In this paper, we propose a new multiuser nonlinear optical cryptosystem using fractional-order vortex speckle (FOVS) patterns as security keys. In conventional optical cryptosystems, mostly random phase masks are used as the security keys which are prone to various attacks such as brute force attack. In the current study, the FOVSs are generated optically by the scattering of the fractional-order vortex beam, known for azimuthal phase and helical wavefronts, through a ground glass diffuser. FOVSs have a remarkable property that makes them almost impossible to replicate. In the input plane, the amplitude image is first phase encoded and then modulated with the FOVS phase mask to obtain the complex image. This complex image is further processed to obtain the encrypted image using the proposed method. Two private security keys are obtained through polar decomposition which enables the multi-user capability in the cryptosystem. The robustness of the proposed method is tested against existing attacks such as the contamination attack and known-plaintext attack. Numerical simulations confirm the validity and feasibility of the proposed method.

In this paper, we propose a new asymmetric cryptosystem for phase image encryption, using the physically unclonable functions (PUFs) as security keys. For encryption, the original amplitude image is first converted into a phase image and modulated with a PUF to obtain a complex image. This complex image is then illuminated with a plane wave, and the complex wavefront at a distance d is recorded. The real part of the complex wavefront is further processed to obtain the encrypted image and the imaginary part is kept as the private key. The polar decomposition approach is utilized to generate two more private security keys and to enable the multi-user capability in the cryptosystem. Numerical simulations confirm the feasibility of the proposed method.

High-magnification optical systems often encounter a fundamental limitation in terms of the available field of view (FOV), which restricts the ability of the system to capture spatially extended scenes. Expanding the FOV in optical imaging is often as important as achieving high magnification. However, conventional imaging systems struggle to balance these two requirements effectively. Through several forms of aperture multiplexing in coded aperture imaging, this study enhances the imaging technique, allowing for FOV engineering without altering the system magnification or sensor size. In all multiplexing methods, the system-to-object response (SOR) is captured by a camera located at the imaging plane of a system equipped with a coded phase mask (CPM) in its aperture. The CPM is designed as a multiplex of N distinct scattering phase masks, where N –1 corresponds to the number of separated object areas to be included within the extended FOV. Each scattering phase generates a unique sparse dot pattern on the camera sensor. By employing the CPM, objects from outside the inherent FOV are effectively brought within the sensor’s active region. The image of the complete object plane with all N objects at their respective positions is reconstructed by deconvolving the SOR with the corresponding point spread functions. Three different methods of aperture phase mask multiplexing are applied to selectively engineer the FOV, and their performances are compared. The simplest and slowest method is time multiplexing, and the noisiest method is parallel spatial multiplexing. In addition to these two well-known methods, we propose a hybrid spatial multiplexing approach. We present simulation studies and experimental validation of all three proposed methods.