Tyre Tester

Evaluation software for a interferometric automobile tire testing device

For non-destructive testing of automobile tires the Beissbarth Automotive Group has developed a testing appliance which detects internal defects of tires at an early stage. This device operates on the basis of a shearographic in­ter­fer­om­e­ter recording intensity images by a CCD-camera. It measures de­for­ma­tions caused by slight deflations of a tire segment so that defects which are invisible to the human eye can be visualized and detected au­to­mat­i­cal­ly. For example these defects may include separations of different lay­ers of the shell or damages of the carcass.

The software module developed by FORWISS evaluates the interferometric im­ages recorded by the tire tester. First the intensity images are trans­form­ed into continuous phase images via a hybrid phase unwrapping al­go­rithm taken over from an earlier project Single-Frame-Real-Time-Inter­fero­me­try and which has been further improved regarding the execution speed and ac­cu­ra­cy. The phase image carries information about the directional de­riv­a­tive of the deformation. Before the actual evaluation the phase images are masked and deskewed. The area of interest is extracted via an adaptive thresh­old­ing technique, and the deskewing is realized by non-linear op­ti­mi­za­tion methods. The actual evaluation algorithm operates on the deskewed phase images. Characteristic deformation profiles are recognized and clas­si­fied.

Sample images
Reifen mit Karkassschaden Berechnetes Deformationsprofil

Tire with carcass damage; interferometric phase image

Resulting deformation profile; generated by the hybrid phase-unwrapping algorithm

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