Is goodness of fit a better metric than circularity?

Questions like these are common, given the sheer number of parameters Ophir's BeamGage software calculates from each beam profile. When faced with all these various metrics, it's natural to wonder which ones are more important or if one parameter is the best one to describe your laser.

The challenge is, all lasers are different and so one parameter that describes a laser well in one instance is not very important in another. In this particular example, "goodness of fit" would determine how close to a Gaussian the measured beam profile is, while "circularity" would determine how round the beam is, often a concern in astigmatism analysis. Which one is "better" is highly dependent on the laser application and so without any further context as to what the customer is trying to accomplish, the question cannot be answered one way or another.

When getting a question like this, rather than tell the customer how to measure their laser, I talk with them about what they are trying to accomplish with a beam profiler. Once we both understand this, we can move on to what parameters from the beam profile will provide the data they need to characterize this performance. In many cases, we will run some tests with a demo beam profiler system on the customer's laser so they can discover for themselves how this equipment helps them in their projects.