Abstract
The sensitivities of heterodyne and direct-detection systems at CO2 laser wavelengths are compared to illuminate the design principles involved. It is shown that destruction of the temporal coherence of scattered radiation is a significant effect when heterodyne systems are used on targets with internal motion. The complete system and the results obtained are then described. The compact optics head contains a waveguide laser, an acousto-optic modulator and SAW chirp devices; it has 45 mm diameter transmit and receive apertures. Whem many returns are integrated, ranges of several kilometres are obtained off natural targets with an accuracy of 10 m. From the Doppler shift off a moving target, radial velocity can be determined simultaneously with the range when an up-chirp/down-chirp technique is used; an accuracy of better than 1 m s−1 is demonstrated.
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Hulme, K.F., Collins, B.S., Constant, G.D. et al. A CO2 laser rangefinder using heterodyne detection and chirp pulse compression. Opt Quant Electron 13, 35–45 (1981). https://doi.org/10.1007/BF00620028
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DOI: https://doi.org/10.1007/BF00620028