JP4348062B2 - Solid-state imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid-state imaging device capable of incorporating a compact, wide-angle, high-resolution camera module in a small portable terminal or the like.
[0002]
[Prior art]
In a conventional imaging device, a large number of pixels are discretely arranged on an image sensor, and a light-shielding plate is inserted into each pixel to cut light from other directions, and an opening is provided. In general, a microlens is provided for each pixel in order to collect light.
FIG. 7 is a diagram for explaining a general configuration of a conventional imaging apparatus, and is a cross-sectional view showing an enlarged part of the imaging apparatus. Figure 8 is a graph showing the relationship between the light output to the pixel position of the solid-state imaging device in FIG.
A light-shielding film 36 that forms an opening is provided on a photodiode 35 that is a pixel of the imaging unit, and a color filter 37 is disposed thereon. Further, a microlens 38 corresponding to the photodiode 35 is bonded to the upper surface thereof. The maximum incident angle of the incident light 39 is limited by the opening formed by the light shielding film 36.
[0003]
In the above configuration, light is efficiently incident on each pixel. Actually, however, the amount of light to the pixels in the peripheral portion is extremely reduced as shown in FIG . That is, there is a reduction in the amount of light due to the cosine fourth power rule around the taking lens, and vignetting occurs at the opening, which increases shading. For this reason, the telecentricity of the taking lens is improved so that light is incident as parallel as possible so that the taking lens can be used in a digital camera or a mobile phone.
[0004]
In a camera attached to a portable terminal, shading restrictions are large in the conventional solid-state imaging device, and the lens configuration is limited as described above, and it is difficult to reduce the size of the camera module including the lens and the solid-state imaging device. . Therefore, it is difficult to incorporate a high-resolution camera in a portable terminal or the like that is being miniaturized.
[0005]
Accordingly, various proposals have been made as imaging devices that solve the above-described problems.
In the proposed 1 (Japanese Patent Laid-Open No. 2002-170944), the principal ray angle incident from the lens becomes larger as it goes to the periphery, but the surrounding pixels are shifted so as to become larger as it goes to the periphery. The light shielding layer is laid out so as not to block the light of the microlens.
Proposed No. 2 (Japanese Patent Laid-Open No. 2002-237404) shifts the light receiving portion outside the center to the outside in the same manner as described above.
Proposed 3 (Japanese Patent Laid-Open No. 2001-160973) shows that the microlens and the light receiving unit are shifted by an appropriate amount.
[Patent Document 1]
JP 2002-170944 A [Patent Document 2]
JP 2002-237404 A [Patent Document 3]
Japanese Patent Laid-Open No. 2001-160973
[Problems to be solved by the invention]
FIG. 9 is a diagram for explaining a specific configuration of Proposition 1 described above.
The photodiode region 34 in the vicinity of the periphery is provided with its arrangement position shifted corresponding to the inclination of the principal axis light beam. Similarly, the opening 30 by the light shielding layer 31 is also shifted. With such a configuration, shading at the periphery is suppressed.
However, although this proposal including this example can achieve a certain size reduction, it is difficult to further reduce the size. In particular, as described above, it is difficult to meet the demand for further downsizing of portable terminals and the like.
[0007]
Further, in the above-described conventional imaging apparatus, the incident angle (θ) in FIG. 9 is set to a predetermined angle or less, for example, 20 degrees or less in order to suppress shading for practical use to a required value or less.
Therefore, there is a demand for an imaging apparatus that can make the chief ray incident angle of the taking lens greater than a predetermined angle.
The reason that the chief ray incident angle cannot be made large is that, as described above, it is difficult to reduce the size of the camera module, and when the chief ray incident angle is large, a sufficient light collection rate cannot be obtained. . Furthermore, it is difficult to reduce the size of the optical system (small overall length) and install an optical system with a wide angle of view.
An object of the present invention is to increase the chief ray incident angle as compared with a conventional imaging apparatus, thereby reducing the size (total length is small) of a camera module provided with an optical system and an optical system with a wide angle of view. An object of the present invention is to provide a solid-state imaging device that can be installed.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an imaging apparatus according to the present invention is configured as follows. In other words, according to the first aspect , an imaging unit in which a plurality of pixels are arranged in parallel , an opening formed by a light-shielding film on each pixel, and a first lens provided on the imaging unit When, that close a condensing center by said first of said first lens is the principal ray and the second lens and a second lens which is provided corresponding to each pixel, on top of the lens characterized as having a curvature.
According to claim 2, deviation of the center of the second lens corresponding to the center and the opening of the aperture, toward the periphery from the center of the imaging unit, and wherein the larger .
According to claim 3, wherein the pixel is characterized by arranging at step shape so as to approach the second lens toward the periphery from the center of the imaging unit.
According to claim 4, characterized in that the said opening, and a center of the second lens corresponding to the opening and the center arranged so as to be substantially coincident.
According to claim 5, wherein the opening is characterized by configuring so as to increase toward the periphery from the center of the imaging unit.
According to a sixth aspect of the present invention, the first lens is made of a resin material and has a concave surface directed toward the object side.
[0009]
[Action]
According to the above configuration, even if the peripheral chief ray incident angle with respect to the imaging apparatus is large, it is possible to suppress the reduction in the amount of light at the periphery of the imaging region. Further, by increasing the peripheral chief ray incident angle with respect to the imaging device, the optical total length can be shortened, and the degree of design freedom can be increased. By arranging an optical system in this imaging apparatus, a small optical module can be configured. Furthermore, an optical system with a wide field angle can be configured.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Figure 1 is a sectional view showing an embodiment of the solid-state image pickup equipment according to the present invention, FIG. 2 is a partial view showing the details of FIG.
FIG. 1A is an exaggerated shape of each pixel (photodiode) and each microlens of the imaging unit of the solid-state imaging device, and is configured with a smaller number of pixels than the actual one. Yes.
In the imaging unit 1, a large number of pixels 1a to 1j are arranged side by side. The planar shape of the imaging unit 1 is, for example, a square shape. An opening made of a light shielding film 16 is formed on the imaging unit 1, and a color filter 5 is further disposed thereon. A resin lens 2 is bonded on the color filter 5. The resin lens 2 is formed with a curvature that brings the principal ray and the condensing center of the microlens closer to each other, and enhances the efficiency of condensing light on the peripheral pixels.
[0011]
Further, microlenses 3 a to 3 j are bonded on the resin lens 2 so as to correspond to the respective pixels.
For example, assuming that the micro lens 3e is at the center position, the center of the micro lens 3e and the center of the opening of the pixel 1e corresponding to the center are matched. However, the aperture centers of the pixels 1a to 1d and 1f to 1j arranged on the outer side from the center are shifted outward with respect to the centers of the corresponding microlenses 3a to 3d and 3f to 3j (FIG. 1B). The pixel shift amount is increased in the peripheral direction. Thereby, the incident amount of the light condensed by the microlens to the peripheral pixel is increased.
[0012]
FIG. 1C shows an embodiment of a staircase-shaped imaging unit that approaches a corresponding microlens as the pixels of the imaging unit 1 are closer to the periphery. In this embodiment, in addition to the configuration in which pixels are shifted outward toward the peripheral direction, the imaging unit 1 is configured in a staircase shape. Moreover, it is also possible to configure the imaging unit 1 in a staircase shape without adding a configuration in which the pixels are shifted outward toward the peripheral direction. By adding this configuration, the amount of light incident on the peripheral pixels can be further increased.
[0013]
Further, FIG. 1d shows an embodiment in which the aperture center of each pixel of the imaging unit 1 and the center of the corresponding microlens are substantially matched. In the case of this embodiment, the configuration in which the pixels are shifted outward toward the peripheral direction is not adopted, and the center of the microlens on the resin lens 2 and the aperture center of each pixel corresponding thereto are all substantially omitted. By configuring so as to match, the amount of light to the peripheral pixels is increased.
Therefore, in the above embodiment, shading can be reduced even if the chief ray incident angle is larger than a predetermined angle, and the chief ray having a large chief ray incident angle, for example, an incident angle of 20 to 35 degrees, has a required performance. A solid-state imaging device can be realized. In some cases, a chief ray incident angle of 35 degrees or more can be handled.
The resin lens is used in the above embodiment because it is easy to manufacture, and other lens materials may be used. For example, a glass material.
[0014]
FIG. 3 is a diagram showing a configuration in which the opening is made larger in the peripheral pixels . An enlarged view of the configuration in the vicinity pixels centered pixel and both neighboring, 3 also FIGS. 1 (a) and which was exaggerated shapes each pixel and each microlens of the imaging section of the same solid state imaging device is there.
With respect to the photodiode regions 11a to 11c which are the respective pixels of the image pickup unit, the light shielding layers 12a-1, 12a-2, 12b-1, 12b-2, 12c-1, and 12c-2 are arranged on the photodiode regions 11a to 11c. Openings 15a to 15c are formed in the diode regions 11a to 11c. Further, microlenses 13a to 13c corresponding to the photodiode regions 11a to 11c are joined thereon.
Light shading is reduced by increasing the opening area of the adjacent openings 15b and 15c with respect to the central opening 15a, and increasing the opening area as the photodiode region is located at the peripheral position.
Configuration of increasing the light receiving surface as the pixel of the peripheral portions may be obtained pressurized to the present embodiment.
[0015]
FIG. 4 is a graph showing an ideal relationship of light output with respect to the pixel position of the solid-state imaging device, and FIG. 5 is a graph when the present invention is applied with respect to the relationship of light output with respect to the pixel position of the solid-state imaging device.
Ideally, the optical output (output voltage) to the central pixel and the peripheral pixel is required to be the same as shown in FIG. 4 , but the conventional configuration has the characteristics shown in FIG. The closer to the periphery, the lower the output voltage and the greater the shading.
However, by applying the present invention, the light output to the peripheral portion as shown in FIG. 5 it can be increased compared to FIG.
[0016]
Specific numerical examples are shown below.
The condensing rate when the microlens is formed on the light receiving surface is as follows.

Principal ray angle (°) 0 10 20 30 40
Condensing rate of light receiving surface (%) 55 30 40 19 8
For the above numerical values, the light collection rate when corrected with a resin lens is
Principal ray angle (°) 0 10 20 30 40
Condensing rate of light receiving surface (%) 60 50 45 35 25
[0017]
A comparison of the light collection efficiency when the principal ray angle is changed to 0 to 40 °, when corrected with a resin lens, for large Kinanushi ray angle, if you do not have the configuration of the present invention In comparison, a large condensing rate is shown. Furthermore, it can be understood that the light condensing rate is higher when the microlens is formed into a Fresnel shape than when the resin lens is formed.
[0018]
FIG. 6 is a diagram showing an apparatus example in which an optical system is arranged in the solid-state imaging apparatus according to the present invention.
The camera module is configured by arranging a solid-state imaging device 22 according to the present invention and a taking lens thereon. The taking lens of this example has a concave lens 21 on the solid-state imaging device 22 side and a convex lens 20 behind it.
In order to reduce the size of the image pickup apparatus, the telephoto type is more advantageous, and a symmetric configuration with respect to the stop is more advantageous for aberration correction. Therefore, the camera module can be further miniaturized when used in the fixed imaging apparatus according to the present invention that can reduce shading even when the incident angle of the chief ray is large.
[0019]
【The invention's effect】
As described above, according to the present invention, it is possible to downsize a camera module including an imaging device and a lens system. Therefore, if the camera module is used for a portable terminal, the portable terminal incorporating the camera can be miniaturized. In addition, an optical system having a large chief ray angle incident on the pixels of the imaging unit can be used, and shading can be reduced.
Furthermore, an optical system with a wide field angle can be formed in the solid-state imaging device.
The camera module comprising the solid-state imaging device according to the present invention and the optical system disposed on the solid-state imaging device is not limited to a portable terminal, and can be widely applied to devices that require miniaturization, such as digital cameras, in-vehicle cameras, and security cameras. It is.
[Brief description of the drawings]
1 is a cross-sectional view illustrating a form of implementation of the solid-state imaging device according to the present invention.
FIG. 2 is a diagram illustrating details of the solid-state imaging device of FIG.
FIG. 3 is a cross-sectional view showing a configuration in which the opening is made larger in the peripheral pixels .
FIG. 4 is a graph showing an ideal relationship of light output with respect to a pixel position of a solid-state imaging device.
5 is a graph of the time according to the present invention the relationship between the light output to the pixel position of the solid-state imaging device.
FIG. 6 is a diagram illustrating an example of an apparatus in which an optical system is arranged in a solid-state imaging apparatus according to the present invention.
FIG. 7 is a diagram for explaining a general configuration of a conventional imaging apparatus.
8 is a graph showing the relationship between the light output to the pixel position of the solid-state imaging device in FIG.
FIG. 9 is a diagram for explaining a specific example of a conventional imaging apparatus.
[Explanation of symbols]
1 imaging unit
2 resin lens unit 3, 1 3a, 13b, 13c microlenses 14a, 14b, 14 c principal ray 5 color filters 11a, 11b, 11c photodiode region 12a-1,12a─2,12b-1,12b-2,12c -1,12c-2 Light-shielding layer 16 Light-shielding film 20 Convex lens 21 Concave lens 22 Solid-state imaging device 30 Opening

Claims (6)

An imaging unit comprising a plurality of pixels arranged in parallel ;
An opening formed by a light shielding film on each pixel;
A first lens provided on the imaging unit;
A second lens provided corresponding to each pixel on the first lens;
It said first lens is a solid-state image sensor you characterized as having a curvature that close a condensing center by the main ray and the second lens. Deviation between the center of the second lens corresponding to the center and the opening of the aperture, toward the periphery from the center of the imaging unit, according to claim 1, characterized in that larger solid Imaging device. The pixel is a solid-state imaging device according to claim 1 or 2, characterized in that arranged in stepped shape so as to approach the second lens toward the periphery from the center of the imaging unit. The solid-state imaging device according to claim 1, characterized in that the said opening, and a center of the second lens corresponding to the opening and the center arranged so as to be substantially coincident. The opening, the solid-state imaging device according to claim 1, characterized in that configured to be larger toward the periphery from the center of the imaging unit. The solid-state imaging device according to claim 1, wherein the first lens is formed of a resin material and has a concave surface directed toward the object side.

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