JPH1051589A - Optical waveguide type reduced image sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the small sized optical waveguide type reduced image sensor with high sensitivity, capable of reading at high S/N and with the simple manufacture process. SOLUTION: The optical waveguide type reduced image sensor is made up of a 1st micro lens array 2, being an array of a plurality of micro lenses condensing an input image, an optical waveguide array board 3 having a plurality of cores 4 to lead the light corrected by the 1st micro lens array 2 for reducing the input image, and a photoelectric conversion element array 6 receiving light emitted from the optical waveguide array board 3 and converting the light into an electric signal. In this case, the 1st micro lens array 2 is placed at a light incident end of the optical waveguide array board 3, so that an image of each single micro lens of the 1st micro lens array 2 is formed to the light incidence end of a plurality of the cores 4 of the optical waveguide array board 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical waveguide type reduced image sensor used for a one-dimensional reading / reducing optical system of a hard copy image such as a facsimile, a copying machine, an image scanner and the like.

[0002]

2. Description of the Related Art In recent years, as the demand for image reading of facsimile machines, image scanners, digital copiers and the like has increased, there has been a demand for higher performance and smaller size of one-dimensional image sensors for converting image information into electric signals. Conventional one-dimensional image sensors include a reduction optical image sensor using a mirror and a lens, a contact image sensor using a selfoc lens, a completely contact image sensor not using an optical system, and the like. Recently, a waveguide-type reduced image sensor that reduces an image using an optical waveguide array has been proposed.

FIG. 3 is a perspective view showing a schematic structure of a conventional reduced optical image sensor. As shown in FIG.
1 is illuminated by a linear light source 18 such as a light emitting diode (LED) array or a fluorescent lamp arranged on a straight line,
The reflected light from the document 11 is reduced and coupled to a photoelectric conversion element array 16 such as a CCD by a lens 13, and the photoelectric conversion element array 16 converts the image information of the document into a time series of electric signals and outputs it. The resolution of the reduced optical image sensor in FIG. 3 is determined by the pixel pitch of the photoelectric conversion element array 15 and the lens performance. For example, the reading resolution is 200 dpi (200 dots per inch),
When the reading width is 256 mm, the distance (optical path length: b) from the document 11 to the photoelectric conversion element array 15 is about 330 mm. This type of reduction type image sensor is inexpensive and capable of high-speed reading. On the other hand, since the light is condensed on the CCD using the lens 13, the size of the device cannot be reduced and the size of the device cannot be reduced. It has the disadvantage of requiring adjustment for each unit.

On the other hand, there is a contact type image sensor which has been generally used in the past, and the image sensor will be described with reference to FIG. 4 which is a schematic perspective view thereof. As shown in FIG. 4, the detector including the photoelectric conversion element array 26 is disposed so as to cover the entire reading width, and the reflected light from the original 21 illuminated by the light source 28 is directly or via the lot lens array 23. The light is incident on the conversion element array 26 and the image information is converted into an electric signal. In this contact type image sensor, the original 21 is
5 (optical path length: b) has the advantage of being small and requiring no adjustment. On the other hand, the size of the photoelectric conversion element array is large, and a complicated electronic circuit for driving the photoelectric conversion element array is required. Therefore, it was difficult to reduce the price.

As described above, in the reduction optical image sensor using the conventional lens system, a long optical path length is required between the document surface and the solid-state image pickup device. Adjustment is required for each unit, and there is a problem that it is susceptible to vibration. Further, in the conventional contact type image sensor, since the photoelectric conversion element array has the same size as the width of the document, the S / N ratio of the photoelectric conversion signal is reduced,
There is a problem that high-speed operation becomes difficult due to parasitic capacitance between wirings.

In order to solve the problems of the reduced optical image sensor and the contact type image sensor, an optical waveguide type reduced image sensor has been proposed. One example is disclosed in Japanese Patent Application Laid-Open No. 60-189256. A plurality of optical waveguide cores for guiding light from the input image to the photoelectric conversion element array are provided, and a reduced image can be obtained by making the pitch of the light emitting end narrower than the pitch of the light incident end of the core.
However, in this image sensor, since only the upper portion is reduced in size using a waveguide utilizing reflection of a metal thin film, there is a problem that crosstalk occurs between adjacent cores.

[0007] Japanese Patent Application Laid-Open No. 7-30716 discloses that
An image sensor that reduces the size of an optical waveguide array substrate by bending an optical waveguide core in the middle has been disclosed. Japanese Patent Application Laid-Open No. 7-301730 discloses an image sensor in which a bent portion is provided in the shape of the optical waveguide core to further reduce the size of the optical waveguide array substrate.
FIG. 5 is a perspective view showing a schematic structure of an optical waveguide type reduced image sensor disclosed in Japanese Patent Application Laid-Open No. 7-301730, and FIG. 6 is a plan view of a main part thereof. As shown in FIGS. 5 and 6, a light source 38 for irradiating a document, a microlens array 32 formed to have a document surface width, and a plurality of optical waveguide cores 34 for guiding light from an input image to a photoelectric conversion element array 36 are provided. The optical waveguide array substrate 33 on which is formed, and the photoelectric conversion element array 36 are provided, and a reduced image is obtained by making the pitch of the light emitting end of the core 34 smaller than the pitch of the light incident end. In particular, a feature is that two bent portions 34a and 34b are provided in the middle of the core 34.
This optical waveguide-type reduced image sensor provides an inexpensive image sensor that is excellent in earthquake resistance by eliminating the need for adjustment during assembly by integrating the coupling optical system, the optical waveguide array substrate, and the photoelectric conversion element array. be able to.

[0008]

However, in the above-mentioned conventional optical waveguide type reduced image sensor, a single microlens corresponds to a single core on a one-to-one basis. Could not be made larger than the interval (pitch). Because the aperture diameter of the microlens is limited in this way, the sensitivity becomes insufficient,
Reading at a high S / N ratio could not be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has high sensitivity, can read at a high S / N ratio, and has a simple manufacturing process and a small optical waveguide. An object of the present invention is to provide a wave path type reduced image sensor.

[0010]

According to the present invention, there is provided a first microlens array in which a plurality of microlenses for condensing an input image are arranged;
An optical waveguide array substrate having a plurality of cores for guiding light condensed by the first microlens array and reducing an input image; receiving light emitted from the optical waveguide array substrate and converting the light into an electric signal; In the optical waveguide type reduced image sensor composed of a photoelectric conversion element array
The first microlens array is placed on the light incident end side of the optical waveguide array substrate such that each single microlens of the first microlens array forms an image on the incident end of a plurality of cores of the optical waveguide array substrate. It is arranged and configured.

According to the present invention, an optical system comprising a microlens having a relatively large lens diameter is used, and a microlens having a large opening diameter is used so as to extend over a plurality of cores. A large amount of light can be collected, and the input image, which is the reflected light from the document surface, can be efficiently incident on the optical waveguide core.

Further, according to the present invention, in the above optical waveguide type reduced image sensor, a single microlens array for inverting light emitted from a plurality of cores of the optical waveguide array substrate to form an image on a photoelectric conversion element array. Are provided in the light emitting end side of the optical waveguide array substrate.

According to the present invention, as described above, an input image captured by each microlens of the first microlens array is formed on a plurality of cores and propagated. In order to prevent the output image from being inverted from the optical waveguide array substrate, the second microlens is used to reverse the image again to form an image on the photoelectric conversion element array. Therefore, the input image taken into the optical waveguide array substrate with high efficiency can be formed on the photoelectric conversion element array without being inverted.

Further, according to the present invention, in the above-described optical waveguide type reduced image sensor, the light incident end of the core of the optical waveguide array substrate is tapered.

According to the present invention, since the light incident end of the core of the optical waveguide array substrate is tapered, the optical coupling efficiency at the light incident end of the core can be improved.

Further, according to the present invention, a first microlens array in which a plurality of microlenses for condensing an input image is arrayed, and light condensed by the first microlens array is guided to form an input image. An optical waveguide array substrate having a plurality of cores to be reduced; a second microlens array in which a plurality of microlenses for imaging light emitted from the optical waveguide array substrate are arranged;
And a photoelectric conversion element array configured to receive light imaged by the microlens array and convert the light into an electric signal, wherein a resin having a pattern of a concave groove serving as a core is formed. A step of molding a pattern substrate made of a material by an injection molding method, and after filling a concave groove of the pattern substrate with a core material having a higher refractive index than the resin material of the pattern substrate, the pattern surface of the pattern substrate is squeegeeed. A step of removing the excess core material by sweeping and filling the core material, and after polymerizing the core material, a flat substrate made of a material having substantially the same refractive index as the resin material of the pattern substrate is formed on the pattern substrate. Forming an optical waveguide array substrate by the step of fixing the optical waveguide array substrate to the pattern surface; Is set to be secured to the first microlens array and a second microlens array optical waveguide array substrate so as to correspond to one of each of the microlenses b lens array and a second microlens.

According to the present invention, an optical waveguide core array comprises:
Since it can be formed into any shape on the optical waveguide array substrate, the mutual arrangement of the coupling optical system and the photoelectric conversion element is free, and the size of the image sensor can be reduced. In addition, by integrating the light source, the coupling optical system, the optical waveguide substrate, and the photoelectric conversion element array, adjustment at the time of assembling becomes unnecessary, and an image sensor having excellent shock resistance can be provided. Furthermore, by employing a polymer optical waveguide array substrate using an organic polymer for the core and cladding materials, a large-area optical waveguide array substrate can be easily manufactured, and the manufacturing cost of the image sensor can be reduced.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below is an example in which the present invention is applied to a one-dimensional image sensor for G3 facsimile having a resolution of 200 dpi (scan width: 256 mm: compatible with B4 paper). As a photoelectric conversion element,
A 14 μm pitch, 2048 pixel CCD, μPD3743D manufactured by NEC Corporation was used.

FIG. 1 is a plan view showing a schematic structure of an optical waveguide type reduced image sensor according to an embodiment of the present invention, and FIG. 2 is an enlarged view thereof. 1 and 2,
1 is a document, 2 is a micro lens array on the light incident side, 3 is an optical waveguide array substrate, 4 is a core, 5 is a micro lens array on the light emitting side, and 6 is a photoelectric conversion element array. The microlenses constituting the microlens array 2 on the light incident side have a large aperture diameter and a long focal length.
The microlenses forming the microlens array on the light emission side have a small aperture diameter and a short focal length.

As shown in FIGS. 1 and 2, in this optical waveguide type reduced image sensor, the microlens array 2 on the light incident side is such that each microlens is incident on a plurality of cores 4 of an optical waveguide array substrate 3. It is arranged on the light incident end side of the optical waveguide array substrate 3 so that an image is formed at the end. In the present embodiment, since the resolution is 200 dpi, the interval between the cores 4 of the optical waveguide array substrate 3 is set to 127 μm.
m, and the shape of each core 4 is 8 μm × 8
It was a square of μm. Since each microlens of the microlens array 2 was designed to condense light to four cores 4, its diameter was 508 μm. In this embodiment, the shape of the light incident end 7 of the core 4 is tapered.
The size was set to 20 μm in width and 40 μm in depth at the light incident end face.

Each of the cores 4 has bent portions 4a and 4b at two locations, and reduces the size of an original (input image) input through the microlens array 2 on the incident end side.
The light exits from the light exit end face.
The optical waveguide array substrate 3 has a compact size by providing the bent portions 4a and 4b at two places.

Further, the microlens array 5 on the light emission side
The optical waveguide array substrate 3 is configured such that light emitted from a plurality of cores 4 corresponding to each microlens of the microlens array 2 on the light incident side is inverted and imaged on the photoelectric conversion element array 6. Are arranged on the light emission side of In the present embodiment, since a CCD array having a pitch of 14 μm is used as the photoelectric conversion element array 6, the light emitted from the four cores 4 is inverted to form an image on the light receiving surface of each CCD of the photoelectric conversion element array 6. Thus, the diameter of each micro lens of the micro lens array 5 was set to 56 μm.

Next, the fabrication of the optical waveguide array substrate 3 will be described. First, a mold for molding a pattern substrate having a rectangular concave groove serving as a core on the substrate surface is manufactured by using an injection molding technique. In this embodiment, as described above, the core has a width of 8 μm and the light incident end has a width of the light incident end face of 2 μm.
A photomask on which a transfer pattern shape was recorded was designed so as to have a taper shape of 0 μm and a depth of 40 μm. First, using such a photomask, an optical waveguide core shape pattern is exposed on a glass substrate coated with a resist film by lithography technology.
By using a developer to etch unnecessary portions of the resist, a master master made of a resist film is manufactured. Then, after a metal film is sputter-deposited on the pattern surface of such a master master, a mold can be produced by electrolytic plating.

In the present embodiment, using the mold manufactured as described above, injection molding of PMMA resin is performed, and a pattern substrate (cladding substrate) made of a polymer material having a concave groove pattern serving as a core formed on the surface is formed. ) Was prepared. And
TB3042 (manufactured by ThreeBond, refractive index: 1.53) is used as an ultraviolet curable resin having a refractive index higher than that of PMMA (refractive index: 1.49) until the ultraviolet curable resin overflows into the groove of the pattern substrate. After filling, the excess UV-curable resin was removed by sweeping with a urethane rubber squeegee material, and only the concave groove was filled with the UV-curable resin as a transparent resin precursor. Then, by irradiating the substrate with ultraviolet rays, the ultraviolet curable resin which is a transparent resin precursor is polymerized to form a core.

Finally, a flat substrate made of a transparent resin is adhered to the pattern surface of the pattern substrate on which the core is formed in this manner using an ultraviolet curable resin having substantially the same refractive index as that of the pattern substrate, and pressed with a clamp. wear.
Thereafter, ultraviolet light is irradiated from above the substrate to cure the ultraviolet effect resin.

In the present embodiment, PMMA made of the same material as the pattern substrate is used as the plane substrate constituting the cladding of the optical waveguide array substrate 3 together with the pattern substrate.
The thickness was 0.5 mm.

Next, the microlens arrays 2 and 5 are fixed to the optical waveguide array substrate 3 manufactured as described above. In the present embodiment, as described above, the four cores 4 of the optical waveguide array substrate 3 are connected to the microlens arrays 2 and 5 using an ultraviolet curable resin having a refractive index substantially equal to the refractive index of the core material 1.53. They were fixed and attached so as to correspond to one of the microlenses.

In order to eliminate crosstalk between adjacent optical waveguides, it is necessary to provide a light limiting member on the end face of the optical waveguide. Therefore, for example, this can be achieved by forming a metal reflective film on the end face of the clad substrate by an evaporation method or a sputter evaporation method, or by applying an organic film containing a dye that absorbs light having a wavelength of a light source.

[0029]

As described above, according to the optical waveguide type reduced image sensor of the present invention, since the microlens having a larger lens diameter than the conventional one is used for the optical coupling system, it is reflected light from the original. An input image can be efficiently condensed and guided to a photoelectric conversion element array, a converted signal having a high S / N ratio can be obtained, and a highly sensitive optical waveguide type reduced image sensor can be realized. .

Further, according to the optical waveguide type reduced image sensor of the present invention, since an organic polymer material is used for the optical waveguide array substrate, an image sensor corresponding to a relatively large original width can be easily manufactured. Thus, there is an effect that the manufacturing process can be simplified and the cost can be reduced. In addition, since the waveguide type image sensor does not bring the photoelectric conversion element close to the document unlike the complete contact type image sensor, there is no need to protect the photoelectric conversion element, it is not affected by static electricity, and the reliability of the device is improved. Can be improved. In addition, it is possible to provide an image sensor that is smaller in size and more excellent in shock resistance than a conventional reduced optical image sensor. Further, since the optical waveguide core connecting the coupling optical system and the photoelectric conversion element can be formed into an arbitrary shape such as a tapered shape, the degree of freedom of design is increased, and the coupling optical system and the photoelectric conversion element can be freely connected. Can be arranged, and there is an effect that the present invention can be applied to various image sensors.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of the optical waveguide type reduced image sensor of FIG.

FIG. 3 is a perspective view showing a schematic structure of a conventional optical reduced image sensor.

FIG. 4 is a perspective view showing a schematic structure of a conventional contact image sensor.

FIG. 5 is a perspective view showing a schematic structure of a conventional optical waveguide type reduced image sensor.

FIG. 6 is a plan view of the optical waveguide type reduced image sensor of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 2,5 Micro lens array 3 Optical waveguide array substrate 4 Core 4a, 4b Bending part 6 Photoelectric conversion element array

Claims (4)

[Claims] 1. A first microlens array in which a plurality of microlenses for condensing an input image are arrayed, and a plurality of microlenses for guiding light condensed by the first microlens array to reduce the input image An optical waveguide array substrate having an optical waveguide array substrate; and a photoelectric conversion element array configured to receive light emitted from the optical waveguide array substrate and convert the light into an electric signal. The first micro lens array is placed on the light incident end side of the optical waveguide array substrate so that each single micro lens of the micro lens array forms an image on the light incident end of a plurality of cores of the optical waveguide array substrate. An optical waveguide type reduced image sensor characterized by being arranged. 2. A second microlens array comprising a plurality of single microlenses for inverting light emitted from a plurality of cores of the optical waveguide array substrate and forming an image on the photoelectric conversion element array. 2. The optical waveguide type reduced image sensor according to claim 1, wherein the optical waveguide array substrate is provided on a light emitting end side of the optical waveguide array substrate. 3. The optical waveguide type reduced image sensor according to claim 1, wherein a light incident end of a core of the optical waveguide array substrate has a tapered shape. 4. A first microlens array in which a plurality of microlenses for condensing an input image are arrayed, and a plurality of microlenses for guiding light condensed by the first microlens array and reducing the input image An optical waveguide array substrate provided with a core, a second microlens array in which a plurality of microlenses for imaging light emitted from the optical waveguide array substrate are arranged, and a second microlens array. A method of manufacturing an optical waveguide type reduced image sensor, comprising: a photoelectric conversion element array for receiving an imaged light and converting the light into an electric signal, wherein a pattern substrate made of a resin material having a pattern of concave grooves serving as a core is formed. Molding by an injection molding method, and after filling the concave groove of the pattern substrate with a core material having a higher refractive index than the resin material of the pattern substrate, A step of removing the excess core material by filling the core material by sweeping the pattern surface of the pattern substrate with a squeegee material; and after polymerizing the core material, having a refractive index substantially the same as the resin material of the pattern substrate. Fixing the flat substrate made of a material to the pattern surface of the pattern substrate to form the optical waveguide array substrate, wherein a plurality of cores of the optical waveguide array substrate include the first micro lens array and the second core. A method of manufacturing an optical waveguide type reduced image sensor, comprising: fixing a first micro lens array and a second micro lens array to an optical waveguide array substrate so as to correspond to each of the micro lenses. .