Direct design of a two-surface lens including an entrance pupil for imaging applications

A multi-fields optical design method aiming to calculate two high-order aspheric lens profiles simultaneously with an embedded entrance pupil is proposed in this paper. The Simultaneous Multiple Surfaces design method in two dimensions (SMS2D) is used to provide a better understanding of how N surfaces allow perfect coupling of N ray-bundles. In contract to this perfect coupling, our multi-fields design approach is based on the partial coupling of multiple ray-bundles. This method allows calculating the Optical Path Lengths (OPL) during the process, directly building connections between different fields of view. Both infinite and finite conjugate objectives can be designed with this approach. Additional constraints like surface continuity and smoothness are taken into account to calculate two smooth and accurate surface contours. Sub-aperture sampling factor is introduced as a weighting function for different fields which allows for a very flexible performance control over a wide field of view. A RMS 2D spot size function is used to optimize the weighting factor to achieve a very well-balanced imaging performance. A wide-field objective and a moderate aperture lens are designed and analyzed to demonstrate the potential of this design method. The impact of different weighting functions for the sub-aperture sampling is evaluated accordingly. It’s shown that this design method provides an excellent starting point for further optimization of the surfaces coefficients and initial design parameters: resulting in a very good and well-balanced imaging performance over the entire field of view.

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