Wide-Angle Lens Aberration Control via Aspherical Surfaces
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Solution Overview
Problem
Existing wide-angle lenses for imaging devices, such as on-vehicle and surveillance cameras, face challenges in achieving high resolution and minimizing aberrations like curvature of field while maintaining a small size, especially with increasing pixel counts.
Innovation Solution
A wide-angle lens system comprising four to six lenses with specific power configurations and aspherical shapes, where the first group has negative power, the second group has positive power, the third group has negative power, and the fourth group has positive power, with conditional expressions governing focal lengths to control aberrations and aperture ratio, and Abbe numbers optimizing chromatic correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens system uses multiple lenses with specific power configurations to reduce curvature of field and improve resolution, then the manufacturing precision and complexity increase, but the imaging quality improves
Solution Approach 1:
The lens system is divided into four distinct lens groups with specific power configurations (negative, positive, negative, positive). Each group serves a specific function in correcting aberrations and achieving the desired imaging performance. This segmentation allows for systematic correction of curvature of field and other aberrations while maintaining manageable complexity through modular design.
Solution Approach 2:
Aspherical surfaces are selectively applied to specific lens surfaces rather than uniformly across all lenses. The patent specifies that at least one lens in the second, third, or fourth group has an aspherical surface with specific curvature constraints. This localized application of aspherical geometry provides precise correction of spherical aberration and curvature of field only where needed, optimizing imaging resolution without unnecessarily increasing manufacturing complexity across the entire system.
2Length of stationary object
If the lens system is designed with specific focal length ratios to control curvature of field, then the design precision increases, but the total lens length can be kept short
Solution Approach 1:
The patent establishes specific parameter ranges for focal lengths that must be satisfied: 1.0 ≤ ff2/f ≤ 2.0 and −2.0 ≤ ff2/ff3 ≤ −1.0. By defining these parameter constraints, the invention enables control over curvature of field and total lens length through quantitative optimization. These parameter specifications allow the lens system to achieve compact dimensions while maintaining proper aberration correction through mathematically defined relationships between focal lengths.
3Measurement precision
If aspherical surfaces are introduced to enlarge aperture ratio and improve resolution, then the manufacturing difficulty increases, but the imaging performance improves
Solution Approach 1:
Aspherical surfaces are selectively applied to specific lens surfaces rather than uniformly across all lenses. The patent specifies that at least one lens in the second, third, or fourth group has an aspherical surface with specific curvature constraints. This localized application of aspherical geometry provides precise correction of spherical aberration and curvature of field only where needed, optimizing imaging resolution without unnecessarily increasing manufacturing complexity across the entire system.
Solution Approach 2:
Instead of making all lens surfaces aspherical, the patent applies aspherical surfaces partially - only to specific lenses where they provide the greatest benefit for aperture ratio enlargement and aberration correction. This partial application achieves the necessary imaging performance improvement while minimizing the increase in manufacturing difficulty compared to making all surfaces aspherical.
4Reliability
If the lens system uses specific Abbe number combinations to correct chromatic aberration, then the material selection complexity increases, but the chromatic correction improves
Solution Approach 1:
The patent employs composite material selection by specifying different Abbe number ranges for different lens groups. The second lens group uses materials with Abbe number 20 ≤ vd < 30, the third group uses 30 ≤ vd < 40, and the fourth group uses vd ≥ 40. This composite approach combines materials with different dispersion properties across multiple lens groups, achieving comprehensive chromatic aberration correction through the synergistic effect of diverse material properties rather than relying on a single material type.
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 short total lens system length, reduced curvature of field, and improved chromatic aberration correction, enabling high-resolution imaging with a compact device capable of handling large diagonal angles of view.
Implementation Method 1
at least one of the lenses constituting the second group lens, the third group lens, and the fourth group lens is made to have an aspherical shape for at least one lens surface among the lens surface on the object side and the lens surface on the image side
Implementation Method 2
a first group lens having negative power, a second group lens having positive power, a third group lens having negative power, and a fourth group lens having positive power arranged in the stated order from an object side toward an image side
Data Source
AI summary
An imaging lens is formed from a first group lens having negative power, a second group lens having positive power, a third group lens having negative power, and a fourth group lens having positive power, disposed in order from the subject side to the image side. Letting f be the focal distance for the entire lens system and ff2 the focal distance for the second group lens, 1.0≤ff2/f≤2.0 is satisfied; therefore, the entire length of the lens system can be kept short and image curvature can be suppressed. In addition, each of the subject side lens surfaces and the image side lens surfaces for the second group lens, third group lens, and fourth group lens are provided with aspherical surface shapes; therefore, the imaging lens is constituted to be bright.