CN115598617A

CN115598617A - Hybrid drive for large aperture tilting mirrors

Info

Publication number: CN115598617A
Application number: CN202210792743.1A
Authority: CN
Inventors: 周勤; 王佑民
Original assignee: Beijing Voyager Technology Co Ltd
Current assignee: Beijing Voyager Technology Co Ltd
Priority date: 2021-07-07
Filing date: 2022-07-07
Publication date: 2023-01-13
Also published as: US20230008705A1

Abstract

Hybrid drive of large aperture tilting mirrors. This specification describes a microelectromechanical systems (MEMS) structure. A first actuator coupled to the substrate and configured to rotate the substrate along a first rotation axis. A set of rotatable MEMS mirror arrays mounted on the substrate and aligned parallel to the first axis of rotation. Each rotatable MEMS mirror is rotatable about a second axis of rotation, each second axis of rotation being perpendicular to the first axis of rotation and parallel to the other second axes of rotation. A second array of actuators configured to rotate each rotatable microelectromechanical mirror about its respective second axis of rotation. A controller configured to control the first actuator to rotate the substrate about the first rotation axis. The controller is further configured to control the second array of actuators to rotate each of the rotatable MEMS mirrors about its respective second axis of rotation.

Description

Hybrid drive for large aperture tilting mirrors

Priority declaration

This application claims priority to U.S. patent application No. 17/369,829, filed 7/2021, the entire contents of which are hereby incorporated by reference.

Technical Field

The technology disclosed herein relates generally to tilting mirrors in optical systems. More specifically, and without limitation, an apparatus and method for synchronously driving a mirror array in two dimensions is disclosed herein.

Background

Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. In particular, various techniques are discussed, which are difficult to discuss together without the teachings of the present invention.

Modern vehicles are often equipped with a variety of sensors for detecting objects and landscape features around the vehicle in real time to implement such technologies as lane change assistance, collision avoidance, and automatic driving. Some commonly used sensors include image sensors (e.g., infrared or visible light cameras), acoustic sensors (e.g., ultrasonic parking sensors), radio detection and ranging (RADAR) sensors, magnetometers (e.g., passive perception of large ferrous objects such as trucks, cars, or railcars), and LiDAR (LiDAR) sensors.

Lidar systems typically use light sources and light detection systems to estimate distances to environmental features (e.g., pedestrians, vehicles, buildings, vegetation, etc.). For example, a lidar system may emit a beam of light (e.g., a pulsed laser beam) to illuminate a target and then measure the time required for the emitted beam to reach the target and then return to a receiver near or at a known location to the transmitter. In some lidar systems, a light beam emitted by a light source may be steered over a two-or three-dimensional region of interest according to a scanning pattern to generate a "point cloud" comprising a set of data points corresponding to target points in the region of interest. The data points in the point cloud may be dynamically and continuously updated and may be used to estimate, for example, the distance, size, position, and velocity of the object relative to the lidar system.

In a lidar system, light steering techniques may be used. Light steering generally involves the projection of light in a predetermined direction to facilitate, for example, detection and ranging of objects, illumination and scanning of objects, and the like. Light steering may be used in many different application areas, including, for example, autonomous vehicles or medical diagnostic devices, and may be configured to perform the transmission and reception of light. For example, the light redirecting emitter may include a micro-mirror for controlling the direction of projection of light to detect/image the object. In addition, the light redirecting receiver may also include micro-mirrors for selecting the direction of incident light to be detected by the receiver to avoid detecting other unwanted signals.

Tilting mirrors have applications in many optical systems. In many cases, the optical aperture of the system is determined by the size of the mirror. In each case, a larger optical aperture is preferred. While this can be achieved by increasing the mirror size, such a solution may sacrifice other performance, such as the speed of operation of the mirror. Another approach is to use the same small mirrors to make up an array, where the total size of the array is equal to the size of the large mirrors. Thus, the total effective aperture increases on any smaller single mirror. One problem with this approach is that each individual mirror in the array needs to be synchronized so that all mirrors are tilted in the same direction at any given time. In an ideal system where each mirror is identical, this can be achieved as long as the drive signal applied to each mirror is the same. Previous solutions attempt to synchronize the motion of each mirror by mechanically coupling them. However, this coupling only addresses synchronization in one direction, as mechanical interference prevents the coupling from being achieved on two orthogonal tilt axes (e.g., the x-scan axis and the y-scan axis of the lidar).

Disclosure of Invention

In some embodiments, microelectromechanical systems (MEMS) structures are described. In these embodiments, the first actuator is coupled to the substrate and configured to rotate the substrate about a first axis of rotation. A rotatable array of micro-electromechanical mirrors (MEMS mirrors) is mounted on the substrate and aligned parallel to the first axis of rotation. Each rotatable MEMS mirror rotates about a second axis of rotation, each second axis of rotation being perpendicular to the first axis of rotation and parallel to each other. A second array of actuators is mounted on the substrate and configured to rotate the rotatable MEMS mirrors about their respective second axes of rotation. Some embodiments further comprise a controller configured to control the first actuator to rotate the substrate along the first axis of rotation within a first range of motion. The controller is further configured to control the second actuator array to rotate each of the array of rotatable MEMS mirrors about a respective second axis of rotation within a second range of motion.

According to some embodiments, the substrate may be a Printed Circuit Board (PCB). The array of rotatable MEMS mirrors and the second array of actuators may be formed on a semiconductor chip. In some embodiments, a semiconductor chip including the array of rotatable MEMS mirrors and the second array of actuators may be mounted on a PCB. The second actuator array may comprise an electrostatic comb configured to rotate each rotatable MEMS mirror about a respective second axis of rotation.

According to some embodiments, the controller is configured to cause the first actuator to rotate the substrate about the first axis of rotation at a first frequency range of 1Hz to 15Hz, inclusive. The controller may be further configured to cause the second actuator array to rotate each rotatable MEMS mirror at a second frequency in the kilohertz range.

In other embodiments, a method of operating a MEMS structure to redirect light in a laser radar system (LiDAR) is described. The controller sends a first control signal to the first actuator. In response to a first control signal, a first actuator rotates the substrate about a first rotation axis. The controller may also send a second control signal to a second actuator array on a semiconductor chip mounted on the substrate. In response to a second control signal, the second actuator array rotates each rotatable MEMS mirror of the array of rotatable MEMS mirrors on the semiconductor chip about a respective second axis of rotation. Each second rotation axis is perpendicular to the first rotation axis and parallel to the other second rotation axes.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof. It will be recognized, however, that various modifications may be made within the scope of the system and method encompassed by the claims. Thus, it should be understood that although the present system and method has been specifically disclosed by way of example and optional features, modification and variation of the concepts herein disclosed will be recognized by those skilled in the art and that such modifications and variations are considered to be within the scope of the system and method as defined by the appended claims.

This description is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used solely to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the appropriate portions of the entire specification of this disclosure, any or all of the drawings, and each claim.

The above described and other features and examples are described in more detail in the following specification, claims and drawings.

Drawings

The features of the various embodiments described above, as well as other features and advantages of certain embodiments of the present invention, will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of an autonomous vehicle equipped with a lidar system, according to some embodiments;

FIG. 2A is an example of a light projection operation shown according to some embodiments;

FIG. 2B is an example of a light detection operation shown according to some embodiments;

FIG. 3A is a schematic diagram of a rotatable MEMS mirror;

FIG. 3B isbase:Sub>A schematic cross-sectional A-A' view of the rotatable MEMS mirror shown in FIG. 3A;

FIG. 4 is a simplified schematic diagram of a MEMS structure including an array of rotatable MEMS mirrors mounted on a substrate;

FIG. 5 is an exemplary block diagram of a MEMS structure with an electromagnetic actuator, shown in accordance with some embodiments;

FIG. 6 is an exemplary flow diagram illustrating a method of synchronously rotating a MEMS mirror array in two dimensions according to some embodiments;

FIG. 7 is an exemplary simplified block diagram of a lidar-based detection system shown in accordance with some embodiments; and

fig. 8 illustrates an example computer system that can be used to implement the techniques disclosed herein, in accordance with some embodiments.

Detailed Description

Embodiments of the present invention relate generally to optical systems, and more particularly to lidar systems that use lasers and MEMS-mirror based scanning environments, and more particularly to two-dimensional synchronization of rotatable MEMS mirrors to improve performance of lidar systems.

In the following description, various examples of mirror structures are described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art that certain embodiments may be practiced or carried out without every detail disclosed. Furthermore, known features may be omitted or simplified in order to prevent any confusion with regard to the new features described herein.

The following high-level abstract is intended to provide a basic understanding of some novel innovations shown in the drawings and described below in the corresponding description. The technology disclosed herein relates generally to rotatable micro-electromechanical system (MEMS) mirrors that may be used, for example, in a laser radar (LiDAR) system or other beam control system. More specifically, and without limitation, embodiments disclosed herein provide a method and mechanism for synchronizing rotation of each rotatable mirror in an array of rotatable MEMS mirrors about two orthogonal axes.

In summary, in some embodiments, microelectromechanical systems (MEMS) structures (400 and 500) include a substrate (404), such as a Printed Circuit Board (PCB). Electromagnetic actuators (510, 511, 512, 513, and 506) rotate the PCB about a first axis of rotation (501). The rotatable MEMS mirrors are arrayed on a semiconductor chip (502) mounted to the PCB and aligned parallel to the first axis of rotation. Each rotatable MEMS mirror is rotatable about a second axis of rotation (405) perpendicular to the first axis of rotation. In some embodiments, the MEMS mirror is rotated or tilted by an electrostatic actuator (306, 310, 314, 316) when the PCB rotates with the electromagnetic actuator. The controller (514) controls the actuator via the driver (516).

The following detailed description and accompanying drawings will first illustrate a general lidar system that includes embodiments. Next, a mirror structure operating at a resonance frequency is described. The rotatable MEMS mirror array is described in detail below. Next, a hybrid drive system capable of synchronously driving an array of rotatable MEMS mirrors in two dimensions is described. This is followed by a control system that can drive actuators of different types and different frequencies to achieve a two-dimensional scan, and a computer system for controlling the system.

In general, embodiments of the present invention are directed to the implementation of light turning, which can be used in many different applications. For example, a lidar system of an autonomous vehicle may include a light steering system. The light steering system may include a transmitter module and a receiver module for steering the transmitted incident light in different directions around the vehicle and receiving reflected light of objects around the vehicle using a sequential scanning process that may be used to determine a distance between the object and the vehicle to facilitate autonomous driving navigation.

Light steering may be accomplished by micro-mirror assemblies as part of an array, each micro-mirror assembly having a movable micro-mirror and one or more actuators. The micro-mirrors and actuators may be formed as micro-electromechanical systems (MEMS) on a semiconductor substrate, which may be integrated with other circuitry (e.g., controllers, interface circuits, etc.) on the semiconductor substrate, thereby enabling simpler, easier, more robust, and more cost-effective manufacturing processes.

In a micromirror assembly, the micromirrors may be mechanically coupled (e.g., anchored) to the semiconductor substrate by coupling structures (e.g., torsion bars, torsion springs, torsion beams, etc.) to form pivot points and axes of rotation. As used herein, "mechanically coupled" or "coupled" may include directly coupled or indirectly coupled. For example, the micro-mirrors may be indirectly connected to the substrate by a connection structure (e.g., a torsion bar or torsion spring) to form a pivot/connection point. The micro-mirror may be rotated about a pivot/connection point ("herein referred to as a pivot point") on a rotation axis by an actuator. Electrostatic actuators are commonly used; however, any suitable type of actuator (e.g., piezoelectric, thermo-mechanical, etc.) may be implemented, and those of ordinary skill in the art will appreciate numerous modifications, combinations, variations, and alternative embodiments thereof.

In some embodiments, each micro-mirror may be configured to rotate an angle or move vertically to reflect (and steer) light to a target direction. For rotation, the link structure may be deformed to accommodate the rotation, but the link structure also has a certain degree of spring stiffness that varies with the rotation angle and corresponds to the rotation of the micromirror to set a target rotation angle. To rotate the micromirror by a target rotation angle, the actuator may apply a torque to the micromirror in accordance with the moment of inertia of the micromirror and the spring rate for a given target rotation angle. Different torques can be applied to rotate (e.g., oscillate) the micro-mirrors at or near the resonant frequency to achieve different target rotation angles. The actuator may then remove the torque and the linkage may return the micro-mirror to its default orientation for the next rotation. In embodiments a vertical actuator may be used, for example an electrostatic force actuator or a thermal actuator with a piston. The rotation or vertical displacement of the micromirror set may be repeated in an oscillating fashion, typically at or near the micromirror set resonance frequency based on the mass of the micromirror set and the spring constant of the attachment structure.

Those of ordinary skill in the art having the benefit of this disclosure will appreciate numerous embodiments and alternatives thereto.

Exemplary System Environment for some embodiments of the invention

FIG. 1 illustrates an autonomous vehicle 100 in which various embodiments described herein may be implemented. Autonomous vehicle 100 may include a lidar module 102. Lidar module 102 allows autonomous vehicle 100 to detect and range targets in the surrounding environment. Based on the results of target detection and ranging, the autonomous vehicle 100 may travel and maneuver according to road rules to avoid collisions with detected targets. Lidar module 102 may include a light steering transmitter 104 and a receiver 106. The light redirecting emitter 104 may project one or more light signals 108 in different directions (e.g., angles of incidence) at different times in any suitable scanning pattern, while the receiver 106 may monitor the light signals 110 generated by the object reflecting the light signals 108. The

optical signals

108 and 110 may include, for example, optical pulses, frequency Modulated Continuous Wave (FMCW) signals, and Amplitude Modulated Continuous Wave (AMCW) signals. Lidar module 102 may detect an object based on the receipt of light signal 110 and may perform a ranging determination (e.g., a range of the object) based on a time difference between

light signals

108 and 110, as persons of ordinary skill in the art will appreciate with the benefit of the present disclosure. For example, as shown in fig. 1, lidar module 102 may transmit a light signal 108 in a direction directly in front of autonomous vehicle 100 at time T1 and receive a light signal 110 reflected by an object 112 (e.g., another vehicle) at time T2. Based on the received light signal 110, the lidar module 102 may determine that an object 112 is located directly in front of the autonomous vehicle 100. Further, based on the time difference between T1 and T2, lidar module 102 may also determine a distance 114 between autonomous vehicle 100 and object 112. Thus, based on the detection and ranging of object 112 by lidar module 102, autonomous vehicle 100 may adjust its speed (e.g., slow down or stop) to avoid collision with object 112.

Fig. 2A and 2B are exemplary simplified block diagrams of a lidar module 200 shown in accordance with some embodiments. Lidar module 200 may be an example of lidar module 102 and may include a transmitter 202, a receiver 204, and a lidar controller 206, where lidar controller 206 may be configured to control operation of transmitter 202 and receiver 204. The transmitter 202 may include a light source 208 and a collimator lens 210, and the receiver 204 may include a lens 214, an optional filter 215, and a photodetector 216. Lidar module 200 may also include a mirror assembly 212 (also referred to as a "mirror structure") and a beam splitter 213. In some embodiments, lidar module 102, transmitter 202, and receiver 204 may be configured as a coaxial system to share a mirror assembly 212 to perform light steering operations, with beam splitter 213 configured to reflect incident light reflected by mirror assembly 212 to receiver 204.

Fig. 2A is a schematic diagram of a light projection operation shown in accordance with some embodiments. To project light, lidar controller 206 may control light source 208 (e.g., a pulsed laser diode, an FMCW signal source, an AMCW signal) to emit optical signal 108 as part of beam 218. The light beam 218 may be dispersed upon exiting the light source 208 and may be converted to a collimated light beam 218 by the collimator lens 210. The collimated light beam 218 may be incident on the mirror assembly 212, and the mirror assembly 212 may reflect the collimated light beam 218 toward the object 112 along an output projection path 219. The mirror assembly 212 may include one or more rotatable mirrors. FIG. 2A shows a mirror assembly 212 having one mirror; however, the micro mirror array may include a plurality of micro mirror assemblies that may collectively provide the steering capabilities described herein. The mirror assembly 212 may also include one or more actuators (not shown in fig. 2A) to rotate the rotatable mirror. The actuator may rotate the rotatable mirror about a first axis of rotation 222 and may rotate the rotatable mirror along a second axis of rotation 226. Rotation about a first rotation axis 222 may change a first angle 224 of the output projection path 219 with respect to a first dimension (e.g., the x-axis), while rotation about a second rotation axis 226 may change a second angle 228 of the output projection path 219 with respect to a second dimension (e.g., the z-axis). Lidar controller 206 may control the actuators to produce different combinations of rotational angles about first rotational axis 222 and second rotational axis 226 such that output projection path 219 may move to follow scan pattern 232. The extent 234 of movement of the output projection path 219 along the x-axis and the extent 238 of movement of the output projection path 219 along the z-axis may define the FOV. Objects within the FOV, such as object 112, may receive and reflect collimated light beam 218 to form a reflected light signal, which may be received by receiver 204 and detected by a lidar module, as described below with respect to fig. 2B. In certain embodiments, the mirror assembly 212 may include one or more comb-shaped spines having comb-shaped electrodes (see, e.g., fig. 3A), as will be described in further detail below.

FIG. 2B is a schematic diagram of a light detection operation shown according to some embodiments. Lidar controller 206 may select an incident light direction 239 for detection of incident light by receiver 204. Selection may be based on setting the angle of rotation of the rotatable mirror of mirror assembly 212 such that only light beam 220 propagating along light direction 239 is reflected to beam splitter 213, and beam splitter 213 may then divert light beam 220 through collimator lens 214 and optional filter 215 to photodetector 216. With this arrangement, the receiver 204 may selectively receive signals related to ranging/imaging of the object 112 (or any other object within the field of view), such as the optical signal 110 generated by the object 112 reflecting the collimated beam 218, while not receiving other signals. Thus, the impact of environmental interference on the ranging and imaging of the target may be reduced and system performance may be improved.

Reflector structure

FIG. 3A is a schematic diagram of a rotatable MEMS mirror. FIG. 3A illustrates a typical electrostatic MEMS mirror structure 300, also referred to herein as a "MEMS mirror" or "rotatable MEMS mirror", having a spring (torsion beam) 302, a mirror group 304, and comb

fingers

306 and 312. The mirror body 304 is suspended by mechanical springs or torsion beams 302, which springs or torsion beams 302 are typically anchored in a silicon dioxide/silicon substrate 308 and anchored to anchors and COM terminals 310 (sometimes referred to simply as "common" or "COM"). The comb fingers 306 are connected to the mirror group 304 and are interleaved with comb fingers 312 connected to anchor and bias (sometimes referred to simply as "bias") terminals 314. Terminal 310 provides Communication (COM) with the mirrors, both providing a drive voltage and sensing the change in capacitance between comb 306 connected to mirror set 304 and interleaved comb 312 connected to anchor and bias terminal 314. Anchor and bias terminal 314 is connected to a bias voltage, which is typically a combination of a dc voltage and an ac voltage. The comb and COM and bias terminals comprise comb actuators.

FIG. 3B isbase:Sub>A schematic cross-sectional view A-A' of the rotatable MEMS mirror shown in FIG. 3A. As can be seen in fig. 3B, the mirror group 304 tilts when a drive voltage 318 (V) is applied across the

fingers

306 and 312 between the COM terminal 310 and the bias terminal 314. Since the overlap area in the comb teeth varies as the mirror group is displaced, the capacitance of the comb teeth varies proportionally and is sensed by the sensing system 316 and used as feedback to control the movement of the mirror group. As shown, the overlap between the

fingers

306 and 312 varies with a change in capacitance Δ C that is proportional to the change in overlap area Δ A, which is proportional to the tilt angle β.

In some embodiments, a MEMS mirror array may be used. The mirrors in the array are mechanically and electrically interconnected and thus can be synchronized. All connections surround the entire array; isolating each mirror reduces the fill factor, thereby affecting optical performance. The use of an array of MEMS mirrors instead of larger mirrors can increase the effective aperture of the optical elements in a lidar system without sacrificing other performance, such as operating speed.

FIG. 4 is a simplified diagram of a MEMS structure including an array of rotatable MEMS mirrors mounted on a substrate. In the example shown in fig. 4, MEMS structure 400 utilizes an array of rotatable MEMS mirrors (as shown in fig. 3A and 3B) to increase the effective optical aperture in a lidar system. FIG. 4 shows an array of rotatable MEMS mirrors 300a-e formed on a semiconductor chip 402 mounted on a substrate 404. The substrate 404 may be a Printed Circuit Board (PCB). The substrate 404 may also include rotatable connectors 406a and 406b operable to communicate electrical signals from a controller (e.g., controller 514 in fig. 5) external to the substrate 404 through metal traces (e.g., aluminum) or other suitable methods. Although two rotatable connectors 406a and b are shown, other embodiments may include more or a single cantilever connector.

The rotatable connector 406 is connected to an actuator 408. The actuator 408 may receive a signal from a controller (e.g., controller 514 in fig. 5) and then rotate the substrate 404 about the axis of rotation 403 within a predetermined range of motion. The actuator 408 may be configured to operate at a suitable frequency. Examples of suitable frequencies are 1Hz to 15Hz (including 1Hz and 15 Hz). In some embodiments, the actuator 408 may be an electromagnetic motor. In other embodiments, the actuator 408 may be an electromagnetic drive, as shown in FIG. 5. Both actuators may be used with the other actuator located at the end of the MEMS structure 400 opposite the actuator 408.

In certain embodiments, each rotatable MEMS mirror 300a-e is mounted linearly such that the axis of rotation 403 bisects each rotatable MEMS mirror 300 a-e. Although FIG. 4 shows five rotatable MEMS mirrors 300a-e, it should be understood that this is merely one example; any number of rotatable MEMS mirrors 300 may be present in the array 400. Further, although one row of rotatable MEMS mirrors 300a-e is shown, it is understood that there may be more rows in the array of MEMS structure 400. Any additional rows may be similarly aligned on an axis parallel to axis 403 and may be rotated about an axis parallel to axis 405.

Each rotatable MEMS mirror 300a-e in MEMS structure 400 is shown connected at both ends to a second actuator array 410, sometimes referred to as an "actuator array". Actuator array 410 includes actuators 410a-e and a '-e', respectively. Each actuator 410a-e and a '-e' is operable to rotate the rotatable MEMS mirror 300 about its axis corresponding to axis 405. Note that reference herein to "rotation" includes tilting, in that the mirror is rotated in the field of view by tilting to capture a pixel position, and then tilting again to obtain the next pixel position. In some embodiments, the actuators 410a-e and a '-e' may be electrostatic MEMS devices as described in FIGS. 3A and 3B, including

comb fingers

306 and 312. In other embodiments, other suitable actuators (e.g., piezoelectric, thermal, mechanical, etc.) may be implemented. One of ordinary skill in the art, with the benefit of this disclosure, will recognize many variations and modifications that are possible.

In some embodiments, mirrors 300a-e each have an axis of rotation that is parallel to axis 405 and perpendicular to axis 403. The actuator array 410 may also be used to receive signals from a controller (as shown in fig. 5) through one or more traces on the PCB. In this way, each rotatable MEMS mirror 300 in the array can be controlled to rotate synchronously at a given frequency over a predetermined range of motion. In some embodiments, the frequency is a resonant frequency of the rotatable MEMS mirror 300. In an embodiment, the frequency is in the kilohertz range.

FIG. 5 is a block diagram of a MEMS structure having an electromagnetic actuator in accordance with certain embodiments. In the example shown in fig. 5, the MEMS structure 500 is rotated about a first axis of rotation 501 by an electromagnetic actuator. Axis 501 corresponds to axis 403 in fig. 4. As depicted in FIG. 4, each rotatable MEMS mirror 300 in the array of rotatable MEMS mirrors can be simultaneously rotated about a respective orthogonal second axis of rotation (e.g., axis 405) so as to synchronously rotate in two dimensions.

In certain embodiments, the semiconductor chip 502 comprises an array of rotatable MEMS mirrors similar to that shown in FIG. 4, the array comprising at least one rotatable MEMS mirror 300, and formed on a semiconductor chip mounted on a substrate (e.g., PCB) 504. The substrate 504 also includes traces or other conductive paths that form a coil 506 around the semiconductor chip 502. A first opening 507 and a second opening 509 are formed in the substrate 504 between the coil 506 and either side of the semiconductor chip 502. The first magnetic element 510 extends through the first opening 507 and the second magnetic element 511 extends through the second opening 509. The third magnetic element 512 is located outside of the substrate 504 such that the coil 506 passes between the first magnetic element 510 and the third magnetic element 512. The fourth magnetic element 513 is positioned outside of the substrate 504 such that the coil 506 passes between the second magnetic element 511 and the fourth magnetic element 513. The

magnetic elements

510, 511, 512, 513 and the coil 506 comprise an electromagnetic actuator. In some embodiments, the magnetic elements 510-513 may be iron, permalloy, neodymium, alnico magnets, ferrite, or other magnetic materials. In one embodiment,

elements

510 and 511 may be permanent magnets.

The controller 514 may include one or more processors. The controller 514 may send a signal to the electromagnetic drive 516. Upon receiving a signal from controller 514, electromagnetic drive 516 causes a current pulse to flow through a trace or other conductive path around coil 506. When current is passed through the coils, a magnetic field is generated by interaction with each pair of magnetic elements 510-513. The substrate 504 is subjected to a lorentz force such that the substrate 504 rotates about the first rotation axis 501. By changing the direction of the current, the substrate 504 may be rotated in alternating directions about the rotation axis 501. The controller 514 may cause the electromagnetic drive 516 to rotate the substrate 504 at a suitable frequency, such as 1Hz to 15Hz, including 1Hz to 15Hz.

In other embodiments, the magnetic elements 510-513 may be electromagnets. The electromagnetic drive 516 may provide a constant current through the coil 506. The electromagnetic driver 516 may also send signals to the magnetic elements 510-513 via traces or other suitable conductive paths, alternating the activation of the first pair of

magnetic elements

510 and 512 with the activation of the second pair of magnetic elements 511 and 513. When each pair of magnetic elements is activated, a magnetic field is generated between the activated pair. When current flows through the coil 506, the substrate 504 experiences a lorentz force. By alternately activating pairs of elements 510-513, the substrate 504 can be rotated in alternating directions about the axis of rotation 501. The controller 514 may cause the electromagnetic drive 516 to rotate the substrate 504 back and forth at an appropriate frequency (e.g., 1Hz to 15Hz, including 1Hz and 15 Hz).

The controller 514 may also be used to send a second signal to the array of rotatable MEMS mirrors on the semiconductor chip 502 through traces on the substrate 504 or other suitable methods. In response to the second signal, each rotatable MEMS mirror 300 in the array of rotatable MEMS mirrors rotates synchronously about a second axis of rotation. The second axis of rotation may be a corresponding axis 405, as described in fig. 4. The second signal may cause each rotatable MEMS mirror 300 in the array of rotatable MEMS mirrors to rotate at a predetermined frequency. In some embodiments, the frequency is a resonant frequency of the rotatable MEMS mirror 300. The frequency may be in the kilohertz range, for example between 300Hz and 20KHz or between 5 and 10 KHz.

By driving the substrate 504 about a first axis of rotation 501 at a first frequency and driving each rotatable MEMS mirror 300 in the array about a corresponding second axis of rotation orthogonal to the first axis of rotation, a two-dimensional scan can be achieved. This allows faster operation than operating one or more larger mirrors, while achieving a larger effective optical aperture. The scan may be a raster scan, similar to the scan used to generate pixels on a television. High frequency rotation of the mirror in the kilohertz range can horizontally scan all pixel positions in a row in the system field of view (FOV). Low frequency rotation is used to move the rear view mirror from one row to the next in the vertical direction. As mentioned above, this may be in the range of, for example, 1-15 Hz. Since the move to the next row is only required after all pixels in a row have been scanned, a lower frequency is required to rotate to switch rows. In an alternative embodiment, these may be reversed, vertical columns of low frequency switches and high frequency scanning of all pixel locations in the columns.

The axis of rotation 501 in fig. 5 may be physically located on a thin portion of the PCB that acts as the axis 503 with a cut-out of the PCB material to form the gap shown in fig. 5. Making the PCB sufficiently thin, the PCB can be rotated without requiring a large electromagnetic force. The PCB is not too thin and can support the structure. Further, the PCB is a material that does not break after multiple rotations. In some embodiments, the PCB material is a composite material, such as FR-4, which can be bent or tilted millions of times without breaking. In some embodiments, the vertical extent is small, and thus only 2-15 degrees of tilt is required through axis 503. In other embodiments, the shaft 503 is a structure that is integral with the substrate 504, but has an electromagnetic driver 516 mounted in a socket on an external PCB518 adjacent its end. The socket need not be a ball bearing element but a low friction element that can rotate. The trace connections of the control device and the coil may be made by short wires connected on each side with sufficient slack to allow rotation.

While FIG. 5 illustrates certain embodiments of a hybrid drive system using electromagnetic actuators, the number and location of the various components illustrated in FIG. 5 is an example and is for illustration only. In other embodiments, the substrate 504 may be made of steel, plastic, carbon composite, or other suitable material. In yet another embodiment, the MEMS structure 400 may be mounted on a dedicated mechanical structure, controlled by the controller 514. Many possible variations and modifications may occur to those skilled in the art having the benefit of this disclosure. Flow chart for rotating a rotatable MEMS mirror array

FIG. 6 is a flow diagram illustrating a method of synchronously rotating a rotatable MEMS mirror array in two dimensions according to some embodiments. It should be understood that the operations described in flow 600 may be performed in a different order and/or that one or more of the operations of flow 600 need not be performed.

In step 602, a first control signal is sent to a first actuator by a controller (e.g., controller 514 in fig. 5). The first actuator may be an electromagnetic actuator as shown in fig. 5. In certain embodiments, the first control signal is sent to the electromagnetic drive 516. The first control signal may be based on information about the operating frequency, the rotation angle or any other necessary information.

In step 604, a first actuator rotates the substrate about a first axis of rotation in response to a first control signal. Referring to fig. 5, an electromagnetic drive 516 may cause current pulses to flow through the coil 506 in either direction. The substrate 504 may be rotated about a first axis of rotation at a suitable frequency. Examples of suitable frequencies are 1Hz to 15Hz (including 1Hz to 15 Hz).

In step 606, at least one second control signal is sent by the controller to a second actuator array formed on a semiconductor chip mounted on the substrate. The second control signal may be sent along traces printed on a Printed Control Board (PCB) or other suitable means. These actuators may be actuators 410a-e as described in fig. 4. The second actuator may be an electrostatic comb actuator or other suitable actuator (e.g., piezoelectric, thermal, mechanical, etc.).

In step 608, each second actuator rotates each rotatable MEMS mirror in the array of rotatable MEMS mirrors on the semiconductor chip about a respective second axis of rotation. Each second rotation axis may be perpendicular to the first rotation axis and parallel to the other second rotation axes. In some embodiments, each second actuator may rotate each rotatable MEMS mirror at a frequency in the kilohertz range. In some embodiments, each second actuator may rotate each rotatable MEMS mirror at a resonant frequency of the rotatable MEMS mirror.

In summary, in some embodiments, an apparatus for tilting a mirror array is provided. The device comprises the following elements:

a micro-electromechanical systems (MEMS) structure (400, 500) configured to redirect light in a lidar system, the MEMS structure comprising:

a substrate 404 comprising a Printed Circuit Board (PCB);

electromagnetic actuators (510, 511, 512, 513, and 506) configured to rotate the PCB about a first rotation axis (501); a set of rotatable MEMS mirror arrays formed on a semiconductor chip (402) mounted on the PCB and aligned parallel to the first axis of rotation, wherein each rotatable mirror is rotatable about a second axis of rotation (405), each second axis of rotation being perpendicular to the first axis of rotation and parallel to each other second axis of rotation;

an array of electrostatic comb actuators (306, 310, 314, 316) configured to rotate each rotatable MEMS mirror of the array of rotatable MEMS mirrors about a respective second axis of rotation; and

a controller (514) configured to cause the electromagnetic actuator to rotate the substrate about the first axis of rotation at a first frequency over a first range of motion and to cause the array of electrostatic comb actuators to synchronously rotate each of the array of rotatable MEMS mirrors about its respective second axis of rotation at a second frequency over a second range of motion.

Example lidar systems to implement aspects of embodiments herein

FIG. 7 is a simplified block diagram illustrating aspects of a lidar-based detection system 700 according to some embodiments in which the above-described embodiments may be embedded and controlled. System 700 may be configured to transmit, detect, and process lidar signals to perform object detection as described above with respect to lidar system 700 depicted in fig. 1. In general, lidar system 700 includes one or more transmitters (e.g., transmit block 710) and one or more receivers (e.g., receive block 750). Lidar system 700 may also include additional systems not shown or described to prevent confusion with respect to the new features described herein.

As described above, the transmit block 710 may include a number Of systems that facilitate the generation and transmission Of optical signals, including dispersion modes (e.g., 360 degree plane detection), pulse shaping and frequency control, time-Of-Flight (TOF) measurements, and any other control system to enable the lidar system to transmit pulses in the manner described above. In the simplified representation of fig. 7, the transmit block 710 may include a processor 720, an optical signal generator 730, an optical/transmitter block 732, a power supply block 715, and a control system 740. Some or all of the system blocks 730-740 may be in electrical communication with the processor 720.

In certain embodiments, processor 720 may include one or more microprocessors (μ C) and may be configured to control the operation of system 700. Alternatively or additionally, processor 720 may include one or more Microcontrollers (MCUs), digital Signal Processors (DSPs), etc., as well as support hardware, firmware (e.g., memory, programmable I/O) and/or software, as will be appreciated by those having ordinary skill in the art. Additionally, MCUs, μ cs, DSPs, ASICs, programmable logic devices, and the like, may be configured in other system blocks of system 700. For example, the control system block 740 may include a local processor for certain control parameters (e.g., operation of the transmitter), particularly the frequency and angular range of motion of the substrate on which the semiconductor chip is mounted. Further, the local processor may control rotation of each rotatable MEMS mirror in the array of rotatable MEMS mirrors. Processor 720 may control some or all aspects of transmit block 710 (e.g., optical/transmitter block 732, control system 740, double mirror 220 position shown in fig. 1, position sensitive device 250, etc.) and receive block 750 (e.g., processor 720) or any aspect of lidar system 700. In some embodiments, multiple processors may enable performance characteristics (e.g., speed and bandwidth) in system 700 to be improved; however, multiple processors are not required, and are not necessarily germane to the novelty of the embodiments described herein. Alternatively or additionally, certain aspects of the processing may be performed by analog circuit design, as understood by one of ordinary skill in the art.

According to some embodiments, optical signal generator 730 may include circuitry (e.g., a laser diode) configured to generate an optical signal that may be used as a lidar transmit signal. In some cases, optical signal generator 730 may generate a laser for generating a continuous or pulsed laser beam at any suitable electromagnetic wavelength spanning the visible and non-visible spectrum (e.g., ultraviolet and infrared). In some embodiments, the wavelength of the laser is typically in the range of 600-1200nm, although other wavelengths are possible, as will be appreciated by those of ordinary skill in the art.

Optical/emitter block 732 (also referred to as emitter 732) may include one or more mirror arrays for redirecting and/or directing the emitted laser light pulses, mechanical structures to control the rotation and/or movement of the emitter system, or other systems to affect the field of view of the system, as will be appreciated by those of ordinary skill in the art with the benefit of this disclosure. For example, some systems may include a beam expander (e.g., a convex lens system) in the transmitter block, which helps reduce beam spread and increase beam diameter. These improved performance characteristics may mitigate background echo scattering, which may add noise to the echo signal. In some cases, the optical/transmitter block 732 may include a beam splitter to split and sample portions of the pulse signal. For example, the sampling signal may be used to start the TOF clock. In some cases, the sample may be used as a reference to compare with the backscatter signal. Some embodiments may employ a micro-electromechanical mirror that can redirect light to a target field. Alternatively, a multi-phase laser array may be used. Any suitable system may be used to transmit the lidar transmitted pulses, as will be appreciated by those of ordinary skill in the art.

The power block 715 may be configured to provide power to the transmit block 710, the receive block 750, and to manage power distribution, charging, power efficiency, and the like. In some embodiments, the power block 715 may include a battery (not shown) and a power grid within the system 700 to provide power to each subsystem (e.g., the control system 740). The functionality provided by power supply block 715 may be included by other elements within transmit block 710, or may provide power to any of lidar system 700. Alternatively, some embodiments may not include a dedicated power block and may be powered by multiple separate power sources independent of each other.

The control system 740 may control aspects of optical signal generation (e.g., pulse shaping), optical/emitter control, TOF timing, or any other function described herein. In some cases, aspects of control system 740 may generally be included by processor 720, optical signal generator 730, or transmit block 710, or any block within laser radar system 700.

The receive block 750 may include circuitry configured to detect and process the return light pulses to determine the distance of the object, and in some cases, the size of the object, the velocity and/or acceleration of the object, and the like. The processor 720 may be configured to perform operations such as processing return pulses received from the detector 760, controlling the operation of the TOF module 734, controlling the threshold control block 780 or the receive block 750, or any other aspect of the functionality of the lidar system 700.

The TOF module 734 may include a counter for measuring the round-trip flight time of the transmitted and returned signals. In some cases, TOF module 734 may be included with other modules in laser radar system 700, such as control system 740, optical/emitter block 732, or other modules. TOF module 734 may implement a return "window" that limits the time laser radar system 700 seeks a particular pulse to return. For example, the return window may be limited to a maximum amount of time (e.g., 250 meters) required for the pulse to return from a maximum range position. Some embodiments may include a buffering time (e.g., maximum time plus 10%). As described above, the TOF module 734 may operate independently or may be controlled by other system blocks (e.g., the processor 720). In some embodiments, the transmit block may also include a TOF detection module. Those of ordinary skill in the art having the benefit of this disclosure will appreciate that many modifications, variations, and alternative methods of TOF detection block may be implemented in the system 700.

The detector 760 may detect incoming return signals reflected from one or more objects. In some cases, lidar system 700 may employ spectral filtering based on wavelength, polarization, and/or range to help reduce interference, filter unwanted frequencies, or other harmful signals that may be detected. In particular, narrow band filters, static or dynamic, may be used. Passbands as narrow as 20nm or even 15nm may be used. In general, detector 760 can detect the intensity of light and record data regarding the return signal (e.g., by coherent detection, photon counting, analog signal detection, etc.). The detector 760 may use any suitable photodetector technology, including a solid-state photodetector (e.g., a silicon avalanche photodiode, a Complementary Metal Oxide Semiconductor (CMOS), a Charge Coupled Device (CCD), a hybrid CMOS/CCD device), or a photomultiplier tube. In some cases, a single receiver may be used, or multiple receivers may be configured to operate in parallel.

The gain sensitivity model 770 may include a system and/or algorithm for determining a gain sensitivity curve that may be adapted to a particular object detection threshold. The gain sensitivity curve may be modified (e.g., based on TOF measurements) based on the distance (range value) of the detected object. In some cases, the gain curve may cause the object detection threshold to vary at a rate that is inversely proportional to the size of the object range value. The gain sensitivity curve may be generated by hardware/software/firmware, or the gain sensitivity model 770 may employ one or more look-up tables (e.g., stored in a local or remote database) that may associate gain values with particular detected distances, or with appropriate mathematical relationships therebetween (e.g., applying a particular gain at a detected target distance that is 10% of the laser radar system's maximum range, applying a different gain at 15% of the maximum range, etc.). In some cases, a Lambertian model may be used to apply a gain sensitivity curve to an object detection threshold. The Lambertian model typically represents a fully diffuse (matte) surface by a constant Bidirectional Reflectance Distribution Function (BRDF), which provides reliable results in the lidar systems described herein. However, any suitable gain sensitivity curve may be used, including, but not limited to, the Oren-Nayar model, the Nanrahan-Krueger model, the Cook-Torrence model, the diffuse reflectance BRDF model, the Limmel-Seeliger model, the Blinn-Phong model, the Ward model, the HTSG model, the fixed-Laforture model, and the like. Many alternatives, modifications, and applications thereof will be apparent to those of ordinary skill in the art having the benefit of this disclosure.

Threshold control block 780 may set an object detection threshold for lidar system 700. For example, threshold control block 780 may set an object detection threshold within a particular full detection range of laser radar system 700. The object detection threshold may be determined based on a number of factors including, but not limited to, noise data corresponding to ambient noise levels (e.g., noise data detected by one or more microphones) and false positive data (typically a constant) corresponding to the incidence of false positive object detections by the lidar system. In some embodiments, the object detection threshold may be applied to the maximum range (farthest detectable distance) and the object detection threshold for distances from the minimum detection range to the maximum range is modified by a gain sensitivity model (e.g., a Lambertian model).

Although some systems may not be explicitly discussed, they should be considered part of system 700, as understood by one of ordinary skill in the art. For example, the system 700 may include a bus system (e.g., CAMBUS) for transferring power and/or data to and from the various systems therein. In some embodiments, system 700 may include a storage subsystem (not shown). The storage subsystem may store one or more software programs that are executed by the processor (e.g., in processor 720). It should be appreciated that "software" may refer to a sequence of instructions that, when executed by a processing unit (e.g., processor, processing device, etc.), cause system 700 to perform certain operations of a software program. These instructions may be stored as firmware resident in a Read Only Memory (ROM) and/or as an application program stored in a media storage that may be read into memory for processing by a processing device. The software may be implemented as a single program or as a collection of separate programs and may be stored in non-volatile memory and copied in whole or in part to volatile working memory during program execution. The software may be implemented as a single program or as a collection of separate programs and may be stored in non-volatile memory and copied in whole or in part to volatile working memory during program execution. Some software control aspects of lidar system 700 may include aspects of gain sensitivity model 770, threshold control block 780, control system 740, TOF module 734, or any other aspect of lidar system 700.

It is understood that system 700 is intended to be illustrative and that many variations and modifications are possible, as will be appreciated by those of ordinary skill in the art. System 700 may include other functions or capabilities not specifically described herein. For example, according to some embodiments, lidar system 700 may include a communication interface (not shown) configured to enable communication between lidar system 700 and other systems of the vehicle or remote resources (e.g., remote servers), or the like. In this case, the communication interface may be configured to provide wireless connectivity in any suitable communication protocol (e.g., radio Frequency (RF), bluetooth, BLE, infrared (IR), zigBee, Z-Wave, wi-Fi, or a combination thereof).

Although the system 700 is described with reference to particular blocks (e.g., the threshold control block 780), it is to be understood that these blocks are defined for the understanding of certain embodiments of the present invention and are not meant or intended to limit the embodiments to a particular physical arrangement of components. The blocks need not correspond to physically distinct components. The blocks may be configured to perform various operations (e.g., by programming a processor or providing an appropriate process), and the various blocks may or may not be reconfigured depending on the manner in which the initial configuration is obtained. Some embodiments may be implemented in various devices, including electronic devices implemented using any combination of circuitry and software. Further, aspects and/or portions of system 700 may be combined with or operated by other subsystems of the design notification. For example, the power block 715 and/or the threshold control block 780 may be integrated with the processor 720, rather than operating as separate entities.

Example computer System implementing aspects of embodiments herein

Fig. 8 is a simplified block diagram of a computing system 800 configured to operate aspects of a lidar-based detection system in accordance with some embodiments. Computing system 800 may be used to implement any of the systems and modules described above with reference to fig. 1-5. For example, computing system 800 may operate aspects of threshold control block 780, TOF module 734, processor 720, control system 740, or lidar system 700, or any other element of other systems described herein. The computing system 800 may include, for example, field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), and general purpose Central Processing Units (CPUs) to implement the disclosed techniques, including those described in fig. 1 through 6, such as the controller 514. In some examples, computing system 800 may also include one or more processors 802, which may communicate with a number of peripheral devices (e.g., input devices) via a bus subsystem 804. The processor 802 may be an FPGA, ASIC, CPU, or the like. These peripheral devices may include storage subsystem 806 (including memory subsystem 808 and file storage subsystem 810), user interface input devices 814, user interface output devices 816, and network interface subsystem 812.

In some examples, internal bus subsystem 804 (e.g., CAMBUS) may provide a mechanism for the various components and subsystems of computer system 800 to communicate with one another as intended. Although internal bus subsystem 804 is shown schematically as a single bus, alternative embodiments of the bus subsystem may utilize multiple buses. In addition, network interface subsystem 812 may serve as an interface for communicating data between computing system 800 and other computer systems or networks. Embodiments of the network interface subsystem 812 may include a wired interface (e.g., ethernet, CAN, RS232, RS485, etc.) or a wireless interface (e.g., zigBee, wi-Fi, cellular network, etc.).

In some cases, user interface input devices 814 may include a keyboard, pointing device (e.g., mouse, trackball, touchpad, etc.), bar code scanner, touch screen incorporated into a display, audio input device (e.g., voice recognition system, microphone, etc.), human-machine interface (HMI), and other types of input devices. In general, use of the term "input device" is intended to include all possible types of devices and mechanisms for inputting information into computing system 800. Further, user interface output devices 816 may include a display subsystem, a printer, or a non-visual display, such as an audio output device, among others. The display subsystem may be any known type of display device. In general, use of the term "output device" is intended to include all possible types of devices and mechanisms for outputting information from computing system 800.

Storage subsystem 806 may include a memory subsystem 808 and a file/disk storage subsystem 810.

Subsystems

808 and 810 represent non-transitory computer-readable storage media that can store program code and/or data that provides functionality for embodiments of the present invention. In some embodiments, memory subsystem 808 may include a plurality of memories, including a main Random Access Memory (RAM) 818 for storing instructions and data during program execution and a Read Only Memory (ROM) 820 that may store fixed instructions. File storage subsystem 810 may provide persistent (i.e., non-volatile) storage for program and data files, and may include a magnetic or solid state hard drive, an optical disk drive and associated removable media (e.g., CD-ROM, DVD, blu-ray, etc.), a removable flash memory-based drive or card, and/or other types of storage media known in the art.

It should be understood that computer system 800 is illustrative and is not intended to limit embodiments of the present invention. Many other configurations are possible with more or fewer components than system 800.

Various embodiments may also be implemented in a wide variety of operating environments that may, in some cases, include one or more user computers, computing devices, or processing devices, which may be used to operate any of a number of application programs. The user or client device may include any of a number of general purpose personal computers, such as desktop or laptop computers running a standard operating system, as well as cellular networks, wireless and handheld devices running mobile software and capable of supporting a number of network and messaging protocols. Such a system may also include a number of workstations running any of a variety of commercially available operating systems and other known applications for development and database management purposes, among others. These devices may also include other electronic devices such as virtual terminals, thin clients, gaming systems, and other devices capable of communicating over a network.

Most embodiments utilize at least one network familiar to those skilled in the art to support communication using various commercially available protocols, such as TCP/IP, UDP, OSI, FTP, UPnP, NFS, CIFS, and the like. For example, the network may be a local area network, a wide area network, a virtual private network, the internet, an intranet, an extranet, a public switched telephone network, an infrared network, a wireless network, and any combination thereof.

In embodiments utilizing a web server, the web server mayAny of a variety of servers or mid-end applications are run, including HTTP servers, FTP servers, CGI servers, data servers, java servers, and business application servers. The server can also execute programs or scripts in response to requests from the user device, such as by executing one or more applications that can be implemented as one or more scripts or programs written in any programming language, including but not limited to

C. C # or C + +, or any scripting language such as Perl, python, or TCL, and combinations thereof. The server may also include a database server, including but not limited to, a slave

And

a commercial database server.

As mentioned above, the environment may include various data stores and other memory and storage media. They may reside in various locations, such as on a storage medium local to (and/or resident in) one or more computers, or remote from any or all computers over a network. In one particular set of embodiments, the information may reside in a Storage Area Network (SAN) familiar to those skilled in the art. Similarly, any necessary files for performing the functions attributed to a computer, server, or other network device may be stored locally and/or remotely as appropriate. Where the system includes computerized devices, each such device may include hardware elements that may be electrically coupled via a bus, including, for example, at least one Central Processing Unit (CPU), at least one input device (e.g., a mouse, keyboard, controller, touch screen, or keyboard), and at least one output device (e.g., a display device, printer, or speaker). Such a system may also include one or more storage devices, such as magnetic disk drives, optical storage devices, and solid state storage devices, such as RAM or ROM, as well as removable media devices, memory cards, flash memory cards, and the like.

As mentioned above, such devices may also include a computer-readable storage media reader, a communication device (e.g., a modem, a network card (wireless or wired), an infrared communication device, etc.), and a working memory. The computer-readable storage media reader may be connected or configured to receive non-transitory computer-readable storage media representing remote, local, fixed, and/or removable storage devices, as well as storage media for temporarily and/or more permanently containing, storing, transmitting, and retrieving computer-readable information. The system and various devices will also typically include a number of software applications, modules, services or other elements located within at least one working memory device, including an operating system and applications such as a client application or browser. It should be understood that alternative embodiments may have many variations other than those described above. For example, certain elements may also be implemented using custom hardware and/or in hardware, software (including portable software, such as applets), or both. In addition, connections to other computing devices, such as network input/output devices, may be employed.

Non-transitory storage media and computer-readable storage media for containing code or portions of code may include any suitable media known or used in the art, such as, but not limited to, volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information, such as computer-readable instructions, data structures, program modules or other data, including RAM, ROM, electrically-erasable programmable read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, DVD or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store the desired information and that may be accessed by a system device. Based on the disclosure and teachings provided herein, a person of ordinary skill in the art will appreciate other ways and/or methods to implement the various embodiments. However, the computer-readable storage medium does not include a temporary medium such as a carrier wave.

Other variations are in accordance with the spirit of the present invention. Accordingly, while the disclosed technology is susceptible to various modifications and alternative constructions, certain illustrated examples thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. For example, any of the examples, alternative examples, etc., and concepts thereof, may be applied to any other examples described and/or within the spirit and scope of the present invention.

For example, rather than using a single laser to illuminate an array of MEMS mirrors, an array of mirrors may be used. Furthermore, in various embodiments, the pattern generation and decoding may be hardwired in firmware or software.

The structure of the present invention may be used in a variety of other applications beyond lidar. The beam steering techniques may also be used in other optical systems, such as optical display systems (e.g., TVs), optical sensing systems, optical imaging systems, and the like. In various beam steering systems, the beam may be steered by, for example, a rotating platform driven by a motor, a multi-dimensional mechanical stage, a galvanometer-controlled mirror, a resonant fiber, an array of rotatable MEMS mirrors, or any combination thereof. The rotatable MEMS micro-mirror may be rotated about a pivot or attachment point by, for example, a micro-motor, an electromagnetic actuator, an electrostatic actuator, or a piezoelectric actuator.

The MEMS mirror array structure of the present invention may have mirror arrays driven by different types of actuators. In some light redirecting systems, transmitted or received light beams may be redirected by a micro-mirror array. Each micro-mirror may be rotated about a pivot or connection point to deflect light incident on the micro-mirror into a desired direction. The performance of the micro-mirrors may directly affect the performance of the light steering system, such as the field of view (FOV), the quality of the point cloud, and the quality of the image generated using the light steering system. For example, to increase the detection range and field of view of a lidar system, micro-mirrors with large rotation angles and large apertures may be used, which may result in an increase in the maximum displacement and moment of inertia of the micro-mirrors. To achieve high resolution, a device with a high resonance frequency may be used, which may be achieved using a rotating structure with high stiffness. Such desired performance may be difficult to achieve using electrostatically driven micromirrors because the comb teeth used in electrostatically driven micromirrors may not provide the required force and motion and may separate at large rotational angles, especially when the aperture of the micromirrors is increased to improve the detection range. Some piezoelectric actuators can be used to achieve large displacements and large scan angles because they can provide much greater driving forces than the relatively low voltage electrostatic drive types.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the disclosed examples (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. The term "connected" is to be construed as partially or wholly contained within, attached to or connected together even if interference exists. The phrase "based on" is to be understood as open-ended, not limiting in any way, and to be interpreted or otherwise read as "based at least in part on" where appropriate. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate examples of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Claims

1. A mems structure configured to redirect light in a lidar system, the mems structure comprising:

a substrate configured to rotate about a first rotation axis; and

an array of rotatable microelectromechanical mirrors formed on a semiconductor chip mounted on the substrate, wherein each rotatable mirror is rotatable about a second axis of rotation that is parallel to each other second axis of rotation.

2. The microelectromechanical systems structure of claim 1, further comprising:

a coil on the substrate surrounding the semiconductor chip;

a first magnetic element extending through a first opening in the substrate on a first side between the semiconductor chip and the coil;

a second magnetic element extending through a second opening in the substrate on a second side opposite the first side between the semiconductor chip and the coil;

a third magnetic element located outside the substrate opposite the first magnetic element such that the first portion of the coil is located between the first magnetic element and the third magnetic element; and

a fourth magnetic element located outside the substrate opposite the second magnetic element such that a second portion of the coil is located between the second magnetic element and the fourth magnetic element.

3. The mems structure of claim 1, further comprising a motor configured to rotate the substrate about the first axis of rotation.

4. The microelectromechanical systems structure of claim 1, further comprising:

a first actuator configured to rotate the substrate about the first axis of rotation within a first range of motion at a first frequency;

a second actuator configured to synchronously rotate each rotatable microelectromechanical mirror of the array of rotatable microelectromechanical mirrors about its respective second axis of rotation at a second frequency over a second range of motion;

wherein the first frequency is between 1-15Hz and the second frequency is in the kilohertz range.

5. The microelectromechanical systems structure of claim 1, further comprising:

wherein the second frequency is a resonant frequency of each rotatable microelectromechanical mirror.

6. The mems structure of claim 1, the first axis of rotation providing vertical scanning.

7. A microelectromechanical systems structure, the microelectromechanical systems structure comprising:

a substrate;

a first actuator configured to rotate the substrate about a first rotation axis;

an array of rotatable microelectromechanical mirrors mounted on the substrate and aligned parallel to the first axis of rotation, wherein each rotatable microelectromechanical mirror is rotatable about a second axis of rotation, each second axis of rotation being perpendicular to the first axis of rotation and parallel to each other second axis of rotation;

a second array of actuators mounted on the substrate configured to rotate each rotatable microelectromechanical mirror of the array of rotatable microelectromechanical mirrors about its respective second axis of rotation; and

a controller configured to control the first actuator to rotate the substrate about the first axis of rotation within a first range of motion and to control the second actuator array to rotate each of the array of rotatable microelectromechanical mirrors about its respective second axis of rotation within a second range of motion.

8. The mems structure of claim 7, the substrate comprising a printed circuit board, the array of rotatable microelectromechanical mirrors and the array of second actuators being formed on a semiconductor chip mounted on the printed circuit board.

9. The microelectromechanical systems structure of claim 8, the first actuator comprising an electromagnetic actuator configured to rotate the substrate about the first axis of rotation, the electromagnetic actuator comprising:

an electromagnetic driver;

a coil on the printed circuit board surrounding the semiconductor chip;

a first magnetic element extending through a first opening in the printed circuit board on a first side between the semiconductor chip and the coil;

a second magnetic element extending through a second opening in the printed circuit board on a second side opposite the first side between the semiconductor chip and the coil;

a third magnetic element located outside the printed circuit board opposite the first magnetic element such that the first portion of the coil is located between the first magnetic element and the third magnetic element; and

a fourth magnetic element located outside the printed circuit board opposite the second magnetic element such that the second portion of the coil is located between the second magnetic element and the fourth magnetic element.

10. The mems structure of claim 7, the first actuator comprising an electromagnetic motor configured to rotate the substrate about the first axis of rotation.

11. The mems structure of claim 7, the first actuator comprising a piezoelectric actuator configured to rotate the substrate about the first axis of rotation.

12. The microelectromechanical systems structure of claim 7, each of the second array of actuators comprising electrostatic comb actuators configured to rotate each rotatable microelectromechanical mirror of the array of rotatable microelectromechanical mirrors about its respective second axis of rotation.

13. The microelectromechanical systems structure of claim 7, the controller configured to cause the first actuator to rotate the substrate about the first axis of rotation at a first frequency between 1-15Hz, and to cause the second actuator array to synchronously rotate each of the array of rotatable microelectromechanical mirrors about its respective second axis of rotation at a second frequency in the kilohertz range.

14. The mems structure of claim 13, the second frequency being a resonant frequency of the mems mirror.

15. The mems structure of claim 7, the first axis of rotation providing vertical scanning.

16. A method of operating a microelectromechanical systems structure to redirect light in a lidar system, comprising:

sending, by the controller, a first control signal to a first actuator;

the first actuator rotates a substrate about a first rotation axis in response to the first control signal;

sending, by the controller, at least one second control signal to a second actuator array formed on a semiconductor chip mounted on the substrate; and

the second array of actuators rotates each rotatable microelectromechanical mirror of the array of rotatable microelectromechanical mirrors on the semiconductor chip about a second axis of rotation in response to the second control signal, wherein each of the second axis of rotation is perpendicular to the first axis of rotation and parallel to each other second axis of rotation.

17. The method of claim 16, further comprising: sending, by the controller, the first control signal and the second control signal via traces on the substrate.

18. The method of claim 16, the method of rotating the first actuator comprising applying an electromagnetic field to rotate the substrate about the first axis of rotation.

19. The method of claim 16, the first actuator responsive to the first control signal to rotate the substrate about the first axis of rotation at a first frequency between 1-15 Hz; and

the second array of actuators rotates each rotatable microelectromechanical mirror of the array of rotatable microelectromechanical mirrors on the semiconductor chip about its respective second axis of rotation at a second frequency in the kilohertz range in response to the second control signal.

20. The method of claim 16, further comprising: rotating the rotatable microelectromechanical mirror at a resonant frequency of the rotatable microelectromechanical mirror.