Freeform surfaces are widely used in optical design, due to the high design degree of freedom. The aberration theory of freeform optics can better lead designers to obtain a good structure. However, the existing aberration theory of freeform optics is only suitable for the optical system with a relatively small field of view (FOV). In this case, each field area (footprint) shows approximately the same shape and size, and positions of footprints across a surface have a linear relationship with fields. A wide FOV freeform optical system is analyzed in this paper. Parameters of all fields based on real-ray trace and non-linear interpolation can be employed to calculate the aberration generated by freeform terms. Then, to correct aberrations, coefficients of freeform terms are calculated using the least-square fitting method. By bringing back the coefficients to the optical system, the result shows great performance when using non-linear interpolation.
It is a meaningful but challenging issue that designing illumination optics for extended sources directly. A number of direct design methods developed specifically to deal with prescribed intensity designs usually fail to produce satisfactory illumination in the near field where the influence of lens size on the irradiance distribution cannot be ignored. In this paper, a direct method of designing aspherical lenses for extended sources is introduced to achieve specified irradiance characteristics. And various types of prescribed irradiance distributions are shown in this paper to verify the broad applicability and high efficiency of the direct design method, especially two examples of producing discontinuous irradiance distributions are analyzed in detail.
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