Analysis indicates that strict attention must be paid to polarization control in fiber gyroscopes in order to ensure drift stability. It is shown that the maximum drift rate that is due to faulty polarization control is proportional to the amplitude-extinction ratio for the rejected polarization channel. Consequently, in the worst circumstances, which on present evidence cannot be excluded, the intensity extinction for the rejected polarization channel in a typical fiber gyroscope must approach 10(-6). Options for achieving this control are indicated by the analysis.
The tedious numerical computations associated with the calculation of partially coherent imagery are alleviated by a method which uses dimensionless coordinates and takes advantage of the properties of the Fourier transform. A 1-D periodic object function can model many objects of practical interest, including nonperiodic objects. The properties of a given optical system are described in terms of the transmission cross coefficient. For aberration-free systems with circular pupils, including annular sources (dark-field illumination), the cross coefficient can be calculated analytically. For aberrated or apodized systems, a 1-D approximation can be used. The effect of a convolving slit in the image plane of a scanning microscope can also be included.
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