DISTANCE MEASUREMENT DEVICE, DISTANCE MEASUREMENT METHOD, AND MACHINE TOOL

A distance measurement device includes: a signal acquisition unit to acquire an electric signal based on interference light from an optical sensor device that splits sweep light having a periodically changing frequency into reference light and irradiation light to be emitted toward an object to be measured, irradiates the object with the irradiation light, generates interference light by causing the reference light to interfere with reflected light that is the irradiation light reflected by the object, and generates the electric signal based on the generated interference light; a frequency calculation unit to calculate, on the basis of the electric signal based on the interference light, a peak frequency of the electric signal using LASSO regression; a distance measurement unit to measure, on the basis of the peak frequency, a distance from a predetermined reference point to the object; and a distance output unit to output distance information indicating the distance.

TECHNICAL FIELD

The present disclosure relates to a distance measurement device, a distance measurement method, and a machine tool.

BACKGROUND ART

There is a technique for measuring a distance from a predetermined reference point to an object to be measured using frequency sweep light.

For example, Patent Literature 1 discloses a technique that, in a machine tool including a machining unit that supplies cutting oil to a work surface of a workpiece and processes the work surface, splits light output from a frequency sweep light source that outputs light having a periodically changing frequency into reference light and irradiation light to be emitted toward a workpiece, irradiates the irradiation light with the workpiece, detects a peak frequency of interference light between reflected light that is the irradiation light reflected by the workpiece and the reference light, and measures a distance from the machine tool to the work surface on the basis of the peak frequency.

The conventional technique described in Patent Literature 1 (hereinafter, simply referred to as “conventional technique”), in a case where cutting oil having a known refractive index is present on a reflecting surface of an object to be measured, acquires, on the basis of first interference light that is interference light between reflected light from a work surface of a workpiece and reference light and second interference light that is interference light between reflected light from the cutting oil and the reference light, a peak frequency of the first interference light and a peak frequency of the second interference light, measures a distance from a machine tool to the work surface.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the conventional technique, there is a problem that due to scattering of reflected light reflected by a substance such as cutting oil present on a reflecting surface of an object to be measured, the intensity of the reflected light cannot be sufficiently obtained, and a distance from a predetermined reference point to the object to be measured cannot be accurately measured in some cases. Scattering of the reflected light may occur also in a case where a reflecting surface of an object to be measured is not uniform with respect to an optical axis direction of irradiation light. Therefore, also in this case, a distance from a predetermined reference point to an object to be measured cannot be accurately measured in some cases.

The present disclosure is intended to solve the above-described problem, and an object of the present disclosure is to provide a distance measurement device capable of accurately measuring a distance from a predetermined reference point to an object to be measured even in a case where the intensity of reflected light reflected by the object to be measured cannot be sufficiently obtained due to scattering of the reflected light.

Solution to Problem

A distance measurement device of the present disclosure includes: processing circuitry to acquire an electric signal based on interference light from an optical sensor device that splits sweep light having a periodically changing frequency into reference light and irradiation light to be emitted toward an object to be measured, irradiates the object to be measured with the irradiation light, generates interference light by causing the reference light to interfere with reflected light that is the irradiation light reflected by the object to be measured, and generates the electric signal based on the generated interference light; to calculate, on the basis of the electric signal based on the acquired interference light, a peak frequency of the electric signal using LASSO regression; to measure, on the basis of the calculated peak frequency, a distance from a predetermined reference point to the object to be measured; and to output distance information indicating the measured distance.

Advantageous Effects of Invention

According to the present disclosure, a distance from a predetermined reference point to an object to be measured can be accurately measured even in a case where the intensity of reflected light reflected by the object to be measured cannot be sufficiently obtained due to scattering of the reflected light.

DESCRIPTION OF EMBODIMENTS

First Embodiment

A distance measurement device100according to a first embodiment will be described with reference toFIGS.1to10.

A configuration of a main part of a machine tool1to which the distance measurement device100according to the first embodiment is applied will be described with reference toFIG.1.

FIG.1is a block diagram illustrating an example of a configuration of a main part of the machine tool1to which the distance measurement device100according to the first embodiment is applied.

The machine tool1includes an optical sensor device20, a machining device40, and the distance measurement device100.

A configuration of a main part of the optical sensor device20included in the machine tool1according to the first embodiment will be described with reference toFIG.2.

FIG.2is a block diagram illustrating an example of a configuration of a main part of the optical sensor device20included in the machine tool1according to the first embodiment.

The optical sensor device20includes a sweep light output unit21, a branching unit22, an irradiation optical system23, an interference unit24, a photoelectric conversion unit25, and an A/D conversion unit26.

The sweep light output unit21outputs sweep light that is light having a periodically changing frequency. A ratio and period of change in the frequency of the sweep light output from the sweep light output unit21are determined in advance. Specifically, for example, the sweep light output unit21includes a laser light source, a diffraction grating, and a sweep control unit (not illustrated). A method for generating and outputting sweep light having a periodically changing frequency is a well-known technique, and therefore description thereof will be omitted.

The branching unit22splits sweep light output from the sweep light output unit21into reference light and irradiation light. The irradiation light is light with which an object4to be measured (hereinafter, simply referred to as “object4”) is irradiated. The branching unit22includes an optical fiber coupler, a beam splitter, or the like.

The irradiation optical system23is an optical system for guiding irradiation light split by the branching unit22to the object4. In addition, the irradiation optical system23guides a reflected wave (hereinafter, referred to as “reflected light”) that is the irradiation light reflected by the object4to the interference unit24. The irradiation optical system23includes one or more transmission type lenses, reflection type lenses, or the like.

The interference unit24generates interference light by causing the reflected light and the reference light to interfere with each other. The interference unit24includes a half mirror or the like.

The photoelectric conversion unit25receives the interference light generated by the interference unit24and converts the interference light into an analog electric signal. The photoelectric conversion unit25includes a photodiode or the like.

The A/D conversion unit26converts the analog electric signal output from the photoelectric conversion unit25into a digital electric signal. The A/D conversion unit26includes an A/D converter or the like.

The optical sensor device20outputs the converted digital electric signal converted by the A/D conversion unit26.

The distance measurement device100receives an electric signal that is a digital electric signal output from the optical sensor device20, measures a distance from a predetermined reference point to the object4, and outputs the measured distance as distance information.

Details of the distance measurement device100will be described later.

A configuration of a main part of the machining device40included in the machine tool1according to the first embodiment will be described with reference toFIG.3.

FIG.3is a block diagram illustrating an example of a configuration of a main part of the machining device40included in the machine tool1according to the first embodiment.

The machining device40includes a table41, a head body unit42, a table drive unit43, a head drive unit44, a cutting oil supply unit45, and a shape calculation unit46.

The table41holds the object4on the head body unit42side thereof.

The head body unit42holds a machining tool47for, for example, cutting the object4on the table41side thereof.

In addition, the head body unit42holds an optical sensor unit48that irradiates the object4with irradiation light from the optical sensor device20and receives reflected light that is the irradiation light reflected by the object4. Specifically, for example, the head body unit42houses the irradiation optical system23included in the optical sensor device20.

The cutting oil supply unit45supplies cutting oil to a work surface of the object4. For example, the cutting oil supply unit45is held by the head body unit42.

The table drive unit43moves the table41in a direction parallel or orthogonal to an optical axis of the irradiation light. The table drive unit43includes an electric motor or the like.

The head drive unit44moves the head body unit42in a direction parallel or orthogonal to the optical axis of the irradiation light. The head drive unit44includes an electric motor or the like. For example, the cutting oil supply unit45, the machining tool47, and the optical sensor unit48move in conjunction with the head body unit42.

The shape calculation unit46acquires distance information output from the distance measurement device100, and calculates the shape of the object4on the basis of the acquired distance information.

Specifically, by controlling the table drive unit43or the head drive unit44and changing an irradiation position of the irradiation light on a work surface of the object4, the shape calculation unit46acquires distance information for each irradiation position from the distance measurement device100, and calculates the shape of the object4.

In addition, by controlling the table drive unit43or the head drive unit44on the basis of the calculated shape of the object4and processing information prepared in advance and bringing the machining tool47into contact with the work surface of the object4, the shape calculation unit46performs control for processing the work surface of the object4into the shape indicated by the processing information.

When the machining tool47is caused to cut the work surface of the object4, the shape calculation unit46controls the cutting oil supply unit45and causes the cutting oil supply unit45to supply cutting oil to the work surface of the object4.

A configuration of a main part of the distance measurement device100according to the first embodiment will be described with reference toFIG.4.

FIG.4is a block diagram illustrating an example of a configuration of a main part of the distance measurement device100according to the first embodiment.

The distance measurement device100includes a signal acquisition unit110, a frequency calculation unit120, a distance measurement unit130, and a distance output unit140.

The signal acquisition unit110acquires, from the optical sensor device20, an electric signal based on interference light output from the optical sensor device20. Specifically, for example, the electric signal acquired by the signal acquisition unit110is a digital electric signal.

The distance measurement device100may include the A/D conversion unit26included in the optical sensor device20. In a case where the distance measurement device100includes the A/D conversion unit26, the optical sensor device20outputs an analog electric signal as an electric signal based on interference light, and the signal acquisition unit110acquires the electric signal based on the interference light output from the optical sensor device20as an analog electric signal. In the distance measurement device100, the A/D conversion unit26included in the distance measurement device100converts the analog electric signal acquired by the signal acquisition unit110into a digital electric signal.

The frequency calculation unit120calculates, on the basis of the electric signal based on the interference light acquired by the signal acquisition unit110, a peak frequency of the electric signal using least absolute shrinkage and selection operator (LASSO) regression.

Details of the frequency calculation unit120will be described later.

The distance measurement unit130measures a distance from a predetermined reference point to the object4on the basis of the peak frequency calculated by the frequency calculation unit120. The predetermined reference point is a surface of the head body unit42included in the machining device40facing the table41, the table41side end portion of the machining tool47held by the head body unit42, or the like.

Since a method for calculating a distance using a peak frequency by sweep light is a well-known technique, description thereof will be omitted.

The distance output unit140outputs distance information indicating the distance measured by the distance measurement unit130.

Details of the frequency calculation unit120will be described.

As described above, the frequency calculation unit120calculates, on the basis of the electric signal based on the interference light acquired by the signal acquisition unit110, a peak frequency of the electric signal using LASSO regression.

The LASSO regression is a power spectrum estimation method by Sparse modeling proposed in Literature 1 described below.

Literature 1: Robert Tibshirani, Journal of the Royal Statistical Society: Series B (Statistical Methodology), 1996, Volume 58, Issue 1.

The LASSO regression is expressed by the following formula (1).

Here, y is time-series data, and is, for example, data obtained by replacing a digital electric signal with time-series data. In a case where F is a determinant for performing a Fourier transform, the vector β is expressed by the following formula (2).

That is, the vector β indicates a power spectrum of y that is time-series data.

∥y−β∥22is a mean value of secondary norms of y−Fβ, and is specifically a mean square of elements represented by y−Fβ.

∥β∥1is a primary norm of the vector β, and is a sum of absolute values of elements of the vector β.

In addition, λ is a threshold value.

The power spectrum estimation method by the LASSO regression expressed by formula (1), that is, by the Sparse modeling proposed in Literature 1 estimates the vector βlassothat is a power spectrum in which frequency components other than a frequency having the highest intensity are set to 0 using λ that is a threshold value.

Specifically, in formula (1), λ∥β∥1acts as a penalty term. The peak frequency estimation method by Sparse modeling proposed in Literature 1 estimates the vector βlassothat is a power spectrum in which frequency components other than a frequency having the highest intensity are set to 0 by determining β having the smallest value of ∥y−β∥22+λ∥β∥1in a regression manner.

Here, when an appropriate value of λ is set among values smaller than the threshold value proposed in Literature 1 by applying formula (1), a value of a penalty term is small. Therefore, it is possible to estimate a power spectrum indicating a value other than 0 not only for the frequency having the highest intensity but also for a frequency having the second highest intensity. In addition, similarly, by setting an appropriate value of λ among smaller values, it is possible to estimate a power spectrum indicating a value other than 0 also for a frequency having the third highest intensity.

The frequency calculation unit120adjusts a threshold value of a penalty term of the LASSO regression to calculate a predetermined number of peak frequencies of the electric signal based on the interference light using the LASSO regression.

For example, the frequency calculation unit120calculates a predetermined number of peak frequencies in descending order of intensity among a plurality of frequency components calculated using the LASSO regression.

A power spectrum of an electric signal estimated using the LASSO regression will be described with reference toFIG.5A to5C.

FIG.5Ais an example of a power spectrum of a certain electric signal estimated using a general Fourier transform.

FIG.5Bis an example of a power spectrum estimated using LASSO regression with λ of formula (1) as a threshold value for the same electric signal as inFIG.5A.

FIG.5Cis an example of a power spectrum estimated using LASSO regression in which λ is an appropriate value among values smaller than the threshold value by applying formula (1) for the same electric signal as inFIG.5A.

As illustrated inFIG.5A, in a case where a power spectrum is estimated using a general Fourier transform, the power spectrum has frequency components at various frequencies, and therefore it is difficult to obtain a frequency having the second highest intensity.

In addition, as illustrated inFIG.5B, in a case where a power spectrum is estimated using the LASSO regression with λ of formula (1) as a threshold value, frequency components other than a signal S1 having a frequency component with the highest intensity are 0, and therefore a frequency having the second highest intensity cannot be obtained.

On the other hand, as illustrated inFIG.5C, in a case where a power spectrum is estimated using the LASSO regression in which λ is an appropriate value among values smaller than the threshold value by applying formula (1), not only the signal S1 having a frequency component with the highest intensity but also a signal S2 having a frequency component with the second highest intensity can be specified.

By adjusting λ to an appropriate value among values smaller than the threshold value, the frequency calculation unit120estimates the power spectrum illustrated inFIG.5C, and calculates the frequencies of the two signals S1 and S2 having high intensities among the frequency components of the estimated power spectrum as peak frequencies.

The distance measurement unit130measures a distance from a predetermined reference point to the object4on the basis of the two peak frequencies calculated by the frequency calculation unit120.

Reflected light in a case where cutting oil is present on a work surface of the object4will be described with reference toFIG.6.

FIG.6is an explanatory diagram illustrating an example of reflected light in a case where cutting oil is present on the work surface of the object4.

As illustrated inFIG.6, a part of irradiation light emitted toward the object4is reflected by an oil surface of the cutting oil. The rest of the irradiation light passes through the cutting oil and is reflected by the work surface of the object4. First reflected that is the irradiation light reflected by the oil surface of the cutting oil, is scattered, and therefore only a part of the first reflected light is directed to the irradiation optical system23illustrated inFIG.2. Therefore, among electric signals acquired by the distance measurement device100, the intensity of an electric signal caused by the first reflected light is smaller than the intensity of an electric signal caused by the second reflected light that is the irradiation light reflected by the work surface of the object4. Therefore, the electric signal caused by the first reflected light included in the electric signals acquired by the distance measurement device100may be mixed in white noise.

That is, in a case where cutting oil is present on the work surface of the object4, a power spectrum estimated using a general Fourier transform for an electric signal acquired by the distance measurement device100may be in a state as illustrated inFIG.5A.

In a case where cutting oil is present on the work surface of the object4, a power spectrum as illustrated inFIG.5Amay be obtained, and therefore the distance measurement unit130cannot measure a distance from a predetermined reference point to an oil surface of the cutting oil present on the work surface of the object4. Since the cutting oil has a refractive index different from that of air or vacuum, as a result, the distance measurement unit130cannot accurately measure a distance from a predetermined reference point to the work surface of the object4.

However, by estimating a power spectrum using the LASSO regression in which λ is adjusted to an appropriate value among values smaller than the threshold value by applying formula (1) for a similar electric signal, the estimated power spectrum is in a state as illustrated inFIG.5C, and a frequency component of reflected light reflected by the oil surface of the cutting oil can be specified as the signal S2.

Therefore, the distance measurement unit130can measure a distance from a predetermined reference point to the oil surface of the cutting oil present on the work surface of the object4, and as a result, the distance measurement unit130can accurately measure a distance from the predetermined reference point to the work surface of the object4.

With the above configuration, the distance measurement device100can accurately measure a distance from a predetermined reference point to the object4to be measured even in a case where the intensity of reflected light reflected by the object4to be measured cannot be sufficiently obtained due to scattering of the reflected light.

Reflected light in a case where a work surface of the object4is not uniform with respect to an optical axis direction of irradiation light will be described with reference toFIGS.7and8A and8B.

FIG.7is an explanatory diagram illustrating an example of reflected light in a case where a work surface of the object4is not uniform with respect to an optical axis direction of irradiation light.

As illustrated inFIG.7, irradiation light emitted toward the object4is reflected by each of surfaces A. B, and C included in the work surface of the object4. Since the surface A or the surface B is uniform with respect to an optical axis direction of the irradiation light, reflected light reflected by the surface A or the surface B is directed to the irradiation optical system23illustrated inFIG.2. On the other hand, since the surface C is not uniform with respect to the optical axis direction of the irradiation light, reflected light reflected by the surface C is scattered, and only a part of the reflected light is directed to the irradiation optical system23illustrated inFIG.2.

FIG.8Ais an example of a power spectrum estimated using a general Fourier transform for an electric signal based on the reflected light reflected by the work surface of the object4illustrated inFIG.7.

FIG.8Bis an example of a power spectrum estimated using the LASSO regression in which λ is an appropriate value among values smaller than the threshold value by applying formula (1) for the same electric signal as inFIG.8A.

For an electric signal based on the reflected light reflected by the work surface of the object4illustrated inFIG.7, the intensity of an electric signal caused by the reflected light reflected by the surface C is smaller than the intensity of an electric signal caused by the reflected light reflected by the surface A or the surface B. Therefore, as illustrated inFIG.8A, there is a case where a signal S3 corresponding to the electric signal caused by the reflected light reflected by the surface C included in the electric signals acquired by distance measurement device100is blended into white noise, a frequency component caused by reflected light reflected by a surface other than the surface C in the work surface of the object4, or the like.

On the other hand, as illustrated inFIG.8B, in a case where a power spectrum is estimated using the LASSO regression in which λ is adjusted to an appropriate value among values smaller than the threshold value by applying formula (1), not only the signal S1 corresponding to the reflected light reflected by the surface A and the signal S2 corresponding to the reflected light reflected by the surface B but also the signal S3 corresponding to the reflected light reflected by the surface C having a frequency component with the third highest intensity can be specified.

Therefore, the distance measurement unit130can measure a distance from a predetermined reference point to each of the surfaces A. B, and C included in the work surface of the object4, and as a result, the distance measurement unit130can accurately measure a distance from the predetermined reference point to the work surface of the object4.

With the above configuration, the distance measurement device100can accurately measure a distance from a predetermined reference point to the object4to be measured even in a case where the intensity of reflected light reflected by the object4to be measured cannot be sufficiently obtained due to scattering of the reflected light, such as in a case where a work surface of the object4is not uniform with respect to an optical axis direction of irradiation light.

A hardware configuration of a main part of the distance measurement device100according to the first embodiment will be described with reference toFIGS.9A and9B.

FIGS.9A and9Bare block diagrams illustrating examples of a hardware configuration of the distance measurement device100according to the first embodiment.

As illustrated inFIG.9A, the distance measurement device100includes a computer, and the computer includes a processor901and a memory902. The memory902stores a program for causing the computer to function as the signal acquisition unit110, the frequency calculation unit120, the distance measurement unit130, and the distance output unit140. The processor901reads and executes the program stored in the memory902, and the functions of the signal acquisition unit110, the frequency calculation unit120, the distance measurement unit130, and the distance output unit140are thereby implemented.

In addition, as illustrated inFIG.9B, the distance measurement device100may include a processing circuitry903. In this case, the functions of the signal acquisition unit110, the frequency calculation unit120, the distance measurement unit130, and the distance output unit140may be implemented by the processing circuitry903.

In addition, the distance measurement device100may include the processor901, the memory902, and the processing circuitry903(not illustrated). In this case, some of the functions of the signal acquisition unit110, the frequency calculation unit120, the distance measurement unit130, and the distance output unit140may be implemented by the processor901and the memory902, and the remaining functions may be implemented by the processing circuitry903.

The processor901uses, for example, a central processing unit (CPU), a graphics processing unit (GPU), a microprocessor, a microcontroller, or a digital signal processor (DSP).

The memory902uses, for example, a semiconductor memory or a magnetic disk. More specifically, the memory902uses a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a solid state drive (SSD), a hard disk drive (HDD), or the like.

The processing circuitry903uses, for example, an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field-programmable gate array (FPGA), a system-on-a-chip (SoC), or a system large-scale integration (LSI).

An operation of the distance measurement device100according to the first embodiment will be described with reference toFIG.10.

FIG.10is a flowchart illustrating an example of processing of the distance measurement device100according to the first embodiment.

For example, the distance measurement device100repeatedly executes the processing of the flowchart.

First, in step ST1001, the signal acquisition unit110acquires an electric signal based on interference light from the optical sensor device20.

Next, in step ST1002, the frequency calculation unit120calculates a peak frequency of the electric signal based on the interference light using the LASSO regression.

Next, in step ST1003, the distance measurement unit130measures a distance from a predetermined reference point to the object4.

Next, in step ST1004, the distance output unit140outputs distance information.

After step ST1004, the distance measurement device100ends the processing of the flowchart. After ending the processing of the flowchart, the distance measurement device100returns to step ST1001, and repeatedly executes the processing of the flowchart.

As described above, the distance measurement device100according to the first embodiment includes: the signal acquisition unit110to acquire an electric signal based on interference light from the optical sensor device20that splits sweep light having a periodically changing frequency into reference light and irradiation light to be emitted toward the object4to be measured, irradiates the object4to be measured with the irradiation light, generates interference light by causing the reference light to interfere with reflected light that is the irradiation light reflected by the object4to be measured, and generates the electric signal based on the generated interference light; the frequency calculation unit120to calculate, on the basis of the electric signal based on the interference light acquired by the signal acquisition unit110, a peak frequency of the electric signal using the LASSO regression; the distance measurement unit130to measure, on the basis of the peak frequency calculated by the frequency calculation unit120, a distance from a predetermined reference point to the object4to be measured; and the distance output unit140to output distance information indicating the distance measured by the distance measurement unit130.

With the above configuration, the distance measurement device100can accurately measure a distance from a predetermined reference point to the object4to be measured even in a case where the intensity of reflected light reflected by the object4to be measured cannot be sufficiently obtained due to scattering of the reflected light.

In addition, as described above, in the distance measurement device100according to the first embodiment, in the above-described configuration, the frequency calculation unit120adjusts a threshold value of a penalty term of the LASSO regression to calculate a predetermined number of peak frequencies of an electric signal based on interference light using the LASSO regression.

With the above configuration, the distance measurement device100can calculate a peak frequency of an electric signal based on reflected light reflected by the object4to be measured even in a case where the intensity of the reflected light cannot be sufficiently obtained due to scattering of the reflected light. As a result, the distance measurement device100can accurately measure a distance from a predetermined reference point to the object4to be measured.

In addition, as described above, in the distance measurement device100according to the first embodiment, in the above-described configuration, the frequency calculation unit120calculates a predetermined number of peak frequencies of an electric signal based on interference light using the LASSO regression and calculates a predetermined number of peak frequencies in descending order of intensity among a plurality of frequency components calculated using the LASSO regression.

With the above configuration, the distance measurement device100can calculate a peak frequency of an electric signal based on reflected light reflected by the object4to be measured even in a case where the intensity of the reflected light cannot be sufficiently obtained due to scattering of the reflected light. As a result, the distance measurement device100can accurately measure a distance from a predetermined reference point to the object4to be measured.

In addition, as described above, in the distance measurement device100according to the first embodiment, in the above-described configuration, the frequency calculation unit120calculates a predetermined number of peak frequencies of an electric signal based on interference light using the LASSO regression, and the distance measurement unit130measures a distance from a predetermined reference point to the object4to be measured on the basis of a predetermined number of peak frequencies calculated by the frequency calculation unit120.

With the above configuration, the distance measurement device100can calculate a peak frequency of an electric signal based on reflected light reflected by the object4to be measured even in a case where the intensity of the reflected light cannot be sufficiently obtained due to scattering of the reflected light. As a result, the distance measurement device100can accurately measure a distance from a predetermined reference point to the object4to be measured.

In addition, as described above, the machine tool1according to the first embodiment includes the distance measurement device100and the shape calculation unit46that calculates the shape of the object4to be measured on the basis of distance information output from the distance measurement device100in the above-described configuration.

With the above configuration, since the distance measurement device100outputs distance information indicating an accurate distance from a predetermined reference point to the object4to be measured even in a case where the intensity of reflected light reflected by the object4to be measured cannot be sufficiently obtained due to scattering of the reflected light, the machine tool1can accurately calculate the shape of the object4to be measured.

Second Embodiment

A distance measurement device100aaccording to a second embodiment will be described with reference toFIGS.11to13.

A configuration of a main part of the distance measurement device100aaccording to the second embodiment will be described with reference toFIG.11.

FIG.11is a block diagram illustrating an example of a configuration of a main part of the distance measurement device100aaccording to the second embodiment.

The distance measurement device100aincludes a signal acquisition unit110, a frequency calculation unit120a, a distance measurement unit130, and a distance output unit140.

The distance measurement device100ais obtained by changing the frequency calculation unit120included in the distance measurement device100according to the first embodiment to the frequency calculation unit120a.

In the configuration of the distance measurement device100a, description of a configuration similar to that of the distance measurement device100according to the first embodiment will be omitted. That is, inFIG.11, the same reference numerals are given to blocks similar to those illustrated inFIG.4, and description thereof will be omitted.

Note that the distance measurement device100ais applied to, for example, a machine tool1similarly to the distance measurement device100according to the first embodiment.

The frequency calculation unit120included in the distance measurement device100according to the first embodiment calculates, on the basis of an electric signal based on interference light acquired by the signal acquisition unit110, a peak frequency of the electric signal using LASSO regression.

On the other hand, the frequency calculation unit120acalculates a predetermined number of peak frequencies of an electric signal based on interference light, and calculates the predetermined number of peak frequencies on the basis of a plurality of frequency components calculated using the LASSO regression and a plurality of frequency components calculated using a Fourier transform.

Specifically, for example, by calculating, for each frequency, a product of each frequency component calculated using the LASSO regression and each frequency component calculated using a Fourier transform corresponding to each frequency component calculated using the LASSO regression, the frequency calculation unit120adetermines a vector βH. For example, by multiplying amplitude values of the same frequency by each other between each frequency component of the power spectrum illustrated inFIG.5Aand each frequency component of the power spectrum illustrated inFIG.5C, the frequency calculation unit120adetermines the vector βH.

Each element of the vector βHdetermined by the frequency calculation unit120acorresponds to a frequency component of an electric signal based on interference light.

The frequency calculation unit120aselects a predetermined number of elements in descending order of element value from among a plurality of elements of the determined vector βHand calculates the selected elements as peak frequencies.

FIG.12is an explanatory diagram illustrating an example of the vector βHdetermined by the frequency calculation unit120aaccording to the second embodiment.

The horizontal axis inFIG.12is similar to the frequency of the power spectrum illustrated inFIG.5A or5C.

A value of the amplitude in a signal S2 of the power spectrum illustrated inFIG.5Cis close to values of the amplitudes of the other frequencies, whereas a value of an element corresponding to the frequency of a signal S2 in the vector βHillustrated inFIG.12is more clearly different from values of elements at the other frequencies.

That is, the frequency calculation unit120acan calculate a peak frequency on the basis of the vector βHhaving a larger signal-to-noise ratio than the power spectrum illustrated inFIG.5C.

As a result, the distance measurement device100acan more accurately measure a distance from a predetermined reference point to the object4to be measured than the distance measurement device100according to the first embodiment.

Since a hardware configuration of a main part of the distance measurement device100ais similar to that described with reference toFIGS.9A and9Bin the first embodiment, illustration thereof and description thereof will be omitted. That is, the functions of the signal acquisition unit110, the frequency calculation unit120a, the distance measurement unit130, and the distance output unit140may be implemented by the processor901and the memory902, or may be implemented by the processing circuitry903.

An operation of the distance measurement device100aaccording to the second embodiment will be described with reference toFIG.13.

FIG.13is a flowchart illustrating an example of processing of the distance measurement device100aaccording to the second embodiment.

For example, the distance measurement device100arepeatedly executes the processing of the flowchart.

First, in step ST1301, the signal acquisition unit110acquires an electric signal based on interference light from the optical sensor device20.

Next, in step ST1302, the frequency calculation unit120adetermines a vector βHon the basis of a plurality of frequency components calculated using the LASSO regression and a plurality of frequency components calculated using a Fourier transform.

Next, in step ST1303, the frequency calculation unit120acalculates a peak frequency of an electric signal based on interference light on the basis of the vector βH.

Next, in step ST1304, the distance measurement unit130measures a distance from a predetermined reference point to the object4.

Next, in step ST1305, the distance output unit140outputs distance information.

After step ST1304, the distance measurement device100aends the processing of the flowchart. After ending the processing of the flowchart, the distance measurement device100areturns to step ST1301, and repeatedly executes the processing of the flowchart.

As described above, the distance measurement device100aaccording to the second embodiment includes: the signal acquisition unit110that acquires an electric signal based on interference light from the optical sensor device20that splits sweep light having a periodically changing frequency into reference light and irradiation light to be emitted toward the object4to be measured, irradiates the object to be measured with the irradiation light, generates interference light by causing the reference light to interfere with reflected light that is the irradiation light reflected by the object4to be measured, and generates the electric signal based on the generated interference light; the frequency calculation unit120ato calculate, on the basis of the electric signal based on the interference light acquired by the signal acquisition unit110, a peak frequency of the electric signal using the LASSO regression; the distance measurement unit130to measure, on the basis of the peak frequency calculated by the frequency calculation unit120a, a distance from a predetermined reference point to the object4to be measured; and the distance output unit140to output distance information indicating the distance measured by the distance measurement unit130, wherein the frequency calculation unit120acalculates a predetermined number of peak frequencies of an electric signal based on interference light, and calculates the predetermined number of peak frequencies on the basis of a plurality of frequency components calculated using the LASSO regression and a plurality of frequency components calculated using a Fourier transform.

With the above configuration, the distance measurement device100acan accurately measure a distance from a predetermined reference point to the object4to be measured even in a case where the intensity of reflected light reflected by the object4to be measured cannot be sufficiently obtained due to scattering of the reflected light.

Note that in the present disclosure, it is possible to freely combine the embodiments to each other, modify any constituent element in each of the embodiments, or omit any constituent element in each of the embodiments within the scope of the disclosure.

INDUSTRIAL APPLICABILITY

The distance measurement device of the present disclosure can be applied to a machine tool.

REFERENCE SIGNS LIST