WHAT ASPECT OF THE PROBLEM WAS MOST DIFFICULT?
The starting point!

WHAT INSIGHTS (IF ANY) DID YOU GAIN FROM WORKING ON THE PROBLEM? 
I would like to know more about the background of the reason, 
posing such a problem. My feeling is that there is no practical 
application. Perhaps Underwater-Photography?

ADDITIONAL COMMENTS:
My feeling is that a best solution can well be diffraction 
limited! But there is not enough time for me to show this!