Laser processing monitoring device

Abstract

This laser processing monitoring device comprises at least two light sensors (16, 17, 23) for detecting emitted light generated from a workpiece being laser processed, and light-attenuating elements (13, 21) disposed in at least one optical path among at least two optical paths to which the emitted light being transmitted to the at least two light sensors is branched, wherein the transmittance of the light-attenuating elements is set such that the measurement ranges of the at least two light sensors are continuous.

Description

Laser processing monitoring device

[0001] The present disclosure relates to a laser processing monitoring device capable of monitoring laser processing.

[0002] Laser welding is a technology in which a workpiece is irradiated with laser light emitted from a laser oscillator, the workpiece is melted by the heat of the laser light, and then welded to another workpiece, thereby mechanically and / or electrically connecting the workpieces. Laser welding is generally widespread in a wide range of fields, such as home appliances, precision instruments, and automobile parts.

[0003] In such laser welding techniques, various adjustment items are generally adjusted by trial and error depending on the shape or size of the individual laser oscillator or the workpiece, but there are cases where such trial and error adjustments are not sufficient to obtain a processed product of the specified quality.

[0004] Patent Document 1 discloses that the laser processing state can be monitored in real time by detecting the welding light at the processing point.

[0005] Japanese Patent Application Laid-Open No. 2021-186848

[0006] As shown in FIG. 7, the laser processing apparatus disclosed in Patent Document 1 includes optical sensors 100 to 102, and each sensor observes the welding light LW100 emitted from a workpiece W100 according to wavelength.

[0007] Therefore, when the light emission intensity of the processing point being observed is high in each sensor, the light amount cannot be adjusted, so the output signal of the optical sensor becomes saturated and the state of the processing point cannot be detected. Also, when an optical element is added to the optical system and used to reduce light, if the optical axis shift occurs due to a change in the optical system configuration, accurate measurement becomes difficult.

[0008] An object of the present disclosure is to provide a laser processing monitoring device that can monitor laser processing over a wide dynamic range without changing the configuration of the optical system.

[0009] A laser processing monitoring device according to one aspect of the present disclosure includes at least two optical sensors that detect emitted light generated from a workpiece during laser processing, and a light-attenuating element that is arranged in at least one of the at least two branched optical paths of the emitted light that is transmitted to the at least two optical sensors, and the transmittance of the light-attenuating element is set so that the measurement ranges of the at least two optical sensors are continuous.

[0010] As a result, the laser processing monitoring device has an optical system in which the light transmittance to each of the at least two optical sensors is different.

[0011] The transmittance of the light-attenuating element is set so that the measurement ranges of the at least two optical sensors are continuous. The at least two optical sensors can be used like a single optical sensor having a continuous measurement range. This laser processing monitoring device has a wider measurement range than a laser processing monitoring device having only one optical sensor.

[0012] Schematic diagram showing the configuration of a laser processing monitoring device according to a first embodiment of the present disclosure. Diagram of an extracted portion from partial reflection mirror 11 to optical sensors 16 and 17 in FIG. 1. Schematic diagram showing the transmittance of a light-attenuating element according to a first embodiment of the present disclosure, with the horizontal axis representing adjustment steps and the vertical axis representing light intensity (W). Measurement flow diagram according to a first embodiment of the present disclosure. Measurement flow diagram according to a first embodiment of the present disclosure. Schematic diagram of gain adjustment according to the light intensity of welding light LW in a gain adjustment unit of the measurement flow. Schematic diagram of gain adjustment in accordance with the light intensity of welding light LW in the gain adjustment section of the measurement flow. Schematic diagram of gain adjustment in accordance with the light intensity of welding light LW in the gain adjustment section of the measurement flow. Schematic diagram of gain adjustment in accordance with the light intensity of welding light LW in the gain adjustment section of the measurement flow. Schematic diagram showing the configuration of the measurement section in embodiment 2 of the present disclosure. Schematic diagram showing the transmittance of the light-attenuating element in embodiment 2 of the present disclosure, where the horizontal axis is a graph of adjustment steps and the vertical axis is light intensity (W). Schematic diagram of a measurement flow when there are n optical sensors in embodiment 2 of the present disclosure. Schematic diagram of a laser processing device in a conventional example.

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

[0014] 1 is a schematic diagram illustrating a configuration of a laser processing monitoring device according to a first embodiment of the present disclosure. Laser processing is a technique for performing welding, cutting, drilling, marking, surface treatment, etching, deposition, or the like using laser light. Here, laser welding is illustrated as an example, but the present disclosure is not limited thereto.

[0015] The laser processing monitoring device includes a laser light supply unit and a light detection unit.

[0016] The laser light supply unit includes a laser oscillator 1, an optical fiber 2 for transmitting laser light, a collimating lens 4, a partial reflection mirror 6, and a condenser lens 5.

[0017] Furthermore, the light detection unit includes a laser output sensor 8, a partially reflecting mirror 7, a condensing lens 9, an imaging camera 10, a partially reflecting mirror 11, a reflective mirror 12, a light-reducing element 13, condensing lenses 14 and 15, and light sensors 16 and 17. Most of these components can be housed inside the lens barrel 3.

[0018] The laser processing monitoring device further includes a computing unit PC as an example of a control unit that controls the entire device.

[0019] The laser oscillator 1 is configured, for example, with a gas laser such as a carbon dioxide laser, or a solid-state laser such as a YAG laser, semiconductor laser, or fiber laser, and generates laser light of a predetermined wavelength and a predetermined output power. As an example, the laser light is a continuous wave (CW) with a wavelength of 1070 nm. The optimal laser wavelength can be selected depending on the light absorption characteristics of the workpiece W. For example, if the workpiece W is copper (Cu) or gold (Au), a relatively short laser wavelength such as 405 to 450 nm is preferable. Furthermore, if the workpiece W is aluminum, a laser wavelength of approximately 800 nm is preferable because aluminum has good light absorption characteristics and enables good welding.

[0020] Here, a case where a continuous wave laser beam is used is exemplified, but a pulsed wave laser beam may also be used. The use of a continuous wave laser beam is preferable in that it allows for a larger amount of heat to be input to the workpiece W, thereby increasing productivity. The use of a pulsed wave laser beam is also preferable in that it reduces the thermal effects during processing compared to a continuous wave laser beam.

[0021] The laser oscillator 1 is communicably connected to the computing unit PC, and the output of the laser light can be controlled in response to commands from the computing unit PC, and in the case of a pulse wave, the period and duty cycle can also be controlled.

[0022] The optical fiber 2 for transmitting laser light has the function of transmitting the light beam LB1 from the laser oscillator 1 to the inside of the lens barrel 3. As an alternative to the optical fiber 2, it is also possible to guide the laser light emitted from the laser oscillator 1 to the lens barrel 3 using an optical element such as a mirror.

[0023] The collimating lens 4 is disposed within the lens barrel 3 and converts the light beam LB2 emitted from the optical fiber 2 into a parallel light beam LB3.

[0024] The partial reflection mirror 6 is disposed within the lens barrel 3 and has the function of reflecting most of the light beam LB3 from the collimator lens 4 and transmitting a portion of it. In the first embodiment, the partial reflection mirror 6 is, for example, a dichroic mirror that reflects 90% or more of the light in the wavelength range of the laser light generated from the laser oscillator 1 and transmits 50% or more of the light in the remaining wavelength range of 350 to 2000 nm. The partial reflection mirror 6 can have desired optical characteristics selected according to the reflection wavelength or transmission wavelength, and the ratio between the amount of transmitted light and the amount of reflected light may be changed as necessary. The light beam LB6 that passes through the partial reflection mirror 6 is received by a laser output sensor 8 that is disposed on the wall of the lens barrel 3 opposite the incident side of the light beam LB6 of the partial reflection mirror 6 and monitors the output of the laser light.

[0025] The laser output sensor 8 includes a photodiode, an A / D converter, etc., and is connected to the computing unit PC so as to be able to communicate with it, and its detection signal is input to the computing unit PC. The detection signal from the laser output sensor 8 correlates with the laser output of the laser oscillator 1. When the laser output is high, an optical element that attenuates light may be installed in front of the laser output sensor 8. In order to reduce surface reflections from the sensor or optical element, the light receiving surface of the laser output sensor 8 may be positioned at an angle with respect to the traveling direction of the light beam LB6.

[0026] The condenser lens 5 is disposed within the lens barrel 3 and condenses the light beam LB4 reflected by the partial reflection mirror 6 to form a light spot of a predetermined shape on the surface of the workpiece W. A large amount of heat energy is input into the area irradiated by the light spot, and the part that exceeds the melting point becomes a molten region M, where, for example, welding of the workpiece W is performed.

[0027] The workpiece W is supported on a processing stage (not shown) that is configured, for example, by an XYZθ table, etc. Such a processing stage is connected to the computing unit PC so that the three-dimensional position of the workpiece W and the angle around the optical axis of the light beam LB5 can be controlled in response to commands from the computing unit PC.

[0028] When scanning the light beam LB5 over the workpiece W, possible methods include: 1) moving the processing stage in a predetermined direction at a predetermined speed while the lens barrel 3 and the light beam LB5 are fixed, 2) mounting the lens barrel 3 on a scanning mechanism such as a robot arm or linear stage, and moving the lens barrel 3 in a predetermined direction at a predetermined speed while the processing stage is fixed, 3) installing an optical scanner such as a galvanometer mirror between the condenser lens 5 and the workpiece W, and 4) a combination of the above methods 1) to 3). The light beam LB5 may be irradiated onto the workpiece W and scanned therewith separately, but a continuous weld can be formed by simultaneously irradiating and scanning the workpiece W with the light beam LB5.

[0029] The computing unit PC is a computer that includes a processor, memory, mass storage, etc., and executes various operations according to preset programs. The computing unit PC also stores the gains of the optical sensors 16 and 17, controls the gain setting and adjustment, and manages the gain adjustment completion flag.

[0030] In the first embodiment, the laser processing monitoring device detects welding light LW1 as an example of emitted light that is generated from melted region M during irradiation with laser light. At least two optical sensors 16, 17 widen the dynamic range of the laser processing monitoring device.

[0031] A portion of the welding light LW1 generated from the molten region M enters the condenser lens 5, passes through the partial reflection mirror 6 in the optical axis direction of the condenser lens 5, and enters the partial reflection mirror 7. The partial reflection mirror 7 has the function of reflecting and transmitting the incident light at a predetermined ratio. In the first embodiment, as an example, the partial reflection mirror 7 is a half mirror that is disposed inside the lens barrel 3 and transmits approximately 50% and reflects approximately 50% in the wavelength range of 350 to 2000 nm. Note that the partial reflection mirror 7 may be a wavelength-dependent dichroic mirror, which changes the ratio between the amount of transmitted light and the amount of reflected light depending on the wavelength.

[0032] The light passing through the partial reflection mirror 7 passes through a condenser lens 9 arranged in the lens barrel 3 and is received by the imaging camera 10. The imaging camera 10 has the function of detecting light generated from the melted region M during irradiation with the laser light and capturing an image of the melted region M and its surrounding area. The imaging camera 10 includes an image sensor, an A / D converter, and the like, and is communicably connected to a computing unit PC. The imaging camera 10 outputs a detection signal. This detection signal is input to the computing unit PC. If the sampling period (measurement period) of the imaging camera 10 is slow, the light within the sampling period will be averaged, resulting in a blurred image. Therefore, in order to obtain a clear image, it is desirable that the sampling period be one-hundredth or less of the time during which the output control of the laser irradiation is performed.

[0033] The light reflected by the partial reflection mirror 7 is incident on the partial reflection mirror 11. In the first embodiment, the partial reflection mirror 11 is configured as a half mirror, as an example, and reflects approximately 50% of the amount of welding light LW1 generated from the melting region M and transmits the remaining approximately 50%. The welding light LW4 transmitted through the partial reflection mirror 11 is condensed by the condenser lens 14 as one optical path and received by the optical sensor 16.

[0034] The welding light LW6 reflected by the partial reflection mirror 11 travels along another optical path and is incident on the reflection mirror 12. The welding light LW7 reflected by the reflection mirror 12 passes through the dimming element 13. The dimming element 13 is configured, for example, by an ND filter. As another example, the dimming element 13 may be configured, instead of an ND filter, by a half mirror, a dichroic mirror, or any combination of these three.

[0035] The light transmitted through the dimming element 13 is condensed by the condenser lens 15 and received by the optical sensor 17 .

[0036] The optical sensors 16 and 17 detect the intensity of the received light and convert it into an electrical signal such as a voltage value or a current value. The optical sensors 16 and 17 each include a photodiode, an A / D converter, etc., and are communicatively connected to the computing unit PC, and their detection signals are input to the computing unit PC. The light received by the optical sensor 17 is attenuated by the dimming element 13. When the gain settings of the optical sensors 16 and 17 are the same, the measurement range of the optical sensor 17 is larger than the measurement range of the optical sensor 16. The computing unit PC functions as a gain control unit for the optical sensors 16 and 17.

[0037] In the first embodiment, the optical sensors 16 and 17 have the same measurement range of light intensity, and when the measurement range is A W to B W (A and B are constants), the light attenuation element 13 has a transmittance α １ (A / B<α １ In place of the reflecting mirror 12, a beam splitter having a desired reflectance may be used as the light-reducing element 13.

[0038] The measurement areas of the optical sensors 16 and 17 are preferably set to include the molten region M of the workpiece W. To change the measurement area, for example, the focal length of the condenser lenses 14 and 15 may be adjusted. For example, if lenses with a focal length of 100 mm are used as the condenser lenses 14 and 15 instead of lenses with a focal length of 200 mm, an area twice the light receiving size of the optical sensors 16 and 17 can be measured. In this way, it is preferable to adjust the focal length to match the selected measurement area. As another example, a method of limiting the measurement area by providing an aperture with a variable opening diameter immediately before the optical sensors 16 and 17 can also be used.

[0039] 2A shows a diagram of an extracted portion (referred to as measurement unit 18) from partial reflection mirror 11 to optical sensors 16 and 17 in FIG. 1, and FIG. 2B shows a graph in which the horizontal axis represents adjustment steps and the vertical axis represents light intensity (W), to explain the transmittance of dimming element 13. In this first embodiment, the transmittance of dimming element 13 is set so that the measurement ranges of optical sensors 16 and 17 are continuous. The transmittance of dimming element 13 is set to α １ (<1.0). The measurement range of optical sensors 16, 17 is A W to B W. The light intensities of welding light LW4 and welding light LW7 are the same, and are indicated by (1) in FIGS. 2A and 2B. The low-intensity portion of the light intensity of (1) is measured by optical sensor 16, and the high-intensity portion is measured by optical sensor 17. By dimming the light using dimming element 13, optical sensor 17 measures the dimmed welding light LW8, i.e., the light intensity of (2) in FIGS. 2A and 2B. In this case, if the effective measurement range of the light intensity of optical sensor 17 at the light intensity of (1) is C W to D W (C and D are constants), the transmittance α １ And the measurement range of LW7 is A W to B W, so C = A / α １ , D=B / α １ In order for the measurement ranges of the optical sensors 16 and 17 to be continuous, the lower limit C of the measurement range of the light intensity of the optical sensor 17 is set to C=A / α. １ is smaller than the upper limit B of the measurement range of the light intensity of the light sensor 16. １By setting A / B, the measurement range of optical sensor 17 becomes continuous with that of optical sensor 16. With this configuration, the transmittance is set in the two branched optical paths of emitted light, such as welding light, transmitted to the two optical sensors 16, 17 so that the measurement ranges of the two optical sensors 16, 17 are continuous.

[0040] As mentioned above, since the dimming element 13 is disposed in one of the two branched optical paths, the optical system has different light transmittances to the respective optical sensors 16 and 17.

[0041] Next, a photodetection method according to the first embodiment of the present disclosure will be described.

[0042] 3A, 3B, and 3C show measurement flow charts under the control of the computing unit PC according to the first embodiment of the present disclosure.

[0043] First, the gain adjustment completion flag is turned off, and the initial value of the gain is set by the calculation unit PC (step S0).

[0044] Next, under the control of the arithmetic unit PC, the laser oscillator 1 emits a light beam LB1 (step S1), and the light beam LB1 passes through the optical fiber 2 (step S2).

[0045] Next, the light beam LB2 is converted into a light beam LB3 by the collimator lens 4 (step S3), and the light beam LB3 passes through the lens barrel 3 (step S4).

[0046] Next, the light beam LB3 is reflected by the partial reflection mirror 6 to become the light beam LB4 (step S5), the light beam LB4 is focused by the focusing lens 5 to become the light beam LB5, which is irradiated onto the workpiece W (step S6), and the welding light LW1 is generated from the workpiece W (step S7).

[0047] Next, the generated welding light LW1 is converted into welding light LW2 by the condenser lens 5 (step S8), and a portion of the welding light LW2 is reflected by the partial reflection mirror 7 to become welding light LW3 (step S9).

[0048] Next, a portion of welding light LW3 reflected by partial reflection mirror 7 is transmitted by partial reflection mirror 11 and becomes welding light LW4, and the remainder is reflected by partial reflection mirror 11 and becomes welding light LW6 (step S10). Welding light LW4 passes through condenser lens 14 and becomes welding light LW5, and is collected at optical sensor 16 (step S11). Welding light LW6 is reflected by reflective mirror 12 and becomes welding light LW7 (step S12-1), and welding light LW7 passes through dimming element 13 and is attenuated to welding light LW8 (step S12-2). Welding light LW8 passes through condenser lens 15 and becomes welding light LW9, and is collected at optical sensor 17 (step S12-3).

[0049] Next, the intensity data of the welding lights LW5 and LW9 detected by the optical sensors 16 and 17 is processed and recorded by the computing unit PC (step S13).

[0050] When the optical sensors 16 and 17 detect the welding light, it is necessary to set the gain and adjust the signal intensity using the calculation unit PC, but although an initial value is set at the time of measurement, it may not be an effective setting. The calculation unit PC checks the gain adjustment completion flag, and if the gain adjustment is not complete, it adjusts the gain and then proceeds to gain recording (step S14).

[0051] 4 is a schematic diagram showing gain adjustment according to the light intensity of the welding light LW in the gain adjustment section (steps S15-S17) of the measurement flow. Welding light LW1 to LW9 may be collectively referred to as welding light LW.

[0052] In the case of gain adjustment by the calculation unit PC, the laser light is adjusted under the condition that is assumed to produce the strongest signal intensity among the conditions that can be used. Generally, the condition that produces the highest laser power or energy density is suitable, but if it is not possible to determine a unique condition, it may be determined by testing multiple conditions.

[0053] The saturation state of the detection signals of the optical sensors 16 and 17 is checked by the calculation unit PC (step S15). To distinguish the saturation state of the detection signals, they are classified into pattern A where both are saturated, pattern B where only the optical sensor 16 is saturated, pattern C where only the optical sensor 17 is saturated, and pattern D where neither is saturated.

[0054] In the case of pattern A, accurate measurement is not possible because both the optical sensors 16 and 17 are saturated. Therefore, gain adjustment is required, and the adjustment flow will be described with reference to FIGS. 4C and 4D.

[0055] In the first adjustment, the gain of the optical sensor 16 is reduced by the calculation unit PC to lower the sensitivity of the optical sensor 16 (step S16-1), and then the process returns to step S1 (FIG. 4C).

[0056] If both the optical sensors 16 and 17 are saturated after one adjustment, the gain of the optical sensor 17 is reduced by the calculation unit PC in the second adjustment to lower the sensitivity of the optical sensor 17 (step S16-2), and then the process returns to step S1 (FIG. 4D).

[0057] If both optical sensors 16 and 17 are saturated even after the second adjustment, the calculation unit PC repeats step S16-1 for odd-numbered adjustments and step S16-2 for even-numbered adjustments, adjusting the optical sensors so that at least one of optical sensors 16 and 17 is not saturated, and after the adjustment is completed, the calculation unit PC turns on the gain adjustment completion flag and records the set gain (step S17).

[0058] In the case of pattern B, at least one of the optical sensors 16 and 17 is not saturated and accurate measurements can be made, so the computing unit PC turns on the gain adjustment completion flag and records the set gain (step S17) (FIG. 4B).

[0059] In the case of pattern C, at least one of the optical sensors 16 and 17 is not saturated and accurate measurements can be made, so the computing unit PC turns on the gain adjustment completion flag and records the set gain (step S17).

[0060] In the case of pattern D, both of the optical sensors 16 and 17 are not saturated and accurate measurements can be made, so the computing unit PC turns on the gain adjustment completion flag and records the set gain (step S17) (FIG. 4A).

[0061] After the adjustment is completed, the calculation unit PC confirms that the gain adjustment flag is on and proceeds to the actual measurement. After repeating the measurement a predetermined number of times until the actual measurement is completed (step S18), the measurement is completed.

[0062] According to the first embodiment, when the emitted light detection signals of all the optical sensors 16, 17 are saturated, the gain of the optical sensor is adjusted and set by the calculation unit PC (as an example of a control unit) so that the emitted light detection signal of at least one of the optical sensors does not saturate. This allows accurate measurement without saturating the emitted light detection signal of at least one of the optical sensors 16, 17. Furthermore, by setting the dynamic ranges of the optical sensors 16, 17 to be continuous, the optical sensors 16, 17 can be used as a single sensor with a continuous measurement range. This laser processing monitoring device has a wider dynamic range than a laser processing monitoring device equipped with a single optical sensor. Therefore, the laser processing monitoring device of the first embodiment can monitor laser processing over a wide dynamic range without changing the optical system configuration.

[0063] Second Embodiment In a second embodiment, a case where measurement light is split into three or more beams will be described.

[0064] Figure 5A is a schematic diagram of the measurement unit of a laser processing monitoring device when the measurement light is split into three beams. Figure 5A shows only the portion corresponding to measurement unit 18 in Figure 1, and the same components are designated by the same reference numerals and will not be described further. Starting from the bottom of the figure, the optical systems with optical sensors are designated columns 1, 2, and 3, respectively. Figure 5B shows a graph with the horizontal axis representing adjustment steps and the vertical axis representing light intensity (W), and explains the transmittance of dimming elements 13 and 21.

[0065] The welding light LW3 incident on the measuring unit 18 is incident on the partial reflection mirror 19.

[0066] In the second embodiment, the partial reflection mirror 19 is configured as a beam splitter, for example, and transmits approximately one-third, or 33%, of the amount of welding light LW1 generated from the melting region M and reflects the remaining approximately 67%. The welding light LW4 transmitted through the partial reflection mirror 19 is collected by the collecting lens 14 and received by the optical sensor 16.

[0067] Like the optical sensors 16 and 17, the optical sensor 23 detects the intensity of the received light and converts it into an electrical signal such as a voltage or current value. The optical sensor 23 includes a photodiode, an A / D converter, and the like, and is connected to the calculation unit PC so as to be able to communicate with the calculation unit PC, and the detection signal is input to the calculation unit PC. Because the light is reduced by the light-reducing elements 13 and 21, the measurement range of the optical sensor 17 is larger than that of the optical sensor 16, and the measurement range of the optical sensor 23 is larger than that of the optical sensor 17, when the gain settings of the optical sensors 16 and 17 are the same. The calculation unit PC functions as a gain control unit for the optical sensors 16, 17, and 23.

[0068] In the second embodiment, the optical sensors 16, 17, and 23 have the same measurement range of light intensity. When the measurement range is A W to B W, the light attenuation element 13 has a transmittance α １ (A / B<α １ <1.0) is used as the light-reducing element 21, and the transmittance α ２ (A ２ / B ２ <α ２ In place of the light-reducing element 13, a partial reflection mirror 20 may be used with its reflectance adjusted, and in place of the light-reducing element 21 and the reflecting mirror 12, a beam splitter having a desired reflectance may be used.

[0069] The welding light LW6 reflected by the partial reflection mirror 19 is incident on the partial reflection mirror 20.

[0070] As an example, in this embodiment 1, the partial reflection mirror 20 is configured as a half mirror, and reflects approximately 50% of the light reflected by the partial reflection mirror 19 and transmits the remaining approximately 50% of the light.

[0071] The amount of welding light LW7 reflected by partial reflection mirror 20 is approximately 33%, which is about one-third of the amount of light emitted from melting region M. Welding light LW7 passes through dimming element 13. Dimming element 13 is formed, for example, by an ND filter. The transmittance of dimming element 13 is set so that the measurement ranges of optical sensors 16 and 17 are continuous. The transmittance α of dimming element 13 １ (<1.0). The measurement range of optical sensors 16 and 17 is A W to B W. The light intensities of welding light LW4 and welding light LW7 are the same, and are indicated by (1)' in the figure. The low-intensity portion of the light intensity of (1)' is measured by optical sensor 16, and the medium-intensity portion is measured by optical sensor 17.

[0072] By reducing the light intensity using the dimming element 13, the optical sensor 17 measures the reduced welding light LW8, i.e., the light intensity of (2)' in the figure. In this case, if the effective measurement range of the light intensity of the optical sensor 17 at the light intensity of (1)' is CW to DW, the transmittance α １ And the measurement range of the optical sensor 17 is A W to B W, so C = A / α １ , D=B / α １ In order for the measurement ranges of the optical sensors 16 and 17 to be continuous, the lower limit C of the measurement range of the light intensity of the optical sensor 17 must be C=A / α. １ is smaller than the upper limit B of the measurement range of the light intensity of the light sensor 16. １ By setting A / B, the measurement range of the optical sensor 17 becomes continuous with that of the optical sensor 16. The light transmitted through the dimming element 13 is condensed by the condenser lens 15 and received by the optical sensor 17.

[0073] The welding light LW10 transmitted through the partial reflection mirror 20 is incident on the reflection mirror 12.

[0074] The amount of welding light LW11 reflected by reflecting mirror 12 is approximately 33%, which is about one-third of the amount of light emitted from melting region M. Welding light LW11 passes through dimming element 21. Dimming element 21 is formed, for example, by an ND filter. The transmittance of dimming element 21 is set so that the measurement ranges of optical sensor 17 and optical sensor 23 are continuous. The transmittance α of dimming element 21 ２(<1.0). The measurement range of optical sensors 17, 23 is A W to B W. The light intensity of welding light LW7 and welding light LW11 is the same, and is indicated by (1)' in the figure. The medium intensity portion of the light intensity of (1)' is measured by optical sensor 17, and the high intensity portion is measured by optical sensor 23. By dimming the light using dimming element 21, optical sensor 23 measures the dimmed welding light LW12, that is, the light intensity of (3)' in the figure. In this case, if the effective measurement range of the light intensity of optical sensor 23 at the light intensity of (1)' is E W to F W, then the transmittance α ２ And the measurement range of the optical sensor 23 is A W to B W, so E = A / α ２ , F=B / α ２ In order for the measurement ranges of the optical sensors 17 and 23 to be continuous, the lower limit E of the measurement range of the light intensity of the optical sensor 23 must be E=A / α ２ is the upper limit D of the measurement range of the light intensity of the optical sensor 17. １ Therefore, the transmittance α of the dimming element 21 is ２ >Aα １ / B>A ２ / B ２ By setting the above, the measurement range of the optical sensor 23 becomes continuous with that of the optical sensor 17.

[0075] The light transmitted through the dimming element 21 is condensed by the condenser lens 22 and received by the optical sensor 23 .

[0076] The measurement areas of the optical sensors 16, 17, and 23 are preferably set to include the molten region M of the workpiece W. To change the measurement area, for example, the focal length of the condenser lenses 14, 15, and 22 may be adjusted. For example, if lenses with a focal length of 100 mm are used as the condenser lenses 14, 15, and 22 instead of lenses with a focal length of 200 mm, an area twice the light receiving size of the optical sensors 16, 17, and 23 can be measured. In this way, it is preferable to adjust the focal length to match the selected measurement area. As another example, a method of limiting the measurement area by providing an aperture with a variable opening diameter immediately before the optical sensors 16, 17, and 23 can also be used.

[0077] Furthermore, when the measurement light is split into n beams (n is an integer of 3 or more), row 1 is composed of a partial reflection mirror, a condenser lens, and an optical sensor, rows 2 to n-1 are composed of a partial reflection mirror, a light-attenuating element, a condenser lens, and an optical sensor, and row n is composed of a reflecting mirror, a light-attenuating element, a condenser lens, and an optical sensor. The amount of light from the partial reflection mirror and the welding light after the reflecting mirror is 100 / n%, which is about one-nth of the light generated from the melting region M. Furthermore, the transmittance α of the light-attenuating element in the m-th row of rows n is ｍ is (A ｍ―１ / B ｍ―１ <α ｍ―１ < 1.0).

[0078] Next, a light detection method according to a second embodiment of the present disclosure will be described. The peak of light intensity is measured. Fig. 6 is a measurement flow diagram for the case where n light sensors are used according to the second embodiment of the present disclosure. Since the components other than the gain adjustment unit are the same as those in the first embodiment, a description thereof will be omitted.

[0079] When the optical sensors in columns 1 to n detect welding light, the calculation unit PC must set the gain and adjust the signal intensity, but there are cases where the initial value set at the time of measurement is not an effective setting. The calculation unit PC checks the gain adjustment completion flag, and if the gain adjustment is not complete, it adjusts the gain and then proceeds to gain recording (step S14).

[0080] In the case of gain adjustment by the calculation unit PC, the laser light is adjusted under the condition that is assumed to produce the strongest signal intensity among the conditions that can be used. Generally, the condition that produces the highest laser power or energy density is suitable, but if it is not possible to determine a unique condition, it may be determined by testing multiple conditions.

[0081] The saturation state of the detection signals of the optical sensors in columns 1 to n is checked by the calculation unit PC (step S15'). To distinguish the saturation state of the detection signals, they are classified into a pattern Xn in which all n optical sensors are saturated, a pattern Yn in which any one of the n optical sensors is not saturated, and a pattern H in which any two or more of the n optical sensors are not saturated.

[0082] In the case of pattern Xn, all n optical sensors are saturated, making accurate measurement impossible. Therefore, the following gain adjustment is required.

[0083] In the first adjustment, the gain of the optical sensors in the first column is reduced by the calculation unit PC to lower the sensitivity of the optical sensors in column 1 (step S16-1'), and then the process returns to step S1.

[0084] If all n optical sensors are saturated even after the second adjustment, the gain of the optical sensors in column 2 is reduced by the calculation unit PC in the second adjustment to lower the sensitivity of the optical sensors in column 2 (step S16-2'), and then the process returns to step S1.

[0085] Similarly, if all n optical sensors are saturated even after m adjustments (m≦n is a natural number) up to the nth adjustment, the sensitivity of the optical sensors in column m is reduced by reducing the gain of the optical sensors in column m using the calculation unit PC in the mth adjustment (step S16-m′), and then the process returns to step S1.

[0086] If all n optical sensors are saturated even after the nth adjustment, the calculation unit PC repeatedly performs step S16-1' for the n+1th adjustment, step S16-2' for the n+2th adjustment, and step S16-m' for the n+mth adjustment, thereby adjusting to pattern Yn in which none of the n optical sensors is saturated, and after the adjustment is completed, the gain adjustment completion flag is turned on and the set gain is recorded (step S17').

[0087] In the case of pattern Yn, any one of the n optical sensors is not saturated and accurate measurement is possible, so the calculation unit PC turns on the gain adjustment completion flag and records the set gain (step S17).

[0088] In the case of pattern Zn, any one of the n optical sensors is not saturated and accurate measurement is possible, so the calculation unit PC turns on the gain adjustment completion flag and records the set gain (step S17).

[0089] According to the second embodiment, when the detection signals of all the emitted light of three or more n optical sensors are saturated, the gain of at least one of the optical sensors is adjusted and set by the calculation unit PC (as an example of a control unit) so that the detection signal of the emitted light of that at least one of the optical sensors does not become saturated, thereby enabling accurate measurement without saturating the detection signal of the emitted light of at least one of all the optical sensors. Furthermore, by setting the dynamic ranges of all the optical sensors to be continuous, it becomes possible to use all three or more optical sensors as if they were one sensor having a continuous measurement area, and measurement can be performed using a wider dynamic range than when using a single sensor.

[0090] (Other embodiments) In each of the first and second embodiments, there are optical paths in which no dimming element is arranged, but the present disclosure is not limited to this. Dimming elements may be arranged in all optical paths to form an optical system in which the light transmittance to each optical sensor is all different.

[0091] It should be noted that any of the various embodiments or modifications described above can be combined appropriately to achieve the effects of each. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, and combinations of features of different embodiments or examples are also possible.

[0092] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0093] (Technology 1) A laser processing method includes at least two optical sensors that detect emitted light generated from a workpiece, and a light-attenuating element that is arranged in at least one of the at least two branched optical paths of the emitted light that is transmitted to the at least two optical sensors, and the transmittance of the light-attenuating element is set so that the measurement ranges of the at least two optical sensors are continuous.

[0094] (Technology 2) The laser processing monitoring device according to Technology 1, wherein a gain of at least one of the at least two optical sensors is set so that the detection signal of the emitted light of the at least one optical sensor is not saturated.

[0095] (Technology 3) The laser processing monitoring device according to Technology 1 or 2, wherein the emitted light includes the wavelength of the processing laser, a visible wavelength of 400 to 700 nm, and an infrared wavelength of 700 to 7000 nm.

[0096] (Technology 4) The laser processing monitoring device according to any one of Technologies 1 to 3, wherein the light-reducing element is at least one of an ND filter, a half mirror, and a dichroic mirror.

[0097] (Technology 5) The laser processing monitoring device according to any one of Technologies 1 to 4, having at least two optical paths in which the light transmittance decreases by 100 / n%, where n is the number of optical paths.

[0098] With each of these configurations, when the emitted light detection signals of all the optical sensors are saturated, the gain of at least one of the optical sensors is adjusted and set so that the emitted light detection signal of that at least one of the optical sensors does not saturate, thereby enabling accurate measurement without saturating the emitted light detection signal of at least one of all the optical sensors. Furthermore, by setting the dynamic ranges of the multiple optical sensors to be continuous, at least two optical sensors can be used as a single sensor with a continuous measurement range. This laser processing monitoring device has a wider dynamic range than a laser processing monitoring device with a single optical sensor. Therefore, this laser processing monitoring device can monitor laser processing over a wide dynamic range without changing the optical system configuration.

[0099] As a result, for example, when the laser output or material is changed, the dynamic range is expanded by changing the optical path and / or automatically adjusting the gain according to the light emission intensity at the processing point, and there is no need to change the configuration of the optical system, saturation of the output signal from the optical sensor can be prevented, and the state of the processing point can be detected with high accuracy.

[0100] The laser processing monitoring device according to the above aspect of the present disclosure is industrially useful in that it can monitor the laser processing state over a wide dynamic range through automatic adjustment without changing the configuration of the optical system.

[0101] 1: Laser oscillator 2: Optical fiber 3: Lens barrel 4: Collimating lens 5: Condenser lens 6, 7: Partially reflecting mirror 8: Laser output sensor 9: Condenser lens 10: Imaging camera 11, 19, 20: Partially reflecting mirror 12: Reflecting mirror 13, 21: Light-attenuating element 14, 15, 22: Condenser lens 16, 17, 23: Optical sensor 18: Measuring unit LB, LB1, LB2, LB3, LB4, LB5, LB6: Light beam LW, LW1, LW2, LW3, LW4, LW5, LW6, LW7, LW8, LW9, LW10, LW11, LW12, LW13: Welding light M: Melting area PC: Computing unit W: Workpiece 100, 101, 102: Optical sensor W100: Workpiece LW100: Welding light

Claims

1. A laser processing monitoring device comprising: at least two optical sensors that detect emitted light generated from a laser processed workpiece; and a light-attenuating element disposed in at least one of the at least two branched optical paths of the emitted light transmitted to the at least two optical sensors, wherein the transmittance of the light-attenuating element is set so that the measurement ranges of the at least two optical sensors are continuous.

2. The laser processing monitoring device according to claim 1, wherein the gain of at least one of said at least two optical sensors is set so that the detection signal of said emitted light of said at least one optical sensor is not saturated.

3. The laser processing monitoring device according to claim 1, wherein the emitted light includes the wavelength of the processing laser, a visible wavelength of 400 to 700 nm, and an infrared wavelength of 700 to 7000 nm.

4. The laser processing monitoring device according to claim 1, wherein the light-reducing element is at least one of an ND filter, a half mirror, and a dichroic mirror.

5. A laser processing monitoring device as described in claim 1, wherein the transmittance of said light-attenuating element is set to decrease by 100 / n%, where n is the number of optical paths.

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