Modulation-free continuous laser ranging system and method

Abstract

The application provides a modulation-free continuous laser ranging system applied to the technical field of laser ranging, and comprises a continuous laser module for generating three same continuous lasers with a preset line width, the three continuous lasers comprising a first continuous laser, a second continuous laser and a third continuous laser; a transceiving optical module for target detection by using the first continuous laser; a coherent detection module for coherent detection of a target by using a second continuous laser and a return wave of the first continuous laser irradiating the target, so as to obtain an interference signal; a phase measurement module for measuring an original phase of the third continuous laser; and a data processing module for calculating a distance to the target according to the interference signal and the original phase. The application also provides a modulation-free continuous laser ranging method, which can improve the ranging precision and reduce the requirement for a laser source.

Description

Technical Field

[0001] This invention relates to the field of laser ranging technology, and in particular to a modulation-free continuous laser ranging system and method. Background Technology

[0002] Laser ranging technology is widely used in remote sensing, urban surveying, industrial automation, and autonomous driving, among other fields. It offers advantages such as high measurement speed, high accuracy, non-contact measurement of the target, and ease of use. Continuous laser ranging is a crucial branch of this technology. Continuous laser ranging uses a continuous, rather than pulsed, laser as the transmitted signal. Before transmission, the amplitude, phase, or polarization of the continuous laser is modulated. By utilizing the autocorrelation of the modulated laser signal, the delay between the target echo and the transmitted signal is detected, thereby obtaining the target distance. A typical characteristic is that the system's transmitting end includes a laser modulation module, and the receiving end includes a corresponding laser demodulation module (implemented in hardware or software).

[0003] Because existing continuous laser ranging (LLR) technologies require laser modulation, their systems are more complex. They typically require additional laser modulators, such as acousto-optic modulators, electro-optic modulators, and magneto-optic modulators. Simultaneously, additional radio frequency (RF) circuitry is needed to generate the baseband signal required for modulation. The bandwidth, accuracy, and noise characteristics of these modulators and baseband signals directly affect the overall performance of the laser ranging system. Therefore, these components usually have high requirements. Furthermore, existing LLR technologies also place high demands on the laser source. For example, amplitude-modulated LLR requires a laser source with stable output power and low relative amplitude noise; phase-modulated LLR requires a laser source with extremely narrow linewidth and extremely low phase noise; and polarization-modulated LLR requires stable and controllable laser polarization characteristics. These issues result in the overall performance of LLR being constrained by the performance of the modulator and laser, leading to system complexity, high cost, and poor stability. Summary of the Invention

[0004] The main objective of this invention is to provide a modulation-free continuous laser ranging system and method, aiming to solve the technical problems of complexity and poor stability in existing continuous laser ranging systems.

[0005] To achieve the above objectives, a first aspect of the present invention provides a modulation-free continuous laser ranging system, comprising:

[0006] A continuous laser module is used to generate three identical continuous lasers with a preset linewidth, the three continuous lasers including a first continuous laser, a second continuous laser, and a third continuous laser;

[0007] A transceiver optical module is used for target detection using the first continuous laser beam.

[0008] The coherent detection module is used to perform coherent detection using the echoes from the second continuous laser and the first continuous laser illuminating the target, and to obtain the interference signal.

[0009] A phase measurement module is used to measure the original phase of the third continuous laser beam;

[0010] The data processing module is used to calculate the distance to the target based on the interference signal and the original phase.

[0011] In one embodiment, the preset linewidth is on the order of MHz to GHz.

[0012] In one embodiment, measuring the original phase of the third continuous laser beam includes:

[0013] The third continuous laser beam is split into two beams;

[0014] One of the two or three third continuous laser paths is delayed for a preset time to obtain a delayed continuous laser;

[0015] The delayed continuous laser is mixed with another of the two third continuous lasers to obtain a mixed signal;

[0016] The mixed signal is photoelectrically detected, and the phase is integrated to obtain the original phase of the continuous laser.

[0017] In one embodiment, calculating the distance to the target based on the interference signal and the original phase includes:

[0018] The original phase is time-shifted to obtain a time-shifted phase, which is time-aligned with the phase of the second continuous laser.

[0019] A compensation signal is constructed using the time-shifted phase;

[0020] Multiply the interference signal by the compensation signal to obtain the compensated signal;

[0021] Using the original phase, a transmitted replica signal is constructed;

[0022] The output signal is calculated based on the transmitted copy signal and the interference signal;

[0023] The distance is obtained based on the output signal.

[0024] In one embodiment, calculating the output signal based on the transmitted replicated signal and the interference signal includes:

[0025] The transmitted copy signal is time-reversed to obtain the time-reversed transmitted copy signal;

[0026] The complex conjugate of the transmitted replicated signal after time deconvolution is used to obtain a time-domain matched filter;

[0027] Calculate the Fourier transform of the time-domain matched filter to obtain the frequency-domain matched filter;

[0028] The frequency domain matched filter is used to perform matched filtering on the interference signal to obtain the output signal.

[0029] In one embodiment, calculating the output signal based on the transmitted replicated signal and the interference signal includes:

[0030] Calculate the Fourier transform result of the transmitted replicated signal;

[0031] Taking the complex conjugate of the Fourier transform result yields a frequency domain matched filter;

[0032] The frequency domain matched filter is used to perform matched filtering on the interference signal to obtain the output signal.

[0033] In one embodiment, calculating the output signal based on the transmitted replicated signal and the interference signal includes:

[0034] The transmitted copy signal is time-reversed to obtain the time-reversed transmitted copy signal;

[0035] The complex conjugate of the transmitted replicated signal after time deconvolution is used to obtain a time-domain matched filter;

[0036] The output signal is obtained by calculating the convolution between the time-domain matched filter and the interference signal.

[0037] In one embodiment, calculating the output signal based on the transmitted replicated signal and the interference signal includes:

[0038] The cross-correlation function between the interference signal and the transmitted replica signal is calculated to obtain the output signal.

[0039] In one embodiment, the length of the time shift is the optical path delay from the continuous laser module to the coherent measurement module.

[0040] A second aspect of this invention provides a modulation-free continuous laser ranging method, comprising:

[0041] Generate three identical continuous laser beams with a preset linewidth, the three continuous laser beams including a first continuous laser beam, a second continuous laser beam, and a third continuous laser beam;

[0042] Target detection is performed using the first continuous laser beam.

[0043] The target is coherently detected by using the echoes from the second continuous laser beam and the first continuous laser beam to obtain an interference signal;

[0044] Measure the original phase of the third continuous laser beam;

[0045] The distance to the target is calculated based on the interference signal and the original phase.

[0046] As can be seen from the above embodiments of the present invention, the modulation-free continuous laser ranging system and method provided by the present invention uses the phase jitter of the laser itself as a natural modulation in the ranging system, avoiding the use of additional laser modulation devices in the ranging system and simplifying the laser ranging system. At the same time, the phase jitter of the laser itself, i.e., the linewidth, can usually easily reach the MHz or even GHz level. This allows the laser ranging to have a larger equivalent modulation bandwidth, improving ranging accuracy; on the other hand, it avoids the use of a single-frequency laser with an extremely narrow linewidth, reducing the requirements for the laser source. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of a modulation-free continuous laser ranging system provided in an embodiment of the present invention;

[0049] Figure 2 This is a schematic flowchart of a modulation-free continuous laser ranging method provided in an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0051] Please see Figure 1 , Figure 1This is a schematic diagram of a modulation-free continuous laser ranging system according to an embodiment of the present invention. The modulation-free continuous laser ranging system includes: a continuous laser module, a transceiver optical module, a phase measurement module, a coherent detection module, and a data processing module.

[0052] A continuous laser module generates three identical continuous laser beams with a preset linewidth, comprising a first continuous laser beam, a second continuous laser beam, and a third continuous laser beam. A transceiver optics module uses the first continuous laser beam for target detection. A coherent detection module uses the echoes from the first and second continuous laser beams illuminating the target to perform coherent detection, obtaining an interference signal. A phase measurement module measures the original phase of the third continuous laser beam. A data processing module calculates the distance to the target based on the interference signal and the original phase.

[0053] In this invention, the continuous laser generated by the continuous laser module is divided into three paths. One path enters the transceiver optical module for transmission and target detection, another path enters the coherent detection module for mixing with the echo to complete coherent detection, and the last path enters the phase measurement module for measuring the phase of the continuous laser. The measured phase and the interference signal obtained from the coherent detection enter the data processing module, and the distance is calculated using the correlation of the laser's own phase.

[0054] The three continuous laser beams generated by the continuous laser module are all single-frequency lasers with a certain degree of coherence. In this invention, the continuous laser module is not required to output lasers with extremely narrow linewidths; instead, the linewidth is required to have a certain width, for example, on the order of MHz to GHz. By utilizing the laser linewidth directly as the natural modulation of the transmitted signal, the use of additional laser modulators and other related devices in the system is avoided.

[0055] The distance resolution Δr of the modulation-free continuous laser ranging system provided by this invention depends on the linewidth Δf of the continuous laser, i.e., Δr = c / 2Δf, where c is the speed of light in the medium. The ranging error is inversely proportional to the linewidth Δf of the continuous laser, i.e., σ∝1 / Δf. Since an extremely narrow linewidth is not required, the laser source of the modulation-free continuous laser ranging system provided by this invention is easier to implement, lower in cost, and easier to achieve higher output power compared to related technologies.

[0056] In one embodiment of the present invention, the above-mentioned measurement of the original phase of the third continuous laser includes: splitting the third continuous laser into two second continuous lasers; delaying one of the two third continuous lasers for a preset time to obtain a delayed continuous laser; mixing the delayed continuous laser with the other of the two third continuous lasers to obtain a mixed signal; performing photoelectric detection on the mixed signal and integrating the signal phase to obtain the original phase of the continuous laser.

[0057] In this invention, the phase measurement module can employ a zero-difference detection mode. Internally, the phase measurement module splits the input third continuous laser beam into two paths. One path, after a certain delay, is mixed with the other path, and the resulting signal is obtained after photoelectric detection. Based on the principle of frequency mixing interference, the phase of this interference signal is the original phase of the input continuous laser beam. The difference between itself and its own slight delay, i.e., the original phase difference Therefore, integrating the phase of the interference signal yields the original phase of the continuous laser. Original phase It will be used in the data processing module to calculate this distance.

[0058] In this invention, in addition to the zero-difference detection mode described above, the coherent measurement module can also employ a heterodyne detection mode. For example, a standard laser source with an extremely narrow linewidth is used. The output of this standard laser source is mixed with the laser input from the continuous laser module to the coherent detection module, and an interference signal is obtained through photoelectric detection. Since the standard laser source has an extremely narrow linewidth, it can be considered an ideal single-frequency signal, and its phase is linear. Therefore, removing the linear phase of the standard laser source from the phase of the interference signal yields the original phase of the laser generated by the continuous laser module.

[0059] In one embodiment of the present invention, calculating the distance to the target based on the interference signal and the original phase includes: time-shifting the original phase to obtain a time-shifted phase, the time-shifted phase being time-aligned with the phase of the second continuous laser; constructing a compensation signal using the time-shifted phase; multiplying the interference signal and the compensation signal to obtain a compensated signal; constructing a transmission replication signal using the original phase; calculating the output signal based on the transmission replication signal and the interference signal; and obtaining the distance based on the output signal.

[0060] Specifically, the original phase of the continuous laser can be obtained through the phase measurement module. Then, based on the optical path delay τ0 from the continuous laser module to the coherent detection module, the original phase information of the continuous laser is time-shifted to obtain the time-shifted phase information. Then, using the time-shifted phase information Constructing compensation signals Then, the interference signal s(t) output by the coherent detection module is multiplied by the compensation signal s0(t) to obtain the compensated signal. Then, using the original phase Constructing a replica signal

[0061] Specifically, this can be achieved by detecting the output signal s. out The distance to the target can be obtained by multiplying the corresponding delay by the speed of light in the medium and dividing by 2.

[0062] In one embodiment of the present invention, the above-mentioned calculation of the output signal based on the transmitted copy signal and the interference signal includes: calculating the transmitted copy signal s t (t) is time-reversed to obtain the time-reversed transmitted copy signal; the complex conjugate of the time-reversed transmitted copy signal is taken to obtain the time-domain matched filter h(t) = conj[s t (-t)]; Calculate the Fourier transform of the time-domain matched filter h(t) to obtain the frequency-domain matched filter H(f) = F{conj[s t Using the frequency domain matched filter H(f), the interference signal s(t) is matched and filtered to obtain the output signal s. out (t)=F -1 {F[s(t)]·H(f)}.

[0063] In one embodiment of the present invention, the above-mentioned calculation of the output signal based on the transmitted copy signal and the interference signal includes: calculating the transmitted copy signal s t The Fourier transform result F[s] of (t) t (t)];The Fourier transform result F[s t Taking the complex conjugate of [(t)], we obtain the frequency domain matched filter H(f) = conj{F[s t Using the frequency domain matched filter H(f), the interference signal s(t) is matched and filtered to obtain the output signal s. out (t)=F -1 {F[s(t)]·H(f)}.

[0064] In one embodiment of the present invention, the above-mentioned calculation of the output signal based on the transmitted copy signal and the interference signal includes: calculating the transmitted copy signal s t (t) is time-reversed to obtain the time-reversed transmitted copy signal; the complex conjugate of the time-reversed transmitted copy signal is taken to obtain the time-domain matched filter h(t) = conj[s t [-t]; Calculate the convolution of the time-domain matched filter h(t) and the interference signal s(t) to obtain the output signal s. out (t) = conv[s(t), h(t)].

[0065] In one embodiment of the present invention, the above-mentioned calculation of the output signal based on the transmitted copy signal and the interference signal includes: calculating the interference signal s(t) and the transmitted copy signal s(t). tThe cross-correlation function of (t) is used to obtain the output signal s. out (t)=xcorr[s(t,s t (t)].

[0066] According to embodiments of the present invention, the modulation-free continuous laser ranging system provides the following: The laser's own phase jitter is used as a natural modulation in the ranging system, avoiding the use of additional laser modulation devices and simplifying the laser ranging system. Simultaneously, the laser's own phase jitter, i.e., the linewidth, can easily reach the MHz or even GHz level. This allows for a larger equivalent modulation bandwidth in laser ranging, improving ranging accuracy; it also avoids the use of extremely narrow linewidth single-frequency lasers, reducing the requirements for the laser source. Finally, since the broadband laser signal required for ranging in this invention is not artificially modulated and has truly random characteristics, its anti-interference and anti-interception capabilities are stronger.

[0067] Please see Figure 2 , Figure 2 This is a flowchart illustrating a modulation-free continuous laser ranging method according to an embodiment of the present invention. The method mainly includes the following steps S201 to S202:

[0068] S201. Generate three identical continuous laser beams with a preset linewidth, the three continuous laser beams including a first continuous laser beam, a second continuous laser beam, and a third continuous laser beam.

[0069] S202. Target detection is performed using the first continuous laser beam.

[0070] S203. The target is coherently detected by using the echo of the second continuous laser and the first continuous laser to illuminate the target, and an interference signal is obtained.

[0071] S204. Measure the original phase of the third continuous laser beam.

[0072] S205. Calculate the distance to the target based on the interference signal and the original phase.

[0073] In one embodiment of the present invention, the preset linewidth is on the order of MHz to GHz.

[0074] In one embodiment of the present invention, S203, measuring the original phase of the third continuous laser beam includes:

[0075] The third continuous laser beam is split into two beams;

[0076] One of the two or the third continuous laser beams is delayed for a preset time to obtain a delayed continuous laser beam;

[0077] The delayed continuous laser is mixed with another of the two or the third continuous laser to obtain a mixed signal;

[0078] The mixed signal is photoelectrically detected, and the phase is integrated to obtain the original phase of the continuous laser.

[0079] In one embodiment of the present invention, S205, calculating the distance to the target based on the interference signal and the original phase includes:

[0080] The original phase is time-shifted to obtain the time-shifted phase, which is time-aligned with the phase of the second continuous laser.

[0081] The compensated signal is constructed using the time-shifted phase.

[0082] Multiply the interference signal by the compensation signal to obtain the compensated signal;

[0083] Using this original phase, a transmitted replica signal is constructed;

[0084] The output signal is calculated based on the transmitted replicated signal and the interference signal;

[0085] The distance is obtained based on the output signal.

[0086] In one embodiment of the present invention, the calculation of the output signal based on the transmitted replica signal and the interference signal includes:

[0087] The transmitted copy signal is time-reversed to obtain the time-reversed transmitted copy signal;

[0088] The complex conjugate of the transmitted copy signal after time deconvolution is used to obtain the time-domain matched filter;

[0089] Calculate the Fourier transform of the time-domain matched filter to obtain the frequency-domain matched filter;

[0090] The frequency domain matched filter is used to perform matched filtering on the interference signal to obtain the output signal.

[0091] In one embodiment of the present invention, the calculation of the output signal based on the transmitted replica signal and the interference signal includes:

[0092] Calculate the Fourier transform of the transmitted replicated signal;

[0093] Taking the complex conjugate of the Fourier transform result yields a frequency domain matched filter;

[0094] The frequency domain matched filter is used to perform matched filtering on the interference signal to obtain the output signal.

[0095] In one embodiment of the present invention, the calculation of the output signal based on the transmitted replica signal and the interference signal includes:

[0096] The transmitted copy signal is time-reversed to obtain the time-reversed transmitted copy signal;

[0097] The complex conjugate of the transmitted copy signal after time deconvolution is used to obtain the time-domain matched filter;

[0098] The output signal is obtained by calculating the convolution between the time-domain matched filter and the interference signal.

[0099] In one embodiment of the present invention, calculating the output signal based on the transmitted replica signal and the interference signal includes:

[0100] The cross-correlation function between the interference signal and the transmitted replica signal is calculated to obtain the output signal.

[0101] In one embodiment of the present invention, the length of the time shift is the optical path delay from the continuous laser module to the coherent measurement module.

[0102] It should be noted that the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0103] If the integrated module is implemented as a software functional module 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 invention, in essence, 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.

[0104] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0105] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0106] The above is a description of a modulation-free continuous laser ranging system and method provided by the present invention. For those skilled in the art, based on the ideas of the embodiments of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A modulation-free continuous laser ranging system, characterized in that, include: A continuous laser module is used to generate three identical continuous lasers with a preset linewidth, the three continuous lasers including a first continuous laser, a second continuous laser, and a third continuous laser; A transceiver optical module is used for target detection using the first continuous laser beam. The coherent detection module is used to coherently detect the target by using the echoes from the second continuous laser and the first continuous laser to illuminate the target, thereby obtaining an interference signal; A phase measurement module is used to measure the original phase of the third continuous laser beam; The data processing module is used to calculate the distance to the target based on the interference signal and the original phase; The measurement of the original phase of the third continuous laser beam includes: The third continuous laser beam is split into two beams; One of the two or three third continuous laser paths is delayed for a preset time to obtain a delayed continuous laser; The delayed continuous laser is mixed with another of the two third continuous lasers to obtain a mixed signal; The mixed signal is photoelectrically detected, and the phase is integrated to obtain the original phase of the continuous laser. The step of calculating the distance to the target based on the interference signal and the original phase includes: The original phase is time-shifted to obtain a time-shifted phase, which is time-aligned with the phase of the second continuous laser. A compensation signal is constructed using the time-shifted phase; Multiply the interference signal by the compensation signal to obtain the compensated signal; Using the original phase, a transmitted replica signal is constructed; The output signal is calculated based on the transmitted replicated signal and the interference signal; The distance is obtained based on the output signal.

2. The modulation-free continuous laser ranging system according to claim 1, characterized in that, The preset linewidth is on the order of MHz to GHz.

3. The modulation-free continuous laser ranging system according to claim 1, characterized in that, The calculation of the output signal based on the transmitted replicated signal and the interference signal includes: The transmitted copy signal is time-reversed to obtain the time-reversed transmitted copy signal; The complex conjugate of the transmitted replicated signal after time deconvolution is used to obtain a time-domain matched filter; Calculate the Fourier transform of the time-domain matched filter to obtain the frequency-domain matched filter; The frequency domain matched filter is used to perform matched filtering on the interference signal to obtain the output signal.

4. The modulation-free continuous laser ranging system according to claim 1, characterized in that, The calculation of the output signal based on the transmitted replicated signal and the interference signal includes: Calculate the Fourier transform result of the transmitted replicated signal; Taking the complex conjugate of the Fourier transform result yields a frequency domain matched filter; The frequency domain matched filter is used to perform matched filtering on the interference signal to obtain the output signal.

5. The modulation-free continuous laser ranging system according to claim 1, characterized in that, The calculation of the output signal based on the transmitted replicated signal and the interference signal includes: The transmitted copy signal is time-reversed to obtain the time-reversed transmitted copy signal; The complex conjugate of the transmitted replicated signal after time deconvolution is used to obtain a time-domain matched filter; The output signal is obtained by calculating the convolution between the time-domain matched filter and the interference signal.

6. The modulation-free continuous laser ranging system according to claim 1, characterized in that, The calculation of the output signal based on the transmitted replicated signal and the interference signal includes: The cross-correlation function between the interference signal and the transmitted replica signal is calculated to obtain the output signal.

7. The modulation-free continuous laser ranging system according to claim 1, characterized in that, The length of the time shift is the optical path delay from the continuous laser module to the coherent detection module.

8. A modulation-free continuous laser ranging method, characterized in that, include: Generate three identical continuous laser beams with a preset linewidth, the three continuous laser beams including a first continuous laser beam, a second continuous laser beam, and a third continuous laser beam; Target detection is performed using the first continuous laser beam. The target is coherently detected by using the echoes from the second continuous laser beam and the first continuous laser beam to obtain an interference signal; Measure the original phase of the third continuous laser beam; The distance to the target is calculated based on the interference signal and the original phase; The measurement of the original phase of the third continuous laser beam includes: The third continuous laser beam is split into two beams; One of the two or three third continuous laser paths is delayed for a preset time to obtain a delayed continuous laser; The delayed continuous laser is mixed with another of the two third continuous lasers to obtain a mixed signal; The mixed signal is photoelectrically detected, and the phase is integrated to obtain the original phase of the continuous laser. The step of calculating the distance to the target based on the interference signal and the original phase includes: The original phase is time-shifted to obtain a time-shifted phase, which is time-aligned with the phase of the second continuous laser. A compensation signal is constructed using the time-shifted phase; Multiply the interference signal by the compensation signal to obtain the compensated signal; Using the original phase, a transmitted replica signal is constructed; The output signal is calculated based on the transmitted replicated signal and the interference signal; The distance is obtained based on the output signal.

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