JPH04243213A - Multislit light projector - Google Patents

Abstract

PURPOSE:To reduce the size of the multislit light projector for making three- dimensional measurement by projecting coded multislit light to an object to be measured. CONSTITUTION:The diameter of collimated beams of light from a light source 1 consisting of a semiconductor laser, etc., is reduced by a beam expander 6 and is made incident on 1st, 2nd diffraction gratings 2, 3. The spot light is made into an oval shape by a circular cylindrical lens 4 and is superposed partly on the adjacent spot light to form the slit light in the major axis direction of the oval shape. The multislit light coded by a shutter array 5 is outputted and the object to be measured is irradiated with this light. The diameter of the collimated beams of light is reduced and, therefore, crosstalks do not arise even if the distance between the 1st, 2nd diffraction gratings 2, 3 and the shutter array 5 is shortened.

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 performing three-dimensional measurement by projecting a plurality of parallel slit lights onto an object to be measured. Slit light is projected onto the object to be measured in three-dimensional vision devices for recognizing objects to be measured in various automatic devices such as robots, or shape input devices to measure and input the shape of objects. A multi-slit projector is known that projects a plurality of parallel slit lights and measures a plurality of points at the same time instead of scanning and measuring.

0002

2. Description of the Related Art FIG. 5 is an explanatory diagram of a conventional multi-slit projector, in which a light source 51 outputs parallel light of a single wavelength using a semiconductor laser 51a and a collimating lens 51b.
This parallel light enters the first diffraction grating 52 and becomes output light 61 consisting of a plurality of oval spot lights. This output light 61 is incident on the second diffraction grating 53,
Since the diffraction directions of the first and second diffraction gratings 52 and 53 are arranged orthogonal to each other, the second diffraction grating 5
The output light 62 of No. 3 becomes a plurality of spot light trains. This output light 62 is incident on a cylindrical lens 54, and when the longitudinal direction of this cylindrical lens 54 is set as the x-axis direction as shown in the figure, the output light 63 is caused by adjacent spot lights partially overlapping in the y-axis direction. It becomes a slit light. This output light 63 is incident on a shutter array 55 consisting of a liquid crystal shutter or the like, and by selectively turning on and off the shutters of this shutter array 55, a coded multi-slit light 64 is output, and the illustration is omitted. The object to be measured is irradiated.

[0003] The slit light pattern on the object to be measured is imaged by an imaging device, the captured image is binarized, and the three-dimensional shape of the object to be measured is determined based on the projection angle and the imaging angle of the multi-slit light. It is something that can be measured.

0004

In order to irradiate the object to be measured with coded multi-slit light, it is necessary to completely block any slit light using the shutter array 55. Furthermore, it is necessary to reduce the size of the light source 51, the diffraction gratings 52 and 53, the cylindrical lens 54, and the shutter array 55. However, there is a problem in that light goes around through the shutter array 55.

FIG. 4 is an explanatory diagram of the wraparound of light, and (b
), when a single-wavelength light 45 from a light source such as a semiconductor laser is irradiated through a diffraction grating 45 with a grating number n and a grating spacing d, a spot is formed at a distance L from the diffraction grating 45. The distance D between the lights is approximately expressed by the following equation, where λ is the wavelength of the light. D=Lλ/d
(1) Therefore, when the shutter S is arranged at a distance L from the diffraction grating 45 as shown in (c), the interval between the slits of the shutter S is selected to be D. In that case, the width nd of the light 44 passing through the diffraction grating 45 (number of gratings n x grating interval d
) is larger than the slit spacing D, as shown in (d), the light may go around the closed (off) shutter S and cause interference. In other words, it goes around the outside of the closed shutter S from both ends of the diffraction grating 45, intersects with the object to be measured 46.
The area on the object to be measured 46 corresponding to the closed shutter S, which should be a dark pattern, becomes brighter. As described above, there is a drawback that the slit light on the object to be measured 46 cannot be completely blocked.

Therefore, as shown in (e), a diffraction grating 4
If the shutter S is placed at a distance L'(L<L') from 5, that is, at a position where nd=D, the wraparound of the shutter S is eliminated and the slit light on the object to be measured 46 is completely blocked. can do. However, as the distance L' becomes larger, there is a drawback that the multi-slit projector becomes larger. The present invention aims to reduce the size of the entire device.

[0007]

[Means for Solving the Problems] The multi-slit projector of the present invention will be described with reference to FIG. 1. A second diffraction grating 2, 3, a cylindrical lens 4 into which the diffracted output light from the first and second diffraction gratings 2, 3 is incident and outputs a plurality of parallel slit lights, and this cylindrical lens. In a multi-slit projector equipped with a shutter array 5 consisting of a liquid crystal shutter or the like that blocks and encodes a predetermined slit light among the parallel slit lights from the lens 4, the diameter of the parallel light from the light source 1 is reduced. Then, the first
, a beam expander 6 is provided for inputting the beam to the second diffraction gratings 2 and 3.

[0008]

[Operation] The beam expander 6 reduces the diameter of the parallel light from the light source 1 and makes it incident on the first and second diffraction gratings 2 and 3.The beam expander 6 reduces the diameter of the parallel light from the light source 1 and makes it incident on the first and second diffraction gratings 2 and 3. The minimum value of the slit spacing at which this does not occur can be significantly lowered. Furthermore, since it is possible to reduce the distance between the diffraction grating and the shutter array, the device can be made smaller.

[0009]

[Embodiment] FIG. 2 is an explanatory diagram of an embodiment of the present invention.
a is a semiconductor laser, 11b is a collimating lens, 11 is a light source, 12 and 13 are first and second diffraction gratings, 14 is a cylindrical lens, 15 is a shutter array, 16a and 16b are lenses, and 16 is a beam expander. be. The light source 11 that outputs parallel light of a single wavelength is shown as being composed of a semiconductor laser 11a and a collimating lens 11b,
The parallel light from this light source 11 is incident on a beam expander 16. This beam expander 16 is connected to the lens 1
6a and 16b, the diameter of the parallel light from the light source 11 is reduced and the parallel light is incident on the first diffraction grating 12.

The output light 21 of the first diffraction grating 12 becomes a plurality of oval spot lights arranged in a direction perpendicular to the grating, and is incident on the second diffraction grating 13. The first and second diffraction gratings 12 and 13 are arranged so that their grating directions are perpendicular to each other, as in the conventional example, and the output light 22 of the second diffraction grating 13 is a two-dimensional array of spot lights. The light is incident on the cylindrical lens 14. This cylindrical lens 1
Although lens 4 can be completely cylindrical, the illustrated lens 14 is formed in a semi-cylindrical shape. Since the longitudinal direction of this cylindrical lens 14 is the x-axis direction, its output light 23 becomes slit light in which the spot light arrays in the y-axis direction partially overlap each other. This output light 23 is incident on a shutter array 15 such as a liquid crystal shutter, and by selectively controlling the shutters of this shutter array 15 on and off, coded multi-slit light 24 is output.

FIG. 3 is an explanatory diagram of a beam expander according to an embodiment of the present invention, in which (a) shows a Kessler type, (b) shows a prism type, and (c) shows a Galileo type. The Kessler type has convex lenses 31, 3 as shown in (a).
2, it reduces the diameter of the light of ω1 to the light of ω2, and the focal lengths of the convex lenses 31 and 32 are set to f1 and f2.
Then, ω2 = (f2 /f1)ω1
...(2) becomes. In this case, it is sufficient that the diameter ω2 of the light incident on the diffraction grating 12 can be reduced in the longitudinal direction of the cylindrical lens 14 (in the illustrated case, the x-axis direction).
It is also possible to use cylindrical lenses 1 and 32.

[0012] Also, the prism type has two
Prisms 33 and 34 are arranged, and light with a diameter ω1 is transmitted with a diameter ω
2 and enters the diffraction grating 12. The Galileo type is composed of a convex lens 35 and a concave lens 36, as shown in (c), and reduces light having a diameter ω1 to a diameter ω2 before entering the diffraction grating 12.

As shown in FIG. 4(a), when the diameter of the light 41 is made small and the light passing through the diffraction grating 42 is irradiated onto the measured object 43, the distance from the diffraction grating 42 is reduced as in the conventional example. L
When the shutter S is placed at the position , if the distance between the slits at that position is D, the relationship ω2 =nd<D is established, so that the shutter S does not cause wraparound. That is, since it becomes possible to arrange the shutter S close to the diffraction grating 42 side, it is possible to reduce the size of the apparatus. Furthermore, by reducing the diameter ω2 of the light incident on the diffraction grating 12, it is possible to increase the density of slits in the shutter array 15, and if the number of gratings is the same, the shutter array 15 can be made smaller.

[0014]

As explained above, the present invention provides a multi-slit projector that irradiates a measured object with coded multi-slit light, including a light source 1 that outputs parallel light;
A beam expander 6 is provided between the first and second diffraction gratings 2 and 3 to reduce the diameter of light incident on the first and second diffraction gratings 2 and 3. 2, 3 and the shutter array 5, or the diffraction grating 2,
This has the advantage that the lattice density of 3 can be increased, and the device can be easily miniaturized.

[Brief explanation of the drawing]

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

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a beam expander according to an embodiment of the present invention, in which (a) is a Kessler type beam expander, (b) is a Kessler type beam expander;
(c) shows a prism-type beam expander, and (c) shows a Galileo-type beam expander.

FIG. 4 is an explanatory diagram of the wraparound of light, (a) is an explanatory diagram in an embodiment of the present invention, (b) is an explanatory diagram of general interference,
(c) is an explanatory diagram of the shutter position, (d) is an explanatory diagram when wraparound occurs, and (e) is an explanatory diagram of a conventional example for eliminating wraparound.

FIG. 5 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1. Light source 2 First diffraction grating 3 Second diffraction grating 4 Cylindrical lens 5 Shutter array 6 Beam expander

Claims (1)

[Claims] 1. First and second diffraction gratings (2) and (3) into which parallel light from a light source (1) is incident and which are arranged such that their diffraction directions are perpendicular to each other; A cylindrical lens (4) into which the diffracted output light from the diffraction gratings (2) and (3) of No. 2 is incident and outputs a plurality of parallel slit lights; Shutter array (5) that blocks and codes predetermined slit light
In a multi-slit floodlight equipped with the light source (
A multi-slit projector characterized in that a beam expander (6) is provided for reducing the diameter of the parallel light from 1) and making it incident on the first and second diffraction gratings (2) and (3). .