Abstract

In the research laboratory the imaging of a target on a detector array using heterodyne detection techniques¹ was performed. The targets were both transmissive and reflective and good results were obtained for both types of targets. Figure 1 is a sketch of a typical experimental set up for a reflective target. A motorized precision rotatable mount held the target so motion was possible. The half waveplate in the local oscillator arm rotated this field's plane of polarization by 90° so only the field components in the plane of the page would interfere also the polarizer before the detector selected this state of polarization. Both the frequencies of the L0 and signal beams were shifted by acousto-optic modulators. A 64×64 element array of the camera was used to record the intensity pattern. The target was moved using a stepping motor so at each sampling interval the target was at rest and the data at each element of the camera was sampled 10 times so the intermediate frequency waveform was recovered. In a given sampling period at least 10 or more different samplings were taken. This number is small but was limited by the camera and electronics. The camera frame speed was slow which restricted the intermediate frequency of the heterodyne signal to be no higher than 10 Hz.

© 1992 Optical Society of America