LENSLET ANALYSIS BY RIGOROUS VECTOR DIFFRACTION THEORY

The accurate analysis of the electromagnetic field scattered by lensle ts of dimensions of the order of the wavelength is considered. Assumin g plane-wave illumination of the lenslet, a pair of coupled integral e quations is derived, starting from the Stratton-Chu solution of Maxwel l's time-harmonic equations. These equations are solved rigorously (in a numerical sense) to obtain the lenslet-scattered field. For compari son, an approximate vector formula based on the aperture field is also derived and is related to the ubiquitous Fresnel-Kirchhoff scalar dif fraction formula. These analytical techniques are then applied to repr esentative lenslets with diameters in the 2-100-wavelength range. The results demonstrate useful focusing characteristics even at 2-waveleng th diameters and confirm that, depending on the accuracy required, the approximate vector formula based on the aperture field can be success fully employed for determining the lenslet-scattering characteristics.