N. P. Cheragin

Absolute Testing of the Profiles of Large-Size Plane Optical Surfaces

We show the results obtained from the measurements of surface profiles of various optical elements using a wide-aperture white-light interferometer. The developed measurement method eliminates fundamental constraints on the size and mass of the samples tested. This method, used along with the high-order white-light interferometry and the original calibration of the reference plate of the interferometer, permit real-time testing of surface profiles with an accuracy of up to 1 Å in a wide technological range.

Method for absolute calibration of reference plates for interferometric inspection of surfaces

A method for absolute calibration of reference plates of interferometers for measuring surface profiles of optical elements is described. It is based on the solution of the inverse problem of reconstruction of a surface profile from the data of relative measurements of three plates by way of minimizing the goal function. The method takes into account the gravitational sagging of the reference plate and allows one to obtain its profile with an accuracy of ∼λ/1000 for λ=6328 Å. The calibration algorithm as well as theoretical calculations and experimental results are presented.

A new controlling system for the solar tower telescope of IZMIRAN: I. Guide

A new guiding system for the solar tower telescope is described. Two mutually perpendicular CCD arrays are used as photodetectors. The guide provides a positional error of no larger than 0.2″ in a frequency band of 0–10 Hz. The software allows for referring the spectrograph slit position to solar coordinate systems and provides for various guide operation modes.

A new controlling system for the solar tower telescope of IZMIRAN: II. A solar image motion compensator

A solar image motion compensator for the solar tower telescope is described. Two mutually perpendicular CCD linear arrays are used as photodetectors. An algorithm for forecasting the system behavior is used for generation of correction signals. Analyzing the solar image motion data obtained using the compensator and without it has shown that, thanks to its use, the total image motion value decreases to 0.5″–0.6″ in a frequency band of 0–100 Hz, being close to the amplitude of noncorrelated image motion component. The compensator operates equally effectively in both the pointing and scanning modes.

Reducing the influence of the premonochromator on the stability of fourier spectrometers

A method is proposed to improve the stability of specialized solar Fourier spectrometers. The method is based on matching the premonochromator bandwidth with the Fourier harmonic frequency of the spectrometer. It is shown that this matching is efficient for both decrease of the measurement errors due to premonochromator instabilities and increase of the linearity of the measurement range. Some possible applications of this procedure for slot spectrometers and Fabry-Perot interference filters are considered.