KR19980031963A - Color image reproducing apparatus and a method for correcting gray scale value of image signal - Google Patents

Abstract

A color image reproducing apparatus and a method of correcting a gray value of an image signal according to the present invention are disclosed. Color image which drives the printer by converting the input RGB image signal into a YMCBK image signal, adjusting the color blending ratio of the converted YMCBK image signal, correcting the gradation for outputting a laser beam corresponding to the output image signal The signal reproducing apparatus includes: a toner deposition amount sensing unit for detecting a deposition amount of toner; a storage unit storing a predetermined reference gray scale correction value; a gradation value corresponding to the toner deposition amount detected from the toner deposition amount detecting unit and stored in the storage unit. A gradation calculator configured to compare the reference gradation correction values and generate new gradation correction values; And a gradation correction unit for correcting the gradation value of an image signal input from the outside by using the gradation correction value obtained from the gradation calculator.

Therefore, as described above, according to the present invention, the gradation value for each gradation step can always be measured by using the toner deposition amount detecting unit, and the difference in print quality can be corrected over time. It has the effect of obtaining the print of chromaticity, and the user can obtain and apply the gradation correction coefficient by simply pressing the gradation correction key or selecting a command, so the gradation correction operation is very simple. It has the effect of not having to leave unnecessary prints by printing on it.

Description

A color image reproducing apparatus and a method for correcting a gray value of an image signal.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reproducing apparatus and a method for correcting a gradation value of an image signal. More particularly, the present invention relates to a color image reproducing apparatus. Color image playback device that converts M, C, and BK to reproduce this signal on paper, for example, a reproduction quality caused by replacing accessories or consumables or deteriorating the accessories while using a digital full color printer. The present invention relates to a color image reproducing apparatus for correcting a difference between and a method of correcting a gray value of an image signal.

1 is a diagram showing the configuration of a conventional color image reproducing apparatus.

In FIG. 1, reference numeral 100 denotes an image signal input unit, and reference numeral 200 denotes a color conversion unit that inversely converts R, G, and B signals output from the image signal input unit 100 into Y, M, and C signals. Reference numeral 201 denotes a black that outputs Y ', M', C ', and BK' signals that generate black and extract black from each signal in order to improve black color reproduction among the image signals output from the color conversion unit 200. The generation unit, reference numeral 202 denotes a color correction unit for correcting a signal output from the black generation unit 201 to a signal suitable for the printer characteristic by the spectral characteristics of the toner, and reference numeral 203 denotes an image output from the color correction unit 202. A selector for selecting and outputting a color to be printed from the signals, reference numeral 204 denotes a gray scale corrector for determining output of a laser beam corresponding to each image signal output from the selector 203, and reference numeral 205 denotes a gray scale corrector 204. Image signal output from Temperature / humidity, a fine adjustment element for making fine adjustments to the output gray-scale gradation suitable for the printer environment, reference numeral 101 denotes a printer driver for printing the image signal output from the output tone fine adjustment section 205, respectively. In addition, the CPU 210, the ROM 212, and the RAM 213 are control blocks for controlling such a series of print operations. The ROM 212 includes a program for driving and controlling the CPU 210. If the RAM 213 contains color data such as a lookup table, the CPU 210 outputs a control signal for controlling the operations of the above-described blocks. In addition, reference numeral 214 denotes an operation unit for allowing a user to feel a change in color and apply a gray scale correction command, and reference numeral 211 denotes a volatile memory, in which a reference gray scale correction value is stored.

Next, the operation of the conventional image reproducing apparatus shown in FIG. 1 will be described.

In a conventional digital full color printer, an image signal reproducing apparatus is represented by three primary colors of additive mixed colors of red (R), blue (B) and green (G), or XYZ CIE color coordinates or Lab coordinate system by a scanner or a computer. An image signal is converted into three primary colors of subtractive mixed color of CYAN (C), MAGENTA (M), and YELLOW (Y) to generate a printed matter after predetermined grayscale correction. Here, in the process of converting the image signals, the coordinate axes are converted into the C, M, and Y image signals of the input R, G, and B coordinate systems to be corrected to colors (Y, M, C, BK) suitable for output to the printer. The printed matter is generated through the steps of converting the image to an appropriate gradation value for each color. At this time, in order to improve the reproduction of black, black (BK) is produced using the black generation unit 201, which is an appropriate correction means, and in particular, in the electrophotographic method, an image signal converted into a C, M, Y, BK signal is obtained. A laser beam signal is used to scan a photosensitive member surface to form a latent image. The toner is selectively applied to the photosensitive member roller to be transferred onto a copy paper, and then a color print is completed through a fixing process.

However, there is a case where printed outputs printed at different intervals for the same original are output in different colors. In particular, very small chromaticities and differences in color manuscripts are easily distinguished, so it is very difficult to reproduce colors of the same chromaticity. That is, since the process of printing an original requires a very complicated process, there are many factors that affect the reproduction of originals of the same chromaticity. In particular, when the image reproducing apparatus is a copying machine, the toner to be supplied periodically or the photosensitive roller to be periodically replaced are affected by the use environment and the period of use. In addition, a corona wire used for a transfer device or the like also affects the reproduction quality for various reasons such as oxidation and contamination. These phenomena become factors that make the characteristics different for each printing time point.

A general method for adjusting this phenomenon is to modify the color correction method in the color correction unit 202. In the case of using the look up table, which is the most common color correction method, the user may not directly However, there is a disadvantage in that a lot of calculation is required to create a lookup table.

Prior art that has simply performed this adjustment work is Japanese Patent No. 64-41375 and Japanese Patent No. 7-162682, which use a method of adjusting the gradation of the output color. The prior art outputs a gradation adjustment test pattern (TEST PATTERN) by printing in order to adjust the output gradation, and compares the data obtained by inputting the printed test pattern through a reflectance device or a scanner and reference data to adjust gradation correction characteristics. The gray scale adjustment unit 204 corrects the gray scale.

However, such a method has to output a test pattern on paper, hassle that the user has to input the test pattern again, and has to go through a series of image data processing. In addition, in order to detect the position of the data of the test pattern input to the scanner and compare it with the reference values, it is also difficult to accurately detect the position of the test patterns input to the scanner.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and by performing gradation correction of the color itself without printing a test pattern on paper, it is possible to reduce the gradation correction operation and do not need to detect the position of the input data. It is an object of the present invention to provide a reproducing apparatus, and another object thereof is to provide a gradation correction method accordingly.

1 is a diagram showing the configuration of a conventional color image reproducing apparatus.

2 is a diagram showing the configuration of a color image reproducing apparatus according to the present invention.

3 is a diagram illustrating a detailed configuration of a gray scale calculator shown in FIG. 2.

4 is a view for explaining a method of measuring the toner deposition amount in the toner deposition amount detecting unit shown in FIG. 2.

5 is a flowchart illustrating a method of changing the gradation correction value according to the present invention.

According to the present invention for achieving the above object, converts the input RGB image signal to a YMCBK image signal, adjusts the color mixing ratio of the converted YMCBK image signal, and outputs a laser beam corresponding to the image signal to be output. A color image signal reproducing apparatus for driving a printer by correcting a gradation for

A toner adhesion amount sensing unit for sensing an adhesion amount of toner;

A storage unit for storing a predetermined reference gradation correction value;

A gradation calculator configured to generate a new gradation correction value by comparing a gradation value corresponding to the toner deposition amount detected by the toner adhesion amount detection unit with a reference gradation correction value stored in the storage unit; And

It is preferable to include a gradation correction unit for correcting the gradation value of an image signal input from the outside by using the gradation correction value obtained from the gradation calculator.

In the color image reproducing apparatus according to the present invention for achieving the above another object, the method of correcting the gradation value of the color image signal

A command applying step of applying a gradation correction command;

A first toner image forming step of forming a toner image with a predetermined reference gray scale correction value;

A first toner adhesion amount measuring step of measuring the toner adhesion amount on the toner image formed from the first toner image forming step;

A first gray scale value converting step of converting the measured value of the toner adhered amount measured from the first toner adhered amount measuring step into a gray scale value;

An averaging step of averaging the tone values converted from the first tone value conversion step;

An input / output characteristic extraction step of extracting an input / output characteristic for the averaged gray value from the averaging step;

A preliminary gradation correction value calculating step of calculating a preliminary gradation correction value by comparing the gradation value extracted from the input / output characteristic extraction step with a reference gradation correction value;

A second toner image forming step of forming a toner image by the preliminary gradation correction value calculated from the preliminary gradation correction value calculating step;

A second toner deposition amount detecting step of measuring the toner deposition amount on the toner by the second toner image forming step;

A second gray scale value converting step of converting the toner deposition amount detected from the second toner image sensing step into a gray scale value; And

If the gradation value correction by the gradation value converted from the second gradation value conversion step is correct, the preliminary gradation correction value may be replaced with a reference gradation correction value and stored.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

Fig. 2 is a diagram showing the configuration of a color image reproducing apparatus according to the present invention, in particular. A color output printer will be described as an example.

The apparatus shown in Fig. 2 is an image signal for receiving an image signal represented by three primary colors of red (R), blue (B), green (G) subtractive mixed color, XYZ CIE color coordinates, Lab coordinate system, etc. from a scanner or a computer. Black color among the image signal output from the color conversion unit 200 and the color conversion unit 200 to inversely convert the image signal output from the input unit 100 and the image signal input unit 100 to Y, M, C signals For better reproduction, the black generation unit 201 and Y ', M', C ', and BK' generated from the black generation unit 201 and the black generation unit 201 generating BK signals by separating black from Y, M, and C signals by a predetermined amount. The color to be printed is selected from the corrected image signals output from the color correcting unit 202 and the color correcting unit 20 for correcting the signal to Y, M, C, and BK signals so as to match the characteristics of the printer due to the spectral characteristics of the toner. Selector 203 and the output of the laser beam corresponding to the image signal output from the selector 203 A gradation correction unit 204 for correcting the gradations for adjusting the gradation, an output gradation fine adjustment unit 205 for finely adjusting the gradation so that the image signal output from the gradation correction unit 204 is adapted to a printing environment such as temperature / humidity, An electrostatic latent image is produced by scanning a laser beam suitable for the image signal output from the output gradation fine adjustment unit 205. After the toner is immersed in the electrostatic latent image and transferred onto the paper, the printed matter is output through the fixing process, and the CPU 210, ROM 212, RAM 213 and the user for controlling the series of operations as described above. In an electrophotographic color image reproducing apparatus, i.e., a digital full color printer, comprising an operation unit 214 for feeling color change and instructing gradation correction, toner adhesion amount such as measurement of toner concentration on toner for gradation correction is measured. Toner adhesion amount detection unit 221 and toner adhesion amount detection unit 221 to be measured by converting the toner deposition amount measurement value to the gradation correction value and then averaged it, compared with the reference gradation correction value stored in the nonvolatile memory 211 And a gradation calculator 220 for calculating a new gradation correction value.

3 is a diagram illustrating a detailed configuration of the gray scale calculator 220 shown in FIG. 2, and reference numeral 301 denotes a signal converter for changing the toner deposition amount detected from the toner deposition amount detecting unit 221 to a gray scale value. Denotes an averaging unit for averaging the gray scale values output from the signal conversion unit 301, reference numeral 303 denotes a register for storing the signal of the averager 302, and reference numeral 304 denotes a ratio of the average gray scale value stored in the register 303. A gradation error comparison section for comparing the reference gradation correction values stored in the volatile memory 211 to calculate the preliminary gradation correction values is shown. Here, in the present invention, the method of calculating the preliminary grayscale correction value by calculating the input / output characteristics and comparing with the reference grayscale correction value includes a method of forming a table having a one-to-one correspondence between correction grayscale values for all grayscale values, and a nonvolatile memory 211. In order to reduce the size of), only a few corresponding values can be obtained, and then the coefficient values can be corrected in other embodiments, such as using a proportional formula, a method of obtaining a slope of a curve, and a method of obtaining an approximated linear function. However, in today's high-priced memory, it is better to use a method of creating a table with one-to-one correspondence of correction coefficient values for all grayscale values.

4 is a view for explaining a method of measuring the toner deposition amount in the toner deposition amount detecting unit 221 shown in FIG. 2, reference numeral 400 denotes a photosensitive roller, and reference numeral 401 denotes a toner image patch of a minimum area. Reference numeral 402 denotes toner image patches in the maximum area, respectively. The image data input to the printer driver 101 generates a laser beam signal and scans the surface of the photosensitive roller 400 to form a latent image. The latent image is selectively splattered to form a toner image. The toner deposition amount detecting unit 221 which measures the deposition amount of the toner, such as the concentration of the toner, is measured from the toner. At this time, since the position of the toner deposition amount detecting unit 221 is fixed, the toner image may be formed only in the vicinity of the toner deposition amount detecting unit 221 as shown by reference numeral 401, but to obtain a stable output, although toner consumption is high, More preferably, it is formed in a band like reference numeral 402. In addition, as another embodiment of the sensing unit 221 for measuring the amount of toner deposition used in the present invention, various types of sensors such as a sensor using reflectance wool, a sensor for measuring the amount of charge, and a sensor for measuring the magnetic force of the toner may be used. .

5 is a flowchart illustrating a method of changing the gradation correction value according to the present invention.

The operation of the color image reproduction shown in FIGS. 2 to 4 will be described with reference to FIG. 5 as follows.

First, the user feels the image quality deterioration of the printed matter and applies a gradation correction command using the operation unit 214 for gradation correction. (Step 500) At this time, the CPU 210 corrects the reference gradation stored in the nonvolatile memory 211. The value is read out, the gray scale correction and the output gray scale fine correction are performed, and are output to the printer driver 101.

The reference gray scale correction value is formed (step 502). That is, the data input to the printer driver 101 generates a laser beam signal and scans the surface of the photosensitive roller 400 shown in FIG. Toner is selectively crushed to form a toner image.

The toner deposition amount is measured from the toner image formed in step 502. In operation 504, that is, the toner deposition amount is measured through the toner deposition amount detecting unit 221 which measures the amount of toner deposition.

The toner measurement value measured in step 504 is converted into a gray scale value (step 506).

The gradation value converted in step 506 is averaged (step 508). At this time, since the position of the toner adhesion amount detecting unit 221 is fixed, the output form of the data is detected by the toner adhesion amount as shown by reference numeral 401 shown in FIG. Although the toner image may be formed only in the vicinity of the portion 401, in order to obtain a stable output, it is preferable to form a strip like the reference numeral 402 shown in FIG.

The average value of all gray levels is obtained by repeating each gray level value from step 508, and the input / output characteristics are calculated accordingly (step 510).

The preliminary gradation correction value is calculated by comparing the input / output characteristic of the step 510 with the reference gradation correction value (step 512). That is, the gradation error comparator 304 shown in FIG. 3 stores the non-volatile memory 211. A preliminary gradation correction value is calculated by comparing the reference gradation value with the gradation value based on the input / output characteristic output from step 510.

The toner image is formed by using the preliminary gradation correction value calculated from step 512. In operation 514, the calculated preliminary gradation correction values are read out one by one, inputted through the output gradation fine adjustment unit 205, and input into the printer driver 101 again. A toner image is formed.

The amount of toner adhered is measured from the toner image formed in step 514. (step 516) The toner measurement amount measured in step 516 is converted into a gray scale value (step 518).

After comparing the reference gray level correction value and the gray level value in step 518 to confirm whether the correction is corrected, the preliminary gray level correction value is stored (step 520). That is, the gray level value is compared by comparing the gray level value in step 518 with the reference gray level correction value. After confirming that the correction is made, it is stored in the nonvolatile memory 211 to change the reference gray scale correction value.

As described above, the toner adhesion amount detecting unit 221 for measuring the adhesion amount of the toner according to the present invention uses a detection unit for measuring the concentration or adhesion amount of the toner adjusted by the printing environment measured by temperature / humidity, If only the averaging section 302, the register 303, the gradation error comparing section 304, and the nonvolatile memory 211 shown in Fig. 3 are further configured, it is possible to maintain a uniform gradation at all times and contribute to the stability of the output. Can be.

It is also noted that the present invention not only applies to digital full color printers but also to copiers and facsimiles in the same manner.

As described above, the color image reproducing apparatus and the coefficient correction method according to the present invention can always measure the gradation value for each gradation step by using the toner deposition amount sensing unit, thereby correcting the difference in print quality over time. Since it is possible to obtain prints of the same chromaticity at the same time for the same original, the user can obtain and apply the gradation correction coefficients with a simple operation such as pressing a gradation correction operation key or selecting a command. Since the operation is performed very simply, it has the effect that it does not have to leave unnecessary prints by printing on paper.

Claims (9)

Color to drive the printer by converting the input RG B image signal into a YMCBK image signal, adjusting the color blending ratio of the converted YMC BK image signal, correcting the gradation for outputting a laser beam corresponding to the output image signal In the image signal reproducing apparatus, A toner adhesion amount sensing unit for sensing an adhesion amount of toner; A storage unit for storing a predetermined reference gray scale correction value; A gradation calculator configured to generate a new gradation correction value by comparing a gradation value corresponding to the toner deposition amount detected by the toner deposition amount detection unit with a reference gradation correction value stored in the storage unit; And And a gradation correction unit for correcting the gradation value of an image signal input from the outside by using the gradation correction value obtained from the gradation calculator. The color image signal reproducing apparatus according to claim 1, wherein the toner deposition amount detecting unit detects the density of the toner and measures a gradation correction value. The color image signal reproducing apparatus according to claim 1, wherein the toner deposition amount detecting unit detects a reflectance of the toner and measures a gradation correction value. The color image signal reproducing apparatus according to claim 1, wherein the toner deposition amount detecting unit detects an amount of charge of the toner and measures a gradation correction value. The color image signal reproducing apparatus according to claim 1, wherein the toner deposition amount detecting unit detects a magnetic force of the toner and measures a gradation correction value. The color image signal reproducing apparatus according to claim 1, wherein the gradation calculator calculates a new gradation correction value having a one-to-one correspondence by obtaining gradation correction values for all gradation values. The method of claim 1, wherein the gradation calculator calculates a gradation correction value for several gradation values, and then calculates a new gradation correction value using a proportional relationship between the gradation value and the corresponding gradation correction value. A color image signal reproducing apparatus. The method of claim 1, wherein the gray level calculation unit A signal converter which changes the amount of toner deposition detected by the toner deposition amount detecting unit to a gray value; An averaging unit for averaging the gray scale values output from the signal converter; A register for storing the image signal of the averaging unit; And And a gradation error comparator for comparing the average gradation value stored in the register with the reference gradation correction value to calculate a preliminary gradation correction value. A color image reproduction apparatus comprising: a method for correcting a gray scale value of a color image signal. A command applying step of applying a gradation correction command; A first toner image forming step of forming a toner image with a predetermined reference gray scale correction value; A first toner adhesion amount measuring step of measuring the toner adhesion amount on the toner image formed from the first toner image forming step; A first gradation value converting step of converting the measured value of the toner amount measured from said first toner deposition amount measuring step into a gradation value; An averaging step of averaging the tone values converted from the first tone value conversion step; An input / output characteristic extraction step of extracting an input / output characteristic for the averaged gray value from the averaging step; A preliminary gradation correction value calculating step of calculating a preliminary gradation correction value by comparing the gradation value extracted from the input / output characteristic extraction step with a reference gradation correction value; A second toner image forming step of forming a toner image by the preliminary gradation correction value calculated from the preliminary gradation correction value calculating step; A second toner deposition amount detecting step of measuring the toner deposition amount on the toner by the second toner image forming step; A second gray scale value converting step of converting the toner deposition amount detected from the second toner image sensing step into a gray scale value; And And if the gradation value correction by the gradation value converted from the second gradation value conversion step is correct, replacing the preliminary gradation correction value with a reference gradation correction value and storing the gradation value of the color image signal.