Fourier Space Utilization in Off-Axis OCT Scanning
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Solution Overview
Problem
Current Off-Axis Full-Field Time-Domain OCT methods poorly utilize the Fourier space, leading to oversampling and limited resolution and image field in sectional imaging of light-scattering specimens.
Innovation Solution
The method involves a light source with a central wavelength and coherence length less than 25 microns, splitting light into specimen and reference beams, and establishing a path length profile with a phase gradient on the camera, allowing for time-dependent displacement of the reference beam to optimize camera image detection and maximize the half bandwidth of the useful signal within the Fourier space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Off-Axis Full-Field Time-Domain OCT methods are used, then the measurement process is simple, but the Fourier space utilization is poor leading to limited resolution and image field
Solution Approach 1:
The patent implements dynamic control of the path length profile through time-dependent displacement of the reference beam, allowing the system to adaptively optimize Fourier space utilization. The path length profile is varied over time to scan different regions of the Fourier space, thereby improving resolution and image field without requiring a static complex optical configuration.
Solution Approach 2:
The patent changes the path length parameter of the reference beam as a function of time, creating a time-dependent path length profile. This parameter variation enables efficient scanning of the Fourier space, maximizing the utilization of available frequency components to improve image resolution and field of view while maintaining a relatively simple optical setup.
2Productivity
If the reference beam is stationary, then the system is simple to operate, but the scanning efficiency and Fourier space utilization are limited
Solution Approach 1:
The patent employs periodic displacement of the reference beam to systematically scan through different path length values. This periodic action enables efficient coverage of the required Fourier space region, improving scanning efficiency compared to stationary reference beam methods while minimizing redundant measurements and time loss.
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 improved scanning and utilization of the Fourier space, resulting in higher resolution and larger image fields without increasing measurement or computing time, allowing for more efficient extraction of structural information from internal sectional areas.
Implementation Method 1
light of a short-coherent light source is split into a specimen light beam and a reference light beam and fed to a specimen arm and a reference arm variable in its length and thereafter superimposed on a two-dimensional light detector
Implementation Method 2
provision of a light source, which emits light with a predetermined central wavelength λ0 and a coherence length less than 25 microns
Implementation Method 3
causing interference of reference light and specimen light on the camera by establishing a path length profile and a phase gradient of the reference light along the predetermined axis in the camera plane
Implementation Method 4
the phase gradient along the camera serves at the same time to separate interference and background light by means of Fourier filtering
Implementation Method 5
The variable reference arm thus allows specimen light from different specimen depths to be brought into a state of interference with the reference light. The change in length of the reference arm can be carried out by the reference mirror displaceable along the optical axis
Data Source
AI summary
The invention relates to a free-beam interferometric method for illuminating a sequence of sectional areas in the interior of the light-scattering object. The method makes it possible for the user to select a larger image field and/or a higher image resolution than previously possible with the occurrence of self-interference of the specimen light from a scattering specimen.