Device for measuring at least one of diffusion, absorption and refraction of a sample, having a radiation source, at least one receiving element, an optical imaging element and a protection element, the radiation source and the receiving element being arranged on the sensor side of the optical imaging element, the protection element being arranged on the sample side of the imaging element and adjacent to the imaging element and the radiation source. A refraction radiation source and a refraction receiver are arranged on the sensor side of the imaging element and arranged relative to the imaging element so that the refraction radiation of the sample specularly reflected by the sample side interface of the protection element can essentially be received by the refraction receiver and the radiation specularly reflected by the imaging element side interface of the protection element essentially cannot be received by the refraction receiver.