Showing papers on "Spatial light modulator published in 1997"

Method of and apparatus for viewing an image

Abstract: Light from an image displayed on a display screen (10) is transmitted to an observer's eye (11) by way of a dynamic optical element (12) (such as a spatial light modulator or an electrically switchable holographic composite) which acts as a lens. Emitters (17) on the display screen (10) emit infrared radiation which is projected by the dynamic lens (12) as a broad wash onto the eye (11). Infrared radiation reflected back from the eye (11) is focused by the dynamic lens (12) onto detectors (18) also provided on the display screen (10). The detectors (18) are thus able to sense the direction of eye gaze, and the dynamic lens (12) is controlled in dependence on this to create an area of high resolution in an area of interest centred on the direction of gaze, which is moved to follow the eye gaze as its direction alters. Other than in the area of interest, the dynamic lens (12) has a relatively low resolution.

Femtosecond pulse shaping by an evolutionary algorithm with feedback

Abstract: We report on computer controlled compression of femtosecond laser pulses using a programmable liquid crys- tal spatial light modulator which is feedback-controlled by an evolutionary algorithm. This algorithm generates the opti- mal laser field on the basis of feedback from the experiment by optimizing the laser pulse iteratively. Without knowledge of the (chirped) input pulses, the experimental signal (second harmonic light=SHG) is maximized by the algorithm, thus re- sulting in fully compressed pulses. This method only makes use of the experiment's response (SHG signal) on the formed pulses. No other parameters need to be considered. This ap- proach leads to many experimental applications in all fields of optics and ultrafast spectroscopy where particularly shaped pulses are advantageous.

Wave-front correction and production of Zernike modes with a liquid-crystal spatial light modulator.

Abstract: I describe a nematic liquid-crystal spatial light modulator that can be used as a high-precision wave-front control device. I present results showing the open-loop correction of wave-front aberrations and demonstrate wave-front shaping by the production and quantification of the first 15 significant Zernike terms.

Modulation coding for pixel-matched holographic data storage.

Abstract: We describe a digital holographic storage system for the study of noise sources and the evaluation of modulation and error-correction codes. A precision zoom lens and Fourier transform optics provide pixel-to-pixel matching between any input spatial light modulator and output CCD array over magnifications from 0.8 to 3. Holograms are angle multiplexed in LiNbO3:Fe by use of the 90° geometry, and reconstructions are detected with a 60-frame/s CCD camera. Modulation codes developed on this platform permit image transmission down to signal levels of ∼2000 photons per on camera pixel, at raw bit-error rates (BER’s) of better than 10-5. Using an 8–12–pixel modulation code, we have stored and retrieved 1200 holograms (each with 45,600 user bits) without error, for a raw BER of <2×10-8.

Confocal spectroscopy system and method

Abstract: A confocal spectral imaging system comprises a light source, a light modulator forming an illumination aperture and directing an illumination pattern to conjugate object locations, and analyzing means with a detection aperture, dispersive elements and a detector, wherein the illumination and detection apertures are in conjugate optical planes, and the light modulator consist of an array of light modulator elements, a group of which being arranged according to the illumination pattern and forming the illumination aperture, and are controlled such that the illumination pattern is directed to time-dependent changing conjugate locations of the object A programmable light source comprises a white light source, dispersion means and a spatial light modulator with an array of individually time-dependent controllable modulator elements being illuminated with the dispersed light and providing a position selective transmittivity or reflectivity, so that a light with a predetermined wavelength distribution passes the light modulator

Observer tracking directional display

Abstract: An observer tracking directional display comprises a spatial light modulator associated with a movable parallax optic. An observer tracker determines the position of an observer and controls the position of the optic by way of an electromechanical transducer and a mechanical transmission. The mechanical tracking arrangement has a plurality of stationary positions for the parallax optic relative to the spatial light modulator (SLM) and steps between these positions so as to optimize the viewing windows for the current position of the observer.

Profilometry using temporal phase unwrapping and a spatial light modulator based fringe projector

Abstract: A fringe projector based on a low-cost spatial light modulator has been used to measure the shapes of discontinuous objects. By changing the fringe phase and the fringe pitch, a sequence of wrapped phase maps can be acquired at different sensitivities. This sequence can then be converted to a surface profile by the recently proposed method of temporal unwrapping rather than by a conventional spatial unwrapping approach. The main advantages are that the method is simple and ro- bust, and that objects with surface discontinuities are profiled as easily and accurately as smooth ones. The absolute distance from the camera to an object is measured at each pixel independently of the other pixels in the image. In addition to accurate measurement of surface shape, one possible application may therefore be as a 3-D robot vision system. A simple calibration procedure is described which avoids the need for ac- curate positioning of the camera and projector and which takes account of instrumental artifacts. A measurement accuracy better than 1/1000 of the field of view has been achieved. A number of practical applications of the technique are illustrated. © 1997 Society of Photo-Optical Instrumentation En- gineers.

Spatial light modulator, directional display and directional light source

Abstract: A spatial light modulator has a modulating region which is capable of operating in two modes in the first clear mode, the region is continuously and substantially uniformly transmissive. In a second or barrier mode, the region can be switched to form parallax barrier comprising slits which are separated by continuous opaque regions. Such A modulator may be used in association with an image liquid crystal display to provide an autostereoscopic 3D display having a 3D mode which may track movement of an observer and a 2D mode in which full resolution of the LCD is used.

Confocal pattern period in multiple-aperture confocal imaging systems with coherent illumination

Abstract: We have built a programmable multiple-aperture confocal imaging system that uses a spatial light modulator (a Texas Instruments digital micromirror device). Excellent axial resolution and confocal imaging quality have been experimentally demonstrated with this system, even when the distance between adjacent on pixels is four times the size of the pixel aperture. By contrast, typical pinhole-based systems (e.g., a Nipkow disk) employ an adjacent aperture distance-to-size ratio of 10×. We have achieved improvement over such systems by 6.25× in both light-utilization efficiency and confocal image rate without adding more components and extra processing time.

Use of liquid-crystal adaptive-optics to alter the refractive state of the eye.

Abstract: We evaluated the potential of wavefront shaping with liquid-crystals for modulating the eye's refractive state. A spatial light modulator with 127 liquid crystals cells was imaged in the entrance pupil of the eye and programmed to induce prismatic, spherical, and astigmatic refractive changes. Psychophysical evaluation of these optical effects was in agreement with expectations for prisms up to approximately 0.08 D and for lenses up to approximately 1.5 D. These maximum dioptric values represent wavefront retardation of about 3 to 4 wavelengths of 584 nm light across a 3-mm diameter pupil. Optical aliasing of high-power prisms was traced to spatial undersampling of the wavefront retardation function by the discrete array of liquid crystal cells. Undersampling may also be the factor which limits the useful dioptric range of the technique.

Selective image extraction by synthesis of the coherence function using two-dimensional optical lock-in amplifier with microchannel spatial light modulator

Abstract: A novel optical information processing system by synthesis of the coherence function is built up to extract a two dimensional image from a three-dimensional object at a tenable depth with neither mechanical scanning nor digital calculation. In this system, a two-dimensional optical lock-in amplifier with the microchannel spatial light modulator is developed to detect selectively the coherence component, so that the limitation to the depth resolution introduced by the holographic detection which was used in our previous systems is overcome. Selective image extraction Is demonstrated successfully.

High efficiency projection displays having thin film polarizing beam-splitters

Abstract: A projection display system includes a thin film polarizing beam splitter/combiner has first and second light transmissive substrates in the form of prisms and a plurality of thin film layers disposed between the prisms. The thin film layers and have predetermined thicknesses and refractive indices which allow unpolarized incident light to be separated into s-polarized and p-polarized light beams. Both frustrated total internal reflection and thin film interference are simultaneously employed to allow s-polarized light to be transmitted and p-polarized light to be reflected over a wide range of wavelengths and angles of incidence. The device further includes two spatial light modulators for encoding an image to be projected. By providing a different signal to each spatial light modulator, a three-dimensional display results.

Eye detection system for providing eye gaze tracking

Abstract: An eye detection system comprises a source, such as an infrared laser diodes for emitting a divergent beam of infrared radiation. A spatial light modulator is controlled so as to act as a deflector for scanning the beam. A detector detects radiation which is retro-reflected by the eye back along the path of the scanning beam. The deflection angle of the SLM and, for a position sensitive detector, the location of the center of illumination on the detector can be used to determine the angle to the center of the pupil of the eye. By subsequently detecting the angle to the glints corresponding to other sources and, the gaze position of the eye on a screen can be determined.

Light source for projection display

Abstract: A compact and energy efficient projection display can be made by starting with relatively pure red, green, and blue light sources. The output beams of the colored light sources are received by at least one spatial light modulator. The modulated output beams are collimated and combined. A projection lens receives the collimated and combined output beams and directs them towards a projection screen. All of the above may be contained in a housing to provide a compact and lightweight projection display.

LCD spatial light modulator as electronic parallax barrier

Abstract: A spatial light modulator (2) has a modulating region which is capable of operating in two modes. In the first clear mode, the region is continuously and substantially uniformly transmissive. In a second or barrier mode, the region can be switched to form a parallax barrier comprising slits (4) which are separated by continuous opaque regions. Such a modulator may be used in association with an image liquid crystal display (1) to provide an autostereoscopic 3D display having a 3D mode which may track movement of an observer and a 2D mode in which full resolution of the LCD (1) is used.

Directional display and method of making a mask for a directional display

Abstract: A directional display comprises a display arrangement such as a spatial light modulator and a rear parallax barrier illuminated by a suitable backlight. The spatial light modulator and the parallax barrier cooperate to produce Fresnel diffraction which results in spatially non-uniform brightness across viewing windows of the display. Also, where the spatial light modulator has pixels of non-constant vertical aperture, further variations in the intensity profile at the windows occurs. In order to compensate for this, a mask is provided, for instance between the parallax barrier and the backlight. The mask cooperates with the parallax barrier to produce an intensity pattern having variations which are the inverse of the variations in intensity pattern produced by the parallax barrier and the spatial light modulator. The variations are superimposed and substantially cancel each other out so as to result in viewing windows which have substantially uniform light intensities.

Color display system with spatial light modulator(s) having color-to-color variations in data sequencing

Abstract: Methods of reducing artifacts in SLM-based display systems (10, 20), whose images are based on data displayed by bit-weight for pulse-width modulated intensity levels. A first method is suitable for systems (20) that use multiple SLMs (14) to concurrently display images of different colors, which are combined at the image plane. The data for each color are staggered in time (FIG. 4). A second method is suitable for either multiple SLM systems (20) or for systems (10) that use a single SLM (14) and a color wheel (17) to display differently colored images sequentially. The data for each color is arranged in a different data sequence (FIG. 5). In either method, the intensity transitions do not occur at the same time.

Directional display for a directional display having an angular intensity profile compensator

Abstract: A directional display comprises a display arrangement such as a spatial light modulator and a rear parallax barrier illuminated by a suitable backlight. The spatial light modulator and the parallax barrier cooperate to produce Fresnel diffraction which results in spatially non-uniform brightness across viewing windows of the display. Also, where the spatial light modulator has pixels of non-constant vertical aperture, further variations in the intensity profile at the windows occurs. In order to compensate for this, a mask is provided, for instance between the parallax barrier and the backlight. The mask cooperates with the parallax barrier to produce an intensity pattern having variations which are the inverse of the variations in intensity pattern produced by the parallax barrier and the spatial light modulator. The variations are superimposed and substantially cancel each other out so as to result in viewing windows which have substantially uniform light intensities.

Complex modulation characterization of liquid crystal devices by interferometric data correlation

Abstract: A new phase modulation spatial light modulator (SLM) characterization procedure is presented, based on the analysis of the interference fringes of a Mach - Zender interferometer arrangement, by means of correlation and Fourier transform methods. This, accompanied by an amplitude calibration technique that makes use of the same experimental set-up, gives a general measurement procedure for SLM full complex characterization. As an experimental application, two different operation curves of an Epson LCTV are determined, in order to use these configurations for an optical pattern recognition procedure: a phase-only high-efficient joint transform correlator.

Multi-colour reflector device and display

Abstract: A reflector device has a stack of three reflective layers 100,102,108 each of which selectively reflects different a part of the spectrum of white light 106 to a different region. The respective regions may or may not overlap each other. The layers 100,102,108 may be reflective cholesteric liquid crystal materials, dichroic mirrors or reflective multi-layer interference structures. The layers 100,102,108 may be, planar, curved or formed from several curved surfaces in series (fig.11) and may be mutually inclined. The third layer 108 may be combined with either a black absorber layer (110, fig.5) or a panchromatic layer (112, fig.6). The incoming light may be focused by a plano-convex lens array (116,fig.13). The reflector device may be used in a display in conjunction with a spatial light modulator 104, such as a liquid crystal device, having pixels 104a-c, selectively illuminated by light from the regions.

LCD with spacers having particular characteristics including compression stress

Abstract: The present invention provides a liquid crystal display element substrate having spacers fixed in non-display regions on the liquid crystal display element substrate, where the load compression displacement of these spacers in terms of a compression stress of 0.5 to 0.6 GPa is from 0.001 to 1 μm/mN. Further, it provides a liquid crystal display device which is characterized in that, in a liquid crystal display device where a liquid crystal layer is held between two liquid crystal display element substrates, at least one of these liquid crystal display element substrates is an aforesaid liquid crystal display element substrate. As well as realizing a sufficient cell gap the present invention has the effect that, by maintaining a uniform cell gap within the screen, the problems of a lowering in the display quality due to change in the cell gap and the generation of bubbles at the time of low temperature are resolved. The liquid crystal display element substrate of the present invention and the liquid crystal display device which employs it may be used as the display screens of personal computers, word processors, engineering work stations, navigation systems, liquid crystal televisions, videos and the like, and they are also suitable for use in liquid crystal projection, etc. Further, in the fields of optical communication and optical data processing, they are suitable for use as a spatial light modulator employing liquid crystals.

Spatial light modulator based on a deformed-helix ferroelectric liquid crystal and a thin a-Si:H amorphous photoconductor.

Abstract: We have developed an optically addressed spatial light modulator (OASLM) based on a deformed-helix ferroelectric liquid crystal (DHFLC) and a thin (0.5-µm) amorphous a-Si:H photoconductor. The thin photoconductor permits operation in the transmission mode of a read beam. The OASLM, operated in the integrated mode, exhibits gray levels, a high contrast (>1:40), and a high spatial resolution (exceeding 57 lines/mm). This is a significant improvement over previously reported OASLM’s based on DHFLC’s.

Optical system for illuminating a spatial light modulator

Abstract: A novel optical system operative to transfer, with high efficiency, optical power from a line source, such as a LDB, built from a plurality of individual light sources with different angular distribution in two orthogonal axis into a rectangular area with a particular aspect ratio and two different numerical apertures. The near field pattern of a LDB is imaged onto the plane of an SLM. The system utilizes light generated from an LDB having a plurality of individual light sources to illuminate a microlens array. The microlens array, consisting of a plurality of microlenses, functions to collimate the light from the LDB in the slow axis. An optical element adjacent the microlens array refracts the light in the fast axis. In the slow axis, the light from the microlens array is incident upon an optical element which focuses the light onto the SLM plane such that the light from each point light source illuminates the entire active pixel area of the SLM. An additional optical element focuses the light in the fast axis to generate the required spot image. The optical system of the present invention utilizes natural aberrations and/or artificial aberrations to decrease the sensitivity of the optical system to the smile phenomena exhibited by most laser diode bars.

Optical system for miniature personal displays using reflective light valves

Abstract: An illumination system and display are disclosed that include a light for providing light, a polarizing beam splitter (PBS) having a first surface that receives the light from the backlight. The PBS passes a first polarization of the received light to a curved mirror located at a second PBS face, which second PBS face is opposite the first PBS face. The curvature of the mirror provides the optical power necessary for proper imaging, while limiting the reflecting area of the mirror provides an aperture stop that determines the numerical aperture of the optical system. The display also includes a quarter wave plate and a spatial light modulator (SLM). The quarter wave plate is located between the PBS and mirror and changes the first polarization of light, directed from the PBS to the mirror, to a second polarization which is reflected from the mirror back to the PBS. The SLM receives this second polarization of light after reflection thereof by the PBS, and selectively rotates the second polarization of light to form an image forming light having the first polarization, which is reflected back to the PBS. Through an exit face, the PBS provides the rotated image forming light to a viewer. Between the viewer and the PBS exit surface, an imaging lens system is provided that includes at least one folding mirror.

Optically produced true-time delays for phased antenna arrays

Abstract: A device is described for generating true-time delays optically for microwave signals used in beam steering and beam shaping in phased-array antennas. The device can be adapted to provide delays from picoseconds to nanoseconds. A single, compact unit should provide parallel delays for more than 64 independent antenna elements with a greater than 6-bit resolution. The time delays are produced by multiple reflections in a mirror configuration with continuous refocusing. A single spatial light modulator selects independent optical path lengths for each of the parallel antenna elements. Amplitude control for beam shaping can be integrated into the device. The unit can be made rugged for harsh environments by use of solid-block construction. The operation of the true-time delay device is described, along with the overall system configuration. Preliminary experimental data are given.

Display system with spatial light modulator with decompression of input image signal

Abstract: An all-digital television system (10), especially designed for receiving and interpreting advanced television (ATV) signals. The system (10) uses a multiprocessor unit (12) for performing decompression and a serial video processor (13) for scaling. A picture quality unit (14) performs colorspace conversion and de-gamma. A bit-plane buffer formats and stores bit-plane data. The display devices are three spatial light modulators (SLMs) (16), each of which generate a red, green, or blue image. The images are combined by an optics unit (17) for full-color full-motion displays.

Combined spatial light modulator and phase mask for holographic storage system

Abstract: A light modulator for both intensity and phase modulating coherent light on a pixel-by-pixel basis includes a modulating material responsive to an electric potential for modulating the intensity of coherent light passing through the modulating material, and electrodes for applying an electric potential across the modulating material on a pixel-by-pixel basis. The coherent light associated with a first set of pixels has a different optical path length through the modulating material than does the coherent light associated with a second set of pixels. The modulating material is a liquid crystal material. The electrodes include a set of first reflective pixel electrodes embedded in the liquid crystal material, the first reflective pixel electrodes having a first thickness, and a set of second reflective pixel electrodes embedded in the liquid crystal material, the second reflective pixel electrodes having a second thickness. The coherent light associated with the first set of pixels is reflected by the first reflective pixel electrodes, and the coherent light associated with the second set of pixels is reflected by the second reflective pixel electrodes. The reflective surfaces of the first reflective pixel electrodes are embedded in the liquid crystal material a different amount than are the reflective surfaces of the second reflective pixels. In particular, the first reflective pixel electrodes are a different thickness than the second reflective pixel electrodes.

Address generator,display and spatial light modulator

Abstract: An address generator for a display or spatial light modulator, comprising a first shift register having a plurality of cascade-connected stages for controlling respective first address electrodes of the display or spatial light modulator. The stages of the first shift register include a first reconfigurable shift register stage which is selectively operable in an alternate mode, in which the output of the first reconfigurable shift register stage follows the output of a preceding stage.

Optical implementation of the stream cipher based on the irreversible cellular automata algorithm

Abstract: A hybrid optical scheme for efficient hardware implementation of the one-dimensional, three-neighborhood binary cellular automata rule ai′=ai-1 XOR ai OR ai+1–based stream cipher is proposed. The system makes full use of the parallel, space-invariant, cascadable, and modular structure of the algorithm and is simple, robust, and compact. The number of cellular automata arrays can be as large as the number of pixels on the spatial light modulator, which results in an increase in speed (number of bits operated in parallel) and security (key length). The system can be made fully optical with the use of an optically addressable spatial light modulator for the input plane and for the nonlinear threshold element.

Complex phase/amplitude spatial light modulator advances and use in a multispectral optical correlator

Abstract: Optical processing systems often require compact high frame rate spatial light modulators (SLMs), usually with application specific modulation requirements in the complex plane. In this paper we discuss several advances at Boulder Nonlinear Systems toward this goal, including our liquid crystal (LC) on VLSI 128 X 128 analog SLM, and our multispectral hybrid incoherent to coherent converter.We also present the analysis of optical modulation possibilities when utilizing zero twist nematic and planar aligned chiral smectic LC on a reflective backplane. Finally we present the design of a multispectral optical correlator for machine vision applications such as food inspection, security, or manufacturing inspection.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.