Objective lens for optical recording device e.g. CD, CD-R or DVD device

摘要

The objective lens (10) has a refractive lens element with a positive refractive force and a diffractive lens structure with several concentric stepped rings at one lens surface (11) of the lens element, The diffractive lens structure is dependent on the wavelength, for providing at least 2 light beams with different wavelengths and identical orders of diffraction provide wave fronts for different types of optical discs with recording layers of different thickness.