Field-Sequential LCD White Color Point Stabilization
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Solution Overview
Problem
Field sequential liquid crystal displays (LCDs) face a challenge in maintaining a stable white color point over time due to variations in the forward voltage of light emitting diodes (LEDs), which affects the calibrated color output.
Innovation Solution
The forward voltages of LEDs are adjusted by monitoring their ON time and brightness, using stored thresholds and look-up tables to calibrate and maintain the white color point, ensuring consistent color representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If voltage control is used for LEDs, then the display can be controlled electronically, but the forward voltage of each LED varies over time causing the white color point to drift
Solution Approach 1:
The system continuously monitors the actual forward voltage of each LED and compares it against stored reference values. When drift is detected, the controller automatically adjusts the drive voltage to compensate and maintain the white color point at its calibrated position throughout the LED's operating life.
Solution Approach 2:
The invention dynamically changes the voltage parameter supplied to each LED based on its aging characteristics. By adjusting the drive voltage in response to measured forward voltage changes, the system compensates for LED degradation and maintains stable color output over time.
2Device complexity
If the forward voltage of LEDs is not adjusted, then the device complexity is low, but the white color point drifts over time affecting display quality
Solution Approach 1:
The system performs self-calibration by automatically monitoring LED forward voltage and adjusting drive parameters without external intervention. The controller uses stored reference data and real-time measurements to autonomously maintain the white color point, eliminating the need for manual recalibration.
Solution Approach 2:
The invention pre-stores reference forward voltage values and calibration data in the controller before operation begins. This preliminary preparation enables the system to automatically compensate for voltage drift as it occurs, maintaining color accuracy throughout the LED's lifespan without requiring complex real-time calculations.
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 method effectively stabilizes the white color point in LCDs, ensuring accurate color representation even as LEDs age, by compensating for voltage changes and usage patterns, thereby maintaining display quality over the lifespan of the device.
Implementation Method 1
Field sequential liquid crystal displays (LCD) use three colour light emitting diodes (LED) to provide full colour displays
Data Source
AI summary
A field sequential liquid crystal display maintains its white colour point through compensation values to at least one colour light emitting diode that illuminates the display. The compensation values may be impedances to control the current or pulsing of the current source according to a pulse width modulation technique. A degradation curve may be used to calculate extrapolate the theoretical forward voltage of the light emitting diode. Additional complexity arises from the need for calculating uptime for multiple light emitting diodes of different colours. Brightness levels may also be factored in.