Aperture metasurface and hybrid refractive metasurface imaging system

Abstract

To provide an aperture metasurface and a hybrid refractive metasurface imaging system.SOLUTION: There is provided a hybrid imaging system incorporating a conventional optical element and a metasurface element together with a light source and / or a detector, and a method of manufacturing and operating such an optical arrangement. The system and method describe the integration of an aperture with metasurface elements and refractive optical systems with metasurface elements in an illumination source and a sensor. The imaging system includes at least one image sensor, a substrate layer having a substrate thickness disposed a first distance above the at least one image sensor, an aperture disposed on a first surface of the substrate and having an aperture opening disposed therein, and a monolayer of a plurality of identical or unique nanostructure elements including a metasurface disposed on a second surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure is directed to optical arrangements of Metasurface elements, integrated systems incorporating refractive optics, light sources and / or detectors having such Metasurface elements, and methods of manufacturing such optical arrangements and integrated systems. [Background technology]

[0002] Metasurface elements are diffractive optical systems in which individual waveguide elements have subwavelength spacing and a planar profile. Metasurface elements have recently been developed for applications in the UV-IR band (300-10,000 nm). Compared to traditional refractive optical systems, Metasurface elements introduce a steep phase shift into the optical field. This allows Metasurface elements to have thicknesses on the order of the wavelength of light they are designed to operate at, whereas traditional refractive surfaces have thicknesses 10-100 times (or even greater) than the wavelength of light they are designed to operate at. Additionally, Metasurface elements have no variance in the thickness of their constituent elements, and therefore can shape light without any curvature, as is required for refractive optical systems. Compared to traditional diffractive optical elements (DOEs), such as binary diffractive optics, Metasurface elements have the ability to impart a range of phase shifts to an incident optical field; at a minimum, Metasurface elements can have a phase shift of 0 to 2π with at least five distinct values ​​from that range, whereas binary DOEs can only impart a phase shift of two distinct values, often limited to a phase shift of either 0 or 1π. Compared to multilevel DOEs, Metasurface elements do not require height variation of the constituent elements along the optical axis; only the in-plane geometry of the Metasurface element features varies. Summary of the Invention [Problem to be solved by the invention]

[0003] The present application is directed to optical arrangements of Metasurface elements, integrated systems incorporating light sources and / or detectors having such Metasurface elements, and methods of manufacturing such optical arrangements and integrated systems. [Means for solving the problem]

[0004] Many embodiments provide an imaging system comprising: at least one image sensor; a substrate layer having a substrate thickness disposed a first distance above the at least one image sensor, the substrate layer configured to be transparent to a wavelength of light of interest, the substrate layer having a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor; an aperture disposed on the first surface of the substrate and having an aperture opening disposed therein; a monolayer of a plurality of identical or unique nanostructured elements comprising a metasurface disposed on the second surface, wherein light impinging on the aperture opening is subjected to a specified angular deflection by passing through at least a portion of the metasurface; the aperture and the layer of Metasurface elements are separated by a second distance determined by the substrate thickness; The present invention relates to an imaging system in which a layer of apertures and metasurface elements is configured to collect light of a specified operating bandwidth over a specified field of view and to shift the incident light to bring it to a focus at at least one image sensor with a chief ray angle of zero degrees or near zero degrees.

[0005] In many further embodiments, the system further includes a glass cover disposed over the at least one image sensor.

[0006] In still many, the first distance is determined by a spacing layer comprised of either a solid spacer material or an air gap.

[0007] In even more embodiments, the field of view is at least ±30 degrees.

[0008] In still many embodiments, the system further includes a narrow bandwidth optical filter disposed between the Metasurface elements and the at least one image sensor.

[0009] Various embodiments provide an imaging system comprising: at least one image sensor; a substrate layer having a substrate thickness, the substrate layer configured to be transparent to a wavelength of light of interest, the substrate layer having a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor; an aperture disposed above the substrate and having an aperture opening disposed therein; a monolayer of a plurality of identical or unique nanostructured elements comprising a metasurface disposed on one of either the first or second surfaces, wherein light impinging on an aperture opening is subjected to a specified angular deflection by passing through at least a portion of the metasurface; the aperture and the metasurface layer are separated by a first distance; The present invention relates to an imaging system in which an aperture and a metasurface layer are configured to collect light of a specified operating bandwidth over a specified field of view and to shift incident light to focus onto at least one image sensor at a chief ray angle of zero degrees or near zero degrees.

[0010] Additionally, in various embodiments, the system further includes an air gap between the second surface of the substrate and the image sensor.

[0011] Still, in various embodiments, a spacer layer is disposed within the air gap.

[0012] Furthermore, in various embodiments, the Metasurface layer is disposed on the first surface.

[0013] In still further various embodiments, the system further includes a narrow bandwidth optical filter disposed on the second surface between the Metasurface elements and the at least one image sensor.

[0014] In still further various embodiments, at least a portion of the aperture is interconnected with the first surface.

[0015] In still further various embodiments, the Metasurface layer is disposed on a second surface.

[0016] In still further various embodiments, the image sensor is in contact with the second surface.

[0017] In still further various embodiments, the field of view is at least ±30 degrees.

[0018] Some embodiments are an imaging system comprising: at least one image sensor; a substrate layer having a substrate thickness, the substrate layer configured to be transparent to a wavelength of light of interest, the substrate layer having a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor; at least one refractive lens disposed above the substrate and configured to focus impinging light onto a first surface of the substrate layer; a monolayer of a plurality of identical or unique nanostructured elements comprising a metasurface disposed on one of either the first or second surfaces, wherein light impinging on the at least one refractive lens is subjected to an angular deflection by passing through at least a portion of the Metasurface elements; a first distance separating the at least one refractive lens from the layer of Metasurface elements; The present invention relates to an imaging system in which a layer of refractive lenses and metasurface elements is configured to collect light of a specified operating bandwidth over a specified field of view and to shift incident light to focus onto at least one image sensor at a chief ray angle of zero degrees or near zero degrees.

[0019] Additionally, in some embodiments, the system further includes an air gap between the second surface of the substrate and the image sensor.

[0020] Still in some embodiments, a spacer layer is disposed within the air gap.

[0021] In still further embodiments, the Metasurface layer is disposed on the first surface.

[0022] In still further embodiments, the system further includes a narrow bandwidth optical filter disposed on the second surface between the Metasurface elements and the at least one image sensor.

[0023] Still further, in some embodiments, at least a portion of at least one of the refractive lenses is interconnected with the first surface.

[0024] In still further embodiments, the Metasurface layer is disposed on a second surface.

[0025] Still further, in some embodiments, the image sensor is in contact with the second surface.

[0026] In still further embodiments, the field of view is at least ±30 degrees.

[0027] In still yet some embodiments, the at least one refractive lens is selected from the group consisting of plano-convex, convex-plano, biconvex, biconcave, plano-concave, or concave-plano.

[0028] In still further embodiments, the system includes at least two refractive lenses, including a convex-concave lens and a concave-convex lens.

[0029] In still further embodiments, the system includes at least three refractive lenses, including a convex-concave lens, a biconvex lens, and a concave-plano lens.

[0030] In various of the above embodiments, at least the imaging sensor and the metasurface have a rectangular geometric shape.

[0031] In further variations of the above embodiments, the metasurface and at least one refractive lens proximate thereto have a circular geometric shape.

[0032] In still various of the above embodiments, the image sensor is characterized by vertical v and horizontal h dimensions, the at least one refractive lens is characterized by an f-number of the lens, N, defined as N=f / D, where f is the focal length of the optical system and D is the diameter of the lens, the lens width of the metalens is given by =v+f / N, and the metalens length l is given by l=h+f / N.

[0033] Additional embodiments and features are set forth in part in the specification which follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by practice of the present disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which form a part of this disclosure. The present invention provides, for example, the following. (Item 1) 1. An imaging system comprising: at least one image sensor; a substrate layer having a substrate thickness disposed a first distance above the at least one image sensor, the substrate layer configured to be transparent to a target wavelength of light, the substrate layer having a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor; an aperture disposed on the first surface of the substrate and having an aperture opening disposed therein; a monolayer of a plurality of identical or unique nanostructured elements comprising a metasurface disposed on said second surface, wherein light impinging on said aperture opening is subjected to a specified angular deflection by passing through at least a portion of said metasurface; the aperture and the metasurface are separated by a second distance determined by the substrate thickness; an imaging system, wherein the aperture and the metasurface are configured to collect light of a specified operating bandwidth over a specified field of view and to shift the incident light to come to a focus at the at least one image sensor with a chief ray angle of zero degrees or near zero degrees. (Item 2) Item 10. The imaging system of item 1, further comprising a glass cover disposed over the at least one image sensor. (Item 3) Item 10. The imaging system of item 1, wherein the first distance is determined by a spacing layer comprised of either a solid spacer material or an air gap. (Item 4) Item 10. The imaging system of item 1, wherein the field of view is at least ±30 degrees. (Item 5) Item 1, the imaging system further comprising a narrow bandwidth optical filter disposed between the Metasurface element and the at least one image sensor. (Item 6) Item 1, wherein at least the imaging sensor and metasurface have a rectangular geometric shape. (Item 7) 1. An imaging system comprising: at least one image sensor; a substrate layer having a substrate thickness, the substrate layer configured to be transparent to a wavelength of light of interest, the substrate layer having a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor; an aperture disposed above the substrate and having an aperture opening disposed therein; a monolayer of a plurality of identical or unique nanostructured elements comprising a metasurface disposed on one of the first or second surfaces, wherein light impinging on the aperture opening is subjected to a specified angular deflection by passing through at least a portion of the metasurface; the aperture and the metasurface are separated by a first distance; an imaging system, wherein the aperture and the metasurface are configured to collect light of a specified operating bandwidth over a specified field of view and to shift the incident light to be focused onto the at least one image sensor at a chief ray angle of zero degrees or near zero degrees. (Item 8) 8. The imaging system of claim 7, further comprising an air gap between the second surface of the substrate and the image sensor. (Item 9) Item 9. The imaging system of item 8, wherein a spacer layer is disposed within the air gap. (Item 10) 9. The imaging system of claim 8, wherein the metasurface is disposed on the first surface. (Item 11) Item 11. The imaging system of item 10, further comprising a narrow bandwidth optical filter disposed on the second surface between the metasurface and the at least one image sensor. (Item 12) Item 11. The imaging system of item 10, wherein at least a portion of the aperture is interconnected with the first surface. (Item 13) 9. The imaging system of claim 8, wherein the metasurface is disposed on the second surface. (Item 14) Item 8. The imaging system of item 7, wherein the image sensor is in contact with the second surface. (Item 15) 8. The imaging system of claim 7, wherein the field of view is at least ±30 degrees. (Item 16) 8. The imaging system of item 7, wherein at least the imaging sensor and metasurface have a rectangular geometric shape. (Item 17) 1. An imaging system comprising: at least one image sensor; a substrate layer having a substrate thickness, the substrate layer configured to be transparent to a wavelength of light of interest, the substrate layer having a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor; at least one refractive lens disposed above the substrate and configured to focus impinging light onto the first surface of the substrate layer; a monolayer of a plurality of identical or unique nanostructured elements comprising a metasurface disposed on one of either the first or second surfaces, wherein light impinging on the at least one refractive lens is subjected to an angular deflection by passing through at least a portion of the Metasurface elements; the at least one refractive lens and the metasurface are separated by a first distance; an imaging system, wherein the refractive lens and the metasurface are configured to collect light of a specified operating bandwidth over a specified field of view and to shift the incident light to focus at the at least one image sensor at a chief ray angle of zero degrees or near zero degrees. (Item 18) Item 18. The imaging system of item 17, further comprising an air gap between the second surface of the substrate and the image sensor. (Item 19) Item 19. The imaging system of item 18, wherein a spacer layer is disposed within the air gap. (Item 20) Item 19. The imaging system of item 18, wherein the metasurface is disposed on the first surface. (Item 21) 21. The imaging system of claim 20, further comprising a narrow bandwidth optical filter disposed on the second surface between the Metasurface elements and the at least one image sensor. (Item 22) Item 18. The imaging system of item 17, wherein at least a portion of at least one of the refractive lenses is interconnected with the first surface. (Item 23) Item 19. The imaging system of item 18, wherein the metasurface is disposed on the second surface. (Item 24) 21. The imaging system of claim 20, wherein the image sensor is in contact with the second surface. (Item 25) 18. The imaging system of item 17, wherein the field of view is at least ±30 degrees. (Item 26) 18. The imaging system of claim 17, wherein the at least one refractive lens is selected from the group consisting of plano-convex, convex-plano, biconvex, biconcave, plano-concave, or concave-plano. (Item 27) Item 18. The imaging system of item 17, comprising at least two refractive lenses comprising a convex-concave lens and a concave-convex lens. (Item 28) Item 18. The imaging system of item 17, comprising at least two refractive lenses including a convex-concave lens, a biconvex lens, and a concave-plano lens. (Item 29) Item 18. The imaging system of item 17, wherein at least the imaging sensor and metasurface have a rectangular geometric shape. (Item 30) 30. The imaging system of item 29, wherein the metasurface and the at least one refractive lens proximate thereto have a circular geometric shape. (Item 31) the image sensor is characterized by vertical v and horizontal h dimensions, the at least one refractive lens is characterized by an F-number of the lens, N, defined as N=f / D, where f is the focal length of the optical system, D is the diameter of the lens, and the lens width of the metalens is is given by w=v+f / N, The metalens length l is 30. The imaging system of item 29, wherein l=h+f / N. [Brief explanation of the drawings]

[0034] The present specification will be more fully understood with reference to the following figures, which are presented as exemplary embodiments of the present invention and should not be construed as a complete recitation of the scope of the invention.

[0035] [Figure 1] 1 provides a schematic illustrating an aperture metasurface imaging system incorporating a cover glass over an image sensor, according to an embodiment of the present invention. [Figure 2] FIG. 2 provides a schematic diagram illustrating a ray tracing diagram including chief ray angles at the image sensor plane for the aperture metasurface imaging system of FIG. 1 in accordance with an embodiment of the present invention. [Figure 3] FIG. 1 provides a schematic illustrating an aperture metasurface imaging system with an air gap between the aperture and the metasurface, according to an embodiment of the present invention. [Figure 4] FIG. 4 provides a schematic diagram illustrating a ray tracing diagram including chief ray angles at the image sensor plane for the aperture metasurface imaging system of FIG. 3 in accordance with an embodiment of the present invention. [Figure 5] 1 provides a schematic illustrating an aperture metasurface imaging system incorporating an air gap above the image sensor, with the metasurface layer closer to the object plane, according to an embodiment of the present invention. [Figure 6] 1 provides a schematic illustrating an aperture metasurface imaging system incorporating an air gap above the image sensor, with the metasurface layer closer to the image plane, according to an embodiment of the present invention. [Figure 7] FIG. 1 provides a schematic illustrating an aperture metasurface imaging system incorporating an air gap above the image sensor and a spacer between the aperture and the metasurface, according to an embodiment of the present invention. [Figure 8A] 1 provides a data graph showing relative illuminance versus field of view for an aperture metasurface imaging system, in accordance with an embodiment of the present invention. [Figure 8B] 1 provides a data graph illustrating the field of view versus degree of distortion for an aperture metasurface imaging system, in accordance with an embodiment of the present invention. [Figure 8C] 10 provides a data graph showing coefficient transfer functions over a 40 degree field of view of an aperture metasurface imaging system in accordance with an embodiment of the present invention. [Figure 8D] 1 provides an image of a standard test subject taken using an aperture metasurface imaging system, according to an embodiment of the present invention. [Figure 9] FIG. 1 provides a schematic illustrating a single refractive element and metasurface hybrid imaging system, according to an embodiment of the present invention. [Figure 10A] (FIGS. 10A and 10B) Schematic diagrams illustrating a multirefractive element and metasurface hybrid imaging system according to embodiments of the present invention are provided. [Figure 10B](FIGS. 10A and 10B) Provide schematic diagrams illustrating a multirefractive element and metasurface hybrid imaging system, according to embodiments of the present invention. [Figure 11A] 1 provides a schematic diagram of an image sensor wafer according to an embodiment of the present invention; [Figure 11B] 1 provides a schematic diagram of an image sensor die according to an embodiment of the present invention; [Figure 12A] 1 provides a schematic diagram of a spacer wafer according to an embodiment of the present invention; [Figure 12B] 1 provides a schematic illustration of a spacer according to an embodiment of the present invention; [Figure 13] 1 provides a schematic illustrating an integrated hybrid imaging system incorporating refractive elements along with Metasurface elements and spacers, according to an embodiment of the present invention. [Figure 14] 1 provides a schematic illustrating an integrated hybrid imaging system incorporating refractive elements along with Metasurface elements, according to an embodiment of the present invention. [Figure 15] 1 provides a schematic illustrating a fabrication process for a hybrid refractive element and metasurface imaging system according to an embodiment of the present invention. [Figure 16] 1 provides a schematic illustrating an imaging system incorporating rectangular Metasurface lens elements, according to an embodiment of the present invention. [Figure 17A] (FIGS. 17A and 17B) Schematic diagrams illustrating the relative dimensions of an imaging sensor (FIG. 17A) and a rectangular Metasurface lens element (FIG. 17B) according to embodiments of the present invention are provided. [Figure 17B] (FIGS. 17A and 17B) Schematic diagrams illustrating the relative dimensions of an imaging sensor (FIG. 17A) and a rectangular Metasurface lens element (FIG. 17B) according to embodiments of the present invention are provided. [Figure 18] 18A-18D provide schematic diagrams illustrating an N aperture / N rectangular lens / single image sensor optical system, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] Returning now to the drawings, hybrid imaging systems incorporating conventional optical elements and Metasurface elements along with light sources and / or detectors, as well as methods of fabricating and operating such optical arrangements, are provided. Many embodiments are directed to systems and methods for integrating apertures with Metasurface elements in illumination sources and sensors. Various embodiments are directed to systems and methods for integrating refractive optics with Metasurface elements in illumination sources and sensors.

[0037] Many optical imaging system embodiments may incorporate a single aperture and a single metasurface layer operable to correct aberrations over a wide field of view. Many embodiments of such single aperture and metasurface imaging systems are configured to have no relative illumination falloff over the field of view (e.g., the intensity from an on-axis ray is nearly identical to the intensity at the edge of the field of view) and to be telecentric over a wide field of view (e.g., the angle of incidence at the image sensor plane is nearly 0 degrees).

[0038] In many embodiments, a hybrid refractive optics and Metasurface imaging system may include a Metasurface element that is freestanding (i.e., not directly integrated into the system with a specific illuminator or sensor). In some embodiments, the optical system may be comprised of a single physical component or substrate with Metasurface elements disposed on both sides of it. In some embodiments, multiple refractive optics may be combined with at least one Metasurface element to create a more complex system.

[0039] In embodiments of a hybrid aperture or refractive optics and metasurface imaging system, the metasurface may be disposed on a surface of a supporting substrate facing either the aperture or the imaging system. In various embodiments, an air gap may be disposed between the aperture and the metasurface structure and / or between the metasurface substrate and the imaging system. The air gap between elements may further include spacer structures to provide support for the elements.

[0040] In many embodiments, the Metasurface elements may be freestanding or embedded within another material. In various such embodiments, the selection of the embedding material involves appropriate selection of refractive index and absorption properties. In many such embodiments, the embedding material may provide mechanical stability and protection, as well as additional design freedom that enables the Metasurface to perform a desired optical function.

[0041] In some embodiments, a spacing layer of defined thickness (e.g., working distance) may be deposited over a CMOS image sensor, LED, VCSEL, etc. to implement an optical distance appropriate for a desired camera design, illuminator design, or optimal system performance. In various such embodiments, the spacing layer material may be organic or inorganic and may have a lower refractive index than the dielectric elements including the metasurface. In some such embodiments, the thickness of the spacing layer may be varied to provide the appropriate optical spacing for a particular optical system.

[0042] Various embodiments are also directed to methods of fabricating hybrid metasurface imaging systems. In some such embodiments, the methods are directed to fabricating Metasurface elements on wafers that incorporate other devices, such as sensors or illuminators, thereby avoiding, in some embodiments, expensive manufacturing processes, such as mechanical assembly of small-dimension elements or active alignment of optics with sensors. In some such embodiments, the Metasurface elements may be integrated with the sensor (or illuminator) in a sequence of operations at a semiconductor foundry. In many such embodiments, the sequence may include: (i) the sensor or illuminator; (ii) an optional microlens array / collimator; an optional filter; an optional spacing layer; an optional Metasurface element; an optional additional spacing layer; an optional refractive optic or aperture element; an optional anti-reflection (AR) layer; and an optional protective layer. In many such embodiments, the array of elements may include: (i) the sensor or illuminator; (ii) an optional microlens array / collimator; an optional filter; an optional spacing layer; an optional Metasurface element; an optional additional spacing layer; and an optional refractive element or aperture.

[0043] Embodiments for Implementing an Aperture / Metasurface Imaging System Typically, to create an optical system that is aberration-corrected over a selected field of view, the system must include multiple optical surfaces or multiple optical elements (e.g., two or more). This applies to both traditional refractive optical systems and metasurface optical systems. Specifically, only optical systems with two or more metasurfaces and sufficiently low aberrations over a field of view have been demonstrated. Various embodiments are directed to imaging systems that integrate an aperture and a single metasurface element, where the combination of the systems can achieve high-quality imaging over a wide field of view, telecentricity over a wide field of view (e.g., near 0 degrees incidence at the image sensor plane), and no degradation in relative illumination.

[0044] Specifically, such systems can be used in imaging systems such as CMOS cameras (such as those used in cell phones, computers, tablets, etc. to collect images of a scene in visible light, or in infrared for biometric authentication). These CMOS imaging systems require an increased field of view (FOV), independent control of chief ray angle (CRA) as a function of field height at the CMOS image sensor, and minimization of optical distortion to image the scene. These terms will be understood to have their conventional meanings to those skilled in the art. Traditional imaging systems constructed from refractive lenses must combine as many as five or six unique lenses to perform this function. Similarly, with traditional metasurfaces, imaging systems provide sufficient degrees of freedom to implement multiple metasurface elements and appropriately control these parameters (CRA, FOV, and distortion minimization). However, various embodiments demonstrate that by combining an aperture with a single metasurface, imaging systems with wide FOV, controllable distortion, and controllable CRA can be realized in accordance with embodiments.

[0045] Exemplary embodiments of such systems are illustrated in Figures 1-7. As shown, in many such embodiments, the systems (10a-10d) generally include aperture structures (12a-12d) disposed a set distance (13a-13d) from a metasurface layer (14a-14d), which itself is set a fixed distance (15a-15d) from an image sensor (16a-16d). As described in more detail below, it will be understood that in such systems, the distance between the aperture and the metasurface layer, and the distance between the metasurface layer and the imaging system (e.g., the back focal length of the imaging system), can take the form of an air gap or an optically transparent material (e.g., a substrate).

[0046] For purposes of many embodiments, the aperture structures (12a-12d) are configured to have a first aperture structure portion (18a-18d) that is opaque to light of the wavelength of interest and a second aperture structure portion (18a-18d) that is opaque to light of the wavelength of interest and a distance (d ap and a second aperture structure portion (20a-20d) that is completely transparent to light of the wavelengths of interest over a wavelength range of 100 . In various embodiments, such aperture structures do not impart any optical function (e.g., do not deflect light rays) but rather limit the lateral spread of the bundle of rays entering the imaging system or, equivalently, variously set the entrance aperture of the imaging system.

[0047] For purposes of many embodiments, the metasurface layers (14a-14e) generally have a substrate thickness (t sub ) disposed on a substrate (24a-24e) defined by a plurality of nanostructures (22a-22e). In many embodiments of the hybrid aperture / metasurface imaging system, the metasurface layer is the only functional layer that significantly deflects incident light to form a focused image (e.g., the metasurface layer acts as an arbitrary phase mask).

[0048] Nanostructured embodiments generally include identical or unique three-dimensional elements (e.g., square, circular, triangular, elliptical, etc.) with feature sizes smaller than the wavelength of light within a specified operating bandwidth and configured to impinge phase shifts on impinging light in multiple planes separated by macroscopic distances (distances of 10 or more wavelengths) so that the metasurface layer in combination performs a single optical function. Each individual metasurface in an optical system can be configured to have some specific 2D phase and transmittance function, φ(x, y) and t(x, y), that the metasurface performs. Generally, each metasurface can have a unique distribution of phase and transmittance, but the nanostructured elements comprising any metasurface embedded in the same material with the same basic configuration and at a specific wavelength are identical. For most practical single-wavelength applications, transmittance can be configured to be maximized (close to 1) and uniform across the metasurface, while phase can be configured to take values ​​between 0 and 2π. Briefly, according to embodiments, for some wavelength of interest, material system (metasurface material and embedding material), fixed thickness and element spacing, a set of in-plane dimensions of the nanostructured material may be configured such that a phase delay between 0 and 2π can be imprinted on the incident optical field. Thus, for different implementations of metasurface designs at fixed material and wavelength conditions, the only variable from design to design is the distribution of suitable nanostructured elements throughout the metasurface.

[0049] The metasurface layer in some embodiments may be designed to be freestanding, i.e., the Metasurface elements may protrude beyond the edge of the substrate with only an air gap separating them, and the process is complete at this step. In other embodiments, the metasurface may be further configured with an AR coating or mechanical protection. In some such embodiments, the Metasurface elements and substrate surface may be coated with several materials or layers of materials to protect the metasurface and provide improved functionality. In embodiments with embedded Metasurface elements, the elements are embedded in a lower refractive index medium, which may be any material with desired optical properties. The low refractive index medium completely encapsulates the metasurface and extends some thickness above the Metasurface elements. The low refractive index medium acts as a protective barrier to the Metasurface elements (i.e., provides mechanical stability) and provides additional design freedom for the system, allowing for optimization of specific properties, such as the overall transmittance or efficiency of the metasurface.

[0050] Metasurface layers or systems according to embodiments can be fabricated in mass production using any suitable processing techniques, including lithography, machining, etching, and standard CMOS processing techniques, as described, for example, in U.S. Patent Application No. 16 / 120,174, filed August 31, 2018, the disclosure of which is incorporated herein by reference. The Metasurface substrate can be any low-index material, such as polymer, SiO2, or glass. The Metasurface elements can also be any material optimized for a particular bandwidth, such as silicon, TiO2, alumina, or metal.

[0051] The imaging system may take the form of a single monolithic imaging sensor or pixel array. Such image sensors and pixel arrays may take any suitable form, including, for example, CMOS sensors.

[0052] FIG. 1 provides a schematic illustration of various implementations of such hybrid aperture / metasurface imaging systems. As shown, in many embodiments, the aperture / metasurface is transparent at the wavelength of interest and has a thickness (t sub ) is provided, the substrate layer (24a) having an aperture structure (12a) disposed on a first side distal to the imager (16a) that is opaque to light at a wavelength of interest and completely transparent to light at the wavelength of interest over a distance; ap and a metasurface layer (14a) comprising nanostructures (22a) of equal height disposed on a second side proximal to the imager (16a). In such an embodiment, the aperture structure (12a) and the metasurface layer (14a) are spaced apart by a thickness greater than or equal to the substrate thickness (t sub ) are separated by a first distance (13a) defined by the substrate (24a). Furthermore, in such an embodiment, the aperture structure (12a) and the metasurface layer (14a) may be deposited directly on the substrate (24a) or may be bonded via an adhesive. An air gap (t air ) is disposed. Although not required, many embodiments of such imaging systems may further include an optional cover glass or filter (26) that does not affect the imaging performance of the device but provides other functionality (e.g., either optical or structural).

[0053] It will be understood that in such embodiments, the aperture does not impart any optical function (does not deflect light rays) but merely limits the lateral spread of the light beam that can enter the imaging system, or equivalently sets the entrance aperture or f / # of the system. On the other hand, the Metasurface layer, in such embodiments, may comprise the only functional optical layer, significantly deflecting light rays to form a focused image. In some such embodiments, the Metasurface layer may function as an arbitrary phase mask, imparting any value of phase shift between 0 and 2π to incident light at any radial position of the lens.

[0054] Referring to Figure 2, a ray tracing diagram is provided through an exemplary embodiment of a system including a single aperture (12a) and a single metasurface (14a) combined on a single substrate (24a) according to the embodiment illustrated in Figure 1. (Although not described in detail here, these Metasurface elements may be fabricated using methods such as those described herein or in previously cited U.S. patent application Ser. No. 16 / 120,174, using a suitable conformal deposition process, such as low-pressure chemical vapor deposition or atomic layer deposition.) In this exemplary embodiment, the aperture and Metasurface elements are configured such that they can, in combination, form a good image over a wide FOV (±40 degrees in this example, although it should be understood that this is not a limiting example). Such a single aperture and single metasurface system embodiment as shown has surprisingly been found to naturally produce a focal beam in an image plane that is telecentric (i.e., has a CRA of 0 degrees). In short, while traditional refractive and metasurface designs require complex multi-element systems to achieve such telecentricity, embodiments require only a single aperture and a single metasurface element to achieve similar telecentricity. This telecentricity, in turn, leads to improved optical performance. In particular, a low CRA (e.g., zero or near-zero) allows for narrower bandwidths of the optical filter (26) for narrowband applications. In traditional refractive designs, CRAs are typically on the order of 15 to 30 degrees, especially for compact mobile applications. These larger CRAs, in turn, require significantly increased filter bandwidths to allow more ambient light to enter the detector. In narrowband applications (e.g., near-IR VCSEL arrays), such ambient light can be a persistent noise source. Therefore, embodiments of combined metasurface / filter systems, such as the one shown in Figure 2, enable better ambient light performance.

[0055] While Figures 1 and 2 provide one arrangement of optical elements for a hybrid aperture / metasurface imaging system, it will be understood that many other arrangements of elements can be realized. For example, Figure 3 provides a schematic illustration of an embodiment of an imaging system in which the positions of the air gap and substrate are swapped. Such a configuration allows for the formation of a thinner imaging system, but involves a more complex assembly process. In particular, as shown in Figure 3, an embodiment of such an imaging system can be fabricated that is transparent at the wavelength of interest and has a thickness (t sub The substrate (24b) is provided with a metasurface layer (14b) of nanostructures (22b) having equal heights disposed on a first side distal to the imager (16b) and on a second side of the imager (16b). In such an embodiment, the metasurface layer (14b) and the imager (16b) may be directly bonded via adhesive or other suitable means. A substrate thickness (t) is provided between the metasurface layer (14b) and the imager (16b). sub ) is disposed. This distance is used as a free parameter to design an imaging system with optimal performance and varies based on, for example, the desired f / # or field of view of the imaging system. In such embodiments, such imaging systems do not require the optional cover glass or filter used in the embodiment shown in FIG. 1 because substrate (24b) provides such dual functionality. In such embodiments, a substrate that is opaque to light of the wavelength of interest and that is at a distance (d ap ) and the metasurface layer (14b) are separated by an air gap (t air ) are separated by a first distance (13b) defined by

[0056] Referring to Figure 4, a ray tracing diagram is provided through an exemplary embodiment of a system including a single aperture (12b) along with a single metasurface (14b) and imager (16b) combined on a single substrate (24b) according to the embodiment illustrated in Figure 3. (Although not described in detail here, these Metasurface elements may be fabricated using a suitable conformal deposition process, such as low-pressure chemical vapor deposition or atomic layer deposition, using methods such as those described herein or in previously cited U.S. patent application Ser. No. 16 / 120,174.) In this exemplary embodiment, the aperture and Metasurface elements are configured such that they can, in combination, form a good image over a wide FOV (±40 degrees in this example, although it should be understood that this is not a limiting example). Such a single aperture and single Metasurface system embodiment as shown has surprisingly been found to naturally produce a focal beam in an image plane that is telecentric (i.e., has a CRA of 0 degrees).

[0057] While Figures 1 and 4 provide optical element arrangements for a hybrid aperture / metasurface imaging system in which the elements are in direct contact with the image sensor, it will be understood that many other arrangements of elements incorporating spacers disposed between the image sensor and the substrate supporting the metasurface layer can be realized. For example, Figure 5 provides a schematic illustration of an embodiment of an imaging system in which a second air gap (28) is disposed within the imaging system.

[0058] In particular, as shown in FIG. 5, an embodiment of such an imaging system may be configured to have a thickness (t subThe substrate (24c) includes a substrate (24c) having a first side distal to the imager (16c), a metasurface layer (14c) comprised of nanostructures (22c) having equal heights, and a second air gap (28) disposed between the second side of the metasurface layer proximal to the imager (16c). One advantage of such an embodiment incorporating an air gap is that light rays travel through the system at higher angles, compared to the embodiment shown in FIG. 1, for example, thus allowing for a reduction in the overall form factor of the metasurface optical system. Additionally, the gap between the metasurface substrate and the image sensor facilitates the introduction of other optical elements, including, for example, a microlens array or an optical color filter, to improve the optical function of the imaging system.

[0059] In such an embodiment, the metasurface layer (14c) and the imager (16c) may be deposited directly on the substrate (24c) or may be bonded via an adhesive. Such an embodiment may also include a suitable spacer (30) to support the substrate (24c) and maintain a distance between the substrate and the image sensor (16c). The thickness of the substrate (t sub ) and spacer height (t spacer The distance (15c) is provided to define the back focal length formed by the combination of the image sensor (16c) and the spacer (30). spacer ) and a substrate layer (24c) located a fixed distance (t spacer ) can be adjustable after assembly. Such an embodiment allows the surface 34 of the image sensor 16c and the proximal substrate 24c to remain unpatterned, allowing for the integration of optional optical filters directly onto this surface.

[0060] While one embodiment of a hybrid aperture / metasurface configuration incorporating an air gap above the image sensor is described as shown in FIG. 6, in various embodiments, the Metasurface layer (14d) may also be disposed on the surface of the image sensor (16d) and proximal substrate (24d) facing the air gap (32) supported by the spacer (30′). Such an implementation allows for protecting the Metasurface elements from environmental contamination. Additionally, such an embodiment allows for the surface (34′) of the image sensor (16d) and distal Metasurface substrate (24d) to remain unpatterned, allowing for the integration of optional optical filters directly onto the substrate. Again, in such an embodiment, the spacer (30′) may be positioned between the image sensor (16d) and (t spacer ) and a substrate (24d) at a fixed distance (t spacer ) can be adjustable after assembly.

[0061] Thus, the embodiments illustrated in Figures 5 and 6 illustrate that the Metasurface elements can be positioned facing inward or outward with respect to the air gap between the substrate and the image sensor. Fabrication of the Metasurface systems illustrated in Figures 5 and 6 can follow, for example, the process described in U.S. Patent Application No. 16 / 120,174. The spacer layer can be any low refractive index material, such as polymer, SiO2, or glass.

[0062] Although embodiments of hybrid aperture / metasurface imaging systems incorporating an air gap between the aperture and metasurface substrate are shown in Figures 3, 5, and 6, these embodiments fix the aperture and allow for a variable aperture distance (t air) remains constant. However, the aperture structure (12e) may also be attached directly to the substrate layer (24e). An exemplary embodiment of such an imaging system is illustrated in FIG. 7. As shown, in this exemplary embodiment, the upper aperture (12e) has a width d ap,top The aperture body (36) has a width that defines the entrance aperture of the system and is spaced a distance (t ap ), and the aperture offset by (t ap ) is set by the width of the metasurface layer, and (d ap,bottom ), and then angled to the width of the aperture at a minimum angle set by the half field of view of the imaging system. While the embodiment shown in FIG. 7 depicts a system in which the metasurface layer (14e) is disposed on a surface of the substrate (24e) distal to the image sensor (16e), it will be understood that the metasurface layer may also be disposed on a surface (34'') of the substrate proximal to the image sensor. Additionally, while the exemplary embodiment incorporates a spacer structure (30'') and an air gap between the substrate (24e) and the image sensor (16e), it will be understood that embodiments may omit this element and mount the substrate directly over the image sensor.

[0063] An attribute of such telecentric design embodiments is that the metasurface imaging system provides more uniform illumination at the image sensor (referred to by those skilled in the art as "relative illumination"). A data plot of relative illumination for an exemplary system according to embodiments is provided in FIG. 8A, demonstrating that the relative illumination of the aperture / metasurface imaging system is maintained at 100% across the entire field of view, a substantial improvement over conventional systems that may have a difference of 50% or more between the center and the edge. Thus, imaging system embodiments can collect greater total illumination across the entire field of view. Metasurface system embodiments also offer an additional design variant with respect to traditional refractive lens systems. Typical CMOS image sensors (CIS) require a microlens to be associated with each pixel. Due to the large variation in CRA across a given sensor plane that is inherent in refractive optical systems, the microlens array on the CIS also requires complex CRA specifications. However, in metasurface system embodiments as described herein, the CRA of the microlens array may be configured to be consistently 0 degrees across the entire CIS, allowing for greater simplification in the design and fabrication of the microlens array. Alternatively, in certain implementations, the microlens array may be completely removed from the CIS, eliminating a process step in CIS fabrication. Furthermore, such an aperture metasurface system with a CRA of zero can limit a persistent problem in traditional imaging systems known to those skilled in the art as "pixel crosstalk." Traditional refractive systems that deliver light to an image sensor are prone to optical coupling into adjacent pixels, which adds noise to the system.

[0064] Conventional metasurface systems can be constructed with multiple metasurface layers to control the field of view (FOV) and distortion. The introduction of one or more additional metasurface elements allows for the realization of distinct, arbitrary phase profiles, providing more degrees of freedom for controlling the path of light rays compared to typical systems constructed with a comparable number of refractive elements. Current imaging system embodiments, in which a single metasurface layer is used, are unable to simultaneously control the CRA and correct grid distortion. As a result, a certain amount of grid distortion is unavoidable. For example, Figure 8B provides a data plot illustrating distortion as a function of field of view on a CMOS image sensor in an imaging system based on the embodiment shown in Figure 1. Figure 8C shows a plot of the coefficient transfer function versus field of view for an embodiment of an imaging system such as that shown in Figure 1. Figure 8D provides a standard test image illustrating grid distortion in an imaging system based on the embodiment shown in Figures 8A-8C. As can be seen, quality degrades at the edges of the field of view. However, embodiments of the present invention demonstrate that all of the wavelengths of light are tightly packed, demonstrating that distortion can be corrected simply by using known image processing software.

[0065] Embodiments Implementing Hybrid Refractive and Metasurface Elements While embodiments incorporating an aperture and a single Metasurface layer have been described, it will be understood that embodiments are also directed to hybrid systems of Metasurface elements incorporating refractive lens elements. Figure 9 provides a schematic illustration of various implementations of such hybrid refractive lens / Metasurface imaging systems. In many embodiments, the hybrid imaging surface consists of at least one of each of the following: a refractive lens having one or more surfaces of curvature; and a Metasurface layer on a substrate, with all of the Metasurface-comprising elements at the same height. More generally, a hybrid optical system can be composed of any number of refractive elements and multiple Metasurface layers. In certain embodiments, having Metasurface elements on a substrate layer, which is the final component before the image sensor, offers the particular advantage of creating a so-called image-space telecentric imaging system. Additionally, the substrate on which the Metasurface layer is formed can have a set of filter layers deposited thereon. As described in embodiments incorporating filters, the Metasurface layer is closer to the object plane of the imaging system, while the near-infrared filter is closer to the image sensor.

[0066] An exemplary embodiment of a hybrid refractive element / metasurface imaging system is illustrated in Figure 9. In many embodiments, the system comprises a substrate layer (40) transparent at the wavelength of interest, disposed a set distance from the substrate layer (40), and having a metasurface layer (42) of equal height nanostructures (44) disposed on a first surface (45) of the substrate layer, distal to an image sensor (46). sub ), and an optional optical filter (48) disposed on a second side (47) of the substrate proximate the imager.

[0067] While the embodiment shown in Figure 9 illustrates a hybrid system having a single refractive optic and a single Metasurface layer, it will be understood that embodiments may also incorporate other arrangements of refractive optics. Diagrams illustrating such metasurface / refractive hybrid systems are provided in Figures 10A and 10B. Specifically, Figure 10A illustrates a hybrid system including two refractive elements (50 and 51) and one Metasurface layer (52) system, where the two refractive elements are convex-concave and concave-concave. Figure 10B illustrates a hybrid system including three refractive elements (54, 55, 56) and one Metasurface element (58), where the three refractive elements are convex-concave, biconvex, and concave-plano, respectively.

[0068] With respect to the refractive optical elements of the hybrid systems described above, i.e., those elements preceding the Metasurface layer, it will be understood that the surface curvature of these elements can take any positive, negative, or infinite value. Thus, although particular arrangements of refractive elements are shown in the figures, the refractive elements may take any suitable form and combination for a particular application, including, for example, plano-convex, convex-plano, biconvex, biconcave, plano-concave, or concave-plano.

[0069] An embodiment in which an image sensor wafer is mounted Imaging systems known in the art typically consist exclusively of traditional refractive lenses (glass or plastic materials with at least one curved surface). According to embodiments, a single metasurface layer is arranged in combination with one or more curved refractive lenses. Surprisingly, it has been discovered that the inclusion of a single metasurface layer makes the optical system telecentric. Specifically, in many such embodiments, the inclusion of a metasurface element as the final element before the image plane makes the system telecentric.

[0070] Embodiments of the metasurface layer can be integrated with a CMOS image sensor (CIS) as a cover glass and filter, while refractive optics can be assembled within the barrel, as is conventionally done in optical imaging modules. In certain embodiments, the glass on which the metasurface layer is fabricated, in addition to serving as the cover glass for the CIS, can be pre-deposited with a dielectric layer to function as a near-infrared bandpass or longpass filter. Such embodiments provide a single component that functions in the optical imaging process while filtering out unwanted wavelengths from entering the image sensor.

[0071] While the above embodiments have focused on hybrid Metasurface imaging systems having a single sensor element, as shown, for example, in FIGS. 1-10B, Metasurface elements can also be integrated with an image sensor wafer containing multiple image sensor dies. A schematic diagram of an image sensor wafer is illustrated in FIG. 11A. As shown, embodiments can include an image sensor wafer (60) including a set of image sensor dies (62), which are shown in a periodically spaced 2D array, although it will be understood that the array need not be periodically spaced. As shown in FIG. 11B, each sensor die (62) includes an image sensor active area (64). While each image sensor may be identical, in many embodiments, the characteristics of each sensor may be generally unique. Because each imager comprising the array may have unique characteristics, it can also be advantageous to have an array of Metasurface elements, each with uniquely designed characteristics.

[0072] It will be appreciated that only the active area (64) need be available for imaging. Areas outside the image sensor active area (66) may be used for mounting lenses or spacers. Additionally, in various embodiments, the Metasurface substrate may be offset from the image array by a spacer. Exemplary embodiments of a spacer wafer (70) containing multiple spacer openings suitable for mounting to a sensor wafer and a spacer die (72) suitable for mounting to an image sensor or lens die are illustrated in Figures 12A and 12B, respectively. The design and thickness of the spacer layer will depend on the particular configuration, but in many embodiments, the thickness is configured to allow sufficient divergence of light from the illumination source before interacting with the image sensor. Again, the function of each Metasurface element in the array may generally be unique and may be patterned on each individual image sensor in the array using any suitable technique, for example, as outlined in U.S. Patent Application No. 16 / 120,174. For example, a metasurface may be fabricated directly on each individual image sensor in the array, or a suitable dielectric spacer may be deposited on the image sensor, followed by integration of the metasurface on the combined dielectric layer and image sensor. In such embodiments, the metasurface may provide a specific radiation pattern for each image sensor, and the entire system (image sensor characteristics, geometric parameters, and corresponding radiation pattern of the metasurface) can be iteratively optimized for a particular set of performance parameters.

[0073] In various other embodiments, a dielectric material with a lower refractive index than that of the constituent image sensor materials may be deposited and planarized so that a single metasurface can be patterned on top of the dielectric material. This is in contrast to embodiments in which each image sensor in the array has a unique metasurface patterned on its facet. Again, in such embodiments, the combined system may be optimized to achieve desired performance. Finally, in all of the above embodiments, integration of the metasurface with the image sensor array may be accomplished using wafer-level optical processes. In such embodiments, the spacer layer may be air rather than a solid dielectric; illustrations of exemplary embodiments of such devices are shown in Figures 13 and 14.

[0074] Specifically, Figure 13 shows a schematic diagram of an embodiment including an image sensor die (74) and a lens die (76) separated by a spacer (78). In such an embodiment, the spacer (78) controls the distance between the metasurface area (80) and the image sensor active area (82). The spacer in such an embodiment can be attached to the image sensor die or image sensor wafer, and then the lens can be attached to the spacer. Alternatively, the spacer can be attached to the lens first, and then the sensor can be attached to the spacer. In such an embodiment, the spacer can be attached using an adhesive (e.g., UV-curable or thermal-curable epoxy), solder, or fusion bonding.

[0075] Figure 14 illustrates an exemplary embodiment that excludes the spacer. In such an embodiment, the thickness of the lens die (84) determines the distance between the image sensor active area (86) and the metasurface area (88). The image sensor die (90) and lens die (84) can be directly attached using adhesives, solder, fusion bonding, bump bonding, etc. Alternatively, the image sensor wafer and lens wafer can be directly attached at the wafer level, as previously described.

[0076] As shown in Figure 15, in certain embodiments, the refractive lens (91) of the hybrid system may first be assembled into a lens barrel (92), as is already known in the art. The Metasurface element (94) may then be combined with a CMOS image sensor (96), as described above with respect to Figures 13 and 14 above. These two subcomponents are then assembled together to form the final system. In such embodiments, the refractive lens may be a combination of a refractive element and a Metasurface (t gap ) may be configured to thread onto the housing (98) so that the distance between the

[0077] Implementation of the embodiment As is well known to those skilled in the art, the image of a scene formed by a circular, radially symmetric lens, or a system of circular, radially symmetric lenses, is also circular. As a result, the geometric shape of the formed image is often referred to as the image circle of the lens. However, in modern photography, the medium that records the image (e.g., a CMOS image sensor) often has a rectangular shape. In camera design, the image circle of a lens is measured by the diameter D of the image circle. image is designed to be at least as large as the diagonal d of the image sensor. However, because the image sensor is rectangular, only a portion of the image circle actually strikes the image sensor. Therefore, much of the lens area onto which light from the scene falls is not used in the final formation of the image from the camera system.

[0078] In traditional injection-molded plastic refractive lenses, the lens shape is ideally kept circular. From a manufacturing standpoint, circular shapes and radially symmetric lenses are the easiest to achieve and offer the best repeatability in fabrication, so circular shapes are used. Furthermore, creating large-area circular lenses rather than small-area rectangular lenses minimizes cost increases. Therefore, traditional cameras use circular lenses, and only a portion of the light that impinges on the entire circular lens is collected by a rectangular image sensor. These portions of the circular lens that receive light but do not contribute to the light impinging on the image sensor are not used in the final image formation.

[0079] For Metasurface lenses according to various embodiments, the shape of the lens can be designed so that the image it forms is uniquely suited to a particular image sensor dimension. In contrast to conventional refractive lenses, in many such embodiments, the lens shape is configured to no longer be circular, and the lens is configured to no longer form an image circle. In various embodiments, the Metasurface lens is formed in a rectangular configuration with specific dimensions, and therefore the formed scene image is also rectangular. In the ideal case of such a design embodiment, all of the light impinging on the rectangular Metasurface lens falls on the image sensor. Metasurface embodiments with rectangular lenses break radial symmetry, and therefore the image formed by the lens is no longer circular or radially symmetric.

[0080] Thus, in many embodiments of the lens system, the metasurface lens elements can be formed in a rectangular configuration. Advantages of such rectangular or non-circular lenses include limiting the total area of ​​the lens, subsequently eliminating portions of the lens that would otherwise impinge light to form an image on the image sensor, and simplifying post-processing of the lens wafer. Specific embodiments of rectangular metasurface lenses and imaging systems are described herein.

[0081] Many embodiments of metasurface lens systems with non-circular configurations have the following in common: an entrance aperture, which is the stop of the lens system, and a metasurface lens, which is the final active optical surface before the image sensor plane. In such embodiments, the entrance aperture (and optical stop) can be circular in cross section, as in traditional optical systems, while the metasurface lens can be patterned as a rectangle or any other shape.

[0082] FIG. 16 provides an illustration of an exemplary embodiment of a clear aperture metasurface, in which an imaging system (100) is composed of a rectangular image sensor (102) offset from a single rectangular metasurface (104) and a circular entrance aperture (106) offset from the rectangular metasurface lens (104). In embodiments implementing a hybrid metasurface refractive system, the optical system is composed of the entrance aperture, at least one refractive lens, and the metasurface lens being the last optical lens element in the system before the image sensor. In these embodiments of such hybrid systems, the entrance aperture and at least one refractive lens can still have a circular or radially symmetric cross section. Thus, an embodiment of such a hybrid system would be composed of a circular aperture (106) offset from at least one circular refractive lens (not shown), as shown in FIG. 16, which is in turn offset from the rectangular metasurface lens (104). Again, in such embodiments, the metasurface lens has rectangular dimensions configured to fit the particular image sensor. Although the examples herein describe implementations in which the Metasurface lens element alone has a rectangular cross section, this is not a limiting example. For example, the entrance aperture (and stop of the optical system) can also be rectangular, or at least one refractive lens can also be rectangular, as long as the Metasurface lens element that is the last lens element before the image sensor has a rectangular cross section.

[0083] In certain cases, the dimensions of a system's rectangular lens can be fully characterized by the dimensions of the system's image sensor and the lens specifications. Specifically, as shown in FIG. 17A, they are characterized by the image sensor's horizontal and vertical dimensions, v and h, respectively. Lens systems are most commonly characterized by the lens's f-number, N, defined as N = f / D, where f is the focal length of the optical system and D is the lens diameter. Thus, as shown in FIG. 17B, the lens width of a desired rectangular metalens can be shown to be w = v + f / N, and the length can be shown to be l = h + f / N. Such definitions of lens dimensions result in an image that nearly perfectly fills the sensor geometry. In practice, it is desirable to have the image formed by the imaging system slightly larger than the dimensions of the image sensor. This image oversizing allows for greater tolerances in the final assembly of the lens system. A typical oversizing range might be to take the nominal rectangular lens dimensions as given above and increase each dimension by 40 microns.

[0084] While the above example specifies a single circular aperture combined with a rectangular lens, in other embodiments, an N aperture / N rectangular lens / single image sensor optical system may also be provided. For example, the circular apertures and rectangular metasurface lenses may be arranged in a 2x2 grid on a single image sensor. An example of such a system is shown in Figures 18A-18B. Figure 18A shows a single image sensor die (110) around which a single spacer (112) may be disposed, as shown in Figure 18B. The spacer sets the distance between the rectangular metasurface (114) and the image sensor (110), as shown in Figure 18C. The final element in the assembly includes a set of circular apertures (116) disposed in association with an additional spacing layer (118) to set the distance between the rectangular metasurface and the circular apertures. A cutaway view of the complete assembly is shown in Figure 18D.

[0085] While Figures 18A-18D illustrate a 2x2 array of circular apertures on a rectangular metasurface, in general, the grid of circular apertures and rectangular metasurface lenses may be arranged in any manner, either symmetric or asymmetric, e.g., 3x3 or 5x2. Additionally, each individual rectangular metasurface and circular aperture comprising the system may have unique dimensions relative to the remaining aperture-metasurface pairs in the system. For example, each aperture diameter within the array may generally be unique, or each rectangular lens may be unique. However, the distance between the metasurface lens and the image sensor and between the metasurface lens and the circular aperture is generally fixed for the entire system. Varying the mechanical parameters (e.g., aperture size) for each individual component of the array allows for unique optical properties for each camera within the array. For example, according to embodiments, each sub-camera may have a unique f / #, field of view, resolution, etc.

[0086] Doctrine of Equivalents Thus, while the present invention has been described in certain specific aspects, many additional modifications and variations will be apparent to those skilled in the art. It is therefore to be understood that the invention may be practiced otherwise than as specifically described. The present embodiments, therefore, are to be considered in all respects as illustrative and not restrictive.

Claims

[Claim 1] The invention described in this specification.

Images