Source coherence and optical sectioning strength in direct-view microscopy

The direct-view microscope is a confocal microscope which allows faster image acquisition rates than typical confocal scanning optical microscopes through the use of a pinhole array rather than the usual single pinhole. We present a theoretical investigation of the effects of source coherence on optical sectioning in direct-view microscopy. As a first step we present an equation which describes the optical sectioning strength of a coherent source brightfield DVM employing an infinite pinhole array. By simulation of both this and the finite array equation which show the existence of certain 'principal' sidelobes which are likely to represent the most problematic artifact of coherent source imaging. By further analysis of the infinite array equation, we arrive at an expression which describes the defocus positions where the principal sidelobes occur. Finally, we move on to show how rectangular arrays are predicted, by the infinite array equation, to outperform square arrays and we show examples of this.