Commercial EUV lithography projection systems are designed with six-mirror, using high order aspherical surfaces or freeform surfaces, which require high processing and inspection requirements. When designing the initial structure of the projection system, it is important to consider the balance between the system's aberration and the difficulty of processing and manufacturing. EUV lithography optical systems minimize the number of mirrors in order to improve light energy utilization. Freeform surfaces or aspherical surfaces are used to provide more degrees of freedom for optimization. For a 6-mirror projection system, there are several ways for group design. There are 2-4, 3-3 and 4-2 combinations when divided into two groups, or into 2-2-2 triple groups. According to the design parameters of the EUV lithography projection optical system, the initial structure obtained by different group methods is analyzed. And choose more reasonable initial structure for further optimization.
KEYWORDS: Light sources and illumination, Microscopes, Design and modelling, Monochromatic aberrations, Systems modeling, Light emitting diodes, LED lighting, Diffusers
Illumination of the object of study is an important part of the research by optical methods. In some devices, it is necessary not only to illuminate the object of study completely, but also to achieve uniform illumination. To do this, in such optical systems as biological microscopes, an illuminating optical system of the Köhler type is used. Modern research in the field of improving the classical Koehler scheme has shown that they are aimed at improving the optical and energy characteristics, and do not take into account the dimensions of the lighting system. In some new models of microscopes, to reduce overall dimensions, only an LED with a frosted diffuser is used as an illuminating optical system, providing complete, but not uniform, illumination of the object. In this work, an illuminating optical system with reduced overall dimensions was developed. The stages of calculation of the collector and condenser of the lighting system are shown.
Optical schemes of aplanatic and afocal compensators of surface curvature and astigmatism are considered. The way of calculation of this kind of compensators and an example of using a doublet lens with an enlarged field with one of it are given.
Various optical schemes of single-component lenses with a remote pupil and a telecentric beam path, as well as a method of their calculation based on the theory of third-order aberrations, are presented. For illustration, the results of the aberration calculation of lenses of this type are given.
The paper considers afocal compensators correcting various aberrations of optical systems such as spherical aberration, coma, astigmatism, surface curvature, chromatic aberrations. For illustration, the considered optical compensator schemes are reproduced.
The possibility of constructing the optical system with an aplanatic correction of aberrations representing generally combination of the thin lens with an aplanatic meniscus and plane-parallel plate of small thickness is shown.
The possibility of a stigmatic and aplanatic correction of third-order aberrations in the image, which is formed by the positive lens system is showed and the conditions for such a correction are determine. The relations defining the position of the entrance pupil of a thin lens, in which the image formed in the absence of primary coma and astigmatism, was obtained.
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