Low coherence interferometric system for phase stepping shearography combined with 3D profilometry

摘要

The present invention relates to a portable industrial instrument for performing, in an integrated and two-way manner, an interferometric fringe projection and shearography, on a object to be tested, so that, when the two-way interferometer (1) is associated with the coherent or quasi-coherent projection device (2), the instrument is able to measure the 3D shape of the object by interferometric fringe projection, also known as moiré method, and, when the two-way interferometer (1) is associated with the recording or imaging device (4), the instrument is able to perform shearographic measurements on the object, the direction of the traversing light beam in the interferometer (1) being reversed when shifting from one measurement configuration to the other one.

主权项

1. A portable industrial instrument for performing, in an integrated and two-way manner, interferometric fringe projection and shearography, on an object to be tested, comprising:
a two-way interferometer (1) including means to generate a bidirectional circularly polarized light beam; a coherent or quasi-coherent light projection device (2); a recording or imaging device (4); a first location (24) where said two-way interferometer (1) is positioned to be functionally associated with the coherent or quasi-coherent light projection device (2) and a second location (44) where said two-way interferometer (1) is positioned to be functionally associated with the recording or imaging device (4); a computational device (6), including a video and analysis display; an excitation device (5) dedicated to the shearographic or fringe projection measurements; so that, when the two-way interferometer (1) is associated with the coherent or quasi-coherent projection device (2) at the first location (24), the instrument is able to measure the 3D shape of the object by interferometric fringe projection, and, when the two-way interferometer (1) is associated with the recording or imaging device (4) at the second location (44), the instrument is able to perform shearographic measurements on the object, the direction of the traversing light beam in the interferometer (1) being reversed when shifting from one measurement configuration to the other one, the direction of the coherent or quasi-coherent light being reversed in the two operation modes, said instrument being characterised in that:
the two-way interferometer (1) is reversible and symmetric about a Savart plate, which is central anda translation device (3) for precisely displacing said two-way interferometer (1) from said first location (24) to said second location (44) and from said second location (44) to said first location (24), comprising a rail that is curved on one of its ends, the curved end having an arc subtending a maximum angle of 90°, so that the precision displacement of the interferometer corresponds to a combination of a strict geometric translation with a rotation angle which does not exceed 45° so as to create a crossing between respective directions of an incident light beam and a reflected light beam, according to the same angle.