Multi-light-path laser ranging method, device and system

Abstract

The invention relates to the technical field of laser measurement, in particular to a multi-light-path laser ranging method, device and system, and the method comprises the steps: transmitting modulated signal light containing high-frequency modulation signals with at least three different frequencies to a target to be subjected to ranging, and determining the phase difference of echoes of the target, a high-frequency band and a low-frequency band of the modulation signal are divided according to a preset standard; simulating an equivalent modulation signal based on the high-frequency modulation signals of three different frequencies carried by the modulated signal light, the equivalent frequency of the equivalent modulation signal being a difference value 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, the equivalent phase difference is two times of the sum of the phase differences of the first modulation signal and the second modulation signal and the phase difference of the third modulation signal; and determining the distance to the to-be-measured target based on the equivalent frequency of the equivalent modulation signal and the corresponding equivalent phase difference. According to the invention, the distance of a long-distance moving object can be accurately measured.

Description

Technical Field

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

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

[0003] Compared with high-frequency modulation signals, low-frequency modulation signals have a larger signal-to-noise ratio, but the measurement accuracy of low-frequency modulation signals is lower than that of high-frequency modulation signals. In order to meet the requirements of high-precision ranging, high-frequency modulation signals are generally used in laser phase ranging, and then the direct measurement results of low-frequency modulation signals are equivalent through algorithms. In order to meet the requirements of sampling accuracy, the sampling rate of digital sampling of high-frequency modulation signals needs to be very high, which puts extremely high requirements on processors and ADCs. At the same time, the ranging accuracy of high-frequency modulation signals is high during phase ranging, but the effective range is short, while the effective range of low-frequency modulation signals is long, but the accuracy is poor. In order to accurately measure the distance of long-distance targets, the distance is generally 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 very different. If the laser phase rangefinder deploys high-frequency and low-frequency processing systems at the same time, the hardware cost will increase greatly.

[0004] The phase change is obtained by comparing the phase difference of the modulated signal carried in the modulated light obtained at different times during the round trip. However, during this time interval, the moving object will be displaced, resulting in motion error. Therefore, laser phase ranging is not suitable for accurate ranging of moving objects. Summary of the invention

[0005] In view of this, an object 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 measure the distance of a moving object at a long distance and has relatively low hardware cost.

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

[0007] The transmitting module is used to send modulated signal light carrying a modulation signal of a specified frequency to a target to be measured;

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

[0009] 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;

[0010] 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.

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

[0012] 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;

[0013] 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.

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

[0015] 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;

[0016] 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;

[0017] 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;

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

[0019] Optionally, a frequency generator is also included, wherein:

[0020] 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;

[0021] 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.

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

[0023] 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;

[0024] 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;

[0025] The estimated distance is corrected based on the high frequency modulation signal to obtain the accurate distance.

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

[0027] Selecting the high frequency modulation signal of 3 frequencies based on a preset rule;

[0028] 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:

[0029] γ′=|γ1+γ3-2γ2|;

[0030]

[0031] 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.

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

[0033]

[0034] Wherein, 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, the correcting the estimated distance based on the high-frequency modulation signal to obtain an accurate distance includes:

[0036] Determining the number of cycles for which the high frequency modulated signal transmits the estimated distance;

[0037] The precise distance to the target to be measured is determined based on the number of cycles, wherein:

[0038]

[0039] 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, and λ is the wavelength of the high frequency modulation signal;

[0040] 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.

[0041] Optionally, after determining the three precise distances, the method further includes:

[0042] If the difference between the precise distances is greater than a preset threshold, the current measurement is invalid.

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

[0044] 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;

[0045] 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;

[0046] The second measurement module is used to correct the estimated distance based on the high-frequency modulation signal to obtain the accurate distance.

[0047] The embodiment of the present invention includes the following beneficial effects: In this embodiment, the high-frequency modulation signal carried in the modulated signal light and the echo is mixed with the local oscillator signal through 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. Because 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; at the same time, this embodiment simulates low-frequency modulation signals based on three high-frequency modulation signals, first estimates the distance of a long-distance target based on an equivalent low-frequency modulation signal, and then corrects the estimated distance based on the high-frequency modulation signal to obtain accurate ranging. Because the advantages of high-frequency and low-frequency modulation signal phase ranging are combined, 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 a high-frequency modulation signal, it is not necessary to actually configure a low-frequency signal processing system, so the hardware cost is further controlled; further, when the present embodiment measures the distance of a moving object through three-frequency modulation signals, the motion errors introduced by the moving object in the measurement gap will offset each other, thereby achieving accurate ranging of the moving object. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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 will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

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

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

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

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

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

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

[0055] Figure 7 A schematic diagram of a multi-path laser ranging device provided for some embodiments of the present invention.

[0056] Figure 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. microprocessing unit; 9. field programmable logic array; 10. frequency generator. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with 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 order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first", "second", etc. in the specification, claims and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

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

[0060] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0061] The block diagrams shown in the accompanying 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 in one or more hardware charging modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0062] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

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

[0064] Figure 1 It is a schematic diagram of the propagation of modulated signal light and the echo formed by the reflection of modulated signal light at the target to be measured. Figure 1 As shown in the figure, the modulated signal light flies from the starting point to the end point and then returns to the starting point, propagating a distance twice the distance. During this period, the modulated signal has N complete cycles and 1 incomplete cycle, so:

[0065] 2L=(N+ΔN)λ (1);

[0066] Among them, L is the distance from the starting point to the end point, N is the number of complete cycles, and ΔN is the phase tail number. The ratio of λ to 2π represents the wavelength of the modulated signal.

[0067] Simplifying, we get:

[0068]

[0069] This is direct distance measurement, where λ / 2 is the length of the ruler L s , which is the range. Since the number of whole cycles N is uncountable, and the phase tail number Can be measured (by comparing the departure and return states of the same signal).

[0070] So if and only if N = 0, From the definition of ΔN, we know that: At the same time, because

[0071] So we have:

[0072] This is the phase ranging distance calculation formula for short distance (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 range is λ / 2, and the accuracy is generally 1 / 1000 of the range, that is, λ / 2000. From this, we can see that the larger the range, the worse the measurement accuracy, and vice versa.

[0074] Therefore, laser phase ranging generally uses high-frequency modulation signals to obtain higher ranging accuracy. Shannon's theorem stipulates that the minimum sampling rate cannot be less than 5 times the signal frequency, so if a 100MHz high-frequency modulation signal is used (the division of high-frequency and low-frequency bands in this application is based on the customary division of the effective range, which may be inconsistent with the division of optical high-frequency and low-frequency bands), the sampling rate must be at least 500MHz. Such a high sampling rate places extremely high requirements on the processor and ADC chip, and the cost is also extremely high.

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

[0076] Laser phase ranging of moving objects also faces a basic problem: the distance L depends on the phase difference If the phase of the modulated signal is measured at time t0 The phase of the modulated signal is measured at time t1 The phase difference The distance L is obtained from equation (3). However, because the target to be measured is moving, the target to be measured moves ΔL within the phase difference measurement time interval Δt (Δt = (t1-t0)). This is the motion error introduced by the moving object.

[0077] It can be seen that single-frequency laser direct ranging cannot measure motion errors, that is to say, laser phase ranging based on single-frequency laser direct ranging cannot accurately measure the distance of moving objects.

[0078] In order to solve the above problems, the present invention has developed a multi-path laser ranging system, which measures the distance by using modulated signal light equipped with three high-frequency modulation signals, simulates an equivalent modulation signal in a low-frequency band with three high-frequency modulation signals, measures the distance with the low-frequency equivalent modulation signal, and then measures the accuracy with the high-frequency modulation signal. Because the advantages of high-frequency and low-frequency modulation signal ranging are combined, 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, it is not necessary to actually configure a low-frequency signal processing system, so the hardware cost is controlled.

[0079] When the modulated signals of three frequencies are transmitted at fixed time intervals and the echoes are received and processed at fixed time intervals to obtain the phase difference, the motion errors during ranging will cancel each other out, thus obtaining accurate ranging of the moving target. The explanation is as follows:

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

[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 into the phase difference. When the modulated signals of three frequencies are transmitted at a fixed time interval and the echoes are received and processed at a fixed time interval to obtain the phase difference, if the modulated signal of γ1 is received at time t1, its phase difference is The modulated signal of γ2 is received at time t2, and its phase difference is t3 receives the modulation signal of γ3, and its phase difference is Then the equivalent phase difference of the equivalent modulated 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 the three frequencies with motion errors, the equivalent phase difference errors introduced by the motion errors have offset each other and disappeared, so the moving target can be accurately measured.

[0086] In addition, the present invention mixes the high-frequency modulated signal carried in the modulated signal light and the echo with the local oscillator signal through the mixing module to generate a low-frequency signal with the same phase and amplitude as the high-frequency modulated signal, and obtains the phase difference between the modulated signal light and the high-frequency modulated signal carried in the echo 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 modulated signals, the hardware cost is reduced.

[0087] Figure 2 is a schematic diagram of the structure of the laser phase ranging system in some embodiments of the present invention; Figure 2 As shown, the laser ranging system includes a data-connected transmitting module 2, a receiving module 3 and a control module 1, wherein:

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

[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 also includes signal demodulation, ADC and other modules. When the modulated signal light is emitted, it is reflected back through the beam splitter not far away, forming a reference light signal 5; the other path is reflected back by the target to be measured to form an echo, which becomes the received light signal 4 of the receiving module 3. The receiving module 3 demodulates and AD-converts the received light signal 4 to obtain the modulated signal carried by the echo, and demodulates and AD-converts the reference light signal 5 to obtain the modulated signal carried by the modulated signal light, and the receiving module 3 sends the modulated signal to the control module 1.

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

[0091] The control module 1 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 signal of three 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 signal to obtain an accurate distance.

[0092] Figure 2 The laser phase ranging system shown is based on laser ranging with at least three high-frequency modulation signals of different frequencies, so it can accurately measure the distance of moving targets. At the same time, because an equivalent modulation signal of a low frequency band is simulated based on three high-frequency modulation signals, the low-frequency equivalent modulation signal is used for ranging, and the high-frequency modulation signal is used for accuracy, so accurate ranging of remote targets can be achieved. Because the low-frequency modulation signal is an equivalent modulation signal simulated by the high-frequency modulation signal, it does not need to actually configure a low-frequency signal processing system, so the hardware cost is controlled.

[0093] However, direct processing of high-frequency modulated signals places high demands on the processor and ADC, which greatly increases the hardware cost. To this end, some embodiments of the present invention add a mixing module to convert the high-frequency modulated signal into a low-frequency signal for processing.

[0094] Figure 3 Schematic diagram of the structure of the laser phase ranging system in some other embodiments of the present invention. Figure 3As shown, in the laser ranging system, the received optical signal 4 and the reference optical signal 5 are mixed with the local oscillator signal 7 by the mixing module 6 to generate a low-frequency signal that is 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, the low-frequency signal with a frequency of 15K is used to calculate the phase after mixing by the mixing module 6, which greatly reduces the performance requirements of the processing system.

[0095] However, in the above embodiments, the control module 1 is used for both distance calculation based on phase difference and other high-level control work for the laser ranging system, and low-level control work for signal switching, transmission signal control and reception signal processing. The control work at different levels is carried out in an interlaced manner, which places high demands on the controller, resulting in increased difficulty in system development and increased costs. Some other embodiments of the present invention reduce the difficulty of system design and further reduce costs by dividing the control module into an MCU and an FPGA, with the MCU handling the distance calculation based on phase difference and other high-level management work for the laser ranging system, and the FPGA handling the low-level control work for signal switching, transmission signal control and reception signal processing.

[0096] Figure 4 Schematic diagram of the structure of the laser phase ranging system in some other embodiments of the present invention. Figure 4 As shown, the control module 1 in the laser ranging system is composed 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 three modulation signals based on preset rules and send them to the field programmable logic array; the field programmable logic array 9 is used to obtain the modulation signal and control the sending module to modulate and emit the laser based on the modulation signal; the field programmable logic array 9 is also used to determine the phase difference corresponding to the high-frequency modulation signal respectively carried in the modulated signal light and the echo 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 ADC, and only collects 5 cycles of each signal, and then switches to the next frequency for repeated measurement. The first cycle of the 5 cycles of the 15k signal is discarded, and the remaining 4 cycles are taken for FFT operation. Finally, the phase difference of the 15k signal corresponding to the received optical signal 4 and the reference optical signal 5 is calculated respectively, and then sent to the microprocessor unit 8 through SPI communication for the final distance calculation.

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

[0099] like Figure 5 In the laser ranging system shown, the field programmable logic array 9 controls the transmitting module 2 to perform modulation and emission of 100MHz, 96MHz, and 92.4MHz lasers in turn in a preset order based on the control signal, and generates the phase difference based on the corresponding 15K signal, respectively. The phase difference is sent to the microprocessor unit 8 to calculate the final distance.

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

[0101] S610, transmitting modulated signal light containing at least three high-frequency modulation 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 modulation signal respectively carried in the echo based on a low-frequency signal generated by mixing the modulated signal light and the high-frequency modulation signal carried in 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;

[0102] S620, 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.

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

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

[0105] γ′=|γ1+γ3-2γ2|;

[0106]

[0107] 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. 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] Use a modulation signal of a frequency as γ1 respectively. Among the three equivalent modulation signals obtained by γ′=|γ1+γ3-2γ2|, at least one equivalent modulation signal must be in the low frequency band.

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

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

[0112] After obtaining the estimated distance, the number of cycles of the high-frequency modulated 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 is possible to calculate how many complete cycles are required for the high-frequency modulated signals of 100M, 96M, and 92.4M to transmit 102 meters respectively. After obtaining the number of cycles N, the distance can be accurately measured based on the following formula.

[0113]

[0114] Wherein, 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 distance measurement method has certain applicable conditions, such as when estimating the distance, the distance cannot exceed the range of the low-frequency equivalent modulation signal, and when accurately measuring the distance, the calculation of the number of cycles must be accurate. If the applicable conditions are not met, the distance measurement result will have a large error. In order to determine whether this measurement is valid, the present invention verifies the results obtained by accurately measuring the distance using 3 medium and high frequency lasers. The verification conditions are:

[0116] If the difference between the precise distances is greater than a preset threshold, the current measurement is invalid.

[0117] As in the example above, the preset threshold is 13mm.

[0118] Specifically, when comparing the current ranging result with the previous ranging result, the measured object is measured continuously, so the position change (as long as the speed is lower than a certain value) is basically within a certain range. The threshold of this motion change range is given a width of ±10mm, plus the ±3mm measurement noise of the static measurement of the test equipment itself, and ±13mm is taken as the final threshold range.

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

[0120] The phase difference determination module 710 is used to transmit a modulated signal light containing at least three high-frequency modulation signals of different frequencies to a target to be measured and receive an echo, and determine the 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;

[0121] The first measurement module 720 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.

[0122] The second measurement module 730 is used to correct the estimated distance based on the high-frequency modulation signal to obtain an accurate distance.

[0123] The embodiment of the present invention includes the following beneficial effects: In this embodiment, the high-frequency modulation signal carried in the modulated signal light and the echo is mixed with the local oscillator signal through 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. Because 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; at the same time, this embodiment simulates low-frequency modulation signals based on three high-frequency modulation signals, first estimates the distance of a long-distance target based on an equivalent low-frequency modulation signal, and then corrects the estimated distance based on the high-frequency modulation signal to obtain accurate ranging. Because the advantages of high-frequency and low-frequency modulation signal phase ranging are combined, 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 a high-frequency modulation signal, it is not necessary to actually configure a low-frequency signal processing system, so the hardware cost is further controlled; further, when the present embodiment measures the distance of a moving object through three-frequency modulation signals, the motion errors introduced by the moving object in the measurement gap will offset each other, thereby achieving accurate ranging of the moving object.

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

[0125] Those skilled in the art will appreciate that all or some of the steps in the methods disclosed above, and the functional charging modules / units in the systems and devices may be implemented as software, firmware, hardware, or appropriate combinations thereof.

[0126] It should be understood that in the present application, the terms "include" and "have" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. "At least one (item)" refers to one or more, and "plurality" refers to two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist, for example, "A and / or B" can represent: only A exists, only B exists, and A and B exist at the same time, wherein A, B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in a "or" relationship. "At least one of the following (individuals)" or similar expressions thereof refer to any combination of these items, including any combination of singular (individuals) or plural (individuals). For example, at least one item among a, b or c can be represented by: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or plural.

[0127] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, 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 software functional units.

[0128] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including multiple instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, referred to as ROM), random access memory (Random Access Memory, referred to as RAM), disk or optical disk and other media that can store programs.

[0129] The preferred embodiments of the present application are described above with reference to the accompanying drawings, but the scope of the rights of the present application is not limited thereto. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present application should be within the scope of the rights of the present application.

Claims

1. A multi-path laser ranging system, 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.

2. The system according to claim 1, 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.

3. The system according to claim 2, 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.

4. The system according to claim 3, 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.

5. A multi-path laser ranging method, applied to the system according to any one of claims 1 to 4, 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; The estimated distance is corrected based on the high frequency modulation signal to obtain the accurate distance.

6. The method according to claim 5, characterized in that: 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.

7. The method according to claim 6, characterized in that: The generating an estimated 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, γ′ is the equivalent frequency, is the equivalent phase difference.

8. The method according to claim 7, characterized in that: 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, and λ 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.

9. The method according to claim 5, characterized in that: After determining the three precise distances, the method further includes: If the difference between the precise distances is greater than a preset threshold, the current measurement is invalid.

10. A multi-path laser distance measuring device, applied to the system according to any one of claims 1 to 4, 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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