Window for laser radar, laser radar and preparation method of window

Abstract

The invention provides a window for a laser radar, the laser radar and a preparation method of the window for the laser radar. The window is made of an organic material and comprises a first structural layer with an optical axis; when the window is placed in the vertical direction, the included angle between the optical axis direction of the first structure layer and the vertical plane where the first structure layer is located ranges from 35 degrees to 55 degrees. A light beam is transmitted at the first structural layer, and when the light beam is vertically incident relative to the first structural layer, the difference value between the phase difference generated after the light beam is transmitted by the first structural layer and the half-wavelength of the light beam is not larger than one fourth of the wavelength of the light beam.

Description

Technical Field

[0001] This disclosure relates to the field of lidar technology, and in particular to a window for lidar, lidar, and a method for fabricating the window. Background Technology

[0002] In addition to protecting the internal components of a lidar system, the viewing window also functions as an optical element in the lidar's optical imaging. The lidar's detection light passes through the viewing window and exits to the outside of the lidar; the echo generated after being reflected by an object also passes through the viewing window and enters the lidar's interior.

[0003] When probe light and echoes pass through the window, stress birefringence may occur, affecting the detection accuracy of the lidar. Windows made of certain materials are insensitive to stress, reducing or eliminating the effects of stress birefringence; for example, windows made of glass. However, glass is expensive to manufacture, and since the window is located near the outer edge of the lidar, glass windows have poor impact resistance and are easily damaged.

[0004] The content of the background section is merely the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention

[0005] To address one or more deficiencies in the prior art, this disclosure provides a window for lidar, the window being made of an organic material, and the window comprising:

[0006] The first structural layer has an optical axis; when the window is placed in a preset posture along the vertical direction, the angle between the optical axis direction of the first structural layer and the vertical direction is 35°-55°.

[0007] The light beam is transmitted through the first structural layer, and when the light beam is incident perpendicularly to the first structural layer, the difference between the phase difference generated by the light beam after transmission through the first structural layer and half the wavelength of the light beam is not greater than one-quarter of the wavelength of the light beam.

[0008] Optionally, the difference between the phase difference generated by the light beam after transmission through the first structural layer and half the wavelength of the light beam is not greater than one-tenth of the wavelength of the light beam. Preferably, the difference between the phase difference generated by the light beam after transmission through the first structural layer and half the wavelength of the light beam is not greater than one-twentieth of the wavelength of the light beam.

[0009] Optionally, the phase difference generated by the beam passing through the first structural layer is no greater than 20 orders relative to the wavelength of the beam.

[0010] Optionally, the phase difference order generated by the beam passing through the first structural layer is negatively correlated with the maximum incident angle of the beam relative to the first structural layer.

[0011] Optionally, the first structural layer is planar, or the first structural layer has curvature in at least one direction.

[0012] Optionally, the window may further include:

[0013] The second structural layer is arranged parallel to the first structural layer; the second structural layer has an optical axis, and the optical axis of the second structural layer is approximately perpendicular to the optical axis of the first structural layer.

[0014] Optionally, the window may further include:

[0015] A filling layer is located between the first structural layer and the second structural layer, and the light beam does not undergo birefringence when propagating within the filling layer.

[0016] Optionally, the phase difference and phase difference order of the beam passing through the second structural layer are approximately equal to the phase difference and phase difference order of the beam passing through the first structural layer.

[0017] Optionally, this disclosure also relates to a lidar, comprising:

[0018] shell;

[0019] A transmitter configured to emit a probe light;

[0020] A receiver configured to receive the echo generated by the detection light being reflected by an object and convert the echo into an electrical signal;

[0021] An optomechanical structure is disposed within the housing and configured to guide the probe light to the outside of the lidar and guide the echo to the receiver;

[0022] The window as described above is fixedly connected to the housing.

[0023] Optionally, the incident angle of the probe light relative to the first structural layer is in the range of 0-60°.

[0024] Optionally, the optomechanical structure further includes:

[0025] A quarter-wave plate is disposed in the optical path of the probe light and the echo, and is configured to convert the polarization state of the probe light and the echo.

[0026] Optionally, this disclosure also relates to a method for fabricating a window for a lidar, the method comprising:

[0027] A first structural layer blank is provided, wherein the first structural layer blank satisfies the following: when a beam of light of a preset wavelength is incident perpendicularly on the first structural layer blank, the difference between the phase difference generated by the beam after transmission through the first structural layer blank and half the wavelength of the beam is not greater than one-quarter of the wavelength of the beam.

[0028] Obtain the optical axis direction of the first structural layer blank;

[0029] The first structural layer blank is cut according to the optical axis direction of the first structural layer blank and the size of the detection window of the lidar shell to obtain the first structural layer. When the first structural layer is placed in a preset posture along the vertical direction, the angle between the optical axis direction of the first structural layer and the vertical direction is 35°-55°.

[0030] Optionally, the preparation method further includes:

[0031] Provide the blank for the second structural layer;

[0032] Obtain the optical axis direction of the second structural layer blank;

[0033] The second structural layer blank is cut according to the optical axis direction of the first structural layer and the size of the detection window of the lidar housing to obtain the second structural layer. The optical axis of the second structural layer is approximately perpendicular to the optical axis of the first structural layer.

[0034] Fix the second structural layer and the first structural layer so that the second structural layer and the first structural layer are parallel to each other.

[0035] Optionally, the first structural layer blank and the second structural layer blank are made using the same process and processing parameters.

[0036] Compared with existing technologies, the embodiments of this disclosure provide a window for lidar made of organic materials, which helps reduce production costs and improve impact resistance. The first structural layer in the window has an optical axis, which represents the optical axis of the material itself. When the window is placed vertically in a preset orientation, the angle between the optical axis and the vertical direction is within the range of 35°-55°. After the light beam passes through the first structural layer at a certain angle, the resulting stress birefringence is not significant. When the light beam is incident perpendicularly to the first structural layer at different positions, the phase difference distribution is relatively uniform. This improves the polarization efficiency of the window, making it suitable for lidar employing polarization optics and enhancing the lidar's rangefinding capability.

[0037] This disclosure also relates to a lidar in which the aforementioned window is applied.

[0038] This disclosure also relates to a method for preparing a window for a lidar, used to prepare the aforementioned lidar window. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the embodiments of the present disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings:

[0040] Figure 1 A schematic diagram of a lidar window being vertically positioned is shown in some embodiments of this disclosure;

[0041] Figure 2 A schematic diagram is shown for a lidar window with curvature in some embodiments of this disclosure;

[0042] Figure 3 A side view of a window including a second structural layer is shown in some embodiments of this disclosure;

[0043] Figure 4 This illustration shows a schematic diagram of a window including a second structural layer when it is vertically positioned in some embodiments of this disclosure;

[0044] Figure 5 Schematic diagrams of lidars in some embodiments of this disclosure are shown;

[0045] Figure 6 A flowchart illustrating the window preparation method in some embodiments of this disclosure is shown;

[0046] Figure 7 A flowchart illustrating a method for preparing a window including a second structural layer in some embodiments of this disclosure is shown. Detailed Implementation

[0047] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this disclosure. Therefore, the drawings and description are to be considered exemplary in nature and not restrictive.

[0048] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly and specifically defined.

[0049] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or connections that allow for communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0050] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0051] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this disclosure, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0052] The embodiments of this disclosure are described below with reference to the accompanying drawings. It should be understood that the embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0053] This disclosure relates to a window for a lidar system, the window being made of an organic material. The window includes a first structural layer. The first structural layer has an optical axis, and when the window is positioned vertically in a predetermined orientation, the angle between the optical axis of the first structural layer and the vertical direction is 35°-55°. A light beam is transmitted through the first structural layer, and when the light beam is incident perpendicularly to the first structural layer, the difference between the phase difference generated after the light beam is transmitted through the first structural layer and half the wavelength of the light beam is not greater than one-quarter of the wavelength of the light beam.

[0054] In this disclosure, the window material includes organic materials, which helps reduce production costs and improves the window's impact resistance. At different locations in the first structural layer, the optical axis direction exhibits good consistency, with the angle to the vertical direction within a certain numerical range. The phase difference transmitted through the beam incident at a certain angle at different locations is relatively uniform, reducing the likelihood of stress birefringence, or allowing the generated phase difference to be corrected using relatively fixed compensation parameters, thus improving the accuracy of lidar detection. The window provided in this disclosure is suitable for lidar using polarized light detection, reducing optical signal loss due to phase difference and improving the lidar's rangefinding capability.

[0055] Figure 1 and Figure 2 The structure of window 1 for lidar according to some embodiments of the present disclosure is shown below, in conjunction with... Figure 1 and Figure 2 The window 1 used for lidar is described.

[0056] In this disclosure, the material of window 1 includes organic materials, such as one or more of polymethyl methacrylate (PMMA), polypropylene (PP), polycarbonate (PC), polystyrene (PS), and polyethylene (PE). Compared with inorganic materials such as glass, organic materials have lower production and processing costs, and they can withstand a certain degree of elastic deformation and have stronger impact resistance, which is beneficial to improving the service life of the lidar and reducing the risk of lidar damage.

[0057] Window 1 includes a first structural layer 11, and the material of the first structural layer 11 may include organic materials. For example... Figure 1 As shown, in some embodiments of this disclosure, the first structural layer 11 is generally planar. In other embodiments, such as Figure 2 As shown, the first structural layer 11 can also be configured to have curvature in at least one direction, for example, the first structural layer 11 is an arc surface or a sphere. The first structural layer 11 can be configured as a plane or a curved surface according to the requirements of the lidar. For example, the magnitude and direction of the curvature of the first structural layer 11 can be configured to match the detection angle range of the lidar.

[0058] The first structural layer 11 has an optical axis, for example Figure 1 The X direction in the diagram represents the optical axis direction of the first structural layer 11. Figure 1 In the diagram, the Y direction represents the normal direction of the first structural layer 11, and the Z direction represents the vertical direction. When the window 1 is placed vertically in a preset posture, the angle between the optical axis direction X and the vertical direction Z of the first structural layer 11 is within the range of 35°-55°. In some embodiments, the angle between the optical axis direction X and the vertical direction Z of the first structural layer 11 can be any range such as 35-50°, 40-55°, or 40-50°. For example, the angle between the optical axis direction and the vertical direction can be 35°, 40°, 43°, 45°, 46°, 47°, 48°, 50°, or 55°.

[0059] For example, when the window is rectangular, the window can be positioned vertically in a preset posture, such that the long side of the window is in the horizontal plane and the short side of the window is parallel to the vertical direction.

[0060] In this embodiment, the optical axis of the first structural layer 11 represents the optical axis of the material of the first structural layer 11. When a light beam passes through the material along the optical axis, birefringence does not occur, or the birefringence phenomenon is not obvious. The optical axis is a material property, related to molecular characteristics and arrangement, and is independent of the shape and size of the processed first structural layer 11.

[0061] According to some embodiments of this disclosure, the first structural layer 11 has curvature. For example... Figure 2 As shown, the first structural layer 11 is bent into an arc surface.

[0062] For example, when the first structural layer 11 has curvature, the window can be placed in a preset posture along the vertical direction, such that the long side of the window is located in the horizontal plane and the tangent of the geometric center of the window is parallel to the vertical direction. Figure 2 In this diagram, the X direction represents the optical axis direction of the first structural layer 11, the Y direction represents the normal direction of the geometric center of the window, and the Z direction represents the vertical direction. The angle between the optical axis direction and the vertical direction of the first structural layer 11 is in the range of 35°-55°. In some embodiments, the angle between the optical axis direction and the vertical direction of the first structural layer 11 can be any range such as 35-50°, 40-55°, or 40-50°. For example, the angle between the optical axis direction and the vertical direction can be 35°, 40°, 43°, 45°, 46°, 47°, 48°, 50°, or 55°.

[0063] In some embodiments, the window 1 is mounted along a vertical plane. The mounting posture of the window 1 can be set in a preset posture along the vertical direction.

[0064] In other embodiments, the window 1 is mounted at an angle relative to the vertical direction. The mounting orientation of the window 1 may differ from the preset orientation.

[0065] In this embodiment, the light beam is transmitted through the first structural layer 11, and when the light beam is incident perpendicularly to the first structural layer 11, the difference between the phase difference generated by the light beam after transmission through the first structural layer 11 and half the wavelength of the light beam is no greater than one-quarter of the wavelength of the light beam. The phase difference generated by the light beam after transmission through the first structural layer 11 satisfies:

[0066]

[0067] Δφ represents the phase difference generated after the light beam is transmitted through the first structural layer 11, and λ represents the wavelength of the light beam. When the phase difference Δφ is equal to the wavelength λ of the light beam, the phase difference Δφ is recalculated. When the first structural layer 11 has curvature, the light beam is perpendicular to the first structural layer 11, meaning the angle between the light beam and the tangent at the incident position is approximately 90°.

[0068] In this embodiment, the optical axis direction is well consistent at different positions of the first structural layer 11. When the incident light beam is incident at different positions or at different angles, the stress birefringence phenomenon is not obvious, reducing the range of phase difference generated after the light beam passes through the first structural layer 11 (indicating the uniformity of the phase difference distribution after the light beam passes through the first structural layer 11 at different positions or at different angles). This not only improves the accuracy of lidar detection but also improves the polarization efficiency of window 1, reduces energy loss, and is beneficial to improving the lidar's rangefinding capability. Even if there is a partial phase difference, it can be compensated by setting a fixed compensation parameter in the lidar, with minimal impact on the lidar's detection results.

[0069] According to some embodiments of this disclosure, the phase difference generated by the light beam passing through the first structural layer 11 is no greater than 20 on the order of the light beam's wavelength (hereinafter referred to as the phase difference order). The phase difference order indicates that when the phase difference generated after the light beam passes through the first structural layer 11 reaches one wavelength but less than twice the wavelength, the phase difference order is 1. When the phase difference generated after the light beam passes through the first structural layer 11 is less than one wavelength, the phase difference order is 0, and so on. In this embodiment, the phase difference order generated by the light beam passing through the first structural layer 11 ranges from 0 to 20. The phase difference order generated by the light beam passing through the first structural layer 11 is affected by the processing technology, material, and thickness of the first structural layer 11.

[0070] The greater the order of the phase difference generated by the beam passing through the first structural layer 11, the greater the impact on the polarization efficiency of window 1. The smaller the order of the phase difference generated by the beam passing through the first structural layer 11, the more stable the polarization efficiency of the first structural layer 11.

[0071] The smaller the difference between the phase difference generated by the light beam after transmission through the first structural layer 11 and the half-wavelength of the light beam, the higher the polarization efficiency of the first structural layer 11. In some embodiments of this disclosure, the first structural layer 11 can also be configured such that the phase difference generated by the light beam after transmission through the first structural layer 11 satisfies:

[0072] or

[0073]

[0074] The difference between the phase difference generated by the light beam after transmission through the first structural layer 11 and half the wavelength of the light beam is no greater than one-tenth of the wavelength of the light beam. Preferably, the first structural layer 11 can be configured such that the difference between the phase difference generated by the light beam after transmission through the first structural layer 11 and half the wavelength of the light beam is no greater than one-twentieth of the wavelength of the light beam. Limiting the difference between the phase difference and half the wavelength of the light beam is beneficial to further improve the deflection efficiency of the window 11 and the uniformity of the phase difference after the light beam passes through the first structural layer at different positions.

[0075] In some embodiments of this disclosure, the phase difference order generated by the beam passing through the first structural layer 11 is negatively correlated with the maximum incident angle of the beam relative to the first structural layer 11. The window 1 is applied in a lidar system, where the beam emitted by the lidar has a preset incident angle range relative to the first structural layer 11. For beams incident at large angles, the optical path length of the beam within the first structural layer 11 is longer. Reducing the phase difference order of the first structural layer 11 can decrease the impact on beams with large incident angles.

[0076] In some embodiments, the phase difference order of the first structural layer 11 can be set according to the maximum incident angle of the beam relative to the first structural layer 11 in the lidar. When the maximum incident angle is large, the phase difference order of the first structural layer 11 can be reduced.

[0077] like Figure 3 and Figure 4 As shown, according to some embodiments of this disclosure, window 1 further includes a second structural layer 12. The material of the second structural layer 12 includes organic materials. For example, the material of the second structural layer 12 includes one or more of polymethyl methacrylate (PMMA), polypropylene (PP), polycarbonate (PC), polystyrene (PS), and polyethylene (PE). The second structural layer 12 is disposed parallel to the first structural layer 11, and the second structural layer 12 has an optical axis, which is substantially perpendicular to the optical axis of the first structural layer 11. The optical axis of the second structural layer 12 represents the optical axis of the material of the second structural layer 12.

[0078] In some embodiments, when the window 1 is placed vertically in a preset posture (the preset posture in this embodiment is approximately the same as the preset posture in the aforementioned embodiments), the angle between the optical axis of the second structural layer 12 and the vertical direction is within the range of 35°-55°. Figure 4 As shown, X1 represents the optical axis direction of the first structural layer 11, and X2 represents the optical axis direction of the second structural layer 12. The angles between X1 and X2 and the vertical direction Z are both within the range of 35°-55°. X1 and X2 are perpendicular to each other.

[0079] In some embodiments, the angle between the optical axis direction X2 and the vertical direction Z of the second structural layer 12 can be any range such as 35-50°, 40-55°, or 40-50°. For example, the angle between the optical axis direction and the vertical direction of the second structural layer 12 can be 35°, 40°, 43°, 45°, 46°, 47°, 48°, 50°, or 55°.

[0080] For example, the angle between the optical axis of the first structural layer 11 and the vertical direction is equal to the angle between the second structural layer 12 and the vertical direction.

[0081] like Figure 3 As shown, according to some embodiments of this disclosure, window 1 further includes a filler layer 13 located between the first structural layer 11 and the second structural layer 12. No birefringence occurs when a light beam propagates within the filler layer 13. For example, the filler layer 13 may include an optical adhesive, filling the space between the first structural layer 11 and the second structural layer 12, and serving as an adhesive to improve the bonding strength between the first structural layer 11 and the second structural layer 12.

[0082] In other embodiments of this disclosure, the first structural layer 11 and the second structural layer 12 may be configured to be tightly fitted together, without any filler between them. For example, the materials of the first structural layer 11 and the second structural layer 12 may include organic materials, and the first structural layer 11 and the second structural layer 12 may be bonded together by hot pressing or co-extrusion.

[0083] According to some embodiments of this disclosure, the phase difference generated by the light beam passing through the first structural layer 11 is approximately equal to the phase difference generated by the light beam passing through the second structural layer 12. The order of the phase difference generated by the light beam passing through the first structural layer 11 is approximately equal to the order of the phase difference generated by the light beam passing through the second structural layer 12. For example, the first structural layer 11 and the second structural layer 12 are manufactured using the same processing technology, or the first structural layer 11 and the second structural layer 12 are cut from the same piece of material, which helps to reduce processing difficulty and production costs, and improve product yield.

[0084] In some embodiments, the optical axes of the first structural layer 11 and the second structural layer 12 are substantially perpendicular. The phase difference generated by the light beam passing through the first structural layer 11 is substantially equal to the phase difference generated by the light beam passing through the second structural layer 12. The order of the phase difference generated by the light beam passing through the first structural layer 11 is substantially equal to the order of the phase difference generated by the light beam passing through the second structural layer 12. In this case, the phase difference generated by the light beam during its passage through the first structural layer 11 and the second structural layer 12 can be compensated for by the substantially perpendicular optical axes, without needing to limit the absolute values ​​of the phase difference and the order of the phase difference between the first structural layer 11 and the second structural layer 12.

[0085] In some embodiments, the optical axes of the first structural layer 11 and the second structural layer 12 are perpendicular to each other. The phase difference generated by the beam passing through the first structural layer 11 is approximately equal to the phase difference generated by the beam passing through the second structural layer 12. The order of the phase difference generated by the beam passing through the first structural layer 11 is approximately equal to the order of the phase difference generated by the beam passing through the second structural layer 12. When the beam is incident on the first structural layer 11 and the second structural layer 12 at different angles, the generated phase difference is within the range of 0-1λ, and a large polarization efficiency can be achieved.

[0086] This disclosure also relates to a lidar 10, Figure 5The structure of a lidar 10 according to some embodiments of the present disclosure is shown. For example... Figure 5 As shown, the lidar 10 includes a housing 2, a transmitter 3, a receiver 4, an optomechanical structure 5, and a viewing window 1. The viewing window 1 may be the same as or similar to the viewing window described in the foregoing embodiments.

[0087] Emitter 3 is configured to emit probe light. Emitter 3 may include, for example, a laser or a laser array. The laser may include a semiconductor laser, a solid-state laser, or other types of lasers. The semiconductor laser may include one or more of the following: a vertical-cavity surface-emitting laser (VCSEL), an edge-emitting laser (EEL), and a distributed feedback laser (DFB).

[0088] Receiver 4 is configured to receive the echo generated after the probe light is reflected by an object and convert the echo into an electrical signal. Receiver 4 may include, for example, a photodetector or a photodetector array. The photodetector may include one or more of the following: a single-photon avalanche diode (SPAD), a silicon photomultiplier (SiPM), and an avalanche photodiode (APD).

[0089] The detection light emitted by transmitter 3 is reflected by an obstacle outside lidar 10, generating an echo. This echo illuminates receiver 4, which converts it into an electrical signal. Lidar 10 can then obtain information about the object based on this electrical signal. For example, it can determine the time of flight to ascertain the distance of the object relative to lidar 10, or determine the intensity of the echo to determine the reflectivity of the object's reflective surface.

[0090] The optomechanical structure 5 is housed within the housing 2. The optomechanical structure 5 is positioned along the emission path of the probe light, used to shape the probe light emitted by the laser and adjust its exit path. The optomechanical structure 5 is also positioned along the echo receiving path, used to collect the echo reflected from the object and converge it onto the photosensitive surface of the detector. For example, the optomechanical structure 5 includes an emitting optical element. The emitting optical element may include one or more optical elements such as an emitting lens, a mirror, a homogenizer, or a beam splitter. For example, the receiving optical element includes one or more optical elements such as a receiving lens, a mirror, a filter, or a beam splitter (or beam splitter mirror). The emitting and receiving optical elements can be independent, partially multiplexed, or fully multiplexed. For example, a lidar may include independent emitting and receiving optical elements, such as independent emitting and receiving lenses. For example, a lidar may include optical elements shared by the transmitting and receiving optical paths, such as a beam splitter, for separating the transmitting and receiving optical paths; for example, a lidar may include a shared lens for shaping the coaxial beams on the transmitting and receiving optical paths.

[0091] In some embodiments, such as Figure 5 As shown, the optomechanical structure 5 includes one or more lenses 51. Lenses 51 can collimate the probe light or converge the echo. The optomechanical structure 5 may also include optical devices for reflecting the probe light or echo, such as one or more mirrors 52. Mirrors 52 can adjust the optical path of the probe light or echo, optimize the internal layout of the lidar 10, or change the direction of the probe light emitted from the lidar 10 so that the emission direction of the probe light covers the detection angle range of the lidar 10.

[0092] The viewing window 1 and the housing 2 are fixedly connected. The viewing window 1 and the housing 2 cooperate to protect the optoelectronic components inside the lidar 10. Both the detection light and the echo can pass through the viewing window 1. The size, dimensions, and installation orientation of the viewing window 1 can be set to match the detection angle range of the lidar 1.

[0093] In some embodiments of this disclosure, the incident angle of the probe light relative to the first structural layer 11 can be in the range of 0-60°. When the incident angle of the probe light relative to the first structural layer 11 is too large, for example, when the incident angle of the probe light relative to the first structural layer 11 is greater than 60°, it will cause the optical path of the probe light incident at a large angle to increase inside the first structural layer 11, affecting the polarization efficiency of the window 1.

[0094] In this embodiment, the incident angle of the probe light relative to the first structural layer 11 matches the detection range of the lidar 10. The incident angle range of the probe light relative to the first structural layer 11 is 0-60°, providing a detection angle range of 120°. In other embodiments, the first structural layer 11 may be configured to have curvature, and the incident angle of the probe light relative to the first structural layer 11 represents the angle between the probe light and the normal of the tangent plane at the incident position.

[0095] In some embodiments, the incident angle of the probe light relative to the first structural layer 11 can be 0-55°, or it can be 0-50°, 0-45°, etc.

[0096] In some embodiments of this disclosure, the probe light emitted by the transmitter 3 is linearly polarized. The optomechanical structure 5 also includes a quarter-wave plate 53. The quarter-wave plate 53 is disposed in the optical path of the probe light and the echo, and is configured to convert the polarization state of the probe light and the echo. Using linearly polarized probe light is beneficial to enhancing the anti-interference capability of the lidar 10, improving the signal-to-noise ratio, and enabling the lidar 10 to have better applicability in different environments.

[0097] For example, in some embodiments, the probe light emitted by transmitter 3 is S-polarized light (vertically polarized light). After passing through quarter-wave plate 53, the probe light is converted into circularly polarized light and emitted outwards from lidar 10. After being reflected by the surface of an object, the probe light generates an echo, which is circularly polarized light. The echo enters the lidar 10, and after passing through quarter-wave plate 53, the circularly polarized light is converted into P-polarized light (parallel polarized light), which is then received by receiver 4.

[0098] In some embodiments, a polarization beam splitter 54 may also be disposed between the quarter-wave plate 53 and the transmitter 3 and receiver 4 to split polarized light in different directions. For example Figure 5 As shown, the probe light is reflected at polarization beam splitter 54, and the echo is transmitted at polarization beam splitter 54.

[0099] In some embodiments, the probe light can be transmitted through the polarization beam splitter 54, and the echo is reflected by the polarization beam splitter 54.

[0100] In some embodiments, the optical paths of the probe light and the echo can be made to partially overlap. For example... Figure 5 As shown, after the probe light passes through the polarization beam splitter 54, the optical paths of the probe light and the echo roughly overlap. The probe light and the echo can share the lens 51 and the reflector 52, reducing the number of optical components, saving the cost of the lidar 10, and facilitating the miniaturization of the lidar 10. The polarization beam splitter 54 can split the probe light and the echo whose optical paths partially overlap, preventing positional conflicts between the transmitter 3 and the receiver 4.

[0101] This disclosure also relates to a method for preparing a window for a lidar. Figure 6 The following illustrates a process flow of a method 100 for fabricating a lidar window according to some embodiments of the present disclosure, in conjunction with... Figure 6 Preparation method 100 is described.

[0102] In step S101, a first structural layer blank is provided. The first structural layer blank satisfies the following condition: when a beam of a preset wavelength is incident perpendicularly to the first structural layer blank, the difference between the phase difference generated after the beam is transmitted through the first structural layer blank and half the wavelength of the beam is not greater than one-quarter of the beam wavelength. The preset wavelength can be set to the wavelength of the detection light of a lidar, for example, 905 nm or 1550 nm.

[0103] Preferably, the difference between the phase difference generated by the light beam after transmission through the first structural layer blank and half the wavelength of the light beam is not greater than one-tenth of the wavelength of the light beam; or further, the difference between the phase difference generated by the light beam after transmission through the first structural layer blank and half the wavelength of the light beam is not greater than one-twentieth of the wavelength of the light beam.

[0104] In this embodiment, the first structural layer blank is a planar sheet structure or has a preset curvature. The first structural layer blank may include organic materials. For example, the first structural layer blank may include one or more of polymethyl methacrylate (PMMA), polypropylene (PP), polycarbonate (PC), polystyrene (PS), and polyethylene (PE). The size of the first structural layer blank is not smaller than the size of the window in the lidar. The processed first structural layer blank can be of standard workpiece size, determined by the processing equipment and process. One first structural layer blank can be cut to obtain multiple first structural layers.

[0105] In some embodiments, the first structural layer preform can be processed by an extrusion process. The extrusion process is beneficial for improving the control accuracy of the thickness of the first structural layer preform and for making the phase difference and phase difference order generated after the light beam is transmitted through different positions in the first structural layer preform more uniform.

[0106] In step S102, the optical axis direction of the first structural layer blank is obtained. The optical axis of the first structural layer blank represents the material optical axis of the first structural layer blank. No birefringence occurs when a light beam is incident along the optical axis direction. The optical axis direction of the first structural layer blank can be determined by testing it.

[0107] In step S103, the first structural layer blank is cut according to the optical axis direction of the first structural layer blank and the size of the detection window of the lidar housing to obtain the first structural layer. The first structural layer satisfies the condition that when placed vertically in a preset posture, the angle between the optical axis direction of the first structural layer (i.e., the optical axis direction of the first structural layer blank) and the vertical direction is within the range of 35°-55°.

[0108] In some embodiments, the angle between the optical axis direction of the first structural layer and the vertical direction can be any range such as 35-50°, 40-55°, or 40-50°. For example, the angle between the optical axis direction of the first structural layer and the vertical direction can be 35°, 40°, 43°, 45°, 46°, 47°, 48°, 50°, or 55°.

[0109] For example, when the first structural layer is a plane and the shape of the first structural layer is rectangular, placing it in a preset posture along the vertical direction can mean that the long side of the first structural layer is in the horizontal plane and the short side of the first structural layer is parallel to the vertical direction.

[0110] For example, when the first structural layer has curvature, placing it in a preset posture along the vertical direction can mean that the long side of the first structural layer is located in the horizontal plane, and the tangent of the geometric center of the first structural layer is parallel to the vertical direction.

[0111] Figure 7 The flowchart of a method 200 for preparing a window according to some embodiments of the present disclosure is shown, including the process of obtaining a second structural layer. In the preparation method 200, steps S201, S202 and S203 are substantially the same as steps S101, S102 and S103 in the preparation method 100 in the foregoing embodiments, and will not be described again.

[0112] In step S204, a second structural layer blank is provided. The second structural layer blank is used to cut and obtain the second structural layer. The second structural layer blank is a planar sheet structure or has a preset curvature. The second structural layer blank may include organic materials. For example, the second structural layer blank may include one or more of polymethyl methacrylate (PMMA), polypropylene (PP), polycarbonate (PC), polystyrene (PS), and polyethylene (PE). The size of the second structural layer blank is not smaller than the size of the viewing window in the lidar.

[0113] In some embodiments, the second structural layer blank and the first structural layer blank can be manufactured using the same process and processing parameters. In other embodiments, the second structural layer blank and the first structural layer blank can be the same blank, and the first and second structural layers can be cut in different directions on the same blank.

[0114] In step S205, the optical axis direction of the second structural layer blank is obtained, wherein the optical axis direction of the second structural layer blank represents the optical axis direction of the material. In some embodiments, the processing technology and processing parameters of the second structural layer blank and the first structural layer blank are the same, or the second structural layer blank and the first structural layer blank are the same blank. In this step, the optical axis direction of the first structural layer blank obtained in step S202 can be used as the optical axis direction of the second structural layer blank.

[0115] In step S206, the second structural layer blank is cut according to the optical axis direction of the first structural layer and the size of the detection window of the lidar housing to obtain the second structural layer. The optical axis direction of the second structural layer is approximately perpendicular to the optical axis direction of the first structural layer. The shape and size of the second structural layer can be approximately the same as those of the first structural layer. When the second structural layer is placed parallel to the first structural layer, the optical axis of the second structural layer is perpendicular to the optical axis of the first structural layer.

[0116] In step S207, the second structural layer and the first structural layer are fixed so that they are parallel to each other. For example, the second structural layer and the first structural layer can be glued and fixed by optical adhesive, or they can be fixed by hot pressing or co-extrusion.

[0117] Finally, it should be noted that the above descriptions are merely embodiments of this disclosure and are not intended to limit this disclosure. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1.A window for a lidar, wherein a material of the window comprises an organic material, and the window comprises: a first structure layer, wherein the first structure layer has an optical axis; when the window is placed in a preset posture along a vertical direction, an included angle between a direction of the optical axis of the first structure layer and the vertical direction is 35°-55°; wherein a light beam is transmitted at the first structure layer, and when the light beam is perpendicularly incident on the first structure layer, a phase difference generated by the light beam after being transmitted by the first structure layer is not more than one fourth of a wavelength of the light beam. 2.The window according to claim 1, wherein the phase difference generated by the light beam after being transmitted by the first structure layer is not more than one tenth of the wavelength of the light beam, preferably, the phase difference generated by the light beam after being transmitted by the first structure layer is not more than one twentieth of the wavelength of the light beam. 3.The window according to claim 1, wherein a phase difference order of the light beam passing through the first structure layer is not more than 20 with respect to the wavelength of the light beam. 4.The window according to claim 3, wherein the phase difference order of the light beam passing through the first structure layer is negatively correlated with a maximum incident angle of the light beam with respect to the first structure layer. 5.The window according to claim 1, wherein the first structure layer is a plane, or the first structure layer has a curvature in at least one direction. 6.The window according to claim 1, further comprising: a second structure layer, wherein the second structure layer is arranged in parallel with respect to the first structure layer; the second structure layer has an optical axis, and the optical axis of the second structure layer is substantially perpendicular to the optical axis of the first structure layer. 7.The window according to claim 6, further comprising: a filling layer, wherein the filling layer is located between the first structure layer and the second structure layer, and the light beam does not experience birefringence when propagating in the filling layer. 8.The window according to claim 6, wherein a phase difference and a phase difference order of the light beam passing through the second structure layer are substantially equal to a phase difference and a phase difference order of the light beam passing through the first structure layer. 9.A lidar, comprising: a housing; a transmitter configured to emit a probe light; a receiver configured to receive a return wave generated by the probe light being reflected by an object, and convert the return wave into an electrical signal; an optical-mechanical structure arranged in the housing and configured to guide the probe light to outside of the lidar, and guide the return wave to the receiver; the window according to any one of claims 1-8, wherein the window is fixedly connected with the housing. 10.The lidar according to claim 9, wherein an incident angle range of the probe light with respect to the first structure layer is 0-60°. 11.The lidar according to claim 9, wherein the probe light is linearly polarized light, and the optical-mechanical structure further comprises: a quarter wave plate disposed in an optical path of the probe light and the echo and configured to convert a polarization state of the probe light and the echo. 12.A method for manufacturing a window of a lidar, comprising: providing a first structure layer blank, the first structure layer blank satisfying: when a light beam of a preset wavelength is perpendicularly incident on the first structure layer blank, a phase difference generated by the light beam after being transmitted by the first structure layer blank is not more than a quarter of a wavelength of the light beam from a half wavelength of the light beam; obtaining an optical axis direction of the first structure layer blank; cutting the first structure layer blank according to the optical axis direction of the first structure layer blank and a size of a detection window of the lidar shell to obtain a first structure layer, the first structure layer being placed in a preset posture along a vertical direction, and an included angle between the optical axis direction of the first structure layer and the vertical direction being 35°-55°. 13.The method according to claim 12, further comprising: providing a second structure layer blank; obtaining an optical axis direction of the second structure layer blank; cutting the second structure layer blank according to the optical axis direction of the first structure layer and the size of the detection window of the lidar shell to obtain a second structure layer, the optical axis of the second structure layer being substantially perpendicular to the optical axis of the first structure layer; fixing the second structure layer and the first structure layer to make the second structure layer and the first structure layer parallel to each other. 14.The method according to claim 13, wherein the first structure layer blank and the second structure layer blank are made by using the same process and processing parameters.

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