Sookyung Kim

A mobile auto-focus actuator based on a rotary VCM with the zero holding current

In this work, an auto-focus actuator moving lens in mobile phone cameras is developed by applying a rotary VCM (voice coil motor). A novel inclined cam structure is used to convert the rotational motion by the VCM by into the linear motion of the focusing lens. The new focusing design enables the zero holding current required to maintain the lens module in the focusing position as well as the reduction of the module thickness. This paper presents the theoretical analysis and optimal design for the VCM actuator, cam structure and preload spring. We manufacture a prototype module with the size of 9.9x9.9x5.9 mm(3). The experimental results agree with the theoretical predictions and meet the required specifications for mobile camera applications.

Optical detection of nanoparticle-enhanced human papillomavirus genotyping microarrays

In this study, we propose a new detection method of nanoparticle-enhanced human papillomavirus genotyping microarrays using a DVD optical pick-up with a photodiode. The HPV genotyping DNA chip was labeled using Au/Ag core-shell nanoparticles, prepared on a treatment glass substrate. Then, the bio information of the HPV genotyping target DNA was detected by measuring the difference of the optical signals between the DNA spots and the background parts for cervical cancer diagnosis. Moreover the approximate linear relationship between the concentration of the HPV genotyping target DNA and the optical signal depending on the density of Au/Ag core-shell nanoparticles was obtained by performing a spot finding algorithm. It is shown that the nanoparticle-labeled HPV genotyping target DNA can be measured and quantified by collecting the low-cost photodiode signal on the treatment glass chip, replacing high-cost fluorescence microarray scanners using a photomultiplier tube.

A study on the flying stability of optical flying head on the plastic disks

In the optical drive system, adopting the optical-flying-type head (OFH) flying on a removable plastic disk, the flying stability of the small OFH should be carefully considered to ensure the reliability for the first surface recording. This study gives two simulation results on the flying stability of the OFH: one is the dependence of the flying height and pitch angle variations on the wavelength and amplitude of disk waviness, and the other is the flying stability of the slider and suspension system during the dynamic load/unload process.

Nano-pulsed laser irradiation scanning system for phase-change materials

Recently, the demand of a laser irradiation tester is increasing for phase change random access memory (PRAM) as well as conventional optical storage media. In this study, a nano-pulsed laser irradiation system is developed to characterize the optical property and writing performance of phase-change materials, based on a commercially available digital versatile disk (DVD) optical pick-up. The precisely controlled focusing and scanning on the materials surface are implemented using the auto-focusing mechanism and a voice coil motor (VCM) of the commercial DVD pick-up. The laser irradiation system provides various writing and reading functions such as adjustable laser power, pulse duration, recording pattern (spot, line and area), and writing/reading repetition, phase transition, and in situ reflectivity measurement before/after irradiation. Measurements of power time effect (PTE) diagram and reflectivity map of Ge(2)Sb(2)Te(5) samples show that the proposed laser irradiation system provides the powerful scanning tool to quantify the optical characteristics of phase-change materials.