Tone-Level Correction in Digital Printers
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Solution Overview
Problem
Digital printing systems, such as electrophotographic printers, face challenges in correcting tone-level non-uniformities, particularly image streaks that vary with cross-track and in-track positions, leading to suboptimal print quality.
Innovation Solution
A method involving the use of digital image data for a test target with uniform patches to capture and analyze tone-level errors, determining a tone-level correction function using one-dimensional feature vectors, and applying these corrections to input image data to reduce tone-level errors in printed images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional tone-level correction methods are used, then some uniformity artifacts can be reduced, but cross-track varying streaks and other tone-level errors cannot be effectively corrected
Solution Approach 1:
The patent applies local quality by creating position-specific correction values for different locations across the track and in-track directions. Instead of using a single global correction factor, the system determines correction values tailored to specific cross-track positions and in-track positions, allowing localized correction of tone-level errors that vary across the image area.
Solution Approach 2:
The patent segments the correction process into multiple independent correction functions: one for cross-track position variations and another for in-track position variations. This segmentation allows the system to address different types of uniformity artifacts separately and combine their effects for comprehensive correction.
2Manufacturing precision
If comprehensive correction functions are applied to all image pixels, then tone-level errors are reduced, but processing time and computational complexity increase
Solution Approach 1:
The patent performs preliminary action by pre-calculating correction functions using test target images before actual printing. The system captures test patches, determines correction values, and stores these correction functions for reuse. This preliminary correction setup eliminates the need for real-time complex calculations during actual image processing.
Solution Approach 2:
The patent uses copying by capturing test target images with a digital imaging device and using these copies to determine correction functions. The correction values derived from test patches are then applied to correct actual printed images, avoiding direct measurement and correction of every production image.
3Manufacturing precision
If correction data for all positions and tone levels is stored, then accurate correction is achieved, but memory requirements increase significantly
Solution Approach 1:
The patent applies parameter changes by representing correction functions in terms of varying parameters (cross-track position and in-track position) rather than storing fixed correction values for every possible combination. The system uses parametric models that can generate correction values for any position within the image area, reducing storage requirements while maintaining accuracy.
4Manufacturing precision
If multiple correction functions are combined, then both cross-track and in-track errors are corrected, but system complexity increases
Solution Approach 1:
The patent segments the correction system into distinct functional components: a cross-track correction function and an in-track correction function. Each function handles a specific type of position variation independently, making the overall system more manageable and easier to implement than a single monolithic correction algorithm.
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
Significantly reduces tone-level errors like image streaks across the print, requires less memory for storage, and can correct errors varying with both cross-track and in-track positions, enhancing print quality and compatibility with various pre-processing systems.
Implementation Method 1
an electrostatic latent image is formed on a photoreceptor by uniformly charging the photoreceptor and then discharging selected areas of the uniform charge to yield an electrostatic charge pattern corresponding to the desired image
Implementation Method 2
charged toner particles are brought into the vicinity of the photoreceptor and are attracted to the latent image to develop the latent image into a toner image
Implementation Method 3
A suitable electric field is applied to transfer the toner particles of the toner image to the receiver to form the desired print image on the receiver
Implementation Method 4
The receiver is then removed from its operative association with the photoreceptor and subjected to heat or pressure to permanently fix (i.e., 'fuse') the print image to the receiver
Data Source
AI summary
A method for correcting tone-level non-uniformities in a digital printing system includes printing a test target having a set of uniform test patches. The printed test target is automatically analyzed to determine tone-level errors as a function of cross-track position for each of the test patches. A tone-level correction function is determined and represented using a set of one-dimensional feature vectors which specifies tone-level corrections as a function of cross-track position and pixel value. Corrected image data is determined by using the tone-level correction function to determine a tone-level correction value for each image pixel responsive to the input pixel value and cross-track position of the image pixel. The corrected image data is printed using the digital printing system to provide a printed image with reduced tone-level errors.