Galvos were fairly common back on those days. For such a simple device (it's just a voicecoil) you can get very precise alignment assuming it's well designed me

Galvos were fairly common back on those days. For such a simple device (it's just a voicecoil) you can get very precise alignment assuming it's well designed mechanically (e.g. properly damped). Not sure about spinning mirrors like those used in barcode scanners, but I'm guessing gavos were preferrable at the time for things like this. Galvos were heavily used in laser light shows back then which would have been very popular when this was being designed. To be honest, when I heard single line LED display utilizing 2 mirrors (one for each eye), my first thought was "Just like a laser light display." Clever, but relatively evolutionary if you know how existing tech worked at the time. The other reply below/above isn't correct about there being a pause between scans. A common implementation for rotating mirrors is to use an octagonal mirror [1]. With that implementation, there's no pause. The image just jumps immediately back to the left/right. The issue is more likely controlling the speed of the motors would be difficult to keep synced with the requisite precision. [1] http://cdn.iopscience.com/images/0034-4885/76/8/086801/Full/rpp437052f02_online.jpg http://cdn.iopscience.com/images/0034-4885/76/8/086801/Full/...