Zoom Lens Focusing Mechanism Using Fifth Lens Group
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Solution Overview
Problem
Existing zoom lens systems for digital cameras are bulky and heavy, making them unsuitable for compact designs and high optical performance, especially when performing automatic focusing during moving image shooting, as they require large driving actuators and lens barrels due to the weight and movement of focusing lens groups.
Innovation Solution
A zoom lens configuration with six lens groups, where the fifth lens group travels along the optical axis for focusing, optimizing refractive power arrangements to reduce size and weight, allowing the fourth and sixth lens groups to travel together, and incorporating image blur compensation through perpendicular movement of the fourth lens group's sub-lens group, satisfying specific conditional expressions for reduced size and improved optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the second lens group is allowed to travel along the optical axis for focusing, then the focusing operation can be performed, but the second lens group has large weight which increases the size of the driving actuator and lens barrel
Solution Approach 1:
The lens system is divided into multiple lens groups (first through sixth) with different functions. The fifth lens group is specifically designated as the focusing lens group, separating the focusing function from other optical functions performed by other groups. This segmentation allows the focusing group to be optimized for light weight while other groups handle other optical requirements.
Solution Approach 2:
Instead of using a heavy lens group near the object side (second group in prior art) for focusing, the invention uses a lighter lens group near the image side (fifth group) for focusing. This inversion of the conventional approach allows reducing the weight of the moving focusing group while maintaining focusing capability.
2Adaptability or versatility
If all six lens groups travel with different loci during zooming, then the zooming function is achieved, but the mechanism becomes complicated and the lens barrel size increases
Solution Approach 1:
The fourth and sixth lens groups are merged in their movement behavior, as they travel together along the optical axis during zooming operations. This reduces the number of independent movement mechanisms required, simplifying the overall drive mechanism while still achieving the necessary zooming function through coordinated movement of lens groups.
3Ease of operation
If the second lens group travels along the optical axis for focusing, then focusing is achieved, but the amount of variation in angle of view increases during moving image shooting
Solution Approach 1:
The focusing operation is performed by moving the fifth lens group along the optical axis (one dimension), while the fourth lens group's sub-lens group moves in a direction perpendicular to the optical axis (another dimension) for image blur compensation. This multi-dimensional movement strategy allows focusing while maintaining angle of view stability through compensatory movements.
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 a compact, high-performance zoom lens suitable for moving image shooting with reduced size and weight, allowing for efficient automatic focusing and minimizing angle of view variation, while simplifying the mechanical structure and reducing the size of the lens barrel.
Implementation Method 1
a fifth lens group GR5 having negative refractive power... A focusing operation is performed through allowing the fifth lens group to travel along an optical axis in accordance with variation in a subject distance
Implementation Method 2
an image is shifted through allowing a sub-lens group of the fourth lens group to move in a direction perpendicular to the optical axis
Data Source
AI summary
A zoom lens includes: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having positive refractive power; a fifth lens group having negative refractive power; and a sixth lens group having positive refractive power. The first to sixth lens groups are arranged in order from an object side. A total length of the zoom lens varies when a lens position state varies from a wide end state to a telephoto end state. A focusing operation is performed through allowing the fifth lens group to travel along an optical axis in accordance with variation in a subject distance from infinite to a closer distance.