Abstract

Subject of study. The correlation between the modulation transfer function (MTF) and the veiling glare index (VGI) was investigated. The MTF is a measure of the optical system’s ability to resolve fine details, while the VGI is a measure of the amount of scattered light in the system. The aim of the study was to determine the correlation between the MTF and the VGI in order to derive formulas that could be used to predict one from the other. Method. A theoretical method was derived to compute the MTF decrease from the VGI. A practical method was also developed to compute the VGI from the MTF, which was measured using the Fourier transform of the line spread function (LSF). Main results. An analysis was conducted on standards and research on scattering light in optical systems. The VGI and glare spread function are two measurable characteristics of scattering light in optical systems. Theoretical and practical research were conducted, which ultimately led to the derivation of formulas for predicting the MTF decrease from the VGI and vice versa. To verify the validity of the formulas, the VGI was calculated using the MTF and the LSF for lenses with high and low VGI values. The lenses were tested on a collimator test bench according to the standard MTF test method. The VGI calculation results based on MTF measurements confirmed the validity of the formulas. Recommendations for measuring the VGI of optical systems without a photometric sphere using the MTF were also provided. Practical significance. The results of this study allow optical system developers to set tolerances for the VGI based on the MTF decrease. The results can be used as the basis for developing a new method for measuring the VGI of optical systems without a photometric sphere.

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