LCD Gamma Correction for Uniform Brightness
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Solution Overview
Problem
Color-sequential LCDs face non-uniform brightness due to varying response times of liquid crystals across different areas of the panel, leading to deviations in gamma curves and light transmittance, which affects the display's ability to maintain consistent brightness across the screen.
Innovation Solution
The method involves dividing the LCD panel into areas with distinct voltage-transmittance functions and gamma curves, determining optimal grey level voltages for each area to achieve uniform light transmittance, and using a lookup table to map grey levels to corresponding voltages, ensuring consistent brightness across the panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If color filters are used for color display in LCD panels, then color display capability is improved, but manufacturing cost increases and light transmission is reduced
Solution Approach 1:
The patent removes the color filter layer from the LCD panel structure, extracting the problematic component that caused both reduced light transmission and increased manufacturing cost. Instead of using color filters, the invention employs a color sequential display method with a color conversion layer that converts blue backlight light into red and green wavelengths, eliminating the need for traditional color filters while maintaining color display capability.
2Measurement precision
If color sequential display is used to increase resolution, then resolution is improved three times, but response time requirement becomes much shorter (less than 5.56 ms)
Solution Approach 1:
The patent changes the operational parameters of the liquid crystal molecules by introducing a color conversion layer that modifies the light wavelength. This allows the liquid crystals to operate at lower frequencies (60 Hz refresh rate) compared to traditional color sequential displays that require much higher frequencies, thereby reducing the response time requirement while maintaining the resolution benefits of color sequential display.
3Productivity
If liquid crystals are driven sequentially across different gate lines, then gate scanning is completed, but non-uniform brightness occurs due to varying response times across different areas
Solution Approach 1:
The patent applies preliminary action by pre-compensating for the brightness non-uniformity through gamma correction. Before displaying the actual image, the system performs gamma correction processing that adjusts the voltage levels for different gate lines based on their specific response characteristics. This preliminary adjustment ensures that all areas of the display panel achieve uniform brightness despite the sequential scanning process and varying liquid crystal response times.
Solution Approach 2:
The patent implements local quality by applying different gamma correction parameters to different gate line groups. Instead of using a single uniform correction for the entire display, the system divides the panel into multiple groups (e.g., odd and even gate lines) and applies area-specific correction factors. This localized approach accounts for the varying response times of liquid crystals in different regions, ensuring uniform brightness across the entire display while maintaining efficient sequential scanning.
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 approach ensures uniform brightness across the LCD panel by optimizing grey level voltages based on the voltage-transmittance functions and desired gamma curves, addressing the issue of non-uniformity caused by differing response times and scanning times.
Implementation Method 1
align states of the liquid crystals to control light transmission through the pixels
Implementation Method 2
a backlight unit capable of emitting, for example, red light 822, green light 824 and blue light 826
Data Source
AI summary
A method of gamma correction for a liquid crystal display (LCD) having an LCD panel. In one embodiment, the method includes the steps of dividing the LCD panel into N areas along a gate scanning direction, each area having a corresponding gamma and being characterized with a corresponding voltage-transmittance function, and determining grey level voltages of each area for each of a set of grey levels from the corresponding voltage-transmittance function of the area and a desired gamma curve of the LCD panel such that when the grey level voltages are respectively applied to the N areas for a grey level, a light transmittance through each area is substantially uniform and equals to a corresponding brightness.