The invention relates to a medical observation device (1) such as a microscope or endoscope. Further, the invention relates to a method for processing medical images. Input image data (52) are generated by a visible-light camera (28) and overlaid with auxiliary input data (58) such as fluorescent-light image data (65) generated from auxiliary input data (58) e.g. a fluorescence camera (32) or an ultrasound sensor (40, 42). From the auxiliary input data (58), subsequent sets (84) of pseudo-color image data (86) are generated by an image processor (80). The pseudo-color images (84) are merged with the input image data (52) to obtain three-dimensional output image data (94). The image processor (80) is configured to generate pseudo-color image data (86) at different depth layers of the three-dimensional output image data depending on the content of the auxiliary input data (58).
