Scanning Mirror

Acuity Research sells a line-scanning attachment which is a rotating mirror tilted at 45 degrees. The mirror rotates at speeds from 2 Hz to 40 Hz, allowing range measurements in a 300 degrees sweep (the supporting frame obscures 60 degrees). We typically run the scanning mirror at 2-10 Hz (allows acquisition of 5-20 samples per degree). The motor has a shaft encoder with 2000 positions per revolution (however, the high-speed interface card can only read the lower 8 bits, leading to some interesting estimation software) with a pulse generated at an unknown ``zero-position.'' We have mounted the scanner to measure vertical planes.