Spatial filtering and optical tomography of edge enhancement of a phase object

Abstract

Using a 4f optical system, the Hilbert transform [1] of the projections of the object slice is implemented to reconstruct its edge enhancement using the parallel projection tomography. The projection going out of the object is considered as the entrance to the 4f optical system, the filter employed in the Fourier plane consisting of a phase step of π radians, in the image plane, as it is well known, the output function is given by the convolution of the impulse response and the input function, then in the image plane the Hilbert transform of the projection is obtained. We show that the reconstruction in this case is the Hilbert transform in vertical direction of the slice function, which is a special case. Also study in detail the synthesis of the filter in order to obtain the reconstruction the edge enhanced in an arbitrary direction, which is general case.

Electric-Driven Polarization Meta-Optics for Tunable Edge-Enhanced Images

“…Optical metasurfaces, planar and lightweight optical elements consisting of artificial and subwavelength resonators with tailored electromagnetic properties, have attracted extensive attention due to the possibility of powerful and flexible control over the amplitude, phase, and polarization of light [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Metasurface-enabled optical analog computation has made significant progress towards optical differential operations and edged-enhanced imaging through elaborately designed metasurface devices (metadevices) with a conventional 4f Fourier filtering system [21][22][23][24][25][26][27][28][29]. However, this inevitably introduces a complex and bulky optical system, which runs counter to the compactness of metasurfaces.…”