JPH04258165A - Image sensor - Google Patents

Abstract

PURPOSE:To obtain a small-sized, light-weighted inexpensive image sensor by laminating an optical low pass filter made of a diffraction grating and a solid state image sensing element through a spacer, and integrally sealing an image sensing member, a mount, part of outer leads with resin. CONSTITUTION:An optical low pass filter 1 made of a diffraction grating and a solid state image sensing element 3 are laminated through a spacer 2 having a square-shaped flat shape. An image sensing element having a hollow part 30 at an image sensing surface side of the element 3, a mount 5 mounted with the member, bonding wires 8a, b for connecting the element 3 to outer leads 7a, 7b, and part of the leads 7a, 7b are sealed with resin 9. A grating surface of the filter 1 is opposed to the element. A color filter array may be formed on the imaging surface of the element 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device used in video movies, electronic still cameras, and the like.

0002

[Prior Art] A single-chip solid-state imaging device such as a video movie or an electronic still camera is equipped with a color filter array to obtain a color signal, which contains high frequency components corresponding to the pitch of the color filter array. False color signals are generated from the subject. In addition, single-chip solid-state imaging devices are equipped with solid-state imaging elements that have pixels arranged discontinuously and regularly, and false signals are generated from objects that contain high-frequency components corresponding to the pixel pitch. . Therefore, an optical low-pass filter is installed in the optical system of the single-chip solid-state imaging device to prevent the generation of false signals and false color signals. Optical low-pass filters are usually
A structure in which three or more crystal plates and one infrared cutoff filter are laminated is used.

FIG. 2 shows a schematic configuration diagram of an example of a conventional imaging device equipped with the above-mentioned optical low-pass filter. In the imaging device shown in FIG. 2, a solid-state imaging device 10 and a ceramic package 13 are fixed at the bottom of the package 13 via an adhesive layer 14, and the solid-state imaging device 10 is fixed via bonding wires 15a and 15b. It is connected to external leads 16a and 16b. package 1
A glass protection plate 12 is attached to the opening 3 via an adhesive layer 11. An optical low-pass filter formed by stacking crystal plates 17a, 17b, and 17c and an infrared cutoff filter 18 is arranged on the light incident surface side of the solid-state image sensor 10. A microlens array 19 may be formed on the imaging surface of the solid-state imaging device 10.

[0004] Furthermore, in order to reduce the size of an imaging device equipped with the above-mentioned optical low-pass filter, an imaging device having a structure in which a solid-state imaging device is sealed using a transparent resin has been proposed ( Institute of Electronics, Information and Communication Engineers Technical Research Report CP
(See M90-41). FIG. 3 shows a schematic configuration diagram of an imaging device having the above structure. In the imaging device shown in FIG.
The solid-state image sensor 20 and the mount section 21 are fixed via an adhesive layer 22, and the solid-state image sensor 20 and external leads 23a and 23b are connected via bonding wires 24a and 24b. The solid-state image sensor 20, the mount section 21, the bonding wires 24a and 24b, and a portion of the external leads 23a and 23b,
It is integrally sealed with transparent resin 25. An optical low-pass filter formed by laminating a quartz plate and an infrared cutoff filter is arranged on the light incident surface side of the solid-state image sensor as in the image pickup device shown in FIG. Here, the light incident surface 25a of the transparent resin 25 is sufficiently polished. In addition, a glass plate may be installed on this surface (Japanese Patent Laid-Open No. 60-1
(See Publication No. 8941).

[0005]

The package 13 in the image pickup device shown in FIG. 2 has problems in that it is heavy, large, and expensive. The imaging device shown in FIG. 3 has a problem in that the surface of the imaging surface of the solid-state image sensor is covered with transparent resin, and a microlens array cannot be installed on the imaging surface.

On the other hand, the optical low-pass filter having a structure in which a crystal plate and an infrared cutoff filter are laminated is heavy and large, and furthermore, the surface of each crystal plate needs to be thoroughly polished one by one. Because of this, it is inferior to mass production,
It has the problem of being expensive. In order to solve the above problems, optical low-pass filters consisting of diffraction gratings have been developed (Japanese Patent Publications No. 49-20105, 53741-1974, and 57-4
(See Publication No. 2849). MTF (Mo
duration Transfer Function
ion) characteristics are shown in FIG. The period of the diffraction grating is represented by d, the width of the convex part of the diffraction grating is represented by a, and the diffraction grating and the solid-state imaging device surface or the color filter array surface formed on this surface (hereinafter, these are collectively referred to as the imaging surface) ) is represented by b, and the wavelength of the incident light is represented by λ, the cutoff frequencies fa and fb shown in the MTF characteristics of FIG. 4 are expressed by the following formulas. (i) When a≦d/2, fa=a/bλ (1) fb=(d
-a)/bλ (2) (ii) When d/2<a<d, fa=(d-a)/bλ (3) fb=a/bλ (4)

0007
] The spatial frequency of an object that generates a false signal is determined by the pixel period of the solid-state image sensor, and the spatial frequency of an object that generates a false color signal is determined by the period of a set of color filter arrays. Set the cutoff frequencies fa and fb so that these spatial frequencies are cut off, and use formulas (1) and (2) or formulas (3) and (4) according to the values to perform the above calculation. Find d, a and b. By using the diffraction grating thus obtained, generation of false signals and false color signals can be prevented.

The cutoff frequency of the optical low-pass filter made of the above-mentioned diffraction grating changes depending on the value of the distance b between the optical low-pass filter and the imaging surface, as is clear from the above formulas (1) to (4). . If the cutoff frequency deviates from the above preset value, false signals and/or false color signals may occur, so make sure that the distance b between the optical low-pass filter and the imaging plane is an accurate value. It is necessary to arrange an optical low-pass filter and a solid-state image sensor. However, the above-mentioned distance b is small, typically in the range of 5 to 1000 microns, and it is difficult to arrange it at an accurate position.

An object of the present invention is to integrate a solid-state image sensor with an optical low-pass filter made of a diffraction grating that is placed at a position with an accurate distance from the imaging surface and blocks false signals and/or false color signals. The objective is to provide a compact, lightweight, and low-cost imaging device.

0010

[Means for Solving the Problems] According to the present invention, the above object is achieved by stacking an optical low-pass filter consisting of a diffraction grating and a solid-state image sensor with a spacer interposed therebetween, so that the image-sensing surface side of the solid-state image sensor An imaging member having a hollow part, a mount part on which the imaging member is placed, bonding wires connecting the solid-state imaging element and the external leads, and a part of the external leads are integrally sealed with resin. This is achieved by providing an imaging device characterized by the following.

In the above-mentioned imaging member, a microlens array is formed on the imaging surface of the solid-state imaging device, and the imaging device having a hollow portion above the microlens array has an improved light collection efficiency due to the microlens array. Has high sensitivity.

0012

[Examples] The present invention will be specifically explained below with reference to Examples.

Embodiment 1 FIG. 1 shows a schematic configuration diagram of an example of an imaging apparatus according to the present invention. The imaging device shown in FIG. 1 includes an optical low-pass filter 1 consisting of a diffraction grating and a solid-state imaging device 3, which are stacked together with a spacer 2 having a square-shaped planar shape interposed therebetween. An imaging member having a hollow portion 30 on its side, a mount portion 5 on which the imaging member is placed, bonding wires 8a and 8b connecting the solid-state imaging device 3 and external leads 7a and 7b, and external leads 7a and 7b. A part of it is sealed with resin 9. The lattice plane of the optical low-pass filter 1 faces the solid-state image sensor. A color filter array may be formed on the imaging surface of the solid-state image sensor 3. Further, the microlens array 4 may be formed on the imaging surface of the solid-state image sensor 3 or on a color filter array formed thereon. The light incident surface 1a of the optical low-pass filter 1 may be covered with a sealing resin 9.

Optical low-pass filter 1 in the present invention
has a lattice in one direction or a lattice in two directions that intersect with each other. The grating has a cross-sectional shape such as rectangular, trapezoidal, or sinusoidal waves, and typically has a depth in the range of 0.1 to 1 micron. The grating plane of the optical low-pass filter 1 may face the light incident surface side.

The microlens array 4 has a size corresponding to the pixels of the solid-state image sensor, and is made of a hemispherical transparent material. The incident light is focused due to the difference in refractive index between the air in the hollow portion and the transparent material, and the efficiency of focusing the light onto the solid-state image sensor is increased. This improves the sensitivity of the solid-state image sensor.

The spacer 2 may be a resin film of a predetermined thickness, a patterned photosensitive resin of a predetermined thickness, a material containing beads or rods of a predetermined diameter in adhesive, or the like. can. Preferably, the thickness of the spacer is in the range of 5 to 1000 microns. The thickness of the spacer provides a distance between the optical low-pass filter and the imaging plane at which spatial frequencies that generate false and/or false color signals are blocked. The spacer 2 is installed on the solid-state image sensor 3 so as not to cover the imaging area of the solid-state image sensor 3. When installing the spacer 2 on the solid-state image sensor 3, the spacer 2 is installed so that no gap is created in which the sealing resin flows into the hollow portion 30 between the optical low-pass filter 1 and the solid-state image sensor 3.

Epoxy resin or the like can be used as the sealing resin 9. When the light incident surface 1a of the optical low-pass filter 1 is covered with a sealing resin, the resin needs to be transparent. on the other hand,
If the light incident surface 1a of the optical low-pass filter 1 is not covered with the sealing resin 9, the resin does not need to be transparent, and a resin containing a filler made of an inorganic material such as silica may be used. Can be used. A resin containing a filler is preferable because it has a small molding shrinkage rate and a low coefficient of thermal expansion. Further, as the sealing resin 9, a resin containing a black pigment can be used,
By using this resin, it is also possible to prevent the generation of stray light.

[0018]

According to the present invention, an optical low-pass filter made of a diffraction grating that is placed at a position with an accurate distance from the imaging surface and blocks false signals and/or false color signals is integrated with a solid-state imaging device. As a result, a compact, lightweight, and low-cost imaging device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an example of an imaging device of the present invention.

FIG. 2 is a schematic configuration diagram of an example of a conventional imaging device.

FIG. 3 is a schematic configuration diagram of another example of a conventional imaging device.

FIG. 4 M of an optical low-pass filter consisting of a diffraction grating
It is a TF characteristic diagram.

[Explanation of symbols]

1 Optical low-pass filter 2
Spacer 3 Solid-state image sensor 4 Microlens array 5
Mount parts 7a, 7b External leads 8a, 8b Bonding wire 30 Hollow part 9 Sealing resin

Claims (2)

[Claims] Claim 1: An optical low-pass filter consisting of a diffraction grating and a solid-state imaging device are stacked with a spacer interposed therebetween, and an imaging member having a hollow portion on the imaging surface side of the solid-state imaging device, and the imaging member placed on the imaging member. What is claimed is: 1. An imaging device comprising: a mounting portion for connecting a solid-state imaging device; a bonding wire for connecting a solid-state imaging device and an external lead; and a part of the external lead, which are integrally sealed with resin. 2. The imaging device according to claim 1, wherein a microlens array is formed on an imaging surface of a solid-state imaging device, and a hollow portion is provided above the microlens array.