Optical System Inner Focusing Aberration Control
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Solution Overview
Problem
Existing image pickup optical systems face challenges in achieving quick focusing, maintaining high optical performance over the entire object distance, and effectively stabilizing images during hand-shaking or movement, particularly with the inner focusing method, which results in increased aberration variations and difficulty in correcting decentering aberrations during image stabilization.
Innovation Solution
The optical system comprises a first lens unit with positive refractive power, a second lens unit with negative refractive power, and a third lens unit with positive refractive power, where the second lens unit moves during focusing, and specific sub-units within the first lens unit are configured for image stabilization, with a meniscus positive lens having a concave surface facing the object side, satisfying the conditional expression 0.78 < DB/DL < 0.95 to optimize lens configurations and refractive powers for reduced aberration and improved stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inner focusing method is used to reduce the movement amount and size of the focusing lens unit, then the focusing speed and compactness are improved, but the aberration variation increases and it becomes difficult to maintain high optical performance over the entire object distance
Solution Approach 1:
The optical system is divided into three lens units with different refractive powers (positive, negative, positive). The second lens unit with negative refractive power is specifically designated as the focusing lens unit, separating the focusing function from the entire optical system. This segmentation allows the focusing unit to be small and lightweight for fast focusing, while the other lens units compensate for aberration variations during focusing operations.
Solution Approach 2:
Each lens unit is assigned specific local characteristics: the first lens unit has positive refractive power for overall light convergence, the second lens unit has negative refractive power optimized for focusing with minimal aberration variation, and the third lens unit has positive refractive power for final image formation. This local optimization of refractive powers allows each component to contribute to both fast focusing and aberration control.
2Reliability
If a lens unit is moved perpendicular to the optical axis for image stabilization, then the image stabilization function is achieved, but large decentering aberration occurs and high optical performance cannot be maintained
Solution Approach 1:
The first lens unit is further divided into sub-units with different functions: one sub-unit is optimized for image stabilization by moving perpendicular to the optical axis, while other sub-units maintain the overall positive refractive power of the first lens unit. This local differentiation allows the stabilization sub-unit to correct hand-shaking without introducing excessive decentering aberration, while the other sub-units compensate to maintain overall optical performance.
Solution Approach 2:
The image stabilization function is merged into the first lens unit rather than being a separate mechanism. By combining the stabilization capability within the existing positive refractive power structure of the first lens unit, the system achieves image stabilization while the positive refractive power of the first and third lens units together compensate for any decentering aberration introduced during stabilization operations.
3Measurement precision
If the aperture diameter is reduced to increase the effective F-number for macro imaging, then the depth of field is reduced and macro image pickup is enabled, but the shutter speed must be reduced and image quality deteriorates due to hand shaking
Solution Approach 1:
The first lens unit serves multiple functions: it provides the overall positive refractive power for image formation, contains sub-units that can move for image stabilization during macro photography, and works with the third lens unit to compensate for decentering aberration. This multi-functionality allows the system to achieve macro imaging with reduced aperture while maintaining image quality through the stabilization and aberration compensation capabilities built into the lens unit structure.
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 enables quick focusing, maintains high optical performance over the entire object distance, and effectively stabilizes images during image stabilization, achieving a compact size while minimizing aberrations and ensuring excellent image quality.
Implementation Method 1
a meniscus positive lens LIS having a concave surface facing the object side
Data Source
AI summary
Provided is an optical system, comprising, in order from an object side: a positive first unit; a negative second unit; and a positive third unit, in which, during focusing from infinity to a close distance, the second unit moves toward the image side, and an interval between adjacent units is changed, in which the first unit consists of, in order from the object side: a negative first sub-unit, which does not move for image stabilization; a positive second sub-unit, which moves during the image stabilization; and a third sub-unit, which does not moves for the image stabilization, and in which a distance from a lens surface closest to the object side in the first unit to an image plane when focusing at infinity, and a distance from a lens surface closest to the object side in the second sub-unit to the image plane when focusing at infinity are appropriately set.