An imager for imaging a document moving in a document track in a table top document processing machine. The imager includes a housing which is made of several portions which are designed to be assembled quickly with a minimum of fasteners. A first line of green LEDs and a second line of red LEDs are located in the housing to illuminate a scanning line from which image data about the document is obtained by an optical system including a CCDs. The imager is also designed so that the same imager can be used on either side of the document track to image the front or back of the document. When two such imagers are used, a white reference member (for calibrating the imager to ensure repeatable and uniform data) located in one of the imagers is used by the other imager.