JP2003124449A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microminiaturized solid-state image pickup device. SOLUTION: An image pickup lens and the image pickup device having a small inexpensive apodized aperture is realized by means of a high-efficiency processing method such as two-color molding of resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microminiature image pickup device mainly used for portable information equipment and the like.

[0002]

In recent years, advances in semiconductor design and manufacturing techniques have made it possible to miniaturize the pixel size of image pickup devices such as CCDs and CMOSs. The focal length of the lens used in these image pickup devices is generally the same as the screen size of the image pickup element, specifically, the length substantially equal to the diagonal line of the screen. Therefore, if the size of the image pickup device is reduced, the focal length of the lens can be shortened, and the size of the entire image pickup device can be reduced.

However, when the focal length of the lens is reduced to about several millimeters or less, deterioration of resolution due to light diffraction cannot be ignored. This is because the resolution limit due to diffraction is determined by the aperture ratio of the image pickup lens and has nothing to do with the focal length. Therefore, if the screen size and the focal length are both small, the resolution limit relative to the screen size becomes relatively large.

In order to avoid this, a lens having a small aperture ratio and high resolution is required. However, since such a lens generally corrects aberrations by combining several lenses, the image pickup apparatus is expensive and large. There is a difficulty of becoming.

On the other hand, in order to reduce diffraction fringes in an image pickup lens having a large aperture ratio, that is, a relatively dark image pickup lens, there is known a method of adding a filter in which the central portion is transparent and the density increases toward the periphery. This is called apodization, and is described in detail, for example, on pages 172 to 174 of "Optical Technology Handbook Supplement" (Asakura Shoten, 1975).

In order to realize such a transmittance distribution type optical component, a mask vapor deposition method or the like has been conventionally known, but in order to realize a diaphragm having a diameter of about several millimeters,
There is a problem in that the accuracy of the transmittance distribution is poor, the manufacturing time is long, and the cost is high.

Further, as shown in FIG. 4, a plano-concave lens 12 out of two lenses of plano-concave type 12 and plano-convex type 13 is made of colored glass, and both are bonded to realize an apodization diaphragm (for example, US No. 3,843,235 Minolta camera) is also known.

However, in such a method, the two lenses 12 and 13 and the imaging lens 1 are inserted into the holes of the holding member 22 and assembled by the fixing member 23, so that the number of parts is large and the assembly is required. Since it will increase trouble,
It is hard to say that it is suitable for downsizing and cost reduction.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and uses an imaging lens having a small and inexpensive apodization diaphragm and an imaging method by a high-efficiency processing method such as two-color molding of resin. It realizes the device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) FIGS. 1A and 1B show a first embodiment of the present invention. Reference numeral 1 is an imaging lens, 1a is a first surface of the imaging lens, and 1b is a second surface. The second surface 2b of the holding member 2 is molded so as to be in close contact with 1a without any gap. The image pickup device 3 is housed and fixed in the case 4, and is connected to a terminal 41 for electrical connection by a thin metal wire 42. The case 4 and the holding member 2 are assembled by means such as adhesion.

Here, the holding member 2 has an index of refraction substantially equal to that of the image pickup lens 1 and an ND (neutral density) glass having a substantially constant light absorption rate in the visible light region regardless of wavelength, or an equivalent characteristic. It is composed of a resin having. Therefore, the light rays are hardly reflected or refracted at the interface between 2b and 1a, and the thickness distribution of the member 2 constitutes the apodization diaphragm. That is, the light ray 1 passing near the optical axis 11
01 has almost no absorption, whereas 102 and 103 have a distribution in which more is absorbed as the distance from the optical axis increases. As a result, the image formed on the surface of the image sensor 3 is less susceptible to the influence of diffraction fringes as described in the above-mentioned literature. The curved surface shapes of 2b and 1a may be designed so as to realize a desired transmittance distribution.

Such a structure can be easily manufactured by a two-color molding method.

That is, a method in which the lens 1 prepared in advance by molding or polishing is fixed in a mold (not shown), and then glass or resin as a material of the holding member 2 is injected and cured in a molten state.

The material of the holding member 2 is held in a semi-molten state,
For example, a method of burying the lens 1 therein and then curing the lens 1 may be used.

Reference numeral 21 denotes a light-shielding film, which may be provided for the purpose of preventing a light ray which does not pass through the image pickup lens 1 but passes through only the holding member 2 from reaching the image pickup element 3. If necessary, an antireflection film (not shown) may be provided on one or both of the light entrance surface side 2a of the holding member 2 and the light exit surface side 1b of the imaging lens 1 by vacuum vapor deposition, coating, or the like.

If the color mosaic filter 3a for each pixel is formed on the surface of the image pickup device 3, the image is color-separated to obtain a color image.

(Second Embodiment) FIG. 2 shows a second embodiment. A plurality of imaging lenses 1 are attached to the holding member 2 with their optical axes 11 parallel to each other. Each lens forms an image 201 corresponding to the same subject 200. However, compared with the distance 300 from the lens 1 to the subject 200, the distance 301 between the optical axes and the distance from the lens to the image pickup element 30
When 2 is small enough, the images 201 can be considered to be identical to each other. Under this condition, the imaging lens 1
If a color filter 3b is inserted between the image sensor 3 and the image sensor 3 or on the surface of the image sensor, a color image is obtained by color separation. Compared with the first embodiment, an expensive mosaic filter becomes unnecessary.

(Embodiment 3) FIG. 3 shows a third embodiment. A plurality of image pickup lenses 1 are attached with their optical axes 11 parallel to each other, and a plurality of image pickup elements 3 are also attached corresponding to the lenses. Unlike the second embodiment, if the optical axis interval 11 is made relatively larger than the distance 300 to the subject 200, the outputs of the individual image pickup devices 3 are combined to obtain a wide range image while approaching the subject. . A scanner that mainly converts a flat original into a digital one can be made extremely compact. By using the image sensor 3 as a one-dimensional line sensor and mechanically moving the subject 200, that is, the document, an image pickup apparatus applicable to a facsimile or the like can be configured in a small size.

[0019]

As described above, according to the present invention, an image pickup apparatus, particularly an image pickup apparatus using a semiconductor image pickup device, can be constructed in a very small size and at a low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional apodization diaphragm.

[Explanation of symbols]

1 Imaging lens 11 optical axis 12 Plano-concave lens 13 Plano-convex lens 2,22 holding member 21 Light-shielding film 23 Fixing member 3 image sensor 3a Mosaic filter 3b filter 4 cases 101-103 rays 200 subjects 201 statue

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H04N 5/335 H01L 27/14 DF Term (Reference) 2H043 AE01 AE02 2H044 AA02 AA11 AA17 AA20 AD01 AG01 4M118 AB01 GB01 GD01 GD03 GD07 HA19 HA23 HA24 5C024 AX01 CX37 CY47 CY48 CY49 EX43 GY01 GY31

Claims (2)

[Claims] 1. An image pickup device comprising a semiconductor image pickup element, a biconvex image pickup lens having a first convex surface and a second convex surface, and a holding member for holding the image pickup lens, wherein the holding member is black. A resin or glass that is semi-transparent and has a substantially uniform light absorption coefficient in the visible light range and a refractive index almost equal to that of the image pickup lens. Furthermore, it holds the first convex surface of the image pickup lens so that it is buried. An imaging device characterized by the above. 2. The plurality of imaging lenses are arranged such that their optical axes are parallel to each other.
Imaging device.