Browsing by Author "McKelvie, J."

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    Fabrication Of Holographic Gratings Using A Moving Point-Source
    Post, Daniel; McKelvie, J.; Tu, M. R.; Dai, F. L. (Optical Society of America, 1989-02-01)
    In the manufacture of holographic gratings using coherent light there is an associated problem of optical noise, the conventional remedies for which involve various restrictions. In this work a moving point source is adopted and analysis indicates that if the path is a circle several of these restrictions are removed. The scheme is implemented and the results are highly satisfactory with high-efficiency gratings being produced at frequencies up to 2400 lines/mm, in sizes up to 65 mm square. Significant operational advantages also accrue in relation to alignment procedures and light utilization.
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    Grating Speckle Method For In-Plane Displacement Measurement
    Tu, M. R.; McKelvie, J.; Dai, F. L.; Post, Daniel (Optical Society of America, 1989-12-01)
    A high sensitivity technique combining lensless speckle photography and a grid technique is proposed and demonstrated. A high frequency grid is applied to the specimen surface and contact specklegrams are made in white light before and after loading, in the double exposure mode. Subsequent optical processing yields the various components of in-plane displacement. The sensitivity can be chosen equivalent to the grid frequency or multiples thereof. The method is simple and gives low-noise fringe patterns with high contrast. It is suitable for application in the mechanical laboratory and field environments, because vibration isolation precautions are not necessary.