High Field Rate Display Two-Stage Reprojection for Latency and Color Artifacts
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Solution Overview
Problem
High field rate displays, such as field sequential color (FSC) displays, suffer from motion-to-photon latency and color separation artifacts due to the high computational demands of reprojection, which are typically limited by resource constraints in head-mounted displays (HMDs), leading to inconsistent image rendering and user discomfort.
Innovation Solution
A two-stage reprojection method is employed, where an early stage reprojection runs at a lower frequency using more computational resources to correct large pose errors, followed by a late stage reprojection at the field rate to minimize residual latency and artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reprojection is applied at high field rate to reduce motion-to-photon latency, then image consistency and user comfort improve, but computational resource demands exceed available resources in HMDs
Solution Approach 1:
The reprojection process is divided into two distinct stages: an early stage reprojection that operates at a lower frame rate using more computational resources to correct large pose errors, and a late stage reprojection that operates at the full field rate using optimized algorithms to minimize residual latency. This segmentation allows the system to distribute computational load across different time scales and resource requirements.
Solution Approach 2:
The early stage reprojection performs preliminary corrections on rendered frames before they are displayed at the high field rate. By pre-processing frames at a lower rate with more computational resources available, the system prepares corrected image data in advance, reducing the computational burden on the late stage reprojection that must operate at the full field rate.
2Measurement precision
If early stage reprojection uses more computational resources to correct large pose errors, then accuracy of pose correction improves, but resource constraints in HMDs are exceeded
Solution Approach 1:
The reprojection workload is segmented into two stages with different computational requirements. The early stage handles the computationally intensive task of correcting large pose errors at a lower frame rate, while the late stage handles smaller corrections at the full field rate. This segmentation allows the system to match computational resource usage with the actual needs of each processing stage.
Solution Approach 2:
The system changes the operating parameters of reprojection based on the stage of processing. Early stage reprojection operates at a lower frame rate with higher computational resources allocated per frame, while late stage reprojection operates at the full field rate with optimized computational efficiency. This parameter adaptation allows the system to maintain accuracy while managing resource consumption.
3Reliability
If field rate is increased to reduce motion-to-photon latency, then user comfort improves, but color separation artifacts increase due to temporal integration issues
Solution Approach 1:
The early stage reprojection performs preliminary corrections to the rendered frames before they are displayed at the high field rate. By pre-processing the frames to account for predicted head pose movements, the system reduces the magnitude of pose changes between fields, thereby minimizing the color separation artifacts that would otherwise occur during temporal integration in the human visual system.
Data Source
AI summary
In various examples there is a method performed by a Head Mounted Display, HMD, comprising a high field rate display configured to display fields of rendered frames at a field rate. The method comprises receiving a stream of the rendered frames for display on the high field rate display, the stream of rendered frames having a frame rate. The process applies an early stage reprojection to the rendered frames of the stream of rendered frames at a rate which is lower than the field rate. The process applies a late stage reprojection to fields of the rendered frames at the field rate, wherein the early stage reprojection uses more computational resources than the late reprojection.