Distance measuring device, distance measuring method and radar device

Abstract

The distance measuring device (2) is constructed to include: a signal distribution unit (21) which distributes digital signals representing interference light into N digital signals, wherein the interference light is interference light between reflected light from a distance measuring object generated when a part of a frequency scanning light whose frequency changes with the passage of time is irradiated onto the distance measuring object and reference light which is the remaining part of the frequency scanning light, and N is an integer greater than 2; a frequency shift unit (22) which shifts the frequencies of the N digital signals distributed by the signal distribution unit (21) by different amounts; and a Fourier transform unit (24) which performs Fourier transformation on the frequency scanning light. The frequency shifting unit (22) performs Fourier transform on the N digital signals after the Fourier transform by the Fourier transforming unit (24); and a distance calculating unit (26) determines a frequency component related to the distance measurement object from a plurality of frequency components included in all the N signals after the Fourier transform by the Fourier transforming unit (24), determines an offset related to the Fourier transformed signal including the determined frequency component from a plurality of offsets used in the frequency shifting unit (22), and calculates the distance from the distance measuring device (2) to the distance measurement object based on the sum of the frequency of the determined frequency component and the determined offset.

Description

Technical Field

[0001] The present invention relates to a distance measuring device for calculating the distance from the distance measuring device to a distance measuring object, a distance measuring method, and a radar device having the distance measuring device. Background Art

[0002] There is a ranging device as follows (hereinafter referred to as "existing ranging device") in the ranging device: it has an FFT converter that performs Fourier transform (FFT: Fast Fourier Transform) on a digital signal representing interference light, and calculates the distance from the ranging device to a ranging object based on the signal after FFT by the FFT converter, wherein the interference light is interference light between reflected light from the ranging object generated when a part of the frequency scanning light is irradiated on the ranging object and reference light which is the remaining part of the frequency scanning light.

[0003] In addition, there is a millimeter wave radar device having a zoom FFT converter that performs zoom FFT on a digital signal (for example, see Patent Document 1). The zoom FFT converter thins out a part of the digital signal and performs FFT on the thinned digital signal.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-43139 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In the existing distance measuring device, by increasing the number of sampling points of FFT in the FFT converter, the higher the frequency resolution is, the higher the distance calculation accuracy can be. However, it is difficult to increase the number of sampling points of FFT indefinitely. Therefore, in the existing distance measuring device, there is the following problem: the desired frequency resolution cannot be obtained, and therefore, the desired distance calculation accuracy cannot be obtained sometimes.

[0009] If the zoom FFT converter disclosed in Patent Document 1 is applied to an existing distance measuring device, the frequency resolution may be improved even with the same number of sampling points. However, the zoom FFT converter thins out a portion of the digital signal, which may cause spurious signals to occur or the desired signal to be buried by noise. In the case of spurious signals or the desired signal to be buried by noise, even if the frequency resolution is improved, the distance may not be calculated, and thus the above-mentioned problem cannot be solved.

[0010] The present invention is completed to solve the above-mentioned problems, and its purpose is to obtain a distance measuring device and a distance measuring method, which can improve the calculation accuracy of the distance compared with the existing distance measuring device even if the number of sampling points is the same.

[0011] Means for solving problems

[0012] The distance measuring device of the present invention comprises: a signal distribution unit that distributes digital signals representing interference light into N signals, wherein the interference light is interference light between reflected light from the distance measuring object generated when a part of the frequency sweep light whose frequency changes with the passage of time is irradiated on the distance measuring object and reference light which is the remaining part of the frequency sweep light, and N is an integer greater than or equal to 2; a frequency shift unit that shifts the frequency of each of the N digital signals distributed by the signal distribution unit by an offset amount different from each other; a Fourier transform unit that performs Fourier transform on each of the N digital signals after the frequency shift by the frequency shift unit; and a distance calculation unit that determines a frequency component related to the distance measuring object from among a plurality of frequency components included in all the N signals after the Fourier transform by the Fourier transform unit, determines an offset amount related to the Fourier transformed signal including the determined frequency component from among a plurality of offset amounts used by the frequency shift unit in shifting the frequency, and calculates the distance from the distance measuring device to the distance measuring object based on the sum of the frequency of the determined frequency component and the determined offset amount.

[0013] Effects of the Invention

[0014] According to the present invention, even if the number of sampling points is the same, the distance calculation accuracy can be improved compared with the existing distance measuring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 1 is a diagram showing a configuration of a radar device including the distance measuring device 2 according to the first embodiment.

[0016] Figure 2 1 is a diagram showing the internal structure of the optical transmission and reception unit 1 .

[0017] Figure 3 This is an explanatory diagram showing an example of frequency swept light.

[0018] Figure 4 1 is a hardware configuration diagram showing the hardware of the distance measuring device 2 according to the first embodiment.

[0019] Figure 5 This is a hardware configuration diagram of a computer when the distance measuring device 2 is realized by software, firmware, or the like.

[0020] Figure 6 1 is a flowchart showing a distance measuring method as a processing procedure of the distance measuring device 2 according to the first embodiment.

[0021] Figure 7 is a diagram showing a signal F after Fourier transformation by the Fourier transform processing unit 25-n (n=1, ..., N). n (f) contains multiple frequency components FC n The largest frequency component FC n，max 's illustration.

[0022] Figure 8 1 is a diagram showing a configuration of a radar device including a distance measuring device 2 according to a second embodiment.

[0023] Fig. 9 1 is a hardware configuration diagram showing the hardware of the distance measuring device 2 according to the second embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, in order to explain the present invention in more detail, the mode for carrying out the present invention will be described with reference to the drawings.

[0025] Implementation Method 1

[0026] Figure 1 1 is a diagram showing a configuration of a radar device including the distance measuring device 2 according to the first embodiment.

[0027] Figure 1 The radar device shown includes an optical transmitting and receiving unit 1 and a distance measuring device 2 .

[0028] The optical transmitting and receiving unit 1 irradiates a part of the frequency swept light whose frequency changes with the passage of time onto the distance measurement object, and then receives reflected light of the frequency swept light reflected by the distance measurement object.

[0029] The optical transmitting and receiving unit 1 outputs a digital signal f(t) indicating interference light between the reflected light and the reference light which is the remaining part of the frequency swept light to the distance measuring device 2. t is a time.

[0030] Figure 2 1 is a diagram showing the internal structure of the optical transmission and reception unit 1 .

[0031] The optical transmitting and receiving unit 1 includes a frequency sweep light source 11 , a light branching unit 12 , a sensor head 15 , an optical interferometer 17 , a photodetector 18 , and an analog-to-digital converter (hereinafter referred to as “A / D converter”) 19 .

[0032] The frequency swept light source 11 outputs frequency swept light whose frequency changes with the passage of time to the light branching unit 12 .

[0033] Figure 3 This is an explanatory diagram showing an example of frequency swept light.

[0034] The frequency of the frequency sweep light changes with time, from the lowest frequency f min Change to the highest frequency fmax The frequency of the frequency scanning light reaches the highest frequency f max When the frequency is temporarily returned to the lowest frequency f min Then, again from the lowest frequency f min Change to the highest frequency f max .

[0035] The optical branching unit 12 includes an optical coupler 13 and a circulator 14 .

[0036] The optical coupler 13 branches the frequency-sweep light output from the frequency-sweep light source 11 into irradiation light and reference light.

[0037] The optical coupler 13 outputs the irradiation light to the circulator 14 , and outputs the reference light to the optical interferometer 17 .

[0038] The circulator 14 outputs the irradiation light output from the optical coupler 13 to the light focusing optical element 16 of the sensor head 15 .

[0039] The circulator 14 outputs the reflected light output from the light-collecting optical element 16 to the optical interferometer 17 .

[0040] The sensor head 15 has a light-collecting optical element 16 .

[0041] The light-collecting optical element 16 is realized by, for example, two aspherical lenses.

[0042] The focusing optical element 16 focuses the irradiation light output from the circulator 14 onto the distance measurement object.

[0043] That is, the aspheric lens at the front stage of the two aspheric lenses included in the light focusing optical element 16 converts the irradiation light output from the circulator 14 into parallel light.

[0044] The aspherical lens at the subsequent stage converges the parallel light converted by the aspherical lens at the preceding stage, and causes the light to illuminate the distance measurement object.

[0045] Furthermore, the focusing optical element 16 focuses the reflected light from the distance measurement object and outputs the reflected light to the circulator 14 .

[0046] The optical interferometer 17 generates interference light between the reflected light output from the circulator 14 and the reference light output from the optical coupler 13 , and outputs the interference light to the photodetector 18 .

[0047] The photodetector 18 detects the interference light output from the optical interferometer 17 and converts the interference light into an electric signal.

[0048] The photodetector 18 outputs an electric signal to the A / D converter 19 .

[0049] The A / D converter 19 converts the electric signal output from the photodetector 18 from an analog signal into a digital signal f(t), and outputs the digital signal f(t) to the distance measuring device 2 .

[0050] Figure 1 The distance measuring device 2 shown includes a signal distribution unit 21 , a frequency shift unit 22 , a Fourier transform unit 24 , and a distance calculation unit 26 .

[0051] Figure 4 1 is a hardware configuration diagram showing the hardware of the distance measuring device 2 according to the first embodiment.

[0052] The signal distribution unit 21 is configured to generate a signal through Figure 4 The signal distribution circuit 31 shown is implemented.

[0053] The signal distributor 21 distributes the digital signal f(t) output from the optical transmission / reception unit 1 into N signals. N is an integer greater than or equal to 2.

[0054] The signal distributor 21 outputs N digital signals f(t) to the frequency shifter 22 .

[0055] The frequency shift unit 22 is, for example, Figure 4 The frequency shifting circuit 32 shown is implemented.

[0056] The frequency shift unit 22 includes N frequency shift processing units 23 - 1 to 23 -N.

[0057] The frequency shift unit 22 shifts the frequencies of the N digital signals distributed by the signal distribution unit 21 by different amounts.

[0058] The frequency shift unit 22 converts the frequency-shifted N digital signals f(t)×exp(jω1t) to f(t)×exp(jω N t) is output to the Fourier transform unit 24.

[0059] The frequency shift processing unit 23-1 shifts the frequency of the digital signal f(t) output from the optical transmission and reception unit 1 by the offset Δf1, and outputs the frequency-shifted digital signal f(t)×exp(jω1t) to the Fourier transform processing unit 25-1 of the Fourier transform unit 24. ω1 is an angular frequency obtained by multiplying the offset Δf1 by 2π.

[0060] exist Figure 1 In the distance measuring device 2 shown, the offset Δf1=0, and the frequency shift processing unit 23-1 does not shift the frequency of the digital signal f(t). Therefore, f(t)=f(t)×exp(jω1t).

[0061] Therefore, the distance measuring device 2 may not include the frequency shift processing unit 23 - 1 , but may directly connect the optical transmission and reception unit 1 to the Fourier transform processing unit 24 - 1 .

[0062] However, the offset Δf1 = 0 is just an example, and the offset Δf1 ≠ 0 may be satisfied. If the offset Δf1 ≠ 0, the distance measuring device 2 needs to include the frequency shift processing unit 23 - 1 .

[0063] The frequency shift processing unit 23-2 shifts the frequency of the digital signal f(t) output from the optical transmission and reception unit 1 by the offset Δf2, and outputs the frequency-shifted digital signal f(t)×exp(jω2t) to the Fourier transform processing unit 25-2 of the Fourier transform unit 24. ω2 is an angular frequency obtained by multiplying the offset Δf2 by 2π.

[0064] The frequency shift processing unit 23-3 shifts the frequency of the digital signal f(t) output from the optical transmitting and receiving unit 1 by the offset Δf3, and outputs the frequency-shifted digital signal f(t)×exp(jω3t) to the Fourier transform processing unit 25-3 of the Fourier transform unit 24. ω3 is an angular frequency obtained by multiplying the offset Δf3 by 2π.

[0065] The frequency shift processing unit 23-N shifts the frequency of the digital signal f(t) output from the optical transmission and reception unit 1 by an amount Δf N , the frequency-shifted digital signal f(t)×exp(jω N t) is output to the Fourier transform processing unit 25-N of the Fourier transform unit 24. N is the offset Δf N Multiply by 2π to get the angular frequency.

[0066] In addition, Δf1<Δf2<Δf3<…<Δf N .

[0067] The Fourier transform unit 24 performs, for example, Figure 4 The Fourier transform circuit 33 shown is implemented.

[0068] The Fourier transform unit 24 includes N Fourier transform processing units 25 - 1 to 25 -N.

[0069] The Fourier transform unit 24 performs frequency transformation on the N digital signals f(t)×exp(jω) after the frequency shift by the frequency shift unit 22. n t)(n=1,…,N) are subjected to Fourier transform respectively.

[0070] The Fourier transform unit 24 transforms the N signals F1(f) to F N (f) is output to the distance calculation unit 26. f is the frequency.

[0071] The Fourier transform processing unit 25 - 1 performs Fourier transform on the digital signal f(t)×exp(jω1t) that has been frequency-shifted by the frequency shift processing unit 23 - 1 .

[0072] The Fourier transform processing unit 25 - 1 outputs the Fourier transformed signal F1 (f) to the distance calculation unit 26 .

[0073] The Fourier transform processing unit 25 - 2 performs Fourier transform on the digital signal f(t)×exp(jω2t) that has been frequency-shifted by the frequency shift processing unit 23 - 2 .

[0074] The Fourier transform processing unit 25 - 2 outputs the Fourier transformed signal F2 (f) to the distance calculation unit 26 .

[0075] The Fourier transform processing unit 25 - 3 performs Fourier transform on the digital signal f(t)×exp(jω3t) that has been frequency-shifted by the frequency shift processing unit 23 - 3 .

[0076] The Fourier transform processing unit 25 - 3 outputs the Fourier transformed signal F3 (f) to the distance calculation unit 26 .

[0077] The Fourier transform processing unit 25-N performs the frequency shift of the digital signal f(t)×exp(jω) by the frequency shift processing unit 23-N. N t) Perform Fourier transform.

[0078] The Fourier transform processing unit 25-N converts the Fourier transformed signal F N (f) Output to the distance calculation unit 26.

[0079] The distance calculation unit 26 calculates the distance by, for example, Figure 4 The distance calculation circuit 34 shown is implemented.

[0080] The distance calculation unit 26 includes a frequency component determination unit 27 , an offset determination unit 28 , and a distance calculation processing unit 29 .

[0081] The distance calculation unit 26 calculates the total number of N signals F1(f) to F1(f) after the Fourier transformation by the Fourier transformation unit 24. N Among the multiple frequency components included in (f), the frequency component FC(f) related to the distance measurement object is determined. T ).

[0082] The distance calculation unit 26 calculates the frequency shift amount Δf1 to Δf2 from the plurality of shift amounts Δf1 to Δf3 used by the frequency shift unit 22 to shift the frequency. N In the above, the frequency component FC(f T ) after Fourier transformation n (f) The associated offset Δf n .

[0083] The distance calculation unit 26 calculates the frequency component FC(f T ) frequency f T With the determined offset Δf nThe distance L from the distance measuring device 2 to the distance measuring object is calculated by summing the values.

[0084] The frequency component determination unit 27 obtains the frequency component of all the signals F1(f) to F1(f) after the Fourier transformation by the Fourier transformation processing units 25-1 to 25-N. N Among the multiple frequency components included in (f), the frequency component FC(f) related to the distance measurement object is determined. T ).

[0085] The frequency component identification unit 27 determines the frequency component FC (f T ) is output to the offset determination unit 28, and the determined frequency component FC (f T ) frequency f T Output to the distance calculation processing unit 29.

[0086] The offset determination unit 28 determines the offsets Δf1 to Δf2 used by the frequency shift processing units 23 - 1 to 23 -N for frequency shifting. N The frequency component FC(f T ) after Fourier transformation n (f) The associated offset Δf n .

[0087] The offset determination unit 28 converts the determined offset Δf into n Output to the distance calculation processing unit 29.

[0088] The distance calculation processing unit 29 calculates the frequency component FC (f T ) frequency f T The offset Δf determined by the offset determination unit 28 n sum.

[0089] The distance calculation processing unit 29 calculates the frequency component FC(f T ) frequency f T With the offset Δf n The sum of f T +Δf n , calculate the distance L from the distance measuring device 2 to the distance measuring object.

[0090] exist Figure 1 In the embodiment, it is assumed that the signal distribution unit 21, the frequency shift unit 22, the Fourier transform unit 24 and the distance calculation unit 26 as the structural elements of the distance measuring device 2 are respectively Figure 4 Specifically, it is assumed that the distance measuring device 2 is implemented by a signal distribution circuit 31, a frequency shift circuit 32, a Fourier transform circuit 33 and a distance calculation circuit 34.

[0091] The signal distribution circuit 31, the frequency shift circuit 32, the Fourier transform circuit 33 and the distance calculation circuit 34 are, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array) or a combination thereof.

[0092] The structural elements of the distance measuring device 2 are not limited to being implemented by dedicated hardware, and the distance measuring device 2 may also be implemented by software, firmware, or a combination of software and firmware.

[0093] Software or firmware is stored as a program in a computer's memory. A computer refers to hardware that executes programs, such as a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor).

[0094] Figure 5 This is a hardware configuration diagram of a computer when the distance measuring device 2 is realized by software, firmware, or the like.

[0095] When the distance measuring device 2 is implemented by software or firmware, a program for causing a computer to execute the processing of the signal distribution unit 21, the frequency shift unit 22, the Fourier transform unit 24, and the distance calculation unit 26 is stored in the memory 41. Then, the processor 42 of the computer executes the program stored in the memory 41.

[0096] In addition, Figure 4 In FIG. 1 , an example is shown in which the components of the distance measuring device 2 are respectively implemented by dedicated hardware. Figure 5 , an example is shown in which the distance measuring device 2 is implemented by software or firmware. However, this is just an example, and some components of the distance measuring device 2 may be implemented by dedicated hardware, and the remaining components may be implemented by software or firmware.

[0097] Next, Figure 1 The operation of the radar device shown will be described.

[0098] First, if Figure 3 As shown, the frequency swept light source 11 of the optical transmitting and receiving unit 1 outputs frequency swept light whose frequency changes with the passage of time to the optical coupler 13 of the optical branching unit 12 .

[0099] When receiving the frequency-sweep light from the frequency-sweep light source 11 , the optical coupler 13 branches the frequency-sweep light into the irradiation light and the reference light.

[0100] The optical coupler 13 outputs the irradiation light to the circulator 14 , and outputs the reference light to the optical interferometer 17 .

[0101] When receiving the irradiation light from the optical coupler 13 , the circulator 14 outputs the irradiation light to the light focusing optical element 16 of the sensor head 15 .

[0102] When receiving the irradiation light from the circulator 14 , the condensing optical element 16 condenses the irradiation light onto the distance measurement object.

[0103] Furthermore, the focusing optical element 16 focuses the reflected light from the distance measurement object and outputs the reflected light to the circulator 14 .

[0104] When receiving the reflected light from the light-collecting optical element 16 , the circulator 14 outputs the reflected light to the optical interferometer 17 .

[0105] The optical interferometer 17 generates interference light between the reflected light output from the circulator 14 and the reference light output from the optical coupler 13 .

[0106] The optical interferometer 17 outputs interference light to the photodetector 18 .

[0107] The photodetector 18 detects the interference light output from the optical interferometer 17 and converts the interference light into an electric signal.

[0108] The photodetector 18 outputs an electric signal to the A / D converter 19 .

[0109] When receiving the electric signal from the photodetector 18 , the A / D converter 19 converts the electric signal from an analog signal into a digital signal f(t).

[0110] The A / D converter 19 outputs the digital signal f(t) to the distance measuring device 2 .

[0111] The distance measuring device 2 calculates the distance L from the distance measuring device 2 to the distance measuring object based on the digital signal f(t) output from the optical transmitting and receiving unit 1 .

[0112] Figure 6 1 is a flowchart showing a distance measuring method as a processing procedure of the distance measuring device 2 according to the first embodiment.

[0113] The operation of the distance measuring device 2 will be described in detail below.

[0114] When receiving the digital signal f(t) from the optical transmission and reception unit 1, the signal distribution unit 21 distributes the digital signal f(t) into N ( Figure 6 Step ST1).

[0115] The signal distributor 21 outputs N digital signals f(t) to the frequency shifter 22 .

[0116] The frequency shift unit 22 shifts the frequencies of the N digital signals f(t) distributed by the signal distribution unit 21 by different offset amounts ( Figure 6 Step ST2).

[0117] That is, when the frequency shift processing unit 23-n (n=1, ..., N) of the frequency shift unit 22 receives the digital signal f(t) from the optical transmission and reception unit 1, it shifts the frequency of the digital signal f(t) by the shift amount Δf n Δf1<Δf2<Δf3<…<Δf N .

[0118] The frequency shift processing unit 23-n performs frequency shift on the digital signal f(t)×exp(jω n t) is output to the Fourier transform processing unit 25-n of the Fourier transform unit 24.

[0119] Multiple offsets Δf1~Δf N The frequency shift processing unit 23 - n may be stored in an internal memory, or provided from outside the distance measuring device 2 .

[0120] exist Figure 1 In the distance measuring device 2 shown, for example, the offset Δf1 = 0, and the frequency shift processing unit 23-1 does not shift the frequency of the digital signal f(t). Therefore, f(t) = f(t) × exp(jω1t).

[0121] Δf1, Δf2, Δf3,…, Δf N For example, it is shown in the following formula (1).

[0122]

[0123] In the formula (1), R is the signal F after Fourier transformation by the Fourier transform processing unit 25-n. n (f) Frequency resolution.

[0124] f 1，max is the maximum frequency component FC among the plurality of frequency components FC1 included in the signal F1(f) after the Fourier transform by the Fourier transform processing unit 25-1. 1，max frequency.

[0125] As shown in formula (1), the offset Δf1~Δf N The frequency resolution is based on the Fourier transformed signal F n (f) is set by the frequency resolution R. That is, the offset Δf1 to Δf NThe frequency resolution is set according to the ranging resolution of the object being measured.

[0126] ω n is the offset Δf n Multiply by 2π to get the angular frequency.

[0127] Angular frequency ω n It is necessary to be smaller than the ratio of the sampling rate of the digital signal f(t) to the number of sampling points of FFT in the Fourier transform processing unit 25 - n .

[0128] For example, when the sampling rate is 1 [GSa / s], the number of FFT sampling points is 4096, and N = 64, the Fourier transform processing unit 25-n can calculate the peak frequency described later according to the frequency resolution R of 244.1 [kHz]. 244.1 [kHz] = 1 [GSa / s] / 4096. Therefore, if the angular frequency is ω n =(244.1 / 64)×2π=3.8[kHz]×2π, the Fourier transform processing unit 25-n can calculate the peak frequency with the same frequency resolution as the Fourier transform processing unit whose FFT sampling point number is 262144.

[0129] In addition, if the number of FFT sampling points is 262144, the frequency resolution R is 3.8 [kHz] = 1 [GSa / s] / 262144.

[0130] On the other hand, if the number of FFT sampling points is 4096, the frequency resolution R is 244.1 [kHz] = 1 [GSa / s] / 4096.

[0131] For example, when the number of sampling points of FFT is 4096, the frequency shift unit 22 shifts the frequency of the digital signal by 3.8 [kHz] at different frequency offsets. Then, if the Fourier transform unit 24 described later performs FFT on each of the frequency-shifted digital signals, the amplitude value of the frequency component is obtained according to the frequency resolution R of 244.1 [kHz]. The amplitude value of the frequency component tends to become larger as it is more related to the distance from the distance measuring device 2 to the distance measuring object.

[0132] Therefore, if the distance calculation unit 26 described later obtains the amplitude value of the frequency component, such as the frequency offset and the peak frequency when it is maximum, from the results of all FFTs, it can obtain the distance from the ranging device 2 to the ranging object according to the same frequency resolution R as when the number of FFT sampling points is 262144.

[0133] The Fourier transform unit 24 performs frequency shifting on the N digital signals f(t)×exp(jω1t) to f(t)×exp(jω1t) after the frequency shifting by the frequency shift unit 22. Nt) respectively perform Fourier transform ( Figure 6 Step ST3).

[0134] That is, the Fourier transform processing unit 25-n (n=1, ..., N) of the Fourier transform unit 24 performs frequency shifting on the digital signal f(t)×exp(jω) performed by the frequency shift processing unit 23-1. n t) Perform Fourier transform.

[0135] The Fourier transform processing unit 25-n converts the Fourier transformed signal F n (f) Output to the distance calculation unit 26.

[0136] The frequency component identification unit 27 of the distance calculation unit 26 obtains the Fourier transformed signals F1(f) to F1(f) from the Fourier transform processing units 25-1 to 25-N. N (f).

[0137] The frequency component determination unit 27 performs Fourier transformation on all the signals F1(f) to F1(f) after the Fourier transformation by the Fourier transformation processing units 25-1 to 25-N. N The multiple frequency components included in (f) are compared with each other, and the largest frequency component FC is extracted from the multiple frequency components. n，max ( Figure 6 Step ST4).

[0138] Figure 7 is a diagram showing a signal F after Fourier transformation by the Fourier transform processing unit 25-n (n=1, ..., N). n (f) contains multiple frequency components FC n The maximum frequency component FC in n，max 's illustration.

[0139] FC 1，max It is the maximum frequency component among the multiple frequency components FC1 included in the Fourier transformed signal F1(f).

[0140] FC 2，max It is the maximum frequency component among the multiple frequency components FC2 included in the signal F2(f) after Fourier transformation.

[0141] FC N，max is the Fourier transformed signal F N (f) contains multiple frequency components FC N The maximum frequency component in .

[0142] exist Figure 7 The following example is shown: At the maximum frequency component FC 1，max ~FC N，max In the example, the offset Δf n The signal F is 50[kHz]n The maximum frequency component FC of (f) n，max That is, the following example is shown: at the maximum frequency component FC 1，max ~FC N，max The maximum frequency component FC of the Fourier transformed signal F4(f) is 4，max maximum.

[0143] exist Figure 7 In the example, the maximum frequency component FC of the signal F4(f) with an offset Δf4 of 50 [kHz] is 4，max The frequency is the peak frequency f T It is about 40.45[MHz].

[0144] The frequency component determination unit 27 extracts the maximum frequency component FC n，max As the frequency component FC(f T ) is output to the offset determination unit 28.

[0145] In addition, the frequency component determination unit 27 sets the maximum frequency component FC n，max The peak frequency f T Output to the distance calculation processing unit 29.

[0146] exist Figure 1 In the radar device shown in FIG. 1 , the frequency component determination unit 27 extracts the maximum frequency component FC from a plurality of frequency components. n，max As the frequency component FC(f T However, the frequency component FC (f T ) is not limited to the maximum frequency component FC n，max If there is no problem in practice, the frequency component determination unit 27 may also extract, for example, the second largest frequency component from the plurality of frequency components as the frequency component FC (f T ).

[0147] The offset determination unit 28 obtains the frequency component FC (f T ).

[0148] The offset determination unit 28 determines the offsets Δf1 to Δf2 used by the frequency shift processing units 23 - 1 to 23 -N for frequency shifting. N In the above equation, determine the frequency component FC(f T ) after Fourier transformation n (f) The associated offset Δf n ( Figure 6 Step ST5).

[0149] Multiple offsets Δf1~Δf N The information may be stored in the internal memory of the offset determination unit 28 or provided from outside the distance measuring device 2 .

[0150] The offset determination unit 28 converts the determined offset Δf into n Output to the distance calculation processing unit 29.

[0151] The distance calculation processing unit 29 obtains the maximum frequency component FC from the frequency component identification unit 27. n，max The peak frequency f T , obtain the offset Δf from the offset determination unit 28 n .

[0152] As shown in the following formula (2), the distance calculation processing unit 29 calculates the peak frequency f T With the offset Δf n The sum Σf( Figure 6 Step ST6).

[0153] Σf=f T +Δf n (2)

[0154] As shown in the following formula (3), the distance calculation processing unit 29 calculates the peak frequency f T With the offset Δf n The sum Σf is used to calculate the distance L from the distance measuring device 2 to the distance measuring object ( Figure 6 Step ST7).

[0155] L=Σf×k (3)

[0156] In the formula (3), k is a coefficient related to the light sensing condition in the optical transmitting and receiving unit 1. The coefficient k may be stored in the internal memory of the distance calculation processing unit 29, or may be provided from outside the distance measuring device 2.

[0157] The distance calculation processing unit 29 outputs the calculated distance L to the outside.

[0158] In the above-mentioned first embodiment, the distance measuring device 2 is configured as follows: it has: a signal distribution unit 21 that distributes digital signals representing interference light into N signals, wherein the interference light is interference light between reflected light from the distance measuring object generated when a part of the frequency scanning light whose frequency changes with the passage of time is irradiated on the distance measuring object and reference light which is the remaining part of the frequency scanning light, and N is an integer greater than 2; a frequency shift unit 22 that shifts the frequencies of the N digital signals distributed by the signal distribution unit 21 by different offset amounts; and a Fourier transform unit 22. 4, which performs Fourier transform on the N digital signals after the frequency shift by the frequency shift unit 22 respectively; and a distance calculation unit 26, which determines the frequency component related to the distance measurement object from the multiple frequency components contained in all the N signals after the Fourier transform by the Fourier transform unit 24, determines the offset related to the Fourier transformed signal containing the determined frequency component from the multiple offsets used by the frequency shift unit 22 in the frequency shift, and calculates the distance from the distance measurement device 2 to the distance measurement object based on the sum of the frequency of the determined frequency component and the determined offset. Therefore, even if the number of sampling points is the same, the distance measurement device 2 can improve the calculation accuracy of the distance compared with the conventional distance measurement device.

[0159] Implementation Method 2

[0160] In the second embodiment, a distance measuring device 2 including a calculator 51 instead of the signal distribution unit 21 , the frequency shift unit 22 , and the Fourier transform unit 24 is described.

[0161] Figure 8 1 is a diagram showing a configuration of a radar device including a distance measuring device 2 according to a second embodiment.

[0162] Figure 8 The radar device shown includes an optical transmitting and receiving unit 1 and a distance measuring device 2 .

[0163] The distance measuring device 2 includes a calculator 51 , a data storage unit 52 , and a distance calculation unit 26 .

[0164] Fig. 9 1 is a hardware configuration diagram showing the hardware of the distance measuring device 2 according to the second embodiment.

[0165] The calculator 51 is for example Fig. 9 The calculation circuit 61 shown is implemented.

[0166] The calculator 51 obtains a digital signal f(t) representing the interference light from the optical transmitting and receiving unit 1 .

[0167] The calculator 51 shifts the frequency of the digital signal f(t) N times by different shift amounts Δf n (n=1,…,N).

[0168] The calculator 51 calculates the frequency-shifted digital signals f(t)×exp(jω n t) Perform Fourier transform.

[0169] The calculator 51 converts the Fourier transformed signal F n (f) Output to the data storage unit 52.

[0170] exist Figure 8 In the radar device shown, the processing of the calculator 51 is described. That is, as the frequency shift processing in the calculator 51, "frequency shift" is described, and as the Fourier transform processing in the calculator 51, "FFT" is described.

[0171] The data storage unit 52 is configured to store data of the same type as the data stored in the storage unit 52. Fig. 9 The data accumulation circuit 62 shown is implemented.

[0172] The data storage unit 52 stores the Fourier transformed signals F1(f) to F1(f) output from the calculator 51. N (f).

[0173] exist Figure 8 In the embodiment, it is assumed that the calculator 51, the data storage unit 52 and the distance calculation unit 26 as the components of the distance measuring device 2 are respectively Fig. 9 Specifically, it is assumed that the distance measuring device 2 is implemented by the calculation circuit 61 , the data storage circuit 62 , and the distance calculation circuit 34 .

[0174] Here, the data storage circuit 62 is, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), a magnetic disk, a floppy disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc).

[0175] The calculation circuit 61 and the distance calculation circuit 34 are, for example, a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0176] The components of the distance measuring device 2 are not limited to being implemented by dedicated hardware, and the distance measuring device 2 may be implemented by software, firmware, or a combination of software and firmware.

[0177] When the distance measuring device 2 is implemented by software or firmware, the data storage unit 52 is configured in Figure 5 In addition, a program for causing the computer to execute the processing of the calculator 51 and the distance calculation unit 26 is stored in the memory 41. Figure 5 The illustrated processor 42 executes programs stored in the memory 41 .

[0178] In addition, Fig. 9 In FIG. 1 , an example is shown in which the components of the distance measuring device 2 are respectively implemented by dedicated hardware. Figure 5 , an example is shown in which the distance measuring device 2 is implemented by software or firmware. However, this is just an example, and some components of the distance measuring device 2 may be implemented by dedicated hardware, and the remaining components may be implemented by software or firmware.

[0179] Next, Figure 8 The operation of the radar device shown will be described.

[0180] The calculator 51 and the data storage unit 52 are Figure 1 The radar devices shown are the same, and therefore only the operations of the calculator 51 and the data storage unit 52 will be described here.

[0181] The calculator 51 obtains a digital signal f(t) representing the interference light from the optical transmitting and receiving unit 1 .

[0182] The calculator 51 shifts the frequency of the digital signal f(t) N times by different shift amounts Δf n (n=1,…,N).

[0183] That is, the calculator 51 performs the frequency shift processing N times in series to shift the frequency of the digital signal f(t) by different shift amounts Δf n (n=1,…,N).

[0184] exist Figure 1 In the radar device shown in the figure, N frequency shift processing units 23-1 to 23-N perform frequency shift processing in parallel, so that the frequencies of the N digital signals f(t) are shifted by different shift amounts Δf1 to Δf N .

[0185] The frequency-shifted digital signal f(t)×exp(jω1t) to f(t)×exp(jω1t) obtained by the calculator 51 is N t) and the frequency-shifted digital signals f(t)×exp(jω1t) to f(t)×exp(jω1t) obtained by the frequency shift processing units 23-1 to 23-N. N t) are the same.

[0186] The calculator 51 calculates the frequency-shifted digital signals f(t)×exp(jω n t) Perform Fourier transform.

[0187] That is, the calculator 51 performs Fourier transform processing N times in series to obtain the frequency-shifted digital signals f(t)×exp(jω n t)(n=1,…,N) to perform Fourier transform.

[0188] exist Figure 1 In the radar device shown in the figure, the N Fourier transform processing units 25-1 to 25-N perform Fourier transform processing in parallel to obtain N frequency-shifted digital signals f(t)×exp(jω n t)(n=1,…,N) to perform Fourier transform.

[0189] The Fourier transformed signals F1(f) to F1(f) obtained by the calculator 51 are N (f) and the Fourier transformed signals F1(f) to F2(f) obtained by the Fourier transform processing units 25-1 to 25-N. N (f) Same.

[0190] The calculator 51 converts the Fourier transformed signals F1(f) to F N (f) Output to the data storage unit 52.

[0191] The data storage unit 52 stores the Fourier transformed signals F1(f) to F1(f) output from the calculator 51. N (f).

[0192] The distance calculation unit 26 obtains the N signals F1(f) to F1(f) after Fourier transformation from the data storage unit 52. N (f).

[0193] The distance calculation unit 26 calculates the distance of the N signals F1(f) to F1(f) after Fourier transformation using the method described in the first embodiment. N (f) Calculate the distance L from the distance measuring device 2 to the distance measuring object.

[0194] exist Figure 8 In the radar device shown in FIG. 1 , the calculator 51 performs the frequency shift processing N times in series and performs the Fourier transform processing N times in series. However, this is only an example. Figure 1 The signal distribution unit 21 shown in FIG. Figure 1 The frequency shift unit 22 shown in FIG. 1 performs frequency shift processing in parallel with the frequency shift unit 22 shown in FIG. Figure 1 The Fourier transform unit 24 shown in the figure also performs Fourier transform processing in parallel.

[0195] In addition, the present invention can freely combine the various embodiments, modify arbitrary components of the various embodiments, or omit arbitrary components in the various embodiments.

[0196] Industrial Applicability

[0197] The present invention is suitable for a distance measuring device and a distance measuring method for measuring the distance of a distance measuring object.

[0198] The present invention is suitable for a radar device having a distance measuring device.

[0199] Description of symbols

[0200] 1: optical transmitting and receiving unit; 2: distance measuring device; 11: frequency scanning light source; 12: optical branching unit; 13: optical coupler; 14: circulator; 15: sensor head; 16: focusing optical element; 17: optical interferometer; 18: optical detector; 19: A / D converter; 21: signal distribution unit; 22: frequency shift unit; 23-1 to 23-N: frequency shift processing unit; 24: Fourier transform unit; 25-1 to 25-N: Fourier transform processing unit; 26: distance calculation unit; 31: signal distribution circuit; 32: frequency shift circuit; 33: Fourier transform circuit; 34: distance calculation circuit; 41: memory; 42: processor; 51: calculator; 52: data storage unit; 61: calculation circuit; 62: data storage circuit.

Claims

1. A distance measuring device, wherein: The distance measuring device has: a signal distribution unit that distributes a digital signal representing interference light into N signals, wherein the interference light is interference light between reflected light from the distance measurement object generated when a part of the frequency scanning light whose frequency changes with the passage of time is irradiated onto the distance measurement object and reference light which is the remaining part of the frequency scanning light, and N is an integer greater than or equal to 2; a frequency shifting unit for shifting the frequencies of the N digital signals distributed by the signal distribution unit by different amounts; a Fourier transform unit for performing Fourier transform on each of the N digital signals frequency-shifted by the frequency shift unit; and a distance calculation unit that determines a frequency component related to the distance measurement object from a plurality of frequency components included in all N signals after Fourier transform by the Fourier transform unit, determines an offset related to the Fourier transformed signal including the determined frequency component from a plurality of offsets used by the frequency shift unit in shifting the frequency, and calculates the distance from the distance measurement device to the distance measurement object based on the sum of the frequency of the determined frequency component and the determined offset.

2. The distance measuring device according to claim 1, characterized in that: The frequency shift unit includes N frequency shift processing units, each of which shifts the frequency of the N digital signals distributed by the signal distribution unit. Each of the N frequency shift processing units shifts the frequency of a digital signal different from that of the other frequency shift processing units by an offset amount different from that of the other frequency shift processing units.

3. The distance measuring device according to claim 2, characterized in that: The Fourier transform unit includes N Fourier transform processing units, and the N Fourier transform processing units respectively perform Fourier transform on the N digital signals frequency-shifted by the N frequency shift processing units.

4. The distance measuring device according to claim 3, characterized in that: The distance calculation unit has: a frequency component determination unit that determines a frequency component related to the distance measurement object from a plurality of frequency components included in all signals after the Fourier transform by the N Fourier transform processing units; an offset determination unit that determines an offset associated with the Fourier-transformed signal including the frequency component determined by the frequency component determination unit from among a plurality of offsets used by the frequency shift unit to shift the frequency; as well as A distance calculation processing unit calculates the distance from the distance measuring device to the distance measuring object based on the sum of the frequency of the frequency component determined by the frequency component determination unit and the offset determined by the offset determination unit.

5. The distance measuring device according to claim 1, characterized in that: The distance measuring device includes a calculator instead of the signal distribution unit, the frequency shift unit and the Fourier transform unit. The calculator shifts the frequency of the digital signal representing the interference light by N times of different shift amounts, and performs Fourier transform on each of the frequency-shifted digital signals.

6. A distance measurement method, wherein: The signal distribution unit distributes the digital signals representing the interference light into N signals, wherein the interference light is interference light between the reflected light from the distance measurement object generated when a part of the frequency scanning light whose frequency changes with the passage of time is irradiated onto the distance measurement object and the reference light which is the remaining part of the frequency scanning light, and N is an integer greater than or equal to 2. The frequency shifting unit shifts the frequencies of the N digital signals distributed by the signal distribution unit by different amounts. The Fourier transform unit performs Fourier transform on each of the N digital signals after the frequency shift by the frequency shift unit. The distance calculation unit determines a frequency component related to the distance measurement object from a plurality of frequency components included in all N signals after Fourier transform by the Fourier transform unit, determines an offset related to the Fourier transformed signal including the determined frequency component from a plurality of offsets used by the frequency shift unit in shifting the frequency, and calculates the distance from the distance measuring device to the distance measurement object based on the sum of the frequency of the determined frequency component and the determined offset.

7. A radar device, characterized in that: The radar device has: The distance measuring device according to any one of claims 1 to 5; and An optical transmitting and receiving unit receives reflected light of the frequency scanning light reflected by the distance measuring object after irradiating a part of the frequency scanning light whose frequency changes with the passage of time onto the distance measuring object, and outputs a digital signal representing interference light between the reflected light and reference light which is the remaining part of the frequency scanning light to the distance measuring device.

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