A device for optical characterisation of a sample, with a laser scanner system with a laser which is oriented such that it one- or two-dimensionally scans a sample spatial portion into which the sample is introduced, and which emits polarised laser light, a receiver for receiving the light reflected by the sample introduced into the sample spatial portion, wherein the receiver comprises: • a polarisation-maintaining beam splitter for the light reflected by the sample for dividing the laser light incident on the receiver into a first and a second partial beam path, • in each case in the first and in the second partial beam path (T1, T2): a polarising optical element (10a, 10b) with which the light of the respective partial beam path (T1, T2) can be split into two different polarisation fractions, wherein in each case a receiving element (11a, 11b, 11c, 11d) for detecting light of the respective polarisation fraction is arranged in the beam path of each of the two polarisation fractions thus separated, and • merely in one of the two partial beam paths (T1, T2) after the beam splitter and before the polarising optical element, a polarisation-changing element with which the polarisation of the light of this partial beam path can be changed, and an evaluation unit with which, on the basis of the different polarisation fractions detected by the receiving elements (11a, 11b, 11c, 11d) of the receiver, the polarisation state of the light reflected by the sample can be determined for the optical characterisation thereof, characterised in that the laser and the receiver are designed as a combined transmitting and receiving unit comprising a further beam splitter, and in that the device comprises a polarisation-maintaining retroreflector as follows: the laser, the receiver and the retroreflector are arranged and oriented such • that the sample introduced into the sample spatial portion can be illuminated with the laser, and • that laser light scattered, diffusely reflected, specularly reflected or transmitted on the sample can be reflected back in itself on the retroreflector such that the laser light reflected back in itself passes via the sample into the combined transmitting and receiving unit and there, via the further beam splitter, passes into a receiver beam path for splitting there into the first and the second partial beam path of the receiver. • a polarisation-maintaining beam splitter for the light reflected by the sample for dividing the laser light incident on the receiver into a first and a second partial beam path, • in each case in the first and in the second partial beam path (T1, T2): a polarising optical element (10a, 10b) with which the light of the respective partial beam path (T1, T2) can be split into two different polarisation fractions, wherein in each case a receiving element (11a, 11b, 11c, 11d) for detecting light of the respective polarisation fraction is arranged in the beam path of each of the two polarisation fractions thus separated, and • merely in one of the two partial beam paths (T1, T2) after the beam splitter and before the polarising optical element, a polarisation-changing element with which the polarisation of the light of this partial beam path can be changed, and the laser, the receiver and the retroreflector are arranged and oriented such • that the sample introduced into the sample spatial portion can be illuminated with the laser, and • that laser light scattered, diffusely reflected, specularly reflected or transmitted on the sample can be reflected back in itself on the retroreflector such that the laser light reflected back in itself passes via the sample into the combined transmitting and receiving unit and there, via the further beam splitter, passes into a receiver beam path for splitting there into the first and the second partial beam path of the receiver. • that the sample introduced into the sample spatial portion can be illuminated with the laser, and • that laser light scattered, diffusely reflected, specularly reflected or transmitted on the sample can be reflected back in itself on the retroreflector such that the laser light reflected back in itself passes via the sample into the combined transmitting and receiving unit and there, via the further beam splitter, passes into a receiver beam path for splitting there into the first and the second partial beam path of the receiver.