Optical element, imaging element, and imaging device

Abstract

The optical element array (120) has: a transparent layer (150) for covering the pixel (130) containing the photoelectric conversion element; and a plurality of columnar structures (160) arranged on or within the transparent layer (150) along the surface direction of the transparent layer (150) to guide incident light toward the corresponding photoelectric conversion element, wherein the plurality of columnar structures (160) are formed on the entire surface of the transparent layer (150) at intervals shorter than the wavelength of the incident light.

Description

Technical Field

[0001] This invention relates to optical elements, imaging elements, and imaging devices. Background Technology

[0002] Typical camera devices use lens optical systems and 2D imaging elements such as CCD (Charge Coupled Device) sensors or CMOS (Complementary Metal Oxide Semiconductor) sensors to obtain 2D images composed of light intensity and color information from the object being photographed.

[0003] In a camera device, in order to separate the color of incident light on each pixel containing a photoelectric conversion element, a color filter corresponding to each pixel is provided on a pixel array having pixels containing photoelectric conversion elements arranged in a 2D array. Furthermore, in order to improve sensitivity characteristics, an on-chip microlens (hereinafter referred to as an on-chip lens) is formed on the color filter, and the on-chip lens, which is used for incident light, focuses the light onto the photoelectric conversion element.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-084608 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Figure 25 and Figure 26 This is a top view of the on-plate lens. For example... Figure 25 and Figure 26 As shown, on-chip lenses 220 or 320 are formed on each pixel 200R, 200G, and 200B of the pixel array 210. However, gaps 220E and 320E exist between the on-chip lenses 220 and 320. Light incident outside the lens opening areas such as the gaps 220E and 320E cannot be effectively focused onto the photoelectric conversion element. Therefore, in the existing on-chip lenses 220 and 320, not all incident light can be received, and the light-receiving efficiency is limited.

[0009] The present invention was made in view of the above circumstances, and its object is to provide an optical element, a camera element, and a camera device that can improve light-receiving efficiency compared with the past.

[0010] Methods for solving problems

[0011] To solve the above-mentioned problems and achieve the objective, the optical element of the present invention is characterized by having: a transparent layer for covering a pixel including a photoelectric conversion element; and a plurality of columnar structures arranged on or within the transparent layer along the surface direction of the transparent layer to guide incident light toward the corresponding photoelectric conversion element, wherein the plurality of columnar structures are formed on the entire surface of the transparent layer at intervals shorter than the wavelength of the incident light.

[0012] Furthermore, the imaging element of the present invention is characterized by having the optical element described above and a plurality of pixels each comprising a photoelectric conversion element.

[0013] Furthermore, the camera device of the present invention is characterized by having: the camera element described above; and a signal processing unit that processes the electrical signal output by the camera element and generates an image.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to provide an imaging element and imaging device that can improve light-receiving efficiency compared with the past. Attached Figure Description

[0016] Figure 1 This is a side view illustrating the schematic structure of the camera device in an embodiment.

[0017] Figure 2 This is a diagram schematically illustrating a portion of the cross-section of the pixel array and the polarization wavelength separation lens array of the imaging element in an embodiment.

[0018] Figure 3 This is a diagram schematically showing a portion of a cross-section of the pixel array and optical element array at the central portion of the imaging element in an embodiment.

[0019] Figure 4 This is a diagram schematically showing a portion of a cross-section of the pixel array and optical element array on the outer periphery of the camera element in an embodiment.

[0020] Figure 5 This is a top view of the optical element array at the center of the camera element in the embodiment.

[0021] Figure 6 This is a diagram showing the minimum structural height and maximum aspect ratio of a medium-approximate structure in the prior art and a columnar structure in the embodiment.

[0022] Figure 7 This is a side view of a columnar structure.

[0023] Figure 8 This is a top view of the columnar structure.

[0024] Figure 9This is a graph showing the relationship between the width of a columnar structure and the transmittance of light.

[0025] Figure 10 This is a diagram showing the relationship between the width of the columnar structure and the phase characteristics of the light emitted by the columnar structure.

[0026] Figure 11 It is a diagram illustrating the definition of the angle of incidence.

[0027] Figure 12 It shows that light at θ = 0°, The diagram shows the phase distribution as the design objective of the lens and the lens pattern that achieves this phase distribution, under the condition of incident angle.

[0028] Figure 13 It shows that light travels at θ = 45°. The diagram shows the phase distribution as the design objective of the lens and the lens pattern that achieves this phase distribution, under the condition of incident angle.

[0029] Figure 14 It shows that light travels at θ = 45°. The diagram shows the phase distribution as the design objective of the lens and the lens pattern that achieves this phase distribution, under the condition of incident angle.

[0030] Figure 15 This is a graph showing the focusing intensity of an optical element unit and its wavelength dependence.

[0031] Figure 16 This is a graph showing the focusing intensity of an optical element unit and its wavelength dependence.

[0032] Figure 17 This is a graph showing the focusing intensity of an optical element unit and its wavelength dependence.

[0033] Figure 18 It is shown A graph showing the dependence of the focusing intensity of an optical element unit on the incident angle of parallel light (λ = 520 nm) incident on the incident light.

[0034] Figure 19 It is shown A graph showing the dependence of the focusing intensity of an optical element unit on the incident angle of parallel light (λ = 520 nm) incident on the incident light.

[0035] Figure 20 It is shown A graph showing the dependence of the focusing intensity of an optical element unit on the incident angle of parallel light (λ = 520 nm) incident on the incident light.

[0036] Figure 21 It is shown A graph showing the dependence of the focusing intensity of an optical element unit on the incident angle of parallel light (λ = 520 nm) incident on the incident light.

[0037] Figure 22 It is shown A graph showing the dependence of the focusing intensity of an optical element unit on the incident angle of parallel light (λ = 520 nm) incident on the incident light.

[0038] Figure 23 It is shown A graph showing the dependence of the focusing intensity of an optical element unit on the incident angle of parallel light (λ = 520 nm) incident on the incident light.

[0039] Figure 24 This is another example of a cross-section schematically showing a portion of the pixel array and optical element array in a camera element of an embodiment.

[0040] Figure 25 This is a top view of the lens on the film.

[0041] Figure 26 This is a top view of the lens on the film. Detailed Implementation

[0042] The following describes the best mode for carrying out the present invention and accompanying drawings. Figure 1 A detailed description will follow. Furthermore, in the following description, the figures are only schematic representations of shapes, sizes, and positional relationships to the extent that the content of the invention can be understood; therefore, the invention is not limited to the shapes, sizes, and positional relationships illustrated in the figures. Additionally, in the accompanying drawings, the same symbols are used to denote the same parts.

[0043] [Implementation Method]

[0044] [Camera device]

[0045] First, the camera device according to an embodiment of the present invention will be described. Figure 1 This is a side view showing the schematic structure of the camera device according to the embodiment.

[0046] like Figure 1 As shown, the imaging device 10 of the embodiment includes a lens optical system 11, an imaging element 12, and a signal processing unit 13. The imaging element 12 has a photoelectric conversion element such as a CCD or CMOS. The signal processing unit 13 processes the photoelectric conversion signal output from the imaging element 12 to generate an image signal.

[0047] Natural light, illumination light, or other light is shone onto object 1. Light that passes through object 1, is reflected / scattered by object 1, or is emitted from object 1, forms an optical image on the imaging element 12 through the lens optical system 11. Generally, to correct various optical aberrations, the lens optical system 11 consists of a lens group, which is composed of multiple lenses arranged along the optical axis. Figure 1 A single lens is shown in the simplified accompanying drawings. The signal processing unit 13 has an image signal output that sends the generated image signal to the outside.

[0048] Furthermore, the imaging device 10 may include known structural elements such as an optical filter for blocking infrared light, an electronic shutter, a viewfinder, a power supply (battery), and a flash, but their descriptions are not particularly necessary for understanding the present invention, and therefore are omitted. Also, the above structure is merely an example; in embodiments, known elements can be appropriately combined and used as structural elements other than the lens optical system 11, the imaging element 12, and the signal processing unit 13.

[0049] [Camera Components]

[0050] Next, a general description of the imaging element 12 in the embodiment will be given. Figure 2 This is a schematic cross-sectional view showing the main parts of the lens optical system 11 and the imaging element 12 of the embodiment. Figure 2 From now on, a portion of the imaging element 12 will be described as the imaging element 100. The imaging element 100 has an optical element array (optical elements) formed on the entire surface of a color filter. This optical element is composed of multiple columnar structures that guide incident light to photoelectric conversion elements of the pixel array. Furthermore, in the imaging element 100, as... Figure 2 As shown, since the incident angle θ of light from the lens optical system 11 to the imaging element 100 is different in the central and peripheral portions, the plurality of columnar structures formed in the optical element array are configured to have a phase characteristic that guides the incident light downwards to the photoelectric conversion element corresponding to the incident angle of the incident light. Hereinafter, using... Figures 3 to 5 The structure of the camera element 100 will be explained.

[0051] Figure 3 This is a diagram schematically showing a portion of a cross-section of the pixel array and optical element array at the central portion of the imaging element in an embodiment. Figure 4 This is a diagram schematically showing a portion of a cross-section of the pixel array and optical element array in the outer periphery of the imaging element according to an embodiment. Figure 5 This is a top view of the optical element array at the center of the camera element in the embodiment.

[0052] like Figure 3and Figure 4 As shown, the imaging element 100 has a pixel array 110 and an optical element array 120 disposed opposite to the pixel array 110. The optical element array 120 is disposed on the side where light from the lens optical system 11 is incident. The optical element array 120 is formed on the upper surface of the transparent layer 150 formed on the pixel array 110. A color filter 170 corresponding to each pixel is provided on the pixel array 110. In addition, the transparent layer 150 is a low refractive index transparent layer made of a material such as SiO2 (refractive index n = 1.45).

[0053] The pixel array 110 has a wiring layer 180 and pixels 130 containing photoelectric conversion elements arranged in a 2D array. Pixels 130 of pixel unit 140L, for example, receive G light, and pixels 130 of pixel unit 140R receive R light.

[0054] The optical element array 120 consists of optical elements arranged in a two-dimensional array, each optical element comprising a plurality of columnar structures 160 that guide incident light toward the photoelectric conversion element of the corresponding pixel 130 directly below it. For example, in Figure 5 The image shows the case where the wavelength regions separated by color filter 170 are red (R), green (G), and blue (B). Figure 5 In the optical element array 120, optical element units 120R (optical element) corresponding to R pixel units, two optical element units 120G (optical elements) corresponding to G pixel units, and optical element units 120B (optical elements) corresponding to B pixel units are formed as a group on a 2D array. Directly below the aforementioned optical element units 120R (optical element) corresponding to R pixel units, two optical element units 120G (optical elements) corresponding to G pixel units, and optical element units 120B (optical elements) corresponding to B pixel units, the R pixel units receiving R light, the two G pixel units receiving G light, and the B pixel units receiving B light on the pixel array 110 are arranged.

[0055] Multiple columnar structures 160 are formed using a material with a refractive index higher than that of the surrounding materials (transparent layer 150, air). This effectively traps light within the columnar structures 160, preventing light coupling with adjacent columnar structures. The columnar structures 160 are formed, for example, using SiN (refractive index n = 2.05) or TiO2 (refractive index n = 2.4).

[0056] like Figure 3 and Figure 4 As shown, multiple columnar structures 160 are formed to the same height when viewed from the side. The multiple columnar structures 160 are formed across the entire surface of the optical element array 120 at intervals shorter than the wavelength of the incident light. Figure 5As shown, when viewed from above, the optical element units 120R, 120G, and 120B exhibit a lattice-like structure formed by multiple columnar structures 160. These multiple columnar structures 160 are prisms. Furthermore, Figure 5 One example is that columnar structures can also be structures that are 4-fold rotationally symmetric when viewed from above, such as hollow squares, circles, hollow circles, or crosses.

[0057] When viewed from above, the plurality of columnar structures 160 are formed with a width w having a phase characteristic that guides incident light to the photoelectric conversion element of the corresponding pixel 130 directly below, corresponding to the incident angle of the incident light from each columnar structure. Each of the plurality of columnar structures 160 imparts an optical phase delay to the incident light corresponding to the width of the columnar structure 160 when viewed from above.

[0058] In optical element units 120R, 120G, and 120B, each of the plurality of columnar structures 160 constituting the optical element units 120R, 120G, and 120B has a width that imparts an optical phase retardation distribution for guiding incident light to the photoelectric conversion elements of the corresponding R pixel unit, G pixel unit, and B pixel unit. In optical element units 120R, 120G, and 120B, the top-view width of each of the plurality of columnar structures 160 forming the optical element units 120R, 120G, and 120B is set to impart an optical phase retardation distribution that guides incident light to the photoelectric conversion elements directly below the optical element units 120R, 120G, and 120B, corresponding to the incident angle of the incident light. Furthermore, the optical phase retardation distribution is an optical phase retardation amount used for converging light.

[0059] In the imaging element 100, a lens function is achieved by forming columnar structures 160 with the same height and gradually varying widths on the entire surface of the optical element array 120. Each columnar structure 160 operates like a columnar optical waveguide. Therefore, in the imaging element 100, by varying the width of the columnar structure 160, the effective refractive index of the columnar structure 160 can be varied, and the phase of the transmitted light can be freely controlled.

[0060] In other words, each columnar structure 160 functions as a subwavelength optical waveguide, and due to the confinement of light, there is almost no optical coupling between it and adjacent columnar structures 160. Therefore, by designing the top-view width w of each columnar structure 160 separately, different optical properties (e.g., phase retardation properties) can be assigned to each of the multiple columnar structures 160. By making the spatial distribution of this phase retardation similar to that of a (Fresnel) lens, the columnar structures 160 can be given lens functionality.

[0061] Here, Non-Patent Document 1 describes a structure made of low-refractive materials such as SiO2 that functions as a lens.

[0062] Non-Patent Document 1 describes an approximation where, when the structure is very small compared to the wavelength, the effective refractive index of the structure can be represented by the approximate average of the refractive indices of the structure lens and the surrounding material. However, when the difference between the refractive index of the structure and the surrounding material is large, and the size of the structure is approximately subwavelength, light is confined inside the structure, exciting waveguide modes and resonant modes, thus making this approximation unsuitable. Therefore, the structure described in Non-Patent Document 1 is limited to a combination of materials with a small refractive index difference, such as SiO2 and air, resulting in a larger aspect ratio of the structure.

[0063] In contrast, in the imaging element 100, each columnar structure 160 is formed using a high-refractive-index material such as SiN or TiO2. Therefore, the minimum height of the columnar structure 160 required to achieve a phase change of 0–2π is lower than that of structures made of low-refractive-index materials such as SiO2 (see Non-Patent Document 1). Consequently, the minimum structural height required for 0–2π phase control of the imaging element 100 is relatively small, and the lens function can be achieved with easily manufactured, low-aspect-ratio columnar structures 160.

[0064] Furthermore, the multiple columnar structures 160 are prisms with square bases. Thus, in the imaging element 100, by making each columnar structure 160 a square with four-fold rotational symmetry when viewed from above, it achieves a characteristic that is independent of polarized light. It should be noted that, according to the theoretical formula, the effective refractive index of the structure described in Non-Patent Document 1 is clearly polarization-dependent.

[0065] Furthermore, Non-Patent Document 1 describes a structure with curved surfaces and steps. In contrast, each columnar structure 160 in this embodiment is a binary prismatic pattern without step differences. Therefore, the imaging element 100 can exclude curved surfaces and steps from the cross-section of the columnar structure, and thus the columnar structure 160 is easier to manufacture than the structure described in Non-Patent Document 1.

[0066] In addition, in the camera element 100, a lens function is achieved by forming a plurality of columnar structures 160 on the entire surface of the optical element array 120, so that all incident light can be received and the lens opening can be maximized.

[0067] Furthermore, each columnar structure 160, when viewed from above, is formed with a width w having a phase characteristic corresponding to the incident angle of the incident light on each columnar structure 160, which guides the photoelectric conversion element of the pixel 130 directly below. That is, in the imaging element 100, the structural pattern of the columnar structure 160 can be optimized for each pixel to improve light-receiving efficiency based on the principal incident angle. In other words, in the imaging element 100, the shape pattern of the columnar structure 160 when viewed from above is optimized based on the incident angle θ of the light incident on each columnar structure 160.

[0068] Therefore, in the imaging element 100, the outer periphery (refer to) where light is incident at a large incident angle θ Figure 4 ) and the central part where light is incident perpendicularly (refer to Figure 3 In any of the components, the columnar structure 160 can focus light onto the photoelectric conversion element of the pixel 130 directly below. Therefore, the image sensor 100 can focus more light onto the photoelectric conversion element directly below, and can generate an image signal with uniform brightness throughout the image sensor 100.

[0069] [Height of the columnar structure]

[0070] Next, the height of the columnar structure 160 as viewed from the side will be explained. Hereinafter, the height of the columnar structure 160 as viewed from the side will be recorded as the height of the columnar structure 160. Furthermore, the width of the columnar structure 160 as viewed from above will be recorded as the width of the columnar structure 160. Here, the minimum height of the columnar structure 160 required for phase control from 0 to 2π will be explained.

[0071] If we define the wavelength of light in a vacuum as λ, the height of the columnar structure 160 as h, and the effective refractive index of the columnar structure 160 as n... eff If the refractive index of the surrounding material is set to n0, then the phase retardation based on the columnar structure 160 is... It is represented by equation (1).

[0072] [Mathematical Expression 1]

[0073]

[0074] Formula (1) applies to both the columnar structure 160 of the imaging element 100 and the structure described in Non-Patent Document 1 (hereinafter referred to as the effective medium approximation structure).

[0075] Given that the effective refractive index n is approximately 100% in the case of an effective medium approximation structure. eff It is determined by the area ratio of the structure to the surrounding material. In the case where the effective medium approximates the structure, n... effThe value of also varies with polarized light. Furthermore, in the case of the columnar structure 160, the optical waveguide mode depends to a large extent on the width of the columnar structure 160, thus the effective refractive index n can be determined. eff It is expressed as a function of the width w of the columnar structure 160. Whether in the case of the effective medium approximation structure or the columnar structure 160, n0 < n eff < The value of n1. Additionally, n1 is the refractive index of the material that makes up the structure.

[0076] Therefore, in order to control the phase change between 0 and 2π, the height of the structure needs to be set as Equation (2).

[0077] [Mathematical Expression 2]

[0078] h≥λ0 / (n1-n0)…(2)

[0079] Figure 6 This is a diagram showing the minimum structural height and maximum aspect ratio of the prior art's medium-approximate structure and the columnar structure 160 in the embodiment. Figure 6 In this study, the minimum structural width when the wavelength of light is 635nm is set to 100nm, and the maximum aspect ratio is calculated.

[0080] To apply the effective medium approximation, n1-n0 needs to be reduced. Therefore, in the case of the construct with the effective medium approximation, the required height of the construct is necessarily... Figure 6 As shown, it reaches a height of 1411nm, requiring several wavelengths.

[0081] In contrast, in the case of columnar structure 160, from the viewpoint of blocking light, it is preferable to have a larger n1, so the value of n1-n0 is larger than that of the effective medium approximation structure. For example, the material forming columnar structure 160 is SiN (n=2.05) or TiO2 (n=2.4), and n1-n0≥0.7.

[0082] Therefore, in columnar structure 160, the required structural height is lower than that of the effective medium approximation structure, such as... Figure 6 As shown, it is generally less than one wavelength. Thus, the aspect ratio of the columnar structure 160 is lower than that of the effective medium approximation structure.

[0083] [Structure of columnar structures]

[0084] An example of the structure of columnar structure 160 is described. Figure 7 This is a side view of columnar structure 160. Figure 8 This is a top view of the columnar structure 160. (Example) Figure 7 and Figure 8As shown, for example, columnar structures 160 are formed on the upper surface of a transparent layer 150u made of quartz. Furthermore, the height (length in the z-axis direction) of the columnar structures 160 is set to h = 1000 nm, and the arrangement period of the columnar structures 160 is set to 320 nm. The width w of the columnar structures 160 is set corresponding to the phase of 0–2π that should be controlled.

[0085] Figure 9 This is a graph showing the relationship between the width w of the columnar structure 160 and the light transmittance. Figure 10 This is a diagram showing the relationship between the width w of the columnar structure 160 and the phase characteristics of the light emitted by the columnar structure 160.

[0086] like Figure 9 As shown, even when the width w of the columnar structure 160 is varied between 100 and 240 nm, high transmittance can be maintained. Furthermore, by adjusting the width w of the columnar structure 160 between 100 and 240 nm, the phase of the light transmitted through the columnar structure 160 can be controlled to a desired phase between 0 and 2π. Additionally, in Figure 9 and Figure 10 Even when the width of the columnar structure 160 is reduced to 100 nm, the maximum aspect ratio of the columnar structure 160 can be suppressed to 10.

[0087] [Lens Design]

[0088] In the imaging element 100 of this embodiment, the phase distribution of the columnar structure 160, which functions as a lens, is designed to focus light towards the center of the pixel 130 below the optical element array 120, corresponding to the angle of incidence. Furthermore, in the imaging element 100, by referring to... Figure 10 The phase characteristics are determined by setting the width w of each columnar structure 160 to achieve the designed phase distribution, thereby realizing the ideal phase distribution as the design goal.

[0089] For example, the parameters of a design example are shown below.

[0090] The size of one photoelectric conversion element is equal to the area of ​​the lens: 3.2μm × 3.2μm

[0091] Focal length: 3.2μm

[0092] Design wavelength: 520nm

[0093] Figure 11 This is a diagram illustrating the definition of the angle of incidence. For example... Figure 11 As shown, for light with The case of incidence at a certain angle of incidence will be explained. The phase distribution of light converges at a point directly below the center of the lens (cylindrical structure 160) with a focal length f. It is represented by the following equation (3).

[0094] [Mathematical Expression 3]

[0095]

[0096] In equation (3), λ d Where f is the design wavelength, f is the focal length, and n is the focal length. in It is the refractive index of the material on the incident side, n out is the refractive index of the material on the exit side, and C is an arbitrary constant.

[0097] For example, f = 3.2 μm, n in =1.0 (air), n out =1.445 (quartz glass). It is transformed in a manner that converges to the range of 0 to 2π. For example, in Converting from -0.5π to 1.5π, in Converted to 0.5 when the value is 2.5π. In this setting, refer to... Figures 12-14 This describes the phase distribution that serves as the design objective for a lens when light is incident at any angle, and the lens pattern (cylindrical structure 160) that can achieve this phase distribution. The phase distribution that serves as the design objective for a lens refers to the phase distribution of a lens that converges at a focal length f towards a point directly below the center of the lens for light at a certain angle of incidence.

[0098] Figure 12 This indicates that light travels at θ = 0°. A diagram showing the phase distribution as the design objective of the lens under the condition of incident angle, and the pattern of the lens (cylindrical structure 160) that realizes the phase distribution. Figure 13 This indicates that light travels at θ = 45°. The diagram shows the phase distribution as the design objective of the lens and the lens pattern that achieves this phase distribution, under the condition of incident angle. Figure 14 This indicates that light travels at θ = 45°. A diagram showing the phase distribution as the design objective of the lens under the condition of incident angle, and the lens pattern that achieves this phase distribution. Figure 12 (1) Figure 13 (1) Figure 14 (1) is the phase distribution of the lens as the design target when light is incident at various incident angles. Figure 12 (2) Figure 13 (2) Figure 14 (2) is capable of being implemented separately. Figure 12 (1) Figure 13 (1) Figure 14 The top view of the columnar structure 160 with phase distribution of (1) is a shape pattern of the columnar structure 160 designed for 1 pixel.

[0099] like Figure 12 (2) Figure 13 (2) Figure 14 As shown in (2), the columnar structure 160 is a prism with a square base. Furthermore, the width w of the columnar structure 160 is based on... Figure 10 The relationship between the width w of the columnar structure 160 and the phase characteristics of the light emitted by the columnar structure 160 is set to a width that enables the following: Figure 12 (1) Figure 13 (1) Figure 14 The phase of each corresponding position in the phase distribution of (1).

[0100] For example, Figure 12 The optical element unit 120-1 shown in (2) is used to realize light at θ = 0°. The shape pattern of the columnar structure 160, which is the phase distribution of the lens as the design target when the incident angle is at a certain incident angle. Figure 13 The optical element unit 120-2 shown in (2) is used to realize light at θ = 45°. The shape pattern of the columnar structure 160, which is the phase distribution of the lens as the design target when the incident angle is at a certain incident angle. Figure 14 The optical element unit 120-3 shown in (2) is used to realize light at θ = 45°. The shape pattern of the columnar structure 160, which is the phase distribution of the lens as the design target when the incident angle is at a certain incident angle.

[0101] [Wavelength dependence of concentrated light intensity]

[0102] In the implementation method, such as Figure 5 As shown in the optical element units 120R, 120G, and 120B, the patterns of each columnar structure 160 of the optical element units 120R, 120G, and 120B are designed to correspond to the design wavelength of the photoelectric conversion element of the corresponding pixel unit directly below it. In each optical element unit, the width w of each of the plurality of columnar structures 160 forming the optical element unit when viewed from above is set to a width that imparts a phase retardation distribution for guiding light within the wavelength range received by the photoelectric conversion element corresponding to the optical element unit to that photoelectric conversion element. Therefore, the wavelength dependence of the focusing intensity of the optical element array 120 will be explained.

[0103] Figures 15-17 This is a graph representing the focusing intensity of an optical element unit and its wavelength dependence. Figure 15 Corresponding to B light with wavelength λ = 450 nm, Figure 16 Corresponding to G light with wavelength λ = 520 nm, Figure 17 This corresponds to R-light with a wavelength of λ = 635 nm.

[0104] Figure 15 (1) Figure 16 (1) Figure 17 (1) is designed to be most suitable for perpendicular incident light (θ = 0°, The pattern of the lens (cylindrical structure 160) is taken as the average of the two polarized lights. Figure 15 (2) Figure 16 (2) Figure 17 (2) means Figure 15 (1) Figure 16 (1) Figure 17 The diagram shows the focusing intensity of optical element units 120-4, 120-5, and 120-6 of (1). The focusing intensity is the total intensity within the width of the converging spot (λ / NA, where NA is the numerical aperture of the lens) on the photoelectric conversion element surface of pixel 130. Figure 15 (3) Figure 16 (3) Figure 17 (3) is a graph showing the wavelength dependence of the focusing intensity of optical element units 120-4, 120-5, and 120-6.

[0105] like Figure 15 (3) Figure 16 (3) Figure 17 As shown in (3), it can be seen that optical element units 120-4, 120-5, and 120-6 all have light transmission structures of more than 96% and can receive light in pixel 130. In addition, the light-gathering intensity of optical element units 120-4, 120-5, and 120-6 shows the maximum light-gathering intensity around the design wavelength.

[0106] Therefore, in the imaging element 100, by varying the pattern of the columnar structure 160 in accordance with each color band (the transmission band of the R, G, B color filter) as in the optical element units 120-4, 120-5, and 120-6, it is possible to design light-gathering elements that match the design wavelength. In the imaging element 100, the design wavelength of each pixel 130 is determined based on the color filter on the pixel 130, and the optical element units 120-4, 120-5, and 120-6 are integrated according to the design wavelength of the pixel 130 directly below it.

[0107] [Design example of an optical element unit corresponding to the incident angle]

[0108] In this embodiment, the pattern of each columnar structure 160 of the optical element unit is designed according to the incident angle of the incident light. In the optical element unit, the top-view width w of each of the plurality of columnar structures 160 forming the optical element unit is set to impart a phase retardation distribution that guides the incident light to the photoelectric conversion element directly below the optical element unit, corresponding to the incident angle of the incident light. Therefore, a design example of the optical element unit corresponding to the incident angle of the incident light incident onto the optical element array 120 will be described.

[0109] Figures 18-20 It means The graph shows the dependence of the focusing intensity of the optical element unit on the incident angle of parallel light (λ=520nm) incident on the incident light. Figure 18 (1) is designed to be best suited for θ = 15°. The pattern of the columnar structure 160 of the incident light, Figure 19 (1) is designed to be best suited for θ = 30°. The pattern of the columnar structure 160 of the incident light, Figure 20 (1) is designed to be best suited for θ = 45°. The pattern of the columnar structure 160 of the incident light is taken as the average of the two polarized lights. Figure 18 (2) Figure 19 (2) Figure 20 (2) means Figure 18 (1) Figure 19 (1) Figure 20 The diagram shows the light concentration intensity of optical element units 120-7, 120-8, and 120-9 of (1). Figure 18 (3) Figure 19 (3) Figure 20 (3) is a graph showing the dependence of the incident angle on the focusing intensity of optical element units 120-7, 120-8, and 120-9.

[0110] like Figure 18 (3) Figure 19 (3) Figure 20 As shown in (3), the maximum focusing intensity is shown around the design incident angle in any of the optical element units 120-7, 120-8, and 120-9.

[0111] Figures 21-23 It means A graph showing the dependence of the focusing intensity of an optical element unit on the incident angle of parallel light (λ = 520 nm) incident on the incident light. Figure 21 (1) is designed to be best suited for θ = 15°. The pattern of the columnar structure 160 of the incident light, Figure 22 (1) is designed to be best suited for θ = 30°. The pattern of the columnar structure 160 of the incident light, Figure 23 (1) is designed to be best suited for θ = 45°. The pattern of the columnar structure 160 of the incident light is taken as the average of the two polarized lights. Figure 21 (2) Figure 22 (2) Figure 23 (2) means Figure 21 (1) Figure 22 (1) Figure 23 The diagram shows the light concentration intensity of optical element units 120-10, 120-11, and 120-12 of (1). Figure 21 (3) Figure 22 (3) Figure 23 (3) is a graph showing the incident angle dependence of the focusing intensity of optical element units 120-10, 120-11, and 120-12.

[0112] like Figure 21 (3) Figure 22 (3) Figure 23 As shown in (3), in any optical element unit 120-10, 120-11, 120-12, the maximum light concentration intensity is shown around the designed incident angle.

[0113] In the imaging element 100, the aforementioned optical element unit 120-7-120-12 is connected to the incident angle of the incident light. The corresponding arrangement allows light to be focused at a high intensity onto the photoelectric conversion element of pixel 130 directly below.

[0114] [Effects of the Implementation Method]

[0115] Thus, in the imaging element 100 of the embodiment, the lens function is achieved by forming a plurality of columnar structures 160 on the entire surface of the optical element array 120 at intervals shorter than the wavelength of the incident light, thereby enabling the reception of all incident light and improving the light-receiving efficiency.

[0116] Furthermore, in the imaging element 100, the plurality of columnar structures, when viewed from above, each have a width with a phase characteristic that guides the incident light from each columnar structure toward the photoelectric conversion element directly below. When viewed from the side, the plurality of columnar structures have the same height. In the imaging element 100, these plurality of columnar structures 160 enable lens characteristics corresponding to the incident angle for each pixel 130, thus generating an image signal with uniform brightness throughout the imaging element 100.

[0117] Furthermore, in the imaging element 100, a plurality of columnar structures 160 with a binary pattern of a quadrangular prism made of a material having a refractive index higher than that of the surrounding material are used as lenses. Therefore, the plurality of columnar structures 160 used as lenses in the imaging element 100 have a low aspect ratio and a simple structure compared to the structure described in Non-Patent Document 1, and are therefore easy to manufacture.

[0118] Furthermore, the optical element units are not limited to the structure described above; various methods can be employed in terms of quantity, spacing, structural shape, and arrangement pattern. Additionally, the columnar structures 160 can be individually connected or embedded within a transparent material.

[0119] In addition, Figure 3 and Figure 4 In this process, an optical element array 120 is formed on the upper surface of the transparent layer 150, but is not limited thereto. Figure 24 This is another example of a cross-section schematically illustrating a portion of the pixel array and optical element array in a camera element according to an embodiment. (See diagram below.) Figure 24 As shown in the imaging element 100A, an optical element array 120A is formed on the bottom surface of a separate transparent substrate 190. In this way, multiple columnar structures 160 can also be formed inside the transparent layer 150A (e.g., air).

[0120] Furthermore, the example described above, in which four pixels are located directly below one optical element unit, is not limited to this.

[0121] Furthermore, examples of using SiN and TiO2 as materials for the columnar structure 160 are shown in the embodiments, but the invention is not limited to these. For example, when using imaging elements 100 and 100A in the visible to near-infrared light region with wavelengths ranging from 380 nm to 1000 nm, materials such as SiN, SiC, TiO2, and GaN are suitable for the columnar structure 160 due to their high refractive index and low absorption loss. Additionally, when using imaging elements 100 and 100A in the near-infrared light region with wavelengths ranging from 800 to 1000 nm, materials such as Si, SiC, SiN, TiO2, GaAs, and GaN are suitable as materials for the columnar structure 160, which exhibits low loss for these wavelengths. Moreover, in the long-wavelength near-infrared region (such as communication wavelengths of 1.3 μm and 1.55 μm), in addition to the aforementioned materials, materials such as InP can also be used as materials for the columnar structure 160.

[0122] Furthermore, when attaching and coating to form a small spectral element such as a columnar structure 160, materials can include polyimides such as fluorinated polyimides, BCB (benzocyclobutene), light-curing resins, UV epoxy resins, acrylic resins such as PMMA, and polymers such as common photoresists.

[0123] Similarly, in the embodiment, examples of SiO2 and an air layer being assumed as the materials for transparent layers 150 and 150A are shown, but this is not a limitation. The materials for transparent layers 150 and 150A can be any material with a lower refractive index than the material of the columnar structure 160, such as general glass, SiO2, or an air layer, and which exhibits low loss relative to the wavelength of incident light. Alternatively, transparent layers 150 and 150A can also be transparent layers having a layered structure composed of multiple materials.

[0124] In this embodiment, the example is given where the light corresponding to the columnar structure 160 is light of the three primary colors R, G, and B. However, it is also possible for at least one of the three bands to be light of a wavelength other than the three primary colors (e.g., infrared light, ultraviolet light).

[0125] Furthermore, in optical element arrays 120 and 120A, based on Figure 10The relationship between the width of the illustrated columnar structure 160 and the phase characteristics of light is explained by setting the width of at least a portion of the columnar structures 160, when viewed from above, to a width that imparts a phase retardation distribution for guiding incident light to the corresponding photoelectric conversion element directly below. Thus, in the optical element arrays 120, 120A, lens characteristics corresponding to the angle of incidence and the wavelength range in the photoelectric conversion element are achieved for each pixel 130. Not limited to this, in this embodiment, the columnar structures 160 may also have a refractive index with phase characteristics that guide the incident light from each columnar structure to the photoelectric conversion element directly below. In other words, in this embodiment, lens characteristics corresponding to the angle of incidence and the wavelength range in the photoelectric conversion element can also be achieved for each pixel 130 by setting the columnar structures 160 to have different refractive indices. In addition, in this embodiment, by changing the width of the columnar structure 160 when viewed from above and the refractive index of the columnar structure 160 for each columnar structure, lens characteristics corresponding to the incident angle and the wavelength range in the photoelectric conversion element can be achieved for each pixel 130.

[0126] Furthermore, the optical element arrays 120 and 120A in this embodiment are, for example, metasurfaces. As described above, a metasurface is an element composed of multiple microstructures having a width below the wavelength of light; it can be a 2D or 3D structure. By using a metasurface in the optical element, the phase and light intensity can be controlled according to the characteristics of light (wavelength, polarized light, incident angle) simply by changing the parameters of the microstructures. Moreover, when the metasurface is a 3D structure, the aforementioned design freedom is increased.

[0127] The present invention has been described above based on specific embodiments, but the present invention is not limited to the above embodiments, and various changes can be made without departing from its spirit.

[0128] Label Explanation

[0129] 1 object

[0130] 10 camera devices

[0131] 11-lens optical system

[0132] 12, 100, 100A camera elements

[0133] 13 signal processing units

[0134] 110 pixel array

[0135] 120, 120A optical element arrays; 120R, 120G, 120B, 120-1 to 120-12 optical element units; 130 pixels.

[0136] 140L and 140R pixel units

[0137] 150, 150A transparent layer

[0138] 160 columnar structures

[0139] 170 color filter

[0140] 180 wiring layer

[0141] 190 transparent substrate

Claims

1. An optical element, characterized in that, have: A transparent layer for covering a pixel array comprising multiple pixels, wherein the pixels include photoelectric conversion elements; Multiple columnar structures, arranged on or within the transparent layer along the surface of the transparent layer, guide incident light toward the corresponding photoelectric conversion element. The plurality of columnar structures are formed on the entire surface of the transparent layer at intervals shorter than the wavelength of the incident light. The plurality of columnar structures respectively impart an optical phase delay to the incident light corresponding to the width of the columnar structure when viewed from above. Each of the plurality of columnar structures has a width that imparts an optical phase retardation distribution, which is used to guide the incident light to the corresponding photoelectric conversion element according to the design wavelength of the corresponding photoelectric conversion element and the incident angle (θ, φ) of the incident light. The θ is the angle between the normal to the xy plane of the optical element (i.e., the z-axis) and the incident light, provided that the plane of the optical element is the xy plane and the incident light is incident at the origin of the xy plane of the optical element. φ is the angle between the projection of the incident light onto the xy plane of the optical element and the x-axis.

2. The optical element according to claim 1, characterized in that, When viewed from above, the multiple columnar structures form a lattice structure.

3. The optical element according to claim 1 or 2, characterized in that, The plurality of columnar structures have a refractive index that is higher than that of the material surrounding the plurality of columnar structures. When viewed from above, at least a portion of the plurality of columnar structures have widths that differ from each other. When viewed from the side, the plurality of columnar structures have the same height.

4. The optical element according to claim 1 or 2, characterized in that, The plurality of columnar structures have a refractive index that is higher than that of the material surrounding the plurality of columnar structures. At least a portion of the plurality of columnar structures have different refractive indices than each other. When viewed from the side, the plurality of columnar structures have the same height.

5. The optical element according to claim 1, characterized in that, In this optical element, the width of each of the plurality of columnar structures constituting the optical element when viewed from above is set to a width that imparts an optical phase retardation distribution for guiding light of the wavelength range received by the photoelectric conversion element corresponding to the optical element to the photoelectric conversion element corresponding to the optical element.

6. The optical element according to claim 5, characterized in that, The width of each of the plurality of columnar structures when viewed from above is set to a value that varies according to the wavelength range of the corresponding photoelectric conversion element.

7. The optical element according to claim 5, characterized in that, The optical phase delay distribution is the optical phase delay used to converge light.

8. The optical element according to claim 1 or 2, characterized in that, The plurality of columnar structures are formed using a material having a higher refractive index than the transparent layer.

9. The optical element according to claim 1 or 2, characterized in that, The plurality of columnar structures exhibit four rotational symmetries when viewed from above.

10. A camera element, characterized in that, have: The optical element according to any one of claims 1 to 9; and Multiple pixels, each of which includes the photoelectric conversion element.

11. A camera device, characterized in that, have: The imaging element as claimed in claim 10; and The signal processing unit processes the electrical signals output by the imaging element and generates an image.

Images