JP2009159305A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image reading apparatus capable of achieving almost uniform light distribution from both sides and suitably utilizing an electroluminescent element of power saving and/or low heat generation as a light source. <P>SOLUTION: The image reading apparatus reads a document image of one line at a time by a CCD line sensor. A light source unit 10 for illuminating a document reading position R uses a lamp 21 to be a first light source and an EL element 22 to be a second light source. The reading position R is irradiated with light from the lamp 21 and the EL element 22. Light radiated from the lamp 21 to the EL element 22 is reflected by a cathode electrode 26 of the EL element 22 to irradiate the reading position R with the reflected light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus for optically reading a document image.

  2. Description of the Related Art In recent years, an image reading device mounted on a copying machine or printer, or used as an image input device to a personal computer or the like, illuminates a document with a light source, and forms an imaging lens through a mirror with reflected light from the document. In this case, an image formed on a line sensor composed of a CCD (photoelectric conversion element) is known.

  In this type of image reading apparatus, conventionally, fluorescent lamps and halogen lamps have been mainly used as light sources, and recently, LEDs and electroluminescent elements (hereinafter also referred to as EL elements) are power-saving. It attracts attention as a low heat source.

  By the way, light is applied to the original reading position from the upstream side and the downstream side in the moving direction of the optical system so that a shadow due to light irradiation does not appear when reading a book document or the like. Specifically, as a first method, a reflecting mirror is arranged at a position facing one light source, and the radiated light from the light source is reflected to the document reading position. As a second method, the lamp is placed upstream. Arranging one by one on the side and one on the downstream side is adopted.

  However, in the first method, since the light amount reflected by the reflecting mirror is smaller than the light amount from the light source at the document reading position, the light cannot be evenly distributed on the left and right, and the book document or the original document with a wrinkle Thus, it is difficult to reliably eliminate the occurrence of shadows. Further, in the second method, the amount of heat generated by the lamp is doubled, and there is a concern that the performance of an optical element such as a lens located in the vicinity will change.

Japanese Patent Application Laid-Open No. 2004-228561 describes a document reading apparatus in which light from an organic EL element is reflected by a reflecting mirror to increase the amount of light. However, it is not possible to distribute light almost evenly by simply reflecting the light, as in the first method.
JP 2007-13913 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that enables substantially uniform light distribution from the left and right, and that can suitably use a power-saving and low-heat-generating electroluminescence element as a light source.

In order to achieve the above object, the present invention provides:
In an image reading apparatus comprising: a light source unit for illuminating a document; an imaging unit for imaging reflected light from the document; and a reading unit for reading an image formed on the document.
The light source unit includes a first light source and a second light source disposed to face a side from which light is emitted from the first light source,
At least the second light source of the first light source and the second light source has a light emitting surface and a reflecting surface;
It is characterized by.

  In the image reading apparatus according to the present invention, the first light source and the second light source facing each other are arranged, and at least the second light source has a light emitting surface and a reflecting surface. In addition to the radiated light from the first light source and the second light source, at least the radiated light from the first light source is irradiated with the reflected light reflected by the second light source. Therefore, it is possible to increase the amount of light emitted from the document, or to reduce power consumption if the amount of light is the same as the conventional one.

  In the document reading apparatus according to the present invention, a power-saving and low-heat-generating electroluminescence element can be suitably used as a light source having a light emitting surface and a reflecting surface. The light emitting surface and the reflecting surface may be curved so as to optimize the amount of light at the document reading position, and can be easily curved as long as they are EL elements.

  Further, the light emitting surface may overlap with only a part of the reflecting surface, or the reflecting surface may be provided at a portion not overlapping with the light emitting surface.

  Further, the second light source may be controlled to emit light only when reading, for example, a book document with a shadow or a wrinkled document, if necessary. The lifetime of the second light source can be extended, and the second light source is suitable for an electroluminescence element having a problem with the lifetime.

  Embodiments of an image reading apparatus according to the present invention will be described below with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same member and part, and the overlapping description is abbreviate | omitted.

(Refer to the schematic configuration of the image reader, FIGS. 1 and 2)
FIG. 1 shows a schematic configuration of an image reading apparatus 1A according to the first embodiment of the present invention. This image reading apparatus 1A reads an image of a document D placed on the platen glass 2 by using a reduction optical system, and irradiates the document D placed on the platen glass 2 by a light source unit 10. Reflected light from the original surface enters the imaging lens 18 via the mirrors 15, 16, and 17, and the imaging lens 18 forms an image on the CCD line sensor 19 (photoelectric conversion element).

  The light source unit 10 and the mirror 15 are mounted on the first slider 11, and the mirrors 16 and 17 are mounted on the second slider 12, and each is moved in the direction of arrow X by a motor (not shown). The CCD line sensor 19 is arranged in a line shape in the direction orthogonal to the arrow X direction (main scanning direction Y), and the light source unit 10 and the mirror 15 also extend in the main scanning direction Y. The main scanning direction Y is also referred to as the longitudinal direction.

  FIG. 2 shows a schematic configuration of an image reading apparatus 1B according to the second embodiment of the present invention. The image reading apparatus 1B includes a light source unit 10, mirrors 15, 16, and 17, an imaging lens 18, and a CCD line sensor 19 housed in a single slider 13, and these optical systems are integrated with each other in the direction of arrow X. To read the image of the document D placed on the platen glass 2. The second embodiment has the advantages that the optical system has higher accuracy and the drive system is simpler than the first embodiment.

(Electroluminescence element, see FIG. 3)
In the light source unit 10, a lamp 21 such as a fluorescent lamp or a halogen lamp is disposed on the upstream side in the movement direction X, and the electroluminescence element 22 is disposed on the downstream side. An electroluminescent element may be disposed in place of the lamp 21.

  Here, the EL element 22 will be described with reference to FIG. The EL element 22 has a light emitting layer 28 sealed with a transparent glass substrate 25 having a transparent anode electrode 24 and a substrate 27 having a cathode electrode 26. In the inorganic EL, light is emitted by applying an electric field to the light emitting layer 28. In the organic EL, light is emitted by combining electrons in the electron transport layer and holes in the hole transport layer in the light emitting layer 28.

  Light from the light emitting layer 28 is emitted in the direction of arrow a to the outside of the transparent glass substrate 25. Since light is emitted from the transparent glass substrate 25, the transparent glass substrate 25 is referred to as a light emitting surface. A reflective material (for example, aluminum) is used for the cathode electrode 26 to increase the irradiation efficiency. The light b incident from the outside of the transparent glass substrate 25 is reflected by the cathode electrode 26 and radiated from the transparent glass substrate 25 to the outside. In this sense, the cathode electrode 26 is referred to as a reflecting surface.

(Refer to the first example of the light source unit, FIG. 4)
In the first example, as shown in FIG. 4, a lamp 21 such as a fluorescent lamp or a halogen lamp is used as the first light source A, and an EL element 22 is used as the second light source B. As described above, the light emitting surface (transparent glass substrate 25) and the reflecting surface (cathode electrode 26) are provided.

  The light from the first light source A is emitted toward the document reading position R, and part of the light is emitted toward the second light source B. The light emitted toward the second light source B is incident on the inside from the transparent glass substrate 25 and is reflected by the cathode electrode 26 to irradiate the original reading position R. The light from the second light source B itself also irradiates the document reading position R.

  In the first example, the first light source A and the second light source B facing each other are arranged, and the EL element 22 having the light emitting surface and the reflecting surface is used as the second light source B, so that the document reading position is used. For R, in addition to the light emitted from the first light source A and the second light source B, the light emitted from the first light source A is irradiated with the reflected light reflected by the second light source B. Therefore, it is possible to irradiate almost uniformly from the left and right, and it is possible to increase the amount of document irradiation light. Alternatively, the power consumption can be reduced if the amount of light is the same as before.

(Refer to the second example of the light source unit, FIG. 5)
In the second example, as shown in FIG. 5, the EL element 22 as the second light source B is curved so as to optimize the light amount at the document reading position R. The EL element 22 is extremely thin and can be easily bent. Other configurations are the same as those in the first example. The EL element 22 may be bent at an obtuse angle instead of being curved.

(Lighting efficiency by simulation)
Here, Table 1 below shows the simulation results of the illumination efficiency according to the first example and the second example, that is, how much the light emitted from the first light source A is reflected by the second light source B. .

  When the light quantity of the first light source A is “1”, the case where the second light source B does not reflect light at all is referred to as simulation (a). A case where the planar EL element 22 shown in the first example (see FIG. 4) is used is assumed to be a simulation (b). Furthermore, the case where the curved EL element 22 shown in the second example (see FIG. 5) is used is referred to as simulation (c). The numerical values in Table 1 are ratios when the light amount of the first light source A is “1”.

  As shown in Table 1, the amount of reflection at the second light source B is “0” for simulation (a), “0.43” for simulation (b), and for simulation (c). “0.50”. Therefore, the amount of light required in the second light source B to make the desired light distribution ratio from the first light source A and the second light source B 5: 5 is “1” in the simulation (a). It is “0.57” in (b) and “0.50” in simulation (c).

(Refer to the third example of the light source unit, FIG. 6)
In the third example, as shown in FIG. 6, in the EL element 22, a part of the light emitting layer 28 is omitted, the light emitting surface is the region H1, and the region H2 where the cathode electrode 26 extends is only the reflecting surface. is there. That is, the reflection areas are areas H1 and H2 where the cathode electrode 26 is provided, and the light emitting area H1 overlaps only a part of the reflection area.

  In the third example, the light emission amount of the EL element 22 is relatively small, but power saving can be achieved by reducing the area of the light emitting layer 28. At the reading position R, it is sufficient if a necessary light amount can be secured together with the reflected light in the region H2.

(Refer to the fourth example of the light source unit, FIG. 7)
In the fourth example, as shown in FIG. 7, the second light source B is provided with a reflection surface 29, which is a separate member from the EL element 22, in a portion that does not overlap the light emitting surface (transparent glass substrate 25). . The reflective surface 29 can be attached at an arbitrary position.

(Light emission control for the second light source)
For example, the second light source B may perform light emission control only when reading a book original or a flawed original that is likely to cause a shadow. Information indicating that the document is a book document is input to the control unit from the operation panel. By selectively lighting the second light source B, it is possible to extend the life of the second light source B, which is suitable for an electroluminescence element having a problem with the life. When reading a normal document, only the first light source is turned on. Even in this case, the amount of light from the first light source is small because the reflected light from the second light source irradiates the document surface. I'll do it.

(Other examples)
The image reading apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  For example, as an image reading apparatus to which the present invention is applied, in addition to a method of reading an image of a stationary original by moving an optical system, the original is conveyed at a predetermined speed directly above a reading optical system that is stationary at a predetermined position. A through sheet method for reading an image may be used. The arrangement relationship between the first and second light sources, the configuration of the light guide member that guides the illumination light from the light source unit to the document surface, and the configuration of the mirror that guides the reflected light from the document surface are arbitrary.

1 is a schematic configuration diagram illustrating a first embodiment of an image reading apparatus according to the present invention. It is a schematic block diagram which shows 2nd Example of the image reader which concerns on this invention. It is sectional drawing which shows the general structure of EL element. It is explanatory drawing which shows the 1st example of a light source unit. It is explanatory drawing which shows the 2nd example of a light source unit. It is sectional drawing which shows the 3rd example of a light source unit. It is explanatory drawing which shows the 4th example of a light source unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B ... Image reader 10 ... Light source unit 18 ... Imaging lens 19 ... CCD line sensor 21 ... Lamp 22 ... Electroluminescence element 25 ... Transparent glass substrate (light emission surface)
26 ... Cathode electrode (reflection surface)
A ... First light source B ... Second light source

Claims (6)

In an image reading apparatus comprising: a light source unit for illuminating a document; an imaging unit for imaging reflected light from the document; and a reading unit for reading an image formed on the document.
The light source unit includes a first light source and a second light source disposed to face a side from which light is emitted from the first light source,
At least the second light source of the first light source and the second light source has a light emitting surface and a reflecting surface;
An image reading apparatus.   The image reading apparatus according to claim 1, wherein the light source having a light emitting surface and a reflecting surface is an electroluminescence element.   3. The image reading apparatus according to claim 1, wherein the light emitting surface and the reflecting surface are curved so as to optimize the amount of light at the document reading position.   4. The image reading apparatus according to claim 1, wherein the light emitting surface overlaps only part of the reflecting surface.   5. The image reading apparatus according to claim 1, wherein a reflection surface is provided also in a portion not overlapping with the light emitting surface.   6. The image reading apparatus according to claim 1, wherein the second light source is controlled to emit light as necessary.

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