Patent ID: 7590042
Filing Date: 2009-09-15
Classification: G11B,H04N

Abstract:
1. A read-only optical recording medium having formed therein a land and pits contiguously to each other along a recording track correspondingly to a modulated bit string resulted from variable-length modulation of an information bit string, wherein a postscript area having a predetermined postscript pattern formed therein is provided in each of a plurality of predetermined positions on the recording track, the postscript pattern formed in each postscript area takes the form of a pit-land-pit pattern, the length of pit-land-pit postscript pattern is equal to or less than the longest code length of the modulated bit string and 3 times or more of the shortest code length, modulated bit strings before and after the pit-land-pit postscript pattern are formed so that the pit-land-pit postscript pattern complies with the rule of the variable-length modulation even when the pit-land-pit postscript pattern is replaced as a whole with a pit-only pattern, and the land in the middle of the pit-land-pit postscript pattern is formed from a material which will not physically change when irradiated with laser light having a reading-level one but will show a reflectivity equal to that of the pit when irradiated with laser light having a power higher than the reading-level one.