Multiple Driver LCD Backlight for VR Latency Reduction
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Solution Overview
Problem
Liquid Crystal Displays (LCDs) in virtual reality, mixed reality, or augmented reality systems face challenges in achieving a short duty cycle and short illumination times due to slow liquid crystal switching times, which limit their speed and cause image streaking and latency issues.
Innovation Solution
The implementation of a display device with a liquid crystal (LC) panel, a backlight unit (BLU), and multiple data drivers that write data during a write portion of the frame period when the BLU is not emitting light, allowing the LC material to complete transition before illumination, and using modes like global illumination, black insertion, or hybrid modes to optimize frame cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid crystal displays use traditional single data driver and continuous backlight illumination, then the display can maintain stable image output, but the liquid crystal switching time is too slow causing image streaking and latency issues in virtual reality applications
Solution Approach 1:
The patent divides the display panel into multiple zones (first portion and second portion) that are driven by separate data drivers. This segmentation allows different regions to be updated independently and simultaneously, effectively doubling the data writing throughput and reducing the overall frame update time, which directly addresses the slow liquid crystal switching speed issue.
Solution Approach 2:
The patent implements periodic backlight illumination where the backlight unit alternates between emitting light and not emitting light during the frame period. By synchronizing the backlight OFF periods with the data writing periods, the system can perform liquid crystal switching without illumination interference, then illuminate only after switching is complete, thereby eliminating image streaking while maintaining high switching speed.
2Illumination intensity
If the backlight unit illuminates continuously, then the display maintains consistent brightness, but the liquid crystal material cannot complete its transition before illumination causing image quality degradation
Solution Approach 1:
The backlight unit operates in periodic cycles, turning OFF during data writing and liquid crystal transition periods, then turning ON only after the liquid crystal material has completed its transition. This periodic illumination strategy ensures that brightness is maintained during display while allowing complete liquid crystal switching to occur without illumination interference, preventing image quality degradation.
Solution Approach 2:
The system performs liquid crystal switching actions before initiating backlight illumination. By completing the liquid crystal transition in advance during the backlight OFF period, the system ensures that the liquid crystal material is fully switched before light is emitted, guaranteeing accurate image display without partial transition artifacts.
3Device complexity
If a single data driver writes data to the entire pixel array sequentially, then the system structure remains simple, but the data writing time exceeds the available frame period causing incomplete updates
Solution Approach 1:
The patent segments the pixel array into distinct portions (first and second portions) and assigns separate data drivers to each portion. This allows parallel data writing operations where both drivers write simultaneously to their respective portions, effectively doubling the data writing throughput and completing the entire frame update within the available time period.
Solution Approach 2:
The patent combines multiple data drivers operating in parallel to achieve higher overall productivity. By merging the capabilities of multiple drivers working simultaneously on different portions of the display, the system achieves data writing speeds that would be impossible with a single driver, while maintaining manageable individual driver complexity.
4Manufacturing precision
If the frame period is extended to allow complete liquid crystal transition, then image quality improves, but the illumination time increases causing increased power consumption and reduced refresh rate
Solution Approach 1:
The backlight operates periodically, illuminating only during specific windows when liquid crystal transitions are complete. This allows the system to use shorter illumination durations while ensuring complete transitions occur during the non-illumination periods, thereby reducing overall power consumption while maintaining image quality and enabling higher refresh rates.
Solution Approach 2:
The system maintains continuous operation by overlapping the data writing and liquid crystal transition actions with the backlight OFF periods. This continuous utilization of the non-illumination time for productive switching operations ensures that no time is wasted, allowing complete transitions to occur within the frame period without extending the illumination duration.
Data Source
AI summary
A display device that includes a liquid crystal (LC) panel, a back light unit (BLU), a first data driver, and a second data driver. The back light unit (BLU) emits light during an illumination portion of a frame period and does not emit light during a remaining portion of the frame period. A first data driver writes data to a first portion of the pixels of the LC panel. A second data driver writes data to a second portion of the pixels of the LC panel. The first and second data drivers write data at an overlapping time during a write portion of the frame period. The write portion overlaps in time with the remaining portion of the frame period during which the BLU does not emit light.