Analytical transfer function for the nonlinear response of a resonant medium in the spatio-temporal Fourier-transform domain

Monjur, Mehjabin Sultana; Fouda, Mohamed; Shahriar, Selim M.

doi:10.1364/josab.34.000397

Cited by 2 publications

(2 citation statements)

References 22 publications

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“…To mathematically depict the process of correlation, the transfer function of the temporal correlator is derived through a frequency domain analysis, as described in references [ 2,13 ]. The three temporal signals are defined as A(t), B(t) and C(t) for the recording pulse, the query signal, and the reference signal, respectively.…”

Section: Analytical Model and Time Code Of The Temporal Correlatormentioning

confidence: 99%

Investigation of frequency invariance in automated event recognition using resonant atomic media

Shen,

Gamboa,

Hamidfar

et al. 2024

Practical Holography XXXVIII: Displays, Materials, and Applications

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Coherent excitation of a resonant medium yields a nonlinear response to the Fourier spectrum of the input signals. This property can be exploited to produce a 1D temporal correlator by applying two signals simultaneously, and subsequently reading out the state of the medium. This intricate process of nonlinear responses generates multiple time-delayed outputs, where we are only interested in the specific segment that pertains to the cross-correlation. To this end, the Schrödinger equation is used as a model to accurately determine the precise time code and location of the desired output. Here, we show via simulations how this may be used for 1D event recognition. By comparing a reference signal to a query signal, we can expect a prominent peak in the cross-correlation if there is a match. Such a system is inherently delay-invariant due to the properties of the Fourier transform but is not invariant to scaling in the time-domain (i.e., frequency shifting). We additionally show how frequency-shift invariant correlation can be achieved by pre-processing the input signals via the Mellin transform. This technique is tested using audio signals to achieve speech recognition, where invariance to frequency shifts means that individual phrases may be recognized independently of the voice of the speaker. This approach can be extended to three-dimensional video recognition systems for real-time event recognition. By utilizing the frequencyshift invariant technique, the system can effectively correlate videos with different time scales, making it applicable to various fields, such as surveillance and copyright plagiarism detection.

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Section: Analytical Model and Time Code Of The Temporal Correlatormentioning

confidence: 99%

Investigation of frequency invariance in automated event recognition using resonant atomic media

Shen,

Gamboa,

Hamidfar

et al. 2024

Practical Holography XXXVIII: Displays, Materials, and Applications

Self Cite

View full text Add to dashboard Cite

show abstract

“…The authors also presented a method for obtaining a practical version of the device [ 117 ]. The same group developed an analytical method, using the STFT (spatio-temporal Fourier transform), and obtained an improvement with many orders of magnitude of the response speed of an AER system based on the STC, as compared to numerical methods based on the Schrödinger equation [ 118 ]. Alternatively, digital approaches have also been proposed.…”

Section: Recent Applications and Implementations Of Optical Correlatorsmentioning

confidence: 99%

Optical Correlators for Cryptosystems and Image Recognition: A Review

Drăgulinescu

2023

Sensors

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Optical correlators are efficient optical systems that have gained a wide range of applications both in image recognition and encryption, due to their special properties that benefit from the optoelectronic setup instead of an all-electronic one. This paper presents, to the best of our knowledge, the most extensive review of optical correlators to date. The main types are overviewed, together with their most frequent applications in the newest contributions, ranging from security uses in cryptosystems, to medical and space applications, femtosecond pulse detection and various other image recognition proposals. The paper also includes a comparison between various optical correlators developed recently, highlighting their advantages and weaknesses, to gain a better perspective towards finding the best solutions in any specific domain where these devices might prove highly efficient and useful.

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Analytical transfer function for the nonlinear response of a resonant medium in the spatio-temporal Fourier-transform domain

Cited by 2 publications

References 22 publications

Investigation of frequency invariance in automated event recognition using resonant atomic media

Investigation of frequency invariance in automated event recognition using resonant atomic media

Optical Correlators for Cryptosystems and Image Recognition: A Review

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