Light to be sensed is spreaded across an entry surface of a transmission structure with a laterally varying energy transmission function. For example, the light could be output from a stimulus-wavelength converter, provided through an optical fiber, or it could come from a point-like source or broad area source. Output photons from the transmission structure can be photosensed by photosensing components such as an array, position sensor, or array of position sensors. Wavelength information from the light can be obtained in response to the photosensing component. Spreading can be performed by air, gas, transparent material, or vacuum in a gap, by a region or other part of a lens, or by an optical fiber end surface. If the light comes from more than one source, a propagation component can both spread the light and also keep light from the sources separate.