Polarization Spectral Filter, Polarization Spectral Filter Array, and Polarization Spectral Sensor

Abstract

A polarization spectral filter is provided, comprising: a first reflector and a second reflector, which are arranged to face each other in a first direction; and a grating layer, which is arranged between the first reflector and the second reflector. The grating layer includes a plurality of first grating elements and a plurality of second grating elements, and the plurality of first grating elements and the plurality of second grating elements are alternately arranged in a second direction perpendicular to the first direction. The plurality of first grating elements include a first dielectric material having a first refractive index. The plurality of second grating elements include a second dielectric material having a second refractive index different from the first refractive index.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10 - 2019 - 0171993, filed with the Korean Intellectual Property Office on December 20, 2019, the disclosure of which is incorporated herein by reference in its entirety. Technical field

[0003] Example embodiments consistent with the present disclosure relate to a polarization - spectroscopic filter, an array of polarization - spectroscopic filters, and a polarization - spectroscopic sensor, and more particularly, to a polarization - spectroscopic filter and an array of polarization - spectroscopic filters capable of selectively transmitting light having a specific wavelength band and a specific linear polarization component, and a polarization - spectroscopic sensor capable of simultaneously obtaining polarization information and spectroscopic information about incident light by using the array of polarization - spectroscopic filters. Background art

[0004] Spectrometers are widely used, for example, to analyze agricultural conditions, mineral distribution, vegetation on the ground surface, pollution, etc. by capturing ground images via drones, satellites, airplanes, etc. Such analysis is used in various fields such as food safety, skin / facial analysis, authentication and identification, and biological tissue analysis. Recently, applications using spectrometers have been extended to other fields such as mobile healthcare.

[0005] In addition to general red, green, and blue (RGB) information, polarization images can also provide additional information such as stress, surface defects, and scratches. This additional information can be used in applications such as industrial equipment and automotive application components. Additionally, even in cloudy or foggy weather, polarization images can enable more accurate object recognition.

[0006] Therefore, the application fields of sensors capable of obtaining spectral images or polarization images have been extended. In addition, with the miniaturization of image sensors and the improvement of their resolution, research has been conducted to obtain high - resolution spectral images or polarization images by integrating image sensors with other devices. Summary of the invention

[0007] One or more example embodiments provide a polarization - spectroscopic filter and an array of polarization - spectroscopic filters, both of which are capable of selectively transmitting light having a specified linear polarization component in a specified wavelength band.

[0008] In addition, one or more example embodiments provide a polarization - spectroscopic sensor that can simultaneously obtain polarization information and spectroscopic information about incident light by using the array of polarization - spectroscopic filters.

[0009] According to one aspect of the exemplary embodiment, a polarization spectral filter is provided, comprising: a first reflector; a second reflector, the first reflector and the second reflector being arranged to face each other in a first direction; and a grating layer disposed between the first reflector and the second reflector, wherein the grating layer includes a plurality of first grating elements and a plurality of second grating elements, the first grating elements and the second grating elements being alternately arranged with each other in a second direction perpendicular to the first direction, wherein each of the plurality of first grating elements includes a first dielectric material having a first refractive index, and wherein each of the plurality of second grating elements includes a second dielectric material having a second refractive index different from the first refractive index.

[0010] Both the first grating elements and the second grating elements may have a rod shape, and the plurality of first grating elements and the plurality of second grating elements may be arranged one-dimensionally.

[0011] A first surface of each of the plurality of first grating elements and a first surface of each of the plurality of second grating elements may be in contact with the first reflector, and a second surface of each of the plurality of first grating elements opposite to the first surface of each of the plurality of first grating elements and a second surface of each of the plurality of second grating elements opposite to the first surface of each of the plurality of second grating elements may be in contact with the second reflector.

[0012] Based on at least one of the thicknesses of the plurality of first grating elements and the plurality of second grating elements, the arrangement period of the plurality of first grating elements and the arrangement period of the plurality of second grating elements, and the ratio of the plurality of first grating elements to the plurality of second grating elements, the polarization spectral filter may be configured to transmit light in a first band among light having a first linear polarization component, and transmit light in a second band different from the first band among light having a second linear polarization component perpendicular to the first linear polarization component.

[0013] The thickness of each of the plurality of first grating elements and the plurality of second grating elements may be about 90 nm to about 350 nm.

[0014] The arrangement period of the plurality of first grating elements and the arrangement period of the plurality of second grating elements may be in the range from about 150 nm to about 300 nm.

[0015] The ratio of the plurality of first grating elements to the plurality of second grating elements may be in the range from about 0.2 to about 0.7.

[0016] The first dielectric material and the second dielectric material may be transparent to light in the first band and light in the second band.

[0017] The polarization spectral filter may further include: a band-pass filter disposed on the surface of the first reflector, the band-pass filter being configured to block light in a first band and transmit light in a second band.

[0018] The polarization spectral filter may further include a quarter-wave plate disposed on the surface of the first reflector.

[0019] The first reflector may include a plurality of first dielectric layers and a plurality of second dielectric layers, the plurality of first dielectric layers and the plurality of second dielectric layers being alternately stacked with each other in a third direction, the second reflector may include a plurality of third dielectric layers and a plurality of fourth dielectric layers, the plurality of third dielectric layers and the plurality of fourth dielectric layers being alternately stacked with each other in the third direction, each of the plurality of first dielectric layers may include a dielectric material having a refractive index different from that of the dielectric material included in each of the plurality of second dielectric layers, and each of the third dielectric layers may include a dielectric material having a refractive index different from that of the dielectric material included in each of the plurality of fourth dielectric layers.

[0020] Each of the plurality of first dielectric layers and each of the plurality of third dielectric layers may include a first dielectric material, and each of the plurality of second dielectric layers and each of the plurality of fourth dielectric layers may include a second dielectric material.

[0021] The grating layer may further include a plurality of third grating elements, each of the plurality of third grating elements including a third dielectric material having a third refractive index different from the first refractive index and the second refractive index, and the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements may be alternately arranged with each other in a second direction.

[0022] According to one aspect of the exemplary embodiment, a polarization spectral filter array is provided, including: a plurality of unit filter arrays arranged two-dimensionally, wherein each unit filter array includes: a first polarization spectral filter group configured to transmit light in a first band; and a second polarization spectral filter group configured to transmit light in a second band different from the first band. The first polarization spectral filter group includes: a first polarization spectral filter configured to transmit light having a first linear polarization component among the light in the first band; and a second polarization spectral filter configured to transmit light having a second linear polarization component perpendicular to the first linear polarization component among the light in the first band. The second polarization spectral filter group includes: a third polarization spectral filter configured to transmit light having a first linear polarization component among the light in the second band; and a fourth polarization spectral filter configured to transmit light having a second linear polarization component among the light in the second band. Each of the first polarization spectral filter, the second polarization spectral filter, the third polarization spectral filter, and the fourth polarization spectral filter includes: a first reflector and a second reflector arranged to face each other in a first direction; and a grating layer disposed between the first reflector and the second reflector. The grating layer includes a plurality of first grating elements and a plurality of second grating elements, and the plurality of first grating elements and the plurality of second grating elements are alternately arranged with each other in a second direction perpendicular to the first direction. Each of the plurality of first grating elements includes a first dielectric material having a first refractive index, and each of the plurality of second grating elements includes a second dielectric material having a second refractive index different from the first refractive index.

[0023] The plurality of first grating elements and the plurality of second grating elements of the grating layer of the second polarization spectral filter may be rotated 90 degrees in a plane perpendicular to the first direction with respect to the plurality of first grating elements and the plurality of second grating elements of the grating layer of the first polarization spectral filter, and the plurality of first grating elements and the plurality of second grating elements of the grating layer of the fourth polarization spectral filter may be rotated 90 degrees in a plane perpendicular to the first direction with respect to the plurality of first grating elements and the plurality of second grating elements of the grating layer of the third polarization spectral filter.

[0024] Each of the plurality of first grating elements and each of the plurality of second grating elements may have a rod shape, and the plurality of first grating elements and the plurality of second grating elements may be arranged one-dimensionally.

[0025] For each of the first polarization spectral filter, the second polarization spectral filter, the third polarization spectral filter, and the fourth polarization spectral filter, based on at least one of the thicknesses of the plurality of first grating elements and the plurality of second grating elements, the arrangement periods of the plurality of first grating elements and the plurality of second grating elements, and the ratio of the plurality of first grating elements to the plurality of second grating elements, the first polarization spectral filter may further be configured to transmit light in a first band among light having a first linear polarization component, the second polarization spectral filter may further be configured to transmit light in a first band among light having a second linear polarization component, the third polarization spectral filter may further be configured to transmit light in a second band among light having a first linear polarization component, and the fourth polarization spectral filter may further be configured to transmit light in a second band among light having a second linear polarization component.

[0026] The width and thickness of each of the plurality of first grating elements of the first polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the first polarization spectral filter, and the ratio of the plurality of first grating elements to the plurality of second grating elements of the first polarization spectral filter may be the same as the width and thickness of each of the plurality of first grating elements of the second polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the second polarization spectral filter, and the ratio of the plurality of first grating elements to the plurality of second grating elements of the second polarization spectral filter, respectively, and the width and thickness of each of the plurality of first grating elements of the third polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the third polarization spectral filter, and the ratio of the plurality of first grating elements to the plurality of second grating elements of the third polarization spectral filter may be the same as the width and thickness of each of the plurality of first grating elements of the fourth polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the fourth polarization spectral filter, and the ratio of the plurality of first grating elements to the plurality of second grating elements of the fourth polarization spectral filter, respectively.

[0027] Each of the first polarization spectral filter, the second polarization spectral filter, the third polarization spectral filter, and the fourth polarization spectral filter may further include a band - pass filter disposed on the surface of a first reflector, the band - pass filter being configured to transmit light in the first band and the second band and block light in other bands.

[0028] The first polarization spectral filter bank may further include a fifth polarization spectral filter configured to transmit light having a third linear polarization component that is rotated 45 degrees relative to the first linear polarization component among the light in the first band. The second polarization spectral filter bank may further include a sixth polarization spectral filter configured to transmit light having a third linear polarization component that is rotated 45 degrees relative to the first linear polarization component among the light in the second band. Both the fifth polarization spectral filter and the sixth polarization spectral filter may include a first reflector, a second reflector, and a grating layer.

[0029] The plurality of first grating elements and the plurality of second grating elements of the grating layer of the fifth polarization spectral filter may be rotated 45 degrees in a plane perpendicular to the first direction relative to the plurality of first grating elements and the plurality of second grating elements of the grating layer of the first polarization spectral filter.

[0030] The plurality of first grating elements and the plurality of second grating elements of the grating layer of the sixth polarization spectral filter may be rotated 45 degrees in a plane perpendicular to the first direction relative to the plurality of first grating elements and the plurality of second grating elements of the grating layer of the third polarization spectral filter.

[0031] The first polarization spectral filter bank may further include a fifth polarization spectral filter configured to transmit light having a first linear polarization component among the light having the first band. The second polarization spectral filter bank may further include a sixth polarization spectral filter configured to transmit light having a first linear polarization component among the light in the second band. Both the fifth polarization spectral filter and the sixth polarization spectral filter may include a first reflector, a second reflector, a grating layer, and a quarter-wave plate disposed on the surface of the first reflector.

[0032] According to an aspect of an example embodiment, there is provided a polarization spectroscopy sensor including: a polarization spectroscopy filter array including a plurality of unit filter arrays arranged two-dimensionally; and an image sensor including a plurality of sensing pixels arranged two-dimensionally, the plurality of sensing pixels being configured to sense the intensity of light transmitted through the polarization spectroscopy filter array, wherein each of the plurality of unit filter arrays includes: a first polarization spectroscopy filter group that transmits light in a first wavelength band; and a second polarization spectroscopy filter group that transmits light in a second wavelength band different from the first wavelength band, wherein the first polarization spectroscopy filter group includes: a first polarization spectroscopy filter configured to transmit light having a first linear polarization component among the light in the first wavelength band; and a second polarization spectroscopy filter configured to transmit light having a second linear polarization component perpendicular to the first linear polarization component among the light in the first wavelength band, wherein the second polarization spectroscopy filter group includes: a third polarization spectroscopy filter configured to transmit light having a first linear polarization component among the light in the second wavelength band; and a fourth polarization spectroscopy filter configured to transmit light having a second linear polarization component among the light in the second wavelength band, wherein each of the first polarization spectroscopy filter, the second polarization spectroscopy filter, the third polarization spectroscopy filter, and the fourth polarization spectroscopy filter includes: a first reflector and a second reflector arranged to face each other in a first direction; and a grating layer disposed between the first reflector and the second reflector, wherein the grating layer includes a plurality of first grating elements and a plurality of second grating elements, the plurality of first grating elements and the plurality of second grating elements being alternately arranged with each other in a second direction perpendicular to the first direction, wherein each of the plurality of first grating elements includes a first dielectric material having a first refractive index, and wherein each of the plurality of second grating elements includes a second dielectric material having a second refractive index different from the first refractive index. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other aspects, features, and advantages of specific example embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 is a cross-sectional view schematically showing the configuration of a polarization spectroscopy filter according to an example embodiment;

[0035] Figure 2 is schematically showing Figure 1 a perspective view of the configuration of the grating layer of the polarization spectroscopy filter shown in ;

[0036] Figure 3 is showing Figure 1 an example of the transmission characteristics of the polarization spectroscopy filter shown in ;

[0037] Figure 4is a graph showing an example of the transmission properties of the polarization angles of two different transmission bands of a polarization spectral filter as shown in Figure 1 ;

[0038] Figure 5 is a graph showing an example of the change in the transmission properties of a polarization spectral filter as shown in Figure 1 ;

[0039] Figure 6 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment;

[0040] Figure 7 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment;

[0041] Figure 8 is a graph showing an example of the transmission properties of a polarization spectral filter as shown in Figure 7 ;

[0042] Figure 9 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment;

[0043] Figure 10 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment;

[0044] Figure 11 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment;

[0045] Figure 12 is a perspective view schematically showing the configuration of a polarization spectral filter array and a polarization spectral sensor including the polarization spectral filter array according to an exemplary embodiment;

[0046] Figure 13 shows an example of the configuration of the polarization spectral filter array as shown in Figure 12 ;

[0047] Figure 14 shows an example of the arrangement of polarization spectral filters in a polarization spectral filter group of the polarization spectral filter array as shown in Figure 12 ;

[0048] Figure 15 is a cross-sectional view taken along line Figure 14 A-A' of

[0049] Figure 16 shows another example of the arrangement of polarization spectral filters in a polarization spectral filter group of the polarization spectral filter array as shown in Figure 12 ;

[0050] Figure 17 shows an example of a cross-sectional view taken along line B-B' of Figure 16 ;

[0051] Figure 18 shows another example of a cross-sectional view taken along line B-B' of Figure 16 ; and

[0052] Figure 19 shows yet another example of a cross-sectional view taken along line B-B' of Figure 16 . DETAILED DESCRIPTION

[0053] Hereinafter, a polarization spectral filter, a polarization spectral filter array, and a polarization spectral sensor according to exemplary embodiments will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals denote like elements, and for clarity and ease of explanation, the dimensions of each element in the drawings may be enlarged. Additionally, the exemplary embodiments to be described below are merely examples, and various modifications may be made according to the exemplary embodiments.

[0054] Hereinafter, what is described as "above" or "on" not only includes directly above and in contact with, but also includes above without contact. Unless the context clearly indicates otherwise, singular expressions include plural expressions. Additionally, when a component is described as "including" a certain configuration element, this means that the component may also include other configuration elements, unless other configuration elements are excluded as otherwise stated.

[0055] The terms "above-mentioned" and similar terms may be used for both singular and plural. If the sequence of steps of a configuration method is clearly described or there is no conflicting description, the sequence may be executed in an appropriate order and is not limited to the described order.

[0056] Additionally, terms such as "... unit / part", "module", etc. described in the specification refer to a unit for processing at least one function or operation, and the unit may be implemented as hardware or software or a combination of hardware and software.

[0057] The connection of the lines between the configuration elements or connection members shown in the drawings represents functional connection and / or physical or circuit connection by way of example, and may be replaced or represented as various other functional connections, physical connections, or circuit connections in an actual device.

[0058] All examples or specific terms are only for the purpose of describing the technical concept in detail, and the scope is not limited by these examples or terms unless defined by the claims.

[0059] A statement such as “at least one of...” modifies the entire list of elements when it follows the list of elements, rather than modifying an individual element in the list. For example, the statement “at least one of a, b, or c” means only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof.

[0060] Figure 1 is a cross-sectional view schematically showing a configuration of a polarization spectral filter according to an exemplary embodiment. Refer to Figure 1 , a polarization spectral filter 100 according to an exemplary embodiment may include: a first reflector 110; a grating layer 120 disposed on the first reflector 110; and a second reflector 130 disposed on the grating layer 120. Thus, the first reflector 110 and the second reflector 130 may be arranged to face each other in a thickness direction (or, perpendicular to the top-to-bottom direction of the polarization spectral filter 100), and the grating layer 120 may be disposed between the first reflector 110 and the second reflector 130.

[0061] The first reflector 110 and the second reflector 130 may be, for example, distributed Bragg reflectors (DBRs), which are formed by repeatedly and alternately stacking two dielectric layers having different refractive indices. For example, the first reflector 110 may include a plurality of first dielectric layers 110a and a plurality of second dielectric layers 110b alternately stacked in a thickness direction. The second reflector 130 may include a plurality of third dielectric layers 130a and a plurality of fourth dielectric layers 130b alternately stacked in a thickness direction. Each first dielectric layer 110a and each second dielectric layer 110b may include a dielectric material having a different refractive index. Additionally, each third dielectric layer 130a and each fourth dielectric layer 130b may also include a dielectric material having a different refractive index. For example, each first dielectric layer 110a may include a first dielectric material having a first refractive index, each second dielectric layer 110b may include a second dielectric material having a second refractive index different from the first refractive index, each third dielectric layer 130a may include a third dielectric material having a third refractive index, and each fourth dielectric layer 130b may include a fourth dielectric material having a fourth refractive index different from the third refractive index.

[0062] For example, the first dielectric layer 110a and the second dielectric layer 110b may include two different dielectric materials selected from Si, TiO2, SiO2, and Si2N3, and the third dielectric layer 130a and the fourth dielectric layer 130b may also include two different dielectric materials selected from Si, TiO2, SiO2, and Si2N3. For example, the first dielectric layer 110a may have one dielectric material selected from Si, TiO2, SiO2, and Si2N3, and the second dielectric layer 110b may have another dielectric material selected from Si, TiO2, SiO2, and Si2N3. Additionally, the first dielectric layer 110a of the first reflector 110 and the third dielectric layer 130a of the second reflector 130 may include the same dielectric material, and the second dielectric layer 110b of the first reflector 110 and the fourth dielectric layer 130b of the second reflector 130 may include the same dielectric material. Alternatively, the first dielectric layer 110a of the first reflector 110 and the fourth dielectric layer 130b of the second reflector 130 may include the same dielectric material, and the second dielectric layer 110b of the first reflector 110 and the third dielectric layer 130a of the second reflector 130 may include the same dielectric material.

[0063] According to the structures of the first reflector 110 and the second reflector 130, reflection occurs at the interfaces between the first dielectric layer 110a and the second dielectric layer 110b having different refractive indices, and between the third dielectric layer 130a and the fourth dielectric layer 130b having different refractive indices, and a high reflectivity can be obtained by matching the phases of all the reflected light. To this end, the optical thickness (i.e., the value obtained by multiplying the physical thickness by the refractive index of the material of the layer) of each of the first dielectric layer to the fourth dielectric layer 110a, 110b, 130a, and 130b may be selected to be approximately one quarter of the wavelength band of the light to be transmitted through the polarization spectral filter 100.

[0064] The first reflector 110 and the second reflector 130 which are arranged to face each other may form a resonator to resonate light. The grating layer 120 may be disposed inside the resonator formed by the first reflector 110 and the second reflector 130. The light incident on the upper surface of the first reflector 110 may be emitted through the lower surface of the second reflector 130 while resonating between the first reflector 110 and the second reflector 130. The light repeatedly passes through the grating layer 120 while resonating between the first reflector 110 and the second reflector 130. Therefore, the properties of the light emitted through the lower surface of the second reflector 130 may be mainly determined by the structure of the grating layer 120.

[0065] In an exemplary embodiment, the grating layer 120 may be configured to have polarization-dependent properties. To this end, the grating layer 120 may include a plurality of first grating elements 120a and a plurality of second grating elements 120b that are alternately arranged in a horizontal direction perpendicular to the thickness direction. For example, the plurality of first grating elements 120a and the plurality of second grating elements 120b may be arranged such that the lower surfaces of the plurality of first grating elements 120a in the thickness direction and the lower surfaces of the plurality of second grating elements 120b in the thickness direction are in contact with the first reflector 110 and lie in the same plane, and the upper surfaces of the plurality of first grating elements 120a in the thickness direction and the upper surfaces of the plurality of second grating elements 120b in the thickness direction are in contact with the second reflector 130 and lie in the same plane.

[0066] The first grating elements 120a and the second grating elements 120b may include dielectric materials having different refractive indices. In other words, each first grating element 120a may include a first dielectric material having a first refractive index, and each second grating element 120b may include a second dielectric material having a second refractive index different from the first refractive index. For example, the first grating elements 120a and the second grating elements 120b may include two different dielectric materials selected from Si, TiO2, SiO2, and Si2N3. In addition to the above material examples, the first dielectric material and the second dielectric material that respectively form the first grating elements 120a and the second grating elements 120b may include materials that are transparent to light in the transmission band of the polarization spectral filter 100.

[0067] In addition, the first grating elements 120a may include the same dielectric material as the first dielectric layer 110a of the first reflector 110 and the third dielectric layer 130a of the second reflector 130, and the second grating elements 120b may include the same dielectric material as the second dielectric layer 110b of the first reflector 110 and the fourth dielectric layer 130b of the second reflector 130. Alternatively, the first grating elements 120a may include the same dielectric material as the first dielectric layer 110a of the first reflector 110 and the fourth dielectric layer 130b of the second reflector 130, and the second grating elements 120b may include the same dielectric material as the second dielectric layer 110b of the first reflector 110 and the third dielectric layer 130a of the second reflector 130.

[0068] Figure 2 is schematically shown Figure 1 in a perspective view of the configuration of the grating layer 120 of the polarization spectral filter 100 shown in Figure 2, each of the first grating elements 120a and each of the second grating elements 120b of the grating layer 120 may have the shape of a rod extending in the longitudinal direction. In addition, the plurality of first grating elements 120a and the plurality of second grating elements 120b are alternately and repeatedly arranged in their width direction. The first grating element 120a and the second grating element 120b have the same thickness T. In addition, the plurality of first grating elements 120a have the same width W1, and the plurality of second grating elements 120b have the same width W2. Therefore, the plurality of first grating elements 120a and the plurality of second grating elements 120b are arranged at a constant period P.

[0069] Since the plurality of first grating elements 120a and the plurality of second grating elements 120b are arranged one-dimensionally in the above manner, the grating layer 120 and the polarization spectral filter 100 may have polarization-dependent properties. For example, among the light resonating between the first reflector 110 and the second reflector 130, the transmittance of the polarization spectral filter 100 for light having a polarization component parallel to the longitudinal direction of the first grating element 120a and the second grating element 120b may be different from the transmittance of the polarization spectral filter 100 for light having a polarization component perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b. In particular, in the polarization spectral filter 100 according to the exemplary embodiment, the transmission band may change depending on the polarization direction of the light beam.

[0070] Figure 3 Illustrates Figure 1 A graph showing an example of the transmission characteristics of the polarization spectral filter 100 shown in Figure 3 , the wavelength of the light transmitted through the polarization spectral filter 100 may have peaks in two narrow bands separated from each other. For example, the light transmitted through the polarization spectral filter 100 may have a first spectrum SP1 with a central wavelength of about 825 nm and a second spectrum SP2 with a central wavelength of about 875 nm. The first spectrum SP1 and the second spectrum SP2 may have a narrow wavelength width. For example, the full width at half maximum (FWHM) of the first spectrum SP1 and the FWHM of the second spectrum SP2 may be in the range of about 1 nm to about 10 nm. Therefore, the first spectrum SP1 and the second spectrum SP2 may not overlap each other, and the transmittance of the polarization spectral filter 100 is approximately zero in the band between the first spectrum SP1 and the second spectrum SP2. As the number of pairs of the first dielectric layer 110a and the second dielectric layer 110b included in the first reflector 110 and the number of pairs of the third dielectric layer 130a and the fourth dielectric layer 130b included in the second reflector 130 increase, the FWHM of the first spectrum SP1 and the FWHM of the second spectrum SP2 may decrease.

[0071] Specifically, the light of the first spectrum SP1 may have a polarization component perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b of the grating layer 120, and the light of the second spectrum SP2 may have a polarization component parallel to the longitudinal direction of the first grating element 120a and the second grating element 120b of the grating layer 120. Therefore, the polarization spectrum filter 100 may have two different transmission bands with polarization directions perpendicular to each other. In other words, the polarization spectrum filter 100 may have two different transmission bands, and for these two transmission bands, the polarization spectrum filter 100 may have polarization properties perpendicular to each other.

[0072] Figure 4 is a graph showing an example of the transmission properties of the polarization angles of two different transmission bands of the polarization spectrum filter 100 according to Figure 1 shown in. Referring to Figure 4 , in the light of the first spectrum SP1, the light parallel to the longitudinal direction of the first grating element 120a and the second grating element 120b may have a transmittance of approximately zero for the polarization spectrum filter 100. In the light of the first spectrum SP1, the light perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b may have a transmittance of approximately 0.9 for the polarization spectrum filter 100. On the other hand, in the light of the second spectrum SP2, the light perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b may have a transmittance of approximately zero for the polarization spectrum filter 100. Additionally, in the light of the second spectrum SP2, the light parallel to the longitudinal direction (or, the length direction) of the first grating element 120a and the second grating element 120b may have a transmittance of approximately 0.9 for the polarization spectrum filter 100.

[0073] The specific transmission bands and polarization properties of the polarization spectrum filter 100 may be determined by the thickness T of each of the first grating element 120a and each of the second grating element 120b, the arrangement period P of the plurality of first grating elements 120a and the plurality of second grating elements 120b, the ratio of the first grating element 120a to the second grating element 120b, etc. For example, the thickness of each of the first grating element 120a and each of the second grating element 120b may be in the range from about 90 nm to about 350 nm. Additionally, the arrangement period P of the plurality of first grating elements 120a and the plurality of second grating elements 120b may be in the range from 150 nm to 300 nm.

[0074] Therefore, the size of each first grating element 120a and the size of each second grating element 120b can be smaller than the transmission wavelength of the polarization spectral filter 100. For example, the thickness of each first grating element 120a and the thickness of each second grating element 120b can be less than 1 / 2 or 1 / 3 of the transmission wavelength of the polarization spectral filter 100. Additionally, the arrangement period P of the plurality of first grating elements 120a and the plurality of second grating elements 120b can be less than 1 / 2 or 1 / 3 of the transmission wavelength of the polarization spectral filter 100.

[0075] Since the first grating element 120a and the second grating element 120b have the same thickness T, the ratio of the first grating element 120a to the second grating element 120b can be the same as the ratio of the width W1 of the first grating element 120a to the width W2 of the second grating element 120b. For example, when the first refractive index of the first dielectric material forming the first grating element 120a is lower than the second refractive index of the second dielectric material forming the second grating element 120b, the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b can be in the range from about 0.2 to about 0.7. The thickness T of the first grating element 120a and the second grating element 120b and the arrangement period P of the plurality of first grating elements 120a and the plurality of second grating elements 120b are fixed, and by adjusting the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b, the transmission properties of the polarization spectral filter 100 can be adjusted.

[0076] Figure 5 A graph illustrating the change in the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b according to the grating layer 120 is shown. Figure 1 An example of a graph showing the change in the transmission properties of the polarization spectral filter 100 shown in. In Figure 5 the curve labeled "str1" represents the case where the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b is 0.7, the curve labeled "str2" represents the case where the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b is 0.5, and the curve labeled "str3" represents the case where the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b is 0.3. Additionally, in Figure 5 the three peaks on the left represent the polarization components perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b of the grating layer 120, and the three peaks on the right represent the polarization components parallel to the longitudinal direction of the first grating element 120a and the second grating element 120b of the grating layer 120. Refer to Figure 5, it can be seen that as the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b increases, the two transmission bands of the polarization spectral filter 100 increase and thus gradually shift toward longer wavelengths.

[0077] Although it has been described above that the grating layer 120 includes only the first grating element 120a and the second grating element 120b, the grating layer 120 according to the exemplary embodiment is not limited thereto. The grating layer 120 may be configured by alternately arranging three, four, or more grating elements having different refractive indices. The number of grating elements alternately arranged in the grating layer 120 is not limited.

[0078] Figure 6 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment. Except that the grating layer 121 includes three grating elements, Figure 6 the polarization spectral filter 200 shown in Figure 1 is similar in configuration to the polarization spectral filter 100 shown in Figure 6 . Referring to

[0079] again, the grating layer 121 may include a plurality of first grating elements 121a, a plurality of second grating elements 121b, and a plurality of third grating elements 121c that are alternately arranged. Each first grating element 121a includes a first dielectric material having a first refractive index, each second grating element 121b includes a second dielectric material having a second refractive index different from the first refractive index, and each third grating element 121c may include a third dielectric material having a third refractive index different from the first refractive index and the second refractive index. The plurality of first grating elements 121a, the plurality of second grating elements 121b, and the plurality of third grating elements 121c may be arranged one-dimensionally in a horizontal direction perpendicular to the thickness direction.

[0079] Referring again to Figure 3 and Figure 5 of the graph, the polarization spectral filter 100 may have two different transmission bands having polarization properties perpendicular to each other. In addition, the two transmission bands may be completely separated from each other and may not overlap each other. Therefore, if only one of the two different transmission bands is selected, the polarization spectral filter 100 may be configured to transmit only the light having a specific polarization component among the light beams in a specific transmission band. Alternatively, a method of selecting one transmission band in a polarization spectral filter according to another exemplary embodiment is described below.

[0080] Figure 7 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment. Except that the polarization spectral filter 300 further includes a bandpass filter 140 disposed on the upper surface of the second reflector 130, Figure 7The polarization spectral filter 300 shown in is similar to the configuration of the polarization spectral filter 100 shown in Figure 1 In other words, the bandpass filter 140 is provided on the light incident surface of the polarization spectral filter 300. The bandpass filter 140 may be configured to allow only Figure 3 One of the bands of the first spectrum SP1 and the band of the second spectrum SP2 shown in passes through it, and is configured to block the other band. For example, the bandpass filter 140 may be configured to block light in the wavelength range of 800 nm to 850 nm, and is configured to transmit light in the wavelength range of 850 nm to 900 nm. Then, the polarization spectral filter 300 may be configured to transmit only the light of the second spectrum SP2 having a polarization component parallel to the longitudinal direction of the first grating element 120a and the second grating element 120b, and block the light of the first spectrum SP1 having a polarization component perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b.

[0081] Figure 8 Shows an example of Figure 7 The graph of the transmission properties of the polarization spectral filter 300. In Figure 8 The curve labeled "str1" represents the case where the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b is 0.7, the curve labeled "str2" represents the case where the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b is 0.5, and the curve labeled "str3" represents the case where the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b is 0.3. Referring to Figure 8 , when the bandpass filter 140 is used, the light having a polarization component parallel to the longitudinal direction of the first grating element 120a and the second grating element 120b of the grating layer 120 passes through the polarization spectral filter 300, and the band of the light passing through the polarization spectral filter 300 can be adjusted according to the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b.

[0082] The bandpass filter 140 may be configured to transmit light, for example, in the wavelength range of 800 nm to 850 nm, and is configured to block light in the wavelength range of 850 nm to 900 nm. In this case, the polarization spectral filter 300 may transmit only the light having a polarization component perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b. In addition, by adjusting the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b, the transmission band of the light having a polarization component perpendicular to the longitudinal direction of the first grating element 120a and the second grating element 120b can be adjusted.

[0083] Figure 9 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment. Although Figure 7 the band-pass filter 140 is shown disposed on the upper surface of the second reflector 130, the position of the band-pass filter 140 is not limited thereto. The band-pass filter 140 may be disposed anywhere outside the resonator formed by the first reflector 110 and the second reflector 130. For example, referring to Figure 9 , the polarization spectral filter 400 may include a band-pass filter 140 disposed on the lower surface of the first reflector 110. In other words, the band-pass filter 140 may be disposed on the light-emitting surface of the polarization spectral filter 400.

[0084] Figure 10 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment. Referring to Figure 10 , the polarization spectral filter 500 is similar to the configuration of the polarization spectral filter 300 shown in Figure 7 , and may further include a quarter-wave plate 150 disposed between the band-pass filter 140 and the second reflector 130. The quarter-wave plate 150 is configured to delay the phase of the incident light by a quarter wavelength of the wavelength of the incident light beam. The quarter-wave plate 150 may be formed by patterning a dielectric material having a relatively high refractive index into a nanostructure smaller than the wavelength of the light beam. For example, the quarter-wave plate 150 may be formed of a metasurface including Si, TiO2, or Si2N3.

[0085] If the phase of the incident light is delayed by a quarter wavelength of the wavelength of the incident light by the quarter-wave plate 150, the linear polarization component of the incident light is changed to a circular polarization component, and the circular polarization component is changed to a linear polarization component. In other words, the quarter-wave plate 150 may be used to change linearly polarized light to circularly polarized light and circularly polarized light to linearly polarized light beams. For example, a first linear polarization component is changed to a first circular polarization component by the quarter-wave plate 150, and a second linear polarization component perpendicular to the first linear polarization component is changed to a second circular polarization component rotating in a direction opposite to the first circular polarization component by the quarter-wave plate 150. Therefore, by using the quarter-wave plate 150, light having a circular polarization component passes through the polarization spectral filter 500.

[0086] Figure 11 is a cross-sectional view schematically showing the configuration of a polarization spectral filter according to an exemplary embodiment. Although Figure 10The quarter-wave plate 150 is shown disposed on the upper surface of the second reflector 130, but the position of the quarter-wave plate 150 is not limited thereto. The quarter-wave plate 150 may be disposed anywhere outside the resonator formed by the first reflector 110 and the second reflector 130. For example, referring to Figure 11 , the polarization spectral filter 600 may include a quarter-wave plate 150 disposed on the lower surface of the first reflector 110. In other words, the quarter-wave plate 150 may be disposed on the light-emitting surface of the polarization spectral filter 600.

[0087] In addition, in Figure 10 and Figure 11 shown in the exemplary embodiments, the positions of the quarter-wave plate 150 and the band-pass filter 140 may be interchanged. For example, the band-pass filter 140 may be disposed on the upper surface of the second reflector 130, and the quarter-wave plate 150 may be disposed on the upper surface of the band-pass filter 140. In addition, the band-pass filter 140 may be disposed on the lower surface of the first reflector 110, and the quarter-wave plate 150 may be disposed on the lower surface of the band-pass filter 140.

[0088] In addition, the quarter-wave plate 150 and the band-pass filter 140 may be disposed opposite to each other. For example, the quarter-wave plate 150 may be disposed on the upper surface of the second reflector 130, and the band-pass filter 140 may be disposed on the lower surface of the first reflector 110. Alternatively, the band-pass filter 140 may be disposed on the upper surface of the second reflector 130, and the quarter-wave plate 150 may be disposed on the lower surface of the first reflector 110.

[0089] The polarization spectral filter according to the above exemplary embodiments can transmit light in a specific band having a specific linear polarization component or a specific circular polarization component without using a separate polarization filter and / or a separate spectral filter. In addition, the polarization spectral filter according to the above exemplary embodiments can be manufactured in a small size such as the pixel size of an image sensor. Therefore, an array of polarization spectral filters according to the above exemplary embodiments can be integrated with an image sensor to simultaneously obtain polarization information and spectral information. In addition, by integrating an image sensor with an array of polarization spectral filters according to the above exemplary embodiments, for example, a miniaturized polarization spectral image sensor that can be mounted in a small mobile device such as a smart phone can be provided.

[0090] Figure 12 is a perspective view schematically showing the configuration of an array of polarization spectral filters and a polarization spectral sensor including the array of polarization spectral filters according to an exemplary embodiment. Referring to Figure 12, according to an exemplary embodiment, the polarization spectral sensor 1000 may include an image sensor 1100 and a polarization spectral filter array 1200 disposed on the image sensor 1100. The polarization spectral filter array 1200 may include a plurality of unit filter arrays UPF arranged in a two-dimensional layout (e.g., arranged in rows and columns). 11 , UPF 12 , UPF 21 ,... Additionally, the image sensor 1100 may include a plurality of sensing pixels arranged in a two-dimensional layout and convert the intensity of incident light into an electrical signal. Thus, the sensing pixels of the image sensor 1100 may sense the intensity of the light transmitted through the polarization spectral filter array 1200.

[0091] Figure 13 shows an Figure 12 example of the configuration of the polarization spectral filter array 1200 shown in. Referring to Figure 13 , the polarization spectral filter array 1200 may include a plurality of unit filter arrays UPF arranged in a two-dimensional layout. 11 , UPF 12 , UPF 21 ,... Each unit filter array UPF of the polarization spectral filter array 1200 11 , UPF 12 , UPF 21 ,... may be configured to analyze a plurality of different polarization states of light having a plurality of different wavelengths. Each unit filter array UPF 11 , UPF 12 , UPF 21 ,... is the minimum unit of the polarization spectral filter array 1200 for simultaneously obtaining both polarization information and spectral information about incident light.

[0092] The unit filter array UPF 11 , UPF 12 , UPF 21 ,... Each of them may include a group WF of a plurality of polarization spectral filters that transmit light having different wavelengths. Figure 13 shows such an example, in which each of the unit filter arrays UPF 11 , UPF 12 , UPF 21 ,... includes 16 polarization spectral filters that respectively transmit light λ1 to λ16 in the first to sixteenth bands. However, arranged in each unit filter array UPF 11 , UPF 12 , UPF 21, the number of polarization spectral filters in... is not limited to this, and more polarization spectral filters can be arranged, or fewer polarization spectral filters can be arranged. The plurality of polarization spectral filters can be arranged in a two-dimensional array in each unit filter array UPF 11 , UPF 12 , UPF 21 ,... inside.

[0093] Figure 14 shows in Figure 12 each unit filter array UPF of the polarization spectral filter array 1200 shown in 11 , UPF 12 , UPF 21 ,... an example of the arrangement of the polarization spectral filters in a polarization spectral filter group WF. Refer to Figure 14 , each polarization spectral filter group WF can include, for example, a first polarization spectral filter to a fourth polarization spectral filter PF1, PF2, PF3, and PF4 arranged in a 2×2 array. The first polarization spectral filter to the fourth polarization spectral filter PF1, PF2, PF3, and PF4 can be configured to transmit light having linearly polarized components in different directions. For example, the first polarization spectral filter PF1 can be configured to transmit light having a first linearly polarized component. The second polarization spectral filter PF2 can be configured to transmit light having a second linearly polarized component perpendicular to the first linearly polarized component. The third polarization spectral filter PF3 can be configured to transmit light having a third linearly polarized component inclined 45 degrees with respect to the first linearly polarized component. Additionally, the fourth polarization spectral filter PF4 can be configured to transmit light having a fourth linearly polarized component inclined 135 degrees with respect to the first linearly polarized component.

[0094] Figure 15 is a cross-sectional view taken along the line A-A' of Figure 14 . Figure 15 schematically shows Figure 14 an example of the arrangement of the polarization spectral filters in a polarization spectral filter group WF shown in Figure 15 , and the local configuration of the polarization spectral sensor 1000 including the image sensor 1100. Refer to Figure 7 shown in Figure 15Only the first polarization spectral filter PF1 and the third polarization spectral filter PF3 are shown, but it should be understood that the above description can be equivalently applied to the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4. In other words, each of the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 may include a first reflector 110, a grating layer 120, a second reflector 130, and a band-pass filter 140. In the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4, the first reflector 110, the second reflector 130, and the band-pass filter 140 may extend integrally with each other as a common configuration.

[0095] The plurality of first grating elements 120a and the plurality of second grating elements 120b of the grating layer 120 may be arranged in different directions in the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 such that the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 transmit light having different linear polarization components. For example, the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the second polarization spectral filter PF2 may be arranged perpendicular to the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the first polarization spectral filter PF1. In other words, the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the second polarization spectral filter PF2 may be rotated 90 degrees in the horizontal plane with respect to the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the first polarization spectral filter PF1.

[0096] In addition, the first grating elements 120a and the second grating elements 120b of the third polarization spectral filter PF3 may be arranged to be inclined 45 degrees with respect to the first grating elements 120a and the second grating elements 120b of the first polarization spectral filter PF1. In other words, the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the third polarization spectral filter PF3 may be rotated 45 degrees in the horizontal plane with respect to the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the first polarization spectral filter PF1. In addition, the first grating elements 120a and the second grating elements 120b of the fourth polarization spectral filter PF4 may be arranged to be inclined 135 degrees with respect to the first grating elements 120a and the second grating elements 120b of the first polarization spectral filter PF1. In other words, the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the fourth polarization spectral filter PF4 may be rotated 135 degrees in the horizontal plane with respect to the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the first polarization spectral filter PF1.

[0097] The first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 arranged in the same polarization spectral filter group WF can be configured to transmit light with the same wavelength band. As described above, the transmission wavelength bands of the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 can be determined by the thickness T of the first grating element 120a and the second grating element 120b, the arrangement period P of the plurality of first grating elements 120a and the plurality of second grating elements 120b, the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b, etc. Therefore, in the same polarization spectral filter group WF, the thicknesses T of the first grating element 120a and the second grating element 120b of the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 can be the same, the arrangement periods P of the plurality of first grating elements 120a and the plurality of second grating elements 120b can be the same, and the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b can be the same.

[0098] The light transmitted through the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 can be incident on different pixels of the image sensor 1100. For this purpose, the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 can be arranged to correspond to the pixels of the image sensor 1100 one by one. Based on this configuration, by analyzing the electrical signals output from the pixels of the image sensor 1100 corresponding to the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4, information about the intensity of the light with the first linear polarization component, the intensity of the light with the second linear polarization component, the intensity of the light with the third linear polarization component, and the intensity of the light with the fourth linear polarization component can be extracted from the light beams with the same wavelength band.

[0099] Each polarization spectral filter bank WF may include a first to a fourth polarization spectral filter PF1, PF2, PF3, and PF4. The first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 arranged in different polarization spectral filter banks WF may be configured to transmit light in different wavelength bands. For example, the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 in the polarization spectral filter bank WF for analyzing the linear polarization component of light 1 in the first wavelength band may be configured to transmit light 1 in the first wavelength band, and the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 in the polarization spectral filter bank WF for analyzing the linear polarization component of light 2 in the second wavelength band may be configured to transmit light 2 in the second wavelength band.

[0100] For convenience of the manufacturing process, in an exemplary embodiment, the thickness T of all the first grating elements 120a and the second grating elements 120b may be the same in the polarization spectral filter array 1200. In this case, the transmission wavelength bands of the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 may be mainly determined by the arrangement period P of the plurality of first grating elements 120a and the plurality of second grating elements 120b and / or the ratio (W1 / W2) of the first grating element 120a to the second grating element 120b. In the exemplary embodiment, the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 respectively arranged in different polarization spectral filter banks WF may have different arrangement periods P of the plurality of first grating elements 120a and the plurality of second grating elements 120b, and / or may have different ratios (W1 / W2) between the first grating element 120a and the second grating element 120b.

[0101] In the exemplary embodiment, the thickness T and the arrangement period P of all the plurality of first grating elements 120a and the plurality of second grating elements 120b may be the same in the polarization spectral filter array 1200. In this case, the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 respectively arranged in different polarization spectral filter banks WF may have different ratios (W1 / W2) between the first grating element 120a and the second grating element 120b.

[0102] In addition, the transmission bands of the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 can also be determined by the passband of the bandpass filter 140. For example, the passbands of the bandpass filters 140 in different polarization spectral filter groups WF can be different. In another example, a common bandpass filter 140 can be used throughout the polarization spectral filter array 1200. In this case, the bandpass filter 140 can be configured to transmit light beams λ1 to λ16 in the first to sixteenth bands and to block light in the remaining bands.

[0103] Figure 16 shows Figure 12 each unit filter array UPF of the polarization spectral filter array 1200 shown in 11 、UPF 12 、UPF 21 、... in a polarization spectral filter group WF of the polarization spectral filter array 1200 shown in Figure 17 shows an example of a cross-sectional view taken along line B-B' of Figure 16 the polarization spectral filter array 1200 shown in Figure 17 schematically shows Figure 16 a partial configuration of the arrangement of the polarization spectral filters in a polarization spectral filter group WF shown in

[0104] Reference Figure 16 , each polarization spectral filter group WF can include, for example, the first to sixth polarization spectral filters PF1, PF2, PF3, PF4, PF5, and PF6 arranged in a 2×3 array. The first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 can be configured to transmit light having linearly polarized components in different directions. Since the configuration and operation of the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4 are the same as those described above with reference to Figure 14 , their description will be omitted.

[0105] The fifth polarization spectral filter PF5 can be configured to transmit light having a first circular polarization component, and the sixth polarization spectral filter PF6 can be configured to transmit light having a second circular polarization component that rotates in a direction opposite to the first circular polarization component. To this end, as shown in Figure 17 , the fifth polarization spectral filter PF5 can further include a quarter-wave plate 150 disposed between the second reflector 130 and the bandpass filter 140. Although in Figure 17Although not shown in the figure, the sixth polarization spectral filter PF6 may further include a quarter-wave plate 150 disposed between the second reflector 130 and the band-pass filter 140. Therefore, the configurations of the fifth polarization spectral filter PF5 and the sixth polarization spectral filter PF6 may be the same as the configuration of the polarization spectral filter 500 shown in Figure 10 the polarization spectral filter shown in

[0106] The first grating elements 120a and the second grating elements 120b of the grating layer 120 of the fifth polarization spectral filter PF5 may be arranged parallel to the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the first polarization spectral filter PF1. On the other hand, the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the sixth polarization spectral filter PF6 may be arranged perpendicular to the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the first polarization spectral filter PF1. Therefore, the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the sixth polarization spectral filter PF6 may be arranged parallel to the first grating elements 120a and the second grating elements 120b of the grating layer 120 of the second polarization spectral filter PF2. Therefore, the light transmitted through the fifth polarization spectral filter PF5 and the light transmitted through the sixth polarization spectral filter PF6 may have information about circular polarization components rotating in opposite directions.

[0107] According to Figure 16 and Figure 17 the exemplary embodiments shown in

[0108] As Figure 17 shown in

[0109] Figure 18 the first polarization spectral filter to the fourth polarization spectral filter PF1, PF2, PF3, and PF4 may further include spacers 160 disposed on the second reflector 130 to maintain a constant position of the band-pass filter 140 in the thickness direction. The thickness of the spacers 160 may be the same as the thickness of the quarter-wave plate 150.

[0109] Figure 18 Another example of a cross-sectional view taken along line B-B’ of Figure 16 is shown. Figure 18 is schematically shown Figure 16Another example of the arrangement of polarization spectral filters in a polarization spectral filter bank WF shown in the figure and the partial configuration of a polarization spectral sensor 1000 including an image sensor 1100. Refer to Figure 18 , the band-pass filter 140 may be disposed below the first reflector 110. In this case, the band-pass filter 140 may be arranged to face the image sensor 1100. Additionally, in the fifth polarization spectral filter PF5 and the sixth polarization spectral filter PF6, a quarter-wave plate 150 may be disposed between the first reflector 110 and the band-pass filter 140. In Figure 18 the example embodiment shown, the quarter-wave plate 150 may be embedded in the band-pass filter 140. Then, a separate spacer may not be used.

[0110] Figure 19 Shows yet another example of a cross-sectional view taken along line B-B’ of Figure 16 . Figure 19 Schematically shows Figure 16 yet another example of the arrangement of polarization spectral filters in a polarization spectral filter bank WF shown in the figure and the partial configuration of a polarization spectral sensor 1000 including an image sensor 1100. Refer to Figure 19 , in the fifth polarization spectral filter PF5 and the sixth polarization spectral filter PF6, the band-pass filter 140 may be disposed on the upper surface of the second reflector 130 and the quarter-wave plate 150 may be disposed on the lower surface of the first reflector 110. Additionally, spacers 160 may also be disposed on the lower surface of the first reflector 110 of the first to fourth polarization spectral filters PF1, PF2, PF3, and PF4. The thickness of the spacers 160 may be the same as the thickness of the quarter-wave plate 150.

[0111] Although the polarization spectral filters, polarization spectral filter arrays, and polarization spectral sensors have been described with reference to the example embodiments shown in the accompanying drawings, these embodiments are merely examples, and it will be understood that those skilled in the art can implement various modifications and equivalent other embodiments. Therefore, the disclosed embodiments should be considered only in a descriptive sense and not for purposes of limitation. The scope of the rights is set forth in the claims rather than the foregoing description, and all differences within that scope should be construed as being included within the scope of the rights.

[0112] Although the present disclosure has been specifically shown and described with reference to the example embodiments of the present disclosure, it will be understood that various changes in form and detail may be made therein without departing from the spirit and scope of the appended claims.

Claims

1. A polarization spectral filter, comprising: A first reflector; A second reflector, the first reflector and the second reflector being arranged to face each other in a first direction; And A grating layer, disposed between the first reflector and the second reflector, Wherein the grating layer includes a plurality of first grating elements, a plurality of second grating elements, and a plurality of third grating elements, and the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements are alternately arranged with each other in a second direction perpendicular to the first direction, Wherein each of the plurality of first grating elements includes a first dielectric material having a first refractive index, Wherein each of the plurality of second grating elements includes a second dielectric material having a second refractive index different from the first refractive index, Wherein each of the plurality of third grating elements includes a third dielectric material having a third refractive index different from the first refractive index and the second refractive index, Wherein a first surface of each of the plurality of first grating elements, a first surface of each of the plurality of second grating elements, and a first surface of each of the plurality of third grating elements are in contact with the first reflector, and Wherein a second surface of each of the plurality of first grating elements, a second surface of each of the plurality of second grating elements, and a second surface of each of the plurality of third grating elements are in contact with the second reflector, wherein the second surface is opposite to the first surface in the first direction.

2. The polarization spectral filter according to claim 1, wherein each of the first grating elements, the second grating elements, and the third grating elements has a rod shape, and the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements are arranged one-dimensionally.

3. The polarization spectral filter according to claim 1, wherein, Based on at least one of the thicknesses of the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements, the arrangement periods of the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements, and the ratio between the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements, the polarization spectral filter is configured to transmit light in a first band among light having a first linear polarization component, and transmit light in a second band different from the first band among light having a second linear polarization component perpendicular to the first linear polarization component.

4. The polarization spectral filter according to claim 3, wherein the thickness of each of the plurality of first grating elements, each of the plurality of second grating elements, and each of the plurality of third grating elements is 90 nm to 350 nm.

5. The polarization spectral filter according to claim 3, wherein the arrangement periods of the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements are in the range from 150 nm to 300 nm.

6. The polarization spectral filter according to claim 3, wherein a ratio between the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements is in a range from 0.2 to 0.

7.

7. The polarization spectral filter according to claim 3, wherein the first dielectric material, the second dielectric material, and the third dielectric material are transparent to light in the first band and light in the second band.

8. The polarization spectrum filter according to claim 3 further comprises: A band - pass filter is disposed on a surface of the first reflector, and the band - pass filter is configured to block light in the first band and transmit light in the second band.

9. The polarization spectrum filter according to claim 1 further comprises: A quarter - wave plate is disposed on a surface of the first reflector.

10. The polarization spectral filter according to claim 1, wherein the first reflector includes a plurality of first dielectric layers and a plurality of second dielectric layers, and the plurality of first dielectric layers and the plurality of second dielectric layers are alternately stacked with each other in a third direction. Wherein the second reflector includes a plurality of third dielectric layers and a plurality of fourth dielectric layers, and the plurality of third dielectric layers and the plurality of fourth dielectric layers are alternately stacked with each other in the third direction. Wherein each of the plurality of first dielectric layers includes a dielectric material having a refractive index different from that of the dielectric material included in each of the plurality of second dielectric layers, and Wherein each of the plurality of third dielectric layers includes a dielectric material having a refractive index different from that of the dielectric material included in each of the plurality of fourth dielectric layers.

11. The polarization spectral filter according to claim 10, wherein each of the plurality of first dielectric layers and each of the plurality of third dielectric layers include the first dielectric material, and Wherein each of the plurality of second dielectric layers and each of the plurality of fourth dielectric layers include the second dielectric material.

12. A polarization spectral filter array, comprising: A plurality of unit filter arrays arranged two - dimensionally, Wherein each of the plurality of unit filter arrays includes: A first polarization spectral filter group configured to transmit light in a first band; and A second polarization spectral filter group configured to transmit light in a second band different from the first band, Wherein the first polarization spectral filter group includes: A first polarization spectral filter configured to transmit light having a first linear polarization component among the light in the first band; and A second polarization spectral filter configured to transmit light having a second linear polarization component perpendicular to the first linear polarization component among the light in the first band, Wherein the second polarization spectral filter group includes: A third polarization spectral filter configured to transmit light having the first linear polarization component among the light in the second band; and A fourth polarization spectral filter configured to transmit light having the second linear polarization component among the light in the second band, Wherein each of the first polarization spectral filter, the second polarization spectral filter, the third polarization spectral filter, and the fourth polarization spectral filter includes the polarization spectral filter according to claim 1.

13. The polarization spectral filter array according to claim 12, wherein the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the second polarization spectral filter are rotated 90 degrees in a plane perpendicular to the first direction with respect to the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the first polarization spectral filter, and wherein the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the fourth polarization spectral filter are rotated 90 degrees in the plane perpendicular to the first direction with respect to the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the third polarization spectral filter.

14. The polarization spectral filter array according to claim 13, wherein each of the plurality of first grating elements, each of the plurality of second grating elements, and each of the plurality of third grating elements has a rod shape, and the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements are arranged one-dimensionally.

15. The polarization spectral filter array according to claim 13, wherein, For each of the first polarization spectral filter, the second polarization spectral filter, the third polarization spectral filter, and the fourth polarization spectral filter, based on at least one of the thicknesses of the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements, the arrangement period of the plurality of first grating elements, the arrangement period of the plurality of second grating elements, and the arrangement period of the plurality of third grating elements, and the ratio among the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements, the first polarization spectral filter is further configured to transmit light in the first band among the light having the first linear polarization component, the second polarization spectral filter is further configured to transmit light in the first band among the light having the second linear polarization component, the third polarization spectral filter is further configured to transmit light in the second band among the light having the first linear polarization component, and the fourth polarization spectral filter is further configured to transmit light in the second band among the light having the second linear polarization component.

16. The polarization spectral filter array according to claim 15, wherein the width and thickness of each of the plurality of first grating elements of the first polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the first polarization spectral filter, the width and thickness of each of the plurality of third grating elements of the first polarization spectral filter, and the ratios among the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the first polarization spectral filter are respectively the same as the width and thickness of each of the plurality of first grating elements of the second polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the second polarization spectral filter, the width and thickness of each of the plurality of third grating elements of the second polarization spectral filter, and the ratios among the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the second polarization spectral filter, and wherein the width and thickness of each of the plurality of first grating elements of the third polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the third polarization spectral filter, the width and thickness of each of the plurality of third grating elements of the third polarization spectral filter, and the ratios among the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the third polarization spectral filter are respectively the same as the width and thickness of each of the plurality of first grating elements of the fourth polarization spectral filter, the width and thickness of each of the plurality of second grating elements of the fourth polarization spectral filter, the width and thickness of each of the plurality of third grating elements of the fourth polarization spectral filter, and the ratios among the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the fourth polarization spectral filter.

17. The polarization spectral filter array according to claim 12, wherein each of the first polarization spectral filter, the second polarization spectral filter, the third polarization spectral filter, and the fourth polarization spectral filter further includes a band - pass filter disposed on the surface of the first reflector, and the band - pass filter is configured to transmit light in the first band and the second band and block light in other bands.

18. The polarization spectral filter array according to claim 12, wherein the first polarization spectral filter group further includes a fifth polarization spectral filter configured to transmit light having a third linear polarization component that is rotated 45 degrees relative to the first linear polarization component among the light in the first band, wherein the second polarization spectral filter group further includes a sixth polarization spectral filter configured to transmit light having a third linear polarization component that is rotated 45 degrees relative to the first linear polarization component among the light in the second band, and Wherein both the fifth polarization spectral filter and the sixth polarization spectral filter include the first reflector, the second reflector, and the grating layer.

19. The polarization spectral filter array according to claim 18, wherein the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the fifth polarization spectral filter are rotated 45 degrees in a plane perpendicular to the first direction with respect to the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the first polarization spectral filter, and wherein the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the sixth polarization spectral filter are rotated 45 degrees in the plane perpendicular to the first direction with respect to the plurality of first grating elements, the plurality of second grating elements, and the plurality of third grating elements of the grating layer of the third polarization spectral filter.

20. The polarization spectral filter array according to claim 12, wherein the first polarization spectral filter group further includes a fifth polarization spectral filter configured to transmit light having the first linear polarization component among the light in the first band, wherein the second polarization spectral filter group further includes a sixth polarization spectral filter configured to transmit light having the first linear polarization component among the light in the second band, wherein both the fifth polarization spectral filter and the sixth polarization spectral filter include the first reflector, the second reflector, the grating layer, and a quarter-wave plate disposed on the surface of the first reflector.

21. A polarization spectral sensor, comprising: The polarization spectral filter array according to claim 12; and an image sensor including a plurality of sensing pixels arranged two-dimensionally, the plurality of sensing pixels being configured to sense the intensity of light transmitted through the polarization spectral filter array.

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