Tri-dimensional optical inspection based on flexible image guide: first step toward 3D industrial endoscopy

Erwan Dupont (1) , Frédéric Lamarque (1) , Christine Prelle (1) , Tanneguy Redarce (2)

1 Roberval - Roberval
2 AMPERE - Ampère

3D optical endoscopy is now a major challenge to allow the high resolution inspection of industrial equipments. The proposed instrument is based on a flexible image guide (70 000 fibres) and a Digital Micro mirror Device (DMD, 1024 x 768 "on-off" micro mirrors). The optical design is as follows: the light emitted by a 532 nm laser diode is dynamically structured by the DMD chip as a fringes pattern which is phase-shifted due to the active control of the DMD chip and projected onto an object on a circular field of 6 mm in diameter. Due to a telecentric and binocular arrangement that creates a stereoscopic angle, it is possible to get a depth of field of 2 mm along the optical axis without keystone distortions and few disturbances created by defocus and coma aberrations. Then, images are captured by a 1024 x 768 digital camera (not yet moved away by fibres) at 15 fps and directly used in the reconstruction algorithm to access the tri-dimensional shape of the unpainted object. The results are compared to incoherent white light results obtained with white painted mechanical objects. The lateral resolution is 31.3 µm and the RMS axial resolution is 10 µm for the laser-based design after speckle attenuation.

Domaines: Energie électrique

Erwan Dupont, Frédéric Lamarque, Christine Prelle, Tanneguy Redarce. Tri-dimensional optical inspection based on flexible image guide: first step toward 3D industrial endoscopy. ESDA, Jul 2012, Nantes, France. pp.82453, ⟨10.1115/ESDA2012-82453⟩. ⟨hal-00800021⟩