An apparatus for calibrating a scattered light measuring device

It is proposed a calibrating device (30) for calibrating a scattered light measuring device which is designed in particular for measuring particle concentration in exhaust gases of motor vehicles. The calibration device (30) has at least one diffuser (34) which when irradiated with a light beam (17a) scattered light (20'a, 20'b) to write with a defined intensity and distribution, wherein said scattering bodies (34) (an emission 35) for the scattered light, which at least one light sensor (15a, 15b) for detecting the emerging (at the emission 35) scattered light (20'a, 20'b) is assigned. The radiating surface (35) of the diffuser (34) is a diaphragm body (37) having at least one aperture (38) is associated through which the scattered light (20'a, 20'b) (15a, 15b) emerges in the direction of the at least one light sensor ,