Projection Screen with Microlens and TIR Layer for Ambient Light Rejection
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Solution Overview
Problem
Current projection screens suffer from low light energy utilization efficiency due to ambient light interference, resulting in reduced image contrast and quality, especially in household settings with strong ambient lighting.
Innovation Solution
A projection screen design featuring a microlens layer, a total internal reflection layer with sawtooth microstructure units, and a light absorbing layer, where the microlens layer converges light onto the total internal reflection layer for efficient reflection and the light absorbing layer minimizes ambient light impact, improving light energy utilization and contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a total internal reflection layer with microstructure units is used to distinguish projection light from ambient light, then image contrast is improved, but light energy utilization efficiency decreases
Solution Approach 1:
The screen is divided into multiple functional layers: a microlens layer for light convergence, a transparent substrate layer, a total internal reflection layer with microstructure units for angle-selective reflection, and a light absorbing layer. This segmentation allows each layer to perform its specific function optimally, with the microlens layer pre-converging light to increase the proportion of light rays that can undergo total internal reflection.
Solution Approach 2:
The microlens layer performs preliminary convergence of incident light rays before they reach the total internal reflection layer. By pre-converging the light, the system increases the likelihood that projection light rays will meet the angle requirements for total internal reflection, thereby improving overall light utilization efficiency before the light even reaches the reflection layer.
2Object-affected harmful factors
If a light absorbing layer is added to eliminate ambient light, then image contrast improves, but the overall light transmission and brightness may be reduced
Solution Approach 1:
The light absorbing layer is positioned at the bottom of the screen structure, creating a localized absorption function. This allows the upper layers (microlens layer, transparent substrate layer, and total internal reflection layer) to primarily handle projection light convergence and reflection, while the light absorbing layer specifically targets ambient light that penetrates through these layers, minimizing its impact on overall brightness.
Solution Approach 2:
The light absorbing layer converts the harmful effect of ambient light penetration into a beneficial contrast enhancement. By selectively absorbing ambient light that passes through the other layers, it prevents ambient light from reaching the viewer's eyes, thereby improving image contrast without significantly affecting the brightness of the projected image which is reflected by the total internal reflection layer.
3Object-affected harmful factors
If multiple layers are stacked to improve contrast, then ambient light rejection improves, but device complexity increases
Solution Approach 1:
The total internal reflection layer serves multiple functions: it reflects projection light rays that meet the angle criteria, allows transmission of light rays that don't meet the criteria to the light absorbing layer, and maintains overall structural transparency. This multi-functionality reduces the need for additional separate layers, simplifying the overall structure while achieving effective ambient light rejection.
Solution Approach 2:
The microlens layer and total internal reflection layer are integrated in a stacked configuration where the microlens layer's convergence function complements the total internal reflection layer's angle-selective reflection function. This merging of functions into a compact multi-layer structure achieves effective ambient light rejection without requiring a complex, bulky design.
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 design significantly enhances the utilization efficiency of projection light rays, achieving higher screen gain and a brighter display image with improved contrast by optimizing the optical path and angle of incidence for total internal reflections.
Implementation Method 1
the microlens units converge at least a portion of the projected light onto the first plane
Implementation Method 2
the portion of the projection light rays converged onto the first plane exits after two consecutive total internal reflections on the first plane and the second plane
Implementation Method 3
the light absorbing layer is capable of absorbing light transmitted through the microlens layer, the transparent substrate layer and the total internal reflection layer
Data Source
AI summary
A screen comprises the following layers sequentially stacked from an incident side of projected light rays: a micro-lens layer, a transparent matrix layer, a total internal reflection layer, and a light-absorbing layer. The light-absorbing layer absorbs light passing through the micro-lens layer, the transparent matrix layer, and the total internal reflection layer. The micro-lens layer comprises a plurality of micro-lens units. The total internal reflection layer comprises a plurality of microstructure units. The microstructure unit has a lower first flat surface and an upper second flat surface. The first flat surface intersects the second flat surface. The plurality of microstructure units forms a serrated structure. The micro-lens units and the microstructure units are at least partially arranged in an alternating manner. The projected light rays converged toward the first flat surface exit after being totally internally reflected by the first flat surface and the second flat surface sequentially.