2008-10-23 15:13:43 UTC
collect ~200 laser beam profiles in video format. However, now that
we have gone back and tried to post-process the files in BeamStar, it
will not let us change critical length and power calibration
parameters, nor let us subtract the background. This is a rather
large stumbling block, as we are trying to measure the beam width and
beam power with accuracy. (Warning to others -- never use BeamStar if
you want to do post-processing)
So, we are working on converting our files stored in the proprietary
BeamStar format to uncompressed .avi files, and then purchase a copy
of Matlab to measure the beam parameters from the .avi files. I was
hoping to find an m-file for beam analysis, but my searches on the web
and in textbooks have not turned up anything yet. So, it looks like
if we go this way, I will be doing it from scratch.
Here is the process as I see it:
1. Take the individual frames from the .avi file and separate them
into individual files.
2. Subtract off the background file.
3. Compute the centroid of the image (hopefully the beam centroid).
4. Define a "Region of interest" around the centroid (hopefully
circular or elliptical, though a square might do).
5. Compute the integrated energy in this region of interest (hopefully
the total beam power).
6. Measure the beam diameter in x and y directions in different ways,
such as fitting a 2-D Gaussian, computing a 90/10 beamwidth, etc...
Basically I am re-inventing the "beam profile measurement" wheel in
Matlab. Further, the last time I really used Matlab was years ago,
but I'm getting stuck with the assignment because that is more than
anybody else in our group.
So, if anyone has any suggestions on whether to use Matlab or some
other product, I would appreciate it. Also, if anyone has any
suggestions on how to define a non-square region of interest, or how
to easily perform the beam diameter measurements, I would appreciate