JPH08292303A - Planar lens array and its manufacture - Google Patents

Abstract

PURPOSE: To provide a planar lens array of low aberration and high numeral aperture. CONSTITUTION: A planar lens array 20 is made into a refraction factor distributed lens in which the central part of a fine lens 22 exposed on the surface of a board has the highest refraction factor and the refraction factor is continuously lowered toward the outside in the diameter direction. Besides, each fine lens 22 except for the fine lens provided at the position along the peripheral edge of a transparent board 21 has a planar view, and the entire periphery of that outer peripheral edge mutually interfers the outer peripheral edge of the adjacent fine lens 22. Then, the refraction factor at a point P1 crossing a line connecting the central points of two fine lenses 22 at the mutually interferred outer peripheral edges is highest and the refraction factor at a point P2, where the outer peripheral edges of four fine lenses 22 are concentrated, becomes the lowest.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate type lens array applied to a solid-state image pickup device and the like and a manufacturing method thereof.

[0002]

2. Description of the Related Art A flat lens array is disclosed in Japanese Patent Application Laid-Open No. 58-220106 as a prior art example in order to increase the utilization rate of incident light to individual photo-detecting rods of a solid-state imaging rod. It has been known.

In this prior art example, a flat plate type lens array for concentrating incident light on the photodetector element is attached to one surface of the semiconductor substrate on which the photodetector element is formed. Further, the above-mentioned prior art discloses two types of flat lens arrays, one of which is to form a large number of concave portions on one surface side of a transparent substrate through a photoresist film and to provide high refractive index in these concave portions. The material is filled into a minute lens, and the other one is to cover one surface of the transparent substrate with an ion permeation preventive film having small openings formed at a predetermined array pitch, and perform ion exchange through the openings. A minute lens having a continuous refractive index distribution is formed in the transparent substrate.

[0004]

Among the flat plate lens arrays shown in the above-mentioned prior examples, the flat plate lens array manufactured by the method of forming a large number of recesses has a refractive index of a portion forming a minute lens. It is constant, and the aberration at the boundary between the transparent substrate and the minute lens is large. In addition, to some extent, the recess can be formed in close contact, but as long as the recess is formed by etching or the like with the photoresist film attached to the one surface side of the transparent substrate, if the post-treatment is not performed completely, It is not possible to realize an array of minute lenses in a highly dense state (where the outer peripheral edges of the minute lenses interfere with each other), and the aperture ratio (the ratio of the amount of light actually photoelectrically converted to the total amount of incident light) is improved. Is limited.

Among the flat plate lens arrays shown in the prior art, the flat plate lens array manufactured by ion exchange can reduce the aberration at the boundary between the transparent substrate and the minute lens, but it is in a completely dense state. There is no disclosure about the point. It is described that the size of the region acting as a lens can be adjusted by controlling the diffusion time of ions, but this is based on the condition that minute lenses are separated from each other, There is no suggestion.

[0006]

In order to solve the above-mentioned problems, a flat plate lens array according to the present invention has a large number of minute lenses having a higher refractive index than a transparent substrate arranged in a transparent substrate whose both surfaces are flat. In the flat lens array, the microlens is a gradient index lens in which the central portion exposed on the surface in plan view has the highest refractive index and the refractive index continuously decreases toward the outside in the radial direction. Except for the microlenses provided at positions along the peripheral edge of the transparent substrate, each microlens has its entire outer peripheral edge interfering with the outer peripheral edges of the adjacent microlenses in plan view, and two of the outer peripheral edges interfering with each other.
The refractive index is highest at the point intersecting with the line connecting the center points of the three microlenses, and is lowest at the point where the outer peripheral edges of the three or four microlenses are concentrated.

Further, in the method of manufacturing a flat plate type lens array according to the present invention, one side of a transparent substrate having flat surfaces on both sides is coated with an ion permeation preventive film having small openings at a predetermined arrangement pitch, The transparent substrate in this state is immersed in a treatment liquid, and in the method for producing a flat plate lens array, the ions for increasing the refractive index in the treatment liquid and the ions in the glass are exchanged through the small opening, The time of immersion in the treatment liquid was such that the entire outer peripheral edge of the microlenses formed in the transparent substrate by ion exchange interfered with the outer peripheral edges of the adjacent microlenses in plan view.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a perspective view showing a main part of a solid-state image pickup device to which the flat-plate lens array according to the present invention is applied, in which 10 is a solid-state image pickup element, and 20 is a flat-plate lens array as a light collector.

As shown in FIG. 2, the image pickup device 10 is formed by arranging a large number of photodetection devices 12 on a semiconductor substrate 11 in a planar arrangement at intervals, and a light receiving surface 12A of the photodetection device 12 is formed.
Is generally about 30% of the surface area of the image sensor 10.

The flat plate type lens array 20 has a large number of minute lenses 22 ... In a light detecting element 12 of an image pickup element 10 in a transparent substrate 21 made of glass, synthetic resin or the like and having flat surfaces on both sides.
And are arranged and formed in a plane at the same arrangement pitch.

As shown in FIG. 2 (cross section) and FIG. 3 (planar), the distribution of the refractive index of each minute lens 22 is maximum at the center and gradually decreases in the radial direction toward the outer circumference. have. That is, the iso-refractive index surface forms a concentric hemisphere. Between the adjacent microlenses 22 and 22, near the outer periphery, the amount of straight transmitted light to the non-detection area between the photodetection elements 12 is minimized, that is, the incident light is refracted and incident on the detection element light-receiving surface without waste. Are in contact with each other, and the shape of the entrance pupil aperture of the single microlens 22 is a quadrilateral pattern, and this pattern is repeated in the vertical and horizontal directions.

In the image pickup device provided with the flat plate lens array 20 as described above, as shown in FIGS. 2 and 4, a light beam 30 emitted from a subject enters one of the lenses 22 in the flat plate lens array 20, The light receiving surface 12A of the light detecting element 12 is bent toward the central axis due to the refractive index gradient in the lens.
Focused on top.

The flat lens array 20 as described above is
For example, while covering the surface of the transparent glass plate with an ion permeation preventive film, the mask film is provided with small openings at a predetermined lens array pitch, and the transparent glass plate is immersed in the treatment liquid,
By exchanging cations that can increase the refractive index of the substrate glass through the opening into the substrate by exchanging with ions in the glass, this diffusion process is performed until the outer peripheral portions of the diffusion regions interfere with each other between adjacent lens portions. Can be manufactured.

In the flat lens array 20 thus formed, the central portion of the minute lens 22 exposed on the surface of the substrate has the highest refractive index, and the refractive index continuously decreases toward the outside in the radial direction. Each microlens 22 is a distributed type lens, and except for the microlenses provided at positions along the peripheral edge of the transparent substrate 21, the entire outer peripheral edge of the microlens 22 interferes with the outer peripheral edges of the adjacent microlenses in plan view. Among the outer peripheral edges that interfere with each other, the refractive index is the highest at the point (P1) that intersects with the line connecting the center points of the two microlenses, and the highest at the point (P2) where the outer peripheral edges of the four microlenses are concentrated. Get lower.

FIG. 5 is a plan view showing another embodiment of the flat plate type lens array, and FIG. 6 is an enlarged view of a main part of the embodiment shown in FIG. 5, where one point (P3) is outside the three microlenses 22. The pattern is such that the periphery is concentrated. Also in this embodiment, each microlens 22 has its entire outer peripheral edge interfering with the outer peripheral edges of the adjacent microlenses in plan view, and connects the center points of two microlenses among the mutually interfering outer peripheral edges. The refractive index is highest at the point (P1) intersecting with the sagittal line and lowest at the point (P3) where the outer peripheral edges of the three microlenses are concentrated.

The shape pattern of the minute lens 22 is not limited to the above, and the lens boundary line is not limited to a straight line and may include a curved portion.

[0017]

According to the flat plate type lens array of the present invention, a large number of microlenses having a higher refractive index than that of the transparent substrate are arranged in the transparent substrate whose both surfaces are flat. This is advantageous for the configuration in which the member, for example, the image pickup device and the like are brought into close contact with each other. Further, since the minute lens is a gradient index lens, it is possible to reduce the aberration (refractive index difference) at the boundary with the transparent substrate. Further, each minute lens has its entire outer peripheral edge adjacent in plan view. The aperture ratio can be increased because they mutually interfere with the outer peripheral edge of the small lens. Further, according to the method of manufacturing the flat lens array according to the present invention, the flat lens array can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of a solid-state imaging device to which a flat plate lens array according to the present invention is applied.

2 is a cross-sectional view of the main part of FIG.

FIG. 3 is a plan view of a main part of a flat plate type lens array according to the present invention.

FIG. 4 is a perspective view schematically showing how light is condensed onto a photodetector by a light-collecting temporary lens in the apparatus shown in FIG.

FIG. 5 is a plan view showing another embodiment of the flat plate type lens array.

FIG. 6 is an enlarged view of a main part of the embodiment shown in FIG.

[Explanation of symbols]

Reference numeral 10 ... Image sensor, 11 ... Semiconductor substrate, 12 ... Photodetector, 12A ... Light receiving surface, 20 ... Flat lens array, 21
... transparent substrate, 22 ... microlens, 30 ... subject light.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuhei Tanaka 3-5-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka Inside Nippon Sheet Glass Co., Ltd.

Claims (2)

[Claims] 1. In a flat lens array in which a large number of microlenses having a higher refractive index than that of a transparent substrate are arranged in a transparent substrate whose both surfaces are flat, the microlenses have a center exposed on the surface in plan view. The part is a gradient index lens with the highest refractive index and the refractive index decreases continuously toward the outside in the radial direction, and each microlens is flat except for the microlenses provided at the positions along the periphery of the transparent substrate. The entire outer peripheral edge of the adjacent microlenses visually interferes with the outer peripheral edges of adjacent microlenses, and the refractive index is highest at the point of the outer peripheral edges that intersect with the line connecting the center points of the two microlenses. A flat-plate lens array having the lowest refractive index at a point where the outer peripheral edges of four or four microlenses are concentrated. 2. A transparent substrate having flat surfaces on both sides is covered with an ion permeation preventive film having small openings formed at a predetermined array pitch, and the transparent substrate in this state is immersed in a treatment liquid, In a method for manufacturing a flat lens array in which ions that increase the refractive index in the treatment liquid and ions in the glass are exchanged through the small opening, the time for immersion in the treatment liquid is transparent by ion exchange. A method for manufacturing a flat-plate lens array, characterized in that the entire outer peripheral edge of the minute lens formed in the substrate is mutually interfered with the outer peripheral edge of the adjacent minute lens in a plan view.