JP2553662B2 - Hologram range finder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical distance measuring device that measures the displacement of an object using light in a non-contact manner, and more particularly, a hologram distance measuring device that measures a distance from an interference fringe pattern using a hologram. It relates to the device.

2. Description of the Related Art The configuration of a conventional optical distance measuring device will be described below with reference to the drawings. FIG. 8 is a block diagram of a conventional optical distance measuring device. 1 is a laser, 2 is a first deflection mirror for scanning a beam in the X direction in the figure, 3 is a second deflection mirror for scanning a beam in the Y direction in the figure, 4 is an object to be measured, and 5 is an object to be measured. A condenser lens for condensing the reflected light from the measurement object 4 and a line sensor 6 arranged behind the condenser lens.

Next, the principle of the conventional optical distance measuring apparatus will be described with reference to FIG. In FIG. 9, S is the center of the condenser lens 5, L is the center of the emitted beam from the laser 1, O is a point on the object to be measured 4, and θ and φ are reflected beams from the point O, respectively.
The angle formed by the beam emitted from the laser 1 and the base line LS, D
If is set to the length of the base line LS, the distance h to the point O is expressed by the equation (1).

h = D tan θ tanΦ (tan θ + tan Φ) Equation (1) Here, the angle θ is the direction of the optical axis of the condenser lens 5 and is given by Equation (2) tan θ = f / d Equation (2) f: Focus Focal length d of lens 5: distance between the center point of the condenser lens 5 and the beam detection point on the line sensor 6. Therefore, the first and second deflection mirrors 2 and 3 scan the laser beam in the X and Y directions. Line sensor 6
The object to be measured 4 is solved by solving the equations (1) and (2) between the beam detection point S on the line sensor 6 condensed above, the center L of the outgoing beam and the point O on the object to be measured 4. The distance h can be measured.

SUMMARY OF THE INVENTION However, in the above-mentioned configuration, from the formulas (1) and (2), the distance measurement accuracy is d, that is, the center point of the condenser lens 5 and the beam detection point on the line sensor 6. Determined by the distance detection accuracy. However, the detection resolution of the beam detection point on the line sensor 6 is determined by the size of the constituent cells of the line sensor 6, and the distance measurement accuracy is on the order of several tens of μm, which is used for an assembly robot or the like that performs precise assembly work. Was not accurate enough.

An object of the present invention is to solve the problems of the conventional optical distance measuring device.

Means for Solving the Problems A hologram distance measuring apparatus according to the present invention is arranged in at least one of a first beam splitting unit for splitting a beam emitted from a light source into two optical paths and this optical path divided into two. The non-parallel light converting means, the second beam splitting means for transmitting and reflecting the beam converted into the non-parallel light by the non-parallel light converting means, and irradiating one of the beams to the object to be measured, A first beam combining means for combining the reflected light and the other beam divided into two by the first beam dividing means; a third beam dividing means for dividing the combined light into two; An optical spatial modulation element for recording an interference fringe formed by the combined light, which is arranged in one optical path divided by the third beam splitting means, a recording pattern reading light from this optical spatial modulation element, and the 3's A second beam combining means for combining one of the beams divided by the beam dividing means, and a beam blocking means for blocking the incidence of the recording light on the spatial light modulator. Is.

Action The present invention, by the above-described configuration, irradiates the object to be measured with non-parallelized light at a certain reference position, and causes the interference fringes of the reflected light from the object to be measured and the reference light to the spatial light modulator. A reference interference fringe pattern obtained by recording and irradiating the spatial light modulator with read light and the reflection obtained from the measured object by irradiating the non-parallel light when the measured object is at an arbitrary position. By forming interference fringes of light and reference light, and measuring the displacement of the measured object from the interference fringe pattern and the reference interference fringes, the displacement of the measured object can be measured with the accuracy of the wavelength order of light. It was done.

Embodiments The present invention will be described below with reference to the drawings illustrating the embodiments.

FIG. 1 shows the first embodiment of the hologram distance measuring device of the present invention.
It is a top view of an Example of. Reference numeral 10 is a first laser, and its emitted light is substantially parallel light. Reference numeral 11a is a first beam splitting means for splitting the beam emitted from the first laser 10 into two optical paths, 11b is an optical path changing means, and 12 is a non-parallel light converting means arranged in one of the two divided optical paths. The means is a confocal optical system including two lenses. As a result, the beam is converted into diverging or converging light, that is, non-parallel light.
Reference numeral 13 denotes a beam expander which is divided into two by the first beam splitting means 11 and which is arranged in the other optical path, and 14 transmits and reflects the beam which is made non-parallel light by the beam parallel light intensity adjusting means 12, A second beam splitting means for irradiating the measured object 15 with the transmitted light, and 16 combines the reflected light from the measured object 15 and the other beam split into two by the first beam splitting means 11. First beam combining means for
Is a third beam splitting means for splitting the combined light into two, 18 is a spatial light modulator, and is arranged in the transmission optical path of the third beam splitting means 17, and 19 and 20 are third beams, respectively. It is an optical path conversion means for the other optical path which is split into two by the splitting means 17. Reference numeral 21 is a second laser for reading the spatial light modulating element 18, and 22 is a second laser for multiplexing the recording pattern reading light from the spatial light modulating element 18 and one beam split by the third beam splitting means 17. Beam light wave means 23, a TV camera 23 for picking up the interference fringe pattern superimposed by the second beam combiner 22, and 24 a beam cutoff means for blocking the incidence of recording light on the spatial light modulator 18. .

The operation of the first embodiment of the present invention configured as described above will be described with reference to FIGS.

First, when the measured object 15 is at the reference position Z = Z ₀ shown in FIG. 1, the beam is emitted from the first laser 10. This emitted light is substantially parallel light and is split into two by the first beam splitting means 11a into transmitted light and reflected light. The reflected light is converted into a substantially right angle by the optical path changing means 11b and is incident on the non-parallel light converting means 12.
For example, by adjusting the focal position of the lens on the rear side, the emitted light which is substantially parallel light of the first laser 10 is converted into divergent light as shown in FIG. This divergent light is split into two by the second beam splitting means 14 into reflected light and transmitted light. The transmitted light is applied to the object to be measured 15 at the reference position, and the reflected light is reflected by the second beam splitting means 14 again, enters the first beam combining means 16, and is transmitted therethrough.

On the other hand, the other beam divided into two by the first beam splitting means 11a is expanded by the beam expander 13 and reflected by the first beam combining means 16.

Therefore, the measured object 15 is measured by the first beam combining means 16.
The reflected light from becomes the object light, and the beam expander 13
The light that has passed through corresponds to the reference light, and concentric interference fringes as shown in FIG. 3 are formed. This interference fringe is one kind of Newton ring caused by the difference in curvature between the diffused light and the parallel light, that is, the wavefront of the spherical wave and the plane wave, and the pitch of the interference fringe is wavelength / 2. This interference fringe pattern is separated into reflected light and transmitted light by the third beam splitter 17, and the transmitted light is incident on the beam blocking means 24, but at this time, the beam blocking means 24 is in the ON state and is transmitted. Therefore, the light enters the spatial light modulator 18.

The structure of the spatial light modulator 18 is shown in FIG. 30 is a nematic liquid crystal layer, 31 is a reflective layer, 32 is a cover glass, 33 is a transparent electrode, 34 is a photoconductor, 35 is a light shielding layer, 36 is a liquid crystal alignment film, and a voltage is applied between the transparent electrodes 33. There is. When the interference fringe pattern is incident from the photoconductor 34 side, the impedance of the photoconductor 34 is lowered in the portion irradiated with light, and a higher voltage is applied as compared with the portion not irradiated with light. As a result, a voltage pattern corresponding to the interference fringe pattern is applied to the nematic liquid crystal layer 30, the alignment state of the liquid crystal molecules of the nematic liquid crystal layer 30 is spatially modulated, and the measured object 15 at the reference position Z = Z ₀ is measured. The interference fringe pattern formed by the reference light is recorded in the spatial light modulator 18.

Next, the measured object 15 is measured at an arbitrary measurement position Z using FIG.
The case where the position is displaced to the position of = Z ₁ will be described. All the numbers 10 to 24 in the figure indicate the same as in FIG. At this time as well, as in the case where the measured object 15 is at the reference position Z = Z ₀ , the beam transmitted through the non-parallel light converting means 1 and converted into divergent light by the first beam combining means 16 The reflected light from the measured object 15 becomes the object light, and the light transmitted through the beam expander 13 corresponds to the reference light, and interference fringes are concentrically formed.

However, the curvature of the wavefront of the divergent light at this arbitrary measurement position Z = Z ₁ is different from the curvature at the reference position Z = Z _0, that is, the curvature of the wavefront at the position of Z = Z ₁ is equal to the longer light wavelength. Becomes smaller. Therefore, the interference fringe pitch becomes wider as shown in FIG.

If the measured object 15 is present at this arbitrary measurement position Z = Z ₁ , the beam blocking means 24 is in the OFF state, so
The interference fringe pattern shown in the figure is not written in the spatial light modulator 18, the optical path is changed by the optical path changing means 19, 20,
It is incident on the second beam combining means 22.

On the other hand, when the spatial light modulator 18 is irradiated with the second laser 21, the spatial light modulator 18 spatially modulates the alignment state of the liquid crystal molecules of the nematic liquid crystal layer 30 as described above, and the reference position Z = Z. _Since the interference fringe pattern formed by the measured object 15 and the reference light at ₀ is recorded, the second laser 21
The polarization state of the incident light from is spatially modulated. Therefore, the reflected light from the spatial light modulator 18 is made incident on the second beam combining means 22 via a polarization beam splitter (not shown), or the second beam combining means 22 itself. Is a polarization beam splitter, the intensity pattern of the incident light can be an interference fringe pattern formed by the reference light and the object 15 to be measured at the reference position Z = Z ₀ .

Therefore, the image captured by the TV camera 23 is the measured object 15
The interference fringe pattern at the reference position Z = Z ₀ and the interference fringe pattern at the measurement position Z = Z ₁ are superimposed. With the resolution, it is possible to measure the curvature change of divergent light, that is, the distance between Z ₀ and Z ₁ .

That is, according to the present embodiment, interference fringes using divergent light as object light and parallel light as reference light are first recorded in the spatial light modulator when the measured object has a reference position, and this interference fringe pattern and the measured object By superimposing and comparing the interference fringe patterns when is at an arbitrary measurement position, the displacement of the object to be measured can be accurately measured with a resolution of wavelength / 2.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram of the variable non-parallel light converting means 40 of the second embodiment of the present invention. 40a is the first convex lens, 4
Reference numeral 0b is a second convex lens, and 40c is a focal position changing means of the second convex lens 40b, which is composed of, for example, a motor and a gear train. Variable non-parallel light converting means 40 configured as described above
1 is used in the hologram distance measuring apparatus shown in FIGS. 1 and 2, the non-parallel light intensity of the object light, that is, the curvature of the wavefront can be arbitrarily set, so that the position of the measured object can be referred to at the reference position and the measurement position. The pitch of interference fringes formed with light and the number of fringes can be set to an optimum value for a desired measurement distance range, in other words, a change range of the curvature of the object light, for example, a visual device of an assembly robot. When used as, the dynamic range and accuracy can be selected according to the work content.

Next, a third embodiment of the present invention will be described with reference to FIG. 50 is a confocal optical system consisting of two lenses with different focal lengths, 50a is a first convex lens with a focal length of f1, 50b is a second convex lens with a focal length of f2, and these two lenses are It constitutes a confocal optical system.

This confocal optical system 50 is arranged between the first beam combining means 16 and the third beam splitting means 17 of the hologram distance measuring device shown in FIGS. Through this confocal optical system 50, the rate of change of the curvature of the wavefront of the object light depending on the distance position of the measured object 15 is the ratio of the focal lengths of the first and second convex lenses, that is, (f2 / f1) = 2. It is multiplied.

Therefore, for example, if you set f1 = 10mm and f2 = 100mm,
The rate of change of the curvature of the wavefront of the object light depending on the distance position of the measured object 15 can be reduced to 1/100. That is, the confocal optical system 5
Since the change in the pitch of the interference fringes and the number of fringes due to the distance of the object to be measured can be increased or decreased through 0, the same effect as that of the second embodiment of the present invention can be obtained.

Advantageous Effects of Invention The hologram distance measuring apparatus of the present invention includes a first beam splitting means for splitting a beam emitted from a light source into two optical paths, and a non-parallel light conversion disposed in at least one of the two split optical paths. Means, an optical spatial modulation element that records interference fringes when the measured object is at the reference position, recording pattern read light from this optical spatial modulation element, and interference when the measured object is at an arbitrary measurement position Since the curvature of the wavefront of the object light which is non-parallel light changes due to the displacement of the measured object, the interference fringes with the reference light at the measurement position of the non-measured object Is a hologram distance measuring device capable of measuring the displacement of the object to be measured with the accuracy of the wavelength order of light by comparing the pattern image with the pattern image with the interference fringe pattern when the object to be measured is at the reference position.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of a hologram distance measuring apparatus according to the present invention, and FIGS. 2, 3, 4, and 5 show the operation of the first embodiment of the present invention. Diagram to explain,
FIG. 6 is a plan view of the variable non-parallel light converting means of the second embodiment of the hologram distance measuring apparatus according to the present invention, and FIG. 7 is a plan view of the confocal optical system of the third embodiment of the present invention. FIG. 8 is a block diagram of a conventional optical distance measuring device, and FIG. 9 is an explanatory diagram of the principle of the device. 10 …… first laser, 12 …… non-parallel light conversion means, 15 ……
Object to be measured, 18 ... Spatial light modulator, 21 ... Second laser, 23 ... TV camera, 24 ... Beam blocking means, 40 ... Variable non-parallel light converting means, 50 ... Confocal optical system .

Continuation of the front page (56) Reference JP-A 63-148109 (JP, A) JP-A 62-9203 (JP, A) JP-A 61-41941 (JP, A) JP-A 60-200112 (JP , A) JP-A-60-67834 (JP, A) JP-A-57-161606 (JP, A) JP-A-57-161605 (JP, A)

Claims (4)

(57) [Claims] 1. An interference fringe pattern reproduced from a hologram in which non-parallel light is radiated to an object to be measured at a certain reference position and interference fringes formed by reflected light from the object to be measured and reference light are recorded. And irradiating the non-parallel light to the measured object at an arbitrary position, the displacement of the measured object by superposing interference fringes formed by the reflected light from the measured object and the reference light A hologram distance measuring device characterized by being capable of measuring. 2. A light source, a first beam splitting means for splitting a beam emitted from the light source into two optical paths, and the second beam splitting means.
A beam parallel light intensity adjusting means arranged in at least one of the divided optical paths, and a second beam irradiating the measured object with one beam transmitted and reflected by the non-parallel light converting means. The beam splitting means, the first beam combining means for multiplexing the reflected light from the object to be measured, and the other beam split into two by the first beam splitting means, and the combined light Third beam splitting means for splitting, an optical spatial modulation element for recording interference fringes formed by the combined light in one optical path split by the third beam splitting means, and from this optical spatial modulation element Second beam combining means for combining the recording pattern reading light with one of the beams divided by the third beam dividing means, and beam blocking means for blocking the incidence of the recording light on the spatial light modulator. Hologram distance measuring apparatus according to claim 1, characterized in that with a. 3. The non-parallel light converting means is constituted by a confocal optical system consisting of two lenses, and at least one lens is provided with a movable means so that the parallel light intensity of the beam is variable. The hologram distance measuring device described. 4. The first beam combining means and the combined light
4. The hologram distance measuring apparatus according to claim 2, wherein a confocal optical system including two lenses having different focal lengths is arranged between the third beam splitting means for splitting.