title: Contouring of diffused objects using lensless Fourier transform digital moiré holography.
abstract: A method is proposed for contouring of diffused objects using digital holographic moiré interferometry in lensless Fourier transform configuration. Fringe projection moiré technique combined with digital double-exposure holography produces the contours in this method. Two digital holograms of a 10 mm aluminum alloy cube are recorded by tilting the illumination angle slightly between exposures, and a third one is recorded by translating the detector a little laterally with the final illumination angle unchanged. Upon numerical processing of the first two holograms, a plane parallel fringe system seems to be projected onto the object. This fringe system can be referred to as the modified grid. Processing of the second and the third hologram results in another grid, the reference grid. In effect, processing of the first and the third hologram combines the modified and the reference grids to produce the moiré contour fringes. The range of contour intervals obtained remains between 2.73 and 0.38 mm with seven different contours in between. The present method can measure details of a great variety of sizes on objects of large dimensional range. Deviations in the measured contour intervals from the theoretically calculated values are found to be within 12%-18%. This seems to be because of the deviation in the present experimental geometry from the ideal theoretical configuration, the hologram digitization, and the particular reconstruction algorithm used in the present experimental arrangement.
authors.affiliation: Space Physics Laboratory, Vikram Sarabhai Space Center, Thiruvananthapuram, Kerala, India.
authors.forename: Md Mosarraf
authors.initials: MM
authors.lastname: Hossain
authors.forename: Gyanendra
authors.initials: G
authors.lastname: Sheoran
authors.forename: Varun
authors.initials: V
authors.lastname: Kumar
authors.forename: Chandra
authors.initials: C
authors.lastname: Shakher