No abstract

High image quality and complex, refractive optical systems, as those used in remote sensing applications, are, in general, very difficult to be manufactured with the required performance. This can be charged to the high sensitivity of such systems to the fabrication tolerances, mainly concerning the relative alignment of the optical components with respect to each other. When the system does not achieve the expected quality, the puzzle is to identify where the problems lies. This is even worsened when the number of optical elements becomes high. Due to these facts, some misalignment characterization and estimation techniques based on Bayesian estimators and wavefront measurements have been proposed in the literature. This paper is the result of a deep study and investigation of these techniques, with emphasis on an application to an intentionally simple system for the sake of illustration that highlights conceptual issues that could be extended to more realistic, complex optical systems. With this purpose, the sensitivity of the wavefront Zernike coefficients to the misalignment parameters, its use in a parameter estimator design that includes nonlinear terms, the study of the system observability, and a statistical analysis of the estimator performance considering the observation noise are addressed in details. Numerical simulation results for the simple system are shown. We also present insights on how to apply the technique to the alignment of a 11-lens optical system used in the Brazilian remote sensing camera MUX, that will fly on-board the upcoming Sino-Brazilian satellites CBERS 3&4.

Misalignments always occur in real optical systems. These misalignments do not generate new aberration forms, but they change the aberration field dependence. Two-mirror telescopes have been used in several applications. We analyze a two-mirror telescope configuration that has negligible sensitivity to decenter misalignments. By applying the wave aberration theory for plane-symmetric optical systems it is shown that the asphericity in the secondary mirror, if properly chosen, can compensate for any decenter perturbation allowing third-order coma unchanged across the field of view. For any two-mirror system it is possible to find a configuration in which decenter misalignments do not generate fielduniform coma.

This paper aims to present the optical system of the Multispectral Camera MUX that is part of the payload for the CBERS 3 & 4 satellite (China Brazil Earth Resources Satellite). The CBERS program was created by Brazil and China for the development of Earth remote sensing satellites. The MUX camera is being developed by the Brazilian company OPTO ELETRÔNICA S.A. and consists of a multispectral camera with four spectral bands covering the wavelength range from blue to near infrared (from 450nm to 890nm) with a ground resolution of 20m and a ground swath width of 120 km. Besides MUX camera (optical system, signal processing electronics and mechanical frame), this company is also developing the Ground Support Equipment -GSE of this camera and is responsible for structural and environmental tests. At the moment, the project is in the Qualification Model (QM). During this phase of the development, the camera shall be submitted to several tests, including environmental, optical and structural tests with the objective of qualify the project and start the flight models manufacturing.

Ao Alan, pela compreensão e paciência ao longo de todos estes anos e pelo incentivo e motivação nos momentos mais difíceis.Aos meus pais pelo apoio irrestrito em todos os momentos, pelo incentivo e compreensão.Ao meu irmão Rogério e à Valdaisa pelo apoio e ajuda.Aos meus familiares e amigos próximos pelo apoio e incentivo.Aos meus sobrinhos Gabriel e Yasmin, pela alegria e descontração.À Nina, pela alegria e companheirismo incondicional.A todos que, de alguma forma, contribuiram para a realização deste trabalho. Although misalignments in optical systems do not generate new aberration forms, they change the field-dependence of the known ones. In this research, the sensitivity of two-mirror optical systems due to misalignments is evaluated in function of the conic constants of the mirrors. Among the different configurations considered in this study, a specific one has shown low sensitivity due to decenter misalignments. The application of the wave aberration theory for plane-symmetric optical systems has revealed that the proper choice of the secondary mirror conic constant allows third-order uniform coma to be compensated, leading to a less sensitive system, free from the most important misalignment-induced aberration.This thesis also presents an alignment methodology based on the analysis of the transmitted wavefront utilizing artificial neural networks to estimate alignment errors in the components of the system. The transmitted wavefront carries information about the aberrations in the optical system, which can be described in terms of Zernike polynomials. Such polynomials are used for the analysis of the effects of misalignments on the aberrations of the system. Artificial neural networks are employed in the analysis of the coefficients of Zernike polynomials and used to evaluate both type and magnitude of the misalignments. Theoretical misalignments estimated in reflexive and refractive optical systems are satisfactory for perfect systems, i.e., systems with no surface errors, and noiseless data. When surface imperfections are considered, the performance of the estimator is reduced. Besides decenter and tilt misalignments, artificial neural networks can estimate axial positioning errors of the elements in the system, therefore they are believed to be a promising alternative for the alignment of complex optical systems.