Wide Angle Lens Correcting Lateral Chromatic Aberration
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Solution Overview
Problem
Retrofocus type wide angle lenses face difficulties in correcting lateral chromatic aberration due to their asymmetric structure, which is insufficient for modern digital camera applications requiring higher optical performance.
Innovation Solution
A wide angle lens configuration comprising a front group with a positive lens and a negative meniscus lens, and a rear group with a biconvex lens, satisfying specific conditional expressions for refractive indices and partial dispersion ratios to effectively correct lateral chromatic aberration, while ensuring a wide angle of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a retrofocus type lens system with asymmetric structure is used, then back focus is ensured, but lateral chromatic aberration correction is difficult
Solution Approach 1:
The patent applies asymmetry principle by designing a retrofocus type lens system with asymmetric structure relative to the stop, where the front group contains a negative meniscus lens with convex surface toward object and the rear group contains a positive lens, creating intentional asymmetric configuration to achieve both sufficient back focus and improved lateral chromatic aberration correction through specific arrangement of asymmetric optical elements
Solution Approach 2:
The patent applies parameter changes by precisely controlling the partial dispersion ratio (θgFf) and Abbe number (νdf) of the negative meniscus lens, and the partial dispersion ratio (θgFr) and Abbe number (νdr) of the positive lens in the rear group, using specific numerical ranges for these optical parameters to simultaneously achieve adequate back focus and satisfactory lateral chromatic aberration correction
2Length of stationary object
If conventional retrofocus lens system is used, then back focus is sufficient, but optical performance for digital cameras is insufficient
Solution Approach 1:
The patent applies parameter changes by establishing specific conditional expressions for the optical parameters: 0.038 < θgFf - 0.6415 + 0.001618×νdf and νdf > 19 for the negative meniscus lens, and 0.020 < θgFr - 0.6415 + 0.001618×νdr and νdr > 75 for the positive lens, thereby optimizing the lens system to deliver high optical performance suitable for digital camera applications while maintaining sufficient back focus
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 configuration achieves high optical performance with well-corrected lateral chromatic aberration and a wide angle of view, suitable for digital cameras, enhancing image quality.
Implementation Method 1
a positive lens with a convex surface on the object side is disposed on the most object side in the front group
Implementation Method 2
a negative meniscus lens with a convex surface on the object side is disposed second from the object side in the front group
Implementation Method 3
the rear group includes one positive lens having a biconvex shape
Data Source
AI summary
A wide angle lens consists of a front group, a stop, and a positive rear group in order from the object side. A positive lens with a convex surface on the object side and a lens having a negative meniscus shape with a convex surface on the object side are respectively disposed first and second from the object side in the front group. When Abbe number with respect to the d-line and the partial dispersion ratio between the g-line and the F-line of the lens having a negative meniscus shape are taken as νdf and θgFf respectively, the wide angle lens satisfies a conditional expression (1): 0.038<θgFf −0.6415+0.001618×νdf and a conditional expression (2): νdf<19.