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Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
I just took a look at the links I posted in a previous post, and it seems that the site I uploaded them to has reduced the image quality. Here they are again, hopefully in better quality. Here are the originals in jpg format. For the "fixed" photos, I used RAW files from the camera, the extra dynamic range is useful when you're increasing the contrast.
These pictures were taken with a dental x-ray tube operated from a dental x-ray transformer. The tube was encased in a cast radiation-shielding ceramic tube with a hole for the beam. The voltage used was 60-80kV, the current was around 8mA, and the exposure time was between 3 and 8 seconds. I don't have the distances noted, but I think the tube-object distance was around 30cm, the screen was placed directly behind the object, and the camera was some 30-50cm behind the screen.
Sorry for hicjacking your thread Freitsu, that wasn't my intention. Hopefully the information is useful.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
This method is an interesting alternative to film. There's no need for a darkroom, developing chemicals, and there are lots of variables like developer temperature, developing time and such. Not impossible to figure out, but it takes some experimentation. It also has some possibilities that are hard to realize with film, like being able to make x-ray video. Digital postprocessing also makes some interesting things possible. It doesn't replace film in all cases, film can have much higher resolution (unless you use it inside an intensifying cassette). No method is "better", but each method has advantages and disadvantages.
Registered Member #3147
Joined: Sun Aug 29 2010, 10:53AM
Location: Finland
Posts: 56
Don't worry Anders, you're contributing more than you can imagine (ie. making me drool over your pictures so I won't give up until I get there aswell!)...
I have come to the conclusion that my digitalcamera is just too crappy, I hope santa is nice this year and bringing me a systemcamera!
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Here's the basis of a very simple medium-resolution imaging set up, Freitsu.
I've taped a piece of front side Fuji G-6 Gd2O2S:Tb intensifying screen to the back of a 300mm x 225mm piece of 11mm lead-barium shielding glass for remote viewing via a MS Lifecam Cinema USB webcam.
The 11mm shielding glass is equivalent to 2.5mm Pb, density is 4.36 g/cm3, visible light transmission is 85%, and refractive index 1.7.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701
Proud Mary wrote ...
The 11mm shielding glass is equivalent to 2.5mm Pb, density is 4.36 g/cm3, visible light transmission is 85%, and refractive index 1.7.
what about barium + lead compounds? Like making a plastic with barium carbonate and lead nitrate? These are some chemicals that I currently have access to, so replacing a heavy metal case with a heavy plastic case might have some uses. I can't test this yet, so what do you think?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
radhoo wrote ...
Proud Mary wrote ...
The 11mm shielding glass is equivalent to 2.5mm Pb, density is 4.36 g/cm3, visible light transmission is 85%, and refractive index 1.7.
what about barium + lead compounds? Like making a plastic with barium carbonate and lead nitrate? These are some chemicals that I currently have access to, so replacing a heavy metal case with a heavy plastic case might have some uses. I can't test this yet, so what do you think?
A quick note so as not to hijack poor Freitsu's thread. I don't know much about leaded clear acrylic shielding, except that it has inferior optical properties to lead glass, is more readily discoloured by X-rays, and is manufactured using toxic organo-lead compounds. Not something I would want to do.
If you think of the transparent shielding as part of the optical pathway, it doesn't make sense to spend a few hundred euros on a decent camera lens, only to have a grungy block of plastic transmitting the image. Even with the much lower specification of so-called 'High Definition' webcams, it doesn't make sense to add a second poor quality element to the optical pathway.
On a cost basis, you could expect to pay 100 euros or so for an A4 size piece of leaded shielding glass, but I would expect to pay much more if I started mucking around with organo-lead compounds in a fume cupboard, and having to pay to dispose of toxic waste and so on. Then you'd have to machine optically parallel sides to your cast acrylic block, and so on - a lot of bother, I'd call it!
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Re. optically clear x-ray shielding.
1) it doesn't have to be as big as the fluorescent screen or x-ray subject, only as big as the camera lens (or your eye).
2) I was expecting a free scrap of x-ray shielding glass from a fellow hobbyist, but it seems to have been lost in the mail. Back to the drawing board.
3) As an alternative to DIY blending of heavy metals into clear plastic, how 'bout heavy metals in aqueous solution enclosed between sheets of window glass? I did some investigations of solubility, toxicity, and x-ray attenuation, but there ain't room for details here.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Klugesmith wrote ...
Re. optically clear x-ray shielding.
1) it doesn't have to be as big as the fluorescent screen or x-ray subject, only as big as the camera lens (or your eye).
2) I was expecting a free scrap of x-ray shielding glass from a fellow hobbyist, but it seems to have been lost in the mail. Back to the drawing board.
3) As an alternative to DIY blending of heavy metals into clear plastic, how 'bout heavy metals in aqueous solution enclosed between sheets of window glass? I did some investigations of solubility, toxicity, and x-ray attenuation, but there ain't room for details here.
The closer the transparent shield is to the lens, the bigger the errors it will introduce.
Making your own transparent shield, you'd have to establish that none of the materials could be excited by the X-rays in use to fluoresce in the visible spectrum, as this would interfere with the image received from the intensifying screen.
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X-ray machine finally done!
