JPH1194514A - Interference device, position detecting device, positioning device, information storing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable non-contact, highly reliable, and highly accurate position detection and positioning without providing a special member for the side of an object or working on the object by further amplitude-dividing a synthetic beam of beams to be interfered into a predetermined number of split beams in the same region. SOLUTION: A reflected beam divided by a probe-shaped polarizing prism PBS is brought to convergently illuminate one side surface of a head arm ARM1, and the reflected light returns to the original light path. On the other hand, a transmitted beam is brought to convergently illuminate a reflection deposition film at the end face, and the reflected light returns to the original path. Then two beams synthesized at the polarizing prism PBS are converted into linear polarized light, reflected by a non-polarizing beam splitter NBS, transmitted through a 1/4 wavelength plate QWP, and further converted from circular polarized light which rotates in directions opposite to each other into linear polarized light which rotates by the change of a phase difference. The linear polarized light is amplitude-divided into four beams by a phase diffraction grating in a staggered grating structure, transmitted through polarizing plates arranged in such a way that their directions of polarization are shifted by 45 degrees from each other, and converted into interference light with phases shifted by 90 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference apparatus, an apparatus, a positioning apparatus, and an information recording apparatus using the same.
The present invention is particularly applicable to a position detecting device for detecting a position change of an object in a non-contact manner, such as an interferometer for an object such as a magnetic head of a hard disk drive, a positioning device, and a hard disk used for a computer using the same. The present invention can be favorably applied to a drive device (hereinafter referred to as an HDD) manufacturing device, among which a device for writing a servo track signal to a hard disk inside the HDD with high accuracy.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view of a conventional apparatus for writing a servo track signal to a hard disk in an HDD.

In FIG. 4, HDD is a hard disk drive, HD is a hard disk, SLID is a slider, AR
M1 is a magnetic head arm, VCM is a voice coil motor, OHD
Is the HD spindle of the hard disk, and O is the rotation axis of the magnetic head arm ARM1.

[0004] A magnetic recording medium is deposited on the surface of each hard disk. Hard disk HD is spindle OHD
, And a magnetic head is arranged near the surface of each hard disk HD at all times.
The magnetic head is incorporated in a substantially rectangular parallelepiped portion called a slider SLID attached to the end of each arm portion of a magnetic head arm ARM1 having a rotation center O outside the hard disk HD.
By rotating this, it is possible to relatively move in a substantially radial direction on the hard disk HD.

Accordingly, magnetic information can be written or read at an arbitrary position (track) on the surface of the disk-shaped hard disk by the rotating hard disk HD and the magnetic head moving in an arc.

[0006] The magnetic recording method on the hard disk HD surface firstly uses the rotation center OHD of the hard disk.
Divided into multiple circular tracks with different concentric circle radii,
Further, each annular track is also divided into a plurality of arcs, and is finally recorded and reproduced in a plurality of arc-shaped areas in a time series along the circumferential direction.

Meanwhile, as a recent trend, there is a demand for an increase in the recording capacity of a hard disk, and there is a demand for increasing the density of information recorded on the hard disk. As a means for increasing the density of information recorded on the hard disk, it is effective to reduce the width of concentrically divided tracks to improve the recording density in the radial direction.

[0008] The recording density in the radial direction is represented by a track density TPI (track / inch) per one inch length.
It is about 000 TPI. This means that the track spacing is about 3 microns. To determine such a fine track pitch, a magnetic head must be mounted on a hard disk.
Resolution of about 1/50 of track width in the radial direction of HD (0.
It is necessary to perform positioning at (05 microns) and write servo track signals in advance. The important technique here is to write servo track signals sequentially while performing high-resolution positioning in a short time.

PROD is a push rod, ARM 2 is an arm for the push rod PROD, MO is a control motor for positioning, RE is a rotary encoder for detecting the rotation amount of the rotating shaft of the motor MO, and SP is a detection output from the rotary encoder RE. A signal processor MD that analyzes and issues a positioning command signal to a magnetic head servo track signal writing position is a motor driver that drives the motor MO according to a command signal of the signal processor SP. These form the rotary positioner RTP.

Conventionally, as shown in FIG. 4, a cylindrical surface of a push rod PROD is pressed against the side of a magnetic head arm ARM1 (an arm portion for a magnetic head for the lower surface of the lowermost hard disk) to form a rotary encoder RE and a signal. While performing feedback control in the system of the processor SP and the motor driver MD, the arm ARM2 is rotated by the motor MO, and the magnetic head arm is finely fed sequentially through the push rod PROD to perform positioning, and the servo track is sequentially transmitted from the signal generator SG. The signal was being written from the magnetic head. At this time, in order to ensure the contact, a slight current was usually passed to the voice coil motor VCM, and the push rod PROD was pressed also from the head arm ARM1 side.

[0011]

Recently, assuming even higher precision positioning, a method of mechanically pressing the magnetic head arm, which may transmit vibration due to rotation of the hard disk to the motor MO, is not employed. A non-contact method for measuring the movement of the magnetic head arm with high precision by optical means has also been devised. FIG. 5 shows an example of such an apparatus.

In FIG. 5, HeNe is a laser light source, M1 and M2.
Is a mirror, BS is a beam splitter, CC is a retroreflector such as a corner cube provided on the magnetic head arm ARM1, and PD is a light receiving element.

In this apparatus, a laser light source HeNe, mirrors M1 and M2, a beam splitter BS, a retro-reflector CC
To form a Michelson interferometer, and the light beam L1 passed through the retro-reflector CC to the mirror M1 and the mirror M2, respectively.
The light receiving element PD detects interference light between the magnetic head arm L2 and the position information of the magnetic head arm ARM1. Then, based on the obtained detection signal, the signal processor SP issues a command,
By controlling the current flowing from the voice coil motor driver VCMD to the voice coil motor VCM, the magnetic head arm is moved directly and appropriate control is added.

However, in such an apparatus, it is necessary to mount a retro-reflector CC such as a corner cube on the magnetic head arm, and the control characteristics are likely to be degraded due to securing of space, troublesome mounting and dismounting, and an increase in weight. .

According to the present invention, in view of the above-mentioned conventional example, the position of an object can be non-contacted with high reliability and high accuracy and high resolution without the need for providing an oversized member or special processing on the object side. It is an object of the present invention to provide a position detection device capable of position detection and positioning, a positioning device, an interference device capable of realizing the same, and an information recording device using the same.

[0016]

According to a first aspect of the present invention, a combined light beam of two light beams to be interfered is divided into three or more divided light beams in the same area by amplitude division. An interferometer characterized in that interference light beams having different phases from each other are obtained from light beams.

In the second invention, the amplitude division is different from the amplitude division by two.
It is performed using a diffraction grating having a diffraction effect in each direction,
The plurality of split light beams are diffracted light beams having the same absolute value of the order generated by the diffraction grating.

According to a third aspect of the present invention, at least one of the two light beams to be caused to interfere is caused to pass through an object whose displacement is to be measured, and a plurality of light beams having different phases obtained by the interference device are obtained. A position detecting device for detecting interference light flux and detecting relative displacement information of the object.

According to a fourth aspect of the present invention, there is provided a positioning device for positioning the object based on a result of detection by the position detecting device.

According to a fifth aspect of the present invention, a light beam is divided into two light beams, and one of the light beams is condensed and reflected on a side surface of a recording / reading head arm means in a hard disk drive. Is superimposed on another light beam to obtain a combined light beam, the combined light beam is amplitude-divided into three or more divided light beams in the same region, and an optical system for obtaining interference light beams having different phases from each other from the plurality of divided light beams. Means, and a control system for positioning the arm means based on a result obtained by detecting each of the interference light fluxes, wherein a signal is written to a hard disk every time the arm means is positioned. It is an information recording device.

According to a sixth aspect of the present invention, the control system further includes means for controlling the distance between the arm means and the optical means to be constant based on the results obtained by detecting the interference light beams, respectively, Means for positioning the means in accordance with the recording position.

According to a seventh aspect of the present invention, a converged light beam is divided in a light transmitting member, and a path from one of the divided light beams to a surface existing in a space outside the light transmitting member is provided. Are reciprocated on the surface in such a manner that they are substantially condensed, and the other of the divided light beams is reciprocated through a path having a wave optical path length substantially equal to the path in the light transmitting member. An interferometer characterized in that it oscillates and selects an area of a part of the obtained combined light beam to obtain an interference signal.

The eighth invention is further characterized in that the selected partially multiplexed light beam is subjected to amplitude division within the same region to obtain interference signals having different phases from each other.

According to a ninth aspect of the present invention, the surface is a surface on an object whose displacement is to be measured, and relative displacement information of the object is detected based on an interference signal obtained by the interference device. A position detecting device characterized by the above-mentioned.

According to a tenth aspect of the present invention for achieving the above object,
A positioning device for positioning the object based on a detection result by the position detection device described above.

An eleventh invention for achieving the above object is
The convergent light beam is split in the light transmitting member, and a path from one of the split light beams to the side surface of the recording / reading head arm means in the hard disk drive in the space outside the light transmitting member is formed on the side surface. After reciprocating in a substantially condensed manner above, and after reciprocating the other of the divided light beams through a path of a wave optical optical path length substantially equal to the path in the light transmitting member,
Optical means for multiplexing the divided light fluxes, selecting a part of the obtained combined light flux to obtain an interference light flux, and the arm means based on a result obtained by detecting the interference light flux And a control system for performing positioning of the arm means, wherein a signal is written to a hard disk every time the arm means is positioned.

In a twelfth aspect of the present invention, the control system further includes means for controlling the distance between the arm means and the optical means to be constant based on a result obtained by detecting the interference light beam; Means for positioning the recording medium in accordance with the recording position.

A thirteenth invention for achieving the above object is as follows.
The light beam is split into two linearly polarized light beams whose polarization planes are orthogonal to each other using a polarization splitting element, and one of the linearly polarized light beams is condensed, illuminated and reflected on a reflecting surface that moves relatively, and the other light beam is used as a reference reflecting means. After returning the two to the polarization splitting element and recombining them, transmitting them through a １ ／ wavelength plate, the light is further divided into a plurality of light fluxes by an amplitude splitting means. An interferometer characterized in that interference light beams having phases shifted from each other are generated by transmitting the light through a polarizing plate arranged in a different direction.

The fourteenth invention is further characterized in that the amplitude dividing means has a diffraction grating.

The fifteenth invention is further characterized in that the reference reflection means is provided on a light transmitting member constituting the polarization splitting element.

A sixteenth invention for achieving the above object is as follows.
The light beam is split into two linearly polarized light beams whose polarization planes are orthogonal to each other using a polarization splitting element, and one of the linearly polarized light beams is condensed, illuminated and reflected on a reflecting surface that moves relatively, and the other light beam is used as a reference reflecting means. After returning the two to the polarization splitting element and recombining them, transmitting them through a １ ／ wavelength plate, the light is further divided into a plurality of light fluxes by an amplitude splitting means. By passing through a polarizing plate arranged in a shifted direction to generate interfering light beams out of phase with each other, and using an electric signal output signal obtained by receiving light with a corresponding light receiving element, a signal is output between the reflecting surfaces. The position detecting device is characterized by measuring a change in distance of the position.

In a seventeenth aspect, a multi-mode laser diode is used as a light source for emitting the light beam, the light beam is split into two light beams by the polarization splitting element, and the one light beam is reflected by the reflection surface. The difference in wave optical path length between the two light beams until the other light beams are reflected by the reference reflecting means, the two light beams are returned to the polarization separation element, and the light beams are superimposed on each other. The image optical path lengths are configured to be different from each other.

According to an eighteenth aspect of the present invention, the other light beam is reflected at a position deviated from the beam waist position by the reference reflection means, and a part of the light beam superimposed by the polarization splitting element is selectively used by using an aperture. And generating a substantially plane wave, and then dividing the light into a plurality of light beams by the amplitude dividing means.

In the nineteenth aspect, the light beam is guided to the polarization splitting means via the non-polarization splitting means, and the light beam superimposed by the polarization splitting means is returned to the non-polarization splitting means and taken out to a side different from the light source. It is characterized by having done.

According to a twentieth aspect of the present invention for achieving the above object,
A positioning device for positioning an object having the reflection surface based on a detection result by the position detection device described above.

A twenty-first invention for achieving the above object is as follows:
The light beam is split into two linearly-polarized light beams whose polarization planes are orthogonal to each other using a polarization splitting element, and one of the linearly-polarized light beams is condensed, illuminated and reflected on the side of the recording / reading head arm means in the hard disk drive. One of the light beams is reflected by the reference reflecting means, the two are returned to the polarization separation element, recombined, and transmitted through a quarter-wave plate, and further divided into a plurality of light beams by the amplitude dividing means. The divided light fluxes are transmitted through a polarizing plate arranged in a direction shifted from each other to generate interference light fluxes that are out of phase with each other, and use the electric signal output signal obtained by receiving light with the corresponding light receiving element. Distance variation measuring means for measuring a variation in the distance between the arm variation means, a rotation positioning means for controlling a rotational position of the distance variation measuring means, and a distance variation detected by the distance variation measuring means. Control means for controlling the rotational position of the arm means so as to cancel out, and a servo track signal is written from the recording / reading head to the hard disk every time the rotational positioning means is positioned. .

[0037]

FIG. 1 is a schematic diagram of a servo track signal writing apparatus according to a first embodiment of the present invention. Hereinafter, the same members as those described above are denoted by the same reference numerals.

The hard disk drive HDD has a magnetic head arm A having a rotation axis O outside the hard disk HD.
RM1 is installed, and the slider SLID attached to the tip of the RM1
It is arranged with a gap of μm (below) and moves in an arc shape by the rotation of the magnetic head arm ARM1. The rotation is performed by passing a current through the voice coil motor VCM.

Such a device is spatially arranged at an appropriate position as shown in FIG. 1 with respect to a hard disk drive HDD including a hard disk HD, a slider SLID, a magnetic head arm ARM1, a voice coil motor VCM, and the like. I have.

SG is a signal generator for generating a servo track signal to be written to the hard disk. This servo track signal is written to the hard disk HD via the magnetic head of the slider SLID.

The position detecting unit NCPU includes a support arm ARM2
The tip of the optical probe NCP is inserted into a slot-shaped opening (not shown) of the base plate of the hard disk drive HDD, and is arranged near the side of the magnetic head arm ARM1. The support arm ARM2 is arranged to be rotatable about a rotation axis coaxial with the rotation center O of the magnetic head arm ARM1. And position detection unit
The rotation position of the NCPU is detected by a high-resolution rotary encoder RE attached to the rotation axis of the support arm ARM2, and based on the detected data, the signal processor SP1 is used.
Drives the motor MO via the motor driver MD. With this form of feedback control, the position detection sensor unit NCPU is rotationally positioned.

Here, the position detecting unit NCPU is constituted by an optical sensor unit as described below.

FIG. 2 is an explanatory view of the configuration of an optical system for explaining the optical sensor unit. The optical sensor unit consists of a multimode laser diode LD, a non-polarizing beam splitter NBS, a probe-type polarizing prism PBS, and a reference reflecting surface.
M, quarter-wave plate QWP, light beam diameter limiting aperture AP, light beam amplitude splitting diffraction grating GBS, polarizing plates PP1 to PP4, photoelectric elements PD1 to PD4
And so on.

The divergent light from the multi-mode laser diode LD is condensed by a collimator lens COL.
M, pass through the non-polarizing beam splitter NBS, and then enter the probe-like polarizing prism PBS composed of a light-transmitting substance of the optical probe NCP, where the light is split by the light-dividing surface of the probe-like polarizing prism PBS for each polarization component. You. The reflected S-polarized light beam is applied to the side of the head arm ARM1 (here, the arm portion for the magnetic head for the lower surface of the lowermost hard disk in this case), which is arranged in a space approximately 300 μm away from the end face of the probe-like polarizing prism PBS. The light is condensed and illuminated near the beam waist, and the reflected light returns to the original optical path as a divergent spherical wave, and returns to the light splitting surface of the probe-like polarizing prism PBS. The P-polarized light flux transmitted by the probe-shaped polarizing prism PBS is condensed and illuminated on the reflective deposition film on the end face at a position shifted from the beam waist (a state before the beam waist),
The reflected light returns to the original optical path, and the probe-shaped polarizing prism PBS
Is returned to the light splitting surface. The wave optical optical path lengths of both optical paths are set so that the optical path length difference between them is within the coherent distance of the light source, that is, they are substantially equal optical path lengths.

Specifically, for example, the shape is given as follows. The width of the probe-shaped polarizing prism PBS made of glass is about 2 mm, and the light beam reflected by the polarizing prism PBS travels 1 mm in the glass, 0.3 mm travels in the air, and reaches the arm arm side ARM1. Illuminated. Therefore, the reciprocating wave optical path length L1 from the polarizing prism to the reflecting surface
= (1 × 1.5 + 0.3) × 2 = 3.6. On the other hand, polarizing prism PB
The luminous flux transmitted by the S travels 1.2 mm through the glass and illuminates the glass end face. Therefore, the round-trip wave optical path length
L2 = (1.2 × 1.5) × 2 = 3.6. Here, the refractive index of the glass was set to 1.5.

Next, the focus position of the light beam (beam waist)
Is set at a position of 0.3 mm emitted from the polarizing prism. Then, the position of the wave source of the divergent spherical wave reflected from the side of the head arm and the reference reflection surface appears to be shifted in the optical axis direction. Assuming that the inside of the probe-shaped polarizing prism is viewed from the light source side, the focal point (wave source) on the side of the head arm is L1 ′ = (1 + 0.3 × 1.5) = 1.45 from the polarizing prism divided surface.
Look at the position. The position of the divergent spherical wave source from the reference reflecting surface is L2 ′ = 1.2 × 2-1.45 = 0.9 from the polarizing prism division surface.
It looks at position 5. However, both positions are visible in the glass. Therefore, both divergent spherical wave sources
0.5mm deviation (imaging optical path length difference occurs)
That is, when the two light beams are superimposed, the wavefronts do not completely coincide with each other, and if the two light beams are polarized, concentric interference fringes are obtained. In such a case, if the phase of the wavefronts of the two fluctuates due to the relative movement of the head arm, concentric interference fringes will appear and flow from the center. However, since the concentric interference fringes have a small shift amount of about 0.5 mm in the optical axis direction between the two divergent spherical waves, a substantially one-color (same phase) interference fringe portion can be obtained widely at the center. Therefore, an appropriate aperture AP is provided so as to take out only the substantially one-color portion, and a part of the light beam is taken out. Thereafter, it can be treated as a substantially plane wave.

Since the two light beams synthesized by the probe-type polarizing prism PBS are linearly polarized light beams orthogonal to each other, they do not actually interfere with each other as they are, and do not become bright and dark signals even if detected. When the two light beams reflected by the non-polarizing beam splitter NBS pass through the quarter-wave plate QWP, the linearly polarized light beams that are orthogonal to each other are converted into circularly polarized light beams that are opposite to each other. Is converted into one linearly polarized light that rotates due to the fluctuation of the phase difference.

The rotating linearly polarized light is reflected by the aperture AP
After that, four beams (in this case, ± 1st-order diffracted light generated in each of the two orthogonal directions) are generated by a phase diffraction grating having a staggered grating structure (that is, a phase diffraction grating having a diffractive action in each of the two orthogonal directions). ). Due to the amplitude division from the same area, any light flux has a shape and intensity unevenness,
Since the properties such as defects are completely divided equally, even if the interference fringes are not one-color or the contrast is lowered for some reason, the influences are all the same. In particular, the reflected light from the side surface of the head arm is disturbed in wavefront due to the minute uneven structure, and the intensity unevenness is strongly generated. However, the wavefronts of the four light beams are disturbed and the state of the intensity unevenness is equal. The phase diffraction grating is designed to minimize generation of zero-order light at the same time.

The light beam divided into four light beams is polarized by an angle of 45 degrees with respect to each other.
, The light / dark timing is converted into interference light having a phase shifted by 90 degrees. The lowering of the contrast due to the influence of wavefront disturbance and intensity unevenness is all equally affected. Each light and dark luminous flux is transmitted to each light receiving element PD1, PD2, PD3, PD4
Is received.

Light receiving element PD1 having a phase difference of 180 degrees from each other
And the signal of PD2 is detected differentially,
The components (this includes the amount of decrease in contrast due to disturbance of the wavefront and the like) are almost removed. This is an A-phase signal. Similarly, the signals of the light receiving elements PD3 and PD4 having a phase difference of 180 degrees are differentially detected, and the DC component is almost removed. This is a B-phase signal. The A and B phase signals have a phase difference of 90 degrees from each other, and the Lissajous waveform observed by the oscilloscope is circular. The amplitude (the size of the circle) of the waveform of the Lissajous fluctuates due to minute irregularities on the side surface of the head arm, but the center position does not fluctuate. Therefore, essentially no error occurs in phase detection (measurement of relative distance). In particular,
The A and B phase signals are converted to a DC component 0 by a binarization circuit (not shown).
Will be binarized with the threshold value as the threshold level, but even if the original A and B phase signals fluctuate in amplitude, the DC component does not fluctuate at 0, so the phase of the binarized signal No fluctuation occurs, so that highly accurate position detection can be performed by the signal processor SP2 using the binarized signal having a stable phase.

By condensing and illuminating the side surface of the head arm, the influence of the fluctuation of the interference state (one-color deviation) due to the relative angle deviation (alignment deviation) of the head arm side surface is avoided. In other words, by condensing illumination, even if there is a misalignment, the main emission direction of the divergent spherical wave is slightly shifted to avoid vignetting of the spherical wave itself, and the overlapping state of the wavefronts of the two divergent spherical waves Does not change, so that the interference state can be stably obtained. Therefore, it is unnecessary to adjust the side of the head arm and the illuminating light beam, and it operates as an interference-type position detection sensor that is very easy to handle.

Although the illumination position shift (parallel shift) does not contribute to the phase shift of the divergent spherical wave, the interference signal amplitude fluctuates due to a minute change in the unevenness of the head arm according to the illumination position. However, since the center position of the Lissajous waveform does not fluctuate, essentially no error occurs in phase detection.

The positional relationship between the head arm and the position detection sensor does not shift as long as the head arm and the position detection sensor are both rotated about a coaxial rotation axis and the distance between them is kept constant. However, since a perfect coaxial cannot be realized in reality, a relative positional relationship (angular displacement, parallel displacement) occurs during rotation of the two members due to an axis displacement error. However, as described above, essentially no problem occurs even if an alignment shift or a parallel shift occurs.

The signal finally detected is a sinusoidal signal having a cycle of half the wavelength of the light source, since the principle of the measurement is interference measurement by a reciprocating optical path. When using a laser diode with a wavelength of 0.78 μm, the period is 0.39 μm
(Ie, one sine wave every time the distance between the side of the head arm ARM1 and the optical probe NCP changes by 0.39 μm), and the relative distance fluctuation can be detected by counting the number of waves. Further, since two phases (A and B phases) of a sine wave signal having a phase difference of 90 degrees are obtained as described above, the signal is electrically divided by a well-known electric phase dividing device. After counting, the relative positional deviation with finer resolution can be detected. If it is electrically divided into 4096, the relative displacement can be detected to a minimum of 0.095 nm.

The signal processor SP2 supplies a control current to the head arm drive motor (voice coil) VCM via the motor driver VCMD so that the relative displacement thus detected becomes zero. By doing this,
For example, at the above-mentioned wavelength, the relative position of the magnetic head arm ARM1 with respect to the optical probe NCP can be stably maintained (servo applied) at about several times ± 0.095 nm.

On the other hand, a rotary encoder RE for generating a signal of 81000 sine wave / rotation as a specific numerical value is built in,
Optical probe as a position detection sensor attached near the side of the head arm with a radius of 30 mm if using the high-precision rotary positioner RTP that can be divided and positioned in 2048
NCP can be positioned with a resolution several times that of ± 1.4 nm.

Since the relative position stabilization of the position detecting sensor itself is about several times of ± 0.095 nm as described above, the positioning resolution combining the two is about the performance of the high-precision rotary positioner itself.

As described above, by adding a servo for keeping the relative position of the head arm end surface constant to the high-precision rotary positioner via the position detection sensor, the vibration caused by the rotation of the hard disk or the like is applied to the high-precision positioner. Stable positioning accuracy can be obtained without any disturbance such as transmission via the arm ARM1. Signal writing is performed by rotating the arm ARM2 with the motor MO and moving the optical probe NCP while performing feedback control with the system of the rotary encoder RE, signal processor SP, and motor driver MD, and canceling the displacement at this time. By displacing the magnetic head arm ARM1 in the system of SP2, motor driver VCMD, and head arm drive motor VCM, the magnetic head arm is positioned while feeding it minutely sequentially, and the servo track signal from the signal generator SG is sequentially written from the magnetic head. .

The interference between the light beam reflected from the side of the head arm and the light beam reflected from the reference reflecting surface is obtained within the coherent distance of the light source. Single mode laser diodes are
The coherence length is long, but a mode hop occurs, and a phenomenon that the interference phase jumps may occur. In this embodiment, a multi-mode laser is used to make the optical path length substantially equal, and the optical path length equal to or smaller than the coherence distance. Use by difference. As a specific numerical example, assuming that the center wavelength of the light source is λ0 = 780 nm, the full width at half maximum of the multi-mode spectrum envelope is Δλ = 6 nm, and the full width of the coherent distance is generally obtained by dividing the square of λ0 by Δλ, etc. It is about ± 50 μm around the optical path length.

The wavelength of a laser diode generally fluctuates due to fluctuations in the ambient temperature. Center wavelength 780n
Taking a laser diode having an m and a temperature coefficient of 0.06 nm / ° C. as an example, when the optical path length difference ΔL = 50 μm, the deviation of the measured value due to a temperature change of 1 ° C. is about ± 5 nm.

If the distance is kept constant near the coherence peak, an optical path length difference of ± 10 μm can be realized, in which case the measurement error is ± 1 nm. This value is sufficient precision for a servo track writer.

In general, if the laser interferometer is configured such that the optical path is separated and exposed to the air, the signal output is not stable due to fluctuations or the like. However, in the present embodiment, most of the interference optical path is a common optical path, which is separated into two optical paths near the tip of the probe-like polarizing prism but is small and in the glass medium, so that the influence of fluctuation and the like is very small. Is configured.

The main effects of the first embodiment will be described below. 1. Since the position of the side of the head arm can be measured completely without contact, the resolution, accuracy and stability of servo writing are improved. 2. Since the principle of laser interferometry is used, the resolution and accuracy are very high. 3. Since the minute uneven surface on the side of the head arm is directly measured, the versatility is high, and it is not necessary to add a special optical element or the like to the hard disk side. 4. Since there is little adverse effect on the measurement system due to misalignment between the side of the head arm and the illuminating light beam, it is easy to adjust the position associated with attachment, detachment, and replacement, and servo writing work to the hard disk can be performed efficiently. 5. Since an equal optical path length interference system is used, the accuracy is relatively high even under temperature fluctuations. 6. Most of the interference light paths are common light paths, and most of the divided light paths are also in the glass, so that there is little reduction in accuracy due to environmental fluctuations.

FIG. 3 is an explanatory view of the configuration of an optical system according to the second embodiment in which the shape of the probe-like polarizing prism is changed to cope with the case where the side surface of the head arm approaches the hard disk surface. The other configuration is the same as that of the first embodiment, and the description and drawings are omitted.

In the present embodiment, a parallel glass plate G with a reflection film is bonded immediately after the split surface of the probe-shaped polarizing prism PBS, and the P-polarized light flux transmitted through the split surface of the probe-shaped polarizing prism PBS is: The light is reflected by the reflection film M1, passes through the polarization film again, enters the partial reflection film M2 provided on the side surface of the optical probe NCP, and returns to the original optical path. The S-polarized light beam reflected by the splitting surface of the probe-shaped polarizing prism PBS goes out of the optical probe NCP as in the previous embodiment, is condensed and illuminated on the side of the head arm ARM1, and the reflected light returns to the original optical path. .

By adopting this configuration, the optical probe
The gap between the tip of the NCP and the lower surface of the lowermost hard disk HD (see Fig. 1) can be increased, making it possible to measure even the side of the magnetic head arm where the magnetic head arm is close to the hard disk surface. . The most effect is obtained by processing the end of the parallel glass plate G to 45 degrees as shown in FIG.

[0067]

As described above, according to the first aspect, even if three or more interference light beams having different phases from each other are generated even if the wavefront is disturbed due to, for example, a minute uneven structure of the reflection surface, the intensity unevenness is strongly generated. The influence can be obtained in a state where the influences are equal to each other, and an interference device is realized in which individual error factors are unlikely to occur in each interference light beam regardless of the reflection surface.

Further, according to the second aspect of the present invention, an interference light beam in which such individual error factors are unlikely to occur can be obtained with a small and simple configuration.

According to the third aspect of the present invention, it is possible to obtain a plurality of interference light beams in which such individual error factors are unlikely to occur without disposing a special member on the object side. Information can be obtained with high precision and high resolution.

According to the fourth aspect of the present invention, such high precision,
The positioning of the object can be executed with high accuracy and high resolution based on the high-resolution relative displacement information.

According to the fifth aspect of the present invention, three or more interference light beams having different phases from each other are disturbed by, for example, a minute uneven structure on the side surface of the arm means for the recording / reading head, and the wavefront is disturbed to generate strong intensity unevenness. Also, these effects can be obtained in a state where they are equal to each other, and a plurality of interference light beams in which such individual error factors are unlikely to occur can be obtained without arranging a special member on the arm means. Positioning of the arm means with high accuracy and high resolution.
Higher density information recording can be realized.

Further, according to the sixth aspect, even when a light source having a relatively short coherence distance is used as the light beam, the positioning of the arm means can be performed with high accuracy and high resolution over a wide range.

Further, according to the seventh aspect, a light source having a relatively short coherence distance can be used as a light beam, stable reflected light can be obtained irrespective of surface irregularities, and the reference-side branch optical path can be made compact and simple. In addition, it is possible to obtain an interference signal in which the influence of environmental fluctuation can be reduced by further increasing the common optical path of both optical paths, and at the same time, the influence of the phase unevenness of the interference light due to the difference in the geometric optical path length between the two is eliminated. A possible interference device is realized.

Further, according to the eighth aspect, a plurality of interference light beams in which individual error factors hardly occur can be obtained.

Further, according to the ninth aspect, relative displacement information can be obtained with high accuracy and high resolution by using an interference signal obtained by removing the influence of phase unevenness obtained by a small and simple configuration having a small error. Become.

Further, according to the tenth aspect, the object can be positioned with high accuracy and high resolution based on the relative displacement information with high accuracy and high resolution.

Further, according to the eleventh aspect, a light source having a relatively short coherence distance can be used as the light beam, and the reflected light can be obtained stably irrespective of the unevenness of the side surface of the recording / reading head arm means. The branch optical path can be made compact and simple, and the effect of environmental fluctuations can be reduced by increasing the common optical path of both optical paths.At the same time, the effect of the phase unevenness of the interference light caused by the geometric optical path length difference between the two is eliminated. The obtained interference signal can be obtained, and by using the interference signal, the positioning of the arm means can be performed with high accuracy and high resolution, and higher-density information recording can be realized.

Further, according to the twelfth aspect, even when a light source having a relatively short coherence distance is used as the light beam, the positioning of the arm means can be performed with high accuracy and high resolution over a wide range.

Further, according to the thirteenth aspect, there is provided an interferometer capable of generating a plurality of homogeneous phase-shifting interference light beams regardless of the unevenness of the reflection surface and without being affected by relative alignment shift. Is achieved.

Further, according to the fourteenth aspect, a plurality of such interference light beams of the same quality can be obtained with a smaller and simpler configuration.

Further, according to the fifteenth aspect, the reference optical path can be made smaller and simpler.

Further, according to the sixteenth aspect, a plurality of homogeneous phase-shifting interference light beams are generated irrespective of the unevenness of the reflecting surface and without being affected by the relative alignment shift. High-accuracy and high-resolution distance fluctuation measurement can be performed.

Further, according to the seventeenth aspect, a stable and more accurate measurement which does not matter the low coherence is realized by using a small light source which is stable even though the coherence is low. .

According to the eighteenth aspect of the present invention, more accurate measurement can be realized by removing the influence of the unevenness of the phase of the interference light caused by the different optical path lengths.

Further, according to the nineteenth aspect, a simple configuration in which the light source side and the detection side are appropriately separated is realized.

Further, according to the twentieth aspect, it is possible to position an object with higher precision and higher resolution based on the distance fluctuation measurement with higher precision and higher resolution than described above.

According to the twenty-first aspect, a plurality of homogeneous phase-shifting interference light beams are generated irrespective of the unevenness of the side surface of the recording / reading head arm means and without being affected by the relative alignment shift. By using this, distance fluctuation measurement with higher precision and higher resolution can be performed, and the positioning of the arm means can be performed with higher precision and higher resolution. As a result, information recording with higher density can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a servo track signal writing device according to a first embodiment.

FIG. 2 is an explanatory diagram of an optical non-contact distance sensor unit of the servo track signal writing device shown in FIG.

FIG. 3 is an explanatory diagram of an optical non-contact distance sensor unit of the servo track signal writing device according to the second embodiment.

FIG. 4 is an explanatory diagram of a conventional servo track signal writing device using a hard disk drive device and a push rod.

FIG. 5 is an explanatory diagram of a conventional servo track signal writing device using a hard disk drive and a retro-reflector interferometer.

[Explanation of symbols]

NCPU Optical non-contact sensor unit NCP Optical probe (Light guide member) NBS Non-polarized beam splitter PBS Polarized prism film M Reflective film LGT Light source LD Laser diode COL Collimator lens PD Light receiving element PP Polarizing plate G Transparent substrate QWP quarter wave plate SLID Magnetic Head Slider ARM1 Magnetic Head Arm (Rotating Member) ARM2 Rotary Positioner Arm (Rotating Member) RTP Rotary Positioner RE Rotary Encoder MO Motor MOD Motor Driver VCM Magnetic Head Arm Rotating Motor (Voice Coil) VCMD Voice Coil Motor Driver HD Hard disk (recording medium)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shigeki Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Naoki Kawamata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside (72) Inventor Hiroyuki Hagiwara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Shiomi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (21)

[Claims] 1. An interference method comprising: dividing a combined light beam of two light beams to be interfered into three or more divided light beams in the same region; and obtaining interference light beams having different phases from each other from the plurality of divided light beams. apparatus. 2. The method according to claim 1, wherein the amplitude division is performed by using a diffraction grating having a diffractive action in each of two different directions, and the plurality of split light beams are diffracted lights having the same absolute value of the order generated by the diffraction grating. 2. The interference device according to 1. 3. An interference device according to claim 1, wherein at least one of the two light beams to be caused to interfere passes through an object whose displacement is to be measured, and a plurality of interference light beams having different phases obtained by the interference device according to claim 1 or 2 are detected. A position detecting device for detecting relative displacement information of the object. 4. A positioning device for positioning the object based on a detection result by the position detection device according to claim 3. 5. A light beam is split into two light beams, one of the light beams is condensed and reflected on a side surface of a recording / reading head arm means in a hard disk drive, and the reflected light beam is superimposed on another light beam to be synthesized. An optical means for obtaining a light beam, dividing the combined light beam into three or more divided light beams in the same area, obtaining interference light beams having phases different from each other from the plurality of divided light beams, and detecting the interference light beams, respectively. An information recording apparatus, comprising: a control system for positioning the arm means based on the result obtained by the above operation, and writing a signal to a hard disk every time the arm means is positioned. 6. The control system includes means for performing control for maintaining a constant distance between the arm means and the optical means based on a result obtained by detecting each of the interference light fluxes, and 3. The information recording apparatus according to claim 2, further comprising: means for performing positioning according to: 7. A form in which a convergent light beam is split in a light transmitting member, and a path from one of the split light beams to a surface existing in a space outside the light transmitting member is roughly condensed on the surface. After reciprocating, and after reciprocating the other of the divided light beams through a path of a wave optical optical path length substantially equal to the path in the light transmitting member, the divided light beams are multiplexed, and the obtained combined light beam An interference device characterized by obtaining an interference signal by partially selecting a region. 8. The interference apparatus according to claim 7, wherein the selected partially multiplexed light flux is subjected to amplitude division within the same region to obtain interference signals having different phases from each other. 9. A method according to claim 7, wherein the surface is a surface on the object whose displacement is to be measured, and relative displacement information of the object is detected by an interference signal obtained by the interference device according to claim 7 or 8. Position detection device. 10. A positioning device, wherein the object is positioned based on a result of detection by the position detection device according to claim 9. 11. A convergent light beam is split in a light transmitting member, and one of the split light beams is split from a split position to a side surface of a recording / reading head arm means in a hard disk drive device existing in a space outside the light transmitting member. Are reciprocated on the side surface in such a manner that they are substantially condensed, and the other of the divided light beams is reciprocated through a path having a wave optical path length substantially equal to the path in the light transmitting member. Optical means for selecting an area of a part of the obtained combined light beam to obtain an interference light beam, and positioning the arm means based on the result obtained by detecting the interference light beam. An information recording apparatus, comprising: a control system; and writing a signal to a hard disk every time the arm unit is positioned. 12. The control system according to claim 1, further comprising: means for performing control for maintaining a constant distance between said arm means and said optical means based on a result obtained by detecting said interference light beam; The information recording apparatus according to claim 11, further comprising: means for performing positioning according to the information. 13. A light beam is divided into two linearly polarized light beams whose polarization planes are orthogonal to each other by using a polarization splitting element, and one of the linearly polarized light beams is condensed, illuminated and reflected on a reflecting surface which moves relatively, and the other is polarized. The light beam is reflected by the reference reflection means, returned to the polarization splitting element, recombined, transmitted through a quarter-wave plate, and further divided into a plurality of light beams by the amplitude division means. An interferometer characterized in that an interfering device generates interfering light beams having phases shifted from each other by transmitting a polarized light beam through a polarizing plate arranged in a different direction. 14. The interference device according to claim 13, wherein said amplitude dividing means has a diffraction grating. 15. The method according to claim 13, wherein the reference reflection means is provided on a light transmitting member constituting the polarization splitting element.
5. The interference device according to 4. 16. A light beam is divided into two linearly polarized light beams whose polarization planes are orthogonal to each other by using a polarization separation element, and one of the linearly polarized light beams is condensed, illuminated and reflected on a reflection surface which moves relatively, and the other linearly polarized light beam is reflected. The light beam is reflected by the reference reflection means, returned to the polarization splitting element, recombined, transmitted through a quarter-wave plate, and further divided into a plurality of light beams by the amplitude division means. The generated light flux is transmitted through a polarizing plate arranged in a direction shifted from each other to generate interference light fluxes that are out of phase with each other. A position detecting device for measuring a change in a distance from a reflecting surface. 17. A multimode laser diode is used as a light source for emitting the light beam, the light beam is split into two light beams by the polarization splitting element, and the one light beam is reflected by the reflection surface, and the other light beam is reflected by the reflection surface. Are reflected by the reference reflecting means, the two optical fluxes return to the polarization splitting element, and the two optical fluxes have substantially equal wave optical optical path length differences, and the imaging optical optical path. The position detecting device according to claim 16, wherein the lengths are different from each other. 18. The other light beam is reflected at a position deviated from a beam waist position by a reference reflection means, and a part of the superimposed light beam is selectively transmitted through an aperture by the polarization splitting element. 18. The position detecting device according to claim 17, wherein after generating a substantially plane wave, the amplitude dividing means divides the light into a plurality of light beams. 19. A structure in which a light beam is guided to a polarization splitting unit via a non-polarization splitting unit, and a light beam superposed by the polarization splitting unit is returned to the non-polarization splitting unit and taken out to a side different from the light source. The position detecting device according to any one of claims 16 to 18. 20. A positioning device for positioning an object having the reflection surface based on a detection result by the position detection device according to claim 16. Description: 21. A light beam is split into two linearly polarized light beams whose polarization planes are orthogonal to each other by using a polarization splitting element, and one of the linearly polarized light beams is condensed and illuminated on the side of a recording / reading head arm means in a hard disk drive. Then, the other light flux is reflected by the reference reflection means, returned to the polarization splitting element, recombined, and transmitted through a quarter wavelength plate. , And the divided light fluxes are transmitted through a polarizing plate arranged in a direction shifted from each other to generate interference light fluxes that are out of phase with each other. Distance fluctuation measuring means for measuring a distance fluctuation between the arm means using an output signal, rotation positioning means for controlling a rotational position of the distance fluctuation measuring means, and detection of the distance fluctuation measuring means. Control means for controlling the rotation position of the arm means so as to cancel out the variation in the output distance, and a servo track signal is written from the recording / reading head to the hard disk every time the rotation positioning means is positioned. Recording device.