ESPI testing of Arcton containers

Abstract

The paper reports on the application of TV holography, more commonly known as electronic speckle pattern interferometry (ESPI), in the testing of Arcton bottles. A large number of Arcton bottles that have been returned to the factory for refilling exhibit dents of all sizes which occurred while in usage in the industrial environment. A system comprising a pulsed ruby laser, a high resolution CCD camera and a computer with frame grabbing capabilities has been prototyped to test two bottles at a time. The testing consists of providing an initial no-load image which is captured by the speckle camera. A second image of the bottles under-load (small depressurisation), is subtracted from the first, giving good quality interference fringes. The resulting image clearly denotes regions of higher density fringe pattern centred around dents or irregularities of the cylindrical surface of the bottles. The operator homes in with a cursor to measure the fringe density which is compared with the allowable one and acceptance or rejection of the bottle is indicated on the pc's monitor. The whole operation takes place in less than 5 min and is controllable from the pc's keyboard.