I was inspired by Tom Scott’s excellent video and links here https://www.youtube.com/watch?v=d99_h30swtM   where he talks about a particular type of “Inogon” light used to guide ships through channels or harbours. The patent is here:  https://patents.google.com/patent/US4629325 and the military report on the effectiveness is here:  http://www.dtic.mil/dtic/tr/fulltext/u2/a168108.pdf (Hint; They don’t seem to like it much). I decided to build my own to play around with the effect. After a few minutes sketching in inkscape and a few more lasercutting,  I had this: I followed the claims in the patent fairly closely. They advocate between 1.5 to 1.8 ratio of pitch spacing to the width of the dark bands, and I used 1.65 (this yields a mask with a ‘duty cycle’ of around 40%), and to use only a single excess band on the first mask relative to the second.…