JP2002328438A - Light source for image reading device and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source for an image reading device in which homogeneous emission intensity can be obtained in the respective colors. SOLUTION: The required luminance of three colors is obtained by increasing or decreasing the area of each electroluminescence layer of the three colors according to the emission performance and the required luminance of each electroluminescence layer of R(red), G(green) and B(blue) colors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source.
The present invention relates to a light source of an image reading device.

[0002]

2. Description of the Related Art Equipment such as a copier, a scanner, a printer, a facsimile, or a multi-function printer having the functions of a facsimile, a copier, and a printer are known.
Images of characters and designs drawn on paper etc.
(Referred to as an original).

As a light source of the image reading apparatus, a reduction optical system (reduction CCD system) has been well known. However, in this configuration, a document is floated from a document surface by increasing a focal depth of a lens. However, there is an advantage that a clear image can be obtained. However, because of the large size, when considering further miniaturization and thinning, FIG.
As shown in FIG. 1, a close contact method is used in which information from a document is guided to a sensor in an upright magnification.

That is, the LED array 112 as a light source
Are symmetrically arranged diagonally above the original surface and the original surface 10
6 is received by a rod lens array 121 described below, which is disposed at an intermediate upper position between the two LED arrays 112. The LED array 112 has a configuration in which a large number of LED elements 125 are arranged in a main scanning direction on a substrate 124, for example, as shown in FIG. For example, as shown in FIG. 13, the rod lens array 121 has a configuration in which a predetermined number of columnar rod lenses 122 having a predetermined length and a predetermined diameter are arranged adjacent to each other in a plurality of rows and sandwiched between substrates 124. I have.

According to this configuration, a reduction optical system (reduction CC)
D method), the original surface 106 and the rod lens 1
Since the distance to the lens 22 can be reduced, the entire apparatus can be considerably reduced. Further, by reducing the focal length of the rod lens 122, a thinner apparatus can be expected.

To reduce the focal length of the rod lenses 122, the diameter of each rod lens 122 may be reduced. However, if the diameter of each rod lens 121 is reduced, crosstalk between the rod lenses 122 or flare light may occur. Light noise increases, and the image projected on the sensor 108 becomes unclear. In view of this, the applicant of the present application has proposed in Japanese Patent Application No. 2000-224156 a configuration of the rod lens array 121 with less optical noise (described later).

Further, even if the above-mentioned LED array 112 is used, since the LED array 112 is a set of point light sources, a certain distance must be maintained between the original surface 106 and the light source. However, there is a disadvantage that the uniformity of the illuminance cannot be ensured in this case, and in this regard, there is a limit in promoting the thinning and miniaturization of the contact-type device using the LED array 112. Therefore, the applicant of the present application has proposed in Japanese Patent Application No. 2000-217561 or the like to use electroluminescence as a light source for the purpose of further reducing the thickness and size.

The structure is as shown in FIG. 14, for example. That is, a transparent electrode layer 103 is formed on a glass substrate or a transparent substrate 101 made of a transparent resin or the like which is long in the scanning direction, an electroluminescence 100 layer as an optical medium is formed on the back thereof, and a metal electrode layer 102 is further formed on the back thereof.
Are laminated. To realize a light source using the above-described electroluminescence in color, FIG.
As shown in (a), electroluminescent layers 100r, 100 emitting light of each color of RGB having the same width in the sub-scanning direction.
g, 100b, or, as shown in FIG. 15B, electroluminescent layers 100r, 100g having a constant width in the sub-scanning direction and emitting light of each color of R, G, B at equal intervals in the scanning direction. , 100b are arranged repeatedly. The electroluminescence 100 layer is not limited to vapor deposition or the like used for forming a general thin film, and may be formed by printing, coating, or the like.

[0009]

When an image is read at the same density for each color using a color light source, the luminance required for the light source for each color is not the same, for example, G (green)> R (red). > B (blue). Also, the emission luminance of each color of electroluminescence is not the same,
For example, in electroluminescence in which TPD (tetraphenylbenzine derivative) is used for the hole transport layer and Alq3 (aluminoquinolinol complex) is used for the light emitting layer,
G has the highest emission brightness, and R and B have almost the same emission brightness, which is lower than G. As described above, in order to adjust the illuminance required for reading an image or the difference in luminous ability of each electroluminescent material, an electrical adjustment is required. The provision of the additional portion leads to an increase in the cost of the entire apparatus.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and has as its object to provide a light source of an image reading apparatus capable of obtaining uniform light emission luminance for each color.

[0011]

According to the present invention, R
The areas of the three color electroluminescent layers are determined in accordance with the light emitting ability of the electroluminescent layers of each color (red), G (green), and B (blue) and the illuminance on the document surface required for reading an image. . This area is determined by adjusting the width of each of the three color electroluminescent layers in accordance with the light emission capacity and the required illuminance of the strip-shaped three color electroluminescent layers having the same length in the scanning direction. For example, as shown in FIG. 2A, three colors of electroluminescence whose width is adjusted are arranged side by side in the sub-scanning direction, or the length in the sub-scanning direction is adjusted as shown in FIG. 3
There is a method in which color electroluminescence is repeatedly arranged in the scanning direction. Further, not only the area of the electroluminescence of three colors may be increased / decreased, but also the arrangement of the electroluminescence of each color may be adjusted so that the illuminance on the document surface becomes the illuminance necessary for reading an image.

[0012]

FIG. 1 is a plan view showing a light source 5 for an image reading apparatus according to the present invention.

As shown in FIG. 1, a transparent electrode layer 3 is laminated on a transparent substrate 2 which is long in the scanning direction, an electroluminescent layer 1 as an optical medium is formed thereon, and a metal electrode layer 4 is further formed thereon. The laminated structure is the same as the conventional one. Here, the electroluminescent layer 1 is composed of electroluminescent layers 1r, 1g, 1
2b is the same as the conventional one, but FIG.
As shown in the figure, the electroluminescent layer 1r of each color,
The widths of 1g and 1b are larger for the electroluminescent layer of a color having a smaller luminance per unit area.

The electrodes of the electroluminescent layers 1r, 1g and 1b of the respective colors are composed of a transparent electrode layer 3 and a metal electrode layer 4 respectively.
It consists of One of the electrode layers is a common electrode layer for the electroluminescent layers 1r, 1b, and 1g of each color, and the other is an electroluminescent layer for each color.
Individual electrode layers corresponding to r, 1g, and 1b, respectively. Leads 10, 10r, 10g, and 10b are led out to the common electrode layer and the individual electrode layers corresponding to each color.

The electroluminescent layer 1
When r, 1g, and 1b are used as the light source of the image reading device,
In order to read the densities of the R, G, and B colors uniformly, the electroluminescent layers 1r, 1g, and 1b are used at the following width ratios.

The hole transport layer is a tetraphenylbenzine derivative (TPD), and the light emitting layer is an aluminoquinolinol complex (A
lq3), the emission luminance of the electroluminescent layers 1r, 1g and 1b of R, G and B is R: 400 cd / m
² , G: 2000 cd / m ² , B: 400 cd / m ² . Here, when the above-described electroluminescent material is used in an image reading apparatus in which the illuminance on the document surface necessary for reading an image is R: 900 lux, G: 2,000 lux, and B: 500 lux as a light source, theoretically, R, G, B The ratio of the width of each light source is
R: G: B may be 2.25: 1: 1.25. However, since the relationship between the ratio of the width of the light source and the luminance of the light source is not proportional due to various factors, the ratio of the width of the R, G, and B light sources is
R: G: B = 2.8: 1: 1.5.

For example, when the R, G, and B electroluminescent layers 1r, 1g, and 1b each having a thickness of 0.1 μm and a length in the longitudinal direction of 160 mm are used as light sources for an image reading apparatus, for example, R, G , B of each color of the electroluminescent layers 1r, 1g, 1b have a width of R = 2.8 m.
m: G = 1.0 mm: B = 1.5 mm.

In the above example, the electroluminescent layers 1r, 1g, and 1b of each color are laminated on the transparent substrate 2 over the entire scanning direction, but as shown in FIG. , 1g and 1b may be repeated in order and laminated. In this case, the length of the electroluminescence 1r, 1g, 1b of each color in the scanning direction is made constant, and the ratio of the length in the sub-scanning direction is set to the above ratio (R: G: B = 2.8: 1: 1.5). ).

For example, the thickness of the electroluminescent layers 1r, 1g, 1b of each color is 0.1 μm, the width in the scanning direction is 0.3 mm, and the width in the sub-scanning direction is R = 2.8 mm: B =
1.0 mm: G = 1.5 mm, the electroluminescence of each color is alternately stacked in the scanning direction, and the length of the electroluminescence layer 1 in the scanning direction is 160 mm.

When the light source 5 configured as described above is applied to a light source of an image reading apparatus described below, and an image is read, the R, G, and B lights are normally turned on in order, and the three colors R, G, and B are used. Is finally combined with the image data read by the light. As a special use method, it is also possible to execute a reading process under a specific color and erase only the specific color. In this case, the specific color may be any of the above-mentioned R, G, and B colors, or may be a color obtained by combining the respective colors of R, G, and B.

(Embodiment 2) The light source 5 configured as described above is, for example, a light source unit 15 of an image reading apparatus including light sources 5a and 5b and a fiber lens 14 as a condenser lens shown in FIG. It can be used as light sources 5a and 5b. That is, the light source 5 configured as described above
Are used as the light sources 5a and 5b disposed obliquely above the reading position Pa. The fiber lens 14 is
It is arranged vertically above the reading position Pa.

Since the light source 5 according to the present invention emits light from the surface, the illuminance at the reading position Pa does not depend on the longitudinal direction of the light sources 5a and 5b even when the light sources 5a and 5b are brought close to the reading position Pa. By bringing the light sources 5a and 5b closer to the reading position Pa, the size of the light source unit 15 including the light sources 5a and 5b and the fiber lens 14 can be reduced. Further, by reducing the size of the light source unit 15, it is possible to reduce the size of the entire image reading apparatus.

The light sources 5a, 5a, 5
When the LED array 112 is used for b, the LED element 1
When the distance between the central portion O of 25 and the reading position Pa was 7 mm or less, uniform illuminance could not be obtained at the reading position Pa. However, it was confirmed by experiments that when the light source 5 of the present invention was used, uniform illuminance was obtained even when the distance between the central portion O and the reading position Pa was reduced to 1 mm.

In the configuration shown in FIG. 4, the light sources 5a, 5a
b, the angle θ between the line segment L connecting the central portion O of each electroluminescent layer 1 and the reading position Pa and the document surface 6
Is smaller, the illuminance at the reading position Pa is lower, and as the angle θ is larger,
The ratio of the flare light to the light incident on the lens increases, and the image becomes unclear.

When the angle θ is 40 ° to 55 °, the illuminance at the reading position Pa is relatively high, and the amount of reflected light incident on the condenser lens 14 is relatively small. Therefore, as described above, the center point O of the electroluminescent layer 1 of the color requiring the largest light emitting area and the reading position Pa are connected from the relationship between the light emission luminance and the illuminance on the document surface required for reading the image. The angle θ between the line segment L and the document surface 6 is 40
It is preferable to arrange them so as to be at an angle of from 55 ° to 55 °. In the case of the first embodiment, the light sources are arranged such that the angle θ formed between the line segment L connecting the center point O of the red electroluminescent layer 1r and the reading position Pa and the document surface 6 is 40 ° to 55 °. Would be preferred.

When the angle .theta. Between the straight line L connecting the central portion O of the electroluminescent layer 1r and the reading position Pa and the document surface 6 is set to 40.degree. To the transparent substrate 2
On the center of Electroluminescence layer 1
g and 1b are desirably laminated so as to be adjacent to the electroluminescent layer 1r in the lateral direction of the electroluminescent layer 1r.

In this configuration, since the light source according to the present invention emits surface light, it is possible to obtain uniform illuminance at the reading position Pa even when the light source is brought close to the reading position Pa. In order to bring the fiber lens 14 closer to the reading position Pa while keeping the depth of focus of the fiber lens 14 deep, the diameter of the fiber constituting the fiber lens 14 may be reduced compared to the diameter of a conventional rod, or It is necessary to increase the length of the lens in the vertical direction with respect to 9. In the conventional rod lens 122, since there is a limit in reducing the diameter, the conjugate length is increased to keep the depth of focus deep. However, when the conjugate length is increased,
This is contrary to reducing the thickness and size of the image reading device.

Therefore, as shown in FIG. 5, the fiber lens 14 is formed by bundling optical fibers 140 having a small diameter, that is, 0.5 mm or less. As a result, the focal length of the fiber lens 14 can be shortened and the depth of focus can be increased, the overall optical path length can be suppressed, and the image reading apparatus can be made thinner and smaller. And phenomena such as flare become remarkable. Therefore, as shown in FIG. 7, a light absorbing layer 143 is formed on the outer periphery of each optical fiber 140 having a predetermined length, or as shown in FIG. A plurality of fibers are bundled, and a fiber bundle 144 having a light absorbing layer 141 formed on the outer periphery thereof is formed.

Here, the fiber bundle 144 satisfies the following relationship in order to prevent phenomena such as crosstalk and flare. That is, as shown in FIG. 8, a value obtained by dividing the length Y of one side of the fiber bundle 144 by the length N of the optical fiber 140 is an angle between the central axis Z of the optical fiber 140 and the incident light V. The length Y of the one side is set so as to satisfy a relationship that is smaller than a tangent value of a certain opening angle ω. The aperture angle ω is the maximum angle at which light can be transmitted normally. FIG. 8 shows a state in which the light V is incident on the optical fiber 140 at the maximum angle at which the light can be transmitted normally. Therefore, in FIG. The angle with the light V corresponds to the aperture angle ω.

As described above, a plurality of optical fibers 140 each having the light absorbing layer 143 formed thereon or a plurality of fiber bundles 144 each having the light absorbing layer 141 are formed in a mold having a predetermined shape which is open up and down. The optical fibers 140 are filled in parallel in the radial direction with the length direction of the optical fibers 140 up and down, and the adhesive is filled in the gaps between the optical fibers 140, solidified, and deframed. The predetermined shape of the mold frame is a shape necessary for a copier or an image reading device using the fiber lens 14 to exhibit its original function, and is usually a belt shape having a length perpendicular to the document conveying direction. Become. Further, as shown in FIG. 6, if necessary for molding, the optical fiber 140 alone or the fiber bundle 144 is sandwiched between substrates 142 made of opaque glass or resin in the mold so that the substrate 142 and the light Fiber 1
The 40 units alone or the fiber bundles 144 may be bonded to each other by the above-described method.

A plurality of optical fibers 140 each having the light absorbing layer 143 formed thereon or a plurality of fiber bundles 144 each having the light absorbing layer 141 formed therein, for example,
The length direction 40 is closely arranged in parallel in the radial direction, and the gap is filled with an adhesive, sandwiched between two opaque glass or resin substrates 142 having a predetermined shape, and thermocompression-bonded. Is solidified (not shown).

The optical fiber 140 has a refractive index gradually decreasing toward the outer periphery in a direction perpendicular to the axis (for example, decreasing in accordance with the square of the value of the increasing distance), and the light absorbing layers 141 and 143 are reduced. In principle, light converges in the center direction even if the light absorption layers 141 and 143 are not provided. It is necessary to form.

The light absorbing layers 141 and 143 can be formed by coating, dipping, or vapor-depositing a black resin. The adhesive used when the mold is filled with the optical fiber 140 alone or the fiber bundle 144 may be a conventional adhesive, but may be a black adhesive or the like that can prevent the crosstalk or the flare phenomenon. It is preferable to use these, and these adhesives become the light absorbing layer 141. Here, when the light-absorbing layer is also used with the black adhesive or the like, the adhesive is formed on the optical fiber 140 alone or on the outer periphery of the fiber bundle 144, and the upper and lower portions are opened in the same manner as described above. Using a mold having a predetermined shape, or two substrates 1
The fiber lens 14 is manufactured by, for example, a method in which the fiber lens 14 is sandwiched at 42 and thermocompression bonded. Of course, in this production, the adhesive such as black is used for the optical fiber 140 alone or the fiber bundle 1.
44 so as to cover the entire outer periphery. As the adhesive, for example, glass or resin having a low softening point can be used, but this softening point needs to be lower than the material of the optical fiber 140 and the substrate 142 constituting the fiber lens 14. It is.

Now, the diameter of the optical fiber 140 provided in the fiber lens 14 is set to about 0.1 mm, which is 1/6 of the diameter of the conventional rod lens, and
In the case where the length of the reading device 20a · 2 is about 4.0 mm, which is 1/6 of the length of the rod lens,
0b has a thickness in the direction perpendicular to the surface of the document 9 of about 10 mm, which is 1/6 of the image reading apparatus of the contact type.

FIG. 9 shows an image reading apparatus to which the present invention is applied. In this case, both sides of the image reading apparatus can be read. Of course, this image reading device may be used for facsimile or a copier. As in the related art, the original 9 drawn into the apparatus by the pick roller 151 constituting the original transport unit 162 is fed into the horizontal transport path 133 by the upper and lower feed rollers 152a and 152b. This transport path 1
Reference numeral 33 designates the original 9 as upper and lower feed rollers 152a and 15a.
Belt roller 164 received from 2b and transported backward
Is provided, and is controlled to operate when the leading end of the document 9 reaches a predetermined position.

Near the front end of the horizontal transport path 133, two upper and lower readers 120a and 120b are arranged.
When the original 9 is transported, both sides of the original 9 are simultaneously read at the upper and lower reading positions Pa and Pb.

Here, the lower reading device 120b
In order to read a document that floats from the document surface 136, for example, a document with a book opened, a deep depth of focus is required. Therefore, by using the fiber lens 14 shown in FIG. 5 and the light source of the present invention for the lower reader 120b, the entire reader can be designed to be thin. Of course, the upper and lower reading devices 120a
By using the fiber lens 14 shown in FIG. 5 and the light source of the present invention for 120b, the thickness of the image reading apparatus can be further reduced. As described above, when reading images on both sides of the document 9, if the irradiation light from each light source of the upper and lower reading devices 120a and 120b irradiates the same upper and lower positions, mutual irradiation light interferes. Will be. Therefore, the reading device 120a
The respective arrangements of the reading devices 120a.
Irradiation light from each light source 20b is shifted so as not to be at the same position in the vertical direction to prevent the above-described interference.

The reading devices 120a and 120
b has reading characteristics such as a γ value (density vs. sensor output value) and gradation characteristics which affect each read information obtained by reading images on both sides of the document 9. Here, the print quality of the image printed on both sides of the paper or the like provided in the copying machine is:
It is desirable that they are equivalent, and for that purpose, the read information from the upper reader 120a and the read information from the lower reader 120b need to be the same. Therefore, the copying machine is provided with a reading correction unit 13.
2 so that the reading characteristics of the reading devices 120a and 120b are corrected to be the same.

For example, in the above γ value, the relationship between the amount of reflected light from the document 9 (total amount of light flux for a predetermined time), the output of the sensor unit, and the γ value is generally γ, as shown in FIG.
> 1 and γ = 1, or γ <1. here,
When the sensor output is increased at an arbitrary light amount value a, the reading correction unit 132 corrects the γ value so that γ> 1. Similarly, γ =
1 or γ <1 to adjust the light amount and the sensor output value.
The read information of 0a and 120b is made the same.

In addition, of the upper and lower reading devices 120a and 120b of the copying machine, the upper reading device 120a may be fixed and the lower reading device 120b may be of a movable type. A movable type using an optical system (reduced CCD system) may be used.

In the image reading operation in this case, first, the pick 9 and the feed rollers 152a and 152b convey the original 9 inserted into the original conveying section 2 to the reading section 6. As a result, the original 9 is sent to the horizontal transport path 133 while being read by the fixed reading device 120a.
A reading table (not shown) made of glass is disposed below the scanning roller 3, and the belt roller 164 stops once while the original 9 is placed on the reading table, and the fluorescent light source serving as the light source is stopped. The light (that is, the reading position Pb) moves. When the reading by the reading device 120b is completed, the belt roller 164 is further operated to discharge the document 9.

As described above, the lower reading device 120b
Is a movable type using a reduced optical system (reduced CCD system), and has the same configuration as that of a current copy machine capable of placing the original 9 on the glass original table from above, thereby enabling the original such as a book to be read. Documents that cannot be fed by the transport unit 162 can be handled.

Of course, as described above, the reduction optical system (reduction C
Instead of moving the lower reading device 120b using the CD method, the fluorescent lamp may be fixed at a predetermined position and reading may be performed in accordance with the document 9 conveyed by the belt roller 164.

The above is a case where the image reading apparatus using the light source of the present invention is applied to a copying machine. However, the present invention can be similarly applied to a facsimile, an image reading apparatus, a multifunction printer, and the like.

[0045]

As described above, according to the present invention, it is possible to obtain the luminance required for reading an image in accordance with the color. There is an effect that can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing a light source for an image reading apparatus according to the present invention.

FIG. 2 is a plan view showing a light source in which an electroluminescent layer of each color has an area corresponding to required luminance.

FIG. 3 is a plan view showing a light source in which electroluminescent layers of respective colors are repeatedly arranged in a longitudinal direction.

FIG. 4 is a plan view showing a light source incorporated in the image reading apparatus.

FIG. 5 is a perspective view of a fiber lens included in the image reading apparatus.

FIG. 6 is a perspective view of another fiber lens provided in the image reading apparatus.

FIG. 7 is a perspective view of an optical fiber constituting a fiber lens.

FIG. 8 is a sectional view taken along line XX ′ of the fiber lens.

FIG. 9 is a configuration diagram of a copying machine that performs duplex reading.

FIG. 10 is a diagram illustrating an example of correction based on a γ value of a reading correction unit.

FIG. 11 is a configuration diagram of a conventional contact image reading apparatus.

FIG. 12 is a perspective view of a rod lens array provided in a conventional contact image reading apparatus.

FIG. 13 is a perspective view of a light source provided in a conventional contact image reading apparatus.

FIG. 14 is a perspective view of a conventional light source using an electroluminescent layer.

FIG. 15 is a perspective view of a conventional light source using electroluminescent films of three colors of R, G, and B.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electroluminescent layer 1r red electroluminescent layer 1g green electroluminescent layer 1b blue electroluminescent layer 2 transparent substrate 3 transparent electrode layer 4 metal electrode layer

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H109 AA02 AA15 AA27 AB02 DA01 5C051 AA01 DB28 DB31 DC07 EA01 FA01 5C072 AA01 CA02 CA09 QA11 XA01

Claims (8)

[Claims] 1. A light source of an image reading apparatus which forms a film layer on a transparent substrate in the order of a transparent electrode layer, an electroluminescent layer, and a metal electrode layer, and emits light by applying a predetermined voltage to the two electrode layers. R (red) constituting the electroluminescence layer,
The area of the electroluminescence of each color of R, G, and B that emits light of G (green) and B (blue) is set to an area according to the light emission capacity of the electroluminescence of each color and the required illuminance required for reading an image. A light source for an image reading apparatus, comprising: 2. The electroluminescence of each of the R, G, and B colors is band-shaped, and the width of the electroluminescence of R, G, and B in the short direction is a width according to the light emitting ability and required illuminance. 2. The light source of the image reading device according to 1. 3. The light source according to claim 2, wherein a plurality of the R, G, and B electroluminescences are arranged in a longitudinal direction of the transparent substrate. 4. A light source of an image reading apparatus which forms a transparent electrode layer, an electroluminescent layer, and a metal electrode layer on a transparent substrate in this order, and emits light by applying a predetermined voltage to the two electrode layers. R (red) constituting the electroluminescence layer,
The arrangement of the electroluminescence of each color of R, G, and B that emits light of G (green) and B (blue) is set according to the light emission ability of each color of the electroluminescence and the required illuminance required for reading an image. A light source for an image reading apparatus, comprising: 5. Image reading using a light source that forms a transparent electrode layer, an electroluminescent layer, and a metal electrode layer on a transparent substrate in this order, and emits light by applying a predetermined voltage to the two electrode layers. In the device, R constituting the electroluminescence layer
The area of the electroluminescence of each color of R, G, and B that emits light of (red), G (green), and B (blue) is determined according to the emission ability of each color of the electroluminescence and the required illuminance required for reading an image. An image reading device having an area. 6. The electroluminescence of each of the R, G, and B colors is band-shaped, and the width of the electroluminescence of each of the R, G, and B colors in the lateral direction is a width according to the light emitting ability and required illuminance. Item 6. The image reading device according to Item 5. 7. The image reading apparatus according to claim 6, wherein a plurality of the R, G, and B electroluminescences are arranged in a longitudinal direction of the transparent substrate. 8. Image reading using a light source that forms a transparent electrode layer, an electroluminescent layer, and a metal electrode layer in this order on a transparent substrate, and emits light when a predetermined voltage is applied to the two electrode layers. In the device, R (red) constituting the electroluminescence layer,
The arrangement of the electroluminescence of each color of R, G, and B that emits light of G (green) and B (blue) is set according to the light emission ability of each color of the electroluminescence and the required illuminance required for reading an image. Characteristic image reading device.