Three-dimensional imaging with long infrared digital holography

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.