JPH1013684A - Printing equipment - Google Patents

Abstract

(57) [Summary] [Problem] To add an inconspicuous pattern different for each device without changing the image quality of a reproduced image when information for specifying a copying machine is added to a reproduced image of an original image. It is intended to provide a device. SOLUTION: A gradation conversion table circuit 50 for performing gradation conversion of an image signal, a device specific pattern generation circuit 51 for generating a device specific pattern, and a device specific pattern generation position determination unit 44 for determining a generation position of the device specific pattern. ~ 48
An input address determination circuit 49 for switching the pattern generation method in the tone reproduction processing unit according to the position where the device-specific pattern is generated and the device-specific pattern, and an image forming unit for generating an image whose tone is converted by the tone conversion table circuit 50 Thus, when information for specifying a copying machine is added to a reproduced image of an original image, a printing apparatus capable of adding an inconspicuous pattern different for each apparatus without changing the image quality of the reproduced image is obtained. Can be

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus having a function of adding specific information to a reproduced image while retaining a high-quality recorded image.

[0002]

2. Description of the Related Art With the improvement of the performance of printing apparatuses such as color copiers and color printers, it is possible that specific originals such as banknotes and securities are copied and used illegally. Heretofore, it has been a difficult task to identify which device copied an illegally copied copy. To prevent such illegal copying, color copiers,
It has been studied to identify illegal copies by the color printer itself and to forcibly prohibit illegal copies. In this case, a circuit for determining a specific original is used in a color copying machine or a color printer. However, since the number of image patterns that can be registered is limited in such a determination circuit, all types of specific originals are registered. It is impossible. Although it is important to add a means for detecting a specific document to the apparatus itself, since the ability to detect a document is limited as described above, if a document that should not be copied is copied, It is important to identify the copying machine that performed the copying or the person who made the copying. Based on such a background, a technique of adding information or the like which can specify a copied copying machine to a document image has been studied. The technique uses an output color component (for example, yellow) that is least noticeable to human eyes among output color components (for example, magenta, cyan, yellow, and black) of a copying machine, and outputs an image signal of the output color component. For example, a modulation such as adding a constant value is performed on the image data, and a number or a code representing the serial number of the copying machine or a dot formed by patterning the number or the like is struck small, and this is repeated at a constant interval.

However, in the above technique, even though yellow is the least visible output color component, modulating an image signal changes the color component, which results in changing the color of a reproduced image. . For example, when a color copier is used for design purposes, it is troublesome to see a pattern that is not present in the document. When copying a manuscript,
Even if the document has a uniform color, the image signal is not always uniform due to variations in the sensitivity of the CCD. However, when an image on the host computer is printed out using the external interface of the color copier, the CG Since it is possible to directly output (computer graphics), there is a sufficiently uniform area at the image signal level.
At this time, when the yellow component is modulated, the additional pattern is particularly conspicuous in a light gray or light blue uniform portion, and the pattern may emerge because it is added even in an area where no image signal exists. In addition, only yellow consumes a large amount of toner. In the conventional method of forming an additional pattern in which numbers, codes, dot patterns, and the like representing additional information are made into small unit patterns and the unit patterns are repeated at regular intervals, in the case of arranging small unit patterns in a grid pattern However, human eyes are more conspicuous because they recognize regular patterns more easily than random patterns. Therefore, the degree of modulation of the image signal must be reduced,
Depending on the specific document, additional information may not be read.

FIG. 12 is an additional pattern configuration diagram showing an example of a copy result in the prior art. In FIG. 12, the horizontal axis indicates main scanning, and the vertical axis indicates sub-scanning. Further, the inside of the square frame is an image existing area. Conventionally, as shown in FIG. 12, since a fixed amount of pattern is always added, the pattern is printed even in an area where no image exists, regardless of the image area of the copy, so that the pattern is also conspicuous. Had the disadvantage of becoming

[0005]

As described above, in a conventional printing apparatus such as a color copying machine or a color printer, a pattern indicating additional information is conspicuous, and if the pattern is to be prevented, the additional information cannot be read. Had problems.

In this printing apparatus, while maintaining the quality of the original image in the reproduced image, it is difficult for the output image to be recognized by the human eyes in the output image, and the copied image such as a specific original to be processed is subjected to some method. There is a demand for tone modulation and additional patterns that can be identified reliably.

According to the present invention, there is provided a printing apparatus which can add an inconspicuous pattern different for each apparatus without changing the image quality of the reproduced image when information for specifying a copying machine is added to the reproduced image of the original image. The purpose is to provide.

[0008]

In order to solve this problem, a printing apparatus according to the present invention comprises: a tone reproduction processing section for converting a tone of an image signal; a device unique pattern generating section for generating a device unique pattern; A device-specific pattern generation position determining unit for determining a device-specific pattern generation position, and a hierarchy based on the device-specific pattern generation position determined by the device-specific pattern generation position determination unit and the device-specific pattern generated by the device-specific pattern generation unit. The tone reproduction processing unit is configured to include a pattern switching signal generation unit that switches a pattern generation method, and an image forming unit that generates an image whose tone is converted by the tone reproduction processing unit.

Thus, a printing apparatus can be provided which can add an inconspicuous pattern different for each apparatus without changing the image quality of the reproduced image when information for specifying the copying machine is added to the reproduced image of the original image. Can be

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a tone reproduction processing unit for converting a tone of an image signal, a device unique pattern generation unit for generating a device unique pattern, and a device unique pattern generation unit. A device-specific pattern generation position determining unit for determining a generation position, and a tone reproduction processing unit based on the device-specific pattern generation position determined by the device-specific pattern generation position determination unit and the device-specific pattern generated by the device-specific pattern generation unit. And a pattern switching signal generator for switching the pattern generation method, and an image forming unit for generating an image subjected to gradation conversion by the gradation reproduction processing unit, which is determined by the device-specific pattern generation position determining unit. This has the effect of adding the device-specific pattern at a specific position with the pattern switched by the pattern switching signal generator.

According to a second aspect of the present invention, in the first aspect of the present invention, the gradation reproduction processing section divides a pixel constituting the image signal into a plurality of pixels, and the divided pixels have different growth rates. Is set to perform the gradation conversion, and has an effect that pattern switching is performed based on a difference in pixel growth speed.

According to a third aspect of the present invention, in the second aspect of the present invention, the device-specific pattern generation position determining unit comprises:
A plurality of device-specific patterns generated by the device-specific pattern generation unit are arranged in the same pattern on an image plane, and a position between a plurality of same arrangements is determined so that the device-specific pattern is generated so that the device-specific pattern is not arranged. This has the effect that the additional information of the document copy is identified from the arrangement of the device-specific patterns on the screen plane.

According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, the device-specific pattern generating section repeats the generation of the device-specific pattern a plurality of times. This has the effect that the additional information of the object is reliably identified.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a configuration diagram showing a color copying machine as a printing apparatus according to Embodiment 1 of the present invention. FIG.
, The image scanner unit 1 has a resolution of 300 dpi (dot /
inch) and performs digital signal processing. The printer unit 2 prints an image corresponding to the original image read by the image scanner unit 300 at 300 dp.
Print out in full color on paper at i resolution.

In the image scanner section 1, the mirror surface pressing plate 3 presses the original, and the original 5 placed on the original platen glass 4 is illuminated by the lamp 6, and the reflected light is reflected by mirrors 7, 8,
The light is guided to a lens 9 and is imaged by a lens 10 on a line sensor 11 having three CCDs. The line sensor 11 composed of a CCD or the like sequentially sends the image detected by the CCD to the printer unit 2 as each signal of R (red), G (green), and B (blue) components of full color information. The lamp 6 and the mirror 7 are moved at a speed v, and the mirrors 8 and 9 are moved at a speed of 1/2 v mechanically in a direction perpendicular to the electrical scanning (main scanning) direction of the line sensor 11 so that the entire surface of the original document is moved. Is scanned (sub-scan).

In the printer section 2, the line sensor 11
R (red) and G of full color information sent from
The signals of the (green) and B (blue) components are decomposed into respective component signals of M (magenta), C (cyan), Y (yellow), and Bk (black) by the signal processing unit 12, and each signal is divided into color planes. Data for one page is collectively temporarily stored and sent to the printer video processing unit 13 for each color plane. The printer video processing unit 13 modulates and drives the semiconductor laser 14 according to the sent image signal. Laser light emitted from the semiconductor laser 14 scans the photosensitive drum 18 via the polygon mirror 15, the f-θ lens 16, and the mirror 17. The developing unit 19 includes a black developing unit 20, a yellow developing unit 21, a cyan developing unit 22, and a magenta developing unit 23. Each time an image signal of each plane is sent, each developing unit contacts the photosensitive drum 18 in order. Then, the single-color toner images developed on the photosensitive drum 18 are sequentially transferred to the intermediate transfer body 24 to obtain toner images of four colors of toner. The toner image on the intermediate transfer body 24 is transferred to the sheet supplied from the sheet cassette 25 in one pass. The sheet on which the toner image has been transferred passes through the fixing unit 26, and is discharged after the toner is fixed on the sheet.

Next, the electrical configuration of the color copying machine shown in FIG.
The function and the like will be described. FIG. 2 shows the image scanner unit 1.
3 is a block diagram showing a signal processing unit 12 of the printer unit 2, and FIG. 4 is a block diagram showing a printer video processing unit 13 of the printer unit 2.

First, in FIG. 2, the line sensor 11
CCD 27 having R, G, B spectral sensitivity characteristics, sampling hold and A / D conversion circuit (hereinafter referred to as “S / H & A”)
/ D circuit ”) 28, shading correction circuit 2
9, resolution conversion circuit 30, smoothing circuit 31, color correction circuit 32, MTF (modulation transfer function) correction circuit 33, γ
It has a correction circuit 34. RG output from CCD 27
The B image signal is sampled and held by the S / H & A / D circuit 28 and A / D converted, and then output as 8-bit 0-255 signals. S / H & A / D
The signal output from the circuit 28 is subjected to shading correction and black correction by a shading correction circuit 29,
In the resolution conversion circuit 30, data thinning or interpolation is performed so as to obtain data corresponding to the designated resolution. The output signal of the resolution conversion circuit 30 is subjected to color correction, MTF correction, and γ correction by the color correction circuit 32, the MTF correction circuit 33, and the γ correction circuit 34 after the smoothing circuit 31 performs data smoothing. It is output from the image scanner unit 1 as a signal indicating the adjusted value.

In FIG. 3, the signal processing unit 12 includes a density conversion circuit 35, a masking and background removal circuit (hereinafter, referred to as a "masking & UCR circuit") 36, and a page memory 3.
7, gamma correction circuit 38, gradation modulation circuit 39, video interface circuit (hereinafter referred to as "video I / F circuit") 4
Has zero. Line sensor 11 of image scanner unit 1
The 256-level image signals R, G, and B input from the CPU are converted from luminance information into C (cyan), M (magenta), and Y by a density conversion circuit 35 and a masking & UCR circuit 36.
(Yellow) and Bk (black) density information are converted for each pixel data. These density information C, M,
Y and Bk are temporarily stored in the page memory 37 until data for one page is prepared. When you have one page of data,
The density information is input to the gradation modulation circuit 39 through the gamma correction circuit 38 in the order of planes. The gradation modulation circuit 39 performs a gradation conversion on each density information to reproduce a high quality image of the original image and to add a different pattern for each device. The gradation-modulated image data is supplied to a video I / F circuit 40.
Is sent to the printer video processing unit 13 through.

In FIG. 4, the printer video processing section (image forming section) 13 has a D / A converter 41, a pulse width modulation circuit (hereinafter, referred to as a “PWM circuit”) 42, and a laser driver 43. The D / A converter 41 converts a digital video signal into an analog video signal. PWM circuit 42
Converts the analog video signal into a PWM signal,
Send to The laser driver 43 drives the semiconductor laser 14 in accordance with the M, C, Y, and Bk video signals sent from the PWM circuit 42. In this way, it is possible to obtain a print output in which a different dot pattern is printed for each device, which cannot be recognized by human eyes but can be read reliably by using a specific recognition technology.

The operation of the above-structured color copying machine will be described with reference to FIG. 5, focusing on gradation conversion, device-specific pattern addition, and device-specific pattern reading. FIG. 5 is a block diagram showing the gradation modulation circuit 39 of the signal processing unit 12. In FIG. 5, the gradation modulation circuit 39 includes:
Horizontal synchronization signal generation circuit 44, counters 45, 46, 4
8, a dot clock generation circuit 47, an input address determination circuit 49 as a pattern switching signal generation unit, a gradation conversion table circuit 50 as a gradation reproduction processing unit, and a device unique pattern generation circuit 51 as a device unique pattern generation unit. . Further, a horizontal synchronizing signal generation circuit 44 and a counter 45,
The units 46 and 48 and the dot clock generation circuit 47 constitute a device-specific pattern generation position determination unit. The horizontal synchronizing signal generation circuit 44 generates a horizontal synchronizing signal h at a predetermined time interval included in the gradation processing. As a source of the horizontal synchronizing signal, an LBP (laser beam printer) can be used after shaping the waveform of the beam detect signal of the polygon mirror. The binary counter 45 counts the horizontal synchronizing signal h, and the output is switched between on and off each time the horizontal synchronizing signal h is input, and whether the image data currently input is an even line (on) or an odd line (off). Is determined. In the printing apparatus according to the present embodiment, the even-numbered line and the odd-numbered line described above are used for 2-dot gradation reproduction in which the original pixel is divided into two in the sub-scanning direction and the gradation of one pixel is reproduced in two sub-scans. The lines form one pixel in pairs. Therefore, in order to distinguish a line formed by the arrangement of the original pixels in the main scanning direction in the main scanning direction from a line constituted by the original pixels divided in the sub-scanning direction in the main scanning direction, the following description will be made. The former is described as a pixel line, and the latter as an even line or an odd line. That is, one pixel line is 1
It is composed of one even line and one odd line.

The counter 46 counts the output of the binary counter 45 and can count the number of the pixel line being processed from the top. Counter 4
Numeral 6 turns the output on and off according to coincidence or non-coincidence with a preset line. That is, on is output for a pixel line to which a unique pattern different for each device is added, and off for a pixel line to which the unique pattern is not added. Further, the counter 48 receives a dot clock d for synchronizing data processing in the main scanning direction from the dot clock generation circuit 47, receives the horizontal synchronization signal h as a reset signal input, and sets the pixel being processed to the top in the main scanning direction. From which pixel can be counted. The counter 48
An ON signal is output when the count value of the dot clock d matches a preset count. That is, a start point for adding a unique pattern that is different for each device is output. There are a plurality of counts that can be set in advance, and an ON output can be obtained several times in one sub-scan.
It is possible to add a unique pattern several times in one pixel line. The outputs of these counters 45, 46 and 48 are 256 levels of C, M,
The image data v is input to the input address determination circuit 49 together with the Y or Bk image data v. The input address determination circuit 49 determines an input address to the gradation conversion table circuit 50 based on the outputs of the counters 45, 46, and 48 and the image data v. The gradation conversion table circuit 50 is generally realized by a ROM or a RAM.

The determination of the input address to the gradation conversion table circuit 50 will be described. First, when the input from the counter 46 is off, since the pixel line is a pixel line to which no device-specific pattern is added, only the input from the counter 45 and the image data input are used. An address having the data input as the lower bit is generated and determined as an input address to the gradation conversion table circuit 50. That is, the gradation data of the even lines is converted from the even table (input addresses 000h to 0FFh) in the gradation conversion table circuit 50, and the gradation data of the odd lines is converted to the odd table (input addresses 100h to 100h) in the gradation conversion table circuit 50. 1FFh) to determine the address.

Next, when the input from the counter 46 is on, the pixel line is a pixel line to which a device-specific pattern is added. Determine the input address to 50. When the input from the counter 48 is off, it is assumed that no device-specific pattern is added except for a device-specific pattern addition section described later. An address is read so that data is read from an even table (input addresses 000h to 0FFh) in the gradation conversion table circuit 50 and gradation data of an odd line is read from an odd table (input addresses 100h to 1FFh) in the gradation conversion table circuit 50. To determine. When the input from the counter 48 is on, it is regarded as the start point of the device-specific pattern addition section, and an address is generated in which the inverted value of the input from the counter 45 is the most significant bit and the image data input is the least significant bit. It is determined as an input address to the conversion table circuit 50. That is, the gradation data of the even line is converted from the odd table (input addresses 100h to 1FFh) in the gradation conversion table circuit 50, and the gradation data of the odd line is converted to the even table (input address 000h to 000h) in the gradation conversion table circuit 50. 0FFh). From the next pixel whose input from the counter 48 is turned on, it is assumed that a certain section is a section to which a unique pattern for recognizing the device is added.
The input address to the gradation conversion table circuit 50 is determined by adding the device-specific pattern signal p from the device-specific pattern generation circuit 51 to the input from the device and the image data input.

Here, the device-specific pattern signal p is a sequence of numerical values including the model number and the serial number of the device stored in an EEPROM or the like in the device, and is, for example, 16-bit information represented by a binary number. is there. Therefore, the section where the unique pattern for recognizing the device is added is a section covering 16 pixels. This fixed section is called a unique pattern addition section. In the unique pattern addition section for each processing pixel, the device unique pattern signal p is sequentially viewed from the upper bits, and when the bit of the device unique pattern signal p is “0”, the input from the counter 45 is the most significant bit. An address having the lower bit of the image data input is generated and determined as an input address to the gradation conversion table circuit 50. That is, the gradation data of the even line is converted into an even table (input addresses 000h to 0F) in the gradation conversion table circuit 50.
Fh), the gradation data of the odd line is converted into the odd table (input addresses 100h to 100h) in the gradation conversion table circuit 50.
1FFh) to determine the address. When the bit of the device-specific pattern signal p is “1”, the inverted value of the input from the counter 45 is set to the most significant bit,
Generate an address with image data input as lower bits,
It is determined as an input address to the gradation conversion table circuit 50. That is, the gradation data of the even-numbered line is converted into an odd-numbered table (input address 100) in the gradation conversion table circuit 50.
h-1FFh), the gradation data of the odd-numbered line is converted into the even-numbered table (input address 0) in the gradation conversion table circuit 50.
00h to 0FFh).

Here, the gradation conversion table circuit 50 will be described in more detail with reference to FIGS. FIG. 6 is a table diagram showing a tone conversion table in the tone conversion table circuit 50, and FIG. 7 is a graph showing a characteristic curve of the tone conversion table for 2-dot tone reproduction.

First, FIG. 6 will be described. Assuming that the input image signal is 8 bits (256 levels), 256 addresses are required in the table to represent one gradation characteristic. In this embodiment, there are a total of 512 table addresses in order to perform a two-dot gradation reproduction process having two gradation characteristics of an even line and an odd line. Address 0
00h to 0FFh represent the gradation characteristics of even-numbered lines using 2-dot gradation reproduction, and addresses 100h to 1FFh represent the gradation characteristics of odd-numbered lines.

Next, the characteristic curve of FIG. 7 will be described.
In the two-dot gradation conversion table characteristic, when the image density is low, the gradation is reproduced by growing the pixel size of the even-numbered line (curve S2) at a higher speed than the pixel of the odd-numbered line (curve S1). When the image density is high, the dots of the pixels of the even lines maintain a certain level lower than the maximum output, and the gradation of the pixels of the odd lines is adjusted to reproduce the gradation. In other words, the priorities are set for the two pixels on the odd-numbered line and the even-numbered line, and the recording dots are grown with priority given to the pixels on the even-numbered lines, and the dots on the even-numbered lines are completely grown. The characteristics of the gradation conversion table are set so as not to exist. In an electrophotographic printer, a stronger electric field is applied to a micro area of an electrostatic latent image on the photosensitive drum 18 when a dot of a specific pixel is preferentially grown than a dot of each pixel is evenly grown. As a result, the gradation of the recorded image is improved. The present embodiment reproduces a high-quality image by performing image reproduction processing with good gradation using 2-dot gradation conversion on an input image signal, and adds a unique pattern for recognizing a device. A pattern is formed in which even-numbered lines and odd-numbered lines having different pixel growth rates in 2-dot gradation conversion are exchanged. Therefore, a unique pattern for recognizing the device can be added to the reproduced image without superimposing an image signal for a new additional pattern on the reproduced image.

FIG. 8 is an additional pattern configuration diagram showing the configuration of the additional pattern according to the present embodiment. A small square surrounded by a solid line represents one pixel of the original image. In the present embodiment, since two-dot gradation modulation is used, one pixel is divided into two in the sub-scanning direction, and the divided line is indicated by a broken line. The upper side of the broken line is the even line, and the lower side is the odd line. The first, third, and fifth pixel lines “1”, “3”, and “5” in FIG. 1 are pixel lines to which no device-specific pattern is added. In each pixel, even-numbered lines grow more than odd-numbered lines. Speed is getting faster. The second, fourth, and sixth pixel lines “2”, “4”, and “6” in FIG. 1 are pixel lines to which a device-specific pattern is added, and a unique-pattern-added region exists in a hatched region. At the head of the unique pattern addition area, there is always a pixel having a lower pixel growth rate in the even-numbered line than in the odd-numbered line, unlike the previous area. This becomes the start mark bit S, and indicates that the pixels subsequent to this pixel are the unique pattern addition area representing the device unique pattern. In the unique pattern addition area, pixels having even-numbered lines having a faster pixel growth rate than odd-numbered lines represent “0”, and pixels having even-numbered lines having a slower pixel growth rate than odd-numbered lines represent “1”. I have. Therefore, it can be seen that the unique pattern shown in FIG. 8 is "10101110 ...". It is assumed that the device-specific pattern has a predetermined bit length.

In general, when trying to read an apparatus-specific pattern from one end of a print, the orientation of the print and the distinction between even-numbered lines and odd-numbered lines are not known. . As shown in FIG. 8, the method of adding a device unique pattern according to the present embodiment uses at least one device between a pixel line to which a device unique pattern is added and a pixel line to which another device unique pattern is added. Since the pixel line to which the unique pattern is not added is provided, it is inevitably possible to determine the print direction and the distinction between the even line and the odd line.

FIG. 9 is an additional pattern configuration diagram for explaining the operation of reading the device-specific pattern. In the present embodiment, even when there is a device-specific pattern on a print that does not know the orientation of the print and the distinction between the even-numbered lines and the odd-numbered lines, it is necessary to know the orientation of the print and the distinction between the even-numbered lines and the odd-numbered lines. And a device-specific pattern can be read. This will be described. First, the vertical direction and the horizontal direction can be known from the pixel growth direction. Next, a pixel line candidate is created using two vertically adjacent lines as one set. These sets correspond to K1 to K6 in FIG.
Is selected as a set such that the growth rate of the pixels on one line in one set is always faster or slower than the growth rate of the pixels on the other line and is constant. And the relationship between the growth rate of the pixels on one line of the set and the growth rate of the pixels on the other line is not constant (the relationship between the growth rates of the pixels is partially reversed). ) And the pairs appear alternately. FIG.
Then, the sets K1, K3, and K5 are the former sets, and the sets K2, K
4. K6 (partly shaded) is the latter. In this case, it can be seen that the correct pixel line has been selected as a pixel line candidate, and further, the sets K1, K
3. By selecting the pixel line indicated by K5 such that the faster pixel growth rate is the even line and the slower pixel growth rate is the odd line, it is possible to know the print direction and the distinction between the even line and the odd line. .

The set of pixel line candidates is K7 to K1.
When selected as a set such as 1, there is no regularity between the growth rate of the pixels existing on one line of the set and the growth rate of the pixels existing on the other line, and the set K1,
A regular arrangement like K3 and K5 is not seen. In this case, it can be seen that an erroneous pixel line has been selected as a pixel line candidate, and it is possible to reselect as a group such as K1 to K6 by shifting one line. Therefore, even when there is a device-specific pattern on a print whose orientation and the distinction between the even-numbered lines and the odd-numbered lines are not known, it is possible to know the orientation of the print and the distinction between the even-numbered lines and the odd-numbered lines. The pattern can be read, and the copied device can be specified from the copy.

In reading the device-specific pattern, the growth of each dot shows a similar value at a high or low density, making it difficult to determine the difference in dot growth speed. In particular, it is often difficult to determine when 1-bit information of a unique pattern is added to an image or the like including a dither pattern or the like in units of one pixel. In this case, the determination can be facilitated by adding 1-bit information over a plurality of pixels. FIG. 10 shows that 1-bit information
FIG. 3 is an additional pattern configuration diagram illustrating a case where the pixel is added to a pixel;
The figure shows the start mark bit S and the bit information of the device-specific pattern added in units of two pixels.

FIG. 11 shows an additional pattern configuration showing an example of a copy result in this embodiment.

In this embodiment, as described above, an additional pattern is not newly added, and two gradation modulation processes are switched and used for an input image signal, and a dot for reproducing an image is used. Since the pattern is added by changing the growth, the pattern is not added in the area where the input image signal does not exist, and the additional pattern is formed according to the image signal level. It is possible to reproduce without loss. Conventionally, an inconspicuous yellow component is used in the additional pattern. However, by switching between the two tone reproduction processes according to the present embodiment, the other three colors (cyan, magenta, and black) can be used. Similarly, it is possible to add a pattern.

In this embodiment, the priority of dot growth of the additional pattern is divided into two lines, an even line and an odd line. However, the priority is not limited to two lines, but may be divided into a plurality of lines of three or more lines. There may be. Further, the present invention can be applied to the case of dot growth in which priority is provided not only on the sub-scanning side but also on the main scanning side. Furthermore, in this embodiment, an electrophotographic apparatus using a laser beam printer has been described as an example. However, the scope of the present invention is not limited to an electrophotographic apparatus, and may be applied to an inkjet printer, a thermal transfer printer, and an LED printer. It is applicable and is not limited to a color printer. In particular, a so-called bubble jet type printer using a head that discharges liquid droplets using film boiling due to thermal energy may be used. Further, in the present embodiment, the image scanner unit 1
However, the present invention is not limited to this, and may be input by a still video camera or video camera, or may be input by computer graphics. Further, the present invention can be applied to an apparatus including one device or a system including a plurality of devices, and can also be applied to a case where a system or an apparatus is operated by supplying a program. .

As described above, according to the present embodiment, the pixel line is divided into two upper and lower lines, the upper line is an even line, the pixel growth speed is increased, and the lower line is an odd line. When the speed is reduced and the device-specific pattern is inserted, the vertical relationship is reversed for “1” and the vertical relationship is maintained for “0”. Instead of adding a new pattern, the pattern is added by changing the growth of the dots that reproduce the image, so that the pattern is not added in an area where the input image signal does not exist. Since the additional pattern is formed, it is possible to reproduce the image without deteriorating the gradation. In addition, since 1-bit information of the device-specific pattern is added over two pixels, pattern determination can be facilitated.

[0038]

As described above, according to the printing apparatus of the present invention, a device-specific pattern is added at a specific position determined by the device-specific pattern generation position determining unit with a pattern switched by the pattern switching signal generating unit. Therefore, for example, the arrangement of image data patterns can be switched to be a device-specific pattern, and it is not necessary to add an additional pattern. Further, in an area where an input image signal does not exist, a pattern can be used. Can be prevented from being added, and an additional effect can be obtained in which an additional pattern corresponding to the image signal level can be formed so as not to impair the gradation of the image.

Further, by dividing the pixels constituting the image signal into a plurality of pixels and performing gradation conversion by setting the divided pixels to have different growth rates, pattern switching based on the difference in pixel growth rates can be performed. And the same effect as above can be obtained.

Further, the device-specific patterns generated by the device-specific pattern generating section are arranged in a plurality on the image plane in the same order, and the device-specific patterns are generated so as not to arrange the device-specific patterns in the plurality of same rows. By determining the position, additional information of the document copy can be identified from the arrangement of the device-specific patterns on the screen plane,
An advantageous effect that reading of the device-specific pattern is facilitated is obtained.

Further, by repeating the generation of the device-specific pattern a plurality of times, there is an advantageous effect that the additional information of the original copy can be reliably identified even when the difference in the pixel growth rate is small.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a color copying machine as a printing apparatus according to a first embodiment of the present invention;

FIG. 2 is a block diagram illustrating a line sensor of the image scanner unit.

FIG. 3 is a block diagram illustrating a signal processing unit of the printer unit.

FIG. 4 is a block diagram illustrating a printer video processing unit of the printer unit.

FIG. 5 is a block diagram showing a gradation modulation circuit of a signal processing unit.

FIG. 6 is a table diagram showing a gradation conversion table in a gradation conversion table circuit;

FIG. 7 is a graph showing a characteristic curve of a tone conversion table for 2-dot tone reproduction.

FIG. 8 is an additional pattern configuration diagram showing the configuration of an additional pattern in the present embodiment.

FIG. 9 is an additional pattern configuration diagram for explaining an operation of reading a device-specific pattern.

FIG. 10 is an additional pattern configuration diagram showing a case where 1-bit information is added to two pixels.

FIG. 11 is an additional pattern configuration diagram showing an example of a copy result according to the embodiment;

FIG. 12 is an additional pattern configuration diagram showing an example of a copy result in the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image scanner unit 2 printer unit 3 mirror surface pressure plate 4 platen glass 5 document 6 lamp 7, 8, 9 mirror 10 lens 11 line sensor 12 signal processing unit 13 printer video processing unit 14 semiconductor laser 15 polygon mirror 16 f-θ lens 17 Mirror 18 Photosensitive drum 19 Developing device 19 20 Black developing unit 21 Yellow developing unit 22 Cyan developing unit 23 Magenta developing unit 24 Intermediate transfer member 25 Paper cassette 26 Fixing unit 27 CCD 28 S / H & A / D circuit 29 Shading correction circuit 30 Resolution conversion Circuit 31 Smoothing circuit 32 Color correction circuit 33 MTF correction circuit 34 γ correction circuit 35 Density conversion circuit 36 Masking & UCR circuit 37 Page memory 38 γ correction circuit 39 Gradation modulation circuit 40 Video I / F circuit 41 D / A conversion Vessel 42 PWM circuit 43 a laser driver 44 a horizontal synchronizing signal generating circuit 45, 46, 48 counter 47 dot clock generating circuit 49 inputs the address determining circuit 50 gradation conversion table circuit 51 device-specific pattern generator

Claims (4)

[Claims] A device for generating a device-specific pattern; a device-specific pattern generating portion for determining a device-specific pattern generation position; A pattern switching signal generation unit that switches a pattern generation method in the tone reproduction processing unit according to the generation position of the device-specific pattern determined by the device-specific pattern generation position determination unit and the device-specific pattern generated by the device-specific pattern generation unit And an image forming unit for generating an image whose gradation has been converted by the gradation reproduction processing unit. 2. The gradation conversion unit according to claim 1, wherein the gradation reproduction processing section divides the pixels constituting the image signal into a plurality of pixels, and performs gradation conversion by setting the divided pixels to have different growth rates. Printing equipment. 3. The apparatus-specific pattern generation position determining unit according to claim 1,
A plurality of device-specific patterns generated by the device-specific pattern generation unit are arranged on the image plane in the same arrangement, and a position between the plurality of same arrangements is determined so as not to arrange the device-specific patterns. The printing apparatus according to claim 2, wherein 4. The apparatus-specific pattern generating section repeats generation of a device-specific pattern a plurality of times.
The printing apparatus according to any one of the above.