Laser Galvanometer Calibration Using a Defocused Reference Beam
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Solution Overview
Problem
Existing calibration methods for precision marking and cutting tools are time-consuming, expensive, and prone to human error, especially when performed offline. Additionally, real-time calibration techniques using position sensing diodes are at risk of being destroyed by high-power laser beams and struggle with accurately determining the position of the laser beam due to its small spot size.
Innovation Solution
The proposed solution involves a method for precision calibration of lasers and other cutting tools by minimizing errors between the galvanometer and the XY stage through relative error calibration. This is achieved by directing a defocused laser beam onto the XY stage and using position sensing diodes to center the beam, thereby recording offsets for each position. The calibration can be performed with the laser focused at different distances above and below the XY stage, allowing for accurate offset calculation and minimization of errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offline calibration using CMM measurements is performed, then calibration accuracy can be achieved, but the process is time-consuming and expensive
Solution Approach 1:
The patent replaces the mechanical CMM measurement system with an optical sensing system. Position sensing diodes (PSDs) detect the laser beam position optically, eliminating the need for mechanical contact and manual CMM measurements. This substitution enables real-time calibration while maintaining accuracy, directly resolving the time-consuming nature of offline CMM-based calibration.
Solution Approach 2:
The system enables self-calibration by using the laser beam itself as the reference for positioning. The PSDs detect the beam position directly, and the system automatically calculates corrections without requiring external CMM measurement or manual intervention. This self-service approach eliminates the need for expensive external calibration equipment and reduces calibration time significantly.
2Productivity
If position sensing diodes are used for real-time calibration, then calibration speed is improved, but the diodes are at risk of being destroyed by high-power laser beams
Solution Approach 1:
The patent extracts the sensing function from the high-power laser path. Position sensing diodes are placed in a separate, low-power reference beam path rather than exposing them directly to the high-power marking laser. This separation allows real-time calibration to proceed at high speed while protecting the sensitive PSDs from damage by keeping them out of the dangerous high-power beam zone.
3Productivity
If PSD sensors are used to detect laser beam position, then real-time calibration is enabled, but accurate determination is difficult due to the small spot size
Solution Approach 1:
The patent introduces a reference beam dimension that is separate from the high-power laser path. This reference beam provides a larger, easier-to-detect signal for the PSDs while still enabling calibration of the main laser system. By adding this auxiliary dimensional reference, the system overcomes the difficulty of detecting the small high-power laser spot size.
4Ease of manufacture
If calibration is performed with the laser in focus or collimated position, then calibration can be completed, but alignment and lens telecentricity errors are introduced
Solution Approach 1:
The patent performs preliminary calibration using a defocused beam at a known distance before conducting the actual focused laser calibration. This preliminary step establishes a reference that compensates for alignment and telecentricity errors, ensuring that the final focused laser calibration is accurate. By preparing the system in advance with the defocused reference measurement, the patent eliminates the need to choose between simplicity and accuracy.
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 method enables fast and accurate calibration of precision marking and cutting tools, reducing the need for extensive offline calibration and minimizing human error. It allows for low micron or submicron accuracy and can be implemented without modifying the laser path, making it a cost-effective and efficient solution.
Implementation Method 1
directing a defocused laser beam through a galvanometer and onto an XY stage; moving the XY stage to a first position that centers the defocused laser beam on a position sensing diode on the XY stage
Data Source
AI summary
A method of calibrating a laser galvanometer to an XY stage by directing a defocused laser beam through a galvanometer and onto an XY stage and re-centering the laser beam at subsequent positions on the XY stage. Offsets are calculated based on the required movement of the galvanometer to recenter the laser beam at each of the positions on the XY stage. The laser beam may be defocused by focusing the laser beam at a distance Z both above or below the XY stage for each position and then calculating the offset for each position by averaging the values calculated at the focus distances Z above and below the XY stage. The laser beam may also be defocused by passing it through a pinhole.