JPH0540021A - Multi-slit projector - Google Patents

Abstract

PURPOSE:To reduce the size of a multi-slit projector which generates a slit light pattern for three-dimensionally measuring an object and to improve the resolution of the projector. CONSTITUTION:Divergent light emitted from the light emitting source 11 of this multi-slit projector 1 is shaped to parallel rays through a collimator lens 12 and the parallel rays produce a two-dimensional spot group 16 when the parallel rays are passed through a diffraction gratings 13 and 15. When the rays are passed through a cylindrical lens 17, the rays are transformed to multi- slit light 18 and a shutter array 19 generates a prescribed slit light pattern. A cylindrical lens 20, the axial direction of which is perpendicular (Y-direction) to the axial direction (X-direction) of the lines 17, is provided in the poststage of the array 19 and the diffracted angle in the X-direction of the slit light passed through the array is reduced by the effect of the lens 20. An object 2 is irradiated with the slit light when the object 2 is three-dimensionally measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-slit projector for generating a slit light pattern used for three-dimensional measurement of an object, and more particularly to a multi-slit projector for downsizing the device and improving resolution.

In order to control the operation of an industrial robot or the like, it is necessary to recognize the three-dimensional shape and spatial arrangement of the object. For that purpose, three-dimensional measurement of an object is performed, and as a measurement method therefor, for example, there is a light section method. This light-section method is a method of irradiating an object with structured multi-slit light and measuring it by imaging it with a camera.By simultaneously measuring multiple points, the measurement time can be significantly reduced. Since it can be done, it is considered as an extremely effective method. The multi-slit projector is a device that generates a slit light pattern suitable for such an application.

[0003]

2. Description of the Related Art FIG. 5 is a diagram showing a three-dimensional measuring method of an object using multi-slit light. In the figure, a multi-slit projector 10 is disclosed in Japanese Patent Application Laid-Open No. 1-27 by the applicant of the present invention.
The one proposed in No. 7707 is used. The slit light 11 and 12 generated by using the multi-slit projector 10 is irradiated on the object 2 to be three-dimensionally measured, and the intersection line between each slit light 11 and 12 and the object 2 (light cutting )
Is captured by the camera 3. The three-dimensional shape of the object 1 is obtained based on the triangulation principle from the imaged data obtained by the light section method.

FIG. 6 is a diagram schematically showing the structure of the multi-slit projector. In the figure, a multi-slit projector 10 comprises a light emitting source 11, diffraction gratings 13 and 15, a cylindrical lens 17 and a shutter array 19, which are sequentially arranged on an optical axis 30. The divergent light emitted from a light emitting source (for example, a semiconductor laser or a light emitting diode) 11 that emits light of a single wavelength is shaped into a parallel light by a collimator lens 12, and the parallel light passes through a diffraction grating 13. , The oval spot light is Y
A group of spots 14 arranged in the direction is generated. The spot group 14 further passes through the diffraction grating 15 to generate a two-dimensional spot group 16 in which a plurality of spot groups are arranged in parallel in the X direction. Fiber gratings are used for the diffraction gratings 13 and 15, for example. When the two-dimensional spot group 16 passes through the cylindrical lens 17, the spot groups in each row are arranged such that the intervals in the Y direction are narrowed and adjacent spot lights partially overlap each other.
Each forms slit light and multi slit light 18
Cause The shutter array 19 at the final stage is composed of a plurality of segments, and each segment is independently turned on and off to block corresponding slit light when the power is off and allow it to pass through when the power is on.
Therefore, the shutter array 19 can be used to form an arbitrary slit light pattern from the multi-slit light 18, and the slit light pattern is irradiated on the object 2 and used for three-dimensional measurement of the object 2. Next, the conditions required for the shutter array 19 to exhibit the function as a shutter will be described.

FIGS. 7A and 7B are model diagrams showing the state of interference of light of a single wavelength emitted from a light emitting source. FIG. 7A shows general interference, FIG. 7B shows a case where diffracted light goes around, and FIG. ) Indicates the case where the diffracted light does not wrap around. Figure 7
In (A), the single wavelength light emitted from the light emitting source 70 passes through the diffraction grating 71 and is diffracted, and spot light 72 is formed by the interference. In this case, the relationship of the following expression (1) is approximately established between the grating interval d of the diffraction grating 71 and the interval D of the spot light 72 formed at the position M of the distance L from the diffraction grating 71. ing.

D = Lλ / d (1) (λ: wavelength of light) If the shutter array 73 is placed at the position M to block the spot light 72, the shutter array 73
The width of each segment 73a constituting
The width D must be set. On the other hand, as shown in FIG. 7B, when the width nd of the light passing through the diffraction grating 71 (n: the number of gratings of the diffraction grating 71) is larger than the width D of the segment 73a (nd> D), , Diffracted light is segment 7
3a around it, causing interference at the position N behind it,
It becomes impossible to block light completely. In contrast,
As shown in FIG. 7 (C), when the distance L is large, the distance D in the equation (1) becomes large if the lattice distance d is constant, and therefore D = nd. In this case, the diffracted light does not go around the segment 73a, interference does not occur behind, and the light can be completely blocked. That is, in order to completely block the light passing through the diffraction grating 71 by using the shutter array 73, the width D of the segment 73a needs to satisfy the condition D = nd for preventing the light from wrapping around. The distance L has to be long.

[0007]

[Problems to be Solved by the Invention]
The conventional multi-slit projector 10 has a problem that it becomes impossible to actually install and use it on the hand of the manipulator of the robot or the like because the length thereof becomes long and leads to increase in size. ..

On the other hand, as a method for reducing the size of the multi-slit projector 10 while maintaining the condition D = nd for preventing the light from wrapping around, the grating spacing d in the equation (1) is set to be small and the density of the diffraction grating 71 is set to be small. It is conceivable to increase (in this case, the number of grids n) and decrease the distance L accordingly. By doing so, the condition D = n
The distance L can be shortened while holding d. That is, in the case of the multi-slit projector 10, the diffraction grating 7
The one corresponding to the grating interval d is the fiber grating interval of the diffraction grating 13, and the multi-slit projector 10 can be downsized by reducing the fiber grating interval.

However, the conventional multi-slit projector 10
In the above, if the fiber grating spacing of the diffraction grating 13 is made small and its density is increased, the diffraction angle of the light emitted from the diffraction grating 13 becomes large, so that the spacing of the slit light emitted from the shutter array 19 at the final stage also becomes the same. The density becomes coarse. Therefore, even if the camera 3 images the slit light emitted to the object 2 and performs image processing,
There is a problem that the resolution becomes poor.

Further, the method of increasing the density of the fiber grating spacing of the diffraction grating 13 has the effect of sharpening the waveform of the diffracted light from the diffraction grating 13 because the number of point light sources is increased. ing. Therefore, the slit light emitted from the final stage shutter array 19 also becomes sharper, which is a very effective method for facilitating image processing. However, even in that case, as in the case described above, since the diffraction angle becomes large,
There is a problem that the interval of slit light becomes coarse and the resolution deteriorates.

Further, the conventional multi-slit projector 10 is used.
Then, the projection angle when the slit light emitted from the shutter array 19 is projected on the object 2 is the diffraction gratings 1 and 1.
5 determined by interference only. Therefore, when the slit light is projected on the surface perpendicular to the optical axis, the slit light interval becomes larger as the diffracted light of higher order becomes higher.
Therefore, there is a problem in that the resolution changes depending on the distance from the optical axis, and uniform resolution cannot be obtained. In particular,
The resolution deteriorated at a position away from the light source.

Further, in the conventional multi-slit projector 10, the projection angle of the slit light emitted from the shutter array 19 is already determined by the diffraction gratings 13 and 15 until the light reaches the shutter array 19, as described above. It cannot be controlled arbitrarily. Therefore, for example, even if an attempt was made to irradiate a high density slit light to the predetermined position of the object 2 in order to increase the resolution and improve the measurement accuracy, such a slit light could not be obtained.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a multi-slit projector that is capable of reducing the size of an apparatus and preventing deterioration of resolution due to an increase in diffraction angle caused by the size reduction. The first purpose.

A second object is to irradiate an object with sharp slit light to facilitate image processing. Furthermore, the third object is to make the intervals of the slit light projected on the object uniform and to increase the density.

A fourth object is to arbitrarily control the projection angle of the slit light with which the object is irradiated.

[0016]

FIG. 1 illustrates the principle of the present invention. The multi-slit projector 1 of the present invention is composed of first and second diffraction gratings 13 and 15, a cylindrical lens 17, a shutter array 19 and a cylindrical lens 20.
The first and second diffraction gratings 13 and 15 are arranged so that the diffraction directions are orthogonal to each other on the optical axis of the single wavelength light.
The cylindrical lens 17 is arranged at the subsequent stage of the second diffraction grating 15. The axial direction of the cylindrical lens 17 is orthogonal to the diffraction direction of either one of the first and second diffraction gratings 13 and 15. A shutter array 19 that blocks a predetermined slit light out of the multi-slit light output from the cylindrical lens 17 and outputs a slit light pattern is provided at the subsequent stage of the cylindrical lens 17. Further, a lens 20 having a lens effect is provided at the subsequent stage of the shutter array 19 in a direction perpendicular to the axial direction of the cylindrical lens 17.

[0017]

The divergent light emitted from the light emission source 11 for generating light of a single wavelength is shaped by the collimator lens 12 into parallel light, and the parallel light passes through the diffraction grating 13 to form an elliptical spot light. Generate spot groups 14 arranged in the Y direction. The spot group 14 further passes through the diffraction grating 15 to generate a two-dimensional spot group 16 in which a plurality of spot groups are arranged in parallel in the X direction. Fiber gratings are used for the diffraction gratings 13 and 15, for example. When the two-dimensional spot group 16 passes through the cylindrical lens 17, the spot groups in each row are arranged so that the intervals in the Y direction are narrowed so that adjacent spot lights partially overlap each other, and each spot light is slit light. To generate multi-slit light 18. The shutter array 19 in the subsequent stage of the cylindrical lens 17 is composed of a plurality of segments, and each segment is independently turned on / off to obtain an arbitrary slit light pattern from the multi-slit light 18. Furthermore, since the lens 20 at the final stage has a lens effect in the direction perpendicular to the axial direction of the cylindrical lens 17, the diffraction angle of the slit light passing through the shutter array 19 becomes small due to the lens effect.

With respect to the first object, by increasing the grating spacing density of the first diffraction grating, the length of the multi-slit projector 10 can be shortened and the miniaturization can be realized. In that case, conventionally, the diffraction angle of the slit light is increased with the increase of the lattice spacing density, the spacing of the slit light is coarse, and the resolution is deteriorated. On the other hand, in the present invention, since the lens 20 is provided and the diffraction angle is reduced by the lens effect, the multi-slit projector can be downsized without deteriorating the resolution.

The second object can be realized by increasing the grating spacing density of the first diffraction grating to increase the number of point light sources in the first diffraction grating, but in that case as well. Deterioration of resolution occurs due to the large size. On the other hand, by providing the lens 20, it is possible to reduce the diffraction angle and irradiate the object with sharp slit light without deteriorating the resolution.

Further, for the third object, by using a Fourier transform lens as the lens 20 at the final stage, it is possible to collect slit light due to higher-order diffraction away from the center of the optical axis toward the center. Therefore, it is possible to obtain a slit light having a higher density and more uniform as well as a smaller diffraction angle.

With respect to the fourth object, a grating lens is used as the lens 20, and the refraction angle of each stage of the grating lens is designed to arbitrarily control the projection angle of the slit light irradiated on the object. be able to.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. A first embodiment of the present invention will be described based on FIG. The multi-slit projector 1 of the present invention includes a light emission source 1
1, a diffraction grating 13, 15, a cylindrical lens 17, a shutter array 19, and a lens 20, which are sequentially arranged on the optical axis 30. A light source (for example, a semiconductor laser or a light emitting diode) that emits light of a single wavelength 11
The divergent light emitted from is shaped into parallel light by the collimator lens 12, and the parallel light passes through the diffraction grating 13 to generate spot groups 14 in which elliptical spot lights are arranged in the Y direction. This spot group 14
Further, by passing through the diffraction grating 15, a two-dimensional spot group 16 in which a plurality of spot groups are arranged in parallel in the X direction is generated. For the diffraction gratings 13 and 15, fiber gratings are used in which fibers of a predetermined length are stacked in a row and the lens action of each fiber is used. When the two-dimensional spot group 16 passes through the cylindrical lens 17, the spot groups in each row are arranged such that the intervals in the Y direction are narrowed and adjacent spot lights partially overlap each other.
Each forms slit light and multi slit light 18
Cause

The shutter array 19 arranged in the subsequent stage of the cylindrical lens 17 is composed of a plurality of segments, and each segment is independently turned on / off to cut off the corresponding slit light when the power is turned off. Sometimes configured to be transparent. Therefore, the shutter array 19 can be used to form an arbitrary slit light pattern from the multi-slit light 18, and the arbitrary slit light pattern can be selected as the reference slit light. A cylindrical lens 20 having an axis in a direction perpendicular to the axial direction (X direction) of the cylindrical lens 17 (Y direction) is provided at the subsequent stage of the shutter array 19. Therefore, the slit light passing through the shutter array 19 has a smaller diffraction angle in the X direction due to the lens effect of the cylindrical lens 20. The slit light that has passed through the cylindrical lens 20 is applied to the object 2 and used for three-dimensional measurement of the object 2.

FIG. 2 is a diagram for explaining the effect of the final stage lens. As shown in the figure, the light emitted from the light source (in this case, equivalent to the diffracted light from the diffraction grating 13) 50 with a spread of the angle θ finally passes through the shutter array 19 as slit light, and then is of a cylindrical type. The lens 20 narrows the angle θ. When such an object 2 is irradiated with such slit light, the interval density of the slit light is increased, so that the resolution at the time of image processing of the image pickup screen by the camera 3 is improved.

By the way, the size of the multi-slit projector 1 can be reduced by decreasing the fiber grating spacing of the diffraction grating 13 and increasing its density. Conventionally, however, the slit light is increased as the spacing density of the diffraction grating 13 is increased. The diffraction angle (corresponding to the angle θ in FIG. 2) was increased and the slit light spacing became coarse, resulting in poor resolution. On the other hand, in this embodiment, since the cylindrical lens 20 is provided, the diffraction effect can be reduced due to the lens effect. Therefore, the multi-slit projector 10 can be downsized without deteriorating the resolution.

Further, since the method of increasing the spacing density of the diffraction grating 13 described above increases the number of point light sources, the resulting interference fringes become sharper and the image processing after projecting the slit light is performed. However, in this case as well, the diffraction angle similarly becomes large, and there is a problem in that the resolution deteriorates. On the contrary,
In this embodiment, since the cylindrical lens 20 is provided, the diffraction angle can be reduced. That is, the diffraction grating 13
Even if the interval density is increased, it is possible to irradiate the object with sharp slit light without deteriorating the resolution.

In the above description, the cylindrical lens is used as the final lens, but a lens having the same lens effect as the cylindrical lens, for example, a convex lens may be used.

FIG. 3 is a diagram showing a case where a Fourier transform lens is used as the final stage lens. Fourier transform lens 21
Has a function of collecting slit lights by high-order diffraction away from the center of the optical axis in the central direction and making the slit light intervals uniform. Therefore, by using the Fourier transform lens 21 in the final stage, it is possible to reduce the diffraction angle of the slit light and to obtain the slit light of higher density and uniform. Therefore, the resolution at the time of image processing can be improved.

FIG. 4 is a diagram showing a case where a grating lens is used as the final stage lens. In the grating lens 22, the refraction angle of each step 22a can be arbitrarily set by designing the inclination angle of each step 22a. Therefore, the slit light is reflected by the grating lens 22.
After passing through, the slit light is projected on the object 2 at an angle according to the refraction angle of each step 22a. Therefore, it is possible to arbitrarily control the projection angle of the slit light with which the object is irradiated, and for example, by arranging the Fourier transform lens 22 designed accordingly in a place where the measurement accuracy of the object 2 is desired to be improved, Slit light with high density can be projected at that location.

In the above description, the cylindrical lens 17 is arranged after the diffraction grating 15, but it may be arranged after the collimator lens 12. In addition, the cylindrical lens 17
The cylindrical lens 20 is arranged so that its axial direction is the X direction and the axial direction of the cylindrical lens 20 is the Y direction.
Direction, the cylindrical lens 20 may be in the X direction.

[0031]

As described above, in the present invention, in the multi-slit projector, a lens is further provided in the latter stage of the shutter array, and the diffraction effect of the slit light passing through the shutter array is reduced by the lens effect. .. Therefore, the interval density of the slit light with which the object is irradiated is increased, so that the resolution at the time of image processing can be improved.

Further, the multi-slit projector can be miniaturized by increasing the grating spacing density of the first diffraction grating, but conventionally, the resolution was also deteriorated at that time. On the other hand, since the lens is provided at the final stage, the diffraction effect becomes small due to the lens effect, and the multi-slit projector can be downsized without deteriorating the resolution.
Similarly, when the grating spacing density of the first diffraction grating is increased, sharp slit light can be obtained, but the resolution is deteriorated accordingly, but since the lens is provided at the final stage, it is possible to sharpen the resolution without deteriorating the resolution. The object can be irradiated with various slit light.

Further, since the Fourier transform lens is provided at the final stage, it is possible to collect the slit light, which is separated from the center of the optical axis by diffraction of a higher order, toward the center. Therefore, it is possible to reduce the diffraction angle and obtain uniform slit light with higher density.

Further, since the grating lens is provided at the final stage, the projection angle of the slit light with which the object is irradiated can be arbitrarily controlled by designing the refraction angle of each stage of the grating lens. Therefore, by disposing a Fourier transform lens designed accordingly at a position where the measurement accuracy of the object is desired to be increased, it is possible to project slit light having a high density at that position.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram for explaining an effect of a final stage lens.

FIG. 3 is a diagram showing a case where a Fourier transform lens is used as a final stage lens.

FIG. 4 is a diagram showing a case where a grating lens is used as a final stage lens.

FIG. 5 is a diagram showing a three-dimensional measuring method of an object using multi-slit light.

FIG. 6 is a diagram schematically showing a configuration of a conventional multi-slit projector.

FIG. 7 is a model diagram showing a state of interference of single-wavelength light emitted from a light emitting source, where (A) shows general interference and (B) shows
Shows the case where the diffracted light goes around, and (C) shows the case where the diffracted light goes around.

[Explanation of symbols]

 1 Multi-slit Projector 13,15 Diffraction Grating 17,20 Cylindrical Lens 19 Shutter Array 21 Fourier Transform Lens 22 Grating Lens

Claims (3)

[Claims] 1. A multi-slit projector for generating a slit light pattern used for three-dimensional measurement of an object, comprising: first and second diffraction gratings arranged on an optical axis (30) of a single wavelength light and having diffraction directions orthogonal to each other. Diffraction output light from the diffraction grating (13, 15) and the second diffraction grating (15) is incident,
A cylindrical lens (17) whose axial direction is orthogonal to either one of the first and second diffraction gratings (13, 15), and a multi-slit light output from the cylindrical lens (17). Among them, a shutter array (19) that cuts off a predetermined slit light and outputs a slit light pattern, and a lens effect arranged in a stage subsequent to the shutter array (19) in a direction perpendicular to the axial direction of the cylindrical lens (17). A multi-slit projector comprising: a lens (20) having 2. The multi-slit projector according to claim 1, wherein the lens (20) is a Fourier transform lens. 3. The multi-slit projector according to claim 1, wherein the lens (20) is a grating lens.