Patent Description:
<CIT> relates to an optical scanner including at least one light source configured to emit light, a steering unit configured to perform scanning in a first direction based on the light emitted from the at least one light source, and a polygon mirror configured to perform, by using the light output from the steering unit, scanning in a second direction different than the first direction based on a rotation of the polygon mirror. The steering unit of <CIT> includes a plurality of first prisms, and each of the plurality of first prisms includes an incident facet configured to pass the light emitted from the at least one light source, and an output facet configured to refract and output the light.

<CIT> relates to a distance detection device that comprises a light source for emitting a light beam; a scanning module comprising a first optical module, a second optical module and driving devices; and a detector. The first optical module and the second optical module of <CIT> are sequentially located on the optical path of the light beam emitted from the light source, and the driving devices driving the first optical module and the second optical module.

<CIT> relates to a beam steering device that includes a housing and a transceiver that emits and receives light beams through at least one opening in the housing. A rotator of <CIT> includes a cylindrical body rotatably mounted within the housing axially between the transceiver and the at least one opening. A wedge-shaped prism of <CIT> is secured within the body and includes a first surface extending perpendicular to the axis and a second surface extending transverse to the axis.

<CIT> relates to a system for coaxial LiDAR scanning that includes a first light source configured to provide first light pulses and one or more beam steering apparatuses optically coupled to the first light source. Each beam steering apparatus of <CIT> comprises a rotatable concave reflector and a light beam steering device disposed at least partially within the rotatable concave reflector.

According to a first aspect of the present invention, there is provided a light detection and ranging (LIDAR) system as set out in claim <NUM>. According to a second aspect of the present invention, there is provided an autonomous vehicle control system as set out in claim <NUM>. According to a third aspect of the present invention, there is provided an autonomous vehicle as set out in claim <NUM>. Other embodiments are described in the dependent claims.

Those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Any of the features described herein may be used with any other features, and any subset of such features can be used in combination according to various embodiments. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings.

Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which:.

A method and apparatus and system and computer-readable medium are described for scanning of a LIDAR system. Some implementations are described below in the context of a hi-res LIDAR system. An implementation is described in the context of optimization of scanning a beam by a unidirectional scan element of a LIDAR system, including both Doppler and non-Doppler LIDAR systems. An implementation is described in the context of optimization of scanning a beam by a polygon deflector, such as a polygon deflector that is configured to deflect or refract a beam incident on a facet of the polygon deflector from an interior of the polygon deflector. A polygon deflector can be polygon shaped element with a number of facets based on the polygon structure. Each facet is configured to deflect (e.g. reflect an incident light beam on the facet or refract an incident light beam from within an interior of the polygon shaped element) over a field of view as the polygon deflector is rotated about an axis. The polygon deflector repeatedly scans the beam over the field of view as the beam transitions over a facet break between adjacent facets during the rotation of the polygon deflector. Some implementations are described in the context of single front mounted hi-res Doppler LIDAR system on a personal automobile; but, various implementations are not limited to this context. Some implementations can be used in the context of laser etching, surface treatment, barcode scanning, and refractive scanning of a beam.

Some scanning systems utilize polygon reflectors which are regularly shaped reflective objects that spin relative to a static incident light beam. The reflective facet causes a repeating reflection of light in a direction over a field of view. There can be several drawbacks of such polygon reflectors. For example, the incident light beam on the reflective facet inherently limits the field of view since the field of view cannot include angles encompassing the incident light beam that is coplanar with the reflective facet. Useful return beam data cannot be attained if the field of view extended over angles that encompassed the incident light beam and thus the field of view is inherently limited by the incident light beam. This can also inherently limit the duty cycle or ratio of time when the beam is scanned over the field of view to a total operation time of the polygon reflectors. Various systems and methods in accordance with the present disclosure can use a refractive beam-steering assembly and method that utilizes a polygon deflector that deflects (e.g. refracts) an incident light beam over a field of view rather than reflecting the incident light beam over a field of view. The polygon deflector can enhance both the field of view and the duty cycle since the incident light beam is directed from within an interior of the deflector and thus does not inherently limit the field of view.

A LIDAR apparatus can scan a beam in a first plane between a first angle and a second angle. The apparatus includes a polygon deflector comprising a plurality of facets and a motor rotatably coupled to the polygon deflector and configured to rotate the polygon deflector about a first axis orthogonal to the first plane. The apparatus also includes an optic positioned within an interior of the polygon deflector to collimate the beam incident on the facet from the interior of the polygon deflector. Each facet is configured to refract the beam in the first plane between the first angle and the second angle as the polygon deflector is rotated about the first axis. Systems and methods can be provided that implement the LIDAR apparatus.

Using an optical phase-encoded signal for measurement of range, the transmitted signal is in phase with a carrier (phase = <NUM>) for part of the transmitted signal and then changes by one or more phases changes represented by the symbol Δϕ (so phase = Δϕ) for short time intervals, switching back and forth between the two or more phase values repeatedly over the transmitted signal. The shortest interval of constant phase is a parameter of the encoding called pulse duration τ and is typically the duration of several periods of the lowest frequency in the band. The reciprocal, <NUM>/τ, is baud rate, where each baud indicates a symbol. The number N of such constant phase pulses during the time of the transmitted signal is the number N of symbols and represents the length of the encoding. In binary encoding, there are two phase values and the phase of the shortest interval can be considered a <NUM> for one value and a <NUM> for the other, thus the symbol is one bit, and the baud rate is also called the bit rate. In multiphase encoding, there are multiple phase values. For example, <NUM> phase values such as Δϕ* {<NUM>, <NUM>, <NUM> and <NUM>}, which, for Δϕ = π/<NUM> (<NUM> degrees), equals {<NUM>, π/<NUM>, π and 3π/<NUM>}, respectively; and, thus <NUM> phase values can represent <NUM>, <NUM>, <NUM>, <NUM>, respectively. In this example, each symbol is two bits and the bit rate is twice the baud rate.

Phase-shift keying (PSK) refers to a digital modulation scheme that conveys data by changing (modulating) the phase of a reference signal (the carrier wave). The modulation is impressed by varying the sine and cosine inputs at a precise time. At radio frequencies (RF), PSK is widely used for wireless local area networks (LANs), RF identification (RFID) and Bluetooth communication. Alternatively, instead of operating with respect to a constant reference wave, the transmission can operate with respect to itself. Changes in phase of a single transmitted waveform can be considered the symbol. In this system, the demodulator determines the changes in the phase of the received signal rather than the phase (relative to a reference wave) itself. Since this scheme depends on the difference between successive phases, it is termed differential phase-shift keying (DPSK). DPSK can be significantly simpler to implement in communications applications than ordinary PSK, since there is no need for the demodulator to have a copy of the reference signal to determine the exact phase of the received signal (thus, it is a non-coherent scheme).

Optical detection of range can be accomplished with several different techniques, including direct ranging based on round trip travel time of an optical pulse to an object, and chirped detection based on a frequency difference between a transmitted chirped optical signal and a returned signal scattered from an object, and phase-encoded detection based on a sequence of single frequency phase changes that are distinguishable from natural signals.

To achieve acceptable range accuracy and detection sensitivity, direct long range LIDAR systems may use short pulse lasers with low pulse repetition rate and extremely high pulse peak power. The high pulse power can lead to rapid degradation of optical components. Chirped and phase-encoded LIDAR systems may use long optical pulses with relatively low peak optical power. In this configuration, the range accuracy can increase with the chirp bandwidth or length and bandwidth of the phase codes rather than the pulse duration, and therefore excellent range accuracy can still be obtained.

Useful optical bandwidths have been achieved using wideband radio frequency (RF) electrical signals to modulate an optical carrier. With respect to LIDAR, using the same modulated optical carrier as a reference signal that is combined with the returned signal at an optical detector can produce in the resulting electrical signal a relatively low beat frequency in the RF band that is proportional to the difference in frequencies or phases between the references and returned optical signals. This kind of beat frequency detection of frequency differences at a detector is called heterodyne detection. It has several advantages known in the art, such as the advantage of using RF components of ready and inexpensive availability.

Hi-res range-Doppler LIDAR systems can use an arrangement of optical components and coherent processing to detect Doppler shifts in returned signals to provide improved range and relative signed speed on a vector between the LIDAR system and each external object.

In some instances, these improvements provide range, with or without target speed, in a pencil thin laser beam of proper frequency or phase content. When such beams are swept over a scene, information about the location and speed of surrounding objects can be obtained. This information can be used in control systems for autonomous vehicles, such as self driving, or driver assisted, automobiles.

For optical ranging applications, since the transmitter and receiver are in the same device, coherent PSK can be used. The carrier frequency is an optical frequency fc and a RF f<NUM> is modulated onto the optical carrier. The number N and duration τ of symbols are selected to achieve the desired range accuracy and resolution. The pattern of symbols is selected to be distinguishable from other sources of coded signals and noise. Thus a strong correlation between the transmitted and returned signal can be a strong indication of a reflected or backscattered signal. The transmitted signal is made up of one or more blocks of symbols, where each block is sufficiently long to provide strong correlation with a reflected or backscattered return even in the presence of noise. The transmitted signal can be made up of M blocks of N symbols per block, where M and N are non-negative integers.

<FIG> is a schematic graph <NUM> that illustrates the example transmitted signal as a series of binary digits along with returned optical signals for measurement of range, according to an implementation. The horizontal axis <NUM> indicates time in arbitrary units after a start time at zero. The vertical axis 124a indicates amplitude of an optical transmitted signal at frequency fC+f<NUM> in arbitrary units relative to zero. The vertical axis 124b indicates amplitude of an optical returned signal at frequency fC+f<NUM> in arbitrary units relative to zero, and is offset from axis 124a to separate traces. Trace <NUM> represents a transmitted signal of M*N binary symbols, with phase changes as shown in <FIG> to produce a code starting with <NUM> and continuing as indicated by ellipsis. Trace <NUM> represents an idealized (noiseless) return signal that is scattered from an object that is not moving (and thus the return is not Doppler shifted). The amplitude is reduced, but the code <NUM> is recognizable. Trace <NUM> represents an idealized (noiseless) return signal that is scattered from an object that is moving and is therefore Doppler shifted. The return is not at the proper optical frequency fC+f<NUM> and is not well detected in the expected frequency band, so the amplitude is diminished.

The observed frequency f' of the return differs from the correct frequency f = fC+f<NUM> of the return by the Doppler effect given by Equation <NUM>.

Where c is the speed of light in the medium, vo is the velocity of the observer and vs is the velocity of the source along the vector connecting source to receiver. Note that the two frequencies are the same if the observer and source are moving at the same speed in the same direction on the vector between the two. The difference between the two frequencies, Δf = f'-f , is the Doppler shift, ΔfD, which causes problems for the range measurement, and is given by Equation <NUM>.

Note that the magnitude of the error increases with the frequency f of the signal. Note also that for a stationary LIDAR system (vo = <NUM>), for an object moving at <NUM> meters a second (vs = <NUM>), and visible light of frequency about <NUM> THz, then the size of the error is on the order of <NUM> megahertz (MHz, <NUM> = <NUM><NUM> hertz, Hz, <NUM> = <NUM> cycle per second). In various implementations described below, the Doppler shift error is detected and used to process the data for the calculation of range.

In phase coded ranging, the arrival of the phase coded reflection can be detected in the return by cross correlating the transmitted signal or other reference signal with the returned signal, which can be implemented by cross correlating the code for a RF signal with an electrical signal from an optical detector using heterodyne detection and thus down-mixing back to the RF band. Cross correlation for any one lag can be computed by convolving the two traces, e.g., multiplying corresponding values in the two traces and summing over all points in the trace, and then repeating for each time lag. The cross correlation can be accomplished by a multiplication of the Fourier transforms of each of the two traces followed by an inverse Fourier transform. Forward and inverse Fast Fourier transforms can be efficiently implemented in hardware and software.

Note that the cross correlation computation may be done with analog or digital electrical signals after the amplitude and phase of the return is detected at an optical detector. To move the signal at the optical detector to a RF frequency range that can be digitized easily, the optical return signal is optically mixed with the reference signal before impinging on the detector. A copy of the phase-encoded transmitted optical signal can be used as the reference signal, but it is also possible, and often preferable, to use the continuous wave carrier frequency optical signal output by the laser as the reference signal and capture both the amplitude and phase of the electrical signal output by the detector.

For an idealized (noiseless) return signal that is reflected from an object that is not moving (and thus the return is not Doppler shifted), a peak occurs at a time Δt after the start of the transmitted signal. This indicates that the returned signal includes a version of the transmitted phase code beginning at the time Δt. The range R to the reflecting (or backscattering) object is computed from the two way travel time delay based on the speed of light c in the medium, as given by Equation <NUM>.

For an idealized (noiseless) return signal that is scattered from an object that is moving (and thus the return is Doppler shifted), the return signal does not include the phase encoding in the proper frequency bin, the correlation stays low for all time lags, and a peak is not as readily detected, and is often undetectable in the presence of noise. Thus Δt is not as readily determined and range R is not as readily produced.

The Doppler shift can be determined in the electrical processing of the returned signal, and the Doppler shift can be used to correct the cross correlation calculation. Thus, a peak can be more readily found and range can be more readily determined. <FIG> is a schematic graph <NUM> that illustrates an example spectrum of the transmitted signal and an example spectrum of a Doppler shifted complex return signal, according to an implementation. The horizontal axis <NUM> indicates RF frequency offset from an optical carrier fc in arbitrary units. The vertical axis 144a indicates amplitude of a particular narrow frequency bin, also called spectral density, in arbitrary units relative to zero. The vertical axis 144b indicates spectral density in arbitrary units relative to zero and is offset from axis 144a to separate traces. Trace <NUM> represents a transmitted signal; and, a peak occurs at the proper RF f<NUM>. Trace <NUM> represents an idealized (noiseless) complex return signal that is backscattered from an object that is moving toward the LIDAR system and is therefore Doppler shifted to a higher frequency (called blue shifted). The return does not have a peak at the proper RF f<NUM>; but, instead, is blue shifted by ΔfD to a shifted frequency fS. In practice, a complex return representing both in-phase and quadrature (I/Q) components of the return is used to determine the peak at +ΔfD, 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 detected from a single return.

In some Doppler compensation implementations, rather than finding ΔfD by taking the spectrum of both transmitted and returned signals and searching for peaks in each, then subtracting the frequencies of corresponding peaks, as illustrated in <FIG>, it can more efficient to take the cross spectrum of the in-phase and quadrature component of the down-mixed returned signal in the RF band. <FIG> is a schematic graph <NUM> that illustrates an example cross-spectrum, according to an implementation. The horizontal axis <NUM> indicates frequency shift in arbitrary units relative to the reference spectrum; and, the vertical axis <NUM> indicates amplitude of the cross spectrum in arbitrary units relative to zero. Trace <NUM> represents a cross spectrum with an idealized (noiseless) return signal generated by one object moving toward the LIDAR system (blue shift of ΔfD1 = ΔfD in <FIG>) and a second object moving away from the LIDAR system (red shift of ΔfD2). A peak 156a occurs when one of the components is blue shifted ΔfD1; and, another peak 156b occurs when one of the components is red shifted ΔfD2. Thus, the Doppler shifts are determined. These shifts can be used to determine a signed velocity of approach of objects in the vicinity of the LIDAR, such as for collision avoidance applications. However, if I/Q processing is not done, peaks may appear at both +/- ΔfD1 and both +/- ΔfD2, so there may be ambiguity on the sign of the Doppler shift and thus the direction of movement.

The Doppler shift(s) detected in the cross spectrum can be used to correct the cross correlation so that the peak <NUM> is apparent in the Doppler compensated Doppler shifted return at lag Δt, and range R can be determined. In some implementations, simultaneous I/Q processing can be performed. In some implementations, serial I/Q processing can be used to determine the sign of the Doppler return. In some implementations, errors due to Doppler shifting can be tolerated or ignored; and, no Doppler correction is applied to the range measurements.

<FIG> is a set of graphs that illustrates an example optical chirp measurement of range, according to an implementation. The horizontal axis <NUM> is the same for all four graphs and indicates time in arbitrary units, on the order of milliseconds (ms, <NUM> = <NUM>-<NUM> seconds). Graph <NUM> indicates the power of a beam of light used as a transmitted optical signal. The vertical axis <NUM> in graph <NUM> indicates power of the transmitted signal in arbitrary units. Trace <NUM> indicates that the power is on for a limited pulse duration, τ starting at time <NUM>. Graph <NUM> indicates the frequency of the transmitted signal. The vertical axis <NUM> indicates the frequency transmitted in arbitrary units. The trace <NUM> indicates that the frequency of the pulse increases from f<NUM> to f<NUM> over the duration τ of the pulse, and thus has a bandwidth B = f<NUM> - f<NUM>. The frequency rate of change is (f<NUM> - f<NUM>)/τ.

The returned signal is depicted in graph <NUM> which has a horizontal axis <NUM> that indicates time and a vertical axis <NUM> that indicates frequency as in graph <NUM>. The chirp (e.g., trace <NUM>) of graph <NUM> is also plotted as a dotted line on graph <NUM>. A first returned signal is given by trace 166a, which can represent the transmitted reference signal diminished in intensity (not shown) and delayed by Δt. When the returned signal is received from an external object after covering a distance of 2R, where R is the range to the target, the returned signal start at the delayed time Δt can be given by 2R/c, where c is the speed of light in the medium (approximately 3x10<NUM> meters per second, m/s), related according to Equation <NUM>, described above. Over this time, the frequency has changed by an amount that depends on the range, called fR, and given by the frequency rate of change multiplied by the delay time. This is given by Equation 4a.

The value of fR can be measured by the frequency difference between the transmitted signal <NUM> and returned signal 166a in a time domain mixing operation referred to as de-chirping. So, the range R is given by Equation 4b.

If the returned signal arrives after the pulse is completely transmitted, that is, if 2R/c is greater than τ, then Equations 4a and 4b are not valid. In this case, the reference signal can be delayed a known or fixed amount to ensure the returned signal overlaps 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 range that is added to range computed from Equation 4b. While the absolute range may be off due to uncertainty of the speed of light in the medium, this is a near-constant error and the relative ranges based on the frequency difference are still very precise.

In some circumstances, a spot illuminated (pencil beam cross section) by the transmitted light beam encounters two or more different scatterers at different ranges, such as a front and a back of a semitransparent object, or the closer and farther portions of an object at varying distances from the LIDAR, or two separate objects within the illuminated spot. In such circumstances, a second diminished intensity and differently delayed signal will also be received, indicated on graph <NUM> by trace 166b. This will have a different measured value of fR that gives a different range using Equation 4b. In some circumstances, multiple additional returned signals are received.

Graph <NUM> depicts the difference frequency fR between a first returned signal 166a and the reference chirp <NUM>. The horizontal axis <NUM> indicates time as in all the other aligned graphs in <FIG>, and the vertical axis <NUM> indicates frequency difference on a much expanded scale. Trace <NUM> depicts the constant frequency fR measured in response to the transmitted chirp, which indicates a particular range as given by Equation 4b. The second returned signal 166b, if present, would give rise to a different, larger value of fR (not shown) during de-chirping; and, as a consequence yield a larger range using Equation 4b.

De-chirping can be performed by directing both the reference optical signal and the returned optical signal to the same optical detector. The electrical output of the detector may be dominated by a beat frequency that is equal to, or otherwise depends on, the difference in the frequencies of the two signals converging on the detector. A Fourier transform of this electrical output signal will yield a peak at the beat frequency. This beat frequency is in the radio frequency (RF) range of Megahertz (MHz, <NUM> = <NUM><NUM> Hertz =<NUM><NUM> cycles per second) rather than in the optical frequency range of Terahertz (THz, <NUM> THz = <NUM><NUM> Hertz). Such signals can be processed by RF components, such as a Fast Fourier Transform (FFT) algorithm running on a microprocessor or a specially built FFT or other digital signal processing (DSP) integrated circuit. The return signal can be mixed with a continuous wave (CW) tone acting as the local oscillator (versus a chirp as the local oscillator). This leads to the detected signal which itself is a chirp (or whatever waveform was transmitted). In this case the detected signal can undergo matched filtering in the digital domain, though the digitizer bandwidth requirement may generally be higher. The positive aspects of coherent detection are otherwise retained.

In some implementations, the LIDAR system is changed to produce simultaneous up and down chirps. This approach can eliminate variability introduced by object speed differences, or LIDAR position changes relative to the object which actually does change the range, or transient scatterers in the beam, among others, or some combination. The approach may guarantee that the Doppler shifts and ranges measured on the up and down chirps are indeed identical and can be most usefully combined. The Doppler scheme may guarantee parallel capture of asymmetrically shifted return pairs in frequency space for a high probability of correct compensation.

<FIG> is a graph using a symmetric LO signal and shows the return signal in this frequency time plot as a dashed line when there is no Doppler shift, according to an implementation. The horizontal axis indicates time in example units of <NUM>-<NUM> seconds (tens of microseconds). The vertical axis indicates frequency of the optical transmitted signal relative to the carrier frequency fc or reference signal in example units of GigaHertz (<NUM><NUM> Hertz). During a pulse duration, a light beam comprising two optical frequencies at any time is generated. One frequency increases from f<NUM> to f<NUM> (e.g., <NUM> to <NUM> above the optical carrier) while the other frequency simultaneous decreases from f<NUM> to f<NUM> (e.g., <NUM> to <NUM> below the optical carrier). The two frequency bands e.g., band <NUM> from f<NUM> to f<NUM>, and band <NUM> from f<NUM> to f<NUM>) do not overlap so that both transmitted and return signals can be optically separated by a high pass or a low pass filter, or some combination, with pass bands starting at pass frequency fp. For example f<NUM> < f<NUM> < fp < f<NUM> < f<NUM>. As illustrated, the higher frequencies can provide the up chirp and the lower frequencies can provide the down chirp. In some implementations, the higher frequencies produce the down chirp and the lower frequencies produce the up chirp.

In some implementations, two different laser sources are used to produce the two different optical frequencies in each beam at each time. In some implementations, a single optical carrier is modulated by a single RF chirp to produce symmetrical sidebands that serve as the simultaneous up and down chirps. In some implementations, a double sideband Mach-Zehnder intensity modulator is used that, in general, may not leave much energy in the carrier frequency; instead, almost all of the energy goes into the sidebands.

As a result of sideband symmetry, the bandwidth of the two optical chirps can be the same if the same order sideband is used. In some implementations, other sidebands are used, e.g., two second order sideband are used, or a first order sideband and a non-overlapping second sideband is used, or some other combination.

When selecting the transmit (TX) and local oscillator (LO) chirp waveforms, it can be advantageous to ensure that the frequency shifted bands of the system take maximum advantage of available digitizer bandwidth. In general, this is accomplished by shifting either the up chirp or the down chirp to have a range frequency beat close to zero.

<FIG> is a graph similar to <FIG>, using a symmetric LO signal, and shows the return signal in this frequency time plot as a dashed line when there is a nonzero Doppler shift. In the case of a chirped waveform, the time separated I/Q processing (aka time domain multiplexing) can be used to overcome hardware requirements of other approaches. In that case, an AOM can be used to break the range-Doppler ambiguity for real valued signals. In some implementations, a scoring system can be used to pair the up and down chirp returns. In some implementations, I/Q processing can be used to determine the sign of the Doppler chirp.

<FIG> is a block diagram that illustrates example components of a high resolution range LIDAR system <NUM>, according to an implementation. Optical signals are indicated by arrows. Electronic wired or wireless connections are indicated by segmented lines without arrowheads. A laser source <NUM> emits a beam (e.g., carrier wave <NUM>) that is phase or frequency modulated in modulator 282a, before or after splitter <NUM>, to produce a phase coded or chirped optical signal <NUM> that has a duration D. A splitter <NUM> splits the modulated (or , as shown, the unmodulated) optical signal for use in a reference path <NUM>. A target beam <NUM>, also called transmitted signal herein, with most of the energy of the beam <NUM> can be produced. A modulated or unmodulated reference beam 207a, which can have a much smaller amount of energy that is nonetheless enough to produce good mixing with the returned light <NUM> scattered from an object (not shown), can also be produced. As depicted in <FIG>, the reference beam 207a is separately modulated in modulator 282b. The reference beam 207a passes through reference path <NUM> and is directed to one or more detectors as reference beam 207b. In some implementations, the reference path <NUM> introduces a known delay sufficient for reference beam 207b to arrive at the detector array <NUM> with the scattered light from an object outside the LIDAR within a spread of ranges of interest. In some implementations, the reference beam 207b is called the local oscillator (LO) signal, such as if the reference beam 207b were produced locally from a separate oscillator. In various implementations, from less to more flexible approaches, the reference beam 207b can be caused to arrive with the scattered or reflected field by: <NUM>) putting a mirror in the scene to reflect a portion of the transmit beam back at the detector array so that path lengths are well matched; <NUM>) using a fiber delay to closely match the path length and broadcast the reference beam with optics near the detector array, as suggested in <FIG>, with or without a path length adjustment to compensate for the phase or frequency difference observed or expected for a particular range; or, <NUM>) using a frequency shifting device (acousto-optic modulator) or time delay of a local oscillator waveform modulation (e.g., in modulator 282b) to produce a separate modulation to compensate for path length mismatch; or some combination. In some implementations, the object is close enough and the transmitted duration long enough that the returns sufficiently overlap the reference signal without a delay.

The transmitted signal is then transmitted to illuminate an area of interest, such as through one or more scanning optics <NUM>. The detector array can be a single paired or unpaired detector or a <NUM> dimensional (1D) or <NUM> dimensional (2D) array of paired or unpaired detectors arranged in a plane roughly perpendicular to returned beams <NUM> from the object. The reference beam 207b and returned beam <NUM> can be combined in zero or more optical mixers <NUM> to produce an optical signal of characteristics to be properly detected. The frequency, phase or amplitude of the interference pattern, or some combination, can be recorded by acquisition system <NUM> for each detector at multiple times during the signal duration D. The number of temporal samples processed per signal duration or integration time can affect the down-range extent. The number or integration time can be a practical consideration chosen based on number of symbols per signal, signal repetition rate and available camera frame rate. The frame rate is the sampling bandwidth, often called "digitizer frequency. " The only fundamental limitations of range extent are the coherence length of the laser and the length of the chirp or unique phase code before it repeats (for unambiguous ranging). This is enabled because any digital record of the returned heterodyne signal or bits could be compared or cross correlated with any portion of transmitted bits from the prior transmission history.

The acquired data is made available to a processing system <NUM>, such as a computer system described below with reference to <FIG>, or a chip set described below with reference to <FIG>. A scanner control module <NUM> provides scanning signals to drive the scanning optics <NUM>. The scanner control module <NUM> can include instructions to perform one or more steps of the method <NUM> related to the flowchart of <FIG>. A signed Doppler compensation module (not shown) in processing system <NUM> can determine the sign and size of the Doppler shift and the corrected range based thereon along with any other corrections. The processing system <NUM> can include a modulation signal module (not shown) to send one or more electrical signals that drive modulators 282a, 282b. In some implementations, the processing system also includes a vehicle control module <NUM> to control a vehicle on which the system <NUM> is installed.

Optical coupling to flood or focus on a target or focus past the pupil plane are not depicted. As used herein, an optical coupler is any component that affects the propagation of light within spatial coordinates to direct light from one component to another component, such as a vacuum, air, glass, crystal, mirror, lens, optical circulator, beam splitter, phase plate, polarizer, optical fiber, optical mixer, among others, alone or in some combination.

<FIG> also illustrates example components for a simultaneous up and down chirp LIDAR system according to an implementation. As depicted in <FIG>, the modulator 282a can be a frequency shifter added to the optical path of the transmitted beam <NUM>. In some implementations, the frequency shifter is added to the optical path of the returned beam <NUM> or to the reference path <NUM>. The frequency shifter can be added as modulator 282b on the local oscillator (LO, also called the reference path) side or on the transmit side (before the optical amplifier) as the device used as the modulator (e.g., an acousto-optic modulator, AOM) has some loss associated and it can be disadvantageous to put lossy components on the receive side or after the optical amplifier. The optical shifter can shift the frequency of the transmitted signal (or return signal) relative to the frequency of the reference signal by a known amount Δfs, so that the beat frequencies of the up and down chirps occur in different frequency bands, which can be picked up, e.g., by the FFT component in processing system <NUM>, in the analysis of the electrical signal output by the optical detector <NUM>. For example, if the blue shift causing range effects is fB, then the beat frequency of the up chirp will be increased by the offset and occur at fB + Δfs and the beat frequency of the down chirp will be decreased by the offset to fB - Δfs. Thus, the up chirps will be in a higher frequency band than the down chirps, thereby separating them. If Δfs is greater than any expected Doppler effect, there will be no ambiguity in the ranges associated with up chirps and down chirps. The measured beats can then be corrected with the correctly signed value of the known Δfs to get the proper up-chirp and down-chirp ranges. In some implementations, the RF signal coming out of the balanced detector is digitized directly with the bands being separated via FFT. In some implementations, the RF signal coming out of the balanced detector is pre-processed with analog RF electronics to separate a low-band (corresponding to one of the up chirp or down chip) which can be directly digitized and a high-band (corresponding to the opposite chirp) which can be electronically down-mixed to baseband and then digitized. Various such implementations offer pathways that match the bands of the detected signals to available digitizer resources. In some implementations, the modulator 282a is excluded (e.g. direct ranging).

<FIG> is a block diagram that illustrates a saw tooth scan pattern for a hi-res Doppler system. The scan sweeps through a range of azimuth angles (e.g. horizontally along axis <NUM>) and inclination angles (e.g. vertically along axis <NUM> above and below a level direction at zero inclination). Various can patterns can be used, including adaptive scanning. <FIG> is an image that illustrates an example speed point cloud produced by a hi-res Doppler LIDAR system.

<FIG> is a block diagram that illustrates example components of the scanning optics <NUM> of the system <NUM> of <FIG>. In an implementation, the scanning optics <NUM> is a two-element scan system including an oscillatory scan element <NUM> that controls actuation of the beam <NUM> along one axis (e.g. between angles -A and +A along axis <NUM> of <FIG>) and a unidirectional constant speed scan element <NUM> (e.g. polygon deflector) that controls actuation of the beam <NUM> in one direction along another axis (e.g. along axis <NUM> of <FIG>). The scanning optics <NUM> can be used in the system <NUM> of <FIG>. The scanning optics <NUM> can be used in systems other than LIDAR systems such as the system <NUM>, including laser etching, surface treatment, barcode scanning, and refractive scanning of a beam. In some implementations, the oscillatory scan element <NUM> is provided without the unidirectional scan element <NUM> or in other implementations, the unidirectional scan element <NUM> is provided without the oscillatory scan element <NUM>. In an implementation, the oscillatory scan element <NUM> actuates the beam <NUM> in opposing directions along the axis <NUM> between the angles -A and +A as the unidirectional constant speed scan element <NUM> simultaneously actuates the beam <NUM> in one direction along the axis <NUM>. In an implementation, the actuation speed of the oscillatory scan element <NUM> is bidirectional and greater than the unidirectional actuation speed of the constant speed scan element <NUM>, so that the beam <NUM> is scanned along the axis <NUM> (e.g. between angles -A to +A) back and forth multiple times for each instance that the beam is scanned along the axis <NUM> (e.g. from angle =D to +D).

In some implementations, the scanner control module <NUM> provides signals that are transmitted from the processing system <NUM> to a motor <NUM> that is mechanically coupled to the oscillatory scan element <NUM> and/or the unidirectional scan element <NUM>. In an implementation, two motors are provided where one motor is mechanically coupled to the oscillatory scan element <NUM> and another motor is mechanically coupled to the unidirectional scan element <NUM>. In an implementation, based on the signals received from the processing system <NUM>, the motor <NUM> rotates the oscillatory scan element <NUM> and/or the unidirectional scan element <NUM> based on a value of a parameter (e.g. angular speed, etc.) in the signal. The scanner control module <NUM> can determine the value of the parameter in the signal so that the beam <NUM> is scanned by the oscillatory scan element <NUM> by a desired scan pattern (e.g. between angles -A to +A along axis <NUM>) and/or by the unidirectional constant speed scan element <NUM> in a desired scan pattern (e.g. between angles =D to +D along axis <NUM>).

<FIG> is a block diagram that illustrates an example of an assembly <NUM> including a polygon reflector <NUM> rotated by a motor (not shown) to reflect an incident beam <NUM> over a field of view <NUM> (e.g. between a first and second angle within the plane of <FIG>). The polygon reflector <NUM> includes a plurality of reflective facets <NUM> (e.g. six in a hexagon reflector). Each facet <NUM> reflects the incident beam <NUM> into a reflected beam <NUM> which defines the field of view <NUM> as the reflector <NUM> rotates about a rotation axis. The field of view <NUM> can be defined when the incident beam <NUM> encounters a first and second break in the facet <NUM>. The field of view <NUM> can be limited by the position of the incident beam <NUM> that is co-planar with the facet <NUM>, since the field of view <NUM> cannot encompass angles coinciding with the incident beam <NUM>. The field of view <NUM> cannot encompass the incident beam <NUM> since no useful return beam data can be gathered for those scan angles. Thus, the polygon reflector <NUM> has a limited field of view <NUM> due to the nature of the incident beam <NUM> that is coplanar and incident on the exterior surface of the facet <NUM>. This field of view <NUM> can limit a duty cycle of the polygon reflector <NUM>, which is defined as a time that the facets <NUM> reflect the beam <NUM> over the field of view <NUM> to a total time of operation of the assembly <NUM>. This duty cycle may be about <NUM>% with conventional polygon reflectors <NUM>.

<FIG> is a block diagram that illustrates an example of an assembly <NUM> including a polygon deflector <NUM> rotated by a motor <NUM> to deflect (e.g. refract) an incident beam <NUM> from an interior <NUM> of the deflector <NUM>. The polygon deflector <NUM> can include the unidirectional constant speed scan element <NUM>, which may or may not be used in the system <NUM> of <FIG>. The incident beam <NUM> can be shaped (e.g., collimated) by an optic <NUM> (e.g. one or more lenses or mirrors) positioned within an interior <NUM> of the polygon deflector <NUM>. The incident beam <NUM> can be directed to the interior <NUM> from outside the polygon deflector <NUM> before it is shaped by the optic <NUM> within the interior <NUM>. In some implementations, a plurality of incident beams <NUM> are provided and shaped by the optic <NUM> before being directed at the facet <NUM>. The facet <NUM> can refract the incident beam <NUM> as the refracted beam <NUM> based on Snell's law, according to the index of refraction of the facet <NUM> and angle of incidence of the beam <NUM> on the facet <NUM>. In an implementation, the field of view <NUM> is defined by the refracted beam <NUM> between facet breaks of the incident beam <NUM> on a first facet <NUM>. In an implementation, the field of view <NUM> is greater than the field of view <NUM> in the polygon reflector <NUM>. In an implementation, the field of view <NUM> is about <NUM> degrees (e.g. polygon deflector <NUM> made from high index material such as Silicon) or about <NUM> degrees (e.g. polygon deflector <NUM> made from non-exotic material) as compared with the field of view <NUM> which is less than or about <NUM> degrees. In an implementation, a width of the polygon deflector <NUM> (e.g. defined as a distance between opposing facets <NUM>) is about the same as a width of the polygon reflector <NUM> (e.g. defined as a distance between opposing facets <NUM>) and a width of each facet <NUM> is about the same as a width of each facet <NUM>. Thus, the savings in space of the assembly <NUM> as compared to the assembly <NUM> can be due to the assembly <NUM> not requiring external components of the assembly <NUM> (e.g. collimator to direct the incident beam <NUM>) relative to the polygon deflector <NUM>. In an implementation, the polygon deflector <NUM> has a width of about <NUM> (e.g. measured between facets <NUM> on opposite sides of the deflector <NUM>) and about <NUM> length along each facet <NUM>. In an implementation, the polygon reflector <NUM> has similar dimensions as the polygon deflector <NUM> but has an additional collimator (e.g. to direct the incident beam <NUM>) measuring about <NUM> and spaced about <NUM> from the polygon reflector <NUM>. Thus, the front area length of the polygon deflector <NUM> is about <NUM> as compared to the polygon reflector <NUM> which is about <NUM>. In an implementation, the incident beam <NUM> is continuously refracted over the field of view <NUM> by each facet <NUM> as the polygon deflector404 is rotated by the motor <NUM>. In an implementation, the duty cycle of the polygon deflector404 is greater than <NUM>% and/or greater than about <NUM>% and/or about <NUM>%. The duty cycle can be based on a ratio of a first time based on refraction of the incident beam <NUM> to a second time based on rotation of the polygon deflector <NUM> and shaping of the incident beam <NUM>.

<FIG> is a schematic diagram that illustrates an example of a cross-sectional side view of an assembly <NUM> including a polygon deflector <NUM> rotated by a motor <NUM> to refract an incident beam <NUM> from an interior <NUM> of the deflector <NUM>. <FIG> is a schematic diagram that illustrates an example of a cross-sectional top view of the polygon deflector <NUM> of <FIG>. In an implementation, the polygon deflector <NUM> includes a plurality of facets <NUM>. In an implementation, the polygon deflector <NUM> is made from material that is transmissive or has high transmission characteristics (e.g. above <NUM>%) at a wavelength of the beam <NUM>. Although <FIG> depict a hexagon deflector (e.g. six sides), various implementations are not limited to a hexagon deflector and may include any polygon deflector with any number of facets and need not be a regular polygon with equal angles and equal width of the facets <NUM> but may be an irregular polygon with unequal angles or unequal widths of the facets <NUM>, for example.

The polygon deflector <NUM> can be rotatably coupled to a motor <NUM>. In an implementation, the motor <NUM> rotates the polygon deflector <NUM> about a rotation axis <NUM>. In an implementation, the rotation axis <NUM> is orthogonal to a first plane <NUM> (plane of <FIG>) in which the polygon deflector <NUM> rotates with a rotation velocity <NUM>. Although <FIG> depict that the rotation velocity <NUM> is clockwise, the rotation velocity <NUM> can be counterclockwise. In an implementation, the magnitude of the rotation velocity is about <NUM> revolutions per minute (rpm) to about <NUM> rpm and/or about <NUM> rpm to about <NUM>,<NUM> rpm. In some implementations, the magnitude of the rotation velocity can be an order of magnitude more than the numerical ranges disclosed herein. In an implementation, the motor <NUM> is a brushless DC (BLDC) motor that includes a plurality of bearings 520a, 520b rotatably coupled to an inner surface <NUM> of the polygon deflector <NUM> that defines the interior <NUM>. The motor <NUM> can include a rotor <NUM> actuated by coils <NUM> to rotate the polygon deflector <NUM> about the rotation axis <NUM>. The motor <NUM> can include a stator <NUM> that is partially positioned in the interior <NUM> of the polygon deflector <NUM> and defines a cavity <NUM> where optics are positioned to steer the incident beams <NUM> on the facet <NUM>. The stator can output an electromagnetic field to drive the coils <NUM> to actuate the rotor <NUM>. In an implementation, the motor <NUM> is a BLDC motor manufactured by Nidec® Corporation, Braintree MA.

In an implementation, one or more optic are positioned in the interior <NUM> of the polygon deflector <NUM> to steer the incident beams <NUM> on the facet <NUM>. In an implementation, the optics include a lens assembly <NUM> that includes one or more lenses and/or a pair of mirrors 528a, 528b. In an implementation, the lens assembly <NUM> is a free form toric single lens.

<FIG> is a schematic diagram that illustrates an example of a cut away cross-sectional view of a single toric lens <NUM>' used in the assembly <NUM> of <FIG>. In an implementation, the toric lens <NUM>' is used in place of the lens assembly <NUM>. In an implementation, the toric lens <NUM>' is selected since it features some characteristics of a cylindrical lens and other characteristics of a spherical lens and/or is a hybrid lens in a shape of a doughnut that is an optical combination of the first and second lens of the lens assembly <NUM>. In an implementation, software instructions of the module <NUM> can include one or more instructions to determine one or more parameter values of the toric lens <NUM>' that is equivalent to the lens assembly <NUM>. In an implementation, the beams <NUM> are transmitted to the interior <NUM> with a planar fiber array <NUM> that is mounted in a focal plane (e.g. plane <NUM> of <FIG>) of the lens assembly <NUM>.

<FIG> is a schematic diagram that illustrates an example of a side view of a planar fiber array <NUM> of the assembly <NUM> of <FIG>, according to an implementation. In an implementation, <FIG> is taken along the same plane <NUM> as <FIG> (e.g. the focal plane of the lens assembly <NUM>). In an implementation, the planar fiber array <NUM> includes a plurality of fibers 582a, 582b, 582c that are spaced apart by respective transverse spacing 584a, 584b. Although three fibers <NUM> are depicted in the planar fiber array <NUM> of <FIG>, this is merely one example and more or less than three fibers <NUM> can be provided in the planar fiber array <NUM>. In some implementations, the transverse spacing 584a, 584b is equal between adjacent fiber pairs. In some implementations, the transverse spacing 584a, 584b is unequal between adjacent fiber pairs (e.g. the spacing 584a between fibers 582a, 582b is not the same as spacing 584b between fibers 582b, 582c). In an implementation, a respective beam <NUM> is transmitted from a tip of each fiber <NUM> and thus a plurality of beams <NUM> are transmitted within the interior <NUM> (e.g. the cavity <NUM> of the stator <NUM>) from the tips of the fibers <NUM>. In one example implementation, the planar fiber array <NUM> is a fixed spacing fiber array and planar lightwave circuit (PLC) connections, manufactured by Zhongshan Meisu Technology Company, Zhongshan, Guangdong Province, China.

As depicted in <FIG>, the plurality of beams <NUM> transmitted from the planar fiber array <NUM> can be reflected by a first mirror 528a to a second mirror 528b which in turn reflects the plurality of beams <NUM> to the lens assembly <NUM>. In an implementation, the mirrors 528a, 528b are angled orthogonally to each other (e.g. <NUM> degrees or in a range from about <NUM> degrees to about <NUM> degrees) so that the beams <NUM> reflected by the mirror 528b are oriented in a direction that is about <NUM> degrees from the direction of the beams <NUM> incident on the mirror 528a. In an implementation, the second mirror 528b has a longer reflective surface than the first mirror 528a since the beams <NUM> cover a wider angular spread at the second mirror 528b than the first mirror 528a. In an example implementation, the mirrors <NUM> are manufactured by Edmunds® Optics of Barrington NJ.

<FIG> is a schematic diagram that illustrates an example of a side view of a lens assembly <NUM> of the assembly <NUM> of <FIG>, according to an implementation. In an implementation, <FIG> is taken along the plane <NUM> of <FIG> (e.g. orthogonal to the plane <NUM> of <FIG>). In an implementation, the lens assembly <NUM> includes a first lens <NUM> that collimates diverging beams <NUM> that are reflected to the first lens <NUM> from the second mirror 528b. In an implementation, the first lens <NUM> is an aspheric lens with a focal length that is selected so that the diverging beams <NUM> from the second mirror 528b are collimated by the aspheric lens. In an implementation, the focal length of the aspheric lens extends beyond the second mirror 528b.

As depicted in <FIG>, collimated beams <NUM>' from the first lens <NUM> can be diverted by a second lens <NUM>. In an implementation, where the second lens <NUM> is a positive cylindrical lens that converges the beams based on a focal length of the positive cylindrical lens. In an implementation, the converging beams <NUM>" from the second lens <NUM> are refracted by the inner surface <NUM> of the polygon deflector <NUM> that defines the interior <NUM> so that the beams <NUM>"' are collimated within the polygon deflector <NUM> and incident on the facet <NUM>. In an example implementation, the focal length of the first lens <NUM> is about <NUM> - <NUM> and/or about <NUM> - <NUM>, creating a beam <NUM>' with a diameter of about <NUM> - <NUM> and/or about <NUM> - <NUM> using a standard fiber of about <NUM> mode field diameter (MFD) and/or about <NUM> - <NUM> MFD. In an implementation, a spacing 584a, 584b of the beams in the fiber array <NUM> would be increments or multiples of about <NUM>, yielding a total subtended angular spread <NUM> of about <NUM>-<NUM> degrees. In one implementation, a curvature of the positive cylindrical lens is the same as a curvature of the inner surface <NUM> and/or a transition of an index of refraction from the positive cylindrical lens to air is an opposite of a transition of the index of refraction from air to the polygon deflector <NUM> across the inner surface <NUM>. In an implementation, the index of refraction of the second lens <NUM> is about <NUM> or in a range from about <NUM> to about <NUM> and the index of refraction of the polygon deflector <NUM> is about <NUM> of in a range from about <NUM> to about <NUM> and the curvature of the positive cylindrical lens and inner surface <NUM> is about <NUM> radius and/or in a range from about <NUM> to about <NUM> and/or in a range from about <NUM> to about <NUM>. The collimated beams <NUM>"' incident on the facet 506a are depicted in <FIG> which shows the beams <NUM>"' in the plane <NUM> or plane of <FIG>.

<FIG> is a schematic diagram that illustrates an example of the polygon deflector <NUM> of <FIG> in two rotation positions 550a, 550b. In an implementation, the collimated beams <NUM>"' incident on the facet 506a from the interior <NUM> are refracted by the facet 506a, according to Snell's law: <MAT> where n<NUM> is the index of refraction of the polygon deflector <NUM>, θ<NUM> is the angle of incidence of the beams <NUM>"' on the facet 506a relative to a normal at the (inside of) the facet 506a, n<NUM> is the index of refraction of a medium (e.g. air = <NUM>) surrounding the polygon deflector <NUM> where the beam <NUM> is being refracted and θ<NUM> is the angle of refraction of the beam 512a relative to a normal to the (outside of) the facet 506a. The angle of refraction can be measured as an angle 552a relative to an axis <NUM> that is orthogonal to the rotation axis <NUM>. As depicted in <FIG>, the plurality of beams 512a are refracted at the angle 552a (relative to the axis <NUM>). As the polygon deflector <NUM> rotates from a first rotation position 550a to a second rotation position 550b about the axis <NUM>, the incident beams <NUM>"' can go from being refracted by one side of the facet 506a (e.g. refracted beams 512a at the angle 552a) to an opposite side of the facet 506a (e.g. refracted beams 512b at an angle 552b), relative to the axis <NUM>, to define a field of view <NUM> of the refracted beams <NUM>. In an implementation, the field of view <NUM> is about <NUM> degrees (e.g. where the index of refraction of the polygon deflector <NUM> is about <NUM>) and about <NUM> degrees (e.g. where the index of refraction is higher for high index of refraction material, such as Silicon).

<FIG> is a schematic diagram that illustrates an example of a partial cross-sectional side view of the polygon deflector <NUM> of <FIG>. In an implementation, <FIG> is within the plane <NUM> of <FIG>. In an implementation, the incident beams <NUM>"' are depicted in the plane <NUM> and an angular spread <NUM> of the incident beams <NUM>"' is shown. In an implementation, the angular spread <NUM> is related to the transverse spacing <NUM> of the fibers <NUM> of the planar fiber array <NUM> by: <MAT> where y is a distance of the fibers <NUM> outside the focal plane of the lens assembly <NUM>, e.g. the distance of the fibers <NUM> outside the plane <NUM> and the focal length is the focal length of the lens <NUM> of the lens assembly <NUM>. In some implementations, the facet <NUM> forms a non-orthogonal angle <NUM> with a top or bottom of the polygon deflector <NUM>. In an implementation, the non-orthogonal angle <NUM> is any angle other than <NUM> degrees and/or an angle in a range from about <NUM> degrees to about <NUM> degrees and/or an angle in a range from about <NUM> degrees to about <NUM> degrees. Additionally, although the non-orthogonal angle <NUM> in <FIG> is less than <NUM> degrees, the non-orthogonal angle <NUM> can be greater than <NUM> degrees, for example the non-orthogonal angle <NUM> for the facet 506b in <FIG>. The angle <NUM> can be orthogonal and/or about <NUM> degrees for some or all of the facet <NUM>. The angle <NUM> can be non-orthogonal for each facet <NUM> but varies for one or more facets, e.g. less than about <NUM> degrees for one or more facets <NUM> but greater than about <NUM> degrees for one or more facets <NUM>. An advantage of an arrangement with one or more facets <NUM> with the angle <NUM> less than <NUM> degrees and one or more facets <NUM> with the angle <NUM> greater than <NUM> degrees can be that the refracted beams <NUM> in the plane <NUM> (<FIG>) can alternate between above the horizontal axis <NUM> (for the facet <NUM> with the angle <NUM> less than <NUM> degrees) to below the horizontal axis <NUM> (for the facet <NUM> with the angle <NUM> greater than <NUM> degrees). This can permit the beams <NUM> to be scanned over multiple ranges within the plane <NUM>, e.g. to capture return beam data from objects in these multiple ranges.

In an implementation, the incident beams <NUM>"' on the facet <NUM> have an angular spread <NUM> which widens to a greater angular spread <NUM> after refraction by the facet <NUM>. In an implementation, the angular spread <NUM> widens based on a ratio of the index of refraction of the polygon deflector <NUM> (e.g. n = <NUM>) to an index of refraction of the medium (e.g. air = <NUM>) surrounding the polygon deflector <NUM>. In an example implementation, if each beam <NUM>"' has an angular spacing of about <NUM> degree incident on the facet <NUM>, each refracted beam <NUM> has an angular spacing of about <NUM> degrees, e.g. a product of the angular spacing of the beams <NUM>"' in the polygon deflector and the index ratio.

In an implementation, in addition to widening the angular spread, a net direction of the beams <NUM> in the plane <NUM> is changed by refraction at the facet <NUM>. In an implementation, a centerline <NUM> of the incident beams <NUM>"' on the facet <NUM> is refracted by the facet <NUM> as a centerline <NUM> of the refracted beams <NUM>, based on Snell's law in equation <NUM> within the plane <NUM>. Thus, in addition to the increased angular spread <NUM> of the refracted beams <NUM>, the facet <NUM> can vary the direction of the centerline <NUM> of the refracted beams <NUM>, relative to the centerline <NUM> of the incident beams <NUM>". In an implementation, variation of the angular spread <NUM> changes on the order of <NUM>%, e.g. from angular spread <NUM> of about <NUM> degree between beams <NUM> to angular spread <NUM> of about <NUM> degrees between beams <NUM>. In an implementation, the centerline <NUM> changes on the order of +<NUM>, +<NUM>, -<NUM>, -<NUM> degrees relative to the centerline <NUM>.

In some implementations a vehicle is controlled at least in part based on data received from a hi-res Doppler LIDAR system mounted on the vehicle.

<FIG> is a block diagram that illustrates an example system <NUM> that includes at least one hi-res Doppler LIDAR system <NUM> mounted on a vehicle <NUM>, according to an implementation. In an implementation, the LIDAR system <NUM> is similar to one of the LIDAR systems <NUM>. The vehicle has a center of mass indicted by a star <NUM> and travels in a forward direction given by arrow <NUM>. In some implementations, the vehicle <NUM> includes a component, such as a steering or braking system (not shown), operated in response to a signal from a processor, such as the vehicle control module <NUM> of the processing system <NUM>. In some implementations the vehicle has an on-board processor <NUM>, such as chip set depicted in <FIG>. In some implementations, the on board processor <NUM> is in wired or wireless communication with a remote processor, as depicted in <FIG>. In an implementation, the processing system <NUM> of the LIDAR system is communicatively coupled with the on-board processor <NUM> or the processing system <NUM> of the LIDAR is used to perform the operations of the on board processor <NUM> so that the vehicle control module <NUM> causes the processing system <NUM> to transmit one or more signals to the steering or braking system of the vehicle to control the direction and speed of the vehicle (e.g., to perform collision avoidance with respect to one or more objects detected using information received from the LIDAR system <NUM>). The vehicle control module <NUM> can control operation of the processing system <NUM> using at least one of range data or velocity data (including direction data) determined using the LIDAR system <NUM>. The hi-res Doppler LIDAR uses a scanning beam <NUM> that sweeps from one side to another side, represented by future beam <NUM>, through an azimuthal field of view <NUM>, as well as through vertical angles illuminating spots in the surroundings of vehicle <NUM>. In some implementations, the field of view is <NUM> degrees of azimuth. In some implementations the scanning optics <NUM> including the oscillatory scan element <NUM> and/or unidirectional scan element <NUM> can be used to scan the beam through the azimuthal field of view <NUM> or through vertical angles. In an implementation, inclination angle field of view is from about +<NUM> degrees to about -<NUM> degrees or a subset thereof. In an implementation, the maximum design range over the field of view <NUM> is about <NUM> meters or in a range from about <NUM> meters to about <NUM> meters.

In some implementations, the vehicle includes ancillary sensors (not shown), such as a GPS sensor, odometer, tachometer, temperature sensor, vacuum sensor, electrical voltage or current sensors, among others. In some implementations, a gyroscope <NUM> is included to provide rotation information.

<FIG> is a flow chart that illustrates an example method <NUM> for optimizing a scan pattern of a LIDAR system. In an implementation, the method <NUM> is for optimizing a scan pattern of a beam in a first direction between a first angle and a second angle based on a desired waveform with a linear slope. In some implementations, the method <NUM> is for optimizing the scan pattern of a LIDAR system mounted on an autonomous vehicle. Although steps are depicted in <FIG> as integral steps in a particular order for purposes of illustration, one or more steps, or portions thereof, can be performed in a different order, or overlapping in time, in series or in parallel, or are omitted, or one or more additional steps are added, or the method is changed in some combination of ways.

In step <NUM>, the polygon deflector <NUM> is rotated with a motor about a first axis. In an implementation, in step <NUM> the polygon deflector <NUM> is rotated with the motor <NUM> about the axis <NUM>. In an implementation, in step <NUM> one or more signals is transmitted to the motor <NUM>, <NUM> to rotate the polygon deflector <NUM>, <NUM>, where the signal includes data that indicates one or more values of a parameter of the rotation (e.g. a value of a rotation speed, a direction of the rotation velocity, a duration of the rotation, etc.).

In step <NUM>, one or more beams are transmitted within the interior <NUM> of the polygon deflector <NUM>. In an implementation, in step <NUM> a plurality of beams <NUM> are transmitted from the planar fiber array <NUM> within the interior <NUM> of the polygon deflector <NUM>. In an implementation, in step <NUM> a light source (e.g. laser source) is positioned within the interior <NUM> to transmit the beam from within the interior <NUM>.

In step <NUM>, the one or more beams are shaped with one or more optics <NUM> within the interior <NUM> so that the beams are collimated and incident on the facet <NUM> from the interior <NUM> of the polygon deflector <NUM>. In an implementation, in step <NUM>, the plurality of beam <NUM> from the planar fiber array <NUM> are reflected by a pair of mirrors 528a, 528b to a lens assembly <NUM> including a first lens <NUM> positioned within the interior <NUM>.

In step <NUM>, the plurality of beams <NUM> from the mirrors 528a, 528b in step <NUM> are collimated into beams <NUM>' by the first lens <NUM>. In an implementation, the first lens <NUM> is an aspheric lens.

In step <NUM>, the plurality of beams <NUM>' from the first lens <NUM> in step <NUM> are diverted by a second lens <NUM>. In an implementation, the second lens <NUM> is a positive cylindrical lens and the beams <NUM>' are converged into converging beams <NUM>" that are incident on the inner surface <NUM> of the polygon deflector <NUM>.

In step <NUM>, the converging beams <NUM>" from step <NUM> are collimated by the inner surface <NUM> of the polygon deflector <NUM> so that collimated beams <NUM>"' are transmitted into the polygon deflector <NUM> and incident on the facet <NUM>.

In step <NUM>, the collimated beams <NUM>"' incident on the facet <NUM> are refracted as beams <NUM> by the facet <NUM> into a first plane <NUM> orthogonal to the rotation axis <NUM> from a first angle to a second angle that defines a field of view <NUM> within the plane <NUM>. In an implementation, the field of view <NUM> is defined by the collimated beams <NUM>"' passing from one side to an opposite side of a facet <NUM> and ends when the collimated beams <NUM>"' pass over a break in the facet <NUM>. In an implementation, once the collimated beams <NUM>"' pass onto an adjacent facet <NUM>, the refracted beams <NUM> are re-scanned through the field of view <NUM> within the plane <NUM>. In another implementation, in step <NUM> the collimated beams <NUM>"' incident on the facet <NUM> are refracted as beams <NUM> into a second plane <NUM> that is orthogonal to the first plane <NUM>. In an implementation, the refraction of the beams <NUM>"' in the second plane <NUM> involves an increase of the angular spread <NUM> of the beams <NUM>, and/or a refraction of the centerline of the beams <NUM> and/or rotation of the beams <NUM> within the plane <NUM> based on the rotation of the polygon deflector <NUM>. The polygon deflector <NUM> can have a duty cycle greater than <NUM>%, wherein the duty cycle is based on a ratio of a first time based on the refracting step to a second time based on the rotating and shaping steps. The duty cycle can be greater than <NUM>%.

Systems and methods in accordance with the present disclosure can use multiple scanners to enable outputted beams to be steered in a greater number of directions, such as to output beams across more elevation angles. For example, a LIDAR system can include two concentric polygon scanners with facets that have varied inclination angles. An optic can output a beam of collimated light that a first polygon scanner refracts to a second polygon scanner, which refracts the beam to output the beam from the LIDAR system. The varied inclination angles of the polygon scanners, which can be rotated relative to each other and the optic, can enable varied elevation angles for the outputted beams. This can increase the amount of signal information that can be received based on the outputted beams in a given period of time while maintaining a compact form factor for the LIDAR system, such as to determine range and velocity regarding an object that can be determined from return beams from the object reflecting or otherwise scattering the outputted beams, such as to improve signal to noise ratio.

<FIG> is a schematic diagram of a LIDAR system <NUM> according to the present invention. The LIDAR system <NUM> and components thereof can incorporate features of various devices and systems described herein, such as LIDAR system <NUM>, the assemblies <NUM>, <NUM>, <NUM> and the polygon deflectors <NUM>, <NUM>, and the vehicle control module <NUM>. For example, the LIDAR system <NUM> can operate with or include components of the LIDAR system <NUM>, such as the scanning optics <NUM> or the detector array <NUM>, to determine at least one of range to or velocity of an object using a return beam from the object, as well as to control operation of a vehicle responsive to the at least one of the range or the velocity.

The LIDAR system <NUM> includes a first polygon scanner <NUM>. The first polygon scanner <NUM> includes first facets <NUM> around a first axis of rotation <NUM> and a first body <NUM> outward from the first facets <NUM> relative to the first axis of rotation <NUM>. For example, as depicted in <FIG>, the first polygon scanner <NUM> can include five first facets 708a, 708b, 708c, 708d, and 708e. The first facets <NUM> can form a polygon shape around the first axis of rotation <NUM>, such that each first facet <NUM> is connected with two adjacent first facets <NUM>. The first facets <NUM> can refract received beams of light to change an angle of the light from an entrance, air-to-facet interface (e.g., inward side) to an exit side (e.g., oautward side) of the first facets <NUM>.

The number of first facets <NUM> can be determined based on factors such a number of signal lines to detect, a field of view of the first facets <NUM>, a number of transitions between the first facets <NUM>, and a size of the first polygon scanner <NUM>. For example, as the number of first facets <NUM> increases, more signal lines can be detected (e.g., a greater number of elevation angles can be used for outputting beams), the size of first polygon scanner <NUM> can increase, a field of view of the first facets <NUM> can decrease (e.g., the first facets <NUM> can have a field of view equal to <NUM> / number of facets, such that the five first facets <NUM> as depicted in <FIG> can each have a field of view of <NUM> degrees, while the facets of a polygon scanner having three facets can each have a field of view of <NUM> degrees), and the number of transitions (e.g., transitions between adjacent first facets <NUM>) can increase. The transitions may reduce surface area of the first polygon scanner <NUM> that can effectively be used to output beams. The number of first facets <NUM> can be greater than or equal to three and less than or equal to ten.

The first polygon scanner <NUM> can define a first maximum thickness <NUM> from an innermost portion (e.g., closest to the first axis of rotation <NUM>) to an outermost portion (e.g., furthest from the first axis of rotation <NUM>) of the first polygon scanner <NUM>. The first maximum thickness <NUM> can be greater than or equal to <NUM> millimeters and less than or equal to <NUM> millimeters.

Referring further to <FIG>, the LIDAR system <NUM> includes a second polygon scanner <NUM> that can be located or positioned outward from the first polygon scanner <NUM> relative to the first axis of rotation <NUM> (i.e., the facets of the second polygon scanner are located outward of those of the first polygon scanner). The second polygon scanner <NUM> can incorporate features of the first polygon scanner <NUM>. A bearing <NUM> can be positioned between the first polygon scanner <NUM> and the second polygon scanner <NUM> to enable the first polygon scanner <NUM> to rotate over the second polygon scanner <NUM>. The bearing <NUM> can be a refractive index fluid bearing.

The second polygon scanner <NUM> includes second facets <NUM> around a second axis of rotation. The second axis of rotation is the same as (e.g., coincide with) the first axis of rotation <NUM>, or is parallel with (e.g., parallel with and spaced from) the first axis of rotation <NUM>. As depicted in <FIG>, the second polygon scanner <NUM> can include five second facets 724a, 724b, 724c, 724d, 724e. The second facets <NUM> can form a polygon shape around the second axis of rotation, such that each second facet <NUM> is connected with two adjacent second facets <NUM>. The second facets <NUM> can refract received beams of light to change an angle of the light from an entrance side (e.g., inward side) to an exit, facet-to-air interface (e.g., outward side) of the second facets <NUM>.

The number of second facets <NUM> can be determined based on factors such a number of signal lines to detect, a field of view of the second facets <NUM>, a number of transitions between the second facets <NUM>, and a size of the second polygon scanner <NUM>. For example, as the number of second facets <NUM> increases, more signal lines can be detected, the size of the second polygon scanner <NUM> can increase, a field of view of the second facets <NUM> can decrease, and the number of transitions can increase. The number of second facets 724a can be greater than or equal to three and less than or equal to ten.

The first facets <NUM> and the second facets <NUM> can have varying angles (e.g., inclination angles) relative to the respective first and second axes of rotation, which can be used to control the elevation angle of the light outputted by the second facets <NUM>. For example, as depicted in <FIG>, a particular first facet <NUM> of the first polygon scanner <NUM> can define a first angle <NUM> for an inward surface <NUM> relative to the first axis of rotation <NUM>, and a particular second facet <NUM> of the second polygon scanner <NUM> can define a second angle <NUM> for an outward surface <NUM> relative to the second axis of rotation (which, as depicted in <FIG>, coincides with the first axis of rotation <NUM>).

At least two first facets <NUM> of the first facets <NUM> can define different first angles <NUM> from each other. At least two second facets <NUM> can define different second angles <NUM> relative to each other. An order of the angles <NUM>, <NUM> (e.g., which facets <NUM>, <NUM> define particular angles <NUM>, <NUM>) may be varied, such as to balance the masses of the respective polygon scanners <NUM>, <NUM> relative to the respective first and second axes of rotation. The angles <NUM>, <NUM> can be greater than or equal to negative twelve degrees and less than or equal to twelve degrees. The angles <NUM>, <NUM> can be greater than or equal to negative eight degrees and less than or equal to eight degrees (in the frame of reference depicted in <FIG>, negative angles can indicate that a lower edge of the particular first facet <NUM> or the particular second facet <NUM> is outward from an upper edge of the particular first facet <NUM> or the particular second facet <NUM>). For example, for the particular first facet <NUM> and the particular second facet <NUM> depicted in <FIG>, the first angle <NUM> can be negative four degrees, and the second angle <NUM> can be six degrees.

Referring further to <FIG>, the first polygon scanner <NUM> and the second polygon scanner <NUM> can be made from material that has a relatively high parameters of at least one of index of refraction, transparency (e.g., at wavelengths at which the polygon scanners <NUM>, <NUM> are to refract and output light, such as wavelengths around <NUM> nanometers), or optical quality (e.g., low scattering). The materials of the polygon scanners <NUM>, <NUM> may be selected so that the polygon scanners <NUM>, <NUM> have the same refractive index. The transparency of the polygon scanners <NUM>, <NUM> can enable the polygon scanners <NUM>, <NUM> to operate as transmissive polygons. The polygon scanners <NUM>, <NUM> can be made from polymeric materials. The polygon scanners <NUM>, <NUM> can be made from materials such as polystyrene, REXOLITE ® manufactured by C-Lec Plastics, or ZEONEX ® manufactured by ZEON Corporation.

The LIDAR system <NUM> includes an optic <NUM> (e.g., optical assembly) that outputs a first beam <NUM> to the first polygon scanner <NUM>. The optic <NUM> can collimate the first beam <NUM>. The optic <NUM> can use a laser to output the first beam <NUM>. The optic <NUM> can have a compact form factor to facilitate reducing the size of the LIDAR system <NUM>. The optic <NUM> can include one or more lenses or mirrors that can shape the first beam <NUM> and control a direction of the first beam. At least a portion of the optic <NUM> is positioned so that the laser is transmitted in an interior <NUM> of the first polygon scanner <NUM>.

The first polygon scanner <NUM> (e.g., a particular first facet <NUM> of the first polygon scanner <NUM>) refracts the first beam <NUM> to output a second beam <NUM> that can be incident on a particular second facet <NUM> of the second polygon scanner <NUM>. The second polygon scanner <NUM> (e.g., the particular second facet <NUM> of the second polygon scanner <NUM>) refracts the second beam <NUM> to output a third beam <NUM>.

The optic <NUM> can include a light source <NUM>, such as a laser, that outputs light to at least one mirror <NUM>. For example, as depicted in <FIG>, the at least one mirror <NUM> can include a first mirror <NUM> and a second mirror <NUM>. The at least one mirror <NUM> can reflect the light to a lens <NUM>, which can output the first beam <NUM>.

The LIDAR system <NUM> can include at least one motor <NUM> that rotates the first polygon scanner <NUM> and the second polygon scanner <NUM> relative to the respective first and second axes of rotation. The at least one motor <NUM> can incorporate features of the motor <NUM>. The at least one motor <NUM> can be coupled with the first polygon scanner <NUM> and the second polygon scanner <NUM>. The at least one motor <NUM> can include a first motor 756a coupled with the first polygon scanner <NUM>, and a second motor 756b coupled with the second polygon scanner <NUM>. The at least one motor <NUM> can include a single motor coupled with each of the first polygon scanner <NUM> and the second polygon scanner <NUM>, which can drive the polygon scanners <NUM>, <NUM> using various gears or mechanical linkages (not shown). The at least one motor <NUM> can rotate the polygon scanners <NUM>, <NUM> in the same direction or in different directions (including opposite directions where the first and second axes of rotation are the same or parallel) around the respective first and second axes of rotation.

The at least one motor <NUM> can rotate the first polygon scanner <NUM> at a first rotational frequency ω<NUM>, and can rotate the second polygon scanner <NUM> at a second rotational frequency ω<NUM>. The rotational frequencies ω<NUM>, ω<NUM> can be used to control which first facet <NUM> refracts the first beam <NUM> to output the second beam <NUM>, and which second facet <NUM> refracts the second beam <NUM> to output the third beam <NUM>. As such, the rotational frequencies ω<NUM>, ω<NUM> can be used to control the azimuth angle (based on the angles at which the beams <NUM>, <NUM> impinge on the respective first facet <NUM> and second facet <NUM>) and elevation angle (based on the angles <NUM>, <NUM>) of the third beam <NUM>. The rotational frequencies ω<NUM>, ω<NUM> can be controlled such that one of the first polygon scanner <NUM> or the second polygon scanner <NUM> is steered over relatively large angles, and the other of the first polygon scanner <NUM> or the second polygon scanner <NUM> is steered over relatively small angles (e.g., to perform coarse angle control with one of the scanners <NUM>, <NUM> and fine angle control with the other of the scanners <NUM>, <NUM>). The second, outward polygon scanner <NUM> can be controlled to be steered over relatively large angles, which can allow the first, inward polygon scanner <NUM> to be relatively smaller and decrease space for the first polygon scanner <NUM>.

The LIDAR system <NUM> can include at least one position sensor <NUM>. The position sensor <NUM> can detect a position (e.g., angular position) of at least one of the first polygon scanner <NUM> or the second polygon scanner <NUM>. For example, the position sensor <NUM> can be coupled with or provided as part of the at least one motor <NUM>, such as to detect the position of the at least one of the first polygon scanner <NUM> or the second polygon scanner <NUM> using the position of the at least one motor <NUM> that is coupled with the at least one of the first polygon scanner <NUM> or the second polygon scanner <NUM>. The position sensor <NUM> can output at least one position signal regarding the position of the at least one of the first polygon scanner <NUM> or the second polygon scanner <NUM>, which can be used to control the respective rotational frequencies ω<NUM>, ω<NUM>.

<FIG> depicts a chart <NUM> of azimuth angles θ and elevation angles φ of the third beam <NUM> based on a path of the first beam <NUM> and second beam <NUM> through two of the first facets <NUM> (facets 708a and 708b) and the five second facets <NUM> (facets 724a, 724b, 724c, 724d, and 724e) of the polygon scanners <NUM>, <NUM> depicted in <FIG>. Rotation of the first polygon scanner <NUM> and the second polygon scanner <NUM> results in various combinations <NUM> of first facets <NUM> and second facets <NUM> interacting with the light outputted by the optic <NUM> in order to output the third beam <NUM> (e.g., combinations of a particular first facet <NUM> that refracts the first beam <NUM> and particular second facet <NUM> that refracts the second beam <NUM> corresponding to the first beam <NUM> refracted by the particular first facet <NUM>). The combinations <NUM> of first facets <NUM> and second facets <NUM> can result in various azimuth angles θ and elevation angles φ of the third beam <NUM>. The combinations <NUM> may be made of discrete azimuth and elevation angles and may vary in range of azimuth angle.

<FIG> depicts a method <NUM> of operating a LIDAR system. The method <NUM> can be performed using various devices and systems described herein, including but not limited to the LIDAR system <NUM>.

At <NUM>, a first polygon scanner is rotated at a first rotational frequency around a first axis of rotation. The first polygon scanner can include multiple first facets, which can be arranged at various inclination angles relative to the first axis of rotation. The first polygon scanner can be rotated by at least one motor coupled with the first polygon scanner.

At <NUM>, a second polygon scanner is rotated at a second rotational frequency around a second axis of rotation, which can be aligned with the first axis of rotation. The second polygon scanner can be outward from the first polygon scanner. The second polygon scanner can include multiple second facets, which can be arranged at various inclination angles relative to the second axis of rotation. The second polygon scanner can be rotated by the at least one motor, which can be coupled with the second polygon scanner.

At <NUM>, a first beam is transmitted in an interior of the first polygon scanner to a particular first facet of the plurality of first facets. The first beam can be transmitted by an optic that outputs the first beam as a beam of collimated light. For example, the optic can include a laser source, and can include various mirrors and lenses that can direct and shape the first beam to the particular first facet.

The particular first facet can refract the first beam (e.g., based on a refractive index of the first polygon scanner relative to air in the interior of the first polygon scanner) to output a second beam to a particular second facet of the second polygon scanner. The particular second facet can refract the second beam (e.g., based on a refractive index of the second polygon scanner relative to air outward from the second polygon scanner) to output a third beam. An azimuth angle of the third beam can be controlled based on rotational positions of the polygon scanners relative to the axes of rotation and a direction of the first beam. An elevation angle of the third beam can be controlled based on the rotational positions of the polygon scanners relative to the axes of rotation and a direction of the first beam, as the inclination angles of the particular first facet and the particular second facet can be used to control the elevation angle.

At <NUM>, a fourth beam is received. The fourth beam can be received by a detector array. The fourth beam can result from reflection or other scattering of the third beam by an object. For example, the object can be a vehicle, pedestrian, or bicycle that causes the fourth beam to be outputted responsive to the third beam.

At <NUM>, at least one of a range of the object or a velocity of the object is determined using the fourth beam. For example, the detector array can generate a signal representative of the fourth beam, which can be processed to determine the at least one of the range or the velocity.

At <NUM>, a vehicle (e.g., an autonomous vehicle that may operate either completely or partially in an autonomous manner (i.e., without human interaction)) is controlled responsive to the at least one of the range or the velocity. For example, a steering system or braking system of the vehicle can be controlled to control at least one of a direction or a speed of the vehicle (e.g., to perform collision avoidance with respect to the object).

<FIG> is a block diagram that illustrates a computer system <NUM> that can be used to perform various operations described herein. Computer system <NUM> includes a communication mechanism such as a bus <NUM> for passing information between other internal and external components of the computer system <NUM>. Information is represented as physical signals of a measurable phenomenon, typically electric voltages, but including, in other implementations, such phenomena as magnetic, electromagnetic, pressure, chemical, molecular atomic and quantum interactions. For example, north and south magnetic fields, or a zero and non-zero electric voltage, represent two states (<NUM>, <NUM>) of a binary digit (bit). Other phenomena can represent digits of a higher base. A superposition of multiple simultaneous quantum states before measurement represents a quantum bit (qubit). A sequence of one or more digits constitutes digital data that is used to represent a number or code for a character. In some implementations, information called analog data is represented by a near continuum of measurable values within a particular range. Computer system <NUM>, or a portion thereof, constitutes a means for performing one or more steps of one or more methods described herein.

A sequence of binary digits constitutes digital data that is used to represent a number or code for a character. A bus <NUM> includes many parallel conductors of information so that information is transferred quickly among devices coupled to the bus <NUM>. A processor <NUM> performs a set of operations on information. The set of operations include bringing information in from the bus <NUM> and placing information on the bus <NUM>. The set of operations also typically include comparing two or more units of information, shifting positions of units of information, and combining two or more units of information, such as by addition or multiplication. A sequence of operations to be executed by the processor <NUM> constitutes computer instructions.

Computer system <NUM> also includes a memory <NUM> coupled to bus <NUM>. The memory <NUM>, such as a random access memory (RAM) or other dynamic storage device, stores information including computer instructions. Dynamic memory allows information stored therein to be changed by the computer system <NUM>. RAM allows a unit of information stored at a location called a memory address to be stored and retrieved independently of information at neighboring addresses. The memory <NUM> is also used by the processor <NUM> to store temporary values during execution of computer instructions. The computer system <NUM> also includes a read only memory (ROM) <NUM> or other static storage device coupled to the bus <NUM> for storing static information, including instructions, that is not changed by the computer system <NUM>. Also coupled to bus <NUM> is a non-volatile (persistent) storage device <NUM>, such as a magnetic disk or optical disk, for storing information, including instructions, that persists even when the computer system <NUM> is turned off or otherwise loses power.

Information, including instructions, is provided to the bus <NUM> for use by the processor from an external input device <NUM>, such as a keyboard containing alphanumeric keys operated by a human user, or a sensor. A sensor detects conditions in its vicinity and transforms those detections into signals compatible with the signals used to represent information in computer system <NUM>. Other external devices coupled to bus <NUM>, used primarily for interacting with humans, include a display device <NUM>, such as a cathode ray tube (CRT) or a liquid crystal display (LCD), for presenting images, and a pointing device <NUM>, such as a mouse or a trackball or cursor direction keys, for controlling a position of a small cursor image presented on the display <NUM> and issuing commands associated with graphical elements presented on the display <NUM>.

In the illustrated implementation, special purpose hardware, such as an application specific integrated circuit (IC) <NUM>, is coupled to bus <NUM>.

Computer system <NUM> also includes one or more instances of a communications interface <NUM> coupled to bus <NUM>. Communication interface <NUM> provides a two-way communication coupling to a variety of external devices that operate with their own processors, such as printers, scanners and external disks. In general the coupling is with a network link <NUM> that is connected to a local network <NUM> to which a variety of external devices with their own processors are connected. For example, communication interface <NUM> may be a parallel port or a serial port or a universal serial bus (USB) port on a personal computer. In some implementations, communications interface <NUM> is an integrated services digital network (ISDN) card or 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 implementations, a communication interface <NUM> is a cable modem that converts signals on bus <NUM> into signals for a communication connection over a coaxial cable or into optical signals for a communication connection over a fiber optic cable. As another example, communications interface <NUM> may be a local area network (LAN) card to provide a data communication connection to a compatible LAN, such as Ethernet. Carrier waves, such as acoustic waves and electromagnetic waves, including radio, optical and infrared waves travel through space without wires or cables. Signals include man-made variations in amplitude, frequency, phase, polarization or other physical properties of carrier waves. For wireless links, the communications interface <NUM> sends and receives electrical, acoustic or electromagnetic signals, including infrared and optical signals, that carry information streams, such as digital data.

Transmission media include, for example, coaxial cables, copper wire, fiber optic cables, and waves that travel through space without wires or cables, such as acoustic waves and electromagnetic waves, including radio, optical and infrared waves. The term computer-readable storage medium is used herein to refer to any medium that participates in providing information to processor <NUM>, except for transmission media.

Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, a hard disk, a magnetic tape, or any other magnetic medium, a compact disk ROM (CD-ROM), a digital video disk (DVD) or any other optical medium, punch cards, paper tape, or any other physical medium with patterns of holes, a RAM, a programmable ROM (PROM), an erasable PROM (EPROM), a 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 <NUM>, except for carrier waves and other signals.

Logic encoded in one or more tangible media includes one or both of processor instructions on a computer-readable storage media and special purpose hardware, such as ASIC <NUM>.

Network link <NUM> typically provides information communication through one or more networks to other devices that use or process the information. For example, network link <NUM> may provide a connection through local network <NUM> to a host computer <NUM> or to equipment <NUM> operated by an Internet Service Provider (ISP). ISP equipment <NUM> in turn provides data communication services through the public, world-wide packet-switching communication network of networks now commonly referred to as the Internet <NUM>. A computer called a server <NUM> connected to the Internet provides a service in response to information received over the Internet. For example, server <NUM> provides information representing video data for presentation at display <NUM>.

The computer system <NUM> can be used to implement various techniques described herein. Techniques can be performed by computer system <NUM> in response to processor <NUM> executing one or more sequences of one or more instructions contained in memory <NUM>. Such instructions, also called software and program code, may be read into memory <NUM> from another computer-readable medium such as storage device <NUM>. Execution of the sequences of instructions contained in memory <NUM> causes processor <NUM> to perform the method steps described herein. In alternative implementations, hardware, such as application specific integrated circuit <NUM>, may be used in place of or in combination with software to implement various operations described herein. Thus, various implementations are not limited to any specific combination of hardware and software.

The signals transmitted over network link <NUM> and other networks through communications interface <NUM>, carry information to and from computer system <NUM>. Computer system <NUM> can send and receive information, including program code, through the networks <NUM>, <NUM> among others, through network link <NUM> and communications interface <NUM>. In an example using the Internet <NUM>, a server <NUM> transmits program code for a particular application, requested by a message sent from computer <NUM>, through Internet <NUM>, ISP equipment <NUM>, local network <NUM> and communications interface <NUM>. The received code may be executed by processor <NUM> as it is received, or may be stored in storage device <NUM> or other non-volatile storage for later execution, or both. In this manner, computer system <NUM> may obtain application program code in the form of a signal on a carrier wave.

Various forms of computer readable media may be involved in carrying one or more sequence of instructions or data or both to processor <NUM> for execution. For example, instructions and data may initially be carried on a magnetic disk of a remote computer such as host <NUM>. 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 the computer system <NUM> receives the instructions and data on a telephone line and uses an infra-red transmitter to convert the instructions and data to a signal on an infra-red a carrier wave serving as the network link <NUM>. An infrared detector serving as communications interface <NUM> receives the instructions and data carried in the infrared signal and places information representing the instructions and data onto bus <NUM>. Bus <NUM> carries the information to memory <NUM> from which processor <NUM> retrieves and executes the instructions using some of the data sent with the instructions. The instructions and data received in memory <NUM> may optionally be stored on storage device <NUM>, either before or after execution by the processor <NUM>.

<FIG> illustrates a chip set <NUM>. Chip set <NUM> is programmed to perform one or more steps of a method described herein and includes, for instance, the processor and memory components described with respect to <FIG> incorporated 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 assembly (e.g., a baseboard) to provide one or more characteristics such as physical strength, conservation of size, and/or limitation of electrical interaction. It is contemplated that in certain implementations the chip set can be implemented in a single chip. Chip set <NUM>, or a portion thereof, constitutes a means for performing one or more steps of a method described herein.

In one implementation, the chip set <NUM> includes a communication mechanism such as a bus <NUM> for passing information among the components of the chip set <NUM>.

The processor <NUM> and accompanying components have connectivity to the memory <NUM> via the bus <NUM>. The memory <NUM> includes both dynamic memory (e.g., RAM, magnetic disk, writable optical disk, etc.) and static memory (e.g., ROM, CD-ROM, etc.) for storing executable instructions that when executed perform one or more steps of a method described herein. The memory <NUM> also stores the data associated with or generated by the execution of one or more steps of the methods described herein.

Having now described some illustrative implementations, it is apparent that the foregoing is illustrative and not limiting, having been presented by way of example. In particular, although many of the examples presented herein involve specific combinations of method acts or system elements, those acts and those elements can be combined in other ways to accomplish the same objectives. Acts, elements and features discussed in connection with one implementation are not intended to be excluded from a similar role in other implementations or implementations.

Any references to implementations or elements or acts of the systems and methods herein referred to in the singular can also embrace implementations including a plurality of these elements, and any references in plural to any implementation or element or act herein can also embrace implementations including only a single element. References to any act or element being based on any information, act or element can include implementations where the act or element is based at least in part on any information, act, or element.

Any implementation disclosed herein can be combined with any other implementation or embodiment, and references to "an implementation," "some implementations," "one implementation" or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described in connection with the implementation can be included in at least one implementation or embodiment. Such terms as used herein are not necessarily all referring to the same implementation. Any implementation can be combined with any other implementation, inclusively or exclusively, in any manner consistent with the aspects and implementations disclosed herein.

Further relative parallel, perpendicular, vertical or other positioning or orientation descriptions include variations within +/-<NUM>% or +/-<NUM> degrees of pure vertical, parallel or perpendicular positioning. References to "approximately," "about" "substantially" or other terms of degree include variations of +/-<NUM>% from the given measurement, unit, or range unless explicitly indicated otherwise. Coupled elements can be electrically, mechanically, or physically coupled with one another directly or with intervening elements. Scope of the systems and methods described herein is thus indicated by the appended claims, rather than the foregoing description, and changes that come within the meaning and range of equivalency of the claims are embraced therein.

The term "coupled" and variations thereof includes the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly with or to each other, with the two members coupled with each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled with each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If "coupled" or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of "coupled" provided above is modified by the plain language meaning of the additional term (e.g., "directly coupled" means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of "coupled" provided above. Such coupling may be mechanical, electrical, or fluidic.

References to "or" can be construed as inclusive so that any terms described using "or" can indicate any of a single, more than one, and all of the described terms. A reference to "at least one of 'A' and 'B'" can include only 'A', only 'B', as well as both 'A' and 'B'. Such references used in conjunction with "comprising" or other open terminology can include additional items.

Modifications of described elements and acts such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations can occur without materially departing from the teachings and advantages of the subject matter disclosed herein. For example, elements shown as integrally formed can be constructed of multiple parts or elements, the position of elements can be reversed or otherwise varied, and the nature or number of discrete elements or positions can be altered or varied.

Claim 1:
A light detection and ranging, LIDAR, system (<NUM>; <NUM>), comprising:
a first polygon scanner (<NUM>) comprising a plurality of first facets (<NUM>; 708a-e) arranged around a first axis of rotation (<NUM>);
a second polygon scanner (<NUM>) comprising a plurality of second facets (<NUM>; 724a-e) arranged around a second axis of rotation (<NUM>), the plurality of second facets located outward from the plurality of first facets relative to the second axis of rotation, wherein the first axis of rotation is the same as or parallel with the second axis of rotation; and
an optic (<NUM>) located inward from the first polygon scanner relative to the first axis of rotation, wherein the optic is configured to transmit a first beam (<NUM>) in an interior (<NUM>) of the first polygon scanner, the first polygon scanner is configured to refract the first beam to output a second beam (<NUM>) to the second polygon scanner, and the second polygon scanner is configured to refract the second beam to output a third beam (<NUM>).