Radial Scanning OCT System with Rotator-Derotator Mechanism
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Solution Overview
Problem
Existing optical coherence tomography (OCT) systems using raster scanning for line-field imaging are not preferred due to limitations in motion artifacts, fringe washout, and sensitivity roll-off, particularly with semiconductor optical amplifier (SOA) based ring laser designs that face significant power loss in negative wavelength tuning.
Innovation Solution
The implementation of a rotator-derotator mechanism in an OCT system for radial scanning, utilizing optical elements like Dove prisms or k-mirror devices, allows for precise control over the light beam's orientation and profile, enhancing image quality and resolution by synchronizing rotational adjustments with image capture and adjusting beam parameters based on real-time feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If raster scanning is used for line-field OCT imaging, then the field of view can be covered, but motion artifacts and fringe washout occur reducing image quality
Solution Approach 1:
The patent inverts the traditional raster scanning approach by using radial scanning where a single galvanometer scans perpendicular to the line extent, combined with an image rotator that rotates the line on the sample. This inversion of the scanning geometry eliminates motion artifacts and fringe washout while maintaining complete field of view coverage.
2Speed
If SOA based ring laser is used for swept-source OCT, then high imaging speed can be achieved, but significant power loss occurs in negative wavelength tuning
Solution Approach 1:
The patent replaces the problematic SOA based ring laser mechanical tuning system with a different swept source architecture that achieves high imaging speed through alternative means, avoiding the four-wave mixing effect that causes power loss in negative tuning directions.
3Device complexity
If a single scanning galvanometer is used instead of orthogonal pair, then device complexity is reduced, but scanning capability is limited
Solution Approach 1:
The patent makes the single galvanometer system universal by combining it with an image rotator mechanism. The galvanometer scans perpendicular to the line extent while the rotator rotates the line orientation, together providing complete two-dimensional scanning capability equivalent to orthogonal galvanometer pairs but with reduced complexity.
4Adaptability or versatility
If image rotator is added to the system, then radial scanning capability is achieved, but device complexity increases
Solution Approach 1:
The patent merges the image rotator function with the existing galvanometer scanning system. The rotator-derotator mechanism is integrated into the optical path to rotate the line on the sample while the galvanometer handles the perpendicular scanning, creating a unified radial scanning system that achieves versatility without excessive complexity.
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 approach enables high-resolution and high-quality imaging in OCT systems by reducing motion artifacts and improving sensitivity and detection efficiency, suitable for a wide range of applications including ophthalmic imaging.
Implementation Method 1
The rotator-derotator mechanism includes one or more optical elements selected from the group consisting of Dove prisms and k-mirror devices. These optical elements are rotated by a control unit to alter the angle of the emitted beam
Implementation Method 2
The rotator-derotator mechanism includes one or more optical elements selected from the group consisting of Dove prisms and k-mirror devices
Implementation Method 3
an optical assembly that manages the propagation of the beam both before and after interaction with the rotator-derotator mechanism
Implementation Method 4
The system comprises a light source configured to emit a beam of light and an optical assembly that manages the propagation of the beam
Implementation Method 5
A detector array captures interference patterns resulting from the interaction of the rotated and wavelength-tuned beam with the sample
Data Source
AI summary
A line-field parallel swept optical coherence tomography (OCT) system optimized for high-resolution ophthalmic imaging and capable of broad industrial applications. The system employs a gain chip using gallium-aluminum-arsenide (GaAlAs) for light amplification within a specific “water window” wavelength range, suitable for deep tissue imaging. The design incorporates a hermetically sealed packaging with an optional thermoelectric cooler and utilizes a single angled facet (SAF) with high reflectivity and antireflective coatings to enhance laser performance. The optical path includes a collimating lens, a cat's eye focusing lens, and a bandpass filter adjustable via an angle control actuator for dynamic wavelength tuning. The system features a rotator-derotator mechanism utilizing Dove prisms or k-mirror devices, for example, for precise radial scanning. This allows for quick, accurate imaging, making it ideal for capturing high-resolution images of the retina and other surfaces.