Optical Fiducial Calibration for Galvanometric Scanner Drift
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Solution Overview
Problem
In 3D metal printing applications, traditional fiducial generation methods are impractical due to the finely controlled metal particle layer covering the work plane, making in-situ drift monitoring and calibration challenging for laser scanners in 3D Select Laser Sintering (SLS) processes.
Innovation Solution
An optical source produces a fiducial source beam, and an optical fiducial pattern generator creates transient optical fiducials on the laser processing target within the scanner's field of view, allowing for adjustable positioning of the laser processing beam relative to these fiducials, which are detected by an optical detector to update scan error correction tables and maintain accurate calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration materials are placed on the work plane, then calibration reference information is provided, but the metal particle layer prevents fiducial generation and in-situ drift monitoring
Solution Approach 1:
The patent introduces a transparent substrate as an intermediary layer between the metal particle powder bed and the calibration fiducials. The fiducials are embedded in this substrate rather than directly in the metal particles, allowing optical detection systems to view the fiducials through the transparent material without interference from the reflective metal particles. This mediator enables both calibration functionality and compatibility with the SLS process.
Solution Approach 2:
The patent creates optical copies (images) of the fiducial markers using transparent materials that allow light transmission. Instead of using traditional opaque calibration materials that block the view of underlying metal particles, the system uses transparent fiducial representations that can be optically detected while allowing the build plate and metal particle layer to remain visible through them, enabling simultaneous calibration and process monitoring.
2Measurement precision
If support platen is made with fiducials for calibration, then calibration reference is provided, but in-situ drift monitoring becomes difficult when print material covers the platen
Solution Approach 1:
The patent embeds fiducial markers in the support platen before the printing process begins. These pre-positioned fiducials remain visible through the transparent substrate even as metal particle layers are deposited, allowing continuous drift monitoring without requiring removal or replacement of calibration materials during the build process.
Solution Approach 2:
The transparent substrate with embedded fiducials allows uninterrupted optical access to calibration markers throughout the entire printing process. The system maintains continuous drift monitoring capability without interruption, as the transparent material allows detection systems to view fiducials through accumulating metal particle layers, eliminating the need to stop calibration activities.
3Measurement precision
If calibration material is placed on work plane, then reference information is available, but the material must be removed after calibration
Solution Approach 1:
The patent merges the calibration fiducial markers with the support platen structure itself by embedding them in the transparent substrate. This integration eliminates the need for separate calibration materials that must be placed and removed, as the fiducials become a permanent part of the platen assembly that remains in place throughout all printing and calibration operations.
Solution Approach 2:
The transparent substrate serves multiple functions simultaneously: it provides structural support for the metal particle layer, embeds calibration fiducials for positioning accuracy, and allows optical transmission for both calibration detection and process monitoring. This multi-functional component eliminates the need for separate calibration materials and simplifies the overall system architecture.
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 solution enables precise and dynamic calibration of the laser processing beam, ensuring accurate scanning and reducing positional errors across the large field of view in 3D metal printing, even as the print material layer builds up, thereby maintaining high precision and accuracy throughout the process.
Implementation Method 1
A diffractive optical element can be used to provide the array of fiducial beamlets
Implementation Method 2
the laser processing target includes a powder material situated to diffusely reflect the at least one transient optical fiducial
Data Source
AI summary
An apparatus includes an optical source situated to produce a fiducial source beam, and an optical fiducial pattern generator situated to produce with the fiducial source beam at least one transient optical fiducial on a laser processing target that is in a field of view of a laser scanner situated to scan a laser processing beam across the laser processing target, so that a positioning of the laser processing beam on the laser processing target becomes adjustable relative to the at least one transient optical fiducial.