JP2006086881A - Tracing pattern detecting apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable selecting whether or not a tracking pattern is detected depending on an image quality mode, and to enable highly accurately detecting the tracing pattern irrespective of whether the ground of an original is white or not. <P>SOLUTION: This apparatus is provided with a scanner for reading an image from an original, a yellow pixel detecting unit 21 and a pattern matching unit 22 for detecting an isolated point of the image data of the original read by the scanner, a dot detecting unit 23 for detecting dots of the image data of the original read by the scanner, and a tracing pattern determining unit 24 for detecting a tracing pattern included in the original from a detection result of the isolated point and a detection result of the dots. The unit 24 decided whether or not detection pattern detection should be performed or not on the basis of an image quality mode signal 3 to be inputted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention detects whether an input document is a generation document, and detects a tracking pattern included in the input document when a tracking pattern exists in the input document, and image formation provided with the tracking pattern detection device Relates to the device.

In recent years, improvement in image processing technology and image forming technology has made it possible to perform image formation so finely that copied banknotes copied by a color copying machine and actual banknotes cannot be easily distinguished. For this reason, an image forming apparatus having a function of determining a copy-prohibited document is provided in order to prohibit illegal copying of a copy-prohibited object in which copying of banknotes and securities is prohibited.

On the other hand, in corporate offices and the like, there are many copy-prohibited manuscripts that are prohibited from being copied from the standpoint of importance of document contents and confidentiality even in the case of general documents other than banknotes and securities. In general, such a copy-prohibited document is stamped with a secret seal, a copy-prohibited mark, and the like so as to be distinguished from a copy-capable document.

  On the other hand, recently, a method has been proposed in which information such as a device number, a manufacturing number, and a user ID of an apparatus is added to a copy as a tracking pattern in a color that is difficult to identify with human eyes. This method is a method of writing on the entire surface of the image with a certain dot size by a certain inconspicuous color (yellow). By applying this method to an image forming apparatus such as a copying machine and adding information to the copy, the origin of the copy can be traced.

Thus, for example, in Patent Document 1, when detecting a tracking pattern of a document (generation document) output by a color copying machine, a yellow isolated point on a white background (paper white) is detected, and the detection result is a generation document. If it is determined that the color correction parameter is selected, the color copy output color of the generation original is matched with the original to improve the image quality. As a related technique, for example, the invention described in Patent Document 2 or 3 is also known.
JP-A-9-186901 JP-A-8-307656 Japanese Patent Laid-Open No. 10-108012

  However, in general, the tracking pattern is written on the entire image regardless of the density of the ground. Therefore, for example, when the entire surface of the output paper is a color background, the written tracking pattern cannot be detected by the method of detecting the yellow isolated point on the white ground. For example, when making a copy in the black and white mode, it is not necessary to select a color correction parameter in order to match a color even for a generation document.

  The present invention has been made in view of such a background, and an object of the present invention is to select whether or not to detect a tracking pattern depending on the image quality mode, and to accurately track whether or not the background of the document is a white background. It is to be able to detect a pattern.

  To achieve the object, the first means includes a reading means for reading an image from a document, an isolated point detecting means for detecting an isolated point of image data of the document read by the reading means, and a document read by the reading means. A halftone dot detecting means for detecting a halftone dot of the image data; and a tracking pattern detecting means for detecting a tracking pattern included in the document from the detection result of the isolated point detecting means and the detection result of the halftone dot detecting means. The tracking pattern detection means determines whether or not to perform tracking pattern detection based on an input image quality mode signal.

  The second means is characterized in that, in the first means, the isolated point detected by the isolated point detecting means is a yellow isolated point.

  A third means is characterized in that, in the first means, the halftone dots detected by the halftone detection means are yellow halftone dots.

  The fourth means is characterized in that the image forming apparatus includes a tracking pattern detection device according to any one of the first to third means.

  In the embodiment described later, the reading means is the scanner 1, the isolated point detecting means is the yellow pixel detecting section 21 and the pattern matching section 22, the halftone detecting means is the halftone detecting section 23, and the tracking pattern detecting means is the tracking. This corresponds to the pattern detection unit 2 and the tracking pattern determination unit 22, respectively.

According to the present invention, since it is possible to select whether or not to detect the tracking pattern according to the input image quality mode, it is possible to accurately detect the tracking pattern regardless of whether the background of the document is white.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a tracking pattern detection apparatus according to an embodiment of the present invention. In the figure, the tracking pattern detection apparatus basically includes a scanner 1 and a tracking pattern detection unit 2. The scanner 1 is configured by a color scanner that reads a document, and a tracking pattern is detected by the tracking pattern detection unit 2 when an RGB image signal read by the scanner 1 is input.

  FIG. 2 is a block diagram showing a detailed configuration of the tracking pattern detection unit 2 in FIG. The tracking pattern detection unit 2 includes a yellow pixel detection unit 21, a pattern matching unit 22, a halftone dot detection unit 23, and a tracking pattern determination unit 24. In the tracking pattern detection unit 2 configured in this way, it is determined whether the input RGB data is a yellow pixel or a yellow pixel in the yellow pixel detection unit 21. Here, it is determined by the following conditional expression whether or not the pixel is a white pixel using the RGB data of the target pixel.

Max {R, G, B} <thw (1)
Here, Max {R, G, B} represents the maximum value of R, G, B data. thw is a preset parameter.

Further, hue determination is performed, and it is determined by the following conditional expression whether or not the hue of the target pixel is in the yellow region.

RY hue region boundary determination R-2 × G + B> 0 (2)
YG hue region boundary determination 11 × R-8 × G-3 × B> 0 (3)
Further, it is determined by the following conditional expression whether the maximum color difference of RGB of the target pixel is larger than the threshold value thy.

Max {R, G, B} -Min {R, G, B}> thy (4)
Here, Max {} represents the maximum value in {}, and Min {} represents the minimum value in {}.

  And the pixel which satisfy | fills all the said (1)-(4) conditions is determined as a yellow pixel.

The result determined to be a yellow pixel by the yellow pixel detection unit 21 is sent to the pattern matching unit 22, and a yellow isolated point is detected by performing pattern matching as shown in FIG. In FIG. 3, the pixel at the center of the 7 × 21 pixel matrix (the pixel marked with “X” in the figure) is the target pixel. For example, in the range of 7x21 pixels,
Yellow isolated point = {the pixel of interest (the pixel marked with x) is a yellow pixel} and {the pixel other than the pixel in the center 5 × 5 matrix (the pixel with a halftone dot) is not a yellow pixel}
If the condition is met, it is determined as a yellow isolated point and output.

  Further, the B signal from the scanner 1 is input to the halftone dot detection unit 202, and it is determined whether or not the pixel of interest is a yellow halftone dot.

  In the halftone dot region, pixels having a high density value and pixels having a low density value appear alternately and periodically. The halftone dot region extraction unit 102 identifies the halftone dot region by detecting the extreme value pixel having the high density value or the low density value. A specific example of the halftone dot region extraction unit 23 is shown in FIG.

  In FIG. 4, the extreme pixel detection unit 23-1 detects an extreme pixel by calculation. In the present embodiment, as shown in FIG. 5, when the following conditions A and B are simultaneously satisfied in a 3 × 3 pixel block, the center pixel is detected as an extreme pixel.

Condition A: The density level (L) of the central pixel is higher or lower than the density level of any surrounding pixels.
Condition B: The density level (L) of the center pixel and the density levels (a, b) of the paired pixels on the diagonal line across the center pixel are all about four pairs.
| 2 × L-a-b |> TH
Are in a relationship. However, TH is a fixed threshold value.

  The halftone dot region detection unit 23-2 determines that the block is a halftone dot candidate region if one or more extreme pixel values detected by the extreme pixel detection unit 23-1 exist in the 4 × 4 pixel unit block. If there is no extreme value pixel, the block is determined as a non-halftone dot candidate region. In response to this determination result, the halftone dot region correction unit 23-3 performs final halftone / non-halftone dot determination. In the present embodiment, as shown in FIG. 6, in a 3 × 3 block (1 block is 3 × 3 pixels) centered on the target block, if four or more blocks are halftone dot candidate regions, the target block is represented as a halftone dot region. Otherwise, the attention block is set as a non-halftone area. Then, “0” is output in correspondence with the pixels in the flock set as the halftone dot region, and “1” is output corresponding to the pixels in the block in the non-halftone region.

From the yellow isolated point detection result and halftone dot detection result obtained as described above, the tracking pattern determination unit 24 makes the determination. The judgment formula is
Tracking pattern = (yellow isolated point detection result is ON) and (halftone detection result is OFF)
If the above judgment formula is not satisfied, it is not a tracking pattern.

By doing so, it becomes possible to detect the tracking pattern with high accuracy regardless of whether the color background or the white background.

  The image quality mode signal 3 is input to the tracking pattern determination unit 24. For example, when the image quality mode signal 3 is in the monochrome mode, the output of the tracking pattern determination unit is forcibly turned off, and when it is in the color mode, it is turned on and the tracking pattern determination result is output.

  FIG. 7 is a diagram showing a schematic configuration of a color printer as a color image forming apparatus according to an embodiment of the present invention. In FIG. 1, the color printer basically includes an image forming unit 100, a paper feed unit 200, a fixing unit 300, and a paper discharge unit 400.

  The image forming unit 100 includes CMYK photosensitive drums 101C, 101M, 101Y, and 101K, a writing unit for each color (not shown) that performs optical writing on the photosensitive drums 101C, 101M, 101Y, and 101K, and a photosensitive drum. Contact with the body drums 101C, 101M, 101Y, and 101K, and face the photosensitive drums 101C, 101M, 101Y, and 101K with the transfer belt 102 sandwiched between the drive pulley and the driven pulley, and the transfer belt 102 interposed therebetween. The transfer roller 103C, 103M, 103Y, 103K provided at the position where the transfer is performed, and the transfer roller 105 provided downstream of the black transfer portion and sandwiching the vertical conveyance path 105 are mainly configured.

  The sheet feeding unit 200 conveys the first and second sheet feeding trays 210 and 220 and the transfer sheets 212 and 222 fed from the sheet feeding trays 210 and 220 by the sheet feeding rollers 211 and 221 to the longitudinal conveyance path 105. A transfer sheet conveyance path 106 for manual transfer, and a manual feed tray 230 for manually feeding the transfer sheet to the vertical conveyance path 105.

  The fixing device 300 is provided on the downstream side of the longitudinal conveyance path 105 in the transfer sheet conveyance direction, and includes a fixing roller 310, a heating roller 320, a fixing belt 330, and a pressure roller 340.

  The paper discharge unit 400 is provided on the downstream side of the fixing device 300 in the transfer paper conveyance direction, and includes a paper discharge roller 410 and a paper discharge tray 420.

  In the color printer configured as described above, the transfer paper fed from the paper feed trays 210 and 220 or the manual feed tray 230 is sent out to the vertical conveyance path 105 and is formed by the image forming unit 100 that performs development and transfer. A full-color image superimposed on the surface of the transfer belt 102 is transferred onto the transfer paper by the transfer roller 104. The unfixed image transferred onto the transfer paper is sent to the fixing device 300 and is formed by a fixing roller 310 and a pressure roller 340 that are driven and driven inside the fixing belt 330 whose surface is heated by a heat source such as a heater. As a result, the sheet is fixed on the surface of the transfer paper and becomes a semi-permanent image, and is discharged to the discharge tray 420.

  As described above, according to this embodiment, since the output image quality mode is input to the tracking pattern determination, the tracking pattern determination can be turned ON / OFF according to the output image quality mode. Further, since the tracking pattern is determined by combining the yellow isolated point detection result and the yellow halftone dot detection result, the tracking pattern can be detected regardless of whether it is a color background or a white background.

It is a block diagram which shows schematic structure of the tracking pattern detection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the detailed structure of the tracking pattern detection part 101 in FIG. It is explanatory drawing of the pattern matching for a yellow isolated point detection. It is a block diagram which shows an example of a halftone dot area extraction part. It is a figure for explanation of extreme value pixel detection. It is a figure for demonstrating halftone dot area | region correction | amendment. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scanner 2 Tracking pattern detection part 3 Image quality mode signal 21 Yellow pixel detection part 22 Pattern matching part 23 Halftone detection part 24 Tracking pattern determination part

Claims (4)

Reading means for reading an image from a document;
An isolated point detecting means for detecting an isolated point of image data of a document read by the reading means;
Halftone dot detecting means for detecting a halftone dot of the image data of the document read by the reading means;
From the detection result of the isolated point detection means and the detection result of the halftone detection means, tracking pattern detection means for detecting a tracking pattern included in the document,
With
The tracking pattern detection unit determines whether or not to perform tracking pattern detection based on an input image quality mode signal.   2. The tracking pattern detection apparatus according to claim 1, wherein the isolated point detected by the isolated point detecting means is a yellow isolated point.   2. The tracking pattern detection apparatus according to claim 1, wherein the halftone dots detected by the halftone dot detection means are yellow halftone dots.   An image forming apparatus comprising the tracking pattern detection device according to claim 1.

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