Optical Coherence Tomography Scanner Position Encoder
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Solution Overview
Problem
Existing optical coherence tomography (OCT) scanners face challenges in achieving geometrically accurate B and C scans due to inaccuracies in MEMS mirror positioning caused by temperature changes, aging, and inertia, which are not optimally addressed by traditional position tracking methods.
Innovation Solution
Incorporating a position encoder with a pattern of alternating transmissivity regions in the optical path of the probing beam, allowing for precise tracking of the beam's position and inclination using a patterned anti-reflective coating layer on a substrate, and utilizing algorithms to generate geometrically correct sub-surface scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position encoder is introduced to accurately track the probing beam position, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary position encoder consisting of a patterned element with alternating transmissivity regions placed in the optical path. This mediator converts the beam position information into detectable optical signal variations without requiring direct contact or complex mechanical sensors, thereby improving measurement precision while keeping the added complexity manageable through optical rather than mechanical means.
2Measurement precision
If the position encoder uses a pattern with high contrast regions, then measurement precision is improved, but the encoder obstructs more of the probing beam, reducing transmissivity
Solution Approach 1:
The position encoder employs a pattern where only specific localized regions have altered transmissivity properties (either increased or decreased), while other regions remain transparent. This local quality approach allows the encoder to provide sufficient positional information through the patterned regions without obstructing the entire beam path, thus maintaining adequate overall transmissivity while achieving precise position detection.
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
Enables the recording of geometrically accurate sub-surface scans by accurately deducing the probing beam position and inclination, correcting for positional differences in A scans, and maintaining high transmissivity to avoid obstructing the view of the scanned object.
Implementation Method 1
the position encoder pattern (200) comprises a substrate (201) on which a patterned anti-reflective coating layer (202) is defined, and wherein the position encoder pattern (200) is at least partly formed by a plurality of first regions of a first transmissivity and a plurality of second regions of a second transmissivity
Implementation Method 2
a patterned anti-reflective coating layer (202) is defined on the substrate (201)
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
Disclosed is an optical coherence tomography scanner and a method for recording sub-surface scans of an object, wherein a position encoder is arranged in the path of the probing beam of an interferometric system. The encoder pattern is detected in a sequence of A scans at generated for different probing beam positions on the scanned object, the probing beam position and/or inclination for at least one A scan of said sequence of A scans is deducing based on the detected encoder pattern, and the sub-surface scan of the object is generated based on the sequence of A scans taking into account the deduced probing beam position and/or inclination.