Patent ID: 7911929

Claim:
An optical disk read only memory having an information recording surface having a concave-convex pattern formed on the basis of a first modulation signal and a reflective film covering the information recording surface, and including a recording track formed by the concave-convex pattern as a first recording data string including a pit and a land, the optical disk read only memory comprising: an additional information recording section disposed on the recording layer being planar on the recording track having the first recording data string including the pit and the land; and a second recording data string including a mark of removing or reducing the reflective film in the additional information recording section on the basis of a second modulation signal in the additional information recording section, wherein a modulation method of information data at the time of forming the first recording data string and a modulation method of information data at the time of forming the second recording data string are identical, and Lh ( n )> Lp 1( n ) (Expression-1) and Wh ( n )>( Wp 1( n )+ Wp 2( n ))/2 (Expression-2) are satisfied; where a reference clock cycle of the modulated information data is T, an information-data length is nT (n is a natural number), a length of the mark corresponding to nT is Lh(n), a width of the mark corresponding to nT is Wh(n), a length of a base of a truncated cone of the pit corresponding to nT is Lp 1 (n), a width of the base of the truncated cone of the pit corresponding to nT is Wp 1 (n), a length of a top surface of the truncated cone of the pit corresponding to nT is Lp 2 (n) being longer than Lp 1 (n), and a width of a top surface of the truncated cone of the pit corresponding to nT is Wp 2 (n) being longer than Wp 1 (n).