JPH1110373A - Method for inspecting appearance of welding trace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To find at high the position of a welding trace formed at the time of welding at high speed and to reduce erroneous discrimination of a normal/ defective condition of the welding trace. SOLUTION: In a gradation image containing a welding trace 9 stored in a storage device inside an image processor, a ternary coding process is performed so as to determine a level of luminance for a welding trace, finding the formation position of the welding trace 9 by the degree projection 10, 11 in the vertical and horizontal axes of the luminance that rises to and above the level so determined. Then, the width 13 of the welding trace determined by the degree projection 11 in the horizontal axis is made the feature level, as is the degree (area) of the luminance to and above the level in the formation position of the welding trace 9, thereby discriminating the normal/defective condition of the welding trace 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting the appearance of a welding mark on a welding mark generated in an automatic machine for welding two plate-like objects mainly by using a laser.

[0002]

2. Description of the Related Art Welding marks generated by an automatic machine for welding two plate-like objects mainly using a laser need to find the generation position because the generation position is not constant. For this position detection, pattern matching using a grayscale image stored in a storage device by an input device for imaging a welding mark is used.

[0003] In addition, the state of the generated welding marks is conventionally
Binary processing is performed on the grayscale image stored in the storage device by the input device for imaging the welding mark, and only the frequency (area) of a luminescent spot having a certain luminance or more is used as a feature amount, so that the welding mark state Pass / fail is determined.

[0004]

[0005] Since welding marks generated in an automatic machine for welding two plate-like objects mainly by using a laser have irregular generation positions, it is necessary to find the generation positions. Conventionally, for this position detection, pattern matching using a grayscale image accumulated in a storage device by an input device for imaging welding marks is used. However, this method has a problem that it takes too much time to specify the position.

[0005] In addition, the state of the generated welding marks is
Binary processing is performed on the grayscale image stored in the storage device by the input device for imaging the welding marks, and the quality of the bright spots is determined based on the frequency (area) of the bright spots having a certain luminance or more. The reason is that the frequency of bright spots whose brightness is higher than a certain brightness due to less reflection from welding marks due to the degree of melting is reduced, or the frequency of bright spots whose brightness is higher than a certain level due to light reflected from other than welding marks increases. Therefore, there is a problem that an erroneous determination is made in the quality determination based on the frequency (area) of the bright spot.

SUMMARY OF THE INVENTION An object of the present invention is to provide a welding mark appearance inspection method for finding a position of a welding mark generated at the time of welding at a high speed and reducing erroneous determination of the quality of the state.

[0007]

According to the welding mark appearance inspection method of the present invention, the position of the welding mark generated at the time of welding is determined with respect to a grayscale image stored in a storage device by an input device for photographing the welding mark. It is found by performing ternarization processing, performing frequency projection of luminance on the vertical direction axis, and frequency projection of luminance on the horizontal direction axis, and finding a position (range) at or above a certain frequency.

In this method, the horizontal width of the position (range) of the weld mark and the luminance frequency (area) of the position (range) of the weld mark are used as characteristic quantities. The quality of the state can be determined.

According to the welding mark appearance inspection method of the present invention, the welding mark is imaged in order to find the position of the welding mark generated in an automatic machine for welding two plate-shaped objects mainly by using a laser. The input device performs a ternarization process on the grayscale image stored in the storage device, obtains a luminance that is a threshold value, performs frequency projection of a bright point having the luminance or more on the vertical direction axis, and performs luminance projection on the horizontal axis. By performing frequency projection of bright spots having the brightness or higher and finding a position (range) where the frequency distribution of bright spots is mountain-shaped for each vertical / horizontal axis, it is possible to quickly and easily find a position where a welding mark is generated. Can be done.

[0010] The state of the generated welding mark is obtained by performing the frequency projection of the luminescent spot on the horizontal axis, and obtaining the width of the welding mark at a position (range) of a certain frequency or more. By judging the quality of a welding mark state by using the luminance frequency (area) within the range obtained by the method as a characteristic quantity of the quality judgment, eliminating the influence of the melting state of the welding mark on the judgment and reducing erroneous judgment. Can be.

[0011]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an operation system according to an embodiment of the present invention. In this embodiment, the detection target 1
The system operates in a system in which the image is captured by the image input device 3 while the (welding mark) is illuminated by the illumination device 2 and the grayscale image is stored in the storage device 5 in the image processing device 4. What means for welding to the detection target 1 is welding using a laser.

FIG. 2 shows images stored in the storage device 5 in this system. In this embodiment, the two-dimensional detection area 6 of the grayscale image including the welding marks 9 stored in the storage device 5 in the image processing device 4 in consideration of the position where the welding marks 9 can be generated is displayed on the board. It detects and inspects welding marks 9 generated on the parts 7 and 8.

FIG. 3 shows an example of the luminance distribution of the image stored in the storage device 5 in the image processing device 4. The brightness distribution of the grayscale image including the welding marks 9 stored in the storage device 5 in the image processing device 4 is determined by the illumination device 2 so that the brightness of the welding marks 9 becomes as high as possible in the system shown in FIG. Since the illumination is performed such that a large amount of specularly reflected light from the illumination device 9 enters the input device 3, there is a “background” portion where the specularly reflected light from the illumination device 2 is small, and a specularly reflected light from the end portion by the illumination device 2. The image processing device 4 is divided into a “plate-shaped” portion and a “weld mark” portion in which the regular reflection light from the illumination device 2 is large.
Performs a ternarization process on the detection area 6 to obtain Levels 1 and 2 (Level 1 <Level 2), so that Level 1 is "Background" and "Plate-shaped part" and Level 2 is "Plate-shaped part""Weldingmarks" can be individually determined.

FIG. 4 shows a flowchart of this embodiment, and FIG. 5 shows an operation example thereof.

First, the position where the welding mark 9 is formed is determined. The input device 3 captures an image of the welding mark 9 illuminated by the illumination device 2, and creates a luminance distribution in the detection area 6 in a grayscale image including the welding mark 9 accumulated in the storage device 5 in the image processing device 4. Level 1 and Level 2 for performing ternarization processing to separate "background", "plate-like portion" and "weld marks"
(Level 1 <Level 2) is calculated by the image processing device 4 (S1). When the vertical frequency projection 10 of the luminance having the level of 1 or more in the detection area 6 is created (S2), the end of the plate-shaped portion has the specular reflected light from the lighting device 2 and thus the plate-shaped portion in the vertical frequency projection. There are many peaks at positions corresponding to the ends of the peaks, and two peaks are formed. In addition, the horizontal frequency projection 11 of the luminance which becomes the level 2 or more in the detection area 6 is created (S4).
Then, a peak of distribution is formed at a position corresponding to the welding mark 9 having the highest luminance in the horizontal frequency projection, and the width of the peak is determined (S5). A position corresponding to a range surrounded by the plate-shaped portion width 12 in the vertical frequency projection 10 and the welding mark width 13 in the horizontal frequency projection 11 is defined as a welding mark area 14.

Next, the welding mark area 14 obtained by the above method is
In, pass / fail judgment is made. The weld mark width 13 obtained by the above method is used as a feature amount, and if the weld mark width 13 is within a predetermined quality specification range, the weld mark width 13 is determined to be a normal weld mark.
The inspection is terminated after determining that the product is “good”. If it is outside the pass / fail specification range, the frequency of the luminance of level 2 or higher (“weld mark”) within the weld mark area 14 surrounded by the plate-like portion width 12 and the weld mark width 13 obtained by the above method ( Area) as a feature quantity, if the value is within a prescribed range specified in advance, the shape of the welding mark is deformed, but it is assumed that the welding mark has the size of the welding mark to be “good”, and “good” If it is out of the specified range, it will be judged that it does not conform to the shape and size,
It is determined as "defective".

In the above-described embodiment, laser welding is exemplified as a welding means for the detection target 1. However, the present invention is not limited to this, and other welding means such as electron beam welding and arc welding may be used. .

[0019]

As described above, the method for inspecting the appearance of welding marks according to the present invention can quickly and easily find the position of welding marks, and eliminates the influence of the degree of melting of welding marks on judgment. Misjudgments can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an operation system according to an embodiment of the present invention.

FIG. 2 is a plan view showing images stored in a storage device in the operation system according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a luminance distribution of an image stored in a storage device in the operation system according to the embodiment of the present invention.

FIG. 4 is a flowchart of the embodiment of the present invention.

FIG. 5 shows an operation state of the embodiment of the present invention;
Is a plan view of an image, and (b) and (c) are graphs of horizontal frequency projection and vertical frequency projection.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 detection target 2 lighting device 3 input device 4 image processing device 5 storage device 6 detection area 7 plate portion 1 8 plate portion 2 9 welding mark 10 brightness vertical direction projection 11 brightness horizontal direction frequency projection 12 plate portion width 13 Welding mark width 14 Welding mark area

Claims (3)

[Claims] A ternary process is performed on a grayscale image stored in a storage device by an input device for photographing the welding mark to determine a position of a welding mark generated at the time of welding. A welding mark appearance inspection method characterized by performing frequency projection and frequency frequency projection of luminance on a horizontal axis, and finding a position (range) where the frequency is equal to or higher than a certain frequency by finding the position (range). 2. A method for determining the quality of the state of the welding mark by using the horizontal width of the position (range) of the welding mark and the luminance frequency (area) of the position (range) of the welding mark as characteristic amounts. The method for inspecting the appearance of welding marks according to claim 1, wherein: 3. The method according to claim 1, wherein the means for performing the welding is laser welding.