A sensor including multiple sensor modules and a processor, each sensor module including lenses, light detectors, each detector positioned along the image plane of a lens so as to receive maximum light intensity when light enters the lens at a particular angle, light emitters, each emitter being positioned in relation to a lens so as to project light into a detection zone, an activating unit synchronously co-activating each emitter with at least one of the detectors, and a calculating unit receiving outputs from the detectors corresponding to amounts of projected light reflected by an object in the detection zone to the detectors, and calculating a two-dimensional location of the object in the detection zone based on the detector outputs and the particular angle, wherein neighboring modules monitor different detection zones, and the processor receiving outputs from the sensor modules and mapping the object location in multiple detection zones over time.