Compact Imaging Lens with Aspheric and Cemented Elements
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Solution Overview
Problem
Existing imaging lenses face challenges in achieving a short total length while maintaining high optical performance and effectively correcting various aberrations.
Innovation Solution
The proposed imaging lens configuration includes a first lens group with a negative lens and two positive lenses, a second lens group with an aspheric lens and cemented lenses, and a third lens group with a single lens, optimized by specific refractive power and Abbe number conditions to satisfy conditional expressions, allowing for reduced system length and improved aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional imaging lens configuration is used, then optical performance can be maintained, but the total length of the lens system becomes long
Solution Approach 1:
The lens system is divided into three distinct lens groups (first lens group with positive refractive power, second lens group with positive refractive power, and third lens group with negative refractive power) arranged in sequence from the object side. This segmentation allows each group to be optimized independently for specific functions while contributing to overall system compactness.
Solution Approach 2:
Each lens group is assigned specific local optical characteristics: the first lens group contains a negative lens with specific refractive power for initial light control, the second lens group incorporates an aspheric lens and cemented lenses for aberration correction, and the third lens group uses a negative lens for focal length adjustment. This local optimization enables compact design while maintaining high optical performance.
2Length of moving object
If the lens system is shortened, then compactness is improved, but aberration correction becomes insufficient
Solution Approach 1:
The patent employs an aspheric lens in the second lens group with specific aspheric coefficients to correct spherical aberration and other off-axis aberrations. The asymmetric aspheric surface profile allows effective aberration correction in a compact lens design where conventional spherical lenses would require additional elements and increased length.
Solution Approach 2:
The patent uses cemented lenses combining different glass materials with specific refractive indexes and Abbe numbers. The first cemented lens combines a positive lens and negative lens with carefully selected glass types to correct chromatic aberration, while the second cemented lens uses different material combinations for complementary aberration correction, achieving high optical performance in a 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 a short total lens system length with high optical performance by effectively correcting spherical, chromatic, and other aberrations, enhancing image quality.
Implementation Method 1
the second lens group includes an aspheric lens
Implementation Method 2
two sets of cemented lenses disposed to be closer to the image side than the aspheric lens
Implementation Method 3
assuming that a maximum value of refractive indexes of the positive lenses included in the cemented lenses in the second lens group at a d line is N2cpmax
Data Source
AI summary
The imaging lens consists of, in order from the object side, a first positive lens group, a stop, a second positive lens group, and a third negative lens group. The first lens group includes a negative lens which has a concave surface on the image side, and two positive lenses which are disposed to be closer to the image side than the negative lens and which have respective convex surfaces on the object side, convex surfaces on the object side. The second lens group includes an aspheric lens, and two sets of cemented lenses disposed to be closer to the image side than the aspheric lens. The third lens group consists of one lens component.