Test Pattern Evaluation for Motion-Induced Chromatic Shift
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Solution Overview
Problem
Liquid crystal display (LCD) devices experience motion-induced chromatic shift due to imbalances in control logic, leading to noticeable color shifts in grayscale areas, causing flickering traces of pink, magenta, or green, which are difficult to diagnose and correct using traditional test patterns.
Innovation Solution
A test pattern evaluation tool generates and renders a test pattern based on a base pattern of pixels with successive offsetting to evaluate chromatic shifts among sub-pixel display elements, specifically configured to trigger shifts caused by imbalances in overdrive adjustments or transition times, facilitating the identification of issues within the LCD's control logic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If traditional test patterns are used for LCD calibration, then general display settings can be adjusted, but motion-induced chromatic shift problems cannot be detected
Solution Approach 1:
The patent segments the display into individual sub-pixel groups (red, green, blue sub-pixels) and tests each group's response independently by offsetting the test pattern by fractional pixel amounts. This segmentation allows detection of chromatic shift in each sub-pixel group separately, making the previously undetectable color value inaccuracies measurable.
Solution Approach 2:
The patent introduces a new dimension of measurement by using fractional pixel offsets (e.g., 0.5 pixel, 0.25 pixel) in addition to integer pixel offsets. This dimensional approach to pattern displacement reveals chromatic shift artifacts that remain hidden when only integer pixel shifts are used, enabling detection of sub-pixel level timing imbalances.
2Speed
If LCD control logic is adjusted to improve response time, then transition speed increases, but chromatic shift artifacts are introduced
Solution Approach 1:
The patent applies partial action by using fractional pixel offsets (less than one full pixel) to trigger and measure chromatic shift. This partial displacement is sufficient to reveal the harmful effect of timing imbalances in overdrive control logic, allowing measurement of the artifact without requiring full pixel movement that would mask the subtle color shifts.
Solution Approach 2:
The patent implements feedback by measuring the chromatic shift artifacts generated by the LCD's overdrive control logic and using this information to diagnose and adjust the control settings. The test pattern reveals the actual color value deviations caused by the control logic, providing feedback for optimizing the balance between response time and color accuracy.
3Loss of time
If overdrive control logic is applied to reduce transition time, then display response improves, but imbalance among sub-pixels causes color shifts
Solution Approach 1:
The patent segments the overdrive control evaluation into individual sub-pixel groups (red, green, blue) and tests each group's transition behavior separately. By offsetting the test pattern to align with specific sub-pixel groups and measuring their response independently, the patent can identify which sub-pixel groups have timing imbalances, allowing targeted adjustment of overdrive control to maintain both fast response and color stability.
Solution Approach 2:
The patent changes the test parameter from integer pixel offsets to fractional pixel offsets (e.g., 0.5, 0.25 pixels) to reveal chromatic shift artifacts. This parameter change in the test methodology enables detection of the reliability issue (color value stability) while the LCD operates with fast transition times enabled by overdrive control logic.
Data Source
AI summary
Display of a test pattern on a liquid crystal display (“LCD”) device or other display device can expose a problem with control logic that causes perceptible shifting in color values away from correct color values. For example, a test pattern evaluation tool determines a test pattern that is based at least in part on a base pattern of pixels. The test pattern evaluation tool successively renders the test pattern for display on a display device. In doing so, the test pattern evaluation tool offsets the base pattern by a number of pixels (e.g., shifting by one pixel horizontally) between successive rendering operations at the native refresh rate of the display device, which facilitates evaluation of whether chromatic shift is induced among at least some sub-pixel display elements of the display device.