JPH03280469A - Close contact type image sensor - Google Patents

Abstract

PURPOSE:To enable a manuscript dweetly under a photoelectrical conversion layer to be brightly illuminated so as to improve a sensor in sensitivity by a method wherein an incident window through which illuminating light is made to impinge is provided to an optical shielding layer, and a light transmitting window larger than the incident window concerned is provided to the photoelectrical conversion layer overlapping the incident window. CONSTITUTION:A photoelectric conversion layer 50 and an optical shielding layer 40 covering the layer 50 are successively provided to the face of an EMA type FAP 10 opposite to a manuscript through the intermediary of a light transmitting body, and an incident window 46 through which illuminating light is made to impinge is provided to the optical shielding layer 40, a light transmitting window larger than the incident window concerned is provided to the photoelectric conversion layer 50 overlapping the incident window 46. The illuminating light incident window 46 provided to the optical shielding layer 40 and the light transmitting window 56 provided to the photoelectric conversion layer are formed into rectangular shapes whose long sides extend in an auxiliary scanning direction. The area of the illuminating light incident window 46 is determined depending on the balance between the volume of incident light and the sensitivity of a sensor, and it is adequate that the short side of the window 46 is set as long as 20-60% of the width of a photoelectric conversion layer photodetective part 54 in a primary scanning direction, and the long side is set as long as 70-95% of the width of the photodetective part 54 in an auxiliary scanning direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contact type image sensor using an optical fiber array plate as an optical system.

[Issue 1 that the prior art and the invention are trying to solve [1i1 Fiber Array Plate (hereinafter referred to as FAP) is a light guide made by bundling a large number of optical fibers, which is sandwiched between base materials. . The type that uses an optical fiber coated with a light absorber is called the EMA type, and the type that uses an optical fiber that is not coated with a light absorber is called the CLEAR type.

The CLEAR type FAP differs from the EMA type in that light exceeding a critical angle within the optical fiber can be refracted and enter an adjacent optical fiber.

Conventional optical reduction type image sensors require a large optical path length because the imaging lens system has a focal length, which has been one of the reasons for preventing miniaturization of facsimile machines and the like in which this sensor is incorporated. Therefore, it is desired to develop a contact type image sensor that does not require a lens system, and the use of the above-mentioned FAP, which is a simple light guide system, is being considered.

One of the close-contact image sensors using FAP was published in Japanese Patent Application Laid-open No. 6
It is disclosed in Japanese Patent No. 4-41368. This sensor has a photoelectric conversion layer and a light shielding layer that completely covers the photoelectric conversion layer on the opposite side of the document side of the CLEAR type FAP, and a certain gap is provided between the document and the FAP. It is. Illumination light for reading a document is obliquely incident on the image sensor from the light shielding layer side.

In a contact image sensor with this configuration, in order to prevent illumination light from directly entering the photoelectric conversion layer, a light shielding layer is provided that completely covers the photoelectric conversion layer, so even if oblique incidence of illumination light is adopted, the light shielding layer It is unavoidable that a shadow is formed on the original, and sufficient illumination cannot be obtained in the part of the original directly under the photoelectric conversion layer via the FAP, that is, the part of the original to be read. Further, in the case where a gap between the document and the FAP is realized by diagonally cutting the document-side end of the optical fiber in the FAP, the processing of the optical fiber increases the cost of the image sensor.

On the other hand, the 107th Institute of Image Electronics Engineers of Japan research conference proceedings, pages 13 to 18, ``a-5i:H using optical fiber array
"Contact Image Sensor" (Masahiro Fujiwara, 1988 1)
The contact image sensor shown on January 4th is CLE
A small area of EMA is placed on the opposite side of the AR type FAP from the document side.
A photoelectric conversion layer is provided through a type FAP, and the illumination light that enters obliquely from the light source at a large angle is CLE.
Provided to the manuscript through AR type FAP.

In a contact image sensor with this configuration, obliquely incident illumination light is reflected by the original and reaches the photoelectric conversion layer.
In the EAR type FAP, the optical fiber must be bent many times between adjacent optical fibers, resulting in a large amount of optical attenuation. Therefore, the amount of light that reaches the photoelectric conversion layer from the portion of the document to be read directly below the photoelectric conversion layer becomes small, and the sensitivity of the sensor deteriorates.

The present invention has been made in view of the above points, and is a close-contact method that improves sensor sensitivity by enabling vertical incidence of illumination light onto the document surface and brightly illuminating the entire document portion directly below the photoelectric conversion layer. The purpose is to provide a type image sensor.

Means for Solving Problem C3] In order to solve the above problems, the contact image sensor according to the present invention has a transparent material such as CLEARluFAP or a transparent plate on the surface of the EMA type FAP opposite to the document side. A photoelectric conversion layer and a light shielding layer covering this photoelectric conversion layer are sequentially provided through the
An incident window for illumination light is provided in the light shielding layer, and a larger light passing window is placed over the incident window to transmit light. This is provided in the tf conversion layer.

[Function] A light source for illuminating the original is placed directly above the light shielding layer. Illumination light emitted from this light source enters the light-transmitting body through the illumination light entrance window of the light shielding layer and the light passage window of the photoelectric conversion layer in sequence. The illumination light beam entering the light-transmitting body has approximately the same geometry as the entrance window, but due to the diffusion of light within the light-transmitting body, the light beam exiting from this light-transmitting body is approximately equal to the outer shape of the photoelectric conversion layer. It has spread to Hodomaro. The expanded light beam reaches the document surface through the optical fiber in the EMA type FAP and illuminates it. Therefore, the entire document portion immediately below the photoelectric conversion layer is brightly illuminated.

The light diffusely reflected by the original passes through the optical fiber and the light-transmitting body in the EMA type FAP and enters the charge conversion layer, where it is converted into an electrical signal.

A configuration is adopted in which a CLEAR type FAP is used as a light transmitting body provided between the EMAIJIFAP and the photoelectric conversion layer, and the illumination light passing through the light passing window of the photoelectric conversion layer is guided to the EMA type FAP through the optical fiber of the CLEAR type FAP. For example, it becomes easy to prevent excessive light diffusion inside the transparent body.

[Embodiment] FIG. 1 is an enlarged sectional view of a contact type image sensor according to an embodiment of the present invention.

The EMA type F A P 10 shown in the figure has a light guide section 12 with a width of 1.4 mm formed by gathering a large number of optical fibers coated with a light absorber in a row, and a base section 18 made of glass.
The thickness in the optical axis direction is 1. It is Omm.

This EMA! ! Details of the structure of FAPIO are shown in Figures 2 to 4.
As shown in the figure. The light guiding section 12 is a three-layer assembly of multi-optical fibers 13, and each multi-optical fiber 13 is an assembly of a large number of single optical fibers 14. The single optical fiber 14 has a wire diameter of 10 μm to 25 μm and a numerical aperture of 0.3.
It is a multi-component step index type glass fiber of 5 to 0.90, with a cladding 1B arranged around a core 15, and a light absorber I7 surrounding the cladding 1B.

As shown in FIG. 1, the CLEAR type FAP 20, which is laminated on one side of the EMA type FAP, is made by bundling a large number of single optical fibers 14 from which the light absorber 17 has been removed and forming a light guide section 22. This is sandwiched between pace parts 28 and 28. In CLEAR'42FAP20, the width of the light guide part 22 is 1.4, which is the same as in the EMA type.
mm, and the light guide portions 12.22 of both FAPs are almost completely overlapped.

However, the thickness of the CLEAR type F A P 20 in the optical axis direction is selected within the range of 0.5 mm to 1.0 mm.

On the other hand, a light-shielding layer 40 made of C" with a thickness of approximately 500 is formed on one surface of a 1.1-mm-thick transparent glass substrate 3o. This light-shielding layer 4o also serves as a common electrode. The detailed shape is shown in Fig. 5.However, in this figure, the transparent substrate 30 is removed to make the drawing easier to see.The light shielding layer 40 has rectangular illumination light incident windows arranged in a row. 46 are formed by etching at a density of 8 pieces per 1 mm (pitch 125 μm).

Each entrance window 46 has a dimension (pl) of 30 μm in the window arrangement direction, and a dimension (I2) of a side perpendicular to the window arrangement direction (pl) of 110 μm. Note that the light shielding layer 40 that also serves as a common electrode is made of Ti or A.
It may also be made of other opaque metals such as No. 11.

On the light shielding layer 40, an amorphous silicon (a-Si) semiconductor layer 52 and a transparent electrode layer 53 are formed as a photoelectric conversion layer 50.
are sequentially formed overlapping the positions of the total incidence windows 46.

The a-5i semiconductor layer 52 has a p/i/n structure,
The film thickness is approximately 8,000 people.

However, three-layer structure of n/i/p, p/i or l
Any of the /p two-layer structure, i/Schottky structure, etc. may be adopted. The transparent electrode layer 53 is made of ITO and has a thickness of approximately 1000 nm. S n 02 instead of ITO
It is also possible to use other transparent conductive materials such as . This photoelectric conversion layer 50 is partitioned into a frame shape by etching for each illumination light incident window 46 of the light shielding layer 40. In this way, the photoelectric conversion layer 50 is partitioned into pixels. Each photoelectric conversion layer 50 includes a rectangular frame-shaped light receiving section 54 and a connecting section 55 extending from the light receiving section.A light passing window 5 provided approximately at the center of the light receiving section 54
6 is one size larger than the entrance window 46 of the light shielding layer 40. The outer shape of the light receiving section 54 is the dimension (L
l) is 110 μm, and the direction perpendicular to this (hereinafter referred to as
This is called the sub-scanning direction. ) dimension (L2) is 125 μm.

Transparent insulating layer 6 made of SiO2 with a thickness of about 1.5 μm
0 fills the light passing window 56 of the photoelectric conversion layer 50 and the illumination light incident window 46 of the light shielding layer 40 and further extends beyond the edge of the light shielding layer 40. The photovoltaic switching layer 5o is completely covered with this transparent insulating layer 60 including the side surfaces. However, a contact hole B2 is formed in the transparent insulating layer 60 by etching at the position of the charge conversion layer connection part 55, and the transparent electrode layer 5
Part 3 is exposed. Si3N instead of S102
Other transparent insulators such as No. 4 may also be used.

Further, for each charge conversion layer 50, an individual electric conduction layer 70 made of two layers of Cr and Al and having a total thickness of approximately 1 μm is provided for external connection. Each individual electrode layer 70 enters the contact hole 62 and the Cr layer contacts each transparent electrode layer 53 to achieve electrical connection. Note that Si3N4 may be further coated as a protective film.

As shown in FIG.
In a position facing the EAR type F A P 20, the CLEAR type F A P is
20. At this time, each entrance window 46 of the light shielding layer 40
The central axis of each light passing window 56 of the photoelectric conversion layer 50 is
The width direction of the AP light guide section 12.22 passes approximately through the center.

As described above, the contact image sensor according to this embodiment has a light transmitting body (CLEAR type F A P 20, ultraviolet curing resin layer 80, and transparent insulating material) on the surface of the EMA type F A P 10 opposite to the document side. photoelectric conversion layer 50 via layer 60)
and sequentially providing a light shielding layer 40 covering this photoelectric conversion layer 50,
An incident window 46 for illumination light is provided in the light shielding layer 40, and a larger light passing window 56 is provided in the photoelectric conversion layer 50, overlapping this incident window 4B.

The EMA type FAP 10 is brought into close contact with the original P.

A light source (not shown) for illuminating the original P is arranged directly above the light shielding layer entrance window 4B on the transparent substrate 30 side.

Illumination light B emitted from this light source enters the surface of the original P almost perpendicularly, passes through the transparent U plate 30, and enters the entrance window 4B of the light shielding layer 40. This illumination light B passes through the light passing window 5B of the photoelectric conversion layer 50 and passes through the transparent body consisting of the transparent insulating layer 60, the ultraviolet curing resin layer 80, and the light guide section 22 of the CLEAR12FAP20, and then passes through the EMA type FAP10.
The light enters the light guide section 12 of. At this time, since light is diffused in the transparent body, the light guide section 2 of the CLEAR type F A P 20
The light beam emitted from the photoelectric conversion layer 50 is spread to an extent almost equal to the outer shape of the light receiving portion 54 of the photoelectric conversion layer 50. At this time, CLE
Since AR type F A P 20 is used, unnecessary light diffusion can be prevented, and the number of refraction and transmission between adjacent optical fibers can be small. The expanded light beam is EM
The light is guided by the optical fiber 14 constituting the light guide section 12 in the A-type FAP 10 and reaches the document P, where it is illuminated.

Therefore, the entire document portion immediately below the photoelectric conversion layer light-receiving section 54 is brightly illuminated. The light diffusely reflected by the original P is the EMA
The light passes through the light guide portion 12 of the type F A P 10 and the light transmitting body in the opposite direction, enters the photoelectric conversion layer 50, and enters the a-Si semiconductor layer 52.
is converted into an electrical signal. The individual electrode layer 70 functions as a signal extraction electrode from each photoelectric conversion layer 50. On this occasion,
The transparent insulating layer BO not only achieves interlayer insulation between the light shielding layer 40, which also serves as a common electrode layer, and the individual electrode layer 70, but also
Side leakage of the photoelectric conversion layer 50 consisting of the a-8i semiconductor layer 52 and the transparent electrode layer 53 is prevented.

In this embodiment, the illumination light entrance window 46 of the light shielding layer 40 and the light passage window 56 of the photoelectric conversion layer 50 have a rectangular shape with the long side in the sub-scanning direction. In order to effectively utilize the light reflected from the original directly under the entrance window 46, it is preferable to increase the width of the photoelectric conversion layer 50 in the main scanning direction. In other words, the area of the illumination light entrance window 4B is determined by the balance between the amount of light and the sensor sensitivity, and the short side dimension of this window 46 is determined by the photoelectric conversion layer light receiving section 5.
Appropriately is 20% to 60% of the width of light receiving section 54 in the main scanning direction, and the long side dimension is 70% to 60% of the width of light receiving section 54 in the sub scanning direction.
95% is appropriate.

EMA type F A P 10 and CLEAR type F A P
The optimum value of the thickness ratio with respect to 20 in the optical axis direction differs depending on the pixel density. Due to the difference in pixel density, the photoelectric conversion layer light receiving section 5
This is because the dimensions of 4 are different, and the permissible range of light spread is different. The number of pixels per 1 mm is 8 (pixel density 8 dots)
s/mm), EM with a thickness of about 1 mm
CLEAR type F A P for A type F A P 10
The thickness of 20 is 0.5 mm to 1.5 mm as described above. A range of 0 mm is appropriate.

1m when the pixel density is 16 dots/mm
CL for EMA type F A P 10 with a thickness of about m
The thickness of EAR type F A P 20 is 0.・2mm ~
Select within the range of 0.5mm.

Although the EMA type F A P 10 and the original P may be in direct contact with each other, a cover glass having a thickness of about 50 μm may be attached to the EMA type F A P 10 to protect the FAP.

In addition, if the arrangement of both F A P 10, 20 is reversed,
Unlike the above, it becomes difficult for light to enter from the back side of the photoelectric conversion layer 50 for the following two reasons.

■EMA type FAPIO where illumination light B corresponds to the entrance window 46
In order to irradiate the original P after passing through only a narrow range of
Illumination light B tends to concentrate in a narrow area on the document surface <, MTF
(resolution) deteriorates.

Furthermore, the amount of light reflected from the portion of the document directly below the photoelectric conversion layer 50 that is actually desired decreases, resulting in a decrease in sensitivity.

■EMA through the intervention of CLEAR type F A P 20
Since there is a gap between the mold F A P 10 and the original P, not only does the reflected light from the original escape more, but also stray light from adjacent pixels tends to enter, which causes a deterioration of the MTF.

As a countermeasure to this problem, it is possible to make the CLEAR type F A P 10 thinner, but this is difficult to optimize because it is related to the problem (2) above.

On the other hand, in this embodiment, since a gap is provided between the photoelectric conversion layer 50 and the EMA type FAP 10 by the CLEAR type FAP 20, the entire document portion directly under the photoelectric conversion layer 50 is brightly illuminated and the height of the document is high. Sensor sensitivity is obtained. Furthermore, since the EMA type F A P 10 is almost in contact with the document P, there is no deterioration of MTF.

Note that instead of the CLEAR type F A P 20, for example, a transparent plate made of glass may be used. However, C.L.
Since the way the incident light spreads is different between the EAR type F A P 10 and a simple glass plate, the optimum thickness ratio in the optical axis direction is naturally a hole. EMA type F A with a thickness of about 1mm
The thickness of the transparent plate for P 10 is pixel density 8 dor
0.3mm to 0.5mm in s/mm, pixel density 16
A range of 0.1 mm to 0.3 mm in terms of dots/mm is appropriate.

[Effects of the Invention] As described above, the contact type image sensor according to the present invention has a CLEAR type FAP or a light transmitting body such as a transparent plate on the surface opposite to the document side of the EMA type FAP'. A photoelectric conversion layer and a light shielding layer covering this photoelectric conversion layer are sequentially provided, an entrance window for illumination light is provided in the light shielding layer, and a larger light passing window is provided in the photoelectric conversion layer overlapping this entrance window. This makes it possible for the illumination light to enter vertically, and after diffusing to some extent within the transparent body, it enters the EMA type FAP.
The entire document portion immediately below the photoelectric conversion layer can be efficiently illuminated, improving sensor sensitivity. In addition, EMA type FAP
MT is used here because it is used in close contact with the surface of the original.
F drop can be suppressed. Since it is not necessary to diagonally cut the optical fiber inside the EMA type FAP, it is also possible to suppress an increase in cost.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a contact type image sensor according to an embodiment of the present invention, and FIG. 2 is an E
Figure 3 is an enlarged plan view of part A of the EMA type FAP in the previous figure. Figure 4 is an enlarged sectional view of the single optical fiber in the previous figure. Figure 5 is an enlarged sectional view of the single optical fiber in the previous figure. FIG. 3 is a partially enlarged perspective view of the vicinity of the photoelectric conversion layer of the contact image sensor with the transparent substrate removed. Explanation of symbols 1O...EMA type FAP, 12...Light guide section, 13.
...Multi optical fiber, 14...Single optical fiber 15...Core, 16...Clad, 17...
Light absorber, 20... CLEAI12FAP (translucent body), 22... Light guiding section, 30... Transparent substrate, 40...
- Light shielding layer (also common electrode layer), 46... Illumination light incidence window of light shielding layer, 50... Photoelectric conversion layer, 52... Amorphous silicon semiconductor layer, 53... Transparent rv electrode layer 56.
...Light passing window of photoelectric conversion layer, 60...Transparent insulating layer (translucent body), 70...Individual electrode layer, 80...UV curing resin layer (translucent body), B...Lighting Hikari, P...Manuscript.

Claims (1)

[Scope of Claims] 1. A photoelectric conversion layer and this photoelectric conversion layer are attached to the surface opposite to the original side of an EMA type optical fiber array plate, which is made by gathering optical fibers coated with a light absorber in parallel to each other, through a light transmitting material. A contact image sensor characterized in that a light-shielding layer covering a conversion layer is sequentially provided, an incident window for illumination light is provided in the light-shielding layer, and a larger light passing window is provided in the photoelectric conversion layer superimposed on the incident window. . 2. The EMA type optical fiber array consists of a CLEAR type optical fiber array plate in which optical fibers without a light absorbing material are assembled in parallel with each other, and the optical fibers of this plate transmit illumination light passing through the light passing window of the photoelectric conversion layer. The contact type image sensor according to claim 1, which is guided to a plate.