JPH06113113A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to detect changes in the environment and change the superimposed image signals accordingly. [Structure] An environment sensor 2010 detects an environmental condition such as temperature and humidity inside a color copying machine, and a modulation amount control circuit 2016
Changes the machine number pattern signal according to the detected environmental condition, and the comparator circuit 2017 superimposes the changed machine number pattern signal and the image signal read from the CCD 2105 and outputs the superimposed signal to the printer.

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 function of adding a predetermined pattern to a color image, for example.

[0002]

2. Description of the Related Art Conventionally, various measures have been incorporated into color image forming apparatuses in order to prevent counterfeiting of securities and the like. One of the methods is to superimpose an image signal unique to the image forming apparatus on the image in order to identify the image forming apparatus used.

If securities are counterfeited by using the image forming apparatus, if the counterfeit article is read by a specific apparatus and a signal peculiar to the image forming apparatus is read, the used image forming is performed. The device can be identified, providing an effective clue to the tracking of counterfeiters.

[0004]

However, in the above-mentioned conventional example, when the characteristics of the image forming apparatus fluctuate due to changes in the environment, the signal unique to the image forming apparatus to be superimposed becomes unreadable or the image becomes abnormal. I have something to do. For example, in an environment such as high temperature and high humidity, when the image forming apparatus is inferior in image reproducibility and it is difficult to obtain high image quality, the superimposed signal unique to the image forming apparatus cannot be reproduced and becomes unreadable. There was a drawback that it would end up.

On the other hand, in an environment in which the image reproducibility of the image forming apparatus is improved, the superimposed signal peculiar to the image forming apparatus becomes visually recognizable on the image, resulting in an abnormal image. There was a drawback that it would end up. The present invention has been made in view of the above-described drawbacks of the conventional example, and an object of the present invention is to provide an image forming apparatus capable of detecting a change in environment and changing an image signal to be superimposed according to the change. It is in the point of providing.

[0006]

[Means for Solving the Problems]
In order to achieve the object, an image forming apparatus according to the present invention is an image forming apparatus that superimposes a predetermined image signal on an input image signal, and a detecting unit that detects an environmental state of the image forming apparatus, and the detecting unit. Changing means for changing the predetermined image signal according to the environmental condition detected by the means, and superimposing means for superimposing the image signal obtained by the changing means on the input image signal to obtain an output image. Prepare

[0007]

According to this structure, the detecting means detects the environmental state of the image forming apparatus, the changing means changes the predetermined image signal in accordance with the environmental state detected by the detecting means, and the superposing means changes. The output image is obtained by superimposing the image signal obtained by the changing means on the input image signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. An embodiment of the present invention will be described below by taking an electrophotographic full-color image forming apparatus as an example. However, the present invention is also effective for image forming methods such as a silver salt photographic method, a thermal transfer method, and a sublimation method. Needless to say. <First Embodiment> [Apparatus Overview] FIG. 2 is a side sectional view showing the structure of a copying machine according to the first embodiment of the present invention. In FIG. 2, 201 is an image scanner unit, which is 400 dpi.
This is a part that reads a document at a resolution of (dots / inch) and performs digital signal processing. A printer unit 202 is a unit that prints out an image corresponding to the original image read by the image scanner 201 in full color on paper at a resolution of 400 dpi.

In the image scanner unit 201, 20
Reference numeral 0 is a mirror surface pressure plate, which is a platen glass 203.
The upper original 204 is illuminated by the lamp 205, and the mirror 2
06, 207, 208, a lens 209 forms an image on a 3-line sensor (CCD) 210, and sends it to the signal processing unit 211 as full color information red (R), green (G), and blue (B) components. To be In addition,
The carriage 227 fixing the 205 and 206 is at a speed v, and the carriages 207 and 208 are at a speed of 1/2 v, and mechanically moves in a direction perpendicular to the electric scanning (main scanning) direction of the line sensor, thereby causing the entire surface of the original document to move. Is scanned (sub-scanning).

In the signal processing unit 211, the read image signal is electrically processed and decomposed into magenta (M), cyan (C), yellow (Y), and black (Bk) components, and the printer unit. Send to 202. In addition, M, C, and
One component of Y and Bk is sent to the printer unit 202, and a total of four document scans completes one printout.

The M, C, Y and Bk image signals sent from the image scanner unit 201 are supplied to the laser driver 2.
Sent to 12. The laser driver 212 modulates and drives the semiconductor laser 213 according to the sent image signal. The laser light scans the photosensitive drum 217 via the polygon mirror 214, the f-θ lens 215, and the mirror 216. Reference numeral 218 denotes a rotary developing device, which is a magenta developing unit 2
19, a cyan developing unit 220, a yellow developing unit 221, and a black developing unit 222, and four developing units alternately contact the photosensitive drum 217 to develop the electrostatic development formed on the photosensitive drum with toner. Reference numeral 223 denotes a transfer drum, which winds the paper supplied from the paper cassette 224 or 225 around the transfer drum 223, and transfers the image developed on the photosensitive drum to the paper.

In this way, after the four colors M, C, Y and Bk are sequentially transferred, the paper passes through the fixing unit 226, the toner is fixed on the paper, and then the paper is ejected. [Image Scanner Unit] FIG. 1 is a block diagram showing the arrangement of the image scanner unit 201 according to the first embodiment.
In the figure, 210-1, 210-2, and 210-3 are CCD (solid-state image sensor) line sensors having spectral sensitivity characteristics of red (R), green (G), and blue (B), respectively. After the D / D conversion, 8-bit output signals 0 to 255 are output.

Since the CCD line sensors 210-1, 210-2, 210-3 used in this embodiment are arranged at a fixed distance, the spatial shifts of the delay elements 401 and 402 are corrected. It 40
Reference numerals 3, 404 and 405 are log converters, which are constituted by a look-up table ROM or RAM and convert a luminance signal into a density signal. Reference numeral 406 is a known masking and UCR (under color removal) circuit, and although detailed description thereof is omitted, magenta (M), cyan (C), yellow (Y), and black for output by three input signals. Each signal of (Bk) is output in a frame-sequential manner with a predetermined bit length, for example, 8 bits for each reading operation.

Reference numeral 407 is a known spatial filter circuit,
The spatial frequency characteristic (MTF) of the output signal is corrected. Four
Reference numeral 08 denotes a density conversion circuit, which corrects the density characteristic of the printer unit 202, and is a log of 403 to 405.
It is composed of the same ROM or RAM as the converter. On the other hand, 414 is a microcomputer (hereinafter, CPU) that controls the present apparatus, 415 is a ROM that stores programs for operating the CPU 414, and 416 is RAM that is used as a work area for executing various programs. Reference numeral 413 is an input / output port (hereinafter, I / O port) connected to the CPU 414, and reference numeral 409 is a specific manuscript judgment circuit.

Here, the specific manuscript judgment circuit 409 judges whether the manuscript placed on the manuscript table is at least one of a plurality of specific manuscripts, and the judgment signal H is output in multi-valued 2 bits. To be done. That is, H = “3” is output when the possibility that at least one of the plurality of specific documents is being read is the highest, and H = “0” is output when the possibility is the least. To do. The determination circuit 40
9 includes a thinning circuit 301 and a frequency dividing circuit 310, which will be described later with reference to FIG. 3, and also performs thinning processing of the input R, G, B signals.

The CNO signal is a 2-bit frame sequential signal, and is a control signal indicating the sequence of four reading operations (scanning operations) for printing Y, M, C, and K color images. FIG. 16 is a diagram showing the relationship between the CNO signal and the print output according to the first embodiment. The CNO signal is
It is generated from the CPU 414 via the I / O port 413,
The operating conditions of the masking / UCR circuit 406 are switched. Further, the decision circuit 409 also applies the above-mentioned frame sequential signal CNO.
Is input, and for each of the four reading operations,
The determination criteria can be switched to make determinations for different specific originals.

Reference numeral 410 is a pattern addition circuit, which is a CPU
2-bit pattern level selection signal P designated by 414
It is a portion for adding a pattern, which is difficult for human eyes to identify, to the copy image according to S. The pattern to be added is created from the image signal P read by the reader. [Timing Chart] FIG. 4 is a circuit diagram showing the configuration of the thinning circuit according to the first embodiment, and FIG. 5 is a circuit diagram showing the configuration of the frequency dividing circuit according to the first embodiment. And Figure 7
Are timing charts of signals in the main scanning direction in the first embodiment.

The VSYNC signal is a sub-scanning section signal,
It is a signal indicating the image output section of the sub-scan. HSYNC
Is a main scanning synchronization signal, which is a signal for synchronizing the start of main scanning. CLK is a transfer clock of an image and is a basic clock for various image processes in this embodiment. On the other hand, CLK 'is a signal obtained by dividing CLK by 1/4,
It becomes the basic clock in the determination circuit 409. The SEL signal is a timing signal used in the thinning circuit 301 described above. Each of the CLK 'and SEL signals is shown in FIG.
It is generated by the frequency dividing circuit 310 shown in FIG.

Here, the thinning circuit 301 and the frequency dividing circuit 3
10 will be described. In FIG. 4, 455-45
7, 461 to 466 are flip-flops, 458 to 46
0 indicates selectors respectively, and in FIG.
453 is an inverter, 452 is a 2-bit counter, 45
Reference numerals 4 denote AND gates, respectively. Here, flip-flops 455, 456, 457 and 461, 462
463, selectors 458, 459 and 460 hold data at the timing of CLK and flip-flop 46
Data is held by the 4,465,466 CLK 'signals.

In the frequency dividing circuit 310, the 2-bit counter 452 counts the CLK signal after being cleared (initialized) by the HSYNC signal which is the main scanning synchronization signal, and outputs the count value with 2 bits ( D0, D
1). The upper bit D1 is output as the CLK 'signal, and the logical product of the inverted signal of the lower bit D0 and the upper bit D1 is output as the SEL signal.

As a result, the thinning-out circuit 301, as shown in FIG. 7, transfers the R (or G,
B) The signal is thinned out at a rate of 1/4 from the signal, and C
An R '(or G', B ') signal synchronized with LK' can be obtained. [Determination Circuit] FIG. 3 shows a determination circuit 409 according to the first embodiment.
3 is a block diagram showing the configuration of FIG. In the figure, 301
Is a thinning circuit as shown in FIG.
The data is thinned out in order to reduce the addition of the processing circuit of 09 itself. Reference numeral 302 denotes a color matching / lookup table ROM (hereinafter referred to as “color matching LUT”), which performs color matching between a plurality of types of specific originals (such as securities and banknotes) and input data. The tint matching LUT 302 checks the tint distribution of 32 types of specific originals in advance, and determines the bit information when the tint of the pixel matches the tint of the specific originals and the bit information when the tint does not match. Is held as the determination result. Where 3
Two types of specific originals are used for each of four scanning operations for forming M, C, Y, and Bk color images.
This is the total when the judgments of the type of specific original are assigned.

That is, to the LUT 302, the CNO signal, which is a frame sequential signal, is input to the upper 2 bits of the address, and the upper 5 bits of the image signal of each color of RGB, which are thinned out to the lower 15 bits, are input. For each of the values 0 to 3 of each CNO signal, whether or not the tint of the pixel matches the tint of the eight types of specific originals is simultaneously output corresponding to 8-bit data. Therefore, a total of 32 types of specific originals are determined in the four scanning operations.

Then, 303-1, 303-2, ..., 3
Reference numeral 03-8 is a tint determination circuit configured by similar hardware, which includes an integrator 306 and a register 307-.
1, 307-2, 307-3, comparator module 308
It is configured to judge the possibility that each specific manuscript exists in the manuscript, and output the judgment result in 2 bits. Three
Reference numeral 09 denotes a maximum value circuit, which is the tint determination circuits 303-1 to 303-3.
The maximum value of the judgment result outputs of 03-8 is output. That is, the determination result corresponding to the specific original that is most likely to exist among the eight types of specific originals is output.

[Integrator] FIG. 6 is a block diagram showing the configuration of the integrator 306 according to the first embodiment.
FIG. 4 is a diagram showing inputs and outputs of an integrator 306 according to the first embodiment. In FIG. 6, 501 and 505 are flip-flops that hold data at the rising timing of CLK ′. 502 is a multiplier, which inputs an 8-bit 2-input signal (A, B) and outputs an 8-bit signal (A × B / 255) as a multiplication result. Reference numeral 503 is also a multiplier, which inputs a 1-bit input signal (A) and an 8-bit input signal (B), multiplies them, and outputs an 8-bit output signal (A ×
B) is output. 504 is an adder, which is an 8-bit 2
The input signal (A, B) is input and an 8-bit signal (A + B) is output as the addition result.

As a result, in the integrator 306,
For a binary input signal x _i , an 8-bit output signal y _i is
It is expressed by the following equation (1). That is, y _i = (α / 255) y _i-1 + β · x _i-1 (1) Here, α and β are preset constants, and various characteristics of the integrator are determined by the magnitude of these values.

For example, in the case of α = 247 and β = 8, the output y _i as shown in FIG. 9 is output for the input x _{i- 1} as shown in FIG. Here, 701
Input such as 702, which is "1" even though the periphery is almost "0", or "0", even though the periphery is almost "1", such as the point 703. Some inputs are considered to be noise. This is processed by the integrator 306, and the registers 307-1 to 307- of FIG.
3 to 704-1 (R1), 704-2 (R2 value), 70
Noise can be removed by setting an appropriate threshold value such as 4-3 (R3 value) and binarizing the output y _i of the integrator with this.

[Comparison Module] FIG. 10 is a block diagram showing the configuration of the comparator module 310 according to the first embodiment. In the figure, 801, 802 and 803 are comparators, 804 is an inverter, 805 is an AND gate, 80
Reference numerals 6 and 807 denote OR gates, respectively. As described in the description of FIG. 3, the register 307-1 has an R
1, register 307-2 has R2, register 307-3
Is set to the value R3, and R1>R2> R3
There is a relationship. With this configuration, as a result, the determination result is quantized into 2 bits and output. That is, if R1 <(input), 11 (binary number)
Is output and R2 <(input) ≦ R1, 10 (2
0) when R3 <(input) ≤ R2
If 1 (binary number) is output and (input) ≤ R3, 0
0 (binary number) is output.

[Pattern Adding Circuit] FIG. 11 is a block diagram showing the configuration of the pattern adding circuit 410 according to the first embodiment, and FIG. 14 is a top view of the document table according to the first embodiment. In FIG. 11, 901 is a sub-scanning counter, and 9
02 is a main scanning counter, 903 is a look-up table RAM (hereinafter referred to as “LUT”), 905 is a flip-flop, 913 is an AND gate, 906, 907, 90.
8, 909 are registers, 910 is a 4to1 selector, 9
Reference numerals 11 and 913 denote AND gates, and reference numeral 912 denotes an adder. Reference numeral 914 denotes a binarization circuit that binarizes the image signal P after passing through the spatial filter, and outputs 1 when the image signal value is larger than a predetermined threshold value and outputs 0 when the image signal value is smaller. The binarized data output from the binarization circuit 914 is written in the dual port RAM 915. The image to be written in the dual port RAM 915 is the image scanning unit 2 as shown by 1201 in FIG.
It is an image written in a specific place of 01. Moreover, the image is a component that cannot be easily exchanged among the components of the reader, that is, the outside of the platen glass (platen glass) 203 (the frame portion supporting the glass) and the reading range of the image sensor of the carriage 226, for example. It is attached to the lower surface of the upper plate.

When writing an image in the dual port RAM 915, the CNO signal is set to "0" (magenta recording scan). That is, the image signal P is controlled so as to be a signal generated most depending on the green (G) signal of the CCD 210. This is because the green signal is the closest to the luminance signal of the image among the signals that can be easily created.

The dual port RAM 915 is the CPU 4
The stored contents are read by 14 via the data bus Data and the address bus Adr. Also RA
Since the M903 is also a dual port RAM (hereinafter referred to as "RAM"), the CPU 414 uses the data bus Data.
And the address bus Adr are used to write the same data as the data read from the RAM 915 to the RAM 903. Therefore, the above operation will be described.

FIG. 15 is a flow chart for explaining the service mode according to the first embodiment. In the service mode, the CPU 414 sets the CNO signal to 0 (step S1501) and starts the pattern reading operation (step S1502). CPU 414 is a CPU
The address is set to the address of the dual port RAM 915 (step S1503), and the dual port RAM
The data of 915 is read (step S1504).

The CPU 414 stores the CPU address in the RAM.
Set to the address of 903 (step S1505),
The data read from the dual port RAM 915 is written into the RAM 903 (step S1506).
As an example, the pattern to be added to the specific original is read once when the main body is installed in a mode in which the service person can use only the service person.

Here, the sub-scanning counter 901 repeatedly counts the main scanning synchronizing signal HSYNC and the main scanning counter 902 repeatedly counts the pixel synchronizing signal CLK with a 9-bit width, that is, 512 cycles. As described above, the RAM 903 holds the pattern to be added, and the lower 6 bits of each of the count values of the sub-scanning counter 901 and the main scanning counter 902 are input.

Only one bit of the output of the RAM 903 is referred to, and the main scanning counter 90 is operated by the AND gate 904.
1 and the upper 3 bits of the sub-scanning counter 902 are logically ANDed, and the flip-flop 905 outputs the CLK signal.
The AND gate 913 is synchronized with the signal 2
After being ANDed with both the CN0 signal “0” and the CN0 signal “1” of the bit, it is sent to the AND gate 911. This is a valid signal only when CNO = 3, that is, currently being printed in yellow.

On the other hand, the registers 906, 907, 908,
The values P1, P2, P3, and P4 are held in advance in 909, and any one of P1 to P4 is selected according to the pattern level selection signal PS designated by the CPU 414, and the AND gate 911 is selected. After that, the adder 91
The pattern is added to the input signal V by 2 and V'is output. Therefore, when CN0 = 2, that is, when printing is currently performed in yellow, the pattern held in the RAM 903 is repeatedly read and added to the signal to be output.

Here, a relationship of P1 <P2 <P3 <P4 is set among P1, P2, P3 and P4. When s = 00 (binary number), the selector 910
When Y = A and s = 01 (binary number), Y = B and s = 10
The relation is set such that Y = C when (binary) and Y = D when s = 11 (binary). Therefore, when PS = 00 (binary number), V ′ = V + P1,
When PS = 01 (binary number), V '= V + P2, PS =
When 10 (binary number), V '= V + P3 and PS
= 11 (binary number), the pattern is added so that V '= V + P4.

Here, the pattern to be added is added only by the yellow toner so that it is difficult for the human eye to identify it. This is because the human eye distinguishes it from the pattern drawn by the yellow toner. It takes advantage of the weak ability. Further, by varying the level of the pattern to be added according to the possibility that a specific document exists in the input image, it is possible to make the pattern almost unrecognizable to human eyes in a normal copy. The more likely that is, the more clearly the pattern is added.

[Copy Result] FIG. 12 is a diagram showing an example of the copy result according to the first embodiment. In the figure, 10
Reference numeral 01 indicates the added pattern, and the RAM
The contents held in 903 are added. In the example shown in FIG. 12, the two-stage pattern of “ABCD” and “1234” is added in a pattern of 64 pixels × 64 pixels so that it is difficult for human eyes to identify, and 512 pixels for main scanning
This is repeated every 512 lines of sub-scanning. Therefore, by setting this as a machine-specific serial number or by encoding a serial number, it is possible to limit the copying apparatus by validating the copy.

Further, when there is a high possibility that a specific original document that should not be copied is present in the read image,
For example, a clear pattern can be added with black toner. Further, in the present embodiment, the pitch for adding the pattern is set to every 512 pixels (or lines) in the main scanning, but in the present embodiment, it is 400 dpi (dots / inc).
Since the resolution is h), a pattern will be added about every 32.5 mm. On the other hand, the width of banknotes (Bank of Japan notes) in the lateral direction is about 76 mm, and the width in the lateral direction of banknotes of major countries is also between about 60 mm and 120 mm, so the banknotes are copied. If this happens, this pattern will always be added to the inside of the copied bill. Therefore, even if only the banknotes are cut and misused, it is necessary to identify the copy and identify the information such as the machine number of the copying machine used for copying by reading the added pattern. You can

[Flowchart] FIG. 13 is a flow chart for explaining the setting procedure of the pattern level selection signal PS by the CPU 414 of the first embodiment. First, immediately after the start of copying, in step S1102, the pattern level selection signal PS is set to "0". Next, in step S1103, the current judgment level H is compared with the value of PS, and if H is larger,
In step S1104, the value of H is set in PS. If not, the process returns to step S1103. That is, the maximum value from the copy start to the present is set in PS according to the history of the determination signal H.

As described above, according to the first embodiment, as a method for identifying the device, a specific pattern which is difficult to be recognized by human eyes is added to the copy so that the copy is originally performed. If a particular original document (for example, a banknote) that should not be copied is copied, it can be used as a clue to identify the copied device. Furthermore, by repeatedly adding a specific pattern at a pitch shorter than the length of the banknote in the short-side direction, a specific pattern is always added to the copy even if it is misused by cutting off a part of the copy. It is possible to identify or narrow down the copied device or the copied person by appraising this. <Second Embodiment> Now, in the second embodiment, an example in which the first embodiment is further improved will be shown.

First, a method of forming a color image will be described. FIG. 18 is a side sectional view showing the structure of the main part of a color copying machine according to the second embodiment of the present invention. In FIG.
The original 2101 placed on the original table glass 2102 is imaged on the CCD 2105 by the light source 2103 and the optical lens 2104, and converted into an image signal according to the amount of received light.

After being converted into a digital value by the image signal A / D conversion 2106 and subjected to image processing by the control circuit 2107, the laser light source 2108 is driven. The emitted laser light is reflected by the polygon mirror 2001 and the mirror 2002, and is irradiated onto the photosensitive drum 2004. To prevent toner from remaining on the photosensitive drum 2004, the photosensitive drum 2004 is cleaned by the cleaning blade 2110, and then the photosensitive drum 2004 is uniformly charged by the charger 2109.

First, the photosensitive drum 2004 on which a latent image is formed by scanning the laser beam with the Y (yellow) image signal rotates in the direction of the arrow shown in the figure. Then, development is performed by the developing device 2003Y. Further, the photosensitive drum 4 is rotated to transfer the recording material 2006 to the transfer drum 21.
The toner image formed on the photoconductor drum 2004 is transferred onto the recording material 2006 by the transfer charger 2112.

Next, after development is carried out with a latent image format with an M (magenta) image signal, multiple transfer is carried out onto the Y image of the recording material under the positional condition where the registration of the image is adjusted. Similarly, C, Bk image formation, multiple transfer,
The fixing roller pair 200 is separated from the transfer drum 2111.
The image is fixed at 7, and the color image print is completed.

Further, in the present embodiment, in addition to the above configuration, the environment sensor 2 including a temperature sensor and a humidity sensor at a position where the environment of the machine body or the internal environment is well reflected.
010 is installed, and the environmental data signal detected by this environmental sensor 2010 is sent to the control circuit 2107. 2119 is a power supply. Next, the image signal of this embodiment and the processing system for superimposing will be described in detail.

FIG. 17 is a block diagram schematically showing the circuit construction of the color copying machine according to the second embodiment. In the figure, reference numeral 2012 denotes a shading circuit, which performs shading correction on the digital signal obtained from the A / D conversion circuit 2106. In the control circuit 2107, 2013 is a LOG conversion circuit, 2014 is a LUT (look-up table), 2015 is a machine number pattern generation circuit, 2016 is a modulation amount control circuit, 2017 is a comparator circuit, 201
Reference numeral 8 indicates a pulse width modulation circuit, and reference numeral 2019 indicates an LD driver.

Next, the operation of the above configuration will be described. FIG. 19 is a graph showing the relationship between the modulation amount and the water content according to the second embodiment, and FIG. 20 is a diagram showing an example of the machine number pattern according to the second embodiment. Image brightness signal is CC
The luminance signal obtained by D2105 is the A / D conversion circuit 210.
It is converted by 6 into a digital luminance signal. The shading circuit 2012 corrects the sensitivity variation of each CCD element of the obtained luminance signal, and the corrected luminance signal is converted into a density signal by the LOG conversion circuit 13.

Furthermore, the LUT 201 is set so that the original image density and the output image of the γ characteristic of the printer at the time of initial setting match.
Converted in 4. On the other hand, the machine number pattern generation circuit 201
5, a machine-specific pattern is generated. here,
As shown in FIG. 19, the amount of modulation table corresponding to the mixing ratio of the amount of water in the air calculated based on the temperature and humidity detected by the environment sensor 2010 is applied to the image signal of only Y (yellow) that has the lowest resolution visually. And the modulation amount is controlled according to the table. This control is performed by the modulation amount control circuit 2016 in FIG.

The modulated model number pattern is synthesized by the comparator circuit 2017 which is superimposed on the image signal. As for the machine number pattern, as shown in FIG. 20, the machine number is made to correspond to the number pattern, but it is preferable to employ a pattern corresponding to numbers and characters that is not conspicuous.

The image signal on which the machine number pattern is superimposed is then modulated by the pulse width modulation circuit 2018 so that the laser emission time is proportional to the density signal, and is sent to the laser driver 2019 to express the density gradation in the area gradation. By doing so, a gradation image is formed. The machine number pattern can be read by separating only the yellow signal by observing it through a 350 mm sharp band filter after a full-color image has been formed, and even if it is forged, it is performed by any machine. It becomes possible to specify whether or not.

In FIG. 19, the absolute humidity corresponding to the temperature and humidity detected by the environment sensor (mixing ratio of water content in air [g / 1
kg. Air]) is plotted on the horizontal axis, and the modulation amount at which the signal at that time is legible and does not cause image defects is plotted on the vertical axis. The image reproduction capability at this time will be described. FIG. 21 is a diagram showing an example of a pattern when an image is deteriorated.

In the electrophotographic system, for example, when the atmosphere is high temperature and high humidity, the charge amount (tribo) of the developer used for recording is extremely reduced, and the developing ability of the photosensitive member is increased. Therefore, a means for adjusting the density by lowering the contrast potential of development is usually used, but if such means is applied, the difference between the latent image potential and the dark portion potential recorded on the photoconductor becomes small, and as a result, The developer attached to the body becomes disordered as shown in FIG. Therefore, the added signal is buried in the surrounding image and becomes unreadable. Therefore, when the water content is large as shown in FIG. 19, the modulation amount of the added image signal is increased. In FIG. 19, the water content is 1
When the amount is 5.0 g or less, the amount of modulation is almost constant. This is because the developer used in this embodiment uses the contrast potential with good reproducibility in the atmosphere, and This does not apply to materials.

As described above, according to the second embodiment, a full color image is formed by superimposing images formed of color materials of a plurality of colors, and an image of a specific color is
In an image forming apparatus that superimposes information unique to the image forming apparatus, by changing the modulation amount of the superimposition pattern according to the value of an environmental sensor, information unique to the image forming apparatus can be stably formed on an image. The effect is that you will be able to. <Third Embodiment> In the second embodiment, the table corresponding to the graph shown in FIG. 19 is provided, that is, the modulation amount is stored as a function of the water content. Describes a method of reducing the memory amount of the table, reducing the cost, and simplifying the table.

FIG. 22 is a graph showing the relationship between the modulation amount and the output according to the third embodiment. Strictly speaking, the value of the amount of modulation with respect to the amount of water has a one-to-one correspondence as shown in FIG. 19, but since there is some margin for interpretation and image deterioration, it is calculated from the temperature and humidity detected by the environment sensor 2010. Moisture content is 5g or less, 5.0-9.0g, 9.0-1
2 g, 12.0 to 16.5 g, 16.5 to 20.0 g,
Divide into 20.0g or more, and set the flag to Qout1,
Build up to Qout2, Qout3, ..., Qout6.
Then, the modulation amount as shown in FIG. 22 may be output. <Fourth Embodiment> FIG. 23 is a side sectional view showing the arrangement of the main part of a color copying machine according to the fourth embodiment. In the figure, the same components as those in FIG. 18 of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 25 is a graph showing the relationship between the modulation amount and the output according to the fourth embodiment.

Now, in the fourth embodiment, as shown in FIG. 23, the memory 2 which is a data storage means together with the environmental sensor is used.
022 and a rewriting circuit 2021. This is a real-time control only. If there is a large change in the detected temperature and humidity, the modulation amount of the superimposed image signal will also change greatly, but in reality the developer such as the developer used in the machine body will change. Since the material is conditioned for a long time, the amount of modulation is calculated based on a series of environmental data taken at a certain time. This modulation amount has the characteristics shown in FIG.

Next, the operation of the fourth embodiment will be described. FIG. 24 is a flow chart for explaining the method of calculating the modulation amount according to the fourth embodiment. In FIG. 24, the environment sensor 2019 measures, for example, once every 30 minutes or several times in 30 minutes, and calculates the average value. For example, the average value for 8 hours is stored in the buffer area in the memory 2022. Next, in step S1, absolute humidity or a value corresponding thereto, for example, a mixing ratio is obtained from the environmental data for 8 hours by a predetermined calculation and stored in the memory 2022. This is because it is considered that the physical properties of the developer, particularly the resistance value, greatly depend on the absolute humidity, that is, the amount of water in the air. Next, in step S2, it is determined whether or not the absolute humidity (mixing ratio) has been calculated for 8 hours,
If it has been performed for 8 hours (YES), average values x, y, z of absolute humidity (mixing ratio) for the past 2 hours, 4 hours, and 8 hours are obtained in step S3. These average values x, y, z are used for the condition judgment described below.

First, in step S4, it is judged whether the 2-hour average value x is 16.5 g or more, and 1
If it is 6.5 g or more, the flag is set to Qout1 (step S41). This indicates that the high humidity continued for more than 2 hours. Next, in step S5, the current value is 16.
It is determined whether or not it is 5 g or more, and if it is 16.5 g or more, the flag is set to Qout2 (step S51). This indicates that it was low humidity for 2 hours, but is now heading to high humidity. Next, in step S6, it is determined whether the average value z for 8 hours is 9 g or more.
ut3 (step S61). As a result, the humidity is 8
It is instructed to be in a medium-humid state for more than an hour. Next, in step S7, it is determined whether the average value y for 4 hours is 9 g or more, and if it is 9 g or more, the flag is set to Qout4 (step S71). This indicates that we are going from low to moderate humidity. Then, in other cases than the above, that is, when the average value y for four hours is 9 g or less, it is determined that the humidity is low, and the flag is set to Qout5 (step S71).

The above processing is carried out because the speed of moisture absorption / dehumidification of the developer is different between the case of going from low humidity to high humidity and the case of going from high humidity to low humidity. That is, the adsorption state of the developer depends on the absolute humidity, but this is not the humidity of the atmosphere,
Since it is determined by how much the developer absorbs moisture, it is necessary to judge the conditions. Next, in step S8, the modulation amount is determined by the flags Qout1 to Qout5 (output flags) determined as described above.

The present invention may be applied to either 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. In each of the above-described embodiments, the laser beam printer has been described as an example, but the present invention is not limited to this, and can be applied to an inkjet printer and a thermal transfer printer. In particular, a so-called bubble jet type printer that uses a head that ejects droplets by utilizing film boiling due to thermal energy may be used. Further, in each of the above-described embodiments, the color to be added is yellow, but the present invention is not limited to this, for example, an inconspicuous color such as yellow-green or gray, or lightness such as light purple or light green. It may be color.

Further, in each of the above-described embodiments, the document image is input by the reader, but the present invention is not limited to this, and it is input by a still video camera, a video camera, or created by computer graphics. It may have been done.

[0062]

As described above, according to the present invention,
An image forming apparatus that forms a full-color image by superimposing images formed of color materials of a plurality of colors, and that superimposes information specific to the image forming apparatus on the image of a specific color,
By changing the modulation amount of the superposition pattern according to the value of the environment sensor, it is possible to stably form information unique to the image forming apparatus on the image.

[Brief description of drawings]

FIG. 1 is an image scanner unit 201 according to a first embodiment.
3 is a block diagram showing the configuration of FIG.

FIG. 2 is a side sectional view showing the configuration of the copying machine according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a determination circuit 409 according to the first embodiment.

FIG. 4 is a circuit diagram showing a configuration of a thinning circuit according to the first embodiment.

FIG. 5 is a circuit diagram showing a configuration of a frequency dividing circuit according to a first example.

FIG. 6 is a block diagram showing a configuration of an integrator 306 according to the first embodiment.

FIG. 7 is a timing chart of signals in the main scanning direction in the first embodiment.

FIG. 8 is a diagram showing inputs and outputs of an integrator 306 according to the first embodiment.

FIG. 9 is a diagram showing inputs and outputs of an integrator 306 according to the first embodiment.

FIG. 10 shows a comparator module 310 according to the first embodiment.
3 is a block diagram showing the configuration of FIG.

FIG. 11 is a pattern adding circuit 410 according to the first embodiment.
3 is a block diagram showing the configuration of FIG.

FIG. 12 is a diagram showing an example of a copy result according to the first embodiment.

FIG. 13 is a flowchart illustrating a procedure for setting a pattern level selection signal PS by the CPU 414 according to the first embodiment.

FIG. 14 is a top view of a document table according to the first embodiment.

FIG. 15 is a flowchart illustrating a service mode according to the first embodiment.

FIG. 16 is a diagram showing a relationship between a CNO signal and print output according to the first embodiment.

FIG. 17 is a block diagram schematically showing a circuit configuration of a color copying machine according to a second embodiment.

FIG. 18 is a side sectional view showing a configuration of a main part of a color copying machine according to a second embodiment of the present invention.

FIG. 19 is a graph showing the relationship between the amount of modulation and the amount of water according to the second embodiment.

FIG. 20 is a diagram showing an example of a machine number pattern according to the second embodiment.

FIG. 21 is a diagram showing an example of a pattern when an image is deteriorated.

FIG. 22 is a graph showing the relationship between the modulation amount and the output according to the third embodiment.

FIG. 23 is a side sectional view showing a configuration of a main part of a color copying machine according to a fourth embodiment.

FIG. 24 is a flowchart illustrating a method of calculating a modulation amount according to the fourth embodiment.

FIG. 25 is a graph showing the relationship between the modulation amount and the output according to the fourth embodiment.

[Description of Reference Signs] 201 Image Scanner Section 202 Printer Section 203 Original Plate Glass 204 Original Document 205 Lamps 206, 207, 208 Mirror 209 Lens 210 3 Line Sensor 211 Signal Processing Section 226 Carriage 212 Laser Driver 213 Semiconductor Laser 214 Polygon Mirror 215 f- θ lens 216 mirror 217 photosensitive drum 2001 polygon mirror 2002 mirror 2003 developing device 2004 photosensitive drum 2006 recording material 2007 fixing roller 2010 environmental sensor 2101 original 2102 original platen glass 2103 light source 2104 optical lens 2105 CCD 2106 laser 2111 transfer drum

Claims (2)

[Claims] 1. An image forming apparatus for superimposing a predetermined image signal on an input image signal, the detecting section detecting an environmental state of the image forming apparatus, and the detecting section according to the environmental state detected by the detecting section. An image forming apparatus comprising: a changing unit that changes the predetermined image signal; and a superposing unit that superimposes the image signal obtained by the changing unit on an input image signal to obtain an output image. 2. The image forming apparatus according to claim 1, wherein the detection unit has a storage unit that stores the detected environmental condition for a predetermined time.