JPH0769144B2 - Three-dimensional position measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to CAD (Computer Aided Design), CAT (Comput
er Aided Testing) and the like, the present invention relates to a three-dimensional position measuring method suitable for inputting a three-dimensional shape and dimension of a processed product and used as a man-machine interface with a computer by exchanging three-dimensional information.

[Prior Art] A conventional three-dimensional position measuring device of this type has been disclosed in Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent Publication No. 61904. This conventional device, in order to obtain the three-dimensional coordinates of the measurement point on the workpiece surface,
A plurality of light projectors for projecting bright spots on the measurement points, and two image pickup devices for obtaining a stereo image around the bright spots;
A means for calculating the three-dimensional coordinates of a plurality of measurement points from a stereo image by a triangulation method, and a means for obtaining the relative positional relationship between the measurement head (light projector, imager) and the work from the three-dimensional coordinates of the plurality of measurement points. It consists of That is,
In this conventional device, a bright spot projected from a projector is used to teach a measuring point on the surface of a work.

In addition to the above-mentioned conventional technique, a means for directly adding a point light source to a measurement point on the surface of a work is also disclosed [Technical Report of the Institute of Television Engineers, ITA40-2 (1977), page 7, "Kurazawa et al .:
Walking Pattern Measurement System Using Semiconductor Position Detection Method "
reference〕.

Furthermore, three light spots are provided at regular intervals on the axis of the stylus that makes contact with the surface of the object to be measured at the tip, and a stylus is provided by one imaging camera above or below the operating space of the stylus. , And the interval of the above light spots,
A three-dimensional measuring device is also known in which the three-dimensional coordinate value of each point of the object to be measured is calculated from the distance from the light point to the contact point and the information contained in the image of the light point by the image pickup camera (Japanese Patent Laid-Open No. 63-63242). -217205 gazette).

[Problems to be Solved by the Invention] However, the conventional device that teaches the measurement points by the bright spots by the irradiation of the light beam has the following problems.

(A) It is impossible to teach a portion such as the inside of the hole of the work, the back surface, and the side surface that cannot be commonly viewed by the left and right image pickup devices.

(B) When the surface of the work is a mirror surface, scattered light does not occur from the bright spot, and the image cannot be captured.

(C) If the work surface has a low reflectance, a bright spot image cannot be obtained.

(D) Even if the surface of the work is a diffusing surface, if the surface is inclined, bright luminescent spots are generated in the vicinity, which causes an error.

(E) If the shape of the workpiece changes drastically, multiple reflection occurs, and the number of bright spots becomes plural.

In addition, the conventional means for directly adding the point light source to the measurement point has the same problems as (a), (d), and (e) described above, and the position of the point light source varies from the actual surface to the size of the light source. There is also a problem such as a deviation of about half and causing an error.

Furthermore, in the three-dimensional measuring device disclosed in Japanese Patent Laid-Open No. 217205/1988, since one image pickup device photographs three point light sources provided in the measuring symmetry point teaching means, Since the size of the light source is finite and the resolution of the point light source imaged by the imaging device is finite,
Measurement is performed by inclining the axis line connecting the three point light sources arranged in a straight line with the pointing point on the measurement symmetry point teaching means in a direction coinciding with the optical axis of one image pickup device for photographing this. The error gradually increases. In particular, as a result of using three point light sources that cause an error, measurement errors are accumulated one by one. Therefore, when the inclination is advanced as described above, finally, the measurement becomes substantially impossible. The unmeasurable range has a blind spot of a considerable range even if an extremely high-accuracy device is used, and it has a drawback that it is necessary to work while paying attention to that point even while using the equipment. Is.

The present invention is intended to solve such problems,
To provide a three-dimensional position measurement method that improves measurement accuracy while enabling measurement regardless of whether the inside, back, or side of the hole of the workpiece to be measured is a mirror surface, a diffusion surface, or the size of the reflectance. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the three-dimensional position measuring method of the present invention is based on at least two image pickup devices for obtaining a stereo image and a stereo image from the image pickup device. A calculation means for calculating a three-dimensional position, a measurement target point teaching means having a plurality of point light sources having a fixed point relationship known in advance with respect to the designated point for designating the measurement target point,
The measurement target point teaching means in the state where the measurement target point is designated by the designation point and the plurality of point light sources are turned on is imaged by the imaging device, and the arithmetic means is configured to detect the plurality of points from the imaging device. The three-dimensional position of each point light source is calculated based on the stereo image of the light source, the three-dimensional position of the designated point is calculated based on the obtained three-dimensional position and the fixed positional relationship, and the three-dimensional position is calculated. It is characterized in that it is output as a three-dimensional position of the measurement target point.

[Operation] In the above-described three-dimensional position measuring method of the present invention, when the three-dimensional position of the measurement target point is measured, the designated point of the measurement target point teaching means is arranged in contact with the measurement target point, and this state is set. Then, a plurality of point light sources of the measurement target point teaching means are turned on, and a stereo image of the point light sources is taken by the image pickup device.

Then, the calculation means calculates the three-dimensional position of each point light source based on the stereo images of the plurality of point light sources from the image pickup device. Here, since the plurality of point light sources and the pointing point have a known fixed positional relationship in advance, when the three-dimensional position of the plurality of point light sources is known, the fixed positional relationship is added to the three-dimensional position. , The three-dimensional position of the pointing point can be easily calculated. Since the current stereo image is obtained in a state in which the measurement target point is designated by the designation point, the three-dimensional position of the designation point is the three-dimensional position of the measurement target point as it is.

Thereby, even if the stereo image of the measurement target point cannot be directly captured, if the stereo images of the plurality of point light sources of the measurement target point teaching means are obtained, the three-dimensional position of the measurement target point is measured from the image. can do.

[Embodiment of the Invention] A three-dimensional position measuring system as one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view thereof, FIG. 2 is a front view showing a coordinate teaching pen thereof, and FIG. Is a circuit diagram showing a circuit configuration of the coordinate teaching pen, and FIG. 4 is an explanatory diagram showing another example of use of the system of this embodiment.

In FIG. 1, 1 and 2 are two TV cameras (imaging devices) for obtaining a stereo image, and 3 is a bright spot shift (parallax) in the left and right images of the stereo images from these TV cameras 1 and 2. An image processor (calculating means) for calculating a three-dimensional position based on
4 is a work for measuring the three-dimensional position, and this work 4 is
The TV cameras 1 and 2 have a concave portion 4a that cannot be imaged.

Reference numeral 5 is a coordinate teaching pen (measurement target point teaching means). As shown in FIGS. 2 and 3, the coordinate teaching pen 5 is an instruction point 6 for instructing a measurement target point P on the surface of the work 4 and this instruction. Four LEDs (point light sources) 7 having a known fixed positional relationship with respect to the point 6, and a switch that is closed when the pointing point 6 contacts the surface of the work 4 at the tip of the pen 5 including the pointing point 6. 8, a battery 9 serving as a power source for lighting the LED 7, a glass cover 10 covering the LED 7, and a protective resistor 11. each
As shown in FIG. 3, the LEDs 7 are connected in parallel with each other, and when the switch 8 is closed, power is supplied from the battery 9 via the protection resistor 11 and the LEDs 7 are turned on. Further, as shown in FIG. 2, the pointing point 6 and each LED 7 are all arranged on the central axis of the coordinate teaching pen 5, the distance between the pointing point 6 and the LED 7 at the bottom is l ', and between each LED 7,7. Is 1 and is known in advance. Further, each LED 7 has a size of 400 μm square, for example.

With the configuration described above, for example, as shown in FIG. 1, when measuring the three-dimensional position of the measurement target point P in the concave portion 4a of the work 4 that cannot be directly imaged from the TV cameras 1 and 2, First, the pointing point 6 of the coordinate teaching pen 5 is placed in contact with the measurement target point P. When the designated point 6 of the coordinate teaching pen 5 contacts or is pressed against the measurement target point P, the switch 8 is closed and each LED 7 of the coordinate teaching pen 5 is turned on.

In this way, the stereo images of the coordinate teaching pen 5 including the LEDs 7 are captured by the TV cameras 1 and 2 while the LEDs 7 are turned on.

The image pickup result is input to the image processor 3, and the image processor 3 calculates the three-dimensional position of each LED 7 based on the bright spot parallax in the left and right images of the stereo image of the LED 7.

Further, since each LED 7 and the pointing point 6 have a known fixed positional relationship as described above with reference to FIG. 2, when the three-dimensional position of each LED 7 is known, the fixed positional relationship is added to the three-dimensional position. By doing so, the three-dimensional position (three-dimensional coordinate) of the pointing point 6 at a position where the TV cameras 1 and 2 cannot directly image, that is, the three-dimensional position (three-dimensional coordinate) of the measurement target point P
Is easily calculated.

By the way, the coordinate teaching pen 5 described above can be used as a two-dimensional coordinate input device similar to a conventional digitizer or a mouse by moving the coordinate teaching pen 5 in a plane translation on a desk as shown in FIG. In addition, the coordinate teaching pen 5 described above
If the three-dimensional position of a plurality of LEDs 7 is obtained by using, the direction of the central axis of the pen 5 is determined from these three-dimensional positions. Can also be calculated, and a function similar to that of a conventional joystick can be obtained. When these two types of functions are combined, the information "three-dimensional coordinates + direction" that matches the human sense of space can be exchanged with the computer, and can be effectively used as a new man-machine interface device.

As described above, according to the measurement method of the present embodiment, even if the stereo image of the measurement target point P cannot be directly captured,
If a stereo image of each LED 7 of the coordinate teaching pen 5 is obtained,
Since the three-dimensional position of the measurement target point P can be obtained from the image, the three-dimensional position of the surface of the workpiece 4 regardless of whether the inside, the back surface, the side surface, or the surface thereof is a mirror surface, a diffusing surface, or the reflectance is large or small. In addition to enabling measurement, increasing the number of LEDs 7 can significantly improve the measurement accuracy.

Further, the coordinate teaching pen 5 in the measuring method of the present embodiment is
As a man-machine interface device with a computer, it can be used as a three-dimensional digitizer device that has more one-dimensional information than a conventional two-dimensional digitizer such as a mouse. In that case, a man-machine interface that is highly consistent with the human sense of space. Can be realized.

In the above embodiment, the coordinate teaching pen 5 has four LEDs 7, but at least two LEDs are required.
If so, it is possible to obtain the same function as that of the above-described embodiment. Further, a large number of LEDs may be arranged in order to improve the detection accuracy of coordinates and vectors. Further, in the above embodiment, the case where the LEDs 7 are arranged in a straight line has been described, but if the fixed positional relationship with the pointing point 6 is clear, each LE 7
D7 may be arranged in any way.

In addition, in the above-mentioned embodiment, in order to obtain the three-dimensional position of each point light source, a stereo image is picked up by two image pickup devices, and an image processing unit performs an image processing operation. If two light spot position detectors are used instead of the single image pickup device, it is possible to obtain the three-dimensional position of each point light source by a simple calculation without using an image processor. However, since the light spot position detector cannot handle a plurality of point light sources at the same time, in that case, it is necessary to turn on each point light source in time series.

[Effect of the Invention] As described in detail above, according to the three-dimensional position measuring method of the present invention, even if the stereo image of the measurement target point cannot be directly captured, By capturing a stereo image, the three-dimensional position of the measurement target point can be measured based on the stereo image, so that the inside, back, and side of the hole of the measurement target work, or its surface is a mirror surface, a diffusion surface, The measurement can be performed regardless of the magnitude of the reflectance, and the measurement accuracy is significantly improved.

Also, two point light sources are sufficient, and since each of the point light sources is imaged as a stereo image by two image pickup devices, there is a range in which an error that cannot be tolerated for any inclination of the measurement symmetry point teaching means occurs. Since it does not exist, the range of use becomes wider, the measurement work becomes easier, and particularly, even in the case where the inside of the hole of the point-symmetrical work changes intricately, the measurement can be easily performed over a wide range. Moreover, the number of point light sources that cause measurement errors is small, and in order to further improve the accuracy of such a light source with few measurement errors, three, four, ...
And many point light sources can be provided.

[Brief description of drawings]

1 to 4 show a three-dimensional position measuring method as an embodiment of the present invention. FIG. 1 is an explanatory view thereof, FIG. 2 is a front view showing a coordinate teaching pen thereof, and FIG. FIG. 4 is a circuit diagram showing the circuit configuration of the teaching pen, and FIG. 4 is an explanatory diagram showing another example of use of the system of this embodiment. In the figure, 1,2 ... TV camera (imaging device), 3 ... Image processor (calculation means), 4 ... Work, 4a ... Recessed portion, 5
...... Coordinate teaching pen (measurement point teaching means), 6 ... designating point, 7 ... LED (point light source), 8 ... switch, 9 ... battery, 10 ... glass cover, 11 ... protection resistance, P: Point to be measured.

Claims (1)

[Claims] 1. At least two image pickup devices for obtaining a stereo image and arithmetic means for calculating a three-dimensional position based on the stereo image from the image pickup device are provided, and an instruction for indicating a measurement target point. There is provided a measuring point teaching means comprising a point and a plurality of point light sources having a fixed positional relationship known in advance with respect to the pointing point. The point-to-measurement target teaching means in a state where the point light source of
An image is captured by the image capturing device, and the computing unit computes a three-dimensional position of each of the point light sources based on a stereo image of the plurality of point light sources captured by the image capturing device. Based on the three-dimensional position of the point light source and the previously known fixed positional relationship,
A three-dimensional position measuring method, which calculates a three-dimensional position of the pointing point and outputs the obtained three-dimensional position of the pointing point as a three-dimensional position of the measurement target point.