A particle sensor apparatus having an optical emitter device that is configured to emit an optical radiation so that a volume having at least one particle possibly present therein is at least partly illuminatable; an optical detector device having at least one detection surface that is struck by at least a portion of the optical radiation scattered at the at least one particle, at least one information signal regarding an intensity and/or an intensity distribution of the optical radiation striking the at least one detection surface being outputtable; and an evaluation device with which an information item regarding a presence of particles, a number of particles, a particle density, and/or at least one property of particles is identifiable and outputtable, the particle sensor apparatus also encompassing at least one lens element that is disposed so that the emitted optical radiation is focusable onto a focus region inside the volume.