TW202403396A - Optical system and method of forming the same, method of forming a multi-color image - Google Patents

Abstract

Various embodiments may relate to an optical system. The optical system may include a plurality of color filters, a first color filter of the plurality of color filters configured to select light of different wavelength ranges representing different color channels. The optical system may also include a plurality of metalenses, each of the plurality of metalenses associated with a respective color channel of the plurality of color channels. Each of the plurality of metalenses may have a focal length, the plurality of metalenses having equal focal lengths such that the different color channels are combined on a common focal plane to form a multi-color image. Each of the plurality of metalenses may include a plurality of nanostructures, have a (FOV) field of view of more than 30 degrees, and a desired working spectral bandwidth dependent on an extended depth of focus, a central wavelength of the associated color channel, and the focal length at the central wavelength.

Description

Optical system, method of forming optical system, method of forming multi-color image

Various embodiments of the disclosure may relate to an optical system. Various embodiments of the present disclosure may relate to a method of forming an optical system. Various embodiments of the present disclosure may relate to a method of forming a multi-color image.

Conventional refractive lenses are the core of most imaging systems. However, in order to produce high-resolution images with minimal optical aberrations, high-end imaging systems generally consist of complex optical trains (i.e., lenses and/or other optics that guide the input light to the detector). components), such as microscope objectives or photographic objectives. Therefore, such imaging systems are generally large and bulky. On the other hand, for certain applications, such as for mobile phone cameras, drone cameras, satellite cameras, and endoscopic cameras, it is highly desirable to be as light and compact as possible without compromising imaging quality. imaging system. Recent developments in diffractive optics as well as planar optics promise to replace traditional optical tandems with only a few elements, or even a single element, with ultra-thin properties (i.e. thickness below or close to the wavelength of the incident light). This can be achieved using diffractive lenses or planar lenses (the latter are also called metalenses).

The role of a conventional refractive lens is to reshape the plane wavefront of the input light into a spherical wavefront so as to focus the light to a light point close to the diffraction limit. The underlying physical mechanism is related to phase accumulation by light propagating through a material that exhibits a varying thickness in the direction of propagation through the lens. Refractive lenses are typically made from at least one hemispherical surface with a radius of curvature, resulting in a relatively thick device. The diffractive counterpart of refractive lenses are called conventional diffractive lenses (CDL). Conventional diffractive lenses limit this phase modulation to its minimum value of 2π, which generally allows a significant reduction in the lens' Thickness to slightly greater than the maximum thickness of the wavelength of light.

However, diffractive lenses suffer from serious chromatic aberration problems due to their diffractive nature, that is, diffractive lenses only focus a single wavelength (the design wavelength) at the desired location, while other wavelengths are not focused at the same location: longer wavelengths are closer It is focused by the lens, and shorter wavelengths are focused further away from the lens. Chromatic aberration can cause blurry images and rainbow effects. This chromatic aberration of conventional diffractive lenses, in which longer wavelengths are focused closer to the lens, while shorter wavelengths are focused further away from the lens, is different from the usual chromatic aberration of refractive lenses, which is due to Caused by material dispersion (that is, changes in the material's refractive index and wavelength). Positive chromatic dispersion is mentioned for refractive lenses, and negative chromatic dispersion is mentioned for diffractive lenses. Figure 1 provides chromatic aberration diagrams of (a) a conventional refractive lens and (b) a diffractive lens. Wavelengths λ ₁ > λ ₂ > λ ₃ are focused at different places along the optical axis. Refractive lenses exhibit positive dispersion, while diffractive lenses exhibit negative dispersion.

Recently, with the advancement of nanofabrication technology, other physical mechanisms for phase modulation have been explored and exploited. It is based on the interaction of light with patterned nanostructures on a plane, called metaatoms, which locally give the light a certain phase retardation. The main mechanisms are waveguide, geometric phase, and resonant interactions, each with different advantages and limitations. In general, metaatoms constrain phase modulation to 2π and smaller than the wavelength of interest in all directions (except perhaps in the direction of light propagation since it may also have dimensions near the wavelength). Recent implementations of extremely thin focusing surfaces (called metalenses) based on this paradigm have demonstrated superior performance in terms of numerical aperture (NA) and focusing efficiency over diffractive lenses, making them an alternative to refractive lenses. More promising candidates.

However, two main hurdle challenges still limit the applicability of metalenses. First, like diffractive lenses, metalenses have a strong negative dispersion problem. Secondly, most metalenses so far have problems with off-axis monochromatic aberration (focus distortion when the incident angle is non-zero), that is, coma and astigmatism, which greatly limits the ability of the input light to tilt at an angle. The ability of a lens to focus light into a good quality spot when incident into the lens. The range of angles of incidence over which a lens can produce good quality focus is called the field of view (FOV). A large field of view is important for imaging applications. These two challenges have so far prevented metalenses from being widely used and from replacing their refractive counterparts in multispectral as well as broadband imaging.

Various embodiments may relate to an optical system. The optical system may include a plurality of color filters, a first color filter of the plurality of color filters configured to select light representing a first wavelength range of the first color channel, and a second color filter of the plurality of color filters configured to select A second wavelength range of light that is different from the first wavelength range is selected, and the light of the second wavelength range represents a second color channel, so that the plurality of color filters provide different color channels. The optical system may further include a plurality of metalenses, the plurality of metalenses being respectively associated with corresponding color channels of the plurality of color channels. The plurality of metalenses can each have a focal length, and the plurality of metalenses have equal focal lengths, so that different color channels are combined on a common focal plane to form a multicolor image. The plurality of metalenses may each include a plurality of nanostructures, and may have a field of view (FOV) greater than 30 degrees. The plurality of metalenses may each have a desired operating spectral bandwidth that depends on the extended focal depth, the center wavelength of the associated color channel, and the focal length at the center wavelength.

Various embodiments may relate to a method of forming an optical system. The method may include providing a plurality of color filters, a first color filter of the plurality of color filters configured to select light representing a first wavelength range of a first color channel, and a second color filter of the plurality of color filters. Configured to select a second wavelength range of light that is different from the first wavelength range, the second wavelength range of light representing a second color channel, such that the plurality of color filters provide different color channels. The method may also include providing a plurality of metalenses, the plurality of metalenses being respectively associated with corresponding color channels of the plurality of color channels. The plurality of metalenses respectively have focal lengths, and the plurality of metalenses have equal focal lengths, so that different color channels are combined on a common focal plane to form a multicolor image. The plurality of metalenses may each include a plurality of nanostructures, and may have a field of view (FOV) greater than 30 degrees. The plurality of metalenses may each have a desired operating spectral bandwidth that depends on the extended focal depth, the center wavelength of the associated color channel, and the focal length at the center wavelength.

Various embodiments may provide a method of forming a multicolor image. The method may include providing broadband light to an optical system. The optical system can be any suitable optical system as described herein. The optical system may include a plurality of color filters, a first color filter of the plurality of color filters configured to select light representing a first wavelength range of the first color channel, and a second color filter of the plurality of color filters configured to select A second wavelength range of light that is different from the first wavelength range is selected, and the light of the second wavelength range represents a second color channel, so that the plurality of color filters provide different color channels. The optical system may further include a plurality of metalenses, the plurality of metalenses being respectively associated with corresponding color channels of the plurality of color channels. The plurality of metalenses can each have a focal length, and the plurality of metalenses have equal focal lengths, so that different color channels are combined on a common focal plane to form a multicolor image. The plurality of metalenses may each include a plurality of nanostructures and have a field of view greater than 30 degrees. The plurality of metalenses may each have a desired operating spectral bandwidth that depends on the extended focal depth, the center wavelength of the associated color channel, and the focal length at the center wavelength.

The following detailed description refers to the accompanying drawings, which show by way of illustration specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention. The various embodiments are not necessarily mutually exclusive, as some embodiments may be combined with one or more other embodiments to form new embodiments.

Embodiments described in one of the optical systems herein are similarly valid for other optical systems. Similarly, embodiments described in the methods herein are similarly valid for optical systems and vice versa.

Features described in one embodiment herein may correspondingly apply to the same or similar features in other embodiments. Features described in one embodiment herein may correspondingly apply to other embodiments even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or substitutions of a feature described in one embodiment herein may be correspondingly applied to the same or similar features in other embodiments.

In various embodiments herein, use of the articles “a,” “an” and “the” with respect to a feature or element includes reference to one or more features or elements.

In various embodiments herein, the word "about, approximately" when applied to a numerical value includes the exact value as well as reasonable variations.

As used herein, the word "and/or" includes any and all combinations of one or more of the associated listed items.

Diffractive lenses for chromatic compensation: In order to solve the problem of chromatic aberration, different methods have been considered. So-called achromatic diffractive lenses (ADL) can be used to operate at high diffraction orders and provide the same deflection angle for several discrete harmonic wavelengths. Although advanced numerical optimization can help improve focusing efficiency, a recent study shows that there is a considerable limit to the achievable Fresnel number (FN), which translates into a finite numerical aperture (NA) for a given focal length. or lens size. Furthermore, it should be noted that diffractive lenses are subject to parasitic interferences inherent in their blazed profiles as well as shadowing effects, which in turn limit the acceptable incidence angles of diffractive lenses, i.e. diffraction The field of view of the lens.

Metalens for color image compensation: Without further correction of chromatic aberration, a single metalens cannot achieve imaging covering the entire visible light range (white light imaging) due to chromatic aberration. Initially, coverage of the visible spectrum was achieved by using individual metasurfaces for each individual wavelength: red, green, blue (RGB) and even more additional colors. Another approach is to adopt a cascading design with different metalenses operating at different wavelengths (i.e., a stack of several metalenses), which allows compensation of not only chromatic aberrations, but also monochromatic aberrations. However, stacks of these metalenses are difficult to design if interlayer coupling and/or reflections are to be considered and/or minimized. In addition, the required complex manufacturing and alignment processes pose serious challenges to its practical application.

A further development in metalens design aimed at correcting this chromatic aberration within a single element is called a multispectral or broadband achromatic metalens. Multispectral or broadband achromatic metalenses focus several discrete or continuous ranges of wavelengths to on a single point of light.

Different approaches to forward design have been proposed:

(i) Spatial multiplexing of different metaatoms in the "unit-cell" of the metalens, with each metaatom designed to manipulate a specific wavelength. However, in this case, inter-particle coupling can hinder resolution and image quality. Beyond this, as the number of wavelengths increases, the associated efficiency degradation translates into a low number of operating wavelengths and represents a major bottleneck for this solution.

(ii) The use of a single metalens with a non-intuitive point spread function (PSF) generally results in a greatly expanded depth of focus, sufficient to partially compensate for the chromatic focus shift. This subsequently requires image processing techniques for image restoration, which introduces latency in processing the image, which can be problematic for real-time imaging applications.

(iii) Dispersion engineering of individual metaatoms, manipulating not only the phase given to the incident light, but also the group delay and group delay dispersion. Initial attempts at this approach used simple and intuitive geometric shape libraries. However, since these libraries typically cover only a subset of the required phase and group delay variations, the success of this approach is limited to metalenses with very small size, efficiency, numerical aperture, and field of view.

Recently, computer algorithm-based optimization of metaatoms and machine learning methods have helped to some extent to use inverse design technology to design multispectral and broadband achromatic metalenses with higher performance. However, these methods often require high computational power at the expense of fabrication complexity, strong inter-particle coupling, and strong sensitivity to the polarization and angle of incidence of the incoming light. Advances in this field have allowed overcoming some of the problems mentioned in multispectral imaging, for example regarding the relatively large metalens size and numerical aperture.

Metalenses for large fields of view: Regarding the field of view, it should be noted that the field of view depends explicitly on the type of phase profile encoded by the metalens. For example, the hyperbolic phase profile, a common standard used in metalens design, produces an almost diffraction-limited spot with high numerical aperture when light enters the metalens at normal incidence, while exhibiting strong sensitivity for oblique incidence. Coma aberration as well as astigmatic aberration, which greatly limits the field of view of the hyperbolic phase profile to angles of incidence of only a few degrees. The recent introduction of secondary phase profiles alleviates the constraints on the field of view, making such metalenses a very attractive solution for imaging applications. Another alternative solution uses doublets to deal with the limited field of view problem, but introduces significant complexity in manufacturing.

The above attempts address the issues of achromatic imaging and wide field of view imaging separately, without implementing solutions for wide field of view (FOV) and multispectral or broadband achromatic imaging together.

Various embodiments can simultaneously achieve compact wide field of view (FOV) and multispectral imaging, including white light imaging.

Figure 2 is a general illustration of an optical system according to various embodiments. The optical system may include a plurality of color filters 202, a first color filter of the plurality of color filters 202 configured to select light representing a first wavelength range of a first color channel, and a second color filter of the plurality of color filters 202. The filter is configured to select a second wavelength range of light that is different from the first wavelength range, the second wavelength range of light representing a second color channel, such that the plurality of color filters 202 provide different color channels. The optical system may also include a plurality of metalenses 204, the plurality of metalenses 204 being respectively associated with corresponding color channels of the plurality of color channels. The plurality of metalenses may respectively have focal lengths, and the plurality of metalenses 204 have equal focal lengths, so that different color channels are combined on a common focal plane to form a multicolor image. The plurality of metalenses 204 may each include a plurality of nanostructures, and may have a field of view (FOV) greater than 30 degrees. The plurality of metalenses 204 may each have a desired operating spectral bandwidth that depends on the extended focal depth, the center wavelength of the associated color channel, and the focal length at the center wavelength.

In other words, the plurality of color filters 202 are configured to filter light into different color channels, each color channel having a different wavelength range. The optical system may also include a plurality of metal lenses 204 with equal focal lengths, so that different color channels can be focused onto a common focal plane to form a multi-color image.

For the avoidance of doubt, Figure 2 illustrates some features of an optical system in accordance with various embodiments and is not intended to limit the arrangement, orientation, shape, size, etc. of the various features.

In various embodiments, an optical system may include one or more detectors defining a common focal plane.

In various embodiments, color filters 202 may be internal bandpass filters of one or more detectors. In other words, each color filter of the plurality of color filters 202 may be part of a corresponding detector of one or more detectors.

In various other embodiments, color filters 202 may be external to one or more detectors. In other words, the plurality of color filters 202 and the one or more detectors may be separate.

In various embodiments, the plurality of metalenses 204 may be secondary metalenses. In other words, a plurality of metalenses 204 can provide a secondary phase profile. As mentioned above, the plurality of metalenses 204 may each include a plurality of nanostructures. The specific arrangement of the plurality of nanostructures respectively in the plurality of metalenses can provide a secondary phase profile. This secondary phase profile may intrinsically exhibit a certain depth of focus (DOF), such as focal length or focal distance for red, green, and blue (RGB) wavelengths according to various embodiments. Any value from about 5% to about 10%. For example, for a focal length of 83 µm, the depth of focus can be anywhere from about 5 µm to about 7 µm for red, green, and blue (RGB) wavelengths. In various other embodiments, the phase profile (i.e., the placement of the nanostructures within each metalens of the plurality of metalenses 204) may be chosen differently and such that the extended focal depth is different (e.g., greater than quadratic Depth of focus provided by a metalens). In various embodiments, the focal depth of metalens 204 may be engineered to provide a greater desired operating spectral bandwidth.

In various embodiments, the plurality of color filters 202 may be disposed between the plurality of metalenses 204 and the common focal plane, such that the plurality of metalenses 204 are respectively configured to guide broadband light to the plurality of color filters 202 Associated color filters to produce corresponding associated color channels. Each metalens of the plurality of metal lenses 204 associated with a particular color channel may direct a portion of the broadband light to an associated color filter of the plurality of color filters 202 to produce a corresponding associated color channel.

In various other embodiments, the plurality of metalenses 204 may be disposed between the plurality of color filters 202 and the common focal plane, such that the plurality of metalenses 204 are respectively configured to direct light of corresponding associated color channels to on a common focal plane.

In various embodiments, the plurality of metalenses 204 may each have a Fresnel number, and the plurality of metalenses 204 may have different Fresnel numbers, such that the plurality of metalenses 204 have the same focal length.

In various embodiments, the respective nanostructures of the plurality of metalenses 204 may be arranged into a periodic lattice with a predetermined period. In various embodiments, the Fresnel numbers of different metalenses of the plurality of metalenses 204 may differ due to different predetermined periods of the different metalenses (of the plurality of metalenses 204 ).

In various embodiments, the periodic lattice may be a square lattice, a rectangular lattice, a hexagonal lattice, or any other common periodic or quasi-periodic Bravais lattice.

In various embodiments, the optical system may further include a plurality of apertures disposed in front of the plurality of metalenses 204 . The plurality of apertures may each be associated with a corresponding metal lens of the plurality of metal lenses 204 . In various embodiments, a plurality of apertures may be disposed with a plurality of metal lenses 204 such that a plurality of color filters 202 may be disposed between the plurality of metal lenses 204 (and the plurality of apertures) and the common focal plane. In this case, the plurality of apertures may be disposed in front of the plurality of metalenses 204 , and the plurality of color filters 202 may be disposed after the plurality of metalenses 204 (and in front of the common focal plane). In other words, a plurality of metal lenses 204 may be disposed between a plurality of apertures and a plurality of color filters 202 . In various other embodiments, apertures may be disposed with metalenses 204 such that metalenses 204 (and apertures) are disposed between color filters 202 and a common focal plane. In this case, the plurality of apertures may be disposed before the plurality of metalenses 204 and after the plurality of color filters 202 , that is, between the plurality of color filters 202 and the plurality of metalenses 204 .

In various embodiments, metalenses 204 may be made of materials with a refractive index equal to or greater than 2.

In various embodiments, metalenses 204 may include suitable dielectric materials or suitable semiconductor materials.

In various embodiments, the plurality of metalenses 204 may include silicon, gallium phosphide, hafnium oxide, gallium nitride, titanium dioxide, silicon nitride, sapphire, diamond, silicon carbide, aluminum nitride, III-V semiconductors (eg, , gallium arsenide or gallium phosphide) or II-VI semiconductors (e.g., zinc oxide or magnesium oxide).

In various embodiments, the plurality of metalenses 204 may be equal in height or thickness. The optical system may include a substrate. A plurality of metalenses 204 can be on the substrate. Since the plurality of metal lenses are formed on the same planar substrate, the top surfaces of the plurality of metal lenses 204 may have the same height level. The substrate allows light to pass through.

In various embodiments, the plurality of nanostructures can be nanopillars. Nanopillars can have any cross-section, such as circular, elliptical, rectangular, triangular, polygonal, free-form, etc.

In various embodiments, the plurality of nanostructures 204 may be nanoantennas, ie, capable of supporting one or more optical resonances.

In various embodiments, the plurality of color channels may represent different spectral ranges of electromagnetic light.

In various embodiments, a plurality of color channels may be spectrally adjacent to each other or may overlap. In various embodiments, the plurality of color channels may collectively cover a continuous spectrum of wavelengths. In various embodiments, the plurality of color channels may be or include a red (R) channel, a green (G) channel, and a blue (B) channel. The blue channel may have a center wavelength of approximately 460 nm, the green channel may have a center wavelength of approximately 530 nm, and the red channel may have a center wavelength of approximately 620 nm. The bandwidth of each channel can be approximately 40nm.

Figure 3 is a general illustration of a method of forming an optical system according to various embodiments. The method may include providing a plurality of color filters in step 302, a first color filter of the plurality of color filters configured to select light representing a first wavelength range of a first color channel, and a third color filter of the plurality of color filters. The two color filters are configured to select light in a second wavelength range that is different from the first wavelength range, and the light in the second wavelength range represents a second color channel, such that the plurality of color filters provide different color channels. The method may further include providing a plurality of metalenses in step 304, the plurality of metalenses being respectively associated with corresponding color channels of the plurality of color channels. The plurality of metalenses respectively have focal lengths, and the plurality of metalenses have equal focal lengths, so that different color channels are combined on a common focal plane to form a multicolor image. The plurality of metalenses may each include a plurality of nanostructures, and may have a field of view (FOV) greater than 30 degrees. The plurality of metalenses may each have a desired operating spectral bandwidth that depends on the extended focal depth, the center wavelength of the associated color channel, and the focal length at the center wavelength.

For the avoidance of doubt, Figure 3 is intended to illustrate some steps of forming an optical system in accordance with various embodiments, and is not intended to limit the order of the various steps. For example, step 302 may occur before, after, or simultaneously with step 304.

In various embodiments, the method may further include forming or providing one or more detectors defining a common focal plane. In various embodiments, the plurality of color filters may be internal bandpass filters of one or more detectors. In various other embodiments, the plurality of color filters may be external to one or more detectors.

In various embodiments, a plurality of color filters may be disposed between a plurality of metalenses and a common focal plane, such that the plurality of metalenses are each configured to direct broadband light to an associated filter color of the plurality of color filters. processor to produce the corresponding associated color channel. In various other embodiments, a plurality of metalenses may be disposed between a plurality of color filters and a common focal plane, such that the plurality of metalenses are respectively configured to direct light of corresponding associated color channels to the common focal plane. on flat surface.

In various embodiments, the plurality of metalenses may each have a Fresnel number, and the plurality of metalenses may have different Fresnel numbers, such that the plurality of metalenses have equal focal lengths.

In various embodiments, the respective nanostructures of a plurality of metalenses may be arranged in a periodic lattice with a predetermined period. In various embodiments, the Fresnel numbers of different metalenses of the plurality of metalenses may differ due to different predetermined periods of the different metalenses (of the plurality of metalenses 204 ).

In various embodiments, the periodic lattice may be a square lattice, a rectangular lattice, a hexagonal lattice, or any other common periodic or quasi-periodic Bravais lattice.

In various embodiments, the method may further include providing or forming a plurality of apertures disposed in front of a plurality of metalenses.

In various embodiments, the plurality of metalenses may be made of materials with a refractive index equal to or greater than 2.

In various embodiments, the plurality of metalenses may include suitable dielectric materials or suitable semiconductor materials.

In various embodiments, the plurality of metalenses may include silicon, gallium phosphide, hafnium oxide, gallium nitride, titanium dioxide, silicon nitride, sapphire, diamond, silicon carbide, aluminum nitride, III-V semiconductors (e.g., Gallium arsenide or gallium phosphide), or II-VI semiconductors (e.g., zinc oxide or magnesium oxide).

In various embodiments, the plurality of metalenses may be of equal height. The optical system may include a substrate. Multiple metalenses can be on the substrate. The substrate allows light to pass through.

In various embodiments, the plurality of nanostructures can be nanopillars. Nanopillars can have any cross-section, such as circular, elliptical, rectangular, triangular, polygonal, free-form, etc.

In various embodiments, the plurality of nanostructures may be nanoantennas, ie, capable of supporting one or more optical resonances.

In various embodiments, the plurality of color channels may represent different spectral ranges of electromagnetic light.

In various embodiments, a plurality of color channels may be spectrally adjacent to each other or may overlap. In various embodiments, the plurality of color channels may be or include a red (R) channel, a green (G) channel, and a blue (B) channel.

Figure 4 is a general illustration of a method of forming a multicolor image in accordance with various embodiments. The method may include providing broadband light to the optical system in step 402 . The optical system can be any suitable optical system as described herein. The optical system may include a plurality of color filters, a first color filter of the plurality of color filters configured to select light representing a first wavelength range of the first color channel, and a second color filter of the plurality of color filters configured to select A second wavelength range of light that is different from the first wavelength range is selected, and the light of the second wavelength range represents a second color channel, so that the plurality of color filters provide different color channels. The optical system may further include a plurality of metalenses, the plurality of metalenses being respectively associated with corresponding color channels of the plurality of color channels. The plurality of metalenses can each have a focal length, and the plurality of metalenses have equal focal lengths, so that different color channels are combined on a common focal plane to form a multicolor image. The plurality of metalenses may each include a plurality of nanostructures and have a field of view greater than 30 degrees. The plurality of metalenses may each have a desired operating spectral bandwidth that depends on the extended focal depth, the center wavelength of the associated color channel, and the focal length at the center wavelength.

In various embodiments, multicolor images may be detected by one or more detectors defining a common focal plane.

Figure 5A shows a schematic diagram of an optical system according to various embodiments. Light from the object is focused onto a pixelated color detector 506 by a collection of wide-field metalenses 504 fabricated on the same substrate (wafer) and having the same thickness. In various embodiments, a metalens 504 that imparts a secondary phase profile to the incoming light may be used. The collection of metalenses 504 may be arranged in any arbitrarily shaped one-dimensional (1D) or two-dimensional (2D) array. Each metalens in the array can be optimized to operate at a specific color (center wavelength λ _c ) and a corresponding frequency band with a specific bandwidth (i.e., color channel) that is intentionally matched to the color filter 502 in the system bandwidth. In other words, each channel can provide a wide field of view image with a certain bandwidth. Thus, a corresponding image for each color channel can be formed, and the color channels can ultimately be combined to produce a multicolor image. Color filter 502 may be an internal bandpass filter of the detector. Internal bandpass filters may limit the bandwidth of each channel.

Figure 5B shows a schematic diagram of another optical system according to various embodiments. Light from the object is focused onto a pixelated color detector 506 by a collection of metalenses 504 fabricated on the same wafer. Each channel can produce a wide field of view image with a certain bandwidth. Light may pass through color filter 502 before reaching metalens 504 . The images can then be merged to produce the final multicolor image. To limit the bandwidth of each channel, external bandpass filters can be used.

To facilitate post-processing, the images can have the same magnification. This can be ensured by the same focal length f of all metalenses 504, which can also mean that all images are acquired in the same focal plane corresponding to the detector plane (the plane of detector 506). To ensure good image quality over each bandwidth (Δλ), the depth of focus (DOF) of the secondary metalens 504 may need to be adjusted to operate within the desired non-zero bandwidth. In other words, the focal point may need to intersect the detector plane and provide a good point spread function (PSF) for all wavelengths in the bandwidth, which can be achieved by engineering an extended focal depth.

In fact, the color image shift of the focal length of the metalens with the wavelength can be expressed by provided, which Represents the center wavelength of the range of interest the focal length. By considering the maximum acceptable offset from the focal length corresponding to the depth of focus: , the following relationship between the operating spectral bandwidth and focal depth of the metalens Δλ can be found: .

In various embodiments, when the central wavelength is red (R), green (G), or blue (B), a focal depth of ~5%-10% of the focal length _fc can be engineered to cover a bandwidth of ~40nm , which corresponds to the bandwidth of typical filters used in commercial color sensors. Based on this, each channel in the system can have a certain operating bandwidth and can bring multiple-hues into focus. The metalens can form image focused light at a different detector position (as shown in Figure 5A) or at the same position (as shown in Figure 5C) as the detector 506.

Figure 5C shows a schematic diagram of yet another optical system according to various embodiments. Light from the object (passing through the color filter 502) can be focused onto the pixelated color detector 506 by a collection of metalenses 504 fabricated on the same wafer. Metalens 506 can form an image focused light at the same location as detector 502 .

Figure 5D shows a schematic diagram of a specific embodiment of an optical system for achieving red-green-blue (RGB) imaging, in which each metalens is suitable for red (λ _R =620 nm), green (λ _G =530 nm), And the corresponding center wavelength in the blue (λ _B =460nm) region is optimized.

A wide-field metalens may include a collection of nanostructures (often referred to as nanoantennas or metaatoms in the literature). In various embodiments, metaatoms can be: 1) nanopillars, with circular, elliptical, rectangular or polygonal cross-sections, used as waveguides; 2) nanofins, rotated in metalenses to utilize Pancharatnam-Berry phase; 3) Resonant nanoantennas that support one or more optical resonances, such as those constituting a Huygens metasurface, or any other type of metaatomic commonly used to map the desired phase profile. Nanoantennas may or may not be embedded in the medium. Figure 6 shows possible examples of nanoantennas according to various embodiments.

Materials that generate metaatoms can include dielectric and semiconductor materials such as silicon, gallium phosphide (GaP), hafnium oxide, gallium nitride, titanium dioxide, silicon nitride, sapphire, diamond, silicon carbide (SiC), aluminum nitride (AlN), or other Group IV semiconductors, Group III-V semiconductors, or Group II-VI semiconductors, or others with medium or high refractive index (generally n>2), and in the wavelength range of interest (k< 0.1) A relatively transparent oxide.

As an example, in the specific embodiment shown in Figure 5D, gallium phosphide nanopillars with circular cross-sections and the same height (H=300nm) on a glass substrate can be used to create three nanopillars that make up the array. lens. For operation in different spectral ranges, other materials (such as those proposed above) as well as other metaatomic shapes and heights can be used. In principle, metaatoms can have heights that are approximately the same or a lower length than the longest wavelength in the longest operating bandwidth. Importantly, to simplify fabrication for practical implementations, all meta-atoms in all meta-lenses can have the same height. Figure 7 shows an example of a lateral projection of a metalens assembly according to various embodiments. Figure 7 illustrates the above design rules. In various embodiments, metaatoms can be designed to act as local waveguides for incident light. Therefore, metaatoms may introduce variable phase retardation depending on the diameter of the metaatom. Importantly, the circular cross-section ensures polarization-insensitive operation.

For each metalens, the metaatoms can be arranged into some periodic lattice, such as a square lattice, a rectangular lattice, a hexagonal lattice, or any other suitable two-dimensional lattice. The diameter of a metaatom placed at a certain lattice site at a distance r from the lens center to subsequently form a quadratic phase profile The form gives the phase delay this way to choose.

In this expression, is the expected phase retardation at the metaatomic position, f is the focal length of the lens, is an arbitrary initial phase chosen for the lens center, and is the center wavelength or channel of the wavelength band of interest, and the subscript i clearly identifies the specific channel within the channel selection of the multispectral imaging system, for example i=1...N in Figures 5A through 5C, and in Figure 5D In the example shown i=R,G,B.

in order to make different With the same metalens diameter D and focal length f, it can be calculated according to the formula Adjust the Fresnel number (FN) of each metalens. This can be achieved by measuring the central wavelength Each metalens operates to scale down the lattice period to reach. In the red, green, and blue imaging embodiment, gallium phosphide nanopillars on a glass substrate are arranged in a hexagonal lattice with periods p _R =260 nm, p _G =220 nm, and p _B =190 nm, correspondingly for Metalenses operating at red (B), green (G), and blue (R) wavelengths.

Figures 8A-8B show simulated values for transmission and phase values for nanopillars included in red, green, and blue metalenses (depicted as solid, dashed, and dotted lines, respectively) ( Obtained using the finite difference time domain (FDTD) method), given as a function of the duty cycle as the ratio between the nanopillar diameter and the lattice constant. In order to demonstrate the feasibility of the disclosed technology, the red, green, and blue embodiments are achieved experimentally.

Figure 8C shows (top) optical microscope images and (bottom) scanning electron microscope (SEM) images of red (R), green (G), and blue (B) metalenses fabricated according to various embodiments. Metalenses can each have a diameter (D) of 200µm and a focal length (f) of 83µm. The scale bar in the light microscopy image corresponds to 20µm, while the scale bar in the electron microscopy image corresponds to 200nm. The parameters p _R =260 nm, p _G =220 nm, and p _B =190 nm indicate the designed lattice period.

In order to characterize the optical performance of the disclosed imaging system, the point spread function (PSF) and the modulation transfer function of each metalens can be measured for different incident angles and frequency bandwidths around the central wavelength of each metalens. (MTF). This can be accomplished using a collimated laser beam whose incidence angle (φ) and bandwidth (Δλ) on the metalens can be adjusted.

Figure 9 shows (a)-(c) plots of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm), showing red with an ideal quadratic phase profile according to various embodiments. Simulated values of the modulation transfer function of the secondary lens, designed to operate at a bandwidth Δλ near the center wavelength for incident angles φ=0°, 30°, and 50° in the red (R) region (center wavelength λ _R =620 nm) =10 nm, 20 nm, 30 nm, and 40 nm runs, and (d)-(f) are the point spread functions (PSF) corresponding to the conditions in (a)-(c), respectively. For similar numerical aperture = 0.5 and Δλ = 0 nm, a diffraction-limited modulation transfer function can be given. Scale bars in (d)-(f) correspond to 2 µm.

Figure 10 shows the same properties measured for the fabricated metalens. Figure 10 shows (a)-(c) plots of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm), showing red with an ideal quadratic phase profile according to various embodiments. Measured values of modulation transfer functions of secondary lenses designed to operate at bandwidths Δλ near the center wavelength for incident angles φ = 0°, 30°, and 50° in the red (R) region (center wavelength λ _R =620 nm) =10 nm, 20 nm, 30 nm, and 40 nm runs, and (d)-(f) are the point spread functions (PSF) corresponding to the conditions in (a)-(c), respectively. For similar numerical aperture = 0.5 and Δλ = 0 nm, a diffraction-limited modulation transfer function can be given. Scale bars in (d)-(f) correspond to 2 µm.

Clearly, a good match with the simulations is observed. As can be seen, due to the spherical aberration inherent in the metalens phase profile, the modulation transfer function is worse than that of a similar numerical aperture = 0.5 diffraction limited lens. If the application requires, the modulation transfer function can be improved by placing an aperture stop in the front focal plane of the metalens. This embodiment is shown in Figure 11 together with the modulation transfer function improvement. Figure 11 shows (a) a schematic diagram of an optical system including a plurality of apertures 1108 according to various embodiments; (b) a plot of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm) , showing the simulated values of the modulation transfer function of a red secondary metalens (center wavelength λ _R =620 nm) with and without an aperture stop for an incident angle φ = 0° according to various embodiments; and (c) Plot of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm) showing red secondary metalenses (center wavelength λ _R =620 nm) with and without aperture according to various embodiments Simulated values of the modulation transfer function for the incident angle φ=30° in the case of aperture. In addition to apertures 1108 , the optical system may also include filters 1102 , metalenses 1104 , and detectors 1106 .

Importantly, as seen in Figures 9 to 10, the modulation transfer function may be almost insensitive to bandwidth for φ = 0°, and may broaden with the point spread function for φ = 30° and φ = 50° And slowly decline. This degradation associated with chromatic aberration may only increase slowly with φ and Δλ and, importantly, may be acceptable for most applications at certain metalens bandwidths (e.g., 40 nm).

Modulation transfer function data can be converted into imaging quality. To show the uniformity of imaging over the bandwidth, monochromatic imaging simulations were performed for φ=0° when the imaging wavelength deviated from the design wavelength shown in Figure 12.

Figure 12 shows simulated secondary phase profile images for a secondary metalens according to various embodiments in the specific case of red operation (λ _R =620 nm) when the imaging wavelength is changed. For comparison, simulations corresponding to hyperbolic phase profiles previously proposed in the literature are also presented. For the latter, the lens numerical aperture, diameter, and design wavelength are fixed at 0.5µm, 200µm, and 620nm similar to the secondary phase profile. The focal length of the hyperbolic metal lens has been changed to 173µm to obtain the same numerical aperture as the quadratic metal lens. This results in reduced differences, which can be seen by the different sized scale bars. The scale bar for hyperbolic phase profile images is 10µm, while the scale bar for quadratic phase profile images is 5µm. As can be seen, the images at different wavelengths for the secondary phase profile remain essentially unchanged, showing uniform imaging over a 40nm bandwidth. In contrast, the hyperbolic phase profile only shows high-resolution images at the design wavelength (620nm), but is significantly degraded at 600nm and 640nm.

Stability of the modulation transfer function (and corresponding image quality) of an optical system over certain bandwidths according to various embodiments may provide more balanced imaging and may reduce color distortions. More complex metaatoms can be used to improve modulation transfer function stability via dispersion engineering. The nanopillars described here as examples may be simple in terms of their fabrication process.

Various embodiments may also allow for good color reproduction. The color reproduction of an optical system can be characterized by a standard ColorChecker test chart with 24 color patches (often called a Macbeth chart), as depicted in Figure 13(a).

Figure 13 shows (a) the original standard ColorChecker test pattern with 24 color patches; (b) red-green-blue (RGB) for a field of view (FOV) of 30° × 20° by an optical system according to various embodiments. ) results of imaging; (c) results of red-green-blue (RGB) imaging for a field of view (FOV) of 100°×67° by the optical system according to various embodiments.

Figures 13(b) to 13(c) respectively show images of separate red, green, and blue color channels obtained by metalenses made of red, green, and blue. The red, green, and blue color channels show the unprocessed images obtained by each metalens, while the red, green, and blue images are the merged images obtained after post-processing. Red, green, and blue images are obtained through a post-processing merging process that includes a simple normalization procedure to account for the minimum and maximum intensity values (color balance) in each channel.

The quality of color reproduction can be evaluated using CIELAB metrics. For this purpose, the red, green, and blue intensity values used for reference and measurement images can be transformed into brightness (L*), color relationships in red and green (a*), and color relationships in yellow and blue (b*). The color error ΔE is then calculated as the geometric difference in L*a*b* three-dimensional space: . Figure 14 shows (a) ColorChecker red-green-blue (RGB) color ΔE with a field of view (FOV) of 30° × 20° in accordance with various embodiments; (b) color ΔE of a ColorChecker with a field of view (FOV) of 30° × 20° in accordance with various embodiments; ColorChecker red-green-blue (RGB) color ΔE for a field of view (FOV) of 67°; and (c) (left) color after efficiency correction procedure for a field of view of 100° × 67° according to various embodiments Error and (right) the red-green-blue (RGB) image obtained.

For red, green, and blue imaging, for a field of view of 30° × 20° (Fig. 14a), the color error ΔE was found to vary between 5 and 23 for different blocks, and for the larger 100° × 67° The field of view (Figure 14b) is between 5 and 57. The larger errors found for larger fields of view may be related to the angle-dependent focusing efficiency of the metalens. To implement the intensity correction procedure in each of the red, green, and blue channels, the focus efficiency can be measured and used as a calibration curve. This procedure allows for reduction of color errors (Figure 14c shows efficiency corrected red, green and blue images with corresponding color errors, Figure 15 shows the measured metalens focusing efficiency).

Figure 15 shows (a) a graph of efficiency (in percent or %) as a function of angle (in degrees) showing focusing efficiency at 10 nm, 20 nm for red metalenses according to various embodiments. Angular dependence (angular dependence) at the bandwidth near the central wavelength (Δλ) of , 30nm, and 40nm; (b) Graph of efficiency (in percentage or %) as a function of angle (in degrees) , showing the angular dependence of focusing efficiency for green metalenses at bandwidths near central wavelengths (Δλ) of 10 nm, 20 nm, 30 nm, and 40 nm according to various embodiments; and (c) efficiency (in percent or % A graph of (in units) as a function of angle (in degrees) showing focusing efficiency around center wavelengths (Δλ) of 10 nm, 20 nm, 30 nm, and 40 nm for a blue metalens according to various embodiments. Angular dependence at bandwidth.

For general imaging quality assessment, multicolor detailed pictures are available. Figure 16 shows (a) the original still image; (b) the result of red-green-blue (RGB) imaging by an optical system having a field of view (FOV) of 50° x 35° according to various embodiments; and ( c) Results of red-green-blue (RGB) imaging by an optical system with a field of view (FOV) of 100° x 67° according to various embodiments. The red (R), green (G), and blue (B) channels show the unprocessed images produced by each metalens, while the red, green, and blue images represent the results of the fusion of different channels. Images labeled "wiener filter" represent images reconstructed by deconvolution.

You may notice that the resulting red, green, and blue image has lower contrast than the original image. This results from the behavior of the quadratic metalens modulation transfer function, also known as the "veiling glare" effect. However, the modulation transfer function can still be preserved at higher spatial frequencies (see Figure 9(a) to Figure 9(c)) so that the image information is not lost. This property can be further improved by a simple deconvolution algorithm based on the widely used Wenner filter. The reconstructed images (labeled Wenner filters in Figures 16(b) through 16(c)) exhibit much improved sharpness and good color consistency. From a practical perspective, it may be important that the filter is fast and does not consume energy, making it suitable for portable as well as miniaturized devices. Other filters, such as the total variation regularizer, can further improve the image, although they are more resource demanding and take longer to process. This may be a solution for other types of systems that focus on better accuracy and color reproduction, but may not require real-time updates.

Figure 17 is a table comparing an embodiment with a typical cell phone camera and a conventional diffractive lens. "+" indicates the presence of a specific trait, while "-" indicates its absence.

Various embodiments may include or provide an array of secondary metalenses and color detectors on a single wafer, each metalens designed to provide good quality wide field focusing over a range of angles, and using dielectric Materials achieved. The optical system may include additional bandpass color filters and/or apertures in the front focal plane of each metalens. Each metalens (color channel) can operate in a specific spectral bandwidth defined by an internal detector or an external bandpass filter. Each channel can provide a large field of view image. The final multispectral image can be produced by channel fusion. The merging process may include intensity correction, color balancing, and deconvolution.

Various embodiments may relate to the use of quadratic phase profile metalens arrays providing a wide field of view for multispectral as well as white light imaging. Various embodiments may relate to a manner of forming an image in the same detector plane with a detector filter bandwidth similar to the operational bandwidth of the metalens. Various embodiments may involve the use of quadratic phase profile lenses with extended depth of focus, thereby allowing for quality enhanced image processing techniques.

Various embodiments may have significant commercial potential in many applications requiring full-color, wide-field imaging. Various embodiments may be applied to portable cameras, mobile phone cameras, security cameras, miniaturized microscopes for medicine, agriculture, and object recognition, as well as general drone detection.

"Including" means including, but not limited to, anything that follows the word "includes." Thus, use of the word "includes" means that the listed elements are required or required, but that other elements are optional and may or may not be present.

“Consisting of” means including and limited to anything that follows the phrase “consisting of.” Thus, the phrase "consisting of" means that the listed elements are required or required and no other elements may be present.

The inventions shown and described herein may suitably be practiced without any element or elements, limitation or limitations not specifically disclosed herein. Accordingly, terms such as "comprising, including," "containing" and the like are to be construed broadly and without limitation. Furthermore, the words and expressions employed herein have been used as descriptive rather than restrictive terms and their use is not intended to exclude any equivalents of the features shown and described, or parts thereof. , but recognizes that various modifications may be made within the scope of the claimed invention. Therefore, it should be understood that although the present invention has been specifically disclosed in terms of preferred embodiments and optional features, modifications and changes to the invention disclosed herein may be made by those of ordinary skill in the art, and these modifications and changes are considered is within the scope of the present invention.

"Approximately" with respect to a given value (for example, for a focus) means a value included within 10% of the specified value.

The invention has been described broadly and generically herein. Each narrower subcategory and subordinate grouping that falls within the overriding disclosure also forms a part of this invention. This includes the generic description of the invention having a proviso or negative limitation removing any subject matter from the generic description, whether or not the truncated material is specifically cited herein.

Other embodiments are within the scope of the following claims as well as the non-limiting examples. Furthermore, where features or characteristics of the invention are described in terms of Markusian groups, one of ordinary skill in the art will recognize that the invention is therefore also described in terms of any individual or underlying component of a Markusian group.

202,502: A plurality of color filters/color filters 204,504,1104: A plurality of metalenses/metalenses 302,304,402: Step 506: Color detector 1102: Filter 1106: Detector 1108: Aperture P _R , P _G , P _B : Period λ ₁ , λ ₂ , λ ₃ , λ ₄ , λ ₅ : Wavelength λ _R , λ _G , λ _B : Center wavelength

In the drawings, the same reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed generally upon illustrating the principles of the various embodiments. In the following description, various embodiments of the invention will be described with reference to the following drawings. Figure 1 provides chromatic aberration diagrams of (a) a conventional refractive lens and (b) a diffractive lens, in which wavelengths λ ₁ > λ ₂ > λ ₃ are focused at different places along the optical axis. Figure 2 is a general illustration of an optical system according to various embodiments. Figure 3 is a general illustration of a method of forming an optical system according to various embodiments. Figure 4 is a general illustration of a method of forming a multicolor image in accordance with various embodiments. Figure 5A shows a schematic diagram of an optical system according to various embodiments. Figure 5B shows a schematic diagram of another optical system according to various embodiments. Figure 5C shows a schematic diagram of yet another optical system according to various embodiments. Figure 5D shows a schematic diagram of a specific embodiment of an optical system for achieving red-green-blue (RGB) imaging, in which each metalens is suitable for red (λ _R =620 nm), green ( The corresponding center wavelengths in the λ _G =530nm) and blue (λ _B =460nm) regions are optimized. Figure 6 shows possible examples of nanoantennas according to various embodiments. Figure 7 shows an example of a lateral projection of a metalens assembly according to various embodiments. Figure 8A is a graph of transmission as a function of duty cycle showing simulated transmission values for metalenses including nanopillars (using the finite-difference time-domain (FDTD) method) according to various embodiments obtained). Figure 8B is a graph of transmission as a function of duty cycle showing simulated phase values (obtained using a finite difference time domain (FDTD) method) for a metalens including nanopillars according to various embodiments. Figure 8C shows (top) optical microscope images and (bottom) scanning electron microscope (SEM) images of red (R), green (G), and blue (B) metalenses fabricated according to various embodiments. Figure 9 shows (a)-(c) plots of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm), showing red with an ideal quadratic phase profile according to various embodiments. Simulated values of the modulation transfer function of the secondary lens, designed to operate at a bandwidth Δλ near the center wavelength for incident angles φ=0°, 30°, and 50° in the red (R) region (center wavelength λ _R =620 nm) =10nm, 20nm, 30nm, and 40nm runs, and (d)-(f) are point spread functions (PSF) corresponding to the conditions in (a)-(c), respectively. Figure 10 shows (a)-(c) plots of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm), showing red with an ideal quadratic phase profile according to various embodiments. Measured values of modulation transfer functions of secondary lenses designed to operate at bandwidths Δλ near the center wavelength for incident angles φ = 0°, 30°, and 50° in the red (R) region (center wavelength λ _R =620 nm) =10 nm, 20 nm, 30 nm, and 40 nm runs, and (d)-(f) are the point spread functions (PSF) corresponding to the conditions in (a)-(c), respectively. Figure 11 shows (a) a schematic diagram of an optical system including a plurality of apertures according to various embodiments; (b) a plot of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm), Shows simulated modulation transfer function values for a red secondary metalens (center wavelength λ _R =620 nm) with and without an aperture stop for an incident angle φ = 0° according to various embodiments; and (c) Plot of modulation transfer function (MTF) as a function of spatial frequency (cycles per millimeter or cycles/mm), showing that a red secondary metalens (center wavelength λ _R =620 nm) according to various embodiments has And the simulated value of the modulation transfer function for the incident angle φ=30° without aperture diaphragm. Figure 12 shows monochromatic imaging simulations of a hyperbolic phase profile metalens and a quadratic phase profile metalens for an incident angle φ=0° according to various embodiments. Figure 13 shows (a) the original standard ColorChecker test pattern with 24 painted patches; (b) red-green color for a 30° × 20° field of view (FOV) by an optical system according to various embodiments. - Results of blue (RGB) imaging; (c) Results of red-green-blue (RGB) imaging for a field of view (FOV) of 100°×67° by an optical system according to various embodiments. Figure 14 shows (a) ColorChecker red-green-blue (RGB) color ΔE with a field of view (FOV) of 30° × 20° in accordance with various embodiments; (b) color ΔE of a ColorChecker with a field of view (FOV) of 30° × 20° in accordance with various embodiments; ColorChecker red-green-blue (RGB) color ΔE for a field of view (FOV) of 67°; and (c) (left) color after efficiency correction procedure for a field of view of 100° × 67° according to various embodiments Error and (right) the red-green-blue (RGB) image obtained. Figure 15 shows (a) a graph of efficiency (in percent or %) as a function of angle (in degrees) showing focusing efficiency at 10 nm, 20 nm for red metalenses according to various embodiments. Angular dependence (angular dependence) at the bandwidth near the central wavelength (Δλ) of , 30nm, and 40nm; (b) Graph of efficiency (in percentage or %) as a function of angle (in degrees) , showing the angular dependence of focusing efficiency for green metalenses at bandwidths near central wavelengths (Δλ) of 10 nm, 20 nm, 30 nm, and 40 nm according to various embodiments; and (c) efficiency (in percent or % A graph of (in units) as a function of angle (in degrees) showing focusing efficiency around center wavelengths (Δλ) of 10 nm, 20 nm, 30 nm, and 40 nm for a blue metalens according to various embodiments. Angular dependence at bandwidth. Figure 16 shows (a) the original still image; (b) the result of red-green-blue (RGB) imaging by an optical system having a field of view (FOV) of 50° x 35° according to various embodiments; and ( c) Results of red-green-blue (RGB) imaging by an optical system with a field of view (FOV) of 100° x 67° according to various embodiments. Figure 17 is a table comparing an embodiment with a typical cell phone camera and a conventional diffractive lens.

without

202: Multiple color filters

204: Multiple metalenses

Claims (20)

An optical system including: a plurality of color filters, a first color filter of the plurality of color filters configured to select light representing a first wavelength range of a first color channel, and a second color filter of the plurality of color filters The color filters are configured to select a second wavelength range of light that is different from the first wavelength range, and the second wavelength range of light represents a second color channel, so that the plurality of color filters provide different colors. channel; and A plurality of metalenses, the plurality of metalenses are respectively associated with a corresponding color channel of the plurality of color channels; Wherein, the plurality of metalenses each have a focal length, and the plurality of metalenses have equal focal lengths, so that the different color channels are combined on a common focal plane to form a multicolor image; Wherein, the plurality of metalenses respectively include a plurality of nanostructures and have a field of view greater than 30 degrees; and Wherein, the plurality of metalenses each have a desired operating spectral bandwidth, and the desired operating spectral bandwidth depends on an extended focal depth, a center wavelength of the associated color channel, and the focal length at the center wavelength. The optical system of claim 1 further includes: One or more detectors define the common focal plane. Such as the optical system of claim 2, Wherein, the plurality of color filters are internal bandpass filters of the one or more detectors. Such as the optical system of claim 2, Wherein, the plurality of color filters are outside the one or more detectors. Such as the optical system of claim 1, Wherein, the plurality of color filters are disposed between the plurality of metalenses and the common focal plane, so that the plurality of metalenses are respectively configured to guide a broadband light to the plurality of color filters. associated with a color filter to produce the corresponding associated color channel. Such as the optical system of claim 1, Wherein, the plurality of metalenses are disposed between the plurality of color filters and the common focal plane, so that the plurality of metalenses are respectively configured to guide the light of the corresponding associated color channel to on the common focal plane. Such as the optical system of claim 1, Wherein, the plurality of metalenses each have a Fresnel number, and the plurality of metalenses have different Fresnel numbers, so that the plurality of metalenses have the same focal length. Such as the optical system of claim 1, Wherein, the respective nanostructures of the plurality of metalenses are arranged into a periodic lattice with a predetermined period; Wherein, the Fresnel numbers of different metalenses of the plurality of metalenses are different due to the different predetermined periods of the different metalenses. Such as the optical system of claim 8, Wherein, the periodic lattice is a square lattice, a rectangular lattice, a hexagonal lattice or any other common periodic or quasi-periodic Bravais lattice. The optical system of claim 1 further includes: A plurality of apertures are provided in front of the plurality of metalenses. Such as the optical system of claim 1, Wherein, the plurality of metalenses are made of materials with a refractive index equal to or greater than 2. Such as the optical system of claim 1, Wherein, the plurality of metalenses include a suitable dielectric material or a suitable semiconductor material. Such as the optical system of claim 1, Among them, the plurality of metalenses include silicon, gallium phosphide, hafnium oxide, gallium nitride, titanium dioxide, silicon nitride, sapphire, diamond, silicon carbide, aluminum nitride, III-V semiconductor or II-VI semiconductor. Such as the optical system of claim 1, Wherein, the plurality of metalenses have the same height; and Wherein, the optical system further includes a base material, and the plurality of metal lenses are on the base material. Such as the optical system of claim 1, Wherein, the plurality of nanostructures are nanopillars with any suitable cross-section. Such as the optical system of claim 1, Wherein, the plurality of nanostructures are nanoantennas. Such as the optical system of claim 1, The plurality of color channels represent different spectral ranges of electromagnetic light. Such as the optical system of claim 1, The plurality of color channels are spectrally adjacent to or overlapping each other. A method of forming an optical system, including: A plurality of color filters are provided, a first color filter of the plurality of color filters is configured to select light representing a first wavelength range of a first color channel, and a first color filter of the plurality of color filters is provided. The two color filters are configured to select a second wavelength range of light that is different from the first wavelength range, and the second wavelength range of light represents a second color channel, so that the plurality of color filters provide different numbers of color channels; and Provide a plurality of metalenses, the plurality of metalenses being respectively associated with a corresponding color channel of the plurality of color channels; Wherein, the plurality of metalenses each have a focal length, and the plurality of metalenses have equal focal lengths, so that the different color channels are combined on a common focal plane to form a multicolor image; Wherein, the plurality of metalenses respectively include a plurality of nanostructures and have a field of view greater than 30 degrees; and Wherein, the plurality of metalenses each have a desired operating spectral bandwidth, and the desired operating spectral bandwidth depends on an extended focal depth, a center wavelength of the associated color channel, and the focal length at the center wavelength. A method of forming multi-color images consisting of: Provide a broadband light to an optical system, the optical system includes: a plurality of color filters, a first color filter of the plurality of color filters configured to select light representing a first wavelength range of a first color channel, and a second color filter of the plurality of color filters The color filters are configured to select a second wavelength range of light that is different from the first wavelength range, and the light of the second wavelength range represents a second color channel based on the broadband light, so that the plurality of color filters provide different several color channels; and A plurality of metalenses, the plurality of metalenses are respectively associated with a corresponding color channel of the plurality of color channels; Wherein, the plurality of metalenses each have a focal length, and the plurality of metalenses have equal focal lengths, so that the different color channels are combined on a common focal plane to form the multicolor image; Wherein, the plurality of metalenses respectively include a plurality of nanostructures and have a field of view greater than 30 degrees; and Wherein, the plurality of metalenses each have a desired operating spectral bandwidth, and the desired operating spectral bandwidth depends on an extended focal depth, a center wavelength of the associated color channel, and the focal length at the center wavelength.

Images