JP2004297691A - Image reader and image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically detect normal recovery of an abnormal pixel during original reading, and to prevent, as much as possible, a fine line from being extinguished by correction while preventing black streaks caused by the abnormal pixel by means of a correction function. <P>SOLUTION: The image reader is provided with: optical systems 232 to 237 for projecting an image on an original; an imaging device 207 for reading the image projected therewith; means 208 to 210 for converting the read image signal into image data; a means 30 for moving one of the original or the optical systems relative to the other in a sub-scanning direction across the reading field of view 240 extending in the main scanning direction of the optical systems; and an abnormal pixel detecting function 262 for detecting the pixel position of image data made abnormal by a foreign substance that appears in the reading field of view. Recovery detecting functions 264, 265 are provided for judging a predetermined change of the image data in the sub-scanning direction during original reading as disappearance of the foreign substance in a pixel position judged abnormal by the abnormal pixel detecting function. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for reading an image of a document with an image sensor, such as an image scanner, a facsimile, and a digital copying machine.
[0002]
[Prior art]
A sheet document or book document is placed on the contact glass plate, and the optical system is sub-scanned to scan the document to read the image on the contact glass plate. Is also a local point, so it becomes noise of an isolated point on the reproduced image and is not very noticeable. If dust or stains occur locally on the optical system, an image of the dust or stains is always projected on the image sensor along with the original image during sub-scanning. Alternatively, when reproduction drawing is performed on paper, if the dust or dirt has low-level light reflection, a black streak extending in the sub-scanning direction appears on the reproduced image. However, since the optical system is inside the casing, there is a low possibility that dust or dirt will adhere to the optical system. Is low.
[0003]
However, in image reading in which the image of the document is read by the image sensor while the document is being transported to the stationary reading optical system, that is, in sheet-through image reading, if the glass of the document reading unit is dirty, the image of the dirt will be lost. Since the image is always projected on the image sensor together with the original image during the transfer, that is, in the sub-scanning, when the image is reproduced and drawn on the display or on the paper based on the image data obtained by the reading, if the dirt is a low-level light reflection, the reproduced image is A black streak extending in the sub-scanning direction appears in FIG. White lines appear when the dirt is a high level of light reflection. Such a phenomenon often appears in a received image of a facsimile apparatus that performs sheet-through image reading. However, the same applies to a copying machine that performs similar image reading. The above-described phenomenon is conspicuous in sheet-through image reading in which a large number of documents are continuously sent to a reading unit one after another by an ADF (automatic document feeder). Even in the case of using the ADF, the original is fed onto the contact glass plate by the ADF and the optical system is sub-scanned with respect to the original to read the image on the contact glass plate. No streaks or white streaks appear.
[0004]
On the other hand, when the white reference plate for shading correction has dirt, white streaks appear when the dirt has a low reflection level, and black streaks appear when the dirt has a high reflection level. This may occur when shading correction is performed even when an image is read while the document is stationary or when a sheet-through image is read. However, since the white reference plate is separated from the document transfer path, the possibility that the white reference plate is contaminated by dust (paper dust, eraser dust, etc.) attached to the document during the transfer of the document is low. However, in sheet-through image reading, the original touches and passes through the reading window glass, so that there is a high possibility that the reading window glass becomes dirty with dust attached to the original.
[0005]
Japanese Patent Application Laid-Open No. 2001-257877 discloses that when a pixel at an abnormal level (abnormal pixel) is detected in reading a white plate, image data generated at the position of the abnormal pixel is read before and after the original image is read. An image reading apparatus that replaces image data calculated by interpolation using image data generated by normal pixels.
[0006]
Japanese Patent Application Laid-Open No. 2002-185720 discloses an image reading device that detects continuity of image data obtained by reading an image of a document, detects a black streak or a white streak, and corrects the image without the streak or white streak. Is described.
[0007]
[Patent Document 3] Japanese Patent Application Laid-Open No. 2002-247352 discloses that a reading unit reads a detection image for detecting dust on a contact glass constituting the document reading table 3 before reading a document. The read image of one line is binarized into a binary signal indicating whether it is a defective pixel or not and stored in a line memory. When reading an original image, the image at the defective pixel position is referred to by referring to the data in the line memory. The data describes an image processing apparatus to which an average value of peripheral pixels is assigned.
[0008]
Japanese Patent Application Laid-Open No. 2002-262083 discloses that in order to prevent the occurrence of black streaks and white streaks, an image is read without a document, edge enhancement processing is performed on image data, and then a defect pixel is detected. Abnormal pixel detection for binarizing into a binary signal indicating whether or not the pixel data is performed is performed two-dimensionally, and when reading a document image, image data of a peripheral pixel is used as image data at a defective pixel position by referring to data in a line memory. The image processing device to which the message is addressed is described.
[0009]
The general method of correcting the image data of the original reading that occurs at the position of the detected abnormal pixel is to read the original reading data value of the abnormal pixel from the reading data value of peripheral pixels considered to be normal during the original reading. Is estimated and replaced with the estimated calculated value. Although various methods are conceivable for estimation, a method that emphasizes continuity with peripheral pixels is basically effective. For example, one method is to calculate and replace data values by linear interpolation with adjacent pixels (FIG. 15).
[0010]
[Problems to be solved by the invention]
However, such a correction method has side effects that cannot be avoided in principle. This becomes apparent when the original read data value of the abnormal pixel includes a change point of the image such that it does not continue with the peripheral pixels. For example, if a black line having the same width as the abnormal pixel exists at the position of the abnormal pixel in the original image, the influence of the black line is hardly reflected on the read data of the peripheral pixels. (Line) is likely to disappear (FIG. 16).
[0011]
In general, considering that an original is composed of black or other color dots or line segments with respect to an original on a white background, the disappearance of the above-mentioned black line means that image = loss of information, and is reproduced. In a facsimile machine where it is spatially impossible to compare an image with a document, this can sometimes cause serious problems.
[0012]
Further complicating this problem is the limited timing of detecting an abnormal pixel. In order to detect an abnormal pixel, an object having a uniform density in the main scanning direction is read, and the read data is detected based on non-uniformity of brightness in the main scanning direction (FIG. 17). It is not possible to detect an abnormal pixel while reading a non-uniform and fluctuating density such as a manuscript, since the decrease in the brightness of the abnormal pixel is equivalent to the decrease in the brightness of a significant image portion on the manuscript (FIG. 18). Therefore, a method of detecting an abnormal pixel by reading a background plate opposing a glass surface of a reading unit immediately before reading, not during reading of a document, is generally used.
[0013]
For these reasons, conventionally, a pixel determined to be an abnormal pixel immediately before reading a document is often continuously corrected at least while reading one page of the document until the next abnormal pixel detecting operation. However, the reason for the occurrence of abnormal pixels is generally dust or dirt attached to the reading surface.However, during the detection operation immediately before reading the original, the existing dust moves along with the original reading and the abnormal pixels return to a normal state. It is not uncommon. Further, although the reading surface is clean, dust may adhere to the back plate facing the reading surface and may be erroneously detected as dust on the reading surface. Even in such a case, the pixel continues to be determined to be abnormal until the next abnormal pixel detection operation, and as a result of correcting over one page, any thin line at that position disappears from the reproduced image.
[0014]
The first object of the present invention is to automatically detect a normal restoration of an abnormal pixel during reading of a document image, and to prevent a black streak image caused by the abnormal pixel from being corrected by a correction function, and to minimize the disappearance of a fine line due to the correction. Is a second object.
[0015]
[Means for Solving the Problems]
As means for recognizing that the abnormal pixel has returned during reading of the original, the reading is performed by observing the original read data value before being corrected as the abnormal pixel. It is assumed that almost the same level of signal is output from the image sensor regardless of the density of the document surface while dust or the like in the document reading section that causes abnormal pixels blocks the light reflected from the document to the image sensor. Is done. On the other hand, when the dust or the like moves and the light reflected on the document surface is input to the image sensor, the image sensor outputs a signal having a level corresponding to the density of the document surface (FIG. 13). . Further, although the reading surface is clean, dust is attached to the back plate facing the reading surface. If the dust is erroneously detected as dust on the reading surface, when the original enters the field of view of the reading surface, the dust is removed. The effect is gone. Considering that a general document has many white portions, the signal level is almost always increased. The document reading apparatus of the present invention detects such a signal level behavior and detects the restoration of an abnormal pixel when reading a document.
[0016]
(1) An optical system (232 to 237) for projecting an image on a document; an image sensor (207) for reading an image projected by the optical system; a means for converting a read image signal into digital data, that is, image data ( Means (30) for moving at least one of the original and the optical system relative to the other in the sub-scanning direction across the reading field of view (240) that extends in the main scanning direction of the optical system. And an abnormal pixel detection function (262) for detecting a pixel position of image data that has become abnormal due to a foreign substance appearing in the reading field of view.
A recovery detection function (264, 265) for determining a predetermined change in the sub-scanning direction of the image data of the original read at the pixel position determined to be abnormal by the abnormal pixel detection function as the disappearance of the foreign matter; An image reading device (FIG. 8).
[0017]
In addition, in order to facilitate understanding, the symbols of the corresponding elements or corresponding items of the embodiment shown in the drawings and described later are added for reference as examples in parentheses. The same applies to the following.
[0018]
If the foreign matter detected as an abnormal pixel remains present without changing its position during reading of one page of the document, the image data of the document reading obtained at that position will not be scanned even if the scanning line changes, that is, Even if the process proceeds, it remains at substantially the same level, and the data value does not change in the sub-scanning direction. However, if a foreign substance adheres to the original during reading of one page of the original and comes out of the reading unit, the brightness of the image on the original is not always the same as the brightness of the foreign substance. Is changed from the brightness of the foreign matter to the brightness of the document image. This change is detected by the recovery detection function (264, 265), and it is determined that the foreign matter has disappeared. Further, although the reading surface is clean, dust is attached to the back plate facing the reading surface, and if this is erroneously detected as dust on the reading surface, when reading the original is started, the dust is removed from the original. Since it is located on the back side, the image data of the document read at the position of the abnormal pixel changes from the brightness of the foreign substance to the brightness of the document image. This change is detected by the recovery detection function (264, 265), and it is determined that the foreign matter has disappeared. If the image data correction of the original reading at the position of the abnormal pixel is canceled based on this determination result, there is no possibility that the thin line disappears due to the correction.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
(1a) an abnormal pixel correction function (266) for replacing an image data value of a document read with another value;
The abnormal pixel detection function (262) detects whether the image data of the non-image portion (BP) projected by the optical system (232 to 237) has abnormal brightness, and specifies a pixel position detected as abnormal brightness. First information (abnormal pixel: “1”) to be stored in the memory (263);
The recovery detection function (264, 265) holds second information (H: B designation) for specifying the pixel position determined to be the disappearance of the foreign matter in the memory (265c), and stores the first information and the second information. Using the abnormal pixel correction function (266) with respect to the image data of the document read at the pixel position detected as abnormal brightness based on the information, the pixel position is a pixel position where it is not determined that the foreign matter has disappeared. The image reading apparatus according to the above (1) (FIG. 8) outputs the image data after the replacement, and the image data without the replacement when the determination is at a certain pixel position.
[0020]
When the abnormal pixel returns to the normal state, the correction is automatically canceled immediately, and the operation returns to the image reading in which the image of the document is faithfully read. The occurrence of black streak-like images due to abnormal pixels is prevented, and no thin lines are lost due to correction.
[0021]
(2) An optical system (232 to 237) for projecting an image on a document; an image sensor (207) for reading an image projected by the optical system; a means for converting a read image signal into digital data, that is, image data ( Means (30) for moving at least one of the original and the optical system relative to the other in the sub-scanning direction across the reading field of view (240) that extends in the main scanning direction of the optical system. An abnormal pixel detection function (262) for detecting a pixel position of image data that has become abnormal due to a foreign substance appearing in the reading field of view; and image data of a document read at a pixel position determined to be abnormal by the abnormal pixel detection function An abnormal pixel correction function (266) based on replacing a value with another value;
A data variation detection function (264) for detecting a predetermined change in the sub-scanning direction of the image data of the original reading; and, if the change is not detected, the replacement of the abnormal pixel correction function (266) is valid, and if there is a change, An image reading apparatus (FIG. 8) comprising: a correction function control unit (265) for invalidating the image.
[0022]
(2a) an optical system for projecting an image (232 to 237);
An image sensor (207) for reading an image projected by the optical system;
Means for converting the read image signal into digital data, that is, image data (208 to 210);
Means (30) for transporting at least one of the document and the optical system relative to the other in a sub-scanning direction that crosses a reading field of view (240) that extends in the main scanning direction of the optical system;
The memory (263) detects whether the image data of the non-image portion (BP) projected by the optical system (232 to 237) has abnormal brightness, and stores first information for specifying a pixel position detected as abnormal brightness. )), An abnormal pixel detection means (262);
An abnormal pixel correction function (266) for replacing the image data value of the original reading with another value;
A data change detection function (264) for detecting a predetermined change in the sub-scanning direction of the image data of the original reading;
The replacement of the abnormal pixel correction function (266) at the pixel position determined to be abnormal with reference to the first information stored in the memory (263) is valid if no change is detected, and if there is a change. Correction function control means for invalidating (265);
(FIG. 8).
[0023]
According to this, when the abnormal pixel returns to the normal state, the correction is automatically canceled immediately, and the operation returns to the image reading in which the image of the document is faithfully read. The occurrence of black streak-like images due to abnormal pixels is prevented, and no thin lines are lost due to correction.
[0024]
(2b) The correction function control means (265) holds second information (H: B designation) for specifying the pixel position determined to be the disappearance of the foreign matter in the memory (265c), and stores the first information and the second information. Based on the two pieces of information, the abnormal pixel correction function (266) is used for the image data of the original read at the pixel position detected as abnormal brightness, and the pixel position is the pixel position where the predetermined change does not occur. The image reading apparatus according to the above (2a) (FIG. 8) outputs the image data without replacement when the image data after the replacement is at a pixel position where the change occurs.
[0025]
(2c) When the change is detected at the pixel position determined to be abnormal, the correction function control means (265) determines the subsequent image data of another line that occurs later on the same document. Even in this case, the replacement of the abnormal pixel correction function (266) is invalidated; the image reading device according to any one of the above (2) to (2b) (FIG. 8).
[0026]
The abnormal pixel detection operation is performed by setting the period during which the correction function is invalidated until the next abnormal pixel detection operation when the dust or the like that caused the abnormality has been moved and the pixel determined to be the abnormal pixel has been restored. Is normally irreversible, the return to normal pixels accompanying the movement of dust or the like is almost irreversible (whether or not during reading). (It is extremely unlikely that dust or the like moves to the same position again and becomes an abnormal pixel again.) Therefore, the correction function can be operated accurately. Irrespective of the timing specification of the abnormal pixel detection operation, it is possible to prevent the occurrence of a black streak-like image due to the abnormal pixel and to prevent the thin line from being lost due to the correction function.
[0027]
(2d) The image reading device according to (2a) (FIG. 12), wherein the correction function control means (265) erases the first information at the pixel position determined to be the disappearance of the foreign matter. According to this, the abnormal pixel information can be easily erased. The information processing of the abnormal pixel recovery corresponding to the foreign matter disappearance is simple.
[0028]
(3) The predetermined change is an increase in a data value that is equal to or more than a predetermined value in the image reading of the same document than the image data value of the line read earlier; the above-mentioned (1) to (2d). Image reading device (FIG. 8). In the data value fluctuation detection 264 shown in FIG. 8 according to this embodiment, the data value D (n) of the document reading of the abnormal pixel is smaller than the data value D (n−1) of the same document preceding in the sub-scanning. If the brightness is higher than dTh, the pixel does not read the dust or the like on the reading surface that caused the abnormality, but the dust moves and as a result, a brighter area of the document blocked by the dust is read. Judge that there is. That is, it is determined that the foreign matter has disappeared.
[0029]
(4) The image reading device (FIG. 13) according to any one of claims 1 to 2d, wherein the predetermined change is an increase in an image data value to a predetermined threshold or more. If the comparison result indicates that the data value D (n) of the abnormal pixel is higher than the brightness indicated by the threshold (Th) to be compared, the pixel is reading dust or the like on the reading surface that caused the abnormality. It is determined that a brighter area of the document, which is blocked by the movement of dust or the like as a result of movement of dust, is read. That is, it is determined that the foreign matter has disappeared.
[0030]
(5) The threshold value (Th) is the image data itself in which the abnormal pixel detection function (262) has detected an abnormality, or a value determined based on the data value; the image reading described in (4) above. Apparatus (FIG. 13). The movement of the blocked dust and the like is recognized with high accuracy in consideration of the type and size of the dust and the influence of instability factors such as the relative positional relationship with the reading line when an abnormality is detected. It is possible to immediately recognize that the reflected light of the document surface has entered the abnormal pixel of the image sensor that has been blocked by the movement of dust or the like without depending on the drop level of the abnormal pixel.
[0031]
(5a) The predetermined change is a deviation from a region between predetermined upper and lower limits; the image reading device according to any one of (1) to (2d) (FIG. 14). The level determination that determines whether or not the data value of the abnormal pixel is within the range defined by the two values allows the movement of dust or the like on the reading surface that caused the abnormality to occur in the shade of the image being read. Regardless, it is possible to determine. For example, assuming a case where a black portion of a document is applied to the position of an abnormal pixel, if dust or the like has not yet moved, the level of the read data value of that pixel should not change much when an abnormal pixel is detected. If it has moved, it should be the data value that read the black part of the original, so in some cases it may be a data value that is lower in brightness than when abnormal pixels are detected. Also detects the movement of dust and the like. According to this, it is possible to immediately recognize in both the bright and dark directions that the reflected light of the document surface has entered the abnormal pixel of the image sensor which has been blocked by the movement of the dust or the like.
[0032]
(5b) The image reading device according to (5a) above (FIG. 14), wherein the upper limit is equal to or greater than the data value of the image data when an abnormal pixel is detected, and the lower limit is less than the data value. By setting one of the two values to be equal to or less than the data value at the time of abnormal pixel detection and the other to be equal to or greater than the data value, the area defined by the two values can include the data value at the time of abnormal pixel detection, It is possible to appropriately judge a change in the read data value due to movement of dust or the like that has caused an abnormality. That is, it is possible to immediately and accurately recognize in both the bright and dark directions that the reflected light of the document surface has entered the abnormal pixel of the image sensor that has been blocked by the movement of dust or the like.
[0033]
(6) The image reading device according to any one of the above (1) to (5b); and image data generated by reading an original by the image reading device for printing for forming an image on paper. An image data processing means (ACP) for converting the image data into image data. According to this, it is possible to obtain image data for reproducing an image by printout without causing black streaks due to contamination of the reading unit (240) and without missing thin lines due to correction.
[0034]
(7) The image processing apparatus according to (6), further including: a printer (100) for forming an image on paper based on the image data for printing. According to this, it is possible to obtain a copy in which black streaks do not occur due to contamination of the reading unit (240) and there is no thin line missing due to correction.
[0035]
Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0036]
【Example】
-1st Example-
FIG. 1 shows an appearance of a multifunction full-color digital copying machine equipped with an image reading apparatus according to a first embodiment of the present invention. The full-color copying machine generally includes an automatic document feeder (ADF) 30, an operation board 20, a color scanner 10, a color printer 100, and a paper feed bank 35. A finisher 34 with a tray on which a stapler and an imaged sheet can be stacked, a double-sided drive unit 33, and a large-capacity paper feed tray 36 are mounted on the printer 100.
[0037]
A LAN (Local Area Network) to which a personal computer PC is connected is connected to the system controller 630 (FIG. 2) in the machine. The printed paper of the color printer 100 is discharged onto the paper discharge tray 108 or the finisher 34.
[0038]
The finisher 34 has a stacker tray, that is, a stacking and lowering tray 34hs and a sort tray group 34st, and a stacker discharging mode for discharging paper (printed paper and transferred paper) to the stacking and lowering tray 34hs, and a paper discharging mode to the sort tray group 34st. It has a sorter discharge mode.
[0039]
The paper fed from the printer 100 to the finisher 34 is conveyed in the upper left direction, passes through an inverted U-shaped conveyance path, switches the conveyance direction downward, and then discharges the paper in the stacker according to the set mode. In the mode, the sheet is discharged from the discharge port to the loading and lowering tray 34hs. In the sorter discharge mode, the sheet currently discharged in the sorter tray group 34st is discharged to the assigned sorter tray.
[0040]
When the sorter discharge mode is designated, the discharge controller in the finisher drives the sort tray group 34st placed at the lowermost stacking and retract position to the use position indicated by the two-dot chain line in FIG. Increase the interval. In the sorter discharge mode, a single (one) copy or print of the set number of sheets is performed. When the sorter discharge mode is set for the set sort, each transfer sheet on which the same original (image) is printed is sorted by the sort tray group 34st. Sorted and stored in each tray. When the sorter discharge mode is set for page sorting, each tray is assigned to each page (image), and each transfer sheet on which the same page is printed is stacked on one sort tray.
[0041]
FIG. 2 shows a system configuration of an image processing system of the copying machine shown in FIG. In this system, a color document scanner 12 including a reading unit 11, a sensor board unit SBU, and an image data output I / F (Interface: Interface) 12 is used by an image data interface control CDIC (hereinafter simply referred to as CDIC) of an image data processing device ACP. )It is connected to the. A color printer 100 is also connected to the image data processing device ACP. The color printer 100 receives recording image data from the image data processor IPP (Image Processing Processor; hereinafter simply referred to as IPP) of the image data processing device ACP to the writing I / F 134, and prints out the image at the image forming unit 135. .
[0042]
The image data processing device ACP (hereinafter simply referred to as ACP) includes a parallel bus Pb, a memory access control IMAC (hereinafter simply referred to as IMAC), a memory module as an image memory (hereinafter simply referred to as MEM), and a nonvolatile memory. A hard disk drive HDD (hereinafter simply referred to as HDD), a system controller 1, a RAM 4, a nonvolatile memory 5, a font ROM 6, a CDIC, an IPP, and the like are provided. The facsimile control unit FCU (hereinafter simply referred to as FCU) is connected to the parallel bus Pb. The operation board 20 is connected to the system controller 1.
[0043]
The reading unit 11 of the color document scanner 10 for optically reading a document performs photoelectric conversion of the reflected light of the lamp irradiation on the document by an image sensor 207 on a sensor board unit SBU (hereinafter simply referred to as SBU) to generate a R. , G, B image signals are converted to RGB image data by an A / D converter, corrected for shading, and sent to the CDIC via the output I / F 12.
[0044]
The CDIC performs image data transfer between the original scanner 10 (output I / F 12), the parallel bus Pb, and the IPP, and communication between the process controller 131 and the system controller 1 that controls the entire ACP. The RAM 132 is used as a work area of the process controller 131, and the ROM 133 stores an operation program of the process controller 131 and the like.
[0045]
The memory access control IMAC (hereinafter simply referred to as IMAC) controls writing / reading of image data and control data to / from the MEM and the HDD. The system controller 1 controls the operation of each component connected to the parallel bus Pb. The RAM 4 is used as a work area of the system controller 1, and the nonvolatile memory 5 stores an operation program of the system controller 1 and the like.
[0046]
The operation board 20 indicates a process to be performed by the ACP. For example, the type of process (copying, facsimile transmission, image reading, printing, etc.), the number of processes, and the like are input. Thereby, the input of the image data control information can be performed.
[0047]
The image data read by the reading unit 11 of the scanner 10 is subjected to shading correction 260 by the SBU of the scanner 10, and then to image processing for correcting reading distortion such as scanner gamma correction and filter processing by IPP. Store in MEM or HDD. When printing out the image data of the MEM or HDD, the IPP performs color conversion of RGB signals to YMCK signals and performs image quality processing such as printer gamma conversion, gradation conversion, and gradation processing such as dither processing or error diffusion processing. Do it. The image data after the image quality processing is transferred from the IPP to the write I / F 134. The write I / F 134 performs laser control on the signal subjected to the gradation processing by pulse width and power modulation. Thereafter, the image data is sent to the image forming unit 135, and the image forming unit 135 forms a reproduced image on transfer paper.
[0048]
The IMAC controls access to image data and MEM or HDD based on the control of the system controller 1, expands print data of a personal computer PC (hereinafter simply referred to as PC) connected on a LAN, and effectively utilizes MEM and HDD. Compression / decompression of image data for
[0049]
The image data sent to the IMAC is stored in the MEM or HDD after data compression, and the stored image data is read out as needed. The read image data is expanded, returned to the original image data, and returned from the IMAC to the CDIC via the parallel bus Pb. After the transfer from the CDIC to the IPP, the image is processed and output to the write I / F 134, and the image forming unit 135 forms a reproduced image on transfer paper.
[0050]
In the flow of image data, the function of the digital multifunction peripheral is realized by the bus control by the parallel bus Pb and the CDIC. Facsimile transmission is performed by performing image processing on read image data by IPP and transferring the data to the FCU via the CDIC and the parallel bus Pb. The FCU converts the data into a communication network and transmits it to the public line PN as facsimile data. Facsimile reception is performed by converting line data from the public line PN into image data by the FCU and transferring it to the IPP via the parallel bus Pb and CDIC. In this case, the image is output from the writing I / F 134 without performing any special image quality processing, and the image forming unit 135 forms a reproduced image on transfer paper.
[0051]
In a situation where a plurality of jobs, for example, a copy function, a facsimile transmission / reception function, and a printer output function operate in parallel, the right to use the reading unit 11, the imaging unit 135, and the parallel bus Pb is assigned to the job by the system controller 1 and the process. Control is performed by the controller 131. The process controller 131 controls the flow of image data, the system controller 1 controls the entire system, and manages the activation of each resource. The function selection of the digital multi-function peripheral is performed on the operation board 20, and the processing contents such as the copy function and the facsimile function are set by the selection input of the operation board 20.
[0052]
The system controller 1 and the process controller 131 communicate with each other via the parallel bus Pb, the CDIC, and the serial bus Sb. Specifically, communication between the system controller 1 and the process controller 131 is performed by performing data format conversion for data and interface between the parallel bus Pb and the serial bus Sb in the CDIC.
[0053]
Various bus interfaces, for example, a parallel bus I / F 7, a serial bus I / F 9, a local bus I / F 3, and a network I / F 8, are connected to the IMAC. The controller unit 1 is connected to related units via a plurality of types of buses in order to maintain independence in the entire ACP.
[0054]
The system controller 1 controls other functional units via the parallel bus Pb. The parallel bus Pb is used for transferring image data. The system controller 1 issues an operation control command to the IMAC to store the image data in the MEM and the HDD. This operation control command is sent via the IMAC, the parallel bus I / F 7, and the parallel bus Pb.
[0055]
In response to this operation control command, the image data is sent from the CDIC to the IMAC via the parallel bus Pb and the parallel bus I / F7. Then, the image data is stored in the MEM or the HDD under the control of the IMAC.
[0056]
On the other hand, the system controller 1 of the ACP functions as a printer controller, a network controller, and a serial bus controller in the case of calling from a PC as a printer function. In the case of passing through the network B, the IMAC receives print output request data or accumulation (save) request data via the network B via the network I / F 8. The request data (external command) via the network B is notified to the system controller 1, and the IMAC transfers or receives and stores the stored data via the network B according to a command from the system controller 1 responding to the request data.
[0057]
In the case of a general-purpose serial bus connection, the IMAC receives print output request data via the serial bus I / F 9. The general-purpose serial bus I / F 9 supports a plurality of types of standards, for example, an interface of a standard such as USB (Universal Serial Bus), 1284, or 1394.
[0058]
Print output request data from the PC is developed into image data by the system controller 1. The deployment destination is an area in the MEM. Font data necessary for development can be obtained by referring to the font ROM 6 via the local bus I / F 3 and the local bus Rb. The local bus Rb connects the controller 1 to the nonvolatile memory 5 and the RAM 4.
[0059]
As for the serial bus Sb, besides the external serial port 2 for connection with the PC, there is also an interface for transfer with the operation board 20 which is the operation unit of the ACP. It communicates with the system controller 1 via IMAC instead of print development data, accepts processing procedures, displays system status, and the like.
[0060]
Data transmission / reception between the system controller 1 and the MEM, HDD, and various buses is performed via the IMAC. Jobs that use the MEM and HDD are centrally managed in the entire ACP.
[0061]
FIG. 3 shows an outline of a functional configuration of the CDIC. The image data input / output control 161 receives the image data output by the color document scanner 10 (SBU) and outputs it to the IPP. The IPP performs “scanner image processing” 190 (FIG. 4) and sends the image data to the CDIC image data input control 162. The data received by the image data input control 162 is subjected to primary compression of the image data in the data compression section 163 in order to increase the transfer efficiency on the parallel bus Pb. The compressed image data is converted to parallel data by the data conversion unit 164 and sent to the parallel bus Pb via the parallel data I / F 165. Image data input from the parallel data bus Pb via the parallel data I / F 165 is serially converted by the data conversion unit 164. This data is primarily compressed for bus transfer, and is expanded by the data expansion unit 166. The decompressed image data is transferred to the IPP by the image data output control 167. In the IPP, the RGB image data is converted into YMCK image data by “image quality processing” 300 (FIG. 4), converted into image data YpMpCpKp for image output of the printer 100, and output to the color printer 100.
[0062]
The CDIC has a function of converting parallel data transferred on the parallel bus Pb and serial data transferred on the serial bus Sb. The system controller 1 transfers data to the parallel bus Pb, and the process controller 131 transfers data to the serial bus Sb. For communication between the two controllers 1 and 131, the data conversion unit 164 and the serial data I / F 169 perform parallel / serial data conversion. The serial data I / F 168 is for the IPP, and performs serial data transfer with the IPP.
[0063]
FIG. 4 shows an outline of the image processing function of the IPP. IPP is a separation generation (determination of whether an image is a text area or a photograph area: image area separation) 192, background removal 193, scanner gamma conversion 194, filter 195, color correction 302, scaling 303, image processing 304, printer gamma conversion 305 And a gradation process 606 is performed. IPP is a programmable arithmetic processing unit that performs image processing. Image data input to the CDIC from the output I / F 12 of the scanner 10 is transferred to the IPP via the CDIC, and the IPP performs signal degradation due to quantization into optical systems and digital signals (signal degradation of the scanner system). Is corrected and output (transmitted) to the CDIC again. In the IPP, “image quality processing” 300 is performed on the image data returned from the CDIC to the IPP. In the “image quality processing” 300, the RGB signal is color-converted into a YMCK signal by a color correction 302, and a scaling 303, image processing 304, printer gamma conversion 305, and gradation processing such as gradation conversion, dither processing, or error diffusion processing are performed. 306 and so on.
[0064]
FIG. 5 shows a document image reading mechanism of the scanner 10 and the ADF 30 attached thereto. The original placed on the contact glass 231 of the scanner 10 is illuminated by the illumination lamp 232, and reflected light (image light) of the original is reflected by the first mirror 233 in parallel with the sub-scanning direction y. The illumination lamp 232 and the first mirror 233 are mounted on a first carriage (not shown) driven at a constant speed in the sub-scanning direction y. A second carriage (not shown), which is driven in the same direction as the first carriage at half the speed, has second and third mirrors 234 and 235 mounted thereon, and image light reflected by the first mirror 233. Is reflected by the second mirror 234 in the downward direction (z), is reflected by the third mirror 235 in the sub-scanning direction y, is focused by the lens 236, is irradiated on the image sensor 207 as an image sensor, and is converted into an electric signal. Is converted. The first and second carriages are driven forward (scanning original) and backward (return) in the y direction by using the traveling body motor 238 as a driving source.
[0065]
The scanner 10 is equipped with an automatic document feeder ADF 30. The document stacked on the document tray 241 of the ADF 30 is sent between the conveyance drum 244 and the pressing roller 245 by the pickup roller 242 and the registration roller pair 243, and passes over the reading glass 240 in close contact with the conveyance drum 244. Then, the paper is discharged onto the paper discharge tray 248 below the original tray 241 by the paper discharge rollers 246 and 247. The original is illuminated by an illumination lamp 232 moving directly below the original when passing through a reading glass 240 which is a reading unit for sheet-through reading, and the reflected light of the original passes through an optical system below the first mirror 233. Then, the light is irradiated on the image sensor 207 and photoelectrically converted.
[0066]
In the case of sheet-through image reading in which the document is read while the document is being transported by the ADF 30, the document image coming from the glass 240 of the reading unit is read with the first carriage fixed at the home position HP. This position is the reading position for sheet-through image reading. Detection of abnormal pixels is performed by reading the back plate BP above the reading glass through the reading glass 240 before the conveyed document reaches the reading position HP at the reading position HP. As the back plate BP, a white member or a member painted white is used. By reading the back plate BP through the reading glass 240, a process of detecting an abnormal pixel is performed before the document is conveyed. The contents will be described later with reference to FIG.
[0067]
In addition, a roller may be provided instead of the back plate BP, or a transport drum 244 may be used instead of the back plate BP, and the surface thereof may be made of a high-reflectance white member or painted white. However, since the reflected light level of the roller or the transport drum 244 is read at the time of reading the non-image portion for detecting an abnormal pixel performed before reading the original image, if the reflection surface is dirty, the dirt is detected at the abnormal pixel portion ( Since it is detected (dirty of the glass 240 causing black streaks or white streaks) (erroneous detection), cleaning is required. This point is the same when the back plate BP is used. However, since the roller or the transport drum 244 is more easily contaminated than the back plate BP and has a cylindrical and large surface area, it is necessary to maintain the entire surface uniformly clean white. It takes time and effort. Therefore, in this embodiment, a narrow back plate BP is used.
[0068]
A reference white plate 239 and a base point sensor 249 for detecting the first carriage are provided between the reading glass 240 and the scale 251 for positioning the document leading edge. The reference white plate 239 is used to read an original having a uniform density due to variations in the light emission intensity of the illumination lamp 232, variations in the main scanning direction, and variations in sensitivity of each pixel of the image sensor 207. In order to correct the phenomenon that the read data varies (shading correction 260: FIG. 8) and convert the data into image data having a uniform density level. In this shading correction, first, the reference white plate 239 is read for several lines in the main scanning direction before scanning the document, shading correction data is set based on the read white reference data, and image data obtained by scanning the document is corrected. The correction is performed based on
[0069]
Immediately before the lens unit 236, there is a shading adjustment plate 237, which is a light amount for eliminating a difference in reflected light amount between a center portion and an end portion of the image sensor 207 in a main scanning direction (a direction perpendicular to the paper surface of FIG. 5). Plays a coordinating role. This is because if there is too much difference in the amount of reflected light of the reference white plate 239 between the center and the end of the image sensor 207 in shading correction, the correction may possibly include distortion. Then, in order to perform shading correction, the incident light amount of the image sensor 207 is leveled.
[0070]
FIG. 6 shows a configuration of an electric system for reading an image of the scanner 10. The electric signals output from the image sensor 207, that is, the analog image signals of each of the R, G, and B colors are respectively amplified by the signal processing 208 and converted into digital image signals, that is, image data by the A / D converter 209. This image data undergoes correction processing by the brightness correction 210 and is output to the IPP. In the A / D converter 209, the digitally converted image data is converted into data obtained by removing a portion serving as an offset on the black side. In this case, the offset from the black side includes a difference between channels when the output from the image sensor 207 has a two-channel configuration for each of R, G, and B color components. The main purpose of the arithmetic processing here is to remove error components between channels.
[0071]
The scanner control circuit 206 controls the lamp control circuit 205, the timing control circuit 211, and the motor control unit 260 according to instructions from the system controller 630 and the process controller 131. The lamp control circuit 205 controls on / off of the exposure lamps 232 (232 a and 232 b) according to an instruction from the scanner control circuit 206, and adjusts the brightness (light amount) of the exposure lamp 232 to the illuminance (light amount) indicated by the shading correction 210. Time series average or smoothed value). Note that reference numerals 232a and 232b may be collectively indicated by reference numeral 232.
[0072]
The motor control unit 260 controls the sub-scanning drive motor 238 and the ADF motor 224 according to an instruction from the scanner control circuit 206. Each of these motors is a stepping motor, and rotary encoders (E) 221 and 225 are connected to the shaft of the drive system. The scanning position (y) and the driving amount of the first carriage and the leading and trailing edge positions and the feeding amount of the ADF original are counted by counting the electric pulses generated by the rotary encoders 221 and 225. The paper sensor 223 shown in FIG. 6 includes a sensor for detecting whether there is a document on the document tray 241 of the ADF 30, a paper jam detection sensor, and a document size detection sensor.
[0073]
The timing control circuit 211 generates various signals according to instructions or control signals from the scanner control circuit 206, the system controller 630 (CPU 605), and the process controller 131. That is, when the image reading is started, a transfer gate signal for transferring the data of one line to the shift register and a shift clock pulse for outputting the data of the shift register one bit at a time are given to the image sensor 207. , A pixel synchronization clock pulse CLK, a line synchronization signal LSYNC, and a main scanning valid period signal LGATE are output. The pixel synchronization clock pulse CLK is a signal substantially the same as the shift clock pulse applied to the image sensor 207. The line synchronization signal LSYNC is a signal corresponding to the line synchronization signal MSYNC output from the beam sensor of the image forming unit 135 of the printer 100, but the output is prohibited when the image is not read. The main scanning valid period signal LGATE becomes high level H at a timing when the image signal output from the image sensor 207 can be regarded as valid.
[0074]
Upon receiving a reading start instruction from the process controller 131, the scanner control circuit 206 controls the timing control circuit 211 to start reading the image sensor 207, turns on the exposure lamp 232, and drives the sub-scanning drive motor 238 (manual feed mode). Alternatively, the driving of the ADF motor (ADF mode) is started. Further, the sub-scanning effective period signal FGATE is set to a high level H (outside the document area). This signal FGATE is switched to L indicating the inside of the document area when the first carriage reaches the document start position (the position a + b from the home position HP) in the manual feed mode. The feed-out conveyance amount at the front end is the HP position (“the feed amount Df from the registration roller 243 to the base point sensor 249” in the sheet-through image reading mode using the ADF 30) − “the HP position to the base point sensor 249. When the feed amount a ”) is reached, it is switched to L indicating the inside of the document area. Then, when the first carriage passes the tail end of the original in the manual feed mode, and when the tail end of the original passes the HP in the ADF mode, the sub-scanning effective period signal FGATE is returned to H indicating the outside of the original area.
[0075]
FIG. 7 shows a configuration of the scanner control circuit 206. The CPU 254 performs input / output control of the scanner control circuit 206 and drive control of the sub-scanning drive motor 238 and the ADF motor. That is, it controls input reading and display output of the operation board of the document scanner, and performs carriage driving or ADF driving in response to a document reading command from the system controller 630 or the process controller 131. The control program of the scanner control circuit 206 is written in the ROM 255. The RAM 256 is a working memory used by the CPU 254. Reference numeral 252 denotes an input device by which a user inputs system settings by operating input keys and an input panel of an operation board of the document scanner. The display device 253 is provided on the operation board of the document scanner, and displays the setting contents and status of the system to the user, and includes a display lamp and a display panel (display).
[0076]
FIG. 8 shows an outline of a function of a brightness correction 210 for performing shading correction, abnormal pixel detection, and image data correction of an abnormal pixel. The brightness correction 210 shown in FIG. 8 includes three sets in which each set corrects the brightness of each of the R, G, and B component image data of the image reading. Their functions are identical. Hereinafter, the correction function of the set of brightness corrections 210 will be described.
[0077]
The analog video signal output from the image sensor 207 is digitally converted to image data by the A / D converter 209. The shading correction 260 sets shading correction data based on the white waveform data obtained by reading the reference white plate 239. The shading correction 260 includes a shading correction function for performing shading correction on read image data and a shading correction data setting function for generating and updating shading correction data.
[0078]
In the "setting of shading correction data", the shading correction data is set in the FIFO memory in which the shading gate signal shown in FIG. When the shading gate signal falls from the high level H to the low level L, the shading correction 260 performs an average value calculation process over several lines of the reference white plate 239 to read the reference white plate at the same pixel position on several lines. An average value of the data is calculated, and an average level of the entire line is calculated. From the average value of each pixel position and the average level of the entire line, reference data Dhi for uniforming image data at each pixel position. Is calculated and updated and written to the FIFO memory.
[0079]
An L section of the document reading gate signal shown in FIG. 11 is a document reading period, and “shading correction” is performed here. In the "shading correction", the reference data Dhi at the pixel position of the read data Di is read from the FIFO memory, and Di and Dhi are input to the shading correction ROM assigned to the shading correction 260, and stored in the ROM in advance. The data subjected to the shading correction calculation is read out by a look-up table method, and image data Dout subjected to shading correction according to Di and Dhi is output. That is, in the section of the back plate BP reading and the document image reading, the shading correction 260 reads the reference data Dhi at the same pixel position as the read image data Di from the FIFO memory, and stores the image data Di and the reference data Dhi in the shading correction ROM. give. The ROM outputs image data Dout obtained by shading-correcting the input image data Di based on the reference data Dhi. The outline of the correction calculation of the shading correction of this embodiment is Dout = Do · Di / Dhi,
Do is the reference (white) density value of the reference white plate 239,
The shading correction ROM stores the Dout value calculated by the above equation for each of the possible values of Di and Dhi, and stores Di and Dhi as an address. By simultaneously providing the input image data Di and the reference data Dhi at the same pixel position to the shading correction ROM, the image data Dout obtained by shading the input image data Di based on the reference data Dhi can be immediately obtained from the shading correction ROM. .
[0080]
As a general image data flow at the time of reading a document, the image data flows to the scaling process 212 after the shading correction 260. However, in the present embodiment, when the back plate BP is read, the flow proceeds to the abnormal pixel detection 262, and when the original image is read in the sheet-through image reading mode, the flow proceeds to the “delay memory 261-abnormal pixel data correction 266-scaling process 212” In the image reading mode described above, the process flows to the “delay memory 261-scaling process 212”. The delay memory 261 is a buffer memory for temporarily storing image data of three or more lines. FIG. 8 shows only data lines used by the data value fluctuation detection 264 and the abnormal image data correction 266. Is also used by the shading correction 260 and the abnormal pixel detection 262 to temporarily store image data and operation data.
[0081]
The abnormal pixel detection 262 calculates a line average value in the main scanning direction of the image data obtained by reading the back plate BP, and extracts a pixel having a brightness lower than a threshold lower than the average value by a predetermined ratio as a candidate for an abnormal pixel. Next, paying attention to the number of images of the continuous distribution of the abnormal pixel candidates in the main scanning direction, an abnormal pixel candidate group continuously distributed at a predetermined threshold or more is determined as an abnormal pixel group due to dirt, and for each of the abnormal pixels, A binary signal (1 bit data: first information) of high level H: “1” indicating an abnormal pixel is written to an address of the line memory 263 at the address of the position of the abnormal pixel.
[0082]
Note that when the abnormal pixel detection is started, the line memories 263 and 265c are cleared, indicating that all the binary signals (first information) addressed to all the pixels on one line of the line memory 263 are normal pixels. Low level L: a binary signal (1 bit data) of “0”. Similarly, the binary signal (second information) of the line memory 263 has a low level L: “0”.
[0083]
At the time of sheet-through document image reading, the image data of each pixel on one line is sequentially sent to the abnormal image data correction 266 and sequentially set as the processing target pixel (target pixel) of the correction value calculation 266b. The pixel (pixel synchronization pulse) is counted up, and the binary signals corresponding to the count value (at the pixel position of interest), that is, the first information and the second information are read out from the line memories 263 and 265c, The first information is provided to the AND gate 265a of the correction necessity detection 265, and the second information is provided to the OR gate 265b as it is, and is also inverted and provided to the AND gate 265a. This first information indicates whether the target pixel is an abnormal pixel or a normal pixel. At this time, the data value change detection 264 detects whether or not the target pixel has undergone a predetermined change in the sub-scanning direction (the change: H / there is no change: L). Output to As will be described later, the second information is switched from L (output instruction of the correction data A) to H (output instruction of the image data B) when the brightness of the abnormal pixel changes in the sub-scanning direction.
[0084]
The reference matrix configuration 266a of the abnormal pixel data correction 266 is a block that forms a spatial matrix including a target pixel and peripheral pixels in order to correct abnormal pixels with reference to data values of peripheral pixels. Each data of the formed block is sent to a correction value calculation 266b, and the correction value calculation 266b calculates a correction value given to the abnormal pixel when the target pixel is an abnormal pixel. In this embodiment, the matrix is 3 × 3 pixels centered on the target pixel, and the average value of the brightness (image data) of the pixels other than the target pixel is used as the correction value. However, other complementary operations may be used. The correction value data is input to the input terminal A of the data selector 266c. The image data D (n) of the pixel of interest is input to an input terminal B of the data selector 266c, and the data selector 266c inputs the image data D (n) when the control signal given by (the OR gate 265b of) the correction necessity detection 265 is L. The correction value data of A is output to the scaling process 212 as brightness-corrected data, and when the control signal is H, the image data of the input end B (image data on which only shading correction is performed) is converted to brightness-corrected data. Output to the scaling process 212.
[0085]
In the data value change detection 264, the change dD = D (n) -D (n) of the image data D (n) of the target pixel with respect to the image data D (n-1) at the same main scanning position one line before the target pixel. -1) is calculated by the difference value calculation 264c, and if this is larger than the threshold value dTh, that is, if there is a change in brightness between lines, a high-level H signal indicating that there is a change is generated in the comparison 264e to perform correction. Output to the necessity detection 265. When the variation dD is equal to or less than the threshold value dTh, the signal is set to a low level L indicating no change. This signal requires only one bit of information.
[0086]
In the above description, the data value D (n-1) of the line immediately before the pixel of interest is used as the reference value. However, the reference value generation 264b sets the reference value to the data value D (n-1) of the preceding line. Adjustment can also be performed by multiplying coefficients or adding or subtracting constants. Alternatively, the image data several lines before the pixel of interest can be used as a reference value with a delay of one or more lines. The threshold dTh is held in the latch 264f by the CPU 254 of the scanner control circuit 206 transferring the data from the NVRAM 257 to the latch 264f in the initialization immediately after the power of the document scanner 10 is turned on.
[0087]
The correction necessity detection 265 performs a correction process on the target pixel based on the determination result (output of the comparison 264 e) of the data value variation detection 264 for the target pixel and the original abnormal pixel determination result (first information of the line memory 263). It is determined whether to turn ON or OFF, that is, whether to enable or disable, and a control signal for instructing ON / OFF is given from the OR gate 265b to the data selector 266c. If the first information read from the line memory 263 for the target pixel is L (normal pixel), the inverted signal H is output from the OR gate 265b, and the data selector 266c outputs the image read data D of the target pixel at the input terminal B. (N) is output to the scaling process 212. Since L is output when the gate of the AND gate 265a is turned off according to the first information L, the binary signal (second information) addressed to the target pixel in the line memory 265c remains at L (A designation), but the first information L (normal pixel) ) Is output by the OR gate 265b, so that the image read data D (n) itself is always output at normal pixels.
[0088]
As described above, when the first information of the target pixel read from the line memory 263 is H (abnormal pixel), it is cleared when the line memory 265c starts abnormal pixel detection, and the data is L = “0”. And the first information H is supplied to the AND gate 265a together with the inverted signal H = "1", and the output signal of the comparison 264e also supplied to the AND gate 265a is L (no change in brightness in the sub-scanning direction). ), The output of the AND gate 265a is L, the output of the OR gate 265b is L, and the data selector 266c selects the correction data of the input terminal A and outputs it to the scaling process 212.
[0089]
That is, if the brightness of the image data of the abnormal pixel does not change in the sub-scanning direction, the correction data is output. Since the output of the AND gate 265a is L, the second information for the target pixel in the line memory 265c remains at L.
[0090]
However, when the first information read from the line memory 263 relating to the pixel of interest is H (abnormal pixel) and there is a change in brightness in the sub-scanning direction and the output signal of the comparison 264e becomes H, the output of the AND gate 265a becomes It becomes H, the output of the OR gate 265b becomes H, and the first information is H (abnormal pixel), but the data selector 266c outputs the image data D (n) of the pixel of interest. At the same time, the second information addressed to the pixel of interest in the line memory 265c is rewritten to H (B designation). Therefore, in the subsequent image reading of the line, the first information read from the line memory 263 is H (abnormal pixel), but the second information addressed to the pixel of interest in the line memory 265c is H (B designation). Since this is output from the OR gate 265b, the image data D (n) is output instead of the correction data.
[0091]
The delay adjustments 266d, 264a, and 264d delay image data of the processing target pixel (pixel of interest) by the reference matrix configuration 266a and the correction value calculation 266b. It is provided for the purpose of synchronizing the control signal with the target pixel.
[0092]
FIG. 9 shows an outline of document reading control by the CPU 254 of the scanner control circuit 206 in response to an image reading start signal (start instruction) given by the system controller 1. When an image reading start is input from the operation board 20 or the personal computer PC, the system controller 1 provides an image reading start signal to the CPU 254 in response to the input.
[0093]
The CPU 254 starts the forward scanning drive of the first and second carriages from the home position HP in response to the image reading start signal (step 1), and at the timing when the reference white plate 239 enters the reading field of the first mirror 233, The shading gate signal to be applied to the shading correction 260 is switched from “H” to “L”, and the correction gate signal is switched from “H” to “L” at the timing when the reading field advances around the center of the reference white plate 239, and both signals are changed. While the data is "L", the shading correction data is updated by the shading correction 260 (step 2). In the following, the word "step" is omitted in parentheses, and only the step number is described.
[0094]
When the updating of the shading correction data is completed, the CPU 254 returns the shading gate signal and the correction gate signal to “H”. Then, by referring to the detection signal of the sensor for detecting the presence or absence of a document in the document tray of the ADF 30, when the document is not present, the forward scan is continued to read the document image on the contact glass 231 and read the read image data. (4). When the document has passed the tail end of the document on the contact glass 231, the forward scanning drive of the carriage is stopped, and then the carriage is reversed and driven in the backward scan (return) to position the first carriage at the HP, thereby terminating the carriage drive. (5).
[0095]
When the detection signal of the sensor for detecting the presence or absence of the document on the document tray of the ADF 30 indicates that the document is present, the forward drive of the carriage is stopped, and the carriage is returned to the home position HP. That is, the first carriage (first mirror 233) is positioned at the sheet-through image reading position (6). Then, the process proceeds to “Detection of dirt in sheet-through reading position” (7), the line memories 263 and 265c are cleared, the image of the back plate BP of one line in the main scanning is read (71), and shading correction is performed on the read image data. (72), the abnormal pixel detection 262 calculates the line average value of the image data of the one line, and extracts a pixel having a density level equal to or lower than a threshold Th1 lower than the line average value by a predetermined ratio as an abnormal pixel candidate. . Next, an abnormal pixel is determined by paying attention to the number of continuous distribution images of the abnormal pixel candidate in the main scanning direction. An abnormal pixel candidate group that is continuously distributed over a predetermined threshold Th2 for detecting the size of the abnormal pixel candidate group is determined as an abnormal pixel due to dirt, and an H representing the abnormal pixel is stored in the line memory 263 at the position of the abnormal pixel. Write (73).
[0096]
When an abnormal pixel is detected in this way, a dirt warning is displayed on the display of the operation board 20 (8, 10). If reading of an image by feeding the ADF 30 is started in response to an image reading command from the personal computer PC, this dirt warning is transmitted to the PC and displayed on a display connected to the PC. When the abnormal pixel is no longer detected, the dirt warning display is deleted (9).
[0097]
Regardless of whether or not an abnormal pixel is detected, the ADF 30 reads an image of a document to be fed and transferred to the reading glass 240, and performs the shading correction and the abnormal pixel by the function of the brightness correction 210 shown in FIG. Correction is performed (11). When the image reading of one document is completed, the detection signal of the sensor for detecting the presence or absence of the document in the document tray of the ADF 30 is again referred to (12). (7) to "Image reading, shading correction & abnormal pixel correction" (11). Until there are no more documents on the document tray of the ADF 30, the processes of steps 7 to 12 are performed for each document. When the "image reading, shading correction and abnormal pixel correction" (11) of the last document in the ADF 30 is completed, the CPU 254 ends the document image reading control there.
[0098]
FIG. 10 shows only the outline of the control of the "abnormal pixel correction" P11c in the above-mentioned "image reading, shading correction & abnormal pixel correction" (11) in the one-page original reading. The number of sub-scanning lines in the one-page original scanning is L, the number of main scanning pixels is N, and the pixel to be subjected to “abnormal pixel correction” during the original scanning, that is, the target pixel in the sub-scanning direction and the main scanning direction on the original Let the positions be l and n, respectively. Further, if the document read data value of the pixel determined to be an abnormal pixel is once recognized as having fluctuated in the data value fluctuation detection 264, the line memory 265 c The flag FLG (n), which is the second information in the upper pixel unit, is defined. This indicates that when FLG (n) = “0” = L, it has not been recognized as having changed in the past, and when FLG (n) = “1” = H, it has been recognized as having changed in the past. It indicates that.
[0099]
As a control flow, first, FLG (n) of all pixels is initialized to “0” (21), and a target pixel is determined as a start pixel (1, 1) (22, 23). Next, it is determined whether or not the target pixel is an abnormal pixel from the abnormal pixel determination result of the line memory 263, that is, the first information (24, 25). If the pixel is not an abnormal pixel, it is naturally not corrected (25-30). If the pixel is an abnormal pixel, it is determined whether the data has changed by referring to the output result of the data value change detection 264 (25-26). If it is determined that it has changed, FLG (n) is set to 1 and the correction is turned off (26-28-30). If it is determined that there is no change, the FLG is referred to (26-27). If it is determined that there has been a change in the past, the correction is turned off (27-30), and if not, the correction is turned on (27-27). 29). By repeating this operation (31-32-24, 33-34-23), data selection for one page is completed.
[0100]
-2nd Example-
FIG. 12 shows a functional configuration of the brightness correction 210 according to the second embodiment of the present invention. The brightness correction 210 is provided in the above-described digital color copying machine equipped with the image reading apparatus of the first embodiment, replacing the brightness correction 210 shown in FIG. In the correction necessity detection 265 shown in FIG. 12, if the first information addressed to the pixel of interest read from the line memory 263 during image reading is L (normal pixel), the OR gate 265b inverts it to H (B designation). ), And the data selector 266c outputs the image data D (n) of the target pixel. That is, the B input is output.
[0101]
When the first information addressed to the target pixel read from the line memory 263 is H (abnormal pixel), as long as the output of the data change detection 264 is L (no change in brightness), the output of the AND gate 265a is L and the OR gate is When the output of H.265b is L, the data selector 266c outputs the correction data A. When the output of the data change detection 264 becomes H (there is a change in brightness), the output of the AND gate 265a becomes H, whereby the output of the OR gate 265b becomes H, and the data selector 266c sets the image data D (n ) Is output. That is, the B input is output. At this time, the output H of the OR gate 265b is inverted to L by the inverter 265d and written to the line memory 263. That is, the first information of the pixel of interest, which is an abnormal pixel, is rewritten from H (abnormal pixel) to L (normal pixel) in response to the determination of foreign matter erasure. Thereafter, the L is read out, and the inverted signal H is output from the OR gate 265b to the data selector 266c, so that the pixel at the position where the first information has been rewritten is at the end of the original reading process. Until that time, the read image data D (n) is output. The other functions of the brightness correction 210 shown in FIG. 12 are the same as those shown in FIG. 8, and thus description thereof will be omitted.
[0102]
-Third embodiment-
FIG. 13 shows a functional configuration of the brightness correction 210 according to the third embodiment of the present invention. The brightness correction 210 is also provided in the above-described digital color copier equipped with the image reading apparatus of the first embodiment, replacing the brightness correction 210 shown in FIG. When detecting an abnormal pixel, the abnormal pixel detection 262 shown in FIG. 13 writes the first information H and the image data (abnormal lightness) of the abnormal pixel to the line memories 263 and 264g at the positions addressed to the abnormal pixel. Then, during the image reading, the data fluctuation detection 264 reads out the first information and the image data addressed to the pixel of interest from the line memories 263 and 264g, and sets a value obtained by adding an allowable value to the image data as the threshold Th, as the threshold Th. When the image data D (n) of the pixel exceeds the threshold Th, H indicating that there is a change in brightness is output from the comparison 264e to the correction necessity detection 265. That is, in the third embodiment, the threshold value for determining a change in brightness is set based on the back plate BP read data when an abnormal pixel is detected. The other functions of the brightness correction 210 shown in FIG. 13 are the same as those shown in FIG. 8, and the description thereof will be omitted.
[0103]
-Fourth embodiment-
FIG. 14 shows a functional configuration of the brightness correction 210 according to the fourth embodiment of the present invention. The brightness correction 210 is also provided in the above-described digital color copier equipped with the image reading apparatus of the first embodiment, replacing the brightness correction 210 shown in FIG. When the abnormal pixel detection 262 shown in FIG. 14 also detects an abnormal pixel, the first information H and the image data (abnormal lightness) of the abnormal pixel are written into the line memories 263 and 264g at the positions addressed to the abnormal pixel. Then, during the image reading, the data fluctuation detection 264 reads out the first information and the image data addressed to the pixel of interest from the line memories 263 and 264g, and sets a value obtained by adding an allowable value to the image data as the upper limit value ThU. A value obtained by subtracting the value is set as a lower limit value ThL, L is set when the image data D (n) of the target pixel is within the range from the lower limit value ThL to the upper limit value, and H indicating a change in brightness is set outside the range. Output from the OR gate 264k to the correction necessity detection 265. That is, in the fourth embodiment, a pair of thresholds for determining a change in brightness are set based on the back plate BP read data when an abnormal pixel is detected. The other functions of the brightness correction 210 shown in FIG. 14 are the same as those shown in FIG. 8, and a description thereof will be omitted.
[0104]
In the fifth embodiment, in the data value fluctuation detection 264, a fixed value for identifying that the brightness is higher than that at the time of dirt is set as a threshold, and at the time of image reading, the image data of the abnormal pixel is compared with the threshold. Then, when the image data becomes equal to or larger than the threshold value, it is determined that the brightness has changed (the foreign matter has disappeared), and the second information is switched from the correction ON level L to the correction OFF level. In the modification, a first fixed value for identifying that the lightness is higher than that at the time of dirt is set to the first threshold value, and a second fixed value for identifying that the lightness is lower than that at the time of dirt is set to the second threshold. At the time of image reading, it is checked whether or not the image data of the abnormal pixel is out of the range of the first threshold or less and the second threshold or more. The second information is switched from the correction ON level L to the correction OFF level H, or the first information is switched from the abnormal pixel level H to the normal pixel level L.
[0105]
According to the present invention, it is determined that a pixel determined as an abnormal pixel before reading a document is returned to a normal pixel by observing a data value during reading the document, and in that case, the correction function is not immediately activated. There is no particular limitation on the configuration and means other than the above, and also on the above-described realization means. That is, it is added that the implementation means is not related to hardware and software.
[0106]
【The invention's effect】
At the position of the abnormal pixel, the image data of the original read changes from the brightness of the foreign matter to the brightness of the original image. The change detection function (264, 265) detects this change and determines that the foreign matter has disappeared. Further, although the reading surface is clean, dust is attached to the back plate facing the reading surface, and if this is erroneously detected as dust on the reading surface, when reading the original is started, the dust is removed from the original. Since it is located on the back side, the image data of the document read at the position of the abnormal pixel changes from the brightness of the foreign substance to the brightness of the document image. This change is detected by the recovery detection function (264, 265), and it is determined that the foreign matter has disappeared. If the image data correction of the original reading at the position of the abnormal pixel is canceled based on this determination result, there is no possibility that the thin line disappears due to the correction.
[Brief description of the drawings]
FIG. 1 is a front view showing the appearance of a full-color copying machine having a multifunction provided with an image reading apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an outline of an image processing system of the multifunction full-color copying machine shown in FIG. 1;
FIG. 3 is a block diagram showing an outline of a configuration of an image data interface control CDIC shown in FIG. 2;
FIG. 4 is a block diagram schematically showing a functional configuration of an image data processor IPP shown in FIG. 2;
FIG. 5 is an enlarged vertical sectional view showing an outline of a reading mechanism of the original scanner 10 shown in FIG.
FIG. 6 is a block diagram showing a configuration of an image reading electric circuit system of the original scanner 10 shown in FIG.
FIG. 7 is a block diagram showing a configuration of a scanner control circuit 206 shown in FIG.
8 is a block diagram showing a functional configuration of a brightness correction 210 shown in FIG.
FIG. 9 is a flowchart showing an outline of image reading control by a CPU 254 shown in FIG. 7;
10 is mainly a data processing of “abnormal image correction” in “image reading, shading correction & abnormal image correction” (11) shown in FIG. 9 performed by the CPU 254 shown in FIG. 7 via the timing control circuit 211. 9 is a flowchart illustrating control and a function of correction necessity detection 265 illustrated in FIG. 8.
FIG. 11 is a time chart showing a level change of a timing signal generated during scanning of a document by the scanner shown in FIG. 5;
FIG. 12 is a block diagram illustrating a functional configuration of lightness correction according to a second embodiment.
FIG. 13 is a block diagram illustrating a functional configuration of lightness correction according to a third embodiment.
FIG. 14 is a block diagram illustrating a functional configuration of lightness correction according to a fourth embodiment.
FIG. 15 is a graph illustrating a level change in the main scanning direction of read image data that appears due to dust on the image reading unit.
FIG. 16 is a plan view illustrating a defect image on a read image that appears due to dust on the image reading unit.
FIG. 17 is a graph showing a level change in the main scanning direction of back plate read image data that appears due to dust on the image reading unit.
FIG. 18 is a graph illustrating a level change in the main scanning direction of document read image data that appears due to dust on the image reading unit.
FIG. 19 is a graph illustrating a level change in the main scanning direction of document read image data that appears due to dust on the image reading unit.
[Explanation of symbols]
10: Color document scanner 20: Operation board
30: Automatic document feeder 34: Finisher
34hs: loading and lowering tray 34ud: lifting platform
34st: Sort tray group
100: color printer PC: personal computer
PBX: Switch PN: Communication line
ACP: Image data processing device
CDIC: Image data interface control
IMAC: Image memory access control
IPP: Image data processor
221, 225: rotary encoder
224: Stepping motor
231: platen glass 232: illumination lamp
233: First mirror 234: Second mirror
235: Third mirror 236: Lens
207: Image sensor 238: Stepping motor
239: Reference white plate 240: Glass
241: Document tray 242: Pickup roller
243: registration roller pair 244: transport drum
245: Holding roller 246, 247: Discharge roller
248: Pressure plate also used as paper output tray
249: Base point sensor 250: Axis
251: Scale 260: Motor control unit

Claims (7)

An optical system for projecting an image on a document; an image sensor for reading an image projected by the optical system; a means for converting a read image signal into digital data, that is, image data; Means for moving at least one of the document and the optical system relative to the other in the sub-scanning direction across the reading field; and detecting a pixel position of image data which has become abnormal due to a foreign substance appearing in the reading field. An abnormal pixel detection function;
A reading detection function for determining that a predetermined change in the sub-scanning direction of the image data of the original reading at a pixel position determined to be abnormal by the abnormal pixel detecting function is a disappearance of the foreign matter; apparatus. An optical system for projecting an image on a document; an image sensor for reading an image projected by the optical system; a means for converting a read image signal into digital data, that is, image data; Means for moving at least one of the document and the optical system relative to the other in the sub-scanning direction across the reading field; an abnormality for detecting a pixel position of image data which has become abnormal due to a foreign substance appearing in the reading field An image reading apparatus comprising: a pixel detection function; and an abnormal pixel correction function based on replacing an image data value of a document read at a pixel position determined to be abnormal by the abnormal pixel detection function with another value. At
A data variation detection function for detecting a predetermined change in the sub-scanning direction of image data of a document read; and a correction function control for enabling replacement of the abnormal pixel correction function when no change is detected and invalidating when there is a change. Means for reading an image. The image reading apparatus according to claim 1, wherein the predetermined change is an increase in a data value that is equal to or more than a predetermined value than an image data value of a line read earlier in image reading of the same document. The image reading device according to claim 1, wherein the predetermined change is an increase in an image data value to be equal to or more than a predetermined threshold. The image reading device according to claim 4, wherein the threshold value is image data itself in which the abnormal pixel detection function has detected an abnormality, or a value determined based on a data value thereof. 6. An image reading apparatus according to claim 1, wherein the image reading apparatus converts image data generated by reading a document into image data for printing for forming an image on paper. An image processing device comprising: a data processing unit; The image processing apparatus according to claim 6, further comprising: a printer that forms an image on a sheet based on the image data for printing.

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