In this paper we analyze the necessity of design of low temperature readout circuit. Since the photodetector should work in low temperature environment, it is necessary for the readout circuit with low temperature readout function. Meanwhile, the influence factors of ultra - low temperature on the CMOS readout circuit are analyzed. The main influencing factors are carrier freezing analysis, current mutation (Kink) and mobility change. Finally, we used JANIS SHI-4-2 liquid helium cycle refrigeration system as a refrigeration instrument, and do the test for the readout circuit at ultra -low-temperature. When the temperature of cold head of the cooling system reach to the minimum temperature (4.85K) and maintain 5 hours, Si substrate’ temperature reaches the minimum temperature (50.1K). By adjusting the static operating point voltage, we find that the circuit still works well.
In this paper, we studied the structure characteristics of quantum dots-quantum well photodetector with response wavelength range from 400 nm to 1000 nm. It has the characteristics of high sensitivity, low dark current and the high conductance gain. According to the properties of the quantum dots-quantum well photodetectors, we designed a new type of capacitive transimpedence amplifier (CTIA) readout circuit structure with the advantages of adjustable gain, wide bandwidth and high driving ability. We have implemented the chip packaging between CTIA-CDS structure readout circuit and quantum dots detector and tested the readout response characteristics. According to the timing signals requirements of our readout circuit, we designed a real-time spectral data acquisition system based on FPGA and ARM. Parallel processing mode of programmable devices makes the system has high sensitivity and high transmission rate. In addition, we realized blind pixel compensation and smoothing filter algorithm processing to the real time spectrum data by using C++. Through the fluorescence spectrum measurement of carbon quantum dots and the signal acquisition system and computer software system to realize the collection of the spectrum signal processing and analysis, we verified the excellent characteristics of detector. It meets the design requirements of quantum dot spectrum acquisition system with the characteristics of short integration time, real-time and portability.
In this paper, 64 pixels pulse frequency modulation (PFM) capacitive transimpedence amplifier (CTIA) readout integrated circuit (ROIC) for quantum effect photodetector is designed. The ROIC designed with 0.35 μm 2P4M technology achieves 1.24 Ge- large charge handling with 50 fF small integration capacitor and 64 mW power consumption by pulse frequency modulation (PFM) technique. Compared to conventional integrated circuits, it has many advantages of anti-saturation, over 120 dB dynamic range (DR) realized by 10-bit counter, and can sense an input current range from few pA to few μA.
Hyperspectral imaging is an emerging imaging modality for medical applications. It provides more information than traditional optical image for owning two spatial dimensions and one spectral dimension. Multi dimension information of hyperspectral images can be used to classify different tissues and cells, while it’s difficult to distinguish them by traditional methods. The processing method presented in this paper is composed of two main blocks: Support Vector Machine (SVM) algorithm is adopted to identify different components of blood cells through the spectral dimension. In order to make it easy for blood cell counting, some morphological processing methods are used to process images through the spatial dimensions. This strategy, applying SVM and morphological processing methods, has been successfully tested for classifying objects among erythrocytes, leukocytes and serums in raw samples. Experimental results show that the proposed method is effective for red blood cells identification.
A direct spatial and spectral observation of CdSe and CdSe/CdS quantum dots (QDs) as probes in live cells is performed by using a custom molecular hyperspectral imaging (MHI) system. Water-soluble CdSe and CdSe/CdS QDs are synthesized in aqueous solution under the assistance of high-intensity ultrasonic irradiation and incubated with colon cancer cells for bioimaging. Unlike the traditional fluorescence microscopy methods, MHI technology can identify QD probes according to their spectral signatures and generate coexpression and stain titer maps by a clustering method. The experimental results show that the MHI method has potential to unmix biomarkers by their spectral information, which opens up a pathway of optical multiplexing with many different QD probes.
The novel photodetector array has a specific inner multiplication mechanism at low bias voltage in the weak light environment. High current gains are achieved and accompanied by extremely low dark currents. The photocurrent spectrum of the photodetector shows excellent light absorption in visible spectrum (VIS) and near infrared spectrum (NIRS), ranging from 500nm up to 900nm. Capacitor feedback trans-impedance amplifier (CTIA) readout circuit has been designed to acquire the integration voltage of photocurrent with wide wavelength range. Weak light experiments have measured the response voltage is 4mV@0.01pW illumination and 100μs integration time at 300K. The responsivity reaches 4×1011V/W. A high sensitivity spectrometer based on the photodetector array and readout circuit is developing and will be applied to weak signal detection in the fields of the environmental monitoring and biomedicine science.
Hyperspectral blood image has been utilized in biomedical field for a period of time. However, identifying and segmenting blood cells is still a tricky issue. Thus, this paper proposed a new method based on support vector machine (SVM) to solve this issue from hyperspectral images. Then post-processing of holes-filling and noise removing are performed on the segmented results to get completed cell. The experimental results proved the accuracy and accommodation for this new proposed method.
Spectral imaging is a technology that integrates conventional imaging and spectroscopy to get both spatial and spectral information from an object. Although this technology was originally developed for remote sensing, it has been extended to the biomedical engineering field as a powerful analytical tool for biological and biomedical research. This review introduces the basics of spectral imaging, imaging methods, current equipment, and recent advances in biomedical applications. The performance and analytical capabilities of spectral imaging systems for biological and biomedical imaging are discussed. In particular, the current achievements and limitations of this technology in biomedical engineering are presented. The benefits and development trends of biomedical spectral imaging are highlighted to provide the reader with an insight into the current technological advances and its potential for biomedical research.
In this paper, a method on how to design and implement a miniaturized spectrometer with low-light-level (LLL) CCD on
GaAs is introduced. The optical system uses a blazed grating as the dispersive element and a 1×64 CCD on GaAs as the
sensor. We apply a highly integrated Cortex-M4 MCU (STM32F407), to build the data acquisition and analysis unit,
providing Wi-Fi interface to communicate with the PC software. It can complete the tasks like data acquisition, digital
filtering, spectral display, network communication, human-computer interaction etc.
In this paper, we studied the readout circuit for high sensitivity 1×64 InGaAs/GaAs/AlAs quantum dot-in-well
photodetector array based on wide dynamic range. The improved design capacitor feedback trans-impedance amplifier
(CTIA) is researched as a low-noise adaptive gain control (AGC) CTIA readout circuit. The dynamic range and
sensitivity of the circuit was greatly increased. Two switches K1 and K2 were used to controlling two capacitors 5pF and
9pF, respectively. Then four integration capacitors (1pF, 6pF, 10pF and 15pF) were obtained. The dynamic range of the
circuit was increased 23.5dB. The readout circuit was designed in with the area of 3.6mm×2.9mm in 0.35um CMOS
technology.
The weak-light characteristics of the GaAs/InGaAs resonant-cavity-enhanced (RCE) quantum dot photoelectric sensor
with the resonant coupling nature are presented. In order to explore its higher sensitive application because of higher
quantum efficiency, a readout integrated circuit (ROIC) of the capacitor feedback transimpendance amplifier (CTIA) was
designed to deal with voltage response of novel sensor. The readout circuit integration was designed to match 2x8 the array.
A computer-aided system based on the stm32 microcontroller device for obtaining the readout parameters of novel
photoelectric sensor was also developed. A 633nm laser beam shot to the window of sensor with radiation intensity 7nW, the
readout response voltage was over 200mV and 7.14E +07V /W responsivity at 120K and 15.8μs integration time. Integrated
with high reliability and precision of the software and hardware, the system could be applied to two-dimensional gray-scale
display at real-time.
Focused on high sensitivity property of the resonant-cavity-enhanced InGaAs/GaAs quantum dots photodetector, the
wide dynamic range readout was demanded and designed. The Capacitive Trans-Impedance Amplifier (CTIA) readout
structure having bias stability and good linearity compared the characteristic of the Self-Integrated (SI) readout structures
is more suitable for the quantum dots photodetector. However, the CTIA structure needs to expand readout dynamic
range for effective photoelectric conversion signal output of the novel photodetector. Through the different integration
capacitor readout experimental comparison and analysis, a readout structure whose low noise amplification gain could be
automatically adjusted was designed, the output dynamic range extended to over 90dB, and the signal to noise and
sensitivity of the output signal have been significantly improved.
A practical equivalent circuit model of the low dimensional photoelectric sensor with quantum dots-quantum well
(QDs-QW) hybrid hetero-structure is introduced in this article. This model acts as a signal source for ROIC (readout
integrate circuit) simulation. An optimal readout integrated circuit employing capacitor feedback transimpedance
amplifier (CTIA) structure is designed for the QDs-QW hybrid hetero-structure photoelectric sensor. Based on the
photoelectron storage characteristic of the photoelectric sensor, a dumping structure for CTIA readout integrated circuit
is studied. This dumping structure is proposed to release the redundant charge stored by the device for improving the
performance of the photoelectric sensor readout.
Because of the isotropic energy band structure of the Γ electrons in N type GaAs/AlGaAs quantum well infrared photodetector (QWIP), normal incident radiation absorption is impossible so that the optical grating becomes key requirements for such QWIPs. The development of very long wavelength infrared GaAs/AlxGa1-xAs quantum well Infrared photodetectors (QWIPs) is proposed in the paper based on optimization of 2-d period grating design, processing of detector, and a 16μm cutoff wavelength QWIP has been demonstrated at 40K. The blackbody responsibility Rv=3.4847×106V/W is obtained. The peak detectivity reaches D* λ=2.962×1010cm•Hz1/2/W.
A new uncooled bi-material microcantilever detector is based on between bi-material large difference in thermal expansion and Young’s modulus, having light, low cost, high sensitivity to radiation, and very matching with silicon IC technologies. A 3D microcantilever detector model had been built and simulated by ANSYS thermal-stress coupled, and gained responses to IR radiation with temperature changes, contributing to maximum deflection of geometry size.
A low-loss microwave Coplanar Waveguides (CPW) was fabricated on Porous Silicon (PS) substrate oxidated and coated with polyimide. The high frequency performance of PS/Oxidated PS (OPS) was observed through fabrication and measurement of CPW on N/P-type PS. The CPW loss was lowered to 0-7.5dB/1.2cm in 0-40GHZ in comparison with quartz and poly-Si/SiO2/high -resistivity Si, and some conclusions were drawn out.
A surface MEMS miniature switch with the cantilevered arm has been made on low resistivity Si substrate. The switch was inserted into a time domain setup and their lifetimes have been characterized as a function of actuated voltage, demonstrating some relationship among lifetime and threshold voltage. The structure of MEMS RF switch is simulated by ANSYS software, doing some failure analysis and discussing difference comparing the experiment.
A surface micromachined miniature switch has been made on silicon substrate using an electroplated gold micro-beam as the cantilevered arm, a chromium-to-gold electrical contact, and electrostatic actuation as the switching mechanism. The switch has an electrical isolation of -30dB in the 'off' state and an insertion loss of 4-7dB form 1 to 10 Ghz with a return loss of -15dB in the 'on' state. The high insertion loss has attributed to generation of parasitic current in low resistivity of the silicon substrate.
We simulate the structure of surface MEMS RF switch by suing ANSYS electrostatic and mechanical energy coupled analysis with established models. In this paper actuation voltage for different geometrical scales of suspended beam contacted switch are discussed. The dependence of actuation voltage on the Yang's module, size of cantilever and electrode area is calculated.
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