Direction Selective Projection Screen Ambient Light Suppression
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Solution Overview
Problem
Current projection screens struggle with ambient light reflections, which affect the contrast and dynamic range of projected images, especially in lit environments, and existing solutions like micro lenses or micro mirrors are limited in their ability to suppress ambient light effectively across all angles and dimensions.
Innovation Solution
A projection screen with a patterned layer stack comprising a retarder, micro-lens array, and polarizing layer, tailored to accept light from specific projector directions, reducing ambient light reflections by using a pseudo-random micro-lens array and a broadband half-wave retarder to maintain polarization extinction ratio, allowing for High Dynamic Range projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If micro lenses or micro mirrors are used to suppress ambient light, then ambient light reflection is reduced, but the screen has to be tailored for a certain projector configuration and the position of focus points depends upon the incident angle of light
Solution Approach 1:
The screen is divided into multiple segments, each with micro-lenses or micro-mirrors tailored to specific projector positions. This segmentation allows different regions of the screen to handle light from different angles independently, enabling the screen to suppress ambient light while adapting to multiple projector configurations simultaneously
Solution Approach 2:
The patent introduces a third dimension by curving the screen surface. This curvature allows the screen to accept light from projectors positioned at different locations and angles, transforming a 2D flat surface limitation into a 3D adaptive surface that can be optimized for various projection geometries
2Ease of manufacture
If one dimensional structures are used for micro lenses or micro mirrors, then production process is simplified, but ambient light acceptance is restricted in only 1 dimension and light returns as a strip causing vertical band degradation
Solution Approach 1:
The patent transitions from 1D linear structures to 2D planar patterns of micro-lenses or micro-mirrors. This dimensional upgrade allows the screen to suppress ambient light coming from multiple directions simultaneously, eliminating the vertical strip reflection problem while maintaining manufacturability through standard photolithographic patterning processes
3Object-affected harmful factors
If a polarizer and quarter wave retarder are used to suppress ambient light, then ambient light reflection is reduced, but the structure becomes more complex and requires precise focusing positions
Solution Approach 1:
The patent extracts and utilizes the reflective property of metal layers already present in the screen structure. By designing micro-mirror arrays with specific orientations and curvatures, the system achieves ambient light suppression through geometric optics rather than requiring additional polarizing layers, thereby reducing overall structure complexity
Solution Approach 2:
The patent introduces a curved substrate as an intermediary element between the projectors and the reflective layer. This curvature acts as a mediator that redirects light paths, enabling the screen to accept light from multiple projector positions while maintaining effective ambient light suppression without complicating the layer stack
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 suppresses ambient light reflections, enhancing image contrast and dynamic range by ensuring that only light from the intended projector direction is accepted, while diffusing light to provide a wide viewing angle and reducing speckle and optical artefacts.
Implementation Method 1
micro lenses or micro mirrors for focussing light from at least one projector at focus positions where the light can escape from the patterned layer stack
Implementation Method 2
a polarizing layer at least in said remainder of the screen area, wherein the patterned layer stack accepts only light coming from one projector direction per projector
Implementation Method 3
broadband half-wave retarder to maintain polarization extinction ratio
Implementation Method 4
suppresses ambient light reflections, enhancing image contrast and dynamic range by ensuring that only light from the intended projector direction is accepted
Data Source
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AI summary
A projection screen is described with micro lenses or micro mirrors for the purpose of suppressing ambient light by means of a patterned layer stack comprising at least a polarizer and a quarter wave retarder. The projection screen has a surface structure whereby light from a projector is focussed at positions where the light can escape from the structure and is optionally diffused. The location of the focus positions depends upon the incident angle of the light coming from the projector, and therefore the screen is tailored for a certain projector configuration and projector light direction.