Laser Scanner Calibration Using Retroreflectors for Geometric Accuracy
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Solution Overview
Problem
Existing scanner devices for positioning laser beams in processing fields suffer from pincushion-shaped image distortion and geometric errors, requiring accurate calibration to achieve true-to-scale and distortion-free projections.
Innovation Solution
The method employs a retroreflector, which reflects a significant proportion of the laser beam independently of the angle of incidence, allowing for precise determination of the laser beam's actual position in the processing field using increased reflected intensity, and adjusts the scanner device's control settings to compensate for projection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a retroreflector is used to increase reflected laser intensity for position detection, then measurement precision improves, but device complexity increases
Solution Approach 1:
A retroreflector is introduced as an intermediary object between the laser beam and the scanner device. The retroreflector reflects the laser beam back to the scanner with high intensity regardless of the angle of incidence, enabling precise detection of the laser beam's actual position without requiring complex detection systems. This intermediary element simplifies the overall measurement system while improving precision.
2Manufacturing precision
If calibration is performed to correct projection errors, then manufacturing precision improves, but loss of time increases
Solution Approach 1:
The calibration process is performed in advance before actual manufacturing operations. During calibration, the retroreflector is positioned at various known locations in the processing field, and the scanner device's projection errors are measured and stored. These pre-determined correction values are then applied during manufacturing to compensate for any projection errors, ensuring high positioning accuracy without time-consuming real-time calibration.
3Reliability
If the retroreflector has high reflectivity independent of incidence angle, then reliability of position detection improves, but object-generated harmful factors increase due to scattered radiation
Solution Approach 1:
The retroreflector is designed with specific local optical properties that enable it to reflect laser radiation back to the scanner device with high intensity across a wide range of incidence angles. This localized reflective quality ensures reliable position detection while the retroreflector's geometry is optimized to minimize scattered radiation in other directions, reducing harmful effects.
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 enhances the accuracy of laser beam positioning, reducing geometric errors and enabling high-precision calibration of scanner devices in three-dimensional component production machines.
Implementation Method 1
use of a retroreflector for calibrating the scanner device, i.e., a reflective material or object that reflects a significant portion of an incident laser beam back towards the beam source—in this case, the scanner device—essentially independent of the angle of incidence
Data Source
Figure 1~2
AI summary
The invention relates to a method for calibrating a scanner (11) in order to position a laser beam (6) in a machining field (13), having the following steps: arranging at least one retroreflector (19) in the machining field (13) of the scanner (11), said machining field being formed preferably in a machining chamber (15) for irradiating powder layers (3); detecting laser radiation (20) reflected back into the scanner (11) when the laser beam (6) traverses the retroreflector (19); ascertaining an actual position (XP, YP) of the laser beam (6) in the machining field (13) using the detected laser radiation (20); and calibrating the scanner (11) by correcting a laser beam (6) target position (ΧT, ΥT) specified for the scanner (11) in the machining field (13) using the ascertained actual position (XP, YP) of the laser beam (6) in the machining field (13). The invention also relates to a corresponding machining tool (1) for producing three-dimensional components (2) by irradiating powder layers (3).