A study on the use of laser keyboards with regard to typing speed (Wang & Hedge, A Usability Evaluation of a Laser Projection Virtual Keyboard, 2008) showed that the average typing speed on fixed keyboards was 41.07wpm and the laser keyboards was 15.91wpm. Also, error rates were higher on the laser keyboard (10.23% VKB vs 4.09% FKB).
Ergonomically, the use of a laser keyboard is flawed. One has to individually perform key presses while completely removing the previous fingers out of the laser detection field in situations where keys are depressed from the upper row of letters to the lower rows of letters, eg. (problem combinations capitalised) EXit, WArnED, OLd, UMbrella, etc.
This can not only create a situation where one is attempting to type without resting their wrists on the surface immediately behind the keyboard (may have implications on the forearm flexor muscles at the elbow) but may also cause wrist dysfunction due to the extensive use of the finger extensor muscles in order to keep them out of the laser sensitive zone (similar to the way a piano player would strike the keys in a 'staccato' manner).
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