JP2006129347A - Method of standardizing input cmyk value of clustered printing environment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform control so that a printer has substantially the same output color response to substantially the same input CMYK values. <P>SOLUTION: Pre-conversion among C, M, Y and K is carried out before at least one printer to be clustered and the conversion is so designed as to make it secure for a printer handled through the pre-conversion to have substantially the same output color for substantially the same input CMYK values. For example, a 3D LUT among C, M and K and a 1D LUT for K are generated by using sensors in a field. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates generally to the field of standardizing input CMY and K values in a clustered printing environment, and more specifically, in a clustered printing environment, a digital front end (DFE) is defined as CMY and Criteria that relate K values to device-independent L ^* a ^* b ^* values to help ensure that a common set of CMYK values is presented to the DFE for multiple print engines below in the cluster About.

  Closed loop control is continually disrupting the industry as it becomes a substitute for expensive precision parts or wide windows in tolerance products / process designs. In general, they have expanded in scale from individual subsystems to IOTs that complete manufacturing and printing systems. Using closed loop control techniques instead of modeling and designing precision components or robust open loop systems captures Moore's Law cost curve in the electronics industry for electromechanical products. Predictable color distribution control is applied outside the input / output terminal (IOT), rendering all suitably provided colors “just like” to the IOT, and accurately printing the printed color on the display The ability to render opens up color cluster printing as an option for large in-line printers (eg, xerographs and offsets) and distributed printing as a viable alternative to printing, creating a business model for high quality graphic arts. Distribute.

  The present invention is directed to eliminating such barriers by controlling the printer to have substantially the same output color response for substantially the same input CMYK values.

  The present invention performs a CMYK-to-CMYK pre-conversion in front of at least one printer to be clustered, the conversion being substantially the same for input CMYK values that are addressed by the printer being addressed through the pre-conversion. Are designed to ensure that they have the same output color. As one implementation, a method for creating a 3D LUT between CMKs and a 1D LUT for K using sensors in the field is disclosed. Utilizing system LUTs, ie 3D LUTs between CMY and 1D LUTs between K, improves consistency, coherent control strategies, and standardized inputs CMY and K in a clustered environment To provide a means for providing a value, a single or multiple vendor DFEs see substantially the same CMYK value.

  A method of creating a 3D LUT between CMKs and a 1D LUT for K using sensors in the field is disclosed. The present invention performs a CMYK-to-CMYK pre-conversion in front of at least one printer to be clustered, the conversion being substantially the same for input CMYK values that are addressed by the printer being addressed through the pre-conversion. Are designed to ensure that they have the same output color. Utilizing a system LUT, ie a 3D LUT between CMY and a 1D LUT between K, in front of a gray balanced TRC (GB TRC) improves coherency and coherency. A single or multiple vendor DFE has the advantage of looking at substantially the same CMYK values to provide a control strategy and a means of providing standardized input CMY and K values in a clustered environment.

The pre-conversion between CMYK is performed in front of at least one printer to be clustered, and the conversion is substantially the same for printers that are addressed through pre-conversion for substantially the same input CMYK values. Designed to ensure that it has an output color of. Utilizing a system LUT, i.e., a 4D LUT between CMYKs, in front of a gray-balanced TRC improves consistency, provides a coherent control strategy, and inputs CMY and K values in a clustered environment. To provide the means to give, a single or multiple vendor DFE has the advantage of seeing substantially the same CMYK values. As implemented in accordance with the techniques herein, the present invention relates a particular CMY and K value that the DFE goes to the printer to a device independent L ^* a ^* b ^* value in a clustered environment. To help. With the present invention in place, DFE vendors can more easily construct 3D / 4D characteristics, such as ICC characteristics, and more accurately perform color management functions.

Referring now to FIG. 1, the pre-transformation includes system LUTs (3D CMY conversion and 1D K-to-K LUTs, or 4D CMYK inter-LUTs) and sensor LUTs (Lab to CMY and L ⁽ 1D LUT from ^* to K, or LUT / conversion from spectrum to CMYK). In FIG. 1, the digital front end (DFE) is 10, giving input CMYK values, indicated generally at 12 and 14, to the system LUT, resulting in 3D conversion between CMY and conversion between K. Thus, the system LUT gives the block 16 a set of transformed CMYK values denoted C′M′Y ′ and K ′, resulting in a TRC process between gray-balanced CMYKs, resulting in intermediate floors. Gives the key and marking module 18 with modified CMYK values denoted C ″ M ″ Y ″ and K ″ so that the pixels are printed on paper as in any xerographic printing system. The Data generated therefrom is read by the spectrophotometer 20, and the L ^* a ^* b ^* value measured at 22 is given to the sensor LUT 24. Here, the conversion from L ^* a ^* b ^* to CMY and between K produces a measured CMYK value, indicated at 26. Module 28 takes the measured CMYK values generated by sensor LUT 34 and performs a conversion between the CMY and K using a set of CMY and K reference values indicated at 32 and 30, respectively. Generate a set of lookup tables denoted 3D LUT between CMY and LUT between K. At 34, the 3D LUT between CMY and the LUT between K are used by a printer (not shown) to print a test target page. Target printing can also be done by DFE. Module 28 may reside in the DFE. This process is repeated as necessary until the CMYK values from module 28 are provided to modules 12 and 14 and the output color of the printed test target page is satisfactory.

Referring now to FIG. 2, the processing block is used to build a system LUT. For this example, it is assumed that the final system LUT of the 3D LUT between CMY includes 10 ³ data points and 256 data points for the K LUT system. In FIG. 2, the digital front end (DFE) 36 provides the input CMYK values to the system LUT 38, and the 4D conversion between CMYK is denoted C′M′Y ′ and K ′ for the block 40. A modified CMYK value is generated and a TRC process between gray-balanced CMYKs occurs, and the modified CMYK values, denoted as C ″ M ″ Y ″ and K ″, are represented by halftones and markings To module 42. The data generated from this is read by the spectrophotometer 44 and the spectrum value measured at 46 is given to the sensor LUT 48. Here, the conversion from spectrum to CMYK produces a CMYK value measured at 50. Module 52 takes the measured CMYK values generated by sensor LUT 48, performs a 4D conversion between CMYKs using a set of CMY reference values at 54, and designates a 4D LUT between CMYKs. Generate a set of lookup tables. At 56, a 4D LUT between CMYK is used by a printer (not shown) to print a test target page. This process is repeated as necessary until the CMYK values from module 52 are provided to the system LUT 38 and the output color of the printed test target page is satisfactory.

  According to the present invention, the construction of the system LUT includes the following steps that can be divided into two groups: (1) temporary processing steps performed at the factory and (2) execution of field updates.

The full 3D forward map of a gray balanced printer is first measured by printing a test patch that contains CMY patches that do not contain black (ie, K is set to zero). The output CMY from the sensor (ie the output of the sensor LUT, the Lab to CMY LUT) is obtained for these test patches. In this example, 10 ³ patches were selected. C, M, and Y on the test page are varied between 0 and 100% in 10 steps.

  By setting C = M = Y = 0, several K patches are printed on the test target (preferably about 256 patches) and these K values (when C = M = Y = 0) Sensor LUT output).

  Up-sample the measured forward map using interpolation routines commonly found in the art (cubic linear / tetrahedron). Upsampling may not be required depending on how well the printer is linearized by the internal processing control and gray balance system.

  Next, dynamic optimization techniques known to those skilled in the art are applied to generate the optimal nodes to generate a 1D system LUT for K separation. This is an inverse map of the forward LUT using either an iteratively clustered interpolation technique or a moving matrix algorithm.

One way to update the system LUT in the field is by printing and measuring test patches generated at all nodes of the system LUT (eg, having 10 ³ uniformly sampled nodes). CMY and K values). In other words, the required number of patches is selected equal to the number of nodes present in the system LUT. Depending on the particular system, these nodes can be numerous, making measurement and control redundant and time consuming. Therefore, subsampled nodes are preferred.

  A test target having the CMYK value of the critical node (output CMYK in the critical node LUT) is generated using a compression algorithm known to those skilled in the art.

  Subsampled CMYK test targets (for critical patches) are printed and measured by the sensor and its LUT output (CMY values for CMY patches and K values for K patches).

An upsampled form of the inverse map is created using cubic linear / tetrahedral interpolation and CMYK values measured against subsampled CMYK test targets. In this example, the upsampled inverse map has a size of approximately 10 ³ . This includes the desired system LUT (3D LUT between CMY and 1D LUT between K). This can be called post-processing. This post-processing is performed every time an update is requested. One skilled in the art will understand the fact that if all nodes are measured and controlled, no upsampling is required.

  Since the system LUT can include a limited number of nodes, for colors outside these nodes, conversion is preferably accomplished by using an interpolator.

The sensor LUT is required to extract CMY and K values from the measured spectrum / L ^* a ^* b ^* values of the color patch. This is preferably made using high resolution, such as 25 ³ CMY patches and about 1000 K patches, to minimize interpolation errors. CMYK test patch targets are first printed and their L ^* a ^* b ^* values on the selected reference printer are measured. Cubic linear or tetrahedral interpolation is used to construct a uniformly sampled input to the sensor LUT. Uniform sampling is not necessary to perform this task. The same sensor LUT can be used for all other printers in the cluster. This LUT is handled statically in all print engines when compared to the system LUT, so no further updates are needed in the field. However, in order to maintain color consistently across the printer host and ensure that DFE sees substantially the same CMYK values for clustered printers, the system LUT is shown above. Always needs to be updated using the control stage that is being used.

  FIGS. 3 and 4 show the configuration of a clustered print engine, in which the controller is illustrated by an individual loop with two sensors on the output paper path, one sensor for each print engine. In FIG. 4, the controller is shown by individual loops with one sensor in a common paper path.

  Referring now to FIG. 3, a user can view a color picture residing on computer system 58 with clustered printing consisting of two printing devices, each having their own DFE 60 and 74, and print engines 62 and 72. I want to print this by sending it to the environment. These two printing devices share a common finisher 66 and the print is then directed to the output 68. Colors, including pictures that are intended to be printed, are processed using a common AIM curve and provided to the DFE of at least one printer described above. The DFEs 60 and 74 in FIG. 3 embody all processes in either FIG. 1 or FIG. In FIG. 3, the iterative process shown at 64 and 70 associated with each print engine corresponds to what is happening in either FIG. 1 or FIG. As described in FIGS. 1 and 2, the LUT between gray-balanced TRC and CMY and K adjusts color values including color pictures. These LUTs were previously generated according to the description of either FIG. 1 or FIG. In either online or offline manner, DFE 60 and 74 iteratively adjust the color picture as shown at 64 and 70 respectively. Alternatively, in either online or offline manner, print engines 62 and 72 repetitively adjust the color picture as shown at 64 and 70, respectively. The result is advanced to a common finisher 66 before being output at 68.

  Referring now to FIG. 4, a user is able to view a color picture on the computer system 58 from a cluster of two printing devices that share a common DFE 60 and have their own print engines 62 and 72, respectively. I want to print it by sending it to the printing environment. These printing devices share a paper merge module 78 and a common finisher, and the print is then directed to the output 68. Colors including pictures that are intended to be printed are provided to the DFE 60 to embody all the processing in either FIG. 1 or FIG. In FIG. 4, the iterative process shown at 64 and 70 associated with each print engine corresponds to what is happening in either FIG. 1 or FIG. As described in FIGS. 1 and 2, the LUT between gray-balanced TRC and CMY and K adjusts color values including color pictures. These LUTs were previously generated according to the description of either FIG. 1 or FIG. In either online or offline manner, DFE 60 and 74 iteratively adjust the color picture as shown at 64 and 70 respectively. The result is advanced to a common finisher 66 before being output at 68.

  By introducing the control device described above, other core capabilities of cluster printing (job splitting, load balancing, automatic routing, job integrity, etc.) are not compromised. The dotted lines between the control loops in FIGS. 3 and 4 represent communication between printers.

Variations between printers are compensated when the control loop updates the system LUT. For example, a common variation seen between printers of the same family is contrast variation due to different dynamic ranges of the printers (different Dmax / L ^* min). Sensors can measure differences in dynamic range, and CMYK can be normalized to achieve a common dynamic range. Other differences in all regions will also be compensated for and incorporated into the conversion between CMYK.

  In an 8-bit system, a 3D LUT between CMY is preferably a 24-bit system, and a 4D LUT between CMYK is preferably a 32-bit system. In general, a cube of 17 is preferred for a 3D / 4D LUT. If fewer nodes are used in the lookup table, hardware or software based on cubic linear / tetrahedral interpolation is preferred.

Applications of system LUT [3D LUT between CMY and 1D LUT between K] and sensor LUT [3D LUT from Lab to CMY, L ^* 1D LUT for K] shown in printer image path Indicates. The application of the system LUT [4D LUT between CMYK] and sensor LUT [from spectrum to CMYK] shown in the printer image path is shown. Fig. 3 shows a clustered print engine configuration where the controller is shown by individual loops with two sensors on the output paper path, i.e. one sensor for each print engine. Fig. 3 shows a clustered print engine configuration in which the controller is shown by individual loops with one sensor in a common paper path.

Explanation of symbols

10: Digital Front End (DFE)
12: Input CMYK value 14: System LUT
18: Intermediate gradation part and marking module 24: Sensor LUT

Claims (4)

A method for providing standardized input CMYK values to a clustered printer environment, comprising:
a) Build a system LUT between CMYK
b) A method comprising positioning the system LUT in front of at least one printer in the cluster. A method of standardizing input CMYK values in a clustered printer environment so that the printer produces substantially the same output color for substantially the same input CMYK values,
a) Build a system LUT between CMYK
b) positioning the system LUT in front of at least one printer in the cluster;
c) A method comprising handling at least one of the printers through the system LUT. Having a clustered configuration of printers with a common paper path and providing standardized input CMYK values, the at least one printer has substantially the same output for substantially the same input CMYK. A printing system for generating colors,
a) a common sensor with at least one sensor LUT;
b) a system LUT between CMYKs in front of at least one printer in the cluster;
c) a controller module for handling the at least one printer through the system LUT;
A system comprising: A printing system having a clustered configuration and a common finisher to provide standardized input CMYK values,
a) a plurality of sensors having at least one sensor LUT in each paper path of each clustered printer;
b) a system LUT between CMYKs in front of at least one printer in the cluster;
c) a controller module for handling the at least one printer through the system LUT;
And the at least one printer generates substantially the same output color for substantially the same input CMYK value.

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