Influence of Angular and Focus Variations on PTR Measurements

The nitriding of steel components is a common surface treatment process. To reduce scrap during nitriding, the formation of the nitrided layer is to be monitored in situ using the principle of photothermal radiometry (PTR). To establish the method, measurements are planned on a small experimental furnace. There, temperature changes can lead to slight deformations of the experimental setup, which influence the measured signal.

As part of this work, the sensitivity and tolerance limits of the PTR measurement principle with respect to such deformations will be investigated under controlled laboratory conditions. The work includes both simulations and experiments with the PTR prototype to determine the influence of angular and positional changes.

Possible Tasks

• Literature review on photothermal radiometry and geometric influences on optical measurement systems.
• Experimental investigations using the PTR prototype.
• Analysis of the effect of angular and focal changes on spot size and absorbed power.
• Simulation of beam propagation and focal shift (ray tracing).
• Development of a simple sensitivity and uncertainty model for the PTR signal.
• Derivation of tolerance limits for stable PTR measurement operation.