JPH041509A - Noncontact three-dimensional coordinate measuring method - Google Patents

Abstract

PURPOSE:To easily attain measurements in a short time by monitoring variation in the diameter of a beam spot on the surface of an object with a measuring instrument and controlling the focus position, and measuring the controlled variables of respective elements of a three-dimensional beam scanner device. CONSTITUTION:A light beam is projected on the object to e measured which is installed in a measurement space and not optically transparent to measure the coordinates of an optional point on the surface of the object without contacting. By this measuring method, the spot diameter of the beam at the projection point 9' is monitored by the measuring instrument 10 such as a photoelectric converting element array and a CCD array and the variation in the spot diameter is fed back to a uniaxial moving mechanism 4''. For the purpose, the spot diameter of the beam at focus 8 is minimized by controlling the uniaxial moving mechanism 4'' in the direction wherein the spot diameter is always reduced to align the projection point 9' on the surface of the object 9 with the focus 8 at all times, and the coordinate values of the optional point on the surface of the object 9 can be measured from the current inclination and focal length of the laser beam 2 in a reference coordinate system.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for optically measuring the coordinate position of an arbitrary point on the surface of an object to be measured in a non-contact manner.

(B) Conventional technology In the conventional non-contact three-dimensional coordinate measurement method, a laser beam having a specific shape or pattern is projected onto the measurement target, and an image of the laser beam projected onto the surface of the measurement target is captured using a television camera. A method in which a specific point on the surface of the measurement object is extracted by photographing and processing the obtained image, and the three-dimensional coordinates of the specific point are measured using the principle of triangulation. Broadly divided into laser light source type and spatial coding type.

The laser light source type, as disclosed in Japanese Patent Publication No. 50-36374, projects a laser beam extending in a straight line in the horizontal or vertical direction onto the measurement target, and photographs the beam and the vicinity of the light projection part with a camera. Then, by processing the obtained image, a two-dimensional image of the beam light deformed from a linear shape corresponding to the surface shape of the measurement object on the surface of the measurement object is extracted. The obtained two-dimensional image of the light beam corresponds to a perspective view of a horizontal or vertical cross-sectional shape of the object sliced by the linear beam. Using the principle of triangulation, the two-dimensional coordinate system within the camera field of view of the perspective view, the baseline length that is the distance between the beam projection device and the imaging camera, and the inclination angle of the beam projection device and the imaging camera with respect to the baseline, Measures the three-dimensional coordinates of a specific point on the beam projection unit on the surface of the object to be measured.

By sequentially moving the beam projection section, coordinate values of all points on the surface of the object to be measured can be obtained.

On the other hand, in the spatial coding method, a laser beam having multiple types of patterns is sequentially projected onto the measurement target in time series without changing the projection angle, and each type of pattern is By photographing the object to be measured with a camera and processing the resulting image, minute areas on the surface of the object to be measured are classified based on how patterns appear over time, and as a result, specific areas on the surface of the object to be measured are identified. The principle of the triangulation method is based on the base line length, which is the distance between the pattern beam projection device and the imaging camera, and the inclination angle of the line segment connecting the specific point with respect to the baseline and the center of the pattern beam projection device and the imaging camera. is used to measure the three-dimensional coordinates of each specific point on the surface of the object to be measured.

(c) Problems to be solved by the invention By the way, among the coordinate measuring methods mentioned above, the laser light source method applies the principle of triangulation, so the baseline length, which is the distance between the beam projection device and the imaging camera, is requires precise measurement, and calibration jigs and other equipment are required for this purpose. Furthermore, since the three-dimensional coordinates are determined using the coordinate values of the two-dimensional image of the beam light based on the two-dimensional coordinate system within the field of view of the camera, when converting the two-dimensional image into two-dimensional coordinate values, the number of pixels of the camera Quantization errors caused by resolution have a large effect. Increasing the number of camera scans in order to increase the precision of this resolution leads to an increase in image memory capacity and image processing time, and increasing the baseline length causes problems such as an increase in the size of the equipment. .

Furthermore, since the spatial coding method applies the principle of triangulation, it not only has the same problems as the laser light source method described above, but also requires an increase in the types of patterns in order to improve the resolution on the surface of the object to be measured. As a result, a large number of masks, etc. to form patterns are required, and they are required to be processed in minute detail.Furthermore, the number of images taken increases, memory capacity and the number of image processing operations also increase, which increases equipment production costs and processing time during measurement. The problem is that the amount of data is enormous.

In view of the above-mentioned problems, the present invention enables measurement easily and in a short time without using the principle of triangulation and without directly using an image of the surface of a measurement object taken by a camera to calculate three-dimensional coordinates. The purpose of this invention is to provide a non-contact three-dimensional coordinate measurement method.

(d) Means for Solving the Problems In the present invention, by projecting a light beam onto an optically non-transparent measurement object installed in a measurement space, any part of the surface of the object can be detected without contact. In the method of measuring the coordinates of a point, a laser beam is used as the light source of the light beam, and a three-dimensional beam scanner device capable of focusing the laser beam on an arbitrary point in the measurement space is used as a projection means for the laser beam. The projection point of the light beam onto the surface of the object is always controlled so that it becomes the focal point of the light beam, and an arbitrary point on the surface of the object to be measured is determined from the inclination and focal length of the laser beam within the reference coordinate system at that point. I am trying to get the coordinate values of the point.

(E) Effect Since the present invention uses the above means, the focal position is controlled by monitoring changes in the beam spot diameter on the object surface with a measuring instrument such as a photoelectric conversion element array or a CCD array, and the three-dimensional beam is It is possible to easily and quickly measure the three-dimensional coordinates of the object to be measured without using triangulation or image processing by simply measuring the control amount of each silkworm with the scanner device.

(f) Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1I1 shows an example of a schematic arrangement of an optical system of an apparatus for carrying out the measuring method of the present invention. In the figure, a laser beam 2 emitted from a laser oscillator 1 is transmitted through a concave lens 4. Convex lens with focal length f, 5. The beam is focused at a beam focal point 8 on the beam optical axis 3 via a bender mirror 6.7 to minimize the spot diameter, and then the spot diameter is gradually expanded to a beam projection point 9° on the surface of the object 9 to be measured. reach. Here, the concave lens 4 can be moved back and forth parallel to the optical axis 3 by a single-axis moving machine $4'', and the bender mirrors 6 and 7 are perpendicular to each other and are both aligned with the optical axis 3 by a rotation drive mechanism 1112. It is rotatable about orthogonal axes.Originally, the optical axis 3 is bent by the mirrors 6 and 7 as shown in Fig. 2, but since there is no interference with the beam focal position, in Fig. 1 They are arranged in a simplified manner on a straight line.On the other hand, the convex lens 5 is fixed.1
When the concave lens 4 is moved on the optical axis 3 by the axis movement mechanism 4'', the distance a−f+ between the concave lens 4 and the convex lens 5 changes, but since f is the focal length of the concave lens, it remains unchanged. Therefore, the distance a between the focal point 4' of the concave lens 4 and the convex lens 5 also changes.Since the focal length of the convex lens 5 is f, the focal point 8, which is the imaging position of the convex lens 5 with respect to the focal point 4', changes. The distance to the convex lens 5 is expressed as b=a f ,/(a-f , ).The beam spot diameter at the projection point 9° is monitored by a measuring instrument 10 such as a photoelectric element array or a CCD array. The change in spot diameter is fed back to the uniaxial movement mechanism 4''. Therefore, by controlling the uniaxial movement mechanism 4'' in the direction of always reducing the spot diameter to minimize the beam spot diameter at the focal point 8, the projection point 9' on the surface of the object to be measured 9 is always kept at the focal point 8. It is possible to match.

FIG. 2 is a perspective view showing an example of beam scanning by a three-dimensional beam scanner device for carrying out the measurement method of the present invention. The beam passing through the convex lens 5 has its tip axis 3 bent by a bender mirror 6, and then its tip axis is further bent by a bender mirror 7 to form a focal point 8 (projection point 9) on the surface of the measurement object 9. °).

The optical axis 3 is turned in orthogonal directions (13) and (14), respectively, and the rotation axis 15 of the bender mirror 6 and the optical axis 3 are orthogonal to each other at the incident point 17 of the optical axis 3 on the bender mirror 6,
The rotation axis 16 of the bender mirror 7 is on a plane defined by the optical axes 3 and 13 and is arranged to be perpendicular to the optical axis 13 at an incident point 18 of the optical axis 13 onto the bender mirror 7. Therefore, the bender mirror 6 is rotated by the rotary drive mechanism 11.
When rotated by θ1 around the rotation axis 15, the optical axis 3 is tilted 2θ□ (13”) from the orthogonal direction 13, and the pender mirror
7. On the other hand, while the bender mirror 6 remains in its initial position, the bender mirror 7 is rotated by the rotary drive machine tIlf12.
When rotated by θ77 around the rotation axis 16, the optical axis 13 is projected at an angle of 2θa (14') sl from the orthogonal direction 14. Therefore, both vendor mirrors 6.7 and 08. θ
If the optical axis 3 is rotated by a, the optical axis 3 follows a path of 13° 14'' and is projected onto the focal point 8. Therefore, the intersection of the optical axes 13 and 14, that is, the initial incident point 18 of the bender mirror 7, is set as the origin of the reference coordinate system. The rotation axis 16 of the bender mirror 7 is the X axis, the line segment connecting the initial incident point 17 of the bender mirror 6 and the initial incident point 18 of the bender mirror 7 and its extension is the Y axis, and the origin 1
The axis passing through 8 and parallel to the rotating axis 15 of the bender mirror 6 is defined as Z pongee. The coordinates of the focal point 8 in the reference coordinate system are (x
+ y + z). Consider a plane that includes the focal point 8 and is orthogonal to the Z-axis, the intersection of this plane and the Z-axis is 8'', and the optical axis is 14'.
If the intersection with The distance relationship along the path along the path is equivalent to the relationship shown in FIG. 1, and the distance between the center of the convex lens 5 and the point of incidence 17 is g,
The distance between and 18 is e.

FIG. 3 is a principle diagram showing the relationship between the coordinates of the focal point and the control amount of each scanner element in a three-dimensional beam scanner device for carrying out the measurement method of the present invention. Point 17 in Figure 3. 18.8', 8. The figure represented by 18° is originally bent by the bender mirror 7, but by rotating the figure represented by the point 1718.18° with respect to the X axis, the optical axis 13.13' becomes the optical axis 14'14''
As a result, the figure represented by chain points 1718.8° and 8.18' is expanded into a triangle represented by points 17.8' and 8. Z1
8.17.18' is the deflection angle by the bender mirror 6, so it is 2θ, and 1,4:8', 18.8'' is the deflection angle by the bender mirror 6, so it is 2θ.

becomes. Also, the distance between the origins 18 and 8'' of the reference coordinate system is z
The distance between 17 and 18 is the distance between the bender mirror 67, e, and the distance between the focal points 8 and 17 is the distance between the center of the convex lens 5 and the focal point 8, so the distance between the center of the convex lens 5 and the bender mirror 6 is g. It becomes b-g, which is obtained by subtracting . From the above angle and distance relationship, the relationship between the coordinate value X+Y+Z of the focal point 8 and the control amount θ, 011 a of each scanner element is z w ((b − a ) cos2 lx − e
) cos2 #yxm(b-a) sinZ#x y =z tan21y.

(G) Effects of the Invention As described above, according to the non-contact three-dimensional coordinate measuring method of the present invention, changes in the beam spot diameter on the surface of an object are monitored using a measuring instrument such as a photoelectric conversion element array or a CCD array. By simply controlling the focal position and measuring the control amount of each element of the 3D beam scanner device, you can easily and quickly determine the measurement target without using the principles of triangulation or image processing. It is possible to measure the three-dimensional coordinate position of an object.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing the schematic arrangement of an optical system for implementing the non-contact three-dimensional coordinate measuring method according to the present invention, and FIG. FIG. 3 is a schematic configuration diagram showing a beam scanning method. FIG. 3 is a principle diagram showing the relationship between the coordinates of a focal point and the control amount of each scanner element in an embodiment of the non-contact three-dimensional coordinate measuring method according to the present invention. 1... Laser oscillator, 2 ・ ・ 3 ・ − 4φ φ 5 ・ ・ 6.7 8 ・ ・ 11° laser beam, beam optical axis, concave lens, convex lens, ... bender mirror beam focus, measurement object, 2 ...Rotary drive mechanism.

Claims (1)

[Claims] (1) A method of measuring the coordinate position of an arbitrary point on the surface of an optically non-transparent measurement object installed in a measurement space by projecting a light beam onto the object without contacting the object. , using a laser light source and a three-dimensional beam scanner device that can focus the laser beam emitted from the laser light source on any point in the measurement space, to project the beam onto the surface of the object to be measured. The three-dimensional beam scanner device is always controlled so that the beam becomes the focal point, and the coordinate position of any point on the surface of the object to be measured is determined from the inclination and focal length of the laser beam within the reference coordinate system at that point. A non-contact three-dimensional coordinate measuring method characterized by the following: