Laser Cutting Head Wavefront Feedback for Thermal Focus Shift
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Solution Overview
Problem
High-power laser cutting heads experience thermal focus shift due to heat absorption, leading to optical aberrations such as defocus, spherical, coma, and astigmatism, which affect cutting precision and repeatability, especially under prolonged use, and existing compensation methods are either inaccurate or costly.
Innovation Solution
A laser cutting head with a collimating and focusing group supported by linear guiding means, integrated wavefront sensors, and electronic processors to measure and adjust optical aberrations, ensuring precise focal point positioning and minimizing aberrations through controlled movement of optical groups or adaptive optical devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high laser power is used for cutting thick metal sheets, then cutting capability is improved, but thermal focus shift and optical aberrations worsen
Solution Approach 1:
The patent implements dynamic adjustment of the optical system by making the focusing group movable along the optical axis through linear guiding means. This allows real-time compensation for thermal focus shift by adjusting the position of the focusing lens in response to temperature changes, thereby maintaining cutting precision despite high laser power operation
Solution Approach 2:
The patent incorporates wavefront sensors that continuously measure optical aberrations including defocus, spherical, coma, and astigmatism. These measurements provide feedback to a control system that automatically adjusts the optical elements to correct the measured aberrations, creating a closed-loop system that maintains precision under thermal stress
2Productivity
If prolonged use of high laser power occurs, then productivity is improved, but thermal focus shift and optical aberrations worsen
Solution Approach 1:
The patent performs preliminary measurement of the wavefront and identification of optical aberrations before they significantly degrade cutting quality. The control system proactively adjusts the optical elements to prevent aberrations from developing, ensuring consistent cutting repeatability throughout prolonged high-productivity operation
Solution Approach 2:
Continuous wavefront sensing provides real-time feedback on the state of the optical system during prolonged operation. This enables automatic compensation for thermal effects that accumulate over time, maintaining cutting repeatability even during extended high-productivity runs
3Manufacturing precision
If wavefront sensors and electronic processors are added to measure and adjust optical aberrations, then cutting precision is improved, but device complexity increases
Solution Approach 1:
The wavefront sensor serves multiple functions: it measures defocus, spherical aberration, coma, and astigmatism simultaneously. The control system integrates these measurements and coordinates adjustment of multiple optical elements, achieving comprehensive aberration correction with a single multi-functional sensing device rather than requiring separate sensors for each type of aberration
Solution Approach 2:
The patent combines the wavefront sensing function, measurement processing, and optical element adjustment control into an integrated system. The electronic processor merges the complex task of measuring and correcting multiple types of optical aberrations into a unified control algorithm that manages all adjustments through a single coordinated system
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
The solution ensures high precision and repeatability in cutting metal sheets with high laser powers, reduces optical aberrations, and maintains cutting quality over extended machine tool use, while being compact and cost-effective.
Implementation Method 1
at least one wavefront sensor adapted to receive a first focused portion of the laser beam, perform a phase measurement of a wavefront of the first focused portion
Implementation Method 2
a focusing group for focusing, in a focal point placed on a surface of the piece or just below or just above said surface, the laser beam exiting collimated from the collimating group
Implementation Method 3
a collimating group for collimating the laser beam coming from the laser emitting apparatus
Implementation Method 4
an optical element for receiving the laser beam exiting focused from the focusing group, reflecting, with an angle of reflection given, a focused first portion of the received laser beam
Implementation Method 5
a phenomenon commonly known as 'thermal focus shift', which causes the optical aberration of defocus or blurring, i.e. a shift of focus with respect to the desired and optimal point
Data Source
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AI summary
A laser cutting head (1) associable to a machine tool comprises a collimating group (2) to collimate a laser beam (L) coming from a laser emitting apparatus, a focusing group (5) to focus in a focal point (F) the laser beam (L) collimated, an optical element (8; 38) to receive said laser beam (L) focused and reflect a focused first portion (LI) thereof, and a wavefront sensor (9) to receive said focused first portion (LI) of the laser beam (L), perform a phase measurement of a wavefront of said focused first portion (LI), obtain a reconstructed wavefront on the basis of the phase measurement and send the reconstructed wavefront to an electronic processor (12); the electronic processor compares the reconstructed wavefront and a reference wavefront, determines one or more optical aberrations to which the laser beam (L) is subjected, reduces such optical aberrations and changes said focal point (F).