Photoleasticity in the Nano-range

Through the analysis of an image of a 6 micron diameter sphere recorded using evanescent illumination and a conventional optical microscope, speckle patterns, photoelastic fringes moiré fringes and holographic patterns have been detected in the nanometric range. In this paper the formation of photoelastic fringes will be analyzed. The photoelastic fringes play a very important role in the formation of the previously mentioned patterns. Utilizing FFT procedures it is possible to recover from the image spatial frequencies up to the order of few nanometers. This result confirms a conjecture of Toraldo di Francia, one of the originators of the concept of optical super-resolution and of actual procedures to achieve it. Toraldo di Francia in the late 40’s and early 50’s postulated the idea that through evanescent fields optical resolution could be increased almost continuously if enough energy is available to form an image.