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Life & fun · September 12, 2021

DK

Detecting keypresses using laser speckle patterns

Detecting keypresses using laser speckle patterns launched on September 12, 2021 with 31 votes, #1,103 of 2,941 launches that month and more than 75% of that year's launches. The site was still online in September 2026, 5 years on.

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In plain words

This project uses laser speckle patterns to detect keyboard keypresses without physical contact. By analyzing how laser light scatters off a keyboard's surface, it identifies which keys are pressed based on changes in the speckle pattern. It is for people interested in computer vision, security research, or unconventional input detection methods. The approach demonstrates a non-invasive way to monitor keyboard activity through optical sensing.

written from the facts on this page · September 2026

From the sources

I recently came across a really fascinating video – https://www.youtube.com/watch?v=tYFLze9VwB0 where they make use of a micro laser projector to generate a speckle pattern on a surface and then photograph it with a DSLR. They then simply touch a surface with their hand/finger and then take a photo of the speckle pattern again after the hand has been removed from the surface and compare the two speckle patterns to see the areas that have changed. See their paper here – https://ieeexplore.ieee.org/document/6247655 . They note the “approach takes advantage of the fact that tiny surface deformations cause phase changes in reflected coherent light which alter the speckle…from anfractuosity.com

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