Imaging Lens With Off-Axis Aspheric Elements for Compact Length
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Solution Overview
Problem
Existing imaging lenses for portable terminals, despite incorporating four lens elements, fail to adequately reduce thickness and overall length while maintaining optical performance, particularly in correcting field curvature and chromatic aberrations.
Innovation Solution
The imaging lens configuration includes a positive first lens, a negative second lens, and two aspheric lenses with extreme points off the optical axis, where the third lens is a meniscus lens with a concave object-side surface and the fourth lens has a positive image-side surface, satisfying specific conditional expressions to reduce overall length while maintaining aberration correction and improving chromatic aberration compensation using high-dispersion materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four lens elements are incorporated to support higher-density packaging, then optical performance is improved, but overall length cannot be sufficiently reduced
Solution Approach 1:
The patent employs aspheric surfaces on the third and fourth lens elements instead of conventional spherical surfaces. The aspheric coefficients are specifically designed to control the curvature variations, enabling the lens system to achieve compact length while maintaining superior optical performance including field curvature and chromatic aberration correction.
Solution Approach 2:
The patent optimizes specific parameters including the aspheric coefficients (K3, K4), curvature radii (R3R, R4F), and lens spacing to satisfy conditional expressions that reduce overall length. By precisely adjusting these parameters, the lens system achieves compact dimensions without sacrificing optical quality.
2Reliability
If two aspheric lens elements are provided on the image side for aberration correction, then optical performance is improved, but device complexity increases
Solution Approach 1:
The aspheric surfaces on the third and fourth lens elements serve multiple functions simultaneously: they correct various types of aberrations (spherical aberration, astigmatism, field curvature) and also contribute to chromatic aberration correction. This multi-functionality reduces the need for additional dedicated correction elements, thereby managing device complexity.
Solution Approach 2:
The patent utilizes lens elements with different refractive indices and dispersion characteristics arranged in a specific sequence. The combination of these materials with aspheric surfaces creates a composite optical system that achieves superior aberration correction while controlling overall system complexity through efficient material utilization.
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
This configuration significantly reduces the overall length of the lens system while maintaining superior aberration correction, particularly in field curvature, and enhances optical performance by compensating for chromatic aberrations, making it suitable for high-density imaging elements in portable terminals.
Implementation Method 1
a third lens (a third lens element), both surfaces of which are aspheric surfaces, wherein an image-side surface of the third lens has an extreme point at a position other than an optical axis of the imaging lens; and a fourth lens (a fourth lens element), both surfaces of which are aspheric surfaces, wherein an object-side surface of the fourth lens has an extreme point at a position other than the optical axis
Implementation Method 2
a first lens (a first lens element) of a positive lens; a second lens (a second lens element) of a negative lens
Data Source
AI summary
An imaging lens is provided and includes, in order from an object side of the imaging lens: a first lens of a positive lens; a second lens of a negative lens; a third lens of a bi-aspheric lens that has an image-side surface having an extreme point at a position other than an optical axis of the imaging lens; and a fourth lens of a bi-aspheric lens that has an object-side surface having an extreme point at a position other than the optical axis. The imaging lens satisfies Conditional Expressions specified in the specification.