Guiding ships with Moire patterns

gist

A laser-cut reconstruction shows how overlapping striped masks can turn viewing angle into an immediately legible steering signal. The moire effect works with almost no calibration and supports many simultaneous viewers, but it continuously corrects toward one ideal line even when a whole channel is safe. A three-light range communicates the actual boundary better. The optical design fits narrow targets such as submarine cables more naturally than broad navigable corridors.

ideas

• Interference can encode direction without electronics. Two masks with slightly different band counts produce a visible cue that changes with the viewer’s angle.
• The geometry is buildable. A band-pitch ratio of 1.65 and one excess band on the first mask reproduced the patented effect with laser-cut parts.
• Correctness depends on the represented constraint. A precise centerline cue is counterproductive when the operational requirement is merely to remain inside a safe corridor.
• Threshold signals reduce unnecessary control. Three vertically arranged lights tell a pilot when the vessel reaches the edge or leaves the channel instead of demanding constant correction.
• Narrow hazards are the natural use case. A moire range is well matched to marking a cable or another feature where deviation from a thin line is itself dangerous.