Projection Lens Miniaturization via Reflective Optical Path Folding
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Solution Overview
Problem
Conventional projection lenses face challenges in miniaturization while maintaining high imaging quality and large field angles, often resulting in increased length, distortion, and low imaging quality, especially when used in interactive devices that require precise signal generation and processing.
Innovation Solution
A projection lens design comprising a first negative focal power lens, a reflective optical device, and a third positive focal power lens, with specific curvature and focal length ratios, and made of glass material, to achieve miniaturization, large field angles, and high imaging quality, while using a diaphragm and aspheric/spherical shapes to correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional projection lenses use many lenses to eliminate aberrations and improve resolution, then imaging quality is improved, but the length of the projection lens increases
Solution Approach 1:
The projection lens is divided into only three lens groups (first negative lens, second positive lens, third positive lens) rather than using many lenses. This segmentation approach maintains imaging quality by strategically designing each group's optical properties while significantly reducing the overall lens length and achieving miniaturization.
Solution Approach 2:
The patent introduces a reflective optical device to fold the optical path, changing the linear arrangement into a multi-dimensional configuration. This allows the light path to be bent and redirected, achieving compact lens length while maintaining the necessary optical path length for high imaging quality.
2Volume of moving object
If projection lens is miniaturized, then device size is reduced, but field angle and imaging quality deteriorate
Solution Approach 1:
The patent uses aspheric surfaces on the first and second lenses, which provide dynamic optical correction capabilities. The aspheric shapes allow the lens to maintain large field angle coverage and high imaging quality across the entire field of view, even in the miniaturized three-group configuration.
Solution Approach 2:
The patent carefully optimizes specific parameter ratios including focal lengths (f1, f2, f3), curvature radii (R3, R4, R5, R6), and the relationship between image height and lens height (ImgH/D). These parameter changes enable the miniaturized lens to achieve both large field angle and high imaging quality simultaneously.
3Adaptability or versatility
If projection lens is designed for large field angle, then coverage is improved, but distortion increases and imaging quality decreases
Solution Approach 1:
Different lens groups are assigned specific functions: the first negative lens with aspheric surfaces handles field angle expansion, the second positive lens with aspheric surfaces corrects distortion locally, and the third positive lens maintains image quality. This local quality differentiation allows large field angle without sacrificing imaging quality.
Solution Approach 2:
The patent combines different lens materials with specific refractive indices and dispersion properties to correct chromatic aberrations and maintain imaging quality across the large field angle. The composite lens design includes both aspheric and spherical surfaces to address different types of aberrations.
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 design achieves a balance of miniaturization, large field angles, and high imaging quality, reducing production costs and eliminating thermal differences' adverse effects, while maintaining telecentric characteristics and correcting distortion.
Implementation Method 1
a reflective optical device, which enables a light path to be bended
Implementation Method 2
each of the first lens and the second lens has two sides both being in an aspheric shape
Implementation Method 3
a first lens, a reflective optical device, a second lens and a third lens from an image side of the projection lens to an object side of the projection lens in turn
Data Source
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AI summary
Provided is a projection lens including: a first lens, a reflective optical device, a second lens and a third lens from an image side of the projection lens to an object side of the projection lens in turn. The first lens is of a negative focal power, an image side of the first lens is concave; the reflective optical device enables light to be bended; the second lens is of a positive focal power, an object side of the second lens is convex; the third lens is of a positive focal power, an object side of the third lens is convex. A diaphragm is arranged between first lens and second lens, the projection lens meets: 0.4<ImgH/D<0.7, wherein ImgH equals to a half-length of an object diagonal, D represents a vertical height from the image side of the first lens to a center axis perpendicular to an object. The projection lens according to embodiments of the present disclosure has a large filed angle and a large aperture, and miniaturization.