JPH04265063A - Contact image sensor - Google Patents

Abstract

PURPOSE:To obtain a contact image sensor of less variance in optical sensitivity by obtaining a homogeneous light-transmissive optical fiber array which does not require heating for mounting and is free from cut and degeneration. CONSTITUTION:An optical fiber consists of a core 21, a clad 22, and a light absorber 23 on the outer surface, and plural optical fibers are arrayed into an optical fiber array 17. Plural photodetectors 13 are closely brought into contact with one end of the array 17, and photodetectors 13 are brought into contact with one end face of the array 17 with a transparent substrate 16 between them. A document 10 is closely brought into contact with the other end side of the array, and the document 10 is irradiated with light from a light source 19 through the substrate 16 and optical fibers. Optical information from the document 10 is led to photodetectors by plural optical fibers having light absorbers in 1:1 without mixture. Unnecessary light from the external is completely intercepted by a black film 18. As the result, the picture is read with a high resolution.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type image sensor that detects an image of a document or the like and obtains an image signal.

0002

[Prior Art] Optical fiber arrays are made by sandwiching an optical fiber bundle between two glass substrates, heat-pressing them, cutting them, and then cutting them.
Obtained by polishing. Conventionally, image sensor units have been manufactured by forming a circuit conductor layer on the optical fiber array by thick film printing, and placing the circuit conductor layer facing the electrical wiring formed on the circuit board having the photodetecting element. and the electrical wiring of the photodetector element were connected using solder bumps or the like. As a result, as shown in FIG.
A light source 39 is provided at one end side of the optical fiber array 37 provided with
is provided, illuminates the original 30 placed close to the other end of the optical fiber array 37, makes the reflected light from the original 30 enter the optical fiber array 37 on the other end, and converts this light into an optical fiber. It leads to the detection element 33.

In addition, in order to read the reflected light from the original 30 onto the optical fiber array 37 without mutual crosstalk, a light absorber 2 is provided on the outer surface of the cladding 22 of the optical fiber as shown in FIG.
It is desirable to provide 3. However, due to the light absorption of the light absorber 23, the illumination light did not reach the original placed close to the other end of the optical fiber array, so the optical fiber array or the light absorber excluding a part of the light absorber was installed on the outer surface. No need to stack optical fiber arrays.

0004

[Problems to be Solved by the Invention] In the above-described configuration, when the photodetecting element formed on the image sensor chip is mounted on one end side of the optical fiber array using solder bumps or the like so as to face each other, the problem arises when the solder melts. The light transmittance between each of the optical fibers that make up the optical fiber array is significantly reduced due to heat, or due to the heat of firing when forming a thick film on the circuit conductor layer by screen printing, or due to the optical fibers themselves being broken. There was a problem that the image could not be read uniformly due to the occurrence of areas where the image was blurred.

[0005] Furthermore, when stacking an optical fiber array in which a part of the light absorber is removed or an optical fiber array in which the light absorber 23 is not provided on the outer surface of the cladding 22, optical crosstalk increases somewhat and the resolution decreases. was occurring.

In view of the above problems, the present invention provides high resolution,
Another purpose is to enable high-quality image reading with little variation in sensitivity.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the contact type image sensor of the present invention includes an optical fiber array formed by aligning at least a plurality of optical fibers, and a plurality of optical fibers arranged at one end of the optical fiber array. In a close-contact image sensor in which several photodetecting elements are closely arranged, the optical fiber includes a central core, a cladding provided on the outer surface of the core, and a light absorber provided on the outer surface of the cladding. Further, the plurality of photodetecting elements are formed together with a circuit conductor layer on a transparent substrate, and the photodetecting elements are configured to be in contact with one end surface of the optical fiber array via the transparent substrate.

[0008] The optical fiber array also has a structure in which an optical fiber array formed by arranging optical fibers having a light absorber on the outer surface of the cladding is fusion-welded between glass substrates or on an end surface, and a plurality of optical fiber arrays are arranged on one end side of the optical fiber array. In a close-contact image sensor in which several photodetecting elements are closely arranged, the transmittance of the light absorber provided on the outer surface of the cladding of the optical fiber is such that the occupied area ratio of the core of the optical fiber is a, and the area ratio of the optical fiber array is When the transmittance of light incident at an angle less than the critical angle is T, then T
An optical fiber array having /a of 0.85 to 0.76 is used, a light source is provided diagonally above one end of the optical fiber array, and a document placed closely on the other end of the optical fiber array is placed under a glass. The structure is such that the light is illuminated through the substrate and the reflected light from the original is guided to the photodetector element through the optical fiber array.

[0009]

[Function] With the above-described structure, the present invention eliminates the need for heating when mounting a circuit conductor layer or a photodetector element on an optical fiber array, and provides an optical fiber array with homogeneous transmission characteristics without cutting or deterioration of optical fibers. can be obtained. Thereby, a contact type image sensor with less variation in photosensitivity can be obtained.

[0010] Furthermore, the transmittance of the absorber provided on the outer surface of the cladding of the optical fiber is such that the occupied area ratio of the core of the optical fiber is a, and the transmittance of light incident at an angle less than the critical angle of the optical fiber array is When T, T/a is 0.85 to 0.76
By doing so, the light illumination efficiency on the original that is close to the optical fiber array can be equal to or higher than that of a close-contact image sensor using a SELFOC lens array, and the optical information from the original can be transmitted through the optical fiber array. By placing the optical fiber array closer to the image sensor's photodetecting element with high precision, it is possible to guide the image sensor in a one-on-one manner. Reading resolution and light usage efficiency are improved more than ever.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIGS. 1 and 2 are a front sectional view and a side sectional view of a contact type image sensor according to an embodiment of the present invention.

In FIG. 2, 11 is a coating resin;
2 is an image sensor chip, 13 is a plurality of photodetecting elements provided on the image sensor chip 12, 14 is an electrode of the image sensor chip 12, 16 is a transparent substrate made of a transparent material, and 15 is on the transparent substrate 16. circuit conductor layer,
17 is an optical fiber array bonded to the transparent substrate 16 with a transparent adhesive or a photocurable resin (ultraviolet curable resin), 18 is a black film formed on the upper and lower surfaces of the transparent substrate 16, and 19 is an original document. It is a light source that illuminates 10. Also figure 3
is a plan view of the optical fiber array 17, and each optical fiber is composed of a core 21 at the center, a clad 22 on the outer surface of the core 21, and a light absorber 23 provided on the outer surface of the clad 22.

Next, the details of the contact type image sensor constructed as above will be explained in more detail. As shown in FIG. 3, a light absorber 23 with a thickness of 2 to 3 μm is formed on the outer surface of the cladding 22 of an optical fiber with a diameter of approximately 25 μm,
As shown in FIG. 2, a large number of these optical fibers are sandwiched between two glass substrates 20, and while applying pressure from both sides, they are fused together by applying heat to about the melting point of the glass. Furthermore, about 1mm
After cutting into thick pieces, the surface is polished smooth and optical fiber array 1
Create 7. Next, the transparent substrate 16 is preferably a glass sheet or a polymer film having a thickness of 400 μm or less, preferably 40 to 300 μm. Here 40-60 μm
It is made using a transparent polymer film such as polyarylate (PA) or polyether sulfone (PES). A black film 18 is formed on both sides of the transparent substrate 16 and the glass substrate 20 by screen printing. However, the portion where the optical fiber array 17 is bonded and the portion through which illumination light from the light source 19 passes are excluded. Further, on one end surface of the transparent substrate 16, A
100 μm by screen printing method or thin film forming method and photolithography method using noble metals such as u, Ag-Pt, and Cu.
The following circuit conductor layer 15 is formed. Furthermore, the size is 50
~100 μm square photodetecting elements 13 are arranged at regular intervals (62.5
The image sensor chips 12 are mounted using a photocurable resin (ultraviolet curable resin) or the like so that the electrodes 14 of the image sensor chips 12, which are formed in parallel with each other (or 125 μm), are connected to predetermined positions of the circuit conductor layer 15. Furthermore, in order to protect this image sensor chip, it is coated with a coating resin 11 such as silicone resin. Next, the optical fiber array 17 is bonded to the transparent substrate 16 using a transparent adhesive or a photocurable resin (ultraviolet curable resin) so as to match the positions of the plurality of photodetecting elements 13 provided on the image sensor chip 12. do.

Using this contact type image sensor, the original 10 is brought into close contact with the other end of the optical fiber array 17, and the light from the light source (LED array) 19 is incident on the top surface of the transparent substrate 16 to cover the transparent substrate. The original 10 is irradiated through the optical fiber. At this time, the transmittance T/a of the optical fiber array is set to about 80%.

Optical information from the document 10 is guided to the photodetector element 13 in a one-to-one correspondence without any crosstalk by a large number of optical fibers provided with light absorbers 23. Also, unnecessary light from the outside is filtered out by the black film 18.
0% blocked.

In this way, high resolution (MTF value of 4l)
This made it possible to read images at a rate of about 70% (p/mm). (Example 2) A contact type image sensor was created in the same manner as in Example 1. Since the numerical aperture (NA) of the optical fiber array used at this time was 0.57, the critical angle was 22°.
Transmission characteristics were measured using light with an incident angle of 15° or less. Light utilization efficiency and resolution were measured using an optical fiber array with a transmittance T of 0.55 to 0.68. The core occupancy rate a of the optical fiber at this time was 0.7. From this, T/a corresponds to 0.78 to 0.97.

[0017] As a result of these measurements, 0.55 to 0.7
Although the optical fiber array No. 5 has an MTF value of 4lp/mm and a high resolution of approximately 70%, the light illumination efficiency is 0.5 to 0.5% compared to a contact type image sensor using a SELFOC lens array. 7, which required about 1.4 to 2 times the amount of light. On the other hand, when an optical fiber array of 0.86 to 0.97 is used, although the light utilization efficiency improves by 1.5 to 3 times, the MTF value decreases to about 30 to 43% at 4 lp/mm.

[0018] In the range of 0.76 to 0.85, the light utilization efficiency is also 0.
．． 8~1.3 times and MTF value is 45~4lp/mm
Good characteristics of 70% were obtained.

[0019]

[Effects of the Invention] As described above, the present invention provides the following advantages when guiding optical information from a document to a photodetecting element using an optical fiber array.
Since uniform transmission characteristics can be obtained, it is possible to obtain a contact type image sensor with less variation in photosensitivity. In addition, by being able to mount the optical fiber array closer to the image sensor's photodetecting element with high precision, it is possible to provide better guidance through one-on-one correspondence, improving image reading resolution and light usage efficiency. will improve more than ever before.

[Brief explanation of the drawing]

FIG. 1 is a front cross-sectional view of an image sensor in a first embodiment of the present invention.

FIG. 2 is a side sectional view of the image sensor according to the first embodiment of the present invention.

FIG. 3 is a top view of the same optical fiber in the same example.

FIG. 4 is a front cross-sectional view of a conventional image sensor.

[Explanation of symbols]

10 Manuscript 11 Coating resin 12 Image sensor chip 13 Photodetection element 14 Electrode 15 Circuit conductor layer 16 Transparent substrate 17 Optical fiber array 18 Black film 19 Light source 20 Glass substrate 21 Core 22 Clad 23 Light absorber 30 Manuscript 31 Coating resin 32 Image sensor chip 33 Photodetection element 34 Electrode 35 Circuit conductor layer 36 Glass substrate 37 Optical fiber array 38 Black film 39 Light source

Claims (3)

[Claims] 1. A close-contact image sensor comprising an optical fiber array formed by aligning at least a plurality of optical fibers, and a plurality of photodetecting elements closely provided on one end side of the optical fiber array, wherein the optical fibers comprises a central core, a cladding provided on the outer surface of the core, and a light absorber provided on the outer surface of the cladding, and the plurality of photodetecting elements are formed together with a circuit conductor layer on a transparent substrate. , a contact image sensor configured such that a photodetector element is in contact with one end surface of an optical fiber array through a transparent substrate. 2. An optical fiber array formed by arranging optical fibers having a light absorber on the outer surface of the cladding is fusion-welded between glass substrates or on an end surface, and a plurality of optical fiber arrays are arranged on one end side of the optical fiber array. In a close-contact image sensor in which several photodetecting elements are closely arranged, the transmittance of the light absorber provided on the outer surface of the cladding of the optical fiber is such that the occupied area ratio of the core of the optical fiber is a, and the area ratio of the optical fiber array is When the transmittance of light incident at an angle less than the critical angle is T, T/
An optical fiber array having a of 0.85 to 0.76 is used, a light source is provided diagonally above one end of the optical fiber array, and a document placed closely on the other end of the optical fiber array is placed on the glass. A contact image sensor configured to illuminate through a substrate and guide the reflected light from the document to a photodetector element through an optical fiber array. 3. At the other end of the optical fiber array that is in close contact with the original, a wall surface is provided in a direction substantially perpendicular to this end surface,
3. The contact image sensor according to claim 1, wherein the wall surface is provided with a blackish film.