ON-CHIP MONITORING AND CALIBRATION CIRCUITS FOR FREQUENCY MODULATED CONTINUOUS WAVE LiDAR

Abstract

To solve the problem in which conventional LiDAR systems use mechanical moving parts and bulk optical lens elements to steer a laser beam and, for many applications, are too bulky, costly and unreliable.SOLUTION: A LiDAR chip of a solid state frequency modulated continuous wave (FMCW) LiDAR system includes an optical switch network and a switchable coherent pixel array. The optical switch network selectively provides coherent light to one or more of multiple output waveguides. The SCPA includes coherent pixels (CPs), and each of the CPs emits coherent light provided by corresponding one of the multiple output waveguides. The LiDAR chip includes a monitoring assembly for calibration of the optical switch network and / or an interferometer for calibration of a shape of the waveform used to generate the coherent light.SELECTED DRAWING: Figure 1

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 / 965,094, filed January 23, 2020, and U.S. Provisional Patent Application No. 62 / 966,983, filed January 28, 2020, the entire disclosures of which are incorporated herein by reference.

[0002] The subject matter of this disclosure relates generally to Frequency Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR), and more specifically to Solid State FMCW LiDAR systems. [Background technology]

[0003] Reference interferometers are used by conventional FMCW LiDARs to help characterize and correct for laser chirp nonlinearities. Conventional LiDAR or Optical Coherence Tomography (OCT) systems rely on a reference interferometer with a balanced photodiode to indirectly estimate the laser frequency and calibrate the measurement data. To ensure the accuracy of the reference interferometer and phase extraction from the balanced photodiode, the reference interferometer typically has a long delay line or requires a short delay line and careful bias control (i.e., it can be off-chip). Furthermore, long delay lines are generally a challenge for integrated photonics due to the high losses that occur in small waveguides. Also, the performance of the FMCW laser can drift over various time scales over the course of several measurements with temperature or other environmental conditions, or over the lifetime of the FMCW sensor.

[0004] Conventional LiDAR systems use mechanical moving parts and bulk optical lens elements (i.e., refractive lens systems) to steer the laser beam, making them too bulky, expensive, and unreliable for many applications (e.g., automotive). Summary of the Invention

[0005] A LiDAR chip of the solid-state FMCW LiDAR system includes an Optical Switch Network, a Switchable Coherent Pixel Array (SCPA), and a Monitoring Assembly. The Optical Switch Network is on the LiDAR chip. The Optical Switch Network is configured to selectively provide coherent light to one or more of a plurality of output waveguides. The SCPA is on the LiDAR chip. The SCPA includes respective Coherent Pixels (CPs), each CP configured to emit coherent light provided by a corresponding output waveguide of the plurality of output waveguides. The Monitoring Assembly is on the LiDAR chip. The Monitoring Assembly includes a plurality of photodetectors, each of the plurality of photodetectors configured to generate an output signal in response to a level of light detected from a corresponding output waveguide of the plurality of output waveguides. The optical switch network is calibrated (eg, by a controller) by adjusting the Drive Strength of a switch driver for the optical switch network based on an output signal from the monitoring assembly.

[0006] In some embodiments, the LiDAR chip includes a splitter, an interferometer, an optical switch network, and an SCPA. The splitter is on the LiDAR chip. The splitter is configured to separate the coherent light into a first portion and a second portion. The coherent light is chirped based on a waveform. The interferometer is on the LiDAR chip. The interferometer is configured to generate an in-phase (I) signal and a quadrature (Q) signal using the first portion of the coherent light. The optical switch network is on the LiDAR chip. The optical switch network is configured to selectively provide the second portion of the coherent light to one or more of the multiple output waveguides. The SCPA is on the LiDAR chip. The SCPA includes CPs, each CP configured to emit the coherent light provided by a corresponding output waveguide of the multiple output waveguides. The controller is configured to identify a frequency deviation of the coherent light based in part on the I and Q signals, and to control a shape of the waveform based in part on the I and Q signals to compensate for the identified deviation. In some embodiments, the LiDAR chip may also include a monitoring assembly, as described in the previous paragraph.

[0007] In some embodiments, the LiDAR chip is part of a Focal Plane Array (FPA) system of a solid-state FMCW LiDAR system. The FPA system includes a splitter, an interferometer, an optical switch network, an SCPA, a monitoring assembly, and a lens system. The splitter is on the LiDAR chip. The splitter is configured to separate the coherent light into a first portion and a second portion, and the coherent light is chirped according to a waveform. The interferometer is on the LiDAR chip. The interferometer is configured to generate an I signal and a Q signal using the first portion of the coherent light. The optical switch network is on the LiDAR chip. The optical switch network is configured to selectively provide the second portion of the coherent light to one or more of the multiple output waveguides. The SCPA is on the LiDAR chip. The SCPA includes CPs, each CP configured to emit the coherent light provided by a corresponding output waveguide of the multiple output waveguides. The monitoring assembly is on the LiDAR chip. The monitoring assembly includes a plurality of photodetectors, each of the plurality of photodetectors configured to generate an output signal in response to a level of light detected from a corresponding one of the plurality of output waveguides. The lens system is arranged to direct the coherent light emitted from the SCPA into an environment as one or more light beams, each of the one or more light beams being emitted at a particular angle, the particular angle being based in part on a location of CPs on the LiDAR chip that generated the coherent light forming the one or more light beams. The controller identifies a frequency deviation of the coherent light based in part on the I and Q signals, and controls a shape of the waveform based in part on the one to compensate for the identified deviation. The controller is also configured to calibrate the optical switch network based on the output signal of the monitoring assembly. [Brief description of the drawings]

[0008] Other advantages and features of the embodiments of the present disclosure will become more clearly apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawing examples.

[0009] [Figure 1] 1 illustrates solid-state scanning using a switchable coherent pixel array chip on a LiDAR chip in accordance with one or more embodiments.

[0010] [Diagram 2] 1 illustrates the basic structure and signal flow of an On-chip Monitoring Assembly in accordance with one or more embodiments.

[0011] [Diagram 3] FIG. 2 is a diagram of a crossbar readout scheme for a linear array of monitoring photodetectors in a multi-channel switchable coherent pixel array with a reduced number of inputs / outputs (I / O) in accordance with one or more embodiments.

[0012] [Figure 4a] FIG. 1 illustrates a hierarchical readout scheme for a monitoring photodetector of a single channel switchable coherent pixel array with a reduced number of I / Os in accordance with one or more embodiments.

[0013] [Figure 4b] FIG. 1 illustrates a hierarchical readout scheme for a monitoring photodetector of a multi-channel switchable coherent pixel array with a reduced number of I / Os in accordance with one or more embodiments.

[0014] [Figure 5a] FIG. 1 is a diagram of a Hybrid-coupled Interferometer with post-processing feedback for a Direct Laser Drive in accordance with one or more embodiments.

[0015] [Figure 5b] FIG. 1 is a diagram of a hybrid coupled interferometer with post-processing feedback for a modulator driver in accordance with one or more embodiments.

[0016] [Figure 6] 1 illustrates a process for laser waveform generation and FMCW calibration according to one or more embodiments.

[0017] [Figure 7] 1 illustrates a solid-state LiDAR system including an FPA system according to one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A solid-state FMCW LiDAR system determines depth information (e.g., distance, velocity, and acceleration for one or more objects) for the system's Field of View. A solid-state FMCW LiDAR directs a frequency-modulated collimated light beam into a local area to directly measure the distance and velocity of objects. The signal, which is light reflected from objects in the local area, is mixed with a tapped version of the beam called the Local Oscillator (LO). When corrected for Doppler Shift, which requires additional measurements, the frequency of the resulting Radiofrequency (RF) Beat signal is proportional to the distance of the object from the LiDAR system. The two measurements, which may or may not be made simultaneously, provide the range and velocity information of the target.

[0019] The solid-state FMCW LiDAR system uses on-chip monitoring and calibration circuits to achieve high-performance solid-state beam steering and laser chirping. The solid-state FMCW LiDAR system includes a Focal Plane Array (FPA) system. The FPA includes one or more Switchable Coherent Pixel Arrays (SCPA). One or more SCPAs can be placed at the focal plane of the lens system such that the FPA system can perform solid-state beam steering for a single dimension and / or two dimensions. The direction of the incoming beam is mapped to the discrete location of the focused spot and vice versa. One of the challenges of SCPA is to maintain optimal calibration settings for the switch network so that low insertion loss, high extinction ratio, and low crosstalk can be achieved at any time. The solid-state FMCW LiDAR system enables in-situ calibration or real-time closed-loop control of the high-performance solid-state beam steering with an on-chip feedback mechanism.

[0020] The on-chip feedback mechanism facilitates maintaining a high quality laser chirp by solid-state FMCW LiDAR, which senses distance by measuring the interference between local and target path optical signals. By sweeping the frequency of the laser, the interference signal becomes an oscillation with a frequency proportional to the target distance. The FMCW laser is modulated to have a linear frequency sweep from lower to higher and from higher to lower in a triangular fashion. Often, lasers tuned in this manner need to be tuned with a specific drive signal or the frequency sweep may deviate significantly from linear. Linearity deviations cause significant inaccuracies in distance and velocity measurements derived using FMCW LiDAR.

[0021] In some embodiments, the solid-state FMCW LiDAR system uses on-chip monitoring and calibration circuitry for solid-state beam steering realized by one or more integrated SCPAs. The solid-state FMCW LiDAR system enables in-situ calibration or real-time closed-loop control of the optical switch network using on-chip optical power monitoring circuitry. For example, the LiDAR chip includes (i.e., on-chip) an optical switch network, an SCPA, and a monitoring assembly. The optical switch network is configured to selectively provide coherent light to one or more of a plurality of output waveguides. The SCPA includes coherent pixels (CPs), each CP configured to emit the coherent light provided by a corresponding one of the plurality of output waveguides. The monitoring assembly includes a plurality of photodetectors (PDs), each of which is configured to generate an output signal in response to a level of light detected from a corresponding one of the plurality of output waveguides. The optical switch network is calibrated by adjusting (eg, by a controller) the drive strength of a switch driver for the optical switch network based on the output signal of the monitoring assembly.

[0022] One or more SCPAs are placed at the focal plane of the lens system for rapid solid-state beam steering and coaxial FMCW LiDAR operation. An on-chip optical monitoring circuit with optical couplers and monitoring PDs monitors the optical power at the output ports of the optical switch network. This design allows for in-situ calibration and real-time closed-loop control without affecting the CPs or disturbing the normal operation of the LiDAR. For large-scale or multi-channel SCPAs, a crossbar-type or hierarchical (e.g., Binary Tree) connection scheme can be used to read signals from any monitoring PDs, which greatly reduces the number of I / Os and receivers for the monitoring circuit.

[0023] In some embodiments, the solid-state FMCW LiDAR system uses on-chip monitoring and calibration circuitry to generate a high-quality laser chirp signal. For example, the LiDAR chirp may include (i.e., on-chip) a splitter, an interferometer, an optical switch network, and an SCPA. The splitter is configured to separate the coherent light into a first portion and a second portion. The coherent light is chirped according to a waveform. The interferometer is configured to generate an I (In-phase) signal and a Q (Quadrature) signal using the first portion of the coherent light. The optical switch network is configured to selectively provide the second portion of the coherent light to one or more of the multiple output waveguides. The SCPA includes CPs, each CP configured to emit the coherent light provided by a corresponding one of the multiple output waveguides. The controller is configured to identify a frequency deviation of the coherent light based in part on the I and Q signals, and control the shape of the waveform to compensate for the identified deviation. In some embodiments, the LiDAR chirp may include a monitoring assembly, as described in the previous paragraph.

[0024] The solid-state FMCW LiDAR system uses a Frequency Discrimination Interferometer with an Optical Hybrid for calibration of the laser driver and a Swept-Source Laser. In some embodiments, a programmable laser driver (current or voltage source) directly drives a Tuning Laser Source to generate alternating positive and negative frequency sweeps. In other embodiments, a programmable modulator driver directly drives a Modulator to induce positive and negative frequency sweeps in a Seed Laser Beam. This leads to an Interferometer that includes a splitter that sends the light into two paths (one "local" path and one "reference" path), an Optical Combiner known as a "90 degree Optical Hybrid", a Photoreceiver with multiple photodetectors, and a controller for signal processing. The controller uses the output of the Optical Hybrid to calculate the instantaneous signal phase and laser frequency. The resulting instantaneous laser frequency is fed back to the drive signal generator to compensate for the laser frequency deviation from linearity. Interferometers and optical hybrids can also be used to calibrate the residual error of the predistortion process or non-linearity due to laser / environment drift. Thus, the solid-state FMCW LiDAR system performs in-situ generation of the laser driver signal and in-situ calibration of the residual non-linearity and laser performance drift.

[0025] It should be noted that in some embodiments, the monitoring assembly for calibration of the optical switch network and the interferometer with optical hybrid for laser driver calibration can all be implemented on the same LiDAR chip. In this way, the LiDAR chip can not only calibrate the optical switch network, but also the laser driver.

[0026] As mentioned above, conventional LiDAR systems that use interferometers to help characterize and compensate for laser chirp nonlinearities have long or short delay lines and careful bias control. Long delay lines are problematic for Integrated Photonics due to high losses that occur in small waveguides and can be off-chip. Similarly, careful bias control is typically associated with increased complexity in the control circuitry. On the other hand, solid-state FMCW LiDAR systems perform laser frequency measurements using on-chip short delay lines without complex bias control. Solid-state FMCW LiDAR systems are also configured to measure the laser frequency and dynamically adjust the laser drive waveform to account for changes in laser characteristics over time or environmental conditions.

[0027] It should be noted that the LiDAR chip can steer the light emitted from the solid-state LiDAR system in at least a first angular dimension (e.g., altitude). And the solid-state FMCW LiDAR system may include, for example, a scanning mirror (e.g., a moving mirror, a polygon mirror, etc.) to steer the light in a different angular dimension (e.g., azimuth). And in some embodiments, the optical antennas are arranged in two dimensions within one or more SCPAs so that the LiDAR chip can steer the light beam in two dimensions (e.g., azimuth and altitude). The ability to steer the beam without moving parts can alleviate form factor, cost, and reliability issues found in many conventional mechanically driven LiDAR systems.

[0028] FIG. 1 illustrates solid-state scanning using a switchable coherent pixel array chip on a LiDAR chip 106 according to one or more embodiments. The LiDAR chip 106 is part of an FPA system configured to scan a local area. The LiDAR chip 106 is based on a Photonic Integrated Circuit (e.g., Silicon Photonics). The LiDAR chip 106 includes one or more FMCW LiDAR transceiver channels 101. The FMCW LiDAR transceiver channels 101 include an FMCW light source 102, an optical switch network 103, a monitoring assembly 110, and an SCPA 115. As shown, the FMCW light source 102 is integrated directly on the LiDAR chip 106. In other embodiments, the FMCW light source 102 is not part of the LiDAR chip 106, and instead light from the FMCW light source 102 is coupled into the LiDAR chip 106 from an external source. The FMCW light source 102 can be split light between different FMCW LiDAR transceiver channels on the LiDAR chip 106 or different LiDAR chips. The light can also be amplified by a fiber amplifier or semiconductor amplifier chip. The optical switch network 103 switches the guided light between output ports and activates coherent pixels associated with the selected ports. The optical switch network 103 is configured to selectively provide the coherent light to one or more of a plurality of output waveguides that couple to various coherent pixels of the SCPA 115. The monitoring assembly 110 can be located anywhere on the chip after the optical switch network 103 or as an integral part of the optical switch network 103. As an example, the monitoring assembly 110 can be located between the optical switch network 103 and the SCPA 104 as shown. The monitoring assembly 110 includes a plurality of photodetectors.Each of the plurality of photodetectors is configured to generate an output signal in response to a level of light detected from a corresponding one of the plurality of output waveguides. The optical switch network 130 is calibrated by adjusting a drive strength of a switch driver for the optical switch network 103 based on the output signal of the monitoring assembly 110. Embodiments of the monitoring assembly 110 are described below in conjunction with Figures 2, 3, 4a and 4b.

[0029] The SCPA 115 includes coherent pixels, each of which is configured to emit coherent light provided by a corresponding output waveguide among the multiple output waveguides. Each coherent pixel includes an optical antenna 105 for emitting and receiving optical signals and other passive and active optical components for generating an RF signal, such as a waveguide, a coupler, a hybrid, a grating, and a photodetector. The SCPA 115 is disposed at a focal plane of a lens system 107. The lens system 107 includes one or more optical elements (e.g., a positive lens, a freeform lens, a Fresnel lens, etc.) that map the physical location of each coherent pixel to a specific direction. In some embodiments, the lens system 107 is disposed to collimate a transmission signal emitted through the multiple optical antennas 105. The lens system 107 is configured to project a transmission signal emitted from the optical antenna among the multiple antennas to a corresponding portion of the field of view of the FPA system and provide a reflection of the transmission signal to the optical antenna. Each optical antenna transmits and receives light at a different angle. Thus, discrete optical beam scanning is achieved by switching to different antennas. The FPA system scans the laser beam 108 over targets in the field of view of the FPA system, and coherent pixels in the FPA system generate electrical signals that are then digitally processed to generate a LiDAR Point Cloud. The lens system 107 generates collimated transmit signals that scan the transceiver's field of view along one or more angular dimensions (e.g., perform a 2D scan of a local area). Note that by switching light to different coherent pixels, the LiDAR chip 106 emits or receives collimated laser beams 108 at different angles, enabling discrete solid-state scanning and co-axial optical sensing for single or multiple channels in parallel.

[0030] FIG. 2 illustrates a basic structure and signal flow of the on-chip monitoring assembly 110 according to one or more embodiments. The on-chip monitoring assembly 110 monitors the coherent light emitted from the output of the optical switch network 103. The on-chip monitoring assembly 110 includes one or more monitoring circuits 200. The monitoring circuits 200 may include, for example, an optical coupler 202, a monitoring photodetector (PD) 203, and output waveguides 204a, 204b. The optical switch network has a plurality of output ports. The optical switch network 103 is configured to switch light from the FMCW source between the output ports. Each output port is then coupled to a respective output waveguide (e.g., output waveguide 201). Furthermore, some of the output waveguides 201 may be internal routing waveguides in the optical switch. The monitoring assembly 110 includes a number of optical couplers configured to tap a portion of the coherent light provided to a number of output waveguides and provide the portion of the light to a number of optical detectors. In some embodiments, each optical coupler has a different corresponding optical detector among the number of optical detectors to which the optical coupler provides the tapped portion of the coherent light. For example, the optical coupler 202 taps the optical power (i.e., the coherent light) from the output waveguide 201 at the output port of the optical switch network 103 and provides the tapped optical power (i.e., the portion of the coherent light output from the output port) to the monitoring PD 203 via the output waveguide 204a. The optical power is converted to an electrical signal via the monitoring PD 203. The optical coupler 202 outputs the remaining optical power via the output waveguide 204b. The output waveguide 204b provides the light to the next stage (e.g., a coherent pixel) in the FMCW LiDAR transceiver channel 101.

[0031] The electrical signals from the one or more monitoring circuits 200 are then processed through a receiver 206. The receiver may include, for example, an amplifier, an integrator, a switch, etc. The data output from the receiver 206 is quantized by an analog to digital converter (ADC) 207. The output of the ADC 207 is then processed by a controller 208. The controller 207 may include, for example, a control circuit, a computer processor, a field-programmable gate array (FPGA), a digital signal processor, a microcontroller, an application specific integrated circuit (ASIC), or some combination thereof. As shown, the receiver 206, the ADC 207, the controller 208, and the switch driver 209 are separate from the LiDAR chip 106. In other embodiments, some or all of the receiver 206, the ADC 207, the controller 208, and the switch driver 209 may be integrated into the LiDAR chip 106. Additionally, although a single receiver 206 and a single ADC 207 are shown, in some embodiments there may be multiple receivers 206 and corresponding ADCs. For example, there may be a separate receiver 206 and a separate corresponding ADC 207 for each monitoring circuit.

[0032] The closed loop calibration and / or control is performed by adjusting the drive strength of the switch driver 209 for the optical switch network 103 based on the output of the monitoring circuit. The calibration of the optical switch network 103 ensures that light is delivered to one or more target CPs with minimum power and mitigates light delivered to non-target CPs. Note that the calibration of the optical switch network 103 occurs within the solid-state FMCW LiDAR system and no external equipment is required. For large or multi-channel switchable coherent pixel arrays, there may be hundreds of coherent pixels, hundreds of switch ports, and therefore hundreds of monitoring PDs. Thus, in some cases, electrical I / O constraints may make it impractical to assign individual electrical I / O pads / traces to each monitoring PD.

[0033] FIG. 3 is a diagram of a crossbar readout scheme for a linear array of monitoring photodetectors in a multi-channel switchable coherent pixel array with a reduced number of inputs and outputs (I / Os) according to one or more embodiments. The crossbar type interlocking scheme can significantly reduce the number of electrical I / Os required for the monitoring circuitry while reading the signals of any monitoring PD 203. In FIG. 3, the FPA system includes a LiDAR chip 106, which includes multiple LiDAR transceiver channels 101. The LiDAR transceiver channels 101 can also be sub-blocks in a larger switch network. The LiDAR chip includes n channels and N rows of monitoring circuits (and corresponding coherent pixels), where n and N are integers. Thus, each monitoring PD can be identified with a channel and a row. Thus, each photodetector of each monitoring assembly has a corresponding row value ranging from 1 to N and a corresponding channel value ranging from 1 to n. For example, the monitoring PD for channel "k" and row "j" is labeled as "PD_k_j."

[0034] The crossbar type connection scheme is independent of the polarity of the monitoring PD. In this example, the cathodes of the monitoring PDs having the same row number are connected to form a corresponding signal group (also called a node), and the anodes of the monitoring PDs having the same channel value are connected to form a corresponding bias group. For example, as shown, there are n channels, and the cathodes associated with row N are connected to form a corresponding signal group 303. Thus, there are N signal groups. Similarly, the anodes of the monitoring PDs having the same channel value are connected to form a corresponding signal group (also called a node), and accordingly there are n signal groups. For example, as shown, the anodes of the monitoring PDs of channel 1 are connected to form a corresponding signal group 302.

[0035] Any monitoring PD can be selected for reading by selecting the corresponding pixel and row number with one or two analog multiplexers (MUX) (e.g., MUX 304 or MUX 306). MUX 304 and / or MUX 306 can be controlled by the controller 208. For example, the controller 208 can configure MUX 304 and / or MUX 306 to read one or more monitoring PDs. MUXs 304, 306 (e.g., switches) can be implemented on the same LiDAR chip 106 or outside the LiDAR chip 106. For example, the output of MUX 306 can be coupled to a constant bias voltage 307 to provide a reverse bias for the monitoring PDs, and a signal group (e.g., signal group 302) can be used to output a current signal. To read out a current from PD_k_j, the FPA system can open all switches except switch “j” and process the signal of the kth monitoring PD output. In this example, when switch 3 of MUX 306 is on and the remaining switches are off, only the third monitoring PD is activated in each channel. The monitoring PD output can be additionally multiplexed using MUX 304 to reduce the number of receiving channels. This scheme allows independent optical power monitoring at every port of the entire switch network without assigning individual electrical I / O traces / pads to each monitoring PD. To avoid leakage current from unselected monitoring PDs from other activated channels, it is preferable to keep one channel activated during the monitoring and calibration process, which can be achieved by turning off the laser source or laser amplifier for other channels where no monitoring PD is selected. The monitoring and calibration process for such a scheme can occur during power on or frame changeover.

[0036] 4a and 4b show a hierarchical readout scheme for monitoring photodetectors that overcomes the limitations of the crossbar readout scheme. FIG. 4a is a diagram of a hierarchical readout scheme for monitoring photodetectors of a single channel switchable coherent pixel array with reduced number of I / Os according to one or more embodiments. In FIG. 4a, the optical switch network is in the form of a binary tree. In FIG. 4a, multiple Optical Switch Cells, multiple optical couplers, and multiple optical detectors are arranged to form a binary tree with multiple levels. In this example, the 1-to-8 switch tree takes a single input and routes it to one of eight coherent pixels P0-P7 through three stages of 1×2 optical switch cells 402. Each optical switch cell can steer optical power from an input waveguide to one of two output waveguides. In this scheme, there are optical couplers 403 and monitoring PDs 404 at both output ports of each switch cell to monitor the power flow and calibrate the switch tree in a hierarchical manner. For a 1-to-8 switch, there are a total of 14 monitoring PDs.

[0037] To reduce the number of electrical I / Os, the PD biases 406 and PD output signals can be concatenated together. For each level in the binary tree, the outputs of the monitoring PDs with odd indices can be concatenated together to form a first signal, and the outputs of the monitoring PDs with even indices can be concatenated together to form a second signal. For a 1-to-8 switch with 14 hierarchical monitoring PDs, the total number of electrical I / Os for optical power monitoring and corresponding receivers 405 is reduced from 14 to 6. More generally, for a 1-to-2 switch with 14 hierarchical monitoring PDs, the total number of electrical I / Os for optical power monitoring and corresponding receivers 405 is reduced from 14 to 6. N For switches, the number of monitoring I / O and receivers is 2 N+1 pcs to 2 N , which becomes more pronounced as N increases.

[0038] As an example, to calibrate the switch settings so that all light is directed to the coherent pixel P2, the controller 208 starts by reading the monitoring signals from the receivers L0 and H0 and optimizing the control signal for SW0 that maximizes the L0 reading and minimizes the H0 reading. The controller (e.g., the controller 208) then moves to the next stage and optimizes the control signal for SW1_0 that maximizes H1 and minimizes L1. For the last stage, SW2_1, the controller tries to maximize L2 and minimize H2. This hierarchical calibration process minimizes leakage and crosstalk from the unselected photodetectors. It is also electrically isolated from the sensitive coherent pixel cells, which require low noise and high speed operation for FMCW LiDAR. This allows for in-situ calibration and real-time closed-loop control without affecting the coherent pixels or interfering with the normal operation of the LiDAR.

[0039] FIG. 4b is a diagram of a hierarchical readout scheme for a monitoring photodetector of a multi-channel switchable coherent pixel array with a reduced number of I / Os according to one or more embodiments. FIG. 4b shows how to extend the scheme of FIG. 4a from a single channel to multiple channels. In FIG. 4b, the LiDAR chip includes n channels (n=4 in this case, but may have other values ​​in other embodiments), each channel includes a respective optical switch network, a respective SCPA, and a respective monitoring assembly. Each channel includes a plurality of optical switch cells, a plurality of optical couplers, and a plurality of photodetectors arranged to form a binary tree with multiple levels. In FIG. 4b, the output signals of the even or odd monitoring PDs at each level are combined together at the LiDAR chip 106 across different channels. As long as the same pixels are activated at any given moment, the same calibration and closed-loop control can be performed simultaneously by a controller (e.g., controller 208) for all channels.

[0040] FIG. 5a is a diagram of a hybrid coupled interferometer with post-processing feedback for a Direct Laser Driver according to one or more embodiments. A Periodic Wave (voltage or current) waveform from the laser driver 512 is used to drive the laser 506. In general, the output of the laser 506 is a sequence of upward and downward sweeps of the laser frequency, called Up and Down Chirps, respectively. These sequences of laser chirps are used for both FMCW probing and the frequency determination process described below. The splitter 500 diverts a portion of the laser power to the LiDAR transceiver 505 so that the chirped laser is used as a probing field in the FMCW sensor. The LiDAR transceiver 505 may include one or more FMCW LiDAR transceiver channels 101, each including a monitoring assembly 110. Thus, the hybrid coupled interferometer with post-processing feedback for direct laser driver shown herein may also be combined with the features shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4a, FIG. 4b or some combination thereof. In some embodiments, the LiDAR transceiver 505 may not include the monitoring assembly 110. The splitter 500 is configured to split the coherent light chirped according to the waveform into a first part and a second part. The interferometer 550 is configured to generate I and Q signals using the first part of the coherent light. The splitter 500 also diverts some power to another splitter 501 of the interferometer 550. The splitter 501 can distribute the power between two arms, one of which is a delay arm 502. The delay arm 502 is delayed with respect to the other arm such that a beat signal is generated when the two arms are combined at the optical hybrid coupler 503.The optical hybrid coupler 503 has four outputs configured to be optically phase shifted with respect to each other to generate a 0 degree shifted optical signal, a 90 degree shifted optical signal, a 180 degree shifted optical signal, and a 270 degree shifted optical signal. The 0 degree shifted signal and the 180 degree shifted signal are measured with a balanced photodetector 504 which generates an "I-channel" signal, and the 90 degree shifted signal and the 270 degree shifted signal are measured with another balanced photodetector which generates a "Q-channel" signal. The I channel and Q channel signals are phase shifted 90 degrees with respect to each other. Each channel is buffered and amplified by a receiver circuit 509 and sampled by an ADC 510. The sampled I and Q signals are used by a controller 511. The controller 511 may be an embodiment of the controller 208. The resulting measured laser frequency is used by the controller 511 to generate a new waveform to compensate for the linear deviation of the laser frequency. The waveform is generated by controller 511 and used to drive laser driver 510. Since interferometer temperature deviations can cause deviations in the effective index of the delay arm 502, a temperature sensor 507 can be used to compensate for this deviation in the calculations made by controller 511.

[0041] FIG. 5b is a diagram of a hybrid-coupled interferometer with post-processing feedback for a modulator driver according to one or more embodiments. FIG. 5b is substantially similar to FIG. 5b, except that the laser chirp is generated using a seed laser 506 and a laser modulator 514. The laser modulator 514 can be a phase modulator or an intensity modulator, such as a Dual Mach Zehnder Modulator for I / Q modulation. The laser modulator 514 is driven by a voltage or current signal from a modulator driver 513. The generated chirp from the output of the laser modulator 514 is sent through a splitter 500. The components inside the dotted line 515 can be the same blocks as the components inside 515 in FIG. 5a. In the same manner as FIG. 5a, the controller 511 generates a control signal used as an input to the modulator driver 513 to compensate for deviations from a linear laser frequency chirp at the output of the laser modulator 514.

[0042] FIG. 6 illustrates a process for laser waveform generation and FMCW calibration according to one or more embodiments. The calibration process can reduce and remove nonlinearities from the laser's upward and downward chirps. The process illustrated in FIG. 6 may be performed by a controller of a solid-state FMCW LiDAR system. In other embodiments, other entities may perform some or all of the steps in FIG. 6. Embodiments may include different and / or additional steps or perform steps in a different order.

[0043] The solid-state FMCW LiDAR system loads the drive waveform 605. For example, a microcomputer of a LiDAR processing engine of the solid-state FMCW LiDAR system can load the drive waveform. The drive waveform may be a general drive waveform or a previously stored drive waveform.

[0044] The solid-state FMCW LiDAR system frequency modulates a laser source with the loaded drive waveform 610. The modulated light forms one or more laser chirps. The frequency modulation can be performed by a laser controller that modulates a K-channel laser array according to the instructions of the LiDAR processing engine.

[0045] The solid-state FMCW LiDAR system measures one or more laser chirps to form I and Q signals 615. For example, the solid-state FMCW LiDAR system can measure one or more laser chirps using an optical hybrid photodetector to generate an I / Q signal, e.g., as shown and described in connection with Figures 5a and 5b.

[0046] The solid-state FMCW LiDAR system processes the I and Q signals 620. For example, the solid-state FMCW LiDAR system may filter and / or sample the I and Q signals. The solid-state FMCW LiDAR system may process the I and Q signals using a LiDAR processing engine.

[0047] The solid-state FMCW LiDAR system determines the phase of the processed I and Q signals 625. The solid-state FMCW LiDAR system may determine the phase of the processed I and Q signals using the LiDAR processing engine. The phase may be determined, for example, by calculating the arc-tangent of the quotient of the processed I and Q signals. This is equivalent to measuring the phase angle of a signal produced by multiplying the Q channel by the imaginary number i and adding the I channel to the modified Q channel.

[0048] The solid-state FMCW LiDAR system uses the phase to determine the instantaneous frequency of the laser 630. The instantaneous frequency of the laser may be determined, for example, by dividing the phase calculated in the previous step by the optical path time delay of the delay arm (e.g., delay arm 502).

[0049] The solid-state FMCW LiDAR system controls the driving waveform of the laser source based in part on the instantaneous frequency to generate a modified output beam 635. The solid-state FMCW LiDAR system monitors the magnitude of deviation in the instantaneous frequency of the laser at different Time Instances. The solid-state FMCW LiDAR system adjusts the driving waveform (e.g., adjusts the shape of the driving waveform) based on the magnitude of the deviation to compensate for a slower or faster Chirp Rate. Such adjustments may be made one time by updating a pre-loaded laser model and adjusting the driving waveform through an analytical solution, or iteratively by adjusting a parameterized driving waveform through a Gradient Descent Optimization algorithm. The controlled driving waveform is then applied again to the laser source to generate a modified output beam. Note that steps 615-635 may be iterative and may be looped one or more times in a calibration run.

[0050] The solid-state FMCW LiDAR system collects FMCW measurements with the modified output beam 640. The solid-state FMCW LiDAR system scans the modified output beam over a local region (e.g., via an FPA system) and measures reflections of the modified output beam from one or more objects in the local region to generate FMCW measurements.

[0051] The solid-state FMCW LiDAR system uses the FMCW measurements to determine range and / or velocity data 645. The solid-state FMCW LiDAR system estimates range and velocity data using the FMCW measurements based on the expected chirp rate of the laser. If residual deviations from linearity still exist, these are measured by the same process 605-630 and used to adjust the range and / or velocity data calculations. This process results in a more accurate point cloud.

[0052] FIG. 7 illustrates a solid-state LiDAR system including an FPA system 705 according to one or more embodiments. The FPA system 705 may be a reciprocal system. The FPA system 705 includes a lens system 702 and a LiDAR chip 106. The LiDAR chip 106 and the FPA system 705 include some or all of the components and / or some or all of the functions described above in connection with FIGS. 1-6. The CPs in the LiDAR chip 106 are part of one or more SCPAs 101 (e.g., of an FMCW transceiver channel 101) controlled by an FPA driver 710. One or more individual CPs in the LiDAR chip 106 can be activated to emit and receive light. The light emitted by the LiDAR chip 106 is generated by a K-channel laser array 715. The K-channel laser array 715 is a laser array having K parallel channels, where K is an integer. The K-channel laser array 715 may be directly integrated with the LiDAR chip 106 or may be a separate module packaged with the LiDAR chip 106. The K-channel laser array 715 is controlled by a laser controller 720. In some embodiments, the K-channel laser array 715 is tunable over a range of wavelengths.

[0053] The laser controller 720 receives control signals from the LiDAR processing engine 725 via a digital-to-analog converter 730. The processing also controls the FPA driver 710 to send and receive data from the LiDAR chip 106.

[0054] The LiDAR processing engine 725 includes a microcomputer 735. The microcomputer 735 processes data from the FPA system and sends control signals to the FPA system via the FPA driver 710 and the laser controller 720. Note that the microcomputer 735 may include the controller 208 and / or the controller 511. The LiDAR processing engine 725 also includes an N-channel receiver 740. Signals are received by the N-channel receiver 740 and the signals are digitized using a set of M-channel ADCs 745.

[0055] It should be noted that the LiDAR chip 106 can steer the light emitted from the solid-state LiDAR system in one or more angular dimensions. In some embodiments, the LiDAR chip 106 is configured to steer the beam only in a first angular dimension (e.g., elevation). The FPA system 705 can include one or more scan mirrors (not shown) that can steer the light beam in a second dimension (e.g., azimuth) (e.g., orthogonal to the first angular dimension). The scan mirrors receive light from the lens system 705 and direct the received light to a target area along a particular angular field of view determined by the first angular dimension (controlled by the LiDAR chip 106) and the second angular dimension (controlled by the one or more scan mirrors). It should be noted that the above examples using one or more scan mirrors relate to a LiDAR chip 106 configured to scan only in a first angular dimension. However, in some embodiments, one or more scan mirrors can be used with a LiDAR chip 106 configured to scan in multiple angular dimensions (e.g., azimuth and elevation). For example, a two-dimensional array of optical antennas (eg, a rectangular grid) can be used to scan signals from multiple optical antennas in two dimensions within the field of view of one or more scanning mirrors.

[0056] Additional configuration information The drawings and the foregoing description relate to preferred embodiments by way of example only. As noted above, alternative embodiments of the structures and methods disclosed herein are readily discernible as viable alternatives that may be employed without departing from the principles of the claims.

[0057] Although the detailed description includes many details, these should not be interpreted as limiting the scope of the present invention, but merely as illustrating different examples. It should be understood that the scope of the present disclosure includes other embodiments not described in detail above. Various other modifications, changes and changes that are obvious to those of ordinary skill in the art may be made in the arrangement, operation and details of the methods and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims. Therefore, the scope of the present invention should be determined by the appended claims and their legal equivalents.

[0058] Alternative embodiments are implemented in computer hardware, firmware, software and / or combinations thereof. Implementations may be implemented as a computer program product substantially embodied in a machine-readable storage device for execution by a programmable processor, and method steps may be performed by the programmable processor executing an instruction program to perform functions by operating on input data and generating output. The embodiments may advantageously be implemented in one or more computer programs executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and transmit data and instructions from, a data storage system, at least one input device and at least one output device. Each computer program may be implemented in a high level procedural or object-oriented programming language, or assembly or machine language as appropriate, and in any case the language may be a compiled or interpreted language. Suitable processors include, by way of example, general-purpose and special-purpose microprocessors. Typically, the processor receives instructions and data from a read-only memory (ROM) and / or a random access memory (RAM). Typically, a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks, magneto-optical disks, and optical disks. Suitable storage devices for substantially implementing computer program instructions and data include, by way of example, all forms of non-volatile memory, including 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 may be supplemented by, or integrated with, Application-Specific Integrated Circuits (ASICs) and other forms of hardware.

[0059] The present disclosure includes the following embodiments.

[0060] (Embodiment 1) As a LiDAR chip for solid-state Frequency Modulated Continuous Wave (FMCW) LiDAR (Light Detection and Ranging) systems, an optical switch network on the LiDAR chip configured to selectively provide coherent light to one or more of a plurality of output waveguides; A Switchable Coherent Pixel Array (SCPA) on the LiDAR chip, the SCPA including coherent pixels (CPs), each CP configured to emit coherent light provided by a corresponding output waveguide among the plurality of output waveguides; and a monitoring assembly on the LiDAR chip, the monitoring assembly including a plurality of photodetectors, each of the plurality of photodetectors configured to generate an output signal in response to a level of light detected from a corresponding one of the plurality of output waveguides; The optical switch network is calibrated by adjusting a drive strength of a switch driver for the optical switch network based on an output signal of the monitoring assembly LiDAR chip.

[0061] (Embodiment 2) 2. The LiDAR chip of embodiment 1, wherein the monitoring assembly includes a plurality of optical couplers configured to tap a portion of the coherent light provided to the plurality of output waveguides and provide a portion of the light to the plurality of photodetectors.

[0062] (Embodiment 3) 3. The LiDAR chip of embodiment 2, wherein each of the optical couplers has a different corresponding photodetector among the plurality of photodetectors to which the optical coupler provides a tapped portion of the coherent light.

[0063] (Embodiment 4) The LiDAR chip includes n channels, each channel including a respective optical switch network, a respective SCPA including N CPs, and a respective monitoring assembly; the optical switch network, the SCPA, and the monitoring assembly are part of a first channel, n and N are integers; A LiDAR chip as described in embodiment 1, wherein each photodetector of each monitoring assembly has a corresponding row value ranging from 1 to N and a corresponding channel value ranging from 1 to n.

[0064] (Embodiment 5) 5. The LiDAR chip of embodiment 4, wherein first electrodes of photodetectors having the same channel value are coupled together to form respective first nodes, such that there are n first nodes.

[0065] (Embodiment 6) The LiDAR chip of embodiment 5, wherein second electrodes of photodetectors having the same row value and different channel values ​​are coupled together to form respective second nodes, such that there are N second nodes.

[0066] (Embodiment 7) The LiDAR chip of embodiment 6, wherein the first electrode is an anode and the second electrode is a cathode.

[0067] (Embodiment 8) The LiDAR chip of embodiment 6, wherein the n first nodes are electrically coupled to a first switch, and the N second nodes are electrically coupled to a second switch, and the first switch and the second switch are configured to selectively read any photodetector of any monitoring assembly.

[0068] (Embodiment 9) The LiDAR chip of embodiment 3, further comprising a plurality of optical switch cells, wherein the plurality of optical switch cells, the plurality of optical couplers and the plurality of photodetectors are arranged to form a binary tree having a plurality of levels.

[0069] (Embodiment 10) Among the plurality of levels, for a first level, the outputs of the photodetectors having odd indices are coupled together to form a first node coupled to a first receiver; the outputs of the photodetectors having even indices are coupled together to form a second node coupled to a second receiver; Among the plurality of levels, for a second level, the outputs of the photodetectors having odd indices are concatenated together to form a third node coupled to a third receiver; 10. The LiDAR chip of embodiment 9, wherein outputs of photodetectors having even indexes are coupled together to form a fourth node coupled to a fourth receiver.

[0070] (Embodiment 11) the LiDAR chip includes n channels, each channel including a respective optical switch network, a respective SCPA, and a respective monitoring assembly; the optical switch network, the SCPA, and the monitoring assembly are part of a first channel, n is an integer, Each channel includes a plurality of optical switch cells, a plurality of optical couplers, and a plurality of optical detectors arranged to form a binary tree having a plurality of levels; For each of the n channels, The LiDAR chip of embodiment 10, wherein, at the same level among the plurality of levels, outputs of photodetectors having odd indexes are coupled to the first receiver and outputs of photodetectors having even indexes are coupled to the second receiver.

[0071] (Embodiment 12) a first splitter on the LiDAR chip configured to split coherent light into a first portion and a second portion, the coherent light being chirped according to a waveform, the second portion of the coherent light being coherent light that the optical switch network selectively provides to one or more of the plurality of output waveguides; and an interferometer on the LiDAR chip, the interferometer configured to generate a signal using the first portion of the coherent light; 2. The LiDAR chip of embodiment 1, wherein the shape of the waveform is controlled based in part on I and Q signals to compensate for laser frequency deviation.

[0072] (Embodiment 13) As a LiDAR chip for solid-state Frequency Modulated Continuous Wave (FMCW) LiDAR (Light Detection and Ranging) systems, a first splitter on the LiDAR chip, the first splitter being configured to split coherent light into a first portion and a second portion, the coherent light being chirped according to a waveform; an interferometer on the LiDAR chip, the interferometer configured to generate an in-phase (I) signal and a quadrature (Q) signal using a first portion of the coherent light; an Optical Switch Network on the LiDAR chip, the Optical Switch Network configured to selectively provide a second portion of the coherent light to one or more of a plurality of output waveguides; and A Switchable Coherent Pixel Array (SCPA) on the LiDAR chip, the SCPA including coherent pixels (CPs), each CP configured to emit coherent light provided by a corresponding output waveguide among the plurality of output waveguides; and and a controller configured to identify a frequency deviation of the coherent light based in part on the I and Q signals, and control a shape of the waveform based in part on the identified deviation to compensate for the identified deviation.

[0073] (Embodiment 14) further comprising a temperature sensor configured to monitor a temperature of a delay arm of the interferometer; The LiDAR chip of embodiment 13, wherein the controller uses the monitored temperature to compensate for temperature induced deviations in the refractive index of the delay arm.

[0074] (Embodiment 15) The interferometer comprises: a second splitter configured to split a first portion of the coherent light into a first arm and a second arm, the second arm introducing a delay; an Optical Hybrid Combiner configured to receive light output from the first arm and the second arm and output light optically phase shifted with respect to each other across a first output, a second output, a third output, and a fourth output; a first balanced photodetector configured to generate the I signal using the first output and the third output; and a second balanced photodetector configured to generate the Q signal using the second output and the fourth output.

[0075] (Embodiment 16) The LiDAR chip of embodiment 13, wherein the coherent light is generated using a seed laser and a laser modulator, the laser modulator is driven by a modulator driver, and the controller controls the modulator driver to control the shape of the waveform.

[0076] (Embodiment 17) The I and Q signals are processed, and the controller determining a phase of the processed I and Q signals; determining an instantaneous frequency of the coherent light using the phases of the I and Q signals; A LiDAR chip as described in embodiment 13, configured to identify a frequency deviation of the coherent light using the determined instantaneous frequency.

[0077] (Embodiment 18) The LiDAR chip of embodiment 17, wherein the I signal is buffered and amplified using a first receiver to generate the processed I signal, and then sampled using a first analog-to-digital converter (ADC), and the Q signal is buffered and amplified using a second receiver to generate the processed Q signal, and then sampled using a second ADC.

[0078] (Embodiment 19) a Monitoring Assembly on the LiDAR chip, the Monitoring Assembly including a plurality of photodetectors, each configured to generate an output signal in response to a level of light detected from a corresponding one of the plurality of output waveguides; The LiDAR chip of embodiment 13, wherein the optical switch network is calibrated by adjusting a drive strength of a switch driver for the optical switch network based on the output signal of the monitoring assembly.

[0079] (Embodiment 20) As a focal plane array (FPA) system for solid state frequency modulated continuous wave (FMCW) LiDAR (Light Detection and Ranging) systems, a first splitter on the LiDAR chip, the first splitter being configured to split coherent light into a first portion and a second portion, the coherent light being chirped according to a waveform; an interferometer on the LiDAR chip, the interferometer configured to generate an in-phase (I) signal and a quadrature (Q) signal using a first portion of the coherent light; an Optical Switch Network on the LiDAR chip, the Optical Switch Network configured to selectively provide a second portion of the coherent light to one or more of a plurality of output waveguides; and A Switchable Coherent Pixel Array (SCPA) on the LiDAR chip, the SCPA including coherent pixels (CPs), each CP configured to emit coherent light provided by a corresponding output waveguide among the plurality of output waveguides; and a monitoring assembly on the LiDAR chip, the monitoring assembly including a plurality of photodetectors, each of the plurality of photodetectors configured to generate an output signal in response to a level of light detected from a corresponding one of the plurality of output waveguides; a lens system arranged to direct the coherent light emitted from the SCPA into an environment as one or more light beams, each of the one or more light beams being emitted at a particular angle, the particular angle being based in part on the location of the CPs on the LiDAR chip that generated the coherent light forming the one or more light beams; and a controller configured to identify a frequency deviation of the coherent light based in part on the I and Q signals, control a shape of the waveform based in part on the I and Q signals to compensate for the identified deviation, and calibrate the optical switch network based on an output signal of the monitoring assembly.

Claims

1. 1. A Light Detection and Ranging (LiDAR) system for a vehicle, comprising: a first splitter configured to split the coherent light into a first portion and a second portion, the coherent light being chirped according to a waveform; an interferometer configured to generate an in-phase (I) signal and a quadrature (Q) signal using the first portion of the coherent light; an optical switch network configured to selectively provide the second portion of the coherent light to one or more of a plurality of output waveguides; a switchable coherent pixel array (SCPA) including a plurality of coherent pixels (CPs) configured to emit coherent light provided by corresponding ones of the plurality of output waveguides; A LiDAR system comprising:

2. The interferometer comprises: a second splitter configured to split the first portion of the coherent light into a first arm and a second arm, the second arm inducing a delay; and an optical hybrid coupler configured to receive light output from the first arm and the second arm and output light optically phase shifted relative to one another across a first output, a second output, a third output, and a fourth output; a first balanced photodetector configured to generate the I signal using the first output and the third output; a second balanced photodetector configured to generate the Q signal using the second output and the fourth output; The LiDAR system of claim 1 .

3. The controller identifying a frequency deviation of the coherent light based in part on the I and Q signals; 2. The LiDAR system of claim 1 configured to control a shape of the waveform based in part on the identified deviation to compensate.

4. 4. The LiDAR system of claim 3, further comprising a temperature sensor configured to monitor a temperature of a delay arm of the interferometer, the controller using the monitored temperature to compensate for temperature induced deviations in the refractive index of the delay arm.

5. 4. The LiDAR system of claim 3, wherein the coherent light is generated using a seed laser and a laser modulator, the laser modulator driven by a modulator driver, and the controller controls the modulator driver to control the shape of the waveform.

6. The I and Q signals are processed and the controller determining a phase of the processed I and Q signals; determining an instantaneous frequency of the coherent light using the phases of the I and Q signals; The LiDAR system of claim 3 , configured to use the determined instantaneous frequency to identify a frequency deviation of the coherent light.

7. a monitoring assembly including a plurality of optical detectors, each of the plurality of optical detectors configured to generate an output signal in response to a level of light detected from a corresponding one of the plurality of output waveguides; 2. The LiDAR system of claim 1, wherein the optical switch network is calibrated by adjusting a drive strength of a switch driver for the optical switch network based on an output signal of the monitoring assembly.

8. The monitoring assembly includes:

8. The LiDAR system of claim 7, comprising a plurality of optical couplers configured to tap portions of the coherent light provided to the plurality of output waveguides and provide the portions of the coherent light to the plurality of photodetectors.

9. 10. The LiDAR system of claim 8, wherein each of the plurality of optical couplers has a different corresponding optical detector among the plurality of optical detectors to which the optical coupler provides the portion of the coherent light.

10. 8. The LiDAR system of claim 7, wherein the LiDAR system includes n channels, each channel including N coherent pixels, the optical switch network, the SCPA and the monitoring assembly are part of a first one of the n channels, n and N are integers, and each photodetector of the monitoring assembly has a corresponding row value ranging from 1 to N and a corresponding channel value ranging from 1 to n.

11. 1. A Light Detection and Ranging (LiDAR) system, comprising: a first splitter configured to split the coherent light into a first portion and a second portion, the coherent light being chirped according to a waveform; an interferometer configured to generate an in-phase (I) signal and a quadrature (Q) signal using the first portion of the coherent light; an optical switch network configured to selectively provide the second portion of the coherent light to one or more of a plurality of output waveguides; a switchable coherent pixel array (SCPA) including a plurality of coherent pixels (CPs) configured to emit coherent light provided by corresponding ones of the plurality of output waveguides; a monitoring assembly including a plurality of photodetectors configured to generate output signals in response to levels of light detected from corresponding ones of the plurality of output waveguides; a lens system positioned to direct coherent light emitted from the SCPA into an environment as one or more light beams; A LiDAR system comprising:

12. The interferometer comprises: a second splitter configured to split the first portion of the coherent light into a first arm and a second arm, the second arm inducing a delay; and an optical hybrid coupler configured to receive light output from the first arm and the second arm and output light optically phase shifted relative to one another across a first output, a second output, a third output, and a fourth output; a first balanced photodetector configured to generate the I signal using the first output and the third output; a second balanced photodetector configured to generate the Q signal using the second output and the fourth output; The LiDAR system of claim 11 .

13. The controller identifying a frequency deviation of the coherent light based in part on the I and Q signals; 12. The LiDAR system of claim 11 configured to control a shape of the waveform based in part on the identified deviation to compensate.

14. 14. The LiDAR system of claim 13, further comprising a temperature sensor configured to monitor a temperature of a delay arm of the interferometer, the controller using the monitored temperature to compensate for temperature induced deviations in the refractive index of the delay arm.

15. 14. The LiDAR system of claim 13, wherein the coherent light is generated using a seed laser and a laser modulator, the laser modulator driven by a modulator driver, and the controller controls the modulator driver to control the shape of the waveform.

16. The I and Q signals are processed and the controller determining a phase of the processed I and Q signals; determining an instantaneous frequency of the coherent light using the phases of the I and Q signals; 14. The LiDAR system of claim 13, configured to use the determined instantaneous frequency to identify a frequency deviation of the coherent light.

17. 12. The LiDAR system of claim 11, wherein the optical switch network is calibrated by adjusting a drive strength of a switch driver for the optical switch network based on an output signal of the monitoring assembly.

18. The monitoring assembly includes:

20. The LiDAR system of claim 17, comprising a plurality of optical couplers configured to tap portions of the coherent light provided to the plurality of output waveguides and provide the portions of the coherent light to the plurality of photodetectors.

19. 20. The LiDAR system of claim 18, wherein each of the plurality of optical couplers has a different corresponding optical detector among the plurality of optical detectors to which the optical coupler provides the portion of the coherent light.

20. 12. The LiDAR system of claim 11 , wherein the LiDAR system includes n channels, each channel including N coherent pixels, the optical switch network, the SCPA and the monitoring assembly are part of a first one of the n channels, n and N are integers, and each photodetector of the monitoring assembly has a corresponding row value ranging from 1 to N and a corresponding channel value ranging from 1 to n.

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