October 28, 2022, Friday, 03:00PM (GMT+03.00, Moscow)

Abstract:

The issues of assessing the contrast of UV-A images of small-sized objects against the background of the earth's surface and the sky are considered. Objects observed against the background of the sky can be various kinds of aircraft, flocks of birds, as well as television center antennas, tall chimneys, skyscrapers. The use of UV-A sensors for aircraft detection has a number of advantages over infrared sensors. Formulas for calculating the contrast of object images are given. It is shown that the contrast of an object observed against the background of the sky depends exponentially on the optical thickness of the atmosphere and linearly on the value of the reflection coefficient of the object. The experiment procedure for checking validity of the obtained formulas for calculating the contrast and the characteristics of the measuring equipment used are given. In the course of processing the experimental data, it was found that at short probing ranges of reference reflectors, the values of their contrasts are in good agreement with the results of model calculations. However, at low values of the reflection coefficient of the reference reflectors, there is a slight discrepancy between the experimental and model graphs, which is associated with the influence of the dark current and the scattering of the received signal by the optical elements of the receiver lens. It is pointed out that information about the magnitude of the contrast of objects against the background of the sky can also be used to determine the extinction coefficient of the atmosphere.