Can anybody give guidance ref. dark field illumination? 1

[ColinBryant]

Hi,

Colin here,

Got a real bad problem that I need some guidance to crack. I am looking at semi transparent objects using a digital camera and imaging software. My problem is how to build a system using dark field illumination to hopefully see the inside structure details in a form that they can be captured and subsequently analysed. The info on the net is very theoretical and not really helpful regarding applications. Any help or guidance much appreciated.

Thank you
Colin Bryant

 

[lumenharold]

Can you say what what semi transparent material you are trying to illuminate? We have had pretty good success by selecting specific wavelength light depending on the material to be viewed and the flaws we were trying to see.

Harold
SW2009 SP2.0 OPW2009 SP0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[IRstuff]

The main goal is to prevent light from the illuminator from directly entering the imaging lens:

http://www.microscopyu.com/articles/stereomicroscopy/stereodarkfield.html

That's pretty much it. You could probably use side illumination, and that might work well enough.

TTFN

FAQ731-376

 

[ColinBryant]

Hi Lumenharold.

Thanks for coming back. The material in questios
is PMMA supported in a saline bath. Flaw detection
is not required but internal profile viewing of the
object is the whole point of the exercise. I hope this
is of help and that you can make a recommendation that
I can try.

Regards and thanks

Colin Bryant

 

[lumenharold]

Hi Colin.

It is difficult to recommend a solution without a lot more detail. I am out out of the office until Tuesday. Call me if you can discuss the problem in more detail (follow the contact info in my signature). Aside from that, IRStuff mentions side illumination (basically edge lighting) and that might work for your application. We had used LEDs to illuminate translucent grain. Blue back lighting and orange front lighting made the surface transparent to the camera but internal "junk" showed up very dark. Try different combinations based on the properties of your material and your camera/software until you can see waht you need to see.

You might try contacting the camera manufacturer or software provider for a lighting recommendation.

Harold
SW2009 SP2.0 OPW2009 SP0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[hioptix]

If you want to see the stress in the material, probably by using cross-polarizers you can get a lot of information. Not sure what you mean with "see inside": a 3D profile or an integration of information across all the layers inside the bulk material.