Byung Hoon Min

The Small-Sized Optical Module and the Sled Moving Method of a Gap Servo Near-Field Recording

We present two viewpoints of small-sized optical module of a gap servo NFR. One is experimental results on the adjustment system and the other is the sled moving way mounted on the deck mechanism.

Efficient Balanced Code Using Viterbi Algorithm and Section Division for Holographic Data Storage

We propose an error correctible balanced code for holographic data storage. As the transitions of a message word are considered and parity bits that check for errors in the section are appended on encoding, we can decode message words with the Viterbi algorithm and correct errors. The effectiveness of the proposed method is validated by numerical simulations and experiments. An improvement in bit error rate (BER) is achieved.

Hidden marker position estimation during sit-to-stand with walker

Motion capture analysis of sit-to-stand task with assistive device is hard to achieve due to obstruction on reflective makers. Previously developed robotic system, Smart Mobile Walker, is used as an assistive device to perform motion capture analysis in sit-to-stand task. All lower limb markers except hip markers are invisible through whole session. The link-segment and regression method is applied to estimate the marker position during sit-to-stand. Applying a new method, the lost marker positions are restored and the biomechanical evaluation of the sit-to-stand movement with a Smart Mobile Walker could be carried out. The accuracy of the marker position estimation is verified with normal sit-to-stand data from more than 30 clinical trials. Moreover, further research on improving the link segment and regression method is addressed.

Numerical Simulations on a Stepped Solid Immersion Lens Suggested from the Experimental Consideration of the Backflow

When the air flows round the conical solid immersion lens (SIL) due to the disk rotation, the air climbs up along the lateral surface of the conical SIL at the downstream of the SIL. The existence of this backflow, which has opposite direction of the disk rotation, is confirmed numerically and experimentally. The backflow exists below one-quarter of the gap between the rotating disk and the lateral surface of the SIL and it is known to be one of major sources which carries contaminant particles to the SIL top. A step, 40 µm in height and 25 µm below the rotating disk, is fabricated on the lateral surface of the SIL to prevent the backflow. Numerical simulation shows the step reduces the pressure difference between the bottom and the top of the SIL so that the backflow is reduced dramatically.

Readout characteristics of an advanced SIL system of high NA for the near field optical storage with cover layer media

An improved concept of the advanced SIL and its compensation OL of composite effective NA over 1.7 has been designed and manufactured to achieve wider assembling tolerances, higher data capacities and better signal quality. Very clear readout signals were measured from a 25 GB BD-like ROM media with 3 um cover layer and the applying feasibility of the advanced SIL system in near field optical storage was confirmed. With this novel advanced SIL system and multilayer media concept, total capacity over 500 GB per disc was expected to be accomplished.