OBJECTIVE LENS DEVICE CAPABLE OF COMPENSATING CHROMATIC ABERRATION AND OPTICAL PICKUP ADOPTING OBJECTIVE LENS DEVICE

摘要

PURPOSE: An optical pickup adapting an objective lens device is provided to assemble the objective lens device to a three-sheet lens including a lens having power of a sound below 45 abbe numbers, and to form at least one side of the three-sheet lens as an aspheric side, thereby compensating chromatic aberration of blue light. CONSTITUTION: Optical path converters convert paths of a light source(51) and an incident light. An objective lens device(10) focuses the incident light to form an optical spot on a recording medium(30). An optical detector(73) receives the incident light reflected on the recording medium and passing through the optical path converters. The optical path converters are arranged on an optical path between the light source and the objective lens device. The optical path converters are composed of a polarized beam splitter(57) and a quarter wavelength plate(59). The polarized beam splitter transmits or reflects the incident light according to polarization. The quarter wavelength plate changes a phase of the incident light. The optical detector receives the light reflected from the recording medium to detect an information signal and an error signal. A collimating lens(53) focuses a light emitted from the light source to change into a parallel light. A beam shaping prism(55) shapes an oval beam as a circular beam. A sensing lens is an astigmatism lens for causing astigmatism on the incident light.