Laser Keyhole Depth Measurement Using Beam Alignment Correction
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Solution Overview
Problem
Laser processing apparatuses with galvano mirrors and f0 lenses face challenges in accurately measuring keyhole depth due to chromatic aberration, which causes deviations in the irradiation positions of processing and measurement laser light, leading to inaccurate keyhole depth measurement.
Innovation Solution
The apparatus includes a controller that adjusts the operation of first and second mirrors to correct for chromatic aberration, using corrected processing data to ensure accurate alignment of processing and measurement laser light, and an optical interferometer to generate interference signals for precise keyhole depth measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens is used to collect processing laser light and measurement light, then the laser light can be focused at the processing point, but chromatic aberration occurs causing deviation between irradiation positions of processing and measurement light
Solution Approach 1:
The patent divides the optical path into separate channels for processing laser light and measurement light, with independent optical paths from the light source to the workpiece. This segmentation allows each channel to be optimized independently, eliminating the chromatic aberration problem that occurs when a single lens must focus both wavelengths simultaneously.
Solution Approach 2:
The patent introduces a beam combiner as an intermediary device that merges the processing laser light and measurement light onto a common optical path after they have been separately guided. This mediator allows the two different wavelength lights to be combined without causing chromatic aberration, as the beam combiner is positioned such that the chromatic aberration effect is minimized or eliminated.
2Device complexity
If chromatic aberration is not corrected, then the system is simpler, but the deviation between processing and measurement light positions prevents accurate keyhole depth measurement
Solution Approach 1:
The patent performs preliminary correction of the chromatic aberration problem by designing the optical path with separate channels and a beam combiner before the light reaches the workpiece. This preliminary arrangement ensures that the processing and measurement lights are properly aligned at the workpiece plane, preventing measurement errors before they occur.
Solution Approach 2:
The patent addresses the chromatic aberration problem by adding a spatial dimension to the optical path design. Instead of trying to correct the aberration in the same optical path, the system uses separate spatial channels for processing and measurement light, combining them at a specific plane where the chromatic aberration effects are minimized. This dimensional separation allows both functions to coexist without interference.
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 solution allows for accurate measurement of keyhole depth by correcting for chromatic aberration, ensuring that both processing and measurement laser light are accurately aligned, thereby improving the precision of keyhole depth measurement.
Implementation Method 1
generates an optical interference 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
since wavelengths of the processing laser light and the measurement light are different from each other, chromatic aberration occurs in the f0 lens
Implementation Method 3
a lens that collects the processing laser light and the measurement light at the processing point
Implementation Method 4
a first mirror that changes traveling directions of the processing laser light and the measurement light
Implementation Method 5
a second mirror that changes an incidence angle of the measurement light to the first mirror
Data Source
AI summary
A laser processing apparatus sets a processing section passing through a target position on a processing surface, sets a measurement section centered on the target position in the processing section, sets a plurality of data acquisition positions that are trajectories perpendicular to a processing direction in the measurement section. The laser processing apparatus acquires pieces of measurement data indicating shapes of keyholes at the respective data acquisition positions during processing of the processing section, and projects the pieces of measurement data in the processing direction to be superimposed on each other to create projection data. The laser processing apparatus obtains the second instruction value in a direction perpendicular to the processing direction at the target position on the basis of the projection data. Therefore, it is possible to provide a laser processing apparatus and a laser processing method capable of accurately measuring a depth of a keyhole.