| 摘要 |
A hybrid disc whose ROM grooves are less than 170 nanometers deep, and whose pre-recorded ROM data pits are more than 350 nanometers or less than 250 nanometers deep, as measured from the effective land level. The ROM pits may be pre-recorded in ROM grooves that are shallower than the ROM pits, where the ROM pits are narrower, of equivalent width or up to approximately 10% wider than the ROM grooves, respectively measured at half-depth, although the transverse extent of the ROM pits will not typically exceed that of the ROM grooves. The ROM lands intervene between consecutive ROM pits, whether or not a ROM groove is provided. In the preferred embodiment, one beam of a dual beam apparatus records the ROM pits, while the other beam records the R-band pre-grooves, and also records the ROM groove, if present. In most embodiments a thermal mastering process provides smooth feature surfaces to facilitate replication of the hybrid disc masters. The berms normally forming at the radial extremities of the pits and grooves in the masters, by thermal expulsion processes, may be reduced or eliminated by methods taught.
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