n 2006, the City of Minneapolis commissioned a permanent public artwork at the Minneapolis Public Library. Built into the structure of the two glass elevator cabs in Library Hall, “Four Stories” displays the titles of recently checked-out books in large, illuminated text as the elevators move between floors.
The design integrators selected the Acuity laser rangefinders to monitor the position of the elevator and hence control the scroll position of the illuminated text. The laser rangefinders were installed in base of the elevator shaft and aimed upward to a target affixed to the bottom of the elevator cart. Sampling at 100 Hz, the positional data was used in the software controlling the visual display. For more information, contact Acuity.