Hybrid Design of an Optical Detector for Terrestrial Laser Range Finding

Abstract

This paper presents the integration of an InGaAs avalanche photo diode (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 low background 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.