REWRITING TYPE OPTICAL MEMORY MEDIUM

摘要

PURPOSE:To eliminate a gradation characteristic and to have the characteristics approximate to the characteristics of a binary recording by specifying the total film thickness of a photochromic layer and an optical interference layer in the state prior to the recording with respect to the wavelength of light for reproducing. CONSTITUTION:The degree of a change in the absorption quantity by the photoirradiation quantity of the photochromic compd. is determined in the range of a change around the specific irradiation quantity as compared to a light absorption. As a result, the characteristics of the optical memory medium are realized. The optical interference layer 13 is provided in proximity to the photochromic layer 12 and these layers are formed to the total film thickness of the photochromic layer 12 and the optical interference layer 13 in the state prior to the recording equiv. to the optical path length corresponding to approximately (2k+1).lambda/(4n)(n is a refractive index k is an integer including 0) with respect to the wavelength lambda of the light for reproducing in order to distinctly detect the optical change of the photochromic material. The gradation characteristic that the signals vary linearly by the intensity of the recording light and the intensity of light and number of times of reading out is eliminated in this way and the recording and erasing having the pseudo threshold to meet the ordinarily used binary recording are executed.