Color filters including a metasurface layer, imaging device, computer-implemented method

Abstract

A color filter, wherein the color filter includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter, determined by design optimization, is such that the color filter has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

Description

[0001] COLOR FILTERS INCLUDING A METASURFACE LAYER, IMAGING DEVICE, COMPUTER-IMPLEMENTED METHOD

[0002] TECHNICAL FIELD

[0003] The present disclosure generally pertains to narrowband color filters including a metasurface layer, an imaging device, and a computer-implemented method.

[0004] TECHNICAL BACKGROUND

[0005] Multi- and hyperspectral imaging may capture much more information on an imaged scenery than conventional red, green, and blue (“RGB”) color imaging based, for example, on color filters containing dye-doped polymers and thus has a number of applications such as in the fields of agriculture, food processing, remote sensing, forensics, machine vision, and medicine.

[0006] Some known hyperspectral applications require color filters in the ultraviolet (“UV”) to shortwave infrared (“SWIR”) spectral range with a high transmittance (e.g., greater than 80 percent) and narrow wavelength bands (e.g., with a spectral width of less than 30 nanometers).

[0007] However, current color filter technologies may either be very expensive due to demanding fabrication or may not offer high transmittance or narrow bands.

[0008] Although there exist techniques for narrowband color filters, it is desirable to improve the existing techniques.

[0009] SUMMARY

[0010] According to a first aspect, the disclosure provides a color filter, comprising: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter is such that the color filter has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

[0011] According to a second aspect, the disclosure provides a color filter, comprising a plurality of color filter sections, wherein each color filter section includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

[0012] According to a third aspect, the disclosure provides an imaging device, comprising: an image sensor having a plurality of pixels; a color filter arranged on the image sensor, wherein the color filter includes a plurality of color filter sections corresponding to the number of pixels of the image sensor, wherein each color filter section has the same thickness and includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold; wherein each color filter section is matched with a different pixel of the image sensor.

[0013] According to a fourth aspect, the disclosure provides a computer-implemented method, comprising: performing a design optimization of a color filter, including: simulating a transmittance spectrum of a color filter in a target wavelength range including a target wavelength; and determining a configuration of the color filter by minimizing a deviation between the simulated transmittance spectrum and a target transmittance spectrum, wherein the target transmittance spectrum has a Lorentzian shape that has a maximum at the target wavelength and a target spectral width; wherein the color filter includes: a distributed Bragg reflector; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; wherein minimizing the deviation includes iteratively adjusting the configuration of the color filter and simulating the transmittance spectrum for the adjusted configuration of the color filter.

[0014] Further aspects are set forth in the dependent claims, the drawings, and the following description.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments are explained by way of example with respect to the accompanying drawings, in which:

[0017] Fig. 1 A schematically illustrates in a block diagram a side view of an embodiment of a color filter;

[0018] Fig. IB schematically illustrates in a block diagram the working principle of an embodiment of a color filter;

[0019] Fig. 2 schematically illustrates in a block diagram a side view of an embodiment of a color filter;

[0020] Fig. 3 schematically illustrates in a block diagram a side view of an embodiment of an imaging device;

[0021] Fig. 4 schematically illustrates in a block diagram a top view of metasurface layers of color filter sections included in a color filter of an embodiment of an imaging device;

[0022] Fig. 5A schematically illustrates in a block diagram a top view of a metasurface layer of a color filter section included in a color filter of an embodiment of an imaging device;

[0023] Fig. 5B schematically illustrates in a block diagram a closeup view of a portion of the top view depicted in Fig. 5A;

[0024] Fig. 6A schematically illustrates in a block diagram a side view of an embodiment of an imaging device;

[0025] Fig. 6B schematically illustrates in a block diagram a top view of metasurface layers of color filter sections included in a color filter of an embodiment of an imaging device;

[0026] Fig. 7A schematically illustrates a side view of an embodiment of a metasurface layer in a block diagram and a graph of the reflectance spectrum (solid line) and a transmittance spectrum (dashed line) of the embodiment of the metasurface layer as a function of wavelength; Fig. 7B schematically illustrates a side view of an embodiment of a color filter in a block diagram and a graph depicting the widths of nanostructures, included in a metasurface layer of the embodiment of the color filter, that result in a maximum transmittance (solid line) at a given wavelength;

[0027] Fig. 7C schematically illustrates a side view of an embodiment of a color filter including three color filter sections in a block diagram and a graph of the transmittance spectrum of the embodiment of the color filter section highlighted by the dashed box as a function of wavelength;

[0028] Fig. 8 schematically illustrates in a flow diagram an embodiment of a computer-implemented method; and

[0029] Fig. 9 schematically illustrates in a block diagram an embodiment of a multi-purpose computer which can be used for implementing an information processing device.

[0030] DETAILED DESCRIPTION OF EMBODIMENTS

[0031] Before a detailed description of the embodiments under reference of Fig. 1 A is given, general explanations are made.

[0032] As mentioned in the outset, some hyperspectral applications require color filters with a high transmittance (e.g., greater than 80 percent) and narrow wavelength bands (e.g., with a spectral width (e.g., full width at half maximum (“FWHM”)) of less than 30 nanometers), wherein the color filters may be manufactured only at a high cost due to their demanding fabrication.

[0033] Recent developments in the field of multi- and hyperspectral imaging applications include multi- and hyperspectral camera technology based on pixel -level Fabry -Perot (“FP”) based filters, which, in some applications, may consist of two distributed Bragg reflector (“DBR”) mirrors separated by a low index cavity, wherein the height of the cavity determines the transmitted center wavelength of the filter. Therewith, the filters have a different height for each pixel of an image sensor, which may be very challenging to manufacture.

[0034] In some applications, a metasurface may be embedded in the cavity of an FP resonator formed by two DBRs. The working principle relies on an effective medium approach, wherein a high index metasurface in the low index cavity changes the effective refractive index of the cavity. The center wavelength may thus be defined by geometric parameters of nanostructures embedded in the metasurface, such as the diameter, volume, and / or period of the nanostructures. The metasurface embedded in the cavity may be fabricated on a pixel level, wherein each pixel filters a different wavelength, while the DBRs may be fabricated on a chip level.

[0035] It has been recognized that the metasurface may be directly used as the top reflective element to form the FP resonator with a DBR mirror, simplifying the manufacturing process since fabricating another DBR mirror on top of the metasurface becomes obsolete.

[0036] Furthermore, it has been recognized that the broadband DBR mirror may be fabricated at chip level, while the metasurface may be structured at pixel level, which enables chip-level flat filters and thus simplifies fabrication. Therewith, the color filters may be suitable for on-chip integration with an imager to enable hyperspectral snapshot imaging.

[0037] Moreover, it has been recognized that a color filter may be configured to have a high transmittance (e.g., greater than 80 percent) for a specific wavelength and the transmitted light may have a narrow wavelength band (e.g., with a FWHM of less than 30 nanometers) to meet the requirements of some hyperspectral applications.

[0038] In addition, it has further been recognized that the configuration of the color filter having a high transmittance (e.g., greater than 80 percent) and a narrow wavelength band (e.g., with a FWHM of less than 30 nanometers) may be derived by a computer-implemented method.

[0039] Hence, some embodiments pertain to a color filter, wherein the color filter includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter is such that the color filter has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

[0040] The color filter may be used in applications relying on multi- and / or hyperspectral imaging, for example in the fields of agriculture, food processing, remote sensing, forensics, machine vision, or medicine, without limiting the embodiments to these applications.

[0041] The color filter may have, for example, a plate shape or a cylindrical shape or the like.

[0042] The color filter has a layered structure in which the distributed Bragg reflector and the metasurface layer, in some embodiments, form a Fabry -Perot resonator and the thickness or height of the intermediate layer corresponds to a height of the cavity of the Fabry -Perot resonator.

[0043] Hence, the color filter is configured to transmit only specific wavelengths in a typically narrow spectral window. By adjusting structural parameters of the color filter, the wavelengths that are transmitted can be adjusted such that various spectral ranges may be covered with different configurations of the color filter.

[0044] In some embodiments, the configuration of the color filter includes a size of the color filter, the reflectance of the distributed Bragg reflector, the thickness of the intermediate layer and a configuration of the metasurface layer.

[0045] In some embodiments, these structural parameters are optimized for a given combination of materials to obtain a color filter with a narrow transmittance spectrum around a specific target wavelength.

[0046] In the following the different layers of the color filter will be discussed in more detail.

[0047] Generally, the distributed Bragg reflector may function as a mirror having a high reflectance for a specific wavelength range.

[0048] In some embodiments, a mirror can be used instead of the distributed Bragg reflector. For example, a metallic layer may be used.

[0049] In some embodiments, the reflectance threshold is 85, 90 or 95 percent without limiting the disclosure in this regard. The reflectance of the distributed Bragg reflector may be altered by varying the number of layers of the distributed Bragg reflector.

[0050] The first and second predetermined wavelength ranges may reside in the UV, the visible, the near infrared (“NIR”) or the shortwave infrared (“SWIR”) portions of the electromagnetic spectrum and extend, for example, from 600 to 700 nanometers or 650 to 850 nanometers, without limiting the disclosure in this regard.

[0051] In some embodiments, the first predetermined wavelength range is equal to the second predetermined wavelength range. In some other embodiments, the first predetermined wavelength range and the second predetermined wavelength range partially overlap. In some other embodiments, the first predetermined wavelength range and the second predetermined wavelength range are disjunct.

[0052] The second predetermined wavelength range may also be referred to as target wavelength range. The predetermined wavelength is a wavelength included in the second predetermined wavelength range and represents a target wavelength to be filtered by the color filter. In other words, the color filter may be configured such that the target wavelength is transmitted through the color filter.

[0053] The distributed Bragg reflector may include a layered structure comprising alternating layers of different materials.

[0054] In some embodiments, the layered structure may include an alternating sequence of a predetermined number of layers of a first layer type having a first thickness and a first layer material that has a first refractive index, and a second layer type having a second thickness and a second layer material that has a second refractive index different from the first refractive index, wherein the product of the first thickness and the first refractive index equals a quarter of the above mentioned target wavelength and wherein the product of the second thickness and the second refractive index equals a quarter of the target wavelength. In other words, the optical path of each of the layers equals a quarter of the target wavelength, which typically corresponds to a design resulting in a high reflectance of the distributed Bragg reflector at the target wavelength.

[0055] In some other embodiments, the layered structure of the distributed Bragg reflector may include an alternating sequence of a predetermined number of layer types, wherein a first layer type includes a first layer material and a second layer type includes a second layer material different from the first layer material and wherein each layer has an individual thickness configured to achieve broadband reflection in the second predetermined wavelength range.

[0056] In some embodiments, the layered structure includes layer pairs of low refractive index (e.g., silicon dioxide) and high refractive index (e.g., titanium dioxide or tantalum pentoxide).

[0057] The intermediate layer is arranged on the distributed Bragg reflector. The intermediate layer may be parallel to the layers of the distributed Bragg reflector. In some embodiments, the intermediate layer has a thickness or a height that corresponds to the height or length of the cavity formed by the distributed Bragg reflector and the metasurface layer. The cavity height may be optimized for the target wavelength or target wavelength range.

[0058] In some embodiments, the intermediate layer includes a material with a low refractive index. In some embodiments, the material of the intermediate layer is or includes silicon dioxide.

[0059] The metasurface layer is arranged on the intermediate layer. The metasurface layer may be substantially parallel to the intermediate layer. In some embodiments, the metasurface layer has a reflective function. Generally, metasurfaces are two-dimensional metamaterials with a thickness comparable to or below the wavelength of interest. Typically, metamaterials are engineered structures designed to interact with electromagnetic waves in a desired fashion, wherein properties of metamaterials may not be found in naturally occurring materials and may stem from their internal structure and the arrangement of meta-atoms building them rather than their chemical composition.

[0060] Generally, meta-atoms, which may also be referred to as nanostructures, may be building blocks of metamaterials and metasurfaces and may have a size smaller than the wavelengths of interest in a lateral direction. For example, meta-atoms may be smaller or comparable (e.g., up to two times) to the wavelengths of interest in direction of light incidence. Typically, meta-atoms may have a precise shape, geometry, size, orientation, composition, and arrangement, giving the metamaterial or metasurface its novel and smart properties.

[0061] In general, non-identical meta-atoms can be used to build up one metamaterial or metasurface.

[0062] Generally, metasurfaces may be any arrangement in between: spatially highly inhomogeneous, with generally non-identical meta-atoms placed on a generally aperiodic lattice; and (essentially) periodic with identical meta-atoms placed in a periodic lattice (including photonic crystal slab geometries).

[0063] Generally, metasurfaces may dominantly inherit properties from their individual meta-atoms and their resonant properties.

[0064] In some embodiments, the metasurface layer includes a first material with a low refractive index and a second material with a high refractive index, the difference in permittivity between the material with high refractive index and the material with low refractive index is at least 3, and wherein the metasurface layer includes nanostructures including the first or second material. For example, the permittivity of the low refractive index material may be 2.2 and the permittivity of the high refractive index material may be 5.2, without limiting the disclosure in this regard.

[0065] In some embodiments, the first or second material is or includes silicon dioxide and / or lithium fluoride and / or titanium dioxide and / or tantalum pentoxide and / or silicon nitride and / or hafnium dioxide and / or amorphous silicon and / or (poly-)crystalline silicon and / or gallium phosphide.

[0066] In some embodiments, the metasurface layer includes nanostructures, wherein each of the nanostructures include the same material. In some other embodiments, the nanostructures included in the metasurface layer include different materials. The nanostructures included in the metasurface layer may be arranged according to an array pattern, wherein the array pattern may provide an ordered arrangement of the nanostructures. In some embodiments, the nanostructures are arranged in concentric circles or rectangles or squares or checkerboard pattern or any other predetermined pattern.

[0067] In some embodiments, the metasurface layer includes a layer including the first or second material which functions as a matrix embedding the nanostructures, wherein the nanostructures include the second or first material, respectively. The nanostructures and the layer including the first material or the second material have the same height so that the metasurface layer has a constant height. The extent of a nanostructure along one spatial dimension may correspond to the height of the layer of the first or second material.

[0068] In some embodiments, each nanostructure of the nanostructures included in the metasurface layer has the same geometric parameters including a shape and a width and a height. In some other embodiments, the nanostructures include a first nanostructure having a first set of geometric parameters and a second nanostructure having a second set of geometric parameters different from the first set of geometric parameters. For example, the shape of the first nanostructure may differ from the shape of the second nanostructure and / or the width of the first nanostructure may differ from the width of the second nanostructure.

[0069] In some embodiments, the metasurface layer may be coated with a layer including a low refractive index material (e.g., silicon dioxide or polymer based).

[0070] In some embodiments, the configuration of the metasurface layer includes a number of nanostructures, a pitch between adjacent nanostructures and the geometric parameters of the nanostructures. The pitch between adjacent nanostructures may represent the period of the arrangement of the nanostructures, for example, the length between the centers of adjacent nanostructures in a particular arrangement direction.

[0071] In some embodiments, as mentioned above, the arrangement of the distributed Bragg reflector and the metasurface layer form a Fabry -Perot resonator, thereby enclosing the intermediate layer. In some embodiments, the thickness or height of the intermediate layer corresponds to the distance between or spacing of the distributed Bragg reflector and the metasurface layer. In some embodiments, altering the thickness of the intermediate layer may alter the center wavelength transmitted through the color filter. In the embodiments, the arrangement of the distributed Bragg reflector and the metasurface layer forms the Fabry -Perot resonator and the distributed Bragg reflector and the metasurface layer each function as a mirror.

[0072] In some embodiments, as mentioned above, the configuration of the color filter corresponds to a size of the color filter, the reflectance of the distributed Bragg reflector, a thickness of the intermediate layer and a configuration of the metasurface layer. The size of the color filter may represent the spatial extent of the color filter along two spatial dimensions, wherein the spatial dimensions may correspond to a plane perpendicular to a height or a thickness of the color filter.

[0073] In some embodiments, the spatial dimensions are the dimensions parallel to the metasurface layer and / or the intermediate layer and / or the layers of the distributed Bragg reflector.

[0074] As mentioned above, the configuration of the color filter is determined such that the color filter has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

[0075] In other words, the color filter has a transmittance in a second predetermined wavelength range. The peak of the transmittance spectrum may be centered around the predetermined wavelength, which is included in the second predetermined wavelength range, and the peak has a maximum at the predetermined wavelength.

[0076] The peak has a spectral width which may represent the full width at half maximum of the peak. The peak of the transmittance spectrum may be asymmetric with the maximum at the predetermined wavelength. The spectral width of the peak may be below a spectral width threshold.

[0077] As mentioned above, it has been recognized that the layered structure of the color filter including a distributed Bragg reflector, an intermediate layer and a metasurface layer including nanostructures allows configurations in which the color filter has a narrow transmittance spectrum with high amplitude such that a large fraction of the incoming light within the narrow transmittance range is transmitted while other wavelengths are blocked.

[0078] By design optimization, the various structural parameters may be optimized to achieve large transmittance values at the target wavelength and a narrow wavelength range in which light is transmitted by the color filter. The design optimization may include the optimization of the configuration of the color filter with respect to certain design parameters or target parameters that may include the target wavelength and / or the transmittance threshold and / or the spectral width threshold and / or the angular independence of the color filter.

[0079] In some embodiments, the transmittance threshold is at least 30 percent. In some embodiments, the transmittance threshold is 80 percent.

[0080] In some embodiments, the spectral width threshold is in the range of 25 nanometers to 75 nanometers. In some embodiments, the spectral width threshold is 4 nanometers. In some embodiments, the spectral width threshold is 30 nanometers.

[0081] In some embodiments, the transmittance threshold is 80 percent, and the spectral width threshold is 30 nanometers.

[0082] In some embodiments, the angle of incidence may be zero degrees, that is, perpendicular to the layered structure of the color filter.

[0083] In some embodiments, the configuration of the color filter is determined according to the computer-implemented method described herein.

[0084] It has further been recognized that a color filter with various sections be provided, for example, for usage as a color filter on top of an image sensor such that each section covers a different pixel of the image sensor. The various sections of the color filter may have different configurations such that each section transmits a different narrow target wavelength range. In this way, the color filter may be suitable for multi- or hyperspectral imaging applications.

[0085] Hence, some embodiments pertain to a color filter, wherein the color filter includes a plurality of color filter sections, wherein each color filter section includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold. Each color filter section functions as an individual color filter. Each color filter section may have the same characteristics as a color filter as described herein.

[0086] The different color filter sections correspond to different sections of a larger layered structure such that a color filter section is typically not provided as a separate element. The larger layered structure has spatially varying configurations to provide the color filter sections and, thus, to provide spatially varying light transmission properties which may be utilized in multi- or hyperspectral imaging applications.

[0087] As mentioned above, a color filter with different color filter sections may be used on top of an image sensor.

[0088] Hence, some embodiments pertain to an imaging device, wherein the imaging device includes: an image sensor having a plurality of pixels; a color filter arranged on the image sensor, wherein the color filter includes a plurality of color filter sections corresponding to the number of pixels of the image sensor, wherein each color filter section has the same thickness and includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold; wherein each color filter section is matched with a different pixel of the image sensor.

[0089] The imaging device may be used in applications relying on multi- and / or hyperspectral imaging, for example in the fields of agriculture, food processing, remote sensing, forensics, machine vision, or medicine, without limiting the embodiments to these applications.

[0090] In addition, the distributed Bragg reflector may be fabricated at chip level, while the metasurface layer may be structured at pixel level, which may enable chip-level flat filters and thus simplify fabrication. Therewith, the color filters may be suitable for on-chip integration with an imager to enable hyperspectral snapshot imaging.

[0091] The image sensor has a plurality of pixels, wherein each pixel of the plurality of pixels may include a light-sensitive area or site and may detect radiant energy transmitted through the color filter section. Each pixel of the plurality of pixels is matched with a color filter section of the plurality of color filter sections included in the color filter, wherein each two pixels are matched with a different color filter section.

[0092] Each color filter section included in the color filter has the same thickness which may be the same thickness as the thickness of the color filter. The color filter sections included in the color filter may be arranged next to each other.

[0093] As mentioned above, each color filter section includes a broadband distributed Bragg reflector bottom mirror, that may be fabricated on chip level, and a metasurface layer, that may be fabricated on a pixel level, wherein the distributed Bragg reflector and the metasurface layer may be separated by an intermediate layer, which may also be referred to as cavity, forming a Fabry- Perot resonator. The design of the color filters and choice of materials may be suited for on-chip integration on an imager.

[0094] The distributed Bragg reflector, fabricated on a chip level, may include either N number of X / 4- layer pairs of low refractive index (e.g. silicon dioxide) and high refractive index (e.g. titanium dioxide or tantalum pentoxide) materials with thicknesses dl and d2, respectively, wherein denotes a wavelength, or M number of alternating layers of low and high refractive index material with layer thicknesses individually optimized to achieve broadband reflection in the targeted wavelength range.

[0095] The intermediate layer, that may be fabricated on a chip level, may include a low refractive index matrix material (e.g. silicon dioxide) with a height L of the intermediate layer, wherein the height may be optimized for the target wavelength range.

[0096] The metasurface layer, which may be fabricated on a pixel level, may include either nanostructures including a material that has a high refractive index (e.g., amorphous silicon or gallium phosphide), wherein the nanostructures may be embedded, in some embodiments, in a matrix in a material having a low refractive index (e.g. silicon dioxide) and thus form pillars, or nanostructures including a material that has a low refractive index, wherein the nanostructures are embedded, in some embodiments, in a matrix in a material that has a high refractive index and thus form holes, or both.

[0097] The metasurface layer may be structured in finite arrays of nanostructures, wherein the nanostructures may include different numbers of nanostructures and wherein the nanostructures may have different geometrical parameters (e.g., size, period, and shape). Structuring the metasurface layer in finite arrays of nanostructures may form pixel filters each having a different center wavelength of transmitted light.

[0098] The sizes of the finite array pixels may be matched with the pixel size of the imager below. The finite arrays may be separated by a (compared to the pixel size) thin boundary consisting of or including an optical black material or reflective material.

[0099] In some embodiments, the configuration of each of the color filter sections includes a size of the color filter section, the reflectance of the distributed Bragg reflector, a thickness of the intermediate layer and a configuration of the metasurface layer.

[0100] In some embodiments, at least two color filter sections of the plurality of color filter sections have a different configuration such that a first color filter section has a transmittance spectrum with a peak with a maximum at a first predetermined wavelength and a second color filter section has a transmittance spectrum with a peak with a maximum at a second predetermined wavelength different from the first predetermined wavelength.

[0101] In some embodiments, each color filter section has a different configuration such that each color filter section has a different transmittance spectrum with a peak with a maximum at a different predetermined wavelength.

[0102] In some embodiments, a configuration of the first color filter section differs from a configuration of the second color filter section in at least one of the number and thickness of the layers of the distributed Bragg reflector and the thickness of the intermediate layer and the configuration of the metasurface layer.

[0103] For example, the distributed Bragg reflector included in the first color filter section may have more layers than the distributed Bragg reflector included in the second color filter section and the thickness of the intermediate layer of the first color filter section may be smaller than the thickness of the intermediate layer of the second color filter section.

[0104] For the case that the thickness of the distributed Bragg reflector of the first color filter section is greater than the thickness of the distributed Bragg reflector of the second color filter section - due to the greater number of layers of the distributed Bragg reflector - and the metasurface layers of the first and second color filter section both have the same thickness, the thickness of the intermediate layer of the first color filter section is less than the thickness of the intermediate layer of the second color filter section, such that the first color filter section is of the same size or thickness as the second color filter section. In some embodiments, the plurality of color filter sections includes a contiguous block of color filter sections that have the same configuration. As an example, a contiguous block of four color filter sections may represent an arrangement of the four color filter sections in a two-by-two matrix, wherein each of the color filter sections has the same configuration.

[0105] In some embodiments, the plurality of color filters sections includes a plurality of different contiguous blocks of color filter sections that have the same configuration, wherein the color filter sections of different contiguous blocks have a different configuration.

[0106] In some embodiments, the metasurface layers of adjacent color filter sections are separated by a boundary including a material representing, in the first predetermined wavelength range or the second predetermined wavelength range or the first and the second predetermined wavelength range, an optical black material or a reflective material. In some embodiments, the material includes but is not limited to aluminum, tantalum, titanium, titanium nitride, or tungsten.

[0107] In some embodiments, each metasurface layer of the color filter sections included in the color filter has a configuration that includes a number of nanostructures, a pitch between adjacent nanostructures, and geometric parameters of the nanostructures, wherein the geometric parameters include a shape, a width, and a height of the nanostructures.

[0108] In some embodiments, one or more nanostructures of the nanostructures included in the metasurface layer of a color filter section included in the color filter are adjacent to a boundary. One nanostructure may be adjacent to a boundary in case no other nanostructure is arranged between the one nanostructure and the boundary. The distance between a portion of the one nanostructure closest to the boundary and the boundary may be referred to as buffer.

[0109] As mentioned above, it has been recognized that the layered structure of the color filter section including a distributed Bragg reflector, an intermediate layer and a metasurface layer including nanostructures allows configurations in which the color filter has a narrow transmittance spectrum with high amplitude such that a large fraction of the incoming light within the narrow transmittance range is transmitted while other wavelengths are blocked.

[0110] By design optimization, as mentioned above, the various structural parameters may be optimized to achieve large transmittance values at the target wavelength and a narrow wavelength range in which light is transmitted by the color filter.

[0111] The design optimization may include the optimization of the configuration of the color filter with respect to certain design parameters or target parameters that may include the target wavelength and / or the transmittance threshold and / or the spectral width threshold and / or the angular independence of the color filter.

[0112] In some embodiments, the transmittance threshold is at least 30 percent. In some embodiments, the transmittance threshold is 80 percent.

[0113] In some embodiments, the spectral width threshold is in the range of 25 nanometers to 75 nanometers. In some embodiments, the spectral width threshold is 4 nanometers. In some embodiments, the spectral width threshold is 30 nanometers.

[0114] In some embodiments, the transmittance threshold is 80 percent, and the spectral width threshold is 30 nanometers.

[0115] In some embodiments, the first predetermined wavelength range is equal to the second predetermined wavelength range. In some other embodiments, the first predetermined wavelength range and the second predetermined wavelength range partially overlap. In some other embodiments, the first predetermined wavelength range and the second predetermined wavelength range do not overlap.

[0116] Some embodiments pertain to a computer-implemented method, including: performing a design optimization of a color filter including: simulating a transmittance spectrum of a color filter in a target wavelength range including a target wavelength; and determining a configuration of the color filter by minimizing a deviation between the simulated transmittance spectrum and a target transmittance spectrum, wherein the target transmittance spectrum has a Lorentzian shape that has a maximum at the target wavelength and a target spectral width; wherein the color filter includes: a distributed Bragg reflector; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; wherein minimizing the deviation includes iteratively adjusting the configuration of the color filter and simulating the transmittance spectrum for the adjusted configuration of the color filter.

[0117] The computer-implemented method may be performed or executed by an information processing device. The information processing device may be a mobile computing device (e.g., a smartphone, a tablet, a laptop), a computer, a server or the like. The information processing device includes circuitry configured to perform the computer- implemented method. The circuitry may include one or more processors. A processor may be or may include an application processor, a central processing unit (“CPU”), a graphical processing unit (“GPU”), a digital signal processor (“DSP”), a field-programmable gate array (“FPGA”), an application specific integrated circuit (“ASIC”) etc.

[0118] The circuitry may include one or more memory components. A memory component may be or may include volatile and non-volatile memory such as static random-access memory (“SRAM”), dynamic RAM (“DRAM”), non-volatile RAM (“NVRAM”), read-only memory (“ROM”), programmable ROM (“PROM”), electrically PROM (“EPROM”), electrically erasable PROM (“EEPROM”), flash memory (e.g., NOR flash or NAND flash) etc. A memory component may be or may include one or more registers, caches, main memories, hard disk drives, solid-state drives etc.

[0119] The circuitry may include one or more input / output interfaces, wherein to each input / output interface at least one or more peripheral devices and one or more communication interfaces may be connected to exchange data with at least one of the one or more processors and the one or more memory components. The data exchange may be in simplex, half-duplex, or full-duplex mode. The data exchange may be serial or parallel. The data exchange may be synchronous or asynchronous.

[0120] The circuitry may be implemented by typical electronic components configured to achieve the functionality as described herein. The circuitry may be implemented in parts by typical electronic components and in parts by software configured to achieve the functionality as described herein. The circuitry may be implemented by software configured to achieve the functionality as described herein.

[0121] As discussed herein, a color filter may be configured to transmit radiant energy, wherein the radiant energy transmitted through the color filter may have a transmittance spectrum with a nonzero transmittance in a target wavelength range including a target wavelength. The peak of the transmittance spectrum that is centered at the target wavelength may have a maximum at the target wavelength, which may be a global maximum of the transmittance spectrum. The maximum transmittance may exceed a transmittance threshold, and the peak may have a spectral width below a spectral width threshold.

[0122] The configuration of the color filter may include a size of the color filter, a reflectance of the distributed Bragg reflector, a thickness of the intermediate layer, and a configuration of the metasurface layer, wherein the configuration of the metasurface layer may include a number of nanostructures, a pitch between adjacent nanostructures, and geometric parameters of the nanostructures. The geometric parameters of the nanostructures may include a shape, a width, and a height of the nanostructures, as discussed herein.

[0123] It is estimated that the color filter may be configured in various ways to achieve the desired output described above. However, a concrete mathematical relationship between the desired output and the color filter configuration including a great number of parameters to be determined may be difficult to obtain due to the complexity of the interaction between the light and the color filter structure.

[0124] It has thus been recognized that the configuration of the color filter should be determined based on a simulation and an optimization procedure in some embodiments.

[0125] Hence, the computer-implemented method is used to determine the configuration of the color filter in some embodiments.

[0126] The computer-implemented method includes performing a design optimization of a color filter, wherein the design optimization includes simulating a transmittance spectrum of a color filter in a target wavelength range including a target wavelength.

[0127] Since computer-implemented methods for a physical simulation of light propagation through various materials of various structures are generally known, the simulation procedure is not discussed in detail.

[0128] Furthermore, the computer-implemented method includes determining the configuration of the color filter by minimizing a deviation between the simulated transmittance spectrum and a target transmittance spectrum, wherein minimizing the deviation includes iteratively adjusting the configuration of the color filter and simulating the transmittance spectrum for the adjusted configuration of the color filter.

[0129] The design optimization may include the optimization of the configuration of the color filter with respect to certain design parameters or target parameters that may include the target wavelength and / or the transmittance threshold and / or the spectral width threshold and / or the angular independence of the color filter.

[0130] Hence, in some embodiments, the minimization of the deviation between the simulated transmittance spectrum and the target transmittance spectrum is performed with respect to the design parameters or target parameters, for example, with respect to at least one of the target wavelengths, the transmittance threshold and the spectral width threshold.

[0131] The target transmittance spectrum may have a Lorentzian shape, since the layered structure of the color filter forms a Fabry -Perot resonator, wherein the peak of the target transmittance spectrum is centered at the target wavelength and has a target spectral width. In some embodiments, the spectral profile of the target transmittance spectrum may also have other shapes such as a Gaussian or Voigt shape.

[0132] The computer-implemented method as described herein may also be implemented in some embodiments as a computer program causing a computer and / or a processor to perform the method, when being carried out on the computer and / or processor. In some embodiments, also a non-transitory computer-readable recording medium is provided that stores therein a computer program product, which, when executed by a processor, such as the processor described above, causes the methods described herein to be performed.

[0133] Returning to Fig. 1 A, there is schematically illustrated a side view of an embodiment of a color filter 10 in a block diagram, which is discussed in the following.

[0134] The color filter 10 includes a distributed Bragg reflector 11. In the present embodiment, the distributed Bragg reflector 11 includes an alternating sequence of a first layer type I la and a second layer type 1 lb. An intermediate layer 12 is arranged on the distributed Bragg reflector 11 and a metasurface layer 13 is arranged on the intermediate layer 12. The metasurface layer 13 includes a layer 13b of a first material and nanostructures 13a of a second material different from the first material. The nanostructures 13a are embedded in the layer 13b of the first material.

[0135] Fig. IB schematically illustrates some of the basic physical principles underlying the functionality of an embodiment of the color filter 10 of Fig. 1 A, but which also apply to other embodiments of the present disclosure.

[0136] The metasurface layer 13, schematically represented by the nanostructure 13a in Fig. IB, may act as the top mirror and the distributed Bragg reflector 11 as bottom mirror forming a Fabry- Perot resonator having a narrow transmittance spectrum. The distributed Bragg reflector 11 is designed to have broad reflectance in the wavelength range of interest. The metasurface layer 13 may have either broadband or narrowband reflectance in the wavelength range of interest.

[0137] The distributed Bragg reflector 11 reflects light incident on the distributed Bragg reflector 11 according to a reflectance spectrum having a maximum reflectance n and peak with a full width at half maximum wi. Likewise, the metasurface layer 13 reflects light incident on the metasurface layer 13 according to another reflectance spectrum having a maximum reflectance r2 and a peak with a full width at half maximum W2.

[0138] The light that is transmitted through the color filter 10 has a transmittance spectrum with a full width at half maximum W3.

[0139] The magnitude of reflectance of the distributed Bragg reflector 11 and metasurface layer 13 may be matched. The center wavelength of the transmitted light of the Fabry -Perot resonator may be tuned and controlled by varying, for example, the in-plane geometrical parameters of the metasurface layer 13 such as nanostructure size, period, and shape. Varying the in-plane metasurface layer parameters may lead to a shift in the phase of the reflectance of the metasurface layer 13 and with it the wavelength of the transmitted light may be shifted.

[0140] Therewith, the metasurface layer 13 may be structured on a pixel level while having a constant nanostructure height, wherein each pixel has a different wavelength it is filtering.

[0141] The distributed Bragg reflector 11 and intermediate layer 12 may be fabricated on a chip level and each may have a constant height, which may enable a constant height of all color filters over the entire imager chip.

[0142] Depending on the optical properties of the chosen material, the number of layers of the distributed Bragg reflector 11 and thickness of the layer of the distributed Bragg reflector 11 as well as the height of the intermediate layer 12 may be adjusted to control the transmittance and full widths at half maximum of the peaks of the transmittance spectra of the color filters.

[0143] Fig. 2 shows a side view of an embodiment of a color filter 10, which is discussed in the following.

[0144] The distributed Bragg reflector 11 comprises two layer types, wherein the first layer type 1 la is of a first layer material mi and the second layer type 1 lb is of a second layer material m2. In the present embodiment, material mi is titanium dioxide, while material m2 is silicon dioxide.

[0145] The intermediate layer 12 arranged on the distributed Bragg reflector 11 is silicon dioxide and, thus, denoted as material m2 without limiting the disclosure to such a case. The metasurface layer 13 includes a layer 13b of material m3 and nanostructures 13a of material nu. In the present embodiment, material m3 is silicon dioxide, while material mi is gallium phosphide.

[0146] In the present embodiment, the metasurface layer 13 is coated with silicon dioxide and, thus, denoted as a layer of material m2 without limiting the disclosure to such a case. Fig. 3 schematically illustrates a side view of an embodiment of an imaging device 20, which is discussed in the following.

[0147] The imaging device 20 includes a plurality of pixels 24 that are arranged on a substrate (not shown) and detect light transmitted through the color filter 25.

[0148] In the present embodiment, the color filter 25 includes three color filter sections 10. An embodiment of a color filter section 10 is highlighted by the rectangle with the black dashed contour.

[0149] Each color filter section 10 includes a distributed Bragg reflector 21 of the same configuration and an intermediate layer 22 of the same configuration. The configuration of the distributed Bragg reflector 21 includes a sequence of alternating layers of a first layer type 21a and a second layer type 21b different from the first layer type 21a.

[0150] The color filter sections 10 included in the color filter 25 differ in the configuration of the metasurface layer 23. More precisely, in the present embodiment, each nanostructure 23a included in a first plurality of nanostructures of a first color filter section 10 has a first size; each nanostructure 23 a included in a second plurality of nanostructures of a second color filter section 10 has a second size different from the first size; and each nanostructure 23 a included in a third plurality of nanostructures of a third color filter section 10 has a third size different from the first and second size.

[0151] In the present embodiment, the metasurface layers 23 of adjacent color filters 10 are separated by a boundary 23c.

[0152] Fig. 4 schematically illustrates a top view of an embodiment of metasurface layers 23, which is discussed in the following.

[0153] The cross-sectional shapes of nanostructures 23 a include squares with rounded corners, circles, and diamonds. Besides the shape of the nanostructures 23a, the metasurface layers 23 also differ in other parameters of the metasurface layer configuration, namely the width of the nanostructures 23 a, the number of the nanostructures 23 a, and the pitch between adjacent nanostructures 23 a.

[0154] Fig. 5A schematically illustrates a top view 30 an embodiment of a metasurface layer 33 of a color filter section 10 included in a color filter 25, which is discussed in the following.

[0155] Nanostructures 33a included in the metasurface layer 33 are embedded in a layer 33b and are arranged in a nine-by-nine array. The color filter 10 is surrounded by a boundary 33c. Fig. 5B shows a closeup view 31 of the metasurface layer 33 of color filter section 10 and illustrates some parameters of the metasurface layer configuration, which is discussed in the following.

[0156] The parameters of the metasurface layer configuration include a pitch 33d between two adjacent nanostructures 33a, a width 33e of a nanostructure 33a, and a buffer 33f that represents the distance between a nanostructure 33a adjacent to the boundary 33c and the boundary 33c.

[0157] Fig. 6A schematically illustrates a side view of an embodiment of an imaging device 40, which is discussed in the following.

[0158] The imaging device 40 includes a plurality of pixels 44 that are arranged on a substrate (not shown) and detect light transmitted through the color filter 45.

[0159] In the present embodiment, the color filter 45 includes nine color filter sections 10, wherein each color filter section 10 of a first set of three color filter sections 10 has a distributed Bragg reflector 41 of a first configuration and an intermediate layer 42 of a first configuration; each color filter section 10 of a second set of three color filter sections 10 has a distributed Bragg reflector 41 of a second configuration and an intermediate layer 42 of a second configuration; and each color filter sections 10 of a third set of three color filter sections 10 has a distributed Bragg reflector 41 of a third configuration and an intermediate layer 42 of a third configuration, wherein each color filter section 10 of the plurality of color filter sections 10 included in the color filter 45 is included in one of the three sets of color filters 10.

[0160] The first, second, and third configuration of the distributed Bragg reflector 41 differ in the number, thickness, and structure of the layers, while the first, second, and third configuration of the intermediate layer 42 differ in the thickness of the intermediate layer 42.

[0161] The distributed Bragg reflector 41 and the intermediate layer 42 of each of the color filter sections are configured such that the color filter layer 45 has a constant height or thickness.

[0162] The metasurface layers 43 of each of the color filter sections 10 included in the color filter layer 45 differ in the configuration of the nanostructures 43 a that are embedded in a layer 43b. The color filters 10 are surrounded by a boundary 43c.

[0163] To summarize, the filter element is separated into different areas each comprising different distributed Bragg reflectors 41 with varying layer thicknesses, number of layers and overall thickness of the distributed Bragg reflector 41 as well as different heights of the intermediate layer 42. Each of these areas may cover a certain number of finite array metasurface layer pixels. Fig. 6B schematically illustrates a top view of an embodiment of an imaging device 40 that includes a color filter 45 comprising twenty-seven color filter sections 10 that include twentyseven metasurface layers 43, which is discussed in the following.

[0164] The metasurface layers 43 differ in the geometric parameters of the nanostructures 43 a.

[0165] The four color filter sections 10 on the bottom right of the top view highlighted by the black dashed box 46 have identical configurations. Therewith, each of the four color filter sections transmits light of the same target wavelength range including a target wavelength.

[0166] Each one of the four color filter sections 10 is matched with a different one of four pixels 44. Pooling the signals detected at the four pixels 44 results in an enhanced signal for the target wavelength range.

[0167] The above-described approach illustrated by Figs. 6A and 6B may allow for an extended wavelength range of the hyperspectral imager, which might not be possible to cover with only one distributed Bragg reflector. Here, the design may still be with one height of the metasurface layer and the top of the filter elements being flat on a chip level to allow for easier fabrication.

[0168] In addition, some finite array pixels of the metasurface layer may cover several imager pixels to allow for pixel binning, which may increase the sensitivity for certain wavelengths.

[0169] Metasurface layer designs for narrowband color filters based on metasurface layer on mirror may be created via simulation, as will be discussed in the following.

[0170] Fig. 7A schematically illustrates in a block diagram a side view of structure 50 representing an embodiment of an infinite metasurface layer 53, which is discussed in the following.

[0171] The infinite metasurface layer 53 is assumed as including an infinite number of nanostructures 53a, wherein each nanostructure 53a has a squared shape and includes gallium phosphide. The nanostructures 53a are embedded in a layer 53b representing a lithium fluoride matrix.

[0172] The configuration of the metasurface layer 53 is optimized, via simulation, for broad reflection in the wavelength range of 600 to 700 nanometers, which is illustrated in the graph of Fig. 7A, wherein the solid line represents the reflectance and the dashed line represents the transmittance as a function of wavelength. The graph in Fig. 7A shows that the reflectance in the wavelength range of 600 to 700 nanometers is close to 100 percent.

[0173] Fig. 7B schematically illustrates, in a block diagram, a side view of structure 60 representing an embodiment of an infinite metasurface layer 63, which is discussed in the following. The infinite metasurface layer 63 is arranged on an intermediate layer 62 which, in turn, is arranged on a distributed Bragg reflector 61.

[0174] The intermediate layer 62 includes silicon dioxide. The distributed Bragg reflector 61 includes three pairs of alternating layers of two layer types, wherein the first layer type 61a includes silicon dioxide and the second layer type 61b includes titanium dioxide.

[0175] The structure 60 includes the infinite metasurface layer 63, the intermediate layer 62, and the distributed Bragg reflector 61 represents a Fabry-Perot resonator with narrow transmittance.

[0176] The graph in Fig. 7B is a schematic illustration that depicts, for a given wavelength, the width of nanostructures 63a resulting in the highest transmittance. The solid line in the graph in Fig. 7B represents the wavelength-width pairs leading to the highest transmittance.

[0177] By tuning the width of the nanostructures 63a by ±50 nanometers, the center wavelength of the transmitted light can be shifted by around ±50 nanometers, demonstrating the control of the color filter wavelength by changing the configuration of the metasurface layer 63. In other words, varying the geometric parameters of nanostructures 63 a varies the wavelength of the light transmitted through structure 60.

[0178] Fig. 7C schematically illustrates, in a block diagram, a side view of an embodiment of a color filter (section) 70, highlighted by the black dashed rectangle, which is discussed in the following.

[0179] The color filter 70 includes a metasurface layer 73, an intermediate layer 72, and a distributed Bragg reflector 71, wherein the configuration of the metasurface layer 73, the configuration of the intermediate layer 72, and the configuration of the distributed Bragg reflector 71 includes the same parameters as the configurations of the metasurface layer 63, the intermediate layer 62, and the distributed Bragg reflector 61, except that the color filter 70, and thus the number of nanostructures 73a, is finite.

[0180] The metasurface layer 73 includes a finite array of nine-by-nine nanostructures 73a, wherein the pixel size, that is the size of the finite array, is approximately 3.2 micrometers by 3.2 micrometers, corresponding to a nonoptimized configuration. The finite array is surrounded by an aluminum boundary 73c.

[0181] The graph in Fig. 7C schematically illustrates the transmittance spectrum of color filter 70 as a function of wavelength, which is discussed in the following. The maximum transmittance of the transmittance spectrum is approximately 40 percent and the full width at half maximum of the peak including the maximum transmittance is approximately 4 nanometers.

[0182] Fig. 8 schematically illustrates in a flow diagram an embodiment of a computer-implemented method 90.

[0183] The computer-implemented method 90 may be performed by the information processing device as described herein. The computer-implemented method includes performing a design optimization of a color filter which includes:

[0184] At 91, a transmittance spectrum of a color filter in a target wavelength range including a target wavelength is simulated, as discussed herein.

[0185] At 92, a configuration of the color filter is determined by minimizing a deviation between the simulated transmittance spectrum and a target transmittance spectrum, wherein the transmittance spectrum of the target transmittance has a Lorentzian shape which is centered at the target wavelength and which has a target spectral width, wherein minimizing the deviation includes iteratively adjusting the configuration of the color filter and simulating the transmittance for the adjusted configuration of the color filter, as discussed herein.

[0186] Fig. 9 schematically illustrates in a block diagram an embodiment of a multi-purpose computer which can be used for implementing an information processing device configured to perform the computer-implemented method as described herein.

[0187] The computer 100 can be implemented such that it can basically function as any type of information processing device as described herein. The computer has components 101 to 111, which can form a circuitry, such as any one of the circuitries of the information processing device as described herein.

[0188] Embodiments which use software, firmware, programs or the like for performing the methods as described herein can be installed on computer 100, which is then configured to be suitable for the concrete embodiment.

[0189] The computer 100 has a CPU 101 (Central Processing Unit), which can execute various types of procedures and methods as described herein, for example, in accordance with programs stored in a read-only memory (ROM) 102, stored in a storage 107 and loaded into a random-access memory (RAM) 103, stored on a medium 110 which can be inserted in a respective drive 109, etc. The CPU 101, the ROM 102 and the RAM 103 are connected with a bus 111, which in turn is connected to an input / output interface 104. The number of CPUs, memories and storages is only exemplary, and the skilled person will appreciate that the computer 100 can be adapted and configured accordingly for meeting specific requirements which arise, when it functions as an information processing device.

[0190] At the input / output interface 104, several components are connected: an input 105, an output 106, the storage 107, a communication interface 108 and the drive 109, into which a medium 110 (compact disc, digital video disc, compact flash memory, or the like) can be inserted.

[0191] The input 105 can be a pointer device (mouse, graphic table, or the like), a keyboard, a microphone, a camera, a touchscreen, a time-of-flight device, etc.

[0192] The output 106 can have a display (liquid crystal display, cathode ray tube display, light emittance diode display, etc.), loudspeakers, etc.

[0193] The storage 107 can have a hard disk, a solid-state drive and the like.

[0194] The communication interface 108 can be adapted to communicate, for example, via a local area network (LAN), wireless local area network (WLAN), mobile telecommunications system (GSM, UMTS, LTE, NR etc.), Bluetooth, infrared, etc.

[0195] It should be noted that the description above only pertains to an example configuration of computer 100. Alternative configurations may be implemented with additional or other sensors, storage devices, interfaces or the like. For example, the communication interface 108 may support other radio access technologies than the mentioned UMTS, LTE and NR.

[0196] It should be recognized that the embodiments describe methods with an exemplary ordering of method steps. The specific ordering of method steps is however given for illustrative purposes only and should not be construed as binding.

[0197] In so far as the embodiments of the disclosure described above are implemented, at least in part, using software-controlled data processing apparatus, it will be appreciated that a computer program providing such software control and a transmission, storage or other medium by which such a computer program is provided are envisaged as aspects of the present disclosure.

[0198] Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in any manner suitable to implement the technique.

[0199] Note that the present technology can also be configured as described below.

[0200] (1) A color filter, including: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter is such that the color filter has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

[0201] (2) The color filter of (1), wherein the first predetermined wavelength range is equal to the second predetermined wavelength range.

[0202] (3) The color filter of (1) or (2), wherein the transmittance threshold is at least 30 percent.

[0203] (4) The color filter of any one of (1) to (3), wherein the arrangement of the distributed Bragg reflector and the metasurface layer forms a Fabry -Perot resonator.

[0204] (5) The color filter of any one of (1) to (5), wherein the metasurface layer includes a first material with a low refractive index and a second material with a high refractive index, wherein the difference in permittivity between the material with high refractive index and the material with low refractive index is at least 3, and wherein the metasurface layer includes nanostructures including the first material or the second material.

[0205] (6) The color filter of (5), wherein the intermediate layer includes a material with a low refractive index.

[0206] (7) The color filter of any one of (1) to (6), wherein the configuration of the color filter includes a size of the color filter, the reflectance of the distributed Bragg reflector, a thickness of the intermediate layer and a configuration of the metasurface layer.

[0207] (8) The color filter of (7), wherein the metasurface layer includes nanostructures, wherein each nanostructure has the same geometric parameters including a shape and a width and a height, and wherein the configuration of the metasurface layer includes a number of nanostructures, a pitch between adjacent nanostructures and the geometric parameters of the nanostructures.

[0208] (9) The color filter of any one of (1) to (8), wherein the configuration of the color filter is determined according to the computer-implemented method of (38).

[0209] (10) A color filter, including a plurality of color filter sections, wherein each color filter section includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at the predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

[0210] (11) The color filter of (10), wherein the first predetermined wavelength range is equal to the second predetermined wavelength range.

[0211] (12) The color filter of (10) or (11), wherein the transmittance threshold is at least 30 percent.

[0212] (13) The color filter of any one of (10) to (12), wherein the arrangement of the distributed Bragg reflector and the metasurface layer forms a Fabry-Perot resonator.

[0213] (14) The color filter of any one of (10) to (13), wherein the metasurface layer includes a first material with a low refractive index and a second material with a high refractive index, wherein the difference in permittivity between the material with high refractive index and the material with low refractive index is at least 3, and wherein the metasurface layer includes nanostructures including the first material or the second material.

[0214] (15) The color filter of (14), wherein the intermediate layer includes a material with a low refractive index.

[0215] (16) The color filter of any one of (10) to (15), wherein the configuration of the color filter section includes a size of the color filter section, the reflectance of the distributed Bragg reflector, a thickness of the intermediate layer and a configuration of the metasurface layer.

[0216] (17) The color filter of (16), wherein the metasurface layer includes nanostructures, wherein each nanostructure has the same geometric parameters including a shape and a width and a height, and wherein the configuration of the metasurface layer includes a number of nanostructures, a pitch between adjacent nanostructures and the geometric parameters of the nanostructures.

[0217] (18) The color filter of any one of (10) to (17), wherein the configuration of each color filter is determined according to the computer-implemented method of (38).

[0218] (19) The color filter of any one of (10) to (18), wherein the metasurface layers of adjacent color filter sections are separated by a boundary including a material representing, in the predetermined wavelength range, an optical black material or a reflective material.

[0219] (20) The color filter of any one of (10) to (19), wherein at least two color filter sections of the plurality of color filter sections have a different configuration such that a first color filter section has a transmittance spectrum with a peak with a maximum at a first predetermined wavelength and a second color filter section has a transmittance spectrum with a peak with a maximum at a second predetermined wavelength different from the first predetermined wavelength.

[0220] (21) The color filter of (20), wherein a configuration of the first color filter section differs from a configuration of the second color filter section in at least one of the number and the thickness of the layers of the distributed Bragg reflector and the thickness of the intermediate layer and the configuration of the metasurface layer.

[0221] (22) The color filter of any one of (10) to (21), wherein the plurality of color filter sections includes a contiguous block of color filter sections that have the same configuration.

[0222] (23) An imaging device, including: an image sensor having a plurality of pixels; a color filter arranged on the image sensor, wherein the color filter includes a plurality of color filter sections corresponding to the number of pixels of the image sensor, wherein each color filter section has the same thickness and includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold; wherein each color filter section is matched with a different pixel of the image sensor.

[0223] (24) The imaging device of (23), wherein the metasurface layers of adjacent color filter sections are separated by a boundary including a material representing, in the predetermined wavelength range, an optical black material or a reflective material.

[0224] (25) The imaging device of any one of (23) to (24), wherein at least two color filter sections of the plurality of color filter sections have a different configuration such that a first color filter section has a transmittance spectrum with a peak with a maximum at a first predetermined wavelength and a second color filter section has a transmittance spectrum with a peak with a maximum at a second predetermined wavelength different from the first predetermined wavelength.

[0225] (26) The imaging device of (25), wherein a configuration of the first color filter section differs from a configuration of the second color filter section in at least one of the number and the thickness of the layers of the distributed Bragg reflector and the thickness of the intermediate layer and the configuration of the metasurface layer.

[0226] (27) The imaging device of any one of (23) to (26), wherein the plurality of color filter sections includes a contiguous block of color filter sections that have the same configuration.

[0227] (28) The imaging device of any one of (23) to (27), wherein the first predetermined wavelength range is equal to the second predetermined wavelength range.

[0228] (29) The imaging device of any one of (23) to (28), wherein the transmittance threshold is at least 30 percent.

[0229] (30) The imaging device of any one of (23) to (29), wherein the arrangement of the distributed Bragg reflector and the metasurface layer forms a Fabry-Perot resonator.

[0230] (31) The imaging device of any one of (23) to (30), wherein the metasurface layer includes a first material with a low refractive index and a second material with a high refractive index, wherein the difference in permittivity between the material with high refractive index and the material with low refractive index is at least 3, and wherein the metasurface layer includes nanostructures including the first material or the second material.

[0231] (32) The imaging device of (31), wherein the intermediate layer includes a material with a low refractive index. (33) The imaging device of any one of (23) to (32), wherein the configuration of the color filter section includes a size of the color filter section, the reflectance of the distributed Bragg reflector, a thickness of the intermediate layer and a configuration of the metasurface layer.

[0232] (34) The imaging device of (33), wherein the metasurface layer includes nanostructures, wherein each nanostructure has the same geometric parameters including a shape and a width and a height, and wherein the configuration of the metasurface layer includes a number of nanostructures, a pitch between adjacent nanostructures and the geometric parameters of the nanostructures.

[0233] (35) The imaging device of any one of (23) to (34), wherein the configuration of each color filter is determined according to the computer-implemented method of (36).

[0234] (36) A computer-implemented method, including: performing a design optimization of a color filter including: simulating a transmittance spectrum of a color filter in a target wavelength range including a target wavelength; and determining a configuration of the color filter by minimizing a deviation between the simulated transmittance spectrum and a target transmittance spectrum, wherein the target transmittance spectrum has a Lorentzian shape that has a maximum at the target wavelength and a target spectral width; wherein the color filter includes: a distributed Bragg reflector; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; wherein minimizing the deviation includes iteratively adjusting the configuration of the color filter and simulating the transmittance spectrum for the adjusted configuration of the color filter.

[0235] (37) A computer program comprising program code causing a computer to perform the method of (36), when being carried out on a computer.

[0236] (38) A non-transitory computer-readable recording medium that stores therein a computer program product, which, when executed by a processor, causes the method of (36) to be performed.

Claims

CLAIMS1. A color filter, comprising: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter is such that the color filter has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

2. The color filter according to claim 1, wherein the first predetermined wavelength range is equal to the second predetermined wavelength range.

3. The color filter according to claim 1, wherein the transmittance threshold is at least 30 percent.

4. The color filter according to claim 1, wherein the arrangement of the distributed Bragg reflector and the metasurface layer forms a Fabry -Perot resonator.

5. The color filter according to claim 1, wherein the metasurface layer includes a first material with a low refractive index and a second material with a high refractive index, wherein the difference in permittivity between the material with high refractive index and the material with low refractive index is at least 3, and wherein the metasurface layer includes nanostructures including the first material or the second material.

6. The color filter according to claim 5, wherein the intermediate layer includes a material with a low refractive index.

7. The color filter according to claim 1, wherein the configuration of the color filter includes a size of the color filter, the reflectance of the distributed Bragg reflector, a thickness of the intermediate layer and a configuration of the metasurface layer.

8. The color filter according to claim 7, wherein the metasurface layer includes nanostructures, wherein each nanostructure has the same geometric parameters including a shape and a width and a height, and wherein the configuration of the metasurface layer includes a number of nanostructures, a pitch between adjacent nanostructures and the geometric parameters of the nanostructures.

9. The color filter according to claim 1, wherein the configuration of the color filter is determined according to the computer-implemented method of claim 20.

10. A color filter, comprising a plurality of color filter sections, wherein each color filter section includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at the predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold.

11. The color filter according to claim 10, wherein at least two color filter sections of the plurality of color filter sections have a different configuration such that a first color filter section has a transmittance spectrum with a peak with a maximum at a first predetermined wavelength and a second color filter section has a transmittance spectrum with a peak with a maximum at a second predetermined wavelength different from the first predetermined wavelength.

12. The color filter according to claim 10, wherein the metasurface layers of adjacent color filter sections are separated by a boundary including a material representing, in the predetermined wavelength range, an optical black material or a reflective material.

13. An imaging device, comprising: an image sensor having a plurality of pixels; a color filter arranged on the image sensor, wherein the color filter includes a plurality of color filter sections corresponding to the number of pixels of the image sensor, wherein each color filter section has the same thickness and includes: a distributed Bragg reflector having a reflectance above a reflectance threshold in a first predetermined wavelength range; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer; and wherein a configuration of the color filter section is such that the color filter section has a transmittance spectrum with a peak in a second predetermined wavelength range that has a maximum at a predetermined wavelength, wherein the transmittance at the maximum exceeds a transmittance threshold;wherein each color filter section is matched with a different pixel of the image sensor.

14. The imaging device according to claim 13, wherein the metasurface layers of adjacent color filter sections are separated by a boundary including a material representing, in the predetermined wavelength range, an optical black material or a reflective material.

15. The imaging device according to claim 13, wherein at least two color filter sections of the plurality of color filter sections have a different configuration such that a first color filter section has a transmittance spectrum with a peak with a maximum at a first predetermined wavelength and a second color filter section has a transmittance spectrum with a peak with a maximum at a second predetermined wavelength different from the first predetermined wavelength.

16. The imaging device according to claim 15, wherein a configuration of the first color filter section differs from a configuration of the second color filter section in at least one of the number and the thickness of the layers of the distributed Bragg reflector and the thickness of the intermediate layer and the configuration of the metasurface layer.

17. The imaging device according to claim 13, wherein the plurality of color filter sections includes a contiguous block of color filter sections that have the same configuration.

18. The imaging device according to claim 13, wherein the first predetermined wavelength range is equal to the second predetermined wavelength range.

19. The imaging device according to claim 13, wherein the transmittance threshold is at least 30 percent.

20. A computer-implemented method, comprising: performing a design optimization of a color filter including: simulating a transmittance spectrum of a color filter in a target wavelength range including a target wavelength; and determining a configuration of the color filter by minimizing a deviation between the simulated transmittance spectrum and a target transmittance spectrum, wherein the target transmittance spectrum has a Lorentzian shape that has a maximum at the target wavelength and a target spectral width; wherein the color filter includes: a distributed Bragg reflector; an intermediate layer arranged on the distributed Bragg reflector; a metasurface layer arranged on the intermediate layer;wherein minimizing the deviation includes iteratively adjusting the configuration of the color filter and simulating the transmittance spectrum for the adjusted configuration of the color filter.

Images