Resampling frequency modulation continuous wave system capable of simultaneously measuring distance and speed

Abstract

The invention discloses a resampling frequency-modulated continuous wave system capable of simultaneously measuring distance and speed. The resampling frequency-modulated continuous wave system comprises a first laser used for outputting frequency-modulated continuous waves, a second laser used for outputting continuous waves and a data processing module, a laser beam emitted by the first laser can be divided into two beams, one beam enters a reference interference light path, the other beam enters a distance measurement interference light path, and a laser beam emitted by the second laser enters a speed measurement interference light path; and the data processing module can acquire beat frequency signals output by the reference interference light path, the distance measurement interference light path and the speed measurement interference light path, and can perform speed compensation analysis and resampling spectrum analysis based on beat frequency signal data. According to the system, Doppler frequency shift caused by object movement is compensated through signal processing, so that the position information of a moving object can be accurately obtained, and the limitation that only a static object can be measured by a resampling technology is effectively overcome.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radar, and in particular relates to a resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed. Background Art

[0002] Frequency-Modulated Continuous Wave (FMCW) LiDAR is a solution for LiDAR. It has the advantages of high accuracy, wide measurement range, high resolution, and easy automation. It is regarded as one of the future development directions of vehicle-mounted LiDAR. The linear swept laser light source is a key component of FMCW LiDAR. Its coherence length and swept bandwidth determine the maximum distance and spatial resolution that the LiDAR can measure, respectively. However, in practical applications, the frequency modulation of the laser light source cannot be completely linear, that is, the frequency of the laser and the voltage input to the laser cannot be completely linear, which leads to a serious decrease in the measurement accuracy of the FMCW LiDAR technical solution.

[0003] In the prior art, the problem of nonlinear frequency modulation of laser light sources can be effectively solved by resampling technology. The resampling technology introduces a fiber reference interferometer into the measurement system. Since the measurement interferometer and the reference interferometer have the same light source, the nonlinear problem of laser frequency modulation has the same impact on the two beat frequency signals. Therefore, by sampling the interference signal obtained by the measurement interferometer at equal optical frequency intervals, the nonlinear effect can be eliminated.

[0004] At present, resampling to solve the nonlinear problem of laser frequency modulation can only be used to measure stationary objects. When the measured object is moving, the FMCW laser radar distance-velocity coupling phenomenon will occur, that is, the beat frequency signal of the measuring arm contains the Doppler frequency corresponding to the velocity, which will cause a great error in the ranging accuracy. Therefore, resampling not only does not improve the measurement accuracy, but also widens the spectrum, which has certain limitations.

[0005] Therefore, in view of the above technical problems, it is necessary to provide a resampled frequency modulated continuous wave system that can measure distance and speed simultaneously. Summary of the invention

[0006] The object of the present invention is to provide a resampling frequency modulated continuous wave system that can measure distance and speed simultaneously, which can solve the problem that the resampling can only be used to measure stationary objects and has poor measurement accuracy for moving objects.

[0007] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0008] A resampling frequency modulated continuous wave system capable of simultaneously measuring distance and speed, comprising a first laser for outputting frequency modulated continuous waves, a second laser for outputting continuous waves, and a data processing module;

[0009] The laser beam emitted by the first laser can be divided into two beams, one of which enters the reference interference optical path, and the other enters the distance measurement interference optical path, and the laser beam emitted by the second laser enters the speed measurement interference optical path;

[0010] The data processing module can obtain the beat frequency signals output by the reference interference optical path, the distance measurement interference optical path and the speed measurement interference optical path, and can perform speed compensation analysis and resampled spectrum analysis based on the beat frequency signal data.

[0011] In one or more embodiments of the present invention, the ranging interference optical path includes two sub-ranging interference optical paths, and the speed measurement interference optical path includes two sub-speed measurement interference optical paths. The laser light beam in one of the sub-ranging interference optical paths can be combined with the laser light beam in one of the sub-speed measurement interference optical paths to form a composite light. The composite light can be decomposed after being reflected by a moving object and form corresponding beat frequency signals respectively.

[0012] In one or more embodiments of the present invention, the system further comprises a multiplexer, a demultiplexer, a circulator and a collimator, wherein the laser beam in one of the sub-range-measuring interferometric optical paths can be combined with the laser beam in one of the sub-speed-measuring interferometric optical paths through the multiplexer to form the composite light;

[0013] The composite light passes through the circulator and the collimator in sequence and reaches the moving object, and then returns to the demultiplexer through the moving object. The demultiplexer can decompose laser beams of different frequencies.

[0014] In one or more embodiments of the present invention, the system further comprises a first balanced detector, a second balanced detector and a third balanced detector;

[0015] The laser in the reference interference optical path enters the first balanced detector to form a beat signal, the lasers in the two sub-range measurement interference optical paths enter the second balanced detector to form a beat signal, and the lasers in the two sub-speed measurement interference optical paths enter the third balanced detector to form a beat signal.

[0016] In one or more embodiments of the present invention, the laser light in one of the sub-range-measuring interferometric optical paths directly enters the second balanced detector, and the laser light in another sub-range-measuring interferometric optical path enters the second balanced detector after being reflected by the moving object; and / or,

[0017] The laser light in one of the sub-speed measurement interference optical paths directly enters the third balanced detector, and the laser light in the other sub-speed measurement interference optical path enters the third balanced detector after being reflected by the moving object.

[0018] In one or more embodiments of the present invention, the reference interference optical path includes two sub-reference interference optical paths, wherein the laser in one of the sub-reference interference optical paths enters the first balanced detector via a delayed optical fiber, and the laser in the other sub-reference interference optical path directly enters the first balanced detector.

[0019] In one or more embodiments of the present invention, the data processing module can calculate the Doppler frequency of the moving object based on the beat frequency signal obtained by the speed measurement interference optical path, and construct a product and difference function based on the Doppler frequency to perform speed compensation processing on the beat frequency signal obtained by the ranging interference optical path.

[0020] In one or more embodiments of the present invention, the data processing module includes a first signal driver, a first signal converter, and a computer;

[0021] The first signal driver drives the first signal converter to operate. The first signal converter can collect beat frequency signals of the first balanced detector, the second balanced detector and the third balanced detector, and output them to the computer for analysis and processing.

[0022] In one or more embodiments of the present invention, the wavelengths of the laser beams output by the first laser and the second laser are different.

[0023] In one or more embodiments of the present invention, the resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed further comprises a modulation module, and the modulation module can output a modulation signal to control the first laser to output a frequency modulated continuous wave.

[0024] Compared with the prior art, in the resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed of the present invention, the first laser and the second laser can cooperate to complete the distance and speed measurement of the moving object. The speed measurement of the moving object can be completed based on the Doppler frequency shift data, and the data processing module can perform speed compensation analysis and resampled spectrum analysis on the corresponding beat frequency data based on the Doppler frequency, thereby improving the accuracy of the distance measurement of the moving object. The system of the present invention compensates for the Doppler frequency shift caused by the movement of the object through signal processing, so as to accurately obtain the position information of the moving object, effectively overcoming the limitation that the resampling technology can only measure stationary objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of the structure of a resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed in one embodiment of the present invention;

[0027] Figure 2 A data diagram of a stationary object resampling simulation in one embodiment of the present invention;

[0028] Figure 3 A data diagram of a resampling simulation of a moving object in one embodiment of the present invention;

[0029] Figure 4 This is a diagram of data after speed compensation and resampling in one embodiment of the present invention.

[0030] Description of main reference numerals:

[0031] 1. A first laser; 2. A second laser; 3. A multiplexer; 4. A demultiplexer; 5. A circulator; 6. A collimator; 7. A first balanced detector; 8. A second balanced detector; 9. A third balanced detector; 10. A first signal driver; 11. A first signal converter; 12. A computer. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0033] Reference Figure 1 A resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed in one embodiment of the present invention comprises a first laser 1, a second laser 2, a multiplexer 3, a demultiplexer 4, a circulator 5, a collimator 6, a first balanced detector 7, a second balanced detector 8, a third balanced detector 9 and a data processing module.

[0034] The first laser 1 is used to output a frequency modulated continuous wave to measure the distance of a moving object. The second laser 2 is used to output a continuous wave to measure the speed of a moving object. The wavelengths of the laser beams output by the first laser 1 and the second laser 2 are different. In this embodiment, the wavelength of the frequency modulated continuous wave output by the first laser 1 is 1550nm, and the wavelength of the continuous wave output by the second laser 2 is 1310nm as an example to illustrate the wavelengths of the frequency modulated continuous wave and the continuous wave in this implementation, which is not a limitation on the wavelengths of the lasers emitted by the first laser 1 and the second laser 2 of the present application.

[0035] The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed in this embodiment further comprises a modulation module, which can output a modulation signal to control the first laser 1 to output a frequency modulated continuous wave. Specifically, the modulation module can output a variable frequency voltage (such as Figure 1 As shown), the first laser 1 is driven to output a frequency modulated continuous wave. The modulation module may include a signal driver and a signal converter, and the signal driver drives the signal converter to operate to input a voltage signal to the first laser 1 to cooperate with driving the first laser 1 to output a frequency modulated continuous wave.

[0036] Reference Figure 1 , the laser beam emitted by the first laser 1 can be divided into two beams, one of which enters the reference interference optical path, and the other enters the ranging interference optical path, and the laser beam emitted by the second laser 2 enters the speed measurement interference optical path. In this embodiment, the lasers emitted by the first laser 1 and the second laser 2 can be split by a beam splitter. Among them, the reference interference optical path and the speed measurement interference optical path can form a resampling system to reduce the influence of the laser frequency modulation nonlinear problem on the laser ranging.

[0037] The data processing module can obtain the beat frequency signals output by the reference interference optical path, the distance measurement interference optical path and the speed measurement interference optical path, and can perform speed compensation analysis and resampled spectrum analysis based on the beat frequency signal data. Among them, the reference interference optical path, the distance measurement interference optical path and the speed measurement interference optical path of this embodiment can be set as optical fiber optical paths.

[0038] It should be noted that the resampling technology can solve the above problems for the following reasons: the resampling technology introduces a fiber reference interference optical path into the measurement system. Since the measurement interference optical path and the reference interference optical path have the same laser light source, the nonlinear problem of laser frequency modulation has the same impact on the two beat frequency signals. Therefore, by sampling the interference signal obtained by the measurement interference optical path at equal optical frequency intervals, the nonlinear effect can be eliminated. Figure 2 As shown, the spectrum broadening of the resampled signal is reduced, and the distance parameter can be accurately obtained according to the peak value, thereby improving the accuracy of distance measurement.

[0039] Reference Figure 3When measuring the movement of an object, a distance-speed coupling phenomenon will occur, that is, the beat frequency signals of the speed measurement interference optical path and the distance measurement interference optical path contain the Doppler frequency corresponding to the speed. The Doppler frequency shift caused by the moving object will cause the spectrum after resampling to be broadened, so only the approximate range of the object distance can be obtained, and the accuracy is not high. The present invention can complete the speed measurement of the moving object based on the Doppler frequency shift data in the speed measurement interference optical path, and the data processing module can perform speed compensation analysis and resampled spectrum analysis on the corresponding beat frequency data based on the Doppler frequency, thereby improving the accuracy of the distance measurement of the moving object, and effectively overcoming the limitation that the resampling technology can only measure stationary objects.

[0040] Reference Figure 1 The laser in the reference interference optical path enters the first balanced detector 7 to form a beat frequency signal. The reference interference optical path includes two sub-reference interference optical paths. The laser in one of the sub-reference interference optical paths enters the first balanced detector 7 via a delayed optical fiber, and the laser in the other sub-reference interference optical path enters the first balanced detector 7 directly.

[0041] Reference Figure 1 The distance measurement interference optical path includes two sub-distance measurement interference optical paths, and the speed measurement interference optical path includes two sub-speed measurement interference optical paths. The laser beam in one of the sub-distance measurement interference optical paths can be combined with the laser beam in one of the sub-speed measurement interference optical paths to form a composite light. The composite light can be decomposed after being reflected by the moving object and form corresponding beat frequency signals respectively. The laser beams in the two sub-distance measurement interference optical paths enter the second balanced detector 8 to form a beat frequency signal, and the laser beams in the two sub-speed measurement interference optical paths enter the third balanced detector 9 to form a beat frequency signal.

[0042] The laser in one of the sub-range-measuring interference optical paths directly enters the second balanced detector 8, and the laser in the other sub-range-measuring interference optical path returns through the moving object and enters the second balanced detector 8. The laser in one of the sub-speed-measuring interference optical paths directly enters the third balanced detector 9, and the laser in the other sub-speed-measuring interference optical path returns through the moving object and enters the third balanced detector 9.

[0043] Furthermore, the laser beam in one of the sub-distance measurement interference optical paths can be combined with the laser beam in one of the sub-speed measurement interference optical paths into a composite light through the multiplexer 3. The composite light passes through the circulator 5 and the collimator 6 in sequence to the moving object, and then returns to the demultiplexer 4 through the moving object. The demultiplexer 4 can decompose laser beams of different frequencies. Among them, the optical path between the collimator 6 and the moving object can be set as a spatial optical path. In this embodiment, the demultiplexer 4 can decompose a frequency modulated continuous wave with a wavelength of 1550nm and a continuous wave with a wavelength of 1310nm, and make the lasers of corresponding wavelengths travel to the second balanced detector 8 and the third balanced detector 9 respectively.

[0044] Reference Figure 1 , the data processing module includes a first signal driver 10, a first signal converter 11 and a computer 12; the first signal driver 10 drives the first signal converter 11 to operate, and the first signal converter 11 can collect the beat frequency signals of the first balanced detector 7, the second balanced detector 8 and the third balanced detector 9, and output them to the computer 12 for analysis and processing. Among them, the first signal driver 10 can be driven by ADC, and the first signal converter 11 can be driven by ADC. ADC (Analog-to-Digital Converter), that is, an analog-to-digital converter, is a circuit that converts continuous analog signals into digital signals, and its input is an analog signal and its output is a digital signal. The first signal converter 11 can communicate with the computer 12 via Ethernet.

[0045] Among them, the above-mentioned computer 12 can be a personal computer, a server computer, a workstation, a desktop computer, a laptop computer, a notebook computer, a mobile electronic device, a smart phone, a tablet computer, a cellular phone, a personal digital assistant (PDA), a handheld device, a messaging device, a wearable electronic device, a consumer electronic device, etc.

[0046] Specifically, the data processing module can calculate the Doppler frequency of the moving object based on the beat frequency signal obtained by the speed measurement interference optical path, and construct a product-difference function based on the Doppler frequency to perform speed compensation processing on the beat frequency signal obtained by the ranging interference optical path. In this embodiment, the beat frequency signal can be processed by a cosine function, and the formula is as follows:

[0047]

[0048] Where cosα and cosβ represent the beat frequency signal of the measuring arm (speed measurement interferometer optical path and distance measurement interferometer optical path) and the cosine function of the speed compensation construction, respectively.

[0049] In this embodiment, the signal spectrum after speed compensation is as follows: Figure 4 As shown in the figure, due to the nonlinearity of the laser frequency modulation, it can be seen that the spectrum of the measuring arm beat frequency signal is very widened. The signal contains not only the accurate distance information after compensation, but also the redundant items caused by speed compensation. However, after resampling to eliminate nonlinear information, the distance spectrum will become narrower and the redundant items will be further widened, which will not affect the distance measurement accuracy.

[0050] In an optional embodiment, the resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed of the present invention further includes an acousto-optic modulator (AOM), and the moving direction of the moving object can be further determined by performing frequency shift processing through the AOM.

[0051] Therefore, the measurement target of the present invention can be a stationary object or a moving object, and the speed and distance information of the corresponding target object can be measured simultaneously. The system of the present invention compensates the Doppler frequency shift caused by the object movement through signal processing, so as to accurately obtain the position information of the moving object, effectively overcoming the limitation that the resampling technology can only measure stationary objects.

[0052] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0053] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed, characterized in that: It comprises a first laser (1) for outputting a frequency modulated continuous wave, a second laser (2) for outputting a continuous wave, and a data processing module; The laser beam emitted by the first laser (1) can be divided into two beams, one of which enters a reference interference optical path, and the other enters a distance measurement interference optical path, and the laser beam emitted by the second laser (2) enters a speed measurement interference optical path; The data processing module can obtain the beat frequency signals output by the reference interference optical path, the distance measurement interference optical path and the speed measurement interference optical path, and can perform speed compensation analysis and resampled spectrum analysis based on the beat frequency signal data.

2. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 1, characterized in that: The distance measurement interference optical path includes two sub-distance measurement interference optical paths, and the speed measurement interference optical path includes two sub-speed measurement interference optical paths. The laser light beam in one of the sub-distance measurement interference optical paths can be combined with the laser light beam in one of the sub-speed measurement interference optical paths to form a composite light. The composite light can be decomposed after being reflected by the moving object and form corresponding beat frequency signals respectively.

3. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 2, characterized in that: The system further comprises a multiplexer (3), a demultiplexer (4), a circulator (5) and a collimator (6), wherein a laser beam in one of the sub-range-measuring interference optical paths can be combined with a laser beam in one of the sub-speed-measuring interference optical paths to form the composite light through the multiplexer (3); The composite light passes through the circulator (5) and the collimator (6) in sequence before reaching the moving object, and then returns along the original path through the moving object before entering the demultiplexer (4). The demultiplexer (4) can decompose laser beams of different frequencies.

4. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 2, characterized in that: The system further comprises a first balanced detector (7), a second balanced detector (8) and a third balanced detector (9); The laser light in the reference interference optical path enters the first balanced detector (7) to form a beat signal, the laser light in the two sub-distance measurement interference optical paths enters the second balanced detector (8) to form a beat signal, and the laser light in the two sub-speed measurement interference optical paths enters the third balanced detector (9) to form a beat signal.

5. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 4, characterized in that: The laser light in one of the sub-range-measuring interferometric optical paths directly enters the second balanced detector (8), and the laser light in another sub-range-measuring interferometric optical path enters the second balanced detector (8) after being reflected by the moving object; and / or, The laser light in one of the sub-speed measurement interference optical paths directly enters the third balanced detector (9), and the laser light in the other sub-speed measurement interference optical path enters the third balanced detector (9) after being reflected by the moving object.

6. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 4, characterized in that: The reference interference optical path comprises two sub-reference interference optical paths, wherein the laser light in one of the sub-reference interference optical paths enters the first balanced detector (7) via a delay optical fiber, and the laser light in the other sub-reference interference optical path directly enters the first balanced detector (7).

7. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 4, characterized in that: The data processing module can calculate the Doppler frequency of the moving object based on the beat frequency signal obtained by the speed measurement interference optical path, and construct a product-sum-difference function based on the Doppler frequency to perform speed compensation processing on the beat frequency signal obtained by the distance measurement interference optical path.

8. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 7, characterized in that: The data processing module comprises a first signal driver (10), a first signal converter (11) and a computer (12); The first signal driver (10) drives the first signal converter (11) to operate, and the first signal converter (11) can collect beat frequency signals from the first balanced detector (7), the second balanced detector (8) and the third balanced detector (9), and output them to the computer (12) for analysis and processing.

9. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 1, characterized in that: The wavelengths of the laser beams output by the first laser (1) and the second laser (2) are different.

10. The resampled frequency modulated continuous wave system capable of simultaneously measuring distance and speed according to claim 1, characterized in that: It also comprises a modulation module, which can output a modulation signal to control the first laser (1) to output a frequency modulated continuous wave.

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