An apparatus for detecting radiation deflected from a rotating component includes a probe body on a stationary component radially outward of the rotating component; and a pair of arrival time sensors coupled to the probe body. Each arrival time sensor includes a light pipe that receives radiation deflected from the rotating component and that reduces directional variation of the radiation. A detector is optically coupled to each respective light pipe. The detector is positioned to receive the radiation with reduced directional variation from the light pipe. A method of detecting radiation from the rotating component using the apparatus determines a clearance between the rotating component (e.g., a turbomachine blade) and a stationary component (e.g., a casing).