Optical video disks with undulating tracks.

The signal components of a video signal (luminance, color, and sound) are modulated on a main carrier and several subcarriers and then recorded on the video master disk. Apart from the signal distortion that can arise during master and disk manufacture, the optical readout of the disk also yields a nonlinear transfer of the signal. The result of nonlinearities is intermodulation between signal components. Intermodulation products affect the quality of the final TV picture. In this paper a method is described which reduces the contribution of the optical readout system to the intermodulation. An optical coding is introduced such that two signal components hardly influence one another. The spacing of the pits in the track direction carries the luminance information, while the undulation of the track carries the color or sound information. A quadrant photodetector positioned in the far field of the video disk restores the luminance and color or sound bands with a very low amount of intermodulation.