Zoom Lens System Compact Design via Movable Third Unit
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Solution Overview
Problem
Conventional zoom lens systems with variable magnification face challenges in reducing overall length while maintaining excellent optical performance and compactness, leading to increased size and weight of the lens barrel.
Innovation Solution
A zoom lens system comprising a four-unit construction with a third lens unit that moves along the optical axis during focusing, satisfying specific conditions for focal length and optical axial thickness, allowing for a compact and lightweight design with improved optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional zoom lens systems with variable magnification are used, then optical performance can be maintained, but the overall length and lens barrel size increase
Solution Approach 1:
The patent applies dynamics by making the third lens unit movable along the optical axis during focusing operations. This dynamic configuration allows the lens system to adjust its internal structure for close-object focusing while maintaining a compact overall length, resolving the contradiction between compactness and optical performance for near-field imaging
Solution Approach 2:
The patent changes optical parameters by defining specific relationships between the focal length of the third lens unit (f3), its optical axial thickness (d3), and the wide-angle focal length (fW) through conditions (1) and (2). These parameter constraints optimize the lens configuration to achieve both compactness and excellent optical performance across the zoom range
2Ease of operation
If the third lens unit is made movable for focusing, then close-object imaging capability is improved, but the lens barrel size increases
Solution Approach 1:
The third lens unit is configured to move along the optical axis during focusing from infinity to close objects, enabling close-object imaging capability while keeping the movement range optimized to minimize lens barrel volume expansion
Solution Approach 2:
By constraining the ratio of optical axial thickness to focal length of the third lens unit within specific ranges defined in condition (2), the patent optimizes the balance between focusing capability and lens barrel compactness
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 enables a compact and lightweight zoom lens system with excellent optical performance, achieving a shorter overall length and reduced lens barrel size, while maintaining high imaging quality and preventing dust entry through the fixed position of the fourth lens unit closest to the image side.
Implementation Method 1
a third lens unit G3 having negative optical power, which moves along an optical axis in focusing from an infinity in-focus condition to a close-object in-focus condition
Implementation Method 2
a first lens unit G1 having negative optical power, a second lens unit G2 having positive optical power, a third lens unit G3 having negative optical power, and a fourth lens unit G4 having positive optical power
Data Source
AI summary
A zoom lens system, in order from an object side to an image side, comprising a first lens unit having negative optical power, a second lens unit having positive optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power, wherein the third lens unit moves along an optical axis in focusing from an infinity in-focus condition to a close-object in-focus condition, and the conditions: 0.5<|f3/fW|<2.0 and 0.005<d3/fW<0.070 (f3: a focal length of the third lens unit, d3: an optical axial thickness of the third lens unit, fW: a focal length of the entire system at a wide-angle limit) are satisfied; an interchangeable lens apparatus; and a camera system are provided.