Hybrid Design of an Optical Detector for Terrestrial Laser Range Finding

Abstract

This paper presents the integration of an InGaAs avalanche photodiode (APD)with the first amplification stage, comprised of a low capacitance silicon N-channel dual-gate MOS-FET and associated passive components, in the APD case. This combined linear mode optical hybrid detector is used in the field of terrestrial laser range finding. In this case, a reduction of input capacitance by 0.7 pF and an improvement of signal-to-noise ratio (SNR) at lowbackground noise conditions by 32 percent when compared to the equivalent discrete detector was measured. When integrated in a laser range finding system at very strong daylight conditions an improvement in SNR by approximately 10 percent was achieved. Furthermore a significant improvement in immunity to electromagnetic interference (EMI) is shown. Finally, when used in an eye-safe mobile laser range finding system, ranging beyond 10 km with an accuracy of ±2 m on non-cooperative targets using this hybrid detector is demonstrated.