Endoscope Objective Optical System Halation Reduction

Solution Overview

Problem

Existing small objective optical systems for endoscopes, particularly those combined with laser probes, face challenges in reducing halation caused by guiding light and maintaining image quality due to the limitations of absorption and interference type infrared cutoff filters, which are not suitable for mass production and affect durability and adaptability for medical use.

Innovation Solution

The optical system is designed with a first group comprising a cemented lens formed by a first parallel flat plate, a diaphragm, and a plano-convex lens, with the diaphragm placed between the flat plate and an infrared absorption filter, and a second group with a plano-convex lens, optimizing the T/L ratio and focal length to minimize halation and enhance image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If an absorption type infrared cutoff filter is used to reduce halation, then halation is reduced, but the filter is not suited for mass production due to poor processability and easy abrasion

Engineering Contradiction:

ImprovehalationVSAvoidprocessability

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The optical system is divided into multiple functional groups: the first group contains the infrared cutoff filter separated from the diaphragm, while the second group contains the focusing lens. This segmentation allows each component to be optimized independently - the filter for halation reduction and the lens for focusing performance, while both can be manufactured using standard processes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A diaphragm is introduced as an intermediary element between the infrared cutoff filter and the focusing lens. This diaphragm serves as a mediator that controls light passage while allowing the filter to be positioned optimally for halation reduction without compromising manufacturability or mechanical strength.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Volume of moving object

If the lens itself is formed by an absorption type infrared cutoff filter to maintain small size, then the objective optical system is downsized, but durability and adaptability to living bodies deteriorate

Engineering Contradiction:

Improvesize of objective optical systemVSAvoiddurability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The optical system is divided into multiple functional groups: the first group contains the infrared cutoff filter separated from the diaphragm, while the second group contains the focusing lens. This segmentation allows each component to be optimized independently - the filter for halation reduction and the lens for focusing performance, while both can be manufactured using standard processes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The optical system uses a composite structure combining an infrared cutoff filter with a focusing lens, where each component is made from appropriate materials for its function. The filter uses absorption-type material for infrared blocking, while the lens uses transparent material for optimal focusing, achieving both small size and durability through material composition rather than a single material performing all functions.

Inventive Principle:

Principle #40Composite materials

3Object-affected harmful factors

If an interference type infrared cutoff filter is used, then halation is reduced, but characteristics change as a function of oblique incidence requiring space for parallel light entry which baffles downsizing efforts

Engineering Contradiction:

ImprovehalationVSAvoidsize of objective optical system

Core Design Contradiction:

Object-affected harmful factorsVSVolume of moving object

Solution Approach 1:

The optical system changes the parameter of filter type from interference-type to absorption-type infrared cutoff filter. This parameter change allows the filter to effectively block infrared light without the oblique incidence sensitivity of interference filters, eliminating the need for additional space to accommodate parallel light entry requirements while maintaining halation reduction and enabling compact design.

Inventive Principle:

Principle #35Parameter changes

4Device complexity

If the diaphragm is arranged at the image side of the infrared absorption filter or on the flat surface of the plano-convex lens by vapor deposition, then the configuration is achieved, but the processability is poor and not suited for mass production

Engineering Contradiction:

Improveconfiguration of optical systemVSAvoidprocessability

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The optical system is divided into multiple functional groups: the first group contains the infrared cutoff filter separated from the diaphragm, while the second group contains the focusing lens. This segmentation allows each component to be optimized independently - the filter for halation reduction and the lens for focusing performance, while both can be manufactured using standard processes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The diaphragm is extracted from the vapor deposition process and repositioned as a separate mechanical component between the infrared cutoff filter and the focusing lens. This extraction eliminates the need for complex vapor deposition operations while achieving the desired optical configuration through standard mechanical assembly, making the system suitable for mass production.

Inventive Principle:

Principle #2Taking out (Extraction)

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

This configuration results in a compact endoscope with improved color reproducibility and reduced halation, addressing the limitations of previous systems while maintaining a small outer diameter and ensuring image quality.

Implementation Method 1

a second parallel flat plate being formed by an infrared absorption filter

Methodology Applied

Scientific EffectInfrared absorption: Absorption (EM radiation)

Implementation Method 2

a first plano-convex lens with its convex surface facing the image side... a second plano-convex lens with its convex surface facing the object side

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS7843655B2Objective optical system and endoscope

Publication Date: 2010.11.30 OLYMPUS CORPORATION(JP)

AI summary

An objective optical system includes, a first group having positive refractive power, a second group having positive refractive power, the first group having a first parallel flat plate, a diaphragm, a second parallel flat plate and a first plano-convex lens with its convex surface facing the image side in the above mentioned order as viewed from the object side, the first parallel flat plate, the second flat parallel plate and the first plano-convex lens forming a cemented lens, the second parallel flat plate being formed by an infrared absorption filter, the second group having a second plano-convex lens with its convex surface facing the object side.