An anti-jamming laser ranging system and method based on conjugate vortex filtering

Abstract

This invention discloses an anti-interference laser ranging system and method based on conjugate vortex filtering, belonging to the field of anti-interference detection technology. When performing laser ranging in complex environments, the receiving module first receives a mixed optical signal containing target echo and scattering noise. The echo signal is modulated by a first spiral phase plate and enters a 4f optical system. Subsequently, an annular aperture is set in the Fourier plane, allowing only the target echo to pass through while blocking central scattering noise and other non-target area noise. The filtered target echo signal is then demodulated by a second spiral phase plate using conjugate phase modulation, reconverting it into a Gaussian beam, thereby effectively improving the energy concentration of the echo signal and facilitating subsequent photoelectric detection and distance calculation. This invention is suitable for complex application scenarios such as strong background radiation and strong scattering media, and the device structure is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of anti-interference detection technology, specifically relating to an anti-interference laser ranging system and method based on conjugate vortex filtering. Background Technology

[0002] Laser ranging technology, due to its advantages such as high measurement accuracy, good directionality, fast response speed, and non-contact operation, has been widely used in fields such as lidar, target detection, 3D imaging, autonomous driving, and industrial precision measurement. Its basic principle is to obtain the target distance by measuring the flight time between the transmitted signal and the echo signal. However, in complex environments, the received signal contains not only the target's echo signal but also various scattering noises such as background radiation from the sky and cloud scattering. These noise interferences can cause a sharp decrease in the signal-to-noise ratio of the received signal, making echo peak extraction difficult and increasing ranging errors.

[0003] Currently, commonly used anti-interference and noise reduction methods mainly include spectral filtering, spatial filtering, temporal filtering, polarization filtering, and back-end signal processing. However, these methods still have certain limitations. For example, spectral filtering is difficult to filter out noise with the same wavelength as the signal light or within the filtering bandwidth; time-gating technology has poor suppression effect on forward-scattered light, which will reduce both spatial accuracy and distance accuracy; traditional spatial filtering mainly relies on reducing the receiving field of view, but its ability to suppress noise entering the receiving system coaxially is limited; and back-end signal processing cannot improve the quality of the received original signal and often suffers from poor real-time performance and generalization ability.

[0004] Furthermore, while using a single spiral phase element can modulate the coherent target echo into a vortex beam and achieve a certain degree of noise filtering in conjunction with a ring mask, the filtered target echo still maintains a ring-shaped intensity distribution. Due to the limited receiving aperture of practical detectors, such as optical fibers and single-photon detectors, the ring-shaped echo optical field is difficult to fully match its effective receiving area, easily causing echo energy loss, thereby reducing echo energy utilization and system detection sensitivity.

[0005] Therefore, there is an urgent need to develop a simple, efficient laser ranging method that can effectively suppress background noise in complex environments. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing denoising techniques and to propose an anti-interference laser ranging system and method based on conjugate vortex filtering.

[0007] The first aspect discloses an anti-interference laser ranging system based on conjugate vortex filtering, the system comprising:

[0008] The transmitting module 11 is used to control the timing of pulsed laser emission via the control and processing module 14 and to synchronously record the emission time of the pulsed laser. The pulsed laser forms an echo signal after being reflected by the target.

[0009] The receiving module 12 includes a conjugate vortex filter system 15, used to filter out scattering noise from the echo signal to obtain the target echo signal. The conjugate vortex filter system 15 includes a first spiral phase plate 1, a first lens 2, an annular aperture 3, a second lens 4, and a second spiral phase plate 5. The first spiral phase plate 1 applies phase modulation to the echo signal to form an annular vortex light field. The first lens 2 and the second lens 4 form a 4f optical system 10. The annular aperture 3 is located at the Fourier plane of the 4f optical system 10, enabling the modulated echo signal to achieve spatial separation of the target echo signal and scattering noise in the Fourier plane via the annular aperture 3. The second spiral phase plate 5 is located at the output conjugate surface of the 4f optical system 10 and has the same topological charge and opposite sign as the first spiral phase plate 1, and is conjugate in phase, thus converting the target echo signal after conjugate vortex filtering back into a Gaussian beam.

[0010] The control and processing module 14 is used to determine the arrival time of the echo pulse based on the electrical signal converted from the target echo signal after conjugate filtering, and to calculate the distance to the target under test based on the transmission time and arrival time.

[0011] The second aspect discloses an anti-interference laser ranging method based on conjugate vortex filtering, applied to the anti-interference laser ranging system based on conjugate vortex filtering in the first aspect and any embodiment of the first aspect, the method comprising:

[0012] The control and processing module 14 generates a laser emission control signal to control the pulsed laser to be emitted in a time sequence, synchronously records the emission time of the pulsed laser, and forms an echo signal after the pulsed laser is reflected by the surface of the target under test.

[0013] The receiving telescope 7 receives the echo signal, and the scattering noise in the echo signal is filtered out by the conjugate vortex filter system 15 to obtain the target echo signal;

[0014] The target echo signal is converted into an electrical signal by the photodetector 8;

[0015] The control and processing module 14 determines the arrival time of the target echo signal based on the electrical signal, and calculates the distance to the target to be measured based on the transmission time and arrival time.

[0016] As can be seen from the above technical solutions, the present invention has the following beneficial effects:

[0017] In this invention, when performing laser ranging in complex environments, the receiving module first receives a mixed optical signal containing target echo and scattering noise. This signal is modulated by a first spiral phase plate and then enters the 4f optical system. The highly coherent target echo forms a ring-shaped vortex light field in the Fourier plane, while the less coherent scattering noise is mainly focused in the central region. Subsequently, a ring-shaped aperture is placed in the Fourier plane, allowing only the target echo to pass through while blocking the central scattering noise and other non-target region noise. The filtered target echo signal is then demodulated by the conjugate phase of a second spiral phase plate, reconverting it into a Gaussian beam, thereby effectively improving the energy concentration of the echo signal and facilitating subsequent photoelectric detection and distance calculation.

[0018] Compared to traditional methods, this invention utilizes the difference in spatial coherence of echo signals. By combining two phase-conjugate spiral phase plates with a ring aperture, noise can be filtered out at the optical front end. This invention is suitable for complex applications such as those with strong background radiation and strong scattering media. Moreover, the device has a simple structure and is easy to implement. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the anti-interference laser ranging system based on conjugate vortex filtering.

[0020] Figure 2 This is a schematic diagram of a conjugate vortex filter system.

[0021] Figure 3 It is a pair of phase-conjugate spiral phase plates of the receiving module, wherein (a) is the first spiral phase plate with a topological charge number l equal to 20, and (b) is the second spiral phase plate with a topological charge number l equal to -20.

[0022] Figure 4 It is an optical signal obtained by an anti-interference receiving system that has not undergone conjugate vortex filtering.

[0023] Figure 5 It is the light field on the 4f system Fourier plane of the signal containing noise after passing through the first spiral phase plate after using the conjugate vortex filter system.

[0024] Figure 6 This is a schematic diagram of an annular aperture.

[0025] Figure 7 It is the light intensity distribution of the coherent echo signal on the Fourier plane of the 4f optical system after passing through the first spiral phase plate.

[0026] Figure 8 It is the far-field distribution corresponding to the output conjugate surface of the 4f optical system after filtering by the annular aperture.

[0027] Figure 9 This is a schematic diagram of the far-field distribution after passing through a conjugate vortex filter system.

[0028] Figure 10 This is a flowchart of an anti-interference laser ranging method based on conjugate vortex filtering.

[0029] Among them, 1 is the first spiral phase plate, 2 is the first lens, 3 is the annular aperture, 4 is the second lens, 5 is the second spiral phase plate, 6 is the third lens, 7 is the receiving telescope, 8 is the photodetector, 9 is the laser, 10 is the 4f optical system, 11 is the transmitting module, 12 is the receiving module, 13 is the target under test, 14 is the control and processing module, and 15 is the conjugate vortex filter system. Detailed Implementation

[0030] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be thorough and complete.

[0031] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "up," "down," and similar expressions used herein are for illustrative purposes only and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0033] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the related listed items.

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] like Figure 1 As shown in the schematic diagram, the present invention mainly includes a transmitting module 11, a receiving module 12, and a control and processing module 14.

[0036] The transmitting module 11 is used to control the timing of pulsed laser emission via the control and processing module 14 and to synchronously record the emission time of the pulsed laser. The pulsed laser forms an echo signal after being reflected by the target.

[0037] The receiving module 12 includes a conjugate vortex filter system 15, used to filter out scattering noise from the echo signal to obtain the target echo signal. The conjugate vortex filter system 15 includes a first spiral phase plate 1, a first lens 2, an annular aperture 3, a second lens 4, and a second spiral phase plate 5. The first spiral phase plate 1 applies phase modulation to the echo signal to form an annular vortex light field. The first lens 2 and the second lens 4 form a 4f optical system 10. The annular aperture 3 is located at the Fourier plane of the 4f optical system 10, enabling the modulated echo signal to achieve spatial separation of the target echo signal and scattering noise in the Fourier plane via the annular aperture 3. The second spiral phase plate 5 is located at the output conjugate surface of the 4f optical system 10 and has the same topological charge and opposite sign as the first spiral phase plate 1, and is conjugate in phase, thus converting the target echo signal after conjugate vortex filtering back into a Gaussian beam.

[0038] The control and processing module 14 is used to determine the arrival time of the echo pulse based on the electrical signal converted from the target echo signal after conjugate filtering, and to calculate the distance to the target under test based on the transmission time and arrival time.

[0039] Specifically, the control and processing module 14 first generates a laser emission control signal to control the laser 9 of the emission module 11 to emit pulsed lasers in a time sequence, synchronously recording the emission time of the laser pulses. After beam expansion and collimation, the pulsed laser illuminates the target 13 under test through free space. After reflection from the surface of the target under test, the pulsed laser forms an echo signal. The coherent echo signal carries the target distance information and is transmitted back to the receiving module 12 through free space. In a noisy environment, the echo signal received by the receiving module usually contains both the effective target echo and scattered noise. The echo signal is first received by the receiving telescope 7, which performs beam contraction to match the incident aperture of the subsequent conjugate vortex filter system 15. The receiving telescope 7 generally consists of two lenses with focal lengths fa and fb, respectively. When fa is greater than fb, it is a beam contraction system. The focal lengths of the two lenses are adjusted according to the size of the incident aperture to complete the matching.

[0040] Subsequently, the incident light field is phase-modulated by the first spiral phase plate 1 in the conjugate vortex filter system 15, and the laser coherent echo signal can then be expressed as:

[0041] (1)

[0042] in, It is an imaginary number. and These are the radial coordinates and azimuth coordinates on the receiving surface, respectively. The amplitude of the light field. The laser beam waist radius, This represents the initial phase of the echo on the receiving surface. Let be the topological charge number of the first spiral phase plate. Since the incoherent components have random phases, after modulation, a stable phase relationship cannot be formed between the spatial components. Furthermore, after passing through the 4f optical system 10, the coherent echo signal on its Fourier plane appears as a ring-shaped light field, with the scattering noise corresponding to the focused spot at the center. At this point, a specially designed ring stop 3 is placed on this plane, and the ring radius within the light-transmitting region of the ring stop 3 is . The outer ring radius is Then its amplitude transmission function It can be represented as:

[0043] (2)

[0044] The radius of the light-transmitting region can be determined by 1 / e^2 of the maximum light intensity on the ring after the coherent echo signal is modulated by the first spiral phase plate. Therefore, the light field after passing through the annular aperture 3 can be expressed as:

[0045] (3)

[0046] Since the annular aperture 3 only allows the target echo to pass through, the scattering noise in the central region and the stray noise on the outer side are effectively blocked, thereby achieving optical front-end noise reduction.

[0047] Furthermore, when the denoised echo signal, i.e., the target echo signal, propagates to the conjugate output image plane of the 4f optical system 10, it passes through the second spiral phase plate 5, corresponding to a topological charge of -1, and its phase is conjugate with that of the first spiral phase plate 1. After further phase modulation, the output light field is expressed by the following formula:

[0048] (4)

[0049] Because the spiral phase term lθ introduced by the first spiral phase plate 1 is canceled out by the conjugate phase term -lθ introduced by the second spiral phase plate 5, the optical field is restored to the initial Gaussian beam. Finally, the echo signal demodulated by the first spiral phase plate 1 is focused by a lens onto the photodetector 8. The photodetector 8 converts the received optical signal into an electrical signal, and the control and processing module 14 performs subsequent processing on the electrical signal to determine the arrival time of the echo pulse. By using the laser pulse emission time that was initially recorded, the flight time between the emitted pulse and the echo pulse is obtained. Finally, according to The distance to the target is calculated using the following formula:

[0050] (5)

[0051] in, The distance to the target to be measured. y is the speed of light in the transmission medium.

[0052] Figure 2 This is a schematic diagram of a conjugate vortex filter system, as shown below. Figure 2 As shown, the echo signal is first phase-modulated by the first spiral phase plate 1, and then the laser target echo and scattering noise are spatially separated by the first lens 2 and the second lens 4 forming a 4f optical system 10. The scattering noise is filtered out by placing an annular aperture 3 in the Fourier plane of the 4f optical system 10. Finally, the target echo signal is restored to a Gaussian beam by the second spiral phase plate 5, which is phase-conjugate with the first spiral phase plate 1, and the third lens 6.

[0053] It should also be noted that the Fourier plane of the 4f optical system 10 is determined according to the focal length of the first lens 2. For example, if the focal length of the first lens 2 is 100mm, then the Fourier plane of the 4f optical system 10 composed of the first lens 2 and the second lens 4 is located at the 100mm position of the back focal plane of the first lens 2.

[0054] In one specific embodiment: the emitted laser signal wavelength is 1064nm, the topological charge of the first spiral phase plate 1 is equal to 20, and the topological charge of the second spiral phase plate 5 is equal to -20. The focal length of both lenses in the 4f optical system 10 is 60mm.

[0055] To simulate the effect of background noise in free space, a broadband halogen lamp light source with a working wavelength of 360-2500nm is used. The transmitter generates a laser signal with a wavelength of 1064nm, which is collimated and expanded to illuminate the target under test. The echo signal reflected from the target 13, along with the background noise generated by the halogen lamp, enters the receiver. When the conjugate vortex filter system 15 of this invention is not used, the echo signal, after focusing, is as follows... Figure 4 As shown, the signal and noise are completely mixed together, and the signal-to-noise ratio drops sharply. This will make it impossible to detect the true peak value of the target echo signal and make it impossible to achieve accurate distance measurement.

[0056] After employing the conjugate vortex filter system 15 of the present invention, the echo signal first passes through as follows: Figure 3 The first spiral phase plate 1 shown in (a) can be obtained in the Fourier plane of the 4f optical system 10 as follows: Figure 5 The light field distribution shown indicates that the coherent target echo in the echo signal forms a stable ring structure after modulation, while the incoherent scattering noise is focused at the center, thus achieving spatial separation of signal and noise.

[0057] Furthermore, to filter out noise, a [missing information] is placed at the 10 Fourier plane of the 4f optical system. Figure 6 The annular aperture 3 shown is, in which, The radius of the ring within the light-transmitting area. The outer ring radius of the light-transmitting region. Here, the inner and outer ring radii of the light-transmitting region are determined by the vortex intensity distribution formed in the Fourier plane of the 4f optical system after the coherent echo signal is modulated by the first spiral phase plate. For example... Figure 7 As shown, R1 and R2 represent the inner and outer ring radii when the light intensity drops to 1 / e^2 of the maximum energy on the ring, respectively. The measured values ​​are 137 μm and 203 μm. Considering beam broadening and alignment errors in the actual system, to ensure stable passage of the echo signal and suppress noise in the central region, the inner and outer light-passing radii of the annular aperture in this embodiment are designed as R1 and R2, respectively. in =150μm and R out =200μm. Therefore, the light-transmitting area of ​​the annular aperture 3 can match the annular light field formed by the target echo in the Fourier plane, allowing the effective echo signal to pass through while spatially blocking background noise and stray light in the central region. In this way, background noise can be filtered out at the optical front end.

[0058] After passing through the annular aperture 3, a filtered light field distribution is formed on the conjugate surface corresponding to the first spiral phase plate 1, such as... Figure 8 As shown. At this point, the background noise has been significantly removed, retaining only the effective coherent echo signal modulated by the first spiral phase plate 1. At this time, a configuration is set at the conjugate surface as shown... Figure 3 (b) The second spiral phase plate 5. The topological charge of the second spiral phase plate 5 is -20, which is equal in magnitude but opposite in sign to the topological charge of the first spiral phase plate 1. Therefore, it can perform conjugate phase demodulation on the filtered effective echo signal. After passing through the second spiral phase plate 5, the spiral phase introduced by the first spiral phase plate 1 is canceled out, and the filtered ring echo signal is converted back into a Gaussian optical field, such as... Figure 9 As shown, the energy is concentrated at the center of this Gaussian light field, which is more conducive to subsequent signal reception and improves energy concentration.

[0059] Finally, the target echo signal, after being filtered by a conjugate vortex filter, is focused by the third lens 6 onto the photodetector 8. The photodetector 8 receives the signal and inputs it into the control and processing module 14. The control and processing module 14 calculates the distance to the target based on the time delay between the emitted laser pulse and the received echo pulse.

[0060] The experimental results of the above embodiments show that the method of the present invention is simple, does not require complex structure and subsequent processing, and achieves the separation and removal of effective echo signal and background noise in space. Under the conditions of strong background interference and strong scattering medium, the signal-to-noise ratio of the received signal can be greatly improved.

[0061] In one embodiment, the present invention also provides an anti-interference laser ranging method based on conjugate vortex filtering, applied to the aforementioned anti-interference laser ranging system based on conjugate vortex filtering, such as... Figure 10 As shown, the method includes:

[0062] S101, the control and processing module 14 generates a laser emission control signal to control the pulsed laser to be emitted in sequence, synchronously records the emission time of the pulsed laser, and the pulsed laser forms an echo signal after being reflected by the surface of the target under test.

[0063] S102. The receiving telescope 7 receives the echo signal, and the scattering noise in the echo signal is filtered out by the conjugate vortex filter system 15 to obtain the target echo signal.

[0064] S103. The target echo signal is converted into an electrical signal by the photodetector 8;

[0065] S104. The control and processing module 14 determines the arrival time of the target echo signal based on the electrical signal, and calculates the distance to the target to be measured based on the transmission time and arrival time.

[0066] The control and processing module determines the arrival time of the target echo signal based on the electrical signal, and calculates the distance to the target based on the transmission time and arrival time, including:

[0067] The electrical signal is amplified, sampled, and its peak value is extracted to determine the arrival time of the target echo signal.

[0068] The time-of-flight delay between the emitted pulse and the echo pulse is obtained by using the pulsed laser emission and arrival times. The distance to the target is then calculated based on the time-of-flight delay and the speed of light in the transmission medium.

[0069] Since this embodiment corresponds to the above system embodiment, it is described in a relatively simple way. For details of the relevant technical features and the effects of implementation, please refer to the corresponding description of the above-provided system embodiment.

[0070] This invention also provides an electronic device, which includes a processor and a memory. The memory stores at least one instruction or at least one program, which is loaded and executed by the processor. This is an anti-interference laser ranging method based on conjugate vortex filtering provided in the above-described method embodiments.

[0071] Furthermore, the electronic device may participate in or include the apparatus or system provided in the embodiments of the present invention. The electronic device may include one or more processors (processors may include, but are not limited to, processing devices such as microprocessors (MCUs) or programmable logic devices (FPGAs), memory for storing data, and transmission devices for communication functions. In addition, it may also include: a display, an input / output interface (I / O interface), a universal serial bus (USB) port (which may be included as one of the ports of the I / O interface), a network interface, a power supply, and / or a camera.

[0072] It should be noted that the aforementioned one or more processors and / or other data processing circuits are generally referred to herein as "data processing circuits". These data processing circuits may be embodied, in whole or in part, in software, hardware, firmware, or any other combination thereof. Furthermore, the data processing circuit may be a single, independent processing module, or may be integrated, in whole or in part, into any other element within the device (or mobile device). As involved in the embodiments of the present invention, the data processing circuit serves as a processor control mechanism (e.g., selection of a variable resistor termination path connected to an interface).

[0073] The memory can be used to store software programs and modules of application software, such as the program instructions / data storage device corresponding to the method described in the embodiments of the present invention. The processor executes various functional applications and data processing by running the software programs and modules stored in the memory, thereby realizing the above-mentioned data processing method. The memory may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory may further include memory remotely located relative to the processor, and these remote memories can be connected to electronic devices via a network. Examples of the above-mentioned networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0074] The transmission device is used to receive or send data via a network. Specific examples of the network described above may include a wireless network provided by the device's communication provider. In one example, the transmission device includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device may be a Radio Frequency (RF) module, used for wireless communication with the Internet.

[0075] The display can be, for example, a touchscreen liquid crystal display (LCD), which allows users to interact with the user interface of an electronic device (or mobile device).

[0076] This invention also provides a computer storage medium storing at least one instruction or at least one program, which is loaded and executed by a processor to implement the anti-interference laser ranging method based on conjugate vortex filtering provided in the above-described method embodiments.

[0077] Optionally, in this embodiment, the aforementioned computer storage medium may be located at at least one of the multiple network servers in a computer network. Optionally, in this embodiment, the aforementioned storage medium may include, but is not limited to, various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0078] This invention also provides a computer program product or computer program, which includes computer instructions stored in a computer storage medium. The processor of an electronic device reads the computer instructions from the computer storage medium and executes the computer instructions, causing the electronic device to perform the anti-interference laser ranging method based on conjugate vortex filtering provided in the above-described method embodiments.

[0079] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0080] It should be understood that the above description of the preferred embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art, under the guidance of this invention, can make substitutions or modifications without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. An anti-interference laser ranging system based on conjugate vortex filtering, characterized in that, The system includes: The transmitting module (11) is used to control the timing of pulsed laser emission via the control and processing module (14) and synchronously record the emission time of the pulsed laser. The pulsed laser forms an echo signal after being reflected by the target. The receiving module (12) includes a conjugate vortex filter system (15) for filtering out scattering noise from the echo signal to obtain the target echo signal. The conjugate vortex filter system (15) includes a first spiral phase plate (1), a first lens (2), an annular aperture (3), a second lens (4), and a second spiral phase plate (5). The first spiral phase plate (1) applies phase modulation to the echo signal to form an annular vortex light field. The first lens (2) and the second lens (4) form a 4f optical system (1). 0), the annular aperture (3) is set at the Fourier plane of the 4f optical system (10), the 4f optical system (10) enables the modulated echo signal to achieve spatial separation of the target echo signal and scattering noise in the Fourier plane through the annular aperture (3); the second spiral phase plate (5) is set at the output conjugate surface of the 4f optical system (10), and has the same topological charge and opposite sign as the first spiral phase plate (1), and is conjugate with each other, so that the target echo signal after conjugate vortex filtering is converted back into a Gaussian beam; The control and processing module (14) is used to determine the arrival time of the echo pulse based on the electrical signal converted from the target echo signal after conjugate filtering, and to calculate the distance to the target under test based on the transmission time and arrival time.

2. The anti-interference laser ranging system based on conjugate vortex filtering according to claim 1, characterized in that, The receiving module also includes a third lens (6) for focusing the target echo signal after conjugate vortex filtering onto a photodetector (8), which then converts the target echo signal after conjugate filtering into an electrical signal.

3. The anti-interference laser ranging system based on conjugate vortex filtering according to claim 1, characterized in that, The radius of the light transmission area of ​​the annular aperture (3) is determined by 1 / e^2 of the maximum light intensity on the ring after the echo signal is modulated by the first spiral phase plate 1.

4. The anti-interference laser ranging system based on conjugate vortex filtering according to claim 1, characterized in that, The receiving module also includes a receiving telescope (7) for receiving echo signals and performing beam reduction to match the incident aperture of the conjugate vortex filter system (15).

5. The anti-interference laser ranging system based on conjugate vortex filtering according to claim 1, characterized in that, The first spiral phase plate (1) applies phase modulation to the echo signal, forming a ring-shaped vortex optical field. This can be expressed as the following formula: ； in, It is an imaginary number. and These are the radial and azimuth coordinates on the receiving surface, respectively. The amplitude of the light field. The laser beam waist radius, This represents the initial phase of the echo on the receiving surface. Let be the topological charge number of the first spiral phase plate.

6. The anti-interference laser ranging system based on conjugate vortex filtering according to claim 1, characterized in that, The light field after passing through the annular aperture (3) This can be expressed as the following formula: ； in, The amplitude transmission function of the annular aperture (3) is represented. This represents the annular vortex optical field formed by applying phase modulation to the received signal through the first spiral phase plate (1).

7. The anti-interference laser ranging system based on conjugate vortex filtering according to claim 1, characterized in that, After phase modulation by the second spiral phase plate (5), the output light field This can be expressed as the following formula: ； in, φ is an imaginary number, r and θ are the radial and azimuth coordinates on the receiving surface, respectively, A0 is the optical field amplitude, w0 is the laser beam waist radius, φ0 is the initial phase of the echo on the receiving surface, and l is the topological charge of the first spiral phase plate (1).

8. The anti-interference laser ranging system based on conjugate vortex filtering according to claim 1, characterized in that, The transmitting module (11) also includes a laser (9), and the control and processing module (14) controls the laser (9) to emit Gaussian pulse lasers in sequence, which are then expanded and collimated before propagating to the target in free space.

9. An anti-interference laser ranging method based on conjugate vortex filtering, applied to any one of the anti-interference laser ranging systems based on conjugate vortex filtering according to claims 1-8, characterized in that, The method includes: The control and processing module (14) generates a laser emission control signal to control the pulsed laser to be emitted in sequence and synchronously records the emission time of the pulsed laser. The pulsed laser is reflected by the surface of the target to be tested to form an echo signal. The receiving telescope (7) receives the echo signal, and the scattering noise in the echo signal is filtered out by the conjugate vortex filter system (15) to obtain the target echo signal; The target echo signal is converted into an electrical signal by a photodetector (8); The control and processing module (14) determines the arrival time of the target echo signal based on the electrical signal and calculates the distance to the target based on the transmission time and arrival time.

10. The anti-interference laser ranging method based on conjugate vortex filtering according to claim 9, characterized in that, The control and processing module determines the arrival time of the target echo signal based on the electrical signal, and calculates the distance to the target based on the transmission time and arrival time, including: The electrical signal is amplified, sampled, and its peak value is extracted to determine the arrival time of the target echo signal; The time-of-flight delay between the emitted pulse and the echo pulse is obtained by using the pulsed laser emission and arrival times. The distance to the target is then calculated based on the time-of-flight delay and the speed of light in the transmission medium.

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