Analysis of the visual artifact in range-gated active imaging, especially in burst mode.

Abstract

After the demonstration of the occurrence of visual artifacts with an active imaging system in burst mode in a previous paper, the analysis of this phenomenon was realized. A visual artifact resulting from a remote zone in the scene can appear in the image of the real visualized zone when the duty cycle of laser pulses is close to 50%, as in the burst mode. Therefore, the elements of this remote zone will create confusion in the image, with erroneous estimated distances. These misinterpretations can be very embarrassing to those attempting to determine the distance of a target in the scene. From the modeling realized and validated in the previous paper, the behavior of the visual artifact was analyzed with two types of burst mode used in active imaging, the duration of the laser pulse being identical to the duration of the temporal aperture of the imager. In the first mode, the width of the visualized zone is set, depending on the distance. The second mode increases the width of the visualized zone so that the foreground of the zone is constantly visible. The results showed that the distance of the visual artifacts in variable mode increased much more quickly than the distance in fixed mode. In both modes, the most intense visual artifacts appear when the range of the visualized zone remains within the first kilometer. When this range is very short, the illuminance of the visual artifact in fixed mode is much more intense than the illuminance in variable mode. On the other hand, for long distances, the illuminance of the visual artifact in variable mode is greater than the illuminance in fixed mode, but decreases quickly beyond a certain distance, making it insignificant.