Close-Distance Correcting Lens System with Differing Travel Distances
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Solution Overview
Problem
Existing close-distance correction lens systems face challenges in maintaining optical performance and reducing aberration fluctuations, especially when focusing from infinity to closer distances, and they are not optimized for medium format SLR cameras with wider angle-of-view requirements.
Innovation Solution
A close-distance correction lens system with a positive first lens group and a negative second lens group, where the traveling distances differ during focusing, incorporating a cemented lens with specific Abbe number and refractive index conditions to minimize aberration fluctuations and ensure suitable optical performance for medium format SLR cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a part of the negative third lens group distant from the aperture diaphragm is arranged to function as an image-stabilizing lens group, then the lens system can provide image-stabilizing function, but abaxial decentration aberration inevitably and largely occurs when the image-stabilizing lens group is being decentered
Solution Approach 1:
A positive lens group is introduced as an intermediary element between the aperture diaphragm and the image-stabilizing lens group. This positive lens group acts as an optical mediator that compensates for the abaxial decentration aberration generated by the image-stabilizing lens group, enabling the system to maintain both image-stabilizing functionality and acceptable aberration levels
Solution Approach 2:
The patent applies local quality by assigning different functional characteristics to different regions of the lens system. The image-stabilizing lens group is positioned to provide shake correction, while a specific positive lens group is strategically placed to correct the aberrations introduced by the decentered image-stabilizing group, creating localized functional zones that work together
2Adaptability or versatility
If all three lens groups (positive first lens group, negative second lens group, and positive third lens group) are arranged to move independently for focusing operation, then the lens system can focus from infinity to close distance, but the focusing mechanism becomes large and complicated
Solution Approach 1:
The patent merges the focusing functions of multiple lens groups by making them move in a coordinated manner rather than independently. The positive first lens group and negative second lens group are coupled to move together as a unit, reducing the number of independent actuators needed while still achieving the required focusing range from infinity to close distance
Solution Approach 2:
The lens groups are designed with multi-functionality where they simultaneously contribute to both focusing and image stabilization operations. The positive third lens group serves dual purposes in close-distance correction and image stabilization, reducing the need for separate dedicated components
3Device complexity
If the entire lens system is designed to integrally advance for focusing operation, then the lens system structure is simple, but aberration fluctuations become larger at closer distances
Solution Approach 1:
The lens system is segmented into multiple functional groups (positive first lens group, negative second lens group, positive third lens group) that can move relative to each other. This segmentation allows different parts of the system to move at different rates during focusing, correcting aberration fluctuations at close distances while maintaining a relatively simple overall structure
Solution Approach 2:
The patent introduces dynamic movement characteristics where lens groups move at different velocities and distances during focusing operations. The positive first lens group and negative second lens group move together, while the positive third lens group moves independently to correct close-distance aberrations, creating a dynamic focusing system that adapts to different object distances
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 system achieves simplified focusing mechanisms, reduced aberration fluctuations, and sufficient backfocus for medium format SLR cameras, maintaining excellent optical performance across a wide range of distances and angles of view.
Implementation Method 1
the correcting of a changed image-position due to camera shake (image shake) is performed by decentering a part of the photographing lens system (image-stabilizing (anti-shake/image-blur correcting) lens group) in a direction orthogonal to the optical axis
Implementation Method 2
incorporating a cemented lens with specific Abbe number and refractive index conditions to minimize aberration fluctuations
Data Source
AI summary
A close-distance correcting lens system includes a positive first lens group and a negative second lens group, wherein traveling distances of the first lens group and the second lens group toward the object side differ from each other when carrying out a focusing operation on an object at infinity to an object at a close distance. The first lens group includes a positive first sub lens group, a negative second sub lens group, a diaphragm, and a positive third sub lens group, in that order from the object side. The second sub lens group includes an image-stabilizing lens group which is arranged to move in a direction orthogonal to the optical axis to change an imaging position of the object image to thereby correct any image shake of the object image.