A sensing system to process at least one valuable document is described herein. The system includes a light source to generate a light beam. The system also includes at least one light pipe having one or more diverting surfaces to direct the light beam at a predetermined angle of incidence onto the valuable document. At least one reflective surface, to receive a first portion of the light beam transmitted through the valuable document and to reflect off the first portion of the light beam towards the valuable document, is included. A light detector is configured to receive at least a second portion of the light beam re-transmitted through the valuable document.