Zoom Lens Rear Group Segmentation for Image Stabilization
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Solution Overview
Problem
Existing zoom lenses face challenges in reducing the size and weight of the image stabilizing lens unit while maintaining high optical performance, suppressing aberrations, and minimizing sensitivity to assembly errors during image stabilization.
Innovation Solution
A zoom lens configuration with four or five lens groups, including a rearmost lens group composed of a front group with positive refractive power, a middle group with negative refractive power, and a rear group with positive refractive power, where the air spaces between these groups remain constant during magnification and focusing, allowing for image stabilization by shifting only the middle group perpendicular to the optical axis, and satisfying specific condition expressions to optimize refractive power and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the image stabilizing lens group is provided with strong refractive power to increase sensitivity and reduce shift amount, then the sensitivity of image shift is improved, but decentering coma increases and assembly error sensitivity increases
Solution Approach 1:
The rearmost lens group is divided into three sub-groups (front group with positive power, middle group with negative power serving as image stabilizing group, and rear group with positive power). This segmentation allows the image stabilizing function to be separated from the main focusing function, enabling optimized power distribution that reduces decentering coma while maintaining sensitivity.
Solution Approach 2:
Different parts of the rearmost lens group are assigned different refractive powers and functions: the front group (positive power) and rear group (positive power) handle focusing and aberration correction, while the middle group (negative power) specifically handles image stabilization. This local differentiation optimizes each subgroup's contribution to overall performance.
2Weight of moving object
If the front group of the rearmost lens group is provided with strong positive refractive power to reduce incident ray height on the image stabilizing lens group, then the size and weight of the image stabilizing lens group is reduced, but spherical aberration, coma aberration, and chromatic aberration increase
Solution Approach 1:
The rearmost lens group is segmented into three sub-groups with different refractive powers. The front group provides strong positive power to reduce ray height and size, while the rear group provides additional positive power specifically to correct the aberrations introduced by the front group, creating a balanced system.
Solution Approach 2:
The rearmost lens group uses a composite configuration of multiple lens elements with different refractive powers and materials. The combination of positive power lenses (front and rear groups) with the negative power middle group creates a composite optical system that achieves both size reduction and aberration correction.
3Object-generated harmful factors
If the image stabilizing lens group is provided with weak refractive power to suppress decentering coma and reduce sensitivity to assembly errors, then aberration suppression is improved, but the amount of shift of the image stabilizing lens group increases
Solution Approach 1:
The rearmost lens group is divided into three functional sub-groups, allowing the image stabilizing middle group to have moderate power while the front and rear groups compensate for any insufficient stabilization effect through their focusing and aberration correction functions.
Solution Approach 2:
The rearmost lens group serves multiple functions: the front group reduces ray height, the middle group provides image stabilization, and the rear group corrects aberrations. This multi-functionality allows the system to achieve effective image stabilization without requiring the stabilizing group to have excessive power.
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 results in a compact, lightweight zoom lens with suppressed variation of aberrations during image stabilization, achieving high optical performance and reduced sensitivity to assembly errors, while maintaining a constant aperture across the zoom range.
Implementation Method 1
image stabilization is effected by shifting only the middle group in directions perpendicular to the optical axis
Implementation Method 2
a rearmost lens group disposed at the most image side position of the entire system and having a positive refractive power
Data Source
AI summary
A zoom lens consists of four or five lens groups, consisting of, in order from the object side, a positive first group a negative second group, one or two middle groups including a positive mp group, and a positive rearmost group at the most image-side position of the entire system. Zooming is effected by changing all distances between the adjacent groups. The rearmost group consists of, in order from the object side, a positive front group, a negative middle group, and a positive rear group. Air spaces between the front and middle groups, and between the middle and rear groups are constant during zooming and focusing. The front group includes two positive lenses and one negative lens. Image stabilization is effected by shifting the middle group perpendicularly to the optical axis. The rear group includes one positive lens and two negative lenses. The zoom lens satisfies a given condition expression.