Zoom Lens Design for Aberration Control and Ghost Suppression
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Solution Overview
Problem
Conventional retrofocus type zoom lenses with wide angles face challenges in suppressing ghost images and flare, while maintaining optical performance, due to increased complexity and decentering susceptibility, especially when the diameter of the front lens exceeds common filter sizes, leading to issues like astigmatism, coma, and distortion.
Innovation Solution
A zoom lens design comprising a front lens group with negative refractive power and a rear lens group with positive refractive power, including specific lens configurations such as a positive lens, a negative lens with a concave surface, and cemented lenses, with a focusing lens group, and the use of aspherical lenses with varying refractive powers, all optimized by conditional expressions to control aberrations and reduce lens diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multilayer design technology and multilayer coating technology are used to improve optical performance, then ghost images and flare are suppressed, but the composition of the rear lens group becomes complicated and the number of lens elements increases
Solution Approach 1:
The patent extracts and addresses the harmful reflection effects by applying multilayer antireflection coatings on specific lens surfaces, particularly on the negative lens Lb and cemented lenses Lc and Ld in the rear lens group. This targeted approach suppresses ghost images and flare without requiring complete redesign of the entire lens group composition.
Solution Approach 2:
The patent optimizes specific parameters of the lens system, including the focal lengths of individual lens elements and their spacing, to achieve excellent optical performance. By carefully controlling parameters such as the focal length of the negative lens Lb and the arrangement of cemented lenses, the system achieves wide angle of view with reduced complexity.
2Shape
If the diameter of the front lens is increased to achieve wide angle of view, then the angle of view becomes wider, but the lens diameter exceeds commonly used filter sizes and causes serious defects in astigmatism, curvature of field, coma and distortion
Solution Approach 1:
The patent employs aspherical lens surfaces in the front lens group to effectively control aberrations. The aspherical shapes allow for wider angle of view while maintaining proper focus and reducing astigmatism, coma, and distortion that would otherwise occur with conventional spherical lenses of similar diameter.
Solution Approach 2:
The patent optimizes the focal lengths and spacing of lens elements in the front lens group to achieve wide angle of view while controlling aberrations. By carefully adjusting parameters such as the focal length of the negative lens and the arrangement of subsequent positive lenses, the system achieves wide angle coverage with acceptable optical quality.
3Object-affected harmful factors
If the rear lens group is designed with strong negative power (modified triplet type or Ernostar type) to improve optical performance, then optical performance is improved, but decentering susceptibility becomes high and assembling the lens system becomes difficult
Solution Approach 1:
The patent optimizes the focal length of the negative lens Lb in the rear lens group to achieve the right balance between optical performance and decentering susceptibility. By carefully controlling this parameter along with the arrangement of cemented lenses, the system achieves excellent optical performance while maintaining assembly reliability and reducing sensitivity to misalignment.
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 design achieves a downsized zoom lens with excellent optical performance, effectively correcting various aberrations and suppressing ghost images and flare, while maintaining a wide angle of view with fewer lens elements.
Implementation Method 1
a cemented positive lens Lc constructed by a negative lens cemented with a positive lens, and a cemented lens Ld constructed by a positive lens cemented with a negative lens
Implementation Method 2
an aspherical lens component Ga that has negative refractive power and a shape that the negative refractive power becomes smaller toward the periphery, and an aspherical lens component Gb that has positive refractive power and a shape that the positive refractive power turns to negative refractive power toward the periphery
Data Source
AI summary
A zoom lens including, from an object: a front group having negative power; and a rear group having positive power, the rear group including, from the object, a positive lens, a negative lens having a concave surface facing the object, a cemented positive lens constructed by a negative lens and a positive lens, and a cemented lens constructed by a positive lens and a negative lens, the rear group further including a focusing group disposed to the object side of the positive lens La for focusing from infinity to a close object by moving from the object side to an image side, a distance between the front group and the rear group being varied thereby zooming from a wide-angle end state to a telephoto end state, and given condition being satisfied, thereby providing a downsized zoom lens having wide angle of view and excellent optical performance with fewer lenses.