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External Interface for Processing 3-D Holographic and X-Ray Images for Analysis and Control

Objective

The aim of the PHOX project was to develop an external interface system for linking physically generated 3-D images to inspection and analysis procedures. While this had to be a general and flexible system, it was demonstrated through the application of holographic interferograms and X-ray radiographs to real-time testing and inspection and to 3-D measurement. For this task, optical and electronic methods had to be combined in order to extract the relevant information from multiple 3-D images. A further aim of the project was the automation of holographic interferometry and X-ray radioscopy for online testing in the manufacturing process. .
The aim of the project was to develop an external interface system for linking physically generated 3-dimensional images to inspection and analysis procedures. Optical and electronic methods had to be combined in order to extract the relevant information from multiple 3-dimensional images. A further aim of the project was the automation of holographic interferometry and X-ray radioscopy for online testing in the manufacturing process. Two nondestructive testing methods were combined. First, deformations of the surface of materials were detected by a holographic method. The deformations were then interpreted in terms of stress and compression on the material, using finite element methods. The stress and compression were then further explained by the use of X-ray image processing to give information regarding the interior of the materials. Various techniques for quantitative holographic interferometry were investigated, and the phase stepping method and a method based on the Fourier transform were selected. X-ray radiography interface requirements (mainly concerned with filtering noisy signals) were identified. The quality of the images was found to depend on the X-ray source, on the geometrical structure of the inspection system, and on the detector and image processing system. Consequently, controlling hardware and software were developed to optimize these conditions for performing the testing. A manipulator and its control were produced and a source control (microfocus X-ray control) developed. Low level image processing techniques were adapted for use with both X-ray images and interferograms. A common set of objects (honeycomb structures) were selected to test the methods developed for holographic interferometry and X-ray radioscopy, both individually and in combination.
The challenge of the PHOX project was to combine two non-destructive testing methods. This was done by first detecting deformations of the surface of materials by a holographic method. The deformations were then interpreted in terms of stress and compression on the material, using finite element methods. The stress and compression were then further explained by the use of X-ray image-processing to give information regarding the interior of the materials.
Various techniques for quantitative holographic interferometry were investigated, and the phase-stepping method and a method based on the Fourier transform (invented within the project), were selected. Holographic processing combined with finite element analysis had already been successfully demonstrated. X-ray radiography interface requirements (mainly concerned with filtering noisy signals) were identified. The quality of the images was found to depend on the X-ray source, on the geometrical structure of the inspection system, and on the detector and image processing system. Consequently, controlling hardware and software were developed to automatically optimise these conditions for performing the testing. A manipulator and its control were produced and a source control (microfocus X-ray control) developed. Low-level image-processing techniques were adapted for use with both X-ray images and interferograms. A common set of objects (honeycomb structures) were selected to test the methods developed for ho l graphic interferometry and X-ray radioscopy, both individually and in combination.
Exploitation
PHOX advanced the technologies for designing and testing engineering structures, which is a priority for the achieving improved product quality. The creation of a prototype combining optical and electronics technologies successfully demonstrated the feasibility of a low-cost system for online testing for surface defects.
Knowhow about non-destructive testing methods acquired through work in holographic interferometry is to be marketed by one of the partners.

Coordinator

Bias - Forschungs- und Entwicklungslabor Angewandte Strahltechnik GmbH
Address
2,Klagenfurter Strasse
28359 Bremen
Germany

Participants (4)

GEC Engineering Research Centre
United Kingdom
Address
Cambridge Road Whetstone
LE8 3LH Leicester
IRAM
France
Address
Domaine Universitaire De Grenoble
38406 Saint-martin-d'heres
SCANRAY A/S
Denmark
Address
Hammerholmen 9-13
2650 Hvidovre
Universität Dortmund
Germany
Address
Emil-figge-straße 74
44221 Dortmund