head main body, an optical head main body, a magneto-optical head main body, or a support and transfer mechanism thereof .

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