Commercial Charge Coupled Device Research Articles

Electric‐Dipole Gated Two Terminal Phototransistor for Charge‐Coupled Device

AbstractThe demand for charge‐coupled device (CCD) imagers has surged exponentially during the last decade owing to their exceptionally high quality and low noise imaging. However, they are still confronting the performance constraints of high operation power, low speed, and limited charge integration. Here, the electric‐dipole gated phototransistor operation without external gate bias is reported by using high‐k HfO2 dielectric material. The electrostatic coupling of photogenerated charges from the Si with the graphene channel through a 10 nm HfO2 layer is demonstrated. The device exhibits remarkable performance in the broadband spectrum (266–1342 nm) at low drain bias voltage. The high values of responsivity, external quantum efficiency, and detectivity of 3.7 × 103 A W−1, 0.72 × 104, and 6.20 × 1013 cmHz½ W−1, respectively, for 800 nm wavelength and 3.3 × 103 A W−1, 1.31 × 104, and 5.61 × 1013 cmHz½ W−1, respectively, for 400 nm wavelength without gate are achieved. This discovery may potentially eliminate the requirement for gate terminals from commercial CCD devices. The power efficient features of this gateless image sensor can be fabricated at the industrial scale for the future machine vision market.

An FPGA-based dual-wavelength correlated imaging system with flexible frame rates for temperature distributions

A correlated imaging system with a flexible frame rate was proposed and fabricated on a field programmable gate array for the acquisition of temperature images. Real-time images of temperatures are reconstructed on chip at a frame rate of 10 Hz, and higher rates up to 1280 frames per second are also achieved in the case of resolution sacrifice. The compressive sensing method enables the flexible frame rate for dynamic temperature images. An incandescent filament was imaged and compared using the proposed imaging system and a commercial charge-coupled device (CCD) camera. Reconstructed images of temperature distributions agree well with those from the camera in the range from 1500 K to 2500 K. Moreover, the proposed system captures the excitation frequency of an acoustically excited flame by varying the frame rate. The simple structure and flexible frame rate provide an alternative to dynamical temperature imaging, especially in cases where the common CCD camera fails to work due to its slow response.

Prospective study for commercial and low-cost hyperspectral imaging systems to evaluate thermal tissue effect on bovine liver samples

Thermal ablation modalities, for example radiofrequency ablation (RFA) and microwave ablation, are intended to prompt controlled tumour removal by raising tissue temperature. However, monitoring the size of the resulting tissue damage during the thermal removal procedures is a challenging task. The objective of this study was to evaluate the observation of RFA on an ex vivo liver sample with both a commercial and a low-cost system to distinguish between the normal and the ablated regions as well as the thermally affected regions. RFA trials were conducted on five different ex vivo normal bovine samples and monitored initially by a custom hyperspectral (HS) camera to measure the diffuse reflectance (Rd) utilising a polychromatic light source (tungsten halogen lamp) within the spectral range 348–950 nm. Next, the light source was replaced with monochromatic LEDs (415, 565 and 660 nm) and a commercial charge-coupled device (CCD) camera was used instead of the HS camera. The system algorithm comprises image enhancement (normalisation and moving average filter) and image segmentation with K-means clustering, combining spectral and spatial information to assess the variable responses to polychromatic light and monochromatic LEDs to highlight the differences in the Rd properties of thermally affected/normal tissue regions. The measured spectral signatures of the various regions, besides the calculation of the standard deviations (δ) between the generated six groups, guided us to select three optimal wavelengths (420, 540 and 660 nm) to discriminate between these various regions. Next, we selected six spectral images to apply the image processing to (at 450, 500, 550, 600, 650 and 700 nm). We noticed that the optimum image is the superimposed spectral images at 550, 600, 650 and 700 nm, which are capable of discriminating between the various regions. Later, we measured Rd with the CCD camera and commercially available monochromatic LED light sources at 415, 565 and 660 nm. Compared to the HS camera results, this system was more capable of identifying the ablated and the thermally affected regions of surface RFA than the side-penetration RFA of the investigated ex vivo liver samples. However, we succeeded in developing a low-cost system that provides satisfactory information to highlight the ablated and thermally affected region to improve the outcome of surgical tumour ablation with much shorter time for image capture and processing compared to the HS system.

Low-cost design of a PCB imaging system based on laser triangulation

With the increasing miniaturization of electronic products, fanless design is required. The volume of electronic components, especially the height, is critical to the structural design of electronic devices. This paper proposes the design of on-line height measurement equipment based on commercial charge-coupled device (CCD), analyses the principle of height measurement of components, and explains the system composition and working principle of the measurement system. Moreover, it presents a comparative analysis of common methods for determining the center position, which include circle fitting, the gray centroid and extended method or Gaussian fitting, which generally lead to diverse results. The experimental results show that Gaussian fitting is better than other methods under realistic conditions, a three-dimensional model of the components is provided, and the error factors that affect measurement are analyzed.

Calibration and measurement performance analysis for a spectral band charge-coupled-device-based pyrometer.

Commercial charge-coupled device (CCD) cameras are used widely in industrial applications. This paper uses a commercial CCD camera to develop a spectral band CCD-based pyrometer. To improve the calibration accuracy, a thermometry model based on the extended effective wavelength is introduced to describe the pyrometer. The Tikhonov regularization method is employed to acquire the stabilized solutions for the model parameters considering their sensitivities to the perturbations in the calibration data. Therefore, the relationships between the temperature measurement performances and the system parameters, namely, the electron gain and F-number, are analyzed in terms of the temperature measurement range and sensitivity. Meanwhile, the error and uniformity of the temperature measurements are also investigated using a blackbody furnace. The experimental results show that the temperature measurement range for the designed pyrometer is 800-1203 °C, in which the sensitivity is 0.4906-35.64 °C-1 and the average relative error and non-uniformity of the temperature measurements are 2.5‰ and 1.36%, respectively.

Optimization of Adaptive Lighting Technology Based on Varying-Frequency Sinusoidal Grating Projection

In order to enhance the image quality of multi-reflective 3D scenes during machine vision analysis, an active self-adaptive illumination system to solve the overexposure and underexposure problems is introduced. Based on projector-camera system, adaptive illumination was achieved by modulating the projection brightness at each pixel to be proportional to the pixel brightness of the target scenes, which should firstly establish the accurate pixel correspondence between the projector and camera. In this paper, the performance of adaptive illumination is improved by optimizing the correspondence stage compared with previous research. Different grating patterns with different frequency components are projected and compared to acquire the most effective correspondence, which improves the accuracy of corresponding depth map and the experiment results can achieve higher lighting accuracy reducing the number of iterations as well as the computing time. The image quality indexes, image contrast and number of saturated or dark pixels, are combined to analyze and judge the optimized lighting result. The results demonstrate that the developed technology in this research can achieve a rate of 20 frames per second by using a standard commercial CCD (charge coupled device) camera, where it can run in real time and becomes a viable solution for the industry.

Weak biophoton emission after laser surgery application in soft tissues: Analysis of the optical features.

Nowadays, laser scalpels are commonly used in surgery, replacing the traditional surgical scalpels for several applications involving cutting or ablating living biological tissue. Laser scalpels are generally used to concentrate light energy in a very small-sized area; light energy is then converted in heat by the tissues. In other cases, the fiber glass tip of the laser scalpel is heated to high temperature and used to cut the tissues. Depending on the temperature reached in the irradiated area, different effects are visible in the tissues. In this study, we report the discovery and characterization of the light emitted by soft mammalian biological tissues from seconds to hours after laser surgery application. A laser diode (with hot fiber glass tip) working at 808 nm and commercially available for medical and dentistry applications was used. The irradiated tissues (red meat, chicken breast and fat) showed light emission in the visible range, well detectable with a commercial charge coupled device (CCD) camera. The time decay of the light emission, the laser power effects and the spectral features in the range 500 to 840 nm in the different tissues are here reported.

Enhanced spatial resolution of commercial soft X-ray CCD detectors by single-photon centroid reconstruction

Abstract In many back-illuminated Charge Coupled Device (CCD) detectors the electrons liberated by the absorption of one X-ray photon quickly spread and generate charge-spots larger than the pixel dimensions. Such detectors are considered here. In the soft X-ray range this phenomenon drastically limits the effective spatial resolution to approximately 25 μ m , irrespective of the pixel’s lateral size. For very low flux the charge-cloud centroid determination can be used, on each individual spot, to estimate the actual photon impact position with sub-pixel precision. The readout noise and speed, together with the charge and spatial undersampling, are the main factors limiting the accuracy of this procedure in commercial devices. We have experimentally measured a position uncertainty better than 7 μ m and 10 μ m for 13.5 μ m and 20.0 μ m pixel sizes respectively, around 1 keV photon energy using centroiding algorithms. This study was motivated by the need of high resolution detectors in resonant inelastic (soft) X-ray scattering (RIXS).

Enhanced spatial resolution of commercial soft X-ray CCD detectors by single-photon centroid reconstruction: Technical Note

Abstract The spatial resolution achieved in many back-illuminated Charge Coupled Device (CCD) x-ray detectors is limited by the charge spread over the pixels. For low flux measurements charge-cloud centroiding methods can achieve sub-pixel spatial resolution. Experimental measurements have been performed testing the performance of commercially available soft x-ray CCD detectors (Amorese et al., 2019). In this technical note the centroiding methods used and the numerical tests performed to test the method are described. Finally, more advanced corrective algorithms are discussed.

LiCHy: The CAF’s LiDAR, CCD and Hyperspectral Integrated Airborne Observation System

We describe the design, implementation and performance of a novel airborne system, which integrates commercial waveform LiDAR, CCD (Charge-Coupled Device) camera and hyperspectral sensors into a common platform system. CAF’s (The Chinese Academy of Forestry) LiCHy (LiDAR, CCD and Hyperspectral) Airborne Observation System is a unique system that permits simultaneous measurements of vegetation vertical structure, horizontal pattern, and foliar spectra from different view angles at very high spatial resolution (~1 m) on a wide range of airborne platforms. The horizontal geo-location accuracy of LiDAR and CCD is about 0.5 m, with LiDAR vertical resolution and accuracy 0.15 m and 0.3 m, respectively. The geo-location accuracy of hyperspectral image is within 2 pixels for nadir view observations and 5–7 pixels for large off-nadir observations of 55° with multi-angle modular when comparing to LiDAR product. The complementary nature of LiCHy’s sensors makes it an effective and comprehensive system for forest inventory, change detection, biodiversity monitoring, carbon accounting and ecosystem service evaluation. The LiCHy system has acquired more than 8000 km2 of data over typical forests across China. These data are being used to investigate potential LiDAR and optical remote sensing applications in forest management, forest carbon accounting, biodiversity evaluation, and to aid in the development of similar satellite configurations. This paper describes the integration of the LiCHy system, the instrument performance and data processing workflow. We also demonstrate LiCHy’s data characteristics, current coverage, and potential vegetation applications.

Use of CCD to Detect Terrestrial Cosmic Rays at Ground Level: Altitude vs. Underground Experiments, Modeling and Numerical Monte Carlo Simulation

In this work, we used a commercial charge-coupled device (CCD) camera to detect and monitor terrestrial cosmic rays at ground level. Multi-site characterization has been performed at sea level (Marseille), underground (Modane Underground Laboratory) and at mountain altitude (Aiguille du Midi–Chamonix Mont-Blanc at $+3,780~\hbox{m}$ of altitude) to separate the atmospheric and alpha particle emitter’s contributions in the CCD response. An additional experiment at avionics altitude during a long-haul flight has been also conducted. Experiment results demonstrate the importance of the alpha contamination in the CCD response at ground level and its sensitivity to charged particles. Experimental data as a function of CCD orientation also suggests an anisotropy of the particle flux for which the device is sensitive. A complete computational modeling of the CCD imager has been conducted, based on a simplified 3D CCD architecture deduced from a reverse engineering study using electron microscopy and physico-chemical analysis. Monte Carlo simulations evidence the major contribution of low energy (below a few MeV) protons and muons in the CCD response. Comparison between experiments and simulation shows a good agreement at ground level, fully validated at avionics altitudes with a much higher particle flux and a different particle cocktail composition.

Validation of spectral sky radiance derived from all-sky camera images – a case study

Abstract. Spectral sky radiance (380–760 nm) is derived from measurements with a hemispherical sky imager (HSI) system. The HSI consists of a commercial compact CCD (charge coupled device) camera equipped with a fish-eye lens and provides hemispherical sky images in three reference bands such as red, green and blue. To obtain the spectral sky radiance from these images, non-linear regression functions for various sky conditions have been derived. The camera-based spectral sky radiance was validated using spectral sky radiance measured with a CCD spectroradiometer. The spectral sky radiance for complete distribution over the hemisphere between both instruments deviates by less than 20% at 500 nm for all sky conditions and for zenith angles less than 80°. The reconstructed spectra of the wavelengths 380–760 nm between both instruments at various directions deviate by less than 20% for all sky conditions.

동축반전 헬리콥터형 소형 무인항공기 설계 및 제작

The rotorcraft-based unmanned aerial vehicle(UAV) capable of performing close-range surveillance and reconnaissance has been developed. Trade studies on mission feasibility led to the adoption of a coaxial rotorcraft with twin rotors counter-rotating in one axis and driven by electric motors. A commercial off-the-shelf flight control computer(FCC) and a radio frequency modem were adopted for autonomous navigation. In order to achieve an aerial view, commercial charge-coupled device camera was also integrated into the vehicle. The performance of the completed vehicle was proved with manual flight test, and mission capability was verified through waypoint navigation flight after being equipped with FCC. This paper treats the whole process of design and system integration for development of the coaxial rotorcraft UAV.

Microfabricated Channel Array Electrophoresis for Characterization and Screening of Enzymes Using RGS−G Protein Interactions as a Model System

A microfluidic chip consisting of parallel channels designed for rapid electrophoretic enzyme assays was developed. Radial arrangement of channels and a common waste channel allowed chips with 16 and 36 electrophoresis units to be fabricated on a 7.62 x 7.62 cm(2) glass substrate. Fluorescence detection was achieved using a Xe arc lamp source and commercial charge-coupled device (CCD) camera to image migrating analyte zones in individual channels. Chip performance was evaluated by performing electrophoretic assays for G protein GTPase activity on chip using BODIPY-GTP as enzyme substrate. A 16-channel design proved to be useful in extracting kinetic information by allowing serial electrophoretic assays from 16 different enzyme reaction mixtures at 20 s intervals in parallel. This system was used to rapidly determine enzyme concentrations, optimal enzymatic reaction conditions, and Michaelis-Menten constants. A chip with 36 channels was used for screening for modulators of the G protein-RGS protein interaction by assaying the amount of product formed in enzyme reaction mixtures that contained test compounds. Thirty-six electrophoretic assays were performed in 30 s suggesting the potential throughput up to 4320 assays/h with appropriate sample handling procedures. Both designs showed excellent reproducibility of peak migration time and peak area. Relative standard deviations of normalized peak area of enzymatic product BODIPY-GDP were 5% and 11%, respectively, in the 16- and 36-channel designs.

Automatically guiding a telescope to a laser beam on a biaxial antarctic light detection and ranging system

The operating principle of atmospheric Rayleigh LIDAR (light detection and ranging) systems is that the range-corrected return-backscatter signal is directly related to atmospheric density. For this to be the case full overlap is required between the backscattered laser signal and the field of view of the receive telescope. Time-dependent errors in this alignment compromise the experimental method, and confuse the interpretation of geophysical signals present in the data. We describe a means of locking the alignment of a small LIDAR telescope to the backscattered laser beam, using images obtained with a commercial charge-coupled device camera, to reduce the effects of relative movement of telescope and laser on field overlap. This “autoguiding” system is implemented on a biaxial Rayleigh LIDAR in operation in Antarctica. We achieve a positional precision near 3 camera pixels (1 pixel~1 arc second) across the beam, and 7 camera pixels along the beam. Positional corrections are generated once per minute. The system is capable of removing medium- and long-term drifts in the relative alignment of our telescope and laser during an observing run.

Applications of direct detection device in transmission electron microscopy

A prototype direct detection device (DDD) camera system has shown great promise in improving both the spatial resolution and the signal to noise ratio for electron microscopy at 120-400 keV beam energies (Xuong et al., 2007. Methods in Cell Biology, 79, 721-739). Without the need for a resolution-limiting scintillation screen as in the charge coupled device (CCD), the DDD camera can outperform CCD based systems in terms of spatial resolution, due to its small pixel size (5 microm). In this paper, the modulation transfer function (MTF) of the DDD prototype is measured and compared with the specifications of commercial scientific CCD camera systems. Combining the fast speed of the DDD with image mosaic techniques, fast wide-area imaging is now possible. In this paper, the first large area mosaic image and the first tomography dataset from the DDD camera are presented, along with an image processing algorithm to correct the specimen drift utilizing the fast readout of the DDD system.

Characterization and Calibration of a CCD Detector for Light Engineering

This paper describes the methodology developed for characterizing a commercial charge-coupled device (CCD) camera as a luminance meter for analyzing lighting systems and especially for measurements in road light plants. Today, several luminance meters based on commercial CCD cameras are on the market. They are very attractive for the lighting engineer: The availability of a high number of closely spaced small detectors (pixels) on a single chip permits analyses almost impossible with a traditional luminance meter. These commercial-industrial CCD cameras are sold at prices lower than scientific grade ones. They are factory equipped with a dedicated filter to reach the correct photopic sensitivity V(/spl lambda/), and they are factory calibrated in luminance SI units. The main counterparts in using these cameras are in the difficulties to define the measurement accuracy and the influence of the environment luminance on the measured values of the framed scene, in the low resolution of their A/D converter (usually 8 or 12 bit), and the higher noise level (usually the CCD chip is not cooled). To reach the measurement accuracy required by lighting norms, it is necessary to characterize metrologically a camera and quantify all the possible external influences which could degrade its performances, in real measurement situations, and which could affect the measurement results. A carefully controlled measurement set up and operating procedure could limit the causes of errors and improve the accuracy of measurements obtained in operating conditions. In this way, the measurement uncertainties might be evaluated completely, and considerations on the results could suggest particular operating practices to limit the causes of error due to measurement setup and environmental conditions.

Speckle interferometry experiments with a digital photocamera

We discuss a simple experiment for detecting small deformations by speckle interferometry. The optical setup uses a laser diode for the source together with a lens to expand the laser beam and a beam splitter dividing the beam and illuminating two scattering surfaces. A low-cost, commercial charge coupled device (CCD) photocamera provides images of the two superimposed speckle fields through the beam splitter. We first take a picture with the system at rest, and then take a second one after a deformation is made in a surface. By simple subtraction of the digital pictures, we obtain a fringe pattern that gives us information about the deformation.

Vision-based measurement of weld pool geometry in constant-current gas tungsten arc welding

The common commercial charge coupled device (CCD) camera is combined with a composite light filter to form a vision sensing system of low cost. It can capture the whole image of a weld pool clearly during constant-current gas tungsten arc welding (GTAW). Based on the image-processing algorithm, the edges of the weld pool under different welding conditions can be extracted. Calibration is made to obtain the weld pool geometry in real size. The measured results are useful for developing a welding process control system and verifying the mathematical models of weld pool behaviours.

Hard x-ray spectrometers for NIF (abstract)

A National Ignition Facility (NIF) core diagnostic instrument has been designed and will be fabricated to record x-ray spectra in the 1.2–20 keV energy range. The high-energy electronic x-ray instrument has four reflection crystals with overlapping coverage of 1.2–10.9 keV and one transmission crystal covering 8.6–20 keV. The spectral resolving power varies from approximately 1000 at low energies to 315 at 20 keV. The spectrum produced by each crystal is recorded by a modified commercial dental x-ray charge coupled device (CCD) detector. The scintillators on the CCD detectors are optimized for the energy ranges. A one-channel x-ray spectrometer, using one transmission crystal covering 12–60 keV, will be fabricated for the OMEGA laser facility. The transmission crystal spectrometers are based on instruments originally designed at National Institute for Standards and Technology for the purpose of characterizing the x-ray flux from medical radiography sources. Utilizing one of those instruments and a commercial dental x-ray CCD detector, x-ray images were recorded using a single pulse from a laboratory x-ray source with a peak charging voltage of 200 kV. A resolving power of 300 was demonstrated by recording on film the Kα1 and Kα2 characteristic x-ray lines near 17 keV from a molybdenum anode. The continuum radiation from a tungsten anode was recorded in the 20–50 keV energy range. The transmission crystal spectrometer has sufficient spectral resolution and sensitivity to record the line and continuum radiation from high-Z targets irradiated by the NIF laser and the OMEGA laser.