Compact Wide-Angle Imaging Lens Design
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Solution Overview
Problem
Conventional wide angle lenses for digital cameras face challenges in achieving a compact configuration while securing a wide angle of view, often resulting in long lens systems, asymmetrical lens groups, and difficulty in correcting aberrations.
Innovation Solution
The design incorporates a first lens group with negative or positive refractive power, an aperture stop, and a second lens group with positive refractive power, optimized by specific conditional formulae to balance focal lengths, spatial distances, and refractive indices, allowing for a compact and wide-angle imaging lens configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a retro focus type configuration is adopted to secure a wide angle of view and long back focus, then the angle of view and back focus are improved, but the total lens length becomes long
Solution Approach 1:
The patent inverts the conventional retro focus configuration by placing a positive lens group before the aperture stop and a negative lens group after it, rather than the typical negative-before-positive arrangement. This inversion allows achieving wide angle of view with reduced total lens length, directly resolving the contradiction between angle of view and lens length.
2Illumination intensity
If the number of lenses is increased to widen the imaging angle and improve aberration correction, then the imaging angle and image quality are improved, but the lens system becomes large and complex
Solution Approach 1:
The patent divides the lens system into two functional groups separated by the aperture stop: a positive lens group before the stop and a negative lens group after it. This segmentation allows each group to be optimized independently for aberration correction while maintaining a compact overall structure, avoiding the need for excessive lens elements.
Solution Approach 2:
The patent assigns different optical characteristics to different regions of the lens system. The positive lens group before the aperture stop is optimized for one set of aberrations while the negative lens group after the stop addresses different aberrations, allowing localized optimization without increasing overall complexity.
3Manufacturing precision
If the front group spatial distance is increased to correct aberrations, then aberration correction is improved, but the lens system length increases
Solution Approach 1:
The aperture stop serves as an intermediary element that separates the positive and negative lens groups. This intermediary allows for effective aberration correction by enabling the positive group to handle certain aberrations before the stop and the negative group to handle others after the stop, without requiring excessive spacing between lens elements.
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 enables a compact, wide-angle lens system that effectively corrects various aberrations, achieves miniaturization, and secures a necessary back focus, while maintaining high image quality.
Implementation Method 1
a first lens group G1 having a negative or a positive refractive power; an aperture stop St; and a second lens group G2 having a positive refractive power, which are provided in this order from an object side
Data Source
AI summary
An imaging lens includes: a first lens group; an aperture stop; and a second lens group having a positive power, in this order from an object side. The first lens group includes a first lens having a negative power and a second lens having a positive power. The imaging lens satisfies Conditional Formulae (1), (2), and (3): −0.50<f/f1<0.20 (1) 0.08<d12/f<0.35 (2) 2.5<TL/Y<4.0 (3) wherein f is the focal length of the entire system, f1 is the focal length of the first lens group, d12 is a distance along an optical axis from the image side lens surface of the first lens to the object side lens surface of the second lens, TL is the distance along the optical axis from the most object side lens surface within the first lens group to an imaging surface Sim, and Y is a maximum image height, when focused on an object at infinity.