JP3582245B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image with pixels such as a digital copying machine, a digital printer, an ink jet printer, a printing machine, and the like, and particularly to an additional image such as a pattern image different from a main image visually perceived. The present invention relates to an image forming apparatus that embeds the main image without obstructing the image.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when a main image that should not be copied is copied in a device such as a color copying machine, a device serial number, a user identifier, and the like are used for the purpose of identifying a device or a person who copied the main image. Is embedded in the main image.
[0003]
For example, Japanese Patent Laying-Open No. 4-294682 discloses an invention in which a pattern representing a device serial number or the like is embedded in a color main image using yellow toner. The present invention embeds information other than a color main image in a color main image so as not to be obstructive, utilizing the fact that human eyes have low discrimination ability with respect to a pattern drawn with yellow toner. It is.
[0004]
However, in the above-described invention, in order to add a pattern image irrelevant to the color main image to be output to the color main image, the added pattern image becomes noise and the image quality of the original color main image is reduced. There is a drawback that it deteriorates. Further, the invention described above is applied to an image forming apparatus such as a color copying machine equipped with yellow toner, and can be applied to an image forming apparatus such as a monochrome (single color) copying machine or a printer. Did not.
[0005]
[Problems to be solved by the invention]
As described above, an invention in which a pattern image different from the main image is embedded in the main image has been conventionally proposed. However, adding a pattern image deteriorates the image quality of a main image to be originally output. In a monochrome image forming apparatus such as a monochrome copying machine or a monochrome printer, another additional image cannot be embedded in a main image to be output.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional circumstances, and is an image forming apparatus such as a color or monochrome copying machine or a printer which can embed an additional image such as a pattern image without deteriorating the image quality of a main image. It is an object to provide a forming device.
[0007]
[Means for Solving the Problems]
The present invention is characterized in that it focuses on the pixels constituting the main image, and in order to achieve the above-mentioned object, outputs according to whether or not it is an area in the main image forming an image portion included in the additional image. The additional image is embedded in the main image by changing the drawing position of the pixel.
[0008]
The image portion refers to a portion of the additional image having a certain density or higher. In the pattern image 32 shown in FIG. 3, the portion 32a of the character "A" is the image portion. The region in the main image that forms the image portion refers to a region in the main image that reflects the image portion, and is the region 34 in FIG.
The above-mentioned output pixel is a minimum unit that can be drawn by an output device (a printer, a copier, a facsimile, a plate generation device for printing, etc.), and the size, form, and position of the minimum unit are variable.
[0009]
Therefore, in the image forming apparatus according to the present invention, for example , the main image input from the main image input unit is drawn using a line screen that changes the line width according to the density of the pixel to be output by the image drawing unit. When the additional image input from the additional image input unit is embedded in the main image, when the main image is drawn by the image drawing unit, the position changing unit forms the image portion included in the additional image. The drawing position of the output pixel is changed within the screen width in the line width direction of the line screen according to whether or not the region is inside, and the control unit draws an image using the line screen at the position changed by the position changing unit. The pixel is drawn by the means.
[0010]
The width of the line screen refers to the maximum width of the output pixel. For example, in the case of a line screen having 200 lines (200 lines per 25.4 mm), the width is 0.127 mm.
According to the above-described image forming apparatus , the additional image can be embedded in the main image without deteriorating the image quality of the main image by utilizing the property of the line screen.
[0011]
In the image forming apparatus according to the present invention, for example, the main image input from the main image input means, to draw with a dot screen to change the size of the pixel by the density of pixels of the image drawing means to be output . When the embedding additional image input from the additional image input means in the main image, the main image in which the position changing means when the drawing of the main image by the image drawing means for forming an image part included in the additional image The drawing position of the output pixel is changed in the cell in accordance with whether or not the area is a region, and the control unit causes the image drawing unit to draw the pixel at the position changed by the position changing unit using a dot screen.
Note that the above-described cell refers to a unit area constituting the dot screen, and for example, refers to a minimum square area surrounded by a dotted line as shown in FIG.
[0012]
According to the image forming apparatus described above , the additional image can be embedded in the main image without deteriorating the image quality of the main image by utilizing the property of the dot screen.
[0013]
In the image drawing means according to the present invention, for example, in the above-described image forming apparatus, when embedding the additional image input from the additional image input means in the main image, the image drawing means may draw the main image. The change control means controls the position changing means in accordance with the density information of the image portion of the additional image, and changes the drawing position of the output pixel in the area of the main image forming the image portion.
[0014]
In the above-described image forming apparatus , the additional image can be embedded in the main image without deteriorating the image quality of the main image, and the embedded additional image can have density information of the additional image.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a rough configuration of an image forming process according to the present invention will be described with reference to FIG. The image forming apparatus is roughly composed of a pixel generation step 1 and a pixel output step 2, and when an input main image visually perceived and a pattern image different from the input main image are input, The invention is characterized in that, in the pixel generation step 1, the positions of the pixels in the area of the pattern image in the main image are changed according to the density of the pattern image to generate the pixels of the main image. Note that the pixel output step 2 may be performed by any means capable of outputting pixels, such as electrophotography and ink jet.
[0016]
A main part of an electrophotographic color laser printer for generating an image using a line screen according to a first embodiment of the present invention will be described with reference to FIG.
This laser printer includes a D / A converter 21, a triangular wave oscillator 22, a selection circuit 23, a triangular wave selection signal generator 24, a comparator 25, and a laser drive system 26.
[0017]
The D / A converter 21 converts the inputted digital density information representing the main image into analog voltage information, and outputs this to one input terminal of the comparator 25.
The triangular wave oscillator 22 generates a triangular wave for changing the drawing position of the output pixel in the width direction of the line screen (also referred to as the main scanning direction). The four types of triangular waves 27, 28, 29, and 30 at different positions are generated. Note that the width of one unit of the triangular waves 27, 28, 29, and 30 corresponds to one unit of the width of the line screen.
[0018]
The selection circuit 23 selects one of the triangular waves 27, 28, 29, and 30 generated by the triangular wave oscillator 22 and outputs this to the other input terminal of the comparator 25.
The triangular wave selection signal generator 24 outputs a selection signal for selecting a triangular wave based on the density information of the input pattern image or a selection signal for selecting a triangular wave irrespective of the density of the pattern image based on the input control signal. Either is transmitted, and the selection process of the selection circuit 23 is controlled. As a selection signal of a triangular wave based on the density of the pattern image, for example, when the density of the pattern image is represented by “0” to “FF” (hexadecimal), the density is “0” to “3F”. , A triangle wave 30 for an image portion with a density of “40” to “7F”, and a triangle wave 28 for an image portion with a density of “80” to “BF”. When the density is an image portion such as "C0" to "FF", there is a signal for selecting the triangular wave 27. On the other hand, as the selection signal based on the control signal, for example, there is a signal that always selects the triangular wave 30 selected in a portion other than the image portion.
[0019]
In the present embodiment, when scanning is performed in the sub-scanning direction (a direction orthogonal to the main scanning direction), the triangular wave selection signal generator 24 selects a triangular wave 30 based on the control signal and a selection signal of the pattern image. A selection signal for selecting a triangular wave based on the density information is transmitted alternately.
[0020]
The comparator 25 compares the analog voltage of the input main image with the level of the triangular wave (analog voltage). When the level of the triangular wave is higher than the analog voltage of the input main image, the comparator 25 outputs “H” (that is, turns on the laser), and when the level is lower, “H”. L ”(that is, turn off the laser). Therefore, the triangle wave 27 is selected at the latest timing, the triangle wave 28 is selected at the next latest timing, and the triangle wave 29 is selected at the next latest timing. When “30” is selected, the “H” level is input to the laser drive system 26 at the earliest timing among the above four triangular waves including its own triangular wave.
[0021]
The laser drive system 26 is a means for drawing output pixels using a line screen, and draws the output pixels while scanning the output pixels on a recording medium such as a photosensitive drum in response to a laser ON command. Therefore, when the triangular wave 27 is selected, the output pixel is drawn at the rearmost portion in the main scanning direction within the line screen width, and when the triangular wave 30 is selected, the output pixel is drawn in the main scanning direction within the line screen width. Is drawn in the foremost part of.
[0022]
That is, according to the electrophotographic laser printer having the above-described configuration, the input main image is converted into an analog voltage by the D / A converter 21 and input to the comparator 25, and the triangular wave 27 generated by the triangular wave oscillator 22. One of 28, 29, and 30 is selected by the selection circuit 23 in accordance with the density information of the input pattern image, and is input to the comparator 25. Then, the comparator 25 controls the laser drive system 26 at a timing based on the shape of the selected triangular wave, and draws an output pixel at a position displaced in the width direction within the width of the line screen.
[0023]
FIG. 3 shows a state in which a pattern image 32 of a binary image in which a portion 32a forming the character “A” has a density “FF” and the other portion 32b has a density “0” is embedded in the input main image 31. The pattern image 32 is embedded in the output main image 33. That is, in the output main image 33, the portion 32 a which is the image portion of the pattern image 32 is reflected in the region 34. Note that the broken line indicating the region 34 is provided for explanation, and does not actually exist.
[0024]
FIG. 4 is an enlarged view of a portion 35 of the output main image 33 of FIG.
The main image density of the portion 35 is 25%, and the line width of the pixels in the line screen 41 is １ ／ of the line screen width. Since the triangle wave 30 is selected in the portion of the pattern image having the density “0”, a pixel is drawn on the left end of the line screen, and the triangle wave 27 is selected in the portion of the pattern image having the density “FF”. For this purpose, pixels are drawn at the right end of the line screen. Therefore, in the portion belonging to the region 34 in which the character "A" forming the image portion of the pattern image is embedded, pixels are drawn at the right end of the line screen, while the region 36 other than the region 34 forming the portion other than the image portion of the pattern image is displayed. In the portion belonging to, a pixel is drawn at the left end in the line screen.
[0025]
The pixel position is changed every other line in the sub-scanning direction by the control signal input to the triangular wave selection signal generator 24. In other words, in every other drawing unit line 42, 43, 44, 45, 46 in the sub-scanning direction, the pixels of the portion where the density of the pattern image is "FF" are drawn at the right end in the line screen, and the pattern image Are drawn at the left end of the line screen, while the pixel positions of the drawing unit lines other than the drawing unit lines 42, 43, 44, 45, and 46 are changed. It is drawn without being. This makes it possible to minimize the number of pixels whose position is changed, and to prevent the pattern image from being conspicuous in the output main image even when the main image is formed with a low screen ruling.
[0026]
Here, in the conventional image formation, since there is only one kind of triangular wave, all pixel positions in the line screen 51 are drawn at the left end, for example, as shown in FIG. As can be seen by comparing FIG. 4 and FIG. 5, the ratio of the pixels occupying the line screen is the same for both, and the pattern image can be formed without deteriorating the main image such as changing the image density of the main image. Can be embedded.
[0027]
In FIG. 3, the image formation using the pattern image having the binary density information has been described. However, since the above-described laser printer has four types of triangular waves, the pattern image to be embedded in the main image is used. Can have up to four levels of density information. That is, any one of the four types of triangular waves is selected according to the density information of the input pattern image, and the drawing position of the output pixel becomes four in the line screen, so that it is embedded in the main image. The pattern image can hold up to four levels of density information depending on the difference in drawing position.
[0028]
To read out the pattern image embedded in the main image as described above, a system as shown in FIG. 6 is used. For example, in the case of a color main image, the main image is read from the original by the color image reading device 61, the main image is subjected to appropriate image processing such as shading correction by the image processing unit 62, and the pixel position is detected by the pixel position detection unit 63. Detect the position of. Next, the density conversion means 64 detects the density information of the area where the image part included in the pattern image is formed and the embedded image part from the pixel position. As a result, the image part is generated from the area and the image part is generated. A pattern image is created by reflecting the density information on the pattern image, and the pattern image is displayed on the display by the pattern image display means 65. On the other hand, the main image subjected to the image processing by the image processing means 62 is displayed on a display by the image display means 66.
[0029]
Here, in general, when forming an image such as a graphic or a photograph, the number of screen lines is often 100 lines (100 lines per 25.4 mm) or 200 lines (200 lines per 25.4 mm) in many cases. Therefore, if the image reading device 61 has a resolution of 600 dots / 25.4 mm or 1200 dots / 25.4 mm, the position of the pixel can be specified, and the area where the image portion of the pattern image is formed and the density information of the image portion can be easily detected. Can be detected.
[0030]
Next, an electrophotographic color laser printer that generates an image using a dot screen according to a second embodiment of the present invention will be described. The main part of the electrophotographic laser printer according to the second embodiment is the same as that of the first embodiment shown in FIG. 2, and a duplicate description will be omitted.
[0031]
In the laser printer of the second embodiment, the input main image information has a waveform 71 that is alternately switched at a density “0” and a certain density value as shown in FIG. When the density is “40”, the waveform 71 alternately switches between the density “0” and the density “80” so that the average density becomes “40”.
[0032]
FIG. 8 is an enlarged view of a portion 35 of the main image 33 in which the pattern image 32 is embedded in the main image 31 shown in FIG. 3 by this laser printer.
In this laser printer, the laser drive system 26 is driven at intervals of twice the cycle of the triangular wave to draw dots, and the triangular wave 30 is selected in the portion of the pattern image having a density of “0” as shown in the cell 81. The pixel is drawn at the left end in the cell of the dot screen, and the triangular wave 27 is selected at the portion of the density "FF" of the pattern image, and the pixel is drawn at the right end in the cell of the dot screen. Therefore, in the portion belonging to the region 34 forming the image portion, the pixel is drawn at the right end in the cell, whereas in the portion belonging to the region 36 other than the region 34 forming the portion other than the image portion of the pattern image, the pixel is drawn at the left end in the cell. Will be drawn.
[0033]
It should be noted that the drawing position of the pixel is changed every other line in the sub-scanning direction by the control signal input to the triangular wave selection signal generator 24. That is, in every other drawing section line 82, 83, 84, 85, 86 in the sub-scanning direction, the pixels of the portion where the density of the pattern image is "FF" are drawn at the right end in the cell of the dot screen. The pixels of the portion where the density of the pattern image is “00” are drawn at the left end in the cell of the dot screen, while the pixel positions in the drawing portion lines other than the drawing portion lines 82, 83, 84, 85 and 86 are Draw without any changes. As a result, the number of pixels for which the position is changed can be minimized, and even when the main image is formed with a low number of lines of the dot screen, the pattern image can be prevented from being conspicuous in the formed main image.
[0034]
In the first and second embodiments described above, four types of triangular waves are provided. However, the present invention is not limited to this, and N types (N is an arbitrary number) of triangular waves having different vertex positions are provided. When N types are provided, density information up to N values can be given to a pattern image to be embedded in a main image.
[0035]
Further, in the first and second embodiments described above, every other drawing unit line in the sub-scanning direction is targeted for changing the position of a pixel. The drawing position may be changed, and the drawing unit line whose pixel drawing position is changed can be arbitrarily determined.
[0036]
In the above-described first and second embodiments, not only the drawing position of the output pixel is changed depending on whether or not the image is an area in the main image forming the image portion of the pattern image. In the region where the image portion is formed, the drawing position of the output pixel is changed in accordance with the density information of the image portion, but whether or not the region in the main image is the region where the image portion of the pattern image is formed , The pattern image can be embedded in the main image without obstruction only by changing the drawing position of the output pixel.
In the above-described first and second embodiments, whether or not an image portion of a pattern image is grasped by the density information of the pattern image is not limited thereto. It may be provided with information such as whether or not it is, and grasped by the information.
[0037]
Further, in the above-described first and second embodiments, the pattern image 32 shown in FIG. 3 is used as an additional image to be added to the main image. However, as the additional image, for example, the main image 31 shown in FIG. It is possible to use an image or the like that does not represent a simple pattern.
Further, in the first and second embodiments described above, an example in which drawing is performed while scanning pixels has been described. However, for example, as in the case of manufacturing a printing plate, an apparatus that generates an image using pixels without performing scanning is used. The present invention can also be applied. That is, the present invention can be applied to all image forming apparatuses that form pixels, such as digital copiers, digital printers, inkjet printers, printing machines, and the like.
[0038]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, when a main image is formed, drawing of output pixels is performed according to whether or not an area in the main image that forms an image portion included in the additional image. Since the position is changed, the additional image can be embedded without obstruction without deteriorating the image quality of the main image.
According to the image forming apparatus of the present invention, the drawing position of the output pixel in the area in the main image forming the image portion included in the additional image is changed according to the density information of the image portion. In addition, the additional image can be embedded without obstruction without deteriorating the image quality of the main image, and the image portion of the embedded additional image can have the density information of the image portion. Therefore, an additional image having a plurality of density information can be embedded in the main image.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus to which the present invention is applied.
FIG. 2 is a configuration diagram illustrating a main part of an electrophotographic laser printer according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating how a pattern image is embedded in an input image in the embodiment of the present invention.
FIG. 4 is a diagram illustrating a drawing example using a line screen in the first embodiment.
FIG. 5 is a diagram showing a drawing example using a conventional line screen.
FIG. 6 is a schematic configuration diagram illustrating an example of a system for extracting an embedded pattern image.
FIG. 7 is a diagram illustrating an example of main image data in a second embodiment.
FIG. 8 is a diagram illustrating a drawing example using a dot screen in the second embodiment.
[Explanation of symbols]
21 ... D / A converter,
22 ... triangular wave oscillator,
23 ... selection circuit,
24 ... triangle wave selection signal generator,
25 ... Comparator,
26 ... laser drive system,

Claims (3)

Main image input means for inputting a main image ;
Additional image input means for inputting an additional image to be added to the main image,
Image drawing means for drawing output pixels of the main image input by the main image input means ,
When drawing an output pixel of the main image by the image drawing means, the drawing position of the output pixels of the main image into density information of the pixel corresponding with the output pixel of the input added image by the additional image input means Position changing means for changing according to
An image forming apparatus, comprising: a control unit that causes the image drawing unit to draw an output pixel of the main image at a position changed by the position changing unit. The image forming apparatus according to claim 1,
  The image drawing means draws the output pixels of the main image using a line screen that changes the line width according to the density of the main image to be output,
  The position changing means changes a drawing position of an output pixel of the main image in a line width direction of the line screen within a screen width,
  The image forming apparatus, wherein the control unit causes the image drawing unit to draw output pixels of the main image at the position changed by the position changing unit using the line screen. The image forming apparatus according to claim 1,
  The image drawing means draws the output pixels of the main image using a dot screen that changes the size of the output pixels of the main image according to the density of the main image to be output,
  The position changing unit changes a drawing position of an output pixel of the main image in a cell of the dot screen,
  The image forming apparatus, wherein the control unit causes the image drawing unit to draw output pixels of the main image at the position changed by the position changing unit, using the dot screen.

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