Aperture Meta-Surface and Hybrid Refractive Meta-Surface Imaging System

Abstract

A hybrid imaging system incorporating conventional optical elements and Metasurface elements with a light source and / or detector, as well as methods for fabricating and operating such an optical arrangement, is provided. The system and method describe the integration of an aperture having Metasurface elements and a refractive optical system having 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 multiple identical or unique nanostructure elements comprising a metasurface disposed on a second surface.

Description

Technical Field

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

Background Art

[0002] A metasurface element is a diffractive optical system in which individual waveguide elements have a sub-wavelength spacing and a planar profile. Metasurface elements have been recently developed for applications in the UV-IR band (300 - 10,000 nm). Compared to traditional refractive optical systems, metasurface elements introduce a sharp phase shift in the light irradiation field. This enables metasurface elements to have a thickness approximately that of the wavelength of light they are designed to operate at, whereas traditional refractive surfaces have a thickness 10 - 100 times (or greater than) the wavelength of the light for which they are designed to operate. Additionally, metasurface elements have no variation in the thickness of their constituent elements and can thus shape light without any curvature as required for refractive optical systems. Compared to traditional diffractive optical elements (DOEs), such as binary diffractive optical systems, metasurface elements have the ability to impart a range of phase shifts to the incident light field and, at a minimum, metasurface elements can have a phase shift of 0 - 2π with at least five distinct values from that range, whereas binary DOEs can only impart a phase shift of two distinct values and are often limited to a phase shift of either 0 or 1π. Compared to multi-level DOEs, metasurface elements do not require height variation of the constituent elements along the optical axis and only the in-plane geometry of the metasurface element features varies.

Summary of the Invention

Problems to be Solved by the Invention

[0003] This application is directed to an optical arrangement of a metasurface element, an integrated system incorporating a light source and / or a detector having such a metasurface element, and a method of manufacturing such an optical arrangement and integrated system. **Means for Solving the Problem**

[0004] Many embodiments are an imaging system, at least one image sensor, a substrate layer having a substrate thickness disposed above the at least one image sensor by a first distance, the substrate layer being configured to be transparent to the 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, the substrate layer; an aperture disposed on and having an aperture opening therein on the first surface of the substrate, the aperture; a single layer of a plurality of identical or unique nanostructured elements including a metasurface disposed on the second surface, such that light impinging on the aperture opening is subjected to a specified angular deflection by passing through at least a portion of the metasurface, the single layer; The distance between the aperture and the layer of metasurface elements is separated by a second distance determined by the substrate thickness, The aperture and the layer of metasurface elements are configured to collect light within a specified operating bandwidth over a specified field of view and shift the incident light to converge at the at least one image sensor at a chief ray angle of zero or nearly zero degrees. The imaging system is targeted.

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

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

[0007] In still 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 element and at least one image sensor.

[0009] Various embodiments are an imaging system, at least one image sensor, a substrate layer having a substrate thickness, the substrate layer being configured to be transparent to the 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, a substrate layer, an aperture disposed above and having an aperture opening therein, an aperture, a single layer of a plurality of identical or unique nanostructure elements including a metasurface disposed on either the first or second surface, such that light impinging on the aperture opening passes through at least a portion of the metasurface to impose a specified angular deflection, a single layer, the distance between the aperture and the metasurface layer is separated by a first distance, the aperture and the metasurface layer are configured to collect light within a specified operating bandwidth over a specified field of view and shift the incident light to converge at a principal ray angle of zero or nearly zero degrees onto at least one image sensor, an imaging system.

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

[0011] In still many embodiments, a spacer layer is disposed within the air gap.

[0012] In still further embodiments, the metasurface layer is disposed on the first surface.

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

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

[0015] Still further, in various embodiments, the metasurface layer is disposed on the second surface.

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

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

[0018] Some embodiments are imaging systems, at least one image sensor, a substrate layer having a substrate thickness, the substrate layer being configured to be transparent to the 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, at least one refractive lens disposed above the substrate and configured to focus the impinging light on the first surface of the substrate layer, a single layer of a plurality of identical or unique nanostructure elements including a metasurface disposed on either the first or the second surface, such that light impinging on the at least one refractive lens is angularly deflected by passing through at least a portion of the metasurface element, the distance between the at least one refractive lens and the layer of metasurface elements is separated by a first distance, An imaging system is targeted, in which a layer of a refractive lens and a metasurface element is configured to collect light within a specified operating bandwidth over a specified field of view and shift the incident light to focus it onto at least one image sensor at a chief ray angle of zero degrees or nearly zero degrees.

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

[0020] In still some other embodiments, a spacer layer is disposed within the air gap.

[0021] In yet still some other embodiments, the metasurface layer is disposed on the first surface.

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

[0023] In yet still some other embodiments, at least a portion of at least one of the refractive lenses is interconnected with the first surface.

[0024] In still yet some other embodiments, the metasurface layer is disposed on the second surface.

[0025] In yet still some other embodiments, the image sensor is in contact with the second surface.

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

[0027] In yet still some other embodiments, at least one of the refractive lenses 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 yet further embodiments, the system includes at least three refractive lenses including a convex-concave lens, a biconvex lens, and a plano-concave lens.

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

[0031] In still further embodiments of the above, at least one refractive lens proximal to the metasurface has a circular geometry.

[0032] In still various of the above embodiments, the image sensor is characterized by vertical v and horizontal h dimensions, at least one refractive lens is characterized by N defined as the F-number of the lens, 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, in part, described in the remainder of this specification that follows and, in part, will be apparent to those skilled in the art upon examination of this specification or can be learned by practice of the disclosure. A further understanding of the nature and advantages of the present disclosure can be realized by reference to the remaining portions of this specification and the drawings that form a part of this disclosure. The present invention provides, for example, the following. (Item 1) An imaging system, at least one image sensor, a substrate layer having a substrate thickness disposed above the at least one image sensor by a first distance, the substrate layer being 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, a substrate layer; an aperture disposed on and having an aperture opening therein on the first surface of the substrate, an aperture; a single layer of a plurality of identical or unique nanostructure elements including a metasurface disposed on the second surface, such that light impinging on the aperture opening is subjected to a specified angular deflection by passing through at least a portion of the metasurface, a single layer; the distance between the aperture and the metasurface being separated by a second distance determined by the substrate thickness, the aperture and the metasurface being configured to collect light within a specified operating bandwidth over a specified field of view and shift the incident light to converge at a principal ray angle of zero degrees or substantially zero degrees onto the at least one image sensor, an imaging system. (Item 2) The imaging system according to item 1, further comprising a glass cover disposed on the at least one image sensor. (Item 3) The imaging system according to item 1, wherein the first distance is determined by a spacer layer composed of either a solid spacer material or an air gap. (Item 4) The imaging system according to item 1, wherein the field of view is at least ±30 degrees. (Item 5) The imaging system according to item 1, further comprising a narrow bandwidth optical filter disposed between the metasurface element and the at least one image sensor. (Item 6) The imaging system according to item 1, wherein at least the image sensor and the metasurface have a rectangular geometric shape. (Item 7) An imaging system, at least one image sensor, A substrate layer having a substrate thickness, wherein the substrate layer is configured to be transparent to a target wavelength of light, and the substrate layer has a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor, a substrate layer; An aperture disposed above and having an aperture opening disposed therein, an aperture; A single layer of a plurality of identical or unique nanostructure elements including a metasurface disposed on one of the first or second surfaces, such that light impinging on the aperture opening is subjected to a specified angular deflection by passing through at least a portion of the metasurface, a single layer; and The distance between the aperture and the metasurface is separated by a first distance; An imaging system, wherein the aperture and the metasurface are configured to collect light within a specified operating bandwidth over a specified field of view and shift the incident light to be focused on the at least one image sensor at a chief ray angle of zero degrees or substantially zero degrees. (Item 8) The imaging system according to item 7, further including an air gap between the second surface of the substrate and the image sensor. (Item 9) The imaging system according to item 8, wherein a spacer layer is disposed within the air gap. (Item 10) The imaging system according to item 8, wherein the metasurface is disposed on the first surface. (Item 11) The imaging system according to item 10, further including a narrow bandwidth optical filter disposed on the second surface between the metasurface and the at least one image sensor. (Item 12) The imaging system according to item 10, wherein at least a portion of the aperture is interconnected with the first surface. (Item 13) The imaging system according to item 8, wherein the metasurface is disposed on the second surface. (Item 14) The imaging system according to item 7, wherein the image sensor is in contact with the second surface. (Item 15) The imaging system according to item 7, wherein the field of view is at least ±30 degrees. (Item 16) The imaging system according to item 7, wherein at least the imaging sensor and the metasurface have a rectangular geometry. (Item 17) An imaging system, comprising At least one image sensor, A substrate layer having a substrate thickness, wherein the substrate layer is configured to be transparent to a target wavelength of light, and the substrate layer has a first surface distal to the at least one image sensor and a second surface proximal to the at least one image sensor, a substrate layer, At least one refractive lens disposed above the substrate and configured to focus the impinging light on the first surface of the substrate layer, A single layer of a plurality of identical or unique nanostructure elements including a metasurface disposed on one of the first or second surfaces, such that light impinging on the at least one refractive lens passes through at least a portion of the metasurface element, thereby imposing an angular deflection, a single layer, The distance between the at least one refractive lens and the metasurface is separated by a first distance, An imaging system in which the refractive lens and the metasurface are configured to collect light within a specified operating bandwidth over a specified field of view and shift the incident light to be focused on the at least one image sensor at a chief ray angle of zero or approximately zero degrees. (Item 18) The imaging system according to item 17, further including an air gap between the second surface of the substrate and the image sensor. (Item 19) The imaging system according to item 18, wherein a spacer layer is disposed within the air gap. (Item 20) The imaging system according to item 18, wherein the metasurface is disposed on the first surface. (Item 21) The imaging system according to item 20, further including a narrow bandwidth optical filter disposed on the second surface between the metasurface element and the at least one image sensor. (Item 22) The imaging system according to item 17, wherein at least a portion of at least one of the refractive lenses is interconnected with the first surface. (Item 23) The imaging system according to item 18, wherein the metasurface is disposed on the second surface. (Item 24) The imaging system according to item 20, wherein the image sensor is in contact with the second surface. (Item 25) The imaging system according to item 17, wherein the field of view is at least ±30 degrees. (Item 26) The imaging system according to item 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) The imaging system according to item 17, comprising at least two refractive lenses including a convex-concave lens and a concave-convex lens. (Item 28) The imaging system according to item 17, comprising at least two refractive lenses including a convex-concave lens, a biconvex lens, and a plano-concave lens. (Item 29) The imaging system according to item 17, wherein at least the imaging sensor and the metasurface have a rectangular geometric shape. (Item 30) The imaging system according to item 29, wherein the at least one refractive lens proximal to the metasurface has a circular geometric shape. (Item 31) The imaging sensor is characterized by vertical v and horizontal h dimensions, and the at least one refractive lens is characterized by N defined as N = f / D of the lens, where f is the focal length of the optical system and D is the diameter of the lens, and the lens width of the metalens is given by w = v + f / N, and the metalens length l is given by l = h + f / N. The imaging system according to item 29.

Brief Description of the Drawings

[0034] This specification will be more fully understood with reference to the following figures, which are presented as exemplary embodiments of the invention and should not be construed as an exhaustive listing of the scope of the invention.

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 8C

Figure 8D

Figure 9

Figure 10A

Figure 10B

Figure 11A

Figure 11B

Figure 12A

Figure 12B

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17A

Figure 17B

Figure 18

[0036] Returning now to the drawings, provided are a hybrid imaging system incorporating conventional optical elements and metasurface elements together with a light source and / or a detector, and a method for manufacturing and operating such an optical arrangement. Many embodiments are directed to systems and methods for integrating an aperture with metasurface elements within an illumination source and a sensor. Various embodiments are directed to systems and methods for integrating refractive optics with metasurface elements of an illumination source and a sensor.

[0037] Many embodiments of optical imaging systems may incorporate a single aperture and a single metasurface layer operable to correct aberrations across a wide field of view. Many embodiments of such single aperture and metasurface imaging systems are configured to be telecentric across a wide field of view (e.g., the angle of incidence at the image sensor plane is approximately 0 degrees) such that there is no reduction in relative illuminance across the field of view (e.g., the intensity from an on-axis ray is substantially the same as the intensity at the edge of the field of view).

[0038] In many embodiments, the hybrid refractive optical system and the metasurface imaging system can include a metasurface element that is standalone (i.e., not directly integrated with a particular illuminator or sensor into the system). In some embodiments, the optical system can be composed of a single physical component or substrate having metasurface elements disposed on both of its sides. In some embodiments, a plurality of refractive optical systems can be combined with at least one metasurface element to create a more complex system.

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

[0040] In many embodiments, the metasurface element can be standalone or embedded within another material. In various such embodiments, the selection of the embedding material includes an appropriate selection of refractive index and absorption characteristics. In many such embodiments, the embedding material can provide mechanical stability and protection, as well as additional design freedom that enables the metasurface to perform the desired optical function.

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

[0042] Various embodiments also relate to methods of fabricating a hybrid metasurface imaging system. In some such embodiments, the method is directed to the fabrication of metasurface elements on a wafer that incorporates other devices such as sensors or illuminators, thereby, in some embodiments, avoiding expensive manufacturing processes such as the mechanical assembly of small elements or the active alignment of optical systems with sensors. In some such embodiments, the metasurface elements can be integrated with a sensor (or illuminator) in a series of operations in a semiconductor fabrication facility. In many such embodiments, the sequence can include (i) a sensor or illuminator, (ii) an optional microlens array / collimator, an optional filter, an optional spacer layer, an optional metasurface element, an optional additional spacer layer, an optional refractive optical system or aperture element, an optional anti-reflection (AR) layer, and an optional protective layer. In many such embodiments, the arrangement of elements can include (i) a sensor or illuminator, (ii) an optional microlens array / collimator, an optional filter, an optional spacer layer, an optional metasurface element, an optional additional spacer layer, and an optional refractive element or aperture.

[0043] Embodiments for implementing an aperture / metasurface imaging system Typically, to form an optical system with corrected aberrations 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 conventional refractive optical systems and metasurface optical systems. Specifically, only optical systems having two or more metasurfaces and having sufficiently low aberrations over a certain field of view have been demonstrated. Various embodiments are directed to imaging systems that integrate an aperture and a single metasurface element that can achieve high-quality imaging over a wide field of view, telecentricity over a wide field of view (e.g., near 0 degrees of incidence at the image sensor plane), and no reduction in relative illumination, through a combination of the systems.

[0044] Specifically, such a system can be used in an imaging system such as a CMOS camera (e.g., in a mobile phone, computer, tablet, etc. for collecting images of visible light scenes, or those used with infrared for biometric authentication). These CMOS imaging systems require an increase in the field of view (FOV), independent control of the chief ray angle (CRA) as a function of the field height in the CMOS image sensor, and minimization of optical distortion in imaging the scene. These terms will be understood to have their conventional meanings to those skilled in the art. In a traditional imaging system composed of refractive lenses, in order to perform this function, as many as five or six distinct lenses have to be combined. Similarly, in a conventional metasurface, the imaging system implements a plurality of metasurface elements and provides sufficient degrees of freedom for appropriately controlling these parameters (CRA, FOV, and distortion minimization). However, various embodiments show that by combining an aperture with a single metasurface, an imaging system with a wide FOV, controllable distortion, and controllable CRA can be realized according to the embodiments.

[0045] Exemplary embodiments of such a system are illustrated in FIGS. 1-7. As shown, in many such embodiments, the system (10a-10d) generally includes an aperture structure (12a-12d) disposed at a distance (13a-13d) set from a metasurface layer (14a-14d), and this metasurface layer itself is set at a certain distance (15a-15d) from the image sensor (16a-16d). As will be described in more detail below, in such a system, 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 distance of the imaging system) may take the form of an air gap or a light-transmissive material (e.g., a substrate, etc.).

[0046] For the purposes of many embodiments, the aperture structure (12a - 12d) includes a first aperture structure portion (18a - 18d) that is opaque to light at the wavelength of interest and a second aperture structure portion (20a - 20d) that is completely transparent to light at the wavelength of interest over a distance (d ap ). In various embodiments, such an aperture structure restricts the lateral spread of the light beam entering the imaging system or equivalently sets the entrance aperture of the imaging system in various ways without imparting an optical function (e.g., not deflecting the light rays).

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

[0048] Embodiments of the nanostructure generally have feature sizes smaller than the wavelength of light within a specified operating bandwidth and are configured to impart a phase shift to colliding light in a plurality of planes separated by a macroscopic distance (a distance of 10 or more wavelengths), such that the metasurface layer performs a single optical function in combination. It includes the same or unique three - element elements (e.g., square, circular, triangular, elliptical, etc.). Each individual metasurface of the optical system can be configured to have some specific 2D phase and transmittance functions, φ(x, y) and t(x, y), that this metasurface performs. Generally, each metasurface can have a unique distribution of phase and transmittance, but nanostructure elements that have the same basic configuration and contain any metasurface embedded in the same material at a specific wavelength are identical. In most practical single - wavelength applications, the transmittance can be configured to be maximized (close to 1) and uniform across the metasurface, while the phase can be configured to take values from 0 to 2π. Briefly, according to an embodiment, for some wavelengths of interest, material systems (metasurface material and embedding material), fixed thickness, and element spacing, the set of in - plane dimensions of what includes the nanostructure may be configured such that a phase delay of 0 to 2π can be imprinted on the incident light field. Thus, for different implementations of metasurface designs under fixed material and wavelength conditions, the only variable for each design is the distribution of suitable nanostructure elements across the metasurface.

[0049] The meta - surface layer according to some embodiments is designed to be independent, i.e., the meta - surface element may protrude from the edge of the substrate such that only an air - gap separates the meta - surface elements, and the process is completed at this step. In other embodiments, the meta - surface may be further configured to have an AR coating or mechanical protection. In some such embodiments, the meta - surface constituent elements and the substrate surface may be coated with several materials or layers of materials to protect the meta - surface and provide improved functionality. In embodiments having embedded meta - surface elements, the elements, which can be any material having the desired optical properties, are embedded in a lower refractive index medium. The lower refractive index medium completely seals the meta - surface and extends some thickness above the meta - surface elements. The lower refractive index medium functions as a protection barrier for the meta - surface elements (i.e., provides mechanical stability) and provides additional design freedom for the system to optimize certain properties, such as the overall transmittance or efficiency of the meta - surface.

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

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

[0052] FIG. 1 provides a schematic illustration of an implementation of various embodiments of such a hybrid aperture / metasurface imaging system. As shown, in many embodiments, a substrate layer (24a) that is transparent at the wavelength of interest and has a thickness (t sub ) is provided, and the substrate layer (24a) is disposed on a first side distal to the imager (16a) and is opaque to light at the wavelength of interest and is completely transparent to light at the wavelength of interest over a certain distance. An aperture structure (12a) and (d ap ) A metasurface layer (14a) composed of nanostructures (22a) having equal heights and disposed on a second side proximal to the imager (16a) and composed of nanostructures (22a). In such embodiments, the aperture structure (12a) and the metasurface layer (14a) are separated by a first distance (13a) defined by the substrate thickness (t sub ). Further, in such embodiments, the aperture structure (12a) and the metasurface layer (14a) may be directly deposited on the substrate (24a) or joined via an adhesive. Between the metasurface layer (14a) and the imager (16a), a distance (15a) defining a back focal length formed by 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] In such embodiments, it will be understood that the aperture only limits the lateral spread of the light beam that can enter the imaging system without imparting an optical function (not deflecting the light beam) or equivalently sets the entrance aperture or the f / # of the system. On the other hand, in such embodiments, the metasurface layer may include the only functional optical layer that significantly deflects the light beam to form a focused image. In some such embodiments, the metasurface layer may function as an arbitrary phase mask and impart an arbitrary value of a phase shift from 0 to 2π to the incident light at any radial position of the lens.

[0054] Referring to FIG. 2, a ray tracing diagram 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 FIG. 1 is provided. (Although not described in detail herein, these metasurface elements can be processed using suitable conformal deposition processes such as, for example, low pressure chemical vapor deposition or atomic layer deposition, and using methods such as those described herein or in the previously cited U.S. Patent Application No. 16 / 120,174.) In this exemplary embodiment, the aperture and the metasurface elements are configured such that they can form a good image over a wide FOV (in this example, ±40 degrees, but it should be understood that this is not a limiting case). Embodiments of such a single aperture and single metasurface system as shown have surprisingly been found to naturally generate focused rays in an image plane that is telecentric (i.e., has a CRA of 0 degrees). In short, traditional refractive and metasurface designs require complex multi-element systems to achieve such a telecentric design, whereas according to the embodiments, only a single aperture and a single metasurface element are needed to achieve similar telecentricity. This telecentricity in turn leads to an improvement in optical properties. In particular, a low (e.g., zero or near-zero CRA) enables narrowing of the bandwidth of an optical filter (26) for narrowband applications. In traditional refractive designs, especially for particularly compact mobile applications, the CRA is typically on the order of 15 degrees to 30 degrees. These larger CRAs in turn require significantly increasing the filter bandwidth 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. Thus, embodiments of combined metasurface / filter systems such as those shown in FIG. 2 enable better ambient light performance.

[0055] Figures 1 and 2 provide one arrangement of optical elements for a hybrid aperture / metasurface imaging system, but it will be understood that many other arrangements of the elements can be realized. For example, FIG. 3 provides a schematic illustration of an embodiment of an imaging system in which the positions of the air gap and the substrate are interchanged. Such a structure enables the formation of a thinner imaging system, but involves a more complex assembly process. In particular, as shown in FIG. 3, an embodiment of such an imaging system includes a substrate (24b) that is transparent at the wavelength of interest and has a thickness (t sub ), and the substrate is provided with a metasurface layer (14b) composed 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) can be directly bonded via an adhesive or other suitable means. A distance (15b) that defines a back focal length formed by the substrate thickness (t sub ) is disposed between the metasurface layer (14b) and the imager (16b). This distance is used as a free parameter for designing an imaging system with optimal performance and varies, for example, based on the desired f / # or field of view of the imaging system. In such an embodiment, such an imaging system does not require an optional cover glass or filter used in the embodiment shown in FIG. 1 because the substrate (24b) provides such dual functionality. In such an embodiment, an aperture structure (12b) that is opaque to light at the wavelength of interest and completely transparent to light at that wavelength of interest over a certain distance (d ap ) and the metasurface layer (14b) are separated by a first distance (13b) defined by an air gap (t air ).

[0056] Referring to FIG. 4, a ray tracing diagram through an exemplary embodiment of a system including a single aperture (12b), a single metasurface (14b), and an imager (16b) combined on a single substrate (24b) according to the embodiment illustrated in FIG. 3 is provided. (Although not described in detail herein, these metasurface elements can be processed using suitable conformal deposition processes such as low-pressure chemical vapor deposition or atomic layer deposition, using the methods as described herein or in the previously cited U.S. Patent Application No. 16 / 120,174.) In this exemplary embodiment, the aperture and the metasurface elements are configured such that in combination they can form a good image over a wide FOV (in this example, ±40 degrees, but it should be understood that this is not a limiting case). Embodiments of such a single aperture and single metasurface system as shown have surprisingly been found to naturally generate focused rays in an image plane that is telecentric (i.e., has a CRA of 0 degrees).

[0057] FIGS. 1 and 4 provide an arrangement of optical elements for a hybrid aperture / metasurface imaging system where the elements are in direct contact with the image sensor, but it will be understood that many other arrangements of elements incorporating a spacer disposed between the image sensor and the substrate supporting the metasurface layer can be realized. For example, FIG. 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, embodiments of such an imaging system are transparent at the wavelength of interest and have a thickness (t subcomprises a substrate (24c) having and this substrate is provided with a metasurface layer (14c) consisting of nanostructures (22c) having equal heights disposed on a first side distal to the imager (16c), and a second air gap (28) disposed between the second side of the metasurface layer proximal to the imager (16C) and the substrate. One advantage of such embodiments incorporating an air gap is that, for example, compared to the embodiment shown in FIG. 1, light rays travel through the system at a higher angle, thus allowing a reduction in the overall form factor of the metasurface optical system. In addition, the gap between the metasurface substrate and the image sensor allows 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 embodiments, the metasurface layer (14c) and the imager (16c) may be deposited directly on the substrate (24c) or joined via an adhesive. Such embodiments may also include a suitable spacer (30) for supporting the substrate (24c) and maintaining the distance between the substrate and the image sensor (16c). A distance (15c) defining a back focal length formed by the combination of the substrate thickness (t sub ) and the spacer height (t spacer ) is disposed between the metasurface layer (14c) and the imager (16c). The spacer (30) can be fixed to the image sensor (16c) and the substrate layer (24c) a fixed distance (t spacer ) ahead, or the substrate can be placed in a standard optical barrel and made adjustable after assembly (t spacer ). Such embodiments allow the surface (34) of the image sensor (16c) and the proximal substrate (24c) to remain unpatterned and allow the direct integration of an optional optical filter on this surface.

[0060] As shown in FIG. 6, an embodiment of a hybrid aperture / metasurface configuration incorporating an air gap above the image sensor is described. In various embodiments, the metasurface layer (14d) may also be disposed on the surface of the proximal substrate (24d) facing the image sensor (16d) of the air gap (32) supported by the spacer (30'). Such an implementation allows protecting the metasurface elements from environmental contamination. Additionally, such embodiments allow the surfaces (34') of the distal metasurface substrate (24d) and the image sensor (16d) to remain unpatterned and allow direct integration of an optional optical filter on the substrate. Here too, in such embodiments, the spacer (30') can be fixed to the substrate (24d) a fixed distance ahead of the image sensor (16d) and (t spacer ) or the substrate (24d) can be placed in a standard optical barrel and (t spacer ) can be made adjustable after assembly.

[0061] Thus, the embodiments illustrated in FIGS. 5 and 6 illustrate that the metasurface elements can be arranged inwardly or outwardly with respect to the air gap between the substrate and the image sensor. The fabrication of the metasurface systems illustrated in FIGS. 5 and 6 can follow, for example, the process described in U.S. Patent Application No. 16 / 120,174. The spacer layer may be any low refractive index material, such as a polymer, SiO2, glass.

[0062] Embodiments of a hybrid aperture / metasurface imaging system incorporating an air gap between the aperture and the metasurface substrate are shown in FIGS. 3, 5, and 6. These embodiments fix the aperture and the aperture distance (t air) would require a separate support structure to ensure that it 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 an aperture body (36) with a width d ap,top that sets the entrance aperture of the system and has an aperture offset of a distance (t ap ) from the substrate, and the distance along the optical axis set by (t ap ) is set by the width of the metasurface layer, and after being given by (d ap,bottom ), the width of the aperture is angled at a minimum angle set by the half field of view of the imaging system. The embodiment shown in FIG. 7 depicts a system in which the metasurface layer (14e) is disposed on the surface of the substrate (24e) distal from the image sensor (16e), but it will be understood that the metasurface layer may also be disposed on the surface of the substrate proximal to the image sensor (34''). In addition, the exemplary embodiment incorporates a spacer structure (30'') and an air gap between the substrate (24e) and the image sensor (16e), but it will be understood that the embodiment may omit this element and attach the substrate directly on top of the image sensor.

[0063] An attribute of such an embodiment of a telecentric design is that the metasurface imaging system provides more uniform illumination (referred to by those skilled in the art as "relative illumination") at the image sensor. A data plot of the relative illumination of an exemplary system according to an embodiment 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, which is a substantial improvement over conventional systems that can have a difference of 50% or more between the center and the edge. Thus, embodiments of the imaging system can collect a greater total illumination across the entire field of view. Embodiments of the metasurface system also provide additional design variations with respect to traditional refractive lens systems. A typical complementary metal-oxide-semiconductor (CMOS) image sensor (CIS) requires microlenses to be associated with each pixel. Because there is significant variation in the chief ray angle (CRA) across a given sensor plane that is inherent to refractive optical systems, the microlens array on a CIS also requires complex CRA specifications. However, in embodiments of the metasurface system as described herein, the CRA of the microlens array may be configured to be constantly 0 degrees across the entire CIS, allowing for a 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, omitting a process step in the fabrication of the CIS. Further, such an aperture metasurface system with a CRA of 0 enables limiting a persistent problem in traditional imaging systems known to those skilled in the art as "pixel crosstalk". Traditional refractive systems that send light to the image sensor are prone to optically coupling light to adjacent pixels, which adds noise to the system.

[0064] Conventional metasurface systems can be composed of multiple metasurface layers to control FOV and distortion. The introduction of one or more additional metasurface elements enables the realization of arbitrary phase profiles and provides more degrees of freedom for controlling the ray path compared to a typical system composed of an equivalent number of refractive elements. In current imaging system embodiments where a single metasurface layer is used, it is not possible to simultaneously control the CRA and correct grid distortion. As a result, a certain amount of grid distortion is inevitable. For example, FIG. 8B provides a data plot illustrating distortion as a function of the field of view in the CMOS image sensor of the imaging system, based on the embodiment shown in FIG. 1. FIG. 8C shows a plot of the coefficient transfer function versus the field of view of an imaging system embodiment as shown in FIG. 1. FIG. 8D provides a standard test image exemplifying the grid distortion of an imaging system based on the embodiments shown in FIGS. 8A-8C. As shown, the quality deteriorates at the edges of the field of view. However, embodiments of the present invention show that all wavelengths of light can be tightly focused and that the distortion can be corrected using only 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 also contemplate hybrid systems of metasurface elements incorporating refractive lens elements. FIG. 9 provides a schematic illustration of implementations of various embodiments of such a hybrid refractive lens / metasurface imaging system. In many embodiments, the hybrid imaging surface comprises at least one of each of the following: a refractive lens having one or more curved surfaces, and a metasurface layer on a substrate where all of the elements including the metasurface are 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 a metasurface element on a substrate layer that is the final component before the image sensor provides certain advantages in creating a so-called image space telecentric imaging system. Additionally, the substrate on which the metasurface layer is formed can have a set of deposited filter layers. 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 FIG. 9. In many embodiments, the system includes a metasurface layer (42) consisting of nanostructures (44) having equal height disposed on a first surface (45) of a substrate layer (40) that is set at a distance away from and distal to an image sensor (46) and is transparent at the wavelength of interest, and having a thickness (t sub ) and at least one refractive optical system (38), and an optional optical filter (48) disposed on a second side (47) of the substrate proximal to the imager.

[0067] The embodiment shown in FIG. 9 illustrates a hybrid system having a single refractive optical system and a single metasurface layer, but it will be understood that the embodiment may also incorporate other arrangements of refractive optical systems. FIGS. 10A and 10B provide diagrams illustrating such metasurface / refractive hybrid systems. Specifically, FIG. 10A illustrates a hybrid system including two refractive elements (50 and 51) and a single metasurface layer (52) system where the two refractive elements are uneven and uneven. FIG. 10B illustrates a hybrid system including three refractive elements (54, 55, 56) and a single metasurface element (58), where the three refractive elements are uneven, biconvex, and concave-flat, respectively.

[0068] Regarding the refractive optical elements of the hybrid system described above, i.e., those elements preceding the metasurface layer, it will be understood that the surface curvature of these elements can take on any positive, negative, or infinite value. Thus, while a particular arrangement of refractive elements is shown in the figures, the refractive elements may take on any suitable form and combination for a particular application, including, for example, plano-convex, convex-plano, biconvex, biconcave, plano-concave, or concave-plano.

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

[0070] Embodiments of the metasurface layer can be integrated with a complementary metal-oxide-semiconductor (CMOS) image sensor (CIS) as a cover glass and a filter, while a refractive optical system can be assembled within a barrel as conventionally done in an optical imaging module. In certain embodiments, in addition to using the glass on which the metasurface layer is processed as the cover glass of the CIS, it can be deposited together with a dielectric layer in advance and function as a near-infrared bandpass or long-pass filter. Such embodiments provide a single component having functions in an optical imaging process and exclude unnecessary wavelengths from entering the image sensor.

[0071] The above embodiments focus on a hybrid metasurface imaging system having a single sensor element, as shown, for example, in FIGS. 1 to 10B. However, the metasurface elements can also be integrated with an image sensor wafer that includes a plurality of image sensor dies. A schematic diagram of an image sensor wafer is illustrated in FIG. 11A. As shown, an embodiment can include an image sensor wafer (60) that includes a set of image sensor dies (62), which are shown in a periodically spaced 2D array, although it will be understood that it is not necessary to space the array periodically. As shown in FIG. 11B, each sensor die (62) includes an image sensor active area (64). Each image sensor may be the same, but in many embodiments, the characteristics of each sensor may generally be unique. Since each imager including the array can have unique characteristics, it may also be advantageous to have an array of metasurface elements each having uniquely designed characteristics.

[0072] It should be understood that only the active region (64) needs to be available for imaging. The region outside the image sensor active area (66) can be used to attach a lens or spacer. Further, in various embodiments, the metasurface substrate may be offset from the image array by a spacer. Exemplary embodiments of a spacer wafer (70) including a plurality of spacer openings suitable for attachment to a sensor wafer and a spacer die (72) suitable for attachment to an image sensor or lens die are illustrated in FIGS. 12A and 12B, respectively. The design and thickness of the spacer layer depend on the particular configuration, but in many embodiments, the thickness is configured such that the light from the illumination source diverges sufficiently before interacting with the image sensor. Again, the function of each metasurface element within the array may generally be unique and may be patterned over each individual image sensor within the array using any suitable technique outlined, for example, in U.S. Patent Application No. 16 / 120,174. For example, the metasurface may be fabricated directly on each individual image sensor within the array, or a suitable dielectric spacer may be deposited on the image sensor, followed by the integration of the metasurface over the combined dielectric layer and image sensor. In such embodiments, the metasurface may provide a specific radiation pattern for each image sensor, and the overall system (image sensor characteristics, geometric parameters, and radiation pattern corresponding to the metasurface) can be iteratively optimized for a particular set of performance parameter sets.

[0073] In various other embodiments, a dielectric material having a refractive index lower than that of the constituent image sensor material can be deposited and planarized such that a single metasurface can be patterned on top of the dielectric material. This is in contrast to embodiments where each image sensor in the array has a unique metasurface patterned on the facet of the image sensor. Here too, in such embodiments, the combined system can be optimized to achieve the desired performance. Finally, in all of the above embodiments, the 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, and illustrative embodiments of such devices are shown in FIGS. 13 and 14.

[0074] Specifically, FIG. 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 embodiments, the spacer can be attached using an adhesive (e.g., UV-curable epoxy or thermosetting epoxy), solder, or fusion bonding.

[0075] FIG. 14 illustrates an exemplary embodiment excluding 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 the lens die (84) can be attached directly using an adhesive, solder, fusion bonding, bump bonding, etc. Alternatively, the image sensor wafer and the lens wafer can be attached directly at the wafer level as described above.

[0076] As shown in FIG. 15, in certain embodiments, the refractive lens (91) of the hybrid system may first be assembled within the lens barrel (92), as is already known in the art. The metasurface element (94) can then be combined with the CMOS image sensor (96) as described above with respect to FIGS. 13 and 14. These two sub-components are then assembled together to form the final system. In such embodiments, the refractive lens may be configured to screw-fit into the housing (98) such that the distance between the refractive element and the metasurface (t gap ) can be adjusted.

[0077] Implementation of Embodiments 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 geometry of the formed image is often referred to as the lens image circle. However, in modern photography, the medium on which the image is recorded (e.g., a CMOS image sensor) often has a rectangular shape. In camera design, the lens image circle is designed such that the diameter D image of the image circle is at least as large as the diagonal d of the image sensor. However, since the image sensor is rectangular, in practice, only a portion of the image circle impinges on the image sensor. Thus, much of the lens area onto which light from the scene is incident is not used in the final formation of the image from the camera system.

[0078] In traditional injection-molded plastic refractive lenses, the shape of the lens is ideally kept circular. From a manufacturing perspective, circular shapes and radially symmetric lenses are extremely easy to achieve and have the best manufacturing reproducibility, so circular shapes are used. Furthermore, by making large-area circular lenses instead of small-area rectangular lenses, cost increases can be minimized. Therefore, conventional cameras use circular lenses, and only a portion of the light that strikes the entire circular lens is collected by the rectangular image sensor. These portions of the circular lens that do not contribute to the incidence of light on the image sensor even when light is incident are not used for the final image formation.

[0079] For meta-surface lenses according to various embodiments, the shape of the lens can be designed such that the image formed by this lens conforms inherently to a specific 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 meta-surface lens is formed in a rectangular configuration with specific dimensions, and thus the formed scene image is also rectangular. In an ideal case of such a design embodiment, all of the light that strikes the rectangular meta-surface lens is incident on the image sensor. Embodiments of the meta-surface with a rectangular lens break the radial symmetry, and thus the image formed by the lens is no longer circular or radially symmetric.

[0080] Thus, in many embodiments of the lens system, the meta-surface lens element can be formed in a rectangular configuration. The advantages of such rectangular or non-circular lenses include limiting the total area of the lens, subsequently eliminating portions of the lens that otherwise direct light so as not to form an image on the image sensor, and simplifying the post-processing of the lens wafer. Specific embodiments of the rectangular meta-surface lens and imaging system are described herein.

[0081] Many embodiments of metasurface lens systems having non-circular configurations have the following commonalities: an entrance aperture that is the aperture of the lens system, and a metasurface lens that is the final active optical surface in front of the image sensor plane. In such embodiments, the entrance aperture (and the optical aperture) 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 explanatory diagram of an exemplary embodiment of a clear aperture metasurface. The 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 refraction system, the optical system is composed of an entrance aperture, at least one refractive lens, and a metasurface lens that is the last optical lens element in the system in front of 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, in embodiments of such hybrid systems, as shown in FIG. 16, it would be composed of a circular aperture (106) offset from at least one circular refractive lens (not shown), and then this circular refractive lens is offset from the rectangular metasurface lens (104). Again, in such embodiments, the metasurface lens has rectangular dimensions configured to fit a particular image sensor. Here, the example describes an implementation where the metasurface lens element has a rectangular cross-section alone, but this is not a limiting case. For example, the entrance aperture (and the aperture 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, which is the last lens element in front of the image sensor, has a rectangular cross-section.

[0083] In certain cases, the dimensions of the rectangular lens of the system can be fully characterized by the dimensions of the image sensor of the system and the lens specifications. Specifically, as shown in FIG. 17A, it is characterized by the vertical and horizontal dimensions v and h of the image sensor, respectively. The lens system is most commonly characterized by the 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. Thus, as shown in FIG. 17B, the lens width of the desired rectangular metasurface lens can be shown as w = v + f / N, and the length can be shown as l = h + f / N. Such a definition of the lens dimensions results in an image that almost completely fills the sensor geometry. In practice, it is desirable to make the image formed by the imaging system slightly larger than the dimensions of the image sensor. This oversizing of the image allows for a greater tolerance in the final assembly of the lens system. A typical oversizing range can take the nominal rectangular lens dimensions as given above and increase each dimension by 40 microns.

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

[0085] Figures 18A-18D illustrate a 2×2 array of circular apertures on a rectangular metasurface. In general, however, the grid of circular apertures and the rectangular metasurface lens may be arranged in any pattern, symmetric or asymmetric, such as 3×3 or 5×2. Additionally, each individual rectangular metasurface and circular aperture that make up the system may have dimensions that are unique to the remaining aperture-metasurface pairs of the system. For example, each aperture diameter within the array may generally be unique, or each rectangular lens may be unique. However, the distances between the metasurface lens, the image sensor, the metasurface lens, and the circular aperture are generally fixed for the entire system. By varying the mechanical parameters (e.g., aperture size) for each individual component of the array, it is possible to customize the optical characteristics of each camera within the array. For example, according to an embodiment, each sub-camera can have a unique f / #, field of view, resolution, etc.

[0086] Equivalence theory Thus, while the invention has been described in a particular manner, many additional changes and modifications will be apparent to those skilled in the art. Accordingly, it is to be understood that the invention may be practiced otherwise than as specifically described. Therefore, the embodiments of the invention are to be considered in all respects as illustrative and not restrictive.

Claims

1. An imaging system, wherein the imaging system comprises: at least one image sensor; a substrate layer disposed above the at least one image sensor by a first distance, the substrate layer having a substrate thickness, the substrate layer being 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 layer, the aperture having an aperture opening disposed therein; a single layer of a plurality of identical or unique nanostructure elements including a metasurface disposed on the second surface, such that light impinging on the aperture opening is subjected to a specified angular deflection by passing through at least a portion of the metasurface; comprising; the distance between the aperture and the metasurface is separated by a second distance determined by the substrate thickness; the aperture and the metasurface are configured to collect light within a specified operating bandwidth over a specified field of view and to shift the target wavelength of the light to cause focusing at a chief ray angle of zero degrees or substantially zero degrees onto the at least one image sensor; the at least one image sensor and the metasurface have a rectangular geometry; the metasurface is configured to project a rectangular image of the specified field of view completely onto the at least one image sensor.

2. The imaging system according to claim 1, further comprising a glass cover disposed on the at least one image sensor.

3. The imaging system according to claim 1, wherein the first distance is determined by a spacer layer composed of either a solid spacer material or an air gap.

4. The imaging system according to claim 1, wherein the field of view is at least ±30 degrees.

5. The imaging system according to claim 1, further comprising a narrow bandwidth optical filter disposed between the metasurface and the at least one image sensor.

6. The imaging system according to claim 1, further comprising at least one refractive optical system positioned adjacent to the first surface of the substrate layer.

7. The imaging system according to claim 1, wherein the aperture opening does not deflect light rays.

8. The imaging system according to claim 1, further comprising an anti-reflection coating on the metasurface and / or the first surface and / or the second surface.

9. The imaging system according to claim 1, wherein the at least one image sensor includes a plurality of image sensors periodically spaced in a 2D array.

10. The imaging system further comprises at least one refractive lens, the at least one image sensor is characterized by a vertical dimension v and a horizontal dimension h, the at least one refractive lens is characterized by N which is the F-number of the at least one refractive lens, and N is defined by N = f / D, where f is the focal length of the imaging system and D is the diameter of the at least one refractive lens. The imaging system according to claim 9.

11. The metasurface width w is given by w = v + f / N, The metasurface length l is given by l = h + f / N. The imaging system according to claim 10.

12. The aperture has a circular geometry. The imaging system according to claim 1.

Images