OPTICAL DISCS CAPABLE BEING

Brand	Owner	Address	Description
AVIST	TDK KABUSHIKI KAISHA (TDK CORPORATION)	2-5-1 Nihonbashi, Chuo-ku Tokyo 103-6128 Japan	Optical discs capable of being prerecorded with motion pictures, music, computer games and other entertainment or educational programs and computer software;
	Where the owner name is not linked, that owner no longer owns the brand

Technical Examples

There is provided an objective lens for an optical pick-up which is used to record/reproduce data to/from at least three types of optical discs. Thicknesses t1, t2 and t3 of cover layers of first, second third optical discs are t1?0.6 mm, t2?0.6 mm, and t3?1.2 mm. Numerical apertures NA1, NA2 and NA3 for the first, second and third optical discs satisfy a relationship NA1?NA2>NA3. When the first optical disc is used, a substantially collimated light beam is incident on the objective lens. When the second or third optical disc is used, a diverging beam is incident on the objective lens. With regard to magnifications M1, M2 and M3 and focal lengths f1, f2 and f3 of the objective lens for the first, second and third optical discs, the following conditions (1), (2) and (3) are satisfied: