Lidar transceiver, lidar system, and lidar chip

Abstract

To solve the problem in which: exiting LIDAR systems use mechanical moving parts to steer a laser beam, and for many applications (for example, automobile), are too bulky, costly, and unreliable.SOLUTION: An FMCW LIDAR transceiver is implemented on a photonic integrated circuit (PIC). The FMCW LIDAR transceiver performs optical 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 that includes a plurality of FMCW LIDAR transceivers arranged in an array (for example, linear array, two-dimensional array and the like). The FMCW LIDAR system determines depth information (for example, distance to objects within a field of view of the transceiver, velocity of the objects and the like) for the field of view of the transceiver.SELECTED DRAWING: Figure 5a

Description

Technical Field

[0001] Cross-reference to Related Applications This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62 / 826,528, filed Mar. 29, 2019; U.S. Provisional Patent Application No. 62 / 826,536, filed Mar. 29, 2019; U.S. Provisional Patent Application No. 62 / 845,147, filed May 8, 2019; U.S. Provisional Patent Application No. 62 / 845,149, filed May 8, 2019; U.S. Provisional Patent Application No. 62 / 849,807, filed May 17, 2019; and U.S. Provisional Patent Application No. 62 / 940,790, filed Nov. 26, 2019, the entire contents of each of which are hereby incorporated by reference.

[0002] The present disclosure generally relates to frequency modulated continuous wave (FMCW) optical detection and ranging (lidar, LIDAR), and more particularly, to a switchable coherent pixel array for FMCW LIDAR.

Background Art

[0003] Existing LIDAR systems use mechanical moving parts to direct the laser beam. Also, in many use cases (e.g., automotive), they are bulky, costly, and unreliable.

Summary of the Invention

Means for Solving the Problems

[0004] The FMCW LIDAR transceiver is implemented in a photonic integrated circuit (PIC). The FMCW LIDAR transceiver performs optical 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 that includes a plurality of 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 about the field of view of the transceiver (e.g., the distance to an object within the field of view of the transceiver, the velocity of the object, etc.).

[0005] In some embodiments, the FMCW LIDAR transceiver includes one or more sub-arrays. The sub-array can 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 the optical antenna and to form 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, one of the plurality of 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 emitted via the optical antenna, and the reflection of the transmitted signal is received as a signal reflected via the optical antenna. The splitter also outputs a return signal that is part of the reflected signal. For each splitter, one 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 mix the return signal and the local oscillator signal to generate one or more output signals that are used to determine depth information about the field of view of the transceiver.

[0006] In some embodiments, the FMCW LIDAR system includes a LIDAR chip. The LIDAR chip includes an FMCW LIDAR transceiver implemented in an optical integrated circuit. The optical integrated circuit includes one or more sub-arrays. The sub-array 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 and form 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, any one of the plurality of splitters is coupled along the optical path. Each splitter is configured to divide the received portion of the laser signal into a local oscillator signal and a transmitted signal. The transmitted signal is emitted via the optical antenna, and the reflection of the transmitted signal is received as a signal reflected via the optical antenna. The splitter also outputs a return signal that is part of the reflected signal. For each splitter, any one 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 mix the return signal and the local oscillator signal and generate one or more output signals used to determine depth information about the field of view of the FMCW LIDAR system. The FMCW LIDAR system also includes a lens arranged to collimate the transmitted signal emitted via the plurality of antennas. The lens is also arranged to receive the reflected signal and couple the reflected signal to the optical antenna that emits the reflected signal.

Brief Description of the Drawings

[0007] Embodiments of the present disclosure have other advantages and features that will become more apparent from the following detailed description and the appended claims when taken in connection with the examples of the accompanying drawings, in which

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DETAILED DESCRIPTION OF THE INVENTION

[0020] An FMCW LIDAR system determines depth information about the field of view of the system (e.g., distance, velocity, acceleration for one or more objects). The FMCW LIDAR system uses a switchable coherent pixel array (SCPA) on a LIDAR chip (e.g., an optical integrated circuit). The LIDAR chip may include one or more FMCW transceivers (e.g., each FMCW transceiver may be responsible for a different field of view angle within the field of view of the LIDAR system). The FMCW LIDAR system divides the FMCW beam into a signal portion and a mixing portion. The signal portion is conditioned via a lens assembly and output into the field of view of the FMCW LIDAR system. The signal portion forms a reflected signal reflected from one or more objects in the field of view, and the reflection of the corresponding signal portion 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 distance and velocity of one or more objects within the field of view of the FMCW LIDAR system.

[0021] The FMCW LIDAR system transceiver is implemented on an optical integrated circuit. The optical integrated circuit includes sub-arrays of one or more basic functions. Each sub-array includes 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 frequency-modulated laser signal may be external to the transceiver or, in some cases, on the same chip as the optical integrated circuit. The optical switch is configured to switchably couple the input port to the optical antennas and form an optical path between the input port and the optical antennas. In some embodiments, the optical switch optically couples the frequency-modulated laser signal to each of the optical antennas one at a time during the scanning period of the FMCW transceiver.

[0022] For each optical path directed from the input port to one of the optical antennas, any one of the plurality of 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 emitted via the optical antenna, and the reflection of the transmitted signal is received as the signal reflected via the optical antenna. The splitter also outputs a return signal that is a portion of the reflected signal. For each splitter, any one 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 mix the return signal and the local oscillator signal to generate one or more output signals. The frequency of the beat tone due to the mixing is proportional to the distance from the LIDAR system to the optical reflection surface. The one or more output signals are used to determine depth information about the field of view of the LIDAR system. The depth information describes the distances to various surfaces within the field of view of the LIDAR system and may also include information describing the velocities of the objects within the field of view of the LIDAR system.

[0023] It should be noted that the LIDAR chip can direct the light emitted from the LIDAR system in at least one dimension. Also, in some embodiments, the optical antennas are arranged two-dimensionally such that the LIDAR chip can direct the light beam in two dimensions. Without moving parts and being able to direct the beam, the form factor, cost, and reliability issues found in many existing mechanically-driven LIDAR systems can be alleviated.

[0024] FIG. 1 shows a schematic diagram of a switchable coherent pixel array (SCPA) FMCW LIDAR chip 11 according to one or more embodiments. The LIDAR chip is an optical integrated circuit. The chip may include sub-arrays 100 of a plurality of basic functions. Each sub-array 100 includes an optical input / output (I / O) port 102 and a selective 1-K optical splitter 103 (K is an integer) and one or more SCPAs 101. The 1-K optical splitter 103 can be passive or active. Each optical I / O is supplied by a frequency-modulated light source provided by an off-chip or on-chip laser. Optical power can be distributed on-chip via a selective 1-K optical splitter to reduce the number of optical I / Os. In the illustrated embodiment, each output of the 1-K optical splitter 103 is supplied to a corresponding SCPA 101. In the illustrated embodiment, each SCPA 101 includes M coherent pixels 105 (M is an integer) and an optical switch network 104. Note that in some cases, one or more optical switch networks 104, selective 1-K optical splitters 103, or some combination thereof can simply be referred to as an optical switch. The optical switch is configured to switchably couple the input port 102 to an optical antenna within the coherent pixel and form an optical path between the input port and the optical antenna. The optical switch can include a plurality of active optical splitters. In some embodiments, the optical switch optically couples a frequency-modulated laser signal to each of the optical antennas one at a time during the scanning period of the FMCW transceiver.

[0025] The optical switch network 104 selects one or more of the M coherent pixels to transmit and receive frequency-modulated (FM) light for distance measurement 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 rectangle, a regular shape (e.g., a non-random array such as a grid)). In some embodiments, the selected coherent pixels can transmit light into free space, receive the returning optical signal, perform coherent detection, and directly convert the optical signal into an electrical signal for digital signal processing. Note that instead of re-propagating the received optical signal through the switch network for detection, the output is individually routed (not shown in the illustrated embodiment) to reduce loss and thereby improve the quality of the signal.

[0026] Figures 2a through 2d illustrate four versions of coherent pixels according to one or more embodiments. The four versions of coherent pixels can be, for example, the embodiments of the coherent pixels described above in FIG. 1. In FIGS. 2a and 2b, light from an optical switch network (e.g., optical switch network 104) is provided to the optical input port 203 of the coherent pixel. A bidirectional optical 2×2 splitter 202 splits the light into two output ports, called the TX signal 205 and the local oscillator 206 (LO). The TX signal 205 is transmitted from the chip using the optical antenna 200. The optical antenna is a device that emits light from an on-chip waveguide to free space or couples light from free space to an on-chip waveguide, such as a grating coupler, an edge coupler, an integrated reflector, or any spot size converter. The optical antenna can have polarization sensitivity with much higher emission / coupling efficiency for light having one particular polarization (e.g., TE). Since the antenna is reciprocal, it collects the beam reflected from the object under measurement and returns it to the bidirectional 2×2 splitter 202, which splits it again between ports 203 and 204. The bidirectional optical 2×2 splitter 202 functions as a "pseudo circulator" in such a monostatic configuration where the transmitter and receiver are co-located. The signals received at port 204 and LO 206 are mixed for coherent detection by an optical mixer, which can be a balanced 2×2 optical coupler 201 as in FIG. 2a or an optical hybrid 209 as in FIG. 2b. Finally, the pair of photodiodes 207 (PD) in FIG. 2a and the four PDs in FIG. 2b convert the optical signal to an electrical signal for beat tone detection. The version in FIG. 2a is called the balanced photodiode (BPD) version, and the version in FIG. 2b is called the hybrid version. The hybrid version can be used in an FMCW LIDAR system to resolve velocity-distance ambiguities or provide in-phase and quadrature (I / Q) outputs for enabling advanced DSP algorithms.Using a bidirectional optical 2×2 splitter as a "pseudo-circulator" eliminates the need to provide an individual circulator for each of the hundreds of pixels in a large-scale array, which would be impractical. Thus, coherent pixels can significantly reduce the signal-to-noise ratio (SNR) penalty cost and form factor, up to 6 dB (since some of the induced optical power is not available for coherent detection). For example, the received optical signal can be split between port 203 and port 204, with the latter port 204 being used for coherent detection. The coherent pixel designs illustrated in FIGS. 2c and 2d address these limitations by introducing a polarization splitting antenna 210 into the new structure. Light from the optical switch network is provided to the optical input port 203 of the coherent pixel. An optical splitter 212 splits the light into two output ports, a TX signal 215 and a local oscillator 214 (LO). The TX signal 215 is directly transmitted from the chip using a polarization splitting optical antenna 210 with one polarization (e.g., TM). The antenna collects the beam reflected from the measurement object, couples the orthogonal polarization (e.g., TE) into waveguide 213, and directly transmits this to an optical mixer. In this case, the optical signal received by the antenna is not further split by an additional splitter or "pseudo-circulator". The signals received from port 213 and LO 214 are mixed for coherent detection by an optical mixer, which can be a balanced 2×2 optical coupler 201 as in FIG. 2c or an optical hybrid 209 as in FIG. 2d. Finally, the pair of photodiodes 207 (PD) in FIG. 2c and the four PDs in FIG. 2d convert the optical signal to an electrical signal for beat tone detection. This design enables the implementation of a highly efficient integrated circulator for each individual coherent pixel, enabling ultra-high sensitivity on-chip monostatic FMCW LIDAR. The details are further discussed in FIGS. 8 through 10. In some embodiments, for the coherent pixels of FIGS. 2a through 2d on the side of FIG. 1, each of the plurality of optical antennas has a separate splitter, and each splitter is configured to couple along each optical path between the optical switch and the corresponding antenna.

[0027] Figures 3a through 3c illustrate SCPA according to one or more embodiments in which an optical coherent detection block is shared among multiple coherent pixels. As shown in Figure 3a, chip 11 may include a plurality of sub-arrays 100 of basic functions. Each sub-array 100 includes an optical I / O port 102, an optional 1-K optical splitter 103, and one or more SCPAs 101. Each optical I / O is supplied by a frequency-modulated light source provided by an off-chip or on-chip laser. Optical power may be distributed on-chip through an optional 1-K optical splitter 103 to reduce the number of optical I / Os. Each of the 1-K optical splitters is supplied to a selective 1-N optical switch network 107 that selects one out of N columns (N is an integer). Each column includes a coherent receiver block 306. Optical switch network 104 further selects one out of M antennas 105 (M is an integer) to transmit and receive frequency-modulated (FM) light for distance measurement and detection. The antennas may 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 standard array, etc.). In this design, the selected antenna transmits light into free space and passively receives the returned optical signal. The coherent detection function, including optical mixing and opto-electrical conversion, is performed by coherent receiver block 306.

[0028] It should be noted that in some cases, one or more of the optical switch networks 104, the 1-N optical switch network 107, or a combination of some of them can simply be referred to as an optical switch. The optical switch is configured to switchably couple the input port 102 to the optical antenna and form an optical path between the input port and the optical antenna.

[0029] Figures 3b and 3c are examples of coherent receiver blocks (e.g., coherent receiver block 306) that use a "pseudo circulator" and operate similarly to the coherent pixel blocks of FIGS. 2a and 2c. Different from the scheme of FIG. 1, the received optical signal propagates again through the 1-M switch network so as to be detected from the coherent receiver block 306. Compared with the SCPA of FIG. 1, this design significantly reduces the number of photodiodes to reduce the number of electrical outputs and simplifies the electrical routing and / or packaging. Also, the pixel size is significantly reduced, the pitch between pixels becomes smaller, and the resolution of the FMCW LIDAR can be higher.

[0030] In some embodiments, the coherent receiver blocks of FIGS. 3b and 3c in the manner of FIG. 3 each have only one splitter 202 coupled between the input port and the corresponding optical switch network 104 for each optical switch network 104.

[0031] Figures 4a through 4c illustrate examples of the active optical switch 104 of FIGS. 1 and 3a. A Binary Tree Switch Network and its individual switch cells 401 are illustrated in FIG. 4a. A 50 / 50 optical splitter 400 feeds two optical phase shifters 402 that adjust the phase of each arm using control signals 403 and 404. The electrical control of the optical switch can be in a Push-Pull fashion using two control devices or in a Single-Sided fashion using only one control device. The optical signals of the two arms are combined using an optical 2×2 coupler 405. Depending on the control signal, constructive (destructive) interference occurs and the light is switched 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. As shown in FIG. 4b, the switch network can also be implemented with an array of microring resonators (MRRs). The MRR picks up the optical signal from the main bus waveguide only when the resonance frequency of the device is aligned with the laser wavelength. The electrical control signal selects the output port where the FM signal is transmitted and received to set the resonance of the MRRs in the array. Similarly, the switch network can be implemented with an array of microelectromechanical system (MEMS) switches as shown in FIG. 4c. The MEMS switches are configured to direct the light of the main bus waveguide and thus select the output port where the FM signal is transmitted and received.

[0032] Figures 5a through 5c illustrate a method by which an SCPA directs an optical beam for FMCW LIDAR operation, according to one or more embodiments. 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 switch network 503, a coherent pixel cell 504, and one or more optical antennas 505. The LIDAR transceiver 501 can be, for example, the FMCW LIDAR chip 11 described above with reference to FIGS. 1 and 3a. Also, the coherent pixel cell 504 can be, for example, the coherent pixel 105 described above in connection with FIG. 1. Also, in some embodiments, the coherent pixel cell 504 can be composed of the elements of FIG. 3a (e.g., the coherent receiver 304 includes one or more optical antennas and corresponding optical paths therebetween).

[0033] In the illustrated embodiment, the optical antenna of the LIDAR transceiver 501 is disposed at the focal length of the lens system 507. The lens system 507 includes one or more optical elements (e.g., positive lens, free-form lens, Fresnel lens, etc.) that map the physical positions of the respective coherent pixels in a unique direction. In some embodiments, the lens system 507 is positioned to collimate the transmitted signals emitted via the plurality of antennas. The lens system 507 is configured to project the transmitted signal emitted from any one of the plurality of antennas onto a corresponding portion of the field of view of the scanner module and provide the reflected signal of the transmitted signal to the antenna. Each optical antenna transmits and receives light at different angles. Thus, by switching to other antennas, individual light beam scanning is achieved as shown in FIGS. 5b and 5c. In the case of FMCW LIDAR, the laser beam 508 scans across the target 509 within the field of view, and the coherent pixels of the LIDAR transceiver 501 generate electrical signals, which are then digitally processed to generate a LIDAR point cloud. In some embodiments, the lens system 507 generates a collimated transmitted signal that scans the transceiver field of view along one angular dimension (as shown, for example, in FIGS. 5b and 5c).

[0034] As shown in FIGS. 5a to 5c, the coherent pixel cells 504 are arranged in a linear array. However, in other embodiments, the coherent pixel cells 504 may have some other arrangement (e.g., two-dimensional, rectangular, etc.). In some embodiments, since a plurality of transmitted signals can be emitted from a plurality of antennas using a two-dimensional array (as will be described later in connection with FIG. 12), it should be noted that the plurality of transmitted signals scan a portion of the field of view of the scanner module in two dimensions. For example, the scanning is performed in a first dimension and a second dimension, and the field of view of the scanner module is 5 degrees or more along the first dimension and 5 degrees or more along the second dimension.

[0035] FIG. 6 illustrates a LIDAR chip 606 having a plurality of parallel FMCW LIDAR transceivers 501 arranged linearly 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 (represented by the small double-sided arrows at the ends of each dotted line in the drawing) emits and receives light 608 simultaneously with and independently of the assistance of the lens system 607 over the corresponding field of view or angle FoV (Field-of-View). Each SCPA covers a particular angle FoV and provides a particular pixel velocity for the FMCW LIDAR system including the LIDAR chip 606. Z parallel FMCW LIDAR transceivers 501 can cover a Z-fold larger angle FoV and can provide a Z-fold faster pixel velocity, where Z is an integer. In high-performance FMCW LIDAR systems, a wide FoV and high pixel velocity may be important.

[0036] Figures 7a through 7c illustrate examples of mechanically assisted laser beam scanning in an SCPA-based FMCW LIDAR system according to one or more embodiments. In Figure 7a, both the photon chip 606 and the lens system 607 are mounted on a rotating platform 701. The photon chip 606 can be an embodiment of an LIDAR chip 606, an LIDAR transceiver 501, or a combination of some of these. In the illustrated embodiment, the photon chip 606 can achieve solid-state scanning in the first dimension (e.g., vertically), and the rotating platform 701 can achieve 360 degrees in the orthogonal second dimension (e.g., horizontally). In Figure 7b, the photon chip 606 and the lens system 607 are fixed, and the laser beam is directed by a movable mirror 702 (e.g., a Galvo Mirror). In Figure 7c, the photon chip 606 and the lens system 607 are fixed, and the laser beam is directed by a rotating polygon mirror 703. The movable mirror 702 and / or the polygon mirror 703 can generally be referred to as scanning mirrors. Also, the scanning mirror is configured to scan the beam (the transmitted signal) in a second dimension within the field of view of the scanner module, and the second dimension is orthogonal to one angular dimension, as will be described later in connection with Figure 12.

[0037] The photon chip 606 can achieve all-solid-state beam steering and, in some cases, can be two-dimensional (e.g., optical antennas arranged in a two-dimensional array), but the full field of view and addressable positions of FMCW LIDAR can be significantly improved with the assistance of mechanical devices, as described in the examples above.

[0038] FIG. 8 shows a diagram of a coherent pixel 813 of a first embodiment that uses two polarizations of light to improve the performance of an FMCW LIDAR system according to one or more embodiments. Input light 801 generated from a laser is incident on the coherent pixel and is split by an X / (1-X) splitter 802, also referred to as a splitter 802. X% of the light exits from the upper port of the splitter to form a TX signal, and (1-X)% of the light exits from the lower port of the splitter to form a local oscillator (LO) signal. The optimal splitting ratio can be selected according to system parameters. The TX signal is received by 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 will be discussed later in connection with FIG. 9, the polarization splitter 803 and the polarization-insensitive free space coupler 804 are replaced by a single polarization-splitting vertical chip-free space coupler. The polarization splitter 803 is also referred to as a polarizer that separates transverse electric (TE) and transverse magnetic (TM) polarizations. As an example, the input light of FIG. 1 can be TE-polarized. Light polarized in TM can be used without changing this concept. Since the TX signal light is light polarized in TE, the light is coupled to the upper port on the right side of the polarization splitter 803. The TM-polarized light exits through the lower port on the right side of the polarization splitter 803. The TX signal exiting from the polarization splitter 803 is incident on a polarization-insensitive free space coupler 804 that generates a free space light beam 805 having a linear polarization that matches the TE field of 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 can be a vertical grating, an edge coupler (e.g., an inverse tapered waveguide), or an inclined reflector. The free space beam 805 propagates through a quarter-wave plate 806 that converts the linear polarization to a circular polarization 807. The circular polarization 807 propagates over a predetermined distance, which delays the light compared to the LO signal. This beam is reflected from the target surface 808 to generate a reflected light beam 809.Depending on the surface properties, these reflected beams can maintain circular polarization or randomize the polarization. The reflected light beam 809 propagates back through free space and then propagates secondarily through the quarter-wave plate 806. If the reflected beam 809 maintains circular polarization, the transmitted beam 810 will have TM polarization (with respect to the transmitting and receiving optical circuit 813 at the source). If the reflected beam 809 has randomized polarization, the transmitted beam 810 will have random polarization. The transmitted beam 810 is coupled back to the coherent pixel 813 and propagates again to the upper right port of the polarization splitter 803. If the received optical beam is TM polarized, all the light is coupled to the lower left port of the polarization splitter 803. If the received beam is randomly polarized, nominally half of the optical power is coupled to the lower left port. The light coupled to the lower left port of 803 is incident on a 2-input power optical mixer 811 that mixes the delayed received signal and the LO signal. The optical mixer generates one or more electrical signals 812 that are interpreted by the FMCW system. The removal of the quarter-wave plate only affects the system performance for target surfaces that maintain polarization and does not affect the basic principle of this concept.

[0039] The polarization assembly 820 can be configured to, for example, combine optical signals from a first waveguide (e.g., 802) to form a transmitted signal, polarize the transmitted signal to have a first polarization, polarize the reflected signal based on a second polarization orthogonal to the first polarization (incoupled via 804) to form a return signal, and couple the return signal (e.g., towards 811) to a second waveguide for optical detection.

[0040] Coherent pixel 813 can be, for example, coherent pixel 105. Coherent pixel 813 can also be the embodiment of the coherent pixel described above with reference to FIG. 2a. Similarly, coherent pixel 813 can also be the embodiment of the coherent pixel described above with reference to FIG. 2b. For example, the bidirectional optical 2×2 splitter 202 is replaced by an X / (1-X) splitter 802 and a polarization splitter 803, and the optical antenna 200 is replaced by a polarization-insensitive free-space coupler 804. Also, for example, in relation to 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. Also, the polarization splitter is configured to polarize the transmitted signal to have a first polarization (e.g., TE), and polarize the reflected signal to form a return signal having a second polarization (e.g., TM) orthogonal to the first polarization.

[0041] FIG. 9 shows a diagram of a coherent pixel 912 of a second embodiment that uses two polarizations to improve the performance of an FMCW LIDAR system according to one or more embodiments. The second embodiment is substantially similar to the first embodiment except that the polarization splitter 803 and the free-space coupler 804 in the polarization assembly 820 of FIG. 8 are replaced by a single polarization-splitting vertical chip-free-space coupler 903 as shown in FIG. 9. This free-space coupler receives TE light from the left input and generates a free-space beam 904 having TE polarization. On the other hand, the TM light incident on the coupler is coupled to the lower port of the optical device connected to the optical mixer 910. The function and / or structure of the remaining parts of the system according to this second embodiment designated 901, 902, 904, 905, 906, 907, 908, 909, 910, and 911 are substantially the same as 801, 802, 805, 806, 807, 808, 809, 810, 811, and 812.

[0042] Note that in FIG. 9, the functions of the polarization assembly 820 and the polarization - splitting vertical chip - free - space coupler 903 are the same. The polarization assembly 820, for example, combines optical signals from a first waveguide (e.g., 902) to form a transmitted signal, polarizes the transmitted signal to have a first polarization, polarizes a reflected signal (incoupled via 903) based on a second polarization orthogonal to the first polarization to form a return signal, and is configured to couple the return signal (e.g., towards 910) to a second waveguide for optical detection.

[0043] The coherent pixel 912 can be, for example, the coherent pixel 105. The coherent pixel 912 can also be the embodiment of the coherent pixel described above with reference to FIG. 2c. Similarly, the coherent pixel 912 can also be the embodiment of the coherent pixel described above with reference to FIG. 2d. For example, the optical splitter 212 is replaced by an X / (1 - X) splitter 902, and the polarization - splitting antenna 210 is replaced by a single polarization - splitting vertical chip - free - space coupler 903.

[0044] FIG. 10 shows a method of using coherent pixels in a focal plane array (FPA) for FMCW applications according to one or more embodiments. The coherent pixels of FIG. 10 can be, for example, coherent pixel 813 and / or coherent pixel 912. The FPA forms a beam steering device using the coherent pixels. In FIG. 10, light incident on 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 an array of coherent pixels 1004. This array can be one-dimensional or two-dimensional depending on whether one-dimensional or two-dimensional beam steering is required. Each coherent pixel 1005 emits TE-polarized light 1006 that propagates through a quarter-wave plate 1007 that converts the light to circular polarization 1008. The circularly polarized light passes through a lens 1009 composed of one or more lens elements. This lens converts the spatially distributed circularly polarized light beam into an inclined circularly polarized light beam 1010. The output angle of the lens (which is partially determined, for example, by the position of the coherent pixel 1005 that emitted the beam) enables a beam steering operation depending on the position of the input beam and the lens 1009. The inclined beam is reflected from a target 1011. The diffusely reflected light returns to the lens side at the same angle 1012. This reflected light can maintain its circular polarization or be randomly polarized depending on the characteristics of the target. The reflected light beam passes back through the lens 1009 that maps the angle of the beam to a specific position in the FPA. The transmitted beam 1013 passes back through the quarter-wave plate 1007. If the reflected light maintains its circular polarization, the transmitted light 1014 is TM-polarized. If the reflected light is randomly polarized, the transmitted light 1014 has random polarization. The passage of the transmitted light 1014 is recombined, as described above, with the array of coherent pixels 1004 that convert the light to an electrical signal.

[0045] Figures 11a through 11d illustrate electrical wiring schemes for SCPA according to one or more embodiments. The electrical wiring scheme can significantly reduce the number of electrical I / Os for the photon chips of the LIDAR transceiver. Scheme 1 is illustrated in FIGS. 11a and 11b. Scheme 2 is illustrated in FIGS. 11c and 11d. In this example, a 1-8 three-stage binary tree switch network is illustrated with one electrical control signal and a coherent pixel array for each switch, and two electrical outputs (e.g., I / Q signals) for each of the respective coherent pixels. In Scheme 1, switches in the same stage are electrically connected together. With only three switch control signals, the LIDAR system can switch between any of the eight coherent pixels. All the I output signals output from the coherent pixels are connected together as one shared output (RX_I), and all the Q output signals are connected together as another shared output (RX_Q). If only one coherent pixel is activated by the switch network, the remaining coherent pixels receive little light as their transmitter signal or their LO signal. Thus, the shared outputs represent accurate signals from the activated pixel with little crosstalk from adjacent pixels. In this example, Scheme 1 reduces the number of I / O signals to a minimum of five for a total of seven switch inputs and 16 coherent pixel outputs. The reduction in electrical I / Os becomes even more important as the scale of the SCPA increases and / or the number of parallel SCPAs increases. In Scheme 2, two or more coherent pixels can be selected for simultaneous optical transmission and reception. In FIG. 11c, the switch control signals and the coherent pixel output signals are split between the upper and lower halves of a 1-8 binary switch network, generating five switch controls and four receiver outputs. During operation, the first switch is controlled to have a 50 / 50 split ratio at two outputs, transmitting uniform optical power to the upper and lower halves of the 1-8 switch tree.Through independent control and reading capabilities for the upper and lower halves of the tree, one pixel can be activated simultaneously from the upper half and one pixel from the lower half. Method 2 can be applied to Method 1 by operating the first switch stage in normal binary mode, and the splitting ratio of the first switch stage can also be arbitrarily controlled, thus providing a more flexible and potentially software-defined beam scanning option at the cost of some hardware.

[0046] FIG. 12 illustrates a system diagram of an SCPA-based FMCW LIDAR system according to one or more embodiments. Scanner module 1201 includes an SCPA LIDAR chip 1205 having single or multiple FMCW transceiver channels and a lens system 1203 including one or more optical elements. In some embodiments, lens system 1203 is an embodiment of lens system 507.

[0047] 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 circuit for the transceiver may include an input port, multiple optical antennas, an optical switch, multiple splitters, and multiple mixers. The input port is configured to receive a frequency-modulated laser signal. The optical switch is configured to switchably couple the input port to the optical antenna and form an optical path between the input port and the optical antenna. For each optical path directed from the input port to one of the optical antennas, a splitter is coupled along the optical path. The splitter divides the received portion of the laser signal into a local oscillator signal and a transmitted signal - where the transmitted signal is emitted via the optical antenna and the reflection of the transmitted signal is received via the optical antenna as the reflected signal -, and is configured to output a return signal that is a 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, and the mixer is configured to mix the return signal and the local oscillator signal to generate one or more output signals used to determine depth information about the field of view of the LIDAR system (also referred to as the field of view of the scanner module 1201).

[0048] In some embodiments, the lens system 1203 generates a collimated transmitted 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 more along one angular dimension. Also, in embodiments having a two-dimensional array of optical antennas (e.g., a rectangular grid), the signals from the plurality of 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, where the field of view of the scanner module 1201 is 5 degrees or more along the first dimension and 5 degrees or more along the second dimension. The two-dimensional scanning in the above example is performed only by selectively using different coherent pixels from each other.

[0049] 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, a scanning mirror as described above in connection with FIGS. 7b and 7c. In embodiments using the scanning mirror 1202, the field of view of the scanner module 1201 is 5 degrees or more along a first dimension (scanned by selective use of coherent pixels) and 10 degrees or more along a second dimension (scanned at least in part by movement of the scanning mirror 1202). The light source for the LIDAR chip 1205 may be directly integrated on the same chip or coupled via an optical fiber component. As shown, the light source is a FMCW laser source 1207 that generates an optically frequency-modulated signal for FMCW LIDAR operation. The laser source 1207 may be further optically amplified by an optical amplifier 1206 to increase the range of the FMCW LIDAR. The optical amplifier may be a semiconductor optical amplifier (SOA) chip or an erbium-doped optical fiber amplifier (EDFA). The FMCW laser source 1207 is controlled by a laser driver circuit 1208, which is generally a controllable low-noise current source. The output of the coherent pixels is transferred to an array of transimpedance amplifier (TIA) circuits 1211. The on-chip switch is controlled by a switch driver array 1210. The FMCW processing engine can be implemented on one or more FPGA, ASIC, or DSP chips that include the functions of SCPA control and correction 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 correction logic 1213. When implementing the SCPA LIDAR chip 1205 as a CMOS silicon photonics platform, some or all of the electrical circuit functions can be implemented monolithically with a single-chip photonic circuit. The data output 1220 of the FMCW processing engine is depth information.The depth information may include, for example, the 3D position data of a general LIDAR point cloud and other information such as the speed and reflectivity that can be measured by FMCW LIDAR.

[0050] As described above, for a high-performance FMCW LIDAR system, a wide FoV and high pixel speed may be important. It should be noted that the scanner module 1201 can aim for at least 100K points per second across the FoV of the scanning module 1201.

[0051] FIG. 12 illustrates an exemplary LIDAR system. In alternative configurations, different components and / or additional components may be included in the LIDAR system. Further, the functions described in relation to one or more of the components shown in FIG. 12 may be distributed among the components in a different way than that described in relation to FIG. 12. For example, in some embodiments, the SCPA LIDAR chip 1205 can be separated from the scanner module 1201. Additional Configuration Information

[0052] The drawings and the previous description are merely illustrative of preferred embodiments. It should be noted that from what has been discussed above, alternative embodiments of the structures and methods disclosed herein can be readily recognized as viable alternatives that can be adopted without departing from the principles of what is claimed.

[0053] The specific description includes a number of details, but these should not be construed as limiting the scope of the invention and should merely be construed as exemplifying different examples. It should be understood that the scope of the present disclosure includes other embodiments not discussed in detail above. Various other modifications, variations, and changes that will be apparent to those skilled in the art can be made in the arrangement, operation, and details of the methods and apparatuses disclosed herein without departing from the spirit and scope defined in the appended claims. Therefore, the scope of the invention should be determined by the appended claims and their legal equivalents.

[0054] Alternative embodiments are implemented in computer hardware, firmware, software, and / or combinations thereof. An implementation example can be implemented as a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor, and method steps can be performed by a programmable processor executing an instruction program to operate on input data and generate output. Embodiments can be advantageously implemented in one or more executable computer programs in a programmable system including at least one programmable processor coupled to receive and transmit data and instructions for a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language as appropriate, and in some cases, the language can be a compiled or interpreted language. Suitable processors include, by way of example, general-purpose and special-purpose microprocessors. Generally, a processor receives instructions and data from read-only memory and / or random access memory. Generally, a computer includes one or more mass storage devices for storing data files, and these devices include magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and optical disks. Storage devices suitable for tangibly implementing computer program instructions and data include all forms of non-volatile memory, including, by way of example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and CD-ROM disks. All of the foregoing can be supplemented or integrated by application-specific integrated circuits (ASICs) and other forms of hardware. [Items of the Invention] [Item 1] A frequency-modulated continuous-wave (FMCW) LIDAR transceiver implemented on a photonic integrated circuit, wherein the photonic integrated circuit An input port configured to receive a frequency-modulated laser signal, A plurality of optical antennas, An optical switch configured to switchably couple the input port to the optical antennas and form an optical path between the input port and the optical antennas, For each optical path directed to one of the optical antennas from the input port, a splitter coupled along the optical path - the splitter Divides the received portion of the laser signal into a local oscillator signal and a transmitted signal, wherein the transmitted signal is emitted via the optical antenna and the reflection of the transmitted signal is received as a signal reflected via the optical antenna, Is configured to output a return signal that is a part of the reflected signal - and, A mixer coupled to receive the return signal and the local oscillator signal from the splitter for each splitter - the mixer is configured to mix the return signal and the local oscillator signal to generate one or more output signals used to determine depth information about the field of view of the transceiver - and, an FMCW LIDAR transceiver. [Item 2] For each splitter, further includes a polarization assembly coupled along the optical path between the splitter and the optical antenna, the polarization assembly Couples an optical signal from a first waveguide to form the transmitted signal, Polarizes the transmitted signal to have a first polarization, Polarizes the reflected signal based on a second polarization orthogonal to the first polarization to form a return signal, The FMCW LIDAR transceiver according to item 1, configured to couple the return signal to a second waveguide for optical detection. [Item 3] The FMCW LIDAR transceiver according to item 1, including an individual splitter for each of the plurality of antennas, each splitter being coupled along the optical path between the optical switch and the corresponding antenna. [Item 4] The FMCW LIDAR transceiver according to item 1, including only one splitter coupled between the input port and the optical switch. [Item 5] The FMCW LIDAR transceiver according to item 1, wherein the array of the plurality of antennas is selected from a group including a standard array, a linear array, and a rectangular array. [Item 6] The FMCW LIDAR transceiver according to item 1, wherein each of the one or more output signals includes a Quadrature Output Signal and an In-phase Output Signal for each return signal. [Item 7] The optical switch The FMCW LIDAR transceiver according to item 1, including a passive optical splitter that divides the frequency-modulated laser signal between at least two optical paths. [Item 8] The optical switch The FMCW LIDAR transceiver according to item 1, including an active optical splitter that switchably couples the frequency-modulated laser signal to only one of at least two optical paths. [Item 9] The FMCW LIDAR transceiver according to item 8, including a plurality of active optical splitters. [Item 10] The optical switch is the FMCW LIDAR transceiver according to item 1 that optically couples the frequency-modulated laser signals to respective optical antennas one by one during the scanning period of the FMCW transceiver. [Item 11] A frequency-modulated continuous wave (FMCW) LIDAR system, A LIDAR chip including an FMCW LIDAR transceiver implemented on a photonic integrated circuit, A lens, and The photonic integrated circuit An input port configured to receive a frequency-modulated laser signal, A plurality of optical antennas, An optical switch configured to switchably couple the input port to the optical antennas and form an optical path between the input port and the optical antennas, For each optical path directed to one of the optical antennas from the input port, a splitter coupled along the optical path - the splitter Divides the received portion of the laser signal into a local oscillator signal and a transmitted signal, where the transmitted signal is emitted via the optical antenna and the reflection of the transmitted signal is received as a signal reflected via the optical antenna, Is configured to output a return signal that is part of the reflected signal - and For each splitter, a mixer 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 used to determine depth information about the FMCW LIDAR's field of view - and, The lens is positioned to collimate the transmitted signal emitted via the plurality of antennas, The lens also receives the reflected signal and is positioned to couple the reflected signal to the optical antenna that emits the light. FMCW LIDAR system. [Item 12] For each splitter, it further includes a polarization assembly coupled along the optical path between the splitter and the optical antenna, and the polarization assembly couples the optical signal from the first waveguide to form the transmitted signal, polarizes the transmitted signal to have a first polarization, polarizes the reflected signal based on a second polarization orthogonal to the first polarization to form a return signal, The FMCW LIDAR system according to item 11, which is configured to couple the return signal to a second waveguide for optical detection. [Item 13] The FMCW LIDAR system according to item 12, further including a quarter-wave plate positioned along the optical path of the emitted transmitted signal to convert the transmitted signal from a first linear polarization to a circular polarization, and configured to convert the reflected signal from the circular polarization to a second linear polarization orthogonal to the first linear polarization. [Item 14] The lens projects the transmitted signal emitted from the first antenna among the plurality of antennas onto a corresponding portion of the field of view of the FMCW LIDAR system, The FMCW LIDAR system according to item 11, which is configured to provide the reflection of the transmitted signal to the first antenna. [Item 15] The plurality of optical antennas are arranged in a linear array, and the lens generates a collimated transmitted signal that scans the field of view of the transceiver along one angular dimension. The FMCW LIDAR system according to item 11. [Item 16] The FMCW LIDAR system according to item 15, which has a field of view of 5 degrees or more along the one angular dimension. [Item 17] Further includes a scanning mirror configured to scan the transmitted signal in two dimensions within the field of view of the FMCW LIDAR system, wherein the two dimensions are orthogonal to the one angular dimension, and the FMCW LIDAR system according to item 15. [Item 18] The FMCW is configured to emit the plurality of transmitted signals from the plurality of antennas such that the plurality of transmitted signals scan a portion of the field of view of the FMCW LIDAR system in two dimensions, and the FMCW LIDAR system according to item 11. [Item 19] The two dimensions are a first dimension and a second dimension, the field of view of the scanning module is at least 5 degrees along the first dimension, and at least 5 degrees along the second dimension, and the FMCW LIDAR system according to item 18. [Item 20] The FMCW LIDAR system is configured to aim for at least 100K points per second across the field of view of the FMCW LIDAR system, and the FMCW LIDAR system according to item 11.

Claims

1. A light detection and ranging (LiDAR) system for a vehicle, wherein the LiDAR system comprises: a light source configured to emit a light beam; a splitter configured to split the light beam into a transmission signal and a local oscillator signal; a plurality of antennas configured to emit the transmission signal into the environment; a switching device configured to receive the transmission signal, the switching device including a plurality of optical switches arranged in a multi-layer configuration and being operable to sequentially supply the transmission signal to the plurality of antennas; and the transmission signal is emitted via each of the plurality of antennas, and a reflection of the transmission signal is received as a reflected signal via each of the plurality of antennas.

2. The multi-layer configuration comprises: a first group of the plurality of optical switches; a second group of the plurality of optical switches, wherein the second group includes more optical switches than the first group; a third group of the plurality of optical switches, wherein the third group includes more optical switches than the second group; The LiDAR system according to claim 1, comprising.

3. The first group includes one optical switch; The second group includes two optical switches; The LiDAR system according to claim 2, wherein the third group includes four optical switches.

4. The LiDAR system according to claim 1, wherein the switching device includes a binary tree switching network.

5. The LiDAR system according to claim 1, wherein each of the plurality of optical switches includes one or more optical phase shifters.

6. The LiDAR system according to claim 1, wherein each of the plurality of optical switches includes a microring resonator (MRR).

7. The LiDAR system according to claim 1, wherein each of the plurality of optical switches includes a microelectromechanical system (MEMS) switch.

8. The LiDAR system according to claim 1, wherein the plurality of optical switches are independently controlled.

9. The LIDAR system according to claim 8, wherein each of the plurality of optical switches is configured to be electrically controlled using two controls for each optical switch.

10. The LIDAR system according to claim 8, wherein each of the plurality of optical switches is configured as a single-sided optical switch that is electrically controlled using only one control for each optical switch.

11. The LIDAR system according to claim 1, wherein the plurality of optical switches are operable to supply the transmission signal to the plurality of antennas one by one at a time.

12. The LIDAR system according to claim 1, wherein a transmission signal emitted by a first antenna among the plurality of antennas is reflected by an object and becomes a reflected signal received by the first antenna.

13. The LIDAR system according to claim 12, wherein the splitter is further configured to output a return signal that is a part of the reflected signal.

14. The LIDAR system according to claim 1, wherein the light source includes a laser.

15. An FMCW LIDAR transceiver, the FMCW LIDAR transceiver comprising: a light source configured to emit an optical beam; a splitter configured to split the optical beam into a transmission signal and a local oscillator signal; a plurality of antennas configured to emit the transmission signal into the environment; a switching device configured to receive the transmission signal, the switching device including a plurality of optical switches arranged in a multilayer configuration and being operable to sequentially supply the transmission signal to the plurality of antennas; and the transmission signal is emitted through each of the plurality of antennas, and the reflection of the transmission signal is received as a reflected signal through each of the plurality of antennas.

16. The multilayer configuration includes: a first group of the plurality of optical switches; a second group of the plurality of optical switches, wherein the second group includes more optical switches than the first group; a third group of the plurality of optical switches, wherein the third group includes more optical switches than the second group. The FMCW LIDAR transceiver according to claim 15, comprising

17. wherein the first group includes one optical switch, the second group includes two optical switches, the FMCW LIDAR transceiver according to claim 16, wherein the third group includes four optical switches.

18. A LIDAR chip implemented on an optical integrated circuit, the LIDAR chip comprising an FMCW LIDAR transceiver, the FMCW LIDAR transceiver comprising a light source configured to emit a light beam, a splitter configured to split the light beam into a transmission signal and a local oscillator signal, a plurality of antennas configured to emit the transmission signal into the environment, a switching device configured to receive the transmission signal, the switching device including a plurality of optical switches arranged in a multilayer configuration and operable to sequentially supply the transmission signal to the plurality of antennas, comprising a LIDAR chip, wherein the transmission signal is emitted through each of the plurality of antennas, and the reflection of the transmission signal is received as a reflected signal through each of the plurality of antennas.

19. The multilayer configuration of the FMCW LIDAR transceiver includes a first group of the plurality of optical switches, a second group of the plurality of optical switches, wherein the second group includes more optical switches than the first group, a third group of the plurality of optical switches, wherein the third group includes more optical switches than the second group, The LIDAR chip according to claim 18, comprising

20. wherein the first group includes one optical switch, the second group includes two optical switches, the LIDAR chip according to claim 19, wherein the third group includes four optical switches.

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