Device for measuring the particle size distribution of sample material by means of light diffraction, wherein the device defines a main optical axis and a measuring plane and comprises: a light source for generating a primary light beam, a measuring cell having an inlet window and an outlet window, wherein the inlet window and the outlet window delimit a sample space on both sides, in order to irradiate the sample material in the sample space with the primary light beam between the inlet window and the outlet window and to generate a diffraction pattern of the sample material when the measuring cell is arranged in the beam path of the primary light beam, wherein the primary light beam enters the sample space through the inlet window and secondary light, diffracted on the sample in the sample space, exits out of the inlet window and/or out of the outlet window, wherein the measuring cell defines a measuring cell plane, a detector device for detecting the diffraction pattern generated by the sample material, wherein the detector device comprises a plurality of sensor surfaces (84.1-84.43, 86.1-86.9, 48.1-48.5, 28.1-28.4) at different diffraction angles in the measuring plane, in order to be able to detect the diffraction light from the measuring cell at different diffraction angles in the measuring plane, wherein the detector device comprises a forward sensor having a main sensor in the forward direction on the main optical axis, wherein the light source, the measuring cell and the forward sensor define the main optical axis, wherein the measuring cell is oriented in the measuring plane obliquely (κ ≠ 0°) to the main optical axis, characterised in that the forward sensor comprises a beam passage opening for the primary light beam, and in that the forward sensor having the beam passage opening is laterally offset in front of the measuring cell, in the measuring plane, based on the primary light beam, in order to compensate the beam offset on account of the light diffraction of the primary light beam at the inlet window and outlet window of the oblique measuring cell. a light source for generating a primary light beam, a measuring cell having an inlet window and an outlet window, wherein the inlet window and the outlet window delimit a sample space on both sides, in order to irradiate the sample material in the sample space with the primary light beam between the inlet window and the outlet window and to generate a diffraction pattern of the sample material when the measuring cell is arranged in the beam path of the primary light beam, wherein the primary light beam enters the sample space through the inlet window and secondary light, diffracted on the sample in the sample space, exits out of the inlet window and/or out of the outlet window, wherein the measuring cell defines a measuring cell plane, a detector device for detecting the diffraction pattern generated by the sample material, wherein the detector device comprises a plurality of sensor surfaces (84.1-84.43, 86.1-86.9, 48.1-48.5, 28.1-28.4) at different diffraction angles in the measuring plane, in order to be able to detect the diffraction light from the measuring cell at different diffraction angles in the measuring plane, wherein the detector device comprises a forward sensor having a main sensor in the forward direction on the main optical axis, wherein the light source, the measuring cell and the forward sensor define the main optical axis, wherein the measuring cell is oriented in the measuring plane obliquely (κ ≠ 0°) to the main optical axis, characterised in that the forward sensor comprises a beam passage opening for the primary light beam, and in that the forward sensor having the beam passage opening is laterally offset in front of the measuring cell, in the measuring plane, based on the primary light beam, in order to compensate the beam offset on account of the light diffraction of the primary light beam at the inlet window and outlet window of the oblique measuring cell.