Master Thesis: Computer vision for automated laser Galvano mirror calibrat

The research institute Swerim provides applied research within mining engineering, process metallurgy and materials and manufacturing engineering, mainly for the mining, steel and metals industry. Swerim has 190 co-workers in two locations in Sweden - Luleå and Stockholm.

Goal
Design a Matlab (or phyton) class together with a GUI and webcam that automatically can measure the position of the laser. The laser can be located on a plane or surface and the goal is to find a suitable transfer function  so a conversion back and forth between voltage output from the hardware and actual position in millimetres is made possible.

Background

Figure 1 (top) Laser ultrasonic measurements of defects in a transmission component. (bottom) Pattern from the generation laser after measuring the material properties of cold rolled.

Swerim uses Laser Ultrasonics (LUS) to characterize material properties or detect defects in metals. The material properties in the metal are usually varying in different directions so probing (i.e. measuring) the material with the laser ultrasound in different directions give useful information about the studied material. The LUS-system consists of two lasers, a generation- and a detection laser, and it is a great advantage if one of the lasers could be steered along any path while keeping the other laser fixed. This is done at Swerim today but the conversion between hardware-signal and actual position is made manually.

Swerim has a set of Galvano mirrors that can steer the laser beam in an X/Y-plane. The X and Y position is controlled a voltage signal provided by a two-channel function generator (Moku:Go or Tektronix AFG). The voltage can be controlled as a function of time so that any pattern can be drawn. However, for most application the exact position is desired in terms of X and Y position in mm rather than voltage. The LUS setup is often rebuilt which requires a new calibration every time. Swerim has currently a calibration procedure for this laser system, but it is manual and very time consuming so hence an automated calibration method/algorithm is desirable for saving setup time.

Purpose
The purpose of the project is to create software with a graphical user interface (GUI) using Matlab or Phyton with a function generator and a webcam where the positioning of the laser in voltage can be automatically calibrated against the position in any plane or surface (e.g. using a calibration checkerboard). The GUI should find a suitable transfer function  between any desired position in the plane to the corresponding X/Y-voltage. Additionally, the GUI should then be able to take coordinates in terms of millimetres and transfer back into the corresponding voltage and send it to the function generator/Galvano mirrors to steer the laser beam along any desired path.

The results will be in the form of a technical report and an oral presentation.

Milestones


* Communication with the function generator and webcam, has been established.
* Calibration procedure for the plane/surface using the webcam and e.g., a checkerboard.
* Automated method/function for finding the laser spot in the webcam image.
* Calibration procedure for mapping the laser position as a function of voltage.
* Calibration procedure has been automated.
* Designing suitable GUI and filling the GUI class with the methods required for generating and sending waveforms to the function generator.
* Well commented code for the methods/functions of the GUI, including a recorded example demonstration.


The lasers used for the calibration are eye safe. If the time allows a possible extension of the project would be to create a method/function to control the LUS laser (class 4) as a marker to print images on any metal surface.
 
Required qualifications
Experience in object-oriented programming in Matlab (or Phyton) is a prerequisite.
 
Experience about communicating with instruments using Matlab or Phyton is meritorious. If you have designed a GUI please include a quick description and a screenshot of it in your application.
 
The work should be initiated during the beginning of 2023. The master student performing the work will gain a large industry network. Swerim rewards the student with 50 000 SEK for an approved master thesis (30hp).
 
We will evaluate applications continuously.
 
Contact:
Mikael Malmström, seniorforskare, 0702-26 38 88, mikael.malmstrom@swerim.se
Peter Lundin, gruppchef, 0705-08 54 42, peter.lundin@swerim.se