Wide-Angle Zoom Lens Layout for Smaller Focusing Groups
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Solution Overview
Problem
Existing wide-angle zoom lenses face challenges in achieving a small size while maintaining high optical performance due to issues with lens diameter, weight, and movement amounts, particularly in the first and focusing lens groups, which affect the overall size and functionality of imaging apparatuses.
Innovation Solution
A zoom lens configuration comprising a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group, where the focusing lens group moves during focusing and is positioned closer to the image side, with specific refractive index and focal length relationships defined by conditional expressions to optimize size and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-dispersion material is used for the negative lens in the first lens group, then chromatic aberration is corrected, but the refractive index becomes low and the lens diameter must be increased to achieve wide angle
Solution Approach 1:
The patent changes the material parameters by selecting a low-dispersion material with specific refractive index (Nd1: 1.430-1.510) and Abbe number (νd1: 50-90) within defined ranges, balancing chromatic aberration correction with acceptable lens diameter for wide-angle imaging
Solution Approach 2:
The patent applies different material properties to different lens groups: the first lens group uses low-dispersion material optimized for chromatic aberration correction, while subsequent lens groups use materials optimized for their specific functions, allowing each group to have locally optimized properties
2Ease of operation
If the focusing lens group is disposed close to the image side within the first lens group, then the stroke for focusing is secured, but the outer diameter and weight of the lens increase and the driving actuator becomes large
Solution Approach 1:
The patent segments the first lens group into a first-a lens group (three negative lenses) and a first-b lens group (at least one negative and at least one positive lens), allowing the focusing lens group to be a compact subset with reduced weight and size while maintaining adequate focusing stroke
Solution Approach 2:
Instead of placing the focusing lens group close to the object side, the patent inverts the conventional arrangement by positioning it closer to the image side within the first lens group, reducing the required stroke and associated component sizes
3Ease of operation
If the distance between the focusing lens group and the lens group close to the object side is widened, then the focusing stroke is secured, but the outer diameter of the lenses increases
Solution Approach 1:
The patent merges the focusing function with the first lens group by making the focusing lens group a subset of it, allowing the focusing operation to be achieved within the existing group boundaries without requiring additional space that would increase lens outer diameter
4Adaptability or versatility
If the movement amount of the focusing lens group is increased, then the focusing range is extended, but the size of the entire lens system increases
Solution Approach 1:
The patent optimizes the refractive power of the focusing lens group (φ1: 0.01-0.05 mm⁻¹) and its position within the first lens group to achieve adequate focusing range with minimal movement amount, reducing the overall lens system volume while maintaining versatility
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 zoom lens with a wide angle of view and high optical performance, reducing lens diameter and movement amounts, thereby facilitating compact imaging apparatus design.
Implementation Method 1
a first lens group having a negative refractive power, a second lens group having a positive refractive power
Data Source
AI summary
A zoom lens includes a negative first lens group, a positive second lens group, and a subsequent lens group in order from an object side. A focusing lens group closer to an image side than the first lens group moves during focusing. The first lens group consists of a first-a lens group and a first-b lens group in order from the object side. Assuming that an average of refractive indices of the negative lenses of the first-a lens group is Nd1ave, a focal length of the focusing lens group is ff, and a focal length of the first lens group is f1, Conditional Expression (1) of 1.73<Nd1ave<1.95 and Conditional Expression (2) of 1<|ff/f1|<3 are satisfied.