Proceedings Article | 6 August 2009
Li-gang Wu, Wei Huang, Tie-feng Xu, Rui-qin Tan, Yan Yang, Ming-liang Tu
KEYWORDS: Ultraviolet radiation, Visible radiation, Cameras, Ultraviolet telescopes, Coronagraphy, Image fusion, Imaging systems, Combined lens-mirror systems, Video, Optical filters
Corona discharge of high voltage lines and equipment has always been an operational and maintenance problem for
electric power utilities. In addition to causing noise and radio interference problems, these luminous discharges, which
result from the ionization of air around an electrode, may also indicate the presence of faulty, damaged or contaminated
high voltage components. Corona can lead to the some components' premature aging and failure. Therefore, it's
necessary to develop a system to identify corona discharge sources and pinpoint the offending component so that it may
be replaced. The corona emission in the solar-blind ultraviolet (SBUV) region (240 - 280 nm) is much weaker but the
solar background is nil. Accordingly, a beam-split scheme, including a catadioptric UV telescope, a solar-blind UV
filter, an intensified-CCD (ICCD), and a visible camera, is applied in this system. The catadioptric UV telescope is
especially designed in this paper. Twain reflecting spherical surfaces, composed the majority of the UV telescope, are
combined with a pair of positive and negative lenses in the front, and a correction lens in the back-end. To be
emphasized, all the elements' surfaces of the catadioptric telescope are spherical, so that it can be manufactured
conveniently. In addition, it has a large aperture of 68 mm, with a focus length of 180mm, so as to improve the optical
resolution, enhance the power of entrance pupil and elevate the sensitivity of the imaging system. A folding mirror is
positioned in front of the telescope's central obscuration so that the UV and visible cameras have a common axis. In
addition, the bispectral image fusion is based on digital signal processor TMS320DM642 of TI company, where the
DM642 device has three configurable video port peripherals (VP0, VP1, and VP2), and each video port consists of two
channels - A and B with a 5120-byte capture/display buffer that is splittable between the two channels. Therefore,
DM642 has enough video ports to satisfy two video-in channels from the UV ICCD and the visible CCD, and one videoout
channel for bispectral fusion. At last, an image fusion algorithm based on pixel is used in experiments, and a
bispectral fused image is given clearly in this paper.
