Endoscope Objective Optical System Short Baseline Design
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Solution Overview
Problem
In electronic endoscopes, achieving accurate 3D observation is hindered by large baseline lengths between objective optical systems for the left and right eyes, leading to eye strain and difficulty in focus adjustment due to misalignment and aberration issues caused by decentration and manufacturing errors.
Innovation Solution
The objective optical system is designed with a specific refractive power arrangement, including a front group with a plano-concave first lens and a meniscus-shaped second lens, and a rear group with positive refractive power lenses, satisfying conditional expressions to ensure a short baseline length and adequate focus adjustment stroke, while minimizing aberration deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the baseline length between objective optical systems for left and right eyes is increased, then the parallax between images for stereoscopic observation is improved, but the observer experiences eye strain during 3D observation
Solution Approach 1:
The patent optimizes the baseline length parameter to a specific range (0.8-1.2 times the outer diameter of the objective lens) to achieve the best balance between stereoscopic effect and comfort. This parameter optimization resolves the contradiction by finding the optimal value that provides sufficient parallax without causing excessive eye strain.
2Object-affected harmful factors
If the baseline length is decreased to reduce eye strain, then observer comfort is improved, but the parallax between images is reduced making stereoscopic viewing difficult
Solution Approach 1:
The patent establishes a lower limit for the baseline length (0.8 times the outer diameter of the objective lens) to ensure sufficient parallax for stereoscopic viewing. This parameter constraint prevents the baseline from being reduced too much, thereby maintaining adequate stereoscopic effect while still reducing eye strain compared to conventional designs.
Solution Approach 2:
The patent uses a cemented lens structure (fifth lens) combining different glass materials with specific refractive indices and Abbe numbers. This composite lens design corrects chromatic aberration and improves image quality, which compensates for the reduced parallax effect when using a shorter baseline length.
3Ease of manufacture
If conventional objective optical system configurations are used, then manufacturing is simplified, but focus adjustment accuracy is poor due to misalignment and aberration issues
Solution Approach 1:
The patent specifies precise parameter ranges for each lens element (focal lengths, refractive indices, Abbe numbers, surface curvatures) to control aberrations and improve focus adjustment accuracy. The conditional expressions (1) through (7) define critical parameter relationships that ensure high precision focus adjustment while maintaining manufacturing feasibility.
Solution Approach 2:
The patent employs a cemented lens structure combining lenses with different glass materials (specific refractive indices and Abbe numbers) to correct chromatic aberration. This composite lens design improves image quality and focus accuracy without significantly complicating the manufacturing process.
4Object-affected harmful factors
If the baseline length is shortened for 3D observation, then eye strain is reduced, but the objective optical systems become more sensitive to decentering errors
Solution Approach 1:
The patent uses a cemented lens structure (fifth lens) combining different glass materials with specific refractive indices and Abbe numbers. This composite lens design corrects chromatic aberration and improves image quality, which compensates for the reduced parallax effect when using a shorter baseline length and reduces sensitivity to alignment errors.
Solution Approach 2:
The patent incorporates pre-correction of aberrations through the optimized lens design and cemented structure, which compensates for potential decentering errors before they affect the final image quality. This beforehand correction reduces the impact of alignment tolerances.
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 ensures easy focus adjustment and reduces eye strain during 3D observation by maintaining a short baseline length and suppressing aberration performance deterioration due to manufacturing errors, enhancing the optical performance of the endoscope.
Implementation Method 1
the front group includes a first lens L1 having a negative refractive power with a concave surface facing an image side, a meniscus-shaped second lens L2 having a negative refractive power with a convex surface facing the image side, and a third lens L3 having a positive refractive power
Data Source
AI summary
An objective optical system includes a front group FG, an aperture stop S, and a rear group RG in order from an object side. The front group FG includes a first lens L1 having a negative refractive power with a concave surface facing an image side, a meniscus-shaped second lens L2 having a negative refractive power with a convex surface facing the image side, and a third lens L3 having a positive refractive power. The rear group RG includes a fourth lens L4 having a positive refractive power and a fifth lens L5 having a positive refractive power. The fifth lens L5 is a cemented lens. The following Conditional Expression (1) is satisfied: 2.3<f3/f5<20 (1), where f3 is a focal length of the third lens L3, and f5 is a focal length of the fifth lens L5.