Variable Focal Length Lens System Aberration Control
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving a small lens diameter and lightweight configuration while maintaining effective aberration correction across varying focal lengths, particularly due to issues with off-axis light fluxes and aberration control in wide and telescopic end states.
Innovation Solution
A variable focal length lens system with a configuration of positive, negative, positive, and positive power lens groups, where the distances between these groups are adjusted to optimize lens positioning, including an aperture stop between the second and third lens groups, and incorporating specific focal length ratios and curvature relationships to minimize lens diameter and correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the power of the second lens group is increased to reduce size and achieve higher magnification ratio, then the lens diameter can be reduced, but aberration correction becomes insufficient and off-axis aberration correction becomes difficult
Solution Approach 1:
The lens system is divided into four distinct lens groups with specific power distributions. The second lens group has negative power and is separated from the first lens group by a first distance, while the third lens group has positive power and is separated from the second lens group by a second distance. This segmentation allows each group to perform specific functions: the first group collects light, the second group controls magnification, the third group corrects aberrations, and the fourth group finalizes focusing, thereby maintaining aberration correction even with reduced overall lens diameter.
Solution Approach 2:
The aperture stop acts as an intermediary element positioned between the second and third lens groups. It controls the light flux and helps manage off-axis aberrations by selectively blocking certain light paths. The specific spacing relationships (first distance and second distance) are designed to optimize the interaction between these groups, allowing the aperture stop to effectively correct off-axis aberrations without requiring excessive lens diameter.
2Volume of moving object
If the lens diameter of the first lens group is reduced to make the lens compact, then the overall size decreases, but off-axis light fluxes shift away from the optical axis resulting in insufficient light reach
Solution Approach 1:
The lens system employs variable spacing between lens groups that can be adjusted during zooming operations. The first distance between the first and second lens groups, and the second distance between the second and third lens groups, are designed to be variable. This dynamic adjustment allows the system to maintain optimal light flux distribution across different focal lengths, preventing off-axis light from being lost while keeping the lens compact at each zoom position.
Solution Approach 2:
The patent specifies precise parameter relationships: the first distance is set to be equal to or greater than the focal length of the first lens group, and the second distance is set to be equal to or greater than the focal length of the third lens group. These parameter changes optimize the optical paths to ensure that off-axis light fluxes are properly directed through the aperture stop and onto the image sensor, maintaining illumination intensity while reducing lens diameter.
3Adaptability or versatility
If a standard zoom lens configuration is used to achieve wide angle to telephoto range, then the focal length variation is achieved, but the lens diameter and weight increase
Solution Approach 1:
The lens system employs an asymmetric four-group configuration with specific power distributions: the first lens group has positive power for light collection, the second lens group has negative power for magnification control, the third lens group has positive power for aberration correction, and the fourth lens group has positive power for final focusing. This asymmetric arrangement optimizes the optical paths for both wide-angle and telephoto modes, achieving a zoom ratio of approximately 6x or higher while maintaining a compact diameter through efficient use of optical space.
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 and lightweight lens system with improved aberration correction and reduced lens diameter, effectively addressing the challenges of off-axis light fluxes and aberration control across the zoom range.
Implementation Method 1
a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, and a fourth lens group having positive power sequentially arranged from a side where an object is present
Data Source
AI summary
A variable focal length lens system including: a first lens group having positive power; a second lens group having negative power; a third lens group having positive power; and a fourth lens group having positive power sequentially arranged from a side where an object is present. An aperture stop is disposed between the second and third lens groups. The first to fourth lens groups are so moved that the distance between the first and second lens groups increases, the distance between the second and third lens groups decreases, and the distance between the third and fourth lens groups decreases when a lens position setting is changed from a wide angle end state to a telescopic end state. The third lens group includes a negative lens and a positive lens disposed on the image side thereof. The variable focal length lens system satisfies the conditional expression, 0.35<f3/|f3a|<0.8.