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  • 1
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    Development of an effusive inlet for mass spectrometric gas analysis of hypersonic boundary layer (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The use of a microchannel plate (MCP) as a mass spectrometer inlet device to allow nonintrusive sampling of flight vehicle boundary layers is investigated. Two possible configurations for mounting the inlet are studied: (1) flow coaxial with the channels; and (2) flow perpendicular to the channel axis. The test gases are pure Kr; pure Ne; and a mixture of 10 pct Kr, 10 pct Ne, and 80 pct N2. The pressure ranges studied vary from 500 to 10 microns. A mass discrimination at the quadrupole mass spectrometer is observed, indicating an enrichment in the heavier gas. Possible explanations for this enrichment are discussed. It is shown that an MCP is capable of acting as a nonintrusive sampling device. Further work that will enable quantitative determination of the species at the surface is discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''87 - International Congress on Instrumentation in Aerospace Simulation Facilities; Jun 22, 1987 - Jun 25, 1987; Williamsburg, VA; United States
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  • 2
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    Phase conjugate Twyman-Green interferometer for testing conicoidal surfaces (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An application of a phase conjugate Twyman-Green interferometer for testing a parabolic mirror is demonstrated. The interferometer is free from aberrations due to the self-focusing property of the phase conjugate mirror in one arm of the interferometer. It does not require a precision spherical mirror in the reference arm.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Testing and Metrology III: Recent Advances in Industrial Optical Inspection; Jul 08, 1990 - Jul 13, 1990; San Diego, CA; United States
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  • 3
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    Measurement of birefringence of optical materials using a wedged plate interferometer (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A nondestructive technique for measuring the birefringence of optical materials such as calcite using wedged plate interferometer is presented. The sample needed for measuring the refractive index must be polished in the form of a parallel plate. The method is based on the measurement of the longitudinal displacement of the focus when the parallel plate is inserted in a converging beam of light. The displacement of the focus is a measure of the refractive index of the optical material. In the case of a uniaxial crystal, the displacement of the focus for the extraordinary ray is different from the displacement of the focus for the ordinary ray. Hence the birefringence of the crystal is determined by measuring the difference between the two focii. It is possible to obtain an accuracy up to 0.0002 in the measurement of birefringence depending on the sample thickness. The method should find its application for the characterization of new crystals in various material research and crystal growth laboratories.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optics Communications (ISSN 0030-4018); 78; 7-12
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  • 4
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    Hex-square moire patterns in imagers using microchannel plates (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: In electronic imaging detectors using microchannel plates, the mismatch between the pixels on a square mesh and the microchannels on a hexagonal mesh produces moire image defects. Theoretical statistical estimates of the sizes of the microposition offsets and the flat field intensity errors are calculated, showing the trade-off between resolution and position accuracy. A distinction is made between moments of spot images and moments of the single-pixel-response functions. As the resolution between the hex and square meshes is improved, the detector resolution is improved, but at the expense of an about 10 percent moire pattern. These moire patterns will not be properly corrected by dividing by the flat field image.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 28; 4337-434
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  • 5
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    Phase conjugate Twyman-Green interferometer for testing spherical surfaces and lenses and for measuring refractive indices of liquids or solid transparent materials (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The present paper describes an application of a phase conjugate Twyman-Green interferometer using barium titanate as a self-pumping mirror for testing optical components like concave and convex spherical mirrors and lenses. The aberrations introduced by the beam splitter while testing concave or convex spherical mirrors of large aperture are automatically eliminated due to self-focussing property of the phase conjugate mirror. There is no necessity for a good spherical surface as a reference surface unlike in classical Twyman-Green interferometer or Williams interferometer. The phase conjugate Twyman Green interferometer with a divergent illumination can be used as a test plate for checking spherical surfaces. A nondestructive technique for measuring the refractive indices of a Fabry Perot etalon by using a phase conjugate interferometer is also suggested. The interferometer is found to be useful for measuring the refractive indices of liquids and solid transparent materials with an accuracy of the order of + or - 0.0004.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optics Communications (ISSN 0030-4018); 78; 407-415
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  • 6
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    Determination of refractive index of a simple negative, positive, or zero power lens using wedged plated interferometer (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A nondestructive technique for measuring the refractive index of a negative lens using a wedged plate interferometer is described. The method can be also used for measuring the refractive index of convex or zero power lenses. Schematic diagrams are presented for the use of a wedged plate interferometer for measuring the refractive index of a concave lens and of a convex lens.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 29; 4541-454
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