Optical Scanner Alignment Using Back-Reflected Beam Calibration
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Solution Overview
Problem
Existing methods for calibrating optical scanners in additive manufacturing, such as powder bed fusion apparatus, are time-consuming and prone to inaccuracies due to the resolution limitations of scanners and variations in laser intensity and quality.
Innovation Solution
A method using a photodetector to detect back-reflected electromagnetic radiation, allowing for calibration of optical scanners without the need for spatial detectors like cameras or PSDs, and utilizing a reference element with a curved reflective surface to determine alignment by analyzing intensity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods using cameras or PSDs are used, then spatial detection is achieved, but device complexity and calibration time increase
Solution Approach 1:
The patent extracts the detection function from external complex devices (cameras, PSDs) and integrates it into a simple photodetector within the optical scanner's existing optical path. The photodetector detects back-reflected laser radiation, eliminating the need for separate spatial detection systems while maintaining alignment measurement capability.
Solution Approach 2:
The photodetector serves multiple functions: it detects the position of the laser beam, measures alignment accuracy, and provides feedback for calibration. By making the detection system multi-functional, the patent reduces overall device complexity while maintaining measurement precision.
2Measurement precision
If multiple iterations of calibration process are performed to achieve desired accuracy, then measurement precision improves, but productivity decreases
Solution Approach 1:
The photodetector provides real-time feedback on laser beam position by detecting back-reflected radiation intensity. This immediate feedback allows for single-pass or minimal-iteration calibration, as the system can directly measure and correct alignment errors without requiring multiple repeated measurements and adjustments.
Solution Approach 2:
The patent replaces iterative mechanical adjustment processes with an optical detection and computational correction system. The photodetector measures alignment errors optically, and the control system automatically calculates correction factors, eliminating the need for repeated manual calibration iterations.
3Reliability
If laser intensity and quality variations are present across the working plane, then calibration complexity increases, but if a robust detection method is used, then reliability improves
Solution Approach 1:
The patent changes the detection parameter from spatial position (requiring cameras or PSDs) to radiation intensity (detected by simple photodetectors). By detecting the intensity of back-reflected laser radiation, the system becomes insensitive to laser intensity and quality variations across the working plane, as the photodetector measures the reflected signal strength rather than requiring precise spatial mapping.
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 reduces calibration time and improves accuracy by leveraging the spatial resolution of the optical scanner's beam positioning rather than detector resolution, and provides higher signal-to-noise ratios through back-reflected specular reflection.
Implementation Method 1
A method using a photodetector to detect back-reflected electromagnetic radiation, allowing for calibration of optical scanners without the need for spatial detectors like cameras or PSDs, and utilizing a reference element with a curved reflective surface to determine alignment by analyzing intensity changes
Data Source
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AI summary
A method and apparatus for determining an alignment of an optical scanner (106a, 106c) for directing an electromagnetic beam to locations within a scan field. The method may comprise locating a reference element (113) within the scan field of the optical scanner (106a, 106c) and controlling the optical scanner (106a, 106c) to cause the electromagnetic beam to be directed to a plurality of different points in the scan field, including at least one point on the reference element (113). Reflected electromagnetic radiation is detected. The method may comprise determining when the electromagnetic beam is directed to a reference position in the scan field given by the reference element (113) from a comparison of an intensity of the detected electromagnetic radiation for the different points and determining a corresponding demand signal that causes the optical scanner (106a, 106c) to direct the electromagnetic beam to the reference position.