Endoscope Objective Lens Assembly with Centering Member
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Solution Overview
Problem
The design of objective lenses for video endoscopes faces challenges in achieving a wide field of view, flexibility, and adaptability to varying brightness and cavity conditions, while maintaining a compact and robust structure to navigate narrow body cavities effectively.
Innovation Solution
A compact objective lens system comprising five lenses, including a plan concave lens, a plan convex lens, an aperture stop, and an achromatic lens, along with a centering assembly that aligns optically with the video chip's photosensitive area, utilizing high refractive index glasses to minimize length and aberrations, and a mechanical housing for robust assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the rigid portion length is reduced to improve flexibility and maneuverability, then the overall length of the rigid tip becomes shorter, but the objective lens design becomes more difficult due to extreme length constraints
Solution Approach 1:
The patent embeds the objective lens system within a compact housing structure that integrates multiple optical elements in a nested arrangement. The lens elements are positioned within the rigid portion at the tip, with the objective lens housing containing the lens elements and aperture stop in a space-efficient configuration that accommodates the reduced length constraint while maintaining optical performance
Solution Approach 2:
The patent transitions from a traditional linear arrangement of optical elements to a three-dimensional compact configuration. By utilizing spatial arrangement in multiple dimensions within the constrained rigid portion, the design achieves the required optical path length and focus capability despite the reduced overall length of the rigid tip
2Area of moving object
If the field of view is increased to improve overview capability in narrow body cavities, then the field of view can reach up to 155°, but the objective lens design becomes more difficult to achieve even performance over the full chip format
Solution Approach 1:
The patent employs an achromatic lens composed of bi-convex and plan concave elements with specific refractive properties positioned at the image side of the objective lens. This local optimization of lens quality and material properties compensates for chromatic aberrations and maintains even performance across the wide field of view and full chip format
Solution Approach 2:
The patent incorporates an aperture stop that can be adjusted to adapt the F-number between 2.8 and 5.6, allowing the objective lens to dynamically adapt to varying brightness conditions in body cavities. This dynamic adjustment capability enables the system to maintain optimal performance across the wide field of view under different illumination conditions
3Adaptability or versatility
If the F-number is reduced to improve depth of field in well-illuminated body cavities, then the depth of field increases, but the objective lens must be adapted for use under varying brightness conditions
Solution Approach 1:
The patent incorporates an aperture stop with adjustable opening size that enables dynamic adaptation of the F-number between 2.8 and 5.6. This mechanical adjustment mechanism allows the objective lens to optimize its performance for different brightness conditions in body cavities, transitioning between wide aperture for low light and narrow aperture for deep of field in well-illuminated areas
4Manufacturing precision
If the objective lens is moved backward and forward to achieve focus on the video chip, then the focus can be optimized, but the minimum distance from the last lens surface to the video chip must be maintained
Solution Approach 1:
The patent pre-positions the objective lens at an optimized distance from the video chip sensor during assembly, establishing the focal plane in advance. The lens housing and mounting structure are designed to maintain this predetermined optimal distance, eliminating the need for post-assembly focus adjustment while ensuring sharp focus on the video chip sensor
5Manufacturing precision
If the objective lens is aligned optically to the photo sensitive area rather than the video chip housing, then the alignment precision is improved, but the centering process becomes more difficult
Solution Approach 1:
The patent introduces a centering member as an intermediary component that features a passageway optically aligned with the photo sensitive area of the video chip. This centering member serves as a mechanical reference that guides the objective lens into correct optical alignment during assembly, simplifying the centering process while maintaining high alignment precision
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 high-performance, compact objective lens with a 155° field of view, improved image quality, and robustness, capable of withstanding daily handling, while maintaining a short rigid portion length for enhanced maneuverability within body cavities.
Implementation Method 1
an achromatic lens composed of bi-convex lens cemented to a plan concave lens
Implementation Method 2
a centering member which is at first centered over a photosensitive area of a video chip and bonded to the surface of a video chip cover glass for holding the mechanical housing with the lenses centered to the photosensitive area
Implementation Method 3
utilizing high refractive index glasses to minimize length and aberrations
Data Source
AI summary
A wide field video endoscope objective and method of assembly the objective including four groups with five lenses, a mechanical housing containing the entire image forming elements, a aperture stop, a centering member and a retainer sleeve. The centering member is at first centered over the photo sensitive area of the chip and bonded to the surface of the cover glass. The retainer sleeve slides over said centering member and is glued to the centering member and the housing of the video chip. The objective housing with the optical elements is screwed on the centering member to adjust for focusing.