Acousto-optical main beam splitter for a scanning microscope, which acousto-optical main beam splitter is configured and intended to direct illumination light of a preselected or preselectable illumination light wavelength onto an illumination beam path for illuminating a sample and to direct detection light coming from a sample onto a detection beam path, wherein one mechanical wave of a sound frequency assigned to the illumination light wavelength or a plurality of mechanical waves having the same sound frequency assigned to the illumination light wavelength propagates or propagate in a crystal of the acousto-optical main beam splitter, characterized in that the acousto-optical main beam splitter comprises at least one dispersive optical component which compensates for a spatial colour splitting of a primary light and/or of the illumination light, said spatial colour splitting being brought about at least partly by the crystal of the acousto-optical main beam splitter through which the mechanical wave propagates, and has a first entrance surface for light having a first linear polarization direction and a second entrance surface for lighting having a second linear polarization direction, which is perpendicular to the first linear polarization direction, wherein a. from the detection light beam coming from a sample, as a result of interaction with said one mechanical wave or as a result of interaction with the mechanical waves, both a portion of the detection light beam that has the illumination light wavelength and a first linear polarization direction and a portion of the detection light that has the illumination light wavelength and a second linear polarization direction perpendicular to the first linear polarization direction are deflected and thereby removed from the detection light beam, and/or in that b. the acousto-optical main beam splitter is configured, as a result of interaction with said one mechanical wave or as a result of interaction with the mechanical waves, to direct both the portion of illumination light that has the preselected illumination light wavelength and a first linear polarization direction and the portion of illumination light that has the preselected illumination light wavelength and a second linear polarization direction, which is different from, in particular perpendicular to, the first linear polarization direction, onto an illumination beam path for illuminating a sample. a. from the detection light beam coming from a sample, as a result of interaction with said one mechanical wave or as a result of interaction with the mechanical waves, both a portion of the detection light beam that has the illumination light wavelength and a first linear polarization direction and a portion of the detection light that has the illumination light wavelength and a second linear polarization direction perpendicular to the first linear polarization direction are deflected and thereby removed from the detection light beam, and/or in that b. the acousto-optical main beam splitter is configured, as a result of interaction with said one mechanical wave or as a result of interaction with the mechanical waves, to direct both the portion of illumination light that has the preselected illumination light wavelength and a first linear polarization direction and the portion of illumination light that has the preselected illumination light wavelength and a second linear polarization direction, which is different from, in particular perpendicular to, the first linear polarization direction, onto an illumination beam path for illuminating a sample.