• Journal of Institute of Control, Robotics and Systems
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• v.14 no.5
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• pp.462-466
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• 2008

This paper proposes a stable gain scheduling method of linear time invariant controllers for tracking servo system. In order to read and write the data on the optical disc, the pick-up head should be moved to the exact track quickly and follow the track immediately. Two different controllers are used for each moving and track-following. In pull-in period, a transition period from moving to track-following, the head might slip and miss the target track. This brings on another searching process and increases the total time. One way to avoid slipping is to extend the bandwidth of the track-following controller. But, extending the bandwidth could degrade the following performance. More prevalent way is to use one more controller in this pull-in period and switch to the following controller. In general, however, switching or scheduling of stable controllers cannot guarantee the stability. This paper suggests an scheduling method guaranteeing the overall stability not only in a generalized form but also in special form for SISO system. The sufficient condition is derived from the fact that Q factor of a stable controller should be stay in $RH_{\infty}$ space. In the experiment, the proposed method shows better performance than the switching method such as shorter time and lower current consumption.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1157-1164
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• 2003

Dynamic Load/unload (L/UL) mechanism is an alternative to the contact start stop (CSS) technology which eliminates stiction and wear failure modes associated with CSS. Other benefits of L/UL include increased areal density due to smooth disk surfaces, thinner overcoats, and lower head flying height Improved shock resistance due to elimination of head slap, and reduced power consumption. Inertia latch mechanism becomes important for mobile disk drives because of non operating shock performance. Various types of latch designs have been introduced in hard disk drives to limit a rotary actuator from sudden uncontrolled motion. In this paper, a single spring inertia latch is introduced for a small form optical disk drive, which uses a rotary actuator for moving an optical pick-up. A new small inertia latch with single spring is designed to ensure both feasible and small size. The shock performance of the new inertia latch is experimentally verified.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.184-187
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• 2005

This paper is described about the technique of ultra-precision machining for optical parts in HMD system. Machining technique for PMMA and BK7 with single point diamond turning machining is reported in this paper. The main factors influencing on the machined surface quality are discovered and regularities of machining process are drawn. The purpose of our research is to find the optimum machining conditions fur cutting of PMMA and grinding of BK7. Also, apply the SPDTM technique to the manufacturing of ultra precision optical components of HMD system. Aspheric PMMA lens without a polishing process, the surface roughness of 5 nm Ra, and the form error of ${\lambda}/2\;({\lambda}=632.8nm)$ for reference curved surface 30 mm has been required.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.65-69
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• 2004

The small form factor optical data storage devices are developing rapidly nowadays. Since it is designed for portable and compatibility with flash memory, its components such as disk, head, focusing actuator, and spindle motor should be assembled within 5 m thickness. The thickness of focusing actuator is within 2 mm and the total working range is $+/-100{\mu}m$, with the resolution of less than $1{\mu}m$. Since the thickness is limited tightly, it is hard to place the yoke that closes the magnetic circuit and hard to make strong flux density without yoke. Therefore, Halbach array is adopted to increase the magnetic flux of one side without yoke. The proposed Halbach array type focusing actuator has the advantage of thin actuation structure with sacrificing less flux density than conventional magnetic array. The optical head unit is moved on the swing arm type tracking actuator. Focusing coil is attached to swing arm, and Halbach magnet array is positioned at the bottom of deck along the tracking line, and focusing actuator exerts force by the Fleming's left hand rule. The working range and resolution of focusing actuator are analyzed with FEM and experiment.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.253.2-253.2
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• 2007

• Proceedings of the KIEE Conference
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• 1986.07a
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• pp.422-424
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• 1986

• Bulletin of the Korean Space Science Society
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• 2007.10a
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• pp.112-112
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• 2007

• Korean Journal of Head & Neck Oncology
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• v.27 no.2
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• pp.210-214
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• 2011

Background and Objectives : Narrow Band Imaging(NBI) is a novel optical technique that enhances the visualization of superficial microvascular architecture which is commonly increased and founded as an irregular shape in a neoplastic lesion. The aim of this study is the evaluation of the usefulness of NBI in the diagnosis of Head and Neck Cancer. Subjects and Methods : From December 2009 to January 2011, 31 consecutive patients who were diagnosed with head and neck malignancy were enrolled in this prospective study. The malignant findings of NBI were demarcated brownish lesion or increased intraepithelial papillary capillary loops(IPCLs) with or without irregularity. Results : There were 29 cases(93.5%) of well demarcated brownish lesion, 26 cases(83.9%) of increased IPCLs and 4 cases(12.9%) of satellite lesions. Diagnostic accuracy of endoscopic examination was increased from 83.9% to 93.5%, when NBI was applied to the conventional endoscopy(p>0.05). Conclusion : NBI is a powerful and safe screening test, which can be performed in out patient clinic without any supplementary procedure.

• Broadcasting and Media Magazine
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• v.16 no.2
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• pp.73-83
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• 2011

홀로그래픽 광학소자(HOE; holographic optical elements)는 높은 회절효율과 협대역 주파수 특성, 그리고 여러 가지 기능을 하나의 소자로 구현할 수 있다는 특성을 갖고 있어 비행기와 자동차의 정보 표시를 위한 HUD(head-up display), 증강현실용 HMD(head mounted display), 2D/3D 디스플레이용 스크린 등에 널리 활용되고 있다. 이에 홀로그래픽 광학소자(HOE)의 동작특성과 디스플레이에 활용되고 있는 몇 가지 예를 통해 그 활용가치와 앞으로 홀로그래픽 광학소자가 좀 더 보편화되기 위해 풀어야 할 당면과제 등에 대해 다루고자 한다.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.225-230
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• 1994

Main parameters and equations necessary for developing the holographic HUD are investigated. Air reflection recording method of obtaining good holographic reflection filters with minimized interference pattern noises is presented. Especially, a new method of correcting the center wavelength shift which takes place after the processing of the DCG film is suggested.gested.