Figure 6-19. Sketch Showing Procedure for Making and Viewing Stereo Radiographs.
It should be remembered that the radiographic image produced does not define the surfaces of the object as in a photo
or by direct vision. This is because no radiation is reflected from the surface as under normal optical means.
Therefore, in order to obtain apparent depth it is usually necessary to define the surfaces of an industrial object by
means of an X-ray attenuating marker such as a very coarse, high-absorption mesh or grid. These grids can be easily
constructed by using 1/16-inch solid lead solder. Such grids, especially on objects with plane surfaces, should be placed
on both the source and the film side.
It is important that in taking the radiographs, the distance of shift of sources be approximately one-tenth the focal film
distance. Also, in viewing the resultant radiographs, each film must be positioned so as to duplicate the exact
conditions of exposure. That is, the eyes of the viewer should be in the same relative position as the focal spot of the X-
ray tube or source. This positioning is facilitated by placing a different lead marker on each of the two films. The eyes
will then see a true representation of the part just as the X-ray tube saw the actual part.
Stereo radioscopic methods can also be used to present stereo images in real time.
For some applications it is desirable to magnify the radiographic image. This can be done optically after the
radiograph is taken, or it can be done during the radiographic process by using geometric magnification. This is