Beam displacement device for optical detection and distance measurement.

Abstract

To provide a novel LIDAR system.SOLUTION: The LIDAR system includes a transmitter, a receiving pixel, a rotating mirror, and a beam displacement apparatus. The transmitter is configured to emit a transmit beam. The receiving pixel is configured to receive a returning beam. The rotating mirror is configured to direct the transmit beam to a target and direct the returning beam to the receiving pixel. The beam displacement apparatus is disposed between the receiving pixel and the rotating mirror. The beam displacement apparatus is configured to introduce a displacement to the returning beam to compensate for a spacing between the transmitter and the receiving pixel.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 17 / 463,860, filed September 1, 2021, which claims priority to U.S. Provisional Application No. 63 / 074,834, filed September 4, 2020, and U.S. Provisional Application No. 63 / 074,837, filed September 4, 2020. U.S. Patent Application Nos. 17 / 463,860, 63 / 074,834, and 63 / 074,837 are incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE This disclosure relates generally to optics, and more particularly to Light Detection and Ranging (LIDAR). [Background technology]

[0003] FMCW (Frequency Modulated Continuous Wave) LIDAR directs a frequency-modulated, collimated beam of light at a target to directly measure the object's range and velocity. Target range and velocity information is derived from the FMCW LIDAR signal. Designs and techniques that increase the accuracy of the LIDAR signal are preferred.

[0004] The automotive industry is currently developing autonomous features to control vehicles in certain situations. According to SAE International Standard J3016, there are six levels of autonomy ranging from Level 0 (no autonomy) to Level 5 (vehicle that can operate without driver input in all conditions). Vehicles with autonomous features use sensors to sense the environment in which the vehicle is traveling. Acquiring and processing data from the sensors allows the vehicle to navigate through the environment. An autonomous vehicle may include one or more FMCW LIDAR devices to sense its environment. Summary of the Invention

[0005] An embodiment of the present disclosure includes a LIDAR system including a transmitter, a receiving pixel, a rotating mirror, and a beam displacer. The transmitter is configured to emit a transmit beam. The receiving pixel is configured to receive a return beam. The rotating mirror is configured to direct the transmit beam toward a target and direct the return beam toward the receiving pixel. The beam displacer is disposed between the receiving pixel and the rotating mirror. The beam displacer is configured to introduce a displacement into the return beam to compensate for a spacing between the transmitter and the receiving pixel.

[0006] In one embodiment, the beam displacement device is configured to compensate for differences in the reflection angles between the transmitted and returned beams reflected from the rotating mirror.

[0007] In one embodiment, the beam displacement device includes a beam displacement element including a birefringent material, and the transmit beam has a first polarization orientation when the transmit beam encounters the beam displacement element, and the birefringent material introduces a displacement in a second polarization orientation of the return beam that is orthogonal to the first polarization orientation of the transmit beam.

[0008] In one embodiment, the beam displacement device includes a beam rotator disposed between the transmitter and the beam displacement element, the beam rotator configured to rotate the transmit polarization of the transmit beam so that the transmit polarization of the transmit beam is perpendicular to the optical axis of the beam displacement element.

[0009] In one embodiment, the beam rotator is a switchable beam rotator, and the rotating mirror is configured to rotate in a first direction and a second opposite direction during regular operation, and the switchable beam rotator can be driven with a first retardation value when the rotating mirror rotates in the first direction and with a second retardation value when the rotating mirror rotates in the second opposite direction.

[0010] In one embodiment, the first delay value is 0 degrees and the second delay value is 90 degrees.

[0011] In one embodiment, the beam displacement device includes a waveplate disposed between the beam displacement element and the rotating mirror.

[0012] In one embodiment, the wave plate is a quarter wave plate.

[0013] In one embodiment, the beam displacement device includes a lens disposed between the beam displacement element and the rotating mirror, the lens configured to collimate the transmit beam.

[0014] In one embodiment, the beam displacer is configured to make the transmitter and receiver pixels non-coaxial.

[0015] In one embodiment, the return beam is the transmitted beam that reflects from the target.

[0016] In one embodiment, the transmit beam has a near-infrared wavelength and the return beam has a near-infrared wavelength.

[0017] An embodiment of the present disclosure includes an autonomous vehicle control system for an autonomous vehicle including a Light Detection and Ranging (LIDAR) device and one or more processors configured to control the autonomous vehicle in response to outputs of receiving pixels of the LIDAR device. The LIDAR device includes a transmitter, receiving pixels, a rotating mirror, and a beam displacement device. The transmitter is configured to emit a transmit beam. The receiving pixels are configured to receive a return beam. The rotating mirror is configured to direct the transmit beam toward a target and direct the return beam toward the receiving pixels. The beam displacement device is configured to introduce a displacement into the return beam to compensate for a spacing between the transmitter and the receiving pixels.

[0018] In one embodiment, the beam displacement device is configured to compensate for differences in the reflection angles between the transmitted and returned beams reflected from the rotating mirror.

[0019] In one embodiment, the beam displacement device includes a beam displacement element including a birefringent material, and the transmitted beam has a first polarization orientation when the transmitted beam encounters the beam displacement element, and the birefringent material introduces a displacement in a second polarization orientation of the returned beam that is orthogonal to the first polarization orientation of the transmitted beam.

[0020] In one embodiment, the beam displacement device includes a beam rotator disposed between the transmitter and the beam displacement element, the beam rotator configured to rotate the transmit polarization of the transmit beam so that the transmit polarization of the transmit beam is perpendicular to the optical axis of the beam displacement element.

[0021] In one embodiment, the beam rotator is a switchable beam rotator, and the rotating mirror is configured to rotate in a first direction and a second opposite direction during normal operation, the switchable beam rotator being driven with a first delay value when the rotating mirror rotates in the first direction and with a second delay value when the rotating mirror rotates in the second opposite direction.

[0022]

[0003] An embodiment of the present disclosure includes an autonomous vehicle including a transmitter, a receiving pixel, a rotating mirror, and a beam displacement device, and a control system configured to control the autonomous vehicle in response to an infrared return beam. The transmitter is configured to emit an infrared transmit beam. The receiving pixel is configured to receive the infrared return beam. The rotating mirror is configured to direct the infrared transmit beam toward a target and direct the infrared return beam toward the receiving pixel. The beam displacement device is disposed along an optical path between the receiving pixel and the rotating mirror, and the beam displacement device is configured to introduce a displacement into the infrared return beam to compensate for a spacing between the transmitter and the receiving pixel and to introduce a displacement to compensate for a difference in the angle of reflection between the infrared transmit beam and the infrared return beam reflected from the rotating mirror.

[0023] In one embodiment, the beam displacement device includes a beam displacement element including a birefringent material, and the infrared transmit beam has a first polarization orientation when the infrared transmit beam encounters the beam displacement element, and the birefringent material introduces a displacement in a second polarization orientation of the infrared return beam that is orthogonal to the first polarization orientation of the infrared transmit beam.

[0024] In one embodiment, the beam displacement device includes a beam rotator disposed between the transmitter and the beam displacement element, the beam rotator configured to rotate the transmit polarization of the infrared transmit beam such that the transmit polarization of the infrared transmit beam is perpendicular to the optical axis of the beam displacement element.

[0025] An embodiment of the present disclosure includes a LIDAR system including a first receive optical coupler, a second receive optical coupler, a first optical mixer, a second optical mixer, and an optical switch. The first optical mixer is configured to receive a first receive signal from the first receive optical coupler. The second optical mixer is configured to receive a second receive signal from the second receive optical coupler. The optical switch is configured to switch an oscillator optical signal between the first optical mixer and the second optical mixer. The first optical mixer is configured to generate a first electrical signal in response to receiving the oscillator optical signal and the first receive signal. The second optical mixer is configured to generate a second electrical signal in response to receiving the oscillator optical signal and the second receive signal.

[0026] In one embodiment, the LIDAR system further includes a rotating mirror configured to rotate in a first direction when the optical switch is switched to provide the oscillator optical signal to the first optical mixer. The rotating mirror can be configured to rotate in a second direction when the optical switch is switched to provide the oscillator optical signal to the second optical mixer. The first direction can be opposite to the second direction.

[0027] In one embodiment, the LIDAR system further includes processing logic configured to receive a first electrical signal from the first optical mixer when the optical switch is switched to provide the oscillator optical signal to the first optical mixer, and to receive a second electrical signal from the second optical mixer when the optical switch is switched to provide the oscillator optical signal to the second optical mixer.

[0028] In one embodiment, the rotating mirror is configured to direct the return beam toward a first receiving optical coupler when the rotating mirror rotates in a first direction, and the rotating mirror is also configured to direct the return beam toward a second receiving optical coupler when the rotating mirror rotates in a second direction.

[0029] In one embodiment, the LIDAR system further includes a transmit optical coupler disposed between the first receive optical coupler and the second receive optical coupler.

[0030] In one embodiment, the first receive optical coupler is orthogonal to the transmit optical coupler, and the second receive optical coupler is orthogonal to the transmit optical coupler.

[0031] In one embodiment, the transmit optical coupler is configured to emit a transmit beam having a first polarization orientation, the first receive optical coupler is configured to receive a second polarization orientation that is orthogonal to the first polarization orientation, and the second receive optical coupler is also configured to receive the second polarization orientation.

[0032] In one embodiment, the LIDAR system further includes a splitter configured to receive the laser light, the splitter configured to provide a first percentage of the laser light to the transmitting optical coupler, and the splitter configured to provide a second percentage of the laser light to the optical switch.

[0033] In one embodiment, the laser light has an infrared wavelength.

[0034] An embodiment of the present disclosure includes a method of operating a Light Detection and Ranging (LIDAR) device, the method including: activating an optical switch to provide an oscillator optical signal to a first optical mixer when a rotating mirror rotates in a first direction, sampling a first signal generated by the first optical mixer while the first optical mixer receives the oscillator optical signal, activating the optical switch to provide the oscillator optical signal to a second optical mixer when the rotating mirror rotates in a second direction opposite the first direction, and sampling a second signal generated by the second optical mixer while the second optical mixer receives the oscillator optical signal.

[0035] In one embodiment, the first signal is generated in response to the oscillator optical signal and a first receive signal generated by a first receive optical coupler, and the second signal is generated in response to the oscillator optical signal and a second receive signal generated by a second receive optical coupler.

[0036] In one embodiment, a rotating mirror is configured to direct the return beam to a first receiving optical coupler, and a rotating mirror is configured to direct the return beam to a second receiving optical coupler.

[0037] In one embodiment, the rotating mirror is further configured to direct the transmit beam from the transmit optical coupler to a target, and the return beam is the transmit beam reflected from the target.

[0038] In one embodiment, the transmitting optical coupler is disposed between the first receiving optical coupler and the second receiving optical coupler.

[0039] In one embodiment, the transmit optical coupler is configured to emit a transmit beam having a first polarization orientation, the first receive optical coupler is configured to receive a second polarization orientation that is orthogonal to the first polarization orientation, and the second receive optical coupler is also configured to receive the second polarization orientation.

[0040] In one embodiment, the oscillator optical signal has an infrared wavelength, and the first and second receive signals have infrared wavelengths.

[0041] An embodiment of the present disclosure includes an autonomous vehicle control system for an autonomous vehicle including a Light Detection and Ranging (LIDAR) device and one or more processors configured to control the autonomous vehicle in response to first and second electrical signals generated by the LIDAR device. The LIDAR device includes a first receive optical coupler, a second receive optical coupler, a first optical mixer, a second optical mixer, and an optical switch. The first optical mixer is configured to receive a first receive signal from the first receive optical coupler. The second optical mixer is configured to receive a second receive signal from the second receive optical coupler. The optical switch is configured to switch an oscillator optical signal between the first and second optical mixers. The first optical mixer is configured to generate a first electrical signal in response to receiving the oscillator optical signal and the first receive signal. The second optical mixer is configured to generate a second electrical signal in response to receiving the oscillator optical signal and the second receive signal.

[0042] In one embodiment, the LIDAR device further includes a rotating mirror configured to rotate in a first direction when the optical switch is switched to provide the oscillator optical signal to the first optical mixer, and the rotating mirror configured to rotate in a second direction when the optical switch is switched to provide the oscillator optical signal to the second optical mixer, the first direction being opposite to the second direction.

[0043] In one embodiment, the LIDAR device further includes processing logic configured to receive a first electrical signal from the first optical mixer when the optical switch is switched to provide the oscillator optical signal to the first optical mixer, and to receive a second electrical signal from the second optical mixer when the optical switch is switched to provide the oscillator optical signal to the second optical mixer.

[0044] In one embodiment, a rotating mirror is configured to direct the return beam to a first receiving optical coupler, and a rotating mirror is configured to direct the return beam to a second receiving optical coupler. [Brief explanation of the drawings]

[0045] Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings, in which like reference numerals refer to like parts throughout the various drawings unless otherwise stated.

[0046] [Figure 1] 1 illustrates a hybrid silicon / III-V photonics implementation of a solid state FMCW LIDAR system using a beam shifter to implement a non-coaxial transmitter and receiver according to an embodiment of the present disclosure.

[0047] [Figure 2] 1 illustrates a hybrid silicon / SiO2 implementation of a solid-state FMCW LIDAR system using a beam shifter to implement a non-coaxial transmitter and receiver according to an embodiment of the present disclosure.

[0048] [Figure 3] 1 illustrates an exemplary beam displacement device according to an embodiment of the present disclosure.

[0049] [Figure 4] 1 illustrates an exemplary beam displacement device including a switchable beam rotator according to an embodiment of the present disclosure.

[0050] [Figure 5a] 1 illustrates an autonomous vehicle including an exemplary sensor array according to an embodiment of the present disclosure.

[0051] [Figure 5b] 1 illustrates a plan view of an autonomous vehicle including an exemplary sensor array according to an embodiment of the present disclosure.

[0052] [Figure 5c] 1 illustrates an exemplary vehicle control system including a sensor, a drivetrain, and a control system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0053] An implementation of beam displacement for LIDAR is described. In the following description, several details are presented to provide a thorough understanding of the implementation. However, those skilled in the relevant art will recognize that the techniques described herein may be practiced without one or more specific details, or using other methods, components, or materials. In other cases, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring certain aspects.

[0054] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Also, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0055] Throughout this specification, several technical terms are used. These terms should take their general meaning in the technical field from which they originate, unless specifically defined herein or the context of use clearly dictates otherwise. For purposes of this disclosure, the term "autonomous vehicle" includes vehicles having autonomous functionality at the SAE International Standard J3016 autonomy level.

[0056] In an embodiment of the present disclosure, visible light can be defined as having a wavelength range of approximately 380 nm to 700 nm. Invisible light can be defined as light having a wavelength outside the visible light range, such as ultraviolet light and infrared light. Infrared light having a wavelength range of approximately 700 nm to 1 mm includes near-infrared light. In an embodiment of the present disclosure, near-infrared light can be defined as having a wavelength range of approximately 700 nm to 1.6 μm.

[0057] In aspects of the present disclosure, the term "transparent" can be defined as having a light transmittance of greater than 90%. In some embodiments, the term "transparent" can be defined as a material that has a transmittance of greater than 90% of visible light.

[0058] FMCW (Frequency Modulated Continuous Wave) LIDAR directs a frequency-modulated, collimated beam of light at an object to directly measure the object's distance and velocity. Light reflected from the object is combined with a tapped version of the beam. The frequency of the resulting beat tone, once corrected for Doppler shift, is proportional to the object's distance from the LIDAR system, which may require a second measurement. Both measurements, which may or may not be performed simultaneously, provide both distance and velocity information.

[0059] FMCW LIDAR can leverage integrated photonics for improved manufacturability and performance. Integrated photonic systems typically use micron-scale waveguide devices to manipulate a single optical mode.

[0060] LIDAR systems may contain one or more continuously moving mirrors that steer outgoing light toward a target and reflect received light from the target back to a receiver. Due to the transit time of light traveling from the LIDAR to the target and back, the continuous movement of the mirrors causes the received light to move away from the transceiver, which is several microns in size. This "beam walkoff" effect can lead to reduced system performance.

[0061] FMCW LIDAR operation typically involves splitting the optical source power into a "local oscillator (LO)" component and a "signal" component. A simple integrated implementation of FMCW LIDAR involves co-locating the transmitter and receiver. However, this can result in additional losses as the received optical power must pass through the LO / signal splitter again. To improve performance, it may be preferable to separate the transmitter and receiver so that this splitter does not add additional losses to the optical system. In such an embodiment, the transmitter and receiver are non-coaxial and spaced apart from each other.

[0062] In an embodiment of the present disclosure, a LIDAR system includes a non-coaxial transmitter and receiver pixel, a rotating mirror, and a beam displacement device configured to introduce a displacement in the return beam to compensate for the spacing between the transmitter and receiver pixel. The beam displacement device may also be configured to compensate for the difference in reflection angle between the transmit beam and the return beam reflected from the rotating mirror. The beam displacement device may include a beam displacement element including a birefringent material that introduces a displacement in the specific polarization orientation of the return beam to direct the return beam toward the receiver pixel. The transmit beam and the return beam (the transmit beam reflected / scattered from the target) may have near-infrared wavelengths.

[0063] In one embodiment, the beam displacement device includes a beam rotator that rotates the transmit polarization of the transmit beam (emitted by the transmitter). In one embodiment, the beam rotator is a switchable beam rotator (e.g., a switchable waveplate). The switchable beam rotator can be driven to a first delay value (e.g., 0 degrees) when the rotating mirror rotates in a first direction (e.g., clockwise) and to a second delay value (e.g., 90 degrees) when the rotating mirror rotates in a second, opposite direction (e.g., counterclockwise).

[0064] In some aspects of the present disclosure, an apparatus for correcting beam walk-off in LIDAR applications is described, including a hybrid silicon / III-V or hybrid silicon / SiO2 platform. Light can be emitted from a transmitter array with polarization A that passes through a birefringent material. As the light passes through the birefringent material, the beam is offset relative to the light source as a result of birefringence. The light exits the LIDAR system and is reflected off a diffuse surface slightly away from the system. The light reflected from the diffuse surface can have any polarization. Light polarized orthogonal to the emitted polarization A propagates again through the birefringent material, introducing a different displacement into the beam compared to the emitted light. The beam illuminates a coherent pixel array located on a silicon chip that receives light with the orthogonal polarization to the transmitter. The birefringent material and geometry can be selected to select a specific set of transmit and receive offsets that mitigate beam walk-off in the LIDAR system. The birefringent material and geometry can also be selected to select a specific set of transmit and receive offsets that implement non-coaxial transmitters and receivers. These and other embodiments are described in more detail in conjunction with Figures 1-5c.

[0065] FIG. 1 illustrates a hybrid silicon / III-V photonics implementation of a solid-state FMCW LIDAR system that uses a beam displacer 111 to implement a non-coaxial transmitter and receiver according to an embodiment of the present disclosure. FIG. 1 shows a top view of an optical assembly 101 and a side view of assembly 102. A laser 103 provides optical power to the system. The laser 103 can be solid-state and may be packaged with the silicon chip 102 or external to the silicon chip 102. Light 179 emitted by the laser 103 passes through a 1×2 splitter 104, which splits X% of the power to the lower port and Y% of the power (generally, X>>Y) to the upper port. The coupled light exiting the lower port is routed to a 1×M splitter 105, which splits the power evenly among M output waveguides 136 of M-channel semiconductor optical amplifiers (SOAs) 106 / 107, which amplify the optical power of each channel. 1 shows multiple waveguides 136A, 136B, 136C, and 136D (collectively referred to as waveguides 136) where M is the integer 4, but M can be any integer. The SOAs 106 / 107 are packaged in recessed pockets 181 in the silicon chip 102. After amplification, light is coupled out at the ends of the SOAs 106 / 107 and reflected from angled mirrors 109 / 110 formed in the silicon chip 102 using, for example, wet etching. The reflected beam of light (reflected by the mirrors 109 / 110) is the transmitted beam 108 that propagates through the beam displacer 111 and propagates perpendicularly away from the silicon chip 102. The mirrors 109 / 110 can be formed in the angled sidewalls of the recessed pockets 181 in the silicon chip 102 in which the SOAs 106 / 107 are located. The beam displacer 111 can partially overhang a recessed pocket 181 in the silicon chip 102 to receive the transmitted beam 108 reflected from the mirror 110 on the angled sidewall.

[0066] After propagating through the beam displacer 111, the transmit beam 108 propagates into the environment, reflects off the target, and returns through the beam displacer 111 as a return beam 112. The return beam 112 is focused onto one of M receive grating couplers 114 / 115, which provide the return beam to an array of M silicon photonic coherent pixels 113. While FIG. 1 illustrates multiple grating couplers 114A, 114B, 114C, and 114D (collectively referred to as grating couplers 114), the array may include more or fewer grating couplers 114. While FIG. 1 illustrates multiple coherent pixels 116A, 116B, 116C, and 116D (collectively referred to as coherent pixels 116), the array may include more or fewer coherent pixels 116. Light is routed to each coherent pixel 116 and combined with the LO light field.

[0067] The LO light field is derived from the optical power exiting the top port of splitter 104. In some embodiments, the LO light field comes from a separate laser source with its own modulation. The light is routed to a second optical amplifier 117, which can be packaged in a similar manner to the SOA 106 or packaged off-chip. The amplified light is routed to a 1×M splitter 118, which distributes the LO field evenly among the M coherent pixels 116.

[0068] Each coherent pixel 116 mixes the received optical field (produced by the return beam 112 incident on its respective grating coupler) with the LO field and converts the resulting beat signal into an electrical signal 119 that is read by the FMCW LIDAR system. While FIG. 1 shows multiple electrical signals 119A, 119B, 119C, 119D (collectively referred to as electrical signals 119), more or fewer electrical signals 119 may be included in the plurality corresponding to the M coherent pixels 116.

[0069] FIG. 2 shows a hybrid silicon / SiO2 implementation of a solid-state FMCW LIDAR system that uses a beam displacer 213 to implement a non-coaxial transmitter and receiver according to an embodiment of the present disclosure. FIG. 2 shows a top view of optical assembly 201 and a side view of assembly 202. Laser 203 provides optical power to the system. Laser 203 may be solid-state and may be packaged with or external to the silicon chip 202. Light 279 emitted by laser 203 passes through optical amplifier 204 and then through 1×2 splitter 205, which splits X% of the power to the lower port and Y% of the power (generally, X>>Y) to the upper port. Both optical amplifier 204 and 1×2 splitter 205 may be discrete fiber components or solid-state components packaged with the silicon chip assembly 202. Light exiting the bottom port is routed to a Glass Planar Lightwave Circuit (PLC) that includes a 1×M splitter 208 and M free-space edge couplers 209. In the example of Figure 2, M is the integer 4, and the four free-space edge couplers 209A, 209B, 209C, and 209D are collectively referred to as free-space edge couplers 209.

[0070] Light exiting edge coupler 209 of PLC 206 is reflected from angled mirrors 211 / 212 formed in the silicon chip using, for example, wet etching. The reflected beam of light (reflected by mirrors 211 / 212) is transmitted beam 210, which propagates through beam displacer 213 and perpendicularly away from silicon chip 202.

[0071] After propagating through the beam displacer 213, the transmit beam 210 propagates into the environment, reflects off the target, and returns through the beam displacer 213 as a return beam 214. The return beam 214 is focused onto one of M receive grating couplers 216 / 217, which provide the return beam to an array of M silicon photonic coherent pixels 215. While FIG. 2 shows multiple grating couplers 216A, 216B, 216C, and 216D (collectively referred to as grating couplers 216), the plurality may include more or fewer grating couplers 216. While FIG. 2 shows multiple coherent pixels 218A, 218B, 218C, and 218D (collectively referred to as coherent pixels 218), the plurality may include more or fewer coherent pixels 218. Light is routed to each coherent pixel 218 and combined with the LO light field.

[0072] The LO light field is derived from the optical power exiting the top port of splitter 205. The light is routed to a silicon photonic 1xM splitter 119 which distributes the LO field evenly among M coherent pixels 218.

[0073] Each coherent pixel 218 mixes the received optical field (produced by the return beam 215 incident on its respective grating coupler) with the LO field and converts the resulting beat signal into an electrical signal 220 that is read by the FMCW LIDAR system. While Figure 2 shows multiple electrical signals 220A, 220B, 220C, 220D (collectively referred to as electrical signals 220), more or fewer electrical signals 119 may be included in the plurality corresponding to the M coherent pixels 116.

[0074] 3 illustrates an exemplary beam displacer 333 according to an embodiment of the present disclosure. The exemplary beam displacer 333 can be used, for example, as beam displacer 111 or 213. FIG. 3 illustrates the operation of the beam displacer to implement a non-coaxial transmitter and receiver in an FMCW LIDAR and correct for beam walk-off. The operation of the beam displacer 333 can be described for the transmit path 301 and the receive path 314.

[0075] In the transmit path 301, the transmitter 302 emits a transmit beam 303 having a particular polarization. The transmit beam 303 may be, for example, laser light 179 / 279 generated by the laser 103 / 203. The transmit beam 303 may be infrared light. In some embodiments, the transmit beam 303 is near-infrared light. In some embodiments, the illustrated position of the transmitter 302 may be in the same position as the mirror 110 or 212. In the example of FIG. 3, the transmit polarization of the transmit beam 303 is 45 degrees, although this initial polarization may be different in different embodiments. The transmit beam 303 propagates through an optional beam rotator 304, which rotates the transmit polarization, illustrated as transmit beam 305, so that it is perpendicular to the optical axis of the beam displacement element 306. The selective beam rotator 304 may be implemented using a half-wave plate or other anisotropic crystal. In FIG. 3, the beam displacement element 306 is positioned between the coherent pixel 302 and the turning mirror 311 .

[0076] After propagating through beam displacement element 306, transmitted beam 307 propagates along its original axis, and its polarization remains unchanged (compared to the example of transmitted beam 305). In FIG. 3, transmitted beam 307 enters lens 308, located between beam displacement element 306 and turning mirror 311. Lens 308 can collimate and steer the light in a desired direction. Lens 308 can be implemented using one or more bulk optic lens elements, microlenses, or thin diffraction gratings. After propagating through lens 308, the light can propagate through optional waveplate 309, located between beam displacement element 306 and turning mirror 311. Waveplate 309 can be a quarter-waveplate configured to shift the polarization axis of the incident light by 45 degrees. Thus, incident linearly polarized light can be converted to circularly polarized light by waveplate 309. Similarly, incident circularly polarized light can be converted to linearly polarized light by waveplate 309. Waveplate 309 may be formed from a birefringent material such as, for example, quartz, a sheet of organic material, or liquid crystal.

[0077] In the illustrated embodiment, the circularly polarized transmit beam 310 is reflected off a turning mirror 311. The turning mirror 311 may be a continuously turning mirror that rotates in a particular direction 381 (e.g., counterclockwise 381 in FIG. 3 ). The turning mirror 311 is configured to direct the transmit beam 310 toward a target 313 in the environment of the LIDAR system or device. The turning mirror 311 is also configured to direct the return beam in a receive path 314 toward one or more receiving pixels 328.

[0078] After striking the target, the transmit beam returns as return beam 316, as shown in receive path 314 of Figure 3. That is, return beam 316 is transmit beam 312 reflected / scattered from target 313. Therefore, return beam 316 may have the same wavelength as transmit beam 312.

[0079] Return beam 316, reflected / scattered from target 313, propagates back to rotating mirror 311. During the time it takes for the light to propagate to target 313 and back again, rotating mirror 311 rotates slightly in direction 381. As a result, the light in return beam 316 is reflected from rotating mirror 311 at a small angle (reflection angle difference 393) with respect to the light propagating along transmit path 301, as shown by return beam 318. Return beam 318 propagates to beam displacer 333, which is positioned between receiving pixel 328 and rotating mirror 311. Beam displacer 333 is configured to introduce a displacement D2 395 into the return beam to compensate for spacing 391 between transmitter 302 and receiving pixel 328. In FIG. 3 , beam displacer 333 is also configured to compensate for reflection angle difference 393 between transmit beam 310 and return beam 318 reflected from rotating mirror 311.

[0080] This light passes again through quarter-wave plate 309. If the target surface preserves the incident polarization, the return beam exiting quarter-wave plate 309 will have a linear polarization perpendicular to the polarization leaving the lens in the transmit direction. If the target randomizes the polarization, the polarization of the return beam exiting quarter-wave plate 309 will contain both the transmit and perpendicular polarizations. This light passes again through lens 308. Due to small changes in the mirror angle (reflection angle difference 393), the return beam enters lens 308 at a small angle, which translates into a small offset, or "beam walk-off" 322, in the position of the return beam 321 below the lens relative to the transmit path. A component of this return beam's polarization orientation 323 has a non-zero projection onto the optical axis of beam displacement element 306. This displaces the return beam by a fixed displacement 395 as it propagates through beam displacement element 306. The beam displacement element 306 parameters (e.g., material, thickness, optical axis orientation) can be selected to produce a displacement dimension D2 395 that eliminates (or at least adjusts) beam walk-off for a target at a specified distance. That is, the beam displacement element 306 can be configured to compensate for the reflection angle difference 393 between the transmit beam 310 and the return beam 318 reflected from the mirror. The beam displacement element 306 can also be configured to produce a displacement dimension D2 395 that compensates for the spacing 391 between the transmitter 302 and the receiving pixel 328.

[0081] In some embodiments, the beam displacing element 306 includes a birefringent material. In some embodiments, the birefringent material can be LiNO3 (Lithium Nitrate). In some embodiments, the birefringent material can be YVO4 (Yttrium Orthovanadate). In some embodiments, the beam displacing element 306 does not include a birefringent material. In FIG. 3, the transmitted beam 305 has a first polarization orientation when the transmitted beam 305 encounters the beam displacing element 306, and the return beam 323 has a second polarization orientation that is orthogonal to the first polarization orientation of the transmitted beam 305. The birefringent material of the beam displacing element 306 can be selected / configured to introduce a displacement dimension D2395 in the second polarization orientation but not in the first polarization orientation.

[0082] In some embodiments, after passing through the beam displacement element 306, the return beam 325 propagates along a similar axis as the transmit beam 305 (which may be approximately parallel to the axis of the transmit beam 305), but has a polarization perpendicular to the transmit polarization of the transmit beam 305. In some embodiments, the spacing between the axis of the return beam 325 and the axis of the transmit beam 305 is approximately the same as the spacing 391 between the transmitter 302 and the receive pixel 328. In some embodiments, after passing through the beam displacement element 306, the return beam 325 propagates along the same axis as the transmit beam, but has a polarization perpendicular to the transmit polarization of the transmit beam 305. The return beam 325 propagates through a selective beam rotator 304 (disposed between the transmitter 302 and the beam displacement element 306), which rotates the polarization by a desired amount to generate a return beam 327 having a polarization orientation orthogonal to the transmit beam 303. The receive pixel 328 is configured to receive the return beam 327.

[0083] 4 illustrates an exemplary beam displacement device 433 including a switchable beam rotator 404 according to an embodiment of the present disclosure. The switchable beam rotator 404 is configured to change the beam displacement direction in response to an electrical signal 405. The switchable beam rotator 404 may be a switchable half-wave plate including a liquid crystal.

[0084] In FIG. 4, the behavior of 401-404 and 406-429 is the same as or similar to 601-628, except that switchable beam rotator 404 can be controlled using electrical signal 405. Switchable beam rotator 404 can be driven to a first delay value (e.g., 0 degrees) when the rotating mirror rotates in a first direction (e.g., direction 481) and to a second delay value (e.g., 90 degrees) when the rotating mirror rotates in a second, opposite direction (e.g., direction 482). Thus, the polarization orientation of transmit beam 406 can be dynamically changed by 90 degrees, displacing the beam in different directions. This is useful when rotating mirror 412 rotates both clockwise (e.g., direction 482) and counterclockwise (e.g., direction 481) during normal operation (reversing the walk-off direction).

[0085] FIG. 5a illustrates an example autonomous vehicle 500 that may include the LIDAR designs of FIGS. 1-4 according to embodiments of the present disclosure. The illustrated autonomous vehicle 500 includes a sensor array configured to capture one or more objects in the autonomous vehicle's external environment and generate sensor data related to the captured one or more objects for the purpose of controlling the operation of the autonomous vehicle 500. FIG. 5a illustrates sensors 533A, 533B, 533C, 533D, and 533E. FIG. 5b illustrates a top view of the autonomous vehicle 500 that includes sensors 533A, 533B, 533C, 533D, and 533E, as well as sensors 533F, 533G, 533H, and 533I. Any of sensors 533A, 533B, 533C, 533D, 533E, 533F, 533G, 533H, and / or 533I may include a LIDAR device that includes the designs of FIGS. 1-4. 5c shows a block diagram of an example system 599 for an autonomous vehicle 500. For example, the autonomous vehicle 500 may include a powertrain 502 including a prime mover 504 that may be powered by an energy source 506 and provide power to a drivetrain 508. The autonomous vehicle 500 may further include a control system 510 that includes directional control 512, powertrain control 514, and brake control 516. The autonomous vehicle 500 may be embodied as many different vehicles, including vehicles that may transport people and / or cargo and that may operate in a variety of different environments. It will be understood that the components 502-516 described above may vary widely depending on the type of vehicle in which these components are used.

[0086] For example, the embodiments described below focus on wheeled land vehicles such as cars, vans, trucks, or buses. In such embodiments, the prime mover 504 may include one or more electric motors and / or internal combustion engines (among other things). The energy source may include, for example, a fuel system (e.g., providing gasoline, diesel, hydrogen), a battery system, solar panels or other renewable energy sources, and / or a fuel cell system. The drivetrain 508 may include wheels and / or tires along with a transmission and / or any other mechanical drive components suitable for converting the power output of the prime mover 504 into vehicle motion, as well as one or more brakes configured to controllably stop or slow the autonomous vehicle 500 and a steering or steering component suitable for controlling the trajectory of the autonomous vehicle 500 (e.g., a rack-and-pinion steering connection that allows one or more wheels of the autonomous vehicle 500 to pivot about a generally vertical axis to change the angle of the wheel's plane of rotation relative to the vehicle's longitudinal axis). In some embodiments, a combination of powertrain and energy source may be used (e.g., in the case of an electric / gas hybrid vehicle). In some embodiments, multiple electric motors (e.g., dedicated to individual wheels or axles) can be used as prime movers.

[0087] Directional control 512 may include one or more actuators and / or sensors for controlling and receiving feedback from directional or steering components to enable autonomous vehicle 500 to follow a desired trajectory. Powertrain control 514 may be configured to control the output of powertrain 502, such as by controlling the output power of prime mover 504 and controlling the transmission gears of drivetrain 508, thereby controlling the speed and / or direction of autonomous vehicle 500. Brake control 516 may be configured to control one or more brakes, such as disc or drum brakes coupled to the vehicle's wheels, to slow or stop autonomous vehicle 500.

[0088] Other vehicle types, including, but not limited to, off-road vehicles, all-terrain or track vehicles, or construction equipment, will necessarily utilize other powertrains, drivetrains, energy sources, directional control, powertrain control, and braking control as would be understood by one of ordinary skill in the art having the benefit of this disclosure. Also, in some embodiments, some components may be combined; for example, vehicle directional control may be handled primarily by modifying the output of one or more prime movers. Accordingly, the embodiments disclosed herein are not limited to the specific application of the technology described herein to wheeled, land-based autonomous vehicles.

[0089] In the illustrated embodiment, autonomous control for autonomous vehicle 500 is embodied in vehicle control system 520, which may include one or more processors and one or more memories 524 within processing logic 522, where processing logic 522 is configured to execute program code (e.g., instructions 526) stored in memory 524. Processing logic 522 may include, for example, a graphics processing unit (GPU) and / or a central processing unit (CPU). Vehicle control system 520 may be configured to control powertrain 502 of autonomous vehicle 500 in response to a return beam (e.g., return beam 316 or 417) or in response to signals 119 and 120. Vehicle control system 520 may be configured to control powertrain 502 of autonomous vehicle 500 in response to outputs from multiple LIDAR pixels.

[0090] The sensors 533A-533I may include various sensors suitable for collecting data from the autonomous vehicle's surrounding environment for use in controlling the operation of the autonomous vehicle. For example, the sensors 533A-533I may include a RADAR unit 534, a LIDAR unit 536, a 3D positioning sensor 538, and a satellite navigation system such as GPS, GLONASS, BeiDou, Galileo, or Compass. The LIDAR design of FIGS. 1-4 may be included in the LIDAR unit 536. The LIDAR unit 536 may include, for example, multiple LIDAR sensors distributed around the autonomous vehicle 500. In some embodiments, the 3D positioning sensor 538 may determine the vehicle's position on Earth using satellite signals. The sensors 533A-533I may optionally include one or more ultrasonic sensors, one or more cameras 540, and / or an inertial measurement unit (IMU) 542. In some embodiments, camera 540 may be a monographic or stereographic camera and may record still and / or video images. Camera 540 may include a complementary metal-oxide-semiconductor (CMOS) image sensor configured to capture images of one or more objects in the environment external to autonomous vehicle 500. IMU 542 may include multiple gyroscopes and accelerometers capable of detecting linear and rotational motion of autonomous vehicle 500 in three directions. One or more encoders (not shown), such as wheel encoders, may be used to monitor the rotation of one or more wheels of autonomous vehicle 500.

[0091] The outputs of sensors 533A-533I may be provided to a control subsystem 550, which includes a localization subsystem 552, a trajectory subsystem 556, a perception subsystem 554, and a control system interface 558. Localization subsystem 552 may be configured to determine the position and orientation (also sometimes referred to as “attitude”) of autonomous vehicle 500 within the surrounding environment, and generally within a particular geographic region. The autonomous vehicle's position can be compared to the positions of additional vehicles in the same environment as part of labeled autonomous vehicle data generation. Perception subsystem 554 may be configured to detect, track, classify, and / or determine objects within the environment surrounding autonomous vehicle 500. Trajectory subsystem 556 may be configured to generate trajectories for stationary and moving objects in the environment, as well as trajectories for autonomous vehicle 500 given a desired destination over a particular time frame. Machine learning models, according to some embodiments, may be utilized to generate the vehicle trajectory. Control system interface 558 is configured to communicate with control system 510 to enforce the trajectory of autonomous vehicle 500. In some embodiments, machine learning models can be utilized to control an autonomous vehicle to execute a planned trajectory.

[0092] It will be understood that the collection of components for vehicle control system 520 shown in FIG. 5c is merely exemplary in nature. Individual sensors may be omitted in some embodiments. In some embodiments, the different types of sensors shown in FIG. 5c may be used redundantly and / or to cover different areas in the environment surrounding the autonomous vehicle. In some embodiments, different types and / or combinations of control subsystems may be used. Also, while subsystems 552-558 are shown as separate from processing logic 522 and memory 524, it will be understood that in some embodiments, some or all of the functionality of subsystems 552-558 may be embodied in program code, such as instructions 526, resident in memory 524 and executed by processing logic 522, and that these subsystems 552-558 may, in some cases, be embodied using the same processor and / or memory. In some embodiments, the subsystems may be embodied in various dedicated circuit logic, various processors, various field programmable gate arrays (FPGAs), various application-specific integrated circuits (ASICs), various real-time controllers, etc., and as previously described, multiple subsystems may utilize circuits, processors, sensors, and / or other components. Additionally, the various components of vehicle control system 520 may be networked in various ways.

[0093] In some embodiments, autonomous vehicle 500 may also include a secondary vehicle control system (not shown) that can be used as a redundant or backup control system for autonomous vehicle 500. In some embodiments, the secondary vehicle control system can operate autonomous vehicle 500 in response to specific events. The secondary vehicle control system may have only limited functionality in response to specific events detected by primary vehicle control system 520. In yet other embodiments, the secondary vehicle control system may be omitted.

[0094] In some embodiments, different architectures including various combinations of software, hardware, circuit logic, sensors, and networks can be used to implement the various components shown in FIG. 5c. Each processor can be embodied, for example, as a microprocessor, and each memory can represent not only main storage but also any auxiliary levels of memory, such as cache memory, non-volatile or backup memory (e.g., programmable or flash memory), or read-only memory. Each memory can also be considered to include memory storage physically located elsewhere in autonomous vehicle 500, such as any cache memory of the processor, as well as any storage capacity used as virtual memory, such as that stored in mass storage or other computer controllers. Processing logic 522 shown in FIG. 5c, or entirely separate processing logic, can be used to perform additional functions in autonomous vehicle 500 beyond those of autonomous control, such as controlling an entertainment system or operating doors, lights, or convenience features.

[0095] For additional storage, autonomous vehicle 500 may also include one or more mass storage devices, such as a removable disk drive, a hard disk drive, a direct access storage device ("DASD"), an optical drive (e.g., CD drive, DVD drive), a solid state storage drive (SSD), a network attached storage, a storage area network, and / or a tape drive. Autonomous vehicle 500 may also include a user interface 564, such as one or more displays, touchscreens, voice and / or gesture interfaces, buttons, and other tactile controls, through which autonomous vehicle 500 receives inputs from and generates outputs for the passenger. In some embodiments, inputs from the passenger may be received via another computer or electronic device, for example, via an app on a mobile device or via a web interface.

[0096] In some embodiments, autonomous vehicle 500 may include one or more network interfaces, e.g., network interface 562, suitable for communicating with one or more networks 570 (e.g., a local area network (“LAN”), a wide area network (“WAN”), a wireless network, and / or the Internet, etc.), which may enable communication of information with other computers and electronic devices, including, for example, a central service such as a cloud service for autonomous vehicle 500 to receive environmental and other data for use in autonomous control. In some embodiments, data collected by one or more sensors 533A-533I may be uploaded via network 570 to computing system 572 for further processing. In such embodiments, a timestamp may be associated with each instance of vehicle data prior to uploading.

[0097] 5c, as well as the various additional controllers and subsystems disclosed herein, generally operate and execute under the control of an operating system or otherwise rely on various computer software applications, components, programs, objects, modules, or data structures, as described in detail below. Also, the various applications, components, programs, objects, or modules may execute on one or more processors of other computers coupled to the autonomous vehicle 500 via a network 570, for example, in a distributed, cloud-based, or client-server computing environment, whereby the processing required to carry out the functions of a computer program is allocated across multiple computers and / or services via the network.

[0098] The routines executed to implement the various embodiments described herein are referred to herein as "program code," whether embodied as part of an operating system or as part of a specific application, component, program, object, module, or instruction sequence, or a subset thereof. Program code generally comprises one or more instructions resident in various memory and storage devices that, when read and executed by one or more processors, perform the steps necessary to perform the steps or elements embodying various aspects of the present disclosure. Also, while the embodiments have been and will continue to be described in the context of fully functional computers and systems, it will be understood that the various embodiments described herein can be distributed as program products in various forms and can be embodied regardless of the particular type of computer-readable medium used to actually effect the distribution. Examples of computer-readable media include types of non-transitory media, such as volatile and non-volatile memory devices, floppy and other removable disks, solid-state drives, hard disk drives, magnetic tape, and optical disks (e.g., CD-ROM, DVD).

[0099] Additionally, various program code described below may be identified based on the application for which it is implemented in a particular embodiment. However, it should be understood that any particular program nomenclature below is used merely for convenience, and thus the present invention should not be limited to use with only any particular application identified and / or implied by such nomenclature. Furthermore, it should be understood that the present disclosure is not limited to the specific organization and allocation of program functionality described herein, given the generally infinite number of ways in which a computer program can be organized into routines, procedures, methods, modules, objects, etc., and the various ways in which program functionality is allocated among the various software layers resident within a typical computer (e.g., operating system, libraries, APIs, applications, applets).

[0100] Those skilled in the art having the benefit of this disclosure will recognize that the exemplary environment illustrated in Figure 5c is not intended to limit the embodiments disclosed herein. Indeed, those skilled in the art will recognize that other alternative hardware and / or software environments may be used without departing from the scope of the embodiments disclosed herein.

[0101] As used herein, the term "processing logic" (e.g., processing logic 522) may include one or more processors, microprocessors, multi-core processors, application specific integrated circuits (ASICs), and / or field programmable gate arrays (FPGAs) for performing the operations disclosed herein. In some embodiments, memory (not shown) is integrated with the processing logic for storing instructions for performing operations and / or storing data. Additionally, the processing logic may include analog or digital circuitry for performing operations according to embodiments of the present disclosure.

[0102] "Memory" or "memories" as described herein may include one or more volatile or non-volatile memory architectures. "Memory" or "memories" may be removable and non-removable media embodied in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Example memory technologies may include RAM, ROM, EEPROM, flash memory, CD-ROM, DVD, high-definition multimedia / data storage disks or other optical storage devices, magnetic cassettes, magnetic tape, magnetic disk storage devices, or other non-transmission media that can be used to store information so that it can be accessed by a computing device.

[0103] The network includes any network or network system, such as, but not limited to, a peer-to-peer network, a local area network (LAN), a wide area network (WAN), a public network such as the Internet, a private network, a cellular network, a wireless network, a wired network, a combined wired and wireless network, and a satellite network.

[0104] The communication channel may include or be routed by one or more wired or wireless communications using the IEEE 802.11 protocol, Serial Peripheral Interface (SPI), Inter-Integrated Circuit (I2C), Universal Serial Port (USB), Controller Area Network (CAN), cellular data protocols (e.g., 3G, 4G, LTE, 5G), optical communications networks, Internet Service Providers (ISPs), peer-to-peer networks, LANs, WANs, public networks (e.g., the “Internet”), private networks, satellite networks, or others.

[0105] The computing devices may include desktop computers, laptop computers, tablets, phablets, smartphones, feature phones, server computers, etc. The server computers may be located remotely in a data center or stored locally.

[0106] The processes described above are described in terms of computer software and hardware. The described techniques may constitute machine-executable instructions embodied in a tangible or non-transitory machine (e.g., computer) readable storage medium that, when executed by a machine, causes the machine to perform the described operations. The processes may also be embodied in hardware, such as an application-specific integrated circuit ("ASIC").

[0107] A tangible, non-transitory, machine-readable storage medium may include any mechanism for providing (e.g., storing) information in a form accessible by a machine (e.g., a computer, a network device, a PDA, a manufacturing tool, any device having one or more processor sets, etc.). For example, machine-readable storage media include recordable / non-recordable media (e.g., Read Only Memory (ROM), Random Access Memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.).

[0108] The foregoing description of illustrated embodiments of the present disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise form disclosed. While specific embodiments of and examples for the invention have been described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.

[0109] Such modifications to the invention can be made in light of the foregoing detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. [Explanation of symbols]

[0110] 302...transmitter, 303...transmitting beam, 311...rotating mirror, 313...target, 316...return beam, 328...receiving pixel, 333...beam displacement device.

Claims

1. 1. A LIDAR system for a vehicle, comprising: a transmitter configured to emit a transmit beam at the object; a receiving pixel including a grating coupler and configured to receive the return beam reflected from the object via the grating coupler; a beam displacement device positioned relative to the receiving pixel, the beam displacement device including a beam displacement element, the beam displacement device configured to introduce a displacement into the return beam incident on the beam displacement element along a path that makes a finite angle with a transmission path of a transmit beam emitted from the beam displacement element to compensate for a spacing between the transmitter and the receiving pixel; A LIDAR system comprising:

2. 10. The LIDAR system of claim 1, comprising one or more mirrors configured to direct the transmit beam toward the object and direct the return beam reflected from the object toward the receive pixel.

3. 3. The LIDAR system of claim 2, wherein the one or more mirrors comprise a fixed mirror configured to direct the transmit beam from the transmitter to the beam displacer.

4. 3. The LIDAR system of claim 2, wherein the one or more mirrors comprise a rotating mirror configured to direct the transmit beam toward the object and the return beam toward the receive pixel.

5. 5. The LIDAR system of claim 4, wherein the beam displacement device is configured to compensate for differences in reflection angles between the transmit beam and the return beam reflected from the rotating mirror.

6. 5. The LIDAR system of claim 4, wherein the rotating mirror is configured to selectively rotate in a first direction or a second opposite direction during normal operation.

7. 5. The LIDAR system of claim 4, wherein the beam displacement device includes a wave plate and a beam displacement element, the wave plate being disposed between the beam displacement element and the rotating mirror.

8. 8. The LIDAR system of claim 7, wherein the wave plate is a quarter wave plate.

9. 5. The LIDAR system of claim 4, wherein the beam displacement device includes a lens and a beam displacement element, the lens being disposed between the beam displacement element and the rotating mirror, the lens being configured to collimate the transmit beam.

10. 10. The LIDAR system of claim 1, wherein the beam displacer includes a switchable beam rotator configured to rotate a transmit polarization of the transmit beam.

11. 11. The LIDAR system of claim 10, wherein the beam displacement device includes a beam displacement element, and the switchable beam rotator is disposed between the transmitter and the beam displacement element.

12. 10. The LIDAR system of claim 1, wherein the beam displacer includes a beam displacer element including a birefringent material configured to introduce the displacement in a second polarization orientation of the return beam defined based on a first polarization orientation of the transmit beam.

13. 1. An autonomous vehicle control system for an autonomous vehicle, comprising: Equipped with a LIDAR device, The LIDAR device is a transmitter configured to emit a transmit beam at the object; a receiving pixel including a grating coupler and configured to receive the return beam reflected from the object via the grating coupler; a beam displacement device positioned relative to the receiving pixel, the beam displacement device including a beam displacement element, the beam displacement device configured to introduce a displacement into the return beam incident on the beam displacement element along a path that makes a finite angle with a transmission path of a transmit beam emitted from the beam displacement element to compensate for a spacing between the transmitter and the receiving pixel; an autonomous vehicle control system,

14. 14. The autonomous vehicle control system of claim 13, comprising one or more mirrors configured to direct the transmit beam towards the object and direct the return beam reflected from the object towards the receiving pixel.

15. The autonomous vehicle control system of claim 14 , wherein the one or more mirrors include a rotating mirror configured to direct the transmit beam toward the object and the return beam toward the receiving pixel.

16. The autonomous vehicle control system of claim 15 , wherein the beam displacement device is configured to compensate for differences in the angles of reflection between the transmit beam and the return beam reflected from the rotating mirror.

17. 16. The autonomous vehicle control system of claim 15, wherein the rotating mirror is configured to selectively rotate in a first direction or a second opposite direction during normal operation.

18. The autonomous vehicle control system of claim 13 , wherein the beam displacer includes a switchable beam rotator configured to rotate a transmit polarization of the transmit beam.

19. 1. An autonomous vehicle, comprising: Equipped with a LIDAR device, The LIDAR device is a transmitter configured to emit a transmit beam at the object; a receiving pixel including a grating coupler and configured to receive the return beam reflected from the object via the grating coupler; a beam displacement device positioned relative to the receiving pixel, the beam displacement device including a beam displacement element, the beam displacement device configured to introduce a displacement into the return beam incident on the beam displacement element along a path that makes a finite angle with a transmission path of a transmit beam emitted from the beam displacement element to compensate for a spacing between the transmitter and the receiving pixel; An autonomous vehicle comprising:

20. 20. The autonomous vehicle of claim 19, wherein the beam displacer includes a switchable beam rotator configured to rotate a transmit polarization of the transmit beam.

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