[kach22i]

Mannequin Français 39/45 - matériels militaire 14\18 39\45


Coincidence rangefinder
https://en.wikipedia.org/wiki/Coincidence_rangefinder

A coincidence rangefinder (stereoscopic, parallax, or split-image rangefinder) is a type of rangefinder that uses mechanical and optical principles to allow an operator to determine the distance to a visible object.

The device consists of a long tube, with two lenses facing forwards at each end, and an operator eyepiece in the center. Two prism wedges which, when aligned result in no deviation of the light, are inserted into the light path of one of the two lenses. By rotating the prisms in opposite directions using a differential gear, a degree of horizontal displacement of the image can be achieved.

https://en.wikipedia.org/wiki/Coincidence_rangefinder

Eyepiece image of a naval rangefinder, showing the displaced image when not yet adjusted for range

Dazzle camouflage
https://en.wikipedia.org/wiki/Dazzle_camouflage

That dazzle did indeed work along these lines is suggested by the testimony of a U-boat captain:[1]

It was not until she was within half a mile that I could make out she was one ship [not several] steering a course at right angles, crossing from starboard to port. The dark painted stripes on her after part made her stern appear her bow, and a broad cut of green paint amidships looks like a patch of water. The weather was bright and visibility good; this was the best camouflage I have ever seen.[1]