Multi-unit Optical System Aberration Control
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Solution Overview
Problem
Existing optical systems for image pickup apparatuses face challenges in miniaturizing the focus lens unit while maintaining high optical performance, particularly in suppressing aberration fluctuations during focusing, especially when the system has a large aperture.
Innovation Solution
The optical system comprises a configuration of a first lens unit with positive refractive power, a second lens unit with negative refractive power, a third lens unit with positive refractive power, and a fourth lens unit with positive refractive power, where the first and fourth lens units are fixed during focusing, and the second and third lens units are moved, allowing for independent movement to correct spherical aberration and curvature of field over a wide object distance range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the optical system is made to have a large aperture, then the light gathering ability and imaging brightness are improved, but the aberration fluctuations during focusing become difficult to suppress
Solution Approach 1:
The focus lens unit is divided into two separate lens units (second lens unit with negative refractive power and third lens unit with positive refractive power) instead of using a single focus lens unit. This segmentation allows independent movement of each unit to correct different types of aberrations, enabling effective aberration suppression even with large aperture while maintaining high imaging brightness
Solution Approach 2:
The patent specifies precise focal length relationships between lens units (|f2| < 0.5×|f0| and f3 < 1.5×|f0|) and movement amounts during focusing. By controlling these parameters within specific ranges, the system achieves both large aperture capability and aberration suppression through optimized optical path management
2Length of moving object
If the focus lens unit is miniaturized, then the overall lens length is reduced, but the aberration correction capability deteriorates
Solution Approach 1:
The focus lens unit is segmented into two smaller lens units (second and third lens units) that can be moved independently. This segmentation enables compact design with reduced overall length while maintaining effective aberration correction capability through coordinated movement of the divided units
Solution Approach 2:
Instead of reducing aberration correction through a single linear movement, the patent uses two-dimensional coordinated movement of two lens units with different refractive powers. The second lens unit (negative power) and third lens unit (positive power) move in opposite directions during focusing, enabling effective aberration control in a compact configuration
3Device complexity
If a single focus lens unit is used, then the device complexity is reduced, but the aberration fluctuation suppression during focusing becomes insufficient
Solution Approach 1:
The focus lens unit is divided into two lens units (second and third lens units) that move independently during focusing. This segmentation provides the additional degree of freedom needed to suppress both spherical aberration and curvature of field simultaneously, achieving superior aberration control compared to a single lens unit configuration
4Ease of manufacture
If the relationship between focal lengths of focus lens units is not properly set, then the optical system design is simplified, but the aberration suppression during focusing fails
Solution Approach 1:
The patent establishes specific parameter ranges for focal lengths (|f2| < 0.5×|f0| and f3 < 1.5×|f0|) and their relationships to the overall focal length f0. These parameter constraints provide clear design guidelines that ensure aberration suppression while maintaining design simplicity and manufacturability
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 corrects aberrations and miniaturizes the focus lens unit, enabling quick focusing and reducing the overall lens length while maintaining high optical performance even with a large aperture.
Implementation Method 1
The first lens unit includes a positive lens disposed closest to an object
Implementation Method 2
The fourth lens unit includes a negative lens disposed closest to an image plane
Data Source
AI summary
An optical system includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power. During focusing, the first lens unit and the fourth lens unit are fixed, and the second lens unit and the third lens unit are moved. The first lens unit includes a positive lens disposed closest to an object. The fourth lens unit includes a negative lens disposed closest to an image plane.