An apparatus for depth-resolved measurements of properties of tissue includes an illuminator that illuminates the tissue with light, a collector for collecting light which has not been absorbed by the tissue, and a determination device configured to determine properties of the tissue in different depths from the collected light. A casing for advancing into a hollow object includes at least a part of the illuminator and collector. The illuminator and collector are configured to collect light depth-resolved, and the determination device is configured to determine depth-resolved properties of the tissue from the light which has been collected depth-resolved.
