An objective lens system for an optical pickup apparatus, includes in order from an object side: a first lens group having negative paraxial power P1 ; and a second lens group having positive paraxial power P2 for converging a light flux emitted from the first lens group on an information recording surface of an optical information recording medium. The sensor logarithmically generates a first signal in response to the ambient light near the lighted display. The piercing base has a piercing head and a second suction plate. In response to an API call seeking to know which virtual addresses in a process have been modified since last checked, the memory manager walks the bitmap in the relevant VAD for the specified virtual address range for the requested process.