Optical Coherence Tomography Frequency Shifting for Mirror Artifact Reduction
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Solution Overview
Problem
Optical coherence tomography (OCT) instruments face challenges in distinguishing real structures from complex conjugate mirror artifacts, which overlap and corrupt clinical information, particularly in imaging the retina, due to the symmetry properties of Fourier transforms, requiring additional hardware or computationally expensive post-processing.
Innovation Solution
An OCT instrument with an adjustable optical frequency shifter controlled by a frequency shift controller compensates for the inclination of the sample by varying the optical frequency during scanning, reducing the inclination of the image relative to the lateral direction, thereby minimizing artifact overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OCT measurement setups are used, then the imaging process is simple, but complex conjugate mirror artifacts overlap with real structures and corrupt clinical information
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the optical frequency of the reference light through an adjustable optical frequency shifter. This frequency modulation parameter change enables the system to distinguish between real structures and complex conjugate mirror artifacts, improving imaging reliability without adding complex hardware components.
Solution Approach 2:
The system implements dynamics by making the optical frequency shift adjustable and time-varying during the measurement process. The frequency shifter dynamically modifies the reference light frequency based on the sample characteristics, allowing real-time adaptation to different imaging conditions and maintaining high reliability across varying scenarios.
2Reliability
If post-processing techniques like dispersion-encoded full-range OCT are used to cancel complex conjugate mirror terms, then artifact cancellation is effective, but computational cost increases significantly
Solution Approach 1:
The patent applies preliminary action by performing frequency shifting on the reference light before the interference measurement is taken. This pre-processing of the optical signal eliminates the need for complex post-processing computations, as the frequency modulation is already embedded in the measured signal, thereby reducing computational expense while maintaining effective artifact cancellation.
Solution Approach 2:
The system replaces complex computational post-processing with an optical-domain solution. By using an adjustable optical frequency shifter to encode frequency information during acquisition, the patent substitutes heavy computational algorithms with a more efficient optical measurement approach, reducing computational power requirements while achieving the same artifact cancellation effect.
3Reliability
If additional hardware components are added to cancel complex conjugate mirror artifacts, then artifact reduction is achieved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the adjustable optical frequency shifter a multi-functional component that serves multiple purposes: it generates sideband light for interference measurements, dynamically compensates for sample inclination, and enables artifact cancellation. This single component performs multiple functions that would otherwise require separate hardware systems, thereby improving image quality without proportionally increasing device complexity.
Solution Approach 2:
The system uses parameter changes through the adjustable optical frequency shifter to achieve artifact cancellation without additional hardware. By dynamically modifying the optical frequency parameter during measurements, the patent enables the same hardware to handle various imaging conditions and artifact types, improving reliability while avoiding the need for multiple specialized components.
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 effectively reduces the impact of complex conjugate mirror artifacts, allowing for accurate extraction of anatomical information without the need for additional hardware or complex post-processing, enhancing the reliability of OCT imaging.
Implementation Method 1
an adjustable optical frequency shifter arranged to generate a sideband light by adjustably increasing, adjustably decreasing, or adjustably both increasing and decreasing, an optical frequency of one of the returned reference light or the returned signal light
Implementation Method 2
an optical coupler arranged to accept light from a swept narrowband light source and to split the light into at least signal light and reference light
Implementation Method 3
a detector unit arranged to sample, for each of the scan locations, a respective 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
Data Source
AI summary
An OCT instrument operable to acquire a B-scan representing a section of a sample, the sample being inclined relative to a plane normal to an axial direction along which depth information of the B-scan is acquired, the OCT instrument being configured to: split light from a swept light source into signal light and reference light; receive signal light reflected from scan locations on the sample; generate sideband light by adjusting an optical frequency of the reference light; sample, for each scan location, a respective time-varying interference signal resulting from interference between the sideband light and the received signal light; generate the B-scan from the sampled signals; and control the optical frequency during the scan such that an image of the sample in the B-scan is less inclined to a lateral direction in the B-scan than in a B-scan of the section acquired by the OCT instrument without the control.