| 摘要 |
The invented optical record carrier has a plurality of information layers (3, 4, 5) stored in different depth of the record carrier, whereby the information layers (3, 4, and 5) are separated by spacer layers (6, 7). Thickness of the stack (2) of layers (2), defined as a distance between upper surface of the uppermost information layer (5) and bottom surface of the lowermost information layer (3), is less than a value 2d being defined by the equation: 2d = 34 ne3 {lambda}.SQRT.r/(ne2-1)(NA)e4 wherein n is a refractive index of the spacer layers, {lambda} is the vacuum wavelength of the radiation beam intended for scanning the information layer during record or writing, NA is a numerical aperture of focusing means of the radiation beam at a scanning spot, by means of which the information layer is to be scanned during record or writing, and r is the maximally admissible decrease of the Strehl intensity of the radiation beam at the scanning spot on the record carrier due to spherical aberration that is at the most equal to 0.05. Scanning method of the invented optical record carrier is characterized in that the optical record carrier is scanned during record or writing the information by a radiation beam, in which a constant spherical aberration has been introduced by a focusing means, whereby this constant spherical aberration is assigned to a stack of layers (3, 6, 4, 7, 5) on the record carrier that compensates the spherical aberration generated in the radiation beam when focused at approximately half of the information layer stack thickness. In the present invention there is also suggested a device for making the invented scanning method. |
