Commercial Charge-coupled Device Camera Research Articles

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.

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.

Microvibration Measurement Based on Multichannel Projector-Camera System

A noncontact rapid microvibration measurement method is proposed based on multichannel projector-camera system and phase shift profilometry. The multichannel characteristics of color image can be used to calculate vibration information dynamically by collecting only one piece of image. The waveform within a frequency range from 0.1 to 2 Hz is measured accurately by means of this vibration measurement technology, and minimum vibration amplitude is about 163 um. The system can be achieved by a standard low cost commercial charge coupled device camera with 30 frames/s.

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.

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.

A simple colorimetric device for rapid detection of Hg2+ in water

A 'turn-on' fluorescent colorimetric device for Hg(2+) sensing was built using a dual light-emitting diode system. Fluorescence generated from a rhodamine derivative (RHD), an indicator for Hg(2+) sensing, was combined with a background red light, and the complex light was captured by a commercial charge coupled device camera or by the naked eye.

Colorimetric optical pH sensor production using a dual-color system

Utilizing a dual color design, a rapid, convenient and in situ applicable pH sensor was constructed based on a dual light-emitting diode (LED) system. One LED lamp with a maximum emission wavelength of 465 nm was used to excite the pH fluorescent indicator, 5(6)-carboxyfluorescein (CF), and the other LED lamp with red color emission ( λ max 660 nm) was selected to supply a stable color background (the reference light). The dual light from the fluorescent emission of CF and the background light were captured using a commercial charge coupled device camera. Under constant and stable background light, the change of the CF fluorescence intensity in solutions at different pH values appeared as different colors. The sensor characteristics, including the effects of temperature, co-existing ions, and the sample analysis performance, were investigated.

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.

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.

Construction and testing of a computer-based intraoral laser scanner for determining tooth positions

An optical set-up for intraoral data acquisition based on the principle of laser triangulation was developed. The system consists of a pig-tailed laser with line generating optics, a stepping motor driven positioning stage, a commercial CCD (charge coupled device) camera system with frame grabber interface, a control personal computer and a mirror system compensating for the fact that there is no possibility of watching an object directly in the mouth under a certain angle except from a facial position during intraoral scanning. Due to the size of the prototype measurements were still restricted to plaster casts. In order to evaluate its accuracy, the measurements were compared with those taken with a commercial laser scanner and a coordinate measurement table. The accuracy of the prototype scanner was determined to be Δ XYZ=0.04 mm using gauge blocks of given dimensions and proved to range between the commercial laser scanner and the coordinate measurement table (i.e., it was slightly better than that of the commercial scanner). Applications in orthodontics were demonstrated by scanning plaster casts and measuring distances on reconstructed surfaces. The measured distances showed a maximum deviation of about ±0.2 mm compared with the data of the coordinate measurement table, which served as a reference. In addition, reconstruction of three-dimensional tooth movements was performed on the scan data. The translational and rotational parameters gained from the superimposition of scanned point clouds and describing tooth movement were also in good accordance with the reference. The achieved accuracy proved to be sufficient for further development which should include a reduction in size and the use of more precise device components.