Image Processing Reference
of the material can change the pulse shape, making it possible to determine what
is inside packages without opening them.
Figure 3.2 shows a T-ray image of an integrated circuit inside a plastic package.
The plastic absorbs very little T-ray energy, and thus the interior components
(circuit and conductive traces) are revealed. Figure 3.3 shows two T-ray views of a
leaf: one after it has been freshly picked and one after 48 hours. Water in the leaf
absorbs T-rays, and the right image shows that water has selectively evaporated
from the leaf. The color bar indicates the relative water concentration inside the
leaf. The edges of the leaf have dried out, but there is still water contained in the
center of the leaf and in the veins. Figure 3.4 shows a milk chocolate bar with
almonds in both visible and T-ray light. The T-ray image is a map of the time
it takes for a T-ray pulse to reach the receiver. Changes in the thickness of the
bar change the pulse arrival time, since the T-rays slow down in the chocolate.
The letters on the bar are visible because they change the thickness of the bar—
the letters are molded into the surface. The almonds produce a sharp increase in
the pulse arrival time, since the T-rays are slowed down even more than in the
Figure3.2 T-Ray image of an integrated circuit. (CourtesyofProf.DanielMittlemanand
Figure3.3 T-ray image of a leaf at 48-hour interval. (CourtesyofProf.DanielMittleman