Dual-Modulation Projection With Multi-Halftone Frames for Low-Light Contrast
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dual modulation projectors face challenges with reduced contrast ratio at low light levels due to small tile sizes and sub-optimal point spread functions (PSFs) in the relay optics, leading to halo artifacts and reduced local contrast.
Innovation Solution
Implementing multiple halftones per frame in the pre-modulator synchronized with a modified bit sequence in the primary modulator, along with pre-compensation for relay optics PSF imperfections, to enhance contrast and reduce artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If small tile sizes are used in the pre-modulator, then the projector can achieve higher resolution and reduced artifact size, but the contrast ratio deteriorates at low light levels
Solution Approach 1:
The patent divides the frame into multiple subframes, with each subframe containing a different halftone image. This segmentation allows the system to use smaller tile sizes for higher resolution while maintaining adequate contrast ratio by distributing the halftoning across multiple temporal segments rather than requiring high contrast in a single frame
Solution Approach 2:
The patent employs periodic switching between multiple halftone images across successive subframes. By cycling through different halftone patterns (e.g., first halftone image in odd subframes, second halftone image in even subframes), the system maintains temporal averaging that preserves contrast ratio while using small tile sizes for high resolution display
2Object-generated harmful factors
If small PSF sizes are used in the relay optics, then the projector can reduce halo artifacts, but the contrast ratio deteriorates at low light levels
Solution Approach 1:
The patent segments the halftoning process into multiple subframes with different halftone images, allowing small PSF sizes to be used for reducing halo artifacts while maintaining contrast ratio through temporal integration of multiple halftone patterns across the subframe sequence
Solution Approach 2:
The patent changes the halftone parameter (different halftone images) across successive subframes while maintaining small PSF sizes. This parameter variation allows the system to benefit from reduced halo artifacts with small PSFs while the temporal averaging across subframes preserves the contrast ratio
3Manufacturing precision
If multiple halftones per frame are implemented, then the number of effective levels increases for a given tile size, but the device complexity increases
Solution Approach 1:
The patent segments the multiple halftone images into different subframes rather than attempting to display multiple halftones simultaneously. This temporal segmentation allows the system to achieve increased effective levels through the combination of multiple halftone patterns across time, while the modulator itself maintains simple binary or multi-level operation within each subframe
Solution Approach 2:
The patent employs periodic switching between different halftone images across subframes to achieve increased effective levels. By cycling through different halftone patterns in a periodic manner, the system effectively multiplies the number of displayable levels without requiring the modulator to simultaneously handle complex multi-halftone patterns, thus managing device complexity
Data Source
AI summary
Smaller halftone tiles are implemented on a first modulator of a dual modulation projection system. This techniques uses multiple halftones per frame in the pre-modulator synchronized with a modified bit sequence in the primary modulator to effectively increase the number of levels provided by a given tile size in the halftone modulator. It addresses the issue of reduced contrast ratio at low light levels for small tile sizes and allows the use of smaller PSFs which reduce halo artifacts in the projected image and may be utilized in 3D projecting and viewing.