Compact Zoom Lens with Fixed First Unit for Large Aperture
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving a balance between miniaturization, large aperture, and high optical performance, as previous designs either struggle to miniaturize when image sensors grow, compromise on aperture for compact size, or struggle to reduce weight while maintaining optical quality.
Innovation Solution
A zoom lens configuration with a first lens unit having positive refractive power, a front group with negative refractive power, and an aperture stop, where the first lens unit is fixed relative to the image plane during focusing and zooming, and specific inequalities are satisfied to optimize refractive indices and air intervals, allowing for a compact design with a large aperture while maintaining high optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of converter lenses is increased to achieve telephoto performance, then telephoto capability is improved, but the lens becomes larger and heavier
Solution Approach 1:
The patent combines multiple lens units with different refractive powers (positive first lens unit, negative second lens unit, positive third lens unit) into a single integrated zoom lens system. This merging approach achieves telephoto capability without requiring separate converter lenses, thereby reducing overall weight while maintaining the desired optical performance across the zoom range.
2Length of stationary object
If lens units are optimized for miniaturization, then compact size is achieved, but aperture size is reduced
Solution Approach 1:
The patent applies local quality by assigning different refractive powers and optical characteristics to different lens units. The first lens unit has positive refractive power with specific constraints on its focal length ratio, the second lens unit has negative refractive power, and the third lens unit has positive refractive power. This localized optimization of optical properties allows the lens to maintain a compact overall length while ensuring sufficient aperture size for high optical performance.
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the focal length ratios (0.30 < |f2/fw| < 0.50 and 0.45 < |f3/fw| < 0.70) and refractive powers of individual lens units. These parameter optimizations enable the lens to achieve miniaturization while maintaining large aperture capability, resolving the contradiction between compact size and aperture area.
3Ease of operation
If the first lens unit is made movable during focusing, then focusing flexibility is improved, but structural complexity increases
Solution Approach 1:
The patent segments the zoom lens into distinct functional units: a first lens unit with positive refractive power that remains fixed during focusing, a second lens unit with negative refractive power, and a third lens unit with positive refractive power. By fixing the first lens unit during focusing operations, the patent simplifies the overall structure and reduces mechanical complexity while maintaining effective focusing capability through the movement of other lens units.
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 enables a compact zoom lens with a large aperture that effectively corrects various aberrations and reduces weight, ensuring high optical performance across the entire zoom range.
Implementation Method 1
a first lens unit having a positive refractive power
Implementation Method 2
a front group including one or two lens unit and having a negative refractive power as a whole
Data Source
AI summary
A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a front group including one or two lens unit and having a negative refractive power as a whole, and a rear group including an aperture stop and one or more lens unit. Each distance between adjacent lens units changes during zooming. The first lens unit is fixed relative to an image plane during focusing. The first lens unit includes a positive lens disposed closest to an object. At least four lens units move during zooming from a wide-angle end to a telephoto end. At the telephoto end, a combined refractive power from the positive lens to a lens disposed closest to an image in the front group is negative. A predetermined inequality is satisfied.