Distance measuring device, distance measuring method and working device

Abstract

The distance measuring device (42) is configured to include a frequency shift unit (61) that shifts the frequency of interference light between light irradiated from the sensor head unit (21) onto the processing surface (3a) of the workpiece (3) and light received by the sensor head unit (21) and reflected by the processing surface (3a), a band limiting unit (62) that limits the frequency band of the interference light after frequency shift by the frequency shift unit (61), and a signal conversion unit (63) that converts the interference light after frequency band limiting by the band limiting unit (62) into a frequency domain signal. The distance measuring device (42) also includes a shift amount change unit (64) that changes the amount of shift of the frequency of the interference light by the frequency shift unit (61) if the frequency domain signal after conversion by the signal conversion unit (63) does not include a signal whose signal intensity is equal to or greater than a threshold, and a distance calculation unit (65) that calculates the distance from the sensor head unit (21) to the processing surface (3a) based on the signal whose signal intensity is equal to or greater than the threshold if the frequency domain signal after conversion by the signal conversion unit (63) includes a signal whose signal intensity is equal to or greater than a threshold.

Description

[Technical field]

[0001] The present disclosure relates to a distance measuring device, a distance measuring method, and a machining device. [Background technology]

[0002] There is a distance measuring device that irradiates light onto a processing surface of a workpiece, and then calculates the distance from a sensor head unit that receives the light reflected from the processing surface to the processing surface. For example, Patent Document 1 discloses a distance measuring device including a sensor body connected to a sensor head via an optical fiber. The sensor body includes a light interference unit and a distance calculation unit. The optical interference unit detects interference light between the light irradiated from the sensor head and the light received by the sensor head. The distance calculation unit converts the interference light into a frequency domain signal and calculates the distance from the sensor head to the processing surface of the workpiece based on the frequency domain signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020-070884 Summary of the Invention [Problem to be solved by the invention]

[0004] When a typical distance measuring device is implemented in, for example, an FPGA (Field-Programmable Gate Array), the frequency range of the frequency domain signal into which the interference light can be converted (hereinafter referred to as the "convertible frequency range") may be limited in order to shorten the distance measuring time or reduce the memory capacity. In the distance measuring device disclosed in Patent Document 1, the convertible frequency range may be limited. In addition, the optical fiber connecting the sensor body and the sensor head may be broken as the processing head on which the sensor head is mounted moves. When the optical fiber is broken, it is necessary to replace the broken optical fiber with another optical fiber. If the optical path length of the broken optical fiber and the optical path length of another optical fiber match, the distance calculation unit of the distance measuring device can calculate the distance from the sensor head to the processing surface of the workpiece. However, it is rare that the optical path lengths of both match, and depending on the difference between the optical path lengths of both, a situation may occur in which the frequency of the signal in the frequency domain deviates from the convertible frequency range. In such a case, there is a problem that the distance calculation unit cannot calculate the distance from the sensor head to the processing surface of the workpiece.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a distance measuring device that can calculate the distance from the sensor head to the machining surface of a workpiece even if a situation occurs in which the frequency of a signal in the frequency domain deviates from the convertible frequency range. [Means for solving the problem]

[0006] The distance measuring device according to the present disclosure includes a frequency shift unit that shifts the frequency of interference light between light irradiated from the sensor head unit onto the processing surface of the workpiece and light received by the sensor head unit and reflected by the processing surface, a band limiting unit that limits the frequency band of the interference light after frequency shift by the frequency shift unit, and a signal conversion unit that converts the interference light after frequency band limiting by the band limiting unit into a frequency domain signal.The distance measuring device also includes a shift amount changing unit that changes the amount of shift of the frequency of the interference light by the frequency shift unit if the frequency domain signal after conversion by the signal conversion unit does not include a signal whose signal strength is equal to or greater than a threshold, and a distance calculation unit that calculates the distance from the sensor head unit to the processing surface based on the signal whose signal strength is equal to or greater than the threshold if the frequency domain signal after conversion by the signal conversion unit includes a signal whose signal strength is equal to or greater than a threshold. Effect of the Invention

[0007] According to the present disclosure, even if a situation occurs in which the frequency of a signal in the frequency domain deviates from the convertible frequency range, the distance from the sensor head to the processing surface of the workpiece can be calculated. [Brief description of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing a machining device according to a first embodiment. [Diagram 2] 1 is a configuration diagram showing a sensor unit 20 of a machining device according to a first embodiment. [Diagram 3] FIG. 4 is an explanatory diagram showing a time waveform of frequency swept light. [Figure 4] 1 is a configuration diagram showing a distance measuring device 42 according to the first embodiment. [Diagram 5] 2 is a hardware configuration diagram showing hardware of a distance measuring device 42 according to the first embodiment. FIG. [Figure 6] FIG. 13 is a hardware configuration diagram of a computer in the case where the distance measuring device 42 is realized by software, firmware, or the like. [Figure 7] 13 is a flowchart showing a distance measuring method which is a processing procedure of the distance measuring device 42. [Figure 8] 10 is an explanatory diagram showing that the reflected light spectrum, which is a peak signal, is included in the convertible frequency band. FIG. [Figure 9] FIG. 11 is an explanatory diagram showing an example of a reference workpiece. [Figure 10] 11 is an explanatory diagram showing a state in which the reflected light spectrum is included in a convertible frequency band by changing the amount of frequency shift. FIG. [Figure 11] FIG. 11 is a configuration diagram showing a machining device according to a second embodiment. [Figure 12] 10 is a configuration diagram showing a sensor unit 20 of a machining device according to a second embodiment. FIG. [Figure 13] 1 is an explanatory diagram showing an example of a reference workpiece having oil attached to its machining surface 3a. FIG. [Figure 14]13 is an explanatory diagram showing two peak signals output from a shift amount changing unit 64. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In order to describe the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] Embodiment 1 FIG. 1 is a configuration diagram showing a machining device according to a first embodiment. The machining device shown in FIG. 1 includes a table 1, a vice 2, a processing unit 10, a sensor unit 20, and a control unit 50. The table 1 is a platform on which a workpiece 3 to be processed is placed. The vice 2 is a fixture that fixes the workpiece 3 so that it does not move when the workpiece 3 is processed. The workpiece 3 corresponds to a metal or the like whose processing surface 3a is processed by the processing part 10.

[0011] The machining section 10 includes a machining head 11, a machining tool 12, a head drive section 13, and a cutting oil nozzle 14. The processing unit 10 supplies cutting oil to the processing surface 3a of the workpiece 3, and cuts the processing surface 3a of the workpiece 3.

[0012] The processing head 11 includes a head main body portion 11a and a spindle 11b. The head main body 11a is a metal structure that supports the spindle 11b and the sensor head 21. The spindle 11b incorporates a chuck device (not shown) for detachably holding the machining tool 12. The spindle 11b is a metallic shaft-shaped part that is driven to rotate while holding the machining tool 12. The outer circumferential surface 11c is the outer circumferential surface facing the table 1 among the multiple outer circumferential surfaces that the head main body 11a has.

[0013] The machining tool 12 is a metal machining blade such as a milling cutter, an end mill, a drill, or a tap. The machining tool 12 cuts the machining surface 3a of the workpiece 3 by a rotating motion. The head driving unit 13 is a driving mechanism that changes the position of the head main body 11a relatively to the processing surface 3a in accordance with a control signal output from the control unit 50. The direction in which the position of the head main body 11a is changed by the head driving unit 13 is the x-axis direction, the y-axis direction, or the z-axis direction shown in FIG. The cutting oil nozzle 14 is a nozzle for applying cutting oil to the machining surface 3a of the workpiece 3 when a cutting oil supply command is received from the control unit 50.

[0014] The sensor unit 20 includes a sensor head unit 21, a sensor body unit 22, and a light transmission unit . The sensor unit 20 calculates the distance from the tip 21 a of the sensor head unit 21 to the processing surface 3 a of the workpiece 3 .

[0015] The sensor head portion 21 is attached to the outer circumferential surface 11c of the head main body portion 11a. The sensor head portion 21 irradiates the irradiation light output from the sensor main body portion 22 toward the processing surface 3a, and receives reflected light that is the irradiation light reflected by the processing surface 3a. The sensor head 21 outputs the reflected light to the sensor body 22 via the light transmitting section 23 . Here, the sensor head unit 21 irradiates the irradiation light toward the processing surface 3a and receives the reflected light, which is the irradiation light reflected by the processing surface 3a. However, this is merely an example, and the sensor head unit 21 may irradiate the light toward the surface of a reference workpiece as the processing surface 3a of the workpiece 3 and receive the reflected light, which is the irradiation light reflected by the surface of the reference workpiece. The reference workpiece is, for example, a metal or the like having a desired shape after cutting of the workpiece 3 .

[0016] The sensor body 22 outputs the irradiated light to the sensor head 21 via the light transmission section 23 . The sensor body 22 receives reflected light from the sensor head 21 via the light transmitting section 23 . The sensor body 22 detects interference light between the irradiated light and the reflected light, and calculates the distance from the tip 21a of the sensor head 21 to the processing surface 3a based on the interference light. The sensor body 22 outputs to the control unit 50 the distance from the tip 21a of the sensor head 21 to the processing surface 3a.

[0017] The optical transmission section 23 is realized by, for example, an optical fiber. The optical transmission section 23 is a transmission path for light traveling from the sensor body 22 to the sensor head section 21 and for light traveling from the sensor head section 21 to the sensor body 22 . 1 is provided with the optical transmission unit 23. However, this is merely an example, and the optical transmission unit 23 may not be provided in the machining device. In this case, the optical transmission between the sensor head unit 21 and the sensor main body unit 22 is performed through space.

[0018] The control unit 50 outputs a control signal indicating the movement position of the head main body 11 a to the head drive unit 13 , and outputs a cutting oil supply command to the cutting oil nozzle 14 .

[0019] FIG. 2 is a configuration diagram showing a sensor unit 20 of the machining tool according to the first embodiment. The sensor unit 20 includes a sensor head unit 21, a sensor main body unit 22, and an optical transmission unit 23, and the sensor head unit 21 includes a light collecting optical element 35. The sensor main body unit 22 includes a frequency sweep optical output unit 31, an optical branching unit 32, an optical interference unit 36, an analog-to-digital converter (hereinafter referred to as an "A / D converter") 39, an A / D converter 40, a register 41, and a distance measuring device 42.

[0020] The frequency swept light output unit 31 includes a frequency swept light source 31a that outputs frequency swept light whose frequency changes over time. The frequency swept light output unit 31 outputs the frequency swept light to the optical branching unit 32. The frequency swept light output unit 31 outputs to the A / D converter 40 a trigger signal indicating the timing at which the frequency swept light is output, or an amplitude signal indicating the amplitude of the frequency swept light.

[0021] FIG. 3 is an explanatory diagram showing the time waveform of the frequency swept light. The frequency swept light changes over time from the lowest frequency f min to the highest frequency f max The frequency of the light changes from the highest frequency f max Once the frequency reaches the lowest frequency f min Then, the frequency goes back to the lowest frequency f min to the highest frequency f max The frequency swept light is sometimes called chirped signal light. 3, the horizontal axis represents time, the vertical axis represents frequency, the solid line represents the reference light, and the dashed line represents the reflected light. The interference light is light having a frequency which is the difference between the frequency of the reference light and the frequency of the reflected light.

[0022] The optical branching unit 32 includes an optical coupler 33 and a circulator 34 . The optical coupler 33 is an optical branching element that branches the frequency swept light output from the frequency swept light output section 31 into a reference light and an irradiation light. The optical coupler 33 outputs the reference light to an optical interferometer 37 and outputs the illumination light to a circulator 34 .

[0023] The circulator 34 outputs the irradiation light output from the optical coupler 33 to the light collecting optical element 35 of the sensor head unit 21 via the optical transmission unit 23 . The circulator 34 outputs the reflected light output from the focusing optical element 35 to an optical interferometer 37 .

[0024] The light collecting optical element 35 collects the irradiation light output from the circulator 34 onto the processing surface 3a. Specifically, the focusing optical element 35 includes two aspherical lenses. Of the two aspherical lenses, the aspherical lens on the circulator 34 side converts the irradiation light output from the circulator 34 into parallel light. The aspherical lens on the processing surface 3a side focuses the parallel light on the processing surface 3a. The light collecting optical element 35 also receives reflected light, which is the irradiation light reflected by the processing surface 3a, and outputs the reflected light to the circulator 34 via the light transmitting section 23.

[0025] The optical interference section 36 includes an optical interferometer 37 and a photodetector 38 . The optical interference section 36 generates an interference light between the reference light and the reflected light output from the optical branching section 32 . The optical interference section 36 converts the interference light into an electrical signal, and outputs the electrical signal to the A / D converter 39 .

[0026] The optical interferometer 37 generates interference light between the reference light output from the optical coupler 33 and the reflected light output from the circulator 34, and outputs the interference light to a photodetector 38. The photodetector 38 detects the interference light output from the optical interferometer 37 and converts the interference light into an electrical signal. The photodetector 38 outputs an electrical signal to an A / D converter 39 .

[0027] The A / D converter 39 converts the electrical signal output from the photodetector 38 from an analog signal to a digital signal, and outputs the digital signal to the distance measuring device 42 . The A / D converter 40 obtains from the frequency swept light output unit 31 a trigger signal indicating the timing at which the frequency swept light is output, or an amplitude signal indicating the amplitude of the frequency swept light. The A / D converter 40 converts the trigger signal or the amplitude signal from an analog signal to a digital signal, and outputs the digital signal to the distance measuring device 42 .

[0028] The register 41 is, for example, a recording medium that records the amount of frequency shift and the refractive index of cutting oil. In the register 41, the amount of frequency shift is recorded for each focal position of the light irradiated from the sensor head portion 21 onto the processing surface 3a. The amount of frequency shift is a value determined by the optical path length of the optical fiber that realizes the optical transmission section 23 . The cutting oil refractive index is a value determined by the type of cutting oil supplied to the processing surface 3a from the cutting oil nozzle 14, the concentration of the cutting oil, the ambient temperature of the machining device, and the like.

[0029] The distance measuring device 42 is a device that calculates the distance from the tip 21 a of the sensor head portion 21 to the processing surface 3 a of the workpiece 3 . FIG. 4 is a configuration diagram showing a distance measuring device 42 according to the first embodiment. FIG. 5 is a hardware configuration diagram showing the hardware of the distance measuring device 42 according to the first embodiment. The distance measuring device 42 includes a frequency shifter 61 , a band limiter 62 , a signal converter 63 , a shift amount changer 64 , and a distance calculator 65 .

[0030] The frequency shift unit 61 is realized by, for example, a frequency shift circuit 71 shown in FIG. The frequency shift unit 61 acquires a digital signal related to the interference light (hereinafter referred to as "interference light data") from the A / D converter 39, and acquires a digital signal related to the trigger signal (hereinafter referred to as "trigger data") or a digital signal related to the amplitude signal (hereinafter referred to as "amplitude data") from the A / D converter 40. For example, if the frequency shifter 61 acquires the interference light data after acquiring the trigger data, the frequency shifter 61 shifts the frequency of the interference light data by the frequency shift amount recorded in the register 41 . The frequency shifter 61 outputs the interference light data after the frequency shift to the band limiter 62 .

[0031] The band limiting unit 62 is realized by, for example, a band limiting circuit 72 shown in FIG. The band limiting unit 62 includes, for example, a low-pass filter, a band-pass filter, or a high-pass filter. The band limiting unit 62 acquires the interference light data after frequency shifting from the frequency shifter 61 . The band limiting unit 62 limits the frequency band of the interference light data after frequency shift. The band limiting unit 62 outputs the interference light data after frequency band limiting to the signal converting unit 63 .

[0032] The signal conversion unit 63 is realized by, for example, a signal conversion circuit 73 shown in FIG. The signal conversion unit 63 acquires the interference light data after frequency band limitation from the band limitation unit 62 . The signal conversion unit 63 converts the interference light data after frequency band limitation into a signal in the frequency domain by, for example, FFT (Fast Fourier Transformation). The signal conversion unit 63 outputs the frequency domain signal to the shift amount change unit 64 .

[0033] The shift amount changing unit 64 is realized by, for example, a shift amount changing circuit 74 shown in FIG. The shift amount changing unit 64 obtains the frequency domain signal from the signal converting unit 63 . The shift amount changing unit 64 changes the amount of frequency shift by the frequency shift unit 61 if the frequency domain signal does not include a signal whose signal strength is equal to or greater than a threshold (hereinafter referred to as a "peak signal"). If a peak signal is included in the frequency domain signal, the shift amount changing unit 64 outputs the peak signal to the distance calculation unit 65 .

[0034] The distance calculation unit 65 is realized by, for example, a distance calculation circuit 75 shown in FIG. Since a peak signal is included in the frequency domain signal, when a peak signal is output from the shift amount change unit 64, the distance calculation unit 65 calculates the distance from the tip 21a of the sensor head unit 21 to the processing surface 3a based on the peak signal. The distance calculation unit 65 outputs the calculated distance to the shape calculation unit 66 .

[0035] The shape calculation unit 66 is built into the control unit 50, for example. The shape calculation unit 66 acquires the distance calculated by the distance calculation unit 65 every time the position of the sensor head unit 21 is moved. The shape calculation unit 66 calculates the shape of the workpiece 3 based on the multiple distances. Here, the shape calculation unit 66 is built into the control unit 50. However, this is merely an example, and the shape calculation unit 66 may be built into the distance measuring device 42, for example.

[0036] In Fig. 4, it is assumed that each of the components of the distance measuring device 42, that is, the frequency shifter 61, the band limiter 62, the signal converter 63, the shift amount changer 64, and the distance calculator 65, is realized by dedicated hardware as shown in Fig. 5. That is, it is assumed that the distance measuring device 42 is realized by a frequency shifter 71, a band limiter 72, a signal converter 73, a shift amount changer 74, and a distance calculator 75. Each of the frequency shift circuit 71, the band limiting circuit 72, the signal conversion circuit 73, the shift amount changing circuit 74 and the distance calculation circuit 75 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these.

[0037] The components of the distance measuring device 42 are not limited to those realized by dedicated hardware, and the distance measuring device 42 may be realized by software, firmware, or a combination of software and firmware. The software or firmware is stored as a program in the memory of a computer. The computer means hardware that executes the program, and includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor).

[0038] FIG. 6 is a hardware configuration diagram of a computer in the case where the distance measuring device 42 is realized by software, firmware, or the like. When the distance measuring device 42 is realized by software, firmware, or the like, a program for causing a computer to execute the respective processing procedures in the frequency shifter 61, the band limiter 62, the signal converter 63, the shift amount changer 64, and the distance calculator 65 is stored in a memory 81. Then, a processor 82 of the computer executes the program stored in the memory 81.

[0039] 5 shows an example in which each of the components of the distance measuring device 42 is realized by dedicated hardware, and FIG 6 shows an example in which the distance measuring device 42 is realized by software, firmware, etc. However, this is merely one example, and some of the components in the distance measuring device 42 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0040] Next, the operation of the machining device shown in FIG. 1 will be described. First, an operation of the machining device for calculating the shape of the workpiece 3 when the optical fiber realizing the optical transmission section 23 is not broken will be described. In the machining device shown in Fig. 1, the workpiece 3 is assumed to be an object that has already been machined by the machining device. However, this is merely an example, and the workpiece 3 may be an object that has not yet been machined by the machining device, or an object that is in the middle of being machined.

[0041] The control unit 50 outputs to the head driving unit 13 a control signal indicating the movement position of the head main body 11a. Here, for the sake of simplicity, it is assumed that the control unit 50 does not output a cutting oil supply command to the cutting oil nozzle 14 . The head driving unit 13 changes the position of the head main body 11a relative to the processing surface 3a in accordance with a control signal output from the control unit 50.

[0042] The frequency sweep light output unit 31 outputs, to the optical branching unit 32, for example, frequency sweep light as shown in FIG. 3, as frequency sweep light whose frequency changes over time every time the position of the head body 11a relative to the processing surface 3a changes. Furthermore, the frequency swept light output unit 31 outputs to the A / D converter 40 a trigger signal indicating the timing at which the frequency swept light is output, or an amplitude signal indicating the amplitude of the frequency swept light.

[0043] The optical coupler 33 receives the frequency swept light from the frequency swept light output unit 31 . The optical coupler 33 splits the frequency swept light into a reference light and an illumination light. The optical coupler 33 outputs the reference light to an optical interferometer 37 and outputs the illumination light to a circulator 34 . The circulator 34 outputs the irradiation light output from the optical coupler 33 to the light collecting optical element 35 via the light transmitting section 23 .

[0044] The light collecting optical element 35 collects the irradiation light output from the circulator 34 onto the processing surface 3a. The light collecting optical element 35 receives the reflected light, which is the irradiation light reflected by the processing surface 3a, and outputs the reflected light to the circulator 34 via the light transmitting section 23. The circulator 34 outputs the reflected light output from the focusing optical element 35 to an optical interferometer 37 .

[0045] The optical interferometer 37 receives the reference light from the optical coupler 33 and receives the reflected light from the circulator 34 . As shown in FIG. 3, the optical interferometer 37 generates light having a frequency difference between the frequency of the reference light and the frequency of the reflected light as interference light between the reference light and the reflected light. The optical interferometer 37 outputs the interference light to a photodetector 38 . The photodetector 38 detects the interference light output from the optical interferometer 37 and converts the interference light into an electrical signal. The photodetector 38 outputs an electrical signal to an A / D converter 39 .

[0046] The A / D converter 39 obtains from the photodetector 38 an electrical signal indicative of the interference light. The A / D converter 39 converts the electrical signal representing the interference light from an analog signal to a digital signal, and outputs the digital signal to the distance measuring device 42 . The A / D converter 40 obtains from the frequency swept light output unit 31 a trigger signal indicating the timing at which the frequency swept light is output, or an amplitude signal indicating the amplitude of the frequency swept light. When the A / D converter 40 receives the trigger signal, it converts the trigger signal from an analog signal to a digital signal and outputs the digital signal to the distance measuring device 42 . When the A / D converter 40 acquires the amplitude signal, it converts the amplitude signal from an analog signal to a digital signal and outputs the digital signal to the distance measuring device 42 .

[0047] FIG. 7 is a flowchart showing a distance measuring method which is a processing procedure of the distance measuring device 42. The register 41 records a frequency shift amount corresponding to the optical path length of the uncut optical transmission section 23. This frequency shift amount is a frequency shift amount by which the shift amount change section 64 shifts the frequency of the interference light data so that a peak signal, which is a signal with a signal intensity equal to or greater than a threshold, among signals in the frequency domain related to the interference light data after frequency band limitation by the band limiting section 62, is included in a frequency band in which the peak signal can be detected. In other words, the register 41 records a frequency shift amount such that the reflected light spectrum, which is a peak signal, is included in a convertible frequency band as shown in FIG. 8. The convertible frequency band is a frequency band limited by the band limiting section 62. FIG. 8 is an explanatory diagram showing that the reflected light spectrum, which is a peak signal, is included in the convertible frequency band. In FIG. 8, the horizontal axis represents frequency, and the vertical axis represents signal strength.

[0048] The frequency shift unit 61 acquires from the register 41 the amount of frequency shift corresponding to the focal position of the light irradiated from the sensor head unit 21 onto the processing surface 3a. The frequency shift unit 61 obtains interference light data, which is a digital signal related to the interference light, from the A / D converter 39, and obtains trigger data, which is a digital signal related to the trigger signal, or amplitude data, which is a digital signal related to the amplitude signal, from the A / D converter 40. If the frequency shifter 61 acquires interference light data after acquiring the trigger data, it shifts the frequency of the interference light data by the frequency shift amount (step ST1 in FIG. 7).

[0049] When the frequency shifter 61 acquires the amplitude data, the frequency shifter 61 determines whether the frequency of the frequency sweep light is equal to or lower than the minimum frequency f min Detect the timing when the switch returns to The frequency shifter 61 shifts the frequency of the frequency sweep light to the lowest frequency f min If the interference light data is acquired after detecting the timing at which the frequency has returned to the original frequency, the frequency of the interference light data is shifted by the frequency shift amount (step ST1 in FIG. 7). The frequency shifter 61 outputs the interference light data after the frequency shift to the band limiter 62 .

[0050] The band limiting unit 62 acquires the interference light data after frequency shifting from the frequency shifter 61 . The band limiting unit 62 limits the frequency band of the interference light data after frequency shift (step ST2 in FIG. 7). The frequency band limited by the band limiting unit 62 corresponds to the convertible frequency band shown in FIG. The band limiting unit 62 outputs the interference light data after frequency band limiting to the signal converting unit 63 .

[0051] The signal conversion unit 63 acquires the interference light data after frequency band limitation from the band limitation unit 62 . The signal conversion unit 63 converts the interference light data after frequency band limitation into a signal in the frequency domain by, for example, performing FFT on the interference light data (step ST3 in FIG. 7). The signal conversion unit 63 outputs the frequency domain signal to the shift amount change unit 64 .

[0052] The shift amount changing unit 64 obtains the frequency domain signal from the signal converting unit 63 . The shift amount changing unit 64 determines whether or not a peak signal, which is a signal whose signal strength is equal to or greater than a threshold, is included in the frequency domain signal. When the optical transmission section 23 is not disconnected, the frequency shift section 61 shifts the frequency of the interference light data by the frequency shift amount recorded in the register 41. Therefore, the peak signal is included in the convertible frequency band, as shown in Fig. 8. Therefore, when the optical transmission section 23 is not disconnected, the peak signal is included in the signal in the frequency domain. If a peak signal is included in the frequency domain signal (step ST4 in FIG. 7: YES), the shift amount changing unit 64 outputs the peak signal to the distance calculation unit 65.

[0053] When a peak signal is output from the shift amount change unit 64, the distance calculation unit 65 calculates the distance from the tip 21a of the sensor head unit 21 to the processing surface 3a based on the peak signal (step ST5 in FIG. 7). The distance from the tip 21a of the sensor head unit 21 to the processing surface 3a can be obtained from the frequency of the peak signal. The process of calculating the distance from the frequency of the peak signal is a known technique, so a detailed description will be omitted. The distance calculation unit 65 outputs the calculated distance to the shape calculation unit 66 .

[0054] If the position of the head main body 11a is changed by the control unit 50 outputting a control signal indicating the movement position of the head main body 11a to the head driving unit 13 (step ST6 in FIG. 7: YES), the processing of steps ST1 to ST5 is repeated. When the calculation of the distance is completed and the position of the head main body 11a is not changed (step ST6 in FIG. 7: NO), the machining device ends the series of processes.

[0055] The shape calculation unit 66 acquires the distance calculated by the distance calculation unit 65 every time the position of the sensor head unit 21 is moved. The shape calculation unit 66 calculates the shape of the workpiece 3 based on the multiple distances. The process of calculating the shape of the workpiece 3 based on the multiple distances is a known technique, and therefore a detailed description thereof will be omitted.

[0056] Next, the operation of the machining device when the optical fiber that realizes the optical transmission section 23 is broken and replaced with another optical fiber will be described. In this case, a reference workpiece is placed on the table 1 instead of the workpiece 3 . FIG. 9 is an explanatory diagram showing an example of a reference workpiece.

[0057] The control unit 50 outputs to the head driving unit 13 a control signal indicating the movement position of the head main body 11a. The head driving unit 13 changes the position of the head main body 11a relative to the processing surface 3a in accordance with a control signal output from the control unit 50.

[0058] The frequency sweep light output unit 31 outputs, to the optical branching unit 32, for example, frequency sweep light as shown in FIG. 3, as frequency sweep light whose frequency changes over time every time the position of the head body 11a relative to the processing surface 3a changes. Furthermore, the frequency swept light output unit 31 outputs to the A / D converter 40 a trigger signal indicating the timing at which the frequency swept light is output, or an amplitude signal indicating the amplitude of the frequency swept light.

[0059] The optical coupler 33 receives the frequency swept light from the frequency swept light output unit 31 . The optical coupler 33 splits the frequency swept light into a reference light and an illumination light. The optical coupler 33 outputs the reference light to an optical interferometer 37 and outputs the illumination light to a circulator 34 . The circulator 34 outputs the irradiation light output from the optical coupler 33 to the light collecting optical element 35 via the light transmitting section 23 .

[0060] The light collecting optical element 35 collects the irradiation light output from the circulator 34 onto the processing surface 3a. The light collecting optical element 35 receives the reflected light, which is the irradiation light reflected by the processing surface 3a, and outputs the reflected light to the circulator 34 via the light transmitting section 23. The circulator 34 outputs the reflected light output from the focusing optical element 35 to an optical interferometer 37 .

[0061] The optical interferometer 37 receives the reference light from the optical coupler 33 and receives the reflected light from the circulator 34 . As shown in FIG. 3, the optical interferometer 37 generates light having a frequency difference between the frequency of the reference light and the frequency of the reflected light as interference light between the reference light and the reflected light. The optical interferometer 37 outputs the interference light to a photodetector 38 . The photodetector 38 detects the interference light output from the optical interferometer 37 and converts the interference light into an electrical signal. The photodetector 38 outputs an electrical signal to an A / D converter 39 .

[0062] The A / D converter 39 obtains from the photodetector 38 an electrical signal indicative of the interference light. The A / D converter 39 converts the electrical signal representing the interference light from an analog signal to a digital signal, and outputs the digital signal to the distance measuring device 42 . The A / D converter 40 obtains from the frequency swept light output unit 31 a trigger signal indicating the timing at which the frequency swept light is output, or an amplitude signal indicating the amplitude of the frequency swept light. When the A / D converter 40 receives the trigger signal, it converts the trigger signal from an analog signal to a digital signal and outputs the digital signal to the distance measuring device 42 . When the A / D converter 40 acquires the amplitude signal, it converts the amplitude signal from an analog signal to a digital signal and outputs the digital signal to the distance measuring device 42 .

[0063] The frequency shift unit 61 of the distance measuring device 42 obtains from the register 41 the amount of frequency shift corresponding to the focal position of the light irradiated from the sensor head unit 21 onto the processing surface 3a. The frequency shift unit 61 obtains interference light data, which is a digital signal related to the interference light, from the A / D converter 39, and obtains trigger data, which is a digital signal related to the trigger signal, or amplitude data, which is a digital signal related to the amplitude signal, from the A / D converter 40. If the frequency shifter 61 acquires interference light data after acquiring the trigger data, it shifts the frequency of the interference light data by the frequency shift amount (step ST1 in FIG. 7).

[0064] When the frequency shifter 61 acquires the amplitude data, the frequency shifter 61 determines whether the frequency of the frequency sweep light is equal to or lower than the minimum frequency f min Detect the timing when the switch returns to The frequency shifter 61 shifts the frequency of the frequency sweep light to the lowest frequency f min If the interference light data is acquired after detecting the timing at which the frequency has returned to the original frequency, the frequency of the interference light data is shifted by the frequency shift amount (step ST1 in FIG. 7). The frequency shifter 61 outputs the interference light data after the frequency shift to the band limiter 62 .

[0065] The band limiting unit 62 acquires the interference light data after frequency shifting from the frequency shifter 61 . The band limiting unit 62 limits the frequency band of the interference light data after frequency shift (step ST2 in FIG. 7). The band limiting unit 62 outputs the interference light data after frequency band limiting to the signal converting unit 63 .

[0066] The signal conversion unit 63 acquires the interference light data after frequency band limitation from the band limitation unit 62 . The signal conversion unit 63 converts the interference light data after frequency band limitation into a signal in the frequency domain by, for example, performing FFT on the interference light data (step ST3 in FIG. 7). The signal conversion unit 63 outputs the frequency domain signal to the shift amount change unit 64 .

[0067] The shift amount changing unit 64 obtains the frequency domain signal from the signal converting unit 63 . The shift amount changing unit 64 determines whether or not a peak signal, which is a signal whose signal strength is equal to or greater than a threshold, is included in the frequency domain signal. The frequency shift amount recorded in the register 41 is the shift amount corresponding to the uncut optical transmission section 23. Therefore, if there is a large difference between the optical path length of the broken optical transmission section 23 and the optical path length of the replaced different optical fiber, the peak signal may not be included in the convertible frequency band. Therefore, when the broken optical transmission section 23 is replaced with a different optical transmission section 23, the peak signal may not be included in the signal in the frequency domain. If no peak signal is included in the frequency domain signal (step ST4 in FIG. 7: NO), the shift amount changing unit 64 outputs a command to change the frequency shift amount to the frequency shift unit 61 (step ST7 in FIG. 7).

[0068] When the frequency shift unit 61 receives a command to change the frequency shift amount from the shift amount changing unit 64, it changes the frequency shift amount and shifts the frequency of the interference light data by the changed frequency shift amount (step ST8 in FIG. 7). The changed frequency shift amount is a frequency shift amount obtained by adding or subtracting, for example, a preset frequency from the frequency shift amount recorded in the register 41. The frequency shifter 61 causes the register 41 to record the changed frequency shift amount. The frequency shifter 61 outputs the interference light data after the frequency shift to the band limiter 62 .

[0069] The band limiting unit 62 acquires the interference light data after frequency shifting from the frequency shifter 61 . The band limiting unit 62 limits the frequency band of the interference light data after frequency shift (step ST2 in FIG. 7). The band limiting unit 62 outputs the interference light data after frequency band limiting to the signal converting unit 63 .

[0070] The signal conversion unit 63 acquires the interference light data after frequency band limitation from the band limitation unit 62 . The signal conversion unit 63 converts the interference light data after frequency band limitation into a signal in the frequency domain by, for example, performing FFT on the interference light data (step ST3 in FIG. 7). The signal conversion unit 63 outputs the frequency domain signal to the shift amount change unit 64 .

[0071] The shift amount changing unit 64 obtains the frequency domain signal from the signal converting unit 63 . The shift amount changing unit 64 determines whether or not a peak signal, which is a signal whose signal strength is equal to or greater than a threshold, is included in the frequency domain signal. If no peak signal is included in the frequency domain signal (step ST4 in FIG. 7: NO), the shift amount changing unit 64 outputs a frequency shift amount change command to the frequency shift unit 61, thereby causing the frequency shift unit 61 to further change the frequency shift amount (step ST7 in FIG. 7). When the frequency shifter 61 receives a command to change the frequency shift amount from the shift amount changing unit 64, it further changes the frequency shift amount and shifts the frequency of the interference light data by the changed frequency shift amount (step ST8 in FIG. 7). The frequency shifter 61 causes the register 41 to record the changed frequency shift amount. The frequency shifter 61 outputs the interference light data after the frequency shift to the band limiter 62 .

[0072] The processes of steps ST2 to ST4, ST7, and ST8 are repeated until a peak signal is included in the frequency domain signal. As shown in FIG. 10, if a peak signal is included in the frequency domain signal, the workpiece 3 is placed on the table 1 instead of the reference workpiece. FIG. 10 is an explanatory diagram showing a state in which the reflected light spectrum is included in the convertible frequency band by changing the amount of frequency shift. In FIG. 10, the horizontal axis represents frequency, and the vertical axis represents signal strength. After the workpiece 3 is placed on the table 1, the machining device calculates the shape of the workpiece 3 in the same manner as when the optical fiber realizing the optical transmission section 23 is not broken. However, the frequency shift amount used by the frequency shift section 61 is the frequency shift amount when a peak signal is included in the signal in the frequency domain.

[0073] Here, when the optical fiber realizing the optical transmission section 23 is broken and replaced with another optical fiber, a reference work is placed on the table 1 instead of the workpiece 3, and thereafter, if a peak signal is included in the frequency domain signal, the workpiece 3 is placed on the table 1 instead of the reference work. However, this is merely an example, and even if the optical fiber is broken and replaced with another optical fiber, the processing of steps ST1 to ST8 in Fig. 7 may be performed with the workpiece 3 placed on the table 1.

[0074] In the above-described first embodiment, the distance measuring device 42 is configured to include a frequency shifter 61 for shifting the frequency of the interference light between the light irradiated from the sensor head 21 onto the processing surface 3a of the workpiece 3 and the light received by the sensor head 21 and reflected by the processing surface 3a, a band limiter 62 for limiting the frequency band of the interference light after the frequency shift by the frequency shifter 61, and a signal converter 63 for converting the interference light after the frequency band limiter by the band limiter 62 into a frequency domain signal. The distance measuring device 42 also includes a shift amount changer 64 for changing the amount of shift of the frequency of the interference light by the frequency shifter 61 if the frequency domain signal after the conversion by the signal converter 63 does not include a signal having a signal strength equal to or greater than a threshold, and a distance calculator 65 for calculating the distance from the sensor head 21 to the processing surface 3a based on the signal having a signal strength equal to or greater than the threshold if the frequency domain signal after the conversion by the signal converter 63 includes a signal having a signal strength equal to or greater than a threshold. Therefore, the distance measuring device 42 can calculate the distance from the sensor head portion 21 to the processing surface 3a of the workpiece 3 even if a situation occurs in which the frequency of the signal in the frequency domain deviates from the convertible frequency range.

[0075] 1, when the frequency shift unit 61 acquires the interference light data from the A / D converter 39, it shifts the frequency of the interference light data by the frequency shift amount. When the frequency shift unit 61 acquires the interference light data from the A / D converter 39 before shifting the frequency of the interference light data, the frequency shift unit 61 may perform nonlinearity compensation of the frequency sweep light source 31a on the interference light data based on the trigger data or the amplitude data output from the A / D converter 40. The compensation process for nonlinearity compensation itself is a known technique, so a detailed description will be omitted. Furthermore, the frequency shifter 61 may perform downsampling processing such as signal thinning by decimation on the interference light data. The downsampling processing itself is a known technique, and therefore a detailed description thereof will be omitted.

[0076] Embodiment 2 In the second embodiment, a distance measuring device 42 including a distance calculation unit 67 that calculates the distance from the sensor head unit 21 to the processing surface 3a on which oil is attached will be described.

[0077] The configuration of the machining device other than the distance measuring device 42 is similar to that of the machining device shown in FIG. Fig. 11 is a configuration diagram showing a distance measuring device 42 according to embodiment 2. In Fig. 11, the same reference numerals as in Fig. 4 indicate the same or corresponding parts, and detailed description thereof will be omitted. Fig. 12 is a hardware configuration diagram showing the hardware of a distance measuring device 42 according to embodiment 2. In Fig. 12, the same reference numerals as in Fig. 5 indicate the same or corresponding parts, and detailed description thereof will be omitted. The distance measuring device 42 includes a frequency shifter 61 , a band limiter 62 , a signal converter 63 , a shift amount changer 64 , and a distance calculator 67 .

[0078] The distance calculation unit 67 is realized by, for example, a distance calculation circuit 77 shown in FIG. Since a peak signal is included in the frequency domain signal, when a peak signal is output from the shift amount change unit 64, the distance calculation unit 67 calculates the distance from the sensor head unit 21 to the processing surface 3a based on the peak signal, in the same manner as the distance calculation unit 65 shown in Figure 4. If two peak signals are contained in the frequency domain signal after conversion by the signal conversion unit 63 because oil is attached to the machining surface 3a, the distance calculation unit 67 calculates the thickness of the oil film attached to the machining surface 3a and the distance from the sensor head unit 21 to the oil surface based on the two peak signals. The distance calculation unit 67 calculates the distance from the sensor head unit 21 to the processing surface 3a from the film thickness and the distance to the oil surface. The distance calculation unit 67 outputs the calculated distance to the shape calculation unit 66 .

[0079] 11, it is assumed that the frequency shifter 61, the band limiter 62, the signal converter 63, the shift amount changer 64, and the distance calculator 67, which are components of the distance measuring device 42, are realized by dedicated hardware as shown in Fig. 12. That is, it is assumed that the distance measuring device 42 is realized by a frequency shifter 71, a band limiter 72, a signal converter 73, a shift amount changer 74, and a distance calculator 77. Each of the frequency shift circuit 71, the band limiting circuit 72, the signal conversion circuit 73, the shift amount changing circuit 74 and the distance calculation circuit 77 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination of these.

[0080] The components of the distance measuring device 42 are not limited to those realized by dedicated hardware, and the distance measuring device 42 may be realized by software, firmware, or a combination of software and firmware. When the distance measuring device 42 is realized by software, firmware, or the like, a program for causing a computer to execute the respective processing procedures in the frequency shifter 61, the band limiter 62, the signal converter 63, the shift amount changer 64, and the distance calculator 67 is stored in a memory 81 shown in Fig. 6. Then, a processor 82 shown in Fig. 6 executes the program stored in the memory 81.

[0081] 12 shows an example in which each of the components of the distance measuring device 42 is realized by dedicated hardware, while Fig. 6 shows an example in which the distance measuring device 42 is realized by software, firmware, etc. However, this is merely one example, and some of the components in the distance measuring device 42 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0082] Next, the operation of distance measuring device 42 shown in Fig. 11 will be described. The components other than distance calculation section 67 are the same as distance measuring device 42 shown in Fig. 4. Therefore, only the operation of distance calculation section 67 will be described here.

[0083] The distance calculation unit 67 acquires the peak signal from the shift amount change unit 64 . For example, when oil is attached to the machining surface 3a as shown in Fig. 13, two peak signals may be output from the shift amount change unit 64 as shown in Fig. 14. The machining surface 3a is the surface of a reference workpiece or the machining surface of the workpiece 3. FIG. 13 is an explanatory diagram showing an example of a reference workpiece having oil attached to its machining surface 3a. FIG. 14 is an explanatory diagram showing two peak signals output from the shift amount changing section 64. As shown in FIG. In FIG. 14, the horizontal axis represents frequency, and the vertical axis represents signal strength. Of the two peak signals, one peak signal is the spectrum of light reflected by the oil surface, and the other peak signal is the spectrum of light that passes through the oil surface and is reflected by the processing surface 3a. The oil adhering to the machining surface 3 a is cutting oil supplied from a cutting oil nozzle 14 .

[0084] The distance calculation unit 67 calculates the distance L from the sensor head unit 21 to the oil surface based on one of the peak signals. 1 Based on the peak signal, the distance to the oil level L 1 The process of calculating the value of is a known technique, and therefore a detailed description thereof will be omitted. Further, the distance calculation unit 67 calculates the distance L from the sensor head unit 21 to the processing surface 3a based on the other peak signal. 2 However, since the speed of light passing through oil changes depending on the refractive index of the oil, the distance L calculated based on the other peak signal is 2 may contain errors. As shown in the following equation (1), if the refractive index of light in a vacuum is "1," the higher the refractive index n of the oil, the slower the speed of light v, and the lower the refractive index of the oil, the faster the speed of light v. n=c / v (1) In formula (1), c is the speed of light in a vacuum. The speed of light in air, c', is 1.000292 at 0 degrees Celsius and 1 atmospheric pressure. The relationship between the speed of light in air, c', and the speed of light passing through oil, v, is expressed by the following formula (2). n=c' / v (2)

[0085] The distance calculation unit 67 calculates the distance L 2 To compensate for this, the refractive index n of the oil is calculated as shown in the following equation (3). n= {((FFT 12 -FFT 11 )-(FFT 02 -FFT 01 ))×L bin} / (d 1 -d 0 ) (3) In formula (3), d 0 , d1 are the distances of positions on the processing surface 3a whose distances to the processing surface 3a are known among a plurality of positions on the processing surface 3a. 0 Position and distance d 1 The positions are different from each other. FFT 01 is the distance d 0 is the number of FFTBin, which is the frequency axis showing the peak signal from the machining surface 3a at the position 01 is the distance d 0 is the FFTBin number from the oil surface at the position. FFT 11 is the distance d 1 is the number of FFTBin from the machining surface 3a at the position of FFT 12 is the distance d 1 is the FFTBin number from the oil surface at the position. L bin is FFTBin, which depends on, for example, the FFT size.

[0086] The distance calculation unit 67 calculates the speed v of light passing through the oil by substituting the refractive index n of the oil into equation (2). Then, the distance calculation unit 67 calculates the oil film thickness W based on the speed v of light passing through the oil. The film thickness W can be calculated based on, for example, the time difference between the time when light is emitted from the sensor head 21 and the time when the reflected light is received by the sensor head 21, and the speed v. The distance calculation unit 67 calculates the distance L to the oil level as shown in the following equation (4). 1 Using the oil film thickness W, the compensated distance L 2 ' is calculated. L 2 '=L 1 +W (4)

[0087] In the above-described second embodiment, the distance measuring device 42 is configured so that, if two signals having a signal intensity equal to or greater than a threshold are included in the frequency domain signals converted by the signal converting unit 63 because oil is attached to the processing surface 3a, the distance calculating unit 67 calculates the thickness of the oil film attached to the processing surface 3a and the distance from the sensor head unit 21 to the oil surface based on the two signals having a signal intensity equal to or greater than a threshold, and calculates the distance from the sensor head unit 21 to the processing surface 3a from the film thickness and the distance to the oil surface. Therefore, even if a situation occurs in which the frequency of the signal in the frequency domain deviates from the convertible frequency range when oil is attached to the processing surface 3a, the distance measuring device 42 can calculate the distance from the sensor head unit 21 to the processing surface 3a of the workpiece 3.

[0088] In addition, the present disclosure allows free combination of the respective embodiments, modification of any of the components of each embodiment, or omission of any of the components of each embodiment. [Industrial Applicability]

[0089] The present disclosure is suitable for a distance measuring device, a distance measuring method, and a machining device. [Explanation of symbols]

[0090] 1 table, 2 vice, 3 workpiece, 3a machining surface, 10 machining section, 11 machining head, 11a head main body, 11b spindle, 11c outer peripheral surface, 12 machining tool, 13 head drive section, 14 cutting oil nozzle, 20 sensor section, 21 sensor head section, 22 sensor main body, 23 optical transmission section, 31 frequency sweep optical output section, 31a frequency sweep light source, 32 optical branching section, 33 optical coupler, 34 circulator, 35 focusing optical element, 36 optical interference section, 37 optical interferometer, 38 optical detector, 39, 40 A / D converter, 41 register, 42 distance measuring device, 50 control section, 61 frequency shift section, 62 band limiting section, 63 signal conversion section, 64 shift amount changing section, 65 distance calculation section, 66 shape calculation section, 67 Distance calculation unit, 71 frequency shift circuit, 72 band limiting circuit, 73 signal conversion circuit, 74 shift amount changing circuit, 75 distance calculation circuit, 77 distance calculation circuit, 81 memory, 82 processor.

Claims

1. a frequency shifter that shifts the frequency of interference light between light irradiated from a sensor head onto a processing surface of a workpiece and light reflected from the processing surface and received by the sensor head; a band limiting unit that limits a frequency band of the interference light after the frequency shift by the frequency shifter; a signal conversion unit that converts the interference light after the frequency band limitation by the band limiting unit into a signal in a frequency domain; a shift amount changing unit that changes an amount of shift of the frequency of the interference light by the frequency shift unit if the frequency domain signal after conversion by the signal conversion unit does not include a signal having a signal intensity equal to or greater than a threshold value; a distance calculation unit that calculates a distance from the sensor head unit to the processing surface based on a signal having a signal strength equal to or greater than a threshold value if the signal having a signal strength equal to or greater than a threshold value is included in the frequency domain signal after conversion by the signal conversion unit; A distance measuring device comprising:

2. Light is irradiated from the sensor head unit onto a surface of a reference workpiece having a desired shape after machining of the workpiece as the machining surface of the workpiece; The frequency shift unit is Shifting the frequency of interference light between the light irradiated onto the surface of the reference workpiece and the light reflected off the surface of the reference workpiece; The distance calculation unit 2. The distance measuring device according to claim 1, wherein the distance from the sensor head to the surface of the reference workpiece is calculated as the distance from the sensor head to the processed surface.

3. The distance calculation unit The distance measuring device described in claim 1, characterized in that if the frequency domain signal after conversion by the signal conversion unit contains two signals whose signal strength is above a threshold because oil is attached to the machining surface received by the sensor head unit, the thickness of the oil attached to the machining surface and the distance from the sensor head unit to the oil surface are calculated based on the two signals whose signal strength is above a threshold, and the distance from the sensor head unit to the machining surface is calculated from the film thickness and the distance to the oil surface.

4. The frequency shift unit shifts the frequency of interference light between light irradiated from the sensor head unit onto the processing surface of the workpiece and light reflected from the processing surface and received by the sensor head unit; a band limiting unit that limits a frequency band of the interference light after the frequency shift by the frequency shifter; a signal conversion unit converting the interference light after the frequency band limitation by the band limiting unit into a frequency domain signal; a shift amount changing unit, when the frequency domain signal after conversion by the signal conversion unit does not include a signal having a signal intensity equal to or greater than a threshold, changing an amount of shift of the frequency of the interference light by the frequency shift unit; If a signal having a signal strength equal to or greater than a threshold is included in the frequency domain signals converted by the signal conversion unit, a distance calculation unit calculates a distance from the sensor head unit to the processing surface based on the signal having a signal strength equal to or greater than a threshold. Distance measurement method.

5. a sensor head unit that irradiates light onto a processing surface of a workpiece and receives light reflected from the processing surface; a light interference unit that detects interference light between light irradiated from the sensor head unit and light received by the sensor head unit; a frequency shift unit that shifts the frequency of the interference light detected by the light interference unit; a band limiting unit that limits a frequency band of the interference light after the frequency shift by the frequency shifter; a signal conversion unit that converts the interference light after the frequency band limitation by the band limiting unit into a signal in a frequency domain; a shift amount changing unit that changes an amount of shift of the frequency of the interference light by the frequency shift unit if the frequency domain signal after conversion by the signal conversion unit does not include a signal having a signal intensity equal to or greater than a threshold value; a distance calculation unit that calculates a distance from the sensor head unit to the processing surface based on a signal having a signal strength equal to or greater than a threshold value if the signal having a signal strength equal to or greater than a threshold value is included in the frequency domain signal after conversion by the signal conversion unit; A machining device equipped with the above.

6. The distance calculation unit Each time the position of the sensor head is moved, a distance from the sensor head to the processing surface is calculated; 6. The machining device according to claim 5, further comprising a shape calculation unit that calculates a shape of the workpiece based on the plurality of distances calculated by the distance calculation unit.

Images