JP3267342B2 - Image processing apparatus and image processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and an image processing method.

[0002]

2. Description of the Related Art Conventionally, various measures have been considered to prevent forgery of securities and the like.

One of the methods is to superimpose a symbol unique to the image forming apparatus, which is difficult to see visually, on the image with a constant modulation amount on the image in order to identify the used image forming apparatus. Proposed by the applicant.

[0004] If securities are forged using the image forming apparatus, a reading device capable of extracting the forged product only in a specific wavelength range is read by reading a symbol unique to the image forming apparatus. The used image forming apparatus can be specified, and can be an effective clue for tracking a counterfeiter.

[0005]

However, in the case where the symbol is superimposed on the image information by the above-described method, if the characteristics of the image forming apparatus are changed by use,
There have been adverse effects such as an overly conspicuous or invisible pattern being superimposed.

Therefore, the present invention eliminates such adverse effects,
An object of the present invention is to satisfactorily control the image quality when superimposing predetermined information on an image.

[0007]

According to another aspect of the present invention, there is provided an image processing apparatus for embedding predetermined information in an image, comprising: an input unit for inputting an image; Generating means for generating a specific pattern representing, a detecting means for detecting a use situation of the image processing apparatus, and a modulation amount determined so that the specific pattern is inconspicuous according to the detected use situation. It is characterized in that it has a modulating means for modulating the generated specific pattern and an adding means for adding the modulated specific pattern to the image. In order to solve the above problems,
An image processing method according to the present invention is an image processing method in an image processing apparatus that embeds predetermined information in an image, and includes an inputting step of inputting an image, a generating step of generating a specific pattern representing the predetermined information, and an image processing method. A detection step of detecting a use state of the device, and a modulation step of modulating the generated specific pattern based on a modulation amount determined so that the specific pattern is inconspicuous according to the detected use state,
An adding step of adding the modulated specific pattern to the image.

[0008]

(Embodiment 1) FIG. 6 shows the configuration of a color copying apparatus.

First, a method of forming a color image will be described.

In FIG. 6, a document 101 placed on a document glass 102 is imaged on a CCD 105 by a light source 103 and an optical lens 104, and is converted into an image signal corresponding to the amount of received light.

The image signal is converted into a digital value by an A / D converter 106, subjected to image processing by a CPU 107, and then drives a laser light source 108.

The emitted laser light is reflected by the polygon mirror 1 and the mirror 2 and is irradiated on the photosensitive drum 4.

The photosensitive drum 4 is cleaned by a cleaning blade 110 so that the toner is not loaded on the photosensitive drum 4 in advance.

First, the photosensitive drum 4, on which a latent image is formed by scanning with a laser beam using a Y (yellow) image signal, rotates in the direction of the arrow shown in the figure, and is developed by the developing unit 3Y. You.

Further, the photosensitive drum 4 is rotated to adsorb the recording material 6 to the transfer drum 111, and the toner image formed on the photosensitive drum 4 is transferred onto the recording material 6 by the transfer charger 112.

Next, after a latent image is formed and developed with an M (magenta) image signal, the image is multiplex-transferred onto a Y image on a recording material under a position condition that matches the registration of the image.

Similarly, C and Bk are also subjected to image formation and multiple transfer, separated from the transfer drum 111, and
And the color image print is completed.

FIG. 5 is a block diagram showing an image signal processing for obtaining a gradation image.

An image luminance signal is obtained by the CCD 10, and the luminance signal is converted into a digital luminance signal by the A / D conversion circuit 11.

In the obtained luminance signal, the sensitivity variation of each CCD element is corrected by the shading circuit 12,
The corrected luminance signal is converted by the LOG conversion circuit 13 into a density signal.

Further, the LUT (look-up table) 14 converts the γ characteristics of the printer at the time of initial setting so that the original image density and the output image match.

On the other hand, the machine number pattern generation circuit 15
Generates machine-specific patterns. Here, the image signal of only Y (yellow), which has the lowest resolution visually, is added to FIG.
As described above, the modulation amount is changed according to the magnitude of the density signal. This control is performed by the modulation amount control circuit 16 in FIG.

The modulated machine number pattern is synthesized by a comparator circuit 17 which is superimposed on the image signal.

As shown in FIG. 8, the machine number pattern corresponds to the machine number by a number pattern, but there is also a pattern number corresponding to a number or a character which is hard to be discerned.

The image signal on which the serial number pattern is superimposed is then modulated by a pulse width modulation circuit 18 so that the laser emission time is proportional to the density signal, sent to a laser driver 19 circuit, and the density gradation is converted to an area gradation. By expressing, a gradation image is formed.

The machine number pattern can be read by observing through a 350 nm sharp band filter after a full-color image is formed, and by separating only the yellow signal, it can be read. Can be specified.

FIG. 9 is a 4-limit chart showing how the gradation is reproduced.

The first quadrant indicates a reader characteristic for converting a document density into a density signal, the second quadrant indicates an LUT for converting a density signal into a laser output signal, and the third quadrant indicates an output density from a laser output signal. , And the fourth quadrant indicates the total gradation characteristic of the image forming apparatus indicating the relationship between the original density and the output density.

The number of gradations is 256, since processing is performed using an 8-bit digital signal.

It is known that the printer characteristics in the third quadrant take various forms depending on conditions such as photoreceptor characteristics, laser spot diameter and development characteristics.

Here, the case of the printer characteristic of the S-character characteristic will be described.

It is important to make the total gradation characteristic linear indicating the relationship between the document density in the fourth quadrant and the output density in order to faithfully reproduce a full-color image. The LUT needs to be bent into an S shape as shown in FIG.

The modulation signal of the machine number pattern is added to the image signal by ΔDi from Di ₁ after the LUT of the third quadrant (Di ₂ ) and set.

However, since the symbol ΔDi unique to the image forming apparatus to be superimposed is set so as to be inconspicuous in the initial printer characteristics shown in FIG. 5, the photosensitive drum 4 is scraped by the cleaning blade 110 as it is durable. The printer characteristic changes as shown in the third quadrant of FIG. 10 and a problem arises that the highlight part gradually becomes noticeable.

Therefore, in the present embodiment, a full-color image is formed by superimposing images formed by a plurality of color materials, and an image forming apparatus that superimposes information unique to the image forming apparatus on a specific color image. The use state of the image forming apparatus is detected, and the superimposition pattern is made variable.

The details will be described below.

FIG. 2 is a block diagram of an electrophotographic full-color image forming apparatus embodying the present invention, and FIG. 1 is a block diagram of image signal processing.

In FIG. 2, reference numeral 120 denotes an HP (home position) detection sensor for counting the number of rotations of the photosensitive drum. A color image is formed in the same manner as in the conventional example.

In FIG. 1, the luminance signal of the image is
0, and the luminance signal is converted into a digital luminance signal by the A / D conversion circuit 11.

In the obtained luminance signal, the sensitivity variation of each CCD element is corrected by the shading circuit 12, and
The corrected luminance signal is converted by the LOG conversion circuit 13 into a density signal.

The LUT (look-up table) 14 converts the γ characteristics of the printer at the time of initial setting so that the original image density and the output image match.

On the other hand, the machine number pattern generation circuit 15
A pattern peculiar to the machine is generated, and the density signal is converted into a Y image signal based on the modulation amount corresponding to the rotation speed (cumulative rotation speed) of the photosensitive drum detected by the HP detection sensor 20 by the modulation amount control circuit 16 '. Change the modulation amount.

The modulated machine number pattern is synthesized by the comparator circuit 17 which is superimposed on the image signal.

The image signal on which the serial number pattern is superimposed is then modulated by a pulse width modulation circuit 18 so that the laser emission time is proportional to the density signal, and sent to a laser driver 19 circuit, where the density gradation is converted to the area gradation. By expressing, a gradation image is formed.

The machine number pattern can be read by observing through a 350 nm sharp band filter after a full-color image is formed, and by separating only the yellow signal, any machine pattern can be read even if forgery is performed. Can be specified.

FIG. 3 shows the modulation amount with respect to the rotation speed of the photosensitive drum focusing on Di ₁ in FIG.

As described above, by making the density step ΔD _{0 of the} output constant as shown in FIG. 4 even during durability, it was possible to make the output less noticeable.

When the photosensitive drum is replaced, the rotation speed of the photosensitive drum is set to zero.

(Embodiment 2) In full-color image formation,
The average speed of the photosensitive drum was 8 revolutions / copy, and the same effect as in Example 1 was obtained even when the modulation amount (FIG. 11) corresponding to the number of copies was used.

Here, full color was performed.
The same can be applied to a mono color or the like.

(Embodiment 3) The modulation amount (FIG. 12) may be controlled by the number of times the developing device is used instead of the rotation speed of the photosensitive drum.

(Embodiment 4) The present invention can be applied to the accumulated time when the power is turned on. Normally, full-color copiers
It operates all day, and the average number of copies per month is about 20
Since the number is 00, the number of rotations of the photosensitive drum can be determined.

Therefore, control may be performed in accordance with the amount of modulation (FIG. 13) based on the cumulative power-on time.

As described above, if the parameter indicating the state of the photosensitive drum can be calculated, the present invention can be applied.

Further, the superposition pattern may be changed according to the state of other image forming means such as a charger and a developing device without being limited to the photosensitive drum.

As described above, a color image is formed by superimposing images formed by a plurality of color materials, and
In an image forming apparatus that superimposes information unique to the image forming apparatus on an image of a specific color, a use state of the image forming apparatus is detected, and the superimposition pattern is made variable to thereby superimpose a symbol unique to the image forming apparatus. Can be made inconspicuous regardless of the state of the device.

[0057]

As described above, according to the present invention, the image quality can be improved when the predetermined information is superimposed on the image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of an image forming apparatus showing one embodiment of the present invention.

FIG. 3 is a graph showing gradation characteristics due to endurance fluctuation according to one embodiment of the present invention

FIG. 4 is a 4-limit chart showing gradation characteristic conversion according to an embodiment of the present invention.

FIG. 5 is a block diagram for explaining an embodiment of the present invention.

FIG. 6 is a configuration diagram of an image forming apparatus.

FIG. 7 is a diagram in which a signal unique to the image forming apparatus is superimposed.

FIG. 8 shows an example of a pattern unique to the image forming apparatus.

FIG. 9 is a 4-limit chart showing gradation characteristic conversion.

FIG. 10 is a fourth-limit chart showing gradation characteristic conversion after durability.

FIG. 11 is a diagram illustrating another embodiment of the present invention.

FIG. 12 is a diagram illustrating another embodiment of the present invention.

FIG. 13 is a diagram illustrating another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polygon mirror 2 Mirror 3 Developing device 4 Photosensitive drum 6 Recording material 7 Fixing roller 101 Document 102 Platen glass 103 Light source 104 Optical lens 105 CCD 106 Laser 111 Transfer drum

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/38-1/393 G06T 1/00 500

Claims (10)

(57) [Claims] An image processing apparatus for embedding predetermined information in an image.
A location input means for inputting an image, and generating means for generating a particular pattern representing the predetermined information detection means for detecting the use status of the image processing apparatus, wherein in response to the sensed usage Eye is a specific pattern
Based on the amount of modulation determined not to stand
Modulating means for modulating the modulated specific pattern, and adding the modulated specific pattern to the image
And an image processing apparatus. 2. The image processing apparatus according to claim 1, wherein the detection unit detects a change in image reproducibility of the image processing apparatus. 3. The image processing apparatus according to claim 1, wherein the use status is a rotation speed of the image carrier. 4. The image processing apparatus according to claim 1, wherein the use status is the number of copies. 5. The image processing apparatus according to claim 1, wherein the use status is the number of times the developing device has been used. 6. The image processing apparatus according to claim 1, wherein the use status is an accumulated time of power-on. 7. The method according to claim 7, wherein the adding means adds the specific pattern to a previous position.
To be added to the image of some of the color components that make up the image
The image processing apparatus according to claim 1, wherein: 8. A color component of the image is yellow.
The image processing apparatus according to claim 7, wherein: 9. The information processing apparatus according to claim 1, wherein the predetermined information is specific to the image processing apparatus.
2. The image processing apparatus according to claim 1, wherein the information is provided information.
Equipment. 10. Image processing for embedding predetermined information in an image
An image processing method in an apparatus, comprising: an inputting step of inputting an image; a generating step of generating a specific pattern representing predetermined information; a detecting step of detecting a use state of the image processing apparatus; and the detected use state According to the specific pattern
Based on the amount of modulation determined not to stand
Modulating the modulated specific pattern, and adding the modulated specific pattern to the image
And an image processing method.