Dynamic LUT Adjustment for Printing Density Stability
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Solution Overview
Problem
Electrophotographic and ink jet printing systems face instability in toner density due to environmental factors like temperature and humidity, leading to issues such as jaggies, discontinuity, toner scattering, and ink blurring, which existing correction methods fail to balance effectively.
Innovation Solution
A method that generates multi-valued color material amount data using a computer program to control tone levels by updating Look Up Tables (LUTs) for gamma correction and Pulse Width Modulation (PWM) control, ensuring stable density output and preventing excessive toner usage, thereby maintaining optimal gradation properties and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LUT suppresses the upper limit value of density to avoid toner scattering and ink blurring, then the stability of color material fixation is improved, but jaggies and discontinuity occur in maximum density portions and thin lines
Solution Approach 1:
The patent applies dynamics by making the LUT adjustment adaptable to different image types. The system dynamically selects between two LUT adjustment approaches: terminal endpoint correction for images requiring maximum density output (avoiding jaggies) and upper limit suppression for images where color material stability is critical (avoiding scattering and blurring). This dynamic selection resolves the contradiction by allowing the system to optimize for either image quality or fixation stability depending on the specific printing requirements.
Solution Approach 2:
The patent changes the parameter of LUT adjustment mode based on image characteristics. By detecting whether an image contains maximum density regions or thin lines, the system switches between different LUT correction strategies. This parameter change enables the system to prevent toner scattering and ink blurring while maintaining image quality in critical areas, thus resolving the technical contradiction.
2Manufacturing precision
If the LUT performs terminal endpoint correction to guarantee maximum density output, then jaggies and discontinuity are eliminated, but the amount of color material exceeds the upper limit value causing poor fixing
Solution Approach 1:
The system dynamically determines whether to apply terminal endpoint correction or upper limit suppression based on image analysis. When the image contains maximum density regions or thin lines, terminal endpoint correction is applied to prevent jaggies. When the image does not require maximum density output, upper limit suppression is applied to prevent color material scattering and blurring. This dynamic approach resolves the contradiction between image quality and fixation stability.
Solution Approach 2:
The patent changes the LUT adjustment parameter based on image characteristics. The system analyzes the input image to determine whether terminal endpoint correction or upper limit suppression is more appropriate, then switches between these two parameter settings. This parameter change strategy allows the system to achieve both high image quality and stable color material fixation under different printing conditions.
3Reliability
If the amount of color material is reduced to prevent scattering and blurring, then fixation stability is improved, but gradation properties and tone level deteriorate
Solution Approach 1:
The patent applies local quality by selectively adjusting color material amounts in different regions of the image. Through LUT-based correction, the system locally suppresses color material in areas prone to scattering and blurring while maintaining or enhancing color material levels in areas requiring good gradation properties. This localized adjustment resolves the contradiction by preserving fixation stability in critical areas while maintaining gradation quality in other areas.
Solution Approach 2:
The system changes the color material amount parameter selectively based on spatial location and image characteristics. The LUT applies different correction factors to different tonal values and image regions, allowing the system to reduce color material where necessary to prevent scattering while maintaining gradation properties where important. This parameter change strategy resolves the contradiction between fixation stability and gradation quality.
Data Source
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AI summary
An apparatus according to the present invention includes: an acquisition unit (S505) configured to acquire, based on the results of reading a test pattern output by a printing unit (112), tone level correction data for bringing the reproduction characteristics of an image that is output by the printing unit close to a target value; a unit (S506, S507) configured to generate adjusted tone level correction data obtained by adjusting the tone level correction data so that a predetermined density area increases in density; and a unit (Fig. 9) configured to generate color material amount correction data adjusted so that the amount of color material that is used for image formation becomes small in accordance with a degree of the adjustment in the adjusted tone level correction data.