Compact Wide-Angle Lens Design for Aberration Control
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Solution Overview
Problem
Conventional wide-angle single focus lenses, such as retrofocus type image-forming lenses, face challenges in achieving miniaturization while maintaining high performance, as they tend to be large due to asymmetrical refractive power arrangements, leading to incomplete correction of aberrations like comatic aberration, distortion, and transverse chromatic aberration.
Innovation Solution
The design incorporates a specific configuration of lens groups with negative and positive refractive powers, including a first lens group with a negative refractive power and a second lens group with a positive refractive power, where the first lens group consists of a first F lens group and a first R lens group, and the second lens group includes a second F lens group, a second M lens group, and a second R lens group, optimized to satisfy specific conditional expressions that control the lens length, curvature radii, and refractive indices to balance aberrations and ensure miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a retrofocus type image-forming lens with asymmetrical refractive power arrangement is used, then a wide field angle (half-field angle of about 38 degrees) and large diameter (smallest f-number less than F2.8) are achieved, but the lens length becomes excessively long and miniaturization cannot be achieved
Solution Approach 1:
The patent applies asymmetry principle by arranging lens groups with different refractive powers (positive and negative) in a non-symmetrical configuration. Specifically, the first lens group has positive refractive power and the second lens group has negative refractive power, creating an asymmetrical refractive power arrangement that enables wide-angle imaging while controlling lens length through optimized group positioning and power distribution.
Solution Approach 2:
The patent employs parameter changes by optimizing the refractive powers, curvature radii, and axial positions of individual lens groups and their components. By adjusting parameters such as the refractive power of the first and second lens groups, the curvature radii of lens surfaces, and the spacing between groups, the design achieves a compact lens length while maintaining the required wide field angle and large diameter characteristics.
2Area of stationary object
If a retrofocus type image-forming lens with asymmetrical refractive power arrangement is used, then a wide field angle is achieved, but aberration corrections (comatic aberration, distortion, transverse chromatic aberration) become incomplete
Solution Approach 1:
The patent applies segmentation by dividing the lens system into multiple distinct lens groups (first lens group with positive refractive power, second lens group with negative refractive power, and additional lens groups) that can be independently optimized. Each group is designed to correct specific types of aberrations, allowing comprehensive aberration control across the wide field angle without requiring excessive lens length.
Solution Approach 2:
The patent uses asymmetry principle with a balanced approach by arranging positive and negative refractive power groups in a specific asymmetrical pattern that addresses aberration corrections. The first lens group (positive power) and second lens group (negative power) are positioned and sized to mutually compensate for various aberrations including comatic aberration, distortion, and transverse chromatic aberration, achieving complete correction while maintaining wide field angle.
3Length of stationary object
If the lens length is shortened to achieve miniaturization, then portability is improved, but it becomes difficult to maintain high performance with a large diameter and wide field angle
Solution Approach 1:
The patent employs parameter changes by optimizing the refractive powers, curvature radii, and axial positions of lens groups to achieve a compact design. By carefully selecting parameters such as the refractive power ratio between positive and negative groups, the curvature radii of lens surfaces, and the spacing between groups, the design shortens lens length while maintaining large diameter (smallest f-number less than F2.8) and wide field angle (half-field angle of about 38 degrees) for high optical performance.
Solution Approach 2:
The patent applies segmentation by dividing the lens system into functionally distinct lens groups that can be compactly arranged. The first lens group (positive power), second lens group (negative power), and additional groups are positioned to minimize overall length while each group contributes to maintaining optical performance through its specific function in the compact configuration.
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 results in an image-forming lens that is compact, wide-angle, and high-performance, with reduced astigmatism, field curvature, transverse chromatic aberration, and comatic aberration, capable of maintaining excellent optical performance with a half-field angle of about 38 degrees and a smallest f-number less than 2.8, suitable for digital cameras with image sensors of 10 to 20 million pixels.
Implementation Method 1
a first lens group G1 having a positive refractive power or being substantially afocal; an aperture stop ST; and a second lens group G2 having a negative refractive power
Data Source
AI summary
An image-forming lens includes, from an object side to an image side in order: a first lens group; an aperture; and a second lens group with a positive refractive power, the first lens group including, from the object side in order: a first F lens group with a negative refractive power; and a first R lens group with a positive refractive power, the first F lens group including, from the object side in order: a first negative lens; and a second negative lens, and the first R lens group including: any one of a positive lens and a cemented lens with a positive refractive power as a whole, wherein a distance from a surface on a most object side of the first lens group to an image plane in a state of focusing on an object at infinity: L, and a maximum image height: Y′ satisfy Conditional expression 1: 2.8<L/Y′<4.3.