LIDAR transceivers, LIDAR systems, and LIDAR chips

Abstract

A LIDAR transceiver, a LIDAR system, and a LIDAR chip are disclosed. The LIDAR transceiver includes: a source input configured to receive a laser signal; a plurality of coherent units; and an optical switch configured to switchably couple the source input to the plurality of coherent units. At least one of the plurality of coherent units includes: an input port coupled to the optical switch; an optical antenna; and a splitter coupled between the input port and the optical antenna. The splitter is configured to: split a received portion of the laser signal into a local oscillator signal and a transmitted signal, wherein the transmitted signal is transmitted through the optical antenna and a reflection of the transmitted signal is received by the optical antenna as a reflected signal; and output a return signal as a part of the reflected signal.

Description

[0001] This application is a divisional application of National Application No. 202080026180.4 (International Application No. PCT / US2020 / 025042, International Application Date March 26, 2020, Invention Title "Switchable Coherent Pixel Array for Frequency Modulated Continuous Wave Light Detection and Ranging").

[0002] Cross-references to related applications

[0003] This application claims priority under 35 § 119(e) of the following: U.S. Provisional Patent Application Serial No. 62 / 826,528, filed March 29, 2019; U.S. Provisional Patent Application Serial No. 62 / 826,536, filed March 29, 2019; U.S. Provisional Patent Application Serial No. 62 / 845,147, filed May 8, 2019; U.S. Provisional Patent Application Serial No. 62 / 845,149, filed May 8, 2019; U.S. Provisional Patent Application Serial No. 62 / 849,807, filed May 17, 2019; and U.S. Provisional Patent Application Serial No. 62 / 940,790, filed November 26, 2019, all of which are incorporated herein by reference in their entirety. Technical Field

[0004] This disclosure generally relates to frequency modulated continuous wave (FMCW) optical detection and ranging (LiDAR), and more specifically, to a switchable coherent pixel array for FMCW LiDAR. Background Technology

[0005] Conventional LiDAR systems use mechanically moving parts to steer the laser beam. Furthermore, they are too bulky, costly, and unreliable for many applications, such as automotive. Summary of the Invention

[0006] An FMCW LiDAR transceiver is implemented on a photonic integrated circuit. The FMCW LiDAR transceiver performs beam steering in at least one dimension via a switchable coherent pixel array. In some embodiments, the FMCW LiDAR transceiver is part of a LiDAR chip comprising multiple FMCW LiDAR transceivers arranged in an array (e.g., a linear array, a two-dimensional array, etc.). The FMCW LiDAR transceiver and / or the LiDAR chip can be part of an FMCW LiDAR system. The FMCW LiDAR system determines depth information of the transceiver's field of view (e.g., the range to objects within the transceiver's field of view, the velocity of the objects, etc.).

[0007] In some embodiments, the FMCW LiDAR transceiver includes one or more subarrays. The subarrays may include an input port, an optical switch, multiple splitters, multiple mixers, and multiple antennas. The input port is configured to receive a frequency-modulated laser signal. The optical switch is configured to switchably couple the input port to an optical antenna, thereby forming an optical path between the input port and the optical antenna. For each optical path from the input port to one of the optical antennas, a splitter of the multiple splitters is coupled along the optical path. Each splitter is configured to split a received portion of the laser signal into a local oscillator signal and a transmitted signal. The transmitted signal is transmitted via the optical antenna, and the reflection of the transmitted signal is received via the optical antenna as a reflected signal. The splitter also outputs a return signal as part of the reflected signal. For each splitter, a mixer of the multiple mixers is coupled to receive the return signal and the local oscillator signal from the splitter. The mixer is configured to mix the return signal and the local oscillator signal to generate one or more output signals for determining depth information of the transceiver's field of view.

[0008] In some embodiments, the FMCW LiDAR system includes a LiDAR chip. The LiDAR chip includes an FMCW LiDAR transceiver implemented on a photonic integrated circuit. The photonic integrated circuit includes one or more subarrays. The subarrays may include an input port, an optical switch, a plurality of splitters, a plurality of mixers, and a plurality of antennas. The input port is configured to receive a frequency-modulated laser signal. The optical switch is configured to switchably couple the input port to an optical antenna, thereby forming an optical path between the input port and the optical antenna. For each optical path from the input port to one of the optical antennas, a splitter of the plurality of splitters is coupled along the optical path. Each splitter is configured to split a received portion of the laser signal into a local oscillator signal and a transmitted signal. The transmitted signal is transmitted via the optical antenna, and the reflection of the transmitted signal is received via the optical antenna as a reflected signal. The splitter also outputs a return signal as part of the reflected signal. For each splitter, a mixer of the plurality of mixers is coupled to receive the return signal and the local oscillator signal from the splitter. The mixer is configured to combine the returned signal and the local oscillator signal to generate one or more output signals for determining depth information of the field of view of the FMCW LiDAR system. The FMCW LiDAR system also includes a lens positioned to collimate transmitted signals transmitted via multiple antennas. The lens is also positioned to receive reflected signals and couple them to the transmitting optical antenna. Attached Figure Description

[0009] When taken in conjunction with the examples in the accompanying drawings, embodiments of this disclosure have other advantages and features that will be more readily apparent from the following detailed description and the appended claims, in which:

[0010] Figure 1 A simplified diagram of a switchable coherent pixel array (FMCW) LiDAR chip according to one or more embodiments is shown.

[0011] Figures 2a-2d Four versions of coherent pixels according to one or more embodiments are shown.

[0012] Figures 3a-3c A switchable coherent pixel array is shown, according to one or more embodiments, in which an optical coherent detection block is shared among a plurality of coherent pixels.

[0013] Figures 4a-4c Show Figure 1 and Figure 3a An example of an active optical switch.

[0014] Figures 5a-5c This illustrates how a switchable coherent pixel array, according to one or more embodiments, can steer a beam for FMCW LiDAR operation.

[0015] Figure 6 A LiDAR chip with multiple parallel FMCW LiDAR transceivers arranged linearly is shown according to one or more embodiments.

[0016] Figures 7a-7c An example of mechanically assisted laser beam scanning in an FMCW LiDAR system based on a switchable coherent pixel array, according to one or more embodiments, is shown.

[0017] Figure 8 A diagram illustrating a first embodiment of a coherent pixel that utilizes two polarizations of light to improve the performance of an FMCW LiDAR system according to one or more embodiments.

[0018] Figure 9 A diagram illustrating a second embodiment of a coherent pixel that utilizes two polarizations of light to improve the performance of an FMCW LiDAR system according to one or more embodiments.

[0019] Figure 10 This illustrates how coherent pixels, according to one or more embodiments, can be used in a focal plane array for FMCW applications.

[0020] Figures 11a-11d The illustration shows an electrical wiring scheme for a switchable coherent pixel array according to one or more embodiments.

[0021] Figure 12 A system diagram of an FMCW LiDAR system based on a switchable coherent pixel array according to one or more embodiments is shown. Detailed Implementation

[0022] An FMCW LiDAR system determines depth information (e.g., distance, velocity, acceleration of one or more objects) within the system's field of view. The FMCW LiDAR system uses a switchable coherent pixel array (SCPA) on a LiDAR chip (e.g., a photonic integrated circuit). The LiDAR chip may include one or more FMCW transceivers (e.g., each FMCW transceiver may be responsible for different angles within the LiDAR system's field of view). The FMCW LiDAR system splits the FMCW beam into a signal portion and a mixing portion. The signal portion is modulated via a lens assembly and output into the FMCW LiDAR system's field of view. The signal portion is reflected off one or more objects in the field of view to form a reflected signal, and this reflection is detected by the FMCW LiDAR system. A portion of the reflected signal is mixed with the mixing portion of the beam to directly measure the range and velocity of one or more objects within the FMCW LiDAR system's field of view.

[0023] An FMCW LiDAR system transceiver is implemented on a photonic integrated circuit. The photonic integrated circuit includes one or more basic functional subarrays. Each subarray includes an input port, an optical switch, multiple splitters, multiple mixers, and multiple antennas. The input port is configured to receive a frequency-modulated laser signal. The frequency-modulated laser signal may be external to the transceiver or, in some cases, located on the same chip as the photonic integrated circuit. The optical switch is configured to switchably couple the input port to the optical antennas, thereby forming an optical path between the input port and the optical antennas. In some embodiments, the optical switch optically couples the frequency-modulated laser signal one at a time to each of the optical antennas during the scanning period of the FMCW transceiver.

[0024] For each optical path from the input port to one of the optical antennas, a splitter among multiple splitters is coupled along the optical path. Each splitter is configured to split the received portion of the laser signal into a local oscillator signal and a transmitted signal. The transmitted signal is transmitted via the optical antenna, and the reflection of the transmitted signal is received via the optical antenna as a reflected signal. The splitter also outputs a return signal as part of the reflected signal. For each splitter, a mixer among multiple mixers is coupled to receive the return signal and the local oscillator signal from the splitter. The mixer is configured to mix the return signal and the local oscillator signal to generate one or more output signals. The frequency of the beat generated by the mixing is proportional to the distance from the LiDAR system to the surface that reflected the light. One or more output signals are used to determine depth information of the LiDAR system's field of view. The depth information describes the range of various surfaces within the LiDAR system's field of view and may also include information describing the velocity of objects within the LiDAR system's field of view.

[0025] Note that the LiDAR chip enables light emitted from the LiDAR system to be redirected in at least one dimension. Furthermore, in some embodiments, the optical antenna is arranged in two dimensions, allowing the LiDAR chip to redirect the beam in both dimensions. The ability to redirect the beam without moving parts can alleviate many of the shape factor, cost, and reliability issues found in conventional mechanically driven LiDAR systems.

[0026] Figure 1 A simplified diagram of a switchable coherent pixel array (SCPA) FMCW LiDAR chip (11) according to one or more embodiments is shown. The LiDAR chip is a photonic integrated circuit. The chip is capable of including multiple basic functional subarrays (100). Each subarray (100) includes an optical input / output (I / O) port (102) and optional 1 to K optical splitters (103), where K is an integer, and includes one or more SCPAs (101). The 1 to K optical splitters (103) can be passive or active. Each of the optical I / Os is fed by a frequency-modulated light source provided by an off-chip or on-chip laser. Optical power can be distributed on-chip via the optional 1 to K optical splitters to reduce the number of optical I / Os. In the illustrated embodiment, the corresponding output of the 1 to K optical splitter (103) feeds the corresponding SPCA 101. In the illustrated embodiment, each SCPA 101 includes M coherent pixels (105) and an optical switch network (104), where M is an integer. Note that in some cases, one or more, optionally 1 to K, optical splitters (103) in the optical switch network (104), or a combination thereof, may be simply referred to as optical switches. The optical switches are configured to switchably couple an input port 102 to an optical antenna within the coherent pixels, thereby forming an optical path between the input port and the optical antenna. The optical switches may include multiple active optical splitters. In some embodiments, the optical switches optically couple a frequency-modulated laser signal one at a time to each of the optical antennas during the scanning period of the FMCW transceiver.

[0027] An optical switching network (104) selects one or more of M coherent pixels to transmit and receive frequency-modulated (FM) light for ranging and detection. The coherent pixels can be physically arranged on the chip in a one-dimensional array (e.g., a linear array) or a two-dimensional array (e.g., a rectangular array, a regular array (e.g., a non-random arrangement like a grid)). In some embodiments, the selected coherent pixels can transmit light into free space, receive the returned optical signal, perform coherent detection, and directly convert the optical signal into an electrical signal for digital signal processing. Note that the received optical signal is no longer propagated through the switching network for detection; instead, the output is individually routed (not shown in the illustrated embodiment), which reduces losses and thus improves signal quality.

[0028] Figures 2a-2d Four versions of coherent pixels according to one or more embodiments are shown. The four versions of coherent pixels can be, for example, those shown above. Figure 1 An embodiment of coherent pixels described herein. Figure 2a and Figure 2b In this configuration, light from an optical switching network (e.g., optical switching network 104) is supplied to the optical input port (203) of a coherent pixel. A bidirectional 2×2 optical splitter (202) splits the light into two output ports, referred to as the TX signal (205) and the local oscillator LO (206). The TX signal (205) is emitted from the chip using an optical antenna (200). An optical antenna is a device that emits light from an on-chip waveguide into free space or couples light from free space into an on-chip waveguide, such as a grating coupler, edge coupler, integrated reflector, or any light spot converter. Optical antennas are typically sensitive to the polarization of light with a specific polarization (e.g., TE) due to their much higher transmit / coupler efficiency. The antenna is reciprocal, as it collects the reflected beam from the object under test and sends it back to the bidirectional 2×2 splitter (202), which in turn splits it between ports 203 and 204. A bidirectional optical 2×2 splitter (202) acts as a "pseudo-circuit" in this single-site configuration where the transmitter and receiver are juxtaposed. Signals received from ports 204 and LO 206 are mixed for coherent detection by an optical mixer, which can be as follows: Figure 2a The same balanced 2×2 optical combiner (201) or as in Figure 2b The same optical mixer (209) as in the middle. Finally, Figure 2a A pair of photodiodes (PD) (207) and Figure 2b The four PDs in the system convert optical signals into electrical signals for beat detection. Figure 2a The version in the document is called the Balanced Photodiode (BPD) version, while Figure 2bThe version in this example is called the hybrid version. The hybrid version provides in-phase and quadrature outputs (I / Q), which can be used to resolve velocity-distance ambiguity or enable advanced DSP algorithms in FMCW LiDAR systems. Using a bidirectional optical 2×2 splitter as a "pseudo-circuit" eliminates the need for discrete circuitrists for each single pixel, which is impractical for large-scale arrays with hundreds of pixels. Therefore, coherent pixels can significantly reduce cost and shape factor, while incurring a signal-to-noise ratio (SNR) penalty of up to 6 dB (because some of the guiding optical power cannot be used for coherent detection). For example, the received optical signal can be split between port 203 and port 204, where the latter is used for coherent detection. Figure 2c and Figure 2d The coherent pixel design shown overcomes this limitation by introducing a polarization-splitter antenna 210 into the new structure. Light from the optical switching network is supplied to the optical input port (203) of the coherent pixel. An optical splitter (212) splits the light into two output ports, referred to as the TX signal (215) and the local oscillator LO (214), respectively. The TX signal (215) is emitted directly from the chip using a polarization-splitter optical antenna (210) with a single polarization (e.g., TM). The antenna collects the reflected beam from the object under test, couples the orthogonal polarization (e.g., TE) into a waveguide (213), and sends it directly to the optical mixer. In this case, the optical signal received by the antenna is not further split by any additional splitter or "pseudo-circuit". The signals received from the port (213) and LO (214) are mixed for coherent detection by the optical mixer, which can be as shown in Figure 2c The same balanced 2×2 optical combiner (201) or as in Figure 2d The same optical mixer (209) as in the middle. Finally, Figure 2c A pair of photodiodes (PD) (207) and Figure 2d The four photodiodes (PDs) convert optical signals into electrical signals for beat detection. This design enables a highly efficient integrated circulator for each single coherent pixel and achieves an on-chip single-static FMCW LiDAR with ultra-high sensitivity. [The following text appears to be incomplete and requires further context: "will be..."] Figures 8 to 10 Further details will be discussed in the following sections. In some embodiments, in Figure 1 In the scene, Figures 2a-2d The coherent pixels enable each of the multiple optical antennas to have a separate splitter, and each splitter is coupled between the optical switch and the corresponding antenna along the respective optical path.

[0029] Figures 3a-3c This illustrates an SCPA (Optical Coherent Detection Block) that shares an optical coherent detection block among multiple coherent pixels according to one or more embodiments. Figure 3aAs shown, the chip (11) can include multiple basic functional subarrays (100). Each subarray (100) includes optical I / O ports (102) and optional 1 to K optical splitters (103) and one or more SCPA (101). Each of the optical I / Os is fed by a frequency-modulated light source provided by an off-chip or on-chip laser. Optical power can be distributed on-chip via optional 1 to K optical splitters (103) to reduce the number of optical I / Os. Each of the 1 to K optical splitters is fed to an optional 1 to N optical switch network (107) selected from N rows, where N is an integer. Each row includes a coherent receiver block (306). The optical switch network (104) further selects one antenna from M antennas (105), where M is an integer, to transmit and receive frequency-modulated (FM) light for ranging and detection. Antennas can be physically arranged on the chip in a one-dimensional array (e.g., a linear array) or a two-dimensional array (e.g., a rectangular array, a regular array, etc.). In this design, the selected antenna transmits light into free space and passively receives the returned optical signal. Coherent detection functions, including optical mixing and photoelectric conversion, are performed in the coherent receiver block (306).

[0030] Note that in some cases, one or more of the optical switch networks (104), the 1 to N optical switch networks (107), or a combination thereof may be simply referred to as optical switches. The optical switches are configured to switchably couple the input port 102 to the optical antenna, thereby forming an optical path between the input port and the optical antenna.

[0031] Figure 3b and Figure 3c It uses a "pseudo-circuit" and behaves similarly Figure 2a and Figure 2c An example of a coherent receiver block (e.g., coherent receiver block (306)) in a coherent pixel block. With Figure 1 Unlike the scheme described above, the received optical signal is again propagated through a 1-to-M switch network so that it can be detected at the coherent receiver block 306. Figure 1 Compared to SCPA, this design significantly reduces the number of photodiodes, thereby reducing the number of electrical outputs and simplifying electrical wiring and / or packaging. Additionally, the pixel size is greatly reduced, allowing for smaller pixel spacing and achieving higher resolution for FMCW LiDAR.

[0032] In some embodiments, Figure 3a In the scene Figure 3b and Figure 3c The coherent receiver block is such that for each optical switch network (104), only one splitter (202) is coupled between the input port and the corresponding optical switch network (104).

[0033] Figures 4a-4c Show Figure 1 and Figure 3a An example of an active optical switch (104). Figure 4a The diagram depicts a binary tree switching network and its individual switching units (401). A 50 / 50 optical splitter (400) feeds two optical phase shifters (402), which use control signals 403 and 404 to tune the phase of each arm. The electrical control of the optical switches can be a push-pull configuration using two controls or it can be a single-sided control. The optical signals in the two arms are combined using an optical 2×2 combiner (405). Depending on the control signals, constructive (destructive) interference occurs, thus the light switches between the two outputs. The optical phase shifter (402) can be, but is not limited to, a thermo-optical phase shifter or an electro-optical phase shifter. Figure 4b As depicted, the switching network can also be implemented using a microring resonator (MRR) array (410). When the resonant frequency of the device is aligned with the laser wavelength, the MRR picks up the optical signal only from the main bus waveguide. Electrical control signals set the resonance of the MRR in the array and thus select the output port through which to transmit and receive FM signals. Similarly, the switching network can also be implemented using... Figure 4c This is implemented using a similar microelectromechanical system (MEMS) switch array. The MEMS switches are configured to redirect light from the main bus waveguide and thus select the output port through which to transmit and receive FM signals.

[0034] Figures 5a-5c This illustration demonstrates how an SCPA, according to one or more embodiments, directs a light beam for FMCW LIDAR operation. In this example, a single SCPA-based LIDAR transceiver (501) is used for illustration. The LiDAR transceiver 501 includes an FMCW light source input (502), an optical switching network (503), coherent pixel units (504), and one or more optical antennas (505). The LiDAR transceiver (501) can be, for example, as referenced above. Figure 1 and Figure 3a The FMCW LiDAR chip (11) is described. And the coherent pixel unit 504 can be, for example, as described above regarding... Figure 1 The coherent pixel 105 is described. Furthermore, in some embodiments, the coherent pixel unit 504 may be composed of… Figure 3a It consists of components (e.g., coherent receiver 304, one or more optical antennas and corresponding optical paths therebetween).

[0035] In the illustrated embodiment, the optical antenna of the LiDAR transceiver 501 is positioned at the focal length of a lens system (507). The lens system (507) includes one or more optical elements (e.g., positive lenses, freeform lenses, Fresnel lenses, etc.) that map the physical location of each coherent pixel to a unique direction. In some embodiments, the lens system (507) is positioned to collimate transmitted signals emitted via multiple antennas. The lens system (507) is configured to project a transmitted signal emitted from one of the multiple antennas into a corresponding portion of the scanner module's field of view and to provide reflection of the transmitted signal to the antenna. Each optical antenna transmits and receives light from a different angle. Therefore, by switching to different antennas, such as... Figure 5b and Figure 5c Discrete beam scanning is implemented as illustrated. For FMCW LIDAR, the laser beam (508) scans across the target (509) in the field of view, and coherent pixels in the LiDAR transceiver (501) generate electrical signals, which are then digitally processed to create a LiDAR point cloud. In some embodiments, the lens system (507) generates collimated transmission signals that scan the transceiver's field of view along an angular dimension (e.g., as shown in the figure). Figure 5b and Figure 5c (As shown).

[0036] like Figures 5a-5c As shown, the coherent pixel units 504 are arranged in a linear array. However, in other embodiments, the coherent pixel units 504 may have some other arrangement (e.g., two-dimensional, rectangular, etc.). Note—in some embodiments, a two-dimensional arrangement can be used to transmit multiple transmit signals from multiple antennas, such that the multiple transmit signals scan a portion of the scanner module's field of view in two dimensions (as shown below regarding...). Figure 12 (As described). For example, scanning in the first and second dimensions, and the scanner module's field of view is 5 degrees or better along the first dimension and 5 degrees or better along the second dimension.

[0037] Figure 6A LiDAR chip (606) with a plurality of parallel FMCW LiDAR transceivers (501) arranged linearly is shown according to one or more embodiments. As illustrated, the LiDAR chip 606 includes eight FMCW LiDAR transceivers (501) arranged in a linear array. However, in other embodiments, the FMCW LiDAR transceivers (501) may have some other arrangement (e.g., two-dimensional, rectangular, etc.). Each SCPA, covering a corresponding angular field of view (FoV) (depicted in the figure as small double-sided arrows at the end of each dashed line), simultaneously and independently emits and receives light (608) by means of a lens system (607). Each SCPA covers a certain angular FoV and provides a certain pixel rate for the FMCW LiDAR system including the LiDAR chip 606. Z parallel FMCW LiDAR transceivers (501) can cover a Z times larger angular FoV and provide a Z times faster pixel rate, where Z is an integer. Wide FoV and fast pixel rate may be important for high-performance FMCW LiDAR systems.

[0038] Figures 7a-7c An example of mechanically assisted laser beam scanning in an SCPA-based FMCW LiDAR system according to one or more embodiments is shown. Figure 7a In this embodiment, a photonic chip (606) and a lens system (607) are both mounted on a rotating platform (701). The photonic chip 606 may be an embodiment of a LiDAR chip 606, a LiDAR transceiver 501, or a combination thereof. In the illustrated embodiment, the photonic chip (606) is capable of solid-state scanning in a first dimension (e.g., vertical), and the rotating platform (701) is capable of 360 degrees in an orthogonal second dimension (e.g., horizontal). Figure 7b In this configuration, the photonic chip (606) and lens system (607) are stationary, and the laser beam is directed by a moving mirror (702) (e.g., a galvanometer). Figure 7c In this configuration, the photonic chip (606) and lens system (607) are stationary, and the laser beam is directed by rotating the polygon mirror (703). The moving mirror (702) and / or the polygon mirror (703) are typically referred to as scanning mirrors. The scanning mirrors are configured to scan the beam (transmitting signals) in a second dimension within the field of view of the scanner module (as described below). Figure 12 (As described), the second dimension is orthogonal to an angular dimension.

[0039] Although the photonic chip 606 is capable of all-solid-state beam steering, and in some cases it may be in two dimensions (e.g., an optical antenna arranged in a two-dimensional array), it can significantly improve the overall field of view and addressable location of the FMCW LiDAR by means of mechanical devices, as illustrated in the example.

[0040] Figure 8 A diagram illustrating a first embodiment of a coherent pixel (813) that utilizes two polarizations of light to improve the performance of an FMCW LiDAR system according to one or more embodiments is shown. Input light (801) originating from a laser enters the coherent pixel and is split by an X / (1-X) splitter (802) (also referred to as a splitter (802)). The X% of the light exits the top port of the splitter, forming the TX signal, while the (1-X)% of the light exits the bottom port of the splitter, forming the local oscillator (LO) signal. An optimal splitting ratio can be selected depending on system parameters. The TX signal enters a polarization assembly 820. In the illustrated embodiment, the polarization assembly 820 includes a polarization splitter (803) and a polarization-insensitive free-space coupler (804). However, in other embodiments, for example, as described below regarding... Figure 9 The polarization splitter (803) and polarization-insensitive free-space coupler (804) discussed can be replaced by a single polarization splitter vertical chip-to-free-space coupler. The polarization splitter (803), also called a polarizer, separates transversely electrically (TE) polarized light from transversely magnetically (TM) polarized light. As an example, Figure 1The input light can be TE-polarized. TM-polarized light can be used without modifying this idea. Because the TX signal light is TE-polarized, it is coupled to the top port on the right-hand side of the polarization splitter (803). The TM-polarized light exits through the bottom port on the right-hand side of the polarization splitter (803). The TX signal exiting the polarization splitter (803) enters the polarization-insensitive free-space coupler (804), which generates a free-space beam (805) with linear polarization matching the TE field in the preceding optical circuit (813). The polarization-insensitive free-space coupler (804) is an example of an optical antenna. For example, the polarization-insensitive free-space coupler could be a vertical grating, an edge coupler (e.g., an anti-conical waveguide), or an angled reflector. The free-space beam (805) propagates through a quarter-wave plate (806), which converts the linearly polarized beam into a circularly polarized beam (807). The circularly polarized light (807) now propagates a certain distance, causing a delay of the light relative to the LO signal. This beam is reflected from the target surface (808), resulting in a reflected beam (809). Depending on the surface properties, this reflected beam may maintain its circular polarization or its polarization may become randomized. The reflected beam (809) propagates back through free space and passes a second time through a quarter-wave plate (806). If the reflected beam (809) maintains its circular polarization, the transmitted beam (810) will have TM polarization (relative to the originating transmit and receive optical paths (813)). If the reflected beam (809) has randomized polarization, the transmitted beam (810) will have random polarization. The transmitted beam (810) is coupled back into the coherent pixel (813) and propagates back to the top right-hand port of the polarization splitter (803). If the received beam is TM polarized, all light will be coupled to the bottom left port of the polarization splitter (803). If the received beam is randomly polarized, nominally half of the optical power will be coupled to the bottom left port. Light coupled to the bottom left port of (803) enters a dual-input power optical mixer (811), which mixes the delayed received signal with the LO signal. The optical mixer generates one or more electrical signals (812) interpreted by the FMCW system. Removing the quarter-wave plate only affects the system performance of the polarization-maintaining target surface, without affecting the fundamental principle of this idea.

[0041] The polarization component (820) can be configured, for example, to couple an optical signal from a first waveguide (e.g., from (802)) to form a transmitted signal; to polarize the transmitted signal to have a first polarization; to polarize a reflected signal (coupled via (804)) based on a second polarization orthogonal to the first polarization to form a returned signal; and to couple the returned signal into a second waveguide (e.g., toward (811)) for optical detection.

[0042] The coherent pixel (813) can be, for example, coherent pixel 105. The coherent pixel (813) can also be the one referenced above. Figure 2a An embodiment of the coherent pixel described. Similarly, the coherent pixel (813) could also be the one referenced above. Figure 2b An embodiment of the coherent pixel described. For example, the bidirectional optical 2×2 splitter (202) can be replaced by an X / (1-X) splitter (802) and a polarization splitter (803), and the optical antenna 200 can be replaced by a polarization-insensitive free-space coupler (804). And in a scenario such as a LiDAR transceiver, for each X / (1-X) splitter, the polarization splitter is coupled along the optical path between the splitter and the optical antenna. The polarization splitter is configured to polarize the transmitted signal to have a first polarization (e.g., TE); and to polarize the reflected signal to form a return signal, such that the return signal has a second polarization orthogonal to the first polarization (e.g., TM).

[0043] Figure 9 A diagram illustrating a second embodiment of a coherent pixel (912) that utilizes two polarizations of light to improve the performance of an FMCW LiDAR system according to one or more embodiments. In addition... Figure 8 The polarization splitter (803) and free-space coupler (804) within the polarization assembly 820 are used as follows: Figure 9 The second embodiment is substantially similar to the first embodiment, except that the single polarization-splitter vertical chip to free-space coupler (903) shown in the illustration is replaced. This free-space coupler receives TE light from its left input and generates a free-space beam (904) with TE polarization. Simultaneously, TM light incident on the coupler is coupled to the bottom port of the optical device, which is connected to the optical mixer (910). The remaining functionality and / or structure of the system in the second embodiment, labeled (901), (902), (904), (905), (906), (907), (908), (909), (910), and (911), are substantially the same as those in (801), (802), (805), (806), (807), (808), (809), (810), (811), and (812).

[0044] Note Figure 9 In this configuration, the polarization (820) and the polarization splitter vertical chip-to-free space coupler (903) are functionally identical. The polarization component (820) can be configured, for example, to couple an optical signal from a first waveguide (e.g., from (902)) to form a transmitted signal; to polarize the transmitted signal to have a first polarization; to polarize a reflected signal (coupled via (903)) based on a second polarization orthogonal to the first polarization to form a returned signal; and to couple the returned signal into a second waveguide (e.g., towards (910)) for optical detection.

[0045] The coherent pixel (912) can be, for example, coherent pixel 105. The coherent pixel (912) can also be the one referenced above. Figure 2c An embodiment of the coherent pixel described. Similarly, the coherent pixel (912) could also be the one referenced above. Figure 2d Examples of coherent pixels described. For example, the optical splitter (212) can be replaced by an X / (1-X) optical splitter (902), and the polarization splitter antenna (210) will be replaced by a single polarization splitter vertical chip to free space coupler (903).

[0046] Figure 10 This illustrates how coherent pixels, according to one or more embodiments, can be used in a focal plane array (FPA) for FMCW applications. Figure 10 The coherent pixels in the image can be, for example, coherent pixel 813 and / or coherent pixel 912. The FPA uses coherent pixels to form the beam steering mechanism. Figure 10 In this configuration, light entering M input waveguides (1001) is split among N output waveguides (1003) by an M×N splitter (1002), where M and N are integers. The N output waveguides are connected to a coherent pixel array (1004). This array can be one-dimensional or two-dimensional, depending on whether one-dimensional or two-dimensional beam steering is desired. Each coherent pixel (1005) emits TE-polarized light (1006), which propagates through a quarter-wave plate (1007) that converts the light to circular polarization (1008). The circularly polarized light passes through a lens (1009), which may consist of one or more lens elements. This lens converts the spatially distributed circularly polarized beam into an angled circularly polarized beam (1010). The output angle of the lens depends on the position of the input beam (e.g., determined in part based on the position of the coherent pixel (1005) that emitted the beam) and the position of the lens (1009), thus achieving beam steering. The angled beam is reflected away from the target (1011). The diffuse light returns towards the lens at the same angle (1012). Depending on the nature of the target, this reflected light may maintain its circular polarization or become randomly polarized. The reflected beam returns through the lens (1009), which maps the angle of the beam to a specific location on the FPA. The transmitted beam (1013) returns through the quarter-wave plate (1007). If the reflected light maintains its circular polarization, the transmitted light (1014) will be TM polarized. If the reflected light is randomly polarized, the transmitted light (1014) will have random polarization. The transmitted light (1014) is coupled back into the coherent pixel array (1004), which converts the light into an electrical signal as previously described.

[0047] Figures 11a-11dElectrical wiring schemes for SCPA are illustrated according to one or more embodiments. These electrical wiring schemes can significantly reduce the number of electrical I / Os for photonic chips in LiDAR transceivers. Scheme 1 is illustrated in... Figure 11a and Figure 11b Scheme 2 is illustrated in the diagram. Figure 11c and Figure 11d In this example, a 1-8 three-level binary tree switch network is shown, where each switch has an electrical control signal and a coherent pixel array, where each coherent pixel has two electrical outputs (e.g., I / Q signals). In Scheme 1, switches at the same level are electrically connected together. Using only three switch control signals, the LiDAR system can switch between any of the eight coherent pixels. All I output signals from the coherent pixels are connected together as a shared output (RX_I) and all Q output signals are connected together as another shared output (RX_Q). When only one coherent pixel is activated by the switch network, the remaining coherent pixels receive very little light as their transmitter signal or their LO signal. Therefore, the shared output represents the correct signal from the activated pixel, while crosstalk from neighboring pixels is minimal. In this example, Scheme 1 reduces the number of I / O signals to a minimum of five for a total of 7 switch inputs and 16 coherent pixel outputs. The reduction in electrical I / O becomes even more significant as the size of the SCPA increases and / or the number of parallel SCPAs increases. In scheme 2, more than one coherent pixel can be selected to simultaneously transmit and receive light. Figure 11c In this configuration, the switch control signals and coherent pixel output signals are split between the upper and lower halves of a 1-to-8 binary switch network, resulting in 5 switch controls and 4 receiver outputs. During operation, the first switch is controlled to have a 50 / 50 split ratio at both outputs, thereby delivering uniform optical power to both the upper and lower halves of the 1-to-8 switch tree. Utilizing the independent control and readout capabilities of the upper and lower halves of the tree, it is possible to simultaneously activate one pixel from the upper half and one pixel from the lower half. Configuration 2 can be adapted to Configuration 1 by operating the first switch stage in normal binary mode, and it also allows for arbitrary control of the split ratio of the first switch stage, thus providing a more flexible and potentially software-defined beam scanning option at a certain hardware cost.

[0048] Figure 12 A system diagram of an SCPA-based FMCW LiDAR system according to one or more embodiments is shown. The scanner module (1201) includes an SCPA LiDAR chip (1205) having one or more FMCW transceiver channels and a lens system (1203) including one or more optical elements. In some embodiments, the lens system (1203) is an embodiment of the lens system (507).

[0049] The SCPA LiDAR chip (1205) includes one or more frequency-modulated continuous wave (FMCW) LiDAR transceivers implemented as one or more photonic integrated circuits. The photonic integrated circuits used for the transceivers may include input ports, multiple optical antennas, optical switches, multiple splitters, and multiple mixers.

[0050] An input port is configured to receive a frequency-modulated laser signal. An optical switch is configured to switchably couple the input port to an optical antenna, thereby forming an optical path between the input port and the optical antenna. For each optical path from the input port to one of the optical antennas, a splitter is coupled along the optical path and configured to: split the received portion of the laser signal into a local oscillator signal and a transmitted signal, wherein the transmitted signal is transmitted via the optical antenna and the reflection of the transmitted signal is received via the optical antenna as a reflected signal; and output a return signal as part of the reflected signal. For each splitter, a mixer is coupled to receive the return signal and the local oscillator signal from the splitter, the mixer being configured to mix the return signal and the local oscillator signal to generate one or more output signals for determining depth information of the field of view of the LiDAR system (also referred to as the field of view of the scanner module (1201)).

[0051] In some embodiments, the lens system (1203) generates a collimated transmission signal that scans the field of view of the scanner module (1201) along one or more angular dimensions (e.g., azimuth or elevation). The scanner module (1201) has a field of view of 5 degrees or better along one angular dimension. And in embodiments with a two-dimensional arrangement of optical antennas (e.g., a rectangular grid), signals from multiple optical antennas can be scanned in two dimensions within the field of view of the scanner module (1201). For example, scanning is performed in a first dimension and a second dimension, and the field of view of the scanner module (1201) is 5 degrees or better along the first dimension and 5 degrees or better along the second dimension. Note that the two-dimensional scanning in the above examples is accomplished purely through the selective use of different coherent pixels.

[0052] The scanner module (1201) may also include a scanner (1202) for assisting laser beam scanning and / or a quarter-wave plate (QWP) (1204) for improving polarization-dependent sensitivity. The scanning mirror (1202) is, for example, as described above regarding... Figure 7b and Figure 7cThe scanning mirror described. In embodiments using the scanning mirror (1202), the field of view of the scanner module (1201) is 5 degrees or better along the first dimension (scanned via selective use of coherent pixels) and 10 degrees or better along the second dimension (scanned at least partially via movement of the scanning mirror (1202)). The light source for the LiDAR chip (1205) can be directly integrated onto the same chip or coupled via fiber optic components. As shown, the light source is an FMCW laser source (1207) that generates a frequency-modulated optical signal for FMCW LiDAR operation. The laser source (1207) can be further amplified by an optical amplifier (1206) to increase the range of the FMCW LiDAR. The optical amplifier can be a semiconductor optical amplifier (SOA) chip or an erbium-doped fiber amplifier (EDFA). The FMCW laser source (1207) is controlled by a laser driver circuit (1208), which is typically a controllable low-noise current source. The output of the coherent pixels is directed to a transimpedance amplifier (TIA) circuit array (1211). On-chip switches are controlled by a switch driver array (1210). The FMCW processing engine can be implemented using one or more FPGA, ASIC, or DSP chips containing the following functionalities: SCPA control and calibration logic (1215), FMCW LiDAR frame management and point cloud processing (1214), a multi-channel analog-to-digital converter (1216), an FMCW LiDAR DSP (1212), and FMCW laser chirp control and calibration logic (1213). In the case of implementing the SCPA LiDAR chip (1205) using a CMOS silicon photonics platform, some or all of the circuit functionalities can be implemented using a single-chip photonic circuit monolith. The data output (1220) of the FMCW processing engine is depth information. Depth information may include, for example, three-dimensional position data of a typical LiDAR point cloud and other information that the FMCW LiDAR can measure, such as velocity, reflectivity, etc.

[0053] As mentioned above, a wide FoV and a fast pixel rate can be important for a high-performance FMCW LiDAR system. Note that the scanner module (1201) is capable of targeting at least 100K points per second above the FoV of the scanning module (1201).

[0054] Figure 12 An example LiDAR system is shown. In alternative configurations, different components and / or additional components can be included in the LiDAR system. Additionally, combined with... Figure 12 The functionality described in one or more of the components shown can be combined with Figure 12 The components are distributed in different ways. For example, in some embodiments, the SCPA LiDAR chip 1205 may be separate from the scanner module (1201).

[0055] Additional configuration information

[0056] The figures and foregoing descriptions are illustrated only with respect to preferred embodiments. It should be noted that, based on the foregoing discussion, alternative embodiments of the structures and methods disclosed herein will be readily identified as feasible alternatives that can be employed without departing from the claimed principles.

[0057] Although the detailed description contains numerous details, these should not be construed as limiting the scope of the invention, but merely as illustrating different examples. It should be understood that the scope of this disclosure includes other embodiments not discussed in detail above. Various other modifications, alterations, and variations in the arrangement, operation, and details of the methods and apparatus disclosed herein may be made, without departing from the spirit and scope defined in the appended claims, in a manner that will be apparent to those skilled in the art. Therefore, the scope of the invention should be determined by the appended claims and their legal equivalents.

[0058] Alternative embodiments can be implemented in computer hardware, firmware, software, and / or combinations thereof. Implementations can be carried out in computer program products tangibly embodied in machine-readable storage devices for execution by a programmable processor; and method steps can be performed by a program that executes instructions via a programmable processor to perform functions by manipulating input data and generating output. Embodiments can be advantageously implemented in one or more computer programs that can be executed on a programmable system including at least one programmable processor coupled to receive data and instructions from a data storage system, at least one input device, and at least one output device, and to transfer data and instructions to the data storage system, at least one input device, and at least one output. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or, as needed, in assembly or machine language; and in any case, the language can be a compiled language or an interpreted language. As an example, suitable processors include both general-purpose microprocessors and special-purpose microprocessors. Typically, the processor receives instructions and data from read-only memory and / or random access memory. Typically, a computer will include one or more mass storage devices for storing data files; such devices include disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly representing computer program instructions and data include all forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the above can be supplemented by ASICs (Application-Specific Integrated Circuits) and other forms of hardware, or incorporated into ASICs and other forms of hardware.

Claims

1. A LiDAR transceiver, comprising: Source input, configured to receive laser signals; Multiple coherent units; as well as An optical switch configured to switchably couple the source input to the plurality of coherent units, wherein at least one of the plurality of coherent units includes: An input port, which is coupled to the optical switch; Optical antennas; and A splitter, coupled between the input port and the optical antenna, wherein the splitter is configured to: The receiving portion of the laser signal is split into a local oscillator signal and a transmitted signal, wherein the transmitted signal is transmitted through the optical antenna and the reflection of the transmitted signal is received by the optical antenna as a reflected signal; and The output is a return signal that is part of the reflected signal.

2. The LIDAR transceiver according to claim 1, wherein, The at least one coherent unit further includes: A mixer coupled to receive the return signal and the local oscillator signal from the splitter, the mixer being configured to mix the return signal and the local oscillator signal to generate one or more output signals.

3. The LIDAR transceiver according to claim 2, further comprising: One or more processors are configured to determine depth information of the LIDAR transceiver's field of view based on the one or more output signals.

4. The LIDAR transceiver according to claim 2, wherein, The one or more output signals include quadrature output signals and in-phase output signals for the return signal.

5. The LIDAR transceiver according to claim 2, wherein, The at least one coherent unit further includes at least one photodiode coupled to the mixer to provide the one or more output signals as electrical signals.

6. The LIDAR transceiver according to claim 1, wherein, Multiple optical paths are defined between the source input of the transceiver and the plurality of coherent units.

7. The LIDAR transceiver according to claim 1, wherein, The at least one coherent unit further includes: A polarization component is disposed between the splitter and the optical antenna, and the polarization component is configured to: Optical signals from the first waveguide are coupled to form the transmitted signal; and The transmitted signal is polarized to have a first polarization; The reflected signal is polarized based on a second polarization to form the return signal; and The returned signal is coupled to a second waveguide for optical detection.

8. The LIDAR transceiver according to claim 7, wherein, The first polarization is orthogonal to the second polarization.

9. The LIDAR transceiver according to claim 1, wherein, The plurality of coherent units are arranged in a linear array or a two-dimensional array.

10. The LIDAR transceiver according to claim 1, wherein, The optical switch includes: A passive optical splitter that splits the laser signal between at least two optical paths.

11. The LIDAR transceiver according to claim 1, wherein, The optical switch includes: An active optical splitter that can switchably couple the laser signal to only one of at least two optical paths.

12. The LIDAR transceiver according to claim 1, wherein, The optical switch optically couples the laser signal to the plurality of coherent units one at a time during the scanning period of the LIDAR transceiver.

13. The LIDAR transceiver according to claim 1, wherein, The laser signal includes a frequency modulated continuous wave (FMCW) laser signal.

14. A car-mounted LiDAR system, comprising: At least one LIDAR transceiver, the at least one LIDAR transceiver comprising: Source input, configured to receive laser signals; Multiple coherent units; and An optical switch configured to switchably couple the source input to the plurality of coherent units, wherein at least one of the plurality of coherent units includes: An input port, which is coupled to the optical switch; Optical antennas; and A splitter, coupled between the input port and the optical antenna, wherein the splitter is configured to: The receiving portion of the laser signal is split into a local oscillator signal and a transmitted signal, wherein the transmitted signal is transmitted through the optical antenna and the reflection of the transmitted signal is received by the optical antenna as a reflected signal; and Output a return signal as part of the reflected signal; and A lens, which is coupled to the LIDAR transceiver and configured to: Collimate the transmitted signal emitted by the optical antenna; and The reflected signal is received and coupled to the optical antenna.

15. The automotive LIDAR system according to claim 14, wherein, The at least one coherent unit further includes: A mixer coupled to receive the return signal and the local oscillator signal from the splitter, the mixer being configured to mix the return signal and the local oscillator signal to generate one or more electrical output signals.

16. The automotive LIDAR system according to claim 15, further comprising: One or more processors are coupled to the LIDAR transceiver and configured to determine depth information of the LIDAR transceiver's field of view based on the one or more electrical output signals.

17. The automotive LIDAR system according to claim 15, wherein, The one or more electrical output signals include quadrature output signals and in-phase output signals.

18. A LIDAR chip, comprising: A plurality of LiDAR transceivers, wherein at least one of the plurality of LiDAR transceivers comprises: Source input, configured to receive laser signals; At least one coherent unit; and An optical switch configured to switchably couple the source input to the at least one coherent unit, wherein the at least one coherent unit includes: An input port, which is coupled to the optical switch; Optical antennas; and A splitter, coupled between the input port and the optical antenna, wherein the splitter is configured to: The receiving portion of the laser signal is split into a local oscillator signal and a transmitted signal, wherein the transmitted signal is transmitted through the optical antenna and the reflection of the transmitted signal is received by the optical antenna as a reflected signal; and The output is a return signal that is part of the reflected signal.

19. The LIDAR chip according to claim 18, wherein, The at least one coherent unit further includes: A mixer coupled to receive the return signal and the local oscillator signal from the splitter, the mixer being configured to mix the return signal and the local oscillator signal to generate one or more electrical output signals.

20. The LIDAR chip according to claim 19, wherein, The one or more electrical output signals include quadrature output signals and in-phase output signals.

Images