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 depth measurement.
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 control the angles of processing and measurement light, using optical interference signals to accurately measure the keyhole depth by correcting for chromatic aberration through controlled operation of mirrors and deflection units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a galvano mirror combined with an fθ lens is used to direct processing laser light, then the processing speed and coverage area are improved, but chromatic aberration causes deviation between processing laser light and measurement light, deteriorating measurement precision
Solution Approach 1:
The patent divides the optical path into separate channels for processing laser light and measurement light. By using independent optical paths with separate mirrors and lenses, the system eliminates chromatic aberration effects that occur when both lights share the same optical components, thereby maintaining measurement precision while preserving processing speed through the galvano mirror system.
Solution Approach 2:
The patent introduces a beam combiner/splitter as an intermediary component that allows processing laser light and measurement light to coexist in the same optical path without interfering with each other. This intermediary enables the system to maintain the high-speed scanning capability of the galvano mirror while separately guiding measurement light to avoid chromatic aberration-induced deviations.
2Device complexity
If the incident angle of measurement light on the coupling mirror is fixed, then the optical path is simplified, but the ability to correct chromatic aberration and align light paths is reduced
Solution Approach 1:
The patent makes the incident angle of measurement light on the coupling mirror dynamically adjustable rather than fixed. By incorporating an angle adjustment mechanism that can change the measurement light's incident angle, the system can dynamically correct for chromatic aberration effects and align the measurement light path with the processing laser light path, thereby improving measurement precision without significantly increasing overall system complexity.
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 keyhole depth by aligning processing and measurement light paths, overcoming chromatic aberration issues, thereby improving measurement precision.
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
Data Source
AI summary
A laser processing apparatus includes a laser oscillator that oscillates processing laser light to be incident on a processing point on a processing surface of a workpiece, 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, 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 that controls the laser oscillator and the measurement light deflection unit, 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, and a beam position measurement unit that measures positions of the processing laser light and the measurement light.