Optical head device

Abstract

Abstract PURPOSE:To correct the spherical aberration by inserting a parallel flat plate optical element in a converging luminous flux of a converging luminous flux system so as to generate a spherical aberration thereby cancelling the substantial spherical aberration of the head optical system. CONSTITUTION:If an optical system of an optical head has a spherical aberration of omega4, the spherical aberration of omega<1>4=-omega4 is to be generated in order to cancel the spherical aberation. The parallel flat plate to be inserted in this case generates only a positive spherical aberration and if the original optical system has a positive spherical aberration, the aberration omega<1>4 satisfying the condition does not exist and no correction is attained. In order to solve it, a condensor lens 4 is designed to generate a negative spherical aberration in advance to generate a spherical aberration of -DELTAomega4 when the spherical aberration to be generated is estimated as a maximum of + or -DELTAomega4, then the positive spherical aberration is not generated by the optical system of the optical head. Thus, the deterioration of a recording/reproducing signal due to the spherical aberration is improved remarkably.

Inventors

• 👤 Hidekazu Tode
• 👤 都出　英一
• 👤 Mitsushige Kondo
• 👤 近藤　光重
• 👤 Shinsuke Shikama
• 👤 信介 鹿間

Bibliographic Details