Flaw Detection by Spatially Coded Backscatter Radiography

摘要

Backscatter imaging is suited for the inspection of extended structures like airframes,rnbridge structures, floors etc., which cannot be inspected with conventional radiography.rnHowever indications obtained from backscattering are convoluted and difficult torninterpret. The spatial coding technique used in astronomical physics to detect feeblernemissions is investigated for the detection of the weak indications produced by the flawrnin backscatter imaging. Spatial coding involves the positioning of a mask with open andrnclosed holes (aperture) to selectively permit and block the passage of radiation. Thernobtained “coded” indications are then mathematically decoded to detect the presence ofrnanomalies. Monte Carlo simulations were employed to investigate the applicability of thisrntechnique. This paper introduces the coded aperture technique, describes how it is appliedrnto scatter radiography, present the results obtained from the simulations and concludesrnwith a discussion on future work.