A particle sensor comprising a laser sensor module for detecting particles, the laser sensor module comprises: - at least a first laser being adapted to emit a first measurement beam and at least a second laser being adapted to emit a second measurement beam, - an optical device being arranged to redirect at least the first measurement beam such that the first measurement beam and the second measurement beam enclose an angle between 45° and 135°, - one common detector being adapted to determine at least a first self-mixing interference signal of a first optical wave within a first laser cavity of the first laser and at least a second self-mixing interference signal of a second optical wave within a second laser cavity of the second laser, - the particle sensor further comprising an evaluator, wherein the evaluator is adapted to receive detection signals generated by the detector in reaction to the determined self-mixing interference signals, wherein the evaluator is further adapted to determine at least one average velocity of particles by means of the detection signals received in a predetermined time period, and wherein the evaluator is further adapted to determine a particle density based on the number of self-mixing interference signals determined in the predetermined time period and the at least one average velocity, wherein the at least first laser and the at least second laser comprise semiconductor layers provided on a common semiconductor chip, wherein the optical device comprises micro-optical components for redirecting the measurement beams (111', 112',) emitted by the lasers (111, 112,), and wherein each micro-optical component is attached to one laser (111, 112,), wherein the optical device further comprises at least one focusing element associated to each measurement beam (111', 112',), wherein the at least one focusing element is arranged to focus the respective measurement beam to a focus region. - at least a first laser being adapted to emit a first measurement beam and at least a second laser being adapted to emit a second measurement beam, - an optical device being arranged to redirect at least the first measurement beam such that the first measurement beam and the second measurement beam enclose an angle between 45° and 135°, - one common detector being adapted to determine at least a first self-mixing interference signal of a first optical wave within a first laser cavity of the first laser and at least a second self-mixing interference signal of a second optical wave within a second laser cavity of the second laser, - the particle sensor further comprising an evaluator, wherein the evaluator is adapted to receive detection signals generated by the detector in reaction to the determined self-mixing interference signals, wherein the evaluator is further adapted to determine at least one average velocity of particles by means of the detection signals received in a predetermined time period, and wherein the evaluator is further adapted to determine a particle density based on the number of self-mixing interference signals determined in the predetermined time period and the at least one average velocity, wherein the at least first laser and the at least second laser comprise semiconductor layers provided on a common semiconductor chip, wherein the optical device comprises micro-optical components for redirecting the measurement beams (111', 112',) emitted by the lasers (111, 112,), and wherein each micro-optical component is attached to one laser (111, 112,), wherein the optical device further comprises at least one focusing element associated to each measurement beam (111', 112',), wherein the at least one focusing element is arranged to focus the respective measurement beam to a focus region.