Showing papers on "Spatial light modulator published in 2009"
TL;DR: A prototype system for simulating exotic microscope illumination modalities and correcting for optical aberrations digitally is described and demonstrated, and two applications for it are demonstrated.
Abstract: Summary Byinsertingamicrolensarrayattheintermediateimageplane of an optical microscope, one can record four-dimensional light fields of biological specimens in a single snapshot. Unlike a conventional photograph, light fields permit manipulation of viewpoint and focus after the snapshot has been taken, subject to the resolution of the camera and the diffraction limit of the optical system. By inserting a second microlens array and video projector into the microscope’s illumination path, one can control the incident light field falling on the specimen in a similar way. In this paper, we describe a prototype system we have built that implements these ideas, and we demonstrate two applications for it: simulating exotic microscope illumination modalities and correcting for optical aberrations digitally.
318 citations
TL;DR: In this paper, a multi-pixel spatial modulator for terahertz beams using active metamaterials has been proposed, where each pixel is an array of subwavelength-sized split-ring resonator elements fabricated on a semiconductor substrate, and is independently controlled by applying an external voltage.
Abstract: We design and implement a multipixel spatial modulator for terahertz beams using active terahertz metamaterials. Our first-generation device consists of a 4×4 pixel array, where each pixel is an array of subwavelength-sized split-ring resonator elements fabricated on a semiconductor substrate, and is independently controlled by applying an external voltage. Through terahertz transmission experiments, we show that the spatial modulator has a uniform modulation depth of around 40% across all pixels, and negligible crosstalk, at the resonant frequency. This device can operate under small voltage levels, at room temperature, with low power consumption and reasonably high switching speed.
315 citations
TL;DR: The first experimental generation of the superposition of higher-order Bessel beams is reported, by means of a spatial light modulator (SLM) and a ring slit aperture, and the experimentally produced fields are in good agreement with those calculated theoretically.
Abstract: We report the first experimental generation of the superposition of higher-order Bessel beams, by means of a spatial light modulator (SLM) and a ring slit aperture. We present illuminating a ring slit aperture with light which has an azimuthal phase dependence, such that the field produced is a superposition of two or more higher-order Bessel beams. The experimentally produced fields are in good agreement with those calculated theoretically. The significance of these fields is that even though one is able to generate fields which carry zero orbital angular momentum, a rotation in the field's intensity profile as it propagates is observed.
165 citations
TL;DR: A technique is proposed theoretically and verified experimentally to eliminate a zero-order beam caused by a pixelated phase-only spatial light modulator (SLM) for holographic projection that results in higher reconstruction quality and diffraction efficiency.
Abstract: A technique is proposed theoretically and verified experimentally to eliminate a zero-order beam caused by a pixelated phase-only spatial light modulator (SLM) for holographic projection. The formulas for determination of the optical field in the Fourier plane are deduced, and the influence of the pixelated structure of a SLM on the intensity of the zero-order beam is numerically investigated. Two currently existing techniques are studied and a new one is presented. These three techniques are used separately to eliminate the zero-order interruption, and the optical performances of the reconstructed patterns are compared. The new technique results in higher reconstruction quality and diffraction efficiency. A short animated movie is illuminated for holographic projection display. The experimental results show that the zero-order beam can be efficiently eliminated by the new technique. It is believed that this technique can be used in various optical systems that are based on pixelated phase-only SLMs, such as holographic optical tweezers and optical testing systems.
156 citations
TL;DR: This work demonstrated the generation of a hologram having a 15 degrees horizontal viewing zone angle and an image size of 3.4 inches using a digital micromirror device with a frame rate of 13.333 kHz as a high-speed SLM.
Abstract: In order to increase the image size and the viewing zone angle of a hologram, a high-speed spatial light modulator (SLM) is imaged as a vertically long image by an anamorphic imaging system, and this image is scanned horizontally by a galvano scanner. The reduction in horizontal pixel pitch of the SLM provides a wide viewing zone angle. The increased image height and horizontal scanning increased the image size. We demonstrated the generation of a hologram having a 15° horizontal viewing zone angle and an image size of 3.4 inches with a frame rate of 60 Hz using a digital micromirror device with a frame rate of 13.333 kHz as a high-speed SLM.
112 citations
TL;DR: In this article, the Gratings and Lenses algorithm was used to calculate computer generated holograms (CGHs) producing diffractive multiple beams for the parallel processing of femtosecond laser surface micro-structuring.
96 citations
TL;DR: A modified Gabor-like setup able to recover the complex amplitude distribution of the object wavefront from a set of inline recorded holograms is presented and superior results to the Gabor method are produced.
Abstract: We present a modified Gabor-like setup able to recover the complex amplitude distribution of the object wavefront from a set of inline recorded holograms. The proposed configuration is characterized by the insertion of a condenser lens and a spatial light modulator (SLM) into the classical Gabor configuration. The phase shift is introduced by the SLM that modulates the central spot (dc term) in an intermediate plane, without an additional reference beam. Experimental results validate the proposed method and produce superior results to the Gabor method.
87 citations
TL;DR: A reduction of 44% in the variance of the bead's position is obtained, corresponding to an increase in effective trap stiffness of 77%.
Abstract: We present a holographic optical tweezers system capable of position clamping multiple particles. Moving an optical trap in response to the trapped object's motion is a powerful technique for optical control and force measurement. We have now realised this experimentally using a Boulder Nonlinear Systems Spatial Light Modulator (SLM) with a refresh rate of 203Hz. We obtain a reduction of 44% in the variance of the bead's position, corresponding to an increase in effective trap stiffness of 77%. This reduction relies on the generation of holograms at high speed. We present software capable of calculating holograms in under 1ms using a graphics processor unit. © 2009 Optical Society of America.
74 citations
Patent•
22 May 2009TL;DR: In this article, a display has a first and second spatial light modulators for modulating light from a light source, where the first has a plurality of elements switchable between ON and OFF states according to a pattern having a spatially-varying density.
Abstract: A display has first and second spatial light modulators for modulating light from a light source. The first spatial light modulator has a plurality of elements switchable between ON and OFF states according to a pattern having a spatially-varying density. Transfer optics blur and carry light modulated by the first spatial light modulator to the second spatial light modulator to yield a light field at the second spatial light modulator. The second spatial light modulator has a plurality of elements switchable between ON and OFF states to perform temporal dithering of the light field to provide a reconstruction of the image.
74 citations
TL;DR: The reconstructed images of 200-nm beads at various depths and fine structures of actin filaments near the edge of a HeLa cell are presented to demonstrate the intensity distributions in the axial direction and the prospective application to biological systems.
Abstract: We developed a structured illumination microscopy (SIM) system that uses a spatial light modulator (SLM) to generate interference illumination patterns at four orientations - 0 degrees, 45 degrees, 90 degrees, and 135 degrees, to reconstruct a high-resolution image. The use of a SLM for pattern alterations is rapid and precise, without mechanical calibration; moreover, our design of SLM patterns allows generating the four illumination patterns of high contrast and nearly equivalent periods to achieve a near isotropic enhancement in lateral resolution. We compare the conventional image of 100-nm beads with those reconstructed from two (0 degrees +90 degrees or 45 degrees +135 degrees) and four (0 degrees +45 degrees +90 degrees +135 degrees) pattern orientations to show the differences in resolution and image, with the support of simulations. The reconstructed images of 200-nm beads at various depths and fine structures of actin filaments near the edge of a HeLa cell are presented to demonstrate the intensity distributions in the axial direction and the prospective application to biological systems.
70 citations
TL;DR: A digital micromirror device (DMD)-based optical system that converts a spatially noisy quasi-Gaussian to an eighth-order super-Lorentzian flat-top beam and can be used to generate the homogeneous optical lattice required for Bose-Einstein condensate cold atom experiments.
Abstract: We demonstrate a digital micromirror device (DMD)-based optical system that converts a spatially noisy quasi-Gaussian to an eighth-order super-Lorentzian flat-top beam. We use an error-diffusion algorithm to design the binary pattern for the Texas Instruments DLP device. Following the DMD, a telescope with a pinhole low-pass filters the beam and scales it to the desired sized image. Experimental measurements show a 1% root-mean-square (RMS) flatness over a diameter of 0.28 mm in the center of the flat-top beam and better than 1.5% RMS flatness over its entire 1.43 mm diameter. The power conversion efficiency is 37%. We develop an alignment technique to ensure that the DMD pattern is correctly positioned on the incident beam. An interferometric measurement of the DMD surface flatness shows that phase uniformity is maintained in the output beam. Our approach is highly flexible and is able to produce not only flat-top beams with different parameters, but also any slowly varying target beam shape. It can be used to generate the homogeneous optical lattice required for Bose-Einstein condensate cold atom experiments.
Patent•
26 Jun 2009TL;DR: In this article, a digital image projector includes a plurality of light modulation assemblies and a dichroic combiner, which directs the output modulated light from each of the plurality of modulated assemblies toward a projection lens for projection onto a display surface.
Abstract: A digital image projector includes a plurality of light modulation assemblies and a dichroic combiner. Each light modulation assembly includes at least one laser light source configured to provide an illumination beam, an optional a coated surface, and a spatial light modulator. If the coated surface is present, the respective laser light source is configured to direct the illumination beam to the coated surface, which directs the illumination beam toward the respective spatial light modulator. Otherwise, the respective laser light source is configured to direct the illumination beam directly toward the respective spatial light modulator. The spatial light modulator redirects output modulated light back to the coated surface, if present, and out of the corresponding light modulation assembly. The dichroic combiner directs the output modulated light from each of the plurality of light modulation assemblies toward a projection lens for projection onto a display surface.
TL;DR: In this paper, a computer generated holography technique is employed to generate a custom defined wavefront, realized in the + 1 diffraction order when a collimated laser beam is diffracted by a binary transmission hologram.
Abstract: This article describes a graduate level optics laboratory experiment on the manipulation of the wavefront of a laser beam using a spatial light modulator. A computer generated holography technique is employed to generate a custom defined wavefront, realized in the +1 diffraction order when a collimated laser beam is diffracted by a binary transmission hologram. The hologram is written on a liquid crystal spatial light modulator and can be updated at a video rate using a personal computer interface.
TL;DR: This work experimentally investigates an optical mirror trap that is created after reflection of two holographically shaped collinear beams on a mirror, and presents measurements that characterize the mirror traps in terms of trap stiffness, maximum trapping force and capture range.
Abstract: Holographic optical tweezers typically require microscope objectives with high numerical aperture and thus usually suffer from the disadvantage of a small field of view and a small working distance. We experimentally investigate an optical mirror trap that is created after reflection of two holographically shaped collinear beams on a mirror. This approach combines a large field of view and a large working distance with the possibility to manipulate particles in a large size range, since it allows to use a microscope objective with a numerical aperture as low as 0.2. In this work we demonstrate robust optical three-dimensional trapping in a range of 1mm x 1mm x 2mm with particle sizes ranging from 1.4 mum up to 45 mum. The use of spatial light modulator based holographic methods to create the trapping beams allows to simultaneously trap many beads in complex, dynamic configurations. We present measurements that characterize the mirror traps in terms of trap stiffness, maximum trapping force and capture range.
TL;DR: This work demonstrates a versatile electronically controlled variant of differential interference contrast microscopy using a liquid-crystal spatial light modulator that displays a diffractive optical element and steers the beam separation.
Abstract: Differential interference contrast microscopy, imaging by interferometric superposition of two displaced beams passed through a transparent sample, is one of the most sophisticated methods in classical microscopy. Here we demonstrate a versatile electronically controlled variant using a liquid-crystal spatial light modulator that displays a diffractive optical element and steers the beam separation. The orientation and magnitude of the shear angle and the relative phase of the two interfering beams can all be varied at video rates. The technique is demonstrated by imaging polystyrene beads in immersion oil and a sample of red blood cells. The method expands the capabilities of previous implementations of differential interference contrast microscopy by its nonmechanical control over all imaging parameters.
TL;DR: The utility of the method uses a Sagnac interferometer that incorporates a spatial light modulator to combine beams that possess oppositely charged phase vortices in order to achieve the desired polarization vortex is demonstrated.
Abstract: We present a method for producing laser beams of nonuniform polarization where the polarization direction rotates on a trajectory about the beam propagation direction. Our method uses a Sagnac interferometer that incorporates a spatial light modulator to combine beams that possess oppositely charged phase vortices in order to achieve the desired polarization vortex. We demonstrate the utility of our method by producing polarization vortices characterized by a fractional index, and we compare the results with calculations of the expected fields.
TL;DR: The method is based on inverse ray tracing and can generate correction phase patterns whose peak-to-valley values are minimized and is useful in cases where a large phase modulation is needed, such as when employing a high-NA lens or focusing a beam deep inside a sample.
Abstract: We propose a simple method to correct a large amount of spherical aberration caused by a refractive index mismatch The method is based on inverse ray tracing and can generate correction phase patterns whose peak-to-valley values are minimized We also demonstrated spherical aberration correction in a transparent acrylic block using a liquid-crystal-on-silicon spatial light modulator (LCOS-SLM) A distorted focal volume without correction was substantially improved with correction This method is useful in cases where a large phase modulation is needed, such as when employing a high-NA lens or focusing a beam deep inside a sample
TL;DR: It is demonstrated trapping single neutral Rb atoms in micro traps of an optical ring lattice formed by superposing the +/-l components of the Laguerre-Gaussian mode, and generated by reflecting a single laser beam from a computer controlled spatial light modulator.
Abstract: We demonstrated trapping single neutral Rb atoms in micro traps of an optical ring lattice formed by superposing the +/- l components of the Laguerre-Gaussian mode, and generated by reflecting a single laser beam from a computer controlled spatial light modulator. A single atom in one trap or two atoms with one each in two traps were identified by observing the fluorescence. The trap array loaded with single atoms was rotated by dynamically displaying the hologram animation movie on the modulator. The modulation period in the fluorescence indicates the rotation of one or two single atoms in the lattice. (C) 2009 Optical Society of America
Patent•
09 Feb 2009TL;DR: In this article, the authors present a model of a stereoscopic digital image projector with a plurality of light modulation assemblies, each comprising at least one solid-state light source energizable to provide illumination having a first polarization axis; a polarization rotator disposed in the path of the polarized illumination from the solid state light source(s) and actuable to controllably rotate the polarization axis from one solid state to a second polarized axis.
Abstract: A stereoscopic digital image projector includes (a) a plurality of light modulation assemblies, each comprising: (i) at least one solid-state light source energizable to provide illumination having a first polarization axis; (ii) a polarization rotator disposed in the path of the polarized illumination from the solid-state light source(s) and actuable to controllably rotate the polarization axis from the solid-state light source(s) to a second polarized axis; (iii) a micro-electromechanical spatial light modulator in the path of the polarized illumination and energizable to modulate the polarized illumination to form a first modulated light from illumination of the first polarization state and to form a second modulated light from illumination of the second polarization state; and (b) a synchronizing means to temporally control the polarization rotation to match the appropriate image data on the spatial light modulator; and (c) projection optics for directing the first and second modulated light toward a display surface.
TL;DR: In this paper, a method to improve the quality of the reconstructed light field by eliminating the higher diffraction orders and by modifying hologram data based on the characteristic modulation properties of the SLM is presented.
Abstract: Spatial light modulators (SLMs) can be used to optically reconstruct the complex amplitude of a wavefield. The reconstructed wavefield in the far-field is corrupted by effects arising from the non-ideal modulation properties and the discrete nature of SLMs. These effects are regarded as drawbacks and particularly disturb the visual impression and reduce the light efficiency of the reconstruction in the region of interest. In this paper we present a novel method to improve the quality of the reconstructed light field by eliminating the higher diffraction orders and by modifying hologram data based on the characteristic modulation properties of the SLM. We achieve the elimination of the higher orders optically using only one lens in a 4f configuration with an appropriate amplitude mask inserted in the Fourier plane. For compensating the non-ideal modulation properties of the SLM we characterize the device to alter the digital hologram data in an appropriate way. The basic principle of this technique and its experimental verification are described.
TL;DR: This paper demonstrates how to use this technique to characterize the phase shifting properties of a liquid-crystal modulator, and in turn it uses the characterized modulator as the modulation device in the presented phase retrieval method.
Abstract: Recently a phase retrieval method using a movable phase plate as modulator has been proposed [Phys. Rev. A75, 043805 (2007)]. This method is applicable to general complex-valued fields and exhibits rapid convergence and high robustness to noise. In this paper, we demonstrate how to use this technique to characterize the phase shifting properties of a liquid-crystal modulator, and in turn we use the characterized modulator as the modulation device in the presented phase retrieval method. The adoption of a dynamic modulator gives a much more robust and flexible setup.
TL;DR: In this paper, a high repetition rate femtosecond laser system is combined with a spatial light modulator (SLM) for diffractive multiple beam processing, and the effect of the zero order beam is eliminated by adding a Fresnel zone lens to defocus the undiffracted beam at the processing plane.
TL;DR: Fast, efficient beam steering is demonstrated using a single 1x32 analog ferroelectric liquid crystal (FLC) spatial light modulator, which gives 200 micros response-time analog modulation.
Abstract: We demonstrate fast, efficient beam steering using a single 1×32 analog ferroelectric liquid crystal (FLC) spatial light modulator. A high-tilt FLC material with 82° optic-axis switching provides, in a reflective-mode device with a passive quarter-wave retarder between a half-wave FLC layer and a mirror, 91% of full 0-2π phase modulation. Electronic drive based on applied charge gives 200 μs response-time analog modulation.
TL;DR: This experiment represents a physical realization of Saari's proposal of spatio-temporally nondiffracting "flying images" on a few-femtosecond time scale and demonstrated that digitized image information encoded in amplitudephase maps of the needle beams is propagated over considerably large distances at minimal cross talk without the need for additional relay optics.
Abstract: We report the generation of programmable two-dimensional arrangements of ultrashort-pulsed fringe-less Bessel-like beams of extended depth of focus (referred to as needle beams) without truncating apertures. A sub-20-fs Ti:sapphire laser and a liquid-crystal-on-silicon spatial light modulator (LCoS-SLM) of high-fidelity temporal transfer in phase-only operation mode were used in the experiments. Axicon profiles with ultra-small conical angles were approximated by adapted gray scale distributions. It was demonstrated that digitized image information encoded in amplitude-phase maps of the needle beams is propagated over considerably large distances at minimal cross talk without the need for additional relay optics. This experiment represents a physical realization of Saari’s proposal of spatio-temporally nondiffracting “flying images” on a few-femtosecond time scale.
TL;DR: In this article, a method that enables the generation of arbitrary positioned dual-beam traps without additional hardware in a single-beam holographic optical tweezers setup is presented, and stable trapping at medium numerical aperture and long working distance is realized on a standard Zeiss Axiovert 200mm research microscope.
Abstract: We present a new method that enables the generation of arbitrary positioned dual-beam traps without additional hardware in a single-beam holographic optical tweezers setup. By this approach, stable trapping at medium numerical aperture and long working distance is realized on a standard Zeiss Axiovert 200 M research microscope. Simulations of focus separations and spherical aberrations were performed and first experimental results are presented.
Patent•
23 Sep 2009TL;DR: In this article, a display has a light source, a spatial light modulator and an intermediate spatial modulator, where the light source may comprise an array of controllable light-emitters.
Abstract: A display has a light source, a spatial light modulator and an intermediate spatial light modulator. The display may be a front projection display or a rear-projection display. The spatial light modulator is illuminated with light from a light source. The intermediate spatial light modulator is located in a light path between the light source and the spatial light modulator. The light source may comprise an array of controllable light-emitters. The display may provide a high dynamic range.
TL;DR: The fabricated 648 pixel, two-dimensional spatial light modulator with a transmittance of more than 85% in the wavelength region from 260 to 1,100 nm suggests that the SLM can be utilized, in the UV to near-IR region, for the generation of monocycle optical pulses, pulse shaping, and other applications.
Abstract: We fabricated a 648 pixel, two-dimensional spatial light modulator (SLM) with a transmittance of more than 85% in the wavelength region from 260 to 1,100 nm. The phase modulation characteristics of the liquid-crystal SLM were clarified. Furthermore, the SLM enabled us to compensate for chirp of 270 fs UV pulses and chirp of 120 fs near-IR pulses so that the former and latter pulse durations, respectively, were shortened to 35 and 25 fs. This suggests that the SLM can be utilized, in the UV to near-IR region, for the generation of monocycle optical pulses, pulse shaping, and other applications.
TL;DR: An efficient full-vectorial finite element beam propagation method is presented that uses higher order vector elements to calculate the wide angle propagation of an optical field through inhomogeneous, anisotropic optical materials such as liquid crystals.
Abstract: An efficient full-vectorial finite element beam propagation method is presented that uses higher order vector elements to calculate the wide angle propagation of an optical field through inhomogeneous, anisotropic optical materials such as liquid crystals. The full dielectric permittivity tensor is considered in solving Maxwell’s equations. The wide applicability of the method is illustrated with different examples: the propagation of a laser beam in a uniaxial medium, the tunability of a directional coupler based on liquid crystals and the near-field diffraction of a plane wave in a structure containing micrometer scale variations in the transverse refractive index, similar to the pixels of a spatial light modulator.
TL;DR: Adapt algorithms for mitigating inter-symbol interference in multimode fiber (MMF) systems using a spatial light modulator (SLM) are proposed and some are shown to converge to the global optimum in the absence of noise.
Abstract: We propose adaptive algorithms for mitigating inter-symbol interference (ISI) in multimode fiber (MMF) systems using a spatial light modulator (SLM). Minimizing ISI in MMF systems using an SLM has previously been posed as a convex optimization problem. Based on these results, we propose a range of algorithms for adapting the SLM settings. Some of these are shown to converge to the global optimum in the absence of noise. We then propose modified versions of these algorithms to improve resilience to noise and speed of convergence. Simulation results are included, showing that these algorithms open an otherwise closed eye pattern.
TL;DR: A shearing interferometer that is based on the birefringent properties of a phase-only spatial light modulator with high flexibility, robustness, and the light efficiency is presented.
Abstract: We present a shearing interferometer that is based on the birefringent properties of a phase-only spatial light modulator. The main advantages of this approach are the high flexibility, the robustness, and the light efficiency. In contrast to already existing methods the suppression of unwanted diffraction orders is not required.