JP5023035B2 - Image processing apparatus, image forming apparatus including the image processing apparatus, image processing method, image processing program, and computer-readable recording medium recording the image processing program - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus and an image forming apparatus including the image processing apparatus that are used when an image of a double-sided original is reproduced by printing a double-sided original using an electrophotographic method The present invention relates to an image processing method, an image processing program, and a computer-readable recording medium on which the program is recorded.

  In general, in an electrophotographic image forming apparatus, when an original image is reproduced, the original image is first read. In this reading, the document is scanned while irradiating light from the slit. The reflected light from the original is received by a photoelectric conversion device (CCD: Charge Coupled Device) and converted into a voltage. Analog image information obtained from the CCD is digitally converted. The document image is thus read. When this image is formed on the recording paper, the digital signal of the image is converted into light, and the uniformly electrostatically charged photoconductor is scanned with the light. As a result, an electrostatic latent image corresponding to the original image is formed on the photosensitive member. This electrostatic latent image is developed with toner (also referred to as “developer”). The toner image on the photosensitive member is transferred onto the recording paper by electricity of reverse polarity. The toner image transferred to the recording paper is heated and pressed to be fixed.

  By the way, there is a case where a document on which nothing is drawn is set on the image forming apparatus. Hereinafter, such an original is called a blank paper or a blank original. Even in such an original, there may be, for example, punch holes, wrinkles, or fine dirt. A human can easily determine that such a manuscript is a blank manuscript. If you are human, you will not copy blank documents.

  Similar to this human processing, when printing a document, it is determined whether or not the document is a blank document. If it is determined that the document is a blank document, the document is not printed on the recording paper. An image forming apparatus is proposed in Patent Document 1 described later. The reason for performing such processing is that if the original is a blank sheet, printing paper and toner for printing it are required, which causes a problem of wasted resources. Furthermore, it is because there is a problem that deterioration of the developer and the photoreceptor is accelerated by performing unnecessary printing. By detecting a blank document and not printing such a document on recording paper, these problems can be avoided.

  The image forming apparatus of Patent Document 1 calculates both the amount of image data of the entire area on one side of the document and the amount of image data of a specific area on one side. The specific area is, for example, an area where the number of pages is drawn. It is assumed that the specific area is predetermined by the user. The more images are drawn on the document, the greater the amount of image data.

  Normally, when printing a plurality of originals on which a series of pages are drawn, it may be desirable to print such originals even if there is an original on which nothing is drawn other than the number of pages. This is because if a sheet for a certain page is missing after printing, the user may be confused as to why the page is not printed.

  The image forming apparatus determines whether the image data amount of the entire area is smaller than a predetermined first reference value and whether the image data amount of a specific area is smaller than a predetermined second reference value. To do. The first reference value is a value for determining whether or not the entire area on one side of the document is a blank document. The second value is a value for determining whether or not the number of pages is drawn in a specific area.

  If the determination result is YES, the image forming apparatus determines that the document is a blank document. If the image forming apparatus determines that the document is a blank document, the image forming apparatus stops the process of printing the document on recording paper, and shifts to the process of printing the image of the next document. When the number of pages is printed, the amount of image data in the specific area is equal to or greater than the second reference value. As a result, the paper on which the number of pages is printed even if the other area is blank is printed on the recording paper.

As described above, the image forming apparatus described in Patent Document 1 prevents wasteful use of resources without performing wasteful printing on recording paper.
JP 2001-268335 A

  However, the image forming apparatus disclosed in Patent Document 1 has the following problems.

  A document read by the image forming apparatus includes a double-sided document. A double-sided document is a document in which images are present on both sides of the document. When the image forming apparatus reads one side of a document with a scanner, an image showing through from the other side may also be read.

  In the technique described in Patent Document 1, it is simply determined whether the amount of image data on one side of the document is smaller than a reference value. For this reason, even a blank document may be determined not to be a blank document due to show-through. This is undesirable both in terms of resource saving and in terms of device life. Conventionally, there has been no awareness of the problem of erroneously determining whether a document is a blank document due to show-through.

  An object of the present invention is to provide an image processing apparatus, an image forming apparatus provided with the image processing apparatus, an image processing method, and an image processing program capable of determining a blank original with high accuracy in consideration of the effect of show-through in a double-sided original. And a computer-readable recording medium on which the program is recorded.

An image processing apparatus according to a first aspect of the present invention is an image processing apparatus for performing image reproduction on one side and / or the other side of a double-sided original read by an image information reading unit, A first region separation processing unit for region separation of one surface input from the reading unit; and a component that can be influenced by a show-through component of the other surface from a region separation result by the first region separation processing unit. a first first for extracting a specific area of the specific region extraction processing means having a total concentration information detection means for counting the number of pixels more than a predetermined concentration in the entire area of hand side, the total concentration Based on the detection result of the information detection means, the first original determination processing means for determining whether one side is a blank original and the other side inputted from the image information reading unit are used for region separation. Second region separation processing means; second A second specific region extraction processing unit for extracting a second specific region having a component that can be a show-through on one side from the region separation result by the region separation processing unit; and a first document determination processing unit. When it is determined that one side is not a blank document, the second specific region is used to determine whether one side is a blank document by comparing the first specific area and the second specific area. Original determination processing means.

  The first region separation processing unit separates one surface of the double-sided document. The first specific area extraction processing means extracts a first specific area having a component that can be influenced by the show-through component of the other surface from the result of the area separation. The total density information detection means counts the number of pixels having a predetermined density or more among the pixels on one surface and outputs the total density information. A first document determination processing unit determines whether one side is a blank document based on the total density information. The second region separation processing unit separates the other surface. The second specific area extraction processing means extracts a second specific area having a component that can be a show-through to one surface based on the region separation result of the other surface. When the first document determination processing unit determines that one side is not a blank document, the second document determination processing unit compares the first specific area with the second specific area. Finally, it is determined whether one side is a blank document.

  In determining the blank document, not only the density information on one side but also the show-through from the other side is taken into account, so that the blank document can be determined more accurately and with high accuracy. Even though it is a blank document, it can be determined that it is not a blank document due to show-through, and wasteful use of resources due to printing even though it is a blank document can be prevented.

Preferably, when the first document determination processing unit determines that one side is not a blank document, the second document determination processing unit determines the show-through component of the other side of the first specific area. Means are included for determining whether one side is a blank document by comparing a partial area having a component that can be affected to the second specific area.

  The means for determining extracts a partial region having a component that can be influenced by the show-through component of the other surface of the first specific region, and compares the extracted region with the second specific region. Thus, it is determined whether one side is a blank document. As a result, the influence of the show-through component can be estimated more correctly, and the blank document can be determined with higher accuracy.

  More preferably, the image processing apparatus further includes a region extracting unit for extracting a region having a predetermined density or more from the first specific region. The means for determining comprises comparing the area extracted by the area extracting means and the second specific area when one side is determined not to be a blank original by the first original determination processing means. Means for determining whether one side is a blank document is included.

  Since the first specific area includes a component that can be influenced by the show-through component, there is a possibility that a component that is not affected by the show-through component is included in the first specific area. The region extracting means extracts a region having a predetermined density or more from the first specific region. Therefore, it is possible to remove components that are considered not affected by the show-through component from the first specific region by the region extraction means. The means for determining determines whether the document is a blank document by comparing the area extracted by the area extracting means with the second specific area. As a result, the influence of the show-through component can be estimated more correctly, and the blank document can be determined with higher accuracy.

  More preferably, the image processing apparatus further includes background density information processing means for detecting the background of one surface input from the image information reading unit and outputting the density of the background. The region extracting unit extracts a region of the first specific region that is equal to or greater than a threshold value in which the background density output by the background density information processing unit is added to a predetermined density.

  When determining the influence of the show-through component on the first specific area, the threshold value considering the background density on one surface is used to receive the influence of the show-through component from the first specific area. Extract the ingredients to obtain. As a result, even if the background of the original is colored, the influence of show-through on the first specific area can be determined with high accuracy, and the determination of the blank original can be performed more correctly.

  The image forming apparatus according to the second aspect of the present invention includes any one of the image processing apparatuses described above.

An image processing method according to a third aspect of the present invention is an image processing method for performing image reproduction on one side and / or the other side of a double-sided original read by an image information reading unit in a computer. In this method, the influence of the show-through component of the other surface is determined from the first region separation processing step for region separation of one surface input from the image information reading unit, and the region separation result by the first region separation processing step. a first specific area extracting process extracting a first specific area including the receivers may component, and the total concentration information detecting step of counting the number of pixels more than a predetermined concentration in the entire area of hand side, the total concentration Based on the detection result of the information detection step, a first document determination processing step for determining whether or not one surface is a blank document and a region separation for image information on the other surface input from the image information reading unit. A second specific region extraction for extracting a second specific region having a component that can be a show-through to one surface from the region separation result of the second region separation processing step and the second region separation processing step When one of the surfaces is determined not to be a blank document by the processing step and the first document determination processing step, one surface is blanked by comparing the first specific region and the second specific region. And a second document determination processing step for determining whether the document is a document.

  Preferably, in the second document determination processing step, when one surface is determined not to be a blank document in the first document determination processing step, the show-through component of the other surface of the first specific region is determined. Determining whether one side is a blank document by comparing a partial area having a component that can be affected to a second specific area.

  More preferably, the method further includes a region extracting step of extracting a region having a predetermined density or more from the first specific region. In the determining step, when it is determined in the first document determination processing step that one side is not a blank document, the one extracted by comparing the region extracted in the region extracting step and the second specific region Determining whether the surface is a blank document.

  More preferably, the method further includes a background density information processing step of detecting a background of one surface input from the image information reading unit and outputting the density of the background. The region extraction step includes a step of extracting, from the first specific region, a region that is equal to or higher than a threshold value that takes into account the background density output by the background density information processing step.

  An image processing program according to the fourth aspect of the present invention causes a computer to function as any of the image processing apparatuses described above.

  A recording medium according to a fifth aspect of the present invention is a computer-readable recording medium that records the above-described image processing program.

  According to the present invention, not only the density information on one side but also the show-through from the other side is considered in the determination of the blank document, so that the blank document can be determined more accurately and with high accuracy. Even though it is a blank document, it can be determined that it is not a blank document due to show-through, and wasteful use of resources due to printing even though it is a blank document can be prevented. As a result, an image processing apparatus, an image forming apparatus provided with an image processing apparatus, an image processing method, an image processing program, and an image processing apparatus capable of determining a blank document with high accuracy in consideration of the effect of show-through in a double-sided document A computer-readable recording medium in which the program is recorded can be provided.

  In the following description of the embodiments, the same parts are denoted by the same reference numerals. Their functions and names are also the same. Therefore, detailed description thereof will not be repeated.

[First Embodiment]
(Functional configuration)
FIG. 1 is a diagram showing an overall configuration of an image forming apparatus 20 according to the first embodiment of the present invention. Referring to FIG. 1, an image forming apparatus 20 is, for example, an electrophotographic multifunction machine that functions as a copying machine, a printer, a facsimile machine, and the like, and (1) image information of a document is stored in the apparatus body 22. Image information reading unit 24 for reading and outputting RGB (R: Red, G: Green, B: Blue) analog image signals, and (2) recording based on image information processed by image processing circuit 82 shown in FIG. An image forming unit 26 that forms an image on paper, (3) a paper supply unit 30 that supplies recording paper from the multi-stage paper feeding cassette 28 to the image forming unit 26, and (4) an image is formed in the image forming unit 26. A fixing unit 32 for fixing the image transferred on the recording paper, (5) a paper discharging unit 36 for discharging the recording paper on which the image is fixed to the paper discharge tray 34, and (6) the entire image forming apparatus 20. Control equipment to control And a 38.

  In the image forming apparatus 20, recording paper is also supplied to the image forming unit 26 from the manual feed tray 40 and the automatic paper feed cassette 42 outside the apparatus main body 22 via the paper supply unit 30. The manual feed tray 40 is disposed on the side opposite to the paper discharge tray 34. The automatic paper feed cassette 42 can accommodate a large amount of recording paper, and is connected to the apparatus main body 22 by an external attachment below the manual feed tray 40.

  The image information reading unit 24 includes an optical system 44 capable of reading a monochrome image or color image of a document, and a document table 46 made of a transparent glass body is disposed above the optical system 44.

  The optical system 44 includes a document scanning unit, an optical lens, a CCD line sensor, and the like, and feeds the document to a document reading position on the document table 46 by an operation related to the automatic document feeder 48 provided on the document table 46. The black and white image or color image of the original document read is relatively read at a predetermined exposure position (reading position). The document image information read by the optical system 44 is output to the image processing circuit 82.

  One end of the automatic document feeder 48 is rotatably supported by the apparatus body 22 at a predetermined angle so that a document can be directly placed on the document table 46. The automatic document feeder 48 includes a document feed tray 50, a reversing path path 52, a document discharge tray 54, and the like, and a plurality of documents placed on the document feed tray 50 are one sheet. Each sheet is automatically fed onto the document reading position on the document table 46.

  In the image information reading unit 24, when the document placed on the document feed tray 50 is a double-sided document, the double-sided document faces downward from the document feed tray 50 onto the document reading position of the document table 46. It will be fed in the state. Image information on the surface of the double-sided document fed to the document reading position is read by the optical system 44. When reading of the image information on the front side is completed, the front and back sides are reversed by the reverse path path 52 in the automatic document feeder 48, and the double-sided original is fed with the back side facing down on the reading position. Image information on the back side of the document is read again by the optical system 44. When the reading of the image information on both the front and back sides of the document is completed, the double-sided document is discharged to the document discharge tray 54 of the automatic document feeder 48.

  The image forming unit 26 includes a photosensitive drum 56, a charger 58, a laser scanning unit (hereinafter referred to as “LSU”) 60 that functions as an exposure unit, a developing unit 62, a transfer unit 63, a cleaning unit 64, and a toner supply unit 66. Including. The charger 58 charges the photosensitive drum 56 to a predetermined potential. The LSU 60 performs laser processing according to image data read by the image information reading unit 24 or image data such as image information transferred from an external device such as a client personal computer (hereinafter referred to as “client PC”) 88 shown in FIG. Light is irradiated to form an electrostatic latent image on the photosensitive drum 56. The developing device 62 supplies toner to the electrostatic latent image formed on the photosensitive drum 56 via a developing roller to visualize the toner image. The transfer unit 63 transfers the toner image formed on the photosensitive drum 56 onto the recording paper. The cleaning device 64 collects the toner remaining on the photosensitive drum 56 after the transfer process is completed. The toner supplier 66 supplies toner into the developing device 62.

  The photosensitive drum 56 is supported by the apparatus main body 22 so as to be rotatable clockwise in FIG. A charger 58, an LSU 60, a developing device 62, a transfer unit 63, and a cleaning device 64 are arranged in this order along the rotation direction of the photosensitive drum 56.

  The fixing unit 32 includes a pair of roller pairs of an upper pressure roller 68 and a lower heating roller 70. The heating roller 70 has a built-in heater, and the temperature of the heating roller 70 is detected by a fixing temperature sensor.

(Hardware configuration)
FIG. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus 20. Referring to FIG. 2, the image forming apparatus 20 includes an image information reading unit 24, an image forming unit 26, a paper supply unit 30, a fixing unit 32, a paper discharge unit 36, an automatic document feeder 48, and an automatic paper feed cassette 42. A network interface card (NIC) 90 that interfaces with a client PC 88, which is one of external devices, via a LAN (Local Area Network) line 86, and an operation panel 84 including a display unit and an operation unit (not shown). Including.

  The image forming apparatus 20 further includes an image information reading unit 24, an image forming unit 26, a paper supply unit 30, a fixing unit 32, a paper discharge unit 36, an automatic document feeder 48, and an automatic paper feed cassette via a common bus line 38L. 42, the NIC 90, and the operation panel 84, and a control device 38 that controls these and functions as an image processing device.

  The control device 38 is substantially a computer, and by executing a computer program for realizing the image processing of the present embodiment, a CPU 72 that realizes a function as an image forming device and a common bus line 38L. All are connected to the CPU 72, the ROM 74 for storing programs executed by the CPU 72, the RAM 76 for providing storage areas for various programs, and holding various programs and data even when the power is cut off. HDD (Hard Disk Drive) 78, which is a possible non-volatile storage device, an image memory 80 for storing image data read by the image information reading unit 24, and a double-sided document read by the image information reading unit 24 To perform image playback of image information on one side, or image information on the other side And an image processing circuit 82 that functions as an image processing apparatus.

  The program stored in the ROM 74 is read from the ROM 74 and stored in the RAM 76 at the time of execution. The stored program is read from an address in the RAM 76 indicated by a register functioning as a program counter (not shown) in the CPU 72. The read program is interpreted and executed by the CPU 72. Data necessary for execution is read from an address specified by an instruction in a register in the CPU 72, the RAM 76, or the HDD 78. Similarly to this, the result of the execution is also stored in an address specified by an instruction in the register in the CPU 72, the RAM 76, or the HDD 78.

  The CPU 72 controls the image information reading unit 24, the image forming unit 26, the paper supply unit 30, the fixing unit 32, the automatic paper feed cassette 42, the automatic document feeder 48, and the NIC 90 to read the document, output the document, and the client PC 88. A desired operation such as communication with the external device is executed, and data is stored in or read from the RAM 76, the HDD 78, and the image memory 80.

  In the image forming apparatus 20, the control device 38 functioning as an image processing apparatus converts image information input from an external device such as the image information reading unit 24 or the client PC 88 into an electrical signal of each color, and Output to LSU 60 respectively.

  Note that the image processing program according to the present embodiment may be transmitted from another device to the control device 38 via the LAN line 86 and the NIC 90 and stored in the HDD 78.

(Configuration of image processing circuit 82)
FIG. 10 is a functional block diagram showing the configuration of the image processing circuit 82. Referring to FIG. 10, the image processing circuit 82 converts the RGB analog image signal read by the image information reading unit 24 into CMYK (C: cyan) according to the setting content designated by the user using the operation panel 84. , M: magenta, Y: yellow, K: black), and outputs the digital signal to the image forming unit 26.

  The image processing circuit 82 includes an A / D (analog / digital) conversion unit 1000 that converts the RGB analog image signal read by the image information reading unit 24 into a digital signal and outputs the digital signal, and the A / D conversion unit 1000. The output digital signal is subjected to processing for removing various distortions generated in the illumination system, imaging system, and imaging system of the image information reading unit 24, and the RGB reflectance signal is converted into a density signal. And a shading correction unit 1020 for performing processing for adjusting color balance.

  The image processing circuit 82 further separates the original image from the RGB digital signal output by the shading correction unit 1020 into, for example, a character edge area, a halftone dot area, a high density photographic area, and a low density photographic area. A blank determination / region separation processing unit 1040 for determining whether the document image is a blank document according to the result and preferably the density information is included. Hereinafter, separating an original image into, for example, a character edge region, a halftone dot region, a high density photographic region, and a low density photographic region is referred to as “region separation”.

  The image processing circuit 82 further performs image quality adjustment processing such as background density removal and contrast on the RGB digital signal output by the shading correction unit 1020 based on the result of region separation by the blank determination / region separation processing unit 1040. In order to achieve faithful color reproduction, the spectral characteristics of the CMY color material including unnecessary absorption components can be obtained for the input gray level correction unit 1060 and the RGB digital signal output by the input gray level correction unit 1060. And a color correction unit 1080 for performing a process of removing color turbidity based on the color correction and outputting a CMY three-color signal after color correction.

  The image processing circuit 82 further generates a black (K) signal from the CMY three-color signal after color correction based on the result of the region separation by the blank determination / region separation processing unit 1040 and the original CMY signal. The black generation and under color removal unit 1100 for executing a process of subtracting the black signal obtained by the black generation process and outputting a new CMY signal, and an image of the CMYK signal output from the black generation and under color removal unit 1100 The data is subjected to spatial filter processing using a digital filter based on the result of region separation by the blank determination / region separation processing unit 1040, and processing is performed so as to prevent blurring of the output image and deterioration of graininess by correcting the spatial frequency characteristics. And a spatial filter processing unit 1120.

  The image processing circuit 82 further enlarges the CMYK signal output from the spatial filter processing unit 1120 to perform image data enlargement or reduction processing according to the magnification set by the user on the operation panel 84. The gradation processing unit 1140 and the CMYK signal output by the enlargement / reduction processing unit 1140 can reproduce the gradation on the optimum screen based on the result of the region separation by the blank determination / region separation processing unit 1040. And a halftone processing unit 1160 for performing halftone processing.

  When the blank determination / region separation processing unit 1040 determines that the document is a blank document, the image processing circuit 82 includes an input tone correction unit 1060, a color correction unit 1080, a black generation and under color removal unit 1100, and a spatial filter processing unit. 1120, the enlargement / reduction processing unit 1140, and the halftone processing unit 1160 are not executed. Further, the image processing circuit 82 does not output the CMYK digital signal to the image forming unit 26. As a result, when it is determined that the document is a blank document, the image forming apparatus 20 does not form an image of the document on a sheet.

  As a general method of black generation processing executed by the black generation and under color removal unit 1100, there is a method of generating black by skeleton black. The method is shown below. Here, the input / output characteristic of the skeleton curve is set to y = f (x), the UCR (Under Color Removal) rate is set to α (0 <α <1), and input from the color correction unit 1080 to the black generation and under color removal unit 1100. The data to be output is C, M, and Y, and the data output by the black generation and under color removal unit 1100 is C ′, M ′, Y ′, and K ′. Then, C ′, M ′, Y ′, and K ′ are output by the following equations.

  In particular, the spatial filter processing unit 1120 has a high-frequency sharpening process in the spatial filter processing in the character edge region that has been separated by the blank determination / region separation processing unit 1040 in order to improve the reproducibility of black characters or color characters. Increase the amount of emphasis. Also, the spatial filter processing unit 1120 performs low-pass filter processing for removing the input halftone dot component on the area determined as the halftone dot area.

  A halftone processing unit 1160 performs a halftone process that enables reproduction of gradation on an optimal screen according to each region separation result.

(Configuration of blank determination / region separation processing unit 1040)
FIG. 3 is a functional block diagram of the blank determination / region separation processing unit 1040. Referring to FIG. 3, blank determination / region separation processing unit 1040 includes a first region separation processing unit 100 for region separation of image information of one surface input from image information reading unit 24, The first specific region extraction processing unit 102 for extracting a first specific region, which will be described later, having a component that can be influenced by the show-through component of the other surface, from the region separation result of the region separation processing unit 100 in FIG. After the processing of the first region separation processing unit 100 is completed, the total density information detection processing unit 104 and the total density information detection processing unit 104 for detecting density information indicating the density of the image as a numerical value are detected. And a first document determination processing unit 106 for temporarily (primarily) determining whether the one surface is a blank document according to the density information.

  The blank determination / region separation processing unit 1040 further includes a second region separation processing unit 108 for region separation of the image information of the other surface input from the image information reading unit 24, and a second region separation processing unit 108. A second specific area extraction processing unit 110 for extracting a second specific area, which will be described later, having a component that can be a show-through on one side, and a first document determination processing unit When it is determined in 106 that one side is not a blank document, the first specific area extracted by the first specific area extraction processing unit 102 and the second specific area extraction processing unit 110 are extracted. A second document determination processing unit 112 for finally determining whether one surface is a blank document by comparing the second specific area.

  The total density information detection processing unit 104 counts the number of pixels whose density value is greater than or equal to the first threshold value in all areas on a certain surface of the document, and outputs the counted number as density information. This density information is an index indicating whether or not some drawing content exists in the document. The more complex images are drawn on the document, the larger the counted number. The first threshold value is predetermined by experiment.

  If the surface on which the document is present is a blank document, the value of the density information detected by the total density information detection processing unit 104 is small. The first document determination processing unit 106 temporarily determines whether one side is a blank document according to whether the density information detected by the total density information detection processing unit 104 is smaller than the second threshold value. To do. The second threshold is also predetermined by experiment.

(Details of area separation processing)
Details of the region separation process will be described below.

In the region separation process, first, a halftone dot determination process for extracting a halftone dot region is performed. In the halftone dot determination process, an image is divided into blocks each consisting of 9 pixels, an average value (D _ave ) of signal levels is obtained for 9 pixels in each block, and each pixel in the block is determined using the average value. Binarize. Also, the maximum pixel signal level (D _max ) and the minimum pixel signal level (D _min ) are obtained at the same time. Thereafter, the halftone dot region is identified as a halftone dot region by utilizing the fact that the fluctuation of the image signal in the small region is large and the density is higher than the background. Specifically, for the binarized data, the number of change points from “0” to “1” and the number of change points from “1” to “0” are obtained in the main scanning and sub-scanning directions, respectively. Te, respectively and K _H and K _V, when both compared with a threshold value T _H and T _V are both above the threshold a dot region. However, in this case, in order to prevent erroneous determination of the background, the difference between the maximum value D _max of the pixel signal level and the average value D _ave of the pixel signal level, and the minimum value D _min of the pixel signal level and the pixel signal level The difference from the average value D _ave is compared with threshold values B ₁ and B ₂ , respectively. If both are greater than the threshold, it is determined that the background is not present.

  In summary, it is determined whether or not the area is a halftone dot area according to the following conditions.

After extracting the halftone dot region, the character edge region is extracted. In the character edge region, the difference between the maximum value and the minimum value of the pixel signal level is large, the maximum density is high, or the minimum density is low. Therefore, the character edge area is identified as follows. In each block divided in the halftone dot determination processing, the maximum value D _max , the minimum value D _min , and the difference (D _sub ) between D _max and D _min of the pixel signal level are respectively set to threshold values P _A , P _B , compared to P _C, the following conditional expression, it is determined whether the character edge region.

  For a pixel determined to be a photographic area, a threshold value THd is further used. If the above density difference is equal to or greater than THd, it is determined as a high density photographic area, and if it is less than THd, it is determined as a low density photographic area. Is done.

  The first specific area described above is a part that is not any of the character edge area, the halftone dot area, and the high density photographic area on a certain surface of the document. The second specific area is an area determined as one of a character edge area, a halftone dot area, and a high density photographic area on a certain surface of the document.

(Software configuration)
FIG. 4 is a flowchart showing a control structure of a program executed by blank determination / region separation processing unit 1040. This program is activated when an RGB digital signal is output by the shading correction unit 1020 when performing image reproduction of the image information of one side of a double-sided document or the image information of the other side. As described above, this program is stored in the ROM 74 in the control device 38 of the image forming apparatus 20. Realization of this function is achieved by the CPU 72 in the control device 38, which is substantially a computer, controlling the image processing circuit 82 in accordance with the program.

  Referring to FIG. 4, after the program is started, step 140 in which first region separation processing unit 100 performs region separation processing on the image information of the input surface, and after step 140, all density information The detection processing unit 104 counts the number of pixels whose density value is equal to or greater than the first threshold in the entire area of the input surface, and outputs the counted number as density information. After step 150, comparing the counted number with a first threshold, and after step 150, determining whether the number counted in step 150 is less than a second threshold; And step 152 for branching the flow of control according to the determination result. With this determination, a temporary determination is made as to whether or not the document is a blank document. That is, if the counted number is smaller than the second threshold value, it is determined as a blank document, and otherwise, it is temporarily determined that the document is not a blank document.

  The program is further executed after NO is determined in step 152, and the first specific region extraction processing unit 102 extracts the first specific region from the region separation result in step 140, and step 146 Step 142 is executed after 146, the second region separation processing unit 108 performs region separation processing on the back side image information, and after step 142, the second specific region extraction processing unit 110 performs the processing in step 142. And a step 148 of extracting a second specific region from the region separation result.

  This program is further determined NO in step 152 (the counted number is equal to or larger than the second threshold value), and is executed after the processing of step 148 is completed. Step 154 for determining whether or not the two specific areas overlap, and Step 154 for determining whether or not it is determined that they overlap in Step 154, and branching the control flow according to the determination result 156. By this determination, it is finally determined whether or not the document is a blank document. That is, if the first specific area and the second specific area overlap, the document is determined to be a blank document. In other cases, it is determined that the document is not a blank document. In step 154, the processing described below is executed. A ratio Rmat at which each extracted first specific area matches the second specific area is obtained. If this Rmat is equal to or greater than a predetermined threshold value THmat, it is determined that the document is a blank document. If Rmat is smaller than THmat, it is determined that the document is not a blank document.

  The program further saves the front image in the HDD 78 and prints it on the recording paper if the determination result in step 156 is NO. If the determination result in step 160 and step 152 is YES, Alternatively, the process includes a step 158 that is executed when the determination result in step 156 is YES, stops storing the front surface image in the HDD 78 and prints on the recording paper, and ends the processing.

  FIG. 5 is a flowchart showing the program structure of a routine for realizing the region separation processing function executed in step 140 and step 142 shown in FIG. Referring to FIG. 5, this routine includes a step 200 for extracting a halftone dot region, and a step for extracting a character edge region, a high-density photo region, and a low-density photo region after step 200 and ending the processing. 202. The processing in these steps is as described above.

(Operation)
1 to 5, image forming apparatus 20 according to the present embodiment having the above-described configuration operates as follows.

  Assume that the user sets an original on the automatic document feeder 48 and instructs the image forming apparatus 20 to copy the image of the original onto a recording sheet.

  The image information reading unit 24 of the image forming apparatus 20 reads images on both sides of the document.

  The image forming apparatus 20 first performs the following processing on one side of the document.

  The A / D conversion unit 1000 of the image forming apparatus 20 converts the RGB analog signal read by the image information reading unit 24 into a digital signal, and outputs the converted signal as an RGB digital signal. The shading correction unit 1020 of the image forming apparatus 20 removes various distortions generated in the illumination system, the imaging system, and the imaging system of the image information reading unit 24 from the RGB digital signal output by the A / D conversion unit 1000. Processing is performed, and RGB RGB reflectance signals are converted into density signals and color balance is adjusted.

  The following processing is performed in the blank / region separation processing unit 1040 of the image forming apparatus 20 on the RGB digital signal subjected to the processing of the shading correction unit 1020.

  The image forming apparatus 20 separates the image on one surface (step 140 shown in FIG. 4), and outputs image density information (step 144 shown in FIG. 4). The image forming apparatus 20 tentatively determines whether one side of the document is a blank document according to the density information (step 150 shown in FIG. 4).

  If it is determined in step 150 that the document is a blank document (YES in step 152 shown in FIG. 4), the image forming apparatus 20 stops storing the image on the front surface in the HDD 78 and printing on the recording paper, and ends the process. (Step 158 shown in FIG. 14).

  If it is determined in step 150 that the document is not a blank document (NO in step 152 shown in FIG. 4), the image forming apparatus 20 extracts the first specific area from the area separation result output in step 140 (FIG. 4). Step 146) shown in FIG. The image forming apparatus 20 separates the back surface (the other surface) (step 142 shown in FIG. 4) and extracts a second specific region (step 148 shown in FIG. 4). The image forming apparatus 20 determines whether one side is a blank document according to whether the first specific area and the second specific area overlap (step 154 shown in FIG. 4). . That is, if both overlap, it is determined that the document is a blank document, and otherwise, it is determined that the document is not a blank document.

  If it is determined in step 154 that the document is a blank document (YES in step 156 shown in FIG. 4), the image forming apparatus 20 stops storing the image on the front surface in the HDD 78 and printing on the recording paper, and performs processing. finish.

  If it is determined in step 154 that the document is not a blank document (NO in step 156 shown in FIG. 4), the image forming apparatus 20 stores the image on one side in the HDD 78 and prints it on recording paper, and ends the process. (Step 160 shown in FIG. 4).

  If the image forming apparatus 20 determines that the blank / region separation processing unit 1040 described above is not a blank document, a printing process is executed. If the image forming apparatus 20 determines that the document is a blank document, the printing process is not executed.

  When the user designates double-sided printing, the image forming apparatus 20 reverses the relationship between one side and the other side of the document, and performs the processing of step 140 to step 160 for the other side. Execute.

(Effect of this embodiment)
According to the present embodiment, the following effects can be obtained.

  (1) In order to confirm the influence of show-through of the other side of one side of a double-sided document, information obtained by separating the image information of both sides is used. Accordingly, it is possible to accurately determine the presence or absence of show-through on a white paper (blank document). As a result, a blank sheet (blank document) can be determined with a simple configuration.

  (2) If it is determined that the sheet is blank (blank document), the document image is not stored in the storage device and printed. Therefore, it is possible to suppress the memory capacity and wasteful consumption of supplies such as printing paper and toner. Also, the printing time can be shortened.

  (3) Blank paper (blank document) is not printed. Therefore, the photoconductor and the developer are not operated wastefully, and the life of the entire image forming apparatus can be increased.

[Second Embodiment]
In the first embodiment, it is determined whether the document is a blank document by comparing the first specific area and the second specific area. In the second embodiment, by considering density information with respect to the first specific area, only areas that are more likely to show through are extracted from the first specific area. Thereafter, the blank area determination accuracy is improved by comparing the extracted area with the second specific area.

  The image forming apparatus according to the second embodiment described below has such a function. The image forming apparatus according to the second embodiment of the present invention is substantially the same as the image forming apparatus 20 according to the first embodiment, but includes a control device described below instead of the control device 38. It differs in point.

  The control device according to the present embodiment is substantially the same as the control device 38 according to the first embodiment, but includes an image processing circuit different from the image processing circuit 82 according to the first embodiment. Different.

  The image processing circuit according to the present embodiment is substantially the same as the image processing circuit 82 according to the first embodiment. However, instead of the blank determination / region separation processing unit 1040, the image processing circuit starts from the first specific region. A blank determination / region separation processing unit 250 (FIG. 6) that determines whether or not the document is a blank document by extracting a region that is highly likely to appear and comparing the extracted region with a second specific region. ).

  FIG. 6 is a functional block diagram of the blank determination / region separation processing unit 250. Referring to FIG. 6, blank determination / region separation processing unit 250 is substantially the same as blank determination / region separation processing unit 1040 according to the first embodiment, but by first specific region extraction processing unit 102. In place of the second document determination processing unit 112, a point further including a density information detection processing unit 252 that extracts and outputs a region that is highly likely to show through from the extracted first specific region, When the first document determination processing unit 106 determines that one side is not a blank document, the region extracted by the density information detection processing unit 252 and the second extracted by the second specific region extraction processing unit 110. Is compared with the specific area in that it includes a second document determination processing unit 254 for determining whether one surface is a blank document.

  The density information detection processing unit 252 extracts a region that is highly likely to show through from the first specific region as follows. The density information detection processing unit 252 extracts a region having a density value equal to or higher than the first threshold value in the first specific region.

  The second document determination processing unit 254 determines whether or not it is a blank document by determining whether or not the region extracted by the density information detection processing unit 252 overlaps the second specific region. . That is, if both areas overlap, it is determined that the document is a blank document, and if the two regions do not overlap, it is determined that the document is not a blank document.

(Software configuration)
FIG. 7 is a flowchart showing a control structure of a program executed by blank determination / region separation processing unit 250. This program is substantially the same as the program executed by the blank determination / region separation processing unit 1040 according to the first embodiment, but after the step 146, the first specific region extracted in the step 146 is used. In addition, the method further includes step 260 for extracting an area that is equal to or greater than the first threshold value, and instead of step 154, the determination result in step 152 is NO, and after the processing in step 148 is completed. The difference is that it includes a step 262 that is executed to determine whether the document is a blank document according to whether or not the region extracted in step 260 and the second specific region overlap.

(Operation)
With reference to FIGS. 6 and 7, the image forming apparatus according to the present embodiment having the above-described configuration operates as follows.

  The operation of the image forming apparatus according to the present embodiment is substantially the same as that of the image forming apparatus 20 according to the first embodiment, but after the image forming apparatus determines that it is not a blank document in step 150. The operation until it is determined whether or not it is the second blank document is different.

  If it is determined in step 150 that the document is not a blank document (NO in step 150 shown in FIG. 7), the image forming apparatus extracts a first specific area from the area separation result output in step 140 (FIG. 7). Step 146). The image forming apparatus extracts an area whose density signal is equal to or higher than the first threshold value from the extracted first specific area (step 260 shown in FIG. 7). The image forming apparatus separates the back side area (step 142 shown in FIG. 7), and extracts a second specific area (step 148 shown in FIG. 7). The image forming apparatus determines whether the document is a blank document according to the overlap between the region extracted in step 260 and the second specific region and the density information of the first specific region (see FIG. 7). Step 262).

  That is, if both areas overlap, it is determined that the document is a blank document, and if not overlapped, it is determined that the document is not a blank document.

(Effect of this embodiment)
According to the present embodiment, in addition to the same effects as (1) to (3) of the first embodiment, the first time when it is determined whether or not the document is a blank document, Among the specific areas, an area that is highly likely to show through is extracted, and the extracted area is compared with the second specific area to determine whether or not the document is a blank document. . Therefore, more accurate and highly accurate determination is executed as compared with the image forming apparatus according to the first embodiment.

[Third Embodiment]
As a problem when a color original is processed by the image processing apparatus, there is a background color of the original. The background refers to a portion of the document where characters, photographs, images, etc. are not printed. In the case of a paper document, the background color that was originally white may turn yellow due to changes over time. In addition, the paper itself may be bluish, such as ink jet paper. In addition, the paper itself may be colored. In these cases as well, it is necessary to accurately determine whether the document is a blank document.

  The image forming apparatus according to the third embodiment described below has such a function.

  An image forming apparatus according to the third embodiment of the present invention is substantially the same as the image forming apparatus according to the third embodiment, but a control apparatus different from the control apparatus according to the second embodiment is provided. It differs in the point to include.

  The control device according to the present embodiment is substantially the same as the control device according to the second embodiment, but differs in that it includes the image processing circuit according to the second embodiment instead of the image processing circuit. .

  The image processing circuit according to the present embodiment is almost the same as the image processing circuit according to the second embodiment, but instead of the blank determination / region separation processing unit 250, the first specific region and the second specific region This includes a blank determination / region separation processing unit 300 that finally determines whether or not the document is a blank document in consideration of the background density of the document in addition to the comparison of the specific regions.

  Various methods for detecting the density of the background when the background is colored have been proposed. For example, the method disclosed in Japanese Patent Application Laid-Open No. 2003-51946 can be applied. The method will be briefly described below.

  In this method, first, a CMY three-color signal is calculated from an image of a read document, and the three-color signal is converted into Gray data that takes a density value from 0 to 255. 0 to 255 are divided into a plurality of sections that do not overlap each other, and a histogram of Gray data in which the frequency is calculated for each section is created.

  Compared to the portion where the image is drawn, the base area is usually considerably large. Therefore, in the gray data histogram, the frequency of the section including the background density is larger than the frequency of the other sections.

  Therefore, the following processing is executed. First, in the histogram of Gray data, it is determined whether or not the frequency of a certain section is greater than or equal to a predetermined threshold value. When the frequency of the section is smaller than a predetermined threshold value, the same determination process is performed for the latest section having a density lower than that section.

  The above determination process is repeated until a segment whose frequency is equal to or greater than a predetermined threshold is found. When such a division is found, the above-described repetitive processing is terminated, and the division is set as a candidate for the division indicating the background density. This category is called a background candidate category. If the background candidate section is not found even after performing the above determination processing up to the section with the lowest density, it is determined that there is no background.

  The frequency of the background candidate category is compared with the frequency of the latest category (hereinafter referred to as the latest category) having a lower density than the background candidate category. When the frequency of the background candidate category is equal to or higher than the frequency of the latest category, the density value included in the background candidate category is determined as the background density. When the frequency of the background candidate category is smaller than the frequency of the latest category, the density value included in the latest category is determined as the background density.

  FIG. 8 is a functional block diagram of the blank determination / region separation processing unit 300. Referring to FIG. 8, a blank determination / region separation processing unit 300 is substantially the same as the image processing circuit 250 according to the second embodiment, but the region separation processing of the first region separation processing unit 100 is performed. After the completion, a background detection processing unit 304 for detecting the background of the document image and a background density detection processing unit 306 for detecting the background density value detected by the background detection processing unit 304 are further included. In place of the dots and the density information detection processing unit 252, the background density output by the background density detection processing unit 306 is applied to the entire area of the first specific area extracted by the first document determination processing unit 106. Therefore, a point including a density information detection processing unit 302 for extracting and outputting a region that is a region where the background is removed from the first specific region and is highly likely to show through, 2 Instead of the document determination processing unit 254, one side is obtained by comparing the region extracted by the density information detection processing unit 302 with the second specific region extracted by the second specific region extraction processing unit 110. Is different from that including a second document determination processing unit 308 for determining whether or not the document is a blank document.

  When the background is white, the density value of the background is close to 0, but when the background is colored, the density value of the background becomes large. As a result, the density of the pixels in the first specific region is also shifted to a larger value as a whole. In the present embodiment, the third threshold value is calculated from the detected background density, and the background is removed from the first specific area using the threshold value, and show-through is performed. An area having a high possibility of being extracted is extracted. In the present embodiment, the third threshold value is obtained by shifting the first threshold value used in the first and second embodiments by the background density. The third threshold value is not limited to a value obtained by shifting the first threshold value by the background density, and any value may be used as long as the background density is taken into consideration.

  In the first specific area, the density information detection processing unit 302 extracts an area whose density value is greater than or equal to the third threshold value. By doing so, an area from which the background is removed and which is highly likely to show through is extracted from the first specific area.

(Software configuration)
FIG. 9 is a flowchart showing a control structure of a program executed by the image processing circuit 300. This program is substantially the same as the program executed by the image processing circuit 250 according to the second embodiment, but is executed in parallel with step 146 after being determined NO in step 152, Step 330 for detecting the background, Step 332 for outputting the detected background density after Step 330, and Step 146 after Step 146 and Step 332 are completed instead of Step 260. In the case where the determination result of step 152 is NO instead of step 262, including a point including step 334 for extracting and outputting a region that is equal to or greater than the third threshold value from the first specific region extracted in step And the area extracted in step 334 and the second special feature are executed after the process of step 148 is completed. According to whether the areas overlap, it differs in a point that comprises determining 336 whether a blank document.

(Operation)
With reference to FIGS. 8 and 9, the image forming apparatus according to the present embodiment having the above-described configuration operates as follows.

  The operation of the image forming apparatus according to the present embodiment is substantially the same as that of the image forming apparatus according to the second embodiment, but after the image forming apparatus determines that it is not a blank document in step 150, The operation is different until it is determined whether or not the document is a second blank document.

  If it is determined in step 150 that the document is not a blank document (NO in step 150 shown in FIG. 9), the image forming apparatus extracts a first specific area from the area separation result output in step 140 (FIG. 9). Step 146). In parallel with the processing in step 146, the image forming apparatus executes processing for detecting the ground on one surface (step 330 shown in FIG. 9). The image forming apparatus outputs the detected background density value (step 332 shown in FIG. 9). The image forming apparatus uses the third threshold value calculated from the density value of the background in all the first specific area, and removes the background from the first specific area, and An area that is highly likely to show through is extracted and output (step 334 shown in FIG. 9). The image forming apparatus separates the back side surface (step 142 shown in FIG. 9) and extracts a second specific region (step 148 shown in FIG. 9). The image forming apparatus determines whether or not the document is a blank document according to the overlap between the region extracted in step 334 and the second specific region, and the density information of the first specific region (see FIG. 9). Step 336).

(Effect of this embodiment)
According to this embodiment, in addition to the same effects as (1) to (3) of the second embodiment, the first time when it is determined whether or not the document is a blank document, Since the determination is made by taking density information in consideration of the background density into the specific area, more accurate determination is executed as compared with the image forming apparatus according to the second embodiment.

[Modification]
In the above-described embodiment, the program executed by the image processing circuit 82 is stored in the ROM 74, but the program may be stored in the HDD 78.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the embodiment described above. The scope of the present invention is indicated by each claim in the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are intended. Including.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment of the present invention. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus. FIG. It is a functional block diagram of a blank determination / region separation processing unit. FIG. 2 is a diagram showing a program structure for realizing an image processing function of the image forming apparatus in a flowchart format. It is a figure which shows the program structure of the routine for implement | achieving an area | region isolation | separation processing function in the flowchart format. FIG. 10 is a functional block diagram of a blank determination / region separation processing unit applied to an image forming apparatus according to a second embodiment of the present invention. FIG. 2 is a diagram showing a program structure for realizing an image processing function of the image forming apparatus in a flowchart format. FIG. 10 is a functional block diagram of a blank determination / region separation processing unit applied to an image forming apparatus according to a third embodiment of the present invention. FIG. 2 is a diagram showing a program structure for realizing an image processing function of the image forming apparatus in a flowchart format. 3 is a functional block diagram showing a configuration of an image processing circuit 82. FIG.

Explanation of symbols

20 Image Forming Device 24 Image Information Reading Unit 38 Control Device 60 LSU
72 CPU
74 ROM
76 RAM
78 HDD
80 image memory 82 image processing circuit 100 first region separation processing unit 102 first specific region extraction processing unit 104 total density information detection processing unit 106 first document determination processing unit 108 second region separation processing unit 110 second Specific area extraction processing unit 112,254,308 Second document determination processing unit 252,302 Density information detection processing unit 304 Background detection processing unit 306 Background density detection processing unit 1000 A / D conversion unit 1020 Shading correction unit 1040,250 , 300 Blank determination / region separation processing unit 1060 Input tone correction unit 1080 Color correction unit 1100 Black generation and under color removal unit 1120 Spatial filter processing unit 1140 Enlargement / reduction processing unit 1160 Halftone processing unit

Claims (11)

An image processing apparatus for reproducing an image on one side and / or the other side of a double-sided document read by an image information reading unit,
First region separation processing means for separating the one surface input from the image information reading unit;
First specific region extraction processing means for extracting a first specific region having a component that can be influenced by the show-through component of the other surface from the region separation result by the first region separation processing unit ;
And the total density information detecting means for counting the number of pixels more than a predetermined concentration in the entire area in front Symbol one surface,
First document determination processing means for determining whether the one surface is a blank document based on a detection result of the total density information detection means;
Second region separation processing means for separating the other surface input from the image information reading unit;
Second specific region extraction processing means for extracting a second specific region having a component that can be a show-through to the one surface from the region separation result by the second region separation processing unit;
When the first document determination processing unit determines that the one surface is not a blank document, the one specific surface is compared by comparing the first specific region and the second specific region. An image processing apparatus comprising: a second document determination processing unit for determining whether the document is a blank document.   The second document determination processing means shows the other surface in the first specific area when the first document determination processing means determines that the one surface is not a blank document. The apparatus according to claim 1, further comprising means for determining whether the one surface is a blank document by comparing a partial region having a component that can be influenced by the component and the second specific region. Image processing apparatus. A region extracting means for extracting a region having a predetermined density or more from the first specific region;
The means for determining includes the region extracted by the region extracting unit and the second specific region when the first document determination processing unit determines that the one side is not a blank document. The image processing apparatus according to claim 2, further comprising means for determining whether the one side is a blank document by comparing. A background density information processing means for detecting the background of the one surface input from the image information reading unit and outputting the density of the background;
The area extracting unit extracts an area of the first specific area that is equal to or higher than a threshold value obtained by adding the background density output by the background density information processing unit to the predetermined density. An image processing apparatus according to 1.   An image forming apparatus comprising the image processing apparatus according to claim 1. An image processing method for reproducing an image on one side and / or the other side of a double-sided original read by an image information reading unit in a computer,
A first region separation processing step for region separation of the one surface input from the image information reading unit;
A first specific region extraction processing step for extracting a first specific region having a component that can be influenced by the show-through component of the other surface from the region separation result of the first region separation processing step ;
And the total concentration information detecting step of counting the number of pixels more than a predetermined concentration in the entire area in front Symbol one surface,
A first document determination processing step for determining whether the one surface is a blank document based on a detection result of the total density information detection step;
A second region separation processing step for region separation of the image information of the other surface input from the image information reading unit;
A second specific region extraction processing step of extracting a second specific region having a component that can be a show-through to the one surface from the region separation result of the second region separation processing step;
When the first document determination processing step determines that the one surface is not a blank document, the one specific surface is compared by comparing the first specific region and the second specific region. A second document determination processing step for determining whether or not the document is a blank document.   In the second document determination processing step, show-through of the other surface of the first specific area is determined when it is determined in the first document determination processing step that the one surface is not a blank document. The image according to claim 6, further comprising a step of determining whether or not the one surface is a blank document by comparing a partial region having a component that can be influenced by the component and the second specific region. Processing method. A region extracting step of extracting a region having a predetermined density or more from the first specific region;
The determining step compares the region extracted in the region extracting step with the second specific region when it is determined in the first document determining process step that the one side is not a blank document. The image processing method according to claim 7, further comprising: determining whether the one surface is a blank document. A background density information processing step of detecting the background of the one surface input from the image information reading unit and outputting the background density;
The region extracting step includes a step of extracting a region of the first specific region that is equal to or higher than a threshold value obtained by adding the background density output by the background density information processing step to the predetermined density. The image processing method according to claim 8.   An image processing program for causing a computer to function as the image processing apparatus according to any one of claims 1 to 4. A computer-readable recording medium on which the image processing program according to claim 10 is recorded.

Images