Zoom Lens Third Group Segmentation for Vibration Proof Weight Reduction
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Solution Overview
Problem
Existing zoom lenses with a four-group configuration face challenges in reducing chromatic aberration during image shake correction while attempting to minimize the weight and size of the vibration proof lens group, leading to increased complexity and size in the drive system.
Innovation Solution
A zoom lens configuration with four lens groups, where the third lens group is divided into fixed and moving components intersecting the optical axis, and specific refractive power and Abbe number conditions are met to minimize weight and size while reducing chromatic aberration, including a vibration proof lens group composed of a positive and negative lens with controlled thickness and focal length ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cemented lens of the third lens group is set as the vibration proof lens group, then the weight of the vibration proof lens group is increased, but chromatic aberration correction becomes possible
Solution Approach 1:
The third lens group is segmented into three sub-groups (third a, third b, and third c lens groups). The third b lens group, consisting of a positive lens and a negative lens with specific thickness ratios, is designated as the vibration proof lens group. This segmentation allows the system to achieve chromatic aberration correction through the combined optical powers of the segmented groups rather than requiring a heavy cemented lens.
Solution Approach 2:
The patent applies local quality by assigning specific optical properties to different parts of the third lens group. The third b lens group has a controlled thickness ratio (0.2 < D3bp/D3bn < 2.0) and specific Abbe number relationships (1.05 < ν3bp/ν3bn < 2.50) to correct chromatic aberration locally, while the other sub-groups have different optical characteristics optimized for their specific functions in the overall lens system.
2Weight of moving object
If one lens of the third lens group is set as the vibration proof lens group, then weight reduction is achieved, but chromatic aberration correction becomes difficult
Solution Approach 1:
The third lens group is divided into three sub-groups, with the third b lens group serving as the vibration proof component. This segmentation enables the use of a lightweight single-lens or simple two-lens configuration for vibration proofing while the other sub-groups (third a and third c) provide the necessary optical compensation for chromatic aberration through their specific refractive powers and Abbe numbers.
Solution Approach 2:
The third lens group as a whole serves multiple functions: the third a, third b, and third c sub-groups collectively provide both vibration proof capability (through the movable third b group) and chromatic aberration correction (through the combined optical properties of all three sub-groups). This multi-functionality eliminates the need for separate dedicated components for each function, reducing overall weight.
3Reliability
If the third lens group is used as the vibration proof lens group, then image shake correction is achieved, but the device complexity increases
Solution Approach 1:
The third lens group is segmented into three sub-groups with the third b lens group designated for vibration proof movement. This segmentation provides a clear functional division that simplifies the control system - only the third b group needs to be moved for image shake correction, while the other sub-groups remain fixed or move only for focusing and zooming, thereby reducing the complexity of the vibration proof drive mechanism.
Solution Approach 2:
The patent implements dynamic functionality by allowing the third b lens group to move in a direction intersecting the optical axis for vibration proof, while maintaining the ability to move other groups for focusing and zooming. This dynamic configuration optimizes the system by enabling independent control of different lens groups for different functions, reducing overall system complexity compared to moving entire lens groups for all operations.
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 effectively reduces chromatic aberration during image shake correction, achieves weight reduction of the vibration proof lens group, and maintains favorable optical performance in a compact size, thereby enhancing the imaging apparatus's performance and usability.
Implementation Method 1
The third b lens group consists of one positive lens and one negative lens. In a case where a thickness of the positive lens of the third b lens group on the optical axis is denoted by D3bp, and a thickness of the negative lens of the third b lens group on the optical axis is denoted by D3bn, Conditional Expression (1) represented by 0.2<D3bp/D3bn<2.0 is satisfied.
Data Source
AI summary
A zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group in order from an object side. In a case of magnification, the first lens group, the second lens group, and the third lens group move. The third lens group consists of a third a lens group that does not move in a case of image shake correction, a third b lens group that moves in the case of the image shake correction, and a third c lens group that does not move in the case of the image shake correction in order from the object side. The third b lens group consists of a positive lens and a negative lens. A predetermined conditional expression related to the third b lens group is satisfied.