Abstract
Patterned illumination is a successful set of techniques in high resolution 3D microscopy. In particular, structured illumination microscopy is based on the projection of 1D periodic patterns onto the 3D sample under study. In this research we propose the implementation of a very simple method for the flexible production of 1D structured illumination. Specifically, we propose the insertion of a Fresnel biprism after a monochromatic point source. The biprism produces a pair of twin, fully coherent, virtual point sources. After imaging the virtual sources onto the objective aperture stop, the expected 1D periodic pattern is produced into the 3D sample. The main advantage of using the Fresnel biprism is that by simply varying the distance between the biprism and the point source one can tune the period of the fringes while keeping their contrast.