Any modulation of a detected signal can be used as a contrast mechanis
m in imaging applications. Insofar as the time dependence of optical p
roperties of imaged structures can be used to elucidate material prope
rties, such time dependences can provide a modulation which can then b
e used as a contrast mechanism in imaging. We introduce a system in wh
ich time can be used as a contrast mechanism in imaging. We introduce
a system in which time can be used as a contrast mechanism to study ma
terial nanostructures. Single-crystal silicon wafers are imaged in the
infrared using a HeNe laser while the wafer is simultaneously pulsed
with visible radiation. By studying the time dependence of the infrare
d transmittance, defect distribution on the nanometer scale can be ima
ged, and sample nanostructure can be studied.