JPS5532091A - Light attenuator - Google Patents

Abstract

PURPOSE:To present light attenuator of high precision, having small insertion loss due to polarization, even with respect to the light not having specific direction of polarization, in a simple constitution, by providing a rotatably analyzer body consisting of two analyzers between two double refractive crystal plates. CONSTITUTION:Between first and second optical fibers 1, 7, and first and second lenses 2, 6, a first refractive crystal plate 8 which separates the input light into two parallel lights of normal beam 9a and abnormal beam 9b is provided, forming as parallel flat plates having a crystal axis 8a in an oblique direction with respect to the surface, and is also provided an analyzer body 10 which is rotatable around a rotary shaft 10c, coupling polarizing plates 10a, 10b of which directions of polarization to pass the specified polarization components of two parallel lights after the crystal plate 8 are vertical with each other. Also by providing a phase compensation plate 12 to compensate the phase of the normal beam 11a of the two parallel lights 11a, 11b passed through each polarizing plate of the analyzer body 10, and a second double refractive crystal plate 13 formed as parallel plates having a crystal axis 13a in the direction oblique to the surface, the two parallel lights passing through the analyzer body 10 are synthesized into one light.