Optical pickup with astigmatism correcting lens

Claim 1

An optical pickup, comprising: a parallel plane plate type beam splitter disposed between an object to be scanned and a photosensitive element; optical means for projecting a light beam from a light source to said beam splitter and then to said object, which reflects said light beam, and for guiding said light beam reflected by said object through said beam splitter to said photosensitive element, said beam splitter imparting astigmatism to said light beam as said light beam passes therethrough; and a correcting lens which has first and second anisotropically curved surfaces and which is disposed between said parallel plane plate type beam splitter and said photosensitive element, wherein said first anisotropically curved surface is on the parallel plane plate type beam splitter side of said correcting lens and is one of a toric and a cylindrical surface producing astigmatism in said light beam which substantially compensates for said astigmatism produced by said parallel plane plate type beam splitter, and wherein said second anisotropically curved surface is on the photosensitive element side of said correcting lens and is one of a toric and a toroidal surface producing astigmatism in a predetermined direction and at the same time setting the magnification of imaging on the surface of said photosensitive element at a predetermined value.