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Visualizing
ray paths
using POVRAY
This is a model of an optical
system
whose purpose is to match the diameter and divergence of a laser beam
to an object at a variable range. The laser beam is
input
to a 'zooming' projector lens formed by three moving elements in two
groups. The
diameter and consequently the beam divergence of the output beam can be
varied over a range of 10x. The quality of the
projector
lens is effectively 'diffraction limited' at any setting of the
zoom position.
The lens was designed in ZEMAX as a 5-configuration lens. The laser beam emerges from the small lens to the left and enters the zoom projector.      This system is modelled in POVRAY using the lens objects files 'lens**.inc ', the glass include file, 'glasses.inc' file and the 'zoomproj.pov' file. The zoomproj.pov file demonstrates both the scattering media and the 'photon mapping' capabilities of POVRAY, developed by Henrik Wann Jensen, and originally introduced by Nathan Kopp into POVRAY via his MEGAPOV patched version of POVRAY. The path of the laser beam through the projector laser beam is shown by embedding the system in a scattering atmosphere. The scattering medium is contained within a box which is 0.2mm thick in the xy direction and rather longer than the system in the z direction. The lens elements are similarly thinned in the xy volume, so as the camera looks into the system it sees photons scattered by the atmosphere and refracted by the lenses.  This technique is more realistic than ZEMAX style raypath tracing, because it allows for the inverse square law of energy inside the beams. The spacings between the lenses can be animated. A 64 frame animation is easily setup in the POVRAY.ini file. |
| ©
Don
Barron 2005 |
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