KR100307581B1 - Color printer having color correction function and method for generating lookup table - Google Patents

Abstract

PURPOSE: A color printer having color correction function and method for generating lookup table is provided to allow users to easily correct colors, by arranging a color sensor and a built-in lookup table generating program. CONSTITUTION: A color printer(10) comprises a color sensor(15) attached to a head(14), and which detects the color patch printed onto a printing material, and generates a color information; and a lookup table generating program for generating a new lookup table by printing the color patch and inputting the color information detected and generated by the color sensor. A method comprises a first step of printing a color patch for each process in accordance with the user request for color correction; a second step of detecting the printed color patch through the use of a color sensor, and generating a color information; a third step of generating a table regarding the relation between the color information and each process, and storing the result; a fourth step of generating a new lookup table through an inverse interpolation method, in consideration of the table generated in the third step and environmental condition.

Description

How to create color printer and lookup table with color correction

1 is a block diagram showing a color printer according to the present invention,

2 is a structural diagram schematically showing the structure of the head and the color sensor of FIG.

3 is a schematic diagram showing a color patch sheet,

4 is a flowchart showing a lookup table manufacturing flow according to the present invention.

* Explanation of symbols for main parts of the drawings

1: computer 2: color printer

11 interface unit 12 print processing and control unit

13 head drive 14 head

15: color sensor 16: look-up table manufacturing unit

17: memory unit 18: panel operation unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color printer, and more particularly, to a color printer and a method for creating a look-up table equipped with software for attaching a color sensor near a head and automatically producing a look-up-table for color correction.

In color printers, a method widely used in recent years to faithfully reproduce a reproduced color copy to an original color, assuming the color reproduction process as a black box, and correlating the output with the input. Experimental methods of finding relationships are widely used. These methods include polyominal regression and lookup table (LUT) methods. The multidirectional regression method is a method of expressing experimental data by a mathematical method, which has been widely used, but has a disadvantage in that it cannot be accurately expressed through all color gamuts. The lookup table (LUT) method is widely used in printers and scanners with severe color distortion, and has the advantage of expressing color deformation reliably across all gamuts, but it is difficult to produce a lookup table (LUT) and has a large amount of memory. There was a downside to requiring it. Since the process of manufacturing the lookup table was very complicated and manual coloration was inconvenient, in the conventional color printer, the lookup table was uniformly manufactured by a color printer manufacturer and used in the color printer.

In other words, in order to accurately reproduce the color using the lookup table, ideally, the output of all possible colors should be measured, but since it is not practically possible, only a part of it is sampled to calculate the correction relationship, and the rest of the values are represented. It was approximated by interpolating the values. Therefore, in order to minimize color distortion, the number of representative values should be increased, which increases cumbersome color retrieval and requires a large amount of memory. In addition, even when a lookup table is manufactured, since the lookup table is manufactured under an environment assumed by a manufacturer, it is difficult to accurately reflect realistic environmental factors. That is, although a new lookup table is required for each color printer due to changes in the user's environment such as paper, ink, and changes in mechanical properties over time, it is usually reproduced because a uniform lookup table provided by a manufacturer is used. There was a problem that a serious discrepancy between the original color and the original color occurs.

Accordingly, an object of the present invention is to provide a color printer having an automatic color correction function that can automatically create a color correction lookup table if necessary by embedding a color sensor to solve the conventional problems as described above.

Another object of the present invention is to provide a method for creating a lookup table of a color printer, which allows a user to automatically create a color correction lookup table if necessary by incorporating a color sensor to solve the conventional problems as described above.

In order to achieve the above object, the apparatus of the present invention converts the color data into color correction data using a look-up table after inputting color data, and accordingly, is attached to the head in a color printer for driving a head to print on a print medium. A color sensor for detecting color patches printed on the printing medium and generating color information; And a color printer incorporating a lookup table manufacturing program for printing the color patch and inputting the color information to create a new lookup table.

In order to achieve the above object, in the method of the present invention, when a user requests color correction through a panel manipulation unit, a color printer prints a color patch on a paper by executing a built-in program, and detects it with a color sensor to create a new lookup table. In the manufacturing method of the look-up table of a color printer to create a color patch, a color patch for printing a color patch in each step of cyan, magenta, yellow, and (black) (C, M, Y (K)) according to the user's color correction request Printing step of; A color sensing step of detecting the printed color patch with the color sensor and generating color information; A correspondence table creation step of creating and storing a correspondence relationship between the color information and each of the steps C, M, and Y (K) in a table; And a lookup table preparing step of creating a new lookup table by using an inverse interpolation method in consideration of the correspondence table and a usage environment factor.

Next, the apparatus of the present invention will be described in detail with reference to the accompanying drawings.

The concept of the present invention is to create a color correction lookup table from time to time to accurately reflect the changes in the use environment so that the reproduced color is faithful to the original color. A color sensor is attached to the color input / output product. Hereinafter, an embodiment in which the present invention is applied to a color printer will be described in detail.

1 is a block diagram showing a color printer according to the present invention, wherein the color printer 10 includes an interface unit 11, a print processing and control unit 12, a head driving unit 13, a head 14, and a color sensor ( 15), the lookup table manufacturing unit 16, the memory 17, and the panel operation unit 18 are provided to print color data input from the computer 1, and a lookup table LUT is created by itself if necessary.

In order to describe the present invention in detail, an inkjet printer will be described as an example. Tone-corrected printer ink Cyan, Magenta, Yellow (Cyan, Magenta, Yellow: These are referred to as navy blue primary colors). In addition, each of the C, M, and Y (K) expressions is output to the step of flattening. If each color has 9 levels, 9 × 9 × 9 = 729 representative values, and the digital values are 0, 32, 64, 96, 128, 192, 224, and 256 for each step. In FIG. 1, the interface unit 11 interfaces the computer 1 and the color printer 10, and the print processing and control unit 12 processes the functions requested by the user through the panel operation unit 18. In FIG. Color data is input from the interface unit 11, converted into data for printing (i.e., color correction data) according to the lookup table, and outputted to the head driving unit 13. The head driver 13 controls the head 14 according to the input data, and the head 14 uses a C, M, Y (K) color ink according to the control of the head driver 13 to print media (eg, For example, paper). The color sensor 15 detects a color printed by the head 14 on a printing medium (not shown) and outputs color information to the lookup table manufacturing unit 16. The lookup table manufacturing unit 16 executes a built-in program according to the print processing and the control of the control unit 12 to display the color information input from the color sensor 15 in correspondence with the C, M, and Y (K) steps. And stores it in the memory 17. The lookup table manufacturing unit 16 and the memory 17 may be included in the print processing and control unit 12 so that the print processing and control unit 12 may directly input color information from the color sensor 15 to create a lookup table. That is, the color printer 10 is almost similar to the conventional color printer, but the color sensor 15 is attached near the head 14, and the lookup table manufacturing program is built in, so that the user can use the key of the panel operation unit 18. If you require the creation of a new lookup table, run the lookup table creation program.

FIG. 2 is a structural diagram schematically showing the structure of the head and the color sensor of FIG. 1, in which a chip-level color sensor 15 is integrally attached to the head 14 at the rear end of the head driving unit 13 so that the color patch paper 20 The color patch is printed with the head 14, and the color sensor 915 detects the color patch.

The output pattern of the color patch is large enough to be read by the color sensor 15 for measurement but is as closely aligned as possible. Taking the size of the color patch as an example, when the measurement size of the color sensor 15 is 3.5 mm in diameter (d) and the alignment deviation in the longitudinal and horizontal directions of the color printer 10 is 3 mm, the minimum color The patch size is 2 (3.5 / 2 + 3) = 9.6 mm. Therefore, it is sufficient to set the size of the output patch to a rectangle of 10 × 10 mm, and about 609 color patches can be obtained on one sheet of A4 paper, so that 609 × 2 = 1218 color patches can be put on two sheets.

In this way, the color prints are printed in the form of color patches, and the color sensors 15 provided at the rear end of the print head traveling direction are sequentially measured to correspond to the digital values of C, M, and Y (K). You get a corresponding table with colorimetric values. The correspondence table thus obtained is stored in a memory, and a lookup table is produced by inverse interpolation using the stored correspondence table.

3 is a schematic diagram showing a color patch paper, wherein each color patch has a square size of about 10 mm by 10 mm in width (a) x length (b). Therefore, if the color patch paper is A4 size, about 609 color patches can be printed.

4 is a flowchart illustrating a lookup table manufacturing flow according to the present invention. In FIG. 4, in step 30, it is determined whether the user inputs the lookup table production key, and if the key is input, the process proceeds to step 32. If the key is not input, the general printer function is performed in step 31. In step 32, when a lookup table production key is input, color patches are printed for each of steps C, M, and Y (K). In step 33, the printed color patch is detected by the color sensor 15 to obtain colorimetric information. In step 34, a corresponding table is created between the colorimetric information output from the color sensor 15 and the respective steps of C, M, and Y (K), and stored in the memory. In step 35, a new lookup table is created by inverse interpolation in consideration of the correspondence table and the environmental factors stored in the memory.

As described above, in the related art, a procedure for manufacturing a lookup table is complicated, and many color patches need to be measured, so that a general user without knowledge of color processing cannot directly color correct a color printer. However, by adding a color sensor to the color printer and incorporating a look-up table manufacturing program according to the present invention, color correction can be easily performed by the general user in consideration of environmental factors, thereby reducing errors occurring during color reproduction. It works.

Claims (2)

A color printer that inputs color data and converts the color data into color correction data using a look-up table. Accordingly, a color printer which drives a head to print on a print medium detects a color patch attached to the head and printed on the print medium. A color sensor generating color information; And a color printer incorporating a lookup table manufacturing program for printing the color patch and inputting the color information to create a new lookup table. Claims [1] A method of creating a lookup table of a color printer, the method comprising: a color patch printing step of printing a color patch for each step of Y, C, and M (K) according to a user's color correction request; A color sensing step of detecting the printed color patch with a color sensor and generating color information; A correspondence table creating step of creating and storing a correspondence relationship between the color information and each of the Y, M, and C (K) steps as a table; And a lookup table creating step of creating a new lookup table by using an inverse interpolation method in consideration of the correspondence table and the use environment factors.