WO2025199223A1

WO2025199223A1 - Metalens for lidar applications

Info

Publication number: WO2025199223A1
Application number: PCT/US2025/020549
Authority: WO
Inventors: Rui ZHU; Namwoong Paik
Original assignee: SRI International Inc; Stanford Research Institute
Current assignee: SRI International Inc
Priority date: 2024-03-20
Filing date: 2025-03-19
Publication date: 2025-09-25
Anticipated expiration: 2026-09-20

Abstract

An example light detection and ranging (lidar) system includes a sensor comprising a plurality of photodetectors and a metalens configured to focus light onto the plurality of photodetectors of the sensor. The metalens is disposed on a sensor surface.

Description

METALENS FOR LIDAR APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application 63/567,750, filed March 20, 2024, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] This disclosure generally relates to imaging devices.

BACKGROUND

[0003] Light detection and ranging (lidar) applications in photon- starved (low light) environments typically require special optics that collect photons from a large area and focus them to a small sensing area. The optics used include microlenses or microlens arrays made from glass or a semiconductor such as silicon (Si) or gallium phosphide (GaP), depending on specific wavelength of light used for lidar. Typical microlenses use the refractive index of the lens material and concave or convex lens surface design to bend and focus light. Each microlens is usually thicker than the wavelength of light that it focuses. Manufacturing of microlenses may be complex and costly, the microlens array may be relatively bulky, and high precision alignment of the array of microlenses to an array of corresponding detectors may be required.

SUMMARY

[0004] In general, systems and techniques are described for a light detection and ranging (lidar) system including a metalens. The metalens may replace a microlens array for focusing light onto a sensor comprising a plurality of photodetectors, e.g., an array of photodetectors. The metalens may be a metasurface that includes a plurality of structures, e.g., microstructures, where each structure is close to, or less than, the wavelength or wavelengths of light being focused. Unlike microlenses, metalenses may be manufactured by relatively inexpensive microfabrication or nanofabrication techniques, such as etching or nanoimprint lithography. In some examples, the metalens and/or microstructures may be disposed on a sensor surface to directly align and incorporate the metalens into an integrated lidar system, such as a lidar camera. In this way, lidar systems may capture and focus light in low light environments without expensive and complex microlenses.

[0005] In one example, this disclosure describes a light detection and ranging (lidar) system including: a sensor including a plurality of photodetectors; and a metalens configured to focus light onto the plurality of photodetectors of the sensor, wherein the metalens is disposed on a sensor surface.

[0006] In another example, this disclosure describes a light detection and ranging (lidar) camera including: a light source configured to illuminate a target; a sensor including a plurality of photodetectors; and a metalens configured to focus light onto the sensor, wherein the metalens is disposed on a sensor surface.

[0007] In another example, this disclosure describes a method of making a light detection and ranging (lidar) camera, the method including: forming a plurality of subwavelength structures; and disposing the plurality of subwavelength structures onto a surface of a sensor including a plurality of photodetectors, wherein the plurality of subwavelength structures are configured to focus light onto the plurality of photodetectors.

[0008] The details of one or more examples of the disclosure are set forth in the accompanying drawings, and in the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. l is a cross-sectional diagram and block diagram illustrating an example lidar system, in accordance with the techniques of the disclosure.

[0010] FIG. 2 is a cross-sectional diagram illustrating another example detection device for a lidar system, in accordance with the techniques of the disclosure.

[0011] FIG. 3 is a cross-sectional diagram illustrating another example detection device for a lidar system, in accordance with the techniques of the disclosure.

[0012] FIG. 4 is a cross-sectional diagram illustrating another example detection device for a lidar system, in accordance with the techniques of the disclosure.

[0013] FIG. 5 is a cross-sectional diagram illustrating another example detection device for a lidar system, in accordance with the techniques of the disclosure.

[0014] FIG. 6 is a cross-sectional diagram illustrating another example detection device for a lidar system, in accordance with the techniques of the disclosure.

[0015] FIG. 7 is a flowchart of an example method of making a light detection and ranging (lidar) camera, in accordance with the techniques of the disclosure.

[0016] Like reference characters denote like elements throughout the figures and description. DETAILED DESCRIPTION

[0017] In general, systems and techniques are described for a lidar system including one or more metalenses. The metalens may replace a microlens array for focusing light onto a sensor comprising a plurality of photodetectors, e.g., an array of photodetectors.

[0018] Typical lidar systems may use microlens arrays to collect and focus light onto photodetectors. Microlenses may be expensive to design and make and may be subject to a limited supply chain. Microlens arrays may be refractive and/or diffractive, and may use traditional lens design techniques based on lens material, e.g., refractive index, convex and/or concave lens surfaces, and/or relatively large diffractive structures (e.g., larger than the wavelength or wavelengths of light), to redirect and/or focus light. The design and fabrication of such microlenses is relatively complicated and costly, and the resultant microlens array is bulky and difficult to integrate and align with lidar sensors.

[0019] Aspects of this disclosure are directed to techniques and systems of lidar systems utilizing a metalens to focus light onto one or more photodetectors. The metalens, which may be a metasurface, a metamaterial, a metamaterial lens, or the like, may comprise a plurality of structures, e.g., microstructures, nanostructures, or subwavelength structures, each having a size close to, or less than, the wavelength or wavelengths of light being manipulated by the metalens, e.g., converged, diverged, focused, redirected, or the like. The subwavelength structures may be formed in a pattern on a surface of a substrate, which may work in conjunction with the shape and size of the individual structures making up the pattern to achieve the desired manipulation of light. For example, the pattern of the metalens may define functional lens units that are aligned with a corresponding photodetector to focus light on the photodetector.

[0020] In some examples, a lidar system may include a transmissive metalens, e.g., configured to converge, diverge, focus, and/or redirect incident light propagating through the metalens from one side of the metalens to the other side of the metalens. In other examples, a lidar system may include a reflective metalens, e.g., configured to converge, diverge, focus, and/or redirect incident light onto the metalens from one side of the metalens and then reflected back to further propagate on the same side of the metalens. In some examples, the subwavelength structures of the metalens may extend from a surface in free space (e.g., air or vacuum), and in some examples, the subwavelength structures of the metalens may extend from a surface and be encapsulated within a material having a different refractive index than the subwavelength structures. [0021] In some examples, lidar systems disclosed here include a substantially planar metalens configured to focus light to one or more of a plurality of photodetectors. In other examples, the metalens may comprise a curved surface, e.g., subwavelength structures disposed on a concave or convex surface. For example, the metalens may be combined with a refractive and/or diffractive lens, and the metalens may be configured to correct for aberrations, change the optical power of the refractive and/or diffractive lens, change the spatial wavefront profile of the light from the refractive and/or diffractive lens, and/or redirect the light.

[0022] In some examples, lidar systems disclosed herein may include a stand-alone metalens, e.g., that replaces a microlens array for focusing light to a lidar sensor chip assembly. In other examples, the metalens may be disposed directly on a surface of a sensor including the plurality of photodetectors. For example, the subwavelength structures may be disposed directly onto a surface of one or more of the photodetectors, e.g., without an air gap. In some examples, the surface of the plurality of photodetectors may be substantially planar, and in other examples, the surface of the plurality of photodetectors may be curved, e.g., similar to a retina. In some examples, lidar systems disclosed here may include a metalens formed via electron beam patterning, photolithography, electron beam lithography or etching, laser etching, wet etching, dry etching, nanofabrication, or any suitable technique for disposing or forming subwavelength structures on a surface. For example, a metalens may be disposed on a surface of a sensor surface by etching a plurality of subwavelength structures into the sensor surface.

[0023] Aspects of this disclosure may provide one or more technical advantages and solve one or more technical problems that may arise during manufacture or operation of lidar systems that use microlenses to focus light. In some examples, a lidar system including a metalens may be less expensive and complex to manufacture and integrate with a lidar system. For example, a metalens may be manufactured using semiconductor wafer fabrication processes, improving the ease of integration with photodetectors, reducing the size, weight, and complexity of the lidar system by enabling compact, flat optics. In some examples, a lidar system including a metalens may have improved performance by reducing and/or eliminating misalignment between the lens and the individual photodetectors of the lidar sensor, e.g., in contrast with a lidar system utilizing a microlens array. In some examples, a metalens may provide improved thermal stability and enable a simplified module structure for the lidar system, such as by ensuring intimate contact with or incorporation into a substrate. In some examples, a metalens may enable reduction and/or elimination of more exotic materials, e.g., gallium phosphide, for the lens by enabling the use of dielectric subwavelength structures (e.g., silica) on a dielectric or semiconductor (e.g., silicon) substrate. Additionally, a metalens may provide for reduced components and complexity by enabling combination of illumination optics and receiver optics, e.g., the metalens may be used for both beam shaping and redirection of light from a light source to illuminate a target (e.g., and object in a scene) as well as light collection and focusing of return light from a target. In some examples, the techniques and systems disclosed may provide a lidar system with a plurality of metalenses, e.g., enabled by the metalenses being substantially planar, such as a first metalens configured to focus light onto one or more photodetectors and a second metalens configured to direct light from a light source to illuminate a target.

[0024] FIG. l is a cross-sectional diagram and block diagram illustrating an example lidar system 100, in accordance with the techniques of the disclosure. In the example shown, lidar system 100 includes detection device 102 for collecting and processing light 152 and computing device 120 communicatively coupled to detection device 102 for processing data related to processed light 152. Detection device 102 includes a sensor 104 for measuring one or more characteristics of light 152 and a metalens 110 for focusing light 152 on sensor 104. FIG. 1 also illustrates computing device 120 that includes processing circuitry 116 communicatively coupled to detection device 102, and memory 124 communicatively coupled to processing circuitry 116.

[0025] Sensor 104 includes an array of photodetectors 114. While the cross-sectional view of detection device 102 in FIG. 1 illustrates detection device 102 in one-dimension (ID), detection device 102 may be a two-dimensional (2D) device, e.g., sensor 104 may be a two- dimensional array of photodetectors 114 in both the x-direction and y-direction.

Photodetectors 114 of sensor 104 may be configured to detect one or more properties, such as an intensity, of electromagnetic radiation, for example, a single photon of light 152. In some examples, light 152 may be infrared and/or visible light. Photodetectors 114 may be -state infrared and/or visible wavelength photodetectors 114 configured to operate with or without cooling. For example, sensor 104 may be a charge-coupled device (CCD) array, metal-oxide- semiconductor based array such as a complementary metal-oxide-semiconductor (CMOS) array or N-type metal-oxide-semiconductor (NMOS) array, or a III-V semiconductor PIN or avalanche photo detector array. Photodetectors 114 may be formed on or within the material of sensor 104, e.g., detector substrate 105. Detector substrate 105 may be a semiconductive material, e.g., silicon. [0026] Sensor 104 may be configured to output one or more signals corresponding to the detected light 152 to computing device 120. The one or more signals may represent spatial and/or temporal representation of light 152 incident on detection device 102, providing information about a distance and image of objects in an environment. For example, sensor 104 may be configured to output a 2D or 3D image of detected light 152. In some examples, sensor 104 may be configured to output a pixelated 2D or 3D image corresponding to light 152 detected in two or three dimensions, e.g., an image comprising a plurality of pixels. In other examples, sensor 104 may comprise a single photodetector 114 (e.g., a large area detector), or a plurality of photodetectors 114 configured to detect light 152 without forming an image or being arranged to form an image.

[0027] Light 152 returned for lidar applications may be relatively weak, particularly for distant or low-reflectivity objects, and may carry precise timing information. Metalens 110 is configured to focus light 152 on photodetectors 114 in an efficient manner that reduces dispersion of light 152. In the example shown, metalens 110 includes a plurality of subwavelength structures 112 extending from substrate 105. The plurality of subwavelength structures 112 are patterned to focus light 152 on photodetectors 114. For example, a region (e.g., a “unit lens”) of the plurality of subwavelength structures 112 may correspond to a particular photodetector 116 to form a focal unit.

[0028] The plurality of subwavelength structures 112 may be placed, formed, and/or otherwise disposed on a sensor surface 140 of sensor 104, e.g., in contact with sensor surface 140 and without an intervening substrate and/or material. Such direct disposition may enable an accurate alignment of metalens 110 with photodetectors 114. For example, unit lenses of metalens 110 may be formed into substrate 105 to directly align each unit lens with a corresponding photodetector 104. In some examples, subwavelength structures 112 may be disposed on an intervening layer such as a coating and/or primer layer, e.g., to improve adhesion of subwavelength structures 112 to sensor surface 140, and in such cases sub wavelength structures 112 may still be considered to be disposed on, or directly on, sensor surface 140 without an intervening substrate.

[0029] In the example of FIG. 1, metalens 110 is incorporated directly into substrate 105, such as via a microfabrication or nanofabrication process. Such processes may be capable of precisely aligning metalens 110 to focus light on photodetectors 114. For example, misalignment of a focusing element, such as a microlens, with a photodetector may result in reduced signal strength, inaccurate depth measurements, distorted imaging, or other errors that result from reduced collection and/or reduced focus of light. [0030] In the example shown, subwavelength structures 112 are separated from photodetectors 114 by a back focal distance BFD, e.g., so as to focus light 152 onto the detection areas of photodetectors 114. In some examples, the BFD may be equal to the effective focal length (EFL) of metalens 110, e.g., the EFL being proportional to the optical power of metalens 110. In other examples, metalens 110 may have an EFL that I different from the BFD. In some examples, the BFD may be less than or equal to 1 mm, or less than or equal to 500 microns, or less than or equal to 100 microns, or any suitable distance for metalens 110 to focus light 152 onto photodetectors 114.

[0031] In some examples, subwavelength structures 112 may be made of a dielectric material, a plastic, a polymer, a glass, quartz (SiO2), or a semiconductive material, e.g., silicon. In some examples, subwavelength structures 112 may comprise a plurality of individual structures where each structure has a size (e.g., in the x-y direction) that is less than or equal to the wavelength or wavelengths of light 152. For example, subwavelength structures 112 may have sizes that are less than or equal to 5 micrometers, or less than or equal to 1 micrometer, or less than or equal to 500 nanometers (nm), or less than or equal to 100 nanometers (nm), or less than or equal to 50 nanometers (nm).

[0032] In some examples, lidar system 100 may comprise a lidar camera configured to capture an image. For example, detection device 102 may be configured to capture an image of a scene with metalens 110 imaging the scene to the plurality of photodetectors 114 arranged in a focal plane array. In such examples, the lidar camera may further include an additional light source (not shown) communicatively coupled to computing device 120 and configured to pulse limited-wavelength light for reflection by an object and detection by detection device 102.

[0033] In some examples, subwavelength structures 112 have a substantially high aspect ratio, e.g., a ratio size or length in the z-direction extending from sensor surface 140 to the average, or maximum, size in the x-y direction that is greater than or equal to 10. In some examples, subwavelength structures 112 may have an aspect ratio that is less than 1, about 1 : 1, greater than 1, or subwavelength structures 112 may comprise high aspect ratio structures, e.g., greater than about 10. Metalens 110 may comprise subwavelength structures 112 having a plurality of aspect ratios, e.g., structures having aspect ratios of less than 1, about 1, greater than 1, or much greater than 1 (e.g., greater than 10), in any amount and/or any suitable pattern or distribution. In some examples, subwavelength structures 112 may comprise any suitable geometry, e.g., cylindrical posts, pyramids, cuboids (e.g., square, right rectangular, oblique rectangular), spheroids, ellipsoids, cones, polyhedrons, or the like. In some examples, subwavelength structures 112 may comprise a distribution of different shapes and sizes in a pattern, e.g., a pattern configured to focus and/or redirect light 152. [0034] Referring back to FIG. 1, computing device 120 may be configured to receive signals from sensor 104 indicative of detected light 152. Computing device 120 includes computation engine 122, memory 124, communication unit 118, processing circuitry 116, one or more hardware user interfaces 128 (hereinafter “hardware user interface 128”), and one or more output devices 126. In the example of FIG. 1, a user of computing device 120 may provide input to computing device 120 via one or more input devices (not shown) such as a keyboard, a mouse, a microphone, a touch screen, a touch pad, or another input device that is coupled to computing device 120 via one or more hardware user interfaces 128. [0035] Output devices 126 may include a display, sound card, video graphics adapter card, speaker, presence-sensitive screen, one or more USB interfaces, video and/or audio output interfaces, or any other type of device capable of generating tactile, audio, video, or other output. Output devices 126 may include a display device, which may function as an output device using technologies including liquid crystal displays (LCD), quantum dot display, dot matrix displays, light emitting diode (LED) displays, organic light-emitting diode (OLED) displays, cathode ray tube (CRT) displays, e-ink, or monochrome, color, or any other type of display capable of generating tactile, audio, and/or visual output.

[0036] Computing device 120, in some examples, includes communication unit 118. Communication unit 118 is configured to receive electrical signal input from one or more sensors, such as sensor 104 and/or photodetectors 114. Communication unit 118 may transmit to and/or receive electrical signal input/output from a light source (FIG. 3) and/or sensor 104 and photodetectors 114 via a wired or a wireless connection. For example, computing device 120 may communicate via communication unit 118 to configure a light source and/or sensor 104 and photodetectors 114. Communication unit 118 may be configured to convert the received electrical signals into a form usable by computing device 120. For example, communication unit 118 may include software or hardware configured to convert a received signal input from an analog signal to a digital signal. In another example, communication unit 118 may include software or hardware configured to compress, decompress, transcode, encrypt, or decrypt a received signal input into a form usable by computing device 120. In another example, communication unit 118 may include a network interface device to receive packetized data representative of image data and/or input/output data. In such examples, an intermediate device may packetize signals to produce the packetized data and send the packetized data to computing device 120. In this manner, communication unit 118 may be configured to interface with, or communicate with a light source and/or sensor 104 and photodetectors 114.

[0037] Computation engine 122 may be implemented in circuitry. For instance, computation engine 122 may include processing circuitry 116, which may be any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry. The functions attributed to processors described herein, including computation engine 122 and processing circuitry 116, may be provided by processing circuitry of a hardware device, e.g., as supported by software and/or firmware. Computation engine 122 may be configured to generate a digital image and/or ranging information based on signals received from sensor 104 and photodetectors 114. Computation engine 122 may also be configured to control the output of a light source (FIG. 3) and receive information indicative of the output of the light sources, e.g., feedback regarding brightness and spectral content of the light source.

[0038] Processing circuitry 116 may be communicatively coupled to lidar system 100, for example via communication unit 118. For example, processing circuitry 116 may process signals received via communication unit 118 from sensor 104 and photodetectors 114 indicative of detected light 152. In some examples, processing circuitry 116 may control the output of a light source (FIG. 3) and receive information indicative of the output of the light source, e.g., feedback regarding brightness and spectral content of the light sources.

[0039] In some examples, computation engine 122 may include memory 124. Memory 124 may include any volatile or non-volatile media, such as a random-access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and the like. Memory 124 may be a storage device or other non-transitory medium. Memory 124 may be used by processing circuitry 116 to, for example, store information related to lidar system 100, such as images, image information, ranging information, sensor 104 settings, light source (FIG. 3) settings, and any other suitable settings for detection device 102. In some examples, processing circuitry 116 may store image information, ranging information, or previously received data from electrical signals in memory 124 for later retrieval. In some examples, processing circuitry 116 may store determined values or any other calculated values, in memory 124 for later retrieval.

[0040] In some examples, computing device 120 may be integrated with lidar system 100. In other examples, computing device 120 may be an external device, e.g., a computing device separate from lidar system 100 and configured to communicate with lidar system 100. [0041] FIG. 2 is a cross-sectional diagram illustrating another example detection device 302 for a lidar system, in accordance with the techniques of the disclosure. Detection device 302 may be substantially similar to detection device 102 of FIG. 1 described above, except for the differences described herein. In the example shown, detection device 302 includes sensor 304 and metalens 310. In the example shown, rather than subwavelength structures 112 being disposed on a sensor surface of sensor 104 as shown for detection device 102, subwavelength structures 312 may be disposed on a surface 340 of separate substrate 316 that is separated from sensor 304 by a distance. While the cross-sectional view of detection device 302 in FIG. 2 illustrates detection device 302 in one-dimension (ID), detection device 302 may be a two-dimensional (2D) system, e.g., sensor 304 may be a two-dimensional array of photodetectors 114 in both the x-direction and y-direction.

[0042] In the example shown, metalens 310 includes a plurality of subwav elength structures 112 placed, formed, and/or otherwise disposed on surface 340 of substrate 316, e.g., in contact with surface 340. In other examples, metalens 310 may include a plurality of subwavelength structures 112 placed, formed, and/or otherwise disposed on opposing surface 342 of substrate 316, e.g., in addition to or instead of subwavelength structures 112 disposed on surface 340. In some examples, subwavelength structures 112 may be disposed on an intervening layer such as a coating and/or primer layer, e.g., to improve adhesion of subwavelength structures 112 to surfaces 340, 342, and in such cases subwavelength structures 112 may still be considered to be disposed on, or directly on, surfaces 340,342. In the example shown, subwavelength structures 112 are separated from photodetectors 114 by a back focal distance BFD, e.g., so as to focus light 152 onto the detection areas of photodetectors 114, and there is a gap between substrate 316 and sensor 304. In some examples, the gap may be an air gap or vacuum, and in other examples the gap may be filled with a fluid or solid material. Similar to metalens 110, in some examples, the BFD of metalens 310 may be equal to the effective focal length (EFL) of metalens 310, e.g., the EFL being proportional to the optical power of metalens 310. In other examples, metalens 310 may have an EFL that I different from the BFD. In some examples, the BFD may be less than or equal to 1 mm, or less than or equal to 500 microns, or less than or equal to 100 microns, or any suitable distance for metalens 310 to focus light 152 onto photodetectors 114. [0043] In the example shown, surface 340 is facing towards sensor 304, however, in some examples, surface 340 may be facing away from sensor 304, e.g., metalens 310 may be “flipped” such that surface 340 and subwavelength features 312 are on the side of substrate 316 facing away from sensor 304. [0044] FIG. 3 is a cross-sectional diagram illustrating another example detection device 402 for a lidar system, in accordance with the techniques of the disclosure. Detection device 402 may be substantially similar to detection device 302 of FIG. 2 described above, except for the differences described herein. In the example shown, detection device 402 includes sensor 404, light source 406, and metalens 410. While the cross-sectional view of detection device 402 in FIG. 3 illustrates detection device 402 in one-dimension (ID), detection device 402 may be a two-dimensional (2D) system, e.g., sensor 404 may be a two-dimensional array of photodetectors 114 in both the x-direction and y-direction.

[0045] Metalens 410 includes a plurality of sub wavelength structures 412 and subwavelength structures 414 placed, formed, and/or otherwise disposed on surface 440 of substrate 416, e.g., in contact with surface 440. In other examples, metalens 410 may include a plurality of subwavelength structures 412, 414 placed, formed, and/or otherwise disposed on opposing surface 442 of substrate 416, e.g., in addition to or instead of subwavelength structures 412, 414 disposed on surface 440. In some examples, subwavelength structures 412, 414 may be disposed on an intervening layer such as a coating and/or primer layer, e.g., to improve adhesion of subwavelength structures 412, 414 to surfaces 440, 442, and in such cases subwavelength structures 412, 414 may still be considered to be disposed on, or directly on, surfaces 440, 442. In the example shown, subwavelength structures 412, 414 are separated from photodetectors 114 by a back focal distance BFD, e.g., so as to focus light 152 onto the detection areas of photodetectors 114.

[0046] In the example shown, light source 406 is configured to emit light 448 towards metalens 410. Metalens 410 may be configured to diffuse, focus, and/or redirect light 448 towards a target 460 (e.g., an object). Diffused, focused, or redirected light 450 may interact with target 460, e.g., reflected from target 460 as light 152, and metalens 410 may be configured to redirect and/or focus light 152 to sensor 404. In some examples, metalens 410 may have multiple portions, or areas, e.g., a first portion 426 configured to diffuse, focus, and/or redirect light 448 towards target 460 and a second portion 424 configured to redirect and/or focus light 152 to sensor 404. For example, a first portion 426 of the area of metalens 410 may comprise a plurality of subwavelength structures 414 configured to diffuse, focus, and/or redirect light 448 towards target 460, and a second portion 424 of the area of metalens 410 may comprise a plurality of subwavelength structures 412 configured to redirect and/or focus light 152 to sensor 404. In some examples, subwavelength structures 412 may be substantially the same as subwavelength structures 414, e.g., first portion 426 and second portion 424 may be a single metalens 410. In some examples, subwavelength structures 412 may be different from subwavelength structures 414, e.g., having a different shape, geometry, aspect ratio, material, and/or arranged in a different pattern.

[0047] In some examples, metalens 410 may be considered to be two metalenses, e.g., a first metal lens 408 including subwavelength structures 412 configured to redirect and/or focus light 152 to sensor 404 and a second metalens 409 including of subwavelength structures 414 configured to diffuse, focus, and/or redirect light 448 towards target 460. For example, second metalens 409 may comprise a negative optical power lens configured to diverge light 448 from light source 406 so as to illuminate target 460 as well as, in some examples, other targets, with a wider illumination solid angle (not shown) of light 450. In other examples, second metalens 409 may comprise a positive optical power lens configured to converge light 448 from light source 406 so as to focus light 450 to illuminate target 460. Although shown on the same substrate 416, metalenses 408 and 409 may comprises different substrates, e.g., separate from each other, and each metalens 408 and 409 may be displaced from each other in any of the x, y, or z directions. For example, of subwavelength structures 414, 412 of metalenses 408 and 409 may be in different planes, or the same plane and separated from each other by a distance. In some example, metalens 408 and 409 may be tilted, e.g., relative to any of the x, y, or z directions. For example, metalens 409 may be tilted to be at an angle relative to a surface normal of sensor 404 (e.g., the z-direction as shown) to focus light 448 toward target 460, and metalens 408 may be tilted at the same or a different angle, or metalens 408 may not be tilted, e.g., so as to have an optical axis of metalens 408 aligned with the surface normal of sensor 404.

[0048] In some examples, first metalens 408 may comprise a plurality of subwavelength structures 412 disposed on surface of sensor 404, e.g., first metalens 408 may be substantially similar to metalens 110 of FIG. 1, and second metalens 409 may comprise a plurality of subwavelength structures 414 disposed on a separate substrate 416 as shown.

[0049] In some examples, the detection device may include a light source may be integrated with the sensor and a metalens, or a plurality of metalenses. FIG. 4 is a cross-sectional diagram illustrating another example detection device 502 for a lidar system, in accordance with the techniques of the disclosure. Detection device 502 may be substantially similar to detection device 402 of FIG. 3 described above, except for the differences described herein. In the example shown, detection device 502 includes sensor 504, light source 506, and metalens 510. While the cross-sectional view of detection device 502 in FIG. 4 illustrates detection device 502 in one-dimension (ID), detection device 502 may be a two-dimensional (2D) system, e.g., sensor 504 may be a two-dimensional array of photodetectors 114 in both the x-direction and y-direction.

[0050] In the example shown, photodetectors 114 and light source 506 may be formed on or within the material of sensor 104, e.g., detector substrate 505. Detector substrate 505 may substantially similar to detector substrate 105, except for the differences described herein. Metalens 510 includes a plurality of sub wavelength structures 512 and subwavelength structures 512 placed, formed, and/or otherwise disposed on surface 540 of sensor 504, e.g., in contact with sensor surface 540. In some examples, subwavelength structures 512, 514 may be disposed on an intervening layer such as a coating and/or primer layer, e.g., to improve adhesion of subwavelength structures 512, 514 to sensor surface 540, and in such cases subwavelength structures 412, 414 may still be considered to be disposed on, or directly on, sensor surface 540. In the example shown, subwavelength structures 512, 514 are separated from photodetectors 114 by a back focal distance BFD, e.g., so as to focus light 152 onto the detection areas of photodetectors 114.

[0051] In the example shown, light source 506 is configured to emit light 448 towards metalens 510. Metalens 510 may be configured to diffuse, focus, and/or redirect light 448, and/or extract light 448 from detector substrate 505, towards a target 460. Diffused, focused, or redirected light 450 may interact with target 460, e.g., reflected from target 460 as light 152, and metalens 510 may be configured to redirect and/or focus light 152 to sensor 504. In some examples, metalens 510 may have multiple portions, or areas, e.g., a first portion 526 configured to diffuse, focus, and/or redirect light 448 towards target 460 and a second portion 524 configured to redirect and/or focus light 152 to sensor 504. For example, a first portion 526 of the area of metalens 510 may comprise a plurality of subwavelength structures 514 configured to diffuse, focus, and/or redirect light 448 towards target 460, and a second portion 524 of the area of metalens 510 may comprise a plurality of subwavelength structures 512 configured to redirect and/or focus light 152 to sensor 504. In some examples, subwavelength structures 512 may be substantially the same as subwavelength structures 514, and in other examples, subwavelength structures 512 may be different from subwavelength structures 514, e.g., having a different shape, geometry, aspect ratio, material, and/or arranged in a different pattern.

[0052] In some examples, metalens 510 may be considered to be two metalenses, e.g., a first metal lens 508 including subwavelength structures 512 configured to redirect and/or focus light 152 to sensor 504 and a second metalens 509 including of subwavelength structures 514 configured to diffuse, focus, and/or redirect light 448 towards target 460. For example, second metalens 509 may comprise a negative optical power lens configured to diverge light 448 from light source 506 so as to illuminate target 460 as well as, in some examples, other targets, with a wider illumination solid angle (not shown) of light 450. In other examples, second metalens 509 may comprise a positive optical power lens configured to converge light 448 from light source 506 so as to focus light 450 to illuminate target 460.

[0053] FIG. 5 is a cross-sectional diagram illustrating another example detection device 602 for a lidar system, in accordance with the techniques of the disclosure. Detection device 602 may be substantially similar to detection device 102 of FIG. 1 described above, except for the differences described herein. For example, detection device 602 may include a curved sensor surface 640 rather than a substantially planar sensor surface 140. In the example shown, detection device 602 includes sensor 604 and metalens 610. While the cross-sectional view of detection device 602 in FIG. 5 illustrates detection device 602 in one-dimension (ID), detection device 602 may be a two-dimensional (2D) system, e.g., sensor 604 may be a two- dimensional array of photodetectors 114 in both the x-direction and y-direction.

[0054] In the example shown, metalens 610 includes a plurality of subwav elength structures 612 placed, formed, and/or otherwise disposed on curved sensor surface 640 of sensor 104, e.g., in contact with curved sensor surface 640 and without an intervening substrate and/or material. In some examples, subwavelength structures 612 may be disposed on an intervening layer such as a coating and/or primer layer, e.g., to improve adhesion of subwavelength structures 612 to curved sensor surface 640, and in such cases subwavelength structures 612 may still be considered to be disposed on, or directly on, curved sensor surface 640 without an intervening substrate. In the example shown, subwavelength structures 612 are separated from photodetectors 114 by a back focal distance BFD, e.g., so as to focus light 152 onto the detection areas of photodetectors 114. In the example shown, BFD may vary as a function of x, y, z position along curved sensor surface 640, e.g., subwav elength structures and curved sensor surface 640 may be configured to focus light 152 to an x-y plane (at a z- position) including photodetectors 114. In other examples, photodetectors 114 may be positioned on or within the material of sensor 604, e.g., detector material 605, along a curve, e.g., such that the BFD may not be variable, or variable to focus light 152 to photodetector 114. In some examples, the optical power of metalens 610 may vary as a function of x, y, z position along curved sensor surface 640. For example, the BFD at a particular x, y, z position along curved sensor surface 640 (e.g., a local BFD) may be equal to the effective focal length (EFL) of metalens 610 at that position, e.g., the EFL being proportional to the optical power of metalens 610 at that x, y, z position. In other examples, metalens 610 may have an EFL that is different from the BFD, and that may be variable as a function of position along curved sensor surface 640, or that may not be variable. In some examples, the BFD may be less than or equal to 1 mm, or less than or equal to 500 microns, or less than or equal to 100 microns, or any suitable distance for metalens 610 to focus light 152 onto photodetectors 114. In the example shown, curved sensor surface 640 is convex, e.g., relative to detectors 114 and opposing surface 642. In other examples, curved sensor surface 640 may be concave. In some examples, any of surfaces 340, 342, 440, 442, or 540 may be curved, e.g., concave or convex relative to detectors 114 and/or opposing surfaces.

[0055] FIG. 6 is a cross-sectional diagram illustrating another example detection device 702 for a lidar system, in accordance with the techniques of the disclosure. Detection device 702 may be substantially similar to detection device 102 of FIG. 1 described above, except for the differences described herein. For example, similar to detection device 302 of FIG. 2, rather than subwavelength structures 112, 612 being disposed on a sensor surface of sensor 104, 604 as shown for detection devices 102, 602, subwavelength structures 712 may be disposed on a surface 740 of separate substrate 716 that is separated from sensor 704 by a distance. Also, rather than a substantially planar surface 340, metalens 710 may include a curved surface 740, and subwavelength structures 712 may be disposed on a curved surface 740. While the cross-sectional view of detection device 702 in FIG. 6 illustrates detection device 702 in one-dimension (ID), detection device 702 may be a two-dimensional (2D) system, e.g., sensor 704 may be a two-dimensional array of photodetectors 114 in both the x-direction and y-direction.

[0056] In the example shown, metalens 710 includes a plurality of subwav elength structures 712 placed, formed, and/or otherwise disposed on curved surface 740 of sensor 104, e.g., in contact with curved surface 740 and without an intervening substrate and/or material. In some examples, subwavelength structures 712 may be disposed on an intervening layer such as a coating and/or primer layer, e.g., to improve adhesion of subwavelength structures 712 to curved surface 740, and in such cases subwavelength structures 712 may still be considered to be disposed on, or directly on, curved surface 740 without an intervening substrate. In the example shown, subwavelength structures 712 are separated from photodetectors 114 by a back focal distance BFD, e.g., so as to focus light 152 onto the detection areas of photodetectors 114. In the example shown, BFD may vary as a function of x, y, z position along curved surface 740, e.g., subwavelength structures and curved surface 740 may be configured to focus light 152 to an x-y plane (at a z-position) including photodetectors 114. In other examples, photodetectors 114 may be positioned on or within the material of sensor 704, e.g., detector material 705, along a curve, e.g., such that the BFD may not be variable, or variable to focus light 152 to photodetector 114. In some examples, the optical power of metalens 710 may vary as a function of x, y, z position along curved surface 740. For example, the BFD at a particular x, y, z position along curved surface 740 (e.g., a local BFD) may be equal to the effective focal length (EFL) of metalens 710 at that position, e.g., the EFL being proportional to the optical power of metalens 710 at that x, y, z position. In other examples, metalens 710 may have an EFL that is different from the BFD, and that may be variable as a function of position along curved surface 740, or that may not be variable. In some examples, the BFD may be less than or equal to 1 mm, or less than or equal to 500 microns, or less than or equal to 100 microns, or any suitable distance for metalens 710 to focus light 152 onto photodetectors 114. In the example shown, curved surface 740 is convex, e.g., relative to detectors opposing surface 742. In other examples, sensor surface 740 may be concave. In the example shown, curved surface 740 is facing towards sensor 704, however, in some examples, curved surface 740 may be facing away from sensor 704, e.g., metalens 710 may be “flipped” such that surface 740 and subwavelength features 712 are on the side of substrate 716 facing away from sensor 704.

[0057] FIG. 7 is a flowchart of an example method of making a light detection and ranging (lidar) camera, in accordance with the techniques of the disclosure. Although the method is described with reference to detection devices 102, 302, 402, 502, and 602, of FIGS. 1-6, the methods discussed herein may include and/or utilize other systems and methods in other examples.

[0058] A manufacturer may form a plurality of subwavelength structures (702), and the manufacturer may dispose the plurality of subwavelength structures onto surface 140 of sensor 104. For example, the manufacturer may dry etch subwavelength structures 112 directly into surface 140.

[0059] The following examples may illustrate one or more aspects of the disclosure: [0060] Example 1 : A light detection and ranging (lidar) system including: a sensor including a plurality of photodetectors; and a metalens configured to focus light onto the plurality of photodetectors of the sensor, wherein the metalens is disposed on a sensor surface.

[0061] Example 2: The lidar system of example 1, wherein the metalens includes a plurality of subwavelength structures disposed on the sensor surface without an intervening substrate. [0062] Example 3: The lidar system of example 1 or example 2, wherein the metalens is configured to direct light from a light source to illuminate a target. [0063] Example 4: The lidar system of any one of examples 1-3, wherein the sensor surface includes a curved surface.

[0064] Example 5: The lidar system of any one of examples 1-4, wherein the metalens includes a first metalens, the lidar system further including a second metalens configured to direct light from a light source to illuminate a target.

[0065] Example 6: The lidar system of example 5, wherein the second metalens includes a plurality of subwavelength structures disposed on a substrate surface, wherein the substrate is separated from the sensor.

[0066] Example 7: The lidar system of example 6, wherein the substrate surface includes a curved surface.

[0067] Example 8: The lidar system of any one of examples 5-7, wherein the second metalens includes a negative optical power lens configured to diverge a beam of light from the light source.

[0068] Example 9: The lidar system of any one of examples 5-7, wherein the second metalens includes a positive optical power lens configured to converge a beam of light from the light source.

[0069] Example 10: A light detection and ranging (lidar) camera including: a sensor including a plurality of photodetectors; and a metalens configured to focus light onto the plurality of photodetectors of the sensor, wherein the metalens comprises a plurality of subwavelength structures disposed on a curved surface of a substrate.

[0070] Example 11 : The lidar camera of example 10, wherein the metalens includes a plurality of subwavelength structures disposed on the curved surface without an intervening substrate.

[0071] Example 12: The lidar camera of example 11, wherein the metalens is configured to direct light from a light source to illuminate a target.

[0072] Example 13: The lidar camera of any one of examples 10-12, wherein the curved surface includes a convex surface.

[0073] Example 14: The lidar camera of any one of examples 10-13, wherein the metalens includes a first metalens, the lidar camera further including a second metalens configured to direct light from a light source to illuminate a target.

[0074] Example 15: The lidar camera of example 14, wherein the second metalens includes a plurality of subwavelength structures disposed on a substrate surface, wherein the substrate is separated from the sensor. [0075] Example 16: The lidar camera of example 15, wherein the substrate surface includes a curved surface.

[0076] Example 17: The lidar camera of any one of examples 14-16, wherein the second metalens includes a negative power lens configured to diverge a beam of light from the light source.

[0077] Example 18: The lidar camera of any one of examples 14-16, wherein the second metalens includes a positive power lens configured to converge a beam of light from the light source.

[0078] Example 19: A method of making a light detection and ranging (lidar) camera, the method including: forming a plurality of subwavelength structures; and disposing the plurality of subwavelength structures onto a surface of a sensor including a plurality of photodetectors, wherein the plurality of subwavelength structures are configured to focus light onto the plurality of photodetectors.

[0079] Example 20: The method of example 19, wherein forming the plurality of subwavelength structures includes dry etching the plurality of subwavelength structures directly into the surface of the sensor.

[0080] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented within one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic QRS circuitry, as well as any combinations of such components, embodied in external devices. The terms “processor” and “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry, and alone or in combination with other digital or analog circuitry.

[0081] For aspects implemented in software, at least some of the functionality ascribed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium such as RAM, DRAM, SRAM, magnetic discs, optical discs, flash memories, or forms of EPROM or EEPROM. The instructions may be executed to support one or more aspects of the functionality described in this disclosure.

[0082] In addition, in some respects, the functionality described herein may be provided within dedicated hardware and/or software modules. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components or integrated within common or separate hardware or software components. Also, the techniques may be fully implemented in one or more circuits or logic elements.

Claims

CLAIMS What is claimed is:

1. A light detection and ranging (lidar) system comprising: a sensor comprising a plurality of photodetectors; and a metalens configured to focus light onto the plurality of photodetectors of the sensor, wherein the metalens is disposed on a sensor surface.

2. The lidar system of claim 1, wherein the metalens comprises a plurality of subwavelength structures disposed on the sensor surface without an intervening substrate.

3. The lidar system of claim 1 or claim 2, wherein the metalens is configured to direct light from a light source to illuminate a target.

4. The lidar system of any one of claims 1-3, wherein the sensor surface comprises a curved surface.

5. The lidar system of any one of claims 1-4, wherein the metalens comprises a first metalens, the lidar system further comprising a second metalens configured to direct light from a light source to illuminate a target.

6. The lidar system of claim 5, wherein the second metalens comprises a plurality of subwavelength structures disposed on a substrate surface, wherein the substrate is separated from the sensor.

7. The lidar system of claim 6, wherein the substrate surface comprises a curved surface.

8. The lidar system of any one of claims 5-7, wherein the second metalens comprises a negative optical power lens configured to diverge a beam of light from the light source.

9. The lidar system of any one of claims 5-7, wherein the second metalens comprises a positive optical power lens configured to converge a beam of light from the light source.

10. A light detection and ranging (lidar) camera comprising: a sensor comprising a plurality of photodetectors; and a metalens configured to focus light onto the plurality of photodetectors of the sensor, wherein the metalens comprises a plurality of subwavelength structures disposed on a curved surface of a substrate.

11. The lidar camera of claim 10, wherein the metalens comprises a plurality of subwavelength structures disposed on the curved surface without an intervening substrate.

12. The lidar camera of claim 11, wherein the metalens is configured to direct light from a light source to illuminate a target.

13. The lidar camera of any one of claims 10-12, wherein the curved surface comprises a convex surface.

14. The lidar camera of any one of claims 10-13, wherein the metalens comprises a first metalens, the lidar camera further comprising a second metalens configured to direct light from a light source to illuminate a target.

15. The lidar camera of claim 14, wherein the second metalens comprises a plurality of subwavelength structures disposed on a substrate surface, wherein the substrate is separated from the sensor.

16. The lidar camera of claim 15, wherein the substrate surface comprises a curved surface.

17. The lidar camera of any one of claims 14-16, wherein the second metalens comprises a negative power lens configured to diverge a beam of light from the light source.

18. The lidar camera of any one of claims 14-16, wherein the second metalens comprises a positive power lens configured to converge a beam of light from the light source.

19. A method of making a light detection and ranging (lidar) camera, the method comprising: forming a plurality of subwavelength structures; and disposing the plurality of subwavelength structures onto a surface of a sensor comprising a plurality of photodetectors, wherein the plurality of subwavelength structures are configured to focus light onto the plurality of photodetectors.

20. The method of claim 19, wherein forming the plurality of subwavelength structures comprises dry etching the plurality of subwavelength structures directly into the surface of the sensor.