JP2006211054A - Image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor capable of eliminating a trouble such that existence of foreign matters appears as a streak continuous in the sub-scanning direction. <P>SOLUTION: The image processor is provided with an image processor 19 for specifying flaws and dirt positions existing on the face of a white roller by reading a reading position mark 15a which is provided on the face of the white roller 15, after verifying white reference data generated on the basis of line data which are obtained by reading the face of the rotating white roller 15 at a reading position for an original manuscript of plural lines with a reading sensor 7 before reading the original manuscript; and a storage means 31 for storing abnormalities of the specified positions. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus that captures image data using a line sensor in an image scanner, a facsimile machine, a copying machine or the like.

Conventionally, in image reading, it is known that streaks that do not exist in a document occur in the sub-scanning direction in the read image data (see, for example, Patent Documents 1 and 2).
It is known that such a streak in the sub-scanning direction is generated by reading some foreign matter on the optical path when reading a document or reading reference data for shading correction.
JP 2002-290671 A JP 2002-152510 A

As described above, in the conventional image processing apparatus, when foreign matter exists at the reading position for each line input to the reading sensor, the streak connected in the sub-scanning direction by the reference white data used for each line for the reading and shading correction processing. Therefore, it is desired to solve this problem.
SUMMARY OF THE INVENTION An object of the present invention is to provide an image processing apparatus that can eliminate the problem that the presence of foreign matter appears as a streak continuous in the sub-scanning direction in consideration of the above situation.

In order to solve the above problems, the invention according to claim 1 is an image processing in which image data is read by a reading sensor of a reading optical system fixed at a predetermined position while a document is conveyed, and the read image data is processed. In the apparatus, white reference data generated based on line data read by the reading sensor is verified at a plurality of line document reading positions before reading the rotating white roller surface, and reading provided on the white roller surface is performed. An image processing unit that specifies a position of a scratch or a dirt existing on the white roller surface by reading a position mark, and a storage unit that stores an abnormality of the specified position are provided.
The image processing according to claim 1, wherein the white reference data is read after the white roller is rotated in advance so that the specified scratch or dirt position is not captured as the white reference data. Features the device.
According to a third aspect of the present invention, when the density reduction occurs in the white reference data, the image processing means has a cause of causing the density reduction in the contact glass between the reading sensor and the white roller. The image processing apparatus according to claim 2, further comprising a determination unit that determines that

  According to the present invention, white reference data generated based on line data obtained by reading a plurality of lines of the white roller surface while rotating the document conveying roller (white roller) at the document reading position before document reading is verified. Since the reading position mark on the surface is read, the position of scratches and dirt existing on the surface of the white roller is specified, and the position can be stored in the storage means, so the presence of foreign matter continues in the sub-scanning direction. The problem that appears as a streak can be solved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram for explaining an embodiment of an image scanner equipped with an image processing apparatus of the present invention.
The image scanner shown in FIG. 1 includes an automatic document feeder (ADF) 2. A document (not shown) is set on a document table 11 and image data is read while the document is conveyed.
A document discharge table 3 is provided below the document table 11, and the document that has been read is discharged to the document discharge table 3. This constitutes a document conveyance processing unit of the image scanner.
In this case, inside the image scanner main body 1 is an exposure scan comprising a light source 4a, a mirror 4b, a lens 6 and a line sensor (a CCD is used in this embodiment) 7 having a one-dimensional photoelectric conversion element. An optical system 9 is provided. The description of the lower structure of the exposure scanning optical system 9 is omitted here.
A stepping motor 12 is provided in the ADF 2 configured as the unit 10. Further, a white reference plate (white roller) 15 for performing shading correction is disposed inside the image scanner main body 1 with moving means (not shown). When the white reference plate 15 is read, the white reference plate 15 is moved to a scan line position (a reading position when an image is read by conveying an original) and read.

FIG. 2 is a schematic block diagram showing the configuration of a control circuit for processing image data read by the exposure scanning optical system of the image scanner of FIG. FIG. 3 is a schematic diagram for explaining the basic operation of image data reading in the ADF mode of the image scanner of FIG.
The CPU 16 shown in FIG. 2 operates a light source driver (light source lighting device) 17 to turn on the light source 4a. Further, the white reference plate 15 shown in FIG. 1 is moved to a predetermined reading position so as to cause the CCD 7 to read white reference data.
The image data read by the CCD 7 is converted from analog to digital by an A / D converter (not shown) in the image processing unit 19 and connected to the image processing unit 19 as reference data for shading correction of the image data. Store in the line buffer 31. At the same time, the CPU 16 drives the stepping motor 12 by a motor driver (drive device) 28.
As a result, the document 13 (FIG. 3) set on the document table 11 is conveyed by the separation roller 29 and the conveyance roller 30 and conveyed to a predetermined reading position. At this time, the document 13 is conveyed at a constant speed, and the image data on the surface of the document 13 is read by the CCD 7.
2 and 3, although not described in detail, an ADF 2 configured as a unit 10, a mirror 4b, a white reference plate 15, a CCD drive unit 18, a scan buffer 25, and an I / F controller 26 are shown. .

FIG. 4 is a block diagram showing a basic internal configuration of the image processing unit of FIG.
The analog video signal a photoelectrically converted by the CCD 7 in FIG. 2 is processed in the analog video processing unit 21 until digital conversion. Thereafter, the shading correction processing unit 22 and the image data processing unit 23 perform shading correction and various types of image data processing, respectively.
After performing various kinds of image data processing on the analog video signal a as described above, a binarization processing unit (image data output unit) 24 creates desired binarized data b that has been binarized. Here, an example is shown as a binarization processing unit, but the same applies to multi-value processing.
Thereafter, the binarized data b is sequentially stored in the scan buffer 25 (FIG. 2). The I / F controller 26 (FIG. 2) performs control to output the data in the scan buffer 25 to an external host computer (not shown) or the like. The buffer controller 27 (FIG. 2) performs input / output management of image data to the scan buffer 25.
FIG. 5 is a schematic circuit diagram showing the image data processing unit related to the present invention in FIG. 4 subdivided and extracted. Explaining each part in the figure, the original 13 on the scan line is illuminated from the light source 4a, the reflected light is condensed by the lens 6 through the shading adjustment plate 32, and the line sensor (CCD) 7 forms an image. .
In FIG. 5, a mirror for folding the reflected light is omitted for the sake of simplicity. The shading adjustment plate 32 shown in this embodiment plays the role of adjusting the amount of light for eliminating the difference in the amount of reflected light between the center and the end of the line sensor 7.
This is because, in the shading calculation process, if there is too much difference in the amount of reflected light between the center and end of the line sensor, only the calculation result including distortion is obtained. This is for performing arithmetic processing.
In FIG. 5, the signal from the line sensor 7 is processed through a preamplifier circuit 33, a variable amplifier circuit 34, an A / D converter 35, a black correction calculation circuit 36, and a shading correction calculation circuit 37, and is output to the next stage process.

FIG. 6 is a diagram showing the reproduction level distribution when the video data of the white reference plate is read when there is no shading adjustment plate. FIG. 7 is a diagram showing a level distribution when a shading adjustment plate is used.
As an example showing the function of the shading adjustment plate, FIG. 6 shows a reproduction level distribution when the video data of the white reference plate is read without the adjustment plate. As shown in FIG. 6, the level at the center is high, and the level falls at the end. FIG. 7 shows the level distribution when the shading adjustment plate is used, and it is not in a state where the level is high at the center and the level is lowered at the end.
As shown in FIG. 5, after performing photoelectric conversion by the line sensor 7, level adjustment is performed as analog video data, and digital conversion is performed by the A / D converter 35. In the digitized video data, the black offset portion is removed by arithmetic processing (black correction arithmetic circuit 36) and sent to the shading correction arithmetic circuit 37.
Although not described in detail, the black offset at this time includes a difference between channels when the output from the line sensor 7 has a two-channel configuration. The main purpose of the arithmetic processing here is to remove a difference component between channels in particular.
For shading correction calculation, the reference data read from the white reference plate (FIG. 1) is stored in the line buffer 31 (FIG. 2), and shading is performed between the reference data and the original read data when actually reading the original. Arithmetic processing is performed and output as image data to the next stage processing unit.

FIG. 8 is a schematic diagram showing an extracted optical reading system in order to explain the detection process of scratches and dirt on the white roller surface.
FIG. 8 shows an optical reading system, a white roller, and a reading glass 38 having an excerpted configuration, and the processing for detecting scratches and dirt on the white roller surface will be described.
In FIG. 8, the white roller 15, the reading glass 38, and the image scanner main body 1 include a light source 4 a, a mirror 4 b, a lens 6, and a line sensor (CCD) 7 having a one-dimensional photoelectric conversion element. The optical path is shown schematically.
Referring to FIG. 8, in the image scanner of the present embodiment, in order to read a document while conveying a document (not shown), image data that enters from reading glass 38 is read. This position is a reading position when an image is read by conveying a document, and is usually called a scan line position.
Before reading the original image, the white reference data is read while rotating the white reference plate (white roller) 15. A shading correction process is performed based on the white reference data. First, the average of the density by the pixels of the read main scanning width of the white roller 15 read as processing is obtained.
FIG. 9 is a graph showing density distribution and a first average example. FIG. 10 is a graph showing a density distribution and a second average example thereof.
FIG. 9 shows a density distribution example in the case where there is relatively no density change in the main scanning direction of the image density that generated the white reference data when the white roller 15 (FIG. 8) is read.

FIG. 10 shows an example of density distribution when the density change is relatively large when the white roller 15 (FIG. 8) is read. In this distribution example, a level drop is recognized in the pixel of the part A and the pixel of the part B indicated by the arrows.
Abnormal pixels are detected by obtaining an average density value for the main scanning width obtained by reading a counter detection plate (not shown), and taking the difference between the average value for the main scanning width obtained for each pixel and the density level. If it is larger, an abnormal pixel candidate is determined. The magnitude of the difference is determined by a preset threshold value. An abnormal pixel candidate is extracted by this determination.
FIG. 11 is a diagram showing an excerpt of main scanning out of the abnormal pixel candidates extracted by taking the difference from the average density. Once the abnormal pixel candidates are extracted, it is detected how long the abnormal pixel candidates continue. That is, the size of the abnormal pixel candidate in the main scanning direction is detected.
In order to detect the size, a threshold value for size detection is set in advance. The pixel is detected as an abnormal pixel after being determined by the threshold value. According to this, A, B, C, and D pixels indicated by arrows in FIG. 11 are abnormal pixel candidates.
If the threshold of continuous pixels is considered as “2”, A and D are independent abnormal pixel candidates and do not match the set abnormal pixels. It is determined that this pixel portion is an abnormal pixel in the portion of B and C continuous abnormal pixel candidates that match. In this way, abnormal pixels can be detected.

FIG. 12 is a schematic view showing a white roller having a reading position mark.
When determining an abnormal pixel, in order to specify the line position of the white roller 15, the white roller having the reading position mark 15a as shown in FIG. 12 is read.
In this example, the reading position mark 15a is provided outside the transport of the document and does not hinder the document reading. The number of lines from this reading position to the line where the abnormality is detected is stored in a storage means (not shown).
The scratch or dirt position on the white roller 15 was specified as described above, and the line position was stored. By using this, when reading the white reference data, the white roller 15 is rotated in advance so that the scratch or dirt position is not taken in as the white reference data.
First, the reference position of the white roller 15 is detected by rotating the white roller 15 and detecting the reading position mark 15a. Next, the white roller 15 is rotated by the number of lines corresponding to the stored scratches or dirt positions, and white reference data is captured from the lines of the white rollers 15 from which the scratches or dirt positions have been removed. By this processing, white reference data that does not include scratches or dirt can be generated.
A method for detecting the presence or absence of abnormal pixels in the white reference data after performing the above-described processing will be described. In the above description, the method for detecting abnormal pixels by reading the white roller 15 has been described. However, similarly to this processing, processing is also performed on white reference data generated for reference data for shading correction.
This process is for detecting an image abnormality due to dirt or dust on the contact glass in addition to scratches or dirt on the white roller 15. By this processing, the detection result is displayed on an operation panel (not shown) or the like, thereby prompting cleaning of the contact glass (reading glass) 38 (FIG. 8) and removing dust.
Accordingly, even when the white reference data avoids scratches or dirt positions due to the rotation of the white roller 15, when the density drop occurs, the density drop occurs in the contact glass 38 between the reading sensor 7 and the white roller 15. It can be determined that there is a cause such as dust adhesion.

1 is a schematic diagram illustrating an embodiment of an image scanner equipped with an image processing apparatus of the present invention. FIG. 2 is a schematic block diagram showing a configuration of a control circuit for processing image data read by an exposure scanning optical system of the image scanner shown in FIG. 1. FIG. 2 is a schematic diagram illustrating a basic operation for reading image data in an ADF mode of the image scanner shown in FIG. 1. FIG. 3 is a block diagram illustrating a basic internal configuration of an image processing unit illustrated in FIG. 2. FIG. 5 is a schematic circuit diagram showing a fragmented and extracted image data processing unit according to the present invention shown in FIG. 4. It is a figure which shows the reproduction level distribution at the time of reading the video data of a white reference board when there is no shading adjustment board. It is a figure which shows level distribution at the time of using a shading adjustment board. It is the schematic which shows with the structure which extracted the optical reading system, in order to demonstrate the detection process of the damage | wound and dirt of a white roller surface. It is a figure which shows density distribution and the 1st average example with a graph. It is a figure which shows density distribution and the 2nd average example with a graph. It is a figure which shows the excerpt part of main scanning among what extracted the abnormal pixel candidate and took the difference with average density. It is the schematic which shows the white roller which has a reading position mark.

Explanation of symbols

  7 Reading sensor (CCD, line sensor), 15 White roller (original transport roller), 15a Reading position mark, 19 Image processing unit, 31 Storage means (line buffer), 38 Reading glass (contact glass)

Claims (3)

  In an image processing apparatus that reads image data by a reading sensor of a reading optical system fixed at a predetermined position while conveying a document, and processes the read image data, a rotating white roller surface is read by a plurality of line documents before reading the document. At the reading position, the white reference data generated based on the line data read by the reading sensor is verified, and the reading position mark provided on the white roller surface is read, whereby the position of scratches or dirt existing on the white roller surface An image processing apparatus comprising: an image processing unit that identifies a position and a storage unit that stores an abnormality of the identified position.   The image processing apparatus according to claim 1, wherein the white reference data is read after the white roller is rotated in advance so that the specified scratch or dirt position is not captured as the white reference data.   The image processing unit includes a determination unit that determines that the contact glass between the reading sensor and the white roller has a cause of density reduction when density reduction occurs in the white reference data. The image processing apparatus according to claim 2.

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