Inner Focusing Macro Lens Aberration Compensation
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Solution Overview
Problem
Prior art inner focusing macro lenses face difficulties in compensating for spherical, astigmatism, and comatic aberrations across the entire object distance from infinity to proximity, especially when designed for a smaller F-number, leading to increased aberration variations.
Innovation Solution
An inner focusing macro lens design with a first lens group of positive refractivity, a second lens group moved toward the imaging plane, and a third lens group moved toward the object, featuring at least four positive lens pieces and one negative lens piece in the first group, along with a trailing lens set of negative refractivity, to effectively compensate for aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inner focusing system is used to enable quick focusing, then focusing speed is improved, but spherical aberration and other optical aberrations increase significantly
Solution Approach 1:
The lens system is divided into multiple lens groups (first through fourth lens groups) with different refractivities and functions. The first lens group (positive) and second lens group (negative) work together to control spherical aberration, while the third lens group (positive) is specifically designated for focusing operations. This segmentation allows the focusing function to be isolated to a specific group, reducing the impact on overall optical quality.
Solution Approach 2:
Different lens groups are assigned different refractivities and specific functions: the first lens group has positive refractivity for overall convergence, the second has negative refractivity for aberration correction, and the third has positive refractivity specifically for focusing. This local differentiation of optical properties allows each group to optimize its specific function while minimizing negative impacts on other aspects.
2Illumination intensity
If the aperture ratio is increased to enable better light gathering, then illumination is improved, but aberration compensation becomes difficult across the entire object distance range
Solution Approach 1:
The lens system employs a composite structure with lens groups of opposite refractivities (positive and negative) combined in a specific sequence. The first positive lens group and second negative lens group form a composite optical system that balances light gathering capability with aberration correction, allowing large aperture operation while maintaining optical quality across the focusing range.
Solution Approach 2:
The patent specifies particular parameter ranges for the lens groups, including the ratio of focal lengths (0.3 ≤ f1/f ≤ 0.7 and -0.5 ≤ f2/f ≤ -0.2), to optimize the balance between aperture ratio and aberration control. By carefully controlling these optical parameters, the system achieves both high illumination and effective aberration compensation.
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 design achieves a large aperture ratio with an F-number of 2.5 or smaller while maintaining a compact size and reducing aberration variations, particularly in spherical aberration, across the entire object distance range.
Implementation Method 1
the first lens group of positive refractivity, the second lens group of negative refractivity, the third lens group of positive refractivity
Data Source
AI summary
The present invention is directed to an inner focusing macro lens that has a large aperture ratio as expressed by 2.5 or even smaller in F-number and still remains compact, and that is adapted to compensate for spherical aberration, astigmatism, and comatic aberration during photographing throughout the entire object distance ranging from infinity to proximity for an up to 1:1-magnification image. The inner focusing macro lens has the leading or first lens group of positive refractivity, the second lens group of negative refractivity, the third lens group of positive refractivity, and the trailing lens set succeeding to the third lens group in sequence from a position closest to an object being photographed. During focusing from a point infinitely far to that as proximal as desired, the first lens group is static while the second lens group is moved toward the imaging plane, and the third lens group is moved toward the object. The first lens group has at least four lens pieces of comprehensively positive refractivity and at least one lens piece of negative refractivity, and three of the lens pieces closest to the object in the first lens group are of positive refractivity.