TIR Prism Optical Path Compensation for Touch Projection
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Solution Overview
Problem
In touch projection systems, the total internal reflection (TIR) prism causes optical path differences in image light, leading to distortion of touch images and incorrect determination of user interactions due to varying optical distances as the light travels through the prism.
Innovation Solution
Incorporating an optical path compensation structure or a hollowed channel within the TIR prism to ensure equivalent optical distances for image light, eliminating distortion and ensuring accurate touch image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a TIR prism is used to reflect projection light to the micromirror device, then the projection system can achieve compact optical path folding, but the image light experiences varying optical distances through the prism causing touch image distortion
Solution Approach 1:
An optical path compensation structure is introduced as an intermediary element within the TIR prism. This compensation structure specifically addresses the optical path difference caused by the prism's geometry, mediating between the prism's light-folding function and the touch image accuracy requirement by extending the optical path for rays entering at different positions.
2Ease of manufacture
If the TIR prism has a standard solid structure, then the device is simple to manufacture, but the optical path difference causes distortion in the touch image
Solution Approach 1:
The TIR prism is designed with non-uniform local quality through the optical path compensation structure. Instead of a uniform solid structure, specific regions are modified (e.g., hollowed channels or varying refractive index zones) to create localized optical path extensions that compensate for position-dependent optical differences while maintaining overall structural simplicity.
3Manufacturing precision
If the optical path compensation structure is added to the TIR prism, then the touch image distortion is eliminated, but the device complexity increases
Solution Approach 1:
The optical path compensation structure is merged with the TIR prism as an integrated component rather than a separate assembly. The compensation features (hollowed channels or refractive index variations) are incorporated directly into the prism's internal structure, combining the light reflection function and optical path compensation function into a single unified element.
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 solution effectively eliminates image light distortion, allowing for precise determination of touch operations on the screen without errors, enhancing the accuracy of user interactions.
Implementation Method 1
a total internal reflection (TIR) prism is disposed in front of the DMD. Projection light produced by a light source device is reflected by the TIR prism to the micromirror device
Implementation Method 2
The micromirror device is used for reflecting the projection light and the image light
Data Source
AI summary
A touch projection system includes a screen, an image-capturing device, a micromirror device, and a TIR prism disposed in front of the micromirror device. The TIR prism includes an optical path compensation structure or a hollowed channel, so that an image light from the screen, traveling through the TIR prism to be reflected by the micromirror device, can travel through the optical path compensation structure or the hollowed channel to avoid a probable optical path difference on the image light due to traveling through the TIR prism. Thereby, the invention can solve that a distortion may be induced in a touch image formed by the image-capturing device receiving the image light reflected by the micromirror device.