Editing Appendix/CGH/ParallelAperturesHolograms (section)

==Basic Concept==
Okay, so what do &sect;&sect;[[Appendix/CGH/ParallelApertures|I.A]] and [[Appendix/CGH/ParallelApertures2D|I.B]] have to do with the numerical construction of a hologram?  Well, this is best explained by borrowing an illustration from the Nishikawa et al. (1997) paper (redrawn here as Figure I.2), and comparing it with [[Appendix/CGH/ParallelApertures#General_Concept|Figure I.1 from our &sect;I.A]].
<table border="1" align="center" cellpadding="8">
<tr><th align="center">Figure I.2</th></tr>
<tr>
<td align="center">[[File:Hologram.illustrate.gif|Hologram illustration]]</td>
</tr>
</table>

In general a hologram is made by combining light of wavelength, <math>\lambda</math>, that is coming from the surface of a 3-dimensional object with coherent light from a reference beam of wavelength <math>\lambda_\mathrm{ref}</math>.  The interference pattern that is created on the "image screen" via the combination of these two separate sources of light is recorded as the hologram &#8212; usually in the form of an exposed piece of photographic film.  Let's consider the behavior of these two sources of light, separately.