Noise Adaptive Solid State LiDAR System

Abstract

To provide a noise adaptive solid LIDAR system.SOLUTION: A LIDAR system includes an optical transmitter provided with a plurality of lasers for respectively illuminating a FOV in an illumination region. A transmitter controller has an output connected to a respective laser input. The transmitter controller generates electric pulses for the output so that the laser generates light in a desired pattern in the illumination region. An optical receiver has an input FOV in the illumination region, and includes: a plurality of detectors, each having a FOV, and being positioned to detect light across the illumination region; and a TOF measurement circuit for measuring TOF from the laser to the detector. The receiver calculates range information. An adaptive optical shutter positioned between the optical transmitter and the optical receiver has a transparent or reflective region FOV, and the optical shutter limits illumination at the input of the optical receiver to a region that is smaller than an optical receiver FOV.SELECTED DRAWING: None

Description

Technical Field

[0001] The headings of the sections used in this specification are for organization purposes only and should not be construed as limiting the subject matter described in this application in any way. (Related Applications)

[0002] This application is a non-provisional application of co-pending U.S. Provisional Patent Application No. 62 / 651,209, filed on April 1, 2018, entitled "Noise Adaptive Solid-State LIDAR System". The entire content of U.S. Patent Application No. 62 / 651,209 is incorporated herein by reference.

Background Art

[0003] Autonomous, self-driving, and semi-autonomous vehicles use combinations of different sensors and technologies, such as radar, image recognition cameras, and sonar, for detecting and locating surrounding objects. These sensors enable numerous improvements in driver safety, including collision warnings, automatic emergency braking, lane departure warnings, lane keeping assistance, adaptive cruise control, and pilot driving. Among these sensor technologies, optical detection and ranging (lidar) systems play an important role and enable real-time high-resolution 3D mapping of the surrounding environment. To address the requirements of an increasing number of complex automotive applications, lidar systems are required to have a sufficiently fast response time to respond to fast-moving objects. Lidar systems must also have a sufficient signal-to-noise ratio for detecting distant objects with respect to the received signals. Furthermore, it is desirable for lidar systems to have a minimum number of moving parts and high reliability.

[0004] In addition, lidar systems can encounter a wide range of conditions and varying sets of requirements regarding resolution and speed during typical operation. Therefore, lidar systems are required to have operating parameters and capabilities that adapt to changing requirements and environments.

SUMMARY OF THE INVENTION

MEANS FOR SOLVING THE PROBLEM

[0005] According to a preferred and exemplary embodiment, the present teachings will be more specifically described in the following forms for carrying out the invention, together with the accompanying drawings and with its further advantages. Those skilled in the art will understand that the drawings described below are for illustrative purposes only. The drawings are not necessarily to scale; instead, generally, emphasis is placed on illustrating the principles of the present teachings. The drawings are not intended to limit the scope of the applicant's teachings in any way. The present invention provides, for example, the following. (Item 1) A light detection and ranging (lidar) system, wherein the light detection and ranging system comprises a) An optical transmitter comprising a plurality of lasers, each of the plurality of lasers illuminating a field of view in an illumination area, the optical transmitter; b) A transmitter controller having a plurality of electrical outputs, each of the plurality of electrical outputs of the transmitter controller being electrically connected to an input of a respective one of the plurality of lasers, the transmitter controller configured to generate electrical pulses at the plurality of electrical outputs, whereby the plurality of lasers are configured to generate light in a desired pattern in the illumination area, the transmitter controller; c) A photoreceiver having an input with a field of view in the illumination area, the photoreceiver comprising a plurality of detectors, each of the plurality of detectors having a field of view in the illumination area and being positioned to detect light in the illumination area, and a time-of-flight measurement circuit for measuring the time of flight of light from the plurality of lasers to the plurality of detectors, the photoreceiver calculating range information from the time-of-flight measurements, the photoreceiver; d) An adaptive optical shutter positioned between the optical transmitter and the photoreceiver and having a field of view of a transparent area in the illumination area and comprising The optical shutter limits the illumination at the input of the optical receiver, whereby the field of view of the transparent region is smaller than the field of view of the input of the optical receiver, for an optical detection and ranging system. (Item 2) For the optical detection and ranging system according to item 1, the field of view of at least some of the plurality of lasers is smaller than the field of view of at least some of the plurality of detectors. (Item 3) For the optical detection and ranging system according to item 1, the field of view of the transparent region of the adaptive optical shutter is different from the field of view of at least some of the plurality of detectors. (Item 4) For the optical detection and ranging system according to item 1, the field of view of the transparent region of the adaptive optical shutter is different from the field of view of each of the plurality of detectors. (Item 5) For the optical detection and ranging system according to item 1, the field of view of the transparent region of the adaptive optical shutter is different from the field of view of at least some of the plurality of lasers. (Item 6) For the optical detection and ranging system according to item 1, the field of view of at least some of the plurality of detectors is larger than the field of view of the transparent region of the adaptive optical shutter. (Item 7) For the optical detection and ranging system according to item 1, the field of view of each of the plurality of detectors is larger than the field of view of the transparent region of the adaptive optical shutter. (Item 8) For the optical detection and ranging system according to item 1, the field of view of at least some of the plurality of detectors is smaller than the field of view of the transparent region of the adaptive optical shutter. (Item 9) For the optical detection and ranging system according to item 1, the field of view of at least some of the plurality of lasers is larger than the field of view of the transparent region of the adaptive optical shutter. (Item 10) The ratio of the field of view of the transparent region of the adaptive optical shutter to the field of view of at least some of the plurality of lasers is selected to achieve a specific resolution of the optical detection and ranging system, the optical detection and ranging system according to item 1. (Item 11) The ratio of the field of view of the transparent region of the adaptive optical shutter to the field of view of at least some of the plurality of lasers is selected to achieve a specific dynamic range of the optical detection and ranging system, the optical detection and ranging system according to item 1. (Item 12) The ratio of the field of view of the transparent region of the adaptive optical shutter to the field of view of at least some of the plurality of detectors is selected to achieve a specific signal-to-noise ratio of the optical detection and ranging system, the optical detection and ranging system according to item 1. (Item 13) The ratio of the field of view of the transparent region of the adaptive optical shutter to the field of view of each of the plurality of detectors is selected to achieve a specific signal-to-noise ratio of the optical detection and ranging system, the optical detection and ranging system according to item 1. (Item 14) The number of the plurality of detectors is smaller than the number of the plurality of lasers, the optical detection and ranging system according to item 1. (Item 15) The field of view of the transparent region of the adaptive optical shutter is configured to be smaller than the size of the desired pattern in the illumination region, the optical detection and ranging system according to item 1. (Item 16) At least two of the plurality of lasers emit light at different wavelengths, the optical detection and ranging system according to item 1. (Item 17) The adaptive optical shutter includes a liquid crystal shutter, the optical detection and ranging system according to item 1. (Item 18) The adaptive optical shutter includes an etalon cavity shutter, the optical detection and ranging system according to item 1. (Item 19) The adaptive optical shutter-equipped light detection and ranging system according to Item 1, wherein the adaptive optical shutter includes a MEMS shutter. (Item 20) A light detection and ranging (lidar) system, wherein the light detection and ranging system includes: a) An optical transmitter including a plurality of lasers, each of the plurality of lasers illuminating a field of view in an illumination area; b) A transmitter controller having a plurality of electrical outputs, each of the plurality of electrical outputs of the transmitter controller being electrically connected to an input of one of the plurality of lasers, the transmitter controller configured to generate electrical pulses at the plurality of electrical outputs, whereby the plurality of lasers are configured to generate light in a desired pattern in the illumination area; c) An optical receiver having an input including a field of view in the illumination area, the optical receiver including a plurality of detectors, each of the plurality of detectors having a field of view in the illumination area and being positioned to detect light in the illumination area, and a time-of-flight measurement circuit configured to measure a time of flight of light from the plurality of lasers to the plurality of detectors, the optical receiver configured to calculate range information from the time-of-flight measurement values; d) An adaptive optical mirror positioned between the optical transmitter and the optical receiver and having a field of view of a reflection area in the illumination area; and the optical mirror is configured to limit illumination at the input of the optical receiver to an area smaller than a field of view of the input of the optical receiver. (Item 21) The light detection and ranging system according to Item 20, wherein a field of view of at least some of the plurality of lasers is smaller than a field of view of at least some of the plurality of detectors. (Item 22) The light detection and ranging system according to Item 20, wherein a field of view of the reflection area of the adaptive optical mirror is different from a field of view of at least some of the plurality of detectors. (Item 23) The light detection and ranging system according to item 20, wherein the field of view of the reflection region of the adaptive optical mirror is different from the field of view of each of the plurality of detectors. (Item 24) The light detection and ranging system according to item 20, wherein the field of view of the reflection region of the adaptive optical mirror is different from the field of view of at least some of the plurality of lasers. (Item 25) The light detection and ranging system according to item 20, wherein the field of view of at least some of the plurality of detectors is larger than the field of view of the reflection region of the adaptive optical mirror. (Item 26) The light detection and ranging system according to item 20, wherein the field of view of each of the plurality of detectors is larger than the field of view of the reflection region of the adaptive optical mirror. (Item 27) The light detection and ranging system according to item 20, wherein the field of view of at least some of the plurality of detectors is smaller than the field of view of the reflection region of the adaptive optical mirror. (Item 28) The light detection and ranging system according to item 20, wherein the field of view of at least some of the plurality of lasers is larger than the field of view of the reflection region of the adaptive optical mirror. (Item 29) The light detection and ranging system according to item 20, wherein the ratio of the field of view of the reflection region of the adaptive optical mirror to the field of view of at least some of the plurality of lasers is selected to achieve a specific resolution of the light detection and ranging system. (Item 30) The light detection and ranging system according to item 20, wherein the ratio of the field of view of the reflection region of the adaptive optical mirror to the field of view of at least some of the plurality of lasers is selected to achieve a specific dynamic range of the light detection and ranging system. (Item 31) The ratio of the field of view of the reflection region of the adaptive optical mirror to the field of view of at least some of the plurality of lasers is selected to achieve a specific resolution, the optical detection and ranging system according to item 20. (Item 32) The ratio of the field of view of the reflection region of the adaptive optical mirror to the field of view of at least some of the plurality of detectors is selected to achieve a specific signal-to-noise ratio of the optical detection and ranging system, the optical detection and ranging system according to item 20. (Item 33) The ratio of the field of view of the reflection region of the adaptive optical mirror to the fields of view of all of the plurality of detectors is selected to achieve a specific signal-to-noise ratio of the optical detection and ranging system, the optical detection and ranging system according to item 20. (Item 34) The number of the plurality of detectors is smaller than the number of the plurality of lasers, the optical detection and ranging system according to item 20. (Item 35) The field of view of the reflection region of the adaptive optical mirror is configured to be smaller than the size of the desired pattern in the illumination region, the optical detection and ranging system according to item 20. (Item 36) The adaptive optical mirror includes MEMS, the optical detection and ranging system according to item 20. (Item 37) The adaptive optical mirror includes digital micromirrors, the optical detection and ranging system according to item 20. (Item 38) At least two of the plurality of lasers emit light at different wavelengths, the optical detection and ranging system according to item 20. (Item 39) An optical detection and ranging method, the method comprising: a) Using a plurality of lasers to illuminate a field of view with a desired pattern in an illumination region; b) Positioning a photoreceiver having an input with a field of view in the illumination area, the photoreceiver comprising a plurality of detectors, the plurality of detectors detecting light across the illumination area, each of the plurality of detectors having a field of view; and c) Measuring the flight time of light from the plurality of lasers to the plurality of detectors; d) Calculating range information from the flight time measurements; e) Limiting the illumination at the input of the photoreceiver to the field of view of the transparent area including wherein the field of view of the transparent area is smaller than the field of view of the input of the photoreceiver, a method of optical detection and ranging. (Item 40) The method of optical detection and ranging according to item 39, wherein the field of view of at least some of the plurality of lasers is smaller than the field of view of at least some of the plurality of detectors. (Item 41) The method of optical detection and ranging according to item 39, wherein the field of view of at least some of the plurality of lasers is smaller than the field of view of all of the plurality of detectors. (Item 42) The method of optical detection and ranging according to item 39, wherein the field of view of all of the plurality of lasers is smaller than the field of view of all of the plurality of detectors. (Item 43) The method of optical detection and ranging according to item 39, wherein the field of view of the transparent area is different from the field of view of at least some of the plurality of detectors. (Item 44) The method of optical detection and ranging according to item 39, wherein the field of view of the transparent area is different from the field of view of at least some of the plurality of lasers. (Item 45) The method of optical detection and ranging according to item 39, wherein the field of view of the transparent area is different from the field of view of each of the plurality of lasers. (Item 46) The method of optical detection and ranging according to item 39, wherein the field of view of at least some of the plurality of detectors is larger than the field of view of the transparent area. (Item 47) The method for optical detection and ranging according to item 39, wherein the field of view of each of the plurality of detectors is larger than the field of view of the transparent region. (Item 48) The method for optical detection and ranging according to item 39, wherein the field of view of at least some of the plurality of detectors is smaller than the field of view of the transparent region. (Item 49) The method for optical detection and ranging according to item 39, wherein the field of view of each of the plurality of detectors is smaller than the field of view of the transparent region. (Item 50) The method for optical detection and ranging according to item 39, wherein the field of view of at least some of the plurality of lasers is larger than the field of view of the transparent region. (Item 51) The method for optical detection and ranging according to item 39, wherein the ratio of the field of view of the transparent region to the field of view of at least some of the plurality of lasers is selected to achieve a specific resolution of the optical detection and ranging system. (Item 52) The method for optical detection and ranging according to item 39, wherein the ratio of the field of view of the transparent region to the field of view of at least some of the plurality of lasers of the adaptive optical shutter is selected to achieve a specific dynamic range of the optical detection and ranging system. (Item 53) The method for optical detection and ranging according to item 39, wherein the ratio of the field of view of the transparent region to the field of view of at least some of the plurality of detectors is selected to achieve a specific signal-to-noise ratio of the optical detection and ranging system. (Item 54) The method for optical detection and ranging according to item 39, wherein the ratio of the field of view of the transparent region to the field of view of each of the plurality of detectors is selected to achieve a specific signal-to-noise ratio of the optical detection and ranging system. (Item 55) The method for optical detection and ranging according to item 39, wherein the number of the plurality of detectors is smaller than the number of the plurality of lasers. (Item 56) The method of optical detection and ranging according to item 39, wherein the field of view of the transparent region is configured to be smaller than the size of the desired pattern in the illumination region. (Item 57) The method of optical detection and ranging according to item 39, wherein at least two of the plurality of lasers emit light at different wavelengths.

Brief Description of the Drawings

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[0021] The present teachings will now be described in more detail with reference to its exemplary embodiments as shown in the accompanying drawings. The present teachings are described in conjunction with various embodiments and examples, but the present teachings are not intended to be limited to such embodiments. Rather, the present teachings include various alternatives, modifications, and equivalents, as will be understood by those skilled in the art. Those skilled in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments within the scope of the present disclosure as described herein, as well as other fields of use.

[0022] The mention of "one embodiment" or "an embodiment" in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present teachings. The appearances of the phrase "in one embodiment" in various places in this specification are not necessarily all referring to the same embodiment.

[0023] It should be understood that the individual steps of the methods of the present teachings can be performed in any order and / or simultaneously as long as the present teachings remain operable. Further, it should be understood that the apparatus and methods of the present teachings can include any number or all of the described embodiments as long as the present teachings remain operable.

[0024] The present teachings relate to a solid-state lidar system that measures distances to various objects or targets that reflect and / or scatter light. In particular, the present teachings describe a noise-adaptive solid-state lidar system that enables reduction of noise in received measurement signals, enabling an improved SNR and thus a longer measurement range.

[0025] Automotive applications require a lidar system with a measurement range exceeding 100 meters to provide sufficient time to respond to fast-moving objects. For example, two vehicles in opposing lanes on an undivided arterial road may have an opposing relative speed of 250 km / h (150 mph) or more. At 250 km / h, it would only take 1.44 seconds to close a 100 m gap between two vehicles.

[0026] The signal-to-noise ratio (SNR) of the received signal determines whether an object can be detected at a specific distance with a specific error rate. The signal strength depends on the optical output transmitted. Higher transmission power provides a stronger reflected feedback signal and increases the range. However, automotive lidar systems are typically constrained by Class 1 eye safety standards, which limit the maximum allowable optical output that can be transmitted. By operating within the range of Class 1 eye safety standards, products that emit laser light are considered eye-safe under all reasonably foreseeable conditions of use. When reaching the Class 1 eye safety transmission optical output limit, further improvement of the SNR is best achieved through improvements in the design of the optical receiver and / or signal processing. It is highly desirable for a lidar system used within automotive applications to be completely solid-state without moving parts to maximize reliability. It is also highly desirable for the lidar system to be able to adapt to changing measurement requirements and conditions.

[0027] FIG. 1A illustrates a schematic diagram of a known solid lidar system. The system illustrated in FIG. 1A does not employ a flash transmitter that illuminates the entire system field of view all at once. Instead, each individual laser in transmitter array 102 can be fired independently, and the optical beam emitted by each laser corresponds to a 3D projection angle for only a portion of the entire system field of view. An example of such a transmitter is described in detail in U.S. Patent Publication No. 2017 / 0307736 A1, which has been assigned to the present assignee. The entire content of U.S. Patent Publication No. 2017 / 0307736 A1 is incorporated herein by reference. In some embodiments, the array of transmitters is a regularly spaced array. In other embodiments, the array of transmitters is an irregularly shaped array. In various embodiments, the array of transmitters can be configured in various shapes and sizes.

[0028] The optical beams from the lasers in laser array 102 share transmitter optics 104, and the reflected light from target 106 shares receiver optics 108. Detector array 110 is a solid without moving parts. Detector array 110 typically has fewer individual detector elements than transmitter array 102 has individual lasers. The measurement resolution of lidar system 100 is not determined by the size of the detector elements in detector array 110, but instead is determined by the number of lasers in transmitter array 102 and the collimation of the individual optical beams. A processor in lidar system 100 performs a time-of-flight (TOF) measurement to determine the distance to target 106, and target 106 reflects the optical beam from the lasers in laser array 102 as detected by detector array 110.

[0029] As will be understood by those skilled in the art, the propagation of light from and through various optical elements in a lidar system can be described as being projected onto a particular reference plane in the optical system. Without loss of generality and for the purposes of the present disclosure, this reference plane is taken to be the plane of the detector array 110. The projection of the light emitted from the laser array 102 onto the reference plane through the lidar system is herein referred to as the illumination area. The detector array 110 is positioned within the reference plane and detects light in the illumination area. For simplicity, the operation of the system is also described in relation to a particular target range, which is a location where an object or target may be located. As is well known, a lidar system can operate in three dimensions, which means that the measurement points are captured over a 2D plane in a plurality of target ranges. These measurements in the various target ranges generally result in what is commonly referred to as a 3D point cloud. The extension to 3D operation based on the description in a particular target range is more widely understood by those skilled in the art.

[0030] When energized, the lasers in the transmission array 102 generate a pattern of light within the illumination area in this plane of the detector array 110. The particular pattern is based on the particular elements in the energized laser array 102 and thus they generate light as described herein. This pattern in the illumination area assumes a uniform reflection over the 2D plane in the target range. As will be understood by those skilled in the art, the reference herein to "a particular pattern of laser illumination within the illumination area" is the pattern generated by this uniform reflection in the target range. During operation, only a portion of the optical illumination from the laser array 102 will be reflected back into the illumination area (or in some configurations, not reflected at all). The optical illumination from the laser array 102 that reaches the detector array 110 during operation depends on the shape and position of the object or target 106 in the target range.

[0031] Figure 1B illustrates a two-dimensional projection of the system field of view 150 of the lidar system of Figure 1A. The system field of view 150 illustrates the illumination region referred to herein. The field of view of an individual detector in the detector array is represented by the small square 152. The illumination measurement points associated with the individual lasers in the transmitter are illustrated by the circles 154. The size of an individual detector within the array is primarily determined by the electrical characteristics of this device. For example, as the size of the active area of an avalanche photodiode (APD) detector increases, the capacitance of the detector increases, reducing the optoelectronic bandwidth of the device. The bandwidth of the APD must be maintained high enough so as not to attenuate or distort the received signal. Typical values for the optical / electrical (O / E) bandwidth of a lidar system with a laser pulse width of <10 nanoseconds and the APD capacitance are, respectively, 350 MHz and less than 2 pF. Generally, an array of detectors must be used in order to target the entire field of view of the lidar system while maintaining acceptable electrical detector performance. The overall physical size and dimensions of the array are determined by the required field of view and the optical lens system of the receiver.

[0032] In an embodiment of the lidar system 100 illustrated in FIGS. 1A-B, the ratio of the number of detectors in the detector array 110 to the number of lasers in the transmitter array 102 is 1 to 9. This can also be seen by the two-dimensional projection of the system field of view 150. In this embodiment, the detector array 110 is a 5×5 array. When compared to a flash system with equivalent angular resolution, the cost of the detector array of the lidar system 100 can be lower since the number of detectors can be fewer. The measurement resolution of the lidar system 100 is not determined by the size of the detector elements, but rather by the number of lasers in the transmitter array 102 and the collimation of the individual laser beams.

[0033] Figures 1A - B illustrate important aspects of the lidar system 100. A single 3D measurement point, i.e., the small circle 154 in the overall field of view 150 of the lidar system 100, is emphasized, and that measurement point 154 is shown as a dark circle. This measurement point circle 154 has a one - to - one correspondence with a specific individual laser in the laser transmitter array 102. Further, it can be seen that the measurement point 154 is present within an individual detector, and the field of view represented by the small square 152 of that individual detector is shown as a square with a thick contour. For example, the overall field of view of the detector array represented by the large square 156, which includes an array of 25 all small squares 152, can be reached as a whole by utilizing the individual laser fields of view shown in Figure 1B by the small circles 154 from an array of 15×15 lasers represented by an array of 15×15 small circles 154. This field of view represented by the large square 156 can be referred to as the input field of view of the optical receiver. It includes any transformation of the various receiving optical elements in the path from the target range.

[0034] The 3D resolution of the lidar system 100 is determined by the number of lasers in the transmitter array 102. Each laser generates an optical beam corresponding to a specific corner point in space as shown by the measurement point circle 154. In the embodiment shown in Figure 1B, when a single laser associated with the (shaded) measurement point circle 154 is illuminated, the pattern within the illumination area is in the shape of the circle 154. The field of view of the detector illuminated by the excited laser is in the shape of the square 152.

[0035] In such a solid state lidar system 100, each element of the detector array 110 does not require its own separate receiving electrical circuit since only one detector is needed to measure any given laser transmission pulse at any given time, and the detectors can instead be coupled to a common receiving circuit. This provides a substantial benefit of reduced circuit complexity and cost. However, if all detectors are coupled onto the same circuit, the noise from all detectors will combine and increase, which will reduce the sensitivity of the system and decrease the measurement range.

[0036] FIG. 2 illustrates a schematic diagram of an embodiment of an adaptive field of view lidar system 200 according to the present teachings. The embodiment shown in FIG. 2 includes a transmitter array 202, a transmission optics 204, a target 206, a receiving optics 208, and a detector array 210 similar to those described in connection with the lidar system 100 of FIG. 1A. However, the embodiment shown in FIG. 2 includes an adaptive optical shutter 212 disposed in front of the detector array 210. The adaptive optical shutter 212 improves system performance as compared to the lidar system 100 of FIG. 1A by reducing the ambient light reaching the detector array 210. In a lidar system 200 operating outdoors, the ambient light from the sun reaching the receiver can generate an optical signal large enough to suppress or obscure the detection of the received laser pulse. The adaptive shutter 212 can be used to block at least a portion of the ambient light from reaching the detector or detectors that are detecting the measurement light from the optical beam emitted by the transmission array 202.

[0037] In some embodiments, the transmitter array 202 comprises a plurality of lasers, each of which generates an optical beam that, when activated, illuminates a field of view in the illumination area. A transmitter controller (not shown) is connected to the transmitter. The controller is described in more detail in connection with FIG. 7A. In many embodiments, the controller is capable of individually controlling each of the plurality of lasers. The transmission controller can thus pulse a desired one of the plurality of lasers in a specific pattern, whereby the plurality of lasers generate light into the illumination area in a corresponding specific pattern based on the specific lasers that are activated. Additionally, the detector array 210 in the optical receiver includes a plurality of detectors positioned to detect light across the illumination area. Each of the plurality of detectors generates an electrical detection signal in response to the detected light reaching within its respective field of view in the illumination area. The detected light is passed to a processor and other circuitry (including a time-of-flight measurement circuit that measures the time of flight of light from the plurality of lasers to the plurality of detectors).

[0038] The processor and other circuitry in the receiving controller calculate range information to an object or objects that reflect light generated by a specific plurality of lasers in the transmission array 202 selected by the controller from the time-of-flight measurements. Thus, different sizes and shapes of the field of view and illumination area are generated based on the performance requirements of the system. For example, a particular measurement resolution and / or signal-to-noise ratio can be provided by varying the size or shape of the field of view of the system. In various embodiments, various numbers of detectors in the detector array 210 and various numbers of lasers in the transmission array 202 are used. Various ratios of the number of detectors in the detector array 210 to the number of lasers in the transmission array 202 are also used.

[0039] One feature of the present teachings is that individual lasers or groups of individual lasers within the transmitter array 202 can operate at different wavelengths. Multi-source and multi-wavelength lidar systems have been proposed by the assignee of the present application. An example of a system using multiple wavelength transmitters is described in U.S. Patent Publication No. 2017 / 0307736 A1, which has been assigned to the present assignee. The entire contents of U.S. Patent Publication No. 2017 / 0307736 A1 are incorporated herein by reference. Using multiple wavelengths in a transmitter results in various illumination patterns with different wavelengths that can be generated simultaneously or separately for various purposes. For example, generating an optical beam that results in a desired illumination pattern with different wavelengths at a target and / or detector (i.e., the illumination area) can be used to achieve various performance metrics (such as reducing processing requirements, generating higher resolution measurements that increase the refresh rate or frame rate, etc.).

[0040] FIG. 3 illustrates a schematic diagram of a photoreceiver 300 of an embodiment of the adaptive lidar system of the present teachings. For simplicity, a 2D figure is shown here, but the principles apply equally to a complete 3D system. A detector array 302 is nominally placed at the imaging plane in the optical system of the photoreceiver. In some embodiments, the detector array 302 is not wavelength sensitive. In other embodiments, the detector array 302 is wavelength selective. The receiving optical system is represented by a receiving lens 310, but may include multiple lenses and / or other optical elements. The size of the detector array 302 in combination with the focal length of the optical system determines the maximum field of view of the photoreceiver 300.

[0041] The schematic diagram shows a ray trace 304 for a received beam imaged at the center of the detector array 302 and a ray trace 306 for a received beam imaged at the uppermost point of the detector array 302. Different points in the receiver field of view are imaged onto different detectors within the detector array depending on their angular positions. The angle 308 between the ray trace 304 for the center of the detector array 302 and the ray trace 306 for the uppermost point of the detector array 302 represents half of the maximum field of view of the optical receiving system.

[0042] The received optical beam reflected from the target passes through one or more light-receiving lenses 310 and an adaptive shutter 312 before arriving at the detector array 302. An optical notch filter 314 is positioned in front of the receiver lens 310. This optical notch filter 314 is used to reduce the solar radiation onto the detector array 302. On a sunny day, at the sea surface, the maximum solar radiation is about 1 kW / m 2 . Typically, the optical notch filter 314 is designed to reduce this irradiation as much as possible and limit the optical reception bandwidth to a wavelength region corresponding to the expected wavelength range of the transmitter laser. For a lidar system operating at a wavelength of about 900 nm, an optical notch filter with a bandwidth of 20 nm will reduce the solar radiation to less than 2% of the full solar radiation. However, even at this reduced level, the incidence of ambient light onto the detectors in the detector array 302 on a sunny day can be significant.

[0043] One feature of the present teachings is that an adaptive shutter positioned between the object being examined and the detector array can be used to block light that can interfere with ranging. FIGS. 4A-B provide a simplified 3D representation for illustrating the concept of adapting the reception field of view. FIG. 4A illustrates a schematic configuration of an embodiment of an adaptive lidar system 400 using the adaptive shutter 402 of the present teachings. The transmitter 404 emits light pulses that are reflected by a target object schematically represented as a cube 406. The light 408 reflected from the target object captured by the receiver lens 410 is focused onto a detector array 412 nominally placed on the imaging plane. Only one detector element 414 within the 2D detector array 412 is required to capture all of the light from the transmitter 404 reflected from the target object 406 because the target object 406 occupies only a portion of the receiver field of view. The adaptive shutter 402 is controlled to block substantially all of the light entering onto the detector array 412 from other angles within the field of view of the 2D detector array 412. This is represented in the figure by the smaller transparent opening 416 within the larger opaque structure 418 that is part of the adaptive shutter 402. In some embodiments, the transmitter 404 is a 2D laser array. In these embodiments, for different lasers in the laser array corresponding to different 3D measurement points, the lidar system varies the adaptive shutter 402 and adjusts the location and size of the substantially transparent area 416 to correspond to the angular position of the current 3D measurement point corresponding to the laser element that is activated within the receiver field of view.

[0044] Figure 4B illustrates a schematic diagram of a second configuration of an adaptive lidar system 450 using the adaptive shutter 452 of the present disclosure. In the embodiment shown in Figure 4B, a transmitter 454, which can be the same transmitter at the same position as the transmitter 404 in Figure 4A, generates light pulses that are reflected by a target object represented as a cube 456 in the schematic diagram. The transmitter 454 can be a two-dimensional array of laser emitters. The target object represented by the cube 456 is at a different position from the target object represented by the cube 406 in Figure 4A. The reflected light 458 from the target object represented by the cube 456 captured by the receiver lens 460 is focused onto a detector array 462 nominally positioned on the imaging plane. Only one detector element 464 within the 2D detector array 462 is required to capture all of the light from the transmitter 454 reflected by the target object (cube 456) since the target object (cube 456) occupies only a portion of the receiver's field of view.

[0045] The adaptive shutter 452 is controlled to block substantially all of the light entering onto the detector array 462 from other angles within the field of view of the 2D detector array 462. This is represented in the figure by a smaller transparent aperture 466 within a larger opaque structure 468 that is part of the adaptive shutter 452. The smaller transparent aperture 466 is at a different position within the larger opaque structure 468 that is part of the adaptive shutter 452. The reflected light 458 affects detector elements 464 at different positions in the 2D detector array 462. Thus, Figures 4A - B show two different configurations of the adaptive shutters 402, 452 corresponding to two different positions of the objects 406, 456 in the field of view when the transmitters 404, 454 and the detector arrays 412, 462 are in the same positions. Those skilled in the art will understand different configurations of elements that can block background light and generate light for passage measurement using the adaptive shutter of the present disclosure.

[0046] An adaptive optical shutter as described herein can be constructed in a variety of ways. For example, one embodiment of an optical shutter is a liquid crystal shutter. The liquid crystal shutter can be configured as a 2D array of pixels where each pixel can be individually controlled. Those pixels corresponding to the current measurement field of view through which light is to pass through the liquid crystal shutter will be controlled to an “open” state, while the remainder of the pixels will be in a “closed” state. The area of the “open” state corresponds to the field of view of the transparent area. The reported contrast ratio of a liquid crystal optical shutter is as high as on the order of 1,000 to 1 with respect to the “open” state versus the “closed” state. The size and shape of the areas of the “open” and “closed” states of the shutter can vary depending on the embodiment based on the shape and size of the areas of the pixels in the “open” or “closed” state. For example, referring to FIG. 4B, the “open” state is an area of pixels represented in the figure by a relatively small transparent aperture 466 within a large opaque structure 468 having pixels in the “closed” state.

[0047] Another embodiment of an optical shutter is an etalon cavity shutter formed using a partially reflective micromirror that can be adjusted to reflect incoming laser light based on wavelength. The etalon cavity shutter consists of a 2D array of pixels where each pixel can be individually adjusted. Each pixel is adjusted as required by the lidar system to reflect or transmit the transmitter light. In such a system, the etalon also has the additional benefit of functioning as a wavelength filter. The wavelength sensitivity of the etalon shutter is different from that of a liquid crystal shutter which is mainly not affected by wavelength in the area of interest. The wavelength sensitivity of the etalon cavity shutter in a multi-wavelength lidar can also provide additional flexibility to the lidar system. This is because, unlike a fixed thin film filter, the etalon cavity can be adjusted to pass or reject various wavelengths as desired to produce an adaptive receiver with respect to both the field of view and wavelength. The above description of the optical adaptive shutter represents only two potential examples. Those skilled in the art will understand that other shutter technologies can also be used to implement the adaptive lidar system of the present teachings.

[0048] In the case of silicon-based detector technologies such as silicon APDs or silicon photomultipliers, all or some portion of the optical shutter can potentially be integrated within the same silicon chip containing the detector array. This is possible for both liquid crystal and microelectromechanical systems (MEMS)-based optical shutter devices. Those skilled in the art will understand that both transmission and reflection devices can be used to provide an optical shutter according to the present teachings. For example, the effective transparent region of a reflection device is that region which reflects or passes a portion of the optical beam from the optical transmitter to the optical receiver.

[0049] One feature of the present teachings is that system performance can be controlled based on the configuration of the shutter. The transmitter and / or detector provide different resolutions and signal-to-noise ratios for different shutter fields of view. FIG. 5A illustrates a two-dimensional projection of a system field of view 500 of the lidar system of FIG. 2 for a particular shutter field of view of the present teachings. The system field of view 500 includes contributions from the various fields of view provided by the various portions of the system. In this embodiment, a two-dimensional array of laser fields of view represented by circle 502 is generated from each collimated optical beam generated by each laser element in the transmitter array.

[0050] The laser field of view shown by the 15×15 array of circles 502 is generated by a 15×15 array of laser elements. Various embodiments utilize various different sizes and shapes of the laser field of view. The individual detector fields of view are represented by the smaller squares 504. The overall detector array field of view is represented by the larger square 506 for the present embodiment of the 5×5 detector array. The larger square 506 comprises a 5×5 array of the smaller squares 504. The field of view blocked by the light shutter is shown by the square region 508 that targets most of the detector array. The transparent field of view of the light shutter is shown by the square 510. The light shutter restricts the field of view to the size represented by the square 510, and the square 510 is smaller than the entire field of view of the detector array, i.e., larger than the field of view of a single detector element represented by the smaller square 512 that is below the transparent field of view provided by the shutter represented by the square 510. A single activated laser element generates an optical beam that provides a measurement signal for a specific field of view shown by the circle 514. In this case, the illumination pattern of the energized laser array in the illumination region is the circle 514 that is inside the field of view of a single detector in the array represented by the square 512. In this configuration, since the shutter field of view is larger than a single detector field of view, ambient light will reach not only the detector elements being used for the laser pulse measurement but also some of the surrounding detectors. However, it will be substantially blocked from other detectors in the array that are not within the transparent field of view of the shutter, i.e., within the square 510.

[0051] FIG. 5B illustrates a two-dimensional projection of the system view 530 of the lidar system of FIG. 2, relating to another embodiment of a specific shutter view of the present disclosure. The system view 530 includes the view from each optical beam generated by laser elements in a two-dimensional array and shown as small circles 532. The small squares 534 represent the views for individual detectors. The large square 536 represents the view for the entire detector array. The large square 538 is the view of the entire optical shutter, and the square 540 is the transparent region of the shutter. The optical shutter is sized to limit the transparent view represented by the square 540 to a size smaller than the view of a specific single detector element 544. The optical shutter is also sized so as not to attenuate the light received from the laser transmitter pulse that generates the optical beam view represented by the circle 542. The optical shutter configuration of the lidar system of FIG. 5B has an improved signal-to-noise ratio performance compared to the optical shutter configuration of the system shown in FIG. 5A, because it reduces more ambient light reaching the detector array without attenuating the transmitted optical pulse output received by at least the optical shutter of FIG. 5B. In other words, the optical shutter blocks more interfering light and does not block the measurement signal light (i.e., the signal light remains the same). Generally, using the present disclosure illustrated in FIG. 5B, the ratio of the view of the transparent region of the optical shutter to the view of at least one of the plurality of detectors in the detector array can be selected to achieve a specific resolution of the lidar system according to the specific requirements of the system.

[0052] FIG. 5C illustrates a two-dimensional projection of the system view 560 of the lidar system of FIG. 2, relating to another embodiment of a specific shutter view according to the present disclosure. Similar to the projections shown in FIGS. 5A-B, there are a laser measurement view represented as a circle 562, an individual detector view represented by a small square 564, an entire 2D detector view represented as a large square 566, and an entire shutter view represented as a large square 568. The open state of the shutter generates a small square 570 near the active detector view represented by the square 572 and an active laser measurement point represented by the circle 574.

[0053] The optical shutter limits the field of view of the transparent region to a size represented by square 570, which is smaller than the field of view of a single detector represented by small square 572 and smaller than the field of view illuminated by the laser transmitter pulse represented by circle 574. In this configuration, only one quarter of the transmission pulse represented by the upper left quadrant impinges on the detector array. The lidar system of the optical shutter configuration of FIG. 5C has a 3D measurement resolution four times greater than the shutter configuration described in connection with the embodiments illustrated in FIGS. 5A or 5B because the optical shutter enables sampling of a portion of the field of view of a single laser pulse represented by circle 574. The 3D measurement resolution of the system of FIG. 5C is determined here by the optical shutter configuration and not by the number of lasers in the system or by the collimation of each laser optical beam. Of course, there are performance trade-offs. The lidar system shown in FIG. 5C will have a lower signal-to-noise ratio because only a portion of the received laser pulse is used for time-of-flight measurement. In general, using the present teachings illustrated in FIG. 5C, the ratio of the field of view of the transparent region of the optical shutter to the field of view of at least one of the plurality of lasers in the laser array can be selected to achieve a particular resolution of the lidar system according to the particular requirements of the system such as the desired SNR.

[0054] To be more explicit regarding the effects of different fields of view of lidar system optical components, the following parameters are defined: (1) FOV T = the divergence (projected cone) of a single laser element in the transmitter, (2) FOV D = the field of view of a single detector element (e.g., pixel) in the detector array, and, (3) FOV s = the field of view corresponding to the effective aperture of a single pixel of the optical shutter or mirror, which is the field of view of the transparent region.

[0055] For many of the embodiments of the lidar system of the present teachings, FOV Tis the FOV D less than. The FOV D less than FOV T Having is a significant difference between the solid lidar system embodiments of the present teachings and known so-called flash-based lidar systems. In flash-based lidars, the FOV T > FOV D is. The measurement resolution of these flash lidar systems is determined by the FOV D and simultaneous 3D measurements are made using a 1D or 2D array of detectors. In contrast, for many embodiments of the lidar systems of the present teachings, the signal-to-noise ratio performance is such that the FOV T < FOV D so that it is significantly improved compared to flash-based lidars.

[0056] In addition, one feature of the present teachings is that some embodiments of the lidar systems of the present teachings implement a shutter or mirror with an FOV T and an FOV D independent of the FOV S . That is, in various embodiments, the FOV S can be different from either the FOV T or the FOV D . For a lidar system configured with FOV S < FOV D > FOV T , the signal-to-noise ratio performance is improved compared to a system without an adaptive shutter / mirror by suppressing ambient solar noise on the detector. For a lidar system configured with FOV S < FOV T > FOV D , the 3D measurement resolution is determined by the adaptive shutter / mirror, enabling a higher measurement resolution. The signal-to-noise ratio is typically reduced in this case because only a portion of the transmitter light is used even if additional suppression of ambient solar noise is implemented.

[0057] FIG. 6 illustrates a schematic diagram of an embodiment of an adaptive FOV lidar system 600 that uses an adaptive mirror 602 according to the present teachings. In this embodiment, the adaptive mirror 602 is used to control the field of view of light that affects the detector 614 instead of an optical shutter. A transmitter 604, which can be a laser array, emits an optical beam 606 that is projected onto a target range by a transmission optical system 608. The transmission optical system 608 can be a single lens or it can include a plurality of lenses and / or other optical elements known in the art. Light is reflected in the target range by an object 610. The reflected light is collected by a reception optical system 612 and projected onto the adaptive mirror 602. The reception optical system 612 can include a single lens, a plurality of lenses, and / or other optical elements that project light reflected from the object 610. The adaptive mirror 602 selectively projects the reflected light onto the detector 614. The detector 614 can be an array of detector elements. As described herein, the area of the adaptive mirror that reflects light to the detector will be considered a transparent area. This area is also referred to as the field of view of the reflection area.

[0058] The adaptive mirror 602 is constructed in such a way as to create a 2D matrix of mirrors that can be controlled in such a way as to reflect a portion of the light in one direction while deflecting the remainder of the light in a different direction. The light corresponding to the desired field of view for measurement is reflected by the adaptive mirror to the detector 614. Thus, the adaptive mirror 602 generates a field of view of the reflection area at the detector 614, thereby restricting the illumination at the input of the photoreceiver to an area smaller than the field of view of the photoreceiver. The configuration of the adaptive 2D mirror 602 depends on the coarseness of the array (e.g., the number of desired pixels) and can be constructed in various ways.

[0059] In one embodiment, an adaptive vision lidar system receiver according to the present teachings utilizes an optical receiver with a 45-degree by 30-degree field of view. This embodiment includes a transmitter with a plurality of lasers, each having a field of view of approximately 0.25 degrees. With respect to an adaptive mirror with 1,920 by 1,080 pixels that can reflect adaptively across the 45-degree by 30-degree field of view of the receiver, a 10 by 9 pixel area would correspond to a 0.25 by 0.25 degree field of view. Thus, 10 × 9 = 90 pixels are needed to capture the entire reflected output from a single laser. However, it can be selected to always use more or fewer pixels to reflect the optical beam from a single laser. In state-of-the-art lidar systems, the receiver must have a large dynamic range to capture both small return signals from distant low-reflectivity objects and large signals from nearby highly reflective objects. Nearby objects will often saturate the receiver with an optical input-output that is too high for the detector.

[0060] In this embodiment of the lidar system with an adaptive mirror, it can be selected to attenuate the laser pulse by using fewer mirrors than those corresponding to the entire return pulse field of view. For example, this embodiment can support a configuration having only one mirror that reflects an optical beam such that 1 / 90 of the return light from the laser pulse will reach the detector. Such a system can be used to further improve the dynamic range of the lidar system, and in particular, can provide the desired dynamic range of the lidar system based on the ratio of the field of view of the transparent region of the optical shutter to the field of view of at least some of the plurality of lasers. The values of the field of view for this particular embodiment are illustrative of the present teachings only, and many other values can also be used.

[0061] Many different types of MEMS, or even hybrid structures, can be used to construct the adaptive 2D mirror 602. An example of an adaptive mirror using MEMS processing techniques with a high pixel count is the DLP6500 digital micromirror device made by Texas Instruments. The DLP6500 contains >2 million micromirrors. The high pixel count of the DLP6500 will enable the implementation of a lidar system with an adaptive mirror that determines the 3D measurement resolution as described in connection with the embodiment illustrated in FIG. 5C. It should be understood that the embodiment of the adaptive lidar system illustrated in FIG. 6 is only intended to represent some features of the present teachings. Additional optical elements such as lenses and prisms will be included in a practical optical design that implements the required beam steering function.

[0062] FIG. 7A illustrates a block diagram of an embodiment of an adaptive lidar system 700 according to the present teachings. The lidar system 700 has six main components: (1) a controller and interface electronics 702, (2) transmission electronics 704 including a laser driver, (3) a laser array 706, (4) receive and time-of-flight calculation electronics 708, (5) a detector array 710, and (6) an adaptive shutter / mirror 712. The controller and interface electronics 702 control the overall functionality of the lidar system 700 and provide digital communication to a host system processor 714. The transmission electronics 704 control the operation of the laser array 706 and set the pattern of laser emission. The receive and time-of-flight calculation electronics 708 receive electrical detection signals from the detector array 710 and then process these electrical detection signals to calculate a range distance through time-of-flight calculations. The receive electronics 708 also control the adaptive shutter 712 based on information received from the controller and interface electronics 702 and / or the transmission electronics 704. In some embodiments, the controller and interface electronics directly control the adaptive shutter / mirror rather than the receive electronics. Downstream transmission and receive optics and objects located in the target range are not shown in the lidar system of FIG. 7A.

[0063] The adaptive lidar system 700 thus comprises an optical transmitter with a plurality of lasers in a laser array 706, each of the plurality of lasers in the laser array 706 illuminating a field of view. A transmitter controller having a plurality of electrical outputs is connected to the laser array 706. In the embodiment illustrated in FIG. 7A, the transmitter controller includes elements in a controller and interface electronics 702 and elements in a transmission electronics and laser driver 704. The laser driver 704 is capable of individually activating the laser elements in the laser array 706. Thus, the transmitter controller includes a plurality of electrical outputs, each one of the plurality of electrical outputs being connected to an input of one of the plurality of lasers in the array 706. In an alternative embodiment, the transmitter controller includes a plurality of electrical outputs that connect to inputs of a plurality of lasers within the array 706 in any desired configuration that uses a matrix address where rows and columns are addressed according to a desired address scheme.

[0064] Referring to both FIGS. 2 and 7A, in some embodiments, the transmitter controller is configured to generate electrical pulses at a plurality of electrical outputs to activate the lasers in the arrays 202, 706, whereby the plurality of lasers generate light in a desired pattern in an illumination region in the plane of the detector arrays 210, 710. The detector arrays 210, 710 have a field of view that includes the field of view of each of a plurality of detectors positioned to detect light across the illumination region. The detectors in the arrays 210, 710 are connected to a receiving electronics 708 that includes a time-of-flight measurement circuit 708 that determines the time-of-flight of light from the plurality of lasers in the array 706 to the plurality of detectors in the array 710. The receiving electronics 708 also calculates range information from the time-of-flight measurements. Adaptive optical shutters 212, 712 positioned between the optical transmitter and the optical receiver have a field of view of a transparent region within the illumination region and limit the illumination at the input of the optical receiver, whereby the field of view of the transparent region is smaller than the field of view of the input of the optical receiver.

[0065] Figure 7B illustrates a detailed block diagram of an embodiment of a receiver and time-of-flight calculation electronics 750 described in connection with Figure 7A. A receive front end 752 is electrically connected to the output (not shown) of a detector array. The receive front end includes an input amplifier 754 that sends signals to various circuits (some of which are optional), such as a time / digital converter (TDC) 756, an amplitude sampler 758, and an analog / digital converter 760. These circuits communicate with a data processor 762. The data processor 762 is connected to a data monitoring and digital communication interface 764 and is also connected to a control and synchronization logic circuit 766 that is connected to the data monitoring and digital communication interface 764.

[0066] The electrical detection signal received from the detector array is input to the receiver front end 752 and transmitted to an input amplifier 754 that enhances the electrical detection signal received from the detector before further processing. The signal output from this amplifier is then split into several different circuits. In various embodiments, three possible circuits, namely, a time / digital converter 756, an amplitude sampler 758, and an analog / digital converter 760, can be used together or in any combination. The time / digital converter 756 is a special circuit that recognizes when the input signal exceeds a certain amplitude threshold and then provides a digital representation of the time of that event. For a time-of-flight measurement system, the event typically corresponds to the arrival of the reflected transmission pulse, and this arrival time corresponds to the distance of the object. The amplitude signal block 758 is a circuit triggered by the same event as the time / digital converter 756, but instead of recording the time, it records the amplitude. The analog / digital circuit 760 converts the analog received electrical detection signal into a digital signal corresponding to a certain sampling rate. The processed signal received from the receiver front end is then input to a data processing circuit 762 that interfaces with a trigger and synchronization logic circuit 766. The data monitoring and digital communication interface 764 then transmits signals to the controller and interface electronics, as shown in FIG. 7A.

[0067] In the embodiment of the receiver electronics and time-of-flight calculation circuit 750 shown in FIG. 7B, the input from the detector array is input to a single time-of-flight measurement circuit. All of the detectors are connected in such a way that their outputs are combined and directed to a single time-of-flight measurement circuit. This feature simplifies the time-of-flight circuit and reduces costs. However, the noise from all of the detectors can combine within the system and reduce the signal-to-noise ratio of the measurement signal. The adaptive shutter / mirror shown in FIG. 7A is used to minimize the contribution of noise from sunlight to the system by reducing the illumination on those portions of the detector array that do not correspond to the current measurement point.

[0068] In other embodiments of the receiving electronics and time-of-flight calculation circuitry of the present teachings, not all detectors are combined into a single TOF measurement circuit. Instead, some subsets of detectors can be grouped into subsets each having its own TOF circuit. In these embodiments, an adaptive shutter / mirror is used to limit the light reaching a subset of detectors that make up one part as defined by a shared time-of-flight measurement circuit.

[0069] One of ordinary skill in the art will understand that the block diagrams shown in FIGS. 7A - B, which illustrate the functionality of the lidar system, do not limit the present teachings to any specific hardware configuration. For example, each of these circuits may be separate or integrated. The transmit and receive blocks may also be on separate printed circuit board assemblies (PCBAs) and / or separate modules. With respect to the receiving electronics block, all or part of the front end may be part of an integrated circuit directly attached to the detector array, or these circuits can be on a PCBA with other circuits. In some embodiments, the controller functionality can be combined with some or all of the transmit and receive electronics within a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a similar type of integrated or hybrid device.

[0070] FIG. 8 illustrates a flowchart of an embodiment of a method 800 for implementing the lidar system algorithm according to the present teachings. In a first step 802 of method 800, a controller is initialized. The controller can be any controller connected to both the transmit array and the detector array of a noise adaptive solid state lidar system. For example, the controller can be the controller described in connection with FIG. 7A.

[0071] In a second step 804 of method 800, a desired illumination pattern for generating a 3D point cloud is selected by a controller. The illumination pattern includes a specific illumination spatial shape that can vary as a function of time. The controller is configured to pulse individual lasers or groups of lasers on and off to provide the desired illumination pattern in an associated illumination area of the target range and detector array. In some embodiments, the pattern is a simple row-by-row scan of each laser element in a certain row that provides a uniform refresh rate. In other embodiments, the pattern is pseudo-random and the system moves from measurement point to measurement point in a discontinuous manner, which still operates to uniformly target the overall field of view of the entire transmitter array over time.

[0072] In a third step 806 of the method, the controller selects individual lasers or groups of lasers and fires them based on the desired pattern. The controller then configures an adaptive shutter / mirror in step 808 of step 4 to block the illumination of a portion of the detector array that is not needed to measure the reflected transmission laser pulses.

[0073] In the fifth step 810 of method 800, the lidar system emits the laser or lasers selected in the third step 806. In the sixth step 812 of method 800, the lidar system receives light pulses from the emitted laser in a controlled detector array, calculates the time of flight, and samples the amplitude / time as desired. The system determines, in a seventh step 814, whether pulse averaging is implemented. If pulse averaging is implemented, the method loops back to the fifth step 810 and the sixth step 812 of the method, emits the same laser or group of lasers, and makes measurements on the signals received from that laser or group of lasers the number of times required by the desired amount of averaging. For example, in one specific method according to the present teachings, averaging emits up to four pulses to improve the SNR. In other specific methods according to the present teachings, averaging emits a larger number of pulses, for example, up to 25 or more pulses. The step of emitting a larger number of pulses takes a longer period of time, but provides more improvement in SNR than pulse averaging.

[0074] Thus, in some embodiments of the present teachings, combinations of multiple measurement points using multiple laser pulses in a particular field of view are averaged to determine the distance of an object and improve the signal-to-noise ratio. Multiple pulses from the same laser are averaged at the detector to increase the signal. Various embodiments use different numbers of pulses. More pulses lead to a better signal-to-noise ratio, but the system is limited in the number of pulses that can be averaged based on the time allowed by the system's refresh rate. In some embodiments, four or more pulses are used. In other embodiments, ten or more pulses are used, and in still other embodiments, more than 25 pulses are used.

[0075] In the eighth step 816 of method 800, after obtaining the desired number of pulses for an individual laser or multiple lasers, the system can apply digital signal processing and manipulate the data in a certain way. After processing, the controller stores and / or communicates the data in the ninth step 818 of method 800. In the tenth step 820 of method 800, a decision to stop or a decision to continue is made. The controller then moves to the next laser in that pattern in the third step 806 of method 800. The system continues to operate continuously to sweep through the desired pattern until it is stopped in the eleventh step 822 of method 800.

[0076] FIG. 9 illustrates a flowchart of an embodiment of a method 900 for implementing an algorithm of a noise-adaptive solid lidar system of the present teachings incorporating smart object detection. Some steps of method 900 are similar to or the same as method 800 described in connection with FIG. 8. In the first step 902 of method 900, the system is initialized. In the second step 904 of method 900, a desired illumination pattern for generating a 3D point cloud is selected by the controller. In the third step 906 of method 900, the controller selects an individual laser or group of lasers to emit based on the desired pattern. The controller then configures an adaptive shutter / mirror in the fourth step 908 to block the illumination of a portion of the detector array not needed to measure the reflected transmitted laser pulses.

[0077] In the fifth step 910 of method 900, the lidar system emits the laser or group of lasers selected in the third step 906. In the sixth step 912 of method 900, the lidar system receives the emitted laser pulses in a controlled detector array, calculates the time of flight, and samples the amplitude / time as desired. The system then determines, in step 914 of step 7 of method 900, whether pulse averaging is implemented, and loops back to the fifth step 910 of method 900 until the desired number of pulses are emitted. In step 916 of step 8 of method 900, after obtaining the desired number of pulses for an individual laser or group of lasers, the system applies digital signal processing and manipulates the data in various ways. After processing, the controller stores and / or communicates the data in the ninth step 918 of method 900.

[0078] In the tenth step 920 of method 900, a decision to stop or continue method 900 is made. If the decision is to continue method 900, the system moves to the eleventh step 922 of method 900 where smart object detection and pattern adjustment are performed. In this eleventh step 922 of method 900, the controller has the ability to analyze the 3D point cloud and determine to adjust the pattern of laser emission and the averaging of pulses, either to address specific rules and / or to optimize overall performance. For example, one rule could be that if the controller determines that an object could potentially collide with the vehicle, the lidar system "locks on" to that object and changes the emission pattern and / or the field of view to increase the refresh rate and / or the accuracy of the measurements of that object. In another embodiment, the controller can adjust the averaging of pulses or the amount of the emission pattern for each individual laser based on various criteria such as the calculated probability of detection, error rate, distance to the object measured for each laser, and / or environmental conditions. The system then moves to the twelfth step 924 of method 900 and, if a decision to stop is made, ends method 900.

[0079] The solid lidar system configuration implementing the algorithm of the noise adaptive solid lidar system of the present teachings described in relation to FIG. 9 has significant performance advantages compared to known lidar systems using mechanical scanning. For example, some of the mechanical scanners used in known lidar systems include a rotating motor, a MEMS mirror, and a galvanometer. In a mechanical scanning lidar system, it is not possible to arbitrarily measure different points within the field of view at any given time because the mirror or motor has to be physically moved. As a result, the number of pulses that can be used for averaging is significantly restricted, for example, when compared to the lidar system according to the present teachings. This point is illustrated in relation to FIG. 10.

[0080] FIG. 10 illustrates Table 1000 of operating parameters for a known MEMS-based scanning lidar system. From the parameters listed in Table 1000, the system's ability to implement pulse averaging can be determined. For light traveling to and fro over 150 meters, the required time is 1 microsecond. As a result, the maximum rate at which the system can fire pulses and unambiguously identify reflections for each pulse, without considering processing overhead, is 1 MHz. The number of measurement points generated by the system for the stated field of view and angular resolution is 25,000 points per frame. At a refresh rate of 30 Hz, the system must be able to measure 750K points per second.

[0081] Comparing this required 3D point measurement rate with the speed of light limited to a maximum pulse repetition rate of 1 MHz, it can be clearly understood that for such a system, pulse averaging cannot be uniformly implemented because for all points, further averaging of 2 pulses would require a pulse repetition rate of 1.5 MHz, which would reduce the maximum range from 150 m to 100 m. Since the mirror is constantly moving, two points do not overlap in the same way, which also poses another limit to pulse averaging. In a lidar system configured as described by Table 1000, the time required to move from one point to the next adjacent point (0.2°) is equal to 1.3 microseconds. Since pulses can only be fired every 1.0 microsecond, this also leads to the step of averaging multiple pulses requiring a significant amount of time averaging. By the time the second pulse is fired, the scanning mechanism of the system has already substantially moved to the next measurement location. A 0.2° angular rotation at 150 m corresponds to 0.5 m in absolute distance in that range. Thus, in these known mechanical scanning lidar systems, pulse averaging clearly cannot be performed for elongated objects such as people at the maximum desired distance.

[0082] In contrast to these known MEMS-based scanning lidar systems, the lidar system and method of operation according to the present teachings can perform averaging of the pulses at the maximum desired distance, and thus the amount of pulse averaging and the emission pattern can be varied for each individual laser based on various criteria such as the calculated probability of detection, error rate, distance to the object measured for each laser, and / or environmental conditions. (equivalents)

[0083] The teachings of the present applicant are described in conjunction with various embodiments, but the present applicant does not intend for the teachings to be limited to such embodiments. Rather, the teachings of the present applicant include various alternatives, modifications, and equivalents, as would be understood by those of ordinary skill in the art, and those can be made without departing from the spirit and scope of the present teachings.

Claims

Claim 1 A method for optical detection and ranging, the method comprising: a) determining a desired illumination pattern for illuminating a field of view in an illumination area illuminated using a plurality of lasers; b) selecting, from the plurality of lasers, a group of lasers that, when energized, generate the determined desired illumination pattern; c) positioning a photoreceiver having an input with a field of view in the illumination area, the photoreceiver comprising a plurality of detectors, the plurality of detectors detecting light across the illumination area, each of the plurality of detectors having a field of view; d) configuring an adaptive shutter / mirror to block illumination of a portion of the field of view of the input of the photoreceiver based on the determined desired illumination pattern; e) energizing the selected group of lasers to generate light pulses in the desired illumination pattern; f) receiving light at the input of the photoreceiver from the light pulses in the desired illumination pattern and measuring the time of flight of the light pulses based on the received light; g) calculating range information from the measured time of flight; h) detecting an object based on the calculated range information and adjusting the desired illumination pattern based on the detected object and configuring the adaptive shutter / mirror to block illumination of a portion of the field of view of the input of the photoreceiver that is smaller than the field of view of the selected group of lasers, the method for optical detection and ranging. Claim 2 The method for optical detection and ranging according to claim 1, wherein determining the desired illumination pattern includes determining a scan for each row of lasers in an array of lasers. Claim 3 The method for optical detection and ranging according to claim 1, wherein determining the desired illumination pattern includes determining a discontinuous pattern. Claim 4 The method for optical detection and ranging according to claim 3, wherein the discontinuous pattern is a pseudo-random pattern. Claim 5 The method for optical detection and ranging according to claim 3, wherein the discontinuous pattern targets the field of view in the illumination area. Claim 6 Configuring the adaptive shutter / mirror to block illumination of a portion of the field of view of the input of the optical receiver includes configuring to achieve a specific resolution of the optical detection and ranging system, the method of optical detection and ranging according to claim 1.

7. Configuring the adaptive shutter / mirror to block illumination of a portion of the field of view of the input of the optical receiver includes configuring to achieve a specific dynamic range of the optical detection and ranging system, the method of optical detection and ranging according to claim 1.

8. Configuring the adaptive shutter / mirror to block illumination of a portion of the field of view of the input of the optical receiver includes configuring to achieve a specific signal-to-noise ratio of the optical detection and ranging system, the method of optical detection and ranging according to claim 1.

9. Adjusting the desired illumination pattern based on the detected object includes increasing the repetition rate of laser emission, the method of optical detection and ranging according to claim 1.

10. Adjusting the desired illumination pattern based on the detected object includes changing a group of lasers among the plurality of lasers, the method of optical detection and ranging according to claim 1.

11. The method of optical detection and ranging according to claim 1 further includes determining whether pulse averaging is desired based on the received light and the measured time of flight, and performing pulse averaging.

12. Determining whether pulse averaging is desired includes determining the number of laser pulses to emit, the method of optical detection and ranging according to claim 11.

13. Determining whether pulse averaging is desired includes determining whether pulse averaging is desired based on the signal-to-noise ratio of the received light, the method of optical detection and ranging according to claim 11.

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