Space-based telescopes are important tools in astronomy and Earth observations. They enable observation in spectral ranges outside of the atmospheric window, e.g. below 300 nm. One of the ways to decrease the mass of space telescopes is to use diffractive optical elements. They have unique capabilities when it comes to aberration corrections. By combining refractive and diffractive components it is possible to obtain a well-corrected system with fewer optical elements compared to purely refractive systems. In this paper we present an optical design of a hybrid refractive-diffractive telescope working in the 200 nm – 300 nm spectral range with improved performance and decreased mass compared to refractive system. The telescope has a large field of view 10°×10°, enabling observations of many objects simultaneously, focal length of 150 mm and f-number equal to F/1.67. We compare the performance of two systems optimized using different merit functions. In the first case the goal was to minimize spot size, in the other a widened point spread function was obtained in order to avoid undersampling. The results of tolerance analysis prove that the satisfactory imaging quality may be obtained with moderate tolerances. Moreover, the influence of the antireflective coating on the efficiency of the diffractive lens is discussed. Performed simulations show that the antireflective coating deposited on the diffractive structure gives an increase of the efficiency at the expected level.
The possibilities of using gradient index (GRIN) lenses as the objective and relay lens in rigid endoscopic systems working in visible spectrum are investigated. The final aim of the project is to obtain a system providing diffraction limited image quality, which could be used for examining the gastrointestinal tract. This paper describes steps of the design of the system with working distance equal to 125 mm and angular field of view 25°. The diameter of the GRIN lenses is equal to 2,2 mm. Influence of the gradient of refractive index on the image quality is shown. Current results are analysed and future steps are described.
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