JPH10243165A - Optical image sensor with reduced light guide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain excellent reading without pixel deviation by using a jig so as to fix a part connecting a polymer waveguide array and a photoelectric conversion element that detects a light propagated through a light guide path and converts the light into an electric signal. SOLUTION: A image sensor is made up of a waveguide type detection section consisting of a micro lens array 2, a light guide board 3 and a photoelectric conversion element 4 and up of a waveguide type linear light source 5. A jig which is, e.g. channel- shaped or square-shaped is provided to a part to which a polymer light guide path on a light guide path board 3 and a photoelectric conversion element 4 that converts a reflected light from an original 1 into an electric signal are connected to prevent a pitch between the photoelectric conversion element 4 and a core from being changed due to a temperature change. That is, even when a linear expansion coefficient of a material of the light guide path differs from that of the photoelectric conversion element 4, since the jig is inserted to the connection part between the light guide path and the photoelectric conversion element 4, the expansion in the transversal direction is suppressed. Since the structure of escaping the distortion in the transversal direction into the longitudinal direction is adopted, no irrational force is exerted to the jig.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction type image sensor using an optical waveguide used for a one-dimensional reading optical system such as a facsimile machine, a copying machine, an image scanner, etc., and more particularly to a case where an external temperature changes. The present invention relates to an optical waveguide reduced optical image sensor capable of performing good reading with no pixel shift even if it is used.

[0002]

2. Description of the Related Art In recent years, demand for image reading in facsimile machines, image scanners, digital copiers and the like has been increasing, and therefore, high-performance and miniaturized one-dimensional image sensors for converting image information into electric signals are expected.
Conventionally, a one-dimensional image sensor includes a reduced optical image sensor that reads an imaged image using a reduced optical system, and a contact image sensor that reads an image image at 1: 1 magnification using a one-to-one optical system. is there.

The reduction optical image sensor has the advantages of being inexpensive and capable of high-speed reading,
Since a reduced image is required by a lens, the size of the element is large and it is difficult to reduce the size. Further, since the adjustment of the optical system is complicated, it has to be adjusted for each unit.

On the other hand, the contact type image sensor has the advantage that the distance from the document to the photoelectric conversion element array is small and no adjustment is required, but the size of the photoelectric conversion element array is large, and the complicated electronic element for driving the photoelectric conversion element array is required. It has the disadvantage that a circuit is required and it is difficult to reduce the price.

For this reason, recently, a reduced image sensor using an optical waveguide array has been proposed. This reduced image sensor includes a microlens formed over the width of a document surface,
It comprises an optical waveguide substrate on which a plurality of waveguides are formed for guiding the light condensed by the microlenses, and a photoelectric conversion element array for receiving light and converting the light into an electric signal. And
If this reduced image sensor is used, low cost and downsizing of the element can be realized, and adjustment of the optical system is unnecessary.

Regarding the optical waveguide of such a reduced image sensor, there are known several manufacturing methods using a polymer material for the core as the material. One is to fill a groove portion of a pattern substrate made of a polymer material such as PMMA with a groove pattern formed therein with a polymer precursor material for a core of a waveguide, and to form a polymer such as PMMA. This is a sandwich method in which a core of an optical waveguide made of a polymer material is formed by bringing a flat substrate into close contact with a groove of a pattern substrate and then performing photopolymerization by irradiation with ultraviolet light.

As another method, a capillary is formed by bringing a pattern surface of a pattern substrate, on which a pattern of grooves serving as a capillary is formed, into close contact with a flat substrate, and then a polymer precursor as a raw material of a core of an optical waveguide is formed. There is a vacuum capillary method in which the capillary is filled by the capillary phenomenon and then the polymer precursor is polymerized.

According to these methods, since no gap is formed at the boundary between the pattern substrate and the planar substrate, there is no crosstalk due to light leaking from between the cores, and the polymer optical waveguide has excellent optical waveguide characteristics. Can be realized.

In a reduction optical image sensor using a polymer optical waveguide for a reduction optical system, an original is illuminated by an LED when reading an image, and information on the original is passed through a core portion of the optical waveguide to a photoelectric conversion element. It is possible to read and read image information.

[0010]

However, according to the above-described image sensor to which the polymer optical waveguide is applied, the linear thermal expansion coefficient of the polymer material such as PMMA forming the optical waveguide having a plurality of cores formed thereon is small. When the material is different from the material for forming the photoelectric conversion element, if there is a temperature change, the pitch between the photoelectric conversion element and the core changes, and as a result, a pixel shift occurs and the output changes, so that good reading cannot be performed.

For this reason, when using such a polymer optical waveguide, it is an extremely important issue how to remove a decrease in image reading accuracy caused by a temperature change.

Therefore, the present invention solves the above problems,
By keeping the pixel pitch of the photoelectric conversion element and the pitch of the core of the polymer optical waveguide unchanged even when the external temperature changes, an optical waveguide reduced optical image sensor capable of performing good reading without pixel shift is provided. The purpose is to provide.

[0013]

According to a first aspect of the present invention, there is provided an optical waveguide reduced optical image sensor for reducing light from a document surface by using a polymer optical waveguide array. The invention is characterized in that a portion connecting a photoelectric conversion element for detecting light propagated through a wave path and converting the light into an electric signal and a polymer waveguide array is fixed with a jig to prevent pixel shift.

According to a second aspect of the present invention, the jig has a U-shape or a U-shape which covers a portion of the polymer optical waveguide which is coupled to the photoelectric conversion element.

Further, a third invention is characterized in that the jig has a gap in a vertical direction.

According to a fourth aspect of the present invention, the jig is formed using a member having a linear thermal expansion coefficient equal to that of the photoelectric conversion element.

Therefore, even if the external temperature changes,
At the joint of the polymer optical waveguide and the photoelectric conversion element, expansion in the long side direction is suppressed, and distortion in the horizontal (long side) direction is released in the vertical (short side) direction. In this manner, it is possible to suppress the expansion in the horizontal direction without exerting excessive force, and to perform good reading without pixel shift without changing the pitch between the polymer optical waveguide and the core of the photoelectric conversion element.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, 200
A case in which the present invention is applied to a one-dimensional image sensor for G3 facsimile having a resolution of dpi (scan width 256 mm: corresponding to B4 paper) will be described. In the present embodiment, the CC of 14 μm pitch and 2048 pixels is used.
D, which is μPD3743D manufactured by NEC Corporation, is used as the photoelectric element.

FIG. 1 is a diagram showing a configuration of an optical waveguide reduced optical image sensor used in the present embodiment. As shown in FIG. 1, this optical waveguide reduced optical image sensor is composed of a waveguide type photodetector comprising a microlens array 2, an optical waveguide substrate 3 and a photoelectric conversion element 4, and a waveguide type linear light source 5. Become.

The microlens array 2 is a lens for condensing the reflected light from the document 1 on the incident surface of the optical waveguide substrate 3, and the optical waveguide substrate 3 converts the light condensed by the microlens array 2 to a photoelectric conversion element. 4 is a pattern substrate having an optical waveguide leading to 4. The photoelectric conversion element 4 is an element that converts light guided by the optical waveguide substrate 3 into an electric signal and outputs the electric signal.

Here, in the optical waveguide reduced optical image sensor used in the present embodiment, the polymer optical waveguide on the optical waveguide substrate 3 and the photoelectric conversion for detecting the reflected light from the original 1 and converting it into an electric signal. By providing a U-shaped or U-shaped jig at a portion where the element 4 is coupled, the pitch between the photoelectric conversion element and the core is not changed due to a temperature change. Note that a member having a linear thermal expansion coefficient equal to that of the photoelectric conversion element is used for the jig.

Next, the optical waveguide substrate 3 shown in FIG. 1 will be specifically described. FIG. 2 shows the optical waveguide substrate 3 shown in FIG.
FIG. 2 is a plan view showing the configuration of FIG. 1, and an optical waveguide 6 for guiding light to a microlens array 7 is provided on a substrate. First, the procedure for manufacturing the optical waveguide substrate 3 shown in FIG. 2 will be described. In the present embodiment, Japanese Patent Application Laid-Open No. 7-1788
No. 25, the optical waveguide substrate 3 is manufactured based on the injection molding method. The substrate material of the optical waveguide substrate 3 is PMMA having a refractive index of 1.49, and the core material of the optical waveguide 6 is a refractive index material manufactured by Three Bond.
1.53 UV curable resin TB3042 is used.

First, a photoresist film having a thickness of 9 μm is formed on a glass substrate, and a groove pattern is transferred using a photolithography technique. Then, when a mask is brought into close contact with the photoresist film and exposed to ultraviolet light to perform development processing, the pattern of the groove of the mask is transferred to the photoresist film, and the pattern of the groove serving as a capillary is formed. However, since the transfer rate at the time of injection molding from the mold is about 90%, the photoresist film thickness is set to be larger than the width and depth size of 8 μm which is the specification of the core.

Next, a 10 μm-thick nickel metal thin plate is formed on the surface of the patterned photoresist film by electroplating using an aqueous solution of nickel chloride, and the pattern surface of the formed metal thin plate is formed. Adhere the support plate to the opposite plane.

Finally, the thin metal plate is separated from the glass substrate by dissolving the photoresist film using a resist stripping agent, and a mold having grooves formed into an 8 μm rectangular capillary usable in an injection molding machine is formed. Is manufactured. P
Injection molding is performed with the mold using PMA, and a patterned PMMA substrate having grooves formed as capillaries is manufactured.

The optical waveguide substrate 3 manufactured in the present embodiment has a size of 260 mm × 25 mm × 2 mm, has 2048 waveguides, and the processed grooves are formed as shown in FIG. A reduced optical waveguide pattern having two bent portions was used. The waveguide pitch is 127 μm at the light entrance end and 4 μm at the light exit end, the core cross section of the waveguide is square, and the width and depth are each 8 μm.
It is.

Next, the fabrication of the optical waveguide 6 on the optical waveguide substrate 3 will be described. The groove portion of the pattern substrate manufactured as described above is filled with a polymer precursor material for the core of the optical waveguide 6, and a flat substrate (0.5 mm thick) is placed so as to be in contact with the groove portion of the pattern substrate. After being brought into close contact with a clamping jig, photopolymerization is performed by irradiation with ultraviolet light.
Then, the side surface of the produced polymer optical waveguide is polished by a standard polishing machine using a diamond-containing suspension having a size of 0.5 μm or less.

As described above, in the present embodiment, the pattern substrate serving as the base of the optical waveguide substrate 3 is manufactured based on the injection molding method, and the optical waveguide 6 is formed on the pattern substrate using the sandwich method. Thus, the optical waveguide substrate 3 is manufactured. In addition, it can manufacture similarly when the vacuum capillary method is used.

Next, the junction between the optical waveguide substrate and the photoelectric conversion element shown in FIG. 2 will be described with reference to FIGS. FIG. 3 is a diagram showing a case where the optical waveguide substrate 8 and the photoelectric conversion element 11 are joined using a U-shaped jig 9 and a flat plate jig 10, and FIG. FIG. 9 is a diagram showing a case where the element 11 is joined using a square-shaped jig 12.

As described above, in this embodiment, the joint between the polymer optical waveguide of the optical waveguide substrate 8 and the photoelectric conversion element 11 is provided with a U-shaped jig or a U-shaped jig at 20 ° C. To fix it.

When the U-shaped jig 9 shown in FIG. 3 is used, after the U-shaped jig 9 is fitted, the portion not covered with the U-shaped jig 9 is further flattened. By covering with a jig 10, it becomes the same as the square-shaped jig 12 shown in FIG. The reason is that if one side of the joint is not suppressed, the optical waveguide substrate 6 will be distorted. When the U-shaped jig 9 is used, the jig 9 can be fitted from two directions, that is, the top and the side, so that the jig 9 can be easily fixed from the direction in which it can be easily fitted.

Here, the sizes of the U-shaped jig 9 and the U-shaped jig 12 shown in FIGS. 3 and 4, respectively, are 30 mm in the horizontal dimension and the optical waveguide 6 in the vertical dimension. The depth of the core is 8 μm even when the pitch is shifted due to expansion and contraction in the vertical direction by increasing the height 4 μm by 4 μm from the thickness 2 mm of the wave path 6
, And the distortion in the horizontal direction was released in the vertical direction even if slightly, and the inner dimension depth was set to 5 mm.

The material of the U-shaped jig 9 and the U-shaped jig 12 has a linear thermal expansion coefficient of the photoelectric conversion element 11.
Use the same member as For example, since the linear thermal expansion coefficient of the silicon portion of the photoelectric conversion element 11 is about 3 × 10 ⁻⁶ / ° C., a member such as ceramics having a linear thermal expansion coefficient of about 2 to 9 × 10 ⁻⁶ / ° C. In this embodiment, SIALON of 3.0 × 10 ⁻⁶ / ° C., that is, SALON
Ceramics of a compound consisting of i, Al, O and N are used.

A micro lens array 7 made of PMMA is attached to the entrance end of the optical waveguide, and the photoelectric conversion element 11 is attached to the exit end surface using an ultraviolet curable resin. Here, the size of the microlens array 7 is 125 μm in diameter.
m, the photoelectric conversion element 11 has a pitch of 14 μm,
ΜP made by NEC Corporation, which is a 048 pixel CCD
D3743D was employed.

In order to eliminate crosstalk between adjacent waveguides, it is necessary to provide a light limiting member on the end face of the waveguide. Therefore, a metal reflection film is formed on the end face of the clad substrate by an evaporation method or a sputter evaporation method,
An organic film containing a dye that absorbs the light of D is applied.

As described above, the photoelectric conversion element 11 is attached to the exit end of the optical waveguide of the optical waveguide substrate 8 via the U-shaped jig 9 or the B-shaped jig 12, and the photoelectric conversion element 11 is attached to the incident end side. By attaching the microlens array 7, an optical waveguide reduced optical image sensor having the appearance shown in FIGS. 5 and 6 can be obtained.

Next, the effect of the optical waveguide reduced optical image sensor will be described in comparison with an image sensor using a conventional polymer optical waveguide. Note that the conventional image sensor used here is an image sensor in which the U-shaped jig 9 and the U-shaped jig 12 are not fitted to the coupling portion of the optical waveguide with the photoelectric conversion element.

Specifically, the reflected light from the original surface irradiated with the light from the light source is made incident on the incident ends of the cores of both the polymer optical waveguides, and the intensity of the light emitted from the polymer optical waveguides is measured. Images were captured by detecting with a conversion element, and the effects of temperature changes were compared between the two. The temperature was increased from 20 ° C. to 70 ° C. in a clean oven.

In a conventional image sensor, the linear thermal expansion coefficient of PMMA, which is a polymer material forming an optical waveguide, is 7 ×.
10 ⁻⁶ / ° C., and the difference between the linear thermal expansion coefficient of the photoelectric conversion element and the linear thermal expansion coefficient changed the pitch of the photoelectric conversion element and the core of the optical waveguide. . For this reason, the resolution was degraded, resulting in an image having poor contrast.

On the other hand, in the optical waveguide reduced optical image sensor used in the present embodiment, even if the linear thermal expansion coefficients of the optical waveguide and the material of the photoelectric conversion element are different, the optical waveguide and the photoelectric conversion element have different linear thermal expansion coefficients. Since the jig was fitted into the joint, lateral expansion was suppressed.

Further, since the structure is such that the distortion in the horizontal direction is released in the vertical direction, the expansion in the horizontal direction can be suppressed without applying excessive force to the jig. As a result, good reading was possible without any pixel shift, and an image with excellent resolution and good contrast was obtained.

[0042]

As described in detail above, the first aspect of the present invention is an optical waveguide reduction optical image sensor for reducing light from a document surface using a polymer optical waveguide array, and which propagates through the optical waveguide. Since the part that couples the photoelectric conversion element that detects light and converts it to an electric signal and the polymer waveguide array is fixed with a jig and configured to prevent pixel displacement,
Even when the external temperature changes, it is possible to suppress a change in the pitch between the core of the polymer optical waveguide and the photoelectric conversion element, and to obtain a good image with excellent contrast without pixel shift.

According to a second aspect of the present invention, the jig is formed to have a U-shape or a R-shape which covers a portion of the polymer optical waveguide which is coupled to the photoelectric conversion element. The waveguide and the photoelectric conversion element can be easily coupled.

According to the third aspect of the present invention, since the jig is configured to have a gap in the up-down direction, it is possible to suppress the expansion in the lateral direction without applying excessive force to the jig.

According to a fourth aspect of the present invention, since the jig is formed by using a member having the same linear thermal expansion coefficient as that of the photoelectric conversion element, the linear thermal expansion of the photoelectric conversion element and the jig can be matched. Therefore, the load on the jig can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a polymer waveguide reduced optical image sensor according to the present invention.

FIG. 2 is a diagram showing a configuration of an optical waveguide substrate of the waveguide-reduced optical image sensor according to the present invention.

FIG. 3 is a perspective view showing a jig configuration of a light detection unit of the waveguide reduced optical image sensor according to the present invention.

FIG. 4 is a perspective view showing a jig configuration of a light detection unit of the waveguide reduced optical image sensor according to the present invention.

FIG. 5 is a plan view showing a light detection unit of the waveguide reduced optical image sensor according to the present invention.

FIG. 6 is a cross-sectional view showing a light detection unit of the waveguide-reduced optical image sensor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 2 Microlens array 3 Optical waveguide board 4 Photoelectric conversion element 5 Light source 6 Optical waveguide 7 Microlens array 8 Waveguide board 9 U-shaped jig 10 Flat jig 11 Photoelectric conversion element 12 Square jig

Claims (4)

[Claims] An optical waveguide reduction optical image sensor for reducing light from a document surface using a polymer optical waveguide array, wherein the photoelectric conversion element detects light propagated through the optical waveguide and converts the light into an electric signal. An optical waveguide-reduced optical image sensor, characterized in that a portion connecting the polymer waveguide array and the polymer waveguide array is fixed with a jig to prevent pixel displacement. 2. The optical waveguide according to claim 1, wherein the jig has a U-shape or a U-shape that covers a portion of the polymer optical waveguide that is coupled to the photoelectric conversion element. Optical image sensor. 3. The optical waveguide reduced optical image sensor according to claim 1, wherein the jig has a gap in a vertical direction. 4. The optical waveguide reduced optical image sensor according to claim 1, wherein said jig is formed using a member having a linear thermal expansion coefficient equal to that of said photoelectric conversion element.