Optical recording medium having a plurality of different diffraction grating cells

摘要

In an optical information recording medium of this invention, at least one cell including diffraction gratings is disposed on a planar substrate. In accordance with exemplary embodiments, a ratio of a line width of the diffraction gratings to a grating pitch of the diffraction gratings is changed based on the data. To read information, an incident light beam is caused to be incident on the cell. Diffracted light components emerging from the cell are received by light receiving elements, thereby reproducing data. Thus, information can be recorded at a very high density, and information can be read at a high speed.