Relay Optical System Aberration Correction in Rigid Endoscopes
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Solution Overview
Problem
Rigid endoscopes face challenges in achieving high-resolution imaging due to uncorrected aberrations such as curvature of field, spherical aberration, and chromatic aberration, which degrade image quality and accuracy.
Innovation Solution
A relay optical system comprising specific configurations of cemented lenses with biconvex and biconcave shapes, along with conditional expressions to optimize refractive powers and lens arrangements, effectively corrects these aberrations, ensuring high imaging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a relay optical system is used in a rigid endoscope to relay images from the objective lens to the eyepiece or camera head, then the basic imaging function is achieved, but aberrations such as curvature of field, spherical aberration, and chromatic aberration are not sufficiently corrected, degrading image quality and diagnostic accuracy
Solution Approach 1:
The relay optical system is divided into multiple discrete cemented lens units, each with specific refractive powers and configurations. The system includes a first relay optical system with a first cemented lens (positive meniscus lens L1 cemented to negative meniscus lens L2) and a second relay optical system with a second cemented lens (positive meniscus lens L3 cemented to negative meniscus lens L4), allowing independent optimization of aberration correction for each segment while maintaining overall system performance
Solution Approach 2:
Each cemented lens is designed with specific local optical properties - the positive meniscus lenses have positive refractive powers optimized for certain wavelength ranges while the negative meniscus lenses have negative refractive powers optimized for other wavelengths. The conditional expressions (1) through (6) define specific ranges for focal lengths and refractive powers to locally optimize correction of different types of aberrations in different parts of the optical spectrum
Solution Approach 3:
The cemented lenses combine different optical materials with distinct refractive indices and dispersion characteristics. The positive meniscus lenses and negative meniscus lenses are made from different glass types that, when cemented together, create composite optical elements that simultaneously correct multiple aberration types through the interaction of their different optical properties
2Illumination intensity
If the numerical aperture of the relay optical system is increased to improve light gathering capability and image brightness, then illumination intensity is improved, but aberrations become more pronounced and harder to correct
Solution Approach 1:
The system specifies conditional ranges for key parameters including the focal lengths of the cemented lenses (fCL1, fCL2), the focal length of the second lens (f2), and the ratio f2/fCL12. These parameter ranges are optimized to maintain aberration correction effectiveness across high numerical aperture values while preserving light gathering capability. The conditional expression (1) specifically addresses the relationship between f2 and fCL12 to control aberrations at high NA
3Ease of operation
If multiple relay optical systems are disposed between the objective lens and the eyepiece to achieve proper image orientation (erect image), then the image orientation requirement is met, but the overall optical path length and device complexity increase
Solution Approach 1:
Multiple relay optical systems are combined in a compact linear arrangement where the first relay optical system and second relay optical system are disposed in sequence between the objective lens and the ocular lens. The cemented lens construction merges multiple lens elements into fewer physical components, reducing the overall optical path length while maintaining the odd number of relays needed for erect image formation
Solution Approach 2:
The relay optical systems are nested within the rigid endoscope shaft with the cemented lenses positioned closely together. The first cemented lens and second cemented lens are arranged in a nested configuration where the optical paths are tightly coupled, minimizing the space required for multiple relay stages while achieving the necessary image inversion correction
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 solution provides a relay optical system capable of suppressing aberrations even at high numerical apertures, enabling the formation of high-resolution images with improved image quality and accuracy in rigid endoscopes.
Implementation Method 1
a first cemented lens, a second cemented lens having a positive refractive power, a third cemented lens which is plane-symmetric to the second cemented lens, and a fourth cemented lens which is plane-symmetric to the first cemented lens
Data Source
AI summary
A relay optical system includes, in order from, an object side, a first cemented lens, a second cemented lens having a positive refractive power, a third cemented lens which is plane-symmetric to the second cemented lens, and a fourth cemented lens which is plane-symmetric to the first cemented lens, the first cemented lens includes a first lens having a positive refractive power and a second lens having a negative refractive power, the second cemented lens includes a third lens and a fourth lens, a shape of the first lens is a biconvex shape, a shape of the second lens is a biconcave shape, and the following conditional expression (1), in which f2 denotes a focal length of the second lens and fCL12 denotes a combined focal length of the first cemented lens and the second cemented lens, is satisfied:−0.4<f2/fCL12<−0.1 (1).