JPH0936337A - Waveguide type reduced image sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple method of manufacturing a waveguide type reduced-image sensor and a polymer optical waveguide which have a structure for reducing the loss of an optical signal at the bend part of the polymer optical waveguide. SOLUTION: A trench 102 for loss reduction of an optical signal at the bend part of an optical waveguide 101 is adjacently formed to the outside of the bend part of the optical waveguide 101. The trench 102 is filled with gas whose refractive index is lower than that of a waveguide core part and further that of a waveguide clad part. The optical waveguide 101 is manufactured as follows; the pattern surface of a pattern substrate wherein a trench having both open ends turning to a capillary and its adjacent trench whose both ends are sealed are formed is made to stuck on a plane substrate, the single end of the capillary is sealed, only the capillary whose single end is an aperture is filled with monomar solution as the material of core of the optical waveguide 101, by the effect of capillarity, and the monomar solution is turned into polymer.

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 in a one-dimensional reading optical system such as a hard copy, and more particularly to a reduced image sensor using an optical waveguide and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the increasing demand for image reading in facsimiles, image scanners, digital copying machines, etc., there has been a demand for higher performance and smaller size of one-dimensional image sensors for converting image information into electric signals. . Conventionally, in a one-dimensional image sensor, a sensor is longer than a document width and a reduction type sensor for reading an image formation screen using a reduction optical system and a one-to-one optical system for reading an image formation screen of the same size. There are contact sensors.

The reduction type image sensor is low in price and capable of high-speed reading, but it requires reduction image formation by a lens, so that the element size is large and downsizing is difficult, and adjustment of an optical system is complicated. However, it has the drawback of requiring adjustment for each unit.

On the other hand, the contact type image sensor has the advantage that the distance from the original to the photoelectric conversion element array is small and no adjustment is required, but on the other hand, the size of the photoelectric conversion element array is large and the photoelectric conversion element array is complicated to drive. It is difficult to reduce the cost because various electronic circuits are required.

Therefore, recently, a reduction type image sensor using a plurality of optical waveguides has been proposed. Japanese Patent Application No. 6-943
No. 46 discloses a waveguide-type reduced image sensor that reduces reflected light from the document surface using a waveguide, and a lens formed in the document surface width and a plurality of guides for guiding the light condensed by the lens. A waveguide-type reduced image sensor is disclosed, which comprises an optical waveguide substrate having a waveguide formed therein and a photoelectric conversion element array into which light guided by the plurality of waveguides is incident. This image sensor has the advantages that it is inexpensive, the element can be downsized, and adjustment of the optical system is unnecessary.

Several methods have been proposed as a method of manufacturing a polymer optical waveguide using a polymer material as a core, which is used in such a reduction type image sensor.

[0007] As a first method, a patterned substrate made of a polymer material such as PMMA in which a groove pattern serving as a capillary is formed is manufactured by using an ordinary injection molding machine.
Then, a polymer precursor material, which is a raw material of a polymer for the core of the waveguide, is filled in the groove portion of the pattern substrate manufactured as described above, and a planar substrate made of a polymer such as PMMA is formed in the groove portion of the pattern substrate. It has been proposed to form a core of an optical waveguide made of a polymer material by polymerizing the polymer by irradiating it with ultraviolet rays or the like after closely contacting the core with the core.

As another method, Japanese Patent Application No. 6-2008
In No. 07, a pattern surface of a pattern substrate on which a groove pattern to be a capillary is formed is brought into close contact with a flat substrate to form a capillary by the groove, and then a monomer solution as a raw material of a core of an optical waveguide is subjected to a capillary phenomenon. A method for producing a polymer optical waveguide has been proposed, which comprises filling the capillaries and polymerizing the monomer solution. According to this method, since no gap is formed at the boundary between the pattern substrate and the flat substrate, there is no crosstalk due to leaked light between cores, and a polymer optical waveguide having excellent optical waveguide characteristics can be realized. .

[0009]

A reduction type image sensor using a conventional lens system requires a long optical path length between a document surface and a solid-state image pickup device, and thus it is difficult to reduce the size. Adjustment is required for each stand, and it is more susceptible to vibration.

Further, in the conventional contact type image sensor, since the photoelectric conversion array has the same size as the document width, the S / N ratio of the photoelectric conversion signal is lowered, and high speed operation is possible due to the parasitic capacitance between the wirings. It can be difficult.

The reduced image sensor using the optical waveguide has the advantages that the device can be downsized and the adjustment of the optical system is not required, as compared with the above two image sensors, and the cost is very low and the performance is high. Although miniaturization can be promoted, the optical signal is greatly attenuated at the bent portion of the waveguide, which is essential for reducing the image of the original.

An object of the present invention is to provide a waveguide type reduction image sensor capable of reducing the attenuation of the optical signal at the bent portion.

Further, there are the following problems in the method of manufacturing the optical waveguide.

In the optical waveguide manufactured by the first method described in the prior art, since the pattern substrate is filled with the core material and then bonded to the flat substrate, the space between the flat substrate and the pattern substrate is The polymer material for the core is polymerized in a protruding state, and a thick gap of about 1 to 10 μm is generated. Therefore, when light is incident on the optical waveguide, the light leaks into the gap, diffuses throughout the device, and cannot propagate normally through the core of the optical waveguide. On the contrary,
If the optical waveguide is manufactured by using the second method described in the conventional technique, the core material is sucked up after the pattern substrate and the flat substrate are bonded together, so that there is no gap between the pattern substrate and the flat substrate. There is no light leakage between cores.

It was confirmed by simulation that the loss of the optical signal in the bent portion of the optical waveguide can be reduced by disposing a groove filled with a substance having a lower refractive index than the surrounding substrate outside the bent portion. Is "J.Ya
mauchi et al: 'Beam-Propagation Analysis of Bent St
ep-Index Slab Waveguides', ELECTRONICS LETTERS, 199
0, Vol. 26, No. 12, p822-p824 ”.

An object of the present invention is to apply the result to the above-mentioned second manufacturing method to provide a manufacturing method of an optical waveguide having a structure for reducing the attenuation of an optical signal at a bent portion.

[0017]

According to the present invention, the above-mentioned object is a waveguide-type reduced image sensor for reducing reflected light from a document surface by using a polymer optical waveguide. The waveguide type according to claim 1, further comprising a groove which is adjacent to an outer side of the provided bent portion and is filled with a substance having a refractive index lower than that of the core portion and the cladding portion of the waveguide. Achieved by a reduced image sensor.

According to the invention, the aforesaid object is achieved by a waveguide-type reduced image sensor according to claim 2, characterized in that the groove is filled with gas.

According to the present invention, the above object is achieved by a waveguide type reduced image sensor according to claim 3, wherein the width of the groove is 2 μm or less.

According to the present invention, the aforementioned object is achieved by a waveguide type reduced image sensor according to claim 4, characterized in that the distance between the groove and the core portion of the waveguide is 2 μm or less. To be done.

According to the present invention, the above-mentioned object is to obtain a relative refractive index difference of 1.5 between materials of the core portion and the cladding portion of the waveguide.
%, Which is achieved by the waveguide-type reduced image sensor according to claim 5.

According to the present invention, the above-mentioned object is such that both ends or one end is open and the first groove, which is a capillary having a bent portion, is adjacent to the outside of the bent portion and both ends are sealed. The pattern surface of the patterned substrate having the second groove which is present is brought into close contact with the flat substrate, and the monomer solution, which is a raw material of the core of the optical waveguide, is filled in the first groove by a capillary phenomenon.
The method of manufacturing a waveguide-type reduced image sensor according to claim 6, wherein the monomer solution is polymerized to form an optical waveguide.

In the waveguide-type reduced image sensor according to the first aspect of the present invention, the material is disposed adjacent to the outside of the bent portion of each optical waveguide and has a lower refractive index than the core portion and the cladding portion of the waveguide. By having a groove filled with
It is possible to reduce the loss that occurs when the light passing through the waveguide passes through the bent portion and increase the light transmittance of the waveguide.

In the waveguide type reduced image sensor according to the second aspect, since the groove adjacent to the outside of the bent portion is filled with gas, when filling the groove with a material having a constant refractive index, Manufacturing in a gas environment allows for easy filling.

In the waveguide-type reduced image sensor according to the third aspect, since the width of the groove is 2 μm or less, the optical loss at the bent portion can be effectively reduced even when the waveguide is downsized. It becomes possible to do.

In the waveguide-type reduced image sensor according to the fourth aspect, the interval between the core portion and the groove of the waveguide is 2 μm.
By the following, it is possible to effectively reduce the optical loss at the bent portion even when the waveguide is downsized.

In the waveguide type reduced image sensor according to the fifth aspect, since the difference in relative refractive index between the materials of the core portion and the cladding portion of the waveguide is 1.5% or less, the waveguide and the groove are reduced. It is possible to more effectively reduce the optical loss at the bent portion when the size and other settings are the same.

In the method of manufacturing a waveguide-type reduced image sensor according to a sixth aspect of the present invention, there are provided a flat substrate and a substrate in which a capillary serving as an optical waveguide and a groove adjacent to a bent portion of the waveguide are formed by photolithography or the like. The capillary is filled with the monomer solution only by the capillary phenomenon, and the groove is filled with the gas under the environment of the adhesion process.
This makes it easy to fill the optical waveguide and the groove with materials having different refractive indexes.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a waveguide type reduced image sensor of the present invention will be described below with reference to the drawings.

First, regarding the method of manufacturing a patterned substrate,
This will be described in detail with reference to FIG. First, as shown in FIG. 2A, a photoresist film 202 having a film thickness of 8 μm is formed on the PMM.
It is formed on the A substrate 201, and then, as shown in FIG. 2B, the groove pattern is transferred by using the photolithography technique. That is, when the mask 203 is brought into close contact with the photoresist film 202, the ultraviolet rays 211 are exposed, and the developing process is performed, the groove pattern of the mask 203 is transferred to the photoresist film 202. Then, as shown in FIG. 2C, a groove pattern 202 to be a capillary is formed. In the embodiment of the present invention, the width of this groove is also 8 μm. Next, by RIE etching, as shown in FIG. 2D, ions 212 are irradiated from the surface of the patterned photoresist film 202 to form a groove having a depth of 10 μm in the portion without the resist film. Finally, by dissolving the photoresist film 202 using a resist remover,
As shown in FIG. 2 (e), a patterned PMMA substrate having a groove having a width of 8 μm and a depth of 10 μm and forming a capillary is manufactured.

The groove processed in the embodiment of the present invention has a pattern of a reduction type optical waveguide having two bent portions as shown in FIG. 1 (a). Then, the optical waveguide 10
On the outside of each bent portion of No. 1, a groove 102 for reducing the loss of the optical signal in the bent portion was formed adjacently. FIG.
(B) is the figure which expanded the detail of a bending part and its adjacent groove. The size of each part is such that the width w of the groove 101 that serves as an optical waveguide is
8 μm, distance d between adjacent grooves = 2 μm, width u of adjacent groove 102 = 2 μm, and curvature R of bent portion of groove 101 = 200
μm. PMM for each groove that becomes an optical waveguide
Adjacent grooves 102 that reach both ends of the A substrate, but do not reach both ends of the PMMA, on the other hand, are concentric arc-shaped bent portions outside the bent portions of the grooves 101 that become the respective optical waveguides. It has a structure arranged with.

Second, the step of bringing the pattern substrate manufactured as described above into close contact with the flat substrate will be described with reference to FIG. As shown in FIG. 3A, the pattern substrate 201 and the flat substrate 301 are set inside the clamp jig 310, and the pattern substrate and the flat substrate are brought into close contact with each other by the clamp jig. Then, the pattern substrate 201
The groove portion becomes hollow and the capillary 302 is formed.
Then, as shown in FIG. 3B, among the four side surfaces formed by bringing the pattern substrate and the flat substrate into close contact with each other, the surface having one opening of the capillary 302 serving as a suction port for the monomer is excluded. The side surface is sealed with a low vacuum sealing resin 303 made of epoxy resin or the like. This allows
The other opening of the capillary 302, which is not the monomer suction port, is also sealed. Further, regarding the groove whose both ends do not reach the end of the PMMA substrate, air is sealed in the cavity.

Thirdly, the step of filling the capillary of the pattern substrate and the flat substrate, which are brought into close contact with each other as described above, with the monomer solution as the raw material of the core will be described with reference to FIG. As shown in FIG. 4A, the vacuum chamber 410 is obtained by clamping the pattern substrate 201 and the flat substrate 301 by the clamping jig 310 as described above.
Set it in the holder 401 inside, here the holder 4
01 is configured to be able to move the clamp jig 310 in the vertical direction. In addition, inside the vacuum chamber 410, 5
Container 40 containing a monomer solution of allyl diglycol carbonate (RAV7) containing 10% benzoyl peroxide
2 is arranged so as to be located directly below the clamping jig 310. The benzoyl peroxide contained in the RAV7 monomer solution acts as a polymerizing agent for polymerizing the RAV7 monomer when heated. next,
The inside of the vacuum chamber 410 is evacuated to a degree of vacuum of 10 −4 Torr to degas the gas contained in the monomer solution of RAV7 and remove the gas in the capillary with one end open, and then the holder 401 Jig for clamping 3
Move 10 downward to open the capillary opening
7 Immerse in monomer solution. Then, inside the vacuum chamber 410,
When leaking so as to gradually change from vacuum to atmospheric pressure, the pressure inside the capillary becomes relatively smaller than the pressure around the RAV7 monomer solution, so the RAV7 monomer solution is sucked into the capillary. As described above, when a relatively long capillary is filled with a monomer, the process of filling the capillary with the monomer can be performed by utilizing a pressure change using a vacuum so as to assist the effect of the capillary phenomenon. . Of course, the sealed grooves at both ends are not filled with the monomer solution, but are still filled with gas.

Finally, after filling the capillary with the RAV7 monomer solution and reaching the atmospheric pressure in the vacuum chamber, the clamping jig 310 is removed from the holder 401 and an oven is used at a temperature of 85 ° C. for 6 hours. The RAV7 monomer solution is polymerized by heating. The surface of the polymer optical waveguide manufactured as described above is polished by a standard polishing machine using a suspension containing diamond having a size of 0.5 μm or less to remove the sealing resin. As described above, the polymer optical waveguide according to the present invention can be manufactured.

The light from the laser is made to enter the entrance end of the core of the polymer optical waveguide manufactured as described above, the light emitted from the polymer optical waveguide is measured, and the light passes through the waveguide. I asked for a loss.

As a result, for an optical waveguide having a curvature of 200 μm, a waveguide having no adjacent groove is 55.
Although the light transmission was%, the light transmission of 92% was observed for the sample in which the groove was formed.

FIG. 5 shows the polymer optical waveguide manufactured according to the embodiment of the present invention, in which the width of the groove, which is shown at u in FIG. 1B, is arranged outside the bent portion of the waveguide core portion. It is a graph which shows the light loss reduction effect at the time of standing. The vertical axis of the figure shows the ratio of the intensity of light emitted from the waveguide with the groove to the intensity of light emitted from the waveguide without the groove. That is, if the value on the vertical axis is greater than 1,
There is the effect of the groove placed outside the bent part of the waveguide core,
It can be said that the larger the value, the greater the effect.
The width of the waveguide core portion was 8 μm, and the distance of the groove from the core portion was 2 μm. From FIG. 5, it can be seen that the width u of the groove arranged outside the bent portion of the waveguide core portion is preferably 2 μm or less from the viewpoint of the miniaturization of the waveguide and the effect of reducing the optical loss. However, it is set to 2 μm in the embodiment of the present invention because of difficulty in fine processing.

FIG. 6 shows a polymer optical waveguide manufactured according to an embodiment of the present invention, in which the groove disposed outside the bent portion of the waveguide core portion and the waveguide core shown by d in FIG. It is a graph which shows the light loss reduction effect when changing the distance to a part. The vertical axis of the figure shows the same contents as in FIG. The width of the waveguide core is 8 μm and the width of the groove is 2 μm.
μm. From FIG. 6, it is understood that the distance d between the groove arranged outside the bent portion of the waveguide core portion and the waveguide core portion is preferably 2 μm or less from the viewpoint of miniaturizing the waveguide and reducing the optical loss. . However, it is set to 2 μm in the embodiment of the present invention because of difficulty in fine processing.

FIG. 7 is a graph showing the effect of reducing optical loss when the relative refractive index difference between the material of the waveguide core and the material of the cladding is changed in the polymer optical waveguide manufactured as described above. . The vertical axis of the figure shows the same contents as in FIG. From Fig. 7, the relative refractive index difference between the core and the clad is 1.5%.
It can be seen that it is appropriate to select each material so as to be less than the above, from the viewpoint of the optical loss reduction effect. In the embodiment of the present invention, a material having a relative refractive index difference of 0.86% is used.

The gas filling the groove adjacent to the bent portion of the optical waveguide is air in the embodiment. However, by performing the step of bonding the pattern substrate and the flat substrate in a gas environment other than air, it is possible to fill the groove adjacent to the bent portion with other various gases, and the invention is not limited to air.

The materials of the clad portion and the core portion are not limited to those in the above embodiment, and various materials can be used in combination with a relative refractive index difference of less than 1.5%.

[0042]

According to the waveguide type reduction image sensor of the first aspect, it is possible to reduce the loss generated when light passes through the bent portion and increase the light transmittance of the waveguide. .

According to the waveguide type reduced image sensor of the second aspect, the groove can be easily filled by manufacturing in a gas environment.

According to the waveguide type reduction image sensor of the third aspect, it is possible to effectively reduce the optical loss at the bent portion even when the waveguide is downsized.

According to the waveguide type reduction image sensor of the fourth aspect, it is possible to effectively reduce the optical loss at the bent portion even when the waveguide is downsized.

According to the waveguide type reduction image sensor of the fifth aspect, it is possible to more effectively reduce the optical loss at the bent portion when the settings of the size of the waveguide and the groove are the same. Becomes

According to the method of manufacturing the waveguide type reduced image sensor of the sixth aspect, the optical waveguide and the groove can be easily filled with materials having different refractive indexes.
Further, by using this method, the optical waveguide having the structure of the present invention can be manufactured very easily.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a waveguide type reduced image sensor of the present invention.

FIG. 2 is a diagram showing a first step of manufacturing the waveguide of FIG.

FIG. 3 is a diagram showing a second step of manufacturing the waveguide of FIG.

FIG. 4 is a diagram showing a third step of manufacturing the waveguide of FIG.

FIG. 5 is a graph showing the optical loss reduction effect with respect to the width of the groove arranged outside the bent portion of the waveguide.

FIG. 6 is a graph showing the optical loss reduction effect with respect to the distance between the groove arranged outside the bent portion of the waveguide core portion and the waveguide core portion.

FIG. 7 is a graph showing an optical loss reduction effect with respect to a relative refractive index difference between materials of a waveguide core portion and a cladding portion.

[Explanation of symbols]

 101 Optical Waveguide 102 Optical Loss Reduction Side Gutter 201 Optical Waveguide Pattern Substrate 202 Resist Film 301 Flat Substrate

Claims (6)

[Claims] 1. A waveguide type reduced image sensor for reducing reflected light from a document surface by using a polymer optical waveguide,
A waveguide type reduced image characterized in that a groove filled with a substance having a refractive index lower than that of a core portion and a cladding portion of the waveguide is provided adjacent to an outer side of a bent portion provided in the waveguide. Sensor. 2. The waveguide type reduced image sensor according to claim 1, wherein the groove is filled with gas. 3. The waveguide type reduced image sensor according to claim 1, wherein the width of the groove is 2 μm or less. 4. The waveguide-type reduced image sensor according to claim 1, wherein an interval between the groove and the core portion of the waveguide is 2 μm or less. 5. The waveguide according to claim 1, wherein the relative refractive index difference between the materials of the core portion and the cladding portion of the waveguide is less than 1.5%. Mold reduction image sensor. 6. A pattern comprising a first groove, which is a capillary having a bent portion and is open at both ends or one end, and a second groove which is adjacent to the outside of the bent portion and whose both ends are sealed. The patterned surface of the substrate is brought into close contact with the flat substrate, and the monomer solution, which is a raw material of the core of the optical waveguide, is filled in the first groove by a capillary phenomenon, and the optical solution is formed by polymerizing the monomer solution. A method of manufacturing a characteristic waveguide-type reduced image sensor.