Patent ID: 7675834

Claim:
An optical pickup comprising: a light source unit having a first radiating unit configured to radiate a light beam of a first wavelength, a second radiating unit configured to radiate a light beam of a second wavelength and a third radiating unit configured to radiate a light beam of a third wavelength; a collimator lens having three different focal lengths that are respectively dependent on one of said first, second, or third wavelengths; and an objective lens configured to condense three different light beams that are respectively radiated from said first, second, and third radiating units on respective signal recording surfaces of three different types of optical discs such that the light beam of the first wavelength is condensed on a first optical disc having a first protective substrate, the light beam of the second wavelength is condensed on a second optical disc having a second protective substrate and the light beam of the third wavelength is condensed on a third optical disc having a third protective substrate, a thickness of the third protective substrate being greater than a thickness of the second protective substrate and the thickness of the second protective substrate being greater than a thickness of the first protective substrate, the collimator lens being provided between the light source unit and a beam splitter configured to cause a light path of return light that is reflected back from a respective signal recording surface of a respective one of the three different types of optical discs to branch from the respective one of the three different types of optical discs such that the collimator lens is configured to collimate light from the light source unit, and such that the objective lens is configured to receive light from the collimator lens.