Abstract: Method and device for eliminating the background brightness variation of a video signal, in which the background brightness in each line of the frame of a video signal has its low frequency brightness signal a(t) limited, as well as being limited by its deviation from the limited brightness of the preceding line of frame. This can be expressed mathematically by stating that .vertline.V(t)-a(t).vertline. is minimized by means of a(t) on the marginal conditions.vertline.a(t)-a(t-T).vertline..ltoreq..epsilon. and.vertline.a(t)-a(t-.DELTA.).vertline..ltoreq..epsilon.,in whichV(t)=the video signal V at the moment t;a(t)=an estimation of the background brightness variation a(t);T=the duration of a line;.DELTA.=h/b T/k, in which h/b=the height/width ratio of the image and k=the number of lines per frame, and.epsilon.=the maximum value of the derivative of a(t) multiplied by .DELTA..