Beam-scanning schemes. (A–F) Two-dimensional scanners: (A) Point scanner uses two galvanometer-driven mirrors; (B) line scanner sweeps laterally to spread out the laser beam with a single galvanometer-operated mirror; (C) rotating polygonal mirrors are used to increase the scan speed in one dimension; (D) multifocal scanners use a microlens array to achieve multiple scan points; (E) scanless beam positioning uses an SLM to control one beam or multiple beams; (F) random-access scanner uses two acousto-optical deflectors to direct a single beam. (G) 3D random-access scanning system uses four AODs to position a laser focus in a volume without moving the objective lens.