The paper is devoted to the description of the on-line course “Geometrical Optics” placed on the national open-education platform. The course is purposed mainly for undergraduate students in optics and related fields. We discuss key features of the on-line form of this course, the issues of its realization and learning outcomes’ evaluation.
Problems of designing dual band lenses were considered. The main problem is color correction in two spectral bands simultaneously because of dispersion issues between two bands for all optical materials. Another challenge is designing the lens with a few optical elements as possible. It results in complication of design dual band lenses compared with single-band lenses design. Dual band lenses design methods using two and three optical materials were discussed. All material combinations in MWIR and LWIR bands for most used materials have been investigated. F/number of single components in infrared lenses has limitation because of high f/number of an overall lens. In the agreement with this fact, we have provided a criterion for selection of good combinations. The results of calculations were tabulated. Manufacturability of all material combinations has been analyzed, and the best combination was obtained. Various designs for the best combinations have been produced. Also, image quality and tolerance sensitivity analysis of these designs was made, so we also provided a criterion for selection of good designs for the same material combination.
Aspherical surfaces are widely used in optical systems of various applications. Optical design tools (Zemax, CODE-V and others) offers various types of aspherical surfaces equations to be used in designs, but it is always a question how properly choose what coefficients and what number of coefficients should be used. It can be shown that usage special type of aspherical equation where the profile is described by dependence of the quadratic height from the z-sag. Each coefficient in this equation affects the only one aberration order. Unfortunately, such type of equation is rather rarely used in optical design tools. Special procedure can be developed for approximation of this equation to the common equation. The routine calculates aspherical coefficients for the most widely used type of an even asphere equation and finds a standard deviation of the initial surface from the approximated. Thus user can decide to use more coefficients or keep the number. The presented routine helps to find the coefficients in aspherical equation that responsible for the each aberration order and helps to find out the optimal number of aspherical coefficients for correction during optimization. Examples of aberration correction using different types of aspherical surfaces equations are presented in the paper.