Oblique-view endoscope objective with total internal reflection
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Solution Overview
Problem
Conventional endoscope objective arrangements with multiple reflection surfaces are limited by the size of reflective coatings, restricting the largest field angle that can be imaged and resulting in a bulky deflection unit.
Innovation Solution
Incorporating a region of total internal reflection on the second reflection surface within the transmission region, allowing for partial deflection of imaging rays by total internal reflection instead of reflective coatings, which reduces the size of the deflection unit and enables larger field angles without increasing the external diameter of the endoscope tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflective coatings are used on the second reflection surface to deflect imaging rays, then reliable light steering is achieved, but the deflection unit becomes bulky and the installation size increases
Solution Approach 1:
The patent applies different reflection mechanisms to different regions of the second reflection surface: total internal reflection in the overlap region with the transmission region, and selective reflective coatings only where absolutely necessary. This local differentiation reduces the overall coating area and deflection unit size while maintaining reliable light steering where required
Solution Approach 2:
The patent extracts the reflective coating from the overlap region between the transmission region and second reflection surface, replacing it with total internal reflection. This removal of unnecessary coatings reduces material usage and allows for a more compact deflection unit design
2Volume of stationary object
If the distance between the first reflection surface and the second reflection surface is reduced to compact the deflection unit, then the installation size decreases, but the field angle may be restricted by reflective coatings
Solution Approach 1:
The patent creates an overlap region where the transmission region and second reflection surface coincide, applying total internal reflection locally in this area. This allows marginal rays at large field angles to be properly deflected even when the distance between reflection surfaces is reduced, maintaining field angle coverage in a compact design
3Volume of stationary object
If the second reflection surface overlaps with the transmission region to enable compact design, then both light transmission and reflection can occur in the same area, but stray light and ghost images may occur
Solution Approach 1:
The patent applies selective reflective coatings only in specific regions of the second reflection surface where they are needed to prevent stray light and ghost images, while leaving the overlap region with the transmission region uncoated to utilize total internal reflection. This localized approach maintains compact size while controlling harmful optical effects
Solution Approach 2:
The patent converts the potential harmful effect of light striking the second reflection surface into a beneficial total internal reflection in the overlap region. By carefully designing the geometry and refractive indices, rays that might otherwise cause stray light are instead totally internally reflected to contribute usefully to the imaging beam path
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 compact deflection units that can handle large field angles, maintaining a small installation size and preventing stray light and ghost images, while ensuring reliable imaging without increasing the endoscope's external diameter.
Implementation Method 1
the second reflection surface (7) has a region of total internal reflection (8) which, at least in part, is arranged in the transmission region (5) and which is configured for the total internal reflection of imaging rays
Data Source
AI summary
In the case of an objective arrangement (1) having a deflection unit (4) which guides an imaging beam path (9) from a light entrance (2) to a light exit (3) via a first reflection surface (6) and a second reflection surface (7), it is provided to embody a region (8) of total internal reflection at least in the second reflection surface (7), with this region being configured for total internal reflection in the imaging beam path (9) and this region forming part of a transmission region (5) that is disposed upstream of the first reflection surface (6), through which imaging rays from the light entrance (2) are incident on the first reflection surface (6).