AUTOMATED SYNTHESIS OF FAST LENSES FOR MODERN NIGHT VISION DEVICES

Abstract

This article is devoted to research of the possibilities of automated design of fast and high-quality multi-lens objectives intended for use in night vision devices with modern image intensifier tubes of generation 4 and 4+, which have photocathodes with a diameter of up to 18 mm. Such image intensifier tubes are characterized by extended spectral sensitivity, high signal-to-noise ratio, and increased resolution. The computer program PODIL, developed earlier for the automated design of arbitrary optical systems, was applied to find out prescription data of fast lenses. For the parametric synthesis of optical systems, the modified evolutionary algorithm implemented in the program was used. The article presents the general methodology and results of automated parametric synthesis of a series of optical systems of objectives with different focal lengths, which contain from 7 to 9 lenses with spherical surfaces. The synthesized lenses provide angular field of view of 10°, 37° and 60° without any vignetting of axial and peripheral beams. The correspondent F numbers are 1.5, 1.33, and 1.4. The working spectral range of the designed lenses is determined by the spectral sensitivity of the photocathodes of the image intensifier tubes. In this research, it covers wavelengths from 0.45 to 0.9 μm. The longitudinal size of the designed optical systems (i.e. the distance from the first optical surface to the photocathode’s plane) is found within the range from 80 to 106 mm. The presented results of aberration analysis confirm the high image quality of the obtained optical systems. In particular, the maximum spatial frequencies of the evaluated polychromatic diffraction modulation transfer functions of the lenses over the entire field in both meridional and sagittal planes exceed 50 mm-1. The maximum values of relative distortion of the lenses are obtained within the range from 1% to 2%.