Backlight Periodic Illumination for VR LCD Latency Reduction
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Solution Overview
Problem
Liquid Crystal Displays (LCDs) face limitations in response time and frame rate due to slow liquid crystal state changes and continuous backlight projection, leading to latency and motion blur in virtual and augmented reality applications.
Innovation Solution
Implementing a liquid crystal display with a backlight unit that projects light only during an illumination time period of the frame time, and not during a non-illumination time period, allowing for sequential liquid crystal state changes and simultaneous illumination of pixels, with a controller managing the liquid crystal control signals and backlight control signals to optimize data scan out and illumination times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the backlight unit continuously projects light towards the liquid crystal layer, then the LCD maintains stable illumination, but motion blur and image streaking occur when images are displayed with fast frame rates
Solution Approach 1:
The backlight unit operates in periodic cycles, switching between ON and OFF states. During the ON period, light is projected towards the liquid crystal layer; during the OFF period, no light is projected. This periodic operation synchronizes with the liquid crystal state changes and frame display timing, ensuring that illumination only occurs when the liquid crystal states are stable, thereby eliminating motion blur and image streaking while maintaining stable illumination during active display periods.
2Productivity
If the liquid crystal layer changes states continuously to update images, then the display follows user movement in real-time, but the response time remains slow (several milliseconds) causing latency
Solution Approach 1:
The liquid crystal control signals are applied during the backlight OFF period, preparing the liquid crystal states in advance before the backlight turns ON. This preliminary action allows the liquid crystal molecules to complete their reorientation before illumination begins, ensuring that the display state is ready for immediate presentation without waiting for the liquid crystal response during the illumination period, thereby reducing perceived latency.
Solution Approach 2:
The frame time is segmented into distinct periods: an OFF period for liquid crystal state changes and a ON period for illumination and display. By dividing the frame time into these functional segments, the system can perform liquid crystal updates without interfering with the illumination process, effectively separating the state change function from the display function to achieve faster overall response.
3Duration of action of stationary object
If the backlight unit projects light during the entire frame time, then continuous illumination is maintained, but latency increases due to the slow response time of liquid crystal state changes
Solution Approach 1:
The backlight unit operates periodically rather than continuously, with illumination duration limited to the display period when liquid crystal states are stable. The backlight remains OFF during the liquid crystal state change period, preventing illumination of transitioning states that would cause blur. This periodic operation reduces the total illumination duration while eliminating latency caused by illuminating during state transitions.
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 latency and image streaking, enabling high-quality image presentation in VR/AR systems without noticeable lag, with improved response time and reduced motion blur.
Implementation Method 1
the LC layer including a plurality of LCs controls an amount of the light passing through according to states of the plurality of LCs
Implementation Method 2
The backlight unit is configured to project light towards the entire pixel area of the liquid crystal layer during an illumination time period of a frame time
Data Source
AI summary
Disclosed is a liquid crystal display device comprising a liquid crystal layer including a plurality of liquid crystals in a pixel area and a backlight unit coupled to the liquid crystal layer. A plurality of pixels are disposed in the pixel area. The backlight unit is configured to project light towards the entire pixel area of the liquid crystal layer during an illumination time period of a frame time, and not to project the light towards any of the pixel area of the liquid crystal layer during a non-illumination time period of the frame time. By enabling the backlight unit for the illumination time period less than the frame time, image streaking and latency can be reduced.