An apparatus images a surface. An imager stage linearly translates the surface in a first direction. A light path has a first end defining an input aperture perpendicular to the first direction and parallel to the surface, and a second end defining an output aperture. A plurality of radiation beams linearly scan and interact in time-multiplexed alternating turns with the surface below the input aperture to produce a time-multiplexed light signal that is collected by the input aperture and transmitted by the light path to the output aperture. A photodetector arrangement detects the light signal at the output aperture. A processor processes the detected time-multiplexed light.