Variable Magnification Optical System with Moving Third Lens Group
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Solution Overview
Problem
Conventional variable magnification optical systems face challenges in downsizing while maintaining a high zoom ratio and achieving excellent optical performance when focusing from an infinite distance to a near distance.
Innovation Solution
A variable magnification optical system comprising specific lens groups with varying distances and refractive powers, including a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, where the third lens group is moved along the optical axis upon focusing, and additional lens groups with positive refractive power are included to satisfy specific conditional expressions for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional variable magnification optical system uses a most object side lens group with positive refractive power and moves lens groups along the optical axis for focusing, then it can focus from infinite distance to near distance, but it is difficult to conduct downsizing while retaining a high zoom ratio and achieving sufficiently excellent optical performance
Solution Approach 1:
The optical system is divided into five distinct lens groups with specific refractive power characteristics. The first lens group (positive), second lens group (negative), third lens group (positive), fourth lens group (positive), and fifth lens group (positive) are segmented to perform different functions. This segmentation allows the system to achieve high zoom ratio and excellent focusing performance while maintaining compact size through specialized functional distribution among groups.
Solution Approach 2:
The patent implements dynamic positioning of lens groups during zooming and focusing operations. Specifically, the third lens group is moved along the optical axis for focusing from infinite distance to near distance objects. The distances between lens groups are varied during zooming from wide-angle to telephoto end states. This dynamic adjustment enables the system to maintain optimal optical performance across different focal lengths and focus distances while managing system compactness.
2Manufacturing precision
If the third lens group is moved along the optical axis for focusing from infinite distance to near distance objects, then focusing performance is improved, but the complexity of the optical system increases
Solution Approach 1:
The patent applies local quality by giving specific functional characteristics to particular lens groups. The third lens group is specifically designed with positive refractive power and positioned to handle focusing from infinite distance to near distance objects. The fourth lens group is specifically positioned to handle telephoto end state characteristics. This localized functional assignment optimizes focusing performance while managing overall system complexity through clear functional division.
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 small-size variable magnification optical system with a high zoom ratio and excellent optical performance, effectively addressing the challenges of size reduction and optical quality maintenance across focus distances.
Implementation Method 1
a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having positive refractive power
Data Source
AI summary
Composing, in order from an object side: a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having positive refractive power; upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group, a distance between the second lens group and the third lens group and a distance between the third lens group and an image plane being varied; on the most image side, a fixed lens group being fixed in a position upon zooming from the wide-angle end state to the telephoto end state; and the third lens group being moved in the direction of the optical axis upon focusing from an infinite distance object to a near distance object, thereby providing a small-size variable magnification optical system having a high zoom ratio and an excellent optical performance upon focusing from an infinite distance object to a near distance object, an optical apparatus, and a method for manufacturing the variable magnification optical system.