Abstract:
A three-dimensional (3D) laser imaging system based on digital holography
has been used as a tool for testing digital holography (DH) in the infrared (IR)
range in several configurations; transmission and reflection mode. The feasibility
of digital holography in the infrared region was demonstrated using two beam
interferometric technique for recording holograms both in reflection and
transmission type geometry which employs a pyroelectric sensor array detector.
The materials used are two euro coins, marble plate, earthenware tree, Aluminum
plate, Lens mount, Bronze statues of Augusto and Traiano, lens mount, Bronze
statue and human size mannequin. Their sizes ranges from 2.3 cm to 170.0 cm.
Images from these different objects were acquired with high resolution miricle
thermoteknix cameras. The recorded images in the form of fringes were
transferred to a computer for analysis using MATLAB software. By making use
of image processing tools and Fast Fourier Transform (FFT) technique, the 3D
images of the samples were analyzed and decoded, to the original real object from
the fringes. IR digital holography has many advantages whenever large object and
hard materials of high depth penetration, recording and reconstruction is required
with respect to digital holography in the visible region. A long wavelength
radiation has a lower sensitivity to sub micrometric vibrations- use of larger
angles, smaller distances between the object and the recording device- this
peculiarity provides a higher fringe visibility when large samples are investigated.
