A simple method for determining distances by range-gated vision systems with different forms of illuminating pulses

摘要

It is proposed to single out two methods for observing object using range-gated vision systems (RGVS). In the first casethe distance between RGVS and an object is fixed. Its observation is made by changing time delay between the leadingedges of pulses of laser illumination and gate-pulses of the receiving block, i.e. neighboring layers of space aresequentially seen along the optical axis (visibility zone shifts). In the second case time delay is fixed. This correspondseither to observation of object moving along the optical axis of the system or to the study of ensemble of objects invisibility zone at different distances, including the observation on inclined path. It is shown that such a division of theobservation methods has a definite physical justification. Division of the two methods for observing object will promotesystematization and better understanding of the investigation results on RGVS.The regularities were investigated of formation of range-energy profiles (REP) of visibility zone for RGVS withilluminating pulses, the shape of which differs from the rectangular (triangular or trapezoidal) one. It was established thatif the illuminating pulse length Δt_L is smaller or equal to the length of gate-pulse Δt_G of the receiving block, then theexpressions for characteristic distances coincide with the case of rectangular-shaped pulses and they can be used todetermine distances to objects for pulses having non-rectangular shape. At Δt_L > Δt_G in a case of illuminating pulseshaving triangular shape REP possesses bell-like shape. For illuminating pulses having trapezoidal shape REP has eitherbell-like or trapezoidal shape. The last shape appears when the duration of the upper base of the illuminating pulsehaving trapezoidal shape exceeds the gate-pulse duration. The empirical method for determining characteristics distancesto the REP maximum and boundary points of plateau area, which can be used for calculation of the distance to theobject. Using calibration constants the method was proposed for calculating the distances to objects and its efficiencywas experimentally proved.