An image acquisition apparatus, including a housing, the housing includes an internal space and a substantially transparent surface for supporting a tangible document during an image acquisition operation, a document sensing device for detecting if at least a portion of the transparent surface is covered by the tangible document, the document sensing device including a transparent support structure for supporting at least one edge of the tangible document, a layer of coating configured to reflect light, wherein the layer of coating covering at least a portion of the external surfaces of the transparent support structure, a first light source and a light intensity sensor disposed inside the internal space.