Browsing by Author "Liu, PY"

Now showing 1 - 3 of 3

A novel dual focus objective lens for DVD/CD pick-up head
(1998-03-01)
Liu, PY
;
Shieh, HPD
;
Ju, JJ
;
Tsai, ST
;
Yang, TM
A new dual focus objective lens of combinig aspherical surfaces of DVD and CD for DVD/CD pick-up head was designed. Numerical analysis based on the diffraction model were studied to trade off the spot size, side lobe, and energy ratio of DVD and CD, The hybrid aspherical surfaces of DVD and CD are optimized for low aberration. The spot size of full wave half maximum (FWHM) are 0.553 and 0.88 mu m for DVD and CD, respectively, measured from thus constructed double rings lens.
Center aperture detection on magnetically induced super resolution magneto-optical disks
(1996-03-01)
Liu, PY
;
Shieh, HPD
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A vector diffraction model has been applied to analyze CAD readout of MSR disks. Numerical results indicate that the read power is optimized with an aperture of the same size as the recorded mark. CNR decreases as recorded density increases even by using optimized aperture. CAD MSR disks applications are limited by the aperture-to-spot ratio of 34%. Also, CNR decreases as the track pitch becomes narrower. The vector model presents a higher sensitivity than the scalar model in analyzing the optical readout characteristics of sub-mu m disk structure and 'below-diffraction-limit' aperture of the readout spot.
Pulse-read on erasable thermal phase-change superresolution disks
(1998-12-10)
Liu, JR
;
Liu, PY
;
Tang, NY
;
Shieh, HPD
;
光電工程學系
New erasable thermal phase-change superresolution (EPSR) disks composed of mask and recording layers can increase recording density by the detection of the below-diffraction-limited marks within the readout spot. The formation of the aperture and the readout signal on the EPSR disk were analyzed. The feasibility of optically designed EPSR disks was evaluated by thermal simulation. A carrier-to-noise ratio of 32 dB at a mark size of 0.4 mu m, 8 dB higher than that of a conventional disk, was obtained by application of a pulse-read method to the EPSR disks at a wavelength of 780 nm and a numerical aperture of 0.55. (C) 1998 Optical Society of America.