Three-Unit Endoscope Objective for Compact Far-Near Imaging
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Solution Overview
Problem
Existing endoscope objective optical systems face challenges in capturing high-quality images of both far and near objects while maintaining a small diameter and ensuring high operability, with issues in aberration correction and size reduction.
Innovation Solution
An endoscope objective optical system comprising a first lens unit with negative refractive power, a second lens unit with positive refractive power, and a third lens unit with positive refractive power, including a positive meniscus lens and a cemented lens, with specific focal length ratios and conditional expressions to ensure favorable aberration correction and downsizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the diameter of the insert part is reduced to improve operability, then ease of operation is improved, but imaging performance deteriorates
Solution Approach 1:
The optical system is divided into three lens units with specific functions: the first lens unit (negative refractive power) for wide-angle imaging and aberration correction, the second lens unit (positive refractive power) for focusing by moving along the optical axis, and the third lens unit (positive refractive power) for image formation. This segmentation allows each unit to be optimized for its specific function while maintaining overall compact size
Solution Approach 2:
The patent applies specific conditional expressions for focal length ratios (0.3 < f1/f2 < 1.5 and 0.5 < f1/f3 < 2.0) and lens curvature radii to optimize the optical parameters. By carefully controlling these parameters, the system achieves high imaging performance despite the small diameter constraint
2Adaptability or versatility
If the optical system is designed to capture both far and near objects, then adaptability is improved, but device complexity increases
Solution Approach 1:
The second lens unit is designed to move along the optical axis for focusing, enabling the system to capture both far and near objects. This dynamic element provides adaptability without requiring multiple fixed optical systems, thereby controlling overall device complexity
Solution Approach 2:
The three-lens-unit configuration serves multiple functions simultaneously: the first lens unit provides wide-angle coverage and initial aberration correction, the second lens unit enables focusing across different object distances, and the third lens unit completes image formation. This multi-functional design achieves adaptability while maintaining relatively simple structure
3Volume of moving object
If the insert part diameter is reduced, then volume of moving object is reduced, but aberration correction becomes more difficult
Solution Approach 1:
Each lens unit is designed with specific local optical properties: the first lens unit uses negative refractive power with specific curvature radii to correct spherical aberration and coma, the second lens unit uses positive refractive power optimized for focusing, and the third lens unit uses positive refractive power for final image formation. This local optimization of optical qualities enables effective aberration correction within compact dimensions
Solution Approach 2:
The optical system combines different lens materials with specific refractive indices and Abbe numbers to correct chromatic aberrations. By carefully selecting and combining materials with complementary optical properties, the system achieves superior aberration correction despite the small size constraint
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 system achieves high imaging performance for both far and near objects with a compact design, allowing for easy alignment and correction of aberrations, thus producing clear images regardless of object distance.
Implementation Method 1
a first lens unit having a negative refractive power
Implementation Method 2
a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power, wherein the second lens unit is moved for focusing
Implementation Method 3
the second lens unit includes a positive meniscus lens having a convex surface facing the image side
Implementation Method 4
the third lens unit includes, in order from the object side, an object side positive lens and a cemented lens made up of a positive lens and a negative lens
Data Source
AI summary
An objective optical system for an endoscope comprising, in order from the object side, a first lens unit G1 having a negative refractive power, a second lens unit G2 having a positive refractive power, and a third lens unit G3 having a positive refractive power. The first lens unit G1 includes a negative lens L1. The second lens unit G2 includes a positive meniscus lens L2 having a convex surface facing the image side. The third lens unit G3 includes, in order from the object side, an object side positive lens L3 and a cemented lens CL made up of a positive lens L4 and a negative lens L5. The second lens unit G2 is moved for focusing. The objective optical system satisfies the following conditional expressions (1) and (2):-0.07<f1/f2<-0.015(1)-0.4<f1/f3<-0.15(2)where f1 is the focal length of the first lens unit, f2 is the focal length of the second lens unit, and f3 is the focal length of the third lens unit.