JPH09331449A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which information to specify a copying machine or the like is added to a reproduced image without changing image quality of the reproduced image. SOLUTION: The device is provided with a gradation conversion table A45 to conduct gradation conversion of a usual image of a reproduced image, a gradation conversion table B46 to conduct gradation conversion of a contour of the reproduced image and a gradation variable table C47 used to conduct gradation display of an equipment specific pattern to display identification information of the device, and when a contour detection circuit 38 detects a contour, a pattern changeover generating circuit 43 selects the gradation variable table B46 and a pattern generating circuit 40 outputs to add an equipment specific pattern, a pattern changeover generating circuit 43 selects the gradation variable table C47. Thus, the reproduced image to which the device specific pattern is added is generated.

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 holding a high quality recorded image and adding specific information to a reproduced image.

[0002]

2. Description of the Related Art It is conceivable that certain originals such as banknotes and securities will be copied due to improvements in the performance of color copiers and color printers, and these will be illegally used. In the past, it has been a difficult task to identify which device copied an illegally copied copy. In order to prevent such illegal copying, it is being considered to identify the color copying machine or the color printer itself to forcibly prohibit illegal copying.

In this case, a circuit for determining a specific original is used in a color copying machine or a color printer, but since the number of image patterns that can be registered is limited in this circuit, all types of specific originals are registered. It has the disadvantage that it is impossible.

Although it is important to add a means for detecting a specific document to the apparatus itself, there is a limit to the detection capability of the specific document. Therefore, if an original that should not have been copied is copied, the copying machine that copied it, or
It is important to identify the person who copied it. Based on such a background, a technique for adding information or the like for identifying a copying machine that has made a copy to a document image is being studied.

The technique is the output color component (eg, yellow) which is the least noticeable to the human eye among the output color components (eg, magenta, cyan, yellow, black) of the copying machine.
To modulate the image signal of the output color component (for example, add a constant value), and then small numbers or symbols representing the serial number of the copying machine, or patterned dots are repeated and repeated at regular intervals. It is a thing.

[0006]

However, in the above technique, even if yellow is the output color component that is the most invisible to the eyes, modulating the image signal means changing the color component, and changing the color of the reproduced image. The result will be changed. 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. Further, when copying an original, even if the original has a uniform color, the image signal is not always uniform due to variations in the sensitivity of the CCD, etc. However, the image on the host computer can be displayed using the external interface of the color copying machine. When printing out, it is possible to directly output CG (Computer Graphics), so there is a sufficient uniform area at the image signal level. At that time, when the yellow component is modulated, the additional pattern is apt to stand out particularly in a light gray or light blue uniform portion and may be added even in a region where the image signal does not exist, so that the pattern may be raised. In addition, the toner consumption amount increases only for yellow.

In the conventionally conceived method of forming a unit pattern in which numbers, signs, and dot patterns representing additional information are made small, and repeating the unit pattern at regular intervals to form an additional pattern, they are made small in a grid pattern. When the unit pattern is arranged, the human eyes can easily recognize a regular pattern rather than a randomly arranged pattern, so that it becomes more conspicuous. Therefore, there is no choice but to reduce the degree of modulation of the image signal, and the additional information may not be read depending on the specific document.

FIG. 17 is a diagram showing an example of a copy result in the conventional technique. Since the conventional apparatus always adds a fixed amount of pattern, there is a drawback that the pattern is printed even in an area where an image does not exist regardless of the image area of the copy. Therefore, it is difficult for the reproduced image to be discerned when viewed by the human eyes while maintaining the image quality of the original image in the reproduced image, and it is possible to surely discriminate it by a certain method in a copy such as a specific original document. It is necessary to consider gradation modulation and additional patterns that satisfy the above conditions.

Therefore, an object of the present invention is to provide an image forming apparatus capable of adding information for specifying a copying machine or the like to a reproduced image of an original image without changing the quality of the reproduced image. .

[0010]

An image forming apparatus according to the present invention is an image forming apparatus for converting an input image signal into gradation and generating a reproduced image to which a display pattern indicating information for identifying the apparatus is added. Pattern generating means for generating a display pattern indicating information for identifying the device, position determining means for determining a position to add the display pattern in the reproduced image based on the output from the pattern generating means, input image signal and position Gradation for receiving the output from the determination means and converting the gradation of the input image signal to generate different gradation display data so as to perform different gradation display at the position where the reproduced image is displayed and the position where the display pattern is added. Reproduction processing means.

By adding a display pattern for identifying the device to the reproduced image with different gradation display from other image portions, it is possible to identify the display pattern using a specific recognition technique. The device that reproduced the image can be easily identified. Moreover, since such a display pattern cannot be recognized by the eyes of the ordinary person, the quality of the reproduced image can be maintained at a high level.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the invention of claim 1 is an image forming apparatus which converts a gradation of an input image signal and generates a reproduced image to which a display pattern indicating information for identifying the apparatus is added. A pattern generating means for generating a display pattern indicating information for identifying the device, a position determining means for determining a position to add the display pattern in the reproduced image based on an output from the pattern generating means, and an input image signal And the output from the position determining means, and gradation-converts the input image signal to generate gradation display data so as to perform different gradation display at the position where the reproduced image is displayed and the position where the display pattern is added. Key reproduction processing means.

Thus, the device that generated the reproduced image can be surely recognized by using the specific recognition technique without deteriorating the quality of the reproduced image.

The image forming apparatus according to the invention of claim 2 is different from the image forming apparatus according to the invention of claim 1 in that it further comprises contour detecting means for extracting the contour portion of the image from the input image signal. The tone reproduction processing means receives the output from the contour detecting means, and performs gradation conversion on the input image signal so that gradation display different from the gradation display at the position where the reproduced image is displayed is performed at the position where the contour portion of the reproduced image is displayed. To do.

As a result, gradation display can be performed with high resolution in the contour portion of the image.

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the second aspect of the invention, wherein the gradation reproduction processing means has a plurality of blocks each having a plurality of blocks into which a predetermined area is divided. Dither matrix table,
It has a switching means for switching a plurality of dither matrix tables according to the outputs from the position determining means and the contour detecting means, and compares the pixel level of the input image with the pixel level of the dither matrix table switched by the switching means. Then, the gradation level of each block is set, and pixels corresponding to the gradation level are grown in the block according to a specific condition.

As a result, it becomes possible to reproduce an image by area gradation in which pixels corresponding to the gradation level are grown for each block and gradation display is performed. Further, by switching the dither matrix table, a plurality of gradation reproduction processes can be switched and performed.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the third aspect of the invention, wherein a plurality of dither matrix tables are provided for each pixel in accordance with a gradation level set for each block. The gradation display is performed by changing the reference positions for growing the.

Thus, it is possible to form pixels having different start positions for growing pixels for each block without changing the reproduced image level by the dither matrix table.

An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to the third aspect of the invention, wherein a plurality of dither matrix tables are provided for each pixel according to a gradation level set for each block. The gradation is displayed at different growth rates.

Thus, it is possible to form pixels having different pixel growth rates for each block without changing the reproduced image level by the dither matrix table.

An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the third aspect of the invention, in which a plurality of dither matrix tables gives priority to each block in which pixels are grown according to a gradation level. The dither matrix table is provided with different degrees to perform gradation display.

With this, it is possible to form pixels having different pixel growth priorities for each block without changing the reproduced image level by the dither matrix table.

An image forming apparatus according to a seventh aspect of the present invention is the image forming apparatus according to the third to sixth aspects of the invention, wherein the switching means specifies the position to which the display pattern is added from the position determining means. In this case, the dither matrix table for generating the display pattern is selected from the plurality of dither matrix tables.

Thus, it is possible to add a display pattern for identifying the device in the reproduced image without changing the reproduced image level.

In the image forming apparatus according to an eighth aspect of the present invention, in the image forming apparatus according to the third to sixth aspects of the present invention, the switching means outputs the contour portion of the image from the contour detecting means. When there is an output indicating the additional position of the display pattern from the position determining means, the output from the contour detecting means is prioritized and the dither matrix table for displaying the contour is selected.

As a result, it is possible to select the gradation modulation processing effective for reproducing the gradation of the contour component without adding the display pattern for identifying the device to the contour portion of the image.

An image forming apparatus according to a ninth aspect of the present invention is the image forming apparatus according to the first to eighth aspects of the invention, wherein the position determining means repeatedly adds a display pattern at regular intervals. .

As a result, a display pattern for identifying the device can be added to any position of the image copy area as long as the image level exists.

The image forming apparatus according to the invention of claim 10 is
In the configuration of the image forming apparatus according to the inventions of claims 1 to 9, the pattern generating means generates a display pattern having a recognition pattern unique to the apparatus and a recognition edge pattern surrounding the recognition pattern.

As a result, the display pattern for identifying the device can be easily identified by reading the recognition edge pattern regardless of the orientation of the input image in the image copy area.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, an example of a color copying machine in which a color scanner and a color printer are combined is shown as an application example of the present invention, but the present invention is not limited to this, and a color printer, a single color copying machine, or the like, Of course, it can be applied to various other devices.

FIG. 1 is a side sectional view showing the internal structure of the color copying machine of this embodiment. In FIG. 1, the color copying machine is composed of an image scanner section 1 and a printer section 2. The image scanner unit 1 reads a document and performs digital signal processing. The printer unit 2 also performs image processing on the image signal read by the image scanner unit 1 and prints it out.

In the image scanner unit 1, the original 4 on the original platen glass 3 is illuminated by the lamp 5, and the mirror 6,
7 and 8, a lens 9 forms an image on a 3-line sensor (hereinafter referred to as “CCD”) 10, and full-color information is sequentially printed as red (R), green (G), and blue (B) components. Sent to. The lamp 5 and the mirror 6 have a speed v, and the mirrors 7 and 8 have a speed 1 / 2v.
Then, the front surface of the document is scanned (sub-scanning) by mechanically moving in a direction perpendicular to the electrical scanning (main-scanning) direction of the line sensor.

The full-color information red (R), green (G) and blue (B) component signals sent to the printer unit 2 are magenta (M), cyan (C) and yellow (Y) in the signal processing unit 11. ) And black (Bk) components are separated and sent to the printer video processing unit 12 for each plane. The printer video processing unit 12 modulates and drives the semiconductor laser 13 according to the sent image signal. The laser light scans the photosensitive drum 17 via the polygon mirror 14, the f-θ lens 15, and the mirror 16. The developing device 18 composed of black, yellow, cyan, and magenta contacts the photosensitive drum 17 in order each time the information of each plane is sent, and electrostatically develops the toner formed on the photosensitive drum 17 into toner. To develop. Intermediate transfer member 19
Develops a monochromatic toner image developed on the photosensitive drum 17 in sequence, and obtains a toner image with four color toners on its surface.

The toner image on the intermediate transfer member 19 is transferred onto the recording paper supplied from the paper cassette 20 in one pass. The recording paper passes through the fixing unit 21, the toner is fixed on the paper, and then the recording paper is ejected.

FIG. 2 is a block diagram showing the circuit configuration of the image scanner unit 1 shown in FIG. In the figure, the image scanner unit 1 includes a CCD line sensor 22 having spectral sensitivity characteristics of R, G, and B, a sampling and holding and AD conversion circuit (hereinafter referred to as S / H & A / D circuit) 23, and a shading correction circuit. 24, resolution conversion circuit 25, smoothing circuit 26, color correction circuit 27, M
It has a TF correction circuit 28 and a γ correction circuit 29.

In the above structure, the CCD line sensor 2
The image signal input from the S / H & A / D circuit 23
After being S / H and A / D converted by, each is output as a signal of 8-bit output 0-255. Further, the shading correction circuit 24 performs shading correction and black correction. The resolution conversion circuit 25 thins out or interpolates the data so as to obtain the data according to the designated resolution. Subsequently, after smoothing the data by the smoothing circuit 26, the color correction circuit 27, the MTF correction circuit 28, and the γ correction circuit 29 perform the color correction, the MTF correction, and the γ correction, and output the output value of the image scanner unit 1. The optimally adjusted value is output.

FIG. 3 is a block diagram showing the configuration of the printer controller unit according to this embodiment. In the figure, the printer controller includes a density conversion circuit 30, a masking and background removal circuit (hereinafter referred to as a masking & UCR circuit) 31, a page memory 32, and a γ correction circuit 3.
3, a gradation modulation circuit 34, and a video interface circuit (hereinafter referred to as a video I / F circuit) 35.

In the above structure, the 256 level image signals R, G, B input from the scanner section 1 shown in FIG. 2 are converted from the luminance information into cyan (C) and magenta (M) by the density conversion circuit 30 and the masking & UCR circuit 31. ), Yellow (Y), and black (Bk) density information is converted pixel by pixel. These density information C, M, Y, B
k is the page memory 3 once until one page of data is collected
2 is stored. When the data for one page is prepared, the density information for each plane is sequentially passed through the γ correction circuit 33 and input to the gradation modulation circuit 34. The gradation modulation circuit 34 performs gradation conversion to reproduce the high quality of the original image, and at the same time, performs processing for adding a different pattern for each device. The gradation-modulated image data is sent to the printer video processing unit 13 via the video I / F circuit 35.

FIG. 4 is a block diagram showing a circuit configuration of the printer video processing unit 12 according to the embodiment. In the figure, a shift register 36 performs serial / parallel signal conversion of gradation-modulated image data and sends the converted image data to a laser driver 37. The laser driver 37 follows the semiconductor laser 1 according to the input C, M, Y, Bk video signals.
Drive 3

In the color copying machine according to the present embodiment, the gradation modulation processing for faithfully reproducing the read original image is performed in this way, and a specific recognition technique that cannot be recognized by human eyes is used. By doing so, it is possible to surely read, and it is possible to obtain a print output to which a unique pattern different for each device is added.

Here, the gradation modulation which is the image reproduction processing in the present embodiment will be described in detail with reference to the drawings.
FIG. 5 is a block diagram of the gradation modulation circuit 34 according to the embodiment. In FIG. 3, the image data stored in the page memory 32 is input to the gradation modulation circuit 34 through the γ correction 33. In FIG. 5, the contour detection circuit 38 detects the contour component of the image in the input image data, and outputs a contour portion switching signal 39.

The pattern generation circuit 40 receives a device-specific pattern 41 which is different for each device, and outputs a pattern portion switching signal 42 to the pattern generation switching circuit 43.
The pattern generation switching circuit 43 uses the contour portion switching signal 39 and the pattern portion switching signal 42 to convert the input image data into the gradation modulation table A4 of the gradation reproducing circuit 44.
5, gradation modulation table B46, gradation modulation table C47
Switch. Normally, an image is reproduced by the gradation modulation table A45 having high gradation and reproducibility, and when the contour detection circuit 38 detects a contour component, the gradation reproduction table B46 holding the contour is selected. Furthermore, when adding a device-specific pattern by the output of the pattern generation circuit 40, the gradation modulation table C47 is selected that can add a recognition pattern while maintaining high image reproducibility. The image data that has been gradation-modulated by the gradation reproduction circuit 44 is output to the video I / F circuit 35.

Here, the contour detection circuit 38 and the pattern generation circuit 40 will be described in more detail with reference to FIGS. 6, 7 and 8.

FIG. 6 shows a contour detecting circuit 38 according to the embodiment.
3 is a 3 × 3 mask table diagram of FIG. The determination of the contour component is
An edge component is extracted from the 3 × 3 mask table shown in the figure by using the sum of the absolute values of the differences between the target pixel X and its peripheral pixels a, b, c, and d, and a threshold value T set in advance is extracted. Determined by comparing

| X−a | + | X−b | + | X−c | + | X−d | ≧ T (1) FIG. 7 is a block diagram of the contour detection circuit 38 according to the embodiment. The input image data is input to the flip-flop circuit 48 that latches the determination pixel a and is also supplied to the line memory 49. The image data held in the line memory 49 is input to the flip-flop circuit 50 that latches the determination pixels b, X, and c, and is also supplied to the line memory 51. Further, the image data stored in the line memory 51 is input to the flip-flop circuit 52 that latches the determination pixel d. Contour determination circuit 53
Is input with decision pixels a, b, c, d, X latched by a flip-flop circuit and a preset contour portion threshold value T54, and the contour is determined by the above-described decision expression (1) to output a switching signal. Output. As a result, the output switching signal is input to the pattern generation switching circuit 43 of FIG. 5, and the gradation modulation table of the gradation reproduction circuit 44 can be switched.

FIG. 8 is a block diagram of the pattern generation circuit 40 according to the embodiment. In the pattern generation circuit 40,
The horizontal sync signal 55 and the video clock signal 56 are input to determine the position to add a pattern in the main scanning direction, and the horizontal pattern position determination circuit 57 is input to determine the position to add a pattern in the sub scanning direction. The vertical pattern position determination circuit 59 determines the position where the device-specific pattern is added to the reproduced image. The outputs of the horizontal pattern position determination circuit 57 and the vertical pattern position determination circuit 59 are counted in the main scanning direction and the sub scanning direction by the horizontal synchronization counter 60 and the vertical synchronization counter 61, respectively, and have counters synchronized in the main scanning direction and the sub scanning direction. It is input to the pattern output circuit 63 together with the device-specific bit pattern 62. The pattern output circuit 63 acquires the bit information of the device-specific bit pattern 62 existing at the selected pattern position in synchronization with the horizontal synchronization counter 60 and the vertical synchronization counter 61, and outputs the presence / absence of bits to which the pattern is added.

The pattern generation determination circuit 64 outputs a switching signal in synchronization with the output of the pattern output circuit 63 and the outputs of the horizontal pattern position determination circuit 57 and the vertical pattern position determination circuit 59. As a result, the output switching signal is input to the pattern generation switching circuit 43 of FIG. 5, and the gradation modulation table of the gradation reproduction circuit 44 to which a device-specific pattern is added can be switched.

The horizontal pattern position determination circuit 57 and the vertical pattern position determination circuit 59 repeatedly output the information of the bit pattern 62 peculiar to the apparatus at regular intervals in the main scanning direction and the sub scanning direction. As a result, no matter which area of the image copy area the input image data is in, the recognition pattern can be added as long as the image level exists. Even when the device-specific bit pattern 62 exists across an area where the image level does not exist, it is possible to recognize the device-specific pattern by determining the pattern of another area that is repeatedly added. Become.

Here, the structure and operation of the gradation reproduction circuit 44 will be described. The gradation reproduction circuit 44 receives the output signals from the contour detection circuit 38 and the pattern generation circuit 40, and outputs gradation reproduction data according to the output signals. Therefore, as shown in FIG.
Are the three types of gradation extension tables A to C4 as described above.
5 to 47 are provided. The gradation modulation table A45 is a gradation modulation table of a general image portion excluding the contour portion, the gradation modulation table B46 is a gradation modulation table of image data of the contour portion, and further the gradation modulation table C.
Reference numeral 47 is a gradation modulation table of image data to which a device-specific pattern should be added.

FIG. 9 is an explanatory diagram of the dither matrix table according to the embodiment in the gradation modulation table A45. In FIG. 9, the dither matrix table 65
Has a table size of 32 pixels in the main scanning direction and a total of 256 pixels of 8 lines in the sub scanning direction, and a predetermined threshold value is set for each pixel. Note that FIG. 9 shows a dot image by the area gradation method set corresponding to the input image data. In the area gradation method according to the present embodiment, the dither matrix table 65 is divided into 8 blocks, and the order of growing pixels is set in the right corner of each block as indicated by the numbers, and the central portion of each block is set. A total of 256 levels of area gradation are reproduced by growing pixels from 66.

One pixel of the dither matrix table 65 has a gradation level of 8-bit width and a threshold value of 0 to 255 can be set. By having a table size of 256 levels and a gradation level of 1-bit 8-bit width, with respect to input image data having a level of 256 gradations,
The image is reproduced by the area gradation of 256 pixels of the dither matrix table 65.

FIG. 10A shows the data structure of the page memory 32 in which the image data scanned by the image scanner unit 1 is stored, and shows the image data input at the level of 256 gradations. FIG.
(B) is a detail of the matrix table block in which the 8-bit width gradation level is set for each pixel in the dither matrix table 65 (gradation modulation table A),
A threshold value of 0 to 255 is set for the table size of 256 pixels. FIG. 10C is a dot image of an image actually output.

In FIG. 10A, the image data 67 scanned and stored in the memory is the gradation level value 70.
10B, the gradation reproduction circuit 44 sets the threshold level group 68 and the gradation level value 70 of the image data 67 set in the same area on the block corresponding to the image data 67 of FIG. Compare the level differences. When the input gradation level value is equal to or exceeds the set threshold value, the output pixel 69 in FIG. 10C is formed at the same position as the position where the threshold value is set. For example,
In the case of FIG. 10, eight threshold values 0, 32, 64, 96, 126, 158, 188 in the threshold value group 68,
Of 220, those that are equal to or exceed the gradation level value 70 of the image data 67 are positions where threshold values of 0, 32, and 64 are set, and three pixels of the output pixel 69 are formed. Similarly for other table areas, level differences are compared and output pixels are formed.

Further, in this embodiment, the threshold value group of the matrix table is set so that the pixels grow on both sides from the central portion 66 of each block. With such a method, it is possible to obtain an output image with high gradation and image reproducibility according to the gradation level of the input image data by the gradation reproduction method using the dither matrix table 65.

Next, the gradation reproduction operation of the gradation reproduction circuit 44 when the contour portion of the image is detected will be described. FIG.
FIG. 1 is a dither matrix table diagram for reproducing the contour according to the embodiment. Pattern generation switching circuit 43
Receives the output signals from the contour detection circuit 38 and the pattern generation circuit 40, and switches to the gradation modulation table B46 of the gradation reproduction circuit 44. In this case, the contour detection circuit 3
When the output signal from 8 indicates that the contour is detected, the gradation modulation for image reproduction of the contour portion is performed regardless of whether the output signal from the pattern generation circuit 40 generates a device-specific pattern. Select table B46. The above-described dither matrix table in FIG. 9 is divided into 8 blocks for gradation reproduction. However, when the contour of an image is reproduced, if the resolution is low, jaggies in the contour portion become conspicuous. Therefore, for the contour portion, the dither matrix table is divided into 16 blocks, and the gradation of the contour portion is reproduced by using the matrix table 90 whose resolution in the main scanning direction is increased. The dither matrix table 90 of FIG. 11 divided into 16 blocks is effective for image reproduction of the contour portion, but since the blocks are closely adjacent to each other, it is difficult to reproduce a gradation image of a wide range of halftone levels. Therefore, normally, the pattern generation switching circuit 4 is divided into eight blocks as shown in FIG. 9 to perform gradation modulation with high gradation reproducibility, and only when the contour component is detected.
3 is switched to the gradation modulation table using the dither matrix table 90 of the gradation reproduction circuit 44 in FIG. 11 to perform gradation modulation for finely reproducing the contour portion. As a result, it is possible to obtain an output image with high gradation that reproduces the contour portion.

Further, the operation of the gradation reproduction circuit 44 when the device-specific pattern is to be added will be described. FIG.
FIG. 6 is a first dither matrix table diagram for adding a pattern according to the embodiment. When the pattern generation circuit 40 determines that it is the position where the device-specific pattern 41 is added to the reproduced image, the pattern generation switching circuit 43
Selects the gradation modulation table C47 of the gradation reproduction circuit 44. In the gradation modulation method using the dither matrix table 91 shown in FIG. 12, the gradation is reproduced by dividing it into 8 blocks, similarly to the dither matrix table 65 in FIG. 9 described above. It is set at a position different from that of the dither matrix table 65 of FIG. 9 used in normal gradation modulation.

That is, while the normal dither matrix table 65 grows pixels centering on the central portion 66 of the block, the dither matrix table 91 of this example in which the device-specific pattern is added is the central portion 71 of the 1/2 block. The pattern information is added by growing a pixel centering on the pixel and adding a phase difference 72 of several pixels (4 pixels in this example). Phase difference 7 at the start position to grow pixels
The settings other than the setting of 2 are exactly the same as those of the dither matrix table 65 of FIG. 9, and for this reason, it is possible to add a pattern while holding an image with high reproducibility.

The human eye cannot recognize the phase difference of several pixels forming a pixel. However, it can be easily discriminated using a specific recognition technique. This makes it possible to add a device-specific tracking pattern that can specify the output image forming apparatus to the reproduced image while maintaining high image reproducibility.

Since the pattern unique to the apparatus is repeatedly output at a constant interval as described above, it can be judged in another area, and the pattern is added at the position where the contour detection circuit 38 determines the contour of the image. If so, the image reproducibility of the contour portion may be deteriorated.
Therefore, as described above, in the pattern generation switching circuit 43 for switching the gradation modulation table, when the input contour portion switching signal 39 of the contour detection circuit 38 and the pattern portion switching signal 42 of the pattern generation circuit 40 are simultaneously generated. Then, priority is given to the contour portion switching signal 39, and the pattern portion switching signal 42 is invalidated.

Next, in the case of adding a pattern peculiar to the apparatus, the pattern is added by a matrix table different from the gradation modulation using the matrix table of FIG. 12 in which a phase difference is added to the start position of pixel growth. A gradation modulation method and a gradation reproduction method using the second and third matrix tables that can be used will be described with reference to FIGS. 13 and 14.

FIG. 13 shows a second dither matrix table to which the pattern according to the embodiment is added. Similar to the dither matrix table 65 in FIG. 9 described above, these dither matrix tables are divided into eight blocks for gradation reproduction, but in this example, the growth rate for forming pixels in each divided block is shown. The growth rate is set to be different from that of the gradation modulation dither matrix table 65 shown in FIG. The matrix table of FIG. 9 grows pixels at a uniform speed in any of the divided blocks, whereas the dither matrix table of FIG. 13 has different growth speeds for each block, that is, for a certain block. Is a block 73 in which pixels grow rapidly, and a block 74 in which some pixels grow slowly. By combining these blocks, pattern information unique to the apparatus is added.

The growth rate can be set variously for each block in the main scanning direction and the sub-scanning direction as shown in FIGS. 13D, 13E and 13F, and as shown in FIG. 13G. The growth rate in one block may be set differently, or a combination thereof may be used. In this method, although the growth rate differs for each block, the total gradation reproduction level of the dither matrix table is the same as that of the dither matrix table of FIG. 9, so that the pattern peculiar to the apparatus is maintained while maintaining the image reproducibility. Can be added.

FIG. 14 is a third dither matrix table to which a pattern according to the embodiment is added, and gradation reproduction is performed by dividing it into 8 blocks like the dither matrix table 65 in FIG. 9 described above. In this example, pixels are formed by giving a specific priority to each of the divided blocks.

The dither matrix table of FIG. 9 uniformly grows the pixels from the central portion 66 of the divided blocks, whereas the dither matrix table of FIG. 14 is provided with a specific priority for each block and is different from each other. Pattern information is added by forming images with different priorities. Various settings can be made for pixel formation for each block in the main scanning and sub-scanning directions, as shown in FIGS. 14 (h), (i), and (j), and by giving a specific priority regularly. It is possible to reproduce gradation with a screen. Compared with the dither matrix 65 of FIG. 9, the priority of each block is different, but the total gradation reproduction level of the matrix table is the same, so a device-specific pattern is added while maintaining image reproducibility. It becomes possible.

The above-mentioned dither matrix tables shown in FIGS. 12, 13 and 14 are not used only when adding a pattern peculiar to the apparatus, but are used as a dither matrix table for reproducing normal gradation. May be. For example, the dither matrix table 90 shown in FIG.
As described above, when the pixel growth rate is set to be different for each block, the macroscopic reproducibility is higher than that when the dither matrix 65 having the uniform pixel growth rate shown in FIG. 9 is used. Images may be obtained.

When a dither matrix table as shown in FIG. 14 is used, a screen reproduced image can be obtained. Therefore, it is possible to obtain a reproduced image in which color misregistration and the like are suppressed by performing gradation modulation by changing the screen for each color.

On the contrary, it is possible to use the dither matrix table 65 of FIG. 9 for gradation modulation for adding a pattern peculiar to the apparatus. In this case, any of the dither matrix tables shown in FIGS. 12 to 14 may be used for the gradation modulation of the normal image area. By using such various dither matrix tables in combination, it is possible to perform image reproduction processing with high gradation and reproducibility, and by maintaining the reproducibility while switching the dither matrix tables. Thus, it is possible to add a device-specific pattern to the reproduced image.

Here, a specific example of the device-specific pattern in the present embodiment will be described in detail with reference to FIG. In the present embodiment, the manufacturing serial number 7 that is different for each device is used as the unique information for specifying the device that copied the image.
Use 5 Serial number 75 is No. 5209
When represented by a decimal number of 0013 of 0013, each digit is converted into 4-bit binary number information. If the odd number information 76 and the even number information 77 of the manufacturing serial number 75 are converted into binary numbers, respectively, the odd number binary information 78 and the even number 2 are converted.
The information unique to the device, which is represented by the decimal number information 79 and has eight decimal digits, is converted into bit information 80 having 32 binary numbers. To the serial number converted into binary 32 bit information,
Furthermore, the pattern recognition edge information 81 is added to add a total of 2
The device-specific bit information 82 having a base number of 60 is used. The bit pattern of this device-specific bit information 82 is shown as a device-specific bit pattern 83 on the left side of FIG. “■” and “□” in the device-specific bit pattern 83 are respectively indicated by “” in the device-specific bit information 82.
This is an area for displaying information of 1 "and" 0 ", and this area is judged by the horizontal pattern position judging circuit 57 and the vertical pattern position judging circuit 59 of the pattern generating circuit 40 shown in FIG.

Here, “■” is the device-specific bit information 82.
When the input image signal is not a signal indicating a contour portion, the gradation modulation table C47 for adding a device-specific pattern in the gradation reproduction circuit 44 is used. Is selected and the gradation modulation table 85 to which pattern information unique to the apparatus is added
Is used.

Further, "□" indicates the device-specific bit information 82.
Is a position represented by "0", and this "0" means that pattern information unique to the device is not added. Therefore, when the input image signal does not indicate the contour portion, the gradation modulation table A45 of the gradation reproduction circuit 44 is selected,
The normal gradation modulation table 84 having high gradation is used.

FIG. 16 is a diagram showing an example of a copy result according to this embodiment. Note that, in FIG. 16, the reproduced image is omitted and only the bit pattern unique to the apparatus is shown. As is apparent from the figure, in the area Y where the image data exists, the pattern is added without changing the image signal level by switching the gradation modulation table, so that the pattern is not added in the area where the image does not exist. . As a result, it is possible to add different patterns to each device that can be surely read by using a specific recognition technique that cannot be recognized by human eyes without deteriorating the quality of the reproduced image.

When an original image is copied by a copying machine or the like, the size of the original image and in which area of the copy area and in which direction the original image is arranged differ depending on the person making the copy. Therefore, when the device-specific pattern information is added to the reproduced image, the device-specific pattern is repeatedly added at regular intervals so that the pattern can be added regardless of which area of the copy area the original image is arranged. Further, by adding the information of the apparatus itself and the edge information surrounding the pattern to the pattern, the apparatus itself can be accurately determined by determining the pattern edge regardless of the orientation in the copy area. It is possible to determine the pattern.

In this embodiment, in the contour detection, the sum of the absolute values of the differences between the target pixel of the 3 × 3 mask table and the four peripheral pixels is compared with the threshold value to make a determination. The determination may be made by a plurality of pixels in the × m table, and the contour determination method is not limited to this.

Further, the dither matrix table in the present embodiment uses a matrix table that holds a gradation level of 32 pixels in the main scanning direction and 8 lines in the sub-scanning direction with 1 pixel 8-bit width. The tone level and the threshold level in the table are not limited to this, and the shape of the matrix table may be circular or rectangular regardless of this.

Furthermore, in the present embodiment, a table divided into 8 blocks and 16 blocks with a uniform size is used in the matrix table, but the unit of the divided blocks and the divided block size are also the same. Of course, the present invention is not limited to this, and can be applied to the case of setting without dividing into blocks.

Further, in the present embodiment, the manufacturing serial number which is different for each device is used as the unique information for specifying the device that copied the image, but the size of the information and the amount of information for specifying the device is It is not limited.

Further, in the present embodiment, the electrophotographic method using the laser beam printer has been described as an example, but the present invention is not limited to this, and it can be applied to an inkjet printer, a thermal transfer printer, an LED printer. Is also applicable. In particular, it may be a so-called baffle jet printer that uses a head that ejects droplets by utilizing film boiling due to thermal energy.

Further, although the original image is input by the image scanner in the above-described embodiment, the present invention is not limited to this, and the still video camera, the input by the video camera, and the computer graphics are input. It may be created.

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

[0082]

As described above, according to the present invention, the following effects can be obtained.

(1) It becomes possible to faithfully reproduce the original image by performing gradation reproduction processing with high reproducibility, and to add information for specifying the copying machine, etc., to the reproduced image.

(2) In the input signal of the switching means,
By giving priority to the switching signal when the contour is detected, it is possible to obtain a reproduced image in which the contour is retained without adding a pattern to the contour portion of the image.

(3) Without deteriorating the image quality of the reproduced image,
It is possible to add different patterns to each device, which can be surely read by using a certain recognition technique which cannot be recognized by human eyes.

(4) A 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, and the pattern can be formed in the area where the input image signal does not exist. Is never added.

(5) An additional pattern corresponding to the image signal level can be formed, and the image can be reproduced without impairing the gradation of the image.

(6) By combining or switching a plurality of gradation modulations in the gradation reproduction processing, a reproduced image with high gradation and reproducibility that is faithful to the original image can be obtained for each color component of cyan, magenta, yellow and black. It is possible to obtain.

(7) By combining or switching a plurality of gradation modulations in the image reproduction processing, it is possible to add a pattern regardless of the color components of cyan, magenta, yellow and black.

(8) Since the device-specific pattern is repeatedly added several times in the main scanning direction and the sub-scanning direction, a recognition pattern can be added regardless of which area of the image copy area the image data exists. .

(9) In the pixel formation of the dither matrix table in the gradation reproduction process, a plurality of different gradations are set without changing the image level of the dither matrix table by setting the start position for forming the pixel, the growth rate, and the priority. It is possible to perform modulation.

(10) By attaching a recognition edge pattern surrounding the recognition pattern to the recognition pattern of the apparatus itself,
It is possible to easily identify the pattern of the device itself by reading the recognition edge pattern, regardless of the orientation of the input image in the image copy area.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an internal configuration of a color copying machine according to an embodiment.

FIG. 2 is a block diagram showing a circuit configuration of an image scanner unit according to an embodiment.

FIG. 3 is a block diagram showing a circuit configuration of a printer controller unit according to the embodiment.

FIG. 4 is a block diagram showing a circuit configuration of a video printer processing unit according to the embodiment.

FIG. 5 is a block diagram of a gradation modulation circuit according to an embodiment.

FIG. 6 is a 3 × 3 matrix table diagram of the contour detection circuit according to the embodiment.

FIG. 7 is a block diagram of a contour detection circuit according to an embodiment.

FIG. 8 is a block diagram of a pattern generation circuit according to an embodiment.

FIG. 9 is an explanatory diagram of a dither matrix table according to the embodiment.

FIG. 10 is a block diagram of a dither matrix table according to the embodiment.

FIG. 11 is a dither matrix table diagram for reproducing the contour according to the embodiment.

FIG. 12 is a first dither matrix table diagram for adding a pattern according to the embodiment.

FIG. 13 is a second dither matrix table diagram for adding a pattern according to the embodiment.

FIG. 14 is a third dither matrix table diagram for adding a pattern according to the embodiment.

FIG. 15 is an explanatory diagram of a device-specific pattern according to the embodiment.

FIG. 16 is a diagram showing an example of a copy result according to the embodiment.

FIG. 17 is a diagram showing an example of a copy result according to a conventional technique.

[Explanation of symbols]

 38 contour detection circuit 39 contour switching signal 40 pattern generation circuit 41 device-specific pattern 42 pattern switching signal 43 pattern generation switching circuit 44 gradation reproduction circuit 45 gradation modulation table A 46 gradation modulation table B 47 gradation modulation table C

Claims (10)

[Claims] 1. An image forming apparatus for converting a gradation of an input image signal to generate a reproduced image to which a display pattern indicating information for identifying a device is added, wherein the display pattern indicating information for identifying the device is displayed. Pattern generating means for generating, position determining means for determining a position to add the display pattern in the reproduced image based on the output from the pattern generating means, the input image signal and the output from the position determining means. A gradation reproduction processing means for receiving and converting the input image signal to generate different gradation display data so that different gradation display is performed at a position where the reproduced image is displayed and a position where the display pattern is added. An image forming apparatus comprising: 2. A contour detecting means for extracting a contour portion of an image from the input image signal is further provided, wherein the gradation reproduction processing means receives an output from the contour detecting means and detects a contour portion of the reproduced image. 2. The image forming apparatus according to claim 1, wherein the input image signal is subjected to gradation conversion so as to perform gradation display different from the gradation display at the position where the reproduced image is displayed at the display position. 3. The gradation reproduction processing means has a plurality of dither matrix tables each having a plurality of blocks into which a predetermined area is divided, and the plurality of dither matrix tables according to outputs from the position determining means and the contour detecting means. It has a switching means for switching the dither matrix table,
The gradation level of each block is set by comparing the pixel level of the input image signal with the pixel level preset in the dither matrix table switched by the switching unit, and according to a specific condition in the block. The pixel forming apparatus according to claim 2, wherein the pixel is grown according to the gradation level. 4. The plurality of dither matrix tables,
4. The image forming apparatus according to claim 3, wherein the gradation display is performed by changing the reference positions for growing the pixels according to the gradation level set for each block. 5. The plurality of dither matrix tables,
4. The pixel forming apparatus according to claim 3, wherein the gray scale display is performed by changing the growth rate of the pixels in accordance with the gray scale level set for each block. 6. The plurality of dither matrix tables,
4. The pixel forming apparatus according to claim 3, wherein a priority is given to each block for growing a pixel in accordance with the gradation level so as to be different for each dither matrix table so that gradation display is performed. 7. The switching means generates gradation display data of the display pattern from the plurality of dither matrix tables when the position to which the display pattern is added is designated by the position determining means. 7. The pixel forming device according to claim 3, wherein the dither matrix table is selected. 8. The contour detecting means, when there is an output from the contour detecting means indicating an outline portion of an image and an output from the position detecting means indicating an additional position of a display pattern. 7. The image forming apparatus according to claim 3, wherein the dither matrix table for displaying the contour is selected with priority given to an output from the image forming apparatus. 9. The image forming apparatus according to claim 1, wherein the position determining unit repeatedly adds the display pattern at regular intervals. 10. The pattern generating means generates the display pattern having a recognition pattern peculiar to an apparatus and a recognition edge pattern surrounding the recognition pattern, according to any one of claims 1 to 9. Image forming apparatus.