A novel dual focus objective lens for DVD/CD pick-up head

A new dual focus objective lens of combining aspherical surfaces of DVD and CD for DVD/CD pick-up head was designed. Numerical analysis based on the diffraction model were studied to trade off the spot size, side lobe, and energy ratio of DVD and CD. The hybrid aspherical surfaces of DVD and CD are optimized for low aberration. The spot size of full wave half maximum (FWHM) are 0.553 and 0.88 /spl mu/m for DVD and CD, respectively, measured from thus constructed double rings lens.