Modified Fizeau interferometer with the 4th order polynomial smoothing algorithm

The modified Fizeau interferometer that allows to diagnose plane and spherical optical elements with the diameter ranging from 10 to 100 mm is discussed. The method of interference patterns reconstruction based on reference lines is modified, the algorithm of 4th order polynomial smoothing is implemented. The modified method increases the reliability and accuracy of interferometric pattern reconstruction and suppress the influence of incoming noise. Accuracy of the measurements is about
$\lambda/10 (\lambda=0.63\ \text{um})$
.