Inline Coherent Imaging for Laser Penetration Depth Feedback
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Solution Overview
Problem
Current laser technologies face challenges in achieving precise axial control during material processing, particularly in surgical and industrial applications, due to limitations in controlling the depth of laser beam penetration, leading to issues such as unintended tissue damage and weld porosity.
Innovation Solution
The implementation of an inline coherent imaging (ICI) system that uses optical interferometry to provide real-time feedback for controlling laser processing parameters, allowing for precise measurement and control of material modification processes by correlating interferometry output with pre-calculated synthesized interferograms to determine the depth of material penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser power is increased to improve processing speed, then productivity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent employs pulsed laser operation with precisely controlled pulse duration and repetition rate to achieve both high processing speed and precise depth control. By using periodic pulsed action instead of continuous wave laser, the system can deliver high peak powers for rapid material removal while controlling average power to prevent excessive penetration. The pulse timing and duration are optimized to achieve the desired balance between productivity and precision.
Solution Approach 2:
Real-time depth measurement feedback allows the system to maintain precise penetration control even at high processing speeds. The OCT system continuously monitors penetration depth and provides feedback that enables dynamic adjustment of laser parameters, ensuring that increased power for faster processing does not compromise depth accuracy. This feedback mechanism decouples the trade-off between speed and precision.
2Ease of operation
If laser processing is used to eliminate mechanical adjustment, then ease of operation is improved, but measurement precision deteriorates due to plasma interference
Solution Approach 1:
The patent introduces optical coherence tomography (OCT) as an intermediary measurement system that operates independently of the laser processing beam. The OCT system uses low-power broadband light to probe the material, providing depth measurements without being affected by the high-power processing laser plasma. This intermediary measurement system resolves the contradiction by providing accurate depth data even in the presence of plasma interference, enabling automated control.
Solution Approach 2:
The patent replaces traditional mechanical measurement systems with optical-based OCT measurement. This substitution eliminates mechanical contact and interference while providing non-intrusive, real-time depth measurement capability. The optical measurement system can operate through the same optical access as the laser processing, providing seamless integration without mechanical adjustment requirements.
3Ease of operation
If conventional laser processing is used to reduce tool wear, then ease of operation is improved, but reliability deteriorates due to lack of depth control
Solution Approach 1:
The patent implements closed-loop feedback control where real-time depth measurements from OCT are used to adjust laser parameters and ensure accurate penetration depth. This feedback mechanism transforms laser processing from an unreliable open-loop process to a controlled system with guaranteed depth accuracy. The system can reliably stop at precise depths, prevent over-penetration, and ensure consistent results across varying materials and conditions.
Solution Approach 2:
The patent performs preliminary characterization of material optical properties using OCT before and during processing. This preliminary information about material structure, density, and optical absorption is used to pre-calculate and optimize laser parameters for the specific material being processed. By preparing the processing parameters in advance based on material characterization, the system ensures reliable and repeatable depth control from the start of processing.
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 precise control of laser cutting and welding processes, reducing unintended tissue damage and improving weld quality by providing real-time feedback on material penetration depth, thus enhancing both surgical precision and industrial productivity.
Implementation Method 1
an optical interferometer that produces an interferometry output using imaging light that is input to the optical interferometer based on a length of at least one optical path to the sample location compared to a length of another optical path
Data Source
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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.