accurately measure distance

Here is what I am trying to do, tell me if it'll work:
Aquire an image of structure using a ccd camera with 10x zoom. Import image into autocad. Scale it back down to its original dimension Measure length of structure using line feature.
The distance ranges from a couple of 100 microns to a few mm.

Hi I think it will be nice with two camera or if you are able to re-possision the camera , it is also an idea to have some point in the scene so you can refere the posision of that , anyway I don't know if the correction can be made that way, but a digitizer in AutoCAD can be callibrated --- that mean that if you pick a known point on the screen , -- that will be your picture on the screen and the digitizer working as digitizer mouse, -- then you can add several other known points callibrating your digitizer from the graphic on the screen.
Now if you can see where this is heading you could have found an ansver ,but this ask some efford and knowleage and ownership of a digitizer.

  Quoted Text Here  
I don't see why not. I import aerial photos in autocad, scale and rotate them, and gain the use of a model that can be measured with ballpark accuracy. My application requires that the photos are scaled up. It sounds like yours will be scaled down. If you have 2, preferably 3, identifiable objects in the photo, and know their precise relationship, you should be able to accurately scale your photo and then query it for distances...
W\/W
  Quoted Text Here