Takatoshi Yamada

BD/DVD/CD Compatible Objective Lens

We have developed an objective lens which can be used for different optical disk formats -Blu-ray Disc, DVD and CD. The compatible technique is based on the diffraction characteristics optimized by tuning refractive index dispersion. This optical configuration can provide suitable designs for optical pick-up system of high speed recording.

Fabrication of a Solid Immersion Mirror and Its Optical Evaluation

We report the optical design of a solid immersion mirror (SIM) incorporated with a flying slider – called a SIM slider – for a near-field recording (NFR) system, its fabrication process, and optical evaluation. To achieve diffraction-limited performance ~λ/14 (rms), a two-step glass-molding process was employed to fabricate the SIM. The numerical aperture of the SIM slider was 1.29. The rms value of the total wavefront aberration was 0.0679λ. The fabricated SIM slider achieves the optical performance estimated by calculation with the fabrication errors considered, and even diffraction-limited performance. However, an rms value of 0.035λ–0.04λ for the total wavefront aberration is generally assigned for condensing optics for practical use because not only condensing optics but also other optical elements are involved in a practical optical disc system. Therefore, the aberration caused by the fabrication errors in the molding process should be reduced to at least 59% of the present level, if the SIM is to be applied to a practical NFR system.