It has been shown that the process of coded imaging of incoherently illuminated extended objects by self-imaging structures (SIS) naturally leads to the formation of Lau-type fringes at finite conjugates. The object grating and the grating representing the SIS need not be of the same period. The generalised Lau fringes are obtained under a conjugate relation characteristic of the SIS imaging and a general matching condition involving the periods and frequencies of the two periodic structures. The classical Lau fringes and the so-called finite conjugate classical Lau fringes are formed under special imaging conditions. Useful applications have been mentioned.

The Generalised Lau Effect

The self-imaging property of the SIS has been utilized for transferring information from extended objects placed at certain distances from the SIS to its self-image planes. The concept of 'reverse shadow magnification' has been introduced, and the most important result is that full object information may be encoded in the self-images by changing this magnification. Typical computed and experimental results for incoherently illuminated objects have been presented in support of some of the conclusions. A simple illustrative application has also been described.

S. C. Som

Papers

Coded Imaging By Self-Imaging Structures (SIS) And Applications