Front-Looking OCT Probe Window with Self-Aligning Reference Mirror
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Solution Overview
Problem
Current optical coherence tomography (OCT) probes face challenges in achieving a front-looking design with a thick window, which complicates alignment and reduces depth of field, and existing fibre-based solutions are incompatible with windows thicker than a few tens of microns, leading to limited penetration depth and complex alignment requirements.
Innovation Solution
A fibre-based OCT system with a front-looking probe featuring a window with an anti-reflection inner face and a partially reflective outer face, allowing for self-alignment and contact with samples without breaking, using an anti-Newton surface to minimize reflections and scattering, and incorporating optical elements like lenses for focussing, with an anti-reflection coated fibre end to reduce reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick window is used in the probe, then the probe can be made safer for contact with samples and maintain structural integrity, but the depth of field is reduced and alignment becomes more complex
Solution Approach 1:
The window's outer face is designed to automatically perform multiple functions: it serves as the protective cover, the reference mirror, and the scattering element. The window itself generates the reference signal through scattering at its outer face, eliminating the need for separate alignment of reference arm elements. This self-service mechanism allows the thick window to maintain structural integrity while automatically providing the necessary optical reference function without complex alignment procedures.
2Ease of operation
If a front-looking probe design is implemented, then the probe structure is simplified and manipulation is easier, but alignment complexity increases and depth of field is reduced
Solution Approach 1:
The invention merges the reference arm function directly into the probe window's outer face. The same optical element (the window's outer face) that provides the front-looking protective barrier also serves as the reference mirror and scattering element. This merging of functions into a single integrated component eliminates the need for separate alignment of reference arm elements, thereby simplifying the overall alignment process while maintaining the front-looking probe design benefits.
3Ease of manufacture
If single mode fibres are used for coupling, then alignment is simpler, but light collection efficiency is very low
Solution Approach 1:
The invention changes the optical parameters at the fibre-probe interface by implementing an anti-reflection coating on the fibre end face. This parameter change (reducing reflection coefficient) enables the use of larger core diameter fibres or improved coupling geometry without suffering from excessive reflection losses, thereby improving light collection efficiency while maintaining reasonable alignment requirements.
4Loss of energy
If multimode fibres are used for coupling, then light collection efficiency is improved, but mode mixing, dispersion, and curvature losses increase
Solution Approach 1:
The invention replaces the mechanical alignment system (requiring precise positioning of separate reference arm elements) with an optical self-alignment mechanism. The window's outer face automatically serves as the reference mirror, and the system uses the scattering properties of this face to generate the reference signal. This substitution of mechanical alignment with optical self-alignment reduces sensitivity to fibre curvature and positioning errors, thereby improving signal stability while maintaining good light collection efficiency.
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 system enables high-quality imaging with improved alignment and compatibility with thicker windows, maintaining image clarity and depth of field, while allowing contact with samples without risk of injury, and achieving axial and lateral resolutions consistent with theoretical specifications.
Implementation Method 1
the window has an inner face with an anti-reflection surface that allows light from the source to pass through it
Implementation Method 2
an outer face that reflects some of the light from the source, the reflected light acting as a reference
Implementation Method 3
the outer face is treated so that the reference signal is a scattered signal
Implementation Method 4
incorporating optical elements like lenses for focussing
Implementation Method 5
with an anti-reflection coated fibre end to reduce reflections
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
An optical coherence tomography system comprising a light source (a) and a probe (e) that has a window at a front facing end. The window has an inner face (i) that has an anti-reflection surface and allows light from the source to pass through it, and an outer face (j) that reflects some of the light from the source and transmits some of the light to and from the sample (k). The reflected light acts as a reference.