Optical pick-up device

An optical pick-up device for focusing a light emitted from a light source on a optical recording medium, comprising:

• a convex lens having a flat surface opposed to a light-incident surface of said optical recording medium, and having a predetermined refractive index;
• an objective lens disposed such that said convex lens is interposed between said optical recording medium and the objective lens;
• a converging optical system for converging the light reflected from the light-incident surface of the optical recording medium and the flat surface of said convex lens;
• a first light-detecting means for detecting the light reflected from the light-incident surface of said optical recording medium and passing through said converging optical system, and generating a first detection signal;
• a second light-detecting means for detecting the light reflected from the flat surface of said convex lens and passing through said converging optical system, and generating a second detection signal;
• a position-detecting means for detecting a positional relation between said the light-incident surface of said optical recording medium and the flat surface of said convex lens, based on said first and second detection signals;
• and
• a drive means for driving said convex lens along an optical axis thereof such that said convex lens moves in the opposite directions toward said optical recording medium or said objective lens, whereby a distance between the light-incident surface of said optical recording medium and the flat surface of said convex lens is controlled corresponding to said first and second detection signals.