• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.771-776
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• 2002

Optimal shape of the NFR suspension is studied and developed to improve the dynamic performance and reduce the vibration of the suspension system including a optical head slider. Since accurate position control and stability of the slider motion are highly required in NFR due to the narrower track width and the heavier slider than HDD slider with the low flying height, the dynamic characteristics of the suspension are very important to the mechanical performance of the system. The first natural frequencies in flexural and lateral motion of the suspension are critical factors affecting the dynamics and stability of the flying head, so that the dynamic parameters should be designed properly to avoid an excessive vibration or a crash of the slider on the disk. This paper optimizes the shape of the suspension based on homogenization method in NASTRAN and develops a new suspension shape for NFR system. The suspension is tested on experiment to verify the improvement of the dynamic characteristics.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.874-875
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• 2008

Gap servo NFR (Near Field Recording) system is one of technologies to reduce beam spot size by increasing NA (Numerical Aperture) of lens. To achieve high NA, SIL (Solid Immersion Lens) is used. In case of using a blue LD (405 nm) as the light source the gap distance should be controlled under 100 nm with much tighter margin. To develop NFR disc drive with very small gap distance between SIL bottom and the surface of media, we need to research for the vibration characteristics and design considerations. This paper deals with a study on vibration characteristic of NFR disc drive.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.14-15
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• 2005

In near-field recording (NFR) optics using solid immersion lens (SIL), near-field air gap induces unwanted spherical aberration, defocus and astigmatism. This phenomenon can be explained with the apodization of phase and amplitude between each linearly polarized light. In this paper, we analyzed the effect of phase and amplitude apodization with the fundamental multiple beam interference theory, and we compared resultant diffracted patterns on the image plane for the Si-disk first surface media structure and cover-layer incident media structure.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.4-11
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• 2005

In this paper, we propose novel optics design for media inside near-field recording (NFR) using hemispherical solid immersion lens (HMS). To obtain strong advantage of data protection and high data capacity simultaneously, HMS based near field optics using aplanatic position of super hemisphere is designed. In this design, to improve small optical tolerance of this aplanatic position, additional aspheric lens surface is added on top of the HMS and it is combined with zoom optics which composed of two single lenses having low numerical aperture (NA). Also, to compensate chromatic aberration which happens seriously in optics using blue laser diode, diffractive optical element is used. Using zoom optics, additional aspheric lens surface, and diffractive optical element together, wavefront aberration and chromatic aberration are effectively reduced in broad range of cover layer thickness and wavelength variation. In addition, In this paper, effect of gap induced aberration is investigated by analyzing different behavior of each TM and TE wave for designed media inside dual-layer NFR optics.

• 정보저장시스템학회논문집
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• 제2권1호
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• pp.13-20
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• 2006

In this paper, we propose novel optics design for media inside near-field recording(NFR) using hemispherical solid immersion lens(HMS). To obtain strong advantage of data protection and high data capacity simultaneously, HMS based near field optics using aplanatic position of super hemisphere is designed. In this design, to improve small optical tolerance of this aplanatic position, additional aspheric lens surface is added on top of the HMS and it is combined with zoom optics which composed of two single lenses having low numerical aperture(NA). Also, to compensate chromatic aberration which happens seriously in optics using blue laser diode, diffractive optical element is used. Using zoom optics, additional aspheric lens surface, and diffractive optical element together, wavefront aberration and chromatic aberration are effectively reduced in broad range of cover layer thickness and wavelength variation. In addition, in this paper, effect of gap induced aberration is investigated by analyzing different behavior of each TM and TE wave for designed media inside dual-layer NFR optics.

• 한국소음진동공학회논문집
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• 제17권6호
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• pp.539-546
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• 2007

Information storage devices using disks have a disk vibration at the frequency which is equivalent to the disk rotational speed. They also have a track vibration due to the disk eccentricity at the same frequency. In near field recording systems, the former affects the air-gap servo and the latter affects the tracking servo. In this paper, we introduce a novel control algorithm based on the internal model principle to both servos. A controller block designed by the principle is connected to the base lead-lag type compensator in parallel in order to cancel the repeatable run-out due to the disk vibration or eccentricity. Simulation and practical application of the algorithm on a near field recording system show good servo performance.

• 한국소음진동공학회논문집
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• 제14권4호
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• pp.295-302
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• 2004

In this study the optimization of a NFR suspension is performed using finite element method and experimental modal analysis. NFR suspensions are required to have low compliance modes to allow the slider to comply with the rotating disk, and high tracking stiffness modes to maximize the servo bandwidth of the tracking controller First of all, the dual suspension model is designed based on the characteristics of NFR drives. And the parametric study on the sensitivities of compliance modes and tracking stiffness modes is investigated. Finally, the model satisfying static characteristics is selected and shape optimization is performed to improve dynamic characteristics. A prototype of a NFR suspension is made by etching and modal ekperiment in free state is performed. The results of experiment almost agree with those of finite element method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.688-693
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• 2002

Identification method is formulated to evaluate the dynamic characteristics of air bearings under NFR(Near Field Recording) sliders. Impulse responses and frequency response functions of NFR sliders are obtained on numerical non-linear models including rigid motion of slider and fluid motion of air bearing under the slider. Modal parameters and system parameters are identified by modal analysis method and instrumental variable method. The parameters of sliders are utilized to evaluate the dynamic characteristics of air bearings. Also, this study shows the difference between the dynamic characteristics of NFR and HDD slides, and squeeze effect of air bearings.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.359-360
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• 2008

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2003년도 추계학술대회 발표 논문집
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• pp.200-206
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• 2003

Identification method is formulated to evaluate the dynamic characteristics of air bearings under NFR (Near Field Recording) sliders. Using dynamic analysis, impulse responses and frequency response functions of NFR sliders are obtained on numerical non-linear models including rigid motion of slider and fluid motion of air bearing under the slider. System parameters are identified by modal analysis method and instrumental variable method. The identified system parameters of sliders are utilized to evaluate the dynamic characteristics of air bearings.