JP2924514B2 - Cross-sectional shape measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called light-section type sectional shape measuring apparatus, and more particularly, to variably control an exposure time of an imaging camera to an optimum value automatically according to the intensity of light reflected from the surface of an object to be measured. About what can be done.

[0002]

2. Description of the Related Art As a method for measuring the surface shape of various panels constituting a body of an automobile, for example, recently, a light cutting method for optically measuring a cross-sectional shape of an object to be measured using a so-called light cutting method. Is becoming popular. Here, the light-section method is a method of irradiating slit light on the surface of an object to be measured, observing the shape of the reflected light, and measuring the cross-sectional shape of the object to be measured.

FIG. 9 shows an example of such a light-section type cross-sectional shape measuring apparatus. This cross-sectional shape measuring apparatus has a measuring head 1, which has a laser projector 2 that generates a slit-shaped laser beam and projects the laser beam on the surface of the workpiece W, and receives the reflected light. And a camera unit 3 for observing and recognizing the shape of a cutting line generated on the surface of the workpiece W. The camera unit 3 has a light receiving lens 4 and a CC
D camera 5 and usually, a light receiving lens 4
Is fixed, and the exposure time of the CCD camera 5 (which depends on the shutter speed) is fixed at a fixed time. Image data corresponding to the shape of the surface of the device under test W captured by the CCD camera 5 in the measuring head 1 is output to the outside in the form of a video signal, and is converted into a digital signal by the A / D converter 6. Are stored in the image memory 7. The arithmetic processing unit 8 performs arithmetic processing on the image data in accordance with the principle of triangulation to measure the cross-sectional shape of the workpiece W. This measurement result is output from a measurement result output unit 9 such as a plotter. In addition, the display for display 10
In accordance with the position of the internal switch 11 for switching,
An image measured by the CD camera 5 is displayed in real time, or an image after processing is displayed on a screen. The position of the internal switch 11 is switched by the arithmetic processing unit 8 based on the operation of the operator.

[0004]

However, in such a conventional cross-sectional shape measuring device, since the aperture cannot be adjusted optically or electrically, the color of the object W to be measured and the measuring position can not be adjusted. In some cases, the intensity of the reflected light of the slit light may vary depending on the brightness of the surrounding area, the slit image may not be clearly formed, and the cross-sectional shape of the workpiece W may not be accurately measured.
For example, when the color of the device under test W is black or the same color as the color of the laser beam, the reflected light is weak, and the slit image captured by the CCD camera 5 is dark and cut off (FIG. 10).
(See FIG. 10A), and the shape of the processed image becomes unclear (see FIG. 10B). On the other hand, when the measurement place is too bright or in direct sunlight, the reflected light is strong, and the slit image becomes thick.
Since the entire image is captured (see FIG. 11A), an error occurs in the processed image (see FIG. 11B), and the measurement accuracy of the cross-sectional shape is reduced. For comparison, FIG.
(A) and (B) show images before and after processing in a normal case where only a slit image is projected, respectively.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to provide a light source capable of always accurately measuring the cross-sectional shape without being affected by the color of the object to be measured or the surrounding brightness. An object of the present invention is to provide a cross-sectional shape measuring apparatus of a cutting system.

[0006]

In order to achieve the above object, the present invention provides a light projecting means for irradiating a slit light on a surface of an object to be measured and a plurality of exposure times set in advance.
The slit illuminated by the light emitting means from the surface of the workpiece
Receiving the reflected light including the scanning light to image the surface of the object to be measured
Image capturing means, storage means for storing image data from the image capturing means, and a plurality of image data set in advance by the image capturing means.
Imaged by one of a number of exposure times
The image of the surface of the DUT stored in the storage means
From the data, the maximum brightness of the entire screen and the average brightness
Arithmetic means for obtaining the average value, the advance by the calculating means
The brightness of the entire screen is changed for each of the set exposure times.
Find the maximum value and average value, and find the difference between the maximum value and average value.
Characterized in that it has a selection unit configured to <br/> select even greater exposure time as the optimal exposure time of the imaging means, and control means for controlling the exposure time of said image pickup means in accordance with the selection result of the selecting means.

[0007]

According to the present invention, the light projecting means irradiates slit light to the surface of the object to be measured, and the imaging means receives light reflected from the surface , and sets a predetermined number of light beams.
The shape is imaged by the exposure time . The storage unit stores the image data output from the imaging unit. The calculation means is
An image was taken with one exposure time stored in the storage means
From the image data of the image, the brightness of the entire screen
Find the maximum and average. The selection means is determined by the arithmetic means.
Maximum brightness of the entire screen for multiple exposure times
The exposure time with the largest difference between the value and the average value is selected as the optimal exposure time of the imaging means. Then, the control means controls the exposure time of the imaging means according to the selection result. As a result, it is possible to always obtain image data that is not affected by the color of the device under test or the brightness of the surroundings.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a cross-sectional shape measuring apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart of exposure time control according to the embodiment, FIGS. 3 to 7 are diagrams for explanation thereof, and FIG. 9 is a flowchart illustrating a procedure of measurement according to an example. Note that the same reference numerals are given to portions common to FIG.

As shown in FIG. 1, the cross-sectional shape measuring apparatus has a measuring head 20.
A laser projector 2 that generates a slit-shaped laser beam and projects it on the surface of the workpiece W, and a camera unit 3 that receives the reflected light and observes and recognizes the shape of a cutting line generated on the surface of the workpiece W Are provided. The camera unit 3 includes a light receiving lens 4 and a CCD camera 5, and the aperture of the light receiving lens 4 is fixed. The exposure time (shutter speed) of the CCD camera 5 is variable, and several types of shutter speeds are set in advance. At the time of measurement, as described later, an optimal shutter speed is automatically selected according to the situation. Also,
The measurement head 20 is provided with a timing adjustment start switch 21 for setting the shutter speed of the CCD camera 5 to the automatic control mode. Further, the measuring head 2
At 0, a measurement start switch (not shown) for starting the measurement operation is also provided.

An A / D converter 6 for converting an analog video signal from the CCD camera 5 into a digital signal and a video signal digitized by the A / D converter 6 are provided outside the measuring head 20. And the image data in the image memory 7 is selected to calculate the optimum shutter speed, and the image data captured at the optimum shutter speed is calculated to process the cross-sectional shape of the DUT W. Processing unit 2 for measuring
And a timing control unit 2 for outputting a timing signal for variably controlling the shutter speed of the CCD camera 5 to the optimum shutter speed selected by the arithmetic processing unit 22.
3 are provided. A display 10 is connected to the CCD camera 5 and the image memory 7 via an internal switch 11 for switching.
According to the position 1, the image measured by the CCD camera 5 is displayed in real time, or the processed image is displayed on the screen. The position of the internal switch 11 at this time is switched by the arithmetic processing unit 22 based on the operation of the operator. A timing controller 23 is connected to the input of the display 10 so that the input timing of the captured image is changed according to the shutter speed of the CCD camera 5 and displayed. The measurement result processed by the arithmetic processing unit 22 is output from a measurement result output unit 9 such as a plotter.

The light projecting means is a laser projector 2, the imaging means is a CCD camera 5, the storage means is an image memory 7, the calculating means and selecting means are a processing section 22, and the control means is a timing control section. 23.

Next, the operation of the thus configured cross-sectional shape measuring apparatus will be described. In the measurement, the surface of the workpiece W is irradiated with laser slit light from the laser projector 2 in the measuring head 20, and the reflected light is imaged by the CCD camera 5 in the measuring head 20. At this time, the timing adjustment start switch 2 provided on the measuring head 20
When 1 is turned on, the exposure time (shutter speed) of the CCD camera 5 is automatically controlled to an optimum value. The flowchart of this process is as shown in FIG.

Although the shutter speed (exposure time) of the CCD camera 5 is set in advance as described above, first, the shutter speed of the CCD camera 5 is set to one of them (S1). Then, the video signal captured at the shutter speed is taken into the image memory 7 through the A / D converter 6 as image data (S
2).

Then, the arithmetic processing section 22 executes the following arithmetic processing on the fetched image data (S3).
That, L ₀ ~L the y-axis direction of the screen as shown in FIG. 3
_N (N + 1) scan lines are set, a brightness curve for the y-axis is obtained for each line, and the maximum value and average value are calculated (see FIG. 4). This operation is performed for all lines. Then, in the sense of ignoring lines where there is no possibility that a slit image exists, a line in which the difference between the maximum value of brightness and the average value is equal to or greater than a predetermined value is regarded as valid, and all such lines are targeted. Then, the maximum value and the average of the line average values are calculated to determine the maximum value and the average value (screen average value) of the entire screen. In this way, the maximum value and the average value of the brightness of the entire screen at a certain shutter speed are calculated.

Then, it is determined whether or not the maximum value and the average value of the brightness of the entire screen have been obtained at all the set shutter speeds (S4). The operations of steps 1 to 3 are repeated for the remaining shutter speeds. On the other hand, if all shutter speeds have been completed, the shutter speed at which the difference between the calculated maximum value and the average value of the entire screen is the largest is determined as the optimal shutter speed at which the slit image is most clearly captured. Then, this optimum value is selected as the shutter speed of the CCD camera 5 (S5).

The reason why the shutter speed at which the difference between the maximum value and the average value of the entire screen is the largest should be selected as the optimum value is as follows. That is, FIG.
FIG. 7 shows a monitor screen when the shutter speed of the CCD camera 5 is changed and a brightness curve at a certain line in the screen. When the shutter speed is too fast, as shown in FIG. The slit image is dark and intermittent with respect to the surroundings (see (A) in the figure), and the difference between the maximum value and the average value of the brightness is small (see (B) in the figure). On the other hand, when the shutter speed is the optimum value, the slit image is clearly seen on the screen as shown in FIG. 6 (see FIG. 6A), and the difference between the maximum value and the average value of the brightness is obtained. (See FIG. 3B). However, if the shutter speed is too slow, as shown in FIG. 7, the whole DUT other than the slit image is captured on the screen (see FIG. 7A). The difference between the value and the average value becomes small (see FIG. 3B). Therefore, as is clear from the comparison of FIGS. 5 to 7 (particularly, FIG. 7B), it is understood that the greater the difference between the maximum brightness value and the average brightness value, the more optimal the shutter speed.

In relation to a specific measurement situation, for example, when the color of the object to be measured W is black or the same color as the laser beam and the reflected light is weak, the situation as shown in FIG. 5 is obtained. Therefore, while the exposure time of the CCD camera 5 is increased by lowering the shutter speed, the reflected light is strong, for example, when the measurement place is too bright or in direct sunlight, and the situation shown in FIG. 7 tends to occur. Therefore, conversely, control is performed to increase the shutter speed and shorten the exposure time of the CCD camera 5.

When the optimum value of the shutter speed is selected by the arithmetic processing unit 22 in step 5, a timing signal is output from the timing control unit 23 to the CCD camera 5, and the shutter speed of the CCD camera 5 is set to the optimum value. Will be.

Next, the procedure of measurement using this cross-sectional shape measuring apparatus will be described with reference to the flowchart of FIG. First, the measurer brings the measuring head 20 close to the measured object W, irradiates the surface of the measured object W with a laser slit light, and determines the measurement site while looking at the monitor screen of the display 10 (S10). The monitor screen at this time is a moving image, and when the measuring head 20 is moved, the image on the monitor screen also moves (see FIG. 8A). Then, the timing adjustment start switch 21 of the measuring head 20 is turned on, and C
The exposure time (shutter speed) of the CD camera 5 is optimized, and the shutter speed of the CCD camera 5 is automatically controlled to the optimum value (S11). This shutter speed
The optimization of the code has already been described with reference to FIGS.
It is as expected. By such adjustment of the shutter speed, the moving image on the monitor screen has a clear slit image without being affected by the color of the object W to be measured or the surrounding brightness (see FIG. 2B). Then, when a measurement start switch (not shown) provided on the measurement head 20 is turned on, the C in the measurement head 20 at that time is turned on.
The video signal captured by the CD camera 5 is taken into the image memory 7 through the A / D converter 6 as 8-bit density information of, for example, 512 × 512 points (S12). As a result, the monitor screen is fixed to the screen at the time when the measurement start switch is turned on (see FIG. 3C). Based on this memory screen, the arithmetic processing unit 22 calculates, for each line in the y-axis direction of the screen, a center position of a portion of the y-axis exceeding a certain threshold value of brightness by a load average, and obtains the line average. The position of the upper slit image is calculated in the form of coordinates such as (x ₀ , y ₀ ) (S13) (see FIGS. 3D and 3E).
Then, the position of the slit image calculated in step 13 is displayed as a sequence of dots on the monitor screen as shown in FIG. Then, the slit image position is drawn as a curve by the plotter 9 and output as shown in FIG. At this time, since high-quality image data is captured by optimizing the shutter speed as described above, a curve of a slit image corresponding to a cross-sectional shape is accurately output.

As described above, according to the present embodiment, the shutter speed (exposure time) of the CCD camera 5 is automatically controlled to an optimum value such that a slit image is clearly seen. Image data can be obtained without being affected by the color of the device under test W or the brightness of the surroundings. Accordingly, the cross-sectional shape of the surface of the object W can be accurately measured without being affected by the color of the object W or the brightness of the surroundings.

[0021]

As described above, according to the present invention, there are provided multiple
For each screen imaged with a number of exposure times, the entire screen
Calculate the maximum and average brightness of the
Optimize the exposure time for the screen with the largest difference
Because the time was selected, the slit image
The image can be clearly photographed, and the measurement accuracy of the cross-sectional shape of the surface of the measured object is improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a cross-sectional shape measuring apparatus according to one embodiment of the present invention.

FIG. 2 is a flowchart of exposure time control according to the embodiment.

FIG. 3 is a diagram provided for explanation of FIG. 2;

FIG. 4 is a diagram also used for explaining FIG. 2;

FIG. 5 is a diagram also used for explaining FIG.

FIG. 6 is a diagram also used for explaining FIG. 2;

FIG. 7 is a diagram also used for explaining FIG.

FIG. 8 is a flowchart illustrating a measurement procedure according to the present embodiment.

FIG. 9 is a schematic configuration diagram showing an example of a conventional cross-sectional shape measuring device.

FIG. 10 is a diagram provided for explanation of a conventional technique.

FIG. 11 is a diagram also provided for explanation of a conventional technique.

FIG. 12 is a diagram also provided for explanation of a conventional technique.

[Explanation of symbols]

2 ... Laser projector (light emitting means) 5 ... CCD camera ( imaging means) 7 ... Image memory (storage means) 20 ... Measurement head 21 ... Timing adjustment start switch 22 ... Operation processing unit (arithmetic means, selecting means) 23 ... Timing Control unit (control means) W: DUT

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁶ , DB name) G01B 11/00-11/30 102 G06T 7/00

Claims (1)

(57) [Claims] A light projecting means for irradiating slit light onto a surface of the object; and a surface of the object to be measured by a plurality of preset exposure times.
Including slit light emitted by the light projecting means from
An imaging hand for receiving the reflected light and imaging the surface of the object to be measured
A stage, a storage means for storing image data from the imaging means, a plurality of exposure time set in advance by the image pickup means
An image is taken by one of the exposure times, and
From the image data of the surface of the measured object stored in
Calculating means for calculating the maximum value and the average value of the brightness of the entire screen, and the plurality of exposure times set in advance by the calculating means.
The maximum and average brightness of the entire screen for each
The meta maximum value and the difference between the average value is largest exposure time Ta
Sectional shape measuring apparatus characterized by comprising selecting means for selecting as the optimal exposure time of the image means, and control means for controlling the exposure time of said image pickup means in accordance with the selection result of the selecting means.