Electronic speckle pattern interferometer launched

Electronic speckle pattern interferometer launched Defect detectton and wbratton analysis us=ng electrontc speckle pattern mterferometry 0s now possible in the field, following the launch of the Vldlspec system from Eahng Electro-optics of Watford, UK~ Since the UK launch in October 1985, stx systems have been sold for purposes ranging from quality control of turbme blades and wbrat=on analys0s of car engines to loudspeaker development. The company says it has also received favourable responses from West German car manufacturers and from American firms present at the US launch on Los Angeles =n January Weighing 20 kg and costing around £ 2 5 0 0 0 for a complete system, including a vibrat~on isolation table, the V0dlspec is satd to be an engmeenng tool able to be easdy set up and used by unskdled operators Unhke holography, the usual method for analysts of small

displacements of stressed objects, speckle mterferometry can be used on dayhght. The techmque mvolves the dlummatton of components by a spht laser beam, which is then reflected and recombmed wtth the reference beam to produce an mterference pattern recorded by a vtdeo camera. For static stresses a stored tmage of the unstressed component ts subtracted from the interference pattern to gwe a fringe pattern on the wdeo monttor. The fnnges represent equal displacements of the object's surface. Using a 10 mW He/Ne laser the fnnges mdtcate d~splacements of half the 0.6328 /zm wavelength, le approximately 0.3 /zm. With a maximum of 40 frmges on the screen, the V~d~spec has a displacement range of 12 /zm across the field of wew. Parts can also be stressed dynamically (eg with ptezoelectnc transducers), a ttme averaged fnnge pattern showing contours of constant vtbrat=on amphtude.

Vidlspec examines loudspeaker performance

VanatMons of vibration w~th frequency can then be followed m real tome. The techntque, developed at Loughborough Unwersity, was prev.ously commerclahzed by W. Vmten Ltd, but the I.cence passed to Eahng Electro-optics a httle over a year ago. A basic explanat=on of the techmque appeared in NDT International, Vol 15, No 3, pp 143-5.

Eahng Electro-optics plc, Greycame Road, Watford WD2 4PW, UK

Direct-reading depth gauge A crack depth measurement system which uses the AC field measurement technique ts now avadable from Inspectorate-Un0t Inspection of Swansea, UK. The U8 MiCroGauge gives direct dlgttal readmgs of crack depth and ~s portable and battery powered. Its measurement range goes up to 199.9 mm with a clatmed resolution of 0.1 mm. The unit has already been used on structural components in the North Sea and on petrochemical plant, slzmg defects w~thm vessels and plpework system& Smce tt uses the ratio of measured voltages, cahbratlon ts unnecessary and the effects of changes in material properttes are said to be stgntftcantly reduced.

Inspectorate- Unit Inspection, Sketty Haft, Sketty Park Road, Swansea SA2 8QE, UK

Measuring fibrescope An X-ray dewce which can work m con/unction with a machine ws/on system has been announced by Lixi Inc of Downes Grove, IL USA The company foresees advantages m areas including semi-conductor inspection where the die-bond can be respected in addition to the chip ahgnmentThe photograph shows the Lixl Imaging Scope's wew of a phono plug. Lixl Inc, 1438 Brook Drive, Downers Grove, IL 60515, USA

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Measurement of defects using a fibrescope is sa~d to be possible wtth the Olympus Measuring Fibrescope from KeyMed Industrial. The fibrescope has a scale and a mov0ng cursor m the eyeptece For a demonstration contact: KMI Customer Liamor~ KMI, KeyMed House, Stock Road, Southend-onSea, Essex SS2 5QH, UK

NDT INTERNATIONAL

FEBRUARY 1986