Talbot interferometer with computer generated gratings

In a Talbot interferometer the self image of a periodic pattern, such as a Ronchi ruling of period d , illuminated by a monochromatic plane wavefront of wavelength λ, is formed at distances which are integral multiples of 2 d 2 /λ. A refracting object placed in front of the Ronchi ruling distorts the self image. A computer generated pattern can be designed, such that, when placed in a self imaging plane, a uniform intensity or a distinct moire pattern characterising a standard object is obtained. A method of computing the required patterns and experimental results for some aspherical objects are described.