WO2025007246A1 - 一种光学模组、激光雷达和终端 - Google Patents

一种光学模组、激光雷达和终端 Download PDF

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Publication number
WO2025007246A1
WO2025007246A1 PCT/CN2023/105547 CN2023105547W WO2025007246A1 WO 2025007246 A1 WO2025007246 A1 WO 2025007246A1 CN 2023105547 W CN2023105547 W CN 2023105547W WO 2025007246 A1 WO2025007246 A1 WO 2025007246A1
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WO
WIPO (PCT)
Prior art keywords
optical module
module
light beam
angle
receiving
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CN2023/105547
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English (en)
French (fr)
Inventor
林娇
刘军
王兴武
李庚禹
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Shenzhen Yinwang Intelligent Technology Co Ltd
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Shenzhen Yinwang Intelligent Technology Co Ltd
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Filing date
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Application filed by Shenzhen Yinwang Intelligent Technology Co Ltd filed Critical Shenzhen Yinwang Intelligent Technology Co Ltd
Priority to EP23943980.5A priority Critical patent/EP4722754A1/en
Priority to PCT/CN2023/105547 priority patent/WO2025007246A1/zh
Priority to CN202380086282.9A priority patent/CN120359435A/zh
Publication of WO2025007246A1 publication Critical patent/WO2025007246A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements

Definitions

  • the present application relates to the field of detection technology, and in particular to an optical module, a laser radar and a terminal.
  • Detection devices can be regarded as the "eyes" of the device to perceive the environment, including visual sensors such as cameras and radar sensors such as millimeter wave radar, lidar and ultrasonic radar.
  • Lidar light detection and ranging
  • Scanning Lidar is a widely used type of Lidar, which uses scanning to detect the object space.
  • the scanning detection device includes a transmitter, a receiver and a scanning module. Since the scanning module rotates or swings, the scanner will produce a deviation angle during the period when the light beam is projected from the scanner to the target and then reflected by the target to illuminate the scanner. This deviation angle between the transmitted light beam and the returned light beam caused by the scanner activity is called the walk-off angle in the detection field. The existence of the walk-off angle prevents the returned light beam from irradiating the center of the receiving end, causing the return light signal strength to decrease, affecting the ranging performance.
  • the embodiments of the present application provide an optical module, a laser radar and a terminal, which can reduce the signal loss caused by the walk off angle, improve the effectiveness of the received echo signal, and improve the detection performance.
  • an embodiment of the present application provides an optical module, including a transmitting optical module, a coaxial optical module, a scanning module and a receiving optical module, wherein:
  • the transmitting optical module is used to transmit the first light beam emitted by the light source to the coaxial optical module;
  • the coaxial optical module is used to transmit the first light beam to the scanning module;
  • the scanning module is used to scan the first light beam to the object space, and is also used to transmit the first return light beam to the coaxial optical module, wherein the first return light beam is a return light beam of the first light beam;
  • the coaxial optical module is further used to transmit the first return light beam to the receiving optical module, wherein there is a first angle between the first light beam after entering the coaxial optical module and the first return light beam before returning to the coaxial optical module, and the first angle is greater than 0° and less than 90°;
  • the receiving optical module is used to receive the first returning light beam
  • the ideal receiving light beam is a return light beam parallel to the first light beam.
  • the return light beam of the first light beam will propagate along the optical path of the ideal receiving light beam.
  • the scanner continuously scans, after the first light beam is propagated to the target object in the object space, it can be reflected by the target object in the object space to obtain a first reflected light beam. Since there is a certain distance between the target object in the object space and the scanner, when the first return light beam passes through the scanner, the scanner has already rotated a certain angle. Therefore, the first return light beam no longer propagates along the ideal receiving light beam, that is, there is an offset angle between the first return light beam and the ideal receiving light beam.
  • the present application deviates the receiving module from the optical path of the ideal receiving beam, thereby compensating for the offset of the first return beam compared to the ideal receiving beam, and reducing the signal loss caused by the walk off angle.
  • the offset angle between the first return beam and the ideal receiving beam is the first angle
  • the receiving optical module is also offset compared to the ideal receiving beam. Therefore, the offset of the receiving optical module compensates for the offset of the first beam, so that the light spot of the first return beam can be closer to the effective receiving area of the receiving optical module, and even coincide with the center of the effective receiving area. In this way, the receiving optical module can receive the first return beam more accurately, improve the effectiveness of the received echo signal, and improve the detection performance.
  • the effective receiving area refers to the area where the receiving module can be used to receive the first return light beam, including but not limited to the light-transmitting surface of the microlens array, the receiving mode field of the optical fiber, or the detector of the receiver.
  • the first offset is related to the first angle.
  • the first angle is the angle between the return light beam and the emission light beam.
  • the offset of the first return light beam when propagating to the receiving optical module can be determined by the angle and the distance of the optical path from the scanner to the receiving optical module, so that the compensation amount of the receiving optical module can be designed. This enables the receiving optical module to receive the first return light beam more accurately, thereby improving the effectiveness of the received echo signal and improving the detection performance.
  • the coaxial optical module includes a splitter module and a beam expansion module, and the splitter module is disposed between the emitting optical module and the beam expansion module.
  • the "between” here means the middle of the optical path, that is, the first light beam is transmitted through the beam splitting module and the beam expanding module to the scanning module, and the first return light beam is transmitted through the beam expanding module and the beam splitting module to the receiving module.
  • the splitter module refers to an optical device that divides a light beam into multiple paths.
  • the splitter module may include a polarization beam splitter (PBS), a semi-transparent and semi-reflective beam splitter, or a combination of one or more thereof.
  • the splitter module may also include other modules for assisting in splitting or improving splitting efficiency and beam quality.
  • the splitter module may also include one or more of a wave plate (such as a quarter wave plate, a half wave plate, or an eighth wave plate, etc.), an anti-reflection film, or a filter.
  • the splitter module may include a PBS and a quarter-wave plate (QWP).
  • the first light beam passes through the PBS and the quarter wave plate in sequence, and the first return light beam passes through the quarter wave plate and the PBS in sequence. Since the quarter wave plate can change the polarization state, and the PBS can transmit or reflect the passing light beam according to the polarization state, the optical paths of the first light beam and the first return light beam can be separated to achieve coaxial transmission and reception.
  • the beam expansion module refers to a module used to increase or reduce the diameter of a beam.
  • the beam expansion module may be a telescope beam expansion module, which realizes beam expansion/reduction by setting at least two groups of lenses.
  • the beam expansion module is arranged at the rear end.
  • the light beam When transmitting, the light beam is split and then expanded. Therefore, the diameter of the first light beam is relatively small when it passes through the beam splitting module. After the beam expansion, the diameter of the light beam becomes larger, so that the light spot propagated to the object space is relatively large, thereby improving the detection efficiency.
  • the diameter of the return light beam When receiving, the diameter of the return light beam is reduced after passing through the beam expansion unit, making it easier to be received by the light receiving unit, thereby improving the effectiveness of the received signal.
  • the path of a thin light beam is more controllable than that of a thick light beam, it is easy to solve the technical problem of eccentricity of the transmitting end and the receiving end.
  • the transmitting light beam and the receiving light beam can share the same set of beam expansion lenses, which improves the integration of the device and reduces the size of the module.
  • the receiving optical module includes a first microlens array, and the first microlens array is used to receive the first return light beam after passing through the light splitting module;
  • the second angle is related to the maximum offset angle and the beam expansion multiple of the beam expansion module, and the maximum offset angle is related to the farthest detection distance of the optical module and the scanning speed of the scanning module.
  • the beam expansion multiple of the beam expansion module can also be replaced by the focal length of the lens in the beam expansion module.
  • the first microlens array can be used to converge the first return light beam, so that the receiver can receive the first return light beam more accurately.
  • the first microlens array when the first microlens array is placed, its optical axis is angularly offset from the optical path of the ideal receiving light beam, thereby compensating for the angular offset of the first return light beam, improving the validity of the received echo signal, and improving the detection performance.
  • the third angle ⁇ can fall within the following range, ⁇ max is the second angle, and the second angle is equal to the maximum deviation angle (expressed as ), the magnification of the beam expansion module.
  • the magnification of the above beam expansion module can also be replaced by the focal length of the two groups of lenses in the beam expansion module.
  • the offset angle i.e., the first angle
  • the maximum offset angle is the maximum value of the first angle, that is, the maximum offset angle is the angle between the first return light beam (referred to as the maximum offset light beam) formed by the first light beam reflected by the target object at the farthest detection distance and the ideal receiving light beam.
  • the maximum offset angle is the angle between the maximum offset light beam and the static receiving light beam
  • the maximum offset light beam is the light beam formed by the first light beam reflected by the target object at the farthest detection distance of the optical module.
  • the farthest detection distance can be the farthest detection distance of the optical module, that is, the farthest detection distance of the detection device where the optical module is located, which can be predefined or pre-designed.
  • the maximum offset angle is related to the maximum detection distance and the scanning speed of the scanning module.
  • v is the angular velocity of the scanner
  • c is the speed of light
  • D is the maximum detection distance
  • k is a coefficient. Since there is a correlation between the mechanical angle and the optical angle, k is used to convert the mechanical angle and the optical angle. For example, the optical angle is twice the mechanical angle, and here the light beam passes through the scanner twice, then k can be 4, that is:
  • the beam expansion module includes two groups of lenses, the two groups of lenses have different focal lengths, and the focal length of the lens close to the object space is larger than the focal length of the lens far from the object space.
  • the beam expansion module includes a second microlens array and a collimation lens (CL), and the second microlens array and the collimation lens have a common first focal plane.
  • the second microlens array is arranged between the light splitting module and the collimation lens.
  • the focal length of the second microlens array is smaller than the focal length of the collimator.
  • the magnification of the beam expansion module is related to the focal length of the second microlens array and the focal length of the collimator.
  • D2 is the diameter of the light beam after passing through the beam expansion module
  • D1 is the diameter of the light beam before passing through the beam expansion module
  • fc is the focal length of the collimator
  • f2 is the focal length of the second microlens array.
  • the aforementioned second angle and the maximum offset angle The focal length of the second microlens array is related to the focal length of the collimator.
  • the second angle may satisfy the following equation:
  • the first offset distance between the first microlens array and the ideal received light beam is related to the third angle, the distance between the first microlens array and the spectrometer module, the distance between the spectrometer module and the beam expansion module, and the second offset of the spot of the first return light beam on the first focal plane.
  • the second offset is a distance between a light spot of the first return light beam and a light spot of an ideal receiving light beam of the first return light beam on the first focal plane when the first angle is a maximum offset angle.
  • the second offset is related to the third angle and the focal lengths of the two lens groups in the beam expansion module.
  • the second offset ⁇ y satisfies the following formula:
  • fc is the focal length of the collimating lens
  • f2 is the focal length of the second microlens array
  • ⁇ is the third angle.
  • d1 is the distance between the first microlens array and the light splitting module
  • d2 is the distance between the light splitting module and the beam expansion module (or the second microlens array)
  • ⁇ is the third angle
  • ⁇ y is the second offset.
  • the receiving optical module further includes a receiving optical element, and the receiving optical element is used to receive the first return light beam passing through the first microlens array.
  • the distance between the receiving optical element and the ideal received light beam is a second offset distance
  • the second offset distance is related to the third angle, the distance between the first microlens array and the spectrometer module, the distance between the spectrometer module and the beam expansion module, the focal length of the second microlens array, the focal length of the collimator, and the third offset of the spot of the first return light beam on the first focal plane.
  • the third offset is the distance between the spot of the first return light beam on the first focal plane and the spot of the maximum offset light beam on the focal plane, and the maximum offset light beam is the first return light beam when the first angle is the maximum offset angle.
  • the third offset and the maximum offset angle are related.
  • the third offset ( ⁇ y′) satisfies the following equation:
  • the second offset distance ( ⁇ x′) satisfies the following formula:
  • a clear aperture of the first microlens array is related to at least one of the first offset distance and the second offset distance and a diameter of the first light beam before passing through the beam expansion unit.
  • the light aperture w3 of the first microlens array satisfies the following formula: w3 ⁇ 2*max( ⁇ x, ⁇ x′)+D1
  • max() represents the maximum value
  • D1 is the beam diameter of the first light beam before passing through the beam expansion module or the beam diameter of the first return light beam after passing through the beam expansion module
  • other parameters refer to the above.
  • the period p of the first microlens array is related to the transition zone of the first microlens, the first offset distance, the second offset distance, and the beam diameter of the first light beam before passing through the beam expansion module.
  • the beam diameter of the first light beam before passing through the beam expansion module can be replaced by the beam diameter of the first return light beam after passing through the beam expansion module.
  • ⁇ is the transition zone of the first microlens array, and the parameters are as mentioned above.
  • the transmitting optical module includes a waveguide or an optical fiber.
  • the receiving optical module includes a waveguide or an optical fiber.
  • the transmitting optical module, the receiving optical module and the splitting module are packaged on a glass base to form a first optical component, and a light-transmitting window of the first optical component is aligned with a light-transmitting surface of the beam expansion unit.
  • the transmitting optical module, the receiving optical module, the splitting module and the second microlens array are packaged on a glass base to form a second optical component, and the light-transmitting window of the second optical component is aligned with the light-transmitting surface of the collimating mirror.
  • the coaxial optical module includes a polarization beam splitter PBS and a quarter wave plate.
  • an embodiment of the present application provides a laser radar, which includes the optical module described in any one of the first aspects.
  • the laser radar further includes a light source.
  • the light source is a laser.
  • the laser radar further includes a detector, which is used to obtain an electrical signal based on the light beam.
  • an embodiment of the present application provides a terminal, wherein the terminal includes the optical module described in any one of the first aspect, or the terminal includes the laser radar described in any one of the second aspect.
  • the terminal can be a smart terminal or means of transportation such as a vehicle, a drone, or a robot.
  • the terminal can also be replaced by industrial equipment, entertainment and leisure equipment, etc.
  • Smart terminals such as mobile phones, tablets, laptops, smart bracelets, smart watches, or smart glasses.
  • Transportation tools such as vehicles, ships, aircraft, or logistics robots.
  • Industrial equipment such as industrial robots and robotic arms.
  • Leisure and entertainment equipment such as virtual reality (VR) equipment, mixed reality (MR) equipment, massage chairs, or 4D cinema cabins. This application does not impose strict restrictions on the devices to which the electrical connector can be applied.
  • FIG1 is a schematic diagram of a detection process
  • FIG2 is a schematic structural diagram of an optical module provided in an embodiment of the present application.
  • FIG3 is a schematic diagram of the structure of another optical module provided in an embodiment of the present application.
  • FIG4 is a schematic diagram of the structure of another optical module provided in an embodiment of the present application.
  • FIG5 is a schematic diagram of the structure of another transmitting module provided in an embodiment of the present application.
  • FIG6A is a schematic diagram of the structure of another optical module provided in an embodiment of the present application.
  • FIG6B is a schematic diagram of an optical path of an optical module provided in an embodiment of the present application.
  • FIG6C is a schematic diagram of parameters of an optical module provided in an embodiment of the present application.
  • FIG7 is a schematic diagram of a possible simulation result provided by an embodiment of the present application.
  • FIG8 is a schematic diagram of a possible simulation result provided by an embodiment of the present application.
  • FIG9 is a schematic diagram of the structure and optical path of another optical module provided in an embodiment of the present application.
  • FIG10 is a schematic diagram of the structure of another optical module provided in an embodiment of the present application.
  • FIG. 11 is a schematic diagram of the structure of an optical module provided in an embodiment of the present application.
  • a scanning detection device is a device that scans the object space through a scanning mechanism to complete the detection of the entire field of view.
  • a scanning detection device usually projects the transmission signal into the object space at multiple angles through the activities of the scanning mechanism (such as swinging, rotating, etc.), so the scanning mechanism will be continuously active.
  • the scanning mechanism When the laser radar is working, due to the high-speed rotation (or swinging) of the scanning mechanism, the scanning mechanism has generated a deviation angle during the time when the light beam is emitted by the scanning mechanism, hits the target object and then reflects back.
  • FIG. 1 it is a schematic diagram of the detection process.
  • the scanning mechanism is constantly moving, and the emission beam (indicated by the solid arrow) and the return beam (indicated by the dotted arrow) will produce a deviation angle, namely the walk-off angle.
  • the angle of the walk-off angle is related to the angular velocity of the scanning mechanism and the flight time of the beam in the object space, and they are positively correlated. The longer the flight time of the beam and the faster the angular velocity of the scanning mechanism, the larger the walk-off angle.
  • This deviation angle will cause the beam to deviate at the receiving position, so that the return beam cannot be irradiated at the center of the receiving end, the signal strength of the received return beam is reduced, the signal-to-noise ratio is reduced, and the ranging distance is affected.
  • the walkoff angle of the return beam will cause the return beam to deviate from the receiving mode field, causing the signal of the return beam to drop significantly, affecting the detection performance.
  • ⁇ is approximately 0.036°.
  • f is generally in the range of tens to hundreds of millimeters (mm).
  • the size of ⁇ x is thus in the order of a few um to tens of um, while the mode spot of SMF is usually about 10um. Therefore, the offset of the return beam at the receiving end is very likely to exceed the mode spot of SMF, and the signal strength of the return beam drops significantly, which has a greater impact on the detection performance.
  • the embodiments of the present application provide an optical module, a laser radar and a terminal, which can reduce the signal loss caused by the walk off angle, improve the effectiveness of the received echo signal, and improve the detection performance.
  • the optical module 20 includes a transmitting optical module 201, a coaxial optical module 202, a scanning module 203 and a receiving optical module 204. Among them:
  • the emission optical module 201 is used to transmit the first light beam (the solid line with arrows shown in FIG2 ) emitted by the light source to the coaxial optical module 202.
  • the emission optical module 201 may include a lens, an optical fiber, a waveguide, etc.
  • the light source may be a laser, such as a laser diode (LD), a vertical cavity surface emitting laser (VCSEL), a distributed feedback laser diode (DFB-LD), a distributed Bragg reflection laser diode (DBR-LD), a grating coupled sampling reflection laser diode (GCSR-LD), a micro opto-electro-mechanical system laser diode (MOEMS-LD), and other light-emitting devices.
  • the first light beam can be, for example, a Frequency Modulated Continuous Waves (FMCW) light beam, and its waveform can be a sawtooth, triangle or sine wave.
  • FMCW Frequency Modulated Continuous Waves
  • the coaxial optical module 202 is used to propagate the first light beam to the scanning module 203.
  • the coaxial optical module 202 is used to achieve coaxial transmission and reception.
  • coaxial transmission and reception can be understood as the emission light beam and the receiving light beam passing through some optical elements together, for example, the emission light beam and the receiving light beam pass through the scanning module 203 and the coaxial optical module 202 together.
  • coaxial transmission and reception can be understood as the main optical axis of the emission light beam and the main optical axis of the return light beam are parallel.
  • the parallelism here refers to the ideal situation (such as when the activity of the scanner is not considered).
  • the coaxial optical module 202 can include a lens, a beam splitter, a wave plate, etc.
  • the scanning module 203 is used to scan the first light beam to the object space. That is, the scanning module 203 can swing or rotate to project the light beam to the object space at different angles.
  • the scanning module 203 is also used to transmit the first return light beam (the dotted line with an arrow as shown in FIG. 2 ) to the coaxial optical module, and the first return light beam is the return light beam of the first light beam.
  • the first light beam propagates to the target object in the object space, is reflected by the target object to form a reflection signal, and the first return light beam includes the reflection signal of the first light beam.
  • the first angle ⁇ is the walkoff angle.
  • the first angle is greater than 0° and less than 90°, that is, 0° ⁇ 90°.
  • the coaxial optical module 202 is also used to transmit the first return light beam to the receiving optical module 204.
  • the coaxial optical module 202 includes a polarization beam splitter PBS and a quarter wave plate.
  • the first light beam passes through the PBS and reaches the quarter wave plate, and the polarization state of the first return light beam changes after passing through the quarter wave plate, so that it is reflected by the PBS and propagates to the receiving optical module 204.
  • the position of the receiving optical module 204 is offset from the ideal receiving beam of the first beam (see the dashed line without arrows shown in FIG. 2 ).
  • the ideal receiving beam of the first return beam before returning to the coaxial optical module 202 is parallel to the first beam. That is, the ideal receiving beam is a beam whose main optical axis is parallel to the first beam.
  • the walkoff angle is 0°, for example, when the scanner is stationary (or not rotating), the return beam corresponding to the first beam propagates along the optical path of the ideal receiving beam.
  • the walkoff angle is 0°
  • the return beam of the first light beam will propagate along the optical path of the ideal receiving beam.
  • the scanner due to the continuous movement of the scanner, after the first light beam is propagated to the target object in the object space and is reflected by the target object in the object space to obtain the first reflected light beam, since there is a certain distance between the target in the object space and the scanner, when the first return light beam passes through the scanner, the scanner has rotated a certain angle. Therefore, the first return light beam no longer propagates along the ideal receiving light beam, that is, there is an offset angle between the first return light beam and the ideal receiving light beam.
  • the present application deviates the receiving module from the optical path of the ideal receiving light beam, so as to compensate for the offset of the first return light beam compared to the ideal receiving light beam, and reduce the signal loss caused by the walk off angle.
  • the receiving point of the ideal receiving light beam i.e., the translation position point of the receiving optical module 204
  • the receiving optical module 204 is offset from the receiving point of the ideal receiving light beam.
  • the offset angle between the first return beam and the ideal receiving beam is the first angle
  • the receiving optical module is also offset compared to the ideal receiving beam, so the offset of the receiving optical module compensates for the offset of the first beam, so that the light spot of the first return beam can be closer to the center of the receiving optical module or coincide with the center of the receiving optical module.
  • the receiving optical module can receive the first return beam more accurately, improve the effectiveness of the received echo signal, and improve the detection performance.
  • the first offset is related to a first angle, wherein the first angle is a walkoff angle between the return light beam and the emission light beam, and the offset of the return light beam when propagating to the receiving optical module can be determined by the angle and the distance of the optical path from the scanner to the receiving optical module, so that the compensation amount of the receiving optical module can be designed, so that the receiving optical module can receive the first return light beam more accurately, thereby improving the validity of the received echo signal and improving the detection performance.
  • the maximum value of the first angle may be the angle between the light beam returned from the farthest detection distance and the emitted light beam (such as the first light beam), which is referred to as the maximum deviation angle for ease of description and is expressed as Please refer to FIG. 3, which is a schematic diagram of the structure of another optical module provided in an embodiment of the present application.
  • the offset between the returned light beam and the ideal received light beam at the receiving point i.e., the translation position of the receiving optical module
  • the offset between the receiving optical module 204 and the receiving point of the ideal received light beam can be between x/2 and x.
  • the offset between the receiving optical module 204 and the receiving point of the ideal received light beam can be at x/2.
  • the offset angle between the first returned light beam and the ideal received light beam is relatively large, it is closer to the center of the optical axis of the receiving optical module, which is beneficial to improve the ranging accuracy during long-distance detection.
  • the offset between the receiving optical module 204 and the receiving point of the ideal receiving light beam may be between 0 and x/2, so as to ensure the ranging accuracy during close-range detection.
  • the maximum offset angle is related to the maximum detection distance and the angular velocity of the scanning module 203.
  • the following formula can be satisfied: Where v is the angular velocity of the scanner, c is the speed of light, and D is the maximum detection distance.
  • k is a coefficient. Since there is a correlation between the mechanical angle and the optical angle, k is used to convert the mechanical angle and the optical angle. For example, the optical angle is twice the mechanical angle, and here the light beam passes through the scanner twice, then k can be 4, that is:
  • the maximum detection distance may be pre-defined (or specified) or pre-set by a manufacturer, a standard organization, a user, or a device.
  • the coaxial optical module includes a beam splitter module and a beam expander module, and the beam splitter module is disposed between the transmitting optical module and the beam expander module.
  • the beam expansion module refers to a module used to increase or reduce the diameter of the light beam.
  • the beam splitting module refers to an optical device that divides the light beam into multiple paths.
  • the beam splitting module may include a polarization beam splitter (PBS) and a combination of one or more of a semi-transparent and semi-reflective beam splitter.
  • the beam splitting module may also include other modules for assisting in beam splitting or improving the efficiency of beam splitting and the quality of the light beam.
  • the beam splitting module may also include one or more of a wave plate, an anti-reflection film, or a filter.
  • the beam splitting module may include a PBS and a quarter wave plate.
  • the first light beam passes through the PBS and the quarter wave plate in sequence, and the first return light beam passes through the quarter wave plate and the PBS in sequence. Since the quarter wave plate can change the polarization state, and the PBS can transmit or reflect the passing light beam according to the polarization state, the optical paths of the first light beam and the first return light beam can be separated to achieve coaxial transmission and reception.
  • FIG. 4 is a schematic diagram of the structure of another optical module provided in an embodiment of the present application, wherein the coaxial optical module 202 comprises a beam splitter module 2021 and a beam expander module 2022, wherein the beam splitter module 2021 is disposed between the transmitting optical module 201 and the beam expander module 2022.
  • the "between” here means the middle of the optical path, that is, the first light beam is transmitted to the scanning module 203 through the beam splitter module 2021 and the beam expander module 2022, and the first return light beam is transmitted to the receiving optical module 204 through the beam expander module 2022 and the beam splitter module 2021.
  • the beam expansion module 2022 is arranged at the rear end.
  • the light beam is split and then expanded. Therefore, the diameter of the first light beam is relatively small when it passes through the beam splitting module. After the beam expansion, the diameter of the light beam becomes larger, so that the light spot propagated to the object space is relatively large, thereby improving the detection efficiency.
  • the diameter of the return light beam is reduced after passing through the beam expansion unit, making it easier to be received by the light receiving unit, thereby improving the effectiveness of the received signal.
  • the transmitting light beam and the receiving light beam can share the same beam expansion system, thereby improving the integration of the device and reducing the volume of the module.
  • the angle between the first return light beam and the ideal receiving light beam after passing through the beam expansion module may change.
  • the angle between the first return light beam after passing through the beam expansion module 2022 and the ideal receiving light beam can be expressed as ⁇ .
  • the angle ⁇ is greater than 0° and less than 90°, that is, 0° ⁇ 90°.
  • ⁇ is related to the first angle and the magnification of the beam expansion module 2022.
  • ⁇ satisfies the following formula:
  • the magnification is related to the diameter of the beam before and after expansion, for example: D2 is the diameter of the emitted light beam (such as the first light beam) after passing through the beam expansion module 2022 , and D1 is the diameter of the emitted light beam before passing through the beam expansion module 2022 .
  • the beam expansion module may include two groups of lenses.
  • the two groups of lenses are placed front and back along the optical path of the first light beam and connected by a focal plane, where the focal plane can be a real focal plane or a virtual focal plane.
  • the magnification of the beam expansion module is related to the focal length of the two lenses (described below).
  • ⁇ is related to the first angle and the magnification of the beam expansion module 2022, which can also be replaced by: ⁇ is related to the first angle and the focal length of the two lenses.
  • the receiving optical module 204 includes a lens, and the lens is used to receive the first returning light beam after passing through the light splitting module.
  • the lens can be a microlens array (MLA), which is conveniently distinguished as a first microlens array, denoted as MLA1.
  • MLA microlens array
  • the receiving optical module 204 includes a first microlens array 2041 and a receiving optical element 2042.
  • the second angle is the angle between the return beam at the maximum deviation angle after passing through the beam expansion module and the static receiving beam.
  • the return beam obtained by reflecting the first beam from the farthest detection distance has the second angle with the static receiving beam after passing through the scanning module and the beam expansion module. That is, the second angle is the maximum value of ⁇ , which is conveniently expressed as ⁇ max .
  • the third angle ⁇ can fall within the following range: ⁇ max is the second angle, and the second angle is equal to the maximum deviation angle (expressed as ), the focal length of the collimating lens is related to the focal length of the second microlens array.
  • the offset angle i.e., the first angle
  • the maximum offset angle is the maximum value of the first angle, that is, the maximum offset angle is the angle between the first return light beam (referred to as the maximum offset light beam) formed by the first light beam reflected by the target object at the farthest detection distance and the ideal receiving light beam.
  • the maximum offset angle is the angle between the maximum offset light beam and the static receiving light beam
  • the maximum offset light beam is the light beam formed by the first light beam reflected by the target object at the farthest detection distance of the optical module.
  • the farthest detection distance can be the farthest detection distance of the optical module, that is, the farthest detection distance of the detection device where the optical module is located, which can be predefined or pre-designed.
  • the beam expansion module may include two groups of lenses.
  • the beam expansion module includes a lens and a collimator.
  • the lens may be a microlens array, which is conveniently referred to as a second microlens array.
  • the optical module 20 includes an emitting optical module, a polarization beam splitter PBS, a quarter wave plate QWP, a second microlens array MLA2, a collimator, a scanning module, and a first microlens array MLA1.
  • PBS and QWP are an exemplary splitting module
  • MLA22 and the collimator are an exemplary beam expansion module.
  • MLA1 is included in the receiving optical module.
  • MLA2 is arranged between the splitting module and the collimator.
  • MLA2 can be specifically arranged between the QWP and the collimator.
  • a lens is also arranged between the emitting module and the beam splitting module, such as a microlens array, such as MLA3 shown in Figure 6A.
  • FIG. 6B is a schematic diagram of the optical path of an optical module provided in an embodiment of the present application.
  • MLA2 and the collimator have a common focal plane P1 (optionally a continued focal plane or a real focal plane).
  • the focal length of MLA2 is smaller than the focal length of the collimator.
  • the magnification of the beam expansion module is related to the focal length of the second microlens array and the focal length of the collimator.
  • FIG. 6C is a parameter diagram of an optical module provided in an embodiment of the present application.
  • the structure and optical path of the optical module can be seen in Figures 6A and 6B, respectively.
  • the focal length of MLA2 is represented by f2
  • the focal length of the collimator is fc
  • the diameter of the first light beam before passing through MLA2 (and/or after MLA3) is D1
  • the width of the output light beam of the collimator is D2.
  • the distance from the center of PBS to MLA1 is represented by d1
  • the distance from the center of PBS to MLA2 is represented by d2
  • the offset distance of the transmitted and received signals on the P1 plane is represented by ⁇ y.
  • D2 is the diameter of the light beam after passing through the beam expansion module
  • D1 is the diameter of the light beam before passing through the beam expansion module
  • fc is the focal length of the collimator
  • f2 is the focal length of MLA2.
  • the second angle ⁇ max can satisfy the following formula:
  • the distance between the first microlens array in the receiving module and the ideal receiving light beam may be referred to as a first offset distance.
  • the first offset distance satisfies the following conditions: when the offset angle between the first return light beam after passing through the splitter module and the ideal receiving light beam after passing through the splitter module is a third angle ⁇ , the center of the light spot of the first return light beam coincides with the center of the first microlens array, or the optical axis of the first return light beam is consistent with the optical axis of the first microlens.
  • the first offset distance between the first microlens array and the ideal received light beam is related to the third angle
  • the first The distance between the microlens array and the beam splitting module, the distance between the beam splitting module and the beam expanding module, and the second offset of the light spot of the first return light beam on the first focal plane are related.
  • the second offset is a distance between a light spot of the first return light beam and a light spot of an ideal receiving light beam of the first return light beam on the first focal plane when the first angle is a maximum offset angle.
  • the second offset is related to the third angle and the focal lengths of the two lens groups in the beam expansion module.
  • the second offset ⁇ y satisfies the following equation:
  • fc is the focal length of the collimating lens
  • f2 is the focal length of the second microlens array
  • ⁇ is the third angle.
  • d1 is the distance between the first microlens array and the light splitting module
  • d2 is the distance between the light splitting module and the beam expansion module (or the second microlens array)
  • ⁇ is the third angle
  • ⁇ y is the second offset.
  • the receiving optical module further includes a receiving optical element, and the receiving optical element is used to receive the first return light beam passing through the first microlens array.
  • the walk off angle (i.e., ⁇ angle) is 0 to Since the offset angle of the optical axis of MLA3 is ⁇ from the ideal receiving beam, when the detection distance is 0 to D, the angle offset of the first return beam after MLA3 relative to the ideal receiving beam is
  • the distance between the receiving optical element and the ideal receiving light beam is the second offset distance
  • the second offset distance is related to the third angle, the distance between the first microlens array and the light splitting module, the distance between the light splitting module and the beam expanding module, the focal length of the second microlens array, the focal length of the collimator, and the third offset of the light spot of the first return light beam on the first focal plane.
  • the third offset is the distance between the light spot of the first return light beam on the first focal plane and the light spot of the maximum offset light beam on the focal plane
  • the maximum offset light beam is the first return light beam when the first angle is the maximum offset angle.
  • the third offset and the maximum offset angle are related.
  • the third offset ( ⁇ y′) satisfies the following equation:
  • the second offset distance ( ⁇ x′) satisfies the following formula:
  • the light aperture of the first microlens array is related to at least one of the first offset distance and the second offset distance and a diameter of the first light beam before passing through the beam expansion unit.
  • the light aperture w3 of the first microlens array satisfies the following formula: w3 ⁇ 2*max( ⁇ x, ⁇ x′)+D1
  • max() represents the maximum value
  • D1 is the beam diameter of the first light beam before passing through the beam expansion module or the beam diameter of the first return light beam after passing through the beam expansion module
  • other parameters refer to the above.
  • the period p of the first microlens array is related to the transition zone of the first microlens, the first offset distance, the second offset distance, and the beam diameter of the first light beam before passing through the beam expansion module.
  • the beam diameter of the first light beam before passing through the beam expansion module can be replaced by the beam diameter of the first return light beam after passing through the beam expansion module.
  • ⁇ is the transition zone of the first microlens array, and the parameters are as mentioned above.
  • FIG7 is a schematic diagram of a possible simulation result provided by an embodiment of the present application. If receiving compensation is not adopted, the loss of the return light beam will be large. However, through the solution of the present application, compensation is performed at the receiving end, which can greatly reduce the loss and improve the effectiveness of the signal.
  • FIG. 8 is a schematic diagram of a possible simulation result provided by an embodiment of the present application. If receiving compensation is not adopted, the loss of the return light beam is large. Through the scheme of the present application, compensation is performed at the receiving end, which can greatly reduce the loss and improve the effectiveness of the signal.
  • the transmitting optical module includes a waveguide or an optical fiber.
  • the receiving optical module includes a waveguide or an optical fiber.
  • the receiving optical element 2042 shown in FIG5 can be a waveguide or an optical fiber.
  • the walk angle of the return beam can be compensated through the embodiment of the present application, which can significantly reduce the signal loss caused by the walk off angle, improve the effectiveness of the received echo signal, and improve the detection performance.
  • the optical module may include an emitting optical module, a lens (such as MLA1, MLA2, MLA3, etc.), a PBS, a quarter wave plate (quarter wave plate, QWP), a collimation lens (Collimation Lens, CL), an optical receiving module and a scanner.
  • PBS and QWP are an exemplary beam splitting module
  • MLA2 and CL are an exemplary beam expansion module.
  • the emitting optical module may include one or more of a fiber array (fiber array unit, FAU), a waveguide (waveguide, WG), etc.
  • the optical receiving module may also include one or more of FAU, WG, etc.
  • some devices in the emitting optical module and the receiving optical module can be integrated together, for example, the waveguide can be integrated together, for example, integrated on a silicon photonic chip.
  • the optical module separates the receiving and emitting paths through PBS and QWP; the beam expansion module expands the transmitting beam and converges the return beam.
  • the position of the optical receiving module is offset from the ideal receiving beam.
  • the offset distance (or the position of the optical receiving module) and the angle are related to the walk-off angle, the distance from the center of PBS to MLA2, and the distance from the center of PBS to MLA1.
  • the aperture of MLA2 is related to the emission spot size and translation position.
  • the elements of the optical module shown in this application are exemplary.
  • the optical module may include more or fewer optical elements than the optical elements shown in the embodiments of this application.
  • reflectors, lenses, filters, etc. can be added to the optical module to assist in the realization of light splitting, assist in the realization of beam expansion, improve the light splitting efficiency, improve the beam quality module, and improve the device integration.
  • FIG. 10 is a schematic diagram of the structure of another optical module provided in an embodiment of the present application.
  • the position of the receiving optical element can be made closer to the position of the transmitting optical module, thereby improving the integration of the device.
  • the waveguide or waveguides
  • the waveguide can be integrated together, for example, on the same silicon photonic chip, to improve the integration of the device and reduce the volume of the optical module.
  • some optical components in an optical module can be packaged as an integral module to further improve the stability of the optical components, improve the device integration, and improve the output beam quality.
  • the transmitting optical module, the receiving optical module and the light splitting module are packaged to form a first optical component. Further, the light passing window of the first optical component is aligned with the light passing surface of the beam expansion unit.
  • the optical elements in region 901 namely PBS, QWP, FAU (or WG), MLA1, MLA3, etc.
  • the optical elements in region 902, namely MLA2, CL, etc. can be integrated and packaged to form another optical component, which is conveniently distinguished as the third optical component.
  • the light-transmitting window of the first optical component is aligned with the light-transmitting window of the third optical component.
  • a material with a thermal expansion coefficient close to that of the optical elements in the optical module can be used as a supporting component to achieve high-precision alignment between the optical elements and improve the stability of the system.
  • the supporting components include but are not limited to a base, a substrate, a pad, etc.
  • the material of the pad supporting optical elements such as MLA and PBS can be glass, crystal, ceramic, etc.
  • the optical elements in region 1001 namely PBS, QWP, FAU (or WG), MLA1, MLA3, MLA2, etc.
  • the optical elements in region 1001 can be integrated and packaged to form a group of optical components, which are conveniently distinguished as the second optical components. That is, CL and the like can be integrated and packaged to form another optical component, which is convenient for distinguishing as a fourth optical component.
  • the light-transmitting window of the third optical component is aligned with the light-transmitting window of the fourth optical component.
  • the first optical element and the third optical element can be packaged on the same metal base.
  • Figure 11 is a schematic diagram of the structure of an optical module provided in an embodiment of the present application, wherein FAU (or WG), MLA3, PBS, MLA2, etc. can be packaged on a glass substrate, and if the optical axes of the optical elements cannot be aligned, they can be supported or filled by glass pads.
  • the first optical element and the CL with a metal lens barrel can be packaged on a metal base, so that the optical module is integrated as a whole to improve stability.
  • MLA1 and PBS may be arranged along a direction passing through the paper surface (or a direction perpendicular to the paper surface), and the reflected light beam reaches MLA1 along a direction passing through the paper surface after passing through the PBS.
  • the embodiment of the present application also provides a laser radar, which includes the optical module described in any one of the first aspects. Further, the laser radar also includes a light source, such as a laser. Optionally, the frequency of the light beam emitted by the light source can be continuously variable, such as a frequency modulated continuous wave (FMCW) laser.
  • FMCW frequency modulated continuous wave
  • the laser radar also includes a detector, which is used to obtain an electrical signal according to the light beam.
  • the detector may include a photodiode (PD) capable of detecting light energy, such as InGaAs PD, InP PD, or germanium PD.
  • PD photodiode
  • the embodiment of the present application further provides a terminal, wherein the terminal includes the aforementioned optical module.
  • the terminal includes the aforementioned laser radar.
  • the terminal can be a smart terminal or means of transportation such as a vehicle, a drone, or a robot.
  • the terminal can also be replaced by industrial equipment, entertainment and leisure equipment, etc.
  • Smart terminals such as mobile phones, tablets, laptops, smart bracelets, smart watches, or smart glasses.
  • Transportation tools such as vehicles, ships, aircraft, or logistics robots.
  • Industrial equipment such as industrial robots and robotic arms.
  • Leisure and entertainment equipment such as virtual reality (VR) equipment, mixed reality (MR) equipment, massage chairs, or 4D cinema cabins. This application does not impose strict restrictions on the devices to which the electrical connector can be applied.
  • connection should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, a conflicting connection or an integral connection.
  • connection can be a fixed connection, a detachable connection, a conflicting connection or an integral connection.
  • the words “exemplary” or “for example” are used to indicate examples, illustrations or descriptions. Any embodiment or design described as “exemplary” or “for example” in the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as “exemplary” or “for example” is intended to present related concepts in a specific way.
  • At least one refers to one or more, and “plurality” refers to two or more.
  • At least one of the following” or similar expressions refers to any combination of these items, including any combination of single items or plural items.
  • at least one of a, b, or c can be represented by: a, b, c, (a and b), (a and c), (b and c), or (a and b and c), where a, b, c can be single or multiple.
  • “And/or” describes the association relationship of associated objects, indicating that three relationships can exist.
  • a and/or B can be represented by: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural.
  • the character "/" generally indicates that the associated objects before and after are in an "or” relationship.
  • first and second used in the embodiments of the present application are used to distinguish multiple objects, and are not used to limit the order, timing, priority or importance of multiple objects.
  • first BMU and the second BMU are only used to facilitate the description of the BMUs in the battery unit, and do not indicate the difference in structure, importance, etc. between the first BMU and the second BMU.

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Abstract

一种光学模组（20）、激光雷达和终端，应用于探测技术领域。光学模组（20）包括发射光学模组（201）、同轴光学模组（202）、扫描模组（203）和接收光学模组（204），发射时，第一光束依次经过发射光学模组（201）、同轴光学模组（202）和扫描模组（203）传播到物空间。接收时，第一返回光束依次经过扫描模组（203）和同轴光学模组（202）传播至接收光学模组（204），而经过同轴光学模组（202）后的第一光束和经过同轴光学模组（202）前的第一返回光束存在第一夹角。其中，接收光学模组（204）的位置与第一光束的理想接收光束存在第一偏移，从而补偿第一返回光束的角度偏移，使第一返回光束的光斑更靠近接收光学模组（204）的有效接收区域，甚至与有效接收区域的中心重合。可以降低由walk off角造成的信号损耗，提升回波的有效性，提升探测性能。

Description

一种光学模组、激光雷达和终端 技术领域
本申请涉及探测技术领域，尤其涉及一种光学模组、激光雷达和终端。
背景技术
随着信息技术以及计算机视觉的发展，探测技术取得了飞速发展，各式各样的探测装置给人们的生活、出行带来了极大的便利。探测装置可以看作设备是感知环境的“眼睛”，包括摄像头等视觉系传感器和毫米波雷达、激光雷达和超声波雷达等雷达系传感器。
其中，激光雷达(light detection and ranging，Lidar，或称光探测和测距装置)具有分辨率较高、探测性能好、隐蔽性强的优点，在设备感知环境的过程中发挥着重要的作用。而扫描式激光雷达是被广泛使用的一种激光雷达，其采用扫描的方式对物空间进行探测的激光雷达。
扫描式探测装置包含发射端、接收端和扫描模组。由于扫描模组会旋转或摆动，光束由扫描器投射到目标物，再被目标物反射回来照射到扫描器的这段时间内，扫描器会产生一个偏移角，这个由扫描器活动所造成的发射光束与返回光束之间的偏移角在探测领域被称为称walk off角。walk off角的存在使得返回光束不能照射在接收端中心，造成回光信号强度下降，影响测距性能。
发明内容
本申请实施例提供一种光学模组、激光雷达和终端，能够降低由walk off角造成的信号损耗，提升接收的回波信号的有效性，提升探测性能。
第一方面，本申请实施例提供一种光学模组，包括发射光学模组、同轴光学模组、扫描模组和接收光学模组，其中：
所述发射光学模组用于将光源发出的第一光束传播至所述同轴光学模组；
所述同轴光学模组用于将所述第一光束传播至所述扫描模组；
所述扫描模组用于将所述第一光束扫描至物空间，还用于将所述第一返回光束传输至所述同轴光学模组，所述第一返回光束为所述第一光束的返回光束；
所述同轴光学模组还用于将所述第一返回光束传输至所述接收光学模组，其中，进入同轴光学模组后的第一光束和返回至同轴光学模组前的第一返回光束存在第一夹角，所述第一夹角大于0°且小于90°；
所述接收光学模组用于接收所述第一返回光束；
其中，所述接收光学模组的位置与所述第一光束的理想接收光束存在第一偏移，返回至所述同轴光学模组前的所述第一返回光束的理想接收光束和第一光束平行。
本申请实施例中，理想接收光束是与第一光束平行的返回光束，换句话说，若扫描器处于静止状态，则第一光束的返回光束会沿着理想接收光束的光路传播。由于扫描器不断扫描，第一光束被传播到物空间的目标物上后，可以被物空间的目标物反射得到第一反射光束。由于物空间的目标物与扫描器之间存在一定距离，使得第一返回光束经过扫描器时，扫描器已经转动过了一定角度。因此，第一返回光束不再沿着理想接收光束的传播，也即，第一返回光束与理想接收光束的存在偏移角。
在此基础上，本申请将接收模组偏离理想接收光束的光路，从而可以补偿第一返回光束相比与理想接收光束的偏移，可以降低由walk off角造成的信号损耗。可理解的，第一返回光束与理想接收光束(与第一光束平行)的偏移角为第一夹角，而接收光学模组也相比于理想接收光束的存在偏移，因此接收光学模组的偏移补偿了第一光束的偏移，使得第一返回光束的光斑可以更加靠近接收光学模组有效接收区域，甚至与有效接收区域的中心重合。如此，接收光学模组可以更加准确地接收第一返回光束，提升了接收的回波信号的有效性，提升了探测性能。
其中，有效接收区域是指接收模组可以用于接收第一返回光束的区域，包含但不限于是微透镜阵列的通光面、光纤的接收模场、或接收器的探测器中等。
在第一方面的又一种可能的实施方式中，所述第一偏移与所述第一夹角相关。
其中，第一夹角是返回光束与发射光束之间的夹角，通过该夹角和扫描器至接收光学模组之间的光路的距离，可以确定第一返回光束在传播至接收光学模组的偏移量，从而可以设计接收光学模组的补偿量， 使得接收光学模组可以更加准确地接收第一返回光束，提升了接收的回波信号的有效性，提升了探测性能。
在第一方面的又一种可能的实施方式中，所述同轴光学模组包含分光模组和扩束模组，所述分光模组设置在所述发射光学模组和所述扩束模组之间。
示例性的，这里的之间是表示光路的中间，也即是说，第一光束经过所述分光模组和所述扩束模组传播至所述扫描模组，第一返回光束经过所述扩束模组和所述分光模组传播至接收模组。
其中，分光模组是指将光束分为多路的光学装置。例如，分光模组可以包含偏振分束器(polarization beam splitter，PBS)、半透半反分光镜中的一种或者多种的组合。一些场景中，分光模组还可以包含其他用于辅助实现分光或者提升分光效率、光束质量的模组。例如，分光模组还可以包含波片(例如四分之一波片、二分之一波片、或八分之一波片等)、增透膜、或滤镜等中的一项或者多项。示例性的，分光模组可以包含PBS和四分之一波片(quarter-wave plate，QWP)。第一光束依次经过PBS和四分之一波片，而第一返回光束依次经过四分之一波片和PBS。由于四分之一波片可以改变偏振状态，而PBS可以根据偏振状态透过或反射经过的光束，从而可以将第一光束和第一返回光束的光路分开，实现收发同轴。
扩束模组是指用于增加或者缩小光束直径的模组。例如，扩束模组可以为望远镜扩束模组，其通过设置至少两组透镜来实现扩束/缩束。
在这种实施方式中，扩束模组设置在后端，发射时，光束分光再进行扩束，因此第一光束经过分光模组时直径比较小，经过扩束以后光束的直径变大，使得传播到物空间的光斑比较大，提升探测效率。而在接收时，返回光束经过扩束单元以后直径缩小，使得更容易被光接收单元接收，提升接收信号的有效性。而且，由于细光束比粗光束的路径更可控，从而可以便于解决发射端和接收端偏轴的技术问题。
另外，这种情况下，发射光束和接收光束可以共用同一套扩束镜头，提升了器件的集成度，减小了模组的体积。
在第一方面的又一种可能的实施方式中，所述接收光学模组包含第一微透镜阵列，所述第一微透镜阵列用于接收经过所述分光模组后的所述第一返回光束；
所述第一微透镜阵列的光轴与所述理想接收光束之间存在第三夹角，所述第三夹角小于等于第二夹角且大于等于所述第二夹角的二分之一；
所述第二夹角与最大偏移角度和所述扩束模组的扩束倍数相关，所述最大偏移角度与所述光学模组的最远探测距离和所述扫描模组的扫描速度相关。
可选的，所述扩束模组的扩束倍数也可以替换为所述扩束模组中的透镜的焦距。可选的，第一微透镜阵列可以用于汇聚第一返回光束，从而使得接收器可以更准确的接收第一返回光束。
在上述实施例中，第一微透镜阵列在放置时，其光轴与理想接收光束的光路存在角度偏移，从而可以补偿第一返回光束的角度偏移，提升接收的回波信号的有效性，提升探测性能。
其中，第三夹角θ可以落入以下范围，λmax为第二夹角，第二夹角与最大偏移角度(表示为)、扩束模组的放大倍数相关。上述扩束模组的放大倍数也可以替换为扩束模组中的两组透镜的焦距。
一些场景中，由于物空间中的目标物与光学模组之间的距离有多种可能的情况，因此，第一返回光束与理想接收光束之间的偏移角(即第一夹角)会随着目标物与光学模组之间的距离变化而变化。而最大偏移角度为第一夹角的最大值，也即，最大偏移角度为最远探测距离出的目标物反射第一光束形成的第一返回光束(简称为最大偏移光束)与理想接收光束之间的夹角。换句话说，最大偏移角度为最大偏移光束与静态接收光束的夹角，最大偏移光束为光学模组的最远探测距离的目标物反射第一光束形成的光束。其中，最远探测距离可以为光学模组的最远探测距离，也即光学模组所在的探测装置的最远探测距离，其可以是预先定义、或预先设计的。
示例性的，第二夹角可以满足如下式子：进一步的，放大倍数＝D2/D1，D2为经过扩束模组之后的第一光束的直径，D1为经过扩束模组之前的第一光束的直径。
可选的，最大偏移角度与最远探测距离和扫描模组的扫描速度相关。示例性的，最大偏移角度可以满足如下式子：其中，v为扫描器的角速度，c为光速，D为最远探测距离。k为系数，由于机械角度和光学角度之间存在相关关系，k用于转换为机械角度和光学角度。例如，光学角度为机械角度的两倍，此处光束两次经过扫描器，则k可以为4，即：
在第一方面的又一种可能的实施方式中，扩束模组包含两组透镜，两组透镜的焦距不同，且靠近物空间的透镜的焦距比远离物空间的透镜的焦距更大。
在第一方面的又一种可能的实施方式中，所述扩束模组包含第二微透镜阵列和准直镜(collimation lens，CL)，所述第二微透镜阵列和所述准直镜具有共同的第一焦平面。可选的，第二微透镜阵列设置在分光模组和所述准直镜之间。
进一步的，第二微透镜阵列的焦距小于准直镜的焦距。可选的，扩束模组的放大倍数与第二微透镜阵列的焦距和准直镜的焦距相关。
示例性的，其中，D2为经过扩束模组之后的光束的直径，D1为经过扩束模组之前的光束的直径，fc为准直镜的焦距，f2为第二微透镜阵列的焦距。
一些场景中，前述的第二夹角与最大偏移角度第二微透镜阵列的焦距和准直镜的焦距相关。例如，第二夹角可以满足如下式子：
如此，通过前后两组透镜进行扩束(或称望远镜扩束模组)，使得光学模组实现收发同轴的工艺容差增大，可实现性更好。
在第一方面的又一种可能的实施方式中，第一微透镜阵列与理想接收光束的之间的第一偏移距离与第三夹角、第一微透镜阵列与分光模组之间的距离、分光模组与扩束模组之间的距离和第一返回光束的光斑在所述第一焦平面上的第二偏移相关。
可选的，第二偏移为在第一夹角为最大偏移角度的情况下第一返回光束的光斑和第一返回光束的理想接收光束的光斑在第一焦平面上的距离。
示例性的，第二偏移与第三夹角、扩束模组中的两组透镜的焦距相关。例如，第二偏移Δy满足如下式子：
其中，fc准直镜的焦距，f2为第二微透镜阵列的焦距，θ为第三夹角。
示例性的，第一偏移距离Δx满足如下式子：
Δx＝|(d1+d2)*tanθ-Δy|
其中，d1为第一微透镜阵列与分光模组之间的距离，d1为分光模组与扩束模组(或第二微透镜阵列)之间的距离，θ为第三夹角，Δy为第二偏移。
在第一方面的又一种可能的实施方式中，所述接收光学模组还包含接收光学元件，所述接收光学元件用于接收经过所述第一微透镜阵列的第一返回光束。
可选的，接收光学元件与经过所述理想接收光束之间的距离为第二偏移距离，所述第二偏移距离与所述第三夹角、所述第一微透镜阵列与所述分光模组之间的距离、所述分光模组与所述扩束模组之间的距离、所述第二微透镜阵列的焦距、所述准直镜的焦距和所述第一返回光束的光斑在所述第一焦平面上的第三偏移相关。
其中，第三偏移为第一返回光束在所述第一焦平面上的光斑与最大偏移光束在焦平面上的光斑之间的距离，最大偏移光束为在所述第一夹角为最大偏移角度的情况下的第一返回光束。
示例性的，第三偏移与最大偏移角度所述第二微透镜阵列的焦距f2、所述准直镜的焦距fc和所述第三夹角θ相关。例如，第三偏移(Δy′)满足如下式子：
示例性的，第二偏移距离(Δx′)满足如下式子：
在第一方面的又一种可能的实施方式中，第一微透镜阵列的通光口径与所述第一偏移距离和所述第二偏移距离中的至少一项和所述第一光束在经过所述扩束单元之前的直径相关。
示例性的，所述第一微透镜阵列的通光口径w3满足如下式子：
w3≥2*max(Δx,Δx′)+D1
其中，max()表示取最大值，D1为第一光束在经过扩束模组之前的光束直径或第一返回光束在经过扩束模组之后的光束直径，其余各参数参见前述。
在第一方面的又一种可能的实施方式中，所述第一微透镜阵列的周期p与第一微透镜的过渡带、第一偏移距离、第二偏移距离和第一光束在经过扩束模组之前的光束直径相关。其中，第一光束在经过扩束模组之前的光束直径可以替换为第一返回光束在经过扩束模组之后的光束直径。
示例性的，所述第一微透镜阵列的周期p满足如下式子：
p＝w3+δ
w3≥2*max(Δx,Δx′)+D1
其中，δ为第一微透镜阵列的过渡带，各参数参见前述。
在第一方面的又一种可能的实施方式中，所述发射光学模组包含波导或光纤。
在第一方面的又一种可能的实施方式中，所述接收光学模组包含波导或光纤。
在第一方面的又一种可能的实施方式中，所述发射光学模组、所述接收光学模组和所述分光模组封装在玻璃底座上形成第一光学组件，所述第一光学组件的通光窗口与所述扩束单元的通光面对齐。
在第一方面的又一种可能的实施方式中，所述发射光学模组、所述接收光学模组、所述分光模组和所述第二微透镜阵列封装在玻璃底座上形成第二光学组件，所述第二光学组件的通光窗口与所述准直镜的通光面对齐。
在第一方面的又一种可能的实施方式中，所述同轴光学模组包含偏振分束器PBS和四分之一波片。
第二方面，本申请实施例提供一种激光雷达，所述激光雷达包含第一方面任一项所述的光学模组。
在第二方面的一种可能的实施方式中，激光雷达还包含光源。例如，光源为激光器。
在第二方面的又一种可能的实施方式中，激光雷达还包含探测器，探测器用于根据光束得到电信号。
第三方面，本申请实施例提供一种终端，所述终端包含第一方面任一项所述的光学模组，或者，终端包含第二方面任一项所述的激光雷达。
可选的，终端可以为车辆、无人机、机器人等智能终端或运输工具。当然，终端也可以替换为工业设备、娱乐休闲设备等。智能终端例如手机、平板电脑、笔记本电脑、智能手环、智能手表、或智能眼镜等。交通工具例如车辆、舰船、飞行器、或物流机器人等。工业设备例如工业机器人、机械臂等。休闲娱乐设备例如虚拟现实(virtual reality，VR)设备、混合现实(mixed reality，MR)设备、按摩椅、或4D影院座舱等。本申请对于电连接器可以应用的设备不做严格限制。
附图说明
下面将对实施例描述中所需要使用的附图作简单的介绍。
图1是一种探测过程的示意图；
图2本申请实施例提供的一种光学模组的结构示意图；
图3是本申请实施例提供的又一种光学模组的结构示意图；
图4是本申请实施例提供的又一种光学模组的结构示意图；
图5是本申请实施例提供的又一种发射模组的结构示意图；
图6A是本申请实施例提供的又一种光学模组的结构示意图；
图6B是本申请实施例提供的一种光学模组的光路示意图；
图6C是本申请实施例提供的一种光学模组的参数示意图；
图7是本申请实施例提供的一种可能的仿真结果的示意图；
图8是本申请实施例提供的一种可能的仿真结果的示意图；
图9是本申请实施例提供的又一种光学模组的结构和光路示意图；
图10是本申请实施例提供的又一种光学模组的结构示意图；
图11是本申请实施例提供的有一种光学模组的结构示意图。
具体实施方式
下面将结合附图对本申请实施例进行描述。
扫描型探测装置是通过扫描机构，对物空间进行扫描从而完成对整个视野进行探测的装置。扫描型探测装置通常通过扫描机构的活动(例如摆动、转动等)来将发射信号以多个角度投射到物空间，因此扫描机构会持续处于活动状态。当激光雷达工作时，由于扫描机构高速旋转(或摆动)，光束由扫描机构发射打到目标物再反射回来的时间内，扫描机构已经产生了一个偏移角。
如图1所示是一种探测过程的示意图，扫描机构不断活动，发射光束(以实线箭头表示)和返回光束(以虚线箭头表示)会产生一个偏移角，即walk off角。walk off角的角度大小和扫描机构的角速度以及光束在物空间的飞行时间有关，且正相关。光束的飞行时间越长、扫描机构的角速度越快，则walkoff角度越大。这个偏移角度会使得光束在接收位置产生偏移，使得返回光束不能照射在接收端中心，接收的返回光束的信号强度降低，信噪比减小，影响测距距离。
尤其对于包含光纤、波导等元件的探测装置，由于光纤、波导等光学元件的接收的模场面积比较小， 返回光束的walkoff角会导致返回光束偏离接收模场，使得返回光束的信号显著下降，影响探测性能。例如，对于以单模光纤(single mode fiber，SMF)做发射和接收端的探测装置，返回光束在接收端的偏移距离Δx＝f*tanγ，其中f为接收镜头焦距，γ为walk off角。在3000转每分(r/min)的扫描机构，150m探测距离下，γ大约0.036°。对于车载激光雷达，由于发射角度、接收口径要求，一般其f在几十到几百毫米(mm)。由此得到Δx的大小在几um到几十um量级，而SMF的模斑通常约为10um，因此，返回光束在接收端的偏移极有可能超过SMF的模斑，返回光束的信号强度显著下降，对探测性能影响较大。
有鉴于此，本申请实施例提供一种光学模组、激光雷达和终端，能够降低由walk off角造成的信号损耗，提升接收的回波信号的有效性，提升探测性能。
请参见图2，图2是本申请实施例提供的一种光学模组的结构示意图。光学模组20包含发射光学模组201、同轴光学模组202、扫描模组203和接收光学模组204。其中：
发射光学模组201用于将光源发出的第一光束(如图2所示的带箭头实线)传播至同轴光学模组202。发射光学模组201可以包含透镜、光纤、波导等。光源可以激光器，例如激光二极管(laser diode，LD)、垂直腔面发射激光器(Vertical Cavity Surface Emitting Laser，VCSEL)、分布式反馈激光二极管(distributed feedback LD，DFB-LD)、分布式布拉格反射激光二极管(distributed bragg reflection LD，DBR-LD)、光栅耦合采样反射激光二极管(Grating coupled sampling reflection LD，GCSR-LD)、微光机电系统激光二极管(micro opto electro mechanical system LD，MOEMS-LD)等发光器件。第一光束例如可以为调频连续波(Frequency Modulated Continuous Waves，FMCW)光束，其波形可以为锯齿、三角或者正弦波。
同轴光学模组202用于将第一光束传播至扫描模组203。同轴光学模组202用于实现收发同轴。一些场景中，收发同轴可以理解为发射光束和接收光束共同经过了部分光学元件，例如发射光束和接收光束共同经过了扫描模组203和同轴光学模组202。又一些场景中，收发同轴可以理解为发射光束的主光轴和返回光束的主光轴是平行的，当然，这里的平行是指理想情况下(如不考虑扫描器的活动的情况下)。例如，同轴光学模组202可以包含透镜、分光镜、波片等。
扫描模组203用于将第一光束扫描至物空间。即，扫描模组203可以进行摆动或者转动，以不同的角度将光束投射到物空间。扫描模组203还用于将第一返回光束(如图2所示的带箭头虚线)传输至所述同轴光学模组，第一返回光束为第一光束的返回光束。示例性的，第一光束传播到物空间的目标物上，被目标物反射形成反射信号，第一返回光束包含了第一光束的反射信号。
其中，进入同轴光学模组202后的第一光束和返回至同轴光学模组202前的第一返回光束存在第一夹角γ。其中，第一夹角即walkoff角。可选的，第一夹角大于0°且小于90°，即0°＜γ＜90°。
同轴光学模组202还用于将第一返回光束传输至接收光学模组204。示例性的，同轴光学模组202包含偏振分束器PBS和四分之一波片。第一光束透过PBS到达四分之一波片，而第一返回光束经过四分之一波片后偏振状态改变，从而被PBS反射传播到接收光学模组204。
本申请实施例中，接收光学模组204的位置与第一光束的理想接收光束(参见图2所示的无箭头虚线)存在第一偏移。其中，返回至同轴光学模组202前的第一返回光束的理想接收光束和第一光束平行。也即，理想接收光束是主光轴与第一光束平行的光束，walkoff角为0°的情况下，例如扫描器静止(或者是不转动)的情况，第一光束对应的返回光束则沿理想接收光束的光路传播。
换句话说，若walkoff角为0°，则第一光束的返回光束会沿着理想接收光束的光路传播。而由于扫描器不断活动，第一光束被传播到物空间的目标物上被物空间的目标物反射得到第一反射光束之后，由于物空间的目标与扫描器之间存在一定距离，因此第一返回光束经过扫描器时，扫描器已经转动过了一定角度。因此，第一返回光束不再沿着理想接收光束的传播，也即，第一返回光束与理想接收光束的存在偏移角度。在此基础上，本申请将接收模组偏离理想接收光束的光路，从而可以补偿第一返回光束相比与理想接收光束的偏移，可以降低由walk off角造成的信号损耗。如图1所示，理想接收光束的接收点(即接收光学模组204的平移位置点)通过黑色实心半圆描述，而接收光学模组204与理想接收光束的接收点存在偏移距离。
可理解的，第一返回光束与理想接收光束(与第一光束平行)的偏移角度为第一夹角，而接收光学模组也相比于理想接收光束的存在偏移，因此接收光学模组的偏移补偿了第一光束的偏移，使得第一返回光束的光斑可以更加靠近接收光学模组的中心或者与接收光学模组的中心重合。如此，接收光学模组可以更加准确地接收第一返回光束，提升了接收的回波信号的有效性，提升了探测性能。
在第一方面的又一种可能的实施方式中，第一偏移与第一夹角相关。其中，第一夹角是返回光束与发射光束之间的walkoff角，通过该夹角和扫描器至接收光学模组之间的光路的距离，可以确定返回光束在传播至接收光学模组的偏移量，从而可以设计接收光学模组的补偿量，使得接收光学模组可以更加准确地接收第一返回光束，提升了接收的回波信号的有效性，提升了探测性能。
例如，第一夹角的最大值可以为从最远探测距离处返回的光束与发射光束(如第一光束)之间的夹角，为便于描述称为最大偏移角度，表示为请参见图3，图3是本申请实施例提供的又一种光学模组的结构示意图，在以最大偏移角度返回的光束与理想接收光束在接收点(即接收光学模组的平移位置点)的偏移量为x的情况下，接收光学模组204与理想接收光束的接收点的偏移量可以位于x/2至x之间。如图3所示，接收光学模组204与理想接收光束的接收点的偏移量可以为x/2处。这种情况下，若第一返回光束与理想接收光束的偏移角比较大，反而更加靠近接收光学模组的光轴中心，从而有利于提升远距离探测时的测距精度。
可替换的，接收光学模组204与理想接收光束的接收点的偏移量可以位于0至x/2之间，如此可以保障近距离探测时的测距精度。
进一步的，最大偏移角度为最远探测距离和扫描模组203的角速度相关。示例性的，最大偏移角度可以满足如下式子：其中，v为扫描器的角速度，c为光速，D为最远探测距离。k为系数，由于机械角度和光学角度之间存在相关关系，k用于转换为机械角度和光学角度。例如，光学角度为机械角度的两倍，此处光束两次经过扫描器，则k可以为4，即：其中，最远探测距离可以是厂商、标准组织、用户或者使用设备等预先定义(或规定)、预先设置的。
在一种可能的实施方式中，同轴光学模组包含分光模组和扩束模组，分光模组设置在所述发射光学模组和所述扩束模组之间。
其中，扩束模组是指用于增加或者缩小光束直径的模组。分光模组是指将光束分为多路的光学装置。例如，分光模组可以包含偏振分束器(polarization beam splitter，PBS)、半透半反分光镜中的一种或者多种的组合。一些场景中，分光模组还可以包含其他用于辅助实现分光或者提升分光效率、光束质量的模组。例如，分光模组还可以包含波片、增透膜、或滤镜等中的一项或者多项。示例性的，分光模组可以包含PBS和四分之一波片。第一光束依次经过PBS和四分之一波片，而第一返回光束依次经过四分之一波片和PBS。由于四分之一波片可以改变偏振状态，而PBS可以根据偏振状态透过或反射经过的光束，从而可以将第一光束和第一返回光束的光路分开，实现收发同轴。
请参见图4，图4是本申请实施例提供的又一种光学模组的结构示意图，同轴光学模组202包含分光模组2021和扩束模组2022，分光模组2021设置在发射光学模组201和扩束模组2022之间。可以看出，这里的之间是表示光路的中间，也即是说，第一光束经过分光模组2021和扩束模组2022传播至扫描模组203，第一返回光束经过扩束模组2022和分光模组2021传播至接收光学模组204。
在这种实施方式中，扩束模组2022设置在后端，发射时，光束分光再进行扩束，因此第一光束经过分光模组时直径比较小，经过扩束以后光束的直径变大，使得传播到物空间的光斑比较大，提升探测效率。而在接收时，返回光束经过扩束单元以后直径缩小，使得更容易被光接收单元接收，提升接收信号的有效性。而且，由于细光束比粗光束的路径更可控，从而可以便于解决发射端和接收端偏轴的技术问题。另外，这种情况下，发射光束和接收光束可以共用同一套扩束系统，提升了器件的集成度，减小了模组的体积。
由于扩束模组对光束进行了扩束(或收束)，因为第一返回光束经过扩束模组后与理想接收光束之间的夹角可能产生变化。参见图4，经过扩束模组2022后的第一返回光束与理想接收光束之间的夹角可以表示为λ。可选的，该夹角λ大于0°且小于90°，即0°＜λ＜90°。
可选的，λ与第一夹角和扩束模组2022的放大倍数相关。例如，λ满足如下式子：一些场景中，放大倍数与扩束之前的光束的直径与扩束之后的光束的直径相关，例如：D2为经过扩束模组2022之后的发射光束(如第一光束)的直径，D1为经过扩束模组2022之前的发射光束的直径。
一些场景中，扩束模组可以包含两组透镜。两组透镜沿第一光束的光路前后放置，且通过焦平面连接，这里的焦平面可以是实焦面也可以是虚焦面。此时，扩束模组的放大倍数与两透镜的焦距相关(下文中进行介绍)。此时，λ与第一夹角和扩束模组2022的放大倍数相关也可以替换为：λ与第一夹角和两透镜的焦距相关。
在一种可能的实施方式中，接收光学模组204包含透镜，所述透镜用于接收经过分光模组后的第一返回光束。
示例性的，透镜可以为微透镜阵列(microlens arrays，MLA)，便于区分称为第一微透镜阵列，表示为MLA1。请参见图5，图5是本申请实施例提供的又一种发射模组的示意图。接收光学模组204包含第一微透镜阵列2041和接收光学元件2042。其中，第一微透镜阵列2041的光轴(即图5所示的光轴)与理想接收光束之间存在第三夹角θ，第三夹角θ小于等于第二夹角且大于等于第二夹角的二分之一。
其中，第二夹角为以最大偏移角度返回的返回光束经过扩束模组之后的光束与静态接收光束之间的夹角。换句话说，从最远探测距离处反射第一光束得到返回光束，经过扫描模组和扩束模组之后与静态接收光束之间的夹角为第二夹角。也即，第二夹角为λ的最大值，便于描述表示为λmax。
相应的，第三夹角θ可以落入以下范围，λmax为第二夹角，第二夹角与最大偏移角度(表示为)、所述准直镜的焦距和第二微透镜阵列的焦距相关。
一些场景中，由于物空间中的目标物与光学模组之间的距离有多种可能的情况，因此，第一返回光束与理想接收光束之间的偏移角(即第一夹角)会随着目标物与光学模组之间的距离变化而变化。而最大偏移角度为第一夹角的最大值，也即，最大偏移角度为最远探测距离出的目标物反射第一光束形成的第一返回光束(简称为最大偏移光束)与理想接收光束之间的夹角。换句话说，最大偏移角度为最大偏移光束与静态接收光束的夹角，最大偏移光束为光学模组的最远探测距离的目标物反射第一光束形成的光束。其中，最远探测距离可以为光学模组的最远探测距离，也即光学模组所在的探测装置的最远探测距离，其可以是预先定义、或预先设计的。
示例性的，第二夹角可以满足如下式子：进一步的，放大倍数＝D2/D1，D2为经过扩束模组之后的第一光束的直径，D1为经过扩束模组之前的第一光束的直径。
在前文中我们提到，扩束模组可以包含两组透镜。在一种可能的实施方式中，扩束模组包含透镜和准直镜。例如，透镜可以为微透镜阵列，便于区分称为第二微透镜阵列。
请参见图6A，图6A是本申请实施例提供的又一种光学模组的结构示意图。光学模组20包含发射光学模组、偏振分束器PBS、四分之一波片QWP、第二微透镜阵列MLA2、准直镜、扫描模组、第一微透镜阵列MLA1。其中，PBS和QWP为一种示例性的分光模组，MLA22和准直镜为一种示例性的扩束模组。MLA1包含于接收光学模组中。而MLA2设置在分光模组和准直镜之间，结合图6A，MLA2可以具体设置在QWP和准直镜之间。可选的，在发射模组和分束模组之间还设置有透镜，例如为微透镜阵列，如图6A所示的MLA3。
请参见图6B，图6B是本申请实施例提供的一种光学模组的光路示意图，以透镜为第二微透镜阵列MLA2为例，MLA2和准直镜具有共同的焦平面P1(可选为续焦平面或实焦平面)。进一步的，MLA2的焦距小于准直镜的焦距。可选的，扩束模组的放大倍数与第二微透镜阵列的焦距和准直镜的焦距相关。
参见图6C，图6C是本申请实施例提供的一种光学模组的参数示意图，该光学模组的结构和光路分别可以参见图6A和图6B。其中，MLA2的焦距表示为f2，准直镜的焦距为fc，经过MLA2之前(和/或MLA3之后)的第一光束的直径为D1，而准直镜的出射光束的宽度为D2。PBS中心到MLA1的距离表示为d1，PBS中心到MLA2的距离表示为d2，发射和接收信号在P1面的偏移距离表示为Δy。
如图6C所示，D2为经过扩束模组之后的光束的直径，D1为经过扩束模组之前的光束的直径，fc为准直镜的焦距，f2为MLA2的焦距。其中，表示扩束模组的放大倍数。结合图6C，不难看出：tanγ*fc＝tanλ*f2，
此外，在的情况下，第二夹角λmax可以满足如下式子：
作为一种可能的实施方式，接收模组中的第一微透镜阵列与理想接收光束之间的距离可以称为第一偏移距离。
可选的，第一偏移距离满足如下条件：在经过分光模组后的第一返回光束与经过分光模组后的理想接收光束的偏移角度为第三夹角θ的情况下，第一返回光束的光斑中心与第一微透镜阵列的中心重合，或者，第一返回光束的光轴与第一微透镜的光轴一致。
作为一种可能的实施方式，第一微透镜阵列与理想接收光束的之间的第一偏移距离与第三夹角、第一 微透镜阵列与分光模组之间的距离、分光模组与扩束模组之间的距离和第一返回光束的光斑在所述第一焦平面上的第二偏移相关。
可选的，第二偏移为在第一夹角为最大偏移角度的情况下第一返回光束的光斑和第一返回光束的理想接收光束的光斑在第一焦平面上的距离。
示例性的，第二偏移与第三夹角、扩束模组中的两组透镜的焦距相关。
例如，第二偏移Δy满足如下式子：
其中，fc准直镜的焦距，f2为第二微透镜阵列的焦距，θ为第三夹角。
示例性的，第一偏移距离Δx满足如下式子：
Δx＝|(d1+d2)*tanθ-Δy|
其中，d1为第一微透镜阵列与分光模组之间的距离，d1为分光模组与扩束模组(或第二微透镜阵列)之间的距离，θ为第三夹角，Δy为第二偏移。
在一种可能的实施方式中，所述接收光学模组还包含接收光学元件，接收光学元件用于接收经过第一微透镜阵列的第一返回光束。
当探测距离分别取0至D的情况下，walk off角(即γ角)的角度分别取0至由于MLA3的光轴的偏移角度与理想接收光束的偏移角度为θ，因此，当探测距离分别取0至D的情况下，经过MLA3后的第一返回光束相对于理想接收光束的角度偏移分别取
在一种可能的实施方式中，接收光学元件与经过所述理想接收光束之间的距离为第二偏移距离，第二偏移距离与第三夹角、第一微透镜阵列与所述分光模组之间的距离、分光模组与所述扩束模组之间的距离、第二微透镜阵列的焦距、准直镜的焦距和第一返回光束的光斑在第一焦平面上的第三偏移相关。其中，第三偏移为所述第一返回光束在所述第一焦平面上的光斑与最大偏移光束在所述焦平面上的光斑之间的距离，所述最大偏移光束为在所述第一夹角为所述最大偏移角度的情况下的所述第一返回光束。
示例性的，第三偏移与最大偏移角度所述第二微透镜阵列的焦距f2、所述准直镜的焦距fc和所述第三夹角θ相关。
例如，第三偏移(Δy′)满足如下式子：
示例性的，第二偏移距离(Δx′)满足如下式子：
其中，各个参数的解释可以参见前述。
在一种可能的实施方式中，第一微透镜阵列的通光口径与所述第一偏移距离和所述第二偏移距离中的至少一项和所述第一光束在经过所述扩束单元之前的直径相关。
示例性的，所述第一微透镜阵列的通光口径w3满足如下式子：
w3≥2*max(Δx,Δx′)+D1
其中，max()表示取最大值，D1为第一光束在经过扩束模组之前的光束直径或第一返回光束在经过扩束模组之后的光束直径，其余各参数参见前述。
在一种可能的实施方式中，第一微透镜阵列的周期p与第一微透镜的过渡带、第一偏移距离、第二偏移距离和第一光束在经过扩束模组之前的光束直径相关。其中，第一光束在经过扩束模组之前的光束直径可以替换为第一返回光束在经过扩束模组之后的光束直径。
示例性的，所述第一微透镜阵列的周期p满足如下式子：
p＝w3+δ
w3≥2*max(Δx,Δx′)+D1
其中，δ为第一微透镜阵列的过渡带，各参数参见前述。
为了便于理解，下面示例性的描述两种关于光学模组的各部分参数组合。
作为又一种可能的示例，结合图6B中各器件的安装顺序，各个器件的参数如下：MLA2、MLA3的焦距分别为f1、f2、f3，其中，f1＝f2＝f3＝1.4mm。准直镜的焦距fc＝16mm，MLA1的过渡带p和通光口径w3分别为：p＝0.5mm，w3＝0.48mm。经过MLA3的发射光束的直径D1＝0.28mm，经过扩束模组的发射光束D2＝3.2mm，最大偏移角度第三夹角θ＝0.228°。MLA1与PBS之间的距离d1和PBS与MLA2之间的距离d2满足如下式子：d1+d2＝10mm。第一偏移距离Δx＝0.034mm，第二偏移距离Δx′＝0.034mm。 根据如上参数进行仿真，如图7是本申请实施例提供的一种可能的仿真结果的示意图，若不采用接收补偿，则返回光束的损耗较大，而通过本申请的方案，在接收端进行补偿，可以极大的降低损耗，提升信号的有效性。
作为一种可能的示例，结合图6B中各器件的安装顺序，各个器件的参数如下：MLA2、MLA3的焦距分别为f1、f2、f3，其中，f1＝f2＝f3＝1.4mm。准直镜的焦距fc＝36mm，MLA1的过渡带p和通光口径w3分别为：p＝0.5mm，w3＝0.48mm。经过MLA3的发射光束的直径D1＝0.28mm，经过扩束模组的发射光束D2＝3.2mm，最大偏移角度第三夹角θ＝0.514°。MLA1与PBS之间的距离d1和PBS与MLA2之间的距离d2满足如下式子：d1+d2＝10mm。第一偏移距离Δx＝0.084mm，第二偏移距离Δx′＝0.084mm。根据如上参数进行仿真，如图8是本申请实施例提供的一种可能的仿真结果的示意图，若不采用接收补偿，则返回光束的损耗较大，而通过本申请的方案，在接收端进行补偿，可以极大的降低损耗，提升信号的有效性。
在一种可能的实施方式中，所述发射光学模组包含波导或光纤。和/或，接收光学模组包含波导或光纤。例如，图5所示的接收光学元件2042可以为波导或者光纤。
可理解，在采用波导或光纤作为接收端的光学模组中，由于波导、光纤等的接收模场比较小，对于walkoff角更加敏感，返回光束很容易偏离接收模场。而通过本申请实施例可以对返回光束的walk角进行补偿，能够显著降低由walk off角造成的信号损耗，提升接收的回波信号的有效性，提升探测性能。
请参见图9，图9是本申请实施例提供的又一种光学模组的结构和光路示意图。该光学模组可以包含发射光学模组、透镜(如MLA1、MLA2、MLA3等)、PBS、四分之一波片(quarter wave plate，QWP)、准直镜(Collimation Lens，CL)、光学接收模组和扫描器。其中，PBS和QWP为一种示例性的分束模组，MLA2和CL为一种示例性的扩束模组。其中，发射光学模组可以包含光纤阵列(fiber array unit，FAU)、波导(waveguide，WG)等中的一项或者多项。光学接收模组也可以包含FAU、WG等中的一项或者多项。可选的，发射光学模组和接收光学模组中的部分器件可以被集成在一起，例如波导可以被集成在一起，例如集成在一个硅光芯片上。
如图9，光学模组通过PBS和QWP将收、发光路分离；通过扩束模组将发射光束扩束、将返回光束收束。光学接收模组的位置与理想接收光束存在偏移，偏移的距离(或者说光学接收模组的位置)和角度与walk off角、PBS中心到MLA2、PBS中心到MLA1的距离有关。
进一步的，MLA2的口径与发射光斑尺寸、平移位置相关。
需要说明的是，本申请所示出的光学模组的元件是示例性的，具体实施过程中，光学模组可以包含光学元件可能比本申请的实施方式中示出的光学元件更多或者更少。例如，一下方案中可以在光学模组中增加反射镜、透镜、滤镜等，以用于辅助实现分光、辅助实现扩束、提升分光效率、提升光束质量模组、提升器件集成度等。
作为一种可能的示例，请参见图10，图10是本申请实施例提供的又一种光学模组的结构示意图，通过在PBS至波导之间增加反射镜，可以使得接收光学元件的位置与发射光学模组的位置更加靠近，从而提升器件的集成度。例如在发射模组和接收光学模组通过光纤(或波导)来传播光的情况下，波导(或波导)可以被集成在一起，例如集成在同一块硅光芯片上，提升器件集成度并减小光学模组的体积。
一些场景中，光学模组中的部分光学元件可以被封装为整体的模组，从而进一步提升光学元件的稳定性、提升器件集成度，提升输出的光束质量。
在一种可能的实施方式中，发射光学模组、接收光学模组和分光模组封装形成第一光学组件。进一步的，第一光学组件的通光窗口与扩束单元的通光面对齐。
示例性的，如图9所示，区域901中的光学元件，即PBS、QWP、FAU(或WG)、MLA1、MLA3等，可以被集成封装形成一组光学组件，便于区分称为第一光学组件。区域902中的光学元件，即MLA2、CL等可以被集成封装形成另一光学组件，便于区分称为第三光学组件。第一光学组件的通光窗口与第三光学组件的通光窗口对齐。可选的，在封装时可以使用热膨胀系数与光学模组中的光学元件想接近的材料作为支撑部件，以实现光学元件之间的高精度对准，提升系统的稳定性。其中，支撑部件包含但不限于是底座、衬底、垫块等。例如，支撑MLA、PBS等光学元件的垫块的材料可以为玻璃、水晶、陶瓷等。
示例性的，如图10所示，区域1001中的光学元件，即PBS、QWP、FAU(或WG)、MLA1、MLA3、MLA2等，可以被集成封装形成一组光学组件，便于区分称为第二光学组件。区域1002中的光学元件， 即CL等可以被集成封装形成另一光学组件，便于区分称为第四光学组件。第三光学组件的通光窗口与第四光学组件的通光窗口对齐。
可选的，在封装时，第一光学元件和第三光学元件可以封装在同一金属底座上。请参见图11，图11是本申请实施例提供的有一种光学模组的结构示意图，其中FAU(或WG)、MLA3、PBS、MLA2等可以封装在玻璃衬底上，若光学元件的光轴无法对齐则可以通过玻璃垫块来进行支撑或填充。而第一光学元件和具有金属镜筒的CL可以封装在金属底座上，使得光学模组整体集成，提升稳定性。
可选的，在图11所展示的视角上，MLA1和PBS可以沿穿过纸面方向(或垂直纸面方向)上排列，反光光束沿经过PBS后沿穿过纸面的方向到达MLA1。
本申请实施例还提供一种激光雷达，该激光雷达包含第一方面任一项所述的光学模组。进一步的，激光雷达还包含光源，例如激光器。可选的，光源发射的光束的频率可以是连续变化的，例如调频连续波(frequency modulated continuous wave，FMCW)激光。
进一步的，激光雷达还包含探测器，探测器用于根据光束得到电信号。例如，探测器可以包含能探测光能量的光电二极管(Photo Diode，PD)，例如InGaAs PD、InP PD、或锗PD等。
本申请实施例还提供一种终端，所述终端包含前述的光学模组。或者，终端包含前述的激光雷达。
可选的，终端可以为车辆、无人机、机器人等智能终端或运输工具。当然，终端也可以替换为工业设备、娱乐休闲设备等。智能终端例如手机、平板电脑、笔记本电脑、智能手环、智能手表、或智能眼镜等。交通工具例如车辆、舰船、飞行器、或物流机器人等。工业设备例如工业机器人、机械臂等。休闲娱乐设备例如虚拟现实(virtual reality，VR)设备、混合现实(mixed reality，MR)设备、按摩椅、或4D影院座舱等。本申请对于电连接器可以应用的设备不做严格限制。
在本申请的描述中，需要说明的是，除非另有明确的规定和限定，术语“相连”、“连接”应做广义理解，例如可以是固定连接，也可以是可拆卸连接，还可以是抵触连接或一体的连接；对于本领域的普通技术人员而言，可以具体情况理解上述术语在本申请中的具体含义。
本申请实施例中，“示例性的”或者“例如”等词用于表示作例子、例证或说明。本申请中被描述为“示例性的”或者“例如”的任何实施例或设计方案不应被解释为比其他实施例或设计方案更优选或更具优势。确切而言，使用“示例性的”或者“例如”等词旨在以具体方式呈现相关概念。
本申请中实施例提到的“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，a、b、或c中的至少一项(个)，可以表示：a、b、c、(a和b)、(a和c)、(b和c)、或(a和b和c)，其中a、b、c可以是单个，也可以是多个。“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A、同时存在A和B、单独存在B这三种情况，其中A、B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
以及，除非有相反的说明，本申请实施例使用“第一”、“第二”等序数词是用于对多个对象进行区分，不用于限定多个对象的顺序、时序、优先级或者重要程度。例如，第一BMU和第二BMU，只是为了便于描述电池单元中的BMU，而并不是表示第一BMU和第二BMU的结构、重要程度等的不同。

Claims (15)

  1. 一种光学模组，其特征在于，所述光学模组包括发射光学模组、同轴光学模组、扫描模组和接收光学模组，其中：
    所述发射光学模组用于将光源发出的第一光束传播至所述同轴光学模组；
    所述同轴光学模组用于将所述第一光束传播至所述扫描模组；
    所述扫描模组用于将所述第一光束扫描至物空间，还用于将所述第一返回光束传输至所述同轴光学模组，所述第一返回光束为所述第一光束的返回光束；
    所述同轴光学模组还用于将所述第一返回光束传输至所述接收光学模组，其中，进入同轴光学模组后的第一光束和返回至同轴光学模组前的第一返回光束存在第一夹角，所述第一夹角大于0°且小于90°；
    所述接收光学模组用于接收所述第一返回光束；
    其中，所述接收光学模组的位置与所述第一光束的理想接收光束存在第一偏移，返回至所述同轴光学模组前的所述第一返回光束的理想接收光束和所述第一光束平行。
  2. 根据权利要求1所述的光学模组，其特征在于，所述第一偏移与所述第一夹角相关。
  3. 根据权利要求1所述的光学模组，其特征在于，所述同轴光学模组包含分光模组和扩束模组，所述分光模组设置在所述发射光学模组和所述扩束模组之间。
  4. 根据权利要求3所述的光学模组，其特征在于，所述接收光学模组包含第一微透镜阵列，所述第一微透镜阵列用于接收经过所述分光模组后的所述第一返回光束；
    所述第一微透镜阵列的光轴与所述理想接收光束之间存在第三夹角，所述第三夹角小于等于第二夹角且大于等于所述第二夹角的二分之一；
    所述第二夹角与最大偏移角度和所述扩束模组的扩束倍数相关，所述最大偏移角度与所述光学模组的最远探测距离和所述扫描模组的扫描速度相关。
  5. 根据权利要求3所述的光学模组，其特征在于，所述扩束模组包含第二微透镜阵列和准直镜，所述第二微透镜阵列和所述准直镜具有共同的第一焦平面，所述第二微透镜阵列设置在所述分光模组和所述准直镜之间。
  6. 根据权利要求5述的光学模组，其特征在于，所述第一微透镜阵列与所述理想接收光束的之间的第一偏移距离与所述第三夹角、所述第一微透镜阵列与所述分光模组之间的距离、所述分光模组与所述扩束模组之间的距离和所述第一返回光束的光斑在所述第一焦平面上的第二偏移相关；
    所述第二偏移为在所述第一夹角为所述最大偏移角度的情况下所述第一返回光束的光斑和所述第一返回光束的理想接收光束的光斑在所述第一焦平面上的距离。
  7. 根据权利要求6所述的光学模组，其特征在于，所述接收光学模组还包含第一接收光学元件，所述接收光学元件用于接收经过所述第一微透镜阵列的第一返回光束；
    所述接收光学元件与经过所述理想接收光束之间的距离为第二偏移距离，所述第二偏移距离与所述第三夹角、所述第一微透镜阵列与所述分光模组之间的距离、所述分光模组与所述扩束模组之间的距离、所述第二微透镜阵列的焦距、所述准直镜的焦距和所述第一返回光束的光斑在所述第一焦平面上的第三偏移相关；
    所述第三偏移为所述第一返回光束在所述第一焦平面上的光斑与最大偏移光束在所述焦平面上的光斑之间的距离，所述最大偏移光束为在所述第一夹角为所述最大偏移角度的情况下的所述第一返回光束。
  8. 根据权利要求7所述的光学模组，其特征在于，所述第一微透镜阵列的通光口径与所述第一偏移距离和所述第二偏移距离中的至少一项和所述第一光束在经过所述扩束单元之前的直径相关。
  9. 根据权利要求3-8任一项所述的光学模组，其特征在于，所述发射光学模组、所述接收光学模组和所述分光模组封装在玻璃底座上形成第一光学组件，所述第一光学组件的通光窗口与所述扩束单元的通光 面对齐。
  10. 根据权利要求5-7任一项所述的光学模组，其特征在于，所述发射光学模组、所述接收光学模组、所述分光模组和所述第二微透镜阵列封装在玻璃底座上形成第二光学组件，所述第二光学组件的通光窗口与所述准直镜的通光面对齐。
  11. 根据权利要求1-10任一项所述的光学模组，其特征在于，所述同轴光学模组包含偏振分束器PBS和四分之一波片。
  12. 根据权利要求1-11任一项所述的光学模组，其特征在于，所述发射光学模组为波导或光纤；
    所述接收光学模组包含波导或光纤。
  13. 一种激光雷达，其特征在于，所述激光雷达包含如权利要求1-12任一项所述的光学模组。
  14. 一种终端，其特征在于，所述终端包含如权利要求1-12任一项所述的光学模组或包含如权利要求13所述的激光雷达。
  15. 根据权利要求14所述的终端，其特征在于，所述终端为车辆、无人机或者机器人。
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