Signal processing device, signal processing method, and laser radar device

Abstract

The signal processing device (15) is configured to calculate a relative velocity of each of a plurality of observation objects existing in a space with respect to the laser radar device as a moving speed of each observation object. A plurality of pulsed lights having mutually different optical frequencies are generated from a light source (1), each pulsed light is radiated to the space, each pulsed light scattered by each observation object is received as scattered light, and each scattered light and laser light are combined to generate a beat light. The signal processing device (15) includes a Doppler frequency calculation section (16) configured to calculate a Doppler frequency associated with movement of each observation object included in an optical frequency of each scattered light based on the optical frequencies of the generated plurality of pulsed lights and a detection signal of each beat light, and a speed calculation section (17) configured to calculate a relative velocity of each observation object based on each Doppler frequency calculated by the Doppler frequency calculation section (16).

Description

Technical Field

[0001] This disclosure relates to signal processing apparatus, signal processing method, and lidar device. Background Technology

[0002] Among lidar devices, there is a lidar device that calculates the individual moving speeds of multiple observed objects (hereinafter referred to as "conventional lidar devices").

[0003] Conventional lidar devices include a laser source, a pulse beam generator that generates pulsed light from the laser, a transceiver that repeatedly radiates the pulsed light into space and receives the scattered pulsed light as scattered light from various observed objects, and an optical combiner that detects the combined light of the scattered light and the laser. Furthermore, conventional lidar devices include a signal processing unit that calculates the Doppler frequency associated with the movement of each observed object based on the optical frequency of the combined light detected by the optical combiner, and calculates the movement speed of each observed object based on the Doppler frequency. The movement speed calculated by the signal processing unit is the movement speed in the direction of laser radiation.

[0004] Furthermore, Patent Document 1 discloses a ranging device that calculates the distance from the ranging device to the observed object based on the time from the time after the radiation pulse light to the time before receiving the pulse light scattered by the observed object, i.e., the scattered light.

[0005] This ranging device includes a generating unit that generates multiple pulses of light, a transmitting unit that radiates each pulse of light generated by the generating unit into space, and a receiving unit that receives each pulse of light scattered by the observed object as scattered light. Furthermore, the ranging device includes a distance calculation unit that calculates the distance to the observed object based on the time from when the transmitting unit radiates the pulse of light to when the receiving unit receives the scattered light. When the distance to the observed object is long, or when the radiation period of the pulse of light is short, the transmitting unit may radiate a pulse of light in the (N+1)th order after radiating the Nth pulse of light (N being an integer greater than or equal to 1) and before the receiving unit receives the scattered light corresponding to the Nth pulse of light. To ensure that even in such cases, the receiving unit knows which pulse of light the scattered light corresponds to, the generating unit generates multiple pulses of light with different frequencies and outputs each pulse of light to the transmitting unit.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2020-079776 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] The moving speed of a distant observation object (hereinafter referred to as "distant observation object") existing in the lidar device is sometimes the same as the moving speed of an observation object existing near the lidar device (hereinafter referred to as "nearby observation object"). When the moving speed of the distant observation object and the moving speed of the nearby observation object are the same, the scattered light from the distant observation object (hereinafter referred to as "distant scattered light") and the scattered light from the nearby observation object (hereinafter referred to as "nearby scattered light") sometimes arrive at the lidar device in a state of overlap.

[0011] In conventional lidar devices, when the transceiver unit receives overlapping distant and nearby scattered light, the signal processing unit cannot distinguish between them because the light frequencies of the distant and nearby scattered light are the same. Therefore, a problem exists: even if the signal processing unit can detect the presence of either a nearby or distant object and calculate its movement speed, it cannot detect the presence of the other object.

[0012] The ranging device disclosed in Patent Document 1 includes a generating unit that generates multiple pulses of light with different frequencies. However, the distance calculation unit of this ranging device cannot distinguish between distant and nearby scattered light when they overlap. Therefore, even if this ranging device is applied to a conventional lidar device, the above-mentioned problem cannot be solved.

[0013] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a signal processing apparatus and signal processing method that can calculate the movement speed of each observed object even when the distant scattered light and the nearby scattered light overlap, regardless of whether the movement speed of the distant observed object and the movement speed of the nearby observed object are the same.

[0014] means for solving problems

[0015] The signal processing apparatus disclosed herein calculates the relative velocities of multiple observed objects in space relative to a lidar device as the moving speeds of each observed object. It generates multiple pulses of light with different frequencies from a laser emitted from a light source, radiates these pulses into space, receives the scattered pulses from each observed object as scattered light, and detects the combined light of the scattered light and the laser. The signal processing apparatus includes: a Doppler frequency calculation unit that calculates the Doppler frequencies associated with the movement of each observed object; and a velocity calculation unit that calculates the relative velocities of each observed object based on the Doppler frequencies calculated by the Doppler frequency calculation unit. The Doppler frequency calculation unit includes: an optical frequency correction unit that corrects the optical frequencies of each combined light based on the frequency difference between the optical frequencies of one of the generated pulses and the optical frequencies of the remaining pulses; and a frequency calculation processing unit that calculates the Doppler frequencies contained in the optical frequencies of each scattered light based on the optical frequencies of the combined light corrected by the optical frequency correction unit and the optical frequencies of the generated pulses.

[0016] The effects of the invention

[0017] According to this disclosure, even when distant scattered light and nearby scattered light overlap, the movement speed of each observed object can be calculated regardless of whether the movement speed of the distant observed object and the movement speed of the nearby observed object are the same. Attached Figure Description

[0018] Figure 1 This is a structural diagram showing a lidar device including the signal processing apparatus 15 of Embodiment 1.

[0019] Figure 2 This is a structural diagram showing the internal structure of the trigger generation unit 4.

[0020] Figure 3 This is a structural diagram showing the signal processing device 15 of Embodiment 1.

[0021] Figure 4 This is a hardware structure diagram showing the hardware of the signal processing device 15 according to Embodiment 1.

[0022] Figure 5 This is a hardware structure diagram of a computer when the signal processing device 15 is implemented by software or firmware.

[0023] Figure 6 It is shown Figure 1 The flowchart shows the processing steps of the lidar device.

[0024] Figure 7This is a flowchart illustrating a signal processing method as a processing step of the signal processing apparatus 15.

[0025] Figure 8 This is an explanatory diagram showing the pulsed light P1 radiated from the lidar device, the scattered light R1 from the first observed object, and the scattered light R2 from the second observed object.

[0026] Figure 9 This is an explanatory diagram showing the radiation times T1 and T2 of pulsed light P1 and P2 radiated from the lidar device, the reception times T1' and T3' of scattered light R1 and R3 from the first observed object, and the reception times T2' and T4' of scattered light R2 and R4 from the second observed object.

[0027] Figure 10A This is an explanatory diagram showing the peak spectrum of the distance bin signal (7). Figure 10B This is an explanatory diagram showing the peak spectrum of the distance chamber signal (7) when the optical frequency of pulse light P1 is the same as that of pulse light P2.

[0028] Figure 11 This is an explanatory diagram showing the range chamber containing scattered light R1 associated with the combined beam C1, the range chamber containing scattered light R2 and R3 associated with the combined beams C2 and C3, and the range chamber containing scattered light R4 associated with the combined beam C4.

[0029] Figure 12 This is an explanatory diagram of the distance characteristics (a-scope) showing the correspondence between the distance to the distance bin (n) and the SNR.

[0030] Figure 13 This is a structural diagram showing the pulse modulator 5 of the lidar device according to Embodiment 2.

[0031] Figure 14 This is a structural diagram showing the lidar device of Embodiment 3.

[0032] Figure 15 This is a structural diagram showing a lidar device including the signal processing apparatus 15 of embodiment 4.

[0033] Figure 16 This is a structural diagram showing the signal processing device 15 of Embodiment 4.

[0034] Figure 17 This is a hardware structure diagram showing the hardware of the signal processing device 15 in Embodiment 4.

[0035] Figure 18 This is an explanatory diagram showing the absorption band of the gas, the wavelength of the first laser emitted from the light source 71, and the wavelength of the second laser emitted from the light source 71. Detailed Implementation

[0036] The following description, in order to illustrate the present disclosure in more detail, describes the manner in which the present disclosure is carried out with reference to the accompanying drawings.

[0037] Implementation method 1.

[0038] Figure 1 This is a structural diagram showing a lidar device including the signal processing apparatus 15 of Embodiment 1.

[0039] Figure 1 The lidar device shown includes a light source 1, a pulse modulation unit 2, a transceiver unit 6, an optical detector 11, and a signal processing unit 15.

[0040] A lidar device calculates the relative velocity of multiple objects in space with respect to the lidar device, which is taken as the velocity of each object. The objects can be solids, liquids, or gases.

[0041] exist Figure 1 In the lidar device shown, for the sake of simplicity, it is assumed that there are two observation objects: one is the first observation object, and the other is the second observation object. However, this is just one example, and the number of observation objects can also be three or more.

[0042] Light source 1 is, for example, a laser that emits a single frequency of light, and is realized by a semiconductor laser, fiber laser, or solid-state laser with a linewidth of less than a few MHz. Alternatively, light source 1 is realized by a combination of one or more lasers selected from semiconductor lasers, fiber lasers, and solid-state lasers.

[0043] Light source 1 outputs laser light as continuous light to pulse modulation unit 2. The laser light output from light source 1 has an optical frequency of f0.

[0044] The pulse modulation unit 2 includes an optical splitting unit 3, a trigger generation unit 4, and a pulse modulator 5.

[0045] The pulse modulation unit 2 generates multiple pulses of light with different frequencies based on the laser light output from the light source 1.

[0046] If the multiple pulses generated by the pulse modulation unit 2 are, for example, two pulses P1 and P2, then the optical frequency of pulse P1 is f0 + f IF1 The optical frequency of the pulsed light P2 is f0 + f IF2 For example, f IF2 >f IF1 f IF2 with f IF1 The frequency difference Δf (=f) between them IF2 -fIF1 The frequency difference Δf is greater than twice the absolute value of the Doppler frequency if the first and second observed objects move at the assumed maximum speeds. If the frequency difference Δf is greater than twice the absolute value of the Doppler frequency, then as long as the moving speeds of the first and second observed objects are within the assumed range, the multiple scattered light rays described later will have different optical frequencies.

[0047] If the pulse light generated by the pulse modulation unit 2 is M (M is an integer of 3 or more) pulse light P1, P2, ..., P3... M Then the pulse light P m The optical frequency of (m=1, 2, ..., M) is f0+f IFm For example, f IFM >f IF(M-1) >···>f IF1 .

[0048] exist Figure 1 In the lidar device shown, for the sake of simplicity, the pulse modulation unit 2 is assumed to generate two pulse beams P1 and P2.

[0049] The optical splitter 3 is implemented, for example, by a beam splitter, a fiber optic coupler, or a half-reflector.

[0050] The light splitting section 3 divides the laser emitted from the light source 1 into two parts at a predetermined ratio. For example, the predetermined ratio is 2 on the pulse modulator 5 side and 1 on the light combining section 12 (described later).

[0051] The optical splitter 3 outputs the laser from one of the split beams to the pulse modulator 5, and outputs the laser from the other split beam as a reference beam to the optical combiner 12.

[0052] The trigger generation unit 4 is implemented, for example, by a pulse generator, a function generator, or an FPGA (Field-Programmable Gate Array).

[0053] like Figure 2 As shown, the trigger generation unit 4 includes a pulse signal generation unit 4a, a reference signal generation unit 4b, a first frequency shift signal generation unit 4c, a second frequency shift signal generation unit 4d, and a switch 4e.

[0054] The trigger generation unit 4 outputs the pulse signal to the pulse modulator 5, the analog-to-digital converter (hereinafter referred to as "A / D conversion unit") 14 (described later), and the signal processing device 15, respectively.

[0055] In addition, the trigger generation unit 4 will indicate the modulation frequency f IF1 The first frequency shift signal and the modulation frequency f IF2The second frequency shift signal is output to the pulse modulator 5 and the signal processing device 15 respectively.

[0056] Figure 2 This is a structural diagram showing the internal structure of the trigger generation unit 4.

[0057] The pulse signal generation unit 4a generates a pulse signal with a pulse width ΔT.

[0058] The pulse signal generation unit 4a repeatedly outputs pulse signals with a pulse width ΔT to the pulse modulator 5, the A / D converter 14 and the signal processing device 15 at a period of Treep.

[0059] The reference signal generation unit 4b generates a reference signal as an electrical signal with frequency f.

[0060] The reference signal generation unit 4b outputs the reference signal to the first frequency shift signal generation unit 4c and the second frequency shift signal generation unit 4d, respectively.

[0061] The first frequency shift signal generation unit 4c acquires the reference signal output from the reference signal generation unit 4b, and generates a frequency f based on the reference signal. IF1 The first frequency shift signal.

[0062] The first frequency shift signal generation unit 4c outputs the first frequency shift signal to the switch 4e.

[0063] The second frequency shift signal generation unit 4d acquires the reference signal output from the reference signal generation unit 4b, and generates a frequency f based on the reference signal. IF2 The second frequency shift signal.

[0064] The second frequency shift signal generation unit 4d outputs the second frequency shift signal to the switch 4e.

[0065] Switch 4e outputs the first frequency shift signal from the first frequency shift signal generation unit 4c and the second frequency shift signal from the second frequency shift signal generation unit 4d to the pulse modulator 5 and the signal processing device 15 respectively.

[0066] The pulse modulator 5 is implemented, for example, by a modulation element using acousto-optical elements or a modulation element using lithium niobate crystals, and an optical amplifier such as a semiconductor optical amplifier.

[0067] Each time the pulse modulator 5 receives a pulse signal with a pulse width ΔT from the pulse signal generation unit 4a, it pulse modulates the laser output from the light splitting unit 3 according to the pulse signal. That is, the pulse modulator 5 converts the laser, which is continuous light, into pulsed light with a pulse width ΔT.

[0068] Furthermore, if the first frequency shift signal is output from switch 4e, the pulse modulator 5 shifts the optical frequency f0 of the pulsed light with a pulse width ΔT to the optical frequency f0+f. IF1 Generates light with frequency f0+f IF1 Pulse light P1.

[0069] The pulse modulator 5 outputs the pulsed light P1 to the transmitting optical system 7.

[0070] If the second frequency shift signal is output from switch 4e, then pulse modulator 5 shifts the optical frequency f0 of the pulsed light with pulse width ΔT to the optical frequency f0+f. IF2 Generates light with frequency f0+f IF2 Pulsed light P2.

[0071] The pulse modulator 5 outputs the pulsed light P2 to the transmitting optical system 7.

[0072] The transceiver unit 6 includes a transmitting-side optical system 7, a transceiver separation unit 8, a telescope 9, and a receiving-side optical system 10.

[0073] The transceiver unit 6 radiates pulsed light P1 and P2 generated by the pulse modulation unit 2 into space.

[0074] The transceiver unit 6 receives the pulsed light P1 scattered by the first observation object as scattered light R1, and receives the pulsed light P1 scattered by the second observation object as scattered light R2.

[0075] The transceiver unit 6 receives the pulsed light P2 scattered by the first observed object as scattered light R3, and receives the pulsed light P2 scattered by the second observed object as scattered light R4.

[0076] If the first observed object moves along the radiation direction of the pulsed light P1 and P2, then the optical frequencies of the scattered light R1 and R3 include the Doppler frequency f associated with the movement of the first observed object. dp1 Therefore, the optical frequency of the scattered light R1 is f0 + f IF1 +f dp1 The scattered light R3 has an optical frequency of f0+f IF2 +f dp1 .

[0077] If the second observed object moves along the radiation direction of the pulsed light P1 and P2, then the optical frequencies of the scattered light R2 and R4 include the Doppler frequency f associated with the movement of the second observed object. dp2 Therefore, the optical frequency of the scattered light R2 is f0 + f IF1 +f dp2 The frequency of the scattered light R4 is f0+f IF2 +f dp2.

[0078] The transmitting-side optical system 7 shapes each pulse light P1 and P2 output from the pulse modulator 5, and outputs the shaped pulse light P1 and P2 to the transceiver separation unit 8. As for the shaping of the pulse light, in addition to the shaping of the pulse light beam diameter, it also corresponds to the shaping of the pulse light divergence angle.

[0079] The transceiver separation unit 8 is implemented, for example, by a polarization beam splitter and a wavelength plate.

[0080] The transceiver separation unit 8 is disposed on the optical axis of each shaped pulse light P1, P2 output from the transmitting side optical system 7.

[0081] The transceiver separation unit 8 outputs the shaped pulses P1 and P2 from the transmitting optical system 7 to the telescope 9, and outputs the scattered light R1, R2, R3, and R4 converged by the telescope 9 to the receiving optical system 10.

[0082] Telescope 9 is implemented, for example, by multiple refracting lenses or multiple reflecting mirrors.

[0083] Telescope 9 radiates shaped pulses P1 and P2 from the transceiver separation unit 8 into space.

[0084] Telescope 9 converges the pulsed light P1 scattered by the first observed object as scattered light R1, and converges the pulsed light P1 scattered by the second observed object as scattered light R2.

[0085] Telescope 9 converges the pulsed light P2 scattered by the first observed object as scattered light R3, and converges the pulsed light P2 scattered by the second observed object as scattered light R4.

[0086] Telescope 9 outputs the scattered light R1, R2, R3, and R4 to the transceiver unit 8.

[0087] The receiving-side optical system 10 is configured such that the optical axes of each of the scattered light R1, R2, R3, and R4 output from the transceiver separation unit 8 are aligned with the optical axis of the optical combining unit 12.

[0088] The receiving-side optical system 10 shapes each of the scattered beams R1, R2, R3, and R4 output from the transceiver separation unit 8, and outputs the shaped scattered beams R1, R2, R3, and R4 to the optical combining unit 12. As for the shaping of the scattered beams, in addition to shaping the beam diameter of the scattered beams, it also corresponds to shaping the divergence angle of the scattered beams.

[0089] The optical detector 11 includes an optical combining section 12, a light receiving section 13, and an A / D conversion section 14.

[0090] The optical detector 11 detects the combined light beams C1, C2, C3, and C4 of the scattered light R1, R2, R3, and R4 received by the transceiver 6 and the laser light C1, C2, C3, and C4 output from the light source 1, i.e., the reference light.

[0091] The optical detector 11 outputs the detection signals D1, D2, D3, and D4 of each combined beam C1, C2, C3, and C4 to the signal processing device 15.

[0092] The optical wave section 12 is implemented, for example, by a beam splitter or an optical fiber coupler.

[0093] The optical combining section 12 detects the combined light C1, C2, C3, and C4 of the shaped scattered light R1, R2, R3, and R4 output from the receiving optical system 10 and the reference light output from the optical splitting section 3.

[0094] That is, the optical combining section 12 performs heterodyne detection on the combined beams C1, C2, C3, and C4 by mixing the individual scattered beams R1, R2, R3, and R4 with the reference light output from the light source 1. The combined beam C1 has an optical frequency f. IF1 +f dp1 The combined wave C2 has an optical frequency of f. IF1 +f dp2 The combined wave C3 has an optical frequency of f. IF2 +f dp1 The combined wave C4 has an optical frequency of f. IF2 +f dp2 .

[0095] The light combining section 12 outputs the combined light C1, C2, C3, and C4 to the light receiving section 13.

[0096] The light-receiving part 13 is implemented, for example, by a photodiode.

[0097] The light receiving unit 13 converts the combined light C1, C2, C3, and C4 output from the light combining unit 12 into electrical signals.

[0098] The light-receiving unit 13 outputs each electrical signal to the A / D conversion unit 14.

[0099] During the period when none of the scattered light R1, R2, R3, R4 is output from the receiving optical system 10, the light receiving unit 13 outputs an electrical signal with a voltage of approximately 0 to the A / D conversion unit 14.

[0100] During the period when the pulse signal with a pulse width ΔT is output from the pulse signal generation unit 4a of the trigger generation unit 4, the A / D conversion unit 14 performs the process of converting the electrical signal output from the light receiving unit 13 from an analog signal into a digital signal Dig(t). t is a variable representing the sampling time.

[0101] The A / D converter 14 outputs the digital signal Dig(t) to the signal processing device 15. During the period when the scattered light R1 is output from the receiving optical system 10, the digital signal Dig(t) represents the detection signal D1 of the combined light C1; during the period when the scattered light R2 is output from the receiving optical system 10, the digital signal Dig(t) represents the detection signal D2 of the combined light C2; during the period when the scattered light R3 is output from the receiving optical system 10, the digital signal Dig(t) represents the detection signal D3 of the combined light C3; and during the period when the scattered light R4 is output from the receiving optical system 10, the digital signal Dig(t) represents the detection signal D4 of the combined light C4.

[0102] During the period when none of the scattered light beams R1, R2, R3, and R4 are output, the digital signal Dig(t) represents a value approximately 0.

[0103] Figure 3 This is a structural diagram showing the signal processing device 15 of Embodiment 1.

[0104] The signal processing device 15 includes a Doppler frequency calculation unit 16, a velocity calculation unit 17, an SNR (Signal to Noise Ratio) calculation unit 30, and a distance characteristic calculation unit 31.

[0105] The signal processing device 15 calculates the relative velocity V1 of the first observation object relative to the lidar device and the relative velocity V2 of the second observation object relative to the lidar device based on the digital signal Dig(t) output from the A / D conversion unit 14, and uses them as the respective moving speeds of the first observation object and the second observation object.

[0106] Figure 4 This is a hardware structure diagram showing the hardware of the signal processing device 15 according to Embodiment 1.

[0107] Doppler frequency calculation unit 16, for example, is composed of Figure 4 The Doppler frequency calculation circuit 41 shown is implemented.

[0108] The Doppler frequency calculation unit 16 includes an optical frequency correction unit 21 and a frequency calculation processing unit 28.

[0109] Doppler frequency calculation unit 16 obtains the optical frequencies f0+f of each pulse light P1 and P2 generated by pulse modulation unit 2. IF1 f0+f IF2 The detection signals D1, D2, D3, and D4 of each combined beam C1, C2, C3, and C4 output from the optical detector 11.

[0110] The Doppler frequency calculation unit 16 calculates the optical frequencies f0+f of each pulse light P1 and P2 based on their respective optical frequencies. IF1 f0+fIF2 Given the various detection signals D1, D2, D3, and D4, calculate the Doppler frequencies associated with the movement of each observed object, which are contained in the optical frequencies of each scattered light R1, R2, R3, and R4.

[0111] That is, the Doppler frequency calculation unit 16 calculates the optical frequency f0+f of one pulse P1 out of the multiple pulses P1 and P2. IF1 The remaining pulsed light P2 has an optical frequency f0+f IF2 The frequency difference Δf (=f) between them IF2 -f IF1 ).

[0112] The Doppler frequency calculation unit 16 calculates the Doppler frequency f contained in the optical frequency of each scattered light R1, R3 based on the frequency difference Δf and the various detector signals D1, D3 contained in the digital signal Dig(t). dp1 The Doppler frequency f corresponding to the relative velocity V1 with the first observed object is... dp1 .

[0113] The Doppler frequency calculation unit 16 calculates the Doppler frequency f contained in the optical frequency of each scattered light R2, R4 based on the frequency difference Δf and the various detector signals D2, D4 contained in the digital signal Dig(t). dp2 The Doppler frequency f corresponding to the relative velocity V2 with the second observed object is... dp2 .

[0114] The Doppler frequency calculation unit 16 calculates the Doppler frequency f. dp1 and Doppler frequency f dp2 The output is sent to the frequency calculation and processing unit 28.

[0115] The optical frequency correction unit 21 includes a distance compartment segmentation unit 22, a frequency resolution unit 23, a distance correction unit 24, a frequency correction processing unit 25, a spectrum accumulation unit 26, and a peak frequency detection unit 27.

[0116] The optical frequency correction unit 21 obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit 4, respectively.

[0117] The optical frequency correction unit 21 uses the modulation frequency f represented by the second frequency shift signal. IF2 Subtract the modulation frequency f represented by the first frequency shift signal IF1 To calculate the frequency difference Δf.

[0118] The optical frequency correction unit 21 obtains the digital signal Dig(t) containing each detection signal D1, D2, D3, D4 from the A / D conversion unit 14.

[0119] The optical frequency correction unit 21, based on the frequency difference Δf, adjusts the optical frequency f of the combined light C3. IF2 +f dp1 Perform corrections.

[0120] The optical frequency correction unit 21, based on the frequency difference Δf, adjusts the optical frequency f of the combined light C4. IF2 +f dp2 Perform corrections.

[0121] The distance bin segmentation unit 22 segments the digital signal Dig(t) output from the A / D converter 14 in the time direction. The segmentation width Δt in the time direction of the digital signal Dig(t) corresponds to the distance bin width Rbw. Therefore, the segmented digital signal Dig(1) related to the sampling time t=1 corresponds to the distance bin (1), and the segmented digital signal Dig(2) related to the sampling time t=2 corresponds to the distance bin (2). Furthermore, the segmented digital signal Dig(3) related to the sampling time t=3 corresponds to the distance bin (3).

[0122] The distance bin segmentation unit 22 outputs the segmented digital signals Dig(t) as distance bin signals (n) to the frequency analysis unit 23. n is a variable representing the distance bin, n = 1, 2, 3, ...

[0123] The frequency analysis unit 23 performs FFT (Fast Fourier Transform) processing on each range cell signal (n) output from the range cell segmentation unit 22, thereby calculating the spectrum FS(n) of each range cell signal (n).

[0124] The frequency analysis unit 23 outputs each spectrum FS(n) to the distance correction unit 24.

[0125] The distance correction unit 24 obtains each spectrum FS(n) from the frequency analysis unit 23.

[0126] The distance correction unit 24 obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit 4.

[0127] The distance correction unit 24 detects the peak spectrum S from the spectrum FS(n) respectively. p1 Peak spectrum S p2 Peak spectrum S p3 and peak spectrum S p4 .

[0128] In addition, the distance correction unit 24 detects and the peak spectrum S p1 The corresponding peak frequency f p1 Detection and peak spectrum S p2 The corresponding peak frequency f p2 .

[0129] Distance correction unit 24 detection and peak spectrum S p3 The corresponding peak frequency f p3 Detection and peak spectrum S p4 The corresponding peak frequency f p4 .

[0130] Distance correction unit 24 calculates peak frequency f p1 The modulation frequency f represented by the first frequency shift signal IF1 The absolute value of the difference |Δf 1-1 | and peak frequency f p1 The modulation frequency f represented by the second frequency shift signal IF2 The absolute value of the difference |Δf 1-2 |

[0131] If the absolute value of the difference |Δf 1-1 | is the absolute value of the difference| Δf 1-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p1 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0132] If the absolute value of the difference |Δf 1-1 |Absolute value of the difference|Δf 1-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p1 The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0133] Distance correction unit 24 calculates peak frequency f p2 With modulation frequency f IF1 The absolute value of the difference |Δf 2-1 | and peak frequency f p2 With modulation frequency f IF2 The absolute value of the difference |Δf 2-2 |

[0134] If the absolute value of the difference |Δf 2-1 | is the absolute value of the difference| Δf 2-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p2 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0135] If the absolute value of the difference |Δf 2-1 |Absolute value of the difference|Δf 2-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p2The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0136] Distance correction unit 24 calculates peak frequency f p3 With modulation frequency f IF1 The absolute value of the difference |Δf 3-1 | and peak frequency f p3 With modulation frequency f IF2 The absolute value of the difference |Δf 3-2 |

[0137] If the absolute value of the difference |Δf 3-1 | is the absolute value of the difference| Δf 3-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p3 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0138] If the absolute value of the difference |Δf 3-1 |Absolute value of the difference|Δf 3-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p3 The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0139] Distance correction unit 24 calculates peak frequency f p4 With modulation frequency f IF1 The absolute value of the difference |Δf 4-1 | and peak frequency f p4 With modulation frequency f IF2 The absolute value of the difference |Δf 4-2 |

[0140] If the absolute value of the difference |Δf 4-1 | is the absolute value of the difference| Δf 4-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p4 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0141] If the absolute value of the difference |Δf 4-1 |Absolute value of the difference|Δf 4-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p4 The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0142] For ease of explanation, let's assume it has a peak spectrum S. p1Combined wave light and having peak spectrum S p2 The combined light beams are either C1 or C2 corresponding to pulse light P1.

[0143] Furthermore, let S be a peak spectrum. p3 Combined wave light and having peak spectrum S p4 The combined light beams are either C3 or C4, which are the combined light beams corresponding to pulse light P2.

[0144] In this case, if the peak spectrum S p1 The distance bin is the peak spectrum S p2 If the distance is below the range of the distance chamber, the range correction unit 24 determines that it has a peak spectrum S. p1 The combined light is the combined light C1 corresponding to the pulse light P1, and has a peak spectrum S. p2 The combined light is the combined light C2 corresponding to the pulse light P1. If the peak spectrum S p1 Distance to warehouse peak spectrum S p2 If the distance to the bin is large, then the distance correction unit 24 determines that it has a peak spectrum S. p1 The combined light is the combined light C2 corresponding to the pulse light P1, and has a peak spectrum S. p2 The combined light is the combined light C1 corresponding to the pulse light P1.

[0145] Furthermore, if the peak spectrum S p3 The distance bin is the peak spectrum S p4 If the distance is below the range of the distance chamber, the range correction unit 24 determines that it has a peak spectrum S. p3 The combined light is C3, which corresponds to the combined light of pulse P2, and has a peak spectrum S. p4 The combined light is the combined light C4 corresponding to the pulse light P2. If the peak spectrum S p3 Distance to warehouse peak spectrum S p4 If the distance to the bin is large, then the distance correction unit 24 determines that it has a peak spectrum S. p3 The combined light is C4, which corresponds to the combined light of pulse P2, and has a peak spectrum S. p4 The combined light is the combined light C3 corresponding to the pulse light P2.

[0146] For ease of explanation, let's assume it has a peak spectrum S. p1 The combined light is C1, which has a peak spectrum S. p2 The combined beam is C2. Furthermore, let S be the beam with a peak spectrum. p3 The combined beam is combined beam C3, which has a peak spectrum S. p4 The combined wave light is C4.

[0147] When the distance correction unit 24 determines that the combined beams C1 and C2 are combined beams corresponding to pulse P1 and that the combined beams C3 and C4 are combined beams corresponding to pulse P2, it will proceed as described later. Figure 11 As shown, the distance bin (7) containing scattered light R3 associated with the combined beam C3 and the distance bin (13) containing scattered light R4 associated with the combined beam C4 are corrected.

[0148] That is, the distance correction unit 24 corrects the distance cell (7) containing the scattered light R3 associated with the combined light C3 to the distance cell (1) by subtracting the period Trep (=6) from the distance cell (7) containing the scattered light R3 associated with the combined light C3.

[0149] Furthermore, the distance correction unit 24 corrects the distance cell (13) containing the scattered light R4 associated with the combined beam C4 to the distance cell (7) by subtracting the period Trep (=6) from the distance cell (13) containing the scattered light R4 associated with the combined beam C4.

[0150] exist Figure 11 In the example, the time difference between the radiation time T1 of pulse light P1 and the radiation time T2 of pulse light P2 is equivalent to the range bin (6), and the period Trep is 6. Therefore, n', which is the corrected range bin for the scattered light R3 associated with the combined light C3, becomes 1 (=7-6), and n', which is the corrected range bin for the scattered light R4 associated with the combined light C4, becomes 7 (=13-6).

[0151] The distance correction unit 24 outputs the spectrum FS(n) of the multiple spectra FS(1) to FS(N) concerning the distance bin(n) of the scattered light R1 and R2 that are related to the combined light C1 and C2 to the frequency correction processing unit 25.

[0152] In addition, the distance correction unit 24 outputs the spectrum FS(n') of the multiple spectrums FS(1) to FS(N) with respect to the corrected distance bin (n') with respect to the scattered light R3 and R4 that are related to the combined light C3 and C4 to the frequency correction processing unit 25.

[0153] The distance correction unit 24 measures the optical frequency f of the combined beam C1. IF1 +f dp1 (=f p1 The optical frequency f of the combined wave C2 IF1 +f dp2 (=f p2 The combined wave C3 has an optical frequency f IF2 +f dp1 (=f p3 ), and the optical frequency f of the combined wave C4. IF2 +f dp2 (=fp4 The output is sent to the frequency correction processing unit 25.

[0154] The distance correction unit 24 outputs the distance bin containing the scattered light R1 associated with the combined beam C1 and the distance bin containing the scattered light R2 associated with the combined beam C2 to the distance characteristic calculation unit 31.

[0155] The frequency correction processing unit 25 obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit 4.

[0156] The frequency correction processing unit 25 calculates the modulation frequency f represented by the first frequency shift signal. IF1 The modulation frequency f represented by the second frequency shift signal IF2 The frequency difference Δf (=f) between them IF2 -f IF1 ).

[0157] The frequency correction processing unit 25 obtains from the distance correction unit 24 the spectrum FS(n) of the distance cell (n) containing scattered light R1 and R2 associated with the combined light C1 and C2, and the corrected spectrum FS(n') of the distance cell (n') containing scattered light R3 and R4 associated with the combined light C3 and C4.

[0158] The frequency correction processing unit 25 obtains the optical frequency f of the combined beam C1 from the distance correction unit 24. IF1 +f dp1 The combined wave C2 has an optical frequency f IF1 +f dp2 The combined wave C3 has an optical frequency f IF2 +f dp1 And the optical frequency f of the combined beam C4 after distance chamber correction. IF2 +f dp2 .

[0159] The frequency correction processing unit 25 uses the optical frequency f of the combined beam C3 after correction from the distance chamber. IF2 +f dp1 The frequency difference Δf is subtracted to correct the optical frequency of the combined beam C3. The corrected optical frequency of the combined beam C3 is f. IF1 +f dp1 , is the optical frequency f of the combined wave C1. IF1 +f dp1 Same frequency.

[0160] The frequency correction processing unit 25 uses the optical frequency f of the combined beam C4 after correction from the distance chamber. IF2 +f dp2 The frequency difference Δf is subtracted to correct the optical frequency of the combined beam C4. The corrected optical frequency of the combined beam C4 is f. IF1 +fdp2 , is the optical frequency f of the combined wave C2. IF1 +f dp2 Same frequency.

[0161] exist Figure 3 In the signal processing apparatus 15 shown, the frequency correction processing unit 25 performs correction in a manner that makes the optical frequencies of the combined beams C3 and C4 after range chamber correction match the optical frequencies of the combined beams C1 and C2 without range chamber correction. However, this is only one example; correction can also be performed in a manner that makes the optical frequencies of the combined beams C1 and C2 without range chamber correction match the optical frequencies of the combined beams C3 and C4 after range chamber correction.

[0162] The frequency correction processing unit 25 outputs the spectrum FS (n=1) of the distance bin (n=1) of the scattered light R1 that is associated with the combined light C1 to the spectrum accumulation unit 26.

[0163] The frequency correction processing unit 25 outputs the spectrum FS (n=7) of the distance bin (n=7) of the scattered light R2 that is associated with the combined light C2 to the spectrum accumulation unit 26.

[0164] The frequency correction processing unit 25 changes the optical frequency of the spectrum FS (n'=1) of the scattered light R3 associated with the combined beam C3 to the corrected optical frequency f of the combined beam C3. IF1 +f dp1 .

[0165] The frequency correction processing unit 25 outputs the frequency-modulated spectrum FS (n'=1) to the spectrum accumulation unit 26.

[0166] The frequency correction processing unit 25 changes the optical frequency of the spectrum FS (n'=7) of the scattered light R4 associated with the combined beam C4 to the corrected optical frequency f of the combined beam C4. IF1 +f dp2 .

[0167] The frequency correction processing unit 25 outputs the frequency-modulated spectrum FS (n'=7) to the spectrum accumulation unit 26.

[0168] The spectrum accumulation unit 26 obtains the spectrum FS (n=1), spectrum FS (n=7), spectrum FS after optical frequency change (n'=1), and spectrum FS after optical frequency change (n'=7) from the frequency correction processing unit 25.

[0169] The spectrum accumulation unit 26 accumulates the spectrum FS (n=1), the spectrum FS (n=7), the spectrum FS after optical frequency change (n'=1), and the spectrum FS after optical frequency change (n'=7). Through the accumulation by the spectrum accumulation unit 26, the spectrum corresponding to the optical frequency f... IF1 +f dp1 The spectral intensity of the spectrum and the corresponding optical frequency f IF1 +f dp2 The spectral intensity of the spectrum increases.

[0170] The spectrum accumulation unit 26 outputs the accumulated spectrum ΣHFS to the peak frequency detection unit 27.

[0171] The peak frequency detection unit 27 obtains the accumulated spectrum ΣHFS from the spectrum accumulation unit 26.

[0172] Peak frequency detection unit 27 determines the spectral intensity FS above the threshold from among the multiple spectral intensities contained in the accumulated spectrum ΣHFS. max1 FS max2 Since the first and second observed objects exist in space, two spectral intensities FS are determined. max1 FS max2 The threshold can be stored in the internal memory of the peak frequency detection unit 27, or it can be retrieved from... Figure 1 The threshold is provided externally by the lidar device shown.

[0173] Peak frequency detection unit 27 will be compared with each spectral intensity FS max1 FS max2 The corresponding peak frequency f peak1 f peak2 The accumulated spectrum ΣHFS is output to the frequency calculation and processing unit 28 and then output to the SNR calculation unit 30.

[0174] The frequency calculation and processing unit 28 obtains each peak frequency f from the peak frequency detection unit 27. peak1 f peak2 .

[0175] The frequency calculation and processing unit 28 obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit 4.

[0176] Frequency calculation processing unit 28 calculates the frequency from the peak frequency f. peak1 Subtract the modulation frequency f represented by the first frequency shift signal IF1 To calculate the optical frequency f of the combined wave C1. IF1 +f dp1 The included Doppler frequency f dp1 .

[0177] Frequency calculation processing unit 28 calculates the frequency from the peak frequency f.peak2 Subtract the modulation frequency f represented by the second frequency shift signal IF2 To calculate the optical frequency f of the combined wave C2. IF2 +f dp2 The included Doppler frequency f dp2 .

[0178] The frequency calculation and processing unit 28 calculates each Doppler frequency f dp1 f dp2 Output to speed calculation and processing unit 29.

[0179] Speed ​​calculation unit 17, for example, is composed of Figure 4 The speed calculation circuit 42 shown is implemented.

[0180] The speed calculation unit 17 includes a speed calculation processing unit 29.

[0181] The speed calculation processing unit 29 obtains each Doppler frequency f from the frequency calculation processing unit 28. dp1 f dp2 .

[0182] Speed ​​calculation processing unit 29 calculates based on Doppler frequency f dp1 To calculate the relative velocity V1 of the first observed object.

[0183] Speed ​​calculation processing unit 29 calculates based on Doppler frequency f dp2 To calculate the relative velocity V2 of the second observed object.

[0184] SNR calculation unit 30, for example, is composed of Figure 4 The SNR calculation circuit 43 shown is implemented.

[0185] The SNR calculation unit 30 obtains the accumulated spectrum ΣHFS from the peak frequency detection unit 27.

[0186] The SNR calculation unit 30 calculates the signal of each distance cell (n) by performing inverse FFT processing on the accumulated spectrum ΣHFS.

[0187] The SNR calculation unit 30 calculates the SNR of each distance cell (n) by dividing the signal of each distance cell (n) by the out-of-band noise.

[0188] The SNR calculation unit 30 outputs the SNR of each distance cell (n) to the distance characteristic calculation unit 31.

[0189] Distance characteristic calculation unit 31, for example, is composed of Figure 4 The distance characteristic calculation circuit 44 shown is implemented.

[0190] The distance characteristic calculation unit 31 obtains from the distance correction unit 24 the distance bin (n=1) containing scattered light R1 associated with the combined beam C1 and the distance bin (n=7) containing scattered light R2 associated with the combined beam C2.

[0191] The distance characteristic calculation unit 31 calculates the distance L1 from the lidar device to the first observation object based on the distance bin (n=1) of the scattered light R1 associated with the combined beam C1, the A / D conversion rate Rate of the A / D conversion unit 14, and the distance bin width Rbw.

[0192] The distance characteristic calculation unit 31 calculates the distance L2 from the lidar device to the second observation object based on the distance bin (n=7) of the scattered light R2 associated with the combined beam C2, the A / D conversion rate Rate of the A / D conversion unit 14, and the distance bin width Rbw.

[0193] The distance characteristic calculation unit 31 displays, for example, a distance characteristic (a-scope) representing the correspondence between the distance of the distance bin (n) and the SNR calculated by the SNR calculation unit 30 on a display device not shown.

[0194] exist Figure 1 In this context, it is assumed that the Doppler frequency calculation unit 16, velocity calculation unit 17, SNR calculation unit 30, and distance characteristic calculation unit 31, which are structural elements of the signal processing device 15, are respectively composed of... Figure 4 The dedicated hardware implementation shown is as follows. That is, it is assumed that the signal processing device 15 is implemented by a Doppler frequency calculation circuit 41, a velocity calculation circuit 42, an SNR calculation circuit 43, and a distance characteristic calculation circuit 44.

[0195] The Doppler frequency calculation circuit 41, the speed calculation circuit 42, the SNR calculation circuit 43, and the distance characteristic calculation circuit 44 correspond, for example, to a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA, or a combination thereof.

[0196] The structural elements of the signal processing device 15 are not limited to being implemented by dedicated hardware; the signal processing device 15 can also be implemented by software, firmware, or a combination of software and firmware.

[0197] Software or firmware is stored in the computer's memory in the form of a program. A computer refers to the hardware that executes programs, such as CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor).

[0198] Figure 5 This is a hardware structure diagram of a computer when the signal processing device 15 is implemented by software or firmware.

[0199] When the signal processing device 15 is implemented by software or firmware, the program for causing the computer to execute each processing step in the Doppler frequency calculation unit 16, velocity calculation unit 17, SNR calculation unit 30, and distance characteristic calculation unit 31 is stored in the memory 51. Furthermore, the computer's processor 52 executes the program stored in the memory 51.

[0200] In addition, Figure 4 The diagram shows an example where the structural elements of the signal processing device 15 are implemented by dedicated hardware. Figure 5 The diagram shows an example of the signal processing device 15 being implemented by software or firmware. However, this is only one example; it is also possible that some structural elements of the signal processing device 15 are implemented by dedicated hardware, while the remaining structural elements are implemented by software or firmware.

[0201] Next, regarding Figure 1 The operation of the lidar device shown will be explained.

[0202] Figure 6 It is shown Figure 1 The flowchart shows the processing steps of the lidar device.

[0203] Figure 7 This is a flowchart illustrating a signal processing method as a processing step of the signal processing apparatus 15.

[0204] Light source 1 outputs laser light as continuous light with optical frequency f0 to the light splitting section 3 of pulse modulation section 2. Figure 6 Step ST1).

[0205] When the light splitter 3 receives laser light from the light source 1, it divides the laser light into two parts. Figure 6 Step ST2).

[0206] The optical splitter 3 outputs the laser from one of the split beams to the pulse modulator 5, and outputs the laser from the other split beam as a reference beam to the optical combiner 12.

[0207] The pulse signal generation unit 4a of the trigger generation unit 4 generates a pulse signal with a pulse width ΔT.

[0208] The pulse signal generation unit 4a repeatedly outputs the pulse signal to the pulse modulator 5, the A / D converter 14 and the signal processing device 15 at a periodic Trep.

[0209] The reference signal generation unit 4b of the trigger generation unit 4 generates a reference signal as an electrical signal with frequency f.

[0210] The reference signal generation unit 4b outputs the reference signal to the first frequency shift signal generation unit 4c.

[0211] When the first frequency shift signal generation unit 4c receives the reference signal from the reference signal generation unit 4b, it generates a signal representing the modulation frequency f based on the reference signal. IF1 The first frequency shift signal ( Figure 6 Step ST3).

[0212] The first frequency shift signal generation unit 4c outputs the first frequency shift signal to the switch 4e.

[0213] When switch 4e receives the first frequency shift signal from the first frequency shift signal generation unit 4c, it outputs the first frequency shift signal to the pulse modulator 5 and the signal processing device 15 respectively.

[0214] When the pulse modulator 5 receives a pulse signal with a pulse width ΔT from the pulse signal generation unit 4a each time, it pulse modulates the laser output from the optical splitting unit 3 according to the pulse signal.

[0215] That is, the pulse modulator 5 converts the laser output from the optical splitter 3 into a pulsed light P with a pulse width ΔT.

[0216] When pulse modulator 5 outputs the first frequency shift signal from switch 4e, it shifts the optical frequency f0 of pulsed light P to the optical frequency f0+f. IF1 This generates an optical frequency f0+f IF1 Pulse light P1.

[0217] Pulse modulator 5 outputs pulsed light P1 to the transmitting optical system 7. Figure 6 Step ST4).

[0218] When the transmitting optical system 7 receives the pulse light P1 from the pulse modulator 5, it shapes the pulse light P1 and outputs the shaped pulse light P1 to the transceiver separation unit 8.

[0219] When the transceiver separation unit 8 receives the shaped pulse light P1 from the transmitting side optical system 7, it outputs the shaped pulse light P1 to the telescope 9.

[0220] Telescope 9 radiates shaped pulsed light P1 output from transceiver unit 8 into space. Figure 6 Step ST5).

[0221] If the first and second observed objects exist within the space of the illumination region of pulsed light P1, then as follows Figure 8 As shown, the pulsed light P1 is scattered by the first and second observed objects, respectively.

[0222] Figure 8 This is an explanatory diagram showing the pulsed light P1 radiated from the lidar device, the scattered light R1 from the first observed object, and the scattered light R2 from the second observed object.

[0223] exist Figure 8 In the example, the distance L1 from the lidar device to the first observed object is shorter than the distance L2 from the lidar device to the second observed object. Therefore, the scattered light R1 from the first observed object returns to the lidar device earlier than the scattered light R2 from the second observed object.

[0224] Figure 9 This is an explanatory diagram showing the radiation times T1 and T2 of pulsed light P1 and P2 radiated from the lidar device, the reception times T1' and T3' of scattered light R1 and R3 from the first observed object, and the reception times T2' and T4' of scattered light R2 and R4 from the second observed object.

[0225] exist Figure 9 In the diagram, the horizontal axis represents time, and the vertical axis represents light intensity.

[0226] Telescope 9 converges the pulsed light P1 scattered by the first observed object as scattered light R1, and outputs scattered light R1 to the transceiver unit 8. Figure 6 Step ST6).

[0227] exist Figure 9 In the example, the distance L1 from the lidar device to the first observed object is relatively short. Therefore, before the pulsed light P2 is radiated from the telescope 9, the scattered light R1 from the first observed object is focused by the telescope 9. On the other hand, the distance L2 from the lidar device to the second observed object is relatively long. Therefore, after the pulsed light P2 is radiated from the telescope 9, the scattered light R2 from the second observed object is focused by the telescope 9.

[0228] exist Figure 9 In the example, after the pulsed light P2 is radiated from telescope 9, the scattered light R2 from the second observed object is focused by telescope 9. However, this is just one example; the scattered light R2 from the second observed object can also be focused by telescope 9 before the pulsed light P2 is radiated from telescope 9.

[0229] In addition, Figure 9 In the example, before the pulsed light P2 is radiated from telescope 9, the scattered light R1 from the first observed object is focused by telescope 9. However, this is only one example; it is also possible that after the pulsed light P2 is radiated from telescope 9, the scattered light R1 from the first observed object is focused by telescope 9.

[0230] When the transceiver separation unit 8 receives the scattered light R1 from the first observed object from the telescope 9, it outputs the scattered light R1 to the receiving optical system 10.

[0231] When the receiving optical system 10 receives the scattered light R1 from the transceiver separation unit 8, it shapes the scattered light R1 and outputs the shaped scattered light R1 to the optical wave combining unit 12.

[0232] When the optical combining unit 12 receives the shaped scattered light R1 from the receiving optical system 10, it mixes the shaped scattered light R1 with the reference light output from the light source 1, thereby performing heterodyne detection on the combined light C1. Figure 6 Step ST7). The combined wave C1 has an optical frequency of f. IF1 +f dp1 .

[0233] The light combining section 12 outputs the combined light C1 to the light receiving section 13.

[0234] When the light receiving unit 13 receives the combined light C1 from the light combining unit 12, it converts the combined light C1 into an electrical signal and outputs the electrical signal to the A / D conversion unit 14.

[0235] During the period when the pulse signal with pulse width ΔT is output from the pulse signal generation unit 4a of the trigger generation unit 4, the A / D conversion unit 14 performs the process of converting the electrical signal output from the light receiving unit 13 from an analog signal into a digital signal Dig(t).

[0236] The A / D conversion unit 14 outputs the digital signal Dig(t) of the detector signal D1 containing the combined beam C1 to the distance compartment division unit 22 of the signal processing device 15.

[0237] When the pulse signal generation unit 4a of the trigger generation unit 4 has elapsed for the period of Trep since the output pulse signal, it outputs the pulse signal to the pulse modulator 5, the A / D converter 14 and the signal processing device 15 respectively.

[0238] The reference signal generation unit 4b outputs the reference signal to the second frequency shift signal generation unit 4d after a period of Trep elapses since the reference signal was output to the first frequency shift signal generation unit 4c.

[0239] When the second frequency shift signal generation unit 4d receives the reference signal from the reference signal generation unit 4b, it generates a signal representing the modulation frequency f based on the reference signal.IF2 The second frequency shift signal ( Figure 6 Step ST8).

[0240] The second frequency shift signal generation unit 4d outputs the second frequency shift signal to the switch 4e.

[0241] exist Figure 1 In the lidar device shown, f IF2 >f IF1 modulation frequency f IF2 With modulation frequency f IF1 The frequency difference Δf (=f) between them IF2 -f IF1 The frequency difference Δf is greater than twice the absolute value of the Doppler frequency if the first and second observed objects move at the assumed maximum speeds. If the frequency difference Δf is greater than twice the absolute value of the Doppler frequency, then as long as the moving speeds of the first and second observed objects are within the assumed range, the light frequencies of the scattered light R1, R2, R3, and R4 will be different from each other.

[0242] When switch 4e receives the second frequency shift signal from the second frequency shift signal generation unit 4d, it outputs the second frequency shift signal to the pulse modulator 5 and the signal processing device 15 respectively.

[0243] When pulse modulator 5 outputs the second frequency shift signal from switch 4e, it shifts the optical frequency f0 of pulsed light P to the optical frequency f0+f. IF2 This generates an optical frequency f0+f IF2 Pulsed light P2.

[0244] Pulse modulator 5 outputs pulsed light P2 to the transmitting optical system 7. Figure 6 Step ST9).

[0245] When the transmitting optical system 7 receives the pulse light P2 from the pulse modulator 5, it shapes the pulse light P2 and outputs the shaped pulse light P2 to the transceiver separation unit 8.

[0246] When the transceiver separation unit 8 receives the shaped pulsed light P2 from the transmitting side optical system 7, it outputs the shaped pulsed light P2 to the telescope 9.

[0247] Telescope 9 radiates shaped pulsed light P2 output from transceiver unit 8 into space. Figure 6 Step ST10).

[0248] Telescope 9 converges the pulsed light P1 scattered by the second observed object as scattered light R2, and outputs the scattered light R2 to the transceiver separator 8. Figure 6 Step ST11).

[0249] In addition, telescope 9 converges the pulsed light P2 scattered by the first observed object as scattered light R3, and outputs scattered light R3 to the transceiver separation unit 8. Figure 6 Step ST11).

[0250] exist Figure 9 In the example, the pulsed light P1 scattered by the second observed object, i.e., the scattered light R2, and the pulsed light P2 scattered by the first observed object, i.e., the scattered light R3, are simultaneously converged by telescope 9.

[0251] Regarding "simultaneity" here, it is sufficient that a portion of scattered light R2 overlaps with a portion of scattered light R3, and it is not limited to the fact that the reception times of scattered light R2 and scattered light R3 are strictly the same. Therefore, "simultaneity" here also includes cases where the reception times of scattered light R2 and scattered light R3 are slightly off.

[0252] The transceiver unit 8 receives the overlapping scattered light R2 from the second observed object and the scattered light R3 from the first observed object from the telescope 9. 2，3 At that time, the scattered light R 2，3 Output to the receiving-side optical system 10.

[0253] The receiving-side optical system 10 receives the scattered light R from the transceiver separation unit 8. 2、3 At that time, for the scattered light R 2、3 The scattered light R is shaped and then reshaped. 2，3 Output to the photosynthesis wave section 12.

[0254] The optical wave combiner 12 receives the shaped scattered light R from the receiving optical system 10. 2，3 At that time, the shaped scattered light R 2，3 The combined wave light C is mixed with the reference light output from light source 1. 2，3 Perform heterodyne detection ( Figure 6 Step ST12). Combined wave C 2，3 The optical frequency it has is f IF1 +f dp2 f IF2 +f dp1 .

[0255] The optical wavelet combiner 12 combines the wavelet C 2，3 Output to the light-receiving unit 13.

[0256] The light receiving section 13 receives the combined light C from the light combining section 12. 2，3 At that time, the combined wave C 2，3 It is converted into an electrical signal and output to the A / D conversion unit 14.

[0257] During the period when the pulse signal with pulse width ΔT is output from the pulse signal generation unit 4a of the trigger generation unit 4, the A / D conversion unit 14 performs the process of converting the electrical signal output from the light receiving unit 13 from an analog signal into a digital signal Dig(t).

[0258] The A / D converter 14 will include the combined wave optical C 2，3 The detector signal D 2，3 The digital signal Dig(t) is output to the distance compartment division 22 of the signal processing device 15.

[0259] Then, telescope 9 converges the pulsed light P2 scattered by the second observed object as scattered light R4, and outputs scattered light R4 to the transceiver separation unit 8. Figure 6 Step ST13).

[0260] When the transceiver separation unit 8 receives the scattered light R4 from the second observation object from the telescope 9, it outputs the scattered light R4 to the receiving optical system 10.

[0261] When the receiving optical system 10 receives the scattered light R4 from the transceiver separation unit 8, it shapes the scattered light R4 and outputs the shaped scattered light R4 to the optical wave combining unit 12.

[0262] When the optical combining unit 12 receives the shaped scattered light R4 from the receiving optical system 10, it mixes the shaped scattered light R4 with the reference light output from the light source 1, thereby performing heterodyne detection on the combined light C4. Figure 6 Step ST14). The combined wave C4 has an optical frequency of f. IF2 +f dp2 .

[0263] The light combining section 12 outputs the combined light C4 to the light receiving section 13.

[0264] When the light receiving unit 13 receives the combined light C4 from the light combining unit 12, it converts the combined light C4 into an electrical signal and outputs the electrical signal to the A / D conversion unit 14.

[0265] During the period when the pulse signal with pulse width ΔT is output from the pulse signal generation unit 4a of the trigger generation unit 4, the A / D conversion unit 14 performs the process of converting the electrical signal output from the light receiving unit 13 from an analog signal into a digital signal Dig(t).

[0266] The A / D conversion unit 14 outputs the digital signal Dig(t) containing the detector signal D4 of the combined beam C4 to the distance compartment division unit 22 of the signal processing device 15.

[0267] When the distance compartment segmentation unit 22 receives the digital signal Dig(t) from the A / D conversion unit 14, it segments the digital signal Dig(t) in the time direction. Figure 7 Step ST21).

[0268] The time-direction segmentation width Δt in the digital signal Dig(t) corresponds to the distance bin width Rbw.

[0269] like Figure 11 As shown, assume that telescope 9 radiates pulse light P1 at sampling time t=0, which is equivalent to distance chamber (0), and pulse light P2 at sampling time t=6, which is equivalent to distance chamber (6).

[0270] Furthermore, let L1, the distance from the lidar device to the first observation object, correspond to the distance of the distance chamber (1), and L2, the distance from the lidar device to the second observation object, correspond to the distance of the distance chamber (7).

[0271] In this case, the segmented digital signal Dig(1) contains the detector signal D1 of the multiplexed beam C1, and the segmented digital signal Dig(7) contains the detector signal D1 of the multiplexed beam C1. 2，3 The detector signal D 2，3 The segmented digital signal Dig(13) contains the detection signal D4 of the combined beam C4.

[0272] The distance bin segmentation unit 22 outputs each segmented digital signal Dig(t) as a distance bin signal (n) to the frequency analysis unit 23.

[0273] Frequency analysis unit 23 performs FFT processing on each range cell signal (n) output from range cell segmentation unit 22, thereby calculating the spectrum FS(n) of each range cell signal (n). Figure 7 Step ST22).

[0274] The frequency analysis unit 23 outputs each spectrum FS(n) to the distance correction unit 24.

[0275] The distance chamber signal (7) includes the combined wave C. 2，3 The detector signal D 2，3 Because the combined wave C2 has an optical frequency f IF1 +f dp2 The optical frequency f of the combined wave C3 IF2 +f dp1 Different, therefore, the distance warehouse signal (7) is as follows Figure 10A As shown, it has two peak spectra.

[0276] The distance chamber signal (1) contains the detector signal D1 of the combined beam C1. Therefore, the distance chamber signal (1) has a single peak spectrum.

[0277] The distance chamber signal (13) includes the detector signal D4 of the combined beam C4. Therefore, the distance chamber signal (13) has a single peak spectrum.

[0278] The distance warehouse signal (n) other than the distance warehouse signals (1), (7), and (13) does not have a peak spectrum, and the spectrum of the distance warehouse signal (n) is approximately 0.

[0279] Figure 10A This is an explanatory diagram showing the peak spectrum of the distance bin signal (7).

[0280] Figure 10B This is an explanatory diagram showing the peak spectrum of the distance chamber signal (7) when the optical frequencies of pulsed light P1 and pulsed light P2 are the same. Figure 10B In this case, it is impossible to identify the combined wave C2 and combined wave C3.

[0281] exist Figure 10A and Figure 10B In the diagram, the horizontal axis represents time, and the vertical axis represents spectral intensity.

[0282] The distance correction unit 24 obtains each spectrum FS(n) from the frequency analysis unit 23.

[0283] The distance correction unit 24 obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit 4.

[0284] The distance correction unit 24 detects multiple peak spectra from each spectrum FS(n).

[0285] That is, the distance correction unit 24 detects the peak spectrum S from the spectrum FS(1). p1 .

[0286] Distance correction unit 24 detects peak spectrum S from spectrum FS(7) p2 and peak spectrum S p3 .

[0287] In addition, the distance correction unit 24 detects the peak spectrum S from the spectrum FS (13). p4 .

[0288] In addition, the distance correction unit 24 detects and the peak spectrum S p1 The corresponding peak frequency f p1 And detect the peak spectrum S p2 The corresponding peak frequency f p2 .

[0289] Distance correction unit 24 detection and peak spectrum S p3 The corresponding peak frequency f p3 And detect the peak spectrum S p4 The corresponding peak frequency f p4 .

[0290] Distance correction unit 24 calculates peak frequency f p1 The modulation frequency f represented by the first frequency shift signal IF1 The absolute value of the difference |Δf 1-1 | Calculate the peak frequency f p1 The modulation frequency f represented by the second frequency shift signal IF2 The absolute value of the difference |Δf 1-2 |

[0291] If the absolute value of the difference |Δf 1-1 | is the absolute value of the difference| Δf 1-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p1 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0292] If the absolute value of the difference |Δf 1-1 |Absolute value of the difference|Δf 1-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p1 The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0293] Distance correction unit 24 calculates peak frequency f p2 With modulation frequency f IF1 The absolute value of the difference |Δf 2-1 | and calculate the peak frequency f p2 With modulation frequency f IF2 The absolute value of the difference |Δf 2-2 |

[0294] If the absolute value of the difference |Δf 2-1 | is the absolute value of the difference| Δf 2-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p2 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0295] If the absolute value of the difference |Δf 2-1 |Absolute value of the difference|Δf 2-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p2 The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0296] Distance correction unit 24 calculates peak frequency f p3 With modulation frequency f IF1 The absolute value of the difference |Δf 3-1 | and calculate the peak frequency fp3 With modulation frequency f IF2 The absolute value of the difference |Δf 3-2 |

[0297] If the absolute value of the difference |Δf 3-1 | is the absolute value of the difference| Δf 3-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p3 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0298] If the absolute value of the difference |Δf 3-1 |Absolute value of the difference|Δf 3-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p3 The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0299] Distance correction unit 24 calculates peak frequency f p4 With modulation frequency f IF1 The absolute value of the difference |Δf 4-1 | and calculate the peak frequency f p4 With modulation frequency f IF2 The absolute value of the difference |Δf 4-2 |

[0300] If the absolute value of the difference |Δf 4-1 | is the absolute value of the difference| Δf 4-2 |Then, the distance correction unit 24 determines that it has a peak spectrum S p4 The combined light is either C1, which corresponds to pulse light P1, or C2, which corresponds to pulse light P1.

[0301] If the absolute value of the difference |Δf 4-1 |Absolute value of the difference|Δf 4-2 If the value is large, then the distance correction unit 24 determines that it has a peak spectrum S. p4 The combined light is either C3, which corresponds to pulse light P2, or C4, which corresponds to pulse light P2.

[0302] For ease of explanation, let's assume it has a peak spectrum S. p1 Combined wave light and having peak spectrum S p2 The combined light beams are either C1 or C2 corresponding to pulse light P1.

[0303] Furthermore, let S be a peak spectrum. p3 Combined wave light and having peak spectrum S p4The combined light beams are either C3 or C4, which are the combined light beams corresponding to pulse light P2.

[0304] In this case, if the peak spectrum S p1 The distance bin is the peak spectrum S p2 If the distance is below the range of the distance chamber, the range correction unit 24 determines that it has a peak spectrum S. p1 The combined light is the combined light C1 corresponding to the pulse light P1, and has a peak spectrum S. p2 The combined light is the combined light C2 corresponding to the pulse light P1.

[0305] If the peak spectrum S p1 Distance to warehouse peak spectrum S p2 If the distance to the bin is large, then the distance correction unit 24 determines that it has a peak spectrum S. p1 The combined light is the combined light C2 corresponding to the pulse light P1, and has a peak spectrum S. p2 The combined light is the combined light C1 corresponding to the pulse light P1.

[0306] Furthermore, if the peak spectrum S p3 The distance bin is the peak spectrum S p4 If the distance is below the range of the distance chamber, the range correction unit 24 determines that it has a peak spectrum S. p3 The combined light is C3, which corresponds to the combined light of pulse P2, and has a peak spectrum S. p4 The combined light is C4, which corresponds to the combined light of pulse light P2.

[0307] If the peak spectrum S p3 Distance to warehouse peak spectrum S p4 If the distance to the bin is large, then the distance correction unit 24 determines that it has a peak spectrum S. p3 The combined light beam corresponds to the combined light beam C4 of pulse light P2, and has a peak spectrum S. p4 The combined light beam corresponds to the combined light beam C3 of pulse light P2.

[0308] For ease of explanation, let's assume it has a peak spectrum S. p1 The combined light is C1, which has a peak spectrum S. p2 The combined beam is C2. Furthermore, let S be the beam with a peak spectrum. p3 The combined beam is combined beam C3, which has a peak spectrum S. p4 The combined wave light is C4.

[0309] When it is determined that the combined light beams C1 and C2 are combined light beams corresponding to pulse light P1, and the combined light beams C3 and C4 are combined light beams corresponding to pulse light P2, such as Figure 11As shown, the distance correction unit 24 corrects the distance chamber (7) where the combined beam C3 exists and the distance chamber (13) where the combined beam C4 exists.

[0310] That is, the distance correction unit 24 corrects the distance cell (7) containing the combined beam C3 to the distance cell (1) by subtracting the period Trep (=6) from the distance cell (7) containing the combined beam C3. Figure 7 Step ST23).

[0311] Furthermore, the distance correction unit 24 corrects the distance cell (13) containing the combined beam C4 to the distance cell (7) by subtracting the period Trep (=6) from the distance cell (13) containing the combined beam C4. Figure 7 Step ST23).

[0312] Figure 11 This is an explanatory diagram showing the range chamber containing scattered light R1 associated with the combined beam C1, the range chamber containing scattered light R2 and R3 associated with the combined beams C2 and C3, and the range chamber containing scattered light R4 associated with the combined beam C4.

[0313] exist Figure 11 In the graph, the horizontal axis represents time, and the vertical axis represents light intensity. Figure 11 In China, the distance warehouse is simply referred to as "distance".

[0314] exist Figure 11 In the example, the distance cell containing scattered light R1 is distance cell (1), the distance cell containing scattered light R2 and R3 is distance cell (7), and the distance cell containing scattered light R4 is distance cell (13).

[0315] The time difference between the radiation time T1 of pulse light P1 and the radiation time T2 of pulse light P2 is equivalent to the range bin (6), and the period Trep is 6. Therefore, n', which is the corrected range bin for the scattered light R3 associated with the combined light C3, becomes 1 (=7-6), and n', which is the corrected range bin for the scattered light R4 associated with the combined light C4, becomes 7 (=13-6).

[0316] The distance correction unit 24 outputs the spectrum FS(n) of the multiple spectra FS(1) to FS(N) concerning the distance bin(n) of the scattered light R1 and R2 that are related to the combined light C1 and C2 to the frequency correction processing unit 25.

[0317] In addition, the distance correction unit 24 outputs the spectrum FS(n') of the multiple spectrums FS(1) to FS(N) with respect to the corrected distance bin (n') with respect to the scattered light R3 and R4 that are related to the combined light C3 and C4 to the frequency correction processing unit 25.

[0318] The distance correction unit 24 measures the optical frequency f of the combined beam C1.IF1 +f dp1 (=f p1 The optical frequency f of the combined wave C2 IF1 +f dp2 (=f p2 The combined wave C3 has an optical frequency f IF2 +f dp1 (=f p3 ), and the optical frequency f of the combined wave C4. IF2 +f dp2 (=f p4 The output is sent to the frequency correction processing unit 25.

[0319] The distance correction unit 24 outputs the distance bin containing the scattered light R1 associated with the combined beam C1 and the distance bin containing the scattered light R2 associated with the combined beam C2 to the distance characteristic calculation unit 31.

[0320] The frequency correction processing unit 25 obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit 4.

[0321] The frequency correction processing unit 25 calculates the modulation frequency f represented by the first frequency shift signal. IF1 The modulation frequency f represented by the second frequency shift signal IF2 The frequency difference Δf (=f) between them IF2 -f IF1 ).

[0322] The frequency correction processing unit 25 obtains from the distance correction unit 24 the spectrum FS(n) of the distance cell (n) containing scattered light R1 and R2 associated with the combined light C1 and C2, and the corrected spectrum FS(n') of the distance cell (n') containing scattered light R3 and R4 associated with the combined light C3 and C4.

[0323] The frequency correction processing unit 25 obtains the optical frequency f of the combined beam C1 from the distance correction unit 24. IF1 +f dp1 The combined wave C2 has an optical frequency f IF1 +f dp2 The combined wave C3 has an optical frequency f IF2 +f dp1 And the optical frequency f of the combined wave C4 IF2 +f dp2 .

[0324] The frequency correction processing unit 25 uses the optical frequency f of the combined beam C3 to correct the optical frequency f. IF2 +f dp1 Subtracting the frequency difference Δf to correct the optical frequency of the combined light C3 ( Figure 7 Step ST24). The corrected optical frequency of the combined wave C3 is f.IF1 +f dp1 , is the optical frequency f of the combined wave C1. IF1 +f dp1 Same frequency.

[0325] The frequency correction processing unit 25 uses the optical frequency f of the combined beam C4 to correct the optical frequency f. IF2 +f dp2 Subtracting the frequency difference Δf to correct the optical frequency of the combined beam C4 ( Figure 7 Step ST24). The corrected optical frequency of the combined wave C4 is f. IF1 +f dp2 , is the optical frequency f of the combined wave C2. IF1 +f dp2 Same frequency.

[0326] The frequency correction processing unit 25 outputs the spectrum FS (n=1) of the distance bin (n=1) of the scattered light R1 that is associated with the combined light C1 to the spectrum accumulation unit 26.

[0327] The frequency correction processing unit 25 outputs the spectrum FS (n=7) of the distance bin (n=7) of the scattered light R2 that is associated with the combined light C2 to the spectrum accumulation unit 26.

[0328] The frequency correction processing unit 25 changes the optical frequency of the spectrum FS (n'=1) of the scattered light R3 associated with the combined beam C3 to the corrected optical frequency f of the combined beam C3. IF1 +f dp1 .

[0329] The frequency correction processing unit 25 outputs the frequency-modulated spectrum FS (n'=1) to the spectrum accumulation unit 26.

[0330] The frequency correction processing unit 25 changes the optical frequency of the spectrum FS (n'=7) of the scattered light R4 associated with the combined beam C4 to the corrected optical frequency f of the combined beam C4. IF1 +f dp2 .

[0331] The frequency correction processing unit 25 outputs the frequency-modulated spectrum FS (n'=7) to the spectrum accumulation unit 26.

[0332] The spectrum accumulation unit 26 obtains the spectrum FS (n=1), spectrum FS (n=7), spectrum FS after optical frequency change (n'=1), and spectrum FS after optical frequency change (n'=7) from the frequency correction processing unit 25.

[0333] The spectrum accumulator 26 accumulates the spectrum FS (n=1), the spectrum FS (n=7), the spectrum FS after optical frequency change (n'=1), and the spectrum FS after optical frequency change (n'=7). Figure 7 Step ST25). By accumulating by the spectrum accumulator 26, corresponding to the optical frequency f IF1 +f dp1 The spectral intensity of the spectrum corresponds to the optical frequency f. IF1 +f dp2 The spectral intensity of the spectrum increases.

[0334] The spectrum accumulation unit 26 outputs the accumulated spectrum ΣHFS to the peak frequency detection unit 27.

[0335] The peak frequency detection unit 27 obtains the accumulated spectrum ΣHFS from the spectrum accumulation unit 26.

[0336] Peak frequency detection unit 27 determines the spectral intensity FS above the threshold from among the multiple spectral intensities contained in the accumulated spectrum ΣHFS. max1 FS max2 Since the first and second observed objects exist in space, two spectral intensities FS are determined. max1 FS max2 .

[0337] Peak frequency detection unit 27 will correspond to the spectral intensity FS max1 peak frequency f peak1 and corresponding to the spectral intensity FS max2 peak frequency f peak2 Output to frequency calculation and processing unit 28 ( Figure 7 Step ST26).

[0338] Peak frequency f peak1 The optical frequencies f corresponding to the combined light C1 are respectively IF1 +f dp1 The combined beam C3 after optical frequency correction has an optical frequency f IF1 +f dp1 .

[0339] Peak frequency f peak2 The optical frequencies f corresponding to the combined light C2 are respectively IF1 +f dp2 The combined beam C4 after optical frequency correction has an optical frequency f IF1 +f dp2 .

[0340] In addition, the peak frequency detection unit 27 outputs the accumulated spectrum ΣHFS to the SNR calculation unit 30.

[0341] The frequency calculation and processing unit 28 obtains each peak frequency f from the peak frequency detection unit 27. peak1 f peak2 .

[0342] The frequency calculation and processing unit 28 obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit 4.

[0343] Frequency calculation processing unit 28 calculates the frequency from the peak frequency f. peak1 Subtract the modulation frequency f represented by the first frequency shift signal IF1 To calculate the optical frequencies f of the combined beam C1 and the frequency-corrected combined beam C3. IF1 +f dp1 The included Doppler frequency f dp1 ( Figure 7 Step ST27).

[0344] Frequency calculation processing unit 28 calculates the frequency from the peak frequency f. peak2 Subtract the modulation frequency f represented by the second frequency shift signal IF2 To calculate the optical frequencies f of the combined beam C2 and the frequency-corrected combined beam C4. IF1 +f dp2 The included Doppler frequency f dp2 ( Figure 7 Step ST27).

[0345] The frequency calculation and processing unit 28 calculates each Doppler frequency f dp1 f dp2 Output to speed calculation and processing unit 29.

[0346] The speed calculation processing unit 29 obtains each Doppler frequency f from the frequency calculation processing unit 28. dp1 f dp2 .

[0347] The speed calculation processing unit 29 calculates the speed based on the Doppler frequency f as shown in the following equation (1). dp1 To calculate the relative velocity V1 of the first observed object ( Figure 7 Step ST28).

[0348] V1=λ×f dp1 / twenty one)

[0349] In equation (1), λ is the wavelength of each pulse light P1 and P2.

[0350] The speed calculation processing unit 29 calculates the speed based on the Doppler frequency f as shown in the following equation (2). dp2 To calculate the relative velocity V2 of the second observed object ( Figure 7 Step ST28).

[0351] V2=λ×f dp2 / twenty two)

[0352] The velocity calculation and processing unit 29 displays the relative velocity V1 of the first observed object and the relative velocity V2 of the second observed object, for example, on a display device not shown.

[0353] The SNR calculation unit 30 obtains the accumulated spectrum ΣHFS from the peak frequency detection unit 27.

[0354] The SNR calculation unit 30 calculates the signal of each distance cell (n) by performing inverse FFT processing on the accumulated spectrum ΣHFS.

[0355] The SNR calculation unit 30 calculates the SNR of each distance cell (n) by dividing the signal of each distance cell (n) by the out-of-band noise.

[0356] The SNR calculation unit 30 outputs the SNR of each distance cell (n) to the distance characteristic calculation unit 31.

[0357] The distance characteristic calculation unit 31 obtains from the distance correction unit 24 a distance bin (n=1) containing scattered light R1 associated with the combined beam C1 and a distance bin (n=7) containing scattered light R2 associated with the combined beam C2.

[0358] The distance characteristic calculation unit 31 calculates the distance L1 from the lidar device to the first observation object based on the distance bin (n=1) of the scattered light R1 associated with the combined beam C1, the A / D conversion rate Rate of the A / D conversion unit 14, and the distance bin width Rbw, as shown in the following formula (3).

[0359] L1 = c × Rate × n / 2

[0360] = c × Rate × 1 / 2 (3)

[0361] In equation (3), c is the speed of light.

[0362] The distance characteristic calculation unit 31 calculates the distance L2 from the lidar device to the second observation object based on the distance bin (n=7) of the scattered light R2 associated with the combined beam C2, the A / D conversion rate Rate of the A / D conversion unit 14, and the distance bin width Rbw, as shown in the following formula (4).

[0363] L2 = c × Rate × n / 2

[0364] = c × Rate × 7 / 2 (4)

[0365] like Figure 12As shown, the distance characteristic calculation unit 31 displays, for example, a distance characteristic (a-scope) representing the correspondence between the distance of the distance bin (n) and the SNR calculated by the SNR calculation unit 30 on a display device not shown.

[0366] Figure 12 This is an explanatory diagram of the distance characteristic (a-scope) that shows the correspondence between the distance to the distance bin (n) and the SNR.

[0367] exist Figure 12 In the diagram, the horizontal axis represents the distance [m] from the warehouse (n), and the vertical axis represents the SNR [dB].

[0368] In Embodiment 1 described above, the signal processing device 15 is configured to calculate the relative velocities of multiple objects existing in space relative to the lidar device as the moving speeds of each object. Multiple pulses of light with different frequencies are generated based on laser light output from the light source 1, each pulse of light is radiated into space, and each pulse of light scattered by each object is received as scattered light. The combined beam of each scattered light and the laser light is detected. The signal processing device 15 includes: a Doppler frequency calculation unit 16, which calculates the Doppler frequency associated with the movement of each object based on the optical frequencies of the generated multiple pulses of light and the detection signal of each combined beam; and a velocity calculation unit 17, which calculates the relative velocities of each object based on the Doppler frequencies calculated by the Doppler frequency calculation unit 16. Therefore, even when distant scattered light overlaps with nearby scattered light, the signal processing device 15 can calculate the moving speed of each object regardless of whether the moving speed of the distant object is the same as that of the nearby object.

[0369] Figure 1 The lidar device shown includes multiple structural elements for processing light, each connected to other structural elements via optical fibers. Furthermore, each structural element transmits and receives light from other structural elements via optical fibers. However, this is only one example; each structural element can also transmit and receive light from other structural elements through spatial propagation. The multiple structural elements are: light source 1, light splitter 3, pulse modulator 5, transmitting-side optical system 7, transmitting-receiving separation unit 8, telescope 9, receiving-side optical system 10, light combining unit 12, and light receiving unit 13.

[0370] exist Figure 3In the signal processing apparatus 15 shown, the Doppler frequency calculation unit 16 includes an optical frequency correction unit 21 and a frequency calculation processing unit 28. Furthermore, the optical frequency correction unit 21 includes a range cell segmentation unit 22, a frequency resolution unit 23, a range correction unit 24, a frequency correction processing unit 25, and a spectrum accumulation unit 26 to improve the SNR of each detection signal D1, D2, D3, and D4.

[0371] However, even without improving the SNR of each detection signal D1 and D2, as long as the Doppler frequencies V1 and V2 associated with the movement of each observed object can be calculated, the optical frequency correction unit 21 may not have the range compartment segmentation unit 22, frequency resolution unit 23, range correction unit 24, frequency correction processing unit 25, and spectrum accumulation unit 26.

[0372] In the absence of a range bin segmentation unit 22, a frequency resolution unit 23, a range correction unit 24, a frequency correction processing unit 25, and a spectrum accumulation unit 26 in the optical frequency correction unit 21, the peak frequency detection unit 27 performs FFT processing on each detected signal D1 and D2 to obtain the spectrum of each detected signal D1 and D2. Then, the peak frequency detection unit 27 determines the spectrum intensity FS above a threshold among the multiple spectrum intensities contained in each spectrum. max1 FS max2 The peak frequency detection unit 27 will correspond to the spectral intensity FS. max1 peak frequency f peak1 and corresponding to the spectral intensity FS max2 peak frequency f peak2 The output is sent to the frequency calculation and processing unit 28.

[0373] Implementation method 2.

[0374] In Embodiment 2, the following lidar device will be described: the pulse modulator 5 includes an optical branching section 5a, a first modulation section 5b, a second modulation section 5c, and an optical wave combining section 5d.

[0375] The structure of the lidar device in Embodiment 2 is the same as that of the lidar device in Embodiment 1. Figure 1 This is a structural diagram showing the lidar device according to Embodiment 2.

[0376] Figure 13 This is a structural diagram showing the pulse modulator 5 of the lidar device according to Embodiment 2.

[0377] Figure 13 The pulse modulator 5 shown includes an optical branching section 5a, a first modulation section 5b, a second modulation section 5c, and an optical wave combining section 5d.

[0378] The optical branch 5a is implemented by a coupler or an optical switch, etc.

[0379] The optical branching section 5a splits the laser output from the optical splitting section 3 into two parts, outputs one of the split laser parts to the first modulation section 5b, and outputs the other split laser part to the second modulation section 5c.

[0380] Figure 13 The optical branch 5a shown splits the laser output from the optical splitter 3 into two parts. However, this is just one example; the optical branch 5a could also be a switch that alternately switches the output destination of the laser output from the optical splitter 3 to the first modulation section 5b or the second modulation section 5c.

[0381] The first modulation unit 5b is implemented, for example, by a modulation element using acousto-optical elements or a modulation element using lithium niobate crystals, and an optical amplifier such as a semiconductor optical amplifier.

[0382] Each time the first modulation unit 5b receives a pulse signal with a pulse width ΔT from the pulse signal generation unit 4a, it performs pulse modulation on the laser output from the optical branch unit 5a according to the pulse signal, thereby converting the laser into pulse light with a pulse width ΔT.

[0383] Furthermore, the first modulation unit 5b shifts the optical frequency f0 of the pulsed light to the optical frequency f0+f according to the first frequency shift signal output from the switch 4e of the trigger generation unit 4. IF1 This generates an optical frequency f0+f IF1 Pulse light P1.

[0384] The first modulation unit 5b outputs pulsed light P1 to the light combining unit 5d.

[0385] The second modulation unit 5c is implemented, for example, by a modulation element using acousto-optical elements or a modulation element using lithium niobate crystals, and an optical amplifier such as a semiconductor optical amplifier.

[0386] When the second modulation unit 5c receives a pulse signal with a pulse width ΔT from the pulse signal generation unit 4a each time, it performs pulse modulation on the laser output from the optical branch unit 5a according to the pulse signal, thereby converting the laser into pulse light with a pulse width ΔT.

[0387] Furthermore, the second modulation unit 5c shifts the light frequency f0 of the pulsed light to the light frequency f0+f according to the second frequency shift signal output from the switch 4e of the trigger generation unit 4. IF2 Thus, an optical frequency f0+f is generated. IF2 Pulsed light P2.

[0388] The second modulation unit 5c outputs the pulsed light P2 to the light combining unit 5d.

[0389] When the optical wave combining unit 5d receives the pulsed light P1 from the first modulation unit 5b, it outputs the pulsed light P1 to the transmitting side optical system 7.

[0390] When the optical wave combining unit 5d receives the pulsed light P2 from the second modulation unit 5c, it outputs the pulsed light P2 to the transmitting side optical system 7.

[0391] Next, the operation of the lidar device in Embodiment 2 will be explained. (The pulse modulator 5 and...) Figure 1 Since the lidar device shown is the same, the operation of the pulse modulator 5 will be mainly explained here.

[0392] When the light branching section 5a receives laser light as continuous light from the light splitting section 3, it splits the laser light into two parts.

[0393] The optical branching section 5a outputs one of the laser beams after it has been split into two parts to the first modulation section 5b, and outputs the other of the laser beams after it has been split into two parts to the second modulation section 5c.

[0394] Each time the first modulation unit 5b receives a pulse signal with a pulse width ΔT from the pulse signal generation unit 4a, it performs pulse modulation on the laser output from the optical branch unit 5a according to the pulse signal, thereby converting the laser into pulse light with a pulse width ΔT.

[0395] When the first modulation unit 5b receives the first frequency shift signal from the switch 4e of the trigger generation unit 4, it shifts the optical frequency f0 of the pulsed light to the optical frequency f0+f according to the first frequency shift signal. IF1 This generates an optical frequency f0+f IF1 Pulse light P1.

[0396] The first modulation unit 5b outputs pulsed light P1 to the light combining unit 5d.

[0397] When the second modulation unit 5c receives a pulse signal with a pulse width ΔT from the pulse signal generation unit 4a each time, it performs pulse modulation on the laser output from the optical branch unit 5a according to the pulse signal, thereby converting the laser into pulse light with a pulse width ΔT.

[0398] When the time interval Trep e e has elapsed since the first frequency shift signal was output to the first modulation unit 5b, the switch 4e of the trigger generation unit 4 outputs the second frequency shift signal to the second modulation unit 5c.

[0399] When the second modulation unit 5c receives the second frequency shift signal from the switch 4e of the trigger generation unit 4, it shifts the optical frequency f0 of the pulse light to the optical frequency f0+f according to the second frequency shift signal. IF2 Thus, an optical frequency f0+f is generated. IF2 Pulsed light P2.

[0400] The second modulation unit 5c outputs the pulsed light P2 to the light combining unit 5d.

[0401] When the optical wave combining unit 5d receives the pulsed light P1 from the first modulation unit 5b, it outputs the pulsed light P1 to the transmitting side optical system 7.

[0402] After receiving pulsed light P1 from the first modulation unit 5b, the optical wave combining unit 5d receives pulsed light P2 from the second modulation unit 5c after a period of Trep, and then outputs pulsed light P2 to the transmitting side optical system 7.

[0403] The pulse modulator 5 includes a lidar device comprising an optical branch section 5a, a first modulation section 5b, a second modulation section 5c, and an optical wave combining section 5d. Figure 1 Similarly, the lidar device shown can calculate the movement speed of each object, even when the distant scattered light overlaps with the nearby scattered light, regardless of whether the movement speed of the distant observed object is the same as that of the nearby observed object.

[0404] Implementation method 3.

[0405] In Embodiment 3, a lidar device equipped with a scanner 61 and a switching speed control unit 62 will be described.

[0406] Figure 14 This is a structural diagram showing the lidar device according to Embodiment 3. Figure 14 In, with Figure 1 The same labels indicate the same or equivalent parts, so the description is omitted.

[0407] Scanner 61 switches the radiation direction of each pulse of light P1, P2 radiated from telescope 9 of transceiver unit 6.

[0408] That is, the scanner 61 scans the scanning range of each pulse light P1, P2 by scanning the optical axis of each pulse light P1, P2 radiated from the telescope 9 in time.

[0409] The switching speed control unit 62 controls the switching speed of the radiation direction of the scanner 61.

[0410] That is, the switching speed control unit 62 controls the switching speed according to the repetition frequency of pulse light P1 and pulse light P2, so that each pulse light P1 and P2 radiated by the transceiver unit 6 meets the eye safety conditions.

[0411] Next, regarding Figure 14 The operation of the lidar device shown will be explained. Except for the scanner 61 and the switching speed control unit 62, [the following is an explanation of the operation of the lidar device shown]. Figure 1Since the lidar device shown is the same, only the operation of the scanner 61 and the switching speed control unit 62 will be described here.

[0412] Figure 14 The lidar device shown limits the power of each pulse light P1 and P2 and the scanning speed of each pulse light P1 and P2 while radiating each pulse light P1 and P2, so as to meet the eye safety requirements.

[0413] Therefore, if shortening from Figure 14 The laser period Trep emitted by the lidar device shown can accelerate the scanning speed V of the scanning range of each pulse P1 and P2. scan On the other hand, if growth comes from... Figure 14 The laser period Trep emitted by the lidar device shown requires slowing down the scanning speed V of each pulse P1 and P2. scan .

[0414] As an indicator for determining whether a lidar device meets eye safety requirements, the achievable emission limit (AEL) of the pulsed laser is sometimes used (see, for example, non-patent literature 1).

[0415] [Non-patent literature 1]

[0416] "Razer Safety Guidebook", edited by the Optical Industry Technology Promotion Association, 2006, New Technology Newsletter Publication.

[0417] from Figure 14 The wavelengths of the pulsed light P1 and P2 emitted by the lidar device shown are, for example, in the 1.5μm band.

[0418] In the case of pulsed laser with a wavelength of 1.5 μm, the exposure for a single pulse is 8 × 10⁻⁶. -3 [J].

[0419] When scanning the emitted pulsed laser with a duration of less than 3 seconds and a wavelength of 1.5 μm, the time reference T is defined by the time it takes to cross a circular aperture stop with a diameter of Φ 1 [mm].

[0420] The time base T is expressed as shown in equation (5) below.

[0421]

[0422] The total number of pulses of pulsed laser contained in the time base T is represented by Total = frep × T. frep = 1 / Trep.

[0423] Furthermore, as shown in Equation (6) below, the energy of each pulse, Epulse = Power × Trep, cannot exceed the achievable emission limit AELs for a single pulse, multiplied by a correction factor K that depends on the total number of pulses, Total. The correction factor K is a known value.

[0424] Epulse < AELs×K (6)

[0425] Therefore, in order to make from Figure 14 The laser radar device shown radiates pulses P1 and P2 that meet eye safety requirements, and the repetition frequency frep and scanning speed V... scan The following relation (7) must be satisfied.

[0426]

[0427] The switching speed control unit 62 acquires frequency information representing the repetition frequency frep, substitutes the repetition frequency frep and correction coefficient K represented by the frequency information into the relation (7), and calculates the scanning speed V that meets the eye safety conditions. scan .

[0428] The switching speed control unit 62 generates a value for achieving the scanning speed V. scan The scanner drive signal is output to the scanner 61.

[0429] If from Figure 14 If the repetition frequency frep of the pulsed light radiated by the lidar device shown decreases, the switching speed control unit 62 generates a speed V to accelerate the scanning speed. scan The scanner drive signal.

[0430] If from Figure 14 If the repetition frequency frep of the pulsed light radiated by the lidar device shown increases, the switching speed control unit 62 generates a V to slow down the scanning speed. scan The scanner drive signal.

[0431] The scanning speed V of scanner 61 scan It is controlled by the scanner drive signal output from the switching speed control unit 62.

[0432] Scanner 61 at scanning speed V scan Switch the radiation direction of each pulse light P1 and P2 radiated from the telescope 9 of the transceiver unit 6.

[0433] In the above implementation method 3, Figure 14The lidar device shown is configured to include: a scanner 61 that switches the radiation direction of pulsed light radiated from the transceiver unit 6; and a switching speed control unit 62 that controls the switching speed of the radiation direction of the scanner 61 based on the repetition frequency of the pulsed light, so that the pulsed light radiated from the transceiver unit 6 meets eye safety requirements. Therefore, Figure 14 The lidar device shown is Figure 1 Similarly, the lidar device shown can calculate the movement speed of each observed object, even when distant and nearby scattered light overlap, regardless of whether the movement speed of the distant observed object is the same as that of the nearby observed object. Furthermore, Figure 14 The lidar device shown can switch the radiation direction of the pulsed light while ensuring that the pulsed light meets the safety requirements for the eyes.

[0434] Implementation method 4.

[0435] In Embodiment 4, a lidar device that observes a gas and is equipped with a light source 71 will be described. The light source 71 sequentially outputs a first laser and a second laser having wavelengths included in the absorption band of the gas. The absorption rate of the gas to the second laser is lower than that to the first laser.

[0436] In Embodiment 4, it is assumed that a gas that is the object of observation (hereinafter referred to as "object of observation gas") exists in the air in which the lidar device is installed. However, this is only one example. It is also possible that the object of observation gas does not exist in the air in which the lidar device is installed, but exists in other spaces such as through a window.

[0437] The gas being observed corresponds, for example, to the constituent molecules of the atmosphere. Atmospheric molecules are nitrogen, oxygen, carbon dioxide, or water vapor. Atmospheric molecules also include air pollutants such as nitrogen oxides (NOx). In a lidar device, the absorption band of the gas is known. The observed gas includes scatterers. These scatterers correspond to clouds, smoke, dust, aerosols, or raindrops, etc.

[0438] The signal processing apparatus 15 in Embodiment 4 includes a density calculation unit 72, which calculates the density of the gas based on the frequency of the detection signal when the light source 71 outputs the first laser and the frequency of the detection signal when the light source 71 outputs the second laser.

[0439] Figure 15 This is a structural diagram showing a lidar device including the signal processing apparatus 15 of embodiment 4. Figure 15 In, with Figure 1 The same labels indicate the same or equivalent parts, so the description is omitted.

[0440] Figure 16 This is a structural diagram showing the signal processing device 15 of Embodiment 4. Figure 17 This is a hardware structure diagram showing the hardware of the signal processing device 15 in Embodiment 4.

[0441] exist Figure 16 and Figure 17 In, with Figure 3 and Figure 4 The same labels indicate the same or equivalent parts, so the description is omitted.

[0442] The light source 71 is, for example, a laser that emits a single frequency of laser light, and is implemented by a semiconductor laser, fiber laser, or solid-state laser with a linewidth of less than a few MHz in the emission spectrum. Alternatively, the light source 71 is implemented by a combination of one or more lasers selected from semiconductor lasers, fiber lasers, and solid-state lasers.

[0443] The light source 71 sequentially outputs a first laser with a wavelength contained in the absorption band of the gas and a second laser with a lower absorption rate in the gas to the light splitting section 3 of the pulse modulation section 2.

[0444] Density calculation unit 72, for example, is composed of Figure 17 The density calculation circuit 81 shown is implemented.

[0445] When the first laser is output from the light source 71, the density calculation unit 72 analyzes the frequencies of each detection signal D1 to D4 output from the optical detector 11. When the second laser is output from the light source 71, the density calculation unit 72 analyzes the frequencies of each detection signal D1 to D4 output from the optical detector 11.

[0446] The density calculation unit 72 calculates the density density density of the gas based on the analysis results of each frequency.

[0447] exist Figure 16 In this context, it is assumed that the Doppler frequency calculation unit 16, velocity calculation unit 17, SNR calculation unit 30, distance characteristic calculation unit 31, and density calculation unit 72, which are structural elements of the signal processing device 15, are respectively composed of... Figure 17 The dedicated hardware implementation shown is as follows. That is, it is assumed that the signal processing device 15 is implemented by a Doppler frequency calculation circuit 41, a velocity calculation circuit 42, an SNR calculation circuit 43, a distance characteristic calculation circuit 44, and a density calculation circuit 81.

[0448] The Doppler frequency calculation circuit 41, the velocity calculation circuit 42, the SNR calculation circuit 43, the distance characteristic calculation circuit 44, and the density calculation circuit 81 correspond, for example, to a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0449] The structural elements of the signal processing device 15 are not limited to being implemented by dedicated hardware; the signal processing device 15 can also be implemented by software, firmware, or a combination of software and firmware.

[0450] When the signal processing device 15 is implemented by software or firmware, the program for causing the computer to execute each processing step in the Doppler frequency calculation unit 16, velocity calculation unit 17, SNR calculation unit 30, distance characteristic calculation unit 31, and density calculation unit 72 is stored in the memory. Figure 5 In the memory 51 shown. Furthermore, Figure 5 The processor 52 shown executes the program stored in the memory 51.

[0451] In addition, Figure 17 The diagram shows an example where the structural elements of the signal processing device 15 are implemented by dedicated hardware. Figure 5 The diagram shows an example of the signal processing device 15 being implemented by software or firmware. However, this is only one example; it is also possible that some structural elements of the signal processing device 15 are implemented by dedicated hardware, while the remaining structural elements are implemented by software or firmware.

[0452] right Figure 15 The operation of the lidar device shown will be explained. (Except for the light source 71 and density calculation unit 72, etc.) Figure 1 Since the lidar device shown is the same, the operation of the light source 71 and the density calculation unit 72 will be mainly explained here.

[0453] First, the light source 71 outputs a first laser beam with a wavelength contained in the absorption band of the gas to the light splitting section 3 of the pulse modulation section 2. The first laser beam output from the light source 71 has an optical frequency of f. 0A .

[0454] When the first laser beam is output from the light source 71, the optical detector 11, in the same manner as in Embodiment 1, detects the combined beam of each scattered light R1, R2, R3, R4 received by the transceiver 6 and the reference light that serves as the laser beam output from the light source 1.

[0455] Here, for ease of explanation, such as C 1A C 2A C 3A C 4A That is to describe the combined light detected by the optical detector 11.

[0456] The optical detector 11 combines the various wavelengths of light C 1A C 2A C 3A C 4A The detection signal D 1A D2A D 3A D 4A The signal is output to the signal processing device 15.

[0457] The distance compartment segmentation unit 22, frequency analysis unit 23, distance correction unit 24, frequency correction processing unit 25, and spectrum accumulation unit 26 operate in the same manner as in Embodiment 1.

[0458] The spectrum accumulation unit 26 outputs the accumulated spectrum to the density calculation unit 72.

[0459] For ease of explanation, here, such as ΣHFS A That is to describe the accumulated spectrum output from the spectrum accumulation unit 26.

[0460] Next, the light source 71 outputs a second laser beam, whose absorptivity in the gas is lower than that of the first laser beam, to the light splitting section 3 of the pulse modulation section 2. The second laser beam output from the light source 71 has an optical frequency of f. 0B .

[0461] Figure 18 This is an explanatory diagram showing the absorption band of the gas, the wavelength of the first laser emitted from the light source 71, and the wavelength of the second laser emitted from the light source 71.

[0462] exist Figure 18 In the diagram, the horizontal axis represents wavelength, and the vertical axis represents the transmittance of the laser relative to the gas.

[0463] The dashed line represents the first laser beam output from light source 71, and the dotted-dash line represents the second laser beam output from light source 71. The solid line represents the absorption band of the gas. The first wavelength is included in the absorption band of the gas, while the second wavelength is not. The transmittance of the second wavelength in the gas is greater than that of the first wavelength. That is, the absorptivity of the second wavelength in the gas is less than that of the first wavelength.

[0464] When the second laser is output from the light source 71, the optical detector 11, in the same manner as in Embodiment 1, detects the combined light of each scattered light R1, R2, R3, R4 received by the transceiver 6 and the reference light of the laser output from the light source 1.

[0465] Here, for ease of explanation, such as C 1B C 2B C 3B C 4B That is to describe the combined light detected by the optical detector 11.

[0466] The optical detector 11 combines the various wavelengths of light C 1B C 2B C 3B C 4BThe detector signal D 1B D 2B D 3B D 4B The signal is output to the signal processing device 15.

[0467] When the first laser beam is output from the light source 71, the density calculation unit 72 calculates each detection signal D output from the optical detector 11. 1A ~D 4A The frequencies of the detection signals D1 to D4 output from the optical detector 11 are analyzed when the second laser is output from the light source 71.

[0468] The density calculation unit 72 calculates the density density density of the gas based on the analysis results of each frequency.

[0469] The following is a detailed explanation of the density calculation process of the density calculation unit 72.

[0470] The density calculation unit 72 obtains the various spectral intensities FS when the first laser beam is output from the light source 71 from the optical frequency correction unit 21. max1 FS max2 For ease of explanation, here, such as FS... max1A (n 1A ),FS max2A (n 2A The intensity of each spectrum obtained by the density calculation unit 72 is expressed in that manner. 1A Indicates spectral intensity FS max1A The distance of the warehouse, n 2A Indicates spectral intensity FS max2A The distance to the warehouse.

[0471] Furthermore, the density calculation unit 72 obtains the spectral intensity FS when the second laser beam is output from the light source 71 from the optical frequency correction unit 21. max1 FS max2 For ease of explanation, here, such as FS... max1B (n 1B ),FS max2B (n 2B The intensity of each spectrum obtained by the density calculation unit 72 is expressed in that manner. 1B Indicates spectral intensity FS max1B The distance of the warehouse, n 2B Indicates spectral intensity FS max2B The distance to the warehouse.

[0472] exist Figure 16 In the signal processing device 15 shown, the density calculation unit 72 obtains the spectral intensity FS from the optical frequency correction unit 21. max1A (n 1A ),FS max2A(n 2A ),FS max1B (n 1B ),FS max2B (n 2B However, this is just one example. If the density calculation unit 72 has the same optical frequency correction unit as the optical frequency correction unit 21, then the spectral intensity FS can also be obtained from that optical frequency correction unit. max1A (n 1A ),FS max2A (n 2A ),FS max1B (n 1B ),FS max2B (n 2B ).

[0473] Density calculation unit 72 calculates the spectral intensity FS max1A (n 1A ),FS max2A (n 2A ),FS max1B (n 1B ),FS max2B (n 2B Substitute into the following equation (8) to calculate the density density of the gas.

[0474]

[0475] In equation (8), k ON is the absorption coefficient of the first laser at its wavelength, and it is a coefficient with a known value. k OFF is the absorption coefficient of the second laser at its wavelength, and is a coefficient with a known value. ln is the mathematical symbol for a logarithmic function with base e.

[0476] In the above-described embodiment 4, the object of observation is a gas, and the light source 71 sequentially outputs a first laser and a second laser. The first laser has a wavelength contained in the absorption band of the gas, and the gas's absorption rate of the second laser is lower than its absorption rate of the first laser. Figure 15 The lidar device shown is configured to include a density calculation unit 72. This unit 72 analyzes the frequencies of each detection signal output from the optical detector 11 when a first laser beam is emitted from the light source 71, and analyzes the frequencies of each detection signal output from the optical detector 11 when a second laser beam is emitted from the light source 71. Based on the analysis results of each frequency, it calculates the density of the gas. Therefore, Figure 15 The lidar device shown is Figure 1Similarly, the lidar device shown can calculate the movement speed of each observed object, even when distant and nearby scattered light overlap, regardless of whether the movement speed of the distant observed object is the same as that of the nearby observed object. Furthermore, Figure 15 The lidar device shown can calculate the density of the gas being observed.

[0477] Furthermore, this disclosure allows for free combination of various embodiments or modification of any structural elements of each embodiment, or allows for the omission of any structural elements in each embodiment.

[0478] Industrial availability

[0479] This disclosure is applicable to signal processing apparatus, signal processing methods, and lidar devices.

[0480] Explanation of reference numerals in the attached figures

[0481] 1. Light source, 2. Pulse modulation unit, 3. Optical splitter, 4. Trigger generation unit, 4a. Pulse signal generation unit, 4b. Reference signal generation unit, 4c. First frequency shift signal generation unit, 4d. Second frequency shift signal generation unit, 4e. Switch, 5. Pulse modulator, 5a. Optical splitter, 5b. First modulation unit, 5c. Second modulation unit, 5d. Optical combiner, 6. Transceiver unit, 7. Transmitter-side optical system, 8. Transceiver splitter, 9. Telescope, 10. Receiver-side optical system, 11. Optical detector, 12. Optical combiner, 13. Light receiving unit, 14. A / D converter, 15. Signal processing device, 16. Doppler frequency calculation unit, 17. Speed 21 Optical frequency correction unit, 22 Distance compartment segmentation unit, 23 Frequency resolution unit, 24 Distance correction unit, 25 Frequency correction processing unit, 26 Spectrum accumulation unit, 27 Peak frequency detection unit, 28 Frequency calculation processing unit, 29 Velocity calculation processing unit, 30 SNR calculation unit, 31 Distance characteristic calculation unit, 41 Doppler frequency calculation circuit, 42 Velocity calculation circuit, 43 SNR calculation circuit, 44 Distance characteristic calculation circuit, 51 Memory, 52 Processor, 61 Scanner, 62 Switching speed control unit, 71 Light source, 72 Density calculation unit, 81 Density calculation circuit.

Claims

1. A signal processing device that calculates the relative velocities of multiple observed objects in space relative to a lidar device, as the moving speeds of each observed object, wherein, The system generates multiple pulses of light with different frequencies from the laser light emitted from the light source, radiates these pulses into space, and receives the scattered pulses from various observed objects as scattered light. The combined beam of these scattered pulses and the laser light is then detected. The signal processing device includes: The Doppler frequency calculation unit calculates the Doppler frequencies associated with the movement of each observed object; and The velocity calculation unit calculates the relative velocity of each observed object based on the various Doppler frequencies calculated by the Doppler frequency calculation unit. The Doppler frequency calculation unit includes: An optical frequency correction unit corrects the optical frequency of each combined light beam based on the frequency difference between the optical frequency of one of the generated multiple pulses and the optical frequencies of the remaining pulses; and The frequency calculation and processing unit calculates the Doppler frequency contained in the optical frequency of each scattered light based on the optical frequency of each combined light after being corrected by the optical frequency correction unit and the optical frequency of each generated pulse light. The optical frequency correction unit includes a distance bin segmentation unit, a frequency resolution unit, a distance correction unit, a frequency correction processing unit, a spectrum accumulation unit, and a peak frequency detection unit. The distance cell segmentation unit is used to divide the digital signal corresponding to each combined beam into multiple distance cell signals in the time direction; The frequency analysis unit is used to perform fast Fourier transform processing on each range cell signal and calculate the spectrum of each range cell signal; The distance correction unit is used to obtain the spectrum of each distance chamber signal from the frequency analysis unit, obtain the first frequency shift signal and the second frequency shift signal from the trigger generation unit, detect multiple peak spectra corresponding to the number of multiple pulse lights from each spectrum, calculate the peak frequency of each peak spectrum, calculate the absolute value of the difference between each peak frequency and the modulation frequency represented by the first frequency shift signal and the absolute value of the difference between each peak frequency and the modulation frequency represented by the second frequency shift signal, and if the absolute value of the difference between the peak frequency and the modulation frequency represented by the first frequency shift signal is less than or equal to the absolute value of the difference between the peak frequency and the modulation frequency represented by the second frequency shift signal, determine that the combined light with the peak spectrum corresponding to the peak frequency is the combined light corresponding to one of the multiple pulse lights, and correct the distance chambers with scattered light related to the combined light; The frequency correction processing unit is used to obtain from the distance correction unit the spectrum of the distance chamber with scattered light associated with the combined beam and the corrected spectrum of the distance chamber with scattered light associated with the combined beam, and to obtain the optical frequency of each combined beam after distance chamber correction from the distance correction unit, and to correct the optical frequency of each combined beam by subtracting the frequency difference from the optical frequency of each combined beam after distance chamber correction. The spectrum accumulation unit is used to accumulate the spectrum of each combined light beam after optical frequency correction. The peak frequency detection unit is used to obtain the accumulated spectrum from the spectrum accumulation unit, and determine the spectrum intensity above the threshold among the multiple spectrum intensities contained in the accumulated spectrum. The frequency calculation processing unit is used to obtain the peak frequency corresponding to the spectral intensity above each threshold from the peak frequency detection unit, and to obtain the first frequency shift signal and the second frequency shift signal from the trigger generation unit. The unit calculates the Doppler frequency contained in the optical frequency of the combined light by subtracting the modulation frequency represented by the first frequency shift signal or the modulation frequency represented by the second frequency shift signal from each peak frequency.

2. A signal processing method that calculates the relative velocities of multiple observed objects in space relative to a lidar device, as the moving speeds of each observed object, wherein, Multiple pulses of light with different frequencies are generated from the laser emitted from the light source, and these pulses are radiated into space. The scattered pulses from various observed objects are collected as scattered light, and the combined light of the scattered light and the laser is detected. The optical frequency correction unit of the Doppler frequency calculation unit divides the digital signal corresponding to each combined beam into multiple range cell signals in the time direction; The frequency analysis unit of the optical frequency correction unit of the Doppler frequency calculation unit performs fast Fourier transform processing on the signals of each range cell to calculate the spectrum of the signals of each range cell. The distance correction unit of the optical frequency correction unit of the Doppler frequency calculation unit obtains the spectrum of each distance chamber signal from the frequency analysis unit, obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit, detects multiple peak spectra corresponding to the number of multiple pulses from each spectrum, calculates the peak frequency of each peak spectrum, calculates the absolute value of the difference between each peak frequency and the modulation frequency represented by the first frequency shift signal and the absolute value of the difference between each peak frequency and the modulation frequency represented by the second frequency shift signal, and if the absolute value of the difference between the peak frequency and the modulation frequency represented by the first frequency shift signal is less than or equal to the absolute value of the difference between the peak frequency and the modulation frequency represented by the second frequency shift signal, it determines that the combined light with the peak spectrum corresponding to the peak frequency is the combined light corresponding to one of the multiple pulses, and corrects the distance chambers with scattered light related to the combined light; The frequency correction processing unit of the optical frequency correction unit of the Doppler frequency calculation unit obtains the spectrum of the range cell with scattered light associated with the combined beam and the corrected spectrum of the range cell with scattered light associated with the combined beam from the range correction unit, and obtains the optical frequency of each combined beam after range cell correction from the range correction unit, and corrects the optical frequency of each combined beam by subtracting the frequency difference between the optical frequency of one of the multiple pulse beams and the optical frequencies of the remaining pulse beams from the optical frequency of each combined beam after range cell correction; The spectrum accumulation unit of the optical frequency correction unit of the Doppler frequency calculation unit accumulates the spectrum of each combined wave after optical frequency correction; The peak frequency detection unit of the optical frequency correction unit of the Doppler frequency calculation unit obtains the accumulated spectrum from the spectrum accumulation unit, and determines the spectrum intensity above the threshold among the multiple spectrum intensities contained in the accumulated spectrum. The frequency calculation processing unit of the Doppler frequency calculation unit obtains the peak frequencies corresponding to the spectral intensities above each threshold from the peak frequency detection unit, and obtains the first frequency shift signal and the second frequency shift signal from the trigger generation unit. It then calculates the Doppler frequency contained in the optical frequency of the combined light by subtracting the modulation frequency represented by the first frequency shift signal or the modulation frequency represented by the second frequency shift signal from each peak frequency. The velocity calculation unit calculates the relative velocity of each observed object based on the Doppler frequencies calculated by the Doppler frequency calculation unit.

3. A lidar device that calculates the relative velocities of multiple objects existing in space relative to the lidar device, as the moving speeds of each object, wherein... The lidar device includes: The light source outputs laser light; The pulse modulation unit generates multiple pulses of light with different frequencies based on the laser light output from the light source; The transceiver unit radiates pulses of light generated by the pulse modulation unit into space and receives pulses of light scattered by various observed objects as scattered light. The optical detector detects the combined light of each scattered light received by the transceiver and the laser light output from the light source, and outputs the detection signal of each combined light. The Doppler frequency calculation unit calculates the Doppler frequencies associated with the movement of each observed object; as well as The velocity calculation unit calculates the relative velocity of each observed object based on the various Doppler frequencies calculated by the Doppler frequency calculation unit. The Doppler frequency calculation unit includes: An optical frequency correction unit corrects the optical frequency of each combined light beam based on the frequency difference between the optical frequency of one of the generated multiple pulses and the optical frequencies of the remaining pulses; and The frequency calculation and processing unit calculates the Doppler frequency contained in the optical frequency of each scattered light based on the optical frequency of each combined light after being corrected by the optical frequency correction unit and the optical frequency of each generated pulse light. The optical frequency correction unit includes a distance bin segmentation unit, a frequency resolution unit, a distance correction unit, a frequency correction processing unit, a spectrum accumulation unit, and a peak frequency detection unit. The distance cell segmentation unit is used to divide the digital signal corresponding to each combined beam into multiple distance cell signals in the time direction; The frequency analysis unit is used to perform fast Fourier transform processing on each range cell signal and calculate the spectrum of each range cell signal; The distance correction unit is used to obtain the spectrum of each distance chamber signal from the frequency analysis unit, obtain the first frequency shift signal and the second frequency shift signal from the trigger generation unit, detect multiple peak spectra corresponding to the number of multiple pulse lights from each spectrum, calculate the peak frequency of each peak spectrum, calculate the absolute value of the difference between each peak frequency and the modulation frequency represented by the first frequency shift signal and the absolute value of the difference between each peak frequency and the modulation frequency represented by the second frequency shift signal, and if the absolute value of the difference between the peak frequency and the modulation frequency represented by the first frequency shift signal is less than or equal to the absolute value of the difference between the peak frequency and the modulation frequency represented by the second frequency shift signal, determine that the combined light with the peak spectrum corresponding to the peak frequency is the combined light corresponding to one of the multiple pulse lights, and correct the distance chambers with scattered light related to the combined light; The frequency correction processing unit is used to obtain from the distance correction unit the spectrum of the distance chamber with scattered light associated with the combined beam and the corrected spectrum of the distance chamber with scattered light associated with the combined beam, and to obtain the optical frequency of each combined beam after distance chamber correction from the distance correction unit, and to correct the optical frequency of each combined beam by subtracting the frequency difference from the optical frequency of each combined beam after distance chamber correction. The spectrum accumulation unit is used to accumulate the spectrum of each combined light beam after optical frequency correction. The peak frequency detection unit is used to obtain the accumulated spectrum from the spectrum accumulation unit, and determine the spectrum intensity above the threshold among the multiple spectrum intensities contained in the accumulated spectrum. The frequency calculation processing unit is used to obtain the peak frequency corresponding to the spectral intensity above each threshold from the peak frequency detection unit, and to obtain the first frequency shift signal and the second frequency shift signal from the trigger generation unit. The unit calculates the Doppler frequency contained in the optical frequency of the combined light by subtracting the modulation frequency represented by the first frequency shift signal or the modulation frequency represented by the second frequency shift signal from each peak frequency.

4. The lidar device according to claim 3, characterized in that, The lidar device includes: A scanner that switches the radiation direction of the pulsed light radiated from the transceiver; and The switching speed control unit controls the switching speed of the scanner's radiation direction.

5. The lidar device according to claim 4, characterized in that, The switching speed control unit controls the switching speed based on the repetition frequency of the pulse light radiated from the transceiver unit, so that the pulse light radiated from the transceiver unit meets the eye safety requirements.

6. The lidar device according to claim 3, characterized in that, The object of observation is a gas. The light source sequentially outputs a first laser and a second laser to the pulse modulation unit. The first laser has a wavelength contained in the absorption band of the gas, and the gas has a lower absorption rate of the second laser than that of the first laser.

7. The lidar device according to claim 6, characterized in that, The lidar device includes a density calculation unit. When the first laser is output from the light source, the density calculation unit analyzes the frequency of each detection signal output from the optical detector. When the second laser is output from the light source, the density calculation unit analyzes the frequency of each detection signal output from the optical detector. The density of the gas is calculated based on the analysis results of each frequency.

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