Using two laser confocal imaging methods to optimize laser excitation and detector sensitivity range, the Controlled Light Exposure Microscopy (CLEM) unit reduces photo-bleaching effects and saturation of detector signal. When the unit senses the lack of a fluorescence return signal it attenuates the illumination, reducing the unnecessary excitation of fluorophores in the background and out of the plane of focus objects. A second method senses optimum return signal levels and can then attenuate the excitation source reducing the deleterious over-excitation of fluorophores in bright areas or out of the plane of focus objects.