THE USE OF ANNULAR PUPIL PLANE FILTERS TO TUNE THE IMAGING PROPERTIES IN CONFOCAL MICROSCOPY

We consider the use of pupil plane filters to modify the imaging properties of confocal optical systems. We specialize to the annular filter as it is useful in itself and as part of a more complex filter. We show, inter alia, that by changing the size of the annular obscuration we can tune the strength of the optical sectioning. The question of spherical aberration is considered and it is found both theoretically and experimentally that the effects are reduced in the annular case. We also discuss the problem of where best to place the filters in reflection systems where different filter functions are required for the two imaging lenses. The use of filters in both bright-field and fluorescence imaging modes is considered. © 1990 Taylor & Francis Ltd.