Four-Group Imaging Lens for Compact Semi-Wide Angle Imaging
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Solution Overview
Problem
Existing imaging lenses for digital cameras with semi-wide angles are either too large in size or lack sufficient imaging performance, particularly those derived from film camera designs.
Innovation Solution
A four-lens-group configuration comprising a first lens group with a positive lens and a negative lens, a second lens group with a negative and positive lens, a third lens group with positive and negative lenses, and a fourth lens group with a negative lens, optimized for a compact design and high performance, including aspherical surfaces and specific power arrangements to correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a substantially symmetrical lens type or telephoto type is used to achieve semi-wide angle, then the angle of view is improved, but the lens total length and total thickness become large
Solution Approach 1:
The lens system is divided into four distinct lens groups with specific refractive power assignments. The first lens group (positive+negative lenses) handles initial light convergence, the second lens group (negative+positive lenses) controls aberrations, the third lens group (positive+negative lenses) fine-tunes focus, and the fourth lens group (negative lens) adjusts final image formation. This segmented approach allows optimization of each group's contribution to achieve compact dimensions while maintaining semi-wide angle capability.
Solution Approach 2:
Each lens group is designed with specific local characteristics - the first group has strong positive refractive power for initial convergence, the second group balances positive and negative powers for aberration correction, the third group provides additional positive power for focus adjustment, and the fourth group contributes negative power for compactness. This localized optimization of optical properties enables the system to achieve both compact size and wide angle of view.
2Device complexity
If a film camera design is used for semi-wide angle lens, then the structure is simplified, but the imaging performance is insufficient for digital cameras
Solution Approach 1:
The lens design transitions from traditional film camera parameters to digital camera-optimized parameters. The conditional expressions specify precise ranges for refractive powers (e.g., 0.4≤f1P/f<1.5, -0.5<f4/f1<0.2), curvature radii, and spacing distances that are optimized for digital sensor characteristics. This parameter optimization corrects aberrations specifically relevant to digital imaging while maintaining a relatively simple four-group structure.
3Length of stationary object
If a telephoto type lens is used to achieve compact size, then the lens total length is reduced, but the imaging performance deteriorates
Solution Approach 1:
The lens system combines multiple lens groups with different refractive characteristics (positive and negative powers) in a composite structure. The first lens group provides strong positive power for convergence, the second group balances powers for aberration correction, the third group adds positive power for focus control, and the fourth group contributes negative power for compactness. This composite approach allows the system to achieve compact dimensions while maintaining high imaging performance through balanced optical characteristics.
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 provides a compact imaging lens with high performance and semi-wide angle capabilities, effectively correcting aberrations and achieving a half angle of view between 25 to 33 degrees, suitable for digital cameras with large imaging elements.
Implementation Method 1
a first lens group, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power
Implementation Method 2
including aspherical surfaces and specific power arrangements to correct aberrations
Data Source
AI summary
An imaging lens includes sequentially a first lens group, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group. The first lens group includes, sequentially from the object side to the image side, a positive lens having a convex surface facing the object side, and a negative lens having a concave surface facing the image side. The second lens group includes a negative lens disposed closest to the object side and having a concave surface facing the object side, and a positive lens disposed closer than the negative lens to the image side and having a convex surface facing the object side. The third lens group includes a positive lens having a convex surface facing the image side, and a negative lens. The fourth lens group includes a negative lens having a concave surface.