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Corresponding Author

El_Mashade, Mohamed

Subject Area

Electrical Engineering

Article Type

Original Study

Abstract

LADAR systems constitute a direct extension of the conventional radar techniques. Because they operate at much shorter wavelengths, LADARs have the unique capability to generate 3D images of objects. These laser systems have many applications in the defense gelds concerning target detection and identification. The extraction of these features depends on the processing algorithms, target properties and 3D images quality. Our scope in this research is to use the Avalanche photodiode as a basic detector in three dimensional imaging LADAR systems and analyze its behavior against different operating conditions. Avalanche photodiode in its linear mode gives good performance only for high count rate of photo-electrons. In the case of low count rates (extremely weak signals), this device must be biased above its breakdown voltage in order to have higher sensitivity. This situation is known in the literature as Geiger-mode operation. This mode of operation suffers from mean primary noise rates in the measured interval. This in turn may cause the detector not respond before receiving the desired signal. When the Avalanche photodiode is biased below its breakdown voltage with highest achievable gain value, and followed by an ultra low noise amplifier, it becomes sensitive to the single photo-electron. This operating mode is called Linear-mode single photon. The operation of the detector in this mode overcomes the drawbacks of the Geiger-mode. Detection and false alarm probabilities are analyzed for each one of these operating situations.

Keywords

Avalanche photodiode; Three-Dimensional Imaging; Direct detection; Ladar

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