Patent ID: 6980505

Claim:
An optical head apparatus, comprising: a first light source for emitting a first light beam having a first wavelength; a second light source for emitting a second light beam having a second wavelength different from said first wavelength; an objective lens; a photodetector; first and second optical combining/splitting elements, said first optical combining/splitting element receiving said first light beam from said first light source to transmit or reflect most of said first light beam therefrom to said second optical combining/splitting element and receiving said first and second light beams from said second optical combining/splitting element to transmit or reflect most of said first and second light beams therefrom to said photodetector, said second optical combining/splitting element receiving said first light beam from said first optical combining/splitting element and said second light beam from said second light source to transmit or reflect most of said first and second light beams therefrom to said objective lens and receiving said first and second light beams from said objective lens to transmit or reflect most of said first and second light beams therefrom to said first optical combining/splitting element; and a quarter-wave plate disposed between said second optical combining/splitting element and said objective lens, said quarter-wave plate converting said first and second light beams having said first and second wavelengths between a linearly-polarized light mode and a circularly-polarized light mode.