Compact Lens Assembly with Negative Power Elements
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Solution Overview
Problem
Conventional compact optical lens systems face challenges in achieving a compact size while maintaining good image quality due to limitations in reducing back focal length and minimizing aberration and peripheral brightness loss, primarily because they rely on a three-element lens structure with insufficient negative refractive power distribution.
Innovation Solution
A photographing lens assembly comprising a first lens element with positive refractive power, a second lens element with negative refractive power made of plastic and featuring aspheric surfaces, and a third lens element with negative refractive power, where the curvature radii and focal lengths of these elements are optimized to reduce total track length, correct aberrations, and minimize refraction angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional three-element lens structure with positive refractive power elements is used, then the lens assembly can be kept compact, but the back focal length cannot be reduced sufficiently and image quality deteriorates
Solution Approach 1:
The patent changes the refractive power parameters of the lens elements by introducing a fourth element with negative refractive power and adjusting the curvature radii of existing elements. Specifically, the object-side surface curvature radius of the second lens element and image-side surface curvature radius of the third lens element are optimized to reduce back focal length while maintaining compact size and improving image quality.
Solution Approach 2:
The patent employs a composite lens structure combining multiple materials with different refractive indices. The first lens element has positive refractive power, while the second and third lens elements have negative refractive power, creating a composite optical system that balances compactness with image quality through material property differentiation.
2Object-affected harmful factors
If the curvature of surfaces of the second and third lens elements is increased to reduce refraction angle, then aberration and peripheral brightness loss increase
Solution Approach 1:
The patent optimizes the curvature radius parameters of the lens surfaces to achieve the minimum refraction angle. Specifically, the object-side surface curvature radius of the second lens element (R3) and image-side surface curvature radius of the third lens element (R6) are carefully selected to balance aberration correction with peripheral brightness maintenance.
Solution Approach 2:
The patent applies different surface curvature characteristics to different regions of the lens elements. The aspheric coefficients are specifically designed for each lens element's object-side and image-side surfaces to locally optimize optical performance, with the second lens element having one set of aspheric parameters and the third lens element having another set tailored to their specific positions and functions.
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 optimized lens assembly achieves a compact size with improved image quality by effectively reducing total track length, correcting aberrations, and minimizing sensitivity and peripheral brightness loss, while allowing for flexible design with both glass and plastic materials.
Implementation Method 1
a first lens element with positive refractive power, a second lens element with negative refractive power... the refraction angle from the optical lens system cannot be minimized by the curvature of the surfaces
Data Source
AI summary
A photographing lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element and a third lens element. The first lens element with positive refractive power has an object-side surface being convex at a paraxial region. The second lens element with negative refractive power has an object-side surface being concave at a paraxial region and an image-side surface being concave or planar at a paraxial region, wherein the second lens element is made of plastic material and the surfaces thereof are aspheric. The third lens element with negative refractive power has an object-side surface being concave at a paraxial region, and an image-side surface being concave at a paraxial region and being convex at a peripheral region, wherein the third lens element is made of plastic material, and the surfaces thereof are aspheric.