Differential Imaging Technique Research Articles

Quantitative analysis of thin samples by differential absorption imaging using a laser-plasma soft X-ray source

We consider the application of the differential absorption imaging technique in the soft X-ray region. The surface-density maps of test samples containing bromine, resulting from the application of the differential absorption imaging technique, are presented. Images of the samples were obtained in an X-ray monochromatic projection imaging scheme based on a spherically bent crystal using line emission close to the $L_2$ edge of bromine from a microplasma produced by focusing a nanosecond laser on the surface of an aluminum target.

Differential absorption imaging for elemental analysis of thin samples using a soft laser-plasma X-ray source

The differential X-ray imaging technique is a powerful tool for the detection of small concentrations of contrast agents in samples, as demonstrated recently by many biological and medical applications using synchrotron radiation. In this paper, we present an implementation of this technique using a laser-plasma soft X-ray source combined with an X-ray imaging system based upon a spherically bent Bragg crystal. Using a test sample containing a solution of LiBr of known concentration, we demonstrate that the use of our table-top configuration is suitable to detect Br inside our sample via differential imaging at the L 2 edge of Br at 7.7684 Å .

Soft laser-plasma X-ray source for differential absorption imaging of tracing elements in thin samples

The differential imaging technique is particularly suitable for the detection of small concentrations of contrasts agents for biological and medical applications in samples using X-ray radiography. In this paper, we present an application of this technique using a laser-plasma soft X-ray source combined with a bent crystal. Using a Fresnel plate as a test object, we were able to obtain spatial resolutions of the order of a few tens of microns. The use of our configuration to perform differential imaging of a test-sample at the L2 edge of Br at 1,596 eV is finally demonstrated.

NACO polarimetric differential imaging of TW Hya

We present high-contrast imaging data on the disk of the classical T Tauri star TW Hya. The images were obtained through the polarimetric differential imaging technique with the adaptive optics system NACO. Our commissioning data show the presence of polarized disk emission between 0.1´´ and 1.4´´ from the star. We derive the first Ks-band radial polarized intensity distribution. We show that the polarized intensity compares well to shorter wavelengths surface brightness observations and confirm the previously reported gradual slope change around 0.8´´. These results show the potential of the new polarimetric differential imaging technique at 8 m-class telescopes to map the inner regions of protoplanetary disks.

Nondestructive imaging of a type I optical fiber Bragg grating.

Nondestructive images of refractive-index variation within a type I fiber Bragg grating have been recorded by the differential interference contrast imaging technique. The images reveal detailed structure within the fiber core that is consistent with the formation of Talbot planes in the diffraction pattern behind the phase mask that had been used to fabricate the grating.

Effects of Quasi-Static Aberrations in Faint Companion Searches

We present the first results obtained at CFHT with the TRIDENT infrared camera, dedicated to the detection of faint companions close to bright nearby stars. The camera's main feature is the acquisition of three simultaneous images in three wavelengths (simultaneous differential imaging) across the methane absorption bandhead at 1.6 micron, that enables a precise subtraction of the primary star PSF while keeping the companion signal. The main limitation is non-common path aberrations between the three optical paths that slightly decorrelate the PSFs. Two types of PSF calibrations are combined with the differential simultaneous imaging technique to further attenuate the PSF: reference star subtraction and instrument rotation to smooth aberrations. It is shown that a faint companion with a DeltaH of 10 magnitudes would be detected at 0.5 arcsec from the primary.

High Dynamic Range and the Search for Planets

General arguments for optimized coronagraphy in the search for planets are presented. First, off-axis telescopes provide the best telescopic platforms for use with coronagraphy, and telescope fabrication technology now allows the fabrication of such telescopes with diameters of up to 6.5 m. We show that in certain circumstances a smaller telescope with an off-axis primary has a signal-to-noise advantage compared with larger Cassegrain telescopes. Second, to fully exploit the advantages of the coronagraph for suppressing stray light, it is necessary to use a high Strehl ratio adaptive optics system. This can be best achieved initially with modest aperture telescopes of 3–4 m in diameter. Third, application of simultaneous differential imaging and simultaneous polarimetric techniques are required to reach the photon-limit of coronagraphic imaging. These three developments, if pursued together, will yield significant improvements in the search for planets.

Investigating the vortex melting phenomenon in BSCCO crystals using magneto-optical imaging technique

Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals of Bi_2Sr_2CaCu_2O_8 (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface with varying field (H) or temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder or inhomogeneities across the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local melting temperature / field, we have constructed maps of the melting landscape T_m(H,r), viz., the melting temperature (T_m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite effects on the local melting transition.

Magneto-optical imaging of vortex lattice melting transition in Bi 2Sr 2CaCu 2O 8+ y

Magneto-optical differential imaging technique is applied to the observation of the vortex lattice melting transition in Bi 2Sr 2CaCu 2O 8+ y . Contrary to the naive expectation, the nucleation of the vortex liquid paddle occurs in a rather inhomogeneous manner. The front of the vortex solid–liquid interface propagates reflecting the intrinsic inhomogeneities of the crystal. Direct compositional mapping of the constituent atoms indicates that the change in the chemical composition have some correlation with the behavior of the vortex solid–liquid interface. Changes in the superconducting parameters due to the variation of the local doping level could be the origin of such an effect.

Helical computed tomographic angiography in obstructed total anomalous pulmonary venous drainage

Helical computed tomographic angiography with differential color imaging technique clearly demonstrated pulmonary venous obstruction in an infant with total anomalous pulmonary venous drainage before and after operation. This technique is less invasive and provides precise spatial information of complicated vascular anomalies.

Images in cardiovascular medicine. Differential color imaging technique of helical CT angiography in the diagnosis of total anomalous pulmonary venous drainage.

Three-dimensional images obtained by helical CT are very informative for the diagnosis of various kinds of cardiovascular diseases. However, it is sometimes difficult to recognize spatial relationships of arteries, veins, tracheae, and bronchi in some complicated congenital heart diseases, such as total anomalous pulmonary venous drainage (TAPVD), major aortopulmonary collateral arteries, vascular rings, etc. Because the spatial information is essential for successful surgical intervention, we have developed a differential 3D color imaging technique that uses helical CT angiography. After arteries and veins had been determined by the shape, continuity, and CT density on sequential CT images, …

Normalized Differential Kerr Microscopy An Advanced Method for Magnetic Imaging

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Optoelectronic device mapping using differential imaging techniques

A mapping technique has been developed that uses differential imaging to characterize semiconductor optoelectronic devices. Although the technique was developed for examination of optical modulators, it has been extended to provide information on the uniformity and bandgap of any material through which one can transmit light. The sharpness of the bandedge, maximum absorption strength, and the film thickness determine the sensitivity of the technique for any particular application. For example, the bandedge sensitivity in 100 periods of InGaAs/GaAs multiple quantum wells was ±20 μeV and can be detected at each location in the field of view in under three minutes. This technique has been applied to modulators designed using strained layer materials for use at a 1-μm operating wavelength.

Determination of thin film media model parameters using DPC imaging and torque measurements

A micromagnetic model consisting of coupled hexagonal grains has been used to investigate the remanent-state ripple structure, the expected torque, and the rotational hysteresis behavior of thin magnetic films. The parameters of the model are the anisotropy field, the magnetostatic coupling, and the phenomenological exchange coupling between grains. The scale of the ripple pattern as measured by Lorentz microscopy using the differential phase contrast imaging technique can be used to fix the model parameters unambiguously, under the assumption that the parameters have fixed single values. Experimental rotational hysteresis curves cannot by fitted in detail without assuming a fairly broad distribution of anisotropy fields. It should be possible, given both kinds of data on a single sample, to determine the exchange coupling and average anisotropy field as well as a distribution of anisotropy fields which fits the width of the rotational hysteresis curve. >

Design and application of a computer-controlled confocal scanning differential polarization microscope

Based on the confocal scanning and differential polarization imaging technique, a computer-controlled confocal scanning differential polarization microscope has been built. This system possesses extensive image processing capability that provides digitized regular and/or differential polarization images. This microscope combines the advantages of the confocal design and the extended electronic sensitivity of polarization modulated instrumentation to achieve the measurement of an anisotropy ratio as small as 10−5. In this paper, the basic theory and the instrument are described. In addition, some samples are used to test the actual performance of the system, and it is found that the system provides high resolution (0.3 μm at wavelength 546 nm), reduced depth of field, and high signal-to-noise ratio (83 dB at 10-ms integration time) images. Finally, some biological applications are shown.

The H-alpha chromosphere of Alpha Orionis

view Abstract Citations (31) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The H alpha Chromosphere of Alpha Orionis Hebden, Jeremy C. ; Eckart, Andreas ; Hege, E. Keith Abstract Images have been obtained of the H-alpha chromospheric envelope of Alpha Ori at the diffraction-limited resolution of the cophased Multiple Mirror Telescope. A phaseless image reconstruction was applied to speckle interferometric data obtained at continuum wavelengths, and the result was used to produce images of the highly extended H-alpha region from results achieved using the differential imaging technique. Two such images are presented which were obtained from observations made almost 2 yr apart. Significant, and highly isotropic emission out to several stellar radii is exhibited. A very large optical depth in H-alpha is indicated. A simple mathematical expression for the radially averaged profile of the images is derived empirically. Publication: The Astrophysical Journal Pub Date: March 1987 DOI: 10.1086/165097 Bibcode: 1987ApJ...314..690H Keywords: Chromosphere; Stellar Atmospheres; Supergiant Stars; Absorption Spectra; H Alpha Line; Image Reconstruction; Optical Thickness; Speckle Interferometry; Stellar Envelopes; Astrophysics; INTERFEROMETRY; STARS: CHROMOSPHERES; STARS: INDIVIDUAL CONSTELLATION NAME: ALPHA ORIONIS full text sources ADS | data products SIMBAD (2)