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Electrical and Electronics
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Professor of Electrical Science and Engineering
Introduction
Research Interests Vision Sensors
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Now showing 1 - 10 of 47
Publication A CMOS Linear Voltage/Current Dual-Mode Imager(2006-05-01) Gruev, Viktor; Yang, Zheng; Van der Spiegel, JanWe present a CMOS image sensor capable of both voltage- and current-mode operations. Each pixel on the image has a single transistor acting as either source follower for voltage readout, or transconductor for current readout. The two modes share the same readout lines, but have their own correlated double sampling (CDS) units for noise suppression. We also propose a novel current-mode readout technique using a velocity saturated short-channel transistor, which achieves high linearity. The 300x200 image array is a mixture of 3 types of pixels with identical photodiodes and access switches; while the readout transistors are sized for their designated mode of operation. This ensures a fair comparison on the performance of the different modes.Publication A Foveated Silicon Retina for Two-Dimensional Tracking(2000-06-01) Etienne-Cummings, Ralph; Van der Spiegel, Jan; Mueller, Paul; Zhang, Mao-zhuA silicon retina chip with a central foveal region for smooth-pursuit tracking and a peripheral region for saccadic target acquisition is presented. The foveal region contains a 9 x 9 dense array of large dynamic range photoreceptors and edge detectors. Two-dimensional direction of foveal motion is computed outside the imaging array. The peripheral region contains a sparse array of 19 x 17 similar, but larger, photoreceptors with in-pixel edge and temporal ON-set detection. The coordinates of moving or flashing targets are computed with two one-dimensional centroid localization circuits located on the outskirts of the peripheral region. The chip is operational for ambient intensities ranging over six orders of magnitude, targets contrast as low as 10%, foveal speed ranging from 1.5 to 10K pixels/s, and peripheral ON-set frequencies from <0.1 to 800 kHz. The chip is implemented in 2-μm N well CMOS process and consumes 15 mW (V dd = 4 V) in normal indoor light (25 μW/cm2). It has been used as a person tracker in a smart surveillance system and a road follower in an autonomous navigation system.Publication Combined Software/Hardware Implementation of a Filterbank Front-End for Speech Recognition(2005-11-01) Mouchtaris, Athanasios; Cao, Yuan; Khan, Shehzad; Van der Spiegel, Jan; Mueller, PaulIn this paper, a cost-effective implementation of a programmable filterbank front-end for speech recognition is presented. The objective has been to design a real-time bandpass filtering system with a filterbank of 16 filters, with analog audio input and analog output. The output consists of 16 analog signals, which are the envelopes of the filter outputs of the audio signal. These analog signals are then led to an analog neural computer, which performs the feature-based recognition task. One of the main objectives has been to allow the user to easily change the filter specifications without affecting the remaining system, thus a software implementation of the filterbank was preferred. In addition, the neural computer requires analog input. Therefore, we implemented the filterbank on a PC, with the input A/D and the output D/A performed by the PC stereo soundcard. Since multiple analog outputs are necessary for the neural computer (one for each filter), it then follows that the soundcard output should contain the multiplexed 16 filter outputs, while a hardware module is needed for demultiplexing the soundcard output into the final 16 analog signals.Publication Fabrication of a Dual-Tier Thin Film Micro Polarization Array(2007-04-16) Gruev, Viktor; Ortu, Alessandro; Van der Spiegel, Jan; Lazarus, Nathan; Engheta, NaderA thin film polarization filter has been patterned and etched using reactive ion etching (RIE) in order to create 8 by 8 microns square periodic structures. The micropolarization filters retain the original extinction ratios of the unpatterned thin film. The measured extinction ratios on the micropolarization filters are ~1000 in the blue and green visible spectrum and ~100 in the red spectrum. Various gas combinations for RIE have been explored in order to determine the right concentration mix of CF4 and O2 that gives optimum etching rate, in terms of speed and under-etching. Theoretical explanation for the optimum etching rate has also been presented. In addition, anisotropic etching with 1μm under cutting of a 10μm thick film has been achieved. Experimental results for the patterned structures under polarized light are presented. The array of micropolarizers will be deposited on top of a custom made CMOS imaging sensor in order to compute the first three Stokes parameters in real time.Publication A Spectral Conversion Approach to Feature Denoising and Speech Enhancement(2005-09-01) Mouchtaris, Athanasios; Van der Spiegel, Jan; Mueller, Paul; Tsakalides, P.In this paper we demonstrate that spectral conversion can be successfully applied to the speech enhancement problem as a feature denoising method. The enhanced spectral features can be used in the context of the Kalman filter for estimating the clean speech signal. In essence, instead of estimating the clean speech features and the clean speech signal using the iterative Kalman filter, we show that is more efficient to initially estimate the clean speech features from the noisy speech features using spectral conversion (using a training speech corpus) and then apply the standard Kalman filter. Our results show an average improvement compared to the iterative Kalman filter that can reach 6 dB in the average segmental output Signal-to-Noise Ratio (SNR), in low input SNR's.Publication A Low Distortion MOS Sampling Circuit(2002-05-26) Sonkusale, Sameer R.; Van der Spiegel, JanThis paper presents a sampling technique with reduced distortion for use in a sample-and-hold circuit for high resolution analog-to-digital converters and switched capacitor filters. The technique involves bootstrapping both the gate and the bulk terminal of the sampling switch to improve linearity. Circuit implementation and SPICE level simulation results are presented.Publication Biologically Inspired Vision Sensor for the Detection of Higher-Level Image Features(2003-12-16) Van der Spiegel, Jan; Nishimura, MasatoshiThe paper briefly reviews certain aspects of the biological visual system and presents a smart vision sensor for the detection of higher-level features. The visual system processes information in a hierarchical manner starting from the retina up to the visual cortex. It decomposes the image in simple features (edges, orientation, line stops, corners, etc) using spatial and temporal information. At the higher level it integrates these primitive features, resulting in the recognition of complex objects. The sensor described in the paper is loosely modeled after the visual system and incorporates pixel level, programmable elements which extract orientation, end stops, corners and junctions from a line drawing. The architecture resembles a CNN-UM that can be programmed with a 30-bit word. The 16 x 16 pixels array detects these higher-level features in about 54 μseconds.Publication A Fully Integrated CMOS Phase-Locked Loop With 30MHz to 2GHz Locking Range and ±35 ps Jitter(2003-07-01) Xu, Chao; Laker, Kenneth R; Sargeant, Winslow; Van der Spiegel, JanA fully integrated phase-locked loop (PLL) fabricated in a 0.24μm, 2.5v digital CMOS technology is described. The PLL is intended for use in multi-gigabit-per-second clock recovery circuits in fiber-optic communication chips. This PLL first time achieved a very large locking range measured to be from 30MHz up to 2GHz in 0.24μm CMOS technologies. Also it has very low peak-to-peak jitter less than ±35ps at 1.25GHz output frequency.Publication Auditory-based speech processing based on the average localized synchrony detection(2000-06-05) Abdelatty Ali, Ahmed M; Van der Spiegel, Jan; Mueller, PaulIn this paper, a new auditory-based speech processing system based on the biologically rooted property of average localized synchrony detection (ALSD) is proposed. The system detects periodicity in the speech signal at Bark-scaled frequencies while reducing the response's spurious peaks and sensitivity to implementation mismatches, and hence presents a consistent and robust representation of the formants. The system is evaluated for its formant extraction ability while reducing spurious peaks. It is compared with other auditory-based front-end processing systems in the task of vowel recognition on clean speech from the TIMIT database and in the presence of noise. The results illustrate the advantage of the ALSD system in extracting the formants and reducing the spurious peaks. They also indicate the superiority of the synchrony measures over the mean-rate in the presence of noise.Publication Robust Classification of Stop Consonants Using Auditory-Based Speech Processing(2001-05-07) Abdelatty Ali, Ahmed M; Van der Spiegel, Jan; Mueller, PaulIn this work, a feature-based system for the automatic classification of stop consonants, in speaker independent continuous speech, is reported. The system uses a new auditory-based speech processing front-end that is based on the biologically rooted property of average localized synchrony detection (ALSD). It incorporates new algorithms for the extraction and manipulation of the acoustic-phonetic features that proved, statistically, to be rich in their information content. The experiments are performed on stop consonants extracted from the TIMIT database with additive white Gaussian noise at various signal-to-noise ratios. The obtained classification accuracy compares favorably with previous work. The results also showed a consistent improvement of 3% in the place detection over the Generalized Synchrony Detector (GSD) system under identical circumstances on clean and noisy speech. This illustrates the superior ability of the ALSD to suppress the spurious peaks and produce a consistent and robust formant (peak) representation.