Abstract: A material monitoring apparatus and method for determining the quality of a sheet of material by detecting dirt particles, flaws in the contents of the material or the composition of the material. The apparatus includes a housing held by a support and positioned above the sheet of material being monitored. A plurality of photoelectric sensing devices are located within the housing. A series of apertures of progressively different sizes are located one behind the other in the longitudinal direction on the bottom of the housing facing the sheet of material. Each of the photoelectric sensing devices are positioned to receive light entering through a respective one of the apertures, wherein the amount of light received is dependent upon the quality of the sheet material being monitored. The light received by the photoelectric sensing devices are converted into electrical signals by means of electronic control circuitry.