Measurement of elongation of rubber or similar test=bar - optical fibres fixed on test bar observe reference optical image

In this process, a reference optical image (46) is projected near the test-bar (1) which undergoes an elongation. The displacement of at least one point of the test-bar (1) in relation to the optical image (46) is measured. In one application, the image is formed by a series of lines of light separated by dark lines. Two optical fibres (8,9) are fixed onto the cross-bar (1) so that one of their ends (43,44) is placed in the optical image (46). Two photosensitive detectors (16,17) are placed at the other end (14,15) of the fibres (8,9). These detectors (16,17) give signals which represent the light sensed by the fibres (8,9). A system including a threshold pulse generator and a counter is used to count the number of passages from light to darkness that the fibres do and deduces the elongation. LA PRESENTE INVENTION CONCERNE LES PROCEDES ET LES DISPOSITIFS POUR MESURER L'ALLONGEMENT D'UNE EPROUVETTE 1.L'INVENTION SE CARACTERISE ESSENTIELLEMENT PAR LE FAIT QU'ELLE CONSISTE A PROJETER UNE IMAGE OPTIQUE DE REFERENCE 41, 42, 46 DANS L'ESPACE A PARTIR D'UN OBJET-SOURCE 40, ET A COMPARER LE DEPLACEMENT D'AU MOINS UN POINT 12, 13 DE LADITE EPROUVETTE 1 SUR LAQUELLE ON EXERCE DES DEFORMATIONS PAR RAPPORT A LADITE IMAGE OPTIQUE.APPLICATION A LA MESURE DES DEFORMATIONS DES MATERIAUX AYANT UN COEFFICIENT D'ALLONGEMENT IMPORTANT.