JPH0879512A - Image forming device - Google Patents

Abstract

PURPOSE: To quickly permit the formation of an image for an original on which no copy prohibiting mark is printed by detecting first the copy prohibiting mark with low detection accuracy and detecting the copy prohibiting mark with raised detection accuracy when the copy prohibiting mark is detected. CONSTITUTION: The original from which no copy prohibiting mark is detected by resolution of, for example. 200dpi by a copy prohibiting mark detecting means 131 is Judged as the one on which copying can surely be performed, and a copy operation can be quickly permitted to a print head part 31. One the other hand, when the copy prohibiting mark is detected, the detection of the copy prohibiting mark is performed again by raising reading resolution to 400dpi considering an erroneous detection. When the copy prohibiting mark is detected, the print head part 31 performs in invalidating processing to paint out copy paper in black. Also, when no copy prohibiting mark is detected. it is judged as the erroneous detection, and the copy operation is permitted to the print head part 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a digital copying machine having a function of preventing forgery of bills and the like.

[0002]

2. Description of the Related Art As the accuracy of digital color copying machines has improved, how to effectively prevent counterfeiting of banknotes has become a problem. To deal with this, JP-A-55-
In the copying machine disclosed in Japanese Patent No. 111977, the image data of copy prohibited objects such as banknotes, checks and securities are stored in advance, and the image data of the document and the image data of the copy prohibited objects are stored during the copying operation. Pattern matching with. Here, if it is determined that the original document is a copy prohibited item, image formation on the copy paper is prohibited. In addition,
In addition to the above, coupons, various tickets, stamps, revenue stamps, parking tickets, etc. correspond to the copy prohibited items. In addition, JP-A-2-
In the image recording apparatus described in Japanese Patent No. 73283, the image data of the copy-prohibited object such as the banknote, check, and securities is stored in advance, and the image data of the document and the copy-prohibited object are stored during the copying operation. Performs pattern matching with image data. Here, if it is determined that the original document is a copy prohibited item, an invalidation process such as blackening the image printed on the sheet until then is executed.

However, the above-mentioned copying machine requires a large-capacity memory for storing the image data of each copy-inhibited object such as a banknote, a check, and a securities for which copying is prohibited. In addition, since bills and the like are regularly wicketed, it is difficult to deal with them completely. The conventional model in which the image data of the new bill is not input cannot prevent the forgery of the new bill. Some banknotes have light colors or very fine lines forming an image, and it is difficult to reliably recognize these images without erroneous recognition. In addition, it is difficult to deal with only banknotes completely, but securities and checks have different designs in banks and the like even in the same country, and it is more difficult to deal with them than banknotes.

Therefore, a mark for prohibiting copying is printed at a plurality of locations on the surface of a bill printed with process ink or the like, and at the time of copying, for example, two or more copying prohibition marks are provided from the original. A system has been proposed that prohibits or cancels the copying operation when detected. FIG. 1 (a)
Is an example of a mark indicating copy prohibition (hereinafter, this is referred to as a copy prohibition mark). The copy prohibition mark is composed of a circle 1 and a "prohibited" character 2 printed inside the circle 1. FIG. 1B is an example in which the copy prohibition mark shown in FIG. 1A is printed on a plurality of places of a bill. If the above-mentioned copy prohibition mark is used, instead of storing the image data of various copy-prohibited objects for which copying is prohibited, it is only necessary to store the data of the mark, and the total amount of data to be stored in the copying machine body is greatly reduced. can do. In addition, pattern matching for fine patterns such as banknotes is not required, and the time required for the matching process can be significantly reduced. Further, by printing the copy prohibition marks at a plurality of positions on the surface of the original, even if a part of the original is hidden, copying of the original can be prohibited. However, since the above copy prohibition mark is a visible mark,
Forgery can be easily made by pasting paper etc. on the copy prohibition mark part at the time of copying and adding the copy prohibition mark to the corresponding part of the copy obtained by the copy or attaching the copy prohibition mark. be able to.
Moreover, it is difficult to accept the visible mark on a bill or the like because of its design. Therefore, if the above-mentioned copy prohibition mark is overwritten on the surface of the original with a colorless and transparent ink that absorbs a predetermined light beam outside the visible region, the following advantages can be brought about. The solid line graph shown in FIG.
The reflectance (%) of the light of each wavelength (nm) of ordinary ink is shown. Further, the dotted line graph shows the reflectance (%) with respect to a light beam of each wavelength (nm) of a colorless transparent ink that absorbs infrared rays (does not reflect) (hereinafter referred to as infrared ink). In the figure, the shaded area has a wavelength of about 7
It represents a visible region of 00 (nm) or less. As shown in the figure, the normal ink has a light ray outside the visible region of about 70-8.
0 (%) is reflected. The copy prohibition mark printed on a banknote or the like using this colorless and transparent infrared ink is not visually recognized, but is recognized as a negative pattern by a sensor that detects only infrared rays. Since the detection of the copy prohibition mark is not affected by the data in the visible region, it can be performed more accurately. Since the copy prohibition mark printed using this infrared ink is usually invisible, it is possible to prevent fraudulent acts such as printing the mark after the mark is hidden and copied. Further, even when a plurality of copy prohibition marks are printed on the surface of a bill, the display of the description contents such as bills is not restricted, and it is possible to print more than in the case of visible marks, which facilitates detection. There is an advantage such as.

[0005]

A sensor for detecting only infrared rays (hereinafter referred to as an IR sensor) is necessary for recognizing a copy prohibition mark printed on a bill or the like with the colorless and transparent infrared ink. is there. FIG. 3A shows a scanner 31 using a 4-line CCD image sensor 303.
0 is an example. 4-line CCD image sensor 30
As shown in FIG. 3B, 3 is a CCD sensor for R data that reads RGB digital image data, a CCD sensor for G data, a CCD sensor for B data, and an IR.
The sensor is provided in parallel. The reflected light of the original 300 exposed by the exposure lamp 301 is focused on the 4-line CCD sensor 303 by the rod lens array 302. The scanner 310 moves in the direction of the arrow and reads the RGB digital image data of the original, and at the same time, reads the infrared data. According to this configuration, it is impossible to easily carry out the camouflage work such as blocking the reflected light incident on the IR sensor or cutting the circuit of the IR sensor to make it impossible to detect the copy prohibition mark. However, if a photo of a document on which a copy prohibition mark is printed with infrared ink is taken and a copying operation is performed using the taken photo as a document, the copy prohibition mark printed with infrared ink will not be detected and There is a risk that banknotes will be forged.

An object of the present invention is to provide an image forming apparatus that detects a copy prohibition mark printed on a document more accurately and reliably prevents forgery.

[0007]

In the image forming apparatus of the present invention, a reading unit for reading image data of an original, a memory for storing a copy prohibition mark, and a sheet for printing on a sheet based on the image data read by the reading unit. An image forming unit that forms an image, a detection unit that can read the data of the copy prohibition mark from the memory, and that detects the copy prohibition mark from the image data read by the reading unit, and a switchable detection accuracy, and a low detection accuracy. When the copy prohibition mark is detected by the detection means, and when the copy prohibition mark is detected, the detection means is again made to detect the copy prohibition mark with high detection accuracy, and after the detection accuracy is increased, the copy is performed by the detection means. A control unit is provided which prohibits the image forming unit from forming an image on the sheet when the prohibition mark is detected.

[0008]

The control means of the image forming apparatus of the present invention does not immediately prohibit the image forming means from forming an image on the sheet when the copy prohibiting mark is detected by the detecting means, but first, it is low. Roughly detect the copy prohibition mark with the detection accuracy. When the copy prohibition mark is detected, the detection accuracy of the detection means is increased and the detection means is made to detect the copy prohibition mark again. Even if the detection accuracy is increased, the formation of an image on a sheet by the image forming unit is prohibited for a document in which the copy prohibition mark is detected. in this way,
By switching the detection accuracy of the copy prohibition mark stepwise, erroneous detection can be prevented, and at the same time, it is possible to quickly permit the formation of an image on a document on which the copy prohibition mark is not printed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital color copying machine of this embodiment will be described below in the following order with reference to the accompanying drawings. (1) Copy prohibition mark (2) Configuration of digital color copying machine (3) Read signal processing unit (4) Copy prohibition mark detection processing

(1) Copy prohibition mark Conventionally, as a device having a function of preventing forgery of copy prohibited items such as banknotes, checks, securities, etc., JP-A-55-111
In the copying machine disclosed in Japanese Patent Publication No. 977, image data of copy prohibited objects such as banknotes, checks and securities are stored in advance, and image data of an original document and image data of the copy prohibited object during a copying operation. Pattern matching with. In the copying machine, when it is determined that the document corresponds to the copy prohibited item, the image formation on the copy paper is prohibited. In addition,
Other than the above, the copy prohibited items include coupon tickets, various tickets, stamps, revenue stamps, parking tickets, and the like. In addition, Japanese Unexamined Patent Publication
In the image recording apparatus described in Japanese Patent Laid-Open No. 73283, image data of copy prohibited objects such as banknotes, checks, securities, etc. is stored in advance, and the image data of the document and the copy prohibited during the copying operation. Pattern matching with the image data of the object is performed. Here, if it is determined that the original document is a copy prohibited item, an invalidation process such as blackening the image printed on the sheet until then is executed.

However, the above-mentioned copying machine requires a large-capacity memory for storing the image data of each copy-inhibited object such as banknotes, checks, securities, etc. for which copying is prohibited. It is difficult to deal completely with bills, etc., since they are regularly ticketed. The conventional model in which the image data of the new bill is not input cannot prevent the forgery of the new bill. In addition, some banknotes have a light color or ones that form an image with very fine lines, and it is difficult to reliably and reliably recognize these images. In this way, it is difficult to fully deal with only banknotes, but securities and checks are
Even in the same country, banks have different designs, which makes it more difficult to handle than banknotes.

Therefore, in the digital copying machine of this embodiment,
The copy prohibition mark is printed on a plurality of places on the surface of the original such as a bill, and the copy prohibition mark is printed from the original at the time of copying.
When one or more are detected, the copy operation is prohibited or stopped.
FIG. 1A shows an example of a copy prohibition mark detected by the copying machine of this embodiment. The copy prohibition mark is composed of a circle 1 and a "prohibited" character 2 printed inside the circle 1.
FIG. 1B is an example in which the copy prohibition mark shown in FIG. 1A is printed on a plurality of places of a bill. If the copy prohibition mark is used, instead of storing the image data of various copy-prohibited objects for which copying is prohibited, only the data of the mark need be stored, and the total amount of data to be stored in the main body of the copying machine is greatly reduced. be able to. In addition, pattern matching for fine patterns such as banknotes is not necessary, and the time required for the matching process can be significantly reduced. Further, by printing the copy prohibition marks at a plurality of positions on the surface of the original, even if a part of the original is hidden, copying of the original can be prohibited. Further, a part of the copy prohibition mark is printed by using a colorless transparent ink that absorbs a predetermined light beam other than the visible region. The reason why all the copy prohibition marks are not printed with the above ink is to allow forgery prevention even when a photograph of a document is taken and the photographed photo is used as a document for copying. The solid line graph shown in FIG. 2 shows the reflectance (%) of the light of each wavelength (nm) of ordinary ink. Further, the dotted line graph shows the reflectance (%) with respect to a light beam of each wavelength (nm) of a colorless transparent ink that absorbs infrared rays (does not reflect) (hereinafter referred to as infrared ink). In the figure, the shaded region represents a visible region having a wavelength of about 700 (nm) or less. As shown in the figure, a normal ink has a light beam outside the visible region of about 70.
Reflects -80 (%). The copy prohibition mark printed on a banknote or the like using this colorless and transparent infrared ink is not visually recognized, but is recognized as a negative pattern by a sensor that detects only infrared rays. Since the detection of the copy prohibition mark is not affected by the data in the visible region, it can be performed more accurately. Since the copy prohibition mark printed with this infrared ink is usually invisible,
It is possible to prevent fraudulent acts such as printing the mark after the mark is hidden and copied. Further, even when a plurality of copy prohibition marks are printed on the surface of a bill, the display of the description contents such as a bill is not restricted. The ink for printing the invisible copy prohibition mark may absorb ultraviolet rays as long as it is a light ray outside the visible region.
However, it is appropriate to use an ink that absorbs infrared rays because ultraviolet rays are attenuated by the platen glass and erroneous detection is likely to occur, and the human body is adversely affected.

(2) Configuration of Digital Color Copying Machine FIG. 4 is a sectional view of the configuration of the digital color copying machine. The digital color copying machine is roughly divided into an image reader unit 100 that reads an original image and a main body unit 200 that reproduces the image read by the image reader unit 100. The scanner 10 includes an exposure lamp 12 that irradiates a document, a rod lens array 13 that collects the reflected light from the document, and a contact-type 4-line CCD that converts the collected light into an electric signal.
The sensor 14 is provided. The 4-line CCD image sensor 14 includes an R data CCD sensor for reading RGB digital image data, a G data CCD sensor, and a B data CCD sensor.
A data CCD sensor and an IR sensor are provided in parallel. The reading resolution of the CCD image sensor 14 is 400 dpi. The IR sensor reads the image data ir in the infrared region. Scanner 10
Is scanned by the motor 11 during document reading, and moves in the direction of the arrow (sub-scanning direction) to scan the document placed on the platen 15. The image of the original surface illuminated by the exposure lamp 12 is photoelectrically converted by the 4-line CCD sensor 14. The 4-line CCD sensor 14 outputs four multivalued electrical signals of r, g, b and ir. The multi-valued electrical signals of the three colors r, g, and b are read by the next read signal processing unit 20 by yellow (Y), magenta (M), cyan (C), and black (Bk).
Of the 256 grayscale data, and is used for the visible copy prohibition mark detection processing. Further, the multi-valued electric signal of ir is converted into 256 gray scale data in the read signal processing section 20, and then subjected to invisible copy prohibition mark detection processing. Print head 3
1 is yellow output from the read signal processing unit 20
256 grayscale data of any one of (Y), magenta (M), cyan (C), and black (Bk) is subjected to dithering as necessary, and the corrected image data is D / D. The laser diode drive signal is generated by A conversion, and the laser diode in the print head unit 31 is driven by this drive signal.

The print head unit 3 corresponding to gradation data
The laser beam emitted by the laser diode in 1 exposes the photosensitive drum 41, which is rotationally driven, via the reflecting mirror 37. As a result, an image of the original is formed on the photoconductor of the photoconductor drum 41. The photoconductor drum 41 is irradiated with an eraser lamp 42 and charged by a charging charger 43 before being exposed for each copy. When exposed in this uniformly charged state, an electrostatic latent image is formed on the photosensitive drum 41. Only one of the yellow, magenta, cyan, and black toner developing devices 45a to 45d is selected to develop the electrostatic latent image on the photosensitive drum 41. The developed image is transferred by the transfer charger 46 onto the copy paper wound around the transfer drum 51.

The above printing process is repeated for yellow (Y), magenta (M), cyan (C) 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. After that, 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 discharge tray 49. The copy paper is fed from the paper cassette 50, and its tip is chucked by the chucking mechanism 52 on the transfer drum 51 so that the positional deviation does not occur during transfer. It should be noted that it takes time for the copy prohibition mark detection processing in the copy prohibition mark detection unit 131 described later, and cyan (C), magenta (M), yellow (Y), and black (Bk) are detected before the detection processing ends. When the four-color printing process is completed, the copy paper is temporarily held without being separated from the transfer drum 51, and processing is performed according to the result of the detection processing. That is, when the copy prohibition mark is detected, as the fifth color printing step, the black toner is used to blacken the copy paper, and then the fixing and discharging are performed. When the copy prohibition mark is not detected, the copy paper is separated from the transfer drum and fixed and discharged.

(3) Description of Read Signal Processing Unit FIG. 5 is a block diagram of the read signal processing unit 20 shown in FIG. The r-, g-, and b-color multivalued electric signals and the ir multivalued electric signals obtained by the 4-line CCD image sensor 14 are first amplified and optimized by the analog processing unit 121. The A / D conversion unit 122 after
Are converted into multivalued digital signals of R, G, B and IR respectively. The digital signal output from the A / D conversion unit 122 is converted into a serial signal by the serial signal conversion processing unit 123, and then input to the shading correction unit 124. The shading correction unit 124 executes shading correction based on the RGB digital image data. CCD
The image sensor 14 is composed of four-line CCD sensors arranged at a predetermined interval, and each RGB data to be read has a timing shift. The shading-corrected data is corrected by the sensor window position correction unit 125 so that the timing shift is corrected and the data is synchronized. The position-corrected R, G, B, and IR data are stored in the reflectance / density conversion unit 12
6 is input. The reflectance / density conversion unit 126 converts the reflectance data R, G, B, IR data into 256 grayscale data DR, DG, DB, DIR data. The DR, DG, and DB data are output to the UCR / BP masking processing unit 127 and the copy prohibition mark detection unit 131. The DIR data is input to the copy prohibition mark detection unit 131. The DR, DG, and DB data input to the copy prohibition mark detection unit 131 is stored in the RAM 134 via the visible pattern matching unit 132. Further, the DIR data is stored in the RAM 137 via the invisible pattern matching unit 133. RA
M135 and 136 store visible and invisible copy prohibition mark data. The control unit 138 controls the copy prohibition mark detection processing in the copy prohibition mark detection unit 131. The process of detecting the copy prohibition mark in the copy prohibition mark detection unit 131 will be described later. UC
In the R / BP masking processing unit 127, DR, DG, D
After converting the B data into 256 grayscale data of cyan (C), magenta (M), yellow (Y), and black (Bk), in order to improve the reproducibility of black, C is applied to the black portion. , M, Y data values are removed (UCR process), and black (Bk) grayscale data is added instead (BP process). After that, in consideration of the reading characteristics of the CCD image sensor 14 and the adhesion characteristics of the toner to the copy paper, a predetermined masking process is performed so that the same color as the original is reproduced on the copy paper, and then the printing process is performed. Output color data. The data of any one of C, M, Y, and Bk output from the UCR / BP masking processing unit 127 is subjected to spatial filter processing such as smoothing and edge enhancement in the MTF correction unit 128. The scaling movement processing unit 129 uses the data from the MTF correction unit 128 to execute a predetermined scaling movement processing according to the set copy magnification and edit contents. The γ correction unit 130 performs a predetermined gradation correction on the input data, and then executes the gradation correction via the buffer 30 (not shown).
Output to. The printer head unit 31 D / A-converts the input grayscale data to generate a semiconductor laser drive signal, and causes the semiconductor laser to emit light by this drive signal to expose the photosensitive drum 41. However, when the value of the prohibition flag F input from the copy prohibition mark detection unit 131 is 1, cyan (C), magenta (M), and yellow (Y) data are converted to pure white data (value of gradation data). Is changed to 0), the black (Bk) data is changed to pure black data (the value of the gradation data is 255), and the copy paper is painted black.

(4) Copy Prohibition Mark Detection Processing In the copy prohibition mark detection unit 131, first, the copy inhibition mark printed on the copy inhibition original document using infrared ink is used as the copy inhibition mark 20.
Detection is performed with a reading resolution of 0 dpi. In the copying machine of the present embodiment, the data read at the read resolution of 400 dpi is halved and used. The invisible copy prohibition mark printed with the infrared ink is recognized as a negative pattern, and unlike the case of the copy prohibition mark printed with normal process ink, there is no data that is erroneously detected. Therefore, it is possible to perform detection with sufficient accuracy and speed even at a resolution of 200 dpi. When the copy prohibition mark printed with the infrared ink is detected, the print head unit 31 is caused to execute the invalidation processing for painting the copy paper black. When the copy inhibition mark printed with the infrared ink is not detected, the visible copy inhibition mark printed with the normal process ink is detected at the reading resolution of 200 dpi. In the copying machine of this embodiment, 400 dpi
The data read at the reading resolution of is thinned out to half. On the original, there are relatively many figures similar to the copy prohibition mark printed with normal process ink. If the reading resolution is 200 dpi,
A figure similar to the copy prohibition mark on the original may be erroneously detected as a copy prohibition mark. However, increasing the detection accuracy from the beginning to 400 dpi for detection is not preferable from the viewpoint of processing time and memory capacity. In other words, it is possible to determine that the document in which the copy prohibition mark is not detected is a document that can be surely copied, and the print head unit 31 can be quickly permitted to perform the copy operation. On the other hand, when the copy prohibition mark is detected, the reading resolution is increased to 400 dpi and the copy prohibition mark is detected again in consideration of the case of erroneous detection. That is, in the detection, the data read at the reading resolution of 400 dpi is used as it is. When the copy prohibition mark is detected, the print head unit 31 is caused to execute the invalidation processing for painting the copy paper black. If the copy prohibition mark is not detected, it is determined that the copy prohibition mark is erroneous, and the print head unit 31 is permitted to perform the copy operation. Note that if it takes time to detect the copy prohibition mark and the four-color printing process of cyan (C), magenta (M), yellow (Y), and black (Bk) is completed before the detection process is completed, The copy paper is temporarily held without being separated from the transfer drum 51, and processing is performed according to the result of the detection processing. That is, when the value of the prohibition flag F is 1, the copy paper is painted black by using black toner in the five-color printing process, and when the value of the prohibition flag F is 0, the copy paper is separated from the transfer drum. Eject the paper.

FIG. 6 is a flowchart of a copy prohibition mark detection process executed by the control unit 138 included in the copy prohibition mark detection unit 131. DR, DG, DB which are RGB image data output from the reflectance / density conversion unit 126
Is input to the visible pattern matching unit 132. The visible pattern matching unit 132 stores the input data in the RAM 134. In addition, the DIR data, which is image data in the infrared region, is the infrared pattern matching unit 1.
33 is input. The infrared pattern matching unit 133 stores the input DIR data in the RAM 137.
After the reading of the data for one screen is completed, the control unit 138 causes the infrared pattern matching unit 133 to execute the detection process of the copy prohibition mark printed with the infrared ink. The infrared pattern matching unit 133 has the ROM 13
The data of the invisible copy prohibition mark is read from 6 (step S100), and the DIR stored in the RAM 137 is read.
Pattern matching is executed using the data at a reading resolution of 200 dpi (step S101). The 200 dpi data used for this detection is the read data of 400 dpi thinned in half. When the invisible copy prohibition mark is detected (YES in step S102), the control unit 138 sets the value of the prohibition flag F to 1 and outputs it to the print head unit 31 (step S110). When the invisible copy prohibition mark is not detected (NO in step S102), the control unit 138 causes the visible pattern matching unit 132 to execute the visible copy prohibition mark detection process. Visible pattern matching unit 13
2 reads the visible copy prohibition mark data from the ROM 135 (step S103), and uses the DR, DG, and DB data stored in the RAM 134 for 200d.
Pattern matching is executed with a pi reading resolution (step S104). The 200 dpi data used in this pattern matching is obtained by thinning the read data of 400 dpi in half. When the visible copy prohibition mark is not detected (NO in step S105), the control unit 138 sets the value of the prohibition flag F to 0 and outputs it to the print head unit 31 (step S10).
9). When the visible copy prohibition mark is detected (YES in step S105), the control unit 138 sets the detection level to the visible pattern matching unit 132 to 400 dpi.
To the reading resolution (using the data read at the reading resolution of 400 dpi as it is), and the visible mark detection processing is executed again (step S10).
8). This is because the visible copy prohibition mark has a relatively large number of similar figures as compared with the invisible copy prohibition mark, and is likely to be erroneously detected. When the visible copy prohibition mark is detected again after raising the detection level to the reading resolution of 400 dpi (step S108).
YES), the control unit 138 sets the value of the prohibition flag F to 1 and outputs it to the print head unit 31 (step S110). Further, when the visible copy prohibition mark is not detected when the detection level is increased to the reading resolution of 400 dpi (NO in step S108), the control unit 1
38 determines that the detection of the visible copy prohibition mark in step S105 is incorrect, sets the value of the prohibition flag F to 0, and outputs this to the print head unit 31 (step S109).

[0019]

In the image forming apparatus of the present invention, the copy prohibition mark is first detected with low detection accuracy, and when the copy prohibition mark is detected, the image forming means immediately forms the image on the sheet. Instead of prohibiting, the detection accuracy of the detection means is increased and the copy prohibition mark is detected again. When the copy prohibition mark is detected again, the image forming unit prohibits the image formation on the sheet. By switching the detection accuracy of the detection means in stages as described above, more accurate detection can be realized, and at the same time, it is possible to quickly output the permission to form the image on the document on which the copy prohibition mark is not printed. .

[Brief description of drawings]

FIG. 1A shows an example of a copy prohibition mark,
(B) shows an example when a plurality of copy prohibition marks are printed on a bill.

FIG. 2 shows a reflection characteristic curve of a normal process ink, and a dotted line shows a reflection characteristic curve of ink that absorbs infrared rays.

3A shows a scanner equipped with a 4-line CCD image sensor, and FIG. 3B shows the 4-line CCD.
It is a figure which shows the structure of an image sensor.

FIG. 4 is a sectional view showing the configuration of a digital color copying machine.

5 is a diagram showing each processing unit that constitutes the read signal processing unit 20. FIG.

FIG. 6 is a diagram showing a flowchart of copy prohibition mark detection processing executed by a control unit 138 included in the copy prohibition mark detection unit 131.

[Explanation of symbols]

 14 ... CCD image sensor 31 ... Print head part 131 ... Copy prohibition mark detection part 132 ... Visible pattern matching part 133 ... Infrared pattern matching part 134, 136 ... RAM 135, 137 ... ROM 138 ... Control part

Claims (1)

[Claims] 1. A reading unit for reading image data of an original, a memory for storing a copy prohibition mark, an image forming unit for forming an image on a sheet based on the image data read by the reading unit, and a copy from the memory. The data of the prohibition mark is read, and the detection of the copy prohibition mark is performed from the image data read by the reading means. The detection means can switch the detection accuracy, and the detection means executes the detection of the copy prohibition mark with low detection accuracy. When the copy prohibition mark is detected, the detection means is made to detect the copy prohibition mark again with high detection accuracy,
An image forming apparatus comprising: a control unit that prohibits the image forming unit from forming an image on a sheet when a copy prohibition mark is detected by the detecting unit after increasing the detection accuracy.