Aspheric Lens Design for Endoscope Imaging Aberration Correction
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Solution Overview
Problem
Existing endoscope imaging optical systems fail to produce high-quality images when integrated into a hemispherical or nearly hemispherical transparent cover, particularly in capsule endoscopes, due to design limitations that prioritize cost reduction over image quality.
Innovation Solution
The development of an imaging optical system with a single aspheric lens element and a solid-state image sensor, optimized for a spherical or nearly spherical viewing port, which includes specific conditions for sagittal and meridional image surface depths and focal lengths to ensure adequate image focus and brightness, using a diaphragm as an aperture stop and a lens frame for alignment and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single aspheric lens element is used to reduce production costs and miniaturize the imaging optical system, then manufacturing cost and device size are reduced, but image quality deteriorates due to astigmatism and distortion on curved surfaces
Solution Approach 1:
The patent applies parameter changes by optimizing the aspheric lens design with specific aspheric coefficients and curvature parameters. The lens uses an aspheric surface defined by mathematical parameters (k, A4, A6, A8 coefficients) to correct astigmatism and distortion, transforming a simple spherical lens into a precision aspheric lens that maintains both low cost and high image quality on curved endoscope surfaces
Solution Approach 2:
The patent employs spheroidality by using an aspheric lens surface instead of a spherical surface. The aspheric surface profile is designed with specific curvature variations to match the curved geometry of the endoscope's viewing port, correcting optical aberrations while maintaining the compact single-element structure
2Ease of manufacture
If the imaging optical system is designed for outdoor settings with a single lens element, then production cost is reduced, but image quality on curved medical surfaces deteriorates due to uncorrected astigmatism and distortion
Solution Approach 1:
The patent modifies the optical parameters of the single lens element by implementing an aspheric surface with specifically calculated coefficients. This parameter optimization enables the lens to adapt to curved medical surfaces while maintaining outdoor-style simplicity and low cost, correcting astigmatism and distortion through precise mathematical surface definition
Solution Approach 2:
The patent achieves universality by designing a single aspheric lens that performs multiple functions: it focuses light, corrects astigmatism, reduces distortion, and adapts to curved surfaces. This multi-functional single-element design eliminates the need for complex multi-lens systems while maintaining versatility across different endoscope applications
3Volume of moving object
If a single aspheric lens element is used to miniaturize the imaging optical system, then device size is reduced, but image quality deteriorates due to uncorrected optical aberrations on curved surfaces
Solution Approach 1:
The patent uses spheroidality by implementing an aspheric lens surface with controlled curvature variations. This curved-aspheric surface design corrects optical aberrations within the compact single-element structure, maintaining miniaturization while achieving high image quality on curved endoscope viewing ports
Solution Approach 2:
The patent applies parameter changes by optimizing the aspheric lens geometry with specific mathematical parameters. The aspheric coefficients and surface curvature are precisely controlled to correct astigmatism and distortion within the miniaturized single-element structure, achieving both small size and high image quality
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 allows for high-quality image capture with a wide angle of view, improved focus adjustment, and reduced production costs, while maintaining image clarity and brightness, even in confined spaces like body cavities.
Implementation Method 1
an imaging optical system comprising, in order from an object side: a transparent viewing port having a spherical surface; an objective lens including an aspheric surface
Implementation Method 2
the aspheric surface of the objective lens has a curvature toward the periphery that is smaller than the on-axis curvature
Data Source
AI summary
An imaging optical system includes a spherical or nearly spherical viewing port, an objective lens that includes an aspheric surface and is formed as a single lens element, and a solid-state image sensor that receives an image formed by the imaging optical system. Specified conditions are satisfied by the imaging optical system and the objective lens so that an in-focus image having low distortion, sufficient contrast, and formed by light rays of restricted angles of incidence is formed even for an object in contact with the viewing port. The specified conditions relate to features of the imaging optical system such as focal length and f-number of the imaging optical system, astigmatism and distortion of the imaging optical system, and pixel pitch of the solid-state image sensor. An endoscope that includes the imaging optical system is also disclosed.