LIDAR system based on light modulator and coherent receiver for simultaneous range and velocity measurement

A LIDAR system and method for determining a distance and a velocity of a target. The LIDAR system can include a laser modulated by a laser modulator, an optical combiner, an optical splitter, a photoreceiver, and a control circuit. The optical splitter can optically split the modulated laser beam into a first laser beam and a second laser beam and direct the first laser beam at the target such that the first laser beam is reflected by the target to the optical combiner. The optical combiner can optically combine the first laser beam and the second laser beam. The output an I-output and a Q-output according to the optically combined first laser beam and second laser beam. The control circuit can determine a nominal beat frequency, which corresponds to the distance of the target, and a frequency shift, which corresponds to the velocity of the target, accordingly.

BACKGROUND

The present disclosure is in the technical field of frequency-modulated continuous-wave (FMCW) light detection and ranging (LIDAR).

Generally, FMCW LIDAR systems sense range by measuring interference between optical signals from a local path and a target path. By sweeping the frequency of a laser, the interference signal becomes an oscillation with a frequency proportional to target distance. FMCW lasers may be modulated to have a linear frequency sweep from lower frequency to higher frequency, and then from higher frequency to lower frequency, in a triangular fashion.

Moving reflectors may cause a shift in the measured frequency proportional to the velocity of the reflector. To tell the difference between the effect of reflector's distance and velocity, one may measure the interference frequency during the positive laser sweep, and then the interference frequency during the negative frequency sweep.

The speed with which measurements are attained may be important, and the method of making two measurements to obtain velocity may take twice as long as the method of only measuring range. Thus, a method to use multiple frequency-modulated lasers with complementary frequency sweeps combined with a method to discriminate the complementary frequency sweeps may enhance the measurement speed of a distance and velocity LIDAR sensor. The method of discriminating the complementary frequency sweeps resolves ambiguity problems where the time delay and frequency shift effects cannot be sufficiently decoupled.

Further, generally, FMCW LIDAR systems use swept-source lasers to measure distance and velocity. The frequency of a reflected signal may be proportional to a target's distance. Moving targets shift a reflected signal's frequency proportional to the velocity of the target due to the Doppler effect, which can be measured simultaneously.

Beam steering modules may scan laser beams across a target environment. Having multiple laser channels in an optical system may involve several scanning elements to capture a larger field of view (FOV). A scheme that would allow several laser beams to share scanning elements may help reduce the complexity and cost of the system. It would further reduce cost of the system by implementing such scheme on integrated photonic chips.

SUMMARY

In one general aspect, the present disclosure is directed to an example FMCW LIDAR system that uses an optical modulator and a coherent receiver to simultaneously detect range and velocity. A laser may be modulated by a light modulator, which modulates the intensity of the light to create two frequency sweeps, one with an increasing optical frequency and one with a decreasing optical frequency. This may be followed by an interferometer comprising an optical splitter, which sends light down two paths (a “local” path and a “target” path), an optical combiner known as an “90-degree optical hybrid,” a photoreceiver with multiple photodiodes, and a control circuit or computer for signal processing. The 90-degree optical hybrid and multiple photodiodes may allow the discrimination of positive beat frequencies and negative beat frequencies. This illustrative disclosure enables FMCW LIDAR to generate and discriminate simultaneous laser frequency sweeps using multiple sidebands, which may shorten the measurement time required to make range and velocity estimates. Several parts of the system, including the optical splitters, combiners, scanning optics, transmission optics, receiver optics, and photoreceivers, can be implemented using integrated photonics to make the system compact.

DESCRIPTION

Light Modulator and Coherent Receiver for Simultaneous Range and Velocity Measurement

FIG. 1is a block diagram showing an example of the FMCW LIDAR system, according to one aspect of the present disclosure. In this example, the system includes a laser1that is coupled to a laser modulator2(e.g., an optical intensity modulator). The laser modulator2is configured to modulate an intensity or an amplitude, for example, of a laser beam output by the laser1. The system can further include a splitter3(e.g., a 2×2 splitter or coupler). Output light from the laser modulator2may be injected into the splitter3, which is configured to separate the light into two paths (e.g., using a directional coupler or a multi-mode interferometer). The system can further include a combiner5(e.g., a 2×4 combiner or coupler). Some light generated by the laser2(as modulated by the laser modulator2), may be directly coupled, via the splitter3, to one input of the combiner5. The rest of the light generated by the laser2may be transmitted, via the splitter3, through the target path to a target arm4(examples of which are described below in connection withFIGS. 8A-8C) before being coupled to the other input of the combiner5. In one aspect, the combiner5may be implemented as an “optical hybrid” or “90-degree optical hybrid,” which is configured to split the light into four paths to be detected at a four-channel photoreceiver6, also referred to as an “I-Q detector.” An optical hybrid is configured to receive two optical signals (S and L) and, in response, generate four output signals: S+L, S−L, S+jL, S−jL (where j is the imaginary number). The output of the I-Q detector6may be in the form of two electrical signals: the I-channel7and the Q-channel8. The system can further include a control circuit9coupled to the I-Q detector6. The control circuit9can be configured to simultaneously process the I- and Q-channels7,8.

FIG. 2is a graph illustrating laser frequency as a function of time illustrating an exemplary generation of signals at the output of the I-Q detector6, according to one aspect of the present disclosure. In this example, the modulator2is configured to generate laser light with dual-sideband frequency modulation. In one aspect, the modulator2can be configured to directly transmit the upper sideband10and the lower sideband11to the combiner5, which, as noted above, can be implemented as an optical hybrid. Further, the modulator2can also be configured to transmit the upper sideband10and the lower sideband11through the target path to be directed at the target, incurring both a time delay12due to the distance between the system and the target and a frequency shift13due to movement by the target before being received by the combiner5. The received upper sideband14and the received lower sideband15can be combined with the transmitted upper sideband10and the transmitted lower side band11at the combiner5. Interference between the transmitted and received upper sidebands10,14may create a beat frequency equal to their separation16in laser frequency. Further, interference between the transmitted and received sidebands11,15may likewise create a beat frequency equal to their separation17in laser frequency.

In this example, the I- and Q-channels7,8generated by the combiner5can be summed to create the complex-valued signal I+jQ (where j is the imaginary number). The power spectral density (PSD) of this complex sum is illustrated in exemplaryFIG. 3, which is a graph illustrating power-spectral-density (PSD) measurements performed using the output-channels of the I-Q detector as a function of frequency, according to one aspect of the present disclosure. The PSD measurements are processed (e.g., by the control circuit9) to yield estimates for the range and velocity of the target without the need for successive measurements. The PSD may have a first peak value18at a first frequency value16(which is likewise indicated onFIG. 2) and a second peak value19at a second frequency value17(which is likewise indicated onFIG. 2). In this example, the first frequency value16is positive and the negative frequency value17is negative. The first frequency value16is shifted from a first nominal frequency value20(also referred to as the “nominal beat frequency”). The second frequency value17is shifted from a second nominal frequency value21, which is the opposite sign of the first nominal frequency value20. In one aspect, the control circuit9can be configured to calculate the nominal beat frequency20by subtracting the second frequency value17from the first frequency value16and dividing by two. Further, the control circuit9can be configured to calculate the frequency shift of the signals away from frequency value20by adding the first frequency value16and the second frequency value17and dividing by two. The nominal beat frequency20may be proportional to the target distance (i.e., the distance to the target from the emitter of the system), while the frequency shift may be proportional to the target velocity (i.e., the velocity at which the target is moving). If the target is moving in the opposite direction from the example shown inFIGS. 2 and 3, the measured peaks18,19may be shifted in the opposite direction. This would thus lead to a differently signed value for the frequency shift, but the nominal beat frequency may still be calculated to be frequency value20.

Complementary Modulation of Multiple Lasers and Coherent Receiver for Simultaneous Range and Velocity Measurement

FIG. 4is a diagram of a laser bank comprising N lasers and an N×1 incoherent combiner, according to one aspect of the present disclosure, which can be configured with as few as two lasers. In various aspects, N can be any integer >1. In the example, the system can include a first laser driver51that is coupled to and directly modulates a first laser52. The system can further include a second laser driver53that is coupled to and directly modulates a second laser54independently from the first laser driver51. This configuration may include a laser pair55. The laser pair55may be repeated many times, as demonstrated by the second laser pair60in the particular example of the system shown inFIG. 4. Each laser may be coupled into a single waveguide via the N×1 optical coupler61. In one aspect, the first laser52may be modulated to emit laser beams having a positive frequency sweep and the second laser54may be simultaneously modulated to emit laser beams having a negative frequency sweep. The N×1 optical coupler61can be configured to generate a laser field from each of the laser beams generated by the lasers52,54,57,59. The laser field generated from the laser beams having positive and negative frequency sweeps is then output by the laser bank.

FIG. 5is a diagram of the FMCW LIDAR system with an N×1 laser bank62and coherent detection, according to one aspect of the present disclosure. In this example, the system includes a laser bank62(also referred to as a “laser array”), such as the laser bank illustrated inFIG. 4. In one aspect, the system further includes an optical coupler63(e.g., a 2×2 optical coupler) coupled to the laser bank62, which is configured to split the light (i.e., the laser field) from the laser bank62(e.g., using a directional coupler or a multi-mode interferometer). The system can further include a combiner65(e.g., a 2×4 combiner or coupler). Some or a portion of the light generated by the laser bank62may be may transmitted, via the coupler63, through the target path to a target arm64(examples of which are described below in connection withFIGS. 8A-8C) before being coupled into the combiner65. The rest or remaining portion of the light generated by the laser bank62may be directly coupled, via the coupler63, into the combiner65. In one aspect, the combiner65may be implemented as an “optical hybrid,” which is configured to split the light into four paths to be detected at a four-channel photoreceiver66, also referred to as an “I-Q detector.” An optical hybrid is configured to receive two optical signals (S and L) and, in response, generate four output signals: S+L, S−L, S+jL, S−jL (where j is the imaginary number). The output of the I-Q detector66may be in the form of two electrical signals: the I-channel67and the Q-channel68. The system can further include a control circuit69coupled to the I-Q detector66. The control circuit69can be configured to simultaneously process the I- and Q-channels67,68.

FIG. 6is a graph illustrating laser frequency as a function of time illustrating an exemplary generation of signals at the output of the I-Q detector66, according to one aspect of the present disclosure. Notably,FIG. 6is similar to the graph depicted inFIG. 2; however, in this example, the laser bank62is configured to simultaneously generate two optical frequency sweeps. In one aspect, the coupler63can be configured to direct or transmit a first portion of the positive sweep70and the negative sweep71directly to the combiner65, which, as noted above, can be implemented as an optical hybrid. Further, the coupler63can be configured to direct or transmit a second portion of the positive sweep70and the negative sweep71through the target path, incurring both a time delay72due to the distance between the system and the target and a frequency shift73due to movement by the target before being received by the combiner65. The received positive sweep74and the received negative sweep75can be combined with the transmitted positive sweep70and the transmitted negative sweep71at the combiner65. Interference between the transmitted and received positive sweeps70,74may create a beat frequency equal to their separation in laser frequency76. Further, interference between the transmitted and received negative sweeps71,75may likewise create a beat frequency equal to their separation77in laser frequency.

In this example, the I- and Q-channels67,68generated by the combiner65can be summed to create the complex-valued signal, I+jQ (where j is the imaginary number). The power spectral density (PSD) of this complex sum may be illustrated in exemplaryFIG. 7, which is a graph illustrating power-spectral-density (PSD) measurements performed using the output-channels of the I-Q detector as a function of frequency, according to one aspect of the present disclosure. The PSD measurements are processed (e.g., by the control circuit69) to yield estimates for the range and velocity of the target without the need for successive measurements. The PSD may have a first peak value78at a first frequency value76(which is likewise indicated onFIG. 6) and a second peak value79at a second frequency value77(which is likewise indicated onFIG. 6). In this example, the first frequency value76is positive and the negative frequency value77is negative. The first frequency value76is shifted from a first nominal frequency value80(also referred to as the “nominal beat frequency”). The second frequency value77is shifted from a second nominal frequency value81, which is the opposite sign of the first nominal frequency value80. In one aspect, the control circuit69can be configured to calculate the nominal beat frequency80by subtracting the second frequency value77from the first frequency value76and dividing by two. Further, the control circuit69can be configured to calculate the frequency shift of the signals away from frequency value80by adding the first frequency value76and the second frequency value77and dividing by two. The nominal beat frequency80may be proportional to the target distance (i.e., the distance to the target from the emitter of the system), while the frequency shift may be proportional to the target velocity (i.e., the velocity at which the target is moving). If the target is moving in the opposite direction from the example shown inFIGS. 6 and 7, the measured peaks78,79may be shifted in the opposite direction. This would thus lead to a differently signed value for the frequency shift, but the nominal beat frequency may still be calculated to be frequency value70.

Target Arm Assemblies

FIGS. 8A-8Cillustrate three illustrative implementations of a target arm, which can be utilized in conjunction with any of the systems described above in connection withFIGS. 1-7. In these various implementations, light can be coupled to a coaxial optical transceiver through discrete fiber components such as a fiber circulator or a 2×2 coupler (such as a directional coupler or multi-mode interferometer). Further, the light can be shaped and steered by a lens combined with mechanical scanning or light can be shaped and steered by an integrated photonic transceiver. Each example implementation illustrated inFIGS. 8A-8Cincludes a coaxial optical transceiver, where input light is coupled into scanning optics, transmitted to a target object, received by the same scanning optics, and delivered to the output of the target arm4,64. In a first example implementation of the target arm shown inFIG. 8A, input light is delivered to the input arm501of a fiber circulator502. The first output light of the circulator502is delivered to a fiber facet503and the output beam is shaped by optics504. The shaped beam is transmitted through scanning optics505(such as galvanometric scanning mirrors or MEMS-based scanning mirrors). The steered and shaped beam506is transmitted to a target that reflects some of the light. The scanning optics505can be used to receive the reflected light and the optics504can be used to focus the received light back into the fiber facet503. Input light from the fiber facet503is delivered back to the fiber circulator502and coupled to the output507of the fiber circulator502.

In a second example implementation of the target arm4,64shown inFIG. 8B, the fiber circulator502output is delivered to an integrated photonic device508that shapes and directs an output beam509to the target. The same integrated photonic device508can be used to receive light reflected by the target and then deliver the received light back to the fiber circulator502such that the received light is coupled to the output507of the fiber circulator502.

In a third example implementation of the target arm4,64shown inFIG. 8C, input light is delivered to the input arm510of an optical coupler511(e.g., a 2×2 coupler). The output of the 2×2 coupler511is delivered to an integrated photonic device508that shapes and directs an output beam509to the target. The same integrated photonic device508can be used to receive light reflected by the target and then deliver the received light back to the 2×2 coupler511such that the received light is coupled to the output512of the 2×2 coupler511. In one aspect, the 2×2 coupler511can be implemented as, for example, a fiber coupled module or as an integrated photonic component (such as directional coupler or multi-mode interferometer), which can be fabricated in tandem with the integrated photonic device508.

Multi-Channel Frequency Modulated Continuous Wave LIDAR System

FIG. 9is a diagram of an example multi-channel FMCW LIDAR system, according to one aspect of the present disclosure. In one aspect, the system can include a laser module211with N laser diodes212, where N is an integer >2, coupled to a photonics assembly228. In the illustrated example, the system includes a single pair of laser diodes212(i.e., N=2). In the following description, the system will be discussed primarily in terms of have two or a pair of laser diodes212; however, this is merely for brevity and should be understood to not be limiting. In one aspect, the system further includes laser drives227coupled to the laser module211for generating laser beams therefrom and a control circuit218coupled to the laser drivers227. In this example, the lasers diodes212are modulated by signals from the laser drivers227, which are in turn controlled by the control circuit218to generate a frequency-swept waveform from each of the laser diodes212. The two outputs from the laser diodes212run separate, but identical, paths215,216, where each path215,216includes an interferometer structure for frequency measurement. The system further includes an optical power tap214(which can also be referred to as an “optical splitter”) coupled to each path215,216. The optical power tap214is configured to direct the light output received from the laser diodes212along a “target” path221(at a first port of the optical power tap214) leading to the beam steering module229(and indirectly to the coherent receiver220) and a “local” path213(at a second port of the optical power tap214). In the illustrated aspect, the target path221comprises an optical circulator217. In other aspects, the target path221can include a directional coupler instead of the optical circulator217. The optical circulator217(or directional coupler) is configured to direct outgoing beams223to a beam steering module229and direct returning beams222to the signal port of a coherent receiver220. In the illustrated aspect, the local path213leads directly to the local oscillator (LO) port of the coherent receiver220. Therefore, each coherent receiver220is configured to receive a first or target laser beam reflected from the target and a second or local laser beam directly from the laser module211generated from a respective laser diode212of the laser module211. In one aspect, each combination of an optical power tap214, a circulator217, and a respective coherent receiver220can be collectively referred to as an “optical system.” Although the photonics assembly228illustrated inFIG. 9includes two optical systems, this is merely illustrative and the photonics assembly228can include n optical systems, where n is an integer >0.

In the aspect of the system illustrated inFIG. 9, the coherent receiver220can be configured to generate two electrical signals by mixing the two optical signals (i.e., the returning beam222and the local beam deliver via the local path213) via an optical hybrid structure and feeding the optical signals to two pairs of balanced photodiodes, referred to as the “I-channel”24and the “Q-channel”27. In an alternative aspect of the system, the coherent receiver220can be configured to generate a single electrical signal by mixing the two optical signals via an optical coupler and feeding to a single pair of balanced photodiodes. An example of such a coherent receiver220is illustrated inFIG. 11Band described below. These signals may be amplified by transimpedance amplifiers (TIAs)226, digitized by analog-to-digital converters (ADCs)225, and processed simultaneously through digital signal processing (DSP)224on or via a control circuit. The separate, but identical, paths215,216lead to Beam_1and Beam_2, respectively, at the beam steering module229. All or part of the components, modules, and/or circuits of the photonics assembly228can be implemented on an integrated photonic chip including, but not limited to, silicon photonic chips or planar lightwave circuits (PLC), such as the chips illustrated inFIGS. 11A-12B.

FIGS. 10A and 10Billustrates two examples of alternative arrangements for the beam steering module229, according to various aspects of the present disclosure. In this aspect shown inFIG. 10A, the beam steering module229comprises a bundle of free-space interfaces37configured to receive the laser beams arriving from the circulator39of the photonics assembly228(FIG. 9). The beam steering module229further includes an optical lens system35that receives the laser beams from the free-space interfaces37and projects the laser beams onto a single beam scanner36. With the aid of the optical lens system35, the different beams may cover an extended FOV, in either 1- or 2-dimensions. In one aspect, the free-space interfaces37are placed at the focal plane of the optical lens system35and are configured to send and receive optical signals at the same angles or different angles.

In an alternative example shown inFIG. 10B, the beam steering module229comprises multiple free-space interfaces37, multiple optical lens systems35, and multiple beam scanners36. In this aspect, laser beams arriving from the circulator39of the photonics assembly (FIG. 9) enter the beam steering module229and each passes through a free-space interface37into an optical lens systems35, where the beams are projected onto multiple scanners36and aimed at the target environment in different directions to cover a large FOV in either 1- or 2-dimensions.

The multi-channel architecture depicted inFIG. 9and the beam steering modules229depicted inFIGS. 10A and 10Bcan be implemented on integrated photonic chips to significantly reduce the size and cost of the FMCW LIDAR system.FIG. 11Aillustrates one implementation of an integrated photonic chip101with on-chip multichannel FMCW LIDAR transceivers. In one aspect, the integrated photonic chip101comprises a series of on-chip couplers102(e.g., edge couplers or surface grating couplers) that are configured to receive the frequency modulated light signals (e.g., as generated by the laser module211according to the laser drives227) and distribute the light signals to parallel transceiver slices via an optical distribution network103(e.g., a binary tree structure). Each transceiver slice consists of a coherent receiver (CR)104and an optical antenna105.FIGS. 11B and 11Cshows two versions of a CR, for example. The optical distribution network103is configured to provide the received light (e.g., frequency modulated laser beams) to a first line123(i.e., the optical input) of the CR104. The CR further includes a splitter122(e.g., a 2×2 bidirectional splitter) that is configured to split the light into a first output, which is directed through a second line125, and a second output, which is directed through a third line126. The second line125is coupled to the optical antenna105; accordingly, the CR104is configured to direct the second output out of the chip using the optical antenna105. Further, the optical antenna105is reciprocal and is thus configured to collect the reflected beam from the object (target) and send the reflected beam back to the CR104through the same line (i.e., the second line125). The third line126corresponds to the LO for the CR104. The splitter122is further configured to split the returned signal (i.e., the beam reflected from the target as received by the optical antenna105) between the first line123and a fourth line124. In the aspect illustrated inFIG. 11B, the third line126and the fourth line124are coupled to a balanced 2×2121, which is configured to mix the transmitted optical signal (received via the third line126) and the reflected optical signal (received via the fourth line124). In the aspect illustrated inFIG. 11C, the third line126and the fourth line124are coupled to an optical hybrid129. Further, the CR104includes photodiodes (PDs)127that are configured to convert an optical signal into an electrical signal for beat tone detection. For example, the aspect depicted inFIG. 11Bincludes a pair of PDs127, whereas the aspect depicted inFIG. 11Cincludes four PDs127. The aspect illustrated inFIG. 11Bcan be referred to as a “Balanced Photo Diode” (BPD) CR. The BPD CR is configured to provide a single electrical signal output. The aspect illustrated inFIG. 11Ccan be referred to as a “hybrid” CR. The hybrid CR is configured to provide in-phase (I) and quadrature (Q) outputs, which are used to determine the sign of the velocity from the Doppler shift in the measured beat tone.

FIGS. 12A and 12Billustrate how various aspects of the integrated photonic chip101can be configured to emit and receive multiple light beams203depending on the type of optical antennas105(e.g., surface grating couplers301as shown inFIG. 12Aor edge couplers302as shown inFIG. 12B). In various aspects, mode field convertors can be used as part of the antennas105to shape the divergence angle of the multiple light beams203. The exit angle of the light beams can be the same or different depending on the lens system202design.

FIG. 13is a diagram of a beam steering module arrangement and scanning patterns for the multi-channel FMCW LIDAR system implemented on an integrated photonic chip, according to one aspect of the present disclosure. InFIG. 13, a lens system202is configured to create collimated beams204pointing at different angles when the integrated photonics chip101(FIGS. 12A and 12B) is placed at its focal plane. A single-axis or dual-axis beam scanner201scans the light beams204across the entire FOV. In the depicted example, there are four beams204, but this is merely for illustrative purposes and should not be interpreted to be limiting. Further,FIG. 13depicts an example of a raster scan pattern in far field, where the four light spots205correspond to the four beams204are scanning together as a group in a scanning trajectory206. Note that the scanning step of the raster scan can be non-uniform (e.g., denser at the center of the FOV) and be a fraction of angular span of the four points to address higher resolution requirement at the center.

EXAMPLES

Various aspects of the subject matter described herein are set out in the following numbered examples:

A LIDAR system for determining a distance and a velocity of a target, the LIDAR system comprising: a laser configured to output a laser beam; a laser modulator coupled to the laser, the laser modulator configured to modulate an intensity of the laser beam; an optical combiner; an optical splitter coupled to the laser modulator, the optical splitter configured to: optically split the modulated laser beam into a first laser beam and a second laser beam; and direct the first laser beam at the target such that the first laser beam is reflected by the target to the optical combiner; wherein the optical combiner is configured to: receive the first laser beam reflected from the target; receive the second laser beam directly from the optical splitter; and optically combine the first laser beam and the second laser beam; a photoreceiver coupled to the optical combiner, the photoreceiver configured to output an I-output and a Q-output according to the optically combined first laser beam and second laser beam; and a control circuit coupled to the photoreceiver, the control circuit configured to: determine a power spectral density (PSD) according to the I-output and the Q-output; determine a first peak PSD at a positive frequency value; determine a second peak PSD at a negative frequency value; determine a nominal beat frequency according to a difference between the positive frequency value and the negative frequency value; and determine a frequency shift from the nominal beat frequency according to a sum of the positive frequency value and the negative frequency value; wherein the distance of the target corresponds to the nominal beat frequency; wherein the velocity of the target corresponds to the frequency shift.

The LIDAR system of Example 1, wherein the photoreceiver comprises an I-Q detector.

The LIDAR system of Examples 1 or 2, wherein the laser modulator is configured to frequency modulate the laser beam output by the laser.

The LIDAR system of any one of Examples 1-3, wherein the optical combiner comprises an optical hybrid configured generate four output signals: S+L, S−L, S+jL, S−jL based on input signals S and L.

The LIDAR system of Example 4, wherein the photoreceiver comprises a four-channel photoreceiver configured to receive each of the output signals of the optical hybrid.

The LIDAR system of any one of Examples 1-5, wherein the optical splitter comprises a 2×2 coupler.

The LIDAR system of any one of Examples 1-6, further comprising a target arm assembly coupled to the optical splitter, the target arm assembly configured to direct the first laser beam at the target and direct the reflected first laser beam to the optical combiner.

The LIDAR system of Example 7, wherein the target arm assembly comprises: a circulator configured to: receive the first laser beam from the optical splitter; and direct the reflected first laser beam to the optical combiner; and scanning optics coupled to the circulator, the scanning optics configured to: receive the first laser beam from the circulator; direct the first laser beam at a target; receive the reflected first laser beam from the target; and direct the reflected first laser beam to the circulator.

The LIDAR system of Example 8, wherein the scanning optics is selected from the group consisting of galvanometric scanning mirrors or MEMS-based scanning mirrors.

The LIDAR system of Example 7, wherein the target arm assembly comprises: a circulator configured to: receive the first laser beam from the optical splitter; and direct the reflected first laser beam to the optical combiner; and an integrated photonic device coupled to the circulator, the integrated photonic device configured to: receive the first laser beam from the circulator; direct the first laser beam at a target; receive the reflected first laser beam from the target; and direct the reflected first laser beam to the circulator.

The LIDAR system of Example 7, wherein the target arm assembly comprises: a 2×2 coupler configured to: receive the first laser beam from the optical splitter; and direct the reflected first laser beam to the optical combiner; and an integrated photonic device coupled to the 2×2 coupler, the integrated photonic device configured to: receive the first laser beam from the 2×2 coupler; direct the first laser beam at a target; receive the reflected first laser beam from the target; and direct the reflected first laser beam to the 2×2 coupler.

A method for determining a distance and a velocity of a target via a LIDAR system, the method comprising: generating, by a laser, a laser beam; modulating, by a laser modulator, the laser beam; optically splitting, by an optical splitter, the modulated laser beam into a first laser beam and a second laser beam; directing, by the optical splitter, the first laser beam at the target such that the first laser beam is reflected by the target to an optical combiner; receiving, by the optical combiner, the first laser beam reflected from the target; receiving, by the optical combiner, the second laser beam directly from the optical splitter; optically combining, by the optical combiner, the reflected first laser beam and the second laser beam; outputting, by a photoreceiver, an I-output and a Q-output according to the optically combined reflected first laser beam and second laser beam; determining, by a control circuit coupled to the photoreceiver, a power spectral density (PSD) according to the I-output and the Q-output; determining, by the control circuit, a first peak PSD at a positive frequency value; determining, by the control circuit, a second peak PSD at a negative frequency value; determining, by the control circuit, a nominal beat frequency according to a difference between the positive frequency value and the negative frequency value; and determining, by the control circuit, a frequency shift from the nominal beat frequency according to a sum of the positive frequency value and the negative frequency value; wherein the distance of the target corresponds to the nominal beat frequency; wherein the velocity of the target corresponds to the frequency shift.

The method of Example 12, wherein the photoreceiver comprises an I-Q detector.

The method of Examples 12 or 13, wherein the laser modulator is configured to frequency modulate the laser beam output by the laser.

The method of any one of Examples 12-14, wherein the optical combiner comprises an optical hybrid configured generate four output signals: S+L, S−L, S+jL, S−jL based on input signals S and L.

The method of Example 15, wherein the photoreceiver comprises a four-channel photoreceiver configured to receive each of the output signals of the optical hybrid.

The method of any one of Examples 12-16, wherein the optical splitter comprises a 2×2 coupler.

The method of any one of Examples 12-17, wherein the LIDAR system comprises a target arm assembly coupled to the optical splitter, the target arm assembly configured to direct the first laser beam at the target and direct the reflected first laser beam to the optical combiner.

The method of Example 18, further comprising: receiving, by a circulator of the target arm assembly, the first laser beam from the optical splitter; directing, by the circulator, the reflected first laser beam to the optical combiner; receiving, by scanning optics of the target arm assembly, the first laser beam from the circulator; directing, by the scanning optics, the first laser beam at a target; receiving, by the scanning optics, the reflected first laser beam from the target; and directing, by the scanning optics, the reflected first laser beam to the circulator.

The method of Example 19, wherein the scanning optics is selected from the group consisting of galvanometric scanning mirrors or MEMS-based scanning mirrors.

The method of Example 18, further comprising: receiving, by a circulator of the target arm assembly, the first laser beam from the optical splitter; directing, by the circulator, the reflected first laser beam to the optical combiner; receiving, by an integrated photonic device of the target arm assembly, the first laser beam from the circulator; directing, by the integrated photonic device, the first laser beam at a target; receiving, by the integrated photonic device, the reflected first laser beam from the target; and directing, by the integrated photonic device, the reflected first laser beam to the circulator.

The method of Example 18, further comprising: receiving, by a circulator of the target arm assembly, the first laser beam from the optical splitter; directing, by the circulator, the reflected first laser beam to the optical combiner; receiving, by a 2×2 coupler of the target arm assembly, the first laser beam from the circulator; directing, by the 2×2 coupler, the first laser beam at a target; receiving, by the 2×2 coupler, the reflected first laser beam from the target; and directing, by the 2×2 coupler, the reflected first laser beam to the circulator.

A LIDAR system for determining a distance and a velocity of a target, the LIDAR system comprising: a laser bank comprising: a first laser configured to output a first laser beam having a positive frequency sweep; a second laser configured to output a second laser beam having a negative frequency sweep; wherein the laser bank is configured to generate a laser field from the first laser beam and the second laser beam; an optical combiner; an optical coupler coupled to the laser bank, the optical coupler configured to: direct a first portion of the laser field at the target such that the first portion of the laser field is reflected by the target to the optical combiner; and direct a second portion of the laser field directly at the optical combiner; wherein the optical combiner is configured to: receive the reflected first portion of the laser field; and optically combine the reflected first portion of the laser field and the second portion of the laser field; a photoreceiver coupled to the optical coupler, the photoreceiver configured to output an I-output and a Q-output according to the optically combined portions of the laser field; and a control circuit coupled to the photoreceiver, the control circuit configured to: determine a power spectral density (PSD) according to the I-output and the Q-output; determine a first peak PSD at a positive frequency value; determine a second peak PSD at a negative frequency value; determine a nominal PSD frequency according to a difference between the positive frequency value and the negative frequency value; and determine a frequency shift from the nominal PSD frequency according to a sum of the positive frequency value and the negative frequency value; wherein the distance of the target corresponds to the nominal PSD frequency; wherein the velocity of the target corresponds to the frequency shift.

The LIDAR system of Example 23, wherein the photoreceiver comprises an I-Q detector.

The LIDAR system of Examples 23 or 24, wherein the laser bank comprises an N×1 incoherent coupler coupled to each of the first laser and the second laser.

The LIDAR system of any one of Examples 23-25, wherein the optical combiner comprises an optical hybrid configured generate four output signals: S+L, S−L, S+jL, S−jL based on input signals S and L.

The LIDAR system of Example 26, wherein the photoreceiver comprises a four-channel photoreceiver configured to receive each of the output signals of the optical hybrid.

The LIDAR system of any one of Examples 23-27, wherein the optical coupler comprises a 2×2 coupler.

The LIDAR system of any one of Examples 23-28, further comprising a target arm assembly coupled to the optical coupler, the target arm assembly configured to direct the first portion of the laser field at the target and direct the reflected first portion of the laser field to the optical combiner.

The LIDAR system of Example 29, wherein the target arm assembly comprises: a circulator configured to: receive the first laser beam from the optical coupler; and direct the reflected first laser beam to the optical combiner; and scanning optics coupled to the circulator, the scanning optics configured to: receive the first laser beam from the circulator; direct the first laser beam at a target; receive the reflected first laser beam from the target; and direct the reflected first laser beam to the circulator.

The LIDAR system of Example 30, wherein the scanning optics is selected from the group consisting of galvanometric scanning mirrors or MEMS-based scanning mirrors.

The LIDAR system of Example 29, wherein the target arm assembly comprises: a circulator configured to: receive the first laser beam from the optical coupler; and direct the reflected first laser beam to the optical combiner; and an integrated photonic device coupled to the circulator, the integrated photonic device configured to: receive the first laser beam from the circulator; direct the first laser beam at a target; receive the reflected first laser beam from the target; and direct the reflected first laser beam to the circulator.

The LIDAR system of Example 29, wherein the target arm assembly comprises: a 2×2 coupler configured to: receive the first laser beam from the optical coupler; and direct the reflected first laser beam to the optical combiner; and an integrated photonic device coupled to the 2×2 coupler, the integrated photonic device configured to: receive the first laser beam from the 2×2 coupler; direct the first laser beam at a target; receive the reflected first laser beam from the target; and direct the reflected first laser beam to the 2×2 coupler.

The LIDAR system of any one of Examples 23-33, wherein: the first laser is further configured to output a third laser beam having a negative frequency sweep; and the second laser is further configured to output a fourth laser beam having a positive frequency sweep.

A method for determining a distance and a velocity of a target via a LIDAR system, the method comprising: generating, by a laser bank, a first laser beam having a positive frequency sweep and a second laser beam having a negative frequency sweep; directing, by an optical coupler, a first portion of the laser field at the target such that the first portion of the laser field is reflected by the target to an optical combiner; receiving, by the optical combiner, the first portion of the laser field reflected from the target; receiving, by the optical combiner, a second portion of the laser field directly from the optical coupler; optically combining, by the optical combiner, the reflected first portion of the laser field and the second portion of the laser field; outputting, by a photoreceiver, an I-output and a Q-output according to the optically combined portions of the laser field; determining, by a control circuit coupled to the photoreceiver, a power spectral density (PSD) according to the I-output and the Q-output; determining, by the control circuit, a first peak PSD at a positive frequency value; determining, by the control circuit, a second peak PSD at a negative frequency value; determining, by the control circuit, a nominal beat frequency according to a difference between the positive frequency value and the negative frequency value; and determining, by the control circuit, a frequency shift from the nominal beat frequency according to a sum of the positive frequency value and the negative frequency value; wherein the distance of the target corresponds to the nominal beat frequency; wherein the velocity of the target corresponds to the frequency shift.

The method of Example 35, wherein the photoreceiver comprises an I-Q detector.

The method of Examples 35 or 36, wherein the laser bank comprises an N×1 incoherent coupler coupled to each of the first laser and the second laser.

The method of any one of Examples 35-37, wherein the optical combiner comprises an optical hybrid configured generate four output signals: S+L, S−L, S+jL, S−jL based on input signals S and L.

The method of Example 38, wherein the photoreceiver comprises a four-channel photoreceiver configured to receive each of the output signals of the optical hybrid.

The method of any one of Examples 35-39, wherein the optical coupler comprises a 2×2 coupler.

The method of any one of Examples 35-40, wherein the LIDAR system comprises a target arm assembly coupled to the optical coupler, the target arm assembly configured to direct the first laser beam at the target and direct the reflected first laser beam to the optical combiner.

The method of Example 41, further comprising: receiving, by a circulator of the target arm assembly, the first portion of the laser field from the optical coupler; directing, by the circulator, the reflected first of the laser field to the optical combiner; receiving, by scanning optics of the target arm assembly, the first portion of the laser field from the circulator; directing, by the scanning optics, the first portion of the laser field at a target; receiving, by the scanning optics, the reflected first portion of the laser field from the target; and directing, by the scanning optics, the reflected first portion of the laser field to the circulator.

The method of Example 42, wherein the scanning optics is selected from the group consisting of galvanometric scanning mirrors or MEMS-based scanning mirrors.

The method of Example 41, further comprising: receiving, by a circulator of the target arm assembly, the first portion of the laser field from the optical coupler; directing, by the circulator, the reflected first portion of the laser field to the optical combiner; receiving, by an integrated photonic device of the target arm assembly, the first portion of the laser field from the circulator; directing, by the integrated photonic device, the first portion of the laser field at a target; receiving, by the integrated photonic device, the reflected first portion of the laser field from the target; and directing, by the integrated photonic device, the reflected first portion of the laser field to the circulator.

The method of Example 41, further comprising: receiving, by a circulator of the target arm assembly, the first portion of the laser field from the optical coupler; directing, by the circulator, the reflected first portion of the laser field to the optical combiner; receiving, by a 2×2 coupler of the target arm assembly, the first portion of the laser field from the circulator; directing, by the 2×2 coupler, the first portion of the laser field at a target; receiving, by the 2×2 coupler, the reflected first portion of the laser field from the target; and directing, by the 2×2 coupler, the reflected first portion of the laser field to the circulator.

A photonics assembly couplable to a beam steering module, the photonics assembly comprising: an optical system configured to receive a frequency modulated laser beam, the optical system comprising: an optical splitter couplable to the beam steering module, the optical splitter configured to: optically split the frequency modulated laser beam into a local laser beam and a target laser beam; deliver the target laser beam to the beam steering module; and receive the target laser beam reflected by a target from the beam steering module; and a coherent receiver coupled to the optical splitter, the coherent receiver configured to: receive the local laser beam from the optical splitter; receive the reflected target laser beam from the optical splitter; and mix the local laser beam and the target laser beam to produce an output signal.

The photonics assembly of Example 46, wherein the optical splitter comprises an optical power tap configured to optically split the frequency modulated laser beam into the local laser beam and the target laser beam.

The photonics assembly of Examples 46 or 47, wherein the optical splitter comprises an optical circulator configured to: deliver the target laser beam to the beam steering module; receive the target laser beam reflected by a target from the beam steering module; and deliver the reflected target laser beam to the coherent receiver.

The photonics assembly of any one of Examples 46-48, wherein the photonics assembly comprises an integrated photonic chip.

The photonics assembly of any one of Examples 46-49, further comprising the beam steering module.

The photonics assembly of Example 50, wherein the beam steering module further comprises: a beam scanner; and an optical lens system configured to: receive the target laser beam from the optical splitter; project the target laser beam to the beam scanner; receive the reflected target laser beam from the beam scanner; and direct the reflected target laser beam to the optical splitter.

The photonics assembly of any one of Examples 46-49, wherein the optical system comprises a first optical system, the frequency modulated laser beam comprises a first frequency modulated laser beam, the optical splitter comprises a first optical splitter, and the coherent receiver comprises a first coherent receiver, the photonics assembly further comprising: a second optical system configured to receive a second frequency modulated laser beam simultaneously as the first frequency modulated laser beam is received by the first optical system, the second optical system comprising: a second optical splitter couplable to the beam steering module, the second optical splitter configured to: optically split the second frequency modulated laser beam into a second local laser beam and a second target laser beam; deliver the second target laser beam to the beam steering module; and receive the second target laser beam reflected by a target from the beam steering module; and a second coherent receiver coupled to the second optical splitter, the second coherent receiver configured to: receive the second local laser beam from the second optical splitter; receive the reflected second target laser beam from the second optical splitter; and mix the second local laser beam and the second target laser beam to produce a second output signal.

The photonics assembly of Example 52, further comprising the beam steering module.

The photonics assembly of Example 53, wherein the beam steering module further comprises: a beam scanner; and an optical lens system configured to: receive the first target laser beam and the second target laser beam from each of the first optical splitter and the second optical splitter; project the first target laser beam and the second target laser beam to the beam scanner; receive the reflected first target laser beam and the reflected second target laser beam from the beam scanner; and direct the reflected first target laser beam and the reflected second target laser beam to the first optical splitter and the second optical splitter, respectively.

The photonics assembly of Example 53, wherein the beam steering module further comprises: a first beam scanner; a first optical lens system configured to: receive the first target laser beam from the first optical splitter; project the first target laser beam to the first beam scanner; receive the reflected first target laser beam from the first beam scanner; and direct the reflected first target laser beam to the first optical splitter; a second beam scanner; and a second optical lens system configured to: receive the second target laser beam from the second optical splitter; project the second target laser beam to the second beam scanner; receive the reflected second target laser beam from the second beam scanner; and direct the reflected second target laser beam to the second optical splitter.

The photonics assembly of any one of Examples 46-55, wherein the output signal comprises an I-channel signal and a Q-channel signal.

The photonics assembly of any one of Examples 46-56, wherein the coherent receiver comprises an optical hybrid.

The photonics assembly of any one of Examples 46-56, wherein the coherent receiver comprises a pair of balanced photodiodes configured to output the output signal.

A method for scanning a target environment via a photonics assembly comprising an optical system, the optical system comprising an optical splitter and a coherent receiver coupled to the optical splitter, the method comprising: receiving, by the optical system, a frequency modulated laser beam; optically splitting, by the optical splitter, the frequency modulated laser beam into a local laser beam and a target laser beam; delivering, by the optical splitter, the target laser beam to the beam steering module; receiving, by the optical splitter, the target laser beam reflected by a target from the beam steering module; receiving, by the coherent receiver, the local laser beam from the optical splitter; receiving, by the coherent receiver, the reflected target laser beam from the optical splitter; and mixing, by the coherent receiver, the local laser beam and the target laser beam to produce an output signal.

The method of Example 59, wherein the optical splitter comprises an optical power tap configured to optically split the frequency modulated laser beam into the local laser beam and the target laser beam.

The method of Examples 59 or 60, wherein the optical splitter comprises an optical circulator, the method further comprising: delivering, by the optical circulator, the target laser beam to the beam steering module; receiving, by the optical circulator, the target laser beam reflected by a target from the beam steering module; and delivering, by the optical circulator, the reflected target laser beam to the coherent receiver.

The method of any one of Examples 59-61, wherein the photonics assembly comprises an integrated photonic chip.

The method of any one of Examples 59-62, wherein the photonics assembly further comprises the beam steering module.

The method of Example 63, wherein the beam steering module further comprises a beam scanner an optical lens system, the method further comprising: receiving, by the optical lens system, the target laser beam from the optical splitter; projecting, by the optical lens system, the target laser beam to the beam scanner; receiving, by the optical lens system, the reflected target laser beam from the beam scanner; and directing, by the optical lens system, the reflected target laser beam to the optical splitter.

The method of any one of Examples 59-62, wherein the optical system comprises a first optical system, the frequency modulated laser beam comprises a first frequency modulated laser beam, the optical splitter comprises a first optical splitter, and the coherent receiver comprises a first coherent receiver, the method further comprising: receiving, by a second optical system, a second frequency modulated laser beam simultaneously as the first frequency modulated laser beam is received by the first optical system; optically splitting, by a optical splitter, the second frequency modulated laser beam into a second local laser beam and a second target laser beam; delivering, by the optical splitter, the second target laser beam to the beam steering module; receiving, by the optical splitter, the second target laser beam reflected by a target from the beam steering module; receiving, by a second coherent receiver, the second local laser beam from the second optical splitter; receiving, by the second coherent receiver, the reflected second target laser beam from the second optical splitter; and mixing, by the second coherent receiver, the second local laser beam and the second target laser beam to produce a second output signal.

The method of Example 65, wherein the photonics assembly further comprises the beam steering module.

The method of Example 66, wherein the beam steering module further comprises a beam scanner and an optical lens system, the method further comprising: receiving, by the optical lens system, the first target laser beam and the second target laser beam from each of the first optical splitter and the second optical splitter; projecting, by the optical lens system, the first target laser beam and the second target laser beam to the beam scanner; receiving, by the optical lens system, the reflected first target laser beam and the reflected second target laser beam from the beam scanner; and directing, by the optical lens system, the reflected first target laser beam and the reflected second target laser beam to the first optical splitter and the second optical splitter, respectively.

The method of Example 66, wherein the beam steering module further comprises a first beam scanner, a first optical lens system, a second beam scanner, and a second optical lens system, the method further comprising: receiving, by the first optical lens system, the first target laser beam from the first optical splitter; projecting, by the first optical lens system, the first target laser beam to the first beam scanner; receiving, by the first optical lens system, the reflected first target laser beam from the first beam scanner; directing, by the first optical lens system, the reflected first target laser beam to the first optical splitter; receiving, by the second optical lens system, the second target laser beam from the second optical splitter; projecting, by the second optical lens system, the second target laser beam to the second beam scanner; receiving, by the second optical lens system, the reflected second target laser beam from the second beam scanner; and directing, by the second optical lens system, the reflected second target laser beam to the second optical splitter.

The method of any one of Examples 59-68, wherein the output signal comprises an I-channel signal and a Q-channel signal.

The method of any one of Examples 59-69, wherein the coherent receiver comprises an optical hybrid.

The method of any one of Examples 59-70, wherein the coherent receiver comprises a pair of balanced photodiodes configured to output the output signal.