Laser Keyhole Depth Measurement With Chromatic Aberration Correction
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Solution Overview
Problem
Laser processing apparatuses with combined galvano mirrors and fθ lenses face challenges in accurately measuring keyhole depth due to chromatic aberration, causing deviations in the irradiation positions of processing and measurement lights, which affects the accuracy of keyhole depth measurement.
Innovation Solution
A laser processing apparatus that includes a movable mirror, a stage to adjust the incident angle of measurement light, and a controller to correct for chromatic aberration by generating and applying correction data, ensuring accurate alignment of processing and measurement lights using an optical interferometer to measure keyhole depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a lens is used to condense both laser light for processing and measurement light, then both lights can be focused on the processing point, but chromatic aberration causes deviation in arrival positions of the lights
Solution Approach 1:
The system performs preliminary measurement to obtain actual arrival positions of laser light and measurement light on the workpiece surface before processing. Based on these measured positions, correction data is generated in advance to compensate for chromatic aberration. This preliminary action allows the system to pre-calculate the deviation caused by chromatic aberration and create correction values that will be applied during subsequent processing operations.
Solution Approach 2:
The system changes the parameters of the correction data based on the measured arrival positions and wavelengths of the lights. By adjusting the correction values according to the specific chromatic aberration characteristics observed in measurements, the system dynamically adapts the correction parameters to match the actual optical conditions, thereby compensating for wavelength-dependent focal shifts.
2Measurement precision
If correction data is generated to eliminate deviation caused by chromatic aberration, then arrival position accuracy is improved, but data processing complexity increases
Solution Approach 1:
The system performs preliminary measurement to obtain actual arrival positions of laser light and measurement light on the workpiece surface before processing. Based on these measured positions, correction data is generated in advance to compensate for chromatic aberration. This preliminary action allows the system to pre-calculate the deviation caused by chromatic aberration and create correction values that will be applied during subsequent processing operations.
Solution Approach 2:
The system creates correction data that replicates the chromatic aberration compensation pattern. By measuring the actual deviation and creating a correction map or lookup table, the system copies the correction approach into a reusable data structure that can be applied without real-time complex calculations during 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
The solution enables precise measurement of keyhole depth by correcting for chromatic aberration, ensuring accurate alignment and enhancing the accuracy of keyhole depth measurement in laser processing.
Implementation Method 1
generates an optical interference intensity signal based on interference caused by an optical path difference between the measurement light reflected at the processing point and reference light
Implementation Method 2
chromatic aberration occurs in the fθ lens. As a result, a deviation occurs between irradiation positions of the laser light for processing and the measurement light on the surface of the workpiece
Implementation Method 3
a lens that condenses the laser light for processing and the measurement light on the processing point
Data Source
AI summary
Laser processing apparatus includes movable mirror for changing paths of laser light for processing and measurement light, and stage for changing an incident angle of measuring light. Furthermore, laser processing apparatus includes lens for condensing laser light for processing and measurement light on processing point, controller for controlling laser oscillator, movable mirror, and stage based on corrected data for processing, and measurement processor for measuring a depth of keyhole generated at processing point. The corrected data for processing is data corrected so as to a deviation of an arrival position of at least one of laser light for processing and measurement light caused by chromatic aberration of lens on the surface of workpiece. With this configuration, an accurate depth of keyhole can be measured.