Method and system for one-transmitter and one-receiver scanning in coherent LIDAR

Abstract

The present invention relates to a method and system for one-transmitter and one-receiver scanning for coherent LIDAR. A technique for optimizing a scan pattern of a LIDAR system including a bistatic transceiver includes: receiving a first SNR value based on a value of a distance to a target, wherein the first SNR value is for a corresponding scan rate. The technique further includes receiving a second SNR value based on a value of a distance to the target, wherein the second SNR value is for a corresponding integration time. The technique further includes receiving a maximum design distance of the target at each angle within an angular range. The technique further includes determining a maximum scan rate and a minimum integration time for each angle within the angular range. The technique further includes defining a scan pattern of the LIDAR system based on the maximum scan rate and the minimum integration time at each angle, and operating the LIDAR system according to the scan pattern.

Description

[0001] This application is a divisional application of the application with PCT application number PCT / US2019 / 046537, international filing date of August 14, 2019, Chinese application number 201980065586.0, and invention title "Method and System for One-Transmitter-One-Receiver Scanning for Coherent LIDAR", which entered the Chinese national phase on April 2, 2021.

[0002] Cross-reference to related applications

[0003] According to 35 U.S.C.§119(e), this application claims the priority of U.S. Application No. 62 / 727,294 filed on September 5, 2018, the entire content of which is incorporated herein by reference as if fully set forth herein. Background art

[0004] Optical distance detection for optical detection and ranging using a laser (commonly represented by the mnemonic LIDAR), sometimes also referred to as laser RADAR (radio wave detection and ranging), is used for a variety of applications from altitude determination to imaging to collision avoidance. LIDAR provides a finer scale of distance resolution with a smaller beam size compared to conventional microwave ranging systems such as RADAR. Optical detection of distance can be achieved with several different techniques, including direct ranging based on the round-trip travel time of an optical pulse to an object, and chirp detection based on the frequency difference between a transmitted chirped optical signal and a return signal scattered from an object, as well as phase-encoded detection based on a sequence of single-frequency phase changes distinguishable from natural signals.

[0005] To achieve acceptable distance accuracy and detection sensitivity, direct long-range LIDAR systems use short-pulse lasers with a low pulse repetition rate and extremely high pulse peak power. The high pulse power can lead to rapid degradation of optical components. Chirp and phase-encoded LIDAR systems use long optical pulses with relatively low peak optical power. In this configuration, the distance accuracy increases with the chirp bandwidth or the length and bandwidth of the phase code rather than the pulse duration, and thus excellent distance accuracy can still be obtained.

[0006] Useful optical bandwidth has been achieved by modulating an optical carrier with a broadband radio frequency (RF) electrical signal. Recent advances in LIDAR include using the same modulated optical carrier as a reference signal, which is combined with the return signal at an optical detector to generate a relatively low beat frequency in the RF band in the resulting electrical signal, and the beat frequency is proportional to the frequency or phase difference between the reference optical signal and the return optical signal. This beat frequency detection of the frequency difference at the detector is called heterodyne detection. It has several advantages known in the art, such as the advantage of using off-the-shelf and inexpensive RF components.

[0007] The recent work of the present inventors has shown a novel arrangement for optical components and coherent processing for detecting Doppler shifts in return signals, which provides not only improved range but also relative signed velocity on the vector between the LIDAR system and each external object. These systems are referred to herein as high-resolution range-Doppler LIDAR. See, for example, the published texts WO 2018 / 160240 and WO 2018 / 144853 of the World Intellectual Property Organization (WIPO).

[0008] These improvements provide range in a pencil-thin laser beam having appropriate frequency or phase content, with or without target velocity. As this beam sweeps across the scene, information about the position and velocity of surrounding objects can be obtained. Such information is expected to be valuable in control systems for autonomous vehicles such as self-driving cars or driver-assist cars. SUMMARY OF THE INVENTION

[0009] Sampling and processing for providing range accuracy and target velocity accuracy involves integrating one or more laser signals of various durations over a time interval called the integration time. Covering the scene in a timely manner involves repeating measurements with sufficient accuracy (involving one or more signals typically on the order of one to tens of microseconds), which is typically sufficient to sample various angles around the autonomous vehicle (usually on the order of thousands), to understand the environment around the vehicle before the vehicle moves too far into the space in front of it (a distance on the order of one meter to tens of meters, typically covered within a specific time on the order of one second to several seconds). The number of different angles that can be covered within a specific time (usually called the period or sampling time) depends on the sampling rate. It is recognized here that a trade-off can be made between the integration time, sampling rate, and the pattern of sampling different angles using one or more LIDAR beams for range and velocity accuracy, to effectively determine the environment near the vehicle as the autonomous vehicle moves through the environment.

[0010] In a first set of embodiments, a method for optimizing a scan pattern of a LIDAR system on an autonomous vehicle includes: receiving, on a processor, data representing a first signal-to-noise ratio (SNR) value of a signal that is reflected by a target after being transmitted by a transmit waveguide of a bistatic transceiver and received by a receive waveguide of the bistatic transceiver, the transmit waveguide being spaced apart from the receive waveguide. The first SNR value is a value based on the distance to the target, and the first SNR value is a corresponding value for a scan rate of the LIDAR system. The method further includes receiving, on the processor, data representing a second SNR value of a signal based on a value of the distance to the target, where the second SNR value is a corresponding value for an integration time of the LIDAR system. The method also includes receiving, on the processor, data for indicating a first angle and a second angle that define an angular range of the scan pattern. The method also includes receiving, on the processor, data for indicating a maximum design distance of a target at each angle within the angular range. The method also includes, for each angle within the angular range, determining a maximum scan rate of the LIDAR system based on the maximum value among those scan rates in which the first SNR value based on the maximum design distance exceeds a minimum SNR threshold. The method also includes, for each angle within the angular range, determining a minimum integration time of the LIDAR system based on the minimum value among those integration times in which the second SNR value based on the maximum design distance exceeds a minimum SNR threshold. The method also includes using the processor to define a scan pattern of the LIDAR system based on the maximum scan rate and the minimum integration time at each angle within the angular range. The method also includes operating the LIDAR system according to the scan pattern.

[0011] In other embodiments, a system or device or computer-readable medium is configured to perform one or more steps of the above method.

[0012] By the following detailed description, only by way of illustration of many specific embodiments and implementations (including the best mode contemplated for carrying out the present invention), other aspects, features, and advantages will become apparent. Other embodiments can have other and different features and advantages, and several details thereof can be modified in various obvious aspects, all without departing from the spirit and scope of the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like reference numerals indicate similar elements, and in which:

[0014] Figure 1A is a schematic diagram according to an embodiment for illustrating an example transmit signal of a series of binary digits and a returned optical signal for distance measurement;

[0015] Figure 1B is a schematic diagram according to an embodiment for showing an example spectrum of a reference signal and an example spectrum of a Doppler frequency shift return signal;

[0016] Figure 1C is a schematic diagram according to an embodiment for showing an example cross-spectrum of the phase component of a Doppler frequency shift return signal.

[0017] Figure 1D is a set of graphs according to an embodiment for showing an example optical chirp distance measurement;

[0018] Figure 1E is a graph according to an embodiment using a symmetric LO signal, and shows the return signal in this frequency-time plot when there is no Doppler frequency shift as a dashed line.

[0019] Figure 1F is according to an embodiment similar to Figure 1E a graph using a symmetric LO signal, and shows the return signal in this frequency-time plot when there is a non-zero Doppler frequency shift as a dashed line;

[0020] Figure 2A is a block diagram according to an embodiment for showing example components of a high-resolution (HR) LIDAR system;

[0021] Figure 2B is a block diagram for showing a sawtooth scan pattern for a high-resolution Doppler system used in some embodiments;

[0022] Figure 2C is an image according to an embodiment for showing an example velocity point cloud generated by a high-resolution Doppler LIDAR system;

[0023] Figure 2D is a block diagram according to an embodiment for showing example components of a high-resolution (HR) LIDAR system;

[0024] Figure 2E is a block diagram according to an embodiment for showing a side view of example components of a high-resolution (HR) LIDAR system;

[0025] Figure 2F is according to an embodiment for showing Figure 2E a top view of example components of a high-resolution (HR) LIDAR system;

[0026] Figure 3A is a block diagram according to an embodiment for showing an example system including at least one high-resolution LIDAR system mounted on a vehicle;

[0027] Figure 3Bis a block diagram for showing an example system according to an embodiment, the example system including at least one high-resolution LIDAR system mounted on a vehicle;

[0028] Figure 3C is according to an embodiment for showing from Figure 3B a block diagram of an example of light beams emitted at multiple angles from a LIDAR system;

[0029] Figure 3D is a block diagram for showing an example system according to an embodiment, the example system including at least one high-resolution LIDAR system mounted on a vehicle;

[0030] Figure 4A is according to an embodiment for showing an exemplary signal-to-noise ratio (SNR) of an emitted signal in a system of Figure 2D versus target distance without scanning;

[0031] Figure 4B is according to an embodiment for showing a trace of a 1 / r squared loss indicating the shape of an SNR trace for driving in the far field of Figure 4A an example of a graph;

[0032] Figure 4C is according to an embodiment for showing a collimated beam diameter of an emitted signal in a system of Figure 2D versus distance without scanning;

[0033] Figure 4D is according to an embodiment for showing an SNR associated with collection efficiency of an emitted signal in a system of Figure 2D versus distance without scanning;

[0034] Figure 4E is according to an embodiment for showing an example of an image of beam walk-off for various target distances and scan speeds in a system of Figure 2E ;

[0035] Figure 4F is according to an embodiment for showing an example of a graph of coupling efficiency versus target distance for various scan rates in a system of Figure 2E ;

[0036] Figure 4G is according to an embodiment for showing an example of a graph of SNR versus target distance for various scan rates in a system of Figure 2E ;

[0037] Figure 4H is according to an embodiment for showing when mounted on a moving vehicle Figure 2EA diagram of an example of a conventional scan trajectory of a light beam in a system;

[0038] Figure 4I is a diagram according to an embodiment for showing the SNR versus target distance for various integration times in a Figure 2E system;

[0039] Figure 4J is a diagram according to an embodiment for showing the measurement rate versus target distance in a Figure 2E system;

[0040] Figure 4K is a diagram according to an embodiment for showing the SNR versus target distance for various separation values in a Figure 2E system;

[0041] Figure 4L is a diagram according to an embodiment for showing the separation of various SNR values versus target distance in a Figure 2E system;

[0042] Figure 4M is a diagram according to an embodiment for showing the SNR versus target distance for various separation values in a Figure 2E system;

[0043] Figure 4N is a diagram according to an embodiment for showing the separation of various SNR values versus target distance in a Figure 2E system;

[0044] Figure 4O is a diagram according to an embodiment for showing the separation of various target distance values with a minimum threshold SNR versus scan speed in a Figure 2E system;

[0045] Figure 5 is a diagram according to an embodiment for showing an example of the vertical angle over time in multiple angular ranges in a Figure 2E system;

[0046] Figure 6 is a flowchart according to an embodiment for showing an example method of optimizing the scan pattern of a LIDAR system;

[0047] Figure 7 is a block diagram of a computer system on which embodiments of the present invention can be implemented; and

[0048] Figure 8 shows a chipset on which embodiments of the present invention can be implemented. Detailed Description

[0049] A method and apparatus for scanning in a LIDAR system, as well as a system and a computer-readable medium, are described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form to avoid unnecessarily obscuring the present invention.

[0050] Although a wide range of numerical ranges and parameters are presented as approximations, the numerical values set forth in the specific non-limiting examples are reported as precisely as possible. However, any numerical value inherently contains certain errors that are necessarily caused by the standard deviation found in their respective test measurements at the time of writing. Additionally, unless clearly apparent from the context, the numerical values presented herein have an implied precision given by the least significant bit. Thus, the value 1.1 means a value from 1.05 to 1.15. The term "about" is used to denote a wider range centered on a given value and, unless clearly apparent from the context, denotes a wider range near the least significant bit, e.g., "about 1.1" means a range from 1.0 to 1.2. If the least significant bit is not clear, the term "about" means twice, e.g., "about X" means a value in the range from 0.5X to 2X, e.g., about 100 means a value in the range from 50 - 200. Additionally, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein. For example, a range of "less than 10" for a parameter that is only positive can include any and all sub-ranges between (and including) a minimum value of zero and a maximum value of 10, i.e., any and all sub-ranges having a minimum value equal to or greater than zero and a maximum value equal to or less than 10, such as 1 to 4.

[0051] Some embodiments of the present invention are described below in the context of a high-resolution LIDAR system. One embodiment of the present invention is described in the context of a high-resolution bistatic LIDAR system. Other embodiments of the present invention are described in the context of a single front-mounted high-resolution Doppler LIDAR system on a personal vehicle; however, the embodiments are not limited to this context. In other embodiments, one or more systems of the same type or other high-resolution LIDARs with or without a Doppler component, having overlapping or non-overlapping fields of view, or one or more such systems mounted on a leading or autonomous, smaller or larger, land, sea, or air vehicle are employed.

[0052] 1. Overview of Phase Encoding Detection

[0053] An optical phase-coded signal for distance measurement is used. The transmitted signal is in phase with the carrier (phase = 0) for a part of the transmitted signal, and then one or more phase changes represented by the symbol Δφ are changed within a short time interval (so the phase = 0, Δφ, 2Δφ...), and it repeatedly switches back and forth between two or more phase values on the transmitted signal. The shortest interval of constant phase is a parameter of the coding, called the pulse duration τ, and is typically the duration of several cycles of the lowest frequency in the frequency band. The reciprocal 1 / τ is the baud rate, where each baud represents a symbol. During the time of the transmitted signal, the number N of such constant-phase pulses is the number N of symbols and represents the length of the coding. In binary coding, there are two phase values, and the phase of the shortest interval can be considered 0 for one value and 1 for the other value, so the symbol is a bit, and the baud rate is also called the bit rate. In multiphase coding, there are multiple phase values. For example, 4 phase values such as Δφ*{0, 1, 2, and 3}, where for Δφ = π / 2 (90 degrees), they are respectively equal to {0, π / 2, π, and 3π / 2}; and thus, the 4 phase values can represent 0, 1, 2, 3 respectively. In this example, each symbol is two bits, and the bit rate is twice the baud rate.

[0054] Phase Shift Keying (PSK) refers to a digital modulation scheme for transmitting data by changing (modulating) the phase of a reference signal (carrier). Modulation is applied by changing the sine and cosine inputs at precise times. At radio frequency (RF), PSK is widely used in wireless local area networks (LANs), RF identification (RFID), and Bluetooth communications. Alternatively, instead of operating relative to a constant reference wave, the transmission can operate relative to itself. The phase change of a single transmitted waveform can be considered a symbol. In this system, the demodulator determines the change in the phase of the received signal rather than the phase (relative to the reference wave) itself. Since this scheme depends on the difference between consecutive phases, it is called Differential Phase Shift Keying (DPSK). The implementation of DPSK in communication applications is much simpler than ordinary PSK because the demodulator does not need to have a copy of the reference signal to determine the exact phase of the received signal (therefore, it is a non-coherent scheme).

[0055] For optical ranging applications, since the transmitter and receiver are in the same device, coherent PSK can be used. The carrier frequency is the optical frequency fc, and the RF fo is modulated onto the optical carrier. The number of symbols N and the duration τ are chosen to achieve the desired distance accuracy and resolution. The pattern of the symbols is chosen to distinguish it from other sources of coded signals and noise. Thus, a strong correlation between the transmitted signal and the returned signal can be a strong indication of a reflected or backscattered signal. The transmitted signal consists of one or more blocks of symbols, where each block is long enough to provide a strong correlation with the reflected or backscattered return even in the presence of noise. In the following discussion, it is assumed that the transmitted signal can consist of M blocks of N symbols each, where M and N are non-negative integers.

[0056] Figure 1A FIG. 120 is a schematic diagram according to an embodiment, which shows an exemplary transmitted signal as a series of binary digits and a returned optical signal for distance measurement. The horizontal axis 122 represents time in arbitrary units after the start time at zero. The vertical axis 124a represents the amplitude of the optical transmitted signal at the frequency fc + fo in arbitrary units relative to zero. The vertical axis 124b represents the amplitude of the optical returned signal at the frequency fc + fo in arbitrary units relative to zero and is offset from axis 124a to separate the traces. The trace 125 represents the transmitted signal of M * N binary symbols, having phase changes as shown Figure 1A to produce a code that starts with 00011010 and indicates subsequent ones with an ellipsis. The trace 126 represents an idealized (noise-free) returned signal scattered from a non-moving object (and thus, the return is without Doppler shift). The amplitude is reduced, but the code 00011010 is recognizable. The trace 127 represents an idealized (noise-free) returned signal scattered from a moving object and is thus Doppler shifted. The return is not at the proper optical frequency fc + fo and is not well detected in the expected frequency band, so the amplitude is reduced.

[0057] Due to the Doppler effect given by Equation 1, the observed frequency f’ of the return is different from the correct frequency f = fc + fo of the return.

[0058]

[0059] where c is the speed of light in the medium, v0 is the speed of the observer, and v s is the speed of the source along the vector connecting the source to the receiver. Note that if the observer and the source move at the same speed in the same direction along their vector, the two frequencies are the same. The difference Δf = f' - f between the two frequencies is the Doppler shift Δf D which causes problems for distance measurement and is given by Equation 2.

[0060]

[0061] Note that the magnitude of the error increases with increasing signal frequency f. Also note that for a fixed LIDAR system (v0 = 0), for an object moving at 10 meters per second (v s = 10), and with the frequency of visible light being approximately 500 THz, the magnitude of the Doppler frequency shift is on the order of 16 megahertz (MHz, 1 MHz = 10 6 hertz (Hz), 1 Hz = 1 cycle per second). In the various embodiments described below, the Doppler frequency shift error is detected and used to process data for distance calculation.

[0062] In phase-coded ranging, the arrival of the phase-coded return can be detected in the return signal by cross-correlating the transmitted signal or other reference signal with the return signal, which can be achieved by using heterodyne detection to cross-correlate the code of the RF signal with the electrical signal from the optical detector and thus down-convert back to the RF frequency band. The cross-correlation for any one lag can be calculated by convolving the two traces, i.e., by multiplying the corresponding values in the two traces and summing over all points in the traces, and then repeating for each time lag. Alternatively, the cross-correlation can be achieved by multiplication of the Fourier transforms of each of the two traces, followed by an inverse Fourier transform. Efficient hardware and software implementations of the fast Fourier transform (FFT) are widely available for both the forward and inverse Fourier transforms.

[0063] Note that the cross-correlation calculation can be performed using analog or digital electrical signals after the magnitude and phase of the return have been detected at the optical detector. To shift the signal at the optical detector to an RF frequency range that can be easily digitized, the optical return signal is optically mixed with a reference signal before impinging on the detector. A copy of the phase-coded transmitted optical signal can be used as the reference signal, but it is also possible and generally preferred to use an optical signal of a continuous wave carrier frequency output by a laser as the reference signal and obtain both the magnitude and phase of the electrical signal output by the detector.

[0064] For an idealized (noiseless) return signal reflected from an object that never moves (and thus returns without a Doppler frequency shift), the peak occurs at time Δt after the start of the transmitted signal. This indicates that the return signal includes a version of the transmitted phase code starting at time Δt. The distance R of the reflecting (or backscattering) object is calculated based on the round-trip time delay based on the speed of light c in the medium, as given by Equation 3.

[0065] R = c*Δt / 2 (3)

[0066] For an idealized (noise-free) return signal scattered from a moving object (and thus returned Doppler-shifted), the return signal does not include phase encoding in the appropriate frequency bin, the correlation remains low for all time lags, and the peak is not easily detectable and is generally undetectable in the presence of noise. Thus, Δt is not easily determined, and the range R is not easily generated.

[0067] According to various embodiments of the inventors' previous work, the Doppler shift is determined in the electrical processing of the return signal; and the Doppler shift can be used to correct the cross-correlation calculation. Thus, the peak can be more easily found, and the range can be more easily determined. Figure 1B FIG. 140 is a schematic diagram according to an embodiment, which shows an example spectrum of an emitted signal and an example spectrum of a Doppler-shifted complex return signal. The horizontal axis 142 represents the RF frequency offset from the optical carrier fc in arbitrary units. The vertical axis 144a represents the magnitude of a particular narrow frequency bin in arbitrary units relative to zero, also referred to as the spectral density. The vertical axis 144b represents the spectral density in arbitrary units relative to zero and is offset from axis 144a to separate the traces. The trace 145 represents the emitted signal; and, the peak appears at the appropriate RF f0. The trace 146 represents the idealized (noise-free) complex return signal, which is backscattered from an object moving towards the LIDAR system and is thus Doppler-shifted to a higher frequency (referred to as blue shift). The return does not have a peak at the appropriate RF f0; rather, it is blue-shifted by Δf D to the shifted frequency f S . In fact, the complex return representing both the in-phase and quadrature (I / Q) components of the return is used to determine the peak at +Δf D . Thus, the direction of the Doppler shift and the direction of motion of the target on the vector between the sensor and the object can be evident from a single return.

[0068] In some Doppler compensation embodiments, instead of obtaining Δf as Figure 1B shown by taking the spectra of both the emitted signal and the return signal and searching for peaks in each signal and then subtracting the frequencies of the corresponding peaks D , it can be more efficient to take the cross-spectrum of the in-phase and quadrature components of the down-converted return signal in the RF band. Figure 1C FIG. 150 is a schematic diagram showing an example cross-spectrum according to an embodiment. The horizontal axis 152 represents the frequency shift relative to a reference spectrum in arbitrary units; and, the vertical axis 154 represents the magnitude of the cross-spectrum in arbitrary units relative to zero. The trace 155 represents the cross-spectrum with an idealized (noise-free) return signal, the return signal being from an object moving towards the LIDAR system ( Figure 1B with a blue shift Δf inD1 = Δf D ) and a second object moving away from the LIDAR system (redshift Δf D2 ) is generated. When one of the components is blueshifted by Δf D1 , a peak 156a appears; and when one of the components is redshifted by Δf D2 , another peak 156b appears. Thus, the Doppler frequency shift is determined. These frequency shifts can be used to determine the signed approach velocity of an object near the LIDAR, for example, for collision avoidance applications. However, if I / Q processing is not performed, peaks may appear at both + / -Δf D1 and both + / -Δf D2 , so the sign of the Doppler frequency shift and the direction of movement may be ambiguous.

[0069] As described in more detail in the inventor's previous work, the Doppler frequency shift detected in the cross-spectrum can be used to correct the cross-correlation such that the Doppler compensation Doppler frequency shift return at a lag Δt of peak 135 is evident and the distance R can be determined. In some embodiments, simultaneous I / Q processing can be performed, as described in more detail in the World Intellectual Property Organization publication WO 2018 / 144853, titled "Method and system for Doppler detection and Doppler correction of optical phase-encoded range detection", the entire content of which is incorporated herein by reference as if fully set forth herein. In other embodiments, serial I / Q processing is used to determine the sign of the Doppler return, as described in more detail in the patent application publication of S. Crouch et al., titled "Method and System for Time-Separated Quadrature Detection of Doppler Effects in Optical Range Measurements", the entire content of which is incorporated herein by reference as if fully set forth herein. In other embodiments, other means are used to determine the Doppler correction; and in various embodiments, any method known in the art for performing Doppler correction is used. In some embodiments, the error caused by the Doppler frequency shift is tolerable or negligible; and no Doppler correction is applied to the distance measurement.

[0070] 2. Overview of Chirp Detection

[0071] Figure 1D A set of curves showing an example optical chirp distance measurement according to an embodiment. The horizontal axis 102 is the same for all four curves and represents time in arbitrary units on the order of milliseconds (ms, 1 ms = 10 -3 seconds). Curve 100 represents the power of the light beam used to transmit the optical signal. The vertical axis 104 in curve 100 represents the power of the transmitted signal in arbitrary units. Trace 106 indicates that the power is on during a finite pulse duration τ starting from time 0. Curve 110 represents the frequency of the transmitted signal. The vertical axis 114 represents the transmitted frequency in arbitrary units. Trace 116 indicates that the frequency of the pulse increases from f1 to f2 over the duration τ of the pulse and thus has a bandwidth B = f2 - f1. The rate of change of the frequency is (f2 - f1) / τ.

[0072] The return signal is depicted in curve 160, which has a horizontal axis 102 representing time and a vertical axis 114 representing frequency, as in curve 110. The chirp 116 of curve 110 is also plotted as a dashed line on curve 160. The first return signal is given by trace 166a, which is simply the transmitted reference signal with reduced intensity (not shown) and delayed by ΔT. When the return signal is received from an external object after traveling a distance of 2R, where R is the distance to the target, the return signal starting at the delay time Δt is given by 2R / c, where c is the speed of light in the medium related by Equation 3 above (about 3 x 10 8 meters per second, m / s). During this time, the frequency has changed by an amount depending on the distance, called f R and is given by multiplying the rate of change of the frequency by the delay time. This is given by Equation 4a.

[0073] f R = (f2 - f1) / τ / 2R / c = 2BR / cτ (4a)

[0074] In a time-domain mixing operation called de-chirping, the value of f R is measured by the frequency difference between the transmitted signal 116 and the return signal 166a. Thus the distance R is given by Equation 4b.

[0075] R = f R cτ / 2B (4b)

[0076] Of course, if the return signal arrives after the pulse has been fully transmitted, i.e., if 2R / c is greater than τ, equations 4a and 4b are invalid. In this case, the reference signal can be delayed by a known or fixed amount to ensure that the return signal overlaps with the reference signal. The fixed or known delay time of the reference signal can be multiplied by the speed of light c to give an additional distance, which is added to the distance calculated by equation 4b. Although the absolute distance may deviate due to the uncertainty of the speed of light in the medium, this is an approximately constant error, and the relative distance based on the frequency difference is still very accurate.

[0077] In some cases, the point (pencil beam cross-section) illuminated by the transmitted light beam encounters two or more different scatterers at different distances, such as the front and back of a translucent object, or the nearer and farther parts of an object at different distances from the LIDAR, or two separate objects within the illuminated point. In this case, a second signal with a reduced intensity and a different delay will also be received, as shown by trace 166b on graph 160. This will have different measured values f R , which gives different distances by using equation 4b. In some cases, multiple additional return signals are received.

[0078] Graph 170 depicts the difference frequency f R . As in all other aligned graphs Figure 1D , the horizontal axis 102 represents time, and the vertical axis 164 represents the frequency difference on a very large expanded scale. Trace 176 depicts a constant frequency f R measured in response to the transmitted chirp, which represents a specific distance as given by equation 4b. The second return signal 166b (if present) will produce a different and larger f R value (not shown) during de-chirping; and thus a larger distance is produced by using equation 4b.

[0079] A common method for de-chirping is to direct both the reference optical signal and the return optical signal to the same optical detector. The electrical output of the detector can be controlled by a beat frequency equal to or otherwise depending on the frequency difference between the two signals converging on the detector. The Fourier transform of this electrical output signal will produce a peak at the beat frequency. This beat frequency is in the radio frequency (RF) range of megahertz (MHz, 1 MHz = 10 6 hertz = 10 6 cycles per second), rather than in the terahertz (THz, 1 THz = 10 12within the optical frequency range of (in Hz). Such signals can be easily processed by ordinary and inexpensive RF components, such as the fast Fourier transform (FFT) algorithm running on a microprocessor or a specially constructed FFT or other digital signal processing (DSP) integrated circuit. In other embodiments, the return signal can be mixed with a continuous wave (CW) tone (as opposed to a chirp as the local oscillator). This results in a detected signal that is itself a chirp (or whatever waveform is transmitted). In this case, as described in Kachelmyer 1990, the detected signal will be matched filtered in the digital domain, the entire content of which is incorporated herein by reference as if fully set forth herein, except for inconsistencies with the terms used herein. The disadvantage is that the bandwidth requirements of the digitizer are usually higher. The positive aspects of coherent detection are retained in other respects.

[0080] In some embodiments, the LIDAR system is modified to generate both up-chirps and down-chirps simultaneously. This method can eliminate the variability introduced by differences in object velocities, or changes in the LIDAR position relative to the object that actually do change the distance, or instantaneous scatterers in the beam, etc., or some combination thereof. This method can ensure that the Doppler shifts and distances measured on the up-chirps and down-chirps are actually the same and can be most usefully combined. The Doppler scheme can ensure the parallel acquisition in frequency space of return pairs with asymmetric frequency shifts for high-likelihood correct compensation.

[0081] Figure 1E is a graph using a symmetric LO signal according to an embodiment, and shows the return signal in this frequency-time plot as a dashed line when there is no Doppler shift. The horizontal axis represents an example time in units of 10 -5 seconds (tens of microseconds). The vertical axis represents the frequency of the optical emission signal relative to the carrier frequency f c or an example reference signal, e.g., in units of gigahertz (GHz, 1 GHz = 10 9 Hz). During the pulse duration, a beam including two optical frequencies at any time is generated. One frequency increases from f1 to f2 (e.g., 1 to 2 GHz above the optical carrier), while the other frequency simultaneously decreases from f4 to f3 (e.g., 1 to 2 GHz below the optical carrier). The two frequency bands (e.g., band 1 from f1 to f2 and band 2 from f3 to f4) do not overlap, such that both the transmitted and return signals can be optically separated by a high-pass or low-pass filter or some combination, where the passband starts at the pass frequency f P . For example, f1 < f2 < f P < f3 < f4. Although in the illustrated embodiment, the higher frequency can provide the up-chirp and the lower frequency can provide the down-chirp, in other embodiments, the higher frequency generates the down-chirp and the lower frequency generates the up-chirp.

[0082] In some embodiments, two different laser sources are used to generate two different optical frequencies in each beam at each time. However, in some embodiments, a single optical carrier is modulated by a single RF chirp to generate symmetric sidebands that serve as simultaneous up-chirps and down-chirps. In some of these embodiments, a double-sideband Mach-Zehnder intensity modulator is used, which typically does not leave much energy at the carrier frequency; rather, almost all of the energy goes into the sidebands.

[0083] Due to the sideband symmetry, if sidebands of the same order are used, the bandwidths of the two optical chirps can be the same. In other embodiments, other sidebands are used, for example, two second-order sidebands are used, or a first-order sideband and a non-overlapping second sideband are used, or some other combination.

[0084] As described in the published text WO 2018 / 160240, the invention name of which is "Methods and Systems for Doppler Detection and Doppler Correction for Optical Chirp Distance Detection", the entire content of which is incorporated herein by reference as if fully set forth herein, when selecting the transmit (TX) and local oscillator (LO) chirp waveforms, it is advantageous to ensure that the frequency shift bands of the system make maximum use of the available digitizer bandwidth. Generally, this can be achieved by shifting the up-chirp or the down-chirp to have a range frequency beat close to zero.

[0085] Figure 1F is similar to Figure 1E a graph of the use of a symmetric LO signal, and in this frequency-time plot, the return signal when there is a non-zero Doppler frequency shift is shown as a dashed line. For example, if the blue shift causing the range effect is f B , then the beat frequency of the up-chirp will increase by the offset and occur at f B + Δf S , and the beat frequency of the down-chirp will decrease by the offset to f B - Δf S . Thus, the up-chirp will be in a higher frequency band than the down-chirp, separating them. If Δf S is greater than any expected Doppler effect, the ranges associated with the up-chirp and the down-chirp will be unambiguous. Then, with a known Δf SThe correct symbol value is used to correct the measured beat frequency to obtain the correct up-chirp and down-chirp ranges. In the case of a chirped waveform, time-separated I / Q processing (also known as time-domain multiplexing) can be used to overcome the hardware requirements of other methods as above. In this case, an AOM can be used to eliminate range-Doppler ambiguity for real-valued signals. In some embodiments, a scoring system can be used to pair up the up-chirp and down-chirp returns, as described in more detail in the cited publications. In other embodiments, I / Q processing can be used to determine the sign of the Doppler chirp, as described in more detail above.

[0086] 3. Overview of Optical Detection Hardware

[0087] To describe how to use a high-resolution range-Doppler detection system, some general hardware methods are described. Figure 2A is a block diagram showing example components of a high-resolution range LIDAR system 200 according to an embodiment. Optical signals are represented by arrows. Electrical wired or wireless connections are represented by segmented lines without arrows. A laser source 212 emits a carrier 201, and the beam is phase or frequency modulated in a modulator 282a before or after a beam splitter 216 to produce a phase-encoded or chirped optical signal 203 having a duration D. The beam splitter 216 separates the modulated (or, as shown, unmodulated) optical signal for a reference path 220. A target beam 205 having most of the energy of the beam 201 can be produced, also referred to herein as the transmit signal. A modulated or unmodulated reference beam 207a can also be produced, which can have very little energy but is sufficient to produce a good mixing with the return light 291 scattered from an object (not shown). In the illustrated embodiment, the reference beam 207a is separately modulated in a modulator 282b. The reference beam 207a travels through the reference path 220 and is directed to one or more detectors as the reference beam 207b. In some embodiments, the reference path 220 introduces a known delay that is sufficient to cause the reference beam 207b to reach the detector array 230 together with the scattered light from an object outside the LIDAR within the range of distances of interest. In some embodiments, the reference beam 207b is referred to as a local oscillator (LO) signal, which refers to the old scheme where the reference beam 207b was locally generated from an additional oscillator. In various embodiments, in a scheme from less flexibility to more flexibility, the reference can be made to reach together with the scattered or reflected field by: 1) placing a mirror in the scene to reflect a portion of the transmit beam back to the detector array so that the path lengths are well matched; 2) using a fiber optic delay to closely match the path lengths and propagating the reference beam using optics near the detector array, as Figure 2Aas suggested, with or without path length adjustment to compensate for observed or expected phase or frequency differences for a particular distance; or, 3) using a frequency shift device (acousto-optic modulator) or time delay of a local oscillator waveform modulation (e.g., in modulator 282b) to generate additional modulation to compensate for path length mismatch; or some combination. In some embodiments, the object is close enough and the emission duration is long enough such that the return overlaps sufficiently with the reference signal without delay.

[0088] Then, the transmit signal is transmitted to illuminate the area of interest, typically through some scanning optics 218. The detector array can be a single paired or unpaired detector, or a one-dimensional (1D) or two-dimensional (2D) array of paired or unpaired detectors arranged in a plane generally perpendicular to the return beam 291 from the object. The reference beam 207b and the return beam 291 can be combined in zero or more optical mixers 284 to produce an optical signal with characteristics to be appropriately detected. The acquisition system 240 can record the frequency, phase, or amplitude, or some combination, of the interference pattern multiple times for each detector during the signal duration D. The number of time samples processed per signal duration or integration time can affect the down-range extent. The number or integration time is typically a practical consideration based on the number of symbols per signal, the signal repetition rate, and the available camera frame rate. The frame rate is the sampling bandwidth, often referred to as the "digitizer frequency". The only fundamental limitation on the distance range is the coherence length of the laser and the length of the chirp or unique phase code before its repetition (for unambiguous ranging). The reason for enabling this feature is that any digital record of the returned heterodyne signal or bits can be compared or cross-correlated with any portion of the transmitted bits from the previous transmit history.

[0089] The acquired data is available to a processing system 250, which is, for example, a computer system described below with reference to Figure 7 or a chipset described below with reference to Figure 8 According to one or more embodiments described below, the scanner control module 270 provides a scan signal to drive the scanning optics 218. In one embodiment, the scanner control module 270 can include instructions for performing the operations described below with reference to Figure 6One or more steps of method 600 described by the flowchart. A signed Doppler compensation module (not shown) in processing system 250 may determine the sign and magnitude of the Doppler shift and the correction range based thereon and any other corrections. Processing system 250 may also include a modulation signal module (not shown) to send one or more electrical signals for driving modulators 282a, 282b. In some embodiments, the processing system further includes a vehicle control module 272 to control the vehicle on which system 200 is mounted.

[0090] Any known device or system may be used to implement laser source 212, modulators 282a, 282b, beam splitter 216, reference path 220, optical mixer 284, detector array 230, scanning optics 218, or acquisition system 240. Optical coupling for diffusing or focusing on the target or focusing across the pupil plane is not depicted. As used herein, an optical coupler is any component used to affect the propagation of light within spatial coordinates to direct light from one component to another, such as vacuum, air, glass, crystal, mirror, lens, optical circulator, beam splitter, phase plate, polarizer, optical fiber, optical mixer, etc., individually or in some combination.

[0091] Figure 2AAlso shown are example components for a simultaneous up-chirp and down-chirp LIDAR system according to one embodiment. In this embodiment, modulator 282a can be a frequency shifter added to the optical path of transmit beam 205. In other embodiments, the frequency shifter is alternatively added to the optical path of return beam 291 or reference path 220. Generally, since the device used as a modulator (such as an acousto-optic modulator AOM) has some associated losses, and it is disadvantageous to place a loss component on the receiving side or after an optical amplifier, a frequency shift element can be added as modulator 282b on the local oscillator (LO, also referred to as the reference path) side or on the transmit side (before the optical amplifier). The purpose of the optical frequency shifter is to shift the frequency of the transmit signal (or return signal) by a known amount Δfs relative to the frequency of the reference signal, such that the beat frequencies of the up-chirp and down-chirp occur in different frequency bands, and the beat frequencies can be picked up, for example, by an FFT component in processing system 250 in the analysis of the electrical signal output by optical detector 230. In some embodiments, the RF signal coming out of the balanced detector is directly digitized, where the frequency bands are separated via an FFT. In some embodiments, the RF signal coming out of the balanced detector is preprocessed with analog RF electronics to separate the low frequency band (corresponding to one of the up-chirp or down-chirp) and the high frequency band (corresponding to the opposite chirp), the low frequency band can be directly digitized, and the high frequency band can be electronically downmixed to baseband and then digitized. Both embodiments provide a path to match the frequency bands of the detected signal with the available digitizer resources. In some embodiments, modulator 282a is excluded (such as in a direct ranging embodiment).

[0092] Figure 2B is a block diagram showing a simple sawtooth scan pattern used in some prior art embodiments for a high-resolution Doppler system. The scan sweeps through a range of azimuth (horizontally) and tilt angle (vertically above and below the horizontal direction at zero tilt). In the various embodiments described below, other scan patterns are used. Any scan pattern known in the art can be used in the various embodiments. For example, in some embodiments, the methods described in World Intellectual Property Organization published texts WO2018 / 125438 and WO 2018 / 102188 are used to perform an adaptive scan, the entire content of each of which is incorporated herein by reference as if fully set forth herein.

[0093] Figure 2C is an image showing an example velocity point cloud generated by a high-resolution Doppler LIDAR system according to an embodiment. Each pixel in the image represents a point in the point cloud, and the point represents the distance or intensity or relative velocity or some combination thereof at the tilt angle and azimuth associated with that pixel.

[0094] Figure 2DFIG. 0 is a block diagram of an example component for illustrating a high-resolution LIDAR system 200'. In one embodiment, system 200' may be similar to system 200, except for the features discussed herein. In one embodiment, system 200' may be a coherent LIDAR system constructed with a monostatic transceiver. System 200' may include a source 212 that transmits a carrier 201 along a single-mode optical waveguide 225 on a transmission path 222, through a circulator 226 and out of the tip 217 of the single-mode optical waveguide 225 located in the focal plane of a collimating optical device 229. In one embodiment, the tip 217 may be positioned within a threshold distance (e.g., approximately 100 μm) of the focal plane of the collimating optical device 229 or within a range from approximately 0.1% to approximately 0.5% of the focal length of the collimating optical device 229. In another embodiment, the collimating optical device 229 may include one or more of a doublet lens, an aspheric, or a multi-element design. In one embodiment, the carrier 201 exiting the optical waveguide tip 217 may be shaped by the optical device 229 into a collimated target beam 205' that is scanned by a scanning optical device 218 within an angular range 227. In some embodiments, the carrier 201 is phase or frequency modulated in a modulator 282a located upstream of the collimating optical device 229. In other embodiments, the modulator 282 is not included. In one embodiment, a return beam 291 from an object may be directed by the scanning optical device 218 and focused by the collimating optical device 229 onto the tip 217 such that the return beam 291 is received in the single-mode optical waveguide tip 217. In one embodiment, the circulator 226 may then redirect the return beam 291 along a reception path 224 into the single-mode optical waveguide and back to an optical mixer 284 where the return beam 291 is combined with a reference beam 207b that is directed through the single-mode optical waveguide along a local oscillator path 220. In one embodiment, system 200' may operate on the principle that the maximum spatial mode overlap between the return beam 291 and the reference signal 207b will maximize the heterodyne mixing (optical interference) efficiency between the return signal 291 and the local oscillator 207b. This monostatic arrangement is advantageous because it can help avoid the challenging alignment process associated with a bistatic LIDAR system.

[0095] Figure 2E FIG. 4 is a side view block diagram of an example component for illustrating a bistatic LIDAR system 200". Figure 2F FIG. 6 is according to an embodiment for illustrating Figure 2E a top view block diagram of an example component of a bistatic LIDAR system 200". In one embodiment, the bistatic system 200" is similar to Figure 2D system 200' in FIG. 0 and includes the features discussed herein.

[0096] In one embodiment, system 200” includes a bistatic transceiver 215 that includes a transmission waveguide 223 and one or more receiving waveguides 225a, 225b. The first receiving waveguide 225a is separated from the transmission waveguide 223 by a separation 221a. This separation of the receiving waveguide from the transmission waveguide is referred to as a transmit-receive arrangement because light is emitted (projected) at one location and received (captured) at a different location. The second receiving waveguide 225b is separated from the transmission waveguide 223 by a separation 221b that is greater than the separation 221a. Although Figure 2F two receiving waveguides 225a, 225b are shown, the system is not limited to two receiving waveguides and may include one or more than two receiving waveguides. In an example embodiment, the bistatic transceiver 215 is supported by an on-chip waveguide technology such as a planar lightwave circuit, which allows for the fabrication of closely spaced waveguides to be used as the bistatic transceiver apertures. In an example embodiment, the bistatic transceiver 215 is characterized by planar lightwave circuit technology developed by a company in San Jose, California In another example embodiment, the bistatic transceiver 215 is customized with minimal modification to the standard manufacturing process for planar lightwave circuit technology. In yet another example embodiment, the bistatic transceiver 215 is manufactured by PLC in Columbus, Ohio

[0097] In one embodiment, in system 200”, a source 212 transmits a carrier as a light beam 201 along the transmission waveguide 223 on a transmission path 222 to a tip 217 of the transmission waveguide 223. In one embodiment, system 200” does not include a circulator 226, which advantageously reduces the cost and complexity of system 200”. The carrier 201 exiting the tip 217 of the transmission waveguide 223 is shaped by collimating optics 229 into a collimated target beam 205’ as in system 200’.

[0098] In one embodiment, the scanning optical device 218 is a polygon scanner 244 that has a plurality of mirrors or facets 245a, 245b and is configured to rotate about a rotation axis 243 at an angular velocity 249. In one embodiment, the polygon scanner 244 is configured to rotate about the rotation axis 243 at a constant speed. In an example embodiment, the polygon scanner 244 has one or more of the following characteristics: by ​Sensors are manufactured with a Copal rotating mirror having an inscribed diameter of about 2 inches or in the range of about 1 inch to about 3 inches, each mirror being about 0.5 inches high or in the range of about 0.25 inches to about 0.75 inches, having a total height of about 2.5 inches or in the range of about 2 inches to about 3 inches, powered by a three-phase brushless DC (BLDC) motor with encoder pole pair switching, having a rotational speed in the range of about 1000 revolutions per minute (rpm) to about 5000 rpm, having a reduction ratio of about 5:1, and being at a distance of about 1.5 inches or in the range of about 1 inch to about 2 inches from the collimator 231. In other embodiments, the scanning optical device 218 of the system 200” is any optical device other than the polygon scanner 244.

[0099] In one embodiment, the collimated target beam 205’ is reflected from one of the polygon faces 245 into a scanned beam 205”, and as the polygon scanner 244 rotates at an angular velocity 249, it scans through an angular range 227. In one embodiment, the bistatic transceiver 215 including the transmit waveguide 223 and the receive waveguide 225 is arranged in a first plane (e.g., Figure 2F the plane), and the polygon scanner 244 adjusts the direction of the beam 205” over the angular range 227 in the same first plane (or in a plane parallel to the first plane). In another embodiment, the first plane is orthogonal to the axis of rotation 243. For the purposes of this specification, “parallel” means within ±10 degrees, and “orthogonal” means within 90 ± 10 degrees.

[0100] In one embodiment, the beam 205” is backscattered by a target within a certain range, and after a slight movement of the surface indicated by the dashed contour, the returned beam 291’ is reflected by one of the faces 245 to the collimating optics 229, which focuses the returned beam 291’ to an offset position at the tip 217 of the receive waveguide 225a or 225b, and the receive waveguide 225a or 225b etc. (if any) are collectively referred to as the receive waveguide 225 hereinafter. In various embodiments, the offset generated by the rotating polygon is utilized to separate the separation between the transmit and receive waveguides to improve the signal-to-noise ratio (SNR) of the system 200”.

[0101] As Figure 2FAs shown, during the round-trip time to the target, for example, between the time when the light beam 205” is reflected from the surface 245a to the target and the time when the return light beam 291’ is reflected by the surface 245a to the optical device 229, the polygon scanner 244 rotates from a first orientation (e.g., solid line) to a second orientation (e.g., dashed line). In one embodiment, the rotation of the surface 245a between these times takes into account the deflection angle 228 of the return light beam 291’ by the surface 245a relative to the incident light beam 205’. In one embodiment, the target distance (e.g., based on the round-trip time) and / or the rotation speed of the polygon scanner 244 and / or the diameter of the image 418 ( Figure 4E ) of the return light beam 291’ on the bistatic transceiver 215 determine the angle 228, and thus determine the separation 221a, and the separation 221a is selected to position the receiving waveguide 225a relative to the transmission waveguide 223 such that the return light beam 291’ is focused in the tip of the receiving waveguide 225a. In one embodiment, Equation 5 expresses the relationship between the separation 221, the rotation speed of the polygon scanner 244, and the target distance:

[0102]

[0103] where y is the separation 221, the focal length is the focal length of the collimating optical device 229 (in meters); the rotation rate is the rotation speed of the polygon scanner 244 (in radians per second), c is the speed of light (in meters per second), and the distance is the target distance (in meters).

[0104] In one embodiment, the values of one or more parameters of the system 200” are selected during the design phase of the system 200” to optimize the signal-to-noise ratio (SNR) of the return light beam 291’. In one embodiment, the values of these parameters include the value of the rotation speed of the polygon scanner 244 selected based on the target design distance within the angular range 227 to optimize the SNR. Figure 4G is according to an embodiment for showing for Figure 2EGraph of examples of SNR at various scan rates in the system 200” versus target distance. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 404 is the SNR in decibels (dB). The first trace 440d depicts the SNR of the focused return beam 291’ on the tip 217 of the receiving waveguide 225 based on the target distance where the beam is not scanned. The second trace 440b depicts the SNR of the focused return beam 291’ on the tip 217 of the receiving waveguide 225 based on the target distance where the beam is scanned at a slow scan rate (e.g., approximately 2500 degrees per second). The third trace 440c depicts the SNR of the focused return beam 291’ on the tip 217 of the receiving waveguide 225 based on the target distance where the beam is scanned at an optimized scan rate (e.g., approximately 5500 degrees / second). An SNR threshold 442 (e.g., about 10 dB) is also depicted. Thus, when designing the system 200”, the user first determines the target design distance over an angular range (e.g., 0 m - 150 m), and then uses Figure 4G to quickly determine which of the traces 440b, 440c, 440d maintains an SNR above the SNR threshold 442 at that target design distance. In this example embodiment, the trace 440c maintains an SNR above the SNR threshold 442 within the target design distance (e.g., 0 m - 150 m), so the user selects the optimized scan speed (e.g., approximately 5500 degrees / second) associated with the trace 440c when designing the system 200”. Thus, based on this optimized scan speed, the polygon scanner 244 is set to have a fixed rotational speed. Thus, the traces 440 advantageously provide the user with an effective way to design the system 200”, particularly when selecting the fixed scan speed of the polygon scanner 244. In one embodiment, each trace 440 is generated by using the system 200” and measuring the SNR of the return beam 291’ at each scan speed of the polygon scanner associated with each trace 440. The traces 440 are not limited to Figure 4G those described in

[0105] and include any SNR trajectory generated by using a similar process. Figure 4K is a diagram showing at a low fixed scan rate (e.g., 4000 degrees per second) in accordance with an embodiment Figure 2E221 values ​​for the system 200. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 404 is the SNR in decibels (dB). The first trace 464a depicts the SNR of the focused return beam 291' at the tip 217 of the receive waveguide 225 based on the target distance for a separation 221 of 4w0, where w0 is the diameter of the transmission waveguide 223. The second trace 464b depicts the SNR of the focused return beam 291' at the tip 217 of the receive waveguide 225 based on the target distance for a separation 221 of 0 (e.g., 0w0). 91'. Each trace 464 between the first trace 464a and the second trace 464b represents a 0.25w0 decrement in the separation 221 value. In one embodiment, for a target design distance (e.g., 0m-250m), trace 464c is selected because it has an SNR value above the SNR threshold 442 at the target design distance. The separation 221 value associated with trace 464c is 0.25w0, so when designing a system 200" with a target design distance (e.g., 0m-250m) and a low fixed scan speed (e.g., 4000 degrees / second), the separation 221 is set to 0.25w0. Figure 4L 4 is a graph depicting multiple SNR traces 466 for a system 200" having a low fixed scan speed (e.g., 4000 degrees / second). For a particular design target distance along horizontal axis 402 (e.g., 250m), SNR trace 466 conveys the values ​​of separation 221 (along vertical axis 409) that are capable of maintaining the SNR level associated with trace 466. In the example embodiment, for a design target distance of 250 meters, trace 466a indicates that an SNR of 18dB can be maintained at multiple values ​​of separation 221 (e.g., approximately 0.25w0 and approximately 2.75w0), and thus gives the user different options when designing system 200". In addition Figure 4K In addition, trace 466 provides a quick lookup tool for the user when designing system 200" based on a known design target distance and a fixed scan speed. In one embodiment, Figure 4K Like the trace 464 of FIG. 2 , the trace 466 is generated using the system 200 ″ by measuring the SNR of the return beam 291 ′ at multiple separation 221 values ​​at multiple target distance values. In addition, the trace 466 is not limited to Figure 4L those depicted in ; rather, they can be simulated or measured by using other device parameters.

[0106] Figure 4M is similar to Figure 4K, but for a high fixed scan speed (e.g., 12,000 degrees / second). The first trace 465a is similar to the first trace 464a and is used for a separation 221 of 4w0. The second trace 465b is similar to the second trace 464b and is used for a separation 221 of 0 (e.g., 0w0). Using the same target design distance (e.g., 0m-250m), trace 465c is selected because it has an SNR value above the SNR threshold 442 at the target design distance. The separation 221 value associated with trace 465c is 2.75w0, so if the polygon scanner 244 is operating at a high fixed scan speed (e.g., 12,000 degrees / second), the separation 221 in system 200" is set to 2.75w0. Therefore, when designing system 200", the user can first determine the target design distance over the angular range (e.g., 0m-250m) and then use Figure 4M to quickly determine which of the traces 465 maintains an SNR above the SNR threshold 442 at the target design distance and fixed scan speed of the polygon scanner 244. The traces can be used to design hardware to provide the desired separation 221 between the transmit waveguide 223 and the receive waveguide 225.

[0107] Figure 4N 4 is a graph depicting a plurality of SNR traces 467 for a system 200" having a high fixed sweep speed (e.g., 12,000 degrees / second). For a particular design target distance (e.g., 100 meters) along horizontal axis 402, SNR trace 467 conveys values ​​of separation 221 (along vertical axis 409) that are capable of maintaining the SNR level associated with trace 467. In the example embodiment, for a design target distance of 100 meters, trace 467a indicates that an SNR of 28 dB can be maintained at a plurality of values ​​of separation 221 (e.g., approximately 0.75w0 and approximately 2.25w0). In addition to Figure 4M In addition, trace 467 provides a quick search tool for the user when designing system 200" based on a known design target distance and a fixed scanning speed. In one embodiment, as shown in FIG. Figure 4M The trace 465 of FIG. 4 is generated by using the system 200″ to measure the SNR of the return beam 291′ at multiple separation 221 values ​​at multiple target distance values. In addition, the trace 467 is not limited to Figure 4N Those depicted in .

[0108] Figure 4O is a graph according to an embodiment, which shows Figure 2EExamples of the intervals for various target distance values with a minimum SNR threshold in the system, relative to the scan speed. The horizontal axis 403 is the scan speed in thousands of degrees per second. The vertical axis 409 is the separation 221 in units of w0 (e.g., the fiber mode radius). At a particular scan speed along the horizontal axis 403, the trace 469 provides the value of the separation 221 to maintain the SNR threshold 442 (e.g., 10 dB) at the design target distance value associated with the trace 469. In one example embodiment, for a scan speed of 12,000 degrees per second, the trace 469a indicates a separation 221 value of approximately 2.75w0 to maintain the SNR threshold 442 at a design target distance of 250 meters. This is consistent with Figure 4M the example embodiment of the trace 465c. Additionally, in an example embodiment, for a scan speed of 4,000 degrees per second, the trace 469a indicates a separation 221 value of approximately 0.25w0 to maintain the SNR threshold 442 for a design target distance of 250 meters. This is consistent with Figure 4K the example embodiment of the trace 464c. Thus, Figure 4O provides additional useful look-up curves during the design and manufacture of the system 200”.

[0109] In one embodiment, the receiving waveguide 225a has a separation 221a that is approximately 2 - 5 times the diameter w0 of the transmitting waveguide 223 and is used to receive the return beam 291' from a target located at a greater distance (e.g., greater than approximately 50 meters). For a target located at a greater distance, the round-trip time is longer, and the degree of rotation of the face 245a is greater than that shown in Figure 2F , so the return beam 291' is deflected through a greater angle 228 to the collimating optics 229. However, for a target located at a greater distance, the diameter of the image 418 ( Figure 4E ) of the return beam 291' on the bistatic transceiver 215 is smaller, so the separation 221a is smaller in magnitude and distance (e.g., increased precision) to ensure that the image 418 is shifted by the appropriate separation 221a into the receiving waveguide 225a. In one embodiment, the separation 221 is based on the ratio of the diameter of the image 418 (e.g., less than one).

[0110] In one embodiment, the receiving waveguide 225B has a separation 221B that is approximately 5 - 10 times the diameter w0 of the transmitting waveguide 223 and is used to receive the return beam 291' from a target located at a smaller distance (e.g., less than approximately 50 meters). For a target located at a smaller distance, the round-trip time is shorter, and the degree of rotation of the face 245a is less than that shown in Figure 2F , so the return beam 291' is deflected through a smaller angle 228 to the collimating optics 229. However, for a target located at a smaller distance, the diameter of the image 418 (Figure 4E ) has a larger diameter, so the separation 221b is larger in amplitude and distance (e.g., reduced precision) because the tolerance for whether the larger image 418 is offset by a specific amount is wider to achieve a minimum SNR in the receiving waveguide 225b.

[0111] Thus, in one embodiment, when the beam 205” is scanned at a fixed rotational speed over the angular range 227, the receiving waveguides 225a, 225b can be used to receive the return beam 291’ from targets at different distances. In an exemplary embodiment, waveguide 225A receives the return beam 291’ from a target at a longer distance located on the first portion of the angular range 227, and waveguide 225B receives the return beam 291’ from a target at a shorter distance located on the second portion of the angular range 227. However, in other embodiments, when the beam 205” is scanned over the angular range 227 (e.g., from about 0 meters to about 250 meters), only one receiving waveguide 225a or 225b is used to receive the return beam 291’ from a target within a value of the target distance or within a range of values of the target distance.

[0112] In one embodiment, the system 200” does not include the circulator 226 because the return is not on the same path as the transmitted beam; thus the receiving waveguide 225a is disposed along the offset receiving path 224 and is connected to the optical mixer 284. The reference beam 207b is transmitted in the waveguide along the LO path 220 such that the reference beam 207b is combined with the return beam 291’ from the receiving waveguide 225a in the optical mixer 284. In an embodiment where multiple receiving waveguides 225a, 225b are provided that are tuned for multiple different distances, a similar arrangement is provided for the receiving waveguide 225b such that the receiving waveguide 225b is provided along the receiving path 224 and is connected to a corresponding optical mixer 284, where the corresponding reference beam 207b is combined with the return beam 291’ from the receiving waveguide 225b. In one embodiment, where one of the receiving waveguides 225a is located in the bistatic transceiver 215, only one processing channel (e.g., one receiving waveguide, one optical mixer, one waveguide along the LO path) is provided. In another embodiment where multiple receiving waveguides 225a, 225b are provided, multiple processing channels are provided. Thus, the system 200” includes a number of processing channels equal to the number of receiving waveguides 225.

[0113] In one embodiment, acquisition system 240 and / or processing system 250 are configured to process return beam 291’ from receiving waveguide 225 over successive time periods (e.g., process return beam 291’ from receiving waveguide 225a over a first time period and process return beam 291’ from receiving waveguide 225b over a second time period) because return beam 291’ is successively received from receiving waveguides 225a, 225b over non-overlapping time periods.

[0114] 4. Coherent LIDAR System Parameters

[0115] In one embodiment, the monostatic coherent LIDAR performance of system 200’ is modeled by including system parameters in a so-called “link budget”. The link budget estimates the expected value of the signal-to-noise ratio (SNR) for various system and target parameters. In one embodiment, on the system side, the link budget may include one or more of output optical power, integration time, detector characteristics, insertion loss in waveguide connections, mode overlap between the imaged spot and the monostatic collection waveguide, and optical transceiver characteristics. In another embodiment, on the target side, the link budget may include one or more of atmospheric characteristics, target reflectivity, and target range.

[0116] Figure 4A is a plot showing Figure 2D the example signal-to-noise ratio (SNR) of return beam 291 in system 200’ according to an embodiment relative to target range without scanning. In other embodiments, Figure 4A describes Figure 2A an example of the SNR of return beam 291 in system 200 relative to target range. The horizontal axis 402 is the target range in meters (m). The vertical axis 404 is the SNR in decibels (dB). Trace 410 depicts the value of the SNR relative to the range divided into a near field 406 and a far field 408, where there is a transition from the near field 406 of trace 410 with a relatively flat slope to the far field 408 of trace 410 with a negative slope (e.g., approximately -20 dB / 10 m). The reduction in SNR in the far field 408 is dominated by the “r squared” loss because the scattered air through which return beam 291 passes grows with the square of the distance to the target, while the surface area of the optical waveguide tip 217 used to collect return beam 291 is fixed. Figure 4B is a plot according to an embodiment for showing an example of trace 411 that represents the 1 / r squared loss driving the shape of SNR trace 410 in the far field 408. The horizontal axis 402 is the range in meters (m), and the vertical axis 407 is the unitless power loss.

[0117] In the near field 406, the main driver of the SNR is the diameter of the collimated return beam 291 before it is focused onto the tip 217 by the collimating optics 229. Figure 4C is a graph showing an example of the collimated beam diameter of the return beam 291 in the system 200' without scanning according to an embodiment Figure 2D versus range. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 405 is the diameter of the return beam 291 in meters (m). In one embodiment, the trace 414 depicts the diameter of the collimated return beam 291 incident on the collimating optics 229 before the return beam 291 is focused onto the tip 217 of the optical waveguide. The trace 414 shows that the diameter of the collimated return beam 291 incident on the collimating optics 229 increases as the target distance increases.

[0118] In one embodiment, in the near field 406, as the diameter of the collimated return beam 291 increases at greater target distances, the diameter of the return beam 291 focused by the collimating optics 229 at the tip 217 decreases. Figure 4D is a graph according to an embodiment showing an example of the SNR related to the collection efficiency of the return beam 291 at the tip 217 in the system Figure 2D without scanning versus the distance of the transmitted signal. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 404 is the SNR in decibels (dB). The trace 416 depicts the near field SNR of the return beam 291 focused by the collimating optics 229 at the tip 217 based on the target distance. At close distances within the near field 406, the image 418a of the return beam 291 focused by the collimating optics 229 at the tip 217 is sufficiently larger than the core size of the single-mode fiber tip 217. Therefore, the SNR related to the collection efficiency is relatively low. At longer distances within the near field 406, the image 418b of the return beam 291 focused by the collimating optics 229 at the tip 217 is much smaller than the image 418a, and thus the SNR attributable to the collection efficiency increases at longer distances. In one embodiment, the trace 416 shows that, based on the improved collection efficiency of the focused return beam 291 at longer distances, the SNR in the near field 406 has a positive slope (e.g., +20 dB per 10 m). In one embodiment, this positive slope in the near field SNR cancels out Figure 4B the negative slope in the near field SNR discussed in Figure 4D which can be attributed to "r squared" losses, and thus results in a relatively flat region of the SNR trace 410 in the near field 406. Figure 4BThe "r squared" loss dominates the far - field 408 SNR, as shown in the SNR trace 410 in the far - field 408.

[0119] Although the discussion regarding Figure 4A - 4D predicted the SNR of the return beam 291 based on the target distance, the predicted SNR in Figure 4A - 4D was for the monostatic coherent LIDAR system 200' and did not fully characterize the performance of the scanning monostatic coherent LIDAR system 200' because it did not account for the scan rate of the scanning optics 218 or the offset of the return beam described in Figure 2E . The following Figure 4E - 4G is discussed in the context of the bistatic coherent LIDAR system 200", where the beam 205" is scanned at a scan rate greater than zero. In one embodiment, due to the round - trip delay of the return beam 291', when the beam is being scanned by the scanning optics 218 (e.g., polygon scanner 244), the reception pattern of the return beam 291' will be laterally offset or "walk - off" from the transmission waveguide of the transmission beam 205'. In one embodiment, if the lateral offset or "walk - off" corresponds to or is within the threshold of the separation 221a, the return beam 291' is deflected at an angle 228 with respect to the transmission beam 205', and the collimation optics 229 focuses the return beam 291' into the tip 217 of the receiving waveguide 225a. In one embodiment, the threshold is the maximum ratio (e.g., a ratio less than 1) of the diameter of the image of the return beam 291' on the tip 217 of the receiving waveguide 225. In one embodiment, advantageously, the walk - off causes the overlap of the image 418 of the return beam 291' with the receiving waveguide 225 to result in optimized collection efficiency, e.g., the walk - off causes the center of the image 418 to be within ±10% of the tip 217 of the receiving waveguide 225.

[0120] Figure 4E Illustrates an example of beam walk - off for various target distances and scan speeds in the system 200" according to an embodiment. The horizontal axis 402 is the target distance, and the vertical axis 422 is the scan speed of the beam using the scanning optics 218. As Figure 2E Figure 4EAs shown, when the beam is not scanned (bottom row), no beam walks off because the image 418a of the focused return beam 291' is centered on the tip 217 of the transmission waveguide 223, indicating that no beam walks off at short target distances, and the image 418b of the focused return beam 291' is also centered on the tip 217 of the transmission waveguide 223, indicating that no beam walks off at long target distances. In one embodiment, since the beam 291' is not centered on or near the tip 217 of the receiving waveguide 225 and / or there is little or no beam walk-off, and thus the beam walk-off is not within the threshold of the separation 221 between the transmission waveguide 223 and the receiving waveguide 225. Therefore, this is not an optimized arrangement of the bistatic transceiver system 200". As Figure 4E shown, the diameter of the image 418a is greater than the separation 221, so the image 418a of the return beam 291' partially overlaps with the tip 217 of the receiving waveguide 225. Thus, some portions of the return beam 291' are received by the tip 217 of the receiving waveguide 225 at short target distances, and thus the signal-to-noise ratio (SNR) is greater than zero, even when the beam 205" is not scanned. Additionally, as Figure 4E shown, the diameter of the image 418b is less than or approximately equal to the separation 221, so the image 418b of the return beam 291' may not overlap with the tip 217 of the receiving waveguide 225 for longer target distances. As a result, when the beam 205" is not scanned, little or no return beam 291' is received at the tip of the receiving waveguide 225 at long target distances.

[0121] When the beam 205" is scanned at a medium scan speed ( Figure 4Ein the middle row), for small target distances, a medium beam walk-off 419a was observed between the image 418a of the focused return beam 291' and the tip 217 of the transmission waveguide 223, while for large target distances, a larger beam walk-off 419b was observed between the image 418b of the focused return beam 291' and the tip 217 of the transmission waveguide 223. Although the beam walk-off 419b for larger target distances is greater than the beam walk-off 419a for smaller target distances, due to the much larger diameter of the image 418a on the receiving waveguide 225, the return beam 291' has a higher SNR at smaller target distances. Since the ratio of the walk-off 419b to the diameter of the image 418b is less than one, this is not an optimized arrangement for the bistatic transceiver system 200" for large target distances. However, in some embodiments, the separation 221 is selected based on the walk-off 419a such that the receiving waveguide 225a is configured to receive the return beam 291' at short distances when the polygon scanner 244 rotates at a medium scan speed, because the increased diameter of the image 418a for short target distances may result in an SNR of the return beam 291' greater than the SNR threshold, despite the small walk-off 419a.

[0122] When the beam 205" is scanned at a high scan speed ([ Figure 4E in the top row), the beam walk-off 421a observed at short distances exceeds the beam walk-off 419a at medium scan speeds, and the beam walk-off 421b observed at large distances exceeds the beam walk-off 419b at medium scan speeds. Thus, the beam walk-off increases with increasing target distance and scan speed. In one embodiment, the increasing target distance causes a time delay during which the images 418a, 418b are offset from the tip 217 of the transmission waveguide 223. Thus, the model of mode overlap appropriately accounts for this walk-off. In one embodiment, such a model should limit the beam walk-offs 419, 421 based on the diameter of the image 418 (e.g., not greater than half of the diameter of the image 418), and thus there is a wider tolerance for the acceptable range of the beam walk-offs 419, 421 for the target 418a at smaller target distances. In one embodiment, the spacing 221b is adjusted based on the beam walk-off 421a and the spacing 221a is adjusted based on the beam walk-off 421b such that the polygon scanner 244 can be set at a fixed optimized scan speed and the return beam 291' from a target at a shorter distance is deflected into the receiving waveguide 225b while the return beam 291' from a target at a longer distance is deflected into the receiving waveguide 225a. In this exemplary embodiment, the beam walk-off 421a is within the threshold of the spacing 221a and the beam walk-off 421b is within the threshold of the spacing 221b.

[0123] Figure 4F is shown in accordance with an embodiment inFigure 2E Graph of the coupling efficiency at various scan rates in the system 200” versus the target distance, for example. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 430 is the coupling efficiency in dimensionless units. In one embodiment, the coupling efficiency is inversely proportional to the difference between the separation 221 and the beam walk-off 419, 421 and / or the diameter of the image 418 (e.g., for a larger diameter, the tolerance for the difference between the separation 221 and the beam walk-off 419, 421 is wider, and for a smaller diameter, the tolerance in the difference is narrower). The first trace 432a depicts the coupling efficiency of the focused return beam 291 into the fiber tip 217 in the monostatic system 200’ for various target distances based on scanning without the beam 205’. The coupling efficiency remains relatively high and constant over a wide range of target distances. The second trace 432c describes the coupling efficiency of the focused return beam 291’ into the tip 217 of the receiving waveguide 225 for various target distances based on a medium scan rate of the beam. In one embodiment, the coupling efficiency at the medium scan rate peaks at a high target distance (e.g., about 450 m), and then decreases for target distances above and below this high target distance. The third trace 432b depicts the coupling efficiency of the focused return beam 291’ into the tip 217 of the receiving waveguide 225 for various target distances based on a high scan rate of the beam. In one embodiment, the coupling efficiency at the high scan rate peaks at a medium target distance (e.g., about 180 m), and then decreases as the target distance increases. The fourth trace 432d depicts the coupling efficiency of the focused return beam 291’ into the tip 217 of the receiving waveguide 225 for various target distances based on scanning without the beam. Since scanning without the beam causes the return beam 29 to be centered on the transmitting waveguide 223 ( Figure 4E bottom row), the coupling efficiency is approximately 0 over the entire target distance. Therefore, for the bistatic LADAR system 200”, scanning without the beam 205” is not a favorable operating mode.

[0124] Based on Figure 4F the traces in, scanning without results in little or no coupling efficiency into the receiving waveguide 225 and is therefore not optimized for the bistatic LIDAR system 200”. Also, scanning too slowly makes it impossible to see over a wide range of target distances (e.g., < 300 m). In this case, the beam walk-off 419b of the image 418b of the focused return beam 291’ approaches the separation 221 only at very large target distances (e.g., greater than 300 m). Therefore, operating the bistatic LIDAR system 200” at a slow scan speed is not optimized, at least for acquiring data of the return beam 291’ for targets with distances shorter than this very large distance (e.g., for targets with distances < 300 m). Figure 4FIt is also depicted that scanning at an optimized speed (e.g., trace 432b) enables targets located at wide target distances (e.g., from about 100 m to about 300 m) to be seen. This is based on the beam walk-off 421b being within the threshold of the separator 221. In an example embodiment, the medium scanning speed is in the range from about 1000 degrees per second to about 2000 degrees per second, while the optimized scanning speed is in the range from about 4000 degrees per second to about 7000 degrees per second.

[0125] Figure 4G is a graph showing an example of the SNR versus target distance for various scan rates in the system 200” according to an embodiment. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 404 is the SNR in decibels (dB). The first trace 440d depicts the SNR of the focused return beam 291' on the tip 217 of the receiving waveguide 225 based on the target distance without scanning the beam. Although there is no beam walk-off when the beam is not scanned, the image 418a of the focused return beam 291' partially overlaps with the tip 217 of the receiving waveguide 225 ( Figure 2E the bottom row), so the SNR is greater than zero, and since the diameter of the image 418a is relatively large, the SNR can be greater than the SNR threshold 442. Additionally, when the beam is not scanned for large target distances ( Figure 4E the bottom row), the diameter of the image 418b of the focused return beam 291' is much smaller compared to smaller target distances and cannot overlap with the tip 217 of the receiving waveguide 225. Therefore, beyond a certain target distance (e.g., about 90 m), the SNR of the trace 440d approaches zero. Figure 4E the bottom row)

[0126] The second trace 440b depicts the SNR of the focused return beam 291' on the tip 217 of the receiving waveguide 225 based on the target distance, where the beam is scanned at a slow scan rate. In an example embodiment, the slow scan rate is approximately 2500 degrees per second (deg / sec) or in the range of approximately 1000 deg / sec to approximately 4000 deg / sec or in the range of approximately 500 deg / sec to approximately 5000 deg / sec. The third trace 440c depicts the SNR of the focused return beam 291' on the tip 217 of the receiving waveguide 225 based on the target distance, where the beam is scanned at an optimized scan rate. In an example embodiment, the optimized scan rate is approximately 5500 deg / sec, or in the range of approximately 4000 deg / sec to approximately 7000 deg / sec, or in the range of approximately 3000 deg / sec to approximately 8000 deg / sec. In one embodiment, the slow scan rate and the optimized scan rate are based on one or more parameters of the system 200", including the beam size and / or the separation 221 and / or the target of the system 200". In an example embodiment, the numerical ranges of the above slow scan rate and optimized scan rate are based on a collimated beam having a diameter of approximately 1 centimeter (cm), which is used to scan an image to a maximum target distance of approximately 400 meters (m).

[0127] Finally, the difference between the beam walk-off 419, 421 and the separation 221 is a significant suppression of the SNR in the coherent bistatic LIDAR system 200", and / or the diameter indication difference tolerance or precision of the image 418 for a particular target distance to achieve a threshold SNR. In one embodiment, the scan rate of the beam in the bistatic system 200" is set to a fixed scan rate (e.g., the fixed speed of the angular velocity 249 of the polygon scanner 244) over the angular range and the resulting target distances, where the fixed scan rate is selected such that the associated SNR of the fixed scan rate is above the SNR threshold over the target distances. In a conventional coherent LIDAR system, this results in using a relatively low fixed scan rate to scan the beam over the scan trajectory 460, which results in large gaps 462 between adjacent scans, as Figure 4H shown. The scan speed limitation results in dense sampling along the beam trajectory 460. When the beam is scanned over several reasonably large fields (e.g., 10 degrees in either dimension), the beam trajectory 460 leaves large gaps 462 in the angular coverage. This is not ideal because targets located in the large gaps 462 cannot be detected. A "square grid" of rectangular sampling is not achieved. Instead, an asymmetry is observed between the sampling along the scan trajectory 460 and the gaps 462 between the trajectories 460, which can be greater than 10:1. Considering this problem, several complementary solutions are proposed here, including maximizing the fixed beam scan speed and generating one or more effective hardware solutions (e.g., the polygon scanner 244) for these concepts.

[0128] In addition to the scan rate of the light beam, the SNR of the return beam 291’ is also affected by the integration time, during which the acquisition system 240 and / or the processing system 250 samples and processes the return beam 291’. In some embodiments, the light beam is scanned between discrete angles and remains stationary or nearly stationary at the discrete angles within the angular range 227 for a corresponding integration time at each discrete angle. In other embodiments, the light beam is scanned at a fixed scan rate (e.g., using the polygon scanner 244) across the entire angular range 227. The SNR of the return beam 291’ is affected by the integration time and / or the target distance and / or the scan rate and / or the value of the separation 221. As previously described, the cross-sectional area of the light beam increases with the target distance, resulting in increased atmospheric scattering, and thus the intensity of the return beam 291’ decreases with increasing distance. Therefore, a longer integration time is required to achieve the same SNR for the return beam 291’ from a longer target distance.

[0129] Figure 4I is a diagram showing according to an embodiment Figure 2E of the system 200” an example graph of SNR versus target distance for various integration times. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 404 is the SNR in decibels (dB). The first trace 450a depicts the SNR values of the return beam 291 at the target distance where the system 200” is set to the first integration time (e.g., 3.2 μs). The second trace 450b depicts the SNR values of the return beam 291 at the target distance where the system 200” is set to the second integration time (e.g., 1.6 μs). The third trace 450c depicts the SNR values of the return beam 291 at the target distance where the system 200” is set to the third integration time (e.g., 800 ns). The fourth trace 450d depicts the SNR values of the return beam 291 at the target distance where the system 200” is set to the fourth integration time (e.g., 400 ns). The traces 450 indicate that for a fixed target distance, the SNR increases with increasing integration time. The traces 450 also indicate that for a fixed integration time, the SNR of the return beam 291’ decreases with increasing distance for the reasons discussed above. In one embodiment, a fixed integration time (e.g., 1.6 μs) is selected for the scan at the angular range 227 and the resulting target distance such that the SNR associated with the fixed integration time exceeds the SNR threshold 452 at the target distance.

[0130] Another embodiment involves minimizing the integration time at each angle within the angular range 227 by using the target distance at each angle, so as to minimize the integration time across the angular range 227. Figure 4J is a diagram showing according to an embodimentFigure 2E Graph of an example of the measurement rate in the system 200” relative to the target distance. The horizontal axis 402 is the target distance in meters (m), and the vertical axis 474 is the number of measurements allowed per unit time in millions of allowable measurements per second. The trace 476 shows the number of allowable measurements per second at each target distance. In one embodiment, the trace 476 represents the reciprocal of the integration time, e.g., the number of return beams 291’ that can be detected at each target distance per second, and the integration time represents the time taken to process the return beams 291’ at each target distance. Also provided is a trace 478, which is a good target for the number of measurements allowed per second at each target distance. The trace 478 is based on the power of 2 for two intervals for a given ADC (analog-to-digital conversion) rate. The trace 478 represents a good target for the number of allowable measurements per second because the fast Fourier transform of such long signals is more efficient when the number of digitized samples is a power of 2. The trace 450 varies based on one or more system parameters of the system 200”, including but not limited to the waveguide separation 221, the power of the transmitted signal 205’, and the focal length of the collimating optics 229.

[0131] 5. Overview of Vehicle Control

[0132] In some embodiments, the vehicle is controlled at least in part based on data received from a high-resolution Doppler LIDAR system mounted on the vehicle.

[0133] Figure 3A is a block diagram showing an example system 301 including at least one high-resolution Doppler LIDAR system 320 mounted on a vehicle 310 according to an embodiment. In the embodiment, the LIDAR system 320 is similar to one of the LIDAR systems 200, 200’, 200”. The vehicle has a center of mass represented by an asterisk 311 and travels in the forward direction given by the arrow 313. In some embodiments, the vehicle 310 includes components that operate in response to signals from a processor, such as a steering or braking system (not shown), and the processor is, for example, the vehicle control module 272 of the processing system 250. In some embodiments, the vehicle has an on-board processor 314, such as Figure 8 the chipset shown in. In some embodiments, the on-board processor 314 communicates with a remote processor, either wired or wirelessly, as Figure 7as shown. In one embodiment, the processing system 250 of the LIDAR system is communicatively coupled to the vehicle processor 314, or the processing system 250 of the LIDAR is used to perform the operations of the vehicle processor 314 such that the vehicle control module 272 causes the processing system 250 to send one or more signals to the steering or braking system of the vehicle to control the direction and speed of the vehicle. The high-resolution Doppler LIDAR uses a scanning beam 322 that scans from one side to the other, represented by the future beam 323, through the azimuth field of view 324 and through the vertical angle ( Figure 3B ) to illuminate a spot around the vehicle 310. In some embodiments, the field of view is 360 degrees azimuth. In some embodiments, the tilt angle field of view is from about +10 degrees to about -10 degrees or a subset thereof. In some embodiments, when the system 320 is the system 200”, the field of view 324 is defined by the angular range 227. When designing the system 301, the predetermined maximum design distance of the beam at each angle on the field of view 324 is determined and represents the maximum expected target distance at each angle within the range of the field of view 324. In an example embodiment, the maximum design distance is a fixed value or a fixed range of values on the field of view 324. In one embodiment, the maximum design distance on the field of view 324 is about 200 meters or within the range of about 150 meters to about 300 meters.

[0134] In some embodiments, the vehicle includes auxiliary sensors (not shown), such as GPS sensors, odometers, tachometers, temperature sensors, vacuum sensors, voltage or current sensors, etc., known in the prior art. In some embodiments, a gyroscope 330 is included to provide rotational information.

[0135] Figure 3B is a block diagram showing an example system 301’ including at least one high-resolution LIDAR system 320 mounted on a vehicle 310. The LIDAR system 320 can be similar to the system 200 or the system 200’ or the system 200”. In one embodiment, the vehicle 310 can move in a forward direction based on the arrow 313 on a surface 349 (e.g., a road). The LIDAR system 320 scans over an angular range 326 from a first beam 342 oriented at a first angle measured relative to the arrow 313 to a second beam 346 oriented at a second angle measured relative to the arrow 313. In one embodiment, the first angle and the second angle are vertical angles in a vertical plane oriented substantially orthogonally to the surface 349. For the purposes of this specification, “substantially orthogonal” means within ±20 degrees of the normal to the surface 349. In some embodiments, where the LIDAR system 320 is similar to the system 200”, the angular range 326 is defined by the angular range 227.

[0136] When designing the system 301’, the predetermined maximum design distance of the light beam at each angle is determined, and represents the maximum expected target distance at each angle in the distance 326. In other embodiments, the maximum design distance at each angle is not predetermined, but is periodically measured and updated in the memory of the processing system 250 at increasing time intervals. In one embodiment, the first light beam 342 is oriented towards the surface 349 and intersects the surface 349 within a certain maximum design distance from the vehicle 310. Thus, at the first angle, the system 320 does not consider targets located outside the surface 349. In an exemplary embodiment, the first angle of the first light beam 342 is approximately -15 degrees relative to the arrow 313 or within the range from approximately -25 degrees to approximately -10 degrees, and the maximum design distance is approximately 4 meters (m) or within the range from approximately 1m to approximately 10m or within the range from approximately 2m to approximately 6m. In one embodiment, the second light beam 346 is oriented towards the sky and intersects the upper limit 347 within a certain maximum design distance from the vehicle 310. Thus, at the second angle, the system 320 does not consider targets located above the upper limit 347. In an exemplary embodiment, the upper limit 347 is located at a height of approximately 12m from the surface 349 or within the range from approximately 8m to approximately 15m (e.g., which defines a height of 0m), the second angle of the second light beam 346 is approximately 15 degrees relative to the arrow 313 or within the range from approximately 10 degrees to approximately 20 degrees, and the maximum design distance is approximately 7m or within the range from approximately 4m to approximately 10m or within the range from approximately 1m to approximately 15m. In some embodiments, the height of the upper limit 347 depends on the height of the LIDAR system 320 (e.g., approximately 1.5m or within the range from approximately 1m to approximately 4m, where the surface 349 is defined as 0m). In one embodiment, the intermediate light beam 344 between the first light beam 342 and the second light beam 346 is oriented generally parallel to the arrow 313 and intersects the target 343 located at the maximum design distance from the vehicle 310. In an exemplary embodiment, Figure 3B Not drawn to scale, and the target 343 is positioned at a distance from the vehicle 310 farther than depicted. For the purposes of this specification, "generally parallel" means within approximately ±10 degrees or approximately ±15 degrees of the arrow 313. In an exemplary embodiment, the maximum design distance of the target 343 is approximately 200m or within the range from approximately 150m to approximately 300m or within the range from approximately 100m to approximately 500m.

[0137] Although Figure 3BDepicts a LIDAR system mounted on a vehicle 310 configured to travel over a surface 349. However, embodiments of the present invention are not limited to this type of vehicle, and the LIDAR system can be mounted on an air vehicle 310' configured to fly (e.g., a passenger air vehicle). In one embodiment, the vehicle 310' is configured to fly over a surface 349 in the presence of one or more targets 343. Figure 3D Is a block diagram showing an example system 301” according to an embodiment, which includes at least one high-resolution LIDAR system 320 mounted on a vehicle 310' configured to fly over a surface 349. In one embodiment, the LIDAR system 320 operates in a manner similar to the LIDAR system 320 of the system 301', except that the maximum design distance of a first light beam 342' at a first angle relative to the arrow 313 is defined based on the ground 348 relative to the surface 349. In an example embodiment, the height of the ground 348 relative to the height of the system 320 is in the range from about 0 m to about -10 m or in the range from about 0 m to about -2 m. In another example embodiment, the height of the upper limit 347 relative to the height of the system 320 is in the range from about 0 m to about 10 m. In another example embodiment, the first angle is about -30 degrees or in the range from about -60 degrees to about -15 degrees. In some embodiments, the first angle will be equal to and opposite a second angle equal to the upper limit 347.

[0138] 6. Method for optimizing a scan pattern in a coherent LIDAR system

[0139] Figure 6 Is a flowchart showing an example method 600 for optimizing a bistatic scan pattern of a LIDAR system. In some embodiments, the system 600 is used to optimize the scan pattern of a LIDAR system mounted on an autonomous vehicle. Although, for illustrative purposes, the steps are described as integral steps in a particular order in Figure 6 In other embodiments, one or more steps or portions thereof are performed in a different order, or overlapping in time, serially or in parallel, or one or more steps are omitted or added, or the method is changed by combining in some way.

[0140] In step 601, data is received on a processor, the data indicating a first SNR value of a signal reflected by a target after being transmitted by a transmission waveguide of a bistatic transceiver and received by a receiving waveguide of the bistatic transceiver, wherein the receiving waveguide is spaced apart from the transmission waveguide by a separation. The first SNR value is based on a value of the target distance, and the first SNR value is for a corresponding value of the scan rate of the LIDAR system. In one embodiment, in step 601, the first SNR value is the first SNR value of a return beam 291' that is reflected by a target after being transmitted by a transmission waveguide 223 and received by a receiving waveguide 225 of the bistatic transceiver 215, wherein the receiving waveguide 225 is spaced apart from the transmission waveguide 223 by a separation 221. In one embodiment, the data is the first SNR value of a focused return beam 291' at the tip 217 of either or both of the receiving waveguides 225a, 225b in the system 200". In another embodiment, in step 601, the data is the first SNR value of a focused return beam 291' on a detector array 230 in the system 200". In one embodiment, the data includes values of a trace 440b and / or a trace 440c and / or a trace 440d for indicating the SNR value of the return beam 291', wherein each trace 440 is for a corresponding value of the scan rate of the beam. In an example embodiment, the traces 440b, 440c, 440d are based on the same value of the separation 221, and in step 601, multiple sets of traces 440b, 440c, 440d are received for corresponding multiple values of the separation 221. In some embodiments, the data is not limited to the traces 440b, 440c, 440d and includes SNR values of fewer or more traces than Figure 4G described therein, wherein each SNR trace is based on a corresponding value of the scan rate and / or the traces 440b, 440c, 440d are based on a specific value of the separation 221.

[0141] In other embodiments, the data received in step 601 includes SNR values, which can be used to form traces at a target distance for each corresponding value of the scan rate and / or for each value of the separation 221. In one embodiment, traces 464, 466 are provided based on a fixed value of the scan rate (e.g., 4000 degrees per second) and multiple values of the separation 221. In another embodiment, traces 465, 467 are provided based on a fixed value of the scan rate (e.g., 12000 degrees per second) and multiple values of the separation 221. In yet another embodiment, in step 601, trace 469 is provided for a corresponding target distance to achieve an SNR threshold, and trace 469 indicates the required value of the separation 221 for a particular fixed scan speed. In an example embodiment, in step 601, the data is stored in the memory of the processing system 250, and each set of first SNR values is stored together with the associated value of the scan rate of the LIDAR system and / or the associated value of the separation 221. In one embodiment, in step 601, the first SNR values are obtained in a range from about 0 meters to about 500 meters (e.g., a motor vehicle) or in a range from about 0 meters to about 1000 meters (e.g., an air vehicle), and for scan rate values in a range from about 2000 degrees per second to about 6000 degrees per second or in a range from about 1000 degrees per second to about 7000 degrees per second, and / or for values of the separation 221 in a range from about 0w0 to 4w0 or from about 0w0 to about 10w0, where w0 is the diameter of the transmission waveguide 223. In some embodiments, the first SNR values are predefined and received by the processor in step 601. In other embodiments, the first SNR values are measured by the LIDAR system and subsequently received by the processor in step 601. In one embodiment, in step 601, the data is input using the input device 712, and / or uploaded to the memory 704 of the processing system 250 from a local area network 780, the Internet 790, or an external server 792 via the network link 778.

[0142] In one embodiment, in step 601, a first SNR value (e.g., traces 440b, 440c, 440d) of the return beam 291' received by the first receiving waveguide 225a is received based on a first separation 221a, and another set of first SNR values (e.g., traces 440b, 440c, 440d) of the return beam 291' received by the second receiving waveguide 225b is received based on a second separation 221b. In an example embodiment, in step 601, the first SNR values of the return beam 291' received by the receiving waveguides 225a, 225b are predefined and received by the processor. In another example embodiment, in step 601, the first SNR values of the return beam 291' received by the receiving waveguides 225a, 225b are measured by the LIDAR system and subsequently received by the processor.

[0143] In step 603, data is received on a processor, the data representing a second SNR value of a signal reflected by a target and detected by the LIDAR system based on a value of a target distance, where the second SNR value corresponds to a respective value of the integration time of the LIDAR system. In one embodiment, in step 603, the data is the second SNR value of the focused return beam 291 in the system 200” for the respective integration time, and the system 240 and / or the processing system 250 processes the beam over the integration time. In one embodiment, the data includes values of trace 450a and / or trace 450b and / or trace 450c and / or trace 450d for representing the SNR value of the return beam 291, where each trace 450 corresponds to a respective value of the integration time for which the beam is processed by the acquisition system 240 and / or the processing system 250. In some embodiments, the data is not limited to traces 450a, 450b, 450c, 450d and includes fewer or more traces than Figure 4I those depicted therein, where each SNR trace is based on a respective value of the integration time. In some embodiments, the data need not be a trace, but rather is an SNR value for forming a trace over the target distance for each respective value of the integration time. In an example embodiment, in step 603, the data is stored in the memory of the processing system 250, and each set of second SNR values is stored together with an associated value of the integration time of the LIDAR system. In one embodiment, in step 603, the second SNR value is obtained for a range from about 0 meters to about 500 meters (e.g., a motor vehicle) or from about 0 meters to about 1000 meters (e.g., an air vehicle) and for integration time values from about 100 nanoseconds (ns) to about 5 microseconds (μs). In some embodiments, the second SNR value is predefined and is received by the processor in step 603. In other embodiments, the second SNR value is measured by the LIDAR system and is subsequently received by the processor in step 603. In one embodiment, in step 603, the data is input using the input device 712 and / or uploaded to the memory 704 of the processing system 250 over the network link 778 from a local area network 780, the Internet 790, or an external server 792.

[0144] In step 605, data is received on a processor, which represents a first angle and a second angle for defining the angular range 227. In one embodiment, in step 605, the first angle and the second angle are input using the input device 712 (e.g., a mouse or a pointing device 716), and / or uploaded to the processing system 250 over the network link 778. In one embodiment, where the angular range 227 is Figure 3AThe field of view 324, the first angle is defined as the angle between the first light beam 322 and the arrow 313 for indicating the traveling direction of the vehicle 310, and the second angle is defined as the angle between the second light beam 323 and the arrow 313.

[0145] In another embodiment, wherein the angular range 227 is Figure 3B The angular range 326, the first angle is defined as the angle between the first light beam 342 and the arrow 313 for indicating the traveling direction of the vehicle 310, and the second angle is defined as the angle between the second light beam 346 and the arrow 313. In one embodiment, the first angle and the second angle are symmetric with respect to the arrow 313. For example, the first angle and the second angle are equal and opposite to each other. In one embodiment, the first angle is selected such that the first light beam 342 is oriented towards the surface 349, and the second angle is selected such that the second light beam 346 is oriented away from the surface 349 and towards the upper limit 347.

[0146] In one embodiment, steps 601, 603, and 605 are performed simultaneously in one step, wherein the data in steps 601, 603, and 605 are received by the processor in one simultaneous step.

[0147] In step 607, data is received on the processor, the data indicating the maximum design distance of the target at each angle within the angular range. In one embodiment, the maximum design distance is a predetermined maximum range of the target at each angle within the angular range 227. In one embodiment, in step 607, the maximum design distance of the target at each angle is based on Figure 3A The field of view 324. In an exemplary embodiment, the maximum design distance is a fixed value or a fixed range of values on the field of view 324. In an exemplary embodiment, the maximum design distance on the field of view 324 is about 250 meters or in the range from about 150 meters to about 300 meters.

[0148] In another embodiment, the data in step 607 is provided in a first angular range greater than the angular range 326. In one embodiment, the data in step 607 is provided at incremental angles within the angular range, wherein the incremental angle is selected in the range of about 0.005 degrees to about 0.01 degrees or in the range of about 0.0005 degrees to about 0.01 degrees.

[0149] In an example embodiment, the data in step 607 is input by using an input device 712 (e.g., a mouse or a pointing device 716) and / or uploaded to the processing system 250 via a network link 778. In some embodiments, the maximum design distance is predetermined and received during step 607. In other embodiments, the systems 200, 200', 200'' are used to measure the maximum design distance at each angle in the angular range 227, and the maximum design distance at each angle is then received by the processing system 250 in step 607.

[0150] In step 609, the maximum scan rate of the LIDAR system is determined at each angle in the angular range 227 such that the SNR of the LIDAR system is greater than a minimum SNR threshold. In one embodiment, in step 609, a fixed maximum scan rate is determined for the angles in the angular range 227. In step 607, first, a range of values of the maximum design distance over the angular range 227 is determined based on the received data. Then, the first SNR values received in step 601 are determined for the values or range of values of the maximum design distance over the angular range 227 (e.g., from about 150 m to about 300 m), and it is further determined which of these first SNR values exceed the minimum SNR threshold. In one embodiment, the values of the traces 440b, 440c, 440d are determined for a range of values of the maximum design distance over the angular range 227 (e.g., from about 80 m to about 120 m), and it is also determined that, for the range of values of the maximum design distance (e.g., from about 80 m to about 120 m), only the value of the trace 440d exceeds the minimum SNR threshold 442. Since only the value of the trace 440d exceeds the minimum SNR threshold 442, the fixed maximum scan rate over the angular range 227 is set to the scan rate corresponding to the trace 440d. In the example embodiment, determining the maximum scan rate in step 609 ensures that the beam walk-off 419, 421 of the return beam 291' on the tips 217 of the receiving waveguides 225a, 225b Figure 4E ) is within the threshold of the separation 221, where the threshold is based on the diameter of the image 418 of the return beam 291' on the tip (e.g., a larger threshold for a larger diameter, a smaller threshold for a smaller diameter). In the example embodiment, the threshold is the ratio of the diameter of the image 418 of the return beam 291' on the tip 217 of the receiving waveguide 225. In one example embodiment, the ratio is about 0.5 or in the range from about 0.3 to about 0.7.

[0151] In another embodiment, in step 609, first SNR values (e.g., traces 464, 465, 466, 467, 469) corresponding to different values of the separation 221 are used to determine a first SNR value (e.g., one of the traces 464 for a fixed scan speed of 4000 degrees per second or one of the traces 465 for a fixed scan speed of 12000 degrees per second) that exceeds the minimum SNR threshold 442 and is the maximum value among those first SNR values that exceed the minimum SNR threshold 442. In one embodiment, during the design phase of system 200”, the separation 221 between the transmit waveguide 223 and the receive waveguide 225 is selected based on the value of the separation 221 corresponding to the determined first SNR value, and the fixed maximum scan speed is selected based on the scan rate corresponding to the determined first SNR value (e.g., the value of the separation 221 is selected based on trace 465c for a target design distance of 0m - 250m at 2.75w0, and / or for trace 465, the fixed scan speed is selected based on a fixed scan rate of 12,000 degrees per second). In an example embodiment, a first SNR value (e.g., trace 464c) corresponding to a first separation 221a (e.g., 0.25w0) is used for a fixed scan speed (e.g., 4000 degrees per second) such that the SNR exceeds the SNR threshold 442 over a first portion of the angular range 227 (e.g., for target distances > 80m), and a first SNR value (e.g., trace 464a) corresponding to a second separation 221b (e.g., 4w0) is used for a fixed scan speed such that the SNR exceeds the SNR threshold 442 over a second portion of the angular range 227 (e.g., for target distances < 80m). In this embodiment, the fixed maximum scan speed over the angular range 227 is set to optimize the scan rate. This embodiment advantageously uses multiple receive waveguides 225a, 225b to detect return beam 291’ data from different portions of the maximum design distance over the angular range 227 (e.g., receive waveguide 225a receives the return beam 291’ from a target at a longer distance, and receive waveguide 225b receives the return beam 291’ from a target at a shorter distance), while the scan rate is fixed over the angular range 227. In an example embodiment, where the angular range 227 is the angular range 326, receive waveguide 225b receives the return beam 291’ based on the transmitted beams 342, 346 at the first and second angles, and receive waveguide 225a receives the return beam 291’ based on the intermediate transmitted beam 344.

[0152] In another embodiment, in step 609, a corresponding maximum scan rate is determined for each angle in angle range 227. At each angle, first in step 607, the maximum design distance for that angle is determined based on the received data. Then, for the maximum design distance at that angle, the first SNR value received in step 601 is determined, and further which of these first SNR values exceed the minimum SNR threshold is determined. In one embodiment, for the maximum design distance (e.g., about 90 m), the values of traces 440b, 440c, 440d are determined, and further it is determined that the values of traces 440b, 440c exceed the minimum SNR threshold 442. Among those first SNR values that exceed the minimum SNR threshold, the first SNR value with the maximum scan rate is selected, and the maximum scan rate is determined for that angle in step 609. In the above embodiment, among the values of traces 440b, 440c that exceed the minimum SNR threshold 442 at the maximum design distance (e.g., about 90 m), the value of trace 440c is selected as the maximum scan rate, and the maximum scan rate (e.g., the optimized scan rate associated with trace 440c) is determined for that angle in step 609. In an example embodiment, Figure 4G illustrates that the maximum scan rates (e.g., the optimized scan rate based on trace 440c) determined in step 609 for the light beams 342, 346 at the first and second angles are greater than the maximum scan rate determined in step 609 for the light beam 344 between the first angle and the second angle (e.g., the slow scan rate based on trace 440b). In this example embodiment, the scan rate of the scanning optical device 218 varies over the angle range 227, and the return beam 291' scans the portion of the angle range 227 corresponding to the shorter target distances (e.g., light beams 342, 346) at a fast scan rate, and scans the portion of the angle range 227 corresponding to the longer target distances (e.g., light beam 344) at a slow scan rate. In this example embodiment, one receiving waveguide 225 is used to acquire the return beam 291' over the angle range 227. In an example embodiment, determining the maximum scan rate in step 609 ensures that the beam walk-off 419 ( Figure 4E ) of the return beam 291' at the tip 217 of the receiving waveguide 225 is within the threshold of the separation 221, where the threshold is less than the ratio of the diameter of the image 418 of the return beam 291' at the tip 217. In the example embodiment, the ratio is about 0.5 or in the range of about 0.3 to about 0.7.

[0153] Figure 3C shows according to one embodiment from Figure 3BBlock diagram of an example of beams 343a, 343b emitted by LIDAR system 320 at multiple angles 345a, 345b. In one embodiment, beams 343a, 343b are intermediate beams between a first beam 342 and an intermediate beam 344. In other embodiments, beam 343a is the first beam 342, and beam 343b is a subsequent beam processed after the first beam 342. In step 609, the maximum scan rate of LIDAR system 320 is determined at angle 345a. First, the maximum design distance (e.g., 30 m) of beam 343a at angle 345a is determined by using the data in step 607. Then the first SNR value from step 601 for the maximum design distance is determined. In one example embodiment, the first SNR values include the values of traces 440b, 440c, 440d. Then it is determined which of those first SNR values at the maximum design distance exceed the minimum SNR threshold. In this example embodiment, the values of traces 440b, 440c, 440d at the maximum design distance (e.g., 30 m) all exceed the minimum SNR threshold 442. Then it is determined which of these first SNR values has the maximum scan rate, and this maximum scan rate is determined for that angle in step 609. In the example embodiment, trace 440c has the maximum scan rate, and thus this maximum scan rate is used to scan beam 343a at angle 345a. In one embodiment, Figure 4I It is shown that the minimum scan rate (e.g., 400 ns based on trace 450d) determined in step 611 for beams 342, 346 at the first and second angles is shorter than the minimum integration time (e.g., 3.2 μs based on trace 450a) determined in step 611 for beam 344 at the angle between the first and second angles.

[0154] In step 611, the minimum integration time of the LIDAR system is determined at each angle within the angular range 227 such that the SNR of the LIDAR system is greater than a minimum SNR threshold. In some embodiments, where the maximum design distance has a fixed value or a fixed range of values over the angular range 227, in step 611, a fixed minimum integration time is determined over the angular range 227 based on a fixed maximum design distance (e.g., 200 m) or a fixed range of values of the maximum design distance (e.g., 180 m - 220 m). In other embodiments, at each angle within the angular range 227, the maximum design distance for that angle is first determined based on the data received in step 607. Then, a second SNR value received in step 603 is determined for the maximum design distance at that angle, and it is further determined which of these second SNR values exceed the minimum SNR threshold. In one embodiment, the values of traces 450a, 450b, 450c, 450d are determined for a maximum design distance (e.g., approximately 120 m) or a range of values of the maximum design distance, and it is also determined that the values of traces 450a, 450b, 450c exceed the minimum SNR threshold 452. Among those second SNR values that exceed the minimum SNR threshold, the second SNR value having the minimum integration time is selected, and the minimum integration time is determined in step 611 for that angle or the angular range 227. In the above embodiment, among the values of traces 450a, 450b, 450c that exceed the minimum SNR threshold 452 at the maximum design distance (e.g., approximately 120 m), the value of trace 450c is selected as having the minimum integration time, and the minimum integration time (e.g., approximately 800 ns) is determined in step 611 for that angle.

[0155] In step 611, the minimum integration time of the LIDAR system 320 is determined at angle 345a. First, the maximum design distance (e.g., 30 m) of the beam 343a at angle 345a is determined by using the data from step 607. Then, the second SNR value for the maximum design distance from step 603 is determined. In an example embodiment, the second SNR value includes the values of traces 450a, 450b, 450c, 450d. Then it is determined which of those second SNR values at the maximum design distance exceed the minimum SNR threshold. In the example embodiment, the values of traces 450a, 450b, 450c, 450d at the maximum design distance (e.g., 30 m) all exceed the minimum SNR threshold 452. Then it is determined which of these second SNR values has the minimum integration time, and this minimum integration time is determined in step 611 for that angle. In the example embodiment, trace 450d has the minimum integration time (e.g., approximately 400 ns), and thus this minimum integration time is used to process the beam 343a at angle 345a.

[0156] In step 613, it is determined whether the additional angle remains within angle range 227 to perform another iteration of steps 609, 611. In some embodiments, where the maximum design distance has a fixed value or a fixed range of values over angle range 227, steps 609, 611 are each performed once based on this fixed value or fixed range of values of the maximum design distance, steps 613 and 615 are omitted, and method 600 proceeds to step 617. In this embodiment, in step 609, a fixed maximum scan rate is determined based on the fixed value or fixed range of values of the maximum design distance, and in step 611, a fixed minimum integration time is determined based on the fixed value or fixed range of values of the maximum design distance.

[0157] In one embodiment, in step 613, for angle range 326, where the initial iteration of steps 609, 611 is at the first angle of the first beam 342 within range 326, step 613 involves determining whether the previous iteration of steps 609, 611 is at or beyond the second angle of the second beam 346 within angle range 326. In another embodiment, where the initial iteration of steps 609, 611 is at the second angle of range 326, step 613 involves determining whether the previous iteration of steps 609, 611 is at or beyond the first angle of angle range 326. If step 613 determines that there are more angles remaining within range 326, the method proceeds to block 615. If step 613 determines that there are no further angles within range 326, the method proceeds to block 617.

[0158] In step 615, after the previous iteration of steps 609, 611 has been performed at the initial angle, the subsequent angle for the iterative steps 609, 611 is determined. In one embodiment, Figure 3C is depicted the subsequent angle 345b of the subsequent beam 343b for the iterative steps 609, 611 after the previous iteration of steps 609, 611 has been performed at the initial beam 343a at the initial angle 345a. In one embodiment, step 615 involves determining the subsequent angle 345b and the angle increment 350a between the initial angle 345a and the subsequent angle 345b. In one embodiment, the subsequent angle 345b is based on the initial angle 345a, the maximum scan rate at angle 345a determined in step 609, and the minimum integration time at angle 345a determined in step 611. In an example embodiment, the subsequent angle θ S is based on the initial angle θ i , the maximum scan rate S m and the minimum integration time I m , which uses:

[0159] θ s = θi +S m I m (6)

[0160] In an example embodiment, if the initial angle 345a is -15 degrees, the maximum scan rate is 15 degrees per second, and the minimum integration time is 2 μs, then the subsequent angle 345b is approximately -14.97 degrees by using Equation 6. After determining the subsequent angle in step 615, the method returns to block 609 such that steps 609, 611 are iterated at the subsequent angle.

[0161] In step 617, after determining that no further iteration of steps 609, 611 needs to be performed, a scan pattern of the LIDAR system is defined based on the maximum scan rate from step 609 and the minimum integration time at each angle in the angle range 326 from step 611. In some embodiments, where the maximum design distance has a fixed value or a fixed range of values over the angle range 227, in step 609, a fixed maximum scan rate is determined based on the fixed value or the fixed range of values of the maximum design distance, and in step 611, a fixed minimum integration time is determined based on the fixed value or the fixed range of values of the maximum design distance. In this embodiment, in step 617, the scan pattern is defined based on the fixed maximum scan rate and the fixed minimum integration time at each angle over the angle range 227.

[0162] In another embodiment, the scan pattern includes a maximum scan pattern and a minimum integration time for each angle in the angle range 326 between the first angle of the first beam 342 and the second angle of the second beam 346. In an example embodiment, the scan pattern is stored in a memory (e.g., memory 704) of the processing system 250. In another example embodiment, the angular increment between adjacent angles in the scan pattern is determined in step 615. For example, in step 615, the angular increment is the interval between the subsequent angle and the initial angle. In another example embodiment, Figure 3C An angular increment 350a between the subsequent angle 345b and the initial angle 345a is depicted for the purposes of step 615 and the scan pattern determined in step 617.

[0163] In step 619, the LIDAR system is operated according to the scan pattern determined in step 617. In one embodiment, where the maximum design distance has a fixed value or a fixed range of values over the angular range 227, a fixed maximum scan rate is determined in step 609 based on the fixed value or the fixed range of values of the maximum design distance. In this embodiment, in step 619, the beam of the LIDAR system is scanned over the angular range 227 at the fixed maximum scan rate using the scanning optics 218. In an example embodiment, in step 619, the polygon scanner 244 is used to scan the beam 205” at the fixed maximum scan rate. In one embodiment, the processing system 250 sends a signal to the polygon scanner 244 to cause the polygon scanner 244 to rotate at an angular velocity 249 that is the fixed maximum scan rate. Additionally, in this embodiment, the minimum integration time of the LIDAR system is based on a fixed minimum integration time, which is based on the fixed value or the fixed range of values of the maximum design distance. In one embodiment, when the beam 205” is scanned by adjacent faces 245 of the polygon scanner 244, the beam 205” is continuously scanned over the angular range 227. Thus, in an example embodiment, the beam 205” is scanned over the angular range 227 by face 245a, and the beam 205” is subsequently scanned over the angular range 227 by face 245b. During step 619, the return beam 291’ is focused by the collimation optics 229 into the tip 217 of the receiving waveguide 225. In an example embodiment, where multiple receiving waveguides 225a, 225b are provided, when the beam 205” is scanned at the fixed maximum scan rate over a first portion of the angular range 227 (e.g., a farther target distance; beam 344), the return beam 291’ is focused into the tip 217 of the first receiving waveguide 225a, and when the beam 205” is scanned at the fixed maximum scan rate over a second portion of the angular range 227 (e.g., a shorter target distance; beams 342, 346), the return beam 291’ is focused into the tip of the second receiving waveguide 225b. In another example embodiment, one of the receiving waveguides 225a and the receiving waveguide 225b is omitted, and the return beam 291’ is received in the tip of the receiving waveguide 225a when the beam 205” is scanned at the fixed maximum scan rate over the angular range 227 (e.g., the field of view 324).

[0164] In step 619, one or more parameters of the LIDAR system are selected during the design phase of system 200. In an example embodiment, the value of the separation 221 between the transmit waveguide 223 and the receive waveguide 225 is selected based on the use of one or more of the graphs 464, 465, 466, 467, 469, where the user determines the value of the separation 221 based on known values of the design target distance and the scan speed in order to achieve the SNR threshold of the return beam 291'. In another example embodiment, the value of the scan speed of the polygon scanner 244 is selected based on the use of graphs 464, 465, 466, 467, 469 and graph 440, where the user determines the value of the scan speed based on known values of the design target distance and the scan speed in order to achieve the SNR threshold of the return beam 291'.

[0165] In another embodiment, in step 619, the beam of the LIDAR system is scanned within the angular range 326 in one or more cycles, where the scan rate of the beam at each angle is the maximum scan rate in the scan pattern for that angle, and the integration time of the LIDAR system at each angle is the minimum integration time for the angle. In one embodiment, in step 619, the processing system 250 of the LIDAR system sends one or more signals to the scanning optics 218 at each angle such that the scan rate at each angle is the maximum scan rate of the scan pattern for that angle. Additionally, in one embodiment, in step 619, the processing system 250 of the LIDAR system adjusts the integration time of the acquisition system 240 and / or the processing system 250 for the return beam 291 received at each angle such that the integration time is the minimum integration time of the scan pattern for that angle. This advantageously ensures that the beam is scanned at the maximum scan rate and that the return beam is processed at the shortest integration time at each angle, while ensuring that the LIDAR system maintains sufficient SNR at each angle.

[0166] Figure 5 is shown in accordance with an embodiment in Figure 2EA graph showing an example of the vertical angle over time across multiple angular ranges in the system. The horizontal axis 502 is time in seconds (s), and the vertical axis is the angle in radians (rad). Trace 540 depicts the angle of the beam over time during the scan of the beam during multiple scan patterns in step 619. The slope of trace 540 at an instant in time represents the scan rate of the beam at that time. In one embodiment, region 542 of trace 540 represents a faster scan rate (e.g., a high slope of trace 540) when the beam is oriented towards the upper limit 347; region 544 of trace 540 also represents a faster scan rate (e.g., a high slope of trace 540) when the beam is oriented towards surface 349; and region 546 of trace 540 represents a slower scan rate (e.g., a lower slope of trace 540) when the beam is oriented approximately parallel to surface 349. In other embodiments, where the beam 205” is scanned at a fixed maximum scan rate, the trace will exhibit a fixed slope over the angular range 227.

[0167] In another embodiment, during or after step 619, the processor may operate the vehicle 310 at least in part based on data collected by the LIDAR system during step 619. In one embodiment, the processing system 250 of the LIDAR system and / or the processor 314 of the vehicle 310 send one or more signals to the steering and / or braking system of the vehicle based on data collected by the LIDAR system in step 619. In an example embodiment, the processing system 250 sends one or more signals to the steering or braking system of the vehicle 310 in response to the LIDAR data to control the position of the vehicle 310. In some embodiments, the processing system 250 sends one or more signals to the processor 314 of the vehicle 310 based on the LIDAR data collected in step 619, and the processor 314 in turn sends one or more signals to the steering and braking systems of the vehicle 310.

[0168] 7. Overview of Computing Hardware

[0169] Figure 7FIG. 0 is a block diagram showing a computer system 700 in which embodiments of the present invention may be implemented. The computer system 700 includes a communication mechanism such as a bus 710 for transferring information between other internal and external components of the computer system 700. The information is represented as a physical signal of a measurable phenomenon, typically a voltage, but in other embodiments includes phenomena such as magnetic, electromagnetic, pressure, chemical, molecular atomic, and quantum interactions. For example, north and south magnetic fields, or zero and non-zero voltages, represent two states (0, 1) of a binary digit (bit). Other phenomena may represent higher radix numbers. The superposition of multiple simultaneous quantum states before measurement represents a quantum bit (qubit). A sequence of one or more digits constitutes digital data representing a number or code for a character. In some embodiments, information called analog data is represented by a near continuum of measurable values within a particular range. The computer system 700 or a portion thereof constitutes means for performing one or more steps of one or more methods described herein.

[0170] A sequence of binary digits constitutes digital data representing a number or code for a character. The bus 710 includes a number of parallel information conductors such that information is transferred rapidly among the devices coupled to the bus 710. One or more processors 702 for processing information are coupled to the bus 710. The processor 702 performs a set of operations on the information. The set of operations includes introducing information from the bus 710 and placing information on the bus 710. The set of operations typically also includes comparing two or more information units, moving the position of information units, and combining two or more information units, such as by addition or multiplication. A series of operations performed by the processor 702 constitutes computer instructions.

[0171] The computer system 700 also includes a memory 704 coupled to the bus 710. The memory 704, such as a random access memory (RAM) or other dynamic storage device, stores information including computer instructions. The dynamic memory allows the information stored therein to be changed by the computer system 700. The RAM allows information units stored at locations called memory addresses to be stored and retrieved independently of the information at adjacent addresses. The memory 704 is also used by the processor 702 to store temporary values during the execution of computer instructions. The computer system 700 also includes a read only memory (ROM) 706 or other static storage device coupled to the bus 710 for storing static information that is not changed by the computer system 700, including instructions. Also coupled to the bus 710 is a non-volatile (permanent) storage device 708, such as a magnetic disk or optical disk, for storing information that persists even when the computer system 700 is turned off or otherwise powered down, including instructions.

[0172] Information (including instructions) is provided from an external input device 712 (such as a keyboard or a sensor including alphanumeric keys operated by a human user) to the bus 710 for use by the processor. The sensor detects conditions in its vicinity and converts these detections into signals compatible with signals used to represent information in the computer system 700. Other external devices coupled to the bus 710 that are primarily used for human interaction include a display device 714 for presenting images (such as a cathode ray tube (CRT) or a liquid crystal display (LCD)), and a pointing device 716 (such as a mouse or a trackball or cursor direction keys), the pointing device being used to control the position of a small cursor image presented on the display 714 and to issue commands associated with graphical elements presented on the display 714.

[0173] In the illustrated embodiment, dedicated hardware such as a dedicated integrated circuit (IC) 720 is coupled to the bus 710. The dedicated hardware is configured to perform operations not performed by the processor 702 fast enough for a dedicated purpose. Examples of dedicated ICs include a graphics acceleration card for generating images for the display 714, a cryptographic board for encrypting and decrypting messages sent over a network, speech recognition, and an interface to special external devices such as robotic arms and medical scanning equipment that are used to repeatedly execute certain complex sequences of operations, the operations being implemented more efficiently in hardware.

[0174] The computer system 700 also includes one or more instances of a communication interface 770 coupled to the bus 710. The communication interface 770 provides a two-way communication coupling to various external devices that operate with their own processors, such as printers, scanners, and external disks. Typically, the coupling is made with a network link 778 connected to a local network 780 to which various external devices with their own processors are connected. For example, the communication interface 770 can be a parallel port, a serial port, or a universal serial bus (USB) port on a personal computer. In some embodiments, the communication interface 770 is an integrated services digital network (ISDN) card, a digital subscriber line (DSL) card, or a telephone modem that provides an information communication connection to a corresponding type of telephone line. In some embodiments, the communication interface 770 is a cable modem that converts the signals on the bus 710 into signals for a communication connection over coaxial cable or into optical signals for a communication connection over fiber optic cable. As another example, the communication interface 770 can be a local area network (LAN) card to provide a data communication connection to a compatible LAN, such as Ethernet. A wireless link can also be implemented. Carriers, such as acoustic and electromagnetic waves, including radio waves, light waves, and infrared waves, travel through space without wires or cables. Signals include an artificial change in the amplitude, frequency, phase, polarization, or other physical property of a carrier. For a wireless link, the communication interface 770 transmits and receives electrical, acoustic, or electromagnetic signals, including infrared and optical signals, for carrying an information data stream, such as digital data.

[0175] The term computer-readable medium is used herein to refer to any medium that participates in providing information to the processor 702, the information including instructions for execution. Such a medium can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as the storage device 708. Volatile media includes, for example, dynamic memory 704. Transmission media includes, for example, coaxial cable, copper wire, fiber optic cable, and waves that travel through space without wires or cables, such as acoustic and electromagnetic waves, including radio waves, light waves, and infrared waves. The term computer-readable storage medium is used herein to refer to any medium other than a transmission medium that participates in providing information to the processor 702.

[0176] Common forms of computer-readable media include, for example, floppy disks, flexible disks, hard disks, magnetic tape, or any other magnetic medium, compact disk ROM (CD-ROM), digital video disk (DVD), or any other optical medium, punch cards, paper tape, or any other physical medium with patterns of holes, RAM, programmable ROM (PROM), erasable PROM (EPROM), FLASH-EPROM, or any other memory chip or cartridge, a carrier wave, or any other medium from which a computer can read. The term non-transitory computer-readable storage medium is used herein to refer to any medium that participates in providing information to processor 702 other than a carrier wave and other signals.

[0177] Logic encoded in one or more tangible media includes one or both of processor instructions on a computer-readable storage medium and special-purpose hardware such as ASIC 720.

[0178] Network link 778 generally provides information communication to other devices that use or process information via one or more networks. For example, network link 778 can provide a connection to host computer 782 or to device 784 operated by an Internet service provider (ISP) via local network 780. ISP device 784 in turn provides data communication services via the public global packet-switching communication network of the network now commonly known as the Internet 790. A computer, called server 792, connected to the Internet provides services in response to information received on the Internet. For example, server 792 provides information for representing video data for presentation on display 714.

[0179] The present invention relates to using computer system 700 to implement the techniques described herein. In accordance with one embodiment of the present invention, those techniques are performed by computer system 700 in response to one or more sequences of one or more instructions contained in memory 704 being executed by processor 702. Such instructions, also referred to as software and program code, can be read into memory 704 from another computer-readable medium such as storage device 708. Execution of the sequence of instructions contained in memory 704 causes processor 702 to perform the method steps described herein. In an alternative embodiment, hardware such as special-purpose integrated circuit 720 can be used in place of or in combination with software to implement the present invention. Accordingly, embodiments of the present invention are not limited to any particular combination of hardware and software.

[0180] Signals transmitted over network link 778 and other networks via communication interface 770 carry information to and from computer system 700. Computer system 700 can send and receive information including program code via networks 780, 790, etc., over network link 778 and communication interface 770. In an example using the Internet 790, server 792 sends program code for a particular application requested by a message from computer 700 via the Internet 790, ISP device 784, local network 780, and communication interface 770. The received code can be executed by processor 702 when it is received, or can be stored in storage device 708 or other non-volatile storage for later execution, or both. In this way, computer system 700 can obtain application program code in the form of signals on a carrier wave.

[0181] Various forms of computer-readable media can be involved in carrying one or more sequences of instructions or data or both to processor 702 for execution. For example, the instructions and data can initially be borne on a magnetic disk of a remote computer such as host 782. The remote computer loads the instructions and data into its dynamic memory and sends the instructions and data over a telephone line using a modem. A modem local to computer system 700 receives the instructions and data on the telephone line and converts the instructions and data into signals on an infrared carrier wave used as network link 778 using an infrared transmitter. An infrared detector serving as communication interface 770 receives the instructions and data carried in the infrared signal and places information representing the instructions and data on bus 710. Bus 710 transfers the information to memory 704, from which processor 702 retrieves the instructions and executes the instructions using some of the data sent with the instructions. The instructions and data received in memory 704 can optionally be stored on storage device 708 before or after being executed by processor 702.

[0182] Figure 8 Chipset 800 is shown in which embodiments of the present invention can be implemented. Chipset 800 is programmed to perform one or more steps of the methods described herein and includes, for example, processor and memory components as described in one or more physical packages (e.g., chips). By way of example, a physical package includes an arrangement of one or more materials, components, and / or wires on a structural component (e.g., a substrate) to provide one or more characteristics such as physical strength, dimensional retention, and / or electrical interaction confinement. It is contemplated that in some embodiments, the chipset can be implemented in a single chip. Chipset 800 or a portion thereof constitutes means for performing one or more steps of the methods described herein. Figure 7

[0183] ​In one embodiment, chipset 800 includes a communication mechanism such as bus 801 for passing information among the components of chipset 800. Processor 803 has a connection to bus 801 to execute instructions and process information stored in, for example, memory 805. Processor 803 may include one or more processing cores, where each core is configured to execute independently. A multi-core processor enables multi-processing within a single physical package. Examples of multi-core processors include two, four, eight, or more processing cores. Alternatively or additionally, processor 803 may include one or more microprocessors configured in series via bus 801 to be able to execute instructions, pipelines, and multi-threading independently. Processor 803 may also be accompanied by one or more specialized components to perform certain processing functions and tasks, such as one or more digital signal processors (DSPs) 807 or one or more application specific integrated circuits (ASICs) 809. DSP 807 is typically configured to process real-world signals (e.g., sound) in real time independent of processor 803. Similarly, ASIC 809 may be configured to perform specialized functions not easily performed by a general-purpose processor. Other specialized components that assist in performing the inventive functions described herein include one or more field programmable gate arrays (FPGAs) (not shown), one or more controllers (not shown), or one or more other specialized computer chips.

[0184] Processor 803 and the attached components have connectivity to memory 805 via bus 801. Memory 805 includes both dynamic memory (e.g., RAM, disk, writable optical disk, etc.) for storing executable instructions and static memory (e.g., ROM, CD-ROM, etc.) that, when the executable instructions are executed, will perform one or more steps of the methods herein. Memory 805 also stores data associated with the execution of one or more steps of the methods herein or data generated by the execution of one or more steps of the methods herein.

[0185] 8. Changes, Extensions, and Modifications

[0186] In the foregoing specification, the present invention has been described with reference to specific embodiments of the invention. However, it will be apparent that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive. Throughout the specification and claims, unless the context requires otherwise, the word "comprise" and its variations, such as "comprises" and "comprising", will be understood to imply the stated item, element or step or a group of items, elements or steps, but not to exclude any other item, element or step or a group of items, elements or steps. Further, the indefinite article "a" or "an" is intended to denote one or more of the items, elements or steps modified by the article.

Claims

1. A light detection and ranging (LIDAR) sensor system for a vehicle, comprising: A laser source configured to generate a light beam; A transmission waveguide configured to output a transmission signal based on the light beam; One or more scanning optical devices configured to receive the transmission signal and output the transmission signal towards an object at a scanning rate; And A receiving waveguide spaced apart from the transmission waveguide by a distance related to the scanning rate and a target distance for detecting the object, the receiving waveguide being configured to receive a return signal resulting from reflection or scattering of the transmission signal by the object.

2. The LIDAR sensor system according to claim 1, wherein, The one or more scanning optical devices are configured to receive the transmission signal at a first angle and output the transmission signal at the scanning rate over an angular range between a second angle and a third angle.

3. The LIDAR sensor system according to claim 1, wherein, The target distance is between approximately 100 meters and approximately 300 meters.

4. The LIDAR sensor system according to claim 1, wherein, The scanning rate is between approximately 1000 degrees per second and approximately 7000 degrees per second.

5. The LIDAR sensor system according to claim 1, further comprising collimating optics between the one or more scanning optics and the receiving waveguide, the collimating optics being configured to focus the return signal from the one or more scanning optics onto the tip of the receiving waveguide.

6. The LIDAR sensor system according to claim 2, wherein: The distance is a first distance, the receiving waveguide is a first receiving waveguide, and the return signal is a first return signal, the first receiving waveguide being configured to receive the first return signal at the first distance over a first portion of the angular range; and The LIDAR sensor system further includes a second receiving waveguide spaced apart from the transmission waveguide by a second distance greater than the first distance, the second receiving waveguide being configured to receive a second return signal at the second distance over a second portion of the angular range.

7. The LIDAR sensor system according to claim 1, wherein, At least one of the one or more scanning optical devices includes a polygon scanner.

8. An autonomous vehicle control system, comprising: A LIDAR sensor system, comprising: A laser source configured to generate a light beam; A transmission waveguide configured to output a transmission signal based on the light beam; One or more scanning optical devices configured to receive the transmission signal and output the transmission signal towards an object at a scanning rate; and A receiving waveguide spaced apart from the transmission waveguide by a distance related to the scanning rate and a target distance for detecting the object, the receiving waveguide being configured to receive a return signal resulting from reflection or scattering of the transmission signal by the object; and One or more processors configured to: Determine at least one of a distance to the object and a velocity of the object based on the return signal; and Control an operation of an autonomous vehicle based on at least one of the distance and the velocity.

9. The autonomous vehicle control system according to claim 8, wherein, The one or more scanning optical devices are configured to receive the transmission signal at a first angle and output the transmission signal at the scanning rate over an angular range between a second angle and a third angle.

10. The autonomous vehicle control system according to claim 8, wherein, The target distance is between approximately 100 meters and approximately 300 meters.

11. The autonomous vehicle control system according to claim 8, wherein, The scanning rate is between approximately 1000 degrees per second and approximately 7000 degrees per second.

12. The autonomous vehicle control system according to claim 8, wherein,It further includes a collimating optical device between the one or more scanning optical devices and the receiving waveguide, and the collimating optical device is configured to focus the return signal from the one or more scanning optical devices on the tip of the receiving waveguide.

13. The autonomous vehicle control system according to claim 9, wherein: The distance is a first distance, the receiving waveguide is a first receiving waveguide, and the return signal is a first return signal. The first receiving waveguide is configured to receive the first return signal at the first distance on a first portion of the angular range; and The LIDAR sensor system further includes a second receiving waveguide spaced from the transmitting waveguide by a second distance greater than the first distance. The second receiving waveguide is configured to receive a second return signal at the second distance on a second portion of the angular range.

14. The autonomous vehicle control system according to claim 8, wherein, At least one of the one or more scanning optical devices includes a polygon scanner.

15. An autonomous vehicle, comprising: A LIDAR sensor system, comprising: A laser source configured to generate a light beam; A transmitting waveguide configured to output a transmission signal based on the light beam; One or more scanning optical devices configured to receive the transmission signal and output the transmission signal towards an object at a scanning rate; A receiving waveguide spaced from the transmitting waveguide by a distance related to the scanning rate and a target distance for detecting the object, the receiving waveguide being configured to receive a return signal from the reflection or scattering of the transmission signal by the object; and One or more processors configured to determine at least one of a distance to the object and a speed of the object based on the return signal; A steering system; A braking system; and A vehicle controller configured to control at least one of the steering system and the braking system based on at least one of the distance to the object and the speed of the object.

16. The autonomous vehicle according to claim 15, wherein, The one or more scanning optical devices are configured to receive the transmission signal at a first angle and output the transmission signal at the scanning rate over an angular range between a second angle and a third angle.

17. The autonomous vehicle according to claim 15, wherein: The target distance is between approximately 100 meters and approximately 300 meters; and The scanning rate is between approximately 1000 degrees per second and approximately 7000 degrees per second.

18. The autonomous vehicle according to claim 15, further comprising a collimating optical device between the one or more scanning optical devices and the receiving waveguide, the collimating optical device being configured to focus the return signal from the one or more scanning optical devices on the tip of the receiving waveguide.

19. The autonomous vehicle according to claim 16, wherein: The distance is a first distance, the receiving waveguide is a first receiving waveguide, and the return signal is a first return signal. The first receiving waveguide is configured to receive the first return signal at the first distance on a first portion of the angular range; and The LIDAR sensor system further includes a second receiving waveguide spaced from the transmitting waveguide by a second distance greater than the first distance. The second receiving waveguide is configured to receive a second return signal at the second distance on a second portion of the angular range.

20. The autonomous vehicle according to claim 15, wherein, At least one of the one or more scanning optical devices includes a polygon scanner.

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