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Limited By:	Author = Kelly, D.P.;

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A Practical Guide to Digital Holography and Generalized Sampling (2008)

Kelly, D.P.; Hennelly, Bryan M.; McElhinney, Conor P.; Naughton, Thomas J.

A Practical Guide to Digital Holography and Generalized Sampling (2008)

Kelly, D.P.; Hennelly, Bryan M.; McElhinney, Conor P.; Naughton, Thomas J.

Abstract:

The theorems of Nyquist, Shannon and Whittaker have long held true for sampling optical signals. They showed that a signal (with finite bandwidth) should be sampled at a rate at least as fast as twice the maximum spatial frequency of the signal. They proceeded to show how the continuous signal could be reconstructed perfectly from its well sampled counterpart by convolving a Sinc function with the sampled signal. Recent years have seen the emergence of a new generalized sampling theorem of which Nyquist Shannon is a special case. This new theorem suggests that it is possible to sample and reconstruct certain signals at rates much slower than those predicted by Nyquist-Shannon. One application in which this new theorem is of considerable interest is Fresnel Holography. A number of papers have recently suggested that the sampling rate for the digital recording of Fresnel holograms can be relaxed considerably. This may allow the positioning of the object closer to the camera allowing f...

http://mural.maynoothuniversity.ie/2358/

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Quantifying the 2.5D imaging performance of digital holographic systems (2011)

Kelly, D.P.; Healy, J.J.; Hennelly, Bryan M.; Sheridan, J. T.

Quantifying the 2.5D imaging performance of digital holographic systems (2011)

Kelly, D.P.; Healy, J.J.; Hennelly, Bryan M.; Sheridan, J. T.

Abstract:

Digital holographic systems are a class of two step, opto-numerical, three-dimensional imaging techniques. The role of the digital camera in limiting the resolution and ﬁeld of view of the reconstructed image, and the interaction of these limits with a general optical system is poorly understood. The linear canonical transform describes any optical system consisting of lenses and/or free space in a uniﬁed manner. Expressions derived using it are parametrised in terms of the parameters of the optical system, as well as those of the digital camera: aperture size, pixel size and pixel pitch. We develop rules of thumb for selecting an optical system to minimise mean squared error for given input and digital camera parameters. In the limit, our results constitute a point spread function analysis. The results presented in this paper will allow digital holography practitioners to select an optical system to maximise the quality of their reconstructed image using a priori knowledge of the c...

http://mural.maynoothuniversity.ie/5786/

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Spread-space spread-spectrum technique for secure multiplexing (2007)

Hennelly, Bryan M.; Naughton, Thomas J.; McDonald, John; Sheridan, J. T.; Unnikrishnan,...

Spread-space spread-spectrum technique for secure multiplexing (2007)

Hennelly, Bryan M.; Naughton, Thomas J.; McDonald, John; Sheridan, J. T.; Unnikrishnan, G.; Kelly, D.P.; Javidi, B.

Abstract:

A novel technique for multiplexing complex images is proposed in which each image may be demultiplexed only if a set of random encryption keys is known. The technique utilizes the ability of the double random phase encoding method to spread a signals’ energy in both the space and the spatial frequency domains in a controlled manner. To multiplex, images are independently encrypted with different phase keys and then superimposed by recording sequentially on the same material. Each image is extracted by using the particular key associated with it. During decryption the energy from the other images is further spread, making it possible to minimize its effects by using suitable filters. Wigner analysis is applied to the technique, and numerical results are presented.

http://mural.maynoothuniversity.ie/5791/

Displaying Results 1 - 3 of 3 on page 1 of 1

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