  We introduce diffraction-based interaction-free measurements. In contrast
with previous work where a set of discrete paths is engaged, good quality
interaction-free measurements can be realized with a continuous set of paths,
as is typical of optical propagation. If a bomb is present in a given spatial
region -- so sensitive that a single photon will set it off -- its presence can
still be detected without exploding it. This is possible because, by not
absorbing the photon, the bomb causes the single photon to diffract around it.
The resulting diffraction pattern can then be statistically distinguished from
the bomb-free case. We work out the case of single- versus double- slit in
detail, where the double-slit arises because of a bomb excluding the middle
region.
