Profile Correction for Gray Tone Stability in Image Forming Devices
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Solution Overview
Problem
Conventional image-forming devices require frequent calibration to maintain gray tone stability, leading to wastage of colorant and time due to fluctuations in CMY toner densities, which results in unwanted color shifts.
Innovation Solution
A profile correcting method that adjusts CMYK values to maintain gray color values within a blue hue range by setting a* and b* values within specific margins, reducing the need for frequent calibration by ensuring color differences remain within perceivable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequent calibration is performed to maintain gray tone stability, then gray tone stability is improved, but colorant waste and time loss increase
Solution Approach 1:
The patent applies preliminary action by pre-defining acceptable gray tone ranges (a* and b* value margins) and creating correction profiles in advance. Instead of waiting for calibration to be needed, the system proactively establishes correction data that compensates for toner density fluctuations, allowing the printer to maintain gray tone stability without frequent calibration interventions.
Solution Approach 2:
The patent changes parameters by adjusting CMYK output values based on measured toner densities. The system dynamically modifies the relationship between input gray values and output CMYK values by applying correction profiles that adjust chromatic values (a* and b*), thereby maintaining gray tone stability despite variations in toner density without requiring physical recalibration.
2Reliability
If frequent calibration is performed to maintain gray tone stability, then gray tone stability is improved, but time consumption increases
Solution Approach 1:
The system performs calibration-related actions preliminarily by pre-measuring toner densities and pre-calculating correction profiles. This upfront work eliminates the need for frequent time-consuming calibration cycles, as the correction data is ready to be applied automatically based on toner density measurements.
Solution Approach 2:
The system implements self-service by automatically measuring toner densities, selecting appropriate correction profiles, and applying corrections without requiring user intervention or manual calibration processes. The printer autonomously maintains gray tone stability by selecting and applying the most suitable correction profile based on current toner density measurements.
3Reliability
If output CMYK values are adjusted to compensate for toner density changes, then gray tone stability is improved, but color accuracy may deteriorate
Solution Approach 1:
The patent applies local quality by creating separate correction profiles for different gray levels and density ranges. Instead of applying a uniform correction that might compromise overall color accuracy, the system selects specific correction profiles tailored to particular gray level ranges, thereby maintaining both gray tone stability and color accuracy in their respective domains.
Solution Approach 2:
The patent carefully changes parameters by selectively adjusting only the chromatic values (a* and b*) relevant to gray tones while preserving other color characteristics. The correction profiles modify CMYK output values in a controlled manner that compensates for toner density changes in gray areas without introducing excessive color shifts in colored regions.
4Reliability
If correction profiles are created for multiple density ranges, then gray tone stability across all densities is improved, but device complexity increases
Solution Approach 1:
The patent manages complexity by organizing correction profiles according to clear parameter thresholds (density ranges and gray levels). The system uses straightforward selection logic based on measured toner densities to choose the appropriate profile, avoiding complex algorithms while still providing comprehensive coverage across different density ranges.
Data Source
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Figure 3A~3B
AI summary
A profile correcting method includes: acquiring a device profile indicating correspondence relationships between a plurality of input values and a plurality of sets of first output values, each first output value set corresponding to one of the plurality of input values, each input value representing an achromatic color having a density level, each first output value set including a plurality of chromatic values each representing a chromatic color, the achromatic color being reproduced by mixing the chromatic color; and, performing a process for each input value. The process includes: forming a test patch based on one first output value set corresponding to the each input value; measuring color of the test patch, the color being represented by a set of a*b* values, the a*b* value set including a first a* value and a first b* value which are defined in a CIEL*a*b* color space; determining whether or not the one first output value set is a to-be-corrected first output value set, the to-be-corrected first output value set corresponding to a test patch whose color is represented by an a* b* value set including at least one of the first a* value greater than an a* prescribed value and the first b* value greater than a b* prescribed value, the a* prescribed value and the b* prescribed value being smaller than zero; and correcting, if the one first output value set is the to-be-corrected first output value set, the one first output value set to a second output value set which is to form color that is represented by an a* b* value set including a second a* value and a second b* value, the second a* value being smaller than or equal to the a* prescribed value, the second b* value being smaller than or equal to the b* prescribed value.