sentences:  When the revealing layer is shifted up perpendicularly to the layer lines by one full period ("p"r) of its pattern, the superposition optical image must be the same as the initial one.It means that the moiré lines traverse a distance equal to the period of the superposition image "p"m while the revealing layer traverses the distance equal to its period "p"r. Assuming that the base layer is immobile ("v"b=0), the following equation represents the ratio of the optical speed to the revealing layer’s speed