Laser Focus Position Sensing via Coaxial Sub-Beams
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Solution Overview
Problem
Existing laser material processing systems face challenges in accurately determining the focus position of a laser beam in real time due to thermal lens effects, which cause focus shifts and deteriorate beam quality, making precise focus position control difficult.
Innovation Solution
A device comprising at least two optical elements that couple out coaxial sub-beams, a spatially resolving sensor to detect intensity distributions, and an evaluation unit to determine beam diameters and focus position, allowing for real-time focus position determination using a model or function to analyze beam caustics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single back-reflection method is used to determine focus position, then the device complexity is low, but the measurement precision is insufficient due to thermal lens effects causing focus shifts and beam quality deterioration
Solution Approach 1:
The patent divides the focus position determination into multiple independent measurements by using at least two different back-reflection paths (e.g., front surface and rear surface reflections of an optical element). Each back-reflection provides a separate measurement that can be individually evaluated and combined, thereby improving measurement precision without requiring a completely complex new system architecture.
Solution Approach 2:
The patent introduces an intermediary optical element (such as a protective glass or beam splitter) that creates multiple back-reflection paths. This intermediary component enables the separation of measurement paths while maintaining a relatively simple overall device structure, resolving the contradiction between measurement precision and device complexity.
2Productivity
If real-time focus position determination is implemented, then the productivity is improved through fast focus control, but the device complexity increases due to the need for multiple optical elements and real-time processing
Solution Approach 1:
The patent implements continuous real-time focus position determination by continuously monitoring multiple back-reflection paths simultaneously. This continuous measurement approach enables fast focus control and improves productivity, as the system can track focus position changes dynamically without interruption or significant delay.
Solution Approach 2:
The patent combines multiple back-reflection measurements into a unified focus position determination process. By merging the information from different reflection paths (e.g., front surface and rear surface reflections) and evaluating them together, the system achieves real-time focus control while managing device complexity through integrated processing.
3Measurement precision
If multiple back-reflection paths are used to improve measurement accuracy, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent makes the optical elements serve multiple functions: they both guide the laser beam for processing and create back-reflection paths for focus position measurement. For example, the protective glass or beam splitter serves as both a functional optical component and a measurement reference, thereby improving measurement precision without proportionally increasing device 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 precise and real-time determination of the laser beam focus position, improving processing quality by compensating for thermal lens effects and maintaining beam quality.
Implementation Method 1
at least two surfaces of at least one optical element, each configured to reflect a portion of the laser beam to output a sub-beam
Implementation Method 2
a spatially resolving sensor for detecting an intensity distribution of the superimposed sub-beams
Data Source
Figure 1
Figure 2
Figure 3(a)~3(d)
AI summary
The present invention relates to a device (200) for determining a focus position (F) of a laser beam (10) in a laser machining system (100). The device (200) comprises a first optical element (210) which is designed to reflect a portion of the laser beam (10) in order to uncouple a first sub-beam (12) of the laser beam (10), a second optical element (220) which is designed to reflect another portion of the laser beam (10) in order to uncouple a second sub-beam (14) of the laser beam (10) substantially coaxially to the first sub-beam (12), a spatially-resolving sensor (230) to which the first sub-beam (12) and the second sub-beam (14) can be directed, and an evaluation unit (240) which is designed to determine a focus position (F) of the laser beam (10) on the basis of the first and second sub-beams (12, 14) hitting the spatially-resolving sensor (230).