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Hobby Grade Laser Beam Profiler

klick

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Are there any hobby grade laser beam profilers on the market? Ones that would give a picture, such as this the picture below, that costs under $1000 ?


I know I posted before about a beam profiler, but in my pursuit of profiling my own beams, I figured out a way to get a very nice beam profile image by using what is basically a linear CCD. Now it only gives a line, but i'm thinking of using a stepper motor, or something, to move it back and forth to get the whole image. I did this manually with the sensor and just moved the laser beam back and forth over the sensor and it gave a surprisingly good output.

I know LPM's are very popular, and I would think beam profiles are of interest as well, but not many talk or post about them, perhaps because the cheapest one I found was $2000. I was thinking of spending the time to try turn my idea into a product, but i'm not sure enough people even want laser beam profilers. If it could be made for under $300, would that be of interest to anyone?

It would plug into the computer, where there would be host software. There might be an external (small) power supply to drive the motor that moves the sensor, it would probably do 1 frame per second, maybe 2. Oh yea, the resolution is 400dpi, or as other beam profilers state, 63.5um per pixel. For me that's enough to give me the info I need, but it's obviously not as small as the $4000 profilers. I'm also not sure what the max laser power would be, I ordered an LPM so I can start to test which neutral density filters bring down the power range into manageable range. I was thinking of having slits in the front, where you could drop additional filters to reduce the power of the incoming laser. Other profilers do that as well, so it's a standard practice.

So I was just curious if there is demand for such a thing.

Thanks.
 

wee40811

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Microscope CCD camera with some neutral density filter. Easily under 200 dollar.
 
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klick

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Well, I couldn't stand it anymore, so I went ahead and attempted to use the CCD's on webcams directly, so i tore apart 2 webcams, a cheap gearhead, and a logitech c920 1080p. I used the small neutral density filter I got from edmunds, and surprise surprise, it works.

If you hover over the images you can see which one is is from the gearhead, and the last 2 are from the c920. The c920's CCD is about 0.2" by 0.14", the gearheads is smaller. Even the cheap gearhead gives a very detailed view of the beam.

I do think the linear sensor scans I got gave possibly cleaner results, although it was a different filter, so not really a valid comparison. I think some of the anomolies in the CCD pictures are from refractions in teh neutral density filter. I have on order a couple of different sheet type neutral density filters, so perhaps they will have better results.

So if you can aim your beam under 0.1" (for the gearhead) and the beam diameter is under 0.1", for a $15 webcam, and a neutral density filter, basically I have a hobby grade beam profiler... The C920 isn't very cost effective, the extra resolution doesn't seem to do much, and it's harder to disassemble. The gearhead took 45 seconds, the c920 took 10 minutes.

It begs the question, why are the "professional" beam profilers so expensive, i mean the CCD's they are using are actually lower resolution then the C920. Perhaps they provide a better wavelength responsitivity, or other details I don't know about, as I'm not a laser expert anyway...
 

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wee40811

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Unfortunately after examining your image in Photoshop, the image you taken didn't provide a lot of information. The center part of the beam is basically saturated. You need to filter out more light.
 

klick

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Yea, well I just did that real quick, as I said I have other filters in transit, so I was going to revist this once I get them and try them out. Also there are webcam settings which I didn't even play with this time.

During testing the linear image sensor, I got a nice curve, much like what is expected. Looked exactly like most of the professional ccd beam profiler cross sections, like in the bottom and left of the first pic I posted.

The only real way to know if the CCD or linear sensor works as a profiler would be to have a profession beam profiler and to compare it against that.
 

wee40811

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I'll try to see if the lab I work in has one. According to some people in the lab, there's a profiler somewhere. I just need to find it....
 

klick

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Well i placed a few other gel filters, the ones used to put in the flash bulb for a flash photography to change the colors, well i layered red green and blue to make it as neutral as possible, and put the edmunds neutral density filter i used before. In a few cases I got the power down enough to finally get a realistic beam profile (I think).

I did 3d height map renderings in blender, I couldn't figure out how to color them like beam profilers, but the 3d picture gives a decent perspective. The one that says "focused not moving" was focused pretty well, I believe the 4 anomalies on top/left/right/bottom where some refraction between the gel filters, perhaps they separated a tiny bit, but still it's a decent image. I also purposely blurred the focus a bit to try and reduce the power, which it did, still have a pretty consistent top value.

The focused one did max out the sensor, as you can see from the flat top.

The flat part of the focuses one is 0.00625", which is pretty focused. The other stuff around it is powerful enough that's it's not focused exactly to 0.00625, probably the core of this beam is 0.02 or 0.03". I also took a picture while moving it, and it showed that the width of the beam was 1 thousandth of a inch thick, i've never obtained focusing like this, because I could never see it so clearly. So really this has allowed me to accomplish what I need, I can now focus the beam very very accurately.

The "unfocused" beam was 0.06" beam diameter, still decently focused.

Since I already basically sacrificed the c920 webcam, I think i'm gonna make a box for it, and make it a permanent beam profiler for me, perhaps even write some software to give the nice 3d look. The c920 CCD resolution is basically 6400DPI, which is far better then the 400dpi of the linear sensor, although you pay for it a little bit. 400dpi is still enough for me, I didn't expect to focus the laser down to a thousandth of an inch, and actually that's to focused for me, but a hundredth of an inch, perhaps 2 hundredths is perfect.

My whole reason for doing all of this is so I can make an auto-focuser for the laser, and the linear sensors are better for this purpose, as they are very cheap, and the 3d printer will have a method to scan the laser past it back and forth. I rigged a stepper motor upto the focusing mechanism and am writing software to adjust the focus for printing.
 

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I will read through this on my computer, rather than my phone, as this looks very interesting. I've wanted something like this for my gas lasers.

Those 3D Blender renderings look awesome, I'd be very interested in knowing how you did that.
 

wee40811

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I will read through this on my computer, rather than my phone, as this looks very interesting. I've wanted something like this for my gas lasers.

Those 3D Blender renderings look awesome, I'd be very interested in knowing how you did that.
Yes please. I am looking for that kind if software for a while. But no success. Please show us!!!
 

klick

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I use Blender 2.6, It's called a Displace Modifier.

Doc:2.6/Manual/Modifiers/Deform/Displace - BlenderWiki

Basically, make a plane, the subdivide it to the resolution you would want the output. Then add the modifier Displace. For displace, you use a texture, click the texture stuff, switch to the texture pane, and load the texture from a file.

Here's a good video:
https://www.youtube.com/watch?v=EnrrsVzkqnc

It's also refered to as a height map. Search on google for "blender 2.6 height map tutorial" or "blender 2.6 displace modifier"

I couldn't figure out how to change the color with the Z axis height, that would be nice. I'm not very good at blender, I barely know how to use it.
 

wee40811

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I watched the video, but I still don't know how you get to do the height map with the data from the webcam. :thinking:
 

ARG

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I have looked into doing a beam profiler on a hobby scale. Only problem is I would need a professional one to compare the results, and they are not cheap.
 

klick

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Yes, I agree. If I actually went ahead and built a fully working model, I think the only way to verify is to find if someone on here has a beam profiler, and send them my hobby grade one, if they were interested, to verify if it works.

I think it's difficult to figure out how much filtering you need, plus different power lasers would require different filters. I ordered an auto-darkening welding lens, also I bought a neutral density filter that when you rotate varies between ND2 to ND400, whatever that means. I'm hoping one, or both are potentially good methods of reducing the beam. You would start it at the darkest/highest setting, and slowly go down. If it's with the welding auto-darkening, I know those are run by voltage, so I should be able to control if from a microcontroller. I actually have one for my welder upstairs, but I don't want to dismantle that one, since I use it. The variable neutral density filter you have to spin, it's meant for DSLR, that would have to be done manually or motorize it. I do have a DSLR camera, the lens matches it, I'm wondering if I might be able to use my DSLR with the variable density filter to get a profile, it's 18MP I think, would be a heck of a picture potentially, but i don't want to destroy the cameras CCD either. If i destroy the webcam I won't be that upset.

ARG, where you planning to use a webcam CCD? or similar?

I don't even know, are there other techniques for beam profiling? Besides my linear sensor idea, which is really just a linear CCD, so technically it's still a CCD approach.

Thanks
 

ARG

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ARG, where you planning to use a webcam CCD? or similar?

I don't even know, are there other techniques for beam profiling? Besides my linear sensor idea, which is really just a linear CCD, so technically it's still a CCD approach.

Thanks
I was thinking of using a linear CCD, from a scanner since those are abundant and cheap.
 

klick

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Oh yea, I never thought about those, the ones I have must be a similiar technology, or probably exactly the same. The ones I got were super cheap, and pretty easy to use.

This one is 400dpi, but not very long, unless you want to profile huge beams though, it's fine. It's what I did my testing with:
Invalid Request

I also got this one:
Invalid Request
Which is much longer, but even though it's the same company and same everything, I couldn't get it to work. I probably just had one wire wrong, I plan to attempt it again. It gives you almost 2 inches where the beam could be though, then just move it back and forth and it gives a nice snapshot.

Webcam CCD's are of course cheap, and my last test shows they have potential, but as you said again, we'd need a professional beam profiler to compare against.

Anyway, i'm not sure how much more time i'm going to spend on this, the linear sensor should do what I need with a cheap gel filter. The profile I need doesn't need to be perfect, or even close, just a rough image to modify the focus with, or really just verify the focus, and throw an error if the machine isn't focused properly.

If there was a small photo scanner, the linear sensor wouldn't be that long, maybe 4 or 5 inches, and it should have super high resolution. Hacking it might be a pain, but it probably works much like the sensor I linked to above, but figuring out the pins is a pain. Would get you better then 400dpi though, like the sensor I have. Course the c920 webcam has about 6400dpi, since the CCD is only 0.2" wide, actually i wasn't capturing at the highest resolution, so I guess it's even higher then that. Pretty decent though if I can get a filtering technique down.
 




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