The method of skin blood flow imaging in the far infrared spectrum using a thermal imager has been described. An analogy of the thermal properties of the skin and the electrical properties of the low-pass filter was used. A filtration method is developed that allows the conversion of a signal used in a signal proportional to the blood flow under the skin. An example of the use of the developed method in the field of visualization of hemodynamics has been given. The electric circuit of the filter realizing the mutual transformation of temperature into blood flow in real time has been given.