Field Sequential Color Display Backlight Dimming Control
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Solution Overview
Problem
Field sequential color (FSC) displays face limitations in dimming capability and color instability over a wide range of temperatures and drive conditions, which hinders their use in military and avionics applications requiring high dimming ratios and consistent color performance.
Innovation Solution
A method and system that utilize a backlight with first and second light sources, where the video signal includes video frames with sub-frames corresponding to each light source, allowing for adjustable operation durations to control luminance and implement pulse width modulation and temperature compensation to enhance dimming and color stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If FSC displays use sequential writing with RGB emitters to eliminate color filters and reduce power consumption, then power efficiency is greatly reduced and thermal management is improved, but dimming capability is significantly limited or eliminated
Solution Approach 1:
The patent applies periodic action by implementing pulse width modulation (PWM) where the backlight emitters are switched on and off in sequential cycles corresponding to RGB sub-frames. By varying the duty cycle of these periodic pulses, the display achieves dimming control while maintaining the power-efficient FSC architecture without color filters
Solution Approach 2:
The patent implements dynamics by making the emitter operation durations variable and adjustable. The controller dynamically changes the on-time duration of each RGB emitter within its sub-frame based on desired luminance levels, enabling continuous dimming control while maintaining sequential color generation
2Manufacturing precision
If FSC displays sequentially write each pixel with RGB emitters to triple display resolution, then full color is generated at each individual pixel, but color stability deteriorates over wide temperature ranges and drive conditions
Solution Approach 1:
The patent implements feedback by incorporating temperature sensors that continuously monitor the operating temperature of the backlight emitters. The controller uses this temperature feedback information to dynamically adjust the emission duration and intensity of each RGB emitter, compensating for temperature-induced color shifts and maintaining stable display color across wide temperature ranges
Solution Approach 2:
The patent applies parameter changes by adjusting the operational parameters (duration and intensity) of the RGB emitters based on measured temperature and drive conditions. By changing these parameters dynamically, the system compensates for environmental variations and maintains consistent color output while preserving the high resolution benefit of sequential writing
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
The solution significantly improves dimming range and color uniformity, enabling dimming ratios exceeding 2000:1 and maintaining color stability across various temperatures, thus addressing the limitations of FSC displays.
Implementation Method 1
The first light source is operated for a first duration during a first sub-frame of a first video frame. The first light source is operated for a second duration during a first sub-frame of a second video frame.
Implementation Method 2
The second duration is different from the first duration. The solution significantly improves dimming range and color uniformity, enabling dimming ratios exceeding 2000:1
Data Source
AI summary
Methods and systems for displaying an image on a display device having first and second light sources are provided. A video signal is provided to the display device. The video signal includes first and second video frames. Each video frame includes first and second sub-frames corresponding to the respective first and second light sources. The first light source is operated for a first duration during the first sub-frame of the first video frame. The first light source is operated for a second duration during the first sub-frame of the second video frame. The second duration is different from the first duration.