Abstract: A non-copiable videotape recording system includes a synchro signal separator adapted to separate a horizontal and a vertical synchro signal from a synchro signal section of a video signal, a first-pulse generator adapted to generate a first pulse while the video signal is in the duration of the back porch which follows the horizontal synchro signal, wherein the first pulse has a narrower width than that of the back porch, a second-pulse generator adapted to generate a second pulse having a lower level than that of the first pulse while the video signal is in the duration of the back porch following the horizontal synchro signal, wherein the second pulse has a narrow width than that of the back porch and has a substantially equal pulse-area to that of the first pulse, and means for adding the first pulse and the second pulse alternately to the back porch of the video signal at predetermined time intervals.

Abstract: The invention provides a lens attachment adapted for use as a supplemental attachment to optical instruments, such as cameras, enlargers, when they are employed to form wide-ranging images upon a wide screen for example.According to the invention, the lens attachment comprises a master lens having focal length f.sub.M and a front member having focal length f.sub.A and a rear member having focal length f.sub.B, each member including cylindrical lenses, said front member and said rear member as a whole being located in front of said master lens, wherein said f.sub.B satisfies: 4f.sub.M .gtoreq..vertline.f.sub.B .vertline..gtoreq.2f.sub.MIn addition, the lenses are readily combined on a mount in fitting relationship with the use of tenons and recesses adapted to receive said tenons, thereby securing precise centering of the lenses.Thus, the distance between the rear member and the master lens is extremely shortened, and the diameters of both lenses are made substantially equal.