Modeling an optical correlator for visualising phase objects

Optical Correlators for Cryptosystems and Image Recognition: A Review

“…The authors also proposed a method to optimize the filters, to avoid errors in recognition due to additional phase modulation of light present in amplitude LC SLMs. Khonin [ 111 ] modelled a VLC correlator based on the Hilbert transform, applied for visualizing phase objects. The optical implementation of the Hilbert transform can be obtained by using a confocal system, with two lenses and, between them, a spatial optical filter.…”

“…The parameters in these expressions can be obtained as: and , respectively. The Hilbert radial transform can be implemented using a spiral phase plate (SSP) and can show distinctly both the phase contrast and the contours of an object [ 111 ]. In [ 111 ], the Hilbert transform was used in an optical correlator and a comparison was made between the effects of Zernike and vortex filters, where the latter obtain, using the Hilbert transform, information not only about the phase, as in a Zernike filter, but also about the amplitude of the wavefront.…”

“…The Hilbert radial transform can be implemented using a spiral phase plate (SSP) and can show distinctly both the phase contrast and the contours of an object [ 111 ]. In [ 111 ], the Hilbert transform was used in an optical correlator and a comparison was made between the effects of Zernike and vortex filters, where the latter obtain, using the Hilbert transform, information not only about the phase, as in a Zernike filter, but also about the amplitude of the wavefront. Thus, additional data can be gathered about the input image, with the use of the directional Hilbert transform to select the contours of the image in a specified direction.…”