Zoom Lens Ghosting Reduction via Cemented Lens Curvature Control
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Solution Overview
Problem
Conventional zoom lenses with high zoom ratios tend to experience ghosting issues, particularly when zooming from the wide-angle end to the telephoto end, leading to conspicuous ghosting in captured images.
Innovation Solution
A zoom lens configuration featuring a first lens unit with positive refractive power, a second lens unit with negative refractive power, and a third lens unit, along with an N-1-th and N-th lens unit, where the N-1-th and N-th lens units include cemented lenses with specific curvature and movement characteristics, minimizing boundary surfaces and optimizing the radius of curvature, focal lengths, and movement ranges to inhibit ghosting and enhance optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the number of boundary surfaces between air and lenses is reduced by using cemented lenses in the N-1-th and N-th lens units, then ghosting is inhibited, but when high zoom ratio is implemented, ghosts are condensed onto the image plane during booming from wide-angle to telephoto end
Solution Approach 1:
The patent applies parameter changes by precisely controlling the radius of curvature of the cemented surface (Rcem) and the movement distance (len) of the N-1-th and N-th lens units during zooming. The conditional expression 0.00 < len/Rcem ≤ 0.15 optimizes the relationship between these parameters to prevent ghost condensation while maintaining compact structure. This quantitative parameter optimization resolves the contradiction between reducing boundary surfaces and preventing ghosting during high-zoom-ratio operation.
Solution Approach 2:
The patent implements dynamics by making the N-1-th and N-th lens units movable during zooming operations. These lens units change their positions dynamically as the focal length changes, which allows the cemented surfaces to move in a controlled manner that prevents ghost condensation on the image plane during the transition from wide-angle to telephoto end, while still maintaining the reduced boundary surface structure.
2Adaptability or versatility
If the zoom lens is designed with high zoom ratio, then the zooming capability is improved, but ghosts are more likely to be condensed onto the image plane
Solution Approach 1:
The patent uses parameter changes by establishing specific conditional expressions for the zoom lens structure: 0.00 < len/Rcem ≤ 0.15, 0.20 < m_max/tdw ≤ 1.00, and 1.20 < fw/skw ≤ 2.60. These parameter constraints optimize the lens configuration to achieve high zoom ratio while preventing ghost condensation during the zooming process, particularly during the transition from wide-angle to telephoto end.
Solution Approach 2:
The patent applies dynamics by designing the N-1-th and N-th lens units to move during zooming operations. This dynamic configuration allows the lens system to maintain high zoom ratio capability while the movement of these specific lens units prevents ghost condensation on the image plane during the zooming process, resolving the contradiction between zoom ratio and ghosting.
3Object-affected harmful factors
If the N-1-th and N-th lens units are made movable during zooming, then ghost condensation is reduced, but the device complexity increases
Solution Approach 1:
The patent implements dynamics by making only the N-1-th and N-th lens units movable during zooming, rather than all lens units. This selective dynamic configuration reduces ghost condensation effectively while minimizing the increase in device complexity. The movement mechanism is simplified by limiting the number of movable components to only those necessary for ghost prevention.
Solution Approach 2:
The patent uses parameter changes by optimizing the movement characteristics of the N-1-th and N-th lens units through the conditional expression 0.00 < len/Rcem ≤ 0.15. This parameter optimization ensures that the lens units move just enough to prevent ghost condensation without requiring complex movement mechanisms, thereby balancing ghost reduction with device 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
The solution achieves a compact, high-zoom-ratio system with reduced ghosting and high optical performance across the entire zoom range, ensuring minimal aberrations and effective correction of chromatic aberrations.
Implementation Method 1
the N-1-th lens unit and the N-th lens unit each include one or more cemented lens including a positive lens and a negative lens
Data Source
AI summary
A zoom lens includes an N-1-th lens unit disposed second closest to the image side and an N-th lens unit disposed closest to the image side. The N-1-th lens unit and the N-th lens unit each includes a cemented lens, and move at zooming. For at least one of the N-1-th lens unit and the N-th lens unit, the relationship between the radius of curvature of a cemented surface of the cemented lens and the distance from the cemented surface to an image plane, the value of the larger amount of the amount of movement of the N-1-th lens unit and the amount of movement of the N-th lens unit at zooming from the wide-angle end to the telephoto end, the overall lens length at the wide-angle end, the focal length of the zoom lens at the wide-angle end, and a back focus at the wide-angle end are determined.