Distance Correction of Corona Discharge Photon Count in Ultraviolet Imaging Detection
Wang Sheng-hu · Gao dianya jishu · 2015
To reasonably compare the discharge photon count measured at different observation distances using solar-blind ultraviolet(UV) imagers, it is necessary to normalize the results with a common distance. Hence, we selected three discharge models as the objects, and used Coro CAM504 UV imager to measure discharges with different intensities at different distances in laboratory. Moreover, we analyzed the variation of photon count regarding to different observation distances, fitted the results with power functions and exponential functions, and proposed an empirical formula for the distance correction of photon count. The results show that because of the external interference and the UV imager's count error, when the discharge is too weak or the observation distance is far, the photon count no longer reduces but tends to increase with increasing distance. When the photon count is more than 10 and more than d/2, where d is the observation distance, it can be taken as an effective value. Within the range of observation distances 4~50 m, the relation between effective photon count and observation distance approximately meets power functions, the power exponent of which is about 1.222 for all the three tested discharge models. Further tests show that the proposed empirical formula is accurate enough to satisfy the needs of field engineering detection.