Effect of masking phase-only holograms on the quality of reconstructed images

Abstract

A phase-only hologram modulates the phase of the incident light and diffracts it efficiently with low energy loss because of the minimum absorption. Much research attention has been focused on how to generate phase-only holograms, and little work has been done to understand the effect and limitation of their partial implementation, possibly due to physical defects and constraints, in particular as in the practical situations where a phase-only hologram is confined or needs to be sliced or tiled. The present study simulates the effect of masking phase-only holograms on the quality of reconstructed images in three different scenarios with different filling factors, filling positions, and illumination intensity profiles. Quantitative analysis confirms that the width of the image point spread function becomes wider and the image quality decreases, as expected, when the filling factor decreases, and the image quality remains the same for different filling positions as well. The width of the image point spread function as derived from different filling factors shows a consistent behavior to that as measured directly from the reconstructed image, especially as the filling factor becomes small. Finally, mask profiles of different shapes and intensity distributions are shown to have more complicated effects on the image point spread function, which in turn affects the quality and textures of the reconstructed image.

Coherence properties of different light sources and their effect on the image sharpness and speckle of holographic displays

“…For an extended light source in the shape of a square or a circle, the corresponding Fourier transform is a 2D sinc function or a 2D Bessel function 29 , which is then multiplied with the representation of the reconstructed image in the frequency domain. As a result, the Fourier transform of the light source shape will directly “filter” the frequency information of the reconstructed image and hence its quality for the output.…”

“…Secondly, in digital holographic display system, the overall intensity profile in the replay plane is decided by the aperture of the hologram pixel, while the intensity profile of one spatial frequency pixel in the replay plane is decided by the overall aperture of the hologram 29 . For example, if the overall aperture of the hologram is square, then the profile of one spatial frequency pixel is 2D sinc function.…”

Diffractive optical elements 75 years on: from micro-optics to metasurfaces

“…In certain types of DOEs, especially dynamic CGHs, continuous phase profiles are transformed into pixelated structures because of the characteristics of modulators. The conversion process can be mathematically expressed as follows [162] : E(x,y)rect(xax,yay){Econ(x,y)pxpycomb(xpx,ypy)}dis,where ax and ay represent the pixel dimensions, px and py denote the pixel pitches, Edis stands for the discrete pixelated distribution, and Econ represents the continuous profile. The filling factor can be defined as the ratio between pixel dimensions and pixel pitches, and it is expressed as follows: μfill=(ax...…”

“…In certain types of DOEs, especially dynamic CGHs, continuous phase profiles are transformed into pixelated structures because of the characteristics of modulators. The conversion process can be mathematically expressed as follows [162] :…”

A compact synthetic aperture digital holographic microscope with mechanical movement-free beam scanning and optimized active aberration compensation for isotropic resolution enhancement

“…When applying the phase Fresnel lens, we also need to consider the masking effect of the CGH displayed on LCoS device [37,38]. The aperture shape and profile decides the PSF in the hologram plane.…”