Modeling and Rectification of Rolling Shutter Effect in CMOS Aerial Cameras

In recent years, Universiti Tun Hussein Onn Malaysia has experienced several developments in buildings and road construction. A stormwater retention pond was built as a part of the construction plan to prevent the occurrence of floods downstream of the development sites. However, poor monitoring and maintenance of the pond caused water contamination, which had bad effects on the nearby environment and lake ecosystem. Therefore, this study was conducted to assess the current water quality in the pond by using a combination between Multispectral Unmanned Aerial Vehicle images and in-situ sampling. Four water quality parameters were investigated, namely turbidity, dissolved oxygen, temperature, and pH. Aerial images were taken using a multispectral aerial mapping camera attached to UAV. The in-situ testing was performed on the same day of image capturing at 5 different locations. According to the results, it was found that the pH and water temperature were within the normal levels with maximum and minimum values of 7.34 and 6.94 for pH and 28.39oC and 28.04oC for temperature, respectively. Turbidity readings appaired with a significant variation with a maximum value of 30.9 NTU at the lake outlet and a minimum value of 18.8 NTU at the middle of the lake. Dissolved oxygen concentration was noticed to be low, with an average value of 4.3 mg/l. Water quality mapping showed the concentration distribution of each water quality parameter along the lake surface. In each map, the differences in terms of colors were found to be not significant because of the size of the lake, which is relatively small, as well as because of the small differences in terms of water quality ridings at each sampling point

The star tracker is widely used in attitude control systems of spacecraft for attitude measurement. The attitude update rate of a star tracker is important to guarantee the attitude control performance. In this paper, we propose a novel approach to improve the attitude update rate of a star tracker. The electronic Rolling Shutter (RS) imaging mode of the complementary metal-oxide semiconductor (CMOS) image sensor in the star tracker is applied to acquire star images in which the star spots are exposed with row-to-row time offsets, thereby reflecting the rotation of star tracker at different times. The attitude estimation method with a single star spot is developed to realize the multiple attitude updates by a star image, so as to reach a high update rate. The simulation and experiment are performed to verify the proposed approaches. The test results demonstrate that the proposed approach is effective and the attitude update rate of a star tracker is increased significantly.

Critical utility infrastructure like power grids are vast (in hundreds of kilometers), linear, and operated 24×7 throughout the year. Maintenance inspections using low-cost unmanned aerial vehicles and aerial imaging are therefore gaining popularity. To have low-cost framework, the quality of the camera used is not of high quality or a stereo-rig one. Also, the sensors used are limited in variety and efficiency. 3-D reconstruction of a power grid will help to improve access, detect anomalies (damages), and reduce projection error. The depth estimation of wiry objects, like powerlines, in a cluttered background is challenging. The background clutter includes trees, pavement, greenery patches, and man-made objects. In this article, we propose an efficient framework for 3-D anomaly detection in power grids using UAV-based aerial images. The framework uses context information to become adaptive with different nonlinear movements that are unavoidable in aerial imaging. The proposed work is tested on real-data captured using a low-cost framework consisting of a non-stereo-rig aerial camera and a mini-UAV.

The difference between the topographic digital aerial cameras and the analogue ones are analyzed. The first one allows considering a digital aerial camera as a means of measurement. A regular rectangular grid of pixels of digital aerial cameras image sensor is a two-dimensional scale with divisions equal to the physical size of the pixel. It allows determining the position of interest points of the image in the coordinate system of a matrix of pixels, the axis of which is directed along rows and columns of the matrix. Wherein the measured value for aerial cameras, should be considered as the coordinates of the vector pointing from the perspective center to the point of interest in the coordinate system of aerial cameras, the beginning of which is located at the front nodal point of the lens, and the Sz axis is directed along the principal ray. Exactly they are directly used in the solutions of photogrammetric tasks for determination of coordinates of the locality object point. The accuracy of the result of determining the coordinates depends on the accuracy of the coordinates of a direction vector and the accuracy of the exterior orientation parameters of aerial cameras (the image). Metrological characteristics of digital topographic aerial cameras should be considered measurement range (the frame size in pixels and pixel size) and the error of a measuring instrument (the error of the coordinates of a direction vector) as the accuracy characteristics and the parameters of calibration of aerial cameras, allowing to determine the measured values according to indications of measurements with estimates of the errors of the calibration parameters.

Noncontact measurement for rotational motion has advantages over the traditional method which measures rotational motion by means of installing some devices on the object, such as a rotary encoder. Cameras can be employed as remote monitoring or inspecting sensors to measure the angular velocity of a propeller because of their commonplace availability, simplicity, and potentially low cost. A defect of the measurement with cameras is to process the massive data generated by cameras. In order to reduce the collected data from the camera, a camera using ERS (electronic rolling shutter) is applied to measure angular velocities which are higher than the speed of the camera. The effect of rolling shutter can induce geometric distortion in the image, when the propeller rotates during capturing an image. In order to reveal the relationship between the angular velocity and the image distortion, a rotation model has been established. The proposed method was applied to measure the angular velocities of the two-blade propeller and the multiblade propeller. The experimental results showed that this method could detect the angular velocities which were higher than the camera speed, and the accuracy was acceptable.

In this paper, a comparison between two particle image velocimetry (PIV) systems, one based on a standard cross-correlation charge coupled device (CCD) camera with pulsed laser and another using high-speed complementary metal oxide semiconductor (CMOS) camera with continuous laser is performed. The objective of the paper is to point out advantages and disadvantages of the two systems when computing large and small flow scale statistics. The comparison is performed on velocity measurements in the near and far fields of a circular water jet: on this flow several experimental data and empirical self-similarity laws are available for comparisons. The results show that both systems are suitable for measurements with a preference for the standard one when investigating small-scale statistics. This result depends on the lower number of effectively independent samples acquired by a high-speed system and on the higher noise levels of CMOS sensors in comparison to CCDs.

Abstract. This article presents (comparatively) the methodology for creating a 3D model of the urban area, based on terrestrial laser scanner, traditional technologies of terrestrial photogrammetry and aerial images. We are reviewing the data sources, their preliminary processing to be brought in a common system and the software used for this purpose. The case study presents the comparative results obtained using the methods listed above. To obtain the 3D models with terrestrial laser scanner systems have been used the dates achieved with ScanStation 2. To obtain the 3D model drawn by traditional photogrammetric methods using the UMK terrestrial camera, have been used auxiliary dates from topographic measurements with GPS systems and total stations as well as the current topographic plans. For the 3D model creation based on the dates taken with aerial digital cameras, were used the aerial images, taken with the ADS40 photogrammetric aerial camera. The comparative study between the three methods was accomplished by analyzing the object space representation fidelity, the precision of the 3D models obtained by comparison of the distances, areas and volumes, comparing the execution time and execution costs. The article presents the conclusions, the advantages and disadvantages of the three technologies based on the criteria listed above.

In this study we propose the fabrication of advanced high-speed complementary metal oxide semiconductor field effect transistor (AHCMOS) by combining a P-carbon nanotube with n-metal oxide semiconductor (NMOS) on a single chip. The target is to achieve extremely high speed low-power dissipating miniaturized device with improved functionalities.  The technology of conventional metal oxide semiconductor field effect transistor (MOSFET) and nanotechnology are applied in this research. A P-carbon nanotube is complemented with the conventional NMOS all embedded on the same chip.  Although it is possible to fabricate both a P and N carbon nanotube to form a complementary pair, and also a PMOS and NMOS to form a complementary pair, however in this research we propose a hybrid structure with carbon nanotube transistor technology and complementary MOSFET technology. This device therefore combines the best characteristics of carbon nanotube technology and CMOS technology to provide enhanced logic functions that are optimized for the high-speed, low-power systems and miniaturized size ideal for very large scale integration (VLSI).

Objective To evaluate the role of periodically rotated overlapping parallel lines enhanced reconstruction (PROPELLER) DWI in skull base.Methods Both PROPELLER and echo-planar imaging (EPI) DWI with b values of 500 and 1 000 s/mm2 in skull base were performed in 61 consecutive patients who had been examined with routine head and neck MRI because of symptoms of ear or nose or throat.All of 61 patients were divided into two groups:the normal group without lesion and the lesion group with lesions on MRI.The mean distortion scores and SNRs of structures in skull base with different DWI sequences (PROPELLER and EPI) and b values were compared by paired sample t test in each group.Moreover,the positive rates of PROPELLER DWI were contrasted with those of EPI DWI by paired data x2 test in the lesion group.Results The normal group included 16 patients,and the lesion group included 45 patients.With b values of 1 000 s/mm2,the mean distortion scores of EPI DWI and PROPELLER DWI in normal group were 1.34 ± 0.48,3.94 ± 0.25 respectively,and were 1.57 ± 0.54,3.94 ± 0.23 respectively in the lesion group.With b values of 500 s/mm2,the mean distortion scores of EPI DWI and PROPELLER DWI in nommal group were 1.38 ± 0.49,3.97 ± 0.18,respectively,and were 1.60 ± 0.54,3.97 ±0.18 respectively in the lesion group.There were significant difference in the mean distortion scores between EPI DWI and PROPELLER DWI with b values of 1 000 or 500 s/mm2 in both groups (with t values of-29.40,-40.84,-29.40,and-42.45 respectively,and P ＜0.01).With b value of 1 000 s/mm2,the mean SNRs of PROPELLER DWIs in all of the skull base structures except for cerebellar hemisphere and temporal pole were higher than those of EPI DWIs (P ＜ 0.05).Also,with b value of 500 s/mm2,the mean SNRs of PROPELLER DWIs in all of the skull base structures were higher than those of EPI DWIs except for eerebellar hemisphere,temporal pole and temporalis.Moreover,the positive rate of PROPELLER DWI (97.78％,44/45) in the lesion group with masses was significantly higher (x2 =16.317,P ＜ 0.01) than that of EPI DWI (64.44％,29/45).Conclusions PROPELLER technique can reduce or eliminate distortion and artifacts,increase the image quality and the positive rate of lesion on diffusion-weighted images.Therefore,PROPELLER DWI is regarded useful in the diagnoses and the evaluation of therapeutic effect in patients with lesions in skull base. Key words: Skull base; Magnetic resonance imaging; Image quality

The tunneling magnetoresistance micro-sensors (TMR) developed by magnetic multilayer material has many advantages, such as high sensitivity, high frequency response, and good reliability. It is widely used in military and civil fields. This work presents a high-performance interface circuit for TMR sensors. Because of the nonlinearity of signal conversion between sensitive structure and interface circuit in feedback loop and forward path, large harmonic distortion occurs in output signal spectrum, which greatly leads to the reduction of SNDR (signal noise distortion rate). In this paper, we analyzed the main source of harmonic distortion in closed-loop detection circuit and establish an accurate harmonic distortion model in TMR micro-sensors system. Some factors are considered, including non-linear gain of operational amplifier unit, effective gain bandwidth, conversion speed, nonlinearity of analog transmission gate, and nonlinearity of polycrystalline capacitance in high-order sigma-delta system. We optimized the CMOS switch and first-stage integrator in the switched-capacitor circuit. The harmonic distortion parameter is optimally designed in the TMR sensors system, aiming at the mismatch of misalignment of front-end system, non-linearity of quantizer, non-linearity of capacitor, and non-linearity of analog switch. The digital output is attained by the interface circuit based on a low-noise front-end interface circuit and a third-order sigma-delta modulator. The digital interface circuit is implemented by 0.35μm CMOS (complementary metal oxide semiconductor) technology. The high-performance digital TMR sensors system is implemented by double chip integration and the active interface circuit area is about 3.2 × 2 mm. The TMR sensors system consumes 20 mW at a single 5 V supply voltage. The TMR sensors system can achieve a linearity of 0.3% at full scale range (±105 nT) and a resolution of 0.25 nT/Hz1/2(@1Hz).

Since the birth of charge coupled devices (CCD) and the complementary metal-oxide-semiconductor (CMOS) active pixel sensors, pixel pitch of digital image sensors has been continuously shrinking to meet the resolution and size requirements of the cameras. However, shrinking pixels reduces the maximum number of photons a sensor can hold, a phenomenon broadly known as the full-well capacity limit. The drop in full-well capacity causes drop in signal-to-noise ratio and dynamic range.The Quanta Image Sensor (QIS) is a class of solid-state image sensors proposed by Eric Fossum in 2005 as a potential solution for the limited full-well capacity problem. QIS is envisioned to be the next generation image sensor after CCD and CMOS since it enables sub-diffraction-limit pixels without the inherited problems of pixel shrinking. Equipped with a massive number of detectors that have single-photon sensitivity, the sensor counts the incoming photons and triggers a binary response “1” if the photon count exceeds a threshold, or “0” otherwise. To acquire an image, the sensor oversamples the space and time to generate a sequence of binary bit maps. Because of this binary sensing mechanism, the full-well capacity, signal-to-noise ratio and the dynamic range can all be improved using an appropriate image reconstruction algorithm. The contribution of this thesis is to address three image processing problems in QIS: 1) Image reconstruction, 2) Threshold design and 3) Color filter array design.Part 1 of the thesis focuses on reconstructing the latent grayscale image from the QIS binary measurements. Image reconstruction is a necessary step for QIS because the raw binary measurements are not images. Previous methods in the literature use iterative algorithms which are computationally expensive. By modeling the QIS binary measurements as quantized Poisson random variables, a new non-iterative image reconstruction method based on the Transform-Denoise framework is proposed. Experimental results show that the new method produces better quality images while requiring less computing time.Part 2 of the thesis considers the threshold design problem of a QIS. A spatially-varying threshold can significantly improve the reconstruction quality and the dynamic range. However, no known method of how to achieve this can be found in the literature. The theoretical analysis of this part shows that the optimal threshold should match with the underlying pixel intensity. In addition, the analysis proves the existence of a set of thresholds around the optimal threshold that give asymptotically unbiased reconstructions. The asymptotic unbiasedness has a phase transition behavior. A new threshold update scheme based on this idea is proposed. Experimentally, the new method can provide good estimates of the thresholds with less computing budget compared to existing methods.Part 3 of the thesis extends QIS capabilities to color imaging by studying how a color filter array should be designed. Because of the small pixel pitch of QIS, crosstalk between neighboring pixels is inevitable and should be considered when designing the color filter arrays. However, optimizing the light efficiency while suppressing aliasing and crosstalk in a color filter array are conflicting tasks. A new optimization framework is proposed to solve the problem. The new framework unifies several mainstream design criteria while offering generality and flexibility. Extensive experimental comparisons demonstrate the effectiveness of the framework.

Refined, petroleum-based diesel fuel composes hundreds of hydrocarbons with distinct physio-chemical and combustion characteristics. This range of components leads to difficulties and complexities in accurate computational modeling and experimental investigations. For simplification, different surrogate fuels (single, binary or multi component) are utilized by researchers to satisfactorily mimic the target characteristics of interest (be they physio-chemical, combustion, or both). The present work is focused on combustion characteristics, and particularly those for single droplet combustion. Single component surrogates are n-Dodecane, n-Hexadecane, 2,2,4,4,6,8,8-heptamethylnonane(Iso-cetane), decahydronapth-alene (decalin), and 1-methylnaphthalene, which are representative of the four major hydrocarbon classes (normal-alkanes, iso-alkanes, cyclo-alkanes, and aromatics) found in petroleum-based diesel fuel. The multicomponent surrogate is composed from the single component surrogates with the volume fractions being n-hexadecane = 37.00% v/v, heptamethylnonane = 33.00% v/v, decahydronaphthalene = 18.00% v/v and methylnaphthalene = 12.00% v/v. All of the surrogates are chosen from previous published works based on the availability of the combustion chemical kinetics and through matching target properties include derived cetane number (DCN), hydrogen to carbon (H/C) ratio, molecular weight (MW), and threshold soot index (TSI). Experiments are carried out by suspending a single isolated sub-millimeter sized droplet on three 16 μm silicon carbide wires for different fuel blends as well as neat fuels. The combustion of the single isolated droplet is initiated by utilizing two hot wire loops which are positioned on either side of the droplet for uniform heating. The combustion of the droplet is captured using a high-speed CCD (charge-coupled device) camera and a high-speed CMOS (complementary metal-oxide-semiconductor) camera. These high-speed images are post processed and analyzed to differentiate the combustion characteristics of the single component surrogates, multicomponent surrogates, and petroleum-based commercial diesel fuel. The chosen droplet combustion characteristics are burning rate, ignition delay, burning period, morphological evolution of droplet, and flame dynamics. Different droplet combustion characteristics of both single and multicomponent surrogates are compared with petroleum-based commercial diesel. The outcome shows that the target combustion characteristics of diesel fuel can be reproduced with multicomponent surrogates at the droplet scale and particular aspects can be captured by single component surrogates. In general, Diesel, single component surrogates, and multicomponent surrogate fuel droplets follow the d2 -law combustion. Based on flame shape, size and luminosity, multicomponent surrogate fuel closely resembles diesel while both decalin and multicomponent surrogate resemble the burning rate of diesel. Decalin and multicomponent surrogate fuel resemble the ignition delay trends of diesel while Hexadecane, Decalin, and multicomponent surrogate resemble the burning period of diesel.

Target detection is one of research focuses for precision chemical application. This study developed a method to identify seedling cabbages and weeds using hyperspectral imaging. In processing the image data with ENVI software, after dimension reduction, noise reduction, de-correlation for high-dimensional data, and selection of the region of interest, the SAM (Spectral Angle Mapping) model was built for automatic identification of cabbages and weeds. With the HSI (Hyper Spectral Imaging) Analyzer, the training pixels were used to calculate the average spectrum as the standard spectrum. The parameters of the SAM model, which had the best classification results with 3-point smoothing, zero-order derivative, and 6-degrees spectral angle, was determined to achieve the accurate identification of the background, weeds, and cabbages. In comparison, the SAM model can completely separate the plants from the soil background but not perfect for weeds to be separated from the cabbages. In conclusion, the SAM classification model with the HSI analyzer could completely distinguish weeds from background and cabbages. Keywords: hyperspectral imaging, weed identification, cabbage, seedlings DOI: 10.3965/j.ijabe.20150805.1492 Citation: Deng W, Huang Y B, Zhao C J, Wang X. Identification of seedling cabbages and weeds using hyperspectral imaging. Int J Agric & Biol Eng, 2015; 8(5): 65－72.

In the field of UAV information processing and aerial image processing technology, data collected from MUAV platform is more and more widely used in emergency rescues. The traditional way of aerial photogrammetry, which has a limited accuracy in aerial camera locations from the UAV, makes measurements of the object location on pairwise images inaccurate. A method is presented in this paper to fast construct the stereo aerial image using high-precision GPS and INS data. It also allows users to do correct measurements based on aerial images as the high-frequency DGPS promoting the accuracy and reliability of aerial camera locations. The main steps to construct a stereo aerial image are: 1) image acquisition and overlap calculation, making a route planning for the flight based on the height of the MUAV and the objects types in the flight area to get image sequences with adequate overlap.2) Fast stitching of aerial images: We used high-precision GPS and INS data to pre-align images roughly which would make the matching process much faster and then stitch the images with matched feature points.3) Stereo aerial image synthesis, two mosaic images over the same flight area are synthesized. We adjust the parallax of the synthesized image to a scale properly fitting the human eyes to make it more dynamic. Due to a stable low-altitude flying of the MUAV as well as the high density position and attitude data acquired, it would enable us to measure objects in the stereo image with a longer baseline. In order to verify the practicability and the measurement accuracy of this method, an experiment was done along the Kelan River in Xinjiang. We obtained high-resolution images and accurate camera locations with the MUAV platform. Afterwards, a stereo aerial image was quickly constructed and measurements were taken by improved aerial photogrammetry to get detail information of the image. In the accuracy analysis of the measurements results, it demonstrated fine efficiency and a good accuracy of the method.

Direct emission spectrometry determination of fluorine in carbon materials: Argon dc arc and spark radiation sources