JPH1050968A - Optical waveguide type demagnetification image sensor and fabrication of optical waveguide array therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small optical waveguide type demagnetification image sensor in which reading can be performed with high sensitivity and high S/N while simplifying the manufacturing process. SOLUTION: The optical waveguide type demagnetification image sensor comprises an optical waveguide array 2 to be introduced with an input light from an object, and a photoelectric conversion element array 3 for converting the output light from the optical waveguide array 2 into an electric signal. The optical waveguide 1 of the optical waveguide array 2 has an input end tapered to enlarge in the main and sub-scanning directions so that the input light from the object enters directly into the incident end part of the optical waveguide 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical waveguide reduced optical image sensor used in a one-dimensional readout optical system for hard copy images and a method of manufacturing an optical waveguide array used therefor.

[0002]

2. Description of the Related Art As conventional image sensors of this type, a contact type image sensor and a reduction optical image sensor using a single lens system and a mirror (lens reduction optical image sensor) are known. The former contact-type image sensor has the advantage of being small in size, but on the other hand, the photoelectric conversion element, which is a component thereof, and the self-fox lens for guiding the reflected light from the document to the photoelectric conversion element are expensive, and the depth of focus is high. However, it has the disadvantage that it is shallow. On the other hand, the latter lens-reduced optical image sensor has the advantages that the depth of focus is deep, the light-receiving element is small and inexpensive, and the overall apparatus is inexpensive. However, there is a limit to miniaturization of the device. This lens-reduced optical image sensor is
It also has the disadvantage of lacking mechanical stability and reliability.

[0003] In order to solve these drawbacks,
2. Related Art A reduction optical image sensor (optical waveguide reduction optical image sensor) including a reduction optical system using an optical waveguide has been proposed. The schematic structure is shown in the plan view of FIG.
In this optical waveguide reduced optical image sensor, reflected light from a document is introduced into an optical waveguide 11 of an optical waveguide array 12 via a microlens array 10, and output light from the CCD 13 is a photoelectric conversion element. Is irradiated on the element and converted into an electric signal.

[0004] Here, the optical waveguide 1 of the optical waveguide array 12 is used.
The interval of 1 is set in accordance with the resolution of the image sensor. If an image sensor having a resolution of 200 dpi is configured, the optical waveguide array 12 used for the image sensor has a resolution of 200 dpi.
Are 125 μm intervals. Assuming that a general-purpose linear CCD having a device interval of about 14 μm is used as the CCD 13 as the photoelectric conversion element array,
Since the interval between the optical waveguides of the output section is made equal to the element interval (14 μm), as shown in FIG. 11, the optical waveguide 11 is provided with two bent portions and bent twice so that the input of the optical waveguide array The distance is set to about 1/9 of the distance between the optical waveguides at the ends (125 μm).

[0005]

However, the above-mentioned conventional contact type image sensor, although small in size, is expensive and has a short focal depth. In addition, the above-mentioned conventional lens-reduced optical image sensor has a disadvantage that, although inexpensive, it is relatively large in size and is vulnerable to mechanical shock.

Accordingly, as described above, an optical waveguide reduced optical image sensor has been proposed as an image sensor that solves these drawbacks. In this conventional optical waveguide reduced optical image sensor, if an inexpensive and highly sensitive linear CCD is used as the photoelectric conversion element array, the interval between the optical waveguides at the output end of the optical waveguide array is set to tens of μm as described above. The wave path width needs to be 10 μm or less. The interval between the optical waveguides on the input side of the optical waveguide array must correspond to the resolution of the original document. In the case of a general-purpose FAX, the resolution is 200 dpi, so that the interval between the optical waveguides is 125 μm. Under these conditions, as an optical waveguide array connecting the input and the output, a structure in which the optical waveguide is bent twice at about 90 ° on the way has been proposed as described above to reduce the size of the device.

However, in such a structure in which the optical waveguide is bent twice in the middle, light loss occurs due to sharp bending of the optical waveguide. In order to suppress this optical loss, it is necessary to increase the radius of curvature of the bent portion of the optical waveguide as the NA of the optical waveguide decreases. However, when the radius of curvature is increased in such a manner, the device size increases.

In the conventional optical waveguide reduced optical image sensor, in order to efficiently introduce input light from a document at the input end of the optical waveguide array, as shown in a conceptual diagram of FIG. , It is necessary to form an image of a document on the input end of the optical waveguide. However, the use of a microlens array is expensive in itself, requires high-precision adjustment of the coupling between the microlens array and the optical waveguide array, and furthermore, such as crosstalk due to the coupling portion with the adjacent microlens. It creates problems.

As shown in the conceptual diagram of FIG. 13, when the optical waveguide array and the microlens array are coupled,
For one optical waveguide, adjacent microlenses a,
Since the images formed by b overlap each other, the output light of the optical waveguide array reflects the overlap and lowers the resolution of the image sensor. As a solution to this, it is conceivable to make the NA of the microlens coincide with the NA of the optical waveguide. However, the NA of the microlens needs to be set small in order to cope with the floating of the document (unevenness of the document surface distance) by increasing the depth of focus. Therefore, the NA of the optical waveguide must also be reduced. When the NA of the optical waveguide is reduced, it is necessary to increase the curvature of the bent portion of the optical waveguide, which also becomes a factor for increasing the device size.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and does not require an expensive microlens array, is inexpensive, and can reduce the size of an optical waveguide. It is an object of the present invention to provide a method of manufacturing a type image sensor and an optical waveguide array used therein.

[0011]

According to the present invention, there is provided an optical waveguide array into which input light from a subject is introduced, and a photoelectric conversion device for converting output light from the optical waveguide array into an electric signal. In an optical waveguide reduced optical image sensor comprising an element array, the input end of the optical waveguide of the optical waveguide array is tapered so as to spread in the main scanning direction and the sub-scanning direction, and input light from a subject is directly incident on the optical waveguide. It is configured to be incident on the end.

Further, according to the present invention, an optical waveguide reduced optical image comprising an optical waveguide array into which input light from a subject is introduced, and a photoelectric conversion element array for converting output light from the optical waveguide array into an electric signal. In the sensor, a cylindrical lens is provided at the input end of the optical waveguide array, and the input end of the optical waveguide of the optical waveguide array is configured to have a tapered shape extending in the main scanning direction.

Further, in the present invention, in the optical waveguide reduced optical image sensor described above, the angle of the tapered shape of the input end of the optical waveguide is set to 0.5 ° or more and 2 ° or less.

Further, according to the present invention, in the above-described optical waveguide reduced optical image sensor, a light emitting element for irradiating a subject to obtain input light from the subject is provided. Further, according to the present invention, in a method of manufacturing an optical waveguide array including a tapered optical waveguide having an input end portion that is widened in a main scanning direction and a sub-scanning direction, the amount of laser irradiation energy is controlled to form a tapered groove. To form a master by processing into a plastic substrate, a step of forming a metal by forming a metal on the tapered groove processing surface of the master, and forming a core by injection molding technology using the die Producing an optical waveguide substrate having a groove,
Filling a groove of the optical waveguide substrate with a core material and polymerizing the core material to form a core.

According to the optical waveguide reduced optical image sensor of the present invention, a micro lens array is not used to introduce input light from a subject into the optical waveguide. This eliminates the need for high-precision adjustment that was required to combine the above and the cost can be reduced. It should be noted that, even in the case of using a cylindrical lens, high-precision adjustment is not required as compared with a conventional device using a microlens array, so that the cost can be similarly reduced.

Furthermore, according to the optical waveguide reduced optical image sensor of the present invention, the tapered optical waveguide does not lower the contrast even if the refractive index difference between the core and the clad of the optical waveguide is large. In comparison with the optical waveguide, the width of the optical waveguide can be reduced, the radius of curvature of the bent portion of the optical waveguide can be reduced, and the device size can be reduced.

Further, according to the method for manufacturing an optical waveguide array of the present invention, it is possible to manufacture an optical waveguide array having the above-described tapered optical waveguide.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view of an optical waveguide reduced optical image sensor according to a first embodiment of the present invention, and FIG. 2 is an enlarged perspective view of a main part of the optical waveguide array.

As shown in FIG. 1, the optical waveguide reduced optical image sensor according to the present embodiment has an optical waveguide formed by arraying a tapered waveguide 1 which is an optical waveguide having an input end tapered and having a bent portion. It comprises a waveguide array 2 and a CCD 3 which is a photoelectric conversion element array that receives light from an output end of the optical waveguide array 2 and converts it into an electric signal. As shown in FIG. 2, the tapered waveguide 1 is a three-dimensional tapered waveguide 1 having a three-dimensional tapered shape that spreads in both the main scanning direction and the sub-scanning direction. Array 2 is configured.

The main scanning direction refers to the direction in which the tapered waveguides 1 are linearly arrayed, and the sub-scanning direction refers to the thickness direction of the optical waveguide array 2, that is, the depth direction in FIG. It is.

Next, the principle of propagation of reflected light from a document, which is input light from a subject, in the tapered waveguide 1 will be described with reference to FIG. Each time light incident on such a tapered waveguide 1 is repeatedly reflected on the side surface,
The angle of incidence on the side is reduced. Then, as shown in the tapered waveguide B of FIG. 3, the light that has been nearly perpendicularly incident on the input surface of the tapered waveguide 1 repeats reflection on the side surface of the taper, and then the linear portion (straight waveguide) of the optical waveguide. Can be incident. However, the tapered waveguide A of FIG.
As shown in the figure, the light incident on the input surface of the tapered waveguide 1 at an angle decreases the incident angle every time the reflection on the tapered surface is repeated, and finally goes backward and exits the input surface. The light exits the optical waveguide beyond the critical angle of total reflection.

This means that the NA of the optical waveguide is substantially smaller than the NA determined by the refractive index difference between the core and the clad. Therefore, even if the refractive index difference of the optical waveguide is designed to be large, the angle of light that can enter the optical waveguide becomes small, and the reflected light from the original surface corresponding to each optical waveguide input section can be obtained without using a microlens. Only the light enters the optical waveguide, and crosstalk can be reduced. In addition, since a microlens is not used, the refractive index difference between the core and the clad can be increased, thereby increasing the light confinement efficiency as compared with a conventional microlens, and improving the optical waveguide. Can reduce the radius of curvature at the bent portion.

Here, as an example, FIG. 4 shows that the width of the input end face of the tapered waveguide is 125 μm, the taper angle is 1.1 °,
Using a tapered waveguide having an optical waveguide spacing of 125 μm, 2
The contrast when reading an original with four black and white lines per mm corresponding to 00 dpi is shown as a change in MTF depending on the distance between the original and the waveguide. Assuming that the output from the optical waveguide at the black line reading position is IB and the output from the optical waveguide at the white line reading position is IW, MTF = (IW−IB) / (IW + I
B).

The crosstalk increases the value of IB and lowers the contrast. Therefore, in practice, it is necessary to increase the MTF to 0.33 or more. FIG. 4 shows that in this example, when the document position is set to 1 mm from the incident surface of the optical waveguide, a good contrast of MTF of 0.33 or more can be maintained even when the 2 mm document floats.

Next, the angle of the tapered portion of the tapered waveguide will be described. In the above example (the taper angle is changed), the distance between the document and the waveguide is 1 mm, 2 mm, 3 m
FIG. 5 shows the dependence of the MTF on the taper angle when changed to m and 4 mm. FIG. 5 shows that the MTF can be increased as the taper angle of the tapered waveguide is reduced (smaller). In practice, the distance from the input end face of the optical waveguide to the document is considered to be about 2 mm or less. Therefore, when the distance is 2 mm in FIG. 5, the taper angle is set to 2 ° to make the MTF 0.33 or more. It turns out that it is necessary to do the following. Therefore, the taper angle of the tapered waveguide is preferably set to 2 ° or less.

In a straight straight waveguide corresponding to the case where the taper angle of the tapered waveguide is set to 0 °, the half-value width becomes very large, the incident angle dependency is reduced, and crosstalk occurs. I will. Therefore, as a result of examining the minimum limit of the taper angle, it depends on the processing accuracy of the taper angle, the flatness of the side surface, the device size, and the like. Is obtained.

From the above, the taper angle of the tapered waveguide of the present invention is preferably 0.5 ° or more and 2 ° or less.

An LED array 4 which is a light emitting element for irradiating an original (subject) to the optical waveguide reduced optical image sensor of the first embodiment and obtaining input light to the optical waveguide array as reflected light from the original. Is schematically shown in FIG. 6 (A) is a plan view, FIG. 6 (B) is a side view from the direction B in FIG. 1, and FIG. 6 (C) is a side view from the direction C in FIG.

As shown in FIG. 6, this optical waveguide reduced optical image sensor is an LE which is a light source for irradiating a document.
The D array 4 is inclined at an angle of about 45 ° with respect to the optical waveguide array 2.
It is arranged in. If the input side of the optical waveguide array 2 of this image sensor is arranged perpendicular to the original,
The LED array 4 irradiates the document surface almost uniformly from an oblique angle of about 45 °, and the light reflected almost perpendicularly to the document among the reflected light from the document does not pass through the microlens array unlike the conventional one, It is introduced directly into the tapered waveguide 1 from its input end. At this time, as described above, since the input end of the tapered waveguide 1 has a three-dimensional tapered shape, the light that is obliquely incident on the tapered waveguide 1 goes backward while repeating reflection at the tapered portion. Excluded from the optical waveguide beyond the critical angle. Then, the light that has propagated in the optical waveguide is received by the CCD 3 from its output end and is converted into an electric signal.

Next, as a method of manufacturing the optical waveguide array of the first embodiment, an example of manufacturing an A4 size optical waveguide reduced optical image sensor having a resolution of 200 dpi will be described.

First, the production of a master master of a three-dimensional tapered waveguide array will be described with reference to FIG. As shown in FIG. 7, grooves are formed in a plastic substrate by processing by excimer laser irradiation, and a master master is manufactured. At this time, the depth of the groove is proportional to the irradiation energy amount of the excimer laser. Therefore,
By controlling the irradiation energy of the excimer laser by changing the moving speed of the plastic substrate or the oscillation rate of the excimer laser, the depth of the groove can be changed. The width of the groove can be adjusted by irradiating a laser through a mask and changing the spot size.

Next, FIG. 8 is an explanatory view showing a process of manufacturing an optical waveguide array using the master master.
This will be described with reference to FIG. In FIG. 8, the left column in the drawing shows a side view from the input end of the tapered waveguide, and the right column in the drawing shows a side sectional view of a surface in the light propagation direction including the tapered waveguide.

The master master produced as described above is as shown in FIG. 8A. A nickel metal film is deposited on the grooved surface to form an electrode (FIG. 8B). Then, nickel metal is laminated by electrolytic plating and electrolytic plating is performed (FIG. 8C). Then, by peeling off the nickel metal film, the master master is released, and a mold made of nickel metal is manufactured (FIG. 8D). Next, injection molding is performed using this mold (FIG. 8 (e)).
An injection molded product is released from the mold to produce an optical waveguide substrate having a groove serving as a tapered optical waveguide. In this embodiment, PMMA which is acrylic is used as the plastic material for injection molding.

Thereafter, a core material is applied and filled into the grooves of the optical waveguide substrate (FIG. 8 (g)), and a flat substrate, which is an upper clad substrate, is overlaid thereon and adhered tightly by applying pressure (FIG. 8). (H)). In this embodiment, since an ultraviolet curable resin (TB3042 manufactured by Three Bond Co.) as an optical adhesive was used as the core material, as shown in FIG. And the flat substrate. Further, the optical waveguide substrate and the planar substrate which are to be clad of the optical waveguide need to have a lower refractive index than the core, and PMMA which is the same acrylic as the optical waveguide substrate is used for the material of the planar substrate.

Finally, the input end face and the output end are polished to remove the protruding core material, thereby completing the manufacture of the optical waveguide array. By coupling a CCD, which is a photoelectric conversion element array, to the output end face of the optical waveguide array manufactured in this way, and attaching an LED array for illuminating a document on the input side surface of the optical waveguide array,
The above-described optical waveguide reduced optical image sensor as shown in FIG. 6 is obtained. Here, unlike the conventional microlens array, high-precision adjustment required for coupling the microlenses so as to correspond to the optical waveguide is unnecessary, so that the optical waveguide reduced optical image can be easily obtained. A sensor can be manufactured.

Next, as a second embodiment, an optical waveguide reduced optical image sensor in which the input end of the optical waveguide of the optical waveguide array has a tapered shape extending in the main scanning direction and a cylindrical lens is provided on the input side. explain.

The schematic plan view of the optical waveguide reduced optical image sensor according to the second embodiment is the same as that shown in FIG. 1 used in the description of the first embodiment, but a cylindrical lens is provided on the input end side of the optical waveguide array 2. Is arranged. That is, as shown in FIG. 9 which is an enlarged perspective view of the main part, a two-dimensional tapered waveguide array in which a two-dimensional tapered waveguide 1 ′ having a two-dimensional tapered shape extending only in the main scanning direction is arrayed. 2 ', and a cylindrical lens 5 which is a cylindrical lens is arranged on the input end side. Therefore, the structure other than the two-dimensional tapered optical waveguide array 2 ′ and the cylindrical lens 5 is the same as that of the first embodiment.

In the second embodiment, of the reflected light from the original, which is the input light from the subject, the light that has spread in the sub-scanning direction is narrowed down by the cylindrical lens 5 to the two-dimensional tapered waveguide. The light spread in the scanning direction is introduced into the linear straight waveguide portion by the two-dimensional tapered waveguide 1 'according to the principle described in the first embodiment. Further, also in the two-dimensional tapered waveguide 1 ′ of the second embodiment, the taper angle is preferably 0.5 ° or more and 2 ° or less, as in the first embodiment.

An LED array 4 which is a light emitting element for irradiating an original (subject) to the optical waveguide reduced optical image sensor of the second embodiment and obtaining input light to the optical waveguide array as reflected light from the original. Is schematically shown in FIG. 10A is a plan view, FIG. 10B is a side view from the direction B in FIG.
(C) corresponds to a side view from the C direction in FIG. 1.

As shown in FIG. 10, this optical waveguide reduced optical image sensor has a light source L for illuminating a document.
The ED array 4 is inclined by about 4 with respect to the optical waveguide array 2 '.
They are arranged at 5 °. If the input side of the optical waveguide array 2 ′ of this image sensor is arranged perpendicular to the document, the LED array 4 irradiates the document surface almost uniformly from an oblique angle of about 45 °, and the reflected light from the document reflects the document. The light reflected almost perpendicularly to the lens is not passed through a microlens array as in the conventional case, but is replaced by a cylindrical lens 4.
Through the input end of the tapered waveguide 1 ′. At this time, light in the sub-scanning direction is introduced into the tapered waveguide 2 ′ by the cylindrical lens 5. As described above, since the input end of the tapered waveguide 1 ′ has a two-dimensional tapered shape, light incident on the tapered waveguide 1 ′ obliquely in the main scanning direction is reflected by the tapered portion. As it repeats, it goes backwards or exceeds the critical angle and is removed from the optical waveguide. Then, the light that has propagated in the optical waveguide is received by the CCD 3 from its output end and converted into an electric signal.

Next, as a method of manufacturing the optical waveguide array of the first embodiment, an example of manufacturing an A4 size optical waveguide reduced optical image sensor having a resolution of 200 dpi will be described.

First, a thick film resist is applied on a glass substrate to form a tapered waveguide pattern, which is used as a master master. A nickel master is formed on the pattern surface of the master master in the same manner as in the first embodiment. A metal film is vapor-deposited, nickel metal is electroplated using the metal film as an electrode, and then separated from the glass / resist to form a mold. From now on,
In the same manner as in the first embodiment, an optical waveguide array is manufactured by using an injection molding technique.

When a CCD, which is a photoelectric conversion element array, is coupled to the output end face of the optical waveguide array manufactured as described above, and an LED array for illuminating a document is attached to the input side surface of the optical waveguide array. As shown,
The above-described optical waveguide reduced optical image sensor can be obtained. Here, as in the case of using the conventional microlens array, the high-precision adjustment required for coupling the microlenses so as to correspond to the optical waveguide is unnecessary, and it is sufficient to simply make the cylindrical lenses. The optical waveguide reduced optical image sensor can be easily manufactured.

[0044]

As described above, according to the optical waveguide-reduced optical image sensor of the present invention, a micro-lens is not required in a device using a three-dimensional tapered waveguide, and a device using a two-dimensional tapered waveguide is required. Since a cylindrical lens can be used instead of the micro lens, the cost can be reduced and the adjustment process can be simplified.

Further, according to the optical waveguide reduced optical image sensor of the present invention, the employed tapered waveguide can reduce the critical angle of incidence even if the refractive index difference between the core and the clad of the optical waveguide is large. The NA can be reduced, and the resolution of the optical system can be improved. In addition, since the refractive index difference of the optical waveguide can be set large, the width of the optical waveguide can be reduced, and the radius of curvature of the bent portion of the optical waveguide can be reduced, so that the size of the image sensor can be reduced.

Further, according to the method for manufacturing an optical waveguide array of the present invention, it is possible to manufacture an optical waveguide array having a three-dimensional tapered waveguide used in the optical waveguide reduced optical image sensor.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic structure of an optical waveguide reduced optical image sensor according to a first embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a main part of the optical waveguide array according to the first embodiment.

FIG. 3 is a conceptual diagram illustrating the principle of propagation of reflected light from a document, which is input light from a subject, in a tapered waveguide.

FIG. 4 shows a contrast change MT according to the first embodiment.
FIG. 9 is a diagram showing the dependence of F on the distance between the original and the waveguide.

FIG. 5 shows a contrast change MT according to the first embodiment.
It is a figure showing taper angle dependence of F.

FIG. 6 is a diagram illustrating a schematic structure of an optical waveguide reduced optical image sensor according to the first embodiment in which an LED array is provided.

FIG. 7 is a conceptual diagram for explaining the preparation of a master master used for manufacturing the optical waveguide array according to the first embodiment.

FIG. 8 is a schematic side view for explaining a manufacturing process of the optical waveguide array according to the first embodiment.

FIG. 9 is an enlarged perspective view of a main part of the optical waveguide array according to the second embodiment.

FIG. 10 is a diagram illustrating a schematic structure of an optical waveguide reduced optical image sensor according to a second embodiment in which an LED array is provided.

FIG. 11 is a plan view showing a schematic structure of a conventional optical waveguide reduced optical image sensor.

FIG. 12 is a conceptual diagram illustrating the principle of propagation of reflected light from a document in a conventional optical waveguide reduced optical image sensor.

FIG. 13 is a conceptual diagram illustrating occurrence of crosstalk in adjacent optical waveguides in a conventional optical waveguide reduced optical image sensor.

[Explanation of symbols]

 1, 1 'tapered waveguide 2, 2' tapered waveguide array 3 CCD 4 cylindrical lens 5 LED array

Claims (5)

[Claims] 1. An optical waveguide reduction optical image sensor comprising: an optical waveguide array into which input light from a subject is introduced; and a photoelectric conversion element array that converts output light from the optical waveguide array into an electric signal. The input end of the optical waveguide of the optical waveguide array has a tapered shape extending in the main scanning direction and the sub-scanning direction, so that the input light from the subject is directly incident on the incident end of the optical waveguide. Characterized optical waveguide reduced optical image sensor. 2. An optical waveguide reduction optical image sensor comprising: an optical waveguide array into which input light from a subject is introduced; and a photoelectric conversion element array for converting output light from the optical waveguide array into an electric signal. An optical waveguide reduced optical image sensor, wherein a cylindrical lens is provided at an input end of the optical waveguide array, and the input end of the optical waveguide of the optical waveguide array is tapered so as to expand in the main scanning direction. 3. The optical waveguide reduced optical image sensor according to claim 1, wherein the angle of the tapered shape of the input end of the optical waveguide is 0.5 ° or more and 2 ° or less. 4. The optical waveguide reduced optical image sensor according to claim 1, further comprising a light emitting element for irradiating the object to obtain input light from the object. 5. A method of manufacturing an optical waveguide array comprising a tapered optical waveguide having an input end extending in a main scanning direction and a sub-scanning direction, wherein a laser irradiation energy amount is controlled to form a tapered groove. Processing a plastic substrate to form a master master; forming a metal on the tapered groove processing surface of the master master to form a mold; and forming a core by injection molding technology using the mold. A method for manufacturing an optical waveguide array, comprising: a step of producing an optical waveguide substrate having: and a step of filling a groove of the optical waveguide substrate with a core material and polymerizing the core material to form a core.