INFRARED HOLOGRAPHY AT 10.6μm
TL;DR: In this article, the authors used a thermochromic material, cuprous mercuric iodide, to record an on-axis interference pattern, which was subsequently reduced in a two-step photographic process, and reconstruction was accomplished in the visible with He-Ne laser light.
Abstract: Infrared holography at 10.6 μm has been accomplished by using a thermochromic material, cuprous mercuric iodide, to record an on‐axis interference pattern. The pattern is subsequently reduced in a two‐step photographic process, and reconstruction is accomplished in the visible with He–Ne laser light.
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TL;DR: The optical reconstruction in the visible range (0.532 microm) of digital holograms recorded at long IR wavelengths by means of a spatial light modulator is demonstrated and the high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.
Abstract: We demonstrate the optical reconstruction in the visible range (0.532μm) of digital holograms recorded at long IR wavelengths (10.6μm) by means of a spatial light modulator. By using an integrated recording-reconstruction system, it is, in fact, feasible to achieve direct imaging of holograms acquired outside the visible range, i.e., in the IR spectrum. By choosing a Fourier recording configuration, the reconstructed image, obtained at about a 20 times shorter wavelength than the acquisition image, exhibits minor aberrations, which do not significantly affect the optical reconstruction. The high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.
49 citations
TL;DR: This work discusses the development of the digital holographic interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test.
Abstract: Digital holographic interferometry in the long-wave infrared domain has been developed by combining a CO2 laser and a microbolometer array The long wavelength allows large deformation measurements, which are of interest in the case of large space reflectors undergoing thermal changes when in orbit We review holography at such wavelengths and present some specific aspects related to this spectral range on our measurements For the design of our digital holographic interferometer, we studied the possibility of illuminating specular objects by a reflective diffuser We discuss the development of the interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test
49 citations
25 Feb 2015
TL;DR: In this paper, a state-of-the-art state of the art of important advances in the field of digital holography is presented. But the authors are interested in detailing advances related to the fundamentals of holographic metrology, digital holographic microscopy, and full-field vibrometry.
Abstract: ew Tech n iq u es in D ig ial H o lo g ap h y E d ied b y P acal P iart This book is devoted to special techniques in digital holography. The authors establish a synthetic state of the art of important advances in the field of digital holography. They are interested in detailing advances related to fundamentals of digital holography, in-line holography, digital color holographic metrology, digital holographic microscopy, infrared holography and special techniques in full-field vibrometry.
40 citations
TL;DR: Three different interferometric techniques are described, using a long-wave infrared radiation produced by a CO(2) laser and recorded on a microbolometer array, for nondestructive testing of electronic speckle pattern interferometry and digital shearography.
Abstract: We describe three different interferometric techniques (electronic speckle pattern interferometry, digital holographic interferometry, and digital shearography), using a long-wave infrared radiation produced by a CO(2) laser and recorded on a microbolometer array. Experimental results showing how these methods can be used for nondestructive testing are presented. Advantages and disadvantages of these approaches are discussed.
40 citations
TL;DR: In this paper, an electron beam gun evaporation system was used to deposit the prepared powder in a thin film form onto a Corning 7059 glass substrate, and the x-ray diffraction study revealed that the as-deposited films are polycrystalline in nature and have a composition corresponding to the Cu2HgI4 single phase.
Abstract: Cu2HgI4 powder has been prepared by precipitation from reactive chemical solutions. An electron beam gun evaporation system was used to deposit the prepared powder in a thin film form onto a Corning 7059 glass substrate. The x-ray diffraction study reveals that the as-deposited films are polycrystalline in nature and have a composition corresponding to the Cu2HgI4 single phase. The differential thermal analysis curve exhibits a strange endothermic peak located at a temperature of 355.5 K, corresponding to the phase change from the first-order phase to the fast ion-conducting phase. The phase change is accompanied by a colour change from bright-red (β-phase) to dark-brown (α-phase). The optical properties of as-deposited films have been calculated from the recorded transmission and reflection data in the spectral range 600–2500 nm. The refractive index of the as-deposited films was found to follow the two-term Cauchy dispersion relation and is adequately described by the effective-single-oscillator model. The refractive index–wavelength variation leads to the determination of the oscillator parameters Eo and Ed to be 3.113 and 9.883, respectively. The static refractive index, no(0), and static dielectric constant, es, were also calculated as a result of the latter data and were found to be 2.043 and 4.175, respectively. The analysis of the optical absorption coefficient confirmed the presence of a direct optical transition with a band gap energy of 1.96 eV.
36 citations
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TL;DR: In this paper, the effect of fluctuations in configuration, which was neglected by Bragg and Williams, was taken into account, which is similar to that used in Weiss's theory of ferromagnetism.
Abstract: In a recent paper, Bragg and Williams have pointed out that the arrangement of the atoms in an alloy depends in a striking way on the temperature. At high temperatures, the atoms are distributed practically at random among the lattice points of the crystal, but at low temperatures a superlattice may be formed such that the atoms of one kind are arranged in a regular lattice of their own and the atoms of the other kind occupy the remaining “sites” in the crystal. The transition from the ordered to the disordered state occurs in a fairly small temperature range, and is accompanied by a large specific heat, an increase in electric resistance, etc. The mathematical method employed by Bragg and Williams is similar to that used in Weiss’s theory of ferromagnetism . Both involve the assumption that the “force” tending to produce order at a given point is uniquely determined by the average state of order throughout the crystal. Actually it will depend on the configuration of the atoms in the immediate neighbourhood of the point under consideration. The order of the crystal as a whole determines this configuration only on the average. In the present paper, the effect of fluctuations in configuration, which was neglected by Bragg and Williams, will be taken into account.
1,054 citations
TL;DR: In this article, the authors derived formulas for angular, lateral, and longitudinal magnification in reconstructed images by holography (imaging by reconstructed wavefronts) and discussed conditions under which one or more of the aberration coefficients vanish, taking into account an off-axis angle of both reference and illuminating beam.
Abstract: Formulas for angular, lateral, and longitudinal magnification in reconstructed images by holography (imaging by reconstructed wavefronts) are derived and discussed as a function of object–hologram distance, radii of spherical reference and illuminating wavefronts, wavelength ratio of reconstructing to recording radiation, and scale-change factor of the hologram. Expressions for third-order aberrations in the reconstructed wavefronts of point objects are given and conditions are established under which one or more of the aberration coefficients vanish, taking into account an off-axis angle of both reference and illuminating beam.
345 citations
59 citations
TL;DR: In this paper, the Tief-Temperaturmodifikation des Cu2HgJ4 and Ag2HGJ4 wurden gefunden, die mit den von KETELAAR angegebenen nicht ubereinstimmen.
Abstract: Fur die Tief-Temperaturmodifikation des Cu2HgJ4 und Ag2HgJ4 wurden Strukturen gefunden, die mit den von KETELAAR angegebenen nicht ubereinstimmen. Beide Verbindungen kristallisieren tetragonal; Cu2HgJ4: a = 6,080 kX; c = 12,218 kX; c/a = 2,011; Ag2HgJ4: a = 6,304 kX; c = 12,608 kX; c/a = 2,000. Die Elementarzellen enthalten zwei Formeleinheiten. Die Verbindungen sind nicht isotyp; β-Cu2HgJ4 kristallisiert in einem Gitter der Raumgruppe DI42m, β-Ag2HgJ4 in der Raumgruppe SI4. Die beiden Strukturen unterscheiden sich dadurch, das beim β-Cu2HgJ4 die Metallatome schichtenartig, beim β-Ag2HgJ4 dagegen besser durchmischt die Tetraederlucken des kubischdicht gepackten Jodgitters besetzen. Mischkristalle der Zusammensetzung CuAgHgJ4 haben die Struktur des β-Cu2HgJ4 mit statistischer Verteilung des Kupfers und Silbers auf die Kupferlagen.
54 citations
25 citations