title: Digital in-line holography in thick optical systems: application to visualization in pipes.
abstract: We apply digital in-line holography to image opaque objects through a thick plano-concave pipe. Opaque fibers and opaque particles are considered. Analytical expression of the intensity distribution in the CCD sensor plane is derived using a generalized Fresnel transform. The proposed model has the ability to deal with various pipe shapes and thicknesses and compensates for the lack of versatility of classical digital in-line holography models. Holograms obtained with a 12 mm thick plano-concave pipe are then reconstructed using a fractional Fourier transform. This method allows us to get rid of astigmatism. Numerical and experimental results are presented.
authors.affiliation: Groupe d'Optique et d'Optoélectronique, UMR-6614 CORIA, Avenue de l'Université, 76801 Saint-Etienne du Rouvray Cedex, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Verrier
authors.forename: Sébastien
authors.initials: S
authors.lastname: Coëtmellec
authors.forename: Marc
authors.initials: M
authors.lastname: Brunel
authors.forename: Denis
authors.initials: D
authors.lastname: Lebrun