JPH04134960A - Picture reader - Google Patents

Abstract

PURPOSE:To prevent an erroneous shading correction by arranging a reading position by a read-out means in a position which is deviated from the nip width of a platen roller. CONSTITUTION:When irradiating the reading position with light from a light source, since there is no original on an original placing glass as well as a reading position 10 is in the position which is deviated from the nip width of a platen roller 1, irradiating light penetrates the original placing glass 5, is applied to a point on the lower part of the slope of the platen roller 1 a little bit separated from the upper surface of the glass and reflected, and by the light reflected at the position defocused upward from the upper surface of the original placing glass as a focus position, shading correction data are read out. In this way, the shading correction data in the light reflected at the defocused position reduces their values and sensitivities than the shading correction data in the light reflected at the focus position, so it is possible to prevent the erroneous shading correction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device such as a facsimile, an image scanner, a digital copier, etc., and particularly relates to an image reading device that reads shading correction data using a platen roller.

[Conventional technology]

As such an image reading device, there is a conventional image reading device as shown in FIG. 4, for example. The image reading device shown in the figure irradiates light from a light source 2 onto an image on the lower surface of a document (not shown) held between a platen roller 1 and a document placement glass 5, and the reflected light is transmitted through an optical lens. By inputting the light to the light receiving element array 4 via the light receiving element 3, the image of the original is read.

[Problem to be solved by the invention]

In such a conventional image reading device, the platen roller 1 is located approximately in the center of the nip width a (a predetermined width centering on the point of contact with the document placement glass 5) and on the top surface of the document placement glass 5. There is a reading position (focus position) R, and a light source 2 irradiates light onto this position R, and the image of the document is read by the reflected light. However, even during shading correction, the light from the light source 2 is irradiated onto the reading position R and the reflected light is input. Since the platen rollers 1 are arranged in contact with each other, if there is any scratch or dirt on the platen roller 1, it will be clearly read as shown by the broken line in FIG. 2, and there is a problem that erroneous shading correction will be performed.

Therefore, the present invention aims to solve such problems.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a reading method in which a light source illuminates an image of a document on a document placement glass, and the reflected light is received by a photoelectric conversion element via an optical system to read the image. and a platen roller that is disposed close to the document placement glass and is used for shading correction due to its white color, the image reading device includes a platen roller that is disposed close to the document placement glass and that is used for shading correction due to its white color. By arranging the reading position, the irradiation light from the light source is reflected by the defocus position of the platen roller during the shading correction, and the photoelectric conversion element reads the shading correction data. be.

[For production]

According to the image reading device configured as described above, when the light from the light source is irradiated to the reading position during shading correction, the reading position is located within the nip width of the platen roller due to the fact that there is no original on the original placing glass. Since the irradiated light passes through the original glass and hits a point on the lower inclined surface of the platen roller that is slightly away from the top surface of the glass, it is reflected from the top surface of the original glass as the focus position. The shading correction data is read by the light reflected at the upwardly defocused position. In this way, the value and sensitivity of the shading correction data for the light reflected at the defocused position is lower than the shading correction data for the light reflected at the focus position, resulting in incorrect shading correction. This can be prevented.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1 and 2 are diagrams showing an embodiment of an image reading device according to the present invention. Parts that are the same as those of the conventional model are given the same reference numerals.

In FIG. 1, reference numeral 10 denotes a reading section (reading means), and this reading section 10 includes an LED that irradiates light for reading an image of an original (not shown) on an original placing glass 5.
It includes an array (light source) 2 and a contact image sensor (photoelectric conversion element) 4 which inputs the reflected light from the original through a cell-hoc lens array (optical system) 3. A white platen roller 1 is placed close to the document placement glass 5, and the nip width a of the platen roller 1 is placed away from the reading position R of the reading unit 10. .

When performing a reading operation in such an image reading device, a document (not shown) is placed on the placement glass 5, and the platen roller 1 rotates to sandwich the document between the document placement glass 5 and the document placement glass 5. The light emitted from the LED array 2 (indicated by the broken line in the figure) is reflected by the document at the reading position R, and the reflected light passes through the self-hock lens array 3. By inputting the reflected light to the contact image sensor 4, the reflected light is photoelectrically converted and an image of the document is read. In this case, since the surface of the image of the document coincides with the reading position R, a clear image can be read.

Next, the case of shading correction will be explained. In this case, since there is no original on the original placing glass 5 and the reading position R is outside the nip width a of the platen opening 1, the light emitted from the LED array 2 (the solid line in the figure ) is reflected by a point M on the lower inclined surface of the platen roller 1, which passes through the document placement glass 5 and moves upward away from the upper surface of the glass 5, and is reflected at a position M defocused upward from the reading position R. Shading correction data is read by the contact image sensor 4 using the reflected light. The shading correction data for the light reflected at the defocused position M is the shading correction data for the light reflected at the focus position R (shown by the broken line in the figure), as shown by the solid line in FIG. ), its value and sensitivity are reduced. Therefore, it is possible to prevent erroneous shading correction from being performed.

FIG. 3 shows another embodiment of the present invention.

In this embodiment, the reading section 1 is placed on the original placing glass 5.
An original holding plate (original holding means) 6 is provided on the opposite side of the center 0 of the platen roller 1 with respect to the reading position R at 0. According to this embodiment, it is possible to prevent the curled original from floating above the original placing glass 5 at the reading position R, and to read the image accurately.

Note that a roller or the like may be used as the document pressing means instead of the document pressing plate 6.

〔Effect of the invention〕

As explained above, according to the present invention, the value and sensitivity of the shading correction data for the light reflected at the defocused position is lower than that for the shading correction data for the light reflected at the focus position. , it is possible to prevent incorrect shading correction from being performed.

In addition, by slightly shifting the position of the platen roller, it is possible to scan documents in the focus position when reading documents, and in the defocus position when correcting shading.
There is no cost increase at all.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an embodiment of an image reading device according to the present invention, FIG. 1 is a configuration diagram thereof, and FIG. 2 is a change in output voltage as shading correction data in main scanning time. FIG. 3 is a diagram showing the configuration of an image reading device according to another embodiment of the present invention, and FIG. 4 is a diagram showing the configuration of a conventional image reading device. 1...Platen roller 2...LED array (light source) 3...Self-hook lens array (optical system) 4.
...Contact image sensor (photoelectric conversion element) 5...
...Original placement glass 6...Original holding plate (original holding means) 10...
...Reading unit (reading means) Patent applicant Rico Co., Ltd. -

Claims (2)

[Claims] (1) A reading means for reading the image by irradiating light onto an image of a document on a document placement glass using a light source and receiving the reflected light on a photoelectric conversion element via an optical system, and the document placement glass. In an image reading device including a platen roller disposed close to the top and used for shading correction due to its white color, by arranging a reading position by the reading means at a position out of the nip width of the platen roller, The image reading device is characterized in that, during the shading correction, the irradiation light from the light source is reflected by a defocused position of the platen roller to cause the photoelectric conversion element to read shading correction data. (2) The image reading apparatus according to claim 1, further comprising a document holding means provided on the document placing glass on a side opposite to the center of the platen roller with respect to the reading position.