A slot scanner illumination system for a convertible slot scanner assembly includes a chassis having an optical cavity and a front opening. The optical cavity has an optical axis therethrough, with the optical axis being an axis along which light may be received by the chassis through the front opening. The front opening further has a first edge and a second edge opposite the first edge. A scanning window is configured to at least partially cover the front opening of the chassis, and the scanning window has a normal axis orthogonal to a flat surface of the scanning window. An illumination element is disposed inside of the optical cavity of the chassis. The illumination element is disposed proximal the first edge of the front opening. The illumination element is configured to provide illumination along an illumination axis, wherein the illumination axis is non-parallel with the optical axis and at an angle directed toward the second edge of the front opening.