JPH05272917A - Displacement measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure the relative three-dimensional displacement in high resolution without a powerfull light source by projecting a plurality of light beams on the light receiving surface of a two-dimensional incident-light-position detecting element, and operating the amount of the displacement at each incident spot position, respectively. CONSTITUTION:The luminous fluxes emitted from light sources 3 and 5, which are provided on a reference supporting stage 1, are condensed on the light receiving surface of a two-dimensional semiconductor position detector (two-dimensional PSD), which is provided on a material to be measured 2 through light projecting lenses 4 and 5 provided at a specified interval B. At this time, the light sources 3 and 5 are alternately lit and driven in time division. Thus, the approximately entire emitted luminous fluxes are condensed on the light receiving surface of the two-dimensional PSD. When the directions, which are in parallel with two longitudinal and lateral sides of the material to be measured 2 are made to be the (x) axis and (z) axis, and the direction orthogonal to two sides is made to be the (y) axis, the amounts of displacements DELTAx, DELTAy and DELTAz of the axes (x), (y) and (z) of the material to be measured have the relationships with the amounts of diaplacements of the spot lights C1, C2 and C3 as DELTAx=-C1, DELTAy=-C2 and DELTAz=C3L/B. L is the interval between the lenses 4 and 6 and the two-dimensional PSD. The amount of displacement of each spot light is obtained, and the three-dimensional displacement of the material to be measured 2 can be measured in high resolution without a powerful light source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement measuring device.

[0002]

2. Description of the Related Art Conventionally, as a method of non-contactly measuring a displacement amount of an object to be measured, a light source is installed on the object to be measured and two two-dimensional semiconductor position detectors (two-dimensional PSD) are used as a reference. Installed at regular intervals in two positions, and two PS by the light receiving lens
A method of detecting the amount of displacement of the object to be measured from the amount of displacement of the position of the light spot that is condensed and incident on D is often used.

FIG. 7 is a block diagram of a general one-dimensional PSD, and FIG. 8 is a block diagram of a displacement measuring device using the PSD of FIG.

In FIG. 7, a general PSD 25 is N
^{A +} -type semiconductor layer 27, a high-resistance N-type semiconductor layer 28, and a P-type semiconductor layer 29 having a uniform resistivity are sequentially stacked. N-type semiconductor layer 28 and P-type semiconductor layer 2
Reference numeral 9 denotes a photodiode, and the N ⁺ type semiconductor layer 27 is provided with a common electrode 30 for applying a reverse bias voltage to the photodiode. Further, a pair of electrodes 31 and 32 are provided on both ends of the P-type semiconductor layer 29.

When a predetermined voltage is applied to the common electrode 30 of the PSD 25 and a light spot is incident on the position SP, the pn junction between the P-type semiconductor layer 29 and the N-type semiconductor layer 28 below the position SP. An electron-hole pair is generated in the portion, and as a result, a photocurrent I _O proportional to the incident energy of the light spot flows from the common electrode 30 toward the P-type semiconductor layer 29.

By the way, the distance between the electrodes 31 and 32 is c, the resistance of the P-type semiconductor layer 29 between them is R _C, and the distance between the light spot incident position SP and the electrode 32 is x.
If the resistance of the P-type semiconductor layer 29 in the meantime is R _X , the photocurrent I _O is at the light spot incident position SP.
Divided by 9 resistors. That is, the current I _A to the electrode 31 and the current I _B to the electrode 32 are respectively the resistance (R _C −R _X ) of the P-type semiconductor layer 29 between the electrode 31 and the light spot incident position SP, and the electrode 32. It is divided in inverse proportion to the resistance R _X of the P-type semiconductor layer 29 between the light spot incident position SP and, I _a = I _O · [R _X / R _C] I _B = I _O · [(R _C -R _X ) / R _C ] ... (1)

As described above, since the resistivity of the P-type semiconductor layer 29 is uniformly distributed, the resistances R _X and R _C are the distance x,
It is proportional to c with the same proportionality constant.

Therefore, the equation (1) is expressed as follows: I _A = I _O · x / c I _B = I _O · [(c−x) / c] (2)

As can be seen from the equation (2), the current I _A · I
The distance x from the electrode 32 to the light spot incident position SP can be obtained by taking _B out of the electrodes 31 and 32 and performing a predetermined analog calculation process in a predetermined calculation circuit (not shown).

FIG. 7 shows the structure of a semiconductor position detector (one-dimensional PSD) for one-dimensional measurement. By arranging a pair of electrodes also in the direction perpendicular to the paper surface of the same figure,
It is possible to realize a PSD for two-dimensional measurement (for example, S1200 of Hamamatsu Photonics KK).

In FIG. 8, in a general displacement measuring apparatus, a light source 10 is installed on an object 9 to be measured, and two sets of light receiving lenses 11 and 13 and a two-dimensional PSD are mounted on a supporting base 15 as a reference.
It has a configuration in which 12, 14 are installed. In the figure, each coordinate axis is set to the x axis, the z axis, or the y axis in the direction perpendicular to the paper surface as shown by the arrow. A part of the luminous flux of the light source 10 is received by the light-receiving lenses 11 and 13 to generate a two-dimensional PS.
The light is condensed on the light receiving surfaces of D12 and D14.

Here, the distance between the light receiving lenses 11 and 13 is 2
B, the distance between the light receiving lenses 11 and 13 and the two-dimensional PSDs 12 and 14 is f, and the distance between the light source 10 and the light receiving lenses 11 and 13 is L, the displacement Δx of the DUT 9 on the x-axis and the y-axis.
_With respect to ₀ and Δy _O , between the displacement amounts Δx ₁ and Δy ₁ of the spot light focused on the light receiving surfaces of the two-dimensional PSDs 12 and 14, the following formula (3) and (4 ) The relationship of formula is established.

[0013] _{△ x 1 = - (f /} L) △ x 0 ... (3) △ y 1 = - Further _{(f / L) △ y 0} ... (4), relative displacement △ z ₀ of the z-axis direction Two-dimensional PSD
When the displacement amounts of the spot lights focused on the light receiving surfaces of 12 and 14 are Δz ₁₂ and Δz ₁₄ , respectively, the following (5),
The relationship of equation (6) holds.

Δz ₁₂ = B · f {1 / (L−Δz ₀ ) −1 / L} (5) Δz ₁₄ = −B · f {1 / (L−Δz ₀ ) −1 / L} ... (6) the amount of displacement of the two spots light detected from the two-dimensional _{PSD △ x 1, △ y 1} , △ z 12, △ than z _14, the object to be measured in the opposite 9
The three-dimensional displacement amount of can be obtained.

[0015]

The advantages of using a PSD in such a displacement measuring device are as follows. That is, in order to obtain the position of the spot light focused on the light receiving surface, the signal photocurrent is detected by resistance division according to the equation (1). Is possible. But in reality PSD
Also, due to the noise generated in the amplifier circuit of the signal photocurrent, the position resolution is limited by the ratio of the signal photocurrent value to the noise equivalent current value converted into the amplifier circuit. That is, as the intensity of the signal light incident on the PSD is higher, the position resolution can be improved.

In the conventional displacement measuring device, only a small part of the luminous flux of the light source installed on the object to be measured is focused on the light receiving surface of the PSD by the light receiving lens, so that high resolution is obtained. In order to do so, the light emission intensity of the light source must be extremely high. Further, the displacement amount of the spot light focused on the light receiving surface of the PSD is, as shown in the equations (3) and (4), the distance L between the “light source and the light receiving lens” and the distance between the “light receiving lens and the PSD”. In the measurement system in which the distance L needs to be long because of the ratio of f, the light receiving lens system becomes very large, which is not suitable for practical use.

In addition to the above problems, in the conventional device,
Although the three-dimensional displacement amount can be measured, there is a problem in that the displacement amount cannot be measured when the object to be measured is accompanied by rotational displacement on each coordinate axis. An object of the present invention is to solve these problems.

[0018]

A displacement measuring device according to the present invention is a displacement measuring device for optically measuring a relative displacement between a first object and a second object. The attached two-dimensional light incident position detecting element, a plurality of light emitting means attached to the second object at a predetermined interval and projecting a light beam on the light receiving surface of the two-dimensional light incident position detecting element, and the light receiving surface. And a calculation means for calculating the displacement amount of the incident spot position of the light beam, and the relative displacement between the first and second objects is measured based on the calculated displacement amount.

[0019]

According to the structure of the present invention, when there is a relative displacement between the first object and the second object, the spot light position of the projection beam from the projection means is displaced on the light receiving surface. .. Here, in the displacement measuring device of the present invention, since almost all of the luminous flux of the light source can be focused on the light receiving surface of the semiconductor position detector, a strong light source is not required, and high resolution three-dimensional displacement and rotation are possible. A displacement measuring device that measures displacement can be realized.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the displacement measuring device of the present invention. In the figure, two types of light sources 3 and 5 and light projecting lenses 4 and 6 are installed at a predetermined interval on a supporting base 1 as a reference,
The luminous fluxes of the two light sources 3 and 5 are condensed by the light projecting lenses 4 and 6 on the light receiving surface of the two-dimensional PSD installed on the object to be measured 2. When the light sources 3 and 5 are driven to be alternately turned on in a time-division manner, almost all of the emitted light beams are PSD for two-dimensional use.
The light can be condensed on the light receiving surface of.

Here, the distance between the light projecting lenses 4 and 6 is B, and the distance between the light projecting lenses 4 and 6 and the two-dimensional PSD is L.
In setting the three-dimensional coordinate system, if the x-axis and the z-axis are set on the plane of the figure and the y-axis is set in a direction perpendicular to the plane of the figure as shown by the arrow on the right side of the figure, the DUT 2 In the z-axis direction (the displacement of the spot light on the light receiving surface of the two-dimensional PSD drawn by the dotted line) are displaced in the opposite directions before and after the reference distance L.

Next, the relationship between the displacement of the DUT 2 in each axial direction in the three-dimensional coordinate system and the displacement of the spot light focused on the light receiving surface of the two-dimensional PSD will be described. In FIG. 2, the state of displacement of the spot light on the light receiving surface of the two-dimensional PSD installed on the DUT 2 is illustrated. When the spot lights SP ₂ and SP ₃ drawn by the solid lines are focused on the light receiving surface by the light sources 3 and 5 and the light projecting lenses 4 and 6 shown in FIG. , Each spot light is shown. When the DUT 2 is displaced in the x-axis direction, the displacement of the two spot lights is shown by the dotted line in FIG. In this case, two spotlight displaced by C _1, the relationship between the displacement amount C ₁ in the displacement △ x and spot light of the object 2 will the following equation (7).

Δx = −C ₁ (7) Similarly, FIG. 2B shows how the spot light is displaced (C ₂ ) with respect to the y-axis displacement (Δy) of the DUT 2. Also at this time, the following equation (8) is established between the displacement amount Δy and C ₂ .

Δy = −C ₂ (8) With respect to the z-axis displacement of the DUT 2, the displacement of the spot light focused on the light receiving surface of the PSD is the x-axis displacement and the y-axis displacement. Different from That is, the displacements of the two spot lights in the displacements of the x-axis and the y-axis have the same value in the same direction, but z
In the case of axial displacement, the displacement directions of the spot lights SP ₂ and SP ₃ condensed as shown in FIG. 2C are opposite to each other. Further, the following equation (9) is established between the z-axis displacement amount Δz of the object to be measured and the displacement amount C ₃ of the two spot lights on the light receiving surface.

Δz = C ₃ L / B (9) The configuration of the embodiment shown in FIG. 1 enables high-resolution three-dimensional displacement measurement without requiring a strong light source. However,
Among the rotational displacements of the three axes, the rotational displacement of the z axis can be detected, but the accurate rotational displacement of the x axis and the y axis cannot be detected.

FIG. 3 shows high-resolution three-dimensional displacement measurement,
It is a block diagram of a displacement measuring device capable of measuring the rotational displacement of three axes. In the figure, a support base 2'made of a rigid body is installed on the object to be measured 2, and a two-dimensional PSD, a semitransparent mirror BS, a light source 7 and a light projecting lens 8 are installed on this. On the other hand, as in FIG. 1, the two types of light sources 3 and 5 and the light projecting lenses 4 and 6 are installed at a predetermined interval on the rigid support base 1 serving as a reference. Is installed.

The luminous flux emitted from the light source 7 is reflected by the semitransparent mirror BS by the light projecting lens 8, further reflected by the reflecting mirror M installed on the support 1, and then enters the semitransparent mirror BS again. Then, the light flux transmitted through the semitransparent mirror BS is
The light is condensed almost at the center on the light receiving surface of the SD.

FIG. 4 is a perspective view of the structure of the embodiment shown in FIG. The light source 7 and the light projecting lens 8 form a light projecting means S ₁ ,
This projection beam is condensed as spot light SP _{1 at} a substantially central position on the light receiving surface of the two-dimensional PSD. Further, the light source 3 and the light projecting lens 4 form a light projecting means S ₂ , and the light source 5 and the light projecting lens 6 form a light projecting means S ₃ , respectively. The light projecting means S ₂ and S ₃ are arranged in the y-axis direction. They are installed with a step difference of 2a, and these projection beams are condensed as spot lights SP ₂ and SP ₃ on the light receiving surface of the two-dimensional PSD. The distance between the spot lights SP ₂ and SP _{3 in} the y-axis direction is set to be equal to the step 2a between the light projecting means S ₂ and S ₃ .

Here, if the rotational displacements with the x-axis, the y-axis, and the z-axis as the rotational axes are θ _x , θ _y , and θ _z , respectively, the three-dimensional movement displacement Δx, Δy of the object 2 to be measured. , Δz and the rotational displacements θ _x , θ _y , θ _z, and the displacement amounts C ₁ of the spot lights SP ₁ , SP ₂ , SP ₃ on the light receiving surface of the two-dimensional PSD.
The relationship with C ₈ is as shown in FIGS.

5 and 6 are explanatory views of displacement of spot light. Three-dimensional displacement amount Δx, Δy, Δz of the object to be measured and spot lights SP ₁ , SP ₂ , SP ₃ focused on the light receiving surface.
The relationship between the displacement amounts C ₁ , C ₂ , and C _{3 of} FIG.
The relational expressions shown in (c) are applicable to the above-mentioned expressions (7) to (9). However, with respect to the displacement amount Δz axis of the z axis, it is necessary to discriminate the displacement amount θ _{z from} the rotation amount. Therefore, the following conditions are related to the displacement amount C ₄ of the interval between the spot lights SP ₂ and SP ₃ . Equation (10) is given.

C ₄ = (4a ² + C ₃ ² ) ^1/2 (10) The meaning of the condition given by the formula (10) is as follows. That is, the spot light SP ₁ is not displaced with respect to the z-axis movement displacement amount Δz of the DUT 2, and the spot light S ₁ is not displaced.
It suggests that P ₂ and SP ₃ are displaced only in the direction parallel to the x-axis, and are displaced in the opposite directions.

FIG. 6A shows the amount of rotational displacement θ _x of the DUT 2 about the x-axis and the displacement of the spot lights SP _{1 to} SP ₃ focused on the light receiving surface. .. Only the spot light SP ₁ is sensitively displaced with respect to the rotational displacement amount θx, and if this displacement amount is C ₅ , then the relationship of equation (11) holds.

Θ _x = sin ⁻¹ {[(L / 2C ₅ ) ² +0.5] ^1/2 −L / 2C ₅ } (11) On the other hand, the spot lights SP ₂ and SP ₃ are on the y-axis. It is only slightly displaced in the direction parallel to the direction, and if the spacing between the spot lights SP ₂ and SP ₃ is C ₆ , the rotational displacement θ _x
Equation (12) holds between and.

Θ _x = cos ^-1 {2a / C ₆ } (12) FIG. 6B shows the amount of rotational displacement θ _y with the y axis as the axis of rotation and the displacement of the spot lights SP _{1 to} SP _3. Indicates. In this case, the spot lights SP ₂ and SP ₃ are not displaced, and only the spot light SP ₁ is sensitively displaced in the x-axis direction. When this displacement amount is C ₇ , the equation (13) is established between the rotational displacement amounts θ _y .

Θ _y = sin ⁻¹ {[(L / 2C ₇ ) ² +0.5] ^1/2 −L / 2C ₇ } (13) However, the spot lights SP ₂ and SP ₃ are not displaced. Becomes

FIG. 6C shows the amount of rotational displacement θ _z about the z-axis and the displacement of the spot lights SP _{1 to} SP ₃ . In this case, the spot light SP ₁ is not displaced, and the spot lights SP ₂ and SP ₃ rotate by Ψ with the spot light SP ₁ as the rotation center. Therefore, the amount of rotational displacement θ _z of the DUT 2
Equation (14) holds between and.

Θ _z = −Ψ (14) Here, it is necessary to discriminate from the displacement amount Δz of the z axis, and if the distance between the spot lights SP ₁ and SP ₂ is C ₈ ,
The following expression (15) is established.

C ₈ = 2a (15) By giving the condition of the expression (15), it is possible to determine the displacement amount Δz of the z axis.

Although not shown in the embodiment, it may be necessary to perform measurement in an environment in which the two types of light projecting means cannot be installed on the reference support. For example, there is a case where there is no space for installing the light projecting means in physical space, or there is a need for measurement under an environment where a semiconductor laser for visible light cannot be used as a light source at high temperature. In such a case, the signal light is transferred to the position of the three types of light projecting means using the optical fiber, and the image of the spot light at the light receiving surface position of the two-dimensional PSD is transferred by the optical image guide. A displacement measuring device equivalent to the configuration shown can be realized.

[0040]

As described above in detail, according to the displacement measuring apparatus of the present invention, it is possible to obtain a high resolution three-dimensional movement displacement amount and a triaxial rotation displacement amount without using a powerful light source. You can Further, even in a measurement system that requires a long distance between the reference support and the object to be measured, almost the total amount of light emitted from the light source is focused on the light receiving surface of the two-dimensional semiconductor position detector (PSD). Therefore, there is an advantage that detection can be performed with high accuracy as in the case of a measurement system in close proximity.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a displacement diagram of spot light in the first embodiment.

FIG. 3 is a configuration diagram of a second embodiment.

FIG. 4 is a perspective view of a second embodiment.

FIG. 5 is a displacement diagram of spot light in the second embodiment.

FIG. 6 is a displacement diagram of spot light in the second embodiment.

FIG. 7 is a configuration diagram of a semiconductor position detector.

FIG. 8 is a conventional configuration diagram.

[Explanation of symbols]

1 ... Support base, 2 ... Object to be measured, 3, 5 ... Light source, 4, 6 ... Projection lens.

Claims (3)

[Claims] 1. A displacement measuring device for optically measuring a relative displacement between a first object and a second object, comprising: a two-dimensional light incident position detecting element attached to the first object; A plurality of light-projecting means attached to the second object at a predetermined interval and projecting a light beam on the light-receiving surface of the two-dimensional light-incidence position detecting element; and an incident spot position of the light beam on the light-receiving surface. A displacement measuring device comprising: a calculating unit that calculates a displacement amount, and measures a relative displacement between the first and second objects based on the calculated displacement amount. 2. The plurality of light projecting means respectively include a light source that is driven to be alternately turned on in a time-sharing manner, and a light projecting lens that focuses a light beam from the light source on the light receiving surface. The displacement measuring device according to claim 1, wherein the means alternately calculates the displacement amount in a time division manner in synchronization with a lighting timing of the light source. 3. A semitransparent mirror attached to the first object in front of the light receiving surface, and another light projecting means attached to the first object so as to project a light beam on the semitransparent mirror. And a total reflection mirror which is attached to the second object so as to face the light receiving surface with the semitransparent mirror interposed therebetween, and which reflects a reflected light beam from the semitransparent mirror toward the semitransparent mirror. 2. The displacement measuring device according to claim 1, wherein among the light beams from said another light projecting means, the reflected light flux of said total reflection mirror which has passed through said semitransparent mirror is made incident on substantially the center of said light receiving surface.