Compact Wide-Angle Zoom Lens With Final-Unit Chromatic Correction
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving high resolution uniformly across the angle of view, correcting chromatic aberration, especially lateral chromatic aberration at wide angles, while maintaining a wide angle of view, high zoom ratio, and small size.
Innovation Solution
A zoom lens design comprising a first fixed lens unit with positive refractive power, at least three movable lens units with specific refractive powers, and a final fixed lens unit with a positive lens, adhering to certain Abbe number and refractive index conditions, to correct aberrations and maintain a high zoom ratio and small size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of lenses is reduced to reduce zoom lens size, then device complexity and size are improved, but chromatic aberration and various errors increase
Solution Approach 1:
The patent applies parameter changes by carefully selecting the Abbe number (vd) and refractive index (Nd) of the positive lens in the final lens unit. The specific constraints (62 ≤ vd ≤ 81.54 and 2.24 ≤ Nd + 0.01vd) are designed to optimize the balance between reducing lens count/size and controlling chromatic aberration. This parameter optimization allows the patent to achieve both compact size and effective aberration correction without simply increasing the number of lenses.
2Adaptability or versatility
If a wider angle of view and higher zoom ratio are acquired, then adaptability is improved, but it becomes difficult to correct various aberrations especially lateral chromatic aberration at wide-angle end
Solution Approach 1:
The patent applies local quality by assigning specific optical properties to the positive lens in the final lens unit that is closest to the image side. By constraining the Abbe number and refractive index of this particular lens element, the patent locally optimizes the correction of lateral chromatic aberration at the wide-angle end. This localized optimization allows the system to achieve wide angle of view and high zoom ratio while maintaining aberration correction performance.
3Device complexity
If refractive power of each lens unit or single lens is increased to reduce lens count, then device complexity is improved, but chromatic aberration and various errors increase
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the refractive power distribution and specifically constraining the Abbe number and refractive index of the positive lens in the final lens unit. This allows the patent to maintain higher refractive power in individual elements (reducing total lens count) while controlling chromatic aberration through carefully selected material parameters.
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 small-sized zoom lens with a wide angle of view, high zoom ratio, and excellent optical performance by effectively correcting aberrations, particularly lateral chromatic aberration, across various focal lengths.
Implementation Method 1
a positive lens closest to the image side in elements having a refractive power in the final lens unit... vdp represents an Abbe number with respect to a d-line of the positive lens, Ndp represents a refractive index with respect to the d-line of the positive lens
Implementation Method 2
correcting chromatic aberration, especially lateral chromatic aberration at wide angles... effectively correcting aberrations, particularly lateral chromatic aberration, across various focal lengths
Data Source
AI summary
A zoom lens includes, from an object side to an image side, a positive first lens unit configured not to move for zooming, at least three movable lens units configured to move for zooming, and a positive final lens unit closest to the image side in lens units and configured not to move for zooming. In the at least three movable lens units, a lens unit closest to the image side has a positive power, and a lens unit second closest to the image side has a negative power. The first lens unit includes a first sub unit closest to the object side and configured not to move for focusing and a second sub unit configured to move for focusing. The final lens unit includes a positive lens closest to the image side in elements having a refractive power in the final lens unit. Predetermined inequalities are satisfied.