PURPOSE: To apply the system for explaining works at museums or the like by utilizing a head mount display (HMD).

CONSTITUTION: For each of respective objects 1a and 1b, optical signal transmission parts 2a and 2b for transmitting information concerning the object as optical signals 5a and 5b are spatially arranged corresponding to the spatial arrangement of each object, and the information is received by a directional optical signal reception part 11. The optical signal reception part is provided at an HMD device 10 and adjusts directivity so as to receive desired information when the face of a user is faced to the object. When the face is turned to the target object, with a natural moving operation, the respective works can be explained by a superimpose function while overlapping the relevant explanation information to an external image for each work at a museum, for example. Switching is automated, and there is no trouble for the user to select any channel or to perform that operation.