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An article about vision anomalies claims that the increased sensitivity to UV light in aphakia sufferers has been put to use to detect UV signal lamps from German submarines in World War II.

"Let the light shine in", The Guardian, 2002-05-30:

However, aphakic patients report that the process has an unusual side effect: they can see ultraviolet light. It is not normally visible because the lens blocks it. Some artificial lenses are also transparent to UV with the same effect. The receptors in the eye for blue light can actually see ultraviolet better than blue. Military intelligence is said to have used this talent in the second world war, recruiting aphakic observers to watch the coastline for German U-boats signalling to agents on the shore with UV lamps.

I have not been able to find any evidence of the German (or any) navy using UV lamps for signalling from submarines. If this technique had indeed been employed, it seems likely that the "agents on the shore" would have had some technical means of detecting the UV signals (short of having to be aphakia sufferers), so the "military intelligence" would presumably have been able to use the same technology for watch for submarines (without relying on finding people with a particular eye condition).

Did the German navy use UV lamps for communication from submarines in World War II?

  • My guess is that this could be a myth aimed at hiding the Enigma/Ultra decryption (here is an example in fiction from a 1944 book). Some German Type XXI U-boats apparently used UV internal lighting. UV signals could be received using fluorescent material – Henry Feb 24 '16 at 21:27
  • @Henry: Thanks for the link to the book. Seems like at least the idea of UV communication existed. I'm not sure about the UV lighting on the XXI u-boats: I can't think of a reason why one would want UV for lighting (unless there's a rave on the boat, or they're using full-spectrum lamps for treating seasonal affective disorder). The description of UV lighting on XXI u-boats only appears on pages about a model kit and seems to be lifted from the promotional material of the manufacturer, Revell – Jake Feb 24 '16 at 21:45
  • Was the question by any chance inspired by my answer on Biology SE? – March Ho Feb 25 '16 at 15:07
  • @MarchHo: It was, actually! It's an interesting anecdote, but it seems almost too good to be true =) – Jake Feb 25 '16 at 15:09
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Yes, the German navy used UV light for signaling, but this was already being done by World War I.

See Signaling by Invisible Rays United States Naval Institute Proceedings, Volume 46, pages 1366-1368

both infra-red and ultraviolet, were accomplished during the war

The article explains how professor R. W. Wood further developed such ultraviolet ship signaling technology for France. Devices had a range of up to 6 miles.

Also, in The Military Engineer, Volume 23, there is a heading "Germany, Heerestechnik, November 1930, Work Done during the War on Direct-Ray Telephony", after which it refers to an article "Ultra-violet or Ultra-red Rays" by Leo Lowenstein.

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