JP2023016170A - Image reading device and image forming apparatus - Google Patents

Abstract

To provide an image reading device that has high accuracy in authenticity determination.SOLUTION: An image reading device according to an aspect of the present invention has: an illumination unit; 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; a second reading unit that outputs a second read image obtained by reading the object illuminated by the illumination unit at a second reading magnification; and a determination unit that outputs authenticity information on the object determined based on the second read image. The second reading magnification is higher than the first reading magnification.SELECTED DRAWING: Figure 2

Description

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

In recent years, with the improvement of image forming performance of copiers and printers, there is concern that objects such as bills, securities, passports, deeds, family registers, resident cards, various certificates, insurance policies, and confidential documents may be copied. What is needed is an apparatus for determining the authenticity of an object.

Such a device acquires reference data representing true individual characteristics of an individual whose readable unique characteristics having randomness are distributed along the surface, and obtains reference data representing the characteristics of the individual of the object. An image reading device that obtains verification data and performs authenticity determination based on reference data and verification data has been disclosed (see, for example, Patent Document 1).

However, the apparatus of Patent Document 1 acquires the reference data and the matching data based on the color and reflectance of the object, so there is a concern that the accuracy of authenticity determination will be low.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading apparatus with high authentication accuracy.

An image reading apparatus according to an aspect of the present invention includes an illumination unit, a first reading unit that reads an object illuminated by the illumination unit at a first reading magnification and outputs a first read image, and a second reading unit that reads the illuminated object at a second reading magnification and outputs a second read image; 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.

According to the present invention, it is possible to provide an image reading apparatus with high authenticity determination accuracy.

4 is a diagram illustrating an example of a read image of printed matter according to the embodiment; FIG. FIG. 5 is a diagram showing an example of density distribution of minute regions in a printed matter according to the embodiment; FIG. 10 is a diagram showing an example of density distribution of a minute area used in authenticity determination according to the embodiment; 2 is a block diagram of a hardware configuration example of an image forming apparatus according to an embodiment; FIG. 1 is a block diagram of an example functional configuration of an image forming apparatus according to an embodiment; FIG. 1 is a diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment; FIG. 4 is a diagram illustrating a configuration example of a scanner unit according to the embodiment; FIG. 4A and 4B are diagrams for explaining a driving method of the scanner unit according to the embodiment; FIG. 3 is a block diagram of a hardware configuration example of a scanner unit according to the embodiment; FIG. It is a block diagram showing an example of functional composition of a judgment part concerning a 1st embodiment. 6 is a flowchart of an example of registration processing by the image reading apparatus according to the first embodiment; FIG. 6 is a flowchart of an example of determination processing by the image reading apparatus according to the first embodiment; FIG. FIG. 9 is a block diagram showing an example of functional configuration of a determination unit according to the second embodiment; FIG. 10 is a diagram illustrating a first read image when there is no positional deviation; FIG. 10 is a diagram illustrating a first read image when there is positional deviation; FIG. 11 is a flowchart of an example of determination processing by an image forming apparatus according to the second embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and overlapping descriptions are omitted as appropriate.

An image reading apparatus according to an embodiment includes 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. This image reading device is, for example, a scanner or the like mounted in an image forming device such as a multi-function peripheral (MFP). The object is, for example, a printed matter in which an image is formed on a recording medium such as paper by an electrophotographic method or an inkjet method.

Images formed on paper by an electrophotographic method or an inkjet method may show uneven adhesion of toner or ink, bleeding or scattering of toner or ink at the edges of patterns such as characters (so-called dust) when a partial area on the paper is enlarged. ), etc.

1 and 2 are diagrams for explaining the concentration distribution in such minute regions. FIG. 1 is a diagram showing an example of a read image of a printed matter in which a character image is formed on a sheet P by an electrophotographic image forming apparatus. As shown in FIG. 1, the read image 110 includes a character image of "CONFIDENTIAL" formed on the paper P. As shown in FIG. FIG. 2 is a diagram showing an enlarged image 120 obtained by enlarging the partial area 111 that is part of the character image "Dense" in the read image 110 of FIG. In the enlarged image 120, for example, a minute area 121 has a density distribution due to uneven toner adhesion. Also, in the minute areas 122a and 122b, a density distribution corresponding to the black dot-like dust caused by scattering of the toner is generated. Such a density distribution in a minute area of the read image 110 has no reproducibility, and becomes unique information that differs from print to print.

In this embodiment, the authenticity of an object such as a printed matter is determined by using the density distribution in a minute area of the object. 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 read image 110 is a genuine printed matter. Then, when performing authenticity determination, a minute area in substantially the same position as the read image 110 is read in the printed matter of the counterfeit, and an enlarged image 130 as shown in FIG. 3 is obtained. In the enlarged image 130 , unlike the enlarged image 120 , there is no black speck-like dust caused by scattered toner in the minute areas 131 and 132 . Based on this difference, it can be determined that the printed matter including the minute area corresponding to the enlarged image 130 is a counterfeit.

However, if the first reading magnification of the first reading unit used as a scanner is increased to the extent that the density distribution in a minute area can be read, the reading range becomes narrower according to the first reading magnification. It impairs the copying function, which is a function.

Therefore, the image reading apparatus according to the embodiment includes a second reading unit that outputs a second read image obtained by reading the printed material illuminated by the illumination unit at the second reading magnification, and an object that is determined based on the second read image. and a determination unit that outputs authentication information, and the second reading magnification is higher than the first reading magnification.

The image reading apparatus according to the embodiment performs authenticity determination using the density distribution of minute regions in the second read image read by the second reading unit having a higher reading magnification than the first reading unit. To enable highly accurate authenticity determination without impairing the copying function, which is the main function.

In the embodiments shown below, an image forming apparatus that is a multi-function peripheral (MFP) will be described as an example. An image forming apparatus according to an embodiment forms an image on a sheet (an example of a recording medium) by an electrophotographic method, and includes an image reading apparatus for reading a printed matter as an example of an object.

<Configuration Example of Image Forming Apparatus 1>
(Hardware Configuration Example of Image Forming Apparatus 1)
FIG. 4 is a block diagram showing the hardware configuration of the image forming apparatus 1 according to this embodiment. The image forming apparatus 1 has the same configuration as an information processing terminal such as a general server or a PC (Personal Computer), and also has an engine that executes image formation.

The image forming apparatus 1 includes 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 bus 18 . The I/F 15 is also connected to an LCD (Liquid Crystal Display) 16 and an input operation section 17 .

A CPU 10 is a computing unit and controls the operation of the image forming apparatus 1 as a whole. The RAM 11 is a volatile storage medium from which information can be read and written at high speed. 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 and stores programs such as firmware. The engine 13 is a mechanism that actually executes image formation in the image forming apparatus 1 . The components other than the engine 13 are collectively referred to as an information processing device 2 .

The HDD 14 is a nonvolatile storage medium from which information can be read and written, and stores an OS (Operating System), various control programs, application programs, and the like. The I/F 15 is an interface that connects and controls the bus 18, various hardware, networks, and the like. The display device 16 is a visual user interface for the user to check the status of the image forming apparatus 1 . The input operation unit 17 is a user interface such as a keyboard and a mouse for the user to input information to the image forming apparatus 1 .

In the hardware configuration described above, the image forming apparatus 1 configures a software control section by reading programs stored in a recording medium such as the ROM 12, HDD 14, or an optical disc into the RAM 11 and operating them under the control of the CPU 10. The image forming apparatus 1 configures a functional block that implements the functions of the image forming apparatus 1 by combining the software control section configured in this way and the hardware.

(Functional Configuration Example of Image Forming Apparatus 1)
FIG. 5 is a block diagram showing an example of the functional configuration of the image forming apparatus 1. As shown in FIG. The image forming apparatus 1 has 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 has an ADF 21 , a scanner unit 22 , and a paper discharge tray 23 .

The controller 20 has a main control section 30 , an engine control section 31 , an input/output control section 32 , an image processing section 33 , an operation display control section 34 and a determination section 35 . The image forming apparatus 1 is configured as a multifunction machine having a scanner unit 22 and a print engine 26 . In FIG. 5, solid-line arrows indicate electrical connections, and dashed-line arrows indicate the flow of paper.

The display panel 24 is an output interface that visually displays the state of the image forming apparatus 1 . Further, the display panel 24 is an input interface (input operation unit) when a user directly operates the image forming apparatus 1 or inputs information to the image forming apparatus 1 as a touch panel.

The network I/F 28 is an interface such as Ethernet (registered trademark) or USB (Universal Serial Bus) for the image forming apparatus 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, HDD 14, and non-volatile recording media such as optical discs are loaded into a volatile memory such as the RAM 11, and are configured under the control of the CPU 10. A controller 20 is configured by a control unit and hardware such as an integrated circuit. The controller 20 functions as a control section that controls the entire image forming apparatus 1 .

The main control section 30 plays a role of controlling each section included in the controller 20 and gives commands to each section of the controller 20 . The engine control unit 31 plays a role of driving means for controlling or driving the print engine 26, the scanner unit 22, and the like.

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 to access other devices via the network I/F 28 .

The image processing unit 33 is an electric circuit that generates drawing information based on print information included in an input print job under the control of the main control unit 30 . The drawing information is information for drawing an image to be formed by the print engine 26 in the image forming operation. The print information included in the print job is image information converted into a format recognizable by the image forming apparatus 1 by a printer driver installed in an information processing apparatus 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 apparatus 1 operates as a printer, first, the input/output control section 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 . Upon receiving the print job, the main control unit 30 controls the image processing unit 33 to generate drawing information based on the print information included in the print job.

When the image processing unit 33 generates the drawing information, the engine control unit 31 forms an image on the paper conveyed from the paper feeding table 25 based on the generated drawing information. That is, the print engine 26 functions as an image forming section. 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 apparatus 1 operates as a scanner, the operation of the display panel 24 by the operator of the image forming apparatus 1 (hereinafter simply referred to as the operator) or the input from an external PC or the like via the network I/F 28 is performed. 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 a scan execution instruction or the like. The main control section 30 controls the engine control section 31 based on the received scan execution signal.

The engine control unit 31 drives the ADF 21 and conveys the printed matter set on the ADF 21 to the scanner unit 22 . The engine control unit 31 also drives the scanner unit 22 to image the printed material conveyed from the ADF 21 . If no printed matter is set on the ADF 21 and the printed matter is directly set on the scanner unit 22 , the scanner unit 22 takes an image of the set printed matter under the control of the engine control section 31 . That is, the scanner unit 22 operates as an imaging section for printed matter.

In the imaging operation, the imaging device included in the scanner unit 22 captures an image of the printed material while being moved in a predetermined direction, and the scanner unit 22 generates imaging information. The engine control section 31 transfers imaging information generated by the scanner unit 22 to the image processing section 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 read image generated by the image processing unit 33 is stored in the HDD 14 or the like as it is, or is transmitted to an external device via the input/output control unit 32 and the network I/F 28 according to the operator's instruction.

When the image forming apparatus 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 as in the printer operation.

The determination unit 35 performs authenticity determination processing of the printed matter based on the read image of the printed matter generated by the scanner unit 22 . The function of this determination unit 35 will be described in detail with reference to FIG. 10 separately.

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

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

The image forming section 300 has an exposure device 331 , a photosensitive drum 332 , a developing device 333 , a transfer belt 334 and a fixing device 335 . The image forming unit 300 exposes the photosensitive drum 332 to the exposure device 331 based on the image data of the printed matter read by the image reading device 100 or the image data input from an external PC or the like via the network I/F 28 . A latent image is formed on the photosensitive drum 332 by exposure. The image forming unit 300 supplies toners of different colors to the photosensitive drum 332 by the developing device 333 for development. The image forming unit 300 transfers the image developed on the photoreceptor drum 332 by the transfer belt 334 onto the paper supplied from the paper supply unit 400 , and then the toner forming the toner image transferred onto the paper by the fixing device 335 . It is fused to fix the color image to the paper.

<Configuration Example of Scanner Unit 22>
(Overall Configuration Example of Scanner Unit 22)
FIG. 7 is a diagram showing an example of the configuration of the scanner unit 22 included in the image forming apparatus 1. As shown in FIG. The scanner unit 22 is, for example, a differential mirror drive type image reading apparatus of an optical sensor integrated type drive type. The dashed-dotted line shown in FIG. 7 represents the light reflected by the 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, a third mirror 208, and the like, both ends of which are supported. Each mirror such as the first mirror 202 is a reflective member that further reflects the illumination light from the light source 200 that is 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 illuminating unit that illuminates a printed material with white light. However, the color of the 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 on the first photoelectric conversion element 214 such as a CCD with the illumination light from the light source 200 reflected by the printed material. The first photoelectric conversion element 214 is mounted on the 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 the printed matter 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 reflected light from the printed material is reflected by the first mirror 202 , the second mirror 206 and the third mirror 208 in this order and guided to the lens 216 . After that, the reflected light is substantially imaged on the first photoelectric conversion element 214 by the lens 216 . The formed image of the printed matter is photoelectrically converted by the first photoelectric conversion element 214 into an analog image signal, whereby the printed matter is read. The white reference plate 218 is a white member that reflects the light emitted 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 section 3 . The first reading unit 3 can output imaging information obtained by reading the printed material illuminated by the light source 200 at a first reading magnification as a first read image. Subject distance a, which is the distance from the printed matter to the principal plane of the lens 216 via the first mirror 202, the second mirror 206, and the third mirror 208, and the imaging surface of the first photoelectric conversion element 214 from the principal plane of the lens 216 b/a, which is the ratio of the image pickup distance b, which is the distance to the object, 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 unit that outputs imaging information obtained by reading the 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 arranged along the main scanning direction 240 and can read the full width of the printed material along the main scanning direction 240 . However, the entire width of the printed matter may not necessarily be readable, and the second photoelectric conversion element 222 may read a portion of the printed matter along the main scanning direction 240 .

In the present embodiment, 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 close to each other. The print can be read by double. That is, the second reading magnification is 1:1 (1×) and is larger than the first reading magnification.

For example, the first reading unit 3 reads 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 resolution higher than that of the first reading unit 3 by setting the second reading magnification higher than the first reading magnification. In order to read one toner image in the image formed on the printed matter, the resolution of the second photoelectric conversion element 222 is 2400 [dpi] or more, and the dot spacing of 10.0 [μm] or less can be resolved. is preferably Therefore, the second reading magnification is preferably two times or more and five times or less the first reading magnification.

More specifically, the second photoelectric conversion element 222 is, for example, a CCD that outputs a second monochrome read image in which 1300 pixels having a square lattice shape are arranged along the main scanning direction 240 . The second photoelectric conversion element 222 can image an area on the printed matter that approximately corresponds to a size of about 4.9 [μm]×4.9 [μm] per pixel as the minimum area. Therefore, the second photoelectric conversion element 222 can read a single toner image in an image formed on a printed matter by the second photoelectric conversion element 222 even when the minimum diameter of the toner is about 5 [μm]. can.

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

When reading printed matter, the first mirror unit 204 moves along the sub-scanning direction 250 at a constant speed. Also, the second mirror unit 210 is interlocked with the first mirror unit 204 and moves along the sub-scanning direction 250 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 indicated by dashed lines represent the first mirror unit 204 and the second mirror unit 210 after moving along the sub-scanning direction 250 . .

By moving the first mirror unit 204 and the second mirror unit 210 in conjunction with each other in the sub-scanning direction 250, the first reading unit 3 can scan the image in the sub-scanning direction 250 while keeping the subject distance a substantially constant. It is possible to read the full width of the print along.

The second photoelectric conversion element 222 provided in the first mirror unit 204 moves along with the movement of the first mirror unit 204 along the sub-scanning direction 250, and reads the full width of the printed matter along the sub-scanning direction 250. be able to.

When sheet-like printed matter is automatically read continuously, the ADF 21 conveys the printed matter over the sheet document reading glass 220 , and the light source 200 irradiates light through the sheet document reading glass 220 . The light reflected by the printed material passes through the sheet document reading glass 220, 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. be killed. After that, this reflected light is substantially 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 conveyed sheet-like printed material in a fixed state. The reading operation is started by pressing a start key provided on the input operation unit 17 .

Note that the first reading unit 3 may be a unit-type unit in which a mirror and a photoelectric conversion element are integrated, or a unit using a contact image sensor (CIS).

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

(Example of electrical configuration of scanner unit 22)
FIG. 9 is a block diagram showing an overview of the electrical configuration of the scanner unit 22. As shown in FIG. The scanner unit 22 executes initialization processing such as homing operation and adjustment of signal processing characteristics of the read image (black level adjustment and white level adjustment) by the electrical configuration shown in FIG.

A CPU (control section) 10 controls the entire operation of the scanner unit 22 including an image forming sequence by controlling each section that configures the scanner unit 22 . Further, CPU 10 receives a position detection signal necessary for homing operation from home position sensor 64 . The CPU 10 controls the scanner motor 230 to move the first mirror unit 204 by driving the scanner motor 230 .

A motor driver 62 drives a scanner motor 230 that moves the first mirror unit 204 and the second mirror unit 210 . A first photoelectric conversion element 214 and the like are mounted on the first sensor board 215 , and the first photoelectric conversion element 214 outputs the first read image Im<b>1 to the CPU 10 . A second photoelectric conversion element 222 and the like are mounted on the second sensor board 223 , and the second photoelectric conversion element 222 outputs the second read image Im<b>2 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, scaling processing, or filter processing on the digital data of the first read image Im1 and the second read image Im2. Further, the CPU 10 obtains black level and white level data necessary for obtaining adjustment values for performing clamping and gain correction on the first sensor board 215 and the second sensor board 223 from the input digital image data. It can be detected by calculation.

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

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

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. The image forming apparatus 1 can determine the authenticity of the printed matter using the second read image Im2.

In the present embodiment, the true printed matter is, for example, the image formed on the paper P by the image forming apparatus 1 . In particular, if the authenticity determination is performed using an image formed with black toner, the determination accuracy can be further improved.

In terms of dot-by-dot reproducibility, it is extremely unlikely that an image formed on a recording medium such as a sheet of paper by an electrophotographic image forming apparatus will have exactly the same toner adhesion state. In an electrophotographic image forming apparatus, a latent image is formed on a photoreceptor, then toner is developed on the photoreceptor with electrostatic force by a developing device, the toner is transferred to a transfer belt, and then transferred to paper. . In a series of processes of development, primary transfer, and secondary transfer, the toner moves to the image carrier three times in total, and the probability that the toner will be in the same state for each dot is extremely low.

In addition, although there is a possibility that stains larger than 1 dot size, such as toner stains and dust adhesion that can be clearly confirmed visually, adhesion of fine stains of 1 dot size or less will not occur. Since this is unlikely to occur, the density distribution of a minute area containing dots is suitable as information used for authenticity determination.

(Example of functional configuration of determination unit 35 according to first embodiment)
Next, FIG. 10 is a diagram showing an example of the functional configuration of the determination section 35. As shown in FIG. The determination unit 35 has a feature quantity extraction unit 281 , a registration unit 282 , a comparison unit 283 and an output unit 284 . Among these, the functions of the feature amount 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, or the like. 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, for example. The function of the output unit 284 is implemented by the CPU 10 executing a program stored in the ROM 12 or HDD 14 and controlling the display device 16 or the communication I/F 15, or the like.

The determination unit 35 causes the feature amount extraction unit 281 to extract the feature amount from the second read image Im<b>2 of the printed matter read by the second photoelectric conversion element 222 . The determination unit 35 registers the extracted feature amount data with the registration unit 282 when performing the feature amount data registration process, and outputs the extracted feature amount data to the comparison unit 283 when performing the authenticity determination process. do.

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

Since the image itself formed on the printed matter includes an unreproducible random density distribution, the density distribution itself of the read second read image Im2 may be used as the feature amount data. However, if the feature amount is obtained by quantizing and sampling the second read image, the feature amount for each printed matter becomes clearer, so that the authenticity determination process can be simplified.

The comparison unit 283 sequentially reads the registered feature amount data registered in the registration unit 282 from the registration unit 282 during authenticity determination, while extracting the extracted feature amount of the second read image Im2 extracted by the feature amount extraction unit 281. Data is compared with all registered feature amount data. The comparison unit 283 determines the authenticity of the printed matter according to the degree of similarity between the two.

The degree of similarity between the extracted feature amount data and the registered feature amount data used for authenticity determination can be calculated from the distance between the two on the feature space. This distance is, for example, the Euclidean distance or the Mahalanobis distance. The closer the calculated distance is, the more similar the two are. The comparison unit 283 compares the extracted feature amount data with all the registered feature amount data, and if the registered feature amount data whose degree of similarity is equal to or greater than a predetermined threshold is already registered in the registration unit 282, the printed matter is genuine. It is determined that On the other hand, if no registered feature amount data having a degree of similarity equal to or higher than the predetermined threshold is registered in the registration unit 282, the printed matter is determined to be a fake.

In this embodiment, a configuration for determining authenticity based on the distance in the feature space between the extracted feature amount data and the registered feature amount data is exemplified, but it is also possible to perform determination using an angle formed by vectors. It is also possible to evaluate the degree of similarity based on correlation values between images, accumulated squared errors, etc., without performing mosaic processing.

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

It is also possible to calculate the centroid positions of minute points scattered like islands in the feature amount data and evaluate the similarity based on the distance and the positions between the centroids. This method has the effect of reducing the amount of data used in the determination process.

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

<Example of processing by the image reading apparatus 100 according to the first embodiment>
(Registration processing example)
FIG. 11 is a flowchart showing an example of registration processing of feature amount data by the image reading device 100 included in the image forming device 1 . The operator of the image forming apparatus 1 places the printed matter to be registered on the document reading glass 212 or inserts the printed matter into the ADF 21 and positions it by being abutted against the abutting member. After that, at the timing when the operator inputs a registration start operation via the operation unit of the image forming apparatus 1, the image reading apparatus 100 starts the process of FIG.

First, in step S<b>211 , the image reading apparatus 100 inputs a second read image Im<b>2 obtained by reading a minute area at a predetermined position on the printed matter by the second photoelectric conversion element 222 through the feature amount extraction unit 281 . The printed matter is positioned by the document reading glass 212 and the abutting member of the ADF 21 . Therefore, the image reading apparatus 100 can easily specify the predetermined position of the minute area based on the distance from the edge of the printed matter.

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

Subsequently, in step S<b>213 , the image reading apparatus 100 uses the feature amount extraction unit 281 to extract the feature amount from the converted mosaic image.

Subsequently, in step S<b>214 , the image reading apparatus 100 registers the extracted feature amount data using the registration unit 282 .

In this manner, the image reading apparatus 100 can register feature amount data that serves as a reference for authenticity determination in the registration unit 282 .

(Authentication judgment processing example)
FIG. 12 is a flowchart showing an example of authenticity determination processing by the image reading device 100 included in the image forming device 1. As shown in FIG. An operator of the image forming apparatus 1 places a printed matter to be authenticated on the document reading glass 212 or inserts the printed matter into the ADF 21 and positions it by being abutted against the abutting member. After that, the image reading apparatus 100 starts the process of FIG. 12 at the timing when the operator inputs an authenticity determination start operation via the operation unit of the image forming apparatus 1 .

Since the processing from step S221 to step S223 is the same as the processing from step S211 to step S213 in FIG. 11, redundant description is omitted here.

In step S224, the image reading apparatus 100 causes the comparison unit 283 to sequentially read the registered feature amount data from the registration unit 282 while comparing the extracted feature amount data of the second read image Im2 with all the registered feature amount data. and calculate the degree of similarity between them.

Subsequently, in step S225, the image reading apparatus 100 uses the comparison unit 283 to determine whether or not there is registered feature amount data whose feature amount similarity to the extracted feature amount data is equal to or greater than a predetermined similarity threshold. .

The similarity threshold is preferably set with an allowable range in consideration of errors in registered feature amount data and extracted feature amount data due to reading errors, quantization sampling errors, and the like. Also, the similarity threshold is appropriately selected depending on whether or not the authenticity determination is to be performed strictly. In addition, when the allowable range differs depending on the type of printed material, the image reading apparatus 100 registers a similarity threshold in association with the registered feature amount data when registering the feature amount data, and registers a similarity threshold in association with the registered feature amount data. The process of step S225 can also be performed using the similarity threshold read out together with the registered feature amount data.

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

Subsequently, in step S228, the image reading apparatus 100 outputs the determination result to the external device through the output unit 284. FIG.

In this manner, the image reading apparatus 100 can determine the authenticity of printed matter. In addition, when determining authenticity, there may be cases where an operator makes an operation mistake or the position of the printed material is misaligned. You may do so.

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

A program for executing each step in FIGS. 11 and 12 can be stored in a recording medium, or the program can be provided by communication means. As a recording medium, for example, a digital versatile disc (DVD), which is a standard established by the DVD Forum, such as "DVD-R, DVD-RW, DVD-RAM, etc.," and a standard established by DVD+RW. Some "DVD+R, DVD+RW, etc.", compact discs (CD), read-only memory (CD-ROM), CD-recordable (CD-R), CD-rewritable (CD-RW), etc., magneto-optical discs (MO) , flexible disk (FD), magnetic tape, hard disk, read-only memory (ROM), electrically erasable and rewritable read-only memory (EEPROM), flash memory, random access memory (RAM), and the like.

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

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

<Effects of the image reading apparatus 100 according to the first embodiment>
As described above, the image reading device 100 included in the image forming apparatus 1 reads the light source 200 (illumination unit) and the printed matter (target object) illuminated by the light source 200 at the first reading magnification to generate the first read image Im1. and a first reading unit 3 for outputting. The image reading apparatus 100 also includes a second photoelectric conversion element 222 (second reading unit) that outputs a second read image Im2 obtained by reading the printed material illuminated by the light source 200 at a second reading magnification, and and a determination unit 35 that outputs an authentication determination result (authentication information) of the printed matter determined based on the second reading magnification, and the second reading magnification is higher than the first reading magnification.

By reading the printed matter with the second reading magnification higher than the first reading magnification, it is possible to obtain a density distribution in which a predetermined minute area in the printed matter is enlarged. By performing authentication using the density distribution of this minute area, the amount of information increases compared to the case of performing authentication using, for example, the color and reflectance of printed matter, so the accuracy of authenticity determination is further improved. be able to. In other words, it is possible to provide the image reading apparatus 100 with high authentication accuracy. The amount of information increases as the number of pixels of the second photoelectric conversion element 222 increases. Since the image reading device 100 copies a printed matter such as a document using the first reading unit 3, the image reading device 100 can perform authentication processing with high accuracy without impairing the copying function, which is the main function of the image reading device 100. .

For copying printed matter, it is preferable to set the first reading magnification so that reading is possible with a resolution of 600 [dpi] or 1200 [dpi]. In addition, since the diameter of one toner particle in electrophotography is about 5 [μm] to 10 [μm], the reading resolution of the second photoelectric conversion element 222 must be 2400 [dpi] or higher in order to read this. is preferred. Therefore, in the present embodiment, the second reading magnification is preferably two times or more and five times or less the first reading magnification. By doing so, the random distribution of each toner can be detected, so that more information can be obtained for authenticity determination.

On the other hand, if the reading magnification is too high, a large number of pixels will be used to capture an image of one toner particle. may decrease to Such a reduction in the amount of information can be avoided by setting the second reading magnification to be two times or more and five times or less the first reading magnification.

Further, in the present embodiment, it is preferable that the second reading magnification is 1:1. By setting the same magnification, the image reading apparatus 100 doubles the second reading magnification with respect to the first reading magnification for realizing the reading resolution of 600 [dpi] or 1200 [dpi] in the first reading section 3. It can be 5 times or less. Also, if the second photoelectric conversion element 222 is arranged close to the printed matter, the second reading magnification can be made equal to the original without using a lens, which is more preferable from the viewpoint of simplifying the configuration.

Further, in this embodiment, the first reading section 3 has a first mirror unit 204 (variable mechanism) that changes the position of the printed matter read by the first reading section 3 along the sub-scanning direction 250 (predetermined direction). A second photoelectric conversion element 222 is installed in the first mirror unit 204 , and the first mirror unit 204 moves the second photoelectric conversion element 222 along the sub-scanning direction 250 . As a result, the second photoelectric conversion element 222 whose second reading magnification is 1:1 can capture the full width of the printed matter along the sub-scanning direction 250 .

The second read image Im2 does not necessarily have to capture the entire width of the printed matter along the sub-scanning direction 250 because it is sufficient to capture a small area of the printed matter. can be arbitrarily selected, it is preferable that the full width of the printed matter can be imaged.

Also, the second photoelectric conversion element 222 may not be movable, and may be fixed at a predetermined position. For example, when using a high-magnification objective lens to obtain a high second reading magnification, the working distance becomes narrow. Risk of collision. Such a risk can be reduced by fixing the second photoelectric conversion element 222 .

[Second embodiment]
Next, an image reading device 100a according to the second embodiment will be described. The image reading device 100 a is provided in the image forming device 1 . In addition, the same code|symbol is attached|subjected to the same structure part as 1st Embodiment, and the overlapping description is abbreviate|omitted suitably.

FIG. 13 is a block diagram showing an example of the functional configuration of the determination section 35a included in the image reading device 100a. The determination unit 35 a 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, or the like. 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, controlling the display device 16, and the like.

Based on the first read image Im1 read by the first photoelectric conversion element 214, the detection unit 285 detects misalignment of the printed matter on the document reading glass 212 or the ADF 21. FIG. This misalignment includes a tilt misalignment in which the printed matter is tilted (in-plane rotation) with respect to the document reading glass 212 or the ADF 21, and a shift misalignment in which the printed matter is shifted. The detection unit 285 outputs the detection result to the notification unit 286 when detecting a tilt deviation equal to or greater than a predetermined tilt threshold value, or when detecting a shift deviation equal to or greater than a predetermined shift threshold value.

The notification unit 286 notifies the 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 a positional deviation, the notification unit 286 outputs a message to that effect 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 . An operator who visually recognizes the message can delete the authentication result or redo the authentication.

When the positional displacement of the printed matter is detected based on the first read image Im1, the determination unit 35a notifies the positional displacement 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.

FIG. 14 is a diagram illustrating the first read image Im1 when there is no misalignment. FIG. 15 is a diagram exemplifying the first read image Im1 when there is a misalignment.

When the printed matter 141 is not misaligned, the first read image Im1 includes only the read image of the printed matter 141 and does not include the edges of the printed matter 141, as shown in FIG. On the other hand, if the printed matter 141 is misaligned, the edge of the printed matter 141 is included in the first read image Im1 as shown in FIG. The detection unit 285 can detect shift deviation and tilt deviation of the printed matter 141 from the shift amount s and the tilt amount t of the end portion.

FIG. 16 is a flowchart showing an example of authenticity determination processing by the image reading device 100a included in the image forming apparatus 1. As shown in FIG. An operator of the image forming apparatus 1 places a printed matter to be authenticated on the document reading glass 212 or inserts the printed matter into the ADF 21 and positions it by being abutted against the abutting member. After that, the image reading device 100a starts the processing of FIG.

First, in step S<b>161 , the image reading device 100 a inputs the first read image Im<b>1 read by the first photoelectric conversion element 214 by the detection unit 285 .

Subsequently, in step S162, the detection unit 285 of the image reading apparatus 100a detects the positional deviation of the printed matter 141, that is, the shift deviation and the tilt deviation.

Subsequently, in step S163, the image reading apparatus 100a uses the detection unit 285 to determine whether the shift deviation of the printed matter 141 is greater than or equal to a predetermined shift threshold value, or whether or not the tilt deviation is greater than or equal to a predetermined tilt threshold value. judge.

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

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

Since the processing from step S165 to step S172 is the same as the processing from step S221 to step S228 in FIG. 13, redundant description is omitted here.

In this manner, the image reading apparatus 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 the present 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 includes a detection unit 285 that detects misalignment of the printed matter 141 based on the first read image Im1, and a notification unit 286 that notifies the misalignment detected by the detection unit 285.

If the printed matter 141 is misaligned on the document reading glass 212 or the ADF 21, the degree of similarity between the extracted feature amount data and the registered feature amount data will be low even though the printed matter 141 is genuine, and an erroneous determination may occur. be. In the present embodiment, the image reading apparatus 100a can notify the fact by the notification unit 286 when the printed matter 141 is misaligned on the document reading glass 212 or the ADF 21 . As a result, the operator of the image forming apparatus 1 can be notified of the misalignment and can be made to recognize that an erroneous determination may occur.

In the present embodiment, when the misalignment of the printed matter 141 is detected, the configuration is shown in which the misalignment is notified, but the present invention is not limited to this. For example, when the detection unit 285 detects the positional deviation of the printed matter 141, the determination unit 35a can correct the second read image Im2 according to the positional deviation. For example, the second read image Im2 is corrected by performing image processing for rotating the second read image Im2 according to the tilt shift t, or performing image processing for shifting the second read image Im2 according to the shift shift s. can. In this way, the image reading apparatus 100a can accurately determine authenticity even when the printed matter 141 is misaligned.

Although the preferred embodiment has been described in detail above, it 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. can be added.

In the above-described embodiment, an electrophotographic image forming apparatus using toner was exemplified, but the present invention is not limited to this, and the embodiments can also be applied to a liquid ejection type image forming apparatus using liquid such as ink. is. Ink also causes uneven adhesion to a recording medium, scatters, spreads, etc. in the same manner as toner.

Numerals such as ordinal numbers and numbers used in the description of the embodiments are all exemplified to specifically describe the technology of the present invention, and the present invention is not limited to the exemplified numbers. Moreover, the connection relationship between the components is an example for specifically describing the technology of the present invention, and the connection relationship for realizing the function of the present invention is not limited to this.

Each function of an embodiment can be implemented by one or more processing circuits. Here, the "processing circuit" in this specification means a processor programmed by software to perform each function, such as a processor implemented by an electronic circuit, or a processor designed to perform each function described above. devices such as ASICs (Application Specific Integrated Circuits), DSPs (digital signal processors), FPGAs (field programmable gate arrays) and conventional circuit modules.

1 image forming apparatus 3 first reading unit 21 ADF
212 Document reading glass 22 Scanner unit 23 Paper discharge tray 35 Judgment unit 100 Image reader 200 Light source (an example of illumination unit)
202 First mirror 204 First mirror unit (an example of 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 unit 240 main scanning direction 250 sub-scanning direction 281 feature extraction unit 282 registration unit 283 comparison unit 284 output unit 285 detection unit 286 notification unit 400 paper supply unit 110 read image 111 partial regions 120 and 130 Enlarged images 121, 122a, 122b, 131, 132 Minute area Im1 First read image Im2 Second read image P Paper

JP 2005-038389 A

Claims (7)

a lighting unit;
a first reading unit that reads an object illuminated by the illumination unit at a first reading magnification and outputs a first read image;
a second reading unit that reads the object illuminated by the illumination unit at a second reading magnification and outputs a second read image;
a determining unit that outputs authenticity information of the object determined based on the second read image;
The image reading device, wherein the second reading magnification is higher than the first reading magnification. 2. The image reading apparatus according to claim 1, wherein the second reading magnification is two times or more and five times or less the first reading magnification. 3. The image reading apparatus according to claim 1, wherein the second reading magnification is 1:1. 4. The image reading apparatus 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
a detection unit that detects positional deviation of the object based on the first read image;
5. The image reading apparatus according to claim 4, further comprising a notification section that notifies the positional deviation detected by the detection section. The first reading unit has a variable mechanism that changes a position read by the first reading unit in the object along a predetermined direction,
The image reading apparatus according to any one of claims 1 to 5, wherein the variable mechanism moves the second reading section along the predetermined direction. 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