The role of detector geometry in confocal imaging

SUMMARY The key property of confocal microscopes is their ability to produce three‐dimensional images. This arises simply by the use of a point detector. We discuss the use of point detectors, slit detectors, detector arrays and finite‐sized detectors on the strength of the optical sectioning when the systems are operated in both fluorescence and non‐fluorescence modes. We find that the sectioning is sharper in the non‐fluorescence case. We also discuss methods of obtaining differential phase contrast information and show that it is not possible to obtain pure differential phase contrast from a simple confocal microscope. However, a scheme consisting of two, suitably configured, confocal microscopes can give differential phase contrast with optical sectioning.