Abstract: A method and system of recording successive holograms in a recording medium including a reflective substrate layer, a polarization shifting layer, and a photorecording medium layer is presented. A reference beam and an object beam are propagated at a first direction to a first area of the photorecording medium layer, where the reference beam and object beam have a same first polarization and interfere to produce a first interference grating. The reference beam and object beam are reflected with the reflective substrate layer to be incident the photorecording medium at a second direction, where the reference beam polarization and object beam polarization are altered with the polarization shifting layer to have a same second polarization. The reflected reference beam and object beam interfere to produce second interference grating, with the first polarization and second polarization being different.

Abstract: A method for the generation of volume spatially-resolved holographic data storage within a photosensitive glass sample that incurs changes of optical properties in response to two-photon absorption, the method including directing non-ultraviolet pulsed laser radiation at the photosensitive glass sample to induce changes of optical properties in the glass sample, splitting of the pulsed laser radiation, prior to reaching the glass sample, into an object beam having a direct optical path of a first predetermined length and a reference beam, changing the path of the reference beam to have an indirect optical path of a second pre-determined length, focusing each of the object beam and the reference beam along the respective optical paths, to intersect at a focal volume of the glass sample, and therein to cause the two-photon absorption, providing a variable time delay in the direct path of the object beam so that it reaches the chosen region within the focal volume of glass at the same time as the reference beam,

Abstract: Holography in which an array of overlapping holograms is recorded or reconstructed in a recording medium, holograms being produced by interference of a reference beam and a signal beam, in which the reference beam is a phase beam which consists essentially of a multitude of rays of varying angle of incidence and non-uniform phase, in which the process comprises changing the orientation of the phase beam for recording or reconstructing different holograms, wherein phase beam orientation is changed relative to the medium while maintaining the medium stationary in order to enable recording or reconstruction of individual holograms at a given location of the medium.

Abstract: A method of correcting errors arising from interpixel cross talk in the detection of a reconstructed holographic data image includes determining any misregistration between the pixels and the bit images. The measured output signals are then corrected to compensate for signal strength lost to or gained by nearby pixels through interference effects resulting from the misregistration, thereby producing a calculated data image that is substantially corrected for interpixel crosstalk. The relevant algorithms are provided and experimental verification is presented.

Abstract: There is provided an apparatus for storing/restoring holographic data and a method for coding/decoding holographic data. In a recording mode, the apparatus divides input data into a plurality of groups, each of which includes two binary digits; and encodes each of the groups into a 2×2 data block wherein a first row of the 2×2 data block has the two binary digits and a second row thereof has another binary digits generated by applying a binary differential calculation on the first row. In a restoring mode, the apparatus divides a signal restored from a storage media into a plurality of 2×2 data blocks; and decodes each of the 2×2 data blocks into two binary digits by comparing values of a first row of the 2×2 data block with those of a second row thereof. In this way, phenomena of isolated “on” or “off” can be avoided.

Abstract: The invention relates to a skip-sorted spatial multiplexing holographic storage technique that addresses the problems of cross-talk, image distortions, and physical change of the medium encountered in current recording processes in which photopolymer media are used. The skip-sorted technique involves storing holograms in layers of arrays, such that a substantially uniform background exposure is provided for subsequent layers.

Abstract: An optical data storage system and method comprising a photopolymer medium having generally a polymerizable monomer, an active binder, a first, hologram recording polymerization initiator, and a second, data writing polymerization initiator. The monomer is preferably a cationic ring-opening monomer. The hologram recording polymerization initiator preferably comprises a sensitizer and photoacid generator which initiate a first polymerization in the medium which defines a format hologram. The format hologram recording is carried out via interference of a signal and reference beam, with the sensitizer being specific for the wavelength(s) of the signal and reference beams. The hologram recording polymerization is only partial and does not consume all of the monomer present in the photopolymer medium.

Abstract: A digital electronic camera includes a holographic medium, an imaging array disposed at a focal plane for converting optical information to digital information; and an optical system configured to store the digital information onto the holographic medium. An optical system for retrieving images stored in the medium may be provided inside the camera or as a separate appliance.

Abstract: The invention involves a holographic system containing a photopolymer-type storage medium located in the system's optical path, where the medium is rotated around a first axis such that the surface of the medium is in a non-orthogonal relationship with the optical path, and a spatial light modulator also located in the optical path, where the modulator is rotated around a second axis that is substantially orthogonal to the first axis, and wherein the surface of the modulator is in a non-orthogonal relationship with the optical path. This arrangement compensates for at least a portion of aberration introduced by the photopolymer media, thereby allowing presentation of a flatter, more focused, and less distorted image at the sensor.

Abstract: A holographic storage medium, a method of manufacturing the holographic storage medium and a holographic storage device incorporating the storage medium. In one embodiment, the holographic storage medium includes: (1) first and second spaced-apart substrates, the first substrate being plastic and (2) a photopolymer core located between said first and second substrates and having a coefficient of thermal expansion such that said first and second substrates and said photopolymer core cooperate to respond substantially isotropically to a change in temperature.

Abstract: Scanning sensor scans on a circumference and simultaneously a radiation wave is received by scanning sensor to generate received signal Sm(f). A radiation wave is received by a fixed sensor at a position not changed with respect to the center of a circle with the circumference to generate received signal Sr(f). The received signal Sm(f) is made to interfere with the received signal Sr(f) to acquire an interference signal. The interference signal is detected to obtain measured data E(r,&phgr;) at each point on the circumference. Also, evaluation data V(&phgr;′) is calculated to estimate a direction of the radiation wave based on measured data E(r,&phgr;) at each point. A multi-dimensional hologram data processing apparatus consists of N-dimensional data array memory, N-dimensional flag array memory, N-dimensional array address generating unit, and digital signal processing unit.

Abstract: A reference beam telescope, which is also referred to as a relay imaging system for a reference beam, using reflection optics is disclosed. The relay imaging system according to the present invention comprises at least one concave mirror and one convex mirror. A reference beam is reflected at least twice by the concave mirror and once by the convex mirror. The output reference beam is collimated if the input reference beam is collimated. This relay imaging system is used in a holographic storage system to deliver the reference beam to the holographic storage medium. In particular, this system can be used for angular multiplexing in a holographic storage system.

Abstract: Digital signal sequences to be recorded in predetermined unitary recording areas are transformed into blocks, a plurality of bit data carrying all digit levels to be read and determined upon reproduction are included in the resultant blocks, and sequences of the data blocks are recorded in the recording medium in the unitary recording areas. Upon reproduction, the blocks of the read signals obtained from a recording medium are recognized, a threshold value is determined for each block on the basis of the values of read signals corresponding to bit data carrying all digit levels to be read and determined, and each digit level of bit data in the read signal are read and determined on the basis of the threshold values.

Abstract: Compositions of bacteriorhodopsin variants with increased memory time and their use for reversible optical information recording are disclosed. The compositions are characterized in that the configuration of the retinal of the photoproduct is different from the configuration of the retinal of the initial state and other than 13-cis; the pH value of the composition lies between 3 and 11; the water content of the composition lies between 1 and 30% by weight with respect to the total weight of the composition; and additives for modulating the proton mobility are present in a concentration between 1 and 80% by weight of the mass of purple membrane composition used, and if required matrix materials in a concentration of up to 10% by weight with respect to the total weight of the composition are present. These compositions may be used in reversible information recording systems.

Abstract: A phase-shift digital holographic apparatus shifts the phase of a reference wave by a phase shifting means, produces holographic image data by a holographic image pickup means having an image forming surface on which an object wave and the reference wave fall simultaneously, processes a plurality of holographic image data produced by the object wave and a plurality of reference waves of different phases determined by shifting the phase of the reference wave by the phase shifting means by an object wave calculating means to calculate phase data on the phase of the object wave and amplitude data on the amplitude of the object wave, and constitutes object wave data of the phase data on the phase of the object wave and the amplitude data on the amplitude of the object wave calculated by the object wave calculating means by a reproduced image calculating means and subjects the object wave data to a predetermined transformation process to calculate a reproduced image.

Abstract: This invention relates to marking the genuine CD in an easily detectable way while difficult to counterfeit. The improved CD has within its layers a second structured surface parallel to the flat surfaces of the CD. The second structured surface acts as a diffractive security device, that is to be read out from the same side of the CD, the verso side, as the data structure. In one example, the second structured surface is defined by a step of the refractive index or by a transparent reflective layer. Despite the diffractive rainbow colors observed on the verso side of the CD, the structure of the security device can be read out visually and/or with a CD-reader, even by a simple hand-held reader, and verified without the need of a bulky apparatus. A CD-reader prevents the playing of embodiments of the improved CDs.

Abstract: A method for improving the quality of holographic images by reducing local noise in a holographic memory system is disclosed. The method is characterized by: storing a white reference image and a black reference image in the memory system, storing a series of data images in the memory system, applying a simple model based on a point-to-point of linear interpolation to the series of data images, the white reference image and the black reference image to provide a series of corrected data images having reduced noise.

Abstract: A method and a compact apparatus to read shift-multiplexed holograms on a storage medium without the need for any lenses, and without the need for moving the storage medium. The shift-multiplexed holograms have centers at different locations. The apparatus can generate an array of diverging spherical waves of reference beams, each for illuminating one of the holograms. Each hologram is read as an image on a detector array by illuminating that hologram with a corresponding diverging spherical wave of reference beam. Different holograms can be read by illuminating the medium with a different diverging spherical reference beam. The diverging beams can be from an array of sources, or can be from switching one source.

Abstract: Digital signal sequences to be recorded in predetermined unitary recording areas are transformed into blocks, a plurality of bit data carrying all digit levels to be read and determined upon reproduction are included in the resultant blocks, and sequences of the data blocks are recorded in the recording medium in the unitary recording areas. Upon reproduction, the blocks of the read signals obtained from a recording medium are recognized, a threshold value is determined for each block on the basis of the values of read signals corresponding to bit data carrying all digit levels to be read and determined, and each digit level of bit data in the read signal are read and determined on the basis of the threshold values.

Abstract: A system and method for controlling the selectivity function in a holographic memory system that permits more rapid location and retrieval of holographically stored data. The system and method direct a reference beam through a filter such as, for example, an aperture, to bandwidth limit the beam before the beam illuminates a holographic optical element having stored therein a hologram of a reference beam.

Abstract: Holographic memory including a beam source for emitting a beam, a beam splitter for splitting the beam into a reference beam and an object beam, a hologram memory unit for recording information designated to a cell when the reference beam and the object beam are incident thereto at a time, and reproducing the information recorded before when only the reference beam is incident thereto, a first optical path changing unit for directing the reference beam to be incident to the hologram memory unit at an arbitrary angle for recording and reproduction of the information, including a first deflector for deflecting the reference beam to an arbitrary angle, a second deflector for re-deflecting the reference beam deflected at the first deflector in a vertical direction, and a telescope having at least one composite HOE(Holographic Optical Element) for directing the reference beam re-deflected at the second deflector to be incident to the hologram memory unit, and a second optical path changing unit for adjusting an op

Abstract: A non-volatile holographic recording method and system based on a doubly-doped photorefractive material. One embodiment of the holographic material is doped to have first and second types of dopants that are operable to produce charge carriers to a common band in response to radiation of a specified wavelengths. Charge carriers in the common band can migrate to a different spatial location. The dopants are also capable of recombining with charge carriers in the common band. The first type of dopants have a first dopant energy level below the band by a first energy gap greater than a second energy gap of a second dopant energy level of the second type of dopants below the common band. The first and second dopant energy levels are separated from each other so that their absorption bands to the common band are substantially separated. In addition, the first and second energy gaps should be much greater than the thermal energy k.sub.

Abstract: A holographic memory system which utilizes the Talbot Effect for the lensless, near-field propagation of repeating image planes of periodic structures. Periodic phase structures at one plane in a holographic memory system are mapped to the input amplitude data plane in the holographic memory system. In a preferred embodiment, coherent light is passed through a lenslet array and propagated via the Talbot Effect to self-image coincident on a spatial light modulator that provides the holographic memory system with input data. The lenslet array is located relative to the spatial light modulator such that the desirable phase image structure is self-imaged in its Fresnel region onto the input amplitude data structure.

Abstract: A holographic storage and retrieval system for use in co-propagating or counter-propagating geometries having a common optical relay for guiding a signal beam and a reference beam along a common optical axis to a holographic medium to write a hologram therein. The optical relay has an object region imaging quality such that at least 65% and preferably at least 80% of the nominal luminous energy from object pixels is encompassed or "ensquared" by the corresponding image pixels. Additionally, the optical relay has a high total numerical aperture (N.A.) of about 0.83, a pixel N.A. of approximately 0.04 for the signal beam. The system of the invention can be used with holographic storage media in the form of disks, tapes or bulk holographic crystals.

Abstract: The holographic storage and retrieval system according to the present invention comprises one convex reflector and one concave reflector having the same optical axis. The reflective surfaces of the two reflectors are opposite each other. The concave reflector is normally larger than the convex reflector. The holographic storage medium is positioned at the focal surface of the concave reflector. The spherical reflector system according to the present invention has nearly ideal performance off-axis: high bandwidth, low aberration imaging is permitted at a number of radial and axial locations. Thus, multiple SLM/CCD pairs can be placed off-axis to access the same storage medium and implement multiple interconnects.

Abstract: An architecture for holographic data storage and processing integrates multifunctional silicon-based optoelectronic devices, rewritable holographic material, optical devices and other electro-optical elements in compact and high-performance systems. A dynamic hologram refresher based on optoelectronic integrated circuits has a smart pixel structure including an electrically addressed SLM to write a new data page, a thresholding detector array for readout, and a memory to latch the data from the detector to the modulator in each pixel. In particular, conjugate reconstruction is used in combination with the dynamic hologram refresher to retrieve data from volume multiplexed holograms in the rewritable holographic material.

Abstract: A method for holographic data storage comprises the step of formatting a page with calibration marks as well as data patterns representing data. The page is then stored in a holographic storage medium. A method for holographic data retrieval comprises the step of detecting locations of the calibration marks. A mathematical function is fitted to the locations, and the function is used to compensate for distortion in the detected image of the page. In the preferred embodiment, the calibration marks are also used to generate an inverse point spread function that is used to digitally sharpen the detected image of the page. In the preferred embodiment, the data patterns are dispersed throughout the page by an interleaving algorithm, so that subsequent data patterns are not stored consecutively in the page.

Abstract: Systems and methods for steering a complex, spatially-modulated incident beam of coherent light to gain access to data locations in a holographic memory cell (HMC). One of the systems includes: (1) a reflective element, locatable proximate a first focal plane of the incident beam, (2) a rotational steering mechanism, coupled to the reflective element, that orients the reflective element according to a desired rotational angle to steer the incident beam in a desired direction and (3) a refractive element that refracts the beam reflected from the reflective element to create a second focal plane for the beam, the HMC locatable proximate the second focal plane to receive the beam at a location thereon that is a function of the desired direction.

Abstract: A method and a compact apparatus to read shift-multiplexed holograms on a storage medium without the need for any lenses, and without the need for moving the storage medium. The shift-multiplexed holograms have centers at different locations. The apparatus can generate an array of diverging spherical waves of reference beams, each for illuminating one of the holograms. Each hologram is read as an image on a detector array by illuminating that hologram with a corresponding diverging spherical wave of reference beam. Different holograms can be read by illuminating the medium with a different diverging spherical reference beam. The diverging beams can be from an array of sources, or can be from switching one source.

Abstract: The data encoder (e.g. an amplitude spatial light modulator, ASLM) in a volume holographic storage system is rotated by 45.degree. relative to the normal to the plane of the reference and signal beams, such that the near-Fourier transform pattern of the encoder at the medium has an X-shape. The encoder rotation allows tight packing of spatial multiplexing subvolumes in a rectangular array, and provides for uniform spatial frequency filtering in a perpendicular geometry.

Abstract: Embodiments of the invention include an off-axis amplitude and phase encoding optical system, apparatus and method of storage in which a holographic optical element (HOE) is used advantageously to reconstruct optical elements typically used to phaseencode an object beam emanating from a spatial light modulator (SLM). The optical system includes a spatial light modulator (SLM) such as a digital micro-mirror device (DMD), a data storage device such as a holographic memory cell (HMC), and the holographic optical element (HOE) for duplicating the phase-encoding functions typically performed on an object beam emanating from the SLM prior to alignment with the holographic memory cell (HMC). Conventionally, a phase mask along with one or more optical elements comprising a four-F lens system typically are needed to phase encode the amplitude-encoded light pattern that propagates from the SLM.

Abstract: A method and an apparatus for increasing detection signal-to-noise ratio, while reading out a hologram from a holographic storage medium, are disclosed. The hologram is written by interfering a write reference beam with an object beam. The method comprises the steps of (1) effecting multiple sequential hologram-read operations using multiple read reference beams separated from each other by a separation angle; (2) shifting the detector array contents in between hologram-read operations such that the data signal patterns incident on the detector array are approximately identical but the incident scatter noise patterns are uncorrelated; and (3) integrating the multiple hologram readouts electronically on the detector array. The apparatus comprises a laser source, a beamsteerer, a detector array and a shifting device.

Abstract: The present invention is a method for optical data storage which compensates for deterministic variations. The method comprises writing a two-dimensional image comprising a plurality of pixels into a recording medium while varying the exposure of individual ON pixels during the recording of the image to expose the weaker pixels more than brighter pixels.

Abstract: A holographic data storage apparatus having no readout lens. The apparatus has a spatial light modulator (SLM), a focusing element such as a lens, a holographic data storage material and a spatial light detector such as a CCD. The lens is located between the SLM and CCD such that the SLM is imaged onto the CCD (i.e. the positions of the SLM, lens, and CCD satisfy the lens equation). The holographic storage material is located between the lens and CCD. Preferably, the storage material is located centered upon a Fourier plane of the lens. In this case, the apparatus also has a phase mask located adjacent to the SLM. Alternatively, the storage material is located a distance away from the Fourier plane or is not centered on the Fourier plane. In yet another embodiment, the holographic storage material is located in contact with the CCD.

Abstract: The present invention is a holographic reconstruction device for reconstructing successive holograms previously recorded by a recording reference beam in a recording medium, each previously recorded successive hologram being spaced apart a recording displacement. The recording reference beam has a recording wavelength in the range where the recording medium is photosensitive and a recording propagation angle. The device comprises a reconstruction mechanism having a reconstruction reference beam with a reconstruction wavelength in the range where the recording medium is relatively photo-insensitive and a reconstruction propagation angle. The reconstruction reference beam is provided onto the recording medium. Also, a succession of relative displacements in the recording medium is produced and each of the displacements are equal to the distance of the recording displacements with which the holograms were previously recorded.

Abstract: Ferroelectric materials are disclosed as reversible holographic recording media (25) for use in two-photon recording systems. The ferroelectric materials disclosed herein provide long-lived electronic states intermediate the ferroelectric material's valence and conduction bands. These intermediate states have a sufficiently long life (on the order of 1 to 100 milliseconds) that low-power continuous wave ("cw") lasers (1) can be used to record interference patterns on them. Thus, two-photon holographic recording systems are also disclosed which do not require high-power, short pulse length, mode-locked or Q-switched lasers. The disclosed two-photon holographic recording systems provide for absorption of a first photon which excites electrons of holographic recording media to an intermediate state. Thereafter, upon absorption of a second photon, the electrons are promoted to the media's conduction band where they are arranged according to the interference pattern provided by the recording system.

Abstract: Fast speed hologram memory device, including a first holographic optical element array for directing a reference beam to a desired hologram memory cell directly and a second holographic optical element array for directing an objective beam to a desired hologram memory cell directly, both having a plurality of holographic optical elements one to one matched to a plurality of the hologram memory cells.

Abstract: Selection of individual holograms during read-out of a multiplexed array depends upon varying relative position of the recording medium in the direction orthogonal to the medium surface.

Abstract: Feedback is employed in a holographic memory system to facilitate rapid access to information in a stored data page. This feedback technique provides compensation for thermal, optical and/or mechanical variations in the system components that tend to interrupt the projection of a data page image on a sensor array. A page indicator or mark is stored in a holographic storage medium with a page of data such that, during playback, a quality, e.g., intensity, of its projected image is indicative of the quality of the corresponding projected data page image. A corresponding page indicator sensor is employed with the associated sensor array to detect the quality of a projected page indicator image. The projected data page image can then be read by sensor elements of the detector based on the detected quality of the page indicator image. Such a detector can be implemented in an active pixel sensor (APS) array with the page indicator sensor being implemented as a region of the APS array.

Abstract: A method and apparatus of encrypting optical images and storing these images in memory using random phase encoding is presented. The encryption technique uses random phase encoding in both the input plane and the Fourier plane. Each image is encrypted and can be read out by a unique code or a universal code. The image to be encrypted is first multiplied by a random phase function. The Fourier transform of the product of the image and the random phase function is then multiplied by another random phase function in the Fourier domain. Taking the inverse Fourier transform, an encrypted image in the output plane is obtained. Each encrypted image can be stored in optical memory. The encryption process of the present invention can be done optically or electronically with one or two dimensional functions for encryption. Further, the image can be phase encoded (optically or digitally) prior to the encryption process, with a phase reading technique employed to obtain the original decrypted image.

Abstract: Molded block optics system (10) writes and reads data from an optical storage medium and includes first molded optics block (12) for receiving reference beam (60) and original object beam (46) that contains a predetermined data set. First molded optics block (12) includes reflective surfaces (18, 20, 22, and 24) and spatial light modulator (50). Reflective surfaces (18, 20, and 24) include reference beam surfaces (24) and object beam surfaces (18, 20, and 22). Reference beam surfaces (24) direct reference beam (60) to optical storage medium (16) at predetermined location (54). Spatial light modulator (50) modulates object beam (46) and directs modulated object beam (46) to predetermined location (54). Reference beam (60) and object beam (46) form an interference pattern that writes data on optical storage medium (16). First molded optics block (12) also directs reference beam (60) to optical storage medium (16) for generating reconstructed object beam (64).

Abstract: A video image F?k! is identified as a basis image and stored as a basis page S?k! in a holographic storage medium. A subsequent image F?k+n! is stored by recording in the medium a page S?k+n!=F?k+n!-a?k!F?k!, where a?k!.noteq.0 and preferably a?k!=1. The page S?k! is recorded with a reference beam R?k!, while S?k+n! is recorded with a reference beam R?k+n! orthogonal to R?k!. The basis page is reset whenever the average intensity of a page to be stored exceeds a predetermined threshold. An image F'?k! is retrieved by reading basis page S?k! and letting F'?k!=S?k!. Subsequent images F'?k+n! are retrieved as S?k+n!+b?k!S?k!, where b?k!.noteq.0 and preferably b?k!=a?k!=1. The page addition step is performed coherently, i.e. by accessing the medium with a reference wave function R?k+n!+b?k!R?k!.

Abstract: In a method for addressing holograms stored in a plurality of separate storage media, a reference beam is directed to a selected one of the plurality of storage media, the reference beam is then focused so as to obtain a substantially flat wavefront within a reference beam plane of the selected storage medium, and the angle of the reference beam is then varied so as to select a hologram stored therein.

Abstract: Systems and methods for steering an optical path to gain access to data locations in a holographic memory cell (HMC). One of the systems includes: (1) a refractive element that receives a complex, spatially-modulated incident beam of light, (2) first and second reflective elements locatable to receive and reflect the incident beam in a Fresnel region thereof and (3) a reflective element steering mechanism, coupled to the first and second reflective elements, that moves the first and second reflective elements in tandem to steer the incident beam with respect to the HMC thereby to cause the incident beam to illuminate a location on the HMC that is a function of a movement of the first and second reflective elements.

Abstract: Systems and methods for steering a complex, spatially-modulated incident beam of light from a spatial light modulator to gain access to data locations in a holographic memory cell (HMC). One of the systems includes (1) a primary beam steering system that receives the incident beam of light from the spatial light modulator and produces a resulting beam of light, wherein the primary beam steering system traverses the resulting beam of light across a plane of the HMC in increments having a first magnitude and 2) a fine-control translation mechanism, coupled to the spatial light modulator, that translates the spatial light modulator relative to the primary beam steering system to cause the resulting beam of light to traverse the plane of the HMC in increments having a second magnitude smaller than the first magnitude.

Abstract: Feedback is employed in a holographic memory system to facilitate rapid access to information in a stored data page. This feedback technique provides compensation for thermal, optical and/or mechanical variations in the system components that tend to interrupt the projection of a data page image on a sensor array. A page indicator or mark is stored in a holographic storage medium with a page of data such that, during playback, a quality, e.g., intensity, of its projected image is indicative of the quality of the corresponding projected data page image. A corresponding page indicator sensor is employed with the associated sensor array to detect the quality of a projected page indicator image. The projected data page image can then be read by sensor elements of the detector based on the detected quality of the page indicator image. Such a detector can be implemented in an active pixel sensor (APS) array with the page indicator sensor being implemented as a region of the APS array.

Abstract: Systems and methods for steering a complex, spatially-modulated incident beam of coherent light to gain access to data locations in a holographic memory cell (HMC). One of the systems includes: (1) a reflective element, locatable proximate a first focal plane of the incident beam, (2) a rotational steering mechanism, coupled to the reflective element, that orients the reflective element according to a desired rotational angle to steer the incident beam in a desired direction and (3) a refractive element that refracts the beam reflected from the reflective element to create a second focal plane for the beam, the HMC locatable proximate the second focal plane and rotatable about an axis of a plane thereof to receive the beam at a location thereon that is a function of the desired direction and an angular position of the HMC.

Abstract: A system for converting an image into a hologram formed from diffraction gratings includes obtaining image data for each pixel in an image to be converted, putting it into digital form and using the image data to control portions of a laser beam split into a reference beam and at least one object beam. The diffraction gratings are formed by an interference pattern of a reference beam and at least one object beam intersecting on the surface of a photoresist material on a pixel-by-pixel basis. Modulation of at least one object beam and adjustment of the angle at which that beam interferes with the reference beam on the photoresist material is used to reflect image data for each pixel of the image being converted into a hologram consisting of diffraction gratings.

Abstract: Systems and methods for steering an optical path to gain access to data locations in a holographic memory cell (HMC). One of the systems includes: (1) a reflective element, locatable proximate a first focal plane of a complex, spatially-modulated incident beam of light, (2) a polar steering mechanism, coupled to the reflective element, that orients the reflective element according to desired tilt and precession angles to steer the incident beam in a desired direction and (3) a refractive element that refracts the beam reflected from the reflective element to create a second focal plane for the beam, the HMC locatable proximate the second focal plane to receive the beam at a location thereon that is a function of the desired direction.

Abstract: A plurality of holograms are simultaneously angularly and spatially multiplexed within a storage medium by writing the holograms at different locations within the storage medium using reference and object beams directed thereto via cooperating reference beam and object beam scanners, respectively. The simultaneously angular and spatially multiplexed holograms are subsequently read-out by directing a reference beam through a desired location within the storage medium using the reference beam scanner. The reference beam is directed from the storage medium to a phase conjugator which conjugates the phase of the reference beam and directs the phase conjugated reference beam back to the same desired location within the storage medium so as to excite a corresponding conjugate object beam which is then directed onto a detector array.