Ultra-wide field-of-view planar optics

Abstract

Wide angle optical functions are beneficial for imaging and image projection devices. Conventionally, wide-angle operation is achieved through complex assembly of optical elements. The recent progress has achieved metasurface lenses or superlenses, which are ultra-thin planar lenses with nano-antennas that control the phase, amplitude and / or polarization of the light. Herein, we present a method that can be used in the gt, which is unprecedented; the invention relates to a super lens for realizing diffraction limited focusing and imaging on a 170-degree field of view (FOV). The lens is integrated on a single piece flat substrate and includes an aperture on one side and a single metasurface on the other side. The metasurface corrects third order Seidel aberrations, including coma, astigmatism, and image field curvature. The superlens has a planar focal plane, which enables the system architecture for imaging and projection to be greatly simplified. The super-lens design is universal and can easily adapt to different super-atom geometrical shapes and wavelength ranges to meet diversified application requirements.

Description

[0001] This invention application is a divisional application based on a patent application with an application date of June 8, 2020, application number 2020800562680, and invention name “Ultra-wide field of view planar optical device”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of priority under 35 USC §119(e) to U.S. Application No. 62 / 897,452, filed on September 9, 2019, and U.S. Application No. 62 / 884,645, filed on August 8, 2019, each of which is incorporated herein by reference in its entirety.

[0004] Government support

[0005] This invention was made with government support under Grant No. HR0011-1-72-0029 awarded by the Defense Advanced Research Projects Agency (DARPA). The government has certain rights in this invention. Background Art

[0006] Wide-angle optical systems are essential for high-performance imaging, detection, and image or beam projection. One of the earliest examples of wide-angle optical systems is the panoramic camera invented by Thomas Sutton in 1858. This panoramic camera consisted of a single water-filled spherical lens that produced an image on a curved glass plate covered with a reactive emulsion. This approach was soon abandoned due to the obvious difficulties in manufacturing and handling the curved plate, but revealed the fundamental challenges in achieving wide-field imaging. Since then, panoramic photography has continued along the path of flat detector planes while relying on composite lens assemblies, commonly called fisheye lenses, to reduce optical aberrations at large field angles. However, this multi-lens architecture increases the size, weight, and assembly complexity of the optical system.

[0007] Metasurface lenses, or metalenses, are devices that are able to control the phase, amplitude, and / or polarization of propagating light using arrays of subwavelength structures. Metalenses present a promising solution to achieve flat and compact individual optical components. Metalenses designs have been implemented to mitigate several types of aberrations, particularly spherical and chromatic aberrations. However, designing metalenses without angle-dependent coma, field curvature, and astigmatism remains challenging. These aberrations limit the usefulness of single-element metalenses.

[0008] The mainstream approach for designing single-element metalenses utilizes a hyperbolic phase profile to achieve a spherical wavefront:

[0009]

[0010] where λ is the wavelength of the incident light, x and y are the coordinates of the metaatom, and f is the focal length of the metalens. This phase profile produces zero spherical aberration at the focal plane for a plane wavefront at normal incidence, but is not optimal for oblique incident beams. in_x ,θ in_y ) is incident on the metasurface, the required phase profile becomes:

[0011]

[0012] The deviation between the two distributions at different angles of incidence (AOI) leads to third-order (Seidel) aberrations, such as coma, astigmatism, and field curvature. These aberrations limit the field of view of the metalens. For example, assuming a baseline metalens design with a 1 mm diameter and a 2 mm focal length, operating at a wavelength of 5.2 μm, the conventional hyperbolic phase profile effectively suppresses spherical aberration and achieves diffraction-limited focusing with a unity Strehl ratio at normal incidence. However, at AOIs greater than about 7°, coma becomes dominant, reducing the Strehl ratio to below 0.8 and rapidly degrading the performance of the metalens from the diffraction limit. The small viewing angle significantly limits the use of a single metalens in imaging and image projection.

[0013] Several metalens designs have been implemented to suppress coma and expand the diffraction-limited FOV. One approach involves carving a metasurface on a spherical surface, but this is challenging. Another approach involves cascading multiple metasurfaces based on traditional bulk optical system design principles. In this doublet metalens design, the focusing function is primarily performed by one doublet metasurface, while the other metasurface is used to correct off-axis aberrations. This type of doublet can achieve a diffraction-limited FOV of up to approximately 56°. In contrast, the FOV of conventional single-layer metalenses is typically limited to approximately 30°, with a large diffraction-limited spot size due to vignetting, low optical efficiency of 6–20%, and sensitivity to assembly misalignment. To date, metalenses with wide-angle performance comparable to their traditional refractive counterparts have not been achieved. Summary of the invention

[0014] Here, we present a metalens that can perform diffraction-limited imaging or beam / image projection over an extremely wide field of view (WFOV) of, for example, 120°, 130°, 140°, 150°, 160°, 170°, or even close to 180°. The exemplary metalens is monolithically integrated on a single flat substrate and includes an aperture on one side and a single metasurface on the other side. The metasurface corrects one or more third-order Seidel aberrations, including coma, astigmatism, and field curvature. Other features of the metalens are a flat focal plane, which enables a significant simplification of the system architecture. Such a metalens can be used for imaging, imaging / pattern projection, display, augmented reality (AR), virtual reality (VR), three-dimensional (3D) sensing, holography, LIDAR, Fourier transform optics, etc. The metalens can be easily adapted to different subwavelength structures and diffractive optical elements (DOEs) and wavelength ranges to meet diverse application requirements.

[0015] The metasurface on the metalens of the present invention may include an array of optically thin (e.g., 0.1 wavelength to 10 wavelengths thick), sub-wavelength arrays of nanoantennae (also called meta-atoms) that can provide arbitrary control of the phase, amplitude, and / or polarization of the incident light wavefront. For imaging applications, the on-demand wavefront manipulation method allows the use of far fewer lenses and other optical elements to eliminate image aberrations. As a result, optical systems based on the metalens of the present invention can have significant size, weight, performance, and cost (SWaP-C) advantages compared to systems made of traditional optical components.

[0016] The optical component of the present invention may include a (transparent) substrate, an opaque layer on a first side of the substrate, and a metasurface on a second side of the substrate opposite the first side. The opaque layer defines an aperture to transmit light over a field of view of at least 120° (e.g., 130°, 140°, 150°, 160°, 170° or more). And the metasurface focuses the light transmitted through the substrate by the aperture.

[0017] The substrate may be planar or curved, with a thickness t sub and the refractive index n at the wavelength of light sub The orifice may have a diameter D in , in this case, the metasurface has a diameter D meta =D in +t sub tan[sin -1 (1 / n sub )].

[0018] The metasurface can be configured to focus light incident on the entire field of view to a focal plane parallel to the second side of the substrate. In this case, the optical component can also include a detector array in the focal plane to detect light focused by the metasurface or a light source array in the focal plane, in which case the metasurface can collimate or focus a light beam emitted by the light source array. The aperture can be configured to emit such a collimated or focused light beam.

[0019] The metasurface can focus light incident on the entire field of view with a Strehl ratio of at least 80%. It can include an array of at least 1000×1000 metaatoms. It can have different but continuous sections configured to capture input beams at different angles of incidence. And it can correct at least one third-order Seidel aberration.

[0020] The optical component may also include a second metasurface disposed in at least a portion of the aperture to filter or modulate the light transmitted by the aperture. For example, the second metasurface may be configured to filter the light transmitted by the aperture or modulate the phase, amplitude, polarization and / or wavelength of the light transmitted by the aperture. The second metasurface may be configured to generate a 2D or 3D optical pattern, image, dot array, hologram, etc. The modulation imparted by the second metasurface may depend on the characteristics of the incident light beam (e.g., angle, space, polarization, spectral characteristics, etc.). The second metasurface may also be configured to, for example, change the polarization of the light transmitted by the aperture or the wavelength of the light transmitted by the aperture using a nonlinear effect. Illumination patterns with customizable or reconfigurable spatial, angular, polarization and / or spectral characteristics may be combined with object reconstruction algorithms associated with such patterns to effectively extract the characteristics of the scene.

[0021] The metalenses of the present invention can be used in sensors and other devices. For example, the sensor of the present invention may include a substrate, an array of light sources supported by a first portion of the substrate, a first metalens, a second metalens, and a detector array supported by a second portion of the substrate. The first metalens and the second metalens include corresponding planar substrates (or corresponding portions of the same planar substrate). Each metalens has a corresponding metasurface on a first side of its planar substrate (portion) and a corresponding aperture on a second side of its planar substrate (portion) facing the object. In operation, the array of light sources emits light, which is projected toward the object by the first metalens over a field of view of at least about 120° (e.g., 130°, 140°, 150°, 160°, 170°, or more). The second metalens collects light scattered and / or reflected by the object over a field of view of at least about 120° (e.g., 130°, 140°, 150°, 160°, 170°, or more). And the detector array detects the light collected by the second metalens.

[0022] All combinations of the foregoing concepts and additional concepts discussed in more detail below (provided that such concepts are not mutually inconsistent) are part of the inventive subject matter disclosed herein. Specifically, all combinations of the claimed subject matter appearing at the end of this disclosure are part of the inventive subject matter disclosed herein. Terms used herein that may also appear in any disclosure incorporated by reference should be given a meaning most consistent with the specific concepts disclosed herein.

[0023] The present invention comprises:

[0024] 1. An optical component, comprising:

[0025] substrate;

[0026] an opaque layer on the first side of the substrate, the opaque layer defining an aperture to transmit light over a field of view of at least 120°; and

[0027] A metasurface on a second side of the substrate opposite the first side to focus light transmitted through the substrate by the aperture.

[0028] 2. An optical component according to item 1, wherein the substrate is planar.

[0029] 3. An optical component according to item 1, wherein the substrate is curved.

[0030] 4. The optical component according to item 1, wherein the substrate has a thickness t sub and the refractive index n at the wavelength of the light sub , the orifice has a diameter D in , and the metasurface has a diameter D meta =D in +t sub tan[sin -1 (1 / n sub )].

[0031] 5. An optical component according to item 1, wherein the metasurface is configured to focus light incident on the entire field of view onto a focal plane parallel to the second side of the substrate.

[0032] 6. The optical component according to item 5, further comprising:

[0033] and a detector array in the focal plane to detect light focused by the metasurface.

[0034] 7. The optical component according to item 5, further comprising:

[0035] an array of light sources in the focal plane, and

[0036] Wherein, the metasurface is configured to collimate light beams emitted by the light source array, and the aperture is configured to emit the light beams.

[0037] 8. An optical component according to item 7, wherein the metasurface and / or the aperture are further configured to modulate the light beam emitted by the light source array.

[0038] 9. An optical component according to claim 1, wherein the metasurface is configured to focus light incident on the entire field of view with a Strehl ratio of at least 80%.

[0039] 10. An optical component according to item 1, wherein the metasurface comprises an array of at least 1000×1000 metaatoms.

[0040] 11. An optical component according to item 1, wherein the metasurface has different but continuous portions, and the different but continuous portions are configured to capture input light beams with different incident angles.

[0041] 12. An optical component according to item 1, wherein the metasurface is configured to correct at least one third-order Seidel aberration.

[0042] 13. An optical component according to item 1, wherein the metasurface is a first metasurface, and the optical component further comprises:

[0043] A second metasurface is disposed in at least a portion of the aperture to modulate and / or filter light transmitted by the aperture.

[0044] 14. An optical component according to item 13, wherein the second metasurface is configured to modulate the light transmitted by the aperture using a spatial modulation pattern that depends on the incident angle of the light transmitted by the aperture.

[0045] 15. A method comprising:

[0046] transmitting light through an aperture formed on a first side of the substrate over a field of view of at least 120°; and

[0047] The light is focused using a metasurface on a second side of the substrate opposite the first side.

[0048] 16. A method according to item 15, wherein focusing the light comprises focusing the light incident on the entire field of view to a focal plane parallel to the second side of the substrate.

[0049] 17. The method according to item 16, further comprising:

[0050] Light focused by the metasurface is detected using an array of detectors in the focal plane.

[0051] 18. The method according to item 16, further comprising:

[0052] collimating light beams emitted by an array of light sources in the focal plane using the metasurface; and

[0053] The light beam is emitted through the aperture.

[0054] 19. A method according to item 15, wherein focusing the light includes focusing the light incident on the entire field of view with a Strehl ratio of at least 80%.

[0055] 20. A method according to item 15, wherein focusing the light includes correcting at least one third-order Seidel aberration.

[0056] 21. The method according to item 15, further comprising:

[0057] Based on the incident angle of the light transmitted by the aperture, at least one of the phase, amplitude, polarization or wavelength of the light transmitted by the aperture is modulated using another metasurface disposed in at least a portion of the aperture.

[0058] 22. The method according to item 15, further comprising:

[0059] Light transmitted by the aperture is filtered using another metasurface disposed in at least a portion of the aperture.

[0060] 23. A sensor comprising:

[0061] substrate;

[0062] an array of light sources supported by the first portion of the substrate to emit light;

[0063] a first metalens in optical communication with the array of light sources to project light emitted by the array of light sources toward an object over a field of view of at least about 120°, the first metalens comprising a first planar substrate having a first metasurface on a first side facing the array of light sources and a first aperture on a second side;

[0064] a second metalens in optical communication with the object to collect light scattered and / or reflected by the object over a field of view of at least about 120°, the second metalens comprising a second planar substrate having a second aperture on a first side facing the object and a second metasurface on a second side; and

[0065] A detector array is supported by the second portion of the substrate and is in optical communication with the second metalens to detect light collected by the second metalens. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The skilled artisan will appreciate that the drawings are primarily for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily drawn to scale; in some cases, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate understanding of different features. In the drawings, similar reference characters generally refer to similar features (e.g., functionally and / or structurally similar elements).

[0067] Figure 1A and 1B A perspective view and a profile view of the WFOV metalens are shown, respectively.

[0068] Figure 2A A perspective view of a rectangular meta-atom used for a WFOV metalens is shown.

[0069] Figure 2B A perspective view of an H-shaped metaatom used for a WFOV metalens is shown.

[0070] Figure 2C Plot of the transmittance and phase shift at normal incidence for a WFOV metalens made from eight different PbTe metaatoms, each with a thickness of 650 nm and a lattice constant P of 2.5 μm along the x- and y-axes. (The metaatoms are shown below this plot.)

[0071] Figure 2D is a plot of the angle-dependent phase retardation imparted by the metaatom: The metaatom is designed to be nearly insensitive to the angle of incidence. The angle of 45.6° coincides with the angle of total internal reflection at the interface between air and calcium fluoride. The incident light is TM polarized.

[0072] Figure 2E is a diagram of the metalens phase distribution, where the black dashed circle at the center of the diagram indicates the location of the aperture on the opposite side of the substrate.

[0073] Figure 2F is a graph of the simulated cross-sectional intensity distribution of the focal spot of the WFOV metalens at different angles of incidence (AOI) and the focal spot formed by a perfect lens with the same numerical aperture (NA) as the simulated WFOV metalens.

[0074] Figure 3 is a plot of the phase profile of the WFOV metalens at y = 0. The 2D phase plot is rotationally symmetric.

[0075] Figure 4 is a plot of the angle-dependent phase profile of the central 1 mm diameter region of the WFOV metasurface.

[0076] Figure 5AAn H-shaped metaatom with linearly polarized light incident along the yz plane is shown.

[0077] Figure 5B An H-shaped superatom is shown with linearly polarized light incident along the 45° plane.

[0078] Figure 5C An H-shaped metaatom is shown for linearly polarized light incident along the xz plane (TM polarized light).

[0079] Figure 5D –5F shows the Figure 5A – Angular responses of metaatoms with different linear polarizations in 5C.

[0080] Fig. 6A An outline of a WFOV metalens designed to operate at a wavelength of 940 nm is shown. The inset shows the metaatom configuration.

[0081] Figure 6B Shows the following Fig. 6A Simulation of the Strehl ratio (right axis) and focusing efficiency (left axis) of the WFOV metalens as the incident angle varies.

[0082] Figure 6C Shows Fig. 6A Simulated modulation transfer function (MTF) of the WFOV metalens and a perfect lens with the same NA at different AOIs.

[0083] Fig.6D Shows Fig. 6A The focal spot of the WFOV metalens at different AOIs.

[0084] Fig. 7A An imaging simulation setup is shown, where the source image is positioned at an infinite distance from the WFOV metalens (not drawn to scale).

[0085] Figure 7B Shown for Fig. 7A Monochrome source image of the imaging simulation setup covering 180° horizontal FOV.

[0086] Figure 7C Shows Fig. 7A A simulated panoramic image formed by the WFOV metalens in the imaging simulation setup.

[0087] Figure 8 A photograph (lower left) and scanning electron microscope (SEM) images (upper left and right) of the fabricated metalens sample are shown.

[0088] Fig. 9 A is a schematic diagram of the experimental setup used to image the focal spot produced by the WFOV metalens at various incident angles.

[0089] Fig. 9 B–9G shows the Fig. 9 Intensity images of the focal spot of the WFOV metalens taken by the FPA camera in the setup of A at 0° (9B), 10° (9C), 30° (9D), 50° (9E), 70° (9F), and 85° (9G).

[0090] Fig. 9 H is a plot of Strehl ratio versus incident angle for the WFOV metalens. The inset shows the focal spot cross-section at 0°, 70°, and 85° incident angles for measured data (solid line) and theoretical results for an aberration-free lens with the same NA (dashed line).

[0091] Fig. 9 I is a plot of the measured WFOV metalens focusing efficiency versus incident angle.

[0092] Fig. 10A Schematic diagram of the imaging setup of the WFOV metalens, where the object is illuminated by a laser beam. A pair of single-side polished silicon wafers in the optical path reduces the spatial coherence of the illumination, thereby reducing speckle. Light scattered by the object is collected by the metalens and redirected to the FPA camera with an attached composite lens.

[0093] Fig. 10B Shown in Fig. 10A Projected images of a 1951 USAF resolution test target with a line width of 15.6 μm at different angles measured in the setup.

[0094] Fig.11A and 11B Shown is structured light-based 3D sensing using a WFOV superlens.

[0095] Fig.12 An ultra-compact superdisplay of WFOV is shown.

[0096] Fig.13A and 13B A profile view of a WFOV metalens is shown with a second metasurface in or defining at least a portion of an aperture. DETAILED DESCRIPTION

[0097] The wide field of view (WFOV) metalens of the present invention has a simple and easy-to-manufacture construction, in which a single metasurface layer and an aperture are integrated on opposite sides of a single thin substrate. It can have a diffraction-limited FOV of more than 170° and a flat focal plane, which greatly simplifies the associated detector (for imaging and detection) or light emitter (for image / beam projection, display, etc.) array design. It can operate at a wide range of wavelengths (e.g., from visible light to infrared (IR)), depending on the design of the metasurface and the materials of the substrate and metasurface. The metasurface can be designed to operate at any wavelength from microwave to ultraviolet (UV) regions of the electromagnetic spectrum, with bandwidths spanning up to an octave.

[0098] Furthermore, the WFOV metalens design principles disclosed herein are general and applicable to arbitrary meta-atom configurations and wavelength ranges to meet a variety of application requirements. With appropriate metasurfaces, the metalens can be panoramic metalens with broadband operation and polarization diversity. As another example, nanorods or nanopillars can be used for polarization-insensitive designs. A variety of metasurface material systems can be selected for the desired wavelength range, including, for example, PbTe and CaF 2 , as well as a-Si and Al 2 O 3 .

[0099] WFOV metalenses can be realized using Huygens meta-surfaces with ultrathin metaatom profiles. Huygens metasurfaces can be easily fabricated, but can constrain sensitivity to wavelength and polarization. In any case, the WFOV design described herein is general and applicable to arbitrary metaatom configurations. By appropriately selecting metaatoms, metalenses can perform panoramic imaging (e.g., FOV exceeding 170°) over broadband with polarization diversity.

[0100] Due to its extremely WFOV, planar surface, and flat focal plane, the metalens of the present invention are particularly suitable for sensing, image projection, lidar, imaging, optical projection, augmented reality / virtual reality, beam steering, and 3D sensing applications. For example, the beam projection function of the device of the present invention can be used in lidar systems when the light emitters are modulated or turned on and off one by one to steer, switch, or tune the output beam for wide-angle illumination. The same WFOV metalens can be used in detection modules for wide-angle signal collection.

[0101] Wide Field of View (WFOV) Metalenses

[0102] Figure 1A and 1B1 and 2 are perspective and profile views of an exemplary WFOV metalens 100, respectively. Metalens 100 includes a single substrate 110 having an input aperture 130 positioned on one surface 112 and a metasurface 120 positioned on another surface 114. Substrate 110 has a refractive index n sub and thickness t sub . At different incident angles θ in The incident beam has a diameter of D in The light beam at the input aperture 130 is refracted into a beam having a total diameter D meta of the back side metasurface 120 and is focused onto the planar focal plane 141.

[0103] The substrate 110 may be made of any suitable material that transmits light at the operating wavelength of the metalens. The substrate 110 may be rigid, flexible, or stretchable. Depending on the application, the substrate may be flat / planar on both sides, such as Figure 1A and 1B Suitable substrate materials include, but are not limited to, halide crystals, sapphire and other oxide crystals, quartz, chalcogenide crystals, glasses (e.g., oxides, chalcogenides, and other types of glasses), plastics, or semiconductor materials.

[0104] The metasurface 120 includes an array of subwavelength optical structures (also referred to as meta-atoms; as described and shown below) that change the amplitude, phase and / or polarization of an incoming wavefront. These meta-atoms can have the same or different shapes, sizes, and orientations. For example, they can be rectangular, cylindrical, H-shaped, or L-shaped. They are arranged on a lattice with a spacing less than or equal to the operating wavelength of the metalens 100. The lattice can have any suitable period and shape (e.g., square, rectangular, or hexagonal). The lattice can also be non-periodic, for example, having a spacing defined by the gaps between adjacent meta-atoms (e.g., a constant gap distance), or having randomly positioned meta-atoms that are patterned to provide a desired phase profile across the metasurface 120.

[0105] The meta-atoms are made of a transparent material (e.g., the same material as substrate 110, where the meta-atoms are formed by patterning one side of substrate 110). The shape, size, and layout of the meta-atoms can be selected so that the spectral response of the metasurface does not change with AOI—optical phase / amplitude changes imparted by the meta-atoms with varying AOI are automatically accounted for in its design. The metasurface 120 can also be designed for rotationally asymmetric focusing (e.g., focusing at some AOIs and not focusing at others).

[0106] (Alternatively, metasurface 120 may be replaced by a metamaterial, multilayer metasurface, or diffractive optical element (DOE) that provides the same or similar effective phase profile. For example, the DOE may be implemented as a binary or multi-level grayscale DOE with a feature size larger than the operating wavelength of the lens. Similarly, the entire lens architecture is applicable to a diffractive optical lens.)

[0107] The aperture stop 130 is defined by a layer 132 of opaque (e.g., absorbing or reflecting) material on the upper surface 112 of the substrate 110. The upper surface 112 may also define a metasurface (not shown) or be partially or completely covered with a metasurface that modulates the intensity and / or phase of the incident light to form an effective aperture stop. (Alternatively, such a metasurface may be replaced by a metamaterial, a multilayer metasurface, or a DOE.) The aperture stop 130 may be circular, with a diameter given by:

[0108] D in =D meta -2t sub tan[sin -1 (1 / n sub )]

[0109] The diameter can range from a few microns to a few millimeters, with a numerical aperture (NA) in the range of 0 to 1. If the metalens is immersed in oil or other high refractive index material, the numerical aperture can be higher (e.g., 1.5).

[0110] The aperture may also be square, elliptical, hexagonal, rectangular, or any other suitable shape. Alternatively, the aperture may include one or more sub-regions, patches, or arrays configured to modulate or encode the input light in terms of spectrum, phase, amplitude, polarization, etc. For example, at least a portion of the aperture 130 may be patterned with another metasurface 134 that filters light passing through the aperture 130. If desired, the edges of the aperture stop 130 may be apodized, for example, with Gaussian or super-Gaussian apodization, to reduce deleterious edge effects.

[0111] By spatially decoupling the metasurface 120 and the aperture stop 130 while positioning them on the same substrate, for example, by optimizing for a quality factor that considers the focus quality at multiple AOIs, the metalens 100 can capture input beams of different angles of incidence (AOIs) on different but continuous portions of the metasurface 120, thereby facilitating local optimization of the phase profile. The metasurface phase profile is designed such that the root mean square (RMS) wavefront error from an ideal spherical wavefront over the input aperture is always less than 0.0745 wavelengths. This ensures that the metalens 100 has a Strehl ratio of more than 80% over its entire field of view, which can be 120°, 130°, 140°, 150°, 160°, 170°, 175°, 179°, or nearly 180° for a flat substrate, thereby achieving diffraction-limited performance under a variety of light illumination conditions. For metalenses with curved, bent, or warped substrates, the field of view can even be greater than 180°. Similar to the case of a flat surface, incident light is refracted (or diffracted using a metasurface) from the input aperture to the backside metasurface. Conventional fisheye lenses achieve FOV>180° using a roughly curved front lens.

[0112] The metalens 100 can operate at any of a variety of wavelengths, depending on its size, metasurface design, and substrate material. For example, a metalens 100 designed to operate at a wavelength of 5.2 μm may have a 2 mm thick calcium fluoride (CaF 2 ) Planar substrate 110 (at 5.2 μm, n sub =1.4), the planar substrate has a 1 mm diameter circular aperture 130 and a 5.2 mm×5.2 mm metasurface 120. The metasurface 120 may contain an array of 2,000×2,000 Huygens metaatoms made of PbTe with a square lattice constant of 2.5 μm. The metasurface 120 may have a constant focal length of 2 mm, corresponding to an effective numerical aperture (NA) of 0.24. At an angle of incidence close to 90°, the maximum angle of light propagation inside the substrate is 45.7°. As shown below, the phase response of the metaatoms that make up the metasurface 120 depends only weakly on the angle of incidence of the beam within the WFOV of the metalens.

[0113] The metalens 100 operates differently from metalens designed with separated angular channels, where non-overlapping regions on the metasurface are dedicated to beams at different AOIs. Due to its dedicated non-overlapping regions, metalens with separated angular channels can only achieve high quality focusing for a discrete set of incident angles. In the metalens 100 of the present invention, judiciously designed metasurface phase profiles and metalens architecture allow for diffraction-limited focusing of beams with continuously varying incident angles and overlapping beam profiles on the metasurface side 114 of the substrate 110. Therefore, the metalens 100 can achieve aberration-free beam focusing or beam collimation, and thus image projection of any light direction from or to any point on the front hemisphere.

[0114] In addition to correcting aberrations such as coma and astigmatism, metalens 100 also features a flat focal plane 141 across the entire FOV. Eliminating Petzval field curvature is beneficial in a wide range of applications including imaging and image projection by facilitating integration of standard planar detector or emitter arrays. For example, Figure 1B An array of light sources 140 in a focal plane 141 is shown for projecting a collimated light beam at different angles using a metalens. The light sources 140 in the array may be light emitting diodes (LEDs), lasers, or any other (apertured) light sources. The array of light sources 140 may include different light sources emitting at different wavelengths. Depending on the application, the light sources 140 may also include broadband or wavelength tunable light sources. (For imaging applications, the light sources 140 may be replaced by an array of planar detectors in the focal plane 141, such as a CMOS or CCD array.)

[0115] Metalens metasurface design and modeling

[0116] Metalenses can be designed using a hierarchical combination of full-wave simulations (such as the finite element method (FEM), the finite-difference time-domain (FDTD) method, and the finite integral technique (FIT)) and Kirchhoff diffraction integrals. At the subwavelength scale, full-wave simulations can be used to design and model meta-atoms in the metasurface to obtain the desired optical response. At the macroscopic system level, the diffraction integral method combined with full-wave simulation results enables computationally efficient verification of the focusing properties of the entire metalens and can be used to optimize the phase profile of the metasurface.

[0117] Figure 2A –2F shows the design and modeling of Huygens superatoms on a metasurface on one side of a metalens operating at a wavelength of 5.2 μm. Each Huygens superatom consists of Figure 2A and 2B The CaF 2Rectangular blocks or H-shaped blocks composed of PbTe on the substrate. 2 The combination of to take advantage of the low optical losses and huge refractive index contrast of these materials in the mid-IR spectral range enables the metasurface to operate in transmission mode while supporting electric dipole (ED) and magnetic dipole (MD) resonances. Their shape is designed to obtain spectrally overlapping ED and MD resonances at the operating wavelength, which is conducive to achieving full 360° (2π) phase coverage using the Kerker effect with near-unity transmittance. The metaatom library includes eight different metaatoms covering 360° phase space, with discrete steps of 45° for linear TM polarized light at a wavelength of 5.2μm.

[0118] Figure 2C The simulated amplitude and phase responses of each of the eight meta-atoms in the meta-atom library at normal incidence are shown. Figure 2C , and includes three H-shaped superatoms and five rectangular atoms. The superatom sizes are listed in Table 1 (below).

[0119] Table 1: Dimensions of meta-atoms used in meta-optical devices.

[0120]

[0121] Figure 2D The simulated phase shift of each metaatom under tilted AOI (inside the substrate) is shown. The incident light is TM polarized. The results show that the metaatom response depends only weakly on the angle of incidence, because the metaatoms are designed to be almost insensitive to the angle of incidence. The angle of 45.6° coincides with the angle of total internal reflection at the interface between air and calcium fluoride. This all-dielectric Huygens metasurface platform is the basis for the high performance of the WFOV metalens.

[0122] Figure 2E The phase distribution of a metalens with a 2000×2000 array of meta-atoms for a metasurface is shown. The black dashed circle at the center of the figure indicates the location of the aperture on the side of the substrate opposite the metasurface.

[0123] Figure 2FThe simulated cross-sectional intensity distribution of the focal spot at different AOIs and the focal spot formed by a perfect lens with the same NA is shown. The intensity distribution is asymmetric due to the tilted AOI. The peak amplitude decreases with increasing AOI, and more and more light appears in the side lobes. At all AOI values ​​(Equation 2), the RMS phase error is always less than 0.0745 wavelengths compared to the ideal phase profile, ensuring a Strehl ratio better than 0.8. Therefore, when compared to a perfect lens with the same NA and focal length, this metalens design achieves diffraction-limited focusing and imaging performance over the entire FOV. The modulation transfer function (MTF) of the simulated focal spot in Figure 6 further supports this conclusion.

[0124] Figure 2A The metaatom simulations shown in Figure 2F were performed using the frequency domain solver in the commercial software package CST Microwave Studio. For each metaatom, unit cell boundary conditions were used in the negative and positive x and y directions, while open boundary conditions were set along the z axis. Each metaatom was illuminated from the substrate side with an x-polarized plane wave pointing in the positive z direction. Figure 2C The results shown in are the phase and amplitude of the complex transmission coefficient derived between two open ports located at the top and bottom of each meta-atom.

[0125] The focusing and imaging behavior of the WFOV metalens is modeled in terms of the Kirchhoff diffraction integral, a physically rigorous form of the Huygens–Fresnel principle. The model starts with the computation of the Huygens point spread function of the optical system. It incorporates the angle-dependent phase profile at the metasurface and propagates the wavefront emitted from each metaatom with corresponding amplitude and phase to the image plane, where its complex amplitude is derived. The diffraction of the wavefront through space is given by the interference or coherence sum of the wavefronts from the Huygens sources. The intensity at each point on the image plane is the square of the resulting complex amplitude sum.

[0126] Can be used (Zemax, LLC) designs the initial optical structure and phase profile of the metalens. An analytical model based on the Kirchhoff diffraction integral can then be used to analyze the overall metasurface performance at different AOIs. The analytical model incorporates an angle-dependent phase mask that follows the response of each metaatom at different AOIs obtained from full-wave simulations (e.g., as in Figure 5A –5F, as described below). The phase profile optimization process involves Iterative evaluation of the focus quality between the Kirchhoff diffraction integral model, i.e., the Strehl ratio (SR AOI(i) ). Numerical optimization is used to maximize the following quality function (figure of merit, FOM):

[0127]

[0128] where w AOI(i) The weighting factors at different AOIs are given. This form of FOM examines multiple beams over the entire FOV simultaneously. For the exemplary design, an initial angular spacing of ΔAOI=5° between adjacent beams is sufficient to sample the entire FOV continuously. Figure 2E The optimized metalens phase profile is shown in Figure 2. At all AOI values, the designed phase profile results in a Strehl ratio better than 0.8 compared to the ideal phase profile. Therefore, the metalens achieves diffraction-limited focusing and imaging performance over the entire FOV when compared to a perfect lens with the same NA and focal length, as shown in Figure 2. Figure 2F shown.

[0129] The commercial optical design software Zemax OpticStudio can be used to obtain the initial phase profile of the metasurface under ideal conditions. The rotationally symmetric phase profile is expressed in polynomial form:

[0130]

[0131] where φ(ρ) is the expected phase response of a particular metaatom, a n is the aspheric coefficient, and R is the normalized radius. Tables 1 and 2 (below) show the normalized radius and aspheric coefficient for example mid-IR and NIR WFOV metalenses, respectively:

[0132] Table 1: Phase profile design coefficients for mid-IR WFOV metalens

[0133]

[0134] Table 2: Phase profile design coefficients for NIR WFOV metalens

[0135]

[0136] The optimization starts with a standard hyperbolic phase profile that meets the optical system specifications (e.g., focal length and f / #) within a small AOI range as the initial input. Once the initial optimization cycle converges for the starting AOI range, the results are used as input for the next optimization iteration cycle with an expanded AOI range. The process continues until the final results converge on the target AOI range (e.g., ±90°).

[0137] More specifically, numerical optimization using the Levenberg–Marquardt algorithm (also known as damped least squares) is implemented to maximize the quality function (e.g., the FOM defined above) in each optimization cycle. Kirchhoff diffraction integrals are used to numerically calculate the Strehl ratio as well as the FOM for each field angle. The angle-dependent response of each superatom is also incorporated to generate an angle-dependent phase mask after spatial and phase discretization / mapping of the initial phase profile. In each optimization cycle, a FOM with equal weights for all AOIs in the range is initially used and maximized. At certain field angles, maximizing this equally weighted FOM can sometimes result in a Strehl ratio less than 0.8. In this case, the optimization is repeated with the adjusted weighting factors until the Strehl ratio is above 0.8 for all AOIs in the target range. The values ​​obtained using the procedure are shown in Table 1. Figure 3 The final phase profile shown in achieves diffraction-limited focusing performance for continuously varying incident angles up to ±90°. The phase profile design coefficients are summarized in Table 1. Figure 4 The angle-dependent phase profile based on the phase shift of individual meta-atoms in the central 1 mm diameter region of the metasurface is shown.

[0138] Figure 5A –5F shows the angular response of the metaatom to different linear polarizations under oblique incidence. Figure 5A –5C shows different linear polarization orientations about the H-shaped superatom, where Figure 5A shows the yz polarization, Figure 5B shows a 45° rotation between yz and xz, and Figure 5C The xz (TM) polarization is shown. The electric field y component is equal to zero. Figure 5D –5F shows the angular response of the metaatom as a function of angular incidence for each of these polarization states.

[0139] Fig. 6A 6D shows a WFOV metalens 600 designed to operate at a wavelength of 940 nm and its performance. The WFOV metalens 600 includes a planar sapphire substrate with a thickness of 3.9 mm, a circular aperture 630 with a diameter of 1 mm on one side, and a metasurface 620 on the other side. The metasurface 620 includes an array of amorphous silicon pillars 622 as meta-atoms and focuses light to a planar focal plane 2.5 mm away from the metasurface 620.

[0140] Figure 6B The simulated Strehl ratio (right axis) and focusing efficiency (left axis) are shown as a function of the target half-angle of WFOV metalens 600. The Strehl ratio is always above 0.8, indicating diffraction limited focusing over the entire FOV of about 180°. Figure 6CThe simulated modulation transfer function (MTF) of the WFOV metalens 600 at different AOIs and different planes of incidence is shown, along with the MTF of a diffraction-limited lens with the same NA. The MTF indicates that the WFOV metalens 600 has a diffraction-limited focal spot at different AOIs.

[0141] Fig. 7A –7C shows simulated panoramic imaging using the WFOV metalens. Fig. 7A An imaging simulation setup is shown, where the source image is positioned at an infinite distance from the metalens (not drawn to scale). Figure 7B A monochromatic source image (here of the Paris sky) covering a 180° horizontal FOV is shown. Figure 7C A simulated panoramic image formed by an ultra-wide FOV metalens is shown, which fully accounts for aberrations and diffraction effects. When used with an image sensor replaced by a microdisplay, the same meta-optical setup can be easily used to project images to the far field with an ultra-wide FOV.

[0142] WFOV metalens fabrication

[0143] Figure 8 The double resist lift-off method is shown in Figure 2. 2 A WFOV metalens fabricated using electron beam lithography on a planar substrate. The meta-atom in this WFOV metalens (shown at top left) is made of thermally evaporated nanocrystalline PbTe and has a uniform thickness of 650 nm. The front-side aperture is defined by a metallic tin layer using standard UV lithography.

[0144] More specifically, in a circular CaF 2 Fabricated on substrate (Edmund Optics) Figure 8 The metalens in the. Considering the symmetry of the metasurface layout, only a 2 mm × 3.6 mm metasurface segment was needed and fabricated to verify the WFOV performance. Prior to fabrication, the substrate surface was cleaned sequentially in acetone and isopropyl alcohol (IPA) ultrasonic treatment baths for 3 minutes each. Subsequently, the sample was baked at 190 ° C for 5 minutes to completely evaporate the solvent and adsorbed moisture on its surface. The substrate was then treated with oxygen plasma (150 W, 1 minute, pressure 0.8 Torr) to remove organic residual contaminants.

[0145] One side of the sample was covered with a double layer of photoresist consisting of PMGI (800 nm thick) and ZEP 520A (400 nm thick). The PMGI layer was spin coated at 2400 revolutions per minute (rpm) for 1 minute and then baked at 190°C for 3 minutes. The baking step is critical to ensure the mechanical stability of the PMGI layer. The ZEP layer was spin coated at 4000 rpm for 1 minute and baked at 190°C for 2 minutes. To prevent charging effects when performing electron beam (e-beam) lithography, the sample was covered with a water-soluble conductive polymer (ESpacer300Z, Showa Denko America, Inc.) and a conductive fixture was placed on top of the substrate.

[0146] At 125 kV, 10 μA and a base dose of 380 μC / cm 2 The metasurface patterns were written using an electron beam lithography system (Elionix ELS F-125) under proximity effect correction (PEC) Figure 8 , right). The ZEP layer was developed by immersing the sample in water, ZEDN50, and IPA for 1 minute each. The PMGI layer was then partially dissolved with RD6 developer diluted with water at a ratio of 1:1. This partial dissolution should be done carefully so that undercutting is achieved without destroying the pattern.

[0147] After the photoresist was developed, the etchants were deposited by thermal evaporation (custom designed system, PVD Products, Inc.) The rate and 10 -6 A 650 nm thick PbTe film was deposited at a base pressure of 1000 Å. Prior to deposition, the sample was pre-cleaned with oxygen plasma to improve film adhesion. Afterwards, the material on top of the photoresist was stripped by soaking in N-methyl-2-pyrrolidone (NMP) overnight to transfer the metasurface pattern.

[0148] The other side of the sample was patterned with a circular orifice of 1 mm in diameter. During orifice fabrication, the side patterned with the PbTe metasurface was protected by a dry film photoresist (DuPont MX5000 series). To make the orifice, the surface was cleaned with oxygen plasma, and a negative photoresist NR1000PY (Futurrex, Inc.) was spin-coated at 1500 rpm for 1 minute. The sample was then soft-baked at 115 ° C, exposed to UV light for 40 seconds through a mask, and hard-baked at 155 ° C. The exposed photoresist was then developed in RD6 for 10 seconds and then rinsed with water. A 200 nm tin layer was then deposited by thermal evaporation, and the tin layer was stripped by removing the photoresist with acetone. Finally, the dry film photoresist covering the metasurface side was removed by an overnight NMP treatment.

[0149] WFOV Metalens Characterization

[0150] Fig. 9 A-9I show experimental characterization of the focal spot quality of the WFOV metalens 700 in FIG. 7 at various AOIs. Fig. 9 A shows a measurement setup 900, where the WFOV metalens 700 is illuminated from the aperture side by a collimated linearly polarized laser beam from a 5.2 μm wavelength laser 910. The laser 910 is mounted on a circular track 912, allowing the AOI to be varied from 0° to 85°. The maximum AOI of 85° is limited by the geometric constraints of the experimental setup 900 rather than the lens performance. The focal spot image is magnified using a pair of mid-IR lenses 920 calibrated to 120 ± 3 magnification and projected onto a liquid nitrogen cooled InSb focal plane array (FPA) camera 930.

[0151] Fig. 9 B-9G show examples of focal spot images measured with the FPA camera 930 . Fig. 9 The inset of H shows the cross-sectional optical intensity profiles of the focal spot at 0°, 70°, and 85° incident angles, along with a simulated ideal focal spot profile from an aberration-free lens with the same NA for comparison. Fig. 9 H also shows the measured Strehl ratio. The Strehl ratio remains above 0.8 for all incident angles, indicating diffraction-limited focusing performance from metalens 700.

[0152] Fig. 9 I is a plot of the focusing efficiency of the metalens versus the AOI for linearly polarized light. The focusing efficiency is defined as the ratio between the power confined at the focal spot and the power incident on the metasurface of the metalens. Fig. 9 The data in Figure 1 show a relatively weak dependence on AOI, with the focusing efficiency varying from 45% to 32% as the AOI varies from 0° to 85°. This relatively flat angular response is a useful feature for providing nearly uniform illumination across the image formed by the metalens.

[0153] The power P focused by the superlens ms,foc (θ i ) can be expressed as the total incident power P transmitted through the front aperture (e.g., a 1 mm circular aperture) 0 、Superlens focusing efficiency f(θ i ) and considering the air and substrate (e.g., CaF 2 ) is the Fresnel transmission factor T of the reflection loss at the interface between p (θ i ) to express:

[0154] P ms,foc (θ i )=P 0 ·TP (θ i )f(θ i ). (3)

[0155] Total incident power P 0 It can be further written as P 0 =P 0 (0)·cos(θ i ), where P 0 (0) is based on normal incidence (θ i =0°). The cosine factor occurs because when the same collimated laser beam (with a beam diameter much larger than the aperture size) is incident on the metalens obliquely, the power density drops by cos(θ) due to the geometric projection. i ) multiples.

[0156] exist Fig. 9 In A–9I, the measured value is (θ i )—the ratio of the power focused by the superlens to the total transmitted power, P ms,trans (θ i ) — the power transmitted by the superlens, and P ref (θ i )—by reference sample (CaF with the same thickness and 1 mm aperture but without backside supersurface 2 The power transmitted by the substrate. According to these definitions:

[0157] η(θ i )=P ms,foc (θ i ) / P ms,trans (θ i ) (4)

[0158] P ref (θ i )=P 0 T P 2 (θ i )=P 0 (0)cos(θ i )T P 2 (θ i ) (5)

[0159] In equation (5), T p (θ i ) factor is squared, since there are two CaF 2 —air interface. Finally, the value of the focusing efficiency f(θ i ) is given by:

[0160]

[0161] Using a large area detector to measure P 0 , P ms,trans (θ i ) and P ref (θ i ) to capture all transmitted power. Then according to equation (5) from P 0 and P ref (θ i ) Calculate T p (θ i ). The transmitted power P incident on a detector integrated with a 200 μm diameter pinhole is measured. 孔 (θ i ) to quantify P ms,foc (θ i ). The FPA camera images the focal plane around the focal spot over an area of ​​200 μm in diameter. The optical intensity values ​​from the FPA camera are integrated pixel by pixel to obtain the ratio of the power concentrated at the focal spot to the total power transmitted through the pinhole, that is, P ms,foc (θ i ) / P 孔 (θ i ). 孔 (θ i )×P ms,foc (θ i ) / P 孔 (θ i ) Extract P ms,foc (θ i (Unfortunately, FPA cameras do not give optical power readings, but instead only specify relative optical intensity in counts.)

[0162] Imaging with WFOV Superlens

[0163] Fig. 10A and 10B The wide-angle imaging capability of WFOV metalens 700 is shown. Fig. 10AA measurement setup 1000 is shown, in which a laser 1010 illuminates an object 1014 through a diffuser 1012. A metalens 700 collects light scattered by the object 1014 and projects it onto an InSb FPA camera 1030 through a mid-IR lens 1020. In the experiment, the distance between the object 1014 and the metalens 700 was fixed to 2 mm to coincide with the planar geometry of the lens focal plane. The mid-IR lens 1020 and the camera 1030 were mounted on a semicircular track 1032 so that they could rotate about an axis extending through the metalens 700 and perpendicular to the optical axis of the metalens 700. The object 1014 consisted of a metallic tin pattern that replicated a USAF resolution test chart. The selected test target pattern (set 5, element 1) contained three stripes, each 15.6 μm wide, close to the ideal diffraction-limited resolution of the lens (13.2 μm).

[0164] Fig. 10B Shown in Fig. 10A Clearly resolved images of the patterns recorded over the full angular range of the experimental setup 1000. The angular range is from 0° to 82° and is defined by the geometrical constraints of the experimental setup 1000. Fig. 10B The images in confirm the diffraction-limited imaging performance of the metalens over an extremely wide angular range.

[0165] Beam / image projection

[0166] When the light emitter array is positioned at the focal plane, the WFOV metalens system can be used for beam or image projection with a large projection angle. Figure 1B In the present invention, for example, light emitted from each light source (pixel) in a light source array 140 (e.g., a micro-LED display) is collimated by a metasurface 120 on one side of a substrate 110 and directed toward an aperture 130 located on the other side of the substrate 110, and directed toward or projected in different directions. The output beam or image is coupled into another medium, such as free space, or into another optical element or waveguide structure. The phase profile of the metasurface is engineered so that diffraction-limited focusing or collimation performance can be achieved over a FOV of nearly 180° in air, which corresponds to a maximum refraction angle of about, for example, about 42° inside a substrate 110 having a refractive index of 1.5 at the operating wavelength. This is in stark contrast to existing meta-optical systems, which use multiple metasurfaces to maintain imaging quality at large angles of incidence.

[0167] WFOV metalens 100 may be used to project an array of light beams generated from emitter array 140 to a wide range of angles for applications such as 3D sensing, detection, ranging, communications, etc. WFOV metalens 100 may also be used to project an image generated from emitter array 140 (e.g., a microdisplay) to a wide range of angles for applications such as display, holography, AR / VR, etc. Some examples are explained below.

[0168] 3D Sensing Using WFOV Super Lenses

[0169] Existing 3D depth sensors based on structured light (SL), time of flight (TOF), or active stereo technology are limited by small FOV (typically less than 70°) and resolution is usually limited to about 1,000×1,000 resolvable spots or angles. A different but related technology is vision-based simultaneous localization and mapping (V-SLAM). Intel's RealSense TM The TrackingCamera T265 offers an impressive stitched FOV of up to 163° using V-SLAM, but it has two fisheye imaging units and suffers from lower resolution due to the lower imaging quality of fisheye lenses compared to standard camera optics, especially at large field angles.

[0170] Fig.11A and 11B A 3D sensor 1100 is shown with two WFOV metalenses 1112 and 1122. Such a 3D sensor 1100 exploits the ultra-wide FOV, diffraction-limited performance, flat focal plane, and simplicity of the WFOV metalenses 1112 and 1122 for 3D sensing applications such as optical touch interfaces, gesture control, facial recognition, object detection / tracking, 3D scanning, navigation, etc.

[0171] The 3D sensor 1100 includes a pattern projection module 1110 having a first WFOV metalens 1112 and an array of light emitters 1114 (e.g., an array of micro-LEDs or vertical cavity surface emitting lasers (VCSELs)), and a camera module 1120 having a second WFOV metalens 1122 and an array of light detectors 1124. (For stereoscopic sensing, the light emitter array 1114 can be replaced by a second array of light detectors, thereby turning the pattern projection module 1110 into another camera module.) The pattern projection module 1110 and the camera module 1120 are mounted on a substrate 1102, which can be a piece of flexible or rigid plastic, glass, or other suitable material. The entire sensor 1100 can be less than 7 mm thick (e.g., 3 mm or thinner) and can be manufactured using commercial light emitters and light detector arrays.

[0172] The pattern projection module 1110 projects a pattern (e.g., an array of dots or stripes) into free space with a large angular range 1111 (e.g., 120°, 130°, 140°, 150°, 160°, 170°, or greater) and onto an object 1101 (e.g., a hand or fingertip). The image of the object 1101 illuminated by the pattern projector 1110 is captured by the camera module 1120 over an equally wide and overlapping FOV 1121. A processor (not shown) coupled to the pattern projection module 1110 and the camera module 1120 analyzes the image captured by the camera module 1120 to generate 3D information about the object 1101.

[0173] The ultra-wide beam projection and detection angles 1111 and 1121 allow 3D sensing over a large spatial and angular range. The diffraction-limited performance of the metalenses 1112 and 1122 allows high-quality pattern generation and high-resolution imaging. The simple optical module configuration facilitates tight integration into mobile devices such as smartphones and tablets, and helps to withstand assembly misalignment. The field of view for structured light projection and imaging can approach 180° with diffraction-limited spatial resolution to provide accurate near-surface 3D sensing / imaging.

[0174] For example, using Fig. 6A The sensor 1100 with the NIR metalens 600 shown in FIG. 1 (operating at 940 nm with an aperture of 1 mm) can operate with an average angular resolution of 0.1° over the entire 180° FOV due to diffraction limited focusing / collimation. Thus, the sensor optics can support a resolution of approximately 1,800×1,800, representing a significant improvement over existing 3D sensors, with further performance improvements likely to be achieved simply by increasing the aperture.

[0175] Fig.11A and 11B The sensor 1100 in can have an ultra-compact low-profile thickness of less than 7 mm and is compatible with integration of micro-LED arrays (now available with <3 μm pitch, commensurate with the 2.9 μm diffraction-limited spatial resolution of the metalens) and imager sensors. While this sensor 1100 registers each unit pixel on the source array 1114 to a point in the far field, the front aperture of the first WFOV metalens 1112 can be coupled with another metasurface (e.g., a WFOV metalens 1112) engineered to further modify the emitted beam pattern (e.g., phase, amplitude, polarization) as well as the wavelength, polarization, and / or angle-dependent responses. Figure 1AThe second metasurface can be integrated with an optional metasurface 134 in the aperture. The other metasurface can be in or on the transparent portion aperture or another portion of the substrate and can further enhance the functionality of the metalens 1112 and increase the complexity and information density of the projected pattern over the 180° FOV. The second metasurface can be configured to filter or change the polarization of light transmitted by the aperture. Alternatively, the second metasurface can be configured to change the wavelength of light transmitted by the aperture, for example by a nonlinear effect induced in the metasurface.

[0176] The metasurface on the aperture side of the metalens 1112 can also "contain" the aperture by modulating the distribution of its phase, amplitude, spectral, and / or polarization response to form an effective aperture. For example, such an aperture-side metasurface can modulate the phase distribution of incident light so that light within the effective aperture region is transmitted or further modulated to propagate toward the backside metasurface, while incident light outside the aperture is scattered or deflected away from the area for WFOV imaging or sensing. The metasurface region outside the effective aperture can also be designed to have minimum transmitted power (e.g., by engineering the reflective or absorptive properties of the metasurface). The metasurface region outside the effective aperture can also be designed to have spectral or polarization filtering properties to block light with a specific wavelength or polarization.

[0177] 3D sensing using WFOV metalenses has many advantages over prior art 3D sensing: (1) it is universally applicable to SL, TOF, and active stereoscopic 3D depth sensing; (2) it simultaneously addresses the FOV limitations associated with both illumination and light receiving (camera) optics; (3) the diffraction-limited imaging and image projection capabilities of metasurface optics enable fine spatial resolution across the entire FOV without aberrations; (4) extremely high (e.g., near unity) optical efficiency can be achieved because the optics are designed to operate at a single NIR wavelength (e.g., for VCSEL illumination) or over a narrow band (e.g., for micro-LED array illumination); (5) ultra-compact form factor and minimal component count; and (6) meta-atoms can be locally configured to reject ambient light outside the operating wavelength as different parts of the metasurface interact with light at different AOIs. Unlike conventional optical filters, whose passbands spectrally shift with AOI and therefore cannot be used over a large angular range, the unique ultra-wide-angle optical filtering capabilities of metasurfaces can significantly improve signal-to-noise ratio (SNR) and dynamic range.

[0178] Fig.11A and 11BApplications of the high-resolution panoramic 3D sensor 1100 in the 1100 include consumer electronics, robotics, augmented / fused reality, automotive, and unmanned aerial vehicles (UAVs). For example, the wide sensing FOV enables near-surface gesture recognition and control using a single-point sensor, which is not possible with current 3D sensing methods. In augmented and virtual reality, fine sensor resolution and a large FOV (matching human vision) allow for fast and accurate reconstruction of the surrounding environment to create an immersive user experience.

[0179] WFOV Metalens for Augmented Reality (AR) and Virtual Reality (VR)

[0180] Microdisplays for augmented and virtual reality applications are attracting a lot of R&D efforts today due to their wide implementation space in next-generation display technologies. In terms of optical architecture, AR / VR displays can be divided into two main groups: bulk optics-based and waveguide-based systems. In recent years, waveguide-based systems have gained increasing attention due to their compact form factors and easy integration with glasses and other devices. State-of-the-art waveguide-based displays are still limited in terms of resolution and FOV. For example, the FOV of existing commercial waveguide AR / VR systems is typically less than 45°×45°, which is much smaller than the range of human vision. To improve display quality, conventional optical engines use complex multi-element optical systems, which increases system size and weight.

[0181] Fig.12 An AR / VR system 1200 is shown having an optical engine 1210 consisting of a micro-LED array 1212 and a high-resolution WFOV projection metalens 1214. The WFOV projection metalens 1214 is coupled to a waveguide 1230 via an optical coupling structure 1220, which is, for example, a 3D free-form coupling structure (such as in Fig.12 ), a sub-wavelength optical structure, or a diffractive optical element. The waveguide 1222 is also coupled to or includes a waveguide out-coupling structure 1224, such as another 3D free-form coupling structure, a sub-wavelength optical structure, or a diffractive optical element. The microdisplay 1212 emits a light beam, which is collimated by the WFOV metasurface projection optics 1214 and then coupled into the waveguide 1230 via the optical coupling structure 1220. The waveguide 1222 guides the light to the waveguide out-coupling structure 1224, where the image is projected directly into the eye 1201 out of the large FOV (e.g., close to 180°).

[0182] Assuming an aperture of 2 mm, the angular resolution of the WFOV metasurface projection optics 1214 is 0.34 mRad at a wavelength of 550 nm, very close to the resolution of the human eye (e.g., about 0.3 mRad), due to its aberration-free imaging performance. Given a 180° FOV, this produces a resolution of over 9000 × × 9000 resolvable spots at each RGB wavelength and produces approximately 9 mm × 9 mm FOV on the microdisplay. The total thickness of the meta-optical system is only a few millimeters.

[0183] Metalens with metasurface apertures

[0184] Fig.13A and 13B Metalenses 1300 and 1302 are shown, respectively, modulating light beams projected by emitters (e.g., LEDs or VCSELs) 1342a-1342c in an array of light emitters 1340. Fig.13A , an array of light emitters 1340 is in the planar focal plane of a metalens 1300, which includes a transparent substrate 1310 having a first metasurface 1320 on one side and a second metasurface 1334 on the other side. The first metasurface 1320 collimates a light beam emitted by a light emitter 1342, which may span a FOV of 120° or greater. The collimated light beam propagates through the substrate 1310 to the second metasurface 1334, which spans an area less than the area of ​​the first metasurface 1310. The second metasurface 1334 modulates the phase, amplitude, polarization, and / or spectral characteristics of the collimated light beam to generate a 2D or 3D optical pattern, dot array / cloud, image, hologram, or pattern with different polarization and / or spectral characteristics. The first metasurface 1320 can also be configured to generate a 2D or 3D pattern that varies based on the incident angle, wavelength, polarization, etc. of the incident light beam.

[0185] Fig. 13BA similar metalens 1302 is shown. The difference is that the second metasurface 1336 is configured to generate a pattern that varies with the incident angle. In this case, the light from the emitter 1342a produces a dot array on a square dot matrix, while the light from the emitters 1342b and 1342c produces a different sparse dot array. The second metasurface 1336 can also be configured to modulate the incident light beam according to other beam characteristics including spatial, polarization and / or spectral characteristics. For example, the second metasurface 1336 can also be configured to generate a pattern related to wavelength or polarization, so that the emitted light with different wavelengths or polarization characteristics from the light emitter array 1340 produces a customizable pattern. The responses of the first metasurface 1320 and the second metasurface 1336 related to the incident beam characteristics can be used in combination. Alternatively, the DOE can be used instead of or in combination with the second metasurface 1334 / 1336. Illumination patterns with customizable or reconfigurable spatial, angular, polarization and / or spectral characteristics can be combined with object reconstruction algorithms associated with such patterns to effectively extract the characteristics of the scene.

[0186] in conclusion

[0187] Although various inventive embodiments have been described and illustrated herein, a person of ordinary skill in the art will readily envision various other devices and / or structures for performing functions and / or obtaining results and / or one or more of the advantages described herein, and each of such variations and / or modifications is considered to be within the scope of the inventive embodiments described herein. More generally, a person of ordinary skill in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the specific application for which the inventive teachings are used. A person of ordinary skill in the art will recognize or be able to determine many equivalents of the specific inventive embodiments described herein using only routine experiments. Therefore, it should be understood that the foregoing embodiments are presented only by way of example, and within the scope of the appended claims and their equivalents, the inventive embodiments may be practiced in other ways than specifically described and claimed. The inventive embodiments of the present disclosure relate to each individual feature, system, article, material, kit, and / or method described herein. In addition, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, any combination of two or more such features, systems, articles, materials, kits, and / or methods is included within the scope of the invention disclosed herein.

[0188] Moreover, various inventive concepts may be embodied as one or more methods, examples of which have been provided. The actions performed as part of the methods may be ordered in any suitable manner. Thus, embodiments may be constructed in which the actions are performed in a different order than shown, which may include performing some actions simultaneously, even though shown as sequential actions in the illustrative embodiments.

[0189] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0190] Unless expressly indicated to the contrary, the indefinite articles "a" and "an" as used herein in the specification and claims should be understood to mean "at least one".

[0191] The phrase "and / or" as used herein in the specification and claims should be understood to mean "either or both" of the elements so combined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and / or" should be interpreted in the same manner, i.e., "one or more" of the elements so combined. In addition to the elements specifically identified by the "and / or" clause, other elements may optionally be present, whether related or unrelated to those specifically identified. Thus, as a non-limiting example, when used in conjunction with open language such as "comprising," a reference to "A and / or B" may refer to only A (optionally including elements other than B) in one embodiment; to only B (optionally including elements other than A) in another embodiment; to both A and B (optionally including other elements) in yet another embodiment; and so on.

[0192] As used herein in the specification and claims, "or" should be understood to have the same meaning as "and / or" defined above. For example, when separating items in a list, "or" or "and / or" should be interpreted as inclusive, that is, including at least one (but also including more than one) of several elements or lists of elements and optionally additional unlisted items. Only terms that are clearly indicated to the contrary, such as "only one of..." or "exactly one of...", or when used in the claims, "consisting of..." will refer to including exactly one element in several elements or lists of elements. In general, the term "or" used herein should be interpreted as indicating exclusive alternatives (i.e., "one or the other, but not both") only when there are exclusive terms such as "any", "one of...", "only one of..." or "exactly one of..." in front. When used in the claims, "essentially consisting of..." should have its ordinary meaning used in the field of patent law.

[0193] As used herein in the specification and claims, the phrase "at least one" with respect to a list of one or more elements should be understood to mean at least one element selected from any one or more elements in the list of elements, but does not necessarily include at least one of each element specifically listed in the list of elements, and does not exclude any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than the elements specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to those specifically identified elements. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B", or equivalently, "at least one of A and / or B") may refer to at least one (optionally including more than one) A without B (and optionally including elements other than B) in one embodiment; may refer to at least one (optionally including more than one) B without A (and optionally including elements other than A) in another embodiment; may refer to at least one (optionally including more than one) B without A (and optionally including elements other than A) in yet another embodiment; may refer to at least one (optionally including more than one) A and at least one (optionally including more than one) B (and optionally including other elements); and so on.

[0194] In the claims and in the foregoing specification, all transitional phrases, such as "comprising," "including," "carrying," "having," "containing," "involving," "having," "consisting of," and the like, shall be understood to be open-ended, i.e., meaning including, but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures Section 2111.03.

Claims

1. An optical component, comprising: substrate; an opaque layer on the first side of the substrate, the opaque layer defining an aperture to transmit light over a field of view of at least 120°; as well as A metasurface on a second side of the substrate opposite the first side to focus light transmitted through the substrate by the aperture.

2. The optical component according to claim 1, wherein The substrate is planar.

3. The optical component according to claim 1, wherein: The substrate is curved.

4. The optical component according to claim 1, wherein The substrate has a thickness t sub and the refractive index n at the wavelength of the light sub , the orifice has a diameter D in , and the metasurface has a diameter D meta =D in +t sub tan[sin -1 (1 / n sub )].

5. The optical component according to claim 1, wherein The metasurface is configured to focus light incident on the entire field of view to a focal plane parallel to the second side of the substrate.

6. The optical component according to claim 5, further comprising: and a detector array in the focal plane to detect light focused by the metasurface.

7. The optical component according to claim 5, further comprising: an array of light sources in the focal plane, and Wherein, the metasurface is configured to collimate light beams emitted by the light source array, and the aperture is configured to emit the light beams.

8. The optical component according to claim 7, wherein: The metasurface and / or the aperture are further configured to modulate light beams emitted by the array of light sources.

9. The optical component according to claim 1, wherein: The metasurface is configured to focus light incident on the entire field of view with a Strehl ratio of at least 80%.

10. The optical component according to claim 1, wherein The metasurface includes an array of at least 1000×1000 metaatoms.

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