Imaging Lens Inner Focus Aberration Control
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Solution Overview
Problem
There is a demand for miniaturizing imaging lenses that use the inner focus method while reducing fluctuations in aberrations caused by focusing operations, as existing lenses are either too long or have excessive aberration fluctuations.
Innovation Solution
The imaging lens configuration consists of a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, where the second lens group moves along the optical axis for focusing, with specific Abbe's number and focal length conditions to minimize aberrations and lens system length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the second lens group is constituted by a single lens or two lenses, then the lens system can be miniaturized, but fluctuations in aberrations caused by focusing operations increase
Solution Approach 1:
The patent applies parameter changes by carefully selecting the Abbe's number of the positive lens material within the second lens group to satisfy conditional formula (1). This material parameter selection enables the lens to maintain compact size while reducing aberration fluctuations during focusing operations.
2Length of moving object
If the total length of the lens system is excessively short with respect to the focal length, then miniaturization is achieved, but various aberrations cannot be corrected
Solution Approach 1:
The patent applies parameter changes by establishing conditional formula (2) that defines the appropriate range for the ratio of total lens length to focal length. This ensures the lens system maintains a compact form factor while preserving sufficient length for effective aberration correction across all focusing positions.
3Speed
If the second lens group moves along the optical axis for focusing, then focusing speed is improved, but aberration fluctuations increase
Solution Approach 1:
The patent applies parameter changes by selecting specific Abbe's number ranges for the positive lens material in the second lens group. This material parameter optimization enables the moving lens group to achieve fast focusing while minimizing aberration fluctuations through the inherent optical properties of the selected materials.
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 achieves miniaturization and reduced aberration fluctuations, enabling high optical performance and compact imaging apparatuses with improved focusing speed and reduced load on the drive system.
Implementation Method 1
a second lens group G2 having a negative refractive power... the second lens group moving along the optical axis from the object side to the image side... to change focus from an object at infinity to an object at a proximal distance
Data Source
AI summary
An imaging lens is constituted by, in order from the object side to the image side, a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a positive refractive power. The second lens group has at least one positive lens and at least one negative lens. The second lens group moves along the optical axis from the object side to the image side while the first lens group and the third lens group are fixed with respect to an image formation plane to change focus from an object at infinity to an object at a proximal distance. Predetermined Conditional Formulae (1) and (2) are satisfied.