Real-time computer-generated hologram by means of liquid-crystal television spatial light modulator

Metasurface Holography with Multiplexing and Reconfigurability

Metasurface holography offers significant advantages, including a broad field of view, minimal noise, and high imaging quality, making it valuable across various optical domains such as 3D displays, VR, and color displays. However, most passive pure-structured metasurface holographic devices face a limitation: once fabricated, as their functionality remains fixed. In recent developments, the introduction of multiplexed and reconfigurable metasurfaces breaks this limitation. Here, the comprehensive progress in holography from single metasurfaces to multiplexed and reconfigurable metasurfaces is reviewed. First, single metasurface holography is briefly introduced. Second, the latest progress in angular momentum multiplexed metasurface holography, including basic characteristics, design strategies, and diverse applications, is discussed. Next, a detailed overview of wavelength-sensitive, angle-sensitive, and polarization-controlled holograms is considered. The recent progress in reconfigurable metasurface holography based on lumped elements is highlighted. Its instant on-site programmability combined with machine learning provides the possibility of realizing movie-like dynamic holographic displays. Finally, we briefly summarize this rapidly growing area of research, proposing future directions and potential applications.

Magneto-optical spatial light modulator driven by current-induced domain wall motion for holographic display applications

We have developed a magneto-optical spatial light modulator (MO-SLM) with a 10 k × 5 k pixel layout and with a pixel pitch horizontally of 1 µm and vertically of 4 µm. An MO-SLM device pixel has a magnetic nanowire made of Gd-Fe magneto-optical material whose magnetization was reversed by current-induced magnetic domain wall motion. We successfully demonstrated the reconstruction of holographic images, showing large viewing zone angles as wide as 30 degrees and visualizing different depths of the objects. These characteristics are unique to holographic images, providing physiological depth cues which may play a vital role in three-dimensional (3D) perception.

Polarization-multiplexed full-space metasurface simultaneously merging with an ultrawide-angle antireflection and a large-angle retroreflection

Multifunctional electromagnetic (EM) metasurfaces are capable of manipulating electromagnetic waves with kaleidoscopic functions flexibly, which will significantly enhance integration and applications of electronic systems. However, most known design schemes only realize the reflection or transmission functions under a specific angle range, which wastes the other half EM space and restricts wider applications of multifunctional metadevices. Herein, an encouraging strategy of broadband and wide-angle EM wavefronts generator is proposed to produce two independent functions, i.e., antireflections for transverse electric (TE) waves and retroreflection for transverse magnetic (TM) waves, which utilizes band-stop and bandpass responses of the metasurface, respectively. As a feasibility verification of this methodology, a three-layer cascaded metasurface, composed of anisotropic crossbar structures patterned on the two surfaces of a dielectric substrate with sandwiched orthogonal metal-gratings, is designed, fabricated, and measured. Both the simulated and experimental results are in good accordance with theoretical analyses. This full-space metasurface opens up a new route to multifunctional metasurfaces and will further promote engineering applications of metasurfaces.

Magneto-optical diffractive deep neural network

We propose a magneto-optical diffractive deep neural network (MO-D²NN). We simulated several MO-D²NNs, each of which consists of five hidden layers made of a magnetic material that contains 100 × 100 magnetic domains with a domain width of 1 µm and an interlayer distance of 0.7 mm. The networks demonstrate a classification accuracy of > 90% for the MNIST dataset when light intensity is used as the classification measure. Moreover, an accuracy of > 80% is obtained even for a small Faraday rotation angle of π/100 rad when the angle of polarization is used as the classification measure. The MO-D²NN allows the hidden layers to be rewritten, which is not possible with previous implementations of D²NNs.

Complex spatial light modulation capability of a dual layer in-plane switching liquid crystal panel

Complex spatial light modulator (SLM), which can simultaneously control the amplitude and phase of light waves, is a key technology for wide-range of wave-optic technologies including holographic three-dimensional displays. This paper presents a flat panel complex spatial light modulator that consists of dual in-plane switching liquid crystal panels with double-degrees of freedom of voltage inputs. The proposed architecture features single-pixel level complex light modulation enabling complex light modulation in entire free space, which is most contrast to conventional macro-pixel based complex modulation techniques. Its complex light modulation capability is verified with theoretical simulation and experimental characterization, and a three-dimensional holographic image reconstruction without conjugate noise. It is believed that the proposed flat panel complex SLM can be an essential device for a wide range of advanced wave optic technologies.

Demonstration of a multicolor metasurface holographic movie based on a cinematographic approach

This study uses a dielectric metasurface to demonstrates a multicolor holographic movie. Overlapping of multiple-wavelength images at 445 nm, 532 nm, and 633 nm was achieved by maintaining the ratio between the wavelengths and the pixel periods constant. Polarization-independent pillar waveguides made of single-crystal silicon are used as meta-atoms. A movie of the rotating earth was designed by the iterative Fourier transform algorithm and fabricated using electron beam lithography to a silicon-on-sapphire substrate. The multicolor movie consists of 20 frames was successfully reproduced at the maximum speed of 30 frames per second.

Aerial holographic 3D display with an enlarged field of view by the time-division method

We propose a method to enlarge the field of view (FOV) of holographic 3D displays in both the horizontal and vertical directions. The FOV was enlarged by using two galvano mirrors and a high-speed spatial light modulator. These optical elements were placed so that the imaging relation was satisfied among them and they were synchronously driven at a high speed to implement the time-division method. Using this method, a floating 3D object could be successfully reconstructed in mid-air near the focal point of the final lens at the rate of 10 Hz. The FOV was enlarged five times and two times in the horizontal and vertical directions, respectively.

Wavefront shaping assisted design of spectral splitters and solar concentrators

Spectral splitters, as well as solar concentrators, are commonly designed and optimized using numerical methods. Here, we present an experimental method to spectrally split and concentrate broadband light (420–875 nm) via wavefront shaping. We manage to spatially control white light using a phase-only spatial light modulator. As a result, we are able to split and concentrate three frequency bands, namely red (560–875 nm), green (425–620 nm), and blue (420–535 nm), to two target spots with a total enhancement factor of 715%. Despite the significant overlap between the color channels, we obtain spectral splitting ratios as 52%, 57%, and 66% for red, green, and blue channels, respectively. We show that a higher number of adjustable superpixels ensures higher spectral splitting and concentration. We provide the methods to convert an optimized phase pattern into a diffractive optical element that can be fabricated at large scale and low cost. The experimental method that we introduce, for the first time, enables the optimization and design of SpliCons, which is \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim 300$$\end{document}∼300 times faster compared to the computational methods.

Diffractive distortion of a pixelated computer-generated hologram with oblique illumination

Computer-generated holograms (CGHs) have their phase and/or amplitude modulation pattern calculated rather than recorded as for traditional holograms. In practice, the CGH devices are normally pixelated, no matter if they are passive or active ones. In many cases, the reconstruction light illuminates on the CGH devices obliquely, and the pattern generated on the target plane will be distorted from the originally desired one, even if the modulation on the CGH devices has been calibrated for the corresponding illumination angle in CGH calculation and optimization. The distortion is purely related to the diffraction behavior resulting from the geometry of the pixel on the CGH, and therefore diffractive distortion has been coined for this specific phenomenon. In this paper, quantitative analysis of diffractive distortion and a corresponding scheme for correction have been given based on scalar diffraction theory. The proposed concept is that the distortion of the reconstructed image is proportional to the distortion of the signal window. An experiment has been conducted with a phase-type liquid crystal on silicon spatial light modulator (SLM). Both the distortion analysis and the correction scheme have been verified quantitatively for various illumination angles and the direction of the reconstruction light.

Dynamic 3D meta-holography in visible range with large frame number and high frame rate

The hologram is an ideal method for displaying three-dimensional images visible to the naked eye. Metasurfaces consisting of subwavelength structures show great potential in light field manipulation, which is useful for overcoming the drawbacks of common computer-generated holography. However, there are long-existing challenges to achieving dynamic meta-holography in the visible range, such as low frame rate and low frame number. In this work, we demonstrate a design of meta-holography that can achieve 228 different holographic frames and an extremely high frame rate (9523 frames per second) in the visible range. The design is based on a space channel metasurface and a high-speed dynamic structured laser beam modulation module. The space channel consists of silicon nitride nanopillars with a high modulation efficiency. This method can satisfy the needs of a holographic display and be useful in other applications, such as laser fabrication, optical storage, optics communications, and information processing.

Aktina Vision: Full-parallax three-dimensional display with 100 million light rays

Natural three-dimensional (3D) images, perceived as real objects in front of the viewer, can be displayed by faithfully reproducing light ray information. However, 3D images with sufficient characteristics for practical use cannot be displayed using conventional technologies because highly accurate reproduction of numerous light rays is required. We propose a novel full-parallax light field 3D display method named ‘Aktina Vision’, which includes a special top-hat diffusing screen with a narrow diffusion angle and an optical system for reproducing high-density light rays. Our prototype system reproduces over 100,000,000 light rays at angle intervals of less than 1° and optimally diffuses light rays with the top-hat diffusing screen. Thus, for the first time, light field 3D image reproduction with a maximum spatial resolution of approximately 330,000 pixels, which is near standard-definition television resolution and three times that of conventional light field display using a lens array, is achieved.

Super-wide viewing-zone holographic 3D display using a convex parabolic mirror

To enlarge both horizontal (azimuthal) and vertical (zenithal) viewing zones simultaneously, a convex parabolic mirror is placed after passing through the hologram. Viewers perceive a three-dimensional (3D) object inside the parabolic mirror as a virtual image by capturing the wavefront radially reflected from the parabolic mirror. The optical experiment using the convex parabolic mirror has demonstrated an extremely wide viewing zone with an azimuthal range of 180° and zenithal range of 90°. The viewing zone and the shape of the parabolic surface are analyzed. The hologram is designed considering the parabolic mirror reflection, and its diffraction calculation method based on Fermat's principle is also proposed.

Optical rotation compensation for a holographic 3D display with a 360 degree horizontal viewing zone

A method for a continuous optical rotation compensation in a time-division-based holographic three-dimensional (3D) display with a rotating mirror is presented. Since the coordinate system of wavefronts after the mirror reflection rotates about the optical axis along with the rotation angle, compensation or cancellation is absolutely necessary to fix the reconstructed 3D object. In this study, we address this problem by introducing an optical image rotator based on a right-angle prism that rotates synchronously with the rotating mirror. The optical and continuous compensation reduces the occurrence of duplicate images, which leads to the improvement of the quality of reconstructed images. The effect of the optical rotation compensation is experimentally verified and a demonstration of holographic 3D display with the optical rotation compensation is presented.

Non-iterative phase hologram computation for low speckle holographic image projection

Phase-only spatial light modulators (SLMs) are widely used in holographic display applications, including holographic image projection (HIP). Most phase computer generated hologram (CGH) calculation algorithms have an iterative structure with a high computational load, and also are prone to speckle noise, as a result of the random phase terms applied on the desired images to mitigate the encoding noise. In this paper, we present a non-iterative algorithm, where simple Discrete Fourier Transform (DFT) relations are exploited to compute phase CGHs that exactly control half of the desired image samples (those on even - or odd - indexed rows - or columns) via a single Fast Fourier Transform (FFT) and trivial arithmetic operations. The encoding noise appearing on the uncontrolled half of the image samples is reduced by the application of structured, non-random initial phase terms so that speckle noise is also kept low. High quality reconstructions are obtained under temporal averaging of several SLM frames. Interlaced video within half of the addressable image area is readily deliverable without frame rate division. Our algorithm provides about 6X and 20X reduction in computational cost compared to IFTA and FIDOC algorithms, respectively. Simulations and experiments verify that the algorithm constitutes a promising option for real-time computation of phase CGHs.

Demonstration of polarization-insensitive spatial light modulation using a single polarization-sensitive spatial light modulator

We present a simple configuration incorporating a single polarization-sensitive phase-only liquid crystal spatial light modulator (LC-SLM) to facilitate polarization-insensitive spatial light modulation. The polarization-insensitive configuration is formed by a polarization beam splitter (PBS), a polarization-sensitive phase-only LC-SLM, a half-wave plate (HWP), and a mirror in a loop structure. We experimentally demonstrate polarization-insensitive spatial light modulations for incident linearly polarized beams with different polarization states and polarization-multiplexed beams. Polarization-insensitive spatial light modulations generating orbital angular momentum (OAM) beams are demonstrated in the experiment. The designed polarization-insensitive configuration may find promising applications in spatial light modulations accommodating diverse incident polarizations.

Magneto-optic spatial light modulator with submicron-size magnetic pixels for wide-viewing-angle holographic displays

Spatial light modulators (SLMs) with submicron-size pixels are promising devices for use in wide-viewing-angle glasses-free holographic 3D displays. In accordance with estimations, an SLM with 1 μm pitch pixels can display holographic images over viewing angles of 30 deg. In the present work, we have studied magneto-optic SLMs (MOSLMs) with submicron-size pixels for wide-viewing-angle holographic displays that are driven by thermomagnetic recording. Amorphous TbFe films were used as a magneto-optic material. The MOSLM with an 800 nm diameter pixels array displayed wide-viewing-angle holographic images. These results demonstrated that MOSLMs with submicron-size pixels have promise for glasses-free holographic 3D displays.

Enhanced resolution and throughput of Fresnel incoherent correlation holography (FINCH) using dual diffractive lenses on a spatial light modulator (SLM)

Fresnel incoherent correlation holography (FINCH) records holograms under incoherent illumination. FINCH was implemented with two focal length diffractive lenses on a spatial light modulator (SLM). Improved image resolution over previous single lens systems and at wider bandwidths was observed. For a given image magnification and light source bandwidth, FINCH with two lenses of close focal lengths yields a better hologram in comparison to a single diffractive lens FINCH. Three techniques of lens multiplexing on the SLM were tested and the best method was randomly and uniformly distributing the two lenses. The improved quality of the hologram results from a reduced optical path difference of the interfering beams and increased efficiency.

Imaging through turbid layers by scanning the phase conjugated second harmonic radiation from a nanoparticle

We demonstrate imaging through a turbid layer by using digital phase conjugation of the second harmonic field radiated from a beacon nanoparticle. We show that the phase-conjugated focus can be displaced from its initial position by illuminating the same region of the turbid layer with an angular offset. An image is obtained by scanning the phase-conjugated focus through the turbid layer in a region around the nanoparticle. We obtain a clear image of the target by measuring the light transmitted through it when scanning the focused beam.

Optical Computing: A 60-Year Adventure

Optical computing is a very interesting 60-year old field of research. This paper gives a brief historical review of the life of optical computing from the early days until today. Optical computing generated a lot of enthusiasm in the sixties with major breakthroughs opening a large number of perspectives. The period between 1980 and 2000 could be called the golden age with numerous new technologies and innovating optical processors designed and constructed for real applications. Today the field of optical computing is not ready to die, it has evolved and its results benefit to new research topics such as nanooptics, biophotonics, or communication systems.

Optical inspection of liquid crystal variable retarder inhomogeneities

Liquid crystal variable retarders (LCVRs) are starting to be widely used in optical systems because of their capacity to provide a controlled variable optical retardance between two orthogonal components of incident polarized light or to introduce a known phase shifting (PS) between coherent waves, both by means of an applied voltage. Typically, the retardance or PS introduced by an LCVR is not homogeneous across the aperture. On the one hand, the LCVR glass substrates present a global bend that causes an overall variation of the retardance or PS. On the other hand, in the manufacturing process of an LCVR, there sometimes appears a set of micro-air bubbles that causes local retardance or PS inhomogeneities. In this work, we present an interferometric technique based on a Mach-Zehnder interferometer that is insensitive to vibrations and capable of inspecting and characterizing the LCVR's retardance or PS inhomogeneities. The feasibility of the proposed method is demonstrated in the experimental results, where the LCVR retardance is measured with an error of about 0.2 rad. The thickness of possible micro-air bubbles is obtained with a resolution of about 50 nm.

Electrically switchable computer-generated hologram using a liquid crystal cell with a proton beam patterned polymethylmethacrylate substrate

An electrically switchable computer-generated hologram (CGH) was fabricated using a liquid crystal (LC) cell. A polymethylmethacrylate (PMMA) film, which was spin-coated on one glass substrate of the LC cell, was patterned by a focused 2 MeV proton beam with a CGH phase pattern (2 microm resolution). With an applied voltage on the LC cell CGH sample, an index modulation was produced between the regions with and without PMMA because of the reorientation of LC molecules under the external electric field. The maximum diffraction efficiency measured was about 28.7%. The operating voltage was below 15 V(rms).

Accurate phase-added stereogram to improve the coherent stereogram

We propose an "accurate" phase-added stereogram, which can be defined as an improved phase-added stereogram. Generally, the macroblock size transformed by the fast Fourier transform is the same as the segmentation size of the phase-added stereogram. However, the proposed method uses a lager macroblock size than does the conventional method to reduce quantization error in discrete spatial frequencies in the spatial frequency domain. Therefore, even when the fast Fourier transform is used for calculation, the quality of the reconstructed image can be improved to be as clear as the Fresnel hologram.

Programmable color liquid-crystal television spatial light modulator: transmittance properties and application to speckle-correlation displacement measurement

Drive electronics developed for a color liquid-crystal television (LCTV) display enable data to be written onto individual pixels. Display transmittance characteristics obtained with the new and the original TV drive electronics are compared. The enhanced performance obtained through this development has some potential for spatial light modulator applications in color, optical information processing based on the low-cost LCTV. As an example, we describe a novel, to our knowledge, speckle metrology technique used to display fringes and to output correlation peaks resulting from in-plane object displacement. This requires only a single LC display to encode, simultaneously in three pixel colors, speckle and fringe patterns for real-time measurements. Relative merits of this technique, including displacement range and temporal resolution, are discussed.

Influence of flatness distortion on the output of a liquid-crystal-television-based joint transform correlator system

The use of liquid-crystal panels from a commercially available Sanyo video projector as spatial light modulators in a standard joint transform correlator system is investigated. It is found that the flatness distortion of the panels disturbs the output correlation signal in general. Since the reported solutions for the flatness corrections are either expensive (liquid gates) or suffer from low light efficiency (holographic techniques), we have investigated a possibility to minimize the influence of these distortions on the correlation output without flatness correction. First, we quantify optical flatness across the transparent panel area, and then we measure the effects of flatness distortion by changing the display location of the input objects and the resulting joint power spectrum. It is found that the correlation peak is 1 order of magnitude more sensitive to phase distortions of the input scene than to the same distortions of the joint power spectrum. Choosing the flattest location on the panel allows the utilization of the panels to be demonstrated through recognition of cuneiform inscription signs.

Interactive three-dimensional holographic displays

Computer graphics is confined chiefly to flat images. Images may look three-dimensional (3D), and sometimes create the illusion of 3D when displayed, for example, on a stereoscopic display [16, 13, 12]. Nevertheless, when viewing an image on most display systems, the human visual system (HVS) sees a flat plane of pixels. Volumetric displays can create a 3D computer graphics image, but fail to provide many visual depth cues (e.g. shading texture gradients) and cannot provide the powerful depth cue of overlap (occlusion). Discrete parallax displays (such as lenticular displays) promise to create 3D images with all of the depth cues, but are limited by achievable resolution. Only a real-time electronic holographic ("holovideo") display [11, 6, 8, 7, 9, 21, 22, 20, 2] can create a truly 3D computer graphics image with all of the depth cues (motion parallax, ocular accommodation, occlusion, etc.) and resolution sufficient to provide extreme realism [13]. Holovideo displays promise to enhance numerous applications in the creation and manipulation of information, including telepresence, education, medical imaging, interactive design and scientific visualization.The technology of electronic interactive three-dimensional holographic displays is in its first decade. Though fancied in popular science fiction, only recently have researchers created the first real holovideo systems by confronting the two basic requirements of electronic holography: computational speed and high-bandwidth modulation of visible light. This article describes the approaches used to address these problems, as well as emerging technologies and techniques that provide firm footing for the development of practical holovideo.

Gray characteristics of a color liquid-crystal television in the beam of a He-Ne laser

Systems of coherent optics with cheaper spatial light modulators are discussed. The aim is toward the behavior differences of the color components of a color liquid-crystal television (CLCTV) screen illuminated by a He-Ne laser (633 nm) and white light. Several conclusions have been derived about (1) the summary effects of numerous components, (2) the response of single components, (3) the comparison of conversion from color to gray between laser and white light, and (4) the approach of encoding and addressing a CLCTV.

Interlacing technique approach for the synthesis of kinoforms

An interlacing technique algorithm is proposed for the synthesis of kinoforms. The conventional iterative methods are quite powerful for optimizing kinoforms, but there is still a large reconstruction error for a quantized kinoform. We suggest the use of a number of subkinoforms interlaced together to synthesize a multikinoform for reconstructing the desired image. The idea of our interlacing technique is to increase the size of a kinoform to reduce the reconstruction error. The first subkinoform is generated from the desired image. Other subkinoforms are generated from the error images between the desired image and the image reconstructed from the previous subkinoforms. A theoretical analysis shows that the reconstruction error will be reduced as the number of subkinoforms is increased. Simulation results show that our interlacing method can reduce the reconstruction error more than do the conventional iterative methods and that the reconstructed image can be improved.

Astigmatic phase correction for the magneto-optic spatial light modulator

We report a simple low-cost technique for evaluating the phase distortion in a magneto-optic spatial light modulator. We find that the dominant distortion is caused by astigmatism and is easily compensated by encoding of the complex-conjugate pattern onto the device. Two experimental results are shown. First, the focused spot size from a Fresnel lens is sharpened when the aberrations are corrected. Second, we show that the pattern that generates a first-order Bessel-function nondiffracting beam does not work unless the aberrations are corrected.

Interaction of multiple distortions in spatial light modulators

Spatial light modulators are the key components in real-time optical image-processing systems. The phase and the intensity of their outputs will often depart from ideal behavior. An experimental method is described that permits the effects of multiple distortions, present simultaneously, to be modeled. A computer simulation of a bismuth silicon oxide-based correlator is presented, with spatial light modulators subject to three types of distortion, including phase and amplitude. The experimental method permits both the main effects of the distortions and their interactions to be predicted. Combining all the distortions simultaneously gives a more accurate assessment of the suitability of a spatial light modulator for a given optical processing task. Images of 256 × 256 pixels were used, and the simulation took 15 min. with a Sun SPARCstation 2.

Dynamic holographic interconnects that use ferroelectric liquid-crystal spatial light modulators

<p>Dynamic interconnect holograms are designed by the use of a simulated annealing algorithm and written to a 128 × 128 pixel ferroelectric spatial light modulator that is used in a binary-phase mode. Dynamic holograms are used to implement a 2 × 2 crossbar with single-mode fiber inputs and outputs, which function with as high as 27 dB of isolation between output ports. The principle is extended to two-dimensional interconnection holograms, and arbitrary fan-out to as high as 64 points is demonstrated with good performance.</p><p>Images of interconnection holograms are transferred from the spatial light modulator to an optically addressed spatial light modulator that is used in a binary-phase mode. The addition of a fixed array generator computer-generated hologram permits replication of the hologram image, thus creating a larger hologram with a high space-bandwidth product on the optically addressed spatial light modulator.</p><p>Results of a preliminary experiment are presented.</p>

Design of an optoelectronic cellular processing system with a reconfigurable holographic interconnect

The design of an optoelectronic parallel processing system is presented. In this system a reconfigurable computer-generated hologram is used to perform a shift-invariant optical interconnection operation. Scalability issues are investigated, and simple cellular processing operations are experimentally demonstrated.

Optical correlator using very-large-scale integrated circuit/ferroelectric-liquid-crystal electrically addressed spatial light modulators

The use of 2-kHz 64 × 64 very-large-scale integrated circuit/ferroelectric-liquid-crystal electrically addressed spatial light modulators as the input and filter planes of a VanderLugt-type optical correlator is discussed. Liquid-crystal layer thickness variations that are present in the devices are analyzed, and the effects on correlator performance are investigated through computer simulations. Experimental results from the very-large-scale-integrated/ferroelectric-liquid-crystal optical-correlator system are presented and are consistent with the level of performance predicted by the simulations.

Anamorphic optical systems using programmable spatial light modulators

Anamorphic optical systems with different horizontal and vertical magnifications are constructed by using programmable anamorphic lenses written on a magneto-optic spatial light modulator.

Programmable coherent source arrays generated by spatial light modulators

Programmable coherent source arrays are generated by using addressable liquid-crystal spatial light modulators and two-dimensional arrays of Fresnel lenses. The modulators used are an optically addressed liquid-crystal light valve, a matrix-addressed pixelated display, and two devices that have individually addressable elements with specially designed patterned electrodes. One such device has a transparent electrode patterned as a Fresnel zone plate array; the other is a gate array used in a hybrid implementation with a Fresnel lens array etched on a glass substrate. The operation of devices that use binary-amplitude and binary-phase Fresnel lenses is described, identifying programmable features, resolution limits, and applications.

Effects and correction of magneto-optic spatial light modulator phase errors in an optical correlator

Here we study the optical phase errors introduced into an optical correlator by the input and filter plane magneto-optic spatial light modulators. We measure and characterize the magnitude of these phase errors, evaluate their effects on the correlation results, and present a means of correction by a design modification of the binary phase-only optical-filter function. The efficacy of the phase-correction technique is quantified and is found to restore the correlation characteristics to those obtained in the absence of errors, to a high degree. The phase errors of other correlator system elements are also discussed and treated in a similar fashion.

Programmable liquid-crystal TV spatial light modulator: modified drive electronics to improve device performance for spatial-light-modulation operation

Liquid crystal television (LCTV) continues to play a useful role as a spatial light modulator in the development and evaluation of systems for optical image processing. We outline new addressing electronics developed for a commercially available LCTV that permit writing to individual pixels at an improved display up-date rate and allow the input video signal to cover a much greater transmittance range of the TV display for black and white pixels. We illustrate this by measuring the diffraction efficiency for gratings written onto the display. For vertical gratings written along the display columns the diffraction efficiency is increased significantly, but there is no improvement for horizontal gratings. Some merits of the modified LCTV modulator for optical processing applications are considered briefly.

Kinoform using an electrically controlled birefringent liquid-crystal spatial light modulator

A programmable kinoform using an electrically controlled birefringent liquid-crystal spatial modulator (ECB-LCSLM) is discussed. The LCSLM is capable of continuous phase modulation from 0 to 2piFor the kinoform generation, the phase distribution is calculated by iterative methods and recorded on the LCSLM with 16 quantizing levels. We discuss the characteristics and the structure of the LCSLM for the implementation of the programmable kinoform while comparing the computed results and optical reconstructions.

Generation of programmable coherent source arrays using spatial light modulators

We demonstrate and characterize arrays of coherent focused spots generated by writing multiple Fresnel zone plates on optically and electrically addressed modulators. The programmable parameters of the array are its size (number of generated spots) and the transmissivity and focal length of each lens. As expected, phase modulators have a better conversion efficiency than amplitude modulators do.

Recording reconfigurable binary computer-generated holograms on bistable optically addressed ferroelectric liquid-crystal spatial light modulators

The capacity of optically addressed bistable ferroelectric liquid-crystal spatial light modulators to be used for recording binary computer-generated holograms is experimentally demonstrated. The recording and reconstruction of cell- and point-oriented holograms are presented.

Optical laboratory morphological inspection processor

Morphological transformations are applied to industrial inspection problems. A real time optical architecture to implement morphological transformations such as erosion, opening, closing, and skeletonization is described and analyzed. The first real time optical laboratory results of erosion and opening are presented for locating string in tobacco.

Liquid crystal TV-based white light optical tracking novelty filter

A compact white light optical tracking novelty filter is demonstrated. Based on the use of two inexpensive liquid crystal televisions, a filtered and collimated white light source, digital delay, and video recorder, this portable white light device performs two major image comparison operations, a real time image subtraction and novelty tracking operations. Some preliminary experimental results are presented.

Liquid crystal television spatial light modulators

The spatial light modulation characteristics and capabilities of the liquid crystal television (LCTV) spatial light modulators (SLMs) are discussed. A comparison of Radio Shack, Epson, and Citizen LCTV SLMs is made.

Phase-only modulation using a twisted nematic liquid crystal television

We used a commercially available liquid crystal television display unit as a spatial optical phase-only modulator. To do this, we removed the integral polarizers from the unit and double passed the light under modulation through it. We found that it was possible to obtain continuous phase modulation from 0 to PI with essentially no change in the state of polarization of the output light and absorption changes of <2.5%. We wrote computer-generated phase-only holograms on the LCTV and reconstructed them optically.

Computer-generated holograms by means of a magnetooptic spatial light modulator

A magnetooptic spatial light modulator is used to reconstruct computer-generated Fourier holograms. Different methods for designing the holgrams are considered including binary and complex quantization in conjunction with an iterative algorithm, carrier techniques, phase manipulations, and cell oriented binary coding. The limitations of binary quantization are discussed, and the trade-offs between space-bandwidth and quantization error are considered. Using a device having an array of 48 x 48 elements the best compromise is achieved using carrier techniques in conjunction with phase manipulations and binary quantization.