Image Processing Reference
Figure6.7Visible( = 0:4-0:7m)photo.
Figure6.8Near-ultraviolet( = 0:35-0:38m)photo.(CourtesyofRandMolnar)
teeth in Fig. 6.9. This image was taken with a conventional film camera with a
special fused silica and calcium fluoride lens that can transmit 254 nm radiation.
The camera is equipped with a bandpass filter that transmits right around 254 nm
but very little else. The light source is a xenon strobe without the usual UV blocking
polymer coating on the strobe tube.
Hair and flesh disappear in the x-ray image in Fig. 6.10, except for a slight
shadow of scalp, right on the vertex of the skull. The teeth and cheekbones
interpose the highest density of matter between the x-ray source and film;
consequently, they record as the darkest areas. The eye sockets act like windows
into the skull, and therefore look lighter. For clarity, the values have been inverted
from what they would be in a typical radiograph, making the regions of highest
density black and lowest white. This image was actually taken in the 1920s, but