ABSTRACT
Holography is a well established technique for three-dimensional (3D) imaging. It was first introduced by D. Gabor in 1948 [2] in order to improve the resolution of the electron microscope. Light scattered from an object is recorded with a reference beam in a photographic plate to form a hologram. Later, the processed photographic plate is illuminated with a wave identical
CONTENTS
6.1 Introduction to Digital Holography ........................................................ 151 6.1.1 Holography and Digital Holography .......................................... 151 6.1.2 Numerical Reconstruction Algorithms ...................................... 161 6.1.3 Phase to Profile ............................................................................... 166
6.2 Digital Holoscopes ..................................................................................... 166 6.2.1 Reflection Digital Holoscope ........................................................ 166
6.2.1.1 Calibration (Height Calibration by Comparison with AFM) ........................................................................ 167
6.2.1.2 MEMS Inspection ............................................................ 169 6.2.1.3 Reflective Microlens Array Characterization ............. 169
6.2.2 Transmission Digital Holoscope .................................................. 170 6.2.2.1 Quantitative Mapping of Domain Inversion
in Ferroelectric Crystal ................................................... 170 6.2.2.2 Characterization of Transmission Microlens Array .... 172 6.2.2.3 Characterization of Diffractive Optical Elements
on Liquid Crystal Spatial Light Modulator ................. 176 6.2.3 Resolution Enhancement in Digital Holography ...................... 182
6.2.3.1 Resolution Enhancement Methods ............................... 182 6.2.3.2 Differences between Hologram Stitching and
Zero Padding ................................................................... 186 6.3 Conclusion .................................................................................................. 190 References ............................................................................................................. 190
to the reference wave, and a wave front is created that is identical to that originally produced by the object. As the development of laser, holography is applied in optical metrology widely. The phase of the test object wave could be reconstructed optically but not measured directly until the introduction of digital recording devices for the hologram recording. The digital recorded hologram can be stored in the computer and the numerical reconstruction method used to extract both the amplitude and phase information of the object wave front. By digital holography, the intensity and the phase of electromagnetic wave fields can be measured, stored, transmitted, applied to simulations, and manipulated in the computer.
