Area Image Sensor Research Articles

Optical fingerprint sensor with FBI certification

Isorg (Limoges, France), a pioneer in organic photodetectors (OPDs) and large area image sensors, announces the FBI certification of Bio1Print30, a large-area optical fingerprint sensor for applications where enhanced mobile security and nomad ID authentication are key

Carrier Blocking Layer Materials and Application in Organic Photodetectors.

As a promising candidate for next-generation photodetectors, organic photodetectors (OPDs) have gained increasing interest as they offer cost-effective fabrication methods using solution processes and a tunable spectral response range, making them particularly attractive for large area image sensors on lightweight flexible substrates. Carrier blocking layers engineering is very important to the high performance of OPDs that can select a certain charge carriers (holes or electrons) to be collected and suppress another carrier. Carrier blocking layers of OPDs play a critical role in reducing dark current, boosting their efficiency and long-time stability. This Review summarizes various materials for carrier blocking layers and some of the latest progress in OPDs. This provides the reader with guidelines to improve the OPD performance via carrier blocking layers engineering.

Experience Control Analysis of English Reading Software Based on Wireless Binocular Line‐of‐Sight Sensing

This paper proposes a segmented combined English text measurement method based on two sets of orthogonal linear image sensors and one area image sensor. This method fully combines the advantages of the linear image sensor and the area image sensor in long‐distance and short‐distance English text measurement and can continuously perform high‐precision English text tracking within a large range of viewing distance. Based on this method, a set of segmented English text measurement system is designed and constructed. This paper presents a method for extracting English word boundaries based on semantic segmentation to solve the problem of global positioning and horizontal initialization of English reading text. The semantic segmentation method based on fully convolutional networks (FCN) is analyzed, and the target classification is defined. We used the classic FCN framework and model, fine‐tuned with manually annotated data, and achieved good segmentation results. For the definition and extraction of English word boundaries in English text, a piecewise linear model is used to measure the projection confidence of each English word boundary point, and the overall observation of the English word boundary is measured. When the observation confidence is high enough, combined with the English word boundaries marked in the high‐precision image, the horizontal positioning is obtained by matching the weights. This paper concludes that English reading software can help learners in English learning to a certain extent, which proves that the English reading software is an effective supplement based on blended learning classrooms. Through the analysis of learners and teaching content, an English teaching model based on English reading software blended learning is designed. Experimental studies have proved that English reading software can help learners learn English, which not only expands their vocabulary but also broadens their horizons.

Transparent phototransistor with high responsivity, sensitivity, and detectivity from heterojunction metal oxide semiconductors

In this work, the high-performance transparent Al:InZnSnO/InZnO/Al:InZnSnO tri-layer thin-film phototransistors are reported. They show a high field-effect mobility of 40.1 cm2/V·s and an excellent high photoresponsivity of 25 000 A/W, a photosensitivity of 3.3 × 107, a specific detectivity of 4.3 × 1017 cm·Hz1/2·W−1 under the illumination at 460 nm with an intensity of 140 μW/cm2. The persistent photoconductivity inherent in phototransistors made of oxide semiconductors overcome by a pulsed gate bias with 1 μs, which accelerates the recombination of photogenerated holes with electrons. This demonstrates that the transparent photosensor array can be integrated monolithically on the display without appreciable loss of transparency for high functionality such as large area image sensor.

Birefringent Field-Modulation Imaging of Transparent Ferroelectrics

Observations of ferroelectric domains and domain walls are essential for understanding ferroelectric switching characteristics. Here, we demonstrate that the use of optical birefringence, coupled with a first-order electro-optic effect (Pockels effect), allows the visualization of ferroelectric domains in transparent ferroelectric materials. We utilize a field-modulation imaging technique, with the use of a complementary metal-oxide-semiconductor (CMOS) area image sensor to detect slight differences in parallel- and crossed-Nicols polarized optical microscopy images between forward- and reverse-electric-field applications. The ferroelectric domains with antiparallel polarizations are clearly discriminated from each other by the sign of the ellipticity modulation of outgoing elliptically polarized light. The observed images are consistent with piezoresponse force microscopy images of transparent single-crystal films of 2-methylbenzimidazole (MBI). The modulation signal at both polarization configurations exhibit clear sign changes in the wavelength dispersion, owing to the anisotropic nature of the MBI films. The unique optical-probe nature also reveals the existence of two types of domain walls with different three-dimensional orientations.

Ferroelectrics field modulation imaging: A useful technique for domain and domain-wall observations

A noncontact optical imaging technique called “ferroelectrics field modulation imaging (FFMI)” is developed to visualize ferroelectric domains and domain walls. The difference image sensing technique with use of area image sensor is utilized to observe the slight modulation of transmitted optical microscope images for ferroelectric films under application of alternating electric fields. We show that the technique allows sensitive, collective and rapid visualization of ferroelectric domains in single-crystal films of hydrogen-bonded organic ferroelectrics. We also investigated further features of ferroelectric domain walls by the technique, regarding the dynamics as well as a tilt in the depth direction of the films.

Development of an Area Image Sensor Pixel for an X-Ray Detector

Area photodetector devices (image sensors) are the main imaging element of digital X-ray systems used in medicine today. Since the cost of a medical diagnostics error is very high, the requirements imposed on the image sensor are very strict. We consider a sequence of procedures for the development of an area image sensor for biomedical X-ray investigations, which must reliably distinguish low-contrast details down to 80–100 µm. The development is aimed, in particular, at combining different parameters for different tasks, which require either a high frame rate at a low digit capacity or a wide dynamic range in the slow image sensing mode. The most important parameters of an image sensor are the fill factor of an optical pixel (photosensitive cell) and the quantum efficiency. The pixel layout and topology are proposed and a solution of merging the four neighboring photocells in a separate functional group (superpixel) with a large sensitive area and a potential well is found. The calculation and simulation allow us to develop specific recommendations and requirements on the photodetector for the developed X-ray sensitive panel, and determine the frame and bit rate ranges in the transmission lines.

Organic Photodetectors and their Application in Large Area and Flexible Image Sensors: The Role of Dark Current

AbstractOrganic photodetectors (OPDs) have gained increasing interest as they offer cost‐effective fabrication methods using low temperature processes, making them particularly attractive for large area image detectors on lightweight flexible plastic substrates. Moreover, their photophysical and optoelectronic properties can be tuned both at a material and device level. Visible‐light OPDs are proposed for use in indirect‐conversion X‐ray detectors, fingerprint scanners, and intelligent surfaces for gesture recognition. Near‐infrared OPDs find applications in biomedical imaging and optical communications. For most applications, minimizing the OPD dark current density (Jd) is crucial to improve important figures of merits such as the signal‐to‐noise ratio, the linear dynamic range, and the specific detectivity (D*). Here, a quantitative analysis of the intrinsic dark current processes shows that charge injection from the electrodes is the dominant contribution to Jd in OPDs. Jd reduction is typically addressed by fine‐tuning the active layer energetics and stratification or by using charge blocking layers. Yet, most experimental Jd values are higher than the calculated intrinsic limit. Possible reasons for this deviation are discussed, including extrinsic defects in the photoactive layer and the presence of trap states. This provides the reader with guidelines to improve the OPD performances in view of imaging applications.

Biology microscopy using well-distributed sphere digital in-line holography

Traditional pinhole spherical wave digital in-line holography has proved to be powerful imaging tools. Image quality is affected by uncertain round of pinhole. Here, we propose a well-distributed sphere wave generation method and it demonstrates wide field of view and high resolution microscopy. The laser focuses into an infinitesimal spot through laser beam expander and microscope objective. Pinhole permutation with different sizes is utilized to match the focal point, and emerges an ideal spherical wave. Interference fringes pattern, formed by reference sphere wave and scattered sphere wave of object, is collected by large area image sensor. The influence of dirty in image sensor and parasitic light is eliminated through subtraction with and without object. Fresnel inverse transformation reconstruction algorithm presents the object information. Biology microscopy experiments demonstrate that the proposed techniques increase the flexibility in producing well-distributed point light source and improve the image quality. Field of view is 3.22 mm×3.22 mm and resolution is 5.09 μm. Furthermore, adjustable field of view with magnification, fast, no-contact make it to be a promising tool in optical element measurement, material identification, biology and medicine.

Разработка фоточувствительной ячейки матричного фотосенсора для детектора рентгеновского изображения

Разработка фоточувствительной ячейки матричного фотосенсора для детектора рентгеновского изображения

Intercolor-Filter Crosstalk Model for Image Sensors With Color Filter Array

A color crosstalk model for an area image sensor with a color filter (CF) array is proposed, which quantifies the crosstalk in a physically intuitive manner by introducing “inter-CF optical crosstalk (inter-CF crosstalk).” The model separates the structural design originated crosstalk from the CF material itself, revealing the sole characteristics of microstructures on a photodiode. A constrained nonlinear estimation is used to solve the model equation of system matrices with an objective function focusing on matching between the modeled quantum efficiency spectra and measured ones at both the peak and crosstalk regions. The model is applied to 1.1- $\mu \text{m}$ backside-illuminated CMOS image sensors having four different kinds of optical structures on the photodiode of the same design, and successfully provides the ground of comparison with excellent matching between the models and the measurement results.

Image Reconstruction for Optical Tomography System based on Complementary Metal Oxide Semiconductor Image Sensor

Quality of food products is important and highly demanded by customers in food industry. All physical attributions (size, shape, texture, concentration and color) of food products have to be considered. Monitoring the particle parameters can affect food flavor, texture, appearance, product size and shelf life. Most of the monitoring systems used in the food industry are based on the grading and sorting inspection such as sampling and Computer Vision technique. However, each of them has their limitations. Therefore, an optical tomography based on Complementary Metal Oxide Semiconductor (CMOS) area image sensor is developed to monitor these particle parameters by visualizing the particle non-invasively inside a flow pipe. The complete optical tomography system has been fabricated to produce a reliable tool to monitor particle characterization and to detect solid particles in flow pipe. The system offers reliable reconstructed images in monitoring particle concentration in air and liquid flows, particle shape and size. The optical tomography system consists of a lighting system, a sensing system that contains a measurement section and CMOS area image sensors, a Data Acquisition System (DAQ) that made up from a microcontroller module, and an image reconstruction system based on MATLAB software. The results obtained are sufficient to collect the qualitative and quantitative information of the particles used in the system to monitor concentration profile in air and liquid.

Imaging of Solid Particle in Air using Optical Tomography based on CMOS Area Image Sensor

This paper presents the use of Complementary Metal Oxide Semiconductor (CMOS) area image sensor in an optical tomographic instrumentation system to image solid particle in air. The image reconstruction is based on two (2) projections with two CMOS area image sensors configured around a flow pipe. The CMOS area image sensor provides 1280x1024 pixels with a pixel size of 5.2 micron x 5.2 micron, which will provide a high resolution image. The advantage of applying a CMOS area image sensor as an optical sensor is it will minimize the time of getting multiple slices of reconstructed images. Thus, it can generate a 3D reconstructed image of the object easier and faster.

Imaging particles in solid/air flows using an optical tomography system based on complementary metal oxide semiconductor area image sensors

Particle characterization has become important in the pharmaceutical, food, paint and chemical industries, among others. For example, particle size and shape can affect the taste, texture, and appearance of food. Particle characterization has become more significant for on-line production control because it influences product quality. Moreover, the images of particles generated from on-line measurements can better characterize the process itself. This paper discusses the development of an optical tomography system based on a complementary metal oxide semiconductor (CMOS) area image sensor, which is used for imaging particles in solid/air flows. The system consists of a lighting system, a measurement system and a data acquisition system. The CMOS area image sensor has a pixel size of 5.2μm×5.2μm, which provides a resolution of 1280×1024 pixels. A two-projection system is adopted to enable image reconstruction; in this system, two CMOS area image sensors are configured around a pipe, and a light source is placed on the opposite side of the pipe. When the light illuminates through the pipe, the shadows of any particles in the pipe will be cast onto the CMOS area image sensors. Four experiments on solid particles in air under different conditions are performed. The output of the CMOS area image sensor is processed to reconstruct the tomographic image. The results indicate that CMOS based optical tomography is capable of imaging particles in solid/air flows.

Cadmium Sulfide Nanocrystal Sensitized Vertically Aligned Titanium Dioxide Rods for Large Area Image Sensors on 3-D Substrates

We discuss here a semiconductors assembly comprising of titanium dioxide (TiO2) rods sensitized by cadmium sulfide (CdS) nanocrystals for potential applications in large area electronics on three dimensional (3-D) substrates. Vertically aligned TiO2 rods are grown on a substrate using a 150° C process flow and then sensitized with CdS by SILAR method at room temperature. This structure forms an effective photoconductor as the photo-generated electrons are rapidly removed from the CdS via the TiO2 thereby permitting a hole rich CdS. Current-voltage characteristics are measured and models illustrate space charge limited photo-current as the mechanism of charge transport at moderate voltage bias. The stable assembly and high speed are achieved. The frequency response with a loading of 10 pF and 9 MΩ shows a half power frequency of 100 Hz.

Velocity measurement for moving surfaces using spatial filtering method based on area image sensor

The idea of using spatial filtering method to measure velocity of vehicles for an inertial navigation system is put forward. Corresponding optical system, including a 532nm solid-state laser as active illumination, is established. A 17.92mm×14.34mm area charge coupled device (CCD) is employed both as detector and as spatial filter. The spatial filtering characteristics are theoretically analyzed using a power spectral density function. The spatial filtering operation of CCD is performed fully by software. Therefore, the parameters of the spatial filter, such as the size and the number of spatial period, are changeable. In addition, the CCD is arranged as two differential spatial filters without any other additional elements. Experiments are carried out to examine the feasibility of CCD as two differential spatial filters and the influence of the number of spatial period on the signal frequency. The results indicate that the more number of spatial period the more accurate measurements can be obtained, and show that the relation between signal frequency and velocity has good linearity. So this velocimeter is suitable to provide velocity information for a vehicle self-contained inertial navigation system.

Updates from the SPADnet project (fully digital, scalable and networked photonic component for Time-of-Flight PET applications).

SPADnet is aimed at a new generation of fully digital, scalable and networked photonic components to enable large area image sensors, with primary target gamma-ray and coincidence detection in (Time-of-Flight) PET. The SPADnet photonic module, which lies at the heart of the concept, is built around an array of tessellated single-photon TSV sensor chips, manufactured in standard CMOS technology. The resulting sensor tile is connected on the back to an FPGA-based data processing and communication unit, whereas its front size is glued to scintillator crystals. The resulting modules are then connected in a token ring structure to form the actual PET system. Coincidence detection occurs directly in the ring itself, in a differed and distributed manner to ensure scalability. We have fabricated and tested the first version of the SPADnet photosensor, a fully digital CMOS SiPM with 8×16 pixels individually capable of photon time stamping and energy accumulation, together with the corresponding sensor tiles. The sensor also provides a real-time output of the total detected energy at up to 100Msamples/s and on-chip discrimination of gamma events. These events can then be routed to the SPADnet ring network, which operates at 2 Gbps providing real-time processing and coincidence determination; this architecture simplifies the construction of the overall system and allows the scaling of the system to larger arrays of detectors. This may result in better and faster image reconstruction. SPADnet will not only impact PET scalability but also performance robustness and cost; another advantage is the capability of being compatible with magnetic resonance imaging (MRI), thus prompting advances in multimodal imaging and medical diagnostics as a whole. SPADnet is being designed with scalability in mind, with the idea of being able to redeploy at reduced effort the SPADnet photonic module in other configurations such as brain PET.

SPADnet: Embedded coincidence in a smart sensor network for PET applications

In this paper we illustrate the core technologies at the basis of the European SPADnet project (www.spadnet.eu), and present the corresponding first results. SPADnet is aimed at a new generation of MRI-compatible, scalable large area image sensors, based on CMOS technology, that are networked to perform gamma-ray detection and coincidence to be used primarily in (Time-of-Flight) Positron Emission Tomography (PET). The project innovates in several areas of PET systems, from optical coupling to single-photon sensor architectures, from intelligent ring networks to reconstruction algorithms. In addition, SPADnet introduced the first computational model enabling study of the full chain from gamma photons to network coincidence detection through scintillation events, optical coupling, etc.

时间延迟积分型面阵CMOS图像传感器MTF速度失配模型研究袁高斌李斌桥

时间延迟积分型面阵CMOS图像传感器MTF速度失配模型研究袁高斌李斌桥

1P1-L05 プロファイルセンサを用いた高速3次元計測モジュール : フラットパネルディスプレイとOpenCVを用いた歪み補正方法の検討(光応用-オプトロニクスの未来-)

We have developed an intelligent CMOS sensor named Profile Sensor with sampling rate at 3200Hz of X and Y projection images. The Profile Sensor is a unique CMOS area image sensor aimed at high-speed position sensing by detecting projection images of X and Y-axes. We have constructed a stereo sensing module by using two pieces of Profile Sensor and confirmed the characteristics of the Profile Sensor for high-speed three-dimensional position detection of multi spots by using LEDs or reflectors as a target patterns. We have demonstrated the sensor has high speed and high accurate position measurement capability and the intelligent sensing technique can be useful for industrial and amusement applications.