OCT Instrument Frequency Shifting for Extended Axial Imaging
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Solution Overview
Problem
Conventional optical coherence tomography instruments are limited by detection bandwidth, restricting the axial imaging depth range and preventing the capture of a broader range of sample depths.
Innovation Solution
An OCT instrument utilizing an adjustable optical frequency shifter and frequency shift controller to generate sideband light and maintain optical frequency, enabling the sampling of time-varying interference signals from both reference and signal light, allowing for the generation of multiple axial depth profiles that extend beyond the conventional detection limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the coherence length of the measurement light is increased to extend the axial imaging depth range, then the interference signal contains information about a larger axial depth range, but the detection bandwidth of the detector limits the available depth information to only a sub-range
Solution Approach 1:
The axial depth range is divided into multiple segments, each captured by a separate interference signal with a different optical frequency. The first interference signal captures depth information in a first axial depth range, while the second interference signal captures depth information in a second axial depth range. This segmentation allows the system to overcome the detector bandwidth limitation by distributing depth information across multiple frequency domains.
Solution Approach 2:
The patent introduces an additional dimension by using an adjustable optical frequency shifter to vary the optical frequency of the measurement light. Instead of relying solely on the temporal dimension (time-varying interference signal), the system now operates in both temporal and frequency dimensions. By adjusting the optical frequency, the system can access different axial depth ranges, effectively adding a frequency dimension to the depth encoding.
2Length of stationary object
If conventional OCT instruments use a fixed optical frequency to sample interference signals, then the detection bandwidth limits the axial depth range, but introducing mechanical moving parts to extend depth range would increase device complexity
Solution Approach 1:
The patent replaces mechanical moving parts with an adjustable optical frequency shifter, which is a non-mechanical device. Instead of physically moving components to change the optical path length or detection parameters, the system uses optical frequency shifting to access different axial depth ranges. This substitution eliminates mechanical complexity while achieving the same functional goal of extending the imaging depth range.
Solution Approach 2:
The system changes the optical frequency parameter of the measurement light using the adjustable optical frequency shifter. By dynamically adjusting this parameter, the system can access different axial depth ranges without any mechanical movement. The frequency parameter acts as a control variable that maps to different depth ranges, allowing flexible and complex-free depth range adjustment.
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 imaging over a broader axial depth range without mechanical moving parts, preserving anatomical information and reducing aliasing effects, thereby enhancing the depth of field in OCT imaging.
Implementation Method 1
The returning light from the sample arm and the reference arm are recombined by the coupler to generate an interference pattern
Implementation Method 2
the detector unit samples a first time-varying interference signal resulting from an interference between the sideband light and the other of the returned reference light or the returned signal light
Implementation Method 3
generate a sideband light by adjustably increasing, adjustably decreasing, or adjustably both increasing and decreasing, an optical frequency of a part of one of the returned reference light or the returned signal light
Data Source
AI summary
An OCT instrument comprising: an optical coupler which generates signal light and reference light from a swept narrowband light source; a detector which samples a time-varying interference signal based on the reference light and signal light returned from a sample; an adjustable optical frequency shifter which: generates a first sideband light by adjusting an optical frequency of the reference light, such that the detector unit samples a first time-varying interference signal resulting from an interference between the sideband light and the returned signal light; and maintains the optical frequency of the reference light such that the detector unit samples a second time-varying interference signal resulting from an interference between the reference light and the returned signal light. The OCT instrument generates a respective axial depth profile of the sample based on each of the sampled first time-varying interference signal and the sampled second time-varying interference signal.