JP2010028656A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the decipherability of a generation copy, by solving the problem, wherein when a manuscript printed once is reprinted again (generation copy) by scanning, it becomes undecipherable because a trace signal added at the time of the first print, and the trace signal added at the time of the second print overlap and are printed out. <P>SOLUTION: An addition configuration, such as, angle to be added or an addition profile is changed, whenever the trace signal is added. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image based on an image signal.

  In recent years, image forming apparatuses such as color printers and color copiers are capable of forming high-quality images due to improved performance. Under such circumstances, it is becoming possible to form images similar to banknotes, banknotes, securities, etc., and problems such as counterfeiting of banknotes, securities, etc. and copyright infringement will increase in the future. It is possible.

  As such suppression measures, for example, an addition method is known in which an additional signal indicating a serial number of the image forming apparatus is added to a printed color image so that it is difficult for human eyes to identify.

  Usually, this additional signal is added to the entire image. When a dot pattern is added to a color image made up of yellow, magenta, cyan, and black planes to make it difficult for human eyes to identify, the dot pattern is usually added only to the yellow plane.

  By performing the above addition, when an image that should be prohibited from image formation or a copy image that should be prohibited from copying appears, an additional signal is extracted from these images and additional information is restored. By doing so, it is possible to specify the device on which these images are formed.

Examples of the above include Patent Document 1 and Patent Document 2 below.
Japanese Patent Laid-Open No. 06-070134 JP2003-335019

  This additional signal is added to all the output images. However, an additional signal is added when a printed page is read with a scanner and printed again, or when a generation machine is copied with a copying machine (a copied version is copied again). There was a problem that it was difficult to restore the additional information.

In order to solve the above problem, an image forming apparatus of the present invention includes a signal adding unit that adds a predetermined additional signal to an input image signal,
Additional form holding means for holding a plurality of additional forms of the additional signal;
Additional form selection means for selecting one of a plurality of additional forms held by the additional form holding means;
Have
The additional signal is added by the signal adding means according to the additional form selected by the additional form selecting means during image formation.

  As described above, according to the present invention, each time an image is formed, a different additional form is selected and an additional signal is added. Thus, even when a generation copy is performed, both additional signals can be easily distinguished, so that signal reading and additional information restoration can be performed easily and reliably.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  FIG. 1 shows an example of an electrophotographic color image forming apparatus to which the present invention is applied.

  FIG. 1 is a block diagram showing a tandem color image forming apparatus that employs an intermediate transfer member 27.

  The operation of the image forming unit in the electrophotographic color image forming apparatus will be described with reference to FIG. An electrostatic latent image is formed by exposure light that is turned on based on the exposure time converted from the input image data, and the electrostatic latent image is developed to form a single color toner image. A color toner image is formed, this multi-color toner image is transferred to the transfer material 11, and the multi-color toner image on the transfer material 11 is fixed. Photoconductors (22Y, 22M, 22C, 22K) for each station, injection charging means (23Y, 23M, 23C, 23K) as primary charging means, toner cartridges (25Y, 25M, 25C, 25K), developing means (26Y, 26M, 26C, 26K), the intermediate transfer member 27, the transfer roller 28, and the fixing unit 30.

  The photosensitive drums (photoconductors) 22Y, 22M, 22C, and 22K are configured by applying an organic optical conductive layer to the outer periphery of an aluminum cylinder, and are rotated by the driving force of a driving motor (not shown) being transmitted. Rotates the photosensitive drums 22Y, 22M, 22C, and 22K in the counterclockwise direction in accordance with the image forming operation.

  As the primary charging means, four injection chargers 23Y, 23M, 23C, and 23K for charging the yellow (Y), magenta (M), cyan (C), and black (K) photoreceptors are provided for each station. In configuration, each injection charger is provided with a sleeve 23YS, 23MS, 23CS, 23KS.

  Exposure light to the photosensitive drums 22Y, 22M, 22C, and 22K is sent from the scanner units 24Y, 24M, 24C, and 24K, and the electrostatic latent images are selectively exposed by exposing the surfaces of the photosensitive drums 22Y, 22M, 22C, and 22K. An image is formed.

  As developing means, in order to visualize the electrostatic latent image, four developing units 26Y, 26M for developing yellow (Y), magenta (M), cyan (C), and black (K) for each station, Each developing device is provided with a sleeve 26YS, 26MS, 26CS, and 26KS. Each developing device is detachably attached.

  The intermediate transfer member 27 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K, and rotates clockwise when forming a color image. The intermediate transfer member 27 rotates in accordance with the rotation of the photosensitive drums 22Y, 22M, 22C, and 22K. The toner image is transferred. Thereafter, a transfer roller 28 to be described later comes into contact with the intermediate transfer member 27 to sandwich and convey the transfer material 11, and the multicolor toner image on the intermediate transfer member 27 is transferred to the transfer material 11.

  The transfer roller 28 contacts the transfer material 11 at a position 28a while the multicolor toner image is being transferred onto the transfer material 11, and is separated to a position 28b after the printing process.

  The fixing unit 30 melts and fixes the transferred multi-color toner image while conveying the transfer material 11, and as shown in FIG. 1, the fixing roller 31 for heating the transfer material 11 and the transfer material 11 are fixed to the fixing roller. A pressure roller 32 is provided for pressure contact with 31. The fixing roller 31 and the pressure roller 32 are formed in a hollow shape, and heaters 33 and 34 are incorporated therein, respectively. That is, the transfer material 11 holding the multicolor toner image is conveyed by the fixing roller 31 and the pressure roller 32, and heat and pressure are applied to fix the toner on the surface.

  After the toner image is fixed, the transfer material 11 is discharged to a discharge tray (not shown) by a discharge roller (not shown) and the image forming operation is finished.

  The cleaning unit 29 cleans the toner remaining on the intermediate transfer member 27. The waste toner after the four-color multicolor toner image formed on the intermediate transfer member 27 is transferred to the transfer material 11 is: Stored in a cleaner container.

  Next, the flow of signal processing in this embodiment will be described with reference to FIG. When a print command is received from an application (not shown), a page description language is transmitted from the driver 201 and input to the controller 211. When outputting a bitmap image, the page description language includes bitmap data. In the controller 211, a decoder 202, a band memory A203, a band memory B204, a color conversion processing unit 205, a γ correction unit 206, and a halftone processing unit 207 are arranged. The input page description language is interpreted by the decoder 202 and converted to RGB 8-bit image data. RGB image data is input to the band memory. The band memory is composed of two memories, a band memory A203 and a band memory B204, and one memory can store several lines of image data. First, the image area for the first predetermined line is developed in the band memory A203, and the image data for RGB is output from the band memory A203 while the image area for the next predetermined number of lines is developed in the band memory B204. The Further, while the image area for the next predetermined number of lines is expanded in the band memory A203, the image data is alternately expanded in the two band memories, such as the RGB image data is output from the band memory B204. It is configured to output. The RGB image data output from the band memory is input to the color conversion processing unit 205 in parallel, subjected to predetermined color conversion processing and UCR processing, and converted into M, C, Y, and K image signals. Since the color electrophotographic printer of this embodiment prints one screen for each of the colors Y, M, C, and K as described above, the color conversion processing unit 205 starts the frame sequential, that is, data for one screen of M, C 1 The image signals are output with a time difference in the order of screen data, Y screen data, and K screen data. Further, the color conversion processing unit 205 sends a color designation signal notifying the currently output color to the engine 212. Next, the γ correction unit 206 performs correction so that the output density curve is optimized, and the halftone processing unit 207 performs halftone processing by a method such as a systematic dither method or an error diffusion method. Thereafter, information is added by an information addition processing unit 208 (to be described later), pulse width modulation is applied by a PWM processing unit 209, D / A conversion is performed, and then input to the laser driving unit 210 for printing.

  Next, a method for adding information in this embodiment will be described. In this embodiment, information is added by performing an operation on yellow pixel data.

  FIG. 3 shows a basic additional form (hereinafter referred to as an additional pattern) of an additional signal on an image.

  The positions indicated by black circles (0, 0) to (4, 4) in the figure are called additional positions. The additional positions are arranged at intervals of Tx in the X direction and Ty in the Y direction. Each additional position represents 1-bit information. When it is 1, an additional signal is added, and when it is 0, no additional signal is added. In addition, two additional signals are added at predetermined intervals in order to indicate the start position of the additional pattern at the position (0, 0). Therefore, 24-bit information can be represented by the entire additional pattern.

In this embodiment, the additional pattern is formed at an arbitrary additional angle α. FIG. 4 shows a state where an additional pattern is formed with respect to an image at an additional angle α. As can be seen from the figure, the relative position Pos (n, m) from (0,0) of each additional position (n, m) is
Pos (n, m) = (m × Tx × cosα−n × Ty × sinα, m × Tx × sinα + n × Ty × cosα)
It is calculated as follows.

  FIG. 5 is a block diagram of the information addition processing unit 208.

  The ROM 501 contains an individual ID of the image forming apparatus. The CPU 502 receives the individual ID from the ROM 501 at the time of image formation and stores it in the RAM 503. The stored data is scrambled, encrypted, converted into ON / OFF information of each additional position, and input to the additional position calculation unit 504.

  On the other hand, the additional angle designation unit 505 determines the additional angle α of the additional signal with a random number when forming an image. The determined additional angle is input to the additional position calculation unit 504. The additional position calculation unit 504 calculates the position Pos (n, m) of each additional position according to the above equation according to the input α, and adds an additional signal according to the ON / OFF information of each additional position input. The position to be processed is determined, and information on the additional position is input to the additional designation processing unit 508.

  The main scanning counter 506 performs a counting operation according to the clock signal VCLK in the main scanning direction of the image signal, and notifies the additional designation processing unit 508 of the count number in the main scanning direction. The sub-scanning counter 507 performs a counting operation according to the sub-scanning direction clock signal LCLK, and notifies the additional designation processing unit 508 of the count number in the sub-scanning direction. The position where the additional signal is to be added based on the information on the additional position input from the additional position calculator 504 only when the color specifying signal (not shown) notified from the CPU 502 specifies yellow. That is, when the count number reaches a value to which an additional signal is to be added, the additional designation signal is turned ON, and the additional signal generated by the additional signal generation unit 509 is input to the signal conversion unit 510. When the additional designation signal is ON, the signal converter 510 superimposes the input additional signal on the input image signal.

  Next, a method for restoring the original information from the additional signal will be described. FIG. 6A is an example in which an image once formed by the image forming apparatus of the present embodiment is read by a scanner or the like, and the image is formed again by the image forming apparatus of the present embodiment. A black circle in the figure indicates an additional pattern added at the first image formation, and a gray circle in the figure indicates an additional pattern added at the second image formation. As described above, since the angle of the additional pattern changes each time an image is formed in the image forming apparatus of this embodiment, the two additional patterns normally form a certain angle as shown in FIG. 6a. When information is restored, first, two aligned dots 601 and 602 indicating the start positions of the respective patterns are searched. Next, since the direction of each additional pattern can be known from the direction of the dots 601 and 602 arranged, a virtual guideline for each additional position is drawn as shown in FIG. The additional pattern formed at the second time can be easily distinguished. It is possible to restore information by examining whether or not there is a dot at each additional position after distinguishing in this way.

  With the above configuration, the processing of the present invention can be performed. In the present embodiment, an arbitrary angle is randomly selected as the additional angle. However, a specific angle may be selected randomly or sequentially.

  Next, a second embodiment using the present invention will be described. In this embodiment, similarly to the first embodiment, a color LBP using an electrophotographic method is used. In this embodiment, the shape of the additional signal is selected.

  The configuration of the color image forming apparatus of the present embodiment, the flow of signal processing, and the form of the additional pattern are the same as those of the first embodiment.

  FIG. 7 is a block diagram of the information addition processing unit 208 in this embodiment.

  The ROM 701 stores the individual ID of the image forming apparatus. The CPU 702 receives the individual ID from the ROM 701 at the time of image formation and stores it in the RAM 703. The stored data is scrambled, encrypted, converted into ON / OFF information of each additional position, and input to the additional position calculation unit 704.

  The additional position calculation unit 704 determines the position to which the additional signal is added according to the ON / OFF information of each additional position that is input, and inputs the additional position information to the additional designation processing unit 707.

  On the other hand, the additional shape designation unit 708 selects and determines one of the additional shapes shown in FIGS. The determined additional shape is input to the additional signal generator 709.

  The main scanning counter 705 performs a counting operation in accordance with the clock signal VCLK in the main scanning direction of the image signal, and notifies the additional designation processing unit 707 of the count number in the main scanning direction. The sub-scanning counter 706 performs a counting operation according to the sub-scanning direction clock signal LCLK, and notifies the additional designation processing unit 707 of the count number in the sub-scanning direction. Only when the color designation signal (not shown) notified from the CPU 702 designates yellow, the addition designation processing unit 707 should add the additional signal based on the information on the additional position input from the addition position calculation unit 704. That is, when the count number reaches the value to which the additional signal is to be added, the additional designation signal is turned ON, and the additional signal generator 709 generates the additional signal according to the input additional shape, and converts the generated additional signal into a signal Input to part 710. When the additional designation signal is ON, the signal conversion unit 710 superimposes the input additional signal on the input image signal.

  Next, a method for restoring the original information from the additional signal will be described. FIG. 9A is an example in which an image once formed by the image forming apparatus of this embodiment is read by a scanner and the image is formed again by the image forming apparatus of this embodiment. The dots shown in black in the figure indicate the additional signal of the additional pattern added at the first image formation, and the dots shown in gray in the figure indicate the additional signal of the additional pattern added at the second image formation. As described above, in this image forming apparatus, the shape of the additional signal changes each time an image is formed. In the example of FIG. 9a, the shape of FIG. 8a is selected for the first image formation, and the shape of FIG. 8c is selected for the second image formation. This is the case. As can be seen from the figure, the additional signal formed at the first time and the additional signal formed at the second time can be easily distinguished from each other because of the difference in shape. It is possible to restore the information by searching for the aligned dots 901 and 902, then drawing virtual guidelines for each additional position as shown in FIG. 9b, and checking whether there is a dot at each additional position. .

  With the above configuration, the processing of the present invention can be performed. In the present embodiment, the additional shape is selected at random, but may be selected in a predetermined order.

FIG. 3 is a diagram illustrating a configuration of a printing unit of a color image forming apparatus according to first and second embodiments of the present invention. FIG. 3 is a diagram illustrating a configuration of a signal processing unit of a color image forming apparatus according to first and second embodiments of the present invention. FIG. 5 is a diagram showing a form of an additional pattern in the first example of the present invention. FIG. 5 is a diagram showing an additional pattern with an additional angle in the first embodiment of the present invention. FIG. 3 is a diagram showing a configuration of an information addition processing unit in the first exemplary embodiment of the present invention. FIG. 5 is a diagram showing an example of addition in the first embodiment of the present invention. It is a figure which shows the structure of the information addition process part in 2nd Example of this invention. It is a figure showing the additional shape in the 2nd Example of this invention. FIG. 10 is a diagram showing an example of addition in the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Transfer material 21 Paper feed part 22 Photoconductor, photosensitive drum 23 Injection charging means 24 Scanner part 25 Toner cartridge part 26 Developing means 27 Intermediate transfer body 28 Transfer roller 29 Cleaning means 30 Fixing device 31 Fixing roller 32 Pressure roller 33, 34 Heater 208 Information addition processing section

Claims (5)

Signal adding means for adding a predetermined additional signal to the input image signal;
Additional form holding means for holding a plurality of additional forms of the additional signal;
An additional form selection means for selecting one of a plurality of additional forms held by the additional form holding means;
An image forming apparatus characterized in that an additional signal is added by the signal adding means in accordance with an additional form selected by the additional form selecting means during image formation.   The image forming apparatus according to claim 1, wherein the additional signal is regularly added in a predetermined direction, and the additional form is an angle of the direction.   The image forming apparatus according to claim 1, wherein the additional form is a shape of an additional signal.   The image forming apparatus according to claim 1, wherein the additional form selection unit selects the additional form in a predetermined order every time an image is formed.   The image forming apparatus according to claim 1, wherein the additional form selection unit selects the additional form in a random order every time an image is formed.

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