Prism Array Screen for Front Projectors
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Solution Overview
Problem
Display screens in image display systems face challenges in maintaining high contrast ratios due to ambient light reflection, which degrades image quality even when projectors have high contrast ratios, especially in environments with lighting.
Innovation Solution
The use of an array of elongated transmissive polygonal prisms that direct image light to viewers while deflecting ambient light away, utilizing totally-internal-reflective reflections to turn incident light between 90 and 135 degrees and incorporating optical diffuser layers to manage light angles and absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional display screen is used in a front projector system, then the projector can display images, but ambient light reflects into the viewer's eyes reducing the perceived contrast ratio
Solution Approach 1:
The screen is segmented into an array of individual elongated prisms, each acting as an independent light-directing element. This segmentation allows each prism to precisely control the path of incident light, directing image light toward viewers while reflecting ambient light away, thereby resolving the contradiction between maintaining image visibility and blocking ambient light reflection.
Solution Approach 2:
The elongated prisms serve as intermediary optical elements between the projected image and the viewer's eyes. These prisms mediate the interaction between light and the viewer by selectively directing image light while blocking ambient light, thus improving the perceived contrast ratio without requiring the viewer to be in complete darkness.
2Illumination intensity
If the screen directs all incident light toward the viewer, then image visibility is maximized, but ambient light also reaches the viewer reducing image quality
Solution Approach 1:
Different regions of the screen surface (different facets of the prisms) have different optical properties. The first facet is optimized for receiving and transmitting image light, while the second facet is configured to reflect ambient light away from the viewer. This local differentiation of optical properties allows the screen to simultaneously maximize image brightness and minimize ambient light interference.
Solution Approach 2:
Instead of trying to block all incident light and then selectively transmit image light, the invention inverts the approach by using the natural reflection properties of the prism geometry to direct ambient light away from the viewer while allowing image light to pass through. This inverted approach of using reflection rather than absorption to achieve the desired effect resolves the contradiction.
3Illumination intensity
If the screen uses complex optical elements to block ambient light, then contrast ratio improves, but device complexity increases
Solution Approach 1:
The elongated prisms are designed to automatically perform the dual function of directing image light and blocking ambient light through their inherent geometric shape and optical properties, without requiring additional active control mechanisms or complex optical components. The prisms serve themselves by using total internal reflection and refraction principles that are intrinsic to their geometry, thereby improving contrast ratio while maintaining relatively simple device structure.
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 solution effectively enhances the perceived contrast ratio by preventing ambient light from reaching the viewer, thereby improving image clarity and quality in lit environments without compromising the viewing angles.
Implementation Method 1
utilizing totally-internal-reflective reflections to turn incident light between 90 and 135 degrees
Implementation Method 2
an array of elongated transmissive polygonal prisms disposed such that light from a light valve of the display system is directed by the screen to a viewer
Data Source
AI summary
A screen for use in image presentations comprises an array of transmissive elongated prisms. The screen is capable of delivering incident light, having an incident angle within a specific incident angle range, to the viewing area, while preventing ambient light, having an incident angle within another angle range, from being directed to the viewing area. According to one embodiment, in operation, the screen, an image source, and the viewing area are positioned such that the light from the image source is directed to the viewing area.