JP3512388B2 - Laser processing monitoring 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 monitoring device and a lighting device for displaying a laser processing state as an image, and more particularly to an in-process monitoring device and a lighting device that can be used for laser welding processing.

[0002]

2. Description of the Related Art In recent years, laser oscillation capability and output control capability have been improved, a large amount of machining data has been accumulated, and laser machining has become widespread such as cutting and welding. Especially YA
G laser welding has many points, such as that it is easy to select and change the working position because it is possible to guide the fiber, high-speed welding of several meters per minute or more, and that there is little heat effect around the joint. Because of its advantages, it is widely used in various manufacturing fields. However, from the viewpoint of quality assurance, the monitoring technology during welding (in-process) and the technology for welding line tracing and welding abnormality detection are not sufficient, and these technologies are required to make a truly practical device. Established is required.

Conventionally, as a method for monitoring a laser processing state in welding or the like, a method of projecting a laser slit light in the vicinity of a processing portion to detect a groove or the like from a light section surface, and a groove portion illuminated in welding pipe manufacturing. A method of obtaining an approximate curve of the open tip edge from the image pickup screen and estimating the intersection of the curves of both edge edges as the welding position (Japanese Patent Laid-Open No. 9-182984), monitoring the change in the amount of light emitted from the welded portion or the reflected light amount of the processing laser light. Method for detecting abnormality (Japanese Patent Laid-Open No. 2000-4276)
9) etc. are disclosed.

The method disclosed in Japanese Patent Laid-Open No. 9-182984 requires the installation of an illuminating device and a camera in front of the processing head.
Further, in the method of Japanese Patent Laid-Open No. 2000-42769, attention is paid to the fact that when laser processing is abnormal, a specific change in light intensity appears. Therefore, an optical system is provided coaxially with the processing laser and the light condensed by the lens is transmitted to the CCD. The judgment is made based on the electric signal corresponding to the light intensity obtained upon incidence, and does not deal with image information. Furthermore, since these methods individually observe the groove and the processed part, a combination of sensors is required to monitor the processed part and the surroundings of the processed part such as the groove. The machining head has to be increased in size because it is necessary to attach the. In addition, two information processing devices are required to perform different signal processing.

The applicant of the present invention has filed Japanese Patent Application Laid-Open No. 11-1463.
87, etc., discloses an arc welding process monitoring device that realizes groove line detection by laser slit light projection and welding point monitoring in the same field of view in arc welding. In this method, the first camera and the second camera have ND filters with different light transmittances mounted on their front surfaces, and both cameras photograph the weld. Then, the image of the arc portion photographed by the first camera and the image of the molten pool and the groove other than the arc portion photographed by the second camera are combined and displayed on the color monitor. This method can detect the groove and monitor the processing point by using the single image information that has been synthesized, but since it is necessary to install the detection head and the slit light projector outside the welding head, the size of the head is increased. Is inevitable.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a compact device for in-process monitoring based on an image of a processing state in a laser processing system, particularly a laser welding processing system. That is.

[0007]

In order to solve the above-mentioned problems, a laser processing monitoring apparatus according to the present invention comprises an image pickup apparatus arranged in the processing head so that the optical axis thereof coincides with that of the processing laser, and an assist device. It is characterized in that it is provided with an illuminating device incorporated in the gas spray nozzle to illuminate the laser processing part, and the laser processing part illuminated by the illuminating device is photographed and an image is displayed. The laser processing monitoring apparatus of the present invention uses a reflecting mirror provided to guide the processing laser to the processing section, and arranges the imaging apparatus at a position coaxial with the processing laser, so that the processing head has an imaging apparatus. In addition to the above, the illumination device is installed in the assist gas blowing nozzle that supplies the assist gas used in association with laser processing to the processing unit, so it is necessary to provide extra accessories to the processing head. And the processing head can be made compact.

The laser processing monitoring apparatus of the present invention is
Only the image processing based on the image information acquired by the imaging device can be used to monitor the processing state such as the groove position, the gap amount of the groove, the irradiation position of the processing laser, the shape of the fusion zone, the bead width, and the detection of the through hole. Information necessary for processing control can be obtained. Further, in the laser processing monitoring apparatus of the present invention, the imaging device includes a first camera adjusted to recognize the laser processed portion and a second camera adjusted to recognize the peripheral portion of the laser processed portion. In addition, the image information captured by each camera can be combined to generate an image showing the state of the laser processing unit.

In the laser processing, the brightness in the processed portion is significantly stronger than that in the peripheral portion of the processed portion, so that it is difficult to clearly recognize the peripheral portion in the image when photographed by one camera. Therefore, two cameras that share the optical axis are provided, and an optical filter or optical diaphragm is installed in front of each camera, or the output amplification factor of the photosensitive element is adjusted to make the first camera illuminate. It is preferable to adjust the sensitivity so as to be compatible with the laser processing portion having a high luminance and to adjust the sensitivity so that the second camera is adapted to the peripheral portion of the processing portion having a low brightness. The images acquired by the two cameras that share such an optical axis capture the same area, so it is possible to acquire the image of the processed part and its surroundings on a single screen by overlapping them as they are. You can

Further, when the image of the first camera and the image of the second camera are combined, the region of the processed portion in the image acquired by the first camera is cut out, and the area other than the processed portion in the image acquired by the second camera is cut out. By cutting out the region and overlapping the two cut-out regions, it is possible to obtain a single image in which both the processed portion and the peripheral portion of the processed portion can be clearly observed. In addition, it is preferable to install the assist gas supply nozzle in front of the illumination optical system inside the assist gas blowing nozzle. In such a configuration, since the assist gas flows from the front of the optical system to the blowout hole of the blowing nozzle,
Not only does the foreign matter not enter the nozzle to keep the optical system clean, but also the optical system does not become unstable due to the gas flow.

The laser processing monitoring apparatus of the present invention is
Further, by providing the control unit, it is possible to determine in real time whether or not the processing position and the processing conditions are appropriate by image processing based on the image information acquired by the image pickup apparatus, and based on this, automatic control of laser processing can be performed. The laser processing monitoring device of the present invention can be applied to welding processing.

At this time, the processing laser position control may be performed based on the groove position information and the laser irradiation position information generated based on the image acquired by the image pickup device. Since the groove and the welded portion are respectively obtained as clear images, the welding head can be guided to the position of the groove for proper welding processing. In addition, the processing conditions can be adjusted online based on the shape of the fusion zone formed in the weld and the state of the through hole.

In particular, when penetration welding or non-penetration welding is performed, it is preferable that the image processing apparatus automatically determines the through hole at the processing laser irradiation position by image processing and notifies it. Further, it is preferable that the image processing result used for the laser processing control is displayed on the image display device so that the operator can observe it.

The illumination device for laser processing monitoring device of the present invention is characterized in that the illumination optical system is provided inside the assist gas blowing nozzle. The illumination device of the present invention combines the illumination function with the assist gas blowing nozzle essential for laser processing, and it is not necessary to add an additional illumination device to the processing head. Therefore, the laser processing device should be made compact. You can Here, if the laser processing assist gas is supplied from the front of the illumination optical system and sprayed onto the laser processing portion, the optical system can be stable and keep clean.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In this embodiment, the monitoring device for arc welding disclosed by the present applicant has been improved so as to be adapted to it by utilizing the characteristics of laser processing. It enables monitoring and processing control. Hereinafter, a laser processing monitoring device and a lighting device according to the present invention will be described in detail based on embodiments. 1 is a block diagram of a laser processing monitoring apparatus of this embodiment, FIG. 2 is an explanatory view of an assist gas nozzle used in this embodiment, and FIG. 3 is a composite image of a laser processing portion when the apparatus of this embodiment is used for welding. FIG. 4 shows an example of FIG.
5 is a drawing for explaining a method for detecting the state of the groove portion from the composite image of FIG. 5, and FIG. 5 is a drawing for explaining a method for detecting a through hole during laser processing.

As shown in FIG. 1, in the laser processing apparatus of the present embodiment, the processing laser beam 2 emitted from the laser beam adjusting apparatus 1 is reflected by the reflecting mirror 3 of the processing head 5 and is applied to the workpiece 4. Irradiate. Laser processing, especially laser welding,
In order to suppress the generation of metal plasma, which is harmful to the processing quality, it is necessary to blow an inert gas such as helium or argon as an assist gas toward the processing point. Also in this embodiment, the assist gas nozzle 6 is additionally provided in front of the processing direction, and the assist gas is supplied to the processing portion.

The assist gas nozzle 6 has a structure as shown in FIG. 2, in which illumination light is introduced into one end portion 8 of the cylindrical main body 7, and a supply nozzle 9 is provided on the side surface of the central portion to assist gas. To supply. The assist gas is blown to the processed portion from the jet port 10 provided at the other end. The illumination light becomes appropriate converged light by the illumination light optical system 11 and is emitted from the ejection port 10 to illuminate the processed portion. The illumination light preferably has a wavelength different from that of the processing laser or heat radiation emitted from the material by the processing, for example, a wavelength of 532n.
m 2-3W YAG second harmonic laser or the like can be used. Since the illumination light optical system 11 is arranged behind the assist gas supply nozzle 9, it is not affected by the flow of the assist gas in the nozzle. Moreover, since the assist gas plays the role of a seal gas, the optical system is prevented from being contaminated by scattered substances during processing and is kept clean.

The processing head 5 has a camera head 14 at the rear.
Is attached, and two color cameras 12 and 13 are set on the camera head 14. The camera is
It is installed so that its optical axis is coaxial with the laser for processing, and the light transmitted through the laser reflection mirror 3 is transmitted through the semi-transmission mirror 15 and the reflection mirror 1.
The light enters through 6 to generate image information of the same area centered on the processed portion. The laser reflecting mirror 3 is made of a material having a large reflectance for the wavelength of the processing laser but a relatively large transmittance for the other regions.
Further, the two cameras 12 and 13 are provided with filters having sensitivities in different wavelength regions, so that one camera (for example, the first camera 12) captures a high-intensity processed portion and the other camera (for example, the second camera 12). The camera 13) captures the peripheral area of the processed part.

The image information of the first camera 12 and the second camera 13 is taken into the image synthesizing device 17, and the area of the processing portion captured by the first camera and the peripheral portion of the processing portion captured by the second camera 13 are captured here. The respective areas are cut and united to form one piece of image information in which the processed portion and the peripheral portion both clearly appear. At this time, an image that is easy to see can be obtained by performing appropriate color conversion. The combined image is displayed on the monitor 18 for observation by the operator, and the image processing device 19 performs image processing to extract information useful for laser processing. The images captured by the first camera and the second camera can be displayed on the monitor 18 as they are.

As useful information that can be obtained by image processing from the image information of the laser processing part and its peripheral area,
There are processing laser irradiation position, shape / area of fusion zone, detection of through hole, size of through hole, groove position in welding, groove gap of groove, bead width, etc. These pieces of information are notified to the operator via the detection result display device 20 and sent to the laser processing control device 21. The detection result display device 20 may be the same as the monitoring monitor 18. When the image of the laser processing part and the image processing result are superimposed and displayed,
The operator can grasp the processing situation more accurately. The laser processing control device 21 controls the laser adjustment device 1 to adjust the processing laser light and adjust the position of the processing head, thereby executing real-time processing control.

For example, it is possible to control the relative positional relationship between the laser irradiation position and the workpiece based on the groove position information to perform automatic groove copying. Further, it is possible to correct the misalignment by measuring the amount of misalignment from the groove position information and the laser position information and adjusting the relative positional relationship between the laser irradiation position and the work. Furthermore, if a through hole is detected during non-through welding, it is determined to be abnormal, and if the through hole is blocked during through welding, it is determined to be abnormal and an operator is alerted. It goes without saying that the image synthesizing device 17 and the image processing device 19 may be configured by a single microcomputer.

FIG. 3 is a view showing a typical example of a composite image obtained by photographing a state where laser welding is performed. The first camera 12 uses a filter that transmits a long wavelength region of visible light and an infrared region, and the second camera 13 uses a filter that cuts red light and infrared light. For this reason, the processing portion 31 irradiated by the processing laser is brightly photographed due to heat generation in almost the center of the image synthesized by the image synthesizing device 17, and the peripheral portion of the molten pool 33 illuminated by the illumination light.
And the weld bead portion 34 is slightly darker in the rear. If there is a small dark circle in the beam irradiation portion, it is a through hole 32.

The material surface 35 illuminated by the illumination light of the YAG second harmonic laser radiated from the front of the welding process is reflected on the outside of the portion emitting red light due to the laser processing heat. The groove portion 36 is displayed in dark because the illumination light does not reach it. In addition, the dark portion 3 is located outside the irradiation area of the illumination light.
It is 7. In order to make the image clearer,
The region appearing as an image on the first camera 12 is cut from the image of the second camera 13, and the first part is cut on the cut portion.
You may fit the image of the camera 12 and synthesize | combine one image.

The material surface 35 is bright due to the reflection of illumination light, while it is dark because no light is reflected from the groove portion 36. Therefore, using the composite image, the groove line 3
The position 6 and the gap, that is, the groove width G can be easily obtained. In the composite image 30 as shown on the right side of FIG. 4, a cutting line AA ′ perpendicular to the direction of the groove 36 is set, and the change in luminance is measured along this cutting line. Then,
As shown on the left side of FIG. 4, the groove portion 36 has a depressed shape. The width of this depressed portion becomes the groove width G.

Since the processing laser irradiates the center of the processing portion 31, the beam irradiation position R can be immediately known from the composite image. Further, the distance between the center line of the groove portion 36 and the beam irradiation position R is the deviation amount D. In the camera image, the beam irradiation part 31 has the highest brightness and the fusion part 33 has the next highest brightness. Since there is a brightness difference between the fusion zone 33 and the portion 34 on the outside thereof, the shape of the fusion zone can be determined by thresholding, and the area of the fusion zone can be easily obtained.

The through hole 32 can be detected as a dark hole existing in the bright beam irradiation portion 31 by a process using an appropriate threshold value, but it is shown in FIG. 5 for mechanical judgment at high speed. A method may be used. That is,
For example, an area consisting of 8 × 8 pixels is used as the window 38, and the average brightness of the central portion 39 of the window 38 and the pixels 40 set at, for example, eight locations around the central portion of the window 38 while slightly swinging the position of the window 38. The difference in average brightness is calculated, and the maximum brightness difference during rocking is compared with an appropriately determined threshold value for determination. If there is the through hole 32, it is darker than the beam irradiating section 31 and the difference in brightness becomes large, so that the presence or absence of the through hole can be immediately determined by a simple calculation. Further, since the weld bead portion following the fusion zone 33 has a convex surface and is not a flat surface, the boundary line can be detected by edge processing. The weld bead width B can be obtained from the shape of the weld bead 34 in the image.

The state of laser processing thus obtained can be displayed to call the operator's attention, or can be supplied to a processing control device and used for automatic control operation.
In recent years, the laser processing speed has become extremely high with the increase of the laser capacity, and a reliable in-process control method has been earnestly desired. However, according to the laser processing monitoring apparatus of the present embodiment, as described above, Laser processing control can be performed in the process. Although this embodiment is applied to laser welding, it goes without saying that the laser processing monitoring apparatus of the present invention can be similarly used for other types of laser processing such as laser cutting and laser drilling.

[0028]

As described above, the laser processing monitoring apparatus and the illuminating apparatus of the present invention incorporate the imaging device in the processing head and use the illuminating apparatus by incorporating it into the assist gas nozzle which is essential for laser processing. , We collect advanced welding information without reducing the number of parts and increasing the size of the processing head part, and generate useful welding information only by image processing based on the obtained information and directly control laser processing. I was able to do it.

[Brief description of drawings]

FIG. 1 is a block diagram of a laser processing monitoring apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of an assist gas nozzle used in this embodiment.

FIG. 3 is a drawing showing an example of a composite image of a laser processing portion when the apparatus of this embodiment is used for welding.

FIG. 4 is a diagram illustrating a method of detecting the state of the groove portion from the composite image of FIG.

FIG. 5 is a diagram illustrating an example of a method of detecting a through hole during laser processing in this embodiment.

[Explanation of symbols]

1 Laser adjustment device 2 Processing laser light 3 Laser reflector 4 Work piece 5 processing head 6 Assist gas nozzle 7 Nozzle body 8 Illumination side end 9 supply nozzles 10 spouts 11 Illumination optical system 12, 13 color camera 14 camera head 15 Semi-transparent mirror 16 Reflector 30 composite images 31 Laser irradiation part 32 through holes 33 Melting part 34 Weld bead 35 Illumination light irradiation unit 36 groove part 37 Areas not illuminated 38 windows 39 Central pixel part 40 peripheral pixels

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiro Nakabayashi 118 Futtsuka, Noda City, Chiba Prefecture Kawasaki Heavy Industries, Ltd. Noda Factory (56) References JP 2000-176673 (JP, A) JP 64 -2795 (JP, A) JP 11-277231 (JP, A) JP 10-328865 (JP, A) JP 5-8067 (JP, A) (58) Fields investigated (Int.Cl) . ^7, DB name) B23K 26/00 - 26/42

Claims (8)

(57) [Claims] 1. An illumination device, which is incorporated in an imaging device disposed in a processing head so that an optical axis thereof coincides with that of a processing laser, and an assist gas blowing nozzle for blowing an assist gas from a jet port to a laser processing portion. An illuminating device for irradiating the laser-processed portion by radiating from the ejection port, and an image display device ,
An image processing device is provided, and the laser processing part illuminated by the illumination device is photographed by the imaging device and displayed on the image display device.
However, the image processing device uses the image processing to process the laser light.
A laser processing monitoring device that detects and reports a through hole at the shooting position . 2. The image pickup device includes a first camera adjusted to recognize a laser processed portion and a second camera adjusted to recognize a peripheral portion of the laser processed portion, and further comprises: the image processing apparatus laser processing monitoring device according to claim 1, wherein by combining the image information captured by the camera, wherein the benzalkonium generate an image showing the state of the laser processing unit. 3. The illumination optical system of the illumination device is provided inside the assist gas blowing nozzle, and the assist gas is supplied in front of the illumination optical system. Laser processing monitoring device. 4. The laser according to claim 1, further comprising a control unit, the control unit performing laser processing control based on information of an image captured by the imaging device. Processing monitoring device. 5. The laser processing monitoring device according to claim 1, wherein the laser processing is welding processing. 6. The laser processing monitoring device according to claim 5, wherein the control unit controls the processing laser position based on the groove position information and the laser irradiation position information. 7. The laser processing monitoring device according to any one of claims 1 to 6, characterized in that said image display device for displaying an image processing result used to perform the laser processing control. 8. The image processing device comprises a window for detecting a through hole.
In the center of the window while rocking the window
Shake by calculating the difference between the average brightness and the average brightness in the surrounding area
Among them, the maximum brightness difference is obtained, and the maximum brightness difference is a predetermined threshold value.
Characterized by determining that there is a through hole when the size is larger
The laser processing model according to any one of claims 1 to 7.
Nittering device.