JP2001141947A - Optical waveguide array coupling body having micro lens array and image reader using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide array coupling body having a micro lens array and an image reader using it which are hardly badly influenced by the deviation between the optical axis of a micro lens and the optical axis of an optical waveguide core. SOLUTION: The optical waveguide array coupling body 4 is composed by incorporating an optical waveguide array 6 wherein plural optical waveguide cores 5 are aligned and arranged within a clad 3 and the micro lens array 8 wherein plural micro lenses 7 individually corresponding to incident ends 5a of respective waveguide cores 5 are aligned and arranged. Reflected light from the surface of a manuscript 1a is condensed by the micro lenses 7 and is wave guided by the optical waveguide cores 5. In the image reader using the optical waveguide array coupling body 4, a light receiving array is provided in the output part of the optical waveguide array 6. The numerical aperture NA1 of each optical waveguide is selected smaller than the numerical aperture NA2 of each micro lens 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microlens array for condensing light reflected from a surface to be read, such as a document, and incident on an incident end of an optical waveguide core. The present invention relates to an optical waveguide array combination for transmitting light to an emission end of a waveguide core, and an image reading apparatus using the optical waveguide array combination for converting light from the optical waveguide array into an electric signal.

[0002]

2. Description of the Related Art An optical waveguide array assembly having a microlens array is used in an image reading apparatus, and this image reading apparatus is mainly provided in a facsimile, an image scanner, and the like.

A combined optical waveguide array includes a plurality of microlenses corresponding to an input end of an optical waveguide array in which a plurality of optical waveguide cores are arranged and arranged in a cladding. Are provided. As the material of each optical waveguide core, a material having a higher refractive index of light than the material of the cladding is selected.
For this reason, the light incident on the input end of the optical waveguide core is totally reflected one after another at the interface between the optical waveguide core and the clad and is guided to the output end if the incident angle is within the maximum light receiving angle of the optical waveguide core. Waved. The maximum light receiving angle of each optical waveguide core can be determined from the numerical aperture NA1 of the optical waveguide determined by the refractive index of light in the optical waveguide core and the refractive index of light in the clad.

[0004] The microlens array and the optical waveguide array are arranged so that light condensed by each microlens can be incident on the incident end of each optical waveguide core. For this reason, the reflected light from the reading symmetry plane such as the original is
The light is condensed by each microlens of the microlens array, guided by each optical waveguide core, and transmitted to the emission end.

In an image reading apparatus using an optical waveguide array combination, light emitted from the emission end of each optical waveguide core is
A light receiving element array is provided at an output portion of the optical waveguide array so that each light receiving element can receive light. The light receiving element array
A plurality of light receiving elements are arranged and convert light received from the combined optical waveguide array into an electric signal.

The image reading device scans the original document line by line, and in synchronism therewith, the original document is moved relative to the image reading device in a sub-scanning direction perpendicular to the direction in which the microlenses are arranged. The document is moved and the entire document surface is scanned.

[0007]

FIGS. 5 and 6 show an optical waveguide array combination 2 having a prior art microlens array 28 disclosed in Japanese Patent Application Laid-Open No. 9-37038.
4 is an enlarged cross-sectional view showing a part of the input side of FIG. FIG.
6 shows a cross section of the combined optical waveguide array 24 viewed from the front side in the sub-scanning direction, and FIG. 6 shows a cross section viewed from one side in the main scanning direction.

The combined optical waveguide array 24 includes a numerical aperture NA1 of each optical waveguide and a numerical aperture NA2 of each microlens 27.
And are chosen equally. In the conventional technique, the optical waveguide array combined body 24 is formed by injection molding. In the injection molding, each microlens 27 and each optical waveguide core 2
5 is determined by the shape of the mold for injection molding, and it is not necessary to perform alignment between each microlens 27 and each optical waveguide core 25 after injection molding, which is suitable for mass production and low cost. Thus, the combined optical waveguide array 24 can be manufactured.

However, the combined optical waveguide array 24 formed by injection molding causes a difference in thermal expansion during molding due to the difference in the material of the mold of the microlens array 28 and the mold of the optical waveguide array 26, and the microexpansion occurs. Lens 2
The optical axis 27a of the optical waveguide 7 and the optical axis 25a of the optical waveguide core 25 are shifted. Further, it is difficult to perform positioning of each mold with high accuracy. Therefore, the optical waveguide array combined body 24
As a whole, the optical axis 27 of the micro lens 27 is
a coincides with the optical axis 25a of the optical waveguide core 25, and the optical axis 27a of the microlens 27 and the optical axis 25a of the optical waveguide core 25 are shifted from each other at another place.

Two two-dot chain lines 32 shown in FIGS.
The region between them indicates the light receiving range of light that can be guided by the optical waveguide core 25. Light incident on the optical waveguide core 25 from outside the region between the two two-dot chain lines 32 in FIGS. 5 and 6 is such that the incident angle on the optical waveguide core 25 is the maximum light reception of the optical waveguide core 25. Since it is larger than the angle, it is not guided by the optical waveguide core 25. The light receiving range is determined by the numerical aperture NA1 of the optical waveguide.

In the combined optical waveguide array 24, the numerical aperture NA1 of each optical waveguide and the numerical aperture NA of each microlens 27
Since the optical axis 27a of the microlens 27 and the optical axis 25a of the optical waveguide core 25 coincide with each other, the light receiving range of light that can be guided by the optical waveguide core 25 and the corresponding microlens 27 to the optical waveguide core 25
And the incident range of the light incident on the light source. Therefore, at a position where the optical axis 27a of the microlens 27 coincides with the optical axis 25a of the optical waveguide core 25, light incident on the optical waveguide core 25 from outside the corresponding microlens 27 is out of the light receiving range. Because there is, it is not guided.

However, at a position where the optical axis 27a of the microlens 27 is shifted from the optical axis 25a of the optical waveguide core 25, the light receiving range is shifted with respect to the corresponding microlens 27. Light incident from outside the corresponding microlens 27 is partially included in the light receiving range of the light that can be guided. That is, in the combined optical waveguide array 24, the numerical aperture NA1 of each optical waveguide is
And the numerical aperture NA2 of the microlens are equal and the optical axis 25
Since the light receiving range and the incident range coincide with each other at a position where a and 27a coincide with each other, the optical axes 25a and 27a
Is slightly deviated, the light receiving range and the incident range deviate from each other, and a part of light incident on the optical waveguide core 25 from the outside of the corresponding microlens 27 is reduced.
5 guided.

As shown in FIG. 5, where the optical axis 27a of the microlens 27 and the optical axis 25a of the optical waveguide core 25 are displaced in the main scanning direction, two dashed lines 32 indicating the light receiving range are shown. Micro lens 27 included in the region between
Are incident on the optical waveguide core 25 from a part of the plane where the is not disposed and a part of the microlens 27 adjacent to the corresponding microlens 27.
Guided by In addition, as shown in FIG. 6, at a position shifted in the sub-scanning direction, two two
Light incident on the optical waveguide core 25 from a part of the plane where the microlenses 27 are not disposed, which is included in the region between the chain lines 32, is guided by the optical waveguide core 25.

Further, at a position where the optical axes 25a and 27a are shifted, a part of the light condensed by the corresponding microlens 27 is out of the light receiving range and is not guided by the optical waveguide core 25. Therefore, the optical axis 25
The amount of guided light at a position where a and 27a do not match is smaller than the amount of guided light at a position where the positions a and 27a match. Here, the amount of guided light is the amount of light guided to the emission end by each optical waveguide core 25. That is, the combined optical waveguide array 24
Since the optical axes 27a and 25a are partially displaced, the amount of guided light is not uniform in the main scanning direction.

As described above, the optical waveguide array combination 24 whose numerical apertures NA1 and NA2 are equally selected is the optical axis 25
Since a and 27a are partially displaced, a problem that light from outside the corresponding microlens 27 is guided and that the amount of guided light is not uniform in the main scanning direction is likely to occur.

In the conventional optical waveguide array combination disclosed in Japanese Patent Application Laid-Open No. 7-301730, a microlens array is formed by ion etching separately from the optical waveguide array, and is bonded to the optical waveguide array while being positioned. Formed. In this conventional optical waveguide array combination, it takes time to align the microlens array and the optical waveguide array and to form the microlens array, and the optical axis of the microlens does not deviate from the optical axis of the optical waveguide core. Is difficult to form.

An object of the present invention is to provide a combined optical waveguide array having a microlens array and an image reading apparatus using the same, which have less adverse effects due to a shift between the optical axis of the microlens and the optical axis of the optical waveguide core. To provide.

[0018]

SUMMARY OF THE INVENTION The present invention is directed to an optical waveguide array having a plurality of optical waveguide cores aligned in a cladding, and a plurality of optical waveguide cores each corresponding to an incident end of each optical waveguide core. The numerical aperture NA1 of each optical waveguide of the optical waveguide array is the numerical aperture NA2 of each microlens of the microlens array.
An optical waveguide array combination is characterized in that it is selected to be smaller than the above.

According to the present invention, the numerical aperture NA of each optical waveguide is
1 is selected to be smaller than the numerical aperture NA2 of each microlens.

When the optical waveguide array combined body is formed by, for example, injection molding, a difference in thermal expansion occurs during molding due to a difference in material between the mold of the microlens array and the mold of the optical waveguide array, and the light of the microlens is generated. A shift occurs between the axis and the optical axis of the optical waveguide core. In the entire optical waveguide array combined body, the optical axis of the microlens coincides with the optical axis of the optical waveguide core at a certain location, and the optical axis of the microlens deviates from the optical axis of the optical waveguide core at another location.

In the combined optical waveguide array according to the present invention,
Since the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens, the incident range of light incident on the optical waveguide core from the corresponding microlens is smaller than the incident range.
The light receiving range of light that can be guided by the optical waveguide core is smaller. Therefore, at a position where the optical axis of the microlens and the optical axis of the optical waveguide core coincide with each other, the light receiving range is included in the incident range, and even at a position where the optical axis is shifted,
If the shift is small, the light receiving range is included in the incident range, so that light incident on the optical waveguide core from outside the corresponding microlens is outside the light receiving range and is not guided.

Also, in the optical waveguide array combination in which the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens, the optical output is higher than when the numerical aperture NA1 is selected to be equal to the numerical aperture NA2. The amount of guided light is small at the position where the axes coincide. Here, the amount of guided light means the amount of light guided to the emission end by the optical waveguide core. However, when considering the entire optical waveguide array combined body, there is almost no difference in the amount of guided light between the optical waveguide core at the position where the optical axes coincide with each other and the optical waveguide core at the position where the optical axes do not coincide. Are uniform in the main scanning direction.

As described above, the combined optical waveguide array according to the present invention has less adverse effects due to the deviation between the optical axis of the optical waveguide core and the optical axis of the microlens.

Further, according to the present invention, the numerical aperture NA1 of each optical waveguide is
Is selected in the range of 80% or more and 95% or less of the numerical aperture NA2 of each microlens.

According to the present invention, the numerical aperture NA of each optical waveguide
1 is selected in a range of 80% or more and 95% or less of the numerical aperture NA2 of each microlens.

As the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens, the light receiving range that can be guided by the optical waveguide core becomes narrower. The adverse effects due to deviation from the optical axis are reduced. Numerical aperture NA1 of each optical waveguide
However, the combined optical waveguide array, which is selected to be 95% or less of the numerical aperture NA2 of each microlens, is capable of receiving light that can be guided by the optical waveguide core within an incident range of light incident on the optical waveguide core from the corresponding microlens. Because the range is included,
There is little adverse effect due to deviation between the optical axis of the optical waveguide core and the optical axis of the microlens.

In a combined optical waveguide array in which the numerical aperture NA1 of each optical waveguide is selected to be 80% of the numerical aperture NA2 of each microlens, the optical axis of the microlens coincides with the optical axis of the optical waveguide core. The guided light quantity of light incident on the optical waveguide core from the corresponding microlens at the corresponding location is about 20% smaller than when the numerical aperture NA1 of the optical waveguide is equal to the numerical aperture NA2 of the microlens. However, if the amount of guided light is reduced by about 20% or less, there is no adverse effect on the actual image quality.

Therefore, the numerical aperture N of each microlens
An optical waveguide array combination in which A2 is selected in a range of 80% or more and 95% or less of the numerical aperture NA1 of each optical waveguide is as follows:
The adverse effect due to the deviation of the optical axis is small, and a sufficient amount of guided light can be obtained.

Further, according to the present invention, a plurality of microlenses are aligned at an input portion of an optical waveguide array in which a plurality of optical waveguide cores are arranged and arranged in a cladding, individually corresponding to an incident end of each optical waveguide core. And a plurality of light receiving elements respectively corresponding to the output ends of the respective optical waveguide cores at the output portion of the optical waveguide array of the optical waveguide array combination. And a light-receiving element array arranged in a line, wherein the numerical aperture NA1 of each optical waveguide of the optical waveguide array is smaller than the numerical aperture NA2 of each microlens of the microlens array. An image reading apparatus characterized by being selected.

According to the present invention, the image reading apparatus is configured such that the light receiving element array is provided at the output section of the optical waveguide array. The light receiving element array is configured to include a plurality of light receiving elements that are aligned and arranged corresponding to the emission end of each optical waveguide core.

Therefore, the image reading apparatus condenses the reflected light from the reading symmetry plane to the incident end of the optical waveguide core by the microlens array and makes the incident light incident. The incident light is guided by the optical waveguide array and received. The light is emitted to each light receiving element of the element array, and the emitted light is converted into an electric signal by the light receiving element array.

In the image reading apparatus according to the present invention, since the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens, a shift between the optical axis of each optical waveguide core and the optical axis of each microlens. Less adverse effect. Therefore, unnecessary light other than the light incident on the corresponding microlens does not enter each light receiving element, and the light receiving amount of each light receiving element of the light receiving element array is equal in the main scanning direction. Therefore, the image reading device can obtain high-quality image data.

Further, according to the present invention, the numerical aperture NA1 of each optical waveguide of the optical waveguide array is equal to the numerical aperture N of each microlens.
A2 is selected in a range of 80% or more and 95% or less of A2.

According to the present invention, in the image reading apparatus, the numerical aperture NA1 of each optical waveguide is equal to the numerical aperture NA2 of each microlens.
Is selected within the range of 80% or more and 95% or less, so that there is little adverse effect due to deviation between the optical axis of each optical waveguide core and the optical axis of each microlens. Therefore, unnecessary light other than the light incident on the corresponding microlens does not enter each light receiving element, and the light receiving amount of each light receiving element of the light receiving element array is uniform in the main scanning direction. Sufficient light is incident on the light receiving element. Therefore, the image reading apparatus according to the present invention can obtain high-quality image data.

[0035]

FIG. 1 is an enlarged sectional view showing a part of an input side of an optical waveguide array combination 4 having a microlens array 8 according to an embodiment of the present invention. The optical waveguide array combined body 4 corresponds to the input section 6a of the optical waveguide array 6 in which the plurality of optical waveguide cores 5 are arranged in the cladding 3 and individually corresponds to the incident end 5a of each optical waveguide core 5. A microlens array 8 in which a plurality of microlenses 7 are arranged is provided.

Each microlens 7 and each optical waveguide core 5 are arranged such that light condensed by each microlens 7 can be incident on the incident end 5a of each optical waveguide core 5. The reflected light from the original surface 1a, which is the reading symmetry plane, is condensed by each micro lens 7 of the micro lens array 8, guided by the optical waveguide array 6, and transmitted to the output unit.

In the combined optical waveguide array 4, the numerical aperture NA1 of the optical waveguide is selected to be smaller than the numerical aperture NA2 of the microlens 7. Numerical aperture NA1 of the optical waveguides and the refractive index n ₂ of the light optical waveguides cores 5, determined by the refractive index n ₁ of the optical cladding 3. The numerical aperture NA2 of each microlens 7 is determined by the focal length f of the object space described later and the diameter D of each microlens 7.

Clad 3 and microlens array 8
Are integrally formed from the same material. The material of each optical waveguide core 5 is the clad 3 and the micro lens array 8.
A material having a higher light refractive index than that of the material is selected. For this reason, the light incident on the incident surface 5a of each optical waveguide core 5 is totally reflected one after another at the interface between the optical waveguide core 5 and the clad 3 if the incident angle is within the maximum light receiving angle δmax, and the light is guided. Is done. The maximum light receiving angle δmax of each optical waveguide core 5 is determined by the numerical aperture NA1 of the optical waveguide.

A region between two two-dot chain lines 12 shown in FIG. 1 indicates a light receiving range of light that can be guided by the optical waveguide core 5. The light incident on the optical waveguide core 5 from outside the region between the two two-dot chain lines 12 is such that the incident angle on the optical waveguide core 5 is the maximum light receiving angle δmax of the optical waveguide core 5.
Therefore, the light is not guided by the optical waveguide core 5.

The combined optical waveguide array 4 is formed, for example, by injection molding. Next, an example of a method of forming the optical waveguide array combination 4 will be described.

First, using a certain polymer material, a substrate including a groove formed at the position where the optical waveguide core 5 is to be disposed and the microlens array 8 is formed by injection molding. Fill the monomer material that is cured by ultraviolet light. As this monomer material, a material whose refractive index of light is larger than that of the polymer material when polymerized is selected. Next, the monomer material is cured by irradiation with ultraviolet rays. Thereafter, an ultraviolet curable resin having the same refractive index as the polymer material used for the substrate is uniformly applied on the optical waveguide core 5, and is cured by irradiating ultraviolet rays. By doing so, the optical waveguide array combined body 4 including the micro lens array 8 and the optical waveguide array 6 is formed.

The method of forming the optical waveguide array combined body 4 is not limited to the above-described forming method, but in the above-mentioned forming method, the arrangement of each microlens 7 and each optical waveguide core 5 is determined by the injection molding die. It is not necessary to perform the alignment between each microlens 7 and each optical waveguide core 5 after injection molding, so that it is suitable for mass production and the optical waveguide array combined body 4 can be manufactured at low cost.

However, the optical axis 7 of the micro lens 7
a is shifted from the optical axis 5c of the optical waveguide core 5 due to the difference in the thermal expansion coefficient between the mold of the microlens array 8 and the mold of the optical waveguide array 6 during injection molding. For this reason, in the whole optical waveguide array combined body 4, the optical axis 7a of the micro lens 7 and the optical axis 5c of the
And the optical axis 7a of the micro lens 7
And the optical axis 5c of the optical waveguide core 5 is shifted.

In the optical waveguide array coupler 4, since the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens 7, the incidence of light incident on the optical waveguide core 5 from the corresponding microlens 7 is made. The light receiving range of light that can be guided by the optical waveguide core 5 is smaller than the range. Therefore, at a position where the optical axis 7a of the microlens 7 and the optical axis 5c of the optical waveguide core 5 coincide with each other, the light receiving range is included in the incident range, so that the optical axes 5c and 7a
Even at a position where is shifted, if the shift is small, the light receiving range is included in the incident range, and light incident on the optical waveguide core 5 from outside the corresponding microlens 7 is outside the light receiving range, Not guided.

In the optical waveguide array combination 4 in which the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens 7, the numerical aperture NA1 is equal to the numerical aperture NA.
As compared with the case where the optical axis 5c is selected to be equal to 2, the guided light quantity at the position where the optical axes 5c and 7a coincide is smaller. Here, the amount of guided light means the amount of light guided to the emission end by the optical waveguide core 5. However, considering the entire optical waveguide array combined body 4, there is almost no difference in the amount of guided light between the optical waveguide core 5 where the optical axes 5c and 7a coincide with each other and the optical waveguide core 5 where the optical axes 5c and 7a do not coincide. In addition, the amount of guided light of each optical waveguide core 5 is uniform in the main scanning direction.

As described above, the combined optical waveguide array 4 is
The optical axis 5c of the optical waveguide core 5 and the optical axis 7 of the microlens 7
There is little adverse effect due to deviation from a. Therefore, the combined optical waveguide array 4 can be easily formed by the injection molding described above. In addition, if the optical waveguide array combined body 4 is formed by a forming method that requires alignment between the microlens array 8 and the optical waveguide array 6, it is not necessary to perform the alignment with high accuracy.

As the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens 7,
Since the light receiving range that can be guided by the optical waveguide core 5 is narrowed, adverse effects due to the deviation between the optical axis 5c of the optical waveguide core 5 and the optical axis 7a of the microlens 7 are reduced. The numerical aperture NA1 of each optical waveguide is equal to the numerical aperture NA2 of each microlens 7.
In the optical waveguide array combined body 4 selected to be 95% or less of the following, the light receiving range that can be guided by the optical waveguide core 5 is included in the incident range of the light that enters the optical waveguide core 5 from the corresponding microlens 7. In addition, there is little adverse effect due to the deviation between the optical axis 5c of the optical waveguide core 5 and the optical axis 7a of the microlens 7.

Also, for example, the numerical aperture NA1 of each optical waveguide
However, the combined optical waveguide array 4 selected to be 80% of the numerical aperture NA2 of each microlens 7 corresponds to a position where the optical axis 7a of the microlens 7 coincides with the optical axis 5c of the optical waveguide core 5. The light quantity of light incident on the optical waveguide core 5 from the microlens 7 is smaller than that when the numerical aperture NA1 of the optical waveguide is equal to the numerical aperture NA2 of the microlens.
About 20% less. However, if the amount of guided light is reduced by about 20% or less, there is no adverse effect on the actual image quality.

Therefore, the numerical aperture NA2 of each microlens 7 is selected to be in the range of 80% or more and 95% or less of the numerical aperture NA1 of each optical waveguide.
Has a small adverse effect due to the displacement of the optical axes 5c and 7a, and a sufficient amount of guided light can be obtained. Although FIG. 1 shows a state in which the optical axis 7a of the microlens 7 and the optical axis 5c of the optical waveguide core 5 are shifted in the main scanning direction, the optical waveguide array combination 4 has a shift in the sub-scanning direction. There are few adverse effects due to.

Hereinafter, the optical waveguide array combination 4 will be described more specifically with reference to FIG. The combined optical waveguide array 4 has a width of 250 mm and is used for a G3 type facsimile machine corresponding to a sheet of B4 size or less.
In this facsimile apparatus, the original 1 has a wavelength of 5 for example.
Scanning is performed by illuminating with 70 nm light.

Micro lens array 8 and clad 3
Consists of polymethyl methacrylate called Acrypet VH (manufactured by Mitsubishi Rayon). The refractive index n ₁ of light at a temperature of 20 ° C. when light having a wavelength of 570 nm is incident on this material is 1.492. Optical waveguide core 5
Is composed of a material called RAV7 H1 (manufactured by Mitex), which is obtained by mixing a substance mainly composed of dimethyl carbonate and benzoyl peroxide and then heating and polymerizing the mixture. When light having a wavelength of 570 nm is incident on this material, the refractive index n ₂ of the light at a temperature of 20 ° C. is 1.503.

The numerical aperture NA1 of each optical waveguide determined by the refractive index n ₂ of light of each optical waveguide core 5 and the refractive index n ₁ of light of the cladding 3 can be calculated by the following equation.

[0053]

(Equation 1)

According to the above equation, the numerical aperture NA1 of each optical waveguide is obtained.
Is 0.18. Each optical waveguide core 5 has a width of 8 μm.
And the end face of the incident end 5a is a square of 8 μm × 8 μm. In the input section 6a of the optical waveguide array 6, 2043 optical waveguide cores 5 are arranged at a pitch of 125 μm. In the output section of the optical waveguide array 6, 2043
The output ends of the optical waveguide cores 5 are arranged at a pitch of 14 μm. Next, each micro lens 7 will be described.

FIG. 2 is a cross-sectional view for explaining each microlens 7 of the optical waveguide array combination 4. The microlens array 8 has 2048 microlenses 7,
It is arranged and arranged at a pitch of 125 μm. Each micro lens 7 has a lens diameter D of 120 μm and a radius of curvature r of 150 μm. In addition, since each microlens 7 has a single spherical surface, the following Gaussian formula holds.

[0056]

(Equation 2)

Here, n ₀ is the refractive index of air, s is the distance from each microlens 7 to the object, and s ′
Is the distance from each microlens 7 to the image. The distance from each microlens 7 to the object when s ′ is infinite is called the focal length f of the object space, and the distance from each microlens 7 to the image when s is infinity is It is called the focal length f 'of the image space. Object space focal length f
When the focal length f ′ of the image space is obtained, the focal length f of the object space is 300 μm, and the focal length f ′ of the image space is 455 μm.

The following equation holds between the numerical aperture NA2 of each microlens 7 and the focal length f of the object space. NA2 = D / 2f (3)

Therefore, the numerical aperture NA2 of each micro lens 7 is 0.20. Since the numerical aperture NA1 of each optical waveguide is 0.18 and the numerical aperture NA2 of each microlens 7 is 0.20, the numerical aperture NA1 is selected to be 90% of the numerical aperture NA2.

Each microlens 7 and each optical waveguide core 5 are arranged such that the light condensed by each microlens 7 can enter the incident end 5 a of each optical waveguide core 5. In the optical waveguide array combination 4, the distance from each micro lens 7 to the incident end 5a of each optical waveguide core 5 is selected to be 455 μm, which is equal to the focal length f ′ of the image space.

The optical axis 7a of the microlens 7 and the optical axis 5c of the optical waveguide core 5 are different from each other in the difference in thermal expansion coefficient between the mold of the microlens array 8 and the mold of the optical waveguide array 6 during injection molding. Causes displacement. In the combined optical waveguide array 4, the average value of the distance between the shifted optical axes 7a and 5c is 1
It is slightly less than 0 μm, and the maximum value is about 20 μm.

The combined optical waveguide array 4 has a numerical aperture NA1 of each optical waveguide of 9 which is equal to the numerical aperture NA2 of each microlens 7.
Since 0% is selected, the light receiving range of light that can be guided by the optical waveguide core 5 is narrower than the incident range of light that enters the optical waveguide core 5 from the corresponding microlens 7. Therefore, adverse effects due to the displacement of the optical axes 7a and 5c are small.

This can be explained by combining the optical waveguide array combination 4 with
A description will be given in comparison with a combined optical waveguide array in which the numerical apertures NA1 and NA2 are both set to 0.20.

When the maximum light receiving angle δmax is obtained from the numerical aperture NA1 of each optical waveguide by the following equation: NA1 = n ₁ · sinδ _max (4) Since the numerical aperture NA1 of each optical waveguide is 0.18, the maximum light receiving angle is The angle δmax is 7.0 °. 0.2 numerical aperture NA1
If 0, the maximum light receiving angle δmax 'is 7.7 °.

When the optical axis 7a of the microlens 7 is deviated from the optical axis 5c of the optical waveguide core 5, the light incident on the optical waveguide core 5 from the outside of the corresponding microlens 7 has an incident angle to the optical waveguide core 5. Some things get smaller. In the conventional optical waveguide array combination in which the numerical aperture NA1 is selected to be equal to the numerical aperture NA2, a part of the light incident on the optical waveguide core from outside the corresponding microlens is transmitted at an incident angle within the maximum light receiving angle δmax '. The light enters the waveguide core and is guided by the optical waveguide core together with the light transmitted through the corresponding microlens. However, since the maximum light receiving angle δmax of the optical waveguide array combination 4 is smaller than that of the optical waveguide array combination having a numerical aperture NA1 of 0.20, light incident on the optical waveguide core 5 from outside the corresponding microlens 7. Is hardly guided.

Next, the combined optical waveguide array 4 will be described in comparison with a combined optical waveguide array whose numerical apertures NA1 and NA2 are both set to 0.18. The combined optical waveguide array 4 having an NA2 of 0.20 has a shorter focal length f ′ of the microlens 7 than the combined optical waveguide array having a numerical aperture NA2 of 0.18. Is short to the incident end 5a. Therefore, in the optical waveguide array coupler 4, light incident on the optical waveguide core 5 from outside the corresponding microlens 7 is transmitted to the optical waveguide core 5 as compared with the optical waveguide array coupler having a numerical aperture NA2 of 0.18. Is large, so that it is difficult to be guided.

As described above, the numerical aperture NA1 is equal to the numerical aperture NA2.
Therefore, in the optical waveguide array combination 4, light incident on the optical waveguide core 5 from outside the corresponding microlens 7 is hardly guided, and the optical axes 5c and 7a are set to 10 μm.
m, the light quantity of light incident on the optical waveguide core 5 from outside the corresponding microlens 7 is equal to the numerical aperture NA.
The reduction is about 70% as compared with the optical waveguide array combination having the same NA1 and NA2.

Also, since the numerical aperture NA1 of each optical waveguide is selected to be 90% of the numerical aperture NA2 of each microlens 7, it coincides with the optical waveguide core 5 where the optical axes 5c and 7a coincide. The difference in the amount of guided light from the optical waveguide core 5 at a position where there is no light is small, and the amount of guided light is uniform in the main scanning direction.

Also, since the numerical aperture NA1 of each optical waveguide is selected to be 90% of the numerical aperture NA2 of each microlens 7, the light guide from the corresponding microlens 7 where the optical axes 7a and 5c coincide. The amount of guided light of light incident on the waveguide core 5 is reduced by about 10% as compared with a combined optical waveguide array having the same numerical aperture NA1 and NA2. However, such a decrease of about 10% does not adversely affect the actual image quality.

As described above, in the optical waveguide array combined body 4 in which the numerical aperture NA2 of each microlens 7 is selected to be 90% of the numerical aperture NA1 of each optical waveguide, the adverse effect due to the displacement of the optical axes 5c and 7a is small. In addition, a sufficient amount of guided light can be obtained.

FIG. 3 is a front view schematically showing an image reading apparatus 11 in which the light receiving element array 2 is provided on the optical waveguide array combination 4. The image reading device 11 is configured such that the light receiving element array 2 is provided on the output section 6b of the optical waveguide array 6. The light receiving element array 2 is configured to include a plurality of light receiving elements 9 arranged in alignment with the emission end 5b of each optical waveguide core 5.

In the image reading device 11, the light reflected from the original surface 1 a is transmitted to the micro lens 7 of the micro lens array 8.
, And is guided by the optical waveguide array 6, transmitted to each of the light receiving elements 9 of the light receiving element array 2, and converted by the light receiving element array 2 into light signals guided by the optical waveguide array 6.

As a specific example, in the image reading apparatus 11, when the output ends 6b of the 2048 optical waveguide cores 5 are arranged at the output section 6b of the optical waveguide array 6 at a pitch of 14 μm, 2048 light receiving elements The light receiving element array 2 in which the light receiving elements 9 are arranged at a pitch of 14 μm is provided.

In the image reading apparatus 11, since the numerical aperture NA1 is selected to be smaller than the numerical aperture NA2, there is little adverse effect due to the deviation between the optical axis 5c of each optical waveguide core 5 and the optical axis 7a of each microlens 7. For this reason, unnecessary light other than the light incident on the corresponding microlens 7 does not enter each light receiving element 9 and the light receiving amount of each light receiving element 9 of the light receiving element array 2 is uniform in the main scanning direction. In addition, each light receiving element 9 can obtain a sufficient amount of received light. Therefore, the image reading device 11 can obtain high-quality image data.

FIG. 4 is a perspective view showing an image reading apparatus 11 using the optical waveguide array combination 4. Image reading device 1
1, a light source 10 for illuminating the original 1 is provided. The image reading device 11 performs main scanning of the document 1 line by line. In synchronization with this, the document 1 is moved relative to the image reading device 11 in a sub-scanning direction perpendicular to the direction in which the microlenses 7 are arranged. And the entire original surface 1a is scanned. The image reading device 11 using the combined optical waveguide array 4 can obtain high-quality image data by being provided in a facsimile, an image scanner, or the like.

[0076]

As described above, according to the present invention, in the optical waveguide array combination in which the numerical aperture NA1 of each optical waveguide is selected to be smaller than the numerical aperture NA2 of each microlens, the optical axis of the microlens and the optical waveguide core Even when the optical axis is shifted from the optical axis, light incident on the optical waveguide core from outside the corresponding microlens is hardly guided. Further, the optical waveguide array combined body, the optical waveguide core of the location where the optical axis coincides,
The difference in the amount of guided light from the optical waveguide core at the position where they do not match is small, and the amount of guided light is uniform in the main scanning direction.

Therefore, the combined optical waveguide array according to the present invention has less adverse effects due to the deviation between the optical axis of the optical waveguide core and the optical axis of the microlens. Therefore, the combined optical waveguide array can be easily formed by, for example, injection molding. Further, if the optical waveguide array combined body is formed by a forming method that requires alignment between the microlens array and the optical waveguide array, it is not necessary to perform the alignment with high accuracy.

Further, according to the present invention, the numerical aperture NA1 of each optical waveguide is selected in a range of 80% or more and 95% or less of the numerical aperture NA2 of each microlens. There is little adverse effect due to misalignment of the axis, and a sufficient amount of guided light can be obtained.

Further, according to the present invention, in the image reading apparatus, the numerical aperture NA1 of each optical waveguide is equal to the numerical aperture N of each microlens.
Since it is selected to be smaller than A2, there is little adverse effect due to the deviation between the optical axis of each optical waveguide core and the optical axis of each microlens. Therefore, unnecessary light other than the light incident on the corresponding microlens does not enter each light receiving element, and the light receiving amount of each light receiving element of the light receiving element array is equal in the main scanning direction. Therefore, the image reading device includes:
High-quality image data can be obtained and can be suitably implemented as an image reading device such as a facsimile and an image sensor.

According to the present invention, in the image reading apparatus, the numerical aperture NA1 of each optical waveguide is equal to the numerical aperture N of each microlens.
Since it is selected to be in the range of 80% or more and 95% or less of A2, there is little adverse effect due to the deviation between the optical axis of each optical waveguide core and the optical axis of each microlens, and the amount of guided light is sufficient. Therefore, unnecessary light other than light incident on the corresponding microlens does not enter each light receiving element, and the light receiving amount of each light receiving element of the light receiving element array is uniform in the main scanning direction. Sufficient light is incident on each light receiving element of the element array. Therefore, the image reading apparatus according to the present invention can obtain high-quality image data and can be suitably implemented as an image reading apparatus such as a facsimile and an image sensor.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a part of an input side of an optical waveguide array combined body 4 including a microlens array 8 according to an embodiment of the present invention.

FIG. 2 shows each micro lens 7 of the combined optical waveguide array 4;
FIG. 6 is a cross-sectional view for explaining the method.

FIG. 3 is a front view schematically showing an image reading apparatus 11 in which a light receiving element array 2 is provided in an optical waveguide array combination 4;

FIG. 4 is a perspective view showing an image reading apparatus 11 using the optical waveguide array combination 4.

FIG. 5 is an enlarged sectional view showing a part of an input side of an optical waveguide array combined body 24 including a microlens array 28 according to the prior art disclosed in Japanese Patent Application Laid-Open No. 9-37038.

FIG. 6 is a cross-sectional view showing, on an enlarged scale, a part of the input side of an optical waveguide array combination 24 including a microlens array 28 according to the prior art disclosed in Japanese Patent Laid-Open No. 9-37038.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 original 1a original surface 2 light receiving element array 3 clad 4 optical waveguide array combined body 5 optical waveguide core 5a incident end 5b emission end 6 optical waveguide array 6a input section 6b output section 7 microlens 8 microlens array 9 light receiving element 10 light source 11 Image reading device

Claims (4)

[Claims] A plurality of microlenses are arranged at an input portion of an optical waveguide array in which a plurality of optical waveguide cores are arranged and arranged in a cladding, individually corresponding to an incident end of each optical waveguide core. In a combined optical waveguide array provided with a microlens array to be provided, the numerical aperture NA1 of each optical waveguide of the optical waveguide array is selected to be smaller than the numerical aperture NA2 of each microlens of the microlens array. Waveguide array combination. 2. The combined optical waveguide array according to claim 1, wherein the numerical aperture NA1 of each optical waveguide is selected in a range of 80% or more and 95% or less of the numerical aperture NA2 of each microlens. . 3. A plurality of microlenses are arranged at an input portion of an optical waveguide array in which a plurality of optical waveguide cores are arranged and arranged in a cladding, individually corresponding to an incident end of each optical waveguide core. An optical waveguide array assembly provided with a microlens array to be provided, and a plurality of light receiving elements are arranged at an output portion of the optical waveguide array of the optical waveguide array assembly, corresponding to the emission ends of the respective optical waveguide cores. And a light-receiving element array arranged in a vertical direction, wherein the numerical aperture NA1 of each optical waveguide of the optical waveguide array is equal to the numerical aperture NA2 of each microlens of the microlens array.
An image reading apparatus, which is selected to be smaller than the above. 4. The numerical aperture NA1 of each optical waveguide of the optical waveguide array is 80% of the numerical aperture NA2 of each microlens.
4. The image reading apparatus according to claim 3, wherein said image reading apparatus is selected within a range not less than 95%.