Optical interference-based image encryption using circular harmonic expansion and spherical illumination in gyrator transform domain

Single-Pixel Compressive Digital Holographic Encryption System Based on Circular Harmonic Key and Parallel Phase Shifting Digital Holography

“…Using a Circular Harmonic Key in DRPE e schematic representation of the optical encryption arrangement of DRPE using the circular harmonic key in the Fresnel domain is shown in Figure 1(a). In this method, the RPM is expressed in terms of polar coordinates using a circular harmonic key [57,58] to enhance the security of the optical system. To obtain the circular harmonic key, the Cartesian coordinates (x, y) are converted to the polar coordinates (ρ, φ) using x � ρ cos φ and y � ρ sin φ. us, the RPM key can be expressed in the Fresnel domain as…”

“…e inclusion of circular harmonic function [57,58] in the random phase masks imparts additional degrees of freedom of encoding such as order of harmonics (m), radius (ρ 1 , ρ 2 ), and rotation angle (φ 1 , φ 2 ) to strengthen the security level of the encryption system. erefore, the proposed encryption scheme with keys in polar coordinates is a solution to the problem of variance in the decryption process.…”

“…Here, RPM 1 and RPM 2 are two independent random phase masks. Now, linear two-step PPSDH [54,55,58,59] is applied for obtaining single-shot inline hologram on the DMD plane, in which a phase array device such as spatial light modulator is used to give phase shifts to the reference wave in an interleaved manner with a periodic phase of θ � 0, − π/2 { }. e complex encrypted field G(x 0 , y 0 ) is interfered by the reference wave R θ (x 0 , y 0 ).…”