Display Grey Level Resolution via Temporal Averaging
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Solution Overview
Problem
Conventional displays, especially mobile displays, face challenges in achieving a large dynamic range and high contrast ratio due to limited grey level resolution and high manufacturing costs, which affects their ability to accurately render images with advanced camera capabilities in various luminous environments.
Innovation Solution
A method that calculates and provides grey levels for each field of a frame by varying the amplitude or subfield composition of a display driving signal and the fluence of simultaneously lit backlight sources for selected primary colors, allowing for a larger grey dynamic range without increasing the number of addressable grey levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of DACs is increased to provide more addressable grey levels, then the grey level resolution is improved, but the cost and power consumption increase
Solution Approach 1:
The patent applies temporal averaging by displaying multiple frames with different grey level combinations that average to the desired grey level. Instead of using a high-resolution DAC, the system uses a low-resolution DAC to display sequences of frames (e.g., alternating between two grey levels) that the human eye perceives as a intermediate grey level due to temporal integration. This periodic switching enables effective grey level resolution beyond the physical DAC capability while avoiding the power penalty of high-resolution DACs.
Solution Approach 2:
The system dynamically adjusts the display parameters by varying the duration and intensity of different grey level displays across multiple frames. The temporal averaging process is controlled dynamically based on the desired output grey level, allowing the system to adaptively achieve any grey level within the dynamic range using only low-resolution DAC outputs.
2Loss of information
If frame rate control is used to extend color depth to 24 bpp, then the color depth is improved, but the moving image quality deteriorates due to lowered refresh rate
Solution Approach 1:
The patent uses periodic frame sequences where multiple frames are displayed in rapid succession with different grey level assignments. The temporal averaging occurs within a short time window that maintains the perceived refresh rate, preventing motion artifacts while achieving extended color depth. The periodic nature of the frame sequence ensures that temporal averaging does not create visible flicker or reduce effective refresh rate for moving images.
3Illumination intensity
If transmissive or emissive displays are used to achieve outdoor readability, then the luminance is improved, but the power consumption increases due to high-power backlight
Solution Approach 1:
The patent implements temporal averaging with multiple frames displayed in sequence, where some frames use higher luminance and others use lower luminance. The human visual system integrates these alternating luminance levels over time, perceiving an intermediate luminance that provides adequate outdoor readability. This approach achieves the required luminance level without continuously operating the backlight at maximum power, thereby reducing overall power consumption.
Data Source
AI summary
The specification and drawings present a new method, apparatus and software product for increasing a grey dynamic range of a display for displaying video data by providing a grey level, calculated for a reduced number of primary colors using a predetermined criterion, for each field of a frame set by the display by varying an amplitude or a subfield composition of a display driving signal and by varying a fluence of simultaneously lit backlight sources (e.g., LEDs) corresponding to selected two or more primary colors of the display. Thus, grey level resolution of the display can be increased to match the higher grey level resolution of the video data provided to the display.