Objective optical system for optical recording media and optical pickup device using the objective optical system

An objective optical system for focusing light from a light source onto at least two different types of optical recording media having different substrate thicknesses in order to record or reproduce information on the optical recording media, the objective optical system comprising:

• at least two lens groups arranged along an optical axis for focusing light of one of two wavelengths from the light source onto a different one of the at least two different types of optical recording media having different substrate thicknesses;
• wherein
• said two wavelengths are the same or very nearly the same;
• the objective optical system is configured so that light of one wavelength of said two wavelengths is focused onto one of the at least two different types of optical recording media having different substrate thicknesses when said two lens groups are separated by a first distance along the optical axis between said two lens groups;
• the objective optical system is configured so that light of the other wavelength of said two wavelengths is focused onto another of the at least two different types of optical recording media having different substrate thicknesses when said two lens groups are separated by a second distance along the optical axis between said two lens groups;
• and
• said first distance and said second distance are different from one another.