Scanning Projector Uniformity Correction for Nonlinear MEMS Scans
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Solution Overview
Problem
Non-linear scanning trajectories in head-mounted display (HMD) projectors using multi-ridge light sources cause image artifacts such as splitting, shearing, banding, and distortion, especially when the viewer's eyes move, due to Lissajous biresonant scanning, which affects image quality and user experience.
Innovation Solution
Implementing static uniformity correction through computational determination of correction factors for pulse events during one frame time, using both analytical and optimization approaches, to optimize color-wise luminance and reduce static non-uniformity effects in non-linear scanning projectors with multi-ridge light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-linear Lissajous biresonant scanning is used to achieve fast scanning rates and compact HMD design, then productivity and device compactness are improved, but image quality deteriorates due to artifacts such as splitting, shearing, banding, and distortion
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction factors in lookup tables before the actual scanning process. The system determines correction factors for each pixel based on the non-linear scanning trajectory, then applies these corrections in advance to the image data before display, thereby compensating for expected distortion artifacts without affecting the fast scanning rate
Solution Approach 2:
The patent changes parameters by introducing correction factors that modify the luminance and color values of pixels based on their position in the non-linear scanning trajectory. The system adjusts display parameters (brightness, color intensity) dynamically according to the scanning position to compensate for artifacts, transforming the fixed scanning pattern into a corrected display output
2Productivity
If multi-ridge light sources are used to enhance display resolution and field of view, then productivity is improved, but image uniformity deteriorates due to static non-uniformity effects and brightness variation
Solution Approach 1:
The patent applies local quality by assigning different correction factors to different regions of the display corresponding to different ridges. Each ridge or region receives customized correction values based on its specific non-uniformity characteristics, allowing localized compensation for brightness variation and color inconsistency across the multi-ridge light source output
Solution Approach 2:
The patent implements feedback by measuring the actual non-uniformity characteristics of the multi-ridge light source and using this information to generate correction factors. The system continuously references these correction factors during operation to maintain uniform image quality, creating a closed-loop correction mechanism that compensates for inherent light source variations
Data Source
AI summary
Static non-uniformity effects in a coherent biresonant scanning projector are mitigated through correction factors for pulse events during one frame time. According to an analytical approach, a set of input parameters such as scan angle, micro-electromechanical system (MEMS) obliquity, ridge spacing, etc. are used to optimize color-wise luminance uniformity. According to an optimization approach, pulse correction factors are determined using a custom-defined cost function that attempts to optimize for both luminance and color uniformity.