Endoscope Objective Lens Design for Oblique Viewing
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Solution Overview
Problem
Rigid endoscopes often face difficulties in aligning the object of interest with the endoscope shaft, necessitating complex beam deflection mechanisms, which complicates the design and increases manufacturing costs.
Innovation Solution
A compact endoscope objective design featuring a plano-convex rod lens and a biconvex lens on the image side, with additional lenses forming a front lens and an image-side lens element that corrects field curvature, allowing for a simple and compact structure with high optical quality, and optional beam deflection using a prism for oblique views.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam deflection mechanisms are added to enable oblique views, then the endoscope can observe objects not on the shaft axis, but the design complexity and manufacturing costs increase
Solution Approach 1:
The patent merges the beam deflection function directly into the lens elements themselves rather than using separate mechanical deflection mechanisms. The object-side lens element is designed with asymmetric curvature that inherently deflects light beams to achieve oblique viewing angles, combining imaging and beam steering functions into a single optical component.
Solution Approach 2:
The invention replaces mechanical beam deflection mechanisms with optical design solutions. Instead of using movable mirrors or prisms that require mechanical actuation, the patent uses specifically designed lens geometries with asymmetric surfaces that passively deflect light paths through refraction, eliminating complex mechanical systems.
2Manufacturing precision
If multiple lens elements are used to correct field curvature and improve optical quality, then image quality improves, but the lens diameter and complexity increase
Solution Approach 1:
The patent applies local quality by giving different regions of the lens elements different curvature characteristics. The object-side lens element has asymmetric curvature where the object-side surface differs from the image-side surface, allowing each region of the lens to optimize for specific parts of the field of view while maintaining overall compactness.
Solution Approach 2:
The invention achieves optical quality improvement by carefully controlling and varying geometric parameters of the lens elements. Specific curvature radii, thicknesses, and spacing between elements are optimized to correct field curvature and reduce distortion while keeping the overall lens assembly compact with controlled diameter.
3Volume of moving object
If a compact lens design is used to reduce diameter, then the endoscope size decreases, but the field of view and optical quality may be compromised
Solution Approach 1:
The patent utilizes optimized spherical and asymmetric curved surfaces in the lens elements to maximize light gathering and field of view within a compact form factor. The curved surfaces are specifically designed to redirect light rays from wide angles through the small aperture, achieving a field of view greater than 70 degrees despite the compact lens diameter.
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 design achieves high optical quality with minimal distortion and astigmatism, enabling a wide field of view while reducing manufacturing and assembly costs through cemented lenses and anti-reflection coatings, and allows for easy adaptation between straight and oblique views.
Implementation Method 1
an objective for an endoscope, having an object-side lens element which contains a plano-convex rod lens, and an image-side lens element which contains a biconvex lens arranged at the image-side end of the objective
Implementation Method 2
anti-reflection coatings
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An objective (1) for an endoscope (24, 25) comprises an object-side lens element (2) containing a plano-convex rod lens (7), and an image-side lens element (3) containing a biconvex lens (13) arranged at the image-side end of the objective (1). The object-side lens element (2) contains a plano-convex first lens (5) and a biconcave second lens (6), which form a front lens (4) and are arranged in this order on the object side of the plano-convex rod lens (7), which forms a third lens. The image-side lens element (3), viewed from the object side, contains a biconvex fourth lens (9), a concave-plane fifth lens (10), and a biconcave sixth lens (12), which are arranged in this order on the object side of the biconvex lens (13) located at the image-side end of the objective (1), which forms a seventh lens.