Range accuracy of a gated-viewing system as a function of the number of averaged images

Abstract

Primarily, a Gated-Viewing (GV) system provides range gated imagery. By increasing the camera delay time from frame to frame, a so-called sliding gates sequence is obtained by which 3-D reconstruction is possible. Scintillation caused by atmospheric turbulence degrades each Gated-Viewing image and thus, the range accuracy that can be achieved with the sliding gates method. By averaging a certain number of images per range, this degradation can be reduced. In this paper we have studied the influence of the number of averaged images on the resulting range accuracy. Therefore, we have combined the Intevac Gated-Viewing detector M506 with a pulsed 1.57 μm laser source. The maximal laser pulse energy was 65 mJ. The target was a 1-m²-plate at a distance of 500 m. The plate was laminated with a Spectralon layer having Lambertian reflection behavior with a homogeneous reflectance of 93 %. It was orientated diagonally to the line of sight of the sensor in order to provide a depth scenario. We have considered different combinations of the four parameters »detector binning mode« (1x1, 2x2), »optics« (f = 250 mm, f/2.1; f = 500 mm, f/3.3; f = 2032 mm, f/10), »gate length« (13.5 m, 23.25 m, 33 m) and »signal-to-noise ratio« (SNR) (1 dB, 2 dB,…, 9 dB). For each considered set of parameters, a sliding gates sequence of the target was recorded. Per range, 20 frames were collected. Finally, the range accuracies were derived as a function of the number of averaged frames per range.