JP3888662B2 - Image reading processing method, image reading apparatus, and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an image reading processing method for processing image data obtained by reading an image with an image reading means so as to clearly display the image, an image reading apparatus and an image forming apparatus using the image reading processing method, and in particular, intended to limit to this. However, the present invention relates to a digital copying machine suitable for processing image data of a character document having a low contrast, such as a blue-printed document, having a sharp background density fluctuation into image data that clearly reproduces the character image.
[0002]
[Prior art]
  In recent years, document digitization has progressed, and there is an increasing demand for reading and digitizing paper documents with a scanner or the like. In particular, there is a demand for digitizing and accumulating blueprints for design and construction. In the blue-printed drawing, there is a density in the background portion which is originally unnecessary information, and there are cases where the background cannot be completely removed by a normal scanner or copy. In some cases, a blue-printed drawing cut and pasted on white paper is read. In this case, only the blue-printed portion is darkened, and the image readability in the copy area corresponding to the blue-printed portion is extremely lowered.
[0003]
  In JP-A-6-311359, a low density peak is detected on each line of image scanning, and a value obtained by adding an offset value to the average value of the low density peaks of each line is used as a threshold value. A ground removal device that removes the ground as a background is disclosed.
[0004]
  Japanese Patent Application Laid-Open No. 9-186872 discloses a background removal device that detects a white peak value in a certain region and uses this as a basic background level.
[0005]
[Problems to be solved by the invention]
  However, since the background removal device described in Japanese Patent Laid-Open No. 6-311359 removes the same background data for each line of image scanning, it cannot cope with the case where the background density varies on one line. In the device disclosed in Japanese Patent Laid-Open No. 9-186872, a white peak value in a certain region is set as a basic background level, and the background density cannot be calculated and removed following the changing background.
[0006]
  In addition, it is sufficient that the background removal processing can be performed with high accuracy by an image processing circuit that corrects deterioration of the read image due to the reading characteristics of the scanner.
1. The image processing circuit has a limited memory area of about several tens of lines in the sub-scanning direction, but the arithmetic processing is fast;
2. Although the memory device has a wide memory space in which all read image data can be stored, a general-purpose processor capable of manipulating the memory contents is low speed, so that only limited processing can be performed in real time. That is, if the background removal process is sufficiently performed by the image processing circuit, the image processing speed, that is, the image reading speed must be reduced.
[0007]
  If the general-purpose processor performs background removal at the time of writing to or reading from the memory device, the writing speed or the reading speed to the memory device decreases, so that the background removal processing is sufficiently performed by the processor. difficult.
[0008]
  The first object of the present invention is to effectively realize the background removal, and the second object is to realize this without significantly reducing the image data processing speed or transfer speed. In particular, the third object is to obtain image data that can reproduce the drawing data satisfactorily without reducing the throughput due to pre-scanning even when the background density changes drastically, such as when a blue-printed drawing is cut out on white paper. The purpose.
[0009]
[Means for Solving the Problems]
  (1) The image is read by the image reading means (200), converted into image data, the image data is corrected and stored in the memory means (MEM), and the reduced image data is extracted or generated from the corrected image data, and the memory means (MEM), the image data and the reduced image data are read from the memory means (MEM) to generate background level data based on the reduced image data, and the image data read from the memory means (MEM) An image reading processing method (FIGS. 3 and 9) for converting the background level data into image data from which the background level represented by the data expanded to correspond to the same size image is removed.
[0010]
  In addition, in order to make an understanding easy, the code | symbol of the corresponding element or the corresponding matter of the Example shown in drawing and mentioned later in parentheses is added for reference. The same applies to the following.
[0011]
  According to this, for example, the image processing device (IPP) that corrects the image data read by the image reading means (200) can obtain reduced image data at high speed, and the image data is stored in the memory means (MEM). There is no need to slow down the speed. Since the background level is calculated based on the reduced image data, the background level calculation time for one line is short in proportion to the reduction rate, so that the background calculation can be performed relatively quickly and with high accuracy.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  (2) The image is read by the image reading means (200) and converted into image data, the image data is corrected and stored in the memory means (MEM),
  Extracting or generating reduced image data reduced in the main scanning direction from the corrected image data, and at least a smoothing level defined by the reduced image data of interest and the reduced image data preceding the reduced image data of interest in the sub-scanning direction , The smoothing level (y background) in the sub-scanning direction addressed to the reduced image data of interest is obtained by weighted addition (IIR filter processing: equation (1)), accumulated in the memory means (MEM),
  Read the image data and the smoothing level (y background) from the memory means (MEM), and generate the background level data (x background) by smoothing it in the main scanning direction based on the smoothing level (y background). The image data read from the memory means (200) is converted into image data from which the background level represented by the data obtained by expanding the background level data (x background) to correspond to the same magnification image is removed (FIG.12& Figure13).
[0013]
  According to this, the IIR filter process (equation (1)) for smoothing in the sub-scanning direction (y), which is the background tracking process in the sub-scanning direction (y), which is a part of the background detection process, is corrected by the scanner. Since this is performed by the unit (IPP), the background detection accuracy can be further improved and speeded up.
[0014]
  (3) Extraction or generation of reduced image data includes smoothing of image data in the main scanning direction (x) and extraction of smoothed image data jumping in the main scanning direction (x).The image reading processing method according to (1) or (2) above.
[0015]
  According to this, since the average density is stored in the reduced image data, and the extraction can select the extracted image data based on the pixel count or the frequency of the pixel synchronization pulse, and the detailed extraction position calculation is unnecessary, so the processing speed Is relatively fast.
[0016]
  (4) Image reading means (200) for reading an image and converting it into digitized image data;
  Image processing means (IPP) for correcting the image data;
  Memory device (MEM) for storing data;
  Reduction processing means (6 / IPP) for extracting reduced image data reduced in the main scanning direction from the image data corrected by the image processing means (IPP);
  Image data corrected by the image processing means (IPP)And the reduced image dataTo the memory device (MEM)Storing and memory device (MEM) The corrected image data and reduced image data are read out fromMeans (6) for generating background level data from the reduced image data; and
  Read from the memory device (MEM)CorrectedA background removal means (IPP) for converting the image data into image data from which the background level represented by the data obtained by expanding the background level data to support the same size image is removed;
An image reading apparatus.
[0017]
  According to this, the image data obtained and corrected by the image reading means (200) is stored in the memory means (MEM), and then the reduced image data is extracted or generated to reduce the reduced image data. Since the background level calculation is performed, the background level calculation time for one line is short in proportion to the reduction rate, so that the background calculation can be performed relatively quickly and with high accuracy. For example, it is possible to read a document having a high density and a low density background, such as a blue-printed document, and obtain image data that clearly represents a binary image such as characters and line drawings on the document.
[0018]
  (5) Image reading means (200) for reading an image and converting it into digitized image data;
  Image processing means (IPP) for correcting the image data;
  Memory device (MEM) for storing data;
  Reduction processing means (6 / IPP) for extracting reduced image data reduced in the main scanning direction from the image data corrected by the image processing means (IPP);
  A smoothing level in the sub-scanning direction addressed to the target reduced image data is obtained by weighted addition of at least the target reduced image data and a smoothing level defined by the reduced image data preceding the target reduced image data in the sub-scanning direction., The image processing means (IPP) The corrected image data and the smoothing level arememoryapparatusAccumulated in (MEM),Memory device (MEM) The corrected image data and the smoothing level are read out fromMeans (6) for generating background level data smoothed in the main scanning direction based on
  Read from the memory device (MEM)CorrectedA background removal means (IPP) for converting the image data into image data from which the background level represented by the data obtained by expanding the background level data to support the same size image is removed;
An image reading apparatus.
[0019]
  According to this, the IIR filter process (equation (1)) for smoothing in the sub-scanning direction (y), which is the background tracking process in the sub-scanning direction (y), which is a part of the background detection process, is corrected by the scanner. Since this is performed by the unit (IPP), the background detection accuracy can be further improved and speeded up.
[0020]
  (6) An image forming apparatus comprising: the image reading apparatus according to (5); and a printer (400) that forms an image represented by the image data output from the image data processing apparatus on a sheet.
[0021]
  According to this, it is possible to obtain a copy that clearly represents a binary image such as a character or a line drawing on a document having a high density and a low density background, such as a blue-printed document.
[0022]
  (7)Means for generating background level data (6) IsReduced image data obtained by smoothing and thinning is subjected to IIR digital filter processing (Equation (1)) in the sub-scanning direction (y).The smoothing level in the sub-scanning direction is calculated according to (5) above.Image processing device (Figure12& Figure13).
[0023]
  According to this, the IIR filter process (equation (1)) for smoothing in the sub-scanning direction (y), which is the background tracking process in the sub-scanning direction (y), which is a part of the background detection process, is corrected by the scanner. Since it is performed by the IPP (IPP), the background detection accuracy can be further improved and speeded up.
[0024]
  (10)Means for generating background level data (6) IsThe background level (JODn) addressed to the target image data by weighted addition (equation (1)) of at least the target image data (IDn) and the background level (JODn-1) defined by the image data preceding the target image data To calculate,As described in (7) aboveImage processing device (Figure12& Figure13).
[0025]
  According to this, the background level (JODn) is determined for the target image data (IDn), and the background level (JODn) is equalized or smoothed when the target image data is sequentially switched. In the region where the background is dark, the level is high (high level), and in the region where the background is thin, the level is low (low level). By adjusting the value of the weight K given to the target image data (IDn), the background level (JODn) following only the background density change having a long fluctuation cycle other than the level fluctuation of each pixel corresponding to the image or several pixel groups. Is obtained. Since the background level (JODn) and the primary background level (JODn) are closely related to the image level, in the preferred embodiment, the primary background level (JODn) is used to provide an offset with respect to the image level. Is multiplied by an adjustment value M of 0 <M <1 to obtain a secondary background level (M · JODn).
[0026]
  Thus, the background level addressed to the target image data (IDn) is generated by leveling or smoothing the preceding image data including the target image data (IDn), and updated following the image data in units of pixels. Therefore, the reliability of representing the background of the image data representing the image in which the background level fluctuation is relatively wide, such as the background level fluctuation on one line, is high.
[0027]
  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0028]
【Example】
  -1st Example-
  An outline of the mechanism of the first embodiment is shown in FIG. This embodiment is a digital full-color copying machine. A color image reading apparatus (hereinafter referred to as a scanner) 200 forms an image of a document 180 on a contact glass 202 on a color sensor 207 via an illumination lamp 205, mirror groups 204A, 204B, and 204C, and a lens 206. The color image information of the original is read for each color separation light of, for example, blue (hereinafter referred to as “B”), green (hereinafter referred to as “G”), and red (hereinafter referred to as “R”), and converted into an electrical image signal. In this example, the color sensor 207 includes a three-line CCD sensor, and reads B, G, and R images for each color. Based on the color separation image signal intensity levels of B, G, and R obtained by the scanner 200, color conversion processing is performed by an image processing unit (not shown) to obtain black (hereinafter referred to as Bk), cyan (hereinafter referred to as “black”). C), magenta (hereinafter referred to as “M”), and yellow (hereinafter referred to as “Y”) color image data including recording color information is obtained.
[0029]
  Using this color image data, Bk, C, M, and Y images are formed on an intermediate transfer belt by a color image recording apparatus (hereinafter referred to as a color printer) 400 described below, and transferred onto transfer paper. The scanner 200 receives a scanner start signal based on the operation and timing of the color printer 400, and the illumination / mirror optical system including the illumination lamp 205 and the mirror groups 204A, 204B, and 204C scans the document in the left arrow direction. One color image data is obtained for each scanning. Each time, the color printer 400 sequentially visualizes the images and superimposes them on the intermediate transfer belt to form a full-color image of four colors.
[0030]
  A writing optical unit 401 as an exposure unit of the color printer 400 converts color image data from the scanner 200 into an optical signal, performs optical writing corresponding to the original image, and forms an electrostatic latent image on the photosensitive drum 414. Form. The optical writing optical unit 401 includes a laser light emitter 441, a light emission drive control unit (not shown) that drives the light emission, a polygon mirror 443, a rotation motor 444 that rotationally drives it, an fθ lens 442, a reflection mirror 446, and the like. Has been. The photoconductive drum 414 rotates counterclockwise as indicated by an arrow, and around the photoconductive drum cleaning unit 421, the charge eliminating lamp 414M, the charger 419, and the latent image potential on the photoconductive drum are detected. A potential sensor 414D, a selected developing device of the revolver developing device 420, a developing density pattern detector 414P, an intermediate transfer belt 415, and the like are arranged.
[0031]
  The revolver developing device 420 includes a BK developing unit 420K, a C developing unit 420C, an M developing unit 420M, a Y developing unit 420Y, and a revolver rotation driving unit (not shown) that rotates each developing unit in a counterclockwise direction as indicated by an arrow. (Omitted). Each of these developing units assembles a developing sleeve 420KS, 420CS, 420MS, 420YS, which rotates by bringing the ears of the developer into contact with the surface of the photosensitive drum 414 in order to visualize the electrostatic latent image. -It consists of a development paddle that rotates to stir. In the standby state, the revolver developing device 420 is set at a position where development is performed by the BK developing device 420. When the copying operation is started, the scanner 200 starts reading BK image data from a predetermined timing. Based on the data, optical writing and latent image formation by laser light starts. Hereinafter, an electrostatic latent image based on Bk image data is referred to as a Bk latent image. The same applies to C, M, and Y image data. In order to enable development from the leading edge of the Bk latent image, before the leading edge of the latent image reaches the developing position of the Bk developing device 420K, the developing sleeve 420KS starts to rotate, and the Bk latent image is developed with Bk toner. . Thereafter, the developing operation of the Bk latent image area is continued. However, when the trailing edge of the latent image passes the Bk latent image position, the developing operation of the next color from the developing position by the Bk developing unit 420K is promptly performed. The revolver developing device 420 is driven and rotated to the position. This rotation operation is completed at least before the leading edge of the latent image by the next image data arrives.
[0032]
  When the image forming cycle is started, the photosensitive drum 414 is rotated counterclockwise as indicated by an arrow, and the intermediate transfer belt 415 is rotated clockwise by a drive motor (not shown). As the intermediate transfer belt 415 rotates, BK toner image formation, C toner image formation, M toner image formation, and Y toner image formation are sequentially performed. Finally, intermediate transfer is performed in the order of BK, C, M, and Y. A toner image is formed over the belt 415. The BK image is formed as follows. That is, the charger 419 uniformly charges the photosensitive drum 414 to about −700 V with a negative charge by corona discharge. Subsequently, the laser diode 441 performs raster exposure based on the Bk signal. When the raster image is exposed in this way, the charge proportional to the exposure light amount disappears in the exposed portion of the uniformly charged photosensitive drum 414, and an electrostatic latent image is formed. The toner in the revolver developing device 420 is negatively charged by stirring with the ferrite carrier, and the BK developing sleeve 420KS of the developing device is connected to the metal base layer of the photosensitive drum 414 by a power supply circuit (not shown). It is biased to a potential in which a negative DC potential and an AC are superimposed. As a result, toner does not adhere to the portion where the charge of the photosensitive drum 414 remains, and Bk toner is adsorbed to the portion without charge, that is, the exposed portion, and Bk visible similar to the latent image. An image is formed. The intermediate transfer belt 415 is stretched around a drive roller 415D, a transfer counter roller 415T, a cleaning counter roller 415C, and a driven roller group, and is rotated by a drive motor (not shown). Now, the Bk toner image formed on the photosensitive drum 414 is applied to a belt transfer corona discharger (hereinafter referred to as a belt transfer unit) 416 on the surface of an intermediate transfer belt 415 that is driven at a constant speed in contact with the photosensitive member. Is transcribed by. Hereinafter, toner image transfer from the photosensitive drum 414 to the intermediate transfer belt 415 is referred to as belt transfer. Some untransferred residual toner on the photoconductor drum 414 is cleaned by the photoconductor cleaning unit 421 in preparation for reuse of the photoconductor drum 414. The toner collected here is stored in a waste toner tank (not shown) via a collection pipe.
[0033]
  The intermediate transfer belt 415 sequentially aligns the Bk, C, M, and Y toner images formed on the photosensitive drum 414 on the same surface to form a four-color superimposed belt transfer image. Thereafter, batch transfer is performed on the transfer paper with a corona discharge transfer device. By the way, on the photosensitive drum 414 side, the process proceeds to the C image forming process after the BK image forming process. At a predetermined timing, reading of the C image data by the scanner 200 starts, and laser light writing by the image data is performed. Then, a C latent image is formed. The C developing device 420C rotates the revolver developing device after the rear end of the previous Bk latent image has passed with respect to the developing position and before the front end of the C latent image has arrived. Develop the image with C toner. Thereafter, the development of the C latent image area is continued. When the trailing edge of the latent image passes, the revolver developing device 420 is driven in the same manner as in the case of the previous Bk developing device, and the C developing device 420C is sent out. The M developing device 420M is positioned at the developing position. This operation is also performed before the leading edge of the next M latent image reaches the developing unit. It should be noted that the image forming process for each of the M and Y images will not be described because the image data reading, latent image forming, and developing operations are in accordance with the Bk image and C image processes described above.
[0034]
  The belt cleaning device 415U includes an inlet seal, a rubber blade, a discharge coil, and a contact / separation mechanism for the inlet seal and the rubber blade. After transferring the first color Bk image to the belt, while transferring the second, third, and fourth color images to the belt, the blade seal mechanism separates the inlet seal, rubber blade, etc. from the intermediate transfer belt surface. deep.
[0035]
  A paper transfer corona discharger (hereinafter referred to as a paper transfer unit) 417 is a corona discharge method for transferring the superimposed toner image on the intermediate transfer belt 415 to the transfer paper. This is applied to the transfer belt.
[0036]
  The transfer paper cassette 482 in the paper supply bank stores transfer paper of various sizes, and is fed in the direction of the registration roller pair 418R by the paper supply roller 483 from the cassette storing the paper of the specified size.・ Conveyed. Reference numeral 412B2 denotes a paper feed tray for manually feeding OHP paper, cardboard, or the like. At the time when the image formation is started, the transfer paper is fed from one of the paper feed trays and stands by at the nip portion of the registration roller pair 418R. When the leading edge of the toner image on the intermediate transfer belt 415 approaches the paper transfer unit 417, the registration roller pair 418R is driven so that the leading edge of the transfer paper coincides with the leading edge of the image, and the paper and the image are transferred. Matching is done. In this way, the transfer paper is superimposed on the color superposition image on the intermediate transfer belt and passes over the paper transfer device 417 connected to a positive potential. At this time, the transfer paper is charged with a positive charge by the corona discharge current, and most of the toner image is transferred onto the transfer paper. Subsequently, when the paper passes through a separation static eliminator (not shown) disposed on the left side of the paper transfer unit 417, the transfer paper is neutralized, separated from the intermediate transfer belt 415, and transferred to the paper conveyance belt 422. The transfer paper onto which the four-color superimposed toner images have been transferred from the intermediate transfer belt surface is conveyed to the fixing device 423 by the paper conveying belt 422, and the toner is transferred to the nip portion between the fixing roller 423A and the pressure roller 423B controlled to a predetermined temperature. The image is melted and fixed, sent out of the main body by a pair of discharge rollers 424, and stacked face up on a copy tray (not shown).
[0037]
  The surface of the photosensitive drum 414 after the belt transfer is cleaned by a photosensitive member cleaning unit 421 including a brush roller, a rubber blade, and the like, and is uniformly discharged by a discharging lamp 414M. The intermediate transfer belt 415 after transferring the toner image to the transfer paper again cleans the surface by pressing the blade with the blade contact / separation mechanism of the cleaning unit 415U. In the case of repeat copying, the operation of the scanner and the image formation on the photosensitive member are continued to the fourth color image process for the first sheet, and then proceed to the first color image process for the second sheet at a predetermined timing. In the intermediate transfer belt 415, the second Bk toner image is belt-transferred to the area where the surface is cleaned by a belt cleaning device following the batch transfer process of the first four-color superimposed image to the transfer paper. So that After that, the operation is the same as the first sheet.
[0038]
  The color copying machine shown in FIG. 1 can print out (image output) with a color printer 400 when print data is given from a host such as a personal computer through a LAN or parallel I / F, and an image read by the scanner 200. This is a color copier with multiple functions that can send data to remote facsimile machines and print out received image data. This copier is connected to the public telephone network via the private branch exchange PBX, and can communicate with a facsimile communication or a service center management server via the public telephone network.
[0039]
  FIG. 2 shows an electric system of the copying machine shown in FIG. In the document scanner 200 that optically reads a document, the reading unit 4 condenses the reflected light of the lamp irradiation on the document on the light receiving element 207 by a mirror and a lens. The light receiving element (CCD in this embodiment) is in a sensor board unit SBU (hereinafter simply referred to as SBU), and an image signal converted into an electric signal in the CCD is a digital signal, that is, a read image on the SBU. After being converted to data, the data is output from the SBU to the compression / decompression and data interface control unit CDIC (hereinafter simply referred to as CDIC).
[0040]
  That is, the image data output from the SBU is input to the CDIC. The CDIC controls all image data transmission between the functional device and the data bus. That is, the CDIC relates to image data, a data transfer between the SBU, the parallel bus Pb, and the image signal processing device IPP (hereinafter simply referred to as IPP), and a system controller 6 that controls the overall control of the digital copying machine shown in FIG. Communication regarding image data transfer and other control between the controllers 1 is performed. The system controller 6 and the process controller 1 communicate with each other via the parallel bus Pb, CDIC, and serial bus Sb. The CDIC performs data format conversion for the data interface between the parallel bus Pb and the serial bus Sb.
[0041]
  The read image data from the SBU is transferred to the IPP via the CDIC, and the IPP is subjected to signal deterioration due to quantization into an optical system and a digital signal (scanner signal deterioration: distortion of read image data due to scanner characteristics). Is corrected and output to the CDIC again. The CDIC transfers the image data to the copy function controller MFC and writes it in the memory MEM. Or, return to the IPP processing system for printer output.
[0042]
  In other words, the CDIC outputs the read image data to the memory MEM and reuses it, and outputs it to the video data control VDC (hereinafter simply referred to as VDC) without storing it in the memory MEM. Some jobs output images. As an example of storing in the memory MEM, when copying a plurality of originals, the reading unit 4 is operated only once, the read image data is stored in the memory MEM, and the stored data is read out a plurality of times. As an example in which the memory MEM is not used, when only one original is copied, the read image data may be processed as it is for printer output, so there is no need to write to the memory MEM.
[0043]
  First, when the memory MEM is not used, the image data transferred from the IPP to the CDIC is returned from the CDIC to the IPP again. In the IPP, image quality processing (15 in FIG. 3) for converting luminance data from the CCD into area gradation is performed. The image data after the image quality processing is transferred from the IPP to the VDC. With respect to the signal changed to the area gradation, post processing relating to dot arrangement and pulse control for reproducing the dots are performed by the VDC, and a reproduced image is formed on the transfer paper in the image forming unit 5 of the laser printer 400.
[0044]
  When additional processing such as rotation in the image direction, image synthesis, etc. is performed when reading from the memory MEM, data transferred from the IPP to the CDIC is transferred from the CDIC to the image via the parallel bus Pb. It is sent to the memory access control IMAC (hereinafter simply referred to as IMAC). Here, based on the control of the system controller 6, access control of image data and a memory module MEM (hereinafter simply referred to as MEM), development of print data (character code / Character bit conversion) and compression / decompression of image data for effective use of memory. The data sent to the IMAC is stored in the MEM after data compression, and the stored data is read out as necessary. The read data is expanded, returned to the original image data, and returned from the IMAC to the CDIC via the parallel bus Pb.
[0045]
  After transfer from the CDIC to the IPP, image quality processing by the IPP and pulse control by the VDC are performed, and a visible image (toner image) is formed on the transfer paper in the image forming unit 5.
[0046]
  In the flow of image data, the composite function of the digital copying machine is realized by the bus control by the parallel bus Pb and the CDIC. The FAX transmission function, which is one of the copying functions, performs image processing on the scanned image data of the scanner 200 by IPP and transfers it to the FAX control unit FCU (hereinafter simply referred to as FCU) via the CDIC and the parallel bus Pb. To do. The FCU performs data conversion to a public line communication network PN (hereinafter simply referred to as PN), and transmits the data to the PN as FAX data. In FAX reception, line data from the PN is converted to image data by the FCU, and transferred to the IPP via the parallel bus Pb and CDIC. In this case, special image quality processing is not performed, dot rearrangement and pulse control are performed in the VDC, and a visible image is formed on the transfer paper in the image forming unit 5.
[0047]
  In a situation where a plurality of jobs, for example, a copy function, a FAX transmission / reception function, and a printer output function operate in parallel, the system controller 6 allocates the reading unit 4, the image forming unit 5, and the parallel bus Pb usage right to the job.AndAnd process controller 1.
[0048]
  The process controller 1 controls the flow of image data, and the system controller 6 controls the entire system and manages the activation of each resource. The function selection of the digital copying function copying machine is selected and input on the operation board OPB, and processing contents such as a copying function and a FAX function are set.
[0049]
  FIG. 3 shows an outline of the image processing function of IPP. The read image data is transmitted from the IPP input I / F (interface) 11 to the scanner image processing 12 via the CDIC from the SBU. The scanner image processing 12 performs shading correction, show-through correction, scanner γ correction, MTF correction, and the like mainly for the purpose of correcting deterioration of image information due to reading. Although not correction processing, enlargement / reduction scaling processing is also performed. After the read image data correction processing is completed, the image data is transferred to the CDIC via the output I / F 13. For output to the transfer paper, image data from the CDIC is received from the input I / F 14, and area gradation processing is performed in the image quality processing 15c. The data after the image quality processing is output to the VDC via the output I / F 16. The area gradation processing includes density conversion, dither processing, error diffusion processing, and the like, and mainly performs area approximation of gradation information.
[0050]
  Once the image data subjected to the scanner image processing 12 is stored in the memory MEM, various reproduced images can be confirmed by changing the processing performed in the image quality processing 15. For example, the atmosphere of the reproduced image can be changed by changing the density of the reproduced image or changing the number of lines in the dither matrix. At this time, it is not necessary to read the image again by the scanner 200 every time the processing is changed, and if the stored image is read from the MEM, different processing can be performed on the same data any number of times.
[0051]
  When performing background level removal, as shown in FIG. 3, the image data input from the scanner 200 is subjected to scanner image correction by IPP via the CDIC. Scanner data that has undergone image correction is directly stored in MEM via CDIC and IMAC, and reduced image data that is smoothed and thinned in the main scanning direction by “main scanning reduction” 12b inside IPP. Are stored in the MEM. Since the reduction is performed by the smoothing and thinning of the main scanning, the average density is preserved. Therefore, the background level can be accurately determined when the background level is determined inside the MEM. Data in the MEM can be calculated by the system controller 6 connected to the IMAC. The background level is detected by the system controller 6.
[0052]
  However, since the system controller 6 is a general-purpose processor, the calculation speed is slow. For this reason, pixels are thinned out at regular intervals in the main scanning direction as background detection data and managed separately from the original image. Since the scanner of this embodiment assumes 600 dpi, the accuracy of the background detection is almost the same even if it is thinned out at intervals of 4 pixels and reduced to 150 dpi (1/4 reduction in the main scanning x direction: 3 pixels skipped and 1 pixel extracted). Not affected. System controller 6 is MEMAccumulate inCut out 1/4 of the image data(12b in FIG. 3)Reduced image data andThen, it is stored in the MEM together with the image data. When the image data stored in the MEM is read out, the reduced image data is also read out to be reduced image data.The background level is calculated from the image data, and the image data and the background level data read from the MEM are returned to the IPP via IMAC and CDIC, respectively.
[0053]
  Since the background level data is reduced to ¼ in the main scanning direction x, main scanning enlargement (15a in FIG. 3) is performed inside the IPP. Then, the background removal process is performed inside the IPP (15b in FIG. 3).
[0054]
  The calculation of the background level by the system controller 6 and the IPP background removal processing will be described in more detail later.
[0055]
  FIG. 4 shows an outline of the internal configuration of the IPP. The IPP has a plurality of input / output ports for data input / output with the outside, and can arbitrarily set input and output. There is a local memory group inside, and the memory area to be used and the path of the data path are controlled by the memory control unit. The input data and the data for output are allocated as local memory groups as buffer memories, stored in each of them, and external I / F is controlled. Various processing is performed on the image data stored in the local memory in the processor array unit, and the output result is stored again in the local memory. The processing procedure of the processor, parameters for processing, and the like are exchanged between the program RAM and the data RAM. The contents of the program RAM and data RAM are downloaded from the process controller through the serial I / F. Alternatively, the process controller reads the contents of the data RAM and monitors the progress of processing. When the processing contents are changed or the processing mode required by the system is changed, the contents of the program RAM and data RAM referred to by the processor array are updated.
[0056]
  FIG. 5 shows an outline of the functional configuration of the CDIC. The image data input / output control 21 inputs the read image data from the SBU and outputs the data to the IPP. The image data input control 22 receives image data that has been subjected to scanner image correction by the scanner image processing 12 using IPP. The input data is subjected to data compression in the data compression unit 23 in order to increase the transfer efficiency on the parallel bus Pb. The compressed image data is sent to the parallel bus Pb via the parallel data I / F 25. Image data input from the parallel data bus Pb via the parallel data I / F 25 is compressed for bus transfer and is expanded by the data expansion unit 26. The expanded image data is transferred to the IPP by the image data output control 27. CDIC has both parallel data and serial data conversion functions. The system controller 6 transfers data to the parallel bus Pb, and the process controller 1 transfers data to the serial bus Sb. For communication between the two controllers 6 and 1, parallel / serial data conversion is performed by the data converter 24 and the serial data I / F 29. The serial data I / F 28 is for IPP, and serial data is transferred with IPP.
[0057]
  FIG. 6 shows an outline of the functional configuration of the VDC. The VDC performs additional processing on the image data input from the IPP according to the characteristics of the image forming unit 5. Dot rearrangement processing by edge smoothing processing and pulse control of image signals for dot formation are performed, and image data is output to the image forming unit 5. Apart from image data conversion, parallel data and serial data format conversion functions 33 to 35 are also provided, and a single VDC can support communication between the system controller 6 and the process controller 1.
[0058]
  FIG. 7 shows an outline of the functional configuration of the IMAC. In the parallel data I / F 41, input / output of image data to / from the parallel bus Pb is managed, storage / reading of image data to / from the MEM, and code data input mainly from an external PC to the image data. Control deployment. Code data input from the PC is stored in the line buffer 42. That is, the data in the local area is stored, and the code data stored in the line buffer 42 is received by the video control 43 based on the expansion processing instruction from the system controller 6 input via the system controller I / F 44. Expand to image data. The developed image data or the image data input from the parallel bus Pb via the parallel data I / F 41 is stored in the MEM. In this case, the data conversion unit 45 selects image data to be stored, the data compression unit 46 performs data compression to increase the memory usage efficiency, and the memory access control unit 47 manages the MEM address. The image data is stored in the MEM. When reading out the image data stored in the MEM, the memory access control unit 47 controls the read destination address, and the data expansion unit 48 expands the read image data. When the decompressed image data is transferred to the parallel bus Pb, the data is transferred via the parallel data I / F 41.
[0059]
  FIG. 8 shows an outline of the functional configuration of the FCU. The FAX transmission / reception unit FCU converts the image data into a communication format and transmits it to the external line PN, and returns the data from the external line PN to the image data and creates it via the external I / F unit 51 and the parallel bus Pb. Recording is output in the image unit 5. The FAX transmission / reception unit FCU includes a FAX image processing 52, an image memory 53, a memory control unit 55, a facsimile control unit 54, an image compression / decompression 56, a modem 57, and a network control unit 58. Among these, regarding the FAX image processing 52, the binary smoothing processing on the received image is performed in the edge smoothing processing 31 of the VDC. Regarding the image memory 53, the output buffer function is partially limited by IMAC and MEM.
[0060]
  In the FAX transmission / reception unit FCU configured as described above, when the transmission of image information is started, the facsimile control unit 54 instructs the memory control unit 55 to sequentially read out the image information accumulated from the image memory 53. The read image information is restored to the original signal by the FAX image processing 52, subjected to density conversion processing and scaling processing, and added to the facsimile control unit 54. The image signal applied to the facsimile control unit 54 is code-compressed by the image compression / decompression unit 56, modulated by the modem 57, and then sent to the destination via the network control unit 58. Then, the image information that has been transmitted is deleted from the image memory 53.
[0061]
  At the time of reception, the received image is temporarily stored in the image memory 53. If the received image can be recorded and output at that time, the received image is recorded and output when reception of one image is completed. Also, when a call is started during a copying operation and reception is started, the image memory 53 is accumulated until the usage rate of the image memory 53 reaches a predetermined value, for example, 80%, and the usage rate of the image memory 53 is increased to 80%. When it reaches, the writing operation being executed at that time is forcibly interrupted, and the received image is read from the image memory 53 and recorded. At this time, the received image read from the image memory 53 is deleted from the image memory 53, the writing operation that was interrupted when the usage rate of the image memory 53 has decreased to a predetermined value, for example, 10%, is resumed, and the writing operation is resumed. When all the processing is completed, the remaining received images are recorded and output. In addition, various parameters for the writing operation at the time of interruption are internally saved so that the writing operation can be resumed after the interruption of the writing operation, and the parameters are internally restored at the time of resumption.
[0062]
  In the above example, the CDIC that is the image bus management means and the IMAC that is the memory management means are connected by the parallel bus Pb that is a set of image buses. Since each independent SBU that is an image reading means, VDC that is a writing means, and IPP that is an image signal processing means are not directly connected to the image bus Pb but are connected to the image bus management means CDIC, in effect, the image bus Pb Is managed only by the image bus management means CDIC and the memory management means IMAC. Therefore, arbitration and transfer control of the bus Pb is easy and efficient.
[0063]
  FIG. 9 shows a flow of processing for accumulating an image in the MEM and processing for reading an image from the MEM. (a) shows image data processing or transfer processes Ip1 to Ip13 until the image data generated by the image scanner 200 is written to the MEM, and (b) shows the process from reading the image data from the MEM to outputting it to the printer 400. Image data processing or transfer processes Op1 to Op13 are shown.
[0064]
  The data flow between such buses and units is controlled by the control by the system controller 6 via the CDIC. With respect to the read image data, scanner image processing Ip1 to Ip13 (12a in FIG., 12b) For image data to be output to the printer 400, the image quality processing Op1 to Op13 (15a to 15c in FIG. 3) in the IPP is performed independently.
[0065]
  First1In the example, figure9The IPP performs “main scanning reduction” Opsb, which is indicated by the block classification in FIG. TheIn other words, 1/4 of the image data stored in the MEM is thinned out and stored in the MEM together with the image data as reduced image data (12b in FIG. 3).Then, “background calculation” Opsc and “main scanning enlargement & background removal processing” Op10 are read out from the MEM and output to the printer 400 in Op1 to Op13. At the same time, the reduced image data is also read from the MEM, respectively. Performed by the controller 6 and the IPP.
[0066]
  The system controller 6 performs “background calculation” Opsc when reading out image data from the MEM and sending it to the printer output path. In this case, IMAC was decrypted and decompressed by reading from MEM.Shrinkimage dataInA simple smoothing filter process (average value calculation) is performed, and the primary background level JODn is calculated as follows:
      JODn = (1-K) .JODn-1 + K.IDn (1)
      JODn: Density after calculation for the nth pixel in the main scanning direction (primary background level)
      IDn: input image density of the nth pixel in the main scanning direction (image data to be processed)
      K: tracking coefficient (0 <K ≦ 1); “adjustment” key of operation unit OPB
          Process characteristic adjustment parameter that can be adjusted by operating
  “·” Means multiplication, and “/” means division. The same applies to the following. The pixel here is a pixel extracted from the image data, and the image dataIs flatThis is reduced image data that has been subjected to a sliding filter process.
[0067]
  FIG. 10A shows an example of the image data IDn to be processed, the calculated primary background level JODn, and the following secondary background level M · JODn. The background level calculated value JODn changes the speed following the original data IDn depending on the value of the weight K. As can be seen from Equation (1), the larger K is, the closer to the original data IDn, the faster the follow-up speed. The smaller K is, the slower the follow-up speed is, and it approaches a constant value. By appropriately adjusting the value of K, it is possible to obtain the primary background level JODn following only the change in the large background other than the peak as shown in FIG.
[0068]
  The primary background level data JODn is given to the IPP by matching the read data without thinning and the timing (position on the image).
[0069]
  In the first embodiment, the original image data is thinned out in the main scanning direction on the MEM, and image data for detecting the background is generated and the background is detected. Therefore, a low-speed general-purpose processor is used for the system controller 6. However, the background detection process can be performed relatively quickly.
[0070]
  The IPP expands one primary background level data JODn to four primary background level data JODm of the same value in the main scanning direction x in the “main scanning enlargement & background removal processing” Op10. Assigned to each image data read from MEM. This is the main scanning magnification at the background level.(15a in FIG. 3)It is. Then, primary image data AODm obtained by subtracting (removing) the background level assigned to each image data is calculated as follows:
      AODm = IDm-M / JODm (2)
      IF (AODm <0) THEN AODm = 0
      M: Background density calculation coefficient (0 <M ≦ 1);
          Processing characteristic adjustment parameters that can be adjusted,
  That is, the secondary background level M · JODm, which is the product of the primary background level JODm and the adjustment coefficient M, is subtracted from the original image data IDm. FIG. 10B shows an example of the primary image data AODm. Note that (a) in FIG. 10 represents reduced image data. Since (b) in FIG. 10 corresponds to the original equal-size image data, the amount of image data is four times that of the reduced image data in FIG. 10 (a) per line. Compared to (a) of FIG. 10, it is shown compressed to ¼.
[0071]
  Although the background removal is completed in this way, the density of the background removal M · JODm is lowered if it is left as it is, and especially in the case of characters or the like, the legibility is lowered. For this reason, the contrast is corrected by the next image quality processing Op11, and the level is enlarged near the maximum value that the full-scale value can take the number of image data bits.
[0072]
  The above-mentioned “main scanning enlargement & background removal processing” Op10 and contrast correction can be completely expressed by an arithmetic expression, and are therefore suitable for being processed by a digital signal processor (DSP) such as IPP. One.
[0073]
  FIG.11 shows a schematic configuration of a SIMD (Single Instruction Stream Multi-Data Stream) type processor for image processing adopted in IPP. SIMD allows a single instruction to be executed in parallel for a plurality of data, and is composed of a plurality of PEs (processor elements) PE1 to PE8 (eight for 1-byte parallel processing in the illustrated example). Each PE has a register (Reg) for storing data, a multiplexer (MUX) for accessing registers of other PEs, a barrel shifter (Shift Expand), a logical operation unit (ALU), and an accumulator (A) for storing a logical result. ) And a temporary register (F) for temporarily comparing the contents of the accumulator. Each register is connected to an address and data bus, and stores an instruction code for defining processing or data to be processed.
[0074]
  Data to be processed by the register is input to the ALU, and the operation processing result is stored in A. In order to take the result out of the PE, it is temporarily saved in F. By extracting the contents of F, the processing result for the target data is obtained. The instruction code is given to each PE with the same contents, the processing target data is given in a different state for each PE, and the operation results are processed in parallel by referring to the Reg contents of adjacent PEs in the MUX and output to each A. The For example, if the content of one line of image data is arranged in the PE for each pixel and arithmetic processing is performed with the same instruction code, a processing result for 1 byte can be obtained in a shorter time than sequential processing for each pixel. Image data processing in IPP is performed by these PEs.
[0075]
  This first1In the embodiment, since the reduced image is thinned out to create the reduced image inside the IPP, the system controller 6 can concentrate on the calculation of the background level, which reduces the processing load and contributes to the speedup.
[0076]
  -Second Example-
  In the second embodiment, the IPP12As shown in FIG. 5, a “main scanning reduction” function 12b and an “IIR filter” processing function 12c (smooth and thinning out main scanning)13(Opsd) is added. First12As shown in the figure, input image data is subjected to scanner image correction by IPP via CDIC. Scanner data that has undergone image correction is stored as it is in MEM via CDIC and IMAC, and after smoothing and thinning out 12b in the main scanning direction within IPP, it is performed in the sub-scanning direction by the IIR filter. Some are smoothed 12c and stored in the MEM.
[0077]
  The IIR filter here performs the calculation of equation (1) in the sub-scanning direction rotated 90 degrees. That is, the smoothing level (y background level) addressed to the attention image data is calculated by weighted addition of the smoothing level (y background level) defined by the attention image data and the image data of the line preceding the attention image data. . Since the smoothing level of the preceding line is necessary, a line buffer 12d is provided, and the calculated smoothing level is updated and written in the line buffer 12 and is associated with the original (same size) image data at the corresponding position. Accumulate in memory MEM.
[0078]
  Since the reduction is performed by the smoothing and thinning of the main scanning, the average density is preserved. Further, since the IIR filter is applied in the sub-scanning direction and then passed to the MEM, the background level can be determined more accurately when the background level is determined inside the MEM.
[0079]
  Figure13Second2The flow of the process which accumulate | stores an image in MEM and the process which reads an image from MEM in an Example is shown. (a) shows image data processing or transfer processes Ip1 to Ip13 until the image data generated by the image scanner 200 is written to the MEM, and (b) shows the process from reading the image data from the MEM to outputting it to the printer 400. Image data processing or transfer processes Op1 to Op13 are shown. Similar to the first embodiment, such a data flow between the bus and the unit is controlled by the control of the system controller 6 via the CDIC.
[0080]
  First2In the example, figure13The IPP performs the “main scanning reduction & y background calculation” Opsd shown by the block classification in FIG. This is described above (Figure1212b to 12d). Then, “x background calculation” Opse and “main scanning enlargement & background removal processing” Op10 are processes Op1 to Op13 in which image data is read from the MEM and output to the printer 400. At the same time, the smoothing level (y background) is also obtained from the MEM. The system controller 6 and the IPP respectively read out.
[0081]
  When the system controller 6 reads the image data from the MEM and sends it to the printer output path, the system controller 6 performs “x background calculation” Opse. In this case, as in the first embodiment, the primary background level JODn is calculated by the equation (1). However, the original data IDn here is smoothing level (y background) data. The contents of the IPP “main scanning enlargement & background removal processing” Op10 and below are the same as those in the first embodiment.
[0082]
  First2In the embodiment, reduced image data is created by thinning out and smoothing in the sub-scanning direction is also performed inside the IPP. Therefore, after accumulation in the MEM, only the background is detected by smoothing in the main scanning direction. This reduces the processing burden on the system controller 6 and contributes to higher speed. In addition, since tracking in the sub-scanning direction (y background detection) is realized by IPP, more accurate background detection is possible.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an outline of the mechanism of a digital color copying machine according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an outline of a configuration of an electric control system of the copying machine shown in FIG.
3 is a block diagram showing a functional configuration of the image signal processing device IPP shown in FIG. 2;
4 is a block diagram showing an outline of hardware of the image signal processing device IPP shown in FIG. 2. FIG.
5 is a block diagram showing a functional configuration of a compression / decompression and data interface control unit CDIC shown in FIG. 2. FIG.
6 is a block diagram showing a functional configuration of the video data control VDC shown in FIG. 2. FIG.
7 is a block diagram showing a functional configuration of the image memory access control IMAC shown in FIG. 2. FIG.
FIG. 8 is a block diagram showing a functional configuration of a FAX transmitting / receiving unit FCU shown in FIG. 2;
9A is a flowchart showing the flow and processing of image data until image data read by the scanner 200 shown in FIG. 2 is written into the image memory MEM, and FIG. 9B is a flowchart showing image data from the image memory MEM. 5 is a flowchart showing the flow and processing of image data from when the image is read out to the printer 400.
FIG. 10A is a graph schematically showing image data IDn obtained by reading a document including a dark background and a light background with the scanner 200, a primary background level JODn, and a secondary background level M · JODn. is there. (B) is a graph showing the background-removed image data AODn obtained by subtracting the secondary background level M · JODn from the image data IDn shown in (a).
11 is a block diagram showing a partial configuration of the processor array PAU shown in FIG. 4;
FIG. 12 is a block diagram showing an outline of a functional configuration of an image signal processing apparatus IIP used in the second embodiment of the present invention.
FIG. 13A is a flowchart showing the flow and processing of image data until image data read by a scanner in the second embodiment is written into the image memory MEM, and FIG. 13B is a flowchart showing image data from the image memory MEM. 5 is a flowchart showing the flow and processing of image data from reading to output to a printer.
[Explanation of symbols]
200: Document reading scanner
400: Full color printer
IPP: Image signal processing device
CDIC: compression / decompression and data interface controller
VDC: Video data control
IMAC: Image memory access control
FCU: FAX transceiver
SBU: Sensor board unit
PN: Public line

Claims (6)

  The image is read by the image reading means and converted into image data, the image data is corrected and stored in the memory means, and the reduced image data is extracted or generated from the corrected image data and stored in the memory means. The image data and the reduced image data are read to generate background level data based on the reduced image data, and the image data read from the memory means is represented by data obtained by expanding the background level data to correspond to the same size image. An image reading processing method for converting image data from which image data has been removed. The image is read by the image reading means and converted into image data, the image data is corrected and stored in the memory means,
Extracting or generating reduced image data reduced in the main scanning direction from the corrected image data, and at least a smoothing level defined by the reduced image data of interest and the reduced image data preceding the reduced image data of interest in the sub-scanning direction The smoothing level in the sub-scanning direction addressed to the reduced image data of interest is obtained by weighted addition of and stored in the memory means,
The image data and the smoothing level are read from the memory means, background level data obtained by smoothing it in the main scanning direction based on the smoothing level is generated, and the image data read from the memory means is converted to the background level data. An image reading processing method for converting image data from which the background level represented by the data expanded to the same size image is removed. Reduced extraction or generation of the image data in the main scanning direction of the smoothing and the main scanning direction in discrete excision of the smoothed image data of the image data, including image scanning method according to claim 1 or claim 2. Image reading means for reading an image and converting it into digitized image data;
Image processing means for correcting the image data;
A memory device for storing data;
Reduction processing means for extracting reduced image data reduced in the main scanning direction from the image data corrected by the image processing means;
The accumulated image processing unit image data and the reduced image data is corrected in the memory device, means for generating a background level data from said corrected image data and the reduced image data is read out the reduced image data from the memory device ;and,
Background correction means for converting the corrected image data read from the memory device into image data from which the background level represented by data obtained by expanding the background level data to correspond to the same size image is removed;
An image reading apparatus. Image reading means for reading an image and converting it into digitized image data;
Image processing means for correcting the image data;
A memory device for storing data;
Reduction processing means for extracting reduced image data reduced in the main scanning direction from the image data corrected by the image processing means;
Obtaining a smoothing level in the sub-scanning direction addressed to the target reduced image data by weighted addition of at least the target reduced image data and a smoothing level defined by the reduced image data preceding the target reduced image data in the sub-scanning direction ; said image data and said flat smoothed-level image processing means has corrected accumulated in the memory device, the then memory device in the main scanning direction on the basis of the smoothed level image data is read out and smoothing levels were the correction Means for generating background level data obtained by smoothing;
Background correction means for converting the corrected image data read from the memory device into image data from which the background level represented by data obtained by expanding the background level data to correspond to the same size image is removed;
An image reading apparatus. Image reading apparatus according to claim 4 or 5; and a printer for forming an image of image data obtained by removing the background level is represented on a sheet; image forming apparatus provided with.

Images