Patent ID: 7796312

Claim:
A holographic recording method for irradiating a recording layer of a holographic recording medium with an object beam and a reference beam through an object optical system and a reference optical system, respectively, so that a data page is recorded thereon in the form of interference fringes, the method comprising: exercising control of the object optical system between an exposure direction and a non-exposure direction, so that the object beam in the object optical system is reflected in an exposure direction so as to be incident on the holographic recording medium or in a non-exposure direction so as not to be incident on the holographic recording medium selectively pixel by pixel in accordance with the data page to be recorded; recording data pages by N exposures, in which N bit map images are exposed in N separate exposure times so that they are summed up for each data page, at (N+1) levels of gradation with respect to each of the areas of the recording layer corresponding to a single pixel of the data page by the object beam with a single exposure time t 1 given by dividing t 0 by N, where t 0 is an exposure time necessary for exposing one of the areas of the recording layer corresponding to a single pixel of the data page as much as approximately 100%, and N is an integer of not less than 2; and exposing the areas as much as approximately 100% by exposure of N times, as much as 0% by exposure of 0′ times and as much as more than 0% and less than 100% by exposure of between 1 and (N−1) times.