Abstract: A device, a computer program, a computer readable medium and a method for controlling focus of a laser beam during a micro sweep are disclosed. The laser beam is received to an acousto-optic deflector, and acoustic waves are provided to the acousto-optic deflector. The acoustic waves are varied in frequency over time to vary a deflection angle of the laser beam over time thereby achieving the micro sweep of the laser beam. Furthermore, a rate of variation in frequency of the acoustic waves is adapted over a time of the micro sweep in such a way that differences in frequencies over the time of the micro sweep of the acoustic waves are caused in the acousto-optic deflector over a width of the laser beam in a direction parallel to the micro sweep when passing through the acousto-optic deflector, where the differences in frequencies over the time of the micro sweep are such that they cause a desired focus of the laser beam in a direction parallel with the micro sweep over the micro sweep.