Field-of-view spliced large-field-of-view high-resolution thousand-beam laser radar optical system

Abstract

The invention discloses a field-of-view spliced large-field-of-view high-resolution thousand-beam laser radar optical system, which comprises a transmitting optical system and a receiving optical system, the emission optical system comprises an emission optical fiber array for outputting nine paths of laser beams, an emission telescope and an emission shaping diffraction element; the receiving optical system comprises a receiving telescope and a receiving detector; nine post-receiving optical paths are arranged corresponding to the transmitting optical system, a receiving telescope adopts a Schmidt structure to realize large-view-field aberration correction, and a free-form surface optical element is introduced to perform distortion correction. The invention aims to solve the core technical bottleneck that high resolution and high detection density are difficult to consider while the existing middle-high altitude airborne laser radar topographic mapping system realizes large-view-field detection.

Description

Technical Field

[0001] This invention relates to the field of airborne lidar detection technology, specifically a large field-of-view, high-resolution, thousand-beam lidar optical system with field-of-view stitching. Background Technology

[0002] With the development of remote sensing technology, lidar (LiDAR) systems have been widely used in topographic mapping, environmental monitoring, and autonomous driving. Traditional LiDAR systems typically use a single beam or a small number of beams for scanning, which suffers from problems such as narrow field of view, low detection density, and low measurement efficiency. To improve detection density and measurement efficiency, researchers have proposed multi-beam lidar systems, which achieve higher spatial resolution and wider coverage by increasing the number of beams.

[0003] In the pursuit of large field of view and high resolution in optical system design, "field of view segmentation and multi-channel parallel reception" is a key technical approach. Chinese invention application CN120065518A discloses a common-aperture optical system for visible light and short-wave infrared, demonstrating a field-of-view stitching scheme. This optical system employs a catadioptric common-aperture structure as its front end. Incident light is first collected and initially converged by an optical system consisting of a primary mirror and a secondary mirror to obtain a long focal length to meet the high-resolution requirement. The primary image plane formed by the primary and secondary mirrors is located in the subsequent optical path. At the primary image plane, a beam-splitting prism is placed to separate the incident composite light rays according to their spectrum, transmitting the visible light band and reflecting the short-wave infrared band. In the short-wave infrared optical path, the reflected light first passes through a short-wave infrared image-side telecentric relay lens group composed of multiple lenses, relaying the primary image plane to a new secondary image plane position and ensuring that the outgoing light follows an image-side telecentric optical path. At the secondary image plane, each reflective surface of the field-of-view splitter reflects a sub-field-of-view beam from a specific region of the secondary image plane in different directions. The beams reflected by the field-of-view splitter enter multiple (N≥2) second imaging units arranged circumferentially around it. Each second imaging unit contains an object-side telecentric relay lens group and a short-wave infrared detector. The object-side telecentric relay lens group is responsible for relaying the beam from the field-of-view splitter again and imaging it onto the corresponding detector target surface, ensuring object-side telecentricity to match the cold aperture of the cooled detector. Finally, the system achieves large field-of-view synthesis by simultaneously reading the sub-images formed on these N detectors and fusing them through a back-end algorithm.

[0004] This technical solution uses a polyhedral mirror (field divider) to divide a large field of view, and then uses multiple relay lens groups arranged around it to image the divided sub-fields of view onto independent detectors, thus achieving large field-of-view imaging. While this solution is effective in its application context, a deeper analysis of its core method of "field-of-view division at the intermediate image plane" reveals inherent technical flaws in pursuing higher optical performance: First, the stitching method leads to information loss and image quality degradation. The "focal plane division" method represented by this solution physically involves cutting and selecting from an already formed, complete image plane. The field of view located at the edge of the dividing prism will inevitably have its beam partially blocked or suffer severe vignetting, resulting in the permanent loss of optical information in this part of the scene. This means that the imaging quality or detection signal-to-noise ratio at the boundary region of the sub-fields of view obtained through stitching is essentially compromised. Second, the stitching method limits the upper limit of system performance and scalability. The number of stitching channels in this technical solution is severely constrained by the space of the intermediate image plane and the structure of the divider. Increasing the number of channels means designing more complex split prisms and more crowded relay optical path layouts, which is difficult to scale up in engineering, resulting in a low performance ceiling. Third, the stitching method introduces unnecessary system complexity and losses. The "focal plane splitting" method requires an additional, fully functional relay imaging system after the main system for each sub-field of view to relay the cut image plane back to the detector. This significantly increases the system's size, complexity, assembly difficulty, and cumulative optical losses.

[0005] In summary, the field-of-view stitching method employed in this technical solution inherently suffers from core weaknesses such as information loss, poor scalability, and inherent complexity. Therefore, a more feasible optical technology approach is needed to address the bottleneck issue of kilopixel-level laser detection.

[0006] Existing airborne lidar topographic mapping systems for medium and high altitudes struggle to simultaneously achieve high resolution and high detection density while maintaining a wide field of view. Current technologies primarily face three interrelated technical challenges: First, the contradiction between large-scale parallel detection and system integration. To meet the high-precision mapping requirements at a scale of 1:2000, the parallel detection scale of the lidar needs to be increased from the hundreds of pixels to the thousands of pixels to significantly improve the density of the ground detection point cloud. However, simply increasing the number of channels leads to an exceptionally complex optical system structure, large size, and difficult assembly and adjustment, making it difficult to achieve engineering integration and application on an airborne platform. Second, the contradiction between a wide field of view and image quality. To achieve a wide mapping bandwidth, the optical system must have a large field of view. However, traditional optical designs introduce significant aberrations and distortions under large field-of-view conditions, resulting in a severe decrease in the imaging quality (spot energy concentration, point cloud positioning accuracy) at the system's edge fields of view, failing to meet the stringent requirements of high-resolution mapping for consistency across the entire field of view. Thirdly, there is the challenge of registration accuracy in multi-channel transmission and reception. In a multi-beam system with thousands of pixels, ensuring high-precision and high-stability spatial registration between thousands of transmitted laser beams and the receiving field of view is an extremely serious challenge. Even tiny registration errors can lead to a large number of invalid detections or data errors, thus rendering large-scale parallel detection meaningless.

[0007] These issues collectively hinder the further development of lidar topographic mapping technology towards greater distances, higher precision, and higher efficiency. Therefore, there is an urgent need for an innovative optical system design that can systematically solve these problems while ensuring long-range ranging capabilities. Summary of the Invention

[0008] The purpose of this invention is to provide a large field-of-view, high-resolution, thousand-beam lidar optical system with stitched field of view, aiming to solve the core technical bottleneck of existing medium- and high-altitude airborne lidar terrain mapping systems, which struggle to achieve both high resolution and high detection density while realizing large field-of-view detection.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A large field-of-view, high-resolution, thousand-beam lidar optical system with field-of-view stitching includes a transmitting optical system and a receiving optical system. The transmitting optical system includes a transmitting fiber array, a transmitting telescope, and a transmitting shaping diffraction element. The transmitting fiber array outputs nine laser beams, which are collimated by the transmitting telescope and then incident on the transmitting shaping diffraction element. The receiving optical system includes a receiving telescope and a receiving detector. The receiving telescope includes a Schmitt mirror, a primary receiving mirror, a secondary receiving mirror, a central receiving lens group, and a rear receiving optical path lens group. Corresponding to the transmitting optical system, nine rear receiving optical paths are set up. Each rear receiving optical path consists of a rear receiving optical path lens group and a detector, and each rear receiving optical path lens group is followed by a receiving detector. Each receiving detector corresponds to a strip of receiving field of view. The receiving telescope uses a Schmitt structure to achieve large field-of-view aberration correction and introduces a freeform surface optical element from the secondary receiving mirror for distortion correction.

[0011] The launching telescope employs a refractive beam expander and collimator system, with a single channel output beam diameter of 80mm. The system's aperture stop is located above the emission shaping diffraction element.

[0012] The transmitting diffraction element uses a customized diffraction optical element to perform wavefront shaping on each beam, forming a beam array in the far field that is consistent with the receiving field of view.

[0013] During operation, the nine laser beams are transformed into nine strip-shaped sub-fields of view after passing through the emission shaping diffraction element; the echo signals are collected by the receiving telescope, and after aberration and distortion correction, they form nine strip-shaped light spots on the focal plane; the echo signals of each sub-field of view are received and processed by the corresponding receiving detector; the nine sub-fields of view are seamlessly fused into the overall field of view through a stitching algorithm, and the data of the overlapping area is used for registration accuracy verification and compensation.

[0014] Nine sub-fields of view are arranged in a 3×3 stripe on the object side, with each sub-field of view maintaining a 0.02° overlap.

[0015] The transmitting fiber and the receiving field of view achieve a precise physical correspondence at the end face, with a registration accuracy of less than 0.3 pixels.

[0016] With a receiver detector pixel spacing of 50µm and a receiver focal length of 2m, the system resolution is 25µm.

[0017] In view of the above technical features, the present invention has the following beneficial effects: 1. The present invention achieves a large field of view coverage through the design of a nine-line array, meeting the needs of high-resolution terrain mapping; the application of shaping diffraction elements improves the flexibility of laser beam shaping and enhances the detection capability of the system; the non-equidistant arrangement of the area array optical fibers ensures high-precision registration between transmission and reception, improving the measurement accuracy of the system; the Schmidt mirror and freeform surface design effectively eliminate optical distortion within the large field of view, improving image quality; 2. To meet the needs of acquiring high-resolution three-dimensional terrain data of the Earth's surface for moving platforms, the present invention realizes thousand-pixel multi-beam mapping radar technology, achieving a 1:2000 scale. Applications of high- and medium-scale airborne topographic mapping; 3. Solving the contradiction between large-scale detection and system integration through the "nine-line array object-space parallel" architecture; solving the contradiction of large field-of-view image quality through the combination correction of "Schmidt mirror + freeform surface"; solving the multi-channel transmission and reception registration problem through "precise arrangement of fiber end faces"; 4. The layout of the transmitting optical system realizes a fundamental methodological innovation from "focal plane segmentation" to "object-space parallel", solving the information loss and scalability limitations of existing technologies; 5. The registration mechanism of the receiving optical system solves the core problem of multi-channel transmission and reception registration through precise correspondence at the physical level; 6. The overall system architecture of this invention successfully balances the three major contradictions of large-scale detection, high image quality requirements and engineering feasibility. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the nine-channel optical arrangement layout of the present invention;

[0020] Figure 3 This is a schematic diagram of the positioning of the nine-channel transmitting fiber array of the present invention.

[0021] In the diagram: 1-Transmitting fiber array; 2-Transmitting telescope; 3-Transmitting shaping diffraction element; 4-Receiving detector; 5-Receiving telescope; 51-Schmidt compensator mirror; 52-Receiving primary mirror; 53-Receiving secondary mirror; 54-Receiving central lens group; 55-Receiving rear optical path lens group. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that some components well-known to those skilled in the art but not related to the main content of the present invention may be omitted in the drawings or description. Additionally, for ease of description, some components in the drawings may be omitted, enlarged, or reduced, but this does not represent the actual size or complete structure of the product.

[0023] A wide-field-of-view, high-resolution, thousand-beam lidar optical system with stitched field of view, such as... Figure 1 As shown, it includes a transmitting optical system and a receiving optical system; the transmitting optical system includes a transmitting fiber array 1, a transmitting telescope 2 and a transmitting shaping diffraction element 3; the transmitting fiber array 1 outputs nine laser beams, which are collimated by the transmitting telescope 2 and then incident on the transmitting shaping diffraction element 3.

[0024] The transmitting telescope 2 consists of four lens assemblies. The transmitting optical system divides the laser into nine laser beams with calculable fixed intervals, enabling precise physical correspondence between the transmitting optical fiber and the receiving field of view at the end face. The registration accuracy reaches the pixel level (<0.3 pixels), ensuring the effectiveness and reliability of large-scale parallel detection.

[0025] In the transmitting optical system, the exit centers of the nine laser beams of the transmitting fiber array 1 are symmetrically distributed with the optical axis of the transmitting telescope 2, ensuring that the beams fully cover the entrance aperture of the transmitting telescope 2. The exit end of the transmitting telescope 2 is fixed coaxially with the transmitting shaping diffraction element 3, and the incident surface of the transmitting shaping diffraction element 3 is parallel to the exit surface of the transmitting telescope 2 with a fixed spacing, ensuring that the collimated nine laser beams form a thousand-wave beam with a stitched field of view after diffraction shaping.

[0026] Preferably, the transmitting telescope 2 adopts a refractive beam expanding and collimating system with a single channel output beam diameter of 80mm, and the system's aperture stop is on the transmitting shaping diffraction element 3.

[0027] The transmitting diffraction element 3 uses a customized diffraction optical element to perform wavefront shaping on each beam, forming a beam array in the far field that is consistent with the receiving field of view.

[0028] The receiving optical system includes a receiving telescope 5 and a receiving detector 4. The receiving telescope 5 includes a Schmidt mirror 51, a primary receiving mirror 52, a secondary receiving mirror 53, a central receiving lens group 54, and a rear receiving optical path lens group 55. Corresponding to the transmitting optical system, nine rear receiving optical paths are set up. Each rear receiving optical path consists of a rear receiving optical path lens group 55 and a detector 4, with one receiving detector 4 connected after each rear receiving optical path lens group 55. Each receiving detector 4 corresponds to a strip of receiving field of view. The receiving telescope 5 uses a Schmidt structure to achieve large field-of-view aberration correction and introduces freeform surface optical elements in the secondary receiving mirror 53 for distortion correction. The nine transmitting linear array corresponds one-to-one with the receiving array, and high-precision transmit-receive registration is achieved through the arrangement of optical fibers on the fiber endfaces. The receiving detectors 4 correspond one-to-one with the transmitting channels to ensure channel independence.

[0029] In the receiving optical system, a Schmidt mirror 51, a primary receiving mirror 52, and a secondary receiving mirror 53 are arranged coaxially along the receiving optical path. The Schmidt mirror 51 is located at the front end of the receiving optical path, and the secondary receiving mirror 53 is fixed on the central through-hole axis of the primary receiving mirror 52, forming a Schmidt correction structure. The central receiving lens group 54 is located on the light-emitting side of the secondary receiving mirror 53 and is coaxially assembled with the primary receiving mirror 52 and the secondary receiving mirror 53. A free-form surface design is superimposed on the secondary receiving mirror 53 to achieve distortion correction under a large field of view. The incident end of the rear receiving optical path lens group 55 is coupled to the light-emitting end of the central receiving lens group 54. The nine rear receiving optical paths are arranged in an array along the light-emitting surface of the central receiving lens group 54. The optical axis of each rear receiving optical path lens group 55 corresponds one-to-one with the field of view of the nine laser beams of the transmitting optical system, and its light-emitting end is directly attached and fixed to the photosensitive surface of the receiving detector 4.

[0030] During operation, nine laser beams are emitted simultaneously, forming nine strip-shaped sub-fields of view after passing through the emission shaping diffraction element 3; the echo signals are collected by the receiving telescope 5, and after aberration and distortion correction, nine strip-shaped light spots are formed on the focal plane; the echo signals of each sub-field of view are received and processed by the corresponding receiving detector 4; the nine sub-fields of view are seamlessly fused into the overall field of view through a stitching algorithm, and the data of the overlapping area is used for registration accuracy verification and compensation.

[0031] Figure 2 This is a schematic diagram illustrating the spatial arrangement of nine sub-fields of view (or optical channels) in an embodiment of the present invention, showing the relative positional relationships and static structure between the channels. The nine sub-fields of view are arranged in a 3×3 stripe pattern on the object side, with an overlap of approximately 0.02° between each sub-field of view. This arrangement ensures seamless coverage of the entire field of view while guaranteeing good engineering feasibility of the system.

[0032] Figure 3 This is a schematic diagram of the fiber optic array end-face arrangement coordinates in this invention. The diagram shows the precise theoretical positions (unit: mm) of the nine optical channel fibers in the end-face coordinate system (with the center as the origin). This precise arrangement at the physical level ensures a one-to-one spatial correspondence between the transmitting and receiving channels, which is the technical basis for achieving high-precision registration in thousand-pixel-level detection.

[0033] The transmitting fiber and the receiving field of view achieve a precise physical correspondence at the end face, with a registration accuracy of less than 0.3 pixels.

[0034] With a receiver detector of 4 pixels spaced at 50µm and a receiving focal length of 2m, the system resolution is 25µm.

[0035] This invention achieves a breakthrough in detection scale, enabling effective detection at the 1024-pixel level and solving the challenge of large-scale parallel detection. It comprehensively improves image quality, controlling optical distortion across the entire field of view to within 0.5 pixels, resolving the image quality contradiction in a large field of view. Registration accuracy is guaranteed through precise arrangement at the physical level, achieving stable high-precision registration. In terms of engineering feasibility, the relaxed assembly tolerances and compact layout ensure the system's reliability on an airborne platform.

[0036] In this invention, the layout of the emission optical system achieves a fundamental methodological innovation from "focal plane segmentation" to "object-space parallelism," solving the problems of information loss and scalability limitations in existing technologies.

[0037] In this invention, the registration mechanism of the receiving optical system solves the core problem of multi-channel transceiver registration through precise physical-level correspondence.

[0038] The overall system architecture of this invention successfully balances the three major contradictions of large-scale detection, high image quality requirements, and engineering feasibility.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. A large field-of-view, high-resolution, thousand-beam lidar optical system with stitched field of view, comprising a transmitting optical system and a receiving optical system; characterized in that: The transmitting optical system includes a transmitting fiber array (1), a transmitting telescope (2), and a transmitting shaping diffraction element (3); the transmitting fiber array (1) outputs nine laser beams, which are collimated by the transmitting telescope (2) and then incident on the transmitting shaping diffraction element (3); the receiving optical system includes a receiving telescope (5) and a receiving detector (4); the receiving telescope (5) includes a Schmidt mirror (51), a receiving primary mirror (52), a receiving secondary mirror (53), a receiving central lens group (54), and a receiving rear optical path lens group (55); corresponding to the transmitting optical system, nine receiving rear optical paths are set up, each receiving rear optical path consists of a receiving rear optical path lens group (55) and a detector (4), each receiving rear optical path lens group (55) is followed by a receiving detector (4), and each receiving detector (4) corresponds to a strip receiving field of view; the receiving telescope (5) adopts a Schmidt structure to achieve large field of view aberration correction, and introduces a freeform surface optical element of the receiving secondary mirror (53) for distortion correction.

2. The thousand-beam lidar optical system as described in claim 1, characterized in that: The launching telescope (2) adopts a refractive beam expansion and collimation system with a single channel output beam diameter of 80 mm. The aperture stop of the system is located on the launching shaping diffraction element (3).

3. The multi-beam lidar optical system as described in claim 2, characterized in that: The transmitting diffraction element (3) adopts a customized diffraction optical element to perform wavefront shaping on each beam and form a beam array in the far field that is consistent with the receiving field of view.

4. The thousand-beam lidar optical system as described in claim 3, characterized in that: During operation, the nine laser beams are transformed into nine strip-shaped sub-fields of view after passing through the emission shaping diffraction element (3); the echo signals are collected by the receiving telescope (5), and after aberration and distortion correction, nine strip-shaped light spots are formed on the focal plane; the echo signals of each sub-field of view are received and processed by the corresponding receiving detector (4); The nine sub-fields of view are seamlessly integrated into the overall field of view through a stitching algorithm, and the data in the overlapping areas are used for registration accuracy verification and compensation.

5. The thousand-beam lidar optical system as described in claim 1, characterized in that: Nine sub-fields of view are arranged in a 3×3 stripe on the object side, with each sub-field of view maintaining a 0.02° overlap.

6. The thousand-beam lidar optical system as described in claim 1, characterized in that: The transmitting fiber and the receiving field of view achieve a precise physical correspondence at the end face, with a registration accuracy of less than 0.3 pixels.

7. The thousand-beam lidar optical system as described in claim 1, characterized in that: With a pixel spacing of 50µm and a receiving focal length of 2m, the system resolution is 25µm.

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