Illumination Effect of Laser Light in Foggy Objects Using an Active Imaging System

Active imaging techniques usually provide improved image information when compared to passive imaging techniques. Active vision is a direct visualization technique using an artificial illuminant. Range-gated imaging (RGI) technique is one of active vision technologies. The RGI technique extracts vision information by summing time sliced vision images. In the RGI system, objects are illuminated for ultra-short time by a high intensity illuminant and then the light reflected from objects is captured by a highly sensitive image sensor with the exposure of ultra-short time. The Range-gated imaging is an emerging technology in the field of surveillance for security application, especially in the visualization of darken night or foggy environment. Although RGI viewing was discovered in the 1960's, this technology is currently more applicable by virtue of the rapid development of optical and sensor technologies, such as highly sensitive imaging sensor and ultra-short pulse laser light. Especially, this system can be adopted in robot-vision system by virtue of the compact system configuration. During the past decades, several applications of this technology have been applied in target recognition and in harsh environments, such as fog, underwater vision. Also, this technology has been demonstrated range imaging based on range-gated imaging. Laser light having a short pulse width is usually used for the range-gated imaging system. In this paper, an illumination effect of laser light in foggy objects is studied using a range-gated imaging system. The used imaging system consists of an ultra-short pulse (0.35 ns) laser light and a gated imaging sensor. The experiment is carried out to monitor objects in a box filled by fog. In this paper, the effects by fog particles in range-gated imaging technique are studied. Edge blurring and range distortion are the generated by fog particles