Chul-woo Lee

TL;DR: In this article, an objective lens is provided along a light path facing a disc and having a predetermined effective diameter, and light controlling means along the light path for controlling the light in an intermediate region between near and far axes of an incident light beam, thus providing a simplified and inexpensive device for using discs of differing thickness in a single disc drive.

TL;DR: In this paper, an optical pickup apparatus having compatibility with a recodable compact disk (CD-R) and a digital video disk (DVD), which uses a wavelength of one of a first light beam and a second light beam according to the recording medium to be used.

TL;DR: In this article, an optical pickup for all optical disk having multiple recording layers is provided to exactly control a focal position according to the thickness of optical disk, by separately controlling focal positions on each recording layer, wherein a Fresnel lens for diffracting an optical beam generated from an optical source and an objective lens for focusing the diffracted beam are separately located.

TL;DR: In this paper, an optical pickup apparatus compatible with at least two types of optical recording media, using light beams having respective different wavelengths for recording and reading information, is presented. But the optical pickup is not suitable for the case where the laser light sources are in an outer region relative to the inner region.

TL;DR: In this article, an optical pickup compatible with a plurality of optical recording media each using light of a different wavelength is proposed, which includes at least one light source, an objective lens having a function of focusing light emitted from the light source into the optimal light spot on an information recording surface on an optical recording surface of one of the plurality of the optical recording medium, and a light detector to detect light transmitted through the objective lens after being reflected from the information recording surfaces on which the light spot is formed.