KEYWORDS: Amplifiers, Signal detection, Sensors, Linear filtering, Optical amplifiers, Optoelectronics, Interference (communication), CMOS sensors, Signal to noise ratio, Phase shifts
We have designed dual lock-in amplifier (LIA) circuits in 0.18 μm CMOS technology for antibody-antigens
(IgG) detection using optoelectronics. The purpose of this work is to develop a lock-in amplifier integrated circuit (IC)
using the dual phase scheme that detect the phase difference between the input signal and the reference signal although a
phase shifter is absent. Our LIA consist of high gain amplifier, signal amplifier, and phase sensitive detection. Amplifier
structure is based on two-stage differential operational amplifier (op-amp) with RC Miller compensation technique. By
using the RC Miller compensation technique, we obtain 60° the phase margin of the op-amp. Here, the resistor works for
increasing the unit gain bandwidth and the capacitor works for increasing the phase margin. The lock-in amplifier
consume 8.6 mA from a 1.8 V supply.
KEYWORDS: Signal detection, Interference (communication), Linear filtering, Biosensors, Switches, Sensors, Modulation, Signal to noise ratio, Photodetectors, Amplifiers
Recently, a number of portable biosensors have been developed to check the health condition of human beings
regardless of time and place. Though those sensors have a merit of a handy one, the signals are inevitably measured with
intensive background noises. In order to detect a weak signal concealed in intensive background noises such as Johnson
noise, 1/f noise, and shot noise, a special technique is essentially required. As of a special technique, the lock-in
detection method is able to minimize the effects of these noises using modulated signal and reference signals. Previously,
we applied the lock-in detection method to infrared detection system. The sensitivity of this system was decided by the
1/f noise at the photodetector. In this work, we have demonstrated the portable bio-sensor system using high frequency
infrared laser diode and photodetector. Therefore, the main signal of interest may keep away from the effect of the 1/f
noise with hybrid-type highly sensitive lock-in detection module. This technique provides the minimum detection range
of 3 mV and the dynamic range of 25.8 dB at the noise level of 120 mV.
Portable bio-optical systems have required not only small size but also high sensitive and precise detection technique.
To achieve high sensitivity, portable bio-optical systems should be set up to minimize the effects of noises such as
Johnson noise, 1/f noise, shot noise etc. In order to reduce the influence from these noises, we have applied a novel lock-in
detection technique. The lock-in detection technique is able to effectively suppress these noises as choosing a
frequency high enough to avoid 1/f noise and low enough to avoid parasitic noises occurred on high frequency. We use
lock-in detection technique with a simple structure - several op-amplifiers and MOSFETs. Using the lock-in scheme, we
recovered signals in the presence of overwhelming background noises without applying multistage amplifiers and filters.
This technique provides high resolution measurements of relatively clean signals over several orders of magnitude and
frequency by compared with conventional detection method. We have demonstrated portable bio-optical system using
infrared LED and PD with our hybrid type lock-in detection module.
KEYWORDS: Resonators, Signal to noise ratio, Refractive index, Waveguides, Optical microcavities, Sensors, Biosensors, Signal detection, Data acquisition, LCDs
We have demonstrated a novel bio-signal processing technique with hybrid bio-systems using an optical microcavity
ring resonator. The intensity of the transmitted light through the ring resonator has a periodic and sensitive region
depending on the wavelength of the incident light into the ring resonator. It is possible to detect biomolecules with the
ring resonator, because the resonance profile is shifted by refractive index changes due to an amount of biomolecules on
the surface of sensing areas. Our processing technique is based on using dual-wavelength. In this scheme, high accuracy
can be achieved by comparing the intensity of two incident lights which has channel spacing of the half period of the
sensitive region. More detailed experimental results on a novel bio-signal processing technique will be presented.
We developed a CMOS-based trans-impedance amplifier (TIA) circuits for analog optical
communication systems. Our TIA structure is based on common-source configuration and a novel functional
active load (FAL). Proposed FAL structure is composed the two PMOSs that have the symmetric structure. In
those schemes, transfer curve of TIA can be tuned by the gate voltage of FAL in the way to improve linearity.
In analog optical transceiver, TIA employing the FAL can suppress the nonlinearity originated from various
sources. Because the nonlinearity deteriorate analog communication systems, enhancement of linearity is
crucial to improve the analog transceiver performances. In this work, we have designed the TIA with FAL in a
0.18 &mgr;m CMOS technology. The linearity of TIA is controlled by the variation of transfer curve with the
change of the FAL bias voltage. As of the simulation results, the IIP3 level of the TIA employing FAL is
enhanced by about 3.393 dB with the Vg variation in FAL.
Latching optical switches and optical logic gates with AND or OR, plus the INVERT functionality are demonstrated for
the first time by the monolithic integration of a single and differential typed vertical cavity lasers with depleted optical
thyristor (VCL-DOT) structure with a low threshold current of 0.65 mA, a high on/off contrast ratio of more than 50 dB,
a high slope efficiency of 0.38 mW/mA, and high sensitivity to input optical light. By simply changing a reference
switching voltage, this single-typed device operates as two logic functions, optical logic AND and OR. The differential-typed
VCL-DOTs operate also as all logic gates, AND/NAND, OR/NOR, and INVERT function by simple change of a
reference input light power. The thyristor laser fabricated by using the oxidation process shows a high optical output
power efficiency and a high sensitivity to the optical input light.
We have proposed a new model of the rate equation for laser diode performance analysis. A modulated signal of LD is analyzed by the rate equation using the finite difference method (FDM) in time domain. For the analysis of modulated optical signal, an injection current term in the rate equation is altered to an appropriated electrical function. L-I curve, intensity modulation frequency response, and nonlinearity of laser diodes are analyzed by the proposed rate equation model. The proposed model can be applied to determine the operating point of LD and to design the analog optical transmitter.
We propose the optical transceiver having reference clock generator and CDR with delayed data topology in this paper. The 125MHz reference clock of optical transmitter have been extracted from 10 × 250 Mb/s data arrays. The clock extraction of reference clock generator is achieved by summing the edge information of the each data. Moreover, our optical transmitter includes 2-stacks NMOS serializer scheme rather than 3-stacks conventional scheme to achieve high speed operation. In optical receiver design, we employ a novel CDR with delayed data topology to overcome the problems in conventional CDR such as instability in locking state, nonlinearity output proportional to phase difference, false locking at harmonic frequency. The optical transceiver is designed by using of 0.35μm CMOS technology.
We propose a new model of the rate equation for the time domain analysis. A modulated signal is analyzed by the rate equation using the finite difference method (FDM) in time domain. For the analysis of modulated optical signal, an injection current term in the rate equation is altered to an appropriated electrical term either for analog or digital signal. The bandwidth, transmission characteristics and nonlinearity of laser diodes are analyzed by the proposed rate equation model.
Optical interconnection is recent issue for high-speed data transmission. The limitation of high-speed electrical data transmission is caused by impedance mismatching, electric field coupling, microwave loss, and different length of the electrical signal lines. To overcome these limitations, the electrical signal in the current electrical system has to be changed by the optical signal. The most suitable optical source in the OPCB (Optical Printed Circuit Board) is VCSEL (Vertical Cavity Surface Emitting Lasers) that is low-priced and has the characteristic of vertical surface emitting.
In this paper, we propose an electrical model of the VCSEL as E/O converting devices for the OPCB. The equivalent circuit of the VCSEL based on the rate equations includes carrier dynamics and material properties. The rate equation parameters are obtained by full analysis based on rate equation and experiment results. The electrical model of the VCSEL has the series resistance determined by I-V characteristic curve, and the parallel capacitance by the parasitic response of the VCSEL chip. The bandwidth of the optical interconnection is analyzed considering those parameters. We design and fabricate the optical transmitter for OPCB considering proposed electrical model of VCSEL.
This paper presents a new approach of combining real video and synthetic objects. The purpose of this work is to use the proposed technology in the fields of advanced animation, virtual reality, games, and so forth. Computer graphics has been used in the fields previously mentioned. Recently, some applications have added real video to graphic scenes for the purpose of augmenting the realism that the computer graphics lacks in. This approach called augmented or mixed reality can produce more realistic environment that the entire use of computer graphics. Our approach differs from the virtual reality and augmented reality in the manner that computer- generated graphic objects are combined to 3D structure extracted from monocular image sequences. The extraction of the 3D structure requires the estimation of 3D depth followed by the construction of a height map. Graphic objects are then combined to the height map. The realization of our proposed approach is carried out in the following steps: (1) We derive 3D structure from test image sequences. The extraction of the 3D structure requires the estimation of depth and the construction of a height map. Due to the contents of the test sequence, the height map represents the 3D structure. (2) The height map is modeled by Delaunay triangulation or Bezier surface and each planar surface is texture-mapped. (3) Finally, graphic objects are combined to the height map. Because 3D structure of the height map is already known, Step (3) is easily manipulated. Following this procedure, we produced an animation video demonstrating the combination of the 3D structure and graphic models. Users can navigate the realistic 3D world whose associated image is rendered on the display monitor.
KEYWORDS: Video, Motion estimation, Cameras, 3D image processing, Image processing, Linear filtering, 3D vision, Video processing, Visualization, 3D displays
We present a new method for converting monoscopic video to stereoscopic video. The key characteristic of our proposed method is that it can process non-horizontal camera/object motion existing in most of image scenes. It is well known that the non-horizontal motion causes the vertical parallax to human eyes and accordingly visual discomfort. The proposed methodology is composed of four major steps. First, given a current video frame, we estimate a motion vector for each block by a conventional block matching motion estimation algorithm. The motion vector is composed of horizontal and vertical disparities. Second, the norm of the motion vector is computed for each block. Here, the vertical disparity is eliminated due to the usage of the norm of the motion vector. Due to the unreliability of estimated motion vectors, a low-pass filter is performed on the norm of the motion vector in order to enhance the reliability. Third, each block is shifted to the horizontal direction by the norm of the motion vector, which is transformed to binocular parallax. The shift of blocks in the horizontal direction eliminates the effects of the vertical disparity. Finally, all the shifted blocks are synthesized and a synthesized image is then generated. A stereoscopic image pair being composed of the original image and its associated synthesized image is produced. With proper 3D viewing devices, users can feel 3D depth from seeing the stereoscopic image. Preliminary experiments have demonstrated that stable stereoscopic image pairs can be produced by applying our proposed method to a variety of monoscopic video with non-horizontal camera panning and/or object motion.
Humans subjectively evaluate the content of a scene. FOr content-based indexing and retrieval, we index and retrieve the scene containing moving objects because they remain in our memory longer than static scene. The importance of processing moving objects has been demonstrated in image compression, content-based data processing, and a variety of video processing techniques. This paper proposes the method of segmenting and then compressing the image including moving objects. The image scene is usually composed of the motion region (MR) and static region (SR). For simplicity, the camera motion region is assigned to the SR, because the region has similar characteristics with the SR. The MR is extracted by our segmentation technique. We propose a line scan-based segmentation method being composed of motion estimation and label assignment. The dominant region owning the largest number of blocks with the same label is classified as SR. The region excluding the SR is MR. Then, the MR is processed by lossless compression or lossy with low-compression ratio to preserve the high quality, and the SR by a lossy method with high compression ratio. Rather than applying separate methods to MR and SR, we use a hybrid compression method based on DCT. Experiments on test video clips show the increase of the compression ratio with respect to the lossless compression and better visualization of the moving objects compared with the lossy compression.
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