Measure beam profiles?

**Roy G. Biv** · 09-17-2009, 04:54

Is there a cheap way to measure the beam profile of a laser? I want to be able to find out the beam diameter, shape of the transverse area, and some way to measure the divergence. It could also be helpful when aligning several beams. I know you can buy profilers in the $1k range, but are there cheaper solutions?

**andy_con** · 09-17-2009, 04:59

a ruler ?

**Roy G. Biv** · 09-17-2009, 05:08

Yes, a ruler is cheap. But, if possible I would like to be able to see the intensity distribution too, and this is difficult with a ruler.

**shrad** · 09-17-2009, 05:15

a really strong attenuator and a webcam, then you grab a frame and use something like pyton or matlab to make computations on the picture

I know there are python modules which are able to grab webcam frames and streams, and was planning myself to make something out of it, by removing the lens of a cheap webcam and projecting the beam over the whole CCD array with a lens, in order to have the higher resolution

**mixedgas** · 09-17-2009, 06:15

Find a old scientific or security cam with a black and white 1/2" ccd. Get one that specifies the ccd chip or the pixel size. Hook it to a decent frame grabber and get either crossed polarizers or a intensity gradient wheel type of attenuator.

download Image J or Scion Image software to run the histogram and measure the beam size.

Have a way to slide the camera back and forth about 100 cm. do math by hand after using scion to make the measurements off the grabs

that is the gist of my 2 kilobuck beam analyser, but it has better far better software then scion that does gaussian fits and its 10 bit instead of 8 bits on the intensity.

the bare ccd does the measuring for you, and there is a guy here with a bunch of nice half inch ccd scientific cameras he's trying to get rid of, search the for sale and trade forum.

Any good USB frame grabber will do.

I can sell you a PAL format (more pxels to work with) half inch scientific grade camera for 75$

Steve

**shrad** · 09-17-2009, 08:55

that's why I suggested matlab or python with scipy, as they do gaussian fits and computation easily, and you may grab frames from an USB camera

usually, you can find CCD pixel size from the datasheet of the chip, or from amateur astronoms who use them

I have a device with an actuator that places 5 attenuators in front of holes and plan to use it for that purpose when I have the time to do that

**krazer** · 09-17-2009, 09:39

Try contacting LaserBen on this forum, he has beam profiler he may be willing to let go for not way more than a decent CCD camera.

**Roy G. Biv** · 09-17-2009, 09:47

Thanks for the advise. So, a B&W ccd camera, a frame grabber, and software to process the images. Are there any free dedicated beam profiler programs available? I have never used Matlab, nor do I know how to program, so if there is a simple dedicated software already available it would be great. I found a sample version of the VBeam analyzer, VBeamAcademic available for download: http://www.visulux.com/home/Support/...6/Default.aspx Has someone any experience with this program? Can the free version be of any use?

I also found a webpage where they talk about the release of source code for a program called LaserTest, however, I can not find any more information about this release or what it means.
http://www.fiberopticsonline.com/pro...?VNETCOOKIE=NO

**mixedgas** · 09-17-2009, 10:13

Originally Posted by Roy G. Biv

Thanks for the advise. So, a B&W ccd camera, a frame grabber, and software to process the images. Are there any free dedicated beam profiler programs available? I have never used Matlab, nor do I know how to program, so if there is a simple dedicated software already available it would be great. I found a sample version of the VBeam analyzer, VBeamAcademic available for download: http://www.visulux.com/home/Support/...6/Default.aspx Has someone any experience with this program? Can the free version be of any use?

I also found a webpage where they talk about the release of source code for a program called LaserTest, however, I can not find any more information about this release or what it means.
http://www.fiberopticsonline.com/pro...?VNETCOOKIE=NO

The first one looks very much like the sphericon user interface. Which pretty good. It depends on what they have done to cripple the freeware software. for 995$ I'd want 10 bit resolution and at least PAL on the CCD.
for example it may do profile but not divergence or some other mix. 640x480 is not bad, but I'd rather have the 760 line pal or megapixel these days.

Oh, well,its free. with the usual strings attached.

As for the Sensorphysics,its not freeware, you'd need license it and buy the sourcecode option. NEVER trust aaything you see in Laser Focus World, Photonics Spectra or the Fiber rags, its almost always polished up marketing.

And student editions of Matlab are not that expensive.

downloaed vbeam demo, the demo does profile and fit, does not do divergence as far as I can tell. may be because of patents?

Steve

**shrad** · 09-17-2009, 10:51

I'm just wondering... is it possible to calculate divergence with only a beam profile, or as I think it is needed to move the laser or the camera for that?

in the same approach, I have some linear CCD arrays I would like to use as sensors for some basic grating wavemeters like monochromators and the like... does anybody know if some easy ways of interfacing them already exist?

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