JPH05260249A - Picture read unit - Google Patents

Abstract

PURPOSE:To eliminate the need for the adjustment of a distance between a lens array and a photodetector sensor in the assembling process by employing the lens array whose size tolerance with respect to a length of the lens is a specific value or below. CONSTITUTION:The lens array is an array by inserting an array comprising lots of gradient index rod lens elements 14 between two bases 12, 13 and adhering the array inbetween. The lens array whose size tolerance with respect to a length of the lens is + or -0.15mm or below, a light source 16 and a photodetector 15 are incorporated in a case 11 made of an aluminum group metal and having lens array insertion projections 18,101. In the case of a plastic-made rod lens elements 14, the array of the gradient index rod lens elements is cut off so that the size tolerance with respect to a length of the lens is + or -0.15mm or below. In the case of a glass-made rod lens elements 14, the length of the lens is decided based on the conjugate length of the array, the array of the gradient index rod lens elements is cut off so that the size tolerance with respect to a length of the lens is + or -0.15mm or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading unit in which a lens array made of an array of gradient index rod-shaped lens elements having a dimensional tolerance with respect to the lens length Z ₀ of ± 0.15 mm or less is incorporated in a housing. In particular, the present invention relates to an image reading unit that enables automatic assembly without manually assembling the lens array into the housing.

[0002]

2. Description of the Related Art An image reading unit combining a lens array in which a large number of gradient index rod-shaped lens elements are arranged and a light receiving element is used as a sensor for a copying machine as disclosed in Japanese Patent Publication No. 59-9230. It is also widely used as a sensor for facsimiles.

As described above, the gradient index rod-shaped lens element used in the image reading sensor is formed by immersing the drawn glass fiber in a skein-like shape in an ion exchange bath,
It is made by a method of imparting a refractive index distribution to the glass fiber by performing an ion exchange treatment from the surface of the glass fiber toward the inside. The gradient index rod-shaped lens element manufactured in this way has a different refractive index distribution constant for each batch of ion exchange treatment in order to keep the conjugate length constant. It is extremely difficult to make a lens array with a uniform lens array, and the dimensional tolerance for the lens length Z ₀ of the lens array is ± 0.3 mm to ± 0.5 mm.
It is in the range of.

In order to assemble the image reading unit using the lens array having a large dimensional tolerance with respect to the lens length Z ₀ , the distance between the original screen and the lens array and the distance between the lens array and the light receiving element are adjusted and assembled. It is necessary to provide an image reading unit that does not cause blurring in the read image by performing the above-mentioned procedure.
As shown in Japanese Patent No. 4265, it is necessary to manually perform this distance adjustment work in the assembly process of the image reading unit, and it has been extremely difficult to rationalize the assembly process.

[0005]

The inventors of the present invention have studied the measures for solving the above-mentioned problems, and found that a lens array consisting of a gradient index rod-shaped lens element having a specific conjugate length is used. When using this to make an image reading unit, the dimensional tolerance for the lens length Z ₀ value is ± 0.15 mm
It has been found that the following lens array can be assembled without adjusting the distance between the lens array and the light receiving element sensor in the assembly process. The gist of the invention is that the gradient index rod lens element is used. An image reading unit in which a lens array in which a large number of arrays are sandwiched and bonded by two substrates and the dimensional tolerance to the lens length Z ₀ is ± 0.15 mm or less, a light source and a light receiving element are incorporated in a housing. It is in.

When the rod-shaped lens element used for carrying out the present invention is a plastic lens element, for example, W
09/05274, a gradient index lens element is manufactured by operating the gradient index constant so as to be constant, and the dimensional tolerance with respect to the lens length Z ₀ is determined from the array of lens elements. Can be made by cutting so that is within ± 0.15 mm. When the lens element is made of glass, a gradient index lens is made by the method disclosed in Japanese Examined Patent Publication No. 47-812 so that the gradient index distribution constant falls within a certain range, and the lens element array is arranged. decide lens length Z ₀ of the body in accordance with the conjugation length, with respect to the lens length Z _0, it can be made by dimensional tolerances for cutting the lens array to be less than ± 0.15 mm.

The lens array used for carrying out the present invention is formed by joining and sandwiching two substrates, and as the substrate, a glass woven cloth impregnated with an epoxy resin or an unsaturated polyester resin, or an ABS is used. A plate-shaped material made of a thermoplastic resin such as resin, polymethylmethacrylate, polycarbonate or polyester resin can be used. When making a lens array, it is preferable to bond the array of lens elements and the substrate with a hot-melt adhesive.

The lens array used in the present invention has a dimensional tolerance of ± 0.15 mm or less, whereas the dimensional tolerance of the lens array developed so far is ± 0.3 mm or more with respect to the lens length Z ₀ . Therefore, it is possible to adjust the distance between the light receiving element and the lens array when it is assembled in the housing by using the projection for holding the lens array.

The lens array made as described above is
Normally, the surface is smoothed only by polishing, but the surface is very uneven as viewed optically,
In order to improve the characteristics of the lens array, it is preferable to ensure the smoothness of the end faces of the lens array.
In order to obtain a lens array having such characteristics, it is preferable to provide a coating layer of cross-linking curable resin on the end surface of the lens array. Examples of crosslinkable curable resins that can be used include ethylene glycol, diethylene glycol, triethylene glycol, 1,6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, and other polyols (meth) acrylates. Examples thereof include UV curable or thermosetting liquid materials such as acrylate monomers, acrylate monomers, methacrylate monomers, furfuryl (meth) acrylates, and fluorinated alkyl (meth) acrylates.

The light source used for carrying out the present invention is preferably a linear light source, and examples thereof include a thin fluorescent lamp, an LED light emitting element array, a cylindrical lens and a linear light source using an optical fiber. A CCD line sensor, a photodiode array, or the like can be used as the light receiving element.

As a housing used for carrying out the present invention, a die cast molded product, a pultruded molded product or the like using a light metal such as aluminum can be used. Since the lens array used for implementing the present invention has a dimensional tolerance of ± 0.15 mm or less with respect to the lens length Z ₀ , the distance between the light receiving element and the lens array can be constant. Unlike the conventional image reading unit assembly work, it is not necessary to perform this distance adjusting operation for each image reading unit, and by providing the housing with the engagement structure with the lens array, Automatic assembly is possible. For this purpose, it is preferable that the housing is provided with a projection for holding the lens array, as indicated by 18,18 ', 101, 101' in FIG.

According to the present invention, the lens length Z of the lens array
_Since a lens array with a dimensional tolerance of ₀ ± 0.15 mm is used, the lens array working distance l ₀ satisfies the dimensions of 3.9 mm and conjugate length Tc 14.4 mm as a housing, and the lens array is mounted by the throw-in method. By using the one with a protrusion that can be fixed to the body, the image reading unit can be automatically assembled.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0014]

Example 1 Polymethylmethacrylate ([η] = 0.5
6, measured in methyl ethyl ketone (MEK) at 25 ° C) 46 parts by weight, benzyl methacrylate 44 parts by weight, methyl methacrylate 10 parts by weight, 1-hydroxycyclohexyl phenyl ketone 0.2 parts by weight and hydroquinone 0.1 parts by weight 70 parts by weight
The mixture was heated and kneaded at 0 ° C. to prepare a first layer (central portion) forming stock solution.
In addition, polymethylmethacrylate ([η] = 0.41, MEK
(Measured at 25 ° C in medium) 50 parts by weight, 50 parts by weight of methyl methacrylate, 1-hydroxycyclohexyl phenyl ketone 0.2
Parts by weight and 0.1 parts by weight of hydroquinone are heated and kneaded at 70 ° C to form a second layer forming stock solution, and further 45 parts by weight of polymethylmethacrylate ([η] = 0.34, measured at 25 ° C in MEK), 2,2 , 3,3,4,4,5,5-octafluoropentyl methacrylate 35 parts by weight, methyl methacrylate 20 parts by weight, 1-
A stock solution for forming the third layer (outer layer part) was prepared by kneading 0.2 parts by weight of hydroxycyclohexyl phenyl ketone and 0.1 parts by weight of hydroquinone at 70 ° C. Using a composite spinning machine equipped with a concentric three-layer composite spinning nozzle, three types of stock solutions were sequentially arranged from the center so that the refractive index of the uncured product was lowered, and simultaneously extruded strand fibers were obtained.
The viscosity of the first layer is 4.5 × 10 ⁴ poise when extruded,
The second layer is 2.0 × 10 ⁴ poise, and the third layer stock solution is 2.2
It was × 10 ⁴ poise. The temperature of the composite spinning nozzle is
It was 55 ° C.

Next, each layer was made to pass through the layer mutual diffusion treatment section of 90 cm in length, and then 12 fluorescent lamps of 120 cm in length and 40 W were passed through the strand fibers at the centers of the light irradiation sections arranged in a circle at equal intervals. The light transmission body having a radius (r 2 _{O 3} ) of 0.50 mm was taken up by a nip roller at a speed of 50 cm / min. The discharge amount ratio was 1st layer: 2nd layer: 3rd layer = 1: 1: 1. Refractive index profile in the center of the obtained refractive index distribution type rod-shaped lenses (n _O) is 1.
512, the peripheral part is 1.470, and the refractive index distribution constant (g) is
It was 0.52.

The rod-shaped lens obtained as described above had a lens length of 7.2 mm, and its both end faces were polished, and the MTF measured using a lattice of 4 line pairs / mm was 57%, and the conjugate at that time was 57%. The length was 15.4 mm. The image of the obtained grating was a clear image with little distortion. This rod-shaped lens element is sandwiched between two grooved substrates,
It was bonded with an adhesive and cut into a lens array with a lens length of 7.2 mm to make a 200-lens array. The surface of these lens arrays is sprayed uniformly and thinly with a liquid UV curable acrylic cross-linking curable resin with a nozzle.
It was cured with an ultraviolet lamp and surface-treated. The size of the lens array at this time is 230 mm, and the lens length is 7.18 to 7.
The thickness was 22 mm, the thickness was 2.8 mm, the dimensional tolerance was ± 0.02 mm with respect to the lens length of 7.2 mm, and the smoothness of the surface was extremely good. A carbon black-containing ABS resin was produced as a substrate by an injection molding method. An epoxy adhesive was used as the adhesive.

As the casing, a casing having a cross section as shown in FIG. 1 was produced by die casting an aluminum base material. The dimensions were as shown in FIG. 1, and the housing was provided with projections for sandwiching the lens array, and the lens array was fixed to the housing by inserting between the projections. The dimensions of the lens array are an optical working distance l ₀₁ = 4.2 mm and a conjugate length Tc = 15.4 mm, which are somewhat different from the actual dimensions. The lens array described above is mounted in this housing without adjustment such as alignment, and the light source 16, CCD sensor 15, and cover glass 17 are built in as shown in FIG.
When F was measured, it was as good as 50% or more.

[0018]

[Embodiment 2] Only the lens length in Embodiment 1 is 7.05 to 7.35.
Example 1 except that 200 lens arrays each having a size of 200 mm were made and a lens having a dimensional tolerance of ± 0.15 mm for a lens length of 7.2 mm was used.
The lens array prepared in the same manner as in Example 1 was mounted in a housing obtained in the same manner as in Example 1 as in Example 1, and the light source, CC
When the D sensor and the cover glass were incorporated and the MTF was measured using a grid of 4 line pairs / mm, it was 50% or more.

[0019]

Comparative Example 1 In Example 1, only the lens length is 7.04 to 7.36.
mm, and the same procedure as in Example 1 except that 200 lens arrays having a dimensional tolerance of ± 0.16 mm with respect to a lens length of 7.2 mm were used, and the light source, CC
When the D sensor and the cover glass were incorporated in the same manner and the MTF was measured using a grid of 4 line pairs / mm, the average value of the MTF was about 35% and the minimum value was 28%. The performance was insufficient as a unit.

[0020]

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of an image reading unit of the present invention.

[Explanation of symbols]

11 ……………………………… Case 12,13 …………………… Substrate 14 ………………………… Index distribution type rod lens element 15 ……………… ………… Light receiving element 16 ………………………… Light source 17 ……………………………… Cover glass 18,18 ', 101,101' ………… Projection for sandwiching the lens array

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Tanaka 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory

Claims (2)

[Claims] 1. A lens array in which a large number of arrays of gradient index rod-shaped lens elements are sandwiched and bonded by two substrates, and a lens array having a dimensional tolerance of ± 0.15 mm or less with respect to a lens length Z _0, a light source and a light receiving An image reading unit characterized in that the element array is made of aluminum-based metal and is incorporated in a housing having projections for holding the lens array. 2. The image reading unit according to claim 1, wherein the lens array is provided with a cross-linking hardening type resin coating on the light input / output end surface of the lens array.