JPH08204943A - Color image recorder - Google Patents

Abstract

PURPOSE: To surely decide whether a tracking pattern is correctly drawn or not. CONSTITUTION: When a received color designation signal 516 designates Y, only the yellow density is read in 400dpi out of a prescribed part of a form put on a transferred object. This read yellow image is sent to a matching part 603 and inputted to a RAM of the part 603. At the same time, the device body number stored in a ROM 504 is also inputted to the part 603. At the part 603, the dot positions of the input image are calculated based on the input device body number and it is checked whether the dots are given to these calculated positions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image recording apparatus for preventing illegal copying of originals.

[0002]

2. Description of the Related Art In recent years, color image recording apparatuses such as printers and copiers have made great progress in terms of performance improvement and diffusion, and full-color image recording apparatuses also include silver salt type, heat sensitive type, Those using a large number of output systems such as an electrophotographic system, an electrostatic recording system, and an inkjet system have been developed, and high-quality images have been obtained, and they have become widespread.

However, with the improvement and spread of performance, a new problem has arisen that anyone can easily forge bills and securities using a full-color image recording apparatus. In view of this, it has become necessary to equip a recording apparatus with a function of preventing forgery, and recent full-color image recording apparatuses have various anti-counterfeit functions.

The most common method among them is to print a regular dot pattern representing a model code of a recording device on a sheet at the time of printing, and when a forged banknote is found, the banknote is printed. This is a so-called tracking pattern method in which the model number is calculated from the dot pattern hit on the top and the recording device that identifies it is specified.
In addition, since this dot pattern is printed on all the images to be output, it is common to print with yellow, which has the lowest visibility, that is, the least visible.

[0005]

However, in the color image recording apparatus equipped with the above-mentioned conventional tracking pattern system, some trouble or intentional modification is required in the process from generation of the tracking pattern to printing. As a result, if the normal code is not printed, there is a problem that the function of preventing forgery does not work.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a color image recording apparatus capable of surely determining whether or not a tracking pattern for preventing illegal copying has been accurately printed. Is to provide.

[0007]

[Means for Solving the Problems] and

To achieve the above object, the present invention is a color image recording apparatus for electrically processing an image read from a document as a full color image signal to perform a printing process. Means for adding a predetermined recognition signal to the color image signal, means for recording the image data to which the recognition signal is added on a recording medium, and the recognition signal recorded on the recording medium for the printing process. A reading means for reading at a predetermined stage is provided.

In the above structure, it functions to check whether or not the tracking pattern is hit correctly.

Further, according to another invention, further, means for reading a specific color density in each of the plurality of areas, means for creating a density correction table based on the color density, and based on the density correction table And a means for converting the density of the color image signal.

As a result, uneven density is corrected and the image quality is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In the following embodiments, an image recording apparatus using a color electrophotographic technique will be described as an example. In the following embodiments, the input density levels are M (magenta), C (cyan), Y (yellow), and
It is assumed that each color of BK (black) is sent in 8 bits and is sent in frame order. Furthermore, it is assumed that the tracking pattern is struck only by the Y plane. <First Embodiment> FIG. 1 is a diagram showing a sectional structure of a color image recording apparatus (hereinafter referred to as a recording apparatus) according to a first embodiment of the present invention. In the recording device shown in FIG.
The photosensitive drum 100 is uniformly charged with a predetermined polarity by 1, and the first latent image of magenta, for example, is formed on the photosensitive drum 100 by exposure with the laser beam light L. Then, in this case, the magenta developing unit D
A required developing bias voltage is applied only to m, the magenta latent image is developed, and the magenta first toner image is formed on the photosensitive drum 100.

On the other hand, the transfer paper P is fed at a predetermined timing, and a transfer bias voltage (-1.8 KV) having a polarity opposite to that of the toner (eg, positive polarity) is transferred immediately before the leading edge of the transfer paper P reaches the transfer start position. The first toner image on the photosensitive drum 100 is transferred to the transfer paper P by being applied to the drum 102, and the transfer paper P is electrostatically attracted to the surface of the transfer drum 102. After that, from the photosensitive drum 100,
The magenta toner remaining on the cleaner 103 is removed to prepare for the next latent image formation and development process.

Next, a second latent image of cyan is formed on the photosensitive drum 100 by the laser beam L, and the second latent image on the photosensitive drum 100 is developed by the cyan developing device Dc. A cyan second toner image is formed. Then, the cyan second toner image is transferred to the transfer paper P in alignment with the position of the magenta first toner image previously transferred to the transfer paper P. In transferring the toner image of the second color, immediately before the transfer paper reaches the transfer portion,
A bias voltage of +2.1 KV is applied to the transfer drum 102.

Similarly, the third and fourth latent images for yellow and black are sequentially formed on the photosensitive drum 100.
Are formed, and each is sequentially developed by the developing devices Dy and Db. Then, the yellow and black third images are aligned with the toner image previously transferred to the transfer paper P.
The fourth toner images are sequentially transferred, and as a result, four color toner images are formed on the transfer paper P in an overlapping state. Further, at the time when yellow is transferred, the scanner 104 measures the density of yellow in a predetermined area.

Next, the tracking pattern printed by the recording apparatus according to this embodiment will be described.

FIG. 2 is a diagram showing the principle of printing the tracking pattern in this embodiment. It should be noted that this recording apparatus is 600
Printing is performed with a resolution of dpi (dots / inch).

One square in FIG. 2 represents one pixel, and for the 6 × 6 pixels in the shaded portion 201, the density is added to the original image data by 256 gradations, and 3 on both sides thereof.
For the portion 202 of x6 pixels, the density is reduced by α. This keeps the overall average density. Also, as a result of the processing, when the density is 255 or more, it is set to 255,
When it is less than 0, it is set to 0.

Here, the region of 12 × 6 pixels formed by the shaded portion 201 and the side portions 202 is one dot. These dots are struck at regular intervals in the main scanning direction, and in this embodiment, this interval is 102 pixels. And the 6th line where this dot is hit is the 0th line,
Call the first line, ....

Next, a 12-line interval is opened in the sub-scanning direction from the 0th line on which dots are printed, and the next 1st line and 2nd line are printed, and after the 15th line is printed,
The same thing is repeated from the 0th line again. Where the nth
The horizontal phase difference (main scanning direction) between the dot position of the line and the dot position of the (n + 1) th line represents one digit of the machine number of the recording apparatus.

FIG. 3 is a diagram showing the phase difference of the tracking pattern according to this embodiment. Here, as shown in the figure, the phase difference can take from 0 to F in hexadecimal, so
There can be 16 values from 0 to F per digit.
Therefore, these dots can represent a 16-digit hexadecimal number, that is, a machine number having a 64-bit length.

FIG. 4 is a diagram showing an example of printing a tracking pattern according to this embodiment. In the figure, two dots are arranged on the 0th line, but the dot located on the right is the 0th line.
It is a mark for indicating the position of the line. In this embodiment, the length of one cycle is 192 in the main scanning direction as described above.
The number of pixels is 12 × 16 = 192 lines in the sub-scanning direction. Since this pattern is printed on all the printed images, it is printed only on the yellow plane with low visibility.

Next, there will be shown a configuration for setting the tracking pattern as described above.

FIG. 5 is a block diagram showing a configuration from receiving the RGB image signal from the controller unit constituting the apparatus according to the present embodiment to transmitting it to the printing unit. In the following description, yellow, magenta, cyan and black are represented as Y, M, C and BK.

First, the color processing unit (hereinafter referred to as the color conversion processing unit) 501 will be described. This color conversion processing unit 5
At 01, the R, G, B signals 513 and the color designation signal 516 are received. In this recording device, as described above, Y, M,
Since one pixel is printed for each color of C and BK, the image data is frame sequential, that is, data for one pixel of M, data for one screen of C, data for one screen of Y, data for one screen of BK. Send in order.

Therefore, in the color conversion processing unit 501, RGB
First, the image data for one screen is converted pixel by pixel into an 8-bit VDO (video) signal of the M signal. Then C
The signal, the Y signal, and the BK signal are converted in this order. Masking and UCR processing are added during this conversion. Color conversion processing unit 5
In 01, the input RGB signals are converted into M, C, Y and BK.
Which color data to convert is designated by a color designation signal 516 sent from a formatter unit (not shown). That is, the color designation signal 516 first designates M, and the designation is changed in the order of C, Y, BK every time data for one screen is sent.

The density correction unit 502 receives an 8-bit image signal of M, C, Y, and BK, and adds a correction to the signal according to the output characteristics of the printing unit. The signal converted by the density correction unit is input to the tracking pattern addition unit 503.
Further, the ROM 504 stores a 64-bit length code representing the model number of the recording apparatus, and the code is input to the tracking pattern generation circuit 505 as a code signal 514.

The tracking pattern generating circuit 505 generates a tracking pattern according to the code signal 514 and inputs the pattern to the tracking pattern adding section 503. The tracking pattern adding unit 503 adds the tracking pattern to the input video signal only when the color specifying signal 516 specifies Y, and does not add to M, C, and BK.

The video signal of each color subjected to such processing is input to the PWM (pulse width modulation) unit 506. In the PWM unit 506, the input 8-bit image signal is input to the image clock PCLK5 by the latch circuit 507.
The signal is input to the analog comparator 509 after being synchronized with the rising edge of 15 and converted into an analog voltage by the D / A converter 508 in the next stage.

On the other hand, the triangular wave generator 511 generates a triangular wave of a predetermined cycle based on the image clock 515 and inputs it to the analog comparator 509. The analog comparator 509 compares the above analog voltage with the two signals of this triangular wave, and outputs a PWM-controlled signal.
Then, the signal is inverted by the inverter 510 to obtain a predetermined PWM signal.

It should be noted that the triangular wave generator 511 according to the present embodiment.
Then, the frequency (number of lines) of the triangular wave is 600 lines and 200 lines.
The signal of the line is generated so that when the analog comparator 509 is compared, the wavelength of each is 1/60.
0 inch and 1/200 inch triangular waves are used.

Further, in the PWM unit 506, the line number changeover switch 517 is changed over by the line number changeover signal 512 inputted from a controller unit (not shown), so that 600 lines and 2 lines outputted from the triangular wave generating unit 511 can be obtained.
Which signal of the triangular wave of the 00 line is input to the analog comparator 509 is selected.

FIG. 6 is a diagram showing the operation of the scanner with respect to the tracking pattern that is driven in as described above.
The scanner 601 shown in the figure is located in the scanner 104 shown in FIG. 1 and has a resolution of 400 dpi.

When the received color designation signal 602 designates Y, the scanner 601 of FIG. 6 reads only the density of yellow in the shaded portion in FIG. 7 of the paper on the transfer body at 400 dpi. . At this time, the three colors Y, M, and C are placed on the sheet, but since black is not yet placed, it is easy to accurately read only yellow.

The starting point of this reading is set in advance so as to match the position of the dot on the 0th line of the tracking pattern, and the reading range is one cycle of the tracking pattern in both the main scanning direction and the sub-scanning direction. The upper part of the sheet is read here for the purpose of determining the pattern earlier and for reducing the error in the read start position.

In the image thus read,
As shown in FIG. 8, dots for one cycle of the tracking pattern are included. Then, this image is the matching unit 603.
And is input to the RAM in the matching unit (not shown). Further, as described above, the interval of one cycle of the tracking pattern in this embodiment is 60 in both the main scanning direction and the sub scanning direction.
There are 192 pixels at 0 dpi, and since this is read at 400 dpi, the size of this image is 128 × 128 = 1.
It is 6384 bytes. Therefore, the RAM capacity is about 1
If 6K bytes is left, it will be good.

Reference numeral 604 is the ROM 504 shown in FIG. 5, and the machine number stored therein is also input to the matching unit 603. Then, the matching unit 603 calculates the position of the dot in the input image from the input machine number, and checks whether or not the dot is hit at that position in the image.

In this way, the 16 dots are checked, and if all 16 dots have been hit at the predetermined positions, the signal 606 is sent to the control unit 605 as "1", and If no dots are hit,
The signal 606 is sent as "0".

That is, if the tracking pattern is normally printed, the signal 606 should be sent as "1", and at this time, the control unit 605 continues the printing operation as it is. However, if the tracking pattern is not normally entered, the signal 606 is sent as "0", and at this time, the printing unit is in the middle of the black printing operation, but the control unit 605
Then, when the status of the signal 606 becomes "0", the printing operation is stopped.

As described above, according to this embodiment,
There is some trouble in the process from the generation of the trace pattern to the printing, by determining whether or not the trace pattern is normally struck by reading the paper with the scanner after the trace pattern is struck. Even if the process is intentionally modified, the anti-counterfeit function based on the tracking pattern can be sufficiently realized. <Second Embodiment> Next, a second embodiment according to the present invention will be described. Also in the case of the present embodiment, the configuration until the tracking pattern is driven is the same as that of the above-described first embodiment, and the method of hitting the tracking pattern is also the same.

FIG. 9 is a block diagram showing the structure of the present embodiment up to receiving the RGB signals and passing the signals to the laser drive section. Here, the flow of data from the scanner to the density correction unit 901 and the internal configuration of the density correction unit 901 will be described. In addition, in FIG.
The same components as those in the configuration block diagram according to the first embodiment shown in FIG.

Generally, in an image recording apparatus, if the image data is output without performing the density correction, the relationship between the image data and the output density becomes non-linear as shown in FIG. 10, and the desired density cannot be obtained. Therefore, by converting the data according to the thick curve shown in FIG. 11, the input data and the output density can be kept linear as shown by the broken line in FIG. Hereinafter, this data conversion will be referred to as γ correction.

However, even if the correction is performed once, the linearity described above may be subtly broken due to a change in process conditions during printing. Further, due to the uneven density, the density of the printed paper changes significantly in the vertical and horizontal directions, and it is not possible to maintain the linearity in each part of the paper with a single data conversion.

Therefore, in the present embodiment, as shown in FIG. 12, nine γs from γ1 to γ9 for each area of the sheet.
Prepare a correction table. Specifically, in this embodiment,
The scanner has a resolution of 600 dpi, and at the time of scanning, the density of yellow in the areas denoted by reference numerals 1201 to 1209 in FIG. 12 is sequentially read.

Each of these areas 1201 to 1209 is
It has a range of 14 × 8 pixels at 600 dpi and is set to match the dot position of the 0th line of the tracking pattern. Therefore, in each area of 1201 to 1209,
The dots shown in 3 are read.

First, the image read in the area 1201 is sent to the average value calculation unit 903 after the reading error is corrected by the error correction unit 902 in FIG. In this average value calculation unit 903, 130 in FIG.
The average value of each of the areas 1, 1302, 1303 is calculated, and the result is sent to the density correction unit 90. At the same time, the area designation signal is set and sent to indicate the area 1201. The above operation is also performed on regions 1202-1209.

FIG. 14 shows the density correction unit 9 in this embodiment.
3 is a block diagram showing the internal configuration of 01. FIG. Note that, here, the average values of the regions 1301 to 1303 of FIG. 13 are D1, D2, and D3, respectively.

The above D1, D2, D3 and the area designation signal are input to the γ calculation section 1401 while the Y, M, C and BK signals 1 input from the color processing section (see FIG. 9).
In contrast to 406, selector 1402 has counter 140
From the value of 3, it is determined which region of γ1 to γ9 the data is in FIG. 12, and if it is γ1, go to the γ1 table,
If it is 2, the data is sent to the table 1404 such as to the γ2 table, and density conversion suitable for the area is performed.

Further, the selector 1402 has a region 1201.
Of the original, that is, the yellow data before density correction and tracking pattern processing are added,
While specifying, follow the instruction of counter 1403
The data is input to the data buffer 1405 for 1 and the data is γ
The data is added in the 1-data buffer 1405. In this γ1 data buffer 1405, 14 × 8 of the area 1201
After adding all the data, the average value is calculated and the average value is stored.

Similarly, the average values of the areas 1202 to 1209 are stored in the γ2 to γ9 data buffer.

In the γ calculation section 1401, D1 to
For example, when the area 1201 is specified by the area specifying signal for the data of D3, the value of the data buffer for γ1 (hereinafter, this is referred to as D0) is read and compared with D1 to D3, The value of the γ1 table 1404 is rewritten.

Here, a method of γ correction will be described.

When the density is correctly corrected, the input density level and the density level read by the scanner (output density level) are linear as shown by the characteristic 1502 in FIG. The density D3 read by the scanner is almost the same as the original density data D0
Represents the actual output concentration for. Similarly, D1 represents the actually output densities for D0-a and D2 for D0 + a. Therefore, it is estimated that the actual concentration curve has a characteristic 1501 shown in FIG.

The γ calculator 1401 rewrites the γ table so that the density curve 1501 approaches the characteristic 1502.
The same operation as described above is performed on the γ tables γ2 to γ9 to correct the γ table in each region.

As described above, according to this embodiment,
By correcting the density unevenness on the top, bottom, left and right of the paper based on the density of the scanned tracking pattern, density correction using the tracking pattern can be realized, and a stable gray image is always formed regardless of density unevenness and changes in process conditions. As a result, the image quality can be improved.

Although the tracking pattern is used in this embodiment, it goes without saying that a dot or patch for the purpose of γ correction may be printed in the image instead of the tracking pattern and used.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0058]

As described above, according to the present invention,
By scanning the recording medium after the tracking pattern has been driven and determining the pattern, it is possible to reliably determine the tracking pattern to be driven and prevent illegal copying based on the tracking pattern.

According to another aspect of the invention, a stable image can be formed by performing density conversion using the density of the tracking pattern.

[0060]

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a color image recording apparatus according to a first embodiment of the invention.

FIG. 2 is a diagram showing a principle of printing a tracking pattern in the embodiment.

FIG. 3 is a diagram showing a phase difference of a tracking pattern.

FIG. 4 is a diagram showing an example of printing a tracking pattern.

FIG. 5 is a block diagram showing a configuration from receiving an RGB image signal from a controller unit to transmitting the RGB image signal to a printing unit.

FIG. 6 is a block diagram of a tracking pattern determination unit according to an embodiment.

FIG. 7 is a diagram showing a reading range with a scanner.

FIG. 8 is a diagram showing an example of an image read by a scanner.

FIG. 9 is a block diagram showing a configuration of a multi-value processing unit according to a second embodiment, which receives RGB signals and passes the signals to a laser drive unit.

FIG. 10 is a diagram showing the principle of density correction of the second embodiment.

FIG. 11 is a diagram showing the principle of density correction of the second embodiment.

FIG. 12 is a diagram showing a reading range of the scanner in the second embodiment.

FIG. 13 is a diagram showing an example of an image read by the scanner of the second embodiment.

FIG. 14 is a block diagram showing an internal configuration of a density correction unit according to the second embodiment.

FIG. 15 is a diagram showing the principle of density correction in the second embodiment.

[Explanation of symbols]

 100 photoconductor drum 101 charger 102 transfer drum 103 cleaner 104 scanner 501 color processing unit 502 density correction unit 503 tracking pattern addition unit 504 ROM 505 tracking pattern generation circuit 513 R, G, B signals 514 code signal 516 color designation signal 1401 γ Calculation unit 1402 Selector 1403 Counter 1404 γ table 1405 γ data buffer

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Claims (8)

[Claims] 1. A color image recording apparatus for electrically processing an image read from a document as a full color image signal to perform a printing process, wherein a predetermined recognition signal for a specific color image signal in the full color image signal. A recording means for recording the image data to which the recognition signal is added to a recording medium, and a reading means for reading the recognition signal recorded on the recording medium at a predetermined stage of the printing process. A color image recording device characterized by. 2. The color image recording apparatus according to claim 1, wherein the predetermined recognition signal is a signal representing a machine number unique to the color image recording apparatus. 3. The color image recording apparatus according to claim 1, further comprising means for determining whether or not the added recognition signal and the recognition signal read in the predetermined step match. 4. If the added recognition signal and the recognition signal read in the predetermined step do not match each other, the printing process after the predetermined step is prohibited. The color image recording device described in 1. 5. The recognition signal is added to a plurality of areas on the recording medium, and the reading unit reads the recognition signal for each area of the plurality of areas. The color image recording device described in 1. 6. The color image recording apparatus according to claim 1, wherein the specific color image signal is yellow. 7. A means for reading a specific color density in each area of the plurality of areas, a means for creating a density correction table based on the color density, and the color image based on the density correction table. 6. The color image recording apparatus according to claim 5, further comprising means for converting a signal density. 8. The color image recording apparatus according to claim 7, wherein the specific color density is a density of yellow.