= Conoscopic interference pattern
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= Conoscopic interference figure
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A <conoscopic interference pattern> is the direction-dependent pattern obtained when a <polarizing microscope> examines convergent illumination passing through a <birefringent> specimen. Different positions in the observed angular pattern correspond to different propagation directions through the specimen, and hence to different accumulated <phase retardations>.
A thin <crystal> between crossed <polarizers> can therefore show bright and dark bands even with nearly uniform thickness. Inspecting the angular pattern, rather than an ordinary image of specimen texture, helps identify optical-axis directions. The pattern depends on crystal orientation, thickness and <wavelength>; it is not a map of surface height.
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