TIR Prism Assembly for DMD Projector Resolution
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Solution Overview
Problem
Existing projection display systems using multi-element prism assemblies for total internal reflection (TIR) face increased build cost and complexity, and introduce multiple air-gaps that degrade image resolution.
Innovation Solution
A compact, low-cost, and lower-complexity optical design using a 2-piece compound TIR prism assembly with congruent sub-prisms, where the input and output sub-prisms share common face angles and materials, minimizing air gaps and optical distortions, and employing selectively adjustable reflecting elements to control light projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-element prism assemblies are employed to direct light via total internal reflection, then light direction control is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The optical system is segmented into distinct functional components: a beam splitter prism and a TIR (total internal reflection) prism assembly. The TIR prism assembly is further segmented into multiple TIR prisms arranged in a specific configuration. This segmentation allows each component to perform its specific function optimally while maintaining overall system adaptability for light direction control.
Solution Approach 2:
Multiple TIR prisms are merged into a single integrated TIR prism assembly that works in conjunction with the beam splitter prism. The prisms are combined such that they share common optical paths and interfaces, reducing the number of separate adjustments needed while maintaining versatile light direction control capabilities.
2Adaptability or versatility
If multi-element prism assemblies are employed to direct light, then light path control is improved, but manufacturing cost increases
Solution Approach 1:
The TIR prisms are constructed from homogeneous optical material with consistent refractive index throughout. The prisms share common face angles and interface geometries, allowing for standardized manufacturing processes. This homogeneity enables批量 production (batch production) and reduces per-unit manufacturing cost while maintaining precise light path control.
Solution Approach 2:
The TIR prism assembly is designed as a universal component that can be used with different beam splitter prism configurations. The standardized interface and geometry of the TIR prisms allow them to serve multiple functions: directing light at various angles, creating multiple virtual images, and working with different display panel types. This multi-functionality reduces the need for custom-designed prism assemblies for each application.
3Ease of operation
If multiple air-gaps are introduced in the light path, then optical component separation is improved, but image resolution degrades
Solution Approach 1:
Optical adhesive or index-matching material is used as an intermediary substance between the optical components (beam splitter prism and TIR prisms). This intermediary eliminates air-gaps by filling the interfaces between prisms, ensuring continuous optical paths. The adhesive material has refractive index matched to the optical components, minimizing reflection and maintaining high image resolution while still allowing for mechanical separation of components for assembly and maintenance.
4Adaptability or versatility
If non-congruent sub-prisms are used in the prism assembly, then design flexibility is improved, but optical path equalization becomes difficult
Solution Approach 1:
The beam splitter prism is designed with asymmetric geometry to direct light at specific angles to the TIR prisms. However, the TIR prisms themselves are designed with symmetric, congruent geometries relative to each other. This asymmetric-symmetric hybrid approach provides design flexibility for light routing while ensuring that optical paths through different TIR prisms are equalized, maintaining image quality and resolution.
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
This design reduces manufacturing costs and complexity while maintaining image quality by equalizing optical paths and minimizing air gaps, thereby enhancing the resolution and efficiency of light projection.
Implementation Method 1
an illumination light from an illumination source, by total internal reflection from the first interface surface
Implementation Method 2
receive display light transmitted through the first interface surface
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
A projection apparatus comprising a prism assembly (7) including an input sub- prism (1) possessing a first interface surface and an output sub-prism (2) adjacent to the input sub-prism possessing a second interface surface. The second interface surface is spaced from the first interface surface immediately proximate to it and extends over it to receive display light (12) transmitted through the first interface surface. A panel (8) comprising a plurality of selectively adjustable reflecting elements is arranged to receive from the input sub-prism an illumination light totally internally reflected from the first interface surface and selectively to reflect received illumination light back through the input sub-prism for transmission through the first interface surface for receipt as display light (13) by the output prism at said second interface surface.