Eye-safe long-range lidar system using actuators

Abstract

A LIDAR system includes a plurality of lasers that generate beams having FOVs. A plurality of detectors are positioned at a location where a FOV of at least one of the plurality of beams generated by the plurality of lasers overlaps a FOV of at least two of the plurality of detectors. A lens system collimates and projects the beams generated by the plurality of lasers. An actuator is coupled to at least one of the plurality of lasers and the lens system to cause relative motion between the plurality of lasers and the lens system in a direction orthogonal to an optical axis of the lens system in order to cause relative motion between the FOVs of the beams generated by the plurality of lasers and the FOVs of the detectors.

Description

[0001] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in any way.

[0002] Cross Reference to Related Applications

[0003] This application is a non-provisional of U.S. Provisional Patent Application No. 62 / 854,782, filed May 30, 2019, entitled “Eye-Safe Long-Range LIDAR System Using Actuator.” The entirety of U.S. Provisional Patent Application 62 / 854,782 is incorporated herein by reference. BACKGROUND

[0004] Autonomous, self-driving, and semi-autonomous cars use a combination of different sensors and technologies, such as radar, image recognition cameras, and sonar, to detect and locate surrounding objects. These sensors enable a number of improvements in driver safety, including collision warning, automatic emergency braking, lane departure warning, lane keep assist, adaptive cruise control, and autonomous driving. Among these sensor technologies, Light Detection and Ranging (LIDAR) systems play a key role, enabling real-time, high-resolution 3D mapping of the surrounding environment. In order for LIDAR systems to be deployed widely and in large numbers, they need to be both low cost and reliable, and physically compact.

[0005] As LIDAR systems become widely available and market prices drop, they will also begin to be deployed in many other applications, such as security surveillance, industrial robots, and drones. These other applications, as well as applications within the autonomous vehicle space itself, have widely varying requirements. For an autonomous car that is able to navigate at high speeds, the maximum range, angular resolution, and frame rate required can be significantly more than for an industrial robot that moves within a building. In this case, the cost and performance of the LIDAR system will be optimized to provide the best match to the application’s specifications. BRIEF DESCRIPTION OF DRAWINGS

[0006] In accordance with preferred and exemplary embodiments, the present teachings, along with further advantages thereof, are described in more detail in the detailed description below, taken in conjunction with the accompanying drawings. Those skilled in the art will appreciate that the following description of the drawings is for illustrative purposes only. The drawings are not necessarily drawn to scale, with emphasis instead being placed upon illustrating the principles of the present teachings. The drawings are not intended to limit the scope of the present teachings in any way.

[0007] Figure 1A A schematic diagram of a known solid-state LIDAR system is shown.

[0008] Figure 1B A schematic diagram of a known solid-state LIDAR system is shown. Figure 1Aa two-dimensional projection of the system field of view (FOV) of a LIDAR system of the present teachings.

[0009] Figure 2A A schematic of a 2D monolithic VCSEL array with 256 individual laser emitters is shown, where each emitter corresponds to a single large aperture that can be used in some embodiments of the LIDAR emitters of the present teachings.

[0010] Figure 2B A schematic of a 2D monolithic VCSEL array with 256 individual laser emitters is shown, where each emitter has nine sub-apertures that can be used in LIDAR emitters according to the present teachings.

[0011] Figure 3A A two-dimensional projection of the LIDAR system FOV for an embodiment of a LIDAR system according to the present teachings is shown, where the divergence of the sixteen laser emitter beams results in gaps between the beams when imaged onto a detector array.

[0012] Figure 3B A two-dimensional projection of the LIDAR system FOV for a LIDAR system is shown, where the divergence of the individual laser emitter beams is the same as shown in Figure 3A but the number of laser emitters has been increased to sixty-four in order to eliminate any gaps between the beams when imaged onto a detector array.

[0013] Figure 4 A schematic of an embodiment of the emitters of the present teachings is shown, where each laser emitter in the array corresponds to a particular projection angle.

[0014] Figure 5 A two-dimensional projection of the LIDAR system FOV for an embodiment of a LIDAR system according to the present teachings is shown, where the divergence of the individual laser emitter beams is the same as the system described in connection with Figure 3A and the relative motion of the lens system and the laser array is used to scan in the pattern shown.

[0015] Figure 6A An implementation of a LIDAR system according to the present teachings using two physically separate emitters is shown.

[0016] Figure 6B A relative position of the lens system and array in the two emitters is shown Figure 6A A two-dimensional projection of the LIDAR system FOV for an embodiment of a LIDAR system of the present teachings.

[0017] Figure 6C Another relative position of the lens system and array in the two emitters is shownFigure 6A a two-dimensional projection of a LIDAR system FOV of an embodiment of a LIDAR system of the present teachings.

[0018] Figure 7 a two-dimensional projection of a LIDAR system FOV of an embodiment of a LIDAR system of the present teachings is shown, wherein the shape of the laser beam is nominally rectangular, and the FOV of a single pixel in the detector array is smaller than the laser beam.

[0019] Figure 8 an implementation of a LIDAR system transmitter of the present teachings is shown, wherein relative motion of a microlens array is used to change the projection angle of the laser beam. DETAILED DESCRIPTION

[0020] The present teachings will now be described in greater detail in connection with the exemplary embodiments of the present teachings illustrated in the drawings. This present teachings is described with reference to various embodiments and examples, but the present teachings is not intended to be limited to these embodiments. Rather, the present teachings is to cover all alternatives, modifications and equivalents which can be included within the scope of the present teachings as defined by the claims. Those skilled in the art having the benefit of the present teachings as taught within the specification will appreciate additional implementations, modifications, and embodiments within the scope of the present teachings as described herein, and other uses of the teachings.

[0021] Reference in the specification to “one embodiment” or “an embodiment” 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 the specification are not necessarily all referring to the same embodiment.

[0022] It should be understood that the various 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. Furthermore, it should be understood that the apparatuses and methods of the present teachings can include any number or all of the described embodiments, as long as the present teachings remain operable.

[0023] The present teachings relate to Light Detection and Ranging (LIDAR), which is a remote sensing method that uses a laser light to measure distances (ranges) to objects. Autonomous vehicles utilize LIDAR systems to generate highly accurate 3D maps of the surrounding environment at high resolution. The systems and methods described herein are directed to providing a pulsed time-of-flight (TOF) LIDAR system with a high level of reliability, while also maintaining a long measurement range and low cost. One aspect of the present teachings focuses on optimizing the cost of the entire LIDAR system, while still providing excellent reliability and performance in a compact physical size.

[0024] The systems and methods described herein that provide a pulsed TOF LIDAR are also configured to maintain a Class 1 eye safety. A Class 1 eye safety rating means that the system is safe under all normal conditions of use. In order to maintain a Class 1 eye safety, the laser energy or laser optical power cannot exceed the maximum permissible exposure (MPE) levels defined by U.S. and international safety standards. However, the measurement range of a LIDAR system is strongly dependent on the maximum emitted optical pulse energy or power level. Thus, it is desirable for automotive LIDAR systems to work intentionally as close as possible to the Class 1 MPE limit.

[0025] Assuming that all LIDAR systems operating at the same wavelength will be subject to the same MPE limit, further range improvements of one LIDAR system relative to another LIDAR system operating at the MPE power limit must be achieved through innovative aspects of the optical system. One aspect of the present teachings is a LIDAR system that uses a highly collimated laser beam, where all of the energy is emitted into a small FOV. This configuration provides a relatively long measurement range compared to a system that disperses the same amount of laser light over a wider FOV. That is, using a highly collimated laser beam, in combination with a receiver design that allows measurements to be made over a similarly small field of view (FOV), will result in a desired ratio of reflected signal power to background light levels, which improves the ranging capability.

[0026] One known LIDAR system is a so-called flash LIDAR system that employs an emission source that emits laser light over a wide FOV. Some flash LIDAR systems are also solid-state without moving parts, while other flash LIDAR systems use a mirror that scans in one direction and illuminates a“line” that steps across the entire field of view. Solid-state flash LIDAR systems without moving parts must illuminate the entire scene with a single illumination event. However, for a LIDAR system operating at the Class 1 eye safety MPE limit, the wide FOV illuminated by a solid-state flash LIDAR significantly limits the measurement range compared to a system where the light from the emission source is highly collimated.

[0027] It should be understood that a measurement or measurement point in a LIDAR system is produced by processing a particular detection signal that is produced by a particular illumination at a target range. The TOF is calculated based on that particular detection signal. Depending on how the system is controlled as further described herein, the particular detection signal for a measurement point can be generated by a single detector or multiple detectors. Also, depending on how the system is controlled, the particular detection signal for a measurement point can be generated by a single laser or multiple lasers.

[0028] Some pulsed TOF LIDAR systems according to the present teachings use collimated emitter laser beams with optical power / energy equal to or slightly below the MPE limit for Class 1 eye safety to provide a significant range increase compared to traditional flash LIDAR systems. In addition, some pulsed TOF LIDAR systems according to the present teachings use pulse averaging and / or pulse histogramming of multiple laser pulses to improve the signal-to-noise ratio (SNR), which further improves the range. These LIDAR systems employ very high single-pulse frame rates, much higher than 60 Hz, even up to several kHz, in order to be able to average multiple pulses.

[0029] One important performance goal for automotive LIDAR systems is the angular resolution of the optical system. In order to be able to clearly define individual objects in space by image analysis and / or perform object recognition, a fine angular resolution is required for automotive LIDAR systems. Currently, automotive LIDAR systems require an angular resolution of less than about 0.2°. These systems would benefit from a higher resolution if it could be achieved.

[0030] Furthermore, there should be no gaps in the coverage between the measurement points, especially at long distances. To illustrate why such gaps should not exist, consider a practical use case of a 200 meter range. A 0.2° angle at 200 meters corresponds to a lateral distance of 0.7 meters. Since the width of a typical human is about 0.15 meters, if the resolution is 0.2° and the collimated laser beam diameter at 200 meters is less than 0.7 meters, the LIDAR system can completely miss the presence of a human at the 200 meter range.

[0031] Reliability is also an important aspect of LIDAR systems designed for autonomous vehicles. The operating environment is particularly challenging for automotive LIDAR systems. Failure of a LIDAR sensor can result in a collision and can also prevent operation of the vehicle. LIDAR systems without moving parts are generally more reliable compared to LIDAR systems that use rotating components or large scanning mirrors. Moving parts are susceptible to mechanical wear and have a finite lifetime. LIDAR systems of the present teachings include motion, but preferably use “frictionless” mechanisms that are not susceptible to wear to the same extent as motors or other large scanning mirrors.

[0032] Figure 1A A schematic diagram of a known solid-state LIDAR system is shown. Figure 1AThe system shown in the middle does not employ a flash emitter that illuminates the entire system field of view at once. The laser array 102 generates various beam patterns. Light beams are emitted from emitters in the array 102 when the emitters are activated by a controlled pulse. One or more emitters can be activated according to a particular sequence. The beams from the lasers in the laser array 102 propagate through common emitter optics 104, which project the beams to a target 106 at a target plane 110. In this particular example, the target 106 is an automobile 106, but it will be appreciated that the target can be any object.

[0033] Portions of the light from the incident beams are reflected by the target 106. These portions of the reflected beams share a receiver optics 112. A detector array 114 receives the reflected light projected by the receiver optics 112. In various embodiments, the detector array 114 is solid state, with no moving parts. The detector array 114 typically has fewer individual detector elements than the emitter array 102 has individual lasers.

[0034] The measurement resolution of the LIDAR system 100 is not determined by the size of the detector elements in the detector array 114, but rather by the number of lasers in the emitter array 102 and the collimation of the individual beams. In other words, the resolution is limited by the field of view of each beam. A processor (not shown) in the LIDAR system 100 performs a time-of-flight (TOF) measurement that determines the distance to the target 106 from the light beams emitted by the laser array 102 that are detected at the detector array 114.

[0035] One feature of a LIDAR system according to the present teachings is that individual lasers and / or groups of lasers in the emitter array 102 can be controlled individually. Each individual emitter in the emitter array can be independently emitted, with the light beam emitted by each laser emitter corresponding to a three-dimensional (3D) projection angle that is directed only to a portion of the overall system field of view. One example of such a LIDAR system is described in U.S. Patent Publication No. 2017 / 0307736 Al, which is assigned to the present assignee. The entirety of U.S. Patent Publication No. 2017 / 0307736 Al is incorporated herein by reference.

[0036] Another feature of a LIDAR system according to the present teachings is that the detectors and / or groups of detectors in the detector array 114 can also be controlled individually. This independent control of the individual lasers and / or groups of lasers in the emitter array 102 and the detectors and / or groups of detectors in the detector array 114 provides various desirable operational features, including control over the system field of view, light power levels, and scanning patterns.

[0037] Figure 1B is shownFigure 1A two-dimensional projection of the system field of view 150 of the LIDAR system of FIG. 1. Referring to FIG. 2, Figure 1A and Figure 1B the field of view of a single detector in the detector array is represented by the small square 152. The circle 154 shows the illuminated measurement point resulting from the detection signal associated with a single emitter in the emitter laser array 102. Figure 1A A single 3D measurement point in the overall field of view of the LIDAR system of FIG. 1 is shown as a particular black circle 158, which corresponds to a particular individual laser in the laser array. In Figure 1B It can also be seen in FIG. 2 that this measurement point falls within a single detector, where the field of view of this single detector in the detector array 114 has been shown in square 156 with a hatch pattern for identification. This figure shows that the 3D resolution of some embodiments of the LIDAR system is determined by the number of lasers, as each laser corresponds to a particular angular projection angle that results in the size of the circle 154 at the target range and the relative size of the circle 154 and the square 152 representing the field of view of the individual detector elements.

[0038] Thus, by controlling particular individual lasers or groups of lasers in the emitter array and / or controlling individual detectors or groups of detectors in the receiving array, a desired field of view can be established. Different relative fields of view for individual or groups of emitters and / or individual or groups of detectors can be used to establish various system fields of view. The field of view can be established so as to produce particular and / or combinations of performance metrics. These performance metrics include, for example, improved signal-to-noise ratio, longer or controlled range, eye-safe operating power levels, and smaller or larger controllable resolution. Importantly, these performance metrics can be modified during operation to optimize LIDAR system performance.

[0039] LIDAR systems according to the present teachings use an array drive control system that is capable of providing selective control of particular laser devices in an array of laser devices so as to illuminate a target according to a desired pattern. Moreover, LIDAR systems according to the present teachings can use a detector array that generates detector signals that can be processed independently. Thus, LIDAR systems according to the present teachings are characterized by the ability to provide various operational capabilities from a LIDAR system that exclusively utilizes electronic, non-mechanical, and / or non-moving components, including a fixed array of emitters and a fixed array of detectors, where shared emission and reception optics are used to project emission and reception beams. Such LIDAR system configurations can result in a flexible system that is compact in size, reliable in operation, and relatively low in cost.

[0040] One feature of LIDAR systems of the present teachings is that they rely on an array of lasers to generate beams, and on an array of detectors to receive a portion of the light from these beams that is reflected from a target. As a result, they benefit from many features of solid state components, i.e., they are relatively compact in size, work reliably, and are low cost. According to the present teachings, various detector technologies can be used to construct the array of detectors for a LIDAR system. For example, an array of single photon avalanche diode detectors (SPADs), an array of avalanche photodiodes (APDs), and an array of silicon photomultipliers (SPAs) can be used. The size of the detectors not only sets the resolution by setting the FOV of an individual detector, but also relates to the speed and detection sensitivity of each device. Two-dimensional arrays of detectors for LIDAR of the prior art have approached the resolution of VGA cameras, and are expected to follow a similar trend of increasing pixel density as CMOS camera technology. As a result, it is expected that over time, ever smaller sizes of the detector FOV represented by square 204 will be implemented. For example, an APD array with 264,000 pixels (688(H) x 384(V)) has recently been reported in “A 250m Direct Time-of-Flight Ranging System Based on a Synthesis of Sub-Ranging Images and a Vertical Avalanche Photo-Diodes (VAPD) CMOS Image Sensor” (Sensors 2018, 18, 3642).

[0041] Various types of laser arrays can also be used in LIDAR systems according to the teachings of the present teachings. One example of a laser array is made from vertical cavity surface emitting laser (VCSEL) laser devices. This can include top emitting VCSELs, bottom emitting VCSELs, and various types of high power VCSELs. These VCSEL devices can be standalone single emitters, or can be part of a multi-emitter VCSEL that can be fabricated on a substrate as a one-dimensional or two-dimensional array. VCSEL contacts that are energized to generate a beam of light from a particular laser can be addressed or energized individually, and / or can be electrically connected together in various configurations to energize groups of VCSELs with a common electrical input signal. One feature of LIDAR systems of the present teachings is a system and method for controlling the energization of one or more VCSEL devices in an array with appropriate drive signals for a particular LIDAR system application. In some embodiments, the VCSEL array is monolithic and the lasers all share a common substrate. Various common substrate types can be used. For example, the common substrate can be a semiconductor material. The common substrate can also include a ceramic material. In some embodiments, the VCSEL array is a 2D VCSEL array and the 2D VCSEL array is assembled from a set of one-dimensional (ID) bars or even from multiple individual dies.

[0042] One feature of LIDAR systems according to the present teachings is that they can provide a controllable field of view for various laser arrays. Some embodiments use a VCSEL array. In some embodiments, the VCSELs are top emitting VCSELs. In other embodiments, the VCSELs are bottom emitting VCSELs. Individual VCSELs can have a single large emission aperture, or individual VCSELs can be formed from two or more sub-apertures within a larger effective emission diameter. A set of sub-apertures that form a larger effective emission area is sometimes referred to as a cluster. The sub-apertures in a cluster can be electrically connected in parallel so that they are electronically activated by a single control signal.

[0043] Figure 2AA schematic diagram of a 2D monolithic VCSEL array 200 with 256 individual laser emitters 202 is shown, where each emitter 202 corresponds to a single large aperture, which is used in some embodiments of the LIDAR emitters of the present teachings. Each laser emitter has a launch aperture with a diameter a 204. The launch from each individual laser emitter 202 substantially fills the entire launch aperture diameter a 204. Thus, each laser emitter generates a laser beam with an initial diameter a that is equal to the diameter of the launch aperture. The laser emitters are uniformly spaced apart in the horizontal direction with a pitch dx 206 and in the vertical direction with a pitch dy 208. The overall dimensions of the array, measured from the center of the outermost lasers, are a distance Dx 210 in the horizontal direction and a distance Dy 212 in the vertical direction. The actual chip size will be slightly larger than the dimensions Dx 210 and Dy 212. In various embodiments, the emitters can produce beams with various shapes. For example, oval, square, rectangular, and various exotic shapes can be implemented. There are regions 214 between the emitters 202 that are gaps that do not have emitters and thus do not provide illumination.

[0044] Figure 2B A schematic diagram of a 2D monolithic VCSEL array 250 with two hundred fifty-six individual laser emitters 252 is shown, where each laser emitter 252 has nine sub-apertures 254, which can be used in some embodiments of the LIDAR emitters of the present teachings. The launch from each individual laser emitter 252 results in launch from all nine sub-apertures 254. In the event that one or more of the nine sub-apertures 254 is unable to emit light due to a manufacturing anomaly or equipment failure, the emitter 252 still operates and generates a beam, albeit at a lower output power. The output beam will correspond to the pattern of the sub-apertures 254, and the sub-apertures 254 can be arranged in various shapes. In the structure shown, the output beam is nominally square, corresponding to the emitter 252 shape of a 3x3 square array of the nine sub-apertures 254. The laser emitters 252 are uniformly spaced apart in the horizontal direction with a pitch dx 256 and in the vertical direction with a pitch dy 258. The overall dimensions of the array, measured from the center of the outermost lasers, are a distance Dx 260 in the horizontal direction and a distance Dy 262 in the vertical direction. The actual chip size will be slightly larger than the distance Dx 260 and the distance Dy 262. Various array patterns, including regular and irregular arrays, are possible. Figures 2A-2B VCSELs of the present teachings include regions of the VCSEL chip that do not emit light, such as regions 214, 264.

[0045] Some embodiments of the present teachings utilize a bottom emitting high power VCSEL array with a single large aperture per laser and configured in a regularly spaced rectangular array, for example Figure 2A Other embodiments of the LIDAR system of the present teachings utilize a top emitting or bottom emitting high power VCSEL array with a total emission area that includes sub-apertures. However, those skilled in the art will appreciate that the present teachings are not limited to any single configuration of top and bottom emitting VCSELs, associated emission apertures, or array spacing or shape.

[0046] One feature of the LIDAR system of the present teachings is that the emitters can not all emit the same wavelength of light. Thus, various emitters in the array can produce light with a different wavelength than other emitters. For example, the emitters in one column or row can emit one wavelength and the emitters in the spaced columns or rows can emit a different wavelength. Various wavelength patterns can be used.

[0047] The use of a 2D VCSEL array as a building block for the LIDAR system of the present teachings establishes an emitter platform that allows for small physical size emitters. For example, a typical 2D array with 256 high power independent laser emitters can be fabricated on a monolithic chip with dimensions of about 4 mm x 4 mm. The monolithic 2D laser array is then used with emission optics selected to keep the physical size as small as possible. For example, some embodiments use a microlens array with dimensions similar to the monolithic chip. Other embodiments use a shared lens with a diameter of, for example, less than 20 mm. Still other embodiments use a diffractive optic with a maximum dimension of, for example, 20 mm diameter.

[0048] One feature of the LIDAR system of the present teachings is that the spacing and / or divergence of the beams produced by the emitters can be configured to generate an emitter FOV with a desired pattern, shape, or other specified characteristic. For example, the beams can be made to overlap or not overlap. The selection of the FOV pattern provides control over, for example, range, eye-safe power level, signal to noise ratio, and / or resolution depending on the particular pattern.

[0049] Figure 3A A two-dimensional projection of a LIDAR system FOV 300 is shown for the operation of an embodiment of the LIDAR system of the present teachings, where the divergence of the sixteen laser emitter beams results in gaps between the beams when imaged onto a detector array. The laser emitter FOV is represented by the circles 302 and the detector element FOV is represented by the squares 304. In this example, the laser emitter FOV is 2.5 mm in diameter and the detector element FOV is 1.5 mm in diameter. The laser emitter FOV is larger than the detector element FOV, which results in the gaps between the beams when imaged onto the detector array. Figure 3AIn the illustrated embodiment, the FOV with the size of the circle 302 nominally completely covers the four detector element FOV squares 304. This optical configuration can result from a highly collimated beam of light. Conversely, an optical configuration that results in a larger transmitter FOV will cover more detector elements and can be achieved by reducing the collimation of the beam of light. In embodiments with higher laser beam collimation, such as in conjunction with Figure 3A The described embodiments result in improved measurement range. This is particularly true for smaller targets that can only be partially covered by the laser beam.

[0050] Consider a numerical example for a collimated laser beam for a LIDAR system with 10 mrad divergence. At a range of 100 meters, there will be a beam width of 1 meter. For example, since a person is approximately only 0.15 meters wide, a portion of the 1 meter beam will not fall on the person and thus will not contribute to the reflected signal for measurement. In this configuration, it is preferable to generate a beam with a smaller divergence and a smaller beam width. However, as Figure 3A illustrated, there is a tradeoff between beam divergence and coverage of the full field of view. In Figure 3A The projection of the LIDAR system FOV 300, as illustrated, uses sixteen laser beams. In this optical configuration, significant gaps 306 are created in the field of view. Figure 3B One possible solution to prevent these gaps is illustrated.

[0051] Figure 3B A two-dimensional projection of the LIDAR system FOV 350 is illustrated for operation of the LIDAR system, where the divergence of the individual laser transmitter beams is the same as Figure 3A the embodiment illustrated in FIG. 3, but the number of laser transmitters has increased to sixty-four beams in order to eliminate any gaps between the beams when imaged onto the detector array. The laser transmitter FOVs are represented by the circles 352 and the detector element FOVs are represented by the squares 354. In this embodiment, the number of laser transmitters has increased from sixteen to sixty-four and the lasers are interleaved in a manner that provides full coverage of the field of view without gaps. Conversely, the beam FOVs have overlap 356. The divergence of the beams from each transmitter is the same as the embodiment illustrated in FIG. 3. Figure 3A A solution for a LIDAR system to achieve Figure 3B is to have a one-to-one correspondence between each FOV 352 and a single laser within the system, thus requiring 64 single lasers in this case. In a practical system, the number of lasers can increase to several thousand or more and the cost of these lasers and associated electronics can be an issue.

[0052] Figure 4A schematic diagram showing an embodiment of a transmitter 400 of the present teachings in which each laser transmitter in an array 402 corresponds to a particular projection angle. A lens system 404 collimates and projects the beams generated by the transmitters in the array 402. The lens system 404 is movable along a relative motion axis 406. One feature of the present teachings is that limited relative motion can be provided between the laser transmitters and the emission optics to provide movement of the beams in the field of view. This movement allows control of additional degrees of freedom to provide a desired beam pattern. The primary reason for introducing relative motion between the lens system and the laser array is to reduce the number of individual lasers required, trading off the additional cost and complexity of introducing limited relative motion / actuation. Depending on the system requirements, there will be an optimum or at least a beneficial cost, performance, and physical size that balances the number of individual lasers and the amount of relative motion required to cover the entire FOV without any gaps in the measurement field.

[0053] The array 402 has a dimension D 408 in the emission plane. At one relative position between the lens system 404 and the array 402, a transmitter 410 at the center of the array 402 generates a beam 412 along a centerline 414. The lens system 404 collimates and projects this beam 412 to a center location 416 at the target range. An outer transmitter 418 at the edge of the array 402 with dimension D 408 generates a beam 420. The lens system 404 collimates and projects this beam 420 to an outer location 422 at the target range. In some embodiments, the projection angle 424 of the outer beam 420 from the edge transmitter 418 relative to the center beam 412 from the center transmitter 410 is equal to one-half of the field of view (FOV / 2). A controller 426 has outputs electrically connected to the inputs of at least some of the transmitters in the laser array 402. The controller is capable of selecting a particular individual laser or group of lasers to be energized among the multiple lasers, resulting in a particular laser FOV with a desired beam pattern.

[0054] Figure 4 The basic working principle of the LIDAR system 400 is also shown, which uses an array of laser transmitters 402 and relative motion of a lens system 404 that serves both to collimate the beam of each laser and to project each laser at a unique projection angle. The lens system 404 is movable along a relative motion axis 406. The controller 426 is capable of selecting a particular individual laser or group of lasers to be energized among the multiple lasers, resulting in a particular laser FOV with a desired beam pattern. Figure 4In particular, the direction of relative motion between the laser array 402 and the lens system 404 is indicated by the arrow 406, which is orthogonal to the optical axis 414 of the lens system 404. The projection angle is defined by the distance from the optical axis of each laser. Thus, if the lens system 404 and the array 402 are moved relative to each other, the projection angle of each light beam generated by a particular laser emitter will also change accordingly. Thus, it is a feature of the present teachings that the relative motion of the lens system 404 and the laser array 402 can be used to change the angular resolution of any application, such as covering gaps in the LIDAR system FOV. Those skilled in the art will appreciate that, Figure 4 The optical configuration shown is one particular example of using relative motion between a laser emitter or laser array and projection optics. The principle of relative motion is not limited to any particular lens system. In particular, it should be appreciated that not all lenses in the lens system have to be moved to produce a change in the projection angle of a particular laser. That is, some or all of the lenses in the lens system 404 can be moved. Moreover, the lens system 404 is not limited to a particular number of lenses.

[0055] It is a feature of the present teachings that the relative motion of the lens system 404 and the array 402 provides a particular pattern of light beam FOVs known to the controller 426. This includes, for example, light beam position, light beam size, and / or light beam overlap. As such, in some embodiments, the relative motion in combination with a firing pattern of the lasers controlled by the controller 426 can be used to manage the power level of the light beams at the target range. In particular, the firing pattern can be used to ensure that a predetermined optical power level is not exceeded in any individual light beam FOV. In some embodiments, the predetermined power level is the Class 1 eye safety limit. The firing pattern can also be controlled so that a predetermined optical power level is not exceeded in any overlapping light beam FOV.

[0056] In combination Figure 2A and Figure 2B The VCSEL devices described can be used with a LIDAR system 400 that employs relative motion between an array of laser emitters 402 and a lens system 404. Reference is made to Figures 2A-2B and Figure 4 If the divergence of the lasers is small enough so as not to cause overlap of the emitted light beams in the far field, the areas of the VCSEL chip that do not emit light (e.g., areas 214, 264) can cause gaps in the field of view. The relative motion of the array 402 and the lens system 404 described herein can be used to fill those gaps in the field of view.

[0057] Figure 5 A two-dimensional projection of a LIDAR system FOV 500 is shown for an embodiment of a LIDAR system of the present teachings in which the divergence of a single laser emitter light beam is combined with Figure 2AThe divergence of the described 2D monolithic VCSEL array with 256 individual laser emitters is the same, and where the relative motion of the lens system and the laser array is used to scan in the indicated pattern. The emitter FOV pattern in the initial position is illustrated by the 4x4 array of solid circles 502. The next three positions move the emitter FOVs in a square pattern, where the moved emitter FOVs are illustrated by the dashed circles. Position two is illustrated as dashed circle 504. Position three is illustrated as dashed circle 504'. Position four is illustrated as dashed circle 504".

[0058] Referring to Figure 4 and Figure 5 Both the laser array 402 and the lens system 404 are moved relative to each other in a rectangular or square pattern illustrated by arrows 506, 506', 506", 506"' such that the moved FOVs cover the entire LIDAR system FOV with only sixteen lasers in the 4x4 array configuration. Note that the relative motion illustrated in this embodiment is required in both the horizontal and vertical directions. The necessary range of relative motion is equivalent to moving the laser pattern half the spacing between any two beams generated by the laser emitters. For some embodiments, the actual relative motion required will be on the order of half the physical distance between emitters of the array, which can be a few hundred microns.

[0059] The relative motion between the laser array 402 and the lens system 404 can be achieved using flexure-based actuators 428. In various embodiments, the actuators 428 include various known actuator technologies. For example, actuators are commercially available from several vendors, including Physik Instrument of Germany. The force to drive the flexure-based actuators can be generated by various electromechanical devices including piezoelectric motors or voice coil actuators.

[0060] Figure 6A An embodiment of a LIDAR system 600 of the present teachings is illustrated that uses two physically separate emitters 602, 604. Each emitter 602, 604 includes a VCSEL array 606, 608 with sixteen laser emitters. The two emitters 602, 604 generate beams from the laser arrays 606, 608 that are collimated and projected by lens systems 610, 612. The emitters 602, 604 can generate light at different frequencies. In various embodiments, the lens systems 610, 612 can include one or more lenses and / or other optical elements (not shown). The beams from the two emitters 602, 604 illuminate a target 614 at a target range 616, which in this illustration is an automobile.

[0061] Reflected light from the emitters 602, 604 is combined at a single receiver 618. The receiver 618 includes a receiving optical system 620, which can include one or more lenses in various configurations. The receiving optical system 620 can also include other optical elements, such as filters, mirrors, and many others. The receiving optical system 620 also includes a detector array 622. The FOVs of the two emitters 602, 604 and the receiver 622 overlap to a large extent.

[0062] Figure 6A The different relative positions of the lens systems 610 and the array 606 of the first emitters 602 and the different relative positions of the lens systems 612 and the array 608 of the second emitters 604 result in desired and controllable positions of the emitter FOVs from the two emitters 602, 604. These controllable positions result from actuators 624, 626, which cause relative motion between the arrays 606, 608 and the lens systems 610, 612. In particular, this configuration allows for the combination of the relative motion changes between the laser arrays 606, 608 and their respective lens systems 610, 612 and the interleaving of the emitter FOVs described in Figure 4 and Figure 5 to provide full coverage across the desired FOV at one or more target ranges. In some embodiments, the interleaved emitter FOVs are generated by beams having different wavelengths.

[0063] A controller 628 is connected to the laser arrays 606, 608, the detector array 622, and the actuators 624, 626. The controller 628 includes outputs electrically connected to inputs of lasers and / or groups of lasers in the laser arrays 606, 608, so that the controller can select particular individual or groups of lasers in the arrays 606, 608 to be energized, thereby producing a particular laser FOV having a desired pattern of beams. The controller 628 includes outputs electrically connected to at least some of the detectors in the detector array 622. Thus, the controller can select particular detectors to be monitored. The controller 628 also includes connections to the actuators 624 in order to control the speed and / or travel and / or direction of the actuators to provide desired speed and / or displacement and / or direction of the relative motion between the arrays 606, 608 and the lens systems 610, 612.

[0064] Figure 6B is shown in one relative position of the lens systems 610, 612 and the laser arrays 606, 608 in the two emitters Figure 6A is shown in one relative position of the lens systems 610, 612 and the laser arrays 606, 608 in the two emitters Figures 6A-6BThe LIDAR system FOV 630 includes the transmitter FOV of the first transmitter 602 represented by the open circle 632, and the transmitter FOV of the second transmitter 604 represented by the differently shaded circle 634. In some embodiments, the beams that generate the first FOV pattern represented by the open circle 632 are one wavelength, and the beams that generate the second FOV pattern represented by the shaded circle 634 are a different wavelength.

[0065] The detector FOVs in the detector array 622 are illustrated as a 16x16 grid of squares 636. Also shown is the FOV 638 of a target, which is the car 614. The beams emitted from the two transmitters 602, 604 interleave in free space to produce a pattern of FOVs that is Figure 6B the array of circles 632, 634 shown in FIG. 6B.

[0066] Figure 6C illustrated in FIG. 6B are shown in another relative position of the lens systems 610, 612 and laser arrays 606, 608 in the two transmitters 602, 604. Figure 6A a two-dimensional projection of the LIDAR system FOV 670 of an embodiment of the LIDAR system of FIG. 6B. Reference is made to all of FIGS. 6A-6B. Figures 6A-6C The LIDAR system FOV 670 includes the transmitter FOV of one transmitter 602 represented by the open circle 672, and the transmitter FOV of the second transmitter 604 represented by the differently shaded circle 674.

[0067] The detector FOVs in the detector array 622 are illustrated as a 16x16 grid of squares 676. Also shown is the FOV of a target, which is the car 678. The beams emitted from the two transmitters 602, 604 interleave in free space to produce a pattern of FOVs that is Figure 6C the array of circles 672, 674 shown in FIG. 6B. The relative position of each array 606, 608 relative to its respective lens system 610, 612 in the direction of relative motion 640, 680 is used to eliminate gaps in the LIDAR system FOV, which would otherwise exist if the position was static, i.e., only working in Figure 6B the position shown in FIG. 6A or Figure 6C the position shown in FIG. 6B. For example, Figure 6B the FOV gap region 642 shown in FIG. 6A is in Figure 6C the coverage region 682 shown in FIG. 6B, as it is covered by the FOV of the laser transmitter shown by the circle 684.

[0068] in conjunction with Figures 6A-6CThe described embodiments are merely one example of how the relative motion (controlled relative position) of the lens system and laser array, alone or in combination with the interleaving and / or use of different wavelength emitters, can produce a desired FOV pattern that leads to various performance improvements in a LIDAR system. It should be understood that, within the scope of this teaching, many other combinations are possible between optical free-space interleaving and lens motion and / or the use of different light wavelengths.

[0069] Most known LiDAR systems use mirrors or motors to scan the field of view (FOV) using a small number of lasers. This motion is continuous in some way. Continuous motion is achieved by constantly scanning the FOV to achieve the desired frame rate. (See reference...) Figures 6A-6C One aspect of this teaching is the appropriate selection of the timing of the laser pulses, the frame rate, and the timing and other aspects of the relative motion of the laser array and lens system. Contrary to known systems, for... Figures 6A-6C The LIDAR system shown does not involve movement of the lens system when pulses are supplied to the laser corresponding to the lens system. This allows multiple pulses to be used for averaging / histogramization without significant time averaging.

[0070] An example of the operating method according to this teaching is as follows. Consider a LIDAR system that operates each laser individually, such that... Figure 6A The thirty-two lasers in the laser arrays 606 and 608 do not emit simultaneously. It is also considered that multiple pulses are used for each laser to generate an average measurement with improved SNR; for example, sixty-four pulses may be available for each distance measurement. The time spent scanning through each transmitter would then be 16 lasers × 64 pulses × T, where T is the pulse repetition rate specified by the measurement range. For a range of 200 m, T must be greater than 1.33 microseconds. Therefore, for this example, the total time to generate a single frame using each transmitter is approximately 1.3 milliseconds. If frames are generated using each transmitter before switching to the next transmitter and then back, an acceptable operating mode is to acquire data using one transmitter while its lens system is stationary, while the lens system / lens array of another transmitter is moved. The time required to complete the motion without affecting system performance would be less than 1.3 milliseconds. Flexural actuators with a stroke of several hundred micrometers typically have the capability to perform such stepping motion within a few milliseconds, which is within the requirements.

[0071] Note that in actual LIDAR systems, the number of lasers in the array can be much higher, for example... Figure 2A and Figure 2B The figure shows 256. Even using a smaller average, say sixteen times, the time required to obtain a single frame with a single transmitter is approximately 5.3 milliseconds. Typically, actuator times will be on the order of a few milliseconds. This timing will match a combination similar to...Figures 6A-6C The range of the described LIDAR configuration depends on the number of lasers per laser array, the number of pulses applied to each laser, the distance range, and the number of emitters, among other factors.

[0072] Figure 7 A two-dimensional projection of a LIDAR system FOV 700 of an embodiment of a LIDAR system of the present teachings is shown, where the shape of the beam FOVs 702, 704 are nominally rectangular. The FOV of a single detector pixel is represented by the small square 706, such that the FOV of a single pixel in the detector array is smaller than the laser beam FOVs 702, 704. In Figure 7 In the middle, the single laser beam FOVs 702, 704 are generally rectangular in shape and, when projected onto the detector array, overlap with tens of pixels in the receiver detector array. In this case, the laser beam can be scanned at a rate such that multiple pulses can be taken with a single pixel without loss of reflected pulses.

[0073] During the motion of the laser beam, the laser beam FOV has a start position 708 and a non-overlapping end position 710. For example, pixel 2 712 is at the rightmost edge of position 1, which is the start position 708 of the beam, which corresponds to a particular offset between the laser array and the optical axis of the lens system. Pixel 2 712 is at the leftmost edge of position 2, which is the end position 710 of the laser beam. This means that, at most times, pixel 2 receives some reflected light from the laser beam. Multiple measurements can be taken from this pixel even though the laser beam is in motion. This allows sufficient time to obtain the required number of measurements. The relative motion in this case will typically be greater than half the pitch of the laser beam pattern. Pixel 1 716 is in the start position 708 of the laser FOV 702. This configuration allows a particular pixel on the edge, such as pixel 3 714, to be illuminated by more than one laser beam.

[0074] Figure 8 An embodiment of a LIDAR system emitter 800 of the present teachings is shown, where the relative motion of a microlens array 802 is used to change the projection angle of laser beams 804, 806. An emitter array 808 generates beams, such as beams 804, 808, from each laser element 810 in the array 808. For example, in some embodiments, the emitter array 808 is a VCSEL array. Further, in some embodiments, the emitter array 808 is a one-dimensional array, while in other embodiments, the emitter array 808 is a two-dimensional array. In some embodiments, the microlens array 802 is a one-dimensional array, while in other embodiments, the microlens array 802 is a two-dimensional array. Beams such as beams 804, 808 pass through the microlens array 802 and then through additional emitter optics 812 to a target plane 814.

[0075] The relative motion between the microlens array 802 and the emitter array 808 is shown by arrow 816. This relative motion is caused by actuator 817. In this embodiment, the relative motion shown by arrow 816 is shown as a vertical motion, but it will be appreciated that there can be relative motion in various directions. The direction of the relative motion used depends on the desired relative position of the light beams (e.g., light beams 804, 808) at the target plane 814. As described herein, this relative motion shown by arrow 816 can be used to provide a desired FOV of the laser FOV relative to the receive FOV to meet various performance goals for a LIDAR system that includes the LIDAR emitter 800 using the microlens array 802.

[0076] The microlens array 802 has many small lenses 818, with each individual laser beam 804, 806 emitted by a corresponding emitter array 808 having at least one small lens 818. The size of the small lenses 818 is of the same order of magnitude as the pitch of the emitter elements in the emitter array 808. This size is typically a few hundred microns. In Figure 8 In the illustrated embodiment, the emitter optics 812 are shown as a fixed additional large lens. The fixed emitter optics 812 also serve to collimate the laser beams 804, 806, and thus help to determine the total FOV of the emitter 800. In the configuration shown in this embodiment, only the microlens array 802 is moved in order to further optimize the speed / response time of the system. The microlens array 802 can be moved quickly because it has a small mass. Also, small motions can generate large angular changes.

[0077] For example, a microlens array in combination with a 2D VCSEL array as described herein can only need to move about ten microns to achieve a desired change in projection angle. The microlens array 802 can be physically small, typically only slightly larger than the VCSEL array, which means that its mass can be kept low, particularly if it is formed of a plastic material rather than glass. The small mass and small motion (which can be on the order of about ten microns) required reduces the requirements for acceleration / force, and allows for short actuation times. In such embodiments, the lens array 802 can be displaced by about ten microns in less than about 50 microseconds, which can provide additional system flexibility in affecting scan patterns and frame rates. A controller 820 is connected to the actuator to provide control of the relative motion, and to the laser array 808 to control the emission of particular individual lasers or groups of lasers.

[0078] Equivalents

[0079] While the Applicant's teachings have been described in conjunction with various embodiments, it will be understood that the Applicant's teachings are not limited to any embodiment. On the contrary, the Applicant's teachings encompass numerous alternatives, modifications and equivalents, which can be made in addition to those expressly disclosed herein, which can be practiced without departing from the spirit and scope of the teachings.

Claims

1. A light detection and ranging (LIDAR) system comprising: a) a plurality of lasers, each of the plurality of lasers generates a beam of light having a field of view (FOV) when energized such that a single emission of the plurality of lasers cannot produce a beam of light covering the entire LIDAR system FOV; b) a plurality of detectors forming an array and positioned in the optical path of the beams of light generated by the plurality of lasers, wherein the FOV of one of the plurality of beams of light generated by the plurality of lasers and the FOV of another of the plurality of beams of light generated by the plurality of lasers when imaged onto the plurality of detectors results in a gap between the beams of light; c) a lens system positioned in the optical path of the beams of light generated by the plurality of lasers and before the plurality of detectors, the lens system collimates and projects the beams of light generated by the plurality of lasers; d) an actuator coupled to at least one of the plurality of lasers and the lens system, the actuator causes relative motion between the plurality of lasers and the lens system in a direction orthogonal to the optical axis of the lens system in order to cause relative motion between the FOV of the beams of light generated by the plurality of lasers and the FOV of the detectors; and e) a controller connected to the actuator and having an output connected to an input of the plurality of lasers, the controller is configured to control the emission pattern of the plurality of lasers and the relative motion of the actuator such that the emission pattern and the relative motion of the actuator produce a beam of light covering the entire LIDAR system FOV.

2. The LIDAR system of claim 1, wherein, At least some of the plurality of lasers are vertical cavity surface emitting lasers.

3. The LIDAR system of claim 1, wherein, At least some of the plurality of lasers comprise two-dimensional monolithic vertical cavity surface emitting lasers.

4. The LIDAR system of claim 1, wherein, The plurality of lasers are configured to maintain Class 1 eye safety in their respective FOVs.

5. The LIDAR system of claim 1, wherein, The controller is further configured to control the lasers individually.

6. The LIDAR system of claim 1, wherein, At least some of the plurality of detectors comprise single photon avalanche diode (SPAD) detectors.

7. The LIDAR system of claim 1, wherein, At least some of the plurality of detectors comprise silicon photomultiplier (SiPM) detectors.

8. The LIDAR system of claim 1, wherein, The actuator comprises a flexure-based actuator.

9. The LIDAR system of claim 1, wherein, The actuator comprises a voice coil.

10. The LIDAR system of claim 1, wherein, The actuator comprises a piezoelectric transducer.

11. The LIDAR system of claim 1, wherein, The actuator comprises an electromechanical device.

12. The LIDAR system of claim 1, wherein, The actuator is configured to cause relative motion between the plurality of lasers and the lens system such that the plurality of beams of light move in a two-dimensional pattern.

13. The LIDAR system of claim 12, wherein, The two-dimensional pattern comprises a rectangular pattern.

14. The LIDAR system of claim 1, wherein, The actuator is configured such that the relative motion between the FOV of the beams of light generated by the plurality of lasers and the FOV of the detectors changes the angular resolution of the LIDAR system.

15. The LIDAR system of claim 1, wherein, The actuator is configured such that the relative motion between the FOV of the beams of light generated by the plurality of lasers and the FOV of the detectors is substantially zero during the time period in which laser pulses are emitted.

16. The LIDAR system of claim 1, wherein, The controller further comprises a plurality of inputs electrically connected to a plurality of outputs of at least some of the plurality of detectors, the controller is configured to select which detectors are to be monitored.

17. A method of light detection and ranging (LIDAR), the method comprising: a) firing selected ones of a plurality of lasers such that each of the selected ones of the plurality of lasers generates a beam of light having a field of view (FOV) and such that a single emission of the plurality of lasers does not produce a beam of light covering the entire LIDAR system FOV; b) collimating and projecting the beams of light generated by the selected ones of the plurality of lasers onto a plurality of detectors with a lens system, wherein the FOV of one of the plurality of beams of light generated by the plurality of lasers and the FOV of another of the plurality of beams of light generated by the plurality of lasers when imaged onto the plurality of detectors results in a gap between the beams of light; c) moving the plurality of lasers relative to the lens system, thereby causing relative motion between the FOVs of the beams of light generated by the plurality of lasers and the FOVs of the plurality of detectors; d) controlling the firing pattern of the plurality of lasers and the movement of the plurality of lasers relative to the lens system such that the firing pattern and the movement of the plurality of lasers relative to the lens system produces a beam of light covering the entire LIDAR system FOV; and e) monitoring selected ones of the plurality of detectors that are within the FOV of at least one of the plurality of beams of light generated by the selected ones of the plurality of lasers. Firing the selected ones of the plurality of lasers includes firing a pattern of laser light such that no more than a predetermined level of optical power is in any individual beam FOV.

18. The method of claim 17, wherein, Firing the selected ones of the plurality of lasers includes firing a pattern of laser light such that no more than a Class 1 eye safety limit is in any individual beam FOV.

19. The method of claim 17, wherein, Firing the selected ones of the plurality of lasers includes firing a pattern of laser light such that no more than a predetermined level of optical power is in any overlapping beam FOV.

20. The method of claim 17, wherein, Firing the selected ones of the plurality of lasers includes firing a pattern of laser light such that no more than a Class 1 eye safety limit is in any overlapping beam FOV.

21. The method of claim 17, wherein, The relative motion between the plurality of lasers and the lens system is in a direction orthogonal to an optical axis of the lens system.

22. The method of claim 17, wherein, The relative motion is about half of a physical distance between emitters of at least some of the plurality of lasers.

23. The method of claim 17, wherein, No relative motion of the plurality of lasers and the lens system occurs during a time of firing a laser pulse.

24. The method of claim 17, wherein, ​

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