Patent Publication Number: US-11037976-B2

Title: Imaging apparatus and image sensor including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation application of U.S. patent application Ser. No. 15/221,719, filed Jul. 28, 2016, in the U.S. Patent and Trademark Office, which claims priority from U.S. Provisional Patent Application No. 62/198,268, filed on Jul. 29, 2015, and Korean Patent Application No. 10-2016-0044268, filed on Apr. 11, 2016, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their respective entireties. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under Grant No. W911NF-14-1-0345 awarded by U.S. Army. The government has certain rights in the invention. 
    
    
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with exemplary embodiments relate to image sensors. 
     2. Description of the Related Art 
     Optical sensors including semiconductor sensor arrays may be used in mobile devices, wearable devices, and the Internet of Things. Although such devices should be small, it is difficult to reduce the thicknesses of imaging apparatuses included in these devices. 
     Also, as demand for a 3-dimensional image sensor to be used in the Internet of Things, game devices, and other mobiles has increased, an optical system capable of controlling pathways of light incident onto the 3-dimensional image sensor is needed. However, because a conventional 3-dimensional image sensor includes complicated optical lenses, it has been difficult to manufacture an appropriate 3-dimensional image sensor for use in such devices. 
     SUMMARY 
     Exemplary embodiments may address at least the above problems and/or disadvantages and other disadvantages not described above. Also, the exemplary embodiments are not required to overcome the disadvantages described above, and may not overcome any of the problems described above. 
     Provided are image sensors that may be configured to have a small size and may be configured to obtain 3-dimensional information about an object. 
     According to an aspect of an exemplary embodiment, an image sensor includes an image sensor includes a substrate, thin lenses disposed on a first surface of the substrate and configured to concentrate lights incident on the first surface, and light-sensing cells disposed on a second surface of the substrate, the second surface facing the first surface, and the light-sensing cells being configured to sense lights passing through the thin lenses, and generate electrical signals based on the sensed lights. A first thin lens and second thin lens of the thin lenses are configured to concentrate a first light and a second light, respectively, of the incident lights onto the light-sensing cells, the first light having a different wavelength than the second light. 
     The substrate may include sub-substrates, and the thin lenses and the light-sensing cells may be respectively disposed on a first surface and a second surface of each of the sub-substrates. 
     Each of the thin lenses may include scatterers, and each of the scatterers may have a pillar structure. 
     An interval distance between a pair of the scatterers may be less than a respective wavelength of light concentrated by a respective one among the thin lenses. 
     A height of the scatterers may be less than a respective wavelength of light concentrated by a respective one among the thin lenses. 
     The scatterers may include at least one from among silicon, gallium phosphide, SiC, SiN, and TiO 2 . 
     Shapes of the scatterers and interval distances between respective pairs of the scatterers may vary with a respective wavelength of light concentrated by a respective one among the thin lenses. 
     The image sensor may further include light filters, each of the light filters being configured to filter a respective wavelength of light incident on a respective one among the light-sensing cells. 
     The image sensor may further include an image synthesizer configured to generate a multi-color image by synthesizing images of different colors, and at least two among the light-sensing cells may produce the images of different colors. 
     The image sensor may further include an image synthesizer configured to generate a stereo image based on images that are produced by the light-sensing cells. 
     The image synthesizer may be further configured to extract depth information about an object appearing in the stereo image. 
     According to an aspect of an exemplary embodiment, an image sensor includes a substrate, thin lenses disposed on a first surface of the substrate and configured to concentrate lights incident on the first surface, and light-sensing cells disposed on a second surface of the substrate, the second surface facing the first surface, and the light-sensing cells being configured to sense lights passing through the thin lenses, and generate electrical signals based on the sensed lights. A first thin lens and second thin lens of the thin lenses may be configured to concentrate a first light and a second light, respectively, of the incident lights to have different focal lengths. 
     The substrate may include sub-substrates, and the thin lenses and the light-sensing cells may be respectively disposed on a first surface and a second surface of each of the sub-substrates. 
     The concentrated lights may have predetermined wavelengths. 
     Each of the thin lenses may include scatterers, and each of the scatterers may have a pillar structure. 
     An interval distance between a pair of the scatterers may be less than a respective wavelength of light concentrated by a respective one among the thin lenses. 
     A height of the scatterers may be less than a respective wavelength of light concentrated by a respective one among the thin lenses. 
     Shapes of the scatterers and interval distances between respective pairs of the scatterers may vary with a respective wavelength of light concentrated by a respective one among the thin lenses. 
     The image sensor may further include a depth map calculator configured to calculate a defocusing degree of an image that is produced on each of the light-sensing cells, and calculate depth map information about an image that is produced by the incident lights, based on the defocusing degree. 
     The image sensor may further include a light filter layer configured to filter a wavelength of light incident on each of the light-sensing cells. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will be more apparent by describing exemplary embodiments with reference to the accompanying drawings. 
         FIG. 1  is a cross-sectional view illustrating an image sensor according to an exemplary embodiment; 
         FIG. 2  is a view illustrating a surface of a thin lens according to an exemplary embodiment; 
         FIGS. 3A, 3B, 3C, and 3D  are perspective views illustrating various shapes of scatterers according to exemplary embodiments; 
         FIG. 4  is a view of a surface illustrating a first thin lens according to an exemplary embodiment; 
         FIG. 5  is a view illustrating a surface of a first thin lens according to another exemplary embodiment; 
         FIG. 6  is a view illustrating an image sensor according to an exemplary embodiment; 
         FIG. 7  is a view illustrating an image sensor according to an exemplary embodiment; 
         FIG. 8  is a view illustrating an image sensor according to an exemplary embodiment; 
         FIG. 9  is a view illustrating an image sensor according to another exemplary embodiment; 
         FIG. 10  is a view illustrating an image sensor including a substrate including a plurality of sub-substrates, according to an exemplary embodiment; 
         FIG. 11  is a view illustrating an image sensor according to an exemplary embodiment; 
         FIG. 12  is a view illustrating an image sensor according to an exemplary embodiment; and 
         FIG. 13  is a view illustrating an image sensor according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments are described in greater detail below with reference to the accompanying drawings. 
     In the following description, like drawing reference numerals are used for like elements, even in different 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. Also, well-known functions or constructions may not be described in detail because they would obscure the description with unnecessary detail. 
     As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     In the drawings, the thicknesses of layers and regions are exaggerated for clarity. It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. 
     The terms used in this specification are those general terms currently widely used in the art in consideration of functions in regard to the inventive concept, but the terms may vary according to the intention of those of ordinary skill in the art, precedents, or new technology in the art. Also, specified terms may be selected by the applicant, and in this case, the detailed meaning thereof will be described in the detailed description. Thus, the terms used in the specification may be understood not as simple names but based on the meaning of the terms and the overall description. 
     Throughout the specification, it will be understood that when a component is connected to another component, the component may be directly connected as well as electrically connected with another element therebetween. 
     It will be further understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. In addition, the terms such as “unit,” “-er (-or),” and “module” described in the specification refer to an element for performing at least one function or operation, and may be implemented in hardware, software, or the combination of hardware and software. 
     Additionally, it will be understood that although the terms “first,” “second,” etc. may be used herein to describe various components, these components may not be limited by these terms. These components are only used to distinguish one component from another. 
     Descriptions of embodiments below may not be understood as limiting the scope of right, but those easily inferred by one of ordinary skill in the art may be understood as belonging to the scope or right of the exemplary embodiments. Hereinafter, embodiments will be described in detail by referring to the accompanying drawings for the purpose of describing examples only. 
       FIG. 1  is a cross-sectional view illustrating an image sensor according to an exemplary embodiment. 
     Referring to  FIG. 1 , the image sensor according to an exemplary embodiment may include a substrate  110 , a plurality of thin lenses  120   a ,  120   b , and  120   c  that are arranged on a first surface S 1 , and a plurality of light-sensing cells  130   a ,  130   b , and  130   c  arranged on a second surface S 1  facing the first surface S 1  of the substrate  110 . At least two from among the thin lenses  120   a ,  120   b , and  120   c  may concentrate lights having different wavelength components on the light-sensing cells  130   a ,  130   b , and  130   c . That is, two or more of the thin lenses  120   a ,  120   b , and  120   c  may have wavelength selectivity with respect to different wavelengths. 
     The substrate  110  may have a plate-like shape. The first surface S 1  and the second surface S 2  of the substrate  110  may be substantially horizontally parallel to each other. However, the first surface S 1  and the second surface S 2  may not be completely horizontally parallel to each other and may be obliquely parallel to each other. The substrate  110  and the light-sensing cells  130   a ,  130   b , and  130   c  may be spaced apart from one another with an air layer therebetween. The substrate  110  may include a transparent material. As used herein, the term “transparent material” denotes a material having a high light transmittance. For example, the substrate  110  may include at least one from among Si 3 N 4 , SiO 2 , and a polymer such as PMMA or PDMS. Once a path of incident light changes at the light-sensing cells  130   a ,  130   b , and  130   c , the incident light may pass through the substrate  110  and become incident on a light sensing layer  130 . 
     Each of the light-sensing cells  130   a ,  130   b , and  130   c  may include scatterers from among a plurality of scatterers  122   a ,  122   b , and  122   c . The term ‘thin-lens’ refers to an optical device that changes a path of light by a difference in phase delays caused by the scatterers  122   a ,  122   b , and  122   c  included in the thin-lenses, unlike related art optical lens. Accordingly, a thickness of the thin-lens may be hardly limited compared to that of an optical lens, and the thin-lens may be configured to be thin. The scatterers  122   a ,  122   b , and  122   c  on surfaces of the thin lenses  120   a ,  120   b , and  120   c  may be configured to resonate light incident on each of the scatterers  122   a ,  122   b , and  122   c . The scatterers  122   a ,  122   b , and  122   c  may be configured to appropriately delay a transmission phase of the light incident on each of the scatterers  122   a ,  122   b , and  122   c.    
     The scatterers  122   a ,  122   b , and  122   c  may be arranged on the first surface S 1  of the substrate  110  to form a desired wave front of light that transmits from the first surface S 1  of the substrate  110 . Also, the thin lenses  120   a ,  120   b , and  120   c  may change a path of transmittant light with respect to incident light by modulating a wave front of light. 
     At least two from among the thin lenses  120   a ,  120   b , and  120   c  may be configured to concentrate pieces of light having different wavelength components among the incident light on the light sensing layer  130 . For example, a first thin-lens  120   a  may be configured to concentrate a piece of light having a first wavelength λ 1  among the incident light. Also, a second thin-lens  120   b  may be configured to concentrate a piece of light having a second wavelength λ 2  among the incident light. Also, a third thin-lens  120   c  may be configured to concentrate a piece of light having a third wavelength λ 3  among the incident light. However, these are provided as examples for illustrative purpose only, and embodiments are not limited thereto. For example, not all of the first to third thin lenses  120   a ,  120   b , and  120   c  have to concentrate pieces of light having different wavelengths, and two from among the first, second, and third thin lenses  120   a ,  120   b , and  120   c  may be configured to concentrate pieces of light having substantially the same wavelength. 
       FIG. 2  is a view illustrating a surface of one from among the thin lenses  120   a ,  120   b , and  120   c  according to an exemplary embodiment. 
     Referring to  FIG. 2 , a plurality of scatterers may be arranged on a surface of a thin-lens. A wave form of light transmitted from the thin-lens may depend on a shape, an interval distance, and a shape of arrangement of the scatterers. When the scatterers are formed on the surface of the thin-lens as shown in  FIG. 2 , light transmitted from the thin-lens may be concentrated. That is, the thin-lens shown in  FIG. 2  maybe configured as a lens having positive refractive power. 
       FIGS. 3A, 3B, 3C, and 3D  are perspective views illustrating various shapes of the scatterers  122   a ,  122   b , and  122   c  according to exemplary embodiments. 
     Referring to  FIGS. 3A through 3D , the scatterers  122   a ,  122   b , and  122   c  included in the thin lenses  120   a ,  120   b , and  120   c  may have pillar structures. A shape of a cross-section of the pillar structure may be from among a circle, an oval, a rectangle, and a square.  FIG. 3A  illustrates a scatterer having a pillar structure with a cross-sectional shape of a circle.  FIG. 3B  illustrates a scatterer having a pillar structure with a cross-sectional shape of an oval.  FIG. 3C  illustrates a scatterer having a pillar structure with a cross-sectional shape of a square.  FIG. 3D  illustrates a scatterer having a pillar structure with a cross-sectional shape of a rectangle. The pillar structure may be appropriately tilted in a height direction. 
       FIGS. 3A through 3D  show examples of shapes of the scatterers  122   a ,  122   b , and  122   c , but embodiments are not limited thereto. For example, at least one from among the scatterers  122   a ,  122   b , and  122   c  may have a polygonal prism shape or a pillar structure with a cross-section having an “L”-like shape. At least one from among the scatterers  122   a ,  122   b , and  122   c  may have a multi-layer structure formed of materials with different refractive indexes in a height direction. Also, shapes of the scatterers  122   a ,  122   b , and  122   c  may not have symmetricity in a direction. For example, a cross-section of the scatterers  122   a ,  122   b , and  122   c  may have shapes that are non-symmetrical in a horizontal direction such as, for example, an oval shape. Also, when cross-sections of the scatterers  122   a ,  122   b , and  122   c  differ according to their height, the shapes of the scatterers  122   a ,  122   b , and  122   c  may not have symmetricity with respect to the height. 
     The scatterers  122   a ,  122   b , and  122   c  may have a shape according to wavelength selectivity of the thin lenses  120   a ,  120   b , and  120   c . Here, the term “wavelength selectivity” refers to each of the thin lenses  120   a ,  120   b , and  120   c  selectively concentrating pieces of light of a predetermined wavelength band on the light sensing layer  130 . For example, the scatterers  122   a  included in the first thin-lens  120   a  may have a shape appropriate to concentrate pieces of light of the first wavelength λ 1 . In one embodiment, a cross-sectional shape of scatterers  122   a  and a ratio between a width and a height of the scatterers  122   a  may change. Also, scatterers  122   b  included in the second thin-lens  120   b  may have a shape appropriate to concentrate pieces of light of the second wavelength λ 2 . Also, scatterers  122   c  included in the third thin-lens  120   c  may have a shape appropriate to concentrate pieces of light of the third wavelength λ 3 . At least two from among the first, second, and third wavelengths λ 1 , λ 2 , and λ 3  may be different from each other. 
       FIG. 4  is a view illustrating a surface of the first thin-lens  120   a  according to an exemplary embodiment. 
     In  FIG. 4 , the first thin-lens  120   a  is used as an example, but the description with reference to  FIG. 4  may be applied to the second and third thin lenses  120   b  and  120   c.    
     Referring to  FIG. 4 , the scatterers  122   a  having pillar structures may be arranged on the substrate  110 . In  FIG. 4 , the scatterers  122   a  have circular pillar structures as an example, but embodiments are not limited thereto. For example, the scatterers  122   a  may have any of various shapes such as polygonal prism shapes, circular cylindrical shapes, or elliptic cylindrical shapes. Alternatively, cross-sections of the scatterers  122   a  may have “L”-like prism shapes. 
     A refractive index of a material included in the scatterers  122   a  may be higher than a refractive index of a material included in the substrate  110 . Thus, the substrate  110  may include a material having a relatively low refractive index, and the scatterers  122   a  may include a material having a relatively high refractive index. For example, the scatterers  122   a  may include at least one from among crystalline silicon (c-Si), polycrystalline silicon (poly Si), amorphous silicon (amorphous Si), Si 3 N 4 , GaP, TiO 2 , AlSb, AlAs, AlGaAs, AlGaInP, BP, and ZnGeP 2 . Also, for example, the substrate  110  may include one from among a polymer such as PMMA or PDMS, Si 3 N 4 , and SiO 2 . An additional clad layer that surrounds and covers the scatterers  122   a  having a high refractive index on the substrate  110  with the material having a low refractive index may be formed. 
     The arrangement of the scatterers  122   a  may be determined according to a wavelength band of light that is concentrated by the first thin-lens  120   a . For example, an interval distance T and an arrangement direction of the scatterers  122   a  included in the first thin-lens  120   a  may be determined in correspondence to the first wavelength λ 1  of light that is concentrated by the first thin-lens  120   a . The interval distance T between the scatterers  122   a  of the first thin-lens  120   a  may be smaller than the first wavelength λ 1 . In one embodiment, the interval distance T between the scatterers  122   a  of the first thin-lens  120   a  may be ¾ of the first wavelength λ 1  or less or ⅔ of the first wavelength λ 1  or less. Also, a height h of the scatterers  122   a  of the first thin-lens  120   a  may be smaller than the first wavelength λ 1 . For example, the height h of the scatterers  122   a  of the first thin-lens  120   a  may be ⅔ of the first wavelength λ 1  or less. 
       FIG. 5  is a view illustrating a surface of the first thin lens  120   a  according to another exemplary embodiment. 
     Referring to  FIG. 5 , the scatterers  122   a  have rectangular parallelepiped shapes and may be arranged on the substrate  110 . Although the scatterers  122   a  have rectangular parallelepiped shapes in  FIG. 5 , exemplary embodiments are not limited thereto. For example, the scatterers  122   a  may have any shape including polygonal prism shapes, circular cylindrical shapes, and elliptic cylindrical shapes. Alternatively, cross-sections of the scatterers  122   a  may have ‘L’-like prism shapes. Also, heights and interval distances of the scatterers  122   a  may vary according to a wavelength selectivity of the first thin-lens  120   a.    
     The description of shapes of the scatterers  122   a  made with reference to  FIGS. 4 and 5  may apply to the scatterers  122   b  and  122   c  included in the second and third thin lenses  120   b  and  120   c . However, shapes, interval distances, and arrangement directions of the scatterers  122   b  and  122   c  may vary according to a wavelength selectivity of each of the second and third thin lenses  120   b  and  120   c . For example, interval distances and heights of the scatterers  122   b  included in the second thin-lens  120   b  may be determined according to the second wavelength λ 2 . The interval distances and heights of the scatterers  122   b  included in the second thin-lens  120   b  may be smaller than the second wavelength λ 2 . Also, interval distances and heights of the scatterers  122   c  included in the third thin-lens  120   c  may be determined according to the third wavelength λ 3 . The interval distances and heights of the scatterers  122   c  included in the third thin-lens  120   c  may be smaller than the third wavelength λ 3 . 
     Referring back to  FIG. 1 , the light-sensing cells  130   a ,  130   b , and  130   c  may be configured to generate electrical signals upon sensing light that transmitted from at least one from among the thin lenses  120   a ,  120   b , and  120   c . The light-sensing cells  130   a ,  130   b , and  130   c  may be formed in the light sensing layer  130 . However, exemplary embodiments are not limited thereto, and the light-sensing cells  130   a ,  130   b , and  130   c  may be separated from each other. 
     The light-sensing cells  130   a ,  130   b , and  130   c  may be prepared in correspondence to the thin lenses  120   a ,  120   b , and  120   c . For example, a first light-sensing cell  130   a  may be configured to sense light that is transmitted from the first thin-lens  120   a . Also, a second light-sensing cell  130   b  may be configured to sense light that is transmitted from the second thin-lens  120   b . Also, a third light-sensing cell  130   c  may be configured to sense light that is transmitted from the third thin-lens  120   c . The first, second, and third light-sensing cells  130   a ,  130   b , and  130   c  may be configured to receive light and thus may output first, second, and third images, respectively. 
     Each of the light-sensing cells  130   a ,  130   b , and  130   c  may include devices that convert light signals into electrical signals. For example, the light-sensing cells  130   a ,  130   b , and  130   c  may include CCD sensors or CMOS sensors. Alternatively, the light-sensing cells  130   a ,  130   b , and  130   c  may include photodiodes that convert light energy into electrical energy. 
     Because at least two from among the first, second, and third thin lenses  120   a ,  120   b , and  120   c  have different wavelength selectivities, at least two of the first, second, and third light-sensing cells  130   a ,  130   b , and  130   c  may be configured to measure images in different colors. Therefore, the first, second, and third images measured by the first, second, and third light-sensing cells  130   a ,  130   b , and  130   c , respectively, may be synthesized to obtain a multi-color image. 
       FIG. 6  is a view illustrating an image sensor according to an exemplary embodiment. 
     In  FIG. 6 , a repeated explanation of the same elements or operations as those in  FIG. 1  will not be given. 
     Referring to  FIG. 6 , the image sensor according to an exemplary embodiment may include an image synthesizer  150  configured to synthesize images in different colors and thus produces a multi-color image. The image synthesizer  150  may synthesize the first, second, and third images obtained by the first, second, and third light-sensing cells  130   a ,  130   b , and  130   c . At least two among the first, second, and third images may be in different colors. Thus, the image synthesizer  150  may produce a multi-color image by synthesizing the first, second, and third images. The multi-color image may be an image in a plurality of colors. Also, when there are four or more light-sensing cells configured to perform an imaging process on four or more different wavelength bands, the multi-color image may be a hyperspectral image. 
     Because locations of the thin-lens  120   a ,  120   b , and  120   c  are different from each other, light reflected by an object may be incident at different angles to the thin-lens  120   a ,  120   b , and  120   c . Thus, images of the object taken from different angles may be obtained from the first, second, and third light-sensing cells  130   a ,  130   b , and  130   c , respectively. The image synthesizer  150  may produce a stereo image from the images of the object taken from different angles. During a process of producing the stereo image, the image synthesizer  150  may extract parallax information among the first, second and third images. Also, the image synthesizer  150  may be configured to extract depth information of the object that is shown in the stereo image. 
       FIG. 7  is a view illustrating an image sensor according to an exemplary embodiment. 
     In  FIG. 7 , a repeated explanation of the same elements or operations as those in  FIG. 1  will not be given. 
     Referring to  FIG. 7 , the substrate  110  may include a plurality of sub-substrates  110   a ,  110   b , and  110   c . The sub-substrates  110   a ,  110   b , and  110   c  may be formed in correspondence to a respective thin lens of the plurality of thin lenses  120   a ,  120   b , and  120   c , and a respective light-sensing cell of the plurality of light-sensing cells  130   a ,  130   b , and  130   c . For example, the first thin-lens  120   a  and the first light-sensing cell  130   a  may be formed on a first and second surface of a first sub-substrate  110   a , respectively. Also, the second thin-lens  120   b  and the second light-sensing cell  130   b  may be formed on a first and second surface of a second sub-substrate  110   b , respectively. Also, the third thin-lens  120   c  and the third light-sensing cell  130   c  may be formed on a first and second surface of a third sub-substrate  110   c , respectively. When the substrate  110  is divided into the sub-substrates  110   a ,  110   b , and  110   c , interference between pieces of light that are incident on each of the light-sensing cells  130   a ,  130   b , and  130   c  may be prevented. 
       FIG. 8  is a view illustrating an image sensor according to an exemplary embodiment. 
     In  FIG. 8 , a repeated explanation of the same elements or operations as those in  FIG. 1  will not be given. 
     Referring to  FIG. 8 , another image sensor according to an exemplary embodiment may include a plurality of light filters  140   a ,  140   b , and  140   c , and each light filter in the plurality of light filters  140   a ,  140   b , and  140   c  is configured to filter wavelength components of pieces of light incident on a respective light-sensing cell of the plurality of light-sensing cells  130   a ,  130   b , and  130   c . The plurality of light filters  140   a ,  140   b , and  140   c  may be included in a single light filter layer  140 . However, this is provided herein as an example, and the plurality of light filters  140   a ,  140   b , and  140   c  may be included in separate light filter layers from one another. The light filters of the plurality of light filters  140   a ,  140   b , and  140   c  may be prepared in correspondence to a respective light-sensing cell of the plurality of light-sensing cells  130   a ,  130   b , and  130   c . For example, a first light filter  140   a  may filter a wavelength of light incident on the first light-sensing cell  130   a . Also, a second light filter  140   b  may filter a wavelength of light incident on the second light-sensing cell  130   b . Also, a third light filter  140   c  may filter a wavelength of light incident on the third light-sensing cell  130   c.    
     The first light filter  140   a  may allow only a predetermined wavelength component from incident light to transmit therethrough according to a wavelength selectivity of the first thin-lens  120   a . For example, light of the first wavelength λ 1  from among incident light may transmit through the first light filter  140   a , and the first light filter  140   a  may allow light of the remaining wavelength components to be reflected or absorbed. In the same manner, light of the second wavelength λ 2  from among incident light may transmit through the second light filter  140   b , and the second light filter  140   b  may allow light of the remaining wavelength components to be reflected or absorbed. Also, light of the third wavelength λ 3  from among incident light may transmit through the third light filter  140   c , and the third light filter  140   c  may allow light of the remaining wavelength components to be reflected or absorbed. 
       FIG. 8  shows an example of the light filters  140   a ,  140   b , and  140   c  formed at locations where light incident on the thin lenses  120   a ,  120   b , and  120   c  transmit therethrough. However, exemplary embodiments are not limited thereto. For example, the light filters  140   a ,  140   b , and  140   c  may be formed between the thin lenses  120   a ,  120   b , and  120   c  and the light-sensing layer  130 . In this case, wavelengths of light transmitted through the light filters  140   a ,  140   b , and  140   c  and the thin lenses  120   a ,  120   b , and  120   c  may be filtered. In any cases, the light filters  140   a ,  140   b , and  140   c  may filter wavelength components of light that is incident on the light-sensing cells  130   a ,  130   b , and  130   c  of the light-sensing layer  130 , respectively. Because the light filters  140   a ,  140   b , and  140   c  filter wavelengths of incident light, a phenomenon of light of a wavelength band beyond the wavelength selectivity of each of the thin lenses  120   a ,  120   b , and  120   c  (where, the phenomenon is also referred to as “optical crosstalk”) may be prevented from being incident on the light-sensing cells  130   a ,  130   b , and  130   c . Also, quality of images obtained from the light-sensing cells  130   a ,  130   b , and  130   c  may improve. 
       FIG. 9  is a view illustrating an image sensor according to another exemplary embodiment. 
     In  FIG. 9 , a repeated explanation of the same elements or operations as those in  FIGS. 1 through 8  will not be given. 
     Referring to  FIG. 9 , the image sensor according to an exemplary embodiment may include a substrate  210 , a plurality of thin lenses  220   a ,  220   b , and  220   c  that are formed on a first surface S 1  of the substrate  210  and concentrate pieces of light that are incident on the first surface S 1 , and a plurality of light-sensing cells  230   a ,  230   b , and  230   c  that are formed on a second surface S 2  facing the first surface S 1  of the substrate  210  and generate electrical signals upon sensing light that has transmitted through the plurality of thin lenses  220   a ,  220   b , and  220   c.    
     The substrate  210  may include a transparent material. As used herein, the term “transparent material” denotes a material having a high light transmittance. For example, the substrate  210  may include at least one from among Si 3 N 4 , SiO 2 , and a polymer such as PMMA or PDMS. Once a path of incident light changes by the thin lenses  220   a ,  220   b , and  220   c , the incident light may pass through the substrate  210  and be incident on a light sensing layer  230 . The substrate  210 , similar to an exemplary embodiment shown in  FIG. 7 , may include a plurality of sub-substrates. 
       FIG. 10  is a view illustrating an example of the substrate  210  including a plurality of sub-substrates  210   a ,  210   b , and  210   c , according to an exemplary embodiment. 
     Referring to  FIG. 10 , the sub-substrates  210   a ,  210   b , and  210   c  may be formed in correspondence to a respective thin lens of the plurality of thin lenses  220   a ,  220   b , and  220   c  and a respective light-sensing cell of the plurality of light-sensing cells  230   a ,  230   b , and  230   c . For example, a first thin-lens  220   a  and a first light-sensing cell  230   a  may be formed on a first and second surface of a first sub-substrate  210   a , respectively. Also, a second thin-lens  220   b  and a second light-sensing cell  230   b  may be formed on a first and second surface of a second sub-substrate  210   b , respectively. Also, a third thin-lens  220   c  and a third light-sensing cell  230   c  may be formed on a first and second surface of a third sub-substrate  210   c , respectively. When the substrate  210  is divided into the plurality of sub-substrates  210   a ,  210   b , and  210   c , interference between pieces of light that are incident on each of the light-sensing cells  130   a ,  130   b , and  130   c  may be prevented. 
     The thin lenses  220   a ,  220   b , and  220   c  may include a plurality of scatterers  222   a ,  222   b , and  222   c . At least two from among the thin lenses  220   a ,  220   b , and  220   c  may be configured to concentrate pieces of the incident light on the light-sensing cells  230   a ,  230   b , and  230   c  to have different focal lengths. For example, the first thin-lens  220   a  may concentrate pieces of the incident light to have a first focal length f 1  in a direction toward the first light-sensing cell  230   a . Also, the second thin-lens  220   b  may concentrate pieces of the incident light to have a second focal length f 2  in a direction toward the second light-sensing cell  230   b . Also, the third thin-lens  220   c  may concentrate pieces of the incident light to have a third focal length f 3  in a direction toward the third light-sensing cell  230   c . This is provided herein as an example only, and exemplary embodiments are not limited thereto. For example, the first through third thin lenses  220   a ,  220   b , and  220   c  do not necessarily have to concentrate pieces of incident light to have focal lengths that are all different from one another, and two from among the first through third thin lenses  220   a ,  220   b , and  220   c  may concentrate pieces of incident light to have substantially the same focal length. 
     Descriptions of exemplary embodiments provided herein with reference to  FIGS. 2 through 5  may apply to surfaces of the thin lenses  220   a ,  220   b , and  220   c . The scatterers  222   a ,  222   b , and  222   c  included in the thin lenses  220   a ,  220   b , and  220   c  may have pillar structures. The scatterers  222   a ,  222   b , and  222   c  may have a shape of a cross-section of the pillar structure that may be from among a circle, an oval, a rectangle, and a square. Also, the scatterers  222   a ,  222   b , and  222   c  may have a polygonal prism shape or a pillar structure with a cross-section having an “L”-like shape. Shapes of the scatterers  222   a ,  222   b , and  222   c  may not have symmetricity in a direction. For example, a cross-section of the scatterers  222   a ,  222   b , and  222   c  may have a shape that is not symmetrical in a horizontal direction as, for example, an oval shape. Also, when cross-sections of the scatterers  222   a ,  222   b , and  222   c  differ according to its height, the shapes of the scatterers  222   a ,  222   b , and  222   c  may be asymmetric with respect to the height. 
     Shapes of the scatterers  222   a ,  222   b , and  222   c  may vary depending on focal lengths of the thin lenses  220   a ,  220   b , and  220   c . For example, scatterers  222   a  included in the first thin-lens  220   a  may have a shape appropriate to concentrate pieces of light to have a first focal length f 1 . In one exemplary embodiment, a cross-sectional shape of the scatterers  222   a  and a ratio between a width and a height of the scatterers  122   a  may change. Also, scatterers  222   b  included in the second thin-lens  220   b  may have a shape appropriate to concentrate pieces of light to have a second focal length f 2 . Also, scatterers  222   c  included in the third thin-lens  220   c  may have a shape appropriate to concentrate pieces of light to have a third focal length f 3 . At least two from among the first through third focal lengths f 1 , f 2 , and f 3  may be different from each other. Also, interval distances among the scatterers  222   a ,  222   b , and  222   c  and heights of the scatterers  222   a ,  222   b , and  222   c  may differ according to focal lengths of the thin lenses  220   a ,  220   b , and  220   c.    
     When the focal lengths of the thin lenses  220   a ,  220   b , and  220   c  change, images that are defocused to different degrees may be formed on the light-sensing cells  230   a ,  230   b , and  230   c . Defocusing degrees of the images formed on the light-sensing cells  230   a ,  230   b , and  230   c  may differ according to the focal lengths of the thin lenses  220   a ,  220   b , and  220   c  and distances between an object and the thin lenses  220   a ,  220   b , and  220   c . Therefore, when a defocusing degree for each position of an image measured by each of the light-sensing cells  230   a ,  230   b , and  230   c  is compared with those of images measured by light-sensing cells and then extracted, distances between the thin lenses  220   a ,  220   b , and  220   c  and the object and a 3-dimensional shape may be obtained. 
       FIG. 11  is a view illustrating an image sensor according to an exemplary embodiment. 
     Referring to  FIG. 11 , the image sensor may further include a depth map calculator  250  that is configured to calculate depth map information of an image corresponding to incident light. The depth map calculator  250  may receive images measured by the light-sensing cells  230   a ,  230   b , and  230   c . Also, the depth map calculator  250  may recognize a relative blur degree for each position of the images measured by one from among the light-sensing cells  230   a ,  230   b , and  230   c . Also, the depth map calculator  250  may calculate a defocusing degree for each position of the images measured by one from among the light-sensing cells  230   a ,  230   b , and  230   c.    
     The depth map calculator  250  may calculate depth map information of an image corresponding to the incident light from the defocusing degree measured by each of the light-sensing cells  230   a ,  230   b , and  230   c  and the focal length of each of the thin lenses  220   a ,  220   b , and  220   c . For example, the depth map calculator  250  may calculate a distance from each of a plurality of points on each of objects or a surface of an object included in the image to each of the thin lenses  220   a ,  220   b , and  220   c . In this regard, as the depth map calculator  250  calculates the depth map information, the image sensor may obtain a 3-dimensional image of the object. 
     The thin lenses  220   a ,  220   b , and  220   c  may each concentrate pieces of light having a predetermined wavelength component. The thin lenses  220   a ,  220   b , and  220   c  may function as an optical device with respect to a predetermined wavelength band of incident light. Shapes, a shape of arrangement, interval distances, and heights of the scatterers  222   a ,  222   b , and  222   c  included in the thin lenses  220   a ,  220   b , and  220   c  may be determined according to wavelength selectivity of the thin lenses  220   a ,  220   b , and  220   c.    
     For example, to output an image with one color, all the thin lenses  220   a ,  220   b , and  220   c  may have substantially the same wavelength selectivity. The thin lenses  220   a ,  220   b , and  220   c  may all concentrate light of substantially the same wavelength component. Also, shapes, a shape of arrangement, interval distances, and heights of the scatterers  222   a ,  222   b , and  222   c  included in the thin lenses  220   a ,  220   b , and  220   c  may be determined according to focal lengths of the thin lenses  220   a ,  220   b , and  220   c . Heights and interval distances of the scatterers  222   a ,  222   b , and  222   c  may be smaller than a wavelength of light that is concentrated by the thin lenses  220   a ,  220   b , and  220   c.    
       FIG. 12  is a view illustrating an image sensor according to an exemplary embodiment. 
     Referring to  FIG. 12 , the image sensor may include a light filter layer  240  that filters wavelength components of light incident on each of the light-sensing cells  230   a ,  230   b , and  230   c . Although the light filter layer  240  illustrated in  FIG. 12  is prepared at a position where the light incident on the light-sensing cells  230   a ,  230   b , and  230   c  travels, exemplary embodiments are not limited thereto. In one or more exemplary embodiments, the light filter layer  240  may be positioned between the thin lenses  220   a ,  220   b , and  220   c  and the light sensing layer  230  including the light-sensing cells  230   a ,  230   b , and  230   c . The light filter layer  240  may allow a predetermined wavelength λ 0  component among the incident light to transmit therethrough and may reflect or absorb the remaining wavelength components. Because the light filter layer  240  filters the wavelengths of the incident light, noise light of undesired wavelengths may be prevented from being incident on the light-sensing cells  230   a ,  230   b , and  230   c . Also, quality of images obtained from the light-sensing cells  230   a ,  230   b , and  230   c  may improve. 
     The thin lenses  220   a ,  220   b , and  220   c  may each concentrate pieces of light having different wavelengths to have different focal lengths. For example, the first thin-lens  220   a  may concentrate light having a first wavelength λ 1  to have a first focal length f 1 . The scatterers  222   a  included in the first thin-lens  220   a  may have a shape of arrangement and interval distances appropriate to concentrate pieces of light having the first wavelength λ 1  to have the first focal length f 1 . Also, the second thin-lens  220   b  may concentrate light having a second wavelength λ 2  to have a second focal length f 2 . The scatterers  222   b  included in the second thin-lens  220   b  may have a shape of arrangement and interval distances appropriate to concentrate pieces of light having the second wavelength λ 2  to have the second focal length f 2 . Also, the third thin-lens  220   c  may concentrate light having a third wavelength λ 3  to have a third focal length f 3 . The scatterers  222   c  included in the third thin-lens  220   c  may have a shape of arrangement and interval distances appropriate to concentrate pieces of light having the third wavelength λ 3  to have the third focal length f 3 . 
     Heights and interval distances of the scatterers  222   a ,  222   b , and  222   c  included in the thin lenses  220   a ,  220   b , and  220   c  may vary according to wavelength selectivities of  220   a ,  220   b , and  220   c , respectively. For example, interval distances between the scatterers  222   a  and heights of the scatterers  222   a  in the first thin-lens  220   a  may be smaller than the first wavelength λ 1 . Also, interval distances between the scatterers  222   b  and heights of the scatterers  222   b  in the second thin-lens  220   b  may be smaller than the second wavelength λ 2 . Also, interval distances between the scatterers  222   c  and heights of the scatterers  222   c  in the third thin-lens  220   c  may be smaller than the third wavelength λ 3 . 
       FIG. 13  is a view illustrating an image sensor according to an exemplary embodiment. 
     Referring to  FIG. 13 , the image sensor may include a light filter layer  240  configured to filter wavelength components of light incident on each of the light-sensing cells  230   a ,  230   b , and  230   c . The light filter layer  240  may include a plurality of light filters  240   a ,  240   b , and  240   c . The light filters  240   a ,  240   b , and  240   c  may be applied in correspondence to the light-sensing cells  230   a ,  230   b , and  230   c . For example, a first light filter  240   a  may be configured to filter a wavelength of light incident on a first light-sensing cell  230   a . Also, a second light filter  240   b  may be configured to filter a wavelength of light incident on a second light-sensing cell  230   b . Also, a third light filter  240   c  may be configured to filter a wavelength of light incident on a third light-sensing cell  230   c.    
     The first light filter  240   a  may transmit a predetermined wavelength component among incident light according to a wavelength selectivity of the first thin-lens  220   a . For example, the first light filter  240   a  may allow light having a first wavelength λ 1  to transmit therethrough and reflect or absorb light of the remaining wavelength components. In the same manner, the second light filter  240   b  may allow light having a second wavelength λ 2  to transmit therethrough and reflect or absorb light of the remaining wavelength components. Also, the third light filter  240   c  may allow light having a third wavelength λ 3  to transmit therethrough and reflect or absorb light of the remaining wavelength components. Because the light filters  240   a ,  240   b , and  240   c  filter wavelengths of incident light, noise light of undesired wavelengths may be prevented from being incident on the light-sensing cells  230   a ,  230   b , and  230   c . Also, quality of images obtained from the light-sensing cells  230   a ,  230   b , and  230   c  may improve. Further, the light-sensing cells  230   a ,  230   b , and  230   c  each generate images in different colors, and thus a multi-color image may be produced by synthesizing the images. 
     As described above, according to the one or more of the above exemplary embodiments, an image sensor has been described with reference to  FIGS. 1 through 13 . The image sensor may concentrate pieces of incident light by using a plurality of thin lenses. In this regard, a size of the image sensor may be reduced. Also, at least one from among a plurality of operation characteristics of the thin lenses may be controlled by changing at least one from among shapes, a shape of arrangement, interval distances, and sizes of the thin lenses. Therefore, the image sensor may be easily manufactured. In addition, a 3-dimensional image, a multi-color image, and depth map information of an object may be easily obtained from imaged generated from a plurality of light-sensing cells. 
     The foregoing exemplary embodiments are examples and are not to be construed as limiting. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.