Grating pseudo-imaging with polychromatic and finite extension sources

Abstract

Abstract:The pseudo-imaging process in a system consisting of two periodic gratings and illuminated by an incoherent polychromatic and finite extension source placed at a finite distance from the gratings is studied. An analytical expression of the irradiance distribution on a plane, also located at a finite distance from the gratings, has been obtained from previous results on monochromatic illumination. In the analysis presented, different imaging regimes are found and related to the parameters which characterize the double grating system. The pseudo-imaging phenomenon strongly depends on both the spatial and temporal coherence of the incident illuminating field. Certain pseudo-images are observed with polychromatic and incoherent incident light under some restrictions. On the other hand, pseudo-image process analogous to Talbot effect appears only by monochromatic and plane illuminating wavefront.

Invariant grating pseudoimaging using polychromatic light and a finite extension source

“…(A4). These experimental results are in good agreement with those numerical simulations performed in [14] for the case of the third regime, isolated pseudoimages, where the light source is polychromatic and spatially incoherent.…”

“…An experimental analysis has also been performed, which corroborates the theoretical results obtained. These simplified theory and experiments explain the numerical results given in [14], and it can be used to optimize the devices that use generalized grating imaging configuration, making them more tolerant to changes in the gap between gratings.…”

“…Therefore, the finite size of the light source has to be considered in the analysis. For standard grating periods and source sizes, pseudoimages only present a significant contrast at narrow bands in the ðz 1 ; z 2 Þ plane (pseudoimage isolation) [14]. This corresponds to regime 3 of the said papers.…”

“…From the first studies based on diffraction theory [5], a model for pseudoimage formation based on Fresnel propagation of light has been progressively improved [6,7], introducing total incoherence [8], partially coherent light [9][10][11][12][13] and finite spectral width [14].…”

“…Double grating systems with polychromatic light have also been numerically analyzed, showing that some pseudoimages maintain a high contrast while other pseudoimages disappear [14]. The appearance, disappearance, and stability of the pseudoimages can be seen in a contrast representation with respect to z 1 and z 2 , z 1 being the distance between gratings and z 2 the distance between the second grating and the observation plane.…”