Zoom Lens with Prism and Meniscus Element for Compact Cameras
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Solution Overview
Problem
Conventional magnification varying optical systems for digital still cameras face challenges in reducing size and thickness while maintaining high performance, as they often require additional aspherical surfaces or increased length to correct off-axial aberrations, which hinders size reduction and performance enhancement.
Innovation Solution
A magnification varying optical system comprising multiple lens units with specific optical power arrangements and movements, including a first lens unit with negative power and an optical prism, a second lens unit with positive power, a third lens unit with negative power, and a fourth lens unit with positive power, where the distances between these units change during zooming to maintain performance and reduce overall length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a prism with a concave surface on the object side is used in the first lens unit, then the overall length can be reduced, but off-axial aberration is caused requiring additional aspherical surfaces or increased length to correct
Solution Approach 1:
The patent introduces a meniscus lens with a convex surface toward the object as an intermediary element between the prism and the second lens unit. This intermediary lens serves as a mediator that corrects the off-axial aberration generated by the prism's concave surface, allowing the system to maintain a reduced overall length without compromising aberration correction performance
Solution Approach 2:
The patent employs parameter changes by setting specific focal length ratios (|f_GR1_o/fm| between 0.3 and 0.6) and configuring the meniscus lens with specific optical power relationships (f_L1/f_men ≥ 0.1). These parameter optimizations enable the system to achieve both compact size and effective aberration correction without requiring additional aspherical surfaces or increased length
2Reliability
If many aspherical surfaces are provided to correct off-axial aberration, then aberration correction is improved, but the overall length cannot be sufficiently reduced
Solution Approach 1:
The patent extracts the aberration correction function from the prism itself and assigns it to a dedicated meniscus lens element. By separating the light-bending function (prism) from the aberration correction function (meniscus lens), the system achieves effective correction without requiring the prism to be made complex with multiple aspherical surfaces, thus maintaining a compact overall length
3Length of moving object
If the distance from the first lens unit to the second lens unit is reduced during zooming, then the overall length is reduced, but it becomes difficult to maintain aberration correction performance
Solution Approach 1:
The patent employs dynamic adjustment mechanisms where the first, second, and third lens units move along the optical axis during zooming operations. The distance relationships between lens units are dynamically optimized at each focal length position, allowing the system to maintain aberration correction performance across the entire zoom range while achieving a reduced overall length in the telephoto state
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 achieves a high-performance, downsized magnification varying optical system that effectively corrects aberrations and ensures a long focal length without increasing the overall length, allowing for efficient mounting on digital still cameras and reducing the camera's thickness and size.
Implementation Method 1
a magnification varying optical system has been developed the overall length of which is reduced by bending the light ray traveling from the object side to the image side, by an optical prism
Implementation Method 2
a plurality of lens units include, from the object side to the image side, at least: a first lens unit having negative optical power and including an optical axis changing element that changes the optical axis
Data Source
AI summary
A magnification varying optical system that directs light from an object to an image sensor includes in order from the object side: a first lens unit having negative optical power and including an optical axis changing element that changes the optical axis; a second lens unit having positive optical power and including three lens elements; a third lens unit having negative optical power; and a fourth lens unit having positive optical power. In this magnification varying optical system, in magnification varying from the wide-angle end to the telephoto end, the first lens unit is stationary, the distance from the first lens unit to the second lens unit decreases, and the distance from the third lens unit to the fourth lens unit increases. The magnification varying optical system satisfies the specified conditions.