Projection Optical System with Concave Mirror for Stable Short-Range Imaging
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Solution Overview
Problem
Conventional projection optical systems for short-distance front projection face challenges in maintaining image stability and focus due to large angle of incidence, leading to significant up/down movement of the projected image with varying projection distance, and are often bulky, obstructing the view and lacking focusing mechanisms.
Innovation Solution
A compact projection optical system incorporating a refractive optical system with positive optical power and a concave-surfaced mirror, forming an intermediate image between the refractive optical system and the concave-surfaced mirror, with at least one movable optical element for focusing, and adhering to specific conditional formulas to minimize image movement and ensure proper focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a convex-surfaced mirror is used for short-distance front projection, then the projection distance is reduced, but the angle of incidence becomes large causing significant up/down movement of the projected image
Solution Approach 1:
The patent inverts the conventional approach by using a concave-surfaced mirror instead of a convex-surfaced mirror as the last surface. This inversion changes the optical path characteristics, reducing the angle of incidence and minimizing image position movement while maintaining short projection distance capability
2Stability of the object's composition
If a concave-surfaced mirror is used to reduce image movement, then the angle of incidence is reduced, but the system dimension in the up/down direction increases making it bulky
Solution Approach 1:
The patent segments the optical system into multiple functional components: a refractive optical system with positive optical power and a concave-surfaced mirror with specific curvature. This segmentation allows each component to be optimized independently, achieving compact dimensions while maintaining image stability
Solution Approach 2:
The patent carefully controls the curvature radius of the concave-surfaced mirror and the optical power of the refractive system to satisfy specific conditional formulas. By optimizing these parameters, the system achieves compact size while minimizing image movement
3Length of moving object
If conventional rear projection systems are adapted for front projection, then the projection distance is reduced, but the focusing mechanism is lost preventing proper focus
Solution Approach 1:
The patent introduces a movable optical element (either the concave-surfaced mirror or a lens within the refractive system) that can be displaced along the optical axis. This dynamic adjustment mechanism enables focusing by changing the optical path length, allowing the system to adapt to different projection distances while maintaining image quality
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 system achieves stable image projection with minimal up/down movement and focusing capability, producing images in the 60 to 100 inches range with reduced variation in projection position, enhancing viewing experience and system compactness.
Implementation Method 1
a refractive optical system which is composed of one or more refractive lenses and which has a positive optical power
Implementation Method 2
a concave-surfaced mirror which is disposed to the screen side of the refractive optical system and which has a plane-symmetric reflective surface
Data Source
AI summary
A projection optical system that receives light from a display element to project an image displayed by the display element onto a screen with enlargement at a varying magnification achieved by varying the projection distance to the screen has: a refractive optical system composed of one or more refractive lenses and having a positive optical power; and a concave-surfaced mirror disposed to the screen side of the refractive optical system and having a plane-symmetric reflective surface. The projection optical system includes at least one optical element designed to be movable for focusing. The projection optical system forms an intermediate image between the refractive optical system and the concave-surfaced mirror. Moreover, a prescribed conditional formula is fulfilled.