Keyboard with optical keys which locates keys which have been operated from transmitter signals reflected from key

摘要

A key board (1) has optical keys (2,3) which operate by interrupting a light beam and a transmitter (5) and a receiver (6). When a key is depressed to the on position it reflects transmitter signals directed at it to the receiver which transmits them to the microcontroller executing the keys command. To identify which key been operated the location of the key relative to a reference point (the edge of the keypad), is measured. e.g. from the signal transit time between the times of reflection and detection.