5,061 research outputs found
Diffraction-grating interferometer for testing aspheric concave mirrors with optimization of fringe visibility
No full textWe describe a diffraction-grating interferometer that enables us to obtain a high contrast ratio of 120 between the test wave and the reference wave by optimizing the groove shape of a blazed-type diffraction grating. The high contrast provides good visibility for the resulting interference fringes when testing aspheric mirrors using computer-generated holograms (CGHs). Generally CGHs perform wavefront nulling, but greatly attenuate the intensity of the test wave. We present experimental results for an aspheric concave mirror of 600 mm diameter obtained using a blazed diffraction grating with a 1/1200 mm groove spacing and a 17-deg blazed angle. The binary-type CGH used for the experiments provided low transmittance efficiency but was cost effective. (C) 2004 Society of Photo-Optical Instrumentation Engineers
Phase-shifting diffraction-grating interferometer for testing concave mirrors
No full textWe present a new concept for a phase-shifting diffraction-grating interferometer, which is intended to test concave mirrors simply using a single reflective diffraction grating and fiber optic confocal microscope focusing optics. Our configuration allows generating a high-quality reference wave from a small active grating area that can be readily fabricated with good homogeneity of grating substrate and uniformity of groove spacing. The test and reference waves encounter no other optical components, so only a small active surface area of the grating affects the test result. The fiber optic confocal microscope design adopted to solve the alignment problem between the grating and the converging wave greatly reduces systematic errors of the interferometer. In addition, the phase-shifting capability provided by translating the grating using a microactuator enables one to attain nanometer accuracy in optical figure metrology. (C) 2003 Society of Photo-Optical Instrumentation Engineers
Efficacy and safety of zotepine for the treatment of Taiwanese schizophrenic patients: a double-blind comparison with haloperidol.
No full textHippocampal Neurochemical Pathology and Thought Disorganization in Schizophrenia: a pilot study.
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