An example device includes an array of sensor modules. A sensor module includes a body to be positioned in alignment with a planar target, a light source coupled to the body to emit light to the planar target along a source optical path, and a plurality of light sensors coupled to the body. Each light sensor is to sense a different wavelength of light received from the planar target along a sensor optical path. The sensor optical path is different from the source optical path. The bodies of the array of sensor modules are arranged in a planar tiling pattern with respect to a longitudinal axis of the planar target.