JPS6071911A - Optical device for measuring displacement and rotation - Google Patents

Abstract

PURPOSE:To enable measurement of two-dimensional and rotating displacements without contact with a target by detecting the extent of the movement of a speckle with photodetectors placed in the position deviated forward and backward from the imaging position of the target and calculating the same. CONSTITUTION:Photodetectors 71, 74 and photodetectors 72, 75 are disposed respectively before and behind an imaging position P and therefore the detectors generate the outputs in the directions opposite from each other with respect to the rotation of a target 4. If the outputs from the photodetectors 71, 74, 72, 75 are designated to be respectively Sx1, Sx2, Sy1, Sy2, Sx1+Sx2 is the displacement in the X-axis direction, Sx1-Sx2 is the rotating displacement around the Y-axis, Sy1+Sy2 is the displacement in the Y-axis direction and Sy1-Sy2 is the rotating displacement around the X-axis. The outputs respectively proportional to X, Y, thetax, thetay are thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an optical displacement/rotation measuring device that measures displacement and rotational displacement using optical interference.

More specifically, the present application combines coherent light from a light source into two
A movable diffusion surface that undergoes dimensional and rotational displacement is irradiated, and the resulting speckle pattern is used to
This invention relates to an optical displacement/rotation measuring device that measures dimensional displacement and rotational displacement.

[Prior art]

An example of such a measuring device is an optical mechanical quantity measuring device already filed by the applicant as Japanese Patent Application No. 109548/1983. This uses optical means to measure the amount of five-dimensional displacement, and its configuration and operation will be explained below.

This optical mechanical quantity measuring device irradiates coherent light from a light source onto a movable diffusing surface on which the root volume to be measured is given, and uses the resulting speckle pattern to measure two-dimensional mechanical quantities. At the same time, this speckle pattern is irradiated with light from a light source as a reference light, and the resulting pattern is used to measure mechanical quantities such as the displacement of the movable diffuser plate in the axial direction orthogonal to the two-dimensional axis. A unique feature of the structure is that it measures .

FIG. 1 is a configuration explanatory diagram showing an example of this device.

In the figure, reference numeral 1 denotes a light source, for example, a HeNe laser light source is used, from which coherent light is emitted.

Lenses 11 and 12 constitute a beam expander Bxft that expands the light emitted from the light source 1 into parallel light. 21 is a first polarizing beam splitter (hereinafter abbreviated as PBS), 22 is a second PBS, and 23 is a fifth PBS.
.

24 is required for the fourth PBS, and 25 is required for the fifth PBS. 1st
゜The 2nd #3rd PBS, 21.22.23 serves to split the incident light beam into two directions, and the 4th PBS
24 serves to convert beams coming from two directions into a one-way beam. Further, the fifth PBS 25 is the fourth PB
It is installed so that it has a positional relationship rotated by 45 degrees with respect to S, and its role is to cause two types of light to interfere and create stripes. 31 and 32 are lenses with focal lengths of fI and Tf2, and 30 is a diaphragm plate installed between lenses 31 and 33 at a distance of fl from lens 31 and fz from lens 32. A through hole d is provided. 4
is a target with a magnifying surface 40, and a lens 32 to 1
(1 is preferably about 0 to 2fz), and is given a three-dimensional measurement machine number in the x, y, and z directions as shown in the figure.051 is the lens 3
λ/4 plate installed between 2 and target 4, 61.6
2 is a mirror, and the light source 1 is divided by the first PBS 21.
The fourth PBS 24 is arranged such that light from the fourth PBS 24 is incident on the fourth PBS 24 . Here, the mirror 61 is inclined by θ1=45° with respect to the optical axis Ct, whereas the mirror 62 is inclined by θ2−4f+Δθ with respect to the optical axis Ct.
52 is a λ/2 plate installed between the mirror 61 and the first pI3S 21, and 53 is the first PBS 21 and the second PB
A λ/4 plate 54 is provided between the S and the second PBS 22
A λ/4 plate is provided between the PBS 23 and the third PBS 23.

71 is an X-axis receiver that receives one of the lights divided by the third PBS 23, and 72 is a Y-axis receiver that receives the other light that is split by the third PBS. An image sensor such as a COD is used, which is constructed by arranging light-receiving elements in a play shape. In addition, each light receiver 71.72
In (5), it is assumed that the light receiving elements are arranged so that the directions are orthogonal to each other.

Reference numeral 73 denotes a light receiver that receives the light emitted from the fifth I'BS. As this light receiver 73, an image sensor such as a CCD is used.

FIG. 2 is a block diagram showing an electrical circuit in the apparatus shown in FIG. In this figure, 70 is) for example C
This is a clock oscillator that drives each of the optical receivers 71, 72, and 73 configured with an OD, and applies a clock signal of, for example, a frequency fc to each optical receiver. 81.82°83 is the output frequency signal fx from each photoreceiver 71.72.73.

Miki inputs fy and fz and mixes them with the reference frequency code fR. , 91.92.93 are low-pass filters that pass specific frequency signals in the output signals from the corresponding mixers, and 41.42.43 are counters that count the frequency signals from the low-pass filters 91.92.93, respectively. , 6 is each counter 41°42,
This is an arithmetic circuit which inputs the count signals fax, foy, foz f from 43, and a microprocessor is used as this arithmetic circuit, for example. Reference numeral 60 denotes a display device, for example, a CRT, which displays (4) the calculation results of the calculation circuit 6.

The operation of the device configured as above is as follows. The light with wavelength λ emitted from light source 1 is transmitted to beam expander B.
The light is expanded by X, becomes parallel light, and enters the first PBS 21. Here, the light component (B wave) that vibrates in the direction perpendicular to the incident surface created by the incident light ray and the normal line to the incident surface is reflected,
Lens 31. Through hole of aperture plate 30, lens 32 and λ/4
The light passes through the plate 51 and is irradiated onto the diffusion surface 40 of the target 4 as parallel light. The parallel light irradiated onto the diffusing surface 40 of the target 4 undergoes random phase modulation due to the unevenness of this diffusing surface and is reflected.
．． Lens 32. The light returns through the through hole of the aperture plate 30 and the lens 31 and enters the first PBS 21 . Here, lens 31. Aperture plate 30. The lens 32 functions as a low-pass filter that realizes a state of pure movement of speckles and lowers the spatial frequency of light passing therethrough. 1st PB
The light re-entering the PBS 21 is a light component (P wave) whose vibration direction is parallel to the plane of incidence, and the light re-enters the PBS 21.
Pass through 1. Diffusion surface 4 of target 4 that passed here
The reflected light from 0 passes through the λ/4 plate 53 and becomes circularly polarized light, and is split into two by the second PBS 22, one of which is a λ/4
The light passes through the plate 54, becomes circularly polarized light, is separated by the fifth PBS 23, and enters the X-axis light receiver 71 and the Y-axis light receiver 72, respectively. A speckle pattern is then created on these light-receiving surfaces.

FIG. 3 shows an example of a speckle pattern obtained on the X-axis photodetector 71 and the Y-axis photodetector 72. In this figure, the speckle pattern moves in the X-axis direction when the target 4 moves in the arrow X direction, and moves in the y-axis direction when the target 4 moves in the arrow y direction. The X-axis light receiver 71 detects the displacement in the X-axis direction of the speckle pattern shown in FIG. 3, which is irradiated onto the light-receiving surface. Further, the y-axis light receiver 72 detects the displacement in the y-axis direction of the speckle pattern as shown in FIG. 3 irradiated onto this light-receiving surface.

On the other hand, the reflected light from the diffusing surface 4o that has entered the fourth PBS 24 passes through until that time and enters the fifth PBS 25. In addition, among the light incident on the first PBS 21 from the light source 1, the P wave component is transmitted through this, passes through the λ/2 plate 52, the plane of polarization is rotated by 90 degrees, and passes through the mirrors 61 and 62. , enters the fourth PBS 24, is reflected here and is transmitted to the fifth PBS 24.
The light is incident on the PBS 25 as a reference light. 5th PBS
25 is placed rotated by 45 degrees with respect to the fourth PBS 24, and here, among the reflected light from the target 4 whose polarization planes are different from each other by 90 degrees, and the reference light from the light source 1, the As shown in Figure 5, the 45° component is transmitted, and 2
Interference fringes are created on the shaft light receiver 73.

Note that a polarizing plate may be used for the fifth PBS 25.

FIG. 4 is a diagram showing an example of a pattern obtained on the two-axis photodetector 73, which resembles a speckle pattern superimposed with Michelson interference fringes.

In this pattern, when the target 4 moves in the direction of the arrow 2, it moves in the gourd direction. The two-axis light receiver 73 detects the displacement in the two-axis direction of the pattern shown in FIG. 4, which is irradiated onto the light-receiving surface.

Here, if the distance between the lenses 31 and 32 is f1+f2 and the target 4 is irradiated with a plane wave, there will be a so-called pure movement state. The average speckle diameter of the speckle pattern obtained is given by (f□λ)/(πd). Therefore, the distance from the lens 31 to each photodetector and the distance between the lens 32 and the target 4 are The distance t is unrelated to the pure movement state and the speckle diameter.

Each receiver 71, 72, 73 has a clock oscillator 7 at one end.
A clock signal of frequency fc is applied and driven from 0 to 1, and fc = fc from each photoreceiver 71, 72, and 73.
Frequency signals fx, fy, fz whose fundamental frequency is /N (where N is the number of light receivers 71, 72, 73)
is output.

FIG. 6 is an explanatory diagram showing the frequency spectra of frequency signals fx, fy, and fz obtained from each light receiver 71, 72, and 73. The frequency spectrum of the signal B has a peak at a point that is an integer multiple of the fundamental frequency fo, and the peak is greatest where the interval between the interference fringes is equal to 17 (an integer) of the total width of each receiver. , moves as the target 4 moves. For example, target 4 is
If the light receiver 71 moves by a certain amount, for example, the peak Pm corresponding to the m-th harmonic of the frequency signal fx from the light receiver 71 shifts in frequency by Δfmx that is proportional to the moving speed dx/dt. Similarly, if one target 4 moves by Y in the y direction, the peak Pm corresponding to the m-th harmonic of the frequency signal fy from the optical receiver 72 is
The frequency is shifted by fmy which is proportional to the moving speed dyldt. The same applies to the frequency signal from the light receiver 73. That is, Δfmx, Δfmy.

By measuring the phase of Δfmz, the amount of displacement of x+ytZ can be measured.

For example, in the circuit shown in Figure 2, MIKI v81.82°83
mixes the m harmonic Pm output from each photoreceiver and its neighboring frequency fR, that is, performs hetero gain detection, passes each output through low-pass filters 91, 92, 93, and outputs the following to the output end. Frequency signals fax, foy, and foz as shown in the equations are obtained, respectively.

fax = mfo -fR±Δ fmxfoy =
mfo −fR±Δfmyfoz = mfo −fR
The ±Δfmz counters 41, 42, and 43 respectively count these frequency signals. The arithmetic circuit 6 receives signals fax, foy, f from each counter 41, 42, 43.
oz t- each arrow x+3' of the target 4 by manually performing predetermined calculations, such as calculations including integrals.
+ The amount of displacement X, Y, Zl in the z direction can be known. Furthermore, since the polarity of Δfmx rΔfmy and Δfmz changes between positive and negative depending on the moving direction of the target 4,
The direction of movement can also be determined at the same time.

The device configured in this manner can simultaneously measure five-dimensional displacements using a beam from one light source, and the overall configuration can be simplified. Furthermore, since the signals obtained from each light receiver are frequency signals, calculation processing is easy and various mechanical quantities can be measured with high resolution.

Here, in such a mechanical quantity measuring device, x+
'V, sz Since the objective is to measure displacement in each axis direction, it is not possible to measure the amount of rotation of the target around each axis.

That is, when the target rotates, the speckles existing in the space on the light receiver side also rotate around the target imaging position. Therefore, if the receiver is placed at a position away from the target imaging position, the speckles on the receiver will move as the target rotates, and the rotation of the target will be incorrectly detected as axial displacement. Therefore, with this device, the only option is to place the light receiver at the imaging position of the target, and it is impossible to measure the amount of rotational displacement of the target around each axis. ! do not have.

[Purpose of the invention]

The present invention aims to eliminate the drawbacks of the conventional devices as described above and to realize an optical displacement/rotation measuring device that can measure not only the two-dimensional displacement amount but also the rotational displacement amount t. It is something.

[Summary of the invention]

The optical displacement/rotation measurement device of the present invention takes advantage of the fact that the speckles that move as the target rotates in opposite directions before and after the target imaging position. It is designed to measure the amount of rotational displacement of the target by detecting the amount of movement of each spade (11) by placing it at a position shifted forward and backward from the imaging position, and by calculating these detection results. be.

〔Example〕

The present invention will be explained in detail below.

FIG. 7 is a configuration diagram showing an embodiment of the optical displacement/rotation measuring device of the present invention. In the figure, the same parts as in FIG. 1 are designated by the same reference numerals. 26 to 28 are half mirrors, and %74.75 is a newly installed light receiver. Light receiver 71. , 74 are provided to detect the displacement X in the X-axis direction and the rotational displacement θyk about the Y-axis in the target 4, and similarly, the light receivers 72.75 are
Axial displacement Y Rotational displacement around the machining X axis θx1
It is provided for the purpose of detection. Here, the point P in the optical path near the half mirrors 27 and 28 is the imaging position sb of the target 4 formed by the lens 31.32, and the light receiver 71.72 is located after this imaging position P. , and the light receivers 74 and 75 are respectively arranged in front of the imaging position P. (12) FIG. 8 is an explanatory diagram showing the movement of speckles when the target 4 rotates. In the figure, when the target 4 rotates, the speckles existing in space also rotate. At this time, if a lens is placed in the middle, the movement of the speckles will be in opposite directions before and after the imaging position Pt-boundary of the target 4. Further, the amount of movement is proportional to the rotation angle θ of the target 4 and the distance 11.12 from the imaging position P.

Now, returning to FIG. 7, since the light receivers 71.74 and 72.75 are placed before and after the imaging position P, they generate outputs in opposite directions for 140 rotations of the turret. It turns out. For example, when the target 4 rotates around the Y axis, the light receiver 71.74 generates an output, and when the target 4 rotates around Xli+III, the light receiver 72.75 generates an output. Note that with respect to the displacement of the target 4 on the x and y axes, the speckle moves in the same direction regardless of whether it is before or after the imaging position P, so the light receivers 71.74 and 72.75 move in the same direction. ◇ Now) If the outputs of the photoreceivers 71, 74, 72, and 75 are respectively sxi'sx2'syl' sy2, then the target, y, 4tv displacements X, Y, and the X axis, Yi
With respect to rotational displacements θX and θy about llll, these outputs have a relationship as shown in the following equation.

5x1-ax+bθy S air aX, bθa 2 Syl = aY + bθ・ S, 2 = aY - bθ・ Yu and b are proportionality constants.

As is clear from the above formula, the output of each light receiver 71, 72, 74° 75 is calculated, (SX1 + SX□) is the displacement in the X-axis direction, and (s - s ) is the rotation x1 around the Y-axis.
x2 displacement amount, (SX1+SX□) is the displacement amount in the Y-axis direction, (S
-S) is the amount of rotational displacement about X@, yt y2 , it is possible to obtain outputs proportional to Y, θX, and θy, respectively.

FIG. 9 is a configuration diagram showing another embodiment of the optical displacement/rotation measuring device of the present invention. In this embodiment, in the apparatus shown in FIG. 7, one of the light receivers 71 and 72 is arranged at the imaging position P of the target 4, respectively. In this way, when one of the light receivers 71 and 72 is placed at the imaging position P,
The output from the light receivers 71 and 72 is not affected by the rotation of the target 4 and corresponds only to the displacement in the X+5' axis direction. As a result, each receiver 71.72.74
．． The output of 75 is
By calculating y2 yl, the amount of rotational displacement of the target 4 can be measured.

In addition, in the above description, an optical system using two lenses 31 and 32i was illustrated, but the optical system is not limited to this, and the image of the target 4 is transmitted to the light receivers 71 and 72.
．． Any configuration may be used as long as it is tied near 75. Further, a retroreflective material may be attached to the diffusion surface 40 of the target 4 to increase the detection sensitivity. Furthermore, (15) Here, it is assumed that an image sensor such as a COD is used as each light receiver, but a pattern detector such as a combination of spatial filters may also be used. [Effects of the Invention] As explained above. As described above, the optical displacement/rotation measuring device of the present invention can measure two of the targets without contacting the target.
It is possible to realize an optical displacement/rotation measuring device that can measure not only dimensional displacement but also rotational displacement.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an example of a conventional optical mechanical quantity measuring device, FIG. 2 is a configuration block diagram showing an electrical circuit,
Figures 3 and 4 show the X-axis receiver (y
Fig. 5 is an explanatory diagram showing an example of a speckle pattern created on the light-receiving surface of a dual-axis optical receiver) and a dual-axis optical receiver.
Fig. 6 is an explanatory diagram showing the polarization plane of nearby light, Fig. 6 is an explanatory diagram showing the frequency spectrum of the signal obtained from each light receiver, and Fig. 7 @ shows an embodiment of the optical displacement/rotation measuring device of the present invention. 1
6) A configuration diagram, FIG. 8 is an explanatory diagram showing the relationship between the rotation of the target 4 and the movement of speckles, and FIG. 9 is a configuration diagram showing another embodiment of the optical displacement/rotation measuring device of the present invention. be. 1...Light source, 21.22.23.24.25...Polarizing beam splitter% 11.12.31.32..."
Lens, 30...Aperture plate, 4...Target, 40
...Diffusion surface, 51.53.54...λ/4 plate, 52
...λ/2 plate, 61.62...Mirror, 71.72
．． 73°74, 75...Receiver, 26.27.2B
,,,No-Fumira. Claw 4 Figure 111→-2 Tsuta 5 Figure Nb 蒐6 Figure A Figure 1-8

Claims (1)

[Claims] An optical measurement device that measures the amount of displacement of the target by irradiating coherent light onto a diffuse surface of a target that is displaced in accordance with the amount to be measured, and detecting the movement of speckles caused by the reflected light, Detection points for detecting the movement of the speckles with respect to the movement of the target in one axial direction are selected at the image formation position of the target or two points before and after the image formation position of the target, and a detection signal obtained from each detection point is selected. An optical displacement/rotation measuring device characterized in that the optical displacement/rotation measuring device calculates the amount of displacement and rotational displacement of the target and generates an output proportional to the amount of displacement and rotational displacement of the target.