JPH0380663A - Close contact type image sensor - Google Patents

Abstract

PURPOSE:To surely cut off a leaked light and to obtain high resolution by arranging an optical fiber array section with/without coated with an absorbing body to a specific side of each optical fiber and providing a light shield between a light source and a photodetector array and/or between the light source and an optical fiber array plate. CONSTITUTION:An optical fiber array section is constituted by laminating an optical fiber array 8 coating an absorbing body to each optical fiber arranged to a photodetector array 1 and an optical fiber array 7 not coating an absorbing body to each optical fiber arranged to an original 18. Moreover, 1st and 2nd light shield bodies 15, 16 are provided between a light source and the photodetector array 1 and/or between the light source and the optical fiber arrays 7, 8 respectively. Thus, before a leaked light deteriorating the picture quality reaches the photodetector array 1, the light is absorbed by the absorbing body to prevent the deterioration in the picture quality on the photodetector array 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a contact type image sensor used in facsimiles and character/image reading/input devices.

(b) Conventional technology Image sensors used in facsimiles and text/image reading/input devices use optical lenses to reduce the information on documents that are illuminated with fluorescent lights or LED (light emitting diode) arrays. Originally, a type having a reduction optical system that forms an image on the C0D) was often used. However, for example, the optical path length of an image sensor optical system with a reduction optical system used in facsimile is approximately 300 mm.
This is an obstacle to downsizing the device. In order to shorten this optical path length, there is a method of repeating reflection using mirrors, but the difficulty of aligning the optical axes between mirrors increases significantly as the number of mirrors increases, and the optical axis fluctuates due to temperature changes, etc. If you think about it, adjustment is very difficult.

In order to solve this difficulty, a contact image sensor has been developed that photoelectrically converts the information of the document by imaging it through a lens (usually a rod lens array) onto a photodetector array of the same size as the document. .

This optical system does not require an optical path length for reduction, making it possible to downsize the device to some extent, but since it is still a lens even though it is a rod lens array, the conjugate length of the original and light receiving element are used for image formation. Because it is necessary to separate the array,
Normally, the thickness of a close-contact image sensor unit is about 30 mm. Furthermore, since a lens system is used, the optical system must be adjusted, and in the case of color reading, chromatic aberration must also be considered.

In response, a contact type image sensor using an optical fiber array without using a lens system has been proposed (Japanese Patent Publication No. 55-31663 and Japanese Patent Publication No. 55-31664).
(see publication).

Since this does not require adjustment of the optical system and does not focus, it is possible to construct an ultra-small and ultra-thin contact image sensor by shortening the length of the optical fiber. Furthermore, since there is no chromatic aberration during color reading, it is very effective.

In addition, an optical fiber array is usually sandwiched between glass plates from both sides or one side, forming an optical fiber array plate, and can be handled like a sheet of glass. It is possible to adopt a structure in which the original is brought directly into contact with the paper. As a result, there is no need for a protective glass (the original is read in close contact with the glass), which is required in the type of image sensor using a rod lens array, which is advantageous in reducing the thickness and cost.

(c) Problems to be Solved by the Invention The contact image sensor using the optical fiber array described above is suitable for ultra-compact and ultra-thin designs, and is also an effective method for color reading, but it has the following problems. There is.

First, among the light that enters the optical fiber, the light that enters the optical fiber at an angle equal to or greater than its mouth angle will be transmitted to the adjacent optical fiber through the cladding, which causes total internal reflection at the interface between the core and the cladding. The light reaches the exit surface repeatedly. Furthermore, the light that enters the cladding of the optical fiber at the entrance surface of the optical fiber array repeatedly passes through the cladding core in the same manner and reaches the exit surface. As described above, when transmitting an image using an optical fiber array, light leakage occurs, and this light leakage becomes a factor in deteriorating image quality.

Therefore, in order to absorb this light leakage, an absorber made of glass that absorbs light is inserted between the optical fibers.
MA (Extra Mural Absorption
An n) type optical fiber array has been devised, but when it is used in a contact type image sensor, there is a problem in that the surface of the document to be read cannot be illuminated.

Furthermore, when a light-transmitting substrate such as a glass substrate is used as the substrate forming the light-receiving element array, the light from the light source is transmitted through the substrate.

Because it enters directly into the translucent substrate through the side surface of the optical substrate,
The light receiving element array will be irradiated from the back side. On the other hand, even if the substrate forming the light-receiving element array is a non-light-transmitting substrate that does not allow light to pass through, the light from the light source enters the gap between the substrate and the optical fiber array, and this light reaches the light-receiving element array. It becomes light leakage. These lights reach the photodetector array directly from the light source without being reflected by the original.
It does not contain necessary document information and instead becomes noise.

Furthermore, the light source that illuminates the original to be read does not illuminate only the part of the original to be read, but has a certain spread, so the light source also irradiates the front and back of the part of the original to be read.

Therefore, if the side closer to the light source than the above reading gap directly above the light receiving element array is, for example, a white document that reflects a large amount of light (a so-called blank portion of the document), the reflected light from this blank portion will be transmitted to the optical fiber array from the side. After repeatedly entering the cladding core and passing through the cladding core, it reaches the exit surface. Although this light is reflected light from the original, it is not reflected from the part of the original to be read, and therefore does not contain information about the original to be read. Therefore, there is a problem in that this light becomes noise that degrades image quality.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a high-quality contact image sensor that is ultra-small and ultra-thin and does not require optical adjustment.

(d) Means for Solving the Problems In order to solve the above problems, the present invention provides a light source that irradiates the original to be read, a light receiving element array that converts reflected light from the original into an electrical signal, and a light receiving element array that converts the reflected light from the original into an electrical signal. and an optical fiber array section disposed between the light receiving element array and the light receiving element array, the optical fiber array section is disposed on the light receiving element array side, an optical fiber array in which each optical fiber is coated with an absorber, and the original document. The first side is arranged so that each optical fiber is laminated with an optical fiber array that is not coated with an absorber, and the first side is arranged so that each optical fiber is stacked with an optical fiber array that is not coated with an absorber to prevent the irradiated light from the light source from directly reaching the light receiving element array without passing through the original. A light shielding body is provided between at least the light source and the light receiving element array to prevent the irradiated light from the light source from being reflected by a portion of the document other than the portion to be read and reaching the light receiving element array. A second light blocking body is provided between the light source and the optical fiber array section.

In the optical fiber array according to the present invention, a plurality of optical fibers composed of a core part and a cladding part are arranged in a direction perpendicular to the traveling direction of the transmission document (direction of arrow E shown in FIG. 1). F shown in Figure 3
They are arranged adjacent to each other in a width corresponding to the width of the document in the middle direction shown by . For example, A4? When using a 4+ original, the optical fiber is 2 in the F direction in Figure 1.
It is composed of a large number of optical fibers having a width of about 16 mm and a width of about 1 to 2jIy in the E direction.

The optical fiber array section is formed by sequentially stacking an optical fiber array in which each optical fiber is coated with an absorber and an optical fiber array in which each optical fiber is not coated with a light absorber, on the light receiving element array.

As the absorber in this invention, it is preferable to use glass that absorbs light, but the point is that it is not limited to this as long as it can absorb light.

Preferred examples of the light shielding body in this invention include resins made of the same material as the case, such as ABS, polycarbonate, black rubber-based materials, and metal thin films such as AI and Cr formed by vapor deposition or sputtering. It will be done.

The light source in this invention is an L light source equipped with a rod-shaped lens.
It is preferable to use an ED array substrate or an LED array substrate equipped with an LED array chip without using a rod-shaped lens.

(E) Effect As described above, in the present invention, the optical fiber array section is constructed by laminating two types of optical fiber arrays, and the optical fiber array, in which each optical fiber is not coated with an absorber, is placed on the side of the document to be read. In addition to easily illuminating the document surface, by arranging an optical fiber array in which each optical fiber is coated with an absorber above the light-receiving element array, the opening of the optical fibers can be easily illuminated to the optical fiber array located in the upper layer that is not coated with an absorber. Light that is incident at an angle greater than the angle or light that is incident on the cladding of the optical fiber, that is, leakage light that degrades image quality, is absorbed by the absorber before it reaches the photodetector array, preventing image quality from deteriorating on the photodetector array surface. I can do that.

Furthermore, by providing a first light shield between the light source that irradiates the document to be read and the light receiving element array, the light from the light source is directly transmitted through one side of the light-transmitting insulating substrate that forms the light receiving element array. It is possible to prevent the light from entering the insulating substrate and irradiating the light receiving element array mounted on the insulating substrate from the back surface.

Further, in the case where the substrate forming the light receiving element array is a non-light-transmitting insulating substrate that does not transmit light, the light from the light source can be prevented from entering the gap between the substrate and the optical fiber array and reaching the light receiving element array. I can do it. Furthermore, by providing a second light shield between the light source and the optical fiber array, when the document is white on the side closer to the light source than the portion of the document to be read immediately above the light-receiving element array, light from the white portion of the document can be read. Reflected light can be prevented from entering the optical fiber from its side and reaching the light receiving element array.

(F) Embodiments Below, embodiments of the present invention will be described in detail with reference to the drawings. Note that this invention is not limited by this.

FIG. 1 shows a contact type image sensor according to a first embodiment of the present invention, and FIG. 2 shows an optical fiber array plate in which each optical fiber is not coated with an absorber. Further, FIG. 3 shows an optical fiber array plate in which each optical fiber is coated with an absorber.

In FIG. 2, reference numeral 19 indicates an optical fiber core portion, 20 indicates an optical fiber cladding portion, and 7 indicates an optical fiber array not covered with an absorber. Further, reference numeral 9 indicates a base glass portion that sandwiches the optical fiber array 7, and by sandwiching and fusing the optical fiber array 7 between the base glass portions 9, it becomes one optical fiber array plate.

In FIG. 2, 21 to 24 indicate the paths of light entering the optical fiber array 7. Reference numeral 22 indicates the path of the light that entered the optical fiber cladding section 20, 23 indicates the course of the light that entered the optical fiber core section 19 at an angle greater than the aperture angle of the optical fiber, and 24 indicates the course of the light that entered the optical fiber array 7 from the side surface. When there is only one optical fiber array plate that indicates the path of light and each optical fiber is not coated with an absorber, that is, when this plate is used alone, the light receiving element array I formed on the insulating substrate 2 It can be seen that light from other than above (light that does not contain necessary information) reaches the light receiving element array 1.

Since the light containing the originally necessary information reaches the light-receiving array I through the path indicated by 21, the light indicated by 22 to 24 becomes noise and causes a deterioration in image quality.

Further, in FIG. 3, 1 is a light receiving element array formed on an insulating substrate 2, 25 is an optical fiber core part, 26 is an optical fiber clad part, 27 is an absorber coated on each optical fiber, and 8 is an optical fiber core part. 1 shows an optical fiber array coated with an absorber. Reference numeral 10 indicates a base glass portion similar to that in FIG.

28 to 31 in FIG. 3 indicate the paths of light entering the optical fiber array 8, and 21 to 24 in FIG. 2, respectively.
corresponds to However, the light 29 to 31 that can become noise is absorbed by the light absorber (hereinafter simply referred to as absorber) 27 coated on each optical fiber, and the light receiving element array 1
will not be reached. Therefore, only the light 28 containing the originally necessary information reaches the light-receiving element array 1, thereby preventing deterioration in image quality. However, when there is only one optical fiber array plate in which each optical fiber is coated with an absorber, that is, when this plate is used alone, the surface of the document cannot be irradiated.

FIG. 1 shows an embodiment of the present invention in which these two different types of optical fiber arrays, namely an optical fiber array 8 and an optical fiber array 7, are sequentially stacked on a light receiving element array l.

In FIG. 1, 1 is a photodetector array formed on an insulating substrate 2, 3 is a substrate on which a driving LSI 5 for the photodiode array 1 is mounted, and 4 is an insulating substrate 2 and a mounting substrate 3 on which a photodetector array 1 is formed. 6 is attached to the integrated auxiliary board, and 6 is the JCB (Junct) that protects the mounted drive LSI 5.
ion Coating Re5in), both sides of the optical fiber array 7 which does not coat each optical fiber with an absorber are sandwiched between the base glass parts 9 and fused together, and the optical fiber array plate A and each optical fiber are coated with an absorber 27. Optical fiber array plates B, in which both sides of the optical fiber array 8 are sandwiched between the base glass parts 1G and fused together, are stacked, and this stack is assembled on the light receiving element array I. As a light source for illuminating the original 18 to be read, an LED array base [11] equipped with a rod-shaped lens 12 is used, and this LED array base [11] is fixed to a heat sink 13 for the LED array board. Further, the above-described components are assembled into a case 14 made of resin such as ABS or polycarbonate, which integrates the first light shield 15 and the second light shield I6, and is finally fixed with a holding plate 17.

Since this embodiment has the above-mentioned configuration, the optical fiber array plate A, in which each optical fiber is not coated with an absorber, is stacked on the original 18 side, and the optical fiber array plate B, in which the absorber 27 is coated, is stacked on the light-receiving element array L side. By doing so, the light that can become noise shown at 22 to 24 in FIG.
is absorbed by the absorber 27 of the optical fiber array 8 coated with the light, and only the light containing the necessary information of the original document I8 reaches the light receiving element array l.

Furthermore, in this embodiment, a first light shielding body 15 and a second light shielding body 1 are integrated into a case shown at 15 and 16 in FIG.
It has 6.

Further, although a light-transmitting glass substrate is used as the insulating substrate 2, the light emitted from the LED array substrate 11 directly enters from the one side surface 2a of the insulating substrate 2 through the i-th light shielding member 15, and passes through the light receiving element array. By irradiating light 1 from the back side, it is possible to prevent direct light from entering the gap Mc between the insulating substrate 2 and the optical fiber array 8 covering the absorber 27 and from reaching the light receiving element array 1.

Furthermore, in FIG. 1, the light emitted from the LED array base 11iE11 is directed by the rod-shaped lens 12, but it is not only directed directly above the light-receiving element array 1 to the necessary portion of the document; Since the document portion 18a on the substrate 11 side is also irradiated, if this portion 18a is a white document, the reflected light from this portion 18a will eventually reach the light receiving element array l. This is because the reflected light enters the coated fiber array 7, which is not coated with an absorber, from its side, and undergoes complex reflections between each optical fiber inside the optical fiber array 7. Optical fiber array 8 with light covering absorber 27
This is thought to be due to being captured by the optical fiber.

Furthermore, if the absorption performance of the absorber 27 of the optical fiber array 8 is poor, it is conceivable that the reflected light enters from the side surface of the optical fiber array 8 and a part of the light reaches the light receiving element array l.

Therefore, in this embodiment, a second light guide 16 is further provided.

That is, in FIG. 1, the second light shield indicated by 16 is provided to prevent the image quality from deteriorating due to the reflected light, so that the light emitted from the LED array board 11 and focused by the rod-shaped lens 12 is It is possible to irradiate only the area immediately above the light receiving element array 1, and narrow down the LED light so that the LED light does not irradiate as much as possible the document portion 18a on the base glass 9 on the LED board 11 side from the optical fiber array 7 that does not cover the absorber. .

As described above, in this embodiment, the optical fiber array plate A, in which each optical fiber is not coated with an absorber, is placed on the document side.
An optical fiber array plate B in which each optical fiber is coated with an absorber 27 is stacked on the light receiving element array side, and a first light shielding body I5 is provided between the light source 12 and the light receiving element array l. By providing the second light shield 16 between the array plate B and the array plate B, a high-quality contact image sensor can be realized.

In addition, in the first embodiment shown in FIG. The second and third embodiments used for this purpose are shown in FIGS. 4 and 5, respectively.

In both FIGS. 4 and 5, the same parts as in FIGS. 1 to 3 are given the same numbers.

First, in FIG. 4, as the first light shielding body 33 between the LED array substrate 11 and the light receiving element array 1, a bar-shaped member made of, for example, a black rubber material that does not transmit light is used. By using this rubber material,
Considering the light blocking property between the first light blocking body 33 and the optical fiber array plate B consisting of the optical fiber array 8 in which optical fibers are coated with an absorber and the base glass IO, the rod-shaped rubber 33 is in close contact with the base glass part 10. Therefore, the light shielding effect can be improved compared to the first embodiment shown in FIG.

Furthermore, in FIG. 4, as the second light shielding body 34,
LED array substrate 111 of base glass part 10 of optical fiber array plate B! For example, At, C
A metal thin film formed of metal such as r by vapor deposition or sputtering is used.

Next, a third example will be described.

In FIG. 5, in this embodiment, an LED array substrate i of an optical fiber array 8 in which each optical fiber is coated with an absorber is shown.
Remove the base glass part (see Figure 1.4) on the t side, and
The light shielding between the ED array substrate 11 and the light-receiving element array 1 can be more easily performed than in the above-mentioned embodiments 1.2.

That is, L of the optical fiber array 8 coated with an absorber
By eliminating the base glass part of the ED array substrate 1t@I, the first light shielding body 36 is integrated into the case, which is advantageous in terms of cost, and the light shielding property between the LED board 11 and the light receiving element array 1 is improved. It can be higher than the embodiment shown in FIG.

Furthermore, in this embodiment, as in the second embodiment shown in FIG. However, the LED array substrate l of the base glass part 9 of the optical fiber array 7 that does not cover the absorber
This embodiment differs from the second embodiment shown in FIG. 4 in that a thin film is formed on the l side surface.

The first to third embodiments having various light shielding bodies have been described above, but the point is that the light shielding between the LED array substrate 11 and the light receiving element array I and/or the LED array substrate 11
Of course, the present invention is not limited to the above embodiments as long as the light can be efficiently blocked between the optical fiber array plates A and B and the optical fiber array plates A and B.

Finally, as a fourth embodiment, an embodiment of an ultra-thin contact type image sensor is shown in FIG.

In this embodiment, an ultra-thin LED array substrate 39 [40 indicates an LED array chip] that does not use a rod-shaped lens is fixed to a release plate 41 for the LED array substrate 39 and then incorporated into a case 42. A close-contact image sensor can be realized.

Here, the first light shielding body 43 and the second light shielding body 44 are the same as those in the third embodiment shown in FIG.

(G) As described in detail, according to the present invention, an optical fiber array plate in which each optical fiber is not coated with an absorber is placed on the document side, and an optical fiber array plate in which each optical fiber is coated with an absorber is placed on the light receiving element array side. After stacking and arranging the
By providing a light shield between the light source and the light receiving element array and/or between the light source and the optical fiber array plate,
Not only can the surface of the document be easily illuminated, but leakage light that can become noise can be reliably cut out to achieve high resolution. Furthermore, since the optical path length can be extremely shortened by using an optical fiber array plate, it is possible to realize a contact image sensor that is much smaller than a rod lens array.

Furthermore, according to the present invention, an LE without lenses is used as a light source.
By using a D-array substrate, it is possible to achieve an extremely thin design.

In addition, compared to conventional image sensors with reduction optical systems and contact image sensors using rod lens arrays, they can be made more compact, and the number of parts can be reduced by having a structure in which the protective glass also serves as an optical fiber array plate. Therefore, the material cost can be reduced, and since adjustment of the optical system is not required, the number of man-hours can be reduced, which is advantageous for cost reduction.

[Brief explanation of drawings]

1, 4, 5, and 6 are configuration explanatory diagrams showing the first to fourth embodiments of the present invention, respectively, and FIG. 2 shows that each optical fiber in each of the above embodiments is not coated with an absorber. FIG. 3 is an explanatory diagram of the main part structure showing an optical fiber. FIG. 3 is an explanatory diagram of the main part structure showing an optical fiber in which each optical fiber in each of the above embodiments is coated with an absorber. 1... Light receiving element array, 7... Optical fiber array in which each optical fiber is not coated with an absorber, 8... Optical fiber array in which each optical fiber is coated with an absorber, 9... ... Base glass part of optical fiber array not coated with absorber, IO... Base glass part of optical fiber array coated with absorber, 11... LED array substrate, I2... ... Rod-shaped lens, 13 ... Heat sink for LED array board, 14.32
, 35.42...Case, 15.36.43...
. . . Case-integrated first light shield, 16. Case-integrated second light shield, 17.
38.45... Pressing plate, 18... Document, 19.25... Optical fiber core section, 20.
26...Optical fiber cladding part, 21.28
・・・・・・Path of the light containing the information of the original to be read 22. 29 ・・・Path of the light incident on the optical fiber cladding part, 23.30 ：Aperture angle of the optical fiber Path of light incident on the optical fiber core at the above angles, 24.31... Path of light incident from the side of the optical fiber array, 27... Absorber coated on the optical fiber, 33
...First light shield using a rod-shaped rubber material, 34.37.44... Second light shield using a metal thin film, 39... Rod-shaped LED array board without lens,
40...LED array chip, 41...
・Heat sink for LED array board without rod-shaped lens.

Claims (1)

[Claims] 1. In a contact image sensor having a light source that illuminates a document to be read, a light-receiving element array that converts reflected light from the document into an electrical signal, and an optical fiber array section disposed between the document and the light-receiving element array. , the optical fiber array section is formed by laminating an optical fiber array in which each optical fiber is coated with a light absorber and an optical fiber array not coated with the light absorber, and the optical fiber array coated with the light absorber is disposed on the light receiving element array side. death,
An optical fiber array not covered with a light absorber is disposed on the document side, and a first optical fiber array is provided between the light source and the light receiving element array and/or between the light source and the optical fiber array.
and a second light shielding body.