1. An information processing apparatus which is equipped with a board on which an original document can be put, the information processing apparatus comprising: a camera; a projector; a memory that stores a set of instructions; and one or more processors that execute the instructions to: cause the camera to image a first original document put in an imaging region on the board; cause the projector to project a first image obtained by imaging the first original document with the camera, into the imaging region on the board; determine a timing of imaging, with the camera, a second original document newly put in the imaging region on the board, after removing the first original document from the imaging region; cause the projector to stop the projection of the first image into the imaging region on the board, before the timing of imaging the second original document comes; cause the camera to image the second original document put in the imaging region on the board, after stopping the projection of the first image; cause the projector to project a second image, obtained by imaging the second original document with the camera, into the imaging region on the board; determine an entering situation of the second original document into a detection region on the board based on an image imaged by the camera; cause the projector to stop the projection of the first image, based on the entering situation of the second original document into the determined detection region; and cause the projector to stop the projection of the first image by thinning a density of the first image in proportion to an increase of a percentage of an overlap between the second original document that entered the detection region and the detection region.