HIGH-DENSITY OPTICAL RECORDING AND REPRODUCING METHOD, AND HIGH-DENSITY OPTICAL RECORDING MEDIUM AND HIGH-DENSITY OPTICAL RECORDING AND REPRODUCING DEVICE USED FOR THE SAME

摘要

PURPOSE:To record and reproduce information with high density by using recording marks which are smaller than a light spot. CONSTITUTION:The optical recording medium M which has a nonlinear layer N showing nonlinear optical effect to irradiating light in addition to a recording layer R is used. Reproducing light and recording light are transmitted through the nonlinear layer N to irradiate the recording layer R. The peak intensity of the reproducing light is set nearly equal to the peak intensity of the recording light. The mean intensity of the reproducing light is made smaller than the mean intensity of the recording light by pulsating the reproducing light and varying its duty ratio, etc. By the nonlinear optical effect, the light spot on the recording layer R is made smaller than the case that there is no nonlinear layer N. The peak intensity of the light is equal, so light spots at the time of recording and reproduction are equal in light spot diameter. Therefore, the information can be recorded and reproduced with high density by using recording marks which are smaller than the light spots.