Four-Group Endoscope Objective Lens Design
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Solution Overview
Problem
Endoscopes require an objective lens that can seamlessly switch between wide-angle observation for overall views and high magnification for detailed observations while maintaining optical performance across the entire object distance range without increasing the size of the optical system.
Innovation Solution
An objective lens for endoscopes comprising four lens groups with specific refractive powers and movements, including a fixed first lens group and movable second and third lens groups, arranged to satisfy conditional expressions for focal lengths and optical axis intervals, ensuring a wide angle of view and high magnification while suppressing system size growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the optical system is designed to achieve both wide angle of view and high magnification, then observation versatility is improved, but the size of the optical system increases
Solution Approach 1:
The optical system is divided into four distinct lens groups (G1, G2, G3, G4) with alternating negative and positive refractive powers. This segmentation allows each group to perform specific functions: G1 and G2 control wide-angle performance, while G3 and G4 enable high magnification. By moving only G2 and G3 during focusing, the system achieves versatile observation capabilities without proportionally increasing overall size.
Solution Approach 2:
The patent implements dynamic focusing by making the second and third lens groups movable along the optical axis, while the first and fourth lens groups remain fixed. This dynamic configuration allows the system to switch between wide-angle and high-magnification states by adjusting the positions of G2 and G3, providing observation versatility without requiring a completely reconfigurable optical system that would increase size.
2Measurement precision
If the lens groups are moved to achieve high magnification, then image formation magnification is improved, but the complexity of the focusing mechanism increases
Solution Approach 1:
The focusing mechanism is segmented to move only two lens groups (G2 and G3) along the optical axis, while G1 and G4 remain fixed. This reduces the complexity compared to moving all lens groups. The alternating negative-positive refractive power structure of the four groups further simplifies the optical path control during focusing.
Solution Approach 2:
The patent optimizes specific parameter ranges for the lens groups to achieve high magnification with controlled complexity. The conditional expressions (1) and (2) define precise relationships between focal lengths (fw/ft ratio and f3/fw ratio), ensuring that the magnification performance is achieved within a controlled parameter space that prevents excessive mechanism complexity.
3Volume of moving object
If the optical system is compacted to reduce size, then system size is reduced, but optical performance deteriorates
Solution Approach 1:
The compact optical system maintains good optical performance by segmenting the four lens groups with alternating refractive powers. This configuration allows efficient use of space where each group contributes specifically to performance: G1 and G2 handle wide-angle light paths, while G3 and G4 enable close-up high magnification. The segmented structure prevents performance deterioration that would result from simple compaction.
Solution Approach 2:
The dynamic focusing mechanism, where G2 and G3 move along the optical axis while G1 and G4 remain fixed, allows the compact system to maintain optimal optical performance across different object distances. The movement of G2 and G3 adjusts the optical path length dynamically, ensuring good imaging performance whether observing distant or near objects, without requiring a larger fixed optical system.
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 good optical performance across the entire object distance range with improved usability and aberration control, achieving both wide-angle and high-magnification observations without increasing the optical system's size, thus enhancing user experience and maintaining airtightness.
Implementation Method 1
a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power that are arranged in this order from the object side toward the image side
Data Source
AI summary
An objective lens for an endoscope includes only four lens groups as lens groups, and the four lens groups consist of a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group that are arranged in this order from an object side. The first lens group is fixed and the second and third lens groups are moved during focusing on an object positioned at the nearest point from an object positioned at the farthest point. The objective lens for an endoscope satisfies a predetermined conditional expression related to a focal length of an entire system and a focal length of the third lens group.