Discrete Fresnel Transform and Its Circular Convolution

TL;DR

This paper introduces a new form of the discrete Fresnel transform (DFnT) with no degeneracy, explores its circular convolution property, and discusses its applications in optical and digital signal processing.

Contribution

The paper derives a non-degenerate DFnT and studies its circular convolution property for the first time, expanding its potential applications.

Findings

DFnT has no degeneracy, unlike previous formulations.

The DFnT of a circular convolution equals the convolution of the DFnT of sequences.

Potential applications in optical and digital signal processing.

Abstract

Discrete trigonometric transformations, such as the discrete Fourier and cosine/sine transforms, are important in a variety of applications due to their useful properties. For example, one well-known property is the convolution theorem for Fourier transform. In this letter, we derive a discrete Fresnel transform (DFnT) from the infinitely periodic optical gratings, as a linear trigonometric transform. Compared to the previous formulations of DFnT, the DFnT in this letter has no degeneracy, which hinders its mathematic applications, due to destructive interferences. The circular convolution property of the DFnT is studied for the first time. It is proved that the DFnT of a circular convolution of two sequences equals either one circularly convolving with the DFnT of the other. As circular convolution is a fundamental process in discrete systems, the DFnT not only gives the coefficients of the Talbot image, but can also be useful for optical and digital signal processing and numerical evaluation of the Fresnel transform.