| 摘要 |
<P>PROBLEM TO BE SOLVED: To attain high density by using a three-dimensional recording and reproducing method. <P>SOLUTION: A three-dimensional information recording and reproducing device has a recording medium 4 obtained by laminating a plurality of recording layers 1 on a substrate 3 and an optical system for focusing light from the substrate 3 side on each of the plurality of recording layers 1 and recording or reproducing information three-dimensionally. In the three-dimensional recording and reproducing device, λ/4≤(1/8NB)(1/NB<SP>2</SP>-1)NAF<SP>4</SP>Δd, wherein λ: wavelength of light, NB: refractive index of the substrate 3, NAF: the number of apertures of a narrowing-down lens 8 for focusing light, and Δd: a positional range in the direction of an optical axis where there are recording layers on which light should be focused is satisfied. By narrowing down a light spot to each layer of a disk with a multilayer film structure, data can be recorded and reproduced with high density and with high reliability. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
