Optical element, imaging element, and imaging device

Abstract

The imaging element (100) includes: a transparent layer (150) for covering a plurality of pixels (130) each including a photoelectric conversion element; and a plurality of structures (160) arranged in a plane direction of the transparent layer (150) on or within the transparent layer (150). The plurality of structures (160) are arranged such that, for the incident angle of incident light corresponding to each structure, light of a first color among the incident light is converged onto a first pixel located directly below, and light of a second color among the incident light is converged onto a second pixel located directly below.

Description

Technical Field

[0001] The present invention relates to an optical element, an imaging element, and an imaging device. Background Art

[0002] Generally, an imaging device uses a lens optical system and a two-dimensional imaging element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor to obtain a two-dimensional image composed of intensity information and color information of light from an imaging object.

[0003] Conventionally, an imaging element of a color sensor is generally configured such that incident light that has passed through an imaging lens is converged by a microlens, and color filters for each color are arranged on each pixel, so that a photoelectric conversion element receives only light of a specific wavelength.

[0004] Prior Art Documents

[0005] Non-Patent Documents

[0006] Non-Patent Document 1: Takanori Kudo, Yuki Nanjo, Yuko Nozaki, Kazuya Nagao, Hidemasa Yamaguchi, Wen-Bing Kang, Georg Pawlowski, “PIGMENTED PHOTORESISTS FOR COLOR FILTERS”, Journal of Photopolymer Science and Technology, 1996, Vol. 9, No. 1, p. 109-119. Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, since the incident angle of incident light that has passed through an imaging lens is different between the central portion and the peripheral portion of the sensor, the light condensing form of the microlens is also different between the central portion and the peripheral portion, and thus there is a problem that the light reception sensitivity deteriorates in the peripheral portion of the sensor.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical element, an imaging element, and an imaging device that can improve the light reception sensitivity of the peripheral portion of a sensor.

[0010] Means for Solving the Problems

[0011] In order to solve the above problems and achieve the object, the optical element according to the present invention is characterized by comprising: a transparent layer for covering a plurality of pixels each including a photoelectric conversion element; and a plurality of structures disposed on or within the transparent layer in a plane direction of the transparent layer, wherein the plurality of structures are arranged such that, corresponding to the incident angle of incident light for each structure, light of a first color in the incident light is converged on a first pixel located directly below, and light of a second color in the incident light is converged on a second pixel located directly below.

[0012] Moreover, the imaging element of the present invention is characterized by having the above-described optical element and a plurality of pixels covered by the transparent layer.

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

[0014] Advantageous Effects of the Invention

[0015] According to the present invention, it is possible to improve the light reception sensitivity of the periphery of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a side view schematically showing the schematic configuration of the imaging device according to Embodiment 1.

[0017] Figure 2 FIG. is a diagram schematically showing a part of a cross section of a pixel array and a polarization wavelength separation lens array of the imaging element according to Embodiment 1.

[0018] Figure 3 FIG. is a diagram schematically showing a part of a cross section of a pixel array and an optical element array in the central portion of the imaging element according to Embodiment 1.

[0019] Figure 4 FIG. is a diagram schematically showing a part of a cross section of a pixel array and an optical element array in the outer peripheral portion of the imaging element according to Embodiment 1.

[0020] Figure 5 FIG. is a diagram showing an example of a schematic configuration of a structure.

[0021] Figure 6 FIG. is a diagram showing an example of a schematic configuration of a structure.

[0022] Figure 7 FIG. is a diagram showing an example of a schematic configuration of a structure.

[0023] Figure 8 FIG. is a diagram showing an example of a schematic configuration of a structure.

[0024] Figure 9This is a diagram showing an example of the schematic configuration of a structure.

[0025] Figure 10 This is a diagram showing an example of the schematic configuration of a structure.

[0026] Figure 11 This is a diagram showing an example of the combination of each wavelength and the optical phase delay amount.

[0027] Figure 12 This is a diagram explaining the definition of the incident angle.

[0028] Figure 13 This is a diagram showing an example of lens design when the structure is SiN.

[0029] Figure 14 This is a diagram showing an example of lens design when the structure is SiN.

[0030] Figure 15 This is a diagram showing an example of lens design when the structure is SiN.

[0031] Figure 16 This is a diagram showing an example of lens design when the structure is SiN.

[0032] Figure 17 This is a diagram schematically showing the pixel configuration of pixel units in a pixel array.

[0033] Figure 18 This is a diagram explaining the definition of the incident angle.

[0034] Figure 19 This is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0035] Figure 20 This is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0036] Figure 21 This is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0037] Figure 22 This is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0038] Figure 23 This is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0039] Figure 24 This is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0040] Figure 25It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0041] Figure 26 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0042] Figure 27 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0043] Figure 28 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0044] Figure 29 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0045] Figure 30 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0046] Figure 31 It is a diagram schematically showing another example of a part of a cross section of a pixel array and an optical element array in the imaging element of Embodiment 1.

[0047] Figure 32 It is a diagram schematically showing another example of a part of a cross section of a pixel array and an optical element array in the imaging element of Embodiment 1.

[0048] Figure 33 It is a diagram showing an example of the cross-sectional shape of a structure.

[0049] Figure 34 It is a diagram schematically showing a part of a cross section of a pixel array and an optical element array in the central part of the imaging element of Embodiment 2.

[0050] Figure 35 It is a diagram schematically showing a part of a cross section of a pixel array and an optical element array in the central part of the imaging element of Embodiment 2.

[0051] Figure 36 It is a diagram schematically showing the pixel configuration of pixel units in a pixel array.

[0052] Figure 37 It is a diagram explaining the definition of the incident angle.

[0053] Figure 38 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0054] Figure 39 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0055] Figure 40 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0056] Figure 41 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0057] Figure 42 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0058] Figure 43 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0059] Figure 44 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0060] Figure 45 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0061] Figure 46 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0062] Figure 47 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0063] Figure 48 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0064] Figure 49 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel.

[0065] Figure 50 It is a diagram schematically showing another pixel configuration of pixel units in a pixel array. Detailed Description of the Invention

[0066] Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings. In addition, in the following description, each drawing schematically shows the shape, size, and positional relationship to the extent that the content of the present invention can be understood. Therefore, the present invention is not limited only to the shape, size, and positional relationship illustrated in each drawing. In addition, in the description of the drawings, the same parts are denoted by the same reference numerals.

[0067] [Embodiment 1]

[0068] [Imaging Device]

[0069] First, the imaging device according to Embodiment 1 of the present invention will be described.Figure 1 This is a side view schematically showing the general structure of the imaging device according to Embodiment 1.

[0070] As Figure 1 shown, the imaging device 10 according to Embodiment 1 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 a CMOS. The signal processing unit 13 processes the photoelectric conversion signal output from the imaging element 12 to generate an image signal.

[0071] Light such as natural light or illumination light is irradiated onto the object 1, and the light that passes through the object 1 or is reflected / scattered by the object 1, or the light emitted from the object 1 forms an optical image on the imaging element 12 through the lens optical system 11. Generally, in order to correct various optical aberrations, the lens optical system 11 is composed of a lens group, which is composed of a plurality of lenses arranged along the optical axis, but in Figure 1 the drawings are simplified to show a single lens. The signal processing unit 13 includes an image signal output for sending the generated image signal to the outside.

[0072] In addition, the imaging device 10 may include known structural elements such as an optical filter for filtering infrared light, an electronic shutter, a viewfinder, a power source (battery), a flash, etc., but their descriptions are not particularly necessary for understanding the present invention, so they are omitted. In addition, the above structure is merely an example, and in the embodiment, structural elements other than the lens optical system 11, the imaging element 12, and the signal processing unit 13 can be appropriately combined and used as known elements.

[0073] [Imaging Element]

[0074] Next, the outline of the imaging element 12 according to Embodiment 1 will be described. Figure 2 This is a diagram schematically showing a cross-section of the main parts of the lens optical system 11 and the imaging element 12 according to Embodiment 1. In Figure 2 the following, a part of the imaging element 12 will be described as the imaging element 100. The imaging element 100 has an optical element array, and a plurality of columnar structures for guiding incident light to the photoelectric conversion elements of the pixel array are formed on the entire surface. In addition, in the imaging element 100, as Figure 2 shown, the incident angle θ of the light incident from the lens optical system 11 to the imaging element 100 is different between the central part and the peripheral part. Therefore, the plurality of columnar structures formed on the optical element array are set to have a shape that gives the following phase characteristics: the phase characteristics are used to separate the incident light in a state of a specified color corresponding to the incident angle of the incident light and guide it to the pixels directly below. That is, the cross-sectional shapes of the plurality of columnar structures formed on the optical element array are set to different shapes between the central part and the peripheral part of the optical element array. Hereinafter, usingFigure 3 and Figure 4 The structure of the imaging element 100 will be described.

[0075] Figure 3 It is a diagram schematically showing a part of a cross section of a pixel array and an optical element array at the central part of the imaging element according to an embodiment. Figure 4 It is a diagram schematically showing a part of a cross section of a pixel array and an optical element array at the outer peripheral part of the imaging element according to an embodiment. In addition, in Figure 3 and Figure 4 , the arrows schematically indicate the light incident on the imaging element 100. An xyz coordinate system is shown in the figure. The xy plane direction corresponds to the plane directions of the pixel array 110, the transparent layer 150, etc. described later. Hereinafter, unless otherwise specified, "top view" means observing in the z-axis direction (for example, the negative z-axis direction). "Side view" means observing in the x-axis direction or the y-axis direction (for example, the negative y-axis direction).

[0076] As Figure 3 and Figure 4 shown, the imaging element 100 has a pixel array 110 and an optical element array 120 arranged opposite to the pixel array 110. The pixel array 110 and the optical element array 120 are sequentially arranged in the positive z-axis direction. The optical element array 120 is arranged on the side where the light from the lens optical system 11 is incident. The optical element array 120 is formed on the upper surface of a transparent layer 150 formed 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).

[0077] The pixel array 110 includes a wiring layer 180 and a plurality of pixels 130 arranged in the xy plane direction. Each pixel 130 is configured to include a photoelectric conversion element. An example of the photoelectric conversion element is a photodiode (PD: Photo Diode). Each pixel corresponds to red (R), green (G), and blue (B). In an example of the wavelength band of red light, if the wavelength is set to λ0, then 600 nm < λ0. An example of the wavelength band of green light is 500 nm < λ0 ≤ 600 nm. An example of the wavelength band of blue light is λ0 ≤ 500 nm. Hereinafter, in order to distinguish each pixel, they are referred to as pixel R, pixel G, and pixel B (not shown) for illustration. These pixel R, two pixel Gs, and pixel B are Bayer arranged as described later and constitute one pixel unit.

[0078] The optical element array 120 is arranged to cover the pixel array 110. An example of the optical element array 120 is a metasurface. The metasurface is configured to include a plurality of microstructures (corresponding to the structure 160), and the structure has a width equal to or less than the wavelength of light. The metasurface may have a two-dimensional structure or a three-dimensional structure. The optical element array 120 can control the phase and light intensity corresponding to the characteristics of light (wavelength, polarization, incident angle) only by changing the parameters of the structure 160. In the case of a three-dimensional structure, the design freedom is increased compared to a two-dimensional structure.

[0079] The optical element array 120 has two functions: a wavelength separation function and a lens function. The wavelength separation function is a function of separating incident light into lights of respective bands. The lens function is a function of converging lights of respective wavelengths onto corresponding pixels. In this example, the incident light is separated into R light, G light, and B light by the wavelength separation function of the optical element array 120. By the lens function, the R light is converged onto the pixel R directly below, the G light is converged onto the pixel G directly below, and the B light is converged onto the pixel B directly below.

[0080] The optical element array 120 includes a transparent layer 150 and a plurality of columnar structures 160. The transparent layer 150 is arranged on the pixel array 110 to cover the pixel array 110. The transparent layer 150 has a refractive index lower than that of the structure 160. An example of the material of the transparent layer 150 is SiO2 or the like. The transparent layer 150 may be voids, and in this case, the refractive index of the transparent layer 150 may be equal to the refractive index of air. The material of the transparent layer 150 may be single or formed into a layered structure by a plurality of materials.

[0081] The plurality of structures 160 are arranged, for example, periodically (having a periodic structure) in the plane direction (xy plane direction) of the transparent layer 150 on or within the transparent layer 150. In this example, the structures 160 are arranged on the transparent layer 150 on the side opposite to the pixel array 110 (the positive z-axis direction side) with the transparent layer 150 interposed therebetween. For ease of design or the like, the plurality of structures 160 may be arranged at equal intervals or at unequal intervals. Each structure 160 is a micro-structure of nanoscale size having a size equal to or smaller than the wavelength of the incident light. The plurality of structures 160 have the same height when viewed from the side.

[0082] The structure 160 guides the incident light to the photoelectric conversion element of the corresponding pixel 130 directly below in a state where the colors are separated. For example, in Embodiment 1, it is shown that the wavelength bands separated by the structure 160 are R, G, and B. The plurality of structures 160 are arranged such that, corresponding to the incident angles of the incident light of each structure, the R-colored light in the incident light is converged to the pixel R directly below, the G light is converged to the pixel G directly below, and the B light is converged to the pixel B directly below.

[0083] The structure 160 is formed of a material having a refractive index higher than that of the surrounding materials (transparent layer 150, air). Thereby, the structure 160 strongly confines the light inside the columnar structure and prevents light coupling between adjacent columnar structures. The structure 160 is formed using, for example, SiN (refractive index n = 2.05) or TiO2 (refractive index n = 2.40).

[0084] When viewed from above, the structure 160 is respectively formed in a shape having the following phase characteristics, which are used to guide the incident light to the photoelectric conversion elements of the corresponding pixels R, G, and B directly below in a state where the incident light is separated into colors R, G, and B corresponding to the incident angles of the incident light of each columnar structure. The structure 160 respectively imparts a light phase delay amount corresponding to the shape of the structure 160 when viewed from above to the incident light. The cross-sectional shapes of the respective structures 160 are different in the central portion and the outer peripheral portion of the optical element array.

[0085] [Structure]

[0086] In order to implement the structure 160 having different condensing positions according to the wavelength band of the incident light, it is necessary to implement a structure that imparts different optical wavefronts to each wavelength band. In the present Embodiment 1, both the wavelength separation function and the condensing function are achieved by utilizing the wavelength dispersion characteristics of the phase delay amount imparted to the incident light by the fine columnar structure 160.

[0087] The structure 160 is formed of the transparent layer 150 surrounding the structure or materials such as SiN and TiO2 having a refractive index n1 higher than the refractive index n0 of air, and the height (length in the z-axis direction) h of the structure 160 when viewed from the side is constant. The structure 160 can be regarded as an optical waveguide that confines the light inside the structure and propagates it according to the refractive index difference from the transparent layer.

[0088] Therefore, when light is incident from the lens optical system 11 side, the light propagates while being strongly confined inside the structure, and is output from the pixel array 110 side under the phase delay effect determined by the effective refractive index n eff of the optical waveguide.

[0089] Specifically, when taking the phase of light that has traveled a distance equal to the thickness of the structure propagated in the transparent layer as a reference, if the wavelength of the light in a vacuum is set to λ, the phase delay amount of the structure 160 is represented by Equation (1).

[0090] [Mathematical formula 1]

[0091]

[0092] This phase delay amount varies according to the wavelength λ of the light. Therefore, in the same structure, different phase delay amounts can be imparted to light according to the wavelength band.

[0093] In addition, it is known that the effective refractive index n of the optical waveguide eff largely depends on the cross-sectional shape of the structure 160, taking values of n0 < n eff < n1. Additionally, the effective refractive index n of the optical waveguide eff varies according to the wavelength λ of the light, and the degree of this variation largely depends on the cross-sectional shape of the structure 160.

[0094] Therefore, as Figures 5 - 10 shown, for example, by using the structure 160 having various cross-sectional shapes such as a square shape, a cross shape, and a circular shape, various combinations of phase delay amounts corresponding to the wavelength λ of the light can be set, and a lens having different condensing positions according to the wavelength band can be newly designed and realized.

[0095] [Shape of the structure]

[0096] Figures 5 - 10 is a diagram showing an example of the schematic structure of the structure 160. Figure 5 is a side view of the structure 160 whose shape is a square shape when viewed from above. Figure 6 is Figure 5 the top view of the structure 160 shown. Figure 7 is a side view of the structure 160 whose shape is an X-shaped when viewed from above. Figure 8 is Figure 7 the top view of the structure 160 shown. Figure 9 is a side view of the structure 160 whose shape is a hollow rhombus shape when viewed from above. Figure 10 is Figure 9 the top view of the structure 160 shown.

[0097] The structure 160 is a columnar structure extending in the z-axis direction and is formed on the transparent layer 150 (for example, a SiO2 substrate (refractive index 1.45)). An example of the material of the structure 160 is SiN (refractive index 2.05). The sides and the top of the structure 160 are air (Air (refractive index 1.0)).

[0098] Set the arrangement period of each structure 160 as P. The arrangement period P is preferably set as shown in Equation (2) so that diffracted light is not generated on the transmission side.

[0099] [Mathematical formula 2]

[0100] P ≤ λ min / n2 …(2)

[0101] λ min is the shortest wavelength in the wavelength band of the light to be received, for example, 410 nm. n2 is the refractive index of the transparent layer 150. When the transparent layer 150 is SiO2, n2 = 1.45. The arrangement period P of the structure 160 is, for example, 280 nm.

[0102] In Figures 5 - 10 , the height (the length in the z-axis direction) of the structure 160 when viewed from the side is shown as height h in the figure. The height h of the structure 160 is constant. The height h is preferably set as shown in Equation (3) so that the structure 160 can impart a light phase delay amount (phase value) of more than 2π to the incident light, that is, the light traveling in the z-axis direction.

[0103] [Mathematical formula 3]

[0104] h ≥ λ r (n1 - n0) …(3)

[0105] The wavelength λ r is the desired central wavelength in the longest wavelength side band of the wavelength band of the light to be wavelength-separated. n1 is the refractive index of the structure 160. When the structure 160 is SiN, n1 = refractive index 2.05, and the height h is, for example, 1600 nm. In addition, the structure 160 can be formed of TiO2 (refractive index 2.40). In this case, n1 = 2.40, and the height h of the structure 160 is, for example, 1250 nm.

[0106] By designing the cross-sectional shape (including size design) of the structure 160, various combinations capable of imparting different light phase delay amounts to light of each wavelength can be achieved. By diversifying the cross-sectional shape to increase the combinations, the design freedom is further improved.

[0107] For example, the structure 160 has a square shape, a cross shape, or a circular shape when viewed from above. The structures 160 with a square shape, a cross shape, and a circular shape each have the same basic shape but different dimensions (length, width, etc.). The shape of the structure 160 when viewed from above can be a four-fold rotationally symmetric shape. Such a shape can be configured to include, for example, at least one of a square shape, a cross shape, and a circular shape. By making each structure 160 a four-fold rotationally symmetric shape when viewed from above, a characteristic independent of polarized light is achieved.

[0108] As described above, as the shape of the structure 160 when viewed from above, a square shape, an X shape obtained by rotating a cross shape by 45° in the plane, and a hollow rhombus shape can also be applied. In addition, the hollow rhombus shape is an example including a square shape and is a shape obtained by rotating a hollow square shape by 45° in the plane.

[0109] Furthermore, when using shapes such as an X shape or a rhombus shape that are rotated by 45° in the plane, the optical coupling between adjacent structures becomes weaker. Therefore, the optical characteristics of each structure are easily maintained without being affected by adjacent structures. As a result, it is easy to reproduce the ideal phase delay amount distribution described later.

[0110] Figure 11 This is a diagram showing an example of the combination of each wavelength and the optical phase delay amount. As an example of blue light, the optical phase delay amount for light with a wavelength of 430 nm (phase @λ = 430 nm (rad / π)) is shown. As an example of green light, the optical phase delay amount for light with a wavelength of 520 nm (phase @λ = 520 nm (rad / π)) is shown. As an example of red light, the optical phase delay amount for light with a wavelength of 635 nm (phase @λ = 635 nm (rad / π)) is shown.

[0111] The square dots show the optical phase delay amounts when the dimensions of the cross-sectional shape of the structure 160 having a square cross-sectional shape are set to various dimensions. The X dots show the optical phase delay amounts when the dimensions of the cross-sectional shape are set to various dimensions in the structure 160 having an X-shaped cross-sectional shape. The rhombus dots show the optical phase delay amounts when the dimensions of the cross-sectional shape are set to various dimensions in the structure 160 having a hollow rhombus cross-sectional shape. The height h is constant throughout. The black dots are the ideal optical phase delay amounts in the lens design described later.

[0112] Figure 11Shows the optical phase delay amount when the structure 160 is SiN. As can be understood, by designing the cross-sectional shape of the structure 160, combinations of light of various colors (light of each wavelength) and the optical phase delay amount can be achieved. That is, even if only columnar structures having the same height h are used, optical phase delay amount characteristics (phase characteristics) with various dispersions can be achieved. This is because, depending on the cross-sectional shape, the generated optical waveguide modes / optical resonance modes and the resulting dispersion characteristics of the optical phase delay amount can be changed.

[0113] Based on the above principle, by the cross-sectional shape and arrangement design of the structure 160 arranged in the plane direction of the transparent layer 150, the following lens function can be achieved, which is a lens function that makes the focal points different for each wavelength. In addition, it is not limited to the case where the number of wavelengths is three, and even when the number of wavelengths is two or four or more, lens design can be achieved.

[0114] In addition, in this embodiment, the phase distribution of the lens is designed so that the incident light converges to the center of the photoelectric conversion element located below the lens corresponding to the incident light incident on the structure 160, referring to Figure 11 the phase characteristics shown. Therefore, a plurality of structures 160 ( Figure 3 、 Figure 4 ) are arranged such that by setting the cross-sectional shape to be different in the central part and the outer peripheral part of the optical element array 12, in either the central part or the outer peripheral part where the incident angle of the incident light is different, the light of the color corresponding to pixel B in the light incident on the outside of the region opposed to pixel B also converges to pixel B. And it is arranged such that the light of the color corresponding to pixel G in the light incident on the outside of the region opposed to pixel G also converges to pixel G. And it is arranged such that the light of the color corresponding to pixel R in the light incident on the outside of the region opposed to pixel R also converges to pixel R. Thereby, the received light amount in each pixel can be increased.

[0115] [Examples of lens design]

[0116] Here, examples of lens design will be described. Figure 12 is a diagram for explaining the definition of the incident angle. As Figure 12 shown, it explains the case where light is incident at an incident angle of . Corresponding to the incident angle , the phase distribution of the lens is designed so as to converge to the center of the photoelectric conversion element below the lens (structure 160), referring to Figure 11The phase characteristics shown are used to design the cross-sectional shape and arrangement of the SiN component structure 160 in accordance with the ideal optical phase delay amount as the design target. For example, the pixel size is 1.68 μm × 1.68 μm. The focal length is 4.2 μm. The center wavelength corresponding to blue light is 430 nm. The center wavelength corresponding to green light is 520 nm. The center wavelength corresponding to red light is 635 nm.

[0117] For a certain incident angle of light, at a point (the center point of an arbitrary pixel) where the light that converges below the lens has left by z f the optical phase delay amount distribution of the lens is represented by the following formula (4).

[0118] [Mathematical formula 4]

[0119]

[0120] In the above formula (4), λ d is the center wavelength (design wavelength). x f , y f and z f are the focusing positions. n in is the refractive index of the material on the incident side. n out is the refractive index of the material on the exit side. C is an arbitrary constant. In the Figure 3 and Figure 4 structure case, n in = 1.0 (air), n out = 1.445 (fused silica).

[0121] The ideal optical phase delay amount distribution is to assign the following phase distributions at the focusing positions to pixel B, pixel G1, G2, and pixel R respectively. In addition, the center positions of the 4 pixels (pixel unit) correspond to x = 0, y = 0.

[0122] Pixel B: x f = +0.84 μm, y f = -0.84 μm, z f = 4.2 μm

[0123] Pixel G1: x f = +0.84 μm, y f = +0.84 μm, z f = 4.2 μm

[0124] Pixel G2: x f = -0.84 μm, y f = -0.84 μm, z f = 4.2

[0125] Pixel R: x f = -0.84 μm, y f = +0.84 μm, z f = 4.2 μm

[0126] It is transformed in a manner that converges within the range of 0 to 2π. For example, -0.5π and 2.5π are respectively converted to 1.5π and 0.5π. The boundary region of the optical phase delay amount distribution is set in such a way that the center (aligning adjacent lenses) of the optical phase delay amount distribution of the lens at each design wavelength becomes the condensing position. The constant C can be optimized in such a way that the error (difference from the ideal value) of the optical phase delay amount distribution at each wavelength becomes the minimum. According to the optical phase delay amount at each wavelength, the structure (the structure with the minimum error) of the optical phase delay amount distribution that is most suitable for the center wavelengths of the above three wavelengths is arranged at the corresponding positions.

[0127] Figures 13 to 16 It is a diagram showing an example of lens design when the structure 160 is SiN. Figures 13 - 16 It shows the case where light is incident at an incident angle of θ = 5°, and shows an example of the design of the lens. As Figure 16 shown, a plurality of structures 160 are formed in a shape and arrangement that converge the light of wavelengths corresponding to pixels R, G1, G2, and B respectively. In addition, Figure 16 the center position corresponds to x = 0, y = 0.

[0128] In Figure 13 it shows the ideal optical phase delay amount distribution (phase (rad / π)) when the center wavelength is 430 nm (blue light). Figure 14 It shows the ideal optical phase delay amount distribution when the center wavelength is 520 nm (green light). Figure 15 It shows the ideal optical phase delay amount distribution when the center wavelength is 635 nm (red light).

[0129] Figure 16 It is a top view of the structure 160 that can respectively achieve Figures 13 - 15 the optical phase delay amount distribution, and is a shape pattern of the structure 160 designed for each pixel unit (refer to Figure 17 described later).

[0130] As Figure 16 shown, the shape of the structure 160 is a square shape, a cross shape, a hollow rhombic prism. The planar shape of the structure 160 is set to the following shape, which can achieve when light is incident at an incident angle of θ = 5°, Figures 13 - 15The phase at each corresponding position in the shown optical phase delay amount distribution. Therefore, the planar shape of the structure 160 can also be set to one type (e.g., square shape) instead of various shapes such as square shape, cross shape, and hollow diamond shape. In addition, the shape of the structure 160 is not limited to the wavelength band to be separated, and any type of shape among square shape, cross shape, and hollow diamond shape can be set. In addition, the type of the planar shape of the structure 160 can also be set for each wavelength band to be separated.

[0131] Figure 17 It is a diagram schematically showing the pixel arrangement of pixel units in the pixel array 110. It is a diagram showing an example of the arrangement. Figure 18 It is a diagram explaining the definition of the incident angle. Figures 19 - 30 It is a diagram showing an example of the incident angle dependence of the light reception intensity in a pixel. Figures 17 - 30 It shows an example of the incident angle dependence when the structure 160 is SiN. In this case, the pattern of the shape of the structure 160 changes according to the main incident angle, that is, according to the pixel position in the sensor (image sensor 100).

[0132] As described above, as Figure 17 shown, in the pixel array 110, a plurality of pixel units including a pixel R, a pixel G1, a pixel G2, and a pixel B are arranged. At this time, as Figure 18 shown, when the angle (Angle) in the xz plane with the z-axis direction being 0° is set as the incident angle, the incident angle dependence of the received light spectra of the pixel R, the pixel G1, the pixel G2, and the pixel B is as Figures 19 - 26 shown.

[0133] Figures 19 - 22 It shows the case of optimally designing the lens for the case where light is incident at an incident angle of θ = 0°, ... Figures 23 - 26 It represents the case of optimally designing the lens for the case where light is incident at an incident angle of θ = 5°, ... In Figure 19 and Figure 23 , the light reception efficiency of the pixel R is shown for each wavelength (Wavelength (μm)) and each incident angle (Incident angle (degree)), that is, the light reception intensity is shown for each incident angle. In Figure 20 and Figure 24 , the light reception efficiency of the pixel G1 is represented by the light reception intensity for each incident angle. In Figure 21 and Figure 25 , the light reception efficiency of the pixel G2 is represented by the light reception intensity for each incident angle. In Figure 22 andFigure 26 In this case, the light reception efficiency of pixel B is expressed by the light reception intensity for each incident angle. Whether the incident angle is θ = 0° or θ = 5°, at the center wavelengths of pixel R, pixel G1, pixel G2, and pixel B, within the range of about ±12° of the incident angle, light can be received with sufficient intensity.

[0134] In addition, Figures 27 - 30 is a graph showing the incident angle dependence of the detection intensity of the light at the center wavelength received by each pixel, and shows the cases of θ = 0° and θ = 5° respectively. Figure 27 is based on the detection intensity of the light with a wavelength of 630 nm of pixel R, Figure 28 is based on the detection intensity of the light with a wavelength of 520 nm of pixel G1, Figure 29 is based on the detection intensity of the light with a wavelength of 520 nm of pixel G2, Figure 30 is based on the detection intensity of the light with a wavelength of 430 nm of pixel B.

[0135] As Figures 27 - 30 shown, in the case where the lens is optimally designed according to the incident angle θ = 5°, compared with the case where the lens is optimally designed according to the incident angle θ = 0°, the range of the incident angle tolerance is shifted by +5° in all pixels.

[0136] [Effect of Embodiment 1]

[0137] In this way, in Embodiment 1, in the imaging element 100, the optical element array 120 realizes both the color separation function and the lens function. Therefore, compared with the conventional imaging element that uses a color filter for color separation, the total light reception amount can also be increased.

[0138] Moreover, in the imaging element 100, while the lens (structure 160) of the optical element array 120 has a color separation function, an angle tolerance corresponding to the main incident angle is given to it. According to the present Embodiment 1, by changing the pattern of the structure 160 according to the pixel position in the imaging element 100, color separation microlenses corresponding to different main incident angles in the center part and the peripheral part of the imaging element 100 can be realized. Therefore, according to the present Embodiment 1, a condensing function corresponding to various incident angles determined by the position in the imaging element 100 can be realized for each pixel. In particular, the light reception sensitivity of the peripheral part of the imaging element 100 can be improved. Therefore, according to the present Embodiment 1, an image signal having uniform brightness and less color error in the entire imaging element 100 can be generated.

[0139] In addition, in the prior art, in order to increase the amount of received light (increase sensitivity) by increasing the aperture ratio, reducing the light incident angle dependence, etc., there is also a technology of setting (integrating) a microlens on the side opposite to the pixel across the filter. In this case, since it becomes a two-layer structure of at least a filter and a microlens, the structure is complicated and the manufacturing cost is also increased. According to the optical element array 120 of the embodiment, the wavelength separation function and the lens function can be achieved only by the optical element array 120, so the structure can be simplified and the manufacturing cost can be reduced. In addition, since a plurality of structures 160 can be arranged without gaps in the plane (in the xy plane), the aperture ratio is increased compared to the microlens.

[0140] In addition, the tolerance of the incident angle mainly depends on the focal length of the color separation lens, so if a lens (structure 160) with a shorter focal length is designed, the allowable angle is also expanded.

[0141] in addition, Figure 1 The signal processing unit 13 shown generates a pixel signal based on the electrical signal obtained from the imaging element 12. In order to obtain the electrical signal, the signal processing unit 13 also controls the imaging element 12. The control of the imaging element 12 includes exposure of pixels of the imaging element 12, conversion of charges accumulated in the pixel array 110 into electrical signals, reading of electrical signals, and the like.

[0142] The optical element array 120 is not limited to the above-described structure, and various methods can be adopted for the number, interval, structure shape, and arrangement pattern of the structures 160. In addition, the structures 160 may be connected to each other or may be embedded in a transparent material.

[0143] In addition, Figure 3 and Figure 4 In the embodiment, the optical element array 120 is formed on the upper surface of the transparent layer 150, but is not limited thereto. Figure 31 and Figure 32 This is a diagram schematically showing another example of a part of the cross section of the pixel array and the optical element array in the image sensor according to the first embodiment.

[0144] like Figure 31 As shown in the imaging element 100A of FIG. 1 , the optical element array 120 may also be embedded in the transparent layer 150A on the pixel 130. In this case, the material of the transparent layer 150A may be a single material or may be formed into a layer of multiple materials. Figure 32As shown in the imaging element 100B, the optical element array 120 may also be formed on the bottom surface of a separate transparent substrate 190. In this case, the region between the optical element array 120 and the pixels 130 is filled with air 150B. At this time, the material of the transparent substrate 190 may be single or multiple materials formed in layers. The imaging elements 100, 100A, and 100B may also be used together with on-chip microlenses, internal microlenses, inter-pixel barriers for reducing crosstalk, etc.

[0145] In addition, in the above, an example in which 4 pixels are located directly below 1 optical element unit has been described, but it is not limited thereto.

[0146] In addition, the cross-sectional shape of the structure 160 is not limited to the Figure 16 shapes shown, etc. Figure 33 is a diagram showing an example of the cross-sectional shape of the structure. The structure 160 may have Figure 33 the various cross-sectional shapes exemplified. The exemplified shapes are, for example, 4-fold rotationally symmetric shapes obtained by various combinations of a square shape, a cross shape, and a circular shape.

[0147] [Embodiment 2]

[0148] In Embodiment 2, a structure in which the imaging element has a filter is described. Figure 34 is a diagram schematically showing a part of the cross-section of the pixel array and the optical element array at the central part of the imaging element of Embodiment 2. Figure 35 is a diagram schematically showing a part of the cross-section of the pixel array and the optical element array at the outer peripheral part of the imaging element of Embodiment 2.

[0149] Figure 34 and Figure 35 the imaging element 200 shown has a filter layer 170 provided between the pixel array 110 and the optical element array 120.

[0150] The filter layer 170 includes: a filter 170R provided so as to cover the pixel R and allowing red light to pass through; a filter 170G provided so as to cover the pixel G and allowing green light to pass through; and a filter 170B provided so as to cover the pixel B and allowing blue light to pass through. Examples of the material of the filter layer 170 are organic materials such as resin.

[0151] The light that has been color-separated by the optical element array 120 further passes through the filter layer 170 and then reaches the pixel array 110. Through the wavelength separation of both the optical element array 120 and the filter layer 170, compared with the case where wavelength separation is performed by only one of them, spectral crosstalk is suppressed (most of the unnecessary other wavelength components are removed), and color reproducibility is improved. In addition, since the incident light passes through the filter layer 170 after being separated by the optical element array 120, the amount of light is not significantly reduced. Therefore, compared with the case where only the filter layer 170 is provided without the optical element array 120, the light reception efficiency of the pixels is improved.

[0152] Figure 36 is a diagram schematically showing the pixel configuration of pixel units in the pixel array 110. Figure 37 is a diagram explaining the definition of the incident angle. Figures 38 - 45 is a diagram showing an example of the incident angle dependence of the light reception intensity in the pixel. Figures 38 - 45 shows an example of the incident angle dependence in the case where the structure 160 is SiN.

[0153] Figures 38 - 41 shows the case of optimally designing the lens for the case where light is incident at an incident angle of θ = 0°, Figures 42 - 45 shows the case of optimally designing the lens for the case where light is incident at an incident angle of θ = 5°, Figure 38 Figure 42 Figure 39 Figure 43 Figure 40 Figure 44 Figure 41 Figure 45

[0154] Figures 46 - 49 is a diagram showing the incident angle dependence of the detection intensity of the light of the central wavelength received by each pixel, and shows the cases of θ = 0° and θ = 5° respectively. Figure 46 is based on the detection intensity of the light of wavelength 630 nm of pixel R, Figure 47 is based on the detection intensity of the light of wavelength 520 nm of pixel G1, Figure 48 is based on the detection intensity of the light of wavelength 520 nm of pixel G2, Figure 49 ​​​​​​​​​​is the detected intensity of light with a wavelength of 430 nm based on pixel B.

[0155] As Figures 38 - 45 shown, it can be seen that for any of the incident angles of θ = 0° and θ = 5°, most of the unnecessary other wavelength components are removed, and the color reproducibility is improved. In addition, regarding the transmission characteristics of the filter layer 170, for example, refer to Figure 20 .

[0156] Reference 1: Kudo, T.; Nanjo, Y.; et al., “Pigmented Photoresists for ColorFilters”. J.Photopolym.Sci.Technol. 1996, 9, 109 - 120.

[0157] In addition, as Figures 46 - 49 shown, when the lens is optimally designed according to the incident angle θ = 5°, compared with the case where the lens is optimally designed according to the incident angle θ = 0°, the range of the incident angle tolerance is shifted by +5° in all pixels.

[0158] [Effect of Embodiment 2]

[0159] In this way, according to the imaging element 200 further including the filter layer 170, the light reception efficiency can be improved, and the color reproducibility can be further improved.

[0160] In addition, in Embodiments 1 and 2, when explaining the pixel configuration of the pixel array 110, an example of a pixel unit in which pixel B, pixel G1, G2, and pixel R are set as one group is described, but it is not limited thereto. Figure 50 is a diagram schematically showing other pixel configurations of pixel units in the pixel array. As Figure 50 shown, the pixel array may also be a pixel configuration that has a pixel NIR (near-infrared) that receives near-infrared (NIR) light instead of Figure 17 the pixel G2 shown. At this time, by setting the center wavelength λ d to, for example, 850 nm, the lens (structure 160) corresponding to the pixel NIR can be designed using Equation (4).

[0161] In addition, in Embodiments 1 and 2, SiN or TiO2 was taken as an example of the material of the structure 160. However, the material of the structure 160 is not limited thereto. For example, for light with a wavelength of 380 nm to 1000 nm (visible light to near-infrared light), in addition to SiN, SiC, TiO2, GaN, etc. can also be used as the material of the structure 6. Since it has a high refractive index and low absorption loss, it is suitable. When using light with a wavelength of 800 - 1000 nm (near-infrared light), Si, SiC, SiN, TiO2, GaAs, GaN, etc. can be used as the material of the structure 6. Since it has low loss, it is suitable. For light in the near-infrared region of the long wavelength band (such as 1.3 μm and 1.55 μm which are communication wavelengths), in addition to the above materials, InP, etc. can also be used as the material of the structure 160.

[0162] In addition, when the structure 160 is formed by pasting, coating, etc., examples of the material include polymers such as polyimide like fluorinated polyimide, BCB (benzocyclobutene), photocurable resin, UV epoxy resin, acrylic resin such as PMMA, and all resists.

[0163] In addition, in Embodiments 1 and 2, an example where SiO2 and an air layer were assumed as the material of the transparent layer 150 was shown, but it is not limited thereto. It also includes general glass materials, etc., as long as it has a refractive index lower than that of the material of the structure 160 and is a material with low loss relative to the wavelength of the incident light. As long as the transparent layer 150 has sufficiently low loss relative to the wavelength of the light that should reach the corresponding pixel, it can be the same material as the color filter, for example, it can also be an organic material such as resin. In this case, the transparent layer 150 can be designed to not only have the same material as the color filter, but also have the same structure as the color filter and have absorption characteristics corresponding to the wavelength of the light that should be guided to the corresponding pixel.

[0164] In addition, in Embodiments 1 and 2, the three primary colors of RGB and near-infrared light were taken as examples of the colors corresponding to the pixels, but the pixels can also correspond to light with wavelengths other than near-infrared light and the three primary colors (for example, infrared light, ultraviolet light, etc.).

[0165] In addition, in Embodiments 1 and 2, as an example of the shape of the structure 160, an example of using a structure with three different cross-sectional shapes of square shape, cross shape, and hollow rhombus was described. This shape is an example, and two structures (for example, only square shape and cross shape) can be used, or four or more structures can be used.

[0166] As described above, the present invention has been described based on specific embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist thereof.

[0167] The techniques described above are determined, for example, in the following manner. As described with reference to Figures 1 - 5 , Figure 31 and Figure 32 and so on, the optical element array 120 includes: a transparent layer 150 that covers a plurality of pixels each including a photoelectric conversion element; and a plurality of structures 160 that are arranged on or in the transparent layer 150 in the plane direction (xy plane direction) of the transparent layer 150. The plurality of structures 160 are arranged such that, corresponding to the incident angle of incident light for each structure, light of a first color (e.g., blue) in the incident light is converged on a first pixel (e.g., pixel B) directly below, and light of a second color (e.g., red) is converged on a second pixel (e.g., pixel R) directly below.

[0168] The above-described optical element array 120 has a color separation function and has an angular tolerance corresponding to the main incident angle. The optical element array 120 can achieve a condensing function corresponding to various incident angles determined by the position within the imaging element 100 for each pixel, and in particular, can improve the light reception sensitivity of the peripheral portion of the sensor. Since the optical element array 120 can arrange a plurality of structures 160 without gaps in the plane, the aperture ratio is also increased compared to a microlens. The color separation function and the lens function can correspond to three colors and can also correspond to the separation of near-infrared light.

[0169] As described with reference to Figures 5 - 10 and so on, the plurality of structures 160 are each a columnar structure having a refractive index higher than that of the transparent layer 5 and imparting a light phase delay amount corresponding to the cross-sectional shape to the incident light. Moreover, the cross-sectional shapes of the plurality of structures are different between the central portion and the outer peripheral portion of the optical element. As described with reference to Figures 11 - 16 and so on, the plurality of structures 160 can be arranged according to the light phase delay amount distribution for realizing the above-described light condensation. For example, by arranging such a plurality of structures 160, both a wavelength separation function and a lens function can be realized.

[0170] As described with reference to Figure 16 and Figure 33 and so on, the cross-sectional shape of each of the plurality of structures 160 can be a four-fold rotationally symmetric shape. Thereby, polarization dependence can be avoided.

[0171] As described with reference to Figures 6 - 8As described above, the plurality of structures 160 may also be configured such that light of the color corresponding to one pixel among the light incident on the outside of the region facing one pixel is also converged on that one pixel. Thus, the amount of received light can be increased compared to the case where only the light incident on the region facing one pixel is converged on that pixel.

[0172] Refer to Figures 1 - 5 The imaging element 100 described above, etc. is also one aspect of the present disclosure. The imaging element 100 includes an optical element array 120 and a plurality of pixels 130 (such as pixel NIR) covered by a transparent layer 150. Thus, as described above, the manufacturing cost can be reduced. The light reception sensitivity can also be improved or the aperture ratio can be increased.

[0173] As referred to Figure 34 and Figure 35 As described with reference to etc., the imaging element 200 may include a filter layer 170 provided between a plurality of pixels (such as pixel NIR) and the transparent layer 150. Thus, the light reception efficiency can be improved, and the color reproducibility can be further improved.

[0174] Refer to Figure 1 The imaging device 10 described above, etc. is also one aspect of the present disclosure. The imaging device 10 includes the above-described imaging element 12 and a signal processing unit 13 that generates an image signal based on the pixel signal from the electrical signal obtained from the imaging element 12. Thus, as described above, the manufacturing cost can be reduced. The light reception sensitivity can also be improved or the aperture ratio can be increased.

[0175] Reference numeral description

[0176] 1 object

[0177] 10 imaging device

[0178] 11 lens optical system

[0179] 12, 100, 100A, 100B, 200 imaging element

[0180] 13 signal processing unit

[0181] 110 pixel array

[0182] 120 optical element array

[0183] 130 pixel

[0184] 150, 150A transparent layer

[0185] 160 structure

[0186] 170 filter layer

[0187] 180 wiring layer

[0188] 190 transparent substrate

Claims

1. An optical element, characterized in that: The optical element has: A transparent layer for covering a plurality of pixels, each of the plurality of pixels including a photoelectric conversion element; and A plurality of structures arranged in a manner covering the entire transparent layer in a plane direction of the transparent layer on or within the transparent layer, The plurality of structures are configured such that, corresponding to the incident angles of incident light of each structure, light of a first color in the incident light is converged onto a first pixel directly below, and light of a second color in the incident light is converged onto a second pixel directly below, Among the plurality of structures, the plurality of structures directly above the first pixel converge the light of the first color onto the first pixel directly below, and the plurality of structures directly above the second pixel converge the light of the second color onto the second pixel directly below.

2. The optical element according to claim 1, characterized in that: The cross-sectional shape of each of the plurality of structures is different between a central portion and an outer peripheral portion of the optical element.

3. The optical element according to claim 1 or 2, characterized in that: Each of the plurality of structures is a columnar structure having a refractive index higher than that of the transparent layer, and imparting a light phase delay amount corresponding to the cross-sectional shape to the incident light, The cross-sectional shape of the plurality of structures is set according to the light phase delay amount distribution for realizing the convergence, and the plurality of structures are arranged according to the light phase delay amount distribution for realizing the convergence.

4. The optical element according to claim 1 or 2, characterized in that: The cross-sectional shape of each of the plurality of structures is a four-fold rotationally symmetric shape.

5. The optical element according to claim 1 or 2, characterized in that: The plurality of structures are configured to converge light of a color corresponding to one pixel among the light incident on the outside of the region opposed to one pixel onto the one pixel.

6. An imaging element, characterized in that, Having: The optical element according to claim 1 or 2; and The plurality of pixels covered by the transparent layer.

7. The imaging element according to claim 6, characterized in that: The imaging element has a filter layer provided between the plurality of pixels and the transparent layer.

8. An imaging device, characterized in that, Having: The imaging element according to claim 6; and A signal processing unit that generates an image signal based on an electrical signal obtained from the imaging element.

Images