Metal Oxide Semiconductor Image Sensor Research Articles

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.

FinFETs With a Deep Buried Channel to Reduce the Readout Noise in CMOS Image Sensors

FinFETs with a deep buried channel (DBC) are proposed for the reduction of readout noise in complementary metal-oxide–semiconductor image sensors (CISs). Simulation results show that the influence of defects at the Si/SiO2 interface on the drain current is reduced for the DBC design as the drain current variation in DBC FinFETs is 50% smaller than those in surface- and buried-channel metal-oxide–semiconductor field-effect transistor. The potential barriers at the fin sidewalls serve to confine electrons away from the defects at the Si/SiO2 interface, resulting in decreased readout noise in the CIS.

Dye-Containing Methacrylic Polymers in the Composition of Photo Resists for Complementary Metal Oxide Semiconductor Image Sensors

The trend in the development and manufacturing of Complementary Metal Oxide Semiconductor (CMOS) image sensors is to miniaturize pixels on the chips and hence to improve their imaging characteristics by providing a higher image resolution. As CMOS technology scales down into submicron regions, the conventional color filters are no longer suitable for generating the desired optical density. The major drawback of the conventional color filters produced from pigment-based positive tone photosensitive compositions, is the heterogeneous dispersion of pigments in photoresist composition resulting in color irregularities due to coarse particles of the pigments. One of the most perspective ways to solve this problem is a replacing the pigment with a dye as a coloring agent and thus, increasing solubility of the latter to obtain a homogeneous colored photoresist composition. In this paper, several novel red dye-containing materials are synthesized and tested to provide a redcolored photosensitive composition. This red-colored photosensitive composition is very promising for application as color filters for CMOS image sensors with high resolution and high level of integration architecture.

Implantable micro-optical semiconductor devices for optical theranostics in deep tissue

Optical therapy and diagnostics using photoactivatable molecular tools are promising approaches in medical applications; however, a method for the delivery of light deep inside biological tissues remains a challenge. Here, we present a method of illumination and detection of light using implantable micro-optical semiconductor devices. Unlike in conventional transdermal light delivery methods using low-energy light (>620 nm or near-infrared light), in our method, high-energy light (470 nm) can also be used for illumination. Implanted submillimeter-sized light-emitting diodes were found to provide sufficient illumination (0.6–4.1 mW/cm2), and a complementary metal–oxide–semiconductor image sensor enabled the detection of fluorescence signals.

A CMOS image sensor with variable frame rate for low-power operation

In this paper, a complementary metal oxide semiconductor (CMOS) image sensor for low-power operation with a variable frame rate is presented. The operating current of the CIS can be reduced by varying the frame rate of the CMOS image sensor (CIS), thus decreasing power consumption effectively. The proposed image sensor has two modes: normal mode and lowpower mode. In the low-power mode, the operating current of the pixel array can be controlled according to the frame rate of the CIS. At lower frame rates, the operating current of the pixel array is smaller than in the normal mode. The power consumption of the proposed CIS is determined by the on and off ratios of the bias current. The proposed image sensor was fabricated and measured with a 2-poly 4-metal 0.35 μm standard CMOS process.

Controlling electromagnetic wave through dual heights micro-lens array of a CMOS image sensor

We demonstrate control of electromagnetic (EM) wave through dual heights micro-lens (DHML) array in 1.1μm pixel size complementary metal oxide semiconductor image sensor. The sensitivity and signal-to-noise ratio (SNR) are significantly improved (>10%) using the DHML structure. This DHML structure acts as an array of fundamental waveguides to enhance the optical throughput and to suppress the spatial crosstalk that is confirmed by evaluating the pixel performance in terms of the confinement factor of fundamental mode in this DHML structure.

Total ionizing dose radiation effects in foue-transistor complementary metal oxide semiconductor image sensors

Radiation effects on four-transistor (4 T) active pixel sensor complementary metal-oxide-semiconductor (CMOS) image sensor induced by -ray are presented. The samples are 4 megapixels resolution CMOS image sensor using 11 upm pitch high dynamic 4 T pixels. They are manufactured with 0.18 upm specialized CMOS image sensortechnology. Three samples have been exposed to 200 krad(Si) 60Co -ray with different biasing condition (1# is static-biased, 2# dynamic-biased, and 3# is grounded during irradiation), and the dose rate is 50 rad(Si)/s. The influences of radiation on full well charge capacity, dark current, and conversion gain of the device are investigated. Experimental result shows that the conversion gain is not sensitive to the ionizing radiation, and it is mainly determined by the CMOS digital or analog circuits. It is known that the total ionizing dose for induced degradation in deep submicron MOSFET is negligible and so there is almost no radiation effect on the digital or analog circuits exposed to the ionizing radiation. Therefore, conversion gain does not have obvious degradation after irradiation. While full well charge capacity has a degradation after irradiation, which is due to the change of TG channel doping profile induced by the radiation. As the dose increases, dark current increases rapidly. The main source of dark current in 4 T CMOS image sensor is the current from STI interface and TG-PD overlap region. Experimental result also shows that different from 3 T CMOS image sensor, there is no biasing effect in 4 T CMOS image sensor. This is because for the 4 T CMOS image sensor most of the degradation come from STI interface and TG-PD overlap region, while biasing condition almost has no influence on both ofthem.

High-Speed Imaging using CMOS Image Sensor with Quasi Pixel-Wise Exposure

Several recent studies in compressive video sensing have realized scene capture beyond the fundamental trade-off limit between spatial resolution and temporal resolution using random space-time sampling. However, most of these studies showed results for higher frame rate video that were produced by simulation experiments or using an optically simulated random sampling camera, because there are currently no commercially available image sensors with random exposure or sampling capabilities. We fabricated a prototype complementary metal oxide semiconductor (CMOS) image sensor with quasi pixel-wise exposure timing that can realize nonuniform space-time sampling. The prototype sensor can reset exposures independently by columns and fix these amount of exposure by rows for each 8x8 pixel block. This CMOS sensor is not fully controllable via the pixels, and has line-dependent controls, but it offers flexibility when compared with regular CMOS or charge-coupled device sensors with global or rolling shutters. We propose a method to realize pseudo-random sampling for high-speed video acquisition that uses the flexibility of the CMOS sensor. We reconstruct the high-speed video sequence from the images produced by pseudo-random sampling using an over-complete dictionary.

Performance Evaluation of a Multichannel All-In-One Phantom Dosimeter for Dose Measurement of Diagnostic X-ray Beam.

We developed a multichannel all-in-one phantom dosimeter system composed of nine sensing probes, a chest phantom, an image intensifier, and a complementary metal-oxide semiconductor (CMOS) image sensor to measure the dose distribution of an X-ray beam used in radiation diagnosis. Nine sensing probes of the phantom dosimeter were fabricated identically by connecting a plastic scintillating fiber (PSF) to a plastic optical fiber (POF). To measure the planar dose distribution on a chest phantom according to exposure parameters used in clinical practice, we divided the top of the chest phantom into nine equal parts virtually and then installed the nine sensing probes at each center of the nine equal parts on the top of the chest phantom as measuring points. Each scintillation signal generated in the nine sensing probes was transmitted through the POFs and then intensified by the image intensifier because the scintillation signal normally has a very low light intensity. Real-time scintillation images (RSIs) containing the intensified scintillation signals were taken by the CMOS image sensor with a single lens optical system and displayed through a software program. Under variation of the exposure parameters, we measured RSIs containing dose information using the multichannel all-in-one phantom dosimeter and compared the results with the absorbed doses obtained by using a semiconductor dosimeter (SCD). From the experimental results of this study, the light intensities of nine regions of interest (ROI) in the RSI measured by the phantom dosimeter were similar to the dose distribution obtained using the SCD. In conclusion, we demonstrated that the planar dose distribution including the entrance surface dose (ESD) can be easily measured by using the proposed phantom dosimeter system.

Fluorescence imaging under background light with a self‐reset complementary metal–oxide–semiconductor image sensor

The authors propose and demonstrate the fluorescence imaging of green fluorescence protein (GFP) expressed in a brain slice with a self-reset complementary metal–oxide–semiconductor image sensor under background light. By using a self-reset function to avoid pixel saturation, the weak fluorescence of GFP was successfully observed, even under background light. The result suggests that the sensor can be applied to in vivo imaging of laboratory animals during light–dark cycles, so that they can observe the different responses to bright and dark environments.

Staining-free cell viability measurement technique using lens-free shadow imaging platform

Tests for cell viability, i.e., an assay quantifying the ratio of viable cells or tissues over the total cells or tissues within an index between 0 and 1 (or 0 and 100%), play an important role in cell or tissue culturing procedures. The viability test result, varying with several biological factors such as mechanical activity, motility, contraction, or mitotic activity of cells or tissues, is a crucial indicator in cell related research protocols including toxicity and anabolic activity assays. There are several well-established methods for evaluating cell viability, such as trypan blue assay, propidium iodide assay, 7-aminoactinomycin D assay and resazurin and formazan (MTT/XTT) assay. However, most of these methods determine viability using stained cell samples, which intern affect the cells morphology eventually making it unable to keep culturing the specimen. To address this issue, we have developed a novel shadow imaging technique to capture the diffraction patterns (shadow patterns) of micro objects without the use of any staining reagent. In this paper, we introduce a shadow imaging platform that can determine cell viability of more than 3000 human cancer cells immediately with a single digital image. Our custom-built lens-free shadow imaging platform consists of a compact, cost-effective light source, i.e., a light-emitting diode, and an optoelectronic image recording device, i.e., a complementary metal-oxide semiconductor image sensor. Three types of human cancer cell lines (Caco-2, HepG2, and MCF7) were incubated in 24-well plates, and H2O2 was added to track and compare the cell viability at each concentration tested. We obtained high correlation indices, with a minimum of 0.94, between the MTT assay and the shadow imaging platform. All these characterizations were done by custom developed automated detection algorithm. This algorithm analyzes the various elements of the diffraction pattern (shadow image), such as pixel intensity and connected pixel numbers, and counts the viable cells automatically, allowing the cell viability to be determined easily and immediately in a staining-free manner.

Development of a single-photon-counting camera with use of a triple-stacked micro-channel plate.

At the quantum-mechanical level, all substances (not merely electromagnetic waves such as light and X-rays) exhibit wave–particle duality. Whereas students of radiation science can easily understand the wave nature of electromagnetic waves, the particle (photon) nature may elude them. Therefore, to assist students in understanding the wave–particle duality of electromagnetic waves, we have developed a photon-counting camera that captures single photons in two-dimensional images. As an image intensifier, this camera has a triple-stacked micro-channel plate (MCP) with an amplification factor of 10(6). The ultra-low light of a single photon entering the camera is first converted to an electron through the photoelectric effect on the photocathode. The electron is intensified by the triple-stacked MCP and then converted to a visible light distribution, which is measured by a high-sensitivity complementary metal oxide semiconductor image sensor. Because it detects individual photons, the photon-counting camera is expected to provide students with a complete understanding of the particle nature of electromagnetic waves. Moreover, it measures ultra-weak light that cannot be detected by ordinary low-sensitivity cameras. Therefore, it is suitable for experimental research on scintillator luminescence, biophoton detection, and similar topics.

Spatial optical crosstalk in CMOS image sensors integrated with plasmonic color filters.

Imaging resolution of complementary metal oxide semiconductor (CMOS) image sensor (CIS) keeps increasing to approximately 7k × 4k. As a result, the pixel size shrinks down to sub-2μm, which greatly increases the spatial optical crosstalk. Recently, plasmonic color filter was proposed as an alternative to conventional colorant pigmented ones. However, there is little work on its size effect and the spatial optical crosstalk in a model of CIS. By numerical simulation, we investigate the size effect of nanocross array plasmonic color filters and analyze the spatial optical crosstalk of each pixel in a Bayer array of a CIS with a pixel size of 1μm. It is found that the small pixel size deteriorates the filtering performance of nanocross color filters and induces substantial spatial color crosstalk. By integrating the plasmonic filters in the low Metal layer in standard CMOS process, the crosstalk reduces significantly, which is compatible to pigmented filters in a state-of-the-art backside illumination CIS.

A Complementary Metal Oxide Semiconductor Image Sensor with Increased Dynamic Range Using Feedback Reset Mechanism

A Complementary Metal Oxide Semiconductor Image Sensor with Increased Dynamic Range Using Feedback Reset Mechanism

Pixel response function experimental techniques and analysis of active pixel sensor star cameras

The pixel response function (PRF) of a pixel within a focal plane is defined as the pixel intensity with respect to the position of a point source within the pixel. One of its main applications is in the field of astrometry, which is a branch of astronomy that deals with positioning data of a celestial body for tracking movement or adjusting the attitude of a spacecraft. Complementary metal oxide semiconductor (CMOS) image sensors generally offer better radiation tolerance to protons and heavy ions than CCDs making them ideal candidates for space applications aboard satellites, but like all image sensors they are limited by their spatial frequency response, better known as the modulation transfer function. Having a well-calibrated PRF allows us to eliminate some of the uncertainty in the spatial response of the system providing better resolution and a more accurate centroid estimation. This paper describes the experimental setup for determining the PRF of a CMOS image sensor and analyzes the effect on the oversampled point spread function (PSF) of an image intensifier, as well as the effects due to the wavelength of light used as a point source. It was found that using electron bombarded active pixel sensor (EBAPS) intensification technology had a significant impact on the PRF of the camera being tested as a result of an increase in the amount of carrier diffusion between collection sites generated by the intensification process. Taking the full width at half maximum (FWHM) of the resulting data, it was found that the intensified version of a CMOS camera exhibited a PSF roughly 16.42% larger than its nonintensified counterpart.

BriGuard: a lightweight indoor intrusion detection system based on infrared light spot displacement

Indoor intrusion detection systems are widely implemented in many special departments and environments. Owing to the special target market, several specific features of such systems are required including high accuracy, high performance, high concealment and ease of deployment. In this study, the authors proposed an infrared light spot displacement-based surveillance system for indoor intrusion detection. This system, named BriGuard, shares a similar idea with radar. A 940 nm infrared light beam goes through an optical diffraction grating to generate light spot matrix imagery in the view of a complementary metal oxide semiconductor image sensor. The coordinates of the light spots are extracted and recorded. When someone enters the monitored area, the imaging plane changes and leads to a variation of the pre-recorded light spots coordinates. The light beam is modulated in order to be distinguished from the light in the environment. The lightweight algorithms require little computation power and data storage. BriGuard achieves a nearly zero false detection rate while covering a distance up to 10 m. It can process 30 full HD (1920 × 1080) frames per second. More importantly, because of unnoticeable infrared lights and very small form factor, the whole detection equipment is very hard to observe.

Fully depleted, thick, monolithic CMOS pixels with high quantum efficiency

The Centre for Electronic Imaging (CEI) has an active programme of evaluating and designing Complementary Metal-Oxide Semiconductor (CMOS) image sensors with high quantum efficiency, for applications in near-infrared and X-ray photon detection. This paper describes the performance characterisation of CMOS devices made on a high resistivity 50 μ m thick p-type substrate with a particular focus on determining the depletion depth and the quantum efficiency. The test devices contain 8 × 8 pixel arrays using CCD-style charge collection, which are manufactured in a low voltage CMOS process by ESPROS Photonics Corporation (EPC). Measurements include determining under which operating conditions the devices become fully depleted. By projecting a spot using a microscope optic and a LED and biasing the devices over a range of voltages, the depletion depth will change, causing the amount of charge collected in the projected spot to change. We determine if the device is fully depleted by measuring the signal collected from the projected spot. The analysis of spot size and shape is still under development.

컬럼 커패시터와 피드백 구조를 이용한 CMOS 이미지 센서의 동작 범위 확장

This paper presents a wide dynamic range complementary metal oxide semiconductor (CMOS) image sensor with column capacitor and feedback structure. The designed circuit has been fabricated by using <TEX>$0.18{\mu}m$</TEX> 1-poly 6-metal standard CMOS technology. This sensor has dual mode operation using combination of active pixel sensor (APS) and passive pixel sensor (PPS) structure. The proposed pixel operates in the APS mode for high-sensitivity in normal light intensity, while it operates in the PPS mode for low-sensitivity in high light intensity. The proposed PPS structure is consisted of a conventional PPS with column capacitor and feedback structure. The capacitance of column capacitor is changed by controlling the reference voltage using feedback structure. By using the proposed structure, it is possible to store more electric charge, which results in a wider dynamic range. The simulation and measurement results demonstrate wide dynamic range feature of the proposed PPS.

Recent Progress in High Refractive Index Polymers

High refractive index polymers have been widely developed in recent years for their potential applications in advanced optoelectronic fabrications, such as high performance components for advanced display devices, encapsulants for light-emitting diode devices, microlens components for complementary metal oxide semiconductor image sensors, plastic lenses for eyeglasses, and camera, pick-up, and projector lenses. This Perspective describes the recent progress in high refractive index (n) polymers over the past decade and focuses on the design concept to increase n values and Abbe’s number (ν) of polymers. After a brief introduction of the basic methodology for developing high-n polymers and important parameters, such as Abbe’s number and birefringence, applications of high-n polymers, such as antirefractive coatings, microlenses for CMOS image sensors, encapsulants for LEDs, and high-n thermoplastic lenses, are highlighted.

고출력 CW 레이저에 의한 CMOS 영상 센서의 손상 분석

This paper presents the results of an experimental analysis of the high-power laser (HPL)-induced damage to a complementary metal-oxide semiconductor (CMOS) image sensor. Although the laser-induced damages to metallic materials have been sufficiently investigated, the damages to electric-optic imaging systems, which are very sensitive to HPLs, have not been studied in detail. In this study, we experimentally analyzed the HPL-induced damages to a CMOS image sensor. A near-infrared continuous-wave (CW) fiber laser was used as the laser source. The influences of the irradiance and irradiation time on the permanent damages to a CMOS image sensor, such as the color error and breakdown, were investigated. The experimental results showed that the color error occurred first, and then the breakdown occurred with an increase in the irradiance and irradiation time. In particular, these damages were more affected by the irradiance than the irradiation time.