Holography Applied To Inspection And Mensuration In An Industrial Environment

The three dimensional imaging capability combined with enormous information storage capacity and the related very high resolution of images when they are correctly reconstructed, combine to make holography an inspection tool of immense power and utility in capital intensive industries. This paper describes work, in the U.K. electricity generating industry, aimed at enabling high grade holograms to be routinely recorded in a wide range of industrial situations where high speed acquisition of visual data is desirable. Specific applications to be described are holography of nuclear reactor cores, and of irradiated fuel elements for inspection after withdrawal from the reactor. Accurate reconstruction of images and precise, three dimensional measurement of reconstructed images in a laboratory environment is then undertaken with computer controlled micromanipulator equipment traversing a television camera within the real image. Measurements of a metre long fuel element to within 0.1 mm have been demonstrated and resolutions of 50 1.p./mm have been obtained on the reconstructed object. The paper describes the engineering required for in-reactor inspection where the pulsed ruby laser used to record the holograms is routinely alignec to a 15 m beam relay and remote holographic head. The requirements for accurate 3-dimensional reconstruction and hologrammetry are described and plans for automated measurement and inspection using image enhancement techniques are discussed.