The invention describes a method for improving the spatial resolution of optical microscopes that use line-scanning excitation, such as line-scanning confocal microscopes, line-scanning STED microscopes, or line-scanning light-sheet microscopes. Common elements of the invention include: a) an apparatus for exciting and scanning a line-like excitation focus through the sample; b) an optical arrangement on the detection side of the microscope for manipulating the spacing and/or width of the resulting fluorescence emissions; c) integration and optional post-processing of the manipulated fluorescence emissions after capture by an area detector such as a camera. The resolution increase may be performed with no or marginal decrease in temporal resolution relative to the conventional line-scanning microscopes upon which the technique is based.