Medical observation device comprising an input interface, an image processor, an output interface, the input interface being configured to receive subsequent sets of input image data and auxiliary input data, a visible-light camera connected to the input interface configured to provide the subsequent sets of the input image data and an ultrasound sensor (40, 42) connected to the input interface configured to provide the auxiliary input data; the output interface being configured to output subsequent sets of output image data at an output data rate, wherein the image processor is connected to the input interface to receive the subsequent sets of the input image data and the auxiliary input data, and to the output interface configured to output the subsequent sets of the output image data at the output data rate, wherein the auxiliary input data comprise ultrasound data, the image processor further being configured to generate subsequent sets of pseudo-color image data depending on a content of at least one of the auxiliary input data and the input image data, and to generate at least one synthetic pseudo-color pattern field within the pseudo-color image data depending on the content of the ultrasound data, the image processor being configured to merge the pseudo-color image data and at least one section of the input image data to generate the sets of output image data containing the pseudo-color pattern field, wherein the pseudo-color pattern field comprises a temporally modulated pattern having a variation rate, wherein the image processor is configured to compute the variation rate of the temporally modulated pattern depending on a momentary flow velocity, or on a frequency and/or amplitude of velocity changes represented in the ultrasound data, and wherein the medical observation device is one of a microscope and an endoscope. an input interface, an image processor, an output interface, the input interface being configured to receive subsequent sets of input image data and auxiliary input data, a visible-light camera connected to the input interface configured to provide the subsequent sets of the input image data and an ultrasound sensor (40, 42) connected to the input interface configured to provide the auxiliary input data; the output interface being configured to output subsequent sets of output image data at an output data rate, wherein the image processor is connected to the input interface to receive the subsequent sets of the input image data and the auxiliary input data, and to the output interface configured to output the subsequent sets of the output image data at the output data rate, wherein the auxiliary input data comprise ultrasound data, the image processor further being configured to generate subsequent sets of pseudo-color image data depending on a content of at least one of the auxiliary input data and the input image data, and to generate at least one synthetic pseudo-color pattern field within the pseudo-color image data depending on the content of the ultrasound data, the image processor being configured to merge the pseudo-color image data and at least one section of the input image data to generate the sets of output image data containing the pseudo-color pattern field, wherein the pseudo-color pattern field comprises a temporally modulated pattern having a variation rate, wherein the image processor is configured to compute the variation rate of the temporally modulated pattern depending on a momentary flow velocity, or on a frequency and/or amplitude of velocity changes represented in the ultrasound data, and wherein the medical observation device is one of a microscope and an endoscope.