The addition of alternative, conventional non-confocal transmitted illumination to the tandem scanning reflected light microscope enables it to be used with all familiar and conventional modes of the microscope to discover a location of interest in a prepared sample, using the confocal modes when desired, or vice versa. Depth of field for the non-confocal transmitted light image can be controlled by the aperture of illumination. Conventional and confocal (coloured) images can be mixed in any proportion in the same frame.
Alan Boyde, Alan Boyde,
"Confocal And Conventional Modes In Tandem Scanning Reflected Light Microscopy", Proc. SPIE 1028, Scanning Imaging, (9 February 1989); doi: 10.1117/12.950318; https://doi.org/10.1117/12.950318