Single CCD Image Research Articles

High-precision laser transverse differential confocal radius measurement method.

To meet the current need for high-precision and environment-insensitive measurement of the radius of curvature (ROC), we proposed a transverse differential confocal radius measurement (TDCRM) method based on the optical system of the confocal ROC measurement. Using a D-shaped aperture and the virtual pinhole technology, two signals, analogous to the pre-focus and post-focus signals in the two-detector-based differential confocal radius measurement (DCRM), can be obtained from two segmentations of a single CCD image. The difference of these two signals can be used to precisely determine the cat's-eye and confocal positions, thereby achieving the high-accuracy ROC measurement as DCRM with a relative repeatability of 3.4 ppm. Furthermore, compared to DCRM, no optical alignment is needed after replacing the objective lens, which significantly reduces the time cost of measurements. We believe this novel and high-precision ROC measurement method will widen its application to optical manufacturing and provide an exciting opportunity for mass production of the ROC measurement instrument.

Astrometric observations of visual binaries using 26-inch refractor during 2007–2014 at Pulkovo

We present the results of 15184 astrometric observations of 322 visual binaries carried out in 2007–2014 at Pulkovo observatory. In 2007, the 26-inch refractor (F = 10413 mm, D = 65 cm) was equipped with the CCD camera FLI ProLine 09000 (FOV 12′ × 12′, 3056 × 3056 pixels, 0.238 arcsec pixel−1). Telescope automation and weather monitoring system installation allowed us to increase the number of observations significantly. Visual binary and multiple systems with an angular distance in the interval 1.ʺ1–78.ʺ6 with 7.ʺ3 on average were included in the observing program. The results were studied in detail for systematic errors using calibration star pairs. There was no detected dependence of errors on temperature, pressure, and hour angle. The dependence of the 26-inch refractor’s scale on temperature was taken into account in calculations. The accuracy of measurement of a single CCD image is in the range of 0.ʺ0005 to 0.ʺ289, 0.ʺ021 on average along both coordinates. Mean errors in annual average values of angular distance and position angle are equal to 0.ʺ005 and 0.°04 respectively. The results are available here http://izmccd.puldb.ru/vds.htmand in the Strasbourg Astronomical Data Center (CDS). In the catalog, the separations and position angles per night of observation and annual average as well as errors for all the values and standard deviations of a single observation are presented. We present the results of comparison of 50 pairs of stars with known orbital solutions with ephemerides.

Image demosaicing using content and colour-correlation analysis

Most digital cameras of today use a single CCD image sensor with alternating arrangement of red, blue and green colour filters in what is known as a Bayer pattern. To extract a full colour image, a demosaicing strategy has to be applied. In this paper we propose a content adaptive demosaicing strategy utilising structure analysis and correlation between the red, green and blue planes. These two aspects are used for the classification of a block of pixels to generated trained filters. The proposed method aims to reconstruct a high quality demosaiced image from a Bayer pattern in a colour filter array efficiently. Experimental results show that the proposed strategy performs comparatively as more expensive methods.

Photonic bandgap fiber bundle spectrometer

By using a photonic bandgap (PBG) fiber bundle and a monochrome CCD camera, we experimentally demonstrate an all-fiber spectrometer. A total of 100 Bragg fibers that have complementary and overlapping bandgaps are chosen to compose the fiber bundle. A monochrome CCD is then used to capture the binned image. To reconstruct the test spectrum from a single CCD image, we develop an algorithm based on pseudoinversion of the spectrometer transmission matrix. We demonstrate that the peak center wavelength can always be reconstructed within several percent of its true value regardless of the peak width or position, and that, although the widths of the individual Bragg fiber bandgaps are quite large (60-180nm), the spectroscopic system has a resolution limit of approximately 30nm. Moreover, we conclude that, by minimizing system errors, the resolution can be further improved down to several nanometers in width. Finally, we report fabrication of PBG fiber bundles containing hundreds of fibers using a two-stage drawing technique. This method constitutes a very promising approach toward industrial-strength fabrication of all-fiber spectrometers.

Cosmic-ray rejection for single spectroscopic CCD images by means of template matching

This article describes a novel algorithm for cosmic-ray rejection in single spectroscopic CCD images. This algorithm is based on a variation of template matching. It focuses on identifying those pixels belong to spectra, while other conventional algorithms tried to locate the cosmic-ray hits directly. The main principle is applying template matching to find suspicious blocks, which is followed by surface patching to locate the legitimate pixels accurately. Therefore, the rest pixels are the ones corrupted by cosmic-ray hits. Meanwhile, almost all the parameters are automatically extracted from the images. Examples of its performance are given for both simulated and observed images. It shows an advantage of significantly low false alarm rate with relatively high detection rate (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cosmic-Ray Detection Based on Gray-Scale Morphology of Spectroscopic CCD Images

AbstractDetection of cosmic-ray hits is important because of their disturbing effects on image processing. An algorithm based on gray-scale morphology to detect cosmic-rays in single spectroscopic CCD images is presented in this paper. Based on the morphological differences between cosmic-ray hits and spectra, the operations of erosion and dilation are used to deal with images successively, with appropriate structuring elements. Points of cosmic-ray hits can be detected by analyzing the variation between data pre- and post-operation. Examples of the algorithm are given at the end of this paper, with several groups of both simulated LAMOST images and observed SDSS images to show its performance.

Detection of Cosmic-Ray Hits for Single Spectroscopic CCD Images

ABSTRACTA new method of detecting cosmic-ray hits from single spectroscopic CCD images is proposed in this paper. First, one-order difference operations in two directions respectively are calculated to detect the candidate points of the cosmic-ray hits by using two thresholds. Second, Bessel curve fitting is adopted to calculate the deviations of the candidate points so as to find the confirmation points of cosmic-ray hits. At the end of this paper, five groups of simulation data and one group of observation data from SDSS are used to demonstrate the effectiveness of the proposed method.

Cost-Effective Color Filter Array Demosaicing Using Spatial Correlation

In this paper, we propose a cost-effective color filter array (CFA) demosaicing method for digital still cameras in which a single CCD or CMOS image sensor is used. Since a CFA is adopted, we must interpolate missing color values in the red, green and blue channels at each pixel location. While most state-of-the-art algorithms invest a great deal of computational effort in the enhancement of the reconstructed image to overcome the color artifacts, we focus on eliminating the color artifacts with low computational complexity. Using spatial correlation of the adjacent pixels, the edge-directional information of the neighbor pixels is used for determining the edge direction of the current pixel. We apply our method to the state-of-the-art algorithms which use edge-directed methods to interpolate the missing color channels. The experiment results show that the proposed method enhances the demosaiced image quality, especially visually, by removing most of the color artifacts.

Automatic Detection Algorithm for Small Moving Objects

Abstract We have devised an automatic detection algorithm for unresolved moving objects, such as asteroids and comets. The algorithm uses many CCD images in order to detect very dark moving objects that are invisible on a single CCD image. We carried out a trial observation to investigate its usefulness, using a 35-cm telescope. By using the algorithm, we succeeded to detect asteroids down to about 21 mag. This algorithm will contribute significantly to searches for near-Earth objects and to solar-system astronomy.

Automated acquisition of cryo-electron micrographs for single particle reconstruction on an FEI Tecnai electron microscope

AutoEM is a software package developed by Zhang et al. [J. Struct. Biol. 1356, 251] for semi-automated acquisition of cryo-electron micrographs from Tecnai series electron microscopes and is used frequently at the lowest level of automation. We report here on the new progress that we have made based on their preliminary work. A fourth low-dose state is created where the system can pre-select all the good holes in a grid square from a single CCD image taken at low magnification, making the system operative at much higher levels of automation. An additional control interface enables the operator to monitor the status of the program and the quality of the data, interact with the program, and direct the execution process according to intermediate results. When data acquisition is in progress, all useful information is automatically saved in certain text files which are easily accessible by a database. More detailed improvements and general advantages are illustrated and discussed. We have started to use the program to perform routine data collection. A number of applications show that the performance of the program is satisfactory and the quality of the micrographs and their power spectra acquired by the program is comparable to those manually collected under the same conditions.

Color interpolation with variable color ratio considering cross-channel correlation

A color interpolation algorithm is necessary to acquire color images of good quality with a digital still camera in which a single CCD image sensor is equiped. Since a color filter array is adopted, we must interpolate missing color values in the red, green, and blue channels at each pixel location. Inappropriate color interpolation causes color arti- facts, resulting in degraded color resolution. A color interpolation algo- rithm with a variable color ratio is proposed by incorporating cross- channel correlation. The color ratio of weighted sums in the color channels is utilized instead of the weighted sum of color ratios, and the color ratio varies with respect to the cross-channel correlation at each pixel. The proposed algorithm is composed of initial color interpolation step and the updating step of the green channel, where the updating step is carried out iteratively. Furthermore, a minus weighted sum based on the external divide, a modified edge indicator function, and a 5 35 support region for the red and blue channels are also adopted to improve the performance. With the proposed algorithm, we have achieved im- provements in the image quality especially along the edges and in the detail of the image by removing color artifacts. The superiority of the proposed algorithm is demonstrated in the experimental results. © 2004

507 単一 CCD 画像の収差影響解析による 3 次元 PTV の検討

507 単一 CCD 画像の収差影響解析による 3 次元 PTV の検討

512 PIV のための単一 CCD 画像による粒子の 3 次元位置推定法

512 PIV のための単一 CCD 画像による粒子の 3 次元位置推定法

Simultaneous three-dimensional dynamic deformation measurements with pulsed digital holography

The three deformation components x, y, z of a vibrating object are measured simultaneously by use of digital holography with a double-pulse ruby laser source. The object is illuminated from three different directions, each optically path matched with three reference beams such that three independent digital holograms are formed and added incoherently in one single CCD image. The optical phase difference between the two recordings taken for each hologram is quantitatively evaluated by the Fourier-transform method so that a set of three phase maps is obtained, representing the deformation along three sensitivity vectors. The total object deformation is obtained as a vector resultant from the data of the three phase maps. To give the full three-dimensional (3-D) description, the shape of the object is measured by the two-wavelength contouring method. Experiments are performed with a cylinder as the test object, transiently and harmonically excited. The 3-D deformation and shape measurement results are presented graphically.