JPH0766931A - Image forming device - Google Patents

Abstract

PURPOSE:To effectively prevent paper money, etc., from being forged by discriminating whether fed copying paper is plain paper or OHP paper, and writing in tracking information in the case of plain paper. CONSTITUTION:A discriminating means for copying paper is constituted of a lamp 70 provided in a transfer drum 51 and a photodetector 71, and a light transmission system, light is cut off, in the case the copying paper is plain paper, and light transmits through, in the case it is OHP paper. Also, paper is discriminated in several parts in the passing-through direction of paper and the direction vertical to the passing-through direction of paper, and the plain paper or the OHP paper is discriminated surely. In the case it is discriminated that the fed copying paper is plain paper, a memory in which tracking information is accessed by a control means, data of the tracking information is read out, added to image data of a document image and outputted. In the case is discriminated that the copying paper is OHP paper which is not used for forgery, the access to the memory in which the tracking information is stored is inhibited.

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 having a forgery preventing function for bills and the like.

[0002]

2. Description of the Related Art In recent years, a high-quality digital color copying machine that provides a copy faithful to an original image has been put into practical use, and there is a fear that banknotes and securities will be easily copied and forged. Countermeasures against counterfeiting, such as determining whether the document set on the document table is copy prohibited or not, stop the copying operation or prevent normal copying. Function is considered. However, it is not possible to memorize all these characteristics and perform pattern matching to prohibit copying for manuscripts such as banknotes, securities, TCs, checks, and official documents in the world that you want to prevent.
It is practically impossible due to storage capacity, processing time, new bill support, etc.

Therefore, although copying itself cannot be prohibited, a special cipher (tracking information) which is not normally visible is written in the copied copy itself, and the manufacturer's model name of the machine used for the copy, serial number. , Date and time of copying, management card No. There are copiers that have the function of specifying or part of them. 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 the block in which the tracking pattern is written is represented. There is a technique of repeatedly writing on a copy paper (hereinafter referred to as a hard copy) on which an original image is copied. Product name, serial number. Is performed by extracting the trace pattern written in the block. As for the range to write the above yellow dots, it is not known where on the platen the illegal copy prohibited manuscripts (banknotes, stamps, revenue stamps, securities, etc.) are placed. The entire image area obtained by Also, it is possible to cut out a part of the hard copy and use the size of the block where the trace pattern is written as much as possible so that even small things such as stamps and revenue stamps can be analyzed when cut out. It is desirable to make it small.

Small yellow dots imprinted in a hard copy as shown in FIG. 1 are seen as reflected light on plain paper and are therefore difficult for the human eye to see. But O
The image printed on the HP paper is projected on the projection screen by the projector. The yellow dots that are printed on the OHP paper block the light of the projector and are therefore displayed as blackish dots (noise) on the projection screen. In addition, it is unlikely that OHP paper will be used to forge bills, securities, and the like. Therefore, the copy paper is OHP
In the case of paper, it is desirable to prohibit writing of yellow dots in the hard copy. In order to deal with this, whether the fed copy paper is plain paper or OH
It is necessary to judge whether it is P paper. Further, it is necessary to confirm that the copy paper has been fed to the transfer drum before the above determination.

The detection of the presence or absence of the fed copy paper is carried out by the transparent electrostatic sheet 5 provided on the transfer drum 51 as shown in FIG.
This is performed by using a pair of lamp 70 and light receiving element 71 (hereinafter, referred to as a sheet detector) with 3 sandwiched therebetween. The light receiving element 71 outputs a high level signal when receiving the light from the lamp 70. As shown in FIG. 3, after holding the copy sheet fed by the gripper 52, the copy sheet held by the gripper 52 is moved in synchronization with the leading edge of the copy sheet crossing the sheet detector. Operate (hereinafter referred to as first detection). Here, when plain paper is fed to the transfer drum 51, the light of the lamp 70 is blocked and the output signal of the light receiving element 71 changes to a low level. By checking this change, it is possible to judge whether or not the copy paper is fed to the transfer drum. However, when the copy sheet fed to the transfer drum 51 is an OHP sheet, the OHP sheet is transparent, and therefore the presence thereof cannot be detected by a transmissive sensor such as the sheet detector. Therefore, as shown in FIG. 4, a tape is attached to the front end, or a front end is painted with opaque ink is used to detect the feeding of the OHP paper to the transfer drum 51.

When it is detected in the first detection that the copy paper is fed to the transfer drum 51, it is determined whether the fed copy paper is plain paper or OHP paper as shown in FIG. Discrimination (hereinafter referred to as second detection)
I do. The second detection is performed by operating the paper detector at the timing shown in FIG. 3 after the first detection. When the fed copy paper is plain paper, the light of the lamp 70 is blocked and the light receiving element 71 outputs a low level signal. When the fed copy paper is OHP paper, the light of the lamp 70 is detected by the light receiving element 71 as it is, and therefore the light receiving element 71 outputs a high level signal. Therefore, by checking the level of the signal output from the light receiving element 71 at this time, it is possible to determine whether the fed copy paper is plain paper or OHP paper.

[0007]

However, in the above-mentioned conventional discrimination method, the above-mentioned paper detection is performed when it is judged whether the fed copy paper is plain paper or OHP paper (second detection). By making a hole in the portion that passes through the container, plain paper can be intentionally misidentified as OHP paper.
Therefore, intentionally prohibiting the writing of the above-mentioned tracking pattern (tracking information) on plain paper may cause counterfeiting of banknotes and securities.

An object of the present invention is to provide an image forming apparatus for surely determining whether the fed copy paper is plain paper or OHP paper.

[0009]

According to another aspect of the present invention, there is provided an image forming apparatus including: a reading unit for reading image data of an original image; a memory for storing tracking information data; and an original image read by the reading unit. When image data is input and access to the memory is permitted, the tracking information data is read from the memory, added to the image data of the original image, and output, and access to the memory is prohibited. Includes a tracking information adding unit for directly outputting the image data of the original image, and whether the fed copy paper is a plain paper or an OHP paper at a plurality of locations of the fed copy paper. When the paper discriminating means for discriminating in step 1 and the paper discriminating means discriminates that the fed copy paper is plain paper, a signal for permitting access to the memory is output to the tracking information adding portion to output the paper. Copying paper another means is paper feeding OHP
When it is determined that the sheet is paper, a toner image is formed based on the control unit that outputs a signal for prohibiting access to the memory to the tracking information adding unit and the image data output from the tracking information adding unit, and the paper is fed. And a printing unit for printing on the copied copy paper.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the paper discriminating means is a in the paper feeding direction on the copy paper fed. And whether the copy paper fed at b points in the direction perpendicular to the paper feed direction, that is, a total of a × b locations, is plain paper,
It is characterized in that it is checked whether it is OHP paper.

[0011]

According to the image forming apparatus of the present invention, the image data of the original image is read by the reading means. Next, whether the copy paper fed by the paper discrimination means is plain paper,
Alternatively, whether the sheet is an OHP sheet or not is determined at a plurality of places on the fed copy sheet. When the paper discriminating means discriminates that the fed copy paper is plain paper, the control means sends a signal permitting access to the memory storing the trace information to the trace information adding section. When the paper discriminating means discriminates that the fed copy paper is an OHP paper, a signal for prohibiting access to the memory is sent to the tracking information adding portion. When the image data of the document image read by the reading unit is input to the tracking information adding unit and the access to the memory is permitted, the tracking information data is read from the memory and converted into the image data of the document image. Add and output. If access to the memory is prohibited, the image data of the input original image is output as it is. The printing unit forms a toner image based on the image data output from the tracking information adding unit and prints the toner image on the fed copy paper.

The image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the paper discriminating means is a in the sheet feeding direction on the copy sheet fed.
And b pieces in a direction perpendicular to the paper feeding direction, that is, a total of a ×
It is checked whether the copy paper fed at the b locations is plain paper or OHP paper.

[0013]

EXAMPLE The image forming apparatus according to the present embodiment surely discriminates (detects) plain paper from OHP paper by detecting the type of copy paper at several places (paper passing direction and the direction perpendicular thereto). To do. If the fed copy paper is plain paper, the manufacturer's model name of the machine used, serial number. The tracking information such as is represented by the arrangement shape of yellow dots in a predetermined block (hereinafter, referred to as a tracking pattern), and the block in which the tracking pattern is written is repeatedly written in a hard copy, so that banknotes, securities, etc. Effectively prevent counterfeiting. If the fed copy paper is OHP paper, the writing of the tracking pattern is prohibited to prevent the deterioration of the image due to the writing of the tracking pattern (noise generated during OHP projection). The image forming apparatus according to this embodiment will be described below.

(1) Construction of Copier FIG. 5 is a sectional view showing the overall construction of a digital color copier according to an embodiment of the present invention. The digital color copying machine is roughly divided into an image reader unit 100 that reads a document image and a copying unit 200 that prints the image read by the image reader unit on a copy sheet.

The image reader unit 100 has the same structure as the conventional one. Here, the scanner 10 includes an exposure lamp 12 that irradiates a document, a rod lens array 13 that collects reflected light from the document, and a contact-type CCD sensor 14 that converts the collected light into an electric signal. ing. Scanner 1
0 is driven by the motor 11 at the time of reading the original, moves in the direction of the arrow (sub-scanning direction), and scans the original placed on the platen 15. The image of the document surface illuminated by the exposure lamp 12 is photoelectrically converted by the CCD sensor 14. C
The R, G, and B multi-valued electrical signals obtained by the CD sensor 14 are read (Y), magenta (M), cyan (C), and black (B) by the read signal processing unit 20.
It is converted into any of the 8-bit gradation data of k) and stored in the synchronization buffer memory 30.

Next, in the copying section 200, the print head section 31 performs gradation correction (γ correction) on the input gradation data according to the gradation characteristics of the photoconductor, and then the corrected image. The data is D / A converted to generate a laser diode drive signal, and the semiconductor laser 264 (FIG. 6) provided in the head unit 31 is caused to emit light by this drive signal.
The print head unit 31 will be described later in detail with reference to FIG. The photoconductor drum 41 is uniformly charged by the charging charger 43 after being irradiated with the eraser lamp 42 before being exposed for each copy. The photosensitive drum 41 forms an electrostatic latent image of a document on the surface of the drum when it is exposed to laser light while being charged. Next, four color toner developing devices 45a of magenta (M), cyan (C), yellow (Y), and black (Bk).
Any one of .about.45d is selected to develop the electrostatic latent image on the photosensitive drum 41. On the other hand, the copy paper is fed from the paper cassette 50 and sent to the transfer drum 51 along the paper feed guide. The copy paper is wound around the transfer drum 51 at a timing while being fed, the leading end of the copy paper is held by the gripper 52 on the transfer drum 51. The toner image developed on the surface of the photoconductor drum 41 is transferred onto the copy paper wound around the transfer drum 51 by the transfer charge 46.

The above printing process is repeated in sequence for four colors of magenta (M), cyan (C), yellow (Y) and black (Bk). At this time, the scanner 10 is synchronized with the operations of the photosensitive drum 41 and the transfer drum 51.
Repeats the scanning operation. In this embodiment, when the copy paper fed from the paper cassette 50 is plain paper, the tracking pattern is also developed when the yellow (Y) toner image is developed. After that, the copy paper is separated from the transfer drum 51 by operating the separation claw 47.
The toner attached to the copy paper is fixed on the copy paper by the fixing device 48. The copy paper (hard copy) on which the toner fixing is completed is discharged to the paper discharge tray 49.

FIG. 6 is a block diagram of image data processing in the print head unit 31. Here, the image data (8 bits) from the image signal processing unit 20 is input to the 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 an image for a predetermined number of rows in the main scanning direction, and an operation clock for the image reader unit 100 and the copying unit 200 shown in FIG. It is provided to absorb the difference in frequency. FIFO memory 2
The data of 52 is then 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 data ROM 203 also stores various gradation correction data (γ table, various correction values, etc.). γ
The data subjected to the γ correction by the correction unit 253 is then input to the tracking pattern addition unit 257. Printer control unit 20
Reference numeral 1 makes the lamp 70 emit light at a timing to be described later, and determines from the level of the signal output from the light receiving element 71 at that time whether the copy paper fed to the transfer drum 51 is plain paper or OHP paper. To do. Tracking pattern R
As shown in FIG. 1, the OM 256 stores tracking pattern data representing the tracking information by the arrangement shape of yellow dots in a predetermined block. Here, when it is determined that the copy paper fed to the transfer drum 51 is plain paper, the printer control unit 201 causes the tracking pattern ROM 25.
Data of the tracking pattern is read from No. 6, and the read data of the tracking pattern is input to the tracking pattern adding unit 257. When the image data input to the FIFO memory via the interface unit 251 is the image data for forming the yellow (Y) toner image on the photoconductor drum 41, the printer control unit 201 causes the tracking pattern addition unit 25
A write enable control signal is sent to 7. The tracking pattern adding unit 257 that has received the write permission control signal adds the data of the tracking pattern to the data from the γ correction unit 253 (see FIG. 1) and outputs it to the D / A conversion unit 254. Even if the copy paper fed to the transfer drum is plain paper, if the copy paper is not image data for forming a yellow (Y) toner image on the photoconductor drum 41, the copy paper fed is When it is determined that the sheet is OHP paper, the printer control unit 201 outputs a write-inhibit control signal to the tracking pattern addition unit 257 and causes the D / A conversion unit 254 to output the data input from the γ correction unit 253 as it is. . D /
The analog voltage converted from the light emission level (digital value) by the A conversion unit 254 is then switched by the gain switching signal generation circuit unit 258 in the gain switching unit 255 in accordance with the gain setting value from the printer control unit 201. SW
1, SW2, ... (corresponding to different power P1, P2 ...)
After being amplified by the switch I / O 261 to the semiconductor laser drive 263, the semiconductor laser 264 is caused to emit light with the light intensity of that value.

(2) Paper Discrimination Processing FIG. 2 shows a lamp 70 and a light receiving element 71 (hereinafter collectively referred to as a paper detector) provided on the transfer drum 51.
The paper detector is installed via a transparent electrostatic sheet 53 between the position where the copy paper is held on the periphery of the transfer drum 51 and the position where the copy paper is transferred. The paper detection method of the paper detector of this embodiment is a light transmission method. The light receiving element 71 outputs a high level signal when receiving the light from the lamp 70. When the transfer drum 51 rotates, the copy paper passes between the paper detectors. When copy paper is fed from the paper cassette 50 to the transfer drum 51, the light of the lamp 70 is cut off and the output level of the light receiving element 71 changes to low level. By checking the level of the signal output from the light receiving element 71, the paper detector determines whether or not copy paper is fed to the transfer drum 51.

FIG. 7 is a perspective view of the transfer drum 51.
As shown in the figure, the copying machine of this embodiment includes three sets of lamps 70 and light receiving elements 71. Further, as shown in FIG.
There are holes. This corresponds to the position of the paper detector, and when this hole passes the paper detector, the gripper 5
It is determined whether or not copy paper is held in 2 (hereinafter,
First detection). Note that the first detection is performed while the transfer drum 51 rotates in the range indicated by A in FIG. As described above, since the OHP paper is transparent, it is not detected by the paper detector even if it is held by the gripper 52. For this reason, as shown in FIG. 4, it is necessary to attach a tape to the front end of the OHP paper or fill the front end with opaque ink.

After checking the presence or absence of the copy paper in the gripper 52 in the first detection, the paper detection for determining the copy paper is performed at the timing and the number of times shown in FIG. 8 or 9 in the area B of FIG. (Hereinafter, referred to as second detection). Here, as shown in both FIG. 8 and FIG. 9, the second detection timing can be exerted even during the development period of the magenta (M) toner image in the copying machine of the present embodiment. This is because a tracking pattern is added when the toner image of (Y) is developed. Therefore, the second detection period can be performed up to a period immediately before the transfer drum makes three revolutions.
For example, when the second detection is performed at the timing shown in FIG. 8, the paper is detected in three lines. If the second detection is performed at the timing shown in FIG. 9, 3 × 3
= 9 sheets are detected. The second detection at the timing shown in FIG. 8 or 9 is performed while the transfer drum 51 rotates in the range indicated by B in FIG. Here, if the copy paper is plain paper, the light is blocked. On the other hand, when the copy paper is OHP paper, light is transmitted. In this way, the paper detection is performed at three points in the direction perpendicular to the paper passing direction and at several places in the paper passing direction, so that the plain paper and the OHP paper are reliably discriminated. For this reason, plain paper is OHP
It is very difficult to deliberately misidentify the paper. Further, it is possible to accurately prohibit the writing of the tracking pattern on the OHP paper. Further, as a paper detection method, a reflection method may be used in which light reflected by a lamp is detected by a sensor, and the presence or absence of paper is determined by the amount of the reflected light.

FIG. 10 is a flow chart of the image forming process including the paper discriminating process executed by the copying machine of this embodiment. When the print switch is pressed by the user (YES in step S300), the lamp 70 determines whether the paper fed in the next step S301 is OHP paper.
And the paper detector including the light receiving element 71. Here, when the fed paper is plain paper (NO in step S301), the process proceeds to step S304, and writing of the tracking pattern is executed. Regarding the development of the magenta (M), cyan (C), and black (Bk) toner images, step S306 is skipped, the process proceeds to step S306, and an image forming process is executed (N in step S304).
O). When developing a toner image for yellow (Y) (YES in step S304), the additional processing of the tracking pattern is permitted, and the tracking pattern data is transferred to the yellow image data of the original read by the image reading unit. After the addition (step S305), image formation is performed in step S306. In the next step S307, it is determined whether development has been completed for all four colors. If completed, the process is terminated, and if not completed, the processes from step S304 are repeated.

On the other hand, when the copy paper fed in step S301 is OHP paper, writing of the trace pattern is prohibited in step S308, and step S30 is executed.
2, image formation is performed, and in step S303, it is determined whether development has been completed for all four colors of magenta (M), cyan (C), yellow (Y), and black (Bk), and at the end (step S303). If YES, the process is completed. If not completed, the process returns to step S302 to repeat the image forming process.

Although the image forming apparatus of this embodiment has been described above, the color of the dot data to be written in the hard copy is not limited to yellow and may be white or a special red color that is invisible to the human eye. Alternatively, ultraviolet or ultraviolet toner may be used. FIG. 1 shows a case where yellow dots are written in a hard copy. However, when the density of the image in the hard copy is high, the adhesion amount of yellow toner may be set to 0 for a specific dot.

[0025]

The image forming apparatus of the present invention determines whether the fed copy paper is plain paper or OHP paper at a plurality of locations on the fed copy paper. Therefore, the fed copy paper is plain paper or O
It can be surely determined whether the paper is HP paper. When the fed copy paper is an OHP paper, it is prohibited to write the tracking information in the hard copy. When the fed copy paper is plain paper, the tracking information is always written. This allows
Forgery of banknotes can be effectively prevented.

[Brief description of drawings]

FIG. 1 shows a written hard copy of a tracking pattern.

FIG. 2 is an arrangement of the lamp 70 and the light receiving element 71 sandwiching the transfer drum 51, a period A for performing the first detection, and a second period
It is a figure which shows the period B which detects.

FIG. 3 is a time chart showing execution timings of first detection and second detection in the conventional technique.

FIG. 4 is a diagram in which an OHP sheet is marked on a front end portion in a sheet passing direction in order to detect a sheet feeding to a transfer drum.

FIG. 5 is a structural cross-sectional view of a digital color copying machine of this embodiment.

FIG. 6 is a diagram illustrating each processing unit that constitutes the print head unit 31.

7 is a perspective view of the entire transfer drum 51. FIG.

FIG. 8 is a process showing an execution timing of first detection and second detection executed by the copying machine of the present embodiment.

FIG. 9 is a timing chart for executing the first detection and the second detection executed by the copying machine of this embodiment.

FIG. 10 is a flowchart of copying operation processing executed by the copying machine of this embodiment.

[Explanation of symbols]

 10 ... Image reader 30 ... Print head part 51 ... Transfer drum 70 ... Lamp 71 ... Light receiving element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03G 21/04

Claims (2)

[Claims] 1. A reading unit for reading image data of a document image, a memory for storing tracking information data, and image data of a document image read by the reading unit are input and access to the memory is permitted. Has
When the trace information data is read from the memory, added to the image data of the original image and output, and the access to the memory is prohibited, the trace information adding unit that outputs the image data of the original image as it is, Whether the copied copy paper is plain paper or OHP
If the paper discriminating means discriminates whether the paper is a paper at a plurality of places of the fed copy paper, and if the paper discriminating means discriminates that the fed copy paper is a plain paper, A control unit that outputs a signal that permits access to the memory, and outputs a signal that prohibits access to the memory to the tracking information adding unit when the paper discriminating unit determines that the fed copy paper is OHP paper. And, based on the image data output from the tracking information adding unit,
An image forming apparatus, comprising: a printing unit that forms a toner image and prints on a fed copy paper. 2. The image forming apparatus according to claim 1, wherein the paper discriminating means is a in the paper feeding direction on the fed copy paper, and b in the direction perpendicular to the paper feeding direction. Total a x
An image forming apparatus characterized by checking whether copy paper fed at b locations is plain paper or OHP paper.