Reducing the sampling rate in LIDAR systems

Abstract

The LIDAR system includes a transmitter that outputs a system output signal from the LIDAR system. The LIDAR system also includes electronics that control the frequency of the system output signal over a series of cycles, the cycles including a plurality of data periods. The electronics vary the frequency of the system output signal at a first rate during a first data period. The electronics vary the frequency of the system output signal at a second rate during a second data period, the second rate being different from the first rate.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. Patent Application No. 16 / 848,829, entitled “REDUCING SAMPLING RATE IN LIDAR SYSTEMS,” filed April 14, 2020, and is hereby incorporated in its entirety. [Technical field]

[0002] The present invention relates to optical devices, and in particular to LIDAR systems. [Background technology]

[0003] Many LIDAR systems include one or more analog-to-digital converters (ADCs) that each receive a pulsating signal. The high frequency of these pulsating signals requires that the analog-to-digital converters (ADCs) be sampled at a high rate. However, the price and power consumption of commercially available analog-to-digital converters (ADCs) are directly related to this sampling rate. As a result, the high sampling rates associated with the one or more analog-to-digital converters (ADCs) in LIDAR systems make these systems impractical for commercial production. Therefore, a practical LIDAR system is needed. Overview

[0004] The LIDAR system has a transmitter that outputs a system output signal from the LIDAR system. The LIDAR system also includes electronics that control a frequency of the system output signal over a series of cycles, the cycles including a plurality of data periods. The electronics vary the frequency of the system output signal at a first rate during a first data period. The electronics vary the frequency of the system output signal at a second rate during a second data period, the second rate being different from the first rate.

[0005] The LIDAR system includes an analog-to-digital converter (ADC) that receives a pulsating signal that pulsates a first signal relative to a second signal. The first signal is generated from light that exits the LIDAR system and is reflected back to the LIDAR system after being reflected by an object outside the LIDAR system. The second signal is generated from light that does not exit the LIDAR system. The frequency of the pulsating signal has a frequency contribution from a separation between the LIDAR system and the object. Electronics generate a plurality of possible first frequency values, each of which is a potential frequency contribution value.

[0006] Operating the LIDAR system can include receiving a pulsating signal at an analog-to-digital converter (ADC). The pulsating signal pulsates a first signal relative to a second signal. The first signal is generated from light that exits the LIDAR system and returns to the LIDAR system after being reflected by an object outside the LIDAR system. The second signal is generated from light that does not exit the LIDAR system. The frequency of the pulsating signal has a frequency contribution from a separation between the LIDAR system and the object. Operating the LIDAR system can also include generating a plurality of possible first frequency values, each of which is a candidate for a frequency contribution value. [Brief description of the drawings]

[0007] FIG. 1A is a schematic top view of a LIDAR system including 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 top view of a LIDAR system including 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 top view of another embodiment of a LIDAR system that includes or consists of a LIDAR chip that outputs a LIDAR output signal and receives multiple LIDAR input signals on different waveguides.

[0010] FIG. 1D is a schematic top view of a LIDAR system including a LIDAR chip receiving an outgoing LIDAR signal from a light source located outside the LIDAR chip.

[0011] FIG. 2 is a top view of an example of a LIDAR adapter suitable for use with the LIDAR chip of FIG. 1B.

[0012] FIG. 3 is a top view of an example of a LIDAR adapter suitable for use with the LIDAR chip of FIG. 1C.

[0013] FIG. 4 is a top view of an example of a LIDAR system including the LIDAR chip of FIG. 1A and the LIDAR adapter of FIG. 2 on a common support.

[0014] FIG. 5A illustrates an example of a processing element suitable for use with a LIDAR system.

[0015] FIG. 5B provides a schematic of electronic equipment suitable for use with a processing element constructed according to FIG. 5A.

[0016] FIG. 5C illustrates another example of a processing element suitable for use with a LIDAR system.

[0017] FIG. 5D provides a schematic of electronics suitable for use with a processing element constructed according to FIG. 5C.

[0018] FIG. 5E is a graph of frequency versus time for one of the channels included in the LIDAR output signal.

[0019] FIG. 5F shows a frequency spectrum for use with a LIDAR system.

[0020] Figure 6 shows a cross-sectional view of a portion of a LIDAR chip containing a waveguide on a silicon-on-insulator platform.

[0021] The LIDAR system transmits a system output signal. Light from the system output signal may be reflected by objects outside the LIDAR system. A portion of the reflected light may return to the LIDAR system. The LIDAR system may combine the returning light with another light signal to form a pulsating signal. The LIDAR system uses the pulsating signal to generate a data signal, which is an electrical signal, that pulsates. The data signal may be received by an analog-to-digital converter (ADC), which outputs a digital data signal. The LIDAR system includes electronics that use the digital data signal to generate LIDAR data (line of sight velocity and / or distance between the LIDAR system and objects outside the LIDAR system).

[0022] During operation of the LIDAR system, the LIDAR system goes through a series of cycles. During each cycle, the LIDAR system illuminates a sample area. LIDAR data of an object in the illuminated sample area can be produced from each cycle. Each cycle includes a number of data periods, and the electronics control the frequency of the system output signal during each different data period. For example, during at least two of the data periods, the electronics can change the frequency of the system output signal during the data period. The rate of frequency change during the two data periods can be selected such that the LIDAR data can be measured even if the analog-to-digital converter (ADC) is undersampled. As a result, the LIDAR system can undersample one or more analog-to-digital converters (ADCs). This is because undersampling reduces the ADC sampling rate required by the LIDAR system compared to previous LIDAR systems. The reduced sampling rate reduces the cost and power consumption of the LIDAR system.

[0023] 1A is a schematic top view of a LIDAR chip that can function as a LIDAR system or can be included in a LIDAR system that includes components other than the LIDAR chip. The LIDAR chip can include a photonic integrated circuit (PIC) and can be an integrated photonic chip. The LIDAR chip includes a light source (10) that outputs an outgoing LIDAR signal. Suitable light sources (10) include, but are not limited to, semiconductor lasers such as external cavity lasers (ECL), distributed feedback lasers (DFB), discrete mode (DM) lasers, and distributed Bragg reflector lasers (DBR).

[0024] The LIDAR chip also includes a utility waveguide (12) that receives the outgoing LIDAR signal from the light source (10). The utility waveguide (12) terminates at a facet (14) to carry the outgoing LIDAR signal to the facet (14). The facet (14) can be positioned such that the outgoing LIDAR signal traveling through the facet (14) exits the LIDAR chip and serves as a LIDAR output signal. For example, the facet (14) can be positioned at an edge of the chip such that the outgoing LIDAR signal traveling through the facet (14) exits the chip and serves as a LIDAR output signal. In some examples, a portion of the LIDAR output signal exiting the LIDAR chip can also be considered a system output signal. As an example, if the exit of the LIDAR output signal from the LIDAR chip is also the exit of the LIDAR output signal from the LIDAR system, the LIDAR output signal can also be considered a system output signal. The facet (14) may function as a transmitter for a LIDAR system, where a portion of the LIDAR output signal serves as a system output signal.

[0025] The LIDAR output signal travels away from the LIDAR system through the empty space in the atmosphere where the LIDAR system is located. The LIDAR output signal may be reflected by one or more objects in the path of the LIDAR output signal. When the LIDAR output signal is reflected, at least a portion of the reflected light returns toward the LIDAR chip as the LIDAR input signal. In some examples, the LIDAR input signal may also be considered as a system return signal. As an example, if the exit of the LIDAR output signal from the LIDAR chip is also the exit of the LIDAR output signal from the LIDAR system, the LIDAR input signal may also be considered as a system return signal.

[0026] A LIDAR input signal may enter the utility waveguide (12) through the facet (14). The portion of the LIDAR input signal that enters the utility waveguide (12) serves as the incident LIDAR signal. The utility waveguide (12) conveys the incident LIDAR signal to a splitter (16), which moves a portion of the outgoing LIDAR signal from the utility waveguide (12) onto a comparison waveguide (18) as a comparison signal. The comparison waveguide (18) conveys the comparison signal to a processing element (22) for further processing. Although FIG. 1A shows a directional coupler operating as the splitter (16), other signal intercepting components may be used as the splitter (16). Suitable splitters (16) include, but are not limited to, directional couplers, optical couplers, y-junctions, tapered couplers, and mixed mode interferometers (MMIs).

[0027] The utility waveguide (12) also carries the outgoing LIDAR signal to a splitter (16), which moves a portion of the outgoing LIDAR signal from the utility waveguide (12) as a reference signal onto a reference waveguide (20), which carries the reference signal to a processing element (22) for further processing.

[0028] The fraction of light transferred by the splitter (16) from the utility waveguide (12) can be fixed or substantially fixed. For example, the splitter (16) can be configured such that the power of the reference signal transmitted to the reference waveguide (20) is an outgoing fraction of the power of the outgoing LIDAR signal, or the power of the comparison signal transmitted to the comparison waveguide (18) is an incoming fraction of the power of the incoming LIDAR signal. In many splitters (16), such as directional couplers and multimode interferometers (MMIs), the outgoing fraction is equal or substantially equal to the incoming fraction. In some examples, the outgoing fraction is greater than 30%, 40%, or 49% and / or less than 51%, 60%, or 70% and / or the incoming fraction is greater than 30%, 40%, or 49% and / or less than 51%, 60%, or 70%. Splitters (16), such as mixed mode interferometers (MMI), typically provide exit and entrance fractions of 50% or approximately 50%. However, mixed mode interferometers (MMI) may be easier to manufacture on platforms such as silicon-on-insulator platforms than some alternatives. In one example, splitter (16) is a mixed mode interferometer (MMI) and the exit and entrance fractions are 50% or substantially 50%. As described in more detail below, processing element (22) combines the comparison signal with the reference signal to form a composite signal carrying LIDAR data of the sample area on the field of view. The composite signal can then be processed to extract LIDAR data of the sample area (line of sight velocity and / or distance between the LIDAR system and an object external to the LIDAR system).

[0029] The LIDAR chip can include a control branch for controlling the operation of the light source (10). The control branch includes a splitter (26) that moves a portion of the outgoing LIDAR signal from the utility waveguide (12) onto a control waveguide (28). The combined portion of the outgoing LIDAR signal serves as a tap signal. Although FIG. 1A shows a directional coupler operating as the splitter (26), other signal intercepting components can be used as the splitter (26). Suitable splitters (26) include, but are not limited to, directional couplers, optical couplers, y-junctions, tapered couplers, and mixed mode interferometers (MMIs).

[0030] A control waveguide (28) carries the tap signal to a control element (30), which may be in electrical communication with electronics (32). In operation, the electronics (32) may adjust the frequency of the outgoing LIDAR signal in response to an output from the control element. A suitable construction of a control element is described in U.S. Patent Application Serial No. 15 / 977,957, entitled "Optical Sensor Chip," filed May 11, 2018, and incorporated herein in its entirety.

[0031] LIDAR systems can be modified so that the incoming and outgoing LIDAR signals are carried in different waveguides. For example, FIG. 1B is a top view of the LIDAR chip of FIG. 1A modified so that the incoming and outgoing LIDAR signals are carried in different waveguides. The outgoing LIDAR signal leaves the LIDAR chip through a facet (14) and serves as a LIDAR output signal. When light from the LIDAR output signal is reflected by an object external to the LIDAR system, at least a portion of the reflected light returns to the LIDAR chip as a first LIDAR input signal. The first LIDAR input signal enters a comparison waveguide (18) through a facet (34) and serves as a comparison signal. The comparison waveguide (18) carries the comparison signal to a processing element (22) for further processing. As described in connection with FIG. 1A, the reference waveguide (20) carries the reference signal to the processing element (22) for further processing. As described in more detail below, the processing element (22) combines the comparison signal with the reference signal to form a composite signal that conveys LIDAR data for the sample area over the field of view.

[0032] The LIDAR chip can be modified to receive multiple LIDAR input signals. For example, FIG. 1C shows the LIDAR chip of FIG. 1B modified to receive two LIDAR input signals. The splitter (40) is configured to place a portion of the reference signal carried on the reference waveguide (20) on the first reference waveguide (42) and place another portion of the reference signal on the second reference waveguide (44). Thus, the first reference waveguide (42) carries the first reference signal and the second reference waveguide (44) carries the second reference signal. The first reference waveguide (42) carries the first reference signal to the first processing element (46) and the second reference waveguide (44) carries the second reference signal to the second processing element (48). Examples of suitable splitters (40) include, but are not limited to, y-junctions, optical couplers, and mixed mode interference couplers (MMI).

[0033] The outgoing LIDAR signal exits the LIDAR chip through a facet (14) and serves as a LIDAR output signal. When light from the LIDAR output signal is reflected by one or more objects external to the LIDAR system, at least a portion of the reflected light returns to the LIDAR chip as a first LIDAR input signal. The first LIDAR input signal enters a comparison waveguide (18) through a facet (34) and serves as a first comparison signal. The comparison waveguide (18) conveys the first comparison signal to a first processing element (46) for further processing.

[0034] Additionally, when light from the LIDAR output signal is reflected by one or more objects external to the LIDAR system, at least a portion of the reflected signal returns to the LIDAR chip as a second LIDAR input signal, which passes through the facet (52) into the second comparison waveguide (50) and serves as a second comparison signal carried by the second comparison waveguide (50). The second comparison waveguide (50) carries the second comparison signal to a second processing element (48) for further processing.

[0035] Although the light source (10) is shown as being located on the LIDAR chip, all or a portion of the light source (10) can be located away from the LIDAR chip. For example, the utility waveguide (12) can terminate at a second facet where an outgoing LIDAR signal can enter the utility waveguide (12) from a light source located away from the LIDAR chip. As an example, FIG. 1D shows the LIDAR system of FIG. 1A modified to include a light source (10) located away from the LIDAR chip. The utility waveguide (12) includes a second facet (53). An optical link (54), such as one or more optical fibers, carries the outgoing LIDAR signal to the second facet (53) of the utility waveguide (12). The optical link (54) is aligned with the utility waveguide (12). This allows an outgoing LIDAR signal produced by the light source (10) to enter the utility waveguide (12) through the second facet (53). An alignment mechanism (55), such as a fiber block, can provide alignment between the optical link (54) and the utility waveguide (12). An optical amplifier (57) can be optionally placed along the optical link to amplify the outgoing LIDAR signal. If the light source is external to the LIDAR chip, suitable light sources include, but are not limited to, semiconductor lasers such as external cavity lasers (ECLs), distributed feedback lasers (DFBs), discrete mode (DM) lasers, and distributed Bragg reflector lasers (DBRs). In some examples, the LIDAR system includes one or more lenses (not shown) that couple the outgoing LIDAR source to the amplifier (57) or utility waveguide (12).

[0036] In some examples, a LIDAR chip constructed according to FIG. 1B or 1C is used in combination with a LIDAR adapter. In some examples, the LIDAR adapter can be physically and optically positioned between the LIDAR chip and one or more reflective objects and / or the field of view, such that the optical paths along which the first LIDAR input signal and / or the LIDAR output signal travel from the LIDAR chip to the field of view pass through the LIDAR adapter. Furthermore, the LIDAR adapter can be configured to operate on the first LIDAR input signal and the LIDAR output signal such that the first LIDAR input signal and the LIDAR output signal travel on different optical paths between the LIDAR adapter and the LIDAR chip, but travel on the same optical path between the LIDAR adapter and the reflective objects in the field of view.

[0037] An example of a LIDAR adapter suitable for use with the LIDAR chip of FIG. 1B is shown in FIG. 2. The LIDAR adapter includes multiple components disposed on a base. For example, the LIDAR adapter includes a circulator (100) disposed on a base (102). The illustrated optical circulator (100) includes three ports, such that light entering one port exits the next port. For example, the illustrated optical circulator includes a first port (104), a second port (106), and a third port (108). The LIDAR output signal enters the first port (104) from the utility waveguide (12) of the LIDAR chip and exits from the second port (106).

[0038] The LIDAR adapter may be configured such that the output of the LIDAR output signal from the second port (106) can also function as an output of the LIDAR output signal from the LIDAR adapter and thus from the LIDAR system. As a result, the LIDAR output signal can be output from the LIDAR adapter such that the LIDAR output signal travels toward a sample area in the field of view. Thus, in some examples, the portion of the LIDAR output signal that exits the LIDAR adapter can also be considered a system output signal. As an example, if the exit of the LIDAR output signal from the LIDAR adapter is also the exit of the LIDAR output signal from the LIDAR system, the LIDAR output signal can also be considered a system output signal. If the LIDAR output signal functions as a system output signal, the second port (106) can function as a transmitter for the LIDAR system.

[0039] The LIDAR output signal output from the LIDAR adapter includes, consists of, or consists essentially of light from the LIDAR output signal received from the LIDAR chip. Thus, the LIDAR output signal output from the LIDAR adapter may be the same or substantially the same as the LIDAR output signal received from the LIDAR chip. However, there may be differences between the LIDAR output signal output from the LIDAR adapter and the LIDAR output signal received from the LIDAR chip. For example, the LIDAR output signal may experience light loss as it passes through the LIDAR adapter, and the LIDAR adapter may optionally include an amplifier configured to amplify the LIDAR output signal as it passes through the LIDAR adapter.

[0040] When one or more objects within the sample volume reflect the LIDAR output signal, at least a portion of the reflected light returns to the circulator (100) as a system return signal, which enters the circulator (100) through a second port (106). Figure 2 shows the LIDAR output signal and the system return signal traveling along the same optical path between the LIDAR adapter and the sample volume.

[0041] The system return signal exits the circulator (100) through a third port (108) and is directed to a comparison waveguide (18) on the LIDAR chip. Thus, all or a portion of the system return signal can function as a first LIDAR input signal, which first LIDAR input signal includes or consists of light from the system return signal. Thus, the LIDAR output signal and the first LIDAR input signal travel along different optical paths between the LIDAR adapter and the LIDAR chip.

[0042] As can be seen from Figure 2, the LIDAR adapter can include optical components in addition to the circulator (100). For example, the LIDAR adapter can include components for directing and controlling the optical paths of the LIDAR output signal and the system return signal. As an example, the adapter of Figure 2 includes an optional amplifier (110) arranged to receive and amplify the LIDAR output signal before it is incident on the circulator (100). The amplifier (110) can be operated by electronics (32) that allow the power of the LIDAR output signal to be controlled.

[0043] FIG. 2 also illustrates a LIDAR adapter including an optional first lens (112) and an optional second lens (114). The first lens (112) can be configured to couple the LIDAR output signal to a desired location. In some examples, the first lens (112) is configured to focus or collimate the LIDAR output signal to a desired location. In one example, if the LIDAR adapter does not include an amplifier (110), the first lens (112) can be configured to couple the LIDAR output signal onto the first port (104). As another example, if the LIDAR adapter includes an amplifier (110), the first lens (112) can be configured to couple the LIDAR output signal onto an input port to the amplifier (110). The second lens (114) can be configured to couple the LIDAR output signal to a desired location. In some examples, the second lens (114) is configured to focus or collimate the LIDAR output signal to a desired location. For example, the second lens (114) can be configured to couple the LIDAR output signal onto a facet (34) of the comparison waveguide (18).

[0044] The LIDAR adapter may also include one or more redirectors, such as mirrors. Figure 2 shows a LIDAR adapter including a mirror as a redirector (116) that redirects the system return signal from the circulator (100) to the facet (20) of the comparison waveguide (18).

[0045] The LIDAR chip includes one or more waveguides that constrain the optical path of one or more optical signals. Although the LIDAR adapter can include waveguides, the optical paths along which the system return signal and the LIDAR output signal travel between components on the LIDAR adapter and / or between the LIDAR chip and components on the LIDAR adapter can be empty space. For example, the system return signal and / or the LIDAR output signal can travel through the space in which the LIDAR chip, the LIDAR adapter, and / or the base (102) are located as they travel between different components on the LIDAR adapter and / or between components on the LIDAR adapter and the LIDAR chip. As a result, optical components such as lenses and redirectors can be used to control the characteristics of the optical paths along which the system return signal and the LIDAR output signal travel on, to, or from the LIDAR adapter.

[0046] Suitable bases (102) for the LIDAR adapter include, but are not limited to, substrates, platforms, and plates. Suitable substrates include, but are not limited to, glass, silicon, and ceramic. The components can be individual components attached to the substrate. Suitable techniques for attaching individual components to the base (102) include, but are not limited to, epoxy, solder, and mechanical clamps. In one example, one or more components are integrated components and the remaining components are individual components. In another example, the LIDAR adapter includes one or more integrated amplifiers and the remaining components are individual components.

[0047] The LIDAR system may be configured to correct for polarization. Since light from a laser source is typically linearly polarized, the LIDAR output signal is also typically linearly polarized. Reflection from an object may change the polarization angle of the returning light. Thus, the system return signal may include light of different linear polarization states. For example, a first portion of the system return signal may include light of a first linear polarization state, and a second portion of the system return signal may include light of a second linear polarization state. The strength of the resulting composite signal is proportional to the cosine squared of the angle between the comparison signal polarization field and the reference signal polarization field. If the angle is 90°, there may be loss of LIDAR data in the resulting composite signal. However, the LIDAR system may be modified to correct for changes in the polarization state of the LIDAR output signal.

[0048] Figure 3 shows the LIDAR system of Figure 3 with the LIDAR adapter modified for use with the LIDAR chip of Figure 1C. The LIDAR adapter includes a beam splitter (120) that receives a system return signal from a circulator (100). The beam splitter (120) splits the system return signal into a first portion of the system return signal and a second portion of the system return signal. Suitable beam splitters include, but are not limited to, a Wollaston prism and a MEMs-based beam splitter.

[0049] A first portion of the system return signal is directed to a comparison waveguide (18) on the LIDAR chip and serves as the first LIDAR input signal described in the context of FIG. 1C. A second portion of the system return signal is directed to a polarization rotator (122) which outputs a second LIDAR input signal that is directed to a second input waveguide (76) on the LIDAR chip and serves as the second LIDAR input signal.

[0050] The beam splitter (120) can be a polarizing beam splitter. One example of a polarizing beam splitter is constructed such that a first portion of the system return signal has a first polarization state but does not have or substantially does not have a second polarization state, and a second portion of the system return signal has a second polarization state but does not have or substantially does not have the first polarization state. The first and second polarization states can be linear polarization states, and the second polarization state is different from the first polarization state. For example, the first polarization state can be TE and the second polarization state can be TM, or the first polarization state can be TM and the second polarization state can be TE. In some examples, the laser source can be linearly polarized such that the LIDAR output signal has the first polarization state. Suitable beam splitters include, but are not limited to, Wollaston prisms and MEMs-based polarizing beam splitters.

[0051] The polarization rotator may be configured to change the polarization state of the first portion of the system return signal and / or the second portion of the system return signal. For example, the polarization rotator (122) shown in FIG. 3 may be configured to change the polarization state of the second portion of the system return signal from the second polarization state to the first polarization state. As a result, the second LIDAR input signal has the first polarization state but does not have or does not substantially have the second polarization state. Thus, the first LIDAR input signal and the second LIDAR input signal each have the same polarization state (in this example, the first polarization state). Despite carrying light of the same polarization state, the first LIDAR input signal and the second LIDAR input signal are associated with different polarization states as a result of the use of the polarizing beam splitter. For example, the first LIDAR input signal carries light reflected with the first polarization state and the second LIDAR input signal carries light reflected with the second polarization state. As a result, the first LIDAR input signal is associated with the first polarization state and the second LIDAR input signal is associated with the second polarization state.

[0052] Because the first LIDAR input signal and the second LIDAR input signal carry light of the same polarization state, the comparison signal resulting from the first LIDAR input signal has the same polarization angle as the comparison signal resulting from the second LIDAR input signal.

[0053] Suitable polarization rotators include, but are not limited to, polarization-maintaining fiber rotators, Faraday rotators, half-wave plates, MEMs-based polarization rotators, and integrated optical polarization rotators using asymmetric y-branches, Mach-Zehnder interferometers, and mixed-mode interference couplers.

[0054] Because the outgoing LIDAR signal is linearly polarized, the first reference signal can have the same linear polarization state as the second reference signal. Also, the components on the LIDAR adapter can be selected such that the first reference signal, the second reference signal, the comparison signal, and the second comparison signal each have the same polarization state. In the example disclosed in the context of FIG. 3, the first comparison signal, the second comparison signal, the first reference signal, and the second reference signal each can have light of a first polarization state.

[0055] As a result of the above configuration, the first composite signal produced by the first processing element (46) and the second composite signal produced by the second processing element (48) will each result from a combination of the reference signal and the comparison signal of the same polarization state, and thus provide a desired pulsation between the reference signal and the comparison signal. For example, the composite signal will result from a combination of the first reference signal and the first comparison signal of the first polarization state, and exclude or substantially exclude light of the second polarization state. Or, the composite signal will result from a combination of the first reference signal and the first comparison signal of the second polarization state, and exclude or substantially exclude light of the first polarization state. Similarly, the second composite signal will include the second reference signal and the second comparison signal of the same polarization state, and thus provide a desired pulsation between the reference signal and the comparison signal. For example, the second composite signal will result from a combination of the second reference signal and the second comparison signal of the first polarization state, and exclude or substantially exclude light of the second polarization state. Alternatively, the second composite signal may result from combining a second reference signal of a second polarization state with a second comparison signal, which excludes or substantially excludes light of the first polarization state.

[0056] The above configuration results in LIDAR data for a single sample area within the field of view produced from a plurality of different composite signals (i.e., the first composite signal and the second composite signal). In some examples, measuring the LIDAR data for the sample area includes electronics combining the LIDAR data from the different composite signals (i.e., the composite signal and the second composite signal). Combining the LIDAR data can include taking the average, median, or mode of the LIDAR data produced from the different composite signals. For example, the electronics can average a distance between the LIDAR system and a reflecting object measured from the composite signal with a distance measured from the second composite signal, and / or the electronics can average a radial velocity between the LIDAR system and a reflecting object measured from the composite signal with a radial velocity measured from the second composite signal.

[0057] In some examples, measuring the LIDAR data of the sample area includes the electronics identifying one or more composite signals (i.e., the composite signal and / or the second composite signal) as the source of the LIDAR data most representative of reality (representative LIDAR data). The electronics can then use the LIDAR data from the identified composite signal as the representative LIDAR data to be used for other processing. For example, the electronics can identify the signal (the composite signal or the second composite signal) having a larger amplitude as having representative LIDAR data and use the LIDAR data from the identified signal for further processing by the LIDAR system. In some examples, the electronics combines identifying the composite signal with the representative LIDAR data with combining LIDAR data from different LIDAR signals. For example, the electronics can identify each of the composite signals having an amplitude equal to or greater than an amplitude threshold as having representative LIDAR data, and if three or more composite signals are identified as having representative LIDAR data, the electronics can combine the LIDAR data from each identified composite signal. If one composite signal is identified as having representative LIDAR data, the electronics may use the LIDAR data from that composite signal as the representative LIDAR data. If none of the composite signals are identified as having representative LIDAR data, the electronics may discard the LIDAR data for the sample regions associated with those composite signals.

[0058] Although the components in FIG. 3 are illustrated as being arranged such that the first comparison signal, the second comparison signal, the first reference signal, and the second reference signal each have a first polarization state, the components in FIG. 3 can alternatively be arranged such that a composite signal results from a combination of the reference signal and the comparison signal with the same linear polarization state, and a second composite signal results from a combination of the reference signal and the comparison signal with the same linear polarization state. For example, the beam splitter (120) can be constructed such that a second portion of the system return signal has a first polarization state, a first portion of the system return signal has a second polarization state, a polarization rotator receives the first portion of the system return signal, and an output LIDAR signal has a second polarization state. In this example, the first LIDAR input signal and the second LIDAR input signal each have a second polarization state.

[0059] The above system configuration directs the first portion of the system return signal and the second portion of the system return signal into different composite signals, such that the first portion of the system return signal and the second portion of the system return signal are associated with different polarization states, but the electronics can process the respective composite signals. The LIDAR system compensates for changes in the polarization state of the LIDAR output signal in response to reflections of the LIDAR output signal.

[0060] The LIDAR adapter of FIG. 3 may include other optical components, including passive optical components. For example, the LIDAR adapter may include an optional third lens (126). The third lens (126) may be configured to couple the second LIDAR output signal to a desired location. In some examples, the third lens (126) focuses or collimates the second LIDAR output signal to a desired location. For example, the third lens (126) may be configured to focus or collimate the second LIDAR output signal onto a facet (52) of the second comparison waveguide (50). The LIDAR adapter may also include a redirector (124), such as one or more mirrors or prisms. FIG. 3 illustrates a LIDAR adapter with a mirror as a redirector (124) that redirects the second portion of the system return signal from the circulator (100) to the facet (52) of the second comparison waveguide (50) and / or to the third lens (126).

[0061] When the LIDAR system includes a LIDAR chip and a LIDAR adapter, the LIDAR chip, electronics, and the LIDAR adapter can be disposed on a common mount. Suitable common mounts include, but are not limited to, glass plates, metal plates, silicon plates, and ceramic plates. As an example, FIG. 4 is a top view of a LIDAR system including the LIDAR chip and electronics (32) of FIG. 1A and the LIDAR adapter of FIG. 2 on a common support (140). Although the electronics (32) is shown disposed on the common support, all or a portion of the electronics can be disposed remotely from the common support. When the light source (10) is disposed remotely from the LIDAR chip, the light source can be disposed on or remotely from the common support (140). Suitable methods for mounting the LIDAR chip, electronics, and / or LIDAR adapter on the common support include, but are not limited to, epoxy, solder, and mechanical clamps.

[0062] The LIDAR system may include components including other passive and / or active optical components. For example, the LIDAR system may include one or more components that receive a LIDAR output signal from a LIDAR chip or a LIDAR adapter. A portion of the LIDAR output signal exiting the one or more components may function as a system output signal. As an example, the LIDAR system may include one or more beam steering elements that receive a LIDAR output signal from a LIDAR chip or a LIDAR adapter and output all or a portion of the LIDAR output signal that functions as a system output signal. Suitable beam steering elements include, but are not limited to, movable mirrors, MEMS mirrors, and optical phased arrays (OPAs). In these cases, the one or more components may function as a transmitter of the system output signal of the LIDAR system.

[0063] 5A to 5D show examples of processing elements suitable for use as all or part of a processing element selected from the group consisting of processing element (22), first processing element (46), and second processing element (48). The processing element receives a comparison signal from a comparison waveguide (196) and a reference signal from a reference waveguide (198). The comparison waveguide (18) and reference waveguide (20) shown in FIGS. 1A and 1B can function as the comparison waveguide (196) and reference waveguide (198). The comparison waveguide (18) and first reference waveguide (42) shown in FIG. 1C can function as the comparison waveguide (196) and reference waveguide (198), or the second comparison waveguide (50) and second reference waveguide (44) shown in FIG. 1C can function as the comparison waveguide (196) and reference waveguide (198).

[0064] The processing element includes a second splitter (200) that splits a comparison signal carried on a comparison waveguide (196) into a first comparison waveguide (204) and a second comparison waveguide (206). The first comparison waveguide (204) carries a first portion of the comparison signal to an optical combining element (211). The second comparison waveguide (208) carries a second portion of the comparison signal to a second optical combining element (212).

[0065] The processing element includes a first splitter (202) that splits a reference signal carried on a reference waveguide (198) into a first reference waveguide (204) and a second reference waveguide (206). The first reference waveguide (204) carries a first portion of the reference signal to an optical combining element (211). The second reference waveguide (208) carries a second portion of the reference signal to a second optical combining element (212).

[0066] A second optical combining element (212) combines the second portion of the comparison signal and the second portion of the reference signal into a second composite signal, the second composite signal pulsating between the second portion of the comparison signal and the second portion of the reference signal due to a difference in frequency between the second portion of the comparison signal and the second portion of the reference signal.

[0067] The second optical combining element (212) also splits the resulting second composite signal onto a first auxiliary detector waveguide (214) and a second auxiliary detector waveguide (216). The first auxiliary detector waveguide (214) conveys a first portion of the second composite signal to a first auxiliary optical sensor (218) that converts the first portion of the second composite signal into a first auxiliary electrical signal. The second auxiliary detector waveguide (216) conveys a second portion of the second composite signal to a second auxiliary optical sensor (220) that 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).

[0068] In some examples, the second optical combining element (212) splits the second composite signal such that a portion of the comparison signal included in the first portion of the second composite signal (i.e., a portion of the second portion of the comparison signal) is phase shifted by 180 degrees relative to a portion of the comparison signal in the second portion of the second composite signal (i.e., a portion of the second portion of the comparison signal), but a portion of the reference signal in the second portion of the second composite signal (i.e., a portion of the second portion of the reference signal) is not phase shifted relative to a portion of the reference signal in the first portion of the second composite signal (i.e., a portion of the second portion of the reference signal). Alternatively, the second optical combining element (212) splits the second composite signal such that the portion of the reference signal in the first portion of the second composite signal (i.e., the portion of the second portion of the reference signal) is phase shifted by 180° with respect to the portion of the reference signal in the second portion of the second composite signal (i.e., the portion of the second portion of the reference signal), but the portion of the comparison signal in the first portion of the second composite signal (i.e., the portion of the two portions of the comparison signal) is not phase shifted with respect to the portion of the comparison signal in the second portion of the second composite signal (i.e., the portion of the second portion of the comparison signal). Examples of suitable optical sensors include germanium photodiodes (PDs) and avalanche photodiodes (APDs).

[0069] A first optical combining element (211) combines the first portion of the comparison signal and the first portion of the reference signal into a first composite signal, the first composite signal pulsating between the first portion of the comparison signal and the first portion of the reference signal due to a frequency difference between the first portion of the comparison signal and the first portion of the reference signal.

[0070] The first optical combining element (211) also splits the first composite signal onto a first detector waveguide (221) and a second detector waveguide (222). The first detector waveguide (221) conveys a first portion of the first composite signal to a first optical sensor (223) that converts a first portion of the second composite signal into a first electrical signal. The second detector waveguide (222) conveys a second portion of the second composite signal to a second optical sensor (224) that converts a 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).

[0071] In some examples, the optical combining element (211) splits the first composite signal such that a 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 phase shifted by 180° with respect to a 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 a 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 not phase shifted with respect to a 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 combining element (211) splits the composite signal such that a 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 phase shifted by 180° with respect to a 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 a 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 phase shifted with respect to a 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).

[0072] If the second optical combining element (212) splits the second composite signal such that a portion of the comparison signal in the first portion of the second composite signal is phase shifted 180° relative to a portion of the comparison signal in the second portion of the second composite signal, the optical combining element (211) also splits the composite signal, such that a portion of the comparison signal in the first portion of the composite signal is phase shifted 180° relative to a portion of the comparison signal in the second portion of the second composite signal. If the second optical combining element (212) splits the second composite signal such that a portion of the reference signal in the first portion of the second composite signal is phase shifted 180° relative to a portion of the reference signal in the second portion of the second composite signal, the optical combining element (211) also splits the composite signal, such that a portion of the reference signal in the first portion of the composite signal is phase shifted 180° relative to a portion of the reference signal in the second portion of the second composite signal.

[0073] The first reference waveguide (210) and the second reference waveguide (208) are constructed 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 constructed to provide a phase shift of 90° 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 can be a quadrature component. Thus, one of the reference signal portions 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 such that the first reference signal portion is a cosine function and the second reference signal portion is a sine function. Thus, the portion of the reference signal in the second composite signal is phase shifted with respect to the portion of the reference signal in the first composite signal, but the portion of the comparison signal in the first composite signal is not phase shifted with respect to the portion of the comparison signal in the second composite signal.

[0074] The first light sensor (223) and the second light sensor (224) can be connected as a balanced detector, and the first auxiliary light sensor (218) and the second auxiliary light sensor (220) can also be connected as a balanced detector. For example, FIG. 5B provides a schematic of the relationship between the electronics, the first light sensor (223), the second light sensor (224), the first auxiliary light sensor (218), and the second auxiliary light sensor (220). Although the symbol of a photodiode is used to represent the first light sensor (223), the second light sensor (224), the first auxiliary light sensor (218), and the second auxiliary light sensor (220), one or more of these sensors can have other structures. In some examples, all of the elements shown in the schematic of FIG. 5B are included on the LIDAR chip. In some examples, the elements shown in the schematic of FIG. 5B are distributed between the LIDAR chip and electronics located away from the LIDAR chip.

[0075] The electronics connects the first photosensor (223) and the second photosensor (224) to form a first balanced detector (225) and connects the first auxiliary photosensor (218) and the second auxiliary photosensor (220) to form a second balanced detector (226). Specifically, the first photosensor (223) and the second photosensor (224) are connected in series. Additionally, 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 the 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 the output from the second balanced detector as a second data signal. The first data signal is an electrical representation of the first composite signal, and the second data signal is an electrical 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 phase shifted relative to 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 includes a portion of a reference signal that is phase shifted relative to a different portion of the reference signal included in the first data signal. Also, the second data signal includes a portion of a comparison signal that is in phase with a different portion of a comparison signal included in the first data signal. As a result of the pulsation between the comparison signal and the reference signal, i.e. the pulsation in the first composite signal and the second composite signal, the first data signal and the second data signal are pulsating.

[0076] The electronics (32) includes a transform mechanism (238) configured to perform a mathematical transformation on the first data signal and the second data signal. For example, the mathematical transformation may be a complex Fourier transform with the first data signal and the second data signal as inputs. The first data signal is an in-phase component and the second data signal is a quadrature component, so that the first data signal and the second data signal together function as a complex data signal, where the first data signal is the real component of the input and the second data signal is the imaginary component of the input.

[0077] The conversion mechanism (238) 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) (264) converts the first data signal from analog to digital form to output a first digital data signal. The conversion mechanism (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) (266) converts the second data signal from analog to digital form to output 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 together function as a composite signal, where the first digital data signal functions as a real component of the composite signal and the second digital data signal functions as an imaginary component of the composite data signal.

[0078] The conversion mechanism (238) includes a conversion element (268) that receives the composite data signal. For example, the conversion element (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 conversion element (268) can be configured to perform a mathematical transformation on the composite signal to convert it from the time domain to the frequency domain. The mathematical transformation can be a complex transformation, such as a complex Fast Fourier Transform (FFT). A complex transformation, such as a complex Fast Fourier Transform (FFT), provides an explicit answer to the frequency shift of the LIDAR input signal relative to the LIDAR output signal due to the radial velocity between the reflecting object and the LIDAR chip. The electronics use the frequency peak or peaks output from the conversion element (268) for further processing to produce LIDAR data (range and / or radial velocity between the reflecting object and the LIDAR chip or LIDAR system). The conversion element (268) may perform the ascribed functions using firmware, hardware, software, or a combination thereof.

[0079] 5A-5B show an optical combining element combining a portion of the reference signal with a portion of the comparison signal, the processing element may include a single optical combining element combining the reference signal with a portion of the comparison signal to form a composite signal. As a result, at least a portion of the reference signal and at least a portion of the comparison signal may be combined to form a composite signal. The combined portion of the reference signal may be the entire reference signal or a portion of the reference signal, and the combined portion of the comparison signal may be the entire comparison signal or a portion of the comparison signal.

[0080] As an example of a processing element that combines a reference signal and a comparison signal to form a composite signal, Figure 5C shows the processing element of Figure 5A modified to include a single optical combining element: the comparison waveguide (196) carries the comparison signal directly to the first optical combining element (211), and the reference waveguide (198) carries the reference signal directly to the first optical combining element (211).

[0081] The first optical combining element (211) combines the comparison signal and the reference signal into a composite signal. Due to the difference in frequency between the comparison signal and the reference signal, the first composite signal pulsates between the comparison signal and the reference signal. The first optical combining element (211) also splits the composite signal into a first detector waveguide (221) and a second detector waveguide (222). The first detector waveguide (221) conveys a first portion of the composite signal to a first optical sensor (223) that converts the first portion of the second composite signal into a first electrical signal. The second detector waveguide (222) conveys a second portion of the composite signal to a second optical sensor (224) that converts the second portion of the second composite signal into a second electrical signal.

[0082] FIG. 5D provides a schematic of the relationship between the electronics, first light sensor (223), and second light sensor (224) of FIG. 5C. Although a photodiode symbol is used to represent the first light sensor (223) and second light sensor (224), one or more of these sensors may have other configurations. In some examples, all of the elements shown in the schematic of FIG. 5D are included on the LIDAR chip. In some examples, the elements shown in the schematic of FIG. 5D are distributed between the LIDAR chip and electronics located away from the LIDAR chip.

[0083] The electronics connects the first photosensor (223) and the second photosensor (224) as a first balanced detector (225). Specifically, the first photosensor (223) and the second photosensor (224) are connected in series. The series connection in the first balanced detector communicates with a first data line (228) that carries the output from the first balanced detector as a first data signal. The first data signal is an electrical representation of the composite signal.

[0084] The electronics (32) includes a transform mechanism (238) configured to perform a mathematical transform on the first data signal. The mathematical transform may be a real Fourier transform using the first data signal as an input. The electronics can use the frequency output from the transform to extract the LIDAR data.

[0085] Each of the balanced detectors disclosed in the context of Figures 5A through 5D may be replaced with a single photosensor. As a result, the processing element may include one or more photosensors each receiving at least a portion of the composite signal, in that the received portion of the composite signal may be the entire composite signal or a portion of the composite signal.

[0086] FIG. 5E illustrates an example of the relationship between frequency, time, cycle, and data period of the LIDAR output signal and / or the system output signal. Although FIG. 5E illustrates frequency versus time for only one channel, the illustrated frequency versus time pattern can represent frequency versus time for each channel. The fundamental frequency (f 0 ) may be the frequency of the LIDAR output signal at the start of the cycle.

[0087] Figure 5E shows the cycle j and cycle j+1 5E shows the frequency versus time relationship for a series of two cycles labeled as . In some examples, as shown in FIG. 5E, the frequency versus time pattern is repeated for each cycle. The illustrated cycles do not include a relocation period and / or the relocation period is not located between the cycles. As a result, FIG. 5E shows the results of successive scans.

[0088] Each cycle is associated with a period index k, and the DP k In the example of FIG. 5E, each cycle includes K data periods denoted as DP k (where k=1, 2, and 3). In some examples, the frequency vs. time pattern is the same for data periods that correspond to each other in different cycles, as shown in FIG. 5E. Corresponding data periods are data periods that have the same period index. As a result, each data period DP 1 can be considered as the corresponding data period, and the associated frequency versus time pattern is the same in Figure 5E. At the end of the cycle, the electronics change the frequency back to the same frequency level at the beginning of the previous cycle.

[0089] Data Period DP 1 During this time, the electronics detects that the frequency of the LIDAR output signal is B 1 (B 1 ≠ 0) by manipulating the light source. 1 The duration of the frequency change in 1 (T 1 >0). 2 During this time, the electronics detects that the frequency of the LIDAR output signal is B 2 (B 2 ≠ 0) by manipulating the light source. 2 The duration of the frequency change in 2 (T 2 >0). 1 The rate of frequency change in 1 (α 1 ≠0). In FIG. 5E, DP 1 The rate of frequency change in 1 ) is B 1 / T 1 It is linearly correlated with the value of DP 2 The rate of frequency change in 2 (α 2 ≠0). In FIG. 5E, DP 2 The rate of frequency change in 2 ) is B 2 / T 2 It is linearly correlated with the value of the data period DP 3 During DP, the electronics operate the light source such that the frequency of the LIDAR output signal is constant during the data period. 3 The duration of T 3 (T 3 >0). T 1 , T 2 , and T 3 The values ​​of may be the same or different. In some examples, T 1 =T 2 In one example, T 1 =T 2 ≠T 3 In another example, T 1 =T 2 =T 3 In some cases, T1 ≠T 2 It is.

[0090] Data Period DP k The pulsation frequency of all or a part of the pulsation signals selected from the first composite signal, the first data signal, the second composite signal, and the second data signal in k (k represents a data period index). For example, when the processing element is configured according to FIG. 5C and FIG. 5D, the pulsation frequency of the first composite signal and the first data signal is F k When the processing element is configured according to Figures 5A and 5B, the pulsation frequencies of the first composite signal, the first data signal, the second composite signal, and the second data signal are represented as F k It is expressed as:

[0091] F 1 is the data period DP 1 represents the pulsation frequency of the pulsation signal in the 1 The value of f r,1 ) and the contribution from the line-of-sight velocity between the LIDAR system and the reflecting object (f d,1 ) can be included. Therefore, F 1 is F 1 =f r,1 + f d,1 Under normal operating conditions of the LIDAR system, F 1 The maximum value that can occur in F 1max It is expressed as:

[0092] Data Period DP 2 The pulsation frequency of the pulsation signal in is F 2 It is expressed as F 2 The value of f r,2 ) and the contribution from the line-of-sight velocity between the LIDAR system and the reflecting object (f d,2 Under normal operating conditions of the LIDAR system, F 2 The maximum value that can occur in F 2max It is expressed as:

[0093] Data Period DP 3 The pulsation frequency of the pulsation signal in is F 3 Under normal operating conditions of the LIDAR system, F 3 The maximum value that can occur in F 3max The frequency of the LIDAR output signal is expressed as the data period DP 3 Since it is constant between 3 is the line-of-sight velocity between the LIDAR system and the reflecting object (Doppler frequency f d,3 ) but no contribution from the distance between the LIDAR system and the reflecting object. As a result, F 3 The value of is the Doppler frequency (f d,3 ), where f d,3 = 2 v / λ, where v represents the radial velocity between the LIDAR system and the reflecting object in the direction from the reflecting object towards the LIDAR system, which is the positive direction, and λ represents the wavelength of the LIDAR output signal. 3 =f d,3 = 2v / λ and F 3max =f dmax =2v max / λ, where f dmax represents the maximum Doppler frequency when operating the LIDAR system under normal conditions, and v max represents the maximum radial velocity when operating under normal conditions.

[0094] Some of the above variables are disclosed in the context of normal operating conditions. Normal operating conditions are the conditions for which the LIDAR system is designed to operate and are usually set out in the LIDAR system's specifications. Thus, when specifications are available, max The value of represents the maximum radial velocity as specified in the specification. 1max is the F that may occur when operating the LIDAR system within the line-of-sight speed and distance specified in the specification. 1 Represents the maximum value of.

[0095] The data period index does not represent a time order. For example, Figure 5E shows that 1 DP 2and D.P. 3 Although cycles occurring before DP 1 DP 2 and D.P. 3 Cycles occurring between, or DP 3 DP 2 occurs before DP 2 DP 1 Examples of cycles that occur before or after a given cycle include, but are not limited to, cycles that occur before or after a given cycle.

[0096] Prior to operating the LIDAR system to produce LIDAR data, values ​​for one or more operating parameters can be selected and / or calculated. The electronics can use the identified values ​​for the one or more parameters in the produced LIDAR data. One example of one of these parameters is the analog-to-digital converter (ADC) sampling rate (f samp ). The processing element includes one or more analog-to-digital converters, such as a first analog-to-digital converter (ADC) (264) of FIGS. 5A and 5C and a second analog-to-digital converter (ADC) (266) of FIG. 5D. The one or more analog-to-digital converters each receive one of the pulsatile signals and sample at an ADC sampling rate (f samp ) is the ADC sampling rate (f) required to produce useful LIDAR data. samp ) may be impractical to achieve. However, the LIDAR system can be operated such that the electronics undersample the analog-to-digital converter (ADC) (264) and / or the second analog-to-digital converter (ADC) (266). Utilizing undersampling allows for the use of the actual sampling rate.

[0097] ADC sampling rate (f samp ) is f samp ≧2|F 3max F 3max =fdmax =2v max / λ, so the ADC sampling rate (f samp ) is f samp ≧2|F 3max |, f samp ≧2|f dmax | or f samp ≧4|v max / λ|. According to the Nyquist sampling theorem, the sampling rate of the analog-to-digital converter (ADC) must be at least twice the highest frequency of the pulsatile signal. Thus, the Nyquist sampling theorem states that f samp ≧2*max|F 1max ,F 2max ,F 3max | according to the sampling rate (f samp ) is provided. The pulsatile signal is sampled at a rate of 2*max|F 1max ,F 2max ,F 3max If the sampling rate is greater than 2*max|F, it is considered oversampled. 1max ,F 2max ,F 3max f is considered undersampled. samp The value of can be chosen such that the signal is undersampled. For example, samp is 2|F 3max |≦f samp ≦2*max|F 1max ,F 2max ,F 3max |, or 2|f dmax |≦f samp ≦2*max|F 1max ,F 2max ,F 3max |, or 4|v max / λ|≦f samp ≦2*max|F 1max ,F 2max ,F 3max can be chosen to be |.

[0098] ADC sampling rate (f sampOnce a frequency spectrum is selected, values ​​for one or more other parameters can be specified for use in generating LIDAR data. For example, a frequency spectrum can be defined according to FIG. 5F. As shown in FIG. 5F, 1 The value ranges from 0.0 to F 1max -F 1max From F 1max The frequency ranges from samp Each zone can be divided into multiple zones with lengths equal to zone index k k where the subscript k represents the data period index, and k k Each value of is an integer. FIG. 5F shows the data period DP 1 k k Value(k 1 ) As shown in FIG. 5F, k 1 The value of -k 1max From 1max for a total of 2*k 1max +1 k 1 In FIG. 5F, k 1max The value has a value of 2. 1max The value of (k 1max -0.5)f samp ≦F 1max <(k 1max +0.5)f samp It can be selected so that

[0099] k 1max The values ​​of parameters p and q can be selected using selected values ​​of p, where p is an integer and q is an integer. The values ​​of p and q are<q、q> 2k 1max +2 and p>q / (2k 1max +2). In some examples, p / q is an irreducible fraction. With the selected values ​​of p and q, B 2 =+ / -(p / q)*B 1 Or, T 1 ≠T 2 In the case of α 2 =+ / -(p / q)*α 1 So that B 1 and B. 2can be selected.

[0100] During operation of the LIDAR system, one or more analog-to-digital converters (ADCs) each have a frequency of f samp The data period DP 1 The frequency output from the transducer element (268) in response to the system output signal output from the LIDAR system during 1,DC can serve as the value of the data period DP 2 The frequency output from the transducer element (268) in response to the system output signal output from the LIDAR system during 2,DC can serve as the value of the data period DP 3 The frequency output from the transducer element (268) in response to the system output signal output from the LIDAR system during 3,DC It can serve as a value for

[0101] Electronic equipment is F1(f d,1 The contribution of the line-of-sight velocity between the LIDAR system and the reflecting object to the (f d,3 ) and F2(f d,2 The contribution of the line-of-sight velocity between the LIDAR system and the reflecting object to the value of f d,3 ) can be approximated as being equal to f d,1 =f d,2 =f d,3 As shown above, f d,3 =F 3 Furthermore, in the data period DP 3 In the middle, f satisfies the Nyquist sampling theorem samp ≧2|F 3max | Therefore, F 3DC is not the result of undersampling. Therefore, the electronics 3 Value F 3,DC As a result, electronic devices can be approximated as being equal to f d,1 =f d,2 =f d,3 =F 3=F 3,DC =f d can be approximated.

[0102] Undersampling of the ADC reduces F 1 (f r,1 There are several possible contributions to the F 2 (f r,2 The contribution of the distance between the LIDAR system and the reflecting object to the DP value has several possible values. 1 f r,1 Possible values ​​of and data period DP 2 f r,2 The possible values ​​of f can be measured. r,k,n,e where k represents the data period index and n is -k 1max ≦n≦k 1max where each value of n is an integer and e represents an equation index that identifies the equation from which the possible values ​​were generated. 1 A set of possible values ​​of f can be measured: r,1,n,A =F 1,DC +f d +n*f samp where -k 1max ≦n≦k 1max Therefore, f r,k,n,e For (2*k 1max +1) possible values. Electronic devices can 2 The rate of frequency change in 2 ) is positive, the following formula 2A:f r,2,n,A =(F 2,DC +f d )*(q / p)+n*f samp *(q / p), or DP 2 The rate of frequency change in 2 ) is positive, the following formula 2B:f r,2,n,B =(F 2,DC +f d )*(q / p)-n*f samp *(q / p) (where k 1max ≦n≦k 1max ) from the data period DP2 We can measure a range of possible values ​​of f r,2,n,e For (2*k 1max +1) possible values.

[0103] Data Period DP 1 f measured from r Possible values ​​of (f above r,1,n,A ) is the data period DP 2 f measured from r Possible values ​​of (f r,2,n,A and f r,2,n,B ) would match or substantially match one of the following: 1max ≦n≦k 1max For values ​​of n within the range of f, there will be only one matching pair per cycle. Values ​​of n outside the range may produce other matches. r The value is f r It acts as a value.

[0104] Electronic equipment is r and / or f d For example, the electronics can measure the LIDAR data for a cycle using the measured values ​​for c*f r *T / (2*B 1 ) and / or the line-of-sight velocity between the object and the LIDAR system v=λ*f d It can be measured from / 2.

[0105] Although FIG. 5D shows three data periods, the number of data periods may vary. For example, 3 may be arbitrary if the reflecting object is stationary relative to the LIDAR system (i.e., v=0.0). In these examples, the LIDAR data is processed using f d,1 =f d,2 =f d,3 =f 3,DC =f d =0.0 can be produced.

[0106] Suitable platforms for LIDAR chips include, but are not limited to, silica, indium phosphide, and silicon-on-insulator wafers. FIG. 6 is a cross-sectional view of a portion of a chip constructed from a silicon-on-insulator wafer. A silicon-on-insulator (SOI) wafer includes a buried layer (310) between a substrate (312) and an optically transmissive medium (314). In a silicon-on-insulator wafer, the buried layer (310) is silica, while the substrate (312) and the optically transmissive medium (314) are silicon. The substrate (312) of an optical platform such as a SOI wafer can serve as the base for the entire LIDAR chip. For example, the optical components shown on the LIDAR chips of FIGS. 1A through 1D can be located on or above the top and / or lateral surfaces of the substrate (312).

[0107] 6 is a cross-sectional view of a portion of a LIDAR chip including a waveguide construction suitable for use in a LIDAR chip constructed from a silicon-on-insulator wafer. A ridge (316) of optically transmissive medium extends away from a slab region (318) of the optically transmissive medium. An optical signal is confined between the top of the ridge (316) and a buried oxide layer (310).

[0108] The dimensions of the ridge waveguide are shown in FIG. 6. For example, the ridge has a width, designated w, and a height, designated h. The thickness of the slab region is designated T. These dimensions may be more important than other dimensions because LIDAR applications require the use of higher levels of optical power than are used in other applications. The ridge width (designated w) is greater than 1 μm and less than 4 μm, the ridge height (designated h) is greater than 1 μm and less than 4 μm, and the thickness of the slab region is greater than 0.5 μm and less than 3 μm. These dimensions may apply to straight or substantially straight portions of the waveguide, curved portions of the waveguide, and tapered portions of the waveguide. Thus, these portions of the waveguide are single mode. However, in some examples, these dimensions apply to straight or substantially straight portions of the waveguide. Alternatively, or in addition, the curved portions of the waveguide may have a reduced slab thickness to reduce the loss of light in the curved portions of the waveguide. For example, the curved portion of the waveguide may have a ridge extending away from the slab region having a thickness of 0.0 μm or more and less than 0.5 μm. The above dimensions generally provide straight or substantially straight portions of the waveguide in a single mode structure, but may result in tapered and / or curved portions that are mixed mode. Coupling between mixed mode and single mode geometries can be achieved using tapers that do not substantially excite higher order modes. Thus, the waveguide can be configured such that signals carried in the waveguide are carried in single mode even when carried in a waveguide section having mixed mode dimensions. The waveguide construction disclosed in the context of FIG. 6 is suitable for all or part of the waveguide on a LIDAR chip constructed according to FIG. 1A to FIG. 1D.

[0109] The light sensor interfaced with the waveguide on the LIDAR chip can be a separate component from the chip and subsequently attached to the chip. For example, the light sensor can be a photodiode or an avalanche photodiode. Examples of suitable light sensor components include, but are not limited to, InGaAs PIN photodiodes manufactured by Hamamatsu Corporation, Hamamatsu, Japan, or InGaAs APD (Avalanche Photodiode) manufactured by Hamamatsu Corporation, Hamamatsu, Japan. These light sensors can be located in the center of the LIDAR chip. Alternatively, all or a portion of the waveguide terminating in the light sensor can terminate in a facet located at the edge of the chip, and the light sensor can be attached to the edge of the chip on the facet such that the light sensor receives light passing through the facet. The use of a light sensor that is a separate component from the chip is suitable for all or a portion of the light sensors selected from the group consisting of the first auxiliary light sensor (218), the second auxiliary light sensor (220), the first light sensor (223), and the second light sensor (224).

[0110] As an alternative to a separate optical sensor, all or part of the optical sensor can be integrated into the chip. For example, examples of optical sensors interfaced with ridge waveguides on chips constructed from silicon-on-insulator wafers can be found in Optics Express Vol. 15, No. 21, 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), all of which are incorporated herein in their entirety. The use of an optical sensor integrated into the chip is suitable for all or part of the optical sensors selected from the group consisting of the auxiliary optical sensor (218), the second auxiliary optical sensor (220), the first optical sensor (223), and the second optical sensor (224).

[0111] The light source (10) interfaced with the utility waveguide (12) can be a laser chip that is separate from the LIDAR chip and then attached to the LIDAR chip. For example, the light source (10) can be a laser chip to the chip using a flip-chip configuration. The use of a flip-chip configuration is suitable when the light source (10) is interfaced with a ridge waveguide on a chip constructed from a silicon-on-insulator wafer. Alternatively, the utility waveguide (12) can include an optical grating (not shown), such as a Bragg grating, that serves as a reflector for an external cavity laser. In these examples, the light source (10) can include a gain element that is separate from the LIDAR chip and that is attached to the LIDAR chip in a flip-chip configuration. Examples of suitable interfaces between flip-chip gain elements and ridge waveguides on chips constructed from silicon-on-insulator wafers can be found in U.S. Patent No. 9,705,278, issued July 11, 2017, and U.S. Patent No. 5,991,484, issued November 23, 1999, both of which are incorporated herein in their entireties. If the light source (10) is a gain element or laser chip, the electronics (32) can change the frequency of the output LIDAR signal by changing the level of current applied through the gain element or laser cavity.

[0112] Suitable electronics (32) may include a controller that includes or consists of analog circuitry, digital circuitry, a processor, a microprocessor, a digital signal processor (DSP), a field programmable gate array (FPGA), a computer, a microcomputer, or any combination suitable for performing the above operation, monitoring, and control functions. In some examples, the controller accesses a memory that contains instructions that are executed by the controller during the performance of the operation, control, and monitoring functions. Although the electronics is shown as a single component in a single location, the electronics may include multiple different components that are located independently of one another and / or in different locations. Also, as noted above, all or a portion of the disclosed electronics may be included on a chip with the electronics integrated with the chip.

[0113] Other embodiments, combinations, and modifications of the present invention will readily occur to those of ordinary skill in the art in view of these teachings. Accordingly, the present invention is to be limited only by the scope of the following claims, which include all such embodiments and modifications, when viewed in conjunction with the above specification and accompanying drawings.

Claims

1. 1. A LIDAR system comprising: an analog-to-digital converter (ADC) for receiving a pulsatile signal that pulsates a first signal relative to a second signal; the first signal is produced from light that leaves the LIDAR system and is reflected back to the LIDAR system after being reflected by an object outside the LIDAR system; the second signal is produced from light not exiting the LIDAR system; the frequency of the pulsating signal has a frequency contribution from a separation between the LIDAR system and the object; and an electronic device for generating a plurality of possible first frequency values, each of which is a candidate for a frequency contribution value; Including, A LIDAR system, wherein the electronics undersamples the analog-to-digital converter (ADC) to produce a digital data signal and use the digital data signal to measure a distance between the object and the LIDAR system.

2. 2. The LIDAR system of claim 1, wherein the electronics identify one of the first possible frequency values ​​that represents a frequency contribution value from a separation between the LIDAR system and the object.

3. The LIDAR system of claim 1 , wherein the electronics generate a plurality of possible second frequency values, each of which is a candidate for the frequency contribution value.

4. 4. The LIDAR system of claim 3, wherein only one of the first frequency possibilities corresponds to one of the second frequency possibilities.

5. The LIDAR system of claim 4 , wherein the electronics identify a first frequency possibility that matches one of the second frequency possibilities.

6. The LIDAR system of claim 5 , wherein the electronics uses the identified frequency value to measure a distance between the object and the LIDAR system.

7. A LIDAR system, comprising: an analog-to-digital converter (ADC) for receiving a pulsatile signal that pulsates a first signal relative to a second signal; the first signal is produced from light that leaves the LIDAR system and is reflected back to the LIDAR system after being reflected by an object outside the LIDAR system; the second signal is produced from light not exiting the LIDAR system; the frequency of the pulsating signal has a frequency contribution from a separation between the LIDAR system and the object; and an electronic device for generating a plurality of possible first frequency values, each of which is a candidate for a frequency contribution value; Including, the light emitted by the LIDAR system is included in a system output signal, and the electronics control the frequency of the system output signal over a series of cycles; the cycle includes a number of data periods; the electronics varying a frequency of the system output signal at a first rate during a first data period; the electronics varies a frequency of the system output signal at a second rate during a second data period; The second speed is lower than the first speed. LIDAR system.

8. The second speed is α 2 = + / -(p / q)*α 1 where α 2 represents the second velocity, and α 1 8. The LIDAR system of claim 7, wherein: denotes the first velocity, p is an integer, q is an integer, p<q, and p / q is an irreducible fraction.

9. q>2k 1max +2 and p>q / (2k 1max +2), where k 1max 9. The LIDAR system of claim 8, wherein is an integer.

10. k 1max But (k 1max -0.5)f samp <F 1max ≦(k 1max +0.5)f samp where f samp represents the sampling rate of the analog-to-digital converter (ADC), and F 1max 10. The LIDAR system of claim 9, wherein x represents a maximum possible value of the pulsatile signal during the first period.

11. 1. A LIDAR system comprising: a transmitter configured to output a LIDAR output signal from the LIDAR system; and electronics for controlling the frequency of the system output signal over a series of cycles such that a frequency versus time pattern of the system output signal is repeated in each cycle; the cycle includes a number of data periods; the electronics varying a frequency of the system output signal at a first rate during a first data period; the electronics varying a frequency of the system output signal at a second rate during a second data period; the second speed is lower than the first speed; A LIDAR system, wherein the second velocity can be expressed as α2 = + / - (p / q) * α1, where α2 represents the second velocity, α1 represents the first velocity, p is an integer, q is an integer, p < q, q > 2k1max +2, and k1max is an integer.

12. 12. The LIDAR system of claim 11, wherein p / q is an irreducible fraction.

13. q>2k 1max +2, where k 1max 12. The LIDAR system of claim 11, wherein is an integer.

14. p>q / (2k 1max +2).

15. k 1max 15. The LIDAR system of claim 14, wherein:

16. α 2 = B 2 / T and α 1 = B 1 / T, where T represents the duration of the first data period, and B 1 represents the frequency change of the system output signal during the first data period, and B 2 12. The LIDAR system of claim 11, wherein: represents a change in frequency of the signal system output during a second data period.

17. 1. A method of operating a LIDAR system, comprising: receiving a pulsatile signal at an analog-to-digital converter (ADC), the pulsatile signal pulsating a first signal relative to a second signal; the first signal is produced from light that leaves the LIDAR system and is reflected back to the LIDAR system after being reflected by an object outside the LIDAR system; the second signal is produced from light not exiting the LIDAR system; the frequency of the pulsating signal has a frequency contribution from a separation between the LIDAR system and the object; generating a plurality of first possible frequency values, each of which is a candidate frequency contribution value; and undersampling the analog-to-digital converter (ADC) to produce a digital data signal and using the digital data signal to measure a distance between the object and the LIDAR system. A method comprising:

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