Variable Magnification Lens Group Weight Reduction
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Solution Overview
Problem
Existing variable magnification optical systems for cameras are not sufficiently lightweight, which affects their performance and size, particularly in focusing mechanisms.
Innovation Solution
A variable magnification optical system configuration that includes a first lens group with positive refractive power, a negative lens group, a positive lens group with an aperture stop, and a focusing group, where the distances between these groups change to achieve varying magnification and focusing, with the focusing group being a single lens component and the positive lens group having a front and rear group with specific refractive powers and air distances, allowing for aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a conventional variable magnification optical system is used, then magnification can be varied, but the focusing group is not sufficiently lightweight
Solution Approach 1:
The optical system is divided into four distinct lens groups (first positive, second negative, third positive, fourth positive) with specific functional assignments. The focusing group is isolated as a separate movable unit between the second and third groups, allowing independent optimization of its weight and focusing function without compromising the overall aberration correction capability of the complete system.
Solution Approach 2:
Different regions of the optical system are assigned different refractive powers and functional roles. The first and third groups have positive refractive power while the second has negative refractive power. The focusing group specifically uses positive refractive power and is positioned to move only during focusing operations, enabling localized optimization of weight and function.
2Object-affected harmful factors
If the focusing group is made lightweight, then autofocus quietness improves, but aberration correction may be compromised
Solution Approach 1:
The focusing group is segmented as a独立的 movable unit containing only the necessary lens elements for focusing (the third positive lens group). This segmentation allows the focusing group to be minimized in mass for quiet autofocus operation, while the remaining lens groups (first, second, and fourth) stay stationary to maintain aberration correction.
Solution Approach 2:
Multiple lens groups with different refractive powers (first positive, second negative, fourth positive) are merged into a fixed composite structure that remains stationary during focusing. This merged stationary structure maintains comprehensive aberration correction while the lightweight third group moves independently for focusing, combining the benefits of both approaches.
3Adaptability or versatility
If lens groups are moved for magnification change, then magnification varies, but the lens barrel size may increase
Solution Approach 1:
The optical system employs dynamic movement of lens groups along the optical axis to achieve magnification variation. The first positive lens group moves during both magnification change and focusing operations, while the second negative lens group moves primarily for magnification change. This dynamic arrangement allows a compact 4.1x magnification range to be achieved within a controlled lens barrel length of approximately 70mm.
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 configuration results in a lightweight focusing group, improved aberration correction, and a compact optical system with high quietness during autofocus, enabling faster and more precise magnification changes without increasing the lens barrel size.
Implementation Method 1
a first lens group having a positive refractive power; a negative lens group having a negative refractive power; a positive lens group which has a positive refractive power... when varying magnification, the first lens group moves with respect to an image plane, a distance between the first lens group and the negative lens group is changed
Data Source
AI summary
A variable magnification optical system includes: a first lens group having a positive refractive power and arranged closest to an object; a negative lens group having a negative refractive power and arranged closer to an image than the first lens group; a positive lens group which has a positive refractive power, which includes at least one lens that moves integrally with an aperture stop, and which is arranged closer to the image than the negative lens group; and a focusing group arranged between the negative lens group and the positive lens group, wherein when varying magnification, the first lens group moves with respect to an image plane, the distance between the first lens group and the negative lens group is changed, and the distance between the negative lens group and the positive lens group is changed, wherein when focusing, the distance between the focusing group and a lens arranged at a position to face an object-side of the focusing group is changed, and the distance between the focusing group and a lens arranged at a position to face an image-side of the focusing group is changed, wherein the focusing group is constituted by a single lens component, wherein the positive lens group is constituted by a front group having a positive refractive power and a rear group having a negative refractive power, and the distance between the front group and the rear group is the largest air distance among air distances in the positive lens group, and wherein the rear group is constituted by two lens components.