Chirp rate identification

Abstract

The LIDAR system includes a signal splitter configured to split a common optical signal into a first optical signal and a second optical signal. The system also includes a signal combiner configured to combine light from the first optical signal and light from the second optical signal to form a combined signal that beats at a beat frequency. The system also includes electronic circuitry including a beat frequency identifier configured to identify the beat frequency of the combined signal. The electronic circuitry also includes a chirp rate generator configured to calculate a chirp rate of the common optical signal from the beat frequency of the combined signal.

Description

Related Applications

[0001] This application is a continuation of U.S. Patent Application No. 17 / 945,072, filed September 14, 2022, entitled "Combining Data from Different Sample Areas Within the Field of View of an Imaging System," the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to optical devices, and more particularly to imaging systems and LIDAR systems that use signals with chirped frequencies.

[0003] There is growing commercial demand for LIDAR systems that can be deployed in applications such as ADAS (Advanced Driver Assistance Systems) and AR (Augmented Reality). These LIDAR systems typically generate a system output signal that is reflected by an object located outside the LIDAR system. At least a portion of the reflected optical signal returns to the LIDAR system. The LIDAR system transmits the received optical signal to an optical sensor that converts the optical signal into an electrical signal. Electronic circuitry can use the optical sensor output to quantify LIDAR data indicative of line-of-sight velocity and distance between the object and the LIDAR system.

[0004] Many LIDAR systems chirp the frequency of the system output signal at a target chirp rate so that data can be measured accurately. However, the actual chirp rate achieved often differs from the target chirp rate. This difference between the target and actual chirp rates is a significant source of error in LIDAR data. As a result, there is a need for LIDAR systems that correct for the difference between the target and actual chirp rates. Summary of the Invention

[0005] The LIDAR system includes a signal splitter configured to split a common optical signal into a first optical signal and a second optical signal. The system also includes a signal combiner configured to combine light from the first optical signal with light from the second optical signal to form a combined signal that beats at a beat frequency. The system also includes electronic circuitry having a beat frequency identifier configured to identify the beat frequency of the combined signal. The electronic circuitry also includes a chirp rate generator configured to calculate a chirp rate of the common optical signal from the beat frequency of the combined signal.

[0006] A method of operating a LIDAR system includes splitting a common optical signal into a first optical signal and a second optical signal, combining light from the first optical signal and light from the second optical signal to form a combined signal that beats at a beat frequency, identifying the beat frequency of the combined signal, and calculating a chirp rate of the common optical signal from the calculated beat frequency of the combined signal. [Brief explanation of the drawings]

[0007] FIG. 1A is a schematic plan view of a LIDAR system having or consisting of a LIDAR chip that outputs a LIDAR output signal and receives a LIDAR input signal on a common waveguide.

[0008] FIG. 1B is a schematic plan view of a LIDAR system having or consisting of a LIDAR chip that outputs a LIDAR output signal and receives a LIDAR input signal on a different waveguide.

[0009] FIG. 1C is a schematic plan view of another embodiment of a LIDAR system having or consisting of a LIDAR chip that outputs a LIDAR output signal and receives multiple LIDAR input signals on different waveguides.

[0010] FIG. 2 is a plan view of an example LIDAR adapter suitable for use with the LIDAR chip of FIG. 1B.

[0011] FIG. 3 is a plan view of an example LIDAR adapter suitable for use with the LIDAR chip of FIG. 1C.

[0012] FIG. 4 is a plan view of an example LIDAR system having the LIDAR chip of FIG. 1A and the LIDAR adapter of FIG. 2 on a common support.

[0013] FIG. 5A shows an example of a signal processor suitable for use with a LIDAR system.

[0014] FIG. 5B is a schematic diagram of electronic circuitry suitable for use with a signal processor constructed in accordance with FIG. 5A.

[0015] FIG. 5C is a frequency versus time graph of the system output signal.

[0016] FIG. 6A shows a LIDAR system with multiple different cores on a common support.

[0017] FIG. 6B illustrates the relationship between the data period and the field of view of the LIDAR system disclosed in FIG. 5C.

[0018] FIG. 6C shows an object in the field of view disclosed in the context of FIG. 6B.

[0019] FIG. 6D shows several different field positions relative to the range and sample area illuminated by the velocity core.

[0020] FIG. 7 is a two-dimensional view of the field of view of a LIDAR system.

[0021] FIG. 8 shows a general electronic circuitry configured to receive auxiliary LIDAR data generated by different cores.

[0022] FIG. 9 shows the target sample area and potential sample area for the field of view of FIG.

[0023] FIG. 10 is a process flow for generating throw distance data for a sample area illuminated by a velocity core of a LIDAR system having throw distance and velocity cores.

[0024] FIG. 11A is a schematic plan view of a LIDAR core suitable for use as a velocity core.

[0025] FIG. 11B is an example of a signal processing section suitable for use with the LIDAR core of FIG. 11A.

[0026] FIG. 11C provides a schematic of electronic circuitry suitable for use with a signal processing section constructed according to FIG. 11B. Detailed Description of the Invention

[0027] The imaging system includes a chirp rate identifier operable by the electronic circuitry to identify a chirp rate of an optical signal output from the imaging system. The identified chirp rate can be used in calculating LIDAR data indicative of line-of-sight velocity and / or distance between the imaging system and an object external to the imaging system. By calculating the LIDAR data using the identified chirp rate rather than using a target chirp rate, errors in the LIDAR data are reduced.

[0028] FIG. 1A is a schematic diagram showing a portion of a LIDAR system having a LIDAR chip 2. FIG. 1A includes a plan view of a portion of the LIDAR chip 2. The LIDAR chip can be a semiconductor chip, such as a silicon-on-insulator chip. The LIDAR chip includes a LIDAR core 4. The LIDAR core 4 includes an optical integrated circuit.

[0029] The LIDAR core 4 can include a light source 10 that outputs an outgoing LIDAR signal. The LIDAR core includes a utility waveguide 12 that receives the outgoing LIDAR signal from the light source 10. The utility waveguide 12 carries the outgoing LIDAR signal to a signal director 14. The LIDAR system includes electronic circuitry that operates the signal director 14. For example, the electronic circuitry can include a director control 15 that operates the signal director 14 to direct light from the light source output signal to any one of a number of different alternative waveguides 16. There are N alternative waveguides, and each alternative waveguide 16 is associated with an alternative waveguide index i, where i has a value from 1 to N. Suitable values ​​for N include, but are not limited to, values ​​less than 128, 64, or 32 and / or greater than 2, 8, or 16. In one example, N is between 2 and 128.

[0030] Each alternative waveguide 16 can receive an outgoing LIDAR signal from the signal director 14. When any one of the alternative waveguides 16 receives an outgoing LIDAR signal, the alternative waveguide 16 functions as an active waveguide and carries the outgoing LIDAR signal to port 18, through which the outgoing LIDAR signal exits the LIDAR chip and functions as the LIDAR output signal. Thus, the outgoing LIDAR signal is output from the active waveguide.

[0031] Optical signals resulting from an outgoing LIDAR signal directed into an alternative waveguide 16 having an alternative waveguide index i are classified as optical signals carrying a channel (Ci). Thus, each LIDAR output signal is associated with a different one of the alternative waveguide indexes i=1 to N. For example, the path of a LIDAR output signal carrying a channel with alternative waveguide index 2 is labeled C2 in FIG. 1A. For purposes of illustration, the LIDAR system is shown as generating three LIDAR output signals (N=3) labeled C1 to C3. Each of the different LIDAR output signals can carry a different channel, but each of the different channels can carry the same wavelength selection, or substantially the same wavelength selection.

[0032] The LIDAR input signal returns to the LIDAR chip such that LIDAR input signals carrying channel Ci enter alternative waveguides 16 associated with the same alternative waveguide index i. As a result, LIDAR input signals carrying different channels are directed to different alternative waveguides. A portion of the LIDAR input signal entering the alternative waveguides 16 serves as the incident LIDAR signal. As a result, the alternative waveguide receiving the incident LIDAR signal can direct an outgoing LIDAR signal while directing the incident LIDAR signal in the opposite direction. The alternative waveguide 16 receiving the incident LIDAR signal carries the incident LIDAR signal to the signal director 14. The signal director 14 outputs the incident LIDAR signal to the utility waveguide 12.

[0033] The utility waveguide 12 conveys the incident LIDAR signal to a 2x2 splitter 24, which moves a portion of the incident LIDAR signal from the utility waveguide 12 to a comparison waveguide 26 as a comparison signal. The comparison signal comprises light from the outgoing LIDAR signal that has exited the imaging system, been reflected by objects outside the imaging system, and returned to the imaging system. The comparison waveguide 26 conveys the comparison signal to a signal processor 28 for further processing. Suitable splitters 24 include, but are not limited to, optical couplers, Y-junctions, and MMIs. In some cases, the splitter 24 is configured so that the power of the incident LIDAR signal is split evenly or nearly evenly between the utility waveguide 12 and the comparison waveguide 26.

[0034] The utility waveguide 12 also conveys the outgoing LIDAR signal to the splitter 24. The splitter 24 conveys a portion of the outgoing LIDAR signal from the utility waveguide 12 as a reference signal to the reference waveguide 32. The reference waveguide 32 conveys the reference signal to the signal processor 28 for further processing.

[0035] As will be explained in more detail below, the signal processor 28 combines the comparison signal and the reference signal to form a composite signal that carries LIDAR data about the sample area on the field of view, and thus can be processed to extract LIDAR data about the sample area (such as the line-of-sight velocity and / or distance between the LIDAR system and objects external to the LIDAR system).

[0036] The LIDAR chip can have a chirp branch for identifying the chirp rate of the outgoing LIDAR signal. The chirp branch can therefore identify the chirp rate of the signal output from the LIDAR system to generate LIDAR data, such as a system output signal. The chirp branch has a signal splitter 66 that transfers a portion of the outgoing LIDAR signal from the utility waveguide 12 to a common waveguide 68. The combined portion of the outgoing LIDAR signal serves as a common signal. The common waveguide 68 carries the common signal to a chirp rate discriminator 70. Examples of suitable signal splitters 66 include, but are not limited to, a directional coupler, a Y-junction, and an MMI.

[0037] The electronic circuitry 62 can include a light source controller 63. The light source controller 63 can operate the light source such that the outgoing LIDAR signal, and therefore the system output signal, has a particular frequency versus time pattern. For example, the light source controller 63 can operate the light source such that the outgoing LIDAR signal, and therefore the system output signal, has different chirp rates during different data periods.

[0038] The light source controller 63 can adjust the voltage and / or current applied to the light source to achieve a desired frequency versus time pattern in the optical signal comprising light from the outgoing LIDAR signal. If the light source 10 is a gain element or a laser chip, the light source controller 63 can change the frequency of the outgoing LIDAR signal by changing the level of current applied through the gain element or laser cavity. Additionally or alternatively, the light source 10 can include a modulator (not shown) configured to modulate the frequency of the outgoing LIDAR signal. If the light source 10 includes a modulator, the light source controller 63 can operate the modulator to achieve a desired frequency versus time pattern in the optical signal comprising light from the outgoing LIDAR signal.

[0039] The LIDAR chip can optionally have a control branch for controlling the operation of the light source 10. For example, the control branch can provide a feedback loop that the light source controller 63 uses in operating the light source so that the outgoing LIDAR signal has a desired frequency versus time pattern.

[0040] The control branch includes a directional coupler 71 that transfers a portion of the outgoing LIDAR signal from the utility waveguide 12 to a control waveguide 72. The combined portion of the outgoing LIDAR signal serves as a tap signal. While FIG. 1A shows a directional coupler 71 transferring a portion of the outgoing LIDAR signal to the control waveguide 72, other signal taps can be used to transfer a portion of the outgoing LIDAR signal from the utility waveguide 12 to the control waveguide 72. Examples of suitable signal taps include, but are not limited to, a Y-junction, an MMI, or the like.

[0041] The control waveguide 72 carries the tap signal to a feedback system 73. The feedback system 73 may include one or more optical sensors (not shown) that convert the optical signal carried by the feedback system 73 into an electrical signal output from the feedback system 73. The light source controller 63 may receive the electrical signal output from the feedback system 73. In operation, the light source controller 63 may adjust the frequency of the output LIDAR signal in response to the power of the electrical signal output from the feedback system 73. Examples of suitable configurations and operations of the feedback system 73 and the light source controller 63 are described in U.S. Patent Application Serial No. 16 / 875,987, filed May 16, 2020, entitled "Monitoring Signal Chirp in a LIDAR Output Signal," which is incorporated herein in its entirety, and in U.S. Patent Application Serial No. 17 / 244,869, filed April 29, 2021, entitled "Reducing the Size of a LIDAR System Control Assembly," which is incorporated herein in its entirety.

[0042] Although FIG. 1A shows the electronic circuitry 62 as a component separate from the signal processing sections 28, portions of the electronic circuitry may be included in each signal processing section 28.

[0043] In FIG. 1A, the incident LIDAR signal passes through the signal director 14. The signal director 14 can be a source of optical loss. This source of optical loss can be eliminated by moving a portion of the incident LIDAR signal, which serves as a comparison signal, to a comparison waveguide 26 before the incident LIDAR signal reaches the signal director 14. As an example, FIG. 1B shows the LIDAR chip of FIG. 1A modified so that a splitter 24 is positioned along each alternative waveguide 16 between the signal director 14 and the port 18. The signal splitter extracts a portion of the outgoing LIDAR signal from the alternative waveguide, which serves as a reference signal, and also extracts at least a portion of the incident LIDAR signal from the alternative waveguide, which serves as a comparison signal. As a result, a comparison signal is extracted from the alternative waveguide 16 before the incident LIDAR signal reaches the signal director 14.

[0044] 1A and 1B, it can be seen that the LIDAR chip of FIG. 1B requires more signal processing sections 28 than the LIDAR chip of FIG. 1A. As will become apparent below, increasing the required number of signal processing sections 28 also increases the number of analog-to-digital converters required for the LIDAR system. However, a common signal processing section 28 can be used to reduce the number of analog-to-digital converters. As an example, FIG. 1C shows the LIDAR chip of FIG. 1B modified so that each comparison waveguide 26 carries one comparison signal to the common signal processing section 74. Additionally, each reference waveguide 32 carries one reference signal to the common signal processing section 74.

[0045] A LIDAR system can have a LIDAR chip with multiple LIDAR cores 4 on a support 77. As an example, FIG. 2 shows a LIDAR chip with multiple different cores. The cores are each labeled core k, where k represents the core index k. Each LIDAR core can be constructed as disclosed in the content of FIGS. 1A-1C or can have an alternative configuration. Each LIDAR core outputs a different LIDAR output signal. The LIDAR output signal output from a core labeled core k can be represented by Sk,i, where i represents an alternative waveguide index. As a result, Sk,i is a function of the alternative waveguide index i and the core index k. As an example, the LIDAR output signal represented by Sk,i is output from core k and received by the alternative waveguide index i. Thus, the LIDAR output signal represented by Sk,i is output from core k and carries channel Ci.

[0046] The LIDAR system can optionally include optical component assemblies 75 that receive LIDAR output signals from different cores and output system output signals, each comprising, consisting of, or consisting essentially of light from the different LIDAR output signals. The optical component assemblies 75 can be operated by assembly control 280 to steer the system output signals to different sample areas within the field of view of the LIDAR system.

[0047] FIG. 2 illustrates an optical component assembly 75 having a signal director 76 that receives each LIDAR output signal. The signal director 76 changes the direction in which at least some of the LIDAR output signals are traveling and outputs each LIDAR output signal as a redirected LIDAR output signal. Suitable signal directors 76 include, but are not limited to, convex lenses and concave mirrors. The optical component assembly 75 has one or more beam directors 78 that receive the redirected LIDAR output signals output from the signal director 76 as system output signals. The direction in which the system output signals travel away from the LIDAR system is labeled d2 in FIG. 2. The assembly controller 280 can operate the one or more beam directors 78 to steer each system output signal to a different sample area within the field of view. As evident from the arrows labeled A and B in FIG. 2, the one or more beam directors 78 can be configured to allow the assembly controller 280 to steer the system output signals in one or two dimensions. As a result, the one or more beam directors 78 can function as beam steering mechanisms operated by the assembly control 280 to steer the system output signal within the field of view of the LIDAR system. Suitable beam directors 78 include, but are not limited to, movable mirrors, MEMS mirrors, optical phased arrays (OPAs), optical gratings, and actuated optical gratings. In some cases, the signal director 76 and / or the one or more beam directors 78 are configured to manipulate the system output signal so that it is collimated or substantially collimated as it travels away from the LIDAR system. Additionally, or alternatively, the LIDAR system can include one or more optical collimators (not shown) that act on the LIDAR output signal, the redirected LIDAR output signal, and / or the system output signal so that it is collimated or substantially collimated as it travels away from the LIDAR system.

[0048] The system output signals may be reflected by objects outside the LIDAR system. All or a portion of the reflected light from the system output signals may return to the LIDAR system as a system return signal. Each system return signal is received by one or more beam directors 78. The one or more beam directors 78 output at least a portion of each system return signal as a return signal. The return signals are received by respective signal directors 76. The signal directors 76 output at least a portion of each return signal as a LIDAR input signal. Each of the different LIDAR input signals is received by a different one of the cores 4. Each LIDAR input signal comprises or is composed of light from a LIDAR output signal output from the core that receives the LIDAR input signal. Additionally, LIDAR input signals received at alternative waveguides comprise or are composed of light from LIDAR output signals output from the same alternative waveguide.

[0049] The one or more signal directors 76 can change the direction in which the LIDAR output signals travel away from the one or more signal directors 76 such that the direction of the resulting redirected LIDAR output signals is different. In some cases, the one or more signal directors 76 are selected such that all or some of the redirected LIDAR output signals travel away from the one or more signal directors 76 in non-parallel directions. As an example, in FIG. 2 , the one or more signal directors 76 are lenses, and each of the different LIDAR output signals is incident on the lens at a different angle of incidence. As a result, each of the redirected LIDAR output signals travels away from the signal director 76 in a different direction. Furthermore, the redirected LIDAR output signals travel away from the signal director 76 in a non-parallel direction. As is apparent from FIG. 2 , the different system output signal directions can result in the system output signals traveling away from the LIDAR system in different directions. In some cases, the system output signals travel in non-parallel directions away from the LIDAR system.

[0050] Manipulating the signal directors 14 on a core can change the location at which the LIDAR output signal is received by one or more signal directors 76 and, therefore, the direction in which the system output signal emanating from that core travels away from the LIDAR system. As an example, the dashed lines in FIG. 2 show the result of manipulating the signal director 14 of core 1 such that core 1 outputs the LIDAR output signal represented by Sk,i+1 instead of the LIDAR output signal represented by Sk,i. As is apparent from FIG. 2 , this manipulation of the signal directors 14 changes the direction in which the system output signal output from core 1 travels away from the LIDAR system. As a result, electronic circuits 62 associated with different cores can operate their associated signal directors 14 to steer the system output signal into the field of view of the LIDAR system. For example, director controls 15 associated with different cores can operate their associated signal directors 14 to steer the system output signal into the field of view of the LIDAR system. Thus, electronics 62 associated with different cores can operate associated signal directors 14 to operate the system output signals within the field of view of the LIDAR system, and / or assembly control 280 can operate one or more beam directors 78 to steer the system output signals within the field of view of the LIDAR system. Suitable methods for operating signal directors 14 and / or one or more beam directors 78 on different cores to steer the system output signals to different sample areas within the field of view of the LIDAR system are disclosed in U.S. Patent Application Serial No. 17 / 580,623, filed January 20, 2022, entitled "IMAGING SYSTEM HAVING MULTIPLE CORES," which is incorporated herein in its entirety.

[0051] 2. For example, one or more beam directors 78 can be disposed between the signal director 76 and the LIDAR chip. Additionally, the optical component assembly 75 can include optical components not shown. For example, the optical component assembly 75 can include one or more lenses configured to enhance collimation of the LIDAR output signal and / or other signals derived from and / or comprising light from the LIDAR output signal.

[0052] The wavelengths of the LIDAR output signals output from the different cores may be the same or different. As a result, the light sources on the different cores can each be configured to output output optical signals having different, the same, or substantially the same wavelength selections. Thus, the wavelength selections in the different system output signals may be different, the same, or substantially the same.

[0053] 2 shows four cores on the LIDAR chip, the LIDAR chip can have one, two, or more than two cores. Suitable numbers of cores on a LIDAR chip include, but are not limited to, 2, 4, 6, or more, and / or numbers less than 32, 64, or 128.

[0054] 3A-3B illustrate an example of a signal processor suitable for use as signal processor 28 in a LIDAR system constructed according to FIGS. 1A and 1B. The signal processor includes an opto-electrical assembly configured to convert an optical signal to an electrical signal. FIG. 3A is a schematic diagram of an example of a suitable opto-electrical assembly including a first splitter 200 that splits a comparison signal received from comparison waveguide 26 into a first comparison waveguide 204 and a second comparison waveguide 206. First comparison waveguide 204 carries a first portion of the comparison signal to signal combiner 211. Second comparison waveguide 208 carries a second portion of the comparison signal to second signal combiner 212.

[0055] 3A also includes a second splitter 202 that splits the reference signal received from the reference waveguide 32 between a first reference waveguide 210 and a second reference waveguide 208. The first reference waveguide 210 carries a first portion of the reference signal to an optical signal combiner 211. The second reference waveguide 208 carries a second portion of the reference signal to a second optical signal combiner 212.

[0056] The second optical signal combiner 212 combines the second portion of the comparison signal and the second portion of the reference signal into a second composite signal. Due to the frequency difference between the second portion of the comparison signal and the second portion of the reference signal, the second composite signal varies between the second portion of the comparison signal and the second portion of the reference signal. The first composite signal and the second composite signal are each an example of a composite signal.

[0057] The second optical signal combiner 212 also splits the resulting second composite signal into a first auxiliary detection waveguide 214 and a second auxiliary detection waveguide 216. The first auxiliary detection waveguide 214 carries a first portion of the second composite signal to a first auxiliary optical sensor 218, which converts the first portion of the second composite signal into a first auxiliary electrical signal. The second auxiliary detection waveguide 216 carries a second portion of the second composite signal to a second auxiliary optical sensor 220, which converts the second portion of the second composite signal into a second auxiliary electrical signal. Examples of suitable optical sensors include germanium photodiodes (PDs) and avalanche photodiodes (APDs).

[0058] In some cases, the second optical signal combining unit 212 splits the second composite signal such that the portion of the comparison signal included in the first portion of the second composite signal (i.e., part of the second portion of the comparison signal) is out of phase with the portion of the comparison signal in the second portion of the second composite signal (i.e., part of the second portion of the comparison signal), by 180°, but the portion of the reference signal in the second portion of the second composite signal (i.e., part of the second portion of the reference signal) is not out of phase with the portion of the reference signal in the first portion of the second composite signal (i.e., part of the second portion of the reference signal). Alternatively, the second optical signal combiner 212 splits the second composite signal such that the reference signal portion in the first portion of the second composite signal (i.e., part of the second portion of the reference signal) is out of phase with the reference signal portion in the second portion of the second composite signal (i.e., part of the second portion of the reference signal), but the comparison signal portion in the first portion of the second composite signal (i.e., part of the second portion of the comparison signal) is not out of phase with the comparison signal portion in the second portion of the second composite signal (i.e., part of the second portion of the comparison signal). Examples of suitable optical sensors include germanium photodiodes (PDs) and avalanche photodiodes (APDs).

[0059] The first optical signal combiner 211 combines the first portion of the comparison signal and the first portion of the reference signal into a first composite signal, and the first composite signal beats between the first portion of the comparison signal and the first portion of the reference signal due to the frequency difference between the first portion of the comparison signal and the first portion of the reference signal.

[0060] The first optical signal combiner 211 also splits the first composite signal into a first detection waveguide 221 and a second detection waveguide 222. The first detection waveguide 221 carries a first portion of the first composite signal to a first optical sensor 223, which converts a first portion of the second composite signal into a first electrical signal. The second detection waveguide 222 carries a second portion of the second composite signal to a second optical sensor 224, which converts the second portion of the second composite signal into a second electrical signal. Examples of suitable optical sensors include germanium photodiodes (PDs) and avalanche photodiodes (APDs).

[0061] In some cases, the optical signal combiner 211 splits the first composite signal such that the portion of the comparison signal included in the first portion of the composite signal (i.e., a portion of the first portion of the comparison signal) is 180° out of phase with the portion of the comparison signal in the second portion of the composite signal (i.e., a portion of the first portion of the comparison signal), but the portion of the reference signal in the first portion of the composite signal (i.e., a portion of the first portion of the comparison signal) is not out of phase with the portion of the reference signal in the second portion of the composite signal (i.e., a portion of the first portion of the reference signal). Alternatively, the optical signal combiner 211 splits the composite signal such that the portion of the reference signal in the first portion of the composite signal (i.e., a portion of the first portion of the reference signal) is 180° out of phase with the portion of the reference signal in the second portion of the composite signal (i.e., a portion of the first portion of the reference signal), but the portion of the comparison signal in the first portion of the composite signal (i.e., a portion of the first portion of the comparison signal) is not out of phase with the portion of the comparison signal in the second portion of the composite signal (i.e., a portion of the first portion of the comparison signal).

[0062] When the second optical signal combiner 212 splits the second composite signal such that the comparison signal portion in the first portion of the second composite signal is 180° out of phase with the comparison signal portion in the second portion of the second composite signal, the optical signal combiner 211 also splits the composite signal such that the comparison signal portion in the first portion of the composite signal is 180° out of phase with the comparison signal portion in the second portion of the composite signal. When the second optical signal combiner 212 splits the second composite signal such that the reference signal portion in the first portion of the second composite signal is 180° out of phase with the reference signal portion in the second portion of the second composite signal, the optical signal combiner 211 also splits the composite signal such that the reference signal portion in the first portion of the composite signal is 180° out of phase with the reference signal portion in the second portion of the composite signal.

[0063] An example of a suitable optical signal combiner 211 and second optical signal combiner 212 is a multi-mode interference (MMI) device, such as a 2x2 MMI device. Other suitable optical signal combiners that can be used as optical signal combiner 211 and second optical signal combiner 212 include, but are not limited to, adiabatic splitters and directional couplers. In some cases, the functions of the illustrated optical signal combiners are performed by multiple optical components or combinations of optical components.

[0064] The first reference waveguide 210 and the second reference waveguide 208 are configured to provide a phase shift between the first portion of the reference signal and the second portion of the reference signal. For example, the first reference waveguide 210 and the second reference waveguide 208 can be configured to provide a 90-degree phase shift between the first portion of the reference signal and the second portion of the reference signal. As an example, one reference signal portion can be an in-phase component and the other a quadrature component. Thus, one reference signal portion can be a sine function and the other reference signal portion can be a cosine function. In one example, the first reference waveguide 210 and the second reference waveguide 208 are constructed so that the first reference signal portion is a cosine function and the second reference signal portion is a sine function. Thus, the reference signal portion in the second composite signal is out of phase with respect to the reference signal portion in the first composite signal, while the comparison signal portion in the first composite signal is out of phase with respect to the comparison signal portion in the second composite signal.

[0065] The first optical sensor 223 and the second optical sensor 224 can be connected as a balanced detector, and the first auxiliary optical sensor 218 and the second auxiliary optical sensor 220 can also be connected as a balanced detector. Parallel detectors function as optical sensors that convert optical signals to electrical signals. FIG. 3B provides a schematic of the relationship between the electronic circuitry, the first optical sensor 223, the second optical sensor 224, the first auxiliary optical sensor 218, and the second auxiliary optical sensor 220. Although symbols for photodiodes are used to represent the first optical sensor 223, the second optical sensor 224, the first auxiliary optical sensor 218, and the second auxiliary optical sensor 220, one or more of these sensors can have other configurations. In some cases, all of the components shown in the schematic diagram of FIG. 3B are included on the LIDAR chip. In some cases, the components shown in the schematic diagram of FIG. 3B are distributed between the LIDAR chip and electronic circuitry located off the LIDAR chip.

[0066] The electronic circuit unit 62 connects the first photosensor 223 and the second photosensor as a first balanced detector 225, and the first auxiliary photosensor 218 and the second auxiliary photosensor 220 as a second balanced detector 226. In particular, the first photosensor 223 and the second photosensor 224 are connected in series. The first auxiliary photosensor 218 and the second auxiliary photosensor 220 are connected in series. The series connection in the first balanced detector communicates with a first data line 228 that carries an output from the first balanced detector as a first data signal. The series connection in the second balanced detector communicates with a second data line 232 that carries an output from the second balanced detector as a second data signal. The first data line and the second data line are each examples of data lines. The first data signal is an electrical data signal that carries a representation of the first composite signal, and the second data signal is an electrical data signal that carries a representation of the second composite signal. Thus, the first data signal includes contributions from a first waveform and a second waveform, and the second data signal is a composite of the first and second waveforms. A portion of the first waveform in the first data signal is out of phase with a portion of the first waveform in the first data signal, while a portion of the second waveform in the first data signal is in phase with a portion of the second waveform in the first data signal. For example, the second data signal has a portion of the reference signal that is out of phase with a different portion of the reference signal included in the first data signal. Additionally, the second data signal has a portion of the comparison signal that is in phase with a different portion of the comparison signal included in the first data signal. The first and second data signals beat as a result of the beat between the comparison signal and the reference signal, i.e., the beat in the first composite signal and the beat in the second composite signal.

[0067] The electronic circuitry 32 includes a data processor 237 configured to generate LIDAR data. The data processor 237 includes a beat frequency identifier 238 configured to identify the beat frequency of the composite signal from the first and second data signals. The beat frequency identifier 238 receives the first and second data signals. Because the first data signal is an in-phase component and the second data signal is its quadrature component, the first and second data signals together act as a complex data signal, with the first data signal being the real component of the composite data signal and the second data signal being the imaginary component of the composite data signal.

[0068] The data processing unit 237 includes a first analog-to-digital converter (ADC) 264 that receives the first data signal from the first data line 228. The first analog-to-digital converter (ADC) converts the first data signal from analog to digital format and outputs a first digital data signal. The beat frequency identification unit 238 includes a second analog-to-digital converter (ADC) 266 that receives the second data signal from the second data line 232. The second analog-to-digital converter (ADC) 226 converts the second data signal from analog to digital format and outputs a second digital data signal. The first digital data signal is a digital representation of the first data signal, and the second digital data signal is a digital representation of the second data signal. Thus, the first digital data signal and the second digital data signal act together as a complex signal, with the first digital data signal acting as the real component of the complex signal and the second digital data signal acting as the imaginary component of the complex data signal.

[0069] The beat frequency identification unit 238 includes a mathematical transform unit 268 that receives a complex data signal. For example, the mathematical transform unit 268 receives as an input a first digital data signal from a first analog-to-digital converter (ADC) 264 and also receives as an input a second digital data signal from a first analog-to-digital converter (ADC) 266. The mathematical transform unit 268 can be configured to perform a mathematical transform on the complex signal to convert it from the time domain to the frequency domain. The mathematical transform can be a complex transform, such as a complex Fast Fourier Transform (FFT). A complex transform, such as a complex Fast Fourier Transform (FFT), provides an unambiguous solution for the frequency shift of the complex signal relative to the system output signal.

[0070] The mathematical transform unit 268 may include a peak detector (not shown) configured to identify peaks in the output of the mathematical transform unit 268. The peak detector may be configured to identify frequency peaks associated with reflections of the system output signal by one or more objects located outside the LIDAR system. For example, frequency peaks associated with reflections of the system output signal by one or more objects located outside the LIDAR system may fall within a frequency range. The peak detector may identify frequency peaks within a range of frequencies associated with reflections of the system output signal by one or more objects located outside the LIDAR system. The frequencies of the identified frequency peaks represent beat frequencies of the composite signal.

[0071] The data processor 237 includes a LIDAR data generator 270 that receives the beat frequencies of the composite signal from the peak detector and processes the beat frequencies of the composite signal to generate LIDAR data (the distance between a reflecting object and the LIDAR tip or LIDAR system and / or the radial velocity).

[0072] 3C shows an example of the relationship between frequency, time, period, and data period of the system output signal. The base frequency (f0) of the system output signal can be the frequency of the system output signal at the start of a period.

[0073] 3C shows the frequency of the system output signal for a sequence of two periods labeled Period j and Period j+1, where j represents the period index. The periods shown do not have rearrangement periods and / or rearrangement periods are not located between the periods. As a result, FIG. 3C shows the result of successive scans in which steering of the system output signal is continuous.

[0074] Each period has K data periods, each associated with a period index n and labeled DPn. In the example of FIG. 3C, each period has three data periods labeled DPn, with n=1, 2, and 3. In some cases, as shown in FIG. 3C, the frequency versus time pattern is the same for corresponding data periods in different periods. Corresponding data periods are data periods with the same period index. As a result, each data period DP1 can be considered a corresponding data period, and the associated frequency versus time pattern is the same in FIG. 3C. At the end of a period, the light source controller 63 returns the frequency to the same frequency level that started the previous period.

[0075] During data periods DP1 and DP2, light source controller 63 operates the light source so that the frequency of the system output signal changes at a linear target chirp rate tαn, where n represents the period index. Calculation of the target chirp rate for one data period, labeled DP1, is shown in FIG. 3C. For example, the duration of the data period is labeled τ, and the magnitude of the frequency change during the data period is labeled B. The target chirp rate tα1 can be determined from tα1 = B / τ.

[0076] The target chirp rate can be different in different data periods. For example, in FIG. 3C, the direction of the target chirp rate during data period DP1 is opposite to the direction of the target chirp rate during data period DP2. However, the magnitude of the target chirp rate for data period DP1 is the same as the magnitude of the target chirp rate for data period DP2. As a result, tα1 = -tα2.

[0077] The electronic circuitry 62 is configured to provide the same target chirp rate for data periods with the same period index. For example, each data period associated with period index n=1 has a target chirp rate equal to α. However, as time passes and the number of periods increases, the reliability of the generated actual chirp rate (α) decreases. When the target chirp rate is used to calculate LIDAR data for each sample area, the difference between the actual chirp rate (α) and the target chirp rate (tα) causes errors in the LIDAR data.

[0078] FIG. 3C labels sample areas, each associated with a label sample area index K and labeled Rnk. FIG. 3C labels sample areas Rnk and Rnk+1. Each sample area is illuminated with the system output signal during the data period that FIG. 3C shows associated with the sample area. For example, sample area Rnk is illuminated with the system output signal during the data periods labeled Dp1 through DP3. Sample area index k can be assigned with respect to time. For example, the sample areas can be illuminated with the system output signal in the sequence indicated by index k. As a result, sample area Rn10 can be illuminated after sample area Rn9 and before Rn11.

[0079] Different sample areas and / or different periods can be associated with different channels. For example, each sample area can be illuminated by a system output signal carrying the same channel during each data period associated with the sample area. In addition, different sample areas can be illuminated by system output signals carrying different channels. Accordingly, the direction control 15 can operate the signal director 14 to direct different alternative waveguides 16 at or between transitions to different periods and / or at or between transitions to different sample areas.

[0080] LIDAR systems are typically configured to provide reliable LIDAR data when an object is within an operating distance range from the LIDAR system. The operating distance range extends from a minimum operating distance to a maximum operating distance. The maximum round trip time is the time required for the system output signal to leave the LIDAR system, travel the maximum operating distance to the object, and return to the LIDAR system, and is labeled τ in FIG. 3C.

[0081] Because there is a delay between the transmitted system output signal and the system output signal returning to the LIDAR system, the composite signal does not have a contribution from the LIDAR signal until the system return signal returns to the LIDAR system. Because the composite signal requires a contribution from the system return signal, in which a beat frequency is present, the beat frequency identifier 238 outputs the beat frequency of the composite signal resulting from the system return signal returning to the LIDAR system during a data window in the data period. The data window is labeled "W" in FIG. 3C. The contribution from the LIDAR signal to the composite signal occurs at a time longer than the maximum action time delay (τ). As a result, the data window is displayed as extending from the maximum action time delay (τ) to the end of the data period.

[0082] The frequency peaks in the output of the complex Fourier transform represent beat frequencies of the composite signal, each having a comparison signal beating relative to the reference signal. Beat frequencies from two or more different data periods can be combined to generate LIDAR data. For example, the beat frequency determined from DP1 in FIG. 3C can be combined with the beat frequency determined from DP2 in FIG. 3C to determine LIDAR data. As an example, during a data period where the frequency of the outgoing LIDAR signal increases during the data period, such as data period DP1 in FIG. 3C, the following equation applies: fub = -fd + αnτ, where fub is the frequency provided by the mathematical conversion unit, fd represents the Doppler shift (fd = 2νfc / c), where fc represents the optical frequency (f0), c represents the speed of light, and ν represents the radial velocity between the reflecting object and the LIDAR system, where the direction from the reflecting object toward the tip is assumed to be the positive direction, τ is the time it takes for light from the system output signal to travel to the object and return to the LIDAR system (round trip time), and c is the speed of light. Additionally, αn represents the chirp rate for a data period having period index n. For example, α1 represents the chirp rate for the same data period DP1 that resulted in fub provided by the mathematical conversion unit. As a result, αn and fub are associated with the same data period DPn.

[0083] During a data period in which the frequency of the outgoing LIDAR signal decreases during the data period, such as data period DP2 in FIG. 3C, the following equation applies: fdb=-fd-αnτ, where fdb is the frequency provided by the mathematical transform unit (here, fi.LDP determined from DP2). In addition, αn represents the chirp rate during the data period with period index n. For example, α2 represents the chirp rate during the same data period DP2 that resulted in fub provided by the mathematical transform unit. As a result, αn and fub are associated with the same data period DPn.

[0084] In these two equations (fdb = -fd - αnτ and fub = -fd + αnτ), fd and τ are unknowns. These two equations can be solved for these two unknowns. The LIDAR data generator can calculate the radial velocity for the sample area from the Doppler shift (ν = c × fd / (2fc)) and / or the separation distance for the sample area from c × fd / 2. For example, when the system output signal has a frequency vs. time pattern as shown in FIG. 3C, the distance (r) between the LIDAR system and an object external to the LIDAR system can be calculated from r = c(fub - fdb) / (2(α1 - α2)), and the radial velocity between the LIDAR system and the object can be calculated from ν = c(α2fub - α1fdb) / (2fc(α1 - α2)). Thus, the calculated chirp rate (α) and the calculated composite signal beat frequency are variables in the equation used by the LIDAR data generator to calculate LIDAR data. Thus, the LIDAR data generator 270 can combine the chirp rates (α) and beat frequencies from different data periods to calculate LIDAR data for the sample area. Because LIDAR data can be generated for each corresponding frequency pair output by the transform, separate LIDAR data can be generated for each object within the sample area. Thus, the data processor 237 can determine multiple line-of-sight velocities and / or line-of-sight separations from a single sampling of a single sample area within the field of view.

[0085] The data period labeled DP3 is optional. As described above, situations exist where more than one object is in the sample area. For example, more than one frequency pair can be matched during the feedback period of DP1 in cycle 2 and also during the feedback period of DP2 in cycle 2. In these situations, it may not be clear which frequency peak from DP2 corresponds to which frequency peak from DP1. As a result, it may not be clear which frequencies need to be used together to generate LIDAR data for objects in the sample area. As a result, it may be necessary to identify corresponding frequencies. This can be performed so that corresponding frequencies are from the same reflecting object in the sample area. The data period labeled DP3 can be used to find the corresponding frequencies. LIDAR data can be generated for each corresponding frequency pair and can be viewed and / or processed as LIDAR data for different reflecting objects in the sample area.

[0086] A specific example of corresponding frequencies uses a LIDAR system whose cycle has three data periods (DP1, DP2, and DP3), as shown in FIG. 3C. If two objects are present in the sample area illuminated by the LIDAR output signal, the mathematical transform unit outputs two different frequencies for fub:fu1 and fu2 during DP1, and two other different frequencies for fdb:fd1 and fd2 during DP2. In this case, the possible frequency pairs are (fd1, fu1); (fd1, fu2); (fd2, fu1); and (fd2, fdu2). Values ​​of fd and τ can be calculated for each possible frequency pair. Each pair of values ​​of fd and τ can be substituted into f3 = -fd + α3τ0 to generate a theoretical f3 for each possible frequency pair. The value of α3 is different from the value of α used in DP1 and DP2. In FIG. 3C, the value of α3 is zero. In this case, the mathematical transform unit also outputs two values ​​for f3, each associated with an object within the sample region. The frequency pairs having theoretical f3 values ​​closest to the actual f3 values ​​are considered corresponding pairs. As described above, LIDAR data can be generated for each corresponding pair and considered and / or processed as relating to a different reflecting object within the sample region. Each set of corresponding frequencies can be used in the equations described above to generate LIDAR data. The generated LIDAR data will be for a single object within the sample region. As a result, multiple different LIDAR data values ​​can be generated for the sample region, each corresponding to a different object within the sample region.

[0087] The signal processor of FIG. 1A receives a series of comparison signals carrying different channels and therefore different sample areas. As a result, the signal processor of FIG. 1A provides LIDAR data for a series of sample areas illuminated by the system output signals carrying different channels. The series of sample areas for which the signal processor provides LIDAR data can be the same as the series of illuminated sample areas. The configuration of the signal processor of FIGS. 3A through 3C can also be used for the signal processor of FIG. 1B. However, the signal processor 28 of FIG. 1B receives a comparison signal carrying only one channel. As a result, when the signal processor 28 of FIG. 1B is configured according to FIGS. 3A through 3C, each signal processor provides LIDAR data for a series of sample areas illuminated by the system output signals carrying only one channel.

[0088] In the LIDAR system of FIG. 1C , components of different signal processors 28 can be combined to combine beat signals electrically rather than optically. For example, each signal processor 28 in the LIDAR system of FIG. 1C can include the optoelectronic assembly of FIG. 3A . FIG. 3D is a schematic diagram illustrating the relationship of the first optical sensor 223, the second optical sensor 224, the first auxiliary optical sensor 218, and the second auxiliary optical sensor 220 of each optoelectronic assembly of FIG. 3A to the electronic circuitry. Because each of the different signal processors 28 receives LIDAR input signals carrying different channels, FIG. 3D illustrates the first optical sensor 223, the second optical sensor 224, the first auxiliary optical sensor 218, and the second auxiliary optical sensor 220 associated with the channel received by the optical sensor.

[0089] In FIG. 3D , components from different signal processing sections 28 ( FIG. 1C ) are combined to form a common signal processing section 74. The first data lines 228 from each of the different first balanced detection sections 225 carry first data signals to a first electrical multiplexer 272. The first electrical multiplexer 272 outputs the first data signals from the different first data lines 228 to a common data line 273. Because system output signals from the same core and carrying different channels are output consecutively from the LIDAR system, a signal processing section 28 ( FIG. 1C ) configured to receive a first comparison signal carrying channel i receives the first comparison signal in response to the signal director 14 on the core being operated to cause the system output signal carrying channel i to be output from the LIDAR system. In addition, a signal processing section 28 not configured to receive a comparison signal carrying channel i does not substantially receive the first comparison signal in response to the signal director 14 being operated to cause the system output signal carrying channel i to be output from the LIDAR system. Because system output signals carrying different channels from the same core are sequentially output from the LIDAR system, comparison signals carrying different channels are received by different signal processors 28, although overlap of the different channels may occur. Because different signal processors 28 sequentially receive comparison signals carrying different channels, first common data line 273 sequentially carries first data signals carrying different channels. Thus, first common data line 273 carries electrical data signals, each of which is an electrical representation of the first composite signal and each of which sequentially carries a different channel. While short-term overlap may occur between channels in the series of first data signals, no overlap occurs in the data window shown in FIG. 3C. First common data line 273 carries the series of first data signals to first analog-to-digital converter (ADC) 264.

[0090] The second data lines 232 from each of the different second balanced detection sections 226 carry second data signals to a second electrical multiplexer 274. The second electrical multiplexer 274 outputs the second data signals from the different second data lines 232 to a second common data line 275. The first common data line and the second common data line are each examples of a common data line. As described above, the signal processing section 28 receives the first comparison signal, which sequentially carries different channels. As a result, the second common data line 275 carries second data signals, which sequentially carry different channels. Thus, the second common data lines 275 carry electrical data signals, each of which is an electrical representation of the second composite signal, and each of which sequentially carries a different channel. While there may be short-term overlap between channels in the series of second data signals, there is no overlap during the data window shown in FIG. 3C. A second common data line 275 carries a second series of data signals to a second analog-to-digital converter (ADC) 266 .

[0091] The beat frequency identifier 238 and LIDAR data generator 270 of Figure 3D can operate as disclosed in the context of Figures 3A-3C. For example, a first analog-to-digital converter (ADC) 264 converts a first data signal from analog format to digital format and outputs a first digital data signal. A second analog-to-digital converter (ADC) 266 converts a second data signal from analog format to digital format and outputs a second digital data signal.

[0092] The first digital data signal and the second digital data signal carrying the same channel together act as a complex signal, with the first digital data signal acting as the real component of the complex signal and the second digital data signal acting as the imaginary component of the complex data signal. The first digital data signal and the second digital data signal carrying the same channel are simultaneously received by the mathematical transform unit 268. As a result, the mathematical transform unit 268 sequentially receives complex signals carrying different channels. Thus, the LIDAR data generator 270 sequentially receives the beat frequencies of the complex signals carrying different channels. As a result, the LIDAR data generator 270 can generate LIDAR data for each of the different channels. Thus, the LIDAR data generator 270 can generate LIDAR data for each sample area illuminated by a system output signal carrying a series of channels.

[0093] In another embodiment of a LIDAR system in which the relationship between the sensors of the optoelectronic assembly of FIG. 3A and the electronic circuitry of the LIDAR system is constructed according to FIG. 3D , the data processor 237 operates the electrical multiplexers as switches operable by the electronics. As a result, the data processor 237 can operate the first electrical multiplexer 272 to select a first data signal to be output onto the common data line 273 and the second electrical multiplexer 274 to select a second data signal to be output onto the second common data line 275. As a result, the LIDAR system can be configured to simultaneously output system output signals carrying different channels. For example, the LIDAR chip can be configured to simultaneously output LIDAR output signals carrying different channels. As a result, the signal director 14 can be configured to direct the output LIDAR signal to one or more alternative waveguides 16. In the example where the signal director 14 is configured to direct the outgoing LIDAR signal into all N alternative waveguides 16, the signal director can be a signal splitter.

[0094] When the LIDAR system simultaneously outputs system output signals carrying different channels, each of the different signal processors 28 can simultaneously receive a first LIDAR input signal carrying one channel. Thus, the first data line 228 from each of the different signal processors 28 simultaneously carries a first data signal to the first electrical multiplexer 272. As a result, the first electrical multiplexer 272 simultaneously receives multiple first data signals, each carrying a different channel and from the different signal processors 28. The data processor 237 uses the switching function of the first electrical multiplexer 272 to operate the first electrical multiplexer 272 so that it sequentially outputs first data signals carrying different channels. As a result, the first common data line 273 sequentially carries the first data signals carrying different channels. Examples of suitable channel series include, but are not limited to, a sequence of channels having alternative waveguide indices i=1 to i=N in a numerical sequence from i=1 to i=N.

[0095] The second data lines 232 from each of the different signal processors 28 simultaneously carry a second data signal to the second electrical multiplexer 274. As a result, the second electrical multiplexer 274 simultaneously receives multiple second data signals, each transmitting a different channel, from the different signal processors 28. The data processor 237 uses the switching function of the second electrical multiplexer 274 to operate the second electrical multiplexer 274 so that the second electrical multiplexer 274 sequentially outputs second data signals carrying different channels. As a result, the second data lines 275 sequentially carry second data signals carrying different channels.

[0096] The beat frequency identifier 238 and LIDAR data generator 270 of Figure 3D can operate as disclosed in the context of Figures 3A-3C. For example, a first analog-to-digital converter (ADC) 264 converts a first data signal from analog format to digital format and outputs a first digital data signal. A second analog-to-digital converter (ADC) 266 converts a second data signal from analog format to digital format and outputs a second digital data signal.

[0097] The first electrical multiplexer 272 and the second electrical multiplexer 274 are operated so that the first data line 273 and the second data line 275 simultaneously carry the same channel. As a result, the first digital data signal and the second digital data signal output from the first analog-to-digital converter (ADC) 264 and the second analog-to-digital converter (ADC) 266 simultaneously carry the same channel. The first digital data signal and the second digital data signal carrying the same channel operate together as a complex signal, with the first digital data signal acting as the real component of the complex signal and the second digital data signal acting as the imaginary component of the complex data signal. The first digital data signal and the second digital data signal carrying the same channel are simultaneously received by the mathematical conversion unit 268. As a result, the mathematical conversion unit 268 receives complex signals carrying different channels consecutively. Thus, the LIDAR data generator 270 receives the beat frequencies of the composite signal carrying the different channels in succession. As a result, the LIDAR data generator 270 can generate LIDAR data for each different channel. Thus, the LIDAR data generator 270 can generate LIDAR data for each sample area illuminated by a system output signal carrying a series of channels.

[0098] An alternative to the first electrical multiplexer 272 and / or the second electrical multiplexer 274 is to provide an electrical node at which the first data lines 228 from each of the different first balanced detection units 225 are in electrical communication with one another, and a second electrical node at which the second data lines 232 from each of the different second balanced detection units 226 are in electrical communication with one another. As a result, the outputs of the photosensors, such as the first balanced detection units 225, are effectively electrically connected to one another, and the outputs of the photosensors, such as the second balanced detection units 226, are effectively electrically connected to one another. As an example, FIG. 3E shows the arrangement of FIG. 3D modified so that the first data lines 228 from each of the different first balanced detection units 225 are in electrical communication with a first common data line 273. Because the LIDAR system outputs system output signals that sequentially carry different channels, the first common data line 273 carries first data signals that sequentially carry different channels. Although there may be some overlap between successively adjacent channels, no overlap occurs during the data window. Additionally, the second data lines 232 from each of the different second balanced detection units 226 are in electrical communication with a second common data line 275. Because the LIDAR system outputs system output signals that successively carry different channels, the second common data line 275 carries second data signals that successively carry different channels. Although there may be some overlap between successively adjacent channels, no overlap occurs during the data window. As can be seen in the LIDAR system of FIG. 3D, the first common data line 273 carries a first data signal carrying different channels in succession, and the second common data line 275 carries a second data signal carrying different channels in succession, so that the beat frequency identification unit 238 and the LIDAR data generation unit 270 can be operated as disclosed in the context of FIG. 3E to generate LIDAR data for each sample area illuminated by the system output signal carrying the series of channels.

[0099] 3E, during a period in which the LIDAR system outputs a system output signal carrying channel i, the opto-electrical assembly included in the signal processor configured to receive current channel i (the active signal processor) receives the first LIDAR input signal carrying channel i at least during the data window, while the signal processor not configured to receive current channel i (the inactive signal processor) does not receive the first LIDAR input signal. However, the inactive signal processor continues to receive the reference signal at least during the data window. Light from the reference signal received by the inactive signal processor can pass through the opto-electrical assembly and become noise in the electrical signals, such as the first data signal and the second data signal.

[0100] In some cases, it may be desirable to fully or partially attenuate all or part of the reference signal received by the inactive signal processing section. For example, each reference waveguide 32 (FIG. 1C) may optionally include an optical attenuator 276. The attenuator 276 may be operated by the electronic circuitry 62 to fully or partially attenuate the reference signal guided by the reference waveguide 32 in which the attenuator 276 is located.

[0101] The signal processors labeled 28 in FIG. 1C that function as active signal processors and the signal processors labeled 28 in FIG. 1C that function as inactive signal processors vary according to the channel carried by the system output signal. As a result, the electronic circuitry 62 can change the attenuated reference signal in response to changes in the channel currently carried in the system output signal. For example, the electronic circuitry 62 can operate the attenuator 276 so that the reference signal received by the active signal processors is not attenuated, or is substantially not attenuated. Furthermore, the electronic circuitry 62 can operate the attenuator 276 so that the reference signal received by all or some of the inactive signal processors is fully or partially attenuated. Because the reference signal received by all or some of the inactive signal processors is fully or partially attenuated, the amount of light from the reference signal actually received by the inactive signal processors is reduced. As a result, the attenuated light is not a source of noise in the first data signal and the second data signal.

[0102] Although optical attenuator 276 is shown disposed on reference waveguide 32 in Figure 1C, optical attenuator 276 can be disposed on all or part of reference waveguide 32 shown in the imaging systems of Figures 1A and 1B. Electronics 62 can operate variable optical attenuator 276 to attenuate the power of the reference signal to a desired level.

[0103] Suitable devices for use as the optical attenuator 276 include, but are not limited to, a variable optical attenuator (VOA), a PIN diode, and a Mach-Zehnder modulator. Examples of suitable optical attenuators are described in U.S. Patent Application Serial No. 17 / 396,616, filed August 6, 2021, entitled "Carrier Injector With Improved Compatibility," which is incorporated herein in its entirety.

[0104] A chirp rate identifier suitable for use as the chirp rate identifier 70 shown in Figures 1A-1C includes a signal splitter configured to split a common optical signal into a first optical signal and a second optical signal. The chirp rate identifier also includes a signal combiner configured to combine light from the first optical signal and light from the second optical signal to form a combined signal that beats at the beat frequency. The chirp rate identifier also includes a signal combiner configured to combine light from the first optical signal and light from the second optical signal to form a combined signal that beats at the beat frequency. The electronic circuitry can include a beat frequency discriminator that identifies the beat frequency of the combined signal, and a chirp rate generator that calculates the chirp rate of the common optical signal from the beat frequency of the combined signal.

[0105] 3F-3H show examples of chirp rate discriminators suitable for use as the chirp rate discriminator 70 shown in FIGS. 1A-1C. FIG. 3F is a schematic diagram of an example of an optoelectronic assembly suitable for use in the chirp rate discriminator 70. The common waveguide 68 carries a common signal to a signal splitter 282 included in the chirp rate discriminator 70. The signal splitter 282 splits the common signal into an early signal received at an early waveguide 284 and a late signal received at a late waveguide 286. The signal splitter 282 can be a wavelength independent splitter. For example, the signal splitter 282 can be configured so that the late and early signals carry the same or substantially the same wavelength selection. Suitable signal splitters 282 include, but are not limited to, a directional coupler, an optical coupler, a Y-junction, a tapered coupler, and a multimode interference (MMI).

[0106] Late waveguide 286 carries the late signal to signal combining portion 288. Early waveguide 284 carries the early signal to signal combining portion 288. Late waveguide 286 has a late section 289 that can be used to make the length of late waveguide 286 longer than the length of early waveguide 284. Although not shown in FIG. 3F , late section 289 can be or have a helical arrangement of late waveguide 286. The longer the length of late waveguide 286, the greater the difference, or delay, between the time required for the late signal to travel between signal splitting portion 282 and signal combining portion 288 and the time required for the early signal to travel between signal splitting portion 282 and signal combining portion 288.

[0107] Signal combiner 288 combines the late and early arriving signals into a combined signal. Due to the delay between the late and early arriving signals, the combined signal beats at the beat frequency. Signal combiner 288 also splits the combined signal into first sensor waveguide 290 and second sensor waveguide 291. First sensor waveguide 290 carries a first portion of the combined signal to first optical sensor 292, which converts a first portion of the second composite signal into a first sensor output signal, which is an electrical signal. Second sensor waveguide 291 carries a second portion of the combined signal to second optical sensor 293, which converts a second portion of the second composite signal into a second sensor output signal, which is an electrical signal. Examples of suitable optical sensors include germanium photodiodes (PDs) and avalanche photodiodes (APDs).

[0108] An example of a suitable signal combiner 288 is a multi-mode interference (MMI) device, such as a 2x2 MMI device. Other suitable signal combiners 288 include, but are not limited to, an adiabatic splitter and a directional coupler. In some cases, the functions of the illustrated signal combiner 288 are performed by one or more optical components or combinations of optical components.

[0109] The first optical sensor 292 and the second optical sensor 293 can be connected as a balanced detector that converts optical signals to electrical signals. Figure 3G is a schematic diagram illustrating the relationship between the electronic circuitry 62 and the optoelectronic assembly of Figure 3F. Although photodiode symbols are used to represent the first optical sensor 292 and the second optical sensor 293, one or more of these sensors can have other configurations. In some cases, all of the components shown in the schematic diagram of Figure 3G may be included on the LIDAR chip. In some cases, the components shown in the schematic diagram of Figure 3G are distributed between the LIDAR chip and electronic circuitry that is off-chip.

[0110] The electronic circuitry 62 connects the first photosensor 292 and the second photosensor 293 as a balanced detector. In particular, the first photosensor 292 and the second photosensor 293 are connected in series. The series connection of the balanced detectors is in communication with a data line 294 that carries the output from the balanced detectors as a data signal. The data signal is an electrical data signal that carries a representation of the combined signal. Thus, the data signal has contributions from both the first waveform and the second waveform.

[0111] The electronic circuitry 62 includes a data processing unit 237 as disclosed in the content of Figures 3A to 3E. The data processing unit 237 includes a beat frequency identification unit 295 configured to identify the beat frequency of the combined signal. The beat frequency identification unit 295 includes an analog-to-digital converter (ADC) 296 that receives the data signal from the data line 294. The analog-to-digital converter (ADC) 296 converts the data signal from analog to digital format and outputs a digital data signal. The digital data signal is a digital representation of the data signal.

[0112] The beat frequency identification unit 295 includes a mathematical transform unit 297 that receives a data signal. For example, the mathematical transform unit 297 receives a digital data signal as input from a first analog-to-digital converter (ADC) 296. The mathematical transform unit 297 is configured to perform a mathematical transform on the digital data signal to convert it from the time domain to the frequency domain. The mathematical transform can be a real transform, such as a real Fast Fourier Transform (FFT).

[0113] The mathematical transformer 297 may include a peak detector (not shown) configured to identify peaks in the output of the mathematical transformer 297. The peak detector may be configured to identify a frequency peak associated with the chirp rate identifier. For example, the frequency peak associated with the chirp rate identifier may fall within a frequency range. The peak detector may identify a frequency peak in the range of frequencies associated with the chirp rate identifier. The frequency of the identified frequency peak represents a beat frequency of the combined signal.

[0114] The data processing unit 237 includes a chirp rate generator 299 that receives the beat frequency of the combined signal from the peak detector. Additionally, the chirp rate generator 299 is configured to calculate a chirp rate (α) from the beat frequency of the combined signal. For example, the chirp rate generator 299 can calculate the magnitude of the chirp rate (α) from mα=f / τ, where mα represents the magnitude of the chirp rate (α), f represents the beat frequency of the combined signal resulting from a data period with period index n, and τ represents the difference, or delay, between the time required for a late-arriving signal to travel between the signal splitting unit 282 and the signal combining unit 288 and the time required for an early-arriving signal to travel between the signal splitting unit 282 and the signal combining unit 288. The value of f can be stored by the chirp rate generator 299 for use in calculating the chirp rate (α). The chirp rate generator 299 can map the direction of the target chirp rate (tαn) for the data period with period index n to the chirp rate magnitude (mαn) to provide a chirp rate (αn) having both magnitude and direction.

[0115] The chirp rate generator 299 can generate a value for the chirp rate (α) for the data period with period index n. Thus, all or some of the data periods can be associated with different chirp rates (α), each of which is generated by the chirp rate generator 299.

[0116] The electronic circuit unit 62 and data processor 237 shown in FIG. 3G include the components shown in the data processor 237 of FIG. 3B, 3D, or 3E, although only some of the components are shown for clarity. For example, FIG. 3G illustrates the electronic circuit unit 62 and data processor 237 including the LIDAR data generator 270 and beat frequency identifier 238 disclosed in the content of FIG. 3A through 3E. Thus, the LIDAR data generator 270 receives beat frequencies of frequency peaks associated with one or more objects external to the LIDAR system from the beat frequency identifier 238 of FIG. 3B, 3D, or 3E. For example, the LIDAR data generator 270 can receive beat frequencies of frequency peaks associated with one or more objects external to the LIDAR system from a peak detector included in the beat frequency identifier 238. Additionally, the LIDAR data generator 270 receives different chirp rates (αn) from the chirp rate generator 299. The LIDAR data generator 270 combines the chirp rate (αn) associated with a sample area with the beat frequency resulting from illuminating the same sample area to calculate LIDAR data for the sample area, as disclosed in the content of FIG. 3C. For a series of sample areas, the LIDAR data generator 270 receives the chirp rate (αn) associated with the sample area and the beat frequency resulting from illuminating the sample area. As a result, the LIDAR data generator 270 calculates LIDAR data for the series of sample areas.

[0117] In the example chirp rate discriminator of Figures 3F-3H, the common signal carried by common waveguide 68 functions as the common optical signal, and common waveguide 68 functions as the common waveguide. In addition, the late arriving signal functions as the second optical signal, while the late arriving waveguide functions as the first waveguide. The early arriving signal functions as the first optical signal, while the early arriving waveguide functions as the first waveguide.

[0118] The chirp branches shown in FIGS. 1A-1C can be selective. For example, the core components of FIGS. 1A-1C can function as components of the chirp rate identifier disclosed in the context of FIGS. 3F-3H. For example, one or more optical components of a LIDAR system positioned after one splitter 24 can function as a chirp rate detection component. A suitable chirp rate detection component can receive an optical signal comprising light from the outgoing LIDAR signal and, as a result, reflect a portion of the optical signal as a reflected signal that travels along an optical path comprising one splitter 24. In a LIDAR core constructed according to FIG. 1A, examples of chirp rate detection components include, but are not limited to, the signal director 14, the port 18, the waveguide facet, and off-chip components such as optical fibers, optical connectors, lenses, collimators, polarizers, polarization rotators, Faraday rotators, beam scanning mirrors, and / or other beam scanning devices. In a LIDAR constructed according to Figure 1A, the utility waveguide 12 can carry the reflected signal to a splitter 24. In a LIDAR core constructed according to Figure 1B or 1C, examples of chirp rate detection components include, but are not limited to, ports 18, waveguide facets, ports 18, and off-chip components such as optical fibers, optical connectors, lenses, collimators, polarizers, polarization rotators, Faraday rotators, beam scanning mirrors, and / or other beam scanning devices. In a LIDAR constructed according to Figure 1B or 1C, an alternative waveguide can carry the reflected signal to one of the splitters 24.

[0119] In some cases, a chirp rate detection component can be added to a LIDAR system constructed according to Figures 1A-1C. For example, a perturbation region can be added to the utility waveguide 12 of Figure 1A to reflect a portion of the outgoing LIDAR signal traveling along the utility waveguide toward the splitter 24. Alternatively, a perturbation region can be added to each of the alternative waveguides 16 of Figures 1B-1C to reflect a portion of the outgoing LIDAR signal traveling along each of the alternative waveguides 16 toward one of the splitters 24. Examples of suitable perturbation regions include, but are not limited to, recesses extending into the waveguide, Bragg gratings, offset waveguides, waveguide tapers, and waveguide bends.

[0120] 1A-1C, the splitter 24 can move a portion of the reflected signal from the utility waveguide 12 to a comparison waveguide 26, or from one of the alternative waveguides 16 to one of the comparison waveguides 26. As described above, the splitter 24 moves a portion of the incident LIDAR signal from the utility waveguide 12 to the comparison waveguide 26 as a comparison signal. A portion of the reflected signal in the comparison waveguide 26 can function as a chirp detection signal. The chirp detection signal is combined with the comparison signal in the comparison waveguide 26. The comparison waveguide 26 conveys the chirp detection signal and the comparison signal to a signal processor 28 for further processing.

[0121] The signal processor 28 combines the comparison signal, the chirp detection signal, and the reference signal to form a composite signal that carries LIDAR data about the sample region of the field of view. For example, as described above, the signal processor 28 may include one or more optical signal combiners that combine the comparison signal, the chirp detection signal, and the reference signal to form a composite signal. The composite signal may then be processed to extract LIDAR data about the sample region (such as the radial velocity and / or distance between the LIDAR system and an object external to the LIDAR system).

[0122] The signal processing unit 28 disclosed in the context of Figures 3A-3E can be modified to include the chirp rate generator 299 disclosed in the context of Figure 3G. For example, Figure 3H shows the schematic diagram of Figure 3B modified to include the chirp rate generator 299 of Figure 3G. The chirp rate generator 299 receives the output from the mathematical transform unit 268. As discussed above, the composite signal has contributions.

[0123] The output from the mathematical transform unit 268 includes frequency peaks from the chirp rate detection component. For example, the output from the mathematical transform unit 268 includes frequency peaks resulting from the chirp detection signal beating relative to the reference signal. Additionally, if one or more objects located outside the LIDAR system reflect the system output signal, the output from the mathematical transform unit 268 includes frequency peaks from the one or more objects. As a result, the output from the mathematical transform unit 268 can include one or more frequency peaks resulting from the comparison signal beating relative to the reference signal. Because the one or more objects have a longer delay between the reference signal and the comparison signal than the delay existing between the reference signal and the chirp detection signal, the frequency peaks from the chirp rate detection component occur at lower frequencies than the frequency peaks from the one or more objects.

[0124] The chirp rate generator 299 may include a peak detector (not shown) configured to identify frequency peaks in the output of the mathematical transformer 297. The peak detector may be configured to identify frequency peaks associated with the chirp rate detection component and any frequency peaks associated with one or more objects. For example, the frequency peaks associated with the chirp rate detection component may fall within a different frequency range than the frequency peaks associated with the one or more objects. Thus, the peak detector may associate frequency peaks within the range associated with the chirp rate detection component as frequency peaks resulting from the chirp rate detection component. Additionally, the peak detector may associate any frequency peaks within the range associated with the one or more objects as frequency peaks resulting from the one or more objects.

[0125] The chirp rate generator 299 receives the frequency of the frequency peak resulting from the chirp rate detection component from the peak detector. Additionally, the chirp rate generator 299 is configured to calculate the chirp rate (α) from the frequency peak resulting from the chirp rate detection component. For example, the chirp rate generator 299 can calculate the magnitude of the chirp rate (α) from mα = f / τ, where mα represents the magnitude of the chirp rate (α), f represents the frequency of the frequency peak resulting from the chirp rate detection component during the data period with period index n, and τ represents the delay between the time required for the reference signal to reach the optical signal combiner (optical signal combiner 211 and second optical signal combiner 2122) from the splitter 24 and the time required for the chirp detection signal to reach the optical signal combiner (optical signal combiner 211 and second optical signal combiner 212) from the splitter 24. The value of τ for a particular chirp rate detection component can be known and stored by the chirp rate generator 299 for calculating the chirp rate (αn). The chirp rate generator 299 can assign a direction corresponding to the target chirp rate (tαn) to the chirp rate magnitude (mαn) to provide a chirp rate (αn) having both magnitude and direction.

[0126] In some cases, the value of τ may or cannot be known. In these cases, the chirp rate generator 299 can estimate the value of τ from τ = |f / tα|, where τ represents the estimated value of τ, tα represents the target chirp rate for the data period associated with period index n, and fα represents the frequency of the frequency peak resulting from the chirp rate detection component during the data period associated with period index n and occurring near the start or startup of operation of the LIDAR system. When operation of the LIDAR system begins, there is a low level of error between the actual chirp rate (α) and the target chirp rate (tα). As a result, the combination of tα and fα can provide an accurate estimate of the value of τ. In some cases, the value of fpinit is associated with a period index n and represents the frequency of a frequency peak resulting from the chirp rate detection component during the data period, occurring within the first 1, 10, or 100 periods after the LIDAR system begins or starts operating to generate LIDAR data. The actual identity of the chirp rate detection component need not be known, as the value of τ can be estimated.

[0127] The chirp rate generator 299 can estimate a single value of τ using one data period and set τ to the value of τ (τ = τ). Alternatively, the chirp rate generator 299 can estimate different values ​​of τ for different data periods. As a result, the final value of τ can be a function of multiple different values ​​of τ. As an example, the chirp rate generator 299 can average multiple different values ​​of τ to generate a value for τ. Once the chirp rate generator 299 estimates a value for τ, the chirp rate generator 299 can calculate the chirp rate (α) from α = f / τ, as described above.

[0128] The LIDAR data generator 270 receives the chirp rate (α) and the frequency of the frequency peak associated with one or more objects outside the LIDAR system from the beat frequency identifier 238. For example, the LIDAR data generator 270 receives the chirp rate (α) and the frequency of the frequency peak associated with one or more objects outside the LIDAR system from the chirp rate generator 299. As a result, the LIDAR generator 270 combines the chirp rate (α) for a sample area with the beat frequency resulting from illuminating the same sample area to calculate LIDAR data for the sample area, as disclosed in the context of FIG. 3C . For a series of sample areas, the LIDAR data generator 270 receives the chirp rate (α) associated with the sample area and the beat frequency resulting from illuminating the sample area. As a result, the LIDAR data generator 270 calculates LIDAR data for the series of sample areas.

[0129] Figure 3H shows the schematic diagram of Figure 3B modified to include a chirp rate generator 299, while the schematic diagrams of Figures 3D and 3E can be modified to include a chirp rate generator 299 as shown in Figures 3I and 3J. The chirp rate generator 299 and IDAR data generator 270 of Figures 3I and 3J are configured and operated as disclosed in the context of Figure 3H.

[0130] When a core constructed according to FIGS. 1A-1C includes a signal processor constructed as disclosed in the context of FIGS. 3H-3J, the core components function as a chirp rate identifier. As described above, the chirp rate identifier includes a signal splitter configured to split a common optical signal into a first optical signal and a second optical signal. Splitter 24 functions as the signal splitter of the chirp rate identifier, with the outgoing LIDAR signal functioning as the common optical signal. In addition, the reference signal functions as the first optical signal, and the reference waveguide functions as the first waveguide. A portion of the outgoing LIDAR signal output from splitter 24, combined with the resulting reflected signal and the resulting chirp detection signal, functions as the second optical signal. For example, the portion of the outgoing LIDAR signal that is present in the chirp detection signal and also in the reflected signal functions as the second optical signal. The chirp rate identifier also includes a signal combiner configured to combine light from the first optical signal and light from the second optical signal to form a combined signal that beats at the beat frequency. The optical signal combiner 211 and / or the second optical signal combiner 212 function as the signal combiner of the chirp rate identifier. For example, the optical signal combiner 211 and / or the second optical signal combiner 212 combine the comparison signal, the chirp detection signal, and the reference signal to form a composite signal. The chirp detection signal and the reference signal beat within the composite signal and thus function as a combined signal for the chirp rate detector. The beat frequency identifier 238 identifies the beat frequency of the combined signal, and the chirp rate generator 270 calculates the chirp rate of the common optical signal.

[0131] 3A to 3J include only some of the components of the electronic circuitry 62. For example, the electronic circuitry 62 shown in FIG. 62 may also include a direction control unit 15 in communication with the data processing unit 237, and a light source control unit 63.

[0132] Although mathematical transform portion 268 is disclosed as performing a complex transform on a complex signal, the complex transform can be replaced with a real transform performed on a real signal. As a result, the optoelectronic assembly of Figure 3A can be simplified to exclude second optical coupling component 212, comparison waveguide 206, second splitter portion 202, second reference waveguide 208, first auxiliary optical sensor 218, second auxiliary optical sensor 220, and related components shown in Figures 3B, 3D, and 3E.

[0133] Suitable platforms for LIDAR chips include, but are not limited to, silica, indium phosphide, and silicon-on-insulator wafers. FIG. 4 shows a cross-sectional view of a silicon-on-insulator wafer. A silicon-on-insulator (SOI) wafer has a buried layer 300 between a substrate 302 and an optically transmissive medium 304. In a silicon-on-insulator wafer, the buried layer 300 is silica, while the substrate 302 and the optically transmissive medium 304 are silicon. The substrate of the optical platform, such as an SOI wafer, can serve as the base of the LIDAR chip. For example, in some cases, the optical components shown in FIGS. 1A through 1C can be located on top and / or on the side of the same substrate. As a result, the substrate of the optical platform, such as an SOI wafer, can serve as the base 305.

[0134] The portion of a LIDAR chip shown in Figure 4 has a waveguide structure suitable for use in a chip constructed from a silicon-on-insulator wafer. A ridge 306 of an optical transmission medium 304 extends away from a slab region 308 of the optical transmission medium 304. The optical signal is confined between the top of the ridge and the buried layer 300. As a result, the ridge 306, at least in part, defines a waveguide.

[0135] In FIG. 4, the dimensions of the ridge waveguide are labeled. For example, the ridge has a width, labeled w, and a height, labeled h. The thickness of the slab region is labeled t. In LIDAR applications, these dimensions may be more important than in other applications due to the need to use higher levels of optical power than in other applications. The ridge width (labeled w) is greater than 1 μm and less than 4 μm, the ridge height (labeled h) is greater than 1 μm and less than 4 μm, and the slab region thickness is greater than 0.5 μm and less than 3 μm. These dimensions apply to straight or substantially straight sections of the waveguide, curved sections of the waveguide, and tapered sections of the waveguide. Therefore, these sections of the waveguide will be single-mode. However, in some cases, these dimensions apply to straight or substantially straight sections of the waveguide. Additionally or alternatively, the curved portion of the waveguide can have a reduced slab thickness to reduce optical loss in the curved portion of the waveguide. For example, the curved portion of the waveguide can have a ridge extending away from the slab region that is greater than or equal to 0.0 μm and less than 0.5 μm thick. While the above dimensions generally provide straight or substantially straight portions of the waveguide with a single-mode structure, they can result in tapered and / or curved portions that are multimode. A taper that does not substantially excite higher-order modes can be used to couple a single-mode geometry to a multimode geometry. Thus, the waveguide can be configured such that a signal carried in the waveguide is carried in single mode even when carried in a waveguide portion with multimode dimensions. The waveguide structure of FIG. 4 is suitable for all or a portion of a waveguide in a LIDAR chip constructed according to FIGS. 1A-1C.

[0136] Suitable signal directors 14 for use in LIDAR chips include, but are not limited to, optical switches such as cascaded Mach-Zehnder interferometers and microring resonator switches. In one example, the signal director 14 includes cascaded Mach-Zehnder interferometers that use thermal or free-carrier-injected phase shifters. Figures 5A and 5B show an example of an optical switch with cascaded Mach-Zehnder interferometers 416. Figure 5A is a plan view of the optical switch. Figure 5B is a cross-sectional view of the optical switch shown in Figure 5A taken along the line labeled B in Figure 5A.

[0137] The optical switch receives the outgoing LIDAR signal from the utility waveguide 12. The optical switch is configured to direct the outgoing LIDAR signal to one of a plurality of alternative waveguides 16. The optical switch includes interconnecting waveguides 414 connecting a plurality of Mach-Zehnder interferometers 416 in a cascade arrangement. Each Mach-Zehnder interferometer 416 directs the outgoing LIDAR signal to one of two interconnecting waveguides 414. The direction control unit 15 can operate each Mach-Zehnder to select which of the two interconnecting waveguides 414 receives the outgoing LIDAR signal from the Mach-Zehnder interferometer 416. The interconnecting waveguide 414 that receives the outgoing LIDAR signal can be selected such that the outgoing LIDAR signal is directed through the optical switch to a specific one of the alternative waveguides 16.

[0138] Each Mach-Zehnder interferometer 416 has two branch waveguides 418 that receive a portion of the outgoing LIDAR signal from the utility waveguide 12 or the interconnecting waveguide 414. Each Mach-Zehnder interferometer 416 has a directional component 420 that receives the two portions of the outgoing LIDAR signal from the branch waveguide 418. The directional component 420 steers the outgoing LIDAR signal to one of the two interconnecting waveguides 414 configured to receive the outgoing LIDAR signal from the directional component 420. The interconnecting waveguide 414 to which the outgoing LIDAR signal is directed is a function of the phase difference between the two different portions of the outgoing LIDAR signal received by the directional component 420. While FIG. 5A shows a directional coupler operating as the directional component 420, other directional components 420 can be used. Suitable alternative directional components 420 include, but are not limited to, a multi-mode interference (MMI) device and a tapered coupler.

[0139] Each Mach-Zehnder interferometer 416 includes a phase shifter 422 disposed along one of the branch waveguides 418. The output component includes conductors 424 in electrical communication with the phase shifters 422. The conductors 424 are shown with dashed lines to easily distinguish them from the underlying structure. Each conductor 424 terminates in a contact pad 426. The contact pads 426 can be used to provide electrical communication between the conductors 424 and electronic circuitry. Thus, the conductors 424 provide electrical communication between the electronic circuitry and the phase shifters 422, and allow the electronic circuitry to operate the phase shifters 422. Suitable conductors 424 include, but are not limited to, metal traces. Suitable materials for the conductors include, but are not limited to, titanium, aluminum, and gold.

[0140] The electronic circuitry can operate each phase shifter 422 to control the phase difference between the portions of the outgoing LIDAR signal received by the directional component 420. In one example, the phase shifters 422 can be operated to change the refractive index of at least a portion of the branch waveguide 418. Changing the index of a portion of the branch waveguide 418 of the Mach-Zehnder interferometer 416 changes the effective length of that branch waveguide 418, which correspondingly changes the phase difference between the portions of the outgoing LIDAR signal received by the directional component 420. The electronic circuitry's ability to change the phase difference allows the electronic circuitry to select which interconnecting waveguide 414 receives the outgoing LIDAR signal from the directional component 420.

[0141] FIG. 5B shows an example of a suitable configuration of a phase shifter 422 on a branch waveguide 418. The branch waveguide 418 is defined, at least in part, by a ridge 306 of the optical transmission medium 304 extending away from a slab region 308 of the optical transmission medium 304. Doped regions 428 extend into the slab region 308, with one doped region having an n-type dopant and one doped region 428 having a p-type dopant. A first cladding 430 is disposed between the optical transmission medium 304 and the conductors 424. The conductors 424 each extend through openings in the first cladding 430 that contact one of the doped regions 428. A second cladding 432 is selectively disposed over the first cladding 430 and over the conductors 424. Electronic circuitry can apply a forward bias to the conductors 424 to generate a current in the branch waveguide 418. As a result, the injection of carriers into branch waveguide 418 causes free carrier absorption that changes the refractive index of branch waveguide 418 .

[0142] The first cladding 430 and / or second cladding 432 shown in FIG. 5B can each represent one or more layers of material. The materials for the first cladding 430 and / or second cladding 432 can be selected to provide electrical insulation for the conductor 424, refractive index reduction relative to the optically transmissive medium 304, stress reduction, and mechanical and environmental protection. Suitable materials for the first cladding 430 and / or second cladding 432 include, but are not limited to, silicon nitride, tetraorthosilicate (TEOS), silicon dioxide, silicon nitride, and aluminum oxide. One or more materials for the first cladding 430 and / or second cladding 432 can be doped or undoped.

[0143] If the LIDAR system has multiple cores, the LIDAR system can have multiple signal directors 76, and different signal directors 76 can receive LIDAR output signals from different selected signal directors 76. As an example, Figure 6 shows the LIDAR system of Figure 2 modified to have multiple signal directors 76, each receiving LIDAR output signals from a different core.

[0144] 1A-1C show each core having a different light source 10. However, multiple cores, all cores, or some cores can receive an outgoing LIDAR signal from a common light source. In some cases, the cores are divided into groups, with each core in a group receiving an outgoing LIDAR signal from the same common light source, and cores in different groups receiving an outgoing LIDAR signal from a different common light source. In some cases, a group of cores can have only one of the multiple cores. As an example, FIG. 7 shows the LIDAR system of FIG. 2 in which the light source 10 is located outside the core and each core receives an outgoing LIDAR signal from the light source.

[0145] The first optical link 440 provides optical communication between the light source 10 and the signal splitter 442. The second optical link 444 provides optical communication between the signal splitter 442 and utility waveguides 12 on different cores 4. The light source 10 outputs an auxiliary signal that is received on the first optical link 440. The signal splitter 442 receives the auxiliary signal from the first optical link 440. The signal splitter 442 splits the auxiliary signal into split signals that are each received on a different one of the second optical links 444. Each utility waveguide 12 receives the split signal from a different one of the optical links 444. A portion of the split signal that enters the utility waveguide serves as the outgoing LIDAR signal.

[0146] The LIDAR system can optionally include an amplifier 446 disposed along the first optical link 440 to amplify the power of the auxiliary signal. Suitable amplifiers 446 for use along the optical link include, but are not limited to, an SOA, an Erbium-Doped Fiber Amplifier (EDFA), or a Pre-Doped Fiber Amplifier (PDFA).

[0147] If it is desired that the different output LIDAR signals have the same or substantially the same wavelength distribution, suitable signal splitters 442 include, but are not limited to, wavelength-independent signal combiners such as optical couplers, Y-junctions, MMIs, cascaded evanescent optical couplers, and cascaded Y-junctions. If it is desired that the different output LIDAR signals have different wavelength distributions, suitable signal splitters 442 include, but are not limited to, wavelength-dependent signal splitters 442 having optical demultiplexers such as arrayed waveguide gratings (AWGs) and echelle gratings.

[0148] If multiple different cores receive the outgoing LIDAR signal from a common light source, only one of the cores receiving the outgoing LIDAR signal from the common light source will have a control branch, and as a result, other cores receiving the outgoing LIDAR signal from the same common light source can omit the directional coupler 66, common waveguide 68, and control branch shown in Figures 1A-1C.

[0149] As can be seen from FIGS. 1A and 1B, the LIDAR system can optionally include one or more optical signal amplifiers 446. For example, amplifiers 446 can be selectively disposed along the utility waveguide, as shown in the LIDAR system of FIG. 1A. In another example, amplifiers 446 can be selectively disposed along all or part of the alternative waveguide 16, as shown in the LIDAR system of FIG. 1B. Electronic circuitry can operate the amplifiers 446 to amplify the power of the outgoing LIDAR signal and, therefore, the system output signal. Electronic circuitry can operate each amplifier 446 to amplify the power of the outgoing LIDAR signal. Suitable amplifiers 446 for use in the LIDAR chip include, but are not limited to, semiconductor optical amplifiers (SOAs).

[0150] 1A and 1B are each disposed immediately before the splitter 24. In some cases, this placement of the amplifier 446 may cause saturation of one or more components selected from the group consisting of the first auxiliary optical sensor 218, the second auxiliary optical sensor 220, the first optical sensor 223, and the second optical sensor 224. For example, the amplifier 446 may increase the power level of the reference signal to a level at which saturation occurs. A beam dump may be used to reduce the power level of the reference signal to a level at which saturation is reduced or eliminated.

[0151] As can be seen from FIGS. 3B, 3D, and 3E, the LIDAR system can optionally include one or more electrical signal amplifiers 447. Each amplifier 447 is positioned to provide amplification of a first data signal traveling between a first photosensor, such as the first balanced detector 225, and an analog-to-digital converter, or a second data signal traveling between a second photosensor, such as the second balanced detector 226, and an analog-to-digital converter. While FIG. 3D illustrates each electrical signal amplifier 447 positioned along the first data line 228 or the second data line 232, the electrical signal amplifiers 447 may alternatively be positioned along the common data line 273 or the second common data line 275. While FIG. 3E illustrates each electrical signal amplifier 447 positioned along the common data line 273 or the second common data line 275, the electrical signal amplifiers 447 may alternatively be positioned along the first data line 228 or the second data line 232. A suitable electrical signal amplifier 447 includes, but is not limited to, a transimpedance amplifier (TIA).

[0152] 8 shows a portion of a LIDAR chip in combination with a reference waveguide 32 and a beam dump configured to reduce the power level of a reference signal carried in the reference waveguide 32. The reference waveguide 32 carries the reference signal to a splitter 448, which carries a portion of the reference signal from the reference waveguide 32 as a dump signal to a dump waveguide 450. The dump waveguide 450 carries the dump signal to a beam dump 452.

[0153] The beam dump 452 is configured to scatter the dump signal without reflecting a significant amount of light from the dump signal back into the dump waveguide 250. For example, the beam dump 452 can be a recess 454 etched into the optical transmission medium of a silicon-on-insulator wafer to a depth such that the dump signal is incident on one or more sides of the recess 454. The recess 454 can be shaped to cause scattering of the dump signal. For example, the recess 454 can have a star-shaped configuration or can have any number of irregularly spaced sides. In some cases, the recess 454 can extend through the optical transmission medium to an underlying layer, such as a buried layer of the silicon-on-insulator wafer.

[0154] The splitter 448 can be configured to control the proportion of the reference signal power carried to the dump waveguide. Increasing the proportion of the reference signal power carried to the dump waveguide increases the attenuation of the reference signal power, and accordingly decreases the power of the signal received by some or all of the optical sensors selected from the group consisting of the first auxiliary optical sensor, the second auxiliary optical sensor, the first optical sensor, and the second optical sensor. Reducing the power of the optical signal received by some or all of the optical sensors reduces the likelihood of saturation. Suitable splitters 448 include, but are not limited to, optical couplers, Y-junctions, and 1x2 splitters including MMIs. In some cases, the splitter 448 is configured to reduce the proportion of the reference signal power carried to the dump waveguide 450 to 0.1%, 0.5%, or 1% or more and 2%, 10%, or 20% or less.

[0155] The optical sensor interfaced with the waveguide on the LIDAR chip can be a component separate from the chip and attached to the chip. For example, the optical sensor can be a photodiode or an avalanche photodiode. Examples of suitable optical sensor components include, but are not limited to, an InGaAPIN photodiode manufactured by Hamamatsu Photonics K.K., Hamamatsu, Japan, or an InGaAs APD (avalanche photodiode) manufactured by Hamamatsu Photonics K.K., Hamamatsu, Japan. These optical sensors can be located in the center of the LIDAR chip. Alternatively, all or a portion of the waveguide terminating in the optical sensor can terminate in a facet located at the edge of the chip, and the optical sensor can be attached to the edge of the chip beyond the facet so that the optical sensor receives light passing through the facet. The use of an optical sensor that is a component separate from the chip is suitable for all or a portion of the optical sensor selected from the group consisting of the first optical sensor and the second optical sensor.

[0156] As an alternative to a separate optical sensor, all or part of the optical sensor can be integrated on the chip. For example, examples of optical sensors interfacing with ridge waveguides on chips constructed from silicon-on-insulator wafers are described in OpticsEXPRESS Vol. 15, No. 21, pp. 13965-13971 (2007), U.S. Patent No. 8,093,080, issued January 10, 2012, U.S. Patent No. 8,242,432, issued August 14, 2012, and U.S. Patent No. 6,108,8472, issued August 22, 2000, each of which is incorporated herein in its entirety. The use of an optical sensor integrated on the chip is suitable for all or part of the optical sensor selected from the group consisting of the first optical sensor and the second optical sensor.

[0157] As described above, the electronic circuitry that operates the system includes the electronic circuitry 62 and the assembly control 280. Each electronic circuitry 62 is associated with one of the cores (i.e., local electronic circuitry), while the assembly control 280 can be associated with multiple cores (i.e., common electronic circuitry). Although the electronic circuitry 62 and the assembly control 280 are shown as being in different locations, the electronic circuitry 62 and the assembly control 280 can be in a common location and / or in a common package. Furthermore, the electronic circuitry 62 and the assembly control 280 for each core can be integrated and need not refer to separate or individual electronic components. For example, the electronic circuitry 62 associated with different cores can be selectively integrated with the assembly control 280. The integrated assembly control 280 can be located on the LIDAR chip or on the support 77. The assembly control unit 280 or the integrated assembly control unit 280 can aggregate or generate LIDAR data results from different cores and / or coordinate the LIDAR data results from different cores to assemble the LIDAR data results relative to the field of view of the LIDAR system.

[0158] Electronic circuitry 62 suitable for use in LIDAR systems includes, but is not limited to, a controller having or consisting of analog circuitry, digital circuitry, a processor, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a computer, a microcomputer, or any combination suitable for performing the above-described operational, monitoring, and control functions. In some cases, the controller has access to a memory containing instructions that are executed by the controller during the performance of the operational, control, and monitoring functions. While the electronic circuitry is shown as a single component in a single location, the electronic circuitry can have multiple different components that are separate from one another and / or located in different locations. Additionally, as discussed above, all or a portion of the disclosed electronic circuitry can be included on a chip with the electronic circuitry integrated on the chip.

[0159] An example of a suitable direction control 15 uses firmware, hardware, software, or a combination thereof to perform the attribute functions. An example of a suitable light source control 63 uses firmware, hardware, software, or a combination thereof to perform the attribute functions. An example of a suitable data control 237 uses firmware, hardware, software, or a combination thereof to perform the attribute functions. An example of a suitable assembly control 280 uses firmware, hardware, software, or a combination thereof to perform the attribute functions.

[0160] Components on a LIDAR chip can be fully or partially integrated with the LIDAR chip. For example, an integrated optical component can include or consist of a portion of the wafer on which the LIDAR chip is fabricated. A wafer that can serve as a platform for a LIDAR chip can have multiple material layers. At least some of the different layers can be made of different materials. One example is a silicon-on-insulator wafer having a buried layer 300 between a substrate 302 and an optically transmissive medium 304, as shown in FIG. 4. The integrated on-chip component can be formed by defining the component features in the optically transmissive medium 304 using etching and masking techniques. For example, a slab 318 defining a waveguide and a stop recess can be formed in desired areas of the wafer using differential etching of the wafer. As a result, the LIDAR chip can include a portion of the wafer, and the integrated on-chip component can each include or consist of a portion of the wafer. Furthermore, the integrated on-chip component can be configured such that an optical signal traveling through the component travels through one or more layers originally included in the wafer. For example, the waveguide in Figure 4 guides the optical signal through the optical transmission medium 304 from the wafer. The integrated component can optionally include materials in addition to those present on the wafer. For example, the integrated component can include reflective materials and / or cladding.

[0161] Numerical labels such as first, second, third, etc. are used to distinguish between different features and components and do not imply an order or presence of lower-numbered features. For example, the second component may be present without the first component being present, and / or the third step may be performed before the first step. Each of the optical signals described above comprises, consists of, or consists essentially of light from a previous optical signal from which it was derived. For example, an incident LIDAR signal comprises, consists of, or consists essentially of light from a LIDAR input signal.

[0162] Although the LIDAR system is disclosed as using complex signals, such as complex data signals, the LIDAR system can also use real signals. As a result, the mathematical transformations can be made real, and components associated with generating and using quadrature components can be removed from the LIDAR system. As a result, the LIDAR system can use a single signal combiner. Additionally, or alternatively, a single optical sensor can replace each balanced detector.

[0163] Although the imaging system and LIDAR system are disclosed as having steerable system output signals, the imaging system and LIDAR system can also be used in applications where the system output signals are not steered. As a result, optical component assembly 75 is optional.

[0164] Other embodiments, combinations, and modifications of the present invention will occur to those skilled in the art in light of these teachings. Accordingly, the present invention is limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.

Claims

1. a signal splitter configured to split the common optical signal into a first optical signal and a second optical signal; a signal combining portion configured to combine light from the first optical signal and light from the second optical signal to form a combined signal that beats at a beat frequency; an electronic circuitry having a beat frequency identifier configured to identify the beat frequency of the combined signal, the electronic circuitry having a chirp rate generator configured to calculate a chirp rate for the common optical signal from the beat frequency of the combined signal; A LIDAR system having:

2. The chirp rate generator configured to calculate the chirp rate comprises: the chirp rate generator configured to calculate the magnitude of the chirp rate according to mαn=fp / τp, where mαn represents the magnitude of the chirp rate, fp represents the beat frequency of the combined signal, and τp represents the delay between the time required for the first signal to travel between the signal splitting unit and the signal combining unit and the time required for the second signal to travel between the signal splitting unit and the signal combining unit; The system of claim 1.

3. The electronic circuit unit includes: a LIDAR data generator configured to calculate LIDAR data from the chirp rate calculated by the chirp rate generator; The LIDAR data is indicating a radial velocity and / or a distance between the imaging system and an object external to the imaging system; The system of claim 1.

4. The signal combining unit also configured to combine light from the first optical signal with light from a comparison signal to form a composite signal beating at a composite signal beat frequency; The light from the comparison signal is having light from the common signal that exits the imaging system, is reflected by an object located outside the imaging system, and is returned to the imaging system; The system of claim 1.

5. The beat frequency discriminator configured to identify composite signal beat frequencies; The system of claim 4.

6. 6. The system of claim 5, The electronic circuit unit includes: a LIDAR data generator configured to calculate LIDAR data from the chirp rate calculated by the chirp rate generator and from the composite signal beat frequencies identified by the pre-beat frequency identifier; The LIDAR data is indicating a radial velocity and / or a distance between the imaging system and an object external to the imaging system; The system of claim 5.

7. a chirp rate detection component that reflects the second optical signal but transmits light from the common signal and that is included in the comparison signal. The system of claim 1.

8. The signal dividing unit and the signal combining unit are included in an optical circuit of a semiconductor chip. The system of claim 1.

9. The second signal dividing unit tapping a common signal from the outgoing LIDAR signal; The system of claim 1.

10. The chirp rate generation unit configured to calculate an approximate duration of the delay between the time required for the first optical signal to travel between the signal splitting unit and the signal combining unit and the time required for the second optical signal to travel between the signal splitting unit and the signal combining unit. The system of claim 1.

11. splitting the common optical signal into a first optical signal and a second optical signal; combining light from the first optical signal and light from the second optical signal to form a combined signal that beats at a beat frequency; identifying a beat frequency of the combined signal; calculating a chirp rate for the common optical signal from the beat frequency of the combined signal; A method for operating a LIDAR system.

12. further calculating LIDAR data from the calculated chirp rate; the LIDAR data indicates a line-of-sight velocity and / or a distance between the imaging system and an object external to the imaging system; 12. The method of operating the LIDAR system of claim 11.

13. The calculation of the chirp rate is calculating the magnitude of the chirp rate according to mαn=fp / τp, where mαn represents the magnitude of the chirp rate, fp represents the beat frequency of the combined signal, and τp represents the delay between the time required for the first signal to travel between the signal splitting unit and the signal combining unit and the time required for the second signal to travel between the signal splitting unit and the signal combining unit.

12. The method of operating the LIDAR system of claim 11.

14. calculating LIDAR data from the calculated chirp rate; the LIDAR data indicates a line-of-sight velocity and / or a distance between the imaging system and an object external to the imaging system; 12. The method of operating the LIDAR system of claim 11.

15. further combining light from the first optical signal with light from a comparison signal to form a composite signal that beats at a composite signal beat frequency; the light from the comparison signal includes light from the common signal that leaves the imaging system, is reflected by an object outside the imaging system, and returns to the imaging system; 12. The method of operating the LIDAR system of claim 11.

16. further identifying a beat frequency of the composite signal; 16. The method of operating the LIDAR system of claim 15.

17. Further, calculating LIDAR data from the chirp rate calculated by the chirp rate generation unit and the composite signal beat frequency identified by the beat frequency identification unit; the LIDAR data indicates a line-of-sight velocity and / or a distance between the imaging system and an object external to the imaging system; 17. The method of operating the LIDAR system of claim 16.

18. a chirp rate detection component that reflects the second optical signal but transmits light from the common signal that is included in the comparison signal; 12. The method of operating the LIDAR system of claim 11.

19. moreover, calculating an approximate duration of a delay between the time required for the first optical signal to travel between a signal splitting unit and a signal combining unit and the time required for the second optical signal to travel between the signal splitting unit and the signal combining unit; the signal splitter is configured to split the common optical signal into the first optical signal and the second optical signal; the signal combiner is configured to combine light from the first optical signal and light from the second optical signal; 12. The method of operating the LIDAR system of claim 11.

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