JP2002071388A - Diffraction grating encoder and positioning device of magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sensitively and accurately detect an interference fringe pattern, regardless of the parallelism between an optical sensor and the interference fringe pattern, and to accurately position a magnetic head using it. SOLUTION: A diffraction grating 123 is mounted to a driving arm 121 which rotates and moves in an arc shape. The interference fringe pattern is generated by the ± first order diffraction beam of an applied light beam. A direction where the interference fringe pattern appears (the grating alignment direction of the diffraction grating) nearly coincides with the linear alignment direction of a photodetector means 61. The shape of the pixel of the photodetector means 61 is a square, where the length and breadth are nearly equal, thus setting each of four pixels to phase difference arrangement of 90 deg., if four pixels correspond to one pitch of the interference fringe pattern. Since the four pixel rows exist repeatedly over the entire region of the photodetector means 61, a signal having sine and cosine components is generated, based on the signal outputted from the photodetector means 61. Based on these sine and cosine components, the rotational position of the driving arm 121 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffraction grating encoder for optically detecting a rotational position of a diffraction grating mounted on a member which rotates and moves in an arc shape. The present invention relates to a diffraction grating encoder having improved light receiving element means capable of detecting an interference fringe pattern. Further, the present invention relates to a magnetic head positioning device configured to position a magnetic head by using a diffraction grating to write a signal to a predetermined position on a magnetic disk.

[0002]

2. Description of the Related Art In recent years, hard disk devices have been generally used as information recording media for computer systems. Servo tracks for controlling the position of a magnetic head are previously set on a magnetic disk in a hard disk drive by a servo track writer. As a positioning method of a magnetic head when setting a servo track on a magnetic disk in a hard disk drive by a servo track writer, an external driving method, a self-driving method, an optical push pin method, and the like are known.

In the external drive system, an appropriate bias current is supplied to a voice coil motor of a carriage mechanism when setting a servo track, and an induction pin attached to a drive arm of an external actuator controlled by a laser length measuring device. Is mechanically brought into contact with the side surface of the support arm of the carriage mechanism, the drive arm is moved by a voice coil motor built in an external actuator, and the carriage mechanism is rotated to position the magnetic head. .

In the self-drive system, when setting a servo track, the magnetic head is positioned by the carriage mechanism of the hard disk drive, instead of using an external actuator as in the external drive system. A mirror is provided on the upper part of the support arm, and the mirror is used to directly measure the amount of movement of the support arm of the carriage mechanism with a laser measuring device, and control the voice coil motor to position the magnetic head. It is.

In the optical push pin system, when setting a servo track, the carriage mechanism is guided in a non-contact manner by using a laser optical system, instead of using mechanical contact by a guide pin as in an external drive system. A mirror is provided above the support arm of the carriage mechanism, and an optical pickup that rotates in the same manner in accordance with the circular rotation of the mirror is provided above the mirror, and the optical pickup is moved to the target position. The positioning of the magnetic head is performed by controlling the voice coil motor of the carriage mechanism so that the positional error between the optical pickup and the mirror becomes equal to or less than a predetermined value.

Recently, however, a technique for writing servo tracks at a high density and at a high speed has been required due to an increase in the storage capacity of a hard disk drive and an increase in the density of recorded information. Therefore, when positioning the magnetic head,
A diffraction grating encoder has been used instead of the laser length measuring device described above. As a diffraction grating encoder,
Japanese Patent Application Laid-Open No. 7-506669 is known. Japanese Patent Application Laid-Open No. 7-220415 discloses an apparatus using a diffraction grating encoder for positioning a magnetic head.
Japanese Patent Application Laid-Open Publication No. H10-163, etc. are known.

[0007] Japanese Patent Publication No. 7-506669 describes a method in which a diffraction grating is provided on a member that moves relatively, a laser beam is irradiated on the diffraction grating, and an interference fringe pattern is created using the ± 1st-order diffraction light. Then, a position signal is detected based on the interference fringe pattern. JP-A-7-220415
Japanese Patent Application Laid-Open Publication No. H11-209,019 relates to a self-driving system, in which an arm is provided with an arc-shaped diffraction grating, and this diffraction grating is irradiated with laser light, and an interference fringe pattern is created using the ± 1st-order diffraction light. Then, a position signal is detected based on the interference fringe pattern to position the magnetic head.

[0008]

SUMMARY OF THE INVENTION The above-mentioned Japanese translation of PCT international publication for publication 7-22
No. 0415 and JP-A-7-220415 disclose at least two signals for generating a signal of a sine component and a cosine component in order to detect the amount of movement of a diffraction grating according to an interference fringe pattern. Optical sensor is required. Usually, the two optical sensors must be arranged at positions where there is a phase difference of 90 ° with respect to the period of the interference fringe pattern. Therefore, the size and shape of the optical sensor itself must be about one-fourth or less of the period of the interference fringe pattern. In order to make the shape of the optical sensor as large as possible, there is also a type in which an arrangement of about one third or less of the period of the interference fringe pattern is arranged and a position signal is detected from three-phase signals. If the light receiving area of the optical sensor is small, high sensitivity cannot be expected. Therefore, in order to increase the sensitivity, conventionally, a large number of optical sensors are arranged in the direction of the interference fringe pattern, or the shape of the optical sensor is elongated in the direction perpendicular to the direction of the interference fringe pattern to improve the sensitivity. ing. However, if the shape of the optical sensor is elongated in the vertical direction, there is a problem that the parallelism with the interference fringe pattern must be accurately adjusted.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a diffraction grating encoder capable of detecting an interference fringe pattern with high sensitivity and high accuracy without considering the parallelism between the optical sensor and the interference fringe pattern. With the goal. Another object of the present invention is to use a diffraction grating encoder that can detect an interference fringe pattern with high sensitivity and high accuracy without worrying about the parallelism between the optical sensor and the interference fringe pattern. An object of the present invention is to provide a magnetic head positioning device capable of positioning a magnetic head with high accuracy.

[0010]

According to a first aspect of the present invention, there is provided a diffraction grating encoder, comprising: a member which rotates and moves in an arc shape; a diffraction grating attached to the member; and an illumination optical system which irradiates the diffraction grating with a light beam. System means, detection optical system means for creating an interference fringe pattern from the ± 1st-order diffracted light generated by the irradiation of the light beam, and pixels formed by linearly arranging pixel groups of substantially equal length and width. Light receiving element means for receiving the interference fringe pattern using a linear light receiving area; and position detecting means for detecting a rotational position of the member based on a signal output from each pixel of the light receiving element means. Things.

When the diffraction grating is attached to a member that rotates and moves in an arc, and when the diffraction grating rotates and moves together with the member in an arc,
An interference fringe pattern is created by ± 1st-order diffracted light of the light beam applied to the grating. The direction in which the interference fringe pattern appears (the grating arrangement direction of the diffraction grating) and the linear arrangement direction of the light-receiving element means are substantially the same.
Since the shape of the pixel of the light receiving element means is a square or a circle having substantially the same length and width, for example, if four pixels correspond to one pitch of the interference fringe pattern, each of the four pixels is 9
A phase difference arrangement of 0 ° is obtained. Since these four pixel rows are repeatedly present over the entire area of the light receiving element means, it is possible to create a sine component and a cosine component signal based on the signal output from the light receiving element means. The rotational position of the member can be detected based on the signals of the sine component and the cosine component. At this time, since the pixel shape is a square or a circle, even if the direction in which the interference fringe pattern appears (the grating arrangement direction of the diffraction grating) and the linear arrangement direction of the light receiving element means are shifted, the four pixels are in the interference fringe pattern. In this case, since the phase difference arrangement of each pixel remains 90 °, the parallelism between the interference fringe pattern and each pixel need not be considered, and the interference fringe pattern can be detected with high sensitivity and high accuracy.

According to a second aspect of the present invention, in the diffraction grating encoder according to the first aspect, the position detection means divides one cycle of the interference fringe pattern into a plurality of phases, and selects each phase in the pixel group. Accumulating means for accumulating the signals of the pixels corresponding to each other, and outputting the accumulated signal, and outputting the signal indicating the rotational position of the member based on the accumulated signal output from the accumulating means. Means. When one cycle of the interference fringe pattern is divided into, for example, four, one pixel of the light receiving element means corresponds to each phase, and the four pixels have a phase difference arrangement of 90 °, respectively. The accumulating means accumulates the signals of the pixels corresponding to the respective phases, since they are present repeatedly over the entire area of the means. Thereby, the sensitivity of the light receiving element means can be improved.

According to a third aspect of the present invention, in the diffraction grating encoder according to the second aspect, a multiplying means for multiplying a signal output from each pixel of the light receiving element means by a coefficient corresponding to an arrangement position of the pixel is provided. The detection range of the light receiving element means can be changed. The interference fringe pattern created by the ± 1st-order diffracted light of the light beam applied to the grating has a large amplitude level at the center and decreases along both sides. The detectable range of the light receiving element is changed so that light can be received.

According to a fourth aspect of the present invention, in the diffraction grating encoder according to the second aspect, the accumulating means is configured to divide each cycle in the pixel group when the period of the interference fringe pattern is divided into four phases. The signal of the corresponding pixels is accumulated, and the accumulated signal of each phase is output. The arithmetic means subtracts the accumulated signal of the fourth phase from the accumulated signal of the second phase from the accumulating means. The obtained sine component signal is divided by the cosine component signal obtained by subtracting the third-phase accumulated signal from the first-phase accumulated signal, and the position data and the position data obtained based on the division result are obtained. The phase data is output as a signal indicating the rotational position of the member. This limits the specific processing contents of the accumulating means and the calculating means when one cycle of the interference fringe pattern is divided into four and one pixel of the light receiving element means is associated with each phase.

According to a fifth aspect of the present invention, there is provided a diffraction grating encoder according to the first aspect, wherein the diffraction grating is constituted by an unequal-length pitch diffraction grating whose grating pitch gradually decreases as the distance from the reference grating increases. Is what it is.
When a linear diffraction grating is attached to a member that rotates and moves in an arc shape, and rotates in an arc with the member, an interference fringe pattern is created by the ± 1st-order diffracted light of the light beam applied to the grating. The direction in which the interference fringe pattern appears (the grating arrangement direction of the diffraction grating) and the arrangement direction of the light receiving element rows of the position detecting means substantially coincide with each other. At this time, if the grating pitch is fixed (equal length), the direction in which the interference fringe pattern appears (the grating arrangement direction of the diffraction grating) and the arrangement of the light receiving element arrays of the position detecting means are caused by the circular rotation of the member. Because the directions do not match,
As the rotation angle increases, the interval (interference fringe pitch) between the interference fringe patterns formed in the light receiving element row gradually increases in the linear arrangement direction of the light receiving element means. Therefore, a linear unequal-length diffraction grating is attached to a member that rotates and moves in an arc shape, and a diffraction grating encoder is configured.
The unequal-length pitch diffraction gratings are arranged such that the gratings are linearly arranged, and the pitch of each grating gradually decreases as the distance from the reference grating toward both sides increases with respect to the center grating. When the reference grating exists at one end, the grating pitch is configured to gradually decrease toward the other end. By attaching this unequal-length pitch diffraction grating to a member that rotates and moves in an arc shape,
The rotational position can be detected with high accuracy.

According to a sixth aspect of the present invention, in the diffraction grating encoder according to the fifth aspect, each of the unequal-length pitch diffraction gratings is arranged such that each of the light beams on the unequal-length pitch diffraction grating is rotated from a rotation center of the member. Let R be the distance to the irradiation position of
If the lattice center coordinate of the lattice N0 of the basic lattice pitch P is X ₀ , and the rotational position θ _{0 of the} member at this coordinate is 0 °, the lattice center coordinate X _{n of the} lattice Nn is X _n = X _n-1. +
Pcos (θ _n-1 ), rotational position θ _n is θ _n = asin (X _n
/ R). This limits the configuration of the unequal-length pitch diffraction grating. When the distance from the rotation center axis O of the rotating member to the light beam irradiation position is R, the rotation position of the reference grating N0 is θ ₀ =
At 0 °, the lattice center coordinate of lattice N0 is X ₀ = 0. At this time, the grid width of the grid N0 is set to a half of the basic grid pitch P.
(P / 2). Next, to determine the grating center coordinate X ₁ of the grating N1 next to the grating N0. The lattice center coordinate X ₁ is given by X _n =
By replacing n of X _n-1 + Pcos (θ _n-1 ) with 1, X ₁ = X ₀ + Pcos (θ ₀ ), so that X ₀ = 0 and θ ₀ = 0 ° are substituted into this. Ask for it. The rotational position θ ₁ of the lattice N1 is given by θ ₁ = asin (X ₁ / R) by replacing n of θ _n = asin (X _n / R) with 1, so that the lattice center coordinate X ₁ Is obtained by substituting
Similarly, for the grid center coordinate X ₂ of the grid N2, X _n =
X _n-1 + Pcos (θ _n-1 ) is replaced with 2 and X ₂ =
It is determined by substituting the grid center coordinate X ₁ and the rotational position θ ₁ of the grid N _{1 into} X ₁ + Pcos (θ ₁ ). Lattice N
Similarly, for the rotational position θ ₂ of θ ₂ , θ _n = asin (X
_n / R) is replaced with 2 and θ ₂ = asin (X ₂ /
Determined by substituting the lattice central coordinate X ₂ of the grating N2 to R).
Hereinafter, similarly, for the n-th lattice Nn, X _n = X
_{n-1 + Pcos (θ n} -1) and _{θ n = asin (X n /} R)
Based on

According to a seventh aspect of the present invention, in the diffraction grating encoder according to any one of the first to sixth aspects, the illumination optical system means includes a light source that emits the light beam and the light source that emits the light beam. A mirror for reflecting the light beam toward the diffraction grating; and a lens for imaging the light beam reflected by the mirror on the diffraction grating. In this method, a light beam emitted from a light source is reflected by a mirror means, formed into an image by a lens means, and irradiated on a diffraction grating.

In the diffraction grating encoder according to the present invention, the illumination optical system may include a light source that emits the light beam and the light source that emits the light beam. A lens means for forming an image of the light beam on the diffraction grating, and a hole for allowing the light beam passing through the lens means to pass through the diffraction grating side as it is and for the 0th-order diffracted light generated by the diffraction grating to also pass therethrough And a perforated mirror means provided with a mirror for reflecting the ± 1st-order diffracted light generated by the diffraction grating to the detection lens side. This is because the light beam emitted from the light source and condensed by the lens means passes through the hole of the perforated mirror and irradiates the diffraction grating, and ± 1st-order diffracted light generated by the diffraction grating is detected by the perforated mirror on the detection lens side. The unnecessary zero-order diffracted light is returned to the light source side through the hole. This can reduce the adverse effect of the zero-order diffracted light on the interference fringe pattern.

According to a ninth aspect of the present invention, in the diffraction grating encoder according to any one of the first to sixth aspects, the detection optical system means is configured to focus the ± 1st-order diffracted light generated by the diffraction grating. A lens unit, a spatial filter unit provided at a focusing position of the lens unit, and having an opening for passing only the ± 1st-order diffracted light, and receiving the ± 1st-order diffracted light after passing through the spatial filter unit. And second lens means for forming the interference fringe pattern by forming an image on the element means. This specifically limits the configuration of the detection optical system means.

According to a tenth aspect of the present invention, in the diffraction grating encoder according to the ninth aspect, the first lens means is arranged so that the diffraction grating and the spatial filter means are at a conjugate position, and the second lens means is provided with a second lens means. The lens means is constituted by a telecentric optical system in which the spatial filter means and the light receiving element means are arranged at conjugate positions. By configuring the detection optical system means with a telecentric optical system in this manner, magnification fluctuation due to defocus can be eliminated, and measurement accuracy can be improved.

12. A magnetic head positioning apparatus according to claim 11, wherein said arm means rotates and moves in an arc shape, a diffraction grating attached to said arm means, and an illumination optical system means for irradiating said diffraction grating with a light beam. Detection optical system means for creating an interference fringe pattern from the ± 1st-order diffracted light generated by the light beam irradiation, and a linear shape formed by linearly arranging pixel groups of substantially equal length and width. Light-receiving element means for receiving the interference fringe pattern using the light-receiving area of the light-receiving element, position detecting means for detecting a rotational position of the arm means based on a signal output from each pixel of the light-receiving element means, and the position detecting means Positioning means for positioning the magnetic head by controlling the rotational position of the arm means detected by the control means. The magnetic head is positioned with high precision by using the diffraction grating encoder according to the first aspect.

According to a twelfth aspect of the present invention, in the magnetic head positioning apparatus according to the eleventh aspect, the position detecting means includes a plurality of phases each of which is obtained by dividing one cycle of the interference fringe pattern into a plurality of phases. Accumulating means for accumulating the signals of the pixels corresponding to the phase, and outputting the accumulated signal, and outputting a signal indicating the rotational position of the member based on the accumulated signal output from the accumulating means. Calculation means for performing the calculation. This corresponds to claim 2.

According to a thirteenth aspect of the present invention, in the magnetic head positioning device according to the twelfth aspect, there is provided a multiplication means for multiplying a signal output from each pixel of the light receiving element means by a coefficient corresponding to an arrangement position of the pixel. , The detectable range of the light receiving element means can be changed. This corresponds to claim 3.

According to a fourteenth aspect of the present invention, in the magnetic head positioning device according to the twelfth aspect, the accumulating means is configured to divide each cycle of the interference fringe pattern into four phases. A signal between pixels corresponding to a phase is accumulated, and an accumulated signal of each phase is output. The arithmetic means outputs an accumulated signal of the fourth phase from the accumulated signal of the second phase from the accumulating means. The sine component signal obtained by the subtraction is divided by the cosine component signal obtained by subtracting the third-phase accumulated signal from the first-phase accumulated signal, and the position obtained based on the division result is obtained. The data and the phase data are output as signals indicating the rotational position of the member. This corresponds to claim 4.

According to a fifteenth aspect of the present invention, in the magnetic head positioning device according to the eleventh aspect, the diffraction grating is an unequal-length pitch diffraction grating whose grating pitch gradually decreases as the distance from the reference grating increases. It is configured. This corresponds to claim 5.

In a magnetic head positioning apparatus according to a sixteenth aspect, in the fifteenth aspect, each of the unequal-length pitch diffraction gratings is arranged on the unequal-length pitch diffraction grating from a rotation center of the member. Let R be the distance to the irradiation position of the light beam, X _{0 be} the grid center coordinate of the grid N 0 at the basic grid pitch P, and 0 ° be the rotational position θ _{0 of the} member at this coordinate.
, The lattice center coordinate _{Xn of the} lattice Nn is _Xn =
X _n-1 + Pcos (θ _{n -1} ), rotation position θ _n is θ _n = asi
n (X _n / R). This corresponds to claim 6.

According to a seventeenth aspect of the present invention, in the magnetic head positioning device according to any one of the eleventh to sixteenth aspects, the illumination optical system means includes a light source that emits the light beam and a light source that emits the light beam. Mirror means for reflecting the light beam to the diffraction grating side, and lens means for forming an image of the light beam reflected by the mirror means on the diffraction grating. This corresponds to claim 7.

[0028] In the magnetic head positioning device according to the present invention, the illumination optical system means may include a light source for emitting the light beam and a light source for emitting light from the light source. Lens means for forming an image of the light beam on the diffraction grating, and passing the light beam passing through the lens means as it is to the diffraction grating side, and passing the 0th-order diffracted light generated by the diffraction grating as well. ± 1 generated by the diffraction grating
Perforated mirror means provided with a mirror for reflecting the next-order diffracted light toward the detection lens.
This corresponds to claim 8.

According to a nineteenth aspect of the present invention, in the magnetic head positioning device according to any one of the eleventh to sixteenth aspects, the detecting optical system means converges ± 1st-order diffracted light generated by the diffraction grating. A first lens means, a spatial filter means provided at a focusing position of the lens means, and having an opening for passing only the ± 1st-order diffracted light, and the ± 1st-order diffracted light after passing through the spatial filter means. And second lens means for forming the interference fringe pattern by forming an image on the light receiving element means. This corresponds to claim 9.

According to a twentieth aspect of the present invention, in the magnetic head positioning apparatus according to the nineteenth aspect, the first lens means is arranged such that the diffraction grating and the spatial filter means are at conjugate positions, and The second lens means is constituted by a telecentric optical system in which the spatial filter means and the light receiving element means are arranged at conjugate positions. This corresponds to claim 10.

[0031]

Embodiments of the present invention will be described below with reference to the accompanying drawings. This embodiment shows a case where a diffraction grating encoder is applied to an externally driven servo track writer. In this embodiment, the mechanical mechanism for mechanically positioning the magnetic head is the same as the conventional one. The present embodiment is different from the conventional one in that an optical sensor for detecting an interference fringe pattern uses a CCD line sensor to control the rotational position of a drive arm to position a magnetic head at a target position. It is.

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a magnetic head positioning apparatus according to the present invention. In the figure, only the main part of the hard disk drive is shown. The magnetic disk 111 is rotated at high speed by the spindle 110. The magnetic head 112 includes a carriage mechanism 113
Is attached to the distal end of the support arm 114. The carriage mechanism 113 includes a voice coil motor (not shown) for rotating the support arm 114 in an arc shape to position the magnetic head 112.

On the other hand, an external actuator 120 constituting a servo track writer is provided above the support arm 114. Drive arm 1 of external actuator 120
21 (on the side of the support arm 114), the guide pin 12
2 are provided. The guide pin 122 mechanically contacts the side surface of the support arm 114 of the carriage mechanism 113. The external actuator 120 has a built-in voice coil motor (not shown), and thereby rotates the drive arm 121 in an arc shape. A linear diffraction grating 123 having an unequal pitch is mounted on the upper part of the drive arm 121. Right above the unequal-length pitch diffraction grating 123, an optical detecting means (not shown)
Is provided. Rotational position data corresponding to the circular rotation of the unequal-length pitch diffraction grating 123 is detected based on the position signal detected by the optical detection means. The detailed configuration of the optical detection means and the unequal-length pitch diffraction grating 123 will be described later.

When setting a servo track on the magnetic disk 111, an appropriate bias current is supplied to the voice coil motor of the carriage mechanism 113, and the magnetic head 112 and the support arm 114 are stopped near the outer periphery of the magnetic disk 111. The guide pin 122 is connected to the carriage mechanism 11
The support arm 114 and the carriage mechanism 113 are mechanically brought into contact with the side surface of the third support arm 114, and the drive arm 121 is rotated by a voice coil motor built in the external actuator 120 to rotate the support arm 114 and the carriage mechanism 113. FIG.
2, the magnetic head 112, the support arm 114 and the drive arm 121 positioned near the outer circumference of the magnetic disk 111 are indicated by solid lines, and those positioned near the inner circumference are indicated by dotted lines. At this time, the optical detecting means is provided at an appropriate position facing the upper side of the unequal-length pitch diffraction grating 123, and is an interference fringe pattern created by ± 1st-order diffracted light reflected from the unequal-length pitch diffraction grating 123. Based on the position signal. The rotational movement amount of the drive arm 121 of the external actuator 120 is measured with high accuracy based on the detected position signal.
The external actuator 120 controls the built-in voice coil motor based on the measurement result of the optical detection means so that the rotational movement amount becomes a predetermined value, and performs positioning of the magnetic head 112.

FIG. 2 is a diagram showing a detailed configuration of the unequal-length pitch diffraction grating 123. As shown in FIG. FIG. 2 schematically shows the pitch between the gratings for convenience of explanation. The actual grating pitch is about 10 [μm], and the total length of the diffraction grating 123 is 4 μm.
In the case of 0 [mm], the number of diffraction gratings is about 4000. Note that this is the case where the grating pitch is the same length, and in the case of the unequal-length pitch diffraction grating according to this embodiment, the number of diffraction gratings is greater than this. In the case of this unequal-length pitch diffraction grating, the grating pitch P of the central grating N0 is set to 1
This is because, when it is set to 0 [μm], the grating pitch is configured to gradually decrease as the distance from both sides increases. The rate of this reduction depends on the distance R from the rotation axis O of the drive arm 121 to which the unequal-length pitch diffraction grating 123 is attached to the laser beam spot 11. This distance R is the same as the radius of rotation when the diffraction grating 123 rotates.

In FIG. 2, the laser beam spot 11
8 schematically shows the shape of the laser beam irradiated by the optical detection means on the diffraction grating 123. As the driving arm 121 rotates in an arc shape, the driving arm 121 moves as shown in FIG.
As shown in (1), the laser beam spot 11 also relatively rotates on the diffraction grating 123 in an arc shape having a radius R around the rotation axis O. FIG. 2 shows a case where the laser beam spot 11 rotates and moves relative to the diffraction grating 123 in an arc shape. However, the diffraction grating 123 actually rotates and moves in an arc shape as shown in FIG. The beam spot 11 always irradiates a fixed position. 3 and 4
FIG. 3 is an enlarged view schematically showing the relationship between the diffraction grating 123 and the laser beam spot 11 irradiated thereon. FIG. 3A shows that the laser beam spot 11 has the grating N0 of FIG.
Above, FIG. 3 (B) is on the grid N3, and FIG.
6 and FIG. 3 (B) show the case where irradiation is performed on the grating N9, respectively. As is clear from FIGS. 3 and 4, the diffraction grating is constituted by a blazed diffraction grating having a blaze angle β of about 2.4 °. The blazed diffraction grating
The order light can be made as small as possible and the ± 1st order diffracted light can be generated with high efficiency and equal intensity.

The laser beam spot 11 is shown in FIGS.
As shown in (A), when irradiating on the grating N0,
Longitudinal direction of laser beam spot 11 (both end arrow lines 31)
) And the traveling direction of the ± 1st-order diffracted light reflected from the diffraction grating 123 (the direction of the arrow line 21 at both ends) coincides with each other. In this state, when an interference fringe pattern is created based on the reflected light of the ± 1st-order diffracted light, the interference fringe pattern appears along the longitudinal direction of the laser beam spot 11 (the direction of the arrow line 31 at both ends). That is, the interference fringe pattern appears along the grating arrangement direction of the diffraction grating. Therefore,
A light receiving element array of the optical detecting means is provided along the direction in which the interference fringe pattern appears. The state in which the laser beam spot 11 irradiates the grid N0 in FIG. 2 is a state in which the rotational position of the drive arm 121 is 0 °. Accordingly, when the drive arm 121 rotates in an arc shape from the rotational position of 0 °, the laser beam spot 11 emits light while rotating and moving on each lattice as shown in FIG.

As shown in FIGS. 2 and 3A, the state where the laser beam spot 11 irradiates the grating N0 is the rotation position 0 °, and the state where the laser beam spot 11 irradiates the grating N3 is the rotation position 10 °. Irradiating the grid N6 with the rotation position 2
0 °, the state of irradiating on the grid N9 is a rotation position of 30 °.
In a state where the drive arm 121 is provided. Therefore, the grating pitch P0 of the grating N0 at the rotational position of 0 ° is P
0 = Pcos 0 °, 10 [μm]. Here, P is a basic lattice pitch, and its value is set to 10 [μm]. The grating pitch P3 of the grating N3 at the rotation position of 10 °
Is P3 = Pcos10 °, 9.848 [μm]. Similarly, the lattice pitch P6 of the lattice N6 at the rotational position of 20 ° is P6 = Pcos20 °, 9.397
[Μm], and the lattice N in the state of the rotation position 30 °
9, the lattice pitch P9 is P9 = Pcos30 °, 8.6
6 [μm]. In FIG. 2, the same applies to the lattices n3, n6, and n9 on the right side of the lattice N0.

As described above, the grating pitch of the diffraction grating 123 is configured to gradually decrease as the distance from the central portion (rotational position 0 °) to both sides (rotational position 30 °) increases. This is because the direction in which the interference fringe pattern created by the laser beam spot 11 irradiated on the diffraction grating (rotational direction of the diffraction grating) and the light receiving element of the optical detection means are rotated by the circular movement of the diffraction grating. This is a technique adopted to eliminate the inconvenience caused by the inconsistency of the arrangement direction of the columns. That is,
If the grating pitch remains fixed (equal length), the direction in which the interference fringe pattern appears (the grating arrangement direction of the diffraction grating) and the arrangement direction of the light receiving element array of the optical detection means are changed by the circular movement of the drive arm. Since they do not coincide with each other, the interval (interference fringe pitch) of the interference fringe patterns formed in the light receiving element array increases as the rotation angle increases, and there is a disadvantage that the device does not function as an encoder.

In the unequal-length pitch diffraction grating according to this embodiment, when the laser beam spot 11 irradiates the grating N3 at a rotation position of 10 ° as shown in FIG. The direction (the direction of the arrow line 32 at both ends) and the direction in which the interference fringe pattern appears (the direction of the arrow line 22 at both ends)
Is shifted by an angle of 10 °. Accordingly, since the interval between the interference fringe patterns is a reduced interval corresponding to the grating pitch of the grating N3 having the reduced pitch width, the interval between the interference fringe patterns is detected in the arrangement direction of the light receiving element rows. Become. If the interval between the interference fringe patterns appearing in the light receiving element row in the state of FIG. 3A is set to 10 μm, which is the same as the grating pitch, the interval between the interference fringe patterns in the case of FIG. Is equal to 9.848 [μm], which is the same as the grating pitch P3, and is detected as an interference fringe pattern of 10 [μm] in the arrangement direction of the light receiving element rows (the direction of the arrow line 32 at both ends).

As shown in FIG. 4A, when the laser beam spot 11 irradiates the grating N6 at a rotation position of 20 °, the arrangement direction of the light receiving element rows (the direction of the arrow line 33 at both ends) is the same as described above. The direction of the interference fringe pattern (direction of the arrow line 23 at both ends) is shifted at an angle of 20 °, but the interval of the interference fringe pattern detected in the light receiving element row does not change. As described above, if the interval between the interference fringe patterns appearing in the light receiving element row in the state of FIG. 3A is 10 μm, the interval between the interference fringe patterns in the case of FIG.
9.397 [μm], which is the same as the lattice pitch P6 of No. 6,
1 in the arrangement direction of the light receiving element rows (the direction of the arrow line 33 at both ends)
This is detected as an interference fringe pattern of 0 [μm].

Also, as shown in FIG. 4B, when the laser beam spot 11 irradiates the grating N9 at a rotational position of 30 °, the arrangement direction of the light receiving element rows (the direction of the arrow line 34 at both ends) is the same as described above. ) And the direction in which the interference fringe pattern appears (the direction of the arrow line 24 at both ends) is shifted by an angle of 30 °, but the interval between the interference fringe patterns detected in the light receiving element row does not change. Similarly to the above, the interval between the interference fringe patterns appearing in the light receiving element row in the state of FIG.
In this case, the interval between the interference fringe patterns in the case of FIG. 4B is 8.66 [μm], which is the same as the grating pitch P9 of the grating N9, and is 10 in the arrangement direction of the light receiving element rows (the direction of the arrow line 34 at both ends). [Μm] is detected as an interference fringe pattern.

In the above description, the unequal-length pitch diffraction grating has been outlined. However, when an unequal-length pitch is actually formed, the rotational positions of 10 °, 20 °, and 30 ° as described above are used. Does not always exist. This is because when actually forming the unequal-length pitch diffraction grating, the pitches of the gratings on both sides are determined based on the basic grating pitch P at the center. Specifically, as shown in FIG. 3A, for a grid N0 located at a distance R from the rotation axis O, the rotational position of the grid N0 is set to θ ₀ = 0 °, and the grid N0
Is set in the X direction, that is, the grid center coordinate is X ₀ = 0. At this time, the grating width of the grating N0 is ２ of the basic grating pitch P (P / 2 = 5 [μm]). Next, the lattice N
0 of determining the grid central coordinate X ₁ of the following lattice N1. The lattice center coordinate X ₁ is obtained by X ₁ = X ₀ + Pcos (θ ₀ ).
Therefore, the lattice central coordinate X ₁ becomes 10 [μm]. Note that the rotational position θ ₁ of the lattice N1 is θ ₁ = asin (X
₁ / R).

Similarly, the lattice center coordinates X ₂ of the lattice N ₂ are similarly obtained by substituting the lattice center coordinates X ₁ and the rotational position θ ₁ of the lattice N ₁ into X ₂ = X ₁ + Pcos (θ ₁ ). , The rotational position θ ₂ of the lattice N2 is the lattice center coordinate X ₂
To θ ₂ = asin (X ₂ / R). Lattice N
For lattice central coordinates X ₃ of 3 similarly as the grating center coordinates X ₂ grid N2 rotational position _{θ 2 X 3 = X 2 +} Pcos
(Θ ₂ ), and the rotational position θ ₃ of the lattice N3 is determined by substituting the lattice center coordinate X ₃ into θ ₃ = asin (X ₃ / R). That is, for the n-th lattice Nn, its lattice center coordinate _Xn is represented by _Xn = _Xn-1 + Pcos.
(Θ _n-1 ), and the rotational position θ _n is given by θ _n = asin (X _n
/ R). By creating a non-equidistant pitch diffraction grating based on the diffraction grating pitch obtained in this way, it is possible to perform highly accurate position detection. In addition,
The symbols of the lattices N1, N2, and N3 used in this description and FIG.
It has nothing to do with the one in.

Next, the configuration of the optical detecting means will be described. FIG. 5 is a diagram showing a configuration of an optical system of an encoder using the unequal-length pitch diffraction grating described above. The semiconductor laser light source 51 emits laser light of a predetermined wavelength. The collimator lens 52 converts the laser light emitted from the semiconductor laser light source 51 into a parallel light flux and guides the laser light to the mirror 53. The mirror 53 reflects the laser beam from the collimator lens 52 in the direction in which the unequal-length pitch diffraction grating 123 is provided. In addition, since the mirror 53 is located in the passage of the ± 1st-order diffracted light, the mirror 53 has a size that does not hinder the passage. The lens 54 is formed of a convex lens, shapes the laser light, and irradiates the uneven pitch diffraction grating 123 with the laser light through the opening window of the opening window member 55. As shown in FIG. 6A, the opening window member 55 is configured by a shielding plate having opening windows 551 to 553.
Only the ± 1st-order diffracted lights pass through the aperture windows 551 and 552, and block the other nth-order diffracted lights. Each of the opening windows 551 and 552 is formed of an elongated opening having a circular end. The opening window 553 allows the laser light reflected by the mirror 53 to pass therethrough, and is constituted by a substantially circular opening.

In the unequal-length pitch diffraction grating 123, 0th order, ± 1st order, ± 2nd order, ± 3rd order,.
・ Diffracted light is generated. The ± 1st-order diffracted light generated by the unequal-length pitch diffraction grating 123 is transmitted through the aperture window 55 of the aperture window member 55.
The light passes through the lens 54 via the lens 1552 and is focused by the lens 54. The spatial filter 56 is arranged at a position where the spatial filter 56 has a conjugate relationship with the unequal-length pitch diffraction grating 123 by the lens 54, and unnecessary ± 2 order, ± 3 order,.
・ ・ Remove the diffracted light and pass only ± 1st-order diffracted light. As shown in FIG. 6B, the spatial filter 56 is configured by a shielding plate having opening windows 561 and 562 similarly to the opening window member 55. Each of the opening windows 561 and 562 is formed of an elongated opening having a circular end as in the case of the opening windows 551 and 552.
It is shorter than 1,552. This is because the spatial filter 56 is disposed at the focal position of the lens 54 and the lens 57.

The lens 57 is arranged at such a position that the spatial filter 56 and the light receiving sensor 61 have a conjugate relationship, and forms the ± 1st-order diffracted light passing through the spatial filter 56 on the light receiving sensor 61. In the above-described detection optical system, the spatial filter 56 and the diffraction grating 123 are disposed on the focal length f1 of the lens 54, and the spatial filter 56 and the light receiving sensor 61
Are disposed on the focal length f2 of the lens 57, and constitute a telecentric detection system on both sides. As a result, a change in magnification due to defocus can be eliminated, and measurement accuracy can be improved. In addition, since the spatial filter 56 functions, the opening window member 55 may be omitted. The reason why the shape of the aperture window of the spatial filter 56 and the aperture window member 55 is elongated is to allow ± 1st-order diffracted light to pass effectively even when the laser beam spot is irradiated on the diffraction grating at a predetermined angle.

FIG. 7 is a diagram showing the configuration of another optical detecting means of the encoder using the unequal-length pitch diffraction grating. 7, the same components as those in FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted. 7 differs from that in FIG. 6 in that the mirror 53 and the opening window member 55 in FIG. 6 are omitted and a perforated mirror 58 is provided. The perforated mirror 58 is provided with a hole at the center for allowing the laser light emitted from the semiconductor laser light source 51 to pass therethrough, and the laser light converted into a parallel light beam by the collimating lens is passed through the hole. Irradiation is performed on the unequal-length pitch diffraction grating 123. Further, the perforated mirror 58 returns the zero-order diffracted light generated by the diffraction grating 123 to the semiconductor laser light source 51 side through the hole, and particularly the ± 1st-order diffracted light among the other higher-order diffracted lights. The configuration is such that only the folded light is positively reflected to the lens 54 side. As a result, the influence of the zero-order light on the interference fringe pattern can be extremely reduced.

Next, the detailed structure of the light receiving sensor 61 will be described. FIG. 8 is a diagram illustrating a detailed configuration of the light receiving sensor 61. The light receiving sensor 61 is constituted by a CCD line sensor, and the size of one pixel is 10 [μm].
Pixels are arranged in a line. As shown in FIG. 8, one cycle of the interference fringe pattern corresponds to four pixels of the CCD line sensor, and the CCD line sensor can detect 128 cycles of the interference fringe pattern. The use of such a CCD line sensor whose light-receiving surface is almost square is, as described above,
This is because the interference fringe pattern is inclined at an angle corresponding to the rotational position of the drive arm 121 with respect to the arrangement direction of the CD line sensors. That is, in the case of a CCD line sensor including a light receiving element having a square light receiving surface, even if the interference fringe pattern is inclined, one interference fringe pattern only affects at least two adjacent light receiving elements. is there. However, when a well-known light receiving element having an elongated light receiving surface provided corresponding to the width of the interference fringe pattern is used, when the interference fringe pattern is inclined,
One interference fringe pattern affects three or at worst four or more light receiving elements, and position detection by the light receiving element means can no longer be performed.

Next, how the position data and the phase data are created based on the detection signal of the light receiving sensor 61 composed of the CDD line sensor will be described in detail with respect to the signal processing circuit. FIG. 9 is a diagram showing a detailed configuration of a signal processing circuit for a detection signal output from the light receiving sensor 61. The light receiving sensor 61 is constituted by the above-described CCD line sensor, and operates according to a driving clock from the timing generation unit 66. The A / D converter 62 sequentially converts the analog detection signal output from the light receiving sensor 61 into a digital signal, and outputs the digital signal to the A terminal of the multiplier 64. A
The / D converter 62 also operates according to the drive clock from the timing generator 66. The memory 63 stores a coefficient value for assigning a data weight (coefficient) corresponding to a pixel position to the digital signal output from the A / D converter 62 or limiting a detection pixel range. It is a memory and outputs a coefficient value Data corresponding to the address signal Adr from the timing generator 66 to a B terminal of the multiplier 64. The multiplier 64 is an A / D converter 62 input to the A terminal.
Is multiplied by the coefficient value Data from the memory 63 input to the B terminal, and data Y indicating the multiplication result is output to the addition circuit 65. In the interference fringe pattern formed on the CCD line sensor, since the level of the pattern gradually decreases from the center toward both ends, in this embodiment, detection is performed using the memory 63 and the multiplier 64. The pixel range can be changed as appropriate. That is, as shown in FIG. 8, when the detection pixel range is used for 512 pixels of all the pixels, or when the detection pixel range is
It can be changed arbitrarily, such as when eight pixels are used. Note that this detection pixel range is an example, and the number of pixels, the range, and the like other than the above can be freely changed as appropriate.

The adder circuit 65 outputs a pixel output of the first phase of φ1 and a pixel output of the second phase of φ2 when the period is divided into four, corresponding to the period of the interference fringe pattern as shown in FIG. Assuming that the pixel output of the third phase is φ3 and the pixel output of the fourth phase is φ4, the signal Y of the light receiving element corresponding to each phase is sequentially accumulated, and the accumulated value of each phase Σφ1, Σφ
2, Σφ3 and Σφ4 are output to the arithmetic processing circuit 67 in the next stage. The arithmetic processing circuit 67 obtains a sine component signal φA by subtracting the accumulated value Σφ4 of the pixel output of the fourth phase from the accumulated value Σφ2 of the pixel output of the second phase, and accumulates the signal φA of the first phase. The signal φB of the cosine component is obtained by subtracting the accumulated value Σφ3 of the pixel output of the third phase from the value Σφ1 to obtain the signal φ of the sine component.
A is divided by the cosine component signal φB to calculate a tangent component signal X.
8 and the phase data calculation circuit 69. When the interference fringe pattern moves for one cycle in the positive direction based on the tangent component signal X output from the arithmetic processing circuit 67, the position counter 68 increments the count value and moves in the negative direction. In this case, a decrement process is performed, and the count value is output as position data. On the other hand, the phase data calculation circuit 69 calculates the arc tangent of the signal X of the tangent component,
It is output as phase data. Based on these position data and phase data, the external actuator 120
Controls the built-in voice coil motor so that the rotational movement amount becomes a predetermined value, and performs positioning of the magnetic head 112.

The above-described embodiment shows a case where the magnetic head positioning device is applied to an externally driven servo track writer. However, the present invention is not limited to this, and can be applied to self-drive type or optical push-pin type servo track writers, as well as hard disk drives themselves and magnetic disk inspection devices. Further, in the above-described embodiment, a blazed diffraction grating has been described as an example, but a diffraction grating structure other than the blazed diffraction grating may be used. Further, in the above-described embodiment, the case where a CCD line sensor is used as the light receiving sensor 61 has been described as an example, but it goes without saying that other sensors may be used. In this case, it is necessary to consider the inclination of the interference fringe pattern and to make the sensor shape corresponding thereto. In the above-described embodiment, an example in which the lattice pitch is always different between adjacent ones has been described. However, for example, the same lattice pitch in a predetermined range, such as changing the lattice pitch every 1 ° with a rotation angle. And may be changed gradually according to the rotational position.
A concave mirror may be used instead of the lens of each optical unit described above.

[0053]

According to the diffraction grating encoder of the present invention,
There is an effect that the interference fringe pattern can be detected with high sensitivity and high accuracy without worrying about the parallelism between the optical sensor and the interference fringe pattern.

According to the magnetic head positioning apparatus of the present invention, the magnetic head can be detected with high sensitivity and high accuracy without concern for the parallelism between the optical sensor and the interference fringe pattern. There is an effect that the positioning can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a magnetic head positioning device according to the present invention.

FIG. 2 is a diagram showing a detailed configuration of the unequal-length pitch diffraction grating of FIG. 1;

FIGS. 3A and 3B are enlarged views schematically showing a relationship between a unequal-length pitch diffraction grating and a laser beam spot irradiated on the diffraction grating. FIG. 3A shows a rotational position of 0 °, and FIG. This corresponds to a position of 10 °.

FIG. 4 is another enlarged view schematically showing the relationship between the unequal-length pitch diffraction grating and the laser beam spot irradiated on the diffraction grating. FIG. 4 (A) is a rotation position of 20 °, and FIG. Corresponds to a rotational position of 30 °.

FIG. 5 is a diagram showing a configuration of an optical detection unit of an encoder using an unequal-length pitch diffraction grating.

6A is a diagram illustrating a detailed configuration of an opening window member in FIG. 5, and FIG. 6B is a diagram illustrating a detailed configuration of a spatial filter in FIG.

FIG. 7 is a diagram illustrating a configuration of another optical detection unit of the encoder using the unequal-length pitch diffraction grating.

FIG. 8 is a diagram showing a detailed configuration of the light receiving sensor of FIG. 5 or FIG.

9 is a diagram showing a detailed configuration of a signal processing circuit of a detection signal output from the light receiving sensor of FIG.

[Explanation of symbols]

 Reference Signs List 110 spindle 111 magnetic disk 112 magnetic head 113 carriage mechanism 114 support arm 120 external actuator 121 drive arm 122 guide pin 11 laser beam spot N0 to N9 diffraction grating 51 semiconductor laser light source 52 collimating lens 53 mirror 54, 57 lens 55 opening window member 56 Spatial filter 61 Light receiving sensor 62 A / D converter 63 Memory 64 Multiplier 65 Addition circuit 66 Timing generator 67 Operation processing circuit 68 Position counter 69 Phase data operation circuit

Continued on the front page (72) Inventor Yasuyuki Moriguchi 3-16-3 Higashi, Shibuya-ku, Tokyo Inside Hitachi Electronics Engineering Co., Ltd. (72) Inventor Fujio Tajima 3-16-3 Higashi, Shibuya-ku, Tokyo Hitachi Electronics Engineering Co., Ltd. Inside the company (72) Inventor Yuji Ota 3-16-3 Higashi, Shibuya-ku, Tokyo Hitachi Electronics Engineering Co., Ltd. (72) Inventor Kazuto Kinoshita 3-16-3 Higashi, 3-3-1 Higashi Shibuya-ku, Tokyo Hitachi Electronics Engineering Co., Ltd. F-term (reference) 2F065 AA03 AA07 AA39 BB02 BB16 BB28 CC03 DD00 FF16 FF48 FF51 GG06 GG12 HH03 HH13 JJ03 JJ09 JJ26 LL00 LL12 LL28 LL42 LL59 MM04 PP13 QQ03 QQ14 UQ1QQ15U08 EB32 EC00 EC03 EC04 EC11 ED00 ED11 ED23 ED27 ED34 FA01 FA02 FA12 2H049 AA04 AA14 AA50 AA55 AA56 5D088 BB01

Claims (20)

[Claims] 1. A member that rotates and moves in an arc shape, a diffraction grating attached to the member, an illumination optical system that irradiates the diffraction grating with a light beam, and ± first-order diffracted light generated by the irradiation of the light beam. Detecting optical system means for creating an interference fringe pattern from the light receiving means for receiving the interference fringe pattern using a linear light receiving area formed by linearly arranging pixel groups having substantially the same length and width. A diffraction grating encoder comprising: element means; and position detection means for detecting a rotational position of the member based on a signal output from each pixel of the light receiving element means. 2. The apparatus according to claim 1, wherein the position detecting means accumulates signals of pixels corresponding to each phase in the pixel group when one cycle of the interference fringe pattern is divided into a plurality of phases. And accumulating means for outputting the accumulated signal, and computing means for outputting a signal indicating the rotational position of the member based on the accumulated signal output from the accumulating means. Diffraction grating encoder. 3. The light receiving element means according to claim 2, further comprising: a multiplying means for multiplying a signal output from each pixel of the light receiving element means by a coefficient corresponding to an arrangement position of the pixel. A diffraction grating encoder characterized in that: 4. The method according to claim 2, wherein the accumulating means accumulates signals of pixels corresponding to each phase in the pixel group when the period of the interference fringe pattern is divided into four phases. And outputting an accumulated signal of each phase. The arithmetic means outputs a sine component signal obtained by subtracting the accumulated signal of the fourth phase from the accumulated signal of the second phase from the accumulating means, The third-phase accumulated signal is subtracted from the one-phase accumulated signal and divided by a cosine component signal, and position data and phase data obtained based on the division result indicate the rotational position of the member. A diffraction grating encoder configured to output as a signal. 5. The diffraction grating encoder according to claim 1, wherein the diffraction grating is constituted by an unequal-length pitch diffraction grating whose grating pitch gradually decreases as the distance from a reference grating increases. . 6. The unequal-length pitch diffraction grating according to claim 5, wherein a distance from a rotation center of the member to an irradiation position of the light beam on the unequal-length pitch diffraction grating is R, When the lattice center coordinate of the lattice N0 of the basic lattice pitch P is X ₀ , and the rotational position θ _{0 of the} member at this coordinate is 0 °, the lattice center coordinate X _{n of the} lattice Nn is X _n = X _n-1. + Pco
s (θ _n-1 ), rotational position θ _n is θ _n = asin (X _n / R)
A diffraction grating encoder characterized in that it is formed so that 7. The illumination optical system according to claim 1, wherein the illumination optical system unit reflects the light beam emitted from the light source toward the diffraction grating. A diffraction grating encoder comprising: mirror means; and lens means for forming an image of the light beam reflected by the mirror means on the diffraction grating. 8. The illumination optical system according to claim 1, wherein the illumination optical system includes: a light source for emitting the light beam; and an image of the light beam emitted from the light source on the diffraction grating. And a hole for allowing the light beam passing through the lens means to pass through the diffraction grating as it is, and also allowing the 0th-order diffracted light generated by the diffraction grating to pass therethrough, generated by the diffraction grating. A perforated mirror provided with a mirror for reflecting the ± 1st-order diffracted light toward the detection lens. 9. The method according to claim 1, wherein the detecting optical system means focuses the ± 1st-order diffracted light generated by the diffraction grating.
Lens means, and a spatial filter means provided at a focusing position of the lens means and having an opening for passing only the ± 1st-order diffracted light, and the ± 1st-order diffracted light after passing through the spatial filter means A second lens means for forming the interference fringe pattern by forming an image on the light receiving element means. 10. The optical system according to claim 9, wherein the first lens means is arranged so that the diffraction grating and the spatial filter means are at conjugate positions, and the second lens means is provided with the spatial filter means and the light receiving means. A diffraction grating encoder comprising a telecentric optical system in which an element means and a conjugate position are arranged. 11. An arm means for rotating and moving in an arc shape, a diffraction grating attached to the arm means, an illumination optical system means for irradiating the diffraction grating with a light beam, and ± 1 generated by the irradiation of the light beam. Detection optical system means for creating an interference fringe pattern from next-order diffracted light, and receiving the interference fringe pattern using a linear light receiving region formed by linearly arranging pixel groups having substantially the same length and width. Light receiving element means, a position detecting means for detecting a rotational position of the arm means based on a signal output from each pixel of the light receiving element means, and a rotational position of the arm means detected by the position detecting means. A magnetic head positioning device, comprising: a positioning means for performing positioning of the magnetic head by controlling. 12. The pixel detecting device according to claim 11, wherein the position detecting means accumulates signals of pixels corresponding to each phase in the pixel group when one cycle of the interference fringe pattern is divided into a plurality of phases. And accumulating means for outputting the accumulated signal, and computing means for outputting a signal indicating the rotational position of the member based on the accumulated signal output from the accumulating means. Positioning device for magnetic head. 13. The light-receiving element means according to claim 12, wherein multiplication means for multiplying a signal output from each pixel of the light-receiving element means by a coefficient corresponding to an arrangement position of said pixel is provided, and a detectable range of said light-receiving element means can be changed. A positioning device for a magnetic head, characterized in that: 14. The method according to claim 12, wherein the accumulating means accumulates signals of pixels corresponding to each phase in the pixel group when the period of the interference fringe pattern is divided into four phases. And outputting an accumulated signal of each phase. The arithmetic means outputs a sine component signal obtained by subtracting the accumulated signal of the fourth phase from the accumulated signal of the second phase from the accumulating means, The third-phase accumulated signal is subtracted from the one-phase accumulated signal and divided by a cosine component signal, and position data and phase data obtained based on the division result indicate the rotational position of the member. A magnetic head positioning device, which is configured to output a signal. 15. The magnetic head according to claim 11, wherein the diffraction grating is constituted by an unequal-length pitch diffraction grating whose grating pitch gradually decreases as the distance from the reference grating increases. Positioning device. 16. The unequal-length pitch diffraction grating according to claim 15, wherein a distance from a rotation center of the member to an irradiation position of the light beam on the unequal-length pitch diffraction grating is R, When the lattice center coordinate of the lattice N0 of the basic lattice pitch P is X ₀ , and the rotational position θ _{0 of the} member at this coordinate is 0 °, the lattice center coordinate X _{n of the} lattice Nn is X _n = X _n-1. + Pco
s (θ _n-1 ), rotational position θ _n is θ _n = asin (X _n / R)
A magnetic head positioning device characterized in that it is formed so as to be as follows. 17. The method according to claim 11, wherein:
In the illumination optical system unit, a light source that emits the light beam, a mirror unit that reflects the light beam emitted from the light source toward the diffraction grating, and a light beam that is reflected by the mirror unit. And a lens means for forming an image on a diffraction grating. 18. One of claims 11 to 16
In the illumination optical system unit, a light source that emits the light beam, a lens unit that forms an image of the light beam emitted from the light source on the diffraction grating, and the light beam that has passed through the lens unit A mirror that has a hole that allows the diffraction grating to pass through as it is, and also allows the zero-order diffraction light generated by the diffraction grating to pass therethrough, and reflects the ± 1st-order diffraction light generated by the diffraction grating to the detection lens side. A magnetic head positioning device comprising: a perforated mirror provided. 19. The method according to claim 11, wherein:
In the first aspect, the detection optical system means may be configured to focus ± 1st order diffracted light generated by the diffraction grating.
Lens means, and a spatial filter means provided at a focusing position of the lens means and having an opening for passing only the ± 1st-order diffracted light, and the ± 1st-order diffracted light after passing through the spatial filter means And a second lens means for forming the interference fringe pattern by forming an image on the light receiving element means. 20. The apparatus according to claim 19, wherein the first lens means is arranged so that the diffraction grating and the spatial filter means are at a conjugate position, and the second lens means is provided with the spatial filter means and the light receiving means. A magnetic head positioning device comprising a telecentric optical system in which an element means and a conjugate position are arranged.