Rigid Endoscope Spacer Tube for Lens Positioning
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Solution Overview
Problem
The existing rigid endoscope design suffers from diameter reduction of the fiber tube due to a step protrusion, leading to increased assembly tolerances, calibration precision issues, and impaired cleanability, as well as interfering reflections from gold plating and soldering residues within the beam path.
Innovation Solution
A spacer tube is directly supported between the objective lens and window, eliminating the need for a landing on the fiber tube, allowing for a larger calibration mandrel and improved cleanability, and serving as a shield to prevent lateral reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a step protrusion is used to form a stop for the objective lens, then the distance of the objective lens from the window is precisely preserved, but the inner diameter of the fiber tube is reduced and assembly tolerances increase
Solution Approach 1:
The invention extracts the stop function from the fiber tube wall and relocates it to a separate spacer device. The spacer is inserted into the fiber tube and provides the stop for the objective lens, while the fiber tube maintains its full inner diameter without the protruding step that would reduce the diameter.
Solution Approach 2:
The spacer acts as an intermediary element between the fiber tube and the objective lens. It provides the necessary stop function while allowing the fiber tube to maintain its structural integrity and full diameter, eliminating the need for a protruding step in the fiber tube wall.
2Manufacturing precision
If a step protrusion is used to form a stop, then the objective lens position is fixed, but cleanability in the region of the stop edge is impaired
Solution Approach 1:
The stop function is extracted from the fiber tube wall and placed in a separate spacer device that can be easily cleaned. The spacer's outer surface is smooth and free of protrusions that would trap flux residue, allowing for easy cleaning while still providing the necessary position fixing for the objective lens.
3Reliability
If gold plating is applied to the inner surface of the fiber tube for secure fixing, then the window can be firmly soldered, but interfering reflections are generated in the beam path
Solution Approach 1:
The gold plating is extracted from the fiber tube inner surface and relocated to the spacer device. The spacer is coated with gold plating on its outer surface that contacts the window, providing secure soldering. The spacer's positioning prevents the gold-plated surface from being in the beam path, eliminating interfering reflections.
Solution Approach 2:
The spacer serves as an intermediary that separates the gold-plated soldering surface from the beam path. It provides the necessary gold plating for secure window fixing while its positioning and design prevent the reflective surface from generating interfering reflections in the optical path.
4Reliability
If a mandrel is pushed through the fiber tube to support the window during soldering, then the window can be held securely, but the diameter of the mandrel must be reduced due to the projection
Solution Approach 1:
The mandrel is extracted from the fiber tube interior and repositioned to the exterior. The spacer device provides external support for the window during soldering, eliminating the need for a mandrel to pass through the fiber tube. This removes the constraint on mandrel diameter caused by the protruding step.
Data Source
AI summary
A rigid endoscope including: a fiber tube; a window disposed at a the distal end of the fiber tube; an objective lens arranged in the fiber tube; a spacer tube to maintain the objective lens at a predetermined-distance from the window; and an objective lens tube for holding the objective lens, the objective lens tube being disposed in the fiber tube between the window and at least a portion of the spacer tube; wherein the spacer tube is supported on a distal end against the window and on a proximal end against the objective lens.