Temperature measurement device

Abstract

To provide a temperature measuring device capable of accurately measuring temperature near a machining point in laser machining.SOLUTION: A temperature measuring device includes a light guide unit, a detection unit, and an optical fiber. The light guide unit is relatively movable relative to a workpiece, and has a mirror for imaging scattered light and radiant light from the workpiece, the optical fiber connects the light guide unit and the detection unit, and propagates light imaged by the mirror from the light guide unit to the detection unit, and the detection unit has a scattered light detector for detecting scattered light from the workpiece, and a first radiant light detector for detecting radiant light in a first wavelength range from the workpiece.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a temperature measuring device. [Background technology]

[0002] In laser processing, the temperature at the processing point of the workpiece is one of the parameters that affect productivity and the quality of the processed product. With the development of high-power light sources, real-time, high-speed temperature measurement is also required in ultrashort pulse laser processing.

[0003] A radiation thermometer is one means of measuring temperature. Patent documents 1 to 3 disclose thermometers that measure temperature by propagating radiant light using optical fibers. Patent document 1 discloses a method of detecting temperature using the intensity ratio of light with different wavelengths. Patent document 2 discloses a method of identifying the position of a processing point by irradiating a workpiece with light from an irradiation light source via an optical fiber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 60-29622 [Patent Document 2] Japanese Patent Application Laid-Open No. 61-182538 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-37476 Summary of the Invention [Problem to be solved by the invention]

[0005] Precision machining using ultrashort pulse lasers is performed in very small spaces. Because ultrashort pulse lasers have extremely short pulse widths of a few picoseconds or less and short pulse repetition periods, it is difficult to precisely measure phenomena occurring at the machining point. For example, the temperature at the machining point fluctuates with each laser pulse, which has a repetition period of approximately 1 to 100 μsec. Furthermore, the focused diameter of the laser beam is 100 μm or less, requiring temperature measurement over an area measuring several tens to several hundred μm. This means that temperature measurement with high spatial and temporal resolution is required to accommodate precision laser machining.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a temperature measuring device that can more accurately measure the temperature in the vicinity of the processing point during laser processing. [Means for solving the problem]

[0007] (1) A temperature measuring device according to a first aspect includes a light guide unit, a detection unit, and an optical fiber. The light guide unit is movable relative to a workpiece and includes a mirror that forms an image of scattered light and radiated light from the workpiece. The optical fiber connects the light guide unit and the detection unit and transmits the light formed by the mirror from the light guide unit to the detection unit. The detection unit includes a scattered light detector that detects scattered light from the workpiece and a first radiated light detector that detects radiated light in a first wavelength range from the workpiece.

[0008] (2) In the temperature measuring device according to the above aspect, the detection unit may further include a second radiant light detector that detects radiant light in a second wavelength range from the workpiece.

[0009] (3) In the temperature measuring device according to the above aspect, the mirror may be configured to form an image of the scattered light and the radiated light on an aperture disposed at the first end of the optical fiber or in front of the first end of the optical fiber.

[0010] (4) The temperature measuring device according to the above aspect may further include a data processing device that identifies a processing point on the workpiece based on the intensity of the scattered light and calculates the temperature of the workpiece based on the radiant light.

[0011] (5) The temperature measuring device according to the above aspect may further include a control device connected to the data processing device, which moves the light guide unit relative to the workpiece so that a temperature measurement point is located at a predetermined position or distance from the processing point.

[0012] (6) The temperature measuring device according to the above aspect may further include a laser light source, and a timing signal for laser irradiation from the laser light source is input to the data processing device.

[0013] (7) The temperature measuring device according to the above aspect may further include a laser light source, which outputs laser light of a first intensity when the scattered light detector detects the scattered light, and outputs laser light of a second intensity that is stronger than the first intensity when laser processing the workpiece. [Effects of the Invention]

[0014] The temperature measuring device according to the above aspect can more accurately measure the temperature at the measurement point during laser processing. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of a temperature measuring device according to a first embodiment. [Figure 2] FIG. 10 is a schematic diagram of a light guide unit according to a first modified example. [Figure 3] FIG. 2 is a diagram showing the relationship between processing points and measurement points of the temperature measuring device according to the first embodiment. [Figure 4] FIG. 2 is a flowchart of a temperature measurement method using the temperature measurement device according to the first embodiment. [Figure 5] FIG. 10 is a schematic diagram of a temperature measuring device according to a second embodiment. [Figure 6]FIG. 10 is a schematic diagram of a temperature measuring device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual ones. The materials, dimensions, arrangements, numbers, numerical values, configurations, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the present invention.

[0017] "First embodiment" 1 is a schematic diagram of a temperature measuring device 100 according to a first embodiment. The temperature measuring device 100 includes, for example, a light guide unit 10, a detection unit 20, an optical fiber 30, a laser light source 40, a data processing device 50, and a control device 60.

[0018] The laser light source 40 irradiates the workpiece 1 with laser light. The scattered light and radiated light from the workpiece 1 are collected by the light guide unit 10 and reach the optical fiber 30. The light guide unit 10 and the detection unit 20 are connected by the optical fiber 30. The light from the light guide unit 10 reaches the detection unit 20 via the optical fiber 30. The detection unit 20 separates the light from the light guide unit 10 and detects it as a signal. The signal detected by the detection unit 20 is sent to the data processing device 50. The data processing device 50 processes the signal and determines the position of the processing point and the temperature of the measurement point.

[0019] The laser light source 40 emits a pulsed laser. The pulsed laser is, for example, an ultrashort pulsed laser having a pulse width of several femtoseconds to several picoseconds. The laser light emitted from the laser light source 40 is focused at a processing point on the workpiece 1 by a focusing lens 41. The laser light source 40 can, for example, move relatively to the workpiece 1, and the position of the laser focusing point relative to the workpiece 1 can be changed.

[0020] The output intensity of the laser light source 40 can be changed depending on the application. As will be described in detail later, the laser light source 40 can output, for example, a laser beam of a first intensity and a laser beam of a second intensity that is stronger than the first intensity.

[0021] The laser light source 40 may be connected to the data processing device 50. The laser light source 40 inputs, for example, a timing signal for laser irradiation to the data processing device 50.

[0022] Although FIG. 1 shows an example in which the laser light source 40 is incorporated into the temperature measuring device 100, the laser light source 40 may be an external unit of the temperature measuring device 100.

[0023] The light guide unit 10 is located near the processing surface of the workpiece 1. The light guide unit 10 can move relative to the workpiece 1. By moving the light guide unit 10 relative to the workpiece 1, the temperature measurement point can be freely changed.

[0024] The light guide unit 10 includes, for example, a mirror 11, a filter 12, and an optical member 13 having an aperture Ap.

[0025] The mirror 11 forms an image on the aperture Ap of the scattered light and radiated light from the workpiece 1. The mirror 11 has little wavelength-dependent aberration, and can form an image on the aperture Ap of both the scattered light and radiated light, which have different wavelengths.

[0026] The filter 12 is located between the mirror 11 and the aperture Ap in the light traveling direction. The filter 12 is a filter that reduces the laser light. The filter 12 reduces damage to the optical fiber 30 and the optical system caused by the laser light. The filter 12 may be removed if it is not necessary.

[0027] The optical member 13 is disposed in front of the first end of the optical fiber 30. An aperture Ap is formed in the optical member 13. The size of the aperture Ap and the distance between the mirror 11 and the aperture Ap relative to the distance between the workpiece 1 and the mirror 11 affect the spatial resolution of the temperature measuring device 100. Reducing the size of the aperture Ap and increasing the distance between the mirror 11 and the aperture Ap relative to the distance between the workpiece 1 and the mirror 11 increases the spatial resolution of the temperature measuring device 100. The size of the aperture Ap is, for example, 100 μm or less.

[0028] 1 shows an example in which the aperture Ap is formed in the optical member 13, but the core at the first end of the optical fiber 30 may be treated as the aperture Ap. In other words, the optical member 13 may be omitted. In this case, the mirror 11 forms an image of the scattered light and radiated light from the workpiece 1 onto the core at the first end of the optical fiber 30.

[0029] 2, the light-guiding unit 10A may use a plurality of mirrors 11 to form an image of the scattered light and the radiated light at an aperture Ap. Fig. 2 shows a modified example of the light-guiding unit 10 according to the first embodiment. The light-guiding unit 10A can be moved relative to the workpiece 1 by a moving stage 14.

[0030] The optical fiber 30 connects the light guiding unit 10 and the detection unit 20. A first end of the optical fiber 30 is disposed near the imaging point of the mirror 11 of the light guiding unit 10. The light imaged by the mirror 11 propagates from the light guiding unit 10 to the detection unit 20 via the optical fiber 30. A second end of the optical fiber 30 is disposed in front of the collimating mirror 24 of the detection unit 20. By connecting the light guiding unit 10 and the detection unit 20 with the optical fiber 30, only the light guiding unit 10 can be moved relative to the workpiece 1 while the detection unit 20 remains fixed.

[0031] The detection unit 20 includes, for example, a scattered light detector 21, a first radiation detector 22, a second radiation detector 23, a collimating mirror 24, dichroic mirrors 25A and 25B, a mirror 25C, filters 26A, 26B and 26C, and condenser lenses 27A, 27B and 27C.

[0032] Collimating mirror 24 collimates the light emitted from the second end of optical fiber 30. The collimated light reaches dichroic mirror 25A. Dichroic mirror 25A reflects the scattered light toward scattered light detector 21 and transmits the radiated light. The radiated light that has passed through dichroic mirror 25A reaches dichroic mirror 25B. Dichroic mirror 25B reflects light of a specific wavelength from the radiated light toward first radiated light detector 22 and transmits light of other wavelengths. The radiated light that has passed through dichroic mirror 25B is reflected by mirror 25C and reaches second radiated light detector 23. While an example using dichroic mirrors 25A and 25B has been shown here, the present invention is not limited to this example. For example, beam splitters may be used instead of dichroic mirrors 25A and 25B.

[0033] Filters 26A, 26B, and 26C are, for example, bandpass filters. Filters 26A, 26B, and 26C transmit only light in the required wavelength band. Collecting lens 27A collects light that has passed through filter 26A toward scattered light detector 21. Collecting lens 27B collects light that has passed through filter 26B toward first radiation detector 22. Collecting lens 27C collects light that has passed through filter 26C toward second radiation detector 23. While an example in which light is collected using collecting lenses 27A, 27B, and 27C has been shown here, the present invention is not limited to this example, and for example, collecting mirrors may be used instead of collecting lenses 27A, 27B, and 27C.

[0034] The scattered light detector 21 detects the laser light scattered from the workpiece 1. The scattered light detector 21 measures the intensity of the laser light. The first radiated light detector 22 detects light of a specific wavelength from the radiated light from the workpiece 1. The second radiated light detector 23 detects light of a wavelength different from the wavelength detected by the first radiated light detector 22 from the radiated light from the workpiece 1.

[0035] The detection unit 20 can be fixed using an optical fiber 30. Therefore, the first radiation detector 22 and the second radiation detector 23 may be large-scale detectors. The first radiation detector 22 and the second radiation detector 23 are, for example, Peltier-element-cooled PIN photodiodes, liquid nitrogen-cooled photomultiplier tubes, etc. These detectors are capable of high-sensitivity measurements with high time resolution.

[0036] The data processing device 50 receives signals from the scattered light detector 21, the first radiation detector 22 and the second radiation detector 23. The data processing device 50 may be incorporated within the detection unit 20. Alternatively, the data processing device 50 may be an external unit to the temperature measuring device 100.

[0037] The data processing device 50 identifies the position of the processing point based on the signal from the scattered light detector 21. The scattered light from the workpiece 1 is stronger the closer it is to the processing point. Therefore, the data processing device 50 identifies the position of the processing point based on the intensity of the scattered light detected by the scattered light detector 21. The data processing device 50 also identifies the position of the measurement point where the temperature is measured based on the distance from the processing point.

[0038] The data processing device 50 also determines the temperature of the measurement point based on the signals from the first radiation detector 22 and the second radiation detector 23. The temperature of the measurement point can be determined with high accuracy by using the intensity ratio of the two radiation beams in different wavelength ranges. The determined temperature of the measurement point is output from the data processing device 50 to an external device.

[0039] The control device 60 is connected to, for example, the data processing device 50 and the light guiding unit 10. The control device 60 moves the light guiding unit 10 relative to the workpiece 1. The control device 60 moves the light guiding unit 10 so that the temperature measurement point is at a position at a specific distance from the processing point.

[0040] 3 is a diagram showing the relationship between the processing point and the measurement point of the temperature measuring device 100 according to the first embodiment. As described above, the data processing device 50 can identify the processing point p1 from the intensity of the scattered light. When measuring the temperature of the measurement point p2, which is a distance d away from the processing point p1, the light-guiding unit 10 is slid in the in-plane direction of the workpiece 1. The control device 60 moves the light-guiding unit 10 to a position where the scattered light and radiated light from the measurement point p2 are imaged on the aperture Ap.

[0041] The temperature measuring device 100 can measure the temperature at any position by moving the light guide unit 10 to any measurement point p2 using the control device 60. For example, when measuring the temperature at the processing point p1, the distance d is set to zero.

[0042] 4 is a flow diagram of a temperature measurement method using the temperature measurement device 100 according to the first embodiment. The temperature measurement method using the temperature measurement device 100 includes a processing point specifying step S1, a measurement point specifying step S2, and a temperature measurement step S3.

[0043] In the processing point specifying step S1, a processing point p1 to be irradiated with laser light is specified. First, laser light of a first intensity is irradiated onto the workpiece 1 (step S1a). The first intensity is an intensity at which processing does not occur on the workpiece 1.

[0044] Next, scattered light from the workpiece 1 is detected by the scattered light detector 21 (step S1b). The scattered light is detected, for example, by moving the light guide unit 10 using the control device 60, while changing the measurement point (step S1c). The point where the scattered light is at its maximum can be considered to be the processing point p1.

[0045] Next, a measurement point specifying step S2 is performed. In the measurement point specifying step S2, the light guide unit 10 is moved to a measurement point p2 where the temperature is measured. If the processing point p1 is set as the measurement point p2, the measurement point specifying step S2 does not need to be performed.

[0046] First, a measurement point p2 where the temperature is to be measured is determined (step S2a). The measurement point can be changed depending on the purpose. For example, if it is desired to measure the temperature of processing point p1, processing point p1 is set as measurement point p2. Also, if it is desired to measure the temperature at a predetermined distance d from processing point p1, a position that is the distance d from processing point p1 is set as measurement point p2.

[0047] Next, the light guide unit 10 is moved to the measurement point p2 (step S2b). The light guide unit 10 is moved by the control device 60.

[0048] Next, a temperature measurement step S3 is performed. In the temperature measurement step S3, the temperature is measured while laser processing is being performed. The laser processing may be, for example, precision processing using an ultrashort pulse laser, or laser welding or laser cutting using a high-power CW laser.

[0049] First, the output of the laser light is changed to a second intensity. The second intensity is stronger than the first intensity and is the intensity used when actually performing laser processing. Then, the laser light of the second intensity is irradiated onto the workpiece 1 (step S3a).

[0050] When the workpiece 1 is irradiated with laser light, the processing point p1 is heated and radiation occurs from the workpiece 1. The radiated light is sent from the light guide unit 10 to the detection unit 20 via the optical fiber 30 and detected by the first radiated light detector 22 and the second radiated light detector 23 (step S3b).

[0051] Then, the detection signals detected by the first radiated light detector 22 and the second radiated light detector 23 are sent to the data processing device 50. The data processing device 50 measures the temperature at the measurement point using the intensity ratio of the two radiated lights in different wavelength ranges (step S3c).

[0052] As described above, the temperature measuring device 100 according to the first embodiment can accurately determine the position of the processing point p1 on the workpiece 1 using scattered light, and can accurately identify the position of the measurement point p2 from the distance d from the processing point p1. Furthermore, by using the mirror 11 to focus the scattered light and radiated light on the aperture Ap, the spatial resolution of the measurement point p2 can be improved. Furthermore, by using the optical fiber 30, the detection unit 20 can be fixed, allowing the use of a detector with high response speed and sensitivity. Furthermore, by using multiple radiated light detectors, the temperature of the measurement point can be accurately measured from the intensity ratio of two radiated lights in different wavelength ranges. Furthermore, by synchronizing the timing of laser light irradiation with the timing of signal processing in the data processing device 50, the temporal processing accuracy of the signal can be further improved.

[0053] "Second embodiment" 5 is a schematic diagram of a temperature measuring device 101 according to the second embodiment. The temperature measuring device 101 differs from the detection unit 20 in that the detection unit 20A does not have a second radiated light detector 23, but only has a first radiated light detector 22.

[0054] The temperature of the processing point p1 can be measured without comparing the intensity ratio of radiant light in different wavelength ranges, and therefore the temperature of the processing point p1 can be measured using only the first radiant light detector 22.

[0055] The temperature measuring device 101 according to the second embodiment can obtain the same effects as the temperature measuring device 100 according to the first embodiment. Furthermore, by omitting the second radiation detector 23, the size of the temperature measuring device 101 can be reduced.

[0056] "Third embodiment" 6 is a schematic diagram of a temperature measuring device 102 according to the third embodiment. The temperature measuring device 102 differs from the detection unit 20 in that a detection unit 20B further includes a light source 28, a filter 29, and a dichroic mirror 25D.

[0057] A known light source can be used as the light source 28. The filter 29 is a filter that prevents laser light from entering the light source 28 side. The filter 29 may be removed if unnecessary. The dichroic mirror 25D reflects the light emitted from the light source toward the collimating mirror 24. The light emitted from the light source 28 reaches the workpiece 1 via the dichroic mirror 25D, the collimating mirror 24, and the optical fiber 30. Although an example using the dichroic mirror 25D has been shown here, the present invention is not limited to this example, and for example, a beam splitter may be used instead of the dichroic mirror 25D.

[0058] The light irradiated onto the workpiece 1 from the light source 28 and the light irradiated onto the workpiece 1 from the laser light source 40 are observed with a CCD camera or an IR viewer, and the light guide unit 10 is moved so that the positions of these light spots coincide. When the positions of these light spots coincide, the approximate position of the processing point can be identified. After the approximate position of the processing point has been identified, the position of the processing point can be identified using the scattered light detector 21, thereby increasing the speed at which the position of the processing point can be identified.

[0059] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments and modifications, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. [Explanation of symbols]

[0060] 1...workpiece, 10, 10A...light guide unit, 11, 25C...mirror, 12, 26A, 26B, 26C, 29...filter, 13...optical member, 14...moving stage, 20, 20A, 20B...detection unit, 21...scattered light detector, 22...first radiation detector, 23...second radiation detector, 24...collimating mirror, 25A, 25B, 25D...dichroic mirror, 27A, 27B, 27C, 41...condensing lens, 28...light source, 30...optical fiber, 40...laser light source, 50...data processing device, 60...control device, 100, 101, 102...temperature measuring device, Ap...aperture, d...distance, p1...processing point, p2...measurement point

Claims

1. a light guide unit, a detection unit, an optical fiber, a data processing device, and a control device connected to the data processing device; the light guide unit is movable relative to the workpiece to be laser processed, and includes a mirror that forms an image of scattered light and radiant light generated from the workpiece when irradiated with a laser; the optical fiber connects the light guide unit and the detection unit, and propagates the light imaged by the mirror from the light guide unit to the detection unit; the detection unit includes a scattered light detector that detects the scattered light from the workpiece, and a first radiated light detector that detects the radiated light in a first wavelength range from the workpiece, the data processing device identifies a processing point on the workpiece based on the intensity of the scattered light, and calculates a temperature of the workpiece based on the radiated light; The control device moves the light guide unit relative to the workpiece so that a temperature measurement point is located at a predetermined position or distance from the processing point.

2. The temperature measuring device according to claim 1 , wherein the detection unit further comprises a second radiation detector that detects the radiation in a second wavelength range from the workpiece.

3. The temperature measuring device according to claim 1 , wherein the mirror forms an image of the scattered light and the radiated light on a first end of the optical fiber or on an aperture disposed in front of the first end of the optical fiber.

4. further comprising a laser light source; 4. The temperature measuring device according to claim 1, wherein a timing signal for laser irradiation from said laser light source is input to said data processing device.

5. further comprising a laser light source; The temperature measuring device according to any one of claims 1 to 4, wherein the laser light source outputs laser light of a first intensity when the scattered light detector detects the scattered light, and outputs laser light of a second intensity stronger than the first intensity when laser processing the workpiece.

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