Zoom Lens Segmented First Group for Compact Design
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Solution Overview
Problem
Existing zoom lenses for electronic cameras struggle to achieve a balance between compact size, lightweight design, and minimal change in angle of view during focusing, while maintaining high optical performance.
Innovation Solution
A zoom lens configuration with a stationary first lens group and movable lens groups, where the first lens group is divided into sub-groups with specific refractive power distributions and focal length ratios, and the final lens group remains stationary, allowing for reduced size and weight while suppressing angle of view changes during focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the first lens group is divided into multiple sub-lens groups with some moving during zooming to suppress angle of view change during focusing, then the angle of view stability is improved, but the number of lenses with large outer diameter increases making it difficult to reduce size and weight
Solution Approach 1:
The first lens group is segmented into three sub-groups (1a, 1b, 1c) with different functions: 1a remains stationary, 1b moves during focusing, and 1c remains stationary. This segmentation allows angle of view stabilization without requiring all lenses to have large diameters, as only the necessary sub-group 1b moves to achieve the effect.
Solution Approach 2:
Different sub-groups within the first lens group are assigned different refractive powers and movement characteristics. Specifically, sub-group 1a has negative refractive power and remains stationary, while sub-group 1b has positive refractive power and moves during focusing. This local differentiation optimizes both angle of view stability and weight reduction.
2Reliability
If the focal length is increased to improve optical performance, then the image quality is improved, but the change in angle of view during focusing tends to increase making it more difficult to suppress angle of view change
Solution Approach 1:
The patent specifies precise parameter ranges for the lens groups to achieve both high optical performance and angle of view stability. Conditional Expression (2) defines the relationship between focal lengths: 0.8 ≤ f1c/f1 ≤ 1.5, where f1c is the focal length of sub-group 1c and f1 is the focal length of the entire first lens group. This parameter control allows long focal lengths for image quality while maintaining angle of view stability through proper power distribution.
3Reliability
If more lenses are added to the first lens group to improve optical performance, then the image quality is improved, but the size and weight of the lens system increase
Solution Approach 1:
The patent makes sub-group 1b movable during focusing while keeping sub-groups 1a and 1c stationary. This dynamic configuration allows the lens system to achieve high optical performance through multiple lens elements without increasing the overall stationary length, as only the necessary focusing sub-group moves.
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 the size and weight of the zoom lens while maintaining high optical performance and minimizing the change in angle of view during focusing, addressing the limitations of previous lens systems.
Implementation Method 1
a first-a lens group that has a negative refractive power and remains stationary with respect to the image plane during focusing
Implementation Method 2
Assuming that a specific gravity of the lens having the negative refractive power in the first-a lens group is Gv1an and an Abbe number of the lens having the negative refractive power in the first-a lens group at a d line is Nud1an, at least one of the first lens or the third lens satisfies Conditional Expression (1): 0.03 ≤ Gv1an/Nud1an × 100 ≤ 0.06
Implementation Method 3
a first-b lens group that has a positive refractive power and is moved by changing a distance in the direction of the optical axis between the first-b lens group and an adjacent lens group during focusing
Implementation Method 4
Conditional Expression (2) is satisfied: 0.8 ≤ f1c/f1 ≤ 1.5, where f1c is the focal length of the first-c lens group and f1 is the focal length of the first lens group
Data Source
AI summary
The zoom lens consists of, in order from an object side: a first lens group that remains stationary during zooming and has a positive refractive power; at least two movable lens groups that are moved during zooming; and a final lens group that remains stationary during zooming and has a positive refractive power. The first lens group consists of, in order from the object side, a first-a lens group that remains stationary during focusing and has a negative refractive power, a first-b lens group that is moved during focusing and has a positive refractive power, and a first-c lens group that remains stationary during focusing and has a positive refractive power. The first-a lens group consists of, in order from the object side, a first lens that has a negative refractive power, a second lens that is convex toward the object side and has a positive refractive power, and a third lens that has a negative refractive power. At least one of the first lens or the third lens satisfies a predetermined conditional expression, and the entire system satisfies the other predetermined conditional expressions.