NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

The D-Sight technique is an optical double pass retroreflection surface inspection technique developed by Diffracto Ltd. in Windsor, Canada. It is a patented method of visualizing very small out-of-plane surface distortions such as indentations and protrusions. It converts variations in surface slope to changes in light intensity. The D-Sight method is a real-time technique that is particularly applicable to the rapid and enhanced visual inspection of large surfaces such as external aircraft surfaces.

An evaluation of the D-Sight technique for the rapid detection and assessment of impact damage in composite aircraft structures is described. The viability, reliability, limitations and possible improvements of the technique are discussed. The work has been performed within the EUCLID framework, RTP 3.1 Aeronautical Application Technology, Work Package 2: Global Diagnostic Damage Detection Methods.

A set of equations has been derived to establish the relation of various parameters of a DSight set-up. To quantify the inspection results, a D-Sight index has been introduced which represents the contrast of the D-Sight signature of a defect. Image processing routines have been designed for automatic detection of defects from D-Sight images. It is concluded that the D-Sight technique can reliably detect significant impact damage, with a damage area equal to or larger than 5 cm², within a field of view of about 0.25 m². The sensitivity of the technique corresponds to indent depths in the range of 0.01 to 0.05 mm. Inspections on a full-scale composite structure show that the D-Sight technique compares favourably with other inspection techniques, for the detection of impact damage and other defects with surface deformation.

1) National Aerospace Laboratory NLR, Structures and Materials Division,P.O. Box 153, NL-8300 AD Emmeloord, The Netherlands

2) TNO Institute of Applied Physics, Optical Instrumentation Division,P.O. Box 155, NL-2600 AD Delft, The Netherlands

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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