Randomly Multiplexed Diffractive Lens and Axicon for Spatial and Spectral Imaging.

Vijayakumar Anand,Saulius Juodkazis,Tomas Katkus

doi:10.3390/mi11040437

Abstract

A new hybrid diffractive optical element (HDOE) was designed by randomly multiplexing an axicon and a Fresnel zone lens. The HDOE generates two mutually coherent waves, namely a conical wave and a spherical wave, for every on-axis point object in the object space. The resulting self-interference intensity distribution is recorded as the point spread function. A library of point spread functions are recorded in terms of the different locations and wavelengths of the on-axis point objects in the object space. A complicated object illuminated by a spatially incoherent multi-wavelength source generated an intensity pattern that was the sum of the shifted and scaled point spread intensity distributions corresponding to every spatially incoherent point and wavelength in the complicated object. The four-dimensional image of the object was reconstructed using computer processing of the object intensity distribution and the point spread function library.

Highlights

Fresnel incoherent correlation holography (FINCH) was invented in 2007 for the three-dimensional imaging of objects [1]
We proposed a new hybrid diffractive optical element (HDOE) designed by random multiplexing an axicon and a Fresnel zone lens
The complex amplitude of the HDOE is given as exp − jπr2/λz1 f (x, y) + exp(− j2πrα/λ)[1 − f (x, y)], where α is the angle of the axicon and f (x,y) is a binary random function with a scattering ratio β

Summary

Introduction

Fresnel incoherent correlation holography (FINCH) was invented in 2007 for the three-dimensional imaging of objects [1]. The two resulting mutually coherent object waves are made to interfere with each other to produce a self-interference hologram Three such self-interference holograms were recorded corresponding to three different relative phase differences (θ = 0, 2π/3, 4π/3) between the two object waves and combined to produce a complex hologram to remove the twin image and bias terms during reconstruction using Fresnel backpropagation. Noise suppression techniques using statistical averaging [2] and a polarization multiplexing scheme [3] were introduced to remove the multiplexing noise in the reconstruction that was prevalent in the earlier random phase multiplexing method [1]. This procedure improved the signal-to-noise ratio of the reconstruction in FINCH

Methods

Results

Conclusion