Hybrid Inline Color Control for Printing Presses
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Solution Overview
Problem
Current color control methods in printing presses face challenges due to the high cost of using multiple spectrophotometers for precise color measurement at high printing speeds and the limitations of RGB cameras in providing absolute color accuracy, especially during setup when color variations are sharp from sheet to sheet.
Innovation Solution
A method that combines a colorimetrically exact spectral measuring instrument with an RGB camera to register and correct color differences across multiple inking zones, allowing for precise color control by calculating and adding color differences between actual and desired colorations in different color spaces, enabling exact color control without the need for extensive spectrophotometer usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple spectrophotometers are used to measure color at high printing speeds, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines a spectral measuring instrument (spectrophotometer) with an RGB camera into a hybrid measuring system. The spectrophotometer provides precise colorimetric measurements at reference positions, while the RGB camera captures color information across the entire printing material area. By merging these two instruments with different measurement capabilities, the system achieves comprehensive color monitoring without requiring multiple separate spectrophotometers, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent introduces a control device as an intermediary that processes measurements from both the spectrophotometer and RGB camera. The control device uses the precise spectral measurements to calibrate and correct the RGB camera's color readings, enabling the camera to provide accurate color information across the entire printing area. This intermediary processing allows the system to achieve spectrophotometer-level precision without placing multiple spectrophotometers throughout the printing press
2Productivity
If an RGB camera is used to register large areas, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The spectrophotometer serves as an intermediary calibration instrument that provides accurate colorimetric reference measurements. The control device uses these reference measurements to correct and calibrate the RGB camera's color readings across the entire captured area. This intermediary calibration process enables the RGB camera to maintain high productivity for large-area registration while achieving colorimetric accuracy comparable to spectrophotometer measurements
Solution Approach 2:
The patent transforms the RGB camera's raw color data into accurate colorimetric values by applying calibration parameters derived from spectrophotometer measurements. The control device adjusts the camera's color space transformations and correction factors based on the spectral reference data, effectively changing the measurement parameters to achieve both high-speed area coverage and precise colorimetric accuracy
3Device complexity
If a hybrid instrument with one calibration is used, then device complexity is reduced, but reliability deteriorates due to lack of continuous calibration
Solution Approach 1:
The patent implements continuous calibration by having the spectrophotometer repeatedly measure reference color patches on the printing material throughout the printing process. The control device continuously compares these spectral reference measurements with the RGB camera readings and dynamically adjusts the calibration parameters. This continuous calibration approach ensures reliable color control accuracy without requiring complex manual recalibration procedures, maintaining both device simplicity and measurement reliability
Solution Approach 2:
The system establishes a feedback loop where the spectrophotometer's precise measurements continuously monitor color accuracy, and the control device uses this feedback to automatically adjust the RGB camera's calibration. The measured color values from both instruments are fed back to the control device, which corrects any drift in the camera's color readings in real-time. This automatic feedback mechanism ensures continuous color control reliability without increasing operational complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for cost-effective, precise color control across all inking zones, reducing the need for multiple spectrophotometers and ensuring accurate color registration, even during continuous printing, by leveraging the strengths of both spectral and RGB measurements.
Implementation Method 1
a first color measuring instrument, with which a color measuring area of a color separation in the print control strip is registered for each color separation
Implementation Method 2
a second color measuring instrument, with which a color measuring area of the color separation in the print control strip is registered
Data Source
AI summary
A method for color control in printing presses having at least one first color measuring instrument and at least one second color measuring instrument, includes registering at least one first inking zone on a printing material with the first color measuring instrument and registering at least one other, second inking zone on the printing material with the second color measuring instrument. In a first step, a color difference between actual colorations of the first and second inking zones is calculated, in a second step, a color difference between an actual coloration of the first inking zone and a desired coloration of the second inking zone is calculated and, in a further step, the calculated color differences are added and supplied to a color control for the second inking zone.