Distributed Aperture Optical Ranging System

Abstract

This disclosure relates to multiple-input multiple-output (MIMO) optical detection and ranging (LiDAR) systems in which the fields of view of multiple illuminators (e.g., lasers) overlap and / or the fields of view of multiple detectors (e.g., photodiodes) overlap. Some embodiments provide illuminators that transmit a sequence of pulses that is substantially white and substantially uncorrelated such that they can be distinguished from one another when detected by a single detector.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 884,651, filed on August 8, 2019, entitled "DISTRIBUTED APERTURE OPTICAL RANGING SYSTEM", and hereby incorporates it by reference herein. Background Art

[0003] There is a continuing need for three - dimensional (3D) object tracking and object scanning for various applications, one of which is autonomous driving. The wavelengths of some types of signals, such as radar, are too long to provide the sub - millimeter resolution required to detect smaller objects. The optical wavelengths used by light detection and ranging (LiDAR) systems can provide finer resolution than other types of systems, thus providing good range, accuracy, and resolution. Generally, a LiDAR system illuminates a target area or scene with pulsed laser light and measures how long it takes for the reflected pulse to return to the receiver.

[0004] One aspect common to some traditional LiDAR systems is that the beams emitted by different lasers are very narrow and are emitted in specific known directions such that the pulses emitted by different lasers simultaneously or approximately simultaneously do not interfere with each other. Each laser has a detector located nearby to detect the reflection of the pulse emitted by the laser. Since it is assumed that the detector senses only the reflection of the pulse emitted by the laser, the position of the target reflecting the emitted pulse can be determined unambiguously. The time between the emission of the light pulse by the laser and the detection of the reflection provides the round - trip time to the target, and the direction in which the transmitter and detector are oriented allows the precise position of the target to be determined. If no reflection is detected, it is assumed that there is no target.

[0005] To reduce the number of lasers and detectors required to provide a sufficient scan of a scene, some LiDAR systems use a relatively small number of lasers and detectors and some method of mechanically scanning the environment. For example, a LiDAR system can include transmit and receive optics located on a rotating motor to provide a 360 - degree horizontal field of view. By rotating in small increments (e.g., 0.1 degrees), these systems can provide high resolution. However, LiDAR systems relying on mechanical scanning are constrained by the receiver and transmitter optics. These constraints limit the overall size and dimensions of the LiDAR system, the size and position of the individual components, as well as the measurement range and signal - to - noise ratio (SNR). In addition, the moving components are prone to failure and may be undesirable for some applications (e.g., autonomous driving).

[0006] Another type of LiDAR system is a flash LiDAR system. The flash LiDAR system directs a pulsed beam of light towards a target object within the field of view, and an array of light detectors receives the light reflected from the target object. For each pulsed beam of light directed towards the target object, the array of light detectors can receive the reflected light corresponding to a frame of data. By using one or more frames of data, the range or distance to the target object can be obtained by determining the time elapsed between when the illumination source emits the pulsed beam of light and when the array of light detectors receives the reflected light. Although the flash LiDAR system avoids moving components, in order to unambiguously detect the angle of reflection, the light detectors use a large number of optical detectors, each corresponding to a certain direction (e.g., elevation angle and azimuth angle) to scan a large scene. For some applications, such as autonomous driving, the cost, size, and / or power consumption of such a system may be prohibitive.

[0007] Accordingly, there is a need for a system that addresses the disadvantages of traditional LiDAR systems. SUMMARY OF THE INVENTION

[0008] This summary represents a non-limiting example of the present disclosure.

[0009] Disclosed herein are novel LiDAR systems that use fewer optical components (illuminators and detectors) than traditional LiDAR systems, but provide higher resolution. Compared to traditional LiDAR systems, both the illuminator (e.g., a laser) and the detector (e.g., a photodiode) have a wider and overlapping field of view, resulting in the possibility that a single illuminator illuminates multiple targets within its field of view and a single detector detects reflections from multiple targets within its field of view (which may be caused by emissions from different illuminators). To allow for resolving the positions (also referred to as coordinates) of multiple targets within a spatial volume, the disclosed LiDAR systems use multiple illuminators and / or detectors that are positioned non-collinearly (meaning they do not all lie on a single straight line). To allow the LiDAR system to distinguish the reflections of optical signals emitted by different illuminators, the illuminators that emit signals within the spatial volume use pulse sequences with specific properties (e.g., they are substantially white and have a low cross-correlation with the pulse sequences used by other illuminators simultaneously emitting within the same field of view). Because they use multiple reflections of optical signals that may originate from multiple illuminators to resolve targets, the novel LiDAR systems are referred to herein as multiple-input multiple-output (MIMO) LiDAR systems.

[0010] In some embodiments, a LiDAR system includes an array of optical components that includes a plurality of illuminators and a plurality of detectors. Each of the plurality of illuminators has a corresponding illuminator field of view (FOV), and each of the plurality of detectors has a corresponding detector FOV, and at least one processor coupled to the array of optical components and configured to execute at least one machine-executable instruction. The at least one machine-executable instruction, when executed, causes the at least one processor to determine a first set of distances, a second set of distances, and a third set of distances, and to estimate, at least in part based on the first set of distances, the second set of distances, and the third set of distances, a corresponding position of each of a plurality of targets in three-dimensional space. In some embodiments, the first set of distances corresponds to a first unique illuminator-detector pair in the array of optical components, and for each of the plurality of targets in the volume of space, the first set of distances includes the corresponding estimated distance traveled by an optical signal emitted by the illuminator of the first unique illuminator-detector pair, reflected by the target, and detected by the detector of the first unique illuminator-detector pair. In some embodiments, the second set of distances corresponds to a second unique illuminator-detector pair in the array of optical components, and for each of the plurality of targets in the volume of space, the second set of distances includes the corresponding estimated distance traveled by an optical signal emitted by the illuminator of the second unique illuminator-detector pair, reflected by the target, and detected by the detector of the second unique illuminator-detector pair. In some embodiments, the third set of distances corresponds to a third unique illuminator-detector pair in the array of optical components, and for each of the plurality of targets in the volume of space, the third set of distances includes the corresponding estimated distance traveled by an optical signal emitted by the illuminator of the third unique illuminator-detector pair, reflected by the target, and detected by the detector of the third unique illuminator-detector pair. In some embodiments, at least two of the illuminator of the first unique illuminator-detector pair, the detector of the first unique illuminator-detector pair, the illuminator of the second unique illuminator-detector pair, the detector of the second unique illuminator-detector pair, the illuminator of the third unique illuminator-detector pair, or the detector of the third unique illuminator-detector pair are non-collinear. In some embodiments, the volume of space is within each of the following: (a) the FOV of the illuminator of the first unique illuminator-detector pair, (b) the FOV of the detector of the first unique illuminator-detector pair, (c) the FOV of the illuminator of the second unique illuminator-detector pair, (d) the FOV of the detector of the second unique illuminator-detector pair, (e) the FOV of the illuminator of the third unique illuminator-detector pair, and (f) the FOV of the detector of the third unique illuminator-detector pair.

[0011] In some embodiments, the at least one machine-executable instruction causes the at least one processor to estimate a respective position of each of the plurality of targets by solving at least one quadratic equation.

[0012] In some embodiments, the at least one machine-executable instruction causes the at least one processor to determine a first set of distances, at least in part, by denoising an optical signal detected by a detector of a first unique illuminator-detector pair, performing a correlation on the denoised detected optical signal and an optical signal transmitted by an illuminator of the first unique illuminator-detector pair, and identifying at least one peak in a result of the correlation. In some embodiments, denoising the optical signal detected by the detector of the first unique illuminator-detector pair includes determining or minimizing an atomic norm.

[0013] In some embodiments, the at least one machine-executable instruction causes the at least one processor to determine a first set of distances, at least in part, by performing a correlation and identifying at least one peak in a result of the correlation.

[0014] In some embodiments, the optical signal transmitted by the illuminator of the first unique illuminator-detector pair includes a first sequence of pulses transmitted during a time window. In some embodiments, where the optical signal transmitted by the illuminator of the first unique illuminator-detector pair includes a first sequence of pulses transmitted during a time window, the first sequence of pulses is sparse. In some embodiments, the first sequence of pulses is substantially white.

[0015] In some embodiments, where the optical signal transmitted by the illuminator of the first unique illuminator-detector pair includes a first sequence of pulses transmitted during a time window, the optical signal transmitted by the illuminator of a second unique illuminator-detector pair includes a second sequence of pulses transmitted during the time window, where the second sequence of pulses is different from the first sequence of pulses. In some embodiments, the first sequence of pulses and the second sequence of pulses are substantially uncorrelated. In some embodiments, the first sequence of pulses and the second sequence of pulses are sparse. In some embodiments, each of the first sequence of pulses and the second sequence of pulses is substantially white. In some embodiments, a maximum value of a cross-correlation of the first sequence of pulses and the second sequence of pulses is less than a threshold (e.g., a maximum number of overlapping pulses).

[0016] In some embodiments, the optical signal emitted by the illuminator of the first unique illuminator-detector pair includes a first pulse sequence transmitted during a time window, and the optical signal emitted by the illuminator of the second unique illuminator-detector pair includes a second pulse sequence transmitted during the time window, and the optical signal emitted by the illuminator of the third unique illuminator-detector pair includes a third pulse sequence transmitted during the time window, wherein the third pulse sequence is different from the first pulse sequence and different from the second pulse sequence. In some such embodiments, the first pulse sequence and the second pulse sequence are substantially uncorrelated, the first pulse sequence and the third pulse sequence are substantially uncorrelated, and the second pulse sequence and the third pulse sequence are substantially uncorrelated. In some embodiments, the first pulse sequence, the second pulse sequence, and the third pulse sequence are sparse. In some embodiments, each of the first pulse sequence, the second pulse sequence, and the third pulse sequence is substantially white.

[0017] In some embodiments, at least two of the illuminators of the first unique illuminator-detector pair, the illuminator of the second unique illuminator-detector pair, or the illuminator of the third unique illuminator-detector pair are the same illuminator.

[0018] In some embodiments, at least two of the detectors of the first unique illuminator-detector pair, the detector of the second unique illuminator-detector pair, or the detector of the third unique illuminator-detector pair are the same detector.

[0019] In some embodiments, at least two of the illuminators of the first unique illuminator-detector pair, the illuminator of the second unique illuminator-detector pair, or the illuminator of the third unique illuminator-detector pair are the same illuminator, and at least two of the detectors of the first unique illuminator-detector pair, the detector of the second unique illuminator-detector pair, or the detector of the third unique illuminator-detector pair are the same detector.

[0020] In some embodiments, when the at least one machine-executable instruction is executed, it causes the at least one processor to estimate the corresponding position of each of the plurality of targets in three-dimensional space by solving at least one optimization problem. In some embodiments, the at least one optimization problem includes

[0021] In some embodiments, when the at least one machine-executable instruction is executed, it causes the at least one processor to estimate the corresponding position of each of the plurality of targets in three-dimensional space by determining whether at least one estimated distance in a first set of distances, a second set of distances, or a third set of distances corresponds to a stored pre-computed distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The objects, features, and advantages of the present disclosure will become apparent from the following description of certain embodiments in conjunction with the accompanying drawings, wherein:

[0023] Figure 1A is a block diagram of certain components of a MIMO LiDAR system according to some embodiments.

[0024] Figure 1B is a more detailed view of an array of optical components of a MIMO LiDAR system according to some embodiments.

[0025] Figure 2A 、 Figure 2B and Figure 2C depict an illuminator according to some embodiments.

[0026] Figure 3A 、 Figure 3B and Figure 3C depict a detector according to some embodiments.

[0027] Figure 4A and Figure 4B is a representation of an array of optical components according to some embodiments.

[0028] Figure 5 illustrates how an exemplary MIMO LiDAR system can provide subsets of illuminators such that each subset is adapted to illuminate and contribute to the detection of targets in a specified range.

[0029] Figure 6A 、 Figure 6B 、 Figure 6C and Figure 6D illustrate several configurations of unique illuminator-detector pairs according to some embodiments.

[0030] Figure 7A 、 Figure 7B 、 Figure 7C and Figure 7D illustrates how an exemplary array of optical components can be used to determine the positions of multiple targets in three-dimensional space within a spatial volume according to some embodiments.

[0031] Figure 8A 、 Figure 8B 、 Figure 8C and Figure 8D illustrates how an exemplary MIMO LiDAR system can use three illuminators and one detector to determine the position of a target in a spatial volume according to some embodiments.

[0032] Figure 9A illustrates two simple pulse sequences according to some embodiments to show the design principle of the pulse sequence.

[0033] Figure 9Bshows, according to some embodiments, Figure 9A the autocorrelation of one of the simple exemplary pulse sequences shown.

[0034] Figure 9C shows, according to some embodiments, Figure 9A the autocorrelation of another simple exemplary pulse sequence shown.

[0035] Figure 9D shows, according to some embodiments, Figure 9A the cross - correlation of the simple pulse sequences shown.

[0036] Figure 10A , Figure 10B , Figure 10C , Figure 10D , Figure 10E and Figure 10F shows how another exemplary MIMO LiDAR system, according to some embodiments, uses two illuminators and two detectors to determine the position of an object in a spatial volume.

[0037] For ease of understanding, where possible, the same reference numerals are used to denote the same elements common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially used in other embodiments without specific recitation. Additionally, the description of an element in the context of one figure applies to other figures showing that element. Detailed Description

[0038] Disclosed herein are novel LiDAR systems and methods for detecting the presence and coordinates of objects (also referred to herein as targets) in a scene using an array of optical components (i.e., multiple illuminators and multiple detectors). Among many other applications, one application of the disclosed LiDAR system is for scene sensing in autonomous driving or for automated transportation.

[0039] The disclosed LiDAR system includes multiple illuminators (e.g., lasers) and multiple optical detectors (e.g., photodiodes, such as avalanche photodetectors). The illuminators and detectors are arranged in an array. Although the description herein refers to a single array (e.g., the optical component array 110 further described and discussed below), it should be understood that the illuminator and detector arrays can be separate (logically and / or physically), depending on how the illuminators and detectors are positioned. To allow the LiDAR system to estimate the position of an object in the sensed scene, the optical component array (or, if the illuminators and detectors are considered in separate arrays, at least one of the arrays (illuminator and / or detector)) is two - dimensional.

[0040] Because multiple optical signals and / or reflections are used to determine the positions of multiple targets (e.g., objects) in three-dimensional space, the system is sometimes referred to herein as a multiple-input multiple-output (MIMO) LiDAR system.

[0041] In the following description, some embodiments include multiple components or elements. These components or elements are generally referred to individually using reference numerals (e.g., (multiple) illuminators 120, (multiple) detectors 130), and specific instances of these components or elements are referred to and illustrated using reference numerals followed by letters (e.g., illuminator 120A, detector 130A). It should be understood that the drawings may only show specific instances of the components or elements (with additional letters), and the specification may refer generally to those shown components or elements (without additional letters).

[0042] Figure 1A is a schematic diagram of certain components of a MIMO LiDAR system 100 according to some embodiments. The system 100 includes an array of optical components 110 coupled to at least one processor 140. The array of optical components 110 may be in the same physical housing (or enclosure) as the at least one processor 140, or it may be physically separate.

[0043] The at least one processor 140 can be, for example, a digital signal processor, a microprocessor, a controller, an application specific integrated circuit, or any other suitable hardware component (which may be adapted to process analog and / or digital signals). The at least one processor 140 can provide control signals 142 to the array of optical components 110. The control signals 142 can, for example, cause one or more illuminators in the array of optical components 110 to emit optical signals (e.g., light) sequentially or simultaneously. As described further below, the control signals 142 can cause the illuminators to emit optical signals in the form of a pulse sequence, which can be different for different illuminators.

[0044] The system 100 may also optionally include one or more analog-to-digital converters (ADCs) 115, which are disposed between the array of optical components 110 and the at least one processor 140. If present, the one or more ADCs 115 convert the analog signals provided by the detectors in the array of optical components 110 into a digital format for processing by the at least one processor 140. The analog signal provided by each detector can be a superposition of reflected optical signals detected by that detector, and then the at least one processor 140 can process it to determine the position of the target corresponding to (causing) the reflected optical signal.

[0045] Figure 1BFIG. 0 is a more detailed view of the optical component array 110 of the MIMO LiDAR system 100 according to some embodiments. As shown, the optical component array 110 includes a plurality of illuminators 120 and a plurality of detectors 130. (As previously mentioned, reference numeral 120 is used herein to generally refer to an illuminator, and reference numerals 120 with appended letters are used to refer to individual illuminators. Similarly, reference numeral 130 is used herein to generally refer to a detector, and reference numerals 130 with appended letters are used to refer to individual detectors). Although Figure 1B Illuminators 120A, 120B, 120C, and 120N are shown, thereby implying that there are 14 illuminators 120 in the optical component array 110, it should be understood that, as used herein, the word "plurality" means "two or more." Thus, the optical component array 110 may include as few as two illuminators 120, or it may include any number of illuminators 120 greater than two. Similarly, although Figure 1B Detectors 130A, 130B, 130C, and 130M are shown, thereby implying that there are thirteen detectors 130 in the optical component array 110, it should be understood that the optical component array 110 may include as few as two detectors 130, or may include any number of detectors 130 greater than two.

[0046] Figure 2A , Figure 2B and Figure 2C Illuminator 120 according to some embodiments is depicted. Illuminator 120 may be, for example, a laser, and it may operate at any wavelength (e.g., 905 nm or 1550 nm). Illuminator 120 is shown as having a spherical shape, which is merely symbolic. Throughout the document, merely to allow illuminator 120 and detector 130 to be easily distinguishable, illuminator 120 is shown as circular or spherical, and detector 130 is shown as a cube or square. In one embodiment, illuminator 120 in the optical component array 110 may be of any suitable size and shape. As is known in the art, illuminator 120 may be equipped with a lens (not shown) to focus and direct the optical signal it emits. Additionally, some or all of illuminators 120 may further include one or more mirrors to direct the emitted optical signal in a specific direction. Illuminator 120 may also contain a diffuser to give its field of view (discussed further below) a specific shape (square, rectangle, circle, ellipse, etc.) and to promote the uniformity of the transmitted beam passing through its field of view.

[0047] Each illuminator 120 in the optical component array 110 has a position in three-dimensional space, which can be characterized by Cartesian coordinates (x, y, z) on the x-axis, y-axis, and z-axis, as Figure 2AAs shown. Alternatively, any other coordinate system (e.g., spherical coordinate system) can be used.

[0048] As Figure 2B shown, in addition to having a position in three-dimensional space, each illuminator 120 has two azimuth angles: the azimuth axis-of-view angle 124 and the azimuth field-of-view (FOV) angle 126. The azimuth angles (124, 126) are in the horizontal plane, using the coordinate system provided in Figure 2A which the horizontal plane is the x-y plane at a certain z value. In other words, the azimuth axis-of-view angle 124 and the azimuth FOV angle 126 specify the "left-to-right" characteristic of the optical signal emitted by the illuminator 120. The azimuth axis-of-view angle 124 specifies the direction in which the illuminator 120 is pointing, which determines the general direction in which the optical signal emitted by the illuminator 120 propagates. The azimuth FOV angle 126 specifies the angular width of a portion of the scene illuminated by the optical signal emitted by the illuminator 120 (e.g., the beam width in the horizontal direction).

[0049] As Figure 2C shown, each illuminator 120 also has two elevation angles: the elevation axis-of-view angle 125 and the elevation FOV angle 127. The elevation angle is relative to the horizontal plane, using the coordinate system provided in Figure 2A which the horizontal plane is the x-y plane at a certain z value. Thus, Figure 2C the horizontal axis shown in

[0050] is labeled "h" to indicate that it is in a certain direction in the x-y plane, which is not necessarily parallel to the x-axis or the y-axis. (The direction of the "h" axis depends on the azimuth axis-of-view angle 124). The elevation axis-of-view angle 125 and the elevation FOV angle 127 specify the "up-and-down" characteristic of the optical signal emitted by the illuminator 120. The elevation axis-of-view angle 125 determines the height or altitude at which the illuminator 120 is pointing, which determines the general direction in which the optical signal emitted by the illuminator 120 propagates. The elevation FOV angle 127 specifies the angular height of a portion of the scene illuminated by the optical signal emitted by the illuminator 120 (e.g., the beam width in the vertical direction).

[0050] The elevation FOV angle 127 of the illuminator 120 can be the same as or different from the azimuth FOV angle 126 of the illuminator 120. As will be understood by those of ordinary skill in the art, the light beam emitted by the illuminator 120 can have any suitable three-dimensional shape. For example, the emitted light beam can generally be conical (where the cone is an object composed of a set of (infinitely many) light rays). The cross-section of the cone can be any shape, such as circular, elliptical, square, rectangular, etc.).

[0051] The volume of space illuminated by an illuminator 120 having boresight angles 124, 125 and FOV angles 126, 127 is referred to herein as illuminator FOV 122. Objects within the illuminator FOV 122 of a particular illuminator 120 are illuminated by the optical signal transmitted by the illuminator 120. The illuminator FOV 122 of an illuminator 120 depends on and is determined by the position of the illuminator 120 within the optical component array 110, as well as the boresight angles 124, 125 and FOV angles 126, 127 of the illuminator 120. The range of the illuminator 120 depends on the optical power.

[0052] The optical assembly array 110 includes a plurality of illuminators 120, which can be identical to one another or differ in one or more characteristics. For example, different illuminators 120 can have different locations within the optical assembly array 110 and, therefore, different positions in space (i.e., they have different (x, y, z) coordinates). The boresight angles 124, 125 and field of view angles 126, 127 of different illuminators 120 can also be the same or different. For example, as further described below, a subset of the illuminators 120 can be configured such that they primarily illuminate targets within a certain range of the MIMO LiDAR system 100 and are used in conjunction with a detector 130 configured to primarily detect targets within that same range. Similarly, the power of the optical signals emitted by different illuminators 120 can be the same or different. For example, illuminators 120 intended to illuminate targets farther away from the MIMO LiDAR system 100 can use more power than illuminators 120 intended to illuminate targets closer to the MIMO LiDAR system 100. Another way to extend the range of objects illuminated by the illuminator 120 is to incorporate repetition of the transmit pulse sequence (described further below) and / or summing / accumulating and / or averaging the received reflected signals at the detector 130. This approach can increase the received SNR without increasing the transmit power.

[0053] As will be described further below, one novel aspect of the LiDAR system 100 disclosed herein is that the boresight angles 124, 125 and FOV angles 126, 127 of the illuminators 120 in the optical assembly array 110 can be selected so that the light beams emitted by different illuminators 120 overlap, thereby causing the different illuminators 120 to illuminate overlapping portions of the scene (and spatial volume). Unlike conventional LiDAR systems, the MIMO LiDAR system 100 disclosed herein is able to resolve the three-dimensional positions of multiple targets within these overlapping spatial regions. Furthermore, they do not require any moving parts. The optical assembly array 110 can be fixed.

[0054] Figure 3A 、 Figure 3B and Figure 3CDepicts detector 130 according to some embodiments. Detector 130 can be, for example, a photodetector. In some embodiments, detector 130 is an avalanche photodiode. As will be understood by those of ordinary skill in the art, an avalanche photodiode operates under high reverse bias conditions, which results in avalanche multiplication of holes and electrons generated by photon collisions. When photons enter the depletion region of the photodiode and generate electron-hole pairs, the generated charge carriers are pulled away from each other by the electric field. Their speed increases, and when they collide with the lattice, they generate additional electron-hole pairs, which are then pulled away from each other, collide with the lattice, and generate more electron-hole pairs, and so on. The avalanche process increases the gain of the diode, thus providing higher sensitivity than a normal diode. Like illuminator 120, detector 130 can include a lens that focuses the received signal. Additionally, like illuminator 120, detector 130 can include one or more mirrors to direct the received light in a selected direction.

[0055] Detector 130 is shown as having a cubic shape, which is merely symbolic. As described above, throughout the document, merely to allow illuminator 120 and detector 130 to be easily distinguishable, illuminator 120 is shown as circular or spherical, and detector 130 is shown as cubic or square. In one embodiment, the detectors 130 in the optical component array 110 can be of any suitable size and shape.

[0056] Each detector 130 in the optical component array 110 has a position in three-dimensional space, which, as previously described, can be characterized by Cartesian coordinates (x, y, z) on the x-axis, y-axis, and z-axis, as Figure 3A shown. Alternatively, any other coordinate system (e.g., spherical coordinate system) can be used.

[0057] As Figure 3B shown, in addition to having a position in three-dimensional space, each detector 130 has two azimuth angles: the azimuthal boresight angle 134 and the azimuthal FOV angle 136. As in the case of illuminator 120, the azimuth angles of detector 130 are in the horizontal plane, using the coordinate system provided in Figure 3A which the horizontal plane is the x-y plane at a certain z value. In other words, the azimuthal boresight angle 134 and the azimuthal FOV angle 136 specify the "left-to-right" positioning of detector 130 (e.g., the position it "looks" at in the horizontal plane). The azimuthal boresight angle 124 specifies the direction in which detector 130 points, which determines the general direction in which it detects optical signals. The azimuthal FOV angle 126 specifies the angular width in the horizontal direction of the portion of the scene sensed by detector 130.

[0058] As Figure 3CAs shown, each detector 130 also has two elevation angles: an elevation boresight angle 135 and an elevation FOV angle 137. The elevation angle is relative to the horizontal plane, using the coordinate system provided in Figure 3A where the horizontal plane is the x-y plane at a certain z value. Thus, Figure 3C the horizontal axis shown in

[0059] is labeled "h" to indicate that it is in a certain direction in the x-y plane, which is not necessarily parallel to the x-axis or the y-axis. (The direction of the "h" axis depends on the azimuth boresight angle 134). The elevation boresight angle 135 and the elevation FOV angle 137 specify the "up and down" positioning of the detector 130. The elevation boresight angle 135 determines the height or altitude at which the detector 130 points, which determines the general direction in which it detects optical signals. The elevation FOV angle 137 specifies the angular height of a portion of the scene sensed by the detector 130 (e.g., the beam width in the vertical direction). The elevation FOV angle 137 of the detector 130 can be the same as or different from the azimuth FOV angle 136 of that detector 130. In other words, the vertical span of the detector 130 can be the same as or different from its horizontal span.

[0060] The volume of space sensed by the detectors 130 with boresight angles 134, 135 and FOV angles 136, 137 is referred to herein as the detector FOV 132. Optical signals reflected by objects within the detector FOV 132 of a particular detector 130 can be detected by that detector 130. The detector FOV 132 of the detector 130 depends on and is determined by: the position of the detector 130 in the optical component array, and the boresight angles 134, 135 and FOV angles 136, 137 of the detector 130. The range of the detector 130 depends on the sensitivity of the detector 130.

[0061] As will be further described below, a novel aspect of the LiDAR system 100 disclosed herein is that the viewing axis angles 134, 135 and FOV angles 136, 137 of the detectors 130 in the optical component array 110 can be selected such that they sense overlapping portions of the scene. Different from traditional LiDAR systems, the MIMO LiDAR system 100 herein is capable of discerning the three-dimensional positions of multiple targets within these overlapping spatial regions. Moreover, they do not require any moving parts. The optical component array 110 can be fixed.

[0062] Figure 4A and Figure 4B is a representation of the optical component array 110 according to some embodiments. Figure 4A is a "direct view" of the optical component array 110 in the y-z plane, which means that the optical signals emitted by the illuminator 120 will come out of the page at various viewing axis angles 124, 125 and have various FOV angles 126, 127, and the optical signals reflected by an object (target) will be sensed by the detectors 130 having various viewing axis angles 134, 135 and various FOV angles 136, 137 that also come out of the page. According to the convention described previously, the illuminator 120 is represented by a circle, most of which is unlabeled, and the detector 130 is represented by a square, most of which is also unlabeled. The exemplary optical component array 110 shown includes more detectors 130 than illuminators 120. As previously mentioned, the optical component array 110 can have an equal or unequal number of illuminators 120 and detectors 130. For example, there can be more illuminators 120 than detectors 130. There can be an equal number of illuminators 120 and detectors 130. Generally, the optical component array 110 has multiple illuminators 120 (which may be different in various aspects as described above) and multiple detectors 130 (which may be different in various aspects as described above).

[0063] Figure 4A An illuminator 120A is marked, and its position (coordinates) are given by a certain x value and y1 and z2. If the x value is assumed to be 0, the position of the illuminator 120A in Cartesian coordinates is (0, y1, z2). Figure 4A A detector 130A is also marked, which has a position (0, y1, z1) under the assumption that the value of x is 0.

[0064] Figure 4B is a simplified cross-sectional view of the optical component array 110 at position y1. Figure 4BThe horizontal axis in [the figure] is labeled "h", but it should be noted that the elevation angles of the illuminator 120A and the detector 130A do not need to be at the same azimuth axis angle 124, 134. In other words, as described above, different illuminators 120 and / or detectors 130 can be oriented in different directions. As shown in the figure, the illuminator 120A emits an optical signal at an elevation FOV 127A and an elevation axis angle 125A. Similarly, the detector 130A is oriented at an elevation axis angle 135A and has an elevation FOV 137A.

[0065] In some embodiments, a subset of the illuminators 120 and / or detectors 130 has characteristics (such as axis angles 124, 125, 134, 135 and FOV angles 126, 127, 136, 137) that are selected such that certain combinations of the illuminators 120 and / or detectors 130 illuminate and / or sense objects within certain ranges (e.g., within a specific distance range from the optical component array 110), respectively. Figure 5 Shows how an exemplary MIMO LiDAR system 100 according to some embodiments can provide a subset of illuminators 120 such that each subset is suitable for illuminating a target within a specified range and aids in the detection of the target. Although Figure 5 the illuminator 120 is shown, it should be understood that the same principles described Figure 5 apply to the detector 130. Specifically, the detector 130 can likewise be configured to be suitable for detecting a subset of targets within a specified range. In this sense, Figure 5 the illuminator 120 in [the figure] can be replaced by the detector 130.

[0066] Figure 5Four distances, namely d1, d2, d3, and d4, are shown on the horizontal axis. Seven illuminators 120, including illuminator 120A and the other illuminators shown without shading, are in a first subset of the illuminators 120 that illuminate targets close to the optical component array 110 of the MIMO LiDAR system 100. Specifically, the line-of-sight angles 124, 125 and the FOV angles 126, 127 of illuminator 120A and the other non-shaded illuminators 120 are selected such that they are most likely to illuminate (and allow detection of) targets at distances from the optical component array 110 in the range of 0 to d1. Four illuminators 120, including illuminator 120B and the other illuminators shown with horizontal stripe shading, are in a second subset of the illuminators 120 that have line-of-sight angles 124, 125 and FOV angles 126, 127 selected such that they are most likely to illuminate (and allow detection of) targets at distances from the optical component array 110 in the range of 0 to d2. Four illuminators 120, including illuminator 120C and the other illuminators shown with diagonal stripe shading, are in a third subset of the illuminators 120 that have line-of-sight angles 124, 125 and FOV angles 126, 127 selected such that they are most likely to illuminate (and allow detection of) targets at distances from the optical component array 110 in the range of 0 to d3. Two illuminators, including illuminator 120D and the other illuminator shown with cross-hatching, are in a fourth subset of the illuminators 120 that have line-of-sight angles 124, 125 and FOV angles 126, 127 selected such that they are most likely to illuminate (and allow detection of) targets at distances from the optical component array 110 in the range of 0 to d4. As shown (but not labeled to avoid obscuring the figure), the FOV angles 126, 127 of the illuminators 120 in the first subset are greater than the FOV angles 126, 126 of the illuminators 120 in the second, third, and fourth subsets. Similarly, the FOV angles 126, 127 of the illuminators 120 in the second subset are greater than the FOV angles 126, 126 of the illuminators 120 in the third and fourth subsets, and the FOV angles 126, 127 of the illuminators 120 in the third subset are greater than the FOV angles 126, 126 of the illuminators 120 in the fourth subset.

[0067] It should be understood that Figure 5 is a two-dimensional representation, and the above discussion assumes that Figure 5 shows the azimuth line-of-sight angles 124, 125 and the FOV angles 126, 127. The above discussion equally applies to the elevation angle, and Figure 5 the elevation angle can also be illustrated. It should also be understood that Figure 5The intention is illustrative and does not necessarily represent how the real MIMO LiDAR system 100 will be configured. For example, one implementation may have detectors 130 (e.g., evenly or unevenly, regularly or irregularly, etc.) scattered between or distributed among the illuminators 120. Additionally, Figure 5 is limited to two dimensions and only shows a "cross-section" of the set of illuminators 120 of the MIMO LiDAR system 100. As further explained below, the (multiple) illuminators 120 and the (multiple) detectors 130 for determining the position (coordinates) of a target in a specific spatial volume are non-collinear, which is not shown in Figure 5 this figure. Figure 5 Nor are any detectors 130 or any other components (optical or otherwise) of the MIMO LiDAR system 100 shown. Additional optical components (e.g., illuminators 120, detectors 130) may be, for example, above, below, to the side of, and / or scattered between the illuminators 120 in the optical component array 110 shown in Figure 5 this figure.

[0068] As Figure 5As a specific example of the principle shown, a first subset of illuminators 120 can have an optical axis angle 124, 125, FOV angle 126, 127, power level, and other characteristics selected such that the emitted optical signal is intended to illuminate all objects within a first range (e.g., 10 to 50 meters) from the MIMO LiDAR system 100, and a first subset of detectors 130 can have an optical axis angle 134, 135, FOV angle 136, 137, and other characteristics (e.g., sensitivity) selected to sense objects within the first range. The optical axis angles 124, 125, 134, 135 and / or FOV angles 126, 127, 136, 137 of the first subset of illuminators 120 and the first subset of detectors 130 can be the same as or different from each other. For example, all optical axis angles 124, 125, 134, 135 can be 0 degrees (perpendicular to the optical component array 110, aiming "straight ahead"), and the FOV angles 126, 127, 13, 137 of the first subset of illuminators 120 and the first subset of detectors 130 can be, for example, 90 degrees (resulting in a "straight ahead" optical axis and a field of view of 45 degrees to either side and up and down (e.g., ±45 degrees)). A second subset of illuminators 120 can have an optical axis angle 124, 125, FOV angle 126, 127, power level, and other characteristics selected such that the emitted optical signal is intended to illuminate objects within a range of 50 to 200 meters, and a second subset of detectors 130 can have an optical axis angle 134, 135, FOV angle 136, 137, and other characteristics selected to sense objects within the second range. The optical axis angles 124, 125, 134, 135 of the second subset of illuminators 120 and the second subset of detectors 130 can be, for example, 0 degrees (perpendicular to the optical component array 110, aiming "straight ahead"), and the FOV angles 126, 127, 136, 137 of the second subset of illuminators 120 and the second subset of detectors 130 can be, for example, 40 degrees (resulting in a "straight ahead" optical axis and a field of view of 20 degrees to either side and up and down (e.g., ±20 degrees)). This strategy can result in improved performance and / or a more efficient system. For example, since the scattered optical power decreases with the square of the distance, the first subset of illuminators 120 targeted at a closer range can be configured to use less power than the second subset of illuminators 120.

[0069] In addition to different subsets of illuminators 120 using different power levels, different subsets of illuminators 120, or even different individual illuminators 120, can use different repetition patterns of transmitted pulses for each range of interest to increase the received SNR. For example, detectors 130 can simply add / accumulate or average their respective received signals.

[0070] In some embodiments, the positions, power levels, optical axis angles 124, 125, and FOV angles 126, 127 of the illuminators 120 in the optical component array 110 are selected such that at least some subsets of the illuminators 120 fully illuminate an entire three-dimensional space volume. For example, a particular space volume can be defined as a three-dimensional space volume between 5 and 20 meters from the optical component array 110, extending 10 meters to the left, 10 meters to the right, and from ground level to 10 meters above the ground. In some embodiments, each point in the selected space volume can be illuminated by an optical signal emitted by at least one illuminator 120 in the optical component array 110. As a result, any object in this space volume can be illuminated by at least one illuminator 120.

[0071] Similarly, in some embodiments, the positions, optical axis angles 134, 135, and FOV angles 136, 137 of the detectors 130 in the optical component array 110 are selected such that the set of detectors 130 senses the entire three-dimensional space volume. Thus, each point in the space volume can be observed by at least one detector 130.

[0072] It is possible to use multiple optical components (e.g., from the optical component array 110) to determine the position of a target within a space volume in three-dimensional space. If the number of illuminators 120 that illuminate a particular point in the illuminated space volume is denoted as n1, and the number of detectors 130 that observe that particular point is denoted as n2, provided that (1) the product of the number of illuminators 120 that illuminate the point and the number of detectors 130 that observe the point is greater than 2 (i.e., n1 × n2 > 2), and (2) the set of n1 illuminators 120 and n2 detectors 130 is non-collinear (i.e., not all of the n1 illuminators 120 and n2 detectors 130 are arranged in a straight line, or in other words, at least one of the n1 illuminators 120 and n2 detectors 130 is not on the same straight line as the remainder of the n1 illuminators 120 and n2 detectors 130). These conditions allow for the determination of three independent equations, thereby enabling the unambiguous determination of the position of each target in the space volume illuminated by the (multiple) illuminators 120 and observed by the (multiple) detectors 130.

[0073] There are various combinations of n1 illuminators 120 and n2 detectors 130 that can be used to satisfy the first condition n1 × n2 > 2. For example, one combination can include one illuminator 120 and three detectors 130. Another combination can include three illuminators 120 and one detector 130. Yet another combination can use two illuminators 120 and two detectors 130. Any other combination of non-collinear n1 illuminators 120 and n2 detectors 130 that satisfies this condition can be used.

[0074] Each set of n1 illuminators 120 and n2 detectors 130 that satisfies the condition n1×n2>2 includes at least three distinct illuminator-detector pairs, meaning that for any chosen distinct illuminator-detector pair, the identity of the illuminator 120 of that pair and / or the identity of the detector 130 of that pair is different from the corresponding components of every other distinct illuminator-detector pair in the set of n1 illuminators 120 and n2 detectors 130. Figure 6A , Figure 6B , Figure 6C and Figure 6D illustrates several configurations of distinct illuminator-detector pairs in a set of n1 illuminators 120 and n2 detectors 130 that satisfies the condition n1×n2>2.

[0075] Figure 6A is an exemplary configuration according to some embodiments that includes three illuminators 120A, 120B, and 120C and three detectors 130A, 130B, and 130C. The three illuminators 120A, 120B, and 120C and the three detectors 130A, 130B, and 130C have been assigned to distinct illuminator-detector pairs 112A, 112B, and 112C. In Figure 6A 's example, the three distinct illuminator-detector pairs 112A, 112B, and 112C do not share common optical components. Instead, each illuminator 120 is assigned to a separate distinct illuminator-detector pair 112, and each detector 130 is also assigned to a separate distinct illuminator-detector pair 112. (3×3 = 9) satisfies the condition n1×n2>2, and the set of three illuminators 120A, 120B, and 120C and three detectors 130A, 130B, and 130C is non-collinear (because the illuminators 120A, 120B, and 120C and the detectors 130A, 130B, and 130C are not all arranged on a single straight line). Assuming that the illuminator FOVs 122A, 122B, 122C and the detector FOVs 132A, 132B, 132C intersect (thereby establishing a spatial volume), then Figure 6A the arrangement shown will provide at least three independent equations that can be solved to determine the position of an object in the intersecting spatial volume illuminated by the illuminators 120A, 120B, 120C and sensed by the detectors 130A, 130B, and 130C.

[0076] Figure 6B illustrates another exemplary configuration according to some embodiments that uses only four optical components (i.e., one illuminator 120A and three detectors 130A, 130B, and 130C) to provide three independent equations. The illuminator 120A and the detectors 130A, 130B, and 130C have been assigned to distinct illuminator-detector pairs 112A, 112B, and 112C. In Figure 6B In the example of, each of the three unique illuminator-detector pairs 112A, 112B, and 112C includes an illuminator 120A and a different detector 130. Specifically, the unique illuminator-detector pair 112A includes illuminator 120A and detector 130A; the unique illuminator-detector pair 112B includes illuminator 120A and detector 130B; and the unique illuminator-detector pair 112C includes illuminator 120A and detector 130C. (1×3 = 3) satisfies the condition n1×n2>2, and the set of the illuminator 120A and the three detectors 130A, 130B, and 130C is non-collinear (i.e., the illuminator 120A and the detectors 130A, 130B, and 130C are not all arranged on a single straight line). Assuming that the illuminator FOV 122A and the detector FOVs 132A, 132B, 132C intersect, then Figure 6B The arrangement shown will provide three independent equations that can be solved to determine the position of an object in the intersecting spatial volume illuminated by the illuminator 120A and observed by the detectors 130A, 130B, and 130C.

[0077] Figure 6C Another exemplary configuration is shown that provides three independent equations using only four optical components (i.e., three illuminators 120A, 120B, and 120C and one detector 130A). The illuminators 120A, 120B, and 120C and the detector 130A have been assigned to the unique illuminator-detector pairs 112A, 112B, and 112C. In Figure 6C the example of, each of the three unique illuminator-detector pairs 112A, 112B, and 112C includes the detector 130A and a different illuminator 120. Specifically, the unique illuminator-detector pair 112A includes illuminator 120A and detector 130A; the unique illuminator-detector pair 112B includes illuminator 120B and detector 130A; and the unique illuminator-detector pair 112C includes illuminator 120C and detector 130A. (3×1 = 3) satisfies the condition n1×n2>2, and the set of the illuminators 120A, 120B, and 120C and the detector 130A is non-collinear (i.e., the illuminators 120A, 120B, and 120C and the detector 130A are not all arranged on a single straight line). Assuming that the illuminator FOVs 122A, 122B, and 122C intersect with the detector FOV 132A, then Figure 6C The arrangement shown will provide three independent equations that can be solved to determine the position of an object in the intersecting spatial volume illuminated by the illuminators 120A, 120B, and 120C and observed by the detector 130A.

[0078] Figure 6DShows yet another exemplary configuration that uses four optical components (i.e., two illuminators 120A, 120B and two detectors 130A, 130B) to provide four equations, three of which are independent and one of which is redundant (where the redundant equation allows for more accurate determination of the target position in the presence of noise). The illuminators 120A, 120B and detectors 130A, 130B have been assigned to unique illuminator-detector pairs 112A, 112B, 112C and 112D. In Figure 6D the example of, each of the four unique illuminator-detector pairs 112A, 112B, 112C and 112D includes a unique combination of one illuminator 120 and one detector 130. Specifically, the unique illuminator-detector pair 112A includes the illuminator 120A and the detector 130A; the unique illuminator-detector pair 112B includes the illuminator 120B and the detector 130B; the unique illuminator-detector pair 112C includes the illuminator 120A and the detector 130B; and the unique illuminator-detector pair 112D includes the illuminator 120B and the detector 130A. (2×2 = 4) satisfies the condition (n1×n2>2), and the set of illuminators 120A, 120B and detectors 130A, 130B is non-collinear (i.e., the illuminators 120A, 120B and detectors 130A, 130B are not all arranged on a single straight line). Assuming that the illuminator FOVs 122A and 122B and the detector FOVs 132A and 132B intersect, then Figure 6D the arrangement shown will provide four equations, three of which are independent and one of which is redundant, and these equations can be solved to determine the position of an object in the intersecting spatial volume illuminated by the illuminators 120A and 120B and sensed by the detectors 130A and 130B. The available fourth redundant equation obtained from using two illuminators 120 and two detectors 130 can be used to improve the accuracy of the estimated position of the target within the spatial volume.

[0079] Figure 7A , Figure 7B , Figure 7C and Figure 7D shows how to use the unique illuminator-detector pairs 112 to determine the positions of multiple targets in a three-dimensional space within a spatial volume according to some embodiments. Figure 7AFIG. 0 shows a MIMO LiDAR system 100 that includes three illuminators 120A, 120B, and 120C and three detectors 130A, 130B, and 130C. In this example, a single illuminator 120A illuminates a spatial volume 160, and the three detectors 130A, 130B, and 130C observe the spatial volume 160. The illuminator 120A has an illuminator FOV 122, shown as an angle for convenience, and the detectors 130A, 130B, and 130C each have detector FOVs 132A, 132B, and 132C, also shown as angles for convenience. Figure 7A Each of the illustrated detector FOVs 132A, 132B, and 132C intersects at least a portion of the illuminator FOV 122. Thus, Figure 7A FIG. 4 shows three exemplary unique illuminator-detector pairs 112. One unique illuminator-detector pair 112 is illuminator 120A and detector 130A; a second unique illuminator-detector pair 112 is illuminator 120A and detector 130B; and a third unique illuminator-detector pair 112 is illuminator 120A and detector 130C.

[0080] The intersection of the illuminator FOV 122 and each detector FOV 132A, 132B, and 132C is the spatial volume 160. Although Figure 7A only two dimensions are shown, it should be understood that the illuminator FOV 122, the detector FOVs 132A, 132B, and 132C, and the spatial volume 160 are generally three-dimensional.

[0081] Figure 7A FIG. 13 shows three targets 150A, 150B, and 150C within the MIMO LiDAR system 100. Targets 150A and 150B are within the spatial volume 160 defined by the illuminator FOV 122 and the detector FOVs 132A, 132B, and 132C. Thus, the positions of targets 150A and 150B within the spatial volume 160 can be determined as further described below. Target 150C is in an area not illuminated by the illuminator 120A. Thus, the position of target 150C cannot be determined using the illuminator 120A (at least not using the illustrated illuminator FOV 122).

[0082] To determine the positions of targets 150A and 150B, the MIMO LiDAR system 100 determines a set of distances for each unique illuminator-detector pair 112. The set of distances for a unique illuminator-detector pair 112 is a collection of distances. Each distance in the set of distances is an estimate of the distance traveled by an optical signal transmitted by the illuminator 120 of the unique illuminator-detector pair 112, reflected by a target in the spatial volume 160, and detected by the detector 130 of the unique illuminator-detector pair 112. Generally, if there are N targets in the spatial volume 160, the set of distances for each unique illuminator-detector pair 112 will include N estimated distances.

[0083] It should be understood that since the illuminator 120 of the MIMO LiDAR system 100 transmits an optical signal and the detector 130 detects the optical signal, the distance traveled by the optical signal can be easily calculated from the time of flight by multiplying the time of flight by the speed of light. Therefore, the set of distances does not strictly require to contain distances (e.g., estimates in terms of distance). As an alternative or in addition, it can include the round-trip time of the transmitted signal. In other words, the term "set of distances" is not limited to estimates of physical distances. As further described below, any surrogate (such as round-trip time) according to which the position or coordinates of a target in the spatial volume can be determined can be used as the set of distances.

[0084] Figure 7B Ray 121 is shown, which represents an optical signal transmitted by illuminator 120A, reflected by targets 150A and 150B, and detected by detectors 130A, 130B, and 130C. Figure 7C The distances traveled by the optical signal between illuminator 120A, target 150A, and detectors 130A, 130B, and 130C are shown. Specifically, the optical signal transmitted by illuminator 120A and reflected by target 150A travels distance 170A before being detected by detector 130A, distance 170B before being detected by detector 130B, and distance 170C before being detected by detector 130C.

[0085] As explained in the context of Figure 1A and Figure 1B The MIMO LiDAR system 100 includes at least one processor 140 coupled to the optical component array 110. The at least one processor 140 can estimate distances 170A, 170B, and 170C based on the time of flight of the optical signal transmitted by illuminator 120A. In other words, knowing when illuminator 120A transmits the optical signal, the at least one processor 140 can use the arrival times of the optical signal at detectors 130A, 130B, and 130C, by multiplying the respective time of flight of the optical signal by the speed of light (3×108 to estimate distances 170A, 170B, and 170C in m / s.

[0086] The estimated distances corresponding to each unique illuminator-detector pair 112 define an ellipsoid having one focus at the coordinates of the illuminator 120 of the unique illuminator-detector pair 112 and the other focus at the coordinates of the detector 130 of the unique illuminator-detector pair 112. The ellipsoid is defined as those points in space whose sum of the distances from the two foci is given by the estimated distances. The detected target lies somewhere on this ellipsoid. For example, again referring to Figure 7C , target 150A lies on each of the three ellipsoids. One focus of each of the three ellipsoids is at the coordinates of illuminator 120A. The other focus of the first ellipsoid is at the coordinates of detector 130A. The other focus of the second ellipsoid is at the coordinates of detector 130B. The other focus of the third ellipsoid is at the coordinates of detector 130C. Because the set of illuminator 120A and detectors 130A, 130B, and 130C is non-collinear and target 150A lies on each ellipsoid, the location of target 150A is at the intersection of the three ellipsoids located within the spatial volume 160. This intersection and thus the coordinates of target 150A can be determined by solving a system of quadratic equations. An exemplary process applicable to any number of illuminators 120 and any number of detectors 130 (as long as the condition n1×n2>2 and the non-collinearity of the set of illuminators 120 and detectors 130 are satisfied) will be described later in this document.

[0087] Figure 7D illustrates the distances traveled by the optical signal between illuminator 120A, target 150B, and detectors 130A, 130B, and 130C. Specifically, the optical signal emitted by illuminator 120A and reflected by target 150B travels distance 170D before being detected by detector 130A, distance 170E before being detected by detector 130B, and distance 170F before being detected by detector 130C. As in Figure 7CAs explained in the discussion of , at least one processor 140 knows when illuminator 120A transmits an optical signal, and it can use the arrival times of the optical signals at detectors 130A, 130B, and 130C to estimate distances 170D, 170E, and 170F by multiplying the respective flight times of the optical signals by the speed of light. Target 150B is located on each of three ellipsoids, each with one focus at the coordinates of illuminator 120A and another focus at the coordinates of detectors 130A, 130B, or 130C, respectively. The location of target 150B is at the intersection of these three ellipsoids located in volume of space 160. The intersection, and therefore the coordinates of target 150B, can be determined by solving another system of quadratic equations, as described further below.

[0088] 7A to 7D The above discussion describes an exemplary MIMO LiDAR system 100 that uses one illuminator 120 and three detectors 130 to determine the position of an object 150 within a volume of space 160. As described above, other combinations of a certain number of illuminators 120 and detectors 130 may also be used (e.g., three illuminators and one detector, two illuminators and two detectors, etc.). Any combination of illuminators 120 and detectors 130 that satisfies the condition n1×n2>2 and that the set of illuminators 120 and detectors 130 is non-collinear may be used.

[0089] Figure 8A 、 Figure 8B 、 Figure 8C and Figure 8D FIG. 1 shows how another exemplary MIMO LiDAR system 100 can determine the position of a target 150 in a volume of space 160 using three illuminators 120 and one detector 130. Specifically, Figure 8A As shown, three illuminators 120A, 120B, and 120C illuminate a spatial volume 160, and one detector 130C detects optical signals reflected by a target 150 within the spatial volume 160. As previously described, the spatial volume 160 is the intersection of the illuminator FOVs 122A, 122B, and 122C and the detector FOV 132. The detector FOV 132 intersects at least a portion of each of the illuminator FOVs 122A, 122B, and 122C. Figure 8A Shown are three exemplary unique illuminator-detector pairs 112. One unique illuminator-detector pair 112 is illuminator 120A and detector 130C; a second unique illuminator-detector pair 112 is illuminator 120B and detector 130C; and a third unique illuminator-detector pair 112 is illuminator 120C and detector 130C.

[0090] The intersections of the illuminator FOVs 122A, 122B, and 122C with the detector FOV 132 are the spatial volume 160. Although Figure 8A only two dimensions are shown, it should be understood that the illuminator FOVs 122A, 122B, and 122C, the detector FOV 132, and the spatial volume 160 are generally three-dimensional.

[0091] Figure 8A Three targets 150A, 150B, and 150C within the range of the MIMO LiDAR system 100 are shown. Targets 150A and 150B are within the spatial volume 160 defined by the illuminator FOVs 122A, 122B, and 122C and the detector FOV 132. Thus, the positions of targets 150A and 150B within the spatial volume 160 can be determined as further described below.

[0092] As Figure 8A shown, target 150C is in the region illuminated by illuminator 120C and detected by detector 130C, but because it is not illuminated by illuminator 120A or 120B, its position cannot be determined using only the set of optical components shown in Figure 8A (i.e., illuminators 120A, 120B, 120C and detector 130C). It should be understood that, for example, if detectors 130A and 130B can sense the spatial volume including the position of target 150C, then illuminator 120C and detectors 130A, 130B, and 130C can be used to determine the coordinates of target 150C in the manner described in the context of 7A to 7D . Similarly, any set of optical components (illuminators 120 and detectors 130) that satisfies the condition n1×n2 > 2 and is non-collinear for the set of illuminators 120 and detectors 130 and results in a spatial volume 160 including target 150C can be used to determine the position of target 150C.

[0093] To determine the positions of targets 150A and 150B, the MIMO LiDAR system 100 determines the set of distances as described above for each unique illuminator-detector pair 112. Figure 8BShows the light rays representing the optical signals emitted by illuminators 120A, 120B, and 120C, reflected by targets 150A and 150B, and detected by detector 130C. Illuminator 120A emits an optical signal represented by light ray 121A, which is reflected by both target 150A and target 150B and then detected by detector 130C. Similarly, illuminator 120B emits an optical signal represented by light ray 121B, which is reflected by both target 150A and target 150B and then detected by detector 130C. Illuminator 120C emits an optical signal represented by light ray 121C, which is reflected by all targets 150A, 150B, and 150C because the illuminator FOV 122C covers the area where target 150C is located. The reflected signal is then detected by detector 130C.

[0094] Figure 8C Shows the distances traveled by the optical signals between illuminators 120A, 120B, and 120C, target 150A, and detector 130C. Specifically, the optical signal emitted by illuminator 120A and reflected by target 150A travels distance 170A before being detected by detector 130C. The optical signal emitted by illuminator 120B and reflected by target 150A travels distance 170B before being detected by detector 130C, and the optical signal emitted by illuminator 120C and reflected by target 150A travels distance 170C before being detected by detector 130C.

[0095] Figure 8D Shows the distances traveled by the optical signals between illuminators 120A, 120B, and 120C, target 150B, and detector 130C. Specifically, the optical signal emitted by illuminator 120A and reflected by target 150B travels distance 170D before being detected by detector 130C. The optical signal emitted by illuminator 120B and reflected by target 150B travels through distance 170E before being detected by detector 130C, and the optical signal emitted by illuminator 120C and reflected by target 150B travels distance 170F before being detected by detector 130C.

[0096] As described above, at least one processor 140 may estimate distances 170A, 170B, 170C, 170D, 170E, and 170F based on time of flight. However, in this case, if three illuminators 120A, 120B, and 120C simultaneously send the same optical signal, the detector 130C may not be able to determine which detected optical signal corresponds to which illuminator 120 and which target 150. Generally speaking, if two or more illuminators 120 simultaneously emit optical signals in an overlapping illuminator FOV 122, there is a possibility that the detector 130 sensing the target 150 in the common area may be confused and / or unable to distinguish the target 150.

[0097] One solution is for the three illuminators 120A, 120B, and 120C to send the same optical signal at different times, such that the identity of the illuminator 120 responsible for the reflected optical signal is known or can be determined or estimated. For example, if two illuminators 120 emit optical signals at different times (e.g., in a cyclic or TDMA manner), or if they illuminate different, non-overlapping fields of view, the optical signals they emit can be the same.

[0098] Another solution is for each illuminator 120 to send an optical signal that can be distinguished from all other optical signals simultaneously transmitted within the same spatial volume 160. Thus, in some embodiments, the optical signals of those illuminators 120 that illuminate the same volume of space 160 and are transmitted simultaneously include unique pulse sequences. The pulse sequence used by a particular illuminator 120 can be globally unique (used by only one illuminator 120 in the entire optical component array 110), or can be locally unique (used by multiple illuminators 120 such that the same pulse sequence does not appear in any spatial volume 160 simultaneously).

[0099] Therefore, in some embodiments, two or more illuminators 120 simultaneously (or within the same time window) emit optical signals and also illuminate overlapping illuminator FOVs 122. In some such embodiments, different illuminators 120 use different pulse sequences that are designed to allow one or more detectors 130 to distinguish the pulse sequences of different illuminators 120.

[0100] Because the illuminator 120 emits optical signals, the pulse trains have an instantaneous amplitude at any selected time, but the phase is uncertain. In other words, they operate in a non-uniform manner. In some embodiments, the pulse trains are sparse, which means that within a specified time window, each pulse train includes only a few non-zero pulses. In other words, if each pulse of the pulse train has a pulse width (duration), and the time window spans an integer number of pulse time slots, each pulse time slot is the duration of one pulse, and the pulses only occupy a small percentage (e.g., <10%) of the total number of pulse time slots.

[0101] Figure 9A Two simple pulse trains 180A and 180B according to some embodiments are shown to illustrate the design principle of the pulse trains. Each of the pulse trains 180A and 180B has three pulses. The pulse train 180A has pulses 181A, 181B, and 181C, and the pulse train 180B has pulses 181D, 181E, and 181F. As Figure 9A shown, within the time window 182, none of the pulses 181A, 181B, 181C of the pulse train 180A overlap with any of the pulses 181D, 181E, 181F of the pulse train 180B.

[0102] Ideally, each pulse train 180 has an "almost white" autocorrelation, meaning that each pulse train 180 has an overlap below a threshold. For example, the threshold can be zero pulses, or at most a small predetermined number of pulses (e.g., 1, 2, or 3, depending on the application), with all its shifted versions. Figure 9B Shown is Figure 9A the autocorrelation of the simple pulse train 180A at various overlap positions, and the number of overlapping pulses 181 is provided on the right side of the figure. Assuming that the time window 182 is placed at a specified position such that each pulse 181 can only fall within one pulse time slot, then for each correlation of the pulse train 180A with each of its shifted versions, the autocorrelation results in an overlap of at most one pulse. The maximum value of the autocorrelation is of course 3, because the pulse train 180A has three pulses in the time window 182.

[0103] Figure 9C Shown is Figure 9AThe autocorrelation of the simple pulse sequence 180B at various overlapping positions is shown. The number of overlapping pulses 181 is provided on the right side of the figure. Assuming that the time window 182 is placed at a specified position such that each pulse 181 can only fall within one pulse time slot, then for each correlation of the pulse sequence 180B with each of its shifted versions, the autocorrelation of the pulse sequence 180B also results in an overlap of at most one pulse. The maximum value of the autocorrelation is of course 3, since the pulse sequence 180B has three pulses in the time window 182.

[0104] Ideally, the pulse sequences 180 used by different illuminators 120 with overlapping illuminator FOVs 122 are substantially uncorrelated with each other, which means that each pulse sequence 180 will have at most a small predetermined number of pulses (e.g., 1, 2, or 3, depending on the application), with all shifted versions of all other pulse sequences 180 used by the illuminators 120 with overlapping illuminator FOVs 122. Figure 9D is shown Figure 9A The cross-correlation of the simple pulse sequences 180A and 180B at different positions is shown. The number of overlapping pulses 181 is provided on the right side of the figure. As shown, for any shift, the maximum number of overlapping pulses is 1. Thus, the simple pulse sequences 180A and 180B can be said to be substantially uncorrelated. It should be understood that a larger amount of pulse overlap can also be considered to be substantially uncorrelated. For example, a maximum overlap amount below a certain threshold (e.g., a specific percentage of the pulses (relative to the total number)) can be considered to make the pulse sequences 180 substantially uncorrelated. As a specific example, if two pulse sequences 180 span a time period of 500 pulse widths and the maximum overlap amount in the cross-correlation is less than 10% (less than 50 pulses ever overlap at one time), then this overlap amount can be considered to result in the two pulse sequences 180 being substantially uncorrelated. The aim is to select the pulse sequences 180 such that the detector 130 can distinguish between the pulse sequences 180 emitted by different illuminators 120 with overlapping FOVs 122.

[0105] It should be understood that although the above discussion describes the use of different pulse sequences in the case of an illuminator 120 with overlapping FOVs 122, when the detector 130 has a detector FOV 132 that intersects multiple illuminator FOVs 122, the illuminator 120 also preferably uses different pulse sequences even if the illuminator FOVs 122 themselves do not overlap. For example, if the detector FOV 132 intersects the illuminator FOV 122A of the first illuminator 120A and the illuminator FOV 122B of the second illuminator 120B, then even if the first and second illuminator FOVs 122A, 122B do not overlap, the pulse sequence 180 used by the first illuminator 120A should be different and distinguishable from the pulse sequence used by the second illuminator 120B such that the detector 130 (or at least one processor 140) can determine which illuminator 120 emitted the optical signal that caused each reflected signal.

[0106] Although 9A to 9D A simple pulse sequence 180 is shown using a pulse 181 with a single amplitude (i.e., the pulse 181 is either on or off in a time slot), but the pulses 181 in the pulse sequence 180 can alternatively have various possible non-zero amplitudes.

[0107] Any number of pulse sequences 180 used in the MIMO LiDAR system 100 can be designed to have any length, any desired weights (e.g., any number of non-zero pulses 181 per sequence / time window 182), any non-origin maximum of the autocorrelation function, and any maximum of the cross-correlation between two different pulse sequences 180. The pulse sequences 180 can be designed using, for example, algebraic tools (such as difference sets and generalized difference sets), by constrained randomization techniques, by convex optimization, or by a combination of these techniques and tools. Brute force methods (e.g., exhaustive search) can also be used to design the pulse sequences 180.

[0108] As previously mentioned, any combination of illuminators 120 and detectors 130 can be used to detect a target in the spatial volume 160 as long as the conditions n1×n2>2 and the non-collinearity of the set of illuminators 120 and detectors 130 are satisfied. Figure 10A 、 Figure 10B 、 Figure 10C 、 Figure 10D 、 Figure 10E and Figure 10F illustrates how an exemplary MIMO LiDAR system 100 according to some embodiments can use two illuminators 120 and two detectors 130 to determine the position of a target 150 in the spatial volume 160. Specifically, as Figure 10AAs shown, two illuminators 120A and 120C illuminate the spatial volume 160, and two detectors 130B and 130C detect optical signals reflected by the target 150 within the spatial volume 160. As previously described, the spatial volume 160 is the intersection of the illuminator FOVs 122A and 122C and the detector FOVs 132B and 132C. Both of the detector FOVs 132B and 132C intersect at least a portion of each of the illuminator FOVs 122A and 122C. Although Figure 10A only two dimensions are shown, it should be understood that the illuminator FOVs 122A and 122C, the detector FOVs 132B and 132C, and the spatial volume 160 are generally three-dimensional.

[0109] Figure 10A Four exemplary unique illuminator-detector pairs 112 are shown. One unique illuminator-detector pair 112 is illuminator 120A and detector 130B; the second unique illuminator-detector pair 112 is illuminator 120A and detector 130C; the third unique illuminator-detector pair 112 is illuminator 120C and detector 130B; and the fourth unique illuminator-detector pair 112 is illuminator 120C and detector 130C.

[0110] Figure 10A Three targets 150A, 150B, and 150C within the range of the MIMO LiDAR system 100 are shown. Targets 150A and 150B are within the spatial volume 160 defined by the illuminator FOVs 122A and 122C and the detector FOVs 132B and 132C. Thus, the positions of the targets 150A and 150B within the spatial volume 160 can be determined as further described below.

[0111] As Figure 10AAs shown, the target 150C is in the area illuminated by the illuminator 120C and detected by the detectors 130B and 130C. However, since it is not illuminated by the illuminator 120A, its position cannot be determined using only the set of optical components whose FOVs are shown (i.e., the illuminators 120A and 120C and the detectors 130B and 130C). It should be understood that if the detector 130A can sense the spatial volume including the position of the target 150C, the illuminator 120C and the detectors 130A, 130B, and 130C can be used to determine the coordinates of the target 150C. Similarly, if the illuminator 120B has an illuminator FOV 122B that overlaps with the position of the target 150C, the combination of the illuminators 120B and 120C and the detectors 130B and 130C can be used to determine the position of the target 150C. As previously mentioned, any set of optical components ((multiple) illuminators 120 and (multiple) detectors 130) that satisfies the condition n1×n2>2 and the non-collinearity of the set of illuminators 120 and detectors 130 can be used to determine the position of the target 150C (or any other target in the applicable spatial volume).

[0112] To determine the positions of the targets 150A and 150B, the MIMO LiDAR system 100 determines the set of distances as described above for each unique illuminator-detector pair 112. Figure 10B The light rays are shown, which represent the optical signals emitted by the illuminators 120A and 120C, reflected by the targets 150A, 150B, and in the case of the illuminator 120C, the target 150C, and detected by the detectors 130B and 130C. The illuminator 120A emits an optical signal represented by the light ray 121A, which is reflected by both the target 150A and the target 150B and then detected by the detectors 130B and 130C. Similarly, the illuminator 120C emits an optical signal represented by the light ray 121C, which is reflected by each of the targets 150A, 150B, and 150C because the illuminator FOV 122C covers the area where the target 150C is located. The optical signals reflected by the targets 150A and 150B are detected by the detectors 130B and 130C, while the optical signal reflected by the target 150C is detected only by the detector 130C.

[0113] Figure 10C The distances traveled by the optical signals between the illuminators 120A and 120C, the target 150A, and the detector 130B are shown. Specifically, the optical signal emitted by the illuminator 120A and reflected by the target 150A travels the distance 170A (solid line) before being detected by the detector 130B. The optical signal emitted by the illuminator 120C and reflected by the target 150A travels the distance 170B (dashed line) before being detected by the detector 130B.

[0114] Figure 10D Shows the distances that optical signals travel between illuminators 120A and 120C, target 150A, and detector 130C. Specifically, the optical signal emitted by illuminator 120A and reflected by target 150A travels distance 170C (solid line) before being detected by detector 130C, and the optical signal emitted by illuminator 120C and reflected by target 150A travels distance 170D (dashed line) before being detected by detector 130C.

[0115] Figure 10E Shows the distances that optical signals travel between illuminators 120A and 120C, target 150B, and detector 130B. Specifically, the optical signal emitted by illuminator 120A and reflected by target 150B travels distance 170E (solid line) before being detected by detector 130B. The optical signal emitted by illuminator 120C and reflected by target 150B travels distance 170F (dashed line) before being detected by detector 130B.

[0116] Figure 10F Shows the distances that optical signals travel between illuminators 120A and 120C, target 150B, and detector 130C. Specifically, the optical signal emitted by illuminator 120A and reflected by target 150B travels distance 170G (solid line) before being detected by detector 130C, and the optical signal emitted by illuminator 120C and reflected by target 150B travels distance 170H (dashed line) before being detected by detector 130C.

[0117] As described above, at least one processor 140 of the MIMO LiDAR system 100 can estimate distances 170A, 170B, 170C, 170D, 170E, 170F, 170G, and 170H based on time-of-flight. However, as described above, if illuminators 120A and 120C simultaneously transmit the same optical signal, detectors 130B and 130C may not be able to determine which detected optical signal corresponds to which illuminator 120 and which target 150. Generally, if two or more illuminators 120 simultaneously emit optical signals in an overlapping illuminator FOV 122 (or detector FOV 132), there is a possibility that detectors 130 sensing a target 150 in the common area may be confused and / or unable to distinguish the target 150. Thus, in some embodiments, as described above, each of illuminators 120A and 120C transmits a corresponding pulse sequence 180 that allows detectors 130B and 130C (and / or at least one processor 140) to distinguish a reflected detection signal originating from illuminator 120A from a reflected detection signal originating from illuminator 120C. As described above, the pulse sequences 180 used by illuminators 120A and 120C can have a substantially white autocorrelation and can be substantially uncorrelated with each other. The previous discussion of pulse sequence 180 (e.g., in the context of 9A to 9D is applicable here and will not be repeated.

[0118] Detection and coordinate estimation

[0119] The following discussion applies to any MIMO LiDAR system 100 where the conditions n1×n2>2 and non-collinearity of the sets of illuminators 120 and detectors 130 are satisfied, including those previously described.

[0120] A target 150 in the spatial volume 160 can be determined by either (a) direct detection and coordinate estimation or (b) scanning the scene. These two methods are described below.

[0121] For direct detection and coordinate estimation, the MIMO LiDAR system 100 determines the time-of-flight of the detected optical signals. In the following discussion, to reduce the likelihood of confusion, certain reference numerals are generally omitted in favor of letters used as indices. For example, illuminator 120 is referred to and indexed by the letter i, detector 130 is referred to and indexed by the letter j, and target 150 is referred to and indexed by the letter k.

[0122] Referring again to Figure 1B , for each of the j detectors of the multiple detectors in the MIMO LiDAR system 100, at least one processor 140 implements a receiver algorithm to identify the pulse sequence received in the detector's FOV 132 and its corresponding delay tijk , where i represents the illuminator 120 that emits the detected optical signal, k represents the k-th delay (associated with the k-th target), and each t ijk corresponds to a specific target 150. (It should be understood that "specific target" is not necessarily the same for each t ijk . In other words, a set of multiple t ijk values can correspond to one or more targets in the detector FOV 132 of detector j).

[0123] At least one processor 140 can identify the pulse sequence present in the detected optical signal and its corresponding delay in a variety of ways. For example, at least one processor 140 can perform the correlation of each possible transmitted pulse sequence with the detected reflected signal, and then identify the peaks in the correlation results to determine which possible transmitted pulse sequence is present and estimate the delay corresponding to the target. For example, the correlation can be performed in the time domain or by performing an equivalent process in the frequency domain.

[0124] As another example, since the pulse sequence 180 described here is sparse, at least one processor 140 can use an optimization process to clearly utilize the structure of the pulse sequence to "denoise" the received optical signal. For example, at least one processor 140 can denoise the received optical signal by using atomic norm minimization (e.g., by minimizing the atomic norm of the denoised received signal, where the denoised received signal is subject to a measure (e.g., squared Euclidean distance, L 1 norm, L ∞ norm, etc.) that characterizes the closeness of the denoised received signal to the transmitted pulse sequence). As used herein, the term "denoised signal" refers to a signal that has undergone an optimization process, which can be analog or digital, and the result is an extracted signal with less noise than the original signal, and the extracted signal can be analog or digital. As used herein, the term "optimization process" refers to any (possibly non-linear) signal processing technique that clearly utilizes the structure of one or more signals being processed to select the best estimate (for a certain criterion) from a set of some (possibly uncountable) alternatives (e.g., possible transmitted pulse sequences). The optimization process can be iterative.

[0125] In the atomic norm framework used according to some embodiments, we assume that we have a set of atoms

[0126]

[0127] where the set can be finite, countably infinite, or even uncountably infinite. If an x signal can be written as the sum of several atoms, say K atoms, then we call it a structured signal, where K is less than the dimension of the ambient space of x, i.e.,

[0128]

[0129] above, α k is a (possibly complex) scalar.

[0130] Relative to the set of atoms the atomic norm of the vector x is defined as

[0131] min ‖c‖1

[0132]

[0133] In other words, the atomic norm of x is the most economical way to represent x as a linear combination of atoms, where economical means minimizing the ‖·‖ norm of the representation, where ‖c‖ = ∑ k |c k |. A small atomic norm means that x can be represented as the sum of a few atoms. Conversely, a large atomic norm means that many atoms are needed to represent x.

[0134] Suppose the pulse sequence 180 used by the MIMO LiDAR system 100 is sparse. To identify the pulse sequences and their corresponding delays, at least one processor 140 can use an atomic norm denoiser (tuned to the corresponding pulse sequence), followed by a correlation receiver.

[0135] As another example, at least one processor 140 can use an atomic norm denoiser, followed by any sinusoid-in-noise estimator, such as MUSIC, ESPRIT, Hankel norm approximation, Prony, Burg, etc. As yet another example, at least one processor 140 can use an atomic norm denoiser that involves a search over a finite set of atoms.

[0136] Each t ijk can be used to determine the time of flight of the optical signal emitted by illuminator i and received by detector j when reflected from target k. In other words, the distance 170 from illuminator i via target k to detector j is simply ct ikj , where c is the speed of light. The distance ct ikj produces an ellipsoid whose foci are the coordinates of illuminator i and detector j, such that target k must lie on this ellipsoid (since the sum of its distances to the foci is ctikj )。

[0137] For the case where n1 = 1 and n2 = 3 (i.e., one illuminator 120 and three detectors 130), each point in the spatial volume 160 is observed by at least three detectors 130. Thus, each target k in this spatial volume 160 is illuminated by (at least) the illuminator i and is observed by (at least) three detectors j1, j2, and j3 (where the sets of illuminators and detectors are arranged non - collinearly). The exact coordinates of the k - th target can be determined according to and by solving a system of quadratic equations that intersect three ellipsoids, as further described below.

[0138] Similarly, for the case where n1 = 2 and n2 = 2 (i.e., two illuminators 120 and two detectors 130), each target k in the spatial volume 160 is illuminated by (at least) two illuminators i1 and i2 and is observed by (at least) two detectors j1 and j2 (where the sets of illuminators and detectors are arranged non - collinearly). The exact coordinates of the k - th target can be determined according to and by solving a system of quadratic equations that intersect four ellipsoids, as further described below.

[0139] Likewise, for the case where n1 = 3 and n2 = 1 (i.e., three illuminators 120 and one detector 130), each point in the spatial volume 160 is illuminated by at least three illuminators 120. Thus, each target k in this spatial volume 160 is illuminated by (at least) three illuminators i1, i2, and i3 and is observed by (at least) one detector j (where the sets of illuminators and detectors are arranged non - collinearly). The exact coordinates of the k - th target can be determined according to and by solving a system of quadratic equations that intersect three ellipsoids, as further described below. It should be understood that there are numerous ways to solve the system of quadratic equations, and the specific method described herein is merely an example of a suitable technique. A person of ordinary skill in the art will be able to identify and apply other solutions without undue experimentation.

[0140] The distances for other combinations of n1 and n2 that satisfy the condition n1×n2 > 2 can be derived similarly.

[0141] The equation of each ellipsoid can be determined as follows. Assume that the illuminator i is at the coordinates (x i , y i , z i ), and the target k is at the coordinates (x k , y k , z k) and the detector j is at the coordinates (x j , y j , z j ). For the round-trip time t, the target k lies on an ellipse given by the following formula

[0142]

[0143] Assume there are n1 illuminators 120 at the coordinates for p = 1, …, n1 to illuminate an unknown target at the coordinates (x, y, z), and there are n2 detectors 130 at the coordinates for q = 1, …, n2 to detect the unknown target at the coordinates (x, y, z). Assume the round-trip time between the illuminator and the detector j (reflection of the unknown target) is t ij . Then the coordinates of the unknown target can be obtained by solving the following optimization problem:

[0144]

[0145] It should be understood that there are many ways to solve the above optimization problem to determine the unknown coordinates x, y, z of the target. These methods include first-order methods such as gradient descent method, mirror descent method, conjugate gradient method, etc., and second-order methods such as Newton's method. There are also Riemannian optimization counterparts of these first-order and second-order methods.

[0146] In addition, the above solution for finding the position of an unknown target in three-dimensional space has been described in a Cartesian coordinate system. As mentioned before, and as will be understood by those of ordinary skill in the art, the position of the unknown target can also be described in a cylindrical coordinate system, a spherical coordinate system, or any other suitable coordinate system. When using cylindrical coordinates or spherical coordinates instead of a system of quadratic equations, an algebraic trigonometric system of equations is obtained. These can also be solved in various ways. For example, first-order and second-order Riemannian optimization methods that consider the trigonometric structure can be used.

[0147] In the case of n1 = 1 and n2 = 3 (i.e., one illuminator 120 and three detectors 130), the algorithm examines the pulse sequence 180 that has arrived from the illuminator i, which has an illuminator FOV 122 that illuminates the spatial volume 160 sensed by the three detectors 130. For each such triple and the algorithm attempts to solve the system of quadratic equations generated by the three corresponding ellipsoids. If the system of quadratic equations has no real solutions, then the target for this triple does not exist. Otherwise, the solution of the system of equations determines the coordinates of the target and confirms its existence.

[0148] Targets can also be detected by scanning the scene. For the point of interest (x, y, z) to be scanned, the round-trip times of (multiple) sets of non-collinear illuminators 120 and detectors 130 (where n1 × n2 > 2) that respectively illuminate and observe the point are pre-computed and stored (e.g., in a database, computer-readable memory, server, etc.). When the MIMO LiDAR system 100 is operating, the delays (distances) detected by the (multiple) detectors 130 are examined to determine if they correspond to any pre-computed round-trip times (or distances). If so, the location of the target is known.

[0149] In the foregoing description and drawings, specific terms have been set forth to provide a thorough understanding of the disclosed embodiments. In some instances, the terms or drawings may imply specific details that are not required to practice the present invention.

[0150] To avoid unnecessarily obscuring the present disclosure, well-known components are shown in block diagram form and / or not discussed in detail, or in some instances not discussed at all.

[0151] Unless explicitly defined otherwise herein, all terms will be given their broadest possible interpretation, including the meanings implied in the specification and drawings and the meanings understood by those skilled in the art and / or as defined in dictionaries, treatises, etc. As explicitly set forth herein, some terms may not conform to their ordinary or customary meanings.

[0152] As used in the specification and the appended claims, the singular forms "a", "an", and "the" do not exclude plural objects unless otherwise stated. The word "or" should be interpreted as inclusive unless otherwise stated. Thus, the phrase "A or B" should be interpreted to mean any of the following: "both A and B", "A but not B", and "B but not A". Any use of "and / or" herein does not mean that the word "or" alone implies exclusivity.

[0153] As used in the specification and the appended claims, phrases of the form "at least one of A, B, and C", "at least one of A, B, or C", "one or more of A, B, or C", and "one or more of A, B, and C" are interchangeable and each includes all of the following meanings: "only A", "only B", "only C", "A and B but not C", "A and C but not B", "B and C but not A", and "all of A, B, and C".

[0154] With respect to the terms "comprising", "having", "include", "with" and variations thereof used in the specific embodiments or claims, these terms are intended to be inclusive in a manner similar to the term "including", i.e., meaning "including but not limited to"

[0155] The terms "exemplary" and "embodiment" are used to denote examples, not preferences or requirements.

[0156] The term "coupled" is used herein to denote both direct connection / attachment and connection / attachment through one or more intermediate elements or structures.

[0157] As used herein, the terms "above", "below", "between", and "on" refer to the relative position of one feature with respect to other features. For example, a feature disposed "above" or "below" another feature may be in direct contact with the other feature or may have intermediate material therebetween. Further, a feature disposed "between" two features may be in direct contact with the two features or may have one or more intermediate features or materials therebetween. In contrast, a first feature "on" which a second feature is disposed is in contact with the second feature.

[0158] The term "substantially" is used to describe structures, configurations, dimensions, etc. This is largely or nearly as described, but due to manufacturing tolerances, etc., there may actually result a situation where structures, configurations, dimensions, etc. are not always or necessarily exactly as described. For example, describing two lengths as "substantially equal" means that the two lengths are the same for all practical purposes, but they may not (and need not) be exactly equal at a sufficiently small scale. As an example, a structure that is "substantially vertical" will be considered vertical even if it is not exactly 90 degrees relative to the horizontal direction.

[0159] The drawings are not necessarily to scale, and the dimensions, shapes, and sizes of features may vary significantly from their depiction in the drawings.

[0160] Although specific embodiments have been disclosed, it will be apparent that various modifications and changes can be made thereto without departing from the broader spirit and scope of the disclosure. For example, at least where practicable, features or aspects of any embodiment can be applied in combination with, or in place of, corresponding features or aspects of any other embodiment. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

Claims

1. A light detection and ranging LiDAR system, comprising: An array of optical components, the array including a plurality of illuminators and a plurality of detectors, each of the plurality of illuminators having a corresponding illuminator field of view (FOV), and each of the plurality of detectors having a corresponding detector FOV; And At least one processor coupled to the array of optical components and configured to execute at least one machine-executable instruction, the at least one machine-executable instruction, when executed, causing the at least one processor to: Determine a first set of distances, where the first set of distances corresponds to a first unique illuminator-detector pair in the array of optical components, and where for each target of a plurality of targets in a spatial volume, the first set of distances includes the respective estimated distances traveled by optical signals emitted by the illuminator of the first unique illuminator-detector pair, reflected by the target, and detected by the detector of the first unique illuminator-detector pair, Determine a second set of distances, where the second set of distances corresponds to a second unique illuminator-detector pair in the array of optical components, and where for each target of the plurality of targets in the spatial volume, the second set of distances includes the respective estimated distances traveled by optical signals emitted by the illuminator of the second unique illuminator-detector pair, reflected by the target, and detected by the detector of the second unique illuminator-detector pair, Determine a third set of distances, where the third set of distances corresponds to a third unique illuminator-detector pair in the array of optical components, and where for each target of the plurality of targets in the spatial volume, the third set of distances includes the respective estimated distances traveled by optical signals emitted by the illuminator of the third unique illuminator-detector pair, reflected by the target, and detected by the detector of the third unique illuminator-detector pair, and Estimate the respective positions in three-dimensional space of each of the plurality of targets, at least in part based on the first set of distances, the second set of distances, and the third set of distances, Where: At least two of the illuminator of the first unique illuminator-detector pair, the detector of the first unique illuminator-detector pair, the illuminator of the second unique illuminator-detector pair, the detector of the second unique illuminator-detector pair, the illuminator of the third unique illuminator-detector pair, or the detector of the third unique illuminator-detector pair are non-collinear, The spatial volume is within each of the following: (a) the FOV of the illuminator of the first unique illuminator-detector pair, (b) the FOV of the detector of the first unique illuminator-detector pair, (c) the FOV of the illuminator of the second unique illuminator-detector pair, (d) the FOV of the detector of the second unique illuminator-detector pair, (e) the FOV of the illuminator of the third unique illuminator-detector pair, and (f) the FOV of the detector of the third unique illuminator-detector pair, and The at least one machine-executable instruction causes the at least one processor to determine the first set of distances, in part, by: performing a correlation, where the correlation is a correlation of an optical signal detected by a detector of the first unique illuminator-detector pair with an optical signal transmitted by an illuminator of the first unique illuminator-detector pair, and identifying at least one peak in the result of the correlation.

2. The LiDAR system according to claim 1, wherein, The at least one machine-executable instruction causes the at least one processor to estimate a respective position of each of the plurality of targets by solving at least one quadratic equation.

3. The LiDAR system according to claim 1, wherein, The at least one machine-executable instruction further causes the at least one processor to determine the first set of distances, in part, by: denoising an optical signal detected by a detector of the first unique illuminator-detector pair prior to performing the correlation, and where the correlation is a correlation of the denoised detected optical signal with an optical signal transmitted by an illuminator of the first unique illuminator-detector pair.

4. The LiDAR system according to claim 3, wherein, Denoising the optical signal detected by a detector of the first unique illuminator-detector pair includes determining or minimizing an atomic norm.

5. The LiDAR system according to claim 1, wherein, The optical signal transmitted by an illuminator of the first unique illuminator-detector pair includes a first pulse sequence transmitted during a time window.

6. The LiDAR system according to claim 5, wherein, The first pulse sequence is sparse.

7. The LiDAR system according to claim 5, wherein, The first pulse sequence is substantially white.

8. The LiDAR system according to claim 5, wherein, The optical signal transmitted by an illuminator of the second unique illuminator-detector pair includes a second pulse sequence transmitted during the time window, where the second pulse sequence is different from the first pulse sequence.

9. The LiDAR system according to claim 8, wherein, The first pulse sequence and the second pulse sequence are substantially uncorrelated.

10. The LiDAR system according to claim 8, wherein, The first pulse sequence and the second pulse sequence are sparse.

11. The LiDAR system according to claim 8, wherein, Each of the first pulse sequence and the second pulse sequence is substantially white.

12. The LiDAR system according to claim 8, wherein, The maximum value of the cross-correlation of the first pulse sequence and the second pulse sequence is less than a threshold.

13. The LiDAR system according to claim 12, wherein, The threshold is the maximum number of overlapping pulses.

14. The LiDAR system according to claim 8, wherein, The optical signal transmitted by an illuminator of the third unique illuminator-detector pair includes a third pulse sequence transmitted during the time window, where the third pulse sequence is different from the first pulse sequence and different from the second pulse sequence.

15. The LiDAR system of claim 14, wherein: the first pulse sequence and the second pulse sequence are substantially uncorrelated, the first pulse sequence and the third pulse sequence are substantially uncorrelated, and the second pulse sequence and the third pulse sequence are substantially uncorrelated.

16. The LiDAR system according to claim 14, wherein, The first pulse sequence, the second pulse sequence, and the third pulse sequence are sparse.

17. The LiDAR system according to claim 14, wherein, Each of the first pulse sequence, the second pulse sequence, and the third pulse sequence is substantially white.

18. The LiDAR system according to claim 1, wherein, At least two of the illuminators of the first unique illuminator-detector pair, the second unique illuminator-detector pair, or the third unique illuminator-detector pair are the same illuminator.

19. The LiDAR system according to claim 1, wherein, At least two of the detectors of the first unique illuminator-detector pair, the detectors of the second unique illuminator-detector pair, or the detectors of the third unique illuminator-detector pair are the same detector.

20. The LiDAR system according to claim 1, wherein: At least two of the illuminators of the first unique illuminator-detector pair, the illuminators of the second unique illuminator-detector pair, or the illuminators of the third unique illuminator-detector pair are the same illuminator, and At least two of the detectors of the first unique illuminator-detector pair, the detectors of the second unique illuminator-detector pair, or the detectors of the third unique illuminator-detector pair are the same detector.

21. The LiDAR system according to claim 1, wherein, When executed, the at least one machine-executable instruction causes the at least one processor to estimate the corresponding position of each of the plurality of targets in three-dimensional space by solving at least one optimization problem.

22. The LiDAR system according to claim 21, wherein, The at least one optimization problem includes where x, y, z represent the coordinates of the target, represents the coordinates of the p-th illuminator, represents the coordinates of the q-th detector, represents the round-trip time between the p-th illuminator and the q-th detector, c represents the speed of light, n1 represents the number of illuminators illuminating the target, n2 represents the number of detectors observing the target, and n1×n2>

2.

23. The LiDAR system according to claim 1, wherein, When executed, the at least one machine-executable instruction causes the at least one processor to estimate the corresponding position of each of the plurality of targets in three-dimensional space by determining whether at least one of the estimated distances in the first distance set, the second distance set, or the third distance set corresponds to a stored pre-computed distance.

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