LIDAR WITH METASURFACE BEAM STEERING

A light detection and ranging system can have a metasurface that continuously extends between a pair of electrical contacts. The metasurface may be separated from an underlying silicon substrate by an air gap with the silicon substate doped with a P-i-N configuration to create electrostatic force that alters a size of the air gap in response to a voltage bias between the pair of electrical contacts.

SUMMARY

Light detection and ranging can be optimized, in various embodiments, by providing a metasurface that continuously extends between a pair of electrical contacts. The metasurface may be separated from an underlying silicon substrate by an air gap with the silicon substate doped with a P-i-N configuration to create electrostatic force that alters a size of the air gap in response to a voltage bias between the pair of electrical contacts.

DETAILED DESCRIPTION

Various embodiments of the present disclosure are generally directed to optimization of an active light detection system.

Advancements in computing capabilities have corresponded with smaller physical form factors that allow intelligent systems to be implemented into a diverse variety of environments. Such intelligent systems can complement, or replace, manual operation, such as with the driving of a vehicle or flying a drone. The detection and ranging of stationary and/or moving objects with radio or sound waves can provide relatively accurate identification of size, shape, and distance. However, the use of radio waves (300 GHz-3 kHz) and/or sound waves (20 kHZ-200 kHz) can be significantly slower than light waves (430-750 Terahertz), which can limit the capability of object detection and ranging while moving.

The advent of light detection and ranging (LiDAR) systems employ light waves that propagate at the speed of light to identify the size, shape, location, and movement of objects with the aid of intelligent computing systems. The ability to utilize multiple light frequencies and/or beams concurrently allows LiDAR systems to provide robust volumes of information about objects in a multitude of environmental conditions, such as rain, snow, wind, and darkness. Yet, current LiDAR systems can suffer from inefficiencies and inaccuracies during operation that jeopardize object identification as well as the execution of actions in response to gathered object information. Hence, embodiments are directed to structural and functional optimization of light detection and ranging systems to provide increased reliability, accuracy, safety, and efficiency for object information gathering.

FIG.1depicts a block representation of portions of an example object detection environment100in which assorted embodiments can be practiced. One or more energy sources102, such as a laser or other optical emitter, can produce photons that travel at the speed of light towards at least one target104object. The photons bounce off the target104and are received by one or more detectors106. An intelligent controller108, such as a microprocessor or other programmable circuitry, can translate the detection of returned photons into information about the target104, such as size and shape.

The use of one or more energy sources102can emit photons over time that allow the controller108to track an object and identify the target's distance, speed, velocity, and direction.FIG.2plots operational information for an example light detection and ranging system120that can be utilized in the environment100ofFIG.1. Solid line122conveys the volume of photons received by a detector over time. The greater the intensity of returned photons (Y axis) can be interpreted by a system controller as surfaces and distances that that can be translated into at least object size and shape.

It is contemplated that a system controller can interpret some, or all, of the collected photon information from line122to determine information about an object. For instance, the peaks124of photon intensity can be identified and used alone as part of a discrete object detection and ranging protocol. A controller, in other embodiments, can utilize the entirety of photon information from line122as part of a full waveform object detection and ranging protocol. Regardless of how collected photon information is processed by a controller, the information can serve to locate and identify objects and surfaces in space in front of the light energy source.

FIGS.3A &3Brespectively depict portions of an example light detection assembly130that can be utilized in a light detection and ranging system140in accordance with various embodiments. In the block representation ofFIG.3A, the light detection assembly130consists of an optical energy source132coupled to a phase modulation module134and an antennae136to form a solid-state light emitter and receiver. Operation of the phase modulation module134can direct beams of optical energy in selected directions relative to the antennae136, which allows the single assembly130to stream one or more light energy beams in different directions over time.

FIG.3Bconveys an example optical phase array (OPA) system140that employs multiple light detection assemblies130to concurrently emit separate optical energy beams142to collect information about any downrange targets104. It is contemplated that the entire system140is physically present on a single system on chip (SOC), such as a silicon substrate. The collective assemblies130can be connected to one or more controllers108that direct operation of the light energy emission and target identification in response to detected return photons. The controller108, for example, can direct the steering of light energy beams142to a particular direction144, such as a direction that is non-normal to the antennae138, like 45°.

The use of the solid-state OPA system140can provide a relatively small physical form factor and fast operation, but can be plagued by interference and complex processing that jeopardizes accurate target104detection. For instance, return photons from different beams142may cancel, or alter, one another and result in an inaccurate target detection. Another non-limiting issue with the OPA system140stems from the speed at which different beam142directions can be executed, which can restrict the practical field of view of an assembly130and system140.

FIG.4depicts a block representation of a mechanical light detection and ranging system150that can be utilized in assorted embodiments. In contrast to the solid-state OPA system140in which all components are physically stationary, the mechanical system150employs a moving reflector152that distributes light energy from a source154downrange towards one or more targets104. While not limiting or required, the reflector152can be a single plane mirror, prism, lens, or polygon with reflecting surfaces. Controlled movement of the reflector152and light energy source154, as directed by the controller108, can produce a continuous, or sporadic, emission of light beams156downrange.

Although the mechanical system150can provide relatively fast distribution of light beams156in different directions, the mechanism to physically move the reflector152can be relatively bulky and larger than the solid-state OPA system140. The physical reflection of light energy off the reflector152also requires a clean environment to operate properly, which restricts the range of conditions and uses for the mechanical system150. The mechanical system150further requires precise operation of the reflector152moving mechanism158, which may be a motor, solenoid, or articulating material, like piezoelectric laminations.

FIG.5depicts a block representation of an example detection system170that is configured and operated in accordance with various embodiments. A light detection and ranging assembly172can be intelligently utilized by a controller108to detect at least the presence of known and unknown targets downrange. As shown, the assembly172employs one or more emitters174of light energy in the form of outward beams176that bounce off downrange targets and surfaces to create return photons178that are sensed by one or more assembly detectors180. It is noted that the assembly172can be physically configured as either a solid-state OPA or mechanical system to generate light energy beams172capable of being detected with the return photons178.

Through the return photons178, the controller108can identify assorted objects positioned downrange from the assembly172. The non-limiting embodiment ofFIG.5illustrates how a first target182can be identified for size, shape, and stationary arrangement while a second target184is identified for size, shape, and moving direction, as conveyed by solid arrow186. The controller108may further identify at least the size and shape of a third target188without determining if the target188is moving.

While identifying targets182/184/188can be carried out through the accumulation of return photon178information, such as intensity and time since emission, it is contemplated that the emitter(s)174employed in the assembly172stream light energy beams176in a single plane, which corresponds with a planar identification of reflected target surfaces, as identified by segmented lines190. By utilizing different emitters174oriented to different downrange planes, or by moving a single emitter174to different downrange planes, the controller108can compile information about a selected range192of the assembly's field of view. That is, the controller108can translate a number of different planar return photons178into an image of what targets, objects, and reflecting surfaces are downrange, within the selected field of view192, by accumulating and correlating return photon178information.

The light detection and ranging assembly172may be configured to emit light beams176in any orientation, such as in polygon regions, circular regions, or random vectors, but various embodiments utilize either vertically or horizontally single planes of beam176dispersion to identify downrange targets182/184/188. The collection and processing of return photons178into an identification of downrange targets can take time, particularly the more planes190of return photons178are utilized. To save time associated with moving emitters174, detecting large volumes of return photons178, and processing photons178into downrange targets182/184/188, the controller108can select a planar resolution194, characterized as the separation between adjacent planes190of light beams176.

In other words, the controller108can execute a particular downrange resolution194for separate emitted beam176patterns to balance the time associated with collecting return photons178and the density of information about a downrange target182/184/188. As a comparison, tighter resolution194provides more target information, which can aid in the identification of at least the size, shape, and movement of a target, but bigger resolution194(larger distance between planes) can be conducted more quickly. Hence, assorted embodiments are directed to selecting an optimal light beam176emission resolution to balance between accuracy and latency of downrange target detection.

FIG.6depicts an example junction200that can be employed in various embodiments to conduct beam steering. The junction200has a pair of doped regions202separated by an insulator region204to provide a PiN type component. Such configuration is not required or limiting as other semiconductor junction arrangements can be utilized to produce an electrostatic force proximal the junction200upon activation of electrical circuitry206.

Incorporation of a semiconductor junction200into a light resonator210, as generally depicted inFIG.7, can selectively utilize applied voltage to manipulate a metasurface212and effectively steer light energy in desired vectors relative to the junction200. As shown, a metasurface212is suspended above the junction202by an air gap214that can be tuned for size and shape to allow the metasurface212to fully react to electrostatic forces produced by the junction200.

The construction of the metasurface212is not limited, but some embodiments continuously extend the metasurface212to a length that is greater than the length of the junction200, as illustrated, and less than 1550 nm. The metasurface212may be arranged as a unitary layer of material, such as any semiconductor material, or as a lamination214of multiple layers of material. For instance, a metasurface212can consist of a SiN layer separated from a Si layer by a continuous air gap, such as 100 nm or less. The suspension of the metasurface212above the junction200can have a default shape in response to a neutral, or default, voltage applied to electrodes216on opposite sides of the junction200, as shown inFIG.7.

FIG.8depicts portions of an example light detection and ranging system200arranged to steer beams of light energy by applying a bias voltage across the electrodes216of the resonator220. The introduction of bias voltage can produce electrostatic energy that physically alters the metasurface212to a shape conducive to reflecting light energy in different vector directions relative to the junction200. As illustrated, different applied voltages can produce different light beam vector directions corresponding with different metasurface212surface shapes. When incorporated into a light detection and ranging system the resonator210/220can provide fast, efficient, and reliable steering of light beams, which can optimize the range and accuracy of the system compared to other static or dynamic light reflectors.

A foundry compatible metasurface212, in various embodiments, has a silicon resonator on a SOI wafer. A 220 nm thick silicon nitride film, for instance, can be suspended on top of silicon with 100 nm air in between. Some embodiments configure a silicon resonator as a doped P-i-N arrangement. As voltage is applied across the P-I-N junction, an electrostatic force is created between silicon and silicon nitride. This electrostatic force changes the gap between the silicon disk and silicon nitride membrane and thus changes the effective index of the mode. Change in effective index can be approximately 10−2, which requires moderate amount of Q. Full 2π phase tuning with low power will provide a two dimensional metasurface212with approximately 60 degrees×60 degrees beam steering.