JP2006003895A - Lens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens array capable of improving sensitivity when it is used for a solid-state image pickup device, and improving the luminance of a screen when it is used for a liquid crystal display element. <P>SOLUTION: The lens array is constituted by arraying a plurality of condenser lenses in length and breadth directions, and used in a state where individual condenser lenses are installed to correspond to respective pixels arrayed on two-dimensional plane 1:1. The condenser lens is a graded index lens, and the surface of the lens array is made nearly plane. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens array used in, for example, a solid-state image sensor or a liquid crystal display device.

  A solid-state imaging device will be described as an example.

  FIG. 15 is a cross-sectional view schematically illustrating the configuration of a general solid-state imaging device.

  In general, as shown in FIG. 15, the solid-state imaging device includes an n-type semiconductor substrate 312, a p-well layer 311, a light receiving unit 310, a charge transfer unit 309, a silicon oxide film or nitride film 307, a polysilicon electrode 308, and a metal light shielding layer. 306, an element surface protective layer 305, a flat film 304, a color filter layer 303, an intermediate transparent film 302, and a lens array (on-chip lens) 301. Note that the color filter layer 303 is not necessary in the case of a three-plate imaging device or a monochrome imaging device, or when color-coded by other wavelength selection means.

  In a general solid-state imaging device, light is received only by the light receiving unit 310, and light rays other than that do not contribute to sensitivity. For this reason, as one of the techniques for increasing the sensitivity, it is known that the lens array 301 is formed on a transparent surface layer on the light receiving unit 310 to collect more light by the light receiving unit 310.

  Each lens of the lens array 301 is arranged corresponding to each light receiving unit 310, and the light incident on the lens is efficiently guided to each light receiving unit 310 using the light collecting action.

  The structure of a conventional lens array is shown in FIG. FIG. 16A is a plan view of the lens array 301 as viewed from above, and FIG. 16B is a cross-sectional view of the lens array 301 as viewed from the direction of the arrow along the line XII-XII in FIG. A region corresponding to one pixel is a region surrounded by a vertical side 355 and a horizontal side 354, and the lens 301 is disposed at the substantially central portion, thereby contributing to an improvement in sensitivity. Here, a gap 353 is provided between adjacent lenses for manufacturing reasons. In FIG. 16, only four pixels are shown in order to simplify the drawing, but in reality, a predetermined number of pixels shown in FIG. 16A are arranged in the vertical and horizontal directions.

  In the lens array, since the gap 353 is provided between the adjacent lenses, the light incident here hardly enters the light receiving element. In addition, since the lens shape is substantially circular or substantially elliptical, a gap is also generated in a corner portion where the lens 301 is not formed in the square pixel region, and almost all light incident on this portion enters the light receiving element. And there is a problem that it does not contribute to sensitivity.

  Similarly, in a liquid crystal display element used in a transmissive liquid crystal display device or the like, a lens array having a gap as shown in FIG. 16 is stacked so as to correspond to each pixel. Has a problem that it does not contribute to the brightness of the screen of the liquid crystal display device.

  In view of the above problems, the present invention can improve the sensitivity when used in a solid-state imaging device, for example, by widening the aperture of a lens, and when used in a liquid crystal display element. An object is to provide a lens array capable of improving luminance.

  In order to achieve the above object, the lens array of the present invention has the following configuration.

  That is, the lens array according to the first configuration of the present invention includes a plurality of condensing lenses arranged in the vertical and horizontal directions, and each of the condensing lenses is in a one-to-one relationship with each pixel arranged in a two-dimensional plane. A lens array that is installed and used in a corresponding manner, wherein the condensing lens is formed in contact with condensing lenses adjacent in the vertical and horizontal directions.

  The lens array according to the second configuration of the present invention includes a plurality of condensing lenses arranged in the vertical and horizontal directions, and each of the condensing lenses corresponds to each pixel arranged in a two-dimensional plane on a one-to-one basis. The condensing lens is a convex lens and is formed over the entire region corresponding to the pixel.

  In the second configuration, the region corresponding to the pixel is rectangular, and when the vertical and horizontal lengths of the region are sequentially X and Y, the radius of curvature R of the condenser lens is expressed by the following formula ( It is preferable to satisfy 1).

(1/2) × (X ² + Y ² ) ^1/2 ≦ R ≦ (2/3) × (X ² + Y ² ) ^1/2 (1)
In the second configuration, when the region corresponding to the pixel is rectangular, the vertical and horizontal lengths of the region are sequentially X and Y, and the radius of curvature of the condenser lens is R. It is preferable that the following formulas (2) and (3) are satisfied.

4 μm ≦ (X ² + Y ² ) ^1/2 ≦ 5.7 μm (2)
2μm ≦ R ≦ 4μm (3)
The lens array according to the third configuration of the present invention includes a plurality of condenser lenses arranged in the vertical and horizontal directions, and each of the condenser lenses has a one-to-one correspondence with each pixel arranged in a two-dimensional plane. The condensing lens includes a first lens formed in a substantially central portion of a region corresponding to the pixel, and the first lens in the region. A second lens formed in a region of the four corners not formed, the first lens is a convex lens, and the second lenses formed in the four corners have a common center of curvature. Features.

  The lens array according to the fourth configuration of the present invention includes a plurality of condenser lenses arranged in the vertical and horizontal directions, and each of the condenser lenses has a one-to-one correspondence with each pixel arranged in a two-dimensional plane. The condensing lens includes a first lens formed in a substantially central portion of a region corresponding to the pixel, and the first lens in the region. A second lens formed in a region of the four corners that are not formed, the first lens is a convex lens, each second lens formed in the four corners has a common center of curvature, The wall surface on the first lens side of the second lens is not perpendicular to the arrangement surface of the condenser lenses.

  The lens array according to the fifth configuration of the present invention includes a plurality of condensing lenses arranged in the vertical and horizontal directions, and each of the condensing lenses has a one-to-one correspondence with each pixel arranged in a two-dimensional plane. The lens array is used in such a manner that the condensing lens is a Fresnel lens.

  The lens array according to the sixth configuration of the present invention includes a plurality of condensing lenses arranged in the vertical and horizontal directions, and each of the condensing lenses corresponds to each pixel arranged in a two-dimensional plane on a one-to-one basis. The lens array is used in such a manner that the condensing lens is a Fresnel lens, and the Fresnel lens has at least two different groove depths for each region corresponding to the pixel. Features.

  In the sixth configuration, the Fresnel lens has a groove depth of mλ / (n−1) where n is the refractive index of the Fresnel lens forming material and λ is the wavelength or center wavelength of the light transmitted through the Fresnel lens. It is preferable that the sawtooth shape is (m: natural number).

  In the fifth or sixth configuration, the Fresnel lens is preferably formed over the entire region corresponding to the pixel.

  In the first to sixth configurations, the condenser lens is preferably formed in a binary shape whose shape approximates a step shape.

  The lens array according to the seventh configuration of the present invention includes a plurality of condenser lenses arranged in the vertical and horizontal directions, and each of the condenser lenses has a one-to-one correspondence with each pixel arranged in a two-dimensional plane. The condensing lens is a lens provided with a lens function by a change in refractive index, and the surface of the lens array is substantially flat.

  In the seventh configuration, it is preferable that the lens provided with a lens function by a change in refractive index is formed in the entire region corresponding to the pixel.

  The lens array according to the eighth configuration of the present invention includes a plurality of condensing lenses arranged in the vertical and horizontal directions, and each of the condensing lenses corresponds to each pixel arranged in a two-dimensional plane on a one-to-one basis. The condensing lens is a refractive index distribution type lens, and the surface of the lens array is substantially flat.

  In the eighth configuration, it is preferable that the gradient index lens is formed in the entire region corresponding to the pixel.

  The lens array according to the ninth configuration of the present invention includes a plurality of condensing lenses arranged in the vertical and horizontal directions, and each of the condensing lenses corresponds to each pixel arranged in a two-dimensional plane on a one-to-one basis. The condensing lens includes a lens to which a lens function is given by a change in refractive index and a convex lens formed on the lens array.

  In the ninth configuration, it is preferable that the lens provided with a lens function by a change in refractive index is formed in the entire region corresponding to the pixel.

  The lens array according to the tenth configuration of the present invention includes a plurality of condensing lenses arranged in the vertical and horizontal directions, and each of the condensing lenses corresponds to each pixel arranged in a two-dimensional plane on a one-to-one basis. The condensing lens includes a first lens formed in a substantially central portion of a region corresponding to the pixel, and the first lens in the region. And a third lens formed in a non-formed region, wherein the first lens is a convex lens, and the third lens is a lens having a lens function provided by a change in refractive index. And

  In the tenth configuration, it is preferable that one of the first lens and the third lens is formed in a region corresponding to the pixel.

  Since the lens array of the present invention has the above first to tenth configurations, for example, when used in a solid-state imaging device, the sensitivity can be improved, and when used in a liquid crystal display element, the screen is displayed. It is possible to provide a lens array capable of improving the luminance of the lens.

  A solid-state imaging device according to the present invention is a solid-state imaging device having a light receiving unit arranged in a two-dimensional plane and the lens array according to any one of the above stacked on the light receiving unit. Each condensing lens of the lens array has a one-to-one correspondence with each of the light receiving portions.

  The solid-state imaging device according to the present invention is a solid-state imaging device having a light receiving unit arranged in a two-dimensional plane and a transparent substrate stacked on the light receiving unit, wherein the transparent substrate is the seventh or the above. The lens array according to an eighth configuration is characterized in that each condenser lens of the lens array has a one-to-one correspondence with each of the light receiving units.

  In the solid-state imaging device, it is preferable that a focal length of the condenser lens is substantially equal to a distance to the light receiving unit.

  The liquid crystal display element according to the present invention is a liquid crystal display element having pixels arranged in a two-dimensional plane, and the lens array according to any one of the above, which is stacked on the pixels. The individual condenser lenses correspond to the individual pixels on a one-to-one basis.

  In the above liquid crystal display element, it is preferable that the focal length of the condenser lens is substantially equal to the distance to the pixel.

  According to the present invention, for example, by effectively using the pixel region by covering the entire pixel region with a convex lens, the sensitivity can be improved when used in, for example, a solid-state imaging device, and the liquid crystal display element When used in a lens array, it is possible to provide a lens array that can improve the brightness of the screen.

  Hereinafter, the lens array of the present invention will be described more specifically with reference to the drawings.

(Embodiment 1)
1A and 1B are conceptual diagrams of a lens array according to a first embodiment of the present invention, in which FIG. 1A is a plan view, and FIG. 1B is an arrow direction along line Ib-Ib in FIG. FIG. 1C is a cross-sectional view taken along the line Ic-Ic in FIG. 1A. In FIG. 1, only four pixels are shown in order to simplify the drawing. However, in actuality, a predetermined number of pixels shown in FIG. 1A are arranged in the vertical and horizontal directions.

  In the lens array of the present embodiment, a condensing lens 111 having a convex lens shape is arranged in a rectangular pixel region arranged in the vertical and horizontal directions, and one condensing lens corresponds to one pixel region. .

  Here, the condensing lens 111 is in contact with condensing lenses adjacent in the vertical and horizontal directions. For example, consider a case where a lens array is formed on a solid-state imaging device having a light receiving element interval of 5 μm. When the gap of the conventional condenser lens (gap 353 in FIG. 16B) is 0.4 μm, the ratio of the area occupied by the condenser lens in the area (pixel region) corresponding to one light receiving element is 66.5. %. On the other hand, when the gap between the condensing lenses adjacent in the vertical and horizontal directions is 0 as in the condensing lens of the present embodiment, the ratio of the area occupied by the condensing lens in the area corresponding to one light receiving element Is 78.5%, and the light ray entering the lens is increased by 18% compared to the conventional case, so that the sensitivity of the solid-state imaging device is increased accordingly.

  As shown in FIG. 15, a p-well layer 311 is provided, a light receiving portion 310 having a side of about 2.5 μm is formed on the surface layer portion, and then a silicon oxide film or nitride film 307 having a thickness of about 0.1 μm is formed. An element surface protective film 305 having a refractive index of 1.55 and a thickness of about 0.9 μm, a flat film 304 having a refractive index of 1.47 and a thickness of about 1 μm, and a refractive index of 1.52 and a thickness of about 2 μm. Assume a solid-state imaging device that constitutes the color filter layer 303 and has a pixel area corresponding to the light receiving element in a square shape having a length and width of about 4.5 μm. The change in the condensing rate when the condensing lens 301 having a refractive index of 1.5 and a radius of curvature of 3 μm is formed in the upper part of the pixel region by changing the interval between the condensing lenses adjacent in the vertical and horizontal directions. Simulated. The results are shown in FIG. In the lens array of the present embodiment, the condensing lenses adjacent to each other in the vertical and horizontal directions are in contact with each other. Therefore, the distance between the condensing lenses is 0, and the condensing rate is 75%. On the other hand, since the condensing lens gap in the vertical and horizontal directions of the conventional general lens array is about 0.4 μm, the condensing rate is 68%, and the condensing rate of the present invention is about 10 compared with the conventional one. % Improvement.

  At this time, the light collection rate is the number of light rays incident on the light receiving element among the number of light rays passing through the pixel region corresponding to one light receiving element when the light ray tracing is arbitrarily performed. However, in this simulation, the incident ray angle to the pixel region is arbitrary in the range of 0 degrees to 15 degrees.

(Embodiment 2)
3A and 3B are conceptual diagrams of a lens array according to the second embodiment of the present invention, in which FIG. 3A is a plan view, and FIG. 3B is an arrow direction along line IIb-IIb in FIG. FIG. 3C is a cross-sectional view taken along the line IIc-IIc in FIG. 3A. In FIG. 3, only four pixels are shown in order to simplify the drawing. However, in actuality, a predetermined number of pixels shown in FIG. 3A are arranged in the vertical and horizontal directions.

  In the lens array of the present embodiment, a condensing lens 121 having a convex lens shape is arranged in a rectangular pixel region arranged in the vertical and horizontal directions, and one condensing lens corresponds to one pixel region. .

  Here, the condensing lens 121 covers the entire pixel region, and there is no region in which no condensing lens is formed in the pixel region. For example, consider a case where a lens array is formed on a solid-state imaging device having a light receiving element interval of 5 μm. When the gap of the conventional condenser lens (gap 353 in FIG. 16B) is 0.4 μm, the ratio of the area occupied by the condenser lens in the area (pixel region) corresponding to one light receiving element is 66.5. %. On the other hand, in the lens array of the present embodiment, the proportion of the condensing lens in the area corresponding to one light receiving element is 100%. Therefore, the light receiving effective area is improved by 50.7% by the lens array of the present embodiment. As a result, the light receiving sensitivity of the solid-state imaging device is also improved.

  For example, in order for the lens to cover the entire area of the pixel area, the radius of curvature of the lens needs to be at least half the length of the diagonal line of the pixel. In addition, if the radius of curvature is too large, the light condensing power is weakened, causing a decrease in sensitivity. For this reason, when the vertical length of the pixel is X and the horizontal length is Y, it is preferable that the radius of curvature R of the condenser lens satisfies the following formula (1). When Expression (1) is satisfied, the lens can cover the entire pixel region and can obtain a sufficient light collecting power. Below the lower limit of equation (1), the lens cannot cover the entire pixel area. On the other hand, if it exceeds the upper limit of Formula (1), sufficient condensing power cannot be obtained.

(1/2) × (X ² + Y ² ) ^1/2 ≦ R ≦ (2/3) × (X ² + Y ² ) ^1/2 (1)
Moreover, it is preferable to satisfy the following formulas (2) and (3) because sufficient sensitivity can be obtained and sufficient resolution can be obtained.

4 μm ≦ (X ² + Y ² ) ^1/2 ≦ 5.7 μm (2)
2μm ≦ R ≦ 4μm (3)
Here, in order to perform the simulation, the shape of the solid-state imaging device was as follows. As shown in FIG. 15, there is a p-well layer 311 having a thickness of about 3 μm, and a light receiving portion 310 having one side of about 1 μm and the other side of about 2.5 μm is formed on the surface layer portion. A silicon oxide film or nitride film 307 of about 0.1 μm was formed. Furthermore, the element surface protective film 305 having a refractive index of 1.55 and a thickness of about 0.9 μm, a refractive index of 1.47, a flat film 304 having a thickness of about 1 μm, and a refractive index of 1.52 and a thickness of about 2 μm. The solid-state image sensor is assumed to be a square having a pixel area corresponding to the light receiving element and having a range of about 4.5 μm in length and width. When a condensing lens having a refractive index of 1.5 is formed above the pixel region, the relationship between the radius of curvature and the condensing rate is as shown in FIG. When the radius of curvature is 3.4 μm, the light collection rate is maximum, and the light collection rate at that time is 94%, which is 38% higher than the conventional light collection rate of 68%.

(Embodiment 3)
5A and 5B are conceptual diagrams of a lens array according to Embodiment 3 of the present invention. FIG. 5A is a plan view, and FIG. 5B is an arrow direction along line IIIb-IIIb in FIG. FIG. 5C is a cross-sectional view taken along the line IIIc-IIIc in FIG. 5A. In FIG. 5, only four pixels are shown in order to simplify the drawing, but in reality, a predetermined number of the respective pixels shown in FIG. 5A are arranged in the vertical and horizontal directions.

  In the lens array of the present embodiment, a first lens 131 having a convex lens shape formed at a substantially central portion of rectangular pixel regions arranged in the vertical and horizontal directions, and a first lens 131 are formed. A condensing lens having one unit of the second lens 132 formed in the remaining area of the pixel area including the four corner areas is arranged so that one condensing lens corresponds to one pixel area. Yes. Here, the second lenses 132 formed at the four corners of the pixel region have a common center of curvature.

  In general, if a convex lens is to be formed in a rectangular pixel region, an area in which no lens is formed at least in the diagonal direction is formed unless the configuration as in the second embodiment is adopted. In the present embodiment, by forming another second lens 132 in this region, the effective light receiving area can be increased. Further, since the curvature of the second lens 132 does not have to be the same as the curvature of the first lens 131 at the center, the combination of the curvatures of the two lenses is optimized by, for example, simulation, and more It is possible to secure the amount of received light.

  Further, according to the present embodiment, by setting the radius of curvature of the second lens 132 to be not less than half of the diagonal length of the pixel region, it is possible to form a lens without any gap across the pixel region. For example, consider a case where a lens array is formed on a solid-state imaging device having a light receiving element interval of 5 μm. When the gap of the conventional condenser lens (gap 353 in FIG. 16B) is 0.4 μm, the ratio of the area occupied by the condenser lens in the area (pixel region) corresponding to one light receiving element is 66.5. %. On the other hand, in the lens array of the present embodiment, the proportion of the condensing lens in the area corresponding to one light receiving element can be almost 100%. Therefore, the light receiving effective area is improved by 50.7% by the lens array of the present embodiment. As a result, the light receiving sensitivity of the solid-state imaging device is also improved.

  In the present embodiment, the second lens 132 is configured around the first lens 131, but another lens having a different curvature may be configured around the second lens 132.

  Here, in order to perform the simulation, the shape of the solid-state imaging device was as follows. As shown in FIG. 15, there is a p-well layer 311 having a thickness of about 3 μm, and a light receiving portion 310 having one side of about 1 μm and the other side of about 2.5 μm is formed on the surface layer portion. A silicon oxide film or nitride film 307 of about 0.1 μm was formed. Furthermore, the element surface protective film 305 having a refractive index of 1.55 and a thickness of about 0.9 μm, a refractive index of 1.47, a flat film 304 having a thickness of about 1 μm, and a refractive index of 1.52 and a thickness of about 2 μm. The solid-state image sensor is assumed to be a square having a pixel area corresponding to the light receiving element and having a range of about 4.5 μm in length and width. When a convex lens (first lens) similar to the conventional one having a refractive index of 1.5 is formed at a substantially central portion above the pixel region, and a second lens having a curvature radius of 4 μm is formed around the convex lens, The rate is 78%, which is a 15% improvement in the light collection rate compared with the conventional light collection rate of 68% with only the central lens.

(Embodiment 4)
6A and 6B are conceptual diagrams of a lens array according to Embodiment 4 of the present invention. FIG. 6A is a plan view, and FIG. 6B is an arrow direction along line IVb-IVb in FIG. FIG. 6C is a cross-sectional view taken along the line IVc-IVc in FIG. 6A. In FIG. 6, only four pixels are shown in order to simplify the drawing. However, in actuality, a predetermined number of the pixels shown in FIG. 6A are arranged in the vertical and horizontal directions.

  In the lens array of the present embodiment, a first lens 141 having a convex lens shape and a first lens 141 formed at substantially the center of rectangular pixel regions arranged in the vertical and horizontal directions are formed. A condensing lens having the second lens 142 formed in the remaining area of the pixel area including no four corner areas as a unit is arranged so that one condensing lens corresponds to one pixel area. Yes. Here, the second lenses 142 formed at the four corners of the pixel region have a common center of curvature.

  In general, if a convex lens is to be formed in a rectangular pixel region, an area in which no lens is formed at least in the diagonal direction is formed unless the configuration as in the second embodiment is adopted. In the present embodiment, by forming another second lens 142 in this region, the effective light receiving area can be increased. Furthermore, since the curvature of the second lens 142 does not need to be the same as the curvature of the first lens 141 at the center, the combination of the curvatures of the two lenses is optimized by, for example, simulation, and more It is possible to secure the amount of received light.

  In addition, the outer second lens 142 is configured such that the inner wall 143 extends outward from the center 145 of the first lens 141 in order to prevent light rays having a relatively small incident angle from being totally reflected by the inner wall 143 and being scattered. It is inclined by an angle θ.

  In addition, according to the present embodiment, by setting the radius of curvature of the second lens 142 to be not less than half the length of the diagonal line of the pixel region, it is possible to form lenses without gaps throughout the pixel region. For example, consider a case where a lens array is formed on a solid-state imaging device having a light receiving element interval of 5 μm. When the gap of the conventional condenser lens (gap 353 in FIG. 16B) is 0.4 μm, the ratio of the area occupied by the condenser lens in the area (pixel region) corresponding to one light receiving element is 66.5. %. On the other hand, in the lens array of the present embodiment, the proportion of the condensing lens in the area corresponding to one light receiving element can be almost 100%. Therefore, the light receiving effective area is improved by 50.7% by the lens array of the present embodiment. As a result, the light receiving sensitivity of the solid-state imaging device is also improved.

  In the present embodiment, the second lens 142 is configured around the first lens 141, but another lens having a different curvature may be configured around the second lens 142.

  Here, in order to perform the simulation, the shape of the solid-state imaging device was as follows. As shown in FIG. 15, there is a p-well layer 311 having a thickness of about 3 μm, and a light receiving portion 310 having one side of about 1 μm and the other side of about 2.5 μm is formed on the surface layer portion. A silicon oxide film or nitride film 307 of about 0.1 μm was formed. Furthermore, the element surface protective film 305 having a refractive index of 1.55 and a thickness of about 0.9 μm, a refractive index of 1.47, a flat film 304 having a thickness of about 1 μm, and a refractive index of 1.52 and a thickness of about 2 μm. The solid-state image sensor is assumed to be a square having a pixel area corresponding to the light receiving element and having a range of about 4.5 μm in length and width. A convex lens (first lens) similar to the conventional one having a refractive index of 1.5 is formed at a substantially central portion above the pixel region, and a second lens having an inner wall surface inclined outward is formed therearound. did. Here, Table 1 shows a change in the light condensing rate when the curvature radius of the second lens and the inclination angle θ of the inner wall of the second lens are changed.

  If the radius of curvature of the second lens is 4 μm and the inclination angle θ is 10 deg., The condensing rate is about 81%, which is compared with the condensing rate of about 78% when the inclination angle θ is 0 deg. With the same curvature radius. The light collection rate is improved by about 3%. In addition, it is improved by about 19% compared with the condensing rate of 68% of the conventional lens.

(Embodiment 5)
7A and 7B are conceptual diagrams of a lens array according to a fifth embodiment of the present invention, in which FIG. 7A is a plan view, and FIG. 7B is an arrow direction along line VV in FIG. It is sectional drawing seen from. In FIG. 7, only four pixels are shown in order to simplify the drawing, but in reality, a predetermined number of pixels shown in FIG. 7A are arranged in the vertical and horizontal directions.

  The lens array of the present embodiment is composed of Fresnel lenses 151 having a condensing function, which are formed in rectangular pixel regions arranged in the vertical and horizontal directions. The Fresnel lens 151 is configured by forming an uneven portion on the lens surface according to the phase modulation amount of the lens. Thus, for example, in a solid-state image sensor, the distance between the light receiving element and the lens is reduced, which is useful for improving sensitivity. Further, by forming a Fresnel lens over the entire pixel region corresponding to one light receiving element, the effective light receiving area can be expanded and the sensitivity can be improved.

(Embodiment 6)
8A and 8B are conceptual diagrams of a lens array according to Embodiment 6 of the present invention, in which FIG. 8A is a plan view, and FIG. 8B is the arrow direction along the VI-VI line in FIG. It is sectional drawing seen from. In FIG. 8, only four pixels are shown in order to simplify the drawing, but in reality, a predetermined number of pixels shown in FIG. 8A are arranged in the vertical and horizontal directions.

  The lens array according to the present embodiment is composed of Fresnel lenses 161, 162, and 163 having a condensing function, which are formed in rectangular pixel regions arranged in the vertical and horizontal directions. Each Fresnel lens has a sawtooth shape with a groove depth of mλ / (n−1) (m: natural number) where n is the refractive index of the Fresnel lens forming material and λ is the wavelength of transmitted light or the center wavelength. . Each Fresnel lens of the lens array in the present embodiment has an optimum shape for each wavelength so as to correspond to three different wavelengths. Therefore, for example, when used in a solid-state imaging device, it is useful for improving the sensitivity to light of a specific wavelength.

  In FIG. 8, the lens array is composed of three types of Fresnel lenses corresponding to three types of wavelengths, but may be composed of two types of Fresnel lenses, or may be composed of four or more types of Fresnel lenses. May be.

  Further, since each Fresnel lens has wavelength selectivity, the wavelength filter can be omitted.

  Further, by forming a Fresnel lens over the entire pixel region corresponding to one light receiving element, the effective light receiving area can be expanded and the sensitivity can be improved.

(Embodiment 7)
9A and 9B are conceptual diagrams of a lens array according to a seventh embodiment of the present invention, in which FIG. 9A is a plan view, and FIG. 9B is an arrow direction along the line VII-VII in FIG. It is sectional drawing seen from. In FIG. 9, only four pixels are shown to simplify the drawing, but in reality, a predetermined number of pixels shown in FIG. 9A are arranged in the vertical and horizontal directions.

  The lens array according to the present embodiment is a lens array of a type in which a rectangular pixel region arranged in the vertical and horizontal directions covers the entire area of one pixel region with a convex lens as shown in the second embodiment (FIG. 3). Thus, a binary lens whose lens shape is approximated by a staircase shape is used.

  A staircase shape 171 is formed so as to approach the original lens shape 172. In this case, the larger the number of steps in the stairs, the closer to the performance of the original lens shape. By using such a binary lens shape, options for manufacturing a lens array can be expanded.

  Although FIG. 9 shows an example in which the lens array shown in Embodiment 2 (FIG. 3) is a binary lens, the lens array shown in the other embodiments described above can be similarly used as a binary lens. .

(Embodiment 8)
FIG. 10 is a conceptual diagram of a lens array according to an eighth embodiment of the present invention. FIG. 10 (a) is a plan view, and FIG. 10 (b) is an arrow direction along line VIIIb-VIIIb in FIG. 10 (a). FIG. 10C is a cross-sectional view seen from the direction of the arrow along the line VIIIc-VIIIc in FIG. In FIG. 10, only four pixels are shown in order to simplify the drawing, but in practice, a predetermined number of the pixels shown in FIG. 10A are arranged in the vertical and horizontal directions.

  In the lens array of the present embodiment, a condensing lens in which a lens function is given to a rectangular pixel region arranged in the vertical and horizontal directions by a change in refractive index corresponds to one condensing lens in one pixel region. Are arranged as follows.

  That is, the lens material layer 183 includes a high refractive index portion 181 and a low refractive index portion 182, and the interface between the two has a predetermined curvature. As a result, the light is refracted when light passes through the interface between them, and the high refractive index portion 181 functions as a condenser lens. Therefore, for example, when applied to a solid-state image sensor, the lens unit is closer to the light receiving element, and works effectively for a light beam having a relatively large incident angle with respect to the lens. Therefore, the light receiving sensitivity is improved.

  In this embodiment, the condensing lens based on the refractive index change is formed over the entire pixel area, but may be a part of the pixel area. By forming a condensing lens over the entire pixel region, the effective light receiving area can be expanded and the sensitivity can be improved.

  In addition, a lens with a refractive index change is not formed in the lens material layer 183 newly provided as shown in FIG. 10, but a refractive index change is directly given inside a solid-state imaging device or a liquid crystal display device. A condensing lens may be formed.

(Embodiment 9)
11A and 11B are conceptual diagrams of a lens array according to a ninth embodiment of the present invention, in which FIG. 11A is a plan view, and FIG. 11B is an arrow direction along line IX-XI in FIG. It is sectional drawing seen from. In FIG. 11, only four pixels are shown in order to simplify the drawing. However, in actuality, a predetermined number of pixels shown in FIG. 11A are arranged in the vertical and horizontal directions.

  In the lens array of the present embodiment, a gradient index lens functioning as a condensing lens is arranged in a rectangular pixel region arranged in the vertical and horizontal directions so that one condensing lens corresponds to one pixel region. Has been.

  That is, the lens material layer 193 in each rectangular pixel region is composed of a plurality of layers having different refractive indexes concentrically around the intersection (center portion) of the diagonal line of the pixel region, and the central portion 191 has the highest refractive index. The refractive index decreases in order as it goes to the peripheral portion 192. The gradient index lens formed as described above functions as a condensing lens as a whole. Therefore, for example, when applied to a solid-state image sensor, the lens unit is closer to the light receiving element, and works effectively for a light beam having a relatively large incident angle with respect to the lens. Therefore, the light receiving sensitivity is improved.

  In this embodiment, the gradient index lens is formed over the entire pixel area, but may be a part of the pixel area. By forming over the entire pixel region, the effective light receiving area can be expanded and the sensitivity can be improved.

  In addition, the refractive index distribution type lens is not provided with a lens material layer 193 newly provided as shown in FIG. 11, but directly with a refractive index distribution inside a solid-state imaging device or a liquid crystal display device. A condensing lens may be formed.

(Embodiment 10)
12A and 12B are conceptual diagrams of a lens array according to a tenth embodiment of the present invention, in which FIG. 12A is a plan view, and FIG. 12B is an arrow direction along line XX in FIG. It is sectional drawing seen from. In FIG. 12, only four pixels are shown in order to simplify the drawing, but in reality, a predetermined number of the respective pixels shown in FIG. 12A are arranged in the vertical and horizontal directions.

  The lens array of the present embodiment is a condensing lens comprising a lens having a lens function given to the rectangular pixel region by the refractive index change described in the eighth embodiment, and a convex lens formed thereon. However, they are arranged in the vertical and horizontal directions so that one condenser lens corresponds to one pixel region.

  That is, on the upper surface of the lens material layer 204, the convex lens 201 is formed at a substantially central portion of the pixel region. The lens material layer 204 includes a high refractive index portion 202 and a low refractive index portion 203, and an interface between the two has a predetermined curvature. As a result, the light is refracted when light passes through the interface between them, and the high refractive index portion 202 functions as a condensing lens.

  As described above, the two lens actions of the convex lens 201 and the lens 202 due to the refractive index change are obtained at the center of the pixel region, and the light condensing power is enhanced. For example, when applied to a solid-state imaging device, the lens unit is closer to the light receiving device due to the presence of the lens 202 due to a change in refractive index, and works effectively for light rays having a relatively large incident angle with respect to the lens. Therefore, the light receiving sensitivity is improved.

  Further, by forming the lens 202 with the refractive index change over the entire pixel region as shown in FIG. 12, the ratio of the lens to the area corresponding to one light receiving element is almost 100%, and the effective light receiving area is expanded. , Sensitivity can be improved.

  Note that the lens 202 due to the refractive index change has a larger area than the convex lens 201 and does not necessarily have to be formed in the entire pixel region corresponding to the light receiving element. However, by forming the lens 202 by changing the refractive index in the entire pixel region, the effective light receiving area can be expanded and the sensitivity can be improved.

  Further, the convex lens 201 is not necessarily formed in a part of the pixel region corresponding to the light receiving element, and may be formed in the entire pixel region. By forming the convex lens 201 over the entire pixel region, the effective light receiving area can be expanded and the sensitivity can be improved.

  In addition, the lens 202 due to the change in refractive index is not formed in the lens material layer 204 newly provided as shown in FIG. 12, but directly has a change in refractive index inside a solid-state imaging device or a liquid crystal display device. A condensing lens may be formed.

(Embodiment 11)
13A and 13B are conceptual diagrams of a lens array according to an eleventh embodiment of the present invention, in which FIG. 13A is a plan view, and FIG. 13B is an arrow direction along line XI-XI in FIG. It is sectional drawing seen from. In FIG. 13, only four pixels are shown to simplify the drawing, but in reality, a predetermined number of the pixels shown in FIG. 13A are arranged in the vertical and horizontal directions.

  The lens array according to the present embodiment has a convex lens (first lens) formed in a substantially central portion of a rectangular pixel region and a change in refractive index formed in a region where the convex lens in the pixel region is not formed. A condensing lens composed of a lens (third lens) provided with a lens function is arranged in the vertical and horizontal directions so that one condensing lens corresponds to one pixel region.

  That is, on the upper surface of the lens material layer 214, a convex lens 211 is formed at a substantially central portion of the pixel region. The lens material layer 214 includes a high refractive index portion 213 and a low refractive index portion 212. Accordingly, the low refractive index portion 212 functions as a diverging lens with respect to the light ray incident from above in FIG.

  As described above, for example, when applied to a solid-state imaging device, light is collected by the convex lens 211 in the central portion of the pixel region, and light rays are received by the lens 212 due to refractive index change in the peripheral portion where the convex lens 211 is not formed. Guided to the element. Therefore, the entire pixel area can be used effectively, contributing to improvement in sensitivity.

  Note that the lens 212 due to refractive index change may be formed over the entire pixel region, or may overlap the convex lens 211. As a result, the effective light receiving area can be expanded and the sensitivity can be improved.

  Further, the lens 212 due to the refractive index change is not formed in the lens material layer 214 newly provided as shown in FIG. 13, but directly has a refractive index change inside the solid-state imaging device or the liquid crystal display device. A condensing lens may be formed.

  When the lens array described in each of the above embodiments is used for a solid-state image sensor, the focal length of the condensing lens constituting the lens array is substantially equal to the distance to the light receiving portion of the solid-state image sensor. Preferably formed. Further, when used in a liquid crystal display element, it is preferable that the focal length of the condensing lens constituting the lens array is substantially equal to the distance to the pixel of the liquid crystal display element. In any case, a clear image can be obtained with such a configuration.

(Embodiment 12)
Hereinafter, an example of a method for manufacturing the lens array of the present invention will be described.

  For example, a case where a lens array is formed on a flat film of a solid-state imaging device will be described with reference to FIG.

  First, a synthetic resin layer 421 serving as a lens material is formed on the flat film 402 by spin coating (FIG. 14A). As a material used for the synthetic resin layer 421, for example, a phenol resin, a styrene resin, and an acrylic resin can be used, and other conventionally used materials can also be used. Specifically, the material of the synthetic resin layer 421 is preferably a photosensitive resin obtained by adding naphthoquinonediazide to a polyparavinylphenol-based resin. This resin can be used as a positive resist, and when heat-treated, the resin liquefies due to thermoplasticity and deforms into a hemispherical shape. Thereafter, shape fixing and solidification by thermosetting proceed, and a cured lens shape is realized. . Further, the photosensitive resin can improve the visible light transmittance to 90% or more by ultraviolet irradiation in the process immediately after development, and can be transformed into a lens shape in this transparent state.

  Next, the applied synthetic resin layer 421 is selectively exposed. In the case of using a positive resist such as the above polyparavinylphenol resin, only the portion to be removed is irradiated with ultraviolet light 423 and developed. By patterning using such an ultraviolet stepper, the synthetic resin layer 421 is divided so as to have a one-to-one correspondence with each light receiving portion (FIG. 14B).

  Further, each of the divided synthetic resin portions 422 is bleached. That is, the opaque material is made transparent by irradiating with ultraviolet light. Thereafter, the synthetic resin portion 422 having a rectangular cross section is covered with the overcoat layer 425 by a method such as spin coating (FIG. 14C).

  Each synthetic resin portion 422 covered with the overcoat layer 425 is softened by being heated, and is deformed into a dome-shaped lens shape 401 whose cross section is formed by a convex curve upward (FIG. 14D )). In this deformation, since the overcoat layer 425 is formed, the adjacent synthetic resin portions are difficult to contact each other. In other words, the overcoat layer 425 exhibits a buffering action so that the synthetic resin portion does not approach rapidly. The material of the overcoat layer 425 can be used without particular limitation as long as it is a material capable of exhibiting the above buffering action. On the other hand, the overcoat layer 425 is required not to completely limit the deformation of the synthetic resin portion 422 at the temperature at which the synthetic resin portion 422 is heated.

  By leaving the overcoat layer 425 as it is, it is possible to form a lens array formed in contact with the condensing lenses adjacent in the vertical and horizontal directions. Further, when a lens is formed over the entire region corresponding to the pixel, it can be created by the same method as described above.

  Further, when the overcoat layer 425 is extremely thin, as shown in FIG. 14E, a lens array in which adjacent condenser lenses 401 are substantially in contact can be obtained even if the overcoat layer is removed.

1A and 1B are conceptual diagrams of a lens array according to a first embodiment of the present invention, where FIG. 1A is a plan view, and FIG. 1B is a view from the direction of an arrow along the Ib-Ib line in FIG. FIG. 1C is a cross-sectional view taken along the line Ic-Ic in FIG. It is the figure which showed the relationship between the space | interval of the convex lens adjacent to the vertical and horizontal direction, and a condensing rate. FIG. 3A is a conceptual diagram of a lens array according to a second embodiment of the present invention, in which FIG. 3A is a plan view, and FIG. 3B is viewed from the direction of the arrow along the line IIb-IIb in FIG. Sectional drawing and FIG.3 (c) are sectional drawings seen from the arrow direction in the IIc-IIc line | wire of Fig.3 (a). It is the figure which showed the relationship between the curvature radius of a convex lens, and a condensing rate. FIGS. 5A and 5B are conceptual diagrams of a lens array according to a third embodiment of the present invention, where FIG. 5A is a plan view and FIG. 5B is viewed from the direction of the arrow along line IIIb-IIIb in FIG. Sectional drawing and FIG.5 (c) are sectional drawings seen from the arrow direction in the IIIc-IIIc line | wire of Fig.5 (a). FIGS. 6A and 6B are conceptual diagrams of a lens array according to a fourth embodiment of the present invention, where FIG. 6A is a plan view and FIG. 6B is viewed from the direction of the arrow along the IVb-IVb line in FIG. Sectional drawing and FIG.6 (c) are sectional drawings seen from the arrow direction in the IVc-IVc line | wire of Fig.6 (a). FIG. 7A is a conceptual diagram of a lens array according to a fifth embodiment of the present invention, where FIG. 7A is a plan view, and FIG. 7B is viewed from the direction of the arrows on the VV line in FIG. It is sectional drawing. FIGS. 8A and 8B are conceptual diagrams of a lens array according to a sixth embodiment of the present invention, in which FIG. 8A is a plan view and FIG. 8B is viewed from the arrow direction along the VI-VI line in FIG. It is sectional drawing. FIG. 9A is a conceptual diagram of a lens array according to a seventh embodiment of the present invention, where FIG. 9A is a plan view, and FIG. 9B is viewed from the direction of the arrow along the line VII-VII in FIG. It is sectional drawing. FIG. 10A is a conceptual diagram of a lens array according to an eighth embodiment of the present invention, where FIG. 10A is a plan view, and FIG. 10B is viewed from the direction of the arrow along the line VIIIb-VIIIb in FIG. Cross-sectional view, FIG. 10C is a cross-sectional view seen from the arrow direction along the line VIIIc-VIIIc in FIG. FIG. 11A is a conceptual diagram of a lens array according to a ninth embodiment of the present invention, in which FIG. 11A is a plan view, and FIG. 11B is viewed from the direction of the arrow along the IX-XI line in FIG. It is sectional drawing. It is a conceptual diagram of the lens array concerning Embodiment 10 of this invention, Comprising: Fig.12 (a) is a top view, FIG.12 (b) was seen from the arrow direction in the XX line of Fig.12 (a). It is sectional drawing. It is a conceptual diagram of the lens array concerning Embodiment 11 of this invention, Comprising: Fig.13 (a) is a top view, FIG.13 (b) was seen from the arrow direction in the XI-XI line of Fig.13 (a). It is sectional drawing. It is sectional drawing which showed the outline of the manufacturing method of the lens array concerning Embodiment 12 of this invention in order of the process. It is sectional drawing which showed the outline of the structure of a general solid-state imaging device. It is the figure which showed the outline of the conventional lens array, Comprising: Fig.16 (a) is a top view, FIG.16 (b) is sectional drawing seen from the arrow direction in the XII-XII line | wire of Fig.16 (a). .

Explanation of symbols

111 Condensing lens (lens array)
121 Condensing lens (lens array)
131 First lens 132 Second lens 141 First lens 142 Second lens 143 Inner wall 151 of second lens Fresnel lenses 161, 162, 163 Fresnel lens 171 Step shape (binary lens)
172 Original lens shape 181 High refractive index part (condensing lens part)
182 Low refractive index portion 183 Lens material layer 191 Central portion (high refractive index portion)
192 Peripheral part (low refractive index part)
193 Lens material layer 201 Convex lens 202 High refractive index portion (condensing lens portion)
203 Low refractive index portion 204 Lens material layer 211 Convex lens 212 Low refractive index portion (divergent lens portion)
213 High refractive index portion 214 Lens material layer 301 Lens array (on-chip lens)
302 Intermediate transparent film 303 Color filter layer 304 Flat film 305 Element surface protective layer 306 Metal light shielding film 307 Silicon oxide film or nitride film 308 Polysilicon electrode 309 Charge transfer unit 310 Light receiving unit 311 p well layer 312 n-type semiconductor substrate 401 Lens 402 Flat film 421 Synthetic resin layer 422 Synthetic resin portion 423 Ultraviolet light 425 Overcoat layer

Claims (7)

  A plurality of condensing lenses are arranged in the vertical and horizontal directions, and each of the condensing lenses is a lens array that is installed and used in a one-to-one correspondence with each pixel arranged in a two-dimensional plane. The lens array is a gradient index lens, and the surface of the lens array is substantially flat.   The lens array according to claim 1, wherein the gradient index lens is formed over the entire region corresponding to the pixel.   A solid-state imaging device having a light receiving section arranged in a two-dimensional plane and the lens array according to claim 1 or 2 stacked on the light receiving section, wherein each condenser lens of the lens array is individually The solid-state imaging device corresponds to the light receiving portion of the one-to-one correspondence.   A solid-state imaging device having a light receiving portion arranged in a two-dimensional plane and a transparent substrate stacked on the light receiving portion, wherein the transparent substrate is the lens array according to claim 1, A solid-state imaging device, wherein each condenser lens of the lens array corresponds to each of the light receiving portions on a one-to-one basis.   The solid-state imaging device according to claim 3 or 4, wherein a focal length of the condensing lens is substantially equal to a distance to the light receiving unit.   A liquid crystal display element having pixels arranged in a two-dimensional plane and the lens array according to claim 1 or 2 stacked on the pixels, wherein each condenser lens of the lens array A liquid crystal display element characterized by corresponding one-to-one with a pixel. The liquid crystal display element according to claim 6, wherein a focal length of the condenser lens is substantially equal to a distance to the pixel.

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