Patent ID: 6222801
Filing Date: 2001-04-24
Classification: G11B

Abstract:
An optical pickup compatible with a plurality of types of optical recording media having information recording surfaces, the optical pickup comprising:a plurality of laser sources to selectively operate depending upon which one of the optical recording media is to be accessed, the plurality of laser sources respectively emitting light of different wavelengths on corresponding ones of the optical recording media;an objective lens to focus the light emitted from the laser sources into optical spots optimized to the information recording surfaces of the corresponding ones of the optical recording media;at least one photo detector to detect the light reflected from the information recording surfaces of the optical recording media where the optical spots are focused and passed through the objective lens;an optical element to adjust optical paths so that the light emitted from the laser sources are directed toward the objective lens and the light emitted from the objective lens are directed to the at least one photo detector; anda variable iris formed between the laser sources and the objective lens, selectively operating according to the wavelengths of the light emitted from the plurality of laser sources;wherein said variable iris totally transmits light with respect to a first one of the laser sources having a relatively shorter wavelength, operates to transmit light with a smaller numerical aperture with respect to a second one of the laser sources having a relatively longer wavelength, and the numerical aperture in a radial direction of the optical recording media to be accessed is set smaller than in a tangential direction of the optical recording media to be accessed for stability of a track signal.