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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 $1k range, but are there cheaper solutions?
a ruler ?
Yes, a ruler is cheap. But, if possible I would like to be able to see the intensity distribution too, and this is difficult with a ruler.
a really strong attenuator and a webcam, then you grab a frame and use something like pyton or matlab to make computations on the picture
I know there are python modules which are able to grab webcam frames and streams, and was planning myself to make something out of it, by removing the lens of a cheap webcam and projecting the beam over the whole CCD array with a lens, in order to have the higher resolution
Find a old scientific or security cam with a black and white 1/2" ccd. Get one that specifies the ccd chip or the pixel size. Hook it to a decent frame grabber and get either crossed polarizers or a intensity gradient wheel type of attenuator.
download Image J or Scion Image software to run the histogram and measure the beam size.
Have a way to slide the camera back and forth about 100 cm. do math by hand after using scion to make the measurements off the grabs
that is the gist of my 2 kilobuck beam analyser, but it has better far better software then scion that does gaussian fits and its 10 bit instead of 8 bits on the intensity.
the bare ccd does the measuring for you, and there is a guy here with a bunch of nice half inch ccd scientific cameras he's trying to get rid of, search the for sale and trade forum.
Any good USB frame grabber will do.
I can sell you a PAL format (more pxels to work with) half inch scientific grade camera for 75$
Steve
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
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.
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
Quote:
Originally Posted by Roy G. Biv
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
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?
I have a box of those for a project that never took off. I was going to sample the data and dump it to serial/USB and read it into an app that measures and allows calibration (thusly replacing the need for a $2000 spectrometer).Quote:
Originally Posted by shrad
Perhaps we can open up the cork on this in a new thread if a patent is not protecting that methodology?
--DDL
Steve,
Do you think it is possible to use a camera with PAL resolution together with the VBeam demo though the program only uses 640x480?
It says:
"Full calculations are performed on all images. Maximum resolution is limited to 640x480 and the report generators are disabled."
I hope this means it is possible to see all the results and calculations made, though you canīt get a report of them.
Shrad,
I asume it would be possible to calculate the divergence by measuring the beam diameter at one point and then move the camera a distance and make a new measurement.
DDL,
A ccd spectrum analyzer, this is something I would like to build also, but it is unfortunately a bit too complicated for me. W has an interesting description on his pages:
http://pagesperso-orange.fr/redlum.x...ratingOSA.html
yes indeed, but the movement needs to be well known to get reliable measurements, so if it is a professional software, I guess the solution is elsewhere... but I may be wrong
if I happen to make something out of python and a webcam, no doubt I'll share my results
I'll move to my new house the 27 of september, and as soon as I have unpacked everything, I start working on lasers related stuff again ;)
1, you dont have to move the camera that accurately, +/- 1 mm in length is easy enough with a piece of plumbing pipe etc and the software handles centration.
My bet is the software will truncate PAL, as will most cheap frame grabbers to make windows happy. I dont have my frame grabber set up here to try it.
Spectrum is easy with a good digital camera, many people have done it with just a slit, a grating and a good camera lens.
I've posted links before.
Steve
A practical technique I have used in the past, which only requires a power meter is:
Set up a horizontal bench some distance away from the source, so that the power meter is vertically centered on the beam. Slide the power meter along the bench in 1cm increments, taking a measurement each time to form a 1D profile. If you want to calculate the divergence, you have to repeat this at a second distance from the source.
If your beam has modest divergence, you can get a good result with one profile 10m from the source and another profile 20m from the source. If your beam has lower divergence or you don't have that much space available, you can use a telescope.
Of course a true 2D beam profiler will give you more information about the beam, but what are you going to do with this information? Probably assume a symmetrical gaussian profile to perform conventional fitting and modeling steps anyway. I used this technique on horrible multi-mode beams without any problem. Here is my result:
http://external.weartronics.com/lase...am_profile.png
http://www.sbf1.sbfisica.org.br/proc...endido/c60.pdf
http://www.bme.vanderbilt.edu/bme286.../knifeEdge.PDF
http://www.uslasercorp.com/envoy/diverge.html
now just decide if you want to use 10-90 or 80-20 or 19-82 as your cutoffs
http://en.wikipedia.org/wiki/Beam_diameter
or the good old Divergence = 2arctan(Df-Di/2l)
there are other ways with pinholes, slits, lenses.....
remember, you should measure at the beam waist and at a point on the far field side.
Steve
Other then a bit of math, why is this such rocket science???
http://www.sbf1.sbfisica.org.br/proc...endido/c60.pdf
http://www.bme.vanderbilt.edu/bme286.../knifeEdge.PDF
http://www.uslasercorp.com/envoy/diverge.html
now just decide if you want to use 10-90 or 80-20 or 19-82 as your cutoffs
http://en.wikipedia.org/wiki/Beam_diameter
or the good old Divergence = 2arctan(Df-Di/2l)
there are other ways with pinholes, slits, lenses.....
remember, you should measure at the beam waist and at a point on the far field side.
In two weeks I'll have access to my library and can scan in:
2. Simple Beam Propagation Measurements on Ion Lasers, SPIE Vol. 1414 Laser Beam Diagnostics, 1991. Its Spectra Physics way of doing it.
Steve[/QUOTE]
I do have a pretty high res (2048 pixel) beam profiler setup with ND filter holder and breadboard mount for $300 shipped. It hooks right up to an oscilloscope and gives a clean reading of the beam profile with actual measurable results.Quote:
Originally Posted by krazer
I use this for my IR beams:
http://www.youtube.com/watch?v=KIizzSHFHEQ
On a unaligned YAG (but still aligned enough to get a small output) it allows me to see exactly which way I need to turn the mirrors.
Works really nice, but it's not exactly cheap.
that's cool! it makes me want to make a reverse lumia projector. ;) is it specific for 1064 or will other flavors of IR work?Quote:
Originally Posted by Daedronus
Not really 1064 specific, in that video it's 650nm, but filtered by glasses to make it "invisible" to the camera.
is the glow material anything other than just standard issue zinc sulfide? i have a 5'x5' section of my garage painted in glow paint for 405nm experiments, maybe i should pick up some IR diodes and do some experiments.Quote:
Originally Posted by Daedronus
I have no idea what is on the plate, there are two separate areas, one that "lags" and one a lot more responsive. The laggy one is meant for pulsed lasers.
I think that to some degree any fluorescent material will show this quenching effect when illuminated by IR. You will have to try and see.
I tried with some fluorescent markers (green) and it didn't work well (at all), on the other hand some glow in the dark stickers did.
There are about 6 phosphors that do it, Its in storage, and would be a week before I can get at it, but I have a Copy of the Phosphor Synthesis handbook, so if anyone is really interested in making some, its doable. Well, doable if you have a lab furnace or similar at 850C.
They are known as IR Quench phosphors, Its a little bit off from the standard cheap ZnS chemistry, has a bit different trace of dopant.
Here ya go, one formulation.
http://www.google.com/patents?id=kXp...age&q=&f=false
Steve
I might be interested in some "simple recipes" if you might get some easily... I'm just wondering if an induction furnace would do, and if I will find a clay recipient which would whitstand such temperatures
Quote:
Originally Posted by shrad
graphite is cheap and readily available.
Steve
thanks! I never thought about graphite, I'll have a look at some suppliers to find what cost a graphite rod I could machine to get a pot
http://www.waleapparatus.com/ They are cheap, I have a few sitting in the other room next to my kiln. Damn I need to get my glass studio up and running again (it is in a box like Steve's book).Quote:
Originally Posted by shrad
-Adam
i need a better IR source for testing than just aiming my co2 laser at the wall... tempting as it is, my kitchen is on the other side.Quote:
Originally Posted by Daedronus
Is a beam profiler useful if you use DPSS lasers only?
Now I only tune with a powermeter and I scan a frame to check the noise.
Arc welders using a H2 assist some times used big graphite rod and they are cheap. That's how I got mine as a kid. Good welding stores sell them by the piece, not the box. Of course having never been to a welding store in Europe, I have no idea how it goes there. 1/2" ones make great crucibles and you can drill them with a drill bit (outside of course, maybe keep wet) If you have never handled finely powdered graphite, well, your in for a shock. They are quite tough, but the dust from cutting/drilling is a learning experience.Quote:
Originally Posted by shrad
here ya go: http://www.engineersedge.com/materia...uging_rods.htm
Steve
thanks Steve!
I think I'll have a look for real crucibles in my area and design my heater coil around the one I'll buy...
I've always wanted a small aluminium and copper crucible, so I think I'll go for something a little bigger ;)
thanks for the tip anyway, you decided me by showing some more thing are possible with a little multifunction furnace, and that's definitely something I want to try
since my mother has a ceramist formation, she'll also be able to teach me how to easily mold some small aluminium and copper pieces with relative precision
If you guys need PAL b/w 1/3" CCD camera's, I have some I'm willing to trade for laser goodies ;)
Does it make sense to use a beam profiler for DPSS tuning?
I just made a beginning of a DIY beamprofiler.
I have a Watec CCIR camera with 795 (H) x 596 (V) pixels connected to a usb frame grabber set at 640x480 capture mode.
On the PC I have VbeamAcedemic running.
The software looks nice.
But now I think I need a ND filter in front of the CCD to attenuate the beam.
Do you have any tips what to use for attenuator?
Do you have any tips what to use for attenuator?
[/QUOTE]
I have a ND wheel, but they are expensive. may I suggest crossed polarizers or picking the beam off with ar coated glass or a microscope slide (slides)
Steve
if you have a polarized beam, you might also use a polarization filter and rotate it until you have a decent attenuation
I have one of 2" of diameter and 1/6" of width, and when rotated in front of an evenly polarized beam, it gors from 98% to approx 1% or 2%
I don't know if it can affect the readings, though
Is it necessary to have a adjustable Digitial shutter on the camera?
I have 3 different B/W ccd camera's
one with no digital shutter
one with a automitical digital shutter
and one with manual digital shutter.
which camera can I use best?
Quote:
Originally Posted by mccarrot
MANUAL IS BEST, all will work with good beam attenuation.
Just watch out for cameras with auto Gamma, or ones that cannot be set to AGC off. You will have to try each camera. Hint, use a low power or dying hene for tests
Steve
some CCD sensors have a pin to be grounded to disable AGC, if info is found in the datasheet...
http://cgi.ebay.com/LOT-THORLABS-DET...mZ160365377498
I don't know if any of that would be useful. I couldn't get all the images to enlarge so :rolleyes:.
-Adam
How much mW/cm2 power can a standard b/w CCD handle before it dies?
Can I also use safety goggles as a attenuator?
I'm testing the software with a lens in front of the CCD :)
Quote:
Originally Posted by mccarrot
I've had 20mW on silicon ccds no problem. Vidicon tubes, however, don't like more then 5 mW before they discolor.
we did some testing at Dr Lavas:
430 nm pointer to excite (60 mW)
808 pointer (1W) to quench:
Phosphor:
ZnS:AG (Post Apple Scientific, 19.95 a bottle ) IR Quench, YES
Chinese Long Persistence Blue (SR:YAG) IR Quench, YES
Chinese medium persistence Red ( ??:YAG) IR QUench, YES
United Nuclear, Super Phosphor , NO QUENCH !
Procedure:
Darkened room, excite with 430, remove excitation, wait a few seconds, attempt quench. No attempt was made to quench and excite at the same time.
Steve