Laser radar ranging system

Abstract

The invention relates to a laser radar ranging system, which belongs to the technical field of laser ranging and comprises a pulse laser light source, an optical fiber circulator, an input laser receiving and transmitting light path, a photoelectric detector and a signal acquisition and analysis unit. The pulse laser light source is used for outputting pulse laser; the optical fiber circulator converts the pulse laser into annular light; the input laser receiving and transmitting optical path takes the annular light as a laser detection signal and receives a laser echo signal; the photoelectric detector converts the laser detection signal and the laser echo signal into an electric signal; and the signal acquisition and analysis unit calculates the detection distance of the laser radar according to the electric signal. The pulse laser is converted into the annular light beam through the optical fiber circulator, the problem that a reflector is blocked due to energy concentration in a central area of a traditional Gaussian beam is avoided, energy loss is reduced, and echo signal strength is enhanced.

Description

Technical Field

[0001] This invention relates to a lidar ranging system, belonging to the field of lidar ranging technology. Background Technology

[0002] As an important branch of modern precision measurement, lidar ranging technology has been widely applied in several key areas such as autonomous driving, industrial automation, environmental monitoring, and military reconnaissance. In autonomous driving scenarios, lidar can perceive the vehicle's surrounding environment in real time, accurately construct 3D maps, and provide crucial data support for autonomous driving decision-making systems. In industrial automation, it can achieve high-precision dimensional measurement and quality control of large mechanical components, improving production efficiency and product quality. In environmental monitoring, it can remotely detect complex terrain and atmospheric composition, contributing to climate change research and disaster early warning. In the military field, its excellent concealment and anti-jamming capabilities enable accurate target identification and positioning.

[0003] However, existing lidar ranging systems have revealed many problems that urgently need to be solved in practical applications. Traditional systems mostly use Gaussian beams, whose energy distribution is concentrated in the central region. When they encounter optical components such as reflectors, they will suffer severe energy loss. Part of the beam will be blocked by the reflectors and cannot be effectively projected onto the target object. As a result, the echo signal strength will drop significantly, which will seriously affect the measurement accuracy and reliability, especially when detecting at long distances, the signal loss will be more significant. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention proposes a lidar ranging system.

[0005] The technical solution of the present invention is as follows:

[0006] A lidar ranging system includes a pulsed laser source, a fiber optic circulator, an input laser receiving and transmitting circuit, a photodetector, and a signal acquisition and analysis unit;

[0007] The pulsed laser source is used to output pulsed laser light;

[0008] The fiber optic circulator converts the pulsed laser into ring light;

[0009] The input laser receiving and transmitting circuit emits the ring light as a laser detection signal and receives the laser echo signal;

[0010] The photodetector converts the laser detection signal and the laser echo signal into electrical signals;

[0011] The signal acquisition and analysis unit calculates the lidar detection range based on the electrical signal.

[0012] Preferably, the fiber optic circulator adopts a reflective telescope structure, including a ring spot transformation module, a first primary reflector, and a second primary reflector;

[0013] The ring spot conversion module converts pulsed laser light into ring light;

[0014] The second primary mirror is configured to reflect the ring light back to the first primary mirror;

[0015] The first primary reflector is configured to collimate the ring light before it passes through the second primary reflector; when the ring light passes through the second primary reflector, the light beam outside the ring center is not blocked by the second primary reflector.

[0016] Preferably, the annular light spot transformation module includes a first plano-convex lens, a second plano-convex lens, and an annular light transformation component;

[0017] The pulsed laser output from the pulsed laser source passes sequentially through the first plano-convex lens, the ring light conversion component, and the second plano-convex lens;

[0018] The first plano-convex lens collimates the pulsed laser;

[0019] The ring light conversion component converts the pulsed laser into ring light;

[0020] The second plano-convex lens focuses the ring light and outputs it.

[0021] Preferably, the focal length of the first plano-convex lens is 18 mm, and the focal length of the second plano-convex lens is 60 mm.

[0022] The ring light conversion component is disposed between the first plano-convex lens and the second plano-convex lens. The distance between the ring light conversion component and the first plano-convex lens is 10 mm, and the distance between the ring light conversion component and the second plano-convex lens is 10 mm.

[0023] Preferably, the annular spot transformation component is a binary phase plate.

[0024] Preferably, the diameter of the central hollow circle of the binary phase plate is 10 mm and the thickness is 3 mm.

[0025] Preferably, the annular light spot transformation component consists of two identical corner-cone lenses placed symmetrically at their cone angles, with the cone angles of the first and second corner-cone lenses being 2°.

[0026] Preferably, the pulsed laser source is an erbium-doped fiber laser with a wavelength of 1550 mm, a pulse repetition rate of 100 kHz, a pulse width of 3 nanoseconds, and an output power of 500 mW.

[0027] The present invention has the following beneficial effects:

[0028] 1. This invention converts pulsed laser light into a ring beam using an optical fiber circulator, avoiding the mirror obstruction problem caused by energy concentration in the central region of traditional Gaussian beams, reducing energy loss, and enhancing the echo signal strength. In long-distance detection, this reduced signal loss directly translates into improved ranging accuracy.

[0029] 2. The energy of the ring beam of the present invention is uniformly distributed in the ring area, avoiding nonlinear effects caused by excessive local energy, and can effectively suppress the influence of interference light in complex environments (such as haze and strong light background).

[0030] 3. This invention combines a ring-shaped light spot transformation module (including a binary phase plate or a corner bevel lens) with a primary reflector to achieve beam collimation and ring-shaped light spot generation. The system is small in size and light in weight, and is suitable for space-constrained scenarios such as airborne and vehicle-mounted applications. Attached Figure Description

[0031] Figure 1 This is a system topology diagram according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the fiber optic circulator structure according to an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the ring spot transformation module according to an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of the first and second pyramidal lenses according to an embodiment of the present invention.

[0035] Figure 5 The detection distances under different conditions are shown in the embodiments of the present invention.

[0036] Figure 6 The light spot distribution at position m=1 after the light beam passes through the hollow part of the binary phase plate in an embodiment of the present invention.

[0037] Figure 7 The light spot distribution at position m=1 after the light beam passes through the non-hollow part of the binary phase plate in an embodiment of the present invention.

[0038] Figure 8 The light spot at positions m = -1, 0, 1 after the light beam passes through the binary phase plate in an embodiment of the present invention.

[0039] Figure 9 This is the central intensity distribution of the light field function along the optical axis in an embodiment of the present invention.

[0040] Figure 10 This is a schematic diagram of a binary phase plate according to an embodiment of the present invention.

[0041] The labels in the diagram are as follows:

[0042] 1. Pulsed laser source; 2. Fiber optic circulator; 3. Input laser receiving and transmitting path; 6. Photodetector; 7. Signal acquisition and analysis unit; 21. Annular spot transformation module; 22. First primary reflector; 23. Second primary reflector; 211. First pyramidal lens; 212. Second pyramidal lens; 213. Binary phase plate; 214. First plano-convex lens; 215. Second plano-convex lens. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be understood that the step numbers used in the text are for ease of description only and are not intended to limit the order in which the steps are performed.

[0045] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0046] The terms “comprising” and “including” indicate the presence of the described feature, whole, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0047] The term “and / or” refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes these combinations.

[0048] Example 1:

[0049] See Figure 1 A lidar ranging system includes a pulsed laser source 1, an optical fiber circulator 2, an input laser receiving and transmitting circuit 3, a photodetector 6, and a signal acquisition and analysis unit 7.

[0050] The pulsed laser source 1 is used to output pulsed laser;

[0051] The fiber optic circulator 2 converts the pulsed laser into ring light;

[0052] The input laser receiving and transmitting circuit 3 transmits the ring light as a laser detection signal and receives the laser echo signal;

[0053] The photodetector 6 converts the laser detection signal and the laser echo signal into electrical signals (specifically, electrical pulse signals);

[0054] The signal acquisition and analysis unit 7 calculates the lidar detection range based on the electrical signal.

[0055] During the transmission from port 1 to port 2 of the fiber optic circulator 2, a portion of the signal is transferred from port 1 to port 3 and converted into an electrical signal by the photodetector 6. This electrical signal then serves as a reference signal and enters the signal acquisition and analysis unit 7. The signal acquisition and analysis unit 7 obtains the distance to the target by comparing the time difference between the reference signal and the corresponding electrical signal of the laser echo signal.

[0056] The pulsed laser light is transmitted from port 1 to port 2 of the fiber optic circulator 2, outputting a ring light as a laser detection signal. The laser echo signal enters from port 2 of the fiber optic circulator 2 and is transmitted to port 3, where it is output to the photodetector 6 and converted into an electrical signal. The output of the photodetector 6 is connected to the input of the signal acquisition and analysis unit 7.

[0057] See Figure 2 Preferably, the fiber optic circulator 2 adopts a reflective telescope structure, including a ring spot conversion module 21, a first primary reflector 22 and a second primary reflector 23;

[0058] The first primary reflector 22 has a diameter of 150 mm and a focal length of 4, while the second primary reflector 23 has a diameter of 40 mm and is a plane reflector.

[0059] The ring spot conversion module 21 converts pulsed laser light into ring light;

[0060] The second primary reflector 23 is configured to reflect the ring light back to the first primary reflector 22;

[0061] The first primary reflector 22 is configured to collimate the ring light and allow it to pass through the second primary reflector 23; when the ring light passes through the second primary reflector 23, the light beam outside the ring center is not blocked by the second primary reflector 23.

[0062] Figure 2 The propagation path of the beam when the output ring light of fiber optic circulator 2 is shown.

[0063] In this disclosure, the ring light, after being reflected by the first primary reflector 22, passes through the second primary reflector 23. Since the second primary reflector 23 is located at the center of the ring beam, this ensures the system is an axisymmetric optical imaging system, reducing imaging errors. Because the second primary reflector 23 is unavoidable, existing technologies would lead to a significant waste of transmission energy, limiting the radar's detection range. This invention uses a ring beam to avoid energy waste and loss, thereby significantly improving signal transmission efficiency and echo signal acquisition efficiency.

[0064] See Figure 3 Preferably, the ring light spot conversion module 21 includes a first plano-convex lens 214, a second plano-convex lens 215, and a ring light conversion component;

[0065] The pulsed laser output from the pulsed laser source 1 passes sequentially through the first plano-convex lens 214, the ring light conversion component, and the second plano-convex lens 215;

[0066] The first plano-convex lens 214 collimates the pulsed laser;

[0067] The ring light conversion component converts the pulsed laser into ring light;

[0068] The second plano-convex lens 215 focuses the ring light and outputs it.

[0069] Preferably, the focal length of the first plano-convex lens 214 is 18 mm, and the focal length of the second plano-convex lens 215 is 60 mm.

[0070] The ring light conversion component is disposed between the first plano-convex lens 214 and the second plano-convex lens 215. The distance between the ring light conversion component and the first plano-convex lens 214 is 10 mm, and the distance between the ring light conversion component and the second plano-convex lens 215 is 10 mm.

[0071] See Figure 10 Preferably, the annular spot conversion component is a binary phase plate 213, and the binary phase plate 213 is made of glass.

[0072] Preferably, the diameter of the central hollow circle of the binary phase plate 213 is 10 mm and the thickness is 3 mm.

[0073] See Figure 4 In another embodiment, the annular spot transformation component consists of two identical and symmetrically placed corner-to-corner lenses, with the first corner-to-corner lens 211 and the second corner-to-corner lens 212 having a cone angle of 2°.

[0074] See Figure 5Preferably, the pulsed laser source 1 is an erbium-doped fiber laser with a wavelength of 1550 mm, a pulse repetition rate of 100 kHz, a pulse width of 3 nanoseconds, and an output power of 500 mW. This improves the detection range of existing lidar systems, enabling them to operate stably in rainy and foggy weather, while ensuring that the laser damage threshold remains below that of the human eye.

[0075] Explanation of the principle of ring light conversion:

[0076] The output laser beam of an erbium-doped fiber laser is approximately a Gaussian beam, and its optical field at the position of the binary phase plate is:

[0077]

[0078] Where q = z + jz r , z r The Rayleigh distance at the waist of the Gaussian beam is the aperture function of the portion passing through the circular aperture. The aperture function of the portion of the medium passing through the window outside the circular hole Where b is the aperture of the binary phase plate, according to the Fresnel-Kirchoff theory, after passing through lens f c and f s , in f s The light field at the focal position is:

[0079]

[0080]

[0081] Wherein the wavefront curvature radius This represents the propagation path from the wavefront of the two-dimensional phase plate to position fc. This represents the transmission path from fc to fs. This represents the transmission path from the fs mirror to the working surface of the reflecting mirror; σ h , σ c , σ s These are the differentials of the surfaces of the binary phase plate, lens fc, and lens fs, respectively. and These are the transfer functions of fc and fs. The calculation of the transfer integral (2) is very complex. Here, we use the physical optics propagation method of the optical design software Zemax to calculate it, which yields the light intensity distribution at the working surface. For example... Figure 6 As shown, the laser spot profile at a distance of 12mm from the focal point is obtained by passing through the hollow part of the binary phase plate. It can be seen that the center of the spot is concave, which is a typical ring profile. This part of the laser accounts for 87% of the total power. Figure 7The laser spot distribution at the edge of the non-hollow region of the binary phase plate is such that there is a small bulge in the center, but the main energy is distributed at the edge, which accounts for about 13% of the power, so it has little effect on the central depression.

[0082] Light intensity at different locations along the axis near the reflector:

[0083] According to the Fresnel-Kirchoff theory, there are two Fresnel regions on the axis on both sides of the focal point, where Fresnel diffraction occurs. The light field distribution at a distance Δ from the mirror on the axis is as follows:

[0084]

[0085] Distribution of light intensity along the axis:

[0086]

[0087] Considering fs diffraction aperture z0 is the distance from the optical fiber to the binary phase plate. Formula (4) shows that when... When I(z) has a minimum value, such as Figure 9 As shown, at this time When the light spot becomes concave, the light spot used in this embodiment is the n = ±1 order diffraction region, based on the focal length f of the collimating lens. c objective lens focal length f s The aperture size 'a' and position 'z0' can be used to calculate Δ = 12.04 mm, and the theoretical value matches the actual measured value. For example... Figure 8 The image shows the measured light spots at different positions. It can be seen that at the position m=0, the beam maintains the characteristics of a Gaussian spot (m=0 is the position where the laser is emitted from the binary phase plate). Figure 8 We can also observe circular diffraction spots at positions m = ±1, with a larger spot base at m = -1, which is caused by insufficient focusing of the edge beam. We used the position of the m = 1 order diffraction spot as the location where the emitted laser passes through the reflector for the second time, thus ensuring that the generated radar laser energy is not wasted due to obstruction by the reflector.

[0088] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0089] Those skilled in the art will recognize that the units and algorithm steps described in the embodiments disclosed herein can be implemented using electronic hardware, computer software, or a combination of electronic hardware and software. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0090] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0091] In the several embodiments provided in this application, any function, if implemented as a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0092] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A laser radar ranging system characterized by, The device comprises a pulsed laser source (1), a fiber-optic circulator (2), an input laser transceiver light path (3), a photoelectric detector (6), and a signal acquisition and analysis unit (7). The pulsed laser source (1) is used for outputting pulsed laser. The fiber-optic circulator (2) converts the pulsed laser into ring-shaped light. The input laser transceiver light path (3) transmits the ring-shaped light as a laser detection signal and receives a laser echo signal. The photoelectric detector (6) converts the laser detection signal and the laser echo signal into an electric signal. The signal acquisition and analysis unit (7) calculates a laser radar detection distance according to the electric signal.

2. The lidar ranging system of claim 1, wherein, The fiber-optic circulator (2) comprises a ring-shaped light spot conversion module (21), a first main mirror (22), and a second main mirror (23). The ring-shaped light spot conversion module (21) converts pulsed laser into ring-shaped light. The second main mirror (23) is arranged to reflect the ring-shaped light to the first main mirror (22). The first main mirror (22) is arranged to collimate the ring-shaped light and pass it through the second main mirror (23). When the ring-shaped light passes through the second main mirror (23), the light beams outside the ring-shaped center are not blocked by the second main mirror (23).

3. The lidar ranging system of claim 2, wherein, The ring-shaped light spot conversion module (21) comprises a first plano-convex lens (214), a second plano-convex lens (215), and a ring-shaped light conversion assembly. The pulsed laser output by the pulsed laser source (1) sequentially passes through the first plano-convex lens (214), the ring-shaped light conversion assembly, and the second plano-convex lens (215). The first plano-convex lens (214) collimates the pulsed laser. The ring-shaped light conversion assembly converts the pulsed laser into ring-shaped light. The second plano-convex lens (215) converges and outputs the ring-shaped light.

4. The lidar ranging system of claim 3, wherein, The focal length of the first plano-convex lens (214) is 18 mm, and the focal length of the second plano-convex lens (215) is 60 mm. The ring-shaped light conversion assembly is arranged between the first plano-convex lens (214) and the second plano-convex lens (215), and the distance between the ring-shaped light conversion assembly and the first plano-convex lens (214) is 10 mm, and the distance between the ring-shaped light conversion assembly and the second plano-convex lens (215) is 10 mm.

5. The lidar ranging system of claim 3, wherein, The ring-shaped light spot conversion assembly is a binary phase plate (213).

6. The lidar ranging system of claim 5, wherein, The diameter of the hollow circle in the center of the binary phase plate (213) is 10 mm, and the thickness is 3 mm.

7. The lidar ranging system of claim 3, wherein, The ring-shaped light spot conversion assembly is two identical and symmetrically placed corner cube lenses, and the cone angle of the first corner cube lens (211) and the second corner cube lens (212) is 2°.

8. The lidar ranging system of claim 1, wherein, The pulsed laser source (1) is an erbium-doped fiber laser with a wavelength of 1550 mm, a pulse repetition frequency of 100 kHz, a pulse width of 3 ns, and an output power of 500 mW.

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