Relationship Between False-Alarm Rate and Probability of False Alarm

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The relationship between the probability of false alarm, as calculated from the false-alarm rate (FAR), and the probability of detection as it relates to measuring target distance with a lidar system, are discussed. In a time-of-flight (TOF) lidar system, the travel times of laser pulses between sensor and target are used to estimate the range to a target. In the TOF method of range estimation, a short laser pulse is transmitted and is subsequently reflected from a target. The times of laser pulse transmission and reception of the backscattered pulse are measured by one or more photoreceivers. The TOF is calculated as the time between the transmission and the reception of the pulse, and the range to the target (R) is calculated as a function of the average group velocity (c) of the laser pulse given atmospheric conditions along the path between sensor and target, on the basis of the relationship.