Laser Machining Head Optics for High-Yield Reflection-Free Monitoring
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Solution Overview
Problem
Current machining heads for laser cutting suffer from low illumination light yield and interfering reflections during process monitoring, limiting the informative value of camera recordings.
Innovation Solution
A machining head equipped with a polarising beam splitter and a retardation plate, which converts linearly polarised illumination light into circular and back to linear polarisation, optimising the use of illuminating light and reducing reflections by guiding up to 100% of the emitted light for detection, while minimising interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a 50:50 beam splitter is used to guide illuminating light through the exit opening, then the illuminating light can be directed to the workpiece and back to the camera, but only a maximum of 25% of the emitted illuminating light can be used due to light loss at each interface
Solution Approach 1:
The patent changes the polarization state of the illuminating light from linear to circular using a retardation plate, and uses a polarizing beam splitter that transmits circularly polarized light while reflecting linearly polarized light. This parameter change in polarization state allows up to 100% of the emitted light to be utilized instead of the maximum 25% with a conventional 50:50 beam splitter, thereby resolving the contradiction between illumination intensity and energy loss.
2Manufacturing precision
If the exit opening has a very small shutter diameter for laser cutting, then the machining precision is improved, but a very steep angle of incidence for the illuminating light is required which reduces light transmission
Solution Approach 1:
The patent uses a polarizing beam splitter with specific polarization properties that allows it to transmit circularly polarized illuminating light effectively even at steep angles of incidence. This enables the use of a small shutter diameter for precise cutting while maintaining adequate light transmission for process monitoring, as the polarizing beam splitter's transmission characteristics are less sensitive to angle variations when dealing with circularly polarized light.
3Ease of operation
If illuminating light passes through multiple optical interfaces and boundary layers, then the light can be guided from the source to the workpiece and back to the camera, but undesired reflections occur at these interfaces reducing the informative value of camera recordings
Solution Approach 1:
The patent employs a polarizing beam splitter that differentiates between circularly polarized transmitted light and linearly polarized reflected light. By converting the illuminating light to circular polarization with a retardation plate, the system allows the transmitted light to pass through interfaces while the reflected light from the workpiece is selectively transmitted to the camera. This polarization-based differentiation eliminates interfering reflections from optical interfaces while preserving the useful reflected light from the workpiece, thereby improving process monitoring capability without harmful reflections.
4Use of energy by moving object
If the illuminating light is deflected at the beam splitter, then the light can be directed toward the exit opening, but 50% of the light is lost at the deflection interface
Solution Approach 1:
The patent uses a polarizing beam splitter that transmits circularly polarized light with minimal loss while reflecting linearly polarized light. By converting the illuminating light to circular polarization, the system achieves near-100% transmission efficiency at the beam splitter interface, eliminating the 50% light loss that occurs with conventional beam splitters. This resolves the contradiction by changing the polarization parameter to match the beam splitter's transmission characteristics.
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 configuration enhances the illumination light yield for monitoring, allowing up to 4 times more illuminating light to be used for process monitoring and significantly reduces interfering reflections, resulting in more informative and reliable camera recordings.
Implementation Method 1
a retardation plate arranged between the polarising beam splitter and the exit opening for converting at least a portion of the emitted linearly polarised illumination light beam into a circularly polarised illumination light beam and for converting at least a portion of the circularly polarised illumination light beam reflected from the workpiece into a linearly polarised illumination light beam
Implementation Method 2
a polarising beam splitter for guiding at least part of the emitted linearly polarised illumination light beam in the direction of the exit opening
Data Source
AI summary
A machining head for the laser machining of a workpiece. The machining head may include a first interface for a machining laser source for emitting a machining laser beam, a second interface for an illumination light source for emitting an illumination light beam, an exit opening for the machining laser beam and the illumination light beam, a third interface for a detector device for detecting the illumination light beam reflected from the workpiece, and guide optics for at least partial coaxial guiding of the emitted illumination light beam through the exit opening and of the illumination light beam reflected from the workpiece, through the exit opening, to the third interface. The guide optics have a polarising beam splitter for guiding at least part of the emitted illumination light beam in the direction of the exit opening, and a retardation plate between the polarising beam splitter and the exit opening.