JPH0298284A - Picture reader - Google Patents

Abstract

PURPOSE:To prevent a phenomenon that light is bypassed to a dark part of an edge part having a large brightness density difference and density reduction is caused by providing an optical absorbing member in the vicinity of or in contact with a face other than the photodetection face of an image sensor. CONSTITUTION:A frosting and insulating black paint member 101 is applied or printed onto the surface (except the upper side of the photodetection face) of a protection layer 41 of a photoelectric convention element 4 in a line sensor. Thus, since the light having being incident in the face of a photodetector mask 42 in a conventional device is absorbed by the paint member 101, the scattering is prevented. Since the direct incident light is surely made to the photodetection face 43, the size of the part 101a not applied with black painting slightly larger than the size of the photodetecting face 43. Thus, the generation of counter of the edge part is suppressed and a picture with high density resolution and sharpness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial Field of Application) The present invention relates to a plane scanning type image reading device using an image sensor.

(Prior art) Image sensor, for example, CCO that constitutes a line sensor
The image light incident on the light receiving surface of the photoelectric conversion element includes, in addition to the image light that is directly incident (hereinafter referred to as direct incident light), the image light that is incident on the light receiving surface of the photoelectric conversion element and inside the optical window glass to protect the photoelectric conversion element. There is light that enters the light after being reflected by a light-receiving part mask surface provided in the vicinity of the light receiving part (hereinafter referred to as flare light). This flare light enters the light-receiving surface of the photoelectric conversion element at a different position from the light-receiving surface of the photoelectric conversion element at the position where it should originally enter, and thus has an adverse effect on the image obtained.

Therefore, the applicant of the present invention developed the line sensor described below in order to prevent the adverse effects of the flare light. FIG. 5 is a perspective view schematically showing an example of the line sensor, and FIG. 6 is a sectional view taken along the line ^-A. In this line sensor, an optical window glass 2 is attached to the casing l above the light receiving surface of the photoelectric conversion element 4 in order to protect the light receiving surface of the photoelectric conversion element 4 mounted on the casing l from scratches caused by dust and deterioration due to outside air. It is bonded with an inert gas interposed therebetween, and the photoelectric conversion element 4° is sealed. The front and back surfaces of the optical window glass 2 are coated with a film (for example, MgF, Sin) to prevent reflection of image light.

etc.) 11.12 is coated. The image light whose flare light has been reduced by the optical window glass 2 is converted into an electrical signal by the photoelectric conversion element 4, and the electrical signal is output to the outside via the lead bin 3, so that a good image can be obtained. (See Utility Model Application No. 82-71798).

FIG. 7 is a perspective view schematically showing another example of a line sensor for preventing the adverse effects of flare light, corresponding to FIG. 5, and FIG. 8 is a cross section taken along line 8-B of FIG. They are diagrams shown in correspondence, and the same components are given the same reference numerals and explanations will be omitted. In this line sensor, a light-transmitting protective film 13 (eg, epoxy resin, silicone resin, etc.) is coated on the light-receiving surface of a photoelectric conversion element 4 mounted on a casing. Since this protective film 13 is a thin film and is in close contact with the photoelectric conversion element 4, there is almost no misalignment between the directly incident light and the flare light, making it possible to obtain a good image (Utility Application No. 62-71799 (see issue).

(Problems to be Solved by the Invention) Although it is possible to reduce flare light to some extent with the line sensor and photoelectric conversion element coated with the above-mentioned optical window glass coated with an antireflection film, it is possible to reduce flare light to some extent. , there were limits. For example, as shown in FIG. 9, the light passes through the optical window glass 2 and the protective layer (for example, 5 in 2) 41 of the photoelectric conversion element 4 and is reflected on the surface of the light-receiving mask (for example, an aluminum vapor-deposited layer for advance light) 42. A part of the light may be reflected again by the antireflection film It, 12 of the optical window glass 2 and enter the light receiving surface 43. In addition, as shown in Figure 1O, the light develops by piping within the protective film.

That is, the image light may be incident on the light-receiving surface 43 due to a phenomenon in which it is repeatedly reflected and transmitted through the protective film 13 .

Therefore, for example, when light with the distribution shown in Figure 11 is incident, the blurring of the incident position is emphasized at the boundary between the bright and dark areas, so the level of the electrical signal output from the photoelectric conversion element is as shown in Figure 12. become that way. That is, the light from the bright area is reflected and enters the light-receiving surface of the photoelectric conversion element that detects the dark area, and the density change at the boundary between the bright area and the mouth 8 becomes ambiguous. In particular, in devices that require image density to be read, reproduced, and recorded at multiple levels, when changes in density at the boundary between bright and dark images are converted into warm electric signals, the reproduced image has a high contrast level. There is a problem in that the image becomes dull and unclear.

This invention was made due to the circumstances mentioned above,
SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that can eliminate the phenomenon in which light enters a dark area at an edge area with a large brightness BIIA power difference and causes a decrease in density.

Structure of the Invention; (Means for Solving Problem 11) The present invention relates to a plane scanning type image reading device using an image sensor. This can be achieved by providing a light absorbing material in contact with or very close to the surface, or by providing an antireflection film on the surface including the light receiving surface of the image sensor. Further, in a plane scanning image reading device using an image sensor having an optical window glass for protecting the light receiving surface, there is a space between the optical window glass and the light receiving surface to protect the light receiving surface. This is achieved by filling an insulating liquid with a refractive index similar to that of the a-layer.

(Function) The image reading device of the present invention has means for preventing light other than regular image light from entering the light receiving surface, that is, means for absorbing light or preventing light reflection near the light receiving surface. , which can significantly reduce flare light.

(Example) FIG. 1 is a perspective view schematically showing an example of a line sensor used in the image reading device of the present invention, corresponding to FIG. 7, and FIG. It is a diagram showing parts corresponding to FIG. 1O, and the same constituent parts are given the same reference numerals and explanations are omitted. This line sensor is made of an insulating matte black painted material (for example, product name: Sunday Paint).
Dainippon Paint ■)) 101 is painted or printed on the surface (excluding the upper part of the light-receiving surface) of the protective layer 41 of the photoelectric conversion element 4 (the shaded area in FIG. 1). Therefore, the light that conventionally entered the surface of the light-receiving mask 42 is absorbed by the coating material 101, so that scattering of the light can be prevented. In order to ensure that direct incident light is incident on the light receiving surface 43, it is desirable that the size of the portion 101a that is not painted black be slightly larger than the size of the light receiving surface 43.

Note that instead of the black coating material 101, an insulating matte black plate provided with slits slightly larger than the light receiving surface is installed on top of the protective layer 41 of the photoelectric conversion element 4 or very close to it. A similar effect can be obtained by doing so. Moreover, the above-mentioned black painting or installation of a black plate can also be applied to a line sensor having an optical window glass.

FIG. 3 is a cross-sectional view showing another example of the line sensor used in the image reading device of the present invention, corresponding to FIG. 2, and the same components are given the same reference numerals and the description thereof will be omitted. This line sensor is coated with an antireflection coating (for example, ^j2203.C
r2 (h, MgFz, etc.) 102 is coated over the entire surface of the protective layer 41 of the photoelectric conversion element 4. Therefore,
The light reflected on the light-receiving mask 42 surface is protected against reflection 11i1.
Since reflection is suppressed by 02, the piping phenomenon within the protective layer 41 can be suppressed.

Note that the antireflection film coating described above can also be applied to a line sensor having an optical window glass.

FIG. 4 is a cross-sectional view showing still another example of the line sensor used in the image reading device of the present invention, corresponding to FIG. 9, and the same components are given the same reference numerals and the description thereof will be omitted. This line sensor uses a transparent insulating liquid 103 (for example, Lani del oil, Cargill oil, etc.) having a refractive index (approximately 1.5) that is approximately the same as that of the protective layer 41 of the photoelectric conversion element 4.
It is filled between the optical window glass 2 and the protective layer 41 instead of the inert gas that is normally filled. Therefore, the light reflected on the surface of the light-receiving mask 42 is not reflected at the interface between the protective layer 41 and the insulating liquid 103, so that the piping phenomenon within the protective layer 41 can be suppressed.

In each of the above-mentioned embodiments, the case where the present invention is applied to a line sensor has been described, but the present invention is not particularly limited, and can also be applied to, for example, an area sensor that reads an image on a surface.

It should be noted that the first embodiment of black painting or installation of a black plate may be combined with the second embodiment of anti-reflection film coating, or the first embodiment of black painting or installation of a black plate and the second embodiment may be combined. By combining the third embodiment with the inclusion of an insulating liquid, it is possible to further suppress the occurrence of flare light.

Effects of the Invention: As described above, according to the image reading device of the present invention, it is possible to suppress the occurrence of outlines at edges and obtain images with high density resolution and sharpness. Furthermore, since the sharpness method can be simplified, signal processing can be performed at higher speeds and at lower costs.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing an example of a line sensor used in the image reading device of the present invention, and FIG. 2 is a C-Cl
i! 3 is a sectional view showing another example of the line sensor used in the image reading device of the present invention, and FIG. 4 is a sectional view showing still another example of the line sensor used in the image reading device of the present invention. 5 and 7 are perspective views schematically showing an example of a conventional line sensor, and FIGS. 6 and 8 are cross-sectional views of the line sensor shown in FIG. 5, respectively.
A sectional view taken along line A, a sectional view taken along line T B of the line sensor shown in FIG. 7, FIGS. 9 and 10, and 1! The figure shows the incident intensity of the image light.
FIG. 1 is a diagram showing the output signal level of a conventional line sensor corresponding to FIG. 1...Casing, 2...Optical window glass, 3...
Lead pin, 4... Photoelectric conversion element, 11.12.1
02...Anti-reflection film, l 3-...Protective film, 41...
- Protective layer, 42... Light receiving portion mask surface, 43... Light receiving surface, 101... Paint material, 103... Insulating liquid.

Claims (1)

[Claims] 1. A plane scanning image reading device using an image sensor, characterized in that a light absorbing material is provided in contact with or very close to a surface other than the light-receiving surface of the image sensor. Image reading device. 2. A plane scanning image reading device using an image sensor, characterized in that an anti-reflection film is provided on a surface including a light-receiving surface of the image sensor. 3. In a plane scanning image reading device using an image sensor having an optical window glass for protecting a light-receiving surface, a layer equivalent to the protective layer of the light-receiving surface is provided between the optical window glass and the light-receiving surface. An image reading device characterized by being filled with an insulating liquid having a refractive index.