Abstract: A method for holographic storage data recovery in a holographic storage system is presented. One exemplary method includes detecting a stored image at a detector such that the image is oversampled. A relationship is determined between a location of the detected image and a location of the source image. Pixel information associated with the source image may be obtained from the detected image based on a fractional delay filter. In one example, the image may be oversampled by magnifying the detected image at the detector and/or having a detector with pixel sizes and spacing less than the image pixel size. Further, coefficients of the fractional delay filter may be determined, at least in part, on magnification and shift information of the image based on known registration marks.

Abstract: A system and method for recording and reproducing holographic interferogram with servos. A servo process is provided by the system and method to continuously record a holographic interferogram in a holographic recording medium with servo trace layers. Also, by the servo process, the intensity distribution of a reference beam is monitored, which is reflected by a reflecting mirror disposed on the other side of the holographic recording medium. By analyzing the distribution, one can adjust the distance and the incidence angle between the reflection mirror and the reference beam. Moreover, a plurality of servo tracks on different layers are provided for recording the holographic interferogram on different layers of holographic recording medium.

Abstract: Provided is a hologram retrieval method and a holographic recording and reproducing apparatus for preventing an increase in SNR, a decrease in retrieval accuracy, or the retrieval itself from being made impossible, which would otherwise occur because of a small size of data used for retrieval. Digital information is recorded on a holographic recording medium as data pages DP formed of a two-dimensional bit map image with each page being multiplexed. The data page DP is divided into a plurality of equal data blocks DB11 to 13, DB21 to DB23, and DB31 to DB33, and each data block DB is provided with a data image that is encoded by an encoding method for providing a certain number of ON pixels within each data block DB. A spatial light modulator allows the to-be-retrieved data image to be encoded by the encoding method and displayed as block information on a retrieval data block associated with the data block, and a signal beam to be thereby modulated.

Abstract: The invention provides a process capable of fabricating a cholesteric liquid crystal medium having a volume hologram with efficiency yet without recourse to complicated steps such as an alignment step. This is achievable as follows. A volume hologram layer is formed on a substrate, and a cholesteric liquid crystal layer is then formed on another substrate comprising a center substrate film that is subjected to bondable treatment. The volume hologram layer is applied to the center substrate film that is subjected to bondable treatment, and placed in a state where the volume hologram layer and cholesteric liquid crystal layer are laminated together via the substrate. The substrate is peeled off the volume hologram layer, and an adhesive layer is formed on the surface of the volume hologram layer off which the substrate is peeled off, followed by the provision of the substrate on the adhesive layer.

Abstract: A holographic recording medium includes a recording layer on a substrate, which records data information in a light interference pattern. Information on a thermal expansion characteristic of a recording material contained in the recording layer and/or information on temperature dependency of the refractive index of the recording material are recorded within the holographic recording medium in advance.

Abstract: A recording medium records therein image data for distributing contents as element holograms with interference fringes generated by interference between an object beam representing the image data and a reference beam. The image data to be distributed which are recorded as the element holograms in the recording medium are reproduced by applying reference beams to the recording medium.

Abstract: A holographic projection system has an optical wave tracking system which adjusts the propagation direction of a modulated wavefront. It provides an adjustable wave tracking system which aligns the modulated wave with a desired eye position of one or more observers and follows the movements of the observer. The system comprises spatial light modulation means which modulate a wave with holographic information for the purpose of holographic reconstruction. The optical wave tracking provides the light path of the modulated wave with a desired propagation direction which guides the modulated wave out of the reconstruction system via a light exit position of a display screen. Position control means set adjustable tracking mirror means in terms of their inclination to a reflection direction for reflecting the modulated wave and deflection means, which are located in the set reflection direction, reflect the wave via the display screen into the desired propagation direction.

Abstract: A recording medium records therein image data for distributing contents as element holograms with interference fringes generated by interference between an object beam representing the image data and a reference beam. The image data to be distributed which are recorded as the element holograms in the recording medium are reproduced by applying reference beams to the recording medium.

Abstract: An apparatus for producing a hologram mask. The apparatus includes a first object light at least partially transmittable through a first original mask having a light transmitting screening pattern, and a first reference light having a first phase difference between it and the first object light. The first object and reference lights cause interference patterns to be recorded a hologram recording material, as do a second object light at least partially transmittable through a second original mask having a light transmitting screening pattern, and a second reference light having a second phase difference between it and the second object light where the second phase difference is not the same as the first phase difference. The resulting first and second original mask images recorded in the hologram recording material can be simultaneously replayed to produce an exposed pattern approximating an exposed pattern of a non-holographic phase shifting photomask.

Abstract: A hologram recording medium includes a first element hologram and a second element hologram. On the first element hologram, main data is recorded such that the main data is converted into a two-dimensional image, object light of the two-dimensional image is interfered with recording reference light, and an interference fringe produced as a result of the interference is recorded on the first element hologram. On the second element hologram, simplified-form data representing the content of the main data using a smaller data size than the data size of the main data is recorded such that the simplified-form data is converted into a two-dimensional image, object light of the two-dimensional image is interfered with recording reference light, and an interference fringe produced as a result of the interference is recorded on the second element hologram.

Abstract: Holographic display device comprising a first EASLM and a second EASLM, the pair permitting independent modification of phase and amplitude, in which holographic reconstruction is visible through one or more virtual observer windows. An advantage is that an observer may view a holographic reconstruction through one or more virtual observer windows from a device housing a pair of EASLMs which permit independent modification of phase and amplitude.

Abstract: An autostereoscopic three-dimensional liquid crystal display system and a method of making the system. The system includes a collimated backlight, a first light diffracting hologram, a second right-left interlacing hologram and a liquid crystal display. If the backlight is not collimated, a micro-collimator array is used to collimate the backlight prior to passing into the first hologram. The second right-left interlacing hologram is formed through a two step process. The process comprises positioning a photolithographic mask and a view region mask in a first position, recording the first holographic recording in the first position, shifting the photolithographic mask and the view region mask to a second position and recording the second holographic recording in the second position.

Abstract: A light deflecting device is a light deflecting device for deflecting an incident light beam and has: a coarse motion light deflecting device which has an optical system having at least two conjugate points on an optical axis and deflects the light beam which has passed through one conjugate point and has entered the optical system as an output light beam which passes through the other conjugate point and has a deflection angle with respect to the optical axis while changing its transmitting direction; and a fine motion light deflecting device which is arranged in the optical system, applies a deflection to the incident light beam, and changes the deflection angle of the output light beam to a second deflection angle different from the deflection angle for a predetermined time.

Abstract: An apparatus for compensating for pixel distortion while reproducing hologram data includes an extraction unit, a determination and calculation unit, a table, and a compensation unit. The extraction unit extracts a reproduced data image from a reproduced image frame including the reproduced data image and borders. The determination and calculation unit determines position values of edges of the extracted reproduced data image, and calculates average magnification error values of pixels within line data from position values of start and end point pixels thereof, which are based on the determined position values of the edges. The table stores misalignment compensation values for the pixels within the line data, wherein the misalignment compensation values correspond to predetermined references for average magnification error values.

Abstract: A method of recording holographic information includes recording a hologram mark and a homogeneous mark in a holographic data storage medium with a volume to alternatively locate the hologram mark and the homogeneous mark. The hologram mark has a varied refractive index distribution due to constructive/destructive interferences between two light beams and indicates information, while the homogeneous mark has a more uniform refractive index distribution than the hologram mark.

Abstract: A holographic multiplex recording method which can keep a recording data rate constant and equalize nonuniformity in recording due to vibrations or the like, and a holographic recording apparatus and a holographic recording medium, which employ the method. In a process of multiplex-recording information, the time of exposure to a laser beam per data page is kept constant, and the laser output power of the laser beam is increased in accordance with a decrease in recording sensitivity of the holographic recording medium.

Abstract: An apparatus for recording or reading high areal density holographically stored information with high signal-to-noise ratio. The apparatus comprises a holographic imaging system for recording or reconstructing a holographic image, having a first numerical aperture and a first focal length and an additional optical system for filtering the signal beam, having a second numerical aperture and a second focal length, wherein the numerical aperture of the additional optical system is less than the numerical aperture of the holographic imaging system and/or the focal length of the additional optical system is greater than the optical length of the holographic imaging system.

Abstract: A method is provided for manufacturing a holographic medium by recording holograms in transmission geometry, and applying a reflective layer to one side of the holographic recording material after recording is completed (alternatively, for example, the playback system may contain a reflective surface or mirror). For readout, the reference beam is incident to the media from a side opposite the reflective layer. This beam propagates through the media to the reflective layer on the opposite side, and is reflected back through the media for readout of the transmission hologram. The diffracted hologram signal also exits the media on the side without the reflective layer, where it can be recovered by a detector on the same side as the laser source. Alternatively, the readout reference beam is positioned so that the incident beam reads out the hologram, and both the reference beam and diffracted hologram are reflected back through the media.

Abstract: A sophisticated volume hologram for dispersing an incident optical signal with uniform spectrum over an input plane to an output pattern with non-uniform spatial-spectral information, where the sophisticated volume hologram includes a plurality of holograms that map different input wavelengths into different locations on an output plane. The system further includes a detector for receiving and detecting light dispersed by the sophisticated volume hologram.

Abstract: A need to effectively record data of various sizes on a large-capacity holographic memory capable of high-speed recording is achieved, for example, by curing a first part of the holographic recording which is able to be multiplex-recorded in one or more units of a predetermined volume, and by not recording/curing a second part which is not able to be multiplex-recorded in a predetermined volume at a timing when the first recording part is cured. Also the above need can be achieved by, another example, by adding dummy data to the second part. Alternatively, the second part can be recorded on another track, in which it is possible to record in different units, e.g. by bit recording in a track that utilizes a DVD recording format. According to the present examples, we can record data of various sizes on the holographic memory effectively while performing large-capacity and high-speed holographic recording.

Abstract: An apparatus and method to produce a hologram of an object includes an electromagnetic radiation assembly configured to receive a received electromagnetic radiation, such as light, from the object. The electromagnetic radiation assembly is further configured to diffract the received electromagnetic radiation and transmit a diffracted electromagnetic radiation. An image capture assembly is configured to capture an image of the diffracted electromagnetic radiation and produce the hologram of the object from the captured image.

Abstract: Systems and methods for recovering data in a holographic memory system. The systems and methods use homodyne detection to introduce a local oscillator beam into a reconstructed data beam of the recovered hologram. An image of the combined beam comprising the reconstructed data beam and local oscillator beam may be processed to obtain contrast level information for the pixels of the detected image. This contrast level information may then be used to obtain an increased contrast image of the recovered hologram, which may increase the SNR of the recovered data.

Abstract: A hologram-reproducing method is adapted to obtain a reproduced image by irradiating a hologram-recording material with a reference-light beam so that a reproduction signal-light beam is generated and picking up an image of the reproduction signal-light beam. The hologram-reproducing method includes the steps of generating a plurality of reproduced images by irradiating the hologram-recording material with a plurality of reference-light beams and generating a single reproduced image by performing image processing for the plurality of reproduced images.

Abstract: A hologram recording apparatus includes an objective lens (7) for illuminating a hologram recording medium (B) with a recording beam (S) in a manner such that the recording beam overlaps a reference beam, thereby performing multiple recording of holograms at a portion illuminated with the reference beam and the recording beam (S). The objective lens (7) includes at least one rotationally symmetric lens (7A, 7B), and at least one rotationally symmetric lens (7A) is so arranged that the lens optical axis is inclined with respect to the direction (S1) in which the recording beam (S) travels.

Abstract: The hologram recording/reproducing apparatus is for recording a hologram by emitting a recording beam (S) modulated by a spatial light modulator and a reference beam (R) having a same wavelength as the recording beam onto a hologram recording medium (B) so that the beams overlap each other with polarization direction (p) of the beams being matched to interfere with each other, and for reproducing the hologram by exposing the hologram recording medium storing the hologram to the reference beam to generate diffracted light and receiving the diffracted light by an imaging device. The spatial light modulator is controlled so as to form a data area (H0) corresponding to information to be recorded and a plurality of mark areas (H1) for detecting a position of the data area in the hologram recording medium (B) in recording of the hologram.

Abstract: A hologram recording carrier that information is recorded into or reproduced from by irradiating light, comprises a hologram recording layer to store an optical interference pattern by coherent reference light and signal light as a hologram therein; and a servo layer laid on top of the hologram recording layer in a film thickness direction, multiple marks being recorded beforehand on the servo layer. The multiple marks form lines as multiple mark rows extending in a direction parallel to a relative movement direction of a light spot of a hologram recording beam irradiated on the hologram recording carrier.

Abstract: A lighting apparatus is provided. The lighting apparatus includes a power supply housing section, a circuit board housing section, a light source housing section, a cutout portion, and a light source. An image recorded on a record medium is displayed in the state that an end portion of the power supply housing section and an end portion of the record medium secured to the cutout portion are placed on a surface where the lighting apparatus is placed.

Abstract: The preferred embodiments of the present invention include a holography attachment device that is attachable to a digital imaging device to form a holographic microscope. The holography attachment device includes a chamber having at least one attachment mechanism to facilitate attachment of the chamber to a digital imaging device. The holography attachment device also includes a light source and a sample holder section, which is located between a proximate end and the distal end of the chamber. The light source is configured to radiate light within the chamber. The light passes through the sample holder section and impinges on an imaging sensor of a digital imaging device when the chamber is attached to the digital imaging device. The digital imaging device is capable of recording hologram information related to a sample held by the sample holder in the sample holder section.

Abstract: For the purpose of preparing a computer-generated hologram, which has very high resolution and many numbers of parallaxes, the present invention provides a computer-generated holographic stereogram, wherein a virtual point light source group (11) is set up spatially on a side opposite to the observation side of the hologram (12), luminance angular distribution AWLci (?xz, ?yz) of divergent light diverged from each of the virtual point light sources of said virtual point light source group toward observation side is divided by angular division, and within the divided angle, among the multiple images positioned on the plane of said virtual point light source group (11), a divergent light to be equal to the divergent light diverged from a point of amplitude equal to the density of pixel of the image corresponding to each of divided angle or equal to a value in a certain fixed relation with the density of the images at the position of the virtual point light source is recorded as the object light (1) at one of th

Abstract: A hologram reconstructing apparatus configured to irradiate a hologram recording medium that stores an interference pattern of a signal beam spatially modulated by data displayed on a spatial modulator and a reference beam emitted simultaneously with the signal beam with a reconstructing reference beam and to reconstruct data by capturing a reconstruction signal beam generated at the hologram recording medium being irradiated includes an image pickup unit that receives a partial reconstruction signal beam that constitutes part of the reconstruction signal beam by a full light-receiving plane; and a moving unit that relatively move the light-receiving surface of the image pickup means within an irradiation range of the reconstruction signal beam.

Abstract: A hologram media reading apparatus including a reference light source, a stop with gray level aperture, and an optical sensor is provided. The reference light source is disposed on one side of a hologram medium, and capable of emitting a reference light beam. The reference light beam is transmitted to the hologram medium. The stop with gray level aperture and the reference light source are disposed on the same side or opposite sides of the hologram medium. The stop with gray level aperture has a light transmissive region, an opaque region, and a transmittance gradually varying region. The opaque region surrounds the light transmissive region. The transmittance gradually varying region surrounds the light transmissive region. A part of the reference beam from the hologram medium passes through the stop with gray level aperture and is transmitted to the optical sensor.

Abstract: The present invention relates to a method for recording data pages in a holographic recording medium, and more specifically to a method for compensating for sensitivity variations of the holographic material of the holographic recording medium. According to the invention, a method for recording data pages on a holographic recording medium has the steps of: modulating a light beam with a spatial light modulator to generate a data page with data to be recorded, and applying a compensation profile to the data pages during recording for reducing contrast variations in the reconstructed data pages, wherein the compensation profile is determined from the irradiation history at the recording position and the sensitivity curve of the material of the holographic recording medium.

Abstract: Disclosed is a hologram reproducing device and a hologram reproducing method capable of reading hologram data at a high speed with low power consumption. When a predetermined voltage is applied to some of the signal electrodes and the scanning electrodes arranged in a matrix, a pixel disposed at an intersection of the signal electrode and the scanning electrode is set as a transmission region, and reproduction light emitted from a hologram recording medium passes through a light control member through the transmission region and is then incident on a light receiving unit. Then, hologram data is reproduced. It is possible to switch the reproduction light passing through the light control member only by changing a combination of voltages applied to the signal electrode and the scanning electrode. Therefore, it is possible to improve the read speed of hologram data.

Abstract: A white-light reconstruction hologram and a Fourier hologram for data can be recorded in a same holographic recording medium. The holographic recording medium includes, in a substantially identical plane, a white-light reconstruction holographic recording layer region capable of forming a white-light reconstruction hologram, having a thickness of 2 ?m to 80 ?m, and a Fourier holographic recording layer region capable of multiplexed hologram recording, having a thickness of 100 ?m to 2 cm.

Abstract: A hologram recording device for recording interference fringes between reference light and signal light modulated by data displayed in a spatial modulator in a hologram recording material, the hologram recording device including a phase mask for diffusing light, the phase mask being disposed in an optical system that the signal light passes, wherein a minimum unit of a light diffusing pattern formed in the phase mask is a natural number of times a minimum unit of display data of the spatial modulator.

Abstract: A system and a method for holographic storage mainly involve forming a holographic interference pattern in a holographic recording medium. The holographic storage system utilizes a light source to emit a coherent beam. The coherent beam is irradiated to a first reflector to form a divergent beam. The divergent beam is then irradiated to a second reflector to form collimating beams (a signal beam and a reference beam). The signal beam goes through a spatial light modulator (SLM) and is modulated by the SLM. After that, the reference beam and the modulated signal beam are irradiated to a convergent unit, and are directed to the holographic recording medium for forming the holographic interference pattern. The holographic storage system that the light source is split into a signal beam and a reference beam by a set of reflectors according to the reflection principle without involving refraction may employ wavelength multiplexing.

Abstract: Disclosed is a hologram recording method using a beam with a very large incident angle, a hologram reproduction apparatus using a holographic reflector, a hologram reproduction method using the same and a flat display element apparatus using a holographic reflector. The hologram recording method using a beam with a very large incident angle comprises the steps of generating a sheet beam as the reference beam, and introducing the reference beam into the recording medium at an incident angle of at least 70°. The hologram reproduction apparatus using a holographic reflector comprises a light, a holographic reflector, an adjustor, and a hologram.

Abstract: A method for inputting commands to a holographic input system, includes the steps of generating a virtual image of an input device by illuminating a hologram of the input device by means of a corresponding reference beam, the hologram being prerecorded on a holographic support; optically detecting a position of at least one actuator for operating the input device with respect to the virtual image of the input device; and issuing at least one command signal corresponding to the position of that at least one actuator as optically detected.

Abstract: A holographic data storage medium, and a method and an apparatus for recording/reproducing holographic data by using the medium includes a substrate; manifold reflective layer between which a part of a signal beam is capable of being reflected at least one time and then being emitted from the manifold reflective layer; and a holographic recording layer in which a plurality of information layers are capable of being formed in a depth direction of the holographic recording layer, wherein interference patterns of a rest of the signal beam and a reference beam constitute each of the plurality of information layers.

Abstract: A holographic recording method and apparatus capable of performing phase code multiplex recording without employing a phase spatial light modulator. The holographic recording apparatus 10 performs phase spatial modulation of a reference beam to be projected onto a holographic recording medium by means of a phase code mask 26 in which phase code patterns are recorded in advance as a hologram and which is employed in place of a phase spatial light modulator in a reference optical system 20.

Abstract: Provided are a holographic data storage medium and an apparatus and method for recording/reproducing holographic data using the same. The holographic data storage medium includes: a substrate; a holographic recording layer disposed on the substrate; and a cover layer covering the holographic recording layer. The holographic recording layer includes: a data recording region including a plurality of data layers to which data is recorded, the data recording region in which interference fringes due to first and second beams are formed in different data layers in a depthwise direction; and a layer discrimination region for providing discrimination between the data layers.

Abstract: This invention relates to improved techniques for reading holograms, in particular volume reflection holograms, and to improved security documents incorporating volume reflection holograms.

Abstract: Methods and systems are provided for obtaining a phase conjugate reconstruction beam for use in retrieving holographic information from a holographic storage medium. These methods and systems include generating a coherent light beam that is a reproduction of the reference beam used in storing the holographic information in the storage medium. This coherent light beam is then directed through the holographic storage medium at the same angle and location of the reference beam during recording of the hologram. The directed coherent beam is then reflected back through the storage medium so that the reflected coherent light beam provides a phase conjugate of the reference beam and passes through the storage medium at the same angle and location that the reference beam passed through the storage medium during recordation of the hologram.

Abstract: A hologram medium manufacturing method is disclosed. The hologram medium manufacturing method includes: disposing a first pair of master hologram media with a predetermined interval so that the first pair of the master hologram media face each other; forming a master hologram in the master hologram media by irradiating the first pair of the master hologram media with spherical wave light and reference light so that the spherical wave light and the reference light interfere with each other in the master hologram media, the spherical wave light and the reference light having a focal point between the first pair of the master hologram media; disposing a hologram medium between the first pair of the master hologram media; and forming a hologram in the hologram medium by irradiating the first pair of the master hologram media with the reference light.

Abstract: An image capture system for a digital holographic printer is disclosed comprising a digital camera (22) having a relatively small horizontal field of view (29). The camera (22) is translated along a rail (21). As the camera (22) is translated along the rail (21) the camera (22) is also rotated so that it faces a target point of an object which is to be reproduced as an hologram. The image data which is obtained by the camera (22) is converted into image data which corresponds with image data which would have been obtained had a non-rotating camera having a substantially higher horizontal field of view been translated along the rail (21) and been used to capture images of the object.

Abstract: The invention provides a process capable of fabricating a cholesteric liquid crystal medium having a volume hologram with efficiency yet without recourse to complicated steps such as an alignment step. This is achievable as follows. A volume hologram layer is formed on a substrate, and a cholesteric liquid crystal layer is then formed on another substrate comprising a center substrate film that is subjected to bondable treatment. The volume hologram layer is applied to the center substrate film that is subjected to bondable treatment, and placed in a state where the volume hologram layer and cholesteric liquid crystal layer are laminated together via the substrate. The substrate is peeled off the volume hologram layer, and an adhesive layer is formed on the surface of the volume hologram layer off which the substrate is peeled off, followed by the provision of the substrate on the adhesive layer.

Abstract: A hologram recording apparatus (300) is provided with: a recording device (100) for recording record information into a hologram recording medium (1); a measuring device (325) for measuring a time elapsed from when the recording of the record information is stopped to when the recording of the record information is restarted; a first controlling device (354) for controlling the recording device to multiplex-record the record information, if the measured elapsed time is shorter than a time length in which the record information can be multiplex-recorded; and a second controlling device (354) for controlling the recording device not to multiplex-record the record information, if the measured elapsed time is longer than the time length in which the record information can be multiplex-recorded.

Abstract: A method of 3D holographic recording by using a very simple optical system includes dividing a femto-second laser pulse into a plurality of light beams by a diffraction beam splitter, focusing four light beams selected from the divided plurality of light beams, controlling each optical phase of the selected four light beams by a phase retarder, and further focusing these four light beams into a sample comprised of a photosensitive material capable of multi-photon exposure so that the photosensitive material is exposed to the interference among the four light beams and multi-photon absorption in the sample is induced, thus recording a 3D phase hologram on the irradiated portion of the sample.

Abstract: A hologram recorder applies a recording beam (S) and a reference beam (R) to the illumination site (p) of a hologram recording medium (B). The interference between the recording beam (S) and the reference beam (R) produces multiple hologram recording at the illumination site (p). The recorder includes a recording-purpose reference beam reflector (10) for reflecting the reference beam (R) to the illumination site (p), and a pivot mechanism for pivoting the reflector (10) about an axis (x) to vary the incident angle (?r) of the reflected reference beam (R) to the recording medium (B). The reflector (10) is disposed to cross a predetermined optical path. The axis (x) of the pivot mechanism is so arranged that the reflected reference beam (R) is directed to the illumination site (p) even when the incident angle (?r) of the beam (R) changes due to the pivoting of the reflector (10).

Abstract: A hologram recording device (A1) includes a laser (1), a beam splitter (3) splitting the laser beam from the laser (1) into recording and reference beams (S), (R), a spatial light modulator (5) modulating the recording beam (S) by record information, a recording opto-system directing the modulated beam (S) to a target site of a hologram recording medium (B), and a reference opto-system directing the reference beam (R) to the target site of the recording medium (B) for interference with the recording beam (S) through difference incident angles. The beam (S)-beam (R) interference enables multiplex hologram recording at the target site. The device (A1) further includes a light amount adjustor (8) that adjusts the amount of the reference beam (R) from the splitter (3) based on the incident angle to the recording medium (B) for keeping the illuminance of the reference beam (R) at the target site at a predetermined level.