Laser machining monitoring device

Abstract

To provide a laser machining monitoring device enabling highly accurate acquisition of a temperature distribution of a laser machining part during laser machining.SOLUTION: A laser machining monitoring device is such a device as to detect light having two different wavelengths and emitted from a laser machining part, and measure a temperature from the ratio of them. The device is provided with: at least two light sensor parts h5, h6 having two sensors sa5, sb5, sa6, sb6 each detecting lights M41, M42 emitted from each of at least two measurement points p5, p6 as one set. At least two light sensor parts have sensor sensitivity detecting light having a shorter wavelength of the light sensor part, as the light emitted from a position closer to a laser irradiation position p2, is detected.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a laser processing monitoring device that can accurately acquire the temperature distribution of a laser processing part during laser processing and monitor the laser processing state.

Background Art

[0002] Laser processing technology is a technology that irradiates a workpiece with laser light to melt and vaporize the workpiece, weld it to another workpiece, or change the shape by melting and evaporating a part of the workpiece. Laser processing technology is generally widespread in a wide range of fields such as household appliances, precision instruments, or automobile parts. In laser processing, there is known a laser processing apparatus that measures the temperature in the processing region by detecting the thermal radiation light emitted from the region irradiated with the laser light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the laser processing apparatus according to Patent Document 1, as shown in FIG. 8, it includes a first light detection unit 34, a second light detection unit 35, and a first temperature detection unit 36. The first light detection unit 34 and the second light detection unit 35 detect thermal radiation light of different wavelengths branched by the light extraction unit 33, and the first temperature detection unit 36 corrects the measurement temperature error due to the temperature change of the housing 31.

[0005] Therefore, even in the case of laser welding where the temperature distribution in the laser processing region is large and the processing state is detected by grasping the temperature distribution, it is not possible to measure the distribution of the thermal radiation light intensity, and it only detects the average temperature of the processing region, and the temperature distribution cannot be measured.

[0006] Also, when the thermal radiation light intensity distribution is large, if the sensitivity of the measurement unit is set according to the region with strong thermal radiation light intensity, the detection light intensity in the region with weak thermal radiation light intensity will decrease, and the temperature in the region with strong thermal radiation light intensity will be detected as the dominant value, making it impossible to accurately measure the temperature distribution. On the other hand, if the sensitivity of the measurement unit is set according to the region with weak thermal radiation light intensity, the measured value itself will saturate in the region with strong thermal radiation light intensity, resulting in the problem that the temperature distribution cannot be measured.

[0007] Therefore, an object of the present invention is to solve the above problems and provide a laser processing monitoring device capable of accurately acquiring the temperature distribution of a laser processing part during laser processing.

Means for Solving the Problems

[0008] In order to solve the above problems, a laser processing monitoring device according to one aspect of the present invention is a device that detects light of two different wavelengths emitted from a laser processing part and measures the temperature from the ratio thereof, and has at least two light sensor units, each of which has a set of two sensors that respectively detect light emitted from at least two or more measurement points, and the at least two light sensor units have a sensor sensitivity to detect light of a shorter wavelength for the light sensor unit that detects light emitted from a position closer to the laser irradiation position.

[0009] In order to solve the above problems, a laser processing monitoring device according to another aspect of the present invention is a device that detects light of two different wavelengths emitted from a laser processing part and measures the temperature from the ratio thereof, and has at least two light sensor units, each of which has a set of two sensors that respectively detect light emitted from at least two or more measurement points, and the at least two light sensor units include an attenuation mechanism with a higher attenuation rate for the light sensor unit that detects light emitted from a position closer to the laser irradiation position, and detect the light attenuated by the attenuation mechanism with the sensor.

[0010] With this configuration, it becomes possible to measure the temperature distribution of the entire melting part.

Advantages of the Invention

[0011] As described above, according to the laser processing monitoring device according to the above aspect of the present invention, an optical sensor unit having a sensor sensitivity for detecting light with a shorter wavelength is used for an optical sensor unit that detects light emitted from a position closer to the laser irradiation position, or an optical sensor unit including an attenuation mechanism having a higher measurement attenuation rate for an optical sensor unit that detects light emitted from a position closer to the laser irradiation position. By measuring the temperature distribution in the vicinity of the laser irradiation unit, the temperature distribution of the laser processing unit during laser processing can be obtained with high accuracy.

Brief Description of the Drawings

[0012]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0014] (First Embodiment) FIG. 1A is a schematic diagram showing the configuration of a laser processing monitoring apparatus according to the first embodiment of the present invention, and FIG. 1B is an enlarged view of the measurement unit. In FIG. 1, the direction in which light travels is indicated by an arrow.

[0015] A laser processing monitoring apparatus is an apparatus that detects two different wavelengths of light emitted from a laser processing unit and measures the temperature from the ratio thereof, and includes a dichroic mirror 1, a condenser lens 2, a lens 4, a measurement unit 20, and a data collection / arithmetic unit 8.

[0016] The laser beam L1 for processing is a laser beam that is emitted from a laser oscillator (not shown) and then collimated by a collimating optical system so as to propagate the laser beam to the processing unit. In the present embodiment, as an example, a continuous wave (CW) having a wavelength of 1070 nm is used, laser welding is assumed, and the output power can be irradiated up to a maximum of 3 kW.

[0017] The dichroic mirror 1 is arranged to be inclined at, for example, 45 degrees with respect to the optical axis of the processing laser beam L1, and has a coating that reflects the wavelength of 1070 nm of the processing laser beam L1 and transmits the radiant light from the processing region. Since the radiant light extends over a wide range in the visible region or the near-infrared region, as an example, light having a wavelength of 350 to 2000 nm excluding the wavelength of 1070 nm of the laser beam L1 is transmitted by 90% or more, and the wavelength of 1070 nm of the laser beam L1 is reflected by 90% or more. Depending on the configuration of the optical system, the reflected wavelength and the transmitted wavelength may be interchanged.

[0018] The condensing lens 2 is disposed on the workpiece 3 side of the dichroic mirror 1, and is a lens for condensing the laser beam L2 that has transmitted the laser beam L1. For example, it has a focal length of 255 mm and transmits 50% or more of the laser beam with a wavelength of 1070 mm.

[0019] The workpiece 3 is supported, for example, on a processing stage 21 composed of an XYZθ table and a jig capable of fixing the workpiece 3. Such a processing stage 21 is operationally controlled so as to be able to scan the irradiation position in accordance with the irradiation of the laser beam L1. As a method of scanning the laser beam L1 with respect to the workpiece 3, (Method 1) a method of moving the processing stage 21 with the laser beam L1 fixed, (Method 2) a method of changing the angle of the laser beam L1 with a mirror and then condensing it with a condensing lens. For example, a method of installing an optical scanner such as a galvanometer mirror, (Method 3) a combination of the above (Method 1 to Method 2), etc. are possible.

[0020] The lens 4 is disposed on the side opposite to the workpiece 3 side of the dichroic mirror 1. As an example, it uses a lens with a focal length of 100 mm that transmits 50% or more of the light with a wavelength of 350 to 2000 nm.

[0021] The measurement unit 20 is disposed on the side opposite to the dichroic mirror 1 side of the lens 4, and includes a half mirror 5 and the like as described below.

[0022] The half mirror 5, as an example, transmits about 50% and reflects about 50% of the light with a wavelength of 350 to 2000 nm.

[0023] The measurement light M1 is the reflected light and the emitted light from the processing part, and includes at least the light with a wavelength of 350 to 2000 nm. Since heat is generated in the processing part, thermal radiation light is also included, and the actually emitted wavelength includes up to the infrared wavelength region. The measurement light M1 becomes parallel measurement light M2 by passing through the condensing lens 2, becomes converging measurement light M3 by passing through the lens 4, and is branched into measurement light M41 and measurement light M42 by passing through the half mirror 5.

[0024] Fig. 1B shows an enlarged view of the measurement unit 20. The measurement unit 20 is composed of a half mirror 5 and optical sensor units h1 to h7. The optical sensor units h1 to h7 are provided with a band-pass filter group 6a, a band-pass filter group 6b, a sensor group 7a, and a sensor group 7b in order to detect the light M41 and M42 respectively radiated from the measurement points p1 to p7.

[0025] The first band-pass filter group 6a is composed of a plurality of filters fa1 to fa7 corresponding to the measurement points p1 to p7 respectively, and is a filter capable of transmitting only wavelengths in the vicinity of wavelengths λa1 to λa7 nm corresponding to the measurement points p1 to p7 respectively. The second band-pass filter group 6b is composed of a plurality of filters fb1 to fb7 corresponding to the measurement points p1 to p7 respectively, and is a filter capable of transmitting only wavelengths in the vicinity of wavelengths λb1 to λb7 nm corresponding to the measurement points p1 to p7 respectively. The corresponding wavelengths of the band-pass filters are not limited to the above wavelengths, and filters with different wavelengths of λaN and λbN (N is a natural number) are acceptable.

[0026] The first sensor group 7a and the second sensor group 7b are each composed of a plurality of sensors sa1 to sa7 and sb1 to sb7 corresponding to the measurement points p1 to p7 respectively, and are sensitive to light transmitted through the corresponding wavelengths λa1 to λa7 nm and λb1 to λb7 nm of the first and second band-pass filter groups 6a and 6b used together with the first and second sensor groups 7a and 7b respectively. By having a sampling period that can achieve a sampling time sufficiently short with respect to the processing time of the laser light, real-time temperature measurement of the processing part becomes possible. For example, for a laser welding time of 100 ms, if the sampling rate is 50 kHz, the sampling time is 2 μs, so 50,000 data points can be obtained and the temperature change every 2 μs at least can be grasped. Fig. 1B shows a state where the measurement light M41 transmitted through the filter fa5 corresponding to the measurement point p5 is incident on the sensor sa5, and the measurement light M42 transmitted through the filter fb5 corresponding to the measurement point p5 is incident on the sensor sb5 respectively.

[0027] Here, in this first embodiment, there are at least two or more measurement points, for example, two sensors that detect the light M41 and M42 emitted from each of p5 and p6, for example, sa5, sb5; sa6, sb6, are provided as a set in a photosensor unit, for example, h5; h6, with at least two such photosensor units. These at least two photosensor units, for example, h5; h6, have a sensor sensitivity to detect light with a shorter wavelength (for example, the photosensor unit h5 has a shorter wavelength than the photosensor unit h6) than the photosensor unit that detects the light emitted from a position closer to the laser irradiation position p2. Thus, each of the photosensor units h1 to h7 is composed of one filter of the band-pass filter group 6a, one filter of the band-pass filter group 6b, one sensor of the sensor group 7a, and one sensor of the sensor group 7b. For example, the photosensor unit h5 is composed of one filter fa5 of the band-pass filter group 6a, one filter fb5 of the band-pass filter group 6b, one sensor sa5 of the sensor group 7a, and one sensor sb5 of the sensor group 7b. Also, for example, the photosensor unit h6 is composed of one filter fa6 of the band-pass filter group 6a, one filter fb6 of the band-pass filter group 6b, one sensor sa6 of the sensor group 7a, and one sensor sb6 of the sensor group 7b.

[0028] The data collection and calculation device 8 is connected to the sensor groups 7a and 7b and collects and calculates the obtained data. Specifically, the data collection and calculation device 8 collects the signal intensities detected by the sensor groups 7a and 7b and calculates the temperature from the ratio.

[0029] According to such a configuration, after the laser beam L1 is reflected by the dichroic mirror 1, it becomes the laser beam L2 that passes through the condenser lens 2 and is irradiated onto the irradiation position P on the workpiece 3. In laser processing, when the irradiation position P corresponds to the focal position, the laser beam L2 is the most focused and the processing efficiency is improved. However, depending on the required processing, it is not limited to processing at the focal position, and processing may also be performed at a defocus position where the irradiation position P does not coincide with the focal position of the lens. At the irradiation position P, a processing phenomenon due to the laser beam L2 appears as a processed portion, and the reflected light from which the laser beam L2 is reflected at the irradiation position P, and the light emitted by the interaction with the workpiece 3, for example, the plasma light emitted when the evaporated workpiece is turned into plasma and emits light, or / and the thermal radiation light emitted when the workpiece 3 is heated up and melted to become a high temperature returns in the direction of the condenser lens 2 as the measurement light M1. At this time, the measurement light M1 includes at least two different wavelengths emitted from the laser processing portion.

[0030] Thereafter, the measurement light M2 that has passed through the condenser lens 2 and the dichroic mirror 1 becomes the converging measurement light M3 after passing through the lens 4 and is branched into two measurement lights M41 and M42 by the half mirror 5.

[0031] The branched measurement light M41 passes through the first band-pass filter group 6a and then forms an image on the first sensor group 7a, and the branched measurement light M42 passes through the second band-pass filter group 6b and then forms an image on the second sensor group 7b.

[0032] Fig. 2A shows the melting state of the workpiece 3 during laser irradiation, and as an example, the processed portion positions are divided into positions p1 to p7 and displayed. The laser irradiation position P corresponds to the processed portion position p2 in this embodiment. Fig. 2B shows the relationship between the processed portion position and the melting portion temperature in the laser-irradiated workpiece 3, and Fig. 2C shows the relationship between the processed portion position and the melting depth.

[0033] At the laser irradiation position p2, since the region with the highest energy density of the focused laser beam L2 is irradiated, the temperature of the molten part is the highest and the melting depth is the deepest. On the other hand, at positions p1, p3 to p7, the temperature of the molten part gradually decreases as the distance from the laser irradiation position p2 increases. Also, since a molten part is formed that trails in the direction opposite to the scanning with respect to the laser scanning direction indicated by the arrow, as shown in Fig. 2B, the temperature drop in the rear of the scanning direction from the laser irradiation position p2, which is the irradiation part, is small, and as shown in Fig. 2C, the change in the melting depth also shows a gentle tendency.

[0034] Fig. 3 shows the measurement optical system. Since the processing part is a wide area from positions p1 to p7 as described in Fig. 2A, the measurement light M2 is also detected separately. The light radiated from the vicinity of position p1 is defined as measurement light ma1, and after the measurement light ma1 passes through the condenser lens 2 and the lens 4, it is defined as measurement light mb1. Similarly, when N is a natural number from 1 to 7, after the measurement light maN passes through the condenser lens 2 and the lens 4, it is defined as measurement light mbN. Hatching is added to and displayed for the measurement lights ma2 and mb2 from the position p2, which is the laser irradiation position. For simplicity, in addition to the measurement light M41 passing through the half mirror 5, the reflected measurement light M42 is also folded back by the half mirror 5, and the explanation is given using Fig. 3, which is a schematic diagram of the same optical system.

[0035] In this embodiment, the temperature of the processing part is measured using a method called the two-color thermometer method. Two wavelengths that are close and have almost the same emissivity are selected, the radiant energies of the two wavelengths are detected, and the temperature is calculated from the energy ratio of the two wavelengths. It is preferable that the difference between the wavelength λaN and the wavelength λbN is about 50 to 300 nm.

[0036] Even when the radiant energy differs due to emissivity at the same temperature, the radiant energy in two wavelength bands increases and decreases in the same manner. Therefore, there is no change in the radiant energy ratio, and the temperature is uniquely determined by the ratio of the radiant energy. In the present embodiment, the sensor groups 7a and 7b detect the radiant energies of two different wavelengths, and the data collection / arithmetic unit 8 collects the signal intensities detected by the sensor groups 7a and 7b, and calculates the temperature from the ratio.

[0037] Fig. 4A shows the relationship between the wavelength and the spectral energy density (radiant energy) according to Planck's law. The white circles in Fig. 4A indicate the wavelengths with the highest radiant energy at each temperature, and Fig. 4B shows the relationship between the temperature and the wavelength at which the radiant energy is maximum. It can be seen that the wavelength at which the radiant energy is maximum tends to increase as the temperature decreases. For example, in the vicinity of wavelength X1 in Fig. 4A, there is a difference in the radiant energy intensity up to about 373K to 2000K, but above 2000K, the distance between the graphs is small, and there is a problem that the influence of measurement error or noise cannot be ignored and the SNR becomes small even when the ratio is obtained. On the other hand, in the vicinity of wavelength X2, it is impossible to measure in the low-temperature region below 2000K, but the distance between the graphs (for example, the distance between E1 and E2 in Fig. 4A) in the high-temperature region above 2000K is large, and it can be seen that the ratio can be obtained with high accuracy. From this, it can be seen that it is preferable to detect light with a long wavelength when detecting a low temperature and to detect light with a short wavelength when detecting a high temperature.

[0038] From the above, in the present embodiment, among the processing part positions p1 to p7, at the laser irradiation position p2 where the temperature of the molten part is the highest, a sensor with high sensitivity to a short wavelength is selected, and as the distance from the laser irradiation position p2 increases, at least a sensor with higher sensitivity to a wavelength longer than the laser irradiation position p2 is selected.

[0039] For example, in the case of iron with a melting point of 1811 K and a boiling point of 3135 K, except for some ultra-high temperature regions near the laser irradiation position p2 where it is difficult to measure plasmas at temperatures above 10000 K, in order to measure the region of 1500 - 6000 K where melting and boiling occur in the vicinity, band-pass filters fa2 and fb2 with λa2 = 500 nm and λb2 = 600 nm and sensors sa2 and sb2 with high sensitivity in the vicinity of 500 - 600 nm are used. Also, at positions p1 and p7, it is a region where melting may or may not occur. To stably measure 1000 K - 2000 K, band-pass filters fa1 and fa7 with a longer wavelength of λa1 = λa7 = 1600 nm and band-pass filters fb1 and fb7 with λb1 = λb7 = 1500 nm are used compared to the laser irradiation position p2, and sensors sa1, sb1, sa7, and sb7 with high sensitivity in the range of 1500 - 1600 nm are used (the wavelength at position X3 in Fig. 4A). For positions p3 - p6, the wavelengths can be evenly allocated, or referring to the estimated temperature of the melting part in Fig. 2B or / and the melting depth in Fig. 2C, the detection wavelengths at positions p3, p4, p5, etc., which are closer to the laser irradiation position p2, can be set shorter than the equal division, and the transmission wavelengths of the band-pass filters and the sensitivities of the sensors can be set.

[0040] By ensuring that at least the transmission wavelength of the band-pass filter satisfies the following relational expression 1 and using a corresponding sensor with the highest sensitivity at the transmission wavelength of the band-pass filter, it is possible to prevent the temperature measurement value from saturating, maintain the SN ratio of the measurement signal, and measure the temperature, enabling the measurement of the temperature distribution of the entire melting part.

[0041] (Relational expression 1) λa2 (laser irradiation position) ≤ λa1 λa2 (laser irradiation position) ≤ λa3 ≤ λa4 ≤ λa5 ≤ λa6 ≤ λa7 λb2 (laser irradiation position) ≤ λb1 λb2 (laser irradiation position) ≤ λb3 ≤ λb4 ≤ λb5 ≤ λb6 ≤ λb7 However, wavelengths λa1 = λa2 = λa3 = λa4 = λa5 = λa6 = λa7 and wavelengths λb1 = λb2 = λb3 = λb4 = λb5 = λb6 = λb7 are excluded. Further, an attenuation filter may be installed in the optical system so that the signal does not saturate according to the sensitivity of the sensor.

[0042] In this first embodiment, the processing part is divided into seven positions, seven sensors and filters are used, and the laser irradiation position is set to p2. However, the present invention is not limited to the number of divisions or the laser irradiation position in this first embodiment, and can be changed according to the size of the melting part, the size of the sensor, or the configuration of the measurement system. Although sensors are used in this embodiment, a camera having a similar function may be used, and each pixel may be regarded as a sensor array.

[0043] Expressing relational expression 1 as a general relational expression 2 results in the following.

[0044] (Relational expression 2) Assuming that the number of divisions of the processing part is N and the laser irradiation position is M λaM (laser irradiation position) ≦ λa (M - 1) ≦ λa (M - 2) ··· ≦ λa1 λaM (laser irradiation position) ≦ λa (M + 1) ≦ λa (M + 2) ··· ≦ λaN λbM (laser irradiation position) ≦ λb (M - 1) ≦ λb (M - 2) ··· ≦ λb1 λbM (laser irradiation position) ≦ λb (M + 1) ≦ λb (M + 2) ··· ≦ λbN However, except for the wavelengths λa1 = λa2 ··· = λaN and the wavelengths λb1 = λb2 ··· = λbN.

[0045] According to the first embodiment, since the optical sensor units h1 to h7 are configured to have a sensor sensitivity for detecting light of a shorter wavelength as the optical sensor unit that detects light radiated from a position closer to the laser irradiation position p2, it is possible to measure the temperature while preventing the temperature measurement value from saturating and maintaining the SN ratio of the measurement signal, and it is possible to measure the temperature distribution of the entire melting part.

[0046] (Second Embodiment) FIG. 5 shows a schematic diagram of the laser processing monitoring apparatus according to the second embodiment of the present invention.

[0047] Those having the same functions as those in the first embodiment are denoted by the same reference numerals and their description is omitted.

[0048] In FIGS. 5A and 5B, as an example of the attenuation mechanism 19, the attenuation filter groups 9a and 9b can be attenuated by partially transmitting, partially absorbing, or reflecting wavelengths in the range of 350 to 2000 nm as an example in this embodiment.

[0049] An enlarged view of the measurement unit 20 is shown in FIG. 5B, and the measurement optical system is shown in FIG. 6. The measurement unit 20 includes a half mirror 5 and optical sensor units h1 to h7. The optical sensor units h1 to h7 are each provided with a band-pass filter group 6a, a band-pass filter group 6b, an attenuation filter group 9a, an attenuation filter group 9b, and sensor groups 10a and 10b in order to detect the light M41 and M42 emitted from each of the measurement points p1 to p7. The attenuation mechanism 19 is composed of, for example, an attenuation filter or a combination of mirrors such as a half mirror or a dichroic mirror. An example of the attenuation filter is an ND filter.

[0050] The attenuation filter group 9a is composed of a plurality of attenuation filters ga1 to ga7 corresponding to each of the measurement points p1 to p7, and each is a filter with attenuation rates da1 to da7. The attenuation filter group 9b is composed of a plurality of attenuation filters gb1 to gb7 corresponding to each of the measurement points p1 to p7, and each is a filter with attenuation rates db1 to db7.

[0051] Since the sensor groups 10a and 10b are each composed of a plurality of the same sensors ta1 to ta7 and tb1 to tb7 corresponding to each of the measurement points p1 to p7, their sensitivity characteristics with respect to wavelength are the same.

[0052] According to such a configuration, when detecting the measurement lights M41 and M42 from the processing unit with the sensors ta1 to ta7, simply setting the transmission wavelength at the laser irradiation unit p2 and the detection wavelength at the sensors to be the shortest with the band-pass filters fa1 to fa7, sensors ta1 to ta7 with the same specifications (i.e., the same sensitivity characteristics with respect to wavelength) cannot be used. This is because the detection signal saturates in sensor ta2 due to strong radiation energy, and the detection signal becomes weak in sensor ta7 due to weak radiation energy. In the present second embodiment, it is characterized in that the attenuation rate of the attenuation filter at the laser irradiation position p2 is set to be the largest, and at least a filter with an attenuation rate smaller than that at the laser irradiation position p2 is used as the distance from the laser irradiation position p2 increases.

[0053] In FIG. 7, based on the data in FIG. 4, the relationship between the radiation energy intensity and the wavelength is shown for the case where there is no attenuation (condition Y) for 373 to 1500K and the case where the radiation is attenuated to 1 / 1000 using an attenuation filter with an optical density OD3 for 2000 to 6000K (condition Z). It can be seen that the maximum radiation intensity is the same when detecting 373 to 1500K using a wavelength of 1500 to 1600nm and when detecting 1500 to 6000K using a wavelength of 500 to 600nm.

[0054] For the laser irradiation position p2, an attenuation filter with the same optical density OD3 as in the above condition Z is used, and for the positions p1 and p7, attenuation is not performed (optical density OD0) as in the above condition Y. For the positions p3 to p6, the attenuation rate may be evenly allocated, or with reference to the estimated temperature of the melting part in FIG. 2B and / or the melting depth in FIG. 2C, the attenuation rate of the attenuation filter corresponding to the positions p3, p4, p5, etc. close to the laser irradiation position p2 may be set higher than the even allocation.

[0055] From the above, by using an attenuation filter having the following relational expression 3 in addition to the band-pass filter, stable temperature measurement can be realized using sensor groups 10a and 10b with the same specifications.

[0056] (Relational Expression 3) da2 (laser irradiation position) ≥ da1 da2 (laser irradiation position) ≥ da3 ≥ da4 ≥ da5 ≥ da6 ≥ da7 db2 (laser irradiation position) ≥ db1 db2 (laser irradiation position) ≥ db3 ≥ db4 ≥ db5 ≥ db6 ≥ db7 However, the attenuation rates da1 = da2 (laser irradiation position) = da3 = da4 = da5 = da6 = da7 and the attenuation rates db1 = db2 (laser irradiation position) = db3 = db4 = db5 = db6 = db7 are excluded.

[0057] Also in this second embodiment, the processing part is divided into seven positions, seven sensors and filters are used, and the laser irradiation position is set to p2. However, it is not limited to the number of divisions or the laser irradiation position in this second embodiment, and can be changed according to the size of the melting part, the size of the sensor, and / or the configuration of the measurement system. Although sensors are used in this second embodiment, a camera having a similar function may be used, and each pixel may be regarded as a sensor array. When expressed as a general relational expression 4, it is as follows.

[0058] (Relational Expression 4) When the number of divisions of the processing part is N and the laser irradiation position is M daM (laser irradiation position) ≥ da(M - 1) ≥ da(M - 2) ··· ≥ da1 daM (laser irradiation position) ≥ da(M + 1) ≥ da(M + 2) ··· ≥ daN dbM (laser irradiation position) ≥ db(M - 1) ≥ db(M - 2) ··· ≥ db1 dbM (laser irradiation position) ≥ db(M + 1) ≥ db(M + 2) ··· ≥ dbN However, the attenuation rates da1 = da2 = da3 = da4 = da5 = da6 ··· = daN and the attenuation rates db1 = db2 = db3 = db4 = db5 = db6 ··· = dbN are excluded.

[0059] Note that the values of the detection wavelength or the attenuation rate vary depending on the type of the workpiece or the laser and / or the processing conditions, and are not limited to the values described above.

[0060] The case where a continuous wave with a maximum output of 3 kW and a wavelength of 1070 nm is used as the laser light is shown. However, it is possible to select the required output and the optimal laser wavelength according to the light absorption characteristics of the workpiece 3, and pulsed laser light may also be used.

[0061] Although wavelengths from 350 to 2000 nm were used as the detection wavelengths, wavelengths less than 350 nm are in the deep ultraviolet region and are not suitable for measurement because they are affected by attenuation due to moisture in the air. Also, as shown in Fig. 4A, by detecting light with wavelengths up to 8 μm, it is possible to measure down to a low temperature range of 373 K. Therefore, it is desirable to detect light with wavelengths from 350 nm to 8 μm. However, the performance such as the cost or responsiveness of a sensor capable of detecting light with wavelengths from 350 nm to 8 μm may not be sufficient. For this reason, a sensor that is excellent in terms of performance such as the cost or responsiveness of the sensor and can detect light with wavelengths from 350 to 2000 nm, which can also measure aluminum (melting point 660 °C = 933 K), the metal with the lowest melting point among aluminum, copper, and iron, which are often used in laser welding, is preferably suitable in practical use.

[0062] In addition, in the present embodiment, a combination of filters having different optical densities is used as the filter group, but a filter with continuously changing optical density may also be used.

[0063] Furthermore, good results can also be obtained by combining the first embodiment and the second embodiment.

[0064] According to the second embodiment, the optical sensor unit includes an attenuation mechanism 19 with a higher measurement attenuation rate for the optical sensor unit that detects light radiated from a position closer to the laser irradiation position p2, and detects the light attenuated by the attenuation mechanism 19. Therefore, it is possible to measure the temperature while preventing the temperature measurement value from saturating and maintaining the signal-to-noise ratio of the measurement signal, and it is possible to measure the temperature distribution of the entire molten part.

[0065] (Effects, etc.) As described above, according to the first or second embodiment, by setting the detection wavelength at the laser irradiation position p2 to be the shortest or setting the attenuation rate of the attenuation filter to be the largest, in other words, a photosensor unit that detects light emitted from a position closer to the laser irradiation position p2 has a sensor sensitivity for detecting light of a shorter wavelength, or a photosensor unit including an attenuation mechanism 19 with a higher measurement attenuation rate for detecting light emitted from a position closer to the laser irradiation position p2 is used to measure the temperature distribution in the vicinity of the laser irradiation unit. As a result, it becomes possible to measure the temperature while preventing the temperature measurement value from saturating and maintaining the signal-to-noise ratio of the measurement signal, and it becomes possible to accurately measure the temperature distribution of the entire molten portion, that is, the temperature distribution of the laser processing portion during laser processing.

[0066] Note that by appropriately combining any of the above-described various embodiments or modification examples, the respective effects can be achieved. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, and combinations of features from different embodiments or examples are also possible.

Industrial Applicability

[0067] The laser processing monitoring device according to the above aspect of the present invention can detect the processing state by monitoring the temperature distribution of the molten portion in laser processing, for example, by evaluating the temperature distribution of the molten portion in real time, and can stabilize laser processing including laser welding.

Explanation of Reference Numerals

[0068] 1: Dichroic mirror 2: Condensing lens 3: Workpiece 4: Lens 5: Half mirror 6a, 6b: First and second band-pass filter groups 7a, 7b: First and second sensor groups 8: Data collection and calculation device 9a, 9b: Attenuation filter group 10a, 10b: Sensor group 19: Attenuation mechanism 20: Measurement unit 21: Processing stage da1~da7, db1~db7: Attenuation rate fa1~fa7, fb1~fb7: Filter ga1~ga7, gb1~gb7: Attenuation filter ha1~ha7, hb1~hb7: Optical sensor part M1: Measurement light M2: Parallel measurement light M3: Converging measurement light M41: Branched measurement light M42: Branched measurement light p1~p7: Measurement points sa1~sa7, sb1~sb7, ta1~ta7, tb1~tb7: Sensors λa1~λa7, λb1~λb7: Wavelength

Claims

1. An apparatus for detecting light of two different wavelengths emitted from a laser processing unit and measuring temperature from the ratio thereof, comprising: at least two optical sensor units, each set having two sensors for respectively detecting light emitted from at least two measurement points; wherein the at least two optical sensor units have a sensor sensitivity for detecting light of a shorter wavelength for the optical sensor unit that detects light emitted from a position closer to the laser irradiation position; a laser processing monitoring apparatus.

2. An apparatus for detecting light of two different wavelengths emitted from a laser processing unit and measuring temperature from the ratio thereof, comprising: at least two optical sensor units, each set having two sensors for respectively detecting light emitted from at least two measurement points; wherein the at least two optical sensor units include an attenuation mechanism having a higher attenuation rate for measurement for the optical sensor unit that detects light emitted from a position closer to the laser irradiation position, and the sensor detects the light attenuated by the attenuation mechanism; a laser processing monitoring apparatus.

3. wherein the two wavelengths are in the range of 350 nm to 8 μm The laser processing monitoring apparatus according to claim 1 or 2.

4. wherein the two wavelengths are in the range of 350 nm to 2000 nm The laser processing monitoring apparatus according to claim 1 or 2.

5. wherein the attenuation mechanism is composed of an attenuation filter or a combination of mirrors such as a half mirror or a dichroic mirror The laser processing monitoring apparatus according to claim 2.

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