Systematic errors of an optical encryption system due to the discrete values of a spatial light modulator

Author(s): David S. Monaghan, Unnikrishnan Gopinathan, Damien P. Kelly, Thomas J. Naughton, John T. Sheridan

Abstract:

“An optical implementation of the amplitude encoded double random phase encryption/decryption technique is implemented, and both numerical and experimental results are presented. In particular, we examine the effect of quantization in the decryption process due to the discrete values and quantized levels, which a spatial light modulator (SLM) can physically display. To do this, we characterize a transmissive SLM using Jones matrices and then map a complex image to the physically achievable levels of the SLM using the pseudorandom encoding technique. We present both numerical and experimental results that quantify the performance of the system. ”

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Publication: SPIE – Optical Engineering
Issue/Year: Opt. Eng., Vol. 48, 027001 (2009);
DOI: 10.1117/1.3076208

Implementation of phase-only modulation utilizing a twisted nematic liquid crystal spatial light modulator

Author(s): Mohammad Sultan Mahmud, Izabela Naydenova and Vincent Toal

Abstract:

“Twisted nematic liquid crystal spatial light modulators (SLM) are widely used for amplitude modulation of light. The technique for measuring phase and amplitude modulation introduced by a twisted nematic cell is not new but the novelty here is that, after characterization of a Holoeye LC2002 TNLC device, we were able to identify specific conditions that allow for its use as a pure 180° or more phase modulator with little or no amplitude modulation at 514.5 nm laser wavelength. The phase shift introduced by the SLM was measured using a near common-path Mach–Zehnder interferometer. The experimentally measured and the theoretically predicted intensity transmission and phase shift as functions of gray levels are compared. Finally, the effects of errors in the angular settings of the polarizers and quarter waveplates on the intensity transmission and phase shift are studied.”

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Publication: Journal of Optics A
Issue/Year: J. Opt. A: Pure Appl. Opt. 10 085007 (7pp), 2008
DOI: 10.1088/1464-4258/10/8/085007

Femtosecond laser ablation inductively coupled plasma mass spectrometry: Fundamentals and capabilities for depth profiling analysis

Author(s): Jorge Pisonero, Detlef Günther

Abstract:

“Laser ablation coupled to inductively coupled plasma mass spectrometry has become a versatile and powerful analytical method for direct solid analysis. The applicability has been demonstrated on a wide variety of samples, where major, minor, and trace element concentrations or isotope ratio determinations have been of interest. The pros and cons of UV-nsec laser ablation have been studied in detail, and indicate that aerosol generation, aerosol transport, and aerosol excitation–ionization within the ICP contribute to fractionation effects, which prevent this method from a more universal application to all matrices and all elements. Recent progresses in IR-fs and UV-fs laser ablation coupled to ICP-MS have been reported, which increase the inter-matrix and multi-element quantification capabilities of this method. These fundamental improvements in LA-ICP-MS are of significant importance for entering new applications in material science and related research fields. In particular, because coatings (conducting and non-conducting) consist of single or multilayers of various elemental composition and of different thickness (nm–mm range), significant progress in the field of depth profiling with fs-laser ablation can be expected. Therefore, in-depth profile analysis of polymers, semiconductors, and metal sample investigations, using ultra-fast laser ablation for sampling and the currently achievable figures of merit, are discussed. In this review manuscript, the enhanced capabilities of fs-LA-ICP-MS for direct solid sampling are highlighted, and it is discussed about current methods used for quantitative analysis and depth profiling, the ablation process of UV-ns and UV-fs, the influence of the laser beam profile, aerosol structure and transport efficiency, as well as the influence of the ICP-MS (e.g., vaporization and ionization efficiency in the plasma, and type of mass analyzer).”

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Publication: Mass Spectrometry Reviews
Issue/Year: Mass Spectrometry Reviews, 2008, Volume 27, Issue 6, pages 609–623,
DOI: 10.1002/mas.20180

Phase dynamics of continuous topological upconversion in vortex beams

Author(s): Carlos López-Mariscal, Daniel Burnham, Daniel Rudd, David McGloin, and Julio C. Gutiérrez-Vega

Abstract:

“The vortex emergence process as an integer order Bessel field progresses continuously onto the contiguous higher order Bessel field is studied in detail. We assess the progressive migration of phase singularities and explain the predicted increase in fractional orbital angular momentum content of the beam in terms of this gradual process.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 15, pp. 11411-11422, (2008)
DOI: 10.1364/OE.16.011411

A Projection System for Real World Three-Dimensional Objects Using Spatial Light Modulators

Author(s): Gopinathan, U. Monaghan, D.S. Hennelly, B.M. McElhinney, C.P. Kelly, D.P. McDonald, J.B. Naughton, T.J. Sheridan, J.T.

Abstract:

“We discuss a projection system for real world three-dimensional objects using spatial light modulators (SLM). An algorithm to encode the digital holograms of real world objects on to an SLM is presented. We present results from experiments to project holograms of real world holograms using a nematic liquid crystal SLM. We discuss the case when the pixel sizes of the charge-coupled device (CCD) and SLM used for recording the hologram and projection are different.”

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Publication: Journal of Display Technology
Issue/Year: Journal of Display Technology, Volume 4, Issue 2, June 2008, Pages 254-261
DOI: 10.1109/JDT.2007.913943

Applying SLODAR to measure aberrations in the eye

Author(s): Andrew Lambert, Benjamin J. Birt, David A. Atchison, and Huanqing Guo

Abstract:

“As a proof of concept we apply a technique called SLODAR as implemented in astronomy to the human eye. The technique uses single exposures of angularly separated “stars” on a Hartmann-Shack sensor to determine a profile of aberration strength localised in altitude in astronomy, or path length into the eye in our application. We report on the success of this process with both model and real human eyes. There are similarities and significant differences between the astronomy and vision applications.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 10, pp. 7309-7322, 2008
DOI: 10.1364/OE.16.007309

Extended fractional wavelet joint transform correlator

Author(s): Alpana Bhagatji, Naveen K. Nishchal, Arun K. Gupta and B.P. Tyagi

Abstract:

“An extended fractional wavelet joint transform correlator is implemented for real-time target recognition applications. The real-time input scene captured using a charge-coupled device camera along with the reference image is fractional Fourier transformed. The obtained joint power spectrum is multiplied by an appropriately scaled wavelet filter and the resultant function is differentiated. The application of wavelet filter enhances the correlation outputs and differential processing of wavelet-filtered joint power spectrum improves the detection efficiency by reducing the zero-order spectra. Targets with Gaussian and speckle noise have also been used to check the correlation output. The performance metrics: correlation peak intensity, peak-to-correlation energy, peak-to-sidelobe ratio and signal to clutter ratio have been calculated. The experimental results are presented in support of the proposed idea.”

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Publication: Optics Communications
Issue/Year: Optics Communications Volume 281, Issue 1, 1 January 2008, Pages 44-48
DOI: 10.1016/j.optcom.2007.09.005

Wavelength-multiplexed submicron holograms for disk-compatible data storage

Author(s): Pengfei Wu, Zhiqiang Liu, Jame J. Yang, Angel Flores, and Michael R. Wang

Abstract:

“By using a hybrid diffractive and refractive achromat with extended depth of focus, we have successfully recorded a micro-hologram array with diffraction-limited individual spot size maintained throughout the thickness of recording medium. An electrically programmable wavelength combiner was constructed in which a white light source was adopted. By modifying on a commercial CD readout head, we configured a compact micro-hologram recording/readout system that is compatible to existing disk storage technology. Base on the wavelength combiner and recording/readout system, wavelength-multiplexed micro-holograms were recorded and recovered. The presented results demonstrate the practicality of our novel storage architecture.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 15, Issue 26, pp. 17798-17804
DOI: 10.1364/OE.15.017798

A high-capacity storage device for communications and multimedia systems

Author(s): Z. Y. Chen, Po S. Chung

Abstract:

“This paper introduces a high-capacity storage device based on the holographic optical disc storage system and applied field. It details a novel configuration of a single beam holographic storage system. Through coding the object light and reference light in same optical beam with a spatial light modulator (SLM), we achieve the aim of interference storage. The experimental results indicated this configuration can be used commercially. This system has the advantages of huge memory capacity and high access speed, thus offering a very useful storage alternative in the internet areas of communications and multimedia systems.”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE, Vol. 6775, 67750S (2007)
DOI: 10.1117/12.730495

Hybrid multinary modulation using a phase modulating spatial light modulator and a low-pass spatial filter

Author(s):

Abstract:Zoltán Göröcs, Gábor Erdei, Tamás Sarkadi, Ferenc Ujhelyi, Judit Reményi, Pál Koppa, and Emoke Lorincz

“We propose a method for performing binary intensity and continuous phase modulation of beams with a spatial light modulator (SLM) and a low-pass spatial filtering 4-f system. With our method it is possible to avoid the use of phase masks in holographic data storage systems or to enhance the phase encoding of the SLM by making it capable of binary amplitude modulation. The data storage capabilities and the limitations of the method are studied.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 32, Issue 16, pp. 2336-2338 (2007)
DOI: 10.1364/OL.32.002336
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