An optical data reader comprises a conveyor, an optical system, and a controller. The conveyor is configured to move a plurality of optical substrates along a plurality of lanes. Each optical substrate includes a plurality of waveplates arranged along its direction of movement within any of the plurality of lanes. The optical system is configured to observe one or more of the waveplates in its field-of-view; the optical axis crosses the plurality of lanes such that movement of at least one of the optical substrates brings one or more different waveplates into the field-of-view. The controller is coupled operatively to the conveyor and configured to control the position of the optical substrate in each occupied lane.