Optical distance measuring device

Abstract

The optical distance measuring device includes a coupler (102) that splits frequency-swept laser light into measurement light and reference light, an optical sensor head (200) that receives the measurement light, irradiates the received measurement light toward an object, and receives reflected light of the measurement light, an optical interferometer (106) that generates interference light by causing interference between the reference light and the received reflected light, a light receiving unit (108, 110) that receives the generated interference light and converts the received interference light into an electrical signal, and a signal processing unit (112) that can calculate the distance from the optical sensor head to the object based on the converted electrical signal, and the optical sensor head includes optical components including a first optical waveguide and a second optical waveguide, and is capable of emitting measurement light from the first optical waveguide and receiving reflected light from the second optical waveguide.

Description

[Technical field]

[0001] The present disclosure relates to an optical distance measuring device. [Background technology]

[0002] Patent Document 1 discloses a technology related to a three-dimensional measuring device including: an irradiation device configured to be able to irradiate an irradiation area of ​​a measured object with irradiation light spatially modulated with a predetermined modulation pattern within the irradiation area; a first multi-core fiber having a plurality of cores capable of receiving outgoing light emitted from the measured object irradiated with the irradiation light and including information of the measured object in the irradiation area; and a light-receiving device including: an optical information calculation unit configured to be able to calculate three-dimensional information of the measured object based on optical information of the outgoing light received by each of the plurality of cores and optical information of the irradiation light, wherein the first multi-core fiber has a numerical aperture determined by the maximum receiving angle of the outgoing light in each of the plurality of cores and the refractive index of a region between the measured object and the first multi-core fiber such that the irradiation area is included in an overlapping region in which receiving angle ranges of the outgoing light that can be received by each of two or more of the plurality of cores overlap with each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-179333 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the technology of Patent Document 1, it is assumed that the light irradiated to the object to be measured and the light reflected from the object to be measured propagate along the same optical path. Therefore, when liquid such as water or cutting oil is attached to the object to be measured, the reflected light does not return to the optical path along which the irradiated light propagated, making it difficult to measure the shape of the object to be measured.

[0005] The present disclosure has been made to solve such problems, and aims to provide an optical distance measuring device that enables measurement of the shape of a measured object even when liquid is attached to the measured object. [Means for solving the problem]

[0006] One aspect of an optical distance measuring device according to an embodiment of the present disclosure includes a coupler that splits frequency-swept laser light into measurement light and reference light, an optical sensor head that receives the measurement light and irradiates the received measurement light toward an object while receiving reflected light of the measurement light, an optical interferometer that generates interference light by causing the reference light to interfere with the received reflected light, a light receiving unit that receives the generated interference light and converts the received interference light into an electrical signal, and a signal processing unit that can calculate a distance from the optical sensor head to the object based on the converted electrical signal, wherein the optical sensor head includes optical components including a first optical waveguide and a second optical waveguide, and is capable of emitting the measurement light from the first optical waveguide and receiving the reflected light from the second optical waveguide. Effect of the Invention

[0007] According to the optical distance measuring device according to the embodiment of the present disclosure, it is possible to measure the shape of a measurement object even if liquid is attached to the measurement object. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 illustrates an example of the configuration of an optical distance measuring device. [Diagram 2] FIG. 4 is a diagram showing the relationship between a reference light and a reflected light. [Diagram 3] 1 is a diagram showing an example of a cross section of a multicore fiber. [Figure 4] 4A, 4B, and 4C are diagrams showing the configuration of an optical sensor head. [Diagram 5] FIG. 2 is a diagram showing the geometric relationship of optical paths. [Figure 6] A table that defines the meaning of parameters or variables. [Figure 7A] FIG. 2 is a diagram illustrating an example of the hardware configuration of a processing unit. [Figure 7B] FIG. 2 is a diagram illustrating an example of the hardware configuration of a processing unit. [Figure 8] 4 is a flowchart of an optical distance measuring method. [Figure 9] 4 is a flowchart of an optical distance measuring method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Various embodiments of the present disclosure will be described in detail below with reference to the drawings. In the drawings, identical or similar parts are denoted by identical or similar reference numerals, and duplicated descriptions of such parts will be omitted. In the present disclosure, the term "or" is used to mean an inclusive logical OR unless otherwise specified.

[0010] Embodiment 1 <Configuration> The configuration of an optical distance measuring device according to a first embodiment of the present disclosure will be described with reference to Fig. 1. As shown in Fig. 1, the optical distance measuring device according to the first embodiment includes an optical sensor body 100 and an optical sensor head 200. The optical sensor body 100 and the optical sensor head 200 are connected by an optical component including a plurality of optical waveguides such as a multi-core fiber MCF.

[0011] The optical sensor body 100 includes, for example, a frequency sweep optical output unit 101, a coupler 102, a fan-in 103, a fan-in 105, a circulator 104, an optical interferometer 106, a fan-out 107, a plurality of optical detectors 108-1 to 108-N, an A / D converter 109, a plurality of A / D converters 110-1 to 110-N, a register 111, a signal processing unit 112, and a shape calculation unit 113. The optical detectors 108-1 to 108-N and the A / D converters 110-1 to 110-N constitute a light receiving unit. The signal processing unit 112 and the shape calculation unit 113 constitute a processing unit 114. N represents the number of optical waveguides connecting the optical sensor body 100 and the optical sensor head 200. The frequency sweep optical output unit 101 may be provided as an external element of the optical sensor body 100.

[0012] The optical sensor head 200 includes, for example, a microlens array 201, a beam expander 202, and an objective lens 203. The detailed configurations of the optical sensor body 100 and the optical sensor head 200 will be described below.

[0013] <Configuration of the optical sensor body> (Frequency sweep optical output section) The frequency swept light output unit 101 sweeps the frequency of a laser light, which is a continuous light emitted from a laser light source such as a semiconductor laser, and outputs the frequency swept frequency swept light. For example, an optical signal shown as a reference light in FIG. 2 corresponds to the frequency swept light. As shown in FIG. 2, the reference light (frequency swept light) is an optical signal whose frequency increases linearly at a constant period. The frequency swept light output from the frequency swept light output unit 101 is guided to a coupler 102 via, for example, a single-core fiber SCF.

[0014] (Coupler) The coupler 102 branches the input frequency swept light into multiple lights and outputs the branched frequency swept light as measurement light or reference light. The coupler 102, for example, branches the input frequency swept light into 1+N laser lights. One of the branched laser lights is output as measurement light. The output measurement light is guided to the fan-in 103, for example, via one single-core fiber SCF. The N branched laser lights are output as N reference lights. The output reference lights are guided to the fan-in 105, for example, via N single-core fibers SCF. The optical path length is adjusted by the single-core fiber SCF between the coupler 102 and the fan-in 105.

[0015] (Fan-in) The fan-in 103 optically couples the input measurement light to a central core (first optical waveguide) of a multi-core fiber MCF having N cores. The measurement light optically coupled to the central core of the multi-core fiber MCF is guided to the circulator 104.

[0016] The fan-in 105 optically couples the input reference light to a central core of a multi-core fiber MCF having N cores.

[0017] (Circulator) The circulator 104 is configured by, for example, a three-port optical circulator, and guides the measurement light to the optical sensor head 200. The circulator 104 also guides reflected light, which is the measurement light irradiated from the optical sensor head 200 and reflected on the object Obj, to an optical interferometer .

[0018] (Optical Interferometer) The optical interferometer 106 is, for example, composed of a fiber coupler, and causes interference between the reference light input from the fan-in 105 via the multi-core fiber MCF and the reflected light input from the circulator 104 via the multi-core fiber MCF. Specifically, a 1×N branch fiber coupler is used as the optical interferometer 106 to cause laser lights propagating through the central core (first optical waveguide) to interfere with each other, and to cause laser lights propagating through the peripheral cores (second optical waveguide) to interfere with each other. The optical interferometer 106 generates a first interference light from the reference light and the reflected light received through the central core (first optical waveguide). In addition, when the optical interferometer 106 receives the reflected light propagating through the peripheral core (second optical waveguide), it generates a second interference light from the reference light and the reflected light received through the peripheral core (second optical waveguide). The optical interferometer 106 outputs one or two of the generated interference lights.

[0019] (Fanout) The fan-out 107 optically couples a multi-core fiber MCF having N cores to N single-core fibers SCF.

[0020] (Photodetector) The multiple photodetectors 108-1 to 108-N photoelectrically convert the interference light and output analog signals indicative of the interference light.

[0021] (A / D converter) The plurality of A / D converters 110-1 to 110-N perform A / D conversion on the analog signals input thereto. That is, the A / D converters 110-1 to 110-N sample the analog signals and output the sampled digital signals as received signals.

[0022] The A / D converter 109 A / D converts the analog electrical signal obtained by photoelectrically converting the laser light output from the frequency swept light output unit 101 by a photodetector (not shown), and outputs the A / D converted digital signal as a trigger signal.

[0023] (Register) The register 111 holds a distance Δx on the principal plane of the objective lens 203 (hereinafter referred to as the “distance on the principal plane”), which corresponds to the inter-core distance between the central core and the peripheral cores of the multi-core fiber MCF.

[0024] The register 111 may also hold the value of the refractive index of each core of the multi-core fiber MCF. When light propagates through an optical fiber, it is affected by the medium that forms the optical fiber, and the propagation of light is slowed down by the refractive index. In the present disclosure, since the measurement light is propagated to each core of the multi-core fiber MCF, if the refractive index of each core is not known, high-precision distance measurement cannot be performed. Therefore, the refractive index of each core is measured in advance using a calibration work. The calibration work may be a diffuser plate, for example, as long as light is simultaneously reflected by the central core and the peripheral cores in a state without cutting oil. The refractive index of each core is calculated from the results of Z0 and Z1, and the calculated refractive index is recorded in the register.

[0025] Similarly, the register 111 may hold a value of the refractive index n of a liquid such as cutting oil. There are various types of cutting oil, some of which are diluted with water before use. In the calculation formula related to the present disclosure, the refractive index n of the liquid changes significantly depending on the refractive index of the liquid such as cutting oil, so an accurate value of the refractive index n of the liquid is required to measure the shape of the target object more accurately. In order to measure the accurate value of the refractive index n, it is sufficient to fill a liquid such as cutting oil on a stepped workpiece with a known step height and perform the measurement.

[0026] The register 111 holds the value of Δx, the value of the refractive index of each core, or the value of the refractive index n of the liquid, for example, in the form of a table.

[0027] (Signal Processing Unit) The signal processing unit 112 measures the distance between the optical sensor head 200 and the surface of the object or the surface of the liquid from the frequency spectrum of the interference light based on the received signal. More specifically, the signal processing unit 112 measures the frequency spectrum of the interference light by Fourier transforming the received signal. The measurement distance is determined by the optical path length difference between the measurement light and the reference light. Since the reflected light is delayed with respect to the reference light depending on the distance to the object to be measured such as the object Obj, as shown in FIG. 2, the reflected light is received delayed with respect to the reference light. The reflected light is delayed with respect to the reference light by the round trip time between the optical sensor head 200 and the object to be measured. If the object to be measured is far away, the delay time becomes large, and the frequency difference also becomes large in proportion to the delay time. When the optical path length difference between the measurement light and the reference light from the coupler 102 is 0, the frequency difference obtained is 0, and the frequency difference becomes large in proportion to the optical path length difference. If the frequency difference is Δf, the distance between the optical sensor head 200 and the object to be measured is d, the frequency sweep bandwidth is B, the frequency sweep period is T, and the speed of light is c, then there is a relationship of Δf=2dB / cT. Therefore, by measuring the frequency difference Δf by Fourier transform, the one-way distance (d) or round-trip distance (2d) between the optical sensor head 200 and the object to be measured is measured.

[0028] The signal processing unit 112 performs frequency analysis on the received signal obtained for each core to obtain an analysis result for each core. As described later with reference to a flowchart, the analysis is performed according to whether the analysis is for the central core or the peripheral core, and by counting the number of frequency peaks. If the distance from the center on the principal plane of the objective lens 203 to the liquid is L1, the distance from the peripheral position on the principal plane of the objective lens 203 to the liquid is L2, the film thickness of the liquid is ΔL, and the refractive index of the liquid is n, the value of the distance to the object Obj (distance measurement result without oil), the value of Z0 (=L1+nΔL) (distance measurement result 1 with oil), and the value of Z1 (=L1+L2) (distance measurement result 2 with oil) are obtained.

[0029] When obtaining distance measurement results, the measured optical path length is analyzed as a relative value with respect to the reference light. In addition, the propagation speed of light in an optical fiber is determined depending on the core refractive index. Therefore, when Z0 is considered as the reference for the laser light propagating through the central core, if the refractive index of the laser light propagating through the peripheral cores is different from that of the former, the distance measurement result is shifted relatively by the optical path length of the reference light, and this needs to be corrected. For example, the deviation values ​​such as the refractive index between the central core and the peripheral cores and the optical path length of the reference light can be used as parameters, analyzed based on known distance measurement results, and correction can be performed by referring to table values. The signal processing unit 112 refers to the register 111, and calculates Z1 by adding a relative value from Z0 according to the acquired parameters of each core and offsetting it.

[0030] In this way, the signal processing unit refers to the table in the register 111 that holds the first refractive index value of the first optical waveguide (central core) and the second refractive index value of the second optical waveguide (peripheral core), acquires the first refractive index value and the second refractive index value, corrects the distance obtained by frequency analysis of the first interference light using the acquired first refractive index value, and corrects the distance obtained by frequency analysis of the second interference light using the acquired second refractive index value.

[0031] The signal processing unit 112 corrects the distance measurement results based on the distance measurement results and the value of the refractive index n of the liquid so as to calculate the distance from the objective lens 203 to the object Obj. The correction of the distance measurement results will be described later under the heading "Method of measuring the film thickness of a liquid."

[0032] (Shape calculation section) The shape calculation unit 113 calculates the shape of the object Obj from the result of the correction by the signal processing unit 112 and the position information of the sensor head 200.

[0033] (Multicore fiber) The multi-core fiber MCF includes a plurality of cores, for example, as shown in Fig. 3. The plurality of cores are covered with a cladding. The example of Fig. 3 shows a case where the number of cores N is 7. In a cross-sectional view of the multi-core fiber MCF, a central core 401 is located at the center of the multi-core fiber MCF, and peripheral cores 402 to 407 are arranged so as to be positioned at equal intervals around the central core 401. The number of cores N is not limited to 7 and may be another number.

[0034] Since the multi-core fiber MCF is an optical component for providing multiple optical waveguides, other optical components that can provide multiple optical waveguides may be used, such as multiple single-core fibers SCF or a bundle fiber that bundles them.

[0035] <Configuration of optical sensor head> The optical sensor head 200 includes an optical component including a central core (first optical waveguide) and a peripheral core (second optical waveguide), and can emit measurement light from the first optical waveguide and receive reflected light from the second optical waveguide. As an example, the optical sensor head 200 includes a spatial optical system in which a microlens array 201, a beam expander 202, and an objective lens 203 are arranged in this order, as shown in Figs. 1 and 4. The microlens array 201, the beam expander 202, and the objective lens 203 are housed in a casing (not shown).

[0036] (Microlens Array) The microlens array 201 is an array in which each microlens constituting the microlens array 201 has an individual optical system. For convenience of explanation, the side of the microlens array 201 connected to the multi-core fiber is called the upstream side, and the side opposite to the light source side is called the downstream side.

[0037] The microlens array 201 is an optical element that functions as an interface that connects the multi-core fiber MCF and free space. Other optical elements may be used instead of the microlens array 201 as long as they can perform such a function. For example, a prism or a diffractive optical element may be used. The following description will be given in the case where the microlens array 201 is used.

[0038] (Beam Expander) The beam expander 202 expands the measurement light emitted from the microlens array 201. The expansion ratio of the beam expander 202 may be adjustable. By expanding the measurement light, it becomes easier to obtain reflected light from the object Obj even if liquid such as cutting oil is present on the object Obj.

[0039] By using the microlens array 201 and the beam expander 202, reflected light can be received by the surrounding core while preventing it from being received by the cladding.

[0040] (Objective lens) The objective lens 203 is a high NA lens made of, for example, silicon. The objective lens 203 is arranged so that the measurement light emitted from the central core 401 (first optical waveguide) of the multi-core fiber MCF passes through the center of the objective lens 203. The objective lens 203 irradiates the measurement light expanded by the beam expander 202 toward an object Obj such as a workpiece, and receives the reflected light reflected from the surface of the object Obj. Note that, when a liquid such as cutting oil is attached on the object Obj, the objective lens 203 receives the reflected light reflected from the surface of the liquid. The objective lens 203 does not need to be a single lens, and may be configured by combining a plurality of lenses.

[0041] <Method of measuring film thickness of liquid> Since the optical sensor head 200 is configured as described above, the microlens that receives the measurement light from the multi-core fiber from the upstream end face of the microlens array 201 sends the measurement light received from its downstream end face into free space. The measurement light sent into this free space is expanded by the beam expander 202 and irradiated onto the object via the objective lens 203.

[0042] Assume that liquid such as cutting oil is attached to the surface of the object facing the optical sensor head 200. Surface tension acts on the liquid, which tries to make the surface area as small as possible. Therefore, the thickness of the liquid is constant in the center of the liquid, but is not constant at the edge of the liquid. When viewed from the side, the edge of the liquid has an arc shape. Therefore, the optical path of the reflected light of the measurement light irradiated to the object is not uniform when the measurement light is irradiated to the center of the liquid and when the measurement light is irradiated to the edge of the liquid.

[0043] When the measurement light is irradiated to the center of the liquid, a part of the measurement light is reflected by the surface of the central part of the liquid where the measurement light is irradiated, and the remaining part of the measurement light is reflected by the surface of the object. Since the thickness of the central part of the liquid is constant, both the reflected light reflected by the surface of the central part of the liquid and the reflected light reflected by the surface of the object return to the central core 401 of the multi-core fiber MCF along the optical path taken by the measurement light.

[0044] In contrast, when the measurement light is irradiated onto the end of the liquid, a part of the measurement light is reflected by the surface of the end of the liquid where the measurement light is irradiated, and the remaining part of the measurement light is reflected by the surface of the object. Since the end of the liquid has an arc shape, the reflected light reflected by the surface of the end of the liquid is reflected in a direction different from the optical path followed by the measurement light. The reflected light reflected by the surface of the end of the liquid is captured by the peripheral part of the objective lens 203, and the captured measurement light is guided to any one of the peripheral cores 402 to 407 of the multi-core fiber via the beam expander 202 and the microlens array 201. The reflected light reflected by the surface of the object returns to the central core 401 of the multi-core fiber MCF along the optical path followed by the measurement light.

[0045] In this way, when the optical sensor head 200 irradiates the edge of the liquid in the case where the liquid is attached to the object, it can capture both the reflected light from the surface of the object and the reflected light from the surface of the liquid. In the conventional technology, it was not possible to capture the reflected light from the surface of the liquid when irradiating the edge of the liquid. The optical distance measuring device according to the present disclosure uses the reflected light captured in this way to calculate the film thickness of the liquid. The method of calculating the film thickness will be described with reference to FIG. 5. The film thickness is calculated by the signal processing unit 112.

[0046] FIG. 5 is a diagram showing that the measurement light and the reflected light reflected on the surface of the end of the liquid follow different optical paths. When the measurement light emitted from the central core 401 of the multi-core fiber MCF is irradiated to the peripheral part of the liquid such as cutting oil, the optical path of the irradiated light and the optical path of the reflected light reflected on the surface of the end of the liquid have a geometric relationship as shown in FIG. 5. As simply described in FIG. 5, L1 is the distance from the center of the objective lens 203 on the principal plane to the liquid. The center of the objective lens 203 corresponds to the position of the central core 401 of the multi-core fiber MCF. L2 is the distance from the peripheral position on the principal plane of the objective lens 203 to the liquid. The peripheral position of the objective lens 203 corresponds to the position of any one of the peripheral cores 402 to 407 of the multi-core fiber MCF. ΔL is the film thickness of the liquid, and Δx is the distance on the principal plane. If the angle between the optical path of L1 and the optical path of L2 is θ, the optical path of L1, the optical path of L2, and the distance on the principal plane form a right-angled triangle.

[0047] The optical path of L1, the optical path of L2, and the distance on the principal plane form a right-angled triangle. Therefore, L1 and L2 are expressed as equations (1) and (2), respectively. TIFF0007675955000001.tif12166 TIFF0007675955000002.tif11166

[0048] The analytical result Z1 for the peripheral core is expressed as follows from equations (1) and (2): TIFF0007675955000003.tif18166

[0049] By transforming equation (3), we obtain the following equation (4). TIFF0007675955000004.tif12166

[0050] Here, L1 = L2 cosθ and Z1 = L1 + L2, so L1 can be written as follows (5). TIFF0007675955000005.tif13166

[0051] When equation (5) is modified so that L1 is expressed in terms of the distance measurement result Z1 and the known distance Δx on the principal plane, the following equation (6) is obtained. TIFF0007675955000006.tif12166

[0052] Also, since Z0=L1+nΔL, ΔL can be written as the following equation (7) using Z0. TIFF0007675955000007.tif9166

[0053] From equations (6) and (7), we obtain the following equation (8). TIFF0007675955000008.tif15166

[0054] As can be seen from equation (8), the value of the film thickness ΔL of the liquid can be obtained from the known values ​​of n and Δx and the measured values ​​of Z0 and Z1. The optical path length nΔL is corrected to the film thickness ΔL of the liquid by dividing the optical path length nΔL by the refractive index n of the liquid held in the register 111. Therefore, the distance to the object Obj can be obtained as the sum of the values ​​of L1 and ΔL. In this way, the distance to the object can be obtained even if liquid is present on the object.

[0055] In this way, the signal processing unit 1122 refers to the table in the register 111 that holds the values ​​of the refractive index of the liquid, such as the processing oil of the object Obj, to obtain the value of the refractive index n of the liquid, and uses the obtained value of the refractive index n of the liquid to correct the distance Z0 obtained by frequency analysis of the first interference light and the distance Z0 obtained by frequency analysis of the second interference light.

[0056] The shape calculation section 113 estimates the three-dimensional shape of the object from the position information of the optical sensor head 200 and the distance to the object obtained by the signal processing section 112.

[0057] The above parameters or variables are summarized in the table in Figure 6.

[0058] <Hardware configuration of processing unit> Next, a hardware configuration example of the processing unit 114 will be described with reference to Figures 7A and 7B. The function of the processing unit 114 is realized by a processing circuit. The processing circuitry may be a dedicated processing circuit 300a as shown in Figure 7A, or a processor 300b that executes a program stored in a memory 300c as shown in Figure 7B.

[0059] When the processing circuitry is a dedicated processing circuit 300a, the dedicated processing circuit 300a may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. The functions of the processing unit 114 may be realized by a plurality of separate processing circuits, or the functions of the processing unit 114 may be realized by a single processing circuit.

[0060] When the processing circuitry is the processor 300b, the function of the processing unit 114 is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 300c. The processor 300b realizes the function of the processing unit 114 by reading and executing the programs stored in the memory 300c. Here, examples of the memory 300c include non-volatile or volatile semiconductor memories such as random access memory (RAM), read-only memory (ROM), flash memory, erasable programmable read-only memory (EPROM), and electrically erasable programmable read-only memory (EEPROM), as well as magnetic disks, flexible disks, optical disks, compact disks, mini disks, and DVDs.

[0061] It should be noted that some of the functions of the processing unit 114 may be realized by dedicated hardware, and the other functions may be realized by software or firmware. In this way, the processing circuit can realize the functions of the processing unit 114 by hardware, software, firmware, or a combination of these.

[0062] <Operation> Next, the operation of the optical distance measuring device will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a flow chart showing the operation of the optical distance measuring method performed by the processing unit 114 of the optical distance measuring device, and Fig. 9 is a flow chart showing a subroutine of step ST805 in Fig. 8.

[0063] (Step ST801) In step ST801, the signal processing unit 112 of the processing unit 114 detects the trigger signal output from the A / D converter 109.

[0064] (Step ST802) In step ST802, the signal processing unit 112 resamples the digital signal sampled and output by the A / D converter 110-N, based on the detected trigger signal.

[0065] (Step ST803) In step ST803, the signal processing unit 112 performs FFT (Fast Fourier Transform) on the resampled digital signal.

[0066] (Step ST804) In step ST804, the signal processing unit 112 detects a peak frequency from the frequency spectrum obtained by FFT.

[0067] (Step ST805) In step ST805, the signal processor 112 obtains the distance from the peak frequency and outputs the distance measurement result. At this time, the signal processor 112 performs different processing depending on whether the analysis target is the central core or the surrounding core. Specifically, the signal processor 112 performs processing according to the flowchart shown in FIG. 9.

[0068] (Step ST901) In step ST901, the signal processing unit 112 analyzes the reflected light received via the central core 401. Specifically, the signal processing unit 112 identifies a peak frequency.

[0069] (Step ST902; Step ST905) In step ST902, the signal processing unit 112 judges whether or not there is a peak frequency. If there is no peak frequency, the process proceeds to step ST905, and the signal processing unit 112 judges that distance measurement is not possible.

[0070] (Step ST903) If there is a peak frequency, in step ST903, the signal processing unit 112 judges whether or not there are multiple identified peak frequencies. If there are multiple peak frequencies, the process proceeds to step ST904. On the other hand, if there are not multiple peak frequencies, that is, if there is only one peak frequency, the process proceeds to step ST908.

[0071] (Step ST904) In step ST904, the signal processing unit 112 derives the distance measurement result as, for example, distance measurement result with oil 1. That is, distance measurement result with oil 1 is Z0 (=L1+nΔL) described above.

[0072] (Step ST906) In step ST906, signal processing unit 112 analyzes the surrounding cores. Specifically, signal processing unit 112 identifies a peak frequency. Note that the processes of steps ST906 and ST907 may be performed in parallel with steps ST901 to ST903.

[0073] (Step ST907) In step ST907, the signal processing unit 112 judges whether or not there is a peak frequency. If there is no peak frequency, the analysis of the surrounding cores is terminated. If there is a peak frequency, the process proceeds to step ST908.

[0074] (Step ST908) In step ST908, the signal processing unit 112 judges whether or not there is one peak each for the central core and the peripheral core. If there is one peak each, the process proceeds to step ST909. If there is not one peak each, the process proceeds to step ST910.

[0075] (Step ST909) In step ST909, the signal processing unit 112 derives the distance measurement result as, for example, the distance measurement result with oil 2. That is, the distance measurement result with oil 2 is Z1 (=L1+L2) described above.

[0076] (Step ST910) In step ST910, the signal processing unit 112 derives the distance measurement result as, for example, an oil-free distance measurement result.

[0077] (Step ST911) In step ST911, the signal processing unit 112 outputs the derived distance measurement result or a result indicating that distance measurement is not possible. After step ST911, the process returns to the flow of FIG.

[0078] (Step ST806) In step ST911, the signal processing unit 112 corrects the distance measurement result output in step ST911 based on the distance measurement result and the value of the refractive index n of the liquid so as to calculate the distance from the objective lens 203 to the object Obj.

[0079] (Step ST807) In step ST807, the shape calculation unit 113 calculates the shape of the object Obj from the distance measurement result corrected by the signal processing unit 112 and the position information of the optical sensor head 200 at each distance measurement. The optical sensor main body 100 outputs information indicating the shape of the object Obj calculated by the shape calculation unit 113 to an external device such as a display device (not shown).

[0080] It is possible to combine the embodiments, and to modify or omit each embodiment as appropriate. [Industrial Applicability]

[0081] The optical distance measuring device of the present disclosure can be used as a distance measuring device that measures the shape of a workpiece being machined by a machining device. [Explanation of symbols]

[0082] 100 optical sensor body, 101 frequency sweep optical output section, 102 coupler, 103 fan-in, 104 circulator, 105 fan-in, 106 optical interferometer, 107 fan-out, 108-1 to 108-N optical detector, 109 A / D converter, 110-1 to 110-NA / D converter, 111 register, 112 signal processing section, 113 shape calculation section, 114 processing section, 200 optical sensor head, 201 microlens array, 202 beam expander, 203 objective lens, 300a processing circuit, 300b processor, 300c memory, 401 central core, 402 to 407 peripheral cores.

Claims

1. a coupler that splits the frequency-swept laser light into a measurement light and a reference light; an optical sensor head that receives the measurement light, irradiates the received measurement light toward an object, and receives reflected light of the measurement light; an optical interferometer that generates interference light by causing the reference light to interfere with the received reflected light; a light receiving unit that receives the generated interference light and converts the received interference light into an electrical signal; a signal processing unit capable of calculating a distance from the optical sensor head to the object based on the converted electrical signal; The optical sensor head includes: an optical component including a first optical waveguide and a second optical waveguide; The measurement light can be emitted from the first optical waveguide, the reflected light can be received from the second optical waveguide; The optical component is a multicore fiber including a central core as the first optical waveguide and a peripheral core as the second optical waveguide. Optical ranging device.

2. the optical sensor head includes a spatial optical system in which an optical element selected from a microlens array, a prism, and a diffractive optical element, a beam expander, and an objective lens are arranged in this order; 2. An optical distance measuring device according to claim 1.

3. The central core is located at the center of the multicore fiber in a cross-sectional view of the multicore fiber, the objective lens is disposed so that the measurement light emitted from the first optical waveguide passes through the center of the objective lens.

3. An optical distance measuring device according to claim 2.

4. the signal processing unit calculates a distance to the object by performing frequency analysis on a first interference light generated from the reference light and the reflected light received via the first optical waveguide, and a second interference light generated from the reference light and the reflected light received via the second optical waveguide; 2. An optical distance measuring device according to claim 1.

5. the signal processing unit refers to a table that holds a first refractive index value of the first optical waveguide and a second refractive index value of the second optical waveguide, acquires a first refractive index value and a second refractive index value, corrects a distance obtained by frequency analysis of the first interference light using the acquired first refractive index value, and corrects a distance obtained by frequency analysis of the second interference light using the acquired second refractive index value.

5. An optical distance measuring device according to claim 4.

6. the signal processing unit refers to a table that stores values ​​of the refractive index of a liquid used in processing the object, acquires the value of the refractive index of the liquid, and corrects the distance obtained by frequency analysis of the first interference light and the distance obtained by frequency analysis of the second interference light using the acquired value of the refractive index of the liquid.

5. An optical distance measuring device according to claim 4.