Abstract

With the advent of large aperture airborne telescope systems, a need has arisen for detailed measurements of optical turbulence data along extended, low-elevation paths at medium and high altitudes. A compact, two beam interferometer has been designed to monitor spatial and temporal wave-front tilt fluctuations induced by the atmosphere between two flying aircraft. The system uses a variation on the classic vertical profiling experiments of Shannon et al. The transmitting aircraft carries a laser that produces two spatially separated circularly polarized beams. The optical phase of one beam is dithered at a precise modulation frequency. Two collimated detectors are located on the receiver aircraft. They detect linearly polarized light, in quadrature. The two detector signals are combined to produce a single-sideband analog of the optical phase difference between the two beams. Comparison of the electrical phase of this analog signal with that of the original dithering modulation signal yields real-time measurements of the effective wave-front tilt.

© 1992 Optical Society of America