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Caution Fill in all cells except the one corresponding to the parameter to be calculated. Choose all parameters unit. All parameters are positive.
Fraunhofer approximation is suitable for small diffraction angles (in the paraxial approximation). Therefore the wavelength must be far smaller than the aperture size and the realism of the calculation is not guaranted if that is not the case. Also, the parameters must be correcly scaled. For example, an aperture size of a few tens of mm, a spot size of a few tens of mm and a focal length of a less than one hundred mm as input parameters may lead to a wavelength in the range of mm or tens of mm which is far away from the optical spectrum.
