Photophones

[Grey Havoc]

http://chris-intel-corner.blogspot.gr/2013/08/german-80mm-photophone-carl-zeiss.html
(h/t paspartoo over at MilitaryPhotos.net)

http://www.bluehaze.com.au/modlight/GrothArticle1.htm
(via the wiki article on photophones)

 

[antigravite]

That's a fascinating feat of engineering.
Maybe one among those zillions blinking stars, is actually engineered by an advanced ET civilization, radiating through series of modulated pulses some sort of communication message, in every possible direction.

 

[fv1620]

There are some IR photophones German & Jap on pages 2-4 on here:

http://www.hmvf.co.uk/pdf/Tabby03.pdf