Optical pickup apparatus

An optical pickup apparatus comprising:

• a laser diode configured to emit a first laser beam having a first wavelength for reading signals recorded in a first optical disc having a first distance from a surface thereof to a signal recording layer thereof;
• a two-wavelength laser diode configured to emit two laser beams, which are a second laser beam having a second wavelength, longer than the first wavelength, for reading signals recorded in a second optical disc having a second distance, longer than the first distance, from a surface thereof to a signal recording layer thereof;
• and a third laser beam having a third wavelength, longer than the second wavelength, for reading signals recorded in a third optical disc having a third distance, longer than the second distance, from a surface thereof to a signal recording layer thereof;
• a first objective lens configured to condense the first laser beam onto the signal recording layer of the first optical disc;
• a second objective lens arranged, along with the first objective lens, in a radial direction of the first to the third optical discs, the second objective lens configured to condense the second laser beam onto the signal recording layer of the second optical disc, as well as condense the third laser beam onto the signal recording layer of the third optical disc;
• a first optical system configured to guide the first laser beam from the laser diode to the first objective lens through reflection by a first raising mirror;
• and
• a second optical system configured to guide the second and the third laser beams from the two-wavelength laser diode to the second objective lens through reflection by a second raising mirror, independently of the first optical system,
• the first optical system including
• a first parallel plate configured to give astigmatism for generating a focus error signal to a reflected light beam of the first laser beam reflected from the first optical disc, and
• a first photodetector configured to be irradiated with the reflected light beam containing the astigmatism caused by the first parallel plate,
• the second optical system including
• a second parallel plate configured to give astigmatism for generating a focus error signal to a reflected light beam of the second laser beam reflected from the second optical disc and a reflected light beam of the third laser beam reflected from the third optical disc, and
• a second photodetector configured to be irradiated with the reflected light beam containing the astigmatism caused by the second parallel plate;
• wherein the first optical system is arranged such that an angle θ1 between an optical axis of the first optical system and a tangent line of the first to the third optical discs satisfies 45 degrees<θ1≦55 degrees, and wherein
• the second optical system is arranged such that an angle θ2, not overlapping with the angle θ1, between an optical axis of the second optical system and a tangent line of the first to the third optical discs satisfies 35 degrees≦θ2<45 degrees.