An optical system comprising: a light source ; a light delivery system comprising a reflector of a first numerical aperture having a first optical axis , the reflector being configured for directing light emitted from the light source to a sample material positioned along the first optical axis ; a light collection system comprising a light collection optical element of a second numerical aperture having a second optical axis , the light collection optical element being configured for collecting light diffusely reflected or emitted from a surface of the illuminated sample material and for transferring the collected light to an analysis device ; and a light displacement optical device positioned between the light source and the sample material comprising a light displacement optical element configured for transferring at least a portion of the light diffusely reflected or emitted from the surface of the sample material to the light collection optical element ; wherein the light displacement optical device comprises a shielding element surrounding, at least partially, the light displacement optical element , the shielding element comprising at least a first opening , through which opening light diffusely reflected or emitted from the surface of the sample material enters the light displacement optical element , and at least a second opening , through which second opening the diffusely reflected or emitted light entered through the first opening exits the light displacement optical element and is transferred to the light collection optical element , characterized in that the light displacement optical element is a prism having a rhomboid shape. a light source ; a light delivery system comprising a reflector of a first numerical aperture having a first optical axis , the reflector being configured for directing light emitted from the light source to a sample material positioned along the first optical axis ; a light collection system comprising a light collection optical element of a second numerical aperture having a second optical axis , the light collection optical element being configured for collecting light diffusely reflected or emitted from a surface of the illuminated sample material and for transferring the collected light to an analysis device ; and a light displacement optical device positioned between the light source and the sample material comprising a light displacement optical element configured for transferring at least a portion of the light diffusely reflected or emitted from the surface of the sample material to the light collection optical element ; wherein the light displacement optical device comprises a shielding element surrounding, at least partially, the light displacement optical element , the shielding element comprising at least a first opening , through which opening light diffusely reflected or emitted from the surface of the sample material enters the light displacement optical element , and at least a second opening , through which second opening the diffusely reflected or emitted light entered through the first opening exits the light displacement optical element and is transferred to the light collection optical element , characterized in that the light displacement optical element is a prism having a rhomboid shape. <EOS>