Patent Description:
Color display devices or color image sensors display an image of various colors or detect a color of incident light by using a color filter. An RGB color filter method, in which, for example, a green filter is arranged at two pixels of four pixels and a blue filter and a red filter are arranged in the other two pixels, is most widely employed by a currently used color display device or color image sensor. In addition to the RGB color filter method, a CYGM color filter method may be employed in which color filters of cyan, yellow, green, and magenta, which are complementary colors, are respectively arranged at four pixels.

However, a color filter may have a low light use efficiency because the color filter absorbs light of other colors except for filtered light. For example, when an RGB color filter is in use, only <NUM>/<NUM> of the incident light is transmitted and the other portion, that is, <NUM>/<NUM>, of the incident light is absorbed. Accordingly, the light use efficiency may be about <NUM>%. Accordingly, for the color display device or a color image sensor, most of a light loss is generated in the color filter.

Recently, to improve the light use efficiency of the color display device or color image sensor, a color separation element is being used instead of the color filter. The color separation element may separate colors of the incident light by using the diffraction or refraction characteristics of a light that varies according to a wavelength of the light. The colors separated by the color separation element may be transferred to pixels corresponding to the transferred colors. Accordingly, use of the color separation element may achieve a higher light use efficiency as compared to a case of using the color filter.

Document <CIT> discloses a solid-state imaging device including: a plurality of pixel cells; and column signal lines.

The present invention is defined by claim <NUM>.

The above and/or other aspects will become more apparent by describing certain exemplary embodiments with reference to the accompanying drawings, in which:.

Certain exemplary embodiments are described in greater detail below with reference to the accompanying drawings.

The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. However, it is apparent that the exemplary embodiments can be practiced without those specifically defined matters.

A color separation element array, an image sensor including the color separation element array, and an image pickup apparatus including the color separation element array are described in detail with reference to the accompanying drawings. In the following descriptions, like reference numerals refer to like elements. In the drawings, the size of each element is exaggerated for clarity and convenience of explanation. Also, in the following description of a layer structure, when a layer is described to exist "on" or "above" another layer, the layer may exist directly on or indirectly above the other layer, or a third layer may be interposed therebetween.

<FIG> is a cross-sectional view schematically illustrating an image pickup apparatus <NUM> and an image sensor <NUM> including a color separation element array according to an exemplary embodiment. Referring to <FIG>, the image pickup apparatus <NUM> according to the present exemplary embodiment may include an objective lens <NUM> and the image sensor <NUM> for converting light focused by the objective lens <NUM> to an electric image signal. The image sensor <NUM> may include a pixel array <NUM> having a plurality of pixels detecting light and arranged in two dimensions (2D), and the color separation element array having a plurality of color separation elements <NUM> arranged in 2D. The image sensor <NUM> may further include a transparent dielectric layer <NUM> arranged on a surface of the pixel array <NUM>. The color separation elements <NUM> may be buried in the transparent dielectric layer <NUM>.

The color separation elements <NUM> are arranged at a light incident side of the pixel array <NUM> and each separate the incident light according to the wavelength of the incident light such that light of different wavelengths may be incident on different pixels. The color separation elements <NUM> may separate colors by changing traveling paths of light according to the wavelengths of the light by using the diffraction or refraction characteristics of the light that vary according to the wavelengths. For example, the color separation elements <NUM> are formed in various shapes such as a rod shape having a transparent symmetric or asymmetric structure or a prism shape having an inclined surface, which are well known, and a variety of designs may be available according to a desired spectrum distribution of an exit light. Light use efficiency may be increased by using the color separation elements <NUM> to optimize a spectrum distribution of light incident on the respective pixels to fit to the pixels. A positional relationship between the pixels of the image sensor <NUM> and the color separation elements <NUM> may be variously designed according to the color separation characteristics of the color separation elements <NUM>.

For example, <FIG> is a plan view exemplarily illustrating a positional relationship between the pixels of the image sensor <NUM> and the color separation elements <NUM>. Referring to <FIG>, the image sensor <NUM> may include the pixel array <NUM> having a plurality of photodetector pixels Px1, Px2, and Px3 arranged in the form of a 2D matrix having a plurality of rows and columns. For example, as illustrated in <FIG>, only the first pixels Px1 may be arranged in a first pixel row P1, and the second pixels Px2 and the third pixels Px3 may be alternately arranged in a second pixel row P2 that is adjacent to the first pixel row P1. The first pixel row P1 and the second pixel row P2 may be alternately arranged in a vertical direction. The color separation elements <NUM> may be arranged facing the second pixels Px2 in the second pixel row P2.

<FIG> is a cross-sectional view exemplarily illustrating a structure of the first pixel Px1 arranged in the first pixel row P1 of the image sensor <NUM> of <FIG>. Referring to <FIG>, the first pixel Px1 may include a light sensing layer <NUM>, a color filter layer <NUM> arranged on a light incident surface of the light sensing layer <NUM>, the transparent dielectric layer <NUM> arranged on the color filter layer <NUM>, and a micro lens <NUM> arranged on the transparent dielectric layer <NUM> to focus the incident light on the light sensing layer <NUM>. The light sensing layer <NUM> converts the incident light to an electric signal according to the intensity of the incident light. In such a structure, the incident light may be focused by the micro lens <NUM> on the light sensing layer <NUM> by passing through the transparent dielectric layer <NUM> and the color filter layer <NUM>. The color filter layer <NUM> may include a first color filter CF1 that transmits only a light in a first wavelength band of the incident light. Accordingly, the first pixel Px1 may detect only the light in the first wavelength band.

<FIG> is a cross-sectional view exemplarily illustrating a structure of the second and third pixels Px2 and Px3 arranged in the second pixel row P2 of the image sensor <NUM> of <FIG>. Referring to <FIG>, the second pixel row P2 may include the light sensing layer <NUM>, a color filter layer <NUM> arranged on a light incident surface of the light sensing layer <NUM>, the transparent dielectric layer <NUM> arranged on the color filter layer <NUM>, the color separation elements <NUM> arranged in the transparent dielectric layer <NUM> of the second pixel Px2, and a micro lens <NUM> arranged on the transparent dielectric layer <NUM> to focus the incident light on the color separation elements <NUM>. The color filter layer <NUM> may include a second color filter CF2 that is arranged in the second pixel Px2 to transmit only a light in a second wavelength band and a third color filter CF3 arranged in the third pixel Px3 to transmit only a light in a third wavelength band. The color separation elements <NUM> may be buried in the transparent dielectric layer <NUM> and may be fixed by being surrounded by the transparent dielectric layer <NUM>.

In the above structure, while passing through the color separation elements <NUM>, the light focused by the micro lens <NUM> may be separated into a light C2 of a second wavelength band and a light C3 of a third wavelength band by the color separation elements <NUM>. The color separation elements <NUM> may be designed, for example, to change a traveling direction of the light C3 of the third wavelength band of the incident light into two inclined lateral directions without changing a traveling direction of the light C2 of the second wavelength band. Then, the light C2 of the second wavelength band may pass through the color separation elements <NUM> and may be incident on the light sensing layer <NUM> of the second pixel Px2 disposed directly under the color separation elements <NUM>. On the other hand, after passing through the color separation elements <NUM>, the light C3 of the third wavelength band may be incident on the light sensing layer <NUM> of each of the third pixels Px3 disposed at the opposite sides of the second pixel Px2.

In the example illustrated in <FIG>, in the first color filter CF1 of the first pixel Px1, only about <NUM>% of the incident light is transmitted and arrives at the light sensing layer <NUM> as in a pixel structure of the related art. In contrast, in the second color filter CF2 of the second pixel Px2 and the third color filter CF3 of the third pixel Px3, since a ratio of a color corresponding to each of the color filters CF2 and CF3 is high, transmissivity of light increases compared to the pixel structure of the related art. Accordingly, light use efficiency in the second pixel Px2 and the third pixel Px3 may be increased. For example, the first wavelength band may be green, the second wavelength band may be blue, and the third wavelength band may be red. In other words, the first pixel Px1 may be a green pixel, the second pixel Px2 may be a blue pixel, and the third pixel Px3 may be a red pixel.

The structure of the pixel array <NUM> of the image sensor <NUM> and the characteristics of the color separation elements <NUM> illustrated in <FIG> are a mere example to help understanding and are not limited to the exemplary embodiment illustrated in <FIG>. A variety of color separation characteristics may be selected according to the design of the color separation elements <NUM>. A variety of structures of the pixel array <NUM> may be selected according to the color separation characteristics of the color separation elements <NUM>. Also, a part or the entire of the micro lenses <NUM> and <NUM> and the color filters CF1, CF2, and CF3 may be omitted according to the design.

Referring back to <FIG>, the objective lens <NUM> focuses an image of an object (not shown) on the image sensor <NUM>. When the image sensor <NUM> is accurately located on a focal plane of the objective lens <NUM>, a light starting from at a certain point of the object arrives at a certain point on the image sensor <NUM> by passing through the objective lens <NUM>. For example, a light starting from a certain point A on an optical axis OX passes through the objective lens <NUM> and then arrives at a center of the image sensor <NUM> on the optical axis OX. Also, light starting from any one of points B, C, and D located out of the optical axis OX travels across the optical axis OX by the objective lens <NUM> and arrives at a point in a peripheral portion of the image sensor <NUM>. For example, a light starting from the point B located above the optical axis OX arrives at a lower peripheral portion of image sensor <NUM>, crossing the optical axis OX, and a light starting from the point C located under the optical axis OX arrives at an upper peripheral portion of the image sensor <NUM>, crossing the optical axis OX. Also, a light starting from the point D located between the optical axis OX and the point B arrives at a position between the lower peripheral portion and the center of image sensor <NUM>, crossing the optical axis OX.

Accordingly, the light starting from the different points A, B, C, and D are incident on the image sensor <NUM> at different incident angles according to the distance between the points A, B, C, and D and the optical axis OX. An incident angle of a light incident on the image sensor <NUM> is typically defined to be a chief ray angle (CRA). A chief ray (CR) denotes a light ray starting from a point of the object and arriving at the image sensor <NUM> by passing through a center of the objective lens <NUM>. The CRA denotes an angle formed by the CR with respect to the optical axis OX. The CRA of the light starting from the point A on the optical axis OX is <NUM>° and the light is perpendicularly incident on the image sensor <NUM>. The CRA increases as the starting point is farther from the optical axis OX.

From the viewpoint of the image sensor <NUM>, the CRA of the light incident on the center portion of the image sensor <NUM> is <NUM>° and the CRA of the incident light gradually increases toward the edge of the image sensor <NUM>. For example, the CRA of the light starting from each of the points B and C and arriving at the outermost edge of the image sensor <NUM> is the largest, whereas the CRA of the light starting from the point A and arriving at the center of the image sensor <NUM> is <NUM>°. The CRA of the light starting from the point D and arriving at a position between the center and the edge of the image sensor <NUM> is greater than <NUM>° and less than the CRA of the light starting from each of the points B and C.

However, the color separation elements <NUM> generally have a structure having directivity. Due to the directivity, the color separation elements <NUM> efficiently operate with respect to the light perpendicularly incident on the color separation elements <NUM>. However, if the incident angle increases over a certain angle, the color separation efficiency of the color separation elements <NUM> is drastically lowered. Accordingly, when the color separation elements <NUM> having the same structure are arranged in the entire area of the image sensor <NUM>, the quality of an image may be more degraded as a distance from the center portion of the image sensor <NUM> increases.

The color separation element array according to the present exemplary embodiment may include the color separation elements <NUM> that are configured to efficiently perform color separation even at the edge of the image sensor <NUM>. For example, each of the color separation elements <NUM> may include a first element 130a and a second element 130b that are sequentially arranged in the direction of the optical axis OX or a traveling direction of the incident light. The first element 130a and the second element 130b of the color separation elements <NUM> may be shifted, i.e. offset by different degrees according to the positions of the color separation elements <NUM> in the image sensor <NUM>. For example, the first element 130a and the second element 130b of the color separation element <NUM> at the center portion of the image sensor <NUM> may be arranged such that the center portions, e.g., center lines, of the first element 130a and the second element 130b may be aligned with each other. The first element 130a and the second element 130b of the color separation element <NUM> arranged in an area other than the center portion of the image sensor <NUM> may be offset with each other. For example, a shift distance between the first element 130a and the second element 130b as a distance from the center portion of the image sensor <NUM> increases. The first element 130a and the second element 130b of the color separation element <NUM> arranged at the outermost edge of the image sensor <NUM> may be offset to the greatest extent with respect to each other.

<FIG> is a cross-sectional view exemplarily illustrating a positional relationship between the first element 130a and the second element 130b of the color separation element <NUM> when a light is perpendicularly incident on the image sensor <NUM>. <FIG> and <FIG> are cross-sectional views exemplarily illustrating in detail a positional relationship between the first element 130a and the second element 130b of the color separation element <NUM> when a light is obliquely incident on the image sensor <NUM>.

Referring to <FIG>, when the incident light is perpendicularly incident on the image sensor <NUM>, the first element 130a and the second element 130b of the color separation element <NUM> are not offset with each other. In this case, the first element 130a and the second element 130b of the color separation element <NUM> may be aligned along a center line (not shown) of a pixel facing the color separation element <NUM> such that the center portions of the first element 130a and the second element 130b may be matched with each other. In contrast, referring to <FIG> and <FIG>, when the incident light is obliquely incident on the image sensor <NUM>, the first element 130a and the second element 130b of the color separation element <NUM> may be offset with each other. The first element 130a and the second element 130b of the color separation element <NUM> may be offset to be aligned with the traveling direction of a light that is obliquely incident. For example, as illustrated in <FIG>, when the incident light is obliquely incident from the left side, the first element 130a may be relatively further offset to the left compared to the second element 130b. Also, as illustrated in <FIG>, when the incident light is obliquely incident from the right side, the first element 130a may be relatively further offset to the right compared to the second element 130b. A relative shift distance "d" of the first element 130a and the second element 130b gradually increases as the incident angle of the incident light increases, that is, the CRA increases.

As described above, when the incident light is perpendicularly incident, the color separation elements <NUM> may be aligned along the center line of a pixel facing the color separation element <NUM>. However, when the incident light is obliquely incident, the first and second elements 130a and 130b are relatively offset with each other according to a direction in which a light is incident. <FIG> and <FIG> are cross-sectional views illustrating a change in the positions of the first element 130a and the second element 130b of the color separation element <NUM> according to a change in a light incident angle.

For example, when the incident angle is θ1 as illustrated in <FIG>, the incident light may be refracted from a surface of the transparent dielectric layer <NUM> to travel inside the transparent dielectric layer <NUM> at an inclined angle of α1. Then, the second element 130b may be moved in the direction toward the incident light such that the light C2 of the second wavelength band exiting from the second element 130b accurately travels toward the center portion of the light sensing layer <NUM> of a pixel corresponding to the light C2 and the light C3 of the third wavelength band travel toward the center portion of the light sensing layer <NUM> of a pixel corresponding to the light C3. The first element 130a is further offset with respect to the second element 130b in the direction toward the incident light such that the first element 130a and the second element 130b are arranged to match the inclined angle α1. As a result, the first element 130a may be moved by D1 from the center line of a pixel facing the color separation element <NUM>.

The inclined angle α1 in which a light travels inside the transparent dielectric layer <NUM> may be calculated by the Snell's law. For example, an equation that n1×sinθ1=n2×sinα1 is established, where "n1" is an external refractive index of the image sensor <NUM> and "n2" is an average refractive index of the transparent dielectric layer <NUM> and the color separation elements <NUM>. The average refractive index n2 is calculated considering a volume ratio of the transparent dielectric layer <NUM> and the color separation elements <NUM>. Since the incident angle θ1 may correspond to the CRA, the angle α at which the first and second elements 130a and 130b of the color separation elements <NUM> at a particular position of the image sensor <NUM> are aligned may satisfy an equation that n1×sin(CRAi)=n2×sinα, where "CRAi" is the CRA at an i-th position.

On the other hand, when the incident angle is θ2 that is greater than θ1 as illustrated in <FIG>, the incident light is refracted on the surface of the transparent dielectric layer <NUM> and travels inside the transparent dielectric layer <NUM> at an inclined angle α2 that is greater than the inclined angle α1. Then, a degree that the first element 130a and the second element 130b are offset in a direction toward the incident light may be increased compared to the case in <FIG>. As a result, the first element 130a may be offset by D2 that is greater than D1 from the center line of a corresponding pixel such that the first element 130a and the second element 130b are arranged to match the inclined angle α2.

<FIG> are cross-sectional views exemplarily illustrating the color separation elements <NUM> according to various exemplary embodiments. First, referring to <FIG> and <FIG>, the first element 130a and the second element 130b of the color separation element <NUM> may be arranged to be separated from each other by a predetermined gap g. Although <FIG> illustrate that the first element 130a and the second element 130b closely contact to each other, the structure thereof is not limited thereto. As illustrated in <FIG> and <FIG>, the first element 130a and the second element 130b may be arranged to be separated from each other. The gap between the first element 130a and the second element 130b may be less than or equal to about <NUM> or <NUM>.

Also, referring to <FIG> and <FIG>, the color separation element <NUM> may further include a third element 130c. The third element 130c may be arranged following the second element 130b in the traveling direction of the incident light. When the incident light is perpendicularly incident, the first to third elements 130a, 130b, and 130c of the color separation element <NUM> may be aligned along the center line of a corresponding pixel such that the center portions of the first to third elements 130a, 130b, and 130c are matched with one another as illustrated in <FIG>. In contract, when the incident light is obliquely incident, the first to third elements 130a, 130b, and 130c of the color separation element <NUM> may be offset with respect to one another as illustrated in <FIG>. A relative shift distance d1 between the first element 130a and the second element 130b may be the same as or different from a relative shift distance d2 between the second element 130b and the third element 130c. The shift distance d1 and the shift distance d2 may be variously selected according to an incident angle of the incident light and a wavelength band to be separated. Although <FIG> and <FIG> exemplarily illustrates that the color separation element <NUM> includes three elements, that is, the first to third elements 130a, 130b, and 130c, the color separation element <NUM> may include four or more elements that are sequentially arranged in a traveling direction of the incident light.

The widths of the first to third elements 130a, 130b, and 130c of the color separation element <NUM> may be the same as or different from one another. For example, the width of the first element 130a located at the foremost of the traveling direction of the incident light may be the largest and the width of the third element 130c located at the rearmost of the traveling direction of the incident light may be the smallest. The width of the second element 130b may be smaller than that of the first element 130a and larger than that of the third element 130c. As the widths of the first to third elements 130a, 130b, and 130c gradually decrease along the traveling direction of the incident light, the use of a material of the color separation elements <NUM> may be reduced while the color separation efficiency is maintained or improved.

On the other hand, the first to third elements 130a, 130b, and 130c of the color separation element <NUM> may be formed of a material having a higher refractive index than the refractive index of a surrounding portion. For example, the refractive indices of the first to third elements 130a, 130b, and 130c may be higher than the refractive index of the transparent dielectric layer <NUM>. For example, the transparent dielectric layer <NUM> may be formed of SiO<NUM> or siloxane-based spin-on glass (SOG), the first to third elements 130a, 130b, and 130c may be formed of a material having a high refractive index, such as, TiO<NUM>, SiN<NUM>, ZnS, ZnSe, and Si<NUM>N<NUM>. Although the first to third elements 130a, 130b, and 130c may have the same refractive index, different refractive indices may be selected to improve the color separation efficiency according to the incident angle of the incident light and a wavelength band to be separated.

Although <FIG> and <FIG> illustrate that the first to third elements 130a, 130b, and 130c closely contact one another, as illustrated in <FIG> and <FIG>, the first to third elements 130a, 130b, and 130c may be arranged to be separated from one another. A gap g1 between the first element 130a and the second element 130b may be the same or different from a gap g2 between the second element 130b and the third element 130c. The gaps g1 and g2 may be selected based on the incident angle of the incident light and the shift distances d1 and d2 between the first to third elements 130a, 130b, and 130c, such that the first to third elements 130a, 130b, and 130c are arranged to match the travelling direction of the incident light. For example, both the gaps g1 and g2 may be selected to be less than or equal to about <NUM> or <NUM>.

<FIG> is a plan view exemplarily illustrating shift forms of first elements and second elements according to the positions of a plurality of color separation elements in the image sensor <NUM>. Referring to <FIG>, since a first element 131a and a second element of the color separation element are arranged to be overlapped with each other at the center portion of the image sensor <NUM>, only the first element 131a is seen whereas the second element covered by the first element 131a is not seen. Also, first elements 132a, 133a, 134a, 135a, 136a, 137a, 138a, and 139a and second elements 132b, 133b, 134b, 135b, 136b, 137b, 138b, and 139b of the color separation elements located at a peripheral portion of the image sensor <NUM> are offset with each other in a direction x and a direction y. Since a z-axis in <FIG> is the same direction as the optical axis OX, the first elements 132a, 133a, 134a, 135a, 136a, 137a, 138a, and 139a and the second elements 132b, 133b, 134b, 135b, 136b, 137b, 138b, and 139b may be offset in a direction perpendicular to the optical axis OX.

For example, the first element 132a and the second element 132b located in the upper area of the image sensor <NUM> are offset in a direction -y; the first element 133a and the second element 133b located in the lower area of the image sensor <NUM> are offset in a direction +y; and the first element 134a and the second element 134b located at the left area of the image sensor <NUM> are offset in a direction +x. The first element 138a and the second element 138b located in the lower right area of the image sensor <NUM> are offset in the direction +y and a direction -x. As illustrated in <FIG>, the first elements 132a, 133a, 134a, 135a, 136a, 137a, 138a, and 139a of the color separation elements arranged in a peripheral portion of the image sensor <NUM> are further offset toward the center area compared to the second elements 132b, 133b, 134b, 135b, 136b, 137b, 138b, and 139b. The first elements 132a, 133a, 134a, 135a, 136a, 137a, 138a, and 139a and the second elements 132b, 133b, 134b, 135b, 136b, 137b, 138b, and 139b may be symmetrically offset with respect to the center area of the image sensor <NUM>. For example, the first elements 131a, 132a, 133a, 134a, 135a, 136a, 137a, 138a, and 139a and the second elements 132b, 133b, 134b, 135b, 136b, 137b, 138b, and 139b of the color separation elements may be offset to be aligned with a traveling direction in the transparent dielectric layer <NUM> of the CR that passed through the objective lens <NUM>.

<FIG> is a graph exemplarily showing color separation efficiency according to a change in a light incident angle. In the graph of <FIG>, curved lines indicated by A, B, and C denote color separation efficiencies when the first element and the second element are offset according to the incident angle of the incident light, whereas curved lines indicated by A', B', and C' denote color separation efficiencies when the first element and the second element are not offset regardless of the incident angle of the incident light. The curved lines A and A' denote color separation efficiencies of blue and red, the curved lines B and B' denote color separation efficiencies of green, and the curved lines C and C' denote average color separation efficiencies of the entire colors. As it may be seen from the graph of <FIG>, the total average efficiencies C and C' for both cases of shifting and not shifting the first element and the second element are similar to each other. However, when the first element and the second element are not offset, as the incident angle increases, the color separation efficiencies of blue and red decrease much and the color separation efficiency of green increases much. Accordingly, color distortion may greatly occur in the peripheral portion of the image sensor <NUM>. In contrast, when the first element and the second element are offset, a change in the color separation efficiency according to a change in the incident angle is not generated much. Accordingly, uniform color characteristics may be obtained through the entire area of the image sensor <NUM>.

Claim 1:
An image pickup apparatus (<NUM>) comprising:
an objective lens (<NUM>); and
an image sensor (<NUM>) configured to convert light focused by the objective lens to an electrical signal, wherein the image sensor comprises:
a pixel array (<NUM>) comprising pixels which are two-dimensionally arranged and configured to detect light; and
a color separation element array,
wherein the color separation element array comprises color separation elements (<NUM>) which are two-dimensionally arranged across a plane and configured to separate an incident light according to a wavelength such that, of the incident light, a light of a first wavelength is directed to a first direction and a light of a second wavelength that is different from the first wavelength is directed to a second direction that is different from the first direction;
wherein each of the color separation elements (<NUM>) comprises a first element (130a) and a second element (130b) that are arranged in the direction normal to the plane to be sequentially arranged along a traveling direction of the incident light;
the first element (130a) and the second element (130b) of one of the color separation elements (<NUM>), which is arranged in the center area of the color separation element array, are aligned with one another with no offset, such that center portions of the first element (130a) and the second element (130b) are aligned;
the first element (130a) and the second element (130b) of respective color separation elements (<NUM>), which are arranged in an area other than the center area of the color separation element array, have an offset with respect to one another to be aligned to fit to the traveling direction of a chief light that passes through the objective lens (<NUM>), thereby forming offset pairs each comprising respective first (130a) and second elements (130b);
wherein the color separation element array further comprising a transparent dielectric layer (<NUM>); and
wherein the color separation elements (<NUM>) are buried in the transparent dielectric layer (<NUM>), and a first refractive index of the first elements (130a) and a second refractive index of the second elements (130b) are greater than that of the transparent dielectric layer (<NUM>).