A spatial light phase modulator with an effective resolution of 4 mega-pixels

Author(s): Daryl Preece; Eric Yao; Graham Gibson; Richard Bowman; Jonathan Leach; Miles Padgett

Abstract:

“We report the design, construction and characterization of a 4 mega-pixel, optically-addressed, spatial light modulator (OSLM). The intensity distribution corresponding to a kinoform is displayed across two wide-screen liquid crystal on silicon displays, the images of which are combined and relayed to the address face of a 40 mm aperture OSLM. This spatially varying intensity profile is converted into a phase hologram on the readout side of the OSLM. When illuminated at 532 nm we measure a first-order diffraction efficiency of ≈50% at 400 line pairs and ≈20% at 900 line pairs. We show that aberration associated with the non-flatness of the device can be corrected within software by modification of the hologram.”

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Publication: Journal of Modern Optics, (subscription required)

Issue/Year/DOI: Journal of Modern Optics, Volume 55, Issue 18 October 2008 , pages 2945 – 2951
DOI: 10.1080/09500340802272357

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, (subscription required)

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

Wavelength dependence of polarimetric and phase-shift characterization of a liquid crystal on silicon display

Author(s): A. Lizana, A. Marquez, I. Moreno, C. Iemmi, J. Campos, M.J. Yzuel

Abstract:

“We present a full characterization of a liquid-crystal-on-silicon (LCoS) display, including a polarimetric analysis based on the Mueller-Stokes formalism, and a phase shift modulation calibration. Results for different wavelengths are compared. The goal of this work is two fold. On one side, previous papers dealing with the illumination wavelength 633 nm have shown that LCoS produce a non negligible amount of depolarized light. This may have a negative impact in certain applications. Here we want to establish how this depolarization varies with the wavelength. On the other side, to use the LCoS as a spatial light modulator (SLM) we need to obtain optimal configurations enabling for phase-only or for amplitude-only modulation. Here we show how phase-only modulation is obtained, and how it evolves with the wavelength. In principle, for shorter wavelengths the phase modulation depth increases and the energy throughput may also be increased. However, these phase-only configurations may be partially degraded by the presence of depolarization at certain gray levels. Thus, the Mueller-Stokes formalism is necessary to get a full picture of the performance exhibited by the LCoS at each wavelength”

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Publication: Journal of the European Optical Society, (free download)

Issue/Year/DOI: Journal of the European Optical Society, Vol 3 (2008)
DOI: 10.2971/jeos.2008.08012

Combined Mueller and Jones matrix method for the evaluation of the complex modulation in a liquid-crystal-on-silicon display

Author(s): I. Moreno, A. Lizana, J. Campos, A. Márquez, C. Iemmi, and M. J. Yzuel

Abstract:

“We apply the polar decomposition of the Mueller matrix describing a liquid-crystal-on-silicon display to identify the diattenuator, depolarizer, and retarder contributions as a function of the gray level. The retarder contribution is expressed in terms of the equivalent Jones matrix to apply previous techniques to evaluate the phase modulation. This allows searching for optimized polarization configurations for phase- or amplitude-only modulation responses. We present results for λ=633 nm showing a phase-only modulation up to 2π rad and flat intensity modulation.”

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Publication: Optics Letters, (subscription required)

Issue/Year/DOI: Optics Letters, Vol. 33, Issue 6, pp. 627-629, 2008
doi:10.1364/OL.33.000627

Efficient compensation of Zernike modes and eye aberration patterns using low-cost spatial light modulators

Author(s): Vicente Durán, Vicent Climent, Enrique Tajahuerce, Zbigniew Jaroszewicz, Justo Arines and Salvador Bará

Abstract:

“Off-the-shelf spatial light modulators (SLMs) like those commonly included in video projection devices have been seldom used for the compensation of eye aberrations, mainly due to the relatively low dynamic range of the phase retardation that can be introduced at each pixel. They present, however, some interesting features, such as high spatial resolution, easy handling, wide availability, and low cost. We describe an efficient four-level phase encoding scheme that allows us to use conventional SLMs for compensating optical aberrations as those typically found in human eyes. Experimental results are obtained with artificial eyes aberrated by refractive phase plates introducing either single Zernike terms or complex eye aberration patterns. This proof-of-concept is a step toward the use of low-cost, general purpose SLMs for the compensation of eye aberrations. ”

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Publication: SPIE Journal of Biomedical Optics, (subscription required)

Issue/Year/DOI: J. Biomed. Opt., Vol. 12, 014037 (2007);
DOI:10.1117/1.2698048

Optimization of Liquid-Crystal Spatial Light Modulator for Precise Phase Generation

Author(s): Seow-Hwang Eng; Dong Mei Cai; Zhenglin Wang; Alameh, K.; Wenhan Jiang;

Abstract:

“Spatial light modulators (SLMs) are recently emerging as wavefront generation or reconstruction devices. In this paper, we use a liquid-crystal SLM (LC-SLM) as a wavefront generation device through the modulation of the spatial phase distribution of an incident light beam. We characterize the phase modulation performance of the LC-SLM, and identified a polarization-configuration to minimize its amplitude modulation effects in order to maximize the contrast of reconstructed phase holograms. We also investigated the feasibility of determining the optical surface uniformity of the LC-SLM through computations of the interference fringes, and identified the disadvantages of this method. This new approach may be used to determine the optical surface quality of other optical devices.”

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Publication: Conference on Optoelectronic and Microelectronic Materials and Devices, (subscription required)

Issue/Year/DOI: Conference on Optoelectronic and Microelectronic Materials and Devices (2006)
doi:10.1109/COMMAD.2006.4429891

Diffraction-based determination of the phase modulation for general spatial light modulators

Author(s): David Engström, Gabriel Milewski, Jörgen Bengtsson, and Sheila Galt

Abstract:

“We describe a characterization method based on diffraction for obtaining the phase response of spatial light modulators (SLMs), which in general exhibit both amplitude and phase modulation. Compared with the conventional interferometer-based approach, the method is characterized by a simple setup that enables in situ measurements, allows for substantial mechanical vibration, and permits the use of a light source with a fairly low temporal coherence. The phase determination is possible even for a SLM with a full amplitude modulation depth, i.e., even if there are nulls in the amplitude transmission characteristic of the SLM. The method successfully determines phase modulation values in the full 2π rad range with high accuracy. The experimental work includes comparisons with interferometer measurements as well as a SLM characterization with a light-emitting diode (LED).”

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Publication: Applied Optics, (subscription required)

Issue/Year/DOI: Applied Optics, Vol. 45, Issue 28, pp. 7195-7204 (2006)
doi:10.1364/AO.45.007195

Optimally tuned spatial light modulators for digital holography

Author(s): Christian Kohler, Xavier Schwab, and Wolfgang Osten

Abstract

“Digital holography and comparative digital holography are applications that require computer-addressable modulators for the optical reconstruction of digital holograms. The quality of the reconstructed holograms depends on the modulator’s properties. Therefore a characterization of the modulators is required. We show the result of a modulator characterization and the modulator’s influence on the quality of the reconstructed hologram. We then compare qualitatively and quantitatively the optical reconstruction of phase and amplitude holograms by considering their level of detail and their diffraction efficiency.”

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Publication: Applied Optics (subscription required)

Issue/Year/DOI: Applied Optics, Vol. 45, Issue 5, pp. 960-967 (2006)
doi:10.1364/AO.45.000960

Determination of the phase- and polarization-changing properties of reflective spatial light modulators in one set-up

Author(s): Kay Gastinger, Ola D. Hunderi and Mikael Lindgren.

Abstract:

“The use of liquid crystal spatial light modulators in applications, require good characterization of phase, polarization and amplitude shifting properties. This report presents a new approach for simultaneously characterizing the depolarization and controlling the polarization properties of a reflective twisted nematic liquid crystal spatial light modulator (LC SLM). The SLM was set up as a part of a Michelson interferometer. The phase response was determined by using a piezo-electric actuator for phase stepping in the reference arm. During the polarization measurement the reference beam was removed and the polarization state of the input and output was determined by a polarization state generator (PSG) and a polarization state analyzer (PSA), each consisting of a polarizer and a quarter-wave plate. Hereby, both phase response and polarization control properties could be determined independently in the same measurement configuration simply by changing static polarization components. The systematic rotation of the quarter wave plates of the PSG and the PSA using stepper motors gives out-put data whose Fourier transform in terms of angular frequency components can be used to determine all the elements of the Mueller matrix. The Mueller matrix of a commercial SLM (Holoeye LC-2500) was determined for 17 evenly spaced voltage levels addressed to the SLM.”

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Publication: SPIE Proceedings, (subscription required)

Issue/Year/DOI: Proc. SPIE, Vol. 5618, 174 (2004);
DOI:10.1117/12.578438

Amplitude, Phase, and Hybrid Ternary Modulation Modes of a Twisted-Nematic Liquid-Crystal Display at ~400 nm

Author(s): Judit Reményi, Péter Várhegyi, László Domján, Pál Koppa, and Emõke Lõrincz

Abstract:

“Applicability of a commercial twisted-nematic liquid-crystal display is examined at ~400 nm. Different modulation modes predicted by Jones-matrix calculus are experimentally tested. High contrast amplitude modulation with negligible loss, high contrast and low loss hybrid ternary modulation, and 1.5π continuous phase delay without intensity modulation and with low loss are presented. Simulation results of a 4f holographic system prove the usefulness of the high contrast for amplitude modulation, and the importance of π phase difference between high transmission white levels in a hybrid ternary modulation.”

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Publication: Applied Optics, (subscription required)

Issue/Year/DOI: Applied Optics, Vol. 42, Issue 17, pp. 3428-3434 (2003)
doi:10.1364/AO.42.003428