Optical pickup apparatus

An optical pickup apparatus, comprising:

• a first light source to emit a light flux with a first wavelength λH;
• a second light source to emit a light flux with a second wavelength λD;
• a light converging system including an objective lens to converge the light flux emitted from said first light source through a protective substrate having a thickness of t1 onto an information recording surface of a first optical information recording medium, and to converge the light flux emitted from said second light source through a protective substrate having a thickness of t2 (t1≦t2)onto an information recording surface of a second optical information recording medium;
• a first diffraction element placed within an optical path from at least one of said first light source and said second light source to one of the first optical information recording medium and the second optical information recording medium;
• an light flux splitting element that is placed within the optical path from said first light source up to said optical information recording medium and that splits the incident light flux;
• a monitor element that receives the light flux that is split by said light flux splitting element and outputs a signal according to the received light amount;
• a second diffraction element placed between said light flux splitting element and said monitor element;
• and
• a control section that controls the drive of said first light source according to the signal from said monitor element.