JP3412279B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a function of preventing counterfeiting of bills and the like. 2. Description of the Related Art In recent years, high-quality digital color copiers that provide a copy faithful to a document image have been put into practical use, and there is a risk that banknotes and securities are easily copied and forged. . As countermeasures against this, countermeasures such as judging whether or not the original set on the original platen is copy-prohibited and stopping the copying operation or preventing normal copying from being performed are possible. Function is conceivable. However, for manuscripts such as banknotes, securities, TCs, checks, and official documents all over the world that we want to prevent forgery, storing all these features, performing pattern matching, and prohibiting copying,
This is practically impossible due to storage capacity, processing time, new bill support, and the like. Therefore, although the copying itself cannot be prohibited, a special code (tracking information) which is not normally visible is written in the copied copy itself, and the manufacturer model name, serial number, copy of the machine used for the copy are written. Date and time of management card No. There is a copier having a function of specifying a part or a part thereof. For example, as shown in FIG. 1, the tracking information is represented by a small yellow (for example, one pixel) dot arrangement shape (hereinafter referred to as a tracking pattern) in a predetermined block, and a block in which the tracking pattern is written is referred to as a tracking pattern. There is a technique of repeatedly writing in a copy sheet (hereinafter, referred to as a hard copy) on which a document image is copied. The specification of the product name and the serial number is executed by extracting the tracking pattern written in the block. The writing range of the above yellow dots is as follows: In which position on the platen, illegal copy prohibited documents (banknotes, stamps, income stamps,
Since it is not known whether or not securities are placed, the image is printed on the entire surface of the copy paper or the entire image area obtained by detecting the document size. In addition, it is conceivable to cut out a part of the hard copy and use it.Also, make it possible to reduce the size of the block where the tracking pattern is written so that it can be analyzed when cutting and using small things such as stamps and stamps. It is desirable to make it smaller. [0004] As shown in FIG. 1, the yellow dots encrypted as shown in FIG. 1 are difficult to be seen by human eyes, but have a certain density or are printed over the entire surface. Noise and background yellowness are noticeable. Also, even if it is difficult to see with yellow dots alone,
It may be visualized by mixing with other color toners by subtractive coloration. However, it is not preferable to excessively weaken the driving level just because the noise is conspicuous, because it is difficult to specify the type and serial number of the copying machine from the copied original, which is the original purpose. That is, it is necessary to set the size of the yellow dot and the level of the applied density to values that can be reliably analyzed and cannot be visually discriminated. [0005] An image forming apparatus according to the present invention is an image forming apparatus for imprinting tracking information on an image, comprising a memory for storing tracking information data, and image data corresponding to densities of a plurality of color images. Image forming means for forming an image on a sheet based on the image data, and increasing the value of the image data of the specific color among the plurality of colors for the pixel at the position where the tracking information is to be printed, and for the other colors other than the specific color. A tracking information adding unit that reduces the value of the image data and outputs the image data to the image forming unit; and, as the value of the image data of the pixel at the position where the tracking information is entered decreases, the image of the specific color in the tracking information adding unit decreases. Other than the level of increase of the data value and the specific color
The reduction level of the image data values of other colors
Setting means for setting the increase and decrease levels . According to the present invention, there is provided an image forming apparatus comprising: a memory for storing tracking information data; an image forming means for forming an image on a sheet based on image data;
Tracking information adding means for adding data of the tracking information to the image data and outputting the data to the image forming means; and tracking information to be added to the image data by the tracking information adding means based on the value of the image data. Setting means for setting the level of the data. The tracking information adding means of the image forming apparatus according to the present invention comprises:
The data of the tracking information is added to the image data of the document. The image forming means forms an image on a sheet based on the value of the image data to which the tracking information has been added. The data level of the tracking information added to the image data by the tracking information adding unit is set by the setting unit based on the image data. This makes it possible to add an appropriate level of tracking information data to the image data. (1) Configuration of Digital Color Copier FIG. 2 is an overall configuration diagram of a digital color copier of this embodiment which sets a tracking pattern recording level based on the density of pixels of a document. . The digital color copying machine is roughly divided into an image reader unit 100 for reading a document image and a copying unit 200 for reproducing image data of the document read by the image reader unit 100 on copy paper. The configuration of the image reader unit 100 is the same as the conventional one. Here, the scanner 10 includes an exposure lamp 12 for irradiating a document.
And a rod lens array 1 for collecting the reflected light from the original
3, and a contact-type CCD color image sensor 14 for converting the collected light into a multi-valued electric signal. The scanner 10 is moved by the motor 11 at the time of scanning the original, moves in the direction of the arrow (sub-scanning direction), and
The original placed on top is scanned. The image of the document surface irradiated by the exposure lamp 12 is photoelectrically converted by the image sensor 14. R obtained by the image sensor 14,
The multi-valued electrical signals of the three colors G and B are converted into 8-bit gradation data of any of cyan (C), magenta (M), yellow (Y), and black (Bk) by the read signal processing unit 20. Converted and synchronized buffer (FIFO memory) 3
0 is stored. In the copying section 200, the print head section 31
Generates a semiconductor laser drive signal by performing D / A conversion on image data for correction after performing gradation correction (γ correction) according to the gradation characteristics of the photoconductor on the input gradation data. Then, the semiconductor laser is caused to emit light by the drive signal. The laser beam emitted from the print head unit 31 with the emission intensity changed in accordance with the gradation data exposes the rotating photosensitive drum 41 via the reflecting mirror 39. The photoreceptor drum 41 is irradiated with an eraser lamp 42 before receiving exposure for each copy, and is uniformly charged by a charger 43. When exposure is performed in this state, an electrostatic latent image of the document is formed on the photosensitive drum 41. cyan,
Magenta, yellow, and black toner developing devices 45a-
Only one of 45d is selected, and the electrostatic latent image on the photosensitive drum 41 is developed. The developed toner image is
The image is transferred to a copying machine wound on a transfer drum 51 by the transfer charger 46. The above-mentioned development is repeated for four colors of cyan (C), magenta (M), yellow (Y) and black (Bk). At this time, the scanner 10 repeats the scanning operation in synchronization with the operations of the photosensitive drum 41 and the transfer drum 51. Thereafter, the copy paper is separated from the transfer drum 51 by operating the separation claw 47, is fixed through the fixing device 48, and is discharged to the waste tray 49. The copy paper is supplied from the paper cassette 50,
The leading end of the transfer drum 51 is chucked by a chucking mechanism 52 so that a displacement does not occur during transfer. (2) Driving a tracking pattern A reading level and a punching level are set for the read data from the image reader unit 100. Here, the low-density portion of the yellow dot forms a tracking yellow pattern by hitting. On the other hand, since the high-density portion of the yellow dot is invisible even when driven,
A pattern is formed by punching. The yellow pattern is a code that can specify the model name and serial number of the copying machine. The model name and serial number are
The printing is performed in a two-dot pair arrangement pattern of a printed dot and a punched dot arranged in a small matrix size. Also, as explained later,
The values of the tracking pattern punching and punching levels are determined based on the value of the image data of the pixel at which the yellow dot is to be punched or punched, that is, the density value of the pixel. As a result, the level of punching and punching of the tracking pattern into the document is maintained at a value that does not cause noise of the document and that can be reliably recognized. FIG. 1 is a color copy 1 of a document including a diagram of a copier. The copy 1 shows a state in which a pattern of a two-dot pair line of yellow dots 2 is arranged at a predetermined position in a plurality of matrices indicated by broken lines. The upper right part of FIG. 1 is an enlarged view of a part of the color copy 1 on the left side, and points in the figure show small yellow dots 2. Further, the lower right diagram in FIG. 1 shows an enlarged two-dot pair of yellow dots. FIG. 3 is a diagram for explaining correction of exposure data at the time of punching and at the time of punching. In the case of punching (when yellow data is emphasized) shown on the upper side, image data (cyan (C), magenta (M), yellow (Y), and black (Bk)) from the image reader shown on the left The yellow (Y) data of the predetermined driving level shown is added, and output image data for driving the laser diode is obtained as shown on the left.
In this example, since the sum of the yellow image data (80) and the driving level (180) exceeds the maximum value 255, the yellow output image data takes the maximum value 255. On the other hand, punching shown below (yellow data deleted)
In the case of, the image data (cyan (C), magenta (M), yellow (Y),
Black (Bk)) is subtracted from yellow (Y) data at a predetermined driving level shown in the center, and output image data shown on the left is obtained. In this example, the image data (80) on the yellow side and the driving level (18)
Since the difference 0) is smaller than the minimum value 0, the yellow output image data takes the minimum value 0. FIG. 4 is a block diagram of image data processing in the print head unit 31. Here, the image data (8 bits) from the read signal processing unit 20 is input to a first-in first-out memory (hereinafter, referred to as a FIFO memory) 252 via the interface unit 251. The FIFO memory 252 is a line buffer memory capable of storing gradation data of a predetermined number of lines of images in the main scanning direction, and operates between the image reader unit 100 and the copying unit 200 shown in FIG. It is provided to absorb frequency differences. FIFO memory 2
Next, the data of 52 is input to the γ correction unit 253. γ
The correction unit 253 corrects the data from the FIFO memory 252 based on the γ correction data from the printer control unit 201. The γ data ROM 203 also stores various tone correction data (γ table, various correction values, etc.).
The data subjected to the γ correction by the γ correction unit 253 is input to the tracking pattern addition unit 257 next. Tracking pattern RO
M256 stores, as shown in FIG. 1, data of a tracking pattern representing the tracking information in the arrangement of yellow dots in a predetermined block. The driving level data ROM 260 stores a driving level data value corresponding to the data subjected to the γ correction. When the tracking pattern addition mode is selected (ON) via the operation panel 70 (not shown), the printer control unit 201 reads the tracking pattern data from the tracking pattern ROM 256 and performs γ correction from the driving level data ROM 260. The driving level data corresponding to the read data is read, and the read data of the tracking pattern and the driving level data are input to the tracking pattern adding unit 257. If the image data input to the FIFO memory 252 via the interface unit 251 is image data for forming a yellow (Y) toner image on the photosensitive drum 41, the printer control unit 201
Sends a write permission control signal to the tracking pattern adding unit 257. The tracking pattern adding unit 257, which has received the write permission control signal, adds the data of the tracking pattern of the set driving level to the data from the γ correction unit 253 (see FIG. 1), and the D / A conversion unit 254 Output to In the case other than image data for forming a yellow (Y) toner image on the photosensitive drum 41, the printer controller 2
01 outputs a write-inhibited control signal to the tracking pattern adding unit 257 and causes the D / A conversion unit 254 to output the data input from the γ correction unit 253 as it is. The analog voltage converted from the light emission level (digital value) by the D / A conversion unit 254 is then output to the gain switching unit 255.
According to the gain setting value from the printer control unit 201, the gain switching signal generation circuit unit 258 controls the switches SW1 and SW1.
SW2,... (Corresponding to different powers P1, P2,...) Are switched and amplified to the set gain.
The laser beam is sent to the semiconductor laser drive 263 via / O 261 and causes the semiconductor laser 264 to emit light at the light intensity of that value. (3) Driving Level Setting Processing It is necessary to discharge yellow dots at a driving level that can be analyzed reliably and is not visible as noise. However, the original image has various densities and patterns, and if a certain level of the image is set, for example, if a dark original is set to a level that can be decoded, a light original becomes noticeable as noise on the entire surface. Also, if the density is set to a level that does not stand out as noise at a light density, it becomes impossible to read a dark original. In order to cope with this, the printer control unit 201 sets the printing level according to the density of the pixel where the yellow dot is to be printed, instead of setting the printing level constant. The density of the pixel at the position where the yellow (Y) dot is to be formed is determined by the γ input to the formation level data ROM 260.
It is determined from the corrected data. The table shown in the following “Table 1” is stored in the driving level data ROM 260. [Table 1] For example, when the value of the input gamma-corrected data is 0 to 32, the driving level data ROM 260
The driving level (ΔY) of the +30 yellow dot is output to the printer control unit 201. The above “Table 1”
Although the setting of the driving level is performed in three stages, the present invention is not limited to this, and the level may be set more finely. In this case, a more appropriate level can be set. (4) Tracking Pattern Addition Processing FIG. 7 is a flowchart showing a tracking pattern addition processing executed by the copying machine main body of this embodiment. First, RGB digital image data of a document placed on a document table is read (step S100), and image processing such as color correction processing (masking processing, UCR / BP processing) and editing scaling processing is executed (step S101). ), Y, C, M, and Bk image data are obtained. In the next step S102, gradation correction (γ correction) is executed to obtain data of each color that has been subjected to γ correction. If the developed color is yellow (Y) (YES in step S103), the driving level (ΔY) is obtained from the above “Table 1” (step S104). In the next step S105, ON / OFF of the tracking pattern addition mode is determined on the operation panel 70, and if it is ON, the next tracking pattern addition processing unit (step S106).
At step S107, the driving level (ΔY) is added to the data subjected to the γ correction of yellow to form an image (step S107). In the case of OFF, image formation is performed without any addition. If the printing process for Y, C, M, and Bk has not been completed (NO in step S108), the processes in steps S100 to S107 are repeatedly executed. If the printing process for Y, C, M, and Bk has been completed (YES in step S108), the process ends. (5) Modified Example of Imprinting Level Setting Process When setting the imprinting level of yellow (Y) dots,
The driving levels of cyan (C), magenta (M), and black (Bk) may be increased or decreased. In this case, the recognition rate of the yellow dot pattern data can be further improved. The following “Table 2” shows the yellow dot setting levels (ΔY) and the cyan, magenta, and black dot setting levels (ΔC, ΔM, ΔBk) set in correspondence with the values of the data subjected to γ correction. ). [Table 2] For example, when the data subjected to γ correction is 0 to 16,
The ejection level (ΔY) of the yellow dot is set to +20, and the ejection levels (ΔC, ΔM, ΔBk) of the cyan, magenta, and black dots are set to −5. During the development of yellow, 20 is added to the value of the data subjected to γ correction. During the development of cyan (C), magenta (M), and black (Bk), the value of the γ-corrected data is subtracted by 5. FIG. 6 is a diagram showing a processing flowchart of a modification of the driving level setting processing. First, RGB digital image data of a document placed on a document table is read (step S200), and image processing such as color correction processing (masking processing, UCR / BP processing) and editing scaling processing is executed (step S201). ), Y, C, M, and Bk image data are obtained. In the next step S202, gradation correction (γ correction) is executed to obtain data of each color that has been subjected to γ correction. If the developed color is yellow (YES in step S203), the driving level (ΔY) is obtained from “Table 2” described earlier (step S204). In step S205, ON / OF of the tracking pattern adding process is performed.
F is determined, and if it is ON, in the next step S206, the driving level (ΔY) is added to the data subjected to the γ correction of yellow, and tracking pattern addition processing for forming an image is executed. If the tracking pattern addition process is OFF (NO in step S205), image formation is performed without adding a tracking level (step S210).
On the other hand, if the developing process is any of the colors cyan, magenta, and black (NO in step S203), the driving level (ΔM, ΔC, ΔBk) is obtained from “Table 2” (step S207). In step S208, ON / OFF of the tracking pattern adding process is determined. If it is ON, the driving level (ΔY) is added to the data subjected to γ correction of yellow in the next step S209,
A tracking pattern adding process for forming an image is executed. If the tracking pattern addition processing is OFF (step S20)
8 (NO in step S8), the image is formed without adding the driving level (step S210). Y, C, M, Bk
If the development is not completed (NO in step S211), the processes in steps S200 to S210 are repeatedly executed. When the development of Y, C, M, and Bk has been completed (YES in step S211), the process ends. By executing the above-described processing, it is possible to set the ejection level of the yellow (Y) dot to an appropriate value based on the density of the original in the technology for tracking a forged original. As a result, the yellow (Y) dots that have been printed on a normal copy image can be recognized without being noticeable. Note that, in the present embodiment, the process of forming yellow (Y) dots has been described, but white dots may be formed. Further, the form of the data to be printed is not limited to the dot pattern, and may be, for example, a barcode. The image forming apparatus of the present invention adds tracking information data of a level based on the image data to the image data. By using this image data, an appropriate level of tracking information can be entered into the image formed by the image forming means on the paper. For this reason, it is possible to make the recorded tracking information inconspicuous and to reliably recognize it.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a case where a yellow dot pattern is printed on copy paper. FIG. 2 is a configuration sectional view of a digital color copying machine. FIG. 3 is a diagram for explaining exposure data correction when a yellow (Y) dot pattern is printed as tracking information and when punching is performed. FIG. 4 is a diagram showing each processing block constituting the print head unit 31. FIG. 5 is a diagram illustrating a flowchart of a shooting level setting process executed by a printer control unit. FIG. 6 is a diagram illustrating a flowchart of a modified example of the shooting level setting process executed by the printer control unit 201. [Description of Signs] 210: Printer control unit 253: γ correction unit 256: Tracking pattern ROM 257: Tracking pattern adding unit 260: Driving level data ROM

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-217108 (JP, A) JP-A-5-219354 (JP, A) JP-A-6-113109 (JP, A) JP-A-6-113109 113107 (JP, A) JP-A-5-301380 (JP, A) JP-A-6-113138 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1 / 38-1 / 393 H04N 1/46-1/64

Claims (1)

(57) A [Claims 1 An image forming apparatus implanting tracking information in the image, a memory for storing data of the tracking information, based on the image data corresponding to the density of a plurality of colors of images hand,
Image forming means for forming an image on paper, and for a pixel at a position where the tracking information is to be printed, the value of image data of a specific color among the plurality of colors is increased,
And tracking information adding unit for the decreasing the other colors the value of the image data other than the specific color, and outputs to the image forming means, the image data value of the pixel position implanting the tracking information
As the size decreases, the level of increase in the value of the image data of the specific color in the tracking information adding means and the color other than the specific color
The decrease level of the image data value of each
A setting unit for setting the increase level and the decrease level .