Optical System with Segmented Lens Units for Quick Focusing
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Solution Overview
Problem
Existing macro lens systems face issues with varying aberration and increased optical member sizes due to strong refractive power in the focusing lens unit, making quick focusing and high optical performance challenging, especially in short-range imaging applications.
Innovation Solution
An optical system comprising a first lens unit with positive refractive power and a second lens unit with negative refractive power, where the second lens unit moves towards the image side during focusing, while the first lens unit remains stationary, satisfying specific conditional expressions to control aberrations and maintain compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the refractive power of the focus lens unit is increased to achieve quick focusing, then the focusing speed is improved, but the degree of aberration varies excessively with focusing
Solution Approach 1:
The optical system divides the focusing function into two separate lens units: the first lens unit (positive refractive power) and the second lens unit (negative refractive power). Each lens unit contributes to the overall focusing action, allowing the system to achieve quick focusing while maintaining aberration consistency through the combined effect of both units rather than relying on a single strong-power lens unit
2Speed
If the focusing lens unit has strong negative refractive power to achieve quick focusing, then the focusing speed is improved, but the sizes of optical members on the image side increase
Solution Approach 1:
The focusing function is segmented between two lens units with different refractive power characteristics. The first lens unit (positive) and second lens unit (negative) work together to provide the necessary focusing power, allowing the system to achieve quick focusing without requiring a single lens unit with excessively strong negative refractive power that would increase optical member sizes
Solution Approach 2:
The system utilizes conditional expressions that define specific ranges for the ratio of focal lengths (|f1/f2| between 3.00 and 3.50) and the product of focal length and F-number (|f2×F| between 15.00 and 25.00). These parameter constraints ensure that the lens units have appropriate refractive powers to achieve quick focusing while maintaining compact optical member dimensions
3Speed
If a lens unit is moved for focusing to achieve quick focusing action, then the focusing speed is improved, but the device complexity increases
Solution Approach 1:
The focusing mechanism is segmented such that only specific lens units (the first and second lens units) are moved during focusing, while other lens units remain stationary. This segmentation reduces the number of moving parts compared to moving the entire lens system, achieving quick focusing action with reduced mechanical complexity
Solution Approach 2:
The system employs dynamic focusing where the distance between consecutive lens units changes during focusing operations. The first lens unit is moved toward the image side when focusing from infinity to short distance, and the second lens unit is moved when focusing from short distance to intermediate distance, creating a dynamic adjustment mechanism that optimizes focusing speed while maintaining structural simplicity
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 high optical performance, quick focusing, and suitable short-range imaging capabilities while maintaining a compact optical system with limited moving parts, addressing issues of aberration and size increase.
Implementation Method 1
a first lens unit L1 having positive refractive power
Implementation Method 2
a second lens unit L2 having negative refractive power
Implementation Method 3
A distance between consecutive ones of the lens units changes when focusing is performed
Data Source
AI summary
An optical system includes, in order from an object side toward an image side, a first lens unit having positive refractive power, and a second lens unit having negative refractive power. A distance between consecutive ones of the lens units changes when focusing is performed. The first lens unit is stationary during focusing. The second lens unit is moved toward the image side when focus is changed from an object at infinity to an object at a short distance. Lateral magnification β2 of the second lens unit when focusing on the object at infinity, focal length f1 of the first lens unit, and focal length f2 of the second lens unit are set appropriately to satisfy predetermined mathematical conditions.