arXiv subjects

Shamima Mitu

Publications and source records attributed to Shamima Mitu.

3 recordsLinked to original sources

arXiv2025

Automatic Event Recognition Employing Optically Excited Electro-Nuclear Spin Coherence

An analog automatic event recognition (AER) system can be realized by combining the technique of holographic image recognition with the process of temporal signal correlation employing stimulated photon echo in an ensemble of two-level atoms. For efficient operation of the AER system, the optical transition in the two-level system must have a large oscillator strength. However, this implies a rapid decay of the excited state, which highly constrains the duration of the event that can be recognized, even when the images are retrieved rapidly from a fast parallel optical memory device. This constraint can be overcome by using a three-level Lambda system to transfer optical coherence to long-lived electro-nuclear spin coherence and vice-versa. Here, we present an analysis of the AER process employing such a Lambda system. We also show that due to the longitudinal and transverse variation of the phases of the optical fields undergoing Fresnel diffraction, the density matrix equations must account for the differences in the phases of the coherence excited in each pixel and the corresponding phases of the optical fields in subsequent pulses.

quant-ph↗

arXiv2025

Shift, Scale and Rotation Invariant Multiple Object Detection using Balanced Joint Transform Correlator

The Polar Mellin Transform (PMT) is a well-known technique that converts images into shift, scale and rotation invariant signatures for object detection using opto-electronic correlators. However, this technique cannot be properly applied when there are multiple targets in a single input. Here, we propose a Segmented PMT (SPMT) that extends this methodology for cases where multiple objects are present within the same frame. Simulations show that this SPMT can be integrated into an opto-electronic joint transform correlator to create a correlation system capable of detecting multiple objects simultaneously, presenting robust detection capabilities across various transformation conditions, with remarkable discrimination between matching and non-matching targets.

eess.IV↗

arXiv2025

Debiased Opto-electronic Joint Transform Correlator for Enhanced Real-Time Pattern Recognition

Opto-electronic joint transform correlators (OJTCs) use a focal plane array (FPA) to detect the joint power spectrum (JPS) of two input images, projecting it onto a spatial light modulator (SLM) to be optically Fourier transformed. The JPS is composed of two self-intensities and two conjugate-products, where only the latter produce the cross-correlation. However, the self-intensity terms are typically much stronger than the conjugate-products, producing a bias that consumes most of the available bit-depth on the FPA and SLM. Here we propose and demonstrate, through simulation and experiment, a debiased OJTC (DOJTC) that electronically pre-processes the JPS to remove the self-intensity terms before sending it to the SLM, thereby enhancing the quality of the cross-correlation result. We show that under some conditions the DOJTC yields a nearly two orders of magnitude improvement in the signal-to-noise ratio compared to an OJTC.

eess.IV↗