Color sensing (as well as detecting empty spaces) settled on IR-based sensors commonly used in line-following robots. You can watch the clock in action in the video embedded below just under the ...

An indirect time-of-flight sensor, the AF0130 from onsemi offers long-distance measurements and 3D imaging of fast-moving ...

Because the photodiodes have a limited angle over which they respond, they can be used to triangulate the distance of the finger above the display. Scanning quickly among the IR lasers and noting ...