Acoustical Holography Matrix Array Imaging System for the Underwater Inspection of Offshore Oil Platform Weldments
This paper describes a diver operated underwater optical-acoustical imaging system for the inspection of internal defects in offshore platform weldments. The two-dimensional acoustic array is electronically programmed with digital techniques to simulate focused and non-focused source-receiver scanning. The electronic simulated reference beam is programmable using erasable programmable read only memories (EPROMS). The imaging device consists of a diver hand held gun containing the acoustic array, miniature television camera and the visible light emitting diode (VLED) display array. The gun is connected via the diver pack and cable to the control unit, digital memory display and data recording units located in the submersible. The television camera provides an optical view of the external weld surface, identification marks, etc., which is integrated with the acoustical image on a standard television monitor. The acoustical array provides complete realtime inspection by electronically scanning and constructing multiple focused holograms through the entire weld volume. The defect images are presented in side, plan and pseudo three-dimensional views with the options of rotation, tilt and zoom magnification. The system has two permanent recording techniques. The focused holographic defect images and optical views are stored on videotape and the basic r-f data on digital tape. This system is now undergoing tests in the North Sea by International Submarine Services.
KeywordsDiver Pack Matrix Array Acoustic Control Digital Tape Shear Wave Image
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