Laser device

Abstract

A laser device (100) is provided with: a first optical comb laser (10); a second optical comb laser (20) having a repetition frequency different from that of the first optical comb laser (10); a detection unit (70) that detects interference light formed by the output light from the first optical comb laser (10) and the output light from the second optical comb laser (20); and a control circuit (90). The control circuit (90) controls, on the basis of the output of the detection unit (70), a first CEO frequency, which is the carrier envelope offset frequency of the first optical comb laser (10), and / or a second CEO frequency, which is the carrier envelope offset frequency of the second optical comb laser (20), so as to change a difference frequency, which is the difference between the first CEO frequency and the second CEO frequency.

Description

Technical Field

[0001] The present disclosure relates to a laser device. Background Art

[0002] Conventionally, there is a known laser source called an optical frequency comb laser or simply an optical comb laser. Specifically, an optical frequency comb laser is a light source that outputs laser light whose pulse waveforms are arranged at equal intervals on the time axis and whose spectra are arranged at equal intervals on the frequency axis.

[0003] Patent Document 1 discloses a coherent dual scanning laser system which is controlled so that the carrier envelopes of two oscillators are shifted in frequency (f CEO ) is stable. In addition, Patent Document 2 discloses a method for controlling an optical comb, which shifts the carrier envelope frequency (f CEO ) is controlled as the repetition frequency (f rep ).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5663499

[0007] Patent Document 2: Japanese Patent No. 6963322 Summary of the invention

[0008] However, as shown in the above-mentioned prior art, it may be impossible to detect the output light with a detector with good accuracy simply by stabilizing the difference in carrier-envelope offset frequency.

[0009] The present disclosure provides a laser device that outputs light that can be detected with high accuracy by a detector.

[0010] A laser device according to one embodiment of the present invention comprises: a first optical comb laser; a second optical comb laser having a repetition frequency different from that of the first optical comb laser; a detection unit for detecting interference light formed by output light of the first optical comb laser and output light of the second optical comb laser; and a control circuit for controlling at least one of a first CEO frequency, which is a carrier-envelope offset frequency of the first optical comb laser, and a second CEO frequency, which is a carrier-envelope offset frequency of the second optical comb laser, based on an output of the detection unit, so as to change a difference frequency, which is a difference between the first CEO frequency and the second CEO frequency.

[0011] According to the present disclosure, it is possible to provide a laser device that outputs light that can be detected with high accuracy by a detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1This is a diagram schematically showing the temporal change of the electric field of the optical comb laser.

[0013] Figure 2 It is a diagram schematically showing the spectrum of optical comb laser light.

[0014] Figure 3 FIG. 1 is a diagram schematically showing the spectra of two optical comb lasers in a dual-comb system.

[0015] Figure 4 FIG. 1 is a diagram schematically showing a spectrum after interference in a dual-comb system.

[0016] Figure 5 This is a diagram schematically showing an example of a laser device according to an embodiment.

[0017] Figure 6 This is a diagram showing the operation of the laser device according to the embodiment, in which δf is controlled based on the lowest frequency mode in the spectrum of the dual-comb signal. CEO Flowchart of the processing.

[0018] Figure 7 This is a diagram showing an example of inappropriateness of the frequency spectrum of a dual-comb signal.

[0019] Figure 8 This is a diagram showing the operation of the laser device according to the embodiment, in which δf is controlled based on the highest frequency mode in the spectrum of the dual-comb signal. CEO Flowchart of the processing.

[0020] Fig. 9 This is a diagram showing an example of inappropriateness of the frequency spectrum of a dual-comb signal.

[0021] Fig.10 The laser device of the embodiment controls δf based on the frequency interval in the spectrum of the dual-comb signal. CEO Flowchart of the processing.

[0022] Fig.11 This is a diagram showing an example of inappropriateness of the frequency spectrum of a dual-comb signal.

[0023] Fig.12 The laser device of the embodiment controls δf based on the spectrum of the dual-comb signal. CEO A flowchart of an example of processing.

[0024] Fig.13 This is a diagram showing how to control δf based on the accuracy of the distance calculated from the dual-comb signal in the operation of the laser device of the embodiment. CEO A flowchart of an example of processing.

[0025] Fig.14 This is a diagram showing the control of δf during the operation of the laser device according to the embodiment. CEOThis is a flowchart as an example of the calibration process before measurement.

[0026] Fig.15 This is a diagram showing the control of δf during the operation of the laser device according to the embodiment. CEO A flowchart as an example of the processing of feedback over time.

[0027] Fig.16 It is a diagram showing the flow of processing according to a modification example. DETAILED DESCRIPTION

[0028] (Abstract of the present disclosure)

[0029] There are two important parameters in a comb laser. One is the "repetition frequency" (f) which represents the frequency spectrum spacing. rep The other is the "carrier envelope offset frequency" (f CEO ). These parameters may change slightly due to external disturbances such as vibration and temperature. In contrast, by incorporating modulation devices such as Peltier elements or piezoelectric elements into the optical comb laser, these parameters can be stabilized. This enables precise measurement.

[0030] The method of preparing two optical comb lasers and interfering and measuring them with each other at slightly different repetition frequencies is called dual comb. rep 、f rep +δf rep The two comb lasers interfere with each other and generate a beat frequency. As a result, a beat frequency with an interval of δf can be obtained. rep What is important here is that the spectrum of the optical comb laser before interference is in the THz region of optical frequencies, while on the other hand, the spectrum after interference becomes in the MHz region of radio frequencies.

[0031] Existing detectors cannot physically detect signals of light in the THz region because their response frequency is below GHz. Therefore, in the past, when determining the wavelength of light, detectors could not be used directly, but instead a spectrometer was used to separate the light into each wavelength and then use the detector for detection. In this case, there is a disadvantage that it takes time to scan the wavelength, so the spectrum cannot be measured in a short time.

[0032] In contrast, in the case of dual comb, light can be down-converted to the MHz region, so it does not need to pass through a spectrometer. Therefore, compared with the past, it has the advantage of being able to measure the spectrum at a high speed. In addition, since the information of light can be directly measured, high-sensitivity and high-precision measurement can be achieved. Therefore, dual comb can be used in a variety of measurements such as spectroscopic measurement, distance measurement, and frequency measurement.

[0033] However, even when using a dual-comb, when using an inexpensive detector with a narrow response band, the carrier envelope offset frequency f of the two optical combs is CEO The difference is δf CEO Depending on the value of , the response band may be exceeded, making measurement difficult.

[0034] A laser device according to one embodiment of the present invention comprises: a first optical comb laser; a second optical comb laser having a repetition frequency different from that of the first optical comb laser; a detection unit for detecting interference light formed by output light of the first optical comb laser and output light of the second optical comb laser; and a control circuit for controlling at least one of a first CEO frequency, which is a carrier-envelope offset frequency of the first optical comb laser, and a second CEO frequency, which is a carrier-envelope offset frequency of the second optical comb laser, based on an output of the detection unit, so as to change a difference frequency, which is a difference between the first CEO frequency and the second CEO frequency.

[0035] Thus, by using the output of the detection unit that detects the interference light, the difference frequency (δf CEO ) so that it falls within the response frequency band of the detection unit. Therefore, even when using a detector with a narrow response frequency band, it is possible to perform detection with good accuracy.

[0036] Furthermore, in a laser device according to one embodiment of the present disclosure, for example, the control circuit may obtain first information on the lowest frequency mode of the spectrum of the interference light based on the output of the detection unit, and increase the difference frequency using the obtained first information.

[0037] This makes it possible to detect the lowest frequency mode within an appropriate range within the response frequency band, thereby preventing a decrease in detection accuracy due to the occurrence of aliasing or the like.

[0038] Furthermore, in a laser device according to one embodiment of the present disclosure, for example, the control circuit may obtain second information on a highest frequency mode of a spectrum of the interference light based on an output of the detection unit, and reduce the difference frequency using the obtained second information.

[0039] This allows the highest frequency mode to be detected within an appropriate range within the response frequency band, thereby preventing a decrease in detection accuracy due to the occurrence of aliasing or the like.

[0040] Furthermore, in the laser device of one embodiment of the present disclosure, for example, the control circuit may acquire third information on the frequency interval of the spectrum of the interference light based on the output of the detection unit, and change the difference frequency using the acquired third information.

[0041] This makes it possible to detect whether or not aliasing occurs. Therefore, when aliasing occurs, the spectrum of the interference light can be brought within the response band, and a decrease in detection accuracy can be suppressed.

[0042] In addition, in a laser device of one embodiment of the present invention, for example, the detection unit detects interference light between reflected light formed by output light of the first optical comb laser reflected by an object and output light of the second optical comb laser, and the laser device includes a signal processing circuit for calculating the distance to the object based on the output of the detection unit.

[0043] This makes it possible to accurately measure the distance to the object and inspect the shape of the object.

[0044] Furthermore, in the laser device according to one aspect of the present disclosure, for example, the control circuit may change the beat frequency based on the accuracy of the distance calculated by the signal processing circuit.

[0045] This can improve the accuracy of the distance.

[0046] Furthermore, in the laser device according to one aspect of the present disclosure, for example, the control circuit may change the difference frequency before calculating the distance.

[0047] Therefore, since the differential frequency (δf CEO ), so that measurements with good accuracy can be performed from the beginning.

[0048] Furthermore, in the laser device according to one aspect of the present disclosure, for example, the control circuit may change the difference frequency while calculating the distance.

[0049] Therefore, since the difference frequency (δf CEO ), so it is possible to improve the accuracy while measuring. In addition, "while calculating the distance" means that the calculation of the distance and the change of the difference frequency are substantially performed simultaneously and in parallel. For example, "while calculating the distance" not only means the situation where the calculation of the distance and the change of the difference frequency are performed completely simultaneously, but also means the situation where the calculation of the distance and the change of the difference frequency are repeated alternately. Alternating repetition can be repeated alternately one at a time, and also includes the situation where one process is performed multiple times and another process is performed once.

[0050] In addition, the laser device according to one embodiment of the present disclosure can be configured by appropriately combining the constituent elements of the laser devices according to the above-described embodiments.

[0051] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0052] In addition, the embodiments described below all represent general or specific examples. The numerical values, shapes, materials, constituent elements, configuration positions and connection methods of constituent elements, steps, and the order of steps shown in the following embodiments are all examples, and their purport is not to limit the present disclosure. In addition, among the constituent elements of the following embodiments, constituent elements not recorded in the independent technical solutions are described as arbitrary constituent elements.

[0053] In addition, each figure is a schematic diagram and does not necessarily illustrate strictly. Therefore, for example, the scales in each figure are not necessarily the same. In addition, in each figure, the same reference numerals are attached to substantially the same structure, and repeated descriptions are omitted or simplified.

[0054] In addition, in this specification, unless otherwise specified, ordinal numbers such as "first" and "second" do not mean the number or order of constituent elements, but are used to distinguish between constituent elements to avoid confusion of the same kind.

[0055] (Implementation Method)

[0056] [Optical comb laser]

[0057] First, refer to Figure 1 and Figure 2 Briefly explain the basic principle of optical comb laser.

[0058] Figure 1 is a diagram schematically showing an example of the time variation of the electric field of the optical comb laser. Figure 1 In FIG. 1 , the horizontal axis represents time and the vertical axis represents the electric field of the optical comb laser. In addition, the optical comb laser is also called an optical frequency comb laser. In addition, in this specification, it is sometimes abbreviated as laser.

[0059] like Figure 1 As shown, the optical comb laser is based on the repetition period T rep The repetition period is T rep For example, it is 1 ps or more and 100 ns or less. The full width at half maximum of each optical pulse is represented by Δt. The full width at half maximum of each optical pulse Δt is, for example, 10 fs or more and 100 ps or less.

[0060] In a laser resonator, the group velocity v of the envelope of a light pulse is g and the phase velocity v of the wave propagation within the optical pulse p Due to the dispersion in the resonator, etc., different values ​​are taken. Since the group velocity v g and phase velocity v pWhen two adjacent light pulses overlap to make the envelopes consistent, the phase of the waves in these light pulses shifts by Δφ. Δφ takes a value between 0 and 2π. That is, 0≤Δφ≤2π. The repetition period of the light pulse train is L, and is determined by T rep =L / v g To express.

[0061] Figure 2 is a diagram schematically showing the spectrum of a comb laser. Figure 2 In the figure, the horizontal axis represents the frequency and the vertical axis represents the intensity of the optical comb laser.

[0062] like Figure 2 As shown, the optical comb laser has a comb-shaped spectrum formed by a plurality of discrete equally spaced lines. The frequency of the plurality of discrete equally spaced lines corresponds to the resonant frequency of the longitudinal mode in the laser resonator. The repetition frequency corresponding to the interval between two adjacent equally spaced lines in the optical comb laser is given by f rep =1 / T rep The repetition frequency f rep For example, it is 10 MHz or more and 1 THz or less. When the round trip length L of the laser resonator is 30 cm and the group velocity v g The speed of light in vacuum (=3×10 8 m / s) are roughly equal, the repetition period T rep is 1ns, and the repetition frequency is f rep is 1GHz.

[0063] When the half-value width of the comb laser is set to Δf, Δf=1 / Δt. The half-value width of the comb laser Δf is, for example, above 10 GHz and below 100 THz. Assuming that the equally spaced lines exist until near zero frequency, the frequency of the equally spaced lines closest to zero frequency is called the carrier envelope offset frequency. The carrier envelope offset frequency is given by f CEO =(Δφ / (2π))f rep To represent. Carrier envelope offset frequency f CEO Take from 0 to repetition frequency f rep That is, 0≤f CEO ≤f rep When the carrier envelope is offset by frequency f CEO When the 0th mode frequency is set, the nth mode frequency f in the optical comb laser is n By n =f CEO +nf rep To express. Figure 1 The electric field of the comb laser shown is given by E(t) = ΣnE n exp[-i(2πf n t+φn )], where the nth mode frequency f n The amplitude and phase of the electric field under n and φ n .

[0064] Repetition frequency f rep and the carrier envelope offset frequency f CEO It may slightly change due to external disturbances such as vibration or temperature change of the optical comb laser source. This is because vibration changes the round trip length L of the laser resonator, and temperature changes change the group velocity v through the refractive index change of the laser resonator. g and phase velocity v p Change. Repetition frequency f rep and the carrier envelope offset frequency f CEO The repetition frequency f is much lower than the frequency of light. Even a slight change in them will affect the determination of the mode frequency in the optical comb laser. Therefore, the conventional optical comb laser source is assembled to make the repetition frequency f rep and carrier envelope offset frequency f CEO Stable modulation element.

[0065] The modulation element includes, for example, a piezoelectric element for suppressing vibration of a piezoelectric element and / or a temperature adjustment element for suppressing temperature changes of a Peltier element. The modulation element may be disposed outside the optical comb laser source. In order to stabilize the repetition frequency f rep , feedback is performed in the following manner, that is, a part of the comb laser is detected, and based on the detected part, the round-trip length L of the laser resonator is made constant using a piezoelectric element and a Peltier element. In order to stabilize the carrier envelope offset frequency f CEO , feedback is performed in the following manner, that is, a part of the optical comb laser is detected using a nonlinear optical effect, and the intensity of the excitation light input to the laser resonator is adjusted based on the detected part, thereby making the nonlinear properties in the laser resonator constant.

[0066] [Double Comb]

[0067] Next, refer to Figure 3 and Figure 4 Briefly explain the principle of double combing.

[0068] Figure 3 is a diagram showing the spectrum of the first optical comb laser and the second optical comb laser in the dual comb. In the first optical comb laser, the nth mode frequency f 1n By 1n =f CEO1 +nf rep1 In the second optical comb laser, the nth mode frequency f 2n By 2n =f CEO2+nf rep2 To indicate. CEO1 is an example of the first CEO frequency and is the carrier envelope offset frequency of the first optical comb laser. CEO2 is an example of the second CEO frequency and is the carrier envelope offset frequency of the second optical comb laser. rep1 is the repetition frequency of the first comb laser. rep2 is the repetition frequency of the second comb laser. rep1 and f rep2 are different from each other, and f rep2 =f rep1 +δf rep The relationship holds true. rep Much smaller than f rep1 δf rep For example, it is 1 Hz or more and 10 MHz or less.

[0069] Figure 4 is a diagram schematically showing the spectrum of interference light in a dual comb. Figure 3 The result of the first optical comb laser and the second optical comb laser interfering with each other most closely in their respective frequency modes is detected. Figure 4 The spectrum of the interference light is also called the dual-comb signal.

[0070] The frequency interval of the spectrum of interference light is δf rep , which is the difference between the repetition frequencies of the first optical comb laser and the second optical comb laser. The X in the figure represents the value from 0 to the lowest frequency mode. F max Indicates the response frequency band of the detector. Figure 4 As shown, if the spectrum of the interference light converges to F max The detection of dual-comb signals is suitable and can be used for various purposes such as distance measurement. The response band of the detector can be interpreted as the frequency band that the detector can detect. Figure 4 In the rep Can be used with any f i Same. It can also be δf rep =(f1+…+f n ) / n. The minimum value of the response frequency band of the detector may be zero. The minimum value of the response frequency band of the detector may be a value other than zero.

[0071] Here, it is assumed that the lowest frequency mode is the i-th frequency mode f of the first optical comb laser. 1i and the jth frequency mode f of the second optical comb laser 2j In this case, X = f 2j -f 1i =(f CEO2 -f CEO1)+(ji)f rep +jδf rep .

[0072] As an example, assuming that f rep =3GHz, δf rep =500kHz, i=65000, j=64989, X=(f CEO2 -f CEO1 )+506MHz. Here, i and j are values ​​when the frequency of light is set to 195THz. On the other hand, when the number of all modes is 200, the band of the spectrum is 100MHz (=δf rep ×200).

[0073] From the above, we can see that if F max ≥X+100MHz=δf CEO +606MHz, it can be accurately detected. Here, δf CEO is an example of a difference frequency between the first CEO frequency and the second CEO frequency. Specifically, δf CEO =f CEO2 -f CEO1 Since δf CEO The maximum value is about 3 GHz, so a detector with a response band of 3.6 GHz is required in some cases.

[0074] Generally speaking, detectors with a high response frequency band exceeding 1 GHz are expensive, which is a problem that hinders industrial application. The inventors of this application have conceived a method that can control δf CEO The laser device enables dual-comb measurement even with an inexpensive detector having a low response band.

[0075] [Structure of laser device]

[0076] Hereinafter, a specific structure of the laser device according to the embodiment of the present disclosure will be described.

[0077] Figure 5 Schematically shows an example of a laser device according to an embodiment. Figure 5 , a basic configuration example of the laser device 100 according to an embodiment of the present disclosure is described. The laser device 100 measures the distance to the object 60 , that is, performs ranging. Alternatively, the laser device 100 may inspect the shape of the object 60 .

[0078] like Figure 5As shown, the laser device 100 includes a first optical comb laser 10, a second optical comb laser 20, a detection unit 70, a signal processing circuit 80, and a control circuit 90. In addition, the laser device 100 also includes couplers 30, 31, 32, and 33, a circulator 40, and a collimator 50 as optical elements for adjusting the optical path.

[0079] The first optical comb laser 10 is an optical comb laser source including a laser resonator. The first optical comb laser 10 outputs a first optical comb laser 10L as output light. Figure 3 As shown in the upper part, the first optical comb laser 10L has a repetition frequency of f rep1 And the carrier envelope offset frequency is f CEO1 of laser.

[0080] The second optical comb laser 20 is an optical comb laser source including a laser resonator. The repetition frequency of the second optical comb laser 20 is different from the repetition frequency of the first optical comb laser 10. The second optical comb laser 20 outputs a second optical comb laser 20L as output light. For example, Figure 3 As shown in the lower part, the second optical comb laser 20L has a repetition frequency of f rep2 And the carrier envelope offset frequency is f CEO2 of laser.

[0081] The couplers 30, 31, 32 and 33 are optical elements for demultiplexing or coupling light, respectively.

[0082] The circulator 40 is an optical element that controls the traveling direction of light.

[0083] The collimator 50 is an optical element that converts light into parallel light and emits the parallel light. A light-collecting element such as a lens may be provided on the light-emitting side of the collimator 50 .

[0084] The detection unit 70 includes detectors 71 and 72. The detectors 71 and 72 are optical elements that generate and output electrical signals by photoelectrically converting incident light. The signal level of the electrical signal corresponds to the intensity of the incident light. The detectors 71 and 72 are photoelectric conversion elements such as photodiodes and phototransistors.

[0085] The signal processing circuit 80 obtains information about the spectrum of the dual-comb signal based on the output of the detection unit 70. The dual-comb signal is a spectrum of interference light, such as Figure 4 The signal shown. A specific example of the information about the spectrum will be described later. The signal processing circuit 80 can (1) send information corresponding to the output of the detection unit 70 (i.e., the electrical signal corresponding to the interference light) to a spectrum analyzer connected to the laser device 100 by wireless or wired connection, and (2) receive a spectrum corresponding to the output of the detection unit 70, i.e., the spectrum corresponding to the interference light, from the spectrum analyzer.

[0086] In addition, the signal processing circuit 80 calculates the distance to the object 60 based on the output of the detection unit 70. The signal processing circuit 80 can calculate the distance to each part of the surface of the object 60 based on the output of the detection unit 70. Thus, the signal processing circuit 80 can obtain information on the surface shape of the object 60.

[0087] The control circuit 90 controls the f CEO1 and f CEO2 At least one of them makes δf CEO The specific processing of the control circuit 90 will be described later.

[0088] The signal processing circuit 80 and the control circuit 90 are respectively implemented by, for example, LSI (Large Scale Integration) which is an integrated circuit (IC). In addition, the integrated circuit is not limited to LSI, and may also be a dedicated circuit or a general-purpose processor. For example, the signal processing circuit 80 and the control circuit 90 may be a microcontroller. The microcontroller includes, for example, a non-volatile memory storing a program, a volatile memory as a temporary storage area for executing the program, an input and output port, and a processor for executing the program. In addition, the signal processing circuit 80 and the control circuit 90 may be a programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor capable of reconfiguring the connection and setting of the circuit units within the LSI. The functions performed by the signal processing circuit 80 and the control circuit 90 may be implemented by software or by hardware. The signal processing circuit 80 and the control circuit 90 may be implemented by a common hardware structure.

[0089] Next, the main connection relationship between the above-mentioned components will be described. Specifically, the connection relationship between the components regarding the optical paths of the first optical comb laser light 10L and the second optical comb laser light 20L will be described.

[0090] Most of the components of the laser device 100 are Figure 5 Specifically, couplers 30, 31, 32 and 33, a circulator 40, a collimator 50 and detectors 71 and 72 are arranged on the path of the optical fiber. The first optical comb laser 10 and the second optical comb laser 20 are connected to the ends of the optical fibers.

[0091] The first comb laser light 10L is split into two parts, light 10Lt and light 10Lr, by the coupler 30. The light 10Lt is a comb laser light for measurement, and is emitted toward the object 60. The light 10Lr is a comb laser light for reference.

[0092] The light 10Lt passes through the circulator 40, exits from the collimator 50, and enters the object 60. Then, the light 10Lt is reflected by the object 60. The reflected light 10R formed by the reflection of the object 60 enters the collimator 50, passes through the circulator 40, and travels toward the coupler 33. In addition, the light 10Lr travels from the coupler 30 toward the coupler 32.

[0093] On the other hand, the second comb laser light 20L is split into two parts, light 20Lr and light 20Lt, by the coupler 31. The light 20Lt is the comb laser light for measurement, and the light 20Lr is the comb laser light for reference.

[0094] The light 20Lr is combined with the light 10Lr through the coupler 32 and is directed toward the detector 71. In addition, the light 20Lt is combined with the reflected light 10R through the coupler 33 and is directed toward the detector 72. The light is respectively interfered at the detector 71 or 72 to generate a beat frequency, and the light information is converted into an electrical signal. The electrical signals output from the respective detectors 71 and 72 are input to the signal processing circuit 80.

[0095] The signal processing circuit 80 performs arithmetic processing using the electric signal output from the detector 71 as a reference signal and the electric signal output from the detector 72 as a measurement signal, thereby calculating the distance to the object 60. In addition, the control circuit 90 controls the value of the carrier envelope offset frequency of at least one of the first optical comb laser 10 and the second optical comb laser 20 based on the electric signal output from the detector 71, so that the differential frequency δf CEO change.

[0096] [δf CEO Specific example of control]

[0097] Next, for δf CEO The laser device 100 starts operating according to a start signal from an input mechanism (not shown). The input mechanism is, for example, a physical button or a touch panel display that can be operated by a user. CEO There are many control methods, and each method is described in order below.

[0098] [Use the lowest frequency mode]

[0099] First, use Figure 6 and Figure 7 An example using the lowest frequency mode will be described.

[0100] Figure 6 This is a diagram showing the operation of the laser device 100 according to the present embodiment, in which δf is controlled based on the lowest frequency mode in the spectrum of the dual-comb signal. CEO Flowchart of the processing.

[0101] Figure 6The process shown is to control so that Figure 4 In the above example, X does not take negative values. Assume that X is negative, such as Figure 7 As shown in FIG. 1 , the spectrum is folded back at the boundary of 0 due to aliasing, and the dual-comb signal cannot be properly detected. In addition, Figure 7 This is a diagram showing an example of inappropriateness of the frequency spectrum of a dual-comb signal.

[0102] (Step S10)

[0103] In step S10, the signal processing circuit 80 obtains the dual-comb signal detected by at least one of the detectors 71 and 72. The dual-comb signal obtained here is as follows: Figure 1 Next, the process proceeds to step S11.

[0104] (Step S11)

[0105] In step S11, the signal processing circuit 80 obtains frequency information by converting the obtained time information. The frequency information obtained here is the spectrum of the interference light, for example, Figure 4 As an example of the operation for conversion, the signal processing circuit 80 performs a fast Fourier transform, but other methods can be used as long as the time information can be converted into frequency information. The signal processing circuit 80 outputs the obtained frequency information to the control circuit 90. Next, the process proceeds to step S12.

[0106] (Step S12)

[0107] In step S12, the control circuit 90 obtains δf which is the difference in repetition frequency. rep For example, the control circuit 90 controls the repetition frequency f of the first optical comb laser 10 rep1 and the repetition frequency f of the second optical comb laser 20 rep2 In the case of rep (=f rep2 -f rep1 As an example of controlling the repetition frequency, feedback control can be used to control the resonator lengths of the first optical comb laser 10 and the second optical comb laser 20, but other methods are also acceptable if the repetition frequency can be controlled. rep The information may be obtained by using a method different from the above. Next, the process proceeds to step S13.

[0108] (Step S13)

[0109] In step S13, the control circuit 90 obtains first information about the lowest frequency mode of the spectrum obtained in step S12. Specifically, the first information is the mode frequency f of the lowest frequency mode.min As an example, the control circuit 90 can detect f by performing peak detection in the spectrum. min But if we can detect f min Other methods may also be used. Next, the process proceeds to step S14.

[0110] (Step S14)

[0111] In step S14, the control circuit 90 determines f min Is it less than δf? rep When in step S14 min Less than δf rep In the case of, that is, in the case of yes in step S14, proceed to step S15. On the other hand, when f min is δf rep In the above case, that is, in the case of No in step S14, δf based on the lowest frequency mode CEO If the answer is No in step S14, δf is not set. CEO change.

[0112] (Step S15)

[0113] In step S15, the control circuit 90 controls the f of the first optical comb laser 10. CEO1 and f of the second optical comb laser 20 CEO2 At least one of them makes δf CEO For example, the control circuit 90 changes f by adjusting the output of the excitation source of the first optical comb laser 10 or the second optical comb laser 20. CEO1 and f CEO2 At least one of them, but if it is possible to change f CEO1 or CEO2 The value of δf can also be changed by other methods such as using AOM (Acoustic Optic Modulator) control. CEO Then, the process returns to step S10 and repeats the above process.

[0114] Figure 7 Shows Figure 4 The example shown in Figure 1 shows an example where X takes a negative value and aliasing occurs. Two frequency modes (indicated by the dotted line) are detected where the mode frequencies have negative values ​​at the position where the boundary is folded back to 0. In this case, Figure 7 As shown, the lowest frequency mode is the third frequency mode from the left where no aliasing occurs. In this case, since f min <δf rep (Yes in step S14), so the control circuit 90 changes f CEO1or CEO2 To increase δf CEO . Increase δf CEO The amount of is appropriately adjusted. CEO If the value is too large, the response frequency band may be exceeded. Figure 8 and Fig. 9 More details will be given later.

[0115] Thus, repeatedly increasing δf CEO The process is continued until there is no frequency mode with negative mode frequency, that is, until f is no longer satisfied. min <δf rep . This can suppress the CEO The generation of aliasing caused by being too small.

[0116] Furthermore, in step S10, the signal processing circuit 80 may obtain dual-comb signals detected by the detectors 71 and 72, respectively. For example, in the case of utilizing the distance measurement result as described later, the dual-comb signals detected by the detectors 71 and 72, respectively, are required. Furthermore, in the case where the object 60 moves at a certain speed, the position of the spectrum may be slightly shifted due to the Doppler effect of light. To cope with this situation, the dual-comb signals of the detectors 71 and 72, respectively, may be obtained, and the obtained dual-comb signals may be processed in steps S11 to S15, respectively, to prevent aliasing from occurring in the detectors 71 and 72, respectively. Figure 8 , Fig.10 and Fig.12 The same is true in .

[0117] [Use the highest frequency mode]

[0118] Next, use Figure 8 and Fig. 9 An example using the highest frequency mode will be described.

[0119] Figure 8 This is a diagram showing the operation of the laser device 100 according to the present embodiment, in which δf is controlled based on the highest frequency mode in the spectrum of the dual-comb signal. CEO Flowchart of the processing.

[0120] Figure 8 The process shown is to control so that Figure 4 The mid-frequency spectrum does not exceed the maximum value F of the response frequency band of detectors 71 and 72. max Assume that the maximum value F of the frequency spectrum exceeds the response band of detectors 71 and 72 max In the case of Fig. 9 As shown in the figure, the spectrum is aliased at F max Due to the boundary foldback, the double comb signal cannot be properly detected. Fig. 9 This is a diagram showing an example of inappropriateness of the frequency spectrum of a dual-comb signal.

[0121] The laser device 100 starts operating in response to a start signal from an input mechanism (not shown). Steps S10, S11, and S12 are Figure 6 The processing shown is the same, so the description is omitted.

[0122] (Step S23)

[0123] In step S23, the control circuit 90 obtains second information about the highest frequency mode of the spectrum obtained in step S11. The second information is the mode frequency f of the highest frequency mode. max As an example, the control circuit 90 can detect f by performing peak detection in the spectrum. max But if we can detect f max Other methods may also be used. Next, the process proceeds to step S24.

[0124] (Step S24)

[0125] In step S24, the control circuit 90 determines f max Is it greater than F? max -δf rep In step S24, max Greater than F max -δf rep In the case of, that is, in the case of yes in step S24, the process proceeds to step S25. On the other hand, in step S24, max F max -δf rep In the following case, that is, in the case of No in step S24, δf based on the highest frequency mode CEO The control ends.

[0126] (Step S25)

[0127] In step S25, the control circuit 90 controls the f of the first optical comb laser 10. CEO1 and f of the second optical comb laser 20 CEO2 At least one of them makes δf CEO For example, the control circuit 90 changes f by adjusting the output of the excitation source of the first optical comb laser 10 or the second optical comb laser 20. CEO1 and f CEO2 At least one of them, but if it is possible to change f CEO1 or CEO2 The value of δf can also be changed by other methods such as using AOM control. CEOThen, the process returns to step S10 and the above process is repeated. If the answer is No in step S24, δf is not set. CEO change.

[0128] Fig. 9 The spectrum shows the maximum value F over the response band max And an example of aliasing occurs. max The mode frequency detected at the position where the boundary is folded back exceeds the maximum value F max In this case, if Fig. 9 As shown, the highest frequency mode is the sixth frequency mode from the right where no aliasing occurs. In this case, since f max >F max -δf rep (Yes in step S24), so the control circuit 90 changes f CEO1 or CEO2 To reduce the value of δf CEO . Reduce δf CEO The amount of is appropriately adjusted. In addition, when δf CEO If is too small, the problem of X taking negative values ​​will occur. To solve this problem, use Figure 6 and Figure 7 The method described above is used to correspond.

[0129] Thus, repeatedly reducing δf CEO until the spectrum converges to the response band, that is, until f is no longer satisfied. max >F max -δf rep . This can suppress the CEO Too large and caused aliasing.

[0130] [Use frequency interval]

[0131] Next, use Fig.10 and Fig.11 An example using frequency intervals will be described.

[0132] Fig.10 This is a diagram showing the operation of the laser device 100 of this embodiment to control δf based on the frequency interval in the spectrum of the dual-comb signal. CEO Flowchart of the processing.

[0133] Fig.10 The processing shown is a process for controlling so as not to generate aliasing. Assuming that the spectrum is folded back due to aliasing, as Fig.11 As shown, using the frequency spectrum to produce less than δf rep The frequency spacing of the

[0134] The laser device 100 starts operating in response to a start signal from an input mechanism (not shown). Steps S10, S11, and S12 are Figure 6 The processing shown is the same, so the description is omitted.

[0135] (Step S33)

[0136] In step S33, the control circuit 90 obtains third information about the frequency interval of the spectrum obtained in step S11. The third information is the frequency interval f of all frequency modes in the spectrum. i As an example, the control circuit 90 can detect f by performing peak detection in the spectrum. i But if we can detect f i Then, other methods may be used. Next, the process proceeds to step S34. i The subscript i of represents the number of the frequency interval. For example, when the number of frequency patterns is N, i is a value greater than or equal to 1 and less than or equal to N-1.

[0137] (Step S34)

[0138] In step S34, the control circuit 90 determines f for each i in i=1 to N-1. i Is it less than δf? rep In step S34, at least one i Less than δf rep In the case of, that is, in the case of yes in step S34, proceed to step S35. On the other hand, in step S34, in all f i Not less than δf rep In the case of No in step S34, based on the frequency interval δf CEO If the answer is No in step S34, δf is not set. CEO change.

[0139] (Step S35)

[0140] In step S35, the control circuit 90 controls the f of the first optical comb laser 10. CEO1 and f of the second optical comb laser 20 CEO2 At least one of them makes δf CEO For example, the control circuit 90 changes f by adjusting the output of the excitation source of the first optical comb laser 10 or the second optical comb laser 20. CEO1 and f CEO2 At least one of them, but if it is possible to change f CEO1 or CEO2 The value of δf can also be changed by other methods such as using AOM control. CEOThen return to step S10 and repeat the above process. Figure 7 same, Fig.11 An example of aliasing in the spectrum is shown. Fig.11 As shown, the frequency intervals of adjacent frequency modes are represented by f1 to f8. By generating aliasing, f1, f2, f3 and f4 all become smaller than δf rep (Yes in step S34), so the control circuit 90 changes f CEO1 or CEO2 The value of δf CEO Change. Make δf CEO The amount of change is adjusted appropriately.

[0141] exist Fig.11 In , the subscript i is assigned in ascending order from the side with lower frequency. Fig.11 As shown, when i is small, f i Less than δf rep In the case of , aliasing occurs with a value of 0 as the boundary. Therefore, the control circuit 90 increases δf CEO On the other hand, when i is large, f i Less than δf rep In the case of F max The value of produces aliasing at the edge (see Fig. 9 ). Therefore, the control circuit 90 reduces δf CEO That's it.

[0142] Thus, repeatedly making δf CEO The change is processed until the spectrum is completely converged within the response frequency band, that is, f is no longer satisfied. i <δf rep In this way, the occurrence of aliasing can be suppressed.

[0143] [Use the lowest frequency mode, the highest frequency mode and the frequency interval]

[0144] Next, use Fig.12 The following describes an example using the lowest frequency mode, the highest frequency mode, and the frequency interval. That is, the control circuit 90 can execute Figure 6 , Figure 8 and Fig.10 Combinations of treatments shown.

[0145] The laser device 100 starts operating in response to a start signal from an input mechanism (not shown). Steps S10, S11, and S12 are Figure 6 The processing shown is the same, so the description is omitted.

[0146] (Step S43)

[0147] In step S43, the control circuit 90 obtains the mode frequency f of the lowest frequency mode for the spectrum obtained in step S11. min , the mode frequency f of the highest frequency mode max and the frequency interval f i As an example, the control circuit 90 can detect f by performing peak detection in the spectrum. min 、f max and f i But if we can detect f min 、f max and f i Then other methods can also be used. Next, after detecting f min In the case of f, the process proceeds to step S14. max In the case of f, the process proceeds to step S24. i In the case of, proceed to step S34. The processing in each step S14, S24 and S34 is the same as Figure 6 , Figure 8 and Fig.10 The same is true for steps S15, S25, and S35.

[0148] (Step S46)

[0149] If the answer is No in each of steps S14, S24 and S34, that is, if the conditions in each step are not satisfied, the control circuit 90 determines whether there are any unexamined conditions. If there are any unexamined conditions, that is, if the answer is Yes in step S46, the control circuit 90 returns to step S43 and obtains the f related to the unexamined conditions. min 、f max or i For example, in step S43, f min , when f is no longer satisfied min <δf rep In the case of (No in S14), when returning to step S43 again, f max or i When the control circuit 90 has finished studying all the conditions, that is, when the answer is No in step S46, δf CEO The control ends.

[0150] In addition, Fig.12 The example of sequentially performing the case of using the lowest frequency mode, the case of using the highest frequency mode, and the case of using the frequency interval is illustrated in FIG. 1 , but the present invention is not limited thereto. The control circuit 90 may perform at least two of the cases in parallel at the same time.

[0151] [Using distance accuracy]

[0152] Next, use Fig.13 An example using the accuracy of the distance to the object 60 will be described.

[0153] Fig.13 This figure shows the control of δf based on the accuracy of the distance calculated from the dual-comb signal in the operation of the laser device 100 of this embodiment. CEO A flowchart of an example of processing.

[0154] Fig.13 The processing shown is to control so that the distance measurement result is accurate without considering aliasing. Since the distance measurement information output in the actual measurement is used in the control, the calculation cost for control can be reduced and the control can be performed quickly.

[0155] The laser device 100 starts operating in response to a start signal from an input mechanism (not shown).

[0156] (Step S50)

[0157] In step S50, the signal processing circuit 80 obtains the dual-comb signals detected by the detectors 71 and 72. The dual-comb signals obtained here are as follows: Figure 1 Next, the process proceeds to step S51.

[0158] (Step S51)

[0159] In step S51, the signal processing circuit 80 uses the dual-comb signal output from the detector 71 as a reference signal and the dual-comb signal output from the detector 72 as a measurement signal to perform arithmetic processing to calculate the distance to the object 60. As an example of a method for calculating the distance, the distance can be obtained based on the peak difference between the reference signal and the pulse in the measurement signal, but other methods can also be used if the distance can be obtained, such as distance calculation using phase information after Fourier transformation. Next, the process proceeds to step S52.

[0160] (Step S52)

[0161] In step S52, the control circuit 90 calculates the accuracy σ of the distance calculated in step S51. i As an example, the control circuit 90 calculates the standard deviation of several dozen measurement results as the accuracy σ i , however, if we can find the accuracy σ i , other methods may be used. Then, the process proceeds to step S53.

[0162] (Step S53)

[0163] In step S53, the control circuit 90 determines the accuracy σ calculated in step S52.i Is it greater than the previous precision σ? i-1 Here, the precision σ i The smaller the value of is, the better the accuracy is, that is, the smaller the error between the distance measurement result and the actual distance is. i Greater than σ i-1 In the case of , that is, in the case of yes in step S53, the process proceeds to step S54. On the other hand, in step S53 i Less than σ i-1 In the case of , that is, in the case of No in step S53, δf based on the accuracy of the distance CEO The control ends. If the answer is No in step S53, δf CEO change.

[0164] (Step S54)

[0165] In step S54, the control circuit 90 controls the f of the first optical comb laser 10. CEO1 and f of the second optical comb laser 20 CEO2 At least one of them makes δf CEO For example, the control circuit 90 changes f by adjusting the output of the excitation source of the first optical comb laser 10 or the second optical comb laser 20. CEO1 and f CEO2 At least one of them, but if it is possible to change f CEO1 or CEO2 The value of δf can also be changed by other methods such as using AOM control. CEO Then the process returns to step S50 and repeats the above process.

[0166] Thus, repeatedly making δf CEO The process of changing is continued until the accuracy of the distance is no longer optimized, that is, until σ is no longer satisfied i <σ i-1 In this way, the accuracy of the distance can be substantially improved.

[0167] In addition, Fig.13 In the above example, the precision σ i The accuracy of the previous i-1 The control circuit 90 can make the accuracy σ i Compare with a predetermined threshold.

[0168] In addition, for example, each time δf CEO When the accuracy σ changes i The calculation is repeated a specified number of times, and the calculated accuracy σ i The control circuit 90 can determine the accuracy σ of the specified number of times.i The best precision σ i , and the control conditions at this time are determined as the control conditions of the first optical comb laser 10 and the second optical comb laser 20.

[0169] [Perform δf CEO Timing of control]

[0170] Next, use Fig.14 and Fig.15 Explanation of the above δf CEO The actual distance is measured when δf CEO There are two types of control: one is to perform the control as calibration before measurement, and the other is to perform the control as feedback over time.

[0171] [calibration]

[0172] Fig.14 This is a diagram showing the control of δf in the operation of the laser device 100 of this embodiment. CEO This is a flowchart as an example of the calibration process before measurement.

[0173] The laser device 100 starts operating in response to a start signal from an input mechanism (not shown).

[0174] (Step S60)

[0175] In step S60, before actually measuring the distance, the control circuit 90 controls δf CEO , so that the spectrum of the dual-comb signal converges to the respective response bands of detectors 71 and 72. The specific control method is as follows Figure 6 , Figure 8 , Fig.10 , Fig.12 , Fig.13 The processing shown in FIG. 1 is the same as that shown in FIG. 1 , so the description is omitted. Next, the process proceeds to step S61. Fig.14 In the example shown, no δf is performed afterwards. CEO Controlled processing.

[0176] (Step S61)

[0177] In step S61, the distance to the object 60 is measured based on the signals output from the detectors 71 and 72. Fig.13 It is the same as step S51 in , so the description is omitted.

[0178] (Step S62)

[0179] In step S62, it is determined whether the distance measurement is terminated. Specifically, the signal processing circuit 80 or the control circuit 90 determines whether an end signal is input from an input mechanism (not shown). If the measurement is terminated in step S62, that is, if the answer is yes in step S62, the distance measurement is terminated. On the other hand, if the measurement is continued in step S62, that is, if the answer is no in step S62, the process proceeds to step S61.

[0180] Thus, it is possible to CEO The distance to the object 60 is repeatedly measured. Therefore, for example, the surface shape of the object 60 and the moving speed of the object 60 can be measured. In addition, since δf is not controlled during actual measurement, CEO Therefore, the amount of calculation is reduced, and the distance can be measured in a short time. Therefore, even when the object 60 moves quickly, the distance to the object 60 and the moving speed can be measured with good accuracy.

[0181] [feedback]

[0182] Fig.15 is a control δf in the operation of the laser device 100 of this embodiment. CEO This is a flowchart as an example of the feedback processing during the measurement period.

[0183] like Fig.15 As shown, steps S61 and S61 are Fig.14 The processing shown is the same, so the description is omitted. Fig.15 The difference is that in the case of No in step S62, the process returns to step S62. That is, the control circuit 90 makes δf CEO Specifically, in the laser device 100, the δf of step S60 is repeatedly executed. CEO The control and distance measurement of step S61.

[0184] During the repeated distance measurement, external disturbances such as temperature changes may cause δf CEO In contrast, Fig.15 As shown, by adjusting δf over time CEO , that is, by providing feedback, it is possible to cope with the δf during the measurement period CEO The change can improve the measurement accuracy.

[0185] (Other embodiments)

[0186] The above describes one or more laser devices based on the embodiments, but the present disclosure is not limited to these embodiments. Without departing from the gist of the present disclosure, various modifications that a person skilled in the art may have thought of are implemented to the present embodiment, and the methods constructed by combining the constituent elements in different embodiments are also included in the scope of the present disclosure.

[0187] For example, in the above-described embodiment, a process executed by a specific processing unit may be executed by another processing unit. In addition, the order of a plurality of processes may be changed, or a plurality of processes may be executed in parallel.

[0188] In addition, for example, the processing described in the above embodiment can be implemented by centralized processing using a single device (system), or can be implemented by decentralized processing using multiple devices. In addition, the processor that executes the above program can be a single processor or multiple processors. That is, centralized processing can be performed, or decentralized processing can be performed.

[0189] In addition, in the above-mentioned embodiment, all or part of the constituent elements such as the signal processing circuit 80 and the control circuit 90 may be formed by dedicated hardware, or may be implemented by executing a software program suitable for each constituent element. Each constituent element may be implemented by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded on a recording medium such as a HDD (Hard Disk Drive) or a semiconductor memory.

[0190] In addition, the signal processing circuit 80 and the control circuit 90 and other components may also be composed of one or more electronic circuits. The one or more electronic circuits may be general-purpose circuits or dedicated circuits.

[0191] One or more electronic circuits may include, for example, semiconductor devices, ICs or LSIs. ICs or LSIs may be integrated into one chip or multiple chips. Here, they are referred to as ICs or LSIs, but the names may vary depending on the degree of integration, and may be referred to as system LSIs, VLSIs (Very Large Scale Integration), or ULSIs (Ultra Large Scale Integration). In addition, FPGAs programmed after LSI manufacturing can also be used for the same purpose.

[0192] In addition, the general or specific methods of the present disclosure may be implemented in a system, device, method, integrated circuit or computer program. Alternatively, it may be implemented in a computer-readable non-temporary recording medium such as an optical disk, HDD or semiconductor memory storing the computer program. In addition, it may be implemented by any combination of a system, device, method, integrated circuit, computer program and recording medium.

[0193] (other)

[0194] Modifications of the embodiments of the present disclosure may be as follows.

[0195] Fig.16 It is a diagram showing the process flow of this modification example.

[0196] The laser device of item 1 comprises:

[0197] The first optical comb laser;

[0198] a second optical comb laser;

[0199] Testing Department; and

[0200] Control circuit,

[0201] The control circuit causes the first optical comb laser to output light (1, p) during the pth period,

[0202] The control circuit causes the second optical comb laser to output light (2, p) in the pth period,

[0203] The detection unit receives light (3, p) based on the light (1, p) and the light (2, p),

[0204] The detection unit outputs p-th information corresponding to the light (3, p),

[0205] f 1，n，p =f CEO，1，p +n×f rep，1 ,

[0206] f 2，n，p =f CEO，2，p +n×f rep，2 ,

[0207] The f 1，n，p is the light frequency of the nth mode shown in the spectral characteristic (1, p) of the light (1, p),

[0208] The f 2，n，p is the light frequency of the nth mode shown in the spectral characteristic (2, p) of the light (2, p),

[0209] The f CEO，1，pis the frequency corresponding to the 0th mode shown in the spectral characteristic (1, p),

[0210] The f CEO，2，p is the frequency corresponding to the 0th mode shown in the spectral characteristic (2, p),

[0211] The f rep，1 and the f rep，2 different,

[0212] The control circuit determines f according to the spectrum characteristic (3, p) of the light (3, p) based on the p-th information. CEO，1，(p+1) and f CEO，2，(p+1) .

[0213] The light (1, p) may be the laser light output by the first optical comb laser 10 in the p-th period.

[0214] The light (2, p) may be the laser light output by the second optical comb laser 20 in the p-th period.

[0215] The light (3, p) may be light based on the light (1, p) and the light (2, p), or may be light received by the detector 32 from the coupler 32.

[0216] The pth period can be p Start and at time t (p+1) Finish.

[0217] The control circuit can make the first optical comb laser at the time t p Afterwards and at the time t (p+1) At the previous moment, the output of the light (1, p) is terminated.

[0218] The moment when the output of the light (1, p) ends may be at the moment t p Afterwards and at the time t (p+1) The moment before.

[0219] The control circuit can make the second optical comb laser at the time t p After that and at the time t (p+1) The previous moment ends the output of the light (2, p).

[0220] The time when the output of the light (2, p) ends may be at the time t p Afterwards and at the time t (p+1) The moment before.

[0221] The laser device of the second item is in the laser device of the first item,

[0222] The spectral characteristic (3, p) represents f min <δf rep ,

[0223] |f CEO，1，(p+1) -f CEO，2，(p+1) |>|f CEO，1，p -f CEO，2，p |,

[0224] The f min is the wavelength corresponding to the lowest frequency mode among the plurality of frequency modes shown in the spectral characteristic (3, p),

[0225] The δf rep It is the absolute value of the difference between two frequencies corresponding to two adjacent frequency modes in the spectral characteristic (3, p).

[0226] The laser device of the third item is the laser device of the first item,

[0227] The spectral characteristic (3, p) represents f max >(F max -δf rep ),

[0228] |f CEO，1，(p+1) -f CEO，2，(p+1) |<|f CEO，1，p -f CEO，2，p |,

[0229] The f max is the wavelength corresponding to the highest frequency mode among the plurality of frequency modes shown in the spectral characteristic (3, p),

[0230] The F max is the maximum frequency included in the frequency band that can be detected by the detection unit,

[0231] The δf rep It is the absolute value of the difference between two frequencies corresponding to two adjacent frequency modes in the spectral characteristic (3, p).

[0232] Furthermore, various changes, substitutions, additions, omissions, etc. may be made to the above-described embodiments within the scope of the claims or the scope equivalent thereto.

[0233] Industrial Applicability

[0234] The present disclosure can be used in an apparatus, system, method, or the like that performs distance measurement or displacement measurement, and can be used in, for example, a distance measuring sensor, a displacement meter, a shape inspection device, and the like.

[0235] Description of the attached figure

[0236] 10 The first optical comb laser

[0237] 10L First Comb Laser

[0238] 10Lr, 10Lt, 20Lr, 20Lt light

[0239] 10R Reflected light

[0240] 20 Second optical comb laser

[0241] 20L Second Comb Laser

[0242] 30, 31, 32, 33 Coupler

[0243] 40 Circulator

[0244] 50 Collimator

[0245] 60 Objects

[0246] 70 Detection Department

[0247] 71, 72 Detector

[0248] 80 Signal processing circuit

[0249] 90 Control circuit

[0250] 100 Laser Device

Claims

1. A laser device, wherein: have: The first optical comb laser; a second optical comb laser, wherein the repetition frequency of the second optical comb laser is different from the repetition frequency of the first optical comb laser; a detection unit configured to detect interference light formed by output light of the first optical comb laser and output light of the second optical comb laser; as well as Control circuit, The control circuit controls at least one of a first CEO frequency, which is a carrier-envelope offset frequency of the first optical comb laser, and a second CEO frequency, which is a carrier-envelope offset frequency of the second optical comb laser, based on the output of the detection unit, thereby changing a difference frequency, which is a difference between the first CEO frequency and the second CEO frequency.

2. The laser device according to claim 1, wherein: The control circuit acquires first information on the lowest frequency mode of the spectrum of the interference light based on the output of the detection unit, and increases the difference frequency using the acquired first information.

3. The laser device according to claim 1, wherein: The control circuit acquires second information on the highest frequency mode of the spectrum of the interference light based on the output of the detection unit, and reduces the difference frequency using the acquired second information.

4. The laser device according to claim 1, wherein: The control circuit acquires third information on the frequency interval of the spectrum of the interference light based on the output of the detection unit, and changes the difference frequency using the acquired third information.

5. The laser device according to any one of claims 1 to 4, wherein: The detection unit detects interference light between reflected light generated by the output light of the first optical comb laser reflected by an object and the output light of the second optical comb laser. The laser device includes a signal processing circuit that calculates the distance to the object based on the output of the detection unit.

6. The laser device according to claim 5, wherein: The control circuit changes the beat frequency based on the accuracy of the distance calculated by the signal processing circuit.

7. The laser device according to claim 5, wherein: The control circuit changes the difference frequency before calculating the distance.

8. The laser device according to claim 5, wherein: The control circuit changes the difference frequency while calculating the distance.

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