Coherent Interferometric Feedback for Laser Depth Control
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Solution Overview
Problem
Current laser systems face challenges in achieving precise axial control during material processing, particularly in surgeries and industrial applications, due to unpredictable laser depth penetration and instability of keyhole formation, leading to issues like unintended tissue damage and weld failure.
Innovation Solution
An apparatus and method utilizing an optical interferometer and feedback controller to monitor and control material processing parameters based on interferometry output, enabling precise control of laser depth and stability through inline coherent imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If laser processing is used to achieve high transverse control and non-contact operation, then ease of operation and infection control are improved, but reliability deteriorates due to poor axial control and unintended tissue damage
Solution Approach 1:
The patent integrates optical coherence tomography-based feedback to continuously monitor the axial depth of laser processing in real-time. This feedback loop allows the system to maintain reliable axial depth control while preserving the non-contact operation benefits, preventing unintended tissue damage by stopping or adjusting the laser when the target depth is reached.
Solution Approach 2:
The patent performs preliminary imaging and planning using optical coherence tomography before laser processing begins. The system creates a 3D map of the target tissue structure, identifies critical boundaries and features, and pre-calculates the optimal laser processing path and parameters. This preliminary action ensures reliable depth control by establishing stop points and safety margins before the non-contact laser processing begins.
2Loss of information
If standard metrology techniques are used to guide laser processing, then measurement capability is provided, but measurement precision deteriorates due to plasma generation, high aspect ratio holes, and blinding by the processing laser
Solution Approach 1:
The patent introduces optical coherence tomography as an intermediary measurement technique that operates in a different optical regime than traditional metrology systems. The OCT system uses low-coherence interferometry to measure depth and structure, which is immune to the plasma generation and blinding effects that plague conventional optical metrology during laser processing. This intermediary approach enables precise depth measurement without being affected by the harsh processing environment.
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 real-time, precise control of laser depth and stability, reducing unintended tissue damage and weld defects by providing accurate feedback on material modification processes.
Implementation Method 1
an optical interferometer that produces an interferometry output using at least a component of the imaging light that is delivered to the sample, the interferometry output based on at least one optical path length to the sample compared to another optical path length
Data Source
AI summary
Methods and systems are provided for using optical interferometry in the context of material modification processes such as surgical laser or welding applications. An imaging optical source that produces imaging light. A feedback controller controls at least one processing parameter of the material modification process based on an interferometry output generated using the imaging light. A method of processing interferograms is provided based on homodyne filtering. A method of generating a record of a material modification process using an interferometry output is provided.