Error Analysis of IR Lens Focal Length Measured by a Goniometric Method

Authors: Kulakova N.N., Kaledin S.B., Sazonov V.N. Published: 02.08.2017
Published in issue: #4(115)/2017  
DOI: 10.18698/0236-3933-2017-4-17-26

Category: Instrument Engineering, Metrology, Information-Measuring Instruments and Systems | Chapter: Optical and Optoelectronic Instruments and Complexes  
Keywords: lens, focal length, error, transmittance, radiation flux, diameter of the scattering spot, photodetector, radiation amplitude, infrared radiation, photodetector sensitivity, scanning slit

The purpose of this work was to analyze the errors in measuring the focal length by the goniometric method at the factory plant. In this research we give an installation diagram, as well as the methods for measuring the IR lens focal length on it. We found a formula for calculating the focal length error at the installation and built a graph showing the dependency of the lens focal length error on the angle of rotation, which makes it possible to determine the lenses’ angles of rotation and to measure the focal lengths with a given accuracy in the range of focal lengths f’ = 10...1000 mhm. We identified the errors in the electron path and in pointing the center of the scanning slit at the center of the scattered spot of the investigated lens. We showed the dependences of the scanning slit transmittance on the spatial frequencies, as well as the distribution function of the radiation amplitude in the image plane of the diaphragm with a circular aperture, and the distribution function of the amplitude of the radiation passing through the scanning slit. Furthermore, we built graphs of the radiation amplitude dependency in the image plane of the diaphragm with a circular aperture and the distribution of the amplitude of the radiation passing through the scanning slit. Findings of the research show that the scanning slit does not change the amplitude of the sinusoidal radiation components in the image plane. Finally, we calculated the minimum radiation flux, which is capable of causing a reaction of the photodetector.


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