Optical pickup having an objective lens compatible with a plurality of optical disk formats

摘要

An optical pickup compatible with a plurality of optical recording media each using light of a different wavelength. The optical pickup includes at least one light source (41), an objective lens (20, 20') having a function of focusing light emitted from the light source (41) into the optimal light spot on an information recording surface of one of the plurality of the optical recording media (30), and a light detector (43) to detect light transmitted through the objective lens (20, 20') after being reflected from the information recording surface of the optical recording medium (30) on which the light spot is formed. The objective lens (20, 20') has an inner area, an annular lens area and an outer area such that the annular lens area divides the inner area from the outer area and has a ring shape centered at a vertex. The inner area, the annular lens area and the outer area have aspherical surface shapes to focus light transmitted through the inner area and the outer area into a single light spot by which information can be read from the information recording surface of a relatively thin first optical recording medium (30A) and scatter light transmitted through the annular lens area located between the inner area and the outer area so that information cannot be read from the information recording surface of the first optical recording medium (30A), during reproduction of the first optical recording medium. The inner area and the annular lens area transmit light into a single light spot by which information can be read from the information recording surface of a relatively thick second optical recording medium (30B) and scatters light transmitted through the outer lens area so that information cannot be read from the information recording surface of the second optical recording medium (30B), during reproduction of the second optical recording medium (30B). <IMAGE>