Polarization-Sensitive OCT Trigger Synchronization for Correct Scan Order
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Solution Overview
Problem
In polarization sensitive OCT, interference waves are not collected in the correct switching order of polarization states due to variations in the timing of collecting interference waves caused by the motor drive unit's operation frequency differing from the light source wavelength sweeping frequency.
Innovation Solution
The image diagnosis apparatus synchronizes the collection of interference waves with the switching order of polarization states by using a trigger signal generation unit to generate AD and modulation trigger signals, which control the electro-optic modulator and A/D conversion unit to align with the encoder pulse signals, ensuring accurate polarization state switching and A/D conversion timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If interference waves are collected according to A line trigger at the same frequency as the light source wavelength sweeping, then the timing of collecting interference waves is synchronized with the light source, but the collection timing varies according to the number of collection lines per one revolution of the motor drive unit, causing interference waves to be collected in incorrect polarization state switching order
Solution Approach 1:
The system uses encoder pulse signals from the motor drive unit as feedback to dynamically adjust the trigger signal generation. The trigger signal generation unit counts encoder pulses and generates modulation trigger signals that switch polarization states in sync with the actual motor position, ensuring that interference waves are collected in the correct polarization state switching order regardless of variations in collection lines per revolution.
Solution Approach 2:
The system transitions from a fixed-frequency trigger approach to a dynamic trigger approach where the polarization state switching is adapted in real-time based on the motor drive unit's actual operation. The trigger signal generation unit dynamically adjusts the switching timing by counting encoder pulses, allowing the system to accommodate variations in the number of collection lines per revolution while maintaining correct polarization state sequencing.
2Adaptability or versatility
If the motor drive unit operates at a different frequency than the light source wavelength sweeping, then the system can accommodate varying imaging requirements, but the timing of collecting interference waves becomes misaligned with the polarization state switching
Solution Approach 1:
The encoder pulse signals serve as an intermediary between the motor drive unit and the trigger signal generation unit. By using these pulses as a reference, the system can decouple the motor drive unit's operation frequency from the light source wavelength sweeping frequency while still maintaining accurate synchronization. The trigger signal generation unit acts as a mediator that translates encoder pulse timing into appropriate polarization state switching and interference wave collection timing.
Solution Approach 2:
The system performs preliminary counting of encoder pulses to determine the appropriate timing for polarization state switching and interference wave collection. The trigger signal generation unit预先 counts encoder pulses and prepares modulation trigger signals in advance, ensuring that even when the motor drive unit operates at different frequencies, the interference waves are collected at the correct timing relative to the polarization state switching.
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 allows for the collection of interference waves in the correct order of polarization states, enhancing the accuracy and reliability of polarization sensitive OCT imaging.
Implementation Method 1
an electro-optic modulator configured to switch a polarization state of light from the light source according to modulation trigger signals
Implementation Method 2
an A/D conversion unit configured to perform A/D conversion on interference light signals from the interference light signal unit at timing determined by AD trigger signals
Implementation Method 3
obtains the polarization characteristics of the sample based on interference light between reflected light from the sample with respect to a plurality of incident lights having different polarization states and reference light
Data Source
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AI summary
An image diagnosis apparatus determines an effective pulse based on a pulse signal corresponding to the rotation of an imaging core from a pulse signal corresponding to an A line indicating a period of a light source and switches the polarization state of light transmitted from an optical transceiver according to the effective pulse. According to the effective pulse, the image diagnosis apparatus acquires a signal of interference light between the light received by the optical transceiver and reference light.