Light Combining System Using Prism Air-Gaps to Reduce Scatter
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Solution Overview
Problem
Current projection systems face challenges in achieving high contrast ratios due to light scatter caused by prisms' internal illumination, off-state light paths, and total internal reflection, which are exacerbated by the need for thin, optically flat dichroic plates to avoid optical aberrations.
Innovation Solution
A light combining system comprising prisms with strategically positioned mirrors and carefully chosen shapes and back working distances to align and transmit on-state light without internal reflection, using air-gaps and spacers to maintain distances and reduce interference between illumination and reflection paths, and employing antireflective coatings to minimize scatter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If prisms with internal illumination and TIR surfaces are used to combine light, then light combination is achieved, but light scatter increases and contrast ratio decreases
Solution Approach 1:
The patent extracts the harmful TIR surfaces and internal illumination paths from the prism structure by introducing air-gaps between separate prisms. This separates the light combination function from the problematic internal reflection surfaces, eliminating light scatter while maintaining the ability to combine multiple light paths.
Solution Approach 2:
The patent introduces air-gaps as intermediary spaces between prisms, which act as mediators to prevent direct contact between optical surfaces. This intermediary layer eliminates unwanted internal reflections and light scatter while allowing the prisms to maintain their light combination function through controlled interfaces.
2Object-affected harmful factors
If dichroic plates are used to combine light, then light scatter is reduced, but the plates must be very thin and optically flat which increases manufacturing complexity
Solution Approach 1:
The patent merges the advantages of multiple components into a single prism assembly with air-gaps. Instead of requiring thin, precision-dichroic plates, the system combines multiple prisms with controlled air-gap interfaces, achieving low light scatter through geometric design rather than material properties, thereby reducing manufacturing precision requirements.
Solution Approach 2:
The patent changes the fundamental parameter from using thin, optically flat dichroic plates to using prisms with air-gaps. This parameter change transforms the solution from requiring extreme manufacturing precision (thin plate flatness) to a more manufacturable approach using standard prism fabrication with controlled spacing.
3Ease of manufacture
If prisms are used with internal illumination paths, then light combination is achieved, but illumination and reflection paths interfere with each other
Solution Approach 1:
The patent segments the single-prism internal illumination structure into multiple separate prisms with air-gaps between them. This segmentation separates the illumination paths and reflection paths into distinct spatial zones, preventing interference while maintaining the overall light combination function through the coordinated arrangement of segmented components.
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
The system effectively reduces light scatter and optical aberrations, allowing for higher contrast ratios and more efficient light combination without the need for complex dichroic plates, resulting in improved image projection quality.
Implementation Method 1
each of respective angles formed by a normal of the mirror and each of the first on-state light and the second on-state light being less than a total internal reflection angle
Implementation Method 2
Faces of the first prism and the second prism through which the first on-state light and the second on-state light travel through, other than the at least one interface, can be coated with respective antireflective coatings
Data Source
AI summary
A light combining system is provided comprising: prisms comprising respective entrance faces enabled to receive respective on-state light from respective digital-micro-mirror devices (DMD). At least one interface between prisms is enabled to receive respective on-state light from the prisms. A mirror at the at least one interface is enabled to transmit first on-state light from a first prism through a second prism and reflect second on-state light from the second prism in alignment with the first on-state light back through the second prism. Respective angles formed by a normal of the mirror and each of the first on-state light and the second on-state light is less than a total internal reflection angle. A combination of respective back working distances of the DMDs and shapes of each of the prisms is chosen such that respective illumination paths and respective reflection paths of each of DMDs do not interfere with each other.