Measurement device for the detection and/or characterization of fluid-borne particles, the measurement device comprising: means (1, 10) for producing a flow of fluid along a fluid flow path; a laser positioned for emitting pulses of laser light polarized in a first direction of polarization, in a measurement volume of the fluid flow path, each of said pulses having a pulse duration; means for directing pulses of laser light polarized in a second direction of polarization in said measurement volume, wherein said second direction of polarization is differentfrom said first direction of polarization, a first optical spectrometer for capturing fluorescent light emitted by individual fluid-borne particles in said measurement volume and measuring intensity of said captured fluorescent light at at least one determined wavelength at a sampling rate of at least three samples per said pulse duration characterized in that said means for directing comprise a first optical mirror located opposite the laser on the other side of the measurementvolume, a second optical mirror for redirecting the pulses of laser light reflected by the first optical mirror towards the measurement volume, and means for rotating the polarization of the laser light, before the pulse of laser light crosses the measurement volume for the second time which are configured such that they direct a pulse of laser light polarized in said second direction of polarization in said measurement volume each time a pulse of laser light emitted by said laser and polarized in said first direction has crossed said measurement volume, the time delay between the moment of crossing said measurement volume by said pulse emitted by said laser and the moment of crossing said measurement volume by said pulse directed by said means for directing is longerthan said pulse duration and shorter than a travel time of the fluid in said measurementvolume. means (1, 10) for producing a flow of fluid along a fluid flow path; a laser positioned for emitting pulses of laser light polarized in a first direction of polarization, in a measurement volume of the fluid flow path, each of said pulses having a pulse duration; means for directing pulses of laser light polarized in a second direction of polarization in said measurement volume, wherein said second direction of polarization is differentfrom said first direction of polarization, a first optical spectrometer for capturing fluorescent light emitted by individual fluid-borne particles in said measurement volume and measuring intensity of said captured fluorescent light at at least one determined wavelength at a sampling rate of at least three samples per said pulse duration characterized in that said means for directing comprise a first optical mirror located opposite the laser on the other side of the measurementvolume, a second optical mirror for redirecting the pulses of laser light reflected by the first optical mirror towards the measurement volume, and means for rotating the polarization of the laser light, before the pulse of laser light crosses the measurement volume for the second time which are configured such that they direct a pulse of laser light polarized in said second direction of polarization in said measurement volume each time a pulse of laser light emitted by said laser and polarized in said first direction has crossed said measurement volume, the time delay between the moment of crossing said measurement volume by said pulse emitted by said laser and the moment of crossing said measurement volume by said pulse directed by said means for directing is longerthan said pulse duration and shorter than a travel time of the fluid in said measurementvolume.