JP2661426B2 - Optical Fiber Array Substrate and Fully Adhesive Image Sensor Using Optical Fiber Array Substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber array substrate for transmitting a one-dimensional optical image and an image sensor for converting an optical image into an electric signal using the optical fiber array substrate, and relates to a facsimile, an image reader, and a digital copying machine. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perfect contact type image sensor which is suitable for a device or the like and which reads an image which is in close contact with a document and corresponds to a width direction of the document.

[0002]

2. Description of the Related Art Conventionally, optical fiber arrays have been used as means for transmitting image (optical image) information. Such an optical fiber array is shown in FIG. 2B as means for removing light having an angle larger than the incident angle corresponding to its numerical aperture (NA) in order to prevent crosstalk of transmitted optical image information. As described above, an optical fiber in which the clad 27 having a small refractive index is formed around the core 25 of the optical fiber, and the light absorber layer 26 is further formed around the clad 27 is used.
Further, in order to obtain an optical fiber array substrate in which a large number of optical fibers are embedded in a glass substrate, a large number of such optical fibers are individually sandwiched between base materials such as base glass, or as shown in FIG. Optical fiber bundles in which a plurality of optical fibers are bundled are stacked in three rows, sandwiched between base materials such as base glass, pressed, heated, and melted to form an optical fiber array substrate.

On the other hand, as an image sensor for converting one-dimensional image information into an electric signal, a reduction type using a one-dimensional CCD element and a one-dimensional image sensor using a long sensor of the same size are commercialized. . Among them, the one-dimensional image sensor using the latter long sensor has excellent features such as high light utilization, high-speed reading, and a small optical system. Such image sensors include a contact image sensor using a converging rod lens array, which is an equal-magnification optical lens, and a complete contact image sensor using no optical lens. The latter fully-contact type image sensor is inexpensive because a converging rod lens array is not required, and it is easier to reduce the size of the device. For this reason, it has been proposed to apply the complete contact type image sensor using the optical fiber array substrate to a facsimile or the like.

[0004]

However, although the above-mentioned fiber array substrate is effective for transmitting image information using transmitted light, the reflected light of a document closely attached to the optical fiber array substrate is used as information. In order to transmit light, the illumination efficiency is significantly reduced because the illumination light is absorbed by the light absorber layer. Conversely, if the illumination efficiency is prioritized and the light absorption efficiency of the light absorber layer is reduced, sufficient resolution is obtained. However, there is a problem that it is difficult to transmit the image information.

[0005] In such a long, fully-contact type image sensor using an optical fiber array substrate, an optical fiber array substrate using a light absorber layer and a light-emitting device are used to achieve both illumination efficiency and resolution of transmitted image information. Means for superposing an optical fiber substrate excluding the absorber layer has been proposed (Japanese Patent Laid-Open No.
However, it has been difficult to provide a complete contact image sensor at low cost by such means.

[0006]

According to the present invention, there is provided an optical fiber array substrate in which a plurality of optical fibers are arranged one-dimensionally and embedded in the substrate.
The light absorption layer having a higher absorbance than the others is arranged at a distance D or less in a shape crossing the direction in which it is arranged in a dimension, the thickness of the optical fiber array substrate is t, the numerical aperture of the optical fiber is NA,
When the refractive index of the core of the optical fiber is n, an optical fiber array substrate characterized by a relationship of D <NA × t / (n ² −NA ² ) ^1/2 is used.

[0007] In the complete contact image sensor, a plurality of optical fibers are arranged one-dimensionally, and a light-transmitting insulating layer is provided on the plurality of optical fibers on an optical fiber array substrate embedded in a glass substrate. In a complete contact type image sensor formed by arranging light receiving elements that are in contact with each other one-dimensionally,
The optical fiber array substrate has a light absorption layer having a higher absorbance than the others arranged at a distance D or less in a shape crossing a plurality of fiber directions in which the optical fiber array substrate is one-dimensionally arranged. An optical fiber array characterized in that, when the numerical aperture of the optical fiber is NA and the refractive index of the core of the optical fiber is n, the relationship is D <NA × t / (n ² −NA ² ) ^1/2. A substrate is used.

[0008]

The optical fiber has an aperture: NA = n0 × si
An incident angle determined by n (i) (n0 is a medium on which light is incident):
Light incident at an angle smaller than i is transmitted through the optical fiber and efficiently exits from the end face opposite to the incident side. However, light incident at an angle equal to or greater than the incident angle i is not transmitted through the fiber but is transmitted across the fiber and does not function as light as image information, but also causes degradation in resolution. Therefore, such light has been prevented by providing a light absorber layer around the optical fiber. However, if an optical fiber array substrate is formed using fibers having a uniform light absorber layer, the light abutting the fiber may be externally illuminated with light to transmit optical image information. Therefore, the improvement of the resolution and the light illumination on the document surface are not compatible.

Therefore, paying attention to the fact that light within the incident angle does not contribute to resolution degradation, a layer having high light absorption efficiency is provided at a position where light incident on the optical fiber array from the document surface is expressed by the following equation. It has been found that the resolution can be effectively prevented from deteriorating.

NA × t / (n ² −NA ² ) ^1/2 where t is the thickness of the fiber array substrate, and n is the refractive index of the core of the optical fiber.

In the optical fiber array substrate thus obtained, the light absorbing efficiency is not increased by forming a light absorbing layer on the entire optical fiber unnecessarily. Since it is formed well, the light illumination efficiency can be satisfied at the same time by illuminating with a light source obliquely from above along the direction in which the optical fiber array is arranged.

In order to obtain a complete contact image sensor using a glass substrate (fiber array plate) in which a fiber array is embedded, a complete contact image can be obtained simply by adhering the fiber portion to the light receiving element. A sensor is obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical fiber array substrate and a perfect contact type image sensor according to an embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 (a) and 1 (b) show a front view of an optical fiber array substrate and a cross-sectional view of each optical fiber bundle in a first embodiment of the present invention. 11
Has a core diameter of 10 to 20 μm (here, 20 μm)
4 shows a bundle of optical fibers having a numerical aperture NA = 0.57. Reference numeral 12 denotes a base glass having substantially the same characteristic as the thermal expansion coefficient of the optical fiber, and the optical fiber bundle is stacked in two rows. The optical fiber bundle, which was initially circular, is sandwiched between base glasses, pressurized, melted by heating and deformed to exhibit a pentagon-like shape. At this time, the distance between the optical fiber bundles is D = 0.5 mm at the maximum. FIG.
(B) is a sectional view of each optical fiber bundle. here,
An optical fiber bundle in which a light absorber layer is formed only around an optical fiber bundle having no light absorber layer is shown. If an optical fiber array substrate is formed using such a bundle, an effective light absorber layer is obtained. It is deposited and formed on the sides of the pentagon, and the portion in contact with the base glass is relatively thin, so that light can be easily transmitted. This optical fiber array is cut to a predetermined thickness t = 1.33 mm or more represented by the following formula and the surface is polished.
(Here, n = 1.62) D <NA × t / (n ² −NA ² ) ^1/2 In order to form a complete contact image sensor using such an optical fiber array substrate 41, As shown in FIG. 4, the optical fiber array 42 sandwiched between the base glasses has the configuration shown in FIG. A light-shielding layer 43 is formed at a position other than the fiber array on the contact side of the document 40. A circuit conductor layer 46 is formed on such an optical fiber array substrate by thick film printing, and an image sensor semiconductor element 4 having a light receiving element 48 is provided.
7 is an electrode 4 formed on the image sensor semiconductor element.
5 and the circuit conductor layer 46 are pressed so as to be in contact with each other by facedown, fixed and mounted using an ultraviolet-curing transparent insulating resin 49, and an LED array 44 is arranged for illumination to provide a complete contact image sensor. obtain.

Next, a method for manufacturing the image sensor configured as described above will be specifically described. First, a light receiving element 48 such as a phototransistor or a photodiode is formed on a single crystal silicon substrate (wafer) by using a semiconductor process.
And an access circuit (not shown) such as a CCD, a MOS, or a bipolar IC. In this embodiment, a light receiving element formed at 8 dots / mm using a bipolar IC is used. The electrode 45 has a structure protruding from the wafer surface by about several μm by a sputtering method using a two-layer Al wiring process. Thereafter, the wafer is cut by a high-precision dicing technique to form an image sensor semiconductor element 47. The optical fiber array substrate 41 has a circuit conductor layer 46 on the surface on which the image sensor semiconductor element is formed by thick film printing, and a light shielding layer 43 on a part of the original surface and the surface on which the circuit conductor layer is formed. Obtain an array substrate. A predetermined amount of an acrylate-based transparent photocurable insulating resin 49 is applied to this substrate by a stamping method, a screen printing method, or the like, and an image sensor semiconductor element 47 is placed thereon such that the electrode 45 contacts the predetermined circuit conductor layer 46. Face down. After that, while applying pressure from above the image sensor semiconductor element 47, the transparent light-curable insulating resin 49 is irradiated with ultraviolet light through the optical fiber array substrate and cured to complete the mounting.

Also, instead of mounting the image sensor semiconductor element directly on the optical fiber array substrate, polyarylate (PA) or polyether sulfone (PES) is used.
On a light-transmitting sheet substrate such as, a metal film such as copper, using a light-transmitting sheet substrate formed as a circuit conductor layer by a photolithography method after forming using a vapor deposition method, a sputtering method, or a foil, Similar to the above mounting method, after mounting the image sensor semiconductor element face down so that the electrode of the image sensor semiconductor element contacts a predetermined circuit conductor layer, the light transmitting sheet substrate may be bonded to the optical fiber array substrate with a transparent adhesive. A complete contact type image sensor unit can be obtained. As described above, by separating the mounting of the image sensor semiconductor element and the manufacturing of the optical fiber array substrate, it is possible to prevent the yield from decreasing.

In the complete contact type image sensor thus obtained, when the original surface is illuminated using the same LED as the conventional contact type image sensor using the selfoc lens array, the light intensity is about 1.4 times as high. A signal output was obtained. The MTF was measured using a 4 lp / mm chart, and a resolution of about 40% or more could be obtained. Similarly, by making the optical fiber array substrate approximately twice as large as 2.7 mm or more, the resolution characteristics were further improved, and a high resolution of 50% or more could be obtained under similar conditions.

FIG. 3 is a front view of an optical fiber array substrate according to a second embodiment of the present invention. Reference numeral 31 denotes a base glass, and an optical fiber bundle 32 is arranged so as to be separated by a light absorber layer 33. In a complete contact image sensor unit using such an optical fiber array substrate,
It has been found that the light illumination efficiency is high and an optical signal output twice as high as that of a conventional contact image sensor unit can be obtained.

FIG. 2B shows a conventional optical fiber in which a fiber bundle having a light absorber layer formed on each optical fiber is arranged in three rows, as shown in FIG. It has been found that the same effect can be obtained by simply forming a single row arrangement as shown in FIG. This is considered to be because the light absorber layer formed around the optical fiber is deposited thickly at a position where the optical fiber bundles come into contact with each other, and thus the same effect is considered to be exhibited. FIG. 1 (a),
In the case of the configuration as shown in FIG. 3, it was possible to obtain a signal output whose light illumination efficiency was about 1.2 times that of the conventional contact type image sensor.

[0020]

The optical fiber array substrate of this embodiment can efficiently illuminate the reflection image information of the original which comes into contact with the fiber, and can effectively transmit the information to the fiber. In addition, the perfect contact type image sensor using this has a relatively deep depth of focus, high illumination efficiency, excellent resolution characteristics, and has little image degradation due to static electricity due to friction or flaws due to wear, and the manufacturing process is simple. Can reduce the yield,
In addition, it is possible to provide an inexpensive perfect contact type image sensor.

[Brief description of the drawings]

FIG. 1A is a front view of an optical fiber array substrate according to a first embodiment of the present invention. FIG. 1B is a cross-sectional view of an optical fiber bundle according to the first embodiment of the present invention.

FIG. 2A is a front view of an optical fiber array substrate in a conventional example, and FIG. 2B is a cross-sectional view of an optical fiber bundle in a conventional example.

FIG. 3 is a front view of an optical fiber array substrate according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a complete contact image sensor according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 optical fiber bundle 12 base glass 15 light absorber layer 16 clad 17 core 21 optical fiber bundle 22 base glass 25 core 26 light absorber layer 27 clad 40 original 41 optical fiber array substrate 42 optical fiber array 43 light shielding layer 44 LED 45 electrode 46 circuit conductor layer 47 image sensor semiconductor element 48 light receiving element 49 ultraviolet curing type transparent insulating resin

Claims (2)

(57) [Claims] 1. An optical fiber array substrate in which a plurality of optical fibers are arranged one-dimensionally, and in an optical fiber array substrate embedded in the substrate, light having a higher absorbance than that of other optical fibers crossing the one-dimensionally arranged direction. When the absorption layers are arranged at intervals D or less, the thickness of the optical fiber array substrate is t, the numerical aperture of the optical fiber is NA, and the refractive index of the core of the optical fiber is n, D <NA × t / (n ² − An optical fiber array substrate characterized by having a relationship of NA ² ) ^1/2 . 2. A plurality of optical fibers are arranged one-dimensionally, and a light receiving element which is in contact with the plurality of optical fibers via a light-transmitting insulating layer is provided on an optical fiber array substrate embedded in a glass substrate. In a complete contact image sensor formed in a three-dimensional arrangement, the optical fiber array substrate has a light absorbing layer having a higher absorbance than the others in a shape crossing the directions of a plurality of fibers arranged one-dimensionally. D <NA × t / (n ² −NA ² ) ^{1 /} where t is the thickness of the optical fiber array substrate, NA is the numerical aperture of the optical fiber, and n is the refractive index of the core of the optical fiber. A completely contact type image sensor using an optical fiber array substrate, characterized in that the image sensor is configured to have a relationship of ^two .