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We present a method for the linearization and minimization of interferometer cyclic error. We utilize a polynomial curve fitting and resampling algorithm to correct for nonlinear mirror displacement. In the frequency domain, this algorithm compresses cyclic error into a single-frequency component and enables the precise measurement of cyclic error in a noise-dominated environment. We have applied the technique to determine the cyclic error for a range of interferometer components. In addition, we have used these measurements to optimize interferometer configuration and performance such that we routinely achieve a cyclic error of ∼50 pm for our custom Glan-Laser interferometer and ∼100 pm for a commercial interferometer.

The design of a tunable Fabry-Perot étalon-based filter that has a passband of 0.01 nm and a free spectral band larger than 50 nm when operated in the center of the visible spectrum is described. The filter consists of two Y-cut lithium niobate étalons having thicknesses in a vernier ratio. The polarization state of light passing through the tandem étalons is rotated 90 degrees before again being transmitted through the étalon pair. If the components are arranged in a symmetrical manner, the filter will operate with unpolarized incident light. Each étalon in double pass will have a greater transmittance than two individual étalons of the same average optical thicknesses, since variations in the physical thickness due to fabrication errors are correlated.

The interpretation of time-averaged holographic fringes recorded with a vibrating object presents problems when the direction of the motion is not known or when points on the object are moving in two or three dimensions. Measurements on additional holograms with properly chosen directions of the sensitivity vector are then required to evaluate the vibration amplitude. However, reduction of the data, even along a single line, is laborious and subject to errors. This paper describes a computerized system which uses stroboscopic illumination in conjunction with digital phase-shifting techniques to evaluate the magnitude and direction of the surface displacements at a uniformly spaced array of points covering the vibrating object. These values are used along with data on the shape of the object to calculate the in-plane and out-of-plane components of the vibration at these points. The operation of the system is illustrated with some results obtained with a compressor blade from a jet engine. Measurements of the surface displacements at different epochs of the vibration cycle permit a detailed analysis of complex vibrations.

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