Laser Focus Adjustment Using Power-Based Thermal Lens Prediction
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Solution Overview
Problem
In laser material processing, the 'thermal lens' effect caused by inhomogeneous heating of optical elements leads to focus shifts and beam quality deterioration, making precise real-time focus position control challenging.
Innovation Solution
A device and method that calculate and adjust the focus position using three parameters: laser power-dependent focus shift, time constant for temperature-induced changes, and current laser power, enabling real-time correction without complex mechanical means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If real-time focus position control is implemented using conventional methods, then processing quality is improved, but device complexity increases due to complex mechanical means
Solution Approach 1:
The patent replaces complex mechanical focus adjustment systems with a computational approach. A computing unit calculates the time-dependent focus position z(t) based on laser power P(t) and predetermined parameters (focus shift per power unit A and time constant τ), eliminating the need for complex mechanical sensing and adjustment mechanisms while achieving real-time focus control precision.
Solution Approach 2:
The patent uses parameter-based control by calculating focus position based on laser power parameters and predetermined characteristics (A and τ). By changing the control approach from mechanical position sensing to parameter-based computation (using power and time parameters), the system achieves precise focus control without mechanical complexity.
2Reliability
If thermal lens effects are compensated in real-time, then beam quality is maintained, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical or optical compensation systems for thermal lens effects with a computational model. The computing unit uses the calculated focus position z(t) to control a simple adjustment unit, replacing elaborate thermal compensation mechanisms while maintaining beam quality through software-based prediction and correction.
Solution Approach 2:
The patent applies preliminary action by calculating the expected focus shift based on laser power and time using the predetermined parameters A and τ, before the actual focus degradation occurs. This allows proactive adjustment of the focus position to compensate for thermal lens effects before they significantly degrade beam quality.
3Manufacturing precision
If complex mechanical means are used for focus adjustment, then focus position precision is improved, but ease of operation deteriorates
Solution Approach 1:
The patent replaces complex mechanical focus adjustment systems with automated computational control. The computing unit automatically calculates z(t) based on laser power and time, and the control unit automatically adjusts the focus position, eliminating the need for manual operation of complex mechanical systems while maintaining high precision.
Solution Approach 2:
The system performs self-service by automatically calculating and adjusting its own focus position based on laser power and time parameters. The computing unit and control unit work autonomously to maintain optimal focus without requiring manual intervention, simplifying operation while preserving precision.
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 approach allows for precise and flexible adjustment of the focus position, improving processing quality by compensating for thermal lens effects and maintaining high beam quality.
Implementation Method 1
a change in laser power and, secondly, contamination of the optical elements. Furthermore, the optical elements may undergo mechanical deformation, resulting in a change in their refractive power
Implementation Method 2
the so-called 'thermal lens,' which results from the heating of optical elements used for laser beam guidance and focusing by the laser power, especially in the multi-kilowatt range, and from the temperature dependence of the refractive index of optical glasses
Implementation Method 3
the temperature dependence of the refractive index of optical glasses. In particular, inhomogeneous heating leads to a thermal gradient in the optics, causing the 'thermal lens' effect. For example, when a multi-kW laser beam passes through a protective glass, the resulting thermal gradient causes it to refract
Data Source
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AI summary
The present disclosure relates to a device (200) for adjusting a focal position (z) of a laser beam (10) in a laser processing system (100). The device (200) comprises a computing unit which is configured to calculate a time-dependent value z t of the focus position (z), wherein the computing unit calculates the time-dependent value z t of the focus position (z) based on a first parameter, a second parameter and a third parameter, and a control unit which is configured to set the focus position (z) of the laser beam (10) based on the time-dependent value z t of the focus position (z) by means of a mechanism for adjusting the focus position (z).