Partial Frame Buffer Overdrive Correction for LCDs
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Solution Overview
Problem
Conventional overdrive correction (ODC) schemes for liquid crystal display devices require significant processing, large frame buffers, and look-up tables, leading to increased silicon area and cost, and are complex to implement, especially for grey level transitions near the extremes of the liquid crystal transmission curve.
Innovation Solution
An active matrix liquid crystal display device with a column driver circuit that uses a resistive digital-to-analog converter (R-DAC) and a partial frame buffer RAM to apply ODC drive voltages based on a consistent starting point, eliminating the need for a two-dimensional matrix look-up table and reducing the size of frame buffers, while allowing for local conversion of video data to include black frames without a full frame store.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ODC schemes are used with frame buffers and look-up tables to calculate correction for each pixel, then overdrive correction accuracy is improved, but device complexity and silicon area increase
Solution Approach 1:
The patent extracts and eliminates the complex two-dimensional look-up table structure from conventional ODC schemes. Instead of using a full frame buffer with voltage pair matrices, the invention uses a simplified partial frame buffer that only stores current frame data, reducing the data structure complexity while maintaining correction accuracy through a different processing approach.
Solution Approach 2:
The patent segments the frame buffer into a partial frame buffer that stores only the current frame's voltage data rather than the complete previous frame data. This segmentation reduces the memory requirements and processing complexity while still enabling accurate overdrive correction by processing voltage pairs in a simplified manner.
2Measurement precision
If conventional ODC schemes with full frame buffers are used to determine voltage pairs, then overdrive correction accuracy is improved, but frame buffer size and cost increase
Solution Approach 1:
The patent removes the requirement for a full frame buffer by extracting only the essential current frame voltage data needed for ODC calculations. The partial frame buffer stores minimal data structures that suffice for processing voltage pairs, eliminating the need for large memory allocations while maintaining correction precision.
Solution Approach 2:
The patent applies partial action by using a partial frame buffer that stores only the necessary current frame data rather than the complete previous frame data. This partial data storage is sufficient for ODC calculations when combined with the simplified processing approach, avoiding the excessive memory requirements of conventional full frame buffers.
3Adaptability or versatility
If additional buffers and selector matrix complexity are added for grey level transitions near extremes, then ODC capability for extreme transitions is improved, but device complexity and cost increase
Solution Approach 1:
The patent handles extreme transitions by changing the drive voltage parameters dynamically based on the current voltage pair and pixel state. Instead of adding complex selector matrices, the system adjusts voltage levels and timing parameters to achieve accurate transitions near the extremes of the liquid crystal transmission curve using the simplified partial frame buffer approach.
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 reduces the processing requirements and memory needs for ODC schemes, enabling efficient overdrive correction and black insertion for improved image clarity without increasing the complexity or cost of the display device, while maintaining the conventional video data format at the display interface.
Implementation Method 1
The level of a data voltage applied to a pixel determines how much light is output by that pixel by controlling the extent of the optical modulation effect of the liquid crystal layer in the pixel
Implementation Method 2
An active matrix liquid crystal display device with a column driver circuit that uses a resistive digital-to-analog converter (R-DAC)
Data Source
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AI summary
An active matrix display device comprises a plurality of pixels, and driving circuitry arranged to drive each pixel with a pre-determined drive voltage level during a first phase (41 ) followed by an overdrive drive voltage level during a second phase (44). A partial frame store is for storing a fraction of the pixel data for the display. Input video data is written into the partial frame store (40) at a first rate and is read out of the partial frame store at a second rate which is greater than the first rate. The data read out of the partial frame store is processed for deriving the overdrive drive voltage level.