Conjugate Mirror Projection Optical System for Ultra-Short Throw
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Solution Overview
Problem
Ultra-short throw projectors face challenges in miniaturization and image quality due to the need for a large optical system and the difficulty in projecting large format images without degrading the image quality, especially when dust or contaminants attach to optical elements near intermediate images.
Innovation Solution
An image displaying apparatus with a projection optical system that includes a lens optical system, a first mirror with a vertically downward-facing optical surface, and a second mirror, which together project an image onto a screen while minimizing the risk of dust attachment and image degradation by positioning the light condensation point close to the second mirror and using a compact dust-proof glass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a lens optical system is used to project images at ultra-short distance, then the projection distance is reduced, but the optical system size becomes large
Solution Approach 1:
The patent combines a lens optical system with a mirror optical system to achieve ultra-short throw projection. The lens system (including condensing lens and projection lens) works together with mirrors (first mirror and second mirror) to fold the optical path and reduce the overall system size while maintaining short projection distance capability
Solution Approach 2:
The patent uses mirrors to fold the optical path in multiple dimensions, changing the linear arrangement into a compact three-dimensional configuration. This allows the optical system to achieve ultra-short throw ratio while keeping the physical footprint small by utilizing vertical and lateral space efficiently
2Volume of stationary object
If a curved mirror is used to reduce projection distance, then the optical system becomes compact, but image quality degrades due to dust attachment
Solution Approach 1:
The patent positions the first mirror at an intermediate image position where light rays converge, creating a region where dust particles are less likely to attach. The optical design ensures that critical imaging surfaces are positioned where contamination has minimal impact on image quality
Solution Approach 2:
The patent introduces a dust-proof glass as an intermediary element between the light source and the imaging path. This dust-proof glass captures and redirects dust particles away from critical optical surfaces, protecting image quality while allowing the compact optical design to function
3Volume of stationary object
If the distance between lens and mirror is reduced for miniaturization, then the optical system becomes compact, but the amount of protrusion from screen surface increases
Solution Approach 1:
The patent employs multiple mirrors to fold the optical path in vertical and lateral dimensions, transforming a long linear optical path into a compact three-dimensional arrangement. This allows the system to maintain ultra-short throw ratio while minimizing the protrusion amount from the screen surface
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
Enables the display of large format images at an ultra-short distance with reduced image degradation and a compact projector design, maintaining image quality by directing contaminants downward and preventing vignetting.
Implementation Method 1
a first mirror for reflecting light transmitted through the lens optical system
Implementation Method 2
a second mirror for reflecting light reflected from the first mirror toward the surface to be projected onto
Data Source
AI summary
An image displaying apparatus including a light source, an image displaying element configured to control exiting of incident light to display an image, an illumination optical system configured to illuminate the image displaying element with light exiting from the light source, and a projection optical system configured to project an image displayed on a display surface of the image displaying element, to provide an enlarged display. The projection optical system includes a lens optical system, a first mirror configured to reflect light transmitted through the lens optical system, and a second mirror configured to reflect light reflected from the first mirror toward the surface to be projected onto, and one of the mirrors is arranged at a position conjugate to the image displaying element, and wherein an optical surface of the one mirror is arranged to face vertically downward.