A multi-optical-path laser ranging method, device and system

Abstract

The present invention relates to the technical field of laser measurement, and in particular to a multi-optical-path laser ranging method, device and system. The method includes: transmitting a modulated signal light containing high-frequency modulation signals of at least three different frequencies to a target to be ranged and determining the phase difference of its echo, wherein the high-frequency band and the low-frequency band of the modulation signal are divided according to a preset standard; simulating an equivalent modulation signal based on the three different-frequency high-frequency modulation signals carried by the modulated signal light, wherein the equivalent frequency of the equivalent modulation signal is the difference between the sum of the frequencies of the first modulation signal and the second modulation signal and twice the frequency of the third modulation signal, and the equivalent phase difference is the difference between the sum of the phase differences of the first modulation signal and the second modulation signal and twice the phase difference of the third modulation signal; determining the distance to the target to be ranged based on the equivalent frequency and the corresponding equivalent phase difference of the equivalent modulation signal. The present invention can accurately range a moving object at a long distance.

Description

Technical Field

[0001] The present invention relates to the technical field of laser measurement, and in particular, to a multi-path laser ranging method, device and system. Background Art

[0002] Laser phase rangefinders are widely used in the field of precise ranging. The principle of phase ranging is to calculate the time and distance by measuring the phase change of the modulation signal carried in the modulated light during the round trip.

[0003] Compared with high-frequency modulation signals, low-frequency modulation signals have a large signal-to-noise ratio, but the measurement accuracy of low-frequency modulation signals is lower than that of high-frequency modulation signals. To meet the requirements of high-precision ranging, generally, laser phase ranging uses high-frequency modulation signals and then uses algorithms to equivalently obtain the direct measurement results of low-frequency modulation signals. To meet the requirements of sampling accuracy, the sampling rate for digital sampling of high-frequency modulation signals needs to be very high, which places extremely high requirements on the processor and ADC. At the same time, when performing phase ranging, the high-frequency modulation signal has high ranging accuracy but a short effective range, while the low-frequency modulation signal has a long effective range but poor accuracy. To accurately range long-distance targets, generally, the distance is estimated based on the low-frequency modulation signal, and then the high-frequency modulation signal is used to obtain the accurate distance based on the estimated distance. However, the hardware processing requirements for high-frequency modulation signals and low-frequency signals are extremely different. If a laser phase rangefinder deploys both high-frequency and low-frequency processing systems simultaneously, the hardware cost will increase significantly.

[0004] The phase change is obtained by comparing the phase differences of the modulation signals carried in the modulated light acquired at different times during the round trip. However, during this time interval, the moving object will also undergo displacement, forming a motion error. Therefore, laser phase ranging is not suitable for accurately ranging moving objects. Summary of the Invention

[0005] In view of this, the purpose of the embodiments of the present invention is to provide a multi-path laser ranging system, method and device, and to provide a laser phase rangefinder that can accurately range long-distance moving objects and has a relatively low hardware cost.

[0006] In a first aspect, the present invention provides a multi-path laser ranging system, including a transmitting module, a receiving module and a control module connected by data, wherein:

[0007] The transmitting module is configured to send a modulated signal light carrying a modulation signal with a specified frequency to a target to be ranged;

[0008] The receiving module is configured to receive the echo of the modulated signal light reflected from the target to be ranged;

[0009] The control module is used to control the transmitting module to transmit the modulated signal light to the distance measurement target to be measured and control the receiving module to receive the echo, and calculate the phase difference corresponding to the high-frequency modulation signals carried in the modulated signal light and the echo respectively; wherein, the modulated signal light carries at least three different frequencies of high-frequency modulation signals;

[0010] The control module is further used to determine the distance to the distance measurement target to be measured based on the phase difference, wherein the control module simulates an equivalent modulation signal located in the low-frequency band based on the three different frequencies of the high-frequency modulation signals carried in the modulated signal light, estimates the distance to the distance measurement target to be measured based on the equivalent modulation signal, and corrects the estimated distance based on the high-frequency modulation signal to obtain the accurate distance, wherein, the high-frequency band and the low-frequency band of the modulation signal frequency are divided according to a preset standard.

[0011] Optionally, the multi-path laser ranging system further includes a mixing module, wherein:

[0012] The mixing module is used to mix the high-frequency modulation signals carried in the modulated signal light and the echo with the local oscillator signal respectively to generate low-frequency signals and send the low-frequency signals to the control module, wherein the local oscillator signal has the same phase and amplitude as the high-frequency modulation signal;

[0013] The control module is further used to determine the phase difference between the high-frequency modulation signals carried in the modulated signal light and the echo based on the low-frequency signals.

[0014] Optionally, the control module includes a field programmable logic array and a microprocessing unit, wherein:

[0015] The microprocessing unit is used to determine the frequencies of the three high-frequency modulation signals based on preset rules and send the frequencies to the field programmable logic array;

[0016] The field programmable logic array is used to obtain the high-frequency modulation signal of a specified frequency and control the transmitting module to modulate and transmit the carrier based on the high-frequency modulation signal;

[0017] The field programmable logic array is further used to determine the phase difference between the high-frequency modulation signals carried in the echo and the modulated signal light based on the low-frequency signals and send the phase difference to the microprocessing unit;

[0018] The microprocessing unit is further used to determine the distance to the distance measurement target to be measured based on the phase difference.

[0019] Optionally, it further includes a frequency generator, wherein:

[0020] The frequency generator is used to generate high-frequency modulation signals of 100 MHz, 96 MHz, and 92.4 MHz respectively, as well as corresponding local oscillator signals, and send them to the field programmable logic array;

[0021] The field programmable logic array is also used to modulate the high-frequency modulation signals of 100 MHz, 96 MHz, and 92.4 MHz in a preset order in the laser, generate the modulated signal light and emit the modulated signal light, and generate the phase difference of the high-frequency modulation signals respectively based on the corresponding low-frequency signals.

[0022] In a second aspect, the present invention provides a multi-path laser ranging method, including:

[0023] Emitting the modulated signal light containing at least three different frequencies of high-frequency modulation signals to the target to be ranged and receiving the echo, and determining the phase differences of the high-frequency modulation signals carried in the modulated signal light and the echo respectively based on the low-frequency signals generated by mixing the high-frequency modulation signals carried in the modulated signal light and the echo with the local oscillator signals, wherein the high-frequency band and the low-frequency band of the modulation signal frequency are divided according to a preset standard;

[0024] Simulating an equivalent modulation signal located in the low-frequency band based on the three different frequencies of high-frequency modulation signals carried in the modulated signal light, and estimating the distance to the target to be ranged based on the equivalent modulation signal;

[0025] Correcting the estimated distance based on the high-frequency modulation signal to obtain the accurate distance.

[0026] Optionally, the simulating an equivalent modulation signal located in the low-frequency band based on the three different frequencies of high-frequency modulation signals carried in the modulated signal light includes:

[0027] Selecting the high-frequency modulation signals of three frequencies based on a preset rule;

[0028] Determining the equivalent frequency and the equivalent phase difference of the equivalent modulation signal respectively based on the frequency and the phase difference of the high-frequency modulation signal, wherein,

[0029] γ′=|γ1+γ3-2γ2|;

[0030]

[0031] wherein, γ′ is the equivalent frequency, is the equivalent phase difference, γ1, γ2, and γ3 are respectively one of the frequencies of the high-frequency modulation signals, are respectively one of the phase differences of the high-frequency modulation signals, and k is an integer.

[0032] Optionally, generating an estimated distance to the target to be measured based on the equivalent modulation signal includes:

[0033]

[0034] where L1 is the estimated distance to the target to be measured, C is the speed of light in the ranging environment, γ′ is the equivalent frequency, is the equivalent phase difference.

[0035] Optionally, correcting the estimated distance based on the high-frequency modulation signal to obtain an accurate distance includes:

[0036] Determining the number of cycles for the high-frequency modulation signal to transmit the estimated distance;

[0037] Determining the accurate distance to the target to be measured based on the number of cycles, where,

[0038]

[0039] where L2 is the accurate distance to the target to be measured, C is the speed of light in the ranging environment, γ is the frequency of the high-frequency modulation signal, is the phase difference corresponding to γ, N is the number of cycles, and λ is the wavelength of the high-frequency modulation signal;

[0040] Determining three accurate distances respectively based on the high-frequency modulation signals of the three frequencies and obtaining the mean value of the accurate distances according to a preset rule.

[0041] Optionally, after determining the three accurate distances, it further includes:

[0042] If the mutual difference of the accurate distances is greater than a preset threshold, the current measurement is invalid.

[0043] In a third aspect, the present invention provides a multi-optical-path laser ranging device, which is applied to the system described in the first aspect of the present disclosure, and includes:

[0044] A phase difference determination module, configured to transmit a modulated signal light carrying a high-frequency modulation signal with at least three different frequencies to the target to be measured and receive an echo, and determine the phase differences of the high-frequency modulation signals respectively carried in the modulated signal light and the echo based on low-frequency signals generated by mixing the high-frequency modulation signals carried in the modulated signal light and the echo with a local oscillator signal respectively, where the high-frequency band and the low-frequency band of the modulation signal frequency are divided according to a preset standard;

[0045] A first measurement module, configured to simulate an equivalent modulation signal located in the low-frequency band based on the three different frequencies of the high-frequency modulation signals carried by the modulated signal light, and estimate the distance to the target to be measured based on the equivalent modulation signal;

[0046] A second measurement module, configured to correct the estimated distance based on the high-frequency modulation signal to obtain an accurate distance.

[0047] The embodiments of the present invention have the following beneficial effects: In this embodiment, the modulated signal light and the high-frequency modulation signal carried in the echo are respectively mixed with the local oscillator signal by the mixing module to generate a low-frequency signal with the same phase and amplitude as the high-frequency modulation signal, and the phase of the high-frequency modulation signal is obtained based on the low-frequency signal. Since the requirements for the processor and ADC for processing low-frequency signals are not as high as those for processing high-frequency modulation signals, the hardware cost is reduced. At the same time, in this embodiment, by simulating the low-frequency modulation signal based on three high-frequency modulation signals, first estimating the distance to a long-distance target based on the equivalent low-frequency modulation signal, and then correcting the estimated distance based on the high-frequency modulation signal to obtain accurate ranging. Since the advantages of phase ranging of high-frequency and low-frequency modulation signals are combined, accurate ranging of long-distance targets can be obtained. At the same time, since the low-frequency modulation signal is an equivalent modulation signal simulated from the high-frequency modulation signal and does not require actual configuration of a low-frequency signal processing system, the hardware cost is further controlled. Furthermore, in this embodiment, when ranging a moving object through modulation signals of three frequencies, the motion errors introduced by the moving object during the measurement interval will cancel each other out, so that accurate ranging of the moving object can be achieved. Description of the Drawings

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0049] Figure 1 is a propagation schematic diagram of the modulated signal light and the echo;

[0050] Figure 2 is a structural schematic diagram of a laser phase ranging system in some embodiments of the present invention;

[0051] Figure 3 is a structural schematic diagram of a laser phase ranging system in some other embodiments of the present invention;

[0052] Figure 4 is a structural schematic diagram of a laser phase ranging system in some other embodiments of the present invention;

[0053] Figure 5 is a structural schematic diagram of a laser phase ranging system in an embodiment of the present invention;

[0054] Figure 6Flowchart of a multi - optical - path laser ranging method provided by an embodiment of the present invention;

[0055] Figure 7 Schematic diagram of a multi - optical - path laser ranging device provided by some embodiments of the present invention.

[0056] Reference numerals: 1, control module; 2, transmitting module; 3, receiving module; 4, received optical signal; 5, reference optical signal; 6, mixing module; 7, local oscillator signal; 8, micro - processing unit; 9, field - programmable logic array; 10, frequency generator. Detailed implementation manners

[0057] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0058] It should be noted that although the functional modules are divided in the device schematic diagram and the logical sequence is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order from the module division in the device or the sequence in the flowchart. Terms such as "first", "second", etc. in the specification, claims and the above - mentioned drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0060] In addition, the described features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to give a full understanding of the embodiments of the present application. However, those skilled in the art will realize that the technical solutions of the present application can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, well - known methods, devices, implementations or operations are not shown or described in detail to avoid obscuring aspects of the present application.

[0061] The block diagrams shown in the drawings are only functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or implemented in one or more hardware charging modules or integrated circuits, or implemented in different networks and / or processor devices and / or micro - controller devices.

[0062] The flowchart shown in the attached drawings is only an exemplary illustration, not necessarily including all contents and operations / steps, nor necessarily executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined. Therefore, the actual execution order may change according to the actual situation.

[0063] Laser phase rangefinders are widely used in the field of precise distance measurement. The principle of phase distance measurement is to calculate the time and distance by measuring the phase change experienced by the modulated light during the round-trip process. It should be noted that in this application, the high-frequency and low-frequency band divisions of the modulation signal are determined by the ranging purpose and are different from the conventional laser band divisions.

[0064] Figure 1 is a propagation schematic diagram of the modulated signal light and the echo formed by the reflection of the modulated signal light at the target to be ranged. As Figure 1 shown, the modulated signal light travels from the starting point to the ending point and then returns to the starting point, covering a total distance of 2 times the path. During this period, the modulation signal has a total of N complete cycles and 1 incomplete cycle. Therefore, there is:

[0065] 2L = (N + ΔN)λ (1);

[0066] where L represents the distance from the starting point to the ending point, N represents the number of complete cycles, ΔN represents the ratio of the phase tail number to 2π, and λ represents the wavelength of the modulation signal.

[0067] Simplifying, we get:

[0068]

[0069] This is direct distance measurement, where λ / 2 is the measuring scale length L s , that is, the measuring range. Since the number of complete cycles N is uncountable, while the phase tail number can be measured (obtained by comparing the starting and returning states of the same signal).

[0070] Therefore, when and only when N = 0, According to the definition of ΔN: At the same time, because

[0071] So there is:

[0072] This is the phase distance measurement distance calculation formula for short distances (N = 0), where is the laser phase difference, v is the laser frequency, λ is the laser wavelength, and c is the speed of light.

[0073] At this time, the measuring range is λ / 2, and the accuracy is generally 1 / 1000 of the measuring range, that is, λ / 2000. It can be seen that the larger the measuring range, the worse the measurement accuracy; vice versa.

[0074] Therefore, laser phase ranging generally uses high-frequency modulation signals to obtain higher ranging accuracy. Shannon's theorem stipulates that the sampling rate cannot be lower than 5 times the signal frequency at the lowest. So if a 100 MHz high-frequency modulation signal is used (in this application, the division of high-frequency and low-frequency bands is determined based on the customary division of the effective measuring range, which may not be consistent with the division of high-frequency and low-frequency bands in optics), then its sampling rate should be at least 500 MHz. Such a high sampling rate places extremely high requirements on the processor and ADC chips, and the cost is also extremely high.

[0075] The ranging accuracy of high-frequency modulation signals is high, but the effective measuring range is short, while the effective measuring range of low-frequency modulation signals is long, but the accuracy is poor. Therefore, in order to accurately range long-distance targets, the dual-band indirect ranging method is generally used, that is, using low-frequency modulation signals to range and high-frequency modulation signals to measure accuracy. However, the hardware processing requirements for high-frequency modulation signals and low-frequency signals are extremely different. If a laser phase rangefinder deploys high-frequency and low-frequency processing systems at the same time, the hardware cost will increase significantly.

[0076] There is also a basic problem in laser phase ranging for moving objects: from equation (3), the distance L depends on the phase difference If the phase of the modulation signal is measured at time t0 The phase of the modulation signal is measured at time t1 Then the phase difference The distance L is obtained from equation (3). However, because the target to be ranged is moving, within the measurement time interval Δt of the phase difference (Δt=(t1 - t0)), the target to be ranged has moved another ΔL. This is the motion error introduced by the moving object.

[0077] It can be seen that single-frequency laser direct ranging cannot measure the motion error, that is, laser phase ranging based on single-frequency laser direct ranging cannot accurately range moving objects.

[0078] To solve the above problems, the present invention has developed a multi-optical-path laser ranging system. It ranges by using the modulated signal light carrying 3 high-frequency modulation signals, simulates an equivalent modulation signal in a low-frequency band with 3 high-frequency modulation signals, ranges with the low-frequency equivalent modulation signal, and then measures the accuracy with the high-frequency modulation signal. Because it combines the advantages of high-frequency and low-frequency modulation signal ranging, accurate ranging of long-distance targets can be obtained. At the same time, because the low-frequency modulation signal is an equivalent modulation signal simulated by the high-frequency modulation signal and does not require the actual configuration of a low-frequency signal processing system, the hardware cost is controlled.

[0079] When modulation signals of three frequencies are transmitted at fixed time intervals, echoes are received at fixed time intervals, processed, and the phase differences are obtained. The motion errors during ranging will cancel each other out, thereby achieving accurate ranging of moving targets. The description is as follows:

[0080] The frequencies are γ1, γ2, and γ3 respectively, and the phase differences are The equivalent frequencies and equivalent phase differences of the equivalent modulation signals simulated by the modulation signals are respectively:

[0081] γ′ = |γ1 - γ2|;

[0082] k is an integer.

[0083] From equation (3), the motion error ΔL can be equivalently considered to introduce a corresponding equivalent phase difference error ΔS in the phase difference. When modulation signals of three frequencies are transmitted at fixed time intervals, echoes are received at fixed time intervals, processed, and the phase differences are obtained. If the modulation signal of γ1 is received at time t1, its phase difference is The modulation signal of γ2 is received at time t2, and its phase difference is The modulation signal of γ3 is received at t3, and its phase difference is Then the equivalent phase difference of the equivalent modulation signal is:

[0084]

[0085] It can be seen that in the equivalent phase difference of the equivalent modulation signal generated by the modulation signals of three frequencies with motion errors, the equivalent phase difference errors introduced by the motion errors have canceled each other out and disappeared. Therefore, accurate ranging of moving targets can be achieved.

[0086] In addition, in the present invention, the modulated signal light and the high-frequency modulation signal carried in the echo of the mixing module are respectively mixed with the local oscillator signal to generate a low-frequency signal with the same phase and amplitude as the high-frequency modulation signal, and the phase difference of the high-frequency modulation signal carried in the modulated signal light and the echo is obtained based on the low-frequency signal. Since the requirements for processing low-frequency signals on the processor and ADC are not as high as those for processing high-frequency modulation signals, the hardware cost is reduced.

[0087] Figure 2 is a schematic structural diagram of a laser phase ranging system in some embodiments of the present invention; as Figure 2 shown, the laser ranging system includes a transmitting module 2, a receiving module 3, and a control module 1 that are connected by data, where:

[0088] The transmitting module 2 is used to send modulated signal light carrying a modulation signal of a specified frequency to the target to be ranged;

[0089] The receiving module 3 is used to receive the echo of the modulated signal light reflected from the target to be measured; the receiving module 3 further includes modules such as signal demodulation and ADC. When the modulated signal light is emitted, one path is reflected back by the beam splitter not far from the emission to form a reference optical signal 5; the other path is reflected back by the target to be measured to form an echo, which becomes the received optical signal 4 of the receiving module 3. The receiving module 3 demodulates and performs AD conversion on the received optical signal 4 to obtain the modulation signal carried by the echo, and demodulates and performs AD conversion on the reference optical signal 5 to obtain the modulation signal carried by the modulated signal light, and the receiving module 3 sends the modulation signal to the control module 1.

[0090] The control module 1 is used to control the transmitting module to transmit the modulated signal light containing high-frequency modulation signals with at least 3 different frequencies and control the receiving module to receive the echo, and calculate the phase difference corresponding to the high-frequency modulation signals carried in the modulated signal light and the echo respectively. Specifically, the control module 1 obtains the modulation signal, modulates the carrier based on the modulation signal, and controls the transmitting module 2 to transmit. The control module 1 also performs FFT operations on the modulation signals carried in the modulated signal light and the echo respectively to obtain the transmitting phase and the receiving phase, so as to obtain the phase difference between the echo and the modulated signal light.

[0091] The control module 1 is further used to determine the distance to the target to be measured based on the phase difference. The control module simulates an equivalent modulation signal located in the low-frequency band based on the high-frequency modulation signals of 3 frequencies, estimates the distance to the target to be measured based on the equivalent modulation signal, and corrects the estimated distance based on the high-frequency modulation signals to obtain the accurate distance.

[0092] Figure 2 The shown laser phase ranging system performs laser ranging based on a laser carrying at least 3 different frequencies of high-frequency modulation signals, so it can accurately measure the distance of a moving target. At the same time, because an equivalent modulation signal in a low-frequency band is simulated based on 3 high-frequency modulation signals, the low-frequency equivalent modulation signal is used for ranging, and the high-frequency modulation signals are used to measure the accuracy, so accurate ranging of a remote target can be achieved. Because the low-frequency modulation signal is an equivalent modulation signal simulated from the high-frequency modulation signals and does not require an actual configuration of a low-frequency signal processing system, the hardware cost is controlled.

[0093] However, directly processing the high-frequency modulation signals requires high requirements for the processor and ADC, which greatly increases the hardware cost. For this reason, some embodiments of the present invention add a mixing module, and the high-frequency modulation signals are converted into low-frequency signals for processing through the mixing module.

[0094] Figure 3 It is a schematic structural diagram of a laser phase ranging system in some other embodiments of the present invention. As Figure 3As shown, in the laser ranging system, the received optical signal 4 and the reference optical signal 5 are respectively mixed with the local oscillator signal 7 through the mixing module 6 to generate low-frequency signals that are easy to process. In some embodiments of the present invention, the local oscillator signal 5 is a signal with the same phase and amplitude as the modulation signal, but with a frequency difference of 15K. Therefore, after mixing through the mixing module 6, the low-frequency signal with a frequency of 15K is used for calculating the phase, greatly reducing the performance requirements for the processing system.

[0095] However, in the above embodiments, the control module 1 is used for both calculating the distance based on the phase difference and other high-level control operations of the laser ranging system, as well as low-level control operations such as signal switching, transmitting signal control, and receiving signal processing. Different levels of control operations are interleaved, which requires a high level of the controller, increasing the system development difficulty and cost. In some other embodiments of the present invention, the control module is divided into an MCU and an FPGA. The MCU processes the calculation of the distance based on the phase difference and other high-level management operations of the laser ranging system, and the FPGA processes low-level control operations such as signal switching, transmitting signal control, and receiving signal processing to reduce the system design difficulty and further reduce the cost.

[0096] Figure 4 It is a schematic structural diagram of the laser phase ranging system in some other embodiments of the present invention. As Figure 4 shown, the control module 1 in the laser ranging system consists of an MCU (microprocessing unit) 8 and an FPGA (field programmable logic array 9). The microprocessing unit is used to determine the frequencies of the 3 modulation signals based on a preset rule and send them to the field programmable logic array; the field programmable logic array 9 is used to obtain the modulation signals and control the transmitting module to modulate and emit the laser based on the modulation signals; the field programmable logic array 9 is also used to determine the phase difference corresponding to the high-frequency modulation signals carried by the modulated signal light and the echo respectively based on the low-frequency signal and send the phase difference to the microprocessing unit; the microprocessing unit is also used to determine the distance to the target to be measured based on the phase difference.

[0097] Specifically, the field programmable logic array 9 collects the 15K signal through an ADC, and only 5 cycles of each signal are collected, and then the next frequency is switched for repeated measurement. The first cycle of the 5 cycles of the 15k signal is discarded, and the remaining 4 cycles are used for FFT operation. Finally, the phase differences of the 15k signals corresponding to the received optical signal 4 and the reference optical signal 5 are calculated respectively, and then sent to the microprocessing unit 8 through SPI communication for the final distance calculation.

[0098] Further, an embodiment of the present invention introduces a frequency generator 10 for generating modulation signals of 100 MHz, 96 MHz, and 92.4 MHz respectively, as well as corresponding local oscillator signals (100M - 15k, 96M - 15k, 92.4M - 15k), and sending them to the field programmable logic array 9, as Figure 5 shown. Since there will be interference if the PLL signals are too close to each other, the field programmable logic array 9 can also generate the two signals of 96M and 92.4M.

[0099] As Figure 5 shown in the laser ranging system, the field programmable logic array 9 controls the emission module 2 to modulate and emit lasers of 100 MHz, 96 MHz, and 92.4 MHz in a preset order based on the control signal, and generates the phase difference based on the corresponding 15K signal respectively. Then, the phase difference is sent to the microprocessing unit 8 for calculating the final distance.

[0100] Figure 6 is a flowchart of a multi - path laser ranging method provided by an embodiment of the present invention, which is applied to Figures 2 to 5 the multi - path laser ranging system described above. The method includes the following steps:

[0101] S610: Transmit a modulated signal light containing high - frequency modulation signals of at least three different frequencies to the target to be ranged, and receive the echo. Determine the phase differences of the high - frequency modulation signals carried by the modulated signal light and the echo respectively based on the low - frequency signals generated by mixing the high - frequency modulation signals carried by the modulated signal light and the echo with the local oscillator signals respectively. Wherein, the high - frequency band and the low - frequency band of the modulation signal frequency are divided according to a preset standard;

[0102] S620: Simulate an equivalent modulation signal located in the low - frequency band based on the three different - frequency high - frequency modulation signals carried by the modulated signal light, and estimate the distance to the target to be ranged based on the equivalent modulation signal.

[0103] S630: Correct the estimated distance based on the high - frequency modulation signal to obtain an accurate distance.

[0104] Specifically, an embodiment of the present invention transmits a modulated signal light containing high - frequency modulation signals of at least three different frequencies to the target to be ranged, and receives the echo. Then, an equivalent frequency - modulation signal located in the low - frequency band is simulated based on the high - frequency modulation signals of the three frequencies. The equivalent frequency and equivalent phase difference of the equivalent laser are respectively:

[0105] γ′ = |γ1 + γ3 - 2γ2|;

[0106]

[0107] Among them, γ′ is the equivalent frequency, is the equivalent phase difference, γ1, γ2, and γ3 are respectively one of the frequencies of the high-frequency modulation signal, are respectively one of the phase differences of the high-frequency modulation signal. k is an integer used to correct the value range of the equivalent phase difference.

[0108] The frequency selection of the three high-frequency modulation signals must meet the following conditions:

[0109] Using the modulation signal of one frequency as γ1 respectively, among the three equivalent modulation signals obtained from γ′ = |γ1 + γ3 - 2γ2|, at least one equivalent modulation signal must be in the low-frequency band.

[0110] In an embodiment of the present invention, γ1, γ2, and γ3 are high-frequency modulation signals of 100M, 96M, and 92.4M respectively, and modulation signals of three frequencies of 0.4M, 11.6M, and 11.2M can be equivalently obtained. Among them, the modulation signal of 0.4M belongs to the low-frequency band.

[0111] The wavelength of the low-frequency modulation signal is very long. Therefore, for a general length of distance, in formula (2), the number N of full cycles can be considered to be 0. Therefore, direct ranging can be used. However, because the ranging accuracy of the low-frequency signal is very poor, the measured distance at this time is only an estimated distance with a large error. In the above example, the equivalent modulation signal of 0.4M can estimate the distance to a target at a distance of 370 meters.

[0112] After obtaining the estimated distance, the number of cycles for the high-frequency modulation signal to transmit the estimated distance can be determined. In the above example, the estimated distance using the equivalent modulation signal of 0.4M is 102 meters. At this time, it can be calculated how many complete cycles are required for the high-frequency modulation signals of 100M, 96M, and 92.4M to transmit 102 meters respectively. After obtaining the number of cycles N, precise ranging can be performed based on the following formula.

[0113]

[0114] Among them, L is the precise distance to the target to be measured, C is the speed of light in the ranging environment, γ is the frequency of the high-frequency laser, is the phase difference corresponding to γ, N is the number of cycles, and λ is the wavelength of the high-frequency laser;

[0115] Each step of the above ranging method has certain applicable conditions. For example, when estimating the distance, the distance cannot exceed the range of the low-frequency equivalent modulation signal. When performing precise ranging, the calculation of the number of cycles must be accurate, etc. If the applicable conditions are not met, the result of the ranging will have a large error. In order to determine whether this measurement is valid, the present invention verifies the results obtained by precise ranging using three high-frequency lasers. The verification conditions are:

[0116] If the mutual difference of the precise distances is greater than a preset threshold value, then this measurement is invalid.

[0117] In the above example, the preset threshold value is 13 mm.

[0118] Specifically, when comparing the current distance measurement result with the previous one, the object to be measured is continuously measured. Therefore, the position change (as long as the speed is lower than a certain value) is basically within a certain range. For the threshold value of this movement change range, we give a width of ±10 mm, and adding the ±3 mm measurement noise of the static measurement of the test equipment itself, we take ±13 mm as the final threshold range.

[0119] Some embodiments of the present invention provide a multi - optical - path laser ranging device, which is applied to Figures 2 to 5 the multi - optical - path laser ranging system described above. As Figure 7 shown, the multi - optical - path laser ranging device includes a phase - difference determination module 710, a first measurement module 720, and a second measurement module 730, where:

[0120] The phase - difference determination module 710 is configured to transmit a modulated signal light containing high - frequency modulation signals of at least 3 different frequencies to the target to be ranged and receive the echo, and determine the phase differences of the high - frequency modulation signals respectively carried in the modulated signal light and the echo based on the low - frequency signals generated by mixing the high - frequency modulation signals carried in the modulated signal light and the echo with the local oscillator signal respectively, where the high - frequency band and the low - frequency band of the modulation signal frequency are divided according to a preset standard;

[0121] The first measurement module 720 is configured to simulate an equivalent modulation signal located in the low - frequency band based on the 3 different - frequency high - frequency modulation signals carried in the modulated signal light, and estimate the distance to the target to be ranged based on the equivalent modulation signal.

[0122] The second measurement module 730 is configured to correct the estimated distance based on the high - frequency modulation signal to obtain a precise distance.

[0123] The embodiments of the present invention have the following beneficial effects: In this embodiment, the modulated signal light and the high-frequency modulation signal carried in the echo are respectively mixed with the local oscillator signal by the mixing module to generate a low-frequency signal with the same phase and amplitude as the high-frequency modulation signal, and the phase of the high-frequency modulation signal is obtained based on the low-frequency signal. Since the requirements for the processor and ADC for processing low-frequency signals are not as high as those for processing high-frequency modulation signals, the hardware cost is reduced; at the same time, in this embodiment, by simulating the low-frequency modulation signal based on three high-frequency modulation signals, the estimated distance of the long-distance target is first estimated based on the equivalent low-frequency modulation signal, and then the estimated distance is corrected based on the high-frequency modulation signal to obtain accurate ranging. Because the advantages of phase ranging of high-frequency and low-frequency modulation signals are combined, accurate ranging of long-distance targets can be obtained. At the same time, since the low-frequency modulation signal is an equivalent modulation signal simulated by the high-frequency modulation signal and does not require an actual configuration of a low-frequency signal processing system, the hardware cost is further controlled; furthermore, when the distance of a moving object is measured by the modulation signals of three frequencies in this embodiment, the motion errors introduced by the moving object during the measurement interval will cancel each other out, so that accurate ranging of the moving object can be achieved.

[0124] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, that is, they may be located in one place or distributed to multiple network units. Some or all of the charging modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0125] Those of ordinary skill in the art can understand that all or some of the steps in the methods disclosed above, and the functional charging modules / units in the systems and devices can be implemented as software, firmware, hardware and their appropriate combinations.

[0126] It should be understood that in this application, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices. "At least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects and indicates that three relationships may exist. For example, "A and / or B" may mean: only A exists, only B exists, and both A and B exist simultaneously. Here, A and B may be singular or plural. The character " / " generally indicates an "or" relationship between the associated objects before and after. "At least one of the following (items)" or a similar expression refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c may mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c may be single or plural.

[0127] In addition, in each embodiment of this application, each functional unit may be integrated into a processing unit, may exist physically separately for each unit, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0128] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, may be embodied in the form of a software product. This computer software product is stored in a storage medium and includes multiple instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of this application. The aforementioned storage medium includes: various media that can store programs such as USB flash drives, mobile hard disks, read-only memories (ROM for short), random access memories (RAM for short), magnetic disks or optical discs.

[0129] The preferred embodiments of the embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of rights of the embodiments of this application. Any modifications, equivalent replacements, and improvements made by those skilled in the art without departing from the scope and essence of the embodiments of this application shall fall within the scope of rights of the embodiments of this application.

Claims

1. A multi-path laser ranging method, characterized in that: include: Transmitting modulated signal light containing at least three high-frequency modulated signals of different frequencies to a target to be measured and receiving an echo, determining a phase difference between the modulated signal light and the high-frequency modulated signal respectively carried in the echo based on a low-frequency signal generated by mixing the high-frequency modulated signal carried in the modulated signal light and the echo with a local oscillator signal, wherein the high-frequency band and the low-frequency band of the modulated signal frequency are divided according to a preset standard; Simulating an equivalent modulation signal located in a low frequency band based on the high-frequency modulation signals of three different frequencies carried by the modulated signal light, and estimating the distance to the target to be measured based on the equivalent modulation signal; Correcting the estimated distance based on the high frequency modulation signal to obtain the accurate distance; The high-frequency modulation signal based on the three different frequencies carried by the modulated signal light simulates an equivalent modulation signal located in a low-frequency band, including: Selecting the high frequency modulation signal of 3 frequencies based on a preset rule; The equivalent frequency and the equivalent phase difference of the equivalent modulation signal are determined based on the frequency and the phase difference of the high-frequency modulation signal, respectively, wherein: γ´=|γ1+γ3-2γ2|; ； where γ´ is the equivalent frequency, is the equivalent phase difference, γ1, γ2, γ3 are respectively one of the frequencies of the high-frequency modulation signal, , , are respectively one of the phase differences of the high frequency modulation signal, and k is an integer not equal to 0; The estimating the distance to the target to be measured based on the equivalent modulation signal comprises: ； Wherein, L1 is the estimated distance to the target to be measured, C is the speed of light in the ranging environment, is the equivalent frequency, is the equivalent phase difference; The correcting the estimated distance based on the high frequency modulation signal to obtain the accurate distance comprises: Determining the number of cycles for which the high frequency modulated signal transmits the estimated distance; The precise distance to the target to be measured is determined based on the number of cycles, wherein: ； Wherein, L2 is the precise distance to the target to be measured, C is the speed of light in the ranging environment, γ is the frequency of the high-frequency modulation signal, is the phase difference corresponding to γ, N is the number of cycles, is the wavelength of the high frequency modulation signal; Three precise distances are determined for the high-frequency modulation signals based on the three frequencies respectively, and the average values ​​of the precise distances are obtained according to a preset rule.

2. The method according to claim 1, characterized in that: The obtaining of the accurate distance further includes: If the difference between the precise distances is greater than a preset threshold, the current measurement is invalid.

3. A multi-path laser ranging system, using the method described in any one of claims 1 to 2, characterized in that: It includes a transmitting module, a receiving module and a control module for data connection; The transmitting module is used to send modulated signal light carrying a modulation signal of a specified frequency to a target to be measured; The receiving module is used to receive the echo of the modulated signal light reflected from the target to be measured; The control module is used to control the transmitting module to transmit the modulated signal light to the target to be measured and control the receiving module to receive the echo, and calculate the phase difference corresponding to the high-frequency modulation signal respectively carried in the modulated signal light and the echo; wherein the modulated signal light carries at least 3 high-frequency modulation signals with different frequencies; The control module is also used to determine the distance to the target to be measured based on the phase difference, wherein the control module simulates an equivalent modulation signal located in a low-frequency band based on the high-frequency modulation signals of three different frequencies carried by the modulated signal light, estimates the distance to the target to be measured based on the equivalent modulation signal, and corrects the estimated distance based on the high-frequency modulation signal to obtain an accurate distance, wherein the high-frequency band and the low-frequency band of the modulation signal frequency are divided according to preset standards.

4. The system according to claim 3, characterized in that: Also included is a mixing module, wherein: The mixing module is used to mix the high-frequency modulation signal carried by the modulated signal light and the echo with the local oscillator signal to generate a low-frequency signal, and send the low-frequency signal to the control module, wherein the local oscillator signal has the same phase and amplitude as the high-frequency modulation signal; The control module is further configured to determine a phase difference between the modulated signal light and the high-frequency modulation signal carried in the echo based on the low-frequency signal.

5. The system according to claim 4, characterized in that: The control module includes a field programmable logic array and a microprocessor unit, wherein: The microprocessing unit is used to determine the frequencies of the three high-frequency modulation signals based on a preset rule and send the frequencies to the field programmable logic array; The field programmable logic array is used to obtain a high-frequency modulation signal of a specified frequency and control the transmission module to modulate and transmit a carrier based on the high-frequency modulation signal; The field programmable logic array is also used to determine the phase difference between the echo and the high-frequency modulation signal carried in the modulated signal light based on the low-frequency signal and send the phase difference to the microprocessing unit; The microprocessing unit is further configured to determine the distance to the target to be measured based on the phase difference.

6. The system according to claim 5, characterized in that: Also included is a frequency generator, wherein: The frequency generator is used to generate high-frequency modulation signals of 100 MHz, 96 MHz, and 92.4 MHz and corresponding local oscillator signals and send them to the field programmable logic array; The field programmable logic array is also used to modulate high-frequency modulation signals of 100 MHz, 96 MHz, and 92.4 MHz in the laser in a preset order, generate modulated signal light and emit the modulated signal light, and generate the phase difference for the high-frequency modulation signal based on the corresponding low-frequency signal.

7. A multi-path laser ranging device, using the method described in any one of claims 1 to 2, characterized in that: include: A phase difference determination module, used for transmitting modulated signal light containing high-frequency modulation signals of at least three different frequencies to a target to be measured and receiving an echo, and determining a phase difference between the modulated signal light and the high-frequency modulation signal respectively carried in the echo based on a low-frequency signal generated by mixing the high-frequency modulation signal carried in the modulated signal light and the echo with a local oscillator signal, wherein the high-frequency band and the low-frequency band of the modulation signal frequency are divided according to a preset standard; A first measurement module is used to simulate an equivalent modulation signal located in a low frequency band based on the high-frequency modulation signals of three different frequencies carried by the modulated signal light, and estimate the distance to the target to be measured based on the equivalent modulation signal; The second measurement module is used to correct the estimated distance based on the high-frequency modulation signal to obtain the accurate distance.

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