Clever Naval Light

How This Clever Naval Light Always Points the Way You Need to Go

A brilliant optical trick makes this sign read correctly from any possible angle.

By Eric Limer

YOUTUBETOM SCOTT

Imagine you're in charge of guiding ships into a harbor and you want to use a sign to direct them all to one specific point, perhaps a dock or a channel. How might you make a single signal light that always points to the right direction depending on the angle you look at it, to the right if you're too far left, and to the left if you're too far right?


Here in 2018, your mind might go to location tracking or some other high tech solution, but in 1982, some clever engineers had already figured out an answer with no electronics required. Well, other than a light. Tom Scott explains:

The Inogon Leading Mark makes use of what's called the moiré effect, that strange type of distortion you see when looking at a series of overlapping, not-quite-parallel lines. You may be familiar with it as a form of digital image artifacting, a strange jaggy cloudiness that can appear in certain images or video, like a clip of a striped shirt.

If you use this phenomenon cleverly, however, you can create an image that can change depending on the angle its viewed from. In the case of the Inogon light, it will always display an arrow or series of arrows (sometimes strange, distorted ones) pointed in the direction you want them to go. It's like an optical illusion that's good for more than just blowing your mind.

Source: Tom Scott