| Summary: | 博士 === 國立交通大學 === 機械工程學系 === 98 === Making use of near-field optics, optical disk drives can overcome the limit of diffraction and reduce laser light spot sizes. The data storage density of the optical disk can be thus increased. A slider on the pickup head of a near-field optical disk drive has to carry both objective lens and solid immersion lens (SIL). The slider maintains flying height about 50 nm above the disk surface. This height is smaller than the mean free path of molecules. Hence, the gas rarefied effect should be taken into account during data reading and writing. In addition, dust particles in disk drives may influence flying stability when pickup heads are reading/writing data. This study presents approaches to cleaning dust that sticks on the SIL of the pickup head. Dealing with the near-field optical disk drive, this study proposes to employ airflow for dust removal at the head-disk interface. Moreover, this study designs two kinds of SILs, i.e. a navel type and a stairway type, and analyzes the pressure distribution on the pickup head. A direct simulation Monte Carlo method is adopted to compute the nano-flow field. As a consequence, the pressure in simulation results by using the proposed stairway SIL design demonstrates dust removal capability.
Furthermore, this study has modified a digital versatile disk (DVD) pickup head as an optical pickup head actuator with a laser diode package for sensing. Tuning a tilting coil in the optical pickup head actuator causes the tilt of a laser diode to compensate misalignment between a target surface and the laser diode facet. Experimental results show that tuning the tilting coil compensates misalignment between both surfaces to achieve effective self-mixing signal. In addition, this study presents the conformity between the output voltage and the target surface displacement from a laser diode package using the self-mixing effect. The resolution in linear region of self-mixing signal is 100 mV/nm. This study presents a sliding mode based fuzzy control method to achieve fast response of an optical pickup head actuator, which is driven in focusing direction. Both simulation and experimental results show the proposed method performs better than sliding mode control.
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