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  • 1
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    Laser holographic detection of tiny thin tapes beneath a thick opaque composite structure (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Real-time laser holographic interferometry technique has been applied successfully in the detection of 1mm x 1mm x 0.025mm duct tapes hidden beneath a 150mm x 150mm x 16mm ceramic-epoxy-fiberglass sandwiched structure. The experimental results clearly demonstrate future applicability of this technique in the optical nondestructive detection of debonds and flaws in such composite structures.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
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  • 2
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    A practical method for holographic interference fringe assessment (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A theory concerning the problem of fringe interpretation reported by Hecht et al. (1973) is extended and a simpler semiquantitative method for the assessment of the fringes is developed. According to the new method, the fringe contrast between any two points on an object, is determined on the basis of the difference of the path-length changes at each point. The theoretical development of the method is discussed and a description of experimental results is given.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering; 16; Mar
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  • 3
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    Applications of laser speckles in a holographic nondestructive test system (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The grainy or speckle phenomenon of laser light is caused by two inherent characteristics of the laser - the coherence and monochromaticity of the radiation. Recent development have shown that this phenomenon can be used to measure minute surface displacements, surface strains, or vibrations of a body. The present paper deals with two techniques employing the speckle effect. One is called speckle beam holographic interferometry, and the other speckle photographic interferometry. A major advantage of the first technique is the elimination of the stringent vibration isolation requirement in existing holographic nondestructive test systems. The advantage of the second technique is that the resulting photographic data are sensitive only to the in-plane components of the surface variations. The basic principles and practical limitations of these techniques are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Southeast Region 3 Conference; Apr 04, 1977 - Apr 06, 1977; Williamsburg, VA
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  • 4
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    Sensor for measuring instantaneous angle of attack of helicopter blades (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Various research activities are reported in the following areas: (1) improving and testing probes; (2) theoretical studies of probe motion; and (3) improving research facilities. It is concluded that a satisfactory solution to the problem of measuring angle of attack of helicopter blades may be found in the near future.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-154808
    Format: application/pdf
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  • 5
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    Optical correlation of surface displacement (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A coherent optical correlation technique is used to measure surface displacements. In the event that the surface roughness of the test object is invariant during the object's translation, the correlation intensity peak remains constant. A simple relationship between the displacement of the surface and the displacement of the peak correlation signal is found and experimentally verified.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering; 18; May-June
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  • 6
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    Dual hologram design study (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A phase modulated triple exposure technique was incorporated into a holographic nondestructive test (HNDT) system. The technique was able to achieve a goal of simultaneously identifying the zero-order fringe and determining the direction of motion (or displacement). Basically, the technique involves the addition of one more exposure, during the loading of the tested object, to the conventional double-exposure hologram. A phase shifter is added to either the object beam or the reference beam during the second and third exposure. Theoretical analysis with the assistance of computer simulation illustrated the feasibility of implementing the phase modulation and triple-exposure in the HNDT systems. Main advantages of the technique are the enhancement of accuracy in data interpretation and a better determination of the nature of the flaws in the tested object.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-150596 , REPT-129-78
    Format: application/pdf
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  • 7
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    Experimental approach toward holographic interferometric fringe interpretation (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Current literature concerning the measurement of small displacements by the laser holographic technique was reviewed. It was found that existing theories are extremely difficult, if not impossible, to apply to any realistic nondestructive testing conditions in which the geometries of the objects are complex and the three-dimensional displacements are irregular. An experimental approach was adopted for interpreting correlation between real time holographic fringe patterns and small displacements. Preliminary results show that the present method is feasible for the quantitative interpretation of the fringes as well as the calibration of the mobile HNDT system.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-120707 , BER-175-74
    Format: application/pdf
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  • 8
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    A theoretical analysis of the MSFC holographic correlation system (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A theoretical analysis was completed for the correlation output signal for the MSFC holographic correlation filtering system. Under appropriate assumptions, the correlation output was derived as a function of the roughness of the tested surface, the displacement of the illuminated area of the test surface, the characteristics of the optical components used in the system, and the system configuration. In addition, an approximate relationship between the displacement of the detected signal (which is focused on the photomultiplier tube) and the displacement of the illuminated area on the test surface was also derived.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-150283 , REPT-122-77
    Format: application/pdf
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  • 9
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    Speckle reference beam holographic and speckle photographic interferometry in non-destructive test systems (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The techniques of speckle beam holographic interferometry and speckle photographic interferometry are described. In particular, their practical limitations and their applications to the existing holographic nondestructive test system are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-150122 , LUMIN-121-76
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  • 10
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    Electro-optic and holographic measurement techniques for the atmospheric sciences (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A comprehensive examination is made of recent advanced research directions in the applications of electro-optical and holographic instrumentations and methods to atmospheric sciences problems. In addition, an overview is given of the in-house research program for environmental and atmospheric measurements with emphasis on particulates systems. Special treatment is made of the instrument methods and applications work in the areas of laser scattering spectrometers and pulsed holography sizing systems. Selected engineering tests data on space simulation chamber programs are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Seminar on Multidisciplinary microscopy; Apr 18, 1977 - Apr 21, 1977; Reston, VA
    Format: text
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