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Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
I just got an idea that I thought I'd share with the community. Feedback is appreciated. This idea is for a simple replacement for the film normally used when making radiographs.
Getting and developing film can be costly and/or expensive, and it takes time, but the results are excellent.
I have seen a couple alternatives to film for hobby radiography, but they can be a bit impractical. One way is the one that c4r0 used, photographing the front of fluorescent film from an intensifying cassette, with the X-ray tube pointed towards the back of the fluorescent film, with the object to be photographed between the tube and the fluorescent film. One problem with this is the fact that the radiation from the tube hits the camera CCD, lighting up pixels. One potential way to circumvent this would be to place some thick leaded glass, for example from the front of a CRT, between the fluorescent screen and the camera. An other way to circumvent this is to have the camera looking at the screen via a mirror, the radiation goes straight through the mirror, and therefore doesn't hit the camera. This method was used by Fabio for a real-time radiography machine he made. I'll try to find the project thread in the forum archives tomorrow.
The problem with these methods are that they can be a bit bulky, and they take up a lot of space and can be tedious to pack away if the space is needed for other projects.
My idea is to take a normal flatbed document scanner, disable the light source in it (usually a CCFL, sometimes LEDs in newer ones), place some fluorescent film from an intensifying screen where the document should go, and then sealing it so that no light can get in. The object to be photographed would be placed on top of the lid (the lid could be replaced with a sheet of black plastic if the scanner lid is too curved), the X-ray source placed above it, and then turned on while the fluorescent screen is scanned. Some scanners are very thin, so this could be made quite compact. The CCDs in scanners are usually looking at the document through a mirror, so shielding the CCD with some lead sheets in the direction where the X-rays come from should be possible.
Possible problems:
* How light-sensitive are scanners? How much light do these intensifying screens put out with a reasonable hobbyist X-ray tube from a reasonable distance? Hopefully this works out to give usable contrast.
* How long time does a modern scanner take to scan a normal page at a reasonable resolution (100-200 DPI)?
Registered Member #122
Joined: Fri Feb 10 2006, 12:55PM
Location: Milano Italy
Posts: 148
This is my original theread:
I don't' know if a modified scanner can be used for digital radiograpy (i think that fluorescent screens aren't enough brighter for a normal scanner, in addition, a small tube usually cannot run for more than a couple of seconds, not enough for a complete acquisition) but i'm sure that an XTV camera is nothing more than an EMPTY BOX, so you could build a camera that could contain entire apparatus while not in use (as my one) or maybe a foldable/demountable camera
Registered Member #1134
Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351
Ok just for the crack, I bought a Cannon cannoscan N640P off eBay to try this out, its an idea I once had before, but didnt think it would be practical.
I disabled the LED light with black insulating tape, loaded in a piece of fluoroscope screen, and placed it under my x-ray machine.
Below is the result: A screwdriver, and light fitting.
The speckles on the image are caused by the x-rays directly affecting the photodiode array (if I had bought a CCD scanner it would have been possible to shield the CCD). The image is B&W since in this model of scanner 3 LED`s (red green, blue) are used to sequentially illuminate the document in normal use. The photodiode array, is physically as wide as the scanner bed, and the optics for each diode is integrated, making it impossible to shield the array from the radiation.
So yes, its possible, and even worthy of some more investigation!
The scan time by the way, was just a few seconds at the lowest resolution, quite acceptable!
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X-ray scanner idea
