Papers by Sebastián Godoy
Applied Physics Letters, Aug 4, 2014
IEEE Access
This paper proposes crowd estimation technology to help authorities make the right decisions in t... more This paper proposes crowd estimation technology to help authorities make the right decisions in times of crisis. Specifically, deep learning models have faced these challenges, achieving excellent results. In particular, the trend of using single-column Fully Convolutional Networks (FCNs) has increased in recent years. A typical architecture that meets these characteristics is the autoencoder. However, this model presents an intrinsic difficulty: the search for the optimal dimensionality of the latent space. In order to alleviate such difficulty, we propose a dual architecture consisting of two cascaded autoencoders. The first autoencoder is responsible for carrying out the masked reconstruction of the original images, whereas the second obtains crowd maps from the outputs of the first one. In this way, our architecture improves the location of people and crowds in Focal Inverse Distance Transform (FIDT) maps, resulting in more reliable count estimates concerning a single autoencoder architecture.
SPIE Proceedings, 2007
In this paper a novel nonuniformity correction method that compensates for the fixed-pattern nois... more In this paper a novel nonuniformity correction method that compensates for the fixed-pattern noise (FPN) in infrared focal-plane array (IRFPA) sensors is developed. The proposed NUC method compensates for the additive component of the FPN statistically processing the read-out signal using a noise-cancellation system. The main assumption of the method is that a source of noise correlated to the additive noise of the IRFPA is available to the system. Under this assumption, a finite impulse response (FIR) filter is designed to synthesize an estimate of the additive noise. Moreover, exploiting the fact that the assumed source of noise is constant in time, we derive a simple expression to calculate the estimate of the additive noise. Finally, the estimate is subtracted to the raw IR imagery to obtain the corrected version of the images. The performance of the proposed system and its ability to compensate for the FPN are tested with infrared images corrupted by both real and simulated nonuniformity.
2014 IEEE 57th International Midwest Symposium on Circuits and Systems (MWSCAS), 2014
A new readout integrated circuit (ROIC) for multispectral classification is presented. The ROIC i... more A new readout integrated circuit (ROIC) for multispectral classification is presented. The ROIC is designed to utilize the spectral response tunability of dot-in-a-well (DWELL) infrared photodetector to exploit the possibility of real-time onchip multispectral imaging for classification in analog domain. The unit cells are designed to include all necessary elements needed for spectral classification, including high-voltage timevarying positive and negative biases, bipolar integration, and selective sample-and-hold circuits. A test chip was designed and fabricated using TSMC's 0.35 μm high-voltage technology. The test chip has successfully completed its initial functional tests and is ready for hybridization to a DWELL focal-plane array.
Infrared Physics & Technology, 2015
Dynamic thermal imaging (DTI) with infrared cameras is a non-invasive technique with the ability ... more Dynamic thermal imaging (DTI) with infrared cameras is a non-invasive technique with the ability to detect the most common types of skin cancer. We discuss and propose a standardized analysis method for DTI of actual patient data, which achieves high levels of sensitivity and specificity by judiciously selecting pixels with the same initial temperature. This process compensates the intrinsic limitations of the cooling unit and is the key enabling tool in the DTI data analysis. We have extensively tested the methodology on human subjects using thermal infrared image sequences from a pilot study conducted jointly with the University of New Mexico Dermatology Clinic in Albuquerque, New Mexico (ClinicalTrials ID number NCT02154451). All individuals were adult subjects who were scheduled for biopsy or adult volunteers with clinically diagnosed benign condition. The sample size was 102 subjects for the present study. Statistically significant results were obtained that allowed us to distinguish between
Sensors
In this article we present the development of a biosensor system that integrates nanotechnology, ... more In this article we present the development of a biosensor system that integrates nanotechnology, optomechanics and a spectral detection algorithm for sensitive quantification of antibiotic residues in raw milk of cow. Firstly, nanobiosensors were designed and synthesized by chemically bonding gold nanoparticles (AuNPs) with aptamer bioreceptors highly selective for four widely used antibiotics in the field of veterinary medicine, namely, Kanamycin, Ampicillin, Oxytetracycline and Sulfadimethoxine. When molecules of the antibiotics are present in the milk sample, the interaction with the aptamers induces random AuNP aggregation. This phenomenon modifies the initial absorption spectrum of the milk sample without antibiotics, producing spectral features that indicate both the presence of antibiotics and, to some extent, its concentration. Secondly, we designed and constructed an electro-opto-mechanic device that performs automatic high-resolution spectral data acquisition in a waveleng...
Microprocessors and Microsystems
Infrared Physics & Technology
Sensors (Basel, Switzerland), Jan 12, 2018
Gold nanoparticles (AuNPs) are currently under intense investigation for biomedical and biotechno... more Gold nanoparticles (AuNPs) are currently under intense investigation for biomedical and biotechnology applications, thanks to their ease in preparation, stability, biocompatibility, multiple surface functionalities, and size-dependent optical properties. The most commonly used method for AuNP synthesis in aqueous solution is the reduction of tetrachloroauric acid (HAuCl₄) with trisodium citrate. We have observed variations in the pH and in the concentration of the gold colloidal suspension synthesized under standard conditions, verifying a reduction in the reaction yield by around 46% from pH 5.3 (2.4 nM) to pH 4.7 (1.29 nM). Citrate-capped AuNPs were characterized by UV-visible spectroscopy, TEM, EDS, and zeta-potential measurements, revealing a linear correlation between pH and the concentration of the generated AuNPs. This result can be attributed to the adverse effect of protons both on citrate oxidation and on citrate adsorption onto the gold surface, which is required to form ...
Biomedical optics express, 2017
Skin cancer is the most common cancer in the United States with over 3.5M annual cases. Presently... more Skin cancer is the most common cancer in the United States with over 3.5M annual cases. Presently, visual inspection by a dermatologist has good sensitivity (> 90%) but poor specificity (< 10%), especially for melanoma, which leads to a high number of unnecessary biopsies. Here we use dynamic thermal imaging (DTI) to demonstrate a rapid, accurate and non-invasive imaging system for detection of skin cancer. In DTI, the lesion is cooled down and the thermal recovery is recorded using infrared imaging. The thermal recovery curves of the suspected lesions are then utilized in the context of continuous-time detection theory in order to define an optimal statistical decision rule such that the sensitivity of the algorithm is guaranteed to be at a maximum for every prescribed false-alarm probability. The proposed methodology was tested in a pilot study including 140 human subjects demonstrating a sensitivity in excess of 99% for a prescribed specificity in excess of 99% for detectio...
International journal of pharmaceutics, Jan 24, 2017
Plume characteristics, such as temperature and velocity, emitted from pMDIs could significantly a... more Plume characteristics, such as temperature and velocity, emitted from pMDIs could significantly affect the dose delivered to the lung. Currently, high speed cameras and thermocouples are used separately to evaluate these parameters. We used a low-noise infrared camera to evaluate both the temperature and velocity of the emitted plume from pMDIs. Additionally, we investigated whether the fine particle fraction (FPF) is affected when time between actuations is varied. We tested three different albuterol sulfate pMDIs: ProAir(®) HFA, Proventil(®) HFA, and Ventolin(®) HFA. The plume and aerodynamic characteristics from these pMDIs were evaluated, after varying the time between actuations (15, 30, 60, and 120s), using the infrared camera and a next generation impactor, respectively. The aerodynamic characteristics were evaluated with and without a valved holding chamber (VHC). ProAir HFA had the softest plume followed by Proventil HFA and Ventolin HFA. Further, Ventolin HFA was slightly ...
Infrared Remote Sensing and Instrumentation XXI, 2013
ABSTRACT There is an increasing interest in the development of high operating temperature (HOT) d... more ABSTRACT There is an increasing interest in the development of high operating temperature (HOT) detectors with InAs/Ga(In)Sb Type-II superlattice (T2-SL) material systems. A wide variety of unipolar barrier structures have been investigated and successfully implemented in low-noise device architectures. In this paper, some of our recent work on the development of HOT mid-IR (MWIR) T2-SL photodetectors with interband cascade schemes will be summarized. In these structures, the discrete InAs/GaSb SL absorbers are sandwiched between quantum-engineered electron and hole barriers, which facilitate photovoltaic operation and efficient photo-carrier extraction. Even at its initial stage of development, such an advanced design has led to the demonstration of mid-IR photodetectors with background-limited operation above 150 K (300 K, 2π field-of-view), as well as above room temperature zero-bias operation. Further understanding of the device operation and design principles will also be discussed.
ABSTRACT Purpose: This study demonstrated the variations in emitted dose when the time interval b... more ABSTRACT Purpose: This study demonstrated the variations in emitted dose when the time interval between individual actuations was altered for commonly used pressurized metered dose inhalers (pMDI’s). This variability could potentially affect the quality, handling, use, efficacy and compliance of pMDIs. Methods: The fine particle mass (FPM) of the aerosol droplets discharged from three pMDI’s (Proventil® HFA, Proair® HFA, Ventolin HFA®) was assessed using a next generation cascade impactor. The studies were performed with and without a valved holding chamber (VHC) after varying the time between multiple actuations. After 10 actuations (each actuation separated by 15, 30, 60 or 120 seconds) the deposited particles were quantified spectrophotometrically. The temperature and velocity (of the leading edge) of the aerosol plume was measured using a high-speed longwave IR Camera for the three inhalers after varying the time between actuations. Three black-body sources at different temperatures were utilized to perform a three-point calibration of the collected imagery in order to measure the plume temperature. Results: A significant increase in the FPM was observed when the time between actuation was increased from 15 s to 120 s for ProAir HFA (without VHC), Proventil HFA (VHC) and Ventolin HFA (VHC and no VHC). ProAir HFA (0.22 s) is the softest plume followed by Proventil HFA (0.18 s) and Ventolin HFA (0.11 s). The spray velocity showed that Ventolin HFA and Proventil HFA were at their highest velocity at 60s between actuations. Conclusions: Our in vitro studies indicate that the emitted dose can vary significantly for commercial pMDI’s by changing the time between actuations. We also showed subtle temperature and spray velocity alterations in the emitted aerosol by using an IR camera. These changes could be due to either the differences between the formulation and/ or the actuator portion of individual inhalers.
Infrared Technology and Applications XXXIX, 2013
ABSTRACT Over the last several years, owing to the implementation of advanced device architecture... more ABSTRACT Over the last several years, owing to the implementation of advanced device architectures, antimony-based type-II superlattice (T2-SL) infrared (IR) photodetectors and their focal plane arrays (FPAs) have achieved significant advancements. Here we present our recent effort towards the development of high operating temperature (HOT) mid-IR (MWIR) photodetectors, which utilizes an interband cascade scheme with discrete InAs/GaSb SL absorbers, sandwiched between electron and hole barriers. This low-noise device architecture has enabled background-limited operation above 150 K (300 K, 2π field-of-view), as well as above room temperature response in the mid-IR region. The detector yields a dark current density of 1.10×10-7 A/cm2 (1.44×10-3 A/cm2) at -5 mV, and a Johnson-limited D* of 2.22×1011 cmHz1/2/W (1.58×109 cmHz1/2/W) at 150 K (room temperature) and 3.6 μm, respectively. In this presentation, we will discuss the operation principles of the interband cascade design and our most recent progress in MWIR photodetectors toward high operating temperatures.
2013 IEEE Photonics Conference, 2013
ABSTRACT In recent years, type-II InAs/GaSb superlattices (T2-SLs) have demonstrated dramatic adv... more ABSTRACT In recent years, type-II InAs/GaSb superlattices (T2-SLs) have demonstrated dramatic advances and are a serious contender for the high performance infrared (IR) imaging market. The improved understanding of the material properties, as well as the implantation of advanced device architectures, has substantially improved the device performance. Here we will report our efforts to develop mid-IR type-II T2-SL photodetectors and focal plane arrays based on interband cascade structure. The interband cascade photodetector exploits the energy band alignment in the nearly lattice-matched “6.1-Å-family” (InAs, GaSb, AlSb, and their alloys) material system. The InAs/GaSb T2-SL is adopted as the absorber, and two unipolar barriers are placed at each side of the absorber.
IEEE Photonics Conference 2012, 2012
ABSTRACT A novel compressive edge-detection algorithm for spectral imagery is demonstrated using ... more ABSTRACT A novel compressive edge-detection algorithm for spectral imagery is demonstrated using real long-wave spectral imagery. The idea of the algorithm is based on identifying joint spatial and spectral features via statistical learning.
Lecture Notes in Computer Science, 2012
In this paper, we use the recently presented wavelet-FFT filter [1] to reduce the nonuniformity n... more In this paper, we use the recently presented wavelet-FFT filter [1] to reduce the nonuniformity noise that affect almost all infrared imaging systems. The wavelet-FFT filter was originally developed to compensate the onedimensional noise known as stripping noise. We perform an extension of this methodology in order to compensate the two-dimensional noise that degrades infrared imagery. The principal hypothesis of this work is that the twodimensional focal-plane array can be considered as the composition of vertical and horizontal one-dimensional array sensors. Under this assumption we use a specific design of the wavelet filter to synthesize a replica of the twodimensional noise and then recover the real incident radiation. The method is evaluated using real mid-and long-wave infrared data from two cameras. The results show the promising performance of the wavelet-FFT filter when is applied in infrared imaging system such as self heating effect.
IEEE Transactions on Image Processing, 2000
Two model-based algorithms for edge detection in spectral imagery are developed that specifically... more Two model-based algorithms for edge detection in spectral imagery are developed that specifically target capturing intrinsic features such as isoluminant edges that are characterized by a jump in color but not in intensity. Given prior knowledge of the classes of reflectance or emittance spectra associated with candidate objects in a scene, a small set of spectral-band ratios, which most profoundly identify the edge between each pair of materials, are selected to define a edge signature. The bands that form the edge signature are fed into a spatial mask, producing a sparse joint spatiospectral nonlinear operator. The first algorithm achieves edge detection for every material pair by matching the response of the operator at every pixel with the edge signature for the pair of materials. The second algorithm is a classifier-enhanced extension of the first algorithm that adaptively accentuates distinctive features before applying the spatiospectral operator. Both algorithms are extensively verified using spectral imagery from the airborne hyperspectral imager and from a dots-in-a-well midinfrared imager. In both cases, the multicolor gradient (MCG) and the hyperspectral/spatial detection of edges (HySPADE) edge detectors are used as a benchmark for comparison. The results demonstrate that the proposed algorithms outperform the MCG and HySPADE edge detectors in accuracy, especially when isoluminant edges are present. By requiring only a few bands as input to the spatiospectral operator, the algorithms enable significant levels of data compression in band selection. In the presented examples, the required operations per pixel are reduced by a factor of 71 with respect to those required by the MCG edge detector.
IEEE Journal of Quantum Electronics, 2000
We report on a systematic study of the effect of barriers on quantum dots-in-a-well infrared phot... more We report on a systematic study of the effect of barriers on quantum dots-in-a-well infrared photodetectors. Four devices are fabricated and characterized with varying composition for barriers adjacent to quantum dots and away from quantum dots. Effects of these "proximity" and "remote" barriers are studied by comparing photoluminescence, responsivity, dark current, background-limited operating temperature, activation energy, and detectivity. The growth mechanism for a conformal coverage of quantum dots with proximity barriers is described and supported with reflection high-energy electron diffraction and transmission electron microscopy images. It is shown that proximity barriers and remote barriers influence the characteristics of the detector very differently, with increases in proximity barrier energy leading to higher responsivity and lower dark current, while remote barriers reduce the responsivity and dark currents simultaneously. It is demonstrated that confinement enhancing barriers as proximity barriers optimize the SNR at low bias range, suitable for focal plane array applications.
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Papers by Sebastián Godoy