Patent ID: 7687773

Claim:
A method of imaging a sample comprising the steps of: generating a signal beam of optical radiation having a frequency between 300 and 3000 gigahertz; generating a reference beam of optical radiation having a frequency between 300 and 3000 gigahertz and different from the signal beam; splitting the signal beam into first and second portions and causing the first portion of the beam to be scanned with respect to the sample; splitting the reference beam into first and second portions; mixing the first portion of the signal beam that has interacted with the sample with the first potion of the reference beam to create a measurement intermediate frequency signal; mixing the second portion of the signal beam and the second portion of the reference beam to create a reference intermediate frequency signal; and processing the measurement and reference intermediate frequency signals in order to derive magnitude and phase information as a function of position of the first portion of the signal beam on the sample and either storing the information or displaying the information in the form of an image.