JP2009267553A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and accurately detect a black stripe with a forward scanning line in front of an image region of a first original under conveyance as a target for determining the occurrence of the black stripe. <P>SOLUTION: An image reader determines that the black stripe has occurred when the peak of concentration of an image exists at the same pixel position in the scanning lines A-C in a document conveyance direction in front of the image region R of a first original M1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that acquires image data from an image on a document.

2. Description of the Related Art Conventionally, in an image reading apparatus provided with an automatic document transport mechanism, black streaks may be included in image data due to foreign matter (dirt or dust) on contact glass. In order to detect the occurrence of black streaks, a technique (Patent Document 1) for determining the presence or absence of foreign matter on the contact glass based on the reading result of the background plate, and storing the image data of the read two-dimensional data Various proposals have been made, such as a technique (Patent Document 2) for detecting the position of occurrence of black streak by performing a general search.
JP 2006-109368 A (released on April 20, 2006) JP 2002-262083 A (published on September 13, 2002)

  However, the technique disclosed in Patent Document 1 has a problem that foreign matter on the contact glass may move during document conveyance, and black stripes cannot be detected accurately.

  Further, the technique of Patent Document 2 has a problem in that it lacks real-time properties because the image processing necessary for detection is performed and image processing such as filter processing is performed to detect the position of the black streak.

  In view of these conventional problems, an object of the present invention is to provide a technique capable of accurately detecting the occurrence of black stripes and detecting the detection result so as to be used quickly.

  In order to solve the above-described problem, an image reading apparatus according to a first aspect of the present invention provides a reading unit that acquires image data on a main scanning line, and one document in a document bundle in a sub-scanning direction orthogonal to the main scanning line. A predetermined image in image data of two or more main scanning lines positioned in front of the image area of the first original in the original bundle of the original bundle in the moving direction of the original; A black streak detection unit that determines that black streaks have occurred if pixel positions that are equal to or higher in density match each other.

  In this image reading apparatus, since the scanning line ahead of the image area of the first original document being conveyed is a target for determining the occurrence of black stripes, it is possible to detect black stripes quickly and accurately.

  According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the two or more main scanning lines include a line positioned in front of the original and a line positioned on the original. May be included.

  According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the two or more main scanning lines may include two or more lines positioned on the document.

  According to a fourth aspect of the present invention, in the image reading device according to any one of the first to third aspects, when the black streak detection unit detects the occurrence of black streak, the image data at the pixel position equal to or higher than the predetermined density is detected. There may be further provided a correction unit for correcting.

  According to a fifth aspect of the present invention, the image reading apparatus according to any one of the first to fourth aspects includes a display unit that presents the setting contents and status of the apparatus to the user, and the black streak detection when a black streak occurs. When the unit determines, a display control unit that causes the display unit to present a cleaning instruction may be provided.

  According to a sixth aspect of the present invention, in the image reading device according to any one of the first to fifth aspects, when the black streak detecting unit detects the occurrence of black streak, the reading position for changing the reading position by the reading unit is provided. You may further provide a moving part.

  In the image reading apparatus of the present invention, the scanning line ahead of the image area of the first original document being conveyed is a target for determining the occurrence of black stripes, so that it is possible to detect black stripes quickly and accurately.

[First Embodiment]
(1) Configuration of Image Reading Device 1 The configuration of the image reading device 1 according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a front view showing a main part configuration of the image reading apparatus 1, and FIG. 2 is a block diagram showing a main part configuration of the image reading apparatus 1.

  As shown in FIG. 1, the image reading apparatus 1 includes a main body 2 and a document conveying device 3.

  The main body 2 includes an image reading unit 20, a DF (Document Feeder) contact glass 21, and a flat bed contact glass 22. The document conveying device 3 is mounted above the main body 2 so as to be openable and closable with respect to the main body 2. The document transport device 3 includes a document placement tray 31, a document discharge tray 32, and a document transport unit 33. The document transport unit 33 is configured to feed the document M from the document stack on the document loading tray 31 one by one, a feed roller 33a that transports the document M, and a document M being transported onto the DF contact glass 21. A conveyance guide 33c that guides the paper and a discharge roller 33d that discharges the document M after reading to the paper discharge tray 32 are provided. On the DF contact glass 21, the document M is conveyed in a direction (sub-scanning direction) perpendicular to a main scanning direction described later.

  The DF contact glass 21 and the flat bed contact glass 22 of the main body 2 are transparent glass plates and are arranged on the surface facing the document conveying device 3.

  The image reading unit 20 includes a light source 23, a mirror group 24, a lens 25, and an image sensor 26.

  The light source 23 irradiates the original M passing through the DF contact glass 21 and the original M placed on the flat bed contact glass 22 with light. The mirror group 24 is arranged to guide the reflected light from the document M to the lens 25, and the lens 25 is arranged to guide the light from the mirror group 24 to the image sensor 26. An optical path from the light source 23 to the image sensor 26 is indicated by a dotted line. The optical member such as the mirror group 24 can scan the document M line by line in the main scanning direction by the light from the light source 23.

  The image sensor 26 can acquire image data for each scanning line by converting the reflected light from the document M into an analog electrical signal. As the image sensor 26, a conventionally known image sensor such as a CCD or a CMOS can be suitably used.

  The light source 23 and the mirror group 24 can be moved in parallel with the document conveyance direction (sub-scanning direction) by a mirror driving unit 71 described later.

  As shown in FIG. 2, the image reading apparatus 1 further includes an A / D conversion unit 41, an image processing circuit 42, a black streak detection unit 5, an image correction unit 6, a mirror driving unit 71, a document conveyance driving unit 72, and a display unit. 73, IF 74, CPU (Central Processing Unit) 81, ROM (Read Only Memory) 82, RAM (Random Access Memory) 83, and the like.

  The A / D conversion unit 41 further converts the image data for one scanning line converted into an analog electric signal by the image sensor 26 into digital multi-value data, and outputs the digital multi-value data to the image processing circuit 42.

  The image processing circuit 42 performs various types of image processing such as edge enhancement processing on the image data converted into digital multi-value data. The image processing circuit 42 outputs the image data to the black stripe detection unit 5.

  As shown in FIG. 2, the black streak detection unit 5 includes a peak pixel detection circuit 51, a peak pixel position storage unit 52, and a comparison unit 53.

  The peak pixel detection circuit 51 detects the position of a predetermined number of pixels from the pixel having the highest density among the predetermined density or higher in the image data of one scanning line. The predetermined density is not specifically limited, but in the present embodiment, the density data has a density of 200/256 with 256 gradations of white: 0 and black: 255. Further, the predetermined number of pixels is the pixel having the fifth highest density.

  The peak pixel position storage unit 52 stores the position of one pixel detected by the peak position detection circuit in one scanning line.

  The comparison unit 53 determines whether or not the positions of the peak pixels of each line stored in the peak pixel position storage unit 52 match each other, and outputs the result to the image correction unit 6 and the CPU 81 or the like. Here, if there is a matching pixel, it means that a black streak has occurred. The comparison unit 53 can detect the occurrence of black stripe not only when the pixel positions of the peaks completely match but also when the pixel position difference is within a predetermined range as “matched”. This is because if the cause of black streaks is dust, it may move. In this embodiment, this “predetermined range” is 16 pixels.

  Based on the comparison result of the comparison unit 53, the image correction unit 6 corrects the data of the peak pixel corresponding to the black streak and eliminates the black streak if the black streak is generated.

  The mirror driving unit 71 includes a motor, a gear, and the like, and moves the light source 23 and the mirror group 24 to scan the stationary original on the flat bed contact glass 22 in the sub-scanning direction or to read the original being conveyed. You can adjust the position.

  The document transport driving unit 72 can drive the various rollers and the like of the document transport unit 33 to transport the document.

  The display unit 73 includes a liquid crystal display panel and the like, and can present various images to the user.

  The IF 74 can transmit image data to a printing device (not shown) or other external device.

  The CPU 81 functions as a control device that controls the operation of each unit in the image reading apparatus 1. The CPU 81 implements various functions as a control device by reading and executing a program in the ROM 82. The RAM 83 functions as a work area for the CPU 81.

(2) Black Streak Detection With reference to FIG. 3, the operation of each part during black streak detection will be described. FIG. 3 is a diagram showing the position of a scanning line used for black stripe detection.

  As shown in FIG. 3, under the control of the CPU 81, the image reading unit 20 is on the scanning line A and the original M1 which are positioned forward in the original conveying direction with respect to the first original M1 in the original bundle. Thus, the image data of the scanning lines B and C ahead of the image region R of the document M1 can be acquired. The image area R is an area on which image data on a document is placed. On the document M, it is considered that the area other than the image area R is usually a white area.

  The black streak detection unit 5 compares the peak pixel positions in the three lines A to C, and can determine that black streaks have occurred if they all match. The reason why black streaks can be detected by comparing the peak positions in the main scanning direction is that black streaks due to foreign matters such as dust on the DF contact glass 21 extend in the sub-scanning direction.

  As described above, since black streak detection is performed during document conveyance, it is possible to cope with the movement of dust, and accurate black streak detection is possible.

  Further, the black streak detection unit 5 uses the scanning lines A to C ahead of the image area R of the first document M1 in the transport direction as a target for black streak detection, so that black is detected after the transport is started. It takes a short time to obtain the stripe detection result, and black stripes can be detected before reading the image area R of the first document M1 or before reading the image area R. As a result, the image data of the first document M1 can be corrected quickly.

  In particular, since the position of the scanning line A is ahead of the document M1, it is possible to quickly detect black stripes.

  Although the positions of the scanning lines A to C are not particularly limited, for example, the positions B and C can be about 1 mm to 1 cm, 1 mm to 5 mm, or 2 mm to 3 mm from the leading edge of the document. The preferred positions B and C vary depending on the assumed size of the image region R, the size of the document M, and the like, and can be set as appropriate.

  Further, the intervals between A and B and B and C can be set larger than the assumed dust size. For example, the distance may be set to about 0.3 mm to 5 mm, 0.3 mm to 2 mm, or 0.5 mm to 1 mm although it varies depending on the use environment.

  Further, the black streak detection unit 5 can perform black streak detection not only for the first document M1 but also for the second and subsequent documents by the same process.

  When the black streak is detected, the CPU 81 can control the display unit 73 to display a message requesting the user to clean the contact glass. In particular, such a display is preferably performed when a peak indicating the occurrence of black stripes repeatedly appears at the same pixel position.

  Further, the CPU 81 can change the reading position for the document M being conveyed when black streaks occur. Specifically, by controlling the mirror driving unit 71, the stationary positions of the light source 23 and the mirror group 24 can be changed, and the reading position can be changed. By moving the reading position in the sub-transport direction, it is possible to shift the reading position from dust that causes black streaks.

[Other Embodiments]
a) In the first embodiment, the black stripe detection target is the three lines A to C. However, if at least two lines ahead of the image area of the first document M1 are black stripe detection targets. Rapid black stripe detection is possible, and the number and position of the lines are not specifically limited.

  b) In the first embodiment, in the comparison unit 53 of the black streak detection unit 5, it is determined that black streaks have occurred if the peak positions of all three lines coincide with each other. It may be determined that black streaks have occurred when the peaks of at least two of the lines match. The number of lines with which the peak is matched can be determined as appropriate depending on the width between the lines and the like, and is not specifically limited.

FIG. 2 is a front view showing a main part configuration of the image reading apparatus 1. FIG. 2 is a block diagram showing a main configuration of the image reading apparatus 1. The figure which shows the position of the scanning lines AC used as the judgment object of black stripe detection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 20 Image reading part 3 Document conveying apparatus 5 Black stripe detection part 6 Image correction part 73 Display part

Claims (6)

A reading unit for acquiring image data on the main scanning line;
An original conveying section that moves the originals in the original bundle one by one in the sub-scanning direction perpendicular to the main scanning line;
In the image data of two or more main scanning lines positioned forward in the moving direction of the original with respect to the image area of the first original in the original bundle, the pixel positions having a predetermined image density or more coincide with each other. For example, a black streak detection unit that determines that black streaks have occurred,
An image reading apparatus comprising: The two or more main scanning lines include a line positioned in front of the document and a line positioned on the document.
The image reading apparatus according to claim 1. The two or more main scanning lines include two or more lines located on the document.
The image reading apparatus according to claim 1. When the black streak detection unit detects the occurrence of black streaks, the black streak detection unit further includes a correction unit that corrects image data at pixel positions equal to or higher than the predetermined density.
The image reading apparatus according to claim 1. A display unit for presenting device settings and status to the user;
When the black streak detection unit determines that black streaks have occurred, the display control unit causes the display unit to present a cleaning instruction;
The image reading apparatus according to claim 1, further comprising: When the black streak detecting unit detects the occurrence of black streaks, the black streak detecting unit further includes a reading position moving unit that changes a reading position by the reading unit,
The image reading apparatus according to claim 1.

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