Abstract: The system performs a correction on the video frequency signal of a television image, for the purpose of avoiding level defects in the image. The method principally consists in defining a particular number of correction points in the image by division into a grid or lattice of horizontal and vertical strips or bands, in imparting to the divisions of this grid a smaller value towards the edges of the image than close to the center, in storing correction signals for each correction point during an acquisition procedure, and in correcting the video frequency signals relating to a correction point by using the correction signal stored for this point.

Abstract: A spatial correction device for an image analyzer having an image restitution support medium and a device for scanning the support medium. A memory is provided for storing, for each of the MN rectangles resulting from dividing the image restitution support medium of the analyzer into a grid of M groups of L lines each and N columns, a predetermined correction signal. Also included is a sequencer for ensuring that the correction signals are properly applied as well as an interpolation device for calculating the intermediate values of the correction signals corresponding to each of the L lines of a given rectangle. This interpolation device also avoids the derivative ruptures of the correction signals during their transition between adjacent rectangles which are situated in the same column.

Abstract: In one of the channels, a trigger circuit 4 supplies for each synchronization pulse a pulse I.sub.0 of which the trailing edge F.sub.0 is staggered by T.sub.0 in relation to said synchronization pulse; in the other channel trigger circuits supply for each synchronization pulse a pulse I of which the beginning is staggered by T.sub.1 in relation to said synchronization pulse and of which the duration is 2.DELTA.t, .DELTA.t defining the permitted tolerance for synchronism. A further circuit detects the noncoincidences of an edge F.sub.0 with the presence of a pulse I.sub.1 and, in the absence of another detection, memorizes the last noncoincidence detected for a given time (at least equal to the image period for the 625 line CCIR standards).