An optical system for fluorescence observation comprises optics including an ocular 17, a camera 55, a display 69, a light source 71, an illumination light filter 84, an observation light filter 57 and a controller 35. The observation filter has multiple transmitting regions which allows light which was generated by a fluorescence to traverse for observation. The transmitting ranges are divided by blocking ranges. At the wavelength ranges at which the observation filter has a transmitting region the illumination filter has a blocking region and the other way round. The multiple transmitting regions of the illumination filter enable an improved color impression under normal light observation. The controller is configured to process a fluorescent light image obtained by the camera by identifying a contiguous fluorescent region in the fluorescent light image, generating an image including a representation of the boundary of the contiguous fluorescent region, and supplying the generated image to the display.
