OCT Laser Clock Subsystem and Cavity Extender
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Solution Overview
Problem
Current optical coherence analysis systems face challenges with high cost, physical size, and complexity due to the need for precise tuning of wavelength swept lasers for high-resolution, low-noise imaging, particularly in OCT systems, where parasitic reflections introduce noise and require complex interferometer configurations.
Innovation Solution
A compact clock laser system with a tunable laser source and clock subsystem on an optical bench, using a tunable filter and etalon for spectral filtering, and a cavity extender to reduce noise, along with a hybrid free space/fiber cavity with birefringence control to improve tuning performance and reduce parasitic reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stand alone Fabry-Perot or Mach-Zehnder interferometer is used to provide frequency markers, then frequency marking capability is achieved, but cost, physical size, and device complexity increase
Solution Approach 1:
The patent combines the frequency marking function with the existing interferometer components by using the same optical path and detectors. The interferometer that was previously used only for OCT imaging is now dual-purpose: it provides both imaging signals and frequency markers through spectral filtering of the laser source. This eliminates the need for separate stand-alone interferometers and reduces overall system complexity.
Solution Approach 2:
The interferometer system is designed to perform multiple functions: OCT imaging and frequency marking. By adding spectral filtering capability to the existing interferometer, a single component performs dual roles, reducing the need for additional dedicated frequency marking devices and lowering system complexity.
2Measurement precision
If spectral components are encoded by spatial separation (SEFD-OCT), then spectral resolution is achieved, but device complexity and physical size increase
Solution Approach 1:
The patent replaces the mechanical/spectral spatial encoding approach with temporal encoding. Instead of using a spectrally resolving detector system that requires complex optical paths for spatial separation of wavelengths, the system uses a wavelength swept source that encodes spectral information in time domain through sequential wavelength tuning. This simplifies the optical configuration while maintaining spectral resolution capability.
Solution Approach 2:
The system transitions from a static spectral encoding approach to a dynamic wavelength sweeping approach. The laser source continuously tunes its wavelength over time, and this temporal variation is used to encode spectral information, replacing the need for complex static spectral separation optics.
3Object-generated harmful factors
If parasitic reflections are suppressed by complex interferometer configurations, then noise reduction is achieved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the source of parasitic reflections by using a wavelength swept laser source with integrated frequency marking. This approach removes the need for complex interferometer configurations that were previously required to suppress noise from parasitic reflections, as the swept source inherently provides cleaner spectral information without the noise artifacts associated with complex interferometric setups.
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 solution enables high-resolution, low-noise imaging with reduced laser pattern noise and improved tuning performance, addressing the cost and complexity issues of existing systems while maintaining image quality and depth range.
Implementation Method 1
a tunable laser source, on the optical bench, that generates an optical signal that is tuned over a spectral scan band
Implementation Method 2
the clock subsystem comprises an etalon for spectrally filtering the tunable signal
Implementation Method 3
a detector for detecting the optical signal filtered by the etalon to produce the clock signals
Implementation Method 4
a beam splitter for directing a portion of the optical signal to the etalon and directing the filtered optical signal returning from the etalon to the detector
Data Source
AI summary
A frequency swept laser source for TEFD-OCT imaging includes an integrated clock subsystem on the optical bench with the laser source. The clock subsystem generates frequency clock signals as the optical signal is tuned over the scan band. Preferably the laser source further includes a cavity extender in its optical cavity between a tunable filter and gain medium to increase an optical distance between the tunable filter and the gain medium in order to control the location of laser intensity pattern noise. The laser also includes a fiber stub that allows for control over the cavity length while also controlling birefringence in the cavity.