Compact Imaging Lens with Aspheric Elements for Wide Field of View
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Solution Overview
Problem
Conventional imaging lenses for compact mobile terminals struggle to achieve a balance between compactness, wide field of view, and low F-value while effectively correcting various aberrations.
Innovation Solution
An imaging lens configuration with specific refractive power distribution and aspheric lens surfaces, including an aperture stop placement, is used to achieve a small F-value and wide field of view, with conditional expressions defining optimal ratios and curvature radii for the lenses to correct aberrations and ensure compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the total track length is reduced to achieve compactness, then the lens becomes more compact, but the field of view becomes narrower and the F-value increases
Solution Approach 1:
The imaging lens is divided into four distinct lenses with specific refractive powers arranged in sequence: a first lens with positive refractive power, a second lens with negative refractive power, a third lens with positive refractive power, and a fourth lens with negative refractive power. This segmentation allows each lens to contribute differently to the overall optical performance, enabling compactness while maintaining wide field of view capability.
Solution Approach 2:
Each lens in the four-element system has locally optimized properties: the first lens has a convex surface on the object side, the second lens has a concave surface on the object side, the third lens has a convex surface on the image side, and the fourth lens has specific curvature characteristics. These local quality variations enable the system to achieve both compactness and wide field of view by optimizing each position's contribution.
2Illumination intensity
If the F-value is reduced to increase brightness, then the lens provides better light transmission, but the total track length increases reducing compactness
Solution Approach 1:
The patent optimizes specific parameter ratios to achieve both small F-value and compactness. The conditional expressions define precise ranges for: (1) the ratio of composite focal lengths f12/f34, (2) the ratio of focal length to curvature radius f/r1, and (3) the ratio of focal lengths f1/f3. By controlling these parameters within specific ranges, the system achieves F-value of 2.4 or smaller while maintaining TLA/2ih of 0.95 or smaller.
3Manufacturing precision
If the refractive power distribution is optimized to correct aberrations, then the image quality improves, but the lens complexity increases
Solution Approach 1:
The aberration correction is achieved through segmentation of optical functions across four lenses. Each lens is assigned a specific refractive power sign and surface configuration: the first lens (positive power, convex object-side surface) handles initial light convergence, the second lens (negative power, concave object-side surface) corrects certain aberrations, the third lens (positive power, convex image-side surface) provides additional convergence, and the fourth lens (negative power) fine-tunes the optical path. This functional segmentation enables comprehensive aberration correction while maintaining a relatively simple four-element structure.
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 solution results in a compact imaging lens with an F-value less than 2.4, providing a wide field of view of 70 degrees or more and effectively correcting various aberrations, suitable for high-performance camera applications in compact mobile terminals.
Implementation Method 1
an imaging lens for a solid-state image sensor includes, in order from an object side to an image side, a first lens L1 with positive refractive power having a convex surface on each of the object side and the image side, a second lens L2 with negative refractive power having a concave surface on the object side near an optical axis X, a third lens L3 with positive refractive power as a meniscus lens having a convex surface on the image side, and a fourth lens L4 with negative refractive power as a meniscus double-sided aspheric lens
Data Source
AI summary
A compact, wide view-field imaging lens with a small F-value which corrects aberrations properly. Its elements are arranged in order from an object side to an image side: an aperture stop, positive first lens having convex surfaces on the object and image sides, negative second lens having a concave object-side surface near an optical axis, positive meniscus third lens having a convex image-side surface, and negative meniscus double-sided aspheric fourth lens having a concave image-side surface near the optical axis. Its F-value is smaller than 2.4 and it satisfies conditional expressions (1) to (3) below: 0.15<f12/f34<0.5 (1) 0.1<|r1/r2|<0.5 (2) 1.0<f1/f3<1.6 (3) where f1: first lens focal length f3: third lens focal length f12: composite focal length of the first and second lenses f34: composite focal length of the third and fourth lenses r1: curvature radius of the first lens object-side surface r2: curvature radius of the first lens image-side surface.