Confocal microscope with enhanced lateral resolution using engineered illumination pupil

The maximum lateral resolution achievable with a confocal microscope is twice that of a wide field microscope. However, the spatial frequency content in the confocal image near the cutoff has very poor signal and is hardly of any practical use. Barring in the fluorescence mode, no technique can provide significant resolution enhancement simultaneously both in the reflection and fluorescence mode of the confocal microscope. This paper describes a technique based on aperture engineering that can significantly enhance the high spatial frequency content in the image of a confocal microscope, in principle, working either in the reflection or the fluorescence mode. Results obtained from numerical simulations and experimental implementation are presented.