We presented the digital holography (DH) system with enhanced image quality. While conventional DH uses highcoherence laser for illuminations, the speckle noise included in the image degrades the quality of the reconstructed data. To reduce the noise regards to the light source, lower-coherence light source could be applied in DH system. In this paper, the quantum dot (QD) based wavelength converter is utilized as the light source. Compared with light-emitting diode (LED), QD-based light source could be applied to versatile system, including dual-wavelength DH. Due to the low coherence both temporally and spatially, spatial filtering and collimation is presented. Also, numerical processes including noise reduction and aberration compensation is described to enhance the quality of the image. By experimental verifications, the proposed DH system shows better quality compared with conventional system, which is enough to utilize the quantitative measurement.
We have characterized a new type STED microscope which combines a high numerical aperture (NA) optical head with a solid immersion lens (SIL), and we call it as SIL-STED microscope. The advantage of a SIL-STED microscope is that its high NA of the SIL makes it superior to a general STED microscope in lateral resolution, thus overcoming the optical diffraction limit at the macromolecular level and enabling advanced super-resolution imaging of cell surface or cell membrane structure and function Do. This study presents the first implementation of higher NA illumination in a STED microscope limiting the fluorescence lateral resolution to about 40 nm. The refractive index of the SIL which is made of material KTaO3 is about 2.23 and 2.20 at a wavelength of 633 nm and 780 nm which are used for excitation and depletion in STED imaging, respectively. Based on the vector diffraction theory, the electric field focused by the SILSTED microscope is numerically calculated so that the numerical results of the point dispersion function of the microscope and the expected resolution could be analyzed. For further investigation, fluorescence imaging of nano size fluorescent beads is fulfilled to show improved performance of the technique.
Ionic polymer metal composites is the proposing material for applications, since it has many attractive qualities that are
durability, aquatic, miniature and light-weighted. Especially, IPMC has extraordinary advantages that are large
displacement at low driving voltage(~3V), low power consumption and simple structure. However, slow time response
prevents IPMC from various applications. Since IPMC is generally used in simply-supported configuration, which has
same characteristic with a cantilever beam, IPMC has natural frequency and it oscillates extremely at natural frequency.
We propose new open loop control method based on frequency response, which is combined with conventional DC
input. This method is experimentally tested and compared with result by conventional input.
Ionic polymer-metal composite (IPMC) is an attractive actuator among many electro-active polymers. In order to
improve the performance of IPMC actuator, an IPMC actuator with the patterned surface was proposed. It is named the
patterned IPMC actuator. In order to make use of its maximum effect, it is needed to establish a valid mathematical
model. Among many models of IPMC actuator, the grey box modeling proposed by Kanno et al. was suited to model the
patterned IPMC actuator. In this paper, we applied the grey box model based on Kanno's model. Theoretical and
experimental results demonstrate that the model is practical and effective enough in predicting the bending displacement
partly.
Ionic Polymer-Metal Composites (IPMCs) of EAP actuators is famous for its good property of response and durability.
The performance of Ionic Polymer-Metal Composites (IPMCs) is an important issue which is affected by many factors.
There are two factors for deciding the performance of IPMC. By treating anisotropic plasma etching process to 6 models
of the IPMCs, enhanced experimental displacement and force results are obtained. Plasma patterning processes are
executed by changing the groove and the land length of 6 patterns. The purpose of the present investigation is to find out
the major factor which mainly affects the IPMC performance. Simulations using ANSYS have been executed to compare
with the experimental results about the values and the tendency of data. Experimental and simulating data of the
performances seem to have similar tendency. In the next part of the paper, we observed the other properties like
capacitance, resistance and stiffness of 6 plasma patterned IPMCs. And we observed that the stiffness is the major factor
which affects the performance of IPMCs. As we seen, our problem has been reduced to investigate about the property of
stiffness. We suggest that the stiffness is largely changed mainly because of the different thickness of Platinum stacked
of the groove and the land part which are produced by anisotropic plasma etching processes. And we understand that
anisotropic plasma patterned IPMCs of better performance can be applied to various applications.
In field of endoscopy, in order to overcome limitation in conventional endoscopy, capsule endoscope has been developed
and has been recently applied in medical field in hospital. However, since capsule endoscope moves passively through
GI tract by peristalsis, it is not able to control direction of head including camera. It is possible to miss symptoms of
disease. Therefore, in this thesis, 2-Axis Tilting Actuator for Endoscope, based on Ionic Polymer Metal Composites
(IPMC), is presented. In order to apply to capsule endoscope, the actuator material should satisfy a size, low energy
consumption and low working voltage. Since IPMC is emerging material that exhibits a large bending deflection at low
voltage, consume low energy and it can be fabricated in any size or any shape, IPMC are selected as an actuator. The
system tilts camera module of endoscope to reduce invisible area of the intestines and a goal of tilting angle is selected to
be an angle of 5 degrees for each axis. In order to control tiling angle, LQR controller and the full order observer is
designed.
Recently, in the magnetic recording, head assisted magnetic recording (HAMR) and patterned media (PM) technology
have been considered as strong candidates to achieve the high recording density beyond the super-paramagnetic limit.
Using E-beam recording (EBR) and UV nano-imprinting, the PM with nano-scale pitches and tracks is fabricated
effectively and delicately. And the optical throughput of the HARM system is improved by optimizing the grating and
the media geometry. In the optical storage, next generation technologies are the near filed recording (NFR) and the
holographic recording. The modified NFR gap servo mechanism is developed and clearance of 30nm is uniformly
maintained. In addition, the anti-shock servo algorithm resists against the external shock of over 2G@10ms. The
advanced holographic system compensates the errors from disturbance by finding the max intensity angle with back
propagation algorithm for angle direction and shifting the reference beam with glass plate controlled by a servo motor for
fractal direction.
DE EAP(Dielectric Elastomer ElectroActive Polymer) has advantages in its weight, ease of fabrication and low
power consumption. There are many efforts applied to various field in recent ten years. But the present modeling is not
enough to appear its characteristics because of its hysteresis. In this paper, we propose modeling of DE EAP with
Preisach Model that is used in order to model the hysteretic response arising in PZT and SMA. The modeling of DE
EAP with Presach model is verified by experiment with various DE EAP actuators.
The IPMC-EMIM actuator is an improved IPMC actuator to replace the water by stable ionic liquids (1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EtMeIM][TA])). Just as a general IPMC actuator which uses the
solvent of water has hysteresis, so do the IPMC-EMIM actuator exhibits hysteresis like other smart materials such as
piezoceramics (PZT), magnetostrictive materials, and shape memory alloys (SMA). Hysteresis can cause it to be
unstable in closed loop control. The Preisach Model has been used to model the hysteretic response arising in PZT and
SMA. Noting the similarity between IPMC-EMIM and other smart materials, we apply the Preisach model for the
hysteresis in the IPMC-EMIN actuator. This paper reviews the basic properties of the Preisach model and confirms
that the Preisach model of IPMC-EMIM actuator is possible.
IPMC-EMIM (Ionic Polyer Metal Composites + 1-ethyl-3- methyl imidazolium trifluromethane sulfonate, EMIM-Tfo)
is fabricated by substituting ionic liquid for water in Nafion film, which improves water sensitiveness of IPMC
and guarantees uniform performance regardless of the surrounding environment. In this paper, we will briefly
introduce the procedure of fabrication of IPMC-EMIM and proceed to introduce the Hook-type actuator using IPMC-EMIM
and application to AF Lens actuator. Parameters of Hook-type actuator are estimated from experimental data.
In the simulation, The proposed AF Lens Actuator is assumed to be a linear system and based on estimated parameters,
PID controller will be designed and controlled motion of AF Lens actuator will be shown through simulation.
We analyzed the effects of an external shock on a collision problem in a solid immersion lens (SIL) based near-field
recording (NFR) through a shock response analysis and proposed a possible solution to this problem with adopting a
protector and safety mode. With this proposed method the collision between SIL and media can be avoided. We showed
possible solution for contamination problem in SIL based NFR through a numerical air flow analysis. We also
introduced possible solid immersion lens designs to increase the fabrication and assembly tolerances of an optical head
with replicated lens. Potentially, these research results could advance NFR technology for commercial product.
In this study, small sized optical pickup corresponding to blu-ray disc specifications has been developed in the array using wafer level packaging technology and verified that signal balance was satisfied with specifications.
KEYWORDS: Servomechanisms, Control systems, Actuators, Signal detection, Optical discs, Signal generators, Analytical research, Data storage, Digital signal processing, Tolerancing
The focus pull-in behavior analysis in a Blu-Ray disk (BD) and various control approach to improve the performance of it are discussed. The focus pull-in work, which locks the beam spot of an optical pick-up to the information layer in an optical disk, is an essential work in an optical disk drive (ODD), and the error tolerance of it depends on the kind of an ODD. In a BD system, the focus pull-in work should be done within a very narrow beam height region (λ/NA =0.4765μm) and a very short period. Therefore, the moment of the focus pull-in is a transient phenomenon, and more careful analysis of it is necessary. In this paper, the focus full-in work is analyzed in depth, and various control approaches to improve the focus pull-in performance are discussed. First, various detected servo signal during the focus pull-in work are summarized briefly. Then, a novel swing arm type actuator which is developed by our center for a small form factor BD is introduced. Finally, three control approaches to perform the focus pull-in are designed and applied to the system: (i) conventional lead-lag, (ii) fuzzy control, (iii) sliding mode control. From the experiments results, we find that two control approaches, fuzzy control and sliding mode and, have more good focus pull-in performances than the conventional lead-lag approach.
As a popularity of a portable digital device such as a cellular phone, a digital camera and a MP3 player is spreading, the demand of the mobile storage device increases rapidly. A Blu-ray technology using 406nm laser diode and 0.85 NA(Numerical Aperture) satisfies a miniaturization and a high capacity which are the requirements of the portable device. Because a Blu-ray optical storage device can store 1.5Gbyte on a 3cm disk, it is possible to distribute the media in great quantities and with cheaper price. In this paper, we analyze the optical performance of the hybrid micro lens which is manufactured using a micro fabrication technology. The measurements of the optical power, the spot size and the wavefront error are performed to evaluate the hybrid micro lens with 0.85 NA and the designed wavelength of 406nm. Using the measured data, we estimate if the performance of hybrid micro lens corresponds to the designed performance. Also, the processes of measuring an optical performance of hybrid micro lens, which is composed of the refractive lens and the diffractive lens, are proposed using laser diode of 406nm and finite optics.
KEYWORDS: Optimization (mathematics), Analytical research, Modulation, Solids, Neural networks, Systems modeling, Contamination, Head, Data storage, Near field
The optical systems using the probe and solid immersion lens (SIL) have been researched as the technology to embody the near field recording (NFR) system. In NFR system, it is very important for the clearance between slider and disk surface to remain under 100nm in order to use effect on evanescent wave. The OFH should also have a small pitch to control the contamination effect. Because the larger the gap between leading edge of slider and disk is, the more particles come into SlL. As a result, they have a lot of bad influence on SIL. However, the flying stability turns bad as the pitch angle becomes small. Accordingly, it is necessary to consider dynamic characteristics in OFH ABS design.
This research made two approximation models through the regression analysis and neural network, which are the parameter analysis based on optimization techniques. This study also used micro-genetic algorithm (GA) and design optimization tool (DOT). ABS shape of flying head was optimized with the object of remaining FH of several ten nano meter in static state. And the dynamic optimization was carried out toward decreasing FH modulation.
As a result of static optimization, the flatness of flying height was restricted within 1% in inner diameter (ID) and outer diameter (OD). Besides, the flying height was remained about 50nm. In the dynamic optimization, the vertical sensitivity of dynamic optimal model was bigger than that of original model and the pitch sensitivities was also improved a bit.
KEYWORDS: Optical storage, Integrated optics, Electronics, Data storage, Actuators, Objectives, Mobile devices, Optical discs, Wafer-level optics, Near field
There are two basic requirements in the field of optical storage data devices. The first is the demand for the improvement of memory capacity to manage the increased data capacity in personal and official purposes. The second is the demand for small sized optical storage devices for mobile multimedia digital electronics, including digital camera, PDA and mobile phones. To summarize, for the sake of mobile applications, it is necessary to develop optical data storage devices which have simultaneously a large capacity and a small size. Small form factor optical disk drive (SFF ODD) is expected to become a good match for mobile applications due its advantages over other devices in cost and removability. Nowadays, many companies and research institutes including universities cooperate together in the research on SFF ODD and other related optical storage devices. Due such active researches, it is expected that SFF ODD will be widely
used in mobile applications in the very near future.
The optical disk drive with more robustness against shock has been rarely studied. This research shows the shock response analysis of conventional optical disk drive. Main base of the optical disk drive is described with the motion of bouncing, pitching, and rolling. The entire model includes pick-up actuator. Finite element model of the entire system is made by ANSYS. And the lumped parameter model is made, which will replace the finite element model. Shock response of finite element model is compared with that of the lumped parameter model. Their shapes and magnitudes are the same. Therefore, the lumped parameter model can replace the finite element model. The lumped parameter model has advantages of cost and time over the finite element model.
Linear drop test and tilt drop test are made in order to verify our shock model. Accelerometer is used for detecting input acceleration. Laser Doppler vibrometer is used for measuring the motion of the main base and pick-up actuator. Then experimental result is compared with the shock response of lumped parameter model. Their shapes are much the same. Therefore, the lumped parameter model of the optical disk drives can represent the real system.
We have developed diffractive optical element (DOE) to compensate chromatic aberration happened in aspheric lens surfaces in micro optical system. The DOE was generated with grayscale lithography using high-energy-beam-sensitive (HEBS)-glass, and we finally obtained DOEs having 4levels and 8levels through this fabrication.
In complicated structures it is difficult to determine causes of vibration because of non-linearity and variation of the system. Though Operating vibration signal has a strong similarity to dynamic characteristics of the structure in static state, it is too early to conclude that resonance of the structure brings out vibration of the structure without source identification. In vibration source identification it is important to decide not only the location and the number of sources but also rankings of sources. With this information one can know vibration generation mechanisms and devise counter plans. This research demonstrates the application for vibration source identification in optical disk drives. There are many vibration sources such as the external disturbance, the disk vibration, airflow, the motor vibration, and the chassis vibration in optical disk drives. These vibration sources are inputs of the system. And focus error signal is an output of the system. Therefore optical disk drive can be defined as a MISO system. In this research, the multiple coherence function between the output and all inputs is evaluated experimentally. The partial coherence functions are used to show which source is the major sources of focus error signal.
KEYWORDS: Actuators, Optical sensors, Ferroelectric materials, Near field, Near field optics, Finite element methods, Reflection, Sensors, Digital signal processing, Optical storage
In this paper, our aim is to develop a system that can not only maintain stable gap distance under 100nm but also compensate the tilting between a pick-up head and disk surface for near-field recording (NFR), which is known as a key technology for a next generation optical storage. Applying total internal reflection (TIR) to the air gap measurement, we design an optical sensor to measure the gap distances at three points. Stack and bimorph piezoelectric actuators are utilized for high precision control with nanometer resolution. To understand dynamic characteristics of the system, an analytical method for boundary coupled beam model is performed and verified by comparison with the results of the finite element method (FEM).
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