OCT Reference Geometry for Galvoscanner Drift Correction
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Solution Overview
Problem
In laser machining systems, the drift of galvanometer scanners due to thermal effects and detector deterioration leads to inaccuracies in determining the position of the measurement spot on the workpiece, as existing position detectors are affected by thermal influences and cannot correct for small deviations between desired and actual positions.
Innovation Solution
A device that uses an optical reference geometry and deflection optics to direct the OCT measuring beam, allowing the evaluation unit to determine the distance between reference planes and calculate the orientation or drift of optical devices like mirrors or gratings, thereby correcting for positional deviations without the need for additional spatially resolving detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the position detector of the galvanometer scanner is used to determine the angular position, then the control loop can correct position deviations, but thermal effects and detector deterioration cause drift that cannot be detected or corrected
Solution Approach 1:
The patent introduces an optical reference geometry as an intermediary object that reflects the measuring beam back to the coherence tomograph. This reference geometry serves as a mediator between the galvanometer scanner and the measurement system, enabling indirect measurement of the scanner's angular position without relying on the deteriorating position detector. The reference geometry provides a stable reference that is not affected by thermal drift or detector deterioration.
Solution Approach 2:
The patent replaces the mechanical position detection system (galvanometer scanner with position detector) with an optical measurement system (coherence tomograph with reference geometry). Instead of using the mechanical position detector that suffers from thermal effects and deterioration, the system uses optical interference measurements to determine the angular position of the scanner mirrors, thereby substituting a failing mechanical sensing mechanism with a more stable optical measurement approach.
2Measurement precision
If additional spatially resolving detectors are introduced to measure drift accurately, then position precision improves, but system complexity and manufacturing costs increase
Solution Approach 1:
The patent makes the coherence tomograph multi-functional by using it for both its primary measurement task and for determining the angular position of the galvanometer scanner. The same optical measuring beam and evaluation unit are used to perform both the workpiece measurement and the scanner position measurement, eliminating the need for separate detection systems and reducing overall system complexity.
Solution Approach 2:
The system uses itself to measure its own state. The coherence tomograph uses its own measuring beam to determine the position of the optical devices that direct the beam. By directing the measuring beam onto the reference geometry and analyzing the reflected light, the system performs self-diagnosis of its angular position without requiring external measurement devices.
3Stability of the object's composition
If expensive high-precision galvoscanners with stable position detectors are used, then position stability improves, but system cost increases
Solution Approach 1:
The patent implements a feedback mechanism where the coherence tomograph continuously measures the angular position of the galvanometer scanner mirrors by directing the beam onto the reference geometry. This measurement feedback is used to detect drift and correct the scanner position, enabling the use of less expensive scanners while maintaining high position stability through active compensation rather than relying on expensive inherently stable hardware.
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 accurate determination and correction of the orientation of optical devices, improving the precision of the measurement spot on the workpiece and allowing the use of inexpensive galvoscanners for high-precision applications, resulting in a simpler and more cost-effective design.
Implementation Method 1
an optical coherence tomograph (OCT) configured to direct an optical measuring beam (13) onto an optical reference geometry (310)
Implementation Method 2
a deflection optics (320) configured to direct an optical measuring beam (13) of the coherence tomograph (200) displaced or reflected by the optical device onto the optical reference geometry (310)
Data Source
AI summary
A device is provided for determining an orientation of an optical device of a coherence tomograph. The device has an optical reference geometry, a deflection optics configured to direct an optical measuring beam reflected by the optical device onto the optical reference geometry, and an evaluation unit configured to determine a distance between a first reference plane and at least one second reference plane of the optical reference geometry in order to determine the orientation of the optical device.