Laser Beam Focal Position Sensing With Chromatic Confocal Optics
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Solution Overview
Problem
Existing methods for determining the focal position of a processing laser beam are indirect, slow, costly, or impractical for fast process cycles, especially in applications with varying workpiece tolerances and thermal fluctuations, and do not accurately account for optical path interferences.
Innovation Solution
A device using a chromatic confocal principle with integrated measurement light sources and detectors in the laser device, guiding measurement light coaxially with the processing laser beam to directly determine the focal position on the workpiece, accounting for optical elements' influence on the beam path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect focal position determination methods are used, then device complexity is reduced, but measurement precision and speed deteriorate
Solution Approach 1:
The patent combines the measurement light source, beam guide with chromatic aberration, and detector into an integrated device that directly determines focal position. This merging of components enables direct measurement while maintaining manageable device complexity through functional integration.
Solution Approach 2:
The patent introduces a beam guide with chromatic aberration as an intermediary optical element that converts axial focal position information into lateral beam displacement. This intermediary enables precise focal position determination by translating depth information into measurable lateral shifts.
2Device complexity
If indirect focal position determination methods are used, then device complexity is reduced, but productivity deteriorates
Solution Approach 1:
The integrated device combines measurement and detection functions in one unit, enabling rapid focal position determination without complex multi-step procedures. This integration significantly reduces measurement time and improves productivity.
Solution Approach 2:
The patent replaces mechanical focal position adjustment and measurement methods with an optical-based chromatic confocal measurement system. This substitution enables non-contact, high-speed focal position determination that is much faster than mechanical methods.
3Device complexity
If measurement light is not guided coaxially with processing laser beam, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent uses asymmetric optical paths where measurement light and processing laser beam are guided coaxially through different optical components. This asymmetric yet coaxial arrangement enables independent optimization of measurement and processing paths while maintaining precise spatial correlation.
Solution Approach 2:
The coaxial beam guide serves multiple functions: it guides both measurement light and processing laser beam, provides chromatic aberration for focal position determination, and maintains precise spatial alignment. This multi-functionality reduces the need for separate alignment systems.
4Manufacturing precision
If chromatic aberration optical elements are not used, then manufacturing precision requirements are reduced, but measurement precision deteriorates
Solution Approach 1:
The patent exploits chromatic aberration, a parameter change in optical path length based on wavelength, to convert axial focal position into lateral beam displacement. This parameter change enables precise focal position measurement while using commercially available optical elements with standard manufacturing tolerances.
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 rapid, direct, and economical focal position determination and monitoring, adaptable to varying conditions, with high accuracy and integration into existing processing systems.
Implementation Method 1
at least one optical element with chromatic aberration, which is passed through by the measurement light and is arranged in the processing head
Data Source
AI summary
A device for determining a focal position of a processing laser beam in relation to a surface of a workpiece, including a measurement light source to emit measurement light at at least two different measurement wavelengths, a processing head to focus the measurement light onto the workpiece, and a beam guide to guide the measurement light to the processing head. The device includes at least one optical element with chromatic aberration, which is passed through by the measurement light and arranged in the processing head and a detector configured to capture an intensity of the measurement light reflected by the surface. The device includes an evaluator configured to determine the focal position of the processing laser beam in relation to the surface using the intensity captured by the detector. The beam guide is configured for jointly beam-guiding the processing laser beam and the measurement light to the processing head.