Fluorescence lifetime imaging microscopy (FLIM) is a powerful technique increasingly used in the life sciences during the past decades. An all-solid-state fluorescence-lifetime-imaging microscope (1) with a simple lock-in imager (4) for fluorescence lifetime detection is described. The lock-in imager (4), originally developed for 3D vision, embeds all the functionalities required for FLIM in a compact system. Its combination with a light-emitting diode (2) yields a cost-effective and user-friendly FLIM unit for wide-field microscopes. The system is suitable for nanosecond lifetime measurements and achieves video-rate imaging capabilities.