This example shows a 0.25m 350GHz Cassegrain type antenna with 3 struts and a subreflector that produce significant diffraction effects.
The following video shows the real-time screen output of a GTX480.
The picture shows a screen dump after completion by phase retrieval.
Top left shows the retrieved complex aperture and bottom left is the reference aperture for comparison. Top right shows the intensity data at plane 2. Bottom right is the intensity data at plane 1. The separation between planes is just 5cm or 0.0029 times the Rayleigh Range. The struts subtend 45 degrees with respect to the aperture and the subreflector diameter is 20% of the main reflector.
The combined diffraction from the engraved text and the three struts produces a difficult case for Phase Retrieval, with lots of interesting traps. To overcome these traps we multiply the intensity data with a weighting function and maintain this weighting during the first 1200 cycles.
We also use a over-tight constraint (-5%) during this initial part of the process.