JPH07218237A - Optical displacement measuring apparatus - Google Patents

Abstract

PURPOSE:To measure a rotary angle, a rotating direction by providing diffraction gratings divided and separated to a plurality corresponding to a multiple spiral grating of a rotary unit at a head, and deciding a displacing direction by using corresponding output signals. CONSTITUTION:Diverged luminous fluxes irradiated from a light emitting element 1 of a head 2 are converted to parallel beams by a collimator lens 4, transmitted and diffracted by a diffraction grating G1 to be divided to three beams. Its straight beam is reflected and diffracted by a multiple spiral grating G2 of a cylinder 5 tap be divided and phase-modulated. The other two beams are reflected and diffracted by the grating G2 to be divided and phase-modulated. A plurality of the beams combined by a diffraction grating G3a (G3b) are incident as interference beam to a photoreceiver 3a (3b). The grating G2 is rotated by one revolution from the interference phase at this time, and bright and dark signal A1 (B1) is generated from the photoreceiver 3a (3b). This is input to rotating direction deciding means and counting means 6 to measure the rotating direction of the grating G2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes the fact that diffracted light generated when light is applied to a rotating or moving object on which a diffraction grating is formed interferes and the interference light flux is modulated. The present invention relates to an optical displacement measuring device that measures physical quantities such as rotation speed and movement displacement.

[0002]

2. Description of the Related Art Conventionally, as such an optical displacement measuring device, for example, an optical linear encoder, an optical rotary encoder, a laser Doppler velocity meter, a laser interferometer, etc. have been used. Since these optical displacement measuring devices are applied to a wider range of fields, they are miniaturized (milli-order size), highly accurate, and have high resolution (0.1 μm).
Higher stability is required. When the size is in the milli-order, it can be directly attached to the target object to be measured for use, and thus the physical quantity of a smaller object can be measured.

FIG. 27 is a perspective view showing a conventional optical rotary encoder disclosed in, for example, Japanese Patent Application Laid-Open No. 5-157583. In FIG. 10, 101 is a light source such as a semiconductor laser, 102 is a lens, and 103 is a beam. A splitter, 104 is a rotating disk plate on which a diffraction grating 105 is formed radially and at regular intervals on a rotation locus of a position where a beam transmitted through the beam splitter 103 is incident at a right angle, and 106 is reflected from the diffraction grating 105, A beam condensing lens for condensing the beam reflected from the beam splitter 103, a beam splitter 107 for reflecting the beam from the condensing lens 106 and incident on the diffraction grating 105 of the rotating disk plate 104 at a right angle, and 108 for diffraction. Lattice 105
Numeral 109 is a mirror for reflecting the beam reflected from the beam splitter 107 and reflected by the beam splitter 107, and numeral 109 is a beam splitter for guiding the reflected beam of the mirror 108 to the light receiving element 110.

[0004]

However, in the above-mentioned conventional example, the measurement accuracy is apt to be deteriorated due to the eccentricity of the mounting of the disk, an optical system for avoiding it is required, and the structure is apt to be complicated. Since the diffraction grating as the light phase modulation means is radially formed on the rotating disk plate, when the irradiation position on the diffraction grating is displaced in the radial direction, the diffraction grating pitch changes and the optical path of the interference optical system is changed. Displacement is difficult to stabilize. When trying to measure the rotation angle and its direction, the optical system becomes complicated, and it is difficult to make it compact and stable. When it is attempted to measure the displacement amount and the displacement direction in two or more directions, one encoder and a mechanism including the encoder are required for each direction, which makes the mechanism large and difficult to downsize. There were problems such as.

It is an object of the present invention to obtain an optical displacement measuring device which solves the above problems.

[0006]

According to a first aspect of the present invention, there is provided an optical displacement measuring device, which comprises a light emitting element, a light receiving element, and a head portion which allows a light beam to enter the light receiving element and which is provided with a diffraction grating.
In an optical displacement measuring device having a rotating part provided with a diffraction grating for phase-modulating a light beam, the diffraction grating provided in the rotating part is formed by multiple spirals and divided into a plurality of parts corresponding to the multiple spiral gratings. And a signal processing means for determining a displacement direction by using output signals corresponding to the diffraction gratings provided in the head section separated by an arbitrary distance in the array direction of the grating and outputting a rotational displacement signal. As a result, the rotation angle and the rotation direction can be measured, and a simple optical system that is not affected by the eccentricity of the rotating body can be configured.

In the optical displacement measuring device according to the second aspect of the present invention, the first diffraction grating for splitting the light flux emitted from the light emitting element, the third diffraction grating for synthesizing the split light flux, and the third diffraction grating are synthesized. In the optical displacement measuring device having a head portion provided with a plurality of light receiving elements for receiving the interference signal light beam, and a rotating portion provided with a second diffraction grating for phase modulating the light beam, the second diffraction The grating is formed into a plurality of separate and independent multiple spirals having mutually different array directions, is divided into a plurality of gratings corresponding to the second diffraction grating, and is separated by an arbitrary distance in the array direction of the grating. Since the displacement direction is determined by using the output signals corresponding to the lattice and the signal processing means for outputting the rotational displacement signal is provided,
It is possible to reduce the influence of axial deviation and stabilize the output.

An optical displacement measuring device according to a third aspect of the present invention is provided with a light emitting element, a light receiving element, and a head portion provided with a diffraction grating for making the light beam incident on the light receiving element, and a diffraction grating for phase modulating the light beam. In the optical displacement measuring device having a rotating part, the diffraction grating provided in the rotating part is formed of a plurality of multiple spirals having different array directions, and a plurality of multiple spirals are provided corresponding to the multiple spirals. A light-receiving element that is divided and that receives the signal light modulated by the spiral grating via a diffraction grating provided in the head section that is separated by an arbitrary distance in the array direction of the grating,
By using the output signals of the respective light receiving elements, by providing a signal processing means for outputting a plurality of types of displacement signals,
It is possible to stably output a plurality of types of displacement signals.

An optical displacement measuring device according to a fourth aspect of the present invention comprises a first diffraction grating for splitting a light beam emitted from a light emitting element, and a third diffraction grating for combining the split light beams,
A head unit provided with a plurality of light receiving elements for receiving the combined interference signal light flux, and a second light modulator for phase-modulating the light flux.
In the optical displacement measuring device having a rotating part provided with the diffraction grating, the second diffraction grating is formed by intersecting a plurality of multiple spirals having different array directions, and
Of the light receiving elements which are respectively divided into a plurality of corresponding diffraction gratings and which are separated by an arbitrary distance in the array direction of the gratings, and which receive the signal light modulated by the third diffraction grating, and the outputs of the respective light receiving elements. By using a signal processing unit that outputs multiple types of displacement signals by using signals, it is possible to reduce the size of millimeter size while maintaining high measurement accuracy, less susceptible to errors during assembly, and Displacement can be measured.

[0010]

【Example】

Example 1. 1 is a perspective view showing a first embodiment of an optical displacement measuring device according to the present invention, and FIG. 2 is a top view showing its optical path.
3 is a side view thereof, FIG. 4 is a view showing the arrangement of the diffraction grating of the head portion, FIGS. 5 and 6 are views showing the configuration of the diffraction grating provided in the rotating portion, and FIG. 7 is a processing circuit diagram of the output signal. Is.

1 to 7, 1 is a light emitting element, 2
Is a head portion, 3a and 3b are light receiving elements, G1 is a first diffraction grating for splitting the emitted light flux, and G2 is a multiple spiral shape on the surface of the cylinder 5 as a rotating portion for phase-modulating the split light flux. The formed second diffraction grating (hereinafter, referred to as a cylindrical multiple spiral grating), G3a and G3b, are arranged by being shifted by a quarter pitch in the arrangement direction of the diffraction grating, and the diffraction grating 4 for combining light beams is It is a collimator lens.

The detailed shape of the spiral of the cylindrical multiple spiral lattice G2 will be described below. A position vector r _V of a spiral curve of a cylindrical surface having a point O as a center and a point q as a starting point and a radius r is a unit vector in the x, y, and z axis directions, respectively, and θ is Letting f (θ) be a linear function of the angle θ, where f (θ) is an angle in the xy plane from the starting point q, r _V = rCos (θ) i + rSin (θ) j + f (θ)
k.

The locus of the above equation is displaced by f (θ) in the z direction each time the cylinder makes one rotation (FIG. 6).
If n spiral lattices are inserted between them, the position vector r _Vm of the m-th spiral curve is r, where P is the pitch between the spiral lattices and z _m is the position in the z direction at the beginning of r _{Vm. Vm} = rCos (θ) i + rSin (θ) j + (nP ′
θ / (2π) + zm) k where P ′ = P / (1- (nP / (2πr)) ² )
^1/2 ... (a)

Each time the cylindrical multiple spiral lattice G2 makes one rotation, it appears that n spiral lattices move in the lattice arrangement direction. As a result, the phase of the ± first-order diffracted light reflected and diffracted by the cylindrical multiple spiral grating G2 is ± 2πn.
Just slip off. That is, the phase shift when rotated by the angle θ is ± nθ.

The principle of the first embodiment will be described below. Figure 3
, The divergent light flux emitted from the light emitting element 1 is made into substantially parallel light by the collimator lens 4, transmitted and diffracted by the diffraction grating G1, and the 0th-order diffracted light R ₀ , the + 1st-order diffracted light R ₊₁ , −.
The first-order diffracted light R ₋₁ is divided into three and emitted.

The light beam R ₀ traveling straight through the diffraction grating G1 is reflected and diffracted at the point P1 of the cylindrical multi-helical grating G2, divided into _{+ 1st order} diffracted light R _{0 + 1} and −1st order diffracted light R _0-1 and phase modulated. The phase of the + _{1st order} diffracted light R _{0 + 1} is shifted by + nθ,
The phase of the first-order diffracted light R _0-1 is shifted by −nθ. Here, n is the number of multiple lattices of the cylindrical multi-helical lattice G2, and θ is the rotation angle (radian) of the cylindrical multi-helical lattice G2.
And

The _{+ 1st-order} diffracted light R _{0 + 1} is transmitted and diffracted by the two-divided diffraction gratings G3a and G3b to obtain the 0th-order diffracted light R 0.
_{The 0 + 10} , -1st-order diffracted light R _{0 + 1-1} and other light beams are split. Of these, the -1st-order diffracted light R _{0 + 1-1} is extracted perpendicularly to the diffraction grating surface, and is wavefront transmitted and diffracted by G3a. Is + nθ, and the phase of the wavefront transmitted and diffracted by G3b is + n
θ + π / 2.

Light flux R ₊₁ which is + 1st order diffracted by the diffraction grating G1
Is reflected and diffracted at a point P2 of the cylindrical multi-helical grating G2, divided into −1st-order diffracted light R _{+ 1-1} , 0-th order diffracted light R ₊₁₀ and other light beams, which are respectively phase-modulated.

Of these, the phase of the −1st order diffracted light R _{+ 1-1} is −
The 0th-order diffracted light R _{+ 1-10} , which has been shifted by nθ and is incident on the diffraction gratings G3a and G3b, goes straight through and is transmitted through G3a, has a phase of −nθ, and the 0th-order diffracted light R _{+ 1−} transmitted through G3b. The phase of the wavefront of ₁₀ is also −nθ.

The light beam R _{+ 1-10} and the light beam R _{0 + 1-1} whose optical paths are superposed by the diffraction grating G3a become interference light and enter the light receiving element 3a. The interference phase at this time is {+ nθ} − {− nθ} = 2nθ, and when the cylindrical multiple spiral grating G2 makes one rotation, a bright / dark signal A1 having a 2n cycle is generated.

The light beam R _{-1 + 10} and the light beam R _{-1 + 1 (} not shown) whose optical paths are superposed by the diffraction grating G3b are incident on the light receiving element 3b as interference light. The interference phase at this time is {nθ + π / 2}-{-nθ} = 2nθ + π / 2, and when the cylindrical multiple spiral grating G2 makes one rotation, a bright / dark signal B1 of 2n cycles is generated. These two signal outputs A1,
Signals that are out of phase with each other by π / 2 to B1 (two-phase signals)
The rotation direction of the cylindrical multiple spiral lattice G2 can be measured by inputting and counting the rotation direction discriminating means / counting means 6 as the signal processing means shown in FIG.

In the first embodiment, the interference optical system has a very simple structure, and the head portion is composed of only the light emitting source, the light receiving element, and the lens. Therefore, the number of parts is small, the assembly is easy, and the size is very small. Is possible. Further, since the multiple spiral lattice is formed on the cylindrical surface, it can be made thin and hollow. As a result, it is possible to realize a displacement measuring device which is very small and easy to install.

Further, since the rotating portion has a structure in which a multiple spiral lattice is formed on a cylindrical surface, the lattice pitch is constant throughout the multiple spiral lattice, and the influence of mounting accuracy such as eccentricity of the rotating portion is affected. I do not receive it.

The first embodiment is a diffraction grating G for splitting a light beam.
1. A diffraction grating G2 that phase-modulates a light flux and diffraction gratings G3a and G3b that combine light fluxes constitute a three-grating optical system. Therefore, one diffraction grating out of three diffraction gratings is a grating. There is a characteristic that a light / dark signal of two cycles is generated on the light receiving element when it is deviated by one pitch in the arrangement direction. In the case of the present embodiment, this displacing multi-helix lattice is formed spirally on the cylindrical surface, so when the rotating part makes one rotation relative to the head part, the front surface of the head part is apparently n. The grid will cross.

Further, when M is an integer, the diffraction grating G3
Since a and G3b are arranged so as to be shifted by (M ± 1/4) P in the array direction of the lattice, a two-phase signal in which the phase of the signal output is shifted by π / 2 is obtained, and the cylindrical multiple spiral lattice G2 It is possible to measure the direction of rotation.

Example 2. 8 is a perspective view showing an embodiment of an optical displacement measuring device according to the present invention, FIG. 9 is a top view showing its optical path, FIG. 10 is its side view, and FIG. 11 shows the arrangement of a diffraction grating of a head part. FIG. 12 and FIG. 12 are output signal processing circuit diagrams. 8 to 1 in which the same parts as those of the first embodiment shown in FIGS. 1 to 7 are denoted by the same reference numerals and duplicate description is omitted.
In FIG. 2, 3a1, 3b1, 3a2, 3b2 are light receiving elements, G3a1, G3b1, G3a2, G3b2 are third diffraction gratings G2a, G2b for combining light fluxes, and second diffraction gratings are the second diffraction gratings, and the arrangement directions are right with respect to each other. It is formed separately by a plurality of spirals different from the left and the left.

The detailed shape of the spiral of the cylindrical multiple spiral lattices G2a and G2b used in the second embodiment will be described below.
Since G2a and G2b are the same, G2a will be described. The basic structure of the cylindrical multiple spiral lattice G2a is the same as that of the first embodiment, and the cylindrical multiple spiral lattice G2 is
± when a deviates by Δz in the z-axis direction for some reason
The phase of the first-order diffracted light is as follows.

When the cylindrical multiple spiral lattice G2a is displaced by Δz, it means that the Δz / P 'lattices are moved in the lattice arrangement direction. The phase of the ± first-order diffracted light reflected and diffracted by the cylindrical multiple spiral grating G2a is ± 2πΔz / P ′ when P ′ in the equation (a) is used.

That is, when the cylindrical multi-helical grating G2a rotates by θ and a deviation of Δz occurs in the z-axis direction, the phase of the ± first-order diffracted light reflected and diffracted by the cylindrical multi-helical grating G2a is ± {nθ + 2πΔz. / P '}.

The principle of the second embodiment will be described below. The divergent light flux emitted from the light emitting element 1 is made into substantially parallel light by the collimator lens 4, transmitted and diffracted at the point O1 on the diffraction grating G1, and the 0th-order diffracted light R ₀ , the + 1st-order diffracted light R ₊₁ and the -1st-order diffracted light. The light is divided into three lights R ₋₁ and emitted.

The light beam R ₀ traveling straight through the diffraction grating G1 is reflected and diffracted at the boundary point P1 between the cylindrical multi-helical gratings G2a and G2b and divided into _{+ 1st order} diffracted light R _{0 + 1} and −1st order diffracted light R _0-1. The phase of the + 1st-order diffracted light R _{0 + 1} is phase-modulated and is + nθ +
The phase of the −1st-order diffracted light R _0-1 shifts by 2πΔz / P ′, and the phase shifts by −nθ + 2πΔz / P ′. However, here
n is the number of lattices of the cylindrical multiple spiral lattices G2a and G2b that are multiplexed, θ is the rotation angle (radian) of the cylindrical multiple spiral lattice G2, and Δz is the amount of deviation in the rotational axis direction of the cylindrical multiple spiral lattices G2a and G2b (hereinafter , Last deviation), P is the pitch of the grating, and R is the radius of the cylindrical multiple spiral gratings G2a and G2b.

The _{+ 1st order} diffracted light R _{0 + 1} is generated by the diffraction grating G3a1,
The light is transmitted and diffracted by G3a2, and the 0th-order diffracted light R _{0 + 10} ,-
The 1st-order diffracted light R _{0 + 1-1} and other light beams are split, and the -1st-order diffracted light R _{0 + 1-1} is extracted perpendicularly to the diffraction grating surface, and the diffraction gratings G3a1 and G3a2 are arranged in the array direction of the grating. If P (M + 1/4) or P (M + 3/4) are displaced (M is an integer), diffraction grating G3a1
The phase of the wavefront transmitted and diffracted by is + nθ + 2πΔz / P '
And the phase of the wavefront transmitted and diffracted by the diffraction grating G3a2 is + nθ + 2πΔz / P ′ + π / 2.

The −1st order diffracted light R _0-1 is generated by the diffraction grating G3b1,
The light is transmitted and diffracted by G3b2, and the 0th-order diffracted light R _0-10 , + 1
The next-order diffracted light R _{0-1 + 1} and other light beams are split, and the _{+ 1st-order} diffracted light R _{0-1 + 1} is extracted perpendicularly to the diffraction grating surface, and the diffraction gratings G3b1 and G3b2 are arranged in the grating array direction P ( If M + 1/4) or P (M + 3/4) is shifted and entered (M is an integer), the phase of the wavefront transmitted through the diffraction grating G3b1 and diffracted is −nθ + 2πΔz / P ′, and transmitted through the diffraction grating G3b2. The phase of the diffracted wavefront is −nθ + 2πΔz / P ′ + π / 2.

Light flux R which is + 1st order diffracted by the diffraction grating G1
₊₁ is reflected and diffracted at the point P2 of the cylindrical multi-spiral grating G2a, divided into -1st-order diffracted light R _{+ 1-1} , 0-th order diffracted light R _+10, and other light beams, which are respectively phase-modulated. Of these, the phase of the −1st order diffracted light R _{+ 1-1} is −nθ + 2πΔz / P ′.
The 0th-order diffracted light R _{+ 1-10} which is incident on the diffraction gratings G3a1 and G3a2 with a slight deviation and travels straight through the diffraction gratings G3a1 and G3a2.
The phase of the wavefront of is nθ + 2πΔz / P '.

Light flux R which is -1st order diffracted by the diffraction grating G1
_-1 is reflected and diffracted at the point P3 of the cylindrical multiple spiral grating G2a, divided into _{+ 1st-order} diffracted light R _{-1 + 1} , 0th-order diffracted light R _-10, and other light fluxes, which are respectively phase-modulated. Of these, the phase of the + _{1st order} diffracted light R _{−1 + 1} is + nθ + 2πΔz / P
By only G3b1 and G3b2,
The phase of the wavefront of the 0th-order diffracted light R _{+ 1-10} traveling straight through b1 and G3b2 is + nθ-2πΔz / P '.

The light beam R _{+ 1-10} and the light beam R _{0 + 1-1} whose optical paths are superposed by the diffraction grating G3a1 enter the light receiving element 3a1 as interference light. The interference phase at this time is {+ nθ + 2πΔz / P '}-{-nθ-2πΔz / P'} = 2nθ + 4πΔz / P '.

The light beam R _{+ 1-10} and the light beam R _{0 + 1-1} whose optical paths are superposed by the diffraction grating G3a2 become interference light and enter the light receiving element 3a2. The interference phase at this time is {+ nθ + 2πΔz / P '+ π / 2}-{-nθ-2πΔz / P'} = 2nθ + 4πΔz / P '+ π / 2, and the light flux and π whose optical paths are matched by the diffraction grating G3a1
An interference phase having a phase difference of / 2 is obtained.

That is, the cylindrical multiple spiral lattices G2a, G2
When b is rotated once and the thrust shift is caused by Δz in the meantime, the light / dark signal A of 2n + 2Δz / P ′ period in which the rotation direction can be discriminated from the two-phase light / dark signals whose phases are shifted by π / 2.
1, A2 are generated from the light receiving elements 3a1 and 3a2.

The light beam R _{0-1 + 1} whose optical path is superposed by the diffraction grating G3b1 becomes interference light and enters the light receiving element 3b1. The interference phase at this time is {nθ−2πΔz / P ′} − {− nθ + 2πΔz / P ′} = 2nθ−4πΔz / P ′.

Further, the light beam R _{-1 + 10} and the light beam R _{0-1 + 1} whose optical paths are superposed by the diffraction grating G3b2 become interference light and enter the light receiving element 3b2. The interference phase at this time is {nθ-2πΔz / P '+ π / 2}-{-nθ + 2πΔz / P'} = 2nθ-4πΔz / P '+ π / 2, and the light flux and π whose optical paths are matched by the diffraction grating G3b1.
An interference phase having a phase difference of / 2 is obtained.

Therefore, the cylindrical multiple spiral lattices G2a, G
When 2b makes one rotation, and a thrust shift occurs by Δz during that, a light / dark signal B of 2n−2Δz / P ′ period in which the rotation direction can be discriminated from the two-phase light / dark signals whose phases are shifted by π / 2.
1, B2 are generated from the light receiving elements 3b1 and 3b2.

When the light / dark signals A1, A2, B1, B2 are input to the rotation direction discriminating means / counting means 6A, 6B and converted into digital outputs, the cylindrical multiple spiral lattice G2 becomes 1.
Each time it rotates and the thrust shift becomes Δz, an output A0 of ± (2n + 2Δz / P ′) pulses is obtained by the output signals A1 and A2, and ± (2n−2Δz / P ′) by the output signals B1 and B2. ) A pulse output B0 is obtained, which is given a positive or negative sign depending on the direction of rotation. The above two outputs A0 and B0 are input to the arithmetic means 7 which constitutes the signal processing means 11 together with the above means 6A and 6B, and the sum thereof is (A0) + (B0) = ± 4n. No, cylindrical multiple spiral lattice G2
When 1 rotates once, a 4n pulse signal is obtained, and the direction of rotation can be identified by the sign of the sign.

In the second embodiment, as described above, the cylindrical multiple spiral lattices G2a and G2b are arranged such that the clockwise and counterclockwise multiple spirals whose arrangement directions are different from each other are vertically divided into two parts. When the cylindrical multiple spiral lattices G2a and G2b rotate, they appear to move in opposite directions. Therefore, by using the sum of the outputs of the light receiving elements 3a1, 3a2, 3b1, 3b2 arranged corresponding to the clockwise and counterclockwise diffraction gratings G2a, G2b as an output signal, the thrust shift of the cylindrical multiple spiral grating G2 is The effect of will disappear.

Example 3. 13 is a perspective view showing a third embodiment of the optical displacement measuring device according to the present invention, FIG. 14 is a top view showing its optical path, FIG. 15 is its side view, and FIG. 16 is a view showing a grid arrangement of the head part. FIG. 17 is a processing circuit diagram of an output signal. 13 to 17 in which the same parts as those of the second embodiment shown in FIGS. 8 to 12 are denoted by the same reference numerals and duplicate description is omitted, 3Aa1, 3Ab1, 3Aa2, 3A
b2, 3Ba1, 3Bb1, 3Ba2, 3Bb2 are light receiving elements, G3Aa1, G3Ab1, G3Aa2, G3Ab
2, G3Ba1, G3Bb1, G3Ba2, G3Bb2
Is a third diffraction grating for combining the light fluxes.

The basic structure of the optical system is the same as that of the second embodiment, and the diffraction gratings G3Aa to G3Ab2, G3Ba1 to G3Bb2 for combining the light beams divided by the diffraction grating G1 are arranged at an arbitrary distance from each other in the arrangement direction of the gratings. It is located apart. Further, light receiving elements 3Aa1 to 3Bb2 are arranged corresponding to the respective divided diffraction gratings. Thereby, the light receiving elements 3Aa1-3Ab2, 3Ba1-3Bb2
It is possible to obtain two sets of four-phase outputs, each of which is deviated by π / 2 from each of the two sets.

When a diffraction grating is arranged in the head portion 2 as shown in FIG. 16, a pair of light receiving elements 3Aa as shown in FIG.
1, 3Aa2, 3Ab1, 3Ab2, 3Bb1, 3Bb
2, 3Ba1, 3Ba2 output signals A1, A2, B1,
Cylindrical multiple spiral lattices G2a, G are obtained by computing B2 by the rotation direction determining means / counting means 6A, 6B and inputting the circumferential forces A0, B0 from both means 6A, 6B to the arithmetic means 7.
When the 2b makes one rotation, a 4n pulse signal can be obtained with high resolution regardless of the thrust deviation, and the rotation direction can be identified by the rotation direction determination means.

In the third embodiment, the cylindrical multiple spiral lattices G2a, G2 are used.
The third diffraction gratings G3Aa1 to G3Bb1 provided in the head section 2 corresponding to 2b are divided and arranged as shown in FIG. 16, and the outputs from the respective light receiving elements 3Aa1 to 3Bb2 are shown in FIG. By performing the arithmetic processing in 6B and 7, it is possible to reduce the influence of offset deviation of the light receiving element output due to external light other than the signal light, and to obtain a stable output capable of high division.

Example 4. 18 is a perspective view showing a fourth embodiment of the optical displacement measuring device according to the present invention, FIG. 9 is a top view showing the optical path thereof, FIG. 20 is a side view thereof, and FIG. 21 shows a lattice arrangement of the head portion 2. FIG. 22 is a circuit diagram of an output signal processing circuit. 18 to 22 in which the same parts as those of the second embodiment shown in FIGS. 8 to 12 are denoted by the same reference numerals and duplicate description is omitted, 3Aa to 3Bb are light receiving elements, and G2 is a phase modulation of the divided light flux. G3A, a plurality of multi-helical diffraction gratings (hereinafter referred to as "cylindrical multi-helical gratings") formed by intersecting the surface of a cylindrical shape and having different arrangement directions from each other.
Reference symbols a to G3Bb are diffraction gratings for combining the light fluxes.

The basic structure of the cylindrical multiple spiral grating G2 used in the fourth embodiment is the same as that of the second embodiment, and the above-described operation is performed every time the cylindrical multiple spiral grating G2 makes one rotation and is displaced by Δz in the direction of the rotation axis. Two-phase bright / dark signals A1 and A2 having a phase of 2n + 2Δz / P 'described in Example 2 with a phase shift of π / 2 are generated.

When these two brightness signals A1 and A2 are input to the displacement direction discriminating means and the counting means 6A such as a counter,
The output signal is 2n + 2Δz / P 'every time the cylindrical multiple spiral gratings G2a and G2b make one rotation, and each time there is a Δz shift in the rotation axis direction.
An output A0 in which the displacement direction of the pulse is determined is obtained.

The light beam R _{-1 + 10} and the light beam R _{0-1 + 1} whose optical paths are superposed by the diffraction grating G3Ba become interference light and enter the photoelectric element 3Ba. The interference phase at this time is {nθ−2πΔz / P ′} − {− nθ + 2πΔz / P ′} = 2nθ−4πΔz / P ′.

The light beam R _{+ 1-10} and the light beam R _{0 + 1-1} whose optical paths are superposed by the diffraction grating G3Bb enter the light receiving element 3Bb as interference light. The interference phase at this time is {nθ-2πΔz / P '}-{-nθ + 2πΔz / P' + π / 2} = 2nθ-4πΔz / P '+ π / 2, and the light flux and π whose optical paths are matched by the diffraction grating G3Ba An interference phase having a phase difference of / 2 is obtained. That is, each time the cylindrical multi-helical gratings G2a and G2b make one rotation, and the phase shifts by π / 2 each time Δz shifts in the rotation axis direction, 2
Bright and dark signals B1 and B2 having a phase of 2n-2Δz / P 'are generated.

When the two light / dark signals B1 and B2 are input to the displacement direction discriminating means and the counting means 6B such as a counter,
As for the output signal, when the cylindrical multiple spiral grating G2 makes one rotation and is displaced by Δz in the rotation axis direction, the output B0 in which the displacement direction of the 2n-2Δz / P 'pulse is discriminated is obtained. If the sum of the outputs of this output A0 and output B0 is taken, (A0)-(B0) = 4n
Therefore, when the cylindrical multiple spiral gratings G2a and G2b make one rotation irrespective of the deviation in the rotation axis direction, a 4n pulse signal in which the rotation direction is determined is obtained. Further, the deviation between the two outputs (assuming that the two outputs are A0 and B0, the deviation S is S
= (A0-B0) / 2), S = 2 [Delta] z / P ', and the output 2 [Delta] z / P' pulse can be obtained only for the determined thrust deviation [Delta] z in the deviation direction. That is, the rotational displacement amount and the rotational displacement direction of the cylinder, and the linear displacement amount and the linear displacement direction are simultaneously measured.

In the fourth embodiment, the interference optical system has a very simple structure, and a displacement measuring device capable of simultaneously measuring an angle and a distance displacement can be realized in a very small size. Further, in the case of the present embodiment, since the multiple spiral diffraction grating is formed on the surface of the cylinder, when the cylinder 5 makes one full rotation relative to the head portion 2, the front surface of the head portion 2 is apparently n gratings. Will be crossed. Since the diffraction grating provided on the head unit 2 is divided into two and arranged with a P / 4 shift, the direction of displacement can be identified by using this two-phase signal. Further, by taking the sum and the difference of the outputs of the light receiving elements, the output with respect to the rotation direction and the rotation amount that is not affected by the displacement of the multi-helical diffraction gratings G2a and G2b in the rotation axis direction, and the thrust displacement that is not affected by the rotation. The amount and the output in the thrust shift direction can be obtained separately. Example 5. 23 is a perspective view showing a fifth embodiment of the optical displacement measuring device according to the present invention, and FIG. 24 is a top view showing its optical path.
FIG. 25 is a side view thereof, and FIG. 26 is a view showing a lattice arrangement of the head portion. 2 in which the same parts as those in Embodiment 4 shown in FIG. 18 to FIG.
3 to FIG. 26, 3Aa1, 3Aa2, 3Ab
1,3Ab2,3Bb1,3Bb2,3Ba1,3Ba
2 is a light receiving element, G3Aa1, G3Ba2, G3Ab1,
G3Ab2, G3Bb1, G3Bb2, G3Ba1, G
3Ba2 is a diffraction grating for combining the light fluxes.

The basic structure of the optical system is the same as that of the fourth embodiment, and the diffraction gratings G3Aa1 to G3Ab2 and G3Ba1 to G3Bb2 for combining the light beams divided by the diffraction grating G1 are arranged at arbitrary distances from each other in the arrangement direction of the gratings. It is located apart. Further, light receiving elements 3Aa1-3Bb2 are arranged corresponding to the divided gratings. This makes 3A
Each of the two sets of a1 to 3Ab2 and 3Ba1 to 3Bb2 can obtain two sets of four-phase outputs shifted by π / 2.

When the grid of the head portion is arranged as shown in FIG. 26, the output signal is processed by the output processing circuit having the same configuration as the output processing circuit of the third embodiment shown in FIG. When the grating G2 makes one rotation and shifts by Δz in the rotation axis direction, a signal of 4n pulses is obtained as the output of the rotation amount, and a signal of 2Δz / P ′ pulses is obtained as the shift amount in the rotation axis direction, except the signal light. It is possible to obtain a stable output that can be highly divided, independent of the influence of external light, and to discriminate the rotation direction and the deviation direction.

[0057]

According to the invention of claim 1, a multi-helical diffraction grating is provided on a rotating body, and a head portion corresponding to this rotating body is provided with a diffraction grating for synthesizing a light beam phase-modulated by the diffraction grating, Since it is divided into a plurality of pieces and separated by an arbitrary distance in the arrangement direction of the lattice, the rotation angle and the rotation direction can be measured, the number of parts is small, the assembly is easy, and the size can be greatly reduced.

According to the second aspect of the invention, a plurality of separate and independent multiple spiral diffraction gratings having different array directions are provided in the rotating body, and the head portion corresponding to the rotating body is phase-modulated by the diffraction grating. Since the diffraction grating that synthesizes the luminous flux is divided into a plurality of pieces and is separated by an arbitrary distance in the arrangement direction of the grating, the influence of the axial shake of the rotating body can be reduced and the output can be stabilized. .

According to the third aspect of the invention, since the light flux from the diffraction grating is made incident on a plurality of light receiving elements and the output from each light receiving element is arithmetically processed, a plurality of types of displacement signals can be stabilized. Can be output to.

According to the fourth aspect of the invention, since a plurality of multiple spiral diffraction gratings having different array directions are provided on the rotating body so as to intersect with each other, the above-mentioned effects can be obtained and it is extremely effective for downsizing the entire apparatus. Is.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part of an optical displacement measuring device showing a first embodiment of the present invention.

FIG. 2 is a top view in which an optical path of Example 1 is written.

FIG. 3 is a side view of FIG.

FIG. 4 is an arrangement diagram of a diffraction grating of a head portion of the first embodiment.

FIG. 5 is a configuration diagram of a cylindrical multiple spiral lattice provided in the rotating unit according to the first embodiment.

FIG. 6 is a spiral shape diagram of a cylindrical multiple spiral lattice.

FIG. 7 is a signal processing circuit diagram of the first embodiment.

FIG. 8 is a perspective view of a main part of an optical displacement measuring device showing a second embodiment of the present invention.

FIG. 9 is a top view in which an optical path of Example 2 is written.

FIG. 10 is a side view of FIG. 9.

FIG. 11 is a layout view of the diffraction grating of the head portion of the second embodiment.

FIG. 12 is a signal processing circuit diagram of the second embodiment.

FIG. 13 is a perspective view of essential parts of an optical displacement measuring device showing a third embodiment of the present invention.

FIG. 14 is a top view in which an optical path of Example 3 is written.

FIG. 15 is a side view of FIG.

FIG. 16 is an arrangement diagram of the diffraction grating of the head portion of the third embodiment.

FIG. 17 is a signal processing circuit diagram of the third embodiment.

FIG. 18 is a perspective view of a main part of an optical displacement measuring device showing a fourth embodiment of the present invention.

FIG. 19 is a top view in which an optical path of Example 4 is written.

FIG. 20 is a side view of FIG.

FIG. 21 is a layout view of the diffraction grating of the head portion of the fourth embodiment.

FIG. 22 is a signal processing circuit diagram of the fourth embodiment.

FIG. 23 is a perspective view of a main part of an optical displacement measuring device showing a fifth embodiment of the present invention.

FIG. 24 is a top view in which an optical path of Example 5 is written.

FIG. 25 is a side view of FIG. 24.

FIG. 26 is a layout view of the diffraction grating of the head portion of the fifth embodiment.

FIG. 27 is a perspective view showing a conventional optical displacement measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Light emitting element 5 Cylinder (rotating part) 3Aa to 3Bb, 3Aa1 to 3Bb2 Light receiving element G1 Diffraction grating (first diffraction grating) for splitting a light beam G2 Cylindrical multiplex recommended grating for phase modulating a split light beam (second grating) Diffraction grating) G3a, G3b, G3Aa to G3Bb, G3Aa1 to G
3Bb2 Diffraction Grating for Combining Luminous Flux (Third Diffraction Grating) 11 Signal Processing Means

Front page continuation (72) Inventor Kenji Hisamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. An optical displacement having a light emitting element, a light receiving element, a head section provided with a diffraction grating for causing a light beam to enter the light receiving element, and a rotating section provided with a diffraction grating for phase modulating the light beam. In the measuring device, the diffraction grating provided on the rotating part is formed by a multiple spiral, and the grating provided on the head part is divided into a plurality of parts corresponding to the multiple spiral grating, and the grating is arranged at an arbitrary distance in the array direction. An optical displacement measuring device, characterized in that it comprises signal processing means which separates and determines a displacement direction using output signals corresponding to the separated diffraction gratings and outputs a rotational displacement signal. 2. A first diffraction grating for splitting the light flux emitted from the light emitting element, a third diffraction grating for synthesizing the split light flux, and a plurality of light receiving elements for receiving the synthesized interference signal light flux. In an optical displacement measuring device having a head part provided with a and a rotating part provided with a second diffraction grating for phase-modulating a light flux, the second diffraction grating has a plurality of separate and independent arraying directions different from each other. Of multiple output signals corresponding to the third diffraction grating, which are formed in a multiple spiral shape and are divided into a plurality of parts corresponding to the second diffraction grating and separated by an arbitrary distance in the array direction of the grating. An optical displacement measuring device comprising signal processing means for determining a displacement direction and outputting a rotational displacement signal. 3. An optical displacement measuring device having a light emitting element, a light receiving element, and a head section provided with a diffraction grating for allowing a light beam to enter the light receiving element, and a rotating section provided with a diffraction grating for phase modulating the light beam. In the above, the diffraction grating provided on the rotating part is formed of a plurality of multiple spirals having different array directions, and is divided into a plurality of multiple spirals corresponding to the multiple spiral diffraction gratings, and an arbitrary distance is provided in the array direction of the grating. A plurality of types of displacement signals are obtained by using the light receiving elements that respectively enter the signal light modulated by the spiral grating through the diffraction gratings provided in the head section that are separated from each other, and the output signals of the respective light receiving elements. An optical displacement measuring device comprising a signal processing means for outputting 4. A first diffraction grating for splitting the light flux emitted from the light emitting element, a third diffraction grating for synthesizing the split light flux, and a plurality of light receiving elements for receiving the synthesized interference signal light flux. In an optical displacement measuring device having a head part provided with a and a rotating part provided with a second diffraction grating for phase-modulating a light beam, the second diffraction grating has a plurality of multiple spirals different in arrangement direction from each other. Signal beams modulated by the third diffraction grating, which are formed by intersecting with each other, are divided into a plurality of portions corresponding to the second diffraction grating, and are separated by an arbitrary distance in the arrangement direction of the gratings. An optical displacement measuring device comprising a light receiving element and signal processing means for outputting a plurality of types of displacement signals by using output signals of the respective light receiving elements. 5. The first and third diffraction gratings provided on the head portion are arranged so as to be parallel to the arrangement direction of the second diffraction gratings formed on the rotating portion. The optical displacement measuring device according to any one of claims 1 to 4. 6. Counting means for counting the number of periods of the output signal from the light receiving element, and addition / subtraction for outputting the result obtained by the arithmetic processing of the sum, difference, etc. of the count values as a plurality of types of displacement signals. The optical displacement measuring device according to claim 3 or 4, further comprising means.