A detachable transparent plate for a scan head assembly in a document scanning system that allows an operator to detach the transparent plate from the scan head assembly located above a media feed path to clean a top face of the transparent plate and easily reattach it to the scan head assembly. The scan head assembly has an optical system and a sealing member detachably mounted to a bottom end of the optical system. The transparent plate is received and supported by the sealing member and defines a portion of a bottom surface of the sealing member. The sealing member is detachable from the bottom end of the optical system to allow an operator access to the top face of the transparent plate of the sealing member for cleaning the top face of the transparent plate.