Real-time speckle metrology using terahertz free electron laser radiation

Real-time speckle photography in the terahertz spectral region was experimentally demonstrated using a 160×120 microbolometer focal plane array (FPA). Novosibirsk free electron laser was employed as a source of 2.3 THz monochromatic coherent radiation. A speckled image of an object which was illuminated by radiation diffusely reflected from a rotating scatterer was projected on the FPA. Two hundred fifty frames of the terahertz “video” recorded by the FPA with a repetition rate of 41 frames/s were used for reconstruction of the amplitude, period, and logarithmic decrement of damped rotational oscillations of the scatterer.