Security holograms for automatic machine inspection

In this paper, a new kind of security hologram using an encoded reference wave is introduced. The hologram is produced with the interference of an encoded reference wave and a convergent object wave. The focus of the convergent wave can be reconstructed only by the illumination with a duplicate of the original encoded reference wave. Because the verification pattern is simply s spot peak rather than an image pattern, this kind of security hologram is suitable for machine inspection. A scheme of machine inspection by using this kind of security holograms is described.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.