Optical pickup and optical recording/reproducing apparatus using the same

An optical pickup apparatus accessing first to third optical discs with a varying density, comprising:

• first and second light sources respectively generating different wavelengths of light beams;
• an optical system allowing a light beam generated by any one of the first and second light sources to be selectively irradiated onto the discs, said optical system including an aperture number controller determining the number of aperture of the light beam to have a different value depending on an optical disc to be accessed, whereby a light beam generated at the first light source is irradiated with a first value of aperture number when the optical disc to be accessed is the first optical disc, said optical system allowing a light beam generated at the second light source to be irradiated with a second value of aperture number smaller than the first value of aperture number when the optical disc to be accessed is the second optical disc, said aperture number controller including a wave selecting member capable of performing a wavelength selecting function for selecting between different wavelengths of light beams;
• and
• a photo detector detecting a light beam reflected from the accessed optical disc and converting the detected light beam into an electrical signal,
• wherein the first light source generates a light beam with a wavelength of about 400 nm, and the second light source generates a light beam with a wavelength of about 650 nm.