According to aspects of the embodiments, there is provided an apparatus that includes a calibration member that is disposed within a calibration holder and is movable to a position within the optical path of the scanner head assembly. The apparatus can perform optical analysis of images on sheets, comprising a structure forming a baffle for passage of a sheet therethrough, and a photosensor disposed to receive light reflected from a sheet in the baffle. In particular, this embodiment employs a shutter plate mounted to a rack and pinion system where the shutter plate serves the dual purpose of presenting the calibration member to the scanner when engaged into the paper path and when retracted, the backside of the shutter serves as a paper guide.