KEYWORDS: Visualization, Current controlled current source, Integral imaging, 3D displays, LCDs, 3D applications, 3D image processing, Image resolution
Depth and resolution are always the trade-off in integral imaging technology. With the dynamic adjustable devices, the two factors of integral imaging can be fully compensated with time-multiplexed addressing. Those dynamic devices can be mechanical or electrical driven. In this presentation, we will mainly focused on discussing various Liquid Crystal devices which can change the focal length, scan and shift the image position, or switched in between 2D/3D mode.
By using the Liquid Crystal devices, dynamic integral imaging have been successfully applied on 3D Display, capturing, and bio-imaging applications.
Virtual mouse based on IR source, lens array and light sensor was designed and implemented. Optical architecture including lens amount, lens pitch, baseline length, sensor length, lens-sensor gap, focal length etc. was carefully designed to achieve low detective error, high resolution, and simultaneously, compact system volume. System volume is 3.1mm (thickness) × 4.5mm (length) × 2, which is much smaller than that of camera-based device. Relative detective error of 0.41mm and minimum resolution of 26ppi were verified in experiments, so that it can replace conventional touchpad/touchscreen. If system thickness is eased to 20mm, resolution higher than 200ppi can be achieved to replace real mouse.
KEYWORDS: 3D displays, 3D image processing, Brain-machine interfaces, Visualization, Signal to noise ratio, Electroencephalography, 3D acquisition, LCDs, Human-machine interfaces, Modulation
Brain-computer interfaces (BCIs) are intuitive systems for users to communicate with outer electronic devices. Steady state visual evoked potential (SSVEP) is one of the common inputs for BCI systems due to its easy detection and high information transfer rates. An advanced interactive platform integrated with liquid crystal displays is leading a trend to provide an alternative option not only for the handicapped but also for the public to make our lives more convenient. Many SSVEP-based BCI systems have been studied in a 2D environment; however there is only little literature about SSVEP-based BCI systems using 3D stimuli. 3D displays have potentials in SSVEP-based BCI systems because they can offer vivid images, good quality in presentation, various stimuli and more entertainment. The purpose of this study was to investigate the effect of two important 3D factors (disparity and crosstalk) on SSVEPs. Twelve participants participated in the experiment with a patterned retarder 3D display. The results show that there is a significant difference (p-value<0.05) between large and small disparity angle, and the signal-to-noise ratios (SNRs) of small disparity angles is higher than those of large disparity angles. The 3D stimuli with smaller disparity and lower crosstalk are more suitable for applications based on the results of 3D perception and SSVEP responses (SNR). Furthermore, we can infer the 3D perception of users by SSVEP responses, and modify the proper disparity of 3D images automatically in the future.
To detect the 3D depth information of objects in a deep scene is not so easy due to the limited depth of field (DoF) of cameras. In this paper, we proposed a 3D depth map capturing system with high dynamic depth range (HDDR). Unlike conventional extending depth of field (EDoF) method, the HDDR method will not deteriorate the image quality. By imitating an active tunable m × n lens array focusing on a sequential of imaging planes, each object in the scene would be clearly captured by at least three elemental lenses. We estimated the elemental depth maps by using the method depth from disparity individually, and then fused them into one all-in-focus depth map. Comparing with the conventional 3D cameras, the working range of HDDR system with 3x3 camera array can be extend from 90cm to 165cm.
A plano-convex electrode is presented for a liquid crystal lens array with a hexagonal arrangement, small inactive region, 30μm cell gap and low applying voltage. It uses circular curved electrodes to provide a smooth, controllable applied potential profile across the aperture to manage the phase profile.
Based on a finite-conjugate objective lens with numerical aperture of 0.62 for a 650-nm wavelength, an optical pickup head composed of a multifunction beamsplitter and a diffractive optical element is designed be used in a swing-arm-type optical pickup head. The diffractive optical element is a lens with an elliptical four-level phase profile to provide both focusing and astigmatism. It is also designed with the goal to simplify the overall optical configuration and provide linear characteristics for the focus error signal.
A pop-up binary-phase micrograting and a pop-up micro polarization beamsplitter, for potential use in micro-optical pickups, have been realized on a single silicon chip using a two-layer polysilicon and one-layer silicon nitride micromachining process. In the case of the micrograting, a diffraction efficiency ratio between 4 and 10 can be achieved provided that the duty cycle is between 0.4 and 0.6 and the depth between 455 and 485 nm, respectively. For a grating designed for a diffraction ratio of 7, the measured ratio is 8.31. The polarization beamsplitter is a silicon nitride thin film placed at the Brewster angle. The transmittance of the TM mode was measured to be more than 98.5%, while the reflectance of the TE mode was 21.4%.
A stress-induced curved \micro actuator with a grating attached at the end is demonstrated for recordable optical
storage applications. The actuator and the grating were fabricated using a two-layer poly-silicon and one-layer silicon
nitride micro-machining process. Three diffracted beams with equal intensity from the grating were generated when a
voltage is applied to the actuator to switch its position. The single-beam and multi-beam configurations can be used for
writing and reading data in the disc, respectively.
A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and
evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid
crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral
smectic C mesophase over 100 °C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1
performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 μm pre-made cell (EHC,
Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid
crystal materials for fast switching field sequential color displays.
The design and fabrication of micro gratings and polarization beam splitters for potential use in micro optical pickups are presented. Silicon nitride is used as the optical material for its low absorption in the visible wavelength. The micro components are framed by a pop-up poly-silicon mechanism as in the standard surface micromachining technology.
The micro grating is a binary phase grating. The diffraction ratio between 4 and 10 can be achieved provided that the duty cycle is between 0.4 and 0.6 and the depth between 455nm and 485nm. For a grating designed for a diffraction ratio of 7, the measured ratio is 8.31.The polarizing beam splitter is a silicon nitride thin film placed at the Brewster angle. The transmittance of the TM mode of a micro polarization beam splitter was measured to be more than 98.50%.
The size and weight of the pickup head will influence the form factor and the bandwidth of DVD. A MEMS-type DVD pickup was proposed, in which the objective lens will be manipulated with a micro actuator for focusing. A high order diffractive objective lens has been designed specially for meeting the request on reduced weight by optimizing the surface relief profile of each zone one by one. The simulation by ray tracing tool shows a well corrected geometrical aberration and a near diffraction limit focal spot. The lens is expected to be produced with gray scale mask photolithography, and the weight will have only one third of that of its refractive counterpart.
The majority of the beam splitters for three beam tracking in commercial DVD pickup employ lamellar phase gratings, which already provides sufficient efficiency. However, for a pickup with all diffractive elements, the power budget becomes more critical, and a higher efficiency of the beam splitter is required. In this paper, we have investigated and will present the influence of the desired energy ratio between the zeroth order central beam to the first order side beam on the total efficiency of the beam splitter. The simulation based on scalar diffraction theory shows that the total efficiency of a lamellar phase grating will drop as the ratio decrease, which can be improved by employing a more sophisticated surface relief. The equal-side triangular profile has been investigated as a solution and the geometrical size of the profile has been optimized for several desired energy ratio. For a low cost fabrication process with photolithography, the total efficiency loss due to quantization with different quantization levels of the triangular surface relief has been estimated with scalar diffraction theory. This paper is concluded with a table of optimal phase level for a given energy ratio and desired minimum total efficiency with the consideration of fabrication cost.
Nitrogen doping was applied to enhance the velocity of amorphous-crystalline phase transformation. The nitrogen doping was able to produce tiny nitride precipitates uniformly distributed in the recording layer and provided numerous preferential sites for amorphous-crystalline transition. At the doping condition of N2/Ar ratio = 3%, the recrystallization velocity of GeInSbTe phase change recording media was increased up to 1.6 times without severely damaging the signal jitter values.
The crystallization process of two types of phase change materials (Ge2Sb2Te5 and AgInSbTe) has been studied by in-situ annealing experiments in the column of a transmission electron microscope. Under the same heating rate (7.5K/s), the Ge2Sb2Te5 material starts to nucleate at 170°C, while AgInSbTe starts to nucleate at 250°C. The measured nucleation rate of Ge2Sb2Te5 is 8.2×1014 cm-3s-1 larger than nucleation is dominant for both Ge2Sb2Te5 and AgInSbTe with ZnS-SiO2 as the dielectric layer in the thinned samples.
As the recording density of longitudinal magnetic storage increases at a 100% annual growth rate, it will soon approach the superparamagnetic limit where the thermal energy at room temperature starts to induce thermal instability to the grains in the small recorded marks. Thermal magnetic recording schemes, such as those used in magneto-optical recording, help alleviate the problems with the superparamagnetic limit. Recently, a hybrid recording system was proposed where data were recorded thermal magnetically on a magneto-optical disk and read back with a GMR head. In this paper, we propose an integrated planar read that combines an optical fiber lens, a solid immersion lens, a sub wavelength aperture, a micro coil, an air bearing surface, and a GMR head for such a hybrid recording system. Preliminary fabrication and calculation are discussed.
KEYWORDS: Polarization, Signal detection, Crystals, Signal analyzers, Polarization analysis, Picosecond phenomena, Reflectivity, Solids, Diffraction, Near field optics
KEYWORDS: Head, Molybdenum, Magnetism, Near field optics, Signal detection, Near field, Magnetic sensors, Sensors, Signal to noise ratio, Electro optical modeling
A physical channel model of readback signals from a hybrid MO recording using magnetic flux detection is presented. The system performance has been investigated using the proposed model, together with the comparison of channel characteristics in the longitudinal, near field and hybrid architectures. Preliminary iterative decoding results with this channel model are also presented.
KEYWORDS: Super resolution, Photoresist materials, Metals, Indium, Thermal effects, Photoresist developing, Absorption, Thermography, Light sources, Picture Archiving and Communication System
We propose a new laser lithography technique using the effect of thermal-induced super resolution and demonstrate that the technique can effectively reduce the exposed spot size on the photoresist layer, thus allowing disk mastering toward higher density by using exiting light source and optics. A mask layer, whose nonlinear optical properties result in formation an aperture in high temperature area near to the center of the laser spot, is deposited on the top of the photoresist layer. Usually, the aperture size is much smaller than the laser spot, thus, achieving thermal- induced super resolution. The simulation and experimental results reveal that the line width on the photoresist layer could be shrunk by more than 40%.
Dual-layer optical disks comprised of two data layers were developed to study readout/write/erase characteristics. This disk was composed of recording layer 1 and 2, of high transmittance and high reflectivity, respectively. Layer 1 and 2 of 15 and 20 nm increase transmittance and reduce writing power for recording. Only 1.5 mW laser power was sufficient for readout, 9 and 16 mW was required for recording on recording layer 1 and 2, respectively. This dual-layer disk can double data capacity on a disk substrate.
Comprehensive analyses based on rigorous vector diffraction theory have been presented to simulate the readout signal contrast using SIL in reading phase change recording disk. De-polarized reflected light (y-polarized from x-polarized incident beam) results in the reduction of total signal contrast, and becomes more obvious for high numerical aperture systems. Due to the signal degradation from de- polarized reflected light, filtering de-polarized light is applied to signal detection. The x-polarized contrast is a factor 1.0 to 1.35 higher than the conventional detection contrast (x+y polarized) at different gap widths, at a cost of 0 to 25 percent total intensity reduction.
Multi-level recording has advantage of increasing the recording density without extensively altering the current optic configuration. In this paper, a new four-level recording phase-change disk using three-recording layers was demonstrated. By modulating the intensity of the laser pulse, marks were chosen to record in any of recording layers, to form four recording regions. Utilizing the property of the phase change media whose amorphous and crystalline states differ largely in refractive indices, each recording region corresponds to different reflectance. For the four-level recording disk, each recording region represents two-bit data, then the recording density of the four-level disk is a factor of two higher than that of a conventional disk recorded by adopting the pulse position modulation.
Pulse readout technique is viewed as a way to improve the CNR ofreadout signal on super resolution disks, such as Magneto-optical Super Resolution Center Aperture Detection disk (MSR-CAD), Erasable Phase change Super Resolution disk (EPSR), Thermal distribution generated by pulse readout scheme results in more regular shape apertures and narrower wall width on those super resolution disks which leads to better signal quality.
An empirical exponential equation is proposed to characterize the transfer functions of the image signals to tristimulus values of twist nematic (TN) liquid crystal displays (LCDs). Parameters of the empirical equation can be determined according to the colorimetric measurements of the test panel without knowing the panel's physical details. A two-stage forward model is also proposed to model the color characteristics of TN LCDs by using the empirical function. Moreover, a backward model is derived to reproduce desired colors accurately on TN LCDs. The main benefit of the study is that only 12 colors should by measured to characterize color rendering on TN LCDs.
A forward model of an LC projector is studied to predict its colorimetric attribution. To identify color characteristics of the projector, 729 colors were measured in a dark room. The forward model was built using three methods: (1) a 3 X 11 multiple-polynomial regression matrix, (2) 3D look- up table (LUT) with cubic interpolation, and (3) a 1D LUT with linear interpolation. In addition, 216 colors were also measured to evaluate the prediction accuracy of the forward model. All methods can be used to obtain acceptable predictions of colorimetric attributions on the lC projector. When the 3 X 11 multiple-polynomial regression matrix was used, the average and maximum prediction differences were 2.18 and 6.68 (Delta) Euv respectively. For the 3D LUT method, those values were 3.3 and 16.4 (Delta) Euv, respectively. The results of the 1D LUT are comparable with those of the 3D LUT if the sampling points per channel of these two approaches are the same. If the sampling points per channel are dense enough, for example 16 points per channel, the performance of the 1D LUT is better than that of the 3 X 11 multiple-polynomial regression matrix.
KEYWORDS: Near field scanning optical microscopy, Near field optics, Near field, Reflection, Optical recording, Thin films, Atomic force microscopy, Optical microscopes, Feedback control, Optical fibers
Near-field scanning optical microscope (NSOM) system with a bent or a straight optical fiber probe has been successfully developed to perform optical recording on the surface of cyanine (C35H35CIN2-O4) dye layer or Ge21Te26Sb53 phase change (PC) thin film. Optical writing bits < 40 nm on the cyanine dye layer of a commercial compact disk-recordable were shown by atomic force microscope images of our tapping mode NSOM. For an vertical reflection mode NSOM, both optical writing and reading can be achieved on Ge21Te26Sb53 PC thin film, and the diameter of 500 nm recording bits are shown.
KEYWORDS: Molybdenum, Head, Data modeling, Magneto-optics, Time metrology, Computing systems, Time multiplexed optical shutter, Control systems, Performance modeling, Error control coding
A low cost byte error rate testing system for 90 mm magneto-optic (MO) disks had been developed. In order to achieve low cost and to perform the testing under realistic operating conditions, commercial magneto-optic disk drives were used instead of a high-priced, specialized disk tester. An IBM compatible 486-DX33 PC was used as the controller. The design goal of the testing system is to find the best cost/performance system configuration. A model was developed to predict the testing system performance based on the DMA data rate, SCSI bus data rate, MO drive data rate, access time, processor speed, and the number of sectors, N, involved in each read/write operation. Three configurations were studied: (1) only one MO drive; (2) two MO drives are connected to PC through separate SCSI host adaptor; and (3) two MO drives connected to PC through one SCSI host adaptor in a daisy-chain manner. The testing time of a disk varies from 40 min. to 24 min. when N is varied from 20 to 109. These testing times include the 10 min. of formatting time which is independent of N. The average access time of the MO disk was found to depend on the number of sectors involved in each read/write operation. Also, the measured access time is always lower than the specified 40 msec. These two phenomena can be explained by the smaller distance that the optical head needed to travel during the byte error rate testing. Based on the measured access time, a refined model was used to predict the optimal cost/performance configuration. A system with 6 or 7 MO disk drives connected to a PC was found to have the best cost/performance ratio.
Birefringence is the difference in refraction index for different polarization states. Birefringence introduces the phase retardation in the optical system or results in double refraction in the optical path. Injection molded polycarbonate (pc) substrates are widely used as disk substrates for magneto-optical (MO) disks. However, birefringence of the pc disk substrates is still a deficiency for MO recording applications. The resultant phase retardation in the polarization detection system degrades the MO readout signal"2. The double refraction induces additional aberration of astigmatism which both smears the readout of writing pits, and also perturbs the servo signal in servo systems such as astigmatic or knife edge methods. Thus, effective methods applied toward measuring birefringence of pc substrates are essential in controlling the quality of MO disk substrate replications. Conventional methods, e.g. phase compensator or ellipsometer'4 proposed for measuring birefringence of disk substrates do not satisfy all of the requirements. The phase compensator finds it rather difficult in measuring in-plane (normal to the disk thickness direction) birefnngence. The ellipsometric methods are difficult to be set up for measuring inplane birefringence, although it is quite efficient and accurate. Another method,5 using disk tester system to measure both in-plane and normal-to-plane birefringence, is only applicable of using in reflective type disk substrates. The relationship of readout signal and birefnngence of a disk substrate is first derived using Jones matrix in this paper. Both in-plane and normal-to-plane birefnngences ofMO disk substrates are then presented, as measured by the conventional and adaptive method proposed in this study. The data are then applied toward assessing the figure of merits. The implementation as a tool for the fabrication process control of disk substrates is also described.
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