JPH0526663A - Optical distance sensor - Google Patents

Abstract

(57) [Summary] [Structure] The light source 1 and the light emitted from the light source are plane lights 7.
A light emitting device including a mirror 2 for projecting light as a light source, a light receiving device 3 for obtaining a two-dimensional image, and a convex mirror 4 for guiding the light 8 projected from the light source to the light receiving device and reflected by the object 10. In the optical distance sensor equipped with the light receiving device, the shape of the convex mirror 4 of the light receiving device is reflected by the reflected light 8 from the object 10 to be measured on the image obtained by the light receiver 3.
And the distance from the point indicating the vertex of the convex mirror 4 on the image to the distance from the sensor to the object to be measured are proportional. [Effect] The actual measured distance has a linear relationship with the distance on the image, the distance measuring accuracy is made uniform, the two-dimensional light receiving field of view can be effectively used, and the distance calculation can be simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light and compact distance sensor suitable for mounting on an industrial robot or the like.

[0002]

2. Description of the Related Art In recent years, are. A. Jarvis and Jen. C. Billund “Un-Automated
Guided Vehicle with Map Building and Path Finding Capabilities "Preprints of the Force International Symposium of Robotics Research Page 155-162 1987 (RAjarvis and J.
C. Byrne “AnAutomated Guided Vehicle with Map Buil
ding and Path Finding Capabilities ”Preprints of T
he 4th International Symposium of Robotics Researc
pp.155-162 1987 and thereafter, referred to as known example 1).

A field of view of the entire circumference (360 °) consisting of a light source for projecting a ring pattern using a slit as in 1) and a conical mirror for reflecting the light of the ring pattern emitted from the light source into plane light. An obstacle sensor is being tested by using a light-receiving device that has. In this method, the conical mirror for receiving light is placed between the light emitting device and the CCD camera,
The field of view is arranged to be suitable for obtaining the reflected light from the side of the light-receiving conical mirror. When this method is used, the position of the reflected light on the image obtained by the light receiving device is closer to the center on the image as the distance to the object to be measured is farther, and farther from the center of the image as the distance is shorter. To be The distance to the object is calculated from the reflected light position on the image,
The reflected light position is obtained in pixel units. In the method of the known example 1, the distance to the object to be measured is constant in the horizontal plane,
If the object to be measured is moved over the entire circumference, the locus of the reflected light position draws a circle on the image. The larger the distance to the object to be measured, the smaller the circle, and the smaller the number of pixels indicating the position. Since the position calculation of the distance measurement target is performed in units of pixels, the number of positions that can be specified decreases when the number of pixels is small. However, in the real world,
When a circle is drawn with the sensor as the center, the greater the distance, the greater the circumference, and the more possible the position of the object to be measured. Therefore, in the method of the first known example, the distance measurement accuracy sharply decreases as the distance increases.

[0004]

A conventional active stereo type optical application sensor for a robot having a wide field of view using a wide field type light receiving device using a plane light projecting surface using a mirror and a convex mirror has a long distance. However, there was a problem that the accuracy dropped sharply. An object of the present invention is to provide an optical distance sensor capable of performing highly accurate measurement at a long distance by specifying the shape of a convex mirror.

[0005]

The above-mentioned object is to provide a light-emitting device comprising a light source and a mirror for projecting light emitted from the light source as plane light, a light-receiving device for obtaining a two-dimensional image and the light-receiving device. In an optical distance sensor provided with a light receiving device consisting of a convex mirror that guides the light projected from the light source and reflected on the object, the reflected light from the object to be measured on the image obtained by the light receiver. The distance on the image from the point shown to the point showing the apex of the convex mirror, and the shape in which the relationship from the sensor to the distance measuring object is proportional, or the shape of the convex mirror to the light receiving surface A shape such that the incident angle of reflected light from the object to be measured and the distance from the sensor to the object to be measured are proportional, or
A relationship is obtained in which the distance from the point on the convex mirror that reflects the reflected light from the object to be measured viewed from the light receiver to the central axis of the convex mirror and the distance from the sensor to the object to be measured are proportional. It is achieved by making the shape or a convex mirror shape made by a combination of a spherical surface and a truncated cone shape to approximate its characteristics.

[0006]

The operation of the present invention will be described with reference to FIG. A light emitting device including a light source 1 and a mirror 2 that projects light emitted from the light source as planar light, a light receiver 3 for obtaining a two-dimensional image, and light projected from the light source to the light receiver is an object. In an optical distance sensor provided with a light receiving device including a convex mirror 4 for guiding the light reflected above, the shape of the convex mirror 4 of the light receiving device is measured from a point indicating the apex of the convex mirror 4 on an image obtained by the light receiver. The shape is such that the distance r to the point showing the reflected light 8 from the object and the distance Lr16 from the sensor to the object to be measured 10 are proportional. Expressing this relationship as an equation,

[0007]

[Equation 1]

[0008] Here, k ₁ is a proportional constant with respect to distance. r can be replaced by the incident angle β15 of the reflected light 8 from the ratio of the maximum viewing angle of the receiver and the image size,

[0009]

[Equation 2]

[0010] Here, a is a proportional constant. Expressing Equation 1 using Equation 2,

[0011]

[Equation 3]

[0012] Furthermore, the reflection point p1 on the convex mirror 4
When expressed using the position coordinates (x13, y12) of 7,

[0013]

[Equation 4]

Here, the surface shape of the convex mirror 4 is

[0015]

[Equation 5]

If the reflection angle with respect to the vertical at the reflection point p17 is θ21,

[0017]

[Equation 6]

[0018]

[Equation 7]

From

[0020]

[Equation 8]

[0021] By solving this differential equation, it is possible to obtain a convex mirror shape having the characteristic of Equation 1. Here, r is calculated based on the reflected light position of each pixel, but by using this shape, the change of the distance on the image with respect to the change of the actual distance, that is, the resolution of the distance is made uniform. You can Therefore, it is possible to prevent a decrease in distance measurement accuracy in a long distance and obtain uniform distance measurement accuracy in the entire area within the sensor effective range.

Further, the convex mirror of the light receiving device is shaped such that the incident angle of reflected light from the object to be measured to the light receiver is proportional to the distance from the sensor to the object to be measured, or The shape is such that the distance from the point on the convex mirror reflecting the reflected light from the object to be measured seen from the light receiver to the central axis of the convex mirror is proportional to the distance from the sensor to the object to be measured. By doing so, it is possible to equalize or approximately equalize the actual change in distance with respect to the change in distance on the image. It is possible to obtain substantially uniform distance measurement accuracy in the entire region.

Further, in the case of forming a convex mirror shape by combining a spherical surface and a truncated cone shape in order to approximately obtain the above-mentioned characteristics, the angle with respect to the bottom surface in the vicinity of the end of the convex mirror shape having the above-mentioned characteristics is calculated. It is configured by a truncated cone having an angle with respect to the bottom surface of the truncated cone and a spherical surface smoothly connecting to the truncated cone with the vertex of the convex mirror obtained by calculation as the vertex of the spherical surface. By using the convex mirror having this shape, it is possible to similarly reduce the deterioration of the distance measurement accuracy at a long distance.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an illustration of an optical distance sensor according to the present invention, FIG. 2 is an illustration of a light emitting device, FIG. 3 is an illustration of a light receiving device, FIG. 4 is an illustration of the principle of distance calculation, and FIG. The distance on the image from the point showing the reflected light from the object to be measured to the point showing the apex of the convex mirror on the image obtained by is proportional to the distance from the sensor to the object to be measured. 6 is a sectional view of the convex mirror, FIG. 6 is a sectional view of the convex mirror in which the sectional shape of the convex mirror shown in FIG. 5 is approximated by a spherical surface and a truncated cone, and FIG.
1 is an explanatory view when the present optical applied distance sensor is applied to an automatic guided vehicle, FIG. 9 is an explanatory view of a sensor visual field on the automatic guided vehicle, FIG.
0 is an explanatory view of an application example to a space manipulator, FIG.
FIG. 4 is an explanatory diagram of an application example to an industrial robot. Hereinafter, description will be given with reference to the drawings.

In FIG. 1, the sensor head is a light emitting device comprising a light source 1 and a plane light projecting mirror, a light receiving device comprising a two-dimensional light receiving surface 3 and a light receiving convex mirror 4, and a colorless transparent cylinder for supporting and protecting them. It is composed of 5. The plane light emitted from the light emitting device hits the distance measuring object 10, and the reflected light 8 enters the light receiving device.
This reflected light image is processed on the processing device 6 to form a distance image.

FIG. 2 shows an example of the structure of the light emitting device. Light source 1
The parallel beam projected from is reflected by the plane light projecting mirror 2 which is a conical mirror having an apex angle of 90 ° and becomes plane light 7 which spreads in the entire circumferential direction in the plane.

FIG. 3 shows an example of the structure of the light receiving device. The reflected light 8 of the plane light on the object to be measured is reflected by the convex mirror 4 for receiving light and guided to the two-dimensional light receiver 3 which is a CCD camera. Get burned.

FIG. 4 is a diagram showing the principle of distance measurement according to this method. The distance Lr16 from the sensor to the object to be measured is the position coordinate of the reflection point p17 on the convex mirror (x13, y1).
2), it is expressed as the sum form of x13 and Ls14, and is expressed by Equations 6 and 7. In advance, the convex mirror shape is the number 5
If the distance r on the image is known from the equations 2 and 9, the actual distance Lr can be obtained.

[0029]

[Equation 9]

Here, if the shape of the light receiving convex mirror satisfies the formula 1, the actual distance Lr can be obtained from the distance r on the image by only one multiplication.

In FIG. 5, the viewing angle of the two-dimensional photodetector is 66 °.
(H) x 66 ° (V), convex mirror radius is 80 mm, height d from the farthest point reflection position on the convex mirror to the plane light is 250 mm
In the case of, the distance r on the image from the point showing the reflected light from the object to be measured on the image obtained by the light receiver to the point showing the apex of the convex mirror, and from the sensor to the object to be measured FIG. 3 is a sectional view of a convex mirror in which the distance Lr is proportional to. This cross-sectional shape is obtained by solving the differential equation of Eq.

FIG. 6 is a sectional view of the convex mirror section obtained by approximating the sectional shape of the convex mirror obtained in FIG. 5 by a spherical surface and a truncated cone shape. The angle at the end of the convex mirror section in FIG. 5 is used as the angle at the truncated cone. Therefore, the pixels can be effectively used without changing the maximum measurement distance as a sensor, and the convex mirror having the sectional shape shown in FIG. 5 is easier to manufacture.

In order to compare these convex mirror shapes, the actual distance Lr with respect to the image distance r when each shape is used.
Is shown in FIG. The conditions are the same as in the case of FIG. 5, and the field of view of the two-dimensional optical receiver is divided into 200 (H) × 200 (V) pixels. As can be seen from this figure, compared to the case where the simple spherical shape is used 24, the case where the shape shown in FIG. 5 is used 25 and the case where the shape shown in FIG. have.

FIG. 8 shows an optical distance sensor 2 according to the present invention.
7 is an example in which 7 is applied to an automated guided vehicle. As a result, FIG.
As shown in, it is possible to detect the distance measurement target object 30 around the automatic guided vehicle 29. Since the distance measurement accuracy of the optical distance sensor according to this method is relatively high even at a long distance, the automated guided vehicle 29 can perform obstacle avoidance, path planning, etc. based on this data.

FIG. 10 shows an example in which the optical distance sensor is applied to the manipulator 33. By mounting it on the hand unit 34, it is possible to effectively find and measure a distance measuring object in front of the hand. Further, it is possible to recognize the three-dimensional shape of the target object by operating the manipulator 33 and moving the sensor to measure one after another.

FIG. 11 shows an example in which the optical distance sensor 27 is mounted on the industrial robot 35 as an obstacle sensor.
By mounting a sensor on the arm, a 360 ° field of view can be secured and an obstacle within the arm turning range can be sensed.

[0037]

According to the present invention, it is possible to improve the distance measurement accuracy in a long distance of the optical application distance sensor having the entire field of view. Since this method equalizes the distance measurement accuracy by specifying the shape of the convex mirror, it is effective for equalizing the distance measurement accuracy within the area even when calculating the accuracy in pixel units or more such as sub-pixel calculation. is there. Further, by making the accuracy uniform, it is possible to increase the number of effective pixels in the calculation for the same light receiver, and it is possible to reduce the burden of increasing the number of pixels of the light receiver for improving accuracy. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical distance sensor according to the present invention.

FIG. 2 is an explanatory diagram of a light emitting device.

FIG. 3 is an explanatory diagram of a light receiving device.

FIG. 4 is an explanatory diagram of a distance calculation principle.

FIG. 5 shows the distance on the image from the point showing the reflected light from the object to be measured on the image obtained by the light receiver to the point showing the apex of the convex mirror, and the distance from the sensor to the object to be measured. It is a convex mirror cross-sectional shape figure that a distance is proportional.

6 is a convex mirror cross-sectional shape diagram in which the convex mirror cross-sectional shape shown in FIG. 5 is approximated by a spherical surface and a truncated cone shape.

FIG. 7 is an explanatory diagram of distance measurement accuracy according to each convex mirror shape.

FIG. 8 is an explanatory diagram when the present optical distance sensor is applied to an automated guided vehicle.

FIG. 9 is an explanatory diagram of a sensor visual field on an automatic guided vehicle.

FIG. 10 is an explanatory diagram of an application example to a space manipulator.

FIG. 11 is an explanatory diagram of an application example to an industrial robot.

[Explanation of symbols]

1 ... Light source, 2 ... Planar light projecting mirror, 3 ... Two-dimensional optical receiver,
4 ... Convex mirror for receiving light, 5 ... Colorless transparent cylinder, 6 ... Processing device,
Reference numeral 7 ... Plane light, 8 ... Reflected light, 9 ... Area on the object to be reflected that is reflected, 10 ... Object to be measured.

Claims (4)

[Claims] 1. A light emitting device comprising a light source and a mirror for projecting light emitted from the light source as plane light, a light receiving surface on which a two-dimensional image is obtained, and a light projected from the light source on the light receiver. In an optical application distance sensor equipped with a light receiving device consisting of a convex mirror that guides light reflected on the object, the shape of the convex mirror of the light receiving device indicates the reflected light from the distance measuring object on the image obtained by the light receiver. An optical application distance sensor having a shape such that a distance on the image from a point indicating the vertex of the convex mirror to the point on the image and a distance from the sensor to the object to be measured are proportional. 2. A light emitting device comprising a light source and a mirror for projecting light emitted from the light source as plane light, a light receiver for obtaining a two-dimensional image, and light projected from the light emitting device to the light receiver. In the optical distance sensor provided with a light receiving device consisting of a convex mirror for guiding the light reflected on the object, the shape of the convex mirror of the light receiving device is the incident angle of the reflected light from the object to be measured to the light receiving device, An optical-applied distance sensor having a shape that provides a relationship in which the distance from the sensor to the object to be measured is proportional. 3. A light emitting device comprising a light source and a mirror for projecting light emitted from the light source as plane light, a light receiver capable of obtaining a two-dimensional image, and light emitted from the light emitting device to the light receiver. In an optical distance sensor provided with a light receiving device consisting of a convex mirror that guides the light reflected on the object, the shape of the convex mirror of the light receiving device reflects the light reflected from the object to be measured when viewed from the light receiver. An optical-applied distance sensor having a shape such that a distance from a point on the convex mirror to a central axis of the convex mirror and a distance from the sensor to an object to be measured are proportional to each other. 4. A means for realizing the optical distance sensor according to any one of claims 1 to 3, wherein the convex mirror is formed by a combination of a spherical surface and a truncated cone shape. Applied distance sensor.