Optical System Aberration Control via Lens Unit Movement
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Solution Overview
Problem
Optical systems with large aperture ratios face challenges in maintaining high optical performance during focusing from infinity to proximity, particularly with increased variations in aberrations such as spherical aberration, making it difficult to achieve high optical performance during photography at proximity with equal magnification.
Innovation Solution
An optical system comprising a first lens unit with positive refractive power, an aperture stop, and a third lens unit with negative refractive power, where the first and second lens units move towards the object side to increase the intervals between lens units during focusing, and the third lens unit consists of a positive and negative lens, satisfying the conditional expression sk/TD < 0.17, which helps in maintaining good optical performance and downsizing the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a large aperture ratio is employed to enable easy photography at proximity, then the aperture ratio is improved, but spherical aberration and other various aberrations increase, reducing optical performance
Solution Approach 1:
The optical system divides the lens into multiple lens units (first lens unit with positive refractive power, second lens unit with positive refractive power, and third lens unit with negative refractive power). Each lens unit can be independently configured and moved during focusing, allowing precise control of aberrations while maintaining a large aperture ratio. The segmentation enables complex aberration correction through coordinated movement of individual units.
Solution Approach 2:
Different lens units are assigned specific functions to correct different types of aberrations. The first lens unit primarily corrects spherical aberration, the second lens unit addresses coma and astigmatism, and the third lens unit controls field curvature and distortion. This localized quality approach allows each lens unit to optimize specific aberration characteristics while contributing to overall system performance.
2Adaptability or versatility
If the image pickup magnification is increased to enable proximity photography, then the magnification is improved, but variations in aberrations during focusing become larger, reducing optical performance
Solution Approach 1:
The optical system employs dynamic focusing mechanisms where lens units move along the optical axis during focusing from infinity to proximity. The first and second lens units move toward the image side, while the third lens unit moves toward the object side. This dynamic configuration allows the system to maintain consistent aberration characteristics across different focus distances and magnifications.
Solution Approach 2:
The system changes the positions of lens units during focusing to maintain optimal optical performance. By adjusting the distances between lens units and the image plane, the system compensates for aberration variations that occur with changing magnification. This parameter change approach ensures high optical performance across the entire focus range from infinity to proximity photography.
3Manufacturing precision
If multiple lens units are configured to move during focusing to correct aberrations, then optical performance is improved, but the device complexity increases
Solution Approach 1:
The optical system combines multiple lens units with different refractive powers into a single integrated focusing mechanism. The first lens unit (positive), second lens unit (positive), and third lens unit (negative) are configured to move in a coordinated manner during focusing. This merging approach allows complex aberration correction to be achieved through a unified focusing action rather than requiring separate adjustment mechanisms for each lens unit.
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 reduces aberration variations, allowing for high optical performance over the entire focus range while maintaining a large aperture ratio, facilitating easy photography at proximity with improved image stabilization and system compactness.
Implementation Method 1
a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power
Data Source
AI summary
An optical system includes, in order from object side, a first unit, a stop, a second unit, and a third unit. The first and second units are moved toward object side to increase respective intervals from the third unit for focusing from infinity to proximity. The first unit includes a negative lens and a positive lens arranged adjacent and on image side of the negative lens. The third unit consists of a positive lens (G3P) and a negative lens (G3N) arranged adjacent and on image side of the positive lens (G3P). An equivalent air length from a lens surface on image side of the negative lens (G3N) to an image plane when focused at infinity, and a distance on an optical axis from a lens surface on object side of a lens (G1F) arranged closest to object side, to the image plane when focused at infinity are appropriately set.