Projection Lens Lateral Chromatic Aberration Correction
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Solution Overview
Problem
Existing projection lenses with high zoom ratios face challenges in minimizing lateral chromatic aberration at both wide-angle and telephoto ends, often requiring a large number of lens elements and experiencing excessive correction and variation in telecentricity.
Innovation Solution
A projection lens design featuring at least two movable lens groups, with one group having a maximum moving amount and including a positive lens element, is arranged on the enlargement side relative to the diaphragm and moves toward the diaphragm from the telephoto end to the wide-angle end, satisfying specific conditional expressions to optimize lateral chromatic aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the zoom ratio is increased in high magnification zoom lenses, then the versatility and coverage range are improved, but lateral chromatic aberration becomes difficult to minimize at both wide-angle and telephoto ends
Solution Approach 1:
The patent applies local quality by using different glass materials with specific dispersion characteristics for different lens elements. Specifically, it employs at least one lens element with anomalous dispersion (Lang or Kurz characteristic) positioned at strategic locations within the lens group to correct lateral chromatic aberration locally, while other elements maintain standard dispersion properties. This localized approach allows high zoom ratio performance without excessive aberration correction throughout the entire lens structure.
Solution Approach 2:
The patent utilizes parameter changes by carefully selecting and adjusting the dispersion characteristics (partial dispersion ratio Pg,F and Abbe number Vd) of the glass materials. By changing these optical parameters to match specific conditions (Pg,F+0.00181Vd>0.652, 0.5<Vd<0.8, 1.25<Lr/L<3.44), the lens achieves effective lateral chromatic aberration correction across the entire zoom range while maintaining high versatility.
2Object-affected harmful factors
If the number of lens elements is increased to correct lateral chromatic aberration, then the aberration correction is improved, but the production cost and device complexity increase
Solution Approach 1:
Instead of increasing the number of lens elements, the patent achieves effective aberration correction by changing the optical parameters (dispersion characteristics) of existing elements. By selecting glass materials with specific Pg,F and Vd values and positioning them strategically, the lens corrects lateral chromatic aberration without requiring additional elements, thereby reducing device complexity and production cost.
3Stability of the object's composition
If a movable lens group is disposed in front of the diaphragm to suppress variation in telecentricity, then telecentricity stability is improved, but excessive correction by positive lens elements causes lateral chromatic aberration to occur on the plus side
Solution Approach 1:
The patent applies local quality by positioning lens elements with specific dispersion characteristics at precise locations within the lens group. By strategically placing anomalous dispersion elements at locations where they can most effectively counteract telecentricity variation without causing excessive correction, the lens achieves stable telecentricity while minimizing lateral chromatic aberration on the plus side.
Solution Approach 2:
The patent uses parameter changes by adjusting the dispersion characteristics of lens elements to balance telecentricity correction and lateral chromatic aberration control. By selecting glass materials with specific Pg,F and Vd values and optimizing their positions, the lens achieves the desired balance between telecentricity stability and aberration correction.
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 design effectively corrects lateral chromatic aberration across the entire zoom range with fewer lens elements and minimal telecentricity variation, enhancing the versatility and performance of the projection lens.
Implementation Method 1
a lens element made of a glass material having an anomalous dispersion characteristic has a feature that a graph representing a relation between a partial dispersion ratio and the Abbe number is greatly displaced from a straight line
Implementation Method 2
the glass material having an anomalous dispersion characteristic has a feature that a graph representing a relation between a partial dispersion ratio and the Abbe number is greatly displaced from a straight line
Data Source
AI summary
An object of the invention is to provide a projection lens capable of sufficiently correcting lateral chromatic aberration at both of the wide-angle end and the telephoto end, with an increased zoom ratio, a less number of lens elements, and less variation in telecentricity.