Patent ID: RE41455

Claim:
A compound objective lens, comprising: lens means, having a first convex surface and a second convex surface opposite to each other, for receiving a beam of incident light of one particular wavelength passing through an optical axis at the first convex surface, refracting the beam of incident light and emitting a beam of refracted light from the second convex surface; and plural focal point generating means for receiving the beam of incident light not yet refracted by the lens means, generating from the beam of incident light a plurality of beams of divided light including a first beam of divided light and a second beam of divided light, converging the beams of divided light at a plurality of focal points which are placed on the optical axis on a side facing the second convex surface of the lens means on condition that the first beam of divided light transmits through a first substrate and is converged on an information recording plane placed at a first distance T 1 from a surface of the first substrate at a diffraction limit and that the second beam of divided light transmits through a second substrate and is converged on an information recording plane placed at a second distance T 2 (T 1 ≠T 2 ) from a surface of the second substrate at a diffraction limit.