JP2014204272A - Image reading device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optically read documents displayed on a self-luminous medium and obtain appropriate images.SOLUTION: In an image forming apparatus 1, when a self-luminous medium is selected on an operation display unit 20, a control unit 10 causes an image reading unit 50 to turn off a light source 121 to read an image of a document displayed on the self-luminous medium; a background area extraction unit 602 extracts a background area of the self-luminous medium from image data acquired by the image reading unit 50; and a gradation conversion unit 605 converts the background area extracted by the background area extraction unit 602 into white.

Description

  The present invention relates to an image reading apparatus and an image forming apparatus.

The copy function and scanner function of a conventional image forming apparatus are for a document recorded on a reflective medium such as paper, and the original is obtained by irradiating the reflective medium with light from the light source of the scanner and receiving the reflected light. Reading images.
On the other hand, there is a desire to copy or scan a document displayed on a self-luminous medium such as a liquid crystal screen of a smartphone or a tablet terminal. However, when copying or scanning is performed on the self-luminous medium with respect to the reflective medium, the reflected light of the irradiated light and the light emission of the self-luminous medium are mixed, and the image of the original cannot be read well.

  In order to solve such a problem, for example, Patent Document 1 describes a color image scanner that performs scanning without turning on an illumination light source when a display to be read is a transmission type. Japanese Patent Laid-Open No. 2003-228867 discloses that the light amount of the reading light source from zero to the maximum value depending on the light emission type (non-light-emitting type, light-emitting type, non-light-emitting and light source) of the thin display device to be read. A copying machine that reads the image of a thin display device by setting the above is described.

JP-A-7-143340 JP 2004-222275 A

  By the way, in many cases, the color of the original displayed on the self-luminous medium (solid area on the screen on which the original is displayed is not printed) is light gray. Even when a document with a white background displayed on a self-luminous medium is read with the light source of the scanner turned off, the charge of the light receiving element such as a CCD (Charge Coupled Devices) is read as white without reaching max. It may not be possible. When printing is performed based on the image data read in such a state, there is a problem that the background color of the printed material is not white and the dynamic range of the printed material is narrowed.

  In addition, when black in a document displayed on a self-luminous medium is read by a scanner, the scanner may not be able to determine that it is completely black, and similarly, there is a problem that the dynamic range of the printed material is narrowed.

  In addition, self-luminous media are mostly non-standard sizes, unlike reflective media with many standard sizes. Therefore, there is a problem in that the effective image area of the self-luminous medium cannot be properly detected in the image forming apparatus.

  Furthermore, the self-luminous medium is often smudged with fingerprints, and there is a problem in that the smudges of fingerprints appear on the printed matter when copied as it is.

  An object of the present invention is to obtain an appropriate image when a document displayed on a self-luminous medium is optically read.

In order to solve the above-described problem, an image reading apparatus according to claim 1 is provided.
An image reading unit having a light source for irradiating light on the document, reading the image of the document by turning on or off the light source, and acquiring image data;
An operation unit for selecting that the medium on which the document is recorded is a self-luminous medium that displays by emitting light;
A control unit that causes the image reading unit to turn off the light source and read an image of a document displayed on the self-emitting medium when the operation unit selects the self-emitting medium;
A ground area extracting unit that extracts a ground area of the document from the image data acquired by the image reading unit when the operation unit selects the self-luminous medium;
A gradation converting unit that converts the ground region extracted by the ground region extracting unit into white;
Is provided.

The invention according to claim 2 is the invention according to claim 1,
An effective image region extraction unit that extracts an effective image region corresponding to the region of the self-luminous medium from the image data acquired by the image reading unit;
The ground area extraction unit extracts the ground area from the effective image area extracted by the effective image area extraction unit.

The invention according to claim 3 is the invention according to claim 2,
The image reading unit includes a platen glass for placing a document, and an upper lid that covers the platen glass at the time of reading,
An open / close detection unit for detecting an open / closed state of the upper lid;
The effective image area extraction unit includes:
When an image of a document is read by the image reading unit in a state where the upper lid is detected to be closed by the open / close detection unit, an area other than black is included in the image data acquired by the image reading unit. When a non-black area is extracted as the effective image area when continuously existing over a predetermined reference area, and when the non-black area does not exist continuously over a predetermined reference area Then, an area including the non-black area is extracted as the effective image area.

The invention according to claim 4 is the invention according to claim 2,
The image reading unit includes a platen glass for placing a document, and an upper lid that covers the platen glass at the time of reading,
An open / close detection unit for detecting an open / closed state of the upper lid;
The effective image area extraction unit includes:
When the image reading unit reads an image of a document in a state where the open / close detection unit detects that the upper lid is open, the image data acquired by the image reading unit is surrounded by black When the area is larger than a predetermined reference area, the area surrounded by black is extracted as the effective image area, and when the area surrounded by black does not exist more than a predetermined reference area The black region and the region surrounded by the black are extracted as the effective image region.

The invention according to claim 5 is the invention according to any one of claims 1 to 4,
The gradation converting unit further performs gradation conversion of an area other than the extracted ground area of the image data so that the highest density in the image of the document is black.

The invention according to claim 6 is the invention according to any one of claims 1 to 5,
The gradation converting unit further includes the background area when the density of the area other than the ground area in the image of the document is lower than the density of the ground area before conversion to white. The ground area is converted to white after gradation conversion is performed so that the brightness is reversed with the area other than the ground area.

The invention according to claim 7 is the invention according to any one of claims 1 to 6,
A fingerprint region extraction unit that extracts a fingerprint region from an image of the document read by the image reading unit;
The fingerprint region extracted by the fingerprint region extraction unit is separated into a fingerprint region on the ground region and a fingerprint region on a region other than the ground region, and a fingerprint region on the ground region is separated. A fingerprint area correction unit that converts density to the density of the ground area, and performs density correction for a density change due to fingerprint contamination on a fingerprint area above the ground area;
Is provided.

An image forming apparatus according to an eighth aspect of the present invention includes:
An image reading apparatus according to any one of claims 1 to 7,
An image forming unit that forms an image on a sheet based on image data read by the image reading device;
Is provided.

  According to the present invention, it is possible to obtain an appropriate image when a document displayed on a self-luminous medium is optically read.

2 is a block diagram illustrating a functional configuration of the image forming apparatus. FIG. 1 is a diagram illustrating a schematic configuration example of an image forming apparatus. 3 is a flowchart showing a copy control process executed by a control unit in FIG. 1. Scanning is performed by the scanner unit 12 with different combinations of the type of medium on which the document is recorded (whether it is a self-luminous medium or a reflective medium), the open / close state of the upper lid 11b, and whether the document is white or not. FIG. 6 is a diagram showing a list of image data input from the scanner unit 12 to the image processing unit 60 at a time. It is a flowchart which shows the process of the effective image area | region extraction performed in step S3 of FIG. It is a flowchart which shows the fingerprint area extraction process performed in step S5 of FIG. It is a flowchart which shows the fingerprint area correction process performed in step S6 of FIG.

  Hereinafter, the configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a functional block diagram of the image forming apparatus 1. FIG. 2 shows a schematic configuration inside the image forming apparatus 1.
As shown in FIG. 1, the image forming apparatus 1 includes a control unit 10, an operation display unit 20, a storage unit 30, a communication unit 40, an image reading unit 50, an image processing unit 60, an image forming unit 70, and the like. Each unit is connected via a bus 80.

The control unit 10 includes a CPU (Central Processing Unit), a RAM (Random Access Memory).
) Etc. The CPU of the control unit 10 reads the system program and various processing programs stored in the storage unit 30 and develops them in the RAM, and centrally controls the operation of each part of the image forming apparatus 1 according to the developed programs.

  The control unit 10 can operate in a plurality of operation modes including a copy mode. In the copy mode, the control unit 10 executes a copy control process (see FIG. 3) to be described later in cooperation with a program stored in the storage unit 30.

  The operation display unit 20 is configured by an LCD (Liquid Crystal Display) or the like, and displays various operation buttons, device statuses, operation statuses of functions, and the like on the display screen in accordance with display signal instructions input from the control unit 10. I do. The LCD display screen is covered with a pressure-sensitive (resistive film pressure) touch panel configured with transparent electrodes arranged in a grid, and the XY coordinates of the force point pressed with a finger or a touch pen are expressed as voltage values. The detected position signal is output to the control unit 10 as an operation signal. The operation display unit 20 includes various operation buttons such as a numeric button and a start button, and outputs an operation signal generated by the button operation to the control unit 10.

  The storage unit 30 is configured by a non-volatile memory or the like, and is a system program that can be executed by the image forming apparatus 1, various processing programs that can be executed by the system program, data that is used when these various processing programs are executed, and a control unit The data of the processing result calculated by 10 is stored.

  The communication unit 40 includes a modem, a LAN adapter, a router, and the like, and controls communication with an external device such as a PC (Personal Computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network). I do.

  As illustrated in FIG. 2, the image reading unit 50 includes an ADF (Auto Document Feeder) unit 11 and a scanner unit 12. The ADF unit 11 conveys a document placed on the document tray 11a to a platen glass 12a that is a reading portion. The document tray 11a of the ADF unit 11 is provided with a document presence / absence detection sensor (not shown). The document presence / absence detection sensor detects the presence / absence of a document on the document tray 11 a and outputs the detection signal to the control unit 10. An opening / closing sensor (not shown) serving as an opening / closing detection unit is provided on the surface of the upper lid 11b of the ADF unit 11 facing the platen glass 12a. The open / close sensor detects the open / closed state of the upper lid 11 b and outputs the detection signal to the control unit 10.

  The scanner unit 12 includes a platen glass 12a for placing a document, an exposure scanning unit 12b including a light source 121 and a mirror 122, a CCD that receives light from the document and outputs an electrical signal (image signal) corresponding to the light intensity, and the like. The image sensor 12c and the image sensor 12c include an optical system 12d that guides the scanning light of the exposure scanning unit 12b. The exposure scanning unit 12b, the image sensor 12c, and the optical system 12d constitute a sensor module.

  In accordance with a scan instruction from the control unit 10, the scanner unit 12 moves the document transported or placed on the reading position of the platen glass 12 a and the sensor module relatively in the sub-scanning direction orthogonal to the main scanning direction. The original image is read, and the read R (red), G (green), and B (blue) image signals are converted into image data via an A / D converter and output to the image processing unit 60. The image data represents, for example, the density gradation value of each color pixel from 0 to 255.

  The image processing unit 60 performs various types of image processing on the image data input from the image reading unit 50 to generate image data as Y (yellow), M (magenta), C (cyan), and K (black) image data. Output to 70. The image processing unit 60 includes an image processing unit for a reflective medium for performing image processing on image data obtained by reading an image of a document recorded on the reflective medium, and a display on the self-luminous medium. An effective image region extraction unit 601, a ground region extraction unit 602, a fingerprint region extraction unit 603, a fingerprint region correction unit 604, and a gradation conversion unit for performing image processing on image data obtained by reading the image of the original document 605, a color conversion unit 606, and the like. Each unit of the image processing unit 60 may be realized by software processing in cooperation with the CPU of the control unit 10 and a program stored in the storage unit 30, or may be realized by dedicated hardware. .

  The image forming unit 70 forms an image on a sheet by electrophotography based on the input image data. As shown in FIG. 2, the image forming unit 70 includes exposure units 2Y, 2M, 2C, and 2K, developing units 3Y, 3M, 3C, and 3K, photosensitive drums 4Y, 4M, 4C, and 4K, and a charging unit 5Y. 5M, 5C, 5K, cleaning units 6Y, 6M, 6C, 6K, primary transfer rollers 7Y, 7M, 7C, 7K, intermediate transfer belt 8, belt cleaning unit 9, secondary transfer roller 21, The image forming apparatus includes a fixing unit 22, a paper feeding unit 25, and a transport unit 26 including a paper discharge roller 27.

  The exposure units 2Y, 2M, 2C, and 2K include a laser light source such as an LD, a polygon mirror, and a plurality of lenses. The exposure units 2Y, 2M, 2C, and 2K scan and expose the surfaces of the photosensitive drums 4Y, 4M, 4C, and 4K with laser beams based on the image data sent from the image processing unit 60. By this laser beam scanning exposure, latent images are formed, that is, images are written at the image forming positions of the photosensitive drums 4Y, 4M, 4C, and 4K charged by the charging units 5Y, 5M, 5C, and 5K. The image forming positions of the photoconductor drums 4Y, 4M, 4C, and 4K are positions where a latent image is formed on the photoconductor drum.

  The latent images formed on the photoconductive drums 4Y, 4M, 4C, and 4K are visualized by development by the corresponding developing units 3Y, 3M, 3C, and 3K, and are formed on the photoconductive drums 4Y, 4M, 4C, and 4K. A toner image is formed on.

The toner images formed and carried on the photosensitive drums 4Y, 4M, 4C, and 4K are sequentially transferred to primary positions on the intermediate transfer belt 8 by the primary transfer rollers 7Y, 7M, 7C, and 7K, and are primarily transferred. .
Residual toner is removed from the surfaces of the photosensitive drums 4Y, 4M, 4C, and 4K after the transfer of the toner image by the cleaning units 6Y, 6M, 6C, and 6K.

The intermediate transfer belt 8 is a semiconductive endless belt that is suspended and supported rotatably by a plurality of rollers, and is driven to rotate as the rollers rotate.
The intermediate transfer belt 8 is pressure-bonded to the photosensitive drums 4Y, 4M, 4C, and 4K by primary transfer rollers 7Y, 7M, 7C, and 7K. As a result, the toner images developed on the surfaces of the photosensitive drums 4Y, 4M, 4C, and 4K are sequentially transferred (primary transfer) to the intermediate transfer belt 8 by the primary transfer rollers 7Y, 7M, 7C, and 7K. On the other hand, in the paper feeding unit 25, the type of paper instructed by the control unit 10 is fed and conveyed by the conveyance unit 26 to a transfer position by the secondary transfer roller 21. The toner image of the color image is transferred (secondary transfer) to the sheet by the roller pair of the transfer roller 21 sandwiching and conveying the sheet at the transfer position by the secondary transfer roller 21. After the transfer, the sheet is conveyed to the fixing unit 22, and the toner image transferred to the sheet is thermally fixed and discharged to the discharge tray 28 by the discharge roller 27. The paper discharge roller 27 is a transport roller located on the downstream side of the fixing unit 22 on the paper transport path. Residual toner on the intermediate transfer belt 8 is removed by the belt cleaning unit 9.

  The fixing unit 22 includes fixing rotation members such as a heating roller 22a and a pressure roller 22b. The fixing rotating member is a rotating member for nipping and conveying the sheet on which the image has been formed while heating, and includes a fixing belt other than the above roller pair.

  The heating roller 22a includes heating means 221 such as a halogen lamp heater extending in the axial direction thereof. The heating roller 22a rotates by being driven by a rotation driving means such as a motor (not shown). The pressure roller 22b is driven by, for example, a pressure-bonding driving unit such as a solenoid (not shown) to pressure-bond to the heating roller 22a and form a fixing nip with the heating roller 22a. At this time, the pressure roller 22b rotates with the rotation of the heating roller 22a. Thus, the heating roller 22a and the pressure roller 22b heat and press the paper while nipping and transporting the paper at the fixing nip to melt and fix the toner image on the paper. The rotation driving means and the crimp driving means are driven and controlled by the control unit 10.

  The heating means 221 may be an induction heater or a resistance heating element in addition to a halogen lamp heater.

(Operation of Image Forming Apparatus 1)
Next, the operation of the image forming apparatus 1 will be described.
FIG. 3 shows a flowchart of the copy control process executed in the copy mode. The copy control process is executed by the control unit 10 when the start button of the operation display unit 20 is pressed in the copy mode.

  In this embodiment, the self-luminous medium is a liquid crystal screen such as a smartphone or a tablet terminal that displays by emitting light, and the screen on which the original is displayed is generally monochrome (grayscale) and has a black edge. A typical screen will be described as an example. That is, the R, G, B values of the pixels of the image data obtained by reading the image of the original displayed on the self-luminous medium in the scanner unit 12 are the same, and are represented by white to black density gradations. Can be handled as image data.

  In the copy control process, first, the control unit 10 displays a selection screen (not shown) on the operation display unit 20 for selecting whether the medium on which the document is recorded is a self-luminous medium or a reflective medium. And waits for selection from the operation display unit 20 (step S1). When the self-luminous medium is selected by the operation display unit 20 (step S1; YES), the control unit 10 causes the scanner unit 12 to turn off the light source 121 and display the original image displayed on the self-luminous medium on the platen glass 12a. Is read (scanned) (step S2).

  Next, the control unit 10 causes the effective image region extraction unit 601 to extract an effective image region from the image data input from the scanner unit 12 (step S3). When the self-luminous medium or the original is an irregular size, the image of the entire area of the platen glass 12a is read from the scanner unit 12 and acquired as image data. This image data includes unnecessary areas that do not need to be imaged. Therefore, the effective image area extraction unit 601 extracts an area corresponding to the area of the self-luminous medium from the image data input from the scanner unit 12 as an effective image area. The area of the self-luminous medium is a screen area on which a document is displayed, and corresponds to an image area of the document.

  Here, when the medium on which the document is recorded is a self-luminous medium or a reflective medium and has an irregular size, the image data input from the scanner unit 12 is the type of medium on which the document is recorded (self-luminous medium). Or the reflective medium), the open / closed state of the upper lid 11b, and whether or not the original is white. FIG. 4 shows the contents of the image data input from the scanner unit 12 to the image processing unit 60 when the scanner unit 12 performs reading under each of the above conditions. Here, the outline means that the density of the background area of the document is high (substantially black), and the density of the information part such as characters and drawings is lower than the density of the ground area. Contrary to the outline, the normal means that the density of the original area of the document is low (substantially white), and the density of the information part such as characters and drawings is higher than the density of the ground area. The ground area (ground area) refers to a solid area in which an information part such as characters is not placed on a medium on which a document is recorded.

The read image 201 in FIG. 4 shows image data from the scanner unit 12 when a normal document displayed (recorded) on the self-luminous medium is scanned by the scanner unit 12 with the upper lid 11b closed. It is. The read image 202 in FIG. 4 shows image data from the scanner unit 12 when a normal document recorded on a reflective medium is scanned by the scanner unit 12 with the upper lid 11b closed.
A scanned image 203 in FIG. 4 shows image data from the scanner unit 12 when a white document displayed on the self-luminous medium is scanned by the scanner unit 12 with the upper lid 11b closed. . A read image 204 in FIG. 4 shows image data from the scanner unit 12 when a white document recorded on a reflective medium is scanned by the scanner unit 12 with the upper lid 11b closed. .
A read image 205 in FIG. 4 shows image data from the scanner unit 12 when a normal document displayed on the self-luminous medium is scanned by the scanner unit 12 with the upper cover 11b opened. A read image 206 in FIG. 4 shows image data from the scanner unit 12 when a normal document recorded on a reflective medium is scanned by the scanner unit 12 with the upper lid 11b opened.
A scanned image 207 in FIG. 4 shows image data from the scanner unit 12 when a white document displayed on the self-luminous medium is scanned by the scanner unit 12 with the upper cover 11b opened. . A scanned image 208 in FIG. 4 shows image data from the scanner unit 12 when a white document recorded on a reflective medium is scanned by the scanner unit 12 with the upper cover 11b opened. .

  As shown in FIG. 4, the image data input from the scanner unit 12 is completely different depending on whether the type of document is a self-luminous medium or a reflective medium, even if other conditions are the same. Therefore, the effective image area extraction unit 601 extracts an effective image area using an algorithm specialized for the self-luminous medium and different from that of the reflective medium. FIG. 5 shows a flowchart of effective image region extraction in the effective image region extraction unit 601.

First, the effective image area extraction unit 601 determines whether the upper lid 11b is open based on a detection signal from the open / close sensor input via the control unit 10 (step S301).
When it is determined that the upper lid 11b is open (step S301; YES), the effective image area extraction unit 601 extracts an area surrounded by black from the image data input from the scanner unit 12 (step S302). The black here is, for example, the maximum density value of image data (in the case of R, G, and B image data, R, G, and B are all 0 values) or a value in the vicinity thereof.

  Next, the effective image area extraction unit 601 determines whether or not the extracted area surrounded by black is equal to or larger than a predetermined reference area (step S303). Here, the area is represented by the number of pixels. Here, when an image of a normal document displayed on the self-luminous medium is read with the upper lid 11b opened, the image data input from the scanner unit 12 is as a read image 205 in FIG. A region surrounded by a black edge in the read image 205 is a region of a self-luminous medium (a screen region on which a document is displayed), and has a certain area or more. On the other hand, when an image of a white document displayed on the self-luminous medium is read with the upper lid 11b opened, the image data input from the scanner unit 12 is as a read image 207 in FIG. In the read image 207, the area of the self-luminous medium and the edge are integrated to form a black area, and the area surrounded by black is a small area of only an information part such as a white character and has a constant area. Less than. Therefore, a predetermined reference area (for example, 10% of the area of the platen glass 12a) is provided, and it is input by determining whether the area of the area surrounded by black is equal to or larger than this reference area. It is possible to identify whether the received image data is image data corresponding to the read image 205 or image data corresponding to the read image 207.

When it is determined that the area surrounded by black is equal to or larger than a predetermined reference area (step S303; YES), the effective image area extraction unit 601 extracts the inside of the area surrounded by black as an effective image area, The coordinate information of the effective image area is output to the control unit 10 (step S304).
On the other hand, when it is determined that the area surrounded by black is less than the predetermined reference area (step S303; NO), the effective image area extraction unit 601 determines the entire black area (including the information part in the black area). Is extracted as an effective image area, and coordinate information of the effective image area is output to the control unit 10 (step S305). In this case, as shown in the read image 207, since the self-luminous medium and the surrounding edge cannot be distinguished, the effective image area including the edge is extracted.

  On the other hand, when it is determined that the upper lid 11b is not open (closed) (step S301; NO), the effective image area extraction unit 601 determines that the continuous area other than black (non-black) from the image data input from the scanner unit 12. Are extracted) (step S306). The black here is, for example, the maximum density value of image data (in the case of R, G, and B image data, R, G, and B are all 0 values) or a value in the vicinity thereof.

  Next, the effective image area extraction unit 601 determines whether or not the extracted continuous area other than black is greater than or equal to a predetermined reference area (step S307). Here, when an image of a normal document displayed on the self-luminous medium is read with the upper lid 11b closed, the image data input from the scanner unit 12 is as a read image 201 in FIG. In the read image 201, a continuous area other than black is a self-luminous medium area (screen area), and has a certain area or more. On the other hand, when an image of a white document displayed on the self-luminous medium is read with the upper lid 11b closed, the image data input from the scanner unit 12 is as a read image 203 in FIG. In the read image 203, the area of the self-luminous medium, the edge around the self-luminous medium, and the area of the platen glass 12a are integrated to form a black area. Area, which is less than a certain area. Therefore, a predetermined reference area (for example, 10% of the area of the platen glass 12a) is provided, and it is determined whether or not the area of the continuous area other than black is equal to or larger than this reference, thereby inputting the input image. Whether the data is image data corresponding to the read image 201 or image data corresponding to the read image 203 can be identified.

When it is determined that the continuous area other than black is greater than or equal to a predetermined reference area (step S307; YES), the effective image area extraction unit 601 determines a continuous area other than black (including the black area inside the continuous area). The effective image area is extracted and the coordinate information of the effective image area is output to the control unit 10 (step S308).
On the other hand, when it is determined that the continuous area other than black does not satisfy the predetermined reference area (step S307; NO), the effective image area extraction unit 601 extracts the minimum rectangular area including pixels other than black. Then, an area having a certain margin on the outer periphery of the rectangle is extracted as an effective image area, and the coordinate information of the effective image area is output to the control unit 10 (step S309). The smallest rectangular area including pixels other than black is a rectangular area in which the outermost pixels among the non-black pixels are obtained from the top, bottom, left, and right, and the obtained four pixels are the top, bottom, right, and left edges. .

  When the extraction of the effective image region is completed, the control unit 10 causes the ground region extraction unit 602 to detect the ground region of the document displayed on the self-luminous medium from the image data of the effective image region extracted by the effective image region extraction unit 601. Extraction is performed (step S4). As described above, the ground area of the document displayed on the self-luminous medium is a solid area in which information such as characters of the screen area on which the document is displayed is not placed, and basically has an area in the effective image area. This is an area having the same pixel value at most. Therefore, the ground area extraction unit 602 first performs a process of lowering the gradation on the image data of the effective image area. For example, if the image data is 256 gradations, it is reduced to 128 gradations, 64 gradations, or 16 gradations. By this processing, fine data value shifts such as noise are removed, and the pixel values in the ground area can be made uniform. Next, the ground area extraction unit 602 determines that the largest pixel value in the effective image area after the gradation is lowered as the ground value, extracts a pixel having this ground value as the ground area, The coordinate information of the ground area is output to the control unit 10.

When the extraction of the ground region ends, the control unit 10 causes the fingerprint region extraction unit 603 to extract the fingerprint region from the effective image region extracted by the effective image region extraction unit 601 (step S5).
Here, the reflection type medium such as paper is not so noticeable for fingerprint stains, but the self-luminous medium is often noticeable for fingerprint stains, and the fingerprint stains remain on the printed matter when copied as it is. Therefore, in step S5, the fingerprint area is extracted from the image data of the effective image area, and in step S6, the smudge of the fingerprint area is corrected. The density of fingerprint stains on the self-luminous medium varies depending on the case, but the image data has a substantially constant frequency and fluctuation intensity, and can be identified by frequency analysis such as wavelet transform. FIG. 6 shows a flowchart of fingerprint area extraction executed by the fingerprint area extraction unit 603.

  As shown in FIG. 6, the fingerprint area extraction unit 603 first converts the image data of the effective image area into luminance data (step S501). For example, the luminance data of the effective image area can be acquired by converting RGB into YCrCb and acquiring Y (luminance) data. In addition, it is good also as converting into brightness data instead of luminance data.

  Next, the fingerprint region extraction unit 603 performs wavelet transform on the acquired luminance data (step S502). By performing wavelet transform, an input signal (in this case, luminance data of an effective image region) can be decomposed into a plurality of frequency band components. Since the wavelet transform is a known method as described in JP-A-2004-127064, description thereof is omitted.

  Next, the fingerprint region extraction unit 603 extracts pixels within a specific intensity range of a specific frequency band of the wavelet transformed data (step S503). The pixels in the fingerprint area are pixels within a specific intensity range of a specific frequency band in the wavelet transformed data. The specific frequency band and the specific intensity range are determined experimentally and empirically. Fingerprint region candidates can be extracted by the processing in step S503.

  Next, the fingerprint region extraction unit 603 performs integration processing of the extracted pixels (step S504), and determines whether the region integrated by the integration processing is equal to or larger than a predetermined reference area (step S505). For example, in step S504, when the extracted pixel and the extracted pixel are adjacent to each other by a simple region expansion method or the like, a process of integrating both is performed. The predetermined reference area is the lower limit size among sizes that can be regarded as fingerprints experimentally and empirically.

When it is determined that the region integrated by the integration process is equal to or larger than a predetermined reference area (step S505; YES), the fingerprint region extraction unit 603 extracts the integrated region as a fingerprint region, and the coordinate information is extracted. It outputs to the control part 10 (step S506), and transfers to the process of step S508.
When it is determined that the region integrated by the integration process does not satisfy a predetermined reference area (step S505; NO), the fingerprint region extraction unit 603 determines that the integrated region is not a fingerprint region (step S505). S507), the process proceeds to step S508.
In step S508, the fingerprint area extraction unit 603 determines whether there is another area integrated by the integration process. If it is determined that there is another integrated region (step S508; YES), the fingerprint region extraction unit 603 returns to the process of step S505. If it is determined that there is no other integrated region (step S508; NO), the fingerprint region extraction unit 603 ends the process.

  When the fingerprint region extraction is completed, the control unit 10 causes the fingerprint region correction unit 604 to perform density correction of the fingerprint region extracted by the fingerprint region extraction unit 603 (step S6). FIG. 7 shows a flowchart of fingerprint area correction executed by the fingerprint area correction unit 604.

The fingerprint area correction unit 604 first reads the coordinate information of the fingerprint area (step S601).
Next, the fingerprint area correction unit 604 extracts an area having a fingerprint on the ground in the fingerprint area from the image data in the effective image area (step S602), and converts the fingerprint area to the fingerprint area on the ground (the ground area). (A fingerprint area above the area) and another area (a fingerprint area above an area other than the ground area. For example, a fingerprint area above an information part such as a character) is separated (step S603). The fingerprint area above the ground basically has the same pixel value with the largest area in the fingerprint area. Therefore, in step S602, a gradation lowering process is performed on the image data in the fingerprint area. For example, if the image data is 256 gradations, it is reduced to 128 gradations, 64 gradations, or 16 gradations. Thereby, it is possible to remove fine data value deviations such as noise. Then, the largest pixel value in the fingerprint area is determined as the value of the fingerprint area above the ground, and the pixel having this value is extracted as the fingerprint area above the ground.

  Next, the fingerprint area correction unit 604 calculates a difference between the density average of the fingerprint area on the ground and the density average of the ground area without the fingerprint (step S604). For example, the absolute value of the difference is calculated.

  Next, the fingerprint area correction unit 604 determines whether the pixels in the fingerprint area are pixels in the fingerprint area above the ground (step S605). If it is determined that the pixel is a pixel in the fingerprint area above the ground (step S605; YES), the fingerprint area correction unit 604 converts the pixel value of the pixel into a density value of the ground area (step S606). That is, it is converted into the density value (ground value) of the ground area extracted in step S4. If it is determined that the pixel is not a pixel in the fingerprint area above the ground (step S605; NO), the fingerprint area correction unit 604 changes density of the pixel due to fingerprint smearing based on the difference value calculated in step S604. Minute density correction is performed (step S607). Steps S605 to S607 are executed for all pixels in the fingerprint area.

  When the processing for all the pixels in the fingerprint area is completed (step S608; YES), the control unit 10 determines whether there is another fingerprint area (step S609). If it is determined that there are other fingerprint areas (step S609; YES), the control unit 10 returns to the process of step S601 and repeatedly executes the processes of steps S601 to S608 for the other fingerprint areas. If it is determined that there is no other fingerprint area (step S609; NO), the fingerprint area correction unit 604 ends the process.

When the fingerprint area correction is completed, the control unit 10 compares the density of the image data of the effective image area with the density of the other areas, and determines whether the color of the ground area has a lower density (step S7). ).
When it is determined that the density of the ground region is lower (step S7; YES), the control unit 10 performs a gradation conversion process by the gradation conversion unit 605 on the image data of the effective image region after the fingerprint region correction. (Step S8). In step S8, the gradation conversion unit 605 converts the ground area of the image data of the effective image area after the fingerprint area correction to white, and converts the highest density part of the area other than the ground to black. In addition, for areas other than the ground, other than the highest density portion, the value of each pixel is multiplied by a conversion coefficient that is multiplied to convert the highest density portion to black.
When it is determined that the density of the ground area is higher (step S7; NO), the control unit 10 causes the gradation conversion unit 605 to check the ground area in the image data of the effective image area after the fingerprint area correction and other than the ground area. After reversing the brightness with the area (step S9), a gradation conversion process is executed (step S10). Specifically, in step S9, the gradation converting unit 605 inverts the gradation of each pixel in the ground region and a region other than the ground region (that is, the entire effective image region). In step S10, the gradation conversion unit 605 converts the ground area of the image data of the effective image area to white, and converts the highest density part (the highest density part after gradation inversion) of the area other than the ground to black. In addition, for areas other than the ground, other than the highest density portion, the value of each pixel is multiplied by a conversion coefficient that is multiplied to convert the highest density portion to black.

  After the gradation conversion process is completed, the control unit 10 causes the color conversion unit 606 to color-convert the image data after the gradation conversion into C, M, Y, and K image data (step S13), and the image after the color conversion. Based on the data, the image forming unit 70 forms an image on the sheet (step S14), and the process is terminated.

  On the other hand, when the reflective medium is selected in step S1 (step S1; NO), the control unit 10 causes the scanner unit 12 to turn on the light source 121 and read the image of the document (step S11). Next, the control unit 10 causes the image processing unit 60 to perform image processing for the reflective medium (step S12), and causes the color conversion unit 606 to perform color conversion of the image data into C, M, Y, and K image data. (Step S13) Based on the color-converted image data, the image forming unit 70 forms an image on the paper (Step S14), and the process is terminated. The image processing for the reflection type medium is a well-known processing that has been performed conventionally, and thus description thereof is omitted.

As described above, according to the image forming apparatus 1 in the above embodiment, when the self-luminous medium is selected by the operation display unit 20, the control unit 10 causes the image reading unit 50 to turn off the light source 121. The image of the original displayed on the self-luminous medium is read, and the ground area extraction unit 602 extracts the area of the original of the original displayed on the self-luminous medium from the image data acquired by the image reading unit 50. The gradation conversion unit 605 converts the ground region extracted by the ground region extraction unit 602 into white.
Therefore, when the original displayed on the self-luminous medium is optically read, it is possible to obtain an easy-to-see image with clear information such as characters and drawings on the ground area.

  The image forming apparatus 1 also includes an effective image area extracting unit 601 that extracts an effective image area corresponding to the area of the self-luminous medium from the image data acquired by the image reading unit 50. The ground area extracting unit 602 includes an effective image area extracting unit 602. A ground area is extracted from the effective image area extracted by the image area extraction unit 601. Accordingly, it is possible to easily extract the ground area from the image data acquired by the image reading unit 50.

  Further, the gradation conversion unit 605 further performs gradation conversion of image data other than the ground area so that the highest density in the effective image area is black. Therefore, since the highest density portion is black with respect to the white background, it is possible to obtain an easy-to-see image with clearer information such as characters and drawings in the background area.

  Further, when the density of the other area other than the ground area in the effective image area is lower than the density of the ground area before being converted to white, the gradation converting unit 605 further reduces the ground area and the ground area. The background area is converted to white after the conversion is performed so that the brightness is reversed with the other areas. Therefore, for example, even when the original is a white character, it is possible to obtain an easy-to-see image with clear information such as characters and drawings on the background area.

The effective image area extraction unit 601 is acquired by the image reading unit 50 when the image reading unit 50 reads an image of a document in a state where the open / close detection unit detects that the upper lid 11b is closed. If the non-black area continuously exists in the image data that exceeds the predetermined reference area, the area is extracted as the effective image area, and the non-black area continuously exceeds the predetermined reference area. If not, a rectangular area including the scattered areas other than black is extracted as the effective image area.
The effective image area extraction unit 601 is acquired by the image reading unit 50 when the image reading unit 50 reads an image of a document in a state where the open / close detection unit detects that the upper lid 11b is opened. If the area surrounded by black in the image data exceeds the predetermined reference area, the area is extracted as an effective image area, and the area surrounded by black does not exist beyond the predetermined reference area. In this case, a black area is extracted as an effective image area.
Therefore, it is possible to appropriately extract the effective image area from the image obtained by reading the image of the original displayed on the self-luminous medium.

  The image forming apparatus 1 also includes a fingerprint region extracting unit 603 that extracts a fingerprint region from the effective image region extracted by the effective image region extracting unit 601 and a fingerprint region extracted by the fingerprint region extracting unit 603 as a ground region. The fingerprint area above and other fingerprint areas are separated, the density of the fingerprint area above the ground area is converted to the density of the ground area, and density correction for density changes due to fingerprint smearing is applied to the other fingerprint areas. And a fingerprint area correction unit 604 to be implemented. Accordingly, it is possible to obtain a good-looking image free from fingerprint smudges even when an image of a document displayed on a self-luminous medium that is easily attached with a fingerprint is read.

  Note that the description in the above embodiment shows a preferred example of the image forming apparatus according to the present invention, and the present invention is not limited to this.

For example, in the above embodiment, in order to facilitate the processing, an effective image region is extracted from the image data acquired by the scanner unit 12 by the effective image extraction unit 601, and the background of the document is extracted from the extracted effective image region. Although an area is extracted, a fingerprint area is extracted, and various gradation conversions are performed, the effective image area extraction by the effective image extraction unit 601 is not essential.
That is, the ground area extraction unit 602 may be any unit that extracts the ground area of the document from the image data acquired by the scanner unit 12. The fingerprint area extraction unit 603 may be any unit that extracts the fingerprint area from the original image of the image data acquired by the scanner unit 12. The gradation conversion unit 605 may be any unit that performs various gradation conversion processes on the image of the document in the image data acquired by the scanner unit 12.

In the above embodiment, the case where the screen of the self-luminous medium copied by the image forming apparatus 1 is monochrome (grayscale) has been described as an example. However, a color screen may be used. In this case, the process flow of the copy control process is the same as that in the above embodiment, but in some steps, a process is performed in consideration of color (the values of R, G, and B may be different). Is called.
For example, the calculation of the difference value between the density average of the fingerprint area on the ground and the density average of the ground area in step S604 of FIG. 7 calculates the density average difference value for each of R, G, and B. In step S607 of FIG. 7, the R, G, and B values in the fingerprint region other than the ground are corrected based on the calculated difference values. Further, the determination in step S7 in FIG. 3 as to whether or not the density of the ground is lower and the extraction of the highest density portion in steps S8 and S10 in FIG. 3 are performed by converting the color image data to gray scale. In addition, in the steps S8 and S10 of FIG. 3, when converting the gradation other than the ground so that the highest density portion is black, the value of the pixel that becomes the highest density portion of the image data when converted to grayscale Is converted for each of R, G, and B, and the pixel values of R, G, and B other than the ground area are multiplied by this coefficient. Further, with respect to the process of reversing the gradation so that the brightness of the ground region and the region other than the ground region is reversed in step S9 in FIG. 3, the brightness is previously set for each combination of R, G, and B. A combination of R, G, and B to be inverted is defined and stored in the storage unit 30 as a LUT (Look Up Table), and conversion is performed using this LUT.

Further, when the self-luminous medium is a color screen, the R, G, B image data acquired by the scanner unit 12 may be converted to gray scale, and the same processing as in the above embodiment may be performed.
In the above embodiment, the case where the image forming apparatus 1 is a color image forming apparatus has been described as an example. However, the present invention can also be realized by a monochrome image forming apparatus. In the above embodiment, the image forming apparatus 1 is an electrophotographic image forming apparatus, but may be an image forming apparatus of another type such as an ink jet type.

  In the above embodiment, the case where the present invention is applied to the copy mode of the image forming apparatus 1 has been described as an example. However, the present invention is not limited to the image reading apparatus or the scanner mode without the image forming unit 70 of FIG. It is also applicable to. In the image reading apparatus or the scanner mode, after the processing of steps S1 to S10 in FIG. 3 is executed, the obtained image data is transmitted to an external device such as a PC (Personal Computer) via the communication unit 40.

  In the above description, an example in which a ROM, a nonvolatile memory, a hard disk, or the like is used as a computer-readable medium for the program according to the present invention is disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also applied as a medium for providing program data according to the present invention via a communication line.

  In addition, the detailed configuration and detailed operation of the image forming apparatus 1 can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Control part 20 Operation display part 30 Storage part 40 Communication part 50 Image reading part 11 ADF part 11a Document tray 11b Upper cover 12 Scanner part 12a Platen glass 12b Exposure scanning part 121 Light source 122 Mirror 12c Image sensor 12d Optical system 60 Image processing unit 601 Effective image region extracting unit 602 Ground region extracting unit 603 Fingerprint region extracting unit 604 Fingerprint region correcting unit 605 Gradation converting unit 606 Color converting unit 70 Image forming unit 80 Bus

Claims (8)

An image reading unit having a light source for irradiating light on the document, reading the image of the document by turning on or off the light source, and acquiring image data;
An operation unit for selecting that the medium on which the document is recorded is a self-luminous medium that displays by emitting light;
A control unit that causes the image reading unit to turn off the light source and read an image of a document displayed on the self-emitting medium when the operation unit selects the self-emitting medium;
A ground area extracting unit that extracts a ground area of the document from the image data acquired by the image reading unit when the operation unit selects the self-luminous medium;
A gradation converting unit that converts the ground region extracted by the ground region extracting unit into white;
An image reading apparatus comprising: An effective image region extraction unit that extracts an effective image region corresponding to the region of the self-luminous medium from the image data acquired by the image reading unit;
The image reading apparatus according to claim 1, wherein the ground area extraction unit extracts the ground area from the effective image area extracted by the effective image area extraction unit. The image reading unit includes a platen glass for placing a document, and an upper lid that covers the platen glass at the time of reading,
An open / close detection unit for detecting an open / closed state of the upper lid;
The effective image area extraction unit includes:
When an image of a document is read by the image reading unit in a state where the upper lid is detected to be closed by the open / close detection unit, an area other than black is included in the image data acquired by the image reading unit. When a non-black area is extracted as the effective image area when continuously existing over a predetermined reference area, and when the non-black area does not exist continuously over a predetermined reference area The image reading apparatus according to claim 2, wherein an area including the area other than black is extracted as the effective image area. The image reading unit includes a platen glass for placing a document, and an upper lid that covers the platen glass at the time of reading,
An open / close detection unit for detecting an open / closed state of the upper lid;
The effective image area extraction unit includes:
When the image reading unit reads an image of a document in a state where the open / close detection unit detects that the upper lid is open, the image data acquired by the image reading unit is surrounded by black When the area is larger than a predetermined reference area, the area surrounded by black is extracted as the effective image area, and when the area surrounded by black does not exist more than a predetermined reference area The image reading apparatus according to claim 2, wherein a black area and an area surrounded by black are extracted as the effective image area.   5. The gradation conversion unit according to claim 1, wherein the gradation conversion unit further performs gradation conversion of a region other than the extracted ground region of the image data so that the highest density in the image of the document is black. The image reading apparatus according to claim 1.   The gradation converting unit further includes the background area when the density of the area other than the ground area in the image of the document is lower than the density of the ground area before conversion to white. The image reading apparatus according to claim 1, wherein gradation conversion is performed so that brightness is reversed with a region other than the ground region, and then the ground region is converted into white. A fingerprint region extraction unit that extracts a fingerprint region from an image of the document read by the image reading unit;
The fingerprint region extracted by the fingerprint region extraction unit is separated into a fingerprint region on the ground region and a fingerprint region on a region other than the ground region, and a fingerprint region on the ground region is separated. A fingerprint area correction unit that converts density to the density of the ground area, and performs density correction for a density change due to fingerprint contamination on a fingerprint area above the ground area;
An image reading apparatus according to any one of claims 1 to 6. An image reading apparatus according to any one of claims 1 to 7,
An image forming unit that forms an image on a sheet based on image data read by the image reading device;
An image forming apparatus comprising:

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