JP2605135B2 - 3D shape measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a three-dimensional shape, and more particularly to a computer graphics or robotics technique which converts a three-dimensional shape of an object into a database or recognizes a three-dimensional shape. The present invention also relates to a three-dimensional shape measuring device for automatically inputting a three-dimensional shape of an object to a computer.

[Prior Art] FIG. 3 is a view for explaining a projection method which is a typical method for generating moire fringes. First, a method for measuring the three-dimensional shape of an object using moire fringes will be described with reference to FIG. In FIG. 3, the measurement object 1
A reference grid 2 is provided at a position separated from the reference grid by a predetermined distance, and a light source 3 is arranged near the reference grid 2. Further, a lens 4 is arranged between the reference grating 2 and the measurement object 1. Therefore, the light emitted from the light source 3 is
And is projected onto the measurement object 1 by the lens 4. Thereby, a shadow of the reference grating 2 (hereinafter, referred to as a deformed grating image) is projected on the measurement target 1.

An observation grating 5 is arranged adjacent to the reference grating 2. The observation grating 5 is for generating moire fringes by causing interference with the deformed grating image. A lens 6 is arranged between the observation grating 5 and the measurement target 1, and this lens 6 forms a deformed grating image on the observation grating 5. Moire fringes generated on the observation grating 5 are photographed by the lens camera 7. In FIG. 3, reference numeral 8 denotes contour lines observed as moiré fringes, N denotes the order of each moiré fringe, Z _N denotes a position at which moiré fringes of order N are generated, and the grid line position is used as a reference. And

The moiré fringes are obtained by placing the reference grating 2 in front of the object 1 to be measured, and forming a modified grating image of the reference grating 2 on the surface of the object 1 by a lens 4 from a point or line light source 3. Further, when an image is formed by the lens 6 from the position at the same height as the light source 3 via the observation grating 5, the interference fringes are generated as a result of spatial frequency modulation between the deformed grating material and the observation grating 5. The three-dimensional shape of the measurement object 1 is represented as contour lines on a map.

In addition to the above-described method, only a deformed lattice image formed on the surface of the measuring object 1 was photographed by a television camera, and a deformed lattice image was generated as necessary for the photographed deformed lattice image. It is also known to generate a moiré fringe of the measurement object 1 by superimposing a grating having a grating interval optically equivalent to the reference grating 2 or by sampling a deformed grating image at the grating interval.

[Problems to be Solved by the Invention] By the way, in order to obtain a three-dimensional shape of an object using moire fringes, it is necessary to obtain three-dimensional position coordinates from contour lines of the moire fringes. The coordinates of the moire fringes in the depth direction are the distance Z _N from the reference grid 2 at the position where moiré fringes of order N are generated, the distance l between the light source 3 and the optical axis of the television camera 7 and the reference grid spacing.
Assuming that p, the distance between the lattice plane and the principal point of the lens 4 is a, and the order of the moiré fringes is N, Z _N = a / l / p · N (1) where N = 1, 2,. . Here, the values of a, p, and l can be obtained based on the imaging conditions and the lattice spacing, but the value of the order N cannot be obtained. If the value of the order of a certain fringe, that is, the absolute order, is obtained, the order of the other fringes is the moire fringe generated by setting the position of the reference grating 2 or the observation grating 5 to a reference value, and It can be determined by comparing the moire fringes generated by shifting the phase, determining the unevenness from the moving direction of the moire fringes, and knowing the relative depth relationship between the fringes and the fringes. A method for obtaining the absolute order of the stripe will be described with reference to FIG.

FIG. 4 is a diagram for explaining a conventional method for obtaining an absolute order, in which a part 101 of a deformed grid image of a reference grid 2 projected on an object is shown. 102 is attached. 103 is part of the observation grid and 10
Reference numeral 4 denotes moiré fringes observed when the deformed lattice image is viewed through the observation lattice. Also, k is the number of the grid with a mark in the reference grid 2, and n is the number of the grid in the observation grid that is seen through the grid with the mark.

A mark 102 is attached to a part of the reference grating 2, and a mark 101 with the mark 102 is measured by optical scanning or the like from a deformed grating image projected and photographed on an object, and n in the observation grating is measured.
If the third lattice 103 is viewed in an overlapping manner, the absolute order of the moiré fringes 104 can be determined from the difference between the number k of the marked lattice and the number of the lattice in which the marked lattice is viewed in an overlapping manner. . However, in such a method, it is necessary to manufacture a special grating with a mark, and furthermore, an apparatus and a process for optical scanning for detecting the mark are required, so that the apparatus itself becomes complicated as a whole. As a result, there is a drawback that there are many problems from the viewpoint of maintainability, economy and feasibility.

Therefore, a main object of the present invention is to measure a three-dimensional shape using a moiré fringe with high accuracy, and to obtain an absolute order of the moiré fringe with high accuracy, and to accurately obtain a three-dimensional shape of a measurement object. It is to provide a device.

[Means for Solving the Problems] The present invention relates to a three-dimensional shape measuring apparatus, comprising: a moiré fringe generating unit for generating moiré fringes on an object; a moiré fringe input unit for inputting the generated moiré fringes; Projecting means for projecting the slit pattern, deformed slit image input means for inputting a deformed slit image of the projected slit pattern, sampling means for sampling a signal of the inputted deformed slit image, and sampling the deformed slit image Thinning means for thinning, adding means for overlapping the input moiré fringe with the deformed slit image thinned by the thinning means, intersection detecting means for detecting an intersection from the superimposed image, and the detected intersection And a three-dimensional coordinate calculating means for calculating the three-dimensional coordinates of the intersection from the coordinates of.

[Operation] The three-dimensional shape measuring apparatus according to the present invention uses a moire fringe from an image obtained by superimposing a moire fringe generated by projecting a reference grating on a measurement target object and a deformed slit image generated by projecting a slit pattern. The intersection between the image and the deformed slit image is determined, the depth coordinate of the intersection is determined based on the principle of triangulation, and the absolute order of the moire fringes is detected.

In the conventional method, a mark is added to the reference grid to determine the absolute order, or a method of separately measuring a certain point on the object as a reference point in advance is used. The intersection of the moiré fringes and the deformed slit image is obtained from an image obtained by superimposing the moiré fringes generated by the projection of the slit pattern and the deformed slit image generated by projecting the slit pattern, and the depth coordinates of the intersections are obtained by the principle of triangulation. The difference is that the absolute order of the fringes is detected.

FIG. 1 is a schematic block diagram of an embodiment of the present invention. Referring to FIG. 1, the configuration of one embodiment of the present invention will be described. The projector 111 is for projecting a reference grid pattern, and the projector 112 is for projecting a slit pattern. The pattern to be projected on the object is switched between the projectors 111 and 112 by the pattern switch 113. The deformed grid image of the reference grid pattern and the deformed slit image of the slit pattern projected on the object are captured by the television camera 12.

When the TV camera 12 captures the deformed grid image of the reference grid pattern and the deformed slit image of the slit pattern,
An analog video signal is output and provided to the A / D converter 13. A / D
The converter 13 is for sampling an analog video signal output from the television camera 12. The sampling output of the A / D converter 13 is input to a filter 14 to remove quantization noise.

The grid pattern generator 15 is for generating a grid pattern electronically, and outputs its output to the multiplier 17.
The multiplier 17 generates moiré fringes by multiplying the electronic grid pattern by the deformed grid image. Multiplier
The output of 17 is applied to a low-pass filter 19, where components having a high spatial frequency, such as a deformed grid image and an electronically generated grid pattern, are removed from the output image, and only moire fringes are extracted. The output image of the low-pass filter 11 is provided to a threshold processing unit 21 and is binarized. The binarized moire fringe output image is supplied to a thinning processing unit 22, which is thinned and supplied to an adder 23.

The output of the above-described filter 14 is also input to the threshold processing unit 211. The threshold value processing unit 211 extracts only a deformed slit image from an image of an object. The output is supplied to a thinning processing unit 212 to thin the deformed slit image. The thinned deformed slit image is added to the adder 23.
Are superimposed on the thinned deformed slit image similarly to the thinned moire fringe image. The output of the adder 23 is supplied to the intersection detection processing unit 24, and the intersection of the moiré fringe and the deformed slit image is detected from an image obtained by superimposing the image of the moiré fringe and the image of the deformed slit image.

The intersection of the moire fringes detected by the intersection detection processing unit 24 and the deformed slit image is given to the three-dimensional coordinate detection processing unit 241 and the three-dimensional coordinates of the intersection are obtained. The obtained three-dimensional coordinates are input to the order determination processing unit 242, and the order of the moiré fringes is determined. Further, the image of the moire fringes superimposed by the adder 23 and the image of the thinned deformed slit image are provided to the image display device 25, where the moiré fringes and the deformed slit image are displayed and the image storage device 26 is displayed. The image data such as moire fringes and contour lines is stored.

Next, a specific operation of the embodiment of the present invention will be described with reference to FIG. The reference grid pattern from the projector 111 and the slit pattern from the projector 112 are projected onto the measurement object, respectively, and the television camera
A deformed lattice image and a deformed slit image are photographed by 12.
At this time, a pattern to be projected is selected by the pattern switch 113. The television camera 12 projects an object to be measured. The analog video signal output from the television camera 12 is discretized and quantized by an A / D converter 13, and after a quantization noise is removed by a filter 14, The electronic grid pattern generated by the pattern generator 15 is superimposed on the deformed grid image by the multiplier 17 to generate Moire fringes.

Note that the same moiré fringes can be obtained even when an observation grid equivalent to the reference grid pattern is installed in front of the television camera 12 and a deformed grid image is taken. The electronic lattice pattern and the modified lattice image multiplied by the multiplier 17 are supplied to a low-pass filter 19, where components having a high spatial frequency, such as the modified lattice image and the electronic lattice pattern, are removed.
The moiré fringes are binarized by 21.

On the other hand, with respect to the image obtained by capturing the deformed slit image, a signal corresponding to only the deformed slit image is extracted by the threshold processing unit 211, and the deformed slit image is thinned by the thinning processing unit 212. The binarized moire fringe image and the binarized deformed slit image are also added to each other.
The intersections of the moire fringes and the deformed slit images are detected by the intersection detection processing unit 24, and the three-dimensional coordinates of each intersection are calculated by the three-dimensional coordinate detection processing unit 241 according to the principle of triangulation.

Of the three-dimensional coordinates obtained for each intersection, the z-coordinate or the absolute order of the moiré fringe including each intersection is obtained by the order determination processing unit 242 using the z-coordinate. As for the moiré fringes having no intersection, the relative order between the moiré fringe having the intersection and the moiré fringe having no intersection can be obtained, and thus the absolute order can be obtained in the same manner.

To determine the relative order of the moiré fringes, for example, the grating pattern generator 15 shifts the phase of the grating pattern in a certain direction by a predetermined amount to generate moiré fringes, and shifts the phase with respect to the moiré fringes that do not shift the phase. Then, there is a method of detecting in which direction the movement has been made. The obtained image is displayed on the image display device 25 and stored by the image storage device 26.

If, for example, the moiré fringes are displayed in red and the deformed slit image is displayed in blue and simultaneously displayed, the common portion of the two overlapped with each other is displayed in purple, and the intersection of the two can be immediately visually confirmed. Further, it is apparent that the display can be confirmed by changing the shading.

FIG. 2 is a diagram for explaining the principle by which the three-dimensional coordinates can be obtained by the light-section method, and is a principle diagram for measuring contour data in the declination θ direction of an object by the light-section method. In FIG. 2, a measurement target object 102 is placed on a table 101, and slit light 103 is projected onto the measurement target 102 from a slit light generation device (not shown). Then, a slit light projection portion (contour line data in the argument θ direction of the cylindrical coordinate system (r, θ, z)) as the deformed slit image 105 is generated on the measurement object 102. Then, the deformed slit image 105 is photographed by the television camera 201 according to the surface shape of the measurement object 102. The optical axis of the slit light 103 and the television camera 201 has a fixed angle, and the position of the modified slit image 105 on the image taken by the television camera 201 is used to form the modified slit image 105 using the principle of triangulation. A three-dimensional position is calculated. In this way, the three-dimensional coordinate value of the measurement target object 102 in an arbitrary declination θ direction can be measured by the light section method.

[Effects of the Invention] As described above, according to the present invention, moire fringes generated from an image captured by projecting a reference grating onto an object and a deformed slit generated from an image captured by projecting a slit pattern onto the object By detecting the intersection with the image and determining the three-dimensional coordinate value of the intersection by triangulation, the absolute order of the moire fringes can be determined, and the three-dimensional shape of the object can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of one embodiment of the present invention.
FIG. 2 is a diagram for explaining the principle of the light sectioning method. FIG. 3 is a diagram showing the principle of a conventional projection method. FIG. 4 is a diagram for explaining a conventional method for obtaining an absolute order. In the figure, 12 is a TV camera, 13 is an A / D converter, 14 is a filter, 15 is a lattice pattern generator, 17 is a multiplier, 19 is a low-pass filter, 21, 211 are threshold processing units, and 22, 212 are thinning processing. , 23 is an adder, 24 is an intersection detection processing unit, 25 is an image display device, 26 is an image storage device, 111 and 112 are projectors, 113 is a pattern switcher, 241 is a three-dimensional coordinate detection processing unit, and 242 is an order determination process. Indicates a part.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Kobayashi 5th Sanraya, Iniya, Seika-cho, Soraku-gun, Kyoto Pref. (JP, A) JP-A-60-257306 (JP, A) JP-A-61-169702 (JP, A) JP-A-61-241612 (JP, A) JP-A-1-221612 (JP, A)

Claims (1)

(57) [Claims] 1. Moiré fringe generating means for generating moiré fringes on an object; moiré fringe input means for inputting moiré fringes generated by the moiré fringe generation means; projection means for projecting a slit pattern on the object; A deformed slit image input means for inputting a deformed slit image of the slit pattern projected by the deformed slit image, a sampling means for sampling a signal of the deformed slit image input by the deformed slit image input means, a deformed slit image sampled by the sampling means Thinning means for thinning, moiré fringe input from the moiré fringe input means and an adding means for overlapping the deformed slit image thinned by the thinning means, and detecting an intersection from the image overlapped by the adding means. Intersection detecting means, and the intersection detecting means With a three-dimensional coordinate calculation means for calculating three-dimensional coordinates of intersection points from the detected intersection of coordinates by the measuring device of the three-dimensional shape.