JP7683377B2 - Image reading device and image forming device - Google Patents

Description

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

In recent years, with the improvement in the performance of image formation by copiers and printers, there has been a concern that objects such as banknotes, securities, passports, title deeds, certified copies of family registers, resident cards, various certificates, insurance policies, and confidential documents may be copied, and there is a demand for devices that can determine the authenticity of objects.

One such device that has been disclosed is an image reading device that acquires reference data representing the true characteristics of an individual object having unique readable features with randomness distributed along its surface, obtains matching data representing the characteristics of the individual object, and performs authenticity determination based on the reference data and matching data (see, for example, Patent Document 1).

However, the device in Patent Document 1 obtains reference data and matching data based on the color and reflectance of the object, which raises concerns about the accuracy of authenticity determination.

The present invention aims to provide an image reading device with high accuracy in authenticity determination.

An image reading device according to one aspect of the present invention is an image reading device that reads a printed image formed on a surface of an object, the image reading device having an illumination unit, a first reading unit including a first photoelectric conversion element and outputting a first read image obtained by reading the printed image illuminated by the illumination unit at a first reading magnification using the first photoelectric conversion element, a second reading unit including a second photoelectric conversion element and outputting a second read image obtained by reading the printed image illuminated by the illumination unit at a second reading magnification using the second photoelectric conversion element, and a determination unit that outputs authenticity information of the object determined based on the second read image, the second read magnification being higher than the first read magnification, and the first reading unit reflects light that is reflected by the object and illuminated by the illumination unit, and is oriented in a predetermined direction along the surface of the object. a first mirror unit that moves at a constant speed in a predetermined direction in conjunction with the movement of the first mirror unit, a second mirror unit that further reflects the reflected light by the first mirror unit and moves in the predetermined direction in conjunction with the movement of the first mirror unit at a speed that is half the moving speed of the first mirror unit, and a lens that transmits the reflected light reflected by the second mirror unit, wherein the first mirror unit and the second mirror unit move in the predetermined direction in conjunction with each other to read the entire printed image, the second photoelectric conversion element is provided in the first mirror unit, and the second reading unit reads the entire printed image by the second photoelectric conversion element moving in the predetermined direction in conjunction with the movement of the first mirror unit .

The present invention provides an image reading device with high accuracy in determining authenticity.

FIG. 4 is a diagram showing an example of a read image of a printed matter according to the embodiment; 6A and 6B are diagrams illustrating an example of density distribution in a minute region in a printed matter according to an embodiment. 11A and 11B are diagrams illustrating an example of density distribution in a minute region used in authenticity determination according to the embodiment; 1 is a block diagram of an example of a hardware configuration of an image forming apparatus according to an embodiment; 2 is a block diagram of an example of a functional configuration of an image forming apparatus according to an embodiment; 1 is a diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a scanner unit according to the embodiment. 3A and 3B are diagrams illustrating a driving method of a scanner unit according to an embodiment. FIG. 2 is a block diagram of an example of a hardware configuration of a scanner unit according to the embodiment. 4 is a block diagram showing an example of a functional configuration of a determination unit according to the first embodiment; FIG. FIG. 4 is a flowchart of an example of a registration process performed by the image reading device according to the first embodiment. 6 is a flowchart of an example of a determination process performed by the image reading apparatus according to the first embodiment. FIG. 11 is a block diagram showing an example of a functional configuration of a determination unit according to the second embodiment. FIG. 11 is a diagram illustrating an example of a first scanned image when there is no misalignment. FIG. 11 is a diagram illustrating an example of a first scanned image when there is a positional deviation. FIG. 11 is a flowchart of an example of a determination process performed by an image forming apparatus according to a second embodiment.

Below, the embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicated descriptions will be omitted as appropriate.

The image reading device according to the embodiment has an illumination unit and a first reading unit that outputs a first read image obtained by reading an object illuminated by the illumination unit at a first reading magnification. The image reading device is, for example, a scanner mounted on an image forming device such as a multifunction peripheral (MFP). The object is, for example, a printed matter on which an image is formed on a recording medium such as paper by an electrophotographic method or an inkjet method.

When an image formed on paper by electrophotography or inkjet printing is enlarged, it contains density distributions that correspond to uneven toner or ink adhesion, bleeding or scattering of toner or ink (so-called dust) at the edges of patterns such as characters, etc.

1 and 2 are diagrams for explaining the density distribution in such a minute region. FIG. 1 is a diagram showing an example of a scanned image of a printed matter in which a character image is formed on paper P by an electrophotographic image forming apparatus. As shown in FIG. 1, the scanned image 110 includes the character image "confidential" formed on paper P. FIG. 2 is a diagram showing an enlarged image 120 obtained by enlarging a partial region 111, which is a part of the character image "secret" in the scanned image 110 of FIG. 1. In the enlarged image 120, for example, a density distribution occurs in the minute region 121 due to uneven adhesion of toner. In addition, in the minute regions 122a and 122b, a density distribution occurs according to black dot-like dust caused by scattered toner. The density distribution in such a minute region of the scanned image 110 is not reproducible and becomes unique information that differs for each printed matter.

In this embodiment, the authenticity of an object is determined by utilizing the density distribution in a minute region of the object such as a printed matter. For example, an enlarged image 120 as shown in FIG. 2 is registered in a registration unit such as a database as individual identification information indicating that the scanned image 110 is a genuine printed matter. Then, when determining authenticity, a minute region in approximately the same position as the scanned image 110 is read in the fake printed matter, and an enlarged image 130 as shown in FIG. 3 is obtained. In the enlarged image 130, unlike the enlarged image 120, there are no black dot-like dust spots caused by toner scattering in the minute regions 131 and 132. Based on this difference, a printed matter including a minute region corresponding to the enlarged image 130 can be determined to be a fake.

However, if the first reading magnification of the first reading unit used as a scanner is increased to a level that enables the density distribution in a minute area to be read, the reading range will become narrower according to the first reading magnification, impairing the copying function, which is the main function of the image reading device.

Therefore, the image reading device according to the embodiment has a second reading unit that outputs a second read image obtained by reading a printed matter illuminated by an illumination unit at a second reading magnification, and a determination unit that outputs authenticity information of the object determined based on the second read image, and the second reading magnification is higher than the first reading magnification.

The image reading device according to the embodiment performs authenticity determination using the density distribution of minute areas in the second read image read by the second reading unit, which has a higher reading magnification than the first reading unit, thereby enabling highly accurate authenticity determination without compromising the copying function, which is the main function of the image reading device.

In the following embodiment, an image forming apparatus that is a multi-function peripheral (MFP) will be described as an example. The image forming apparatus according to the embodiment forms an image on paper (an example of a recording medium) by electrophotography, and includes an image reading device that reads a printed material, which is an example of an object.

<Configuration Example of Image Forming Apparatus 1>
(Example of Hardware Configuration of Image Forming Apparatus 1)
4 is a block diagram showing a hardware configuration of the image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 has an engine for executing image formation in addition to a configuration similar to that of a general information processing terminal such as a server or a PC (Personal Computer).

The image forming device 1 has a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 11, a ROM (Read Only Memory) 12, an engine 13, a HDD (Hard Disk Drive) 14, and an I/F (Interface) 15. These are electrically connected to each other via a bus 18. The I/F 15 is also connected to an LCD (Liquid Crystal Display) 16 and an input operation unit 17.

The CPU 10 is a computing means and controls the operation of the entire image forming device 1. The RAM 11 is a volatile storage medium that allows high-speed reading and writing of information. The CPU 10 uses the RAM 11 as a working area when processing information. The ROM 12 is a read-only non-volatile storage medium that stores programs such as firmware. The engine 13 is a mechanism that actually executes image formation in the image forming device 1. The components other than the engine 13 are collectively referred to as the information processing device 2.

The HDD 14 is a non-volatile storage medium that can read and write information, and stores the OS (Operating System), various control programs, application programs, etc. The I/F 15 is an interface that connects and controls the bus 18 with various hardware and networks, etc. The display device 16 is a visual user interface that allows the user to check the status of the image forming device 1. The input operation unit 17 is a user interface that allows the user to input information to the image forming device 1, such as a keyboard or mouse.

In the above hardware configuration, the image forming device 1 configures a software control unit by reading a program stored in a recording medium such as the ROM 12, HDD 14, or optical disk into the RAM 11 and running the program under the control of the CPU 10. The image forming device 1 configures a functional block that realizes the functions of the image forming device 1 by combining the software control unit configured in this way with hardware.

(Example of functional configuration of image forming apparatus 1)
5 is a block diagram showing an example of a functional configuration of the image forming apparatus 1. The image forming apparatus 1 includes a controller 20, an image reading device 100, a display panel 24, a paper feed table 25, a print engine 26, a paper discharge tray 27, and a network I/F 28. The image reading device 100 also includes an ADF 21, a scanner unit 22, and a paper discharge tray 23.

The controller 20 has a main control unit 30, an engine control unit 31, an input/output control unit 32, an image processing unit 33, an operation display control unit 34, and a determination unit 35. The image forming device 1 is configured as a multifunction device having a scanner unit 22 and a print engine 26. Note that in FIG. 5, electrical connections are indicated by solid arrows, and paper flow is indicated by dashed arrows.

The display panel 24 is an output interface that visually displays the status of the image forming device 1. The display panel 24 also functions as a touch panel that allows a user to directly operate the image forming device 1 or as an input interface (input operation section) when inputting information to the image forming device 1.

The network I/F 28 is an interface such as Ethernet (registered trademark) or USB (Universal Serial Bus) that allows the image forming device 1 to communicate with other devices via a network.

The controller 20 is configured by a combination of software and hardware. Specifically, control programs such as firmware stored in the ROM 12, non-volatile memory, and non-volatile recording media such as the HDD 14 and optical disks are loaded into a volatile memory such as the RAM 11, and the controller 20 is configured by a software control unit configured according to the control of the CPU 10 and hardware such as integrated circuits. The controller 20 functions as a control unit that controls the entire image forming device 1.

The main control unit 30 is responsible for controlling each part included in the controller 20 and issues commands to each part of the controller 20. The engine control unit 31 is responsible for acting as a driving means for controlling or driving the print engine 26, the scanner unit 22, etc.

The input/output control unit 32 inputs signals and commands input via the network I/F 28 to the main control unit 30. The main control unit 30 also controls the input/output control unit 32 and accesses other devices via the network I/F 28.

The image processing unit 33 is an electric circuit that generates drawing information based on the printing information included in the input print job under the control of the main control unit 30. This drawing information is information for the print engine 26 to draw the image to be formed in the image forming operation. The printing information included in the print job is image information that has been converted into a format that can be recognized by the image forming device 1 by a printer driver installed in an information processing device such as a PC. The operation display control unit 34 displays information on the display panel 24 or notifies the main control unit 30 of information input via the display panel 24.

When the image forming device 1 operates as a printer, first, the input/output control unit 32 receives a print job via the network I/F 28. The input/output control unit 32 transfers the received print job to the main control unit 30. When the main control unit 30 receives the print job, it controls the image processing unit 33 to generate drawing information based on the printing information included in the print job.

When the image processing unit 33 generates drawing information, the engine control unit 31 performs image formation on the paper transported from the paper feed table 25 based on the generated drawing information. In other words, the print engine 26 functions as the image forming unit. The paper on which the image has been formed by the print engine 26 is discharged to the paper discharge tray 27.

When the image forming device 1 operates as a scanner, the operation display control unit 34 or the input/output control unit 32 transfers a scan execution signal to the main control unit 30 in response to an operation of the display panel 24 by an operator of the image forming device 1 (hereinafter simply referred to as the operator) or a scan execution instruction input from an external PC or the like via the network I/F 28. The main control unit 30 controls the engine control unit 31 based on the received scan execution signal.

The engine control unit 31 drives the ADF 21 to transport the printed material set in the ADF 21 to the scanner unit 22. The engine control unit 31 also drives the scanner unit 22 to capture an image of the printed material transported from the ADF 21. When no printed material is set in the ADF 21 and a printed material is set directly in the scanner unit 22, the scanner unit 22 captures the set printed material under the control of the engine control unit 31. In other words, the scanner unit 22 operates as an image capture unit for printed materials.

During the imaging operation, the imaging element included in the scanner unit 22 captures an image of a printed material while being moved in a predetermined direction, and the scanner unit 22 generates imaging information. The engine control unit 31 transfers the imaging information generated by the scanner unit 22 to the image processing unit 33. The image processing unit 33 generates a read image based on the imaging information received from the engine control unit 31 under the control of the main control unit 30.

The scanned image generated by the image processing unit 33 is either stored directly in the HDD 14 or transmitted to an external device via the input/output control unit 32 and the network I/F 28, depending on the operator's instructions.

When the image forming device 1 operates as a copier, the image processing unit 33 generates drawing information based on the imaging information received by the engine control unit 31 from the scanner unit 22 or the read image generated by the image processing unit 33. The engine control unit 31 drives the print engine 26 based on this drawing information in the same way as in the case of printer operation.

The determination unit 35 executes a process for determining the authenticity of the printed matter based on the scanned image of the printed matter generated by the scanner unit 22. The function of this determination unit 35 will be described in detail later with reference to FIG. 10.

(Example of overall configuration of image forming apparatus 1)
6 is a diagram showing an example of a schematic configuration of the image forming apparatus 1. As shown in FIG. 6, the image forming apparatus 1 includes an image reading device 100, an image forming section 300, and a paper feeding section 400.

The paper feed section 400 has paper feed cassettes 421 and 422 that store paper of different sizes, and a paper feed means 423 consisting of various rollers that transport the paper stored in the paper feed cassettes 421 and 422 to the image forming position of the image forming section 300.

The image forming unit 300 has an exposure device 331, a photoconductor drum 332, a developing device 333, a transfer belt 334, and a fixing device 335. The image forming unit 300 exposes the photoconductor drum 332 with the exposure device 331 to form a latent image on the photoconductor drum 332 based on image data of a printed matter read by the image reading device 100 or image data input from an external PC or the like via the network I/F 28. The image forming unit 300 develops the image by supplying different color toners to the photoconductor drum 332 with the developing device 333. The image forming unit 300 transfers the image developed on the photoconductor drum 332 by the transfer belt 334 to paper supplied from the paper feed unit 400, and then melts the toner constituting the toner image transferred to the paper by the fixing device 335 to fix the color image to the paper.

<Configuration Example of Scanner Unit 22>
(Example of Overall Configuration of Scanner Unit 22)
Fig. 7 is a diagram showing an example of the configuration of the scanner unit 22 of the image forming apparatus 1. The scanner unit 22 is, for example, a differential mirror drive type, and is an image reading device of an optical sensor integrated drive type. The dashed dotted line shown in Fig. 7 represents light reflected by a printed material.

As shown in FIG. 7, the scanner unit 22 has a first mirror unit 204, a second mirror unit 210, a lens 216, and a first sensor board 215. The first mirror unit 204 has a light source 200, a first mirror 202 supported at both ends, and a second sensor board 223 on which a second photoelectric conversion element 222 such as a CCD (Charge Coupled Device) is mounted. The second mirror unit 210 has a second mirror 206 and a third mirror 208 supported at both ends, etc. Each mirror, such as the first mirror 202, is a reflective member that further reflects light that is illuminating light from the light source 200 and reflected by the printed material.

The light source 200 includes a light emitting unit such as an LED (Light Emitting Diode) and is an example of an illumination unit that illuminates a printed material with white light. However, the color of light emitted by the light source 200 is not limited to white, and may be monochromatic light of any color. The lens 216 forms an image of the illumination light from the light source 200 reflected by the printed material on a first photoelectric conversion element 214 such as a CCD. The first photoelectric conversion element 214 is mounted on a first sensor board 215 together with other hardware, for example. The first photoelectric conversion element 214 is, for example, a CCD.

The light source 200 illuminates a printed material placed on the document reading glass 212 by irradiating it with light through the document reading glass 212. After passing through the document reading glass 212, the light reflected by the printed material is reflected by the first mirror 202, the second mirror 206, and the third mirror 208 in that order and directed to the lens 216. The reflected light is then approximately imaged on the first photoelectric conversion element 214 by the lens 216. The image of the printed material is photoelectrically converted by the first photoelectric conversion element 214 to an analog image signal, thereby reading the printed material. The white reference plate 218 is a white member that reflects the light irradiated by the light source 200 in order to correct the white level.

In the scanner unit 22, the first mirror 202, the second mirror unit 210, the lens 216, and the first photoelectric conversion element 214 constitute the first reading unit 3. The first reading unit 3 can output imaging information obtained by reading the printed matter illuminated by the light source 200 at a first reading magnification as a first read image. The ratio b/a of the subject distance a, which is the distance from the printed matter to the main plane of the lens 216 via the first mirror 202, the second mirror 206, and the third mirror 208, and the imaging distance b, which is the distance from the main plane of the lens 216 to the imaging surface of the first photoelectric conversion element 214, corresponds to the first reading magnification. Since the imaging distance b is shorter than the subject distance a, the first reading magnification is smaller than 1, and the first reading unit 3 outputs the first read image of the printed matter reduced by the reduction optical system.

The second photoelectric conversion element 222 is an example of a second reading section that outputs imaging information obtained by reading a printed matter illuminated by the light source 200 at a second reading magnification as a second read image. The second photoelectric conversion element 222 has a plurality of pixels aligned along the main scanning direction 240, and is capable of reading the entire width of the printed matter along the main scanning direction 240. However, it is not necessarily necessary to be able to read the entire width of the printed matter, and the second photoelectric conversion element 222 may read only a portion of the printed matter along the main scanning direction 240.

In this embodiment, since no lens is provided between the printed matter and the second photoelectric conversion element 222, and the printed matter and the second photoelectric conversion element 222 are in close proximity, the second photoelectric conversion element 222 can read the printed matter at 1x magnification. In other words, the second reading magnification is 1x (1x), which is greater than the first reading magnification.

For example, the first reading unit 3 reads the printed matter at a resolution of 600 dpi (dots per inch) or 1200 dpi. The dot interval at 600 dpi is 42.3 μm, and the dot interval at 1200 dpi is 21.2 μm. The second photoelectric conversion element 222 can read the printed matter at a higher resolution than the first reading unit 3 by setting the second reading magnification higher than the first reading magnification. In order to read the image of one toner particle in the image formed on the printed matter, it is preferable that the resolution of the second photoelectric conversion element 222 is 2400 dpi or higher and can resolve a dot interval of 10.0 μm or less. Therefore, it is preferable that the second reading magnification is 2 times or more and 5 times or less than the first reading magnification.

More specifically, the second photoelectric conversion element 222 is a CCD that outputs a monochrome second read image in which, for example, 1,300 pixels having a square lattice shape are arranged along the main scanning direction 240. The second photoelectric conversion element 222 can capture an image of an area on a printed matter that is approximately equal to the size of one pixel, approximately 4.9 μm × 4.9 μm, as a minimum area. Therefore, even when the minimum diameter of the toner is approximately 5 μm, the second photoelectric conversion element 222 can read the image of one toner particle in the image formed on the printed matter.

The area of the effective imaging area of the second photoelectric conversion element 222 is larger than the area of the effective imaging area of the first photoelectric conversion element 214, and the second photoelectric conversion element 222 reads the printed material with a higher resolution (spatial resolution) than the first reading unit 3. On the other hand, the range on the printed material that can be imaged by the second photoelectric conversion element 222 is narrower than the range on the printed material that can be imaged by the first reading unit 3.

When reading a printed material, the first mirror unit 204 moves at a constant speed along the sub-scanning direction 250. The second mirror unit 210 moves along the sub-scanning direction 250 in conjunction with the first mirror unit 204 at a speed that is approximately half the moving speed of the first mirror unit 204. In FIG. 4, the first mirror unit 204 and the second mirror unit 210 shown by dashed lines respectively represent the first mirror unit 204 and the second mirror unit 210 after they have moved along the sub-scanning direction 250.

The first reading unit 3 can read the entire width of the print in the sub-scanning direction 250 while keeping the subject distance a substantially constant by moving the first mirror unit 204 and the second mirror unit 210 in conjunction with each other along the sub-scanning direction 250.

The second photoelectric conversion element 222 provided in the first mirror unit 204 moves in conjunction with the movement of the first mirror unit 204 along the sub-scanning direction 250, and can read the entire width of the printed material along the sub-scanning direction 250.

When continuously and automatically reading sheet-like printed materials, the ADF 21 transports the printed materials on the sheet document reading glass 220, and the light source 200 irradiates light through the sheet document reading glass 220. The irradiated light is reflected by the printed materials, passes through the sheet document reading glass 220, and is reflected by the first mirror 202, the second mirror 206, and the third mirror 208 in this order, and is guided to the lens 216. The reflected light is then approximately imaged on the first photoelectric conversion element 214 by the lens 216. At this time, the first mirror unit 204 and the second mirror unit 210 read the image of the sheet-like printed materials being transported while in a fixed state. The reading operation is started by pressing the start key provided on the input operation unit 17.

The first reading unit 3 may be a unit type that integrates a mirror and a photoelectric conversion element, or may use a 1:1 contact image sensor (CIS).

(Example of driving method of scanner unit 22)
8 is a diagram showing a driving method of the scanner unit 22. The scanner motor 230 is a stepping motor. When the shaft of the scanner motor 230 rotates, a rotational driving force is transmitted to the shaft 234 via the timing belt 232. When the wire pulleys 236a and 236b provided on the shaft 234 rotate, the first mirror unit 204 and the second mirror unit 210 connected to the wires 238a and 238b move. At this time, the second mirror unit 210 moves at half the speed of the first mirror unit 204. The driving method of the scanner unit 22 may be a method via a timing belt instead of a wire, or the like.

(Example of Electrical Configuration of Scanner Unit 22)
Fig. 9 is a block diagram showing an outline of the electrical configuration of the scanner unit 22. The scanner unit 22 executes initialization processes such as a homing operation and adjustment of signal processing characteristics of a read image (black level adjustment and white level adjustment) by using the electrical configuration shown in Fig. 9.

The CPU (control unit) 10 controls the overall operation of the scanner unit 22, including the image creation sequence, by controlling each component that constitutes the scanner unit 22. The CPU 10 also receives a position detection signal required for the homing operation from the home position sensor 64. The CPU 10 controls the scanner motor 230 so that the scanner motor 230 drives the scanner motor 230 to move the first mirror unit 204.

The motor driver 62 drives the scanner motor 230 that moves the first mirror unit 204 and the second mirror unit 210. The first sensor board 215 is equipped with a first photoelectric conversion element 214 and the like, and the first photoelectric conversion element 214 outputs the first read image Im1 to the CPU 10. The second sensor board 223 is equipped with a second photoelectric conversion element 222 and the like, and the second photoelectric conversion element 222 outputs the second read image Im2 to the CPU 10.

The CPU 10 performs digital processing on the first read image Im1 and the second read image Im2. For example, the CPU 10 performs image correction processing such as shading processing, gamma correction processing, magnification processing, or filter processing on the digital data of the first read image Im1 and the second read image Im2. The CPU 10 can also calculate and detect black level and white level data required to obtain adjustment values for clamping and gain correction on the first sensor board 215 and the second sensor board 223 from the input digital image data.

The home position sensor 64 is, for example, a photointerrupter, and outputs a position detection signal that detects the position of the first mirror unit 204. The NVRAM (Non-Volatile Random Access Memory) 65 stores data necessary for controlling the initialization process.

The first read image Im1 read by the first photoelectric conversion element 214 corresponds to, for example, the read image 110 shown in FIG. 1. The image forming device 1 can provide a copy of the printed matter by forming an image on paper P based on the first read image Im1.

The second read image Im2 read by the second photoelectric conversion element 222 corresponds to, for example, the enlarged image 120 shown in FIG. 2 and the enlarged image 130 shown in FIG. 3. The image forming device 1 can use the second read image Im2 to determine the authenticity of the printed matter.

In this embodiment, the true printed matter is, for example, an image formed on paper P by the image forming device 1. In particular, accuracy of the determination can be improved by performing the authenticity determination using an image formed with black toner.

When it comes to images formed on recording media such as paper by electrophotographic image forming devices, in terms of dot-by-dot reproducibility, it is extremely unlikely that two sheets of paper will have the exact same toner adhesion state. In electrophotographic image forming devices, a latent image is formed on a photoreceptor, then a developer uses electrostatic force to develop toner onto the photoreceptor, and the toner is then transferred to a transfer belt, which is then transferred to paper. In the series of processes of development, primary transfer, and secondary transfer, the toner moves to the image carrier a total of three times, making it extremely unlikely that the same state will be achieved dot by dot.

In addition, although there is a possibility of stains larger than the size of one dot, such as toner stains or dirt adhesion that are clearly visible to the naked eye, the adhesion of minute stains smaller than the size of one dot is unlikely to occur, so the density distribution of a minute area containing dots is suitable information to use in determining authenticity.

(Example of functional configuration of the determination unit 35 according to the first embodiment)
10 is a diagram showing an example of the functional configuration of the determination unit 35. The determination unit 35 has a feature extraction unit 281, a registration unit 282, a comparison unit 283, and an output unit 284. Of these, the functions of the feature extraction unit 281 and the comparison unit 283 are realized by the CPU 10 executing a program stored in the ROM 12 or the HDD 14, etc. The function of the registration unit 282 is realized by the CPU 10 executing a program stored in the ROM 12 or the HDD 14 and controlling the HDD 14, etc. The function of the output unit 284 is realized by the CPU 10 executing a program stored in the ROM 12 or the HDD 14 and controlling the display device 16 or the communication I/F 15, etc.

The determination unit 35 extracts features from the second read image Im2 of the printed matter read by the second photoelectric conversion element 222 using the feature extraction unit 281. When performing feature data registration processing, the determination unit 35 registers the extracted feature data using the registration unit 282, and when performing authenticity determination processing, outputs the extracted feature data to the comparison unit 283.

The feature extraction unit 281 quantizes the input second read image Im2 by dividing it into meshes of appropriate size. The number of meshes d is M [pieces] in the vertical direction × N [pieces] in the horizontal direction. The feature extraction unit 281 also converts the second read image Im2 into a mosaic-like image by sampling each mesh by representing it with a density value of a predetermined density level q. After quantization and sampling, the feature extraction unit 281 represents the second read image Im2 by a vector consisting of x = (x1, x2, ... xd) ^T , where xj is the density of the j-th mesh. Note that T represents a transposed matrix. The vector represented in this way corresponds to the feature data. Each element of the vector gives the density of the corresponding image area. The second read image Im2 is represented as one point on the feature space represented by the vector. Since a different density distribution is obtained for each printed matter in a minute area, the feature also represents a characteristic unique to each printed matter.

Because the image formed on the print itself contains a random density distribution that cannot be reproduced, the density distribution of the read second read image Im2 itself may be used as feature data. However, if the second read image is quantized and sampled to obtain the feature, the feature for each print becomes clearer, simplifying the authenticity determination process.

When determining authenticity, the comparison unit 283 sequentially reads out the registered feature data registered in the registration unit 282 from the registration unit 282, and compares the extracted feature data of the second scanned image Im2 extracted by the feature extraction unit 281 with all the registered feature data. The comparison unit 283 determines the authenticity of the printout according to the similarity between the two.

The similarity between the extracted feature data and the registered feature data used in authenticity determination can be calculated from the distance between them in feature space. This distance is, for example, Euclidean distance or Mahalanobis distance. The closer the calculated distance, the more similar the two are. The comparison unit 283 compares the extracted feature data with all registered feature data, and if registered feature data whose similarity is equal to or exceeds a predetermined threshold has already been registered in the registration unit 282, it determines that the printed matter is genuine. On the other hand, if registered feature data whose similarity is equal to or exceeds a predetermined threshold is not registered in the registration unit 282, it determines that the printed matter is a fake.

In this embodiment, the authenticity is determined based on the distance in the feature space between the extracted feature data and the registered feature data, but the determination can also be made using the angle between the vectors. Also, the similarity can be evaluated based on the correlation value between images, the cumulative squared error, etc., without mosaic processing.

The second read image may further be transformed into the frequency domain by a two-dimensional Fourier transform, and a judgment may be made in frequency space. In this case, the pre-registered second read image and the second read image acquired during the authenticity judgment are synthesized in frequency space, and the synthesis result is subjected to an inverse Fourier transform to obtain a correlation intensity image. The similarity between the two images can be evaluated from the peak value in the correlation intensity image. For example, it can be determined that the image is genuine when the peak value of the amplitude spectrum is equal to or greater than a predetermined amplitude threshold.

It is also possible to calculate the center of gravity of tiny dots scattered like islands in the feature data, and evaluate the similarity based on the distance and position between the centers of gravity. This method has the effect of reducing the amount of data used in the judgment process.

The determination unit 35 outputs the determination result by the comparison unit 283 to an external device via the output unit 284. Examples of this external device include the display device 16 of the image forming device 1 and an external PC. For example, the image forming device 1 can notify the operator of the image forming device 1 whether or not the printed matter is genuine by displaying the determination result on the display device 16. Furthermore, the image forming device 1 can store authenticity information on whether or not the printed matter is genuine by outputting the determination result to the external PC via the network I/F 28.

<Processing Example of Image Reading Apparatus 100 According to First Embodiment>
(Example of registration process)
Fig. 11 is a flow chart showing an example of a registration process of feature amount data by the image reading device 100 of the image forming apparatus 1. The operator of the image forming apparatus 1 places a printed material to be registered on the document reading glass 212, or inserts the printed material into the ADF 21 and positions it by being abutted against an abutting member. After that, when the operator inputs a registration start operation via the operation unit of the image forming apparatus 1, the image reading device 100 starts the process of Fig. 11.

First, in step S211, the image reading device 100 inputs the second read image Im2, in which the second photoelectric conversion element 222 reads a minute area at a predetermined position on the printed material, by the feature extraction unit 281. The printed material is positioned by the document reading glass 212 and the abutting member of the ADF 21. Therefore, the image reading device 100 can easily identify the predetermined position of the minute area based on the distance from the edge of the printed material.

Next, in step S212, the image reading device 100 converts the second read image Im2 into a mosaic image by quantizing and sampling the second read image Im2 using the feature extraction unit 281.

Next, in step S213, the image reading device 100 extracts features from the converted mosaic image using the feature extraction unit 281.

Next, in step S214, the image reading device 100 registers the extracted feature data using the registration unit 282.

In this way, the image reading device 100 can register the feature data that serves as the basis for authenticity determination in the registration unit 282.

(Example of authenticity determination process)
Fig. 12 is a flowchart showing an example of an authenticity determination process by the image reading device 100 of the image forming apparatus 1. The operator of the image forming apparatus 1 places a printed matter to be subjected to an authenticity determination on the document reading glass 212, or inserts the printed matter into the ADF 21 and positions it by being abutted against an abutting member. After that, when the operator inputs an operation to start authenticity determination via the operation unit of the image forming apparatus 1, the image reading device 100 starts the process of Fig. 12.

The processing from step S221 to step S223 is similar to the processing from step S211 to step S213 in FIG. 11, so duplicate explanations will be omitted here.

In step S224, the image reading device 100 uses the comparison unit 283 to sequentially read the registered feature data from the registration unit 282, compare the extracted feature data of the second read image Im2 with all the registered feature data, and calculate the similarity between the two.

Next, in step S225, the image reading device 100 uses the comparison unit 283 to determine whether there is any registered feature data whose feature similarity with the extracted feature data is equal to or greater than a predetermined similarity threshold.

It is preferable to set the similarity threshold with an allowable range, taking into consideration errors in the registered feature data and the extracted feature data due to reading errors or quantization sampling errors, etc. The similarity threshold is selected appropriately depending on whether or not strict authenticity determination is required. Furthermore, if the allowable range differs depending on the type of printed matter, the image reading device 100 can register a similarity threshold in association with the registered feature data when registering the feature data, and perform the processing of step S225 using the similarity threshold read out together with the registered feature data when determining authenticity.

If it is determined in step S225 that registered feature data equal to or greater than the similarity threshold has been registered (Yes in step S225), then in step S226, the image reading device 100 uses the comparison unit 283 to determine that the printed matter is genuine. On the other hand, if it is determined that registered feature data equal to or greater than the similarity threshold has not been registered (No in step S225), then in step S227, the image reading device 100 uses the comparison unit 283 to determine that the printed matter is a fake.

Next, in step S228, the image reading device 100 outputs the determination result to an external device via the output unit 284.

In this way, the image reading device 100 can determine the authenticity of the printed matter. Note that when determining authenticity, there may be operational errors by the operator or misalignment of the printed matter, so in order to reduce the effects of these, a final determination may be made based on the results of multiple determinations.

In this embodiment, the process of comparing all registered feature data registered by the registration unit 282 with the extracted feature data has been exemplified, but the present invention is not limited to this. For example, when registering the registered feature data, an identification code of the printed matter may be associated with the registered feature data and registered in the registration unit 282, and when determining authenticity, the registered feature data read out based on the identification code may be compared with the extracted feature data. In this case, since a comparison process is not performed on all registered feature data, the processing load can be reduced and the processing time can be shortened.

The program for executing each step of Fig. 11 and Fig. 12 can be stored in a recording medium, and the program can also be provided by a communication means. Examples of recording media include digital versatile disks (DVDs) such as "DVD-R, DVD-RW, DVD-RAM, etc.", which are standards established by the DVD Forum, and "DVD+R, DVD+RW, etc.", which are standards established for DVD+RW, compact disks (CDs) such as read-only memory (CD-ROM), CD recordable (CD-R), CD rewritable (CD-RW), magneto-optical disks (MO), flexible disks (FD), magnetic tapes, hard disks, read-only memory (ROM), electrically erasable and rewritable read-only memory (EEPROM), flash memory, random access memory (RAM), etc.

The above program or a part of it can be recorded on the above recording medium and stored or distributed. It can also be transmitted by communication using a transmission medium such as a wired network used in a local area network (LAN), metropolitan area network (MAN), wide area network (WAN), the Internet, an intranet, an extranet, etc., or a wireless communication network, or even a combination of these, and it can also be carried on a carrier wave.

Furthermore, the above-mentioned program may be a part of another program, or may be recorded on a recording medium together with a separate program. Also, it may be divided and recorded on multiple recording media.

<Functions and Effects of Image Reading Device 100 According to First Embodiment>
As described above, the image reading device 100 provided in the image forming apparatus 1 includes the light source 200 (illumination unit) and the first reading unit 3 that outputs a first read image Im1 obtained by reading a printed matter (object) illuminated by the light source 200 at a first reading magnification. The image reading device 100 also includes a second photoelectric conversion element 222 (second reading unit) that outputs a second read image Im2 obtained by reading a printed matter illuminated by the light source 200 at a second reading magnification, and a determination unit 35 that outputs an authenticity determination result (authenticity information) of the printed matter determined based on the second read image Im2, and the second reading magnification is higher than the first reading magnification.

By reading the printed matter at a second reading magnification higher than the first reading magnification, it is possible to obtain a density distribution in which a specific micro-area on the printed matter is enlarged. By performing an authenticity determination using the density distribution of this micro-area, the amount of information is greater than when performing an authenticity determination using, for example, the color or reflectance of the printed matter, and the accuracy of the authenticity determination can be improved. In other words, it is possible to provide an image reading device 100 with high authenticity determination accuracy. The amount of information increases as the number of pixels of the second photoelectric conversion element 222 is increased. Since the image reading device 100 copies a printed matter such as a manuscript using the first reading unit 3, the image reading device 100 can perform an authenticity determination process with high accuracy without impairing its main function, the copying function.

For copying printed matter, it is preferable to set the first reading magnification so that it can be read at a resolution of 600 dpi or 1200 dpi. In addition, since the diameter of a single toner particle in the electrophotographic method is about 5 μm to 10 μm, it is preferable to set the reading resolution of the second photoelectric conversion element 222 to 2400 dpi or higher in order to read this. Therefore, in this embodiment, it is preferable that the second reading magnification is 2 times or more and 5 times or less than the first reading magnification. In this way, the random distribution of each toner particle can be detected, making it possible to obtain more information for authenticity determination.

On the other hand, if the reading magnification is too high, a large number of pixels are used to capture an image of each toner particle, which may result in a decrease in the amount of information required for determining authenticity because the random distribution of each toner particle cannot be detected. By setting the second reading magnification to be at least twice but no more than five times the first reading magnification, this decrease in the amount of information can be avoided.

In addition, in this embodiment, it is preferable that the second reading magnification is life-size. By setting it to life-size, the image reading device 100 can set the second reading magnification to be 2 times or more and 5 times or less than the first reading magnification for achieving a reading resolution of 600 dpi or 1200 dpi in the first reading unit 3. Furthermore, by placing the second photoelectric conversion element 222 close to the printed material, the second reading magnification can be set to life-size without using a lens, which is more preferable in terms of simplifying the configuration.

In addition, in this embodiment, the first reading unit 3 has a first mirror unit 204 (variable mechanism) that changes the position within the printed matter that is read by the first reading unit 3 along the sub-scanning direction 250 (predetermined direction). This first mirror unit 204 has a second photoelectric conversion element 222 installed therein, and the first mirror unit 204 moves the second photoelectric conversion element 222 along the sub-scanning direction 250. This makes it possible to image the entire width of the printed matter along the sub-scanning direction 250 by the second photoelectric conversion element 222, which has a second reading magnification of 1x.

The second read image Im2 does not necessarily need to capture the entire width of the print along the sub-scanning direction 250, since it is sufficient to capture a small area of a portion of the print. However, from the viewpoint of being able to arbitrarily select particularly characteristic small areas of the print, it is preferable to be able to capture the entire width of the print.

The second photoelectric conversion element 222 does not have to be movable, and may be configured to be fixed in a predetermined position. For example, when a high-magnification objective lens is used to obtain a high second reading magnification, the working distance becomes narrow, and there is a risk that the objective lens will collide with the document reading glass 212, etc., when the second photoelectric conversion element 222 moves. By fixing the second photoelectric conversion element 222, such a risk can be reduced.

[Second embodiment]
Next, an image reading device 100a according to a second embodiment will be described. The image reading device 100a is provided in an image forming apparatus 1. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted as appropriate.

Fig. 13 is a block diagram showing an example of the functional configuration of the determination unit 35a of the image reading device 100a. The determination unit 35a has a detection unit 285 and a notification unit 286. The function of the detection unit 285 is realized by the CPU 10 executing a program stored in the ROM 12 or the HDD 14, etc. The function of the notification unit 286 is realized by the CPU 10 executing a program stored in the ROM 12 or the HDD 14 and controlling the display device 16, etc.

The detection unit 285 detects misalignment of the printed matter on the document reading glass 212 or the ADF 21 based on the first read image Im1 read by the first photoelectric conversion element 214. This misalignment includes tilt misalignment, in which the printed matter is placed at an angle (rotated in-plane) relative to the document reading glass 212 or the ADF 21, and shift misalignment, in which the printed matter is placed shifted. When the detection unit 285 detects a tilt misalignment equal to or greater than a predetermined tilt threshold, or detects a shift misalignment equal to or greater than a predetermined shift threshold, it outputs the detection result to the notification unit 286.

The notification unit 286 notifies the operator of the image forming apparatus 1 of misalignment of the printed matter on the document reading glass 212 or the ADF 21 detected by the detection unit 285. For example, when the detection unit 285 detects misalignment, the notification unit 286 outputs a message indicating this to the display device 16 via the output unit 284. The notification unit 286 notifies the operator of the image forming apparatus 1 by displaying a message on the display device 16. The operator who sees the message can erase the authenticity determination result or redo the authenticity determination.

When a positional shift of the printed matter is detected based on the first read image Im1, the determination unit 35a notifies the user of the positional shift and determines the authenticity of the printed matter based on the second read image Im2. In other words, the determination unit can determine the authenticity of the printed matter based on the first read image Im1 and the second read image Im2.

Figure 14 is a diagram illustrating a first scanned image Im1 when there is no misalignment. Figure 15 is a diagram illustrating a first scanned image Im1 when there is a misalignment.

When there is no misalignment of the printed matter 141, as shown in FIG. 14, the first read image Im1 includes only the read image of the printed matter 141, and does not include the end (edge) of the printed matter 141. On the other hand, when there is a misalignment of the printed matter 141, as shown in FIG. 15, the first read image Im1 includes the end of the printed matter 141. The detection unit 285 can detect the shift misalignment and tilt misalignment of the printed matter 141 from the shift amount s and tilt amount t of this end.

Figure 16 is a flow chart showing an example of an authenticity determination process by the image reading device 100a of the image forming device 1. The operator of the image forming device 1 places the printed matter to be subjected to the authenticity determination on the document reading glass 212, or inserts the printed matter into the ADF 21 and positions it by abutting it against the abutment member. After that, when the operator inputs an operation to start the authenticity determination via the operation unit of the image forming device 1, the image reading device 100a starts the process of Figure 16.

First, in step S161, the image reading device 100a inputs the first read image Im1 read by the first photoelectric conversion element 214 via the detection unit 285.

Next, in step S162, the image reading device 100a detects the positional misalignment of the printed matter 141, i.e., shift misalignment and tilt misalignment, using the detection unit 285.

Next, in step S163, the image reading device 100a uses the detection unit 285 to determine whether the shift misalignment of the printed matter 141 is greater than or equal to a predetermined shift threshold, or whether the tilt misalignment is greater than or equal to a predetermined tilt threshold.

If it is determined in step S163 that the shift misalignment of the printed matter 141 is equal to or greater than the predetermined shift threshold value, or that the tilt misalignment is equal to or greater than the predetermined tilt threshold value (Yes in step S163), in step S164, the image reading device 100a outputs the detection result by the detection unit 285 to the notification unit 286. Then, the image reading device 100a causes the notification unit 286 to display on the display device 16 a predetermined message notifying that the printed matter 141 is misaligned. After that, the image reading device 100a proceeds to step S165.

On the other hand, if it is determined in step S163 that the shift misalignment of the printed matter 141 is smaller than the predetermined shift threshold and the tilt misalignment is smaller than the predetermined tilt threshold (step S163, No), the image reading device 100a proceeds to step S165.

The processing from step S165 to step S172 is the same as the processing from step S221 to step S228 in FIG. 13, so duplicate explanations will be omitted here.

In this way, the image reading device 100a can determine the authenticity of the printed matter 141 based on the first read image Im1 and the second read image Im2.

As described above, in this embodiment, the determination unit 35a determines the authenticity of the printed matter 141 based on the first read image Im1 and the second read image Im2. For example, the determination unit 35a has a detection unit 285 that detects a positional shift of the printed matter 141 based on the first read image Im1, and a notification unit 286 that notifies of the positional shift detected by the detection unit 285.

If the printed matter 141 is misaligned on the document reading glass 212 or ADF 21, the similarity between the extracted feature data and the registered feature data will be low, even if the printed matter 141 is genuine, and a misjudgment may occur. In this embodiment, the image reading device 100a can notify the operator of the printed matter 141 being misaligned on the document reading glass 212 or ADF 21 using the notification unit 286. This allows the operator of the image forming device 1 to be notified of the misalignment and to be made aware of the possibility of a misjudgment.

In this embodiment, a configuration has been shown in which, when a positional misalignment of the printed matter 141 is detected, the misalignment is notified, but the present invention is not limited to this. For example, when a positional misalignment of the printed matter 141 is detected by the detection unit 285, the determination unit 35a can also correct the second read image Im2 in accordance with the positional misalignment. For example, the second read image Im2 can be corrected by performing image processing to rotate the second read image Im2 in accordance with the tilt misalignment t, or by performing image processing to shift the second read image Im2 in accordance with the shift misalignment s. In this way, the image reading device 100a can accurately perform authenticity determination even when the printed matter 141 is misaligned.

Although the preferred embodiment has been described above in detail, the present invention is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the claims.

In the above-described embodiment, an electrophotographic image forming apparatus using toner is exemplified, but the present invention is not limited to this, and the embodiment can also be applied to a liquid ejection type image forming apparatus using liquid such as ink. As with toner, ink can also cause uneven adhesion, scattering, bleeding, etc. on the recording medium, so the same effects can be obtained as when toner is used.

The ordinal numbers, quantities, and other numbers used in the description of the embodiments are all provided as examples to specifically explain the technology of the present invention, and the present invention is not limited to the exemplified numbers. In addition, the connections between the components are provided as examples to specifically explain the technology of the present invention, and do not limit the connections that realize the functions of the present invention.

Each function of the embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, and devices such as an ASIC (Application Specific Integrated Circuit), DSP (digital signal processor), FPGA (field programmable gate array), and conventional circuit modules designed to execute each function described above.

1 Image forming device 3 First reading unit 21 ADF
212 Document reading glass 22 Scanner unit 23 Paper discharge tray 35 Determination unit 100 Image reading device 200 Light source (an example of an illumination unit)
202: First mirror 204: First mirror unit (an example of a variable mechanism)
206: second mirror 208: third mirror 210: second mirror unit 214: first photoelectric conversion element 215: first sensor board 216: lens 222: second photoelectric conversion element (an example of a second reading unit)
223 Second sensor board 300 Image forming section 240 Main scanning direction 250 Sub-scanning direction 281 Feature extraction section 282 Registration section 283 Comparison section 284 Output section 285 Detection section 286 Notification section 400 Paper feed section 110 Read image 111 Partial area 120, 130 Enlarged image 121, 122a, 122b, 131, 132 Micro area Im1 First read image Im2 Second read image P Paper

JP 2005-038389 A

Claims (6)

An image reading device for reading a printed image formed on a surface of an object, comprising:
A lighting section;
a first reading unit including a first photoelectric conversion element, the first reading unit reading the printed image illuminated by the illumination unit at a first reading magnification with the first photoelectric conversion element and outputting a first read image;
a second reading unit including a second photoelectric conversion element, the second reading unit reading the printed image illuminated by the illumination unit at a second reading magnification with the second photoelectric conversion element and outputting a second read image;
a determination unit that outputs authenticity information of the object determined based on the second read image,
the second reading magnification is higher than the first reading magnification,
The first reading unit is
a first mirror unit that reflects light that is illuminated by the illumination unit and is reflected by the object, and moves at a constant speed in a predetermined direction along a surface of the object;
a second mirror unit that further reflects the reflected light by the first mirror unit and moves in the predetermined direction in conjunction with the movement of the first mirror unit at a speed that is half the moving speed of the first mirror unit;
a lens that transmits the reflected light reflected by the second mirror unit,
the first mirror unit and the second mirror unit move in the predetermined direction in conjunction with each other to read the entire print image;
the second photoelectric conversion element is provided in the first mirror unit,
The second reading unit reads the entire printed image by the second photoelectric conversion element moving in the predetermined direction in accordance with the movement of the first mirror unit . The image reading device according to claim 1, wherein the second reading magnification is greater than or equal to 2 times and less than or equal to 5 times the first reading magnification. The image reading device according to claim 1 or 2, wherein the second reading magnification is life-size. The image reading device according to any one of claims 1 to 3, wherein the determination unit determines the authenticity of the object based on the first read image and the second read image. The determination unit is
a detection unit that detects a positional deviation of the object based on the first read image;
The image reading device according to claim 4 , further comprising: a notification unit that notifies the positional deviation detected by the detection unit. an image forming unit that forms an image on a recording medium;
An image forming apparatus comprising: the image reading apparatus according to claim 1 .

Images