Illumination of a sample in microscopy may in principle be categorised into two different classes:                Transmission microscopes, wherein the light source is located or one side of the sample and a sensor or detector on the other side of the sample to detect light being transmitted through the sample.        Reflection microscopes, wherein the light source is located on the same side of the sample as the sensor or detector to detect light being reflected from the sample. The light from the light source is deflected by a partially transmitting and deflecting surface, such as a beam splitter, eg. a dichroic mirror, to illuminate the sample. The light reflected from the sample is allowed to be transmitted through the surface towards the detection means.        
In fluorescence microscopy the light source provides excitation light instead of merely illumination. Since the fluorescence signal which is detected is low in intensity compared to the intensity of the excitation light it is of importance that no excitation light is transmitted directly or unfiltered to the detector.
In U.S. Pat. No. 5,805,342 (Gravely) a fluorescence system of the transmission type as well as of the reflection type is shown, wherein the light source travels or scans the sample in the sample plane. The excitation light is either located on the opposite side of the sample or located so that the light is deflected by a partially transmitting and deflecting surface.
In order to produce more compact fluorescence microscopes having more functionalities the present inventors have invented a fluorescence microscope capable of being constructed in a more compact manner than previously known and therefore useable as a portable fluorescence microscope.