JP2004350245A - Original reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of detecting even white dirt as well as black dirt adhering to a read position. <P>SOLUTION: The lightness of a surface with a reference density face 7 that can be irradiated with an optical system 5 is set to a bright gray of about 9.0 of the Munsell value. The difference between the read density when the surface of the reference density face 7 is read and a read density stored in advance is obtained for each one pixel, and whether or not there exists any pixel with a greater density difference is determined. Thus, not only a black ink stain or the like adhering to the read position but also white paper dust or the like adhering to the read position can be detected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a document reading apparatus which is applied to an image forming apparatus such as a digital copying machine and reads an image of a document.
[0002]
[Prior art]
Some image forming apparatuses such as digital copiers can read an image at a reading position by irradiating light toward a reading position while moving documents set on a document tray one by one. Some have a so-called sheet-through type document reading device.
In a sheet-through type document reading apparatus, if a black spot of ink adheres to a reading position, for example, a black line may be included in the read image. In view of this, Japanese Patent Application Laid-Open Publication No. H11-163873 discloses a document reading apparatus that detects whether or not a read image includes a black streak, and, when the black streak is detected, notifies the user of the fact (see Patent Literature 1). .
[0003]
Patent Document 2 discloses a document reading device that notifies a user of a stain on a white reference plate (see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-6-303428 [Patent Document 2]
JP-A-11-252362 [0005]
[Problems to be solved by the invention]
By the way, in a sheet-through type document reading device, if, for example, paper dust adheres to a reading position, a read image may include white stripes. It is not possible to detect the presence of white streaks contained in the image. The device described in Patent Document 2 detects that dirt (colors other than white) has adhered to the white color of the white reference plate. Not detectable.
[0006]
The present invention has been made under such a background, and an original reading apparatus capable of detecting whether a dirt is present in a reading position, whether the dirt is a black dirt or a white dirt, is provided. The purpose is to provide.
Another object of the present invention is to provide a document reading apparatus capable of preventing occurrence of background fogging.
[0007]
Means for Solving the Problems and Effects of the Invention
According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a reading position having a predetermined length in a main scanning direction; and a document passing in a sub-scanning direction orthogonal to the main scanning direction at the reading position. A document feeder for moving the document, a document reading device that reads a document passing through the reading position as line data in the main scanning direction, and outputs the contents from the leading edge to the trailing edge of the passing document as a plurality of line data. Means and a reference density surface which is arranged at the reading position and which can be read as line data by the document reading means when the document does not pass through the reading position, the density of which is approximately 9.0 in Munsell value. The reading of the reference density surface in light gray and the reading of the reference density surface read by the document reading means in a state where the previously stored reading position is clean. Data, compares the read data of the reference concentration plane went prior to reading the document, a document reading apparatus characterized by comprising: a stain determination means for determining the contamination whether the reading position.
[0008]
According to the present invention, the density of the surface of the reference density surface is a light gray with a Munsell value of about 9.0, and data of the reference density surface read in a state where the reading position is not stained is stored. Then, the read data of the reference density surface, which is performed prior to the reading of the document, is compared with the stored data.
The read data when the reference density surface is read in a state where, for example, a black spot of ink is attached to the reading position or in a state where, for example, white paper dust is attached to the reading position is different from the stored data. According to the present invention, it is possible to determine whether or not the reading position is dirty by focusing on whether or not the read data differs from the stored data. Furthermore, not only the read data when the black stain is attached, but also the read data when the white stain is attached are different from the stored data, so not only the black stain attached to the reading position, White stains can also be detected.
[0009]
Further, since the density of the surface of the reference density surface is a light gray with a Munsell value of about 9.0, the reading density can be adjusted based on the brightest density to be reproduced. As a result, it is possible to prevent background fogging that occurs in an image obtained by reading a document whose background color is not pure white (for example, a document having an image recorded on recycled paper or the like).
According to a second aspect of the present invention, there is provided the document reading apparatus according to the first aspect, further comprising a notifying unit for notifying information on the stain in response to the stain determining unit determining that the stain is present. .
[0010]
According to the present invention, when it is determined that there is dirt at the reading position, information on the dirt can be notified. This notification removes dirt from the reading position.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a document reading apparatus according to an embodiment of the present invention. The document reading device 1 is applied to, for example, a digital copying machine.
The document reading device 1 includes a reading position 3 formed on the upper surface of the contact glass 2, a feeding device (document feeding roller) 4 for moving the document on the reading position 3, and an optical system for illuminating the reading position 3. 5 is provided.
[0012]
The reading position 3 has a longitudinal shape extending in a direction perpendicular to the paper surface (main scanning direction). A document holder 6 is provided above the reading position 3 with a certain gap. The originals are moved by the original feed roller 4 one by one over the reading position 3 by the original holder 6 as shown by an arrow A1.
The optical system 5 includes a lamp 8 for illuminating the reading position 3, reflecting mirrors 9, 10, and 11 for guiding light reflected at the reading position 3, and a lens 12 for converging the guided light. And are included.
[0013]
The bottom surface of the document holder 6 (the surface facing the contact glass 2) is a reference density surface 7, and this reference density surface 7 also extends in the main scanning direction in a direction perpendicular to the paper surface. The reference density surface 7 is a light gray with a surface density of about 9.0 in Munsell value.
The document reading apparatus 1 further includes a CCD line sensor 13 for detecting light converged by the lens 12 of the optical system 5, an A / D converter 14 for converting an analog output of the line sensor 13 into a digital signal, A control unit (dirt determination unit) 15 for performing a control operation described below based on a signal supplied from the A / D converter 14 based on a signal supplied from the A / D converter 14, and an output of the control unit 15 A display 16 for displaying is provided.
[0014]
The document reading apparatus 1 adjusts the reading density when reading a document based on the reading density when reading the surface of the reference density surface 7, but adjusts the reading density based on the brightest density to be reproduced. can do. As a result, it is possible to prevent background fogging that occurs in an image obtained by reading a document whose background color is not pure white (for example, a document having an image recorded on recycled paper or the like).
FIG. 2 is a diagram for explaining the contents of one line data read by the CCD line sensor 13. The CCD line sensor 13 detects the light focused by the lens 12 in the main scanning direction and outputs it as one-line data, and sequentially outputs this one-line data in a time-series manner. For this reason, when the document is moved to the reading position 3, the document image is output as data in which one line data in the main scanning direction is arranged in a large number of lines in a direction orthogonal to the main scanning direction (sub scanning direction).
[0015]
FIG. 2 shows data obtained by reading the reference density surface 7. 2A shows a clean state in which the reading position 3 is free from dirt, and FIG. 2B shows a state in which the reading position 3 or the reference density surface 7 is contaminated (black spots of ink, paper dust, etc.). ) Is attached. As shown in FIG. 2A, when the reading position 3 is clean, the read data is a signal having a Munsell value of about 9.0 in density. On the other hand, if there is black dirt on the reading position 3 or the reference density surface 7, the read data is shifted to the black side at the position where the black dirt exists (point a in FIG. 2B). If there is a white stain on the reading position 3 or the reference density surface 7, the read data is shifted to the white side at the position where the white stain is present (point b in FIG. 2B).
[0016]
FIG. 3 is a flowchart showing a control operation of the document reading apparatus 1 shown in FIG. This control operation is performed in the control unit 15.
The control operation will be described with reference to FIG. When a document is set at a set position outside the figure or when reading of the document is completed (step S1), the reference density surface 7 is read (step S2), and the line data is stored in a reading position stored in advance. 3 is compared with the reference line data where there is no stain. Specifically, the reference line data stored in advance is, for example, as shown in FIG. 2A, and the density of the reference line data is compared with the density of the read line data ( In step S3, it is determined whether or not there is a pixel having a large density difference (step S4).
[0017]
Now, assuming that the line data being compared are FIGS. 2A and 2B, pixels having a large density difference exist at points a and b in FIG. The reading position 3 or the reference density surface 7 corresponding to the pixel has dirt. Therefore, by comparing these line data, it can be determined whether or not the reading position 3 or the reference density surface 7 is dirty. Further, it is possible to determine not only the presence / absence of black stains but also the presence / absence of white stains.
[0018]
In addition, since it is determined whether or not the original is set when the original is set and when the reading of the original is completed, for example, when it is determined that the original is set when the original is set, the set original is determined. Is read, it can be determined that black streaks, white streaks, and the like occur in the read image. On the other hand, if it is determined that there is dirt when reading of the original is completed, it can be determined that dirt has adhered to the reading position 3 or the reference density surface 7 when the original has moved to the reading position 3. When the original is read, black streaks, white streaks, and the like appear in the read image.
[0019]
Therefore, when it is determined that there is no pixel having a large density difference (No in step S4), the document is conveyed and read, and a copy operation of the read image is performed (step S5).
On the other hand, if it is determined that there is a pixel having a large density difference (Yes in step S4), a message prompting cleaning is displayed on the display 16 assuming that the reading position 3 is dirty (step S6).
[0020]
If there is a pixel having a large density difference, the reading position 3 or the reference density surface 7 is dirty, and when the document is read in this state, the read image includes black streaks and white streaks. For this reason, it is necessary to remove dirt at the reading position 3, and a message prompting cleaning is displayed on the display 16.
Note that a message prompting cleaning is displayed on the display 16 when it is determined that there is a pixel having a large density difference. Instead of this configuration, for example, a message such as "Please clean the contact glass." May be notified by voice.
[0021]
Further, even if the reading position 3 is cleaned, if there is a density difference, this is due to the contamination of the reference density surface 7, so the user needs to read the reading position 3 and the reference position based on the message prompting the cleaning. What is necessary is just to clean both of the density surfaces 7.
The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims.
Although the configuration in which the document reading apparatus according to the embodiment of the present invention is applied to a digital copying machine has been described, the present invention is not limited to the digital copying machine but can be applied to other image forming apparatuses such as a facsimile.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a document reading apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining the contents of one line data read by a CCD line sensor.
FIG. 3 is a flowchart showing a control operation of the document reading apparatus shown in FIG.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 document reading device 3 reading position 4 feeding device 5 optical system 7 reference surface 13 CCD line sensor 15 control unit 16 display unit

Claims (2)

A reading position having a predetermined length in the main scanning direction;
Document feeding means for moving the document so that the document passes in a sub-scanning direction orthogonal to the main scanning direction of the reading position,
Document reading means for reading a document passing the reading position as line data in the main scanning direction, and outputting the contents from the leading edge to the trailing edge of the passing document as a plurality of line data,
A reference density surface which is disposed at the reading position and which can be read as line data by the document reading means when the document does not pass through the reading position, the density of which is a bright gray having a Munsell value of about 9.0; Reference density surface,
The read data of the reference density surface read by the document reading means in a state where the reading position stored in advance is not stained is compared with the read data of the reference density surface performed prior to reading the document. Dirt determining means for determining the presence or absence of dirt at the reading position;
A document reading device comprising: 2. The document reading apparatus according to claim 1, further comprising a notifying unit that notifies information on the stain in response to the stain determining unit determining that there is stain.

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