Optical ranging device

Abstract

This optical ranging device comprises: 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, radiates the received measurement light toward a subject, 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; light reception units (108, 110) that receive the generated interference light and convert the received interference light into an electrical signal; and a signal processing unit (112) that is capable of calculating the distance from the optical sensor head to the subject on the basis of the converted electrical signal. The optical sensor head comprises an optical component 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.

Description

optical distance measuring device

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

[0002] Patent Document 1 discloses a technology related to a three-dimensional measuring device that includes: an irradiation device configured to be able to irradiate an irradiation area of ​​an object to be measured with irradiation light that has been spatially modulated in a predetermined modulation pattern within the irradiation area; a first multicore fiber having a plurality of cores that can receive outgoing light that is emitted from the object to be measured that has been irradiated with the irradiation light and that contains information about the object to be measured in the irradiation area; and a light-receiving device that has: a first multicore fiber having a plurality of cores that can receive outgoing light that is emitted from the object to be measured that has been irradiated with the irradiation light and that contains information about the object to be measured in the irradiation area; and an optical information calculation unit that is configured to be able to calculate three-dimensional information about the object to be measured based on optical information about the outgoing light received by each of the plurality of cores and the optical information about the irradiation light, wherein the first multicore fiber has a numerical aperture that is determined from the maximum acceptance angle of the outgoing light in each of the plurality of cores and the refractive index of a region between the object to be measured and the first multicore fiber, such that the irradiation area is included in an overlapping region where acceptance 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.

[0003] Japanese Patent Application Laid-Open No. 2021-179333

[0004] According to the technology of Patent Document 1, it is assumed that the light irradiated onto the object to be measured and the light reflected from the object to be measured propagate along the same optical path. Therefore, if a liquid such as water or cutting oil adheres 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 is capable of measuring the shape of a measured object even when liquid is attached to the measured object.

[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, 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, and a signal processing unit that can calculate the 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.

[0007] According to the optical distance measuring device according to the embodiment of the present disclosure, it is possible to measure the shape of the object to be measured even when liquid is attached to the object to be measured.

[0008] 4A, 4B, and 4C are diagrams showing an example of the configuration of an optical distance measuring device; FIG. 4B is a diagram showing the relationship between reference light and reflected light; FIG. 4C is a diagram showing an example of the cross section of a multicore fiber; FIG. 4A, 4B, and 4C are diagrams showing the configuration of an optical sensor head; FIG. 4C is a diagram showing the geometric relationship of optical paths; FIG. 4C is a table defining the meaning of parameters or variables; FIG. 4A is a diagram showing an example of the configuration of hardware of a processing unit ...C is a flowchart of an optical distance measuring method; FIG. 4C is a flowchart of an optical distance measuring method.

[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 designated by identical or similar reference numerals, and redundant explanations of such parts will be omitted. In addition, in this disclosure, the term "or" is used to mean an inclusive logical OR unless otherwise specified.

[0010] First Embodiment <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 multicore fiber MCF.

[0011] The optical sensor body 100 includes, for example, a frequency swept 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 photodetectors 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 photodetectors 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 swept 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 Optical Sensor Main Body> (Frequency Swept Light Output Unit) The frequency swept light output unit 101 sweeps the frequency of laser light, which is continuous light emitted from a laser light source such as a semiconductor laser, and outputs the frequency-swept frequency swept light. For example, the optical signal shown as 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 the coupler 102 via, for example, a single-core fiber (SCF).

[0014] (Coupler) The coupler 102 branches the input frequency swept light into multiple beams 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 beams. One of the branched laser beams 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 beams are output as N reference beams. The output reference beam is guided to the fan-in 105, for example, via N single-core fibers SCF. The optical path length is adjusted by the single-core fibers 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 the 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 the optical interferometer 106.

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

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

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

[0021] (A / D Converter) A plurality of A / D converters 110-1 to 110-N perform A / D conversion on the input analog signals. 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 converts the analog electrical signal obtained by photoelectrically converting the laser light output from the frequency swept light output unit 101 using a photodetector (not shown) into a digital signal, and outputs the digital signal after the A / D conversion 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 amount of the refractive index. In the present disclosure, measurement light is propagated through each core of the multi-core fiber MCF, so high-precision distance measurement cannot be performed unless the refractive index of each core is known. Therefore, a calibration workpiece is used to measure the refractive index of each core in advance. The calibration workpiece only needs to reflect light simultaneously to the central core and peripheral cores in the absence of cutting oil, and a diffuser plate, for example, can be used. Z ０ and Z １ The refractive index of each core is calculated from the results of (a) and (b) and the calculated refractive index is recorded in a register.

[0025] Similarly, the register 111 may store the 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 formulas disclosed herein, the refractive index varies greatly 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 object more accurately. To measure the accurate value of the refractive index n, it is sufficient to fill a stepped workpiece with a known step height with the liquid such as cutting oil 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 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 measured distance is determined by the optical path length difference between the measurement light and the reference light. The reflected light is delayed relative to the reference light depending on the distance to the object under measurement, such as the object Obj, so as shown in FIG. 2, the reflected light is received with a delay relative to the reference light. The reflected light is delayed relative to the reference light by the round-trip time between the optical sensor head 200 and the object under measurement. The further the object under measurement is, the longer the delay time becomes, and the larger the frequency difference becomes 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 zero, the resulting frequency difference is zero, and the frequency difference increases 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 = 2 dB / cT. Therefore, by measuring the frequency difference Δf using a Fourier transform, the one-way distance (d) or round-trip distance (2d) between the optical sensor head 200 and the object to be measured can be 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 will be described later with reference to a flowchart, the analysis is performed depending on whether the analysis is for the central core or the peripheral core, and by counting the number of frequency peaks. The distance from the center of the principal plane of the objective lens 203 to the liquid is defined as L １ , the distance from the peripheral position on the principal plane of the objective lens 203 to the liquid is L ２ , the film thickness of the liquid is ΔL, the refractive index of the liquid is n, the value of the distance to the object Obj (the distance measurement result without oil), Z ０ (=L １ +nΔL) value (oil-present distance measurement result 1), Z １ (=L １ +L ２ ) value (oil-present distance measurement result 2) is obtained.

[0029] When obtaining distance measurement results, the measured optical path length is analyzed as a relative value to the reference light. In addition, the propagation speed of light in an optical fiber is determined depending on the core refractive index. Therefore, for laser light propagating through the central core, Z ０ When considering this as the standard, Z １ In this case, if the refractive index differs from that of the former, the distance measurement result will be 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 corrected by referring to table values. The signal processing unit 112 refers to the register 111 and calculates Z according to the acquired parameters of each core. ０ By adding a relative value from Z and using it as an offset, １ Calculate.

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

[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 explained below under the heading "Method for measuring the film thickness of a liquid."

[0032] (Shape Calculation Unit) 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] (Multi-core fiber) A 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 may be used as long as they can provide multiple optical waveguides. For example, multiple single-core fibers SCF or a bundle fiber in which these are bundled may be used.

[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 is capable of emitting measurement light from the first optical waveguide and receiving 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 multicore fiber will be referred to as the upstream side, and the side opposite to the light source side will be referred to as 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 assuming the use of the microlens array 201.

[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 a 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 peripheral 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 positioned so that 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 onto an object Obj such as a workpiece, and receives reflected light reflected from the surface of the object Obj. Note that if a liquid such as cutting oil is attached to the object Obj, the objective lens 203 receives 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 multiple lenses.

[0041] <Method for Measuring Film Thickness of Liquid> Since the optical sensor head 200 is configured as described above, the microlens receives measurement light from the multi-core fiber at the upstream end face of the microlens array 201, and transmits the received measurement light from its downstream end face into free space. The measurement light transmitted into free space is expanded by the beam expander 202 and irradiated onto the object via the objective lens 203.

[0042] Assume that a 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 minimize the surface area. Therefore, the thickness of the liquid is constant in the center of the liquid, but not 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 irradiated onto the object is not uniform when the measurement light is irradiated onto the center of the liquid and when the light is irradiated onto the edge of the liquid.

[0043] When the measurement light is irradiated onto the center of the liquid, 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 rest of the measurement light is reflected by the surface of the object. Because 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 edge of the liquid, part of the measurement light is reflected by the surface of the edge of the liquid where the measurement light is irradiated, and the remainder of the measurement light is reflected by the surface of the object. Because the edge of the liquid has an arc shape, the reflected light reflected by the surface of the edge of the liquid is reflected in a direction different from the optical path taken by the measurement light. The reflected light reflected by the surface of the edge of the liquid is captured by the peripheral part of the objective lens 203, and the captured measurement light is guided to one of the peripheral cores 402 to 407 of the multicore 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 multicore fiber MCF along the optical path taken by the measurement light.

[0045] In this way, when the optical sensor head 200 illuminates the edge of a liquid adhering to an object, it can capture both the light reflected from the surface of the object and the light reflected from the surface of the liquid. Conventional technology has been unable to capture the light reflected from the surface of the liquid when illuminating the edge of the liquid. The optical distance measuring device according to the present disclosure uses the reflected light captured in this manner to calculate the film thickness of the liquid. The film thickness calculation method will be described with reference to FIG. 5 . The film thickness calculation is performed by the signal processing unit 112.

[0046] 5 is a diagram showing that the measurement light and the reflected light reflected at the surface at the edge 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 onto the peripheral portion of a liquid such as cutting oil, the optical path of the irradiated light and the optical path of the reflected light reflected at the surface at the edge of the liquid have a geometric relationship as shown in FIG. 5. As clearly shown in FIG. 5, L １ 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. ２ 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 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. L １ The optical path of L ２ Let θ be the angle between the optical path of L １ The optical path of L ２ The optical paths and the distances on the principal plane form a right triangle.

[0047] L １ The optical path of L ２ The optical path and the distance on the principal plane form a right triangle. １ and L ２ are expressed as equations (1) and (2), respectively.

[0048] Z1, which is the analysis result for the peripheral core, is expressed as follows from equations (1) and (2):

[0049] By modifying equation (3), the following equation (4) is obtained.

[0050] Here, L １ =L ２ cosθ, and Z １ =L １ +L ２ Therefore, L １ can be written as the following equation (5).

[0051] L １ The distance measurement result is Z １ By transforming equation (5) so as to express it in terms of the known distance Δx on the principal plane, the following equation (6) is obtained.

[0052] Also, Z ０ =L １ +nΔL, so ΔL is Z ０ Using this, it can be written as the following equation (7).

[0053] From equations (6) and (7), the following equation (8) is obtained.

[0054] As can be seen from equation (8), the known values ​​of n and Δx and the measured value Z ０ and Z １ The value of the liquid film thickness ΔL can be obtained from the value of the optical path length nΔL. By dividing the optical path length nΔL by the refractive index n of the liquid held in the register 111, the optical path length nΔL is corrected to the liquid film thickness ΔL. Therefore, the distance to the object Obj is calculated as follows: １ The distance to the object can be calculated as the sum of the value of and the value of ΔL. In this way, the distance to the object can be calculated even if liquid exists on the object.

[0055] In this way, the signal processing unit 1122 refers to the table in the register 111 that stores the refractive index value of the liquid, such as the processing oil of the object Obj, to acquire the refractive index n of the liquid, and calculates the distance Z obtained by frequency analysis of the first interference light using the acquired refractive index n of the liquid. ０ , and the distance Z obtained by frequency analysis of the second interference light０ Correct the following.

[0056] The shape calculation unit 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 unit 112 .

[0057] The above parameters or variables are summarized in the table of FIG.

[0058] <Hardware Configuration of Processing Unit> Next, an example of the hardware configuration of the processing unit 114 will be described with reference to Figures 7A and 7B. The functions of the processing unit 114 are realized by a processing circuitry. 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 dedicated processing circuitry 300a, the dedicated processing circuitry 300a may be, for example, a single circuit, a multiple 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 processing unit 114 may be implemented by separate processing circuits, or the functions of processing unit 114 may be implemented together in a single processing circuit.

[0060] When the processing circuitry is a processor 300b, the functions of the processing unit 114 are 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 functions 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 memory 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, minidisks, and DVDs.

[0061] It is also possible to implement some of the functions of the processing unit 114 using dedicated hardware, and other functions using software or firmware. In this way, the processing circuit can implement the functions of the processing unit 114 using 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 flowchart 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 flowchart showing a subroutine of step ST805 in Fig. 8.

[0063] (Step ST801) In step ST801, the signal processing section 112 of the processing section 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 section 112 performs FFT (Fast Fourier Transform) on the resampled digital signal.

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

[0067] (Step ST805) In step ST805, the signal processing unit 112 calculates the distance from the peak frequency and outputs the distance measurement result. At this time, the signal processing unit 112 performs different processing depending on whether the analysis target is the central core or the peripheral core. Specifically, the signal processing unit 112 performs processing in accordance with 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 the peak frequency.

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

[0070] (Step ST903) If a peak frequency is present, in step ST903, signal processing section 112 determines 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 1 with oil. ０ (=L １ +nΔL).

[0072] (Step ST906) In step ST906, signal processing unit 112 analyzes the surrounding cores. Specifically, signal processing unit 112 identifies the 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, signal processing unit 112 determines whether or not there is a peak frequency. If there is no peak frequency, 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, signal processing unit 112 determines whether 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 for the central core and the peripheral core, 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 the Z １ (=L １ +L ２ )

[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. 8 and proceeds to step ST806.

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

[0079] (Step ST807) In step ST807, the shape calculation unit 113 calculates the shape of the object Obj from the distance measurement results 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.

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

[0082] 100 Optical sensor body, 101 Frequency sweep optical output unit, 102 Coupler, 103 Fan-in, 104 Circulator, 105 Fan-in, 106 Optical interferometer, 107 Fan-out, 108-1 to 108-N Photodetector, 109 A / D converter, 110-1 to 110-N A / D converter, 111 Register, 112 Signal processing unit, 113 Shape calculation unit, 114 Processing unit, 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. An optical distance measuring device comprising: a coupler that splits frequency-swept laser light into measurement light and 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; and a signal processing unit that can calculate the distance from the optical sensor head to the object based on the converted electrical signal, wherein the optical sensor head has 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.

2. The optical distance measuring device according to claim 1, wherein the optical sensor head comprises a spatial optical system in which one optical element selected from the group consisting of a microlens array, a prism, or a diffractive optical element, a beam expander, and an objective lens are arranged in this order.

3. The optical distance measuring device according to claim 2, wherein the optical component is a multi-core fiber including a central core as the first optical waveguide and peripheral cores as the second optical waveguide, the central core being located at the center of the multi-core fiber in a cross-sectional view of the multi-core fiber, and the objective lens is arranged so that the measurement light emitted from the first optical waveguide passes through the center of the objective lens.

4. The optical distance measuring device described in claim 1, wherein the signal processing unit calculates the distance to the object by frequency analysis of 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.

5. The optical distance measuring device described in claim 4, wherein the signal processing unit acquires the first refractive index value and the second refractive index value by referring to a table that stores the first refractive index value of the first optical waveguide and the second refractive index value of the second optical waveguide, 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.

6. An optical distance measuring device as described in claim 4, wherein the signal processing unit obtains the refractive index value of the liquid by referring to a table that stores the refractive index value of the liquid used in processing the object, and uses the obtained refractive index value of the liquid to correct the distance obtained by frequency analysis of the first interference light and the distance obtained by frequency analysis of the second interference light.

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