Laser Keyhole Depth Measurement With Chromatic Aberration Correction
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Solution Overview
Problem
Existing laser processing apparatuses using a galvano mirror combined with an fθ lens face challenges in accurately measuring the depth of a keyhole due to chromatic aberration, causing deviations between processing laser light and measurement light, which prevents precise measurement of the keyhole depth.
Innovation Solution
A laser processing apparatus and method that includes a laser oscillator, a coupling mirror, a measurement light deflection unit, a lens, and a beam position measurement unit to correct for chromatic aberration by adjusting the incident angles of measurement light, ensuring accurate alignment of processing and measurement light on the workpiece surface, and using optical interference to measure the keyhole depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a galvano mirror combined with an fθ lens is used for laser processing, then the laser processing speed and efficiency are improved, but chromatic aberration causes deviations between processing laser light and measurement light, deteriorating measurement precision
Solution Approach 1:
The patent introduces a beam position measurement unit as an intermediary device that measures the actual positions of both processing laser light and measurement light. This intermediary measurement system detects chromatic aberration effects and provides correction data, enabling the system to maintain high productivity while achieving accurate keyhole depth measurements through compensation.
Solution Approach 2:
The patent changes the parameter of incident angle for measurement light using a measurement light deflection unit. By adjusting the incident angle dynamically, the system compensates for chromatic aberration effects caused by the fθ lens, allowing measurement light to reach the correct position on the workpiece surface despite the presence of chromatic aberration, thus maintaining measurement precision while preserving high processing speed.
2Measurement precision
If chromatic aberration correction is implemented by adding a measurement light deflection unit, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The beam position measurement unit serves multiple functions: it measures the position of processing laser light, measures the position of measurement light, and provides correction data for chromatic aberration. By making this single device multi-functional, the patent improves measurement precision without proportionally increasing device complexity, as the same hardware infrastructure supports multiple measurement and correction tasks.
Solution Approach 2:
The patent implements a feedback mechanism where the beam position measurement unit continuously monitors the positions of laser beams and provides correction information to the control system. This feedback loop enables automatic compensation for chromatic aberration, maintaining high measurement precision while managing device complexity through intelligent control rather than purely mechanical additions.
3Measurement precision
If the incident angle of measurement light is adjusted to correct chromatic aberration, then measurement accuracy is improved, but the alignment between processing light and measurement light becomes more difficult to maintain
Solution Approach 1:
The system implements self-service alignment through the beam position measurement unit, which automatically detects positional deviations caused by chromatic aberration and provides correction data. This eliminates the need for manual alignment adjustments, as the system self-corrects by dynamically adjusting the measurement light incident angle based on real-time position measurements, thereby improving measurement accuracy while maintaining ease of operation.
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 accurate measurement of the keyhole depth by correcting for chromatic aberration, allowing for precise laser processing control and improved measurement accuracy.
Implementation Method 1
a measurement processor that measures a depth of a keyhole generated at the processing point by the processing laser light by using an optical interference signal based on an interference generated by an optical path difference between the measurement light reflected at the processing point and reference light
Implementation Method 2
a lens that concentrates the processing laser light and the measurement light on the processing point
Implementation Method 3
a coupling mirror that deflects or transmits the processing laser light and measurement light to be incident on the processing point toward the processing point
Data Source
AI summary
A laser processing apparatus includes a laser oscillator that oscillates processing laser light incident on a processing point on a processing surface, a coupling mirror that deflects or transmits the processing laser light and measurement light incident on the processing point toward the processing point, a measurement light deflection unit that changes an incident angle of the measurement light on the coupling mirror, a lens that concentrates the processing laser light and the measurement light on the processing point, a controller, a measurement processor that measures a depth of a keyhole generated at the processing point by the processing laser light using an optical interference signal based on interference generated by an optical path difference between the measurement light reflected at the processing point and reference light, and a beam position measurement unit that measures positions of the processing laser light and the measurement light.