Dazun Zhao’s research while affiliated with Pennsylvania State University and other places

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Publications (5)


Optical realization of (a) real-value and (b) complex-value representations with a position-encoding method: CCL's, coherent collimated light; FOD's, first-order diffractions.
Hybrid JTC system: FL, Fourier-transform lens.
Position-encoding JTC: (a) the position-encoded inputs, (b) the first-order JFPS, (c) the output correlation distribution.
Conventional JTC: (a) the inputs, (b) the JFPS, (c) the output correlation distribution.
Application of position encoding to a complex joint transform correlator
  • Article
  • Publisher preview available

March 1995

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108 Reads

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39 Citations

F. T. S. Yu

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Dazun Zhao

Because a joint transform correlator can be used as a general optical signal processor, complex-impulse-response implementations in the spatial domain are often requested. We introduce a position-encoding technique with which complex-valued references for the joint transform correlator can be obtained with an amplitude-modulated spatial light modulator. A proof-of-concept experiment is also provided.

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Dynamic fiber specklegram sensing

February 1995

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8 Reads

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14 Citations

We introduce a concept of dynamic sensing that uses fiber speckle fields. By autonomously updating the fiber speckle patterns (i.e., using a moving reference to perform frame-to-frame comparison) on an electronically addressable spatial light modulator, we can exploit the dynamic fiber status. In other words, by joint transforming the rapidly changing speckle patterns from a sensing fiber, we can determine the dynamic aspects of the fiber status. For demonstration, dynamic displacement sensing is illustrated in which we have observed that the rate change and the trend of the fiber perturbation can indeed be detected. We note that the dynamic sensing technique can be applied to a variety of sensing parameters, e.g., strain, stress, temperature, and possibly seismic monitoring.


Fiber vibration sensor that uses the speckle contrast ratio

December 1994

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13 Reads

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27 Citations

Optical Engineering

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Jianzhong Zhang

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Kun Pan

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[...]

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Paul B. Ruffin

A vibration sensing technique using the speckle contrast ratio from a multimode fiber is introduced. This sensing technique is based on time integration by a CCD camera, from which the contrast ratio of the speckle patterns can be measured. Important aspects of the proposed sensor are that it can be applied to high-frequency vibration sensing and that its operation is rather simple.


Anisotropic intrasignal coupling in photorefractive LiNbO3

August 1994

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4 Reads

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2 Citations

Microwave and Optical Technology Letters

Intrasignaling coupling in a LiNbO3 photorefractive crystal is studied. It is shown that the anisotropy nature of the effective electrooptic coefficient of this crystal results in an orientation-dependent intrasignal coupling. Analytical solutions for one-dimensional intrasignal coupling are derived for a-axis and b-axis orientations, which enables us to estimate the maximum beam field angle and the maximum crystal thickness for a given intensity distortion due to the coupling. The results are thus illustrative to applications of this crystal in areas such as holographic data storage, interconnection, spatial mode conversion, et cetera. © 1994 John Wiley & Sons, Inc.


Citations (4)


... By overcoming the limits of system integration and demodulation speed [5,6], these sensors prove to be the most promising future direction in fiber optic sensing [7]. Applications of light-scattering fiber optic sensors include temperature [8,9], current [10][11][12], displacement [13][14][15], and vibration [16][17][18][19] detection, and the applications of fiber optic speckle sensors have advanced significantly. However, since MMFs are affected by factors including the external environment, length, and diameter [20], it is critical to accurately model the speckle pattern changes under conditions of perturbation. ...

Reference:

Deep Learning-Based Simultaneous Temperature- and Curvature-Sensitive Scatterplot Recognition
Fiber vibration sensor that uses the speckle contrast ratio
  • Citing Article
  • December 1994

Optical Engineering

... 6 However, there are several distortive effects that could prevent one from obtaining a high-fidelity, high-resolution PR hologram. These effects can be classified roughly into two categories: 112 those caused by material problems, such as material defects 7,8 and scattering noise, 9,10 and 122 those due to nonlinearities in the recording process, such as PR beam coupling 11,12 and a nonlinear response at high-index modulation depth. 13 In this paper we consider another important distortive effect, which is due to the inherent angledependent diffraction in a thick photorefractive hologram. ...

Anisotropic intrasignal coupling in photorefractive LiNbO3
  • Citing Article
  • August 1994

Microwave and Optical Technology Letters

... The embedding and additive noises give more noncontinuous definition to surfaces and make it almost impossible to discriminate between the target image and the reference one from scene image. There are many modified joint transform correlators: modified amplitude joint transform correlator (MAJTC) [1][2][3], modified phase input joint transform correlator (MPJTC) [4][5][6][7][8][9] and preprocessed modified joint transform correlator (preMPJTC) [10,14] that can detect objects with additive or embedding noises. ...

Application of position encoding to a complex joint transform correlator

... Because a speckle pattern has little correlation with other speckles, a scheme that uses a speckle pattern has also been used for a sensor system. 7 An optical fiber can produce a quasirandom phase code with a simple setup. 5,8 One can obtain different random phase information by shifting a fiber speckle pattern spatially or angularly or by changing speckle patterns with mode scrambling. ...

Dynamic fiber specklegram sensing