Multiple imaging using various types of simple phase gratings.

Diffraction gratings can be used to form multiple images in optical systems utilizing incoherent, monochromatic light. The properties of two-dimensional phase gratings having periodic rectangular, sinusoidal, or triangular surface corrugation have been investigated. It is shown that these gratings can be used to form an array of equally intense images by an optical cascading process, each step in the cascade increasing the number of images by a factor of 9. These simple gratings would be particularly useful for forming relatively small numbers of large images. The efficiency per step would be between 70% and 80% and the distortion less than 2%. If spatially incoherent laser light is used, the resolution and general image quality would be limited mainly by the lenses used. These conclusions are corroborated by experimental results obtained with rectangular-type phase gratings.