Abstract: The present invention concerns an apparatus for coupling light (1) of at least one wavelength of a laser light source (2) into an optical assemblage (3), preferably into a confocal scanning microscope, having an optically active component (4) that serves in particular to select the wavelength and to set the power of the coupled-in light (5). To ensure that changes in the power and/or wavelength of the laser light source do not affect the power of the light (5) coupled into the optical assemblage, the apparatus according to the present invention is characterized in that in order to influence the coupled-in light (5), the component (4) serves as the adjusting element of a control system (11).