Objective Optical System With Moving Focus Group for Deep-Field Endoscopy
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Solution Overview
Problem
Existing objective optical systems for endoscopes face challenges in achieving a short overall length, small diameter, high resolution, and sufficient depth of field, particularly when incorporating auto-focusing capabilities, leading to issues with aberrations and insufficient movement space for lens groups.
Innovation Solution
The objective optical system is composed of a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group with positive refractive power, where the second lens group moves for focusing, and the first and third lens groups are fixed. This configuration includes specific conditional expressions to balance aberrations and ensure a compact design with a deep depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resolution and image quality are improved, then depth of field becomes shallower
Solution Approach 1:
The optical system is divided into multiple lens groups (first lens group with negative refractive power, second lens group with positive refractive power, and third lens group with positive refractive power) that can move independently. This segmentation allows the second lens group to move for focusing while maintaining the overall optical configuration, thereby achieving both high resolution and sufficient depth of field.
Solution Approach 2:
The second lens group is designed to move along the optical axis for focusing from far to near object points. This dynamic adjustment capability allows the system to maintain high resolution across different object distances while preserving adequate depth of field through controlled movement rather than static configuration.
2Extent of automation
If auto-focusing is supported, then movement space for lens group becomes insufficient
Solution Approach 1:
The focusing function is assigned to only the second lens group, while the first and third lens groups remain fixed. This segmentation of functionality concentrates the movement requirement into a single lens group, optimizing the use of available movement space while supporting auto-focusing capability.
Solution Approach 2:
The optical system is configured with multiple lens groups arranged along the optical axis, creating additional spatial dimensions for movement. The second lens group moves within the space between the fixed first and third lens groups, effectively utilizing the available axial space for automated focusing operation.
3Length of moving object
If overall length and diameter are shortened, then aberration correction becomes more difficult
Solution Approach 1:
The compact optical system is divided into three lens groups with specific refractive power distributions (negative, positive, positive). This segmentation allows each group to contribute differently to aberration correction while maintaining a short overall length and small diameter.
Solution Approach 2:
The system uses specific refractive power parameters and curvature radius ratios (satisfying 0.05 < R1_Rr/L1_Rr < 0.20 and 0.10 < L2_Rr/L1_Rr < 0.40) to optimize the balance between compact size and aberration correction. By carefully controlling these optical parameters, the invention achieves effective aberration correction in a miniaturized configuration.
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 a small-diameter, high-performance optical system capable of auto-focusing with a sufficient depth of field and movable region, effectively correcting aberrations while maintaining a compact size.
Implementation Method 1
The first lens group is constituted by two lenses of a first lens that is a negative lens and a second lens that is a negative lens facing a concave surface on the image side
Implementation Method 2
The second lens group is constituted by a single positive meniscus lens facing a convex surface on the object side
Implementation Method 3
The third lens group has a single lens with positive refractive power and a bonded lens of a positive lens and a negative lens, in order from the object side
Data Source
AI summary
An objective optical system is constituted by a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group with positive refractive power, in order from an object side. The second lens group is moved to perform focusing. The first lens group is constituted by two lenses of a first lens that is a negative lens and a second lens that is a negative lens facing a concave surface on an image side. The third lens group has a single lens with positive refractive power and a bonded lens of a positive lens and a negative lens, in order from the object side. Provided that L1_Rr is a radius of curvature of an image side surface of the first lens, and L2_Rr is a radius of curvature of an image side surface of the second lens, 0.01<L1_Rr/L2_Rr<0.95.