JP2000349959A - Image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple configuration, with which an image can be read clearly and which is superior in durability by providing a thin-film shaped light shielding means, having a plurality of pinholes formed with one ratio to a plurality of pixels between an optical sensor array and a read surface and making light from the read surface pass through a pinhole to lead it to a pixel. SOLUTION: The relative position between each pixel 11a and a pinhole 13a in the horizontal direction, etc., unequivocally decides that the pixel 11a is irradiated with the light from which position on a reading surface M. Then, each pixel 11a will not be irradiated with a light from a wide range on the surface M. Light shielding films 15 prevent the light from the same point on the surface M from passing through a different pinhole 13a. The films 15 regulate the correspondence relation to one-to-one between a position on the surface M and a pixel 13a. Thus, light from a separating position on the surface M is prevented from being made incident on the same pixel 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor used for a facsimile, a scanner, and the like.

[0002]

2. Description of the Related Art A simple image reading apparatus such as a facsimile or a scanner uses an image sensor which reads an image while changing a relative position with respect to a document. In such an image sensor, the distance between the reading surface on which the document image is arranged and the optical sensor array is set small, and the document image is read at the same magnification. 9 and 10 show examples of the contact type image sensor.

The image sensor 7 shown in FIG. 9 includes an optical sensor array 71 in which pixels 71a are arranged one-dimensionally.
Further, a micro lens array 72 is provided between the optical sensor array 71 and the reading surface M. (A) is a pixel 71a
Front view as seen from a direction perpendicular to the arrangement direction of (b)
Is a side view seen from the arrangement direction of the pixels 71a. Each lens 72a of the micro lens array 72 has a plurality of pixels 7
1a, and guides light from a neighboring portion on the reading surface M to a plurality of adjacent pixels 71a. The image sensor 7 has a linear light source 73 beside the optical sensor array 71, and illuminates the reading surface M with light from the light source 73.

[0004] The image sensor 8 shown in FIG.
Are provided with an optical sensor array 81 arranged one-dimensionally, but without a microlens array. (A) is a front view, (b) is a side view. In the image sensor 8, the optical sensor array 81 is arranged closer to the reading surface M than the image sensor 7.
Light from the reading surface M is directly guided to a. In order to protect the optical sensor array 81, a protective glass plate 84 in contact with the reading surface M is provided. Optical sensor array 81
Are formed on a transparent substrate 85, and the reading surface M is illuminated with external light transmitted through the substrate 85.

[0005]

In the image sensor 7 shown in FIG. 9, the pixels 71a of the optical sensor array 71 correspond to the positions on the reading surface M by the lenses 72a of the micro lens array 72. In order to make this association strict, the micro lens array 72
It is necessary to manufacture each lens 72a with high accuracy, and it is also necessary to precisely match the relative positions of the optical sensor array 71 and the micro lens array 72. For this reason, there is a possibility that the image sensor may not be able to read an image accurately. Further, the manufacturing process of the image sensor 7 is complicated.

On the other hand, the image sensor 8 shown in FIG. 10 has no means for associating the pixels 81a of the optical sensor array 81 with the positions on the reading surface M. Therefore, the reading surface M
The distance between the optical sensor array 81 and the reading surface M needs to be made as small as possible in order to prevent light from different parts above from being incident on the same pixel 81a to make the read image unclear. Therefore, the protective glass plate 84
Must be made thinner, and the durability is easily impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a contact type image sensor having a simple structure capable of clearly reading an image and having excellent durability. .

[0008]

According to the present invention, there is provided an image sensor for reading an original image by an optical sensor array, wherein the optical sensor array is brought close to a reading surface on which the original image is positioned. In the arrangement, a thin film light-shielding means having a plurality of pinholes formed at one ratio for a plurality of pixels of the optical sensor array is provided between the optical sensor array and the reading surface. Is passed through the pinhole of the light shielding means and guided to the pixels of the optical sensor array.

In this image sensor, light incident on each pixel of the optical sensor array is only from a specific position on the reading surface determined by the positional relationship between the pixel and the pinhole. Do not enter the same pixel. Therefore, an image can be clearly read. This effect is not impaired even if the distance between the reading surface and the optical sensor array is increased, and a relatively thick protective member can be arranged between the reading surface and the light shielding means.

Here, the optical sensor array may be formed on the upper surface of a transparent substrate using an amorphous semiconductor, and the light shielding means may be formed on the lower surface of the substrate. This makes it extremely easy to form the light blocking means having the pinholes, and also facilitates the alignment between the pinholes and the pixels of the optical sensor array, thereby increasing the manufacturing efficiency. The substrate may be made of any material as long as it is transparent and can withstand the temperature at the time of producing the optical sensor array. For example, the substrate may be made of glass. At this time, the use of the amorphous semiconductor does not hinder the formation of the optical sensor array.

Further, it is preferable to provide a regulating means for regulating light from the reading surface so that light from the same point on the reading surface passes through only one of the pin holes of the light shielding means. Light from a distant position on the reading surface is prevented from passing through different pinholes and entering the same pixel, and there is no possibility that the sharpness of the read image is reduced.

The reading surface may be illuminated by external light, or illumination means for illuminating the reading surface may be provided.

The pixels of the optical sensor array and the pinholes of the light shielding means may be two-dimensionally arranged, and a plurality of surface light emitting elements may be provided between the light shielding means and the reading surface as illumination means. In this way, a wide range can be read at a time, and the entire range can be sufficiently illuminated.

The photosensor array is preferably of a multiplication type for multiplying electric charges generated by the received light. In a configuration in which the reading surface is illuminated by external light, the read image may be entirely dark and have low contrast due to insufficient light quantity.However, the use of a multiplication-type optical sensor array solves this problem. Be avoided. Further, even in the configuration including the illumination means, the reading cycle can be shortened by using the multiplication type optical sensor array, and the image can be read quickly.

[0015]

Embodiments of an image sensor according to the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the configuration of the image sensor 1 according to the first embodiment. The image sensor 1 includes an optical sensor array 11 in which a large number of pixels 11a are arranged one-dimensionally, and is configured as a line sensor. 1A is a front cross-sectional view as viewed from a direction perpendicular to the arrangement direction of the pixels 11a, and FIG. 1B is a side cross-sectional view as viewed from the arrangement direction of the pixels 11a.

The optical sensor array 11 is formed of an amorphous semiconductor on an elongated transparent substrate 12 having a thickness of about 1 mm to several mm, and is set to receive light from the substrate 12 side. The substrate 12 is made of glass or plastic, and has a flat and uniform thickness on both upper and lower surfaces. The pixels 11a of the optical sensor array 11 are arranged at a constant pitch, and the size of each pixel 11a is about several tens of μm.

On the lower surface of the substrate 12, a light shielding film 13 having a thickness of several tens μm or less is provided.
A plurality of pinholes 13a are formed along the arrangement direction of "a". The diameter of the pinhole 13a is smaller than or equal to that of the pixel 11a. The pinholes 13a are arranged at a constant pitch at a ratio of one to a plurality of pixels 11a. The light-shielding film 13 and the pinhole 13a are made of, for example, Al by evaporation and photolithography.
It is formed by patterning a deposited film. Although not shown, a light-shielding film is also provided on the side surface and the end surface of the substrate 12, and light enters the substrate 12 from only the pinhole 13a.

The substrate 12 is fixed on a transparent substrate 14, and the light shielding film 13 is in close contact with the upper surface of the substrate 14. The substrate 14 is made of glass or hard plastic,
It has a uniform thickness similar to that of the substrate 12. The substrate 14 is slightly wider than the substrate 12, and a portion of the upper surface of the substrate 14 on the side of the substrate 12 is exposed. A plurality of light-shielding films 15 perpendicular to the arrangement direction of the pinholes 13 a are provided inside the substrate 14.
Is provided. The light-shielding film 15 is formed between adjacent pinholes 1.
It is located at the center of 3a.

The image sensor 1 reads an image of a document while the lower surface of the substrate 14 is in contact with the document. That is,
The lower surface of the substrate 14 is the reading surface M of the image sensor 1. The substrate 14 has a function of keeping the distance between the reading surface M and the light shielding film 13 constant and protecting the light shielding film 13. The reading surface M is illuminated with external light incident from the upper surface of the substrate 14.

The light from the document located on the reading surface M is
The light passes through the pinhole 13 a of the light shielding film 13 and enters the pixel 11 a of the optical sensor array 11. The position on the reading surface M from which light enters the pixel 11a is determined by the pixel 1
1a and the pinhole 13a in the horizontal direction relative to each other,
It is uniquely determined by the thicknesses of the substrates 2 and 14 and the refractive indexes of the substrates 12 and 14. Accordingly, light from a wide range on the reading surface M does not enter each pixel 11a, and the image sensor 1 can clearly read the image of the document.

The thickness of each of the substrates 12 and 14 is
5 so that light in the range of the reading surface M located between the pixels 5 and 5 is incident on all the pixels 11a facing the range.
The values are set in consideration of the refractive indices of the materials 2 and 14.

The light-shielding film 15 restricts the field of view of each pinhole 13a facing the reading surface M, and prevents light from the same point on the reading surface M from passing through different pinholes 13a. That is, the light shielding film 15 defines the correspondence between the position on the reading surface M and the pixel 13a on a one-to-one basis. This prevents light from a distant position on the reading surface M from being incident on the same pixel 11a, and it is possible to reliably prevent the sharpness of the read image from deteriorating. The substrate 14 is formed by joining small pieces each having a light-shielding film 15 formed on an end face.

An output signal from each pixel 11a of the optical sensor array 11 is processed by a signal processing circuit (not shown). The signal processing circuit performs various processes such as A / D conversion, shading correction, and gamma correction on the output signal of the optical sensor array 11 to generate an image signal representing an image for one line. At that time, the signal processing circuit is connected to the same pinhole 13a.
The order of the output signal is inverted for each of a plurality of pixels 11a (hereinafter, this set of pixels is referred to as a pixel block) that receives light from, so that signals of adjacent pixel blocks are continuous. By gradually changing the relative position between the image sensor 1 and the document in a direction perpendicular to the arrangement direction of the pixels 11a of the optical sensor array 11, a two-dimensional document image is read.

FIG. 8 shows the configuration of the optical sensor array 11.
The optical sensor array 11 is formed by sequentially laminating a transparent electrode 16 made of ITO, a photoelectric conversion layer 17, an opaque electrode 18 made of Al, and a protective film 19 on the upper surface of a substrate 12. The photoelectric conversion layer 17 includes a P-type layer 17p of an amorphous semiconductor,
This is an avalanche photodiode having a PIN structure including an intrinsic layer 17i of an amorphous semiconductor and an n-type layer 17n of an amorphous semiconductor. When light is received in a state where a reverse bias voltage is applied between the electrodes 16 and 18, the charge generated in the photoelectric conversion layer 17 is multiplied by the avalanche phenomenon and output.

In the image sensor 1 that illuminates the reading surface M with external light, the reading surface M may be dark depending on environmental conditions. However, the reading is performed by providing the optical sensor array 11 having a multiplication function. The image is always of good quality with high brightness and high contrast. Note that an avalanche photodiode having a configuration in which a layer for performing photoelectric conversion and a layer for performing multiplication are formed as separate layers and both layers are stacked may be used as an optical sensor array.

Although the substrate 12 is fixed on the substrate 14 here, the substrate 14 can be omitted. In this case, the thickness of the substrate 12 is set in consideration of the refractive index of the material of the substrate 12 and air, and the light shielding film 1 is formed.
5 is attached to the lower surface of the substrate 12. Further, a member for keeping the lower surface of the substrate 12, that is, the light shielding film 13 at a fixed distance from the reading surface M is provided. The shape of the pinhole 13a may be set arbitrarily, and is preferably a circle, rectangle, square, or the like.

FIG. 2 is a side sectional view of the image sensor 2 according to the second embodiment. The image sensor 2 includes the image sensor 1 of the first embodiment and a light source 21 for illuminating the reading surface M. The light source 21 is a linear light source including an LED array, a fluorescent tube, an EL element, and the like.
It is arranged along the side surface of the substrate 12. The light emitted from the light source 21 passes through the substrate 14 and uniformly illuminates from one end to the other end of the reading surface M facing the optical sensor array 11. The other configuration is the same as that of the image sensor 1, and a duplicate description will be omitted.

In the image sensor 2 having the light source 21,
Since the reading surface M is always brightly illuminated, the optical sensor array 11 is replaced with a normal optical sensor having no multiplication function, such as a blocking type for blocking external carrier injection or a photoconductive type utilizing photoconductivity. can do. However, if an optical sensor array 11 having a multiplication function is used,
Even if the photoelectric conversion time is shortened, sufficient charges are generated,
An image can be read quickly by shortening the period of photoelectric conversion, which is preferable in terms of reading efficiency.

FIG. 3 is a front sectional view of the image sensor 3 according to the third embodiment. In this image sensor 3, an opaque substrate 20 having an opening 20a is provided between the substrate 12 and the substrate 14 instead of the light shielding film 15 of the image sensor 1,
The visual field of the pinhole 13a is limited by the lower edge of the opening 20a. The opening 20a is a pinhole 13
a are provided at the same pitch as
a is located at the center of the opening 20a. The thickness of the substrate 20 is
For example, it is about several hundred μm to 1 mm. The size of the opening 20a is determined according to the thickness of the substrate 20.

FIG. 4 schematically shows the structure of the image sensor 4 according to the fourth embodiment. The image sensor 4 includes an optical sensor array 31 in which many pixels 31a are two-dimensionally arranged, and is configured as an area sensor. 4A is a front sectional view, and FIG. 4B is a side sectional view.

The optical sensor array 31 is formed of an amorphous semiconductor on the upper surface of a rectangular transparent substrate 32 having a thickness of about 1 to several mm, and is set to receive light from the substrate 32 side. The substrate 32 is made of glass or plastic, and has a flat and uniform thickness on both upper and lower surfaces. The pixels 31a of the optical sensor array 31 are arranged at a constant pitch, and the size of each pixel 31a is several tens μm.
It is about.

On the lower surface of the substrate 32, a light-shielding film 33 having a thickness of several tens of μm or less is provided.
3a are formed two-dimensionally at a constant pitch. The diameter of the pinhole 33a is substantially equal to or smaller than that of the pixel 31a. Although not shown, a light-shielding film is also provided on the side surface of the substrate 32, and light enters the substrate 32 only from the pinhole 33a.

The substrate 32 is fixed on an opaque substrate 40, and the substrate 40 is fixed on a transparent substrate 34. The substrates 34 and 40 have substantially the same size as the substrate 32.
The substrate 34 is made of glass or hard plastic, and has a thickness similar to that of the substrate 32. The lower surface of the substrate 34 is the reading surface M of the image sensor 4,
Keeps the distance between the reading surface M and the light shielding film 33 constant and protects the light shielding film 33.

The substrate 40 is for limiting the visual field of the pinhole 33a, similarly to the substrate 20 shown in FIG.
An opening 40a is two-dimensionally formed corresponding to the pinhole 33a. FIG. 5 shows the lower surface of the substrate 40. Each part surrounded by the opening 40a on the lower surface of the substrate 40 includes an LED, an EL,
A planar light emitting element 41 made of an element or the like is provided.
The entire reading surface M is illuminated with light emitted from the light emitting element 41 with uniform brightness. Due to the provision of the light emitting element 41, the substrate 40 is thicker than the substrate 20 of FIG. 3, and the opening 40a is set to be larger than the opening 20a.

The principle of reading an image of a document by the image sensor 4 is the same as that of the image sensor 1, and each pixel 31a and one pixel on the reading surface M are pinhole 33a.
Are associated with each other. However, 2 of the reading surface M
In the image sensor 4 of the present embodiment that reads a one-dimensional range with a two-dimensional pixel block, the reading efficiency is greatly improved compared to the image sensor 1 that reads a one-dimensional range with a one-dimensional pixel block. In the image sensor 4 including the light emitting element 41 for illuminating the reading surface M, the optical sensor array 31 does not need to have an amplification function. However, it is preferable to provide the amplification function because the reading efficiency is further improved.

FIG. 6 is a front sectional view of the image sensor 5 according to the fifth embodiment. The image sensor 5 replaces the opaque substrate 40 of the image sensor 4 with the image sensor 1
A light shielding film 35 similar to the light shielding film 15 of FIG. The light shielding film 35 is provided in two orthogonal directions so as to surround the pinhole 33a. The light emitting element 41 is provided directly on the lower surface of the light shielding film 33.
Other configurations are the same as those of the image sensor 4.

FIG. 7 is a front sectional view of the image sensor 6 according to the sixth embodiment. The image sensor 6 includes a pixel 31a
Is configured to illuminate the reading surface M from the side in the configuration having the optical sensor array 31 arranged two-dimensionally. Light-shielding film 33 with pinhole 33a formed
An opaque substrate 40 for limiting the field of view of the pinhole 33a is provided on the lower surface of the light guide plate 33, and a light guide plate 43 is provided on the lower surface thereof. On the side surface of the light guide plate 43, an LED array,
A pair of linear light sources 42 including a fluorescent tube, an EL element, and the like are provided.

Light from the light source 42 is guided to the light guide plate 43 to illuminate the entire reading surface M. In this configuration, it is difficult to illuminate the reading surface M with uniform brightness. However, by measuring the intensity of the output signal of each pixel 31a in advance using a white test document, the signal processing circuit can perform processing. Brightness non-uniformity can be corrected. Light source 4
2 may be provided on at least one side surface of the light guide plate 43, and may be provided on all side surfaces.

There is no transparent substrate in contact with the reading surface M like the substrate 34 of the image sensor 4, and the light guide plate 43 is separated from the reading surface M. The image sensor 6 includes a roller (not shown) in contact with the reading surface M.
Can be moved in a direction perpendicular to the axis of the roller while keeping the distance to the roller constant. Of course, a configuration in which a transparent substrate that is in contact with the reading surface M is provided below the light guide plate 43 is also possible.

[0040]

According to the image sensor of the present invention, light can be guided to each pixel of the optical sensor array only from a specific position on the reading surface by the light shielding means having a pinhole.
It is possible to avoid a decrease in contrast due to overlapping of light from neighboring portions on the reading surface. Therefore, it is possible to read an image clearly with a very simple configuration including a light shielding means having a pinhole in addition to the optical sensor array. Further, it is not necessary to dispose the optical sensor array and the light shielding means very close to the reading surface, and a relatively thick protective plate can be provided. Therefore, the optical sensor array and the light shielding means are hardly damaged, and the image sensor has excellent durability.

In a configuration in which the optical sensor array is formed on the upper surface of a transparent substrate using an amorphous semiconductor and the light shielding means is formed on the lower surface of the substrate, the alignment between the pixels of the optical sensor array and the pinholes of the light shielding device is required during assembly. It is not necessary to do so, and the production efficiency is improved. By using an amorphous semiconductor, an optical sensor array can be easily formed using a substrate made of a wide range of materials.

Further, when a regulating means for regulating light from the reading surface is provided so that light from the same point on the reading surface passes through only one of the pinholes of the light shielding means, the sharpness of the read image can be improved. There is no danger of lowering.

In a configuration in which the reading surface is illuminated with external light, a small and lightweight image sensor is obtained. In the configuration including the illumination unit that illuminates the reading surface, the read image is always bright regardless of environmental conditions.

If the pixels of the optical sensor array and the pinholes of the light shielding means are two-dimensionally arranged and a plurality of surface light emitting elements are provided between the light shielding means and the reading surface as illumination means, a wide range can be read at a time. As a result, the reading speed is improved, and the whole of the read image is brighter.

If the photosensor array is of a multiplication type, the read image can be brightened even if it has a configuration without illumination means. Further, the reading cycle can be shortened, and the reading speed is improved.

[Brief description of the drawings]

FIG. 1 is a front sectional view and a side sectional view schematically illustrating a configuration of an image sensor according to a first embodiment.

FIG. 2 is a side cross-sectional view schematically illustrating a configuration of an image sensor according to a second embodiment.

FIG. 3 is a front cross-sectional view schematically illustrating a configuration of an image sensor according to a third embodiment.

FIG. 4 is a front cross-sectional view and a side cross-sectional view schematically illustrating a configuration of an image sensor according to a fourth embodiment.

FIG. 5 is a bottom view of a substrate that limits a visual field of a pinhole of the image sensor according to the fourth embodiment.

FIG. 6 is a front cross-sectional view schematically illustrating a configuration of an image sensor according to a fifth embodiment.

FIG. 7 is a front cross-sectional view schematically illustrating a configuration of an image sensor according to a sixth embodiment.

FIG. 8 is a cross-sectional view schematically illustrating a configuration example of an optical sensor array of the image sensor according to each embodiment.

FIG. 9 is a front view and a side view schematically showing a configuration of a conventional image sensor.

FIG. 10 is a front view and a side view schematically showing a configuration of another conventional image sensor.

[Explanation of symbols]

 1, 2, 3 Image sensor 11 Optical sensor array 11a Pixel 12 Transparent substrate 13 Light-shielding film (light-shielding means) 13a Pinhole 14 Transparent substrate 15 Light-shielding film (restriction means) 16 Electrode 17 Photoelectric conversion layer 18 Electrode 20 Opaque substrate (restriction means) 20a opening 21 light source (illuminating means) 4, 5, 6 image sensor 31 optical sensor array 31a pixel 32 transparent substrate 33 light shielding film (light shielding means) 33a pinhole 34 transparent substrate 35 light shielding film (restriction means) 40 opaque substrate (restriction) Means) 40a opening 41 light emitting element (illuminating means) 42 light source (illuminating means) 43 light guide plate (illuminating means)

Claims (7)

[Claims] 1. An image sensor for reading an original image by an optical sensor array, wherein the optical sensor array is arranged close to a reading surface on which the original image is located. A light-shielding means in the form of a thin film having a plurality of pinholes formed at one ratio between the optical sensor array and the reading surface, and passing light from the reading surface through the pinholes of the light-shielding means. And directing the light to pixels of the optical sensor array. 2. The image sensor according to claim 1, wherein the optical sensor array is formed on an upper surface of a transparent substrate by an amorphous semiconductor, and the light shielding unit is formed on a lower surface of the substrate. . 3. The method according to claim 1, wherein light from the same point on the reading surface passes through only one of the pinholes of the light shielding means.
The image sensor according to claim 1, further comprising a regulation unit that regulates light from the reading surface. 4. The image sensor according to claim 1, wherein the reading surface is illuminated by external light. 5. The image sensor according to claim 1, further comprising illumination means for illuminating the reading surface. 6. The pixel of the optical sensor array and the pinholes of the light shielding unit are two-dimensionally arranged, and a plurality of surface light emitting elements are provided as the illumination unit between the light shielding unit and the reading surface. The image sensor according to claim 5, wherein: 7. The image sensor according to claim 1, wherein the photosensor array is a multiplication type photosensor array that multiplies electric charges generated by received light.