JP4886639B2 - Image reading apparatus and image reading method - Google Patents

Description

  The present invention relates to an image reading apparatus and an image reading method capable of handling paper fingerprint information.

  In recent years, digitalization has progressed due to the spread of the Internet and the like, and various information can be acquired in close proximity. Therefore, security technology for preventing information leakage in information equipment has become an indispensable technology.

  Several techniques have been proposed for guaranteeing originals of originals and printed papers in original paper and printing paper in image processing apparatuses such as copiers and MFPs, and one of them is security technology using paper fingerprint information. Are known. The paper is made up of plant fibers having a thickness of about 20 to 30 microns, and a random pattern is created by the tangling. This random pattern is called paper fingerprint information, and differs from sheet to sheet in the same way as a fingerprint. Therefore, the original can be guaranteed by acquiring (registering) and collating the paper fingerprint information. Registration and verification of the paper fingerprint information is obtained using a reading device having an optical system of the image processing device. In the paper fingerprint acquisition technology, it is necessary to irradiate a document with a light amount darker than a light amount for performing normal image reading in order to acquire a shadow of plant fibers as a pattern from a white area of paper. The gain adjustment amount for the image signal read by the reading device at the time of reading the paper fingerprint is set to a gain adjustment value smaller than the gain adjustment value for reading a normal image. Alternatively, a method is known in which paper fingerprint data, which is paper fingerprint information, is acquired by reducing the amount of light from an optical system lamp.

  In addition, the document is conveyed onto the platen glass and stopped. Thereafter, there has been proposed a document conveying apparatus in which a fixed reading mode for reading an image by moving an optical reading apparatus and a flow reading mode for reading an image while conveying an original while fixing the optical reading apparatus have been proposed. . In a model in which the fixed reading mode and the flow reading mode can be used together, it is possible to perform control such as switching between the fixed reading mode and the flow reading mode according to various setting modes desired by the user. After reading the image by moving the optical system in the reading apparatus in the fixed reading mode, the optical system of the reading apparatus must be returned to the original position again in order to read the image of the next document. Therefore, it is possible to shorten the document exchange time by adopting a method of reading an image while conveying the document in the flow reading mode. (For example, see Patent Document 1)

Japanese Patent Laid-Open No. 07-110642

  However, in the conventional technique described above, when paper fingerprint information is registered and collated and a document image is read, the paper fingerprint data and image data must be read once by the reading device. Therefore, there is a problem regarding a high-speed reading method of a document.

  When the paper fingerprint information registration / collation job and image reading job are read separately, the user must set the document twice, which takes time and effort for the user. In addition, it is possible to acquire the paper fingerprint data and the image data by executing the fixed reading mode twice by using the conventional document conveying device, but the amount of scanning the document twice by moving the optical system, The document exchange time becomes longer. In addition, it is possible to obtain the paper fingerprint data and the image data by executing the flow reading mode twice using the reverse path using the conventional document conveying apparatus. Has to be reversed, and the document exchange time becomes longer.

  Further, if another optical sensor for acquiring paper fingerprint information is added, the cost increases.

To solve the above problem, an image reading apparatus according to the present invention includes: a document feeding means for conveying to the reading position originals, a reading unit having an optical unit for reading the image and the paper fingerprint of the document reads the paper fingerprint of the document while conveying the document to fix the position of the optical unit with document feeding means, then, stops the conveyance of the document by the document feeding unit, an optical unit in front of the leading edge of the document has stopped And a control means for controlling the reading means so that the conveyance of the original is resumed after the position of the optical unit is fixed and the image of the original is read by the optical unit .

  According to the present invention, in a document conveying apparatus capable of using both the fixed reading mode and the sink reading mode, when the paper fingerprint data and the image data are simultaneously read, the document is conveyed when the image fingerprint of the document is read by the image sensor. Read while. Thereafter, the conveyance of the original document is stopped once, the image sensor of the previous period is moved to the stopped original, and the image is read by the image sensor after the conveyance of the original is resumed. For this reason, document replacement can be realized simply and simply without having a reverse path, the document replacement time is fast, and paper fingerprint information acquisition and image reading are possible at low cost without adding an image sensor.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

(Embodiment 1)
An embodiment of an image forming apparatus according to the present invention and a method thereof will be described.
FIG. 1 is a block diagram showing an image reading apparatus according to an embodiment of the present invention. In this image reading apparatus, a host computer (hereinafter referred to as a PC) 40 and three image forming apparatuses (10, 20, and 30) are connected to the LAN 50. The number of connections is not limited. In this embodiment, a LAN is applied as a connection method, but the present invention is not limited to this. For example, an arbitrary network such as a WAN (public line), a serial transmission method such as USB, and a parallel transmission method such as Centronics and SCSI can be applied.

  The PC 40 has a personal computer function. The PC 40 can send and receive files and send and receive e-mails using the FTP and SMB protocols via the LAN 50 and WAN. Further, it is possible to issue a print command from the PC 40 to the image forming apparatuses 10, 20, and 30 via a printer driver.

  The image forming apparatuses 10 and 20 are apparatuses having the same elements. The image forming apparatus 30 is an image forming apparatus having only a print function, and does not have the scanner unit included in the image forming apparatuses 10 and 20. Hereinafter, in order to simplify the description, the image forming apparatus 10 out of the image forming apparatuses 10 and 20 will be described in detail. The image forming apparatus 10 includes a scanner unit 13 that is an image input device, a printer unit 14 that is an image output device, a controller (Controller Unit) 11, and an operation unit 12 that is a user interface (UI). Here, the controller 11 controls the operation of the entire image forming apparatus 10.

  The image forming apparatus 20 includes a scanner unit 23 that is an image input device, a printer unit 24 that is an image output device, a controller (controller unit) 21 that controls operation of the entire image forming apparatus 20, and an operation unit that is a user interface (UI). 22. Here, the controller 21 controls the operation of the entire image forming apparatus 20.

  The image forming apparatus 30 includes a printer unit 33 that is an image output device, a controller (controller unit) 31 that controls operation of the entire image forming apparatus 30, and an operation unit 32 that is a user interface (UI).

  The image forming apparatus 10 is shown in FIG. The scanner unit 13 includes a document conveying device 201 and an optical unit 212. If the sensitivity of the optical unit 212 is different, each pixel is recognized as having a different density even if the density of each pixel on the document is the same. Therefore, the scanner unit 13 first performs exposure scanning on a white plate (uniformly white plate), converts the amount of reflected light obtained by the exposure scanning into an electrical signal, and outputs it to the controller 11. As will be described later, the shading correction unit 500 in the controller 11 recognizes the difference in sensitivity of the optical unit 212 based on the electrical signal obtained from the scanner unit 13. Then, using the recognized difference in sensitivity, the value of the electric signal obtained by scanning the image on the document is corrected. Further, when the shading correction unit 500 receives gain adjustment information from a CPU 301 in the controller 11 described later, the shading correction unit 500 performs gain adjustment according to the information. The gain adjustment is used to adjust how an electric signal value obtained by exposing and scanning a document is assigned to a luminance signal value of 0 to 255. By this gain adjustment, the value of the electrical signal obtained by exposing and scanning the document can be converted into a high luminance signal value or converted into a low luminance signal value. Next, a process for scanning the image on the document will be described.

  The scanner unit 13 converts image information into an electrical signal by inputting reflected light obtained by exposing and scanning the image on the document to the optical unit. Further, the electric signal is converted into a luminance signal composed of R, G, and B colors, and the luminance signal is output to the controller 11 as image data.

  The document is set on the document tray 202 of the document conveying device 201. When the user gives an instruction to start reading from the operation unit 12, a document reading instruction is given from the controller 11 to the scanner unit 13. Upon receiving this instruction, the scanner unit 13 separates and conveys the documents one by one from the document tray 202 of the document conveying device 201 and performs a document reading operation.

  The printer unit 14 is an image forming device that forms image data received from the controller 11 on a sheet. In this embodiment, the image forming method is an electrophotographic method using a photosensitive drum or a photosensitive belt, but the present embodiment is not limited to this. For example, the present invention can also be applied to an ink jet system that prints on paper by ejecting ink from a micro nozzle array. The printer unit 14 is provided with a plurality of paper cassettes 15, 16, and 17 that can select different paper sizes or different paper orientations. The printed paper is discharged to the paper discharge tray 18.

  FIG. 3 is a block diagram showing the controller 11 of the image forming apparatus 10. The controller 11 is electrically connected to the scanner unit 13 and the printer unit 14. On the other hand, the controller 11 is connected to the PC 40 or an external device via the LAN 50 or WAN 331. As a result, image data and device information can be input and output.

  The CPU 301 comprehensively controls access to various connected devices based on a control program stored in the ROM 303, and also performs overall control of various processes performed in the controller. A RAM 302 is a system work memory for the operation of the CPU 301 and also a memory for temporarily storing image data. The RAM 302 includes an SRAM that retains stored contents even after the power is turned off and a DRAM that erases the stored contents after the power is turned off. The ROM 303 stores a boot program for the apparatus. The HDD 304 is a hard disk drive and can store system software and image data.

  The operation unit I / F 305 is an interface unit for connecting the system bus 310 and the operation unit 12. The operation unit I / F 305 receives image data to be displayed on the operation unit 12 from the system bus 310 to the operation unit 12 and outputs information input from the operation unit 12 to the system bus 310.

  A network I / F 306 is connected to the LAN 50 and the system bus 310 to input / output information. The Modem 307 is connected to the WAN 331 and the system bus 310, and inputs and outputs information. A binary image rotation unit 308 converts the direction of image data before transmission. A binary multi-value compression / decompression unit 309 converts the resolution of the image data before transmission into a resolution that matches a predetermined resolution or the partner's ability. For compression and expansion, methods such as JBIG, MMR, MR, and MH are used. The image bus 330 is a transmission path for exchanging image data, and includes a PCI bus or IEEE1394.

  The scanner image processing unit 312 corrects, processes, and edits image data received from the scanner unit 13 via the scanner I / F 311. The scanner image processing unit 312 determines whether the received image data is a color document or a monochrome document, a character document, or a photographic document. Then, the determination result is attached to the image data. Such accompanying information is referred to as attribute data. Details of processing performed by the scanner image processing unit 312 will be described later.

  The compression unit 313 receives the image data and divides the image data into blocks of 32 pixels × 32 pixels. The 32 × 32 pixel image data is referred to as tile data. FIG. 4 conceptually shows this tile data. In a document (paper medium before reading), an area corresponding to the tile data is referred to as a tile image. The tile data is added with the average luminance information in the block of 32 × 32 pixels and the coordinate position of the tile image on the document as header information. Further, the compression unit 313 compresses image data including a plurality of tile data. The decompression unit 316 decompresses image data composed of a plurality of tile data, raster-expands it, and sends it to the printer image processing unit 315.

  The printer image processing unit 315 receives the image data sent from the decompression unit 316 and performs image processing on the image data while referring to attribute data attached to the image data. The image data after the image processing is output to the printer unit 14 via the printer I / F 314. Details of processing performed by the printer image processing unit 315 will be described later.

  The image conversion unit 317 performs a predetermined conversion process on the image data. This processing unit has the following processing units.

  The decompression unit 318 decompresses the received image data. The compression unit 319 compresses the received image data. The rotation unit 320 rotates received image data. The scaling unit 321 performs resolution conversion processing (for example, 600 dpi to 200 dpi) on the received image data. The color space conversion unit 322 converts the color space of the received image data. The color space conversion unit 322 performs a known background removal process using a matrix or a table, performs a known LOG conversion process (RGB → CMY), or performs a known output color correction process (CMY → CMYK). Can be. The binary multi-value conversion unit 323 converts the received two-gradation image data into 256-gradation image data. On the contrary, the multi-value binary conversion unit 324 converts the received 256-gradation image data into 2-gradation image data by a technique such as error diffusion processing.

  The synthesizer 327 synthesizes the two received image data to generate one piece of image data. When combining two pieces of image data, a method of using an average value of luminance values of pixels to be combined as a combined luminance value, or a luminance value of a pixel having a brighter luminance level, A method for obtaining a luminance value is applied. In addition, it is possible to use a method in which the darker pixel is used as a synthesized pixel. Furthermore, a method of determining a luminance value after synthesis by a logical sum operation, a logical product operation, an exclusive logical sum operation, or the like between pixels to be synthesized is also applicable. These synthesis methods are all well-known methods. The thinning unit 326 performs resolution conversion by thinning out the pixels of the received image data, and generates image data such as 1/2, 1/4, and 1/8. The moving unit 325 adds a margin part to the received image data or deletes the margin part.

  The RIP 328 receives intermediate data generated based on PDL code data transmitted from the PC 40 or the like, and generates bitmap data (multi-value).

  The inside of the scanner image processing unit 312 is shown in FIG.

  The scanner image processing unit 312 receives image data composed of RGB 8-bit luminance signals.

  The shading correction unit 500 performs shading correction on the luminance signal. As described above, the shading correction is a process for preventing the brightness of the document from being erroneously recognized due to variations in the sensitivity of the optical unit. Further, as described above, the shading correction unit 500 can perform gain adjustment according to an instruction from the CPU 301.

  Subsequently, the luminance signal is converted into a standard luminance signal that does not depend on the filter color of the optical unit by the masking processing unit 501.

  The filter processing unit 502 arbitrarily corrects the spatial frequency of the received image data. This processing unit performs arithmetic processing using, for example, a 7 × 7 matrix on the received image data. By the way, the operation unit 12 which is a user interface (UI) of the image forming apparatus 10 can select a character mode, a photo mode, or a character / photo mode as a copy mode. When the character mode is selected by the user, the filter processing unit 502 applies a character filter to the entire image data. When the photo mode is selected, a photo filter is applied to the entire image data. When the character / photo mode is selected, the filter is adaptively switched for each pixel in accordance with a character photo determination signal (part of attribute data) described later. In other words, it is determined for each pixel whether to apply a photo filter or a character filter. Note that coefficients for smoothing only high-frequency components are set in the photographic filter. This is because the roughness of the image is not noticeable. In addition, a coefficient for performing strong edge enhancement is set in the character filter. This is to increase the sharpness of the characters.

  The histogram generation unit 503 samples the luminance data of each pixel of the received image data. More specifically, luminance data in a rectangular area surrounded by a start point and an end point specified in the main scanning direction and the sub scanning direction are sampled at a constant pitch in the main scanning direction and the sub scanning direction. Then, histogram data is generated based on the sampling result. The generated histogram data is used to estimate the background level when performing background removal processing. The input-side gamma correction unit 504 converts luminance data having nonlinear characteristics using a table or the like.

  The color / monochrome determination unit 505 determines whether each pixel of the received image data is chromatic or achromatic, and attaches the determination result to the image data as a color / monochrome determination signal (part of attribute data). .

  The character photo determination unit 506 determines whether each pixel of the image data is a pixel of a character, a halftone dot, a character pixel in a halftone dot, or a pixel of a solid image and a pixel value of each pixel. The determination is made based on the pixel values of the peripheral pixels of the pixel. Note that pixels that do not correspond to any of them are pixels in the white area. Then, the determination result is attached to the image data as a character / photo determination signal (part of attribute data).

  The paper fingerprint information acquisition unit 507 determines an appropriate region as the paper fingerprint information acquisition region from the RGB image data input from the shading correction unit 500, and acquires the paper fingerprint data of the determined paper fingerprint information acquisition region To do. An appropriate area and paper fingerprint information acquisition method will be described later.

  A flow of processing performed in the printer image processing 315 is shown in FIG.

  The background removal processing unit 601 uses the histogram generated by the scanner image processing unit 312 to remove (remove) the background color of the image data. The monochrome generation unit 602 converts color data into monochrome data. The Log conversion unit 603 performs luminance density conversion. For example, the Log conversion unit 603 converts RGB input image data into CMY image data. The output color correction unit 604 performs output color correction. For example, image data input as CMY is converted into CMYK image data using a table or a matrix. The output-side gamma correction unit 605 performs correction so that the signal value input to the output-side gamma correction unit 605 is proportional to the reflection density value after copying output. A halftone correction unit 606 performs halftone processing in accordance with the number of gradations of the printer unit to be output. For example, the received high gradation image data is binarized or binarized.

Each processing unit in the scanner image processing unit 312 or the printer image processing unit 315 can output the received image data without performing each processing.
<Registration and verification of paper fingerprint information>
FIG. 7 is a flowchart showing a paper fingerprint information acquisition process performed by the paper fingerprint information acquisition unit 507.

  In step S701, the CPU 301 converts the image data acquired by the paper fingerprint information acquisition unit 507 into grayscale image data. In step S <b> 702, the CPU 301 creates mask data for performing collation by removing an image that has been converted into grayscale image data in step S <b> 701, which can cause misjudgment such as printing or handwritten characters. The mask data is binary data “0” or “1”. In the gray scale image data, the value of the mask data is set to “1” for a pixel whose luminance signal value is equal to or greater than the first threshold (that is, bright). Further, the mask data value is set to “0” for a pixel whose luminance signal value is less than the first threshold value. The above processing is performed on each pixel included in the grayscale image data. In step S703, the CPU 301 acquires and saves two pieces of data, the paper fingerprint information of the paper fingerprint information, the image data converted to grayscale in step S701 and the mask data created in step S702. Note that the image data itself converted to gray scale in step S701 may be referred to as paper fingerprint information, but in the present embodiment, the above two data are referred to as paper fingerprint information (paper fingerprint data). .

  The paper fingerprint information acquisition unit 507 sends the paper fingerprint information in the paper fingerprint information acquisition area to the RAM 302 using a data bus (not shown).

  The paper fingerprint information registration process is realized by the CPU 301 reading paper fingerprint information in a predetermined area sent from the paper fingerprint information acquisition unit 507 to the RAM 302 and registering the read paper fingerprint information in a server (not shown). Is done. When registered in the server, the management number indicating the original is displayed on the operation unit 12, and collation is possible by inputting the management number at the time of paper fingerprint collation. This series of registration processing is performed by executing a program stored in the RAM 302.

  In the paper fingerprint information collation process, the CPU 301 reads the paper fingerprint information of the document to be collated stored in the RAM 302 from the paper fingerprint information acquisition unit 507, and the read paper fingerprint information and other original paper fingerprint information registered. This is realized by collating In addition, in this embodiment, the paper fingerprint information registered in the other original can be collated with the original when the user inputs a management number. The method of matching with the server is not limited to this. This embodiment is realized by inputting a management number. However, a unique ID or the like may be added to the document in the document conveying apparatus during the paper fingerprint information registration process, and the ID may be used to register with the original document during collation.

  FIG. 8 is a flowchart showing the paper fingerprint information matching process. Each step of this flowchart is centrally controlled by the CPU 301.

  In step S <b> 801, the CPU 301 calls and acquires the paper fingerprint information registered in the server from the RAM 302.

In the above formula (1), α ₁ is mask data in the paper fingerprint information extracted (registered) in step S801. f ₁ is grayscale image data in the paper fingerprint information extracted (registered) in step S801. α ₂ is the mask data in the paper fingerprint information sent from the paper fingerprint information acquisition unit 507 in step S802 (which has just been taken out). f ₂ is gray scale image data in the paper fingerprint information (which has just been extracted) sent from the paper fingerprint information acquisition unit 507 in step S802.

  A specific method will be described with reference to FIGS. FIG. 16 shows an image diagram of the registered paper fingerprint information and the paper fingerprint information obtained this time. Each has horizontal n pixels and vertical m pixels.

  In the function shown in equation (1), i and j are shifted by one pixel in the range of −n + 1 to n−1 and −m + 1 to m−1, respectively, and the registered paper fingerprint information and just obtained this time. (2n−1) × (2m−1) error values E (i, j) of the paper fingerprint information of are obtained. That is, E (−n + 1, −m + 1) to E (n−1, m−1) are obtained.

  FIG. 17 shows an image diagram in which the upper left pixel of the registered paper fingerprint information is overlapped by the lower right pixel of the obtained paper fingerprint information. In this state, a value obtained by the function of the expression (1) is assumed to be E (−n + 1, −m + 1). FIG. 18 shows an image diagram obtained by moving the paper fingerprint information obtained this time to the right by one pixel as compared with FIG. In this state, a value obtained by the function of the expression (1) is assumed to be E (−n + 2, −m + 1). Similarly, calculation is performed while moving the paper fingerprint information just obtained this time. In FIG. 19, the paper fingerprint information just obtained this time is moved to a position where it overlaps with the registered paper fingerprint information, and E (0,-(m-1)) is obtained. Further, in FIG. 20, the paper fingerprint information obtained this time is moved to the right end to obtain E (n−1, −m + 1). Thus, when shifted in the horizontal direction, i of E (i, j) is incremented by one.

  Similarly, in FIG. 21, the paper fingerprint information obtained this time by one pixel is moved downward in the vertical direction as compared with FIG. 17, and the value of E (−n + 1, −m + 2) is obtained.

  Further, FIG. 22 obtains the value of E (n−1, −m + 2) by moving the paper fingerprint information obtained this time to the right end with respect to FIG.

  FIG. 23 shows the case where the registered paper fingerprint information and the paper fingerprint information obtained this time are at the same position, and the value of E (i, j) at this time is E (0,0).

  Similarly, the calculation is performed while shifting the images so that each paper fingerprint information overlaps at least one pixel. Finally, as shown in FIG. 24, E (n−1, m−1) is obtained.

  In this way, a set of (2n−1) × (2m−1) error values E (i, j) is obtained.

Here, in order to consider the meaning of the equation (1), i = 0, j = 0, and α ₁ (x, y) = 1 (where x = 0 to n, y = 0 to m ) And α ₂ (x−i, y−j) = 1 (where x = 0 to n and y = 0 to m). That is, α ₁ (x, y) = 1 (where x = 0 to n, y = 0 to m) and α ₂ (x−i, y−j) = 1 (where x = 0). E (0,0) in the case of .about.n, y = 0 to m).

  Note that i = 0 and j = 0 indicate that the registered paper fingerprint information and the paper fingerprint information obtained this time are at the same position as shown in FIG.

Here, α ₁ (x, y) = 1 (where x = 0 to n, y = 0 to m) indicates that all pixels of the registered paper fingerprint information are bright. In other words, when the registered paper fingerprint information is acquired, it indicates that no color material such as toner or ink or dust has been placed on the paper fingerprint acquisition area.

Further, α ₂ (x−i, y−j) = 1 (where x = 0 to n, y = 0 to m) indicates that all pixels of the paper fingerprint information acquired this time are bright. In other words, when the paper fingerprint information just acquired is acquired, it indicates that no color material such as toner or ink or dust is on the paper fingerprint acquisition area.

Thus, when α ₁ (x, y) = 1 and α ₂ (x−i, y−j) = 1 hold in all pixels, the equation (1) becomes

Will be expressed.

This {f ₁ (x, y) −f ₂ (x, y)} ² is the gray scale image data in the registered paper fingerprint information and the gray scale image data in the paper fingerprint information just extracted. The square value of the difference between Therefore, this equation (1) is the sum of the squares of the differences in each pixel between the two pieces of paper fingerprint information. That is, as the number of pixels in which f ₁ (x, y) and f ₂ (x, y) are similar increases, E (0, 0) takes a smaller value.

What has been described above is how to obtain E (0,0), but other E (i, j) are obtained in the same manner. Incidentally, since E (i, j) takes a smaller value the more pixels f ₁ (x, y) and f ₂ (x, y) are similar,
If E (k, l) = min {E (i, j)}, the position when the registered paper fingerprint information is acquired, and the position when the paper fingerprint information just acquired is acquired It can be seen that they were shifted from each other by k and l.

<Significance of α>
The numerator of formula (1) means the result of multiplying {f ₁ (x, y) -f ₂ (xi, y-j)} ² by α ₁ and α ₂ (exactly Is further determined by the Σ symbol). These α ₁ and α ₂ indicate 0 for dark pixels and 1 for light pixels.

Accordingly, when one (or both) of α ₁ and α ₂ is 0, α ₁ α ₂ {f ₁ (x, y) −f ₂ (xi, y−j)} ² Will be 0.

  That is, when one or both (or both) of the paper fingerprint information has a dark pixel, the density difference between the pixels is not considered. This is for ignoring pixels on which dust or color material has been placed.

By this process, the total number increases or decreases depending on the Σ symbol, and normalization is performed by dividing by the total number Σα ₁ (x, y) α ₂ (xi, y−j). Note that an error value E (i, j) at which Σα ₁ (x, y) α ₂ (xi, y−j) in the denominator of equation (1) becomes 0 is a set of error values (E (-(N-1),-(m-1)) to E (n-1, m-1)) are not included.

<Determination method of matching degree>
As described above, when E (k, l) = min {E (i, j)}, the position when the registered paper fingerprint information is acquired and the paper fingerprint information just acquired are acquired. It can be seen that the positions were shifted by k and l from each other.

  Subsequently, a value indicating how much the two pieces of paper fingerprint information are similar (this value is referred to as a matching degree) is obtained using the E (k, l) and other E (i, j). .

First, a set of error values obtained by the function of (1) (for example, E (0,0) = 10 *, E (0,1) = 50, E (1,0) = 50, E (1,1 ) = 50) to obtain the average value (40). ... (A)
Note that * is not related to the value. They are listed only for your attention. The reason I wanted to pay attention will be described later.

Next, each error value (10 *, 50, 50, 50) is subtracted from the average value (40) to obtain a new set (30 *, −10, −10, −10). .... (B)
Then, a standard deviation (30 × 30 + 10 × 10 + 10 × 10 + 10 × 10 = 1200, 1200/4 = 300, √300 = 10√3 = about 17) is obtained from this new set. Then, the new set is divided by 17 to obtain a quotient (1 *, -1, -1, -1). .... (C)
And let the maximum value of the calculated | required values be a matching degree (1 *). The value 1 * corresponds to the value E (0,0) = 10 *. In this case, E (0,0) is a value that satisfies E (0,0) = min {E (i, j)}.

<Conceptual explanation of how to determine the degree of matching>
The process of performing the matching degree determination method eventually calculates how far the smallest error value in the plurality of error value sets is from the average error value (A and B).

  Then, the degree of matching is obtained by dividing the degree of separation by the standard deviation (C).

  Finally, a matching result is obtained by comparing the matching degree with a threshold (D).

  The standard deviation means an average value of “difference between each error value and the average value”. In other words, the standard deviation is a value indicating how much variation occurs in the entire set.

  By dividing the above degree of separation by such an overall variation value, how small is min {E (i, j)} in the set E (i, j) (projectingly small or slightly small) ) Will be understood.

  Then, it is determined to be valid when min {E (i, j)} is very prominent and small in the set E (i, j), and is invalid otherwise (D).

<Reason to determine that min {E (i, j)} is effective only when it is very small in the set E (i, j)>
Here, it is assumed that the registered paper fingerprint information and the paper fingerprint information just acquired are acquired from the same paper.

  Then, there should be a place (shift position) where the registered paper fingerprint information and the paper fingerprint information just acquired are very consistent. At this time, at this misalignment position, the registered paper fingerprint information and the paper fingerprint information just acquired are very coincident, so E (i, j) should be very small.

  On the other hand, if the position is slightly shifted from this position, the registered paper fingerprint information and the paper fingerprint information just acquired are no longer relevant. Therefore, E (i, j) should be a normal large value.

  Therefore, the condition that “two pieces of paper fingerprint information are acquired from the same paper” matches the condition that “the smallest E (i, j) protrudes and is small in the set E (i, j)”.

Return to <Paper fingerprint information collation processing>.
In step S803, the CPU 301 compares the matching degree of the two pieces of paper fingerprint information obtained in step S802 with a predetermined threshold value, and determines “valid” or “invalid”. Note that the degree of matching may be referred to as similarity. A comparison result between the matching degree and a predetermined threshold value may be referred to as a matching result. After step S803, the process proceeds to step S804, and the determination result is output in step S804.

  FIG. 9 is a diagram illustrating the operation unit 12 of the image forming apparatus. The LCD display unit 950 has a touch panel sheet affixed on the LCD, displays an operation screen of the image forming apparatus, and transmits position information to the CPU 301 when a displayed key is pressed. A detailed screen will be described later with reference to FIG. A numeric keypad 901 is used to input numbers such as the number of copies. A start key 902 is used to start a copying operation or a document reading operation after setting user-desired conditions. A stop key 903 is used to stop an operation in operation. A reset key 904 is used when initializing settings from the operation unit. When the guide key 905 is pressed when the function of the key is not understood, an explanation of the key is displayed. A copy mode key 906 is pressed when copying. A fax key 907 is pressed to make settings related to fax. A SEND key 908 is pressed when it is desired to output file data to an external device such as a computer. A scanner key 909 is used when image reading is set from an external device such as a computer.

  FIG. 10 is a basic screen displayed on the LCD display unit 950 of the operation unit 12. The LCD display unit 950 indicates whether or not the image forming apparatus 10 is ready for copying, and indicates the set number of copies. The document selection tab 951 is a tab for selecting a document type, and when this tab is depressed, three types of selection menus of character, photo, and character / photo mode are popped up. The finishing tab 952 is a tab for performing settings related to various finishings. A duplex setting tab 953 is a tab for performing settings relating to duplex reading and duplex printing. A reading mode tab 954 is a tab for selecting an original reading mode. When this tab is pressed, three types of selection menus of color / black / automatic (ACS) are popped up. Note that color copy is performed when color is selected, and monochrome copy is performed when black is selected. When ACS is selected, the copy mode is determined by the monochrome color determination signal described above.

  In the present invention, when there are a plurality of reading modes, they may be referred to as a first reading mode and a second reading mode.

  The paper fingerprint information registration tab 955 is a tab for selecting paper fingerprint information registration processing. The paper fingerprint information registration process will be described later. A paper fingerprint information matching tab 956 is a tab for selecting a paper fingerprint information matching process. This paper fingerprint information matching process will be described later.

  A system status tab 957 is a tab for indicating the status of the image forming apparatus. When this tab is depressed, a list of image data stored in the HDD 304 in the image forming apparatus 10 is displayed on the display screen.

  Next, a method for reading paper fingerprint information and reading an image using the document conveying device 201 in the scanner unit 13 to which the present embodiment is applied will be described in detail.

  Together with a brief description of the scanner unit 13, a description of document conveyance in the flow reading mode, which is a document reading method in the document conveyance device 201, will be added, and a brief description will be given with reference to FIG. 11.

  A document tray 202 serving as a document stacking unit is provided, and documents are stacked on the surface of the document tray 202. In the document feeding unit of the document conveying device 201, a feeding roller (not shown) as a feeding unit and a document bundle stacked on the document tray 202 are drawn into the separation unit 203, and the top sheet of the document bundle is separated one by one. Transport to 204, 205. The registration roller 206 is stopped when the leading edge of the document arrives, forms a loop by conveyance by the conveyance rollers 204 and 205, corrects skew feeding, and then conveys the document to the document reading unit. In the document reading unit of the document conveying device 201, the document conveyed from the document feeding unit is conveyed to the position R1 by the registration roller 206 and the reading belt 208 at a predetermined speed. When the leading edge of the document reaches the reading position R1, an exposure operation is performed by the optical unit 212 fixed at the reading position R1, and the reading operation can be performed while conveying the document. This reading method is referred to as a flow reading mode. .

  When the reading of the original is completed, the original is conveyed by the reading belt 208 to the original discharge section. In the document discharge section, the discharge roller 209 discharges the back side to the discharge tray 210. In addition, when the back side optical unit 211 for back side image reading is provided and reading of a double-sided document is selected, the back side optical unit 211 can be used to acquire a back side image.

  In FIG. 11, sensors S <b> 1 to S <b> 6 and VR <b> 1 are arranged in the document feeder 201 by various sensors.

  Here, the large size detection sensor S <b> 1 and the small size detection sensor S <b> 2 detect the length on the document tray 202. The width detection volume VR1 and the width detection sensor S3 are provided in the document width guide 107. The size sensor S4 detects the separated and fed document by detecting the leading edge and the trailing edge of the document, and simultaneously measures the document length. The read sensor S5 detects the leading edge of the document and notifies a read signal. Reference numeral S6 denotes a paper discharge sensor. A document setting sensor S7 (not shown) determines whether a document is set on the document tray 105.

  FIG. 12 is a block diagram showing the document conveying device 201. The document feeder 201 includes a CPU 251, a ROM 252, a RAM 253, and a CPU interface 254. Here, the CPU 251 is connected to the ROM 252, the RAM 253, and the CPU interface 254.

  Here, the CPU 251 controls the entire automatic document feeder. A program is stored in the ROM 252, and the RAM 253 is used as an area for temporarily holding control data and a work area for operations associated with control. The CPU interface 254 communicates with the controller 11, communicates with the CPU 301 of the controller 11 in real time, and the CPU 251 controls the entire automatic document feeder in response to a command from the CPU 301.

  The document feeder 201 has a width detection volume VR1 and various sensors S1 to S7. As described above, the various sensors include the large size detection sensor S1, the small size detection sensor S2, the width detection sensor S3, the size sensor S4, the lead sensor S5, the paper discharge sensor S6, and the document set sensor S7.

  In the document conveying device 201, the document is separated. Further, the document conveying device 201 includes a separation / feed motor M1, a registration motor M2, a conveyance belt motor M3, a paper discharge motor M4, a clutch CL1, and solenoids SL1 and SL2. Here, the separation feeding motor M1 feeds with the conveying rollers 204 and 205. The registration motor M2 drives the registration roller 206. The conveyor belt motor M3 drives the reading belt 208. The paper discharge motor M4 drives the paper discharge roller 209.

  The width detection volume VR1 and the various sensors S1 to S8 are controlled by the CPU 251.

<Setting the scanning mode using the document feeder>
First, the user places a document on the document tray 202 of the document conveying device 201 and performs a desired document reading setting on the operation unit 12. The user selects the paper fingerprint information registration tab 955 or the paper fingerprint information collation tab 956 and specifies the document size. Here, the designated size is used for image reading. Settings such as whether the document is a double-sided document, whether the document bundle is a mixed document, whether to read the document in the fixed reading mode, and the like are set on the operation unit 12. Then, the start key 902 is pressed.

<Separation using a document feeder>
FIG. 13 is a flowchart showing the separation operation after the start key 902 is pressed. In the present embodiment, the separation operation will be described in the case where two A4 size originals are set on the original tray 202. The separation operation flow is as follows.

  First, when the start key 902 is pressed, a separation operation flow is started in step S1300, and the CPU 251 determines whether or not a document size is specified by the user (step S1301). When the CPU 251 determines that there is no document size designation, the CPU 251 executes the following processing. That is, the CPU 251 determines the document size from the small size detection sensor S1, the large size detection sensor S2, the width detection volume VR1, and the width detection sensor S3 arranged on the document tray 105 (step S1302). In this embodiment, as an example, the A4 size is determined as the document size. At this time, the CPU 251 pulls and separates the first sheet (N = 1) of the document into the separation unit 203 by a feeding roller (not shown), and conveys it to the conveyance rollers 204 and 205. When the trailing edge of the first document passes the size sensor S4 (step S1303).

  Thereafter, the CPU 251 determines whether the reading signal of the size sensor is ON or OFF (step S1304). If the reading signal of the size sensor is OFF, the process continues to stop. If the size sensor read signal is ON, the process proceeds to step S1305. The CPU 251 measures the length of the document from the motor clock of the separation feeding motor M1 (step S1305). This is used to determine the length when the original mixed loading is set. After that, the CPU 251 determines whether or not there is a next document depending on whether or not the reading signal of the document set sensor S7 is ON (step S1306). When the reading signal of the document set sensor S7 is ON, the CPU 251 determines that the next document is on the document tray 105. The CPU 251 performs an operation of N = N + 1 (step S1307), the Nth (N = 2 in this case) document is separated (step S1308), and the above operation is repeated. In step S1306, when the reading signal of the document set sensor S7 is OFF (step S1306), the CPU 251 determines that the document is the final document and ends the separation operation.

<Paper Fingerprint Information Registration Process and Image Reading Process 1 Using Document Feeder>
A description will be given of the reading processing flow of the document feeder 201 when paper fingerprint information registration is enabled on the paper fingerprint information registration tab 955 and a plurality of copies of the document are copied. This operation is a mode used when paper fingerprint information registration is validated for all pages in a document, paper fingerprint information is registered for each original document, and a copy is created together. Hereinafter, a reading process flow of the document conveying apparatus 201 will be described with reference to FIG.

  First, in step S1400, paper fingerprint registration reading and normal reading flow are started.

  After the leading edge of the first document (N = 1) is corrected by the registration roller 206 in the separation operation flow of FIG. 13, the CPU 251 continues until the leading edge of the first document reaches the read sensor S5. Wait (step S1401). That is, if the read signal of the read sensor is OFF, the process continues to stop, and if the read signal of the read sensor is ON, the process proceeds to step S1402.

  Then, after the leading edge of the first document reaches the read sensor S5, the CPU 251 fixes the optical unit 212 and conveys the paper fingerprint information while conveying the first document at the position R1 reaching the optical unit 212. Reading is started (step S1402). The white portion of the paper in the original is an area suitable as a reading position for paper fingerprint information because the paper fiber pattern can be easily detected. Since there is often no information recorded at the leading edge of the document, there is a high possibility that paper white exists. Therefore, the leading edge of the document may be the paper fingerprint reading position. Also, from the RGB signal that captures the original, the RGB value is 8BIT and the area near 255 is considered white. Therefore, this area may be determined and used as the paper fingerprint registration area.

  In step S1402, the CPU 301 in the controller 11 in the scanner image processing unit 312 sets a gain adjustment value smaller than a general gain adjustment value in the shading correction unit 500. Then, the CPU 251 outputs each luminance signal value obtained by applying the small gain adjustment value to the image data to the paper fingerprint information acquisition unit 507. Thereafter, the CPU 251 acquires the paper fingerprint information based on the output data. Then, the CPU 251 sends the acquired paper fingerprint information to the RAM 302 using a data bus (not shown).

  Next, when the CPU 251 determines that reading of the paper fingerprint information is completed when the original is conveyed and the paper fingerprint of the first original reaches the optical unit R1 (step S1403), the position R1 on the original platen glass is determined. Stop the document. At this time, it is not necessary that all the originals pass through the position R1, and it is only necessary that an area for registering the above-described paper fingerprint passes (step S1404).

  If the CPU 251 determines in step S1403 that the reading of the paper fingerprint information has not ended, the processing continues to stop.

  Following step S1404, the CPU 251 moves the optical unit 212 to a position R2 in front of the front end of the document (step S1405).

  Then, the CPU 251 restarts the document conveyance, starts reading the first image at the position R2, and starts fixing the optical unit 212 in the reading mode (step S1406). In this case, since normal document reading is performed, gain adjustment is performed on the read image signal using a general gain adjustment value (for normal image reading) to obtain image data.

  When the CPU 251 determines that there is a next original (step S1407), the CPU 251 performs an operation of N = N + 1 and simultaneously returns the optical unit 212 to the position R1 after the first image reading is completed (step S1407). Step S1408). After the leading edge of the second original reaches the read sensor S5, the CPU 251 fixes the optical unit 212 and conveys the paper fingerprint while transporting the first original to the paper discharge tray at the position R1 reaching the optical unit 212. Reading of information is started (step S1402), and the above operation is repeated.

  If the CPU 251 determines that there is no next original (step S1407), the read final original is discharged, and the reading operation ends.

<Paper fingerprint information collation processing and image reading processing 2 using document feeder>
An explanation will be given of the reading processing flow of the document conveying apparatus 201 when paper fingerprint information matching is enabled on the paper fingerprint information matching tab 956, a management number indicating the original is input, and a plurality of copies of the document are copied. This operation assumes a case where a plurality of copies of the original are copied after the management number indicating the original is input for all pages in the original. That is, it is used when the paper fingerprint information registered by the user is collated with the original for each original, and a copy of the original is created. Hereinafter, the processing flow will be described with reference to FIG.

  First, in step S1500, the paper fingerprint registration reading and normal reading flow are started. After the leading edge of the first document (N = 1) is corrected by the registration roller 206 in the separation operation flow of FIG. 13, the CPU 251 continues until the leading edge of the first document reaches the read sensor S5. Wait (step S1501). That is, if the read signal of the read sensor is OFF, the process continues to stop, and if the read signal of the read sensor is ON, the process proceeds to step S1502.

  Next, after the leading edge of the first document reaches the read sensor S5, the CPU 251 fixes the optical unit 212 and conveys the paper fingerprint information while transporting the first document at the position R1 reaching the optical unit 212. Is started (step S1502). This reading position is as described in <Paper fingerprint information registration processing and image reading processing 1 using the document feeder>.

  When the CPU 251 determines that the reading of the paper fingerprint information has been completed (step S1503), the CPU 251 stops the document at a position R1 on the platen glass. At this time, it is not necessary for all the documents to pass through the position R1, and it is sufficient if a predetermined paper fingerprint has passed (step S1504).

  If the CPU 251 determines in step S1503 that the reading of the paper fingerprint information has not ended, the processing continues to stop.

  In step S1502, the CPU 301 in the controller 11 of the scanner image processing unit 312 sets a gain adjustment value smaller than a general gain adjustment value in the shading correction unit 500. Then, the CPU 251 outputs each luminance signal value obtained by applying the small gain adjustment value to the image data to the paper fingerprint information acquisition unit 507. Thereafter, the CPU 251 acquires the paper fingerprint information based on the output data. Then, the obtained paper fingerprint information is sent to the RAM 302 using a data bus (not shown).

  The CPU 301 collates the paper fingerprint information registered in the server with the paper fingerprint information acquired through the paper fingerprint information acquisition unit 507 (step S1505). When the CPU 301 determines that the collation result in step S1505 is the same as that of the original, the CPU 251 starts moving the document to the position R2 in front of the document front (step S1506).

  Next, the document conveyance is resumed, and the CPU 251 starts reading the first image at the position R2 and starts fixing the optical unit 212 in the reading mode (step S1507). Also in this case, the gain adjustment value for normal reading is used.

  If the CPU 251 determines that there is a next original (step S1508), the CPU 251 performs an operation of N = N + 1 and simultaneously returns the optical unit 212 to the position R1 after the first image reading is completed (step S1508). Step S1509). After the leading edge of the second original reaches the read sensor S5, the CPU 251 fixes the optical unit 212 while transporting the first original to the paper discharge tray at a position R1 that reaches the optical unit 212. Further, reading of the paper fingerprint information of the second original is started (step S1502), and the above operation is repeated. If the CPU 251 determines that there is no next original (step S1508), the read final original is discharged, and the reading operation ends. If it is determined that the collation result by the CPU 301 in step S1505 is different from the original, the read original is discharged, a warning different from the original is notified on the operation unit 12, and the process ends without reading the image. (Step S1510).

(Embodiment 2)
In steps S1402 and S1502, the CPU 301 in the controller 11 in the scanner image processing unit 312 sets a gain adjustment value smaller than a general gain adjustment value in the shading correction unit 500. Instead of this, when paper fingerprint reading is performed in contrast to normal image reading, the amount of light applied to the original of the optical unit 212 may be changed. In this case, while the optical unit 212 moves between the document reading position R1 and the position R2, the image reading light quantity value and the paper fingerprint reading light quantity value are changed in steps S1405, S1409, S1506, and S1509.

  In step S1402 and step S1502, when the CPU 251 reads the paper fingerprint information, it is not necessary to read the entire original, and the range from the leading end of the original to a predetermined paper fingerprint may be read. At this time, the CPU 251 detects the end of the paper fingerprint reading on the document by the image sensor by detecting image information including the paper fingerprint position information on the document. The image information including the position information of the paper fingerprint is, for example, a barcode included in the document image including the position information of the paper fingerprint, a mark for specifying the position, or the like.

(Embodiment 3)
Further, the position detection of the end of the paper fingerprint reading on the document does not use the detection of the image information including the paper fingerprint position information on the document, but the paper fingerprint position information is previously obtained from the CPU 251 via the operation unit 12 or the LAN 50 in advance. It may be input as fingerprint position information.

It is a figure which shows an image reading apparatus. 1 is a diagram illustrating an image forming apparatus 10. 2 is a block diagram showing a controller 11. FIG. It is the figure which showed tile data notionally. FIG. 3 is a diagram showing the inside of a scanner image processing unit 312. FIG. 10 is a diagram illustrating a flow of processing performed in printer image processing 315. 10 is a flowchart illustrating a paper fingerprint information acquisition process performed by a paper fingerprint information acquisition unit 507. It is a flowchart which shows a paper fingerprint information collation process. 3 is a diagram illustrating an operation unit 12 of the image forming apparatus. FIG. FIG. 12 is a diagram of a basic screen displayed on the LCD display unit 950 of the operation unit 12. FIG. 4 is a diagram illustrating a scanner unit 13. 2 is a block diagram showing a document conveying device 201. FIG. This is a separation operation using the document feeder 201. FIG. 5 is a diagram showing a processing flow when registering each original as an original and creating a copy of the original together, and registering paper fingerprint information and reading an image in the original flow reading mode. This is used when one original is collated with the original and a duplicate is created. It is a figure which shows the processing flow about the case where paper fingerprint information collation and image reading are performed in the flow reading mode. It is a figure which shows the registered paper fingerprint information and the paper fingerprint information obtained this time. It is a diagram showing how to determine the E 1 _{× 1.} It is a diagram showing how to determine the E 2 _{× 1.} It is a diagram showing how to determine the E n _{× 1.} It is a figure which shows how to obtain E _{2n-1 × 1} It is a figure which shows how to obtain | require E1 _{* 2} . It is a figure which shows how to obtain | require _{E2n-1 * 2} . It is a diagram showing how to determine the E n _{× m.} It is a figure which shows how to obtain | require _E2n-1x2m-1 .

Explanation of symbols

11 Controller 12 Operation Unit 13 Scanner Unit 201 Document Conveying Device 202 Document Tray 203 Separation Unit 204 Conveying Roller 205 Conveying Roller 206 Registration Roller 208 Reading Belt 209 Discharging Roller 210 Discharging Tray 212 Optical Unit 251 CPU
301 CPU
312 Scanner Image Processing Unit 507 Paper Fingerprint Information Acquisition Unit

Claims (6)

A document feeding means for conveying to the reading position originals,
Reading means having an optical unit for reading an image of the original and a paper fingerprint ;
The paper fingerprint of the original is read while the original is being conveyed by the original feeding means while the position of the optical unit is fixed, and then the conveyance of the original is stopped by the original feeding means , Control means for controlling the reading means to move the optical unit in front of the front end, fix the position of the optical unit and then resume conveyance of the original and read an image of the original by the optical unit ;
Image reading apparatus, characterized in that it comprises a. The gain adjustment value smaller than that at the time of reading the original image after reading the paper fingerprint is applied to the electrical signal obtained by reading the original when reading the paper fingerprint. Image reading apparatus. 2. The image reading apparatus according to claim 1 , wherein when reading the paper fingerprint, the original is read by irradiating a light amount different from that when reading the image of the original after reading the paper fingerprint . A document feeding step for feeding to the reading position originals,
A reading step of reading an image of the original and a paper fingerprint using an optical unit ;
Wherein by fixing the position of the optical unit reads the paper fingerprint of the document while conveying the document, then, stops the conveyance of the document, moving the optical unit in front of the front end of the document that has stopped, the A control step of resuming conveyance of the original after fixing the position of the optical unit and controlling the image of the original to be read by the optical unit ;
Image reading method characterized in that it comprises a. During reading of the paper fingerprint, according to claim 4, characterized by applying a small gain adjustment value than during reading of an image of the document after reading the paper fingerprint into an electric signal obtained by reading the original Image reading method. 5. The image reading method according to claim 4 , wherein when reading the paper fingerprint, the original is read by irradiating a light amount different from that when reading the image of the original after reading the paper fingerprint .

Images