Optical biosensors based in the fluorescence resonance energy transfer (FRET) phenomenon require of fluorophores. The use of fluorophores requires of a complex optical system that often leads to signal loss. Thus, a new approach based in a Black Hole Quencher (BHQ) that further simplifies the biosensor is sought. This approach potentially increases the sensitivity and accuracy. For the development of this approach, the gliadin conjugate with BHQ-10 must be established first. In the present work, we used the physical phenomenon of FRET to study the gliadin conjugation with BHQ-10 molecule. We performed an experiment with a fluorophore (6-Carboxyfluorescein or 6-FAM) labeled aptamer and non-covalently attached to graphene oxide (GO). The gliadin from gluten was conjugated with BHQ using two different cross-linking reagents present in BHQ: BHQ-10 succinimidyl ester and BHQ-10 carboxylic acid. BHQ-10 with carboxylic acid as the cross-linking reagent demonstrated to be an efficient reaction for gliadin conjugation with BHQ-10. The average quenching efficiency obtained was 62% in comparison to the gliadin as a control experiment. This sets the basis for the breakthrough development of a simplified gluten detection biosensor based on absorbance measurements instead of different wavelength ranges as fluorophores do. The aim is to develop a point-of-care microfluidic system that measures gliadin from gluten in a sensitive, accurate and cost-efficient manner.
Picosecond pulsed laser source have applications in areas such as optical communications, biomedical imaging and supercontinuum generation. Direct modulation of a laser diode with ultrashort current pulses offers a compact and efficient approach to generate picosecond laser pulses. A fully integrated complementary metaloxide- semiconductor (CMOS) driver circuit is designed and applied to operate a 4 GHz distributed feedback laser (DFB). The CMOS driver circuit combines sub-circuits including a voltage-controlled ring oscillator, a voltagecontrolled delay line, an exclusive-or (XOR) circuit and a current source circuit. Ultrashort current pulses are generated by the XOR circuit when the delayed square wave is XOR’ed with the original square wave from the on-chip oscillator. Circuit post-layout simulation shows that output current pulses injected into an equivalent circuit load of the laser have a pulse full width at half maximum (FWHM) of 200 ps, a peak current of 80 mA and a repetition rate of 5.8 MHz. This driver circuit is designed in a 0.13 μm CMOS process and taped out on a 0.3 mm2 chip area. This CMOS chip is packaged and interconnected with the laser diode on a printed circuit board (PCB). The optical output waveform from the laser source is captured by a 5 GHz bandwidth photodiode and an 8 GHz bandwidth oscilloscope. Measured results show that the proposed laser source can output light pulses with a pulse FWHM of 151 ps, a peak power of 6.4 mW (55 mA laser peak forward current) and a repetition rate of 5.3 MHz.
A small footprint, low power, cost effective single mode fiber coupled broadband light source and spectrometer is presented. It is based on Super Luminescent Diode (SLED) devices and a compact design enables coverage of the 1250 nm-1750 nm region with a total optical power of 50 mW at the output of the fiber. This Broad Spectrum Tunable Super Luminescent (BeST-SLEDTM) light source can operate at temperatures ranging from -40°C to 60°C, and resides in a custom designed 26-pin package. The fiber is a polarization maintaining fiber with a FC/APC connector at the output. Three variations of the BeST-SLEDTM were developed, BEST-SLED™ Bands, BeST-SLEDTM Tunable and BeST-SLEDTM FTNIR. In the Bands version six SLEDs were packaged allowing for one SLED on at a time or any combination of the SLEDs on. In the Tunable version an Acoustic Optical Tunable Filter (AOTF) was integrated into the package allowing the user to select one wavelength at a time to pass into the fiber with resolution of ~1 nm @1550nm. In the FTNIR version, a Silicon Photonic based interferometer (the Nano-SpecTM) was integrated into the package for a Fourier Transform Near Infrared based Spectrometer and light source. The BeST-SLEDTM is being used in process control applications such as steam quality measurements, oil in water, gas composition and air quality monitoring.
In recent years, much effort has been invested to develop room temperature inexpensive, but sensitive, millimeter wave (MMW) and terahertz (THz) detectors that can be used as pixels in focal plane arrays, which is important for real-time imaging. A new 18×2 neon indicator lamp MMW/THz scanner was developed. The components of the camera include horizontally shifted two-column glow discharge detectors in a scanning array. The detectors, costing about 50 cents each, are wired to a preprocessing card, a VLSI board, and a motor for scanner movement. A description of the VLSI Verilog programmable hardware of the new scanner, the physical architecture, the software user interface, and imaging results at 97 GHz are presented. At this stage, the emphasis is focused on the lamp exposure time and spatial resolution when the scanning is performed horizontally. In the future it is planned to expose all pixels simultaneously for real-time imaging. New software capabilities allow the application of digital image enhancement algorithms. Fast scanning permits obtaining images in 1 to 5 s. Oversampling yields a sharper edge response and a higher signal-to-noise ratio.
The properties of terahertz (THz) radiation are well known. They penetrate well most non-conducting
media; there are no known biological hazards, and atmospheric attenuation and scattering is lower than visual
and IR radiation. Thus THz imaging is very attractive for homeland security, biological, space, and industrial
applications. In the other hand, the resolution of MMW images is lower comparing to IR and visual due to
longer wavelength. Furthermore, the diffraction effects are more noticeable in THz and MMW imaging
systems. Thus the MMW images are blurred and unclear and thus it is difficult to see the details and small
objects. In recent experimental work with 8X8 Glow Discharge Detector (GDD) Focal Plane Array (FPA) we
were able to improve the resolution of MMW images by using oversampling methods with basic DSP
algorithms.
In this work a super resolution method with basic DSP algorithms will be demonstrated using the
2X18 double row camera. MMW images with sub wavelength resolution will be shown using those methods
and small details and small objects will be observed.
KEYWORDS: Terahertz radiation, Super resolution, Sensors, Digital signal processing, Point spread functions, Staring arrays, Modulation transfer functions, Imaging systems, Metals, Lamps
The properties of terahertz (THz) radiation are well known. They penetrate well most non-conducting media; there
are no known biological hazards, and atmospheric attenuation and scattering is lower than visual and IR radiation. Thus
THz imaging is very attractive for homeland security, biological, space, and industrial applications
Recently we have found experimentally that inexpensive miniature neon indicator lamp Glow Discharge Detectors
(GDD) can be used as THz detectors. Based on the GDD we designed, constructed, and experimentally tested an 8×8
GDD array. In order to improve the performance and the resolution of the THz images a larger array is required. In this
work we use a special double row 2×18 moving array detector. The 2×18 GDD array enables us to employ scanning
method in order to obtain 36×36 pixel THz images. Furthermore, using this double row array it will be possible to
employ super resolution methods. Optical properties such as optical transfer function and measurement of point spread
function are presented, as well as first results for the 2×18 GDD array.
Development of focal plane arrays (FPA) for mm wavelength and THz radiation is presented in this paper. The FPA is
based upon inexpensive neon indicator lamp Glow Discharge Detectors (GDDs) that serve as pixels in the FPA. It was
shown in previous investigations that inexpensive neon indicator lamps GDDs are quite sensitive to mm wavelength and
THz radiation. The diameter of GDD lamps are typically 3-6 mm and thus the FPA can be diffraction limited.
Development of an FPA using such devices as detectors is advantageous since the costs of such a lamp is around 30-50
cents per lamp, and it is a room temperature detector sufficiently fast for video frame rates. Recently a new 8×8 GDD
FPA VLSI board was designed, constructed, and experimentally tested. First THz images as well as DSP methods using
this GDD FPA are demonstrated. Super resolution was achieved by moving the 8×8 pixel board appropriately in the
image plane so that 32X32 pixel images are also obtained and shown here, with much improved image quality because
of much reduced pixelization distortion.
The properties of terahertz (THz) radiation are well known. They penetrate well most nonconducting
media; there are no known biological hazards, and atmospheric attenuation and scattering is
lower than for visual and IR radiation.
Recently we have found that common miniature commercial neon glow discharge detector
(GDD) lamps costing typically about 30 cents each exhibit high sensitivity to THz radiation, with
microsecond order rise times, thus making them excellent candidates for such focal plane arrays.
Based on this technology we designed, built and tested 4X4 and 8X8 GDD focal plane arrays.
A line vector of 32 GDD pixels is being designed in order to increase the number of pixels in such
arrays and thus the image resolution. Unique large aperture quasi optic mirrors were design and tested
experimentally in this work. A new technology of light weight large aperture mirrors is proposed in this
work. In this case a metal coating on plastic substrate is demonstrated. According to first experiments
this technology proves to reliable with minimal deformation in LAB conditions. THz Images at 100
GHz were taken using this new inexpensive technology with good quality and resolution.
The recent research is focused on development of mobile vision systems and algorithms suitable for very large-scale integration implementation. These systems can be used in various applications. We propose a novel field-programmable gate array (FPGA)-based architecture for early vision. The central idea is to take into account the perceptual aspects of visual tasks inspired by biological vision systems: shape and color. For this reason, we propose an original approach based on a system implemented in an FPGA connected to a CMOS imager. The proposed algorithm implementation analysis and optimization methodology under resource constraints enable one to implement the algorithm on only one FPGA chip. To prove the proposed concept the system was implemented and tested on an autonomous mobile platform. The implementation framework enables direct algorithm implementation in application-specific integrated circuit.
KEYWORDS: Staring arrays, Terahertz radiation, Signal detection, Heterodyning, Sensors, Signal to noise ratio, Very large scale integration, Video, Switching, Picosecond phenomena
A new kind of 8×8 focal plane array (FPA) based on glow discharge detector (GDD)
elements was constructed and tested experimentally. First THz images of this FPA are presented.
The data acquisition of this system is performed with a special VLSI board designed for this system.
Previously, signal detection of the FPA elements was based upon a lock in amplifier (LIA)
which limited the rate of image formation. This was in order to detect weak signals required for
stand-off remote detection. Switching mode is necessary in order to save energy but stabilization
time of the GDD found to be 0.5 sec.
Recent investigations proved that it is possible to overcome the above timing limitations. It
was shown that heterodyne detection yielded 40 times more sensitivity than the direct detection, thus
in many circumstances obviating the need for a LIA. Moreover, GDD stabilization time of less than
1 msec was achieved.
These developments should enable video rate THz imaging using GDD FPAs.
The advantages of terahertz (THz) imaging are well known. They penetrate well most
non-conducting media and there are no known biological hazards, This makes such
imaging systems important for homeland security, as they can be used to image
concealed objects and often into rooms or buildings from the outside. There are also
biomedical applications that are arising. Unfortunately, THz imaging is quite
expensive, especially for real time systems, largely because of the price of the
detector. Bolometers and pyroelectric detectors can each easily cost at least hundreds
of dollars if not more, thus making focal plane arrays of them quite expensive.
We have found that common miniature commercial neon indicator lamps costing
typically about 30 cents each exhibit high sensitivity to THz radiation [1-3], with
microsecond order rise times, thus making them excellent candidates for such focal
plane arrays. NEP is on the order of 10-10 W/Hz1/2. Significant improvement of
detection performance is expected when heterodyne detection is used
Efforts are being made to develop focal plane array imagers using such devices at 300
GHz. Indeed, preliminary images using 4x4 arrays have already been obtained. An
8x8 VLSI board has been developed and is presently being tested. Since no similar
imaging systems have been developed previously, there are many new problems to be
solved with such a novel and unconventional imaging system.
These devices act as square law detectors, with detected signal proportional to THz
power. This allows them to act as mixers in heterodyne detection, thus allowing NEP
to be reduced further by almost two orders of magnitude.
Plans are to expand the arrays to larger sizes, and to employ super resolution
techniques to improve image quality beyond that ordinarily obtainable at THz
frequencies.
Two possible system integration approaches for portable real time cytometry in microfluidic applications are discussed. An ocular mounted linear CMOS image sensor configured for real time detection of particles being transported in microfluidic channels is first described. This system delivers cytometry functionality utilizing standard microfluidic chips and conventional optics. While this approach affords a certain ease of integration, one significant drawback is the singular field of view onto the microfluidic substrate and the reliance on conventional microscopy. However, the microscopy resolution makes possible a simple device capable of determining precise position, size and trajectory information on a per particle basis. A second architecture comprises flip-chip integration of a custom CMOS active pixel sensor aboard a custom microfluidic glass substrate. At the expense of optical resolution, the near field sensor topology obviates the need for conventional microscopy, affords simultaneous multi-channel sensing and takes strides towards cost effective micro total analysis system (uTAS) deployment. The two platforms share a common microcontroller for processing, control and display as well as a unified host-side application programming interface; an approach which will enable side-by-side comparison of the two hardware architectures in real time. The common user interface, a platform independent .NET application, deploys to both desktop and compact framework pocket PC platforms.
KEYWORDS: Photodiodes, CMOS technology, Standards development, Diffusion, Data modeling, Signal processing, Imaging systems, Palladium, Very large scale integration, Near field optics
This work shows the progress and demonstrates the measurements performed via a unique submicron scanning system developed at the VLSI systems center in Ben-Gurion University.
The system enables the combination of near-field optical and atomic force microscopy measurements with the standard electronic analysis. The obtained signal, i.e., the electrical outcome at each point as a function of the spot position provides a 2D signal map of the pixel response, representing the full 3D charge distribution in the device.
This work present the results obtained by thorough scanning of several various pixel topologies of CMOS APS chips fabricated in two different CMOS technologies (the standard 0.5μm and 0.35μm CMOS technologies).
We demonstrate that our system use enables a detailed, point by point, quantitative determination of the contributions to the total output signal from each particular region of the pixel. It makes possible to understand the influence of the each component composing the pixel (e.g., logic transistors, metal lines, etc.) which is extremely important for CMOS APS where the pixel structure defines a fill factor of less then 100%.
A simple and robust method for expanding the dynamic range of the readout circuits for uncooled microbolometer infrared sensor arrays is presented. The proposed method allows a reduction in the number of bits required for microbolometer nonuniformity compensation, significantly reducing the complexity of the pre-integration compensation circuity.
KEYWORDS: Optical tracking, Visualization, Virtual colonoscopy, Transistors, Signal processing, Image processing, Mirrors, Very large scale integration, Binary data, Digital electronics
A simple adaptive thresholding circuit for visual attention and tracking applications is presented. When used in visual attention systems or in tracking systems, the circuit allows "background" inhibition and false alarm reduction. A test chip with an eight-element adaptive thresholding circuit has been implemented in a standard 0.5-µm CMOS process and is operated via a 3.3-V supply in the saturation region. The circuit architecture is discussed, operation in saturation and subthreshold regions are explained, and measurements from a test chip are reported.
KEYWORDS: Photodiodes, Diffusion, Point spread functions, Imaging systems, Sensors, Modulation transfer functions, Process modeling, Silicon, Absorption, Active sensors
This paper presents the pioneer use of our unique Sub-micron Scanning System (SSS) for point spread function (PSF) and crosstalk (CTK) measurements of focal plane CMOS Active Pixel Sensor (APS) arrays. The system enables the combination of near-field optical and atomic force microscopy measurements with the standard electronic analysis. This SSS enables full PSF extraction for imagers via sub-micron spot light stimulation. This is unique to our system. Other systems provide Modulation Transfer Function (MTF) measurements, and cannot acquire the true PSF, therefore limiting the evaluation of the sensor and its performance grading. A full PSF is required for better knowledge of the sensor and its specific faults, and for research - to enable better optimization of pixel design and imager performance.
In this work based on the thorough scanning of different “L” shaped active area pixel designs (the responsivity variation measurements on a subpixel scale) the full PSF was obtained and the crosstalk distributions of the different APS arrays are calculated. The obtained PSF points out the pronounced asymmetry of the diffusion within the array, mostly caused by the certain pixel architecture and the pixels arrangement within the array. We show that a reliable estimate of the CTK in the imager is possible; the PSF use for the CTK measurements enables not only its magnitude determination (that can be done by regular optical measurements), but also to discover its main causes, enabling the design optimization per each potential pixel application.
This paper addresses the problem of wide dynamic range scenes and presents a new method of compressing the dynamic range of wide dynamic range scenes. This method is based on the Multiscale Retinex Algorithm. The paper presents the performance of the Multiscale Retinex Algorithm on wide dynamic range pictures. Two modifications that enhance the results obtained with the original Multi Scale Retinex algorithm for wide dynamic range pictures are proposed. The first modification is obtained by the recombination of the resulting image with the original picture in a certain weight. The second modification is achieved by adjusting the histogram of the resulting picture. The modifications improve the results of the original Multi Scale Retinex Algorithm in a way that retains the global contrast of brightness and the natural impression of the resulting image. The paper explores the performance of this modified algorithm on different wide dynamic range scenes and points out its advantages over other dynamic range compression algorithms.
This work presents an empirical dark current model for CMOS Active Pixel Sensors (APS). The model is based on experimental data taken of a 256 X 256 APS chip fabricated via HP in a standard 0.5 micrometers CMOS technology process. This quantitative model determines the pixel dark current dependence on two contributing factors: the 'ideal' dark current determined by the photodiode junction, introduced here as a stable shot noise influence of the device active area, and a leakage current due to the device active area shape, i.e., the number of corners present in the photodiode and their angles. This part is introduced as a process induced structure stress effect.
KEYWORDS: Modulation transfer functions, Sensors, Point spread functions, Active sensors, CCD image sensors, Signal to noise ratio, Optical engineering, CMOS sensors, Charge-coupled devices, Image sensors
In this paper, we present results of the investigation of the design and operation of CMOS active pixel sensors for detection of ultra-low light levels. We present a detailed noise model of APS pixel and signal chain. Utilizing the noise model, we have developed APS pixel designs that can achieve ultra-low noise and high responsivity. We present results from two test chips, that indicate (1) that less than 5 electrons of read noise is possible with CMOS APS by reducing the size of the pixel transistors, and (2) that high responsivity can be achieved when the fill-factor of the photodiode is reduced.
KEYWORDS: Stars, Space operations, Cameras, Camera shutters, Navigation systems, Charge-coupled devices, Imaging systems, Data acquisition, Analog electronics, Image sensors
Reducing mass and power demands from engineering and science image sensors, while improving system capability, remains a driving force in the development of Sciencecraft components. The Jet Propulsion Lab (JPL) is developing advanced concepts for future spacecraft celestial trackers by incorporating active pixel sensor (APS) array technology into star and feature tracker designs. We describe fundamental APS array properties and characteristics, and discuss recent progress in APS designs directly applicable to next generation trackers. A description of a new regional electronic shutter design providing extremely high dynamic range and local shuttering capability is given along with test results from a prototype device. A new star and feature tracker concept enabled by this regional shuttering capability is described.
Design considerations and description of a CMOS Active Pixel image sensor (APS) star tracker are reported. APS technology has been thought of being most appropriate for guidance and navigation. However, making APS useful for future star tracker missions means a few challenges have to be overcome. A wider dynamic range is required, while fill factor ought to be high and simple geometry of the pixel active area is desired. These requirements are analyzed and tradeoff considerations are explained for a practical future celestial tracker. A 64 X 64 element CMOS APS array with individual pixel reset is described.
A biologically—inspired modification to MAXNET is proposed. Unlike the original net where the weights are constant, the weights in the new net are dynamically changed. Consequently, the modified net achieves a drastic improvement in convergence rate. A simple hardware implementation for the modified net is presented.
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