JP4272366B2 - Document reading apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet-through-scan type document reading device that transports a document in the sub-scanning direction with respect to the document reading position and reads an image of the document that passes through the image reading position, and an image using this type of document reading device. The present invention relates to a forming apparatus.
[0002]
[Prior art]
There are two types of document feeders: a flat bed type and a sheet-through type. As digitalization has recently become popular, the use of sheet-through type document feeders has increased. In the flat bed type, a document that has been fed is temporarily stopped on a contact glass, and an exposure lamp and a condenser (including a mirror that moves following the document) are moved along the document surface. In the reading method, the sheet-through type means that the exposure lamp, the condenser, and the mirror are in a stopped state, and the original is moved using the condenser and the mirror while the exposure lamp is turned on. Is a method of reading. This sheet-through type has the advantage that the structure of the document supply device is mechanically simple and can be provided at low cost, and has become widespread recently.
[0003]
As a typical example of such a sheet-through method, for example, an invention disclosed in Japanese Patent Application Laid-Open No. 2000-31082 is known. This example is shown in FIG. 6 and FIG. 7, and the description of the publication is cited.
[0004]
In FIG. 6, the original 50 placed on the original table 2 is conveyed one by one to the original reading position 52 shown in FIG. The registration switch 4 and the registration roller 5 serve to regulate the front end of the document by regulating the oblique feeding of the document 50 before the document 50 is conveyed to the reading position 52. The timing switch 6 determines the image leading edge timing of the document 50 being conveyed, and a signal obtained from the timing switch 6 is transmitted as information to a control device inside the digital copying machine 200. Reference numeral 9 denotes a first mirror, 7 denotes a second mirror, and 8 denotes a third mirror. Reference numeral 10 denotes a lens system, and 11 denotes an image sensor composed of a CCD.
[0005]
FIG. 7 is a diagram showing a reading mechanism unit in the document reading apparatus. In the figure, a pair of feed roller 3 and separation roller 21 are conveyed one by one from a bundle of a group of documents 50 placed on the document table 2. The timing switch 6 detects the leading edge of the document 50 and adjusts the reading timing of the conveyed document 50. The original 50 illuminated by the exposure lamp 28 is read at a predetermined reading position 52, and the obtained image information is stored in a memory inside the digital copying machine 200. When the reading of the document 50 by the image sensor 11 is completed, the upper discharge roller 24 and the lower discharge roller 25 are rotated, and the document is discharged to the discharge tray of the document feeder 1. Thereafter, the document 50 placed on the document table 2 is sequentially read.
[0006]
As described above, in the sheet-through type document feeder, since the document is conveyed and read while the optical system is stopped, the mechanism is simple and the document feeder and the document reader can be configured at low cost. However, the image quality of the read image may be a problem.
[0007]
For example, in the case of a conventional reading device, if there is dust or scratches on the reading surface, the image quality deteriorates due to black spots, but in the case of a sheet-through type document feeder, the document moves. If there is dust or scratches at the reading position, it will remain as a black streak and image quality will be significantly degraded.
[0008]
In order to prevent such image quality deterioration, for example, in Japanese Patent Laid-Open No. 2000-50023, read data from a document feeder is stored in a memory for one document, and when black streaks are detected, a document is inserted into the document feeder. The position is mechanically moved and the original is read again to replace the data in the black line portion on the frame memory. Although this method can correct black streaks with considerable accuracy, it requires a mechanical structure that automatically moves the document insertion position when black streaks are detected, and requires more than one frame memory. It is necessary and various restrictions that the document must be scanned twice are difficult to realize.
[0009]
In Japanese Patent Laid-Open No. 2000-310820, data is read before a document arrives at the reading position, and when black streaks are detected, the position of the lamp and mirror is moved in the sub-scanning direction until dust is no longer detected. The document reading is disclosed. However, in this example, the frame memory is not required as in the invention described in Japanese Patent Laid-Open No. 2000-50023, and the scanning twice is not necessary. is there.
[0010]
FIG. 8 is a block diagram showing a schematic configuration of the entire system using a conventional document reading apparatus. This system includes a scanner 101 serving as a document reading device, a sheet-through document feeding device (sheet-through DF) 102 that feeds a document to a document reading position of the scanner 101, and document reading data read by the scanner 101. The image processing unit (IPU) 103 that performs image processing, and the control of the IPU 103 such as setting of parameters necessary for image processing in the IPU 103, the CPU 104 that controls the entire system, and the image data output from the IPU 103 A printer 105 that forms a visible image on a sheet is basically configured. In this system, an original is supplied by the sheet through DF 102, the original is read by the scanner 101, a series of image processing is performed in the IPU 103, image data is output to the printer 104, and paper out is performed. Parameters necessary for image processing in the IPU 103 are set by the CPU 104.
[0011]
In JP 2000-196881 A, one or more lines of data before a document is inserted are read, whether or not there is dust is detected, and if there is dust, the coordinate value is stored, When actually reading a document, a technique is disclosed in which a reading value of dust coordinates is not used, and the pixel data is replaced with surrounding pixel data. That is, as shown in FIG. 9, the scanner reading data is processed in the order of shading correction 201, vertical stripe correction 202, scanner gamma, filter, printer gamma, and gradation processing to correct vertical stripes.
[0012]
FIG. 10 is a block diagram showing the configuration of the vertical stripe correction unit 202 in FIG. The vertical line correction unit 202 includes two processing units, a black line detection unit 301 that detects whether there is dust, a black line correction unit 302 that performs interpolation processing using a peripheral image when there is dust, and a memory. (FIFO) 303.
[0013]
FIG. 11 is a block diagram showing details of the vertical stripe correction unit of FIG. In this embodiment, the black stripe detection unit 301 performs binarization processing 3011, and the black stripe correction unit 302 performs interpolation processing 3021. There are several methods for detecting black streaks. Eventually, binarization is performed, and a dust on / off flag is set at 1 bit per pixel. The binarization may be a simple binarization as shown in FIG. 12, or a method of finally determining dust from the gradient of the surrounding three pixels, for example.
[0014]
When black stripes are detected, first, the exposure lamp 28 is turned on and a dust on / off flag is written in the memory 303 before the original is inserted into the reading position. The black stripe correction unit 302 performs only the interpolation process 3021 and outputs the input data as it is when the dust is off. However, when the dust is on, the input data is subjected to a certain correction process to prevent the occurrence of vertical stripes. Yes. In the case of the example in FIG. 13, a pixel with the number “1” is a pixel that is determined to be dust-on by black streak detection, and is replaced with an adjacent pixel when dust-on. Although there are several methods for interpolation processing, interpolation processing may be performed using data that is two pixels away from the left and right.
[0015]
The above is the details of the vertical stripe correction processing that has been conventionally performed, in other words, the black stripe correction processing.
[0016]
[Problems to be solved by the invention]
This conventional technique is a highly feasible method that does not require a mechanical mechanism, but is limited to a black and white reader that detects black stripes and corrects black stripes. It cannot be applied to the reading device as it is.
[0017]
The present invention has been made in view of the above points, and an object of the present invention is to provide an original reading apparatus capable of correcting color stripes even in sheet-through full color reading without requiring an additional mechanism in the original feeding apparatus. It is to provide.
[0018]
Another object of the present invention is to provide an image forming apparatus provided with an original reading device capable of correcting a color stripe even in sheet full color reading without requiring an additional mechanism in the original feeding device.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, the first means reads a document using a sheet-through type document feeder and converts the read color image information into a digitally converted image signal. And a storage means for detecting dust on the basis of data between a position corresponding to the document surface and between the document reading elements and storing at least one line or more of dust position data ; Correction means that reads out the dust position data stored in the storage means and corrects the original reading data, and the storage means includes a signal converted from input image data into a luminance / color difference signal. storing captures position data of the dust obtained from the luminance signal, said correction means to the luminance signal stored in said storage means And by performing an interpolation process, and corrects the image data all colors inputted to inverse transform the luminance and color difference signals.
[0022]
The second means is a document reading device that reads a document using a sheet-through type document feeder and converts the read color image information into a digitally converted image signal before the document is inserted into the reading position. A storage unit that performs exposure in stages, detects dust based on data between a position corresponding to a document surface and a document reading element, stores at least one line of dust position data, and is stored in the storage unit when reading a document. A correction unit that reads out the dust position data and corrects the document reading data; and a storage data generation unit that generates the dust position data stored in the storage device from a plurality of colors. the data generated by the stored data creation means stores as Gomion / off data, it said correction means setting for each color It is, and correcting for each color.
[0023]
The third means is characterized in that, in the second means, the storage data creation means is dust on / off data for storing an OR signal from the input RGB image data in the storage means.
[0024]
According to a fourth means, the image forming apparatus comprises the original reading device according to the first to third means and the image forming means for forming a visible image on the medium based on the image data read by the original reading device. It is characterized by comprising.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Since the system itself including the sheet-through type document feeder and the scanner is the same as the above-described conventional example, the same reference numerals are given to the same parts, and the duplicated explanation is omitted as appropriate.
[0026]
<First Embodiment>
FIG. 1 is a block diagram showing details of the IPU 103 according to the first embodiment of the present invention. The IPU 103 is the one shown in FIG. In this embodiment, a shading correction unit 1031 that performs shading correction on input image data of three colors R (red), G (green), and B (blue), and a line between lines into which image data after shading correction is input. The correction unit 1032 includes a vertical stripe correction unit 1033 to which image data corrected between lines is input. In this embodiment, R image data is directly input to the shading correction unit 1031, and G image data and B image data are input to the shading correction unit 1031 via the line memories 1034 G and 1034 B, respectively.
[0027]
FIG. 2 is a block diagram showing an internal configuration of the vertical stripe correction unit 1033 according to the embodiment of the present invention. The vertical stripe correction unit 1033 includes a color stripe detection unit 10331, a color stripe correction unit 10332, and a memory 303, as can be seen from FIG. In the present embodiment, the conventional input / output image having one 8-bit system becomes 8-bit three-system data in order to handle a full-color image. In the conventional example shown in FIG. 5, black streak detection and black streak correction are performed. However, in this embodiment, color streak detection and color streak correction are performed for each color.
[0028]
FIG. 3 is a block diagram showing an internal configuration of the color streak detection unit 10331 and the color streak correction unit 10332 of FIG. The color stripe detection unit 10331 includes a luminance / color difference conversion unit 10331a and a binarization unit 10331b, and the color stripe correction unit 10332 includes an interpolation processing unit 10332a and a luminance / color difference reverse conversion unit 10332b. In the color streak detection unit 10331, the input RGB signal is converted into a luminance / color difference signal by the luminance / color difference conversion unit 10331a, dust is detected from only the luminance signal by the binarization unit 10331b, and the interpolation processing unit 10332a Interpolation processing itself is intended only for luminance signals. The binarization process and the interpolation process are the same as those in the conventional example described with reference to FIGS. Therefore, the memory 303 having the dust information can be processed with the same memory capacity of 1 line × 1 bit as in the prior art. Note that the interpolation using only the luminance signal is based on the fact that the color information hardly changes in adjacent pixels.
[0029]
Other parts not specifically described are configured in the same manner as the conventional example described above and function in the same manner.
[0030]
<Second Embodiment>
FIG. 4 is a block diagram showing details of the vertical stripe correction unit 1033 according to the second embodiment. In this embodiment, the luminance / color difference conversion unit 10331a and the luminance / color difference reverse conversion unit 10332b are omitted from the first embodiment, dust detection is performed only from G data, and interpolation processing is performed only for G data. It is. This utilizes the fact that even if full-color reading is performed, if the output color is monochrome data or single color data, processing is performed mainly using only G data. Therefore, this method is applied only for monochrome printing in full color reading. The binarization process and the interpolation process are the same as those in the conventional example described with reference to FIGS. The memory 303 having the dust information can also be processed with the same memory capacity of 1 line × 1 bit as in the prior art.
[0031]
Other parts not specifically described are configured in the same manner as the conventional example and the first embodiment, and function in the same manner.
[0032]
<Third Embodiment>
FIG. 5 is a block diagram showing details of the vertical stripe correction unit 1033 according to the third embodiment. In this embodiment, dust detection is performed using data for all RGB colors, and the same interpolation processing is performed on data for all RGB colors. In this embodiment, the color streak detection unit 10331 calculates the logical sum of the binarization outputs of the binarization units 10331R, 10331G, and 10331B provided for each RGB data and the binarization units 10331R, 10331G, and 10331B. The color streak correction unit 10332 includes interpolation processing units 10332R, 10332G, and 10332B that perform interpolation processing for each color.
[0033]
This is because there are three CCDs for RGB during full-color reading, and they are always 4 lines apart at the same magnification. For example, even if only one color of RGB is used for dust correction, only another color CCD is used. If small dust is placed on the image, dust interpolation cannot be performed for that color, resulting in a color streak. This is a correction process applied in such a case. In the vertical streak correction unit 1033 shown in FIG. 5, the color streak detection unit 10331 obtains binarized data by the binarization units 10331R, 10331G, and 10331B for each GB data, and obtains a dust candidate for RGB. Then, each of the RGB dust candidates is ORed by the OR circuit 10331c to obtain a final dust on / off signal. As the interpolation processing, the result of ORing by the interpolation processing units 10332R, 10332G, and 10332B is performed on all RGB data. In this way, even RGB that need not be interpolated is interpolated, but the occurrence of color streaks can be suppressed by performing interpolation processing independently. This method may be the same as the conventional method regarding the binarization processing and the interpolation processing, and the memory 303 having the dust information can be processed with the same memory capacity of 1 line × 1 bit as the conventional method.
[0034]
Other parts not specifically described are configured in the same manner as the conventional example and the first embodiment, and function in the same manner.
[0035]
【The invention's effect】
As described above, according to the present invention, without requiring additional mechanisms originals feeder, also during full-color reading of a sheet-through method to provide a document reading apparatus or an image forming apparatus capable of correcting the color stripe Can do .
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating details of an IPU processing unit of an image reading apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating details of a vertical stripe correction unit of the IPU processing unit according to the embodiment of the present invention.
FIG. 3 is a block diagram illustrating details of a vertical stripe correction unit according to the first embodiment.
FIG. 4 is a block diagram illustrating details of a vertical stripe correction unit according to a second embodiment.
FIG. 5 is a block diagram illustrating details of a vertical stripe correction unit according to a third embodiment.
FIG. 6 is a schematic configuration diagram illustrating an entire seat-through DF that has been conventionally performed.
7 is an enlarged view of a document reading portion of the sheet-through DF shown in FIG.
FIG. 8 is a block diagram showing an entire digital copying machine with a sheet-through DF that has been conventionally implemented.
FIG. 9 is a block diagram illustrating details of an IPU processing unit according to a conventional example.
10 is a block diagram showing a configuration of a conventional vertical stripe correction unit in FIG. 9. FIG.
11 is a block diagram showing details of a vertical (black) streak correction unit in FIG. 10. FIG.
12 is an explanatory diagram showing an example of binarization of the black stripe correction unit in FIG. 11. FIG.
13 is an explanatory diagram illustrating an example of interpolation processing of a black stripe correction unit in FIG. 11. FIG.
[Explanation of symbols]
101 Scanner 102 Sheet through DF
103 IPU
1031 Shading correction unit 1032 Interline correction unit 1033 Vertical line correction unit 10331 Color streak detection unit 10331a Luminance / color difference conversion unit 10331b Binary unit 10331c OR circuit 10332 Color streak correction unit 10332a Interpolation processing unit 10332b Luminance / color difference reverse conversion unit 10332R Interpolation processing unit 10332G Interpolation processing unit 10332B Interpolation processing unit 104 CPU
105 Printer 301 Black Line Detection Unit 302 Black Line Correction Unit 303 Memory (FIFO)

Claims (4)

In a document reading device that reads a document using a sheet-through type document feeder and converts the read color image information into a digitally converted image signal.
Storage means for performing exposure in a previous stage where a document is not inserted at a reading position, detecting dust based on data between a position corresponding to a document surface and a document reading element, and storing at least one line of dust position data ;
Correction means for reading position data of the dust stored in the storage means at the time of reading a document and correcting the document reading data;
With
The storage means captures and stores the dust position data obtained from the luminance signal among the signals converted from the input image data to the luminance / color difference signal,
The original reading apparatus characterized in that the correction means performs an interpolation process on the luminance signal stored in the storage means, and reversely converts the luminance / color difference signal to correct all the input image data colors. In a document reading device that reads a document using a sheet-through type document feeder and converts the read color image information into a digitally converted image signal.
Storage means for performing exposure in a previous stage where a document is not inserted at a reading position, detecting dust based on data between a position corresponding to a document surface and a document reading element, and storing at least one line of dust position data ;
Correction means for reading position data of the dust stored in the storage means at the time of reading a document and correcting the document reading data;
Storage data creation means for creating position data of the dust stored in the storage device from a plurality of colors;
With
The storage means stores the data created by the stored data creation means as garbage on / off data ,
An original reading apparatus, wherein the correction means is provided for each color and corrects for each color. 3. The document reading apparatus according to claim 2, wherein the storage data creating means is garbage on / off data for storing an OR signal from the input RGB image data in the storage means. The document reading device according to any one of claims 1 to 3,
Image forming means for forming a visible image on a medium based on image data read by the document reading device;
An image forming apparatus.

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