JP2971822B2 - Non-contact image measurement system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact image measurement system for measuring a contour shape and the like of an object to be measured from an image obtained by imaging the object to be measured by an image pickup means such as a CCD camera.

[0002]

2. Description of the Related Art The contours of precision machine parts are often more complicated than those that can be represented by straight lines or arcs, but can be represented only by free curves. Thorough inspection of such contours requires measurement of thousands or more points. Therefore, there is a need for a non-contact image measurement system capable of efficiently measuring a contour shape.

In a conventional non-contact image measurement system, when measuring a contour shape, for example, as shown in FIG.
The first two measurement points (x1, y1) and (x2, y2) are set by the operation of the operator on the edge of the image 41 of the measured object in the imaging visual field S captured by the imaging means such as the CCD camera. And the third and subsequent measurement points (xi, yi)
Are the two previous measured points (xi-2, yi-2), (xi-
1, yi-1) are automatically set in order. Specifically, a straight line L from the point (xi-2, yi-2) to the point (xi-1, yi-1) is generated, and the point (xi-1, yi-
A point (xi ', yi') separated from 1) by a predetermined distance H (H: measurement pitch) is set as a measurement target point. Next, an edge detection tool T having a target length (xi ', yi') as a middle point and a straight line having a predetermined length (search distance) orthogonal to the straight line L is used.
Is generated, and the position of the edge is obtained as a measurement point (xi, yi) from the change in the density of the image on the edge detection tool T.

[0004]

However, such a conventional non-contact image measurement system has the following problems. (1) Since the above-described method of detecting a measurement point is based on the premise that the edge extends substantially along a straight line, as shown in FIG. Is present, the measurement target point (xi ', yi') greatly deviates from the edge, so that edge detection becomes impossible and measurement may be interrupted halfway.

(2) As shown in FIG. 9C, when the measurement target point (xi ′, yi ′) of the next measurement point (xi, yi) deviates from the imaging visual field S, the next measurement target point (xi) xi ', yi') is moved with respect to the object to be measured so that the next measurement target point is located within the next imaging field of view S '. The imaging means is driven so that (xi ', yi') is located at the center of the next imaging field of view S '.
Then, a large overlap portion occurs between the imaging visual field S before driving and the imaging visual field S ′ after driving. For this reason, there is a problem that the number of times of driving of the imaging unit in the entire measurement increases and the measurement time increases.

An object of the present invention is to provide a non-contact image measurement system capable of reliably detecting an edge of a portion having a large curvature. Another object of the present invention is to provide a non-contact image measurement system capable of efficiently measuring the contour shape of the object to be measured by reducing the number of relative movements between the imaging means and the object to be measured. Aim.

[0007]

A first non-contact image measurement system according to the present invention comprises: an image pickup means for picking up an image of an object to be measured;
Control means for sequentially generating a detection tool for detecting the edge along the edge included in the image of the object to be measured imaged by the imaging means; and detecting the edge by the detection tool generated by the control means. Measuring means for measuring a position, and design value storage means for storing a design value relating to the edge of the object to be measured, wherein the control means controls the edge based on a design value stored in the design value storage means. And a measurement target point is set on the generated prediction curve, and the detection tool is generated on the measurement target point.

In a second non-contact image measurement system according to the present invention, in the above configuration, the control means stores as many of the detection tools as possible in an imaging field of view of the imaging means, and In order that the detection tool is not overlapped in different imaging visual fields, the measuring position of the imaging means with respect to the measured object is sequentially moved, and the measuring means is positioned within the imaging visual field at each of the measuring positions. The position of the edge is measured by a detection tool included.

That is, the design value of the contour shape of the object is CA
In the D / CAM system, it is described in a predetermined language,
It is generally stored in the form of a CAD data file. In the present invention, focusing on this point, a design value relating to an edge (contour shape) is stored in a design value storage unit, and an edge prediction curve is generated based on the stored design value. The measurement target point is set on the prediction curve. For this reason, the measurement target point does not largely deviate from the edge regardless of the curvature, and the detection tool can always be generated at a correct position along the edge. This enables continuous measurement without losing an edge from the measurement start point to the measurement end point.

Further, according to the present invention, since the measurement target points are determined based on the design values, all the measurement target points from the measurement start point to the measurement end point are known in advance. For this reason, the measurement position of the imaging unit with respect to the measurement target is set so that as many detection tools as possible are stored in the imaging visual field of the imaging unit, and the same detection tool is not redundantly stored in different imaging fields. By sequentially moving, the overlapping portion between the adjacent imaging visual fields becomes very small. For this reason, the relative movement operation between the imaging means and the object to be measured in the entire measurement can be significantly reduced as compared with the related art, and the measurement efficiency of the contour shape of the object to be measured can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the entire configuration of a non-contact image measurement system according to one embodiment of the present invention. The system includes a non-contact image measurement type coordinate measuring machine 1, a computer system 2 which controls the driving of the coordinate measuring machine 1 and executes necessary data processing, and a printer 3 which prints out measurement results. It consists of.

The coordinate measuring machine 1 is configured as follows. That is, a measurement table 13 on which the work 12 to be measured is placed is mounted on the gantry 11, and the measurement table 13 is driven in the Y-axis direction by a Y-axis driving mechanism (not shown). Support arms 14 and 15 extending upward are fixed to the center of both sides of the gantry 11.
An X-axis guide 16 is fixed so as to connect both upper ends of the support arms 14 and 15. This X-axis guide 16
Supports an imaging unit 17. The imaging unit 17 is driven along the X-axis guide 16 by an X-axis driving mechanism (not shown). At the lower end of the imaging unit 17, a CCD camera 18 is mounted so as to face the measurement table 13. Further, inside the imaging unit 17, in addition to a lighting device and a focusing mechanism (not shown),
A Z-axis drive mechanism for moving the position of the CCD camera 18 in the Z-axis direction is built in.

The computer system 2 includes a computer main body 21, a keyboard 22, a joystick box 23, a mouse 24, and a CRT display 25. The computer main body 21 includes a CPU, a ROM, a RAM, a hard disk drive, and the like (not shown).
Various functions as shown in FIG.

That is, the work 1 captured by the CCD camera 18
The multi-valued image data in the two fields of view are stored in the image memory 31. The multi-valued image data stored in the image memory 31 is displayed on the CRT display 25 by the operation of the display control unit 32. Further, the design value storage unit 33 stores design value data describing the contour shape and the like of the work 12. As the design value data, for example, IGES
(Initial Graphic Exchange Specification) files and DXF files (DXF: a trademark of Autodesk, USA) are used as data described as CAD data files.

The measurement control unit 34 measures the contour of the work 12 in the field of view based on commands from the keyboard 22, the mouse 22, and the joystick box 23 by the operator and the design value data stored in the design value storage unit 33. In order to generate an edge detection tool necessary for the measurement and output a measurement command to the image measurement unit 35 or to move the imaging field of view with respect to the workpiece 12, a movement command of the measurement table 13 is output to the coordinate measuring machine 1. The image measurement unit 35 executes a contour measurement process based on the generated edge detection tool under the control of the measurement control unit 34. This measurement result is given to the measurement result evaluation unit 36. The measurement result evaluation unit 36
The measurement result from the image measurement unit 35 is compared with the design value data stored in the design value storage unit 33 to evaluate the measurement result,
The evaluation result is output to the printer 3.

Next, the contour measuring process of the non-contact image measuring system according to the present embodiment thus configured will be described.
FIG. 3 is a flowchart of the measurement control unit 34 for the contour measurement processing. First, in order to make the coordinate system of the work 12 coincide with the design value coordinate system based on an operator's command from the keyboard 22 and the mouse 24, a plurality of points on the work 12 are measured, and the coordinates of these points are converted to the design value coordinate system. The work coordinate system is set so as to correspond to the coordinates (S1). Next, the design value data of the contour shape of the work 12 is extracted from the design value storage unit 33 (S2), and as shown in FIG. 4, the design value data (xi ", yi") (where i = 1 to n). A predicted curve C of an edge connecting the point sequence (indicated by ○ in the figure) is created by, for example, a spline function, and the predicted curve C is divided from a start point to an end point by a measurement pitch H specified in advance and a measurement target point (xi ', Yi') (where i = 1 to N)
Is calculated (S3). Here, the point sequence of the design value data and the point sequence of the measurement target point are different, but they may be exactly the same.

Subsequently, as shown in FIG. 5, each measurement target point (xi ', yi') is set as a middle point, and a straight line having a predetermined length orthogonal to the prediction curve C is used as an edge detection tool Ti (where i = 1 to
N) (S4). At this time, the start point (xsi, ysi) and end point (xei, yei) of each edge detection tool Ti
Are calculated at the same time.

Next, a measurement control process is executed (S5). In this measurement control process, as shown in FIG. 6, as many edge detection tools Ti as possible fall within the imaging field of view S of the CCD camera 18, and the same edge detection tool Ti overlaps in different imaging fields of view. The edge detection tool T in the visual field is moved while sequentially moving the imaging visual field so as not to be accommodated.
The measurement processing of the edge points along i is executed.

FIG. 7 is a flowchart of the measurement control process. Assuming that the length of the imaging visual field S in the x-axis direction is Sx and the length in the y-axis direction is Sy, in steps S11 to S17, 1
A set of edge detection tools Ti that can be accommodated in one imaging field of view S (Sx × Sy) is determined. That is, first, the number i of the tool closest to the start point and the number j of the tool closest to the end point accommodated in one imaging visual field S are initially set to 1 (S11). Then, while updating the value of j, 1
Parameters for determining the range and position of the imaging visual field S based on the starting point (xsi, ysi) and the ending point (xei, yei) of the j-th tool Tj until one imaging visual field S protrudes;
That is, the maximum value xmax and the minimum value xmin in the x-axis direction and the maximum value ymax and the minimum value ymin in the y-axis direction are obtained while sequentially updating (S12 to S17).

This will be described according to a specific example. For example, as shown in FIG. 8A, when an xy coordinate system is set, for the first (i = j = 1) tool T1,
In step S12, the starting point (xsj, ysj) is (xmin,
ymin), and the end point (xej, yej) is (xmax, yma).
x). Next, as shown in FIG. 8B, when j = 2, xmin and ymax do not change, but xmax and ymin are
Xmax = xej and ymin = ysj based on the start point and end point coordinates of the new tool T2, respectively. Xma like this
It is step S16 that x, xmin, ymax, and ymin are updated. As shown in FIG. 8C, when j = 4 and the range of the tools T1 to T4 is obtained, the length of the range in the y-axis direction exceeds the length Sy of the imaging visual field S in the y-axis direction. This is determined in step S17. Therefore, in the subsequent step S18, as shown in FIG. 8D, j is reduced by one, and xmax and xm obtained up to that time are reduced.
center point (xc, yc) of the range indicated by in, ymax, ymin
(Obtained sequentially in step S15)
A movement command to the three-dimensional measuring machine is output so as to position the center point of, and the image measurement unit 35 is instructed to execute measurement. When the measurement is completed, i and j are updated to j + 1 (S19), and the processing of steps S12 to S18 is repeated until these exceed N.

By this processing, as shown in FIG. 6, efficient measurement is possible while minimizing the overlapping portion of the imaging range S.

[0022]

As described above, according to the present invention, a design value relating to an edge (contour shape) is stored in the design value storage means, and an edge prediction curve is generated based on the stored design value. However, since the measurement target point is set on the generated prediction curve, the measurement target point does not largely deviate from the edge regardless of the curvature, and the measurement ends from the measurement start point. There is an effect that continuous measurement can be performed without losing an edge to a point.

Further, according to the present invention, as many detection tools as possible are stored in the imaging field of view of the imaging means, and the measurement target is measured so that the same detection tool is not redundantly stored in different imaging fields. By sequentially moving the measurement position of the imaging unit with respect to the object, it is possible to reduce the overlapping portion between the adjacent imaging fields, so that the relative movement between the imaging unit and the measurement object in the entire measurement Operation can be significantly reduced than before,
There is an effect that the measurement efficiency of the contour shape of the measured object can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a non-contact image measurement system according to an embodiment of the present invention.

FIG. 2 is a functional block diagram showing functions of a computer system in the system.

FIG. 3 is a flowchart of a contour measurement process in the system.

FIG. 4 is a diagram for explaining a process of setting a measurement target point based on a design value of the contour measurement process.

FIG. 5 is a diagram showing a state where an edge detection tool is set at the measurement target point.

FIG. 6 is a diagram for explaining a method of setting an imaging field of view efficiently in the contour measurement processing.

FIG. 7 is a flowchart of a measurement control process including the setting of the imaging field of view.

FIG. 8 is a diagram for explaining a setting process of the imaging field of view.

FIG. 9 is a diagram illustrating a conventional contour measurement process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Coordinate measuring machine, 2 ... Computer system, 3 ... Printer, 11 ... Stand, 12 ... Work, 13 ... Measurement table, 14, 15 ... Support arm, 16 ... X-axis guide, 17
... Imaging unit, 18 ... CCD camera, 21 ... Computer body, 22 ... Keyboard, 23 ... Joystick box, 24 ... Mouse, 25 ... CRT display,
31 image memory, 32 display control unit, 33 design value storage unit, 34 measurement control unit, 35 image measurement unit, 36 measurement result evaluation unit.

Claims (2)

(57) [Claims] An imaging unit for imaging an object to be measured, and a control unit for sequentially generating a detection tool for detecting the edge along an edge included in the image of the object to be measured captured by the imaging unit And measuring means for measuring the position of the edge by a detection tool generated by the control means, and design value storage means for storing a design value for the edge of the measured object, the control means, Generating a prediction curve of the edge based on the design value stored in the design value storage means, setting a measurement target point on the generated prediction curve, and generating the detection tool on the measurement target point A non-contact image measurement system, characterized in that: 2. The control means stores as many of the detection tools as possible in the imaging field of view of the imaging means, and controls the same detection tool so that the same detection tool is not redundantly stored in different imaging fields. The measurement position of the imaging unit is sequentially moved with respect to the measured object, and the measurement unit measures the position of the edge by a detection tool included in the imaging field of view at each of the measurement positions. The non-contact image measurement system according to claim 1, wherein: