A new method to validate the usage of Fresnel approximation instead of Kirchhoff diffraction formula for calculations concerning camera systems

摘要

The usage of Fresnel diffraction as an approximation of the Kirchhoff formula offers a large variety of advantages concerning diverse calculations for camera systems. However, Fresnel approximations cannot be applied to arbitrary camera systems. For configurations with wide aperture, e.g., the usage of Fresnel approximation is not possible without accepting an unagreeable deviation. It is important to check in advance if a camera system allows such an approximation for the needed calculations. Assuming that focal length f and ground distance g are given quantities, investigations of the real and complex integrands lead to a formula from which the minimal F-number/# (respectively the maximum aperture radius r) is derived, so that Fresnel approximations can still be applied to a system. The analytical results are supported by numerical calculations and audited for three camera configurations outlined for remote sensing.