Zoom Lens Aberration Control via Segmented Movable Groups
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Solution Overview
Problem
Conventional zoom lenses that form intermediate images face challenges in maintaining high optical performance across the zooming range due to significant aberration fluctuations, especially when attempting to increase the angle of view by shortening the focal length, leading to large magnification side lens sizes and increased aberration fluctuations.
Innovation Solution
A zoom lens system that forms an intermediate image with multiple lens groups, where at least two movable lens groups adjust their spacings along the optical axis during zooming, and the final lens group closest to the reduction side remains stationary, satisfying specific conditional expressions to control aberration fluctuations and maintain telecentricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the focal length is shortened to increase the angle of view, then the angle of view is improved, but the magnification side lens diameter becomes excessively large and aberration fluctuations increase
Solution Approach 1:
The zoom lens is divided into multiple lens groups (first through fourth lens groups) with different functions. The first lens group has positive refractive power and contributes to angle of view, the second lens group with negative refractive power controls aberrations, the third lens group with positive refractive power provides intermediate image formation, and the fourth lens group with negative refractive power corrects residual aberrations. This segmentation allows each group to be optimized for its specific function, enabling wide angle of view while controlling lens diameter and aberration fluctuations.
Solution Approach 2:
Different regions of the optical system are assigned different optical properties. The first lens group uses positive refractive power for wide angle, the second uses negative for aberration control, the third uses positive for intermediate imaging, and the fourth uses negative for correction. This local differentiation of optical qualities allows the system to achieve wide angle of view without excessive lens diameter growth and with controlled aberration fluctuations.
2Duration of action of moving object
If the focal length is shortened to increase the angle of view, then the angle of view is improved, but aberration fluctuations become large
Solution Approach 1:
The aberration correction function is segmented across multiple lens groups. The second lens group with negative refractive power primarily controls aberration fluctuations, while the fourth lens group with negative refractive power provides additional correction. This segmentation of the correction function across different groups allows effective aberration control even when the focal length is shortened for wide angle of view.
Solution Approach 2:
Specific lens groups are assigned specific aberration control functions based on their refractive power and position. The second lens group (negative power) and fourth lens group (negative power) are strategically positioned to correct aberrations introduced by the first and third lens groups. This local assignment of correction functions maintains low aberration fluctuations across the zoom range.
3Duration of action of moving object
If a zoom lens forms an intermediate image to achieve wide angle, then the angle of view is improved, but fluctuation in aberrations becomes large making it difficult to maintain high optical performance
Solution Approach 1:
The intermediate image formation is segmented into the third lens group with positive refractive power, which is specifically designed for this function. By isolating the intermediate imaging function to a dedicated group, the other groups can be optimized for their respective functions (wide angle, aberration control, correction), resulting in better overall optical performance consistency across the zoom range.
Solution Approach 2:
The third lens group is assigned the specific local quality of positive refractive power for intermediate image formation, while the second and fourth groups provide negative refractive power for aberration control. This local differentiation ensures that intermediate image formation does not compromise overall optical performance consistency.
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 configuration effectively suppresses aberration fluctuations while achieving a wide angle of view, allowing for a compact magnification side lens diameter and improved optical performance throughout the zooming range.
Implementation Method 1
a zoom lens forms an intermediate image at a position conjugate to a reduction side imaging plane and forms the intermediate image again on a magnification side imaging plane
Data Source
AI summary
A zoom lens forms an intermediate image at a position conjugate to a reduction side imaging plane and forms the intermediate image again on a magnification side imaging plane. The zoom lens includes a plurality of lens groups including at least two movable lens groups, which move by changing spacings between the groups adjacent to each other in a direction of an optical axis during zooming, at a position closer to the reduction side than the intermediate image. Among the plurality of lens groups, a final lens group closest to the reduction side has a positive refractive power, and remains stationary with respect to the reduction side imaging plane during zooming. The zoom lens satisfies predetermined conditional expressions (1) and (2) about the focal lengths of the movable lens groups.