Alessandro Grosso

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ON WAVEFRONT ABERRATIONS IN ASYMMETRIC AND MULTIPLE APERTURE OPTICAL SYSTEMS

Alessandro Grosso

The present work deals with monochromatic wavefront aberrations in optical systems without symmetries. The treatment begins with a class of systems characterized by misaligned spherical surfaces whose behavior is analyzed using the wavefront aberration expansion proposed in the framework of the Nodal Aberration Theory (NAT). It is derived the full field behavior of the Zernike polynomials in the Fringe indexing scheme for this class of systems. Then, the attention is focused on a more general class of asymmetric systems where the misaligned surfaces can be individually double-plane symmetric. In this case, considering aberrations up to the 4th order, it is shown that the field dependence of Zernike terms is described by general second-degree polynomials. The presence of double-plane symmetric optical surfaces induces additional perturbations to the magnitude of the field variation of primary aberrations for this class of systems. In particular, one observes that coma aberration acquires an elliptical conic shape in the field domain, while the full field variation of primary astigmatism magnitude is described by a class of surfaces that we define as âgeneralized Cassini surfacesË® because these are more general than the standard Cassini surfaces describing the binodal behavior of astigmatism in the class of optical systems analyzed with NAT wavefront aberration expansion. These considerations are preliminary to the discussion of the second part of this thesis whose scope is to analyze monochromatic wavefront aberrations in a further class of systems, namely optical systems characterized by multiple apertures. In this sense, it is first introduced a general description of the wavefront aberration function in the framework of Hamiltonian Optics. This consists of a full power series expansion in the ray coordinates that provides the most general representation of optical systems without symmetries. These introductory remarks are necessary to carry out the analysis of optical systems with many apertures. Such a class of systems is well represented by light field (or plenoptic) cameras. Their general structure consists of a main objective followed by an ensemble of apertures whose function is to divide the field of view into many partitions. Each aperture defines an optical channel. The partial overlap between adjacent field of view partitions serves to extract depth information from the scene in a similar manner to stereo cameras. The wavefront aberration analysis of this class of systems is primarily based on the definition of an ensemble of base-rays playing the role of reference axis for the various channels. The wavefront error for each optical channel is described with a general power series in the ray coordinates expanded about the inherent base-ray. Finally, different approaches are expounded to calculate and visualize the evolution of the aberration behavior of the various channels of this class of optical systems.

EPFL2021

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Full field dependence of primary aberrations in perturbed double-plane symmetric systems with a circular pupil

Alessandro Grosso, Toralf Scharf

This paper deals with the theory of primary aberrations for perturbed double-plane symmetric optical systems consisting of a combination of tilted and decentered surfaces and a circular pupil. First, the analytical expressions describing the full field behavior of Zernike polynomials are derived from the fourth-order wavefront aberration function for this class of optical systems. Then, such expressions are combined to retrieve the full field dependence of primary coma, primary astigmatism, and field curvature. They are described by an elliptical conic-shaped surface with a variable apex location over the field of view, by a binodal surface with two nodes over the field of view, and by a general elliptical surface with one node. The proposed analytical expressions provide a better understanding of the primary aberration behavior for these systems and can be of great use in their optical design and aberration correction. An optical system constituted by a pair of tilted and decentered biconic lenses is studied to validate the proposed expressions. (C) 2020 Optical Society of America

OPTICAL SOC AMER2020

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In this paper we derive scalar analytical expressions describing the full field dependence of Zernike polynomials in optical systems without symmetries. We consider the general case of optical systems constituted by arbitrarily tilted and decentered circular symmetric surfaces. The resulting analytical formulae are inferred from a modified version of the full field dependent wavefront aberration function proposed in the Nodal Aberration Theory (NAT). Such formula is modified with the scope of solving few critical points arising when primary and higher order aberrations are both present in an optical system. It is shown that when secondary aberrations are taken into account in the wavefront aberration function, the final effect is a perturbation to the symmetry of the field dependence of the Zernike polynomials. In particular, the centers of symmetry of the Zernike polynomial field dependences are shifted with respect to the locations predicted using the NAT equations as a consequence of the presence of higher order aberrations. The retrieved analytical expressions are verified through surface fitting to real ray-trace data obtained for a simple optical system. (c) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

2020

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