JPS6248162B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of measuring the contour position of an object having a curved surface shape from a certain reference position and, as a result, measuring the shape of the object.

Conventionally, a method for measuring three-dimensional shapes using moiré fringes is known, but in this moiré method, even if the shape of the target object can be displayed by stripes corresponding to contour lines, it is difficult to determine whether the target object is convex or concave. It is unclear whether the stripes are deforming in the direction of , and if the stripes become thick, the center position is unknown, making it impossible to perform accurate measurements.

The present invention aims to provide a method for measuring the shape of an object that solves these problems.

Prior to a detailed explanation of the present invention, first, the basic measurement principle of the present invention will be explained with reference to FIGS. 1 to 3.

In FIG. 1, a projection device 10 projects a projection light consisting of a slit light (the slit is perpendicular to the plane of the drawing) onto a target object 11, and the projection light is a center of rotation where the projection light intersects with the optical axis, for example, the center of a projection lens, etc. It is configured so that it rotates at a point P, and the amount of rotation at that time is given by a linear movement of a constant pitch Δx on an axis L located at a distance _l1 from the point P.

On the other hand, the light receiving device 12 consisting of an ITV camera etc.
The photoelectric conversion surface 13 is arranged on the axis L, and the center point Q of the light receiving lens is arranged at a distance _l1 from the axis L, like the projection lens, so that the direction of reflection from the target object 11 is The configuration is such that the light is received by the conversion element.

In a device having such a configuration, the axis L
Projection light that passes through point P ₁ above passes through point P to target object 1
1, the projected light is reflected at point A ₁ on the target object, passes through point Q, and its image is obtained at point Q ₁ on the photoelectric conversion surface. In addition, the projection light is
Suppose that the projected light is rotated at , and projected onto the target object 11 from point P ₂ through point P, the projected light will be reflected at point A ₂ on target object 11 and will be reflected at point Q ₂ on the photoelectric conversion surface.
image is formed.

Here, if the points A ₁ and A ₂ on the target object 11 are on a contour plane that is a distance l ₂ away from the straight line connecting the points P and Q, then P ₁ P ₂ :A ₁ A ₂ =Q ₁ Q ₂ : A ₁ A ₂ = l ₁ : l ₂ , so P ₁ P ₂ = Q ₁ Q ₂ , that is, the projected light emitted from points P ₁ and P ₂ is at the same height position of the target object ( When an image is created on the photoelectric conversion surface by passing through PQ and reflecting at a point equidistant from a plane perpendicular to the plane of the paper, the distance between the images Q ₁ Q ₂ is always equal to the length of P ₁ P ₂ Become. Conversely, when the projection lights emitted from points P ₁ and P ₂ do not form images at equal intervals to P ₁ P ₂ , those points do not exist on the contour plane.

Therefore, the slit light from points P ₁ , P ₂ , . When the reflected light is imaged on the photoelectric conversion surface of the light receiving device 12, as shown in FIG. 2, images I ₁ , I ₂ , ... are obtained, and _the intersection points a 1 , a of these images I ₁ , I ₂ , ... and scanning lines L ₁ , L ₂ having an interval corresponding to the pitch Δx for rotating the projection device ₂ ,..., _b1 ,
If we find b ₂ ,..., all of these points are on the same contour surface, and by connecting them we can obtain contour lines. To explain more specifically, first, the first slit light creates a deformed image I ₁ on the photoelectric conversion surface.
When the photoelectric conversion surface is obtained, the intersection points a ₁ and b ₁ of the scanning line L ₁ and the image I ₁ of the slit light are obtained by scanning the photoelectric conversion surface, and then the slit light is moved by a fixed pitch Δx to obtain the deformed image.
When _I2 is obtained, the photoelectric conversion surface is scanned and the above scanning line is
Intersection point a ₂ between L ₁ and scanning line L ₂ separated by a certain pitch,
Find b ₂ , and then in the same way, sequentially find the intersections a ₃ , b ₃ , a ₄ ,
By finding b ₄ ,..., we can obtain a group of points on the contour surface.

Furthermore, if the correspondence between the slit light images I ₁ , I ₂ , . . . and the scanning lines L ₁ , L ₂ , . . . is changed, as is clear from FIG. Point clouds can be found. That is, in FIG.
The point group A ₁ , A ₂ , A ₃ , ... on the contour surface S ₁ is the point P ₁ ,
Image of slit light passing through P ₂ ... and scanning lines L ₁ , , L ₂ ,
It can be obtained as the respective intersections with...
Also, the point group B ₁ , B ₂ , B ₃ , ... on the contour surface S ₂ is a point
Image and scanning line of slit light passing through P ₁ , P ₂ , ...
As the respective intersections with L ₂ , L ₃ , ..., the point group C ₁ , C ₂ , C ₃ , ... on the contour surface S ₃ is the point P ₁ ,
Image of slit light passing through P ₂ , ... and scanning line L ₃ ,
It can be obtained as the respective intersections with L ₄ ,... Therefore, by finding and superimposing a group of points on a large number of these contour planes, it is possible to evaluate the shape of the target object.

The present invention attempts to find a contour position on a target object using such a principle,
Compared to the moiré method, it is possible to perform shape measurement that clearly determines whether the object is deformed in a convex or concave direction, and it is easier to thin the image of the slit light. , it is possible to perform highly accurate shape measurement.

That is, in the measurement method of the present invention, a slit beam or a laser beam swinging in the direction perpendicular to the rotation direction is projected onto the target object from a projection device that is rotatable at a rotation center that intersects with the optical axis, and the reflected light is is imaged on the photoelectric conversion surface of the light receiving device, and the projecting device is rotated so as to give a linear movement of a constant pitch on an axis located away from the center of rotation, and the photoelectric conversion surface is focused at each rotational position. A group of points on the contour plane of the target object is detected as the intersection of the locus of the slit image of the reflected light or the image of the spot light obtained on the conversion surface and a straight line with an interval corresponding to the pitch, and based on this, This method is characterized by measuring the shape of an object.

To explain more specifically, FIG. 4 shows a case where slit light is projected by the projection device 10,
Further, FIGS. 5 and 6 show the case where a laser beam is projected by a projection device.

The projection device 10 in the measuring device shown in FIG. 4 includes a rotating table 21 on a base 20 which is rotationally driven by a motor (not shown), and a slit 23 is arranged on the rotating table 21 at its center point P. The slit light projector 22 is fixed, and the light from the light source 24 is projected by the optical system 25 and the slit 23 as a slit light having a long cross section in a direction perpendicular to the rotational direction, that is, a direction perpendicular to the plane of the paper. are doing. The rotational position of the projection device 10 is determined by slidably fitting the pin 30 on the slider 29 that linearly slides within the guide 28 into the groove 27 of the protrusion 26. Measurement is performed by connecting position detectors 31 that constitute a position servo system.

On the other hand, the light receiving device 12 consisting of an ITV camera is mounted on the base 20, and its photoelectric conversion surface 33 is attached to the slider 29.
The video signal is input to the electronic computer via the interface. In addition, although the above explanation is that the photoelectric conversion surface 33 of the light receiving device is positioned on the central axis of the slider 29,
By using necessary coefficients, the photoelectric conversion surface 3
The position of 3 can be set arbitrarily.

In the apparatus having the above configuration, the rotary table 21
is set at a required position, the projector 22 projects the slit light onto the target object 11, and the reflected light is received by the light receiver 12. In this light receiver, the photoelectric conversion surface 33 is approximately 256 x 256 pixels. The light and dark signals of each pixel are AD converted into about 6 bits, and the image of the slit light is stored in the memory of an electronic computer as a digital image. After these operations are completed, the rotating table 21 is rotated under the control of an electronic computer until the position detector 31 moves by Δx. This rotation is controlled by a position servo system consisting of a rotary table motor and a position detector 31. After that, the image of the slit light is again captured by the light receiving device, stored as a digital image in the memory of the electronic computer, and after repeating this as many times as necessary, the digital image of each frame is spatially differentiated. The resulting slit image is thinned, and the slit image is converted into a suitable functional formula.
Approximate by f ₁ , f ₂ , ... From now on, by finding the intersections of the curve group expressed by the above-mentioned functional formula of the slit image and the straight line group having the same interval as the pitch Δx of the slider 29 when rotating the rotary table 21, the equation is calculated. A cloud of points located on a high surface can be obtained, by means of which the shape of the object can be measured as described above.

The measuring device shown in Fig. 5 projects a laser beam, and is basically similar to the device shown in Fig. 4, but since the laser beam is projected as a spot beam, it can be used as a slit. It has a means to convert it into something equivalent to light. That is, as shown in detail in FIG. 6, the projection device 10 in the measuring device shown in FIG.
2 is rotated by a drive motor 43, and a rotation angle detector 4 is attached to the rotation shaft 42.
4 to be able to detect the rotation angle of the mirror 41 and constitute a servo system, and a laser light source 45 that projects a laser beam toward the center of the mirror 41 is fixed on the machine frame 40. The machine frame 40 is moved to the rotary base 21 so that its axis coincides with the center point P of the rotary base 21 (FIG. 5) of the projection device.
It is fixed at 1.

On the other hand, as the light receiving device 12 for detecting the reflected light from the target object 11 on the base 20, a semiconductor position detector commercially available under the trade name Cell Spot is used. This detector has a photoelectric conversion surface 46
A semiconductor position detector that outputs a signal corresponding to the coordinates of the centroid of the spot light received by ing.

Note that the other configurations are the same as in the case of FIG. 4.

When performing measurements using this measuring device, first, the rotary table 21 is set at an appropriate initial position under the control of an electronic computer, and the mirror 41 is rotated from top to bottom in this state. The electronic computer outputs a mirror rotation signal to the servo system of the mirror 41 via the interface, and at the same time sequentially stores the coordinates of the image of the spot from the light receiving device 12 at each rotational position of the mirror in the memory. Thereafter, the rotary table 21 is rotated by moving the rotary table 21 by a fixed pitch Δx using the position detector 31 under the control of an electronic computer, and the same operation is performed, which is repeated for each rotational position of the rotary table. Therefore, regarding the locus of the image of the reflected light obtained on the photoelectric conversion surface 46 at each rotational position,
By performing approximation using the same functional formula as explained in Fig. 4 and finding the intersection of the above trajectory and a group of straight lines with an interval corresponding to the above constant pitch Δx, the position on the contour plane of the target object is determined. It is possible to obtain a point group based on which the shape of the target object can be measured.

As is clear from the above detailed description, the measuring method of the present invention is not based on the generally used principle of triangulation, but is based on a principle unique to the present invention. That is, in the present invention, the target object is irradiated while rotating the slit light by giving a linear movement of a constant pitch on the axis located at a position away from the center of rotation, and the reflected light is reflected at each position. If an image of It is constructed based on the principle that the light is reflected from a contour point, and therefore, when rotating the projection slit light, it is only necessary to keep the pitch of the above linear movement constant, and the slit light is There is no need to measure the angle of the path of the light until it is reflected by an object and returns, or to measure the distance between the reflection points of each device or target object, which greatly simplifies the configuration. , it is possible to accurately and easily measure the shape of a target object, including whether it is deformed in a convex or concave direction.

[Brief explanation of the drawing]

FIGS. 1 to 3 are explanatory diagrams of the measurement principle in the present invention, FIGS. 4 and 5 are configuration diagrams of different apparatus examples of the present invention, and FIG. 6 is a configuration of the projection apparatus of FIG. 5. FIG. 10... Projection device, 11... Target object, 12...
...Light receiving device, 13, 33, 46...Photoelectric conversion surface.

Claims (1)

[Scope of Claims] 1 Projection light consisting of slit light perpendicular to the rotational direction is projected onto a target object from a projection device that is rotatable at a rotation center that intersects with the optical axis, and the reflected light is transmitted to a photodetector of a light receiving device. An image is formed on the photoelectric conversion surface, and the projection device is rotated so as to give a linear movement of a constant pitch on an axis located away from the center of rotation, and an image is obtained on the photoelectric conversion surface at each rotational position. An object shape characterized in that a group of points on a contour plane of a target object is detected as the intersection of an image of reflected light and a straight line having an interval corresponding to the pitch, and the object shape is measured based on this. How to measure. 2. Projecting a laser beam that swings in a direction perpendicular to the rotational direction onto the target object from a rotatable projection device at a rotation center that intersects with the optical axis, and focusing the reflected light on a photoelectric conversion surface of a light receiving device, The projection device is rotated so as to give a linear movement of a constant pitch on an axis located away from the center of rotation, and the locus of the image of the reflected light obtained on the photoelectric conversion surface at each rotational position is A method for measuring the shape of an object, characterized in that a group of points on a contour plane of the target object are detected as points of intersection with a straight line having an interval corresponding to the pitch, and the shape of the object is measured based on the detected points.