Zoom Lens Length Reduction via Prism and Moving Groups
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Solution Overview
Problem
Conventional bending type zoom lenses are designed to reduce thickness but not overall length, which is essential for compact imaging devices like digital still cameras and portable cellular phones, as they primarily focus on radial size reduction rather than length reduction.
Innovation Solution
A zoom lens configuration with a fixed first lens group and a moving third and fourth lens group, where the second lens group includes an optical-path bending prism without refractive power, allowing the positive third and negative fourth lens groups to be arranged behind the prism without a fixed positive lens group, thereby reducing the overall length while maintaining optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed lens group is arranged between the optical-path bending prism and the zooming group, then optical characteristics are maintained, but the overall length increases
Solution Approach 1:
The patent removes the fixed lens group from the optical path between the prism and zooming group, extracting a component that was causing excessive length. The zooming group is placed directly behind the prism, eliminating the need for the intermediate fixed lens group while maintaining optical performance through alternative lens configurations.
Solution Approach 2:
The patent reconfigures the lens arrangement by changing the spatial dimension of the optical path. Instead of having a fixed lens group in a specific position between the prism and zooming group, the system uses a different spatial arrangement where the zooming group is positioned directly behind the prism, achieving length reduction through dimensional reorganization.
2Length of stationary object
If the optical path is bent at approximately 90 degrees by arranging a prism in the first lens group, then thickness is reduced, but the overall length is not sufficiently reduced
Solution Approach 1:
The patent divides the lens system into distinct functional segments: the first lens group with the prism for thickness reduction, and the second lens group (zooming group) positioned directly behind it for length optimization. This segmentation allows each part to optimize its function independently, with the prism handling thickness and the zooming group arrangement handling length reduction.
Solution Approach 2:
The patent inverts the conventional arrangement by placing the zooming group directly behind the prism rather than having a fixed lens group in between. This inversion of the standard configuration allows the system to achieve both thickness and length reduction simultaneously by eliminating the intermediate fixed lens group.
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 reduces the overall length of the zoom lens while preserving optical performance, addressing the limitation of conventional designs that prioritize thickness reduction over length reduction.
Implementation Method 1
the optical path is bent at approximately 90 degrees by arranging a prism in the first lens group
Data Source
AI summary
A zoom lens includes, in order from an object side, a first lens group fixed upon zooming and wholly having a negative refractive power, a second lens group formed by an optical-path bending prism fixed upon zooming and, a third lens group allowed to move upon zooming and wholly having a positive refractive power, a fourth lens group allowed to move upon zooming and wholly having a negative refractive power, and a fifth lens group fixed upon zooming and wholly having a positive refractive power. By arranging a zooming group having the positive third and negative fourth lens groups without arranging a positive fixed lens group in back of the prism, the overall length can be easily reduced as compared to the structure arranging a fixed lens group between a prism and a zooming group.