Patent ID: 8749791

Claim:
An apparatus for measuring optical properties of transparent materials with a first illumination device which illuminates the material to be investigated along a pre-set illumination path (P) with a pre-set radiation, with a radiation recording space which records radiation passed on by the material to be investigated, wherein the radiation recording space is arranged in such a way that the radiation emitted by the first illumination device first strikes the material and then at least for a time an inner wall of the radiation recording space, with a radiation detector device, which is arranged in such a way that it records radiation reflected and/or scattered essentially only from the inner wall of the radiation recording space, and with a second illumination device, which illuminates the inner wall of the radiation recording space, wherein the second illumination device is suitable for emitting modulated radiation, wherein the first and the second illumination devices irradiate the irradiation with angles different at least in art into the radiation recording space.