Endoscope Objective Optical System Aberration Correction
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Solution Overview
Problem
Existing objective optical systems for endoscopes face challenges in miniaturization and aberration correction, particularly in reducing chromatic aberration of magnification, on-axis chromatic aberration, and curvature of field, while maintaining a small size and wide angle of view, which is essential for observing narrow body cavities.
Innovation Solution
The objective optical system consists of a front group with negative refractive power and a rear group with positive refractive power, including a negative single lens and cemented lenses, where specific conditional expressions are satisfied to correct chromatic aberration and curvature of field, and the system is designed to be compact with a retrofocus structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the optical system is miniaturized to fit narrow body cavities, then the size is reduced, but aberration correction becomes more difficult
Solution Approach 1:
The patent applies parameter changes by carefully selecting specific refractive indices and Abbe numbers for lens materials, and by optimizing curvature radii and thicknesses to satisfy conditional expressions. This allows aberration correction in a miniaturized system by precisely controlling optical parameters rather than relying on larger physical dimensions.
Solution Approach 2:
The patent uses composite material principles by combining different glass types (positive and negative lens materials with specific dispersion properties) in a cemented lens structure. This composite approach enables simultaneous correction of multiple aberrations including chromatic aberration of magnification and on-axis chromatic aberration within a compact form factor.
2Manufacturing precision
If chromatic aberration of magnification is corrected by reducing the difference of partial dispersion ratio, then chromatic aberration is improved, but the optical system becomes more complex
Solution Approach 1:
The patent applies local quality by assigning specific optical properties to specific lens components. The negative lens in the cemented lens has a specifically selected Abbe number and partial dispersion ratio, while the positive lens has complementary properties. This localized optimization of material properties enables chromatic aberration correction without requiring complex overall system design.
Solution Approach 2:
The cemented lens structure serves multiple functions simultaneously: it corrects chromatic aberration of magnification, on-axis chromatic aberration, and contributes to overall focal length control. This multi-functional design achieves aberration correction without proportionally increasing system complexity.
3Adaptability or versatility
If a retrofocus structure is used to achieve wide angle of view, then the angle of view is improved, but the total length of the optical system increases
Solution Approach 1:
The patent optimizes the retrofocus structure by carefully controlling the focal lengths of individual lens groups and their spacing. The negative front group has a specifically designed focal length ratio relative to the total system, allowing wide angle of view while minimizing the back focal length and total system length through precise parameter optimization.
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 achieves a compact optical system with improved image quality, effectively correcting chromatic aberration and curvature of field, enabling high-resolution imaging in narrow cavities with a small-sized distal end portion.
Implementation Method 1
an objective optical system includes: in order from an object side to an image side, a front group having a negative refractive power; an aperture stop; and a rear group having a positive refractive power
Data Source
AI summary
An objective optical system includes, in order from an object side to an image side, a front group having a negative refractive power, an aperture stop, and a rear group having a positive refractive power. The front group includes a negative single lens, the rear group includes, in order from the object side, a positive single lens and one or more cemented lenses, and following conditional expressions (1), (2), (3), and (5) are satisfied. 1.95<ndCLn (1), 35<ΔνdCL (2), 1.1<fL2/ft<1.6 (3), −7<R1/ft<−3.6 (5).