Concave Mirror Lens for Short Throw Projection
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Solution Overview
Problem
Conventional projection lenses with curved reflective mirrors face challenges in achieving a smaller throw ratio to project larger images within a shorter distance while maintaining good optical image quality, particularly due to difficulties in dust protection and design complexities associated with convex reflective mirrors.
Innovation Solution
A lens design incorporating a concave reflective mirror and a lens group with specific optical axis alignment and refractive power configurations, allowing for a throw ratio less than 0.3 and projecting a larger image within a shorter distance, while ensuring good optical image quality through precise alignment and refractive power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If convex reflective mirrors are used in projection lenses, then the mirror size can be larger, but dust protecting becomes difficult to design
Solution Approach 1:
The patent inverts the conventional approach by using a concave reflective mirror instead of a convex one. This inversion allows the mirror to be positioned such that the lens group is located between the mirror and the screen, creating a configuration where dust protection can be effectively implemented while maintaining a large effective mirror area for projection.
2Device complexity
If conventional projection lenses are used, then the design is simpler, but the throw ratio cannot be reduced below 0.3
Solution Approach 1:
The patent introduces an intermediate image plane between the lens group and the concave reflective mirror, creating a multi-stage optical path. This dimensional addition to the optical system enables the throw ratio to be reduced below 0.3 by effectively utilizing the space between the lens and mirror through the intermediate imaging stage.
3Area of stationary object
If the throw ratio is reduced to project larger images at shorter distance, then the image size increases, but optical image quality deteriorates
Solution Approach 1:
The patent introduces an intermediate image plane as a mediator between the lens group and the concave reflective mirror. This intermediate stage allows for better control of light paths and reduces optical aberrations, thereby maintaining high image quality even when projecting large images at short distances with a throw ratio below 0.3.
4Length of stationary object
If concave reflective mirrors are used with intermediate images, then the throw ratio can be reduced, but the lens group positioning becomes more complex
Solution Approach 1:
The patent segments the optical system into distinct functional groups: the lens group, the intermediate image plane, and the concave reflective mirror. This segmentation allows each component to be optimized and positioned independently, simplifying the overall positioning complexity while achieving the reduced throw ratio below 0.3.
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 lens achieves a smaller throw ratio, enabling the projection of larger images at a shorter distance with maintained optical image quality, addressing the design challenges of conventional projection lenses.
Implementation Method 1
a concave reflective mirror is disposed in the light path between the lens group and the magnified side
Implementation Method 2
The lens includes a lens group and a concave reflective mirror. The lens group is disposed in a light path between the reduced side and the magnified side
Data Source
AI summary
A lens adapted to image a first image plane at a reduced side onto a magnified side is provided. The lens has an optical axis. The lens includes a lens group and a concave reflective mirror. The lens group is disposed in the light path between the reduced side and the magnified side. The concave reflective mirror is disposed in the light path between the lens group and the magnified side. The offset of the first image plane with respect to the optical axis is greater than 100%. The throw ratio of the lens is less than 0.3.