1. A notebook computer for capturing an image of a document on a working plane, said notebook computer comprising: a base having a keyboard for inputting characters or signs therevia; and an upper cover coupled to said base and rotatable with respect to said base, and comprising: a screen for displaying said image of said document; an image pickup device disposed on an upper edge of said upper cover for capturing said image of said document when said upper cover is rotated with respect to said base to create a specified included angle between said upper cover and said base; a recess structure; and a close-up lens for shortening the focal length of said image pickup device, said close-up lens has a hooking element engaged with said recess structure such that said close-up lens is fixed on said upper cover, wherein an image processing program is installed in said notebook computer for performing an image processing operation on said document after said image of said document on said working plane is captured by said image pickup device.