Local Dimming Backlight Luminance Calculation via Subframe Processing
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Solution Overview
Problem
Existing liquid crystal display (LCD) devices face challenges in achieving high contrast due to black floating caused by light leakage from backlights, particularly when increasing the number of division areas in local dimming techniques, which leads to increased calculation complexity and processing delays.
Innovation Solution
A display device with a variable emission luminance backlight system, where the emission luminance of each division area is calculated and controlled based on input image data, and the process of calculating correction values is divided into partial processes across multiple subframe periods to reduce computational load and prevent processing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the number of division areas of the backlight module is increased to reduce black floating and improve contrast, then the contrast is improved, but the amount of calculation of backlight luminance and image correction significantly increases, causing processing delay and increased circuit scale
Solution Approach 1:
The patent divides the backlight module into multiple division areas (e.g., 106 division areas in a 4K UHD display) to enable local dimming control. By segmenting the backlight into independently controllable regions, the system can reduce luminance in specific areas to minimize black floating while maintaining overall image quality and contrast performance.
Solution Approach 2:
The patent pre-calculates and stores luminance distribution data and correction values in lookup tables (LUTs) before actual image processing. This preliminary action allows the system to quickly retrieve and apply correction values during operation without performing complex real-time calculations, thereby reducing processing delay even when using a large number of division areas.
2Illumination intensity
If the number of division areas of the backlight module is increased to reduce black floating and improve contrast, then the contrast is improved, but the circuit scale increases due to increased calculation requirements
Solution Approach 1:
The patent pre-calculates correction values for each division area and stores them in lookup tables during a preprocessing stage. This eliminates the need for complex real-time product-sum operations during actual image correction, significantly reducing the computational burden and circuit scale required for processing high-resolution images with numerous division areas.
Solution Approach 2:
The patent uses lookup tables to store pre-calculated correction values that can be quickly copied and applied to corresponding pixels during image processing. This copying approach replaces complex mathematical operations with simple data retrieval and application, reducing circuit complexity while maintaining correction accuracy for high-precision local dimming.
3Measurement precision
If product-sum operation is performed for each estimation point to calculate backlight luminance, then the calculation accuracy is improved, but the amount of calculation and processing time significantly increases
Solution Approach 1:
The patent performs product-sum operations to calculate luminance distribution and correction values in advance, storing the results in lookup tables. This preliminary calculation maintains measurement precision for backlight luminance while enabling fast retrieval during actual processing, thus resolving the contradiction between calculation accuracy and processing speed.
Data Source
AI summary
A display device includes a backlight consisting of a plurality of division areas and a display panel. Emission luminance for each division area is calculated based on input image data, a correction value for correcting the input image data is calculated based on the emission luminance, the input image data is corrected based on the calculated correction value, the transmittance of the display panel is controlled based on the corrected image data, and light emission of each division area is controlled based on the calculated emission luminance. One frame period of the input image consists of a plurality of subframe periods, and a process of calculating the correction value for correcting the input image data based on the emission luminance is divided into a plurality of partial processes, which are sequentially performed by executing each partial process in each subframe period.