Abstract: An imaging system with beam focus adjustment, includes an emitter which emits a beam of radiation along a beam path and an optical assembly, having a focus adjustment mechanism, configured to focus the emitted beam on a medium to be imaged. A medium support member supports the medium on its support surface during imaging. A sensor generates temperature data representing a detected temperature of the medium support member and a controller controls the focus adjustment mechanism in accordance with the temperature data to adjust the focus of the emitted beam on the medium.