JPH0526634A - Cross section shape measuring method - Google Patents

Abstract

PURPOSE:To provide a cross section shape drawn by a smooth contour line with no irregularities by moving the laser slit light by a slight distance from an optional position, inputting the reflected light at different positions obtained from an object to be measured, and synthesizing it. CONSTITUTION:A robot controller 10 scans a laser slit light source on the surface of an object to be measured. A laser diode 11 is stored in the laser slit light source and outputs a laser beam to output the laser beam light. A CCD camera 6 receives the reflected light from the object of the laser slit light, photoelectrically transfers the reflected light into an image signal, and outputs it to an image processor 3. The laser beam is moved by a slight distance at this time. The image processor 3 stores the radiation position together with the image, synthesizes all stored images, and calculates the center of gravity position of the average intensity. The cross section shape is displayed on a monitor 7 based on the calculated light center of gravity, and the cross section shape formed by a smooth contour line with no irregularities is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an accurate measurement of an object to be measured (particularly a rough object) which is usually affected by irregular reflection characteristics which are different depending on the position on the surface. The present invention relates to a cross-sectional shape measuring method capable of measuring a cross-sectional shape.

[0002]

2. Description of the Related Art For example, various panels constituting an automobile body, which is an object to be measured, are press-molded into various shapes according to the structure and rigidity of the automobile body, and most of them are welded to a body frame. Assembled. In such various panels, for example, when distortion or deformation due to defective press work or welding occurs, it directly affects the structure and rigidity of the vehicle body. In order to determine whether the processed panel has an appropriate shape, the surface shape of the processed panel is measured in the inspection process. Up to a decade ago, such panels were measured using so-called gauges that correspond to the shape of each panel. However, due to quality problems, poor workability, and high costs, etc. Recently, it has become mainstream to use a measuring device by a so-called optical cutting method as disclosed in, for example, Japanese Patent Laid-Open No. 64-10117.

As a measuring device by the light section method, for example, there is one as shown in FIG. The illustrated measuring device 1 is provided with a laser slit light source 4 for irradiating a laser slit light toward a panel 2 which is an object to be measured, and a CCD camera 6 included in a camera unit 5 is provided from the panel 2 by the laser slit light. Input the reflected light of. The image formed by the reflected light input by the CCD camera 6 is output toward the image processing device 3. The image processing device 3 performs image processing on the input image and displays the processed image on the monitor 7. The robot controller 10 controls the operation of the robot 9 to which the measuring device is attached, and controls the scanning of the laser slit light onto the surface to be measured of the panel 2. That is,
The laser slit light scans the surface of the panel 2 by the measuring device 1 driven by a command from the robot controller 10. The reflected light from the panel 2 due to the laser slit light is scanned by the image processing device 3 according to the scanning.
Then, the computer 8 obtains the sectional shape of the panel 2 by sequentially connecting the image information after the image processing.

[0004]

However, the contour line of the cross-sectional shape obtained by the measuring method adopted by such a conventional measuring apparatus causes unevenness depending on the roughness of the surface of the object to be measured. There's a problem.

For example, when the surface roughness of the panel 2 is very rough, the laser slit reflected light from the panel 2 is not input to the CCD camera 6 in a converged state, but is also input in a state including diffused light. Will be done. Therefore, when the object to be measured is irradiated with laser slit light, the reflected light is captured by the CCD camera 6, and an image is generated based on the reflected light, an image with a shade pattern as shown in FIG. 12A is obtained. .. Enlarging this shade pattern, the same figure (C)
A random shading pattern due to diffused reflection light of laser slit light called a speckle pattern as shown in FIG. The feature of this speckle pattern is that the pattern appears differently depending on the location, but the location, light source, and CCD
Unless the positional relationship of the camera 6 changes, it does not change with time. When the image processing device 7 performs processing (center position of slit light) for an image having such a speckle pattern, a smooth contour line (cross-sectional shape) as originally shown in FIG. ) Should be exhibited, but the cross-sectional shape has fine irregularities as shown in FIG. Such a problem occurs because of a calculation error of the optical center of gravity due to the speckle pattern. As a method of solving such a problem, it is possible to apply a filter when performing the above calculation, but when applying the filter, the unevenness of the obtained contour line is considerably reduced, while the cross-sectional shape itself is It's not always a good idea because it can be inaccurate. The present invention has been made in order to reduce the conventional problems as described above, regardless of the surface roughness of the object to be measured,
An object of the present invention is to provide a cross-sectional shape measuring method capable of obtaining a cross-sectional shape drawn by a smooth contour line without unevenness.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention irradiates a surface of an object to be measured with a laser slit light, and a cross section of the object to be measured based on the reflected light from the object to be measured. In the cross-sectional shape measuring method for measuring the shape, the laser slit light irradiated on the surface of the object to be measured is moved a minute distance from an arbitrary position, and at this time, reflection at different positions obtained from the object to be measured. Input the light respectively, combine the reflected light from the different positions,
It is characterized in that the cross-sectional shape of the measured object at an arbitrary position is measured by the synthesis.

[0007]

If the cross-sectional shape is measured by such a method, one image, that is, the cross-sectional shape at an arbitrary position of the object to be measured can be obtained by combining reflected lights obtained from a plurality of positions. Therefore, the influence of diffused light among reflected light due to the difference in roughness of the DUT is reduced compared to the case where the cross-sectional shape is obtained only by the reflected light at an arbitrary position, and the unevenness is extremely small. The cross-sectional shape drawn by the contour line will be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a cross-sectional shape measuring apparatus that operates by a measuring method according to the present invention, FIG. 2 is a schematic configuration diagram of an optical system of the apparatus shown in FIG. 1, and FIG. 3 is a CCD shown in FIG. It is an enlarged view of a camera part.

A cross-sectional shape measuring apparatus for carrying out the measuring method of the present invention is constructed as shown in FIG. 1. The laser diode 11 is built in the laser slit light source 4 and emits laser light for outputting laser slit light. It is output. The CCD camera 6 inputs the reflected light of the laser slit light from the object to be measured, photoelectrically converts the reflected light, and outputs it as an image signal to the image processing device 3. The image processing device 3 performs image processing on the image signal output from the CCD camera 6, or outputs the image signal after image processing or the image signal output from the CCD camera 6 to the monitor 7 as it is. Monitor 7
Is for displaying the contour line of the cross-sectional shape of the object to be measured as shown in FIG. 12 based on the image signal output via the image processing device 3. The robot controller 10
The operation of the robot for scanning the surface of the object to be measured with the laser slit light source 4 and the operation of the image processing apparatus 3 are controlled. The galvanometer mirror 12 is for swinging the laser slit light output from the laser diode 11 by a minute angle.

The schematic structure of the optical system in the apparatus shown in FIG. 1 is as shown in FIG. Laser diode 1
The cylindrical laser light output from the laser beam No. 1 is once converged by the collimator lens 15 and then diffused by the cylindrical concave lens 16. Next, in the process of being converged again by the cylindrical convex lens 17, the light is shielded by the light shielding plate 18, so that the slit-shaped beam 19 is output to the outside. Furthermore, this beam 19 is reflected by the galvanometer mirror 12,
The panel 2 which is the object to be measured is irradiated. The galvanometer mirror 12 is provided with a rotating mechanism 12B for rotating the mirror 12A.
The rotation of 2A is performed by the voltage applied from the AC power source of the rotation mechanism 12B. The rotation angle and the vibration cycle of the mirror 12A are uniquely determined by the magnitude and frequency of the voltage applied by the AC power supply.
A voltage represented by V = Asin ωt is output from this AC power supply, and its gain constant is K (mm / mA).
In the range where the rotation angle of the mirror 12A is small, the moving distance of the beam with respect to the object to be measured is almost proportional to the rotation angle. Therefore, the image processing device 3 reads the applied voltage of the AC power supply and the robot controller 10 The irradiation position of the beam is accurately grasped by reading the scanning position of the laser slit light by.

The laser slit light emitted from the optical system 20 is reflected by the panel 2 and input to the CCD camera 6. The CCD camera 6 has a two-dimensional line sensor 6S as shown in FIG.
The reflected light from is received by this sensor 6S via the lens 6L. For example, as shown in FIG. 2, the reflected light from the panel 2 in the state where the galvano mirror 12 is not operated is detected at the position a of the sensor 6S shown in the figure, and the galvano mirror 12 is operated to activate the laser beam. When the slit light is moved rightward or leftward by a predetermined distance, it is detected at the position b or the position c in the figure. When the object to be measured has a mirror-like surface, the reflected light intensity at this time has a normal distribution as shown in the graph at the left end of FIG. 3 at each position of the sensor 6S. become. That is, as shown in FIG. 4A, the irradiation positions of the laser slit light on the object to be measured are W0, W1 and W2, respectively, and the irradiation intensity I (w) of the laser slit light at each position is
In the case of a normal distribution as shown in the figure, the reflected light also exhibits a normal distribution although the magnitude thereof is different from the irradiation intensity. The above is the case where the reflection surface of the object to be measured is mirror-like. On the other hand, when the reflection surface of the object to be measured is not a mirror-like surface but a rough surface having a speckle pattern as shown in FIG. 12C, the reflected light intensity at each position on the reflection surface is natural. However, it is easy to imagine that they will be different. The relationship between the reflected light intensity (equivalent to reflectance) and the position is shown in FIG.
It is represented by the characteristic line G (w) as shown in FIG. In this figure, the position W0 'having the highest reflectance is equivalent to the center of gravity of the reflected light. When the reflection position of the laser slit light is different on the reflection surface of the DUT having such a characteristic line, the intensity of the reflected light differs according to the characteristic line G (w). For example, when the reflecting surface is irradiated with the laser slit light as shown in FIG. 7A, the reflected light is assumed to have the characteristics as shown in FIG. That is, the intensity of the reflected light is the characteristic line G
It exhibits the characteristic obtained by the product of (w) and irradiation intensity I (w). For this reason, when the laser slit light as shown in FIG.
W1 to W1 ', W0 to W0', W2 to W2 'are moved according to the characteristic line G (w). This can be said even in the case of irradiating a wide laser slit light as shown in FIG. 5A, and in this case, the reflection surface having the characteristic line as shown in FIG. By the irradiation, the reflected light has the characteristic as shown in FIG. 5B in which the center of gravity of the light is W0 '. In this way, when image processing is performed on the reflected light from the reflecting surface having different reflectance depending on the position, the light center of gravity of the reflected light at each position in the width direction of the laser slit light is different from that of the irradiation light. The light center of gravity becomes a line having fine irregularities as shown in FIG.

According to the cross-sectional shape measuring method of the present invention, even if the reflectance of the reflecting surface is different depending on its position, the optical center of gravity of the reflected light and the optical center of gravity of the irradiation light are Since the contours are processed so as to match as much as possible, the contour line obtained by the processing is smooth. The outline of the cross-sectional shape measuring method according to the present invention will be described below with reference to FIGS. In the measuring method of the present invention, two optimum examples are shown as examples for obtaining a smooth contour line. What can be said in common to these two embodiments is that in obtaining the contour line at one arbitrary position, the reflected lights at a plurality of different positions are input and the reflected lights at the respective positions are combined by some method. That is. The input of the reflected light and the synthesis of the reflected light at the plurality of different positions are performed as follows. As shown in FIG. 2, first, the galvano mirror 12 is not operated and the laser slit light is irradiated to a predetermined position, and the reflected light at this time is input by the CCD camera 6. Next, the galvanometer mirror 12 is operated to swing the laser slit light in the left-right direction by a slight angle. The reflected light from different positions obtained at this time is C
Input with the CD camera 6. The position at which the reflected light is obtained is calculated based on the applied voltage of the AC power source of the galvano mirror 12 and the irradiation position of the laser slit light,
The calculation result is stored together with the image based on the reflected light when the reflected light is input. By the above processing, specifically, the input positions W0, W1, W2 of each reflected light as shown in FIG. 4A and the intensity characteristic line of the reflected light as shown in FIG. 4C are stored. .. The input position and the intensity characteristic line of each reflected light stored in this way are synthesized by using one of the following two methods.

First, in the first method, the stored optical centroids of the respective reflected lights are individually calculated, and the average value of these optical centroids is calculated as shown in FIG. 6 (A). Thus, if the average value of the light centroids of a plurality of reflected lights is set as the light centroid of the reflected light at an arbitrary position, the error due to the speckle pattern described above is averaged, so that the light of one reflected light is simply A smoother contour line is formed than when based on the center of gravity. In the second method, the stored reflected light characteristic lines are combined as shown in FIG. 6B, and the barycentric position of the characteristic line indicating the average intensity obtained as a result of the combination is obtained. Thus, the influence of the speckle pattern will be averaged if the center of gravity position of the average intensity obtained by combining the reflected light characteristics is obtained. This makes it possible to obtain a cross-sectional shape with a smooth contour line. In this way, this effect is suppressed by averaging the speckle pattern depending on the location.

The outline of the processing of the present invention is as described above. The above processing will be described below in more detail with reference to the flowcharts of FIGS. 7 and 8. The flowchart shown in FIG. 7 shows the first process,
It is processed as follows. First, when the panel 2 is irradiated with the laser slit light as shown in FIG. 11, CC
The D camera 6 receives the reflected light input at that time, photoelectrically converts it, and outputs it as an image signal to the image processing apparatus 3.
The image processing device 3 stores the image signal (S1, S
2). Next, the AC power supply of the galvanometer mirror 12 is operated to vibrate the mirror 12A, and the reflected light at different positions of the laser slit light that is shaken with the vibration is input a predetermined number of times. If this predetermined number of times, for example, n times, n images are stored in the image processing device 3. For example, in the case of FIG. 9A, three laser slit reflected lights are stored (S3, S4). Next, the image processing device 3
Calculates the individual light centroids of this stored image,
Further, the average value of the individual light centroids is calculated. The above processing is performed for all dots (S5, S6).
The contour line is formed based on the average value of the optical centers of gravity calculated in this way. For example, when the above process is performed on the reflected light shown in FIG. 9A, the cross-sectional shape of the panel 2 as shown in FIG. 9B is displayed on the monitor 7 (S7). ..

The flowchart shown in FIG. 8 shows the second processing. In this process, first, when the panel 2 is irradiated with the laser slit light as shown in FIG. 11, the CCD camera 6 makes the reflected light input at that time incident and photoelectrically converts the reflected light into an image signal. Output to the processing device 3. The image processing device 3 stores the image signal (S11, S12). Next, the AC power supply of the galvanometer mirror 12 is operated to vibrate the mirror 12A, and the reflected light at different positions of the laser slit light that is shaken with the vibration is input a predetermined number of times. The position of the mirror when the reflected light is input, in other words, the irradiation position of the laser slit light is also input at the same time as the reflected light. The irradiation position is stored in the image processing device 3 together with the n images (S13 to S15). Next, the image processing apparatus 3 synthesizes all the stored images and calculates the center of gravity position of the average intensity obtained as a result of the synthesis. The above process is performed for all dots (S16, S17). The cross-sectional shape of the panel 2 is displayed on the monitor 7 based on the light center of gravity calculated in this way (S18). Even in the above processing, the reflected light as shown in FIG. 9A is input, and as a result, the sectional shape as shown in FIG. 9B is obtained. The cross-sectional shapes shown in FIGS. 10A and 10B are obtained by the measuring method of the present invention, but the cross-sectional shapes are smooth even though both measurement objects are rough objects. You can see that it is drawn with a simple contour line.

In the above-described embodiment, in the first processing, since it is necessary to calculate the optical centroids of all the reflected light input, the processing takes a time substantially proportional to the number of input reflected light. Become. Further, in the second processing, although it can be said that it is necessary to combine all of the input reflected lights, the combination is a simple addition, which does not take time, and the intensity obtained as a result of the combination. Since the calculation of the light center of gravity of the average characteristic line only needs to be performed once, it does not take time as compared with the first processing. Further, if a large number of reflected lights from different positions swung by the galvanometer mirror 12 are input, the influence of the speckle pattern can be reduced as the number of inputs increases, but the number of inputs is allowed. The number should be optimal depending on the processing time and memory capacity.

[0017]

As is apparent from the above description, according to the present invention, even if the surface of the object to be measured is a rough surface, an accurate cross-sectional shape of the object to be measured can be obtained with a smooth contour line. You can

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a cross-sectional shape measuring apparatus that operates by a measuring method according to the present invention.

FIG. 2 is a schematic configuration diagram of an optical system of the apparatus shown in FIG.

FIG. 3 is an enlarged view of the CCD camera portion shown in FIG.

FIG. 4A is a diagram showing a characteristic line of reflected light when the surface of the measured object is a mirror surface, and FIG. 4B is an example of the case where the measured object is a rough object. It is a figure which shows a reflectance characteristic, (C) is a figure which shows the characteristic line of the reflected light from the surface which has a reflectance characteristic like (B).

5A is a diagram showing a characteristic line of a wide laser slit light, and FIG. 5B is a diagram showing a laser slit light having a characteristic as shown in FIG. 4A reflected as shown in FIG. 4B. It is a figure which shows the characteristic line of the reflected light at the time of irradiating the surface of a rate characteristic.

FIG. 6A is a diagram showing a first process according to the present invention, and FIG. 6B is a diagram showing the same second process.

FIG. 7 is a flowchart showing a first process of the present invention.

FIG. 8 is a flowchart showing a second process of the present invention.

FIG. 9 is a diagram showing an example of a process in a panel used for a vehicle in order to easily understand the process of the present invention.

10 (A) and 10 (B) are diagrams showing cross-sectional shapes at arbitrary positions obtained as a result of applying the present invention to a rough surface object. of

FIG. 11 is a schematic configuration diagram of a conventional measuring device that measures a cross-sectional shape by a light section method.

FIG. 12 is a diagram for clarifying a problem caused by the conventional method performed by the apparatus shown in FIG.

[Explanation of symbols]

1 ... Measuring device, 2 ... Panel, 3 ... Image processing device, 4
… Laser slit light source, 5… Camera unit, 6…
CCD camera, 6S ... Two-dimensional line sensor, 7 ... Monitor, 8 ... Computer, 9 ... Robot, 10 ... Robot controller, 11 ... Laser diode, 12
... Galvanometer, 12A ... Mirror, 12B ... Rotation mechanism, 15 ... Collimator lens, 16 ... Cylindrical concave lens, 17 ... Cylindrical convex lens, 18 ...
Light shield, 19 ... Beam.

Claims (1)

Claim: What is claimed is: 1. A cross-sectional shape measuring method for irradiating a surface of an object to be measured with laser slit light and measuring the sectional shape of the object to be measured based on reflected light from the object. , Moving the laser slit light irradiated on the surface of the object to be measured from an arbitrary position by a minute distance, at this time, inputting reflected lights at different positions obtained from the object to be measured, respectively. A cross-sectional shape measuring method comprising: synthesizing reflected light from, and measuring the cross-sectional shape at an arbitrary position of the measured object by the synthesis.