Space profiling system and method

Abstract

A spatial profiling system for profiling an environment is disclosed. The spatial profiling system includes a light emitter for providing light, a beam guider for directing light in one or more directions towards the environment, and a light receiver for receiving return light reflected by a surface or object in the environment. The return light carries information for determining a distance to a surface or object. The light receiver is configured to detect (a) a specular property of the return light and (b) a polarization state of the return light. The spatial profiling system also includes a processing system configured to determine a material associated with the surface or object based on the detected specular property and the detected polarization state.

Description

[0001] field

[0002] The present disclosure relates generally to systems and methods for light-based estimation of an Earth or extraterrestrial environment, for example, to LiDAR systems and methods performed by LiDAR systems.

[0003] background

[0004] Spatial profiling refers to the 2D or 3D mapping of an environment over its two-dimensional (2D) or three-dimensional (3D) field of view. Each point or pixel in the field of view is associated with a distance that forms a 2D or 3D representation of the environment. The spatial distribution can be useful in identifying objects and / or obstacles in the environment, thereby facilitating the automation of tasks.

[0005] One technique for spatial profiling involves sending light into the environment in a specific direction and detecting any light that is reflected back from that direction (e.g., by a reflective surface in the environment). This technique may be referred to as light detection and ranging, or LiDAR. The reflected light carries relevant information for determining the distance to the reflecting surface. The combination of the specific direction and distance forms a point or pixel in a three-dimensional representation of the environment. The above steps may be repeated for multiple different directions to form additional points or pixels of the three-dimensional representation, thereby estimating the spatial distribution of the environment within the desired field of view.

[0006] Public Overview

[0007] Spatial profiling systems and components for spatial profiling systems and related methods are described. The spatial estimate formed by the spatial profiling system may be of an Earth environment or an extraterrestrial environment.

[0008] According to one aspect of the present disclosure, a spatial profiling system for profiling an environment is provided, the spatial profiling system comprising: an optical transmitter for providing light; a beam guide for directing light in one or more directions toward the environment; an optical receiver for receiving return light reflected by a surface or object in the environment, the return light carrying information for determining the distance to the surface or object, the optical receiver being configured to detect (a) specularity of the return light and (b) polarization state of the return light; and a processing system configured to determine a material associated with the surface or object based on the detected specularity and the detected polarization state.

[0009] The processing system may be configured to determine a material associated with the surface or object by classifying the material into one of a plurality of material classes. Classifying the material into one of a plurality of material classes may include classification including applying one or more machine learning algorithms.

[0010] The light receiver may also be configured to detect specularity based on an image or interference pattern associated with the speckle.In one embodiment, the image or interference represents a spatial sample of surfaces or objects from which light is reflected.

[0011] The optical receiver may also be configured to detect specularity based on the plurality of despeckle signals.The optical receiver may also be configured to recover or provide an amplitude measurement and a phase measurement of one or more of the plurality of despeckle signals.

[0012] The processing system may also be configured to determine any one of speckle contrast, speckle granularity, and speckle anisotropy based on the detected specularity. The processing system may also be configured to determine a material associated with the surface or object based on any one or more of the determined speckle contrast, speckle granularity, and speckle anisotropy.

[0013] The optical receiver is further configured to detect the polarization state based on the degree of preservation of the polarization state. The degree of preservation of the polarization state can represent the degree of polarization of the returned light relative to the degree of polarization of the outgoing light or the local oscillator. The processing system can also be configured to determine the material associated with the surface or object based on the degree of preservation of the polarization state.

[0014] As used herein, the terms "first", "second", etc. are used to distinguish one entity from another entity and are not used to indicate or require any particular ordering in time, location, or other aspects. For example, "a first port and a second port" has the same meaning as "a port and another port".

[0015] As used herein, the terms "optical port" and "port" refer to an area of ​​an optical component through which light passes, and do not necessarily require the presence of a physical structure or component. For example, one port may be formed by the end of a waveguide or optical fiber, in which case the perimeter of the port coincides with the inner surface of the waveguide or optical fiber, while another port may be within a larger area of ​​an input or output plate of a wavelength router, in which case the perimeter of the port does not coincide with any structure of the waveguide.

[0016] As used herein, "light" refers to electromagnetic radiation having optical frequencies, including far infrared radiation, infrared radiation, visible radiation, and ultraviolet radiation.

[0017] As used herein, designations of views or orientations, such as top, side, horizontal, or vertical, are arbitrary for purposes of illustration and do not suggest any required orientation.

[0018] Further aspects of the invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The arrangement of the spatial profiling system is shown.

[0021] Figure 2 Shown for Figure 1 Arrangement of light sources of the spatial profiling system.

[0022] Figure 3 Shown for Figure 1 Example arrangement of sensor heads for a spatial profiling system.

[0023] Figure 4 Shows Figure 3 The sensor head is a sensor head component.

[0024] Figure 5 Partially shown for Figure 1 Photodetector for spatial profiling system.

[0025] Figure 6 An example of a processing system for classifying surfaces of different materials is shown.

[0026] Figure 7 An example of an experimental setup used to obtain experimental observations is shown.

[0027] Fig. 8A and Figure 8B The training method disclosed herein is shown. Figure 6 Performance matrix of the processing system.

[0028] Fig. 9 Shows Figure 6 The accuracy of the processing system under different machine learning models trained.

[0029] Fig.10 Shown for Figure 1 The photodetector is part of a spatial profiling system. DETAILED DESCRIPTION

[0030] Light-based spatial profiling systems may be referred to as light detection and ranging (LiDAR) systems. LiDAR involves transmitting light into an environment and detecting light returned by the environment. By detecting the returning light, the system can determine information about the distances of reflective surfaces within its field of view (FOV), such as the surface of an object or obstacle, the contours of the ground, and / or the position of the horizon, and can form a spatial estimate of the environment.

[0031] There are a range of methods for determining distance in or by a LiDAR system. In some embodiments of the LiDAR system, the distance to a reflective surface can be determined based on the round trip time of light. In a simple example, the round trip time of a light pulse is determined, from which the range to the reflective surface in the direction in which the light pulse is transmitted can be determined. Alternatively or additionally, frequency modulated continuous wave (FMCW) technology can be used to determine the distance. Examples of LiDAR range detection, including examples using FMCW technology, are discussed in International Patent Application No. PCT / AU2016 / 050899 (published as WO 2017 / 054036 A1), the entire contents of which are incorporated herein by reference. In some embodiments, light pulses including a time-varying profile are emitted, and the time-varying profile is used for distance determination. In other embodiments, the outgoing light includes a linear frequency chirp or phase change for detecting the round trip time, rather than detecting the round trip time of a series of modulated pulses.

[0032] In three-dimensional mapping, one of the dimensions relates to the range of points from the origin of the outgoing light, while the other two relate to the two-dimensional space through which the light is directed (e.g., a space that can be defined by a Cartesian coordinate system (x, y) or a polar coordinate system (θ, φ)). The area or angular range over which the light is directed for detection of the returning light is the field of view of the spatial profiling system. The field of view of a LiDAR system can be fixed, or can be a controlled variable.

[0033] In some LiDAR systems, one or more light beams are directed into the environment, and the one or more light beams are directed in two dimensions (i.e., the first dimension and the second dimension of a two-dimensional field of view), and the combination of knowledge of the steering and the determined range provides information for spatial profiling.

[0034] In some other LiDAR systems, light is emitted over a wider range (up to the entire field of view of the LiDAR system). For example, light of different colors may be emitted in different directions within the field of view to enable both direction and range to be determined. The remainder of this specification is provided primarily with reference to LiDAR systems having outgoing light in the form of one or more beams (rather than systems that emit light simultaneously over the entire field of view).

[0035] In some embodiments, a LiDAR system or a processing system in communication with a LiDAR system can determine the velocity or speed information of an entity (e.g., a vehicle) in which the LiDAR system is located and / or a reflective surface in the environment. The velocity or speed determination can be based on detected light returned by the environment, or directly, such as based on a Doppler shift signal contained in the returned light, or based on a change in distance determination over time. For example, in an FMCW system, the coherent beat tone of a chirp waveform will reveal the Doppler shift. Additionally or alternatively, the velocity information can be obtained or determined from external information that is not derived from the LiDAR system.

[0036] Figure 1 FIG. 1 shows an example arrangement of a spatial analysis system 100. As shown in the key, Figure 1 In the figure, electrical connections (eg, analog or digital data or control signals) are represented by solid lines, and optical connections (eg, guided or free-space optical transmission) are represented by dashed lines. Optical input ports and optical output ports of components are represented by solid circles.

[0037] The spatial profiling system 100 includes a light transmitter 101, a sensor head 103, a light receiver 104, and a processing and control system 105. The spatial profiling system 100 forms an outgoing light path P1 for providing an outgoing light L1 for spatial profiling to an environment and an incident light path P2 for providing an incident light L2 for detection to the light receiver 104. The incident light L2 includes the outgoing light L1 that has been reflected by the environment.

[0038] The optical transmitter 101 includes a light source 102 for generating an outgoing light L1. The light source 102 may include one or more light generators, such as one or more laser diodes. In some embodiments, the light source 102 is wavelength tunable for selectively providing light of one or more wavelengths in a selectable wavelength range. For example, the light source may include one or more wavelength tunable laser diodes. In some embodiments, the light source 102 provides light having a single polarization orientation. In some embodiments, the optical transmitter 101 includes one or more optical amplifiers for providing gain to the outgoing light L1 and / or one or more optical modulators for imparting a temporal variation to at least one characteristic of the outgoing light L1.

[0039] Outgoing light L1 from the light emitter 101 is provided to the sensor head 103. The outgoing light L1 may be provided to the sensor head 103 directly from the light emitter 101, or indirectly via one or more other optical components (such as a collimator) in the outgoing light path P1.

[0040] The sensor head 103 guides the outgoing light L1 to the environment. In embodiments where the outgoing light L1 is in the form of one or more light beams, the sensor head 103 includes a beam guide for controlling the direction of the outgoing light L1.

[0041] In the case where the light source 102 is wavelength tunable, the sensor head 103 may include one or more wavelength-based beam directors that direct one wavelength of the light source 102 in one direction and another wavelength in another direction. Thus, a range of wavelengths may be directed to a range of directions. Depending on the implementation of the beam director, there may be a one-to-one correspondence between selectable wavelengths and directions, or a set of multiple selectable wavelengths may be directed to a single direction, while another set of selectable wavelengths may be directed to another direction.

[0042] The sensor head 103 may also or alternatively include one or more beam guides including one or more mechanically movable components (e.g., one or more scanning mirrors and / or rotating or tilting dispersive or diffractive components) to control the direction of the outgoing light. Thus, when the mechanically movable component is in one position or orientation, the outgoing light L1 is directed in one direction at one time, and when the mechanically movable component is in another position or orientation, the outgoing light L1 is directed in another direction at another time, and so on, to provide a range of directions.

[0043] The sensor head 103 may include both a wavelength-based beam guide and a mechanical beam guide. For example, the sensor head 103 may include one or more diffractive and / or dispersive components that guide light based on wavelength, wherein the guided light is provided to a scanning mirror for mechanical beam direction. In another example, at least one diffractive or dispersive component for wavelength-based beam direction is mounted on a rotating platform, wherein rotation of the diffractive or dispersive component produces the mechanical beam direction. A spatial profiling system having both wavelength and mechanical beam direction components may be viewed as having a wavelength dimension and a mechanical dimension. The wavelength dimension and the mechanical dimension may be orthogonal or substantially orthogonal.

[0044] The sensor head 103 also receives incident light L2 along the incident light path P2. In the illustrated embodiment, the sensor head 103 includes a bidirectional port through which both the outgoing light L1 and the incident light L2 pass. In other words, the outgoing light path P1 and the incident light path P2 coincide or overlap at least at the bidirectional port of the sensor head 103. The outgoing light path P1 and the incident light path P2 may share a common optical axis or have parallel optical axes at the bidirectional port. Such sharing of a common optical axis or the presence of parallel optical axes may continue through at least one of the one or more beam guides of the sensor head 103.

[0045] In some embodiments, the sensor head 103 separates the incident light L2 from the outgoing light L1. The separation can be achieved by the sensor head 103 directing the incident light L2 to a port different from the port receiving the incident light L1 (e.g., Figure 1 1 and 102) and / or by providing incident light L2 from the sensor head 103 so that the optical path P2 is not parallel to the optical path P2. In other embodiments, the separation occurs at another location along the optical paths P1, P2, such as near or within the optical receiver 104.

[0046] In yet other embodiments, the outgoing optical path P1 and the incoming optical path P2 do not coincide or overlap at or within the sensor head 103. In these embodiments, the sensor head may optionally be divided into two physical components, one physical component for providing the outgoing optical path P1 and one physical component for providing the incoming optical path P2.

[0047] Incident light L2 passing through incident light path P2 is received by light receiver 104. Light may be provided directly to light receiver 104 from sensor head 103, or indirectly to light receiver 104 via one or more other optical components (such as an optical filter) in incident light path P2.

[0048] The optical receiver 104 includes a light detector 106. The light detector generates a signal S1 based on the incident light L2. The signal S1 represents information carried by the detected incident light L2 for determining the distance to the reflective surface. Figure 1 As shown, signal S1 may be an analog data signal. Light detector 106 may include one or more photodetectors. An exemplary photodetector is an avalanche photodiode (APD). Light receiver 104 may include two photodiodes for balanced detection. In the case where processing and control system 105 is a digital system, analog-to-digital converter 107 converts the analog data signal into a digital signal S2.

[0049] In some embodiments, light from the light source 102 is also provided to the detector 106 to provide a reference light signal or a local oscillator light signal L3. The local oscillator light signal L3 is provided to the optical receiver 104. The detector circuit can then be configured to suppress the detection of non-reflected light based on the difference in wavelength or modulation between the outgoing light and the non-reflected light. For example, the light detector 106 may include one or more balanced detectors to coherently detect reflected light in the incident light L2 mixed with the reference light. Thus, the spatial profiling system 100 can achieve coherent (homodyne or heterodyne) detection of the incident light L2. Through coherent detection, the light detector 106 is configured to recover or provide measurements of both the amplitude (E) and phase (φ) of the incident light L2. For example, a function of time (E(t)) and a function of phase (φ(t)). In one example, the light detector 106 includes an in-phase and quadrature (IQ) optical demodulator. The IQ demodulator is configured to combine a first portion of the incident light L2 with a first (in-phase) portion of the reference light L3, for example via an optical coupler, to provide a first combination. The IQ demodulator is also configured to combine a second portion of the incident light L2 with a second (orthogonal) portion of the reference light L3, for example via another optical coupler, to provide a second combination. The first (in-phase) portion and the second (orthogonal) portion of the reference light L3 are phase-separated by 90 degrees of π / 2 radians. The IQ demodulator may include an optical path length, such as an optical delay line, to facilitate phase separation. Alternatively, the IQ demodulator may include one or more multi-mode interference (MMI) couplers to facilitate phase separation. The IQ demodulator is configured to generate an electrical in-phase signal (of amplitude I) based on the first combination, and an electrical quadrature signal (of amplitude Q) based on the second combination. The in-phase signal (of amplitude I) and the quadrature signal (of amplitude Q) can be further combined, for example, when digitized by the ADC 107 discussed below, to recover the amplitude (E) and phase (φ) of the incident light L2. For example, the incident light L2 in a complex valued representation can be characterized as I+jQ=E exp(jφ). In general, the values ​​of I, Q, E, and φ are all functions of time. Other detection methods can be used, such as direct detection. In direct detection, a local oscillator optical signal L3 is not required.

[0050] The digital signal S2 is received and processed by the processing and control system 105. The processing and control system 105 can determine the distance to a reflective surface (or object) in the environment based on the digital signal S2.

[0051] The light transmitter 101 may be controlled by the processing and control system 105 via control signals on the control line C1. In some embodiments, the processing and control system 105 also controls aspects of the operation of other components in the system, such as controlling one or more components of the sensor head 103 via the control line C2 and / or controlling one or more components of the light receiver 104 via the control line C3. Two or more of the control lines C1 to C3, optionally together with other control lines, may be combined into a control bus in which the controlled components are individually addressable.

[0052] The processing and control system 105 may determine the distance to a reflective surface of the environment based on its knowledge of the control of the components of the spatial profiling system 100. The processing and control system 105 may determine a spatial profile of the environment based on the set of distance determinations. Alternatively, the processing and control system 105 may include a communication interface with another data processing system and communicate signals with the other data processing system to enable it to perform a spatial profiling determination based on the distance determination of the processing and control system 105, or to enable it to perform a distance and / or spatial profiling determination.

[0053] The processing and control system 105 may include one or more special-purpose devices configured to perform the operations described herein, such as one or more manufactured or configured programmable logic devices, such as application specific integrated circuits or field programmable gate arrays, or one or more general-purpose computing devices, such as a microcontroller or microprocessor, having a computer-readable memory storing instructions to cause the computing device or devices to perform the operations.

[0054] In the case of a dedicated device, the instructions and / or data for controlling the operation of the processing unit may be implemented in whole or in part by firmware or hardware elements (including configured logic gates). These elements may be integrated on a common substrate, such as a system-on-chip integrated circuit, or distributed on devices on separate substrates.

[0055] In an example of a general-purpose computing device, the processing and control system 105 may include, for example, a single computer processing device (e.g., a central processing unit, a graphics processing unit, or other computing device), or may include multiple computer processing devices. The processing and control system 105 may also include a communication bus for data communication with one or more machine-readable storage (memory) devices, which store instructions and / or data for controlling various aspects of the operation of the processing unit. The memory devices may include system memory (e.g., BIOS), volatile memory (e.g., random access memory), and non-volatile memory (e.g., one or more hard disks or solid-state drives for providing non-transient storage). Operations for spatial profiling are typically controlled by instructions in non-volatile memory and / or volatile memory.

[0056] In addition, the processing and control system 105 includes one or more interfaces, such as an interface for control lines C1 to C3 or a control bus, and an interface for receiving signal S2. The external interface may provide an option to update the firmware and / or software of the processing and control system 105. The external interface may provide an option for multiple LiDAR system communication, such as sharing information for spatial profiling and / or sharing spatial distribution, thereby allowing determination and action based on spatial profiling actions of more than one LiDAR system.

[0057] In some embodiments, control operations and data processing operations are performed by separate physical devices. In other embodiments, one or more physical devices may perform both control and data processing operations.

[0058] In some embodiments, the spatial profiling system 100 divides the functional components into two or more physical units. For example, the sensor head 103 can be included in one of the physical units, and the light emitter 101, the light receiver 104, and the processing and control system 105 can be included in one other physical unit, or one or more of these can be in another physical unit. In some embodiments, the sensor head 103 is far away from one or more other components. The remote sensor head 103 can be coupled to other units via one or more guided optical connections (such as waveguides or optical fibers). The spatial profiling system may include multiple sensor heads 103. Each of the multiple sensor heads 103 can be optically coupled to the light receiver 104 via a corresponding guided optical connection. Multiple sensor heads 103 can be placed in different positions and / or oriented with different fields of view. In one embodiment, the light emitter 101 and the light receiver 104 are implemented on the same optical subassembly. In another embodiment, the light emitter 101 and the light receiver 104 are implemented on different optical subassemblies. In either embodiment, the ADC 107 and the processing and control system 106 may be implemented on the same printed circuit board assembly or on different printed circuit board assemblies, separate from any optical subassembly or subassemblies. One or more printed circuit board assemblies may include or correspond to a system on a chip (SoC) or a system on a module (SoM).

[0059] Figure 2 An example arrangement of a light emitter 201 is shown, which may for example form a reference Figure 1 1 and 2. The spatial profiling system 100 is described with reference to an optical transmitter 101. In this example, the optical transmitter 201 includes a tunable laser 202 (e.g., a wavelength tunable laser diode) as a source of a light beam. The tuning wavelength of the tunable laser 202 can be based on one or more currents applied to the laser diode, such as a current injected into one of a plurality of wavelength tuning elements in a laser cavity. In the spatial profiling system 100, the current is controlled in response to a control signal on a control line C1.

[0060] Therefore, the optical transmitter 201 is configured to transmit light in a plurality of selectable wavelength channels (each having a corresponding central wavelength λ1, λ2, ... λ N) in one or more selected wavelength channels. In some embodiments, the wavelength range of the wavelength tunable light source is at least 20 nm, or at least 25 nm, or at least 30 nm, or at least 35 nm. The resolution (i.e., the minimum wavelength step) of the wavelength tunable light source can be at most 0.2 nm, preferably at most 0.1 nm, more preferably at most 0.05 nm, and even more preferably at most 0.01 nm. In some embodiments, the wavelength channel is at about 1550 nm. Other wavelengths, such as about 905 nm, can be used. The light emitter 201 can select one wavelength channel at a time, or can provide two or more different selected wavelength channels (i.e., channels with different center wavelengths) simultaneously.

[0061] Light from the light source can pass through polarizer 203 so that the outgoing light to the environment is polarized light. In some embodiments, polarizer 203 is a single polarizer. In other embodiments, polarizer 203 is a cross-polarizer, in which case polarizer 203 can include two polarizers oriented perpendicular to each other, or when the source light has a single polarization, provide orthogonal polarization. In some embodiments, the polarizer produces linearly polarized light.

[0062] Polarized light from the light source can pass through the optical splitter 204, where most of the light continues along the exit optical path and the remaining portion of the light is provided as a local oscillator signal. For example, the optical splitter 204 can be a 90 / 10 fiber coupler, providing 90% of the light as the exit light and 10% of the light as the local oscillator signal for coherent detection.

[0063] The optical transmitter 101 may also include an optical amplifier 205 to amplify the outgoing light (provide gain thereto). In some embodiments, the optical amplifier 205 is one or more stages of an erbium doped fiber amplifier (EDFA). In other embodiments, one or more stages of a semiconductor optical amplifier (SOA), a boosted optical amplifier (BOA), or a solid-state amplifier (e.g., a Nd:YAG amplifier) ​​may be used. In the spatial profiling system 100, the gain may be controlled in response to a control signal on the control line C1. In some embodiments, the optical amplifier 205 is omitted.

[0064] In some embodiments, the optical transmitter 201 includes a modulator 206 for imparting a time-varying distribution on the outgoing light. The modulation can be a modulation other than any wavelength tuning as previously described herein. In other words, the modulation will be performed on the light at the tuned wavelength. It should be understood that the tuned wavelength can refer to the center frequency or other measure of the wavelength channel produced. The time-varying distribution can be, for example, one or more of the changes in the intensity, frequency, phase, or code imparted to the outgoing light. The operation of the modulator 206 (e.g., the modulation waveform) can be controlled by the processing and control system 105 through a control signal on the control line C1.

[0065] In one example, the modulator 206 is an external modulator of the laser diode (such as a Mach-Zehnder modulator, an electro-optic modulator, or an external SOA modulator). In another example, the modulator 206 is a phase modulator. Figure 2 An example is shown in which the modulator 206 is located after the optical amplifier 204, but it should be understood that the modulator can be located before or after the optical amplifier 205 in the output light path. In one example, the modulator of the optical transmitter is a semiconductor optical amplifier (SOA) or a Mach-Zehnder modulator integrated on the laser diode of the light source. The current applied to the SOA can vary with time to vary the amplification of the CW light generated by the laser with time, which in turn provides an output light with a time-varying intensity distribution. In another example, instead of including an integrated or external modulator, the light source includes a laser with a gain medium, and the excitation current is controllably injected into the gain medium for imparting a time-varying intensity distribution on the output light. In some embodiments, the light source, optical amplifier and modulator are provided by a sampled grating distributed Bragg reflector (SG-DBR) laser.

[0066] In another example, the optical transmitter 101 may include a broadband light source and one or more tunable spectral filters to provide a substantially continuous wave (CW) light intensity at a selected wavelength. In another example, the optical transmitter 101 includes a plurality of laser diodes, each of which is wavelength tunable within a corresponding range, and whose respective outputs are combined to form a single output. A wavelength combiner such as a beam splitter or an arrayed waveguide grating (AWG) may be used to combine the respective outputs.

[0067] Optical transmitter 101 or optical transmitter 201 may be controllable to provide 10 Gbps modulation, may operate in a 35 nm wavelength range, and change from one wavelength channel to another in less than 500 nanoseconds, or less than 200 nanoseconds, or less than 100 nanoseconds. The center frequencies of these wavelength channels may be spaced about 1 GHz or more apart.

[0068] Figure 3 An example arrangement of a sensor head 301 is shown, which may for example form a reference Figure 1 1 and 2. The sensor head 103 of the spatial profiling system 100 is described. The sensor head 301 includes an optical circulator 302 and a beam guide 303, the beam guide 303 including a fast axis beam guide (such as a wavelength-based beam guide 304) and a slow axis beam guide (such as a mechanical beam guide 305). Generally, the fast axis beam guide is configured to guide the beam along a first axis ("fast axis") faster than the slow axis beam guide is configured to guide the beam along a second axis ("slow axis") that is orthogonal or substantially orthogonal to the first axis. Figure 3 As shown, the beam guide 303 may be downstream of the optical circulator 302 in the direction of the outgoing light. Alternatively, the optical circulator 302 may be downstream of the beam guide 303 in the direction of the outgoing light. Furthermore, in the beam guide 303, the fast-axis beam guide may be downstream of the slow-axis beam guide in the direction of the outgoing light. Alternatively, in the beam guide 303, the fast-axis beam guide may be downstream of the slow-axis beam guide in the direction of the outgoing light.

[0069] In some embodiments, the optical circulator 302 can be omitted. Figure 1 ) can be performed by a 2×1 optical coupler. In addition, as previously described, in some embodiments, only wavelength beam steering or only mechanical beam steering can be performed by a beam guide. In addition, combined wavelength beam steering and mechanical beam steering can be performed by mechanical movement of components for wavelength-based beam steering.

[0070] Figures 1 to 3 The boxes represent functional components of the spatial profiling system 100. Functions may be provided by different or integrated physical components. For example, the optical detector may be separate or integrated with the analog-to-digital converter (ADC). In another example, the optical circulator 302 (or optical coupler) and the wavelength-based beam guide 304 may be separate physical components or a single integrated component.

[0071] Figure 4 A sensor head assembly 400 is shown, for example Figure 3 The components of the sensor head 301 may be formed Figure 1 Part of the spatial analysis system. Figure 4 These components include a wavelength router 401 and an optical circulator 401. The wavelength router 401 can form Figure 3 The optical circulator 401 may be all or part of the wavelength-based beam guide 304. Figure 3 As mentioned above, a 2×1 optical coupler can be used instead of an optical circulator.

[0072] The wavelength router 400 may include or may be an arrayed waveguide grating (AWG) or an echelle grating or a photon lamp. The AWG may be fabricated as an integrated circuit chip in, for example, Si, SiO2, or SiN. The descriptions herein referring to AWGs will be understood by those skilled in the art to be applicable to echelle gratings or photon lamps without minor modifications, all of which may, for example, distinguish high-order modes from low-order or fundamental modes in the return light.

[0073] The wavelength router 400 includes an input slab 402, an output slab 403, and a waveguide array 404. Since the wavelength router is a bidirectional component, the terms input and output are used here with respect to the outgoing optical path P1. For the incident optical path P2, the output slab 403 effectively serves as an input slab for the AWG. The waveguide array 404 includes waveguides of different lengths to create an interference pattern of the AWG. The wavelength router 400 also includes a single-mode optical fiber array 405 distributed on the input slab 402.

[0074] Fiber 407 of single mode fiber array 405 forms part of outgoing optical path P1 and receives outgoing light from optical circulator 401. Optical circulator 401 receives outgoing light L1 through optical path 408, which may be free space or a guided optical component. Fiber 407 is connected to the center of input board 402. Other optical fibers in single mode optical figures array 405 are placed symmetrically across input board 402 around fiber 407.

[0075] The output light L1 comes from the wavelength tunable light source 102, which is used to selectively provide a selectable wavelength range λ1 to λ N For example, the emitted light L1 can circulate through λ1 to λ N Each of the output plates 403 to cover the wavelength dimension. The light source may change wavelength continuously between wavelength channels, or may include a step change in wavelength between wavelength channels. Due to interference caused by the waveguide array 404 in the output plate 403, different wavelengths leave the output plate 403 at different angles. This angular difference can be used for beam direction. In some embodiments, at least one lens or other suitable optical component is arranged in the output light path P1, downstream of the output plate 403, such as a collimating lens for collimating the output light and / or a lens and / or a polarizing wave plate for amplifying the angular difference and thereby increasing the field of view.

[0076] In an ideal scenario without speckle effects, the propagation of reflected light in the incident light L2 through the wavelength router 400 will cause the reflected light to be imaged to where the light originated, i.e., the location where it returns to the optical fiber 407. In a practical scenario, the reflected light in the incident light L2 is speckled (diffuse), and the propagation of reflected light in the return light through the wavelength router 400 causes the reflected light to be imaged as a diffused field at the input plate 402. Some of the reflected light is received by the optical fiber 407, and some of the reflected light is received at other optical fibers in the single-mode optical fiber array 405. Therefore, an image is formed on the single-mode optical fiber array 405, which is formed by the interference signal in the input plate 402. Therefore, the image can be described as an interference pattern. Such an image or interference pattern represents a spatial sample of the surface or object from which the light is reflected. In this way, the target (i.e., a part of the environment that reflects the outgoing light) is spatially sampled, which can be used to detect or mitigate the speckle effect.

[0077] Thus, the single-mode fiber array 405 each provides a return signal R-1-R-7. The return signals R-1-R-7 that resolve or deconstruct the speckle effect are referred to herein as "despeckled" signals. In one example, the despeckled signals include a set of fundamental mode signals and one or more higher-order mode signals. A plurality of these despeckled signals may be provided to the optical receiver 104 for detection, such as coherent detection as described above. The optical detector 106 may be configured to detect specularity of the return signals, such as detecting an image or interference pattern associated with speckle. In the case of coherent detection, the optical detector 106 may be further configured to recover or provide a measurement of the amplitude and phase of each despeckled signal. In other words, the optical detector 106 may be configured to detect specularity based on the amplitude and phase of the incident light in a spatially resolved manner. Although this example shows seven optical fibers, there may be more or fewer optical fibers, with corresponding changes in more or fewer receiver channels, ADCs, and processing resources. In some embodiments, the light detector 106 is further configured to determine a polarization state of the returning light, such as a polarization state of any one or more of the despeckle signals R-1 to R-7. For example, the light detector 106 may include one or more polarizers for each of the despeckle signals R-1 to R-7. The determination of the polarization state provides an indication of the degree of polarization of the returning light, such as how its degree of polarization is maintained when it is reflected from a surface or object. In addition, based on the polarization state of each of the despeckle signals R-1 to R-7, the degree of polarization of the returning light is determined in a spatially resolved manner to indicate material properties of the surface or object. In particular, the degree of polarization of the returning light may be determined relative to the degree of polarization of the outgoing light or the local oscillator.

[0078] In some embodiments, each of the despeckle signals R-1 to R-7 is converted by the optical receiver 104 into an electrical signal, which may be converted into a digital signal, for example, by the ADC 107. Figure 1 The signal S2 can be considered as a composite signal, including signal components corresponding to each of the despeckle signals R-1 to R-7. Signal processing, such as performed by the processing and control system 105, can then combine the digital signals representing the despeckle signals R-1 to R-7 to reduce the speckle effect. In addition, the characteristics of the despeckle signals R-1 to R-7, such as one or more of their spatially resolved amplitude, phase and polarization, can be used to characterize or classify the incident light L2, and thus provide input for at least the characterization or classification of the surface that produces the reflected light component of the incident light L2.

[0079] Figure 5 A light detector 501 is partially shown for use with a light emitter 201 including a polarizer 203 and a sensor head assembly 400, such as Figure 1 The light detector 501 can be used in Figure 1 The spatial profiling system 100 of FIG. 501 may include a polarization diversity photodetector configured for coherent detection, such as in-phase and quadrature (IQ) demodulation.

[0080] The optical detector 501 receives the LO signal, for example, from the optical splitter 204. The LO signal may be further split by the optical splitter 502 to provide N LO signals, where N is the number of detected return signals. Figure 4 and Figure 5 In the example shown, N is 7. In other embodiments, N may be less or more.

[0081] The despeckled signal R-1 and the LO signal are polarized by the first polarizer 503 and the second polarizer 504, respectively. In one example, the first polarizer 503 and the second polarizer 504 are configured to orient the polarized light in orthogonal polarizations, for example, corresponding to polarization orientations aligned and orthogonal to the polarized light from the polarizer 203, respectively. In other words, the first polarizer 503 has a polarization orientation corresponding to one polarization of the polarized light, and the second polarizer 505 has a polarization orientation corresponding to the other polarization of the polarized light. In another example, the first polarizer 503 and the second polarizer 504 are aligned in polarization orientation, for example, both correspond to polarization orientations aligned or orthogonal to the polarized light from the polarizer 203.

[0082] The polarized light from each of the first polarizer 503 and the second polarizer 504 is provided to both the first mixer 505 and the second mixer 506. The first mixer 505 and the second mixer 506 each generate a mixed signal. The mixed signal is provided to the corresponding first photodetector 509 and the second photodetector 510, which generate electrical signals S1-1 and S2-2, respectively. The electrical signals S1-1 and S2-2 carry information for determining the polarization state of the returned light, such as its polarization degree, including the degree of preservation of the polarization state.

[0083] The despeckle signal R-2 is provided to the third mixer 507 together with the LO signal. The third mixer generates a mixed signal for detection by the third photodetector 510, which generates the electrical signal S1-3. The other despeckle signals starting from R-3 are similarly mixed with the LO signal until and including the despeckle signal R-7, which is mixed by the eighth mixer 508 to generate the electrical signal S1-8. The signals S1-1 to S1-8 each include a beat frequency generated by the mixing. The signals S1-1 to S1-8 form Figure 1 These signals are provided to ADC 107 and processing and control system 105.

[0084] exist Figure 5 In the illustrated embodiment, the despeckle signals R-2 to R-7 are not polarized. In other words, their corresponding electrical signals S1-3 to S1-8 are therefore not polarization resolved. However, in other embodiments, some or all of these despeckle signals are also polarized and mixed in a pair of mixers in the same manner as the return signal R-1, resulting in up to twice the signal component in S1 due to the presence of the despeckle signals. In these other embodiments, the electrical signals S1-3 to S1-8 are polarization resolved.

[0085] As mentioned above, Figure 5 The illustrated embodiments are configured for use with polarized output light. When the output light has a single polarization, the second polarizer 504, the second mixer 506 and the second photodetector 510 can be omitted. In these embodiments, the first mixer 1 receives the LO signal from the beam splitter 502.

[0086] The despeckle signals R-1 to R-7 and, in turn, signals S1 and S2, and in particular, components of S1, provide information that can be used, for example, by the processing and control system 105 to make determinations for spatial profiling. Two different reflective surfaces may cause different responses of the return signal to the outgoing polarized light. For example, the different responses may include different detected polarization states. The difference in the detected polarization state may be based on different amplitude ratios between signals S1-1 and S1-2, which carry information for determining the polarization state of any one or more despeckle signals (e.g., R-1). Similarly, two different reflective surfaces may cause different speckle responses of the return signal to the outgoing light. For example, the different responses may include different detected specularity. The difference in detected specularity may be based on an amplitude ratio between signal S1-1 and any one of signals S1-3 to S1-8, or an amplitude ratio between signal S1-2 and any one of signals S1-3 to S1-8. These differences are detectable in components of S1.

[0087] In some embodiments, the absolute intensity and / or relative intensity of or between detected polarizations is used to distinguish between surfaces. For example, metal may have a high degree of polarization preservation, while brick, wood, and leaves may have a low degree of polarization preservation, and fabric may have a moderate degree of polarization preservation. In another example using coherent detection, the phase delay between two (e.g., orthogonal) polarizations detected by the photodetector may be used to distinguish between surfaces. The use of the detected polarization state may be applied only to the despeckle signal R-1, or may be extended to one or more of the despeckle signals R-2 to R-7. In another example, the relative amplitudes of two or more of the despeckle signals R-1 to R-7 may be used to distinguish between surfaces.

[0088] In some embodiments, the detected specularity is used to distinguish surfaces of different materials. The processing and control system 105 can be configured to determine the classification of the surface into different categories based on the detected specularity. The detected specularity can include any one of speckle contrast, speckle granularity, and speckle anisotropy. For example, speckle contrast can be determined based on the standard deviation of the intensity normalized by the mean intensity or the severity of the speckle. For example, speckle granularity can be determined based on the distribution of speckle at different particle sizes. For example, speckle anisotropy can be determined based on directional inhomogeneity or whether the particles are longer in a particular direction.

[0089] In some embodiments, one or more characteristics derived from the detected polarization are used in combination with one or more characteristics derived from the detected specularity to distinguish between surfaces of different materials. In addition, in some embodiments, polarization and / or specularity are used with additional information (e.g., information about the position in the field of view and / or determinations made for areas adjacent to a surface in the field of view).

[0090] In some embodiments, an associated processing system, such as the processing and control system 105, utilizes a lookup process to distinguish between surfaces of different materials. For example, the measured polarization state and / or specularity can be matched to a lookup table, where each row of the table has a unique combination of polarization state and / or specularity and a surface class. The surface class can be specific, such as "wood" or "highly reflective," or can be non-specific, such as "class 1." It should be understood that the surface class can be used, for example, by a control system of an autonomous or semi-autonomous vehicle for determination and / or action.

[0091] In some embodiments, and particularly but not exclusively in embodiments where there are two or more inputs to the process to distinguish between surfaces of different materials, the associated processing system (e.g., processing and control system 105) determines the material class based on a priori machine learning of the relationship between the inputs and the surface class. The machine learning may be supervised machine learning or may be unsupervised machine learning. The machine learning algorithm may include the use of an artificial neural network or other machine learning algorithm.

[0092] In some embodiments, the determination of the material class includes classifying the surface into one of a plurality of material classes based on the detected polarization state and the detected specularity. For example, the correlation processing system is configured to apply a machine learning algorithm such as a support vector machine (SVM), a K-nearest neighbor algorithm (k-NN), or a decision tree.

[0093] Figure 6An example of a processing system 600 for classifying surfaces of different materials based on a machine learning framework is shown. The processing system 600 includes a machine learning model 602, an input for receiving one or more specularity parameters 604 and one or more polarization parameters 606, and an output for material classification 608. The specularity parameters 604 may include relative weights or ratios associated with one or more of the despeckle signals R-1 to R-7. The relative weights or ratios may be based on the magnitude (e.g., power, intensity, or amplitude) of the one or more despeckle signals. Alternatively or additionally, the relative weights or ratios may be based on the phase of the one or more despeckle signals. For example, in a spatial profiling system configured to generate three despeckle signals R-1, R-2, and R-3, where R-1 is associated with a fundamental mode and R-2 and R-3 are associated with higher-order modes, if the reflective surface is a smooth material (e.g., metal), it is expected that the received power of R-1 is significantly higher than the received power of R-2 and R-3. In this case, the specularity parameter 604 may be characterized by a ratio of 90:5:5, indicating that 90% of all received power is contributed by the despeckle signal R-1 alone, and 10% of all received power is contributed equally by the despeckle signals R-2 and R-3 (or 5% each). The ratio 90:5:5 may alternatively be represented by relative weights of 90, 5, and 5 for the respective despeckle signals. In contrast, if the reflective surface is a rough material (e.g., brick), the received power of R-1 is expected to be comparable to the received power of R-2 and R-3. In this case, the specularity parameter 604 may be characterized by a ratio of 40:30:30, indicating that 40% of all received power is contributed by the despeckle signal R-1 alone, and 60% of all received power is contributed equally by the despeckle signals R-2 and R-3 (or 30% each). The ratio 40:30:30 may alternatively be represented by relative weights of 40, 30, and 30 for the respective despeckled signals R-1, R-2, and R-3. The polarization parameters 606 may include one or more Stokes parameters S0, S1, S2, and S3, which are often collectively referred to as Stokes vectors, and each typically ranges from -1 to +1, but each may be scaled by an arbitrary factor.

[0094] In some embodiments, the processing system 600 is trained by a training method based on a training and validation data set. The training method may include obtaining a training data set and a validation data set through experimental observation results. Figure 7An example of an experimental device 700 for obtaining experimental observations is shown. The experimental device 700 includes a spatial profiling system 100, a known material under test 702, and a data storage device 704. The experimental device 700 is configured to measure one or more groups of specular parameters and polarization parameters associated with a plurality of different materials under test via the spatial profiling system 100 once or more times. The experimental device 700 is also configured to store each group of measured specular parameters and polarization parameters in the data storage device 704. In one example, the training method includes obtaining a total of 30,208 measurement sets for four different materials under test, and separating the measurement sets into a training data set of 24,224 measurement sets and a validation data set of 6,056 measurement sets. The training method also includes fitting the obtained data set based on one or more machine learning models, for example, according to a standard machine learning framework (e.g., sklearn). Fitting the obtained data set may include iteratively determining the value of an optimization function (e.g., based on the accuracy of the classification). In each iteration of determining the value of the optimization function, the machine learning model may be adjusted, such as increasing or decreasing the value of one or more parameters of the machine learning model, to achieve different values ​​of the optimization function. In response to producing a predetermined maximum or minimum value (eg, achieving a set accuracy of classification), the iterative determination of the optimization function value may cease.

[0095] Fig. 8A and Figure 8B The performance matrix of the processing system 600 trained according to the disclosed training method under two machine learning models is shown. The different materials tested include black painted panel material, fabric material, 90% diffuse material and wood material. The machine learning model includes a linear classifier, such as logistic regression ( Fig. 8A Alternatively, the machine learning model includes a nonlinear classifier, such as a decision tree ( Figure 8B ). Both machine learning models produced accuracy rates of 99.9% or above when classifying the 4 different materials tested. Fig. 9 The accuracy of the trained processing system under different and further machine learning models is shown. It can be seen that each machine learning model - logistic regression, linear discriminant analysis, K-nearest neighbor, decision tree and Gaussian naive Bayes produces an accuracy of 99% or above.

[0096] In one embodiment, the processing system 600 is configured to classify materials based on a single specularity parameter 604 and a single polarization parameter 606. The single specularity parameter 604 may be associated with a relative amplitude of one of the despeckle signals. The single polarization parameter 606 may be associated with one of the Stokes parameters. In this example, the spatial profiling system 100 is configured to measure the weight (R1-weight) of the received power of the despeckle signal R1 relative to all other despeckle signals. The relative weight is a single numerical value from 0 to 1. The spatial profiling system 100 is also configured to measure the Stokes parameter S1 (R1-S1) of the despeckle signal R1. The Stokes parameter S1 is a single real value (negative or positive). For 4 different materials (wood material, white diffuse material, black panel material, and fabric material), the values ​​of R1-weight and R1-S1 are measured multiple times. Fig.10 It is shown how different materials are associated with such a single specularity parameter and such a single polarization parameter. Fig.10 A clear separation in clusters based on a single specularity parameter and a single polarization parameter is shown, each cluster representing one of the test materials. This clear separation of clusters corresponds to a high accuracy in the machine learning based classification based on a single specularity parameter and a single polarization parameter. Fig.10 It is also implied that if a single specularity parameter or a single polarization parameter is used to classify the material under test, the separation of the clusters will be lost and the machine learning based classification based on either single parameter will be less accurate.

[0097] It should be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All these different combinations constitute various alternative aspects of the invention.

Claims

1. A spatial profiling system for profiling an environment, the spatial profiling system comprising: a light emitter for providing light; a beam director for directing light in one or more directions toward the environment; an optical receiver for receiving return light reflected by a surface or object in the environment, the return light carrying information for determining a distance to the surface or object, the optical receiver being configured to detect (a) specularity of the return light and (b) a polarization state of the return light; A processing system is configured to determine a material associated with the surface or object based on the detected specularity and the detected polarization state.

2. The spatial analysis system according to claim 1, wherein: The processing system is configured to determine the material associated with the surface or object by classifying the material into one of a plurality of material classes.

3. The spatial analysis system according to claim 2, wherein: Classifying the material into one of a plurality of material categories includes classification including applying one or more machine learning algorithms.

4. The spatial analysis system according to any one of claims 1 to 3, wherein: The light receiver is further configured to detect specularity based on an image or interference pattern associated with the speckle.

5. The spatial profiling system according to claim 4, wherein: The image or interference represents a spatial sample of the surface or object from which light is reflected.

6. The spatial analysis system according to any one of claims 1 to 5, wherein: The optical receiver is further configured to detect specularity based on the plurality of despeckle signals.

7. The spatial profiling system according to claim 6, wherein: The optical receiver is further configured to recover or provide an amplitude measurement and / or a phase measurement of one or more of the plurality of despeckled signals.

8. The spatial profiling system according to claim 7, wherein: The specularity is characterized by one or more specularity parameters, each specularity parameter being associated with an amplitude of a despeckle signal of one or more despeckle signals of the plurality of despeckle signals.

9. The spatial profiling system according to claim 8, wherein: The polarization state is characterized by one or more Stokes parameters associated with one of the one or more despeckle signals in the plurality of despeckle signals.

10. The spatial profiling system according to any one of claims 1 to 9, wherein: The processing system is further configured to determine any one of speckle contrast, speckle granularity, and speckle anisotropy based on the detected specularity.

11. The spatial profiling system according to claim 10, wherein: The processing system is further configured to determine the material associated with the surface or object based on any one or more of the determined speckle contrast, speckle granularity, and speckle anisotropy.

12. The spatial profiling system according to any one of claims 1 to 11, wherein: The optical receiver is further configured to detect the polarization state based on a degree of preservation of the polarization state.

13. The spatial profiling system according to claim 12, wherein: The degree of preservation of the polarization state represents the polarization degree of the returning light relative to the polarization degree of the outgoing light or the local oscillator.

14. The spatial analysis system according to claim 12 or 13, wherein: The processing system is also configured to determine the material associated with the surface or object based on the degree of preservation of the polarization state.

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