LSci

2008-10-23 15:13:43 UTC

Recently, we used a vendor-supplied software package (BeamStar) to

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

it.

Thanks.

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

it.

Thanks.