JPH06147850A - Cross-sectional profile measuring equipment - Google Patents

Abstract

PURPOSE:To provide a light cutting system cross-sectional profile measuring equipment which allows accurate measurement regardless of the color of an object to be measured or ambient brightness. CONSTITUTION:The cross-sectional profile measuring equipment comprises a CCD camera 5 having variable shutter speed (exposure time), an operational processing section 22 for taking in image data while varying shutter speed of the CCD camera automatically and processing the image data to select an optimal shutter speed, and a timing control section 23 outputting a signal for controlling the shutter speed of the CCD camera 5 to the optimal value.

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 cross-sectional shape measuring apparatus, and in particular, it automatically controls the exposure time of an image pickup camera to an optimum value in accordance with the intensity of reflected light from the surface of an object to be measured. Regarding possible things.

[0002]

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

FIG. 9 shows an example of such a light-section type sectional shape measuring apparatus. This cross-sectional shape measuring apparatus has a measuring head 1, and the measuring head 1 generates a slit-shaped laser beam and projects the laser beam onto the surface of the object to be measured W, and receives the reflected light. And a camera unit 3 for observing and recognizing the shape of the cutting line generated on the surface of the object to be measured W. The camera unit 3 has a light receiving lens 4 and a CC.
It is composed of a D camera 5 and usually a light receiving lens 4
The diaphragm is fixed, and the exposure time of the CCD camera 5 (which depends on the shutter speed) is fixed to a fixed time. After the image data corresponding to the shape of the surface of the object to be measured 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 converted into a digital signal by the A / D converter 6. Are taken into the image memory 7. The arithmetic processing unit 8 arithmetically processes the image data according to the principle of triangulation and measures the shape of the cross section of the object W to be measured. This measurement result is output from the measurement result output unit 9 such as a plotter. In addition, the display 10 for display
Depending on the position of the switching internal switch 11,
The image measured by the CD camera 5 is displayed in real time, or the processed image is displayed on the 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 apparatus, the diaphragm cannot be adjusted optically or electrically, so that the color of the object to be measured W or the measurement location is not measured. There is a possibility that the reflected light of the slit light may become stronger or weaker due to the brightness of the surroundings, the slit image may not be clearly captured, and the cross-sectional shape of the DUT W may not be accurately measured.
For example, when the color of the object to be measured W is black or the same as the color of the laser light, the reflected light is weak, and the slit image captured by the CCD camera 5 is dark and broken in places (FIG. 10).
(See (A)), but the shape of the image after processing becomes unclear (see FIG. 10B). On the other hand, when the measurement location is too bright or in direct sunlight, the reflected light is strong and the slit image becomes thicker.
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 decreases. For comparison, FIG.
(A) and (B) respectively show images before and after processing in a normal case where only a slit image is projected.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is an optical device that can always accurately measure a cross-sectional shape without being affected by the color of an object to be measured and the brightness of the surroundings. It is an object of the present invention to provide a cutting-type cross-sectional shape measuring device.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a light projecting means for irradiating a surface of an object to be measured with slit light, and a reflected light from the surface for receiving the shape thereof. Recognition means for recognizing, storage means for storing image data from the recognition means, calculation means for calculating the relative brightness of the slit image with respect to the surroundings based on the image data stored in the storage means, and the calculation means. The selection means for selecting the optimum exposure time of the recognizing means based on the calculation result of 1), and the control means for controlling the exposure time of the recognizing means according to the selection result of the selecting means.

[0007]

In the present invention thus constructed, the light projecting means irradiates the surface of the object to be measured with slit light, and the recognizing means receives the reflected light from the surface to recognize its shape.
The storage means stores the image data output from the recognition means. Based on this image data, the calculating means calculates the relative brightness of the slit image with respect to the surroundings. Based on the result of this calculation, the selecting means selects the optimum exposure time of the recognizing means so that the slit image can be clearly seen. For example, the exposure time is lengthened when the reflected light is relatively dark, and conversely, the exposure time is shortened when the reflected light is relatively bright. The control means controls the exposure time of the recognition means according to the selection result. This makes it possible to always obtain image data that is not affected by the color of the object to be measured or the ambient brightness.

[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 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 explaining it, and FIG. It is a flowchart which shows the procedure of the measurement by an example. The same parts as those in FIG. 9 are designated by the same reference numerals.

As shown in FIG. 1, this cross-sectional shape measuring device has a measuring head 20, and this measuring head 20 has:
A laser projector 2 that generates a slit-shaped laser beam and projects it on the surface of the object W to be measured, 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 object W to be measured. And are provided. The camera unit 3 is composed of a light receiving lens 4 and a CCD camera 5, and the diaphragm of the light receiving lens 4 is fixed. The exposure time (shutter speed) of the CCD camera 5 is variable, and several kinds of shutter speeds are preset. When measuring, as described later, the optimum 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. Furthermore, the measuring head 2
0 is also provided with a measurement start switch (not shown) for starting the measurement operation.

Outside the measuring head 20, 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 converted into image data. And the image data in the image memory 7 are processed to select the optimum shutter speed, and the image data captured at the optimum shutter speed is processed to calculate the sectional shape of the object to be measured W. Processing unit 2 for measuring
2 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 and 3 are provided. A display 10 for display is connected to the CCD camera 5 and the image memory 7 via an internal switch 11 for switching.
The image measured by the CCD camera 5 is displayed in real time or the processed image is displayed on the screen according to the position of 1. 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. Further, a timing control section 23 is connected to the input of the display 10 for displaying, and the input timing of the captured image is changed and displayed according to the shutter speed of the CCD camera 5. The measurement result processed by the arithmetic processing unit 22 is output from the measurement result output unit 9 such as a plotter.

The light projecting means is constituted by the laser projector 2, the recognizing means is constituted by the CCD camera 5, the storing means is constituted by the image memory 7, the arithmetic means and the selecting means are constituted by the arithmetic processing section 22, and the control means is constituted by the timing control section 23. ing.

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

Several types of shutter speeds (exposure times) of the CCD camera 5 are 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 captured as image data in the image memory 7 through the A / D converter 6 (S
2).

Then, the arithmetic processing section 22 executes the following arithmetic processing on the captured image data (S3).
That is, as shown in FIG. 3, L ₀ to L in the y-axis direction of the screen.
_N (N + 1) scanning lines are set, a curve of brightness with respect to the y-axis is obtained for each line, and the maximum value and the average value thereof are calculated (see FIG. 4). Perform this operation for all lines. Then, in the sense of ignoring lines that may not have slit images, lines with a difference between the maximum brightness value and the average value that is equal to or greater than a preset value are considered valid, and all such lines are targeted. Then, the maximum value and the average of the line average values are calculated to obtain 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 judged 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), and as a result of this judgment, if all shutter speeds have been reached. , 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 with the largest difference between the calculated maximum and average values for the entire screen is determined to be the optimum shutter speed that produces the clearest slit image. Then, this optimum value is selected as the shutter speed of the CCD camera 5 (S5).

The reason why the shutter speed that maximizes the difference between the maximum value and the average value of the entire screen 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 on a certain line in the screen. When the shutter speed is too fast, as shown in FIG. The slit image is dark with respect to the surroundings and is intermittent (see (A) in the figure), and the difference between the maximum value and the average value of brightness is small (see (B) in the figure). On the other hand, when the shutter speed is the optimum value, the slit image clearly appears on the screen as shown in FIG. 6 (see FIG. 6A), and the difference between the maximum brightness value and the average value. Is also larger (see FIG. 2B). However, when the shutter speed is too slow, the entire object to be measured W is reflected on the screen other than the slit image as shown in FIG. 7 (see FIG. 7A), and the maximum brightness is obtained. The difference between the value and the average value becomes small (see FIG. 7B). Therefore, as is clear from the comparison between FIGS. 5 to 7 (particularly FIG. 7B), it is understood that the greater the difference between the maximum brightness and the average brightness, the more optimal the shutter speed.

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

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 flow chart of FIG. First, the measurer brings the measurement head 20 close to the object to be measured W, irradiates the surface of the object to be measured W with laser slit light, and determines the measurement site while looking at the monitor screen of the display 10 for display (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). By adjusting the shutter speed in this way, the slit image is clearly captured in the moving image on the monitor screen without being affected by the color of the object to be measured W or the brightness of the surroundings (see (b) in the figure). Then, when a measurement start switch (not shown) provided in the measurement head 20 is turned on, the video signal captured by the CCD camera 5 in the measurement head 20 at that time is, for example, 512 × 512 via the A / D converter 6. It is taken into the image memory 7 as 8-bit grayscale information of the point (S1
2). As a result, the monitor screen is fixed to the screen when the measurement start switch is turned on (see (c) in the figure).
Based on this memory screen, the arithmetic processing unit 22 calculates, for each line in the y-axis direction of the screen, the center position of the portion where the brightness with respect to the y-axis exceeds a certain threshold value by weighted averaging. The position of the upper slit image is (x ₀ , y ₀ )
Is calculated in the form of coordinates such as (S13) ((d) in the figure).
(See (e)). Then, the position of the slit image calculated in step 13 is displayed as a series of dots on the monitor screen as shown in FIG. Then, the slit image position is written as a curve by the plotter 9 and output as shown in FIG. At this time,
As described above, since high-quality image data is captured by optimizing the shutter speed, the curve of the slit image corresponding to the cross-sectional shape can be accurately output.

As described above, according to this embodiment, the shutter speed (exposure time) of the CCD camera 5 is automatically controlled to the optimum value so that the slit image can be clearly seen. The image data can be obtained without being affected by the color of the object to be measured W and the brightness of the surroundings. Therefore, the cross-sectional shape of the surface of the object to be measured W can be accurately measured without being affected by the color of the object to be measured W or the brightness of the surroundings.

[0021]

As described above, according to the present invention, it is possible to obtain high-quality image data that is not affected by the color of the object to be measured or the brightness of the surroundings. Measurement accuracy is improved.

[Brief description of 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.

FIG. 3 is a diagram for explaining FIG. 2;

FIG. 4 is a diagram which similarly serves to explain FIG.

FIG. 5 is a diagram for use in explaining FIG. 2 similarly.

FIG. 6 is a diagram for explaining the same in FIG.

FIG. 7 is a diagram for use in explaining FIG.

FIG. 8 is a flowchart showing 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 apparatus.

FIG. 10 is a diagram for explaining a conventional technique.

FIG. 11 is a diagram which is also used for explaining a conventional technique.

FIG. 12 is a diagram for explaining the conventional technique.

[Explanation of symbols]

 2 ... Laser projector (projecting means) 5 ... CCD camera (recognizing means) 7 ... Image memory (storage means) 20 ... Measuring head 21 ... Timing adjustment start switch 22 ... Arithmetic processing unit (arithmetic means, selecting means) 23 ... Timing Control unit (control means) W ... Object to be measured

Claims (1)

[Claims] 1. A light projecting means for irradiating a surface of an object to be measured with slit light, a recognition means for receiving reflected light from the surface and recognizing its shape, and storing image data from the recognition means. A storage unit, a calculation unit that calculates the relative brightness of the slit image with respect to the surroundings based on the image data stored in the storage unit, and an optimum exposure time of the recognition unit is selected based on the calculation result of the calculation unit. A cross-sectional shape measuring apparatus comprising: a selection unit; and a control unit that controls an exposure time of the recognition unit according to a selection result of the selection unit.