OCT Scanner Phase Error Compensation via Bidirectional Scanning
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Solution Overview
Problem
Optical coherence tomography (OCT) systems face errors in phase information due to optical scanners, particularly when incident light is reflected off the rotation axis of the scanner's mirror, leading to inaccuracies in measurements like blood flow velocity, which are difficult to correct due to the need for precise optical alignment and environmental stability.
Innovation Solution
The OCT apparatus employs a controller to perform alternating first and second scans in opposite directions, generating composite phase information by averaging or combining phase data from these scans to cancel out phase offsets caused by the scanner's movement, thereby eliminating measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If incident light is reflected at a position off the rotation axis of the reflecting mirror, then the optical arrangement is easier to implement, but phase information errors occur due to path length changes
Solution Approach 1:
Instead of trying to guide light toward the rotation axis (which requires high precision), the patent inverts the approach by guiding light away from the axis and then using computational methods to correct the resulting phase errors through the relationship between scanner position and phase offset
Solution Approach 2:
The patent changes the parameter of light incident position from 'on rotation axis' to 'off rotation axis', accepting the phase error as a known variable that can be corrected through parameter-based compensation using the scanner's angular position information
2Measurement precision
If incident light is guided toward the rotation axis of the reflecting mirror, then phase information accuracy is improved, but the optical arrangement requires extremely high precision and is sensitive to environmental conditions
Solution Approach 1:
The patent replaces the mechanical/optical precision requirement (guiding light exactly toward the rotation axis) with a computational system that calculates and corrects phase errors based on scanner position, substituting mechanical precision with algorithmic compensation
3Adaptability or versatility
If two reflecting mirrors are arranged in series for three dimensional scanning, then three dimensional scanning capability is achieved, but the incident position on the second mirror varies causing phase information errors
Solution Approach 1:
The patent uses feedback from the scanner's angular position information to calculate and correct phase errors. The system continuously monitors the scanner position and uses this information to compensate for path length changes caused by the scanning mechanism
Solution Approach 2:
The patent accounts for the varying incident position on the second mirror by treating it as a known parameter that changes with scanner angle, and uses this parameter information to calculate the corresponding phase offset for correction
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 eliminates phase information errors caused by optical scanners, enhancing the accuracy of measurements such as blood flow velocity, even under conditions of environmental change, by compensating for scanner-induced offsets through data processing.
Implementation Method 1
When incident light is reflected at a position off the rotation axis of the reflecting mirror like shown in FIG. 1B, the path length of the light changes as the reflecting mirror rotates, and thus changes occur in the phase information
Data Source
AI summary
An exemplary OCT apparatus includes a scanner, controller, phase information generator, phase information processor. The scanner applies an OCT scan to an object using an optical scanner. The controller controls the scanner to perform a first scan that scans a cross section of the object in a first scan direction and a second scan that scans a cross section of the object in a second scan direction opposite to the first scan direction. The phase information generator generates first phase information based on first acquisition data acquired by the first scan and second phase information based on second acquisition data acquired by the second scan. The phase information processor generates composite phase information based on the first phase information and the second phase information.